endothelin-1 and Hypoxia

The association between obstructive sleep apnea (OSA) and cancer is still debated and data are scarce regarding the link between OSA and breast cancer progression. Since conclusive epidemiological studies require large sample sizes and sufficient duration of exposure before incident cancer occurrence, basic science studies represent the most promising approach to appropriately address the topic. Here we assessed the impact of intermittent hypoxia (IH), the major hallmark of OSA, on the development of breast cancer and explored the specific involvement of the endothelin signaling pathway. Original in vitro and in vivo models were used where 3D-spheroids or cultures of murine 4T1 breast cancer cells were submitted to IH cycles, and nude NMRI mice, orthotopically implanted with 4T1 cells, were submitted to chronic IH exposure before and after implantation. The role of the endothelin-1 in promoting cancer cell development was investigated using the dual endothelin receptor antagonist, macitentan. In vitro exposure to IH significantly increased 4T1 cell proliferation and migration. Meta-analysis of 4 independent in vivo experiments showed that chronic IH exposure promoted tumor growth, assessed by caliper measurement (overall standardized mean difference: 1.00 [0.45-1.55], p < 0.001), bioluminescence imaging (1.65 [0.59-2.71]; p < 0.01) and tumor weight (0.86 [0.31-1.41], p < 0.01), and enhanced metastatic pulmonary expansion (0.77 [0.12-1.42]; p = 0.01). Both in vitro and in vivo tumor-promoting effects of IH were reversed by macitentan. Overall, these findings demonstrate that chronic intermittent hypoxia exposure promotes breast cancer growth and malignancy and that dual endothelin receptor blockade prevents intermittent hypoxia-induced tumor development.

Topics: Animals; Endothelin-1; Hypoxia; Mice; Neoplasms; Receptor, Endothelin A; Sleep Apnea, Obstructive

Hypoxic state affects organism primarily by decreasing the amount of oxygen reaching the cells and tissues. To adjust with changing environment organism undergoes mechanisms which are necessary for acclimatization to hypoxic stress. Pulmonary vascular remodelling is one such mechanism controlled by hormonal peptides present in blood circulation for acclimatization. Activation of peptides regulates constriction and relaxation of blood vessels of pulmonary and systemic circulation. Thus, understanding of vascular tone maintenance and hypoxic pulmonary vasoconstriction like pathophysiological condition during hypoxia is of prime importance. Endothelin-1 (ET-1), atrial natriuretic peptide (ANP), and renin angiotensin system (RAS) function, their receptor functioning and signalling during hypoxia in different body parts point them as disease markers. In vivo and in vitro studies have helped understanding the mechanism of hormonal peptides for better acclimatization to hypoxic stress and interventions for better management of vascular remodelling in different models like cell, rat, and human is discussed in this review.

Topics: Animals; Atrial Natriuretic Factor; Endothelin-1; Humans; Hypoxia; Lung; Renin-Angiotensin System; Signal Transduction; Vascular Remodeling

Obstructive sleep apnea (OSA) is now recognized as an independent and important risk factor for cardiovascular diseases such as hypertension, coronary heart disease, heart failure and stroke. Clinical and experimental data have confirmed that intermittent hypoxia is a major contributor to these deleterious consequences. The repetitive occurrence of hypoxia-reoxygenation sequences generates significant amounts of free radicals, particularly in moderate to severe OSA patients. Moreover, in addition to hypoxia, reactive oxygen species (ROS) are potential inducers of the hypoxia inducible transcription factor-1 (HIF-1) that promotes the transcription of numerous adaptive genes some of which being deleterious for the cardiovascular system, such as the endothelin-1 gene. This review will focus on the involvement of the ROS-HIF-1-endothelin signaling pathway in OSA and intermittent hypoxia and discuss current and potential therapeutic approaches targeting this pathway to treat or prevent cardiovascular disease in moderate to severe OSA patients.

Topics: Animals; Cardiovascular Diseases; Endothelin-1; Humans; Hypoxia; Hypoxia-Inducible Factor 1; Reactive Oxygen Species; Risk Factors; Severity of Illness Index; Signal Transduction; Sleep Apnea, Obstructive

The development of pulmonary hypertension (PH) and its effect on long-term survival in bronchiectasis subjects has not been explored. The present study aims to analyze the factors associated with PH and its effect on long-term survival in bronchiectasis subjects.. We prospectively evaluated 23 bronchiectasis subjects without PH and 16 with PH, as well as 20 healthy volunteers.. Bronchiectasis subjects with PH were more hypoxemic and had a greater number of involved lobes in high resolution computed tomography (HRCT) than did the bronchiectasis subjects without PH (P < 0.001 and P < 0.001, respectively). At three years, the survival rate was 95.7% for bronchiectasis subjects without PH and 56.3% for bronchiectasis with PH, and at 5 years, these rates were 95.7% and 62.5%, respectively (P = 0.002). Multivariate Cox regression analysis revealed that only the Medical Research Council (MRC) dyspnea score was independently related to poor survival in all bronchiectasis subjects (hazard ratio: 6.98; 95% CI: 2.41-20.23; P < 0.00001).. Subjects with PH are more hypoxemic and have a greater number of involvements in the lobes of the lungs. Bronchiectasis subjects with PH have worse survival than do bronchiectasis subjects without PH. MRC dyspnea score is an independent predictor of long-term survival.

Topics: Adult; Bronchiectasis; Clinical Trials as Topic; Dyspnea; Echocardiography, Doppler; Endothelin-1; Female; Humans; Hypertension, Pulmonary; Hypoxia; Male; Middle Aged; Oxygen; Patient Outcome Assessment; Prospective Studies; Risk Factors; Survival Rate; Tomography, X-Ray Computed; Turkey; Ventricular Dysfunction, Right

Fibrotic diseases are a significant global burden for which there are limited treatment options. The effector cells of fibrosis are activated fibroblasts called myofibroblasts, a highly contractile cell type characterized by the appearance of α-smooth muscle actin stress fibers. The underlying mechanism behind myofibroblast differentiation and persistence has been under much investigation and is known to involve a complex signaling network involving transforming growth factor-β, endothelin-1, angiotensin II, CCN2 (connective tissue growth factor), and platelet-derived growth factor. This review addresses the contribution of these signaling molecules to cardiac fibrosis.

Topics: Angiotensin II; Angiotensin II Type 1 Receptor Blockers; Animals; Anti-Inflammatory Agents; Arrhythmias, Cardiac; Atrophy; Cicatrix; Connective Tissue Growth Factor; Endothelin Receptor Antagonists; Endothelin-1; Fibrosis; Humans; Hypoxia; Models, Cardiovascular; Molecular Targeted Therapy; Myocardium; Myofibroblasts; Platelet-Derived Growth Factor; Pyridones; Rats; Signal Transduction; Transforming Growth Factor beta

Topics: Animals; Endothelin-1; Gene Expression Regulation; Humans; Hypoxia; Hypoxia-Inducible Factor 1; NF-kappa B; Nitric Oxide; Oxidative Stress; Sleep Apnea, Obstructive; Vascular Endothelial Growth Factor A

It has been long recognized that skeleton represents one of the most favored metastatic sites for common cancers like breast and prostate. During the last decade the molecular mechanisms that are responsible for the development of bone metastasis have been gradually illuminated. It appears that the bone microenvironment has a pivotal role in this process. Metastatic tumor cells interact with bone triggering a cascade of molecular events that produce osteolytic and/or osteoblastic phenomena. In this review, we summarize and discuss the most significant factors and signaling pathways implicated in bone colonization. Moreover, based on the recent literature and data, we foresee the need for designing novel agents that will efficiently disrupt these interactions among cancer cells and bone microenvironment, bringing hope for more effective treatments.

Topics: Animals; beta Catenin; Biphenyl Compounds; Bone Neoplasms; Bone Remodeling; Breast Neoplasms; Cathepsin K; Chemokine CXCL12; Diphosphonates; Endothelin-1; Female; Humans; Hypoxia; Male; Neoplastic Stem Cells; Osteoblasts; Osteoclasts; Osteolysis; Parathyroid Hormone-Related Protein; Prostatic Neoplasms; RANK Ligand; Receptor Activator of Nuclear Factor-kappa B; Receptors, CXCR4; Signal Transduction; Urokinase-Type Plasminogen Activator; Wnt Proteins

Pulmonary hypertension (PH) is a general term comprising a spectrum of pulmonary hypertensive disorders which have in common an elevation of mean pulmonary arterial pressure (mPAP). The prototypical form of the disease, termed pulmonary arterial hypertension (PAH), is a rare but lethal syndrome with a complex aetiology characterised by increased pulmonary vascular resistance (PVR) and progressive elevation of mPAP; patients generally die from heart failure. Current therapies are inadequate and median survival is less than three years. PH due to chronic hypoxia (CH) is a condition separate from PAH and is strongly associated with chronic obstructive pulmonary disease (COPD). An early event in the pathogenesis of this form of PH is hypoxic pulmonary vasoconstriction (HPV), an acute homeostatic process that maintains the ventilation-perfusion ratio during alveolar hypoxia. The mechanisms underlying HPV remain controversial, but RhoA/Rho kinase (ROK)-mediated Ca²+-sensitisation is considered important. Increasing evidence also implicates RhoA/ROK in PASMC proliferation, inflammatory cell recruitment and the regulation of cell motility, all of which are involved in the pulmonary vascular remodelling occurring in all forms of PH. ROK is therefore a potential therapeutic target in treating PH of various aetiologies. Here, we examine current concepts regarding the aetiology of PAH and also PH due to CH, focusing on the contribution that RhoA/ROK-mediated processes may make to their development and on ROK inhibitors as potential therapies.

Topics: Animals; Bone Morphogenetic Protein Receptors, Type II; Cell Proliferation; Endothelin-1; Humans; Hypertension, Pulmonary; Hypoxia; Muscle, Smooth, Vascular; NFATC Transcription Factors; rho-Associated Kinases; rhoA GTP-Binding Protein; Serotonin; Vasoconstriction

Preeclampsia is a pregnancy-induced hypertensive disorder found most commonly in nulliparous women. Recent research performed in animal models of the disease has revealed some of the underlying mechanisms of preeclampsia. Specifically, placental insufficiency and the resulting hypoxia/ischemia have been shown to be crucial to disease progression. In response to placental hypoxia/ischemia, several pathways are activated, which contribute to the clinical manifestations of the disease: increased circulating levels of the anti-angiogenic protein sFlt-1, activation of the maternal inflammatory response, suppressed nitric oxide production, enhanced endothelin-1 production, and induction of reactive oxygen formation. Despite advances in the understanding of the disorder, therapeutic approaches to the treatment of preeclampsia are severely limited. New lines of research, however, indicate some possible new therapeutic approaches for the management of preeclampsia and offer hope for an effective pharmacologic intervention.

Topics: Disease Progression; Endothelin-1; Endothelium, Vascular; Female; Humans; Hypoxia; Inflammation; Phosphodiesterase 5 Inhibitors; Piperazines; Placenta; Pre-Eclampsia; Pregnancy; Purines; Risk Factors; Sildenafil Citrate; Sulfones; Vascular Endothelial Growth Factor A

The voltage-independent background two-pore domain K(+) channel TASK-1 sets the resting membrane potential in excitable cells and renders these cells sensitive to a variety of vasoactive factors. There is clear evidence for TASK-1 in human pulmonary artery smooth muscle cells and TASK-1 channels are likely to regulate the pulmonary vascular tone through their regulation by hypoxia, pH, inhaled anesthetics, and G protein-coupled pathways. Furthermore, TASK-1 is a strong candidate to play a role in hypoxic pulmonary vasoconstriction. On the other hand, consistent with the activation of TASK-1 channels by volatile anesthetics, TASK-1 contributes to the anesthetic-induced pulmonary vasodilation. TASK-1 channels are unique among K(+) channels because they are regulated by both, increases and decreases from physiological pH, thus contributing to their protective effect on the pulmonary arteries. Moreover, TASK-1 may also have a critical role in mediating the vasoactive response of G protein-coupled pathways in resistance arteries which can offer promising therapeutic solutions to target diseases of the pulmonary circulation.

Topics: Anesthetics, Inhalation; Animals; Endothelin-1; Humans; Hydrogen-Ion Concentration; Hypoxia; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Nerve Tissue Proteins; Phylogeny; Potassium Channels, Tandem Pore Domain; Protein Isoforms; Pulmonary Artery; Receptors, G-Protein-Coupled; Signal Transduction; Vasoconstriction

Systemic sclerosis-related pulmonary arterial hypertension (PAH) is a severe disease affecting about 1000 patients in France. In 2008, all scleroderma patients are screened for PAH by a yearly cardiac Doppler ultrasonography. The pathogenesis of systemic sclerosis-related PAH is poorly known but it seems that besides common arteriolar remodeling (media hypertrophy, intimal thickening, endothelial proliferation), venular lesions suggesting obstructive venous disease and inflammatory lesions may be also be involved. Prostacyclin and analogues, phosphodiesterase-5 inhibitors (sildenafil) and endothelin-1 receptor antagonists are proposed as specific treatments for systemic sclerosis-related PAH. Unlike bosentan, which is non-selective, inhibiting both ETA and ETB receptors, sodium sitaxentan is highly selective for ETA receptors; this could favor pulmonary vasodilation.

Topics: Altitude; Antihypertensive Agents; Bosentan; Echocardiography; Endothelin Receptor Antagonists; Endothelin-1; Enzyme Inhibitors; France; Humans; Hypertension, Pulmonary; Hypoxia; Oxygen; Phosphodiesterase 5 Inhibitors; Prognosis; Scleroderma, Systemic; Sulfonamides

1. The most usual form of chronic hypoxia in humans is the intermittent hypoxia resulting from obstructive sleep apnoea (OSA). The OSA syndrome is a highly prevalent sleep breathing disorder that is considered an independent risk factor for hypertension and cardiovascular diseases. Endothelial dysfunction, oxidative stress, inflammation and sympathetic activation have been proposed as potential mechanisms involved in the onset of the hypertension. However, evidence for a unique pathogenic mechanism has been difficult to establish in OSA patients because of concomitant comorbidities. Thus, animal models have been developed to study the pathological consequences of exposure to chronic intermittent hypoxia (CIH). 2. Because OSA patients and animals exposed to CIH show augmented ventilatory, sympathetic and cardiovascular responses to acute hypoxia, it has been proposed that enhanced carotid body responsiveness to hypoxia is involved in the autonomic changes induced by OSA and in the development of the hypertension. Recently, this proposal has received further support from recordings of carotid body chemosensory neural discharges in situ and in vitro showing that exposure of animals to CIH increases basal carotid body chemosensory discharges and enhances the chemosensory response to hypoxia. 3. In the present brief review, we discuss the evidence supporting an important role for the carotid body in the progression of cardiorespiratory changes induced by OSA and the contribution of oxidative stress, endothelin-1 and pro-inflammatory molecules in the potentiation of the carotid body chemosensory function induced by CIH.

Topics: Animals; Cardiovascular System; Carotid Body; Chemoreceptor Cells; Endothelin-1; Humans; Hypertension; Hypoxia; Inflammation Mediators; Models, Biological; Oxidative Stress; Respiratory Mechanics; Respiratory System; Sleep Apnea, Obstructive; Sympathetic Nervous System

Pancreatic encephalopathy (PE) is a serious complication of severe acute pancreatitis (SAP). In recent years, more and more PE cases have been reported worldwide, and the onset PE in the early stage was regarded as a poor prognosis sign of SAP, but the pathogenesis of PE in SAP still has not been clarified in the past decade. The purpose of this review is to elucidate the possible pathogenesis of PE in SAP.. The English-language literature concerning PE in this review came from the Database of MEDLINE (period of 1991-2005), and the keywords of severe acute pancreatitis and pancreatic encephalopathy were used in the searching.. Many factors were involved in the pathogenesis of PE in SAP. Pancreatin activation, excessive release of cytokines and oxygen free radicals, microcirculation abnormalities of hemodynamic disturbance, ET-1/NO ratio, hypoxemia, bacterial infection, water and electrolyte imbalance, and vitamin B1 deficiency participated in the development of PE in SAP.. The pathogenesis of PE in SAP has not yet been fully understood. The development of PE in SAP may be a multi-factor process. To find out the possible inducing factor is essential to the clinical management of PE in SAP.

Topics: Acute Disease; Animals; Brain Diseases; Cytokines; Endothelin-1; Humans; Hypoxia; Nitric Oxide; Pancreatin; Pancreatitis; Thiamine Deficiency

The aims of the present review are to summarize and to discuss the role of hypoxia-inducible factor-1 (HIF-1) and the expression and functions of vasoactive substances in chronic hypoxemia with specific focus in the liver and the carotid body. Vascular remodelling and vasoactive substances play important functional roles in the adaptive response to chronic hypoxemia for the maintenance of oxygen homeostasis in all systems in man. HIF-1 regulates the gene expression of vasoactive substances such as vascular endothelial growth factor (VEGF), endothelin-1 (ET-1) and enzymes for producing nitric oxide (NO). Recent studies have shown the effect of chronic hypoxia on the expression of HIF-1alpha and HIF-1-target genes in multiple organ systems including the liver and the carotid body. Results are consistent with increases in the hematocrit levels, pulmonary arterial pressure and right heart mass developed during chronic hypoxia. In addition, the carotid body is also hyperplastic and increases in organ mass with increased levels of HIF-1alpha and the vasoactive substances. These molecules increase the mitotic activity and modulate the excitability of the chemoreceptor. Intriguingly, the liver morphology, serum alanine aminotransferase and 8-isoprostane levels are within normal range in chronic hypoxia, suggesting the absence of significant oxidative stress. Yet, the HIF-1alpha is upregulated and the mRNA and protein levels of VEGF, ET-1, inducible and constitutive NO synthases are elevated in the liver during chronic hypoxia. In conclusion, the adaptive response to long-term hypoxemia involves compensatory mechanisms mediated by expressing significant levels of HIF-1alpha and vasoactive substances regulated by HIF-1.

Topics: Animals; Carotid Arteries; Chronic Disease; Endothelin-1; Erythropoietin; Humans; Hypoxia; Hypoxia-Inducible Factor 1; Liver; Nitric Oxide; Oxygen; Transcription Factors; Vascular Endothelial Growth Factor A

Topics: Electrocardiography; Endothelin-1; Humans; Hypertension, Pulmonary; Hypoxia; Lung; Magnetic Resonance Imaging; Nitric Oxide; Pulmonary Disease, Chronic Obstructive; Radiography; Spirometry

The carotid body (CB) is the main arterial chemoreceptor that senses arterial PO2, PCO2 and pH. The structural unit of the CB is the glomoid, which is formed by clusters of chemoreceptor (glomus) cells located around the capillaries. The glomus cells are synaptically connected to nerve terminals of petrosal ganglion (PG) neurons and surrounded by sustentacular cells. The most accepted model of CB chemoreception states that glomus cells are the primary sensors. In response to hypoxia, hypercapnia and acidosis, glomus cells release one or more transmitters, which acting on the nerve terminals of sensory PG neurons, increase the chemosensory discharge. The CB has a high blood flow and an elevated metabolism that correlate to its oxygen-sensing function. Thus, vasoactive molecules produced within the CB may modulate the chemosensory process by controlling the CB blood flow and tissue PO2. In this review, we examine recent evidence supporting the idea that endothelins (ETs) and nitric oxide (NO) modulate the CB function acting upon chemoreceptor cells and chemosensory neurons or by regulating the blood flow through the CB parenchyma.

Topics: Animals; Carotid Body; Chemoreceptor Cells; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Interactions; Endothelin-1; Endothelins; Humans; Hypoxia; Models, Biological; Nitric Oxide; Triazenes

The aims of this review are to describe recent data focusing on the anatomical, functional and molecular changes of the carotid body during chronic hypoxemia, and to summarize current views in the literature relevant to the topic. The carotid body is the major peripheral sensor for detecting chemicals in the arterial blood. In acute hypoxia, carotid chemoreceptors transduce the signal to the brain for triggering reflexive responses of the cardiopulmonary system. The carotid body enlarges and changes its hypoxic sensitivity in humans and animals living at high altitude or subject to long-term hypoxemia associated with chronic cardiopulmonary diseases or hematological disorders. Recently, a surge of new evidence suggests that a heterodimeric transcriptional factor directly induced by severe tissue or cellular hypoxia, namely hypoxia-inducible factor-1 (HIF-1), is a key controller for the transcriptional regulation of the gene expression of a spectrum of proteins for the cellular response to hypoxia. These proteins, such as endothelin-1, type II nitric oxide synthase and vascular endothelial growth factor, play important physiological roles in the control of vascular tone and angiogenesis. In the carotid body, chronic hypoxemia induces remodeling of the vasculature, stimulates proliferation of the chemosensitive cells, and changes their excitability and sensitivity to chemical signals. In addition, HIF-1-targeted genes are expressed in the carotid body and the expression is modulated by chronic hypoxemia, suggesting an active role for HIF-1 in moderate levels of hypoxic stress.

Topics: Animals; Carotid Body; Chronic Disease; DNA-Binding Proteins; Endothelin-1; Humans; Hypoxia; Hypoxia-Inducible Factor 1; Hypoxia-Inducible Factor 1, alpha Subunit; Nitric Oxide; Nitric Oxide Synthase; Nuclear Proteins; Receptors, Endothelin; Receptors, Vascular Endothelial Growth Factor; Transcription Factors; Vascular Endothelial Growth Factor A

In the pulmonary circulation, a decrease in oxygen tension results in the development of hypoxic pulmonary vasoconstriction (HPV), although the exact mechanism by which HPV occurs remains unclear. Evidence gathered from many laboratories suggests that while pulmonary arterial smooth muscle cells (PASMCs) can sense and respond to changes in oxygen tension, full expression of HPV requires modulating influences from the endothelium. In this review, we propose a model of HPV, based on recent studies from our laboratory, in which endothelin-1 (ET-1), a vasoactive peptide released from the endothelium, plays a central role and discuss how this model may be involved in the long-term adaptation to hypoxia.

Topics: Acute Disease; Animals; Chronic Disease; Endothelin-1; Hypoxia; Pulmonary Circulation; Vasoconstriction

The Fawn-Hooded Rat (FHR) spontaneously develops pulmonary hypertension (PH) at sea level, and an increased severity of this disease is observed upon exposure to mild hypoxia. A recent report suggested that lung hypoplasia with decreased alveolarization and altered vascular growth led by the decreased activity of endothelial nitric oxide synthase may contribute to the development of PH in the FHR. Exposure to mild hypoxia (P1O2 = 120 mmHg) leads to severe PH in FHR but not in Tester Moriyama rat, a strain that has a serotonin platelet storage-pool deficiency (PSPD) similar to that of the FHR. A serotonin PSPD does not appear to predispose FHR to PH. Endothelin-1 (ET-1) mRNA and peptide levels are increased in the hypertensive lungs of mildly hypoxic FHR. ET-1 may at least partly contribute to the development of PH in this strain.

Topics: Animals; Disease Models, Animal; DNA-Binding Proteins; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Hypoxia-Inducible Factor 1; Hypoxia-Inducible Factor 1, alpha Subunit; Nuclear Proteins; Rats; RNA, Messenger; Serotonin; Transcription Factors

Endothelin (ET)-1 is a potent vasoactive peptide which is mostly secreted toward the vessel wall and the circulatory levels of which are quite low; for these reasons changes in plasma ET-1 may be difficult to detect even after the application of strong stimuli, which, in theory, should profoundly alter its production. We have examined the effects of a number of such stimuli and found that in humans the only one which consistently increased plasma ET-1 was the exposure to hypobaric hypoxia; moreover under these circumstances the increments in plasma ET-1 were correlated with the changes in pulmonary systolic pressure, suggesting a role of circulating ET-1 in the adaptation of pulmonary vessels to high altitude. In contrast no consistent changes of ET-1 were observed in response to sympathetic activation induced either by exposure to cold, standing, reduction in blood pressure and blood withdrawal. In response to angioplasty of renal artery stenosis a concomitant reduction in plasma ET-1 and angiotensin II (AngII) was observed in patients who, prior to angioplasty, had a high degree of activation of the renin system, supporting the possibility that in these specific conditions AngII may actually stimulate ET-1 production in vivo.

Topics: Adaptation, Physiological; Angioplasty; Angiotensin II; Angiotensin-Converting Enzyme Inhibitors; Blood Pressure; Cold Temperature; Endothelin-1; Humans; Hypertension; Hypoxia; Kidney; Renal Artery Obstruction; Renin-Angiotensin System; Sympathetic Nervous System

Biochemical and molecular biological evidence indicates that endothelin (ET)-1 and its receptors are selectively upregulated in the lung during exposure to hypoxia, while functional evidence indicates that ET-1 is a major mediator of hypoxia-induced pulmonary vasoconstriction and vascular remodeling. Hypoxia stimulates ET-1 gene transcription and peptide synthesis in cultured endothelial cells, and plasma ET-1 levels are increased in patients with primary pulmonary hypertension, and in humans exposed to high altitude, while immunoreactive ET-1 and ET-1 mRNA levels are increased in pulmonary artery endothelial cells of patients with primary pulmonary hypertension. Rats exposed to normobaric hypoxia exhibit increased pulmonary artery pressure, increased ET-1 peptide levels in plasma and lung, and selective increases in steady-state ET-1 and ET(A) and ET(B) receptor mRNA levels in lung but not in organs perfused by the systemic vasculature. The observations that both ET-1 and its major vascular smooth-muscle cell receptor are upregulated in response to hypoxia suggest that ET-1 may be a mediator of hypoxia-induced pulmonary hypertension. Moreover, hypoxic pulmonary vasoconstriction and vascular remodeling can be prevented and reversed by administration of either an ET(A)-selective or a combined ET(A) and ET(B) receptor antagonist. These findings support the hypothesis that endogenous ET-1 plays a major role in hypoxic pulmonary vasoconstriction/hypertension, right heart hypertrophy, and pulmonary vascular remodeling and suggest that ET-receptor blockers may be useful in the treatment and prevention of hypoxic pulmonary hypertension in humans.

Topics: Animals; Cells, Cultured; Endothelin Receptor Antagonists; Endothelin-1; Humans; Hypertension, Pulmonary; Hypoxia; Rats; Receptors, Endothelin; Vasoconstriction

The pulmonary endothelium modulates vascular tone by the release of endothelium-derived constricting (EDCF) and relaxing (EDRF) factors, among them endothelin-1, nitric oxide, prostacyclin, and putative endothelium-derived hyperpolarizing factors. Abnormalities in EDCF and EDRF generation have been demonstrated in a number of cardiopulmonary disease states, such as primary and secondary pulmonary hypertension, chronic obstructive lung disease, cardiopulmonary bypass, and congestive heart failure. An imbalance between EDCF and EDRF, termed "pulmonary endothelial dysfunction," may contribute to the alteration in vascular tone characteristic of pulmonary disease. The following review summarizes the present knowledge of the role of EDCF and EDRF in such processes with major focus on pulmonary endothelial dysfunction in hypoxia-induced pulmonary hypertension.

Topics: Animals; Antihypertensive Agents; Atrasentan; Bosentan; Controlled Clinical Trials as Topic; Disease Models, Animal; Endothelin Receptor Antagonists; Endothelin-1; Endothelins; Endothelium, Vascular; Epoprostenol; Heart Failure; Humans; Hypertension, Pulmonary; Hypoxia; Lung Diseases, Obstructive; Nitric Oxide; Oligopeptides; Peptides, Cyclic; Piperidines; Pulmonary Circulation; Pyrrolidines; Receptors, Endothelin; RNA, Messenger; Sulfonamides; Time Factors; Vasoconstriction; Vasodilation

1. The experimental model using periods of ventilation with a gas mixture containing 10% oxygen in the anesthetized pig was found to induce HPV that was reproducible and remained stable for up to two hours. 2. Intrapulmonary infusion of ET-1 during normoxia resulted in a dose-dependent increase in the SVR with a concomitant decrease in CO and rise in PVR. Infusion of ET-3 and S6c evoked similar responses, but of a considerably smaller magnitude. The dose-dependent systemic vasoconstriction evoked by ET-1 infusion was reduced after administration of the combined ETA and ETB receptor antagonist bosentan as well as the selective ETA receptor blockers BMS-182874 and TBC-11251 indicating that this effect is primarily mediated by ETA receptors. ETA receptors are present in porcine pulmonary arteries, since BMS-182874 caused a rightward shift of the concentration-response curve to ET-1 in vitro. 3. Administration of selective ETA- or combined ETA and ETB antagonists but not of a selective ETB antagonist reduced the SVR in normoxic pigs, indicating that ET acting through ETA receptors contributes to systemic vascular tone in the pig. In addition, ETA selective and non-selective ETA and ETB antagonists produced a reduction of PVR, although this effect was less consistent than the influence on SVR. This indicates that ETA receptors may contribute to basal pulmonary vascular tone. The plasma levels of ET-1 increased following the non-selective ET receptor antagonist bosentan but were unaffected by selective ETA receptor antagonism. 4. Intrapulmonary infusion of ET-1 produced in low doses a pulmonary vasodilatation during HPV in the pig. This pulmonary vasodilatory effect was also evident when ET-3 or S6c was infused. The pulmonary vasodilatory effect of ET-1 infusion was abolished following administration of the selective ETB receptor antagonist BQ-788, indicating that the pulmonary vasodilatory effect of ET in HPV in the pig is mediated by ETB receptors. Higher doses of ET-1 infusion during HPV resulted in systemic and pulmonary vasoconstriction. 5. Both combined ETA and ETB blockade using bosentan and selective ETA receptor inhibition using BMS-182874 or TBC-11251 reduced the development of HPV in the pig. In addition, bolus injection of TBC-11251 reversed already established HPV. Selective ETB receptor antagonism had no effect on HPV. These findings suggest that ETA receptor activation contributes to HPV in the pig. 6. The concentration-dependent contraction evok

Topics: Adult; Animals; Child; Endothelin Receptor Antagonists; Endothelin-1; Endothelin-3; Endothelins; Endothelium, Vascular; Female; Humans; Hypertension, Pulmonary; Hypoxia; Male; Pulmonary Circulation; Receptors, Endothelin; Swine; Vasoconstriction

To study the association between hepatocyte growth factor (HGF) and treatment response in mice with hypoxic pulmonary arterial hypertension (HPAH) and the possibility of HGF as a new targeted drug for HPAH.. After successful modeling, the HPAH model mice were randomly divided into two groups: HPAH group and HGF treatment group (tail vein injection of recombinant mouse HGF 1 mg/kg), with 10 mice in each group. Ten normal mice were used as the control group. After 5 weeks, echocardiography was used to measure tricuspid peak velocity, right ventricular systolic pressure, right ventricular hypertrophy index, and right ventricular/body weight ratio; the Griess method was used to measure the content of nitric oxide in serum; ELISA was used to measure the serum level of endothelin-1; transmission electron microscopy was used to observe changes in the ultrastructure of pulmonary artery.. Compared with the HGF treatment and normal control groups, the HPAH group had significantly higher tricuspid peak velocity, right ventricular systolic pressure, right ventricular hypertrophy index, and right ventricular/body weight ratio (. Increasing serum HGF level can alleviate the impact of HPAH on the cardiovascular system of mice, possibly by repairing endothelial cell injury, improving vascular remodeling, and restoring the normal vasomotor function of pulmonary vessels.

Topics: Animals; Body Weight; Endothelial Cells; Endothelin-1; Hepatocyte Growth Factor; Hypertrophy, Right Ventricular; Hypoxia; Mice; Nitric Oxide; Pulmonary Arterial Hypertension

Obstructive sleep apnoea (OSA) is associated with cardiovascular disease. Intermittent hypoxia, endothelial dysfunction and adipose tissue-mediated inflammation have all been linked to cardiovascular disease in OSA. We therefore explored the effect of OSA on relevant associated blood markers: adrenomedullin (ADM), endocan, endothelin-1 (ET-1), resistin and vascular endothelial growth factor (VEGF).. Patients with OSA, established on and compliant with continuous positive airways pressure (CPAP) therapy for >1 year were included from three randomized controlled trials, conducted at two centres. Patients were randomized to either continued therapeutic CPAP or sham CPAP (CPAP withdrawal) for 2 weeks. Blood markers were measured at baseline and at 14 days and the treatment effect between sham CPAP and therapeutic CPAP was analysed.. A total of 109 patients were studied (therapeutic CPAP n = 54, sham CPAP n = 55). Sham CPAP was associated with a return of OSA (between-group difference in oxygen desaturation index (ODI) 36.0/h, 95% CI 29.9-42.2, P < 0.001). Sham CPAP was associated with a reduction in ADM levels at 14 days (-26.0 pg/mL, 95% CI -47.8 to -4.3, P = 0.02), compared to therapeutic CPAP. Return of OSA was not associated with changes in endocan, ET-1, resistin or VEGF.. Whilst CPAP withdrawal was associated with return of OSA, it was associated with an unexpected significant reduction in the vasodilator ADM and not with expected increases in hypoxia-induced markers, markers of endothelial function or resistin. We propose that the vascular effects occurring in OSA may be brought about by other mechanisms, perhaps partly through a reduction in ADM.

Topics: Adrenomedullin; Adult; Aged; Biomarkers; Continuous Positive Airway Pressure; Endothelin-1; Female; Humans; Hypoxia; Inflammation; Male; Middle Aged; Neoplasm Proteins; Patient Compliance; Proteoglycans; Resistin; Sleep Apnea, Obstructive; Vascular Endothelial Growth Factor A; Ventilator Weaning

Air pollution has recently been associated with the development of acute decompensated heart failure, but the underlying biological mechanisms remain unclear. A pulmonary vasoconstrictor effect of air pollution, combined with its systemic effects, may precipitate decompensated heart failure. The aim of the present study was to investigate the effects of acute exposure to diesel exhaust (DE) on pulmonary vascular resistance (PVR) under resting and stress conditions but also to determine whether air pollution may potentiate acquired pulmonary hypertension. Eighteen healthy male volunteers were exposed to ambient air (AA) or dilute DE with a particulate matter of <2.5 μm concentration of 300 μg/m(3) for 2 h in a randomized, crossover study design. The effects of DE on PVR, on the coefficient of distensibilty of pulmonary vessels (α), and on right and left ventricular function were evaluated at rest (n = 18), during dobutamine stress echocardiography (n = 10), and during exercise stress echocardiography performed in hypoxia (n = 8). Serum endothelin-1 and fractional exhaled nitric oxide were also measured. At rest, exposure to DE did not affect PVR. During dobutamine stress, the slope of the mean pulmonary artery pressure-cardiac output relationship increased from 2.8 ± 0.5 mmHg · min · l (-1) in AA to 3.9 ± 0.5 mmHg · min · l (-1) in DE (P < 0.05) and the α coefficient decreased from 0.96 ± 0.15 to 0.64 ± 0.12%/mmHg (P < 0.01). DE did not further enhance the hypoxia-related upper shift of the mean pulmonary artery pressure-cardiac output relationship. Exposure to DE did not affect serum endothelin-1 concentration or fractional exhaled nitric oxide. In conclusion, acute exposure to DE increased pulmonary vasomotor tone by decreasing the distensibility of pulmonary resistive vessels at high cardiac output.

Topics: Air Pollutants; Cardiac Output, High; Cross-Over Studies; Echocardiography, Stress; Endothelin-1; Humans; Hypoxia; Male; Muscle, Smooth, Vascular; Nitric Oxide; Particulate Matter; Pulmonary Circulation; Rest; Vascular Resistance; Vasoconstriction; Vehicle Emissions; Ventricular Function, Left; Young Adult

Four hundred 1-d-old Cobb broilers were distributed in 3 groups: group A comprised broilers maintained under natural hypobaric hypoxia (Bogotá, Colombia); group B comprised broilers under relative normoxia (Villavicencio, Colombia); and group C comprised broilers maintained at 460 m above sea level (Villavicencio, Colombia) from d 1 to 25 of age, and then moved to 2,638 m above sea level (Bogotá, Colombia). Broilers were designated as nonpulmonary hypertensive (NPHB) and pulmonary hypertensive (PHB), to estimate possible differences between them in the lung expression of endothelin 1 (ET-1) mRNA at 24 and 42 d of age. In group A, 12 NPHB and 12 PHB were used for determination of ET-1 mRNA expression at 42 d. In group B, nonPHB were found, and therefore, ET-1 mRNA expression was detected in 48 NPHB, 24 of them in each age group (24 and 42 d). In group C, only NPHB were encountered at 42 and 53 d, and ET-1 mRNA expression was determined at 42 d in 24 birds. The ET-1 mRNA levels of PHB of group A at 42 d were significantly higher than the correspondent ones in NPHB of groups A (P < 0.001) and C (P < 0.05) at the same age. No differences in ET-1 mRNA expression were encountered between NPHB of groups A and B at 42 d (P > 0.05). However, ET-1 mRNA expression was higher in group C than the correspondent one in NPHB of groups A and B at 42 d (P < 0.001). The present data suggest that ET-1 may play a major role in pulmonary hypertension pathophysiology. It is possible that chickens should be exposed to hypobaric hypoxia before d 24, as a requisite to develop pulmonary hypertension. These results might provide clues for future studies in pulmonary vasoconstriction and vascular remodeling.

Topics: Aging; Altitude; Animals; Chickens; Endothelin-1; Gene Expression Regulation; Hypertension, Pulmonary; Hypoxia; Lung; Male; Poultry Diseases; RNA, Messenger

Hypoxic pulmonary vasoconstriction (HPV) helps match pulmonary perfusion to ventilation. The peptide endothelin-1 (ET-1) may be involved in the cellular mechanisms of this response. We hypothesized that increasing plasma ET-1 concentration during hypoxia would enhance HPV in humans and might represent a strategy for improving gas exchange during single-lung anaesthesia or respiratory disease.. Nine healthy volunteers were each exposed twice to a 7-h protocol consisting of 1 h breathing air, 4 h of eucapnic hypoxia (end-tidal Po(2), 50 mm Hg), and 2 h of eucapnic euoxia (end-tidal Po(2), 100 mm Hg). Volunteers received a 7-h i.v. infusion of ET-1 during one protocol (1.0-2.5 ng kg(-1) min(-1)) and normal saline during the other. At intervals of 30-60 min, cardiac output and the maximum tricuspid pressure gradient during systole (DeltaP(max), an index of HPV) were measured using Doppler echocardiography, systemic arterial pressure was measured using sphygmomanometry, and plasma samples were obtained to determine ET-1 concentration.. During hypoxia, DeltaP(max) increased for around 2 h before reaching a plateau. Compared with saline, ET-1 had no effect on DeltaP(max), either at baseline or during hypoxia. ET-1 infusion slightly increased diastolic arterial pressure and reduced cardiac output, but had no specific effect on the change in these variables during hypoxia. During the final 1 h of hypoxia, plasma ET-1 concentration was 1.7 (0.4) pg ml(-1) [mean (sd)] in the saline protocol and 21.9 (12.2) pg ml(-1) in the ET-1 protocol.. ET-1 infusion seems unlikely to represent a therapeutic strategy for enhancing HPV during acute (<4 h) hypoxia.

Topics: Adult; Blood Pressure; Carbon Dioxide; Cardiac Output; Echocardiography, Doppler; Endothelin-1; Female; Humans; Hypoxia; Male; Oxygen; Partial Pressure; Pulmonary Circulation; Vasoconstriction

We sought to determine the influence of sildenafil on the diffusing capacity of the lungs for carbon monoxide (DLCO) and the components of DLCO (pulmonary capillary blood volume VC, and alveolar-capillary membrane conductance DM) at rest and following exercise with normoxia and hypoxia. This double-blind placebo-controlled, cross-over study included 14 healthy subjects (age = 33 +/- 11 years, ht = 181 +/- 8 cm, weight = 85 +/- 14 kg, BMI = 26 +/- 3 kg/m2, peak normoxic VO2 = 36 +/- 6 ml/kg, mean +/- SD). Subjects were randomized to placebo or 100 mg sildenafil 1 h prior to entering a hypoxic tent with an FiO2 of 12.5% for 90 min. DLCO, VC, and DM were assessed at rest, every 3 min during exercise, at peak exercise, and 10 and 30 min post exercise. Sildenafil attenuated the elevation in PAP at rest and during recovery with exposure to hypoxia, but pulmonary arterial pressure immediately post exercise was not different between sildenafil and placebo. Systemic 02 saturation and VO2peak did not differ between the two conditions. DLCO was not different between groups at any time point. VC was higher with exercise in the placebo group, and the difference in DM between sildenafil and placebo was significant only when corrected for changes in VC (DM/VC = 0.57 +/- 0.29 vs. 0.41 +/- 0.16, P = 0.04). These results suggest no effect of sildenafil on DLCO, but an improvement in DM when corrected for changes in VC during short-term hypoxic exposure with exercise.

Topics: Acute Disease; Adult; Capillaries; Cross-Over Studies; Cyclic GMP; Double-Blind Method; Endothelin-1; Exercise; Female; Heart Rate; Humans; Hypoxia; Male; Natriuretic Peptide, Brain; Oxygen; Piperazines; Pulmonary Alveoli; Pulmonary Circulation; Pulmonary Gas Exchange; Purines; Rest; Sildenafil Citrate; Stroke Volume; Sulfones; Vasodilator Agents

The degree of pulmonary hypertension in healthy subjects exposed to acute hypobaric hypoxia at high altitude was found to be related to increased plasma endothelin (ET)-1. The aim of the present study was to investigate the effects of ET-1 antagonism on pulmonary hypertension, renal water, and sodium balance under acute and prolonged exposure to high-altitude-associated hypoxia.. In a double-blind fashion, healthy volunteers were randomly assigned to receive bosentan (62.5 mg for 1 day and 125 mg for the following 2 days; n=10) or placebo (n=10) at sea level and after rapid ascent to high altitude (4559 m). At sea level, bosentan did not induce any significant changes in hemodynamic or renal parameters. At altitude, bosentan induced a significant reduction of systolic pulmonary artery pressure (21+/-7 versus 31+/-7 mm Hg, P<0.03) and a mild increase in arterial oxygen saturation versus placebo after just 1 day of treatment. However, both urinary volume and free water clearance (H2OCl/glomerular filtration rate) were significantly reduced versus placebo after 2 days of ET-1 antagonism (1100+/-200 versus 1610+/-590 mL; -6.7+/-3.5 versus -1.8+/-4.8 mL/min, P<0.05 versus placebo for both). Sodium clearance and segmental tubular function were not significantly affected by bosentan administration.. The present results indicate that the early beneficial effect of ET-1 antagonism on pulmonary blood pressure is followed by an impairment in volume adaptation. These findings must be considered for the prevention and treatment of acute mountain sickness.

Topics: Acute Disease; Adaptation, Physiological; Adult; Altitude; Altitude Sickness; Arginine Vasopressin; Bosentan; Creatinine; Diuresis; Double-Blind Method; Endothelin Receptor Antagonists; Endothelin-1; Female; Glomerular Filtration Rate; Humans; Hypertension, Pulmonary; Hypoxia; Kidney; Kidney Diseases; Male; Middle Aged; Muscle, Smooth, Vascular; Osmolar Concentration; Oxygen; Potassium Channels, Voltage-Gated; Pulmonary Artery; Pulmonary Edema; Receptors, Endothelin; Sulfonamides; Vasoconstriction

High-altitude pulmonary edema (HAPE) is characterized by excessive pulmonary vasoconstriction and is associated with decreased concentrations of nitric oxide (NO) in the lung.. We hypothesized that individuals susceptible to HAPE (HAPE-S) would also have dysfunction of the vascular NO vasodilator pathway during hypoxia in the systemic vasculature.. During normoxia (FI(O(2)) = 0.21) and 4 hours of normobaric hypoxia (FI(O(2)) = 0.12, corresponding to an altitude of 4,500 m above sea level) endothelium-dependent and endothelium-independent vasodilator responses to intraarterial infusion of acetylcholine (ACh) and sodium nitroprusside, respectively, were measured by forearm venous occlusion plethysmography in nine HAPE-S subjects and in nine HAPE-resistant control subjects.. Pulmonary artery systolic pressure increased from 22 +/- 3 to 33 +/- 6 mm Hg (p < 0.001) during hypoxia in control subjects, and from 25 +/- 4 to 50 +/- 9 mm Hg in HAPE-S subjects (p < 0.001). Despite similar responses during normoxia in both groups, ACh-induced changes in forearm blood flow markedly decreased during hypoxia in HAPE-S subjects (p = 0.01) but not in control subjects. The attenuated vascular response to ACh infusion during hypoxia inversely correlated with increased pulmonary artery systolic pressure (p = 0.04) and decreased plasma nitrite correlated with attenuated ACh-induced vasodilation in HAPE-S subjects (p = 0.02).. Hypoxia markedly impairs vascular endothelial function in the systemic circulation in HAPE-S subjects due to a decreased bioavailability of NO. Impairment of the NO pathway could contribute to the enhanced hypoxic pulmonary vasoconstriction that is central to the pathogenesis of HAPE.

Topics: Acetylcholine; Adult; Altitude Sickness; Blood Pressure; Disease Susceptibility; Endothelin-1; Endothelium, Vascular; Female; Forearm; Hemodynamics; Humans; Hypoxia; Male; Middle Aged; Nitrates; Nitrites; Nitroprusside; Pulmonary Artery; Pulmonary Edema; Pulmonary Gas Exchange; Regional Blood Flow; Single-Blind Method; Vasodilation; Vasodilator Agents

Effects of hypobaric hypoxemia on endocrine and renal parameters of body fluid homeostasis were investigated in eight normal men during a sojourn of 8 days at an altitude of 4,559 m. Endocrine and renal responses to an osmotic stimulus (5% hypertonic saline, 3.6 ml/kg over 1 h) were investigated at sea level and on day 6 at altitude. Several days of hypobaric hypoxemia reduced body weight (-2.1 +/- 0.4 kg), increased plasma osmolality (+5.3 +/- 1.4 mosmol/kgH(2)O), elevated blood pressure (+12 +/- 1 mmHg), reduced creatinine clearance (122 +/- 6 to 96 +/- 10 ml/min), inhibited the renin system (19.5 +/- 2.0 to 10.9 +/- 0.9 mU/l) and plasma vasopressin (1.14 +/- 0.16 to 0.38 +/- 0.06 pg/ml), and doubled circulating levels of norepinephrine (103 +/- 16 to 191 +/- 35 pg/ml) and endothelin-1 (3.0 +/- 0.2 to 6.3 +/- 0.6 pg/ml), whereas urodilatin excretion rate decreased from day 2 (all changes P < 0.05 compared with sea level). Plasma arginine vasopressin response and the antidiuretic response to hypertonic saline loading were unchanged, but the natriuretic response was attenuated. In conclusion, chronic hypobaric hypoxemia 1) elevates the set point of plasma osmolality-to-plasma vasopressin relationship, possibly because of concurrent hypertension, thereby causing hypovolemia and hyperosmolality, and 2) blunts the natriuretic response to hypertonic volume expansion, possibly because of elevated circulating levels of norepinephrine and endothelin, reduced urodilatin synthesis, or attenuated inhibition of the renin system.

Topics: Adaptation, Physiological; Adult; Aldosterone; Altitude; Arginine Vasopressin; Atrial Natriuretic Factor; Blood Pressure; Body Weight; Creatinine; Endothelin-1; Epinephrine; Heart Rate; Humans; Hypertonic Solutions; Hypoxia; Infusions, Intravenous; Kidney; Kidney Function Tests; Male; Norepinephrine; Osmolar Concentration; Peptide Fragments; Renin; Sodium Chloride

We studied the contributions of hypoxemia, hypocapnia, and hyperpnea to the acute hypoxic diuretic response (HDR) in humans and evaluated the role of peripheral O(2) chemosensitivity and renal hormones in HDR. Thirteen healthy male subjects (age 19-38 yr) were examined after sodium equilibration (intake: 120 mmol/day) during 90 min of normoxia (NO), poikilocapnic hypoxia (PH), and isocapnic hypoxia (IH) (days 1-3, random order, double blind), as well as normoxic voluntary hyperpnea (HP; day 4), matching ventilation during IH. O(2) saturation during PH and IH was kept equal to a mean level measured between 30 and 90 min of breathing 12% O(2) in a pretest. Urine flow during PH and IH (1.81 +/- 0.92 and 1.94 +/- 1.03 ml/min, respectively) but not during HP (1.64 +/- 0.96 ml/min) significantly exceeded that during NO (control, 1.38 +/- 0.71 ml/min). Urine flow increases vs. each test day's baseline were significant with PH, IH, and HP. Differences in glomerular filtration rate, fractional sodium clearance, urodilatin, systemic blood pressure, or leg venous compliance were excluded as factors of HDR. However, slight increases in plasma and urinary endothelin-1 and epinephrine with PH and IH could play a role. In conclusion, the early HDR in humans is mainly due to hypoxia and hypocapnia. It occurs without natriuresis and is unrelated to O(2) chemosensitivity (hypoxic ventilatory response).

Topics: Adult; Atrial Natriuretic Factor; Blood Gas Analysis; Blood Pressure; Carbon Dioxide; Catecholamines; Diuresis; Double-Blind Method; Endothelin-1; Heart Rate; Hormones; Humans; Hyperventilation; Hypocapnia; Hypoxia; Kidney; Kidney Function Tests; Male; Natriuresis; Oxygen; Partial Pressure; Peptide Fragments; Pulmonary Ventilation; Sodium; Time Factors; Urodynamics

Multiple cancers have been reported to be associated with angiogenesis and are sensitive to anti-angiogenic therapies. Vascular normalization, by restoring proper tumor perfusion and oxygenation, could limit tumor cell invasiveness and improve the effectiveness of anticancer treatments. However, the underlying anticancer mechanisms of antiangiogenic drugs are still unknown. Metformin (MET) and simvastatin (SVA), two metabolic-related drugs, have been shown to play important roles in modulating the hypoxic tumor microenvironment and angiogenesis. Whether the combination of MET and SVA could exert a more effective antitumor effect than individual treatments has not been examined. The antitumor effect of the synergism of SVA and MET was detected in mouse models, breast cancer patient-derived organoids, and multiple tumor cell lines compared with untreated, SVA, or MET alone. RNA sequencing revealed that the combination of MET and SVA (but not MET or SVA alone) inhibited the expression of endothelin 1 (ET-1), an important regulator of angiogenesis and the hypoxia-related pathway. We demonstrate that the MET and SVA combination showed synergistic effects on inhibiting tumor cell proliferation, promoting apoptosis, alleviating hypoxia, decreasing angiogenesis, and increasing vessel normalization compared with the use of a single agent alone. The MET and SVA combination suppressed ET-1-induced hypoxia-inducible factor 1α expression by increasing prolyl hydroxylase 2 (PHD2) expression. Furthermore, the MET and SVA combination showed a more potent anticancer effect compared with bosentan. Together, our findings suggest the potential application of the MET and SVA combination in antitumor therapy.

Topics: Animals; Cell Line, Tumor; Endothelin-1; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Metformin; Mice; Neoplasms; Neovascularization, Pathologic; Simvastatin

Hypoxia and exosomes play important roles in the occurrence and development of glioma. While circRNAs are involved in biological processes of various tumors, the mechanism underlying exosome-dependent regulatory effects of circRNAs on the progression of glioma under hypoxia is unclear. Results suggested that circ101491 was overexpressed in tumor tissues and plasma exosomes of glioma patients, while the overexpression of circ101491 was closely related to the differentiation degree and TNM staging of the patients. Moreover, circ101491 overexpression promoted viability, invasion and migration of glioma cells both in vivo and in vitro; the above regulatory effects can be reversed by inhibition of circ101491 expression. Mechanistic studies revealed that circ101491 upregulated EDN1 expression through sponging miR-125b-5p, thus facilitating glioma progression. In summary, hypoxia could promote circ101491 overexpression in glioma cell-derived exosomes, and circ101491/miR-125b-5p/EDN1 regulatory axis might be implicated in the malignant progression of glioma.

Topics: Cell Line, Tumor; Cell Proliferation; Endothelin-1; Glioma; Humans; Hypoxia; MicroRNAs; RNA, Circular

Acute mountain sickness (AMS) is caused by rapid ascent to altitude (>2500 m) and remains a poorly understood pathophysiological condition. Accordingly, we investigated the relationship between acute exposure to high altitude and hypoxia related biochemical proteins. 21 healthy subjects (Female (8) and male (13), Age: 36.7±8.5, BMI: 23.2±3.1) volunteers participated in this project and fasting blood samples were taken before (sea level) and after 1 and 24-h exposure to high altitude (3,550 m). Blood oxygen saturation (SpO2), AMS status (Lake Louise Score) and serum HIF-1, Endothelin-1, VEGF and Orexin-A were measured (via ELISA) at 1, 6 and 24 h after exposure to high altitude. Pre-ascent measurement of hypoxia related proteins (Orexin-A, HIF-1, VEGF and Endothelin-1) where all significantly (<0.05) higher in the AMS-resistant individuals (No-AMS) when compared to AMS susceptible individuals (AMS+). Upon ascent to high altitude, 11 out of 21 volunteers had AMS (10.1±0.6 in AMS+ vs. 0.9±0.6 in No-AMS, P<0.05) and presented with lower resting SpO2 levels (77.7±0.4 vs. 83.5±0.3 respectively, p<0.05). Orexin-A, HIF-1, VEGF and Endothelin-1, significantly increased 24 hrs after exposure to high altitude in both AMS+ and No-AMS. The response of Orexin-A was similar between two groups, also, HIF-1 elevation 24 hrs after exposure to altitude was more in AMS+ (13% vs. 19%), but the increase of VEGF and Endothelin-1, 1 and 24 hrs after exposure to altitude in No-AMS was double that of AMS+. Hypoxia related proteins include Orexin-A, HIF-1, VEGF and Endothelin-1 may play a pathophysiological role in those who are susceptible to AMS.

Topics: Acute Disease; Adult; Altitude; Altitude Sickness; Endothelin-1; Female; Hormones; Humans; Hypoxia; Male; Middle Aged; Orexins; Vascular Endothelial Growth Factor A

Repeat exposures to low oxygen (intermittent hypoxia, IH), like that observed in sleep apnea, elicit increases in muscle sympathetic nerve activity (MSNA) and blood pressure (BP) in men. Endothelin (ET) receptor antagonists can attenuate the sympathetic and BP response to IH in rodents; whether these data translate to humans are unclear. We hypothesized that ET-receptor antagonism would ameliorate any rise in MSNA and BP following acute IH in humans. Twelve healthy men (31 ± 1 yr) completed two visits (control, bosentan) separated by at least 1 wk. MSNA, BP, and baroreflex sensitivity (modified Oxford) were assessed during normoxic rest before and following 30 min of IH. The midpoint (T50) for each individual's baroreflex curve was calculated. Acute IH increased plasma ET-1 (

Topics: Baroreflex; Blood Pressure; Bosentan; Endothelin-1; Endothelins; Heart Rate; Hemodynamics; Humans; Hypoxia; Male; Muscle, Skeletal; Oxygen; Receptor, Endothelin A; Sympathetic Nervous System

Topics: Altitude; Altitude Sickness; Case-Control Studies; Endothelin-1; Humans; Hypoxia; Vasoconstrictor Agents

A double-hit biological alteration involving exposure to oxygen deprivation in hypothyroid condition may exacerbate cellular oxidative and inflammatory disturbances comparative to a one-hit biological exposure. This study investigated the therapeutic effect of Ginkgo biloba as cardioprotective against aortic oxido-inflammatory disturbances following oxygen deprivation in hypothyroid mice. Male Swiss mice were partitioned into 5 groups (n = 6) for hypothyroidism (Carbimazole 1.2 mg/kg) and hypoxia induction. Group 1 (normal control), group 2 (hypoxic stress control), group 3 (hypoxic and hypothyroid stress), group 4 (hypoxic and hypothyroid stress and Ginkgo biloba 20 mg/kg; p.o) and group 5 (hypoxic and hypothyroid stress and Levothyroxine 10 μg/kg; p.o) for 14 days. Thereafter, serum and aorta was collected for biochemical evaluation. GBS did not up-regulate the serum thyroid hormone imbalances (tri-iodothyronine (T3), thyroxin (T4)) but maintains the TSH levels. The blood glucose level was reduced with decrease oxidative stress and inflammatory mediators in the serum/aorta indicated by inhibited redox status following treatment with GBS. Moreover, endothelin-1/nitric oxide signaling pathways were markedly regulated in the aorta. Conclusively, GBS acts as a therapeutic agent and may be consider as a potential vasodilator candidate in the management and control of hypoxic stress in hypothyroid condition. PRACTICAL APPLICATIONS: Treatment with Gingko biloba supplement abated endothelial abnormalities via elevation of nitric oxide release and suppression of endothelin activity in hypothyroid mice exposed to hypoxic hypoxia. The activity of myeloperoxidase enzyme and redo-inflammatory status was downregulated following treatment with Gingko biloba supplement in hypothyroid mice exposed to hypoxic hypoxia. Treatment with Gingko biloba supplement modulates hypothalamic-pituitary-adrenal (HPA) axis by inhibiting corticosterone release in hypothyroid mice exposed to hypoxic hypoxia.

Topics: Animals; Endothelin-1; Ginkgo biloba; Hypothyroidism; Hypoxia; Inflammation; Male; Mice; Nitric Oxide; Oxidation-Reduction; Oxidative Stress; Oxygen

Hypoxia is the reduction of alveolar partial pressure of oxygen ([Formula: see text]). Military members and people who practice recreational activities from moderate to high altitudes are at risk for hypoxic exposure. Hypoxemia's signs and symptoms vary from asymptomatic to severe responses, such as excessive hypoxic ventilatory responses and residual neurobehavioral impairment. Therefore, it is essential to identify hypoxia-induced biomarkers to indicate people with exposure to hypoxia. Advances have been made in understanding physiological responses to hypoxia, including elevations in circulating levels of endothelin 1 (ET-1) and microRNA 21 (miR-21) and reduction in circulating levels of hydrogen sulfide (H

Topics: Animals; Biomarkers; Endothelin-1; Hydrogen Sulfide; Hypoxia; Male; MicroRNAs; Oxygen; Rats

Intermittent hypoxia (IH), a main characteristic of obstructive sleep apnea (OSA) syndrome, has been known as a dominant cause of OSA-related endothelial dysfunction and hypertension. However, the underlying mechanism still remains unclear. Extracellular vesicles (EVs), small vesicles secreted by various cells, can be absorbed by endothelial cells and then influence vascular function. The aim of this research is to clarify whether and how EVs shedding from red blood cells (RBCs) are involved in IH-induced endothelial dysfunction.. EVs were extracted by ultracentrifugation. After the identification of property and purity, EVs from IH-exposed RBCs (IH REVs) and normoxia-exposed RBCs (NOR REVs) or from OSA and non-OSA patient RBCs were utilized to treat C57BL/6 mouse aortas or human umbilical vein endothelial cells (HUVECs) for mechanistic exploration.. Functional results demonstrated that REVs from OSA patients dramatically impaired endothelium-dependent relaxations (EDRs). Similarly, in vivo and ex vivo studies showed that IH REVs caused significant endothelial dysfunction compared to control group. Further results presented that IH REVs blocked endothelial nitric oxide synthase (eNOS) phosphorylation through inhibiting PI3K/Akt pathway and enhanced endothelin-1 (ET-1) expression through activating Erk1/2 pathway in endothelial cells. Meanwhile, endothelial dysfunction caused by IH REVs was reversed by Akt activator SC79 as well as Erk kinase inhibitor PD98059, suggesting that PI3K/Akt/eNOS and Erk1/2/ET-1 pathways were implicated in IH REV-induced impaired EDRs.. This study reveals a novel role of REVs in endothelial dysfunction under IH and dissects the relevant mechanism involved in this process, which will help to establish a comprehensive understanding of OSA or IH-related endothelial dysfunction from a new scope.

Topics: Animals; Aorta; Endothelin-1; Erythrocytes; Extracellular Vesicles; Human Umbilical Vein Endothelial Cells; Humans; Hypoxia; Male; Mice; Mice, Inbred C57BL; Nitric Oxide Synthase Type III; Phosphorylation

Pulmonary hypertension (PH) causes cardiac hypertrophy in the right ventricle (RV) and eventually leads to RV failure due to persistently elevated ventricular afterload. We hypothesized that the mechanical stress on the RV associated with increased afterload impairs vasodilator function of the right coronary artery (RCA) in PH. Coronary vascular response was assessed using microangiography with synchrotron radiation (SR) in two well-established PH rat models, monocrotaline injection or the combined exposure to chronic hypoxia and vascular endothelial growth factor receptor blockade with Su5416 (SuHx model). In the SuHx model, the effect of the treatment with the nonselective endothelin-1 receptor antagonist (ERA), macitentan, was also examined. Myocardial viability was determined in SuHx model rats, using

Topics: Animals; Antihypertensive Agents; Coronary Angiography; Coronary Vessels; Disease Models, Animal; Endothelin Receptor Antagonists; Endothelin-1; Hypertrophy, Right Ventricular; Hypoxia; Indoles; Monocrotaline; Predictive Value of Tests; Pulmonary Arterial Hypertension; Pyrimidines; Pyrroles; Rats, Sprague-Dawley; Severity of Illness Index; Sulfonamides; Synchrotrons; Vasodilation; Ventricular Dysfunction, Right; Ventricular Function, Right; Ventricular Remodeling

Injury/dysfunction of the endothelium of pulmonary arteries contributes to hypoxia-induced pulmonary hypertension (HPH). We investigated whether C1q/tumor necrosis factor-related protein-9 (CTRP9), a newly identified cardiovascular agent, has protective roles in the development of HPH. HPH was induced in adult male rats by chronic hypobaric hypoxia. CTRP9 overexpression by adeno-associated virus (AAV)-CTRP9 transfection attenuated the increases in right ventricular systolic pressure, right ventricular hypertrophy index, and pulmonary arterial remodeling of rats under hypoxia. Importantly, CTRP9 overexpression improved endothelium-dependent vasodilation in pulmonary arterioles in HPH rats. CTRP9 overexpression enhanced expression of phosphorylated 5'-adenosine monophosphate-activated protein kinase (p-AMPK) and phosphorylated endothelial nitric oxide synthase (p-eNOS), and reduced phosphorylated extracellular signal-regulated protein kinase (p-ERK1/2) expression in pulmonary microvascular endothelial cells (PMVECs) of HPH rats. In cultured PMVECs, CTRP9 not only preserved the decrease of AMPK and eNOS phosphorylation level and nitric oxide (NO) production induced by hypoxia, but also blocked the increase in hypoxia-induced ERK1/2 phosphorylation level and endothelin (ET)-1 production. Furthermore, the effects of CTRP9 were interrupted by inhibitors or knockdown of AMPK. CTRP9 enhances NO production and reduces ET-1 production by regulating AMPK activation. CTRP9 could be a target for HPH.

Topics: Adenylate Kinase; Adiponectin; Animals; Cells, Cultured; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Male; MAP Kinase Signaling System; Nitric Oxide; Nitric Oxide Synthase Type III; Phosphorylation; Rats

Hypertension induced by hypoxia at high altitude is one of the typical symptoms of high-altitude reactions (HARs). Emerging evidence indicates that endothelial abnormalities, including increases in angiotensin-2 (Ang-2) and endothelin-1 (ET-1), are closely associated with hypertension. Thus, low blood oxygen-induced endothelial dysfunction through acceleration of Ang-2 and ET-1 synthesis may alleviate HARs. In this study, we investigated the effects of hypoxia on rat blood pressure (BP) and endothelial injury. We found that BP increased by 10 mmHg after treatment with 10% O

Topics: Angiotensin II; Animals; Endothelial Cells; Endothelin-1; Hypertension; Hypoxia; Nuclear Respiratory Factor 1; Peptidyl-Dipeptidase A; Rats; Testosterone

The environmental hypoxia of high altitude (HA) increases the incidence of intrauterine growth restriction (IUGR) approximately threefold. The peroxisome proliferator-activated receptor γ (PPAR-γ), a ligand-activated nuclear receptor that promotes vasorelaxation by increasing nitric oxide and downregulating endothelin-1 (ET-1) production, has been implicated in IUGR. Based on our prior work indicating that pharmacologic activation of the PPARγ pathway protects against hypoxia-associated IUGR, we used an experimental murine model to determine whether such effects may be attributed to vasodilatory effects in the uteroplacental circulation. Using wire myography, ex vivo vasoreactivity studies were conducted in uterine arteries (UtA) isolated from pregnant mice exposed to hypoxia or normoxia from gestational day 14.5 to 18.5. Exposure to troglitazone, a high-affinity PPARγ agonist-induced vasorelaxation in UtA preconstricted with phenylephrine, with HA-UtA showing increased sensitivity. Troglitazone blunted ET-1-induced contraction of UtA in hypoxic and normoxic dams equivalently. Immunohistological analysis revealed enhanced staining for ET-1 receptors in the placental labyrinthine zone in hypoxic compared to normoxic dams. Our results suggest that pharmacologic PPAR-γ activation, via its vasoactive properties, may protect the fetal growth under hypoxic conditions by improving uteroplacental perfusion and thereby justify further investigation into PPARγ as a therapeutic target for IUGR in pregnancies complicated by hypoxia.

Topics: Animals; Disease Models, Animal; Endothelin-1; Female; Fetal Growth Retardation; Hypoxia; Immunohistochemistry; Mice; Phenylephrine; Placenta; PPAR gamma; Pregnancy; Thiazolidinediones; Troglitazone; Uterine Artery

Endothelin-1 (ET-1) is a potent stimulus for the secretion of atrial natriuretic peptide (ANP) and hypoxia stimulates the release of ET-1, which is involved in the regulation of atrial ANP secretion. However, the precise mechanism of endogenous ET-1 in the regulation of hypoxia-induced ANP secretion is unclear. Therefore, this study aimed to investigate the mechanism of hypoxia-induced endogenous ET-1 regulation of ANP secretion in isolated perfused hypoxic beating rat atria. The results of this study showed that acute hypoxia significantly stimulated ET-1 release and upregulated the expression of its type A as well as type B receptors (ETA and ETB receptors). Endogenous ET-1 induced by hypoxia markedly upregulated the expression of cyclooxygenase 2 (COX2) through activation of its two receptors, leading to an increase in lipocalin-type prostaglandin D synthase (L-PGDS) expression and prostaglandin D2 (PGD2) production. L-PGDS-derived PGD2 activated peroxisome proliferator-activated receptor γ (PPARγ), ultimately promoting hypoxia-induced ANP secretion. Conversely, L-PGDS-derived PGD2 may in turn regulate L-PGDS expression by a nuclear factor erythroid-2-related factor 2 (NRF2)-mediated feedback mechanism. These results indicate that endogenous ET-1 induced by hypoxia promotes hypoxia-induced ANP secretion by activation of COX2-L-PGDS-PPARγ signaling in beating rat atria. In addition, the positive feedback loop between L-PGDS-derived PGD2 and L-PGDS expression induced by hypoxia is part of the mechanism of hypoxia-induced ANP secretion by endogenous ET-1.

Topics: Animals; Atrial Natriuretic Factor; Cyclooxygenase 2; Endothelin-1; Gene Expression Regulation; Heart Atria; Hypoxia; Intramolecular Oxidoreductases; Isolated Heart Preparation; Lipocalins; NF-E2-Related Factor 2; PPAR gamma; Prostaglandin D2; Rats; Signal Transduction

The aim of the present investigation was to study the effect of hypoxia on the expression of genes encoding endothelin-1 (EDN1) and its cognate receptors (EDNRA and EDNRB) as well as endothelin converting enzyme 1 (ECE1) in U87 glioma cells in response to inhibition of endoplasmic reticulum stress signaling mediated by ERN1/IRE1 (endoplasmic reticulum to nucleus signaling 1) for evaluation of their possible significance in the control of glioma growth through ERN1 and hypoxia.. The expression level of EDN1, EDNRA, EDNRB, and ECE1 genes as well as micro-RNA miR-19, miR-96, and miR-206 was studied in control and ERN1 knockdown U87 glioma cells under hypoxia by quantitative polymerase chain reaction.. It was shown that the expression level of EDN1, EDNRA, EDNRB, and ECE1 genes was up-regulated in ERN1 knockdown glioma cells in comparison with the control glioma cells, being more significant for endothelin-1. We also observed down-regulation of microRNA miR-206, miR-96, and miR-19a, which have specific binding sites in mRNA EDN1, EDNRA, and EDNRB, correspondingly, and can participate in posttranscriptional regulation of these mRNA expressions. Furthermore, inhibition of ERN1 endoribonuclease lead to up-regulation of EDNRA and ECE1 gene expressions and down-regulation of the expression level of EDN1 and EDNRB genes in glioma cells. Thus, the expression of EDNRA and ECE1 genes is regulated by ERN1 endoribonuclease, but EDN1 and EDNRB genes preferentially by ERN1 protein kinase. We have also shown that hypoxia enhanced the expression of EDN1, EDNRA, and ECE1 genes and that knockdown of ERN1 signaling enzyme function significantly modified the response of all studied gene expressions to hypoxia. Thus, effect of hypoxia on the expression level of EDN1 and ECE1 genes was significantly or completely reduced in ERN1 knockdown glioma cells since the expression of EDNRA gene was down-regulated under hypoxia. Moreover, hypoxia is induced the expression of EDNRB gene in ERN1 knockdown glioma cells.. Results of this investigation demonstrate that ERN1 knockdown significantly increased the expression of endothelin-1 and its receptors as well as ECE1 genes by different mechanisms and that all studied gene expressions were sensitive to hypoxia. It is possible that hypoxic regulation of the expression of these genes is a result of complex interaction of variable ERN1 related transcription and regulatory factors with HIF1A and possibly contributed to the control of glioma growth.

Topics: Brain Neoplasms; Cell Hypoxia; Cell Line, Tumor; Endoribonucleases; Endothelin-1; Endothelin-Converting Enzymes; Gene Expression Regulation, Neoplastic; Gene Knockdown Techniques; Glioma; Humans; Hypoxia; Protein Serine-Threonine Kinases; Receptor, Endothelin A; Receptor, Endothelin B; Tumor Hypoxia

Endothelin-1 (ET-1), as it functions as a neuromodulator, has been associated with hypertension in chronic intermittent hypoxia (CIH) which attribute to enhanced carotid body sensibility to hypoxia. However, the molecular mechanism of ET-1 on carotid body sensibility in CIH is still not clear. Here, effect of ET-1 on carotid body chemosensory stimulation in rats exposed to either CIH or room air (Normoxia) was explored. Furthermore, Phospholipase C (PLC), Protein kinase C (PKC) or p38 MAPK antagonists were adopted to clarify the signalling pathways involved. Results showed that ET-1 induced a higher increase of carotid sinus nerve activity (CSNA) in animals exposed to CIH. Both ETA and ETB receptor expression were up-regulated by CIH exposure, but only ETA is responsible for ET-1 induced CSNA increase. Additional, the increase was inhibited by PLC, PKC, p38 MAPK antagonists and calcium channel blocker. Our findings support that ETA receptor mediates ET-1-induced CSNA increase through PLC, PKC and p38 MAPK signalling pathways in chronic intermittent hypoxia. Also, our study indicated that calcium influx was necessary for enhancing effect of ET-1 on CSNA.

Topics: Animals; Carotid Arteries; Carotid Body; Endothelin-1; Hypoxia; Intracellular Signaling Peptides and Proteins; Male; p38 Mitogen-Activated Protein Kinases; Protein Kinase C; Rats, Sprague-Dawley; Receptors, Endothelin; Signal Transduction; Type C Phospholipases

Topics: Amides; Animals; Apoptosis; Blood Pressure; Carotid Body; Disease Models, Animal; Endothelin-1; Enzyme Inhibitors; Hypertension; Hypoxia; Male; NADPH Oxidases; Neuronal Plasticity; Onium Compounds; Oxidative Stress; Paraventricular Hypothalamic Nucleus; Pyridines; Rats; Rats, Sprague-Dawley; Receptor, Serotonin, 5-HT2A; rho-Associated Kinases; Signal Transduction

Sustained chronic hypoxia (CH) produces morphological and functional changes in the carotid body (CB). Nitric oxide (NO) and endothelin-1 (ET-1) play a major role as modulators of the CB oxygen chemosensory process. To characterize the effects of CH related to normoxia (Nx) on gene expression, particularly on ET-1 and NO pathways, primary cultures of rat CB cells were exposed to 7 days of CH. Total RNA was extracted, and cDNA-

Topics: Animals; Carotid Body; Down-Regulation; Endothelin-1; Gene Expression; Hypoxia; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Protein Isoforms; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Signal Transduction; Up-Regulation

Cerebral blood flow is reduced early in the onset of Alzheimer's disease (AD). Because most of the vascular resistance within the brain is in capillaries, this could reflect dysfunction of contractile pericytes on capillary walls. We used live and rapidly fixed biopsied human tissue to establish disease relevance, and rodent experiments to define mechanism. We found that in humans with cognitive decline, amyloid β (Aβ) constricts brain capillaries at pericyte locations. This was caused by Aβ generating reactive oxygen species, which evoked the release of endothelin-1 (ET) that activated pericyte ET

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Biopsy; Capillaries; Cerebral Cortex; Cerebrovascular Circulation; Constriction, Pathologic; Endothelin-1; Humans; Hypoxia; Mice; Pericytes; Protein Multimerization; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Receptor, Endothelin A; Signal Transduction; Vascular Resistance

What is the central question of this study? The central goal of this study was to elucidate the role of magnesium in the regulation of pulmonary vascular reactivity in relationship to hypoxic pulmonary hypertension. What is the main finding and its importance? We found that magnesium is essential for normal vasoreactivity of the pulmonary artery. Increasing the magnesium concentration attenuates vasoconstriction and improves vasodilatation via release of nitric oxide. Pulmonary hypertension is associated with endothelial dysfunction resulting in the suppression of magnesium modulation of vasodilatation. These results provide evidence that magnesium is important for the modulation of pulmonary vascular function.. Pulmonary hypertension (PH) is characterized by enhanced vasoreactivity and sustained pulmonary vasoconstriction, arising from aberrant Ca

Topics: Animals; Endothelin-1; Endothelium, Vascular; Hypertension, Pulmonary; Hypoxia; Magnesium; Male; Mice; Mice, Inbred ICR; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Nitric Oxide; Pulmonary Artery; Vasoconstriction; Vasoconstrictor Agents; Vasodilation; Vasodilator Agents

Chronic hypoxia (CH) augments basal and endothelin-1 (ET-1)-induced pulmonary vasoconstrictor reactivity through reactive oxygen species (ROS) generation and RhoA/Rho kinase (ROCK)-dependent myofilament Ca

Topics: Actin Cytoskeleton; Actin Depolymerizing Factors; Actins; Animals; Chronic Disease; Disease Models, Animal; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Male; Oxidative Stress; Phosphorylation; Polymerization; Pulmonary Artery; Rats, Sprague-Dawley; rho GTP-Binding Proteins; rho-Associated Kinases; Vascular Remodeling; Vasoconstriction; Vasoconstrictor Agents

Endothelial dysfunction is one of the main pathological changes in Obstructive sleep apnoea (OSA). The Rho kinase (ROCK) pathway is associated with endothelial dysfunction. However, the interaction between ROCK and nuclear factor of activated T cells isoform c3 (NFATc3) in the development of this pathological response under chronic intermittent hypoxia (CIH) is unclear. To simulate the OSA model, we established a moderate CIH rat model by administering the fraction of inspired O2 (FiO2) from 21% to 9%, 20 times/h, 8 h/day for 3 weeks. Fasudil (ROCK inhibitor, 8 mg/kg/d, i.p.) was administrated in the rats exposed to CIH for 3 weeks. Our results demonstrated that CIH caused significantly endothelial dysfunction, accompanying with increased ET-1 level, decreased eNOS expression and NO production, which reduced ACh-induced vascular relaxation responses. Moreover, RhoA/ROCK-2/NFATc3 expressions were up-regulated. Fasudil significantly improved CIH induced endothelial dysfunction. Data suggested that the ROCK activation is necessary for endothelial dysfunction during CIH.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Animals; Aorta; Endothelin-1; Endothelium, Vascular; Hypoxia; Male; NFATC Transcription Factors; Nitric Oxide; Rats; Rats, Sprague-Dawley; rho-Associated Kinases; rhoA GTP-Binding Protein; Signal Transduction; Time Factors

Topics: Animals; Astrocytes; Behavior, Animal; Endothelin-1; Glucose Transporter Type 1; Hindlimb Suspension; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Infarction, Middle Cerebral Artery; Male; Neurons; Neuroprotection; Psychomotor Performance; Rats; Rats, Sprague-Dawley; Recognition, Psychology; Stroke

The purpose of this study is to investigate the effect of the oral endothelin antagonist Bosentan on blood pressure and renal sympathetic nerve activity (RSNA) in rats exposed to chronic intermittent hypoxia (CIH), and to explore the sympathoexcitation mechanism of endothelin-1 (ET-1) in CIH-induced hypertension. Twenty-four male SD rats were randomly divided into normoxia, CIH and Bosentan groups. Rats in the normoxia group were exposed to normoxic environment, and rats in CIH or Bosentan group were exposed to intermittent hypoxia for 3 weeks. Bosentan was given at 50 mg/kg by intragastric administration before intermittent hypoxia exposure in Bosentan group. Systolic blood pressure (SBP) was measured by BP-2000, and the change of RSNA to sodium nitroprusside (SNP) or phenylephrine (PE) was recorded by PowerLab signal acquisition system. Serums of all rats were collected and the contents of ET-1 and norepinephrine (NE) were measured by ELISA. Results showed that blood pressure was gradually increased following CIH exposure compared with the normoxia group during the 3 weeks (P < 0.01, P < 0.01, P < 0.001). The basal RSNA was increased and baroreflex sensitivity was decreased in rats exposed to CIH. Furthermore, the blood pressure was positively correlated with the level of ET-1 in serum in rats exposed to CIH (r = 0.833, P = 0.01). Bosentan administration significantly decreased SBP and basal RSNA, increased the baroreflex sensitivity, and decreased serum NE level in rats exposed to CIH. These results suggest that ET-1 is related with blood pressure elevation in rats exposed to CIH, and Bosentan reverses CIH-induced hypertension by decreasing RSNA.

Topics: Animals; Baroreflex; Blood Pressure; Bosentan; Endothelin-1; Hypertension; Hypoxia; Kidney; Male; Nitroprusside; Phenylephrine; Rats; Rats, Sprague-Dawley; Sympathetic Nervous System

Cerebral palsy is an irreversible movement disorder resulting from cerebral damage sustained during prenatal or neonatal brain development. As survival outcomes for preterm injury improve, there is increasing need to model ischemic injury at earlier neonatal time-points to better understand the subsequent pathological consequences. Here we demonstrate a novel neonatal ischemic model using focal administration of the potent vasoconstrictor peptide, endothelin-1 (ET-1), in newborn rats. The functional and histopathological outcomes compare favourably to those reported following the widely used hypoxic ischemia (HI) model. These include a robust motor deficit sustained into adulthood and recapitulation of hallmark features of preterm human brain injury, including atrophy of subcortical white matter and periventricular fiber bundles. Compared to procedures involving carotid artery manipulation and periods of hypoxia, the ET-1 ischemia model represents a rapid and technically simplified model more amenable to larger cohorts and with the potential to direct the locus of ischemic damage to specific brain areas.

Topics: Animals; Animals, Newborn; Brain; Brain Injuries; Disease Models, Animal; Endothelin-1; Female; Hypoxia; Hypoxia-Ischemia, Brain; Pregnancy; Rats

Obstructive sleep apnea recently has been associated with a higher frequency of ischemic optic neuropathies. Intermittent hypoxia (IH) has been proposed as a major component of obstructive sleep apnea cardiovascular consequences. However, there currently are no pathophysiologic data regarding the effect of IH on the ocular vascular system. Thus, we assessed the impact of chronic IH exposure on the morphology and vascular reactivity of the rat ophthalmic artery (OA).. Rats were exposed to 14 days of IH or normoxia (NX). Ophthalmic artery reactivity was studied using wire myography in rats treated or not with tempol (1 mM/day). Expression of endothelin-1 (ET-1) and its receptors, and of the three nitric oxide synthase (NOS) isoform genes was quantified using quantitative polymerase chain reaction (qPCR) in the retina and optic nerve. Structural alterations (optical and electron microscopy) and superoxide anion production were studied in OA sections.. Superoxide ion expression in the OA wall was increased by 23% after IH exposure. Ophthalmic artery contractile response to 3.10-8 M ET-1 was increased by 18.6% and nitric oxide-mediated relaxation was significantly delayed in IH compared to NX rats. In the absence of nitric oxide, cytochrome P450 blockade increased relaxation to acetylcholine in IH rats and delayed it in NX rats. Tempol treatment abolished the IH-induced changes in OA reactivity.. These results strongly suggest that chronic IH induces oxidative stress in the rat OA, associated with endothelial dysfunction through alterations of nitric oxide and endothelium-derived hyperpolarising factors (EDHF) pathways.

Topics: Animals; Chronic Disease; Cyclic N-Oxides; Endothelin-1; Hypoxia; Male; Muscle, Smooth, Vascular; Myography; Nitric Oxide Synthase; Ophthalmic Artery; Oxidative Stress; Protein Synthesis Inhibitors; Rats; Rats, Wistar; Real-Time Polymerase Chain Reaction; Receptor, Endothelin A; RNA, Messenger; Spin Labels; Superoxides

Pheochromocytomas (PHEOs) and paragangliomas (PGLs) are rare, neuroendocrine tumors derived from adrenal or extra-adrenal chromaffin cells, respectively. Metastases are discovered in 3-36% of patients at the time of diagnosis. Currently, only suboptimal treatment options exist. Therefore, new therapeutic compounds targeting metastatic PHEOs/PGLs are urgently needed. Here, we investigated if anthracyclines were able to suppress the progression of metastatic PHEO. We explored their effects on experimental mouse PHEO tumor cells using in vitro and in vivo models, and demonstrated that anthracyclines, particularly idarubicin (IDA), suppressed hypoxia signaling by preventing the binding of hypoxia-inducible factor 1 and 2 (HIF-1 and HIF-2) to the hypoxia response element (HRE) sites on DNA. This resulted in reduced transcriptional activation of HIF target genes, including erythropoietin (EPO), phosphoglycerate kinase 1 (PGK1), endothelin 1 (EDN1), glucose transporter 1 (GLUT1), lactate dehydrogenase A (LDHA), and vascular endothelial growth factor (VEGFA), which consequently inhibited the growth of metastatic PHEO. Additionally, IDA downregulated hypoxia signaling by interfering with the transcriptional activation of HIF1A and HIF2A. Furthermore, our animal model demonstrated the dose-dependent suppressive effect of IDA on metastatic PHEO growth in vivo. Our results indicate that anthracyclines are prospective candidates for inclusion in metastatic PHEO/PGL therapy, especially in patients with gene mutations involved in the hypoxia signaling pathway.

Topics: Adrenal Gland Neoplasms; Animals; Antineoplastic Agents; Basic Helix-Loop-Helix Transcription Factors; Cell Growth Processes; Cell Line, Tumor; Endothelin-1; Erythropoietin; Humans; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Idarubicin; Mice; Mice, Nude; Neoplasm Metastasis; Pheochromocytoma; Phosphoglycerate Kinase; Protein Binding; Signal Transduction; Xenograft Model Antitumor Assays

Evidence points to activation of pro-inflammatory and pro-thrombotic stimuli during the haemodialysis process in end-stage renal disease (ESRD) with potential to predispose to cardiovascular events. Diabetes is associated with a higher incidence of cardiovascular disease in haemodialysis patients. We tested the hypothesis that a range of mediators and markers that modulate cardiovascular risk are elevated in haemodialysis patients with diabetes compared to those without.. Men and women with diabetes (n = 6) and without diabetes (n = 6) aged 18-90 years receiving haemodialysis were recruited. Blood samples were collected and analysed pre- and post-haemodialysis sessions for (platelet-monocyte conjugates (PMC), oxidised LDL (Ox-LDL), endothelin 1 (ET-1) and vascular endothelial growth factor (VEGF-A).. PMC levels significantly increased after haemodialysis in both groups (diabetes p = 0.047; non-diabetes p = 0.005). Baseline VEGF-A was significantly higher in people with diabetes (p = 0.009) and post-dialysis levels were significantly reduced in both groups (P = 0.002). Ox-LDL and CRP concentrations were not significantly different between groups nor affected in either group post-dialysis. Similarly, ET-1 concentrations were comparable in all patients at baseline, with no change post-dialysis in either group.. In this pilot study, we have confirmed that circulating PMCs are increased following dialysis irrespective of diabetes status. This is likely to be a mechanistic process and offers a potential explanation for high rates of vascular events associated with haemodialysis. The higher VEGF-A concentrations between patients with and without diabetes is a previously unreported finding in diabetic ESRD. Further research is merited to establish whether VEGF-A is a marker or mediator (or both) of cardiovascular risk in haemodialysis.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Biomarkers; Cardiovascular Diseases; Cholesterol, LDL; Diabetes Complications; Endothelin-1; Female; Humans; Hypoxia; Kidney Failure, Chronic; Male; Middle Aged; Pilot Projects; Renal Dialysis; Risk; Vascular Endothelial Growth Factor A; Young Adult

In utero hypoxia influences the structure and function of most fetal arteries, including those of the developing cerebral circulation. Whereas the signals that initiate this hypoxic remodeling remain uncertain, these appear to be distinct from the mechanisms that maintain the remodeled vascular state. The present study explores the hypothesis that chronic hypoxia elicits sustained changes in fetal cerebrovascular reactivity to endothelin-1 (ET-1), a potent vascular contractant and mitogen. In fetal lambs, chronic hypoxia (3,820-m altitude for the last 110 days of gestation) had no significant effect on plasma ET-1 levels or ETA receptor density in cerebral arteries but enhanced contractile responses to ET-1 in an ETA-dependent manner. In organ culture (24 h), 10 nM ET-1 increased medial thicknesses less in hypoxic than in normoxic arteries, and these increases were ablated by inhibition of PKC (chelerythrine) in both normoxic and hypoxic arteries but were attenuated by inhibition of CaMKII (KN93) and p38 (SB203580) in normoxic but not hypoxic arteries. As indicated by Ki-67 immunostaining, ET-1 increased medial thicknesses via hypertrophy. Measurements of colocalization between MLCK and SMαA revealed that organ culture with ET-1 also promoted contractile dedifferentiation in normoxic, but not hypoxic, arteries through mechanisms attenuated by inhibitors of PKC, CaMKII, and p38. These results support the hypothesis that chronic hypoxia elicits sustained changes in fetal cerebrovascular reactivity to ET-1 through pathways dependent upon PKC, CaMKII, and p38 that cause increased ET-1-mediated contractility, decreased ET-1-mediated smooth muscle hypertrophy, and a depressed ability of ET-1 to promote contractile dedifferentiation.

Topics: Animals; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Cell Differentiation; Cerebral Arteries; Endothelin-1; Female; Fetus; Hypoxia; Muscle Contraction; Organ Culture Techniques; p38 Mitogen-Activated Protein Kinases; Pregnancy; Protein Kinase C; Sheep; Vascular Remodeling; Vasoconstriction

Tanshinone IIA (Tan IIA) may exert significant protective effects against heart oxidative stress damage in obstructive sleep apnoea (OSA) syndrome. Chronic intermittent hypoxia (CIH)-triggered left ventricular dysfunction is used in a rat model to mimic CIH in OSA patients. 48 rats were randomly divided into three groups: normal control (NC) group, CIH group and CIH+Tan IIA group with 16 rats in each group. At the end of experiment (day 21), the blood pressure, Plasma ET-1 and NO content, hemodynamic indexes, heart histology, myocardial apoptosis as well as the expression of eNOS, ET-1, ET

Topics: Abietanes; Animals; Apoptosis; Blood Pressure; Cardiotonic Agents; Chronic Disease; Electrocardiography; Endothelin-1; Heart Function Tests; Hemodynamics; Hypoxia; Male; Myocardium; Myocytes, Cardiac; Nitric Oxide; Nitric Oxide Synthase Type III; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptor, Endothelin B; Signal Transduction; Systole

To investigate the role of hypoxia-inducible factor-1α and its target genes in hypoxic pulmonary hypertension in neonates.. A total of 117 newborns were selected and divided into two groups for clinical experiments: 85 cases in the hypoxic pulmonary hypertension (HPH) group, including mild, moderate and severe subgroups, and 32 cases in the case-control group. ELISA was used to detect the serum HIF-1α, endothelin-1 (ET-1) and adrenomedullin (ADM) levels, and echocardiography was used to detect the dynamic changes in pulmonary artery systolic pressure (PASP), right ventricular ejection fraction (RVEF), tricuspid E peak and A peak ratio (E/A) and right ventricular Tei index.. The average PASP level of the HPH group was significantly higher than that of the control group at 1 d and 3 d after birth (p < 0.05). The average PASP level was still higher in the severe HPH group than that in the control group at 7 d after birth, while the average levels in the mild and moderate HPH groups recovered to the normal. Compared with those in control group, RVEF and E/A of the tricuspid valve were decreased significantly in severe HPH patients (p < 0.05). The Tei indexes of the right ventricle were significantly higher in the mild, moderate and severe HPH groups than those in control group and the right ventricular Tei index was positively correlated with PASP. The levels of serum ADM, HHH-1α and ET-1 in all the three HPH subgroups were significantly higher than those in the control group at 1 d after birth and showed positive correlations with PASP (p < 0.05), except that serum ADM in mild HPH showed no obvious difference from the control group. The levels of serum HIF-1α and ADM in the severe HPH group and the ET-1 levels in the moderate and severe groups were increased significantly at 3 d after birth (p < 0.05).. The PASP level in neonates with HPH is related to the serum HIF-1α, ET-1 and ADM levels, indicating that hypoxia can increase the level of HIF-1α, which in turn will enhance the expression of downstream target genes ET-1 and ADM, further leading to pulmonary hypertension. The right ventricular Tei index can be used to sensitively detect right ventricular dysfunction of mild, moderate and severe HPH groups.

Topics: Adrenomedullin; Animals; Case-Control Studies; Echocardiography; Endothelin-1; Female; Humans; Hypertension, Pulmonary; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Infant, Newborn; Male; Pulmonary Artery; Ventricular Dysfunction, Right; Ventricular Function, Right

Topics: Endothelin-1; Humans; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit

Topics: Endothelin-1; Humans; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit

To investigate the protective effect of heat shock protein 70 (HSP70) against hypoxic pulmonary hypertension (HPH) in neonatal rats.. A total of 128 neonatal rats were randomly divided into blank control group, HPH model group, empty virus group, and HSP70 group, with 32 rats in each group. Before the establishment of an HPH model, the rats in the blank control group and HPH model group were given caudal vein injection of 5 μL sterile saline, those in the empty virus group were given caudal vein injection of 5 μL Ad-GFP (1 010 PFU/mL), and those in the HSP70 group were given caudal vein injection of 5 μL Ad-HSP70 (1 010 PFU/mL). HPH model was prepared in the HPH model, empty virus, and HSP70 groups after transfection. At 3, 7, 10, and 14 days after model establishment, a multi-channel physiological recorder was used to record mean pulmonary arterial pressure (mPAP), optical and electron microscopes were used to observe the structure and remodeling parameters of pulmonary vessels, and Western blot was used to measure the protein expression of HSP70, hypoxia-inducible factor-1α (HIF-1α), endothelin-1 (ET-1), and inducible nitric oxide synthase (iNOS) in lung tissues.. At 3, 7, 10, and 14 days after model establishment, the HPH model group and the empty virus group had a significantly higher mPAP than the blank control group (P<0.05). On days 7 and 10 of hypoxia, the blank control group and the HSP70 group had significantly lower MA% and MT% than the HPH model group and the empty virus group (P<0.01); on day 14 of hypoxia, the HPH model group, empty virus group, and HSP70 group had similar MA% and MT% (P>0.05), but had significantly higher MA% and MT% than the blank control group (P<0.01). On days 3, 7 and 10 of hypoxia, the HSP70 group had significantly higher protein expression of HSP70 than the HPH model group, empty virus group, and blank control group (P<0.01); the HSP70 group had significantly lower expression of HIF-1α, ET-1, and iNOS than the HPH model group and the empty virus group (P<0.05) and similar expression of HIF-1α, ET-1, and iNOS as the blank control group (P>0.05).. In neonatal rats with HPH, HSP70 transfection can increase the expression of HSP70 in lung tissues, downregulate the expression of HIF-1α, ET-1, and iNOS, alleviate pulmonary vascular remodeling, and reduce pulmonary artery pressure; therefore, it may become a new strategy for the treatment of HPH in neonates.

Topics: Animals; Disease Models, Animal; Endothelin-1; HSP70 Heat-Shock Proteins; Hypertension, Pulmonary; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Nitric Oxide Synthase Type II; Pulmonary Artery; Rats; Rats, Wistar; Transfection

Endothelin-1 (ET-1) plays a critical role in endothelial dysfunction and contributes to the pathogenesis of pulmonary hypertension (PH). We hypothesized that peroxisome proliferator-activated receptor γ (PPARγ) stimulates microRNAs that inhibit ET-1 and pulmonary artery endothelial cell (PAEC) proliferation. The objective of this study was to clarify molecular mechanisms by which PPARγ regulates ET-1 expression in vitro and in vivo. In PAECs isolated from patients with pulmonary arterial hypertension, microRNA (miR)-98 expression was reduced, and ET-1 protein levels and proliferation were increased. Similarly, hypoxia reduced miR-98 and increased ET-1 levels and PAEC proliferation in vitro. In vivo, hypoxia reduced miR-98 expression and increased ET-1 and proliferating cell nuclear antigen (PCNA) levels in mouse lung, derangements that were aggravated by treatment with the vascular endothelial growth factor receptor antagonist Sugen5416. Reporter assays confirmed that miR-98 binds directly to the ET-1 3'-untranslated region. Compared with littermate control mice, miR-98 levels were reduced and ET-1 and PCNA expression were increased in lungs from endothelial-targeted PPARγ knockout mice, whereas miR-98 levels were increased and ET-1 and PCNA expression was reduced in lungs from endothelial-targeted PPARγ-overexpression mice. Gain or loss of PPARγ function in PAECs in vitro confirmed that alterations in PPARγ were sufficient to regulate miR-98, ET-1, and PCNA expression. Finally, PPARγ activation with rosiglitazone regimens that attenuated hypoxia-induced PH in vivo and human PAEC proliferation in vitro restored miR-98 levels. The results of this study show that PPARγ regulates miR-98 to modulate ET-1 expression and PAEC proliferation. These results further clarify molecular mechanisms by which PPARγ participates in PH pathogenesis and therapy.

Topics: 3' Untranslated Regions; Animals; Binding Sites; Cell Proliferation; Cells, Cultured; Endothelial Cells; Endothelin-1; Gene Expression Regulation; Humans; Hypertension, Pulmonary; Hypoxia; Indoles; Male; Mice, Inbred C57BL; Mice, Knockout; MicroRNAs; PPAR gamma; Pulmonary Artery; Pyrroles; RNA Interference; Rosiglitazone; Signal Transduction; Thiazolidinediones; Transfection; Vascular Remodeling

Opioids produce delayed pre-conditioning (PC) in vivo and in vitro. Our previous research revealed that opioid‑induced delayed PC has an antiapoptotic effect on pulmonary artery endothelial cells (PAECs) suffering from anoxia/reoxygenation (A/R) injury. The present study hypothesized that activation of endothelial mitochondrial ATP‑sensitive potassium (KATP) channels may result in antiapoptotic effects and against dysfunction in PAECs. Cultured porcine PAECs underwent 16 h anoxia treatment, followed by 1 h reoxygenation, which occurred 24 h following pretreatment with saline (0.9% NaCl; w/v) or morphine (1 µM). To determine the underlying mechanism, a selective mitochondrial KATP inhibitor, 5‑hydroxydecanoic acid (5‑HD; 100 µM), and an opioid receptor antagonist, naloxone (Nal; 10 µM), were administered 30 min prior to the A/R load. The percentage of apoptotic cells was assessed by Annexin V‑fluorescein isothiocyanate staining, using a fluorescence‑activated cell sorter. The mRNA expression of intercellular cell adhesion molecule‑1 (ICAM‑1) was measured by reverse transcription‑quantitative polymerase chain reaction. The endothelin‑1 (ET‑1) content in the supernatant of PAECs cultures was estimated by radioimmunoassay. Compared with the control, A/R caused the apoptosis of PAECs, release of ET‑1 and increased mRNA expression of ICAM‑1. Morphine‑induced delayed PC significantly reduced PAEC apoptosis, increased the release of ET‑1 and reduced the mRNA expression of ICAM‑1 by ~1.7‑times, compared with A/R. The protective effect of morphine was abolished by pretreatment with 5‑HD and Nal, however, the two agents themselves failed to aggravate the A/R injury. These results suggested that morphine-induced delayed PC has a protective effect during A/R injury of PAECs. This effect may be mediated by mitochondrial KATP channels and is opioid receptor-dependent.

Topics: Animals; Apoptosis; Endothelial Cells; Endothelin-1; Gene Expression Regulation; Humans; Hypoxia; Intercellular Adhesion Molecule-1; Morphine; Naloxone; Potassium Channels; Pulmonary Artery; Receptors, Opioid; RNA, Messenger; Swine

Obstructive sleep apnoea syndrome is characterized by repetitive episodes of upper airway collapse during sleep resulting in chronic intermittent hypoxia (IH). Obstructive sleep apnoea syndrome, through IH, promotes cardiovascular and metabolic disorders. Endothelin-1 (ET-1) secretion is upregulated by IH, and is able to modulate adipocyte metabolism. Therefore, the present study aimed to characterize the role of ET-1 in the metabolic consequences of IH on adipose tissue in vivo and in vitro. Wistar rats were submitted to 14 days of IH-cycles (30 s of 21% FiO2 and 30 s of 5% FiO2 ; 8 h day(-1) ) or normoxia (air-air cycles) and were treated or not with bosentan, a dual type A and B endothelin receptor (ETA-R and ETB-R) antagonist. Bosentan treatment decreased plasma free fatty acid and triglyceride levels, and inhibited IH-induced lipolysis in adipose tissue. Moreover, IH induced a 2-fold increase in ET-1 transcription and ETA-R expression in adipose tissue that was reversed by bosentan. In 3T3-L1 adipocytes, ET-1 upregulated its own and its ETA-R transcription and this effect was abolished by bosentan. Moreover, ET-1 induced glycerol release and inhibited insulin-induced glucose uptake. Bosentan and BQ123 inhibited these effects. Bosentan also reversed the ET-1-induced phosphorylation of hormone-sensitive lipase (HSL) on Ser(660) . Finally, ET-1-induced lipolysis and HSL phosphorylation were also observed under hypoxia. Altogether, these data suggest that ET-1 is involved in IH-induced lipolysis in Wistar rats, and that upregulation of ET-1 production and ETA-R expression by ET-1 itself under IH could amplify its effects. Moreover, ET-1-induced lipolysis could be mediated through ETA-R and activation of HSL by Ser(660) phosphorylation.

Topics: 3T3 Cells; Adipose Tissue; Animals; Bosentan; Endothelin Receptor Antagonists; Endothelin-1; Fatty Acids; Hypoxia; Lipolysis; Male; Mice; Phosphorylation; Protein Processing, Post-Translational; Rats; Rats, Wistar; Receptors, Endothelin; Sterol Esterase; Sulfonamides; Triglycerides

Obstructive sleep apnea (OSA) is a major risk factor for cardiovascular mortality, and apnea-induced intermittent hypoxia (IH) is known to promote various cardiovascular alterations such as vascular remodeling. However, the mechanisms that underlie IH remain incompletely investigated. We previously demonstrated that the hypoxia-inducible factor-1 (HIF-1) and endothelin-1 (ET-1) are involved in arterial hypertension and myocardial susceptibility to infarction induced by IH. Thus the objective of the present study was to investigate whether both ET-1 and HIF-1 were also involved in the vascular inflammatory remodeling induced by IH. Mice partially deficient for the Hif1α gene (HIF-1α(+/-)) and their wild-type equivalents, as well as C57BL/6J mice, treated or not with bosentan, a dual endothelin receptor antagonist, were exposed to IH or normoxia for 2 wk, 8 h/day. Splenocyte proliferative and secretory capacities, aortic nuclear factor-κB (NF-κB) and HIF-1 activities, and expression of cytokines and intima-media thickness (IMT) were measured. IH induced a systemic and aortic inflammation characterized by an increase in splenocyte proliferative and secretory capacities, aortic NF-κB activity, and cytokine expression in the aortic wall. This was accompanied by an increase in IMT. These modifications were prevented in HIF-1α(+/-) and bosentan-treated mice. The results of this study suggest that ET-1 is a major contributor to the vascular inflammatory remodeling induced by OSA-related IH, probably through HIF-1-dependent activation of NF-κB.

Topics: Animals; Aorta; Carotid Intima-Media Thickness; Cytokines; Endothelin-1; Hypertension; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Inflammation; Mice; Mice, Inbred C57BL; NF-kappa B; Sleep Apnea, Obstructive; Vascular Remodeling

The cardiac hormone atrial natriuretic peptide (ANP) regulates systemic and pulmonary arterial blood pressure by activation of its cyclic GMP-producing guanylyl cyclase-A (GC-A) receptor. In the lung, these hypotensive effects were mainly attributed to smooth muscle-mediated vasodilatation. It is unknown whether pulmonary endothelial cells participate in the homeostatic actions of ANP. Therefore, we analyzed GC-A/cGMP signalling in lung endothelial cells and the cause and functional impact of lung endothelial GC-A dysfunction. Western blot and cGMP determinations showed that cultured human and murine pulmonary endothelial cells exhibit prominent GC-A expression and activity which were markedly blunted by hypoxia, a condition known to trigger pulmonary hypertension (PH). To elucidate the consequences of impaired endothelial ANP signalling, we studied mice with genetic endothelial cell-restricted ablation of the GC-A receptor (EC GC-A KO). Notably, EC GC-A KO mice exhibit PH already under resting, normoxic conditions, with enhanced muscularization of small arteries and perivascular infiltration of inflammatory cells. These alterations were aggravated on exposure of mice to chronic hypoxia. Lung endothelial GC-A dysfunction was associated with enhanced expression of angiotensin converting enzyme (ACE) and increased pulmonary levels of Angiotensin II. Angiotensin II/AT1-blockade with losartan reversed pulmonary vascular remodelling and perivascular inflammation of EC GC-A KO mice, and prevented their increment by chronic hypoxia. This experimental study indicates that endothelial effects of ANP are critical to prevent pulmonary vascular remodelling and PH. Chronic endothelial ANP/GC-A dysfunction, e.g. provoked by hypoxia, is associated with activation of the ACE-angiotensin pathway in the lung and PH.

Topics: Angiotensin II; Animals; Atrial Natriuretic Factor; Endothelial Cells; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Lung; Mice; Mice, Knockout; Peptidyl-Dipeptidase A; Receptors, Atrial Natriuretic Factor

Sphingosine-1-phosphate (S1P) is emerging to have hypoxic preconditioning potential in various preclinical studies. The study aims to evaluate the preclinical preconditioning efficacy of exogenously administered S1P against acute hypobaric hypoxia (HH)-induced pathological disturbances. Male Sprague Dawley rats (200 ± 20 g) were preconditioned with 1, 10, and 100 μg/kg body weight (b.w.) S1P (i.v.) for three consecutive days. On the third day, S1P preconditioned animals, along with hypoxia control animals, were exposed to HH equivalent to 7,620 m (280 mm Hg) for 6 h. Postexposure status of cardiac energy production, circulatory vasoactive mediators, pulmonary and cerebral oxidative damage, and inflammation were assessed. HH exposure led to cardiac energy deficit indicated by low ATP levels and pronounced AMPK activation levels, raised circulatory levels of brain natriuretic peptide and endothelin-1 with respect to total nitrate (NOx), redox imbalance, inflammation, and alterations in NOx levels in the pulmonary and cerebral tissues. These pathological precursors have been routinely reported to be coincident with high-altitude diseases. Preconditioning with S1P, especially 1 µg/kg b.w. dose, was seen to reverse the manifestation of these pathological disturbances. The protective efficacy could be attributed, at least in part, to enhanced activity of cardioprotective protein kinase C and activation of small GTPase Rac1, which led to further induction of hypoxia-adaptive molecular mediators: hypoxia-inducible factor (HIF)-1α and Hsp70. This is a first such report, to the best of our knowledge, elucidating the mechanism of exogenous S1P-mediated HIF-1α/Hsp70 induction. Conclusively, systemic preconditioning with 1 μg/kg b.w. S1P in rats protects against acute HH-induced pathological disturbances. © 2016 IUBMB Life 68(5):365-375, 2016.

Topics: Animals; Cytokines; Drug Evaluation, Preclinical; Endothelin-1; Energy Metabolism; HSP70 Heat-Shock Proteins; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Lysophospholipids; Male; Myocardium; Natriuretic Peptide, Brain; Nitric Oxide; Oxidation-Reduction; Oxidative Stress; Protein Stability; rac1 GTP-Binding Protein; Rats, Sprague-Dawley; Sphingosine

The mechanisms underlying acute mountain sickness (AMS) and high-altitude pulmonary edema (HAPE) are not fully understood. We hypothesized that regulators of endothelial function, circulatory homeostasis, hypoxia and cell stress contribute to the pathobiology of AMS and HAPE.. We conducted a prospective case-control study of climbers developing altitude illness who were evacuated to the CIWEC clinic in Kathmandu, compared to healthy acclimatized climbers. ELISA was used to measure plasma biomarkers of the above pathways.. Of the 175 participants, there were 71 cases of HAPE, 54 cases of AMS and 50 acclimatized controls (ACs). Markers of endothelial function were associated with HAPE: circulating levels of endothelin-1 (ET-1) were significantly elevated and levels of sKDR (soluble kinase domain receptor) were significantly decreased in cases of HAPE compared to AC or AMS. ET-1 levels were associated with disease severity as indicated by oxygen saturation. Angiopoietin-like 4 (Angptl4) and resistin, a marker of cell stress, were associated with AMS and HAPE irrespective of severity. Corin and angiotensin converting enzyme, regulators of volume homeostasis, were significantly decreased in HAPE compared to AC.. Our findings indicate that regulators of endothelial function, vascular tone and cell stress are altered in altitude illness and may mechanistically contribute to the pathobiology of HAPE.

Topics: Acclimatization; Acute Disease; Adult; Altitude Sickness; Biomarkers; Case-Control Studies; Endothelin-1; Female; Humans; Hypertension, Pulmonary; Hypoxia; Male; Middle Aged; Mountaineering; Nepal; Peptidyl-Dipeptidase A; Prospective Studies; Shock; Travel

We previously proposed that hyperglycemia-induced mitochondrial reactive oxygen species (mtROS) generation is a key event in the development of diabetic complications. Interestingly, some common aspects exist between hyperglycemia and hypoxia-induced phenomena. Thus, hyperglycemia may induce cellular hypoxia, and this phenomenon may also be involved in the pathogenesis of diabetic complications. In endothelial cells (ECs), cellular hypoxia increased after incubation with high glucose (HG). A similar phenomenon was observed in glomeruli of diabetic mice. HG-induced cellular hypoxia was suppressed by mitochondria blockades or manganese superoxide dismutase (MnSOD) overexpression, which is a specific SOD for mtROS. Overexpression of MnSOD also increased the expression of aquaporin-1 (AQP1), a water and oxygen channel. AQP1 overexpression in ECs suppressed hyperglycemia-induced cellular hypoxia, endothelin-1 and fibronectin overproduction, and apoptosis. Therefore, hyperglycemia-induced cellular hypoxia and mtROS generation may promote hyperglycemic damage in a coordinated manner.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Apoptosis; Blotting, Western; Cattle; Cell Hypoxia; Cell Line; Deoxyguanosine; Diabetes Mellitus, Experimental; Endothelial Cells; Endothelin-1; Fibronectins; Glucose; Hyperglycemia; Hypoxia; Mice, Inbred C57BL; Mice, Transgenic; Mitochondria; Reactive Oxygen Species; Reverse Transcriptase Polymerase Chain Reaction; Superoxide Dismutase

Decline in oxygen availability experienced under hypobaric hypoxia (HH) mediates imbalance in lung fluid clearance and is a causative agent of acute lung injury. Here, we investigate the pathological events behind acute HH mediated lung injury and assess the therapeutic efficacy of nanocurcumin in its amelioration. We assess the protective efficacy of nanotized curcumin (nanocurcumin) in ameliorating HH induced lung injury and compare to curcumin. Rats exposed to acute HH (6, 12, 24, 48 and 72 h) were subjected to histopathology, blood-gas analysis and clinical biochemistry, cytokine response and redox damage. HH induced lung injury was analysed using markers of lung injury due to pulmonary vasoconstriction (ET-1/2/3 and endothelin receptors A and B) and trans-vascular fluid balance mediator (Na+/K+ ATPase). The protective efficacy of nanocurcumin was analysed by examination of Akt/Erk signalling cascade by western blot. HH induced lung injury was associated with discrete changes in blood analytes, differential circulatory cytokine response and severe pulmonary redox damages. Up-regulation of ET-1/2/3 and its receptors along with down-regulation of Na+/K+ ATPase confirmed defective pulmonary fluid clearance which promoted edema formation. Nanocurcumin treatment prevented lung edema formation and restored expression levels of ET-1/2/3 and its receptors while restoring the blood analytes, circulatory cytokines and pulmonary redox status better than curcumin. Modulation in Akt/Erk signalling pathway in rat lungs under HH confirmed the protective efficacy of nanocurcumin.

Topics: Acute Lung Injury; Animals; Biomarkers; Curcumin; Disease Models, Animal; Endothelin-1; Endothelin-2; Endothelin-3; Gene Expression Regulation; Hypoxia; Male; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Nanostructures; Oxidation-Reduction; Protective Agents; Proto-Oncogene Proteins c-akt; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptor, Endothelin B; Signal Transduction; Sodium-Potassium-Exchanging ATPase

Alport syndrome, a type IV collagen disorder, manifests as glomerular disease associated with hearing loss with thickening of the glomerular and strial capillary basement membranes (SCBMs). We have identified a role for endothelin-1 (ET-1) activation of endothelin A receptors (ET

Topics: Animals; Basement Membrane; Body Temperature; Capillaries; Cell Line; Collagen Type IV; Disease Models, Animal; Endothelin-1; Extracellular Matrix; Gene Expression Regulation; Hypoxia; Isoxazoles; Laminin; Mice; Nephritis, Hereditary; Oxidative Stress; Phenotype; Stria Vascularis; Thiophenes

What is the central question of this study? This study addresses the relative impact of obesity and intermittent hypoxia in the pathophysiological process of obstructive sleep apnoea by investigating the metabolic, inflammatory and cardiovascular consequences of intermittent hypoxia in lean and obese Zucker rats. What is the main finding and its importance? We found that obesity and intermittent hypoxia have mainly distinct consequences on the investigated inflammatory and cardiometabolic parameters in Zucker rats. This suggests that, for a given severity of sleep apnea, the association of obesity and obstructive sleep apnoea may not necessarily be deleterious. Obstructive sleep apnoea is associated with obesity with a high prevalence, and both co-morbidities are independent cardiovascular risk factors. Intermittent hypoxia (IH) is thought to be the main factor responsible for the obstructive sleep apnoea-related cardiometabolic alterations. The aim of this study was to assess the respective impact of obesity and IH on the inflammatory and cardiometabolic state in rats. Lean and obese Zucker rats were exposed to normoxia or chronic IH, and we assessed metabolic and inflammatory parameters, such as plasma lipids and glucose, serum leptin and adiponectin, liver cytokines, nuclear factor-κB activity and cardiac endothelin-1 levels. Myocardial infarct size was also evaluated following in vitro ischaemia-reperfusion. Circulating lipids, insulin, homeostasis model assessment of insulin resistance (HOMA-IR), leptin and adiponectin levels were higher in obese versus lean rats. Chronic IH did not have a significant impact on metabolic parameters in lean rats. In obese rats, IH increased glycaemia and HOMA-IR. Liver interleukin-6 and tumour necrosis factor-α levels were elevated in lean rats exposed to IH; obesity prevented the increase in interleukin-6 but not in tumour necrosis factor-α. Finally, IH exposure enhanced myocardial sensitivity to infarction in both lean and obese rats and increased cardiac endothelin-1 in lean but not obese rats. In conclusion, this study shows that the dyslipidaemia and insulin resistance induced by obesity of genetic origin does not enhance the deleterious cardiovascular response to IH and may even partly protect against IH-induced inflammation.

Topics: Adiponectin; Animals; Blood Glucose; Cardiovascular Diseases; Cytokines; Disease Models, Animal; Endothelin-1; Hypoxia; Inflammation; Insulin; Interleukin-6; Leptin; Lipids; Liver; Male; Myocardium; NF-kappa B; Obesity; Rats; Rats, Zucker; Tumor Necrosis Factor-alpha

This study was designed to determine whether ET-1 derived from endothelial cells contributes to oxidative stress in the glomerulus of mice subjected to a high-salt diet and/or hypoxia.. C57BL6/J control mice or vascular endothelial cell ET-1 knockout (VEET KO) mice were subjected to 3-h exposure to hypoxia (8% O₂) and/or 2 weeks of high-salt diet (4% NaCl) prior to metabolic cage assessment of renal function and isolation of glomeruli for the determination of reactive oxygen species (ROS).. In control mice, hypoxia significantly increased urinary protein excretion during the initial 24 h, but only in animals on a high-salt diet. Hypoxia increased glomerular ET-1 mRNA expression in control, but not in vascular endothelial cell ET-1 knockout (VEET KO) mice. Under normoxic conditions, mice on a high-salt diet had approx. 150% higher glomerular ET-1 mRNA expression compared with a normal-salt diet (P < 0.05). High-salt diet administration significantly increased glomerular ROS production in flox control, but not in glomeruli isolated from VEET KO mice. In C57BL6/J mice, the ETA receptor-selective antagonist, ABT-627, significantly attenuated the increase in glomerular ROS production produced by high-salt diet. In addition, chronic infusion of C57BL6/J mice with a subpressor dose of ET-1 (osmotic pumps) significantly increased the levels of glomerular ROS that were prevented by ETA antagonist treatment.. These data suggest that both hypoxia and a high-salt diet increase glomerular ROS production via endothelial-derived ET-1-ETA receptor activation and provide a potential mechanism for ET-1-induced nephropathy.

Topics: Animals; Disease Models, Animal; Endothelin A Receptor Antagonists; Endothelin-1; Hypoxia; Kidney Diseases; Kidney Glomerulus; Male; Mice, Inbred C57BL; Mice, Knockout; Oxidative Stress; Proteinuria; Reactive Oxygen Species; Receptor, Endothelin A; Sodium Chloride, Dietary; Time Factors

Endothelin-1 (ET-1) increases pulmonary vascular tone through direct effects on pulmonary artery smooth muscle cells (PASMC) via membrane-bound ET-1 receptors. Circulating ET-1 contributes to vascular remodeling by promoting SMC proliferation and migration and inhibiting SMC apoptosis. Although endothelial cells (EC) are the primary source of ET-1, whether ET-1 produced by SMC modulates pulmonary vascular tone is unknown. Using transgenic mice created by crossbreeding SM22α-Cre mice with ET-1(flox/flox) mice to selectively delete ET-1 in SMC, we tested the hypothesis that PASMC ET-1 gene expression modulates the pulmonary vascular response to hypoxia. ET-1 gene deletion and selective activity of SM22α promoter-driven Cre recombinase were confirmed. Functional assays were performed under normoxic (21% O2) or hypoxic (5% O2) conditions using murine PASMC obtained from ET-1(+/+) and ET-1(-/-) mic and in human PASMC (hPASMC) after silencing of ET-1 using siRNA. Under baseline conditions, there was no difference in right ventricular systolic pressure (RVSP) between SM22α-ET-1(-/-) and SM22α-ET-1(+/+) (control) littermates. After exposure to hypoxia (10% O2, 21-24 days), RVSP was and vascular remodeling were less in SM22α-ET-1(-/-) mice compared with control littermates (P < 0.01). Loss of ET-1 decreased PASMC proliferation and migration and increased apoptosis under normoxic and hypoxic conditions. Exposure to selective ET-1 receptor antagonists had no effect on either the hypoxia-induced hPASMC proliferative or migratory response. SMC-specific ET-1 deletion attenuates hypoxia-induced increases in pulmonary vascular tone and structural remodeling. The observation that loss of ET-1 inhibited SMC proliferation, survival, and migration represents evidence that ET-1 derived from SMC plays a previously undescribed role in modulating the response of the pulmonary circulation to hypoxia. Thus PASMC ET-1 may modulate vascular tone independently of ET-1 produced by EC.

Topics: Animals; Cell Movement; Cell Proliferation; Cell Survival; Cells, Cultured; Chronic Disease; Endothelial Cells; Endothelin-1; Gene Expression Regulation; Gene Silencing; Humans; Hypoxia; Mice; Mice, Knockout; Microfilament Proteins; Muscle Proteins; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Pulmonary Artery; Vascular Remodeling

We investigated the effect of intermittent hypoxia, mimicking sleep apnea, on axonal integrity, blood-brain barrier permeability, and cognitive function of mice. Forty-seven C57BL mice were exposed to intermittent or sham hypoxia, alternating 30s of progressive hypoxia and 30s of reoxigenation, during 8h/day. The axonal integrity in cerebellum was evaluated by transmission electron microscopy. Short- and long-term memories were assessed by novel object recognition test. The levels of endothelin-1 were measured by ELISA. Blood-brain barrier permeability was quantified by Evans Blue dye. After 14 days, animals exposed to intermittent hypoxia showed hypomyelination in cerebellum white matter and higher serum levels of endothelin-1. The short and long-term memories in novel object recognition test was impaired in the group exposed to intermittent hypoxia as compared to controls. Blood-brain barrier permeability was similar between the groups. These results indicated that hypomyelination and impairment of short- and long-term working memories occurred in C57BL mice after 14 days of intermittent hypoxia mimicking sleep apnea.

Topics: Animals; Axons; Blood-Brain Barrier; Capillary Permeability; Cerebellum; Cerebrum; Disease Models, Animal; Endothelin-1; Enzyme-Linked Immunosorbent Assay; Evans Blue; Hypoxia; Male; Memory Disorders; Memory, Short-Term; Mice, Inbred C57BL; Myelin Sheath; Neuropsychological Tests; Recognition, Psychology; Sleep Apnea Syndromes; White Matter

Topics: Animals; Endothelin-1; Hypoxia; Kidney Diseases; Kidney Glomerulus; Male; Oxidative Stress; Reactive Oxygen Species; Sodium Chloride, Dietary

Renal ischemia/reperfusion (I/R) is a common risk factor for renal failure. Expression of endothelin‑1 (ET‑1) and its receptor ETA were also reported to be involved in the development of acute and chronic renal disease. The present study was designed to investigate the association between inflammation and ET‑1/ETA expression in mouse kidneys following acute I/R. The results demonstrated that acute renal I/R caused a significant increase in ET‑1 and ETA gene and transcriptional levels compared with those of the sham group (P<0.01). Ischemia alone also resulted in a marked increase of ET‑1 and ETA expression compared with that of the sham group (P<0.05). In addition, ET‑1 and ETA expression was significantly increased in the I/R group compared with that of the ischemia group (P<0.05 or P<0.01). Of note, the altered expression levels of inflammatory cytokines tumor necrosis factor (TNF)‑α and interleukin (IL)‑6 in kidneys following I/R and ischemia alone were correlated with the expression of ET‑1 and ETA. Hypoxia is the most important stimulus of I/R for tissue injury. In kidneys, ET‑1 is primarily produced by renal glomerular endothelial cells (RGECs). In the present study, treatment with hypoxia alone or hypoxia/reoxygenation were found to increase ET‑1 and ETA expression in human RGECs (P<0.05 or P<0.01). In order to elucidate the role of inflammation in the ischemia‑ and hypoxia‑induced upregulation of ET‑1 and ETA, human RGECs were exposed to different concentrations of TNF‑α. As expected, TNF‑α increased ET‑1 and ETA expression in a dose‑dependent manner; furthermore, application of the TNF‑α inhibitor CAY10500 partially inhibited hypoxia‑induced ET‑1 and ETA expression. In conclusion, these results indicated that I/R induced upregulation of ET‑1 and ETA in the kidneys, which was, at least in part, dependent on the production of inflammatory cytokines.

Topics: Animals; Disease Models, Animal; Endothelial Cells; Endothelin-1; Gene Expression; Humans; Hypoxia; Inflammation; Interleukin-6; Male; Mice; Receptor, Endothelin A; Reperfusion Injury; RNA, Messenger; Tumor Necrosis Factor-alpha

This study examines how heme biosynthesis modulation with δ-aminolevulinic acid (ALA) potentially functions to prevent 21-day hypoxia (10% oxygen)-induced pulmonary hypertension in mice and the effects of 24-h organoid culture with bovine pulmonary arteries (BPA) with the hypoxia and pulmonary hypertension mediator endothelin-1 (ET-1), with a focus on changes in superoxide and regulation of micro-RNA 204 (miR204) expression by src kinase phosphorylation of signal transducer and activator of transcription-3 (STAT3). The treatment of mice with ALA attenuated pulmonary hypertension (assessed through echo Doppler flow of the pulmonary valve, and direct measurements of right ventricular systolic pressure and right ventricular hypertrophy), increases in pulmonary arterial superoxide (detected by lucigenin), and decreases in lung miR204 and mitochondrial superoxide dismutase (SOD2) expression. ALA treatment of BPA attenuated ET-1-induced increases in mitochondrial superoxide (detected by MitoSox), STAT3 phosphorylation, and decreases in miR204 and SOD2 expression. Because ALA increases BPA protoporphyrin IX (a stimulator of guanylate cyclase) and cGMP-mediated protein kinase G (PKG) activity, the effects of the PKG activator 8-bromo-cGMP were examined and found to also attenuate the ET-1-induced increase in superoxide. ET-1 increased superoxide production and the detection of protoporphyrin IX fluorescence, suggesting oxidant conditions might impair heme biosynthesis by ferrochelatase. However, chronic hypoxia actually increased ferrochelatase activity in mouse pulmonary arteries. Thus, a reversal of factors increasing mitochondrial superoxide and oxidant effects that potentially influence remodeling signaling related to miR204 expression and perhaps iron availability needed for the biosynthesis of heme by the ferrochelatase reaction could be factors in the beneficial actions of ALA in pulmonary hypertension.

Topics: Aminolevulinic Acid; Animals; Endothelin-1; Ferrochelatase; Heme; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Male; Mice, Inbred C57BL; MicroRNAs; Mitochondria; Pulmonary Artery; Superoxide Dismutase; Superoxides

To provide pharmacological data for future clinical studies, this study investigated the protective effects of diltiazem on vascular endothelial cell (VEC) injury induced by angiotensin-II (AngII), hypoxia, and a combination of both treatments. The concentration of intracellular free calcium and the mitochondrial membrane potential in VEC were assessed as indicators of cell injury. An in vivo hypoxic animal model was used to test the protective effect of diltiazem on vascular endothelial tissues. Our study showed that AngII and hypoxia decreased the mitochondrial membrane potential in VEC, which was significantly inhibited by diltiazem. Diltiazem protected against VEC injury induced by the increased concentration of intracellular free calcium, which was associated with AngII and hypoxia. Diltiazem reduced the apoptosis of rat VEC under a sustained hypoxic condition. In addition, it reduced AngII and endothelin I levels in rat vascular endothelial tissues. Our study confirmed that AngII and hypoxia induced VEC injury by regulating the levels of mitochondrial membrane potential and intracellular free calcium. Diltiazem, a calcium channel blocker, protected VEC from AngII- and hypoxia-induced injury.

Topics: Angiotensin II; Animals; Apoptosis; Calcitonin Gene-Related Peptide; Calcium Channel Blockers; Calcium Signaling; Cells, Cultured; Cytoprotection; Diltiazem; Disease Models, Animal; Endothelial Cells; Endothelin-1; Humans; Hypoxia; Male; Membrane Potential, Mitochondrial; Mitochondria; Nitric Oxide; Nitric Oxide Synthase Type III; Rats, Wistar; Vascular Diseases

Painschab, Matthew S., Gary E. Malpartida, Victor G. Davila-Roman, Robert H. Gilman, Todd M. Kolb, Fabiola Leon-Velarde, J. Jaime Miranda, and William Checkley. Association between serum concentrations of hypoxia inducible factor responsive proteins and excessive erythrocytosis in high altitude Peru. High Alt Med Biol 16:26-33, 2015.-Long-term residence at high altitude is associated with the development of chronic mountain sickness (CMS), which is characterized by excessive erythrocytosis (EE). EE occurs under chronic hypoxia, and a strongly selected mutation in hypoxia-inducible factor 2α (HIF2A) has been found in native Tibetans that correlates with having a normal hemoglobin at high altitude. We sought to evaluate differences in plasma levels of four HIF-responsive proteins in 20 participants with EE (hemoglobin >21 g/dL in men and >19 in women) and in 20 healthy, age- and sex-matched participants without EE living at high altitude in Puno, Peru. We performed ELISA to measure plasma levels of the four HIF-responsive proteins: vascular endothelial growth factor (VEGF), soluble VEGF receptor 1 (sVEGF-R1), endothelin-1, and erythropoietin. As a secondary aim, we evaluated the association between HIF-responsive proteins and echocardiography-estimated pulmonary artery systolic pressure (PASP) in a subset of 26 participants. sVEGF-R1 was higher in participants with vs. without EE (mean 107 pg/mL vs. 90 pg/mL; p=0.007). Although plasma concentrations of endothelin-1, VEGF, and erythropoietin were higher in participants with vs. without EE, they did not achieve statistical significance (all p>0.25). Both sVEGF-R1 (p=0.04) and erythropoietin (p=0.04) were positively associated with PASP after adjustment for age, sex, and BMI. HIF-responsive proteins may play a pathophysiological role in altitude-related, chronic diseases but our results did not show consistent changes in all measured HIF-responsive proteins. Larger studies are needed to evaluate for additional genetic and environmental risk factors.

Topics: Adult; Aged; Altitude; Altitude Sickness; Basic Helix-Loop-Helix Transcription Factors; Biomarkers; Blood Pressure; Case-Control Studies; Endothelin-1; Erythropoietin; Female; Humans; Hypoxia; Male; Middle Aged; Peru; Polycythemia; Pulmonary Artery; Vascular Endothelial Growth Factor Receptor-1; Vascular Endothelial Growth Factors

Pulmonary hypertension is a fatal disease characterized by a progressive increase in pulmonary artery pressure accompanied by pulmonary vascular remodeling and increased vasomotor tone. Although some biological pathways have been identified in neonatal hypoxia-induced pulmonary hypertension (PH), little is known regarding the role of growth factors in the pathogenesis of PH in neonates. In this study, using a model of hypoxia-induced PH in neonatal mice, we demonstrate that the growth factor insulin-like growth factor-1 (IGF-1), a potent activator of the AKT signaling pathway, is involved in neonatal PH. After exposure to hypoxia, IGF-1 signaling is activated in pulmonary endothelial and smooth muscle cells in vitro, and the IGF-1 downstream signal pAKT(S473) is upregulated in lungs of neonatal mice. We found that IGF-1 regulates ET-1 expression in pulmonary endothelial cells and that IGF-1 expression is regulated by histone deacetylases (HDACs). In addition, there is a differential cytosine methylation site in the IGF-1 promoter region in response to neonatal hypoxia. Moreover, inhibition of HDACs with apicidin decreases neonatal hypoxia-induced global DNA methylation levels in lungs and specific cytosine methylation levels around the pulmonary IGF-1 promoter region. Finally, HDAC inhibition with apicidin reduces chronic hypoxia-induced activation of IGF-1/pAKT signaling in lungs and attenuates right ventricular hypertrophy and pulmonary vascular remodeling. Taken together, we conclude that IGF-1, which is epigenetically regulated, is involved in the pathogenesis of pulmonary hypertension in neonatal mice. This study implicates a novel HDAC/IGF-1 epigenetic pathway in the regulation of hypoxia-induced PH and warrants further study of the role of IGF-1 in neonatal pulmonary hypertensive disease.

Topics: Animals; Animals, Newborn; Arterial Pressure; Cells, Cultured; Disease Models, Animal; DNA Methylation; Endothelin-1; Epigenesis, Genetic; Gene Expression Regulation; Histone Deacetylase Inhibitors; Histone Deacetylases; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Insulin-Like Growth Factor I; Mice, Inbred C57BL; Phosphorylation; Promoter Regions, Genetic; Proto-Oncogene Proteins c-akt; Pulmonary Artery; RNA Interference; Signal Transduction; Time Factors; Transfection; Vascular Remodeling

The anemia of sickle cell disease is associated with a severe inflammatory vasculopathy and endothelial dysfunction, which leads to painful and life-threatening clinical complications. Growing evidence supports the anti-inflammatory properties of ω-3 fatty acids in clinical models of endothelial dysfunction. Promising but limited studies show potential therapeutic effects of ω-3 fatty acid supplementation in sickle cell disease. Here, we treated humanized healthy and sickle cell mice for 6 weeks with ω-3 fatty acid diet (fish-oil diet). We found that a ω-3 fatty acid diet: (i) normalizes red cell membrane ω-6/ω-3 ratio; (ii) reduces neutrophil count; (iii) decreases endothelial activation by targeting endothelin-1 and (iv) improves left ventricular outflow tract dimensions. In a hypoxia-reoxygenation model of acute vaso-occlusive crisis, a ω-3 fatty acid diet reduced systemic and local inflammation and protected against sickle cell-related end-organ injury. Using isolated aortas from sickle cell mice exposed to hypoxia-reoxygenation, we demonstrated a direct impact of a ω-3 fatty acid diet on vascular activation, inflammation, and anti-oxidant systems. Our data provide the rationale for ω-3 dietary supplementation as a therapeutic intervention to reduce vascular dysfunction in sickle cell disease.

Topics: Anemia, Sickle Cell; Animals; Anti-Inflammatory Agents; Blood Vessels; Dietary Supplements; Disease Models, Animal; Endothelin-1; Endothelium, Vascular; Erythrocyte Membrane; Fatty Acids, Omega-3; Humans; Hypoxia; Mice; Mice, Transgenic; Neutrophils; Oxygen

The aim of this study was to evaluate the effects of acute hypobaric hypoxia (HH) on vascular reactivity and biochemical markers associated with endothelial function (EF).. Ten healthy subjects were exposed to a simulated altitude of 4,000 meters above sea level for 4 hours in a hypobaric chamber. Vascular reactivity was measured by the flow-mediated vasodilatation (FMVD) test. Endothelin-1, high sensitive-C reactive protein (hsCRP), vascular cell adhesion molecule 1, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), paraoxonase and adiponectin levels, and FMVD were evaluated before and after the exposure.. Subjects were young (age: 32±6 years), lean [body mass index: 23.9±2.0kg/m(2), waist circumference: 77(IQR: 72-80) cm], and presented normal clinical and biochemical parameters. No significant changes were evidenced in FMVD in response to HH (pre: 0.45 (0.20-0.70) vs. during: 0.50 (0.20-1.22) mm; p=0.594). On the other hand, endothelin-1 (+54%, p<0.05), hsCRP (+37%, p<0.001), IL-6 (+75%, p<0.05), TNF-α (+75%, p<0.05), and adiponectin (-39%, p<0.01) levels were significantly altered post-HH. FMVD was increased in 7 subjects, and it was decreased in 3 individuals during HH exposure. Interestingly, when EF biomarkers were compared between these two subgroups of subjects, only post exposure-adiponectin levels were significantly different (49±5 vs. 38±6μg/ml, respectively, p<0.05).. HH exposure had an effect on endothelin-1, adiponectin, hsCRP, IL-6, and TNF-α concentration. However, adiponectin was the only biomarker associated with an altered vascular reactivity.

Topics: Adiponectin; Adult; Aryldialkylphosphatase; Biomarkers; C-Reactive Protein; Endothelin-1; Endothelium, Vascular; Healthy Volunteers; Humans; Hypoxia; Interleukin-6; Male; Tumor Necrosis Factor-alpha; Vascular Cell Adhesion Molecule-1; Vasodilation; Young Adult

To investigate mechanism underlying the role of nuclear factor Kappa B (NF-κB) which induced inflammatory injury and functional lesions of aortic endothelial cells in rat with emphysema and intermittent hypoxia.. Sixty male Wistar rats were divided randomly into 4 experimental groups (n = 15 each group): control group, emphysema group, intermittent hypoxia (IH) group, emphysema with intermittent hypoxia group. The rats in control group had ad libitum access to food and water under normal circumstance. The rats in the emphysema group were exposed to cigarette smoke twice daily (30 min each time). As for IH group, the rats were exposed to intermittent hypoxia circumstance (8 h/day). Both cigarette smoke twice a day (30 min each time) and intermittent hypoxia circumstance (8 h/day) were imposed on the rats in emphysema with intermittent hypoxia group. All the rats were exposed for 8 weeks. Five rats were randomly selected from each group to measure the blood gas on the ninth week. We collected lung and endothelial tissues of thoracic aorta from the rest sacrificed rats, and observed the pathological changes of lung tissue through HE staining. The levels of ET-1, TNF-α and IL-8 in rat endothelial tissues of thoracic aorta were measured by ELISA testing. Nitrate reductase was used to measure the levels of NO, and RT-PCR to detect the levels of NF-κB mRNA, ICAM-1 mRNA, MMP-9 mRNA and eNOS mRNA.. Lung pathology and blood gas results showed that the rat model of emphysema with intermittent hypoxia was established successfully. The levels of ET-1, TNF-α, IL-8 in emphysema with intermittent hypoxia group were (172.4 ± 1.6) ng/L, (104.1 ± 1.4) ng/L, (272.1 ± 3.6) ng/L respectively, significantly higher than the control group, emphysema group and intermittent hypoxia group (all P < 0.05). The level of NO was (27.07 ± 0.57) µmol/L, which was significant reduced; the expression of NF-κB mRNA, ICAM-1 mRNA, MMP-9 mRNA in emphysema with intermittent hypoxia group was significantly upregulated compared with the control goup, emphysema group and intermittent hypoxia group (all P < 0.05). The levels of eNOS mRNA expression were significantly lower than other three groups. The expression of NF-κB mRNA was positively correlated with MMP-9 mRNA level (r = 0.572, P < 0.001) and the expression of NF-κB mRNA was negatively correlated with eNOS mRNA level (r = 0.534, P < 0.001); there was no statistical difference in levels of NF-κB mRNA and eNOS mRNA expression between intermittent hypoxia and emphysema group (P > 0.05).. Compared with only emphysema or intermittent hypoxia exposure, inflammatory injury of aortic endothelial cells of rats induced by emphysema with intermittent hypoxia was more serious, and may result in more serious cardiovascular complications. The activation of NF-κB pathway may be an important mechanism of its inflammatory response.

Topics: Animals; Aorta; Disease Models, Animal; Endothelial Cells; Endothelin-1; Hypoxia; Inflammation; Intercellular Adhesion Molecule-1; Interleukin-8; Lung; Male; Matrix Metalloproteinase 9; NF-kappa B; Nitric Oxide; Nitric Oxide Synthase Type III; Pulmonary Emphysema; Rats; Rats, Wistar; Smoke; Tumor Necrosis Factor-alpha

Pulmonary arterial hypertension (PAH) is a fatal disease that eventually results in right heart failure and death. Current pharmacologic therapies for PAH are limited, and there are no drugs that could completely cure PAH. Enhanced activity of endothelin system has been implicated in PAH severity and endothelin receptor antagonists have been used clinically to treat PAH. However, there is limited experimental evidence on the direct role of enhanced endothelin system activity in PAH. Here, we investigated the correlation between endothelin-1 (ET-1) and PAH using ET-1 transgenic (ETTG) mice. Exposure to chronic hypoxia increased right ventricular pressure and pulmonary arterial wall thickness in ETTG mice compared to those in wild type mice. Of note, ETTG mice exhibited modest but significant increase in right ventricular pressure and vessel wall thickness relative to wild type mice even under normoxic conditions. To induce severe PAH, we administered SU5416, a vascular endothelial growth factor receptor inhibitor, combined with exposure to chronic hypoxia. Treatment with SU5416 modestly aggravated hypoxia-induced pulmonary hypertension, right ventricular hypertrophy, and pulmonary arterial vessel wall thickening in ETTG mice in association with increased interleukin-6 expression in blood vessels. However, there was no sign of obliterative endothelial cell proliferation and plexiform lesion formation in the lungs. These results demonstrated that enhanced endothelin system activity could be a causative factor in the development of PAH and provided rationale for the inhibition of endothelin system to treat PAH.

Topics: Animals; Biomarkers; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Male; Mice; Mice, Transgenic; Pulmonary Artery

Krüppel-like factor 4 (KLF4) is a transcription factor expressed in the vascular endothelium, where it promotes anti-inflammatory and anticoagulant states, and increases endothelial nitric oxide synthase expression. We examined the role of endothelial KLF4 in pulmonary arterial (PA) hypertension (PAH). Mice with endothelial KLF4 knockdown were exposed to hypoxia for 3 weeks, followed by measurement of right ventricular and PA pressures, pulmonary vascular muscularization, and right ventricular hypertrophy. The effect of KLF4 on target gene expression was assessed in lungs from these mice, verified in vitro by small interfering RNA (siRNA) knockdown of KLF4, and further studied at the promoter level with cotransfection experiments. KLF4 expression was measured in lung tissue from patients with PAH and normal control subjects. We found that, after hypoxia, right ventricular and PA pressures were significantly higher in KLF4 knockdown animals than controls. Knockdown animals also had more severe pulmonary vascular muscularization and right ventricular hypertrophy. KLF4 knockdown resulted in increased pulmonary expression of endothelin-1 and decreased expression of endothelial nitric oxide synthase, endothelin receptor subtype B, and prostacyclin synthase. Concordant findings were observed in vitro, both with siRNA knockdown of KLF4 and promoter activity assays. Finally, KLF4 expression was reduced in lungs from patients with PAH. In conclusion, endothelial KLF4 regulates the transcription of genes involved in key pathways implicated in PAH, and its loss exacerbates pulmonary hypertension in response to chronic hypoxia in mice. These results introduce a novel transcriptional modulator of PAH, with the potential of becoming a new therapeutic target.

Topics: Animals; Arterial Pressure; Case-Control Studies; Cells, Cultured; Cytochrome P-450 Enzyme System; Disease Models, Animal; Endothelial Cells; Endothelin-1; Familial Primary Pulmonary Hypertension; Human Umbilical Vein Endothelial Cells; Humans; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Intramolecular Oxidoreductases; Kruppel-Like Factor 4; Kruppel-Like Transcription Factors; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Nitric Oxide Synthase Type III; Pulmonary Artery; Receptor, Endothelin B; RNA Interference; Time Factors; Transfection; Ventricular Function, Right; Ventricular Pressure

Sleep apnea (SA), defined as intermittent respiratory arrest during sleep, is associated with increased incidence of hypertension, peripheral vascular disease, stroke, and sudden cardiac death. We have shown that intermittent hypoxia with CO2 supplementation (IH), a model for SA, increases blood pressure and circulating ET-1 levels, upregulates lung pre-pro ET-1 mRNA, increases vasoconstrictor reactivity to ET-1 in rat small mesenteric arteries (MA) and increases vascular reactive oxygen species (ROS). NFAT activity is increased in the aorta (AO) and MA of mice exposed to IH in an ET-1-dependent manner, and the genetic ablation of the isoform NFATc3 prevents IH-induced hypertension. We hypothesized that IH causes an increase in arterial ROS generation, which activates NFATc3 to increase vasoconstrictor reactivity to ET-1. In support of our hypothesis, we found that IH increases ROS in AO and MA. In vivo administration of the SOD mimetic tempol during IH exposure prevents IH-induced increases in NFAT activity in mouse MA and AO. We found that IH causes an NFATc3-dependent increase in vasoconstrictor reactivity to ET-1, accompanied by an increase in vessel wall [Ca²⁺]. Our results indicate that IH exposure causes an increase in arterial ROS to activate NFATc3, which then increases vasoconstrictor reactivity and Ca²⁺ response to ET-1. These studies highlight a novel regulatory pathway, and demonstrate the potential clinical relevance of NFAT inhibition to prevent hypertension in SA patients.

Topics: Animals; Calcium; Endothelin-1; Female; Hypoxia; Kv1.5 Potassium Channel; Male; Mice; Mice, Inbred BALB C; NFATC Transcription Factors; Protein Carbonylation; Rats; Reactive Oxygen Species; Sleep Apnea Syndromes; TRPC Cation Channels; TRPC6 Cation Channel; Vasoconstriction

Sleep apnea is associated with cardiovascular disease, and patients with sleep apnea have elevated plasma endothelin (ET)-1 concentrations. Rats exposed to intermittent hypoxia (IH), a model of sleep apnea, also have increased plasma ET-1 concentrations and heightened constriction to ET-1 in mesenteric arteries without an increase in global vascular smooth muscle cell Ca(2+) concentration ([Ca(2+)]). Because ET-1 has been shown to increase the occurrence of propagating Ca(2+) waves, we hypothesized that ET-1 increases Ca(2+) wave activity in mesenteric arteries, rather than global [Ca(2+)], to mediate enhanced vasoconstriction after IH exposure. Male Sprague-Dawley rats were exposed to sham or IH conditions for 7 h/day for 2 wk. Mesenteric arteries from sham- and IH-exposed rats were isolated, cannulated, and pressurized to 75 mmHg to measure ET-1-induced constriction as well as changes in global [Ca(2+)] and Ca(2+) wave activity. A low concentration of ET-1 (1 nM) elicited similar vasoconstriction and global Ca(2+) responses in the two groups. Conversely, ET-1 had no effect on Ca(2+) wave activity in arteries from sham rats but significantly increased wave frequency in arteries from IH-exposed rats. The ET-1-induced increase in Ca(2+) wave frequency in arteries from IH rats was dependent on phospholipase C and inositol 1,4,5-trisphosphate receptor activation, yet inhibition of phospholipase C and the inositol 1,4,5-trisphosphate receptor did not prevent ET-1-mediated vasoconstriction. These results suggest that although ET-1 elevates Ca(2+) wave activity after IH exposure, increases in wave activity are not associated with increased vasoconstriction.

Topics: Animals; Arterial Pressure; Calcium Signaling; Disease Models, Animal; Endothelin-1; Hypoxia; Inositol 1,4,5-Trisphosphate; Inositol 1,4,5-Trisphosphate Receptors; Male; Mesenteric Arteries; Phosphodiesterase Inhibitors; Rats; Rats, Sprague-Dawley; Second Messenger Systems; Time Factors; Type C Phospholipases; Vasoconstriction; Vasoconstrictor Agents

Hypoxia is a major stress on fetal development and leads to induction of endothelin-1 (ET-1) expression. We tested the hypothesis that ET-1 stimulates the terminal differentiation of cardiomyocytes from mononucleate to binucleate in the developing heart.. Hypoxia (10.5% O2) treatment of pregnant rats from day 15 to day 21 resulted in a significant increase in prepro-ET-1 mRNA expression in fetal hearts. ET-1 ex vivo treatment of fetal rat cardiomyocytes increased percent binucleate cells and decreased Ki-67 expression, a marker for proliferation, under both control and hypoxic conditions. Hypoxia alone decreased Ki-67 expression and in conjunction with ET-1 treatment decreased cardiomyocyte size. PD145065, a non-selective ET-receptor antagonist, blocked the changes in binucleation and proliferation caused by ET-1. DNA methylation in fetal cardiomyocytes was significantly increased with ET-1 treatment, which was blocked by 5-aza-2'-deoxycytidine, a DNA methylation inhibitor. In addition, 5-aza-2'-deoxycytidine treatment abrogated the increase in binucleation and decrease in proliferation induced by ET-1.. Hypoxic stress and synthesis of ET-1 increases DNA methylation and promotes terminal differentiation of cardiomyocytes in the developing heart. This premature exit of the cell cycle may lead to a reduced cardiomyocyte endowment in the heart and have a negative impact on cardiac function.

Topics: Animals; DNA Methylation; Endothelin-1; Enzyme-Linked Immunosorbent Assay; Female; Hypoxia; Immunohistochemistry; Myocytes, Cardiac; Pregnancy; Real-Time Polymerase Chain Reaction

To study the selective dilatation effects of iptakalim (Ipt) on basilar and pulmonary arterioles, and endothelial cell function of these arterioles in hypoxic rats.. SD male rats were divided into 2 groups:control and hypoxic group fed in normobaric hypoxic environment (O2 7.8%, 8 h). Arteriole rings about (204 + 5) pm were isolated and the tension of hypoxic arterioles pre-contracted by 6 nmol/L endothelin-1 (ET-1) was observed with wire myograph system model (DMT 610 m). The relaxing response of hypoxic arterioles induced by different concentration of Ipt were detected and endothelial activity was also tested by acetylcholine.. 10(5) mol/L acetylcholine (ACh)-mediated vasodilatation of basilar and pulmonary arterioles was greatly reduced in the hypoxic group than those in control group (P < 0.05). Compared with normal group, a novel ATP-sensitive potassium channel opener Ipt at the concentration ranging from 10(-11) mol/L to 10(3) mol/L, caused stronger dose dependent vasodilatation on hypoxic pulmonary arterioles, and there was no significant difference between control and hypoxic basilar arterioles.. The endothelial function of basilar and pulmonary arterioles was damaged under hypoxic state, and Ipt selectively increased dilatation effects on hypoxic pulmonary arterioles, but not on hypoxic basilar arterioles which could improve high altitude pulmonary edema pathological state and be the novel drug in the treatment of pulmonary hypertension.

Topics: Acetylcholine; Altitude; Altitude Sickness; Animals; Arterioles; Dilatation; Endothelin-1; Hypoxia; KATP Channels; Male; Propylamines; Rats; Vasodilation; Vasodilator Agents

Pulmonary hypertension (PH) is characterized by enhanced pulmonary artery smooth muscle cell (PASMC) proliferation leading to vascular remodeling. Although, multiple factors have been associated with pathogenesis of PH the underlying mechanisms are not fully understood. Here, we hypothesize that already very short exposure to hypoxia may activate molecular cascades leading to vascular remodeling. Microarray studies from lung homogenates of mice exposed to only 3h of hypoxia revealed endothelin-1 (ET-1) and connective tissue growth factor (CTGF) as the most upregulated genes, and the mitogen-activated protein kinase (MAPK) pathway as the most differentially regulated pathway. Evaluation of these results in vitro showed that ET-1 but not CTGF stimulation of human PASMCs increased DNA synthesis and expression of proliferation markers such as Ki67 and cell cycle regulator, cyclin D1. Moreover, ET-1 treatment elevated extracellular signal-regulated kinase (Erk)-dependent c-fos expression and phosphorylation of c-fos and c-jun transcription factors. Silencing of c-fos with siRNA abrogated the ET-1-induced proliferation of PASMCs. Expression and immunohistochemical analyses revealed higher levels of total and phosphorylated c-fos and c-jun in the vessel wall of lung samples of human idiopathic pulmonary arterial hypertension patents, hypoxia-exposed mice and monocrotaline-treated rats as compared to control subjects. These findings shed the light on the involvement of c-fos/c-jun in the proliferative response of PASMCs to ET-1 indicating that already very short hypoxia exposure leads to the regulation of mediators involved in vascular remodeling underlying PH.

Topics: Animals; Apoptosis; Biomarkers; Blotting, Western; Case-Control Studies; Cell Proliferation; Cells, Cultured; Endothelin-1; Extracellular Signal-Regulated MAP Kinases; Familial Primary Pulmonary Hypertension; Fluorescent Antibody Technique; Gene Expression Profiling; Humans; Hypoxia; Immunoenzyme Techniques; Lung; Male; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mitogen-Activated Protein Kinases; Muscle, Smooth, Vascular; Oligonucleotide Array Sequence Analysis; Phosphorylation; Proto-Oncogene Proteins c-fos; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Signal Transduction

Cerebral edema is a potentially life-threatening illness, but knowledge of its underlying mechanisms is limited. Here we report that hypobaric hypoxia induces rat cerebral edema and neuronal apoptosis and increases the expression of corticotrophin releasing factor (CRF), CRF receptor type 1 (CRFR1), aquaporin-4 (AQP4), and endothelin-1 (ET-1) in the cortex. These effects, except for the increased expression of CRF itself, could all be blocked by pretreatment with an antagonist of the CRF receptor CRFR1. We also show that, in cultured primary astrocytes: (i) both CRFR1 and AQP4 are expressed; (ii) exogenous CRF, acting through CRFR1, triggers signaling of cAMP/PKA, intracellular Ca(2+), and PKCε; and (iii) the up-regulated cAMP/PKA signaling contributes to the phosphorylation and expression of AQP4 to enhance water influx into astrocytes and produces an up-regulation of ET-1 expression. Finally, using CHO cells transfected with CRFR1(+) and AQP4(+), we show that transfected CRFR1(+) contributes to edema via transfected AQP4(+). In conclusion, hypoxia triggers cortical release of CRF, which acts on CRFR1 to trigger signaling of cAMP/PKA in cortical astrocytes, leading to activation of AQP4 and cerebral edema.

Topics: Animals; Apoptosis; Aquaporin 4; Astrocytes; Brain Edema; CHO Cells; Corticotropin-Releasing Hormone; Cricetinae; Cricetulus; Endothelin-1; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Male; Neurons; Phosphorylation; Rats, Sprague-Dawley; Receptors, Corticotropin-Releasing Hormone; Signal Transduction; Transfection; Up-Regulation

To observe the effect of chronic intermittent hypoxia (CIH) on rat cardiac function and blood pressure, and the protective role of adiponectin (Ad).. A total of 24 male Wistar rats were randomly and equally divided into 3 groups: normal control group (NC group), chronic intermittent hypoxygen group (CIH group) and CIH+Ad group. Normal air breathing for NC group and CHI for CIH and CIH+Ad groups were conducted for 28 days. In addition, rats in CIH+Ad group were given intravenous adiponectin at a dosage of 20 µg each time, once a week for successive 4 weeks. The results of echocardiography, blood pressure, plasma adiponectin, endothelin-1 (ET-1) and endothelial nitric oxide synthase (eNOS) were compared among the three groups after 28 days.. HE stain showed that the myocardial cells of CIH rats were damaged by CIH. Compared with NC group, rats in CIH group presented with a greater heart/body weight ratio (0.070 ± 0.008 vs. 0.057 ± 0.009, P < 0.05) and systolic blood pressure [(132 ± 4) vs. (123 ± 6) mmHg(1 mmHg = 0.133 kPa), P < 0.05] and a lower LVEF [(70.3 ± 4.1)% vs. (84.1 ± 2.5)%, P < 0.05]. Plasma ET-1 was increased while NO(-)(2)/NO(-)(3) and eNOS decreased in CIH group, compared with NC group [(26.2 ± 6.9) ng/L vs. (7.7 ± 2.7) ng/L, (37 ± 9) µmol/L vs. (65 ± 10) µmol/L, (18 ± 5)µg/L vs. (27 ± 6) µg/L, respectively; P < 0.05]. The heart/body weight ratio, blood pressure and LVEF were improved in CIH+Ad group compared with those in CIH group [0.064 ± 0.009 vs. 0.070 ± 0.008, (127 ± 6) mmHg vs. (132 ± 4) mmHg, P > 0.05; (79 ± 7)% vs. (70 ± 4)%, P < 0.05; respectively]. Plasma ET-1 levels in CIH+Ad and CIH groups showed no significant difference, but were significantly lower in NC group. However, rats in CIH+Ad group had a higher NO(-)(2)/NO(-)(3) level than that in CIH group. Bivariate Correlations showed that NO(-)(2)/NO(-)(3) and eNOS were negatively correlated with systolic blood pressure while heart/body weight ratio, LVEDs, ET-1 and NO(-)(2)/NO(-)(3) were negatively correlated with left ventricular ejection fraction.. Through xidative stress, ET-1 and NO imbalance and impaired vascular endothelial function, cardiac function could be damaged by CIH in rats, while supplement of extrinsic adiponectin could improve these damages.

Topics: Adiponectin; Animals; Blood Pressure; Endothelin-1; Hypoxia; Male; Nitric Oxide Synthase Type III; Rats; Rats, Wistar

Accumulating evidence reveals that intrauterine growth retardation (IUGR) can cause varying degrees of pulmonary arterial hypertension (PAH) later in life. Moreover, epigenetics plays an important role in the fetal origin of adult disease. The goal of this study was to investigate the role of epigenetics in the development of PAH following IUGR.. The IUGR rats were established by maternal undernutrition during pregnancy. Pulmonary vascular endothelial cells (PVEC) were isolated from the rat lungs by magnetic-activated cell sorting (MACS). We investigated epigenetic regulation of the endothelin-1 (ET-1) gene in PVEC of 1-day and 6-week IUGR rats, and response of IUGR rats to hypoxia.. The maternal nutrient restriction increased the histone acetylation and hypoxia inducible factor-1α (HIF-1α) binding levels in the ET-1 gene promoter of PVEC in IUGR newborn rats, and continued up to 6 weeks after birth. These epigenetic changes could result in an IUGR rat being highly sensitive to hypoxia later in life, causing more significant PAH or pulmonary vascular remodeling.. These findings suggest that epigenetics is closely associated with the development of hypoxic PAH following IUGR, further providing a new insight for improved prevention and treatment of IUGR-related PAH.

Topics: Acetylation; Actins; Age Factors; Animals; Animals, Newborn; Binding Sites; Blood Pressure; Cell Separation; Disease Models, Animal; Endothelial Cells; Endothelin-1; Epigenesis, Genetic; Familial Primary Pulmonary Hypertension; Female; Fetal Growth Retardation; Flow Cytometry; Histones; Hypertension, Pulmonary; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Lung; Pregnancy; Promoter Regions, Genetic; Pulmonary Artery; Rats; Rats, Sprague-Dawley

To investigate the association between pulmonary vascular remodeling and expression of hypoxia-inducible factor-1α (HIF-1α), endothelin-1 (ET-1) and inducible nitric oxide synthase (iNOS) in pulmonary vessels in neonatal rats with hypoxic pulmonary hypertension (HPH).. A neonatal rat model of HPH was established as an HPH group, and normal neonatal rats were enrolled as a control group. The mean pulmonary arterial pressure (mPAP) was measured. The percentage of medial thickness to outer diameter of the small pulmonary arteries (MT%) and the percentage of medial cross-section area to total cross-section area of the pulmonary small arteries (MA%) were measured as the indicators for pulmonary vascular remodeling. The immunohistochemical reaction intensities for HIF-1α, ET-1 and iNOS and their mRNA expression in lung tissues of neonatal rats were measured. Correlation analysis was performed to determine the relationship between pulmonary vascular remodeling and mRNA expression of HIF-1α, ET-1 and iNOS.. The mPAP of the HPH group kept increasing on days 3, 5, 7, 10, 14, and 21 of hypoxia, with a significant difference compared with the control group (P<0.05). The HPH group had significantly higher MT% and MA% than the control group from day 7 of hypoxia (P<0.05). HIF-1α protein expression increased significantly on days 3, 5, 7 and 10 days of hypoxia, and HIF-1α mRNA expression increased significantly on days 3, 5 and 7 days of hypoxia in the HPH group compared with the control group (P<0.05). ET-1 protein expression increased significantly on days 3, 5 and 7 days of hypoxia and ET-1 mRNA expression increased significantly on day 3 of hypoxia in the HPH group compared with the control group (P<0.05). Both iNOS protein and mRNA expression were significantly higher on days 3, 5 and 7 days of hypoxia than the control group (P<0.05). Both MT% and MA% were positively correlated with HIF-1α mRNA expression (r=0.835 and 0.850 respectively; P<0.05).. Pulmonary vascular remodeling is developed on day 7 of hypoxia in neonatal rats. HIF-1α, ET-1 and iNOS are all involved in the occurrence and development of HPH in neonatal rats.

Topics: Animals; Animals, Newborn; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Immunohistochemistry; Nitric Oxide Synthase Type II; Pulmonary Artery; Rats; Rats, Wistar

Elevated reactive oxygen species are implicated in pulmonary hypertension (PH). Superoxide dismutase (SOD) limits superoxide bioavailability, and decreased SOD activity is associated with PH. A decrease in SOD activity is expected to increase superoxide and reduce hydrogen peroxide levels. Such an imbalance of superoxide/hydrogen peroxide has been implicated as a mediator of nuclear factor of activated T cells (NFAT) activation in epidermal cells. We have shown that NFATc3 is required for chronic hypoxia-induced PH. However, it is unknown whether NFATc3 is activated in the pulmonary circulation in a mouse model of decreased SOD1 activity and whether this leads to PH. Therefore, we hypothesized that an elevated pulmonary arterial superoxide/hydrogen peroxide ratio activates NFATc3, leading to PH. We found that SOD1 knockout (KO) mice have elevated pulmonary arterial wall superoxide and decreased hydrogen peroxide levels compared with wild-type (WT) littermates. Right ventricular systolic pressure (RVSP) was elevated in SOD1 KO and was associated with pulmonary arterial remodeling. Vasoreactivity to endothelin-1 was also greater in SOD1 KO vs. WT mice. NFAT activity and NFATc3 nuclear localization were increased in pulmonary arteries from SOD1 KO vs. WT mice. Administration of A-285222 (selective NFAT inhibitor) decreased RVSP, arterial wall thickness, vasoreactivity, and NFAT activity in SOD1 KO mice to WT levels. The SOD mimetic, tempol, also reduced NFAT activity, NFATc3 nuclear localization, and RVSP to WT levels. These findings suggest that an elevated superoxide/hydrogen peroxide ratio activates NFAT in pulmonary arteries, which induces vascular remodeling and increases vascular reactivity leading to PH.

Topics: Animals; Cyclic N-Oxides; Endothelin-1; Female; Hydrogen Peroxide; Hypertension, Pulmonary; Hypoxia; Male; Mice; Mice, Knockout; NFATC Transcription Factors; Pulmonary Artery; Pyrazoles; Spin Labels; Superoxide Dismutase; Superoxide Dismutase-1; Superoxides

Exposure to high altitude is a well-known environmental stress with physiological and metabolic consequences, with the major stressor being hypobaric hypoxia. The disruption in cellular homeostasis elicits several acute and chronic adaptations designed to diminish the stress imposed by the hypoxic insult. Highly conserved cellular machinery protects the myocardium from damage under reduced oxygen tension. In the present study, adult Sprague-Dawley rats were exposed to an altitude of 9754 m in a decompression chamber and screened on the basis of the time taken for onset of gasping. The animals were grouped as susceptible (<10 min), normal (10-25 min), and tolerant (>25 min). Histologically, susceptible animals showed increased myocardial inflammation and infiltration and greater CK-MB activity. These animals showed a three-fold increase in reactive oxygen species levels and subsequent oxidative damage to proteins and lipids as compared to control unexposed group. In tolerant animals, the damage was minimal. The resistance to damage in these animals was possibly due to enhanced myocardial antioxidant enzymes, catalase and superoxide dismutase. A significantly higher expression of HIF-1α and its responsive genes, including EPO, HO-1, and GLUT1, was seen in tolerant animals, although VEGF expression was enhanced in the susceptible group. Cytoprotective chaperones, HSP70 and HSP90, were elevated in the tolerant animals. The differential expression of these hypoxia-responsive molecules may thus act as potential biochemical markers for screening and identifying individuals susceptible to environmental stress.

Topics: Altitude; Animals; Atmospheric Pressure; Catalase; Creatine Kinase, MB Form; Dyspnea; Endothelin-1; Erythropoietin; Heme Oxygenase-1; HSP70 Heat-Shock Proteins; HSP90 Heat-Shock Proteins; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Male; Malondialdehyde; Myocarditis; Myocardium; Nitric Oxide; Oxidative Stress; Protein Carbonylation; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Superoxide Dismutase; Time Factors; Up-Regulation; Vascular Endothelial Growth Factor A

Obstructive sleep apnoea (OSA) is a risk factor for cardiovascular disorders and in some cases is complication of pulmonary hypertension. We simulated OSA by exposing rats to cyclic intermittent hypoxia (CIH) to investigate its effect on pulmonary vascular endothelial dysfunction. Sprague-Dawley Rats were exposed to CIH (FiO2 9% for 1 min, repeated every 2 min for 8 h/day, 7 days/wk for 3 wk), and the pulmonary arteries of normoxia and CIH treated rats were analyzed for expression of endothelin-1 (ET-1) and ET receptors by histological, immunohistochemical, RT-PCR and Western Blot analyses, as well as for contractility in response to ET-1. In the pulmonary arteries, ET-1 expression was increased, and ET-1 more potently elicited constriction of the pulmonary artery in CIH rats than in normoxic rats. Exposure to CIH induced marked endothelial cell damage associated with a functional decrease of endothelium-dependent vasodilatation in the pulmonary artery. Compared with normoxic rats, ETA receptor expression was increased in smooth muscle cells of the CIH rats, while the expression of ETB receptors was decreased in endothelial cells. These results demonstrated endothelium-dependent vasodilation was impaired and the vasoconstrictor responsiveness increased by CIH. The increased responsiveness to ET-1 induced by intermittent hypoxia in pulmonary arteries of rats was due to increased expression of ETA receptors predominantly, meanwhile, decreased expression of ETB receptors in the endothelium may also participate in it.

Topics: Animals; Endothelin-1; Endothelium, Vascular; Gene Expression Regulation; Hypertension, Pulmonary; Hypoxia; Male; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Receptors, Endothelin; Sleep Apnea, Obstructive; Vasoconstriction; Vasodilation

The effects of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor apocynin on the enhanced hypoxia induced factor-1α (HIF-1α) and endothelin-1 (ET-1) expression, elevated systolic blood pressure under chronic intermittent hypoxia (CIH) condition and its action mechanism were investigated. Thirty healthy 8-week old Sprague-Dawley (SD) male rats were randomly divided into three groups (n=10 each): sham group, CIH group, and apocynin-treated CIH group. Tail artery systolic blood pressure was measured by tail-cuff method. Real-time fluorescence quantitative polymerase chain reaction (PCR) was used to detect the mRNA expression of HIF-1α and ET-1 in the carotid body, and the HIF-1α protein expression was examined by using Western blotting. The levels of malondialdehyde (MDA) and superoxide dismutase (SOD) were determined by using colorimetric method. In addition, the plasma ET-1 and HIF-1α levels were measured by using enzyme-linked immunosorbent assay. It was found that CIH exposure was associated with increased MDA levels, and apocynin-treated CIH animals showed reduction in MDA levels. Apocynin treatment prevented CIH-induced hypertension as well as CIH-induced decrease in SOD. The increases of HIF-1α and ET-1 mRNA along with HIF-1α protein expression in the carotid body, and elevated circulating HIF-1α and ET-1 levels were observed in CIH-exposed animals. Treatment with apocynin significantly decreased the ET-1 mRNA, HIF-1α protein expression and circulating HIF-1α level in CIH-exposed animals, and there was no statistically significant difference in the HIF-1α mRNA expression between CIH group and apocynin-treated group. These results indicated that apocynin alleviated CIH-induced hypertension by inhibiting NADPH oxidase, further leading to the reduced vasoconstrictor ET-1 level and oxidative stress. HIF-1α/ET-1 system signal pathway may interact with CIH-induced NADPH oxidase-dependent oxidative stress. Inhibition of NADPH oxidase activity may hopefully serve as a useful strategy for prevention and treatment of obstructive sleep apnea hypopnea syndrome-induced hypertension.

Topics: Acetophenones; Animals; Antioxidants; Carotid Body; Endothelin-1; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Male; NADP; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Treatment Outcome

Chronic intermittent hypoxia (CIH) contributes to the development of cardiovascular diseases in patients with obstructive sleep apnoea. Many studies have shown an association between increased circulating endothelin (ET)-1 levels and CIH. The aim of the present study was to determine the role of ET receptors in altered aortic function in an animal model of CIH. Rats were subjected to CIH (Fi o2 9% for 1 min, repeated every 2 min for 8 h/day, 7 days/week) for 3 weeks. After 3 weeks, the rats were killed and their aortas retrieved for use in in vitro experiments (isometric force measurement), histological analysis, immunohistochemistry and western blotting. Aortas from rats subjected to CIH exhibited marked endothelial dysfunction and increased responsiveness to ET-1. Furthermore, CIH induced increased ET-1 and ETA receptor expression, whereas ETB receptor expression was decreased. Aortic contractile responses to ET-1 were inhibited by the ETA and ETB receptor antagonists BQ-123 and BQ-788, respectively. Acetylcholine-induced relaxation responses were significantly attenuated in aortas from rats subjected to CIH, whereas CIH had no significant effect on aortic responses to sodium nitroprusside. The results of the present study suggest that increased expression of ETA receptors, which mediate a potent vasoconstrictor response, plays an important role in the pathogenesis of CIH. In addition, decreased endothelial ETB receptor expression, which is associated with the functional decline of endothelium-dependent vasodilation, also contributes to the pathogenesis of CIH. It appears that the ETB receptor-induced buffering of ET-1 responsiveness is mediated via a nitric oxide-dependent mechanism.

Topics: Animals; Aorta; Disease Models, Animal; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Endothelin-1; Endothelium, Vascular; Hypoxia; Male; Nitric Oxide; Nitric Oxide Synthase Type III; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptor, Endothelin B; Vasoconstriction; Vasodilation

Preeclampsia is a life-threatening pregnancy disorder. However, its pathogenesis remains unclear. We tested the hypothesis that gestational hypoxia induces preeclampsia-like symptoms via heightened endothelin-1 (ET-1) signaling. Time-dated pregnant and nonpregnant rats were divided into normoxic and hypoxic (10.5% O2 from the gestational day 6-21) groups. Chronic hypoxia had no significant effect on blood pressure or proteinuria in nonpregnant rats but significantly increased blood pressure on day 12 (systolic blood pressure, 111.7 ± 6.1 versus 138.5 ± 3.5 mm Hg; P=0.004) and day 20 (systolic blood pressure, 103.4 ± 4.6 versus 125.1 ± 6.1 mm Hg; P=0.02) in pregnant rats and urine protein (μg/μL)/creatinine (nmol/μL) ratio on day 20 (0.10 ± 0.01 versus 0.20 ± 0.04; P=0.04), as compared with the normoxic control group. This was accompanied with asymmetrical fetal growth restriction. Hypoxia resulted in impaired trophoblast invasion and uteroplacental vascular remodeling. In addition, plasma ET-1 levels, as well as the abundance of prepro-ET-1 mRNA, ET-1 type A receptor and angiotensin II type 1 receptor protein in the kidney and placenta were significantly increased in the chronic hypoxic group, as compared with the control animals. Treatment with the ET-1 type A receptor antagonist, BQ123, during the course of hypoxia exposure significantly attenuated the hypoxia-induced hypertension and other preeclampsia-like features. The results demonstrate that chronic hypoxia during gestation induces preeclamptic symptoms in pregnant rats via heightened ET-1 and ET-1 type A receptor-mediated signaling, providing a molecular mechanism linking gestational hypoxia and increased risk of preeclampsia.

Topics: Animals; Blood Pressure; Disease Models, Animal; Endothelin A Receptor Antagonists; Endothelin-1; Female; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Kidney; Peptides, Cyclic; Placenta; Pre-Eclampsia; Pregnancy; Proteinuria; Rats; Rats, Sprague-Dawley; Receptor, Angiotensin, Type 1; Signal Transduction

To investigate the influence of exposure to high-altitude (HA) hypoxia on the expressions of endothelin-1 (ET-1), endothelin type A (ETA) and endothelin type B (ETB) receptors in broiler chickens, immunohistochemistry studies were performed in the lungs. Six hundred 1-day-old male broiler chickens were randomly divided into two groups: group A, birds maintained under rich oxygen conditions (oxygen content 21%); and group B, birds exposed to HA hypoxia (oxygen content 13%). Our data showed that exposure to altitude elevated ET-1 and ETA gene expressions at 21 and 28 days of age when compared with the rich oxygen group. Meanwhile, a marked decline in ETB expression was observed at 28 days of age in the course of HA, although there were no significant changes (P>0.05) at 7, 14 and 21 days of age. The increased response was accompanied by adverse effects on weekly body weight gain and ascites mortality. These observations suggested that ET-1, ETA and ETB genes are normally expressed in the lungs of birds. Increased levels of ET-1 and ETA and decreased ETB gene expression in the lungs are probably involved in the lung dysfunction of broiler chickens with developmental ascites.

Topics: Altitude; Animals; Ascites; Chickens; Down-Regulation; Endothelin-1; Gene Expression Regulation; Hypoxia; Lung; Male; Oxygen; Random Allocation; Receptors, Endothelin; Up-Regulation; Weight Gain

Chronic intermittent hypoxia (CIH) leads to remodelling of the carotid body function, manifested by an augmented sensory response to hypoxia and induction of sensory long-term facilitation (LTF). It was proposed that endothelin-1 (ET-1) contributes to CIH-induced hypoxic hypersensitivity of the carotid body. The objectives of the present study were as follows: (i) to delineate the mechanisms by which CIH upregulates ET-1 expression in the carotid body; and (ii) to assess whether ET-1 also contributes to sensory LTF. Experiments were performed on adult, male rats exposed to alternating cycles of 5% O2 (15 s) and room air (5 min), nine episodes per hour and 8 h per day for 10 days. Chronic intermittent hypoxia increased ET-1 levels in glomus cells without significantly altering prepro-endothelin-1 mRNA levels. The activity of endothelin-converting enzyme increased with concomitant elevation of ET-1 levels in CIH-exposed carotid bodies, and MnTMPyP, a membrane-permeable antioxidant, prevented these effects. Hypoxia facilitated ET-1 release from CIH-treated carotid bodies, which is a prerequisite for activation of ET receptors; however, hypoxia had no effect on ET-1 release from control carotid bodies. In CIH-exposed carotid bodies, mRNAs encoding ETA receptor were upregulated, and an ETA receptor-specific antagonist abolished CIH-induced hypersensitivity of the hypoxic response, whereas it had no effect on the sensory LTF. These results suggest that ECE-dependent increased production of ET-1 coupled with hypoxia-evoked ET-1 release and the ensuing ETA receptor activation mediate the CIH-induced carotid body hypersensitivity to hypoxia, but the ETA signalling pathway is not associated with sensory LTF elicited by CIH.

Topics: Animals; Antioxidants; Aspartic Acid Endopeptidases; Carotid Body; Endothelin-1; Endothelin-Converting Enzymes; Enzyme Activation; Hypoxia; Male; Metalloendopeptidases; Metalloporphyrins; Neuronal Plasticity; Oxidative Stress; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; RNA, Messenger

Prenatal hypoxia can alter the growth trajectory of the fetus and cause lasting health complications including vascular dysfunction. We hypothesized that offspring that were intrauterine growth restricted (IUGR) because of prenatal hypoxia would exhibit altered vascular endothelin-1 (ET-1) signaling in later life. Isolated mesenteric artery responses to big ET-1 (bET-1) and ET-1 were assessed by using wire myography. Male IUGR offspring had 3-fold greater bET-1-induced vasoconstriction compared with controls (n=7 per group; P<0.001); NO synthase inhibition with L-N(G)-nitro-arginine-methyl ester potentiated bET-1-induced vasoconstriction, albeit this effect was 2-fold greater (P<0.05) in male control compared with IUGR offspring. Vascular responses to bET-1 were similar between female IUGR and control offspring (n=9-11 per group). In the presence of L-N(G)-nitro-arginine-methyl ester, pretreatment with the chymase inhibitor chymostatin, the gelatinase inhibitor GM6001, or the neutral endopeptidase inhibitor thiorphan did not alter responses to bET-1; however, the ET-converting enzyme inhibitor CGS35066 almost completely abolished vascular responses to bET-1 in control and IUGR groups. Systolic blood pressure in IUGR male offspring was more responsive to ET-1 antagonism in vivo compared with controls (-9 versus -4 mm Hg; n=5 per group; P=0.02); no such differences were observed in female offspring (n=5-6 per group). These results demonstrate that vascular ET-1 function is programmed by prenatal hypoxia and provide further insights into the sex differences in the long-term vascular effects of developmental stressors.

Topics: Animals; Blood Pressure; Dose-Response Relationship, Drug; Endothelin-1; Endothelium, Vascular; Female; Fetal Growth Retardation; Hypoxia; Male; Mesenteric Arteries; Nitric Oxide; Pregnancy; Prenatal Exposure Delayed Effects; Rats; Rats, Sprague-Dawley; Sex Factors; Vasoconstriction

Topics: Animals; Endothelin-1; Female; Fetal Growth Retardation; Hypoxia; Male; Mesenteric Arteries; Pregnancy; Prenatal Exposure Delayed Effects

Pulmonary hypertension (PH) is a serious disorder that causes significant morbidity and mortality. The pathogenesis of PH involves complex derangements in multiple pathways including reductions in peroxisome proliferator-activated receptor gamma (PPARγ). Hypoxia, a common PH stimulus, reduces PPARγ in experimental models. In contrast, activating PPARγ attenuates hypoxia-induced PH and endothelin 1 (ET-1) expression. To further explore mechanisms of hypoxia-induced PH and reductions in PPARγ, we examined the effects of hypoxia on selected microRNA (miRNA or miR) levels that might reduce PPARγ expression leading to increased ET-1 expression and PH. Our results demonstrate that exposure to hypoxia (10% O2) for 3-weeks increased levels of miR-27a and ET-1 in the lungs of C57BL/6 mice and reduced PPARγ levels. Hypoxia-induced increases in miR-27a were attenuated in mice treated with the PPARγ ligand, rosiglitazone (RSG, 10 mg/kg/d) by gavage for the final 10 d of exposure. In parallel studies, human pulmonary artery endothelial cells (HPAECs) were exposed to control (21% O2) or hypoxic (1% O2) conditions for 72 h. Hypoxia increased HPAEC proliferation, miR-27a and ET-1 expression, and reduced PPARγ expression. These alterations were attenuated by treatment with RSG (10 µM) during the last 24 h of hypoxia exposure. Overexpression of miR-27a or PPARγ knockdown increased HPAEC proliferation and ET-1 expression and decreased PPARγ levels, whereas these effects were reversed by miR-27a inhibition. Further, compared to lungs from littermate control mice, miR-27a levels were upregulated in lungs from endothelial-targeted PPARγ knockout (ePPARγ KO) mice. Knockdown of either SP1 or EGR1 was sufficient to significantly attenuate miR-27a expression in HPAECs. Collectively, these studies provide novel evidence that miR-27a and PPARγ mediate mutually repressive actions in hypoxic pulmonary vasculature and that targeting PPARγ may represent a novel therapeutic approach in PH to attenuate proliferative mediators that stimulate proliferation of pulmonary vascular cells.

Topics: Animals; Base Pairing; Base Sequence; Cell Proliferation; Disease Models, Animal; Early Growth Response Protein 1; Endothelial Cells; Endothelin-1; Gene Expression; Gene Expression Regulation; Gene Knockdown Techniques; Humans; Hypertension, Pulmonary; Hypoxia; Lung; Mice; MicroRNAs; Models, Biological; PPAR gamma; Pulmonary Artery; RNA Interference; Sp1 Transcription Factor

Cell permeable peptides (CPP) aid cellular uptake of targeted cargo across the hydrophobic plasma membrane. CPP-mediated cargo delivery of receptor signaling motifs provides an opportunity to regulate specific receptor initiated signaling cascades. Both endothelin-1 receptors, ETA and ETB, have been targets of antagonist therapies for individuals with pulmonary arterial hypertension (PAH). These therapies have had success but have been accompanied by adverse reactions. Also, unlike the CPP which target specific signaling cascades, the antagonists target the entire function of the receptor. Using the CPP strategy of biased antagonism of the ETB receptor's intracellular loop 2 (ICB2), we demonstrate blunting of hypoxic pulmonary hypertension (HPH) in the rat, including indices of pulmonary arterial pressure, right ventricular hypertrophy and pulmonary vascular remodeling. Further, ex vivo analysis of the pulmonary artery treated with the IC2B peptide upon injection manifests marked reductions in Akt and ERK activation. Both kinases have been intimately related to cell proliferation and vascular contraction, the hallmarks of PAH. These observations in sum illustrate an involvement of the ETB receptor in HPH and furthermore provide a basis for a novel, CPP-based, strategy in the treatment of PAH, ultimately able to target not only ET-1, but also other factors involved in the development of PAH.

Topics: Animals; Cell-Penetrating Peptides; Endothelin-1; Extracellular Signal-Regulated MAP Kinases; Hypertension, Pulmonary; Hypoxia; Intracellular Space; Male; Molecular Targeted Therapy; Proto-Oncogene Proteins c-akt; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Receptor, Endothelin B; Signal Transduction

Obstructive sleep apnea (OSA) is associated with cardiovascular complications including hypertension. Previous findings from our laboratory indicate that exposure to intermittent hypoxia (IH), to mimic sleep apnea, increases blood pressure in rats. IH also increases endothelin-1 (ET-1) constrictor sensitivity in a protein kinase C (PKC) δ-dependent manner in mesenteric arteries. Because phosphoinositide-dependent kinase-1 (PDK-1) regulates PKCδ activity, we hypothesized that PDK-1 contributes to the augmented ET-1 constrictor sensitivity and elevated blood pressure following IH. Male Sprague-Dawley rats were exposed to either sham or IH (cycles between 21% O(2)/0% CO(2) and 5% O(2)/5% CO(2)) conditions for 7 h/day for 14 or 21 days. The contribution of PKCδ and PDK-1 to ET-1-mediated vasoconstriction was assessed in mesenteric arteries using pharmacological inhibitors. Constrictor sensitivity to ET-1 was enhanced in arteries from IH-exposed rats. Inhibition of PKCδ or PDK-1 blunted ET-1 constriction in arteries from IH but not sham group rats. Western analysis revealed similar levels of total and phosphorylated PDK-1 in arteries from sham and IH group rats but decreased protein-protein interaction between PKCδ and PDK-1 in arteries from IH- compared with sham-exposed rats. Blood pressure was increased in rats exposed to IH, and treatment with the PDK-1 inhibitor OSU-03012 [2-amino-N-{4-[5-(2-phenanthrenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]-phenyl}-acetamide] (33 mg/day) lowered blood pressure in IH but not sham group rats. Our results suggest that exposure to IH unmasks a role for PDK-1 in regulating ET-1 constrictor sensitivity and blood pressure that is not present under normal conditions. These novel findings suggest that PDK-1 may be a uniquely effective antihypertensive therapy for OSA patients.

Topics: 3-Phosphoinositide-Dependent Protein Kinases; Animals; Blood Pressure; Endothelin-1; Enzyme Inhibitors; Hypoxia; Immunoprecipitation; Male; Mesenteric Arteries; Phosphorylation; Protein Kinase C-delta; Protein Serine-Threonine Kinases; Pyrazoles; Rats; Rats, Sprague-Dawley; Sleep Apnea Syndromes; Sulfonamides; Vasoconstriction

The mechanisms underlying the reactive component of pulmonary hypertension (PH) in heart failure (HF) are unclear. We examined whether resting systemic oxygen levels are related to pulmonary hemodynamics in HF.. Thirty-nine HF patients underwent right heart catheterization. Subsequently, patients were classified as having: 1) no PH (n = 12); 2) passive PH (n = 10); or 3) reactive PH (n = 17). Blood was drawn from the radial and pulmonary arteries for the determination of PaO(2), SaO(2), PvO(2), SvO(2), and vasoactive neurohormones. PaO(2) and PvO(2) were lower in reactive PH versus no PH and passive PH patients (65.3 ± 8.6 vs 78.3 ± 11.4 mm Hg and 74.5 ± 14.0 mm Hg; 29.2 ± 4.1 vs 36.2 ± 2.8 mm Hg and 33.4 ± 2.3 mm Hg; P < .05). SaO(2) and SvO(2) were lower in reactive PH versus no PH patients (93 ± 3% vs 96 ± 3%; 51 ± 11% vs 68 ± 4%; P < .05), but not different versus passive PH patients. The transpulmonary pressure gradient (TPG) was inversely related to PaO(2), PvO(2), SaO(2), and SvO(2) in the reactive PH patients only (r ≤ -0.557; P < .05). Similarly, plasma endothelin-1 correlated with PaO(2), PvO(2), SvO(2) (r ≤ -0.495), and TPG (r = 0.662; P < .05) in reactive PH patients only.. Systemic hypoxia may play a role in the reactive component of PH in HF, potentially via a hypoxia-induced increase in endothelial release of the vasoconstrictor endothelin-1.

Topics: Adult; Aged; Blood Gas Analysis; Cardiac Catheterization; Cardiac Output, Low; Cohort Studies; Disease Progression; Endothelin-1; Female; Heart Failure; Hemodynamics; Humans; Hypertension, Pulmonary; Hypoxia; Male; Middle Aged; Multivariate Analysis; Neurotransmitter Agents; Oxygen; Prognosis; Prospective Studies; Regression Analysis; Risk Assessment; Severity of Illness Index; Survival Rate; Vascular Resistance

Chronic liver diseases are commonly associated with tissue hypoxia that may cause inflammation, oxidative stress, liver cell injury and increased nuclear transcriptional regulation. The hepatic response to chronic hypoxia at the molecular level has not yet been clearly understood until now. The aim of this study is to investigate whether nuclear transcription factors [hypoxia-inducible factor-1 (HIF-1α), activator protein-1 (AP-1), nuclear factor-kappa B (NF-κB)] exhibit activity changes during hepatic response to chronic hypoxia. Blood and liver samples were collected from adult Sprague-Dawley rats living in atmospheric air or 10% oxygen for four weeks. Levels of serum alanine aminotransferase (ALT), 8-isoprostane and nitrotyrosine were measured. The activities of nuclear transcription factors and the expression of downstream genes (iNOS, eNOS, ET-1 and VEGF) were measured using RT-PCR, Western blotting and Gel shift analysis. Results showed that serum ALT level, 8-isoprostane level and formation of nitrotyrosine were within normal range at all time-points. In the hypoxic liver, DNA-binding activities of HIF-1α, NF-κB and AP-1 increased significantly. Expression levels of iNOS, VEGF and ET-1 progressively increased from day 7 to day 28. eNOS was also elevated in the hypoxic liver. In conclusion, our study suggests that increased activity of HIF-1α, AP-1 and NF-κB may partly play a significant role in the hepatic response to oxidative stress and liver injury under chronic hypoxia. The increased expression of VEGF, ET-1, iNOS and eNOS may be partly due to the compensatory mechanism in the vascular beds of the liver in response to chronic hypoxia.

Topics: Alanine Transaminase; Animals; Biomarkers; Blotting, Western; Chronic Disease; Dinoprost; Disease Models, Animal; Electrophoretic Mobility Shift Assay; Endothelin-1; Gene Expression Regulation; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Liver; Male; NF-kappa B; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Oxidative Stress; Rats; Rats, Sprague-Dawley; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Time Factors; Transcription Factor AP-1; Tyrosine; Vascular Endothelial Growth Factor A

Hypoxic pulmonary hypertension (HPH) is a syndrome characterized by the increase of pulmonary vascular tone and the structural remodeling of peripheral pulmonary arteries. The aim of specific therapies for hypoxic pulmonary hypertension is to reduce pulmonary vascular resistance, reverse pulmonary vascular remodeling, and thereby improving right ventricular function. Iptakalim, a lipophilic para-amino compound with a low molecular weight, has been demonstrated to be a new selective ATP-sensitive potassium (K(ATP)) channel opener via pharmacological, electrophysiological, biochemical studies, and receptor binding tests. In hypoxia-induced animal models, iptakalim decreases the elevated mean pressure in pulmonary arteries, and attenuates remodeling in the right ventricle, pulmonary arteries and airways. Furthermore, iptakalim has selective antihypertensive effects, selective vasorelaxation effects on smaller arteries, and protective effects on endothelial cells, but no effects on the central nervous, respiratory, digestive or endocrine systems at therapeutic dose. Our previous studies demonstrated that iptakalim inhibited the effects of endothelin-1, reduced the intracellular calcium concentration and inhibited the proliferation of pulmonary artery smooth muscle cells. Since iptakalim has been shown safe and effective in both experimental animal models and phase I clinical trials, it can be a potential candidate of HPH in the future.

Topics: Animals; Antihypertensive Agents; Calcium; Disease Models, Animal; Endothelin-1; Hypertension, Pulmonary; Hypoxia; KATP Channels; Myocytes, Smooth Muscle; Propylamines; Pulmonary Artery

Lysophosphatidic acid (LPA) is a bioactive lipid molecule produced by the plasma lysophospholipase D enzyme autotaxin that is present at ≥100 nmol/L in plasma. Local administration of LPA promotes systemic arterial remodeling in rodents. To determine whether LPA contributes to remodeling of the pulmonary vasculature, we examined responses in mice with alterations in LPA signaling and metabolism.. Enpp2(+/-) mice, which are heterozygous for the autotaxin-encoding gene and which have reduced expression of autotaxin/lysophospholipase D and approximately half normal plasma LPA, were hyperresponsive to hypoxia-induced vasoconstriction and remodeling, as evidenced by the development of higher right ventricular (RV) systolic pressure, greater decline in peak flow velocity across the pulmonary valve, and a higher percentage of muscularized arterioles. Mice lacking LPA(1) and LPA(2), 2 LPA receptors abundantly expressed in the vasculature, also had enhanced hypoxia-induced pulmonary remodeling. With age, Lpar1(-/-)2(-/-) mice spontaneously developed elevated RV systolic pressure and RV hypertrophy that was not observed in Lpar1(-/-) mice or Lpar2(-/-) mice. Expression of endothelin-1, a potent vasoconstrictor, was elevated in lungs of Lpar1(-/-)2(-/-) mice, and expression of endothelin(B) receptor, which promotes vasodilation and clears endothelin, was reduced in Enpp2(+/-) and Lpar1(-/-)2(-/-) mice.. Our findings indicate that LPA may negatively regulate pulmonary vascular pressure through LPA(1) and LPA(2) receptors and that in the absence of LPA signaling, upregulation in the endothelin system favors remodeling.

Topics: Animals; Blood Pressure; Endothelin-1; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Lysophospholipids; Mice; Mice, Inbred BALB C; Mice, Knockout; Phosphoric Diester Hydrolases; Pulmonary Artery; Receptors, Lysophosphatidic Acid; Signal Transduction

The objectives of the present study were to examine the effects of intermittent hypoxia (IH) on arterial baroreflex function and assess the underlying mechanism(s). Experiments were performed on adult male rats treated with 14 days of IH (15 s of hypoxia, 5 min of normoxia; 8 h/day) or normoxia (control). Arterial blood pressures were elevated in IH-treated rats, and this effect was associated with attenuated heart rate and splanchnic sympathetic nerve responses to arterial baroreflex activation. In IH-treated rats, carotid baroreceptor responses to elevated sinus pressures were attenuated. Endothelin-1 (ET-1) levels were elevated in the carotid sinus region of IH-treated rats, and this effect was associated with increased endothelin converting enzyme (ECE) activity, which generates biologically active ET-1. ET(A) receptor antagonist prevented the effects of IH on carotid baroreceptor activity. In IH-treated rats, reactive oxygen species (ROS) levels were elevated in the carotid sinus region, and antioxidant treatment prevented the effects of IH on ET-1 levels, ECE activity, carotid baroreceptor activity, and baroreflex function. These results demonstrate that 1) IH attenuates arterial baroreflex function, which is in part due to reduced carotid baroreceptor responses to elevated carotid sinus pressure, and 2) IH-induced carotid baroreceptor dysfunction involves reactive oxygen species-dependent upregulation of ET-1 signaling in the carotid sinus region.

Topics: Animals; Blood Pressure; Carotid Body; Carotid Sinus; Endothelin-1; Hypoxia; Male; Pressoreceptors; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species

We have previously shown that inhibition of transforming growth factor-β (TGF-β) signaling attenuates hypoxia-induced inhibition of alveolar development and abnormal pulmonary vascular remodeling in the newborn mice and that endothelin-A receptor (ETAR) antagonists prevent and reverse the vascular remodeling. The current study tested the hypothesis that inhibition of TGF-β signaling attenuates endothelin-1 (ET-1) expression and thereby reduces effects of hypoxia on the newborn lung. C57BL/6 mice were exposed from birth to 2 wk of age to either air or hypoxia (12% O(2)) while being given either BQ610 (ETAR antagonist), BQ788 (ETBR antagonist), 1D11 (TGF-β neutralizing antibody), or vehicle. Lung function and development and TGF-β and ET-1 synthesis were assessed. Hypoxia inhibited alveolar development, decreased lung compliance, and increased lung resistance. These effects were associated with increased TGF-β synthesis and signaling and increased ET-1 synthesis. BQ610 (but not BQ788) improved lung function, without altering alveolar development or increased TGF-β signaling in hypoxia-exposed animals. Inhibition of TGF-β signaling reduced ET-1 in vivo, which was confirmed in vitro in mouse pulmonary endothelial, fibroblast, and epithelial cells. ETAR blockade improves function but not development of the hypoxic newborn lung. Reduction of ET-1 via inhibition of TGF-β signaling indicates that TGF-β is upstream of ET-1 during hypoxia-induced signaling in the newborn lung.

Topics: Animals; Animals, Newborn; Cells, Cultured; Endothelial Cells; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Endothelin-1; Endothelium, Vascular; Gene Expression; Hypoxia; Lung; Mice; Mice, Inbred C57BL; Oligopeptides; Piperidines; Receptor, Endothelin A; Receptor, Endothelin B; Signal Transduction; Transforming Growth Factor beta

Exposure to chronic hypoxia (CH) causes pulmonary hypertension. The vasoconstrictor endothelin-1 (ET-1) is thought to play a role in the development of hypoxic pulmonary hypertension. In pulmonary arterial smooth muscle cells (PASMCs) from chronically hypoxic rats, ET-1 signaling is altered, with the ET-1-induced change in intracellular calcium concentration (Δ[Ca(2+)](i)) occurring through activation of voltage-dependent Ca(2+) channels (VDCC) even though ET-1-induced depolarization via inhibition of K(+) channels is lost. The mechanism underlying this response is unclear. We hypothesized that activation of VDCCs by ET-1 following CH might be mediated by protein kinase C (PKC) and/or Rho kinase, both of which have been shown to phosphorylate and activate VDCCs. To test this hypothesis, we examined the effects of PKC and Rho kinase inhibitors on the ET-1-induced Δ[Ca(2+)](i) in PASMCs from rats exposed to CH (10% O(2), 3 wk) using the Ca(2+)-sensitive dye fura 2-AM and fluorescent microscopy techniques. We found that staurosporine and GF109203X, inhibitors of PKC, and Y-27632 and HA 1077, Rho kinase inhibitors, reduced the ET-1-induced Δ[Ca(2+)](i) by >70%. Inhibition of tyrosine kinases (TKs) with genistein or tyrphostin A23, or combined inhibition of PKC, TKs, and Rho kinase, reduced the Δ[Ca(2+)](i) to a similar extent as inhibition of either PKC or Rho kinase alone. The ability of PKC or Rho kinase to activate VDCCs in our cells was verified using phorbol 12-myristate 13-acetate and GTP-γ-S. These results suggest that following CH, the ET-1-induced Δ[Ca(2+)](i) in PASMCs occurs via Ca(2+) influx through VDCCs mediated primarily by PKC, TKs, and Rho kinase.

Topics: Animals; Calcium; Calcium Channels; Calcium Signaling; Chronic Disease; Endothelin-1; Fluorescent Dyes; Fura-2; Gene Expression; Hypertension, Pulmonary; Hypoxia; Ion Channel Gating; Male; Microscopy, Fluorescence; Muscle Cells; Muscle, Smooth, Vascular; Protein Kinase C; Protein Kinase Inhibitors; Rats; Rats, Wistar; rho-Associated Kinases

Endothelin-1 (ET-1) contributes to the pathogenesis of cardiovascular diseases with multiple properties such as vasoconstriction. Human ET-1 gene expression is up-regulated by the transcription factor hypoxia-inducible factor-1 (HIF-1) through hypoxia response element (HRE). Although previous studies suggested that 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) alter HIF-1-related gene expression, it remained unclear whether statins modulate HIF-1-mediated ET-1 expression. Therefore, we investigated the effect of fluvastatin on hypoxia-induced human ET-1 expression in vascular smooth muscle cells (VSMC).. Hypoxia (1% O(2)), compared with the normoxic condition (21% O(2)), significantly induced the expression of preproET-1 mRNA, ET-1 protein, and ET-1 secretion in VSMC. Hypoxia induced a 2.3-fold increase in HRE-dependent ET-1 reporter gene activation. Under concentrations of 1 µmol/L or greater, fluvastatin attenuated the hypoxia-induced ET-1 gene expression through the accelerated ubiquitin/proteasome-dependent degradation of HIF-1α, thus consequently attenuating HIF-1α binding to the HRE of the ET-1 gene. These inhibitory effects of fluvastatin were cancelled by concomitant treatment with mevalonate, farnesyl pyrophosphate, or geranylgeranyl pyrophosphate, but not squalene.. The present study suggests that fluvastatin attenuates HIF-1-dependent ET-1 gene expression in conjunction with the stimulation of HIF-1α ubiquitin/proteasome-dependent degradation via isoprenoid-dependent mechanisms.

Topics: Cells, Cultured; Endothelin-1; Fatty Acids, Monounsaturated; Fluvastatin; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Indoles; Myocytes, Smooth Muscle; Proteolysis; Transcription Factors

Ambivalent effects of interleukin-6 on the pathogenesis of ischaemic stroke have been reported. However, to date, the long-term actions of interleukin-6 after stroke have not been investigated. Here, we subjected interleukin-6 knockout (IL-6(-/-)) and wild-type control mice to mild brain ischaemia by 30-min filamentous middle cerebral artery occlusion/reperfusion. While ischaemic tissue damage was comparable at early time points, IL-6(-/-) mice showed significantly increased chronic lesion volumes as well as worse long-term functional outcome. In particular, IL-6(-/-) mice displayed an impaired angiogenic response to brain ischaemia with reduced numbers of newly generated endothelial cells and decreased density of perfused microvessels along with lower absolute regional cerebral blood flow and reduced vessel responsivity in ischaemic striatum at 4 weeks. Similarly, the early genomic activation of angiogenesis-related gene networks was strongly reduced and the ischaemia-induced signal transducer and activator of transcription 3 activation observed in wild-type mice was almost absent in IL-6(-/-) mice. In addition, systemic neoangiogenesis was impaired in IL-6(-/-) mice. Transplantation of interleukin-6 competent bone marrow into IL-6(-/-) mice (IL-6(chi)) did not rescue interleukin-6 messenger RNA expression or the early transcriptional activation of angiogenesis after stroke. Accordingly, chronic stroke outcome in IL-6(chi) mice recapitulated the major effects of interleukin-6 deficiency on post-stroke regeneration with significantly enhanced lesion volumes and reduced vessel densities. Additional in vitro experiments yielded complementary evidence, which showed that after stroke resident brain cells serve as the major source of interleukin-6 in a self-amplifying network. Treatment of primary cortical neurons, mixed glial cultures or immortalized brain endothelia with interleukin 6-induced robust interleukin-6 messenger RNA transcription in each case, whereas oxygen-glucose deprivation did not. However, oxygen-glucose deprivation of organotypic brain slices resulted in strong upregulation of interleukin-6 messenger RNA along with increased transcription of key angiogenesis-associated genes. In conclusion, interleukin-6 produced locally by resident brain cells promotes post-stroke angiogenesis and thereby affords long-term histological and functional protection.

Topics: Analysis of Variance; Angiogenic Proteins; Animals; Bone Marrow Transplantation; Brain; Calcium-Binding Proteins; Cells, Cultured; Cerebral Cortex; Cytokine Receptor gp130; Cytokines; Disease Models, Animal; Embryo, Mammalian; Endothelial Cells; Endothelin-1; Enzyme-Linked Immunosorbent Assay; Gait Disorders, Neurologic; Gene Expression Profiling; Gene Expression Regulation; Glucose; Green Fluorescent Proteins; Hypoxia; Infarction, Middle Cerebral Artery; Interleukin-6; Mice; Mice, Knockout; Microfilament Proteins; Neovascularization, Pathologic; Neuroglia; Neurons; Oligonucleotide Array Sequence Analysis; Perfusion Imaging; Receptor, trkB; Rotarod Performance Test; Signal Transduction; STAT3 Transcription Factor; Tetrazolium Salts; Thiazoles

Altitude illness remains a major cause of mortality. Reduced chemosensitivity, irregular breathing leading to central apnoeas/hypopnoeas, and exaggerated pulmonary vasoconstriction may compromise oxygenation. All factors could enhance susceptibility to acute mountain sickness (AMS). We compared 12 AMS-susceptible individuals with recurrent and severe symptoms (AMS+) with 12 "AMS-nonsusceptible" subjects (AMS-), assessing sleep-breathing disorders in simulated altitude as well as chemoresponsive and pulmonary vasoconstrictive responses to hypoxia. During exposure to simulated altitude, mean blood oxygen saturation during sleep was lower in AMS+ subjects (81.6 ± 2.6 versus 86.0 ± 2.4%, p<0.01), associated with a lower central apnoea/hypopnoea index (18.2 ± 18.1 versus 33.4 ± 24.8 events · h(-1) in AMS+ and AMS- subjects, respectively; p=0.038). A lower hypoxic (isocapnic) chemoresponsiveness was observed in AMS+ subjects (0.40 ± 0.49 versus 0.97 ± 0.46 L · min(-1)·%; p<0.001). This represented the only significant and independent predictive factor for altitude intolerance, despite a higher increase in pulmonary artery systolic pressure in response to hypoxia, a lower lung diffusing capacity and a higher endothelin-1 level at baseline in AMS+ subjects (p<0.05). AMS+ subjects were more hypoxaemic whilst exhibiting fewer respiratory events during sleep owing to lower hypoxic (isocapnic) chemoresponsiveness. In conclusion, the reduction in peripheral hypoxic chemosensitivity appears to be a major causative factor for altitude intolerance.

Topics: Acute Disease; Adult; Altitude Sickness; Apnea; Endothelin-1; Female; Humans; Hypoxia; Male; Middle Aged; Oxygen; Pulmonary Artery; Pulmonary Diffusing Capacity; Severity of Illness Index; Sleep

Topics: Animals; Cerebrovascular Circulation; Endothelin-1; Hypoxia; Male; Somatosensory Cortex

Obstructive sleep apnea, a condition resulting in chronic intermittent hypoxia (CIH), is an independent risk factor for stroke and dementia, but the mechanisms of the effect are unknown. We tested the hypothesis that CIH increases cerebrovascular risk by altering critical mechanisms regulating cerebral blood flow thereby lowering cerebrovascular reserves. Male C57Bl6/J mice were subjected to CIH (10% O(2) for 90 seconds/room air for 90 seconds; during sleep hours) or sham treatment for 35 days. Somatosensory cortex blood flow was assessed by laser Doppler flowmetry in anesthetized mice equipped with a cranial window. CIH increased mean arterial pressure (from 74±2 to 83±3 mm Hg; P<0.05) and attenuated the blood flow increase produced by neural activity (whisker stimulation; -39±2%; P<0.05) or neocortical application of endothelium-dependent vasodilators (acetylcholine response: -41±3%; P<0.05). The cerebrovascular dysfunction was associated with oxidative stress in cerebral resistance arterioles and was abrogated by free radical scavenging or NADPH oxidase inhibition. Furthermore, cerebrovascular dysfunction and free radical increase were not observed in mice lacking the NOX2 subunit of NADPH oxidase. CIH markedly increased endothelin 1 in cerebral blood vessels, whereas cerebrovascular dysfunction and oxidative stress were abrogated by neocortical application of the endothelin type A receptor antagonist BQ123. These data demonstrate for the first time that CIH alters key regulatory mechanisms of the cerebral circulation through endothelin 1 and NADPH oxidase-derived radicals. The ensuing cerebrovascular dysfunction may increase stroke risk in patients with sleep apnea by reducing cerebrovascular reserves and increasing the brain's susceptibility to cerebral ischemia.

Topics: Acetylcholine; Animals; Antihypertensive Agents; Aspartic Acid Endopeptidases; Blood Pressure; Cerebrovascular Circulation; Chronic Disease; Endothelin Receptor Antagonists; Endothelin-1; Endothelin-Converting Enzymes; Enzyme-Linked Immunosorbent Assay; Hypoxia; Laser-Doppler Flowmetry; Male; Membrane Glycoproteins; Metalloendopeptidases; Mice; Mice, Inbred C57BL; Mice, Knockout; NADPH Oxidase 2; NADPH Oxidases; Peptides, Cyclic; Reactive Oxygen Species; Receptors, Endothelin; Reverse Transcriptase Polymerase Chain Reaction; Somatosensory Cortex; Vasodilator Agents

We evaluated the effects of high-altitude hypoxic stress in the murine model. For this purpose, 36 CR-mice in group A were maintained at the altitude of 3,820 m for hypoxia-induced factor (HIF)-1α expression analysis by immunohistochemistry. The 36 Wistar rats in group B were maintained in low-pressure (400-420 kPa) oxygen chamber, and the effects of hypoxia on myocardial mitochondria were studied. In the 36 CR-mice of group C, plasma vascular endothelial growth factor (VEGF) levels were determined using strept-avidin-biotin complex/diaminobenzidine method after exposure to different altitudes/O(2)-concentrations. The data show that in experimental group A1, endothelin (ET)-1α concentrations gradually increased whereas HIF-1α expression in myocardial cells was higher (P < 0.01) than in control group A2. In rats of group B, the myocardial mitochondria numbers were reduced during the initial phase of acute stress response to hypoxia and cellular injury but, later, mitochondrial numbers were restored to normal values. In mice of experimental group C1, plasma VEGF concentrations increased under hypoxia, which were significantly higher (P < 0.01) than those of control group C2. We, therefore, concluded that high-altitude hypoxia: (i) induced HIF-1α expression; (ii) prompted adaptation/acclimatization after initial stress and cellular injury; and (iii) enhanced VEGF expression in murine.

Topics: Acclimatization; Altitude; Animals; Cell Hypoxia; Disease Models, Animal; Endothelin-1; Female; Gene Expression; Heart Atria; Heart Ventricles; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Male; Mice; Mitochondria, Heart; Oxygen; Pericardium; Protein Isoforms; Rats; Rats, Wistar; RNA, Messenger; Stress, Physiological; Vascular Endothelial Growth Factor A

The prognosis of patients after acute kidney injury (AKI) is poor and treatment is limited. AKI is mainly caused by renal ischemia/reperfusion injury (IRI). During the extension phase of IRI, endothelial damage may participate in ischemia and inflammation. Endothelin-1 (ET-1) which is mostly secreted by endothelial cells is an important actor of IRI, particularly through its strong vasoconstrictive properties. We aimed to analyze the specific role of ET-1 from the endothelial cells in AKI.. We used mice lacking ET-1 in the vascular endothelial cells (VEETKO). We induced IRI in VEETKO mice and wild type controls by clamping both kidneys for 30min. Sham operated mice were used as controls. Mice were sacrificed one day after IRI in order to investigate the extension phase of IRI. Kidney function was assessed based on serum creatinine concentration. Levels of expression of ET-1, its receptor ET(A), protein kinase C, eNOS, E-Cadherin and inflammation markers were evaluated by real time PCR or western blot. Tubular injury was scored on periodic acid Schiff stained kidney preparations. Lumen and wall area of small intrarenal arteries were measured on kidney slices stained for alpha smooth muscle cell actin. Oxidative stress, macrophage infiltration and cell proliferation was evaluated on slices stained for 8-hydroxy-2'-deoxyguanosine, F4/80 and PCNA, respectively.. IRI induced kidney failure and increased ET-1 and ET(A) receptor expression. This was accompanied by tubular injury, wall thickening and reduction of lumen area/wall area ratio of small renal arteries, increased oxidative stress and inflammation. These parameters were attenuated in VEETKO mice.. Our results suggest that suppression of ET-1 from the endothelial cells attenuates IRI kidney injury. Blocking ET-1 effects may represent a therapeutic strategy in the management of AKI.

Topics: Acute Kidney Injury; Animals; Cadherins; Endothelial Cells; Endothelin-1; Hypoxia; Kidney; Mice; Mice, Knockout; Nitric Oxide Synthase Type III; Oxidative Stress; Reactive Oxygen Species; Receptor, Endothelin A; Reperfusion Injury; Vasoconstriction

Chronic hypoxia (CH) induces an inflammatory response in rat carotid body that is characterized by immune cell invasion and the expression of pro-inflammatory cytokines. In the present study, we have investigated the role of type-A endothelin (ET-A) receptors in the development of CH-induced inflammation. After 7 days of CH (380 Torr), double-label immunofluorescence studies demonstrated elevated levels of ET-A receptor and tyrosine hydroxylase (TH) in O(2)-sensitive type I cells. Following CH, ET-A receptors were also expressed on resident and invasive CD45+ immune cells distributed in tissue surrounding chemosensory cell lobules. Immnofluorescence and quantitative PCR studies showed that concurrent treatment with the ET-A/B receptor antagonist, bosentan (200 mg/kg/day), blocked CH-induced ED-1+ macrophage invasion and the upregulation of cytokines, including interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor α (TNFα), and monocyte chemoattractant protein-1 (MCP-1). Moreover, bosentan treatment blocked the CH-induced increases in expression of acid-sensitive ion channels (ASICs) in chemoafferent neurons in the petrosal ganglion (PG). Our findings are consistent with the hypothesis that CH-induced inflammation involves the upregulation and release of ET-1 from type I cells. ET-1 may act in an autocrine/paracrine mechanism via ET-A receptors on chemosensory type I cells and immune cells to promote an inflammatory response.

Topics: Acid Sensing Ion Channels; Adaptation, Physiological; Animals; Antihypertensive Agents; Bosentan; Carotid Body; Cell Movement; Chemokine CCL2; Chemoreceptor Cells; Chronic Disease; Endothelin-1; Gene Expression; Hypoxia; Inflammation; Interleukin-1; Interleukin-1beta; Leukocyte Common Antigens; Macrophages; Rats; Receptor, Endothelin A; Sulfonamides; Tumor Necrosis Factor-alpha; Tyrosine 3-Monooxygenase

Right ventricular hypertrophy (RVH) and right ventricular (RV) contractile dysfunction are major determinants of prognosis in pulmonary arterial hypertension (PAH) and PAH remains a severe disease. Recently, direct interruption of left ventricular hypertrophy has been suggested to decrease the risk of left-sided heart failure. Hexamethylene bis-acetamide inducible protein 1 (HEXIM1) is a negative regulator of positive transcription elongation factor b (P-TEFb), which activates RNA polymerase II (RNAPII)-dependent transcription and whose activation is strongly associated with left ventricular hypertrophy. We hypothesized that during the progression of PAH, increased P-TEFb activity might also play a role in RVH, and that HEXIM1 might have a preventive role against such process. We revealed that, in the mouse heart, HEXIM1 is highly expressed in the early postnatal period and its expression is gradually decreased, and that prostaglandin I(2), a therapeutic drug for PAH, increases HEXIM1 levels in cardiomyocytes. These results suggest that HEXIM1 might possess negative effect on cardiomyocyte growth and take part in cardiomyocyte regulation in RV. Using adenovirus-mediated gene delivery to cultured rat cardiomyocytes, we revealed that overexpression of HEXIM1 prevents endothelin-1-induced phosphorylation of RNAPII, cardiomyocyte hypertrophy, and mRNA expression of hypertrophic genes, whereas a HEXIM1 mutant lacking central basic region, which diminishes P-TEFb-suppressing activity, could not. Moreover, we created cardiomyocyte-specific HEXIM1 transgenic mice and revealed that HEXIM1 ameliorates RVH and prevents RV dilatation in hypoxia-induced PAH model. Taken together, these findings indicate that cardiomyocyte-specific overexpression of HEXIM1 inhibits progression to RVH under chronic hypoxia, most possibly via inhibition of P-TEFb-mediated enlargement of cardiomyocytes. We conclude that P-TEFb/HEXIM1-dependent transcriptional regulation may play a pathophysiological role in RVH and be a novel therapeutic target for mitigating RVH in PAH.

Topics: Animals; Disease Progression; Endothelin-1; Gene Expression; Gene Expression Regulation; Humans; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Male; Mice; Mice, Transgenic; Myocytes, Cardiac; Organ Specificity; Positive Transcriptional Elongation Factor B; Rats; RNA-Binding Proteins; Transcription Factors

Recent studies showed that adenosine played important roles in vasodilation. This study aimed to investigate the effects of adenosine, its A1 and A2b receptor agonists on pulmonary artery hypertension (PAH) induced by chronic hypoxia in rats by continuously subcutaneous administration with an osmotic pump for 14 days, and to see if rennin angiotensin system and inducible nitric oxygen synthase (iNOS)/nitric oxide (NO) mediate the effects.. Fifty-six male SD rats were randomly assigned to seven groups. Each group included eight rats. They were normoxic group, hypoxic group, adenosine-treated group [adenosine was administered at a dose of 150 µg(kg·min) under the hypoxic condition], adenosine A1 receptor agonist CPA-treated group [CPA was administered at a dose of 20 µg/(kg·min) under the hypoxic condition], CPA plus selective adenosine A1 antagonist DPCPX-treated group [CPA and DPCPX were administered simultaneously under the hypoxic condition, the dose of CPA was the same as the above, and the dose of DPCPX was 25 µg/(kg·min)], adenosine A2b receptor agonist NECA-treated group [NECA was administered at a dose of 30 µg/(kg·min) under the hypoxic condition], NECA plus selective adenosine A2b receptor antagonist MRS-treated group[ NECA and MRS1754 were administered simultaneously under the hypoxic condition, the dose of NECA was the same as the above, and the dose of MRS1754 was 50 µg/(kg·min)]. Osmotic pumps containing adenosine or selective adenosine A1 receptor agonist (CPA), or nonselective but potent adenosine A2b receptor agonist (NECA) were placed subcutaneously 7 days after hypoxia and continuously administered the agents for 14 days.Mean pulmonary artery pressure (mPAP) was detected after administration of the agents. Then blood samples were taken from heart for measurement of renin activity, angiotensin II (AngII) and endothelin-1 (ET-1) concentration by radioimmunoassay, NO by measuring nitrate. Small pulmonary arteries were prepared for immunoreactivity staining of proliferating cell nuclear antigen (PCNA) and iNOS.. (1) Chronic hypoxia induced PAH [mPAP: (31.38 ± 3.42) mm Hg]. Adenosine or CPA or NECA administered for 14 days by subcutaneous route attenuated the mPAP [(21.17 ± 3.56) mm Hg, (22.88 ± 2.95) mm Hg, (19.81 ± 2.39) mm Hg, respectively], which showed significant difference when compared with hypoxia group (P < 0.05 respectively). (2) Plasma rennin activity and AngII level in hypoxia group [(2.51 ± 0.25) ng/(ml·h), (83.01 ± 9.38) pg/ml] were significantly higher than that in normoxic group (P < 0.05, respectively).(3) Adenosine treatment decreased the rennin activity and AngII level when compared with hypoxic group(P < 0.05, respectively);CPA and NECA attenuated respectively the rennin activity and AngII level of rats induced by chronic hypoxia (P < 0.05, respectively). (4) Adenosine administration for 14 days attenuated the wall thickness induced by chronic hypoxia (P < 0.05). CPA showed no effect on wall thickness, but NECA significantly attenuated the wall thickness (P < 0.05). (5) The number of iNOS staining positive cells in small pulmonary artery was higher in hypoxia group than in that in normoxic rats (23.75 ± 7.91 vs. 8.00 ± 2.20, P < 0.05). Adenosine or CPA, or NECA administration increased respectively the iNOS expression in rats treated with chronic hypoxia. Chronic hypoxia caused significant decrease of nitric oxide level. Adenosine treatment increased the nitric oxide level in rats treated with chronic hypoxia. CPA and NECA also increased respectively the nitric oxide level in rats treated with chronic hypoxia. Chronic hypoxia caused significant increase of ET-1 level. The ET-1 level in rats treated with adenosine, CPA or NCEA respectively were lower than that in chronic hypoxia rats (P < 0.05). (6) Adenosine treatment partially attenuated the number of PCNA-positively stained cells. NECA treatment also attenuated the PCNA expression, but CPA showed no effect.. Adenosine and its agonists CPA, NECA administered continually by subcutaneous route attenuate mPAP of rats induced by chronic hypoxia. CPA attenuates mPAP through reduction of RA/AngII activity and balance of NO/ET-1 level. NECA attenuates mPAP by inhibiting PCNA expression and proliferation of mooth muscle of pulmonary artery.

Topics: Adenosine; Angiotensin II; Animals; Disease Models, Animal; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Male; Nitric Oxide; Nitric Oxide Synthase Type II; Proliferating Cell Nuclear Antigen; Pulmonary Artery; Purinergic P1 Receptor Agonists; Random Allocation; Rats; Rats, Sprague-Dawley; Renin

To study the effect of hypoxia-inducible factor-1α (HIF-1α) in the pathogenesis of hypoxia-induced pulmonary hypertension (HPH) of the neonatal rats through the study on the expression level of HIF-1α and its regulation factors: endothelin-1 (ET-1) and inducible nitric oxide synthase (iNOS) in blood serum and lung tissue.. To make an HPH model of neonatal rats, 120 newborn Wistar rats were divided at random into two groups: HPH group and the regular oxygen controlled group with the same birthday. The rats of the two groups were put in the condition of hypoxia for 3, 5, 7, 10, 14, 21 days and then 10 rats of HPH group and control group were picked up, their mean pulmonary arterial pressure (mPAP), serum HIF-1α, and iNOS, and ET-1 content were tested, and finally their lung tissue was taken after they were sacrificed and the expression level of the gene mRNA of HIF-1α, iNOS and ET-1.. (1) The rats experienced hypoxia for 3, 5, 7, 10, 14 or 21 days had an increasing mPAP: [8.47 ± 1.45, 10.04 ± 1.69, 10.89 ± 2.97, 16.96 ± 1.97, 13.01 ± 1.93, 21.04 ± 2.13 (mm Hg)], which had a significant differences compared with control groups [5.11 ± 1.06, 8.12 ± 1.11, 8.77 ± 0.92, 12.23 ± 1.78, 8.89 ± 0.89, 11.09 ± 1.64 (mm Hg)] (P < 0.05). (2) The rats in hypoxia group had a higher serum HIF-1α [0.83 ± 0.07, 0.84 ± 0.17, 0.97 ± 0.13, 1.10 ± 0.30, 0.92 ± 0.19 (pg/nmol)] than the control group [0.26 ± 0.20, 0.37 ± 0.16, 0.44 ± 0.18, 0.41 ± 0.23, 0.66 ± 0.18 (pg/nmol)] as they experienced hypoxia for 3, 5, 7, 10, and 14 days (P < 0.05); HIF-1α mRNA expression in lung tissue (1.301 ± 0.47, 1.032 ± 0.47, 1.453 ± 0.76) was also significantly higher than that of the control group (0.231 ± 0.26, 0.425 ± 0.59, 0.692 ± 0.13) (P < 0.05); serum ET-1 levels [51.50 ± 3.19, 44.1 ± 10.81, 56.85 ± 9.10, 52.91 ± 9.59, 51.16 ± 8.87, 50.21 ± 10.41 (pg/nmol)] were clearly higher than that of the control group [9.04 ± 2.85, 21.70 ± 8.78, 19.63 ± 9.66, 18.30 ± 7.32, 19.69 ± 5.92, 16.88 ± 6.14 (pg/nmol)] (P < 0.01); ET-1 mRNA expression in lung tissue (0.037 ± 0.018) was significantly increased after 3-day hypoxia as compared with control group (0.006 ± 0.004) (P < 0.05). Serum content of iNOS (5.62 ± 0.79) µmol/L was significantly higher than the control group (1.63 ± 0.67) µmol/L (P < 0.05) after a 3-day hypoxia, but there was no significant difference after a hypoxia for 5, 7 or 10 days, compared with the control group (P > 0.05), and the content of serum iNOS after hypoxia for 14 or 21 days (4.56 ± 0.96, 5.86 ± 1.76) µmol/L was lower than that of the control group (10.35 ± 1.99, 8.44 ± 2.76) µmol/L (P < 0.05). iNOS mRNA expression in lung tissue (0.035 ± 0.024, 0.332 ± 0.198, 0.527 ± 0.098) significantly increased after hypoxia for 3, 5 or 7 days as compared with the control group (0.005 ± 0.0001, 0.008 ± 0.002, 0.040 ± 0.012) (P < 0.05).. As an initial factor, low oxygen made HIF-1α, ET-1 and iNOS expression raised in the pathogenesis of HPH of the neonatal rats and causedn a imbalance of ET-1 and NO. HIF-1α, ET-1 and iNOS altogether contributed to the occurrence and development of HPH in neonatal rats.

Topics: Animals; Animals, Newborn; Arterial Pressure; Disease Models, Animal; Endothelin-1; Female; Hypertension, Pulmonary; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Lung; Male; Nitric Oxide Synthase Type II; Pulmonary Artery; Random Allocation; Rats; Rats, Wistar; RNA, Messenger

To investigate the roles of hypoxia-inducible factor-1α (HIF-1α), endothelin-1 (ET-1) and inducible nitric oxide synthase (iNOS) in the pathogenesis of hypoxia-induced pulmonary hypertension (HPH) of the newborn.. Seventy-five term hospitalized neonates with HPH (mild 29 cases, moderate 25 cases, severe 21 cases) and 22 term hospitalized neonates without HPH (control group) were enrolled between June 2006 and November 2009. Serum levels of HIF-1α, iNOS and ET-1 were measured using ELASA 1, 3 and 7 days after birth.. Serum concentrations of HIF-1α and ET-1 in the mild, moderate and severe HPH groups were significantly higher than those in the control group (P<0.01) 1 day after birth, and were related to the severity of HPH. The serum iNOS concentrations in the moderate and severe HPH groups were also significantly higher than those in the control group (P<0.01). By 3 days after birth, serum ET-1 concentration in the moderate HPH group and serum concentrations of HIF-1α, ET-1 and iNOS in the severe HPH group reminded significantly higher than those in the control group (P<0.05). At 7 days after birth, serum ET-1 concentration in the severe HPH group still remained higher than that in the control group (P<0.05).. Serum levels of HIF-1α, ET-1 and iNOS increase in neonates with HPH, resulting in an imbalance of ET-1 and NO. This may be of importance in the pathogenesis of neonatal HPH.

Topics: Endothelin-1; Female; Humans; Hypertension, Pulmonary; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Infant, Newborn; Male; Nitric Oxide Synthase Type II

Pulmonary hypertension (PH) is characterized by arterial vascular remodelling and alteration in vascular reactivity. Since gap junctions are formed with proteins named connexins (Cx) and contribute to vasoreactivity, we investigated both expression and role of Cx in the pulmonary arterial vasoreactivity in two rat models of PH.. Intrapulmonary arteries (IPA) were isolated from normoxic rats (N), rats exposed to chronic hypoxia (CH) or treated with monocrotaline (MCT). RT-PCR, Western Blot and immunofluorescent labelling were used to study the Cx expression. The role of Cx in arterial reactivity was assessed by using isometric contraction and specific gap junction blockers. Contractile responses were induced by agonists already known to be involved in PH, namely serotonin, endothelin-1 and phenylephrine.. Cx 37, 40 and 43 were expressed in all rat models and Cx43 was increased in CH rats. In IPA from N rats only, the contraction to serotonin was decreased after treatment with 37-43Gap27, a specific Cx-mimetic peptide blocker of Cx 37 and 43. The contraction to endothelin-1 was unchanged after incubation with 40Gap27 (a specific blocker of Cx 40) or 37-43Gap27 in N, CH and MCT rats. In contrast, the contraction to phenylephrine was decreased by 40Gap27 or 37-43Gap27 in CH and MCT rats. Moreover, the contractile sensitivity to high potassium solutions was increased in CH rats and this hypersensitivity was reversed following 37-43Gap27 incubation.. Altogether, Cx 37, 40 and 43 are differently expressed and involved in the vasoreactivity to various stimuli in IPA from different rat models. These data may help to understand alterations of pulmonary arterial reactivity observed in PH and to improve the development of innovative therapies according to PH aetiology.

Topics: Analysis of Variance; Animals; Blood Pressure; Blotting, Western; Connexin 43; Connexins; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelin-1; Fluorescent Antibody Technique; Gap Junction alpha-4 Protein; Gap Junction alpha-5 Protein; Gap Junctions; Hypertension, Pulmonary; Hypoxia; Male; Monocrotaline; Muscle, Smooth, Vascular; Phenylephrine; Pulmonary Artery; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction; Serotonin; Vasoconstriction; Vasoconstrictor Agents

To study the changes and significance of serum hypoxia-inducible factor-1α (HIF-1α), endothelin-1 (ET-1) and calcium (Ca(2+)) levels in neonates with hypoxic pulmonary hypertension (HPH).. Seventy-five neonates with HPH (29 mild, 25 moderate and 21 severe) and 22 hospitalized neonates with non-HPH (control group) were enrolled. Pulmonary artery systolic blood pressure (PASP) was measured by bedside echocardiography within 24 hrs after birth. Serum levels of HIF-1α and ET-1 were measured using ELASA. Serum Ca2+ concentrations were measured with ion selective electrode.. Serum levels of HIF-1α and ET-1 in the HPH group increased significantly compared with those in the control group (P<0.01), and were positively related with PASP (Rhif-1α=0.75, P<0.01; Ret-1=0.56,P<0.05). Serum Ca2+ levels in neonates with severe HPH were significantly lower than those in the control group (P<0.05). There were no correlation between serum Ca2+ levels and PASP.. Serum HIF-1α and ET-1 levels are positively related with PASP in neonates with HPH, suggesting that serum HIF-1α and ET-1 may be involved in the occurrence of neonatal HPH. Serum Ca2+ levels are reduced in severe neonates with HPH, suggesting that serum Ca2+ may play a role in the occurrence of severe HPH.

Topics: Blood Pressure; Calcium; Endothelin-1; Female; Humans; Hypertension, Pulmonary; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Infant, Newborn; Male; Pulmonary Artery

Chronic hypoxia (CH) activates the Ca(2+)-dependent transcription factor nuclear factor of activated T cells isoform c3 (NFATc3) in mouse pulmonary arteries. However, the mechanism of this response has not been explored. Since we have demonstrated that NFATc3 is required for CH-induced pulmonary arterial remodeling, establishing how CH activates NFATc3 is physiologically significant. The goal of this study was to test the hypothesis that endothelin-1 (ET-1) contributes to CH-induced NFATc3 activation. We propose that this mechanism requires increased pulmonary arterial smooth muscle cell (PASMC) intracellular Ca(2+) concentration ([Ca(2+)](i)) and stimulation of RhoA/Rho kinase (ROK), leading to calcineurin activation and actin cytoskeleton polymerization, respectively. We found that: 1) CH increases pulmonary arterial pre-pro-ET-1 mRNA expression and lung RhoA activity; 2) inhibition of ET receptors, calcineurin, L-type Ca(2+) channels, and ROK blunts CH-induced NFATc3 activation in isolated intrapulmonary arteries from NFAT-luciferase reporter mice; and 3) both ET-1-induced NFATc3 activation in isolated mouse pulmonary arteries ex vivo and ET-1-induced NFATc3-green fluorescence protein nuclear import in human PASMC depend on ROK and actin polymerization. This study suggests that CH increases ET-1 expression, thereby elevating PASMC [Ca(2+)](i) and RhoA/ROK activity. As previously demonstrated, elevated [Ca(2+)](i) is required to activate calcineurin, which dephosphorylates NFATc3, allowing its nuclear import. Here, we demonstrate that ROK increases actin polymerization, thus providing structural support for NFATc3 nuclear transport.

Topics: Actins; Active Transport, Cell Nucleus; Animals; Calcineurin; Calcineurin Inhibitors; Calcium Channels, L-Type; Calcium Signaling; Cells, Cultured; Chronic Disease; Cytoskeleton; Disease Models, Animal; Endothelin Receptor Antagonists; Endothelin-1; Genes, Reporter; Humans; Hypoxia; Male; Membrane Transport Modulators; Mice; Mice, Inbred BALB C; Mice, Knockout; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; NFATC Transcription Factors; Phosphorylation; Protein Kinase Inhibitors; Pulmonary Artery; Receptors, Endothelin; Recombinant Fusion Proteins; rho GTP-Binding Proteins; rho-Associated Kinases; rhoA GTP-Binding Protein; RNA, Messenger; Time Factors; Transcriptional Activation; Transfection; Up-Regulation

Maladaptive right ventricular (RV) hypertrophic responses lead to RV dysfunction and failure in patients with pulmonary arterial hypertension, but the mechanisms responsible for these changes are not well understood. The objective of this study was to evaluate the effect of treatment with bosentan on RV hypertrophy (RVH), fibrosis and expression of protein kinase C (PKC) isoforms in the RV of rats exposed to chronic hypoxia.. Adult Sprague-Dawley rats were housed in normoxia or hypoxia (FIO(2) = 10%) and administered vehicle or 100 mg/kg/day bosentan. After 3 weeks, echocardiographic and hemodynamic assessment was performed. PKC, procollagen-1 and collagen expression levels were assessed using immunoblot or colorimetric assay.. RV systolic pressure (RVSP) and RVH were higher in hypoxic compared with normoxic animals (RVSP: 72 ± 4 vs 25 ± 2 mm Hg, p < 0.05; RVH: 1.2 ± 0.06 vs 0.5 ± 0.03 mg/g body weight, p < 0.05). Bosentan had no effect on RVSP or mass in normoxic animals, but did attenuate RVH in hypoxic animals (hypoxic/vehicle: 1.2 ± 0.06; hypoxic/bosentan: 1.0 ± 0.05 mg/g body weight; p < 0.05). Hypoxia increased RV procollagen-1, and total collagen expression, effects that were attenuated by bosentan treatment. Hypoxia increased RV total and cytosolic PKC-δ protein expression, but had no effect on PKC-α or -ε isoforms. Administration with bosentan did not affect total PKC-δ protein expression. However, animals treated with bosentan had an increase in membranous PKC-δ when exposed to hypoxia.. Bosentan inhibits RVH and RV collagen expression in rats exposed to chronic hypoxia, possibly via alteration of PKC-δ activity.

Topics: Animals; Antihypertensive Agents; Bosentan; Collagen; Disease Models, Animal; Endothelin Receptor Antagonists; Endothelin-1; Fibrosis; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Male; Myocardium; Protein Isoforms; Protein Kinase C; Rats; Rats, Sprague-Dawley; Signal Transduction; Sulfonamides; Ventricular Dysfunction, Right

The systemic vascular response to hypoxia is vasodilation. However, reports suggest that the potent vasoconstrictor endothelin-1 (ET-1) is released from the vasculature during hypoxia. ET-1 is reported to augment superoxide anion generation and may counteract nitric oxide (NO) vasodilation. Moreover, ET-1 was proposed to contribute to increased vascular resistance in heart failure by increasing the production of asymmetric dimethylarginine (ADMA). We investigated the role of ET-1, the NO pathway, the potassium channels and radical oxygen species in hypoxia-induced vasodilation of large coronary arteries.. In prostaglandin F2α (PGF2α, 10 μM)-contracted segments with endothelium, gradual lowering of oxygen tension from 95 to 1% O2 resulted in vasodilation. The vasodilation to O2 lowering was rightward shifted in segments without endothelium at all O2 concentrations except at 1% O2. The endothelin receptor antagonist SB217242 (10 μM) markedly increased hypoxic dilation despite the free tissue ET-1 concentration in the arterial wall was unchanged in 1% O2 versus 95% O2. Exogenous ET-1 reversed hypoxic dilation in segments with and without endothelium, and the hypoxic arteries showed an increased sensitivity towards ET-1 compared to the normoxic controls. Without affecting basal NO, hypoxia increased NO concentration in PGF2α-contracted arteries, and an NO synthase inhibitor, L-NOARG,(300 μM, NG-nitro-L-Arginine) reduced hypoxic vasodilation. NO-induced vasodilation was reduced in endothelin-contracted preparations. Arterial wall ADMA concentrations were unchanged by hypoxia. Blocking of potassium channels with TEA (tetraethylammounium chloride)(10 μM) inhibited vasodilation to O2 lowering as well as to NO. The superoxide scavenger tiron (10 μM) and the putative NADPH oxidase inhibitor apocynin (10 μM) leftward shifted concentration-response curves for O2 lowering without changing vasodilation to 1% O2. PEG (polyethylene glycol) catalase (300 u/ml) inhibited H2O2 vasodilation, but failed to affect vasodilation to O2 lowering. Neither did PEG-SOD (polyethylene glycol superoxide dismutase)(70 u/ml) affect vasodilation to O2 lowering. The mitochondrial inhibitors rotenone (1 μM) and antimycin A (1 μM) both inhibited hypoxic vasodilatation.. The present results in porcine coronary arteries suggest NO contributes to hypoxic vasodilation, probably through K channel opening, which is reversed by addition of ET-1 and enhanced by endothelin receptor antagonism. These latter findings suggest that endothelin receptor activation counteracts hypoxic vasodilation.

Topics: Animals; Coronary Vessels; Dinoprost; Endothelin-1; Hypoxia; Models, Animal; Nitric Oxide; Oxygen; Potassium Channels; Reactive Oxygen Species; Swine; Vasodilation

Ghrelin has cardioprotective properties and, recently, has been shown to improve endothelial function and reduce endothelin-1 (ET-1)-mediated vasoconstriction in peripheral vascular disease. Recently, we reported that ghrelin attenuates pulmonary hypertension (PH) caused by chronic hypoxia (CH), which we hypothesized in this study may be via suppression of the ET-1 pathway. We also aimed to determine whether ghrelin's ability to prevent alterations of the ET-1 pathway also prevented adverse changes in pulmonary blood flow distribution associated with PH. Sprague-Dawley rats were exposed to CH (10% O(2) for 2 weeks) with daily subcutaneous injections of ghrelin (150 μg/kg) or saline. Utilizing synchrotron radiation microangiography, we assessed pulmonary vessel branching structure, which is indicative of blood flow distribution, and dynamic changes in vascular responsiveness to (1) ET-1 (1 nmol/kg), (2) the ET-1(A) receptor antagonist, BQ-123 (1 mg/kg), and (3) ACh (3.0 μg kg⁻¹ min⁻¹). CH impaired blood flow distribution throughout the lung. However, this vessel "rarefaction" was attenuated in ghrelin-treated CH-rats. Moreover, ghrelin (1) reduced the magnitude of endothelial dysfunction, (2) prevented an increase in ET-1-mediated vasoconstriction, and (3) reduced pulmonary vascular remodeling and right ventricular hypertrophy-all adverse consequences associated with CH. These results highlight the beneficial effects of ghrelin for maintaining optimal lung perfusion in the face of a hypoxic insult. Further research is now required to establish whether ghrelin is also an effective therapy for restoring normal pulmonary hemodynamics in patients that already have established PH.

Topics: Acetylcholine; Angiography; Animals; Antihypertensive Agents; Endothelin-1; Ghrelin; Hemodynamics; Hypertension, Pulmonary; Hypoxia; Lung; Male; Peptides, Cyclic; Rats; Rats, Sprague-Dawley; Regional Blood Flow; Synchrotrons; Vasoconstriction; Vasodilator Agents

Intermittent hypoxia (IH) resulting from sleep apnea causes both systemic and pulmonary hypertension. Enhanced endothelin-1 (ET-1)-induced vasoconstrictor reactivity is thought to play a central role in the systemic hypertensive response to IH. However, whether IH similarly increases pulmonary vasoreactivity and the signaling mechanisms involved are unknown. The objective of the present study was to test the hypothesis that IH augments ET-1-induced pulmonary vasoconstrictor reactivity through a PKCβ-dependent signaling pathway. Responses to ET-1 were assessed in endothelium-disrupted, pressurized pulmonary arteries (∼150 μm inner diameter) from eucapnic-IH [(E-IH) 3 min cycles, 5% O(2)-5% CO(2)/air flush, 7 h/day; 4 wk] and sham (air-cycled) rats. Arteries were loaded with fura-2 AM to monitor vascular smooth muscle (VSM) intracellular Ca(2+) concentration ([Ca(2+)](i)). E-IH increased vasoconstrictor reactivity without altering Ca(2+) responses, suggestive of myofilament Ca(2+) sensitization. Consistent with our hypothesis, inhibitors of both PKCα/β (myr-PKC) and PKCβ (LY-333-531) selectively decreased vasoconstriction to ET-1 in arteries from E-IH rats and normalized responses between groups, whereas Rho kinase (fasudil) and PKCδ (rottlerin) inhibition were without effect. Although E-IH did not alter arterial PKCα/β mRNA or protein expression, E-IH increased basal PKCβI/II membrane localization and caused ET-1-induced translocation of these isoforms away from the membrane fraction. We conclude that E-IH augments pulmonary vasoconstrictor reactivity to ET-1 through a novel PKCβ-dependent mechanism that is independent of altered PKC expression. These findings provide new insights into signaling mechanisms that contribute to vasoconstriction in the hypertensive pulmonary circulation.

Topics: Animals; Blood Gas Analysis; Blotting, Western; Calcium; Endothelin-1; Fura-2; Gene Expression Regulation; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Male; Muscle, Smooth, Vascular; Protein Kinase C; Protein Kinase C beta; Protein Kinase C-alpha; Protein Kinase Inhibitors; Pulmonary Artery; Rats; Rats, Wistar; rho-Associated Kinases; RNA, Messenger; Signal Transduction; Vasoconstriction; Vasoconstrictor Agents

Peroxisome proliferator-activated receptor (PPAR) γ activation attenuates hypoxia-induced pulmonary hypertension (PH) in mice. The current study examined the hypothesis that PPARγ attenuates hypoxia-induced endothelin-1 (ET-1) signaling to mediate these therapeutic effects. To test this hypothesis, human pulmonary artery endothelial cells (HPAECs) were exposed to normoxia or hypoxia (1% O(2)) for 72 h and treated with or without the PPARγ ligand rosiglitazone (RSG, 10 μM) during the final 24 h of exposure. HPAEC proliferation was measured with MTT assays or cell counting, and mRNA and protein levels of ET-1 signaling components were determined. To explore the role of hypoxia-activated transcription factors, selected HPAECs were treated with inhibitors of hypoxia-inducible factor (HIF)-1α (chetomin) or nuclear factor (NF)-κB (caffeic acid phenethyl ester, CAPE). In parallel studies, male C57BL/6 mice were exposed to normoxia (21% O(2)) or hypoxia (10% O(2)) for 3 wk with or without gavage with RSG (10 mg·kg(-1)·day(-1)) for the final 10 days of exposure. Hypoxia increased ET-1, endothelin-converting enzyme-1, and endothelin receptor A and B levels in mouse lung and in HPAECs and increased HPAEC proliferation. Treatment with RSG attenuated hypoxia-induced activation of HIF-1α, NF-κB activation, and ET-1 signaling pathway components. Similarly, treatment with chetomin or CAPE prevented hypoxia-induced increases in HPAEC ET-1 mRNA and protein levels. These findings indicate that PPARγ activation attenuates a program of hypoxia-induced ET-1 signaling by inhibiting activation of hypoxia-responsive transcription factors. Targeting PPARγ represents a novel therapeutic strategy to inhibit enhanced ET-1 signaling in PH pathogenesis.

Topics: Animals; Aspartic Acid Endopeptidases; Cell Hypoxia; Cell Proliferation; Endothelial Cells; Endothelin-1; Endothelin-Converting Enzymes; Gene Expression; Gene Expression Regulation; Humans; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Lung; Male; Metalloendopeptidases; Mice; Mice, Inbred C57BL; NF-kappa B; PPAR gamma; Pulmonary Artery; Receptor, Endothelin A; Receptor, Endothelin B; Rosiglitazone; Signal Transduction; Thiazolidinediones

Pulmonary arterial hypertension (PAH) is characterized by a progressive increase in pulmonary vascular resistance and elevation of pulmonary arterial pressure, leading to right ventricular failure and eventual death. Currently, no curative therapy for PAH is available, and the overall prognosis is very poor. Recently, direct activators of soluble guanylyl cyclase (sGC) have been tested as a novel therapeutic modality in experimental models of pulmonary arterial hypertension (PAH).. In this study, we used in vitro and in vivo models to evaluate the therapeutic potential of 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1), a dual functioning chemical, as a direct activator of guanylyl cyclase and an inhibitor of hypoxia-inducible factor-1.. We analyzed the effects of YC-1 on cell proliferation and the levels of p21 and p53 in human pulmonary artery smooth muscle cells (HPASMCs) under hypoxia. We also determined the effects of YC-1 on expression of endothelin-1 (ET-1) and phosphorylation status of endothelial nitric oxide synthase (eNOS) at Ser(1179) in human pulmonary artery endothelial cells (HPAECs) under hypoxia. In mice, hypoxic PAH was induced by exposure to normobaric hypoxic conditions for 28 days. To assess preventive or therapeutic effects, randomized mice were subjected to once daily i.p. injections of YC-1 for the entire hypoxic period (5 mg/kg) or for the last seven days of a 28-day hypoxic period (5 and 10 mg/kg). On day 28, we measured the right ventricular systolic pressure (RVSP) and determined the degrees of right ventricular hypertrophy (RVH) and vascular remodeling.. In HPASMCs, YC-1 inhibited hypoxia-induced proliferation and induction of p53 and p21 in a concentration-dependent manner. Also, YC-1 suppressed the hypoxia-induced expression of ET-1 mRNA and dephosphorylation of eNOS at Ser(1179) in HPAECs. In the preventive in vivo model, a daily dose of 5 mg/kg YC-1 significantly prevented the elevation of RVSP, development of RVH, and pulmonary vascular remodeling, which were caused by hypoxic exposure. In the therapeutic model, YC-1 at daily doses of 5 and 10 mg/kg alleviated RVH and pulmonary vascular remodeling but did not prevent the elevation of RVSP.. Our results indicate that YC-1 prevents the development of hypoxia-induced PAH in a preventive model and alleviates RVH and pulmonary vascular remodeling in a therapeutic model. Therefore, these data imply that YC-1 has therapeutic potential for use in a single or combination therapy for PAH.

Topics: Animals; Cell Proliferation; Cells, Cultured; Cyclin-Dependent Kinase Inhibitor p21; Endothelin-1; Enzyme Activators; Familial Primary Pulmonary Hypertension; Humans; Hypertension, Pulmonary; Hypoxia; Indazoles; Male; Mice; Mice, Inbred C57BL; Muscle, Smooth, Vascular; Nitric Oxide Synthase Type III; Pulmonary Artery; Tumor Suppressor Protein p53

1. The aim of the present study was to investigate the in vivo effects of vasonatrin peptide (VNP) on hypoxia-induced pulmonary hypertension (HPH). 2. The HPH model was developed by subjecting rats to hypobaric hypoxia. The HPH rats were then treated with either VNP (50 microg/kg per day, i.p.) or saline (0.5 mL, i.p.) every day for 7 days. Haemodynamic indices, right ventricular hypertrophy (RVH) and remodelling of the pulmonary arteries were evaluated. In addition, plasma levels of atrial natriuretic peptide (ANP), endothelin (ET)-1 and angiotensin II (AngII) were determined, as was natriuretic peptide receptor-C (NPR-C) mRNA expression in the right ventricle. 3. Hypobaric hypoxia induced severe HPH compared with the normoxic control group. Treatment of HPH rats with VNP for 1 week significantly reduced mean pulmonary arterial pressure, pulmonary vascular resistance, RVH and muscularization of the pulmonary arteries, although pulmonary blood flow was increased in this group. In addition, significantly lower levels of plasma ET-1 and AngII and cardiac NPR-C mRNA expression were observed in VNP-treated compared with saline-treated HPH rats, whereas higher plasma concentrations of ANP were found in the former group. Acute intravenous administration of 50 microg/kg VNP significantly ameliorated pulmonary haemodynamics in HPH rats. 4. Taken together, the date indicate that VNP has certain preventative and therapeutic effects against HPH.

Topics: Angiotensin II; Animals; Antihypertensive Agents; Atmospheric Pressure; Atrial Natriuretic Factor; Disease Models, Animal; Endothelin-1; Heart Ventricles; Hemodynamics; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Male; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Receptors, Atrial Natriuretic Factor

We hypothesised that the potential protective effects of endothelial ET(B) are important in limiting pulmonary vascular muscularisation, vasoconstriction and the development of pulmonary arterial hypertension in response to hypoxia.. EC-specific ET(B) knockout mice (EC ET(B)(-/-)) and control mice (ET(B)(f/f)) were subjected to hypobaric hypoxic (10% FiO2) or normoxic conditions for 14 days before assessment of right ventricular pressure and pulmonary vascular morphology and function.. During normoxia, no difference in right ventricular pressure was detected between EC ET(B)(-/-) (23.7 +/- 1.7 mm Hg) and ET(B)(f/f) mice (20.2 +/- 1.5 mm Hg). Hypoxia induced an exaggerated increase in right ventricular pressure in EC ET(B)(-/-) mice (34.4 +/- 1.2 mm Hg vs. 24.6 +/- 1.4 mm Hg), accompanied by an increase in right ventricular mass. No effect was observed in ET(B)(f/f) mice. Endothelin-1 constricted pulmonary arteries from both groups, although maximum response was similar irrespective of inspired oxygen or genotype. Hypoxia increased the percentage of muscularised vessels in both groups of mice, but the percentage increase was significantly greater in EC ET(B)(-/-) mice.. The potential protective effects of endothelial ET(B) are important in limiting pulmonary vascular muscularisation and the development of pulmonary arterial hypertension in response to hypoxia.

Topics: Animals; Blood Pressure; Disease Models, Animal; Endothelin-1; Endothelium, Vascular; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Muscle, Smooth, Vascular; Pulmonary Artery; Receptor, Endothelin B; Vasoconstriction; Ventricular Pressure

Rho-kinase-dependent Ca2+ sensitization is an essential process for contraction of mammalian vascular smooth muscle but the information about its effects in non-mammalian vessels is scarce. We aimed to investigate, using the Rho-kinase inhibitor hydroxyfasudil, the potential role of the Rho-kinase pathway of Ca2+ sensitization in depolarization- and agonist-mediated contraction of chicken embryo (at day 19 of the 21 days of incubation) femoral arteries. Contraction elicited by KCl (125 mM) comprised two phases (phasic and tonic contraction), both of which were abolished in the absence of extracellular Ca2+. Hydroxyfasudil (10 microM) left the initial phasic component nearly intact but abolished the tonic component. Hydroxyfasudil also induced a marked impairment of the contractions elicited by phenylephrine (PE), the thromboxane A2 mimetic U46619, and endothelin-1. In contrast, inhibition of protein kinase C (PKC) by chelerythrine did not affect KCl- or PE-induced contractions, indicating lack of participation of PKC-mediated Ca2+ sensitization. Incubation under chronic hypoxia (15% O2 from day 0) impaired embryonic growth but did not significantly affect hydroxyfasudil-mediated relaxation. In summary, our findings are indicative of a role for Rho-kinase activity in depolarization- and agonist-induced force generation in chicken embryo femoral arteries.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Benzophenanthridines; Body Weight; Calcium; Chick Embryo; Egtazic Acid; Endothelin-1; Enzyme Inhibitors; Femoral Artery; Hypoxia; NG-Nitroarginine Methyl Ester; Oxadiazoles; Phenylephrine; Phorbol 12,13-Dibutyrate; Potassium Chloride; Protein Kinase C; Protein Kinase Inhibitors; Quinoxalines; rho-Associated Kinases; Vasoconstriction

To test the hypothesis that central changes in sympathoregulation might contribute to sympathoexcitation after cyclic intermittent hypoxia (CIH) we exposed male Sprague-Dawley rats to CIH or to room air sham (Sham) for 8h/d for 3 weeks. After completion of the exposure we assessed heart rate, mean arterial pressure and renal sympathetic nerve activity in conscious animals before and after intracerebroventricular (i.c.v.) administration of endothelin-1 (ET-1, 3 pmol). CIH-exposed animals had a significantly greater sympathetic response to ET-1 than did Sham-exposed animals (CIH 137.8+/-15.6% of baseline; Sham 112.2+/-10.0% of baseline; CIH vs. Sham, P=0.0373). This enhanced sympathetic response to i.c.v. ET-1 was associated with greater expression of endothelin receptor A (ETA) protein in the subfornical organs of CIH-exposed relative to Sham-exposed rats. We conclude that 3-week CIH exposure enhances central ET-1 receptor expression and the sympathetic response to i.c.v. ET-1 suggesting central endothelin may contribute to the sympathetic and hemodynamic response to cyclic intermittent hypoxia.

Topics: Animals; Blood Pressure; Consciousness; Endothelin-1; Heart Rate; Hypoxia; Injections, Intraventricular; Kidney; Male; Periodicity; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Subfornical Organ; Sympathetic Nervous System; Time Factors

Pulmonary hypertension (PH) is characterized by elevated pulmonary artery pressure (PAP), pulmonary vascular remodeling and right ventricular hypertrophy, which are mainly due to endothelial dysfunction. Electro-acupuncture has shown beneficial effects on cardiovascular homeostasis, but little evidence has been obtained on pulmonary effects. The goal of the present study was to investigate whether electro-acupuncture on bladder-13 and -15 points can protect against chronic hypoxia-induced PH by regulating endothelium-derived endothelin (ET)-1 and endothelial nitric oxide synthase (eNOS). Male Wistar rats were exposed to hypoxia to induce PH. Hemodynamic analysis revealed that mean PAP was similar under normoxic conditions. Chronic hypoxia increased mean PAP to 37 +/- 3 mmHg, and electro-acupuncture attenuated it to 29 +/- 3 mmHg. Absolute right ventricular weight was ameliorated by electro-acupuncture from 0.288 +/- 0.048 g to 0.228 +/- 0.029 g under hypoxic conditions. Hypoxia-induced right ventricular hypertrophy index decreased from 0.477 +/- 0.069 to 0.378 +/- 0.053 with electro-acupuncture treatment. Histological examination revealed that hypoxic rats showed increased medial pulmonary artery wall thickness as well as muscularization. However, these alternations by chronic hypoxia were attenuated by electro-acupuncture. There was no difference in eNOS or ET-1 between groups under normoxic conditions. Electro-acupuncture treatment significantly improved the circulating eNOS concentration (365.36 +/- 31.51 pg/mL) compared with only hypoxia exposure (247.60 +/- 30.64 pg/mL). In lung homogenate, levels of eNOS under hypoxia increased from 684.96 +/- 117.90 to 869.86 +/- 197.61 pg/mg by electro-acupuncture treatment. Levels of ET-1 changed oppositely to eNOS in response to electro-acupuncture (ET-1 in plasma, 29.44 +/- 2.09 versus 20.70 +/- 2.37 pg/mL; ET-1 in lung homogenate, 120.51 +/- 3.03 versus 110.60 +/- 4.04 pg/mg). In conclusion, these results indicated that treatment with electro-acupuncture can protect against hypoxia-induced PH, possibly by regulating the balance of endothelium-derived vasoconstrictors and vasodilators.

Topics: Animals; Electroacupuncture; Endothelin-1; Endothelium; Hemodynamics; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Lung; Nitric Oxide Synthase Type III; Rats; Rats, Wistar; Tissue Extracts

Pulmonary hypertension is a kind of disease associated with a very high rate of mortality, and there are not many effective drugs for the treatment. Today, endothelin (ET)-1 receptor antagonists were proved to be effective in the treatment of pulmonary hypertension. Aiming at developing new endothelin-A receptor (ETA) antagonist for treatment of pulmonary hypertension, di-n-butylaminocarbamyl-L-leucyl-D-tryptophanyl-D-4-chloro-Phe, named GF063, was synthesized at base of selective ETA receptor antagonist BQ485 and selected for the further pharmacological characterization. The preliminary pharmacodynamics of GF063 was evaluated by radioligand receptor binding assay and test of antivasoconstriction effects in vitro and in vivo. The integrative pharmacodynamics was evaluated in hypoxia-induced rat pulmonary hypertension. In vitro, GF063 bound to ETA receptor with 100,000-fold higher affinity than to ETB receptor. GF063 concentration dependently inhibited contraction of isolated rat aortic ring induced by ET-1 and shifted the cumulative concentration-contraction response curve to right with no change in the maximal response. In vivo, GF063 inhibited the increase of mean systemic arterial pressure induced by ET-1 in anesthetized rat. In hypoxia-induced rat pulmonary hypertension model, pretreatment with GF063 (40 mg/kg, s.c.) significantly decreased pulmonary artery pressure and right ventricular hypertrophy, also significantly inhibited the increase of ET-1 level in lung, improved hemodynamics, and alleviated the wall thickness of pulmonary vessels. This study indicated that GF063, as a selective ETA receptor antagonist, could inhibit vasoconstriction effects in vivo and in vitro, could prevent pulmonary hypertension induced by hypoxia, and may have great potential to be developed as a new drug of antipulmonary hypertension.

Topics: Animals; Aorta, Thoracic; Blood Pressure; Dose-Response Relationship, Drug; Endothelin A Receptor Antagonists; Endothelin-1; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; In Vitro Techniques; Lung; Male; Oligopeptides; Pulmonary Artery; Rats; Rats, Wistar; Vasoconstriction

Expression of peroxisome proliferator-activated receptor gamma (PPARgamma) is decreased in the lungs of patients with pulmonary hypertension, and PPARgamma ligands have been associated with the release of vasoactive substances from vascular endothelial cells and prevention of vascular remodelling. We hypothesized that PPARgamma may play a critical role in the development of pulmonary hypertension induced by chronic hypoxia.. Male adult Sprague-Dawley rats were exposed to normoxia, normoxia and rosiglitazone (8 mg/kg orally, 5 days/week), hypoxia (12% inspired O(2) fraction), or hypoxia and rosiglitazone for 4 weeks. On the last day of the fourth week, pulmonary arterial pressure was measured and morphological changes in pulmonary vessels were assessed. The expression of PPARgamma, endothelin (ET)-1 and vascular endothelial growth factor (VEGF) was also analysed.. Rosiglitazone inhibited the development of pulmonary hypertension, and pulmonary vascular remodelling induced by chronic hypoxia. PPARgamma expression was decreased and expression of ET-1 and VEGF was increased in lung tissues of the hypoxia group. Rosiglitazone treatment prevented the hypoxia-induced reduction in PPARgamma expression, and restored ET-1 and VEGF expression almost to the levels of the normoxia group.. Rosiglitazone inhibited the development of pulmonary hypertension induced by chronic hypoxia, perhaps by reversing the changes in PPARgamma, ET-1 and VEGF expression induced by hypoxia. These findings indicate that rosiglitazone may be beneficial in the treatment of chronic hypoxic pulmonary hypertension.

Topics: Animals; Disease Models, Animal; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Male; PPAR gamma; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Rosiglitazone; Thiazolidinediones; Vascular Endothelial Growth Factors

Chronic pulmonary hypertension in infancy and childhood is characterized by a fixed and progressive increase in pulmonary arterial pressure and resistance, pulmonary arterial remodeling, and right ventricular hypertrophy and systolic dysfunction. These abnormalities are replicated in neonatal rats chronically exposed to hypoxia from birth in which increased activity of Rho-kinase (ROCK) is critical to injury, as evidenced by preventive effects of ROCK inhibitors. Our objective in the present study was to examine the reversing effects of a late or rescue approach to treatment with a ROCK inhibitor on the pulmonary and cardiac manifestations of established chronic hypoxic pulmonary hypertension. Rat pups were exposed to air or hypoxia (13% O(2)) from postnatal day 1 and were treated with Y-27632 (15 mg/kg) or saline vehicle by twice daily subcutaneous injection commencing on day 14, for up to 7 days. Treatment with Y-27632 significantly attenuated right ventricular hypertrophy, reversed arterial wall remodeling, and completely normalized right ventricular systolic function in hypoxia-exposed animals. Reversal of arterial wall remodeling was accompanied by increased apoptosis and attenuated content of endothelin (ET)-1 and ET(A) receptors. Treatment of primary cultured juvenile rat pulmonary artery smooth muscle cells with Y-27632 attenuated serum-stimulated ROCK activity and proliferation and increased apoptosis. Smooth muscle apoptosis was also induced by short interfering RNA-mediated knockdown of ROCK-II, but not of ROCK-I. We conclude that sustained rescue treatment with a ROCK inhibitor reversed both the hemodynamic and structural abnormalities of chronic hypoxic pulmonary hypertension in juvenile rats and normalized right ventricular systolic function. Attenuated expression and activity of ET-1 and its A-type receptor on pulmonary arterial smooth muscle was a likely contributor to the stimulatory effects of ROCK inhibition on apoptosis. In addition, our data suggest that ROCK-II may be dominant in enhancing survival of pulmonary arterial smooth muscle.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Age Factors; Aging; Amides; Animals; Apoptosis; Cell Proliferation; Cells, Cultured; Chronic Disease; Disease Models, Animal; Endothelin-1; Hemodynamics; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Injections, Subcutaneous; Muscle, Smooth, Vascular; Myocardium; Protein Kinase Inhibitors; Pulmonary Artery; Pyridines; Rats; Receptor, Endothelin A; rho-Associated Kinases; RNA Interference; Ventricular Dysfunction, Right; Ventricular Function, Right; Ventricular Remodeling

This study evaluated the contribution of the 20-HETE/cytochrome P450-4A ω-hydroxylase (CYP4A) system to the early development of salt-induced vascular changes in Dahl salt-sensitive (SS) rats.. CYP4A expression and 20-HETE production were evaluated and responses to norepinephrine, endothelin, and reduced PO₂ were determined by video microscopy in isolated mesenteric resistance arteries from SS rats fed high salt (HS; 4% NaCl) diet for three days vs. low salt (LS; 0.4% NaCl) controls.. CYP4A enzyme inhibition with dibromododecenyl methylsulfimide (DDMS) selectively reduced norepinephrine sensitivity and restored impaired vasodilation in response to reduced PO₂ in SS rats fed HS diet. In the presence of DDMS, vasodilatation to reduced PO₂ was eliminated by indomethacin and unaffected by l-NAME in rats fed LS diet, and eliminated by l-NAME and unaffected by indomethacin in rats fed HS diet. The 20-HETE agonist WIT003 restored norepinephrine sensitivity in DDMS-treated arteries of HS-fed rats. HS diet increased vascular 20-HETE production and CYP4A protein levels by ∼24% and ∼31%, respectively, although these differences were not significant.. These findings support the hypothesis that the 20-HETE/CYP4A system modulates vessel responses to norepinephrine and vascular relaxation to reduced PO₂ in mesenteric resistance arteries of SS rats fed HS diet.

Topics: Amides; Animals; Cyclooxygenase Inhibitors; Cytochrome P-450 CYP4A; Endothelin-1; Enzyme Inhibitors; Hydroxyeicosatetraenoic Acids; Hypoxia; In Vitro Techniques; Indomethacin; Male; Mesenteric Arteries; Microscopy, Video; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Norepinephrine; Rats; Rats, Inbred Dahl; Sodium Chloride, Dietary; Sulfones; Vascular Resistance; Vasoconstriction

Although large quantities of glutamate are found in the carotid body, to date this excitatory neurotransmitter has not been assigned a role in chemoreception. To examine the possibility that glutamate and its N-methyl-d-aspartate (NMDA) receptors play a role in acclimatization after exposure to cyclic intermittent hypoxia (CIH), we exposed male Sprague-Dawley rats to cyclic hypoxia or to room air sham (Sham) for 8 h/day for 3 wk. Using RT-PCR, Western blot analysis, and immunohistochemistry, we found that ionotropic NMDA receptors, including NMDAR1, NMDAR2A, NMDAR2A/2B, are strongly expressed in the carotid body and colocalize with tyrosine hydroxylase in glomus cells. CIH exposure enhanced the expression of NMDAR1 and NMDAR2A/2B but did not substantially change the level of NMDAR2A. We assessed in vivo carotid sinus nerve activity (CSNA) at baseline, in response to acute hypoxia, in response to infused NMDA, and in response to infused endothelin-1 (ET-1) with and without MK-801, an NMDA receptor blocker. Infusion of NMDA augmented CSNA in CIH rats (124.61 +/- 2.64% of baseline) but not in sham-exposed rats. Administration of MK-801 did not alter baseline activity or response to acute hypoxia, in either CIH or sham animals but did reduce the effect of ET-1 infusion on CSNA (CSNA after ET-1 = 160.96 +/- 8.05% of baseline; ET-1 after MK-801 = 118.56 +/- 9.12%). We conclude that 3-wk CIH exposure increases expression of NMDA functional receptors in rats, suggesting glutamate and its receptors may play a role in hypoxic acclimatization to CIH.

Topics: Adaptation, Physiological; Animals; Blotting, Western; Carotid Body; Carotid Sinus; Disease Models, Animal; Disks Large Homolog 4 Protein; Endothelin-1; Excitatory Amino Acid Antagonists; Glutamic Acid; Hypoxia; Immunohistochemistry; Intracellular Signaling Peptides and Proteins; Male; Membrane Proteins; N-Methylaspartate; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Reverse Transcriptase Polymerase Chain Reaction; Tyrosine 3-Monooxygenase; Up-Regulation

We previously reported that intermittent hypoxia (IH) augments hypoxic sensory response (HSR) and increases the number of glomus cells in neonatal carotid bodies. In the present study, we tested the hypothesis that recruitment of endothelin-1 (ET-1) signaling by reactive oxygen species (ROS) plays a critical role in IH-evoked changes in neonatal carotid bodies. Experiments were performed on neonatal rats exposed either to 10 days of IH (P0-P10; 8 h/day) or to normoxia. IH augmented HSR of the carotid bodies ex vivo and resulted in hyperplasia of glomus cells. The effects of IH were associated with enhanced basal release of ET-1 under normoxia, sensitization of carotid body response to exogenous ET-1, and upregulation of ET(A) but not an ET(B) receptor mRNA without altering the ET-1 content. An ET(A) but not ET(B) receptor antagonist prevented augmented HSR by IH. ROS levels were elevated in carotid bodies from IH-treated rat pups as evidenced by increased levels of malondialdehyde. Systemic administration of manganese (III) tetrakis(1-methyl-4-pyridyl)porphyrin pentachloride (MnTMPyP; 5 mg/kg ip), a scavenger of O(2)(*-), prevented IH-induced elevation of ROS, basal release of ET-1, upregulation of ET(A) mRNA, and augmented HSR. In striking contrast, MnTMPyP treatment had no significant effect on IH-induced hyperplasia of glomus cells. These results demonstrate that IH-evoked increase in HSR involve a ROS-mediated increase in basal ET-1 release and upregulation of ET(A) receptor mRNA.

Topics: Animals; Animals, Newborn; Carotid Body; Endothelin-1; Endothelins; Hypoxia; Immunohistochemistry; Malondialdehyde; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Receptor, Endothelin A; RNA, Messenger; Signal Transduction; Up-Regulation

Patients with 1-ventricle (1V) physiology may be at risk for peripheral arterial dysfunction at a young age. To determine whether infants and young children with 1V physiology and hypoxemia have peripheral arterial dysfunction before undergoing the Fontan operation, we measured (1) flow-mediated vasodilation (FMD) in the brachial artery, (2) serum levels of vasoactive mediators endothelin-1 (ET-1) and metabolites of nitric oxide, and (3) arterial stiffness with pulse-wave velocity (PWV) in the aorta. Eighteen patients with 1V physiology before the Fontan procedure and hypoxemia and 19 patients with normoxemia and 2-ventricle (2V) physiology were studied. Measurements were collected during cardiac catheterization. FMD in the brachial artery was the diameter gain after 4.5 minutes of forearm occlusion measured with high-resolution ultrasound and edge-detection software. Nitric oxide and ET-1 levels were measured in venous blood. PWV between the left carotid and femoral arteries was measured using pulse Doppler ultrasound. FMD was lower (2.4 +/- 3.7% vs 11.3 +/- 6%, p <0.0005) and ET-1 levels were higher (35.5 +/- 11.3% vs 24.1 +/- 9.7%, p = 0.003) in subjects with 1V physiology versus those with 2V physiology, respectively. There were no differences in nitric oxide levels or PWV. In conclusion, infants and young children with 1V physiology and hypoxemia have blunted FMD and higher ET-1 levels before undergoing the Fontan operation compared with normoxemic subjects with 2V physiology. A further understanding of pathophysiologic mechanisms underlying peripheral arterial dysfunction, including the roles of hypoxemia, low cardiac index, and ET-1, may lead to targeted therapies and improve the long-term survival of patients with 1V physiology.

Topics: Blood Flow Velocity; Brachial Artery; Child, Preschool; Endothelin-1; Female; Heart Defects, Congenital; Heart Ventricles; Humans; Hypoxia; Infant; Male

Berger, Marc M., Christoph Dehnert, Damian M. Bailey, Andrew M. Luks, Elmar Menold, Christian Castell, Guido Schendler, Vitalie Faoro, Heimo Mairbäurl, Peter Bärtsch, and Eric R. Swenson. Transpulmonary plasma ET-1 and nitrite differences in high altitude pulmonary hypertension. High Alt. Med. Biol. 10:17-24, 2009.- Thirty-four mountaineers were studied at low (110 m) and high altitude (4559 m) to evaluate if increased pulmonary artery systolic pressure (PASP) at high altitude is associated with increased pulmonary endothelin-1 (ET-1) availability and alterations in nitrite metabolism across the lung. Blood samples were obtained using central venous and radial artery catheters for plasma ET-1 and nitrite. Pulmonary blood flow was measured by inert gas rebreathing to calculate transpulmonary exchange of plasma ET-1 and nitrite, and PASP was assessed by transthoracic Doppler echocardiography. After ascent to high altitude, PASP increased from 23 +/- 4 to 39 +/- 10 mmHg. Arterial and central venous plasma ET-1 increased, while plasma nitrite did not change significantly. At low altitude there was a transpulmonary loss of plasma ET-1, but a transpulmonary gain at high altitude. In contrast was a transpulmonary gain of plasma nitrite at low altitude and a transpulmonary loss at high altitude. PASP positively correlated with a transpulmonary gain of plasma ET-1 and negatively correlated with a transpulmonary loss of plasma nitrite. These results suggest that a transpulmonary gain of plasma ET- 1 is associated with higher PASP at high altitude. Transpulmonary loss of plasma nitrite indicates either less pulmonary nitric oxide (NO) production, which contributes to higher PASP, or increased NO bioavailability arising from nitrite reduction, which may oppose ET-1-mediated vasoconstriction.

Topics: Adult; Altitude; Blood Gas Analysis; Endothelin-1; Female; Humans; Hypertension, Pulmonary; Hypoxia; Lung; Male; Mountaineering; Nitrites; Oxygen; Systole; Ultrasonography

Our aim was to investigate the involvement of the endothelin (ET) system in the cardiovascular consequences of intermittent hypoxia (IH).. Obstructive sleep apnea (OSA) syndrome is an important risk factor for cardiovascular morbidity. Chronic IH, a major component of OSA, is thought to be responsible for most of the cardiovascular complications occurring during OSA, but the underlying mechanisms remain to be determined.. Chronic IH was applied in rats genetically prone to develop hypertension (spontaneous hypertensive rats [SHR]) and their normotensive controls. The cardiovascular effects were assessed in vivo and in Langendorff perfused hearts. Hypoxia inducible factor (HIF)-1 activity and targeting of the myocardial ET-1 gene and activation of the ET system were investigated using tissue chromatin immunoprecipitation, enzyme-linked immunoadsorbent assay, immunostaining, and Western blotting.. Chronic IH enhanced hypertension development and infarct size in SHR compared with that seen in control rats. This was accompanied by an increase in myocardial big ET-1, ET-1, and ET-A receptor expression and by an enhanced coronary vascular reactivity to ET-1 in SHR only. Myocardial HIF-1 activity was increased, and HIF-1 was shown to be linked to the promoter of the myocardial ET-1 gene after chronic IH only. Moreover, administration of bosentan, a mixed ET receptor antagonist, during chronic IH prevented both the increase in blood pressure and in infarct size.. In SHR, activation of the ET system, mediated by HIF-1 activity, is responsible for the enhanced susceptibility to chronic IH and for its associated cardiovascular consequences leading to hypertension and ischemic injury. Furthermore, the beneficial effects of bosentan suggest exploring ET antagonists as possible therapeutic tools in OSA.

Topics: Animals; Antihypertensive Agents; Blood Pressure; Bosentan; Disease Models, Animal; Endothelin-1; Genetic Predisposition to Disease; Heart; Hypertension; Hypoxia; Hypoxia-Inducible Factor 1; Male; Myocardial Infarction; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Sleep Apnea, Obstructive; Sulfonamides

Phenotypic and contractile changes in pulmonary arterial smooth muscle cells (PASMCs) were examined in rats with pulmonary hypertension induced by hypoxia. Exposure to hypoxia induced pulmonary hypertension within 1-4 weeks. Staining with BrdU revealed that proliferative activities of PASMCs peaked at 1 week of hypoxic exposure, and then moderate proliferative activity was maintained for the next 2-4 weeks. The beta-actin/alpha-actin ratio also increased at 1-2 weeks of exposure to hypoxia. Absolute contractility of the pulmonary arterial ring continuously decreased during hypoxia, whereas the basal active tonus of the pulmonary artery increased at 1-3 weeks. Nicardipine, the ETA-receptor antagonis, CI-1034 and the rho-kinase inhibitor Y27632 partially inhibited the elevated active tonus. Endothelin-1 content in the pulmonary hypertensive lung was continuously increased during exposure to hypoxia. In conclusion, the hypoxia-induced proliferative activity of PASMCs comprised a transient phase followed by a sustained phase. The change in PASMCs from a contractile to a synthetic phenotype also correlated with proliferative activity, which subsequently decreased PASMC contractility. The continuous production of endothelin-1 upon hypoxic exposure might contribute to the increased basal tonus of the pulmonary arterial wall, which might subsequently increase pulmonic arterial pressure, resulting in accelerated pulmonary hypertension.

Topics: Actins; Amides; Animals; Cell Proliferation; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Immunohistochemistry; Male; Muscle Contraction; Muscle, Smooth; Nicardipine; Phenotype; Pulmonary Artery; Pyridines; Rats; Rats, Sprague-Dawley; Thiazines; Time Factors

Effects of chronic hypoxia (CH) on store- and receptor-operated Ca(2+) entry (SOCE, ROCE) in pulmonary vascular smooth muscle (VSM) are controversial, although whether genetic variation explains such discrepancies in commonly studied rat strains is unclear. Since protein kinase C (PKC) can inhibit Ca(2+) permeable nonselective cation channels, we hypothesized that CH differentially alters PKC-dependent inhibition of SOCE and ROCE in pulmonary VSM from Sprague-Dawley and Wistar rats. To test this hypothesis, we examined SOCE and endothelin-1 (ET-1)-induced ROCE in endothelium-disrupted, pressurized pulmonary arteries from control and CH Sprague-Dawley and Wistar rats. Basal VSM Ca(2+) was elevated in CH Wistar, but not Sprague-Dawley, rats. Further, CH attenuated SOCE in VSM from Sprague-Dawley rats, while augmenting this response in Wistar rats. CH reduced ROCE in arteries from both strains. PKC inhibition restored SOCE in CH Sprague-Dawley arteries to control levels, while having no effect on SOCE in Wistar arteries or on ROCE in either strain. We conclude that effects of CH on pulmonary VSM SOCE are strain dependent, whereas inhibitory effects of CH on ROCE are strain independent. Further, PKC inhibits SOCE following CH in Sprague-Dawley, but not Wistar, rats but does not contribute to ET-1-induced ROCE in either strain.

Topics: Animals; Biological Transport; Calcium; Chronic Disease; Endothelin-1; Hypoxia; Muscle, Smooth, Vascular; Protein Kinase C; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Rats, Wistar; Species Specificity

Necrotizing enterocolitis (NEC) has high morbidity in premature infants. Hypoxia-ischemia, infection, and enteral feeding are risk factors associated with NEC, whereas feeding human milk is protective. Vasoactive and inflammatory mediators in NEC remain elusive. Gangliosides are found in human milk and enterocyte membranes. An infant bowel model of NEC was developed to test the hypothesis that gangliosides modulate the inflammatory response to infection and hypoxia.. Viable, noninflamed bowel was obtained from 9 infants between 26 and 40 weeks' gestational age. Infant bowel was treated in culture with Escherichia coli lipopolysaccharide (LPS) and hypoxia in the presence or absence of preexposure to gangliosides. Bowel necrosis and production of nitric oxide, endothelin-1, serotonin, eicosanoids, hydrogen peroxide, and proinflammatory cytokines were measured.. Ganglioside preexposure reduced bowel necrosis and endothelin-1 production in response to LPS. Gangliosides suppressed infant bowel production of nitric oxide, leukotriene B4, prostaglandin E2, hydrogen peroxide, interleukin-1beta, interleukin-6, and interleukin-8 in response to LPS exposure and hypoxia.. A bowel protective effect of gangliosides is indicated by modulation of vasoactive mediators and proinflammatory signal suppression.

Topics: Animals; Anti-Inflammatory Agents; Colon; Endothelin-1; Enterocolitis, Necrotizing; Escherichia coli; Gangliosides; Humans; Hypoxia; In Vitro Techniques; Infant, Newborn; Inflammation; Inflammation Mediators; Lipopolysaccharides; Milk; Necrosis

Hypoxia transiently increases transcription of the gene encoding heme oxygenase-1 (HO-1) and potently activates production of endothelin-1 (ET-1), the latter of which plays a central role in cellular adaptation to hypoxia. The ventilatory response to hypoxia attenuates with aging, and decreased responsiveness to hypoxia is seen in the aged vs. young rats, suggesting that the functionality of the oxygen-sensitive mechanism is age-dependent. In the present study, we examined the effects of aging on the expression of HO-1 and ET-1 in the carotid body, which is a small cluster of chemoreceptors and supporting cells that measure changes in the composition of arterial blood flowing through it. Our results revealed that HO-1 and ET-1 were expressed in carotid bodies of both young and old rats, although less so in the old ones. Exposure to chronic intermittent hypoxia significantly increased both HO-1 and ET-1 immunoreactivity in both young and old carotid body tissues, with the persisting age-dependent inequality to the disadvantage of old age. Considering that ET-1 is capable of enhancing intermittent hypoxia-induced chemosensory responses by the carotid body, our results suggest that decreased induction of ET-1 and HO-1 during aging could form the basis for age-related reductions in chemosensory discharge.

Topics: Aging; Animals; Carotid Body; Chronic Disease; Endothelin-1; Gene Expression Regulation, Enzymologic; Heme Oxygenase-1; Hypoxia; Male; Rats; Rats, Wistar

We have reported that eucapnic intermittent hypoxia (E-IH) causes systemic hypertension, elevates plasma endothelin 1 (ET-1) levels, and augments vascular reactivity to ET-1 and that a nonspecific ET-1 receptor antagonist acutely lowers blood pressure in E-IH-exposed rats. However, the effect of chronic ET-1 receptor inhibition has not been evaluated, and the ET receptor subtype mediating the vascular effects has not been established. We hypothesized that E-IH causes systemic hypertension through the increased ET-1 activation of vascular ET type A (ET(A)) receptors. We found that mean arterial pressure (MAP) increased after 14 days of 7 h/day E-IH exposure (109 +/- 2 to 137 +/- 4 mmHg; P < 0.005) but did not change in sham-exposed rats. The ET(A) receptor antagonist BQ-123 (10 to 1,000 nmol/kg iv) acutely decreased MAP dose dependently in conscious E-IH but not sham rats, and continuous infusion of BQ-123 (100 nmol.kg(-1).day(-1) sc for 14 days) prevented E-IH-induced increases in MAP. ET-1-induced constriction was augmented in small mesenteric arteries from rats exposed 14 days to E-IH compared with those from sham rats. Constriction was blocked by the ET(A) receptor antagonist BQ-123 (10 microM) but not by the ET type B (ET(B)) receptor antagonist BQ-788 (100 microM). ET(A) receptor mRNA content was greater in renal medulla and coronary arteries from E-IH rats. ET(B) receptor mRNA was not different in any tissues examined, whereas ET-1 mRNA was increased in the heart and in the renal medulla. Thus augmented ET-1-dependent vasoconstriction via vascular ET(A) receptors appears to elevate blood pressure in E-IH-exposed rats.

Topics: Animals; Antihypertensive Agents; Blood Pressure; Coronary Vessels; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Endothelin-1; Hypertension; Hypoxia; Infusions, Parenteral; Male; Mesenteric Arteries; Oligopeptides; Peptides, Cyclic; Piperidines; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Renal Artery; Time Factors; Vasoconstriction

To observe the effects of continuous subcutaneous adenosine infusion on pulmonary hypertension in chronically hypoxic rats.. Twenty-four SD rats were randomized into normoxic group, hypoxic group and adenosine-treated hypoxic group. Hypoxic environment was simulated in a chamber filled with 10% oxygen and 90% nitrogen. After 7 days of hypoxia, adenosine were administered subcutaneously in the rats in adenosine-treated group at the rate of 100 microg kg(-1) min(-1) via an Alzet micro-osmotic pump for 14 days, while the pumps in the other two groups contained normal saline. After 21 days of hypoxia, pulmonary artery pressure and tail-cuff blood pressure were measured, with the plasma rennin activity (RA), angiotensin II (AngII), endothelin (ET)-1, and nitric oxide (NO) determined. Inducible nitric oxide synthase (iNOS) expression in the pulmonary artery of the rats was detected using immunohistochemical method.. The mean pulmonary artery pressure (mPAP) was significantly higher in the hypoxic group than that in the normoxic group (P<0.01) and in the adenosine-treated group (P<0.01). Plasma ET-1 was significantly higher but plasma NO significantly lower in the hypoxic group than in the normoxic group (P<0.01) and the adenosine-treated group (P<0.01). iNOS expression in the pulmonary artery was higher in the hypoxic group than in normoxic group (P<0.01), and adenosine significantly increased iNOS expression in comparison with the normoxic and hypoxic groups (P<0.01). Plasma RA and AngII in the hypoxic group were significantly higher than those in the normoxic group (P<0.01) and the adenosine-treated (P<0.01).. Adenosine administered by continuous subcutaneous infusion alleviates chronically hypoxia-induced pulmonary hypertension in rats, in which rennin angiotensin system, ET-1, and iNOS/NO play a role.

Topics: Adenosine; Animals; Chronic Disease; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Infusions, Subcutaneous; Male; Nitric Oxide Synthase Type II; Random Allocation; Rats; Rats, Sprague-Dawley; Renin-Angiotensin System

Pulmonary hypertension is a kind of disease associated with a very high rate of mortality. There are not many effective drugs for the treatment of pulmonary hypertension. Treatment with ET-1 receptor antagonists was proved to be effective in the treatment of pulmonary hypertension. Aiming at developing new endothelin A receptor (ET(A)) antagonist for treatment of pulmonary hypertension, 242 peptide compounds were synthesized by structural optimization of a selective ET(A) receptor antagonist BQ-123. Among these, -azabicyclo[3,2,1]octane-1-yl-l-Leucyl-d-tryptophanyl-d-4-Cl-phenylalanine, named ETP-508, was selected for further harmacological characterization.. Radioligand binding assay was performed to study the binding affinity of ETP-508 for ET(A) and ET(B) receptors. The biological activity of ETP-508 was evaluated in isolated rat aortic ring experiment and in systemic arterial pressure experiment. In addition, hypotensive effect of ETP-508 was investigated on hypoxia-induced pulmonary hypertension.. ETP-508 binds to endothelin ET(A) receptor with >10,000-fold higher affinity than to endothelin B receptor in rat lung tissue preparation. ETP-508 inhibited endothelin-1 (ET-1)-induced contraction of isolated rat aortic ring and shifted the cumulative concentration-contraction response curve to ET-1 to right with no change in the maximal response. In vivo, ETP-508 inhibited the increased effect of ET-1 on mean systemic arterial pressure. Pre-treatment with ETP-508 by intravenous infusion significantly inhibited chronic hypoxia-induced pulmonary hypertension and right ventricular hypertrophy. ETP-508 also significantly inhibited the increase in lung ET-1 expression level, hemoglobin, red-cell count and red-cell hematocrit as induced by hypoxia. Furthermore, ETP-508 partially reversed pre-established pulmonary hypertension and right ventricle hypertrophy by chronic hypoxia.. These results indicated that ETP-508 is a novel highly selective ET(A) receptor antagonist and may have a great potential to be developed as a drug of anti-pulmonary hypertension.

Topics: Animals; Aorta, Thoracic; Azabicyclo Compounds; Azepines; Blood Pressure; Chronic Disease; Dose-Response Relationship, Drug; Endothelin A Receptor Antagonists; Endothelin-1; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; In Vitro Techniques; Lung; Male; Molecular Structure; Oligopeptides; Peptides, Cyclic; Rats; Rats, Wistar; Time Factors; Vasoconstriction

Recent evidence supports a prominent role for Rho kinase (ROK)-mediated pulmonary vasoconstriction in the development and maintenance of chronic hypoxia (CH)-induced pulmonary hypertension. Endothelin (ET)-1 contributes to the pulmonary hypertensive response to CH, and recent studies by our laboratory and others indicate that pulmonary vascular reactivity following CH is largely independent of changes in vascular smooth muscle (VSM) intracellular free calcium concentration ([Ca(2+)](i)). In addition, CH increases generation of reactive oxygen species (ROS) in pulmonary arteries, which may underlie the shift toward ROK-dependent Ca(2+) sensitization. Therefore, we hypothesized that ROS-dependent RhoA/ROK signaling mediates ET-1-induced Ca(2+) sensitization in pulmonary VSM following CH. To test this hypothesis, we determined the effect of pharmacological inhibitors of ROK, myosin light chain kinase (MLCK), tyrosine kinase (TK), and PKC on ET-1-induced vasoconstriction in endothelium-denuded, Ca(2+)-permeabilized small pulmonary arteries from control and CH (4 wk at 0.5 atm) rats. Further experiments examined ET-1-mediated, ROK-dependent phosphorylation of the regulatory subunit of myosin light chain phosphatase (MLCP), MYPT1. Finally, we measured ET-1-induced ROS generation in dihydroethidium-loaded small pulmonary arteries and investigated the role of ROS in mediating ET-1-induced, RhoA/ROK-dependent Ca(2+) sensitization using the superoxide anion scavenger, tiron. We found that CH increases ET-1-induced Ca(2+) sensitization that is sensitive to inhibition of ROK and MLCK, but not PKC or TK, and correlates with ROK-dependent MYPT1(Thr696) phosphorylation. Furthermore, tiron inhibited basal and ET-1-stimulated ROS generation, RhoA activation, and VSM Ca(2+) sensitization following CH. We conclude that CH augments ET-1-induced Ca(2+) sensitization through ROS-dependent activation of RhoA/ROK signaling in pulmonary VSM.

Topics: Animals; Calcium Signaling; Chronic Disease; Endothelin-1; Hypoxia; In Vitro Techniques; Male; Muscle, Smooth, Vascular; Protein Phosphatase 1; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; rho-Associated Kinases; rhoA GTP-Binding Protein; Vasoconstriction

The aim of this study was to investigate how blocking functional endothelin-converting enzyme activity may offer a new approach to inhibition of changes in pulmonary vessels reactivity due to development of hypoxia-induced pulmonary arterial hypertension in rats. This data shows that treatment with endothelin-converting enzyme blocker PP36 significantly reduced pathological changes due to hypoxia-induced pulmonary hypertension. One of the reasons may be the increased production and role of nitric oxide in pulmonary artery tone.

Topics: Animals; Aspartic Acid Endopeptidases; Blood Circulation; Deoxyuridine; Dipeptides; Endothelin-1; Endothelin-Converting Enzymes; Hypertension, Pulmonary; Hypoxia; Injections, Intravenous; Male; Metalloendopeptidases; Nitric Oxide Donors; Nitric Oxide Synthase; Propanolamines; Rats; Rats, Wistar; Succinates

Chronic exposure to hypoxia, a common adverse consequence of most pulmonary disorders, can lead to a sustained increase in pulmonary arterial pressure (PAP), right ventricular hypertrophy, and is, therefore, closely associated with heart failure and increased mortality. Ghrelin, originally identified as an endogenous GH secretagogue, has recently been shown to possess potent vasodilator properties, likely involving modulation of the vascular endothelium and its associated vasoactive peptides. In this study we hypothesized that ghrelin would impede the pathogenesis of pulmonary arterial hypertension during chronic hypoxia (CH). PAP was continuously measured using radiotelemetry, in conscious male Sprague Dawley rats, in normoxia and during 2-wk CH (10% O(2)). During this hypoxic period, rats received a daily sc injection of either saline or ghrelin (150 microg/kg). Subsequently, heart and lung samples were collected for morphological, histological, and molecular analyses. CH significantly elevated PAP in saline-treated rats, increased wall thickness of peripheral pulmonary arteries, and, consequently, induced right ventricular hypertrophy. In these rats, CH also led to the overexpression of endothelial nitric oxide synthase mRNA and protein, as well as endothelin-1 mRNA within the lung. Exogenous ghrelin administration attenuated the CH-induced overexpression of endothelial nitric oxide synthase mRNA and protein, as well as endothelin-1 mRNA. Consequently, ghrelin significantly attenuated the development of pulmonary arterial hypertension, pulmonary vascular remodeling, and right ventricular hypertrophy. These results demonstrate the therapeutic benefits of ghrelin for impeding the pathogenesis of pulmonary hypertension and right ventricular hypertrophy, particularly in subjects prone to CH (e.g. pulmonary disorders).

Topics: Algorithms; Animals; Blood Glucose; Body Weight; Chronic Disease; Consciousness; Disease Progression; Drug Evaluation, Preclinical; Endothelin-1; Fatty Acids, Nonesterified; Ghrelin; Hemodynamics; Hypertension, Pulmonary; Hypoxia; Male; Nitric Oxide Synthase Type III; Rats; Rats, Sprague-Dawley; RNA, Messenger

Prolonged exposure to decreased oxygen tension causes contraction and proliferation of pulmonary arterial smooth muscle cells (PASMCs) and pulmonary hypertension. Hypoxia-induced inhibition of voltage-gated K(+) (K(v)) channels may contribute to the development of pulmonary hypertension by increasing intracellular calcium concentration ([Ca(2+)](i)). The peptide endothelin-1 (ET-1) has been implicated in the development of pulmonary hypertension and acutely decreases K(v) channel activity. ET-1 also activates several transcription factors, although whether ET-1 alters K(V) channel expression is unclear. The hypoxic induction of ET-1 is regulated by the transcription factor hypoxia-inducible factor-1 (HIF-1), which we demonstrated to regulate hypoxia-induced decreases in K(V) channel activity. In this study, we tested the hypothesis that HIF-1-dependent increases in ET-1 lead to decreased K(v) channel expression and subsequent elevation in [Ca(2+)](i). Resting [Ca(2+)](i) and K(v) channel expression were measured in cells exposed to control (18% O(2), 5% CO(2)) and hypoxic (4% O(2), 5% CO(2)) conditions. Hypoxia caused a decrease in expression of K(v)1.5 and K(v)2.1 and a significant increase in resting [Ca(2+)](i). The increase in [Ca(2+)](i) was reduced by nifedipine, an inhibitor of voltage-dependent calcium channels, and removal of extracellular calcium. Treatment with BQ-123, an ET-1 receptor inhibitor, prevented the hypoxia-induced decrease in K(v) channel expression and blunted the hypoxia-induced increase in [Ca(2+)](i) in PASMCs, whereas ET-1 mimicked the effects of hypoxia. Both hypoxia and overexpression of HIF-1 under normoxic conditions increased ET-1 expression. These results suggest that the inhibition of K(v) channel expression and rise in [Ca(2+)](i) during chronic hypoxia may be the result of HIF-1-dependent induction of ET-1.

Topics: Animals; Calcium Signaling; Endothelin-1; Gene Expression Regulation; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Kv1.5 Potassium Channel; Male; Mice; Models, Biological; Myocytes, Smooth Muscle; Oligopeptides; Peptides, Cyclic; Perfusion; Piperidines; Pulmonary Artery; Rats; Rats, Wistar; Shab Potassium Channels

The HIF-1alpha expression in the carotid body (CB) is central to the transcriptional regulation of the CB structural and functional changes in chronic hypoxia (CH). The CB plays pathogenic roles in cardiovascular morbidity in patients with sleep-disordered breathing; yet, the expression and role of HIF-alpha subtypes in intermittent hypoxia (IH), resembling recurrent episodic apnea, are unclear. We hypothesized a divergent role of HIF-alpha subtypes, regulated by differential expression in the CB response to IH. A time-course analysis of the CB volume, and expression profiles of the HIF-1alpha, -2alpha, -3alpha and HIF-regulated gene products, including vascular endothelial growth factor (VEGF), endothelin-1 (ET-1), and tyrosine hydroxylase (TH), showed a significant difference in the lack of increase in the rat CB volume, HIF-1alpha and VEGF expression during IH, despite an increase in the mRNA level of HIF-1alpha and the prominent increase of volume and expression in the CH group. In contrast, there were increased CB expressions of HIF-2alpha and -3alpha, and also ET-1 and TH in both IH and CH groups. Results demonstrated a significant role played by HIF-2alpha and -3alpha in the CB response to IH, which could be complementary to the expression and role of HIF-1alpha under hypoxic conditions. This differential regulation of the HIF-alpha subtypes and pathways could account for the morphological and neurochemical discrepancy in the CB responses to IH and CH.

Topics: Animals; Basic Helix-Loop-Helix Transcription Factors; Carotid Body; Chemoreceptor Cells; Disease Models, Animal; Endothelin-1; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Male; Random Allocation; Rats; Rats, Sprague-Dawley; RNA, Messenger; Sleep Apnea Syndromes; Time Factors; Transcription Factors; Tyrosine 3-Monooxygenase; Vascular Endothelial Growth Factor A

We reported previously that simulating sleep apnea by exposing rats to eucapnic intermittent hypoxia (E-IH) causes endothelin-dependent hypertension and increases constrictor sensitivity to endothelin-1 (ET-1). In addition, augmented ET-1-induced constriction in small mesenteric arteries (sMA) is mediated by increased Ca(2+) sensitization independent of Rho-associated kinase. We hypothesized that exposing rats to E-IH augments ET-1-mediated vasoconstriction by increasing protein kinase C (PKC)-dependent Ca(2+) sensitization. In sMA, the nonselective PKC inhibitor GF-109203x (3 microM) significantly inhibited ET-1-stimulated constriction in E-IH arteries but did not affect ET-1-stimulated constriction in sham arteries. Phospholipase C inhibitor U-73122 (1 microM) also inhibited constriction by ET-1 in E-IH but not sham sMA. In contrast, the classical PKC (cPKC) inhibitor Gö-6976 (1 microM) had no effect on ET-1-mediated vasoconstriction in either group, but a PKCdelta-selective inhibitor (rottlerin, 3 microM) significantly decreased ET-1-mediated constriction in E-IH but not in sham sMA. ET-1 increased PKCdelta phosphorylation in E-IH but not sham sMA. In contrast, ET-1 constriction in thoracic aorta from both sham and E-IH rats was inhibited by Gö-6976 but not by rottlerin. These observations support our hypothesis that E-IH exposure significantly increases ET-1-mediated constriction of sMA through PKCdelta activation and modestly augments ET-1 contraction in thoracic aorta through activation of one or more cPKC isoforms. Therefore, upregulation of a PKC pathway may contribute to elevated ET-1-dependent vascular resistance in this model of hypertension.

Topics: Animals; Aorta, Thoracic; Blood Pressure; Body Weight; Carbon Dioxide; Diglycerides; Endothelin-1; Endothelium, Vascular; Enzyme Inhibitors; Hypoxia; In Vitro Techniques; Male; Mesenteric Arteries; Muscle Contraction; Muscle, Smooth, Vascular; Protein Kinase C-delta; Rats; Rats, Sprague-Dawley; Type C Phospholipases; Vasoconstriction

The effects of intravenous endothelin-1 (ET-1) on the ventilatory response to hypoxia were studied in healthy humans. Nine volunteers were each exposed twice to 4 hr eucapnic hypoxia. They received a continuous infusion of ET-1 during the ET-1 protocol and an infusion of saline during the control protocol. Plasma ET-1 levels and an index of ventilation were measured regularly. Hypoxia caused a rise in plasma ET-1 in the control protocol. Hypoxia also caused the index of ventilation to increase in both protocols, and this increase was greater in the ET-1 protocol than in the control protocol. These results are consistent with the hypothesis that ET-1 plays a role in controlling the ventilatory response to hypoxia in man.

Topics: Adult; Endothelin-1; Female; Humans; Hypoxia; Injections, Intravenous; Male; Respiratory Physiological Phenomena; Tidal Volume

Topics: Animals; Carotid Body; Cats; Endothelin-1; Hypoxia; Male; Oxygen; Oxygen Consumption; Receptor, Endothelin A; Receptor, Endothelin B; Sleep Apnea, Obstructive

The aryl hydrocarbon receptor (AHR) is a basic helix-loop-helix Per-Arnt-Sim transcription factor that mediates induction of metabolic enzymes and toxicity of certain environmental pollutants. Although AHR knockout (KO) mice develop cardiac hypertrophy, conflicting reports associate this pathology with hypotension or endothelin (ET)-1-dependent hypertension. Because hypertension occurred at modest altitude, we tested the hypothesis that loss of AHR increases the sensitivity to hypoxia-induced ET-1, contributing to systemic hypertension. We found that AHR KO mice were hypertensive at modest altitude (1632 m) but hypotensive at low altitude (225 m). When AHR KO mice residing at 1632 m were exposed to the partial pressure of inspired oxygen (PIO(2)) at sea level for 11 days, blood pressure declined to levels measured at 225 m. Although plasma ET-1 in AHR KO mice was significantly elevated at 1632 m and decreased at 225 m and sea level PIO(2), pulmonary prepro-ET-1 mRNA was significantly reduced at 1632 m and decreased further at 225 m and sea level PIO(2). Blood gas analysis revealed that AHR KO mice were hypoxemic, hypercapnic, and acidotic at 1632 m, values that were attenuated and normalized after 24 hours and 11 days under sea level PIO(2), respectively. Lastly, AHR inactivation in endothelial cells by small interfering RNA significantly reduced basal prepro-ET-1 mRNA but did not alter hypoxia-induced expression. Our studies establish the AHR KO mouse as a model in which modest decreases in PIO(2) lead to hypoxemia, increased plasma ET-1, and systemic hypertension without increased pulmonary prepro-ET-1 mRNA expression.

Topics: Altitude; Animals; Blood Gas Analysis; Cells, Cultured; Disease Models, Animal; Endothelin-1; Endothelium, Vascular; Humans; Hydrogen-Ion Concentration; Hypertension; Hypoxia; Mice; Mice, Inbred C57BL; Mice, Knockout; Oxygen; Receptors, Aryl Hydrocarbon; RNA, Messenger; Transfection

Maternal endothelial activation in pre-eclampsia is attributed to the release of unknown factors from a hypoperfused placenta. To further characterize these factors, we have used a serum-free placental villous explant culture model and investigated the effect of the liberated soluble factors produced on human endothelial cell cultures. Term placental villous explants from uncomplicated pregnancies were cultured for 4 days in 20, 6 or 1% O2 to mimic placental hyperoxia, normoxia and hypoxia. Medium collected from viable explants was applied to cultured human uterine microvascular endothelial cells. Medium conditioned by hypoxic explants caused a significant decrease in endothelial cell ATP levels and mitochondrial dehydrogenase activity, suggestive of a reduced metabolic rate. An additional reduction in mitochondrial membrane potential and increased endothelial cell death occurred as the oxygen concentration to which explants had been exposed decreased. Effects of the hypoxic explant medium were also seen ex vivo in a wire myography model of myometrial artery function, with increased vasoconstriction and attenuated vasodilation following exposure to hypoxic explant medium. These results suggest that hypoxia (1% O2) may stimulate the release of soluble factors from the placenta, which have an adverse effect on endothelial cell metabolism and mitochondrial integrity in vitro. These potentially pathogenic factors are now being characterized.

Topics: Apoptosis; Arginine Vasopressin; Benzimidazoles; Bradykinin; Carbocyanines; Cells, Cultured; Chorionic Villi; Dose-Response Relationship, Drug; Endothelin-1; Endothelium, Vascular; Epoprostenol; Female; Formazans; Humans; Hyperoxia; Hypoxia; Membrane Potentials; Mitochondria; Myometrium; Necrosis; Neovascularization, Physiologic; Oxygen; Placenta; Pregnancy; Tetrazolium Salts; Vasodilator Agents

The success of pancreatic islet transplantation depends largely on the capacity of the islet graft to survive the initial phase immediately after transplantation until revascularization is completed. Endothelin-1 (ET-1) is a strong vasoconstrictor which has been involved in solid organ graft failure but is also known to be a potent mitogenic/anti-apoptotic factor which could also potentially enhance the survival of the transplanted islets.. Characterization of the endothelin system with regard to a potential endothelin agonist/antagonist treatment.. Regulated expression of the endothelin system in human and rat pancreatic islets and beta-cell lines was assessed by means of immunohistochemistry, competition binding studies, western blot, RT-PCR, real-time PCR and transplant studies.. ET-1, ETA- and ETB-receptor immunoreactivity was identified in the endocrine cells of human and rat pancreatic islets. The corresponding mRNA was detectable in rat beta-cell lines and isolated rat and human pancreatic islets. Competition binding studies on rat islets revealed binding sites for both receptor types. ET-1 stimulated the phosphorylation of mitogen-activated protein kinase, which was prevented by ETA- and ETB-receptor antagonists. After exposure to hypoxia equal to post-transplant environment oxygen tension, mRNA levels of ET-1 and ETB-receptor of human islets were robustly induced whereas ETA-receptor mRNA did not show significant changes. Immunostaining signals for ET-1 and ETA-receptor of transplanted rat islets were markedly decreased when compared to native pancreatic sections.. In pancreatic islets, ET-1 and its receptors are differentially expressed by hypoxia and after transplantation. Our results provide the biological basis for the study of the potential use of endothelin agonists/antagonists to improve islet transplantation outcome.

Topics: Adult; Aged; Animals; Cell Line; Endothelin-1; Female; Humans; Hypoxia; Immunohistochemistry; Islets of Langerhans; Islets of Langerhans Transplantation; Male; Middle Aged; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Phosphorylation; Rats; Rats, Inbred Lew; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptor, Endothelin B; RNA, Messenger

To determine whether corticotropin-releasing hormone receptor 1 (CRHR1) coexists with endothelin-1 (ET-1) in rat paraventricular nucleus (PVN), ET-1 expression and its regulation by CRH and CRHR1 under hypoxia, rats were exposed to simulated continuous hypoxia at 5 km altitude (CH5km, equal to 10.8% O(2)) in a hypobaric chamber for 1, 2, 5, 10, 15 or 25 days. ET-1, CRH, and its mRNA were measured using radioimmunoassay (RIA), immunohistochemistry, and in situ hybridization. The coexistence of ET-1 and CRHR1 was identified by confocal immunofluorescence. The results showed that CH5km caused a significant decrease of ET-1 level in PVN at 5 days, but decreased CRH on days 1 and 2 while it increased on days 5 and 10. CH5km induced ET-1 mRNA upregulation and ET-1 decrease at 5 days, the effects were completely reversed by treatment with five-daily-injections of a CRHR1 antagonist (butyl-[2,5-dimethyl-7-(2,4,6-trimethylphenyl)-7H-pyrrolo[2,3-d] pyrimidin-4-yl]-ethylamine: CP-154,526). Also, this treatment significantly reversed the CH5km-induced increase in CRH and CRHmRNA in PVN at 5 days. Moreover we found that the changes in expression of ET-1 and CRHR1 induced by CH5km were co-localized in parvocellular PVN cells. In conclusion, CRHR1 coexists with ET-1 in parvocellular PVN, continuous hypoxia stimulates ET-1 and ET-1mRNA as well as CRH and CRHmRNA, and CRHR1 evidently modulates ET-1 release and ET-1mRNA activation caused by continuous hypoxia.

Topics: Animals; Corticosterone; Endothelin-1; Gene Expression Regulation; Hypoxia; Male; Paraventricular Hypothalamic Nucleus; Pyrimidines; Pyrroles; Radioimmunoassay; Rats; Rats, Sprague-Dawley; Receptors, Corticotropin-Releasing Hormone; RNA, Messenger; Time Factors

Sleep apnea, defined as intermittent respiratory arrest during sleep, is associated with increased incidence of hypertension and peripheral vascular disease. Exposure of rodents to brief periods of intermittent hypercarbia/hypoxia (H-IH) during sleep mimics the cyclical hypoxia-normoxia of sleep apnea. Endothelin-1, an upstream activator of nuclear factor of activated T cells (NFAT), is increased during H-IH. Therefore, we hypothesized that NFATc3 is activated by H-IH and is required for H-IH-induced hypertension. Consistent with this hypothesis, we found that H-IH (20 brief exposures per hour to 5% O(2)-5% CO(2) for 7 h/day) induces systemic hypertension in mice [mean arterial pressure (MAP) = 97 +/- 2 vs. 124 +/- 2 mmHg, P < 0.05, n = 5] and increases NFATc3 transcriptional activity in aorta and mesenteric arteries. Cyclosporin A, an NFAT inhibitor, and genetic ablation of NFATc3 [NFATc3 knockout (KO)] prevented NFAT activation. More importantly, H-IH-induced hypertension was attenuated in cyclosporin A-treated mice and prevented in NFATc3 KO mice. MAP was significantly elevated in wild-type mice (Delta = 23.5 +/- 6.1 mmHg), but not in KO mice (Delta = -3.9 +/- 5.7). These results indicate that H-IH-induced increases in MAP require NFATc3 and that NFATc3 may contribute to the vascular changes associated with H-IH-induced hypertension.

Topics: Animals; Aorta; Blood Pressure; Calcineurin; Calcineurin Inhibitors; Cyclosporine; Disease Models, Animal; Endothelin-1; Hypertension; Hypoxia; Lung; Male; Mesenteric Arteries; Mice; Mice, Inbred BALB C; Mice, Knockout; NFATC Transcription Factors; RNA, Messenger; Sleep Apnea Syndromes; Time Factors; Transcription, Genetic; Up-Regulation

Patients with sickle-cell disease (SCD) suffer from tissue damage and life-threatening complications caused by vasoocclusive crisis (VOC). Endothelin receptors (ETRs) are mediators of one of the most potent vasoconstrictor pathways in mammals, but the relationship between vasoconstriction and VOC is not well understood. We report here that pharmacological inhibition of ETRs prevented hypoxia-induced acute VOC and organ damage in a mouse model of SCD. An in vivo ultrasonographic study of renal hemodynamics showed a substantial increase in endothelin-mediated vascular resistance during hypoxia/reoxygenation-induced VOC. This increase was reversed by administration of the dual ETR antagonist (ETRA) bosentan, which had pleiotropic beneficial effects in vivo. It prevented renal and pulmonary microvascular congestion, systemic inflammation, dense rbc formation, and infiltration of activated neutrophils into tissues with subsequent nitrative stress. Bosentan also prevented death of sickle-cell mice exposed to a severe hypoxic challenge. These findings in mice suggest that ETRA could be a potential new therapy for SCD, as it may prevent acute VOC and limit organ damage in sickle-cell patients.

Topics: Anemia, Sickle Cell; Animals; Antihypertensive Agents; Bosentan; Disease Models, Animal; Endothelin Receptor Antagonists; Endothelin-1; Hemodynamics; Humans; Hypoxia; Kidney; Lung; Mice; Mice, Inbred C57BL; Neutrophils; Receptors, Endothelin; Regional Blood Flow; Renal Circulation; Sulfonamides; Vasoconstriction

Cyclooxygenase-2 (COX-2) is upregulated in pulmonary artery smooth muscle cells (PASMCs) during hypoxia and may play a protective role in the response of the lung to hypoxia. Selective COX-2 inhibition may have detrimental pulmonary vascular consequences during hypoxia.. To investigate the role of COX-2 in the pulmonary vascular response to hypoxia, we subjected wild-type and COX-2-deficient mice to a model of chronic normobaric hypoxia. COX-2-null mice developed severe pulmonary hypertension with exaggerated elevation of right ventricular systolic pressure, significant right ventricular hypertrophy, and striking vascular remodeling after hypoxia. Pulmonary vascular remodeling in COX-2-deficient mice was characterized by PASMC hypertrophy but not increased proliferation. Furthermore, COX-2-deficient mice had significant upregulation of the endothelin-1 receptor (ET(A)) in the lung after hypoxia. Similarly, selective pharmacological inhibition of COX-2 in wild-type mice exacerbated hypoxia-induced pulmonary hypertension and resulted in PASMC hypertrophy and increased ET(A) receptor expression in pulmonary arterioles. The absence of COX-2 in vascular smooth muscle cells during hypoxia in vitro augmented traction forces and enhanced contractility of an extracellular matrix. Treatment of COX-2-deficient PASMCs with iloprost, a prostaglandin I(2) analog, and prostaglandin E(2) abrogated the potent contractile response to hypoxia and restored the wild-type phenotype.. Our findings reveal that hypoxia-induced pulmonary hypertension and vascular remodeling are exacerbated in the absence of COX-2 with enhanced ET(A) receptor expression and increased PASMC hypertrophy. COX-2-deficient PASMCs have a maladaptive response to hypoxia manifested by exaggerated contractility, which may be rescued by either COX-2-derived prostaglandin I(2) or prostaglandin E(2).

Topics: Animals; Blood Pressure; Cells, Cultured; Chronic Disease; Collagen; Cyclooxygenase 2; Dinoprostone; Endothelin-1; Gels; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Iloprost; Mice; Mice, Mutant Strains; Muscle Contraction; Muscle, Smooth, Vascular; Pulmonary Artery; Receptor, Endothelin A; Traction; Vasoconstriction; Vasodilator Agents

Hypoxic pulmonary vasoconstriction (HPV) is an adaptive response that diverts pulmonary blood flow from poorly ventilated and hypoxic areas of the lung to better ventilated parts, matching blood perfusion to ventilation. HPV is an ancient and highly conserved response expressed in the respiratory organs of all vertebrates. However, the underlying mechanism and the role of the endothelium remain elusive. Isolated intrapulmonary arteries (internal diameter <346 microm) from the American alligator Alligator mississippiensis were mounted in microvascular myographs for isometric tension recording. Resting vessels and vessels contracted with either serotonin (5-HT) or endothelin-1 (ET-1) were exposed to sustained (45 min) hypoxia (PO2<5 mmHg). In ET-1-contracted vessels, hypoxia induced a monophasic, sustained and fully reversible constriction, which was independent of the endothelium. In relaxed or in 5-HT-contracted vessels, hypoxia did not cause constriction. The effects of ET-1, ET(A) and ET(B) as well as the general ET-receptor antagonist were studied. ET-1 caused a contraction of the pulmonary arteries through stimulation of ET(A)-receptors. ET(A) and ET(B) immunoreactive staining revealed the location of both receptors in the smooth muscle layer and of ET(B) receptors in the endothelium. In conclusion, because precontraction with serotonin did not facilitate HPV, the required precontraction in alligators seems specific to ET-1, which implies that ET-1 plays an important permissive role for the HPV response in alligators.

Topics: Alligators and Crocodiles; Analysis of Variance; Animals; Electromyography; Endothelin-1; Hypoxia; Immunohistochemistry; Pulmonary Artery; Vasoconstriction

To study the effects of endothelin-1 (ET-1) and vascular endothelial growth factor (VEGF) on the mechanism of hypoxic pulmonary hypertension (HPH).. We studied 4 groups of age-controlled male rats, i.e., normal control for 2 weeks group (N2), normal control for 3 weeks group (N3), exposed to hypoxia for 2 weeks group (H2) and for 3 weeks group (H3). Chronic HPH rat models were established by chronic hypobaric hypoxia [(10.0% +/- 0.5% O2] for 2 and 3 weeks, respectively. The rats were anesthetized and fixed, and the levels of mean pulmonary artery pressure (mPAP) and carotid arterial pressure (CAP) were measured using catheters by a microcomputer via transducers. The weight ratio of right ventricle (RV) and left ventricle and septum (LV + S) [RV/ (LV+S)] were determined. The contents of ET-1 in plasma of pulmonary artery and carotid artery and in homogenates of lung and systemic arteries were determined by radioimmunoassay, and the contents of VEGF in serum of pulmonary artery and carotid artery were determined by ABC-ELISA.. HPH rat models were established successfully. Compared with control groups, the values of ET-1 were both enhanced in carotid artery and pulmonary artery plasma in model groups (P < 0.01). In the HPH groups, the level of pulmonary artery plasma ET-1 was significantly lower than that of carotid artery plasma, but just the reverse was ET-1 in control rats. The levels of ET-1 in homogenates of lungs from HPH models were significantly higher than those in homogenates of lungs from control groups (P < 0.01), and markedly higher than those in homogenates of systemic arteries from HPH rats (P < 0.01) SThe values of VEGF in serum of pulmonary artery from H3 group were significantly higher than those from control groups and H2 group (P < 0.01). In serum of carotid artery, the values of VEGF from the HPH models were higher than those from the control groups (P < 0.01).. ET-1 and VEGF play important roles in the pathogenesis of HPH. The result that ET-1 concentration around pulmonary arteries was significantly higher than that around systemic arteries may be one of the mechanisms accounting for the different reaction of them to hypoxia.

Topics: Animals; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Male; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Vascular Endothelial Growth Factor A

Increased levels of endothelin-1 (ET-1) in the carotid body (CB) contribute to the enhancement of chemosensory responses to acute hypoxia in cats exposed to chronic intermittent hypoxia (CIH). However, it is not known if the ET receptor types A (ETA-R) and B (ETB-R) are upregulated. Thus, we studied the expression and localization of ETA-R and ETB-R using Western blot and immunohistochemistry (IHC) in CBs from cats exposed to cyclic hypoxic episodes, repeated during 8 hr for 4 days. In addition, we determined if ET-1 is expressed in the chemoreceptor cells using double immunofluorescence for ET-1 and tyrosine hydroxylase (TH). We found that ET-1 expression was ubiquitous in the blood vessels and CB parenchyma, although double ET-1 and TH-positive chemoreceptor cells were mostly found in the parenchyma. ETAR was expressed in most chemoreceptor cells and blood vessels of the CB vascular pole. ETB-R was expressed in chemoreceptor cells, parenchymal capillaries, and blood vessels of the vascular pole. CIH upregulated ETB-R expression by approximately 2.1 (Western blot) and 1.6-fold (IHC) but did not change ETA-R expression. Present results suggest that ET-1,ETA-R, and ETB-R are involved in the enhanced CB chemosensory responses to acute hypoxia induced by CIH.

Topics: Animals; Blotting, Western; Carotid Body; Cats; Chronic Disease; Endothelin-1; Endothelins; Hypoxia; Immunohistochemistry; Male; Receptor, Endothelin A; Receptor, Endothelin B; Tyrosine 3-Monooxygenase

Topics: Animals; Calcium; Calcium Signaling; Endothelin-1; Endothelins; Endothelium, Vascular; Humans; Hypoxia; Intracellular Signaling Peptides and Proteins; Muscle, Smooth, Vascular; Protein Serine-Threonine Kinases; Pulmonary Artery; rho-Associated Kinases; rhoA GTP-Binding Protein; Vasoconstriction

The vasodilator adrenomedullin (AM) is up-regulated in pulmonary hypertension, and inhaled AM is beneficial in patients. Therefore, we investigated the effects of AM on pulmonary endothelin-1 (ET-1). In normoxic isolated rat lungs (IRL) and rat pulmonary artery endothelial cells (RPAEC), the calcitonin gene-related peptide type-1 receptor (CGRP1R) antagonist human (h)CGRP(8-37) decreased ET-1 secretion, and the AM receptor antagonist hAM(22-52) had no effect. Exogenous AM (1 and 10 pM) increased ET-1 levels, which was abolished by hCGRP(8-37) and protein kinase A (PKA) inhibition. At 50 and 100 pM, AM decreased ET-1, an effect sensitive to hAM(22-52), NO inhibition, and protein kinase G (PKG) inhibition. In RPAEC, these results were attributed to altered ET-1 gene expression; low exogenous AM also promoted activity of endothelin-converting enzyme, and high AM increased the number of endothelin type-B (ETB) receptor sites. Hypoxia significantly elevated AM and ET-1 levels in IRL and RPAEC, and hAM(22-52), NO inhibition, or PKG inhibitors caused a further ET-1 rise. These interventions also prevented the hypoxia-related increase in ETB sites in RPAEC. In RPAEC, both high AM and hypoxia down-regulated receptor activity-modifying protein (RAMP)1, but they up-regulated RAMP2 protein and AM receptor sites, and RAMP2 silencing by small interference RNA proved its pivotal role for signal switching. In conclusion, endogenous pulmonary AM up-regulates ET-1 and endothelin-converting enzyme activity under physiological conditions, via CGRP1R and PKA. In contrast, hypoxia-induced high AM levels, via AM1 receptor and NO/PKG, down-regulate ET-1 gene expression and promote expression of ETB receptors. This hypoxia-related switch of AM signaling can be attributed to up-regulation of the RAMP2/AM1 receptor system.

Topics: Adrenomedullin; Animals; Anti-Inflammatory Agents, Non-Steroidal; Blotting, Western; Calcitonin Gene-Related Peptide; Cyclic AMP; Cyclic GMP; Endothelial Cells; Endothelin-1; Hypoxia; In Vitro Techniques; Intracellular Signaling Peptides and Proteins; Lung; Male; Membrane Proteins; Nitric Oxide; Rats; Rats, Wistar; Receptor Activity-Modifying Protein 2; Receptor Activity-Modifying Proteins; Receptor, Endothelin B; RNA, Messenger; RNA, Small Interfering; Signal Transduction; Solvents

The response of pulmonary arteries to endothelin-1 (ET-1) changes with age in normal pigs and is abnormal in pulmonary hypertension. The purpose of this study was to determine if the same is true of the pulmonary veins. We studied the wall structure and functional response to ET-1 in pulmonary veins from normal pigs from fetal life to adulthood and from pigs subjected to chronic hypobaric hypoxia either from birth for 3 days or from 3 to 6 days of age. In isolated normal veins, the contractile response decreased by 40% between late fetal life and 14 days of age with a concomitant twofold increase in endothelium-dependent relaxant response. The ET(A) antagonist BQ-123 reduced the contractile response significantly more in newborn than older animals, whereas the ET-B antagonist BQ-788 had no effect in fetal animals and maximally increased contraction at 14 days of age. Hypoxic exposure significantly increased pulmonary vein smooth muscle area and contractile response to ET-1. The relaxation response was impaired following hypoxic exposure from birth but not from 3 to 6 days of age. The ET(A) antagonist BQ-123 decreased contractile and increased dilator responses significantly more than in age-matched controls. Thus pulmonary veins show age-related changes similar to those seen in the pulmonary arteries with a decrease in ET(A)-mediated contractile and increase in ET-B-mediated relaxant response with age. Contractile response was also increased in hypoxia as in the arteries. This study suggests that pulmonary veins are involved in postnatal adaptation and the pathogenesis of pulmonary hypertension.

Topics: Aging; Animals; Animals, Newborn; Disease Models, Animal; Endothelin-1; Fetus; Hypoxia; Muscle, Smooth, Vascular; Pulmonary Artery; Pulmonary Veins; Swine

Endothelin-1 (ET-1) mediates hypoxia-mediated pulmonary vascular remodeling (HPVR), and endothelin-A receptor (ET-AR) blockade prevents HPVR in newborn mice. Our objective was to determine postnatal effects of chronic hypoxia and/or ET-AR blockade on lung ET-1, ET-AR, ET-BR, and vascular collagen and elastin. Newborn C57BL/6 mice (n = 6-8/gp) given either BQ610 (ET-AR blocker) or vehicle were exposed to air or hypoxia (12% O2) from birth for 1, 3, or 14 d. Lung ET-1 was assessed by ELISA, and ET-AR and ET-BR by immunohistochemistry. Vascular collagen and elastin were assessed by quantitative image analysis. ET-1, ET-AR, ET-BR, collagen I and III, and tropoelastin mRNA levels were assessed by real-time quantitative RT-PCR. We observed that: 1) hypoxia attenuated the normal postnatal decrease in ET-1 and collagen content; 2) ET-AR blockade reduced collagen independent of O2; 3) hypoxia increased elastin mRNA expression and attenuated the normal postnatal decrease in elastin content; and 4) BQ610 reduced elastin mRNA but not elastin content. We conclude that, in neonatal mice, hypoxia attenuates normal postnatal decreases in ET-1, vascular collagen, and elastin. ET-AR blockade reduces collagen fiber area but not mRNA, and does not decrease elastin despite reducing its expression.

Topics: Animals; Animals, Newborn; Blood Vessels; Collagen; Elastin; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Endothelin-1; Female; Hypoxia; Lung; Mice; Mice, Inbred C57BL; Oligopeptides; Oxygen; Pregnancy; Receptor, Endothelin A; Receptor, Endothelin B

We analyzed the role of the Na+/Ca2+ exchanger (NCX) in endothelin-1-aggravated hypoxia/reoxygenation-induced injury in renal epithelial LLC-PK1 cells. KB-R7943, a selective NCX inhibitor, suppressed hypoxia/reoxygenation-induced cell damage, whereas overexpression of NCX1 into cells enhanced it. Endothelin-1 significantly aggravated hypoxia/reoxygenation-induced injury in parental and NCX1-overexpressing LLC-PK1 cells. Such aggravation by endothelin-1 was not observed in cells overexpressing a deregulated NCX1 mutant, which displays no protein kinase C-dependent activation. These results suggest that Ca2+ overload via NCX plays a critical role in hypoxia/reoxygenation-induced renal tubular injury, and that endothelin-1 aggravates the cell damage through the activation of NCX.

Topics: Animals; Endothelin-1; Epithelial Cells; Hypoxia; Kidney; LLC-PK1 Cells; Oxygen; Swine; Thiourea

Topics: Animals; Calcium; Calcium Signaling; Endothelin-1; Endothelins; Endothelium, Vascular; Humans; Hypoxia; Intracellular Signaling Peptides and Proteins; Ion Channel Gating; Muscle, Smooth, Vascular; Oxygen; Potassium Channel Blockers; Potassium Channels, Voltage-Gated; Protein Kinase Inhibitors; Protein Serine-Threonine Kinases; Pulmonary Artery; Reactive Oxygen Species; rho-Associated Kinases; rhoA GTP-Binding Protein; Vasoconstriction

Topics: Animals; Calcium; Calcium Signaling; Endothelin-1; Endothelins; Endothelium, Vascular; Humans; Hypoxia; Intracellular Signaling Peptides and Proteins; Muscle, Smooth, Vascular; Protein Serine-Threonine Kinases; Pulmonary Artery; rho-Associated Kinases; rhoA GTP-Binding Protein; Vasoconstriction

Topics: Animals; Calcium; Calcium Signaling; Endothelin-1; Endothelins; Endothelium-Dependent Relaxing Factors; Endothelium, Vascular; Humans; Hypoxia; Intracellular Signaling Peptides and Proteins; Ion Channel Gating; Muscle, Smooth, Vascular; Nitric Oxide; Potassium Channels, Voltage-Gated; Protein Serine-Threonine Kinases; Pulmonary Artery; Reactive Oxygen Species; rho-Associated Kinases; rhoA GTP-Binding Protein; Vasoconstriction

Topics: Animals; Calcium; Calcium Signaling; Endothelin-1; Endothelins; Endothelium, Vascular; Humans; Hypoxia; Intracellular Signaling Peptides and Proteins; Muscle, Smooth, Vascular; Potassium Channels, Voltage-Gated; Protein Serine-Threonine Kinases; Pulmonary Artery; rho-Associated Kinases; rhoA GTP-Binding Protein; Vasoconstriction

Topics: Animals; Calcium; Calcium Signaling; Endothelin-1; Endothelins; Endothelium, Vascular; Humans; Hypoxia; Intracellular Signaling Peptides and Proteins; Muscle, Smooth, Vascular; Protein Serine-Threonine Kinases; Pulmonary Artery; rho-Associated Kinases; rhoA GTP-Binding Protein; Vasoconstriction

Topics: Animals; Calcium; Calcium Signaling; Endothelin-1; Endothelins; Endothelium, Vascular; Humans; Hypoxia; Intracellular Signaling Peptides and Proteins; Muscle, Smooth, Vascular; Protein Serine-Threonine Kinases; Pulmonary Artery; rho-Associated Kinases; rhoA GTP-Binding Protein; Vasoconstriction

Endothelin 1 (EDN1) plays a primary role in the pathophysiology of hypoxia-induced fetal growth restriction in the rat. In this study we evaluated the effects of chronic maternal hypoxia on the expression of endothelin and its receptors and on receptor binding activity in the uterus and placenta of the rat, in order to elucidate their roles in hypoxia-induced fetal growth restriction. Timed-pregnant Sprague-Dawley rats were maintained in either a normoxic or a normobaric hypoxic (12% O(2)) atmosphere from Gestational Days 18-21. Uterine and placental tissues collected on Gestational Day 21 were assayed for Edn1, Ednra, and Ednrb (endothelin receptors) mRNA expression by real-time quantitative RT-PCR, for localization of EDN1 and its receptors by immunohistochemistry, for EDNRA and EDNRB protein expression by Western blot, and for receptor binding activity by homologous competitive binding assays. EDN1 mRNA expression was significantly increased in the hypoxic placenta, but not in the uterus, compared with normoxic controls. Immunohistochemistry revealed increased EDN1 specifically in the labyrinth of the placenta. Receptor mRNA levels were not significantly affected by hypoxia, but EDNRA protein expression was significantly decreased specifically in the uterine placental beds. Receptor binding decreased significantly in response to hypoxia in all tissues investigated, compared with controls. These results suggest that chronic maternal hypoxia results in increased expression of EDN1 in the placenta but not in the uterus, and that reduced binding activity, rather than regulation of receptor expression, is a mechanism by which these tissues regulate the local hemodynamic response to increased endogenous placental EDN1 in the setting of hypoxia.

Topics: Animals; Binding, Competitive; Blotting, Western; Endothelin-1; Female; Hypoxia; Immunohistochemistry; Male; Placenta; Pregnancy; Pregnancy Complications; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptor, Endothelin B; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Uterus

We report in the present study the role of endothelin (ET-1) and ET-1 receptors in the sustained hypoxia-induced systemic hypertension.. Wistar rats were randomly assigned to live continuously in hypobaric hypoxia (CH rats) or normoxia (N rats). At the end of hypoxic stress exposure (5 weeks at 450 mm Hg), measurements of mean systemic arterial pressure were done. The effects of ET-1 in the presence or not of the endothelium and/or of specific ET-A inhibitors (BQ-123) or ET-B inhibitors (BQ-788), have been investigated in an isolated model of rat thoracic aorta. Finally, plasmatic ET-1 concentrations have been determined by assay procedure.. Following five weeks of chronic hypoxic stress, CH rats presented a significant increase of mean systemic arterial pressure (N: 129.1+/-6.8 mm Hg vs CH: 152.5+/-3.4 mm Hg; P<0.05). Despite of this hypoxia-induced hypertension, ET-1 plasmatic concentration was not different between N and CH rats. Finally, CH rats presented a reduce response to ET-1 when compared to N rats. This phenomenon seems to be associated to the ET-A vascular smooth muscle cell receptors, since difference between N and CH rats was still present in endothelium denuded aortic rings in the presence or not of the specific ET-B inhibitors (BQ-788). In addition, in the presence of the specific ET-A inhibitor (BQ-123) response to ET-1 was abolished in N and CH rats to the same extent (N:-98%; CH:-99%).. This work clearly suggests that, following long term exposure to hypoxia, ET-1 and ET-1 receptors are not involved in the persistence of systemic hypertension in a rat model, and that chronic exposure to severe hypoxic stress was associated with a downregulation of the ET-A receptors response to ET-1.

Topics: Animals; Aorta, Thoracic; Endothelin-1; Hypertension; Hypoxia; In Vitro Techniques; Male; Muscle, Smooth, Vascular; Oligopeptides; Peptides, Cyclic; Piperidines; Rats; Rats, Wistar; Receptor, Endothelin A; Receptor, Endothelin B; Vasoconstriction

Acute hypoxia causes pulmonary vasoconstriction and coronary vasodilation. The divergent effects of hypoxia on pulmonary and coronary vascular smooth muscle cells suggest that the mechanisms involved in oxygen sensing and downstream effectors are different in these two types of cells. Since production of reactive oxygen species (ROS) is regulated by oxygen tension, ROS have been hypothesized to be a signaling mechanism in hypoxia-induced pulmonary vasoconstriction and vascular remodeling. Furthermore, an increased ROS production is also implicated in arteriosclerosis. In this study, we determined and compared the effects of hypoxia on ROS levels in human pulmonary arterial smooth muscle cells (PASMC) and coronary arterial smooth muscle cells (CASMC). Our results indicated that acute exposure to hypoxia (Po(2) = 25-30 mmHg for 5-10 min) significantly and rapidly decreased ROS levels in both PASMC and CASMC. However, chronic exposure to hypoxia (Po(2) = 30 mmHg for 48 h) markedly increased ROS levels in PASMC, but decreased ROS production in CASMC. Furthermore, chronic treatment with endothelin-1, a potent vasoconstrictor and mitogen, caused a significant increase in ROS production in both PASMC and CASMC. The inhibitory effect of acute hypoxia on ROS production in PASMC was also accelerated in cells chronically treated with endothelin-1. While the decreased ROS in PASMC and CASMC after acute exposure to hypoxia may reflect the lower level of oxygen substrate available for ROS production, the increased ROS production in PASMC during chronic hypoxia may reflect a pathophysiological response unique to the pulmonary vasculature that contributes to the development of pulmonary vascular remodeling in patients with hypoxia-associated pulmonary hypertension.

Topics: Acute Disease; Cells, Cultured; Chronic Disease; Coronary Vessels; Drug Administration Schedule; Endothelin-1; Humans; Hypoxia; Mitogens; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Pulmonary Artery; Reactive Oxygen Species; Superoxides; Vasoconstrictor Agents

We reported previously that intermittent hypoxia with CO(2) to maintain eucapnia (IH-C) elevates plasma endothelin-1 (ET-1) and arterial pressure. In small mesenteric arteries (sMA; inner diameter = 150 microm), IH-C augments ET-1 constrictor sensitivity but diminishes ET-1-induced increases in intracellular Ca(2+) concentration, suggesting IH-C exposure increases both ET-1 levels and ET-1-stimulated Ca(2+) sensitization. Because Rho-associated kinase (ROK) can mediate Ca(2+) sensitization, we hypothesized that augmented vasoconstrictor sensitivity to ET-1 in arteries from IH-C-exposed rats is dependent on ROK activation. In thoracic aortic rings, ET-1 contraction was not different between groups, but ROK inhibition (Y-27632, 3 and 10 microM) attenuated ET-1 contraction more in IH-C than in sham arteries (50 +/- 11 and 78 +/- 7% vs. 41 +/- 12 and 48 +/- 9% inhibition, respectively). Therefore, ROK appears to contribute more to ET-1 contraction in IH-C than in sham aorta. In sMA, ROK inhibitors did not affect ET-1-mediated constriction in sham arteries and only modestly inhibited it in IH-C arteries. In ionomycin-permeabilized sMA with intracellular Ca(2+) concentration held at basal levels, Y-27632 did not affect ET-1-mediated constriction in either IH-C or sham sMA and ET-1 did not stimulate ROK translocation. In contrast, inhibition of myosin light-chain kinase (ML-9, 100 microM) prevented ET-1-mediated constriction in sMA from both groups. Therefore, IH-C exposure increases ET-1 vasoconstrictor sensitivity in sMA but not in aorta. Furthermore, ET-1 constriction is myosin light-chain kinase dependent and mediated by Ca(2+) sensitization that is independent of ROK activation in sMA but not aorta. Thus ET-1-mediated signaling in aorta and sMA is altered by IH-C but is dependent on different second messenger systems in small vs. large arteries.

Topics: Animals; Aorta; Dose-Response Relationship, Drug; Endothelin-1; Enzyme Activation; Hypercapnia; Hypoxia; Male; Mesenteric Arteries; Rats; Rats, Sprague-Dawley; rho-Associated Kinases; Sleep Apnea Syndromes; Vasoconstriction

We have previously reported that vasoconstrictor sensitivity to KCl (a receptor-independent and voltage-gated Ca influx-mediated vasoconstrictor) is augmented in the chronically hypoxic hypertensive rat pulmonary circulation probably through increased Rho kinase-mediated Ca sensitization. However, the upstream mechanism by which the RhoA/Rho kinase signaling pathway is activated is unknown. This study examined if endogenous endothelin-1 (ET-1) and serotonin (5-HT) play roles in the Rho kinase-mediated augmented vasoconstrictor response to KCl and the activation of RhoA in chronically hypoxic hypertensive rat pulmonary arteries. The augmented KCl vasoconstriction in hypertensive lungs was reduced by the ETA receptor antagonist BQ123, while a dual ETA/B antagonist had no further effects. A combination of BQ123 and a 5-HT1B/1D receptor antagonist, GR127935, was more effective than either agent alone. The combined antagonists also reduced augmented contractile sensitivity to KCl in hypertensive intrapulmonary arteries. Membrane-to-cytosol ratio of RhoA expression in hypertensive arteries was greater than that in normotensive arteries and was reduced by BQ123 and GR127935. These results suggest that stimulation of ETA and 5-HT1B/1D receptors by endogenous ET-1 and 5-HT, respectively, is involved in RhoA/Rho kinase-mediated increased Ca sensitization in the chronically hypoxic hypertensive rat pulmonary circulation.

Topics: Amides; Animals; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Endothelin-1; Enzyme Activation; Hypertension, Pulmonary; Hypoxia; In Vitro Techniques; Lung; Male; Peptides, Cyclic; Perfusion; Potassium Chloride; Pulmonary Artery; Pulmonary Circulation; Pyridines; Rats; Rats, Sprague-Dawley; rho-Associated Kinases; rhoA GTP-Binding Protein; Serotonin; Signal Transduction; Vasoconstriction

To investigate the role of vascular endothelial growth factor (VEGF) and endothelin-1 (ET-1) on pulmonary vascular structural remodeling in rats and pika.. The Wistar rats which reside at 2 260 m were carried to 3 417 m. After they were fed 24 hours,2 weeks and 3 weeks respectively, the level of VEGF and ET-1 were measured using a kit by ELISA method. Pulmonary tissue was taken out to stain with elastica-Van Gieson. The amount of pulmonary arteries (< 100 microm) and the component ratio of MA, PMA,and NMA were calculated by using a light microscope. The ratio of right ventricle weight to left ventricle plus septum weight (RV/LV + S) were measured.. The ET-1 was significantly different in pika as compared with 24 h, 2 weeks, 3 weeks hypoxic rats (P < 0.01) respectively. The levels of VEGF in 2 weeks, 3 weeks rats were much higher than that of pika but no difference was found between pika and 24 h hypoxic rats. The ratio of MA, PMA obviously increased, and NMA decreased significantly, right ventricular hypertrophy was developed in differ groups of hypoxic rats.. The VEGF and ET-1 participate the muscularization of pulmonary vessels during hypoxia and play an important role in the process of hypoxic pulmonary hypertension in rats, however the VEGF and ET-1 may be maintainable only normal organic function in pika.

Topics: Animals; Endothelin-1; Female; Hypertension, Pulmonary; Hypoxia; Lagomorpha; Lung; Male; Pulmonary Artery; Rats; Rats, Wistar; Vascular Endothelial Growth Factor A

Endothelin-1 (ET-1), a potent vasoconstrictor, is believed to contribute to the pathogenesis of hypoxic pulmonary hypertension. Previously we demonstrated that contraction induced by ET-1 in intrapulmonary arteries (IPA) from chronically hypoxic (CH) rats occurred independently of changes in intracellular Ca2+ concentration ([Ca2+]i), suggesting that ET-1 increased Ca2+ sensitivity. The mechanisms underlying this effect are unclear but could involve the activation of myosin light chain kinase, Rho kinase, PKC, or tyrosine kinases (TKs), including those from the Src family. In this study, we examined the effect of pharmacological inhibitors of these kinases on maximum tension generated by IPA from CH rats (10% O2 for 21 days) in response to ET-1. Experiments were conducted in the presence of nifedipine, an L-type Ca2+ channel blocker, to isolate the component of contraction that occurred without a change in [Ca2+]i. The mean change in tension caused by ET-1 (10(-8) M) expressed as a percent of the maximum response to KCl was 184.0+/-39.0%. This response was markedly inhibited by the Rho kinase inhibitors Y-27632 and HA-1077 and the TK inhibitors genistein, tyrphostin A23, and PP2. In contrast, staurosporine and GF-109203X, inhibitors of PKC, had no significant inhibitory effect on the tension generated in response to ET-1. We conclude that the component of ET-1-induced contraction that occurs without a change in [Ca2+]i in IPA from CH rats requires activation of Rho kinase and TKs, but not PKC.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Amides; Animals; Azepines; Endothelin-1; Enzyme Inhibitors; Genistein; Hypoxia; Indoles; Intracellular Signaling Peptides and Proteins; Isometric Contraction; Male; Maleimides; Myosin-Light-Chain Kinase; Potassium Chloride; Protein Kinase C; Protein Serine-Threonine Kinases; Protein-Tyrosine Kinases; Pulmonary Artery; Pyridines; Pyrimidines; Rats; Rats, Wistar; rho-Associated Kinases; src-Family Kinases; Staurosporine; Vasoconstriction

Production of reactive oxygen species (ROS) may be increased during hypoxia in pulmonary arteries. In this study, the role of ROS in the effect of hypoxia on endothelin (ET) type B (ETB) receptor-mediated vasocontraction in lungs was determined. In rat intrapulmonary (approximately 0.63 mm ID) arteries, contraction induced by IRL-1620 (a selective ETB receptor agonist) was significantly attenuated after 4 h of hypoxia (30 mmHg Po2) compared with normoxic control (140 mmHg Po2). The effect was abolished by tiron, a scavenger of superoxide anions, but not by polyethylene glycol (PEG)-conjugated catalase, which scavenges H2O2. The hypoxic effect on ETB receptor-mediated vasoconstriction was also abolished by endothelium denudation but not by nitro-L-arginine and indomethacin. Exposure for 4 h to exogenous superoxide anions, but not H2O2, attenuated the vasoconstriction induced by IRL-1620. Confocal study showed that hypoxia increased ROS production in pulmonary arteries that were scavenged by PEG-conjugated SOD. In endothelium-intact pulmonary arteries, the ETB receptor protein was reduced after 4 h of exposure to hypoxia, exogenous superoxide anions, or ET-1. BQ-788, a selective ETB receptor antagonist, prevented these effects. ET-1 production was stimulated in endothelium-intact arteries after 4 h of exposure to hypoxia or exogenous superoxide anions. This effect was blunted by PEG-conjugated SOD. These results demonstrate that exposure to hypoxia attenuates ETB receptor-mediated contraction of rat pulmonary arteries. A hypoxia-induced production of superoxide anions may increase ET-1 release from the endothelium and result in downregulation of ETB receptors on smooth muscle.

Topics: Animals; Down-Regulation; Endothelin-1; Endothelins; Endothelium, Vascular; Hypertension, Pulmonary; Hypoxia; Lung; Male; Muscle Contraction; Muscle, Smooth, Vascular; Peptide Fragments; Pulmonary Artery; Pulmonary Circulation; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Receptor, Endothelin B; Superoxides; Vasoconstriction

MDM2 is an E3 ubiquitin ligase that regulates the proteasomal degradation and activity of proteins involved in cell growth and apoptosis, including the tumor suppressors p53 and retinoblastoma and the transcription factor E2F1. Although the effect of several MDM2 targets on cardiomyocyte survival and hypertrophy has already been investigated, the role of MDM2 in these processes has not yet been established. We have, therefore, analyzed the effect of overexpression as well as inhibition of MDM2 on cardiac ischemia/reperfusion injury and hypertrophy. Here we show that isolated cardiac myocytes overexpressing MDM2 acquired resistance to hypoxia/reoxygenation-induced cell death. Conversely, inactivation of MDM2 by a peptide inhibitor resulted in elevated p53 levels and promoted hypoxia/reoxygenation-induced apoptosis. Consistent with this, decreased expression of MDM2 in a genetic mouse model was accompanied by reduced functional recovery of the left ventricles determined with the Langendorff ex vivo model of ischemia/reperfusion. In contrast to cell survival, cell hypertrophy induced by the alpha-agonists phenylephrine or endothelin-1 was inhibited by MDM2 overexpression. Collectively, our studies indicate that MDM2 promotes survival and attenuates hypertrophy of cardiac myocytes. This differential regulation of cell growth and cell survival is unique, because most other survival factors are prohypertrophic. MDM2, therefore, might be a potential therapeutic target to down-regulate both cell death and pathologic hypertrophy during remodeling upon cardiac infarction. In addition, our data also suggest that cancer treatments with MDM2 inhibitors to reactivate p53 may have adverse cardiac side effects by promoting cardiomyocyte death.

Topics: Adenoviridae; Animals; Animals, Newborn; Antineoplastic Agents; Apoptosis; Cell Line, Transformed; Cell Proliferation; Cell Survival; Endothelin-1; Hypoxia; Immunoblotting; Immunohistochemistry; Mice; Mice, Inbred BALB C; Myocardium; Myocytes, Cardiac; Peptides; Perfusion; Phenylephrine; Proto-Oncogene Proteins c-mdm2; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Transcription, Genetic; Tumor Suppressor Protein p53

High-altitude natives are adapted to hypobaric hypoxia, suggestive of genetic basis of adaptation. Since endothelin-1 (ET-1) is of prime importance in high-altitude disorders in sojourners, we envisaged the role of allelic variants of ET-1 in high-altitude adaptation. Four ET-1 polymorphisms, viz., (CT)(n)-(CA)(n) repeat, -3A/-4A, G2288T, and Lys198Asn, were investigated in 426 highlanders (HLs) and 236 lowlanders (LLs). The plasma ET-1 levels, SBP and BMI were significantly lower in the HLs than those in LLs (p<0.0001). The Longer-repeats (31-45), G allele, Longer-repeats/GG, and Longer-repeats/Lys198Lys combinations were overrepresented in the HLs (p<0.0001, p=0.03, p<0.0001, and p<0.0001, respectively). The Longer-repeats, -3A/-3A, GG and Lys198Lys genotypes associated with significantly lower ET-1 levels in the HLs (p<0.0001, p=0.001, p<0.0001, and p<0.0001, respectively). Combinations of Longer-repeats with -3A/-3A, GG, and Lys198Lys genotypes, and -3A/-3A/Lys198Lys combination revealed association with lower ET-1 levels in the HLs (p<0.001). The study reports over-representation of Longer-repeats, G allele, and wild-type genotype combinations in high-altitude natives. Interaction between these alleles and association with lower ET-1 levels strengthen their association with high-altitude adaptation. Presence of such alleles in sojourners may help in acclimatization.

Topics: Adaptation, Physiological; Adult; Altitude; Altitude Sickness; Asian People; Endothelin-1; Female; Gene Frequency; Genetic Variation; Genotype; Humans; Hypoxia; India; Male; Middle Aged; Repetitive Sequences, Nucleic Acid

We report in the present study the effect of regular exercise on vascular reactivity alterations to endothelin (ET-1) following prolonged exposure to hypoxic stress.. Male Dark Agouti rats were randomly assigned to N (sedentary rats), NCE (normoxic exercised rats), CH (chronic hypoxic sedentary rats) and CHCE (chronic hypoxic exercised rats) groups. The effects of ET-1 in the presence or not of the endothelium and/or of the specific inhibitor, bosentan, have been investigated in an isolated model of rat thoracic aorta.. Prolonged exposure to hypoxia induced a significant increase in aortic sensitivity to ET-1 (-log ED50 in CH = 8.15 +/- 0.01 vs in N = 7.98 +/- 0.02, p < 0.05). Despite exercise training reduced the sensitivity to ET-1 in normoxic rats, it has no effects in hypoxic rats (-log ED50 in CH = 8.15 +/- 0.01 vs in CHCE = 8.19 +/- 0.01, NS). Moreover, although the removal of endothelium has no effect in N rats, it leads, in NCE rats, to a significant increase in sensitivity to ET-1 (-log ED50 in endothelium intact rings = 7.89 +/- 0.04 vs in denuded rings = 8.04 +/- 0.02, p < 0.05). The implication of ET-1 receptors on both endothelial and smooth muscle cells is confirmed by the significant reduced sensitivity to ET-1 in the four groups when bosentan is present in organ bath.. Our study clearly suggests that part of the beneficial effect of chronic exercise could be mediated by enhancing endothelial function associated with endothelin reactivity in peripheric vessels. However, chronic exercise training does not seem to be able to limit the increased vasoconstriction to ET-1 stimulation induced by chronic hypoxia exposure.

Topics: Animals; Aorta, Thoracic; Bosentan; Dose-Response Relationship, Drug; Endothelin-1; Endothelium, Vascular; Hypoxia; Male; Physical Conditioning, Animal; Potassium Chloride; Rats; Receptor, Endothelin A; Sulfonamides; Vasoconstriction; Vasoconstrictor Agents

Chronic intermittent hypoxia (CIH) enhances carotid body (CB) chemosensory responses to acute hypoxia. We tested the hypothesis that endothelin-1 (ET-1), an excitatory modulator of CB chemoreception may contribute to the enhanced CB chemosensory responses in cats exposed to cyclic hypoxic episodes repeated during 8 h for 4 days. Accordingly, we measured the ET-1 immunoreactivity (ET-ir) in the CB and plasma. Using a perfused CB preparation, we studied the effects of exogenous ET-1 and bosentan, a non-selective endothelin receptor type A and B antagonist, on the frequency of chemosensory discharges (f(x)) during normoxia, mild and severe hypoxia. We found that CIH increased ET-ir in the CB by approximately 10-fold leaving ET-1 plasma levels unchanged. Application of ET-1 to control and CIH-treated CBs produced long-lasting dose-dependent increases in f(x), although the dose-response curve showed a rightward-shift in the CIH-treated CBs. CIH increased baseline f(x) and hypoxic chemosensory responses, which were reduced by 50 microM bosentan in CBs from CIH-treated cats. Present results suggest that a local increase of ET-1 in the CB may contribute to the enhanced chemosensory responses induced by CIH predominantly through a vasomotor mechanism.

Topics: Animals; Antihypertensive Agents; Bosentan; Carotid Body; Cats; Chemoreceptor Cells; Dose-Response Relationship, Drug; Drug Interactions; Endothelin-1; Gene Expression; Hypoxia; Immunohistochemistry; Male; Oxygen; Sulfonamides

To study the influence of Radix Astragali (RA) on pulmonary tissue endothelin-1 (ET-1) and nitric oxide (NO) in hypoxic pulmonary hypertension rats.. Twenty one healthy male Wistar rats weighing 210-310 g were divided into three group at random with 7 in each. The rats in control group were raised in ordinary room condition; those in hypoxic group were raised in ordinary pressure hypoxic box [concentration of O(2) was (10.0 +/- 0.5)%] for 8 hours a day, for 30 days; those in RA group were raised in the same condition as hypoxic group and treated with an intraperitoneal injection of RA 8 g/kg per day. The rats in the control group and hypoxic group were given the same volume of intraperitoneal injection of normal saline. Mean pulmonary arterial pressure (mPAP), mean carotid artery pressure (mCAP) were measured via right cardiac catheterization, concentration of NO in pulmonary tissue was measured by radioimmunoassay.. (1) The mPAP (mm Hg) (21.9 +/- 1.6) and ET-1 (pg/ml) (309.1 +/- 58.1) in hypoxemic group were significantly higher than those in RA group (16.2 +/- 0.8, 287.7 +/- 57.5) and control group (15.3 +/- 0.8, 241.1 +/- 52.5) (P < 0.01, < 0.05), but the difference between RA group and control group was not significant. (2) NO (micromol/L) in pulmonary tissue in hypoxemic group (6.5 +/- 0.3) was lower than that in RA group and control group (9.2 +/- 0.9), NO in RA group was higher than that in hypoxic group but lower than that in control group (P < 0.05). (3) There was no significant difference in mCAP among the three groups (P > 0.05). (4) Under electron microscope, the endothelial cells of arterioles of the lung tissue of control group were flat and had normal morphology. However, in the lung tissue of hypoxic group, there were proliferation, hypertrophy and swelling of endothelial cells of pulmonary medium and small arteries and plenty of mitochondria and endoplasmic reticula in cytoplasm.. Chronic hypoxia can result in reconstruction and endothelial lesion in pulmonary arterioles of rats, elevation of mPAP and ET-1 in pulmonary tissue, and decrease of NO. Injection of Radix Astraglai can reverse the reconstruction of pulmonary vessels partially, regulate the concentration of ET-1 and NO in pulmonary tissue, which may have certain therapeutic effects on pulmonary arteriolar changes induced by hypoxia.

Topics: Animals; Drugs, Chinese Herbal; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Lung; Male; Nitric Oxide; Radioimmunoassay; Random Allocation; Rats; Rats, Wistar

Topics: Animals; Carotid Body; Chronic Disease; Endothelin-1; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Immunohistochemistry; Rats; Rats, Sprague-Dawley; Time Factors

Topics: Animals; Bosentan; Carotid Body; Cats; Chronic Disease; Electrophysiology; Endothelin Receptor Antagonists; Endothelin-1; Hypoxia; Immunohistochemistry; In Vitro Techniques; Male; Sulfonamides

Many infants recovering from acute lung disease and pulmonary hypertension still have evidence of reactive airways disease at one year of age, suggesting longer-term airway effects. We hypothesized that parallel changes in smooth muscle would occur in airways and pulmonary arteries from animals with pulmonary hypertension and during normoxic recovery. Thus, two-hour-old piglets were subjected to 3 d chronic hypobaric hypoxia and 3-d-old piglets were subjected to 11 d hypoxia. Some animals were allowed to recover in room air for 3 or 6 d. The amount of smooth muscle and responses of isolated paired bronchial and pulmonary artery rings to endothelin-1 (ET-1) and norepinephrine were studied at the end of hypoxic exposure, on recovery and in age-matched control animals. In all hypoxia induced pulmonary hypertensive animals, smooth muscle area and ET-1 contractile response was increased in the pulmonary arteries and bronchi. Norepinephrine-induced relaxant response was impaired significantly in both bronchi and pulmonary arteries. After 3 d recovery, pulmonary arterial smooth muscle area decreased by 65%, and ET-1-induced contractile responses were normal for age. In the airways, ET-1 contractile response only normalized after six days and bronchial smooth muscle was still increased. After 6 d recovery pulmonary arterial norepinephrine-induced relaxant response had returned to normal, but bronchial response remained impaired. Thus during pulmonary hypertension, both bronchial and pulmonary arterial smooth muscle area and contractile responses are increased. On recovery, regression of bronchial structural and functional abnormalities is slower than in pulmonary arteries.

Topics: Animals; Animals, Newborn; Blood Pressure; Bronchi; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Muscle Contraction; Muscle, Smooth; Muscle, Smooth, Vascular; Norepinephrine; Pulmonary Artery; Recovery of Function; Swine; Time Factors; Vasoconstriction

The precise cellular and molecular mechanisms regulating adventitial vasa vasorum neovascularization, which occurs in the pulmonary arterial circulation in response to hypoxia, remain unknown. Here, using a technique to isolate and culture adventitial fibroblasts (AdvFBs) and vasa vasorum endothelial cells (VVECs) from the adventitia of pulmonary arteries, we report that hypoxia-activated pulmonary artery AdvFBs exhibited pro-angiogenic properties and influenced the angiogenic phenotype of VVEC, in a process of cell-cell communication involving endothelin-1 (ET-1). We demonstrated that AdvFBs, either via co-culture or conditioned media, stimulated VVEC proliferation and augmented the self-assembly and integrity of cord-like networks that formed when VVECs where cultured on Matrigel. In addition, hypoxia-activated AdvFBs produced ET-1, suggesting a paracrine role for this pro-angiogenic molecule in these processes. When co-cultured on Matrigel, AdvFBs and VVECs self-assembled into heterotypic cord-like networks, a process augmented by hypoxia but attenuated by either selective endothelin receptor antagonists or oligonucleotides targeting prepro-ET-1 mRNA. From these observations, we propose that hypoxia-activated AdvFBs exhibit pro-angiogenic properties and, as such, communicate with VVECs, in a process involving ET-1, to regulate vasa vasorum neovascularization occurring in the adventitia of pulmonary arteries in response to chronic hypoxia.

Topics: Animals; Cattle; Cell Culture Techniques; Cell Proliferation; Cells, Cultured; Disease Models, Animal; Endothelin-1; Endothelium, Vascular; Fibroblasts; Hypertension; Hypoxia; Microscopy, Fluorescence; Pulmonary Artery

Endothelin-1 has been associated with development of hypoxia-related pulmonary hypertension and vascular endothelial growth factor (VEGF) with protection from this complication. In Chuvash polycythemia, homozygous germline von Hippel-Lindau (VHL) 598C->T leads to up-regulation during normoxia of hypoxia inducible factor-1a and several hypoxia-controlled genes including erythropoietin and VEGF. We postulated that endothelin-1 and pulmonary artery pressure may be elevated in Chuvash polycythemia.. Systolic pulmonary artery blood pressure was estimated by Doppler echocardiography and plasma concentrations of endothelin-1, VEGF and erythropoietin were determined in 14 patients with Chuvash polycythemia and 14 controls. Results. Plasma endothelin-1 (p=0.010), VEGF (p=0.022) and erythropoietin (p<0.0005) concentrations and Doppler-estimated systolic pulmonary artery pressures (p<0.0005) were higher in the patients while systolic systemic blood pressures were lower (p=0.001). Five (36%) patients and no controls had mild pulmonary hypertension defined as systolic pulmonary artery pressure (c) 35 mmHg. Among the patients with Chuvash polycythemia, the trends of association of estimated pulmonary artery pressure with plasma concentrations of endothelin-1 (R = +0.236), VEGF (R = -0.389) and erythropoietin (R = +0.220) were not statistically significant.. Estimated systolic pulmonary artery pressure and plasma concentrations of endothelin-1 and VEGF are increased in patients with Chuvash polycythemia patients. The lack of significant associations of estimated systolic pulmonary artery pressure with plasma endothelin-1 and VEGF levels could conceivably be due to the small sample size. Further studies are indicated, especially in view of the reported efficacy of endothelin-1 receptor blockers in treating hypoxia-associated pulmonary hypertension.

Topics: Altitude; Electrocardiography; Endothelin-1; Humans; Hypertension, Pulmonary; Hypoxia; Mutation; Polycythemia; Polymorphism, Single Nucleotide; Pulmonary Artery; Reference Values; Russia; Systole; Vascular Endothelial Growth Factor A

Mechanisms that induce the excessive proliferation of vascular wall cells in hypoxic pulmonary hypertension (PH) are not fully understood. Alveolar hypoxia causes sympathoexcitation, and norepinephrine can stimulate alpha(1)-adrenoceptor (alpha(1)-AR)-dependent hypertrophy/hyperplasia of smooth muscle cells and adventitial fibroblasts. Adrenergic trophic activity is augmented in systemic arteries by injury and altered shear stress, which are key pathogenic stimuli in hypoxic PH, and contributes to neointimal formation and flow-mediated hypertrophic remodeling. Here we examined whether norepinephrine stimulates growth of the pulmonary artery (PA) and whether this is augmented in PH. PA from normoxic and hypoxic rats [9 days of 0.1 fraction of inspired O(2) (Fi(O(2)))] was studied in organ culture, where wall tension, Po(2), and Pco(2) were maintained at values present in normal and hypoxic PH rats. Norepinephrine treatment for 72 h increased DNA and protein content modestly in normoxic PA (+10%, P < 0.05). In hypoxic PA, these effects were augmented threefold (P < 0.05), and protein synthesis was increased 34-fold (P < 0.05). Inferior thoracic vena cava from normoxic or hypoxic rats was unaffected. Norepinephrine-induced growth in hypoxic PA was dose dependent, had efficacy greater than or equal to endothelin-1, required the presence of wall tension, and was inhibited by alpha(1A)-AR antagonist. In hypoxic pulmonary vasculature, alpha(1A)-AR was downregulated the least among alpha(1)-AR subtypes. These data demonstrate that norepinephrine has trophic activity in the PA that is augmented by PH. If evident in vivo in the pulmonary vasculature, adrenergic-induced growth may contribute to the vascular hyperplasia that participates in hypoxic PH.

Topics: Adrenergic alpha-1 Receptor Agonists; Adrenergic alpha-1 Receptor Antagonists; Animals; DNA; Dose-Response Relationship, Drug; Endothelin-1; Fibroblasts; Hypertension, Pulmonary; Hypoxia; Male; Muscle, Smooth, Vascular; Norepinephrine; Organ Culture Techniques; Proteins; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Receptors, Adrenergic, alpha-1; Time Factors

Induction of hypercapnia by breathing high concentrations of carbon dioxide (CO(2)) may have beneficial effects on the pulmonary circulation. We tested the hypothesis that exposure to CO(2) would protect against chronic pulmonary hypertension in newborn rats. Atmospheric CO(2) was maintained at <0.5% (normocapnia), 5.5%, or 10% during exposure from birth for 14 days to normoxia (21% O(2)) or moderate hypoxia (13% O(2)). Pulmonary vascular and hemodynamic abnormalities in animals exposed to chronic hypoxia included increased pulmonary arterial resistance, right ventricular hypertrophy and dysfunction, medial thickening of pulmonary resistance arteries, and distal arterial muscularization. Exposure to 10% CO(2) (but not to 5.5% CO(2)) significantly attenuated pulmonary vascular remodeling and increased pulmonary arterial resistance in hypoxia-exposed animals (P < 0.05), whereas both concentrations of CO(2) normalized right ventricular performance. Exposure to 10% CO(2) attenuated increased oxidant stress induced by hypoxia, as quantified by 8-isoprostane content in the lung, and prevented upregulation of endothelin-1, a critical mediator of pulmonary vascular remodeling. We conclude that hypercapnic acidosis has beneficial effects on pulmonary hypertension and vascular remodeling induced by chronic hypoxia, which we speculate derives from antioxidant properties of CO(2) on the lung and consequent modulating effects on the endothelin pathway.

Topics: Animals; Animals, Newborn; Body Weight; Carbon Dioxide; Carboxylic Acids; Chronic Disease; Endothelin Receptor Antagonists; Endothelin-1; Female; Hematocrit; Hypercapnia; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Indans; Oxidative Stress; Oxygen; Pregnancy; Pulmonary Artery; Pulmonary Circulation; Rats; Up-Regulation

It has been hypothesized that autacoids, such as endothelin-1 (ET), may modulate erythropoietin (Epo) secretion. Therefore, we studied the effect of ET-1 infusion and of a nonselective ET(A/B) receptor antagonist on Epo secretion under carbon monoxide (CO) exposure. Anesthetized rats were supplied with room temperature air containing increasing concentrations of CO by an aerating cap. A CO-Epo dose-response curve over the range of 0.02-0.14 vol% CO was conducted. Subpressor doses of ET-1 (3 pmol/min/kg BW) and the ET(A/B) receptor antagonist LU302872 (LU; 30 mg/kg) were applied to anaesthetized rats under normoxia (controls CON, ET, LU) and following hypoxia (CO exposure; H-CON, H-ET, H-LU). Mean arterial blood pressure (MAP), glomerular filtration rate (GFR, inulin clearance), Epo and ET-1 serum concentrations (ELISA) and renal Epo mRNA (Light Cycler) were determined. The EC50 value for CO was 0.1 vol% with a 70-fold increase in Epo serum concentrations. CO exposure increased Epo serum and Epo mRNA concentrations in the expected range in all groups. None of the treatments with ET or LU influenced the effect of hypoxia on Epo serum concentrations and renal Epo mRNA content. Under hypoxia, administration of ET-1 as well as LU prevented the hypoxia-induced decrease in MAP (p<0.05). Under hypoxia, GFR was reduced by 50% except for H-LU with values comparable to normoxia. Taken together, the influence of hypoxia exceeds by far the effect of ET-1 on Epo production, irrespective of the presence or absence of exogenous ET-1. Thus, ET-1 does not appear to be a major modulator of Epo production.

Topics: Animals; Blood Pressure; Carbon Monoxide; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Endothelin-1; Erythropoietin; Glomerular Filtration Rate; Hypoxia; Kidney; Male; Rats; Rats, Sprague-Dawley; RNA, Messenger

Hypertension frequently occurs in obese subjects. It has been reported that leptin and resistin induce endothelin-1 expression in vascular endothelial cells. Altered function of brain microvascular endothelial cells may be related to increased occurrences of stroke in hypertensive patients. In the present study, we therefore studied the effects of leptin and resistin on the expression of endothelin-1 and adrenomedullin in bovine brain microvascular endothelial cells. Northern blot analysis showed that leptin (10(-10)-10(-8) mol/l), resistin (10(-10)-10(-8) mol/l) or a combination of leptin and resistin (10(-8) mol/l for each) had no significant effects on the expression of endothelin-1 mRNA or adrenomedullin mRNA in cultured bovine brain microvascular endothelial cells. On the other hand, hypoxia induced, and tumor necrosis factor-alpha (10 ng/ml) decreased, the expression levels of endothelin-1 and adrenomedullin mRNAs, indicating that the bovine brain microvascular endothelial cells were able to respond to hypoxia and tumor necrosis factor-alpha. Consistent with the results of Northern blot analysis, immunoreactive endothelin and immunoreactive adrenomedullin concentrations in the medium were not significantly changed by the treatment with leptin, resistin, or a combination of leptin and resistin. The present study thus showed that neither leptin nor resistin affects the expression of endothelin-1 or adrenomedullin in bovine brain microvascular endothelial cells.

Topics: Adrenomedullin; Animals; Brain; Cattle; Cells, Cultured; Endothelin-1; Endothelium, Vascular; Gene Expression Regulation; Hypertension; Hypoxia; Leptin; Microcirculation; Peptides; Resistin; RNA, Messenger; Stroke; Tumor Necrosis Factor-alpha

Topics: Altitude; Altitude Sickness; Bosentan; Diuresis; Double-Blind Method; Endothelin Receptor Antagonists; Endothelin-1; Humans; Hypertension, Pulmonary; Hypoxia; Kidney Diseases; Muscle, Smooth, Vascular; Potassium Channels, Voltage-Gated; Randomized Controlled Trials as Topic; Receptors, Endothelin; Sulfonamides; Vasoconstriction; Ventricular Function, Right

The aim of this study was to determine whether increased expression of heme oxygenase (HO) contributes to impairment of aortic contractile responses after hypoxia through effects on reactivity to endothelin-1 (ET-1). Thoracic aortas from normoxic rats and rats exposed to hypoxia (10% O2) for 16 or 48 h were mounted in organ bath myographs for contractile studies, fixed in paraformaldehyde, or frozen in liquid nitrogen for protein extraction. In rings from normoxic rats, the HO inhibitor tin protoporphyrin IX (SnPP IX, 10 microM) did not alter the response to phenylephrine or ET-1. In rings from rats exposed to 16-h hypoxia, maximum tension generated in response to these agonists was higher in endothelium-intact but not -denuded rings in the presence of SnPP IX. In rings from rats exposed to 48-h hypoxia SnPP IX increased contraction in endothelium-intact but not -denuded rings. In endothelium-intact aortic rings from rats exposed to 16-h hypoxia incubated with endothelin A receptor-specific antagonist BQ-123 (10(-7) M), SnPP IX did not alter phenylephrine-induced contraction. Aortic ET-1 protein levels, measured by radioimmunoassay, were increased in rats exposed to hypoxia for 16 and 48 h. Western blotting showed that HO-1 and HO-2 protein were increased after 16 h of hypoxia and returned to near-control levels after 48 h. Increase in HO-1 protein was detected in endothelium-intact and -denuded rings. Removal of endothelium abolished the increase in HO-2 immunoreactivity. Immunohistochemistry localized expression of HO-1 protein to vascular smooth muscle, whereas HO-2 was only detected in endothelium. HO-2 is expressed by aortic endothelial cells early during hypoxic exposure and impairs ET-1-mediated potentiation of contraction to alpha-adrenoceptor stimulation.

Topics: Animals; Aorta, Thoracic; Endothelin-1; Endothelium, Vascular; Enzyme Inhibitors; Heme Oxygenase (Decyclizing); Heme Oxygenase-1; Hypoxia; Male; Metalloporphyrins; NG-Nitroarginine Methyl Ester; Oxygen; Phenylephrine; Protoporphyrins; Rats; Rats, Sprague-Dawley; Vasoconstrictor Agents

In response to reduced oxygen or nutrient supply, the fetus may redistribute cardiac output to conserve brain and heart growth, at the expense of the peripheral tissues; however, it is not known whether alterations in vascular function are maintained after birth or whether reduced fetal oxygen versus nutrient supply produces distinct effects. Using a pressure myograph, we examined isolated carotid and femoral artery responses to phenylephrine and endothelin-1 in neonatal rats, after either reduced maternal oxygen or global nutrient restriction during late gestation. Timed-pregnant Sprague-Dawley rats were randomly assigned to control (n = 10), hypoxia (12% O2, n = 9), or nutrient restriction (NR, 40% of control diet, n = 7) protocol and treated from day 15-21 of pregnancy. Pups were collected 3-12 h after birth. Neonatal weights (P < 0.001) and relative liver weights (P < 0.001) were lower in hypoxia and nutrient restriction treatments compared with control, while relative heart weights were greater in the hypoxia than in the control or nutrient restriction groups (P < 0.01). Constriction to phenylephrine was reduced in carotid arteries from the hypoxia and nutrient restriction groups compared with control (P < 0.001), while the femoral artery response was greater in hypoxia-treated neonates compared with control or nutrient-restricted neonates (P < 0.01). Only the hypoxia reduced carotid responses to endothelin-1, while no differences were observed in the endothelin-1 responses in femoral arteries. Maternal hypoxia and maternal nutrient restriction produced distinct effects on heart growth and neonatal vascular function, suggesting that regional changes in cardiovascular function after poor fetal growth are dependent on the nature of the insult in utero.

Topics: Animals; Animals, Newborn; Carotid Arteries; Diet; Endothelin-1; Female; Femoral Artery; Fetal Hypoxia; Hypoxia; Malnutrition; Phenylephrine; Pregnancy; Pregnancy Complications; Rats; Rats, Sprague-Dawley; Vasoconstriction; Vasoconstrictor Agents; Vasodilation

High-altitude hypoxia causes pulmonary hypertension in humans and animals. Endothelin-1 (ET-1) is a novel and long-lasting vasoconstrictor. However, no study has dealt with the effects of a hypobaric hypoxic environment (HHE) on ET-1 activity in the brain. We examined 134 male rats permanently exposed to the equivalent of 5500 m altitude for 1 to 8 weeks. In these HHE rats, the mean pulmonary arterial pressure was significantly raised. The level of ET-1 protein, measured by enzyme immunoassay, increased rapidly in the lungs on exposure to HHE, but decreased in the brain. The level of ET-1 mRNA, measured by semiquantitative RT-PCR, was raised at 1, 4, and 6 weeks' exposure in the lungs and at 4 or more weeks' exposure in 3 of 8 brain regions. By in situ hybridization and immunohistochemistry of brain sections, ET-1 mRNA and protein were detected in the endothelial cells, neurons, and astrocyte-like cells in control rats. In HHE rats, the immunoreactive intensity for ET-1 protein decreased rapidly with time in these cells within the brain, although a few weakly ET-1 protein-positive cells were detected until 8 weeks' exposure to HHE. Only a few weakly ET-1 mRNA-positive endothelial cells were detected in any HHE rats. Although the reactivity for ET-1 mRNA had decreased significantly in neurons and astrocyte-like cells at 1 and 2 weeks' exposure to HHE, it was again strong in both types of cells at 4 weeks' exposure to HHE. These results raise the possibility that during exposure to HHE, ET-1 production in the lung may play a role in the development of pulmonary hypertension, while a decrease in ET-1 production within the brain may help to protect neurons by preventing or limiting the constriction of cerebral microvessels during the hypoxia induced by HHE.

Topics: Altitude Sickness; Animals; Astrocytes; Brain; Cerebrovascular Circulation; Disease Models, Animal; Down-Regulation; Endothelial Cells; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Hypoxia, Brain; Immunohistochemistry; Lung; Male; Neurons; Rats; Rats, Wistar; Regional Blood Flow; RNA, Messenger; Time Factors; Up-Regulation; Vasoconstriction

We reported previously that simulating sleep apnea in rats by exposing them 7 hours per day to intermittent hypoxia/hypercapnia (IH) elevates plasma endothelin-1 and causes hypertension, which is reversed by an endothelin-1 antagonist. We hypothesized that in this model of sleep apnea-induced hypertension, vascular sensitivity to endothelin-1 is increased in combination with the elevated plasma endothelin-1 to cause the endothelin-1-dependent hypertension. In small mesenteric arteries with endothelial function disabled by passing air through the lumen, diameter and vessel wall [Ca2+] were recorded simultaneously. IH arteries demonstrated increased constrictor sensitivity to endothelin-1 (percentage max constriction 100+/-0% IH versus 80+/-10% Sham; P<0.05). This was accompanied by increased calcium sensitivity of IH arteries. In contrast, constrictor sensitivity and increases in vessel wall [Ca2+] to KCl and phenylephrine were not different between IH and Sham arteries. We have shown previously that endothelin-1 constriction in mesenteric arteries is mediated by endothelin A receptors. In the current study, the selective increase in endothelin-1 constriction in IH resistance arteries was accompanied by increased expression of endothelin A receptor expression (densitometry units 271+/-23 IH versus 158+/-25 Sham; P<0.05). Thus, IH hypertension appears to cause alterations in signaling components unique to endothelin-1 at the receptor level and in postreceptor signaling that increases calcium sensitivity during endothelin A activation. Future studies will determine the specific changes in vascular smooth muscle signaling in IH hypertension causing this augmented contractile phenotype.

Topics: Animals; Blood Pressure; Calcium; Endothelin-1; Hypertension; Hypoxia; In Vitro Techniques; Male; Mesenteric Arteries; Phenylephrine; Potassium Chloride; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Sleep Apnea Syndromes; Vasoconstriction; Vasoconstrictor Agents

To explore the mechanism of the effect of chronic intermittent hypoxia (CIH), an important pathophysiological state of sleep apnea syndrome (SAS), on cardiovascular system.. Thirty male ICR mice were divided into three groups: an experimental group, an air mimic control group and a blank control group. Immunohistochemistry was used to examine the expression of hypoxia inducible factor-1alpha (HIF-1alpha) and inducible nitric oxide synthase (NOS-2) in the myocardial cells. Enzyme-linked immunosorbent assay (ELISA) was used to measure the plasma concentration of vascular endothelial growth factor (VEGF) and endothelin-1 (ET-1).. The expression of HIF-1alpha in myocardial cells of the experimental group significantly increased compared with that of the air mimic control group (t = 3.54, P < 0.05), and that of the blank control group (t = 2.92, P < 0.05). The expression of HIF-1alpha in myocardial cells of the air mimic control group was not significantly different from that of the blank control group (P > 0.05). The plasma concentration of VEGF of the experimental group [(9.57 +/- 1.41) ng/ml] was significantly higher than that of the blank control group [(8.10 +/- 0.62) ng/ml, q = 4.27, P < 0.05], and that of the air mimic control group [(8.32 +/- 0.99) ng/ml, q = 3.64, P < 0.05]. While the plasma concentration of ET-1 of the experimental group [(3.31 +/- 0.81) ng/ml] was significantly higher than that of the blank control group [(2.50 +/- 0.72) ng/ml, q = 3.64, P < 0.05], it was not significantly different from that of the air mimic control group [(2.69 +/- 0.43) ng/ml, P > 0.05]. There was no significant difference between the expression of NOS-2 in myocardial cells of all groups (P > 0.05).. CIH enhances the expression of HIF-1alpha and its target gene products VEGF and ET-1, and therefore affects the cardiovascular system.

Topics: Animals; Endothelin-1; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Immunohistochemistry; Male; Mice; Mice, Inbred ICR; Nitric Oxide Synthase Type II; Sleep Apnea, Obstructive; Transcription Factors; Vascular Endothelial Growth Factors

To investigate the effect of endothelin-1 (ET-1) on voltage-gated K+ current in the pulmonary artery smooth muscle cells (PASMCs) of chronic hypoxic rats.. Twelve male Wistar rats matched with age and body weight were randomly divided into control and chronic hypoxic groups. Single PASMCs were obtained with acute enzyme (collagnase plus papain) dispersing method. Using the whole cell patch clamp technique in freshly isolated PASMCs from normoxic and hypoxic rats, the effects of ET-1 on voltage-gated K+ current were recorded.. The resting membrane potential (Em) in PASMCs from chronic hypoxic rats was significantly depolarized to (-32.6 +/- 1.3) mV compared with (-42.1 +/- 2.8) mV in PASMCs from normoxic rats (P < 0.01, n = 20). In chronic hypoxic rats, the IKv was smaller than that in normotensive rats [+50 mV, the peak current density of control group reduced from (136 +/- 24) pA/pF to (98 +/- 12) pA/pF, percent inhibition was (28.4 +/- 2.4)%, P < 0.01, n = 6]. Application of ET-1 (1 x 10(-8) mol x L(-1)) also depolarized PASMCs of chronic hypoxic rats from (-32.6 +/- 1.3) mV to (-21.5 +/- 1.7) mV (P < 0.05, n = 20) compared with the ET-1 induced depolarization from (-42.1 +/- 2.8) mV to (-22.6 +/- 1.4) mV (P < 0.05, n = 20). The change in membrane potential induced by ET-1 was not significantly different between PASMCs from normoxic and hypoxic rats. ET-1 (1 x 10(-10) to 1 x 10(-7) mol x L(-1)) caused concentration-dependent inhibition of K+ current in PASMCs both from normoxic and hypoxic rats. At higher concentration (1 x 10(-8) - 1 x 10(-7) mol x L(-1)), the effect of ET-1 on K+ current in PASMCs from hypoxic rats was greater than that of normoxic rats [+50 mV, the peak current density of control group reduced from (136 +/- 24) pA/pF to (40 +/- 10) pA/pF, percent inhibition was (71 +/- 7)%, that of hypoxic group was (98 +/- 6) pA/pF to (16 +/- 3) pA/pF, percent inhibition was (85 +/- 10)% at 1 x 10(-7) mol x L(-2), n = 6, P < 0.01].. Chronic hypoxia did not change the effect of ET-1 on the passive electrical properties of PASMCs. In both normotensive and chronic hypoxic hypertensive PASMCs, exogenous ET-1 could cause concentration-dependent inhibition of voltage-gated K+ current, and the inhibition of K+ current in PASMCs from chronic hypoxic rats was greater than that from normoxic rats at higher concentration (1 x 10(-8) - 1 x 10(-7) mol x L(-1)). Chronic hypoxia might alter the sensitivity of PASMCs to ET-1, perhaps PASMCs exposed to chronic hypoxia were more susceptible to ET-1 mediated IKv inhibition.

Topics: Animals; Dose-Response Relationship, Drug; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Male; Membrane Potentials; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Patch-Clamp Techniques; Potassium Channels, Voltage-Gated; Pulmonary Artery; Random Allocation; Rats; Rats, Wistar

In investigation were included 33 children with mild and moderate bronchial asthma of atopic geneses, average duration of the disease 3,5+/-1,9 years, average frequency of asthma attacks was less then once per month (night attacks 2-3 times per week), factors of initiation were dust and sharp smells. It was shown, that in atopic bronchial asthma in children, disbalance in endothelial system is developed, the content of endothelin-1, vasoconstrictor peptide of endotheliocytes, is increased by 64%. At the same time, coefficient of correlation between redox-potential NADP/NADPH and content of IgE decreases from 0,79 (p<0,01) in norm to 0,57 (p<0,05). Obtained data raises the issue of necessity of inclusion in the therapy of bronchial asthma the remedies which prevent bioenergetic failure.

Topics: Asthma; Child; Child, Preschool; Dermatitis, Atopic; Endothelin-1; Female; Humans; Hypoxia; Immunoglobulin A; Immunoglobulin E; Male; Oxidation-Reduction; Skin

Rats with chronic bile duct ligation (CBDL) and portal vein ligation (PVL) are used as models of portal hypertension. CBDL rats show hypoxemia with intrapulmonary vasodilatation (IPVD), and are recognized as a model of hepatopulmonary syndrome (HPS), while PVL rats are normoxemic. We investigated the differences in arterial oxygenation between these models, and the key factors leading to HPS.. Forty-eight Sprague-Dawley rats were prepared as CBDL or PVL models, or as Sham rats. Arterial oxygenation, hemodynamics (reference sample method), and IPVD were simultaneously evaluated in conscious and unrestrained animals, using (141)Ce- or (113)Sn-labeled microspheres (15 microm in diameter), respectively. Endothelin-1 (ET-1) and nitrate/nitrite (end products of nitric oxide; NOx) production by the lung tissue (increment across the lungs) was also determined.. The extent of IPVD was similar in both models, but hypoxemia was only observed in CBDL rats. The ET-1 level and the increment in NOx were significantly increased in CBDL rats, and the increment was directly correlated with impairment of oxygenation. Blood flow through the bronchial arteries (anatomical shunting) was increased in CBDL rats, reaching more than three times the level in PVL rats or Sham rats.. These results support the hypothesis that NO derived from the lung tissues contributes to hypoxemia, and IPVD appears to be a prerequisite for impaired oxygenation. The considerable increase of anatomical shunting may potentially contribute to impaired oxygenation in CBDL rats.

Topics: Animals; Arteries; Disease Models, Animal; Endothelin-1; Hepatopulmonary Syndrome; Hypertension, Portal; Hypoxia; Lung; Male; Microspheres; Nitrates; Nitrites; Oxygen; Rats; Rats, Sprague-Dawley; Vasodilation

Endothelin-1 (ET-1) plays a key role in the pathogenesis of pulmonary hypertension. The present study was conducted to examine the effects of a novel compound p-chlorobenzyltetrahydroberberine (CPU 86017) on endothelin-1 system of hypoxia-induced pulmonary hypertension in rats. SD male rats were divided into control, untreated pulmonary hypertension, nifedipine (10 mg/kg p.o.), and CPU 86017 (80, 40, and 20 mg/kg p.o.) groups. The pulmonary hypertension was established by housing the rats in a hypoxic (10 +/- 0.5% oxygen) chamber 8 hours per day for 4 weeks. Hemodynamic and morphologic assessment exhibited a significant increase in the central vein pressure (CVP), right ventricular systolic pressure (RVSP), and pulmonary arteriole remodeling in the pulmonary hypertensive rats, which were improved by CPU 86017 80 and 40 mg/kg administration (P < 0.01). The elevated pulmonary endothelin-1 level and the over-active preproET-1 and iNOS mRNA expression were also decreased significantly (P < 0.01) in CPU 86017 groups. The maladjustment of redox enzyme system in pulmonary hypertension rats was corrected after treatment. We concluded that CPU 86017 improves pulmonary hypertension mainly to suppress the endothelin-1 pathway at the upstream and downstream via calcium antagonism and antioxidative action, then, resulting in a relief in pathogenesis of the disease.

Topics: Animals; Antioxidants; Berberine; Calcium Channel Blockers; Calcium Channels, L-Type; Endothelin-1; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Male; Malondialdehyde; Nitric Oxide; Nitric Oxide Synthase; Oxidative Stress; Pulmonary Artery; Rats; Rats, Sprague-Dawley

This study examined the effects of training on intrinsic vasorelaxation and vasoconstriction properties of pulmonary hypertensive rat arteries. Fifty seven male Wistar rats were randomly assigned to 4 groups: normotensive sedentary (n = 14), normotensive trained (n = 15), pulmonary hypertensive sedentary (n = 15) and pulmonary hypertensive trained (n = 13). Pulmonary hypertension was obtained using a chronic hypoxia exposure model. Endothelium-dependent vasorelaxation to acetylcholine (10(-8)-10(-4) M), endothelium-independent vasorelaxation to sodium nitro-prusside (10(-8)-10(-4) M), and vasoconstriction to epinephrine (10(-9)-10(-4) M) and endothelin-1 (10(-12)-10(-7) M) were assessed on isolated rings of large pulmonary arteries. Alterations in endothelium-dependent and -independent vasorelaxation properties as well as enhanced vasoconstrictor responses were obtained in pulmonary hypertensive rats. Chronic exercise did not affect those pulmonary vasoreactivity alterations. A predominant effect of chronic hypoxia over training seems to be partially responsible for this phenomenon, probably through impairment in nitric oxide bioavailability and vascular smooth muscle sensitivity.

Topics: Acetylcholine; Animals; Dose-Response Relationship, Drug; Endothelin-1; Endothelium, Vascular; Epinephrine; Hypertension, Pulmonary; Hypoxia; In Vitro Techniques; Male; Nitroprusside; Physical Conditioning, Animal; Potassium Chloride; Pulmonary Artery; Random Allocation; Rats; Rats, Wistar; Vasoconstriction; Vasoconstrictor Agents; Vasodilation; Vasodilator Agents

Topics: Animals; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Interleukin-6; Male; Mice; Mice, Inbred C57BL

Chronic hypoxia (CH) is a common cause of pulmonary hypertension (PH). Accumulating evidence suggests that changes in the activity of endothelin (ET)-1 receptors may play an important role in CH-induced PH. After 3 weeks of CH (10% O2) exposure, we found that the isolated intra-pulmonary artery (PA) constrictor response to ET-1 was significantly increased in wild-type (wt) mice. The administration of Cu/Zn superoxide dismutase (SOD) markedly reduced the CH-enhanced maximal PA constrictor response to ET-1, demonstrating the contribution of superoxide to CH-enhanced PA constrictor responses. Using mice that are completely deficient in gp91phox (a subunit protein of the superoxide producing nicotinamide adenine dinucleotide phosphate [NADPH] oxidase), we found that CH-enhanced PA constriction to ET-1 was completely blocked (decreases in mean [+/- SE] maximal isometric tension from 5.43 +/- 0.35 to 3.33 +/- 0.19 mN; n = 7; p < 0.01). Using a lucigenin-enhanced chemiluminescence technique to measure superoxide, we found that the 3 weeks of CH significantly increased superoxide levels in PA isolated from wt mice. The addition of ET-1 further increased superoxide production. To demonstrate that the increased chemiluminescence is due to superoxide generation, we added Cu/Zn SOD, which markedly decreased chemiluminescence, demonstrating the specificity of this assay. When gp91phox knockout mice were exposed to CH, they had significantly reduced levels of superoxide compared to CH-treated wt mice. Our results demonstrate that the CH-enhanced PA constrictor response to ET-1 is mediated by NADPH oxidase (gp91phox)-derived superoxide overproduction that may contribute to the pathogenesis of CH-induced PH.

Topics: Animals; Chronic Disease; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Luminescence; Luminescent Measurements; Membrane Glycoproteins; Mice; Mice, Inbred C57BL; NADPH Oxidase 2; NADPH Oxidases; Pulmonary Artery; Superoxides; Vasoconstriction

Topics: Animals; Blood Gas Analysis; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Male; Oxygen; Oxygen Inhalation Therapy; Swine

Pulmonary intralobar arteries express heme oxygenase (HO)-1 and -2 and release carbon monoxide (CO) during incubation in Krebs buffer. Acute hypoxia elicits isometric tension development (0.77 +/- 0.06 mN/mm) in pulmonary vascular rings treated with 15 micromol/l chromium mesoporphyrin (CrMP), an inhibitor of HO-dependent CO synthesis, but has no effect in untreated vessels. Acute hypoxia also induces contraction of pulmonary vessels taken from rats injected with HO-2 antisense oligodeoxynucleotides (ODN), which decrease pulmonary HO-2 vascular expression and CO release. Hypoxia-induced contraction of vessels treated with CrMP is attenuated (P < 0.05) by endothelium removal, by CO (1-100 micromol/l) in the bathing buffer, and by endothelin-1 (ET-1) receptor blockade with L-754142 (10 micromol/l). CrMP increases ET-1 levels in pulmonary intralobar arteries, particularly during incubation in hypooxygenated media. CrMP also causes a leftward shift in the concentration-response curve to ET-1, which is offset by exogenous CO. In anesthetized rats, pretreatment with CrMP (40 micromol/kg iv) intensifies the elevation of pulmonary artery pressure elicited by breathing a hypoxic gas mixture. However, acute hypoxia does not elicit augmentation of pulmonary arterial pressure in rats pretreated concurrently with CrMP and the ET-1 receptor antagonist L-745142 (15 mg/kg iv). These data suggest that a product of HO activity, most likely CO, inhibits hypoxia-induced pulmonary vasoconstriction by reducing ET-1 vascular levels and sensitivity.

Topics: Acute Disease; Animals; Carbon Monoxide; Endothelin-1; Heme Oxygenase (Decyclizing); Heme Oxygenase-1; Hypoxia; Male; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Receptors, Endothelin; Vasoconstriction

1. The purpose of this study was to investigate whether a membrane-permeable superoxide dismutase mimetic, tempol, added either alone or in combination with the nitric oxide (NO) donor molsidomine, prevents the development of pulmonary hypertension (PH) in chronic hypoxic rats. 2. Chronic hypobaric hypoxia (10% oxygen) for 2 weeks increased the right ventricular systolic pressure (RVSP), right ventricle and lung wet weight. Relaxations evoked by acetylcholine (ACh) and the molsidomine metabolite SIN-1 were impaired in isolated proximal, but not distal pulmonary arteries, from chronic hypoxic rats. 3. Treatment with tempol (86 mg x kg(-1) day(-1) in drinking water) normalized RVSP and reduced right ventricular hypertrophy, while systemic blood pressure, lung and liver weights, and blunted ACh relaxation of pulmonary arteries were unchanged. 4. Treatment with molsidomine (15 mg x kg(-1) day(-1) in drinking water) had the same effects as tempol, except that liver weight was reduced, and potassium and U46619-evoked vasoconstrictions in pulmonary arteries were increased. Combining tempol and molsidomine did not have additional effects compared to tempol alone. ACh relaxation in pulmonary arteries was not normalized by these treatments. 5. The media to lumen diameter ratio of the pulmonary arteries was greater for the hypoxic rats compared to the normoxic rats, and was not reversed by treatment with tempol, molsidomine, or the combination of tempol and molsidomine. 6. We conclude that tempol, like molsidomine, is able to correct RVSP and reduce right ventricular weight in the rat hypoxic model. Functional and structural properties of pulmonary small arteries were little affected. The results support the possibility that superoxide dismutase mimetics may be a useful means for the treatment of PH.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Acetylcholine; Administration, Oral; Animals; Body Weight; Chronic Disease; Cyclic N-Oxides; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Synergism; Drug Therapy, Combination; Endothelin-1; Free Radical Scavengers; Heart Rate; Hypertrophy, Right Ventricular; Hypoxia; Male; Molsidomine; Muscle, Smooth, Vascular; Organ Size; Pulmonary Artery; Rats; Rats, Wistar; Spin Labels; Superoxide Dismutase; Vasoconstriction; Vasodilation; Ventricular Pressure

Cardioprotective strategies are needed to prevent perioperative myocardial dysfunction in high-risk patients undergoing cardiac surgery. Despite accumulating evidence that statins exert lipid-independent cardioprotective effects, these have been ascribed primarily to improvements in endothelial function and neutrophil-endothelial interaction. The direct effects of statins on cardiomyocytes (independent of endothelial cells) remain unknown. Using a well-characterized model of low-volume hypoxia and reoxygenation, we studied the effects of pravastatin on human ventricular cardiomyocytes. Cardiomyocytes were subjected to 90 min of low-volume hypoxia and 30 min of reoxygenation in the presence and absence of pravastatin (1, 10, and 100 microm) (n = 10 per group). In some experiments, the effects of endothelin (ET) receptor blockade (with bosentan) and nitric oxide synthase (NOS) inhibition (with L-NAME) on pravastatin-mediated cardioprotection were evaluated. Cell survival, NO, and ET-1 production and protein kinase Akt activation were determined. Pravastatin treatment prevented cardiomyocyte cell death following simulated hypoxia and reoxygenation (P < 0.01). This effect was mediated via an increase in NO release, decrease in myocyte ET-1 production/action, and an increase in protein kinase Akt activation. We demonstrate, for the first time, novel protective effects of pravastatin in human ventricular cardiomyocytes independent of endothelial cells or other cell types. Statin therapy may restore ischemic hearts to full functional integrity during cardioplegic arrest through a direct effect on cardiomyocyte survival.

Topics: Acyl Coenzyme A; Cardiotonic Agents; Cell Survival; Cells, Cultured; Child; Endothelin-1; Heart Ventricles; Humans; Hypoxia; Myocytes, Cardiac; Nitric Oxide; Oxygen; Pravastatin; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt

Under normoxic conditions in vitro, isolated pulmonary arteries from broilers exhibit reduced endothelium-dependent relaxation responses when compared with Leghorns. In vivo, hypoxia increases the susceptibility of broiler chickens to pulmonary hypertension syndrome (PHS), whereas Leghorns are considered resistant to PHS. Because L-arginine supplementation decreases the incidence of PHS in vivo and improves the relaxation responses of broiler isolated pulmonary arteries in vitro, we hypothesized that in vitro hypoxia would further reduce the relaxation responses of broilers to endothelium-derived nitric oxide (EDNO)-dependent vasodilators and that L-arginine supplementation would alleviate this impairment. As a test of this hypothesis, pulmonary arteries from broiler and Leghorn chickens were isolated and exposed to normoxia or hypoxia in the presence or absence of L-arginine while their constriction and relaxation responses to vasoactive compounds were recorded. In broilers, hypoxia did not affect the constriction responses of isolated pulmonary arteries but decreased EDNO-dependent acetylcholine-induced relaxation responses. In contrast, in Leghorns hypoxia increased endothelin-1-induced vasoconstriction responses and reduced the EDNO-dependent relaxation responses only to the lowest concentration of acetylcholine used. L-Arginine supplementation augmented the relaxation responses to acetylcholine in broilers and Leghorns under normoxia but failed to augment them under hypoxia. Relaxation responses to the NO donor, sodium nitroprusside, were not affected by hypoxia in Leghorns but were increased by hypoxia in broilers. These results suggest that the increased incidence of PHS in broiler chickens reared under hypoxia may be associated with a hypoxia-induced reduction in the synthesis or activity of EDNO in the pulmonary circulation.

Topics: Acetylcholine; Animals; Arginine; Body Weight; Chickens; Endothelin-1; Endothelium, Vascular; Heart Ventricles; Hypertension, Pulmonary; Hypoxia; Muscle Contraction; Muscle Relaxation; Muscle, Smooth, Vascular; Nitric Oxide; Nitric Oxide Donors; Nitroprusside; Organ Size; Oxygen; Potassium Chloride; Poultry Diseases; Pulmonary Artery

Altered Na(+)/Ca(2+) exchanger (NCX) protein expression or activity is thought to contribute to various aspects of cardiac pathology. In guinea pig ventricular myocytes, NCX-mediated Ca(2+) entry is almost entirely responsible for Ca(2+) overload during hypoxia-reoxygenation. Because Ca(2+) overload is a common initiator of apoptosis, the purpose of this study was to test the hypotheses that NCX activity is critically involved in initiating apoptosis after hypoxia-reoxygenation and that hypoxia-reoxygenation-induced apoptosis can be modulated by changes in NCX protein expression or activity. An NCX antisense oligonucleotide was used to reduce NCX protein expression in cultured adult guinea pig ventricular myocytes. Caspase-3 activation and cytochrome c release were used as markers of apoptosis. Hypoxia-reoxygenation-induced apoptosis was significantly decreased in antisense-treated myocytes compared with untreated control or nonsense-treated myocytes. Pretreatment of cultured myocytes for 24 h with either endothelin-1 or phenylephrine was found to increase both NCX protein expression and evoked NCX activity as well as enhance hypoxia-reoxygenation-induced apoptosis. Control experiments demonstrated that endothelin-1 and phenylephrine did not induce apoptosis on their own nor did they enhance the apoptotic response in a model of Ca(2+)-dependent, NCX-independent apoptosis. Additional control experiments demonstrated that the NCX antisense oligonucleotide did not alter the apoptotic response of myocytes to either H(2)O(2) or isoproterenol. Taken together, these data suggest that the NCX has a critical and specific role in the initiation of apoptosis after hypoxia-reoxygenation in guinea pig myocytes and that hypoxia-reoxygenation-induced apoptosis is quite sensitive to changes in NCX activity.

Topics: Adrenergic alpha-Agonists; Adrenergic beta-Agonists; Animals; Apoptosis; Cells, Cultured; Endothelin-1; Female; Guinea Pigs; Heart Ventricles; Hydrogen Peroxide; Hypoxia; Isoproterenol; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocytes, Cardiac; Oligonucleotides, Antisense; Oxidants; Oxygen; Phenylephrine; Sodium-Calcium Exchanger

Vasodilatory responses to exogenous nitric oxide (NO) are diminished following exposure to chronic hypoxia (CH) in isolated, perfused rat lungs. We hypothesized that both endothelium-derived reactive oxygen species (ROS) and endothelin-1 (ET-1) mediate this attenuated NO-dependent pulmonary vasodilation following CH. To test this hypothesis, we examined vasodilatory and vascular smooth muscle (VSM) Ca2+ responses to the NO donor spermine NONOate in UTP-constricted, isolated pressurized small pulmonary arteries from control and CH rats. Consistent with our previous findings in perfused lungs, we observed attenuated NO-dependent vasodilation following CH in endothelium-intact vessels. However, in endothelium-denuded vessels, responses to spermine NONOate were augmented in CH rats compared with controls, thus demonstrating an inhibitory influence of the endothelium on NO-dependent reactivity following CH. Whereas both the ROS scavenger tiron and the ETA receptor antagonist BQ-123 augmented NO-dependent reactivity in endothelium-intact vessels from CH rats, neither fully restored vasodilatory responses to those observed following endothelium denudation in vessels from CH rats. In contrast, the combination of tiron and BQ-123 or the nonselective ET receptor antagonist PD-145065 enhanced NO responsiveness in endothelium-intact vessels from CH rats similar to that observed following endothelium denudation. We conclude that both endothelium-derived ROS and ET-1 attenuate NO-dependent pulmonary vasodilation following CH. Furthermore, CH augments pulmonary VSM reactivity to NO.

Topics: Animals; Diltiazem; Endothelin-1; Hypoxia; Kinetics; Male; Microcirculation; Muscle, Smooth, Vascular; Nitric Oxide; Nitric Oxide Donors; Nitrogen Oxides; Potassium Chloride; Pulmonary Artery; Pulmonary Circulation; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Spermine; Vasodilation

To study the role of calcineurin in the progression of right ventricle myocardial hypertrophy in rats exposed to chronic hypoxia by examining the effect of Ca(2+) channel blockers on the activation of calcineurin and plasma levels of nitric oxide (NO), NO synthase, and endothelin-1 (ET-1).. Rat models of right ventricle myocardial hypertrophy were established by exposing the rats to chronic hypoxia in 10.0%+/-0.5% O(2) for 7 d. The 24 rat models were assigned into normoxic group, hypoxic group and cyclosporin A (CsA)-treated hypoxic group. The rats in normoxic group were kept under normoxic environment, while those in the other 2 groups were subjected to further hypoxic treatment for 14 d, with the rats in CsA group receiving intraperitoneal CsA injection at 20 mg/kg on a daily basis. On day 21 of the experiment, all the rats were killed to collect the hearts for measuring the weight ratio of the right ventricle to the left ventricle and interventricular septum [RV/ LV+S ], as well as the right ventricle to body weight ratio (RV/BW); blood samples were also drawn from the ventricles for measuring plasma NO, iNOS, and ET-1 levels, with the ventricular myocardial [Ca(2+)](i) and the activity of calcineurin also determined.. The RV/(LV+S) and RV/BW were significantly higher in hypoxic group than those of the normoxic and CsA groups (P<0.01); the right ventricular myocardial [Ca(2+)](i) in CsA group was significantly higher than that in the other two groups (P<0.01). In comparison with the normoxic group, the right ventricular myocardial calcineurin activity was significantly increased in the hypoxic group. CsA treatment significantly suppressed calcineurin activity (P<0.01).. Calcineurin possibly plays a role in the progression of right ventricle myocardial hypertrophy in rats with chronic hypoxia. Blocking L-type Ca(2+) channels with CsA effectively prevents the development of myocardial hypertrophy possibly by inhibiting calcium influx and suppressing calcineurin activity.

Topics: Animals; Calcineurin; Chronic Disease; Cyclosporine; Endothelin-1; Female; Hypoxia; Immunosuppressive Agents; Male; Myocardium; Nitric Oxide; Nitric Oxide Synthase; Rats

Acute hypoxia increases pulmonary arterial pressure and vascular resistance. Previous studies in isolated smooth muscle and perfused lungs have shown that carbonic anhydrase (CA) inhibition reduces the speed and magnitude of hypoxic pulmonary vasoconstriction (HPV). We studied whether CA inhibition by acetazolamide (Acz) is able to prevent HPV in the unanesthetized animal. Ten chronically tracheotomized, conscious dogs were investigated in three protocols. In all protocols, the dogs breathed 21% O(2) for the first hour and then 8 or 10% O(2) for the next 4 h spontaneously via a ventilator circuit. The protocols were as follows: protocol 1: controls given no Acz, inspired O(2) fraction (Fi(O(2))) = 0.10; protocol 2: Acz infused intravenously (250-mg bolus, followed by 167 microg.kg(-1).min(-1) continuously), Fi(O(2)) = 0.10; protocol 3: Acz given as above, but with Fi(O(2)) reduced to 0.08 to match the arterial Po(2) (Pa(O(2))) observed during hypoxia in controls. Pa(O(2)) was 37 Torr during hypoxia in controls, mean pulmonary arterial pressure increased from 17 +/- 1 to 23 +/- 1 mmHg, and pulmonary vascular resistance increased from 464 +/- 26 to 679 +/- 40 dyn.s(-1).cm(-5) (P < 0.05). In both Acz groups, mean pulmonary arterial pressure was 15 +/- 1 mmHg, and pulmonary vascular resistance ranged between 420 and 440 dyn.s(-1).cm(-5). These values did not change during hypoxia. In dogs given Acz at 10% O(2), the arterial Pa(O(2)) was 50 Torr owing to hyperventilation, whereas in those breathing 8% O(2) the Pa(O(2)) was 37 Torr, equivalent to controls. In conclusion, Acz prevents HPV in conscious spontaneously breathing dogs. The effect is not due to Acz-induced hyperventilation and higher alveolar Po(2), nor to changes in plasma endothelin-1, angiotensin-II, or potassium, and HPV suppression occurs despite the systemic acidosis with CA inhibition.

Topics: Acetazolamide; Angiotensin II; Animals; Blood Pressure; Carbon Dioxide; Carbonic Anhydrase Inhibitors; Cardiac Output; Consciousness; Dogs; Endothelin-1; Female; Heart Rate; Hydrogen-Ion Concentration; Hypoxia; Oxygen; Potassium; Pulmonary Circulation; Renin; Respiratory Mechanics; Sodium; Vasoconstriction

Living at 2300-m altitude combined with intermittent training at 3500 m leads to cardiovascular alterations in dogs, including increase in systemic and pulmonary artery pressure. Despite moderate to marked hypoxemia at these altitudes, erythrocytosis does not develop. To study humoral mechanisms of acclimatisation to high altitude, erythropoietin (EPO), endothelin-1 (ET-1), big endothelin (Big-ET) and vascular endothelial growth factor (VEGF) were measured in dogs living at 2300 m and intermittently ascending to 3500 m, and compared to the values obtained in control dogs living at 700-900 m. While the median EPO and ET-1 level in dogs at 2300 m did not differ from the one measured at 700-900 m, exposure from 2300 to 3500 m resulted in significantly elevated EPO and ET-1 levels. Big-ET levels were significantly higher at 2300 and 3500 m compared to dogs at low altitude, but did not differ between 2300 and 3500 m. VEGF was significantly elevated in dogs at 2300 m compared to dogs at low altitude. The increases in EPO, VEGF, ET-1 and Big-ET are thought to reflect the effect of hypoxia on a cellular level in these dogs. Obviously, the mild elevation of EPO levels observed at 3500 m was not sufficient to cause erythrocytosis. Elevations of the vasoconstrictors Big-ET and ET-1 may play some, but not a central role in hypoxic vasoconstriction in these dogs. Finally, serum VEGF measurement may be a sensitive and useful test to assess hypoxic stress in dogs.

Topics: Acclimatization; Altitude; Anaerobiosis; Animals; Dogs; Endothelin-1; Erythropoietin; Hypoxia; Physical Conditioning, Animal; Vascular Endothelial Growth Factor A

Sudden reoxygenation of hypoxic neonates undergoing cardiac operation exacerbates the systemic inflammatory response to cardiopulmonary bypass secondary to reoxygenation injury, worsening cardiopulmonary dysfunction. Reports suggest sildenafil decreases pulmonary hypertension and may affect myocardial function. Sildenafil's efficacy for treating postbypass cardiopulmonary dysfunction remains unknown.. Fourteen neonatal piglets (5 to 7 kg) underwent 90 minutes of hypoxia, 60 minutes of reoxygenation with cardiopulmonary bypass, and 120 minutes of recovery. Six animals received 50 mg oral sildenafil and eight received saline at hypoxia. Data are presented as mean +/- SD.. Sildenafil prevented the high pulmonary vascular resistance observed in controls (controls baseline 81 +/- 37 dynes. s/cm(5) versus recovery 230 +/- 93 dynes. s/cm(5), p = 0.004; sildenafil baseline 38 +/- 17 dynes. s/cm(5) versus recovery 101 +/- 60 dynes. s/cm(5), p = 0.003). Despite lower pulmonary vascular resistance after sildenafil, arterial endothelin-1 (ET-1) was increased in both groups (control baseline 1.3 +/- 0.5 pg/mL versus recovery 4.5 +/- 3.7 pg/mL, p = 0.01; sildenafil baseline 1.3 +/- 0.3 pg/mL versus recovery 9.8 +/- 4.9 pg/mL, p = 0.003). Intravenous nitric oxide (NO) levels were preserved after sildenafil treatment (sildenafil baseline 340 +/- 77 nM versus recovery 394 +/- 85 nM). IV NO levels in controls were decreased when compared with baseline (control baseline 364 +/- 83 nM versus recovery 257 +/- 97 nM, p = 0.028). Although levels of exhaled NO decreased in both groups, the sildenafil-treated animals had higher levels of exhaled NO when compared with controls at the end of recovery (0.6 +/- 0.4 parts per billion versus 1.8 +/- 0.9 parts per billion, respectively, p = 0.029).. Sildenafil alleviated pulmonary hypertension after reoxygenation with cardiopulmonary bypass. Despite increased ET-1 levels, pulmonary vascular resistance was lower with sildenafil treatment, suggesting sildenafil's effect on the pulmonary vasculature is capable of countering vasoconstriction by ET-1. Further study into the role of sildenafil in perioperative therapy and its interactions with ET-1 are warranted.

Topics: Animals; Animals, Newborn; Cardiopulmonary Bypass; Endothelin-1; Hemodynamics; Hypertension, Pulmonary; Hypoxia; Myocardial Reperfusion Injury; Piperazines; Purines; Sildenafil Citrate; Sulfones; Swine; Treatment Outcome; Vasodilator Agents

Wistar rats were deeply anesthetized and perfused by Hanks' solution bubbled with either 95% air and 5% CO2 (normoxic group) or 95% N2 and 5% CO2 (hypoxic group) from the thoracic aorta for 30 minutes. The isolated abdominal aortas were used for electron microscopy, immunocytochemistry of endothelin-1 (ET-1) and endothelin-converting enzyme-1 (ECE-1), and in situ hybridization of preproendothelin-1 mRNA. A remarkable increase in the number of Weibel-Palade bodies, storage sites of ET-1 and ECE-1, occurred in the hypoxic group when compared with the normoxic group. Immunoreactivities for ET-1 and ECE-1, and signals for preproendothelin-1 mRNA were seen along the endothelia of both groups, but the intensities were significantly elevated in the hypoxic group. The increase in the number of ECE-1 immunoreactive gold particles was noticed in Weibel-Palade bodies in the hypoxic group. These findings indicate the enhancement of preproendothelin-1 synthesis in the rat aortic endothelial cells and the acceleration of ET-1 processing in Weibel-Palade bodies of such cells in an acute hypoxic condition.

Topics: Acute Disease; Animals; Aorta, Abdominal; Aspartic Acid Endopeptidases; Endothelin-1; Endothelin-Converting Enzymes; Hypoxia; Immunohistochemistry; In Situ Hybridization; Male; Metalloendopeptidases; Microscopy, Immunoelectron; Protein Precursors; Rats; Rats, Wistar; RNA, Messenger; Up-Regulation; Weibel-Palade Bodies

We tested the hypothesis that pulmonary endothelial nitric oxide synthase (eNOS) gene expression is primarily regulated by hemodynamic factors and is thus increased in rats with chronic hypoxic pulmonary hypertension. Furthermore, we examined the role of endothelin (ET)-1 in this regulatory process, since ET-1 is able to induce eNOS via activation of the ET-B receptor. Therefore, chronic hypoxic rats (10% O(2)) were treated with the selective ET-A receptor antagonist LU-135252 (50 mg x kg(-1) x day(-1)). Right ventricular systolic pressure and cross-sectional medial vascular wall area of pulmonary arteries rose significantly, and eNOS mRNA levels increased 1.8- and 2.6-fold after 2 and 4 wk of hypoxia, respectively (each P < 0.05). Pulmonary ET-1 mRNA and ET-1 plasma levels increased significantly after 4 wk of hypoxia (each P < 0.05). LU-135252 reduced right ventricular systolic pressure, vascular remodeling, and eNOS gene expression in chronic hypoxic rats (each P < 0.05), whereas ET-1 production was not altered. We conclude that eNOS expression in chronic hypoxic rat lungs is modified predominantly by hemodynamic factors, whereas the ET-B receptor-mediated pathway and hypoxia seem to be less important.

Topics: Animals; Chronic Disease; Endothelin Receptor Antagonists; Endothelin-1; Gene Expression; Glyceraldehyde-3-Phosphate Dehydrogenases; Hematocrit; Hemodynamics; Hypertension, Pulmonary; Hypoxia; Lung; Male; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Phenylpropionates; Pressure; Pulmonary Artery; Pulmonary Circulation; Pyrimidines; Rats; Rats, Wistar; Receptor, Endothelin A; RNA, Messenger; Systole; Ventricular Function, Right

Chronic hypoxia induces pulmonary vascular remodeling, leading to pulmonary hypertension, right ventricular hypertrophy, and heart failure. Heterozygous deficiency of hypoxia-inducible factor-1alpha (HIF-1alpha), which mediates the cellular response to hypoxia by increasing expression of genes involved in erythropoiesis and angiogenesis, has been previously shown to delay hypoxia-induced pulmonary hypertension. HIF-2alpha is a homologue of HIF-1alpha and is abundantly expressed in the lung, but its role in pulmonary hypertension remains unknown. Therefore, we analyzed the pulmonary response of WT and viable heterozygous HIF-2alpha-deficient (Hif2alpha(+/-)) mice after exposure to 10% O(2) for 4 weeks. In contrast to WT mice, Hif2alpha(+/-) mice were fully protected against pulmonary hypertension and right ventricular hypertrophy, unveiling a critical role of HIF-2alpha in hypoxia-induced pulmonary vascular remodeling. Pulmonary expression levels of endothelin-1 and plasma catecholamine levels were increased threefold and 12-fold respectively in WT but not in Hif2alpha(+/-) mice after hypoxia, suggesting that HIF-2alpha-mediated upregulation of these vasoconstrictors contributes to the development of hypoxic pulmonary vascular remodeling.

Topics: Animals; Atmosphere Exposure Chambers; Basic Helix-Loop-Helix Transcription Factors; Catecholamines; Endothelin-1; Fetal Viability; Hematocrit; Heterozygote; Hypertension, Pulmonary; Hypoxia; Lung; Mice; Mice, Transgenic; Phenotype; Pulmonary Artery; RNA, Messenger; Time; Trans-Activators; Up-Regulation; Ventricular Dysfunction, Right

Both insulin and IGF-1 have been implicated in control of retinal endothelial cell growth, neovascularization, and diabetic retinopathy. To precisely define the role of insulin and IGF-1 signaling in endothelium in these processes, we have used the oxygen-induced retinopathy model to study mice with a vascular endothelial cell-specific knockout of the insulin receptor (VENIRKO) or IGF-1 receptor (VENIFARKO). Following relative hypoxia, VENIRKO mice show a 57% decrease in retinal neovascularization as compared with controls. This is associated with a blunted rise in VEGF, eNOS, and endothelin-1. By contrast, VENIFARKO mice show only a 34% reduction in neovascularization and a very modest reduction in mediator generation. These data indicate that both insulin and IGF-1 signaling in endothelium play a role in retinal neovascularization through the expression of vascular mediators, with the effect of insulin being most important in this process.

Topics: Animals; Diabetic Retinopathy; Disease Models, Animal; Endothelial Growth Factors; Endothelin-1; Endothelium, Vascular; Humans; Hypoxia; Insulin; Intercellular Signaling Peptides and Proteins; Lymphokines; Mice; Mice, Inbred C57BL; Mice, Inbred DBA; Mice, Knockout; Neovascularization, Pathologic; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Receptor, IGF Type 1; Receptor, Insulin; Retinal Vessels; Signal Transduction; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors

We report here, that a vector constructed based on ppET-1 gene promoter and 5' untranslated region induced a high level of gene expression in endothelial cells and the specificity is even further enhanced under hypoxia-mimic conditions due to a natural hypoxia responsive element within the promoter region. A naked DNA vector that confers endothelial cell specific gene expression as well as efficient levels of gene expression was constructed with an endothelial cell specific naked DNA vector, pETlong, by using the full length promoter of the preproendothelin-1 gene and the entire 5' untranslated region upstream from the start codon. Inclusion of the entire 5' untranslated region in pETlong increased gene expression 2.96 fold as compared with that from pETshort, which contains only the promoter sequences. Reporter gene expression from pETlong was 7.9 fold higher as compared with that from CMV-driven promoter based vector in calf pulmonary endothelial cells. However, in nonendothelial COS cells, luciferase activity from pETlong was only 0.3 fold as compared with that of CMV-based vector. Similar results were observed in other nonendothelial cells. These results demonstrate that the pETlong drives gene expression in endothelial cells with high efficacy and specificity. We have examined hypoxia responsiveness of pETlong as the promoter region of the preproendothelin-1 gene contains hypoxia responsive elements. The activity of the pETlong vector was increased 1.6 fold under hypoxia-mimic conditions using cobalt chloride. The high levels of hypoxia-inducible expression in endothelial cells relative to the low levels of background expression in other cells shows that pETlong could be a useful tool for vascular targeting of vascular disease and cancer gene therapy.

Topics: 5' Untranslated Regions; Animals; Cattle; Endothelial Cells; Endothelin-1; Endothelium, Vascular; Gene Transfer Techniques; Genetic Vectors; Humans; Hypoxia; Promoter Regions, Genetic

Vasoactive agents were examined in arteries from control rats and rats exposed to intermittent hypoxia (10% oxygen; 8 h/day) for 3, 5 or 20 days. Hypoxic rats developed right ventricular hypertrophy after 5 days, but became pulmonary hypertensive (elevated right ventricular systolic pressure; RVSP) only after 20 days. In pulmonary arteries (main and intralobar), responses to acetylcholine and ionomycin (endothelium-dependent vasodilators) were reduced after 20 and 5 days of intermittent hypoxia, whereas contractions to 5-hydroxytryptamine (5-HT) were enhanced (potency increase >10-fold) after 20, 5 and 3 days. Contractions to endothelin-1 and a thromboxane-mimetic, but not Ca(2+), were also increased. No changes in vascular function occurred in aorta. Since changes in pulmonary vascular function preceded the increase in RVSP they do not result from, but may contribute to, the development of hypoxia-induced pulmonary hypertension. If similar changes occur in humans, they may be important in conditions characterised by intermittent, as opposed to continuous, hypoxia.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Acetylcholine; Animals; Endothelin-1; Endothelium, Vascular; Hypoxia; In Vitro Techniques; Ionomycin; Male; Muscle, Smooth, Vascular; Potassium Chloride; Pulmonary Artery; Rats; Rats, Wistar; Serotonin; Vasoconstrictor Agents; Vasodilator Agents

Hypoxemia stimulates endothelin-1 (ET-1) secretion. The reduction in alveolar ventilation during sleep is considered sufficient to account for the hypoxemia observed in patients with respiratory diseases.. The aim of this study was to evaluate the arterial ET-1 levels and their relationship with pulmonary hypertension in patients with interstitial lung disease (ILD) during sleep.. We examined 38 patients with ILD using formal polysomnography (electroencephalogram, electrocardiogram, airflow, respiratory muscle movement, oximeter) to detect the presence of nocturnal, nonapneic, oxyhemoglobin desaturation. All patients desaturated below a baseline sleep saturation of 90% for 5 minutes or more, reaching a nadir saturation of at least 85%. Each patient had already undergone right heart catheterization with a Swan-Ganz catheter for measuring hemodynamic parameters. Sampling of arterial blood from a radial artery line for determination of blood gases and ET-1 values was performed simultaneously, after 5 minutes of the first desaturation.. At rest, arterial ET-1 levels were higher in ILD patients (1.73 +/- 0.37 mgr/mL) than in controls (1.22 +/- 0.15 mgr/mL) ( p < 0.001). Also, the patients with pulmonary hypertension (Pa > 20 mm Hg) presented significantly higher arterial ET-1 levels (1.86 +/- 0.32 mgr/mL) than those without pulmonary hypertension (1.31 +/- 0.13 mgr/mL) ( p < 0.001). Arterial ET-1 levels were significantly correlated with mean pulmonary arterial pressure (PAP) (r = 0.749, p < 0.001), and arterial oxygen partial pressure (PaO2) (r = 0.79, p < 0.001). At sleep, during desaturation, arterial ET-1 levels significantly increased in all patients (2.46 +/- 0.13 mgr/mL) as compared with resting values ( p < 0.001). Arterial ET-1 levels were significantly correlated with PAP (r = 0.657, p < 0.001) and PaO2 (r = 0.93, p < 0.001).. According to our study, arterial ET-1 is markedly increased in ILD patients, especially in those with pulmonary hypertension.

Topics: Electrocardiography; Electroencephalography; Endothelin-1; Female; Hemodynamics; Humans; Hypertension, Pulmonary; Hypoxia; Lung Diseases, Interstitial; Male; Middle Aged; Oximetry; Polysomnography; Sleep

Topics: Adaptation, Physiological; Animals; Carotid Body; Chronic Disease; Endothelin-1; Gene Expression Regulation; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Immunohistochemistry; Models, Neurological; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Rats; Rats, Sprague-Dawley; Transcription Factors; Vascular Endothelial Growth Factor A

In this study, we investigated the production of endothelin 1 (ET-1) by a human microvascular endothelial cell line, HMEC-1, co-cultured with Plasmodium falciparum-parasitized red blood cells (pRBCs). The results indicate that hypoxia increased the basal level of ET-1 production by HMEC-1 cells after 24 or 48 h of treatment. However, the co-incubation of HMEC-1 cells with pRBCs, but not with uninfected RBCs, induced a dose-dependent decrease of both constitutive and hypoxia-induced ET-1 production. The inhibition was not due to a decrease in cell viability, as lactate dehydrogenase release remained constant. These results indicate that pRBCs are able to interfere with both the constitutive and stimulated ET-1 release from the microvascular endothelium, thus inducing local modifications of the vascular tone and of the inflammatory response. This could be of relevance in the pathogenesis of the most severe forms of P. falciparum infections, such as cerebral malaria or malaria during pregnancy.

Topics: Animals; Cell Line; Coculture Techniques; Endothelin-1; Endothelium, Vascular; Erythrocytes; Humans; Hypoxia; L-Lactate Dehydrogenase; Microcirculation; Plasmodium falciparum

To investigate the expression of hypoxia-inducible factor-1 alpha (HIF-1alpha) and endothelin-1 (ET-1) gene in hypoxic pulmonary hypertension (HPH).. The animal model of HPH was replicated. The elastic fiber staining was applied to show the intraacinar pulmonary artery (IAPA). Radioimmunoassay (RIA) and in situ hybridization (ISH) were used for detection of HIF-1a and. ET-1.. ISH showed that HIF-1alpha mRNA was expressed in the IAPA of all hypoxic rat. The expression was stronger in the H14 d (0.256 9 +/- 0.046 8) and H28 d (0.225 8 +/- 0.045 3) groups than in the H5 d (0.1455 +/- 0.072 2) and control (0.110 9 +/- 0.022 4) groups (P < 0.05), the expression of ET-1 mRNA in the H14 d (0.412 2 +/- 0.078 3) and H28 d (0.368 4 +/- 0.072 9) groups was also stronger than that in the H5 d (0.201 7 +/- 0.034 9) and control (0.185 5 +/- 0.036 1) groups (P < 0.05). The amount of ET-1 in pulmonary arteial blood in the H14 d [(158.78 +/- 25.14) pg/ml] and H28 d [(142.93 +/- 23.38) pg/ml] groups was significantly higher than that in the H5 d [(79.68 +/- 12.54) pg/ml] and control [(65.37 +/- 10.82) pg/ml] groups (P < 0.05). The mean pulmonary arterial pressure (mPAP) in the H14 d [(34.0 +/- 5.8) mm Hg] and H 28 d [(29.0 +/- 4.7) mm Hg] groups was markedly higher than that in the H5 d [(19.0 +/- 3.5) mm Hg] and control [(17.0 +/- 2.8) mm Hg] groups (P < 0.05). A positive rank correlation existed between the mPAP and the amount of ET-1 (rs = 0.747, P < 0.05).. Expression of HIF-1alpha and ET-1 mRNA in IAPA increase under long-term hypoxic condition and both show consistent expression, indicating that the expression of HIF-1a and ET-1 gene contribute to pathogenesis of HPH.

Topics: Animals; Endothelin-1; Gene Expression; Hypertension, Pulmonary; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Male; Rats; Rats, Wistar; RNA, Messenger; Transcription Factors

To study the plasma level of endogenous carbon monoxide (CO) in patients with chronic cor pulmonale (CCP) and its relationship with endothelin-1 (ET-1) and hypoxic pulmonary hypertension (HPH).. There were examinations on the plasma levels of endogenous CO and ET-1 in 33 patients with CCP, and their correlation with PaO(2) and the ratio of right ventricular pre-ejection period to the pulmonary flow acceleration time (RVPEP/AT), an indicator of pulmonary hypertension. Thirty healthy subjects served as normal controls.. The levels of endogenous CO, ET-1 and the ET-1/CO ratio in acute exacerbation and remission in the CCP group [CO: (1.34 +/- 0.18) mg/L, (1.07 +/- 0.14) mg/L; ET-1: (82 +/- 15) ng/L, (57 +/- 10) ng/L; ET-1/CO: 61 +/- 6, 53 +/- 5] were higher than those in the normal control group [CO: (0.55 +/- 0.12) mg/L, P < 0.001; ET-1: (27 +/- 9) ng/L, P < 0.001; ET-1/CO: 48 +/- 7, P < 0.05]. The levels of plasma endogenous CO, ET-1, and the ET-1/CO ratio in acute exacerbation were higher than those in the remission stage (P < 0.001, P < 0.001, P < 0.05). The level of endogenous CO was negatively correlated with PaO(2) (r = -0.733, P < 0.01; r = -0.672, P < 0.01) and positively correlated with RVPEP/AT (r = 0.620, P < 0.01; r = 0.557, P < 0.01). The ET-1/CO ratio was positively correlated with RVPEP/AT (r = 0.501, P < 0.01; r = 0.485, P < 0.05) in patients with acute exacerbation or in remission.. The increased level of plasma endogenous CO in patients with CCP suggests the involvement of CO in the pathophysiologic process of HPH. An imbalance between ET-1 and CO may be involved in the development of HPH.

Topics: Adult; Aged; Aged, 80 and over; Carbon Monoxide; Endothelin-1; Female; Humans; Hypertension, Pulmonary; Hypoxia; Male; Middle Aged; Oxygen

Endothelin-1 can cause pulmonary vasoconstriction via endothelin-A (ET(A)) receptor activation. We hypothesized that ET(A) blockers (EMD 122946 and BQ 610) would reduce hypoxia-induced (HYP) but not group B streptococcal infusion (GBS)-induced pulmonary hypertension in a juvenile whole animal model. Pulmonary hypertension was created by exposing chronically instrumented piglets to HYP (n = 12) or heat-killed GBS (n = 11). ET(A) blockade was produced by increasing bolus doses of EMD122946 or BQ 610. Pulmonary arterial pressure (PAP), systemic arterial pressure (SAP), left atrial pressure, central venous pressure, and cardiac output were continuously measured. Pulmonary and systemic vascular resistance indices (PVRI and SVRI) were calculated. HYP doubled PAP and PVRI. Both ET(A) blockers decreased PAP and PVRI in a dose-dependent manner in HYP, with high doses decreasing PVRI to baseline and reducing PAP by 50%. GBS also doubled both PAP and PVRI. EMD 122946 did not change PAP or PVRI in GBS, although BQ 610 markedly increased PVRI (>100% increase with 0.15 mg/kg) and showed a trend toward increasing PAP. Both models showed minimal (<25%) changes in SAP or SVRI. Neither ETA blocker changed baseline hemodynamics in the absence of HYP or GBS. PaO(2) did not change with GBS but decreased with BQ 610. ET(A) receptor blockade attenuated hypoxic, but not GBS induced pulmonary hypertension. BQ 610 worsened PVRI and oxygenation in the GBS model. Differences in response to ET(A) blockade in pulmonary hypertension may be seen depending on the etiology (hypoxia versus infection-associated), and the specific ET(A) antagonist used.

Topics: Animals; Blood Pressure; Carbon Dioxide; Disease Models, Animal; Endothelin Receptor Antagonists; Endothelin-1; Humans; Hypertension, Pulmonary; Hypoxia; Infant, Newborn; NG-Nitroarginine Methyl Ester; Oligopeptides; Oxygen; Pulmonary Circulation; Receptor, Endothelin A; Streptococcal Infections; Streptococcus agalactiae; Sus scrofa; Thiazoles

We report for the first time that penile smooth muscle cells (SMC) not only respond to, but also synthesize, endothelin-1 (ET-1), one of the main regulators of SMC activity. Immunohistochemical studies indicated that, beside endothelial cells (EC), SMC of the human adult and fetal penis also express ET-1 and its converting enzyme, ECE-1. Accordingly, cultures of adult penile stromal cells express these genes. We also prepared and characterized penile SMC from human fetuses. These cells express SMC specific markers such as alpha smooth muscle actin and phosphodiesterase type 5A3 along with hallmarks of androgen-dependent cells (androgen receptor and 5alpha reductase type 2). Human fetal penile SMC (hfPSMC) are immunopositive for ET-1 and release ET-1. ET-1 expression in hfPSMC was strongly increased by several factors such as transforming growth factor-beta1 (TGF-beta1), interleukin-1alpha (IL-1alpha), ET-1 itself and prolonged (24 h) hypoxia. This latter condition not only affected ET-1 expression but also responsiveness. While at normal oxygen tension, hfPSMC responded to ET-1 with a decreased proliferation mediated by the endothelin-A receptors and TGF-beta1; however, during hypoxia, ET-1 stimulated cell growth. Accordingly, prolonged hypoxia up-regulated endothelin-B receptor mRNA expression. In conclusion, our results indicate that in penile tissues SMC produce ET-1 and that such production is modulated by factors involved in penile physiology and tissue remodelling. In addition, the hfPSMC we have characterized might be a useful model for studying biochemical aspects of the human erectile process in vitro.

Topics: Aspartic Acid Endopeptidases; Endothelin-1; Endothelin-Converting Enzymes; Fetus; Gene Expression Regulation; Humans; Hypoxia; Immunohistochemistry; Male; Metalloendopeptidases; Muscle, Smooth; Penis; Receptors, Endothelin

The aryl hydrocarbon receptor (AhR) is a member of the basic helix loop helix PAS (Per-ARNT-SIM) transcription family, which also includes hypoxiainducible factor-1alpha (HIF-1alpha) and its common dimerization partner AhR nuclear translocator (ARNT). Following ligand activation or hypoxia, AhR or HIF-1alpha, respectively, translocate into the nucleus, dimerize with ARNT, and regulate gene expression. Mice lacking the AhR have been shown previously to develop cardiac enlargement. In cardiac hypertrophy, it has been suggested that the myocardium becomes hypoxic, increasing HIF-1alpha stabilization and inducing coronary neovascularization, however, this mechanism has not been demonstrated in vivo. The purpose of this study was to investigate the cardiac enlargement reported in AhR(-/-) mice and to determine if it was associated with myocardial hypoxia and subsequent activation of the HIF-1alpha pathway. We found that AhR(-/-) mice develop significant cardiac hypertrophy at 5 mo. However, this cardiac hypertrophy was not associated with myocardial hypoxia. Despite this finding, cardiac hypertrophy in AhR(-/-) mice was associated with increased cardiac HIF-1alpha protein expression and increased mRNA expression of the neovascularization factor vascular endothelial growth factor (VEGF). These data demonstrate that the development of cardiac hypertrophy in AhR(-/-) mice not associated with myocardial hypoxia, but is correlated with increased cardiac HIF-1alpha protein and VEGF mRNA expression.

Topics: Age Factors; Animals; Atrial Natriuretic Factor; Biomarkers; Body Weight; Cardiac Myosins; Cardiomegaly; Disease Models, Animal; Endothelin-1; Gene Expression Regulation; Heart Ventricles; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Male; Mice; Mice, Mutant Strains; Models, Cardiovascular; Myocardium; Myosin Heavy Chains; Myosin Light Chains; Nonmuscle Myosin Type IIB; Organ Size; Phenotype; Rats; Receptors, Aryl Hydrocarbon; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Statistics as Topic; Time Factors; Transcription Factors; Vascular Endothelial Growth Factor A

To investigate the effects of advanced glycation end products(AGE) and hypoxia on endothelin-1 (ET-1) secretion by cultured bovine retinal microvascular pericytes (BRPs).. BRPs were incubated with different concentrations of AGE (8, 32, 125 microg/ ml) for four days, hypoxia (10% O2, 5% CO2, 85% N2) for 12, 24, 48 hours, respectively and AGE for 2 days firstly and then hypoxia for 48 hours. Finally, ET-1 production was assessed in culture supernatants of BRPs under basal and stimulated conditions by radioimmunoassay.. Hypoxia stimulated ET-1 production in a time-dependent manner in cultured BRPs. AGE could not induce the production significantly, but it could upregulate the effect of hypoxia on ET-1.. These results suggested that AGE and hypoxia could regulate the ET-1 production in BRPs. ET-1 might be related to microvascular dysfunction in diabetes.

Topics: Animals; Cattle; Cells, Cultured; Endothelin-1; Glycation End Products, Advanced; Hypoxia; Microcirculation; Pericytes; Retinal Vessels

Deeply anesthetized male Wistar rats were perfused by Hanks' balanced salt solution bubbled with either 95%air and 5%CO2 (normoxic group) or 95%N2 and 5%CO2 (hypoxic group) from the thoracic aorta for 30 min, and the isolated abdominal aortae from both groups were used for electron microscopy, immunocytochemistry of endothelin (ET)-1 and ET-converting enzyme (ECE)-1, and in situ hybridization of preproET-1 mRNA. A remarkable increase in the number of Weibel-Palade (WP) bodies, storage sites of ET-1 and ECE-1, occurred in the hypoxic group when compared to the normoxic group. Immunoreactivities for ET-1 and ECE-1, and signals for preproET-1 mRNA were seen along the endothelia of both groups, but the intensities were significantly elevated in the hypoxic group. The increase in the number of ECE-1 immunoreactive gold particles was noticed especially in WP bodies in the hypoxic group. These findings indicate the enhancement of preproET-1 synthesis in the aortic endothelial cells as well as the acceleration of ET-1 processing in increased WP bodies in such cells in an experimentally hypoxic condition of the rat aortae.

Topics: Acute Disease; Animals; Aorta, Thoracic; Aspartic Acid Endopeptidases; Endothelin-1; Endothelin-Converting Enzymes; Endothelins; Hypoxia; Immunohistochemistry; In Situ Hybridization; Male; Metalloendopeptidases; Microscopy, Electron; Microscopy, Immunoelectron; Protein Precursors; Rats; Rats, Wistar; RNA, Messenger; Signal Transduction; Vasoconstriction; Weibel-Palade Bodies

Increased serine elastase activity has been implicated in the vascular remodeling associated with chronic hypoxia-related pulmonary hypertension in rats.. In this study we determined the time course of hypoxia-induced serine elastase activity in the murine lung and related this to initiation of a proteolytic cascade characterized by an increase in matrix metalloproteinases (MMPs). We then used transgenic mice in which overexpression of the selective serine elastase inhibitor elafin was targeted to the cardiovascular system to determine whether upregulation of a naturally occurring serine elastase inhibitor suppresses MMPs and the hemodynamic and structural response to chronic hypoxia (air at 380 mm Hg). In nontransgenic but not in elafin-transgenic mice, we documented a transient increase in serine elastase activity after 12 hours of hypoxic exposure attributed to a 30-kDa protein as determined by elastin zymography and fluorophosphonate/fluorophosphate-biotin labeling. Two days after hypoxia, the pro-forms of MMP-2 and MMP-9 were induced in the nontransgenic mice, but MMP-9 was suppressed in elafin-transgenic mice. Acute hypoxic vasoconstriction was similar in nontransgenic and elafin-transgenic littermates. Chronic hypoxia for 26 days resulted in >1-fold increase in right ventricular pressure (P<0.004) in nontransgenic compared with control or elafin-transgenic littermates. In the latter mice, normalization of the right ventricular pressure was associated with reduced muscularization and preservation of the number of distal vessels (P<0.04 for both comparisons).. Modulation of the severity of chronic hypoxia-induced pulmonary vascular disease could be a function of endogenously expressed serine elastase inhibitors.

Topics: Actins; Animals; Elastin; Endothelin-1; Hematocrit; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Kinetics; Matrix Metalloproteinases; Mice; Mice, Transgenic; Pressure; Proteinase Inhibitory Proteins, Secretory; Proteins; Pulmonary Artery; RNA, Messenger; Serine Proteinase Inhibitors; Up-Regulation; Ventricular Pressure

Nitric oxide (NO) attenuates hypoxia-induced endothelin (ET)-1 expression in cultured umbilical vein endothelial cells. We hypothesized that NO similarly attenuates hypoxia-induced increases in ET-1 expression in the lungs of intact animals and reasoned that potentially reduced ET-1 levels may contribute to the protective effects of NO against the development of pulmonary hypertension during chronic hypoxia. As expected, hypoxic exposure (24 h, 10% O(2)) increased rat lung ET-1 peptide and prepro-ET-1 mRNA levels. Contrary to our hypothesis, inhaled NO (iNO) did not attenuate hypoxia-induced increases in pulmonary ET-1 peptide or prepro-ET-1 mRNA levels. Because of this surprising finding, we also examined the effects of NO on hypoxia-induced increases in ET peptide levels in cultured cell experiments. Consistent with the results of iNO experiments, administration of the NO donor S-nitroso-N-acetyl-penicillamine to cultured bovine pulmonary endothelial cells did not attenuate increases in ET peptide levels resulting from hypoxic (24 h, 3% O(2)) exposure. In additional experiments, we examined the effects of NO on the activity of a cloned ET-1 promoter fragment containing a functional hypoxia inducible factor-1 binding site in reporter gene experiments. Whereas moderate hypoxia (24 h, 3% O(2)) had no effect on ET-1 promoter activity, activity was increased by severe hypoxic (24 h, 0.5% O(2)) exposure. ET-1 promoter activity after S-nitroso-N-acetyl-penicillamine administration during severe hypoxia was greater than that in normoxic controls, although activity was reduced compared with that in hypoxic controls. These findings suggest that hypoxia-induced pulmonary ET-1 expression is unaffected by NO.

Topics: Administration, Inhalation; Animals; Blood; Cattle; Cells, Cultured; Endothelin-1; Endothelins; Endothelium, Vascular; Hypoxia; Lung; Male; Nitric Oxide; Nitric Oxide Donors; Promoter Regions, Genetic; Protein Precursors; Pulmonary Artery; Rats; Rats, Sprague-Dawley; RNA, Messenger; S-Nitroso-N-Acetylpenicillamine

Mechanisms by which endothelin (ET)-1 mediates chronic pulmonary hypertension remain incompletely understood. Although activation of the ET type A (ET(A)) receptor causes vasoconstriction, stimulation of ET type B (ET(B)) receptors can elicit vasodilation or vasoconstriction. We hypothesized that the ET(B) receptor attenuates the development of hypoxic pulmonary hypertension and studied a genetic rat model of ET(B) receptor deficiency (transgenic sl/sl). After 3 wk of severe hypoxia, the transgenic sl/sl pulmonary vasculature lacked expression of mRNA for the ET(B) receptor and developed exaggerated pulmonary hypertension that was characterized by elevated pulmonary arterial pressure, diminished cardiac output, and increased total pulmonary resistance. Plasma ET-1 was fivefold higher in transgenic sl/sl rats than in transgenic controls. Although mRNA for prepro-ET-1 was not different, mRNA for ET-converting enzyme-1 was higher in transgenic sl/sl than in transgenic control lungs. Hypertensive lungs of sl/sl rats also produced less nitric oxide metabolites and 6-ketoprostaglandin F(1alpha), a metabolite of prostacyclin, than transgenic controls. These findings suggest that the ET(B) receptor plays a protective role in the pulmonary hypertensive response to chronic hypoxia.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Animals, Genetically Modified; Blotting, Northern; Cytochrome P-450 Enzyme System; Endothelin-1; Endothelins; Epoprostenol; Female; Gene Expression; Hypertension, Pulmonary; Hypoxia; In Situ Hybridization; Intramolecular Oxidoreductases; Lung; Male; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Protein Precursors; Pulmonary Circulation; Rats; Receptor, Endothelin B; Receptors, Endothelin; RNA, Messenger

Endothelin-1 (ET-1) excites carotid body (CB) chemoreceptors and induces mitosis of the chemoreceptors in chronic hypoxia. The aim of the present study was to examine the hypothesis that up-regulation of both ETA receptor and endogenous ET-1 expression in CB chemoreceptors enhances the response of intracellular Ca2+ to ET-1 following adaptation to chronic hypoxia (10% inspired O2 for 3-4 weeks). Cytosolic free [Ca2+] ([Ca2+]i) in type-I (glomus) cells freshly dissociated from rat CBs was measured by spectrofluorometry. Application of exogenous ET-1 (1-100 nM) concentration-dependently elevated [Ca2+]i in the glomus cells. This response to ET-1 (100 nM) was 49% greater in the chronically hypoxic (CH) group. The ET-1 response was abolished completely by the ETA receptor antagonist BQ610 (1 microM), but not by the ETB antagonist BQ788 (1 microM). The transient [Ca2+]i elevation induced by caffeine (30 mM) in the normoxic group was similar to that in the CH group, suggesting no differences in the intracellular Ca2+ stores. In situ hybridization with a digoxigenin-labelled antisense ETA receptor mRNA oligonucleotide probe revealed very intense and ubiquitous specific expression of ETA receptors in the lobules of glomus cells in the CH group, whereas staining in normoxic controls was light. Immunohistochemical studies revealed intense cytoplasmic staining for ET-1-immunoreactivity in most of the cell clusters in glomera in the CBs of CH rats but was faint in normoxic CBs. These findings indicate increased expression of both the ETA receptor and ET-1 in CB chemoreceptors during chronic hypoxia. Taken together, our results suggest that the [Ca2+]i response to ET-1 in rat CB chemoreceptors is augmented by up-regulation of ETA receptors and ET-1 expression. The enhancement of the paracrine/autocrine effect of ET-1 on the chemoreceptors is consistent with an excitatory and mitogenic role of the ET-1 and ETA receptor in the CB during chronic hypoxia.

Topics: Adaptation, Physiological; Animals; Calcium; Carotid Body; Chemoreceptor Cells; Chronic Disease; Endothelin-1; Female; Hypoxia; In Situ Hybridization; Male; Mitosis; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptors, Endothelin; RNA, Messenger; Up-Regulation

Chronic exposure in a low-PO(2) environment (i.e., chronic hypoxia, CH) elicits an elevated hypoxic ventilatory response and increased hypoxic chemosensitivity in arterial chemoreceptors in the carotid body. In the present study, we examine the hypothesis that changes in chemosensitivity are mediated by endothelin (ET), a 21-amino-acid peptide, and ET(A) receptors, both of which are normally expressed by O(2)-sensitive type I cells. Immunocytochemical staining showed incremental increases in ET and ET(A) expression in type I cells after 3, 7, and 14 days of CH (380 Torr). Peptide and receptor upregulation was confirmed in quantitative RT-PCR assays conducted after 14 days of CH. In vitro recordings of carotid sinus nerve activity after in vivo exposure to CH for 1-16 days demonstrated a time-dependent increase in chemoreceptor activity evoked by acute hypoxia. In normal carotid body, the specific ET(A) antagonist BQ-123 (5 microM) inhibited 11% of the nerve discharge elicited by hypoxia, and after 3 days of CH the drug diminished the hypoxia-evoked discharge by 20% (P < 0.01). This inhibitory effect progressed to 45% at day 9 of CH and to nearly 50% after 12, 14, and 16 days of CH. Furthermore, in the presence of BQ-123, the magnitude of the activity evoked by hypoxia did not differ in normal vs. CH preparations, indicating that the increased activity was the result of endogenous ET acting on an increasing number of ET(A). Collectively, our data suggest that ET and ET(A) autoreceptors on O(2)-sensitive type I cells play a critical role in CH-induced increased chemosensitivity in the rat carotid body.

Topics: Adaptation, Physiological; Animals; Antihypertensive Agents; Carotid Body; Chemoreceptor Cells; Chronic Disease; Electrophysiology; Endothelin Receptor Antagonists; Endothelin-1; Hypoxia; In Vitro Techniques; Male; Peptides, Cyclic; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptors, Endothelin; RNA, Messenger; Time Factors

Endothelin 1 (ET-1) is a potent vasoactive peptide that acts at sinusoidal and extrasinusoidal sites in the liver. Sensitivity to ET-1 increases in LPS-primed animals and is associated with impaired liver microcirculation in these animals. We hypothesized that LPS priming leads to an exacerbation in the impaired oxygen delivery in response to intraportal infusion of ET-1. Rats were studied 24 h after LPS injection (1 mg/kg, i.p.). Surface PO2 was determined using a recently developed technology of O2 mapping. The baseline portal pressure was higher in LPS-primed animals (P < 0.05), and increased to'similar magnitude as sham animals after a 10-min infusion of ET-1. The resultant portal pressure remained elevated in LPS compared to sham animals. There was no significant difference in baseline mean arterial pressure, and no significant systemic response to ET-1 in either group. In contrast to the macrohemodynamic, the decrease in tissue surface PO2 in response to ET-1 infusion was potentiated by LPS treatment (increased from baseline levels 33.8+/-9 to 46.8+/-8.3 in sham; 42.3+/-9.1 to 69+/-6.5 gray scale units in LPS; P < 0.01, sham vs. LPS) at end of infusion of ET-1 for 10 min. This indicates tissue hypoxia in response to ET-1, which is exacerbated in livers from LPS-primed animals compared to sham. Frequency distribution analysis showed a shift in mode from lower intensity (higher PO2) to areas with higher fluorescent intensity ranges (lower PO2), indicating areas with shut down in perfusion in LPS-treated animals. In the whole liver, ET-1 suppressed oxygen consumption, and this response was potentiated by LPS pretreatment. We propose that ET-1 impairs oxygen delivery in the liver during endotoxemia, resulting in areas of focal hypoxia. This response is possibly due to potentiated action of ET-1 at both sinusoidal and extrasinusoidal sites in the liver during endotoxemia.

Topics: Animals; Endothelin-1; Endotoxemia; Hemodynamics; Hypoxia; In Vitro Techniques; Lipopolysaccharides; Liver; Male; Oxygen; Oxygen Consumption; Perfusion; Rats; Rats, Sprague-Dawley

The ovarian hormone 17beta-estradiol (E2beta) attenuates chronic hypoxia-induced pulmonary hypertension. We hypothesized that E2beta attenuates this response to hypoxia by decreasing pulmonary expression of the vasoactive and mitogenic peptide endothelin-1 (ET-1). To test this hypothesis, we measured preproET-1 mRNA and ET-1 peptide levels in the lungs of adult female normoxic and hypoxic (24 h or 4 wk at barometric pressure = 380 mmHg) rats with intact ovaries and in hypoxic ovariectomized (OVX) rats administered E2beta or vehicle via subcutaneous osmotic pumps. Hypoxic exposure increased lung preproET-1 mRNA levels in OVX vehicle-treated rats, but not in rats with intact ovaries. In addition, E2beta replacement prevented hypoxia-mediated increases in preproET-1 mRNA and ET-1 peptide expression. Considering that hypoxic induction of ET-1 gene expression is mediated by a hypoxia-inducible transcription factor(s) (HIF), we further hypothesized that E2beta-induced attenuation of pulmonary ET-1 expression during hypoxia results from decreased HIF activity. We found that E2beta abolished HIF-dependent increases in reporter gene activity. Further experiments demonstrated that overexpression of the transcriptional coactivator cAMP response element binding protein (CREB) binding protein (CBP)/p300, a factor common to both the estrogen receptor and HIF pathways, eliminated E2beta-mediated attenuation of hypoxia-induced ET-1 promoter activity. We conclude that E2beta inhibits hypoxic induction of ET-1 gene expression by interfering with HIF activity, possibly through competition for limiting quantities of CBP/p300.

Topics: Animals; Binding, Competitive; CREB-Binding Protein; DNA-Binding Proteins; Endothelin-1; Endothelins; Estradiol; Female; Gene Expression; Genes, Reporter; Hematocrit; Hypertension, Pulmonary; Hypoxia; Hypoxia-Inducible Factor 1; Hypoxia-Inducible Factor 1, alpha Subunit; Lung; Nuclear Proteins; Organ Size; Protein Precursors; Rats; Rats, Sprague-Dawley; Response Elements; RNA, Messenger; Trans-Activators; Transcription Factors; Transcription, Genetic; Uterus

The regulation of pulmonary prostacyclin synthesis is not completely understood. We tested the hypothesis that prostacyclin production is predominantly stimulated by hemodynamic factors, such as increased shear-stress, and is thus increased in rats with chronic hypoxic pulmonary hypertension.. To this end, we determined pulmonary prostacyclin synthase (PGIS) gene expression, circulating levels of the stable prostacyclin metabolite 6-keto prostaglandin F(1alpha) (6-keto-PGF(1alpha)), pulmonary endothelin (ET)-1 gene expression, and ET-1 plasma levels in rats exposed to 4 weeks of hypoxia (10% O(2)) in the presence or absence of either the nitric oxide (NO) donor molsidomine (MD, 15 mg/kg/day) or the ET-A receptor antagonist LU135252 (LU, 50 mg/kg/day).. Right ventricular systolic pressure (RVSP), the cross-sectional medial vascular wall area of pulmonary arteries, and ET-1 production increased significantly during hypoxia. PGIS mRNA levels increased 1.7-fold, and 6-keto-PGF(1alpha) plasma levels rose from 8.2+/-0.8 to 12.2+/-2.2 ng/ml during hypoxia (each P<0.05 vs. normoxic controls). MD and LU reduced RVSP and pulmonary vascular remodeling similarly (each P<0.05 vs. hypoxia), but only MD inhibited pulmonary ET-1 formation (P<0.05 vs. hypoxia). Nevertheless, both drugs attenuated the increase in PGIS gene expression and plasma 6-keto-PGF(1alpha) levels (each P<0.05 vs. hypoxia).. Our data suggest that prostacyclin production in hypertensive rat lungs is predominantly increased by hemodynamic factors while hypoxia, NO and ET-1 per are less important stimuli, and that this increase may serve as a compensatory mechanism to partially negate the hypoxia-induced elevation in pulmonary vascular tone.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Chronic Disease; Cytochrome P-450 Enzyme System; Endothelin Receptor Antagonists; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Intramolecular Oxidoreductases; Male; Models, Animal; Molsidomine; Nitric Oxide Donors; Phenylpropionates; Pulmonary Artery; Pyrimidines; Random Allocation; Rats; Rats, Wistar; Receptor, Endothelin A; RNA, Messenger; Systole; Ventricular Pressure

In this study we examined the effect of polyunsaturated fatty acids (PUFAs), in particular of docosahexaenoic acid (DHA), on calcium homeostasis in isolated adult rat cardiomyocytes exposed to KCl, ET-1 and anoxia. Free [Ca(2+)](i) in rat cardiomyocytes was 135.7 +/- 0.5 nM. Exposure to 50 mM KCl or 100 nM ET-1 resulted in a rise in free [Ca(2+)](i) in freshly isolated cells (465.4 +/- 15.6 nM and 311.3 +/- 12.6 nM, respectively) and in cultured cells (450.8 +/- 14.8 nM and 323.5 +/- 14.8 nM respectively). An acute treatment (20 minutes) with 10 microM DHA significantly reduced the KCl- and ET-1-induced [Ca(2+)](i) increase (300.9 +/- 18.1 nM and 232.08 +/- 11.8 nM, respectively). This reduction was greater after chronic treatment with DHA (72 h; 257.7 +/- 13.08 nM and 192.18 +/- 9.8 nM, respectively). Rat cardiomyocytes exposed to a 20 minute superfusion with anoxic solution, obtained by replacing O(2) with N(2) in gas mixture, showed a massive increase in cytosolic calcium (1200.2 +/- 50.2 nM). Longer exposure to anoxia induced hypercontraction and later death of rat cardiomyocytes. Preincubation with DHA reduced the anoxic effect on [Ca(2+)](i) (498.4 +/- 7.3 nM in acute and 200.2 +/- 12.2 nM in chronic treatment). In anoxic conditions 50 mM KCl and 100 nM ET-1 produced extreme and unmeasurable increases of [Ca(2+)](i.) Preincubation for 20 minutes with DHA reduced this phenomenon (856.1 +/- 20.3 nM and 782.3 +/- 7.6 nM, respectively). This reduction is more evident after a chronic treatment with DHA (257.7 +/- 10.6 nM and 232.2 +/- 12.5 nM, respectively). We conclude that in rat cardiomyocytes KCl, ET-1 and anoxia interfered with intracellular calcium concentrations by either modifying calcium levels or impairing calcium homeostasis. Acute, and especially chronic, DHA administration markedly reduced the damage induced by calcium overload in those cells.

Topics: Animals; Calcium; Docosahexaenoic Acids; Endothelin-1; Heart; Hypoxia; Myocardium; Potassium Chloride; Rats; Rats, Wistar

Topics: Animals; Endothelin-1; Hemodynamics; Hypoxia; Myocardium; Nitric Oxide; Rats; Rats, Wistar; Regional Blood Flow

To investigate the effect of ETA receptor antagonist, WS009A, on the pathogenesis of hypoxic pulmonary hypertension in rats.. In the course of chronic hypoxia, rats were treated with WS009A (10 mg/kg) by a siliastic catheter inserted in the left external jugular vein.. The measured values of mean pulmonary arterial pressure (mPAP) were 2.7 +/- 0.33, 3.97 +/- 0.47 [symbol: see text] 2.39 +/- 0.27 kPa in the control, the hypoxic and the WS009A treated groups, respectively. The percentages of vascular wall area/total vascular area (MA%) were 0.26 +/- 0.03, 0.52 +/- 0.04, 0.32 +/- 0.07, respectively. The percentages of vascular wall thickness/vascular external diameter(MT%) were 0.14 +/- 0.02, 0.31 +/- 0.03, 0.18 +/- 0.05, respectively. The ratios of right ventricular wall to left ventricle plus septum[RV/(LV + S)] were 0.24 +/- 0.02, 0.35 +/- 0.03, 0.26 +/- 0.03, respectively. The variance analysis revealed there were decreases in mPAP and the ratio of RV/(LV + S) in WS009A group (P < 0.01, compared with those in hypoxic group). There were no haemodynamic and right ventricular hypertrophy differences between WS009A group and control group. The MT% and MA% in WS009A groups were higher than those in controls, but there were significantly decreased MT% and MA% in WS009A group as compared with those in hypoxic group (P < 0.01).. The ETA receptor antagonist, WS009A, attenuates the pulmonary vascular wall remodelling and the pulmonary hypertension induced by chronic hypoxia.

Topics: Animals; Anthraquinones; Endothelin Receptor Antagonists; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Male; Pulmonary Artery; Random Allocation; Rats; Rats, Wistar

We investigated the effects of the nitric oxide (NO) donor molsidomine and the nitric oxide synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME) on pulmonary endothelin (ET)-1 gene expression and ET-1 plasma levels in chronic hypoxic rats. Two and four weeks of hypoxia (10% O2) significantly increased right ventricular systolic pressure, the medial cross-sectional vascular wall area of the pulmonary arteries, and pulmonary ET-1 mRNA expression (2-fold and 3.2-fold, respectively). ET-1 plasma levels were elevated after 4 wk of hypoxia. In rats exposed to 4 wk of hypoxia, molsidomine (15 mg x kg(-1) x day(-1)) given either from the beginning or after 2 wk of hypoxia significantly reduced pulmonary hypertension, pulmonary vascular remodeling, pulmonary ET-1 gene expression, and ET-1 plasma levels. L-NAME administration (45 mg x kg(-1) x day(-1)) in rats subjected to 2 wk of hypoxia did not modify these parameters. Our findings suggest that in chronic hypoxic rats, exogenously administered NO acts in part by suppressing the formation of ET-1. In contrast, inhibition of endogenous NO production exerts only minor effects on the pulmonary circulation and pulmonary ET-1 synthesis in these animals.

Topics: Animals; Chronic Disease; Disease Models, Animal; Endothelin-1; Enzyme Inhibitors; Gene Expression Regulation; Glyceraldehyde-3-Phosphate Dehydrogenases; Hematocrit; Hemodynamics; Hypertension, Pulmonary; Hypoxia; Lung; Male; Molsidomine; NG-Nitroarginine Methyl Ester; Nitric Oxide Donors; Nitric Oxide Synthase; Pulmonary Artery; Rats; Rats, Wistar; RNA, Messenger; Vasodilator Agents

We examined whether overproduction of endogenous nitric oxide (NO) can prevent hypoxia-induced pulmonary hypertension and vascular remodeling by using endothelial NO-overexpressing (eNOS-Tg) mice. Male eNOS-Tg mice and their littermates (wild-type, WT) were maintained in normoxic or 10% hypoxic condition for 3 weeks. In normoxia, eNOS protein levels, Ca(2+)-dependent NOS activity, and cGMP levels in the lung of eNOS-Tg mice were higher than those of WT mice. Activity of eNOS and cGMP production in the lung did not change significantly by hypoxic exposure in either genotype. Chronic hypoxia did not induce iNOS expression nor increase its activity in either genotype. Plasma and lung endothelin-1 levels were increased by chronic hypoxia, but these levels were not significantly different between the 2 genotypes. In hemodynamic analysis, right ventricular systolic pressure (RVSP) in eNOS-Tg mice was similar to that in WT mice in normoxia. Chronic hypoxia increased RVSP and induced right ventricular hypertrophy in both genotypes; however, the degrees of these increases were significantly smaller in eNOS-Tg mice. Histological examination revealed that hypoxic mice showed medial wall thickening in pulmonary arteries. However, the increase of the wall thickening in small arteries (diameter <80 microm) by chronic hypoxia was inhibited in eNOS-Tg mice. Furthermore, muscularization of small arterioles was significantly attenuated in eNOS-Tg mice. Thus, we demonstrated directly that overproduction of eNOS-derived NO can inhibit not only the increase in RVSP associated with pulmonary hypertension but also remodeling of the pulmonary vasculature and right ventricular hypertrophy induced by chronic hypoxia.

Topics: Animals; Blood Pressure; Blood Vessels; Cyclic GMP; Endothelin-1; Female; Genotype; Heart Rate; Hematocrit; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Immunoblotting; Lung; Male; Mice; Mice, Transgenic; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Ventricular Function, Right; Ventricular Pressure

To explore the effects of hypoxia on the production and secretion of adrenomedullin (ADM) and endothelin (ET)-1 in human retinal pigment epithelial (RPE) cells.. RPE cells were cultured under normoxic or hypoxic (1% O2) conditions. Expression of ADM and ET-1 was examined by Northern blot analysis and radioimmunoassay. Effects of ADM and ET-1 on the number of RPE cells were examined by modified 3-(4,5-dimetylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay.. ADM mRNA expression levels and immunoreactive ADM levels in the medium were increased by hypoxia in all three human RPE cell lines (ARPE-19, D407, and F-0202). Immunoreactive ET was detected in the cultured media of D407 cells and ARPE-19 cells and identified as ET-1 by reversed-phase high performance liquid chromatography. Hypoxia treatment for 48 hours increased immunoreactive ET levels approximately 1.3-fold in the cultured media of D407, but not ARPE-19 cells. Hypoxia decreased the number of ARPE-19 cells and F-0202 cells, and the treatment with ADM ameliorated the hypoxia-induced decrease in the cell number. In contrast, exogenously added ET-1 had no significant effects on the number of ARPE-19 cells under normoxia and hypoxia.. Hypoxia increased the expression of ADM in all three human RPE cell lines, whereas the induction of ET-1 by hypoxia was found only in D407 cells. ADM induced by hypoxia may have protective roles against hypoxic cell damage in RPE cells.

Topics: Adrenomedullin; Blotting, Northern; Cell Count; Cells, Cultured; Chromatography, High Pressure Liquid; Endothelin-1; Humans; Hypoxia; Peptides; Pigment Epithelium of Eye; Radioimmunoassay; RNA, Messenger; Vasodilator Agents

Sustained hypoxic pulmonary vasoconstriction is dependent upon the presence of an intact endothelium, strongly suggesting that an endothelium-derived constrictor factor is involved in this response. In the present study we have attempted to determine whether hypoxia induces the release of a vasoconstrictor(s) from the lung, and whether this vasoconstrictor shares mechanistic features with the hypoxic constrictor response.. The salt-perfused rat lung, coupled with a simple solid-phase extraction process, and a rat intrapulmonary artery functional bioassay were utilised in this study.. Hypoxic, but not normoxic, perfusion of the isolated lung of the rat induced the release of a vasoconstrictor(s) which appeared to be selective for pulmonary over mesenteric arteries of the rat. The vasoconstriction observed was unaffected by inhibition of voltage-gated Ca(2+) channels, and was not associated with a rise in intracellular [Ca(2+)], suggesting Ca(2+)-sensitisation of the contractile apparatus. The vasoconstriction was also unaffected by the protein kinase C (PKC) inhibitor Ro-31-8220, or the endothelin-1 antagonists BQ123/BQ788 but was markedly potentiated in the presence of prostaglandin F(2alpha).. We conclude that hypoxic perfusion of the rat lung results in the release of a vasoconstrictor(s) which shares some of the facets of the sustained hypoxic constriction of isolated intrapulmonary arteries of the rat, since it involves PKC-independent Ca(2+) sensitisation, is independent of voltage-gated Ca(2+) entry, and is potentiated by the presence of preconstriction.

Topics: Acetonitriles; Animals; Calcium; Dinoprost; Endothelin-1; Enzyme Inhibitors; Hypoxia; Indoles; Ion Channel Gating; Lung; Male; Organ Culture Techniques; Protein Kinase C; Pulmonary Artery; Rats; Vasoconstriction; Vasoconstrictor Agents

Topics: Endothelin-1; Humans; Hypoxia; Lung Diseases, Obstructive; Oxyhemoglobins; Sleep

Nonapneic, oxyhemoglobin desaturation associated with sleep has been described in patients with chronic obstructive pulmonary disease (COPD). Hypoxemia stimulates endothelin-1 (ET-1) secretion. Once released, ET-1 can act locally to elicit sustained pulmonary artery vasoconstriction, bronchoconstriction and activation of alveolar macrophages.. The aim of this study was to examine a possible correlation between ET-1 levels and nocturnal, nonapneic, oxyhemoglobin desaturation during sleep, in patients with COPD.. We examined 48 COPD patients with formal polysomnography (EEG, ECG, airflow, respiratory muscle movement, oximeter) to detect the presence of nocturnal, nonapneic, oxyhemoglobin desaturation. Twelve of them were disqualified because of inadequate sleep or sleep apnea syndrome. Nineteen of them desaturated below a baseline sleep saturation of 90% for 5 min or more, reaching a nadir saturation of at least 85%. We collected arterial samples to measure ET-1 levels, after 5 min of the first period of desaturation, in each of the 19 patients. We also collected arterial samples in the morning, before the study, to measure baseline ET-1 levels in all patients.. Baseline arterial ET-1 levels during the day were very significantly higher in 'desaturator' COPD patients (2.058 +/- 0.252 pg/ml) compared to 'non-desaturator' COPD patients (1.382 +/- 0.159 pg/ml; p < 0.001). Also in 'desaturator' COPD patients ET-1, levels during the night were significantly higher (4.297 +/- 1.107 pg/ml) compared to those during the day (p < or = 0.001) and a significant negative correlation was observed between ET-1 levels and degree of desaturation (p < 0.0001, r = 0.9305).. According to our study we can conclude that (1) ET-1 levels are significantly higher in 'desaturator' COPD patients both during the day and during the night, and (2) ET-1 levels correlate negatively significant with the degree of the oxyhemoglobin desaturation. These findings are consistent with the hypothesis that ET-1 plays a very important role in the pathophysiological manifestations of COPD patients.

Topics: Aged; Endothelin-1; Humans; Hypoxia; Lung Diseases, Obstructive; Middle Aged; Oxyhemoglobins; Polysomnography; Sleep

Topics: Animals; Endothelin-1; Endothelium, Vascular; Hypoxia; Lung; Potassium Channels; Pulmonary Artery; Receptors, Endothelin; Species Specificity; Swine; Vasoconstriction

To determine the role of endothelium in hypoxic pulmonary vasoconstriction (HPV), we measured vasomotor responses to hypoxia in isolated seventh-generation porcine pulmonary arteries < 300 microm in diameter with (E+) and without endothelium. In E+ pulmonary arteries, hypoxia decreased the vascular intraluminal diameter measured at a constant transmural pressure. These constrictions were complete in 30-40 min; maximum at PO(2) of 2 mm Hg; half-maximal at PO(2) of 40 mm Hg; blocked by exposure to Ca(2+)-free conditions, nifedipine, or ryanodine; and absent in E+ bronchial arteries of similar size. Hypoxic constrictions were unaltered by indomethacin, enhanced by indomethacin plus N(G)-nitro-L-arginine methyl ester, abolished by BQ-123 or endothelial denudation, and restored in endothelium-denuded pulmonary arteries pretreated with 10(-10) M endothelin-1 (ET-1). Given previous demonstrations that hypoxia caused contractions in isolated pulmonary arterial myocytes and that ET-1 receptor antagonists inhibited HPV in intact animals, our results suggest that full in vivo expression of HPV requires basal release of ET-1 from the endothelium to facilitate mechanisms of hypoxic reactivity in pulmonary arterial smooth muscle.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Bronchial Arteries; Caffeine; Calcium; Cell Survival; Endothelin-1; Endothelium, Vascular; Enzyme Inhibitors; Hypoxia; In Vitro Techniques; Lung; Male; Pulmonary Artery; Receptors, Endothelin; Ryanodine; Swine; Vasoconstriction; Vasoconstrictor Agents; Vasodilator Agents

Endothelin (ET)-1 contributes to the regulation of pulmonary vascular tone by stimulation of the ET(A) and ET(B) receptors. Although activation of the ET(A) receptor causes vasoconstriction, stimulation of the ET(B) receptors can elicit either vasodilation or vasoconstriction. To examine the physiological role of the ET(B) receptor in the pulmonary circulation, we studied a genetic rat model of ET(B) receptor deficiency [transgenic(sl/sl)]. We hypothesized that deficiency of the ET(B) receptor would predispose the transgenic(sl/sl) rat lung circulation to enhanced pulmonary vasoconstriction. We found that the lungs of transgenic(sl/sl) rats are ET(B) deficient because they lack ET(B) mRNA in the pulmonary vasculature, have minimal ET(B) receptors as determined with an ET-1 radioligand binding assay, and lack ET-1-mediated pulmonary vasodilation. The transgenic(sl/sl) rats have higher basal pulmonary arterial pressure and vasopressor responses to brief hypoxia or ET-1 infusion. Plasma ET-1 levels are elevated and endothelial nitric oxide synthase protein content and nitric oxide production are diminished in the transgenic(sl/sl) rat lung. These findings suggest that the ET(B) receptor plays a major physiological role in modulating resting pulmonary vascular tone and reactivity to acute hypoxia. We speculate that impaired ET(B) receptor activity can contribute to the pathogenesis of pulmonary hypertension.

Topics: Animals; Animals, Genetically Modified; Blood Pressure; Dopamine beta-Hydroxylase; Endothelin-1; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; In Situ Hybridization; In Vitro Techniques; Lung; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Promoter Regions, Genetic; Pulmonary Artery; Pulmonary Circulation; Radioligand Assay; Rats; Rats, Inbred Strains; Receptor, Endothelin B; Receptors, Endothelin; RNA, Messenger; Vascular Resistance; Vasoconstriction

Recurrent episodic hypoxia (EH) is a feature of sleep apnea that may be responsible for some chronic cardiovascular sequelae such as systemic hypertension. Chronic EH (8 h/day for 35 days) causes elevation of diurnal resting (unstimulated) mean arterial blood pressure (MAP) in the rat. We used in vivo video microscopy to examine arteriolar reactivity in the cremaster muscle of male Sprague-Dawley rats subjected to 35 days of EH. Cremaster muscles of EH (n = 6) and control (n = 6) rats were exposed to varying doses of norepinephrine (NE) (10(-10) to 10(-5) M), ACh (10(-9) to 10(-5) M), and endothelin-1 (10(-12) to 10(-8) M). In a separate experiment, EH (n = 5) and control (n = 6) rats were given one dose of a nitric oxide synthase (NOS) inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME; 10(-5) M). We also examined endothelial NOS mRNA from the kidneys of EH-stimulated and control (unstimulated) rats. Telemetry-monitored EH rats showed a 16-mmHg increase in MAP over 35 days, whereas control rats showed no change. The response to NE and endothelin-1 were similar for EH and control rats. ACh vasodilatation of arterioles in EH rats was significantly attenuated compared with that of controls. The degree of vasoconstriction in response to blockade of the nitric oxide system by L-NAME was significantly less (83% of baseline diameter with L-NAME) for arterioles of EH rats compared with that for controls (61% of baseline diameter), implying lower basal resting nitric oxide release in the EH rats. Whole kidney mRNA endothelial NOS levels were not different between groups. These data support the hypothesis that chronic elevation of blood pressure associated with EH involves increased peripheral resistance from decreased basal release or production of nitric oxide after 35 days of EH.

Topics: Acetylcholine; Animals; Arterioles; Blood Pressure; Chronic Disease; Circadian Rhythm; Disease Models, Animal; Endothelin-1; Gene Expression Regulation, Enzymologic; Hypoxia; Kidney; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Norepinephrine; Rats; Rats, Sprague-Dawley; Sleep Apnea Syndromes; Telemetry; Transcription, Genetic; Vasodilation

Pulmonary veins show greater sensitivity to endothelin (ET)-1-induced vasoconstriction than pulmonary arteries, and remodeling was observed in pulmonary veins under hypoxic conditions. We examined, using an immunohistochemical method, the expression of Big ET-1, ET-converting enzyme (ECE), and ET(A) and ET(B) receptors in rat pulmonary veins under normoxic and hypoxic conditions. In control rats, Big ET-1 and ECE were coexpressed in the intima and media of the pulmonary veins, with an even distribution along the axial pathway. ET(A) and ET(B) receptors were expressed in the pulmonary veins, with a predominant distribution in the proximal segments. The expression of Big ET-1 was more abundant in the pulmonary veins than in the pulmonary arteries. After exposure to hypoxia for 7 or 14 days, the expression of Big ET-1, ECE, and ET receptors increased in small pulmonary veins. Increases in the medial thickness, wall thickness, and immunoreactivity for alpha-smooth muscle actin were also observed in the small pulmonary veins under hypoxic conditions. The upregulation of ET-1 and ET receptors in the small pulmonary veins is associated with vascular remodeling, which may lead to the development of hypoxic pulmonary hypertension.

Topics: Actins; Animals; Aspartic Acid Endopeptidases; Endothelin-1; Endothelin-Converting Enzymes; Endothelins; Hypoxia; Immunohistochemistry; Lung; Male; Metalloendopeptidases; Protein Precursors; Pulmonary Veins; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptor, Endothelin B; Receptors, Endothelin; Up-Regulation

The effect of chronic hypoxia (CH) for 14 days on Ca2+ signaling and contraction induced by agonists in the rat main pulmonary artery (MPA) was investigated. In MPA myocytes obtained from control (normoxic) rats, endothelin (ET)-1, angiotensin II (ANG II), and ATP induced oscillations in intracellular Ca2+ concentration ([Ca2+]i) in 85-90% of cells, whereas they disappeared in myocytes from chronically hypoxic rats together with a decrease in the percentage of responding cells. However, both the amount of mobilized Ca2+ and the sources of Ca2+ implicated in the agonist-induced response were not changed. Analysis of the transient caffeine-induced [Ca2+]i response revealed that recovery of the resting [Ca2+]i value was delayed in myocytes from chronically hypoxic rats. The maximal contraction induced by ET-1 or ANG II in MPA rings from chronically hypoxic rats was decreased by 30% compared with control values. Moreover, the D-600- and thapsigargin-resistant component of contraction was decreased by 40% in chronically hypoxic rats. These data indicate that CH alters pulmonary arterial reactivity as a consequence of an effect on both Ca2+ signaling and Ca2+ sensitivity of the contractile apparatus. A Ca2+ reuptake mechanism appears as a CH-sensitive phenomenon that may account for the main effect of CH on Ca2+ signaling.

Topics: Adenosine Triphosphate; Angiotensin II; Animals; Caffeine; Calcium; Calcium Signaling; Chronic Disease; Endothelin-1; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; In Vitro Techniques; Indoles; Intracellular Membranes; Male; Muscle, Smooth, Vascular; Pulmonary Artery; Rats; Rats, Wistar; Reference Values; Vasoconstriction; Vasodilator Agents; Vasomotor System

Topics: Animals; Antioxidants; Calcium; Calcium Signaling; Chloride Channels; Electron Transport; Endothelin Receptor Antagonists; Endothelin-1; Enzyme Inhibitors; Hypoxia; Lung; Methacrylates; Mitochondria; Muscle, Smooth, Vascular; Oxidation-Reduction; Oxygen; Potassium Channel Blockers; Potassium Channels; Pulmonary Artery; Rats; Reactive Oxygen Species; Receptor, Endothelin A; Receptors, Endothelin; Sarcolemma; Sarcoplasmic Reticulum; Signal Transduction; Thiazoles; Vasoconstriction

The role of the thromboxane A(2)/prostaglandin H(2) receptor in endothelin-1 contraction was investigated in aortic rings from rats exposed to normoxia (21% O(2)) or hypoxia (10% O(2)) for 12 h. Indomethacin (10 microM) and SQ 29,548 (0.1 microM, thromboxane A(2)/prostaglandin H(2) receptor antagonist) reduced maximum tension and increased EC(50) in endothelium-intact and -denuded rings from normoxic animals. Neither inhibitor had any effect on rings from hypoxic rats. Thromboxane A(2) and/or prostaglandin H(2) contribute to the response to endothelin-1 in aortas from normoxic rats but not from rats exposed to hypoxia. Loss of prostanoid-enhancement of endothelin-1 contraction contributes to impair vascular reactivity after hypoxia.

Topics: Acetylcholine; Animals; Aorta, Thoracic; Bridged Bicyclo Compounds, Heterocyclic; Dose-Response Relationship, Drug; Endothelin-1; Endothelium, Vascular; Fatty Acids, Unsaturated; Hydrazines; Hypoxia; In Vitro Techniques; Male; Phenylephrine; Rats; Rats, Sprague-Dawley; Receptors, Prostaglandin; Receptors, Thromboxane A2, Prostaglandin H2; Vasoconstriction; Vasoconstrictor Agents; Vasodilator Agents

Circulating and urinary levels of endothelin (ET), an endothelium-derived vasoconstrictive and mitogenic peptide have been reported to increase in patients with chronic obstructive pulmonary disease (COPD), but the mechanisms of these abnormalities are not fully understood. Our study objectives were to evaluate pulmonary and renal ET clearance in COPD patients during an acute exacerbation. Our participants included nine consecutive patients with moderate to severe COPD without signs of right heart failure admitted for acute exacerbation and ten healthy volunteers (HV) as controls. ET was detected by radioimmunoassay in venous and arterial blood as well as in a timed urine specimen. For each subject, arterial/venous immunoreactive ET ratio (ir-ETart/ir-ETven) was evaluated as an index of its pulmonary clearance. Creatinine clearance was employed in each case to obtain a corrected renal ir-ET clearance. Glomerular filtration rate (GFR) was also assessed by dynamic(99m)Tc-diethylenetriamine pentaacetic acid renal scintigraphy in six COPD patients during acute exacerbation and at recovery. The ratio ir-ETart/ir-ETven was comparable in COPD patients (0.75+/-0.12) and in HV (0.82+/-0.09). A significant difference was found with respect to 24 h ir-ET urinary excretion between COPD patients during exacerbation as well as at recovery (respectively 142.1+/-12.8 ng/24 h and 89.0+/-15.1 ng/24 h) and HV (65.1+/-10.1 ng/24 h). ET renal clearance was higher in COPD patients than in HV (29.2+/-5.2 ml min(-1)in COPD during exacerbation; 17.5+/-3.9 ml min(-1)at recovery and 13.6+/-2.4 ml min(-1)in HV, P<0.001). GFR was 69.4+/-10.0 ml min(-1)in COPD patients during exacerbation and it significantly increased at the recovery (95.5+/-20.9 ml min(-1)P<0.001). Corrected renal clearance of the peptide was significantly correlated to GFR values during the exacerbation (r=-0.81, P<0.05). Furthermore change in renal ET production resulted associated with changes in paCO(2)(r=0.83, P<0.001) and in paO(2)(r=-0.73, P<0.05). Acute exacerbation in COPD patients causes an increase in renal ET production which is partially reversible at the recovery, in the absence of significant changes in ET-1 circulating levels. ET might contribute to the renal response to hypoxaemia and hypercapnia in COPD.

Topics: Acute Disease; Aged; Endothelin-1; Glomerular Filtration Rate; Humans; Hypercapnia; Hypoxia; Kidney; Lung Diseases, Obstructive; Male; Middle Aged

The purpose of this study was to test whether the Tester Moriyama rat (TMR), a strain that has a serotonin platelet storage-pool deficiency similar to that of the fawn-hooded rat (FHR), develops severe pulmonary hypertension (PH) upon exposure to mild hypoxia. We compared hemodynamic parameters in catheterized 10-week-old FHR, TMR, and control Wistar rats that had been raised from birth to 10 weeks of age under normoxia (PI(O(2)) approximately 150 mmHg) or mild hypobaric hypoxia (PI(O(2)) approximately 120 mmHg). Mean pulmonary artery pressure and right ventricle to left ventricle plus septum weight ratio were much higher in the mildly hypoxic FHR compared with the normoxic FHR. These parameters were only increased slightly by exposure to mild hypoxia in the TMR and Wistar rats. Mild hypoxia did not affect mean systemic artery pressure in any of the rat strains. Exposure of FHR to mild hypoxia from 4 to 10 weeks of age did not lead to development of PH. Endothelin-1 (ET-1) mRNA and peptide levels were increased in the hypertensive lungs of mildly hypoxic FHR compared with the normotensive lungs of normoxic FHR, and of normoxic and mildly hypoxic TMR and Wistar rats. These results suggest that mild hypoxia causes severe PH and upregulation of lung ET-1 expression in neonatal FHR but not in neonatal TMR, and that the period from birth to 4 weeks of age is critical for the development of the severe PH in the FHR. A serotonin PSPD does not predispose rats to hypoxia-induced PH.

Topics: Animals; Blood Pressure; Blotting, Northern; Endothelin-1; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Lung; Male; Platelet Storage Pool Deficiency; Radioimmunoassay; Rats; Rats, Mutant Strains; Rats, Wistar; RNA, Messenger; Serotonin; Species Specificity

Since pulmonary vasculature is complex in terms of regional difference in structure and function, it is important to understand the site of endothelin (ET) synthesis and the distribution of the ET system along the axial pathways of pulmonary artery. The expression of big ET-1, ET converting enzyme (ECE) and ET(A) receptors were examined in rat pulmonary arteries under normal and hypoxic conditions using an immunohistochemical method and Northern blot analysis. In normal conditions, big ET-1 was expressed in the intima and media of pulmonary arteries with a predominant distribution in the distal segments and a preferential localization in the media, while ETA receptors were dominantly expressed in the proximal segments. ECE was constitutively expressed in the intima and media. Following exposure to hypoxia, messenger ribonucleic acid (mRNA) expression of ET-1 and ET(A) receptors were up-regulated by two-fold and immunoreactivities for big ET-1, ECE, and ET(A) receptors significantly increased by two to five-fold in the distal segments. Smooth muscle cells are an important source of endothelin-1 in the pulmonary artery. The distribution of big endothelin-1 and endothelin A receptors in pulmonary arteries was discrepant in normal conditions while their expression concomitantly increased in the distal segments in hypoxic conditions. This heterogeneity may play an important role in the regulation of pulmonary vascular tone.

Topics: Animals; Aspartic Acid Endopeptidases; Endothelin-1; Endothelin-Converting Enzymes; Endothelins; Gene Expression; Hypoxia; Lung; Male; Metalloendopeptidases; Protein Precursors; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptors, Endothelin; RNA, Messenger; Tunica Intima; Tunica Media

The pulmonary vasculature of newborns with persistent pulmonary hypertension is characterized by active vasoconstriction and vascular remodeling. It has been suggested that endothelin-1 (ET-1), a potent vasoconstrictor and growth promoter, may be involved in the pathogenesis of persistent pulmonary hypertension of the newborn. To determine whether treatment with an ET(A) receptor antagonist can reverse pulmonary hypertension in the neonate, 1-d-old piglets were exposed to hypoxia for 3 d to induce pulmonary hypertension and then treated for the remainder of the 14 d with an orally active, nonpeptidic ET(A) antagonist (TBC3711, 22 mg x kg(-1) x d(-1)). At the end of the exposure, Hb, pulmonary artery pressure, right ventricle to left ventricle plus septum weight ratio, percentage wall thickness, ET-1 circulating levels, perfusion pressure, and dilator response to the nitric oxide (NO) donor, SIN-1 (3-morpholinosydnonimine-N-ethylcarbamide) in isolated perfused lungs were determined. Exhaled NO and hemodynamic variables were also examined in an intact anesthetized animal preparation that had undergone the same treatment. By 3 d of exposure to hypoxia, piglets had already developed significant pulmonary hypertension as estimated by their pulmonary artery pressure (24.0 +/- 1.3 mm Hg versus 14.2 +/- 3.4 mm Hg) and percentage wall thickness (26.6 +/- 5.9% versus 18.7 +/- 2.4% for vessels 0-30 microm). Whereas further exposure to hypoxia for 14 d did not enhance the increase in pulmonary artery pressure and percentage wall thickness, it did augment the right ventricle to left ventricle plus septum weight ratio (0.71 +/- 0.09 versus 0.35 +/- 0.01). ET-1 circulating levels were increased only when exposure to hypoxia was prolonged to 14 d (5.1 +/- 2.4 pg/mL versus 1.0 +/- 0.4 pg/mL). Treatment with TBC3711 from d 3 to d 14, once pulmonary hypertensive changes were established and while hypoxic exposure persisted, caused significant reduction in the right ventricle to left ventricle plus septum weight ratio (0.60 +/- 0.06), pulmonary artery pressure (20.0 +/- 4.8 mm Hg), and percentage wall thickness (18.5 +/- 3.3%) and restored the dilator response to the NO donor SIN-1. Prolonged hypoxia markedly reduced exhaled NO concentrations (0.3 +/- 0.6 ppb), although treatment of hypoxic animals with TBC3711 restored the concentration of exhaled NO (4.4 +/- 2.8 ppb) to the level of normoxic controls (4.9 +/- 3.0 ppb). Lastly, treatment with TBC3711 increased ET-1 circulat

Topics: Animals; Animals, Newborn; Cell Line; Endothelin Receptor Antagonists; Endothelin-1; Humans; Hypertension, Pulmonary; Hypoxia; Iodine Radioisotopes; Lung; Molsidomine; Nitric Oxide; Receptor, Endothelin A; Swine; Vasodilator Agents

The effects on pulmonary artery pressure (PAP) and plasma Endothelin-1 (ET-1) were studied in piglets during severe hypoxemia and reoxygenation for 2 h with selective inhibition of the endothelin receptors. Two groups were subjected to selective ETA (ETA group) or ETB (ETB group) receptor inhibition. During hypoxemia there was an initial increase in PAP to 36.3 and 34.3 mm Hg in the ETA and ETB groups respectively, with a decrease to the end of hypoxemia. During reoxygenation PAP reached a maximum at 5 min with a mean of 29.6 and 38.4 mm Hg in the ETA and ETB groups respectively, and then PAP gradually declined towards baseline. During the 2 h reoxygenation period PAP was higher in the ETB group than in the ETA group (p = 0.02). Plasma ET-1 increased from 1.50 and 1.17 ng/L at baseline to 2.07 and 3.18 ng/L at the end of hypoxemia in the ETA and ETB groups respectively.. ETB receptor inhibition leads to increased pulmonary vasoconstriction during reoxygenation following hypoxemia compared to ETA receptor inhibition. Not only the ETB receptor, but also the ETA receptor plays a role in maintaining plasma ET-1 levels.

Topics: Acid-Base Equilibrium; Animals; Animals, Newborn; Endothelin Receptor Antagonists; Endothelin-1; Hemodynamics; Hypoxia; Lung; Oligopeptides; Peptides, Cyclic; Piperidines; Pulmonary Artery; Receptor, Endothelin A; Receptor, Endothelin B; Swine; Vasoconstriction

To investigate the roles of the vascular endothelial growth factor(VEGF) and endothelin-1(ET-1) in pulmonary vascular remodelling in rats with hypoxia-induced pulmonary hypertension(HPH) and the effect of pinacidil on VEGF and ET-1 in rats with HPH.. 46 male Wister rats were divided into three groups i.e. control group, hypoxic group and treated group (hypoxic rats treated with pinacidil for 4 weeks). Rat models with chronic HPH were established by chronic hypobaric hypoxia [(10.0 +/- 0.5)% O2, 4 weeks]. The levels of VEGF and ET-1 in serum and the mean pulmonary arterial pressure (mPAP) and the weight ratio of right ventricle (RV)/left ventricle and septum (LV + S) [RV/(LV + S)] were measured and the small pulmonary arterial morphologic changes were observed with morphometric analysis under microscopes in the three groups.. (1) The levels of VEGF[(118.73 +/- 55.40) ng/L] and ET-1[(221.2 +/- 56.2) ng/L] in serum, mPAP [(28.4 +/- 2.8) mm Hg, 1 mm Hg = 0.133 kPa] and RV/(LV + S) (0.296 +/- 0.033) were significantly higher in the hypoxic group than those in the control group (P < 0.01). Morphometry showed that the external diameter of the small pulmonary arteries became smaller and the ratio of vascular wall thickness to external diameter (MT%) (25.70 +/- 2.58)% and ratio of vascular wall area to total area (MA%) (75.300 +/- 5.600)% significantly increased in the hypoxic group. (2) The levels of VEGF[(78.20 +/- 16.45) ng/L] and ET-1[(181.6 +/- 30.5) ng/L] in serum, mPAP[(23.3 +/- 2.6) mm Hg], RV/(LV + S) (0.266 +/- 0.037), MT%(22.10 +/- 2.51)% and MA% (66.900 +/- 0.061)% significantly decreased in the treated group.. VEGF and ET-1 play important roles in the development of HPH and pulmonary vascular remodelling. Pinacidil may partly inhibit the development of HPH and pulmonary vascular remodelling by decreasing VEGF and ET-1.

Topics: Animals; Endothelial Growth Factors; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Lymphokines; Male; Pulmonary Veins; Rats; Rats, Wistar; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors

To explore the effect of L-arginine on hypoxic pulmonary vascular structural remodeling and its possible mechanisms.. Eighteen Wistar rats were randomly divided into three groups: the hypoxia group, the hypoxia with L-arginine group and the control group. Pulmonary artery mean pressure was evaluated with right cardiac catheterization. Pulmonary vascular structural changes were also observed. Plasma concentration of nitric oxide (NO) was measured via spectrophotometry, and endothelin-1 (ET-1) mRNA expression in pulmonary artery endothelial cells was detected using in situ hybridization.. The pulmonary artery mean pressure was significantly high in hypoxic rats than in normal controls (20.33 +/- 2.18 mm Hg vs 15.38 +/- 1.05 mm Hg, P < 0.05). Microstructural and ultrastructural analysis revealed the development of hypoxic pulmonary vascular structural remodeling in the hypoxic rats. Meanwhile, the plasma NO concentration was markedly lower in the hypoxic rats than in controls (P < 0.05). The expression signals of ET-1 mRNA by pulmonary artery endothelial cells of hypoxic rats strengthened obviously. L-arginine ameliorated pulmonary hypertension (16.73 +/- 1.35 mm Hg vs 20.33 +/- 2.18 mm Hg, P < 0.05) as well as pulmonary vascular structural remodeling in the hypoxic rats in association with an increase in plasma NO concentration (P < 0.05) and inhibited ET-1 mRNA expression by the endothelial cells of pulmonary arteries.. L-arginine might play an important role in the regulation of hypoxic pulmonary vascular structural remodeling and hypoxic pulmonary hypertension. The mechanism is probably related to promoting NO production and, as a result, inhibiting ET-1 mRNA expression by pulmonary artery endothelial cells in hypoxic rats.

Topics: Animals; Arginine; Blood Pressure; Endothelin-1; Endothelium, Vascular; Gene Expression Regulation; Hypoxia; Male; Nitric Oxide; Pulmonary Artery; Rats; Rats, Wistar; RNA, Messenger

The purpose of this study was to investigate the effects of prolonged (24-h) non-acidemic hypoxemia on plasma endothelin-1 and atrial natriuretic peptide (ANP) in fetal goats.. During continuous infusion of nitrogen into the maternal trachea, fetal plasma endothelin-1 and ANP levels were measured in nine chronically instrumented goat fetuses at 117-129 days' gestation. Endothelin-1 and ANP were measured by radioimmunoassay.. Fetal arterial pO(2) decreased significantly from 23.1 +/- 1.0 mmHg (control) to 15.2 +/- 0.9 mmHg during the first 2 h of hypoxemia and to 15.7 +/- 1.1 mmHg at the end of the experimental period of hypoxemia. The plasma endothelin-1 concentration increased from 10.6 +/- 1.9 pg/ml to 20.4 +/- 4.3 pg/ml (p < 0.05) during the first 2 h and was 19.7 +/- 2.4 pg/ml (p < 0.01) at the end of the experimental period. The plasma ANP concentration also increased, from 20.3 +/- 5.5 pg/ml to 23.0 +/- 4.7 pg/ml in the first 2 h and then to 58.0 +/- 8.8 pg/ml (p < 0.05) at the end of the experimental period. There was a significant negative correlation between fetal plasma endothelin-1 and pO(2), but no significant correlation was found between fetal plasma ANP and pO(2).. Prolonged non-acidemic hypoxemia induces a continuous increase in fetal plasma endothelin-1 and ANP levels. Fetal plasma ANP increases time-dependently but endothelin-1 remains constant during hypoxemia.

Topics: Animals; Atrial Natriuretic Factor; Endothelin-1; Female; Fetal Blood; Goats; Hemodynamics; Hypoxia; Pregnancy; Pregnancy Complications; Radioimmunoassay; Time Factors

The Hilltop (H) strain compared to the Madison (M) strain of Sprague-Dawley rats develops severe pulmonary hypertension in response to chronic hypoxia. We tested the hypothesis that endothelin-1 (ET-1) contributes to these strain-related differences. Plasma ET-1 content was not modified by chronic hypoxia in either strain. The lung ET-1 peptide and preproET-1 mRNA content were significantly increased to the same magnitude in both strains at 2 and 3 weeks of hypoxia. The ET(A) receptor mRNA increased more at 3 weeks of hypoxia in the lungs of H rats than in M rats, but not at other time points. The ET(B) receptor mRNA was not modified by hypoxia in either strain. After 3 days of normoxic recovery following 2 weeks of hypoxia, ET-1 protein and mRNA levels decreased to baseline levels in both rat strains. We conclude that ET-1 does not contribute to the development of cardiopulmonary differences between the H and M strains in response to hypoxia.

Topics: Animals; Chronic Disease; Endothelin-1; Endothelins; Genetic Predisposition to Disease; Hematocrit; Hypertension, Pulmonary; Hypoxia; Immunoblotting; Lung; Male; Organ Size; Protein Precursors; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptor, Endothelin B; Receptors, Endothelin; Reference Standards; Reverse Transcriptase Polymerase Chain Reaction; RNA Probes; RNA, Messenger; Species Specificity; Ventricular Function

The aim of this study was to evaluate the plasma arterial levels of Endothelin-1 (ET-1) and their relationship with hypoxia and pulmonary hypertension (PH) in patients with interstitial lung disease (ILD). Incremental cycle ergometry was performed in all patients up to maximal capacity. ET-1 levels during exercise (2.2 +/- 0.36 pgr/ml) were significantly higher than at rest (1.73 +/- 0.37 pgr/ml) (p < 0.001). ET-1 levels were also significantly correlated with arterial oxygen (PaO2) (r = -0.935, p < 0.001) and mean pulmonary arterial pressure (Ppa) (r = 0.657, p < 0.001). Increased pulmonary and peripheral blood levels of ET-1 have been described in, and postulated to contribute to, the pathophysiology of several lung diseases. In agreement with this, in the current study, the plasma arterial levels of ET-1 were also found to be significantly elevated in patients with various interstitial lung disorders during exercise, especially in those with severe hypoxia and pulmonary hypertension.

Topics: Endothelin-1; Female; Humans; Hypertension, Pulmonary; Hypoxia; Lung Diseases, Interstitial; Male; Middle Aged

This study was aimed to determine the distribution and change of ET-1 in the lung of rat with chronic hypoxic pulmonary hypertension. Immunohistochemical analysis (Avidin-Biotion Complex) was used to localize the ET-1 immunoreactivity in the rat lung. The ET-1 concentration in plasma and in lung homogenate was measured by radioimmunoassay. In normal rats, the mean ET-1 concentration in venous plasma was 2.25 +/- 0.68 ng/L, in arterial plasma 1.52 +/- 0.63 ng/L and in lung 1.75 +/- 0.46 ng/L. There was no significant increase of ET-1 level in rats exposed to hypoxia for 2 hours, but there was significant increase of ET-1 after 24 hours hypoxia, and the high levels of ET-1 were maintained in the sustained hypoxia. There was significant correlation between the ET-1 level in arterial plasma(or in lung homogenate) and the maen pulmonary artery pressure. Similaryly, there was significant negative correlation between ET-1 in arterial plasma(or in lung homogenate) and PaO2. Immunohistochemical analysis revealed that the ET-1 immunoreactivity was seen in the endothelium of pulmonary arteries, particularly more positive staining was seen in the band between the endothelium and the smooth muscle cells. Chronic hypoxia elevated the mean pulmonary arterial pressure, caused vessel remodelling and the right ventricular hypertrophy. These changes were accompained by an increase of ET-1 in plasma and lung homogenate. The expression and production of ET-1 were localized to endothelium and airway epithelium in the lungs.

Topics: Animals; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Immunohistochemistry; Lung; Male; Random Allocation; Rats; Rats, Wistar

This investigation was made to elucidate the role of endothelin (ET) in hypoxic pulmonary hypertension and the preventing effects of BQ-123, an ETA receptor antagonist. Thirty male Wistar rats were divided into three groups and exposed to air, isobaric hypoxia or isobaric hypoxia plus BQ-123 for 3 weeks. The pulmonary artery pressure was measured by right cardiac catheterization. The plasma level of ET-1 was measured by RIA method. Histologic sections of the lungs were examined by a computerized image analyser. In hypoxic rats, the pulmonary artery pressure and the thickness of wall of arteriole were significantly increased, and right ventricular hypertrophy was developed. The plasma level of VEGF in rats treated with hypoxia (192.3 +/- 43.1 pg/ml) was significantly increased as compared with that of normal rats (128.2 +/- 28.1 pg/ml), P < 0.01. Chronic BQ-123 treatment prevented the developments of pulmonary hypertension, thickening of pulmonary arteriole and right ventricular hypertrophy induced by hypoxia. These result indicate that chronic hypoxia can result in hypoxic pulmonary hypertension and increased plasma level of ET-1, and the ETA receptor antagonist can prevent hypoxic pulmonary hypertension.

Topics: Animals; Endothelin Receptor Antagonists; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Male; Peptides, Cyclic; Pulmonary Artery; Rats; Rats, Wistar

The effects of hypoxia on renin secretion and renin gene expression have been controversial. In recent studies, we have demonstrated that acute hypoxia of 6 h duration caused a marked stimulation of renin secretion and renal renin gene expression. This hypoxia-induced stimulation of the renin-angiotensin system might contribute, for example, to the progression of chronic renal failure and to the development of hypertension in the sleep-apnoea syndrome. For this reason, we were interested in the more chronic effects of hypoxia on renal renin gene expression and its possible regulation.. Male rats were exposed to chronic normobaric hypoxia (10% O(2)) for 2 and 4 weeks. Additional groups of rats were treated with an endothelin ET(A) receptor antagonist, LU135252, or a NO donor, molsidomine, respectively. Systolic blood pressure and right ventricular pressures were measured. Renal renin, endothelin-1 and endothelin-3 gene expression were quantitated using RNAase protection assays.. During chronic hypoxia, haematocrit increased to 72+/-2%, and right ventricular pressure increased by a mean of 26 mmHg. Renal renin gene expression was halved during 4 weeks of chronic hypoxia. This decrease was reversed by endothelin receptor blockade (105 or 140% of baseline values after treatment for weeks 3-4 or 1-4). Furthermore, there was a trend of increasing renal endothelin-1 gene expression (to 173% of baseline values) after 4 weeks of hypoxia. Systolic blood pressure increased moderately during 4 weeks of chronic hypoxia from 129+/-2 to 150+/-4 mmHg. This blood pressure increase was higher in rats treated for 4 weeks with an endothelin receptor antagonist (196+/-11 mmHg).. Chronic hypoxia (in contrast to acute hypoxia) suppresses renal renin gene expression. This inhibition presumably is mediated by endothelins.

Topics: Animals; Blood Pressure; Chronic Disease; Endothelin Receptor Antagonists; Endothelin-1; Endothelin-3; Gene Expression; Hypoxia; Kidney; Male; Molsidomine; Nitric Oxide Donors; Phenylpropionates; Pyrimidines; Rats; Rats, Wistar; Renin; RNA, Messenger

We tested the hypothesis that regulation of the pulmonary circulation by endogenous endothelin (ET) during normoxia and hypoxia was altered in conscious dogs 1 mo after left lung autotransplantation (LLA). Sham-operated control and post-LLA dogs were chronically instrumented to measure the left pulmonary vascular pressure-flow (LP-Q) relationship. LP-Q plots were generated on separate days during normoxia and hypoxia (arterial PO(2) approximately 50 Torr) in the intact condition, after selective ET(A)-receptor inhibition (BQ-485), and after combined ET(A+B)-receptor inhibition (bosentan). Although LLA resulted in a chronic increase in pulmonary vascular resistance, the ET-receptor antagonists had no effect on the LP-Q relationship during normoxia in either group. The magnitude of hypoxic pulmonary vasoconstriction (HPV) was flow dependent in both groups, and the HPV response was potentiated post-LLA compared with control. ET(A)-receptor inhibition attenuated the HPV response to the same extent in both groups. ET(A+B)-receptor inhibition attenuated the HPV response to a greater extent than did ET(A)-receptor inhibition alone, and this effect was greater post-LLA compared with control. Plasma ET-1 concentration only increased during hypoxia in the LLA group. These results indicate that ET does not regulate the baseline LP-Q relationship in either group. Both ET(A)- and ET(B)-receptor activation mediate a component of HPV in conscious dogs, and the vasoconstrictor influence of ET(B)-receptor activation is enhanced post-LLA.

Topics: Animals; Azepines; Bosentan; Carbon Dioxide; Consciousness; Dogs; Endothelin Receptor Antagonists; Endothelin-1; Hydrogen-Ion Concentration; Hypoxia; Lung; Lung Transplantation; Male; Oligopeptides; Oxygen; Pulmonary Artery; Pulmonary Circulation; Receptors, Endothelin; Respiration; Sulfonamides; Vascular Resistance; Vasoconstriction

Calcitonin gene-related peptide (CGRP) is believed to play an important role in maintaining low pulmonary vascular resistance (PVR) and in modulating pulmonary vascular responses to chronic hypoxia; however, the effects of adenovirally mediated gene transfer of CGRP on the response to hypoxia are unknown.. In the present study, an adenoviral vector encoding prepro-CGRP (AdRSVCGRP) was used to examine the effects of in vivo gene transfer of CGRP on increases in PVR, right ventricular mass (RVM), and pulmonary vascular remodeling that occur in chronic hypoxia in the mouse. Intratracheal administration of AdRSVCGRP, followed by 16 days of chronic hypoxia (FIO(2) 0.10), increased lung CGRP and cAMP levels. The increase in pulmonary arterial pressure (PAP), PVR, RVM, and pulmonary vascular remodeling in response to chronic hypoxia was attenuated in animals overexpressing prepro-CGRP, whereas systemic pressure was not altered while in chronically hypoxic mice, angiotensin II and endothelin-1-induced increases in PAP were reduced, whereas decreases in PAP in response to CGRP and adrenomedullin were not changed and decreases in PAP in response to a cAMP phosphodiesterase inhibitor were enhanced by AdRSVCGRP.. In vivo CGRP lung gene transfer attenuates the increase in PVR and RVM, pulmonary vascular remodeling, and pressor responses in chronically hypoxic mice, suggesting that CGRP gene transfer alone and with a cAMP phosphodiesterase inhibitor may be useful for the treatment of pulmonary hypertensive disorders.

Topics: Adenoviridae; Adrenomedullin; Animals; beta-Galactosidase; Calcitonin Gene-Related Peptide; Cyclic AMP; Cyclic GMP; Endothelin-1; Genes, Reporter; Genetic Therapy; Genetic Vectors; Hemodynamics; Humans; Hypertension, Pulmonary; Hypoxia; Lung; Mice; NG-Nitroarginine Methyl Ester; Peptides; Phosphodiesterase Inhibitors; Potassium Channels; Protein Precursors; Purinones; Recombinant Fusion Proteins; Rolipram; Second Messenger Systems; Transfection; Vasoconstriction; Vasoconstrictor Agents; Vasodilator Agents

Chronic hypoxia leads to a greater degree of pulmonary hypertension in the Wistar-Kyoto (WKY) rat than in the Fischer 344 (F-344) rat. We questioned whether this difference is associated with baseline differences in pulmonary artery anatomy, a greater degree of hypoxia-induced pulmonary vascular remodeling in the WKY rat, and/or differences in expression of endothelin (ET)-1. Male F-344 and WKY rats were maintained in normoxia or normobaric hypoxia for 21 days. Morphometry revealed that baseline pulmonary artery anatomy was similar in the two strains. However, during chronic hypoxia, the WKY rats developed a greater degree of muscularization of small pulmonary arteries. Baseline plasma and lung immunoreactive ET-1 levels were similar in the WKY and F-344 rats and increased significantly during hypoxia in the WKY rats. Northern analysis demonstrated increased lung preproET-1 mRNA during hypoxia in both strains, with a greater increase in WKY rats. Immunostaining demonstrated increased ET-1 in bronchial epithelium and peripheral pulmonary arteries during hypoxia, although to a greater degree in the WKY rats. We conclude that the WKY strain demonstrates increased susceptibility to hypoxia-induced pulmonary vascular remodeling compared with the F-344 strain and that increased lung and circulating ET-1 levels during hypoxia may partly explain this difference.

Topics: Animals; Blotting, Northern; Chronic Disease; Endothelin-1; Endothelins; Epithelial Cells; Gene Expression; Hypoxia; Immunohistochemistry; Male; Protein Precursors; Pulmonary Artery; Pulmonary Circulation; Rats; Rats, Inbred F344; Rats, Inbred WKY; RNA, Messenger; Species Specificity

Effects of sitaxsentan (TBC11251), an orally active, highly selective antagonist of endothelin A receptors, were examined on the development and maintenance of pulmonary hypertension, pulmonary vascular remodeling, and cardiac hypertrophy in the rat. The pulmonary vasoconstrictor response to acute hypoxia (10% O(2)for 90 min) was prevented with sitaxsentan (5 mg/kg infused iv 10 min prior to the onset of hypoxia) while BQ-788 (a specific endothelin B receptor antagonist) was without effect. The same dose of sitaxsentan delivered iv 50 min after the onset of hypoxia reversed the established pulmonary vasoconstriction. In a 2-week model of hypoxia using 10% O(2), treatment with sitaxsentan (15 mg/kg per day in drinking water) attenuated pulmonary hypertension and the associated right ventricular hypertrophy, and prevented the remodeling of small pulmonary arteries (50-100 microM) without affecting systemic arterial blood pressure or heart rate. Institution of sitaxsentan treatment (15 and 30 mg/kg per day in drinking water) for 4 weeks after 2 weeks of untreated hypoxia produced a significant, dose dependent reversal of the established pulmonary hypertension, right heart hypertrophy, and pulmonary vascular remodeling despite continued hypoxic exposure. Sitaxsentan blocked increased plasma endothelin levels in the prevention protocol but did not affect the established elevated levels in the intervention study. Sitaxsentan dose dependently (10 and 50 mg/kg per day in the drinking water) attenuated right ventricular systolic pressure, right heart hypertrophy, and pulmonary vascular remodeling observed 3 weeks after a single subcutaneous injection of monocrotaline. These findings support the hypothesis that endothelin-1 plays a significant role in the development of pulmonary hypertension, pulmonary vascular remodeling, and the associated cardiac hypertrophy, and further suggest that specific endothelin-A receptor blockade may be useful in the treatment of pulmonary hypertension of diverse etiologies.

Topics: Animals; Cardiomegaly; Disease Models, Animal; Endothelin Receptor Antagonists; Endothelin-1; Hypertension, Pulmonary; Hypertrophy; Hypoxia; Isoxazoles; Male; Monocrotaline; Oxygen; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Thiophenes; Vasoconstriction; Weight Gain

Responses to human urotensin-II (hU-II) were investigated in human and rat pulmonary arteries. Rat pulmonary arteries: hU-II was a potent vasoconstrictor of main pulmonary arteries (2 - 3 mm i.d.) (pEC(50), 8.55+/-0.08, n=21) and was approximately 4 fold more potent than endothelin-1 [ET-1] (P<0.01), although its E(max) was considerably less (approximately 2.5 fold, P<0.001). The potency of hU-II increased 2.5 fold with endothelium removal (P<0.05) and after raising vascular tone with ET-1 (P<0.01). E(max) was enhanced approximately 1.5 fold in the presence of N(omega)-nitro-L-arginine methylester (L-NAME, 100 microM, P<0.01) and approximately 2 fold in vessels from pulmonary hypertensive rats exposed to 2 weeks chronic hypoxia (P<0.05). hU-II did not constrict smaller pulmonary arteries. Human pulmonary arteries ( approximately 250 microm i.d.): in the presence of L-NAME, 3 out of 10 vessels contracted to hU-II and this contraction was highly variable. hU-II is, therefore, a potent vasoconstrictor of rat main pulmonary arteries and this response is increased by endothelial factors, vascular tone and onset of pulmonary hypertension. Inhibition of nitric oxide synthase uncovers contractile responses to hU-II in human pulmonary arteries.

Topics: Animals; Dose-Response Relationship, Drug; Drug Interactions; Endothelial Growth Factors; Endothelin-1; Endothelium, Vascular; Enzyme Inhibitors; Humans; Hypertension, Pulmonary; Hypoxia; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Oxygen; Pulmonary Artery; Rats; Rats, Wistar; Urotensins; Vasoconstriction

We investigated the cause of decreased plasma endothelin-1 (ET-1) during hypoxaemia and reoxygenation in newborn piglets subjected to simultaneous blocking of the ET-1 receptors. Changes in plasma ET-1 and prepro-ET-1 mRNA expression in the main pulmonary artery and the left lower lobe in the lung were studied in 1-2-d-old piglets. Ten minutes prior to hypoxaemia, the hypoxaemia group (n = 10) was given saline, two groups (both n = 9) were given 1 and 5 mg/kg i.v. SB 217242 (an ET-1 receptor antagonist). Two groups served as normoxic controls, with and without SB 217242 5 mg/kg i.v. Hypoxaemia was induced by ventilating with 8% O2 until base excess was <-20 mmol/l or mean arterial blood pressure was <20 mmHg. Reoxygenation was performed for 2 h with room air. During hypoxaemia, plasma ET-1 decreased in the hypoxaemia group, remained unchanged in the 1-mg group and increased in the 5-mg group. At the end of reoxygenation, plasma ET-1 was above baseline in the 1-mg and 5-mg groups. In the pulmonary artery, the hypoxaemia group showed 2- to 5-fold higher prepro-ET- 1 mRNA expression compared to all the other groups (p < 0.05). There were trends for higher prepro-ET-1 mRNA expression in pulmonary tissue in the hypoxaemia group compared to the two receptor-blocking groups (p < 0.07).. We conclude that hypoxaemia and reoxygenation increase prepro-ET-1 mRNA expression in the pulmonary artery in newborn piglets. These observations suggest that the half-life of ET-1 is decreased during hypoxaemia and reoxygenation in newborn piglets.

Topics: Age Factors; Animals; Endothelin Receptor Antagonists; Endothelin-1; Hypoxia; Lung; Molecular Sequence Data; Pulmonary Artery; RNA, Messenger; Swine

The cardiopulmonary profile of three rat strains (Sprague-Dawley, Wistar and High altitude-sensitive) was compared upon exposure to hypoxia (9% O2) for 0, 7 or 14 days. No differences were observed among the in vitro contractile (ET-1) and relaxant (carbachol) responses of pulmonary artery isolated from the three strains during normoxia. Chronic hypoxia decreased ET-1 contractile responses and diminished relaxant responses to carbachol similarly in all strains. In Sprague-Dawley, Wistar and High altitude-sensitive rats, pulmonary arterial pressure rose time-dependently and was elevated by 108%, 116% and 167%, respectively, after 14 days of hypoxia compared to normoxic controls. Right ventricular hypertrophy was increased by 51%, 93% and 55%, respectively, at 14 days. Hypoxia-induced hypertrophy and medial thickening in the pulmonary vasculature were more pronounced in High altitude-sensitive rats. Sprague-Dawley exhibited hypoxia-induced airway hyperresponsiveness to intravenous methacholine, but there were no hypoxia- or strain-related differences in in vitro tracheal contractility. Although each strain exhibited greater sensitivity for a particular hypoxia-induced parameter, pulmonary vascular functional and structural changes suggest that High altitude-sensitive rats represent a choice model of hypoxia-induced pulmonary hypertension.

Topics: Altitude; Animals; Carbachol; Disease Models, Animal; Endothelin-1; Endothelins; Hypertension, Pulmonary; Hypertrophy; Hypertrophy, Right Ventricular; Hypoxia; In Vitro Techniques; Male; Methacholine Chloride; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Rats, Wistar; Species Specificity; Trachea; Vasoconstriction; Vasodilation

We have examined the effect of endothelin-1, sarafotoxin-6C, big-endothelin-1 and other agents on perfused lungs from chronically hypoxic rats. Increases in pulmonary perfusion pressure induced by big-endothelin-1, endothelin-1, phenylephrine and potassium chloride were enhanced in hypoxic lungs, while the constrictor action of sarafotoxin-6C was not increased. When basal pulmonary perfusion pressure was raised, low doses of endothelin-1 and sarafotoxin-6C produced decreases in pulmonary perfusion pressure which were significantly greater in chronically hypoxic lungs, whereas responses to sodium nitroprusside were unchanged. Endothelin ET(B) receptor-mediated bronchoconstrictor responses were also potentiated in hypoxic lungs, whereas responses to carbachol were not. In hypoxic lungs, conversion of big-endothelin-1 to endothelin-1 was significantly increased. These data provide evidence for a generalised increase in vasomotor activity in chronically hypoxic lungs, and a more selective increase in endothelin ET(B) receptor-mediated vasodilator and bronchoconstrictor responses. Hypoxia also augments the conversion of big-endothelin-1 to endothelin-1.

Topics: Animals; Blood Pressure; Carbachol; Endothelin-1; Endothelins; Hypoxia; In Vitro Techniques; Lung; Male; Muscarinic Agonists; Nitroprusside; Phenylephrine; Potassium Chloride; Protein Precursors; Pulmonary Circulation; Rats; Rats, Wistar; Receptor, Endothelin B; Receptors, Endothelin; Vasoconstriction; Vasoconstrictor Agents; Viper Venoms

Viral respiratory infections may increase the susceptibility of young animals to hypoxia-induced pulmonary edema. Because hypoxia stimulates endothelin production, we hypothesized that an increase in lung endothelin contributes to these alterations in lung water. Weanling rats were infected with Sendai virus, causing a mild respiratory infection. At day 7 after infection, animals were exposed to hypoxia (inspired O(2) fraction = 0.1) for 24 h. Exposure to virus plus hypoxia led to increases in lung water compared with control groups (P < 0.001). Lung endothelin levels were significantly higher in the virus plus hypoxia group than in control groups (P < 0.001). A second group of infected animals received bosentan, a nonselective endothelin receptor antagonist, during exposure to hypoxia. Bosentan-treated animals showed less lung water accumulation, less lung lavage fluid protein, and less perivascular fluid cuffing than untreated animals (P < 0.01). We conclude that the combination of a recent viral respiratory infection and exposure to moderate hypoxia led to increases in endothelin in the lungs of young rats and that endothelin receptor blockade ameliorates the hypoxia-induced increases in lung water found in these animals.

Topics: Animals; Aspartic Acid Endopeptidases; Body Water; Bronchoalveolar Lavage Fluid; Capillary Permeability; Endothelin Receptor Antagonists; Endothelin-1; Endothelin-Converting Enzymes; Endothelins; Hypoxia; Lung; Male; Metalloendopeptidases; Protein Precursors; Proteins; Rats; Rats, Sprague-Dawley; Respiratory Tract Infections; Respirovirus; Respirovirus Infections; RNA, Messenger

We studied tone in the human ductus arteriosus and show that the constriction to oxygen is due to inhibition of voltage-gated potassium channels and, in the acute phase, is independent of endothelin-1.

Topics: 4-Aminopyridine; Charybdotoxin; Cyclooxygenase Inhibitors; Ductus Arteriosus; Ductus Arteriosus, Patent; Endothelin-1; Glyburide; Humans; Hypoxia; Ion Channel Gating; Membrane Potentials; Muscle, Smooth, Vascular; Nitric Oxide Synthase; Oxygen Consumption; Potassium Channels

1. The aims of the present study were to determine the characteristics of garlic extract-induced relaxation in rat isolated pulmonary arteries, its susceptibility to changes in oxygen tension and its protective effect against hypoxic pulmonary vasoconstriction. 2. In normoxia, garlic extract (3-500 microg/mL) produced a dose- and nitric oxide (NO)-dependent relaxation. Following 60 min hypoxia, maximum garlic relaxation was reduced compared with control (mean (-SEM) -86 +/- 3 vs-69 +/- 2% of phenylephrine (PE) precontraction, respectively), but recovered after 60 min reoxygenation (-85 +/- 3% PE precontraction). 3. Acetylcholine (0.1 micromol/L)-induced NO-dependent relaxation was reduced from a control value of -76 +/- 1% to -46 +/- 4% during hypoxia and was further reduced to -35 +/- 2 % after reoxygenation. 4. In endothelium-intact arteries, hypoxic exposure resulted in a triphasic response: early transient contraction (+24 +/- 4%), followed by transient relaxation (-37 +/- 7%) and then sustained contraction (+62 +/- 5%). 5. Pretreatment with NG-nitro-L-arginine methyl ester abolished the early transient contraction, moderately attenuated the sustained contraction and had no effect on the transient relaxation. Mechanical endothelial disruption inhibited all hypoxia-induced vascular changes. 6. Garlic pretreatment had no effect on the early transient contraction (+25 +/- 4%), but inhibited the transient relaxation (-5 +/- 3%; P<0.05) and the sustained contraction (+26 +/- 5%; 7. Garlic also significantly inhibited endothelin-l-induced contractions in a dose-dependent manner. 8. These findings show that garlic extract modulates the production and function of both endothelium-derived relaxing and constricting factors and this may contribute to its protective effect against hypoxic pulmonary vasoconstriction.

Topics: Acetylcholine; Animals; Blood Pressure; Dose-Response Relationship, Drug; Endothelin Receptor Antagonists; Endothelin-1; Endothelium, Vascular; Garlic; Hypertension, Pulmonary; Hypoxia; Male; Muscle, Smooth, Vascular; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Phytotherapy; Plant Extracts; Plants, Medicinal; Pulmonary Artery; Rats; Vasodilation

In the lung, chronic hypoxia (CH) causes pulmonary arterial smooth muscle cell (PASMC) depolarization, elevated endothelin-1 (ET-1), and vasoconstriction. We determined whether, during CH, depolarization-driven activation of L-type Ca(2+) channels contributes to 1) maintenance of resting intracellular Ca(2+) concentration ([Ca(2+)](i)), 2) increased [Ca(2+)](i) in response to ET-1 (10(-8) M), and 3) ET-1-induced contraction. Using indo 1 microfluorescence, we determined that resting [Ca(2+)](i) in PASMCs from intrapulmonary arteries of rats exposed to 10% O(2) for 21 days was 293.9 +/- 25.2 nM (vs. 153.6 +/- 28.7 nM in normoxia). Resting [Ca(2+)](i) was decreased after extracellular Ca(2+) removal but not with nifedipine (10(-6) M), an L-type Ca(2+) channel antagonist. After CH, the ET-1-induced increase in [Ca(2+)](i) was reduced and was abolished after extracellular Ca(2+) removal or nifedipine. Removal of extracellular Ca(2+) reduced ET-1-induced tension; however, nifedipine had only a slight effect. These data indicate that maintenance of resting [Ca(2+)](i) in PASMCs from chronically hypoxic rats does not require activation of L-type Ca(2+) channels and suggest that ET-1-induced contraction occurs by a mechanism primarily independent of changes in [Ca(2+)](i).

Topics: Animals; Calcium; Calcium Channels, L-Type; Cells, Cultured; Endothelin-1; Hypoxia; Male; Muscle, Smooth, Vascular; Nifedipine; Potassium Chloride; Pulmonary Artery; Rats; Rats, Wistar

Levels of endothelin-1 (ET-1), a potent endogenous vasoconstrictor, are elevated in plasma and cerebrospinal fluid (CSF) following cerebral ischemia and reperfusion injury. The present study sought insight into the potential differential vasoactive effects on the cerebral vasculature and resultant neural damage of ET-1 during normoxic vs. ischemic conditions and upon reperfusion. Under normoxic conditions, intrastriatal stereotaxic injection of exogenous ET-1 (40 pmol) induced a significant (P<0.05) reduction (

Topics: Animals; Cerebral Infarction; Corpus Striatum; Endothelin-1; Hypoxia; Injections; Oxygen; Rats; Rats, Long-Evans; Reference Values

Endothelin-1 (ET-1) is assigned a mediator role in the constrictor response of the pulmonary vasculature to hypoxia. Accordingly, a recently developed endothelin-A (ETA) antagonist, PD180988, was tested in the chronically instrumented newborn lamb to verify this possibility and, at the same time, to study a potential new treatment for pulmonary hypertension (PH). PD180988, given by infusion after a priming bolus, had an insignificant effect on the pulmonary circulation under normoxia, while it reversed the sustained pulmonary constriction caused by hypoxia. No appreciable change was noted under either experimental condition in the systemic circulation and cardiac contractility. We conclude that PD180988 is a selective inhibitor of hypoxic pulmonary vasoconstriction and lends itself to therapeutic use in infants.

Topics: Animals; Endothelin Receptor Antagonists; Endothelin-1; Hypoxia; Pulmonary Circulation; Receptor, Endothelin A; Sheep; Thiazines; Vasoconstriction

To investigate the effects of hypoxemia, hypercapnia, and cardiovascular hormones (norepinephrine, endothelin-1, and atrial natriuretic factor) on blood pressure during acute respiratory failure.. Patients with chronic obstructive pulmonary disease and acute respiratory failure were divided into four groups of 10 patients each: hypoxemia-normocapnia, hypoxemia-hypercapnia, hypoxemia-hypocapnia, and normoxemia-hypercapnia. Plasma norepinephrine levels were determined by high-performance liquid chromatography with electrochemical detection. Plasma endothelin-1 and atrial natriuretic factor levels were radioimmunoassayed after chromatographic preextraction.. Systolic blood pressure and cardiovascular hormone levels were greater in patients with hypercapnia (whether or not they also had hypoxemia) than in those with normocapnia and hypoxemia. For example, in patients with hypercapnia and normoxemia, the mean (+/- SD) systolic blood pressure was 183+/-31 mm Hg and the mean norepinephrine level was 494+/-107 pg/mL, as compared with 150+/- 6 mm Hg and 243+/-58 pg/mL in those with normocapnia and hypoxemia (both P<0.05). Similar results were seen for endothelin-1 and atrial natriuretic factor levels, and for the comparisons of hypoxemic patients who were hypercapnic with those who were normocapnic.. These results suggest that blood carbon dioxide levels, rather than oxygen levels, are responsible for hypertension during acute respiratory failure, perhaps as a result of enhanced sympatho-adrenergic activity.

Topics: Acute Disease; Adult; Aged; Atrial Natriuretic Factor; Blood Pressure; Carbon Dioxide; Endothelin-1; Female; Heart Rate; Humans; Hypercapnia; Hypertension; Hypocapnia; Hypoxia; Lung Diseases, Obstructive; Male; Middle Aged; Norepinephrine; Oxygen; Respiratory Insufficiency; Severity of Illness Index

Chronic hypoxic pulmonary hypertension (PH) is associated with vasoconstriction and structural remodeling of pulmonary vessels including narrowing of the arterial lumen and loss of distal functional arteries. To test whether lung overexpression of the angiogenic factor vascular endothelial growth factor (VEGF) is beneficial in hypoxic PH, recombinant adenovirus encoding the human VEGF 165 gene under the control of a cytomegalovirus promoter (Ad. VEGF) or control vector containing no gene in the expression cassette (Ad.Null) was administered intratracheally to rats. With Ad. VEGF (10(8) plaque-forming units [pfu]), VEGF protein was present in bronchoalveolar lavage fluid as early as 2 d and until 17 d after gene transfer, but was not detected in serum. Only small patchy areas of mononuclear cells without cell damage, edema, or hemorrhage were observed on lung histology with no significant change in lung permeability. In rats pretreated with Ad.VEGF (10(8) pfu) 2 d before a 2-wk exposure to hypoxia (10% O(2)), lower values versus Ad. Null-pretreated controls were found for pulmonary artery pressure (25 +/- 1 versus 30 +/- 2 mm Hg, P < 0.05), right ventricular over left ventricular-plus-septum weight (0.37 +/- 0.01 versus 0.47 +/- 0. 02, P < 0.001), normalized wall thickness of 50- to 200-microm vessels (P < 0.001), and muscularization of distal vessels (P < 0. 001). Pretreatment with Ad.VEGF (10(8) pfu) increased endothelial nitric oxide synthase activity in lung tissue and partially restored endothelium-dependent vasodilation in isolated lungs from chronically hypoxic rats, as assessed by improvement of ionophore A23187-induced vasodilation and attenuation of endothelin-1 (300 pmol)-induced vasoconstriction, an effect abolished in the presence of nitro-L-arginine methylester. We conclude that adenoviral-mediated VEGF overexpression in the lungs attenuates development of hypoxic PH, in part by protecting endothelium-dependent function.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Adenoviridae; Animals; Bronchoalveolar Lavage Fluid; Calcimycin; Capillary Permeability; DNA, Recombinant; Dose-Response Relationship, Drug; Endothelial Growth Factors; Endothelin-1; Gene Expression Regulation; Gene Transfer, Horizontal; Humans; Hypertension, Pulmonary; Hypoxia; In Vitro Techniques; Ionophores; Lung; Lymphokines; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Rats; Rats, Wistar; Time Factors; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors; Vasodilation

The biologic responses to transforming growth factor-beta (TGF-beta) suggest many potential therapeutic applications; however, in the only clinical trial to examine the effect of the systemic administration of a TGF-beta isoform, patients experienced significant but reversible declines in renal function. We studied the effects of administering human recombinant TGF-beta2 to adult mice.. The effect of daily administration of TGF-beta2 on tissue vasoconstriction, tissue levels of endothelin and angiotensin II, tissue hypoxia, and renal fibrosis were examined.. Daily administration of TGF-beta2 at 10 or 100 microg/kg caused apparent tissue vasoconstriction that was visualized by vascular casting, with the largest impact seen in the kidney. Tissue levels of endothelin 1 and angiotensin II were significantly elevated in kidneys of treated mice, as was urinary thromboxane beta2. Renal fibrosis was observed in the cortical tubular interstitium and vasculature, particularly at the cortical-medullary junction and medullary vasa recta; however, glomerular sclerosis was not observed. Fibrosis was correlated to focal tissue hypoxia as determined by immunohistochemical detection of tissue bound pimondazole.. We conclude that there are significant histopathologic consequences, focused in the kidney, resulting from the daily administration of high doses of human recombinant TGF-beta2, and we propose that selective vascular constriction with consequent tissue hypoxia is a contributing factor.

Topics: Angiotensin II; Animals; Corrosion Casting; Endothelin-1; Fibrosis; Glomerular Filtration Rate; Humans; Hypoxia; Ischemia; Kidney; Kidney Diseases; Male; Mice; Mice, Inbred C57BL; Mice, Inbred ICR; Procollagen; Recombinant Proteins; Transforming Growth Factor beta; Transforming Growth Factor beta2; Vasoconstriction

To investigate the role of nitric oxide (NO), nitric oxide synthase (NOS) and endothelin-1 (ET-1) in the pathogenesis of hypoxic pulmonary hypertension and inhibiting effects of L-Arginine.. 30 rats were divided into 3 groups, normal control group (group NC); Hypoxic group (group HP): exposed to 10% O2 8 h/day, 3 weeks; Hypoxic + L-arginine (group LT): fed L-arginine 200 mg/kg before hypoxia. After exposed to hypoxia 21 days, hemodynamics were measured. Lung speciments were examined by light and electronic microscopes and morphometric analysis. NO, ET-1 levels in lung tissue were measured, the cNOS quantitative in the pulmonary endothelium were examined.. In HP group, the mean pulmonary arterial pressure (m PAP), pulmonary vascular resistance (PVR) the percentage of completely muscular coattype medial muscle layer of pulmonary artery in intra-acine and ET-1 level of HP group increased (P < 0.01), but NO and cNOS level decreased (P < 0.01). Examined by electron micrograph, endothelium cells appeared swollen, broken and pealed of, basal lamina parted. The changes above in LT group reversed partly. But the changes above were still several than that of group NC (P < 0.05).. The structure remodel of pulmonary arteries and endothelium lesion in hypoxia cause m PAP, PVP arising, that are correlated with the levels of ET-1 increasing and NO, cNOS decreasing. For L-arginine can partly supply NO, it may partly reverse the changes of HPH.

Topics: Animals; Arginine; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Male; Nitric Oxide; Nitric Oxide Synthase; Rats; Rats, Wistar

To investigate the effects of chronic hypoxic hypercapnia and ligustrazine on expression of endothelin-1 (ET-1) mRNA and the ultrastructure of pulmonary arterioles in rats.. Thirty rats were randomly divided into three groups: control group (A), hypoxic hypercapnic group (B), hypoxic hypercapnia + ligustrazine (lig.) group (C). ET-1 mRNA was observed in arterioles from rats by the technique of in situ hybridization. The average value of integral light density (LD) of ET-1 mRNA in pulmonary arterioles was detected by an image analysor and the relative content of ET-1 mRNA was calculated.. (1) mPAP was significantly higher in rats of B group than that of A group (P < 0.01) and it was much lower in rats of C group than that of B group (P < 0.01). Differences of mCAP were not significant in three groups (P > 0.05); plasma ET-1 concentration was significantly higher in rats of B group than that of A group (P < 0.01), plasma ET-1 concentration was significantly lower in rats of C group than that of B group (P < 0.01); (2) Light microscopy showed that WA/TA (vessel wall area/total area) and SMC (the density of medial smooth muscle cells) were significantly higher in rats of B group than those of A group (P < 0.01). WA/TA and SMC were significantly lower in rats of C group than those of B group (P < 0.01). Electron microscopy showed proliferation of medial smooth muscle cells and collageous fibers of pulmonary arterioles in rats of B group, and ligustrazine could reverse the changes mentioned above; (3) Hybridization in situ showed that LD of ET-1 mRNA in pulmonary arterioles was significantly higher in rats of B group than that of A group (P < 0.01); LD of ET-1 mRNA in pulmonary arterioles was significantly lower in rats of C group than that of B group (P < 0.01).. Increase of expression of ET-1 mRNA in pulmonary arterioles contributes to the development of pulmonary hypertension and structural remodeling of pulmonary arteries in chronic hypoxic hypercapnic rats. Ligustrazine can inhibit pulmonary hypertension by decreasing the expression of ET-1 mRNA in pulmonary arterioles.

Topics: Animals; Arterioles; Endothelin-1; Hypercapnia; Hypoxia; Male; Pulmonary Artery; Pyrazines; Random Allocation; Rats; Rats, Sprague-Dawley; RNA, Messenger

To explore the mechanism of the therapeutic effect of L-arginine on hypoxic pulmonary vascular structural remodeling.. Eighteen age- and body weight-matched Wistar rats were randomly divided into hypoxic group, hypoxic with L-arginine group or control group. Pulmonary artery mean pressure (mPAP) of each rat was evaluated using right cardiac catheterization. Pulmonary vascular microstructure was measured and the ultrastructural changes in intra-acinar pulmonary muscularized arteries were observed. Meanwhile, indirect plasma concentration of nitric oxide (NO) was measured via spectrophotometry, and endothelin-1 (ET-1) mRNA expression in pulmonary artery endothelial cells was detected using in situ hybridization with a cRNA probe for ET-1.. mPAP was significantly increased in hypoxic rats (2.71 kPa +/- 0.29 kPa) as compared with that of normal controls (2.05 kPa +/- 0.14 kPa) (P < 0.05). Microstructure and ultrastructure of pulmonary arteries changed obviously in hypoxic rats with the development of hypoxic pulmonary vascular structural remodeling. Meanwhile, indirect plasma NO concentration in hypoxic rats (3.54 micromol/L +/- 0.47 micromol/L) was markedly decreased compared with controls (4.79 micromol/L +/- 0.17 micromol/L) (P < 0.05). The expression of ET-1 mRNA of hypoxic rats strengthened obviously. However, mPAP was significantly decreased in hypoxic rats treated with L-arginine (2.23 kPa +/- 0.18 kPa) as compared with that of hypoxic rats (2.71 kPa +/- 0.29 kPa) (P < 0.05). L-arginine ameliorated pulmonary vascular structural remodeling of hypoxic rats in association with an increase in indirect plasma NO concentration (P < 0.05) and an inhibited ET-1 mRNA expression.. L-arginine plays an important role in the regulation of development of hypoxic pulmonary vascular remodeling and hypoxic pulmonary hypertension, promoting NO production and inhibiting ET-1 mRNA expression in hypoxic rats.

Topics: Animals; Arginine; Capillaries; Endothelin-1; Endothelium, Vascular; Gene Expression; Hypoxia; Male; Nitric Oxide; Pulmonary Artery; Pulmonary Wedge Pressure; Rats; Rats, Wistar; RNA, Messenger

These studies document striking pulmonary vasoconstrictor response to nitric oxide synthase (NOS) inhibition in monocrotaline (MCT) pulmonary hypertension in rats. This constriction is caused by elevated endothelin (ET)-1 production acting on ETA receptors. Isolated, red blood cell plus buffer-perfused lungs from rats were studied 3 wk after MCT (60 mg/kg) or saline injection. MCT-injected rats developed pulmonary hypertension, right ventricular hypertrophy, and heightened pulmonary vasoconstriction to ANG II and the NOS inhibitor NG-monomethyl-L-arginine (L-NMMA). In MCT-injected lungs, the magnitude of the pulmonary pressor response to NOS inhibition correlated strongly with the extent of pulmonary hypertension. Pretreatment of isolated MCT-injected lungs with combined ETA (BQ-123) plus ETB (BQ-788) antagonists or ETA antagonist alone prevented the L-NMMA-induced constriction. Addition of ETA antagonist reversed established L-NMMA-induced constriction; ETB antagonist did not. ET-1 concentrations were elevated in MCT-injected lung perfusate compared with sham-injected lung perfusate, but ET-1 levels did not differ before and after NOS inhibition. NOS inhibition enhanced hypoxic pulmonary vasoconstriction in both sham- and MCT-injected lungs, but the enhancement was greater in MCT-injected lungs. Results suggest that in MCT pulmonary hypertension, elevated endogenous ET-1 production acting through ETA receptors causes pulmonary vasoconstriction that is normally masked by endogenous NO production.

Topics: Angiotensin II; Animals; Drug Combinations; Endothelin-1; Endothelins; Enzyme Inhibitors; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; In Vitro Techniques; Lung; Male; Monocrotaline; Oligopeptides; omega-N-Methylarginine; Peptides, Cyclic; Piperidines; Rats; Rats, Sprague-Dawley; Vasoconstriction

The activities related to the flow of genetic information encoded in DNA in a cell are very orderly. This order, in a living cell, is achieved through specific, but noncovalent, interactions of varieties of structurally dynamic macromolecules under constantly changing physiological conditions. Hence, it is expected that there should be some force that can stabilize the multicomponent reaction processes and establish (or maintain) order in genetic regulatory functions under far-from-equilibrium conditions. The genetic regulatory functions in a cell, however, are believed to be energetically coupled. Expression of genes in a cell is often modulated under changing environmental conditions, raising the possibility of a state controlled nature of the genetic regulatory functions. Adenosine triphosphate (ATP) is the major free-energy contributor for these energy-consuming cellular activities. Enzymatic transfer of high-energy phosphate group from ATP to other reactive components is considered to be the chief mode of energy-transduction in a cell for various biosynthetic processes, as well as other activities related to the flow of information. In an effort to find a solution of the paradox, we assessed the contribution of physiological state of a cell in the process of maintaining order in genetic regulatory functions. As an approach, we systematically perturbed the normal energy flow of a cellular system (bovine aortic endothelial [BAE] cell) by a protein kinase inhibitor (staurosporine), and then followed the expression patterns of several constitutively-expressed protein-encoding genes to measure the effects. Staurosporine, as a function of its concentration, disintegrated the membrane structure of these cells, and eventually caused their death. These secondary consequences of staurosporine treatment offered two additional grossly altered physiological states of the cell to study. Under all of these dramatically altered energy states of the system, an extreme degree of functional coherence prevailed at every level of genetic regulatory function. Integrity at the level of gene transcription remained unaffected. Degradation rate of specific mRNA remained unaltered. Translational activities involving varieties of mRNA species continued in an well-ordered manner. Other state changes, resulting from nutrient and metabolic starvation, or inhibition of oxidative phosphorylation, in addition to the staurosporine treatments, also failed to disintegrate these ordered

Topics: Actins; Adenosine Triphosphate; Animals; Blotting, Northern; Cattle; Cell Membrane; Cell Nucleus; Cells, Cultured; Collagenases; Dose-Response Relationship, Drug; Endothelin-1; Endothelium; Enzyme Inhibitors; Gene Expression Regulation; Hypoxia; Luciferases; Protein Biosynthesis; Protein Kinase Inhibitors; Protein Synthesis Inhibitors; RNA, Messenger; Staurosporine; Time Factors

The effects of SB 217242, a non-peptide endothelin (ET) receptor antagonist, were investigated against hypoxia-induced cardiopulmonary changes in high altitude-sensitive rats. In isolated pulmonary artery rings, SB 217242 (30 n m) antagonized ET-1-induced contractions with a p KB of 8.0. There was no difference in the sensitivity to ET-1 or the potency of SB 217242 in pulmonary artery from normoxic rats vs. rats exposed to hypoxia (9% O2) for 14 days. However, there was a marked reduction in the maximum response to ET-1, but not to KCl or phenylephrine, in pulmonary artery from hypoxic rats; this phenomenon was inhibited by treatment of animals with SB 217242 (10.8 mg/day, ip by osmotic pump) for the 14-day hypoxic period. Furthermore, there was a significant reduction in carbachol-induced, endothelium-dependent relaxation of precontracted pulmonary artery from hypoxic animals; SB 217242 treatment during the hypoxic period did not influence this difference. Vehicle-treated rats exposed to 14-day hypoxia had 173% higher pulmonary artery pressures and 75% higher right/left+septum ventricular mass ratios compared to normoxic animals. SB 217242 (3.6 or 10.8 mg/day, ip) markedly reduced (80 and 95%, respectively) hypoxia-induced increases in pulmonary artery pressure. Right ventricular hypertrophy was inhibited by 40% at the 10.8 mg/day dose. Marked medial thickening and luminal stenosis of small and medium-sized pulmonary arteries was observed in hypoxic rats. The SB 217242-treated, hypoxia-exposed rats had comparable small and medium-sized arteries to normoxic rats. Rats treated with SB 217242 (10.8 mg/day) for the last 14 days of a 28-day hypoxic exposure had significantly lower pulmonary artery pressures than those of vehicle-treated rats. In addition, the effects of the selective ETA receptor antagonist, SB 247083, and the selective ETB receptor antagonist, A-192621 (3.6 or 10.8 mg/day, ip), were compared against hypoxia-induced increases in pulmonary artery pressure and plasma ET concentrations. SB 247083, but not A-192621, inhibited hypoxia-induced pulmonary hypertension, whereas A-192621, but not SB 247083, significantly exacerbated hypoxia-induced increases in ET concentrations, suggesting that hypoxia-induced pulmonary pressor responses are mediated via ETA receptor activation, while ETB receptor blockade may alter clearance of hypoxia-induced elevated plasma ET. The inhibitory effects of SB 217242 on the functional and remodeling changes induced by

Topics: Altitude; Animals; Benzofurans; Carboxylic Acids; Endothelin Receptor Antagonists; Endothelin-1; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Indans; Male; Propionates; Pulmonary Artery; Pyrrolidines; Random Allocation; Rats; Receptors, Endothelin

The effects of chronic hypoxia on the responses of rat large pulmonary arteries and veins to vasoactive agents have been examined. Endothelin-1-induced contractions of pulmonary arteries and pulmonary veins were reduced by chronic hypoxia. In contrast, chronic hypoxia augmented sarafotoxin 6c-induced contractile responses in pulmonary veins but not in pulmonary arteries. Chronic hypoxia augmented the constrictor effect of phenylephrine in pulmonary arteries, but not in pulmonary veins. The thromboxane receptor agonist, U46619 (9,11-dideoxy-9alpha,11alpha-epoxy-methanoprostaglandin++ + f2alpha) contracted pulmonary arteries and pulmonary veins, and although maximal responses were not altered in chronically hypoxic preparations, the EC50 value in pulmonary arteries was increased following chronic hypoxia. The relaxant effects of acetylcholine and isoprenaline on pulmonary arteries were potentiated by chronic hypoxia. In contrast, ionomycin-mediated relaxations of pulmonary arteries and pulmonary veins were reduced, while sodium nitroprusside-induced relaxation of pulmonary arteries and veins were not altered by chronic hypoxia. Previous studied have looked primarily at the effects of chronic hypoxia on pulmonary arteries. This data provides evidence that chronic hypoxia also causes selective changes in the reactivity of large pulmonary veins.

Topics: Animals; Endothelin-1; Hematocrit; Hypertrophy, Right Ventricular; Hypoxia; In Vitro Techniques; Male; Pulmonary Artery; Pulmonary Veins; Rats; Rats, Wistar; Time Factors; Vasoconstriction; Vasodilation

Endothelin-1 (ET-1) is a potent vasoconstrictor peptide produced by the vascular endothelium. The purpose of this study was to elucidate the pathophysiological role of ET-1 in patients with pulmonary hypertension secondary to chronic obstructive pulmonary disease (COPD).. We measured plasma ET-1 levels during right heart catheterization both at rest and during exercise on room air and while breathing oxygen in patients with COPD. In addition, we simultaneously measured plasma levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP).. Plasma ET-1 levels at rest were significantly higher in 21 patients with COPD than in 16 control subjects (p < 0.001). For COPD patients, there was no correlation between the plasma ET-1 level and pulmonary arterial pressure or pulmonary vascular resistance at rest. On the other hand, there was a significant negative correlation between plasma ET-1 level and mixed venous oxygen tension (r = -0. 503, p < 0.05). Also, the plasma ET-1 level was positively correlated with those of ANP (r = 0.540, p < 0.05) and BNP (r = 0. 533, p < 0.05) at baseline. Oxygen administration significantly decreased plasma ET-1 levels at rest (p < 0.05). Plasma ET-1 levels did not change significantly with exercise despite the progression of pulmonary hypertension and hypoxemia. In contrast, plasma ANP and BNP levels both increased markedly with exercise (p < 0.01).. We conclude that in patients with COPD, the plasma ET-1 level is not affected by acute progression of pulmonary hypertension and hypoxemia during exercise, and persistent hypoxemia may be associated with an increase in the plasma ET-1 level. In addition, our findings suggest that ANP and BNP may modulate the pulmonary vascular tone by interacting with ET-1 in these patients.

Topics: Aged; Atrial Natriuretic Factor; Endothelin-1; Exercise; Humans; Hypoxia; Lung Diseases, Obstructive; Male; Middle Aged; Natriuretic Peptide, Brain; Reference Values

This study aimed to investigate whether nitric oxide (NO) could inhibit the elevated endothelin-1 (ET-1) gene expression by pulmonary artery endothelial cells or smooth muscle cells in chronically hypoxic rats by use of in situ hybridization. Male Wistar rats (n = 40) were randomly divided into 1-week hypoxia group, 1-week hypoxia with L-arginine (L-arg) group, 1-week hypoxia with N(omega)-nitro-L-arginine methyl ester (L-NAME) group, 2-week hypoxia group, 2-week hypoxia with L-arg group, and 2-week hypoxia with L-NAME group. All rats were put into a normobaric hypoxic chamber with an oxygen concentration of 10 +/- 0.5% for hypoxic challenge. The results showed that most pulmonary arteries had 1-50% of the endothelial cells showing positive signals for ET-1 expression in hypoxic rats, which was significantly suppressed by L-arg. L-NAME, however, significantly augmented ET-1 gene expression in pulmonary artery endothelial cells and smooth muscle cells. The results suggest that endogenous NO markedly inhibits ET-1 mRNA expression in both pulmonary artery endothelial cells and smooth muscle cells in chronically hypoxic rats, which may be one of the mechanisms by which NO modulates hypoxic pulmonary circulation.

Topics: Animals; Arginine; Chronic Disease; Endothelin-1; Endothelium, Vascular; Enzyme Inhibitors; Gene Expression Regulation; Hypoxia; In Situ Hybridization; Male; Muscle, Smooth, Vascular; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Pulmonary Artery; Pulmonary Circulation; Random Allocation; Rats; Rats, Wistar; RNA, Messenger; Vasodilator Agents

The effects of transfer of the endothelial nitric oxide synthase (eNOS) gene to the lung were studied in mice. After intratracheal administration of AdCMVbetagal, expression of the beta-galactosidase reporter gene was detected in pulmonary airway cells, in alveolar cells, and in small pulmonary arteries. Gene expression with AdCMVbetagal peaked 1 day after administration and decayed over a 7- to 14-day period, whereas gene expression after AdRSVbetagal transfection peaked on day 5 and was sustained over a 21- to 28-day period. One day after administration of AdCMVeNOS, eNOS protein levels were increased, and there was a small reduction in mean pulmonary arterial pressure and pulmonary vascular resistance. The pressure-flow relationship in the pulmonary vascular bed was shifted to the right in animals transfected with eNOS, and pulmonary vasodepressor responses to bradykinin and the type V cGMP-selective phosphodiesterase inhibitor zaprinast were enhanced, whereas systemic responses were not altered. Pulmonary vasopressor responses to endothelin-1 (ET-1), angiotensin II, and ventilatory hypoxia were reduced significantly in animals transfected with the eNOS gene, whereas pressor responses to norepinephrine and U46619 were not changed. Systemic pressor responses to ET-1 and angiotensin II were similar in eNOS-transfected mice and in control mice. Intratracheal administration of AdRSVeNOS attenuated the increase in pulmonary arterial pressure in mice exposed to the fibrogenic anticancer agent bleomycin. These data suggest that transfer of the eNOS gene in vivo can selectively reduce pulmonary vascular resistance and pulmonary pressor responses to ET-1, angiotensin II, and hypoxia; enhance pulmonary depressor responses; and attenuate pulmonary hypertension induced by bleomycin. Moreover, these data suggest that in vivo gene transfer may be a useful therapeutic intervention for the treatment of pulmonary hypertensive disorders.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Adenoviridae; Angiotensin II; Animals; Antimetabolites, Antineoplastic; beta-Galactosidase; Bleomycin; Blood Flow Velocity; Blood Pressure; Bradykinin; Cyclic GMP; Endothelin-1; Gene Transfer Techniques; Genes, Reporter; Hypertension, Pulmonary; Hypoxia; Mice; Mice, Inbred Strains; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Norepinephrine; Phosphodiesterase Inhibitors; Pulmonary Alveoli; Pulmonary Artery; Pulmonary Circulation; Pulmonary Wedge Pressure; Purinones; Sympathomimetics; Vasoconstrictor Agents

The pulmonary vascular effects of the endothelium-derived peptide endothelin (ET) vary depending on the existing vascular tone, modes of administration and species studied; ET can cause both pulmonary vasodilatation and vasoconstriction. Increased plasma levels of ET have been reported in hypoxic pulmonary hypertension, although it is unclear whether ET is a mediator or a marker of hypoxia-induced increase in pulmonary vascular resistance (PVR). In our study, the plasma levels of ET-1 and the functional effects of ET-1 infusion in patients (n = 4) with chronic hypoxaemia and elevated PVR were evaluated. At rest, the arterial and venous ET-1-levels (13 +/- 2 and 12 +/- 1 fmol/ml, respectively) were significantly higher than those detected in venous plasma of an age-matched healthy control group (7 +/- 1 fmol/ml). Consecutive 10 min infusions of ET-1 at 1, 5, 10 and 15 ng/kg/min into the pulmonary artery decreased cardiac output (by 32%) and stroke volume (by 33%) and increased the systemic vascular resistance (by 62%) and arteriovenous oxygen difference (by 83%) at the highest dose. No deleterious effect was observed in the pulmonary circulation. The present study therefore suggests that intra-pulmonarily administered ET does not attenuate the increased PVR associated with chronic hypoxaemia.

Topics: Abdominal Pain; Aged; Carbon Dioxide; Cardiac Output; Case-Control Studies; Endothelin-1; Female; Humans; Hypertension, Pulmonary; Hypoxia; Male; Middle Aged; Oxygen; Partial Pressure; Vascular Resistance; Vasoconstriction

Endothelin (ET)-1 has been implicated as a critical mediator in the pathogenesis of hypoxic pulmonary hypertension. We questioned whether, during exposure to chronic hypobaric hypoxia, rat pulmonary artery smooth muscle cells (PASMC) became sensitized to ET-1. Two effects of ET-1, inhibition of voltage-gated K(+) (K(v)) channels and release of intracellular Ca(2+), were studied using whole cell patch clamp and single cell indo 1 fluorescence, respectively. In both normotensive and chronically hypoxic-hypertensive PASMC, ET-1 caused concentration-dependent inhibition of voltage-gated K(+) current [I(K(v))], with maximum inhibition of 12-18% seen at a concentration of 0.1-1 nM. Although the chronically hypoxic-hypertensive PASMC was no more susceptible to ET-1-mediated I(K(v)) inhibition, a switch in coupling between ET-1 and I(K(v)) from ET(B) to ET(A) receptors occurred. This switch in receptor coupling, combined with reduced I(K(v)) density and increased ET-1 production in the hypoxic rat lung, may help explain the ability of ET(A)-receptor blockers to attenuate the development of hypoxic pulmonary hypertension in vivo.

Topics: Animals; Antihypertensive Agents; Calcium; Chronic Disease; Electrophysiology; Endothelin Receptor Antagonists; Endothelin-1; Hypertension; Hypoxia; Male; Muscle, Smooth, Vascular; Oligopeptides; Peptides, Cyclic; Piperidines; Potassium Channel Blockers; Potassium Channels; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptors, Endothelin

Contractile responses to endothelin-1 (ET-1) were investigated in isolated trachea from rats previously exposed to chronic hypoxia (10% O(2)) or room air for 14 days. Concentration-response curves were constructed to ET-1 (10(-11)-3x10(-7)m ) in the presence and absence of the ET(A)receptor antagonist FR 139317 (10(-8), 10(-7)and 10(-6)m ), the ET(B)receptor antagonist BQ 788 (10(-6)and 3x10(-6)m ), the non-selective ET receptor antagonist SB 209670 (10(-7)and 10(-6)m ) and a combination of FR 139317 (10(-6)m ) and BQ 788 (10(-6)m ). Concentration-response curves were also conducted to the ET(B)receptor agonist sarafotoxin S6c (10(-11)-3x10(-7)m ). In addition, responses to ET-1 (10(-11)-3x10(-7)m ) were examined in the presence and absence of the nitric oxide synthase inhibitor, L-NAME. In control rat trachea, both FR 139317 and BQ 788 failed to inhibit ET-1-induced contractions and, indeed, FR 139317 (10(-8)m ) and BQ 788 actually potentiated responses. In trachea from chronic hypoxic rats, FR 139317 did not alter ET-1 responses whereas BQ 788 again potentiated ET-1-induced contractions. The non-selective ET receptor antagonist SB 209670 attenuated ET-1-evoked contractions in trachea from control and chronically hypoxic rats. A combination of FR 139317 (10(-6)m ) and BQ 788 (10(-6)m ) also attenuated ET-1 responses in control rat trachea, but not trachea from chronically hypoxic rats. In trachea from both control and chronically hypoxic rats, L-NAME significantly potentiated responses to ET-1. To investigate ET receptor-mediated relaxation, tissues were preconstricted with methacholine and concentration-response curves were conducted to ET-1 (10(-13)-10(-8)m ) in the presence and absence of BQ 788 (10(-6)m ) and to the ET(B)receptor agonist sarafotoxin S6c (10(-13)-10(-8)m ). In trachea from control and chronic hypoxic rats, ET-1 and sarafotoxin S6c evoked only very small, non-reproducible relaxatory responses.

Topics: Animals; Asthma; Bronchoconstriction; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelin-1; Hypoxia; Male; NG-Nitroarginine Methyl Ester; Rats; Rats, Wistar; Receptors, Endothelin; Trachea

The mechanism of Hypoxic Pulmonary Vasoconstriction is unknown. The role of endothelin-1 in hypoxic pulmonary vasoconstriction was studied in precontracted small and large pulmonary arteries using the endothelin ETA receptor antagonist sodium-2-benzol [1,3]dioxol-5-yl-4-(4-methoxyphenyl)-4-oxo-3-(3,4,5-trimethoxy-ben zyl)-but-2-enoate (CI-1020). Small rat pulmonary arteries exhibit a mixed endothelin ETA receptor and endothelin ETB2 receptor population whereas large rat pulmonary arteries contain only endothelin ETA receptors. CI-1020 inhibited endothelin-1 in small vessels via endothelin ETA receptor blockade (1 and 10 microM) and at high concentrations via endothelin ETA receptor and endothelin ETB2 receptor blockade (100 microM). CI-1020 (0.01, 0.1 and 1 microM) inhibited endothelin-1 in large vessels via endothelin ETA receptor blockade alone. CI-1020 (1, 10 and 100 microM) significantly reduced hypoxic pulmonary vasoconstriction in small vessels, by -9.8+/-1.4, -9.2+/-2.3 and -8.0+/-1.7% 80 mM K+, respectively, compared to +2.5+/-4.2% with vehicle (P < 0.05). CI-1020 (0.01, 0.1 and 1 microM) had no significant effect upon hypoxic pulmonary vasoconstriction in large vessels. In small, but not large, pulmonary arteries hypoxic pulmonary vasoconstriction is due in part to the action of endothelin-1 at the endothelin ETA receptor.

Topics: Animals; Dioxoles; Dose-Response Relationship, Drug; Endothelin Receptor Antagonists; Endothelin-1; Hypoxia; In Vitro Techniques; Male; Pulmonary Artery; Rats; Rats, Wistar; Receptor, Endothelin A; Vasoconstriction

To investigate the roles of endothelin-1 in the pathogenesis of hypoxic pulmonary hypertension, we studied the effects of a selective endothelin ET(A) receptor antagonist, TA-0201 (N-(6-(2-(5-Bromopyrimidin-2-yloxy) ethoxy)-5-(4-methylphenyl) pyrimidin-4-yl)-4-(2-hydroxy-1,1-dimethylethyl) benzensulfonamide sodium salt sesquihydrate), on helical strips of pulmonary arteries isolated from hypoxia-induced pulmonary hypertensive rats as compared with those of normoxic rats. Endothelin-1-induced maximum contractions were significantly inhibited by exposure to hypoxia in the pulmonary arterial strips, but not in the mesenteric arterial strips. The hypoxia also induced right ventricular hypertrophy in rats. Addition of TA-0201 to the bath inhibited the endothelin-1-induced contraction of pulmonary arterial strips isolated from hypoxic rats more effectively than in those of normoxic rats. Oral administration of TA-0201 to hypoxic rats inhibited the hypoxia-induced right ventricular hypertrophy, and decreased the maximum contractile response to endothelin-1 in pulmonary arterial strips isolated from these rats. Those inhibitory effects induced by the oral administration of TA-0201 were not observed in the pulmonary arteries from normoxic rats or in the mesenteric arteries from both hypoxic and normoxic rats. These results suggest that endothelin-1 has important pathophysiological roles in hypoxia-induced pulmonary hypertension, and that TA-0201 may inhibit the endothelin-l-induced contraction through a change in the function of endothelin ET(A) receptor as well as competitive inhibition for endothelin ET(A) receptor.

Topics: Animals; Endothelin Receptor Antagonists; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Male; Pulmonary Artery; Pyrimidines; Rats; Rats, Wistar; Receptor, Endothelin A; Sulfonamides; Vasoconstriction; Vasoconstrictor Agents

We tested the hypothesis that chronic hypoxia alters the regulation of K+ channels in intrapulmonary arterial smooth muscle cells (PASMCs). Charybdotoxin-insensitive, 4-aminopyridine-sensitive voltage-gated K+ (K(V,CI)) and Ca2+-activated K+ (KCa) currents were measured in freshly isolated PASMCs from rats exposed to 21 or 10% O2 for 17-21 days. In chronically hypoxic PASMCs, K(V, CI) current was reduced and KCa current was enhanced. 4-Aminopyridine (10 mM) depolarized both normoxic and chronically hypoxic PASMCs, whereas charybdotoxin (100 nM) had no effect in either group. The inhibitory effect of endothelin (ET)-1 (10(-7) M) on K(V,CI) current was significantly reduced in PASMCs from chronically hypoxic rats, whereas inhibition by angiotensin (ANG) II (10(-7) M) was enhanced. Neither ET-1 nor ANG II altered K(Ca) current in normoxic PASMCs; however, both stimulated K(Ca) current at positive potentials in chronically hypoxic PASMCs. These results suggest that although modulation of K(V,CI) and KCa channels by ET-1 and ANG II is altered by chronic hypoxia, the role of these channels in the regulation of resting membrane potential was not changed.

Topics: Angiotensin II; Animals; Chronic Disease; Electric Conductivity; Endothelin-1; Heart Ventricles; Hypoxia; Male; Muscle, Smooth, Vascular; Myocardium; Organ Size; Potassium Channels; Pulmonary Artery; Rats; Rats, Wistar

To investigate the beta-adrenoceptor-mediated responses in hypoxic coronary arteries, we studied the effect of isoproterenol (Iso) on isolated porcine coronary arteries contracted with endothelin-1 in media aerated with 0, 5, 7.5, and 95% O(2). The concentration-response curve of Iso was significantly shifted to the left by hypoxia (0 and 5% O(2)). In oxygenated and hypoxic arteries, 3 x 10(-8), 10(-6), and 10(-5) M Iso significantly increased the contents of cAMP. However, there was no difference in the increases of cAMP content induced by 3 x 10(-8) M Iso between oxygenated and hypoxic arteries. The content of cAMP induced by high concentrations of Iso (10(-6) and 10(-5) M) was significantly larger in hypoxic than in oxygenated arteries. Furthermore, the potentiation by hypoxia of the Iso-induced vasorelaxation was inhibited by glibenclamide and depolarization by KCl, but not by removal of endothelium and indomethacin. The vasodilatory response to forskolin and dibutyryl cAMP was unaffected by hypoxia. We conclude that activation of the ATP-sensitive K(+) channel may account for the potentiation of the response to Iso in hypoxic coronary arteries.

Topics: Animals; Arteries; Coronary Vessels; Cyclic AMP; Endothelin-1; Glyburide; Hypoxia; In Vitro Techniques; Isoproterenol; Oxygen; Potassium Chloride; Receptors, Adrenergic, beta; Swine; Vasoconstrictor Agents; Vasodilation; Vasodilator Agents

Peptide growth factors are involved in hypoxia-mediated neonatal pulmonary vascular remodeling. The role of hypoxia in the release of selected peptide growth factors from neonatal porcine pulmonary artery smooth muscle cells (PASMC) was examined. PASMC were exposed to different oxygen tensions and the cells were counted electronically and the conditioned media analyzed for basic fibroblast growth factor (bFGF), endothelin-1 (ET-1), platelet-derived growth factor (PDGF), and vascular endothelial growth factor (VEGF). The effect of conditioned media on PASMC proliferation was also measured. Hypoxia (1% oxygen) and hypoxia-conditioned media increased PASMC numbers, and this mitogenic effect was abolished by anti-bFGF, but not by anti-PDGF or anti-VEGF. Hpyoxia increased bFGF and VEGF release but not PDGF or ET-1. This suggests that PASMC-derived bFGF and VEGF may participate in hypoxic neonatal pulmonary vascular remodeling.

Topics: Animals; Animals, Newborn; Blotting, Western; Cell Count; Cell Division; Cells, Cultured; Culture Media, Conditioned; Endothelial Growth Factors; Endothelin-1; Enzyme-Linked Immunosorbent Assay; Fibroblast Growth Factor 2; Growth Substances; Hypoxia; L-Lactate Dehydrogenase; Lymphokines; Muscle, Smooth, Vascular; Platelet-Derived Growth Factor; Pulmonary Artery; Swine; Trypan Blue; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors

The effects of the outward rectifying potassium channel blocker, 4-aminopyridine, on contractile tone and on contractile responses to the spasmogens, 5-hydroxytryptamine and endothelin-1, were examined in pulmonary arteries (main and intralobar) and systemic vessels (aorta and mesenteric artery) from rats with and without hypoxic pulmonary hypertension. Hypoxic pulmonary hypertension was induced by exposure of rats to 10% oxygen for 1 week. The development of pulmonary hypertension was associated with (i) depolarization of the cell membrane in intralobar pulmonary artery, but not aorta, and (ii) an increase in sensitivity to 5-hydroxytryptamine in pulmonary, but not systemic, vessels; sensitivity to endothelin-1 was unchanged. 4-Aminopyridine contracted all of the vessels studied. In pulmonary hypertension the sensitivity to 4-aminopyridine was increased ten-fold in pulmonary vessels but was unchanged in systemic vessels. Threshold concentrations of 4-aminopyridine (< or =3x10(-3) M) augmented contractions to 5-hydroxytryptamine in main pulmonary artery and aorta from control rats but failed to augment contractions to 5-hydroxytryptamine in main pulmonary artery from pulmonary hypertensive rats. Responses to endothelin-1 were not augmented by 4-aminopyridine. The membrane depolarization and the increases in sensitivity to 4-aminopyridine and 5-hydroxytryptamine seen in pulmonary hypertension are compatible with the concept that potassium channel function is altered in pulmonary, but not systemic, vessels from pulmonary hypertensive rats. Our data suggest that in main pulmonary artery a common mechanism is responsible for (i) the augmentation of 5-hydroxytryptamine responses by 4-aminopyridine in control rats, and (ii) the sensitization to 5-hydroxytryptamine seen in pulmonary hypertensive, compared with control, rats in the absence of 4-aminopyridine. Hence, we conclude that the sensitization to 5-hydroxytryptamine may be due to downregulation of 4-aminopyridine-sensitive potassium channels.

Topics: 4-Aminopyridine; Animals; Aorta; Arteries; Endothelin-1; Hypertension, Pulmonary; Hypoxia; In Vitro Techniques; Male; Membrane Potentials; Mesenteric Arteries; Potassium Channel Blockers; Pulmonary Artery; Rats; Rats, Wistar; Serotonin; Vasoconstriction

Endothelin-1 (ET-1) is a potent vasoconstrictor and comitogen implicated in the pathogenesis of pulmonary hypertension (PH). We evaluated the effects of an ET(A)receptor-selective antagonist, ZD1611, on hypoxia-induced PH in rats. <> and <> paradigms were established in which rats were administered placebo or ZD1611 (1-3 mg/kg, q.i.dpo) concomitant with hypoxic exposure (10% O(2)1 ATM) for 14 days or beginning after 7-day hypoxic exposure for 21 days. Compared with normoxic controls, hypoxic exposure plus placebo increased (P<0.05) hematocrit, mass ratio of right ventricle over left ventricle plus septum (RV/LV+S), and right intraventricular peak systolic pressure (RVSP). These latter two effects were decreased (P<0.05) by ZD1611 in both experimental paradigms [RV/LV+S(%)::RVSP(%); prophylactic, 14::32; therapeutic, 28::37]. Hypoxic exposure did not change mean systemic arterial pressure (MSAP). ZD1611 did not affect MSAP, plasma ET-1 concentrations, or blood gases measured when rats respired room air. In mechanistic studies, ZD1611 decreased (P<0.01) smooth muscle hypertrophy of small pulmonary arteries and abolished hypoxia-induced decreases in sensitivity and maximum contraction to ET-1 in isolated extralobar branch pulmonary artery. In conclusion, the ET(A)receptor-selective antagonist, ZD1611, attenuates hypoxia-induced PH in the rat.

Topics: Anesthesia; Animals; Blood Gas Analysis; Blood Pressure; Endothelin Receptor Antagonists; Endothelin-1; Hematocrit; Hypertension, Pulmonary; Hypoxia; Isometric Contraction; Male; Muscle, Smooth, Vascular; Organ Size; Pulmonary Artery; Pulmonary Circulation; Pyrazines; Radioimmunoassay; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Sulfonamides; Ventricular Function, Right

Experimental pulmonary hypertension induced in a hypobaric hypoxic environment (HHE) is characterized by structural remodeling of the heart and pulmonary arteries. Endothelin-1 (ET-1), a 21-amino acid peptide, is a novel and long-lasting vasoconstrictor that increases pulmonary arterial pressure in both in vivo and in vitro experiments. To study the effects of HHE on ET-1 activity in the lungs, 59 male rats were subjected to the equivalent of an altitude of 5500 m for 1 to 4 weeks. In rats exposed to HHE, the mean pulmonary arterial pressure increased significantly from 15.2+/-0.3 (ground level) to 30.6+/-1.5 mm Hg (5500-m level) at 4 weeks, whereas their mean systemic arterial pressure remained normal. The levels of ET-1 mRNA and protein, measured respectively by Northern blot analysis and enzyme immunoassay, increased rapidly in the lungs on exposure to HHE. By in situ hybridization and immunohistochemistry, respectively, ET-1 mRNA and protein were detected in control rats in nonciliated bronchiolar epithelial cells and alveolar epithelial cells, as well as in the endothelial cells of pulmonary arteries, but minimally in the smooth muscle cells of pulmonary arteries. ET-1 mRNA- and protein-reactive smooth muscle cells in pulmonary arteries and ET-1 mRNA-reactive airway epithelial cells were significantly more abundant in rats exposed to HHE than in ground level controls. These results suggest the possibility that in smooth muscle cells in pulmonary arteries and airway epithelial cells, ET-1 may play an autocrine or paracrine role in the remodeling of blood vessels during the development of the pulmonary hypertension that is induced by HHE.

Topics: Altitude; Animals; Blood Pressure; Endothelin-1; Endothelins; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Immunohistochemistry; In Situ Hybridization; Lung; Male; Osmolar Concentration; Protein Precursors; Pulmonary Artery; Rats; Rats, Wistar; Reference Values; RNA, Messenger; Tunica Media

Acute hypoxia results in increased pulmonary vascular resistance. Despite reoxygenation, pulmonary vascular resistance remains elevated and pulmonary function is altered. Endothelin-1 might contribute to hypoxia-reoxygenation-induced pulmonary hypertension and to reoxygenation injury by stimulating leukocytes. This study was carried out using an established model of hypoxia and reoxygenation to determine whether endothelin-1 blockade with Bosentan could prevent hypoxia-reoxygenation-induced pulmonary hypertension and reoxygenation injury.. Twenty neonatal piglets underwent 90 minutes of hypoxia, 60 minutes of reoxygenation on cardiopulmonary bypass, and 2 hours of recovery. Control animals (n = 12) received no drug treatment, whereas the treatment group (n = 8) received the endothelin-1 receptor antagonist, Bosentan, throughout hypoxia.. In controls, pulmonary vascular resistance increased during hypoxia to 491% of baseline and remained elevated after reoxygenation; however in the Bosentan group, it increased to only 160% of baseline by end-hypoxia, then decreased to 76% at end-recovery. Arterial endothelin-1 levels in controls increased to 591% of baseline after reoxygenation. Arterial nitrite levels decreased during hypoxia in controls but were maintained in the Bosentan group. Consequently, animals in the Bosentan group had better postreoxygenation pulmonary vascular resistance, A-a gradient, and airway resistance along with lower myeloperoxidase levels than controls.. Acute hypoxia and postreoxygenation pulmonary hypertension was attenuated by Bosentan, which maintained nitric oxide levels during hypoxia, decreased leukocyte-mediated injury, and improved pulmonary function.

Topics: Animals; Animals, Newborn; Antihypertensive Agents; Bosentan; Cardiopulmonary Bypass; Endothelin Receptor Antagonists; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Nitric Oxide; Oxygen; Pulmonary Artery; Receptor, Endothelin A; Receptors, Endothelin; Sulfonamides; Swine; Vascular Resistance

We investigated the effect of chronic hypoxia (10% O(2) for 14 days) on airway responsiveness in rats. Chronic hypoxia significantly (P<0. 05, P<0.01, P<0.01, respectively) attenuated contractions evoked by methacholine (10(-9)-3x10(-4) M), endothelin-1 (10(-10)-3x10(-7) M) and potassium chloride (10(-3)-7x10(-2) M) in rat isolated trachea. To investigate this attenuation, we studied the effect of epithelial removal, indomethacin (3x10(-6) M), and L-nitro arginine methyl ester (L-NAME, 10(-4) M), on contractile responses in control and chronically hypoxic rat trachea. Indomethacin did not alter contractions evoked by methacholine or endothelin-1 in control or hypoxic rats. In contrast, epithelial removal and L-NAME both significantly potentiated responses to methacholine and endothelin-1 in trachea from control and chronically hypoxic rats. In separate experiments, tracheal rings were first contracted with methacholine (10(-6) M) and then relaxed, either by the nitric oxide donor sodium nitroprusside or by the beta(2)-adrenoceptor agonist, salbutamol. Sodium nitroprusside was significantly (P<0.001) more effective at reversing induced tone in tracheal rings from chronically hypoxic than control rats. Salbutamol, however, was equally effective in chronically hypoxic and control rats. These results suggest that, in trachea from both control and chronically hypoxic rats, contractile responses to methacholine and endothelin-1 are inhibited by nitric oxide, probably released from the epithelium. The attenuation of contractile responses in airways from chronically hypoxic rats may be due to an enhanced guanylyl cyclase activity and hence, an increased response to nitric oxide.

Topics: Albuterol; Animals; Bronchi; Bronchoconstrictor Agents; Bronchodilator Agents; Cyclooxygenase Inhibitors; Dose-Response Relationship, Drug; Endothelin-1; Enzyme Inhibitors; Epithelium; Hypoxia; In Vitro Techniques; Indomethacin; Male; Methacholine Chloride; Muscle Contraction; Muscle Relaxation; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitroprusside; Potassium Chloride; Rats; Rats, Wistar; Trachea

The mammalian carotid body (CB) contains O2-chemoreceptors, i.e. glomus cells, which display increased mitoses and endothelin-1 (ET-1) expression during chronic hypoxia. To investigate whether endogenous ET-1 might mediate these mitogenic effects, we quantified bromodeoxyuridine (BrdU) uptake by tyrosine hydroxylase (TH)-positive glomus cells in rat CB cultures using double-label immunofluorescence. In normoxia (20% O2), 2-day exposure to ET-1 (10-1000 nM) caused a dose-dependent increase in BrdU uptake which peaked (approximately 55% of TH+ cells) at around 500 nM ET-1. In chronic hypoxia (5% O2) alone, BrdU uptake was stimulated (approximately 46% of TH+ cells) relative to normoxia (approximately 30%), but the effect was abolished in the presence of specific (BQ 123) or non-specific (PD 142893) ETA receptor antagonists (10(-5) M). Thus paracrine/autocrine release of ET-1 in the hypoxic carotid body may promote glomus cell mitosis via ET(A) receptors.

Topics: Animals; Bromodeoxyuridine; Carotid Body; Cell Survival; Cells, Cultured; Chemoreceptor Cells; Chronic Disease; Endothelin-1; Hypoxia; Mitosis; Rats; Receptor, Endothelin A; Receptors, Endothelin; Reference Values

To study the interrelation between nitric oxide (NO) and endothelin-1 (ET1) in experimental acute hypoxic rats, and to evaluate the mechanism of acute hypoxic pulmonary hypertension affected by NO and ET1 and its intervention.. Nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase histochemical staining method, Griess biochemical assay and radioimmune assay were applied to investigate the changes of nitric oxide syntheses (NOS), NO and ET1 in normal, hypoxic, and L-Arginine (L-Arg) and dexamethasone treated hypoxic rats.. In normal rats, the NOS stain was localized in pulmonary vascular endothelium, and in the hypoxic rats, the activity of NOS was significantly lower. The level of plasma NO was significantly lower during acute hypoxia, but L-Arg as well as dexamethasone could prevent the drop of plasma NO. The level of plasma ET1 rose up significantly in the acute hypoxic rats, but after L-Arg therapy, it was significantly reduced, however, dexamethasone could not affect plasma ET1. The level of plasma cyclic guanosine monophosphate (cGMP) was significantly lower in the acute hypoxic rats, and L-Arg could prevent the drop of plasma cGMP, but dexamethasone could not prevent the drop of plasma cGMP.. NO and ET1 may modulate hypoxic pulmonary hypertension and acute hypoxia can result in acute hypoxic pulmonary hypertension. L-Arg can reverse the acute hypoxic pulmonary hypertension. Further study is needed if dexamethasone is beneficial in acute hypoxic diseases. NO may play an important role in physiology of the lung and acute hypoxic diseases.

Topics: Animals; Arginine; Dexamethasone; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Male; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Rats

Renal endothelin-1 (ET-1 ) production is increased by hypoxia and has been implicated in ischemia-induced renal hypoperfusion. Because the inner medullary collecting duct (IMCD) is a major source of ET- 1 in the kidney, and because ET- 1--in the setting of ischemic renal failure-may alter medullary perfusion, we sought to determine whether hypoxia modulated ET-1 production by IMCD cells. Primary cultures of rat IMCD cells were exposed to 21%, 3%, or 0%O2. IMCD ET-1 secretion significantly increased after exposure of cultures to 3% O2 (114.1% +/- 4.7% increase over control value) and 0%O2 (171.7% +/- 7.9% increase). ET-1 mRNA levels, as determined by reverse transcription-polymerase chain reaction, also increased 2.5-fold after 24-hour exposure to 0% O2. We speculate that a hypoxia-induced increase in IMCD ET-1 production plays a role in modulating renal medullary perfusion during ischemic renal failure.

Topics: Animals; Culture Techniques; Endothelin-1; Gene Expression; Hypoxia; Kidney Medulla; Kidney Tubules, Collecting; Male; Rats; Rats, Sprague-Dawley; Reperfusion Injury; RNA, Messenger

1. The effect of basal tension (transmural tensions 235 +/- 29 mg wt (low tension: equivalent to approximately 16 mmHg) and 305 +/- 34 mg wt (high tension: equivalent to 35 mmHg)) on rat pulmonary resistance artery responses to endothelin-1 (ET-1) and the selective ET(B)-receptor agonist sarafotoxin S6c (S6c) were studied. The effects of nitric oxide synthase inhibition with N(omega)-nitro-L-arginine methylester (L-NAME, 100 microM) on ET receptor-induced responses, as well as vasodilator responses to acetylcholine (ACh) and S6c, were also investigated. Changes with development of pulmonary hypertension, induced by two weeks of chronic hypoxia, were determined. 2. Control rat preparations showed greatest sensitivity for ET-1 when put under low tension (pEC50: 8.1 +/- 0.1) compared with at the higher tension (pEC50: 7.7 +/- 0.1) and there were significant increases in maximum contractile responses to S6c (approximately 80%) and noradrenaline (approximately 60%) when put under high tension. 3. In control pulmonary resistance arteries, both ET-1 and S6c produced potent vasoconstrictor responses. S6c was 12 fold more potent than ET-1 in vessels set at low tension (S6c pEC50: 9.2 +/- 0.1) and 200 fold more potent than ET-1 when the vessels were set at high tension (S6c pEC50: 9.0 +/- 0.1). Chronic hypoxia did not change the potencies of ET-1 and S6c but did significantly increase the maximum contractile response to ET-1 by 60% (at low tension) and 130% (at high tension). 4. In control rat vessels, L-NAME itself caused small increases in vascular tone (5-8 mg wt tension) in 33-56% of vessels. In the chronic hypoxic rats, in vessels set at high tension, L-NAME-induced tone was evident in 88% of vessels and had increased to 26.9 +/- 6.6 mg wt tension. Vasodilatation to sodium nitroprusside, in non-preconstricted vessels, was small in control rat vessels (2-6 mg wt tension) but increased significantly to 22.5 +/- 8.0 mg wt tension in chronic hypoxic vessels set at the higher tensions. Together, these results indicate an increase in endogenous tone in the vessels from the chronic hypoxic rats which is normally attenuated by nitric oxide production. 5. L-NAME increased the sensitivity to S6c 10 fold (low tension) and 6 fold (high tension) only in chronic hypoxic rat pulmonary resistance arteries. It had no effect on responses to ET-1 in any vessel studied. 6. Vasodilatation of pre-contracted vessels by ACh was markedly greater in the pulmonary resistance arteries fr

Topics: Animals; Endothelin-1; Endothelium, Vascular; Hypertension, Pulmonary; Hypoxia; In Vitro Techniques; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide; Pulmonary Artery; Rats; Rats, Wistar; Vasodilator Agents; Viper Venoms

The purpose of the study was to describe endothelin (ET) production and to characterize the effect of hypoxia on preproendothelin-1 (preproET-1) messenger ribonucleic acid (mRNA) expression and ET secretion by rat type II pneumocytes in vitro. Rat type II pneumocytes were incubated in a sealed chamber containing a normoxic (21% O2) or hypoxic (1% O2) atmosphere for increasing durations. Immunoreactive ET (irET) was measured in cell supernatants using a radioimmunoassay. Rat preproET-1 mRNA was detected by Northern blot. Rat type II pneumocytes expressed preproET-1 mRNA, contained irET and secreted irET in a time-dependent manner. ET secretion was dependent on de novo ribonucleic acid (RNA) and protein synthesis. Hypoxia decreased irET secretion by 27% and reduced the steady-state level of preproET-1 mRNA by 60% whereas intracellular irET concentration was unchanged. Inhibition was partially reversible with the return to a normoxic atmosphere. Inhibition of nitric oxide synthesis did not prevent the inhibitory effect of hypoxia. In conclusion, rat type II pneumocytes in primary culture secreted immunoreactive endothelin and expressed preproendothelin-1 messenger ribonucleic acid. Hypoxia reversibly reduced endothelin-1 production through a reduction of the steady-state preproendothelin-1 messenger ribonucleic acid level. Nitric oxide synthesis did not mediate the inhibitory effect of hypoxia.

Topics: Animals; Cell Survival; Cells, Cultured; Endothelin-1; Endothelins; Hypoxia; Male; Nitric Oxide; Protein Precursors; Pulmonary Alveoli; Radioimmunoassay; Rats; Rats, Sprague-Dawley; Reference Values; RNA, Messenger; Time Factors

Recent studies suggest that the vasoactive peptides endothelin-1 and -3 and the mitogens VEGF and PDGF-A and -B could be involved in the pathogenesis of hypoxic pulmonary hypertension. We were interested to investigate whether these peptides could also be involved in the vascular remodeling occurring during chronic hypoxia (10% oxygen; 1 and 3 weeks) in the rat. Hypoxia increased significantly systolic right ventricular pressure and typical morphological signs of vascular remodeling were found. This was accompanied by increased ET-1 and the ET-3 mRNA expression after acute (6 h; P < 0.05) and chronic hypoxia of 1 (P < 0.05) and 3 weeks (P < 0.05). In contrast, we found no effects of hypoxia on the gene expression of VEGF and PDGF-A and -B in the lung. Our findings indicate that ET-3 in addition to ET-1 could be involved in the process of hypoxia-induced vascular remodeling, whereas it appears less likely that the mitogens VEGF and PDGF-A and -B are essentially involved in the pathogenesis of hypoxic pulmonary hypertension.

Topics: Animals; Endothelial Growth Factors; Endothelin-1; Endothelin-3; Gene Expression; Growth Substances; Hypertension, Pulmonary; Hypoxia; Lung; Lymphokines; Male; Platelet-Derived Growth Factor; Pulmonary Circulation; Rats; Rats, Wistar; RNA, Messenger; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors

Hypoxia (0% O2) evokes a late-phase, endothelium-dependent contractile response in porcine isolated pulmonary arteries that may be caused by a cyclooxygenase-independent, endothelium-derived contractile factor. The aim of this study was to further analyze the mechanism underlying this hypoxic response. Proximal porcine pulmonary arterial rings were suspended for isometric tension recording in organ chambers. Hypoxia (0% O2) caused a late-phase, endothelium-dependent contractile response that was not inhibited by the endothelin (ET)A-receptor antagonist BQ-123 (10(-6) M), by the ETB-receptor antagonist BQ-788 (10(-7) M), or by their combination. In contrast, ET-1 caused a concentration-dependent contraction of arterial rings that was inhibited by BQ-123 (10(-6) M) and a relaxation that was abolished by BQ-788 (10(-7) M) or by endothelial cell removal. Therefore, the endothelium-dependent contraction to hypoxia is not mediated by ET. Hypoxia caused only relaxation in endothelium-denuded rings. However, when a pulmonary valve leaflet, a rich source of pulmonary endothelial cells, was placed into the lumen of endothelium-denuded rings, hypoxia caused a late-phase contractile response that was similar to that observed in arterial rings with native endothelium. This hypoxic contraction persisted in the presence of indomethacin (10(-5) M) and N-nitro-L-arginine methyl ester (3 x 10(-5) M) to block cyclooxygenase and nitric oxide synthase, respectively. These results suggest that hypoxic contraction of pulmonary arteries is mediated by a diffusible, contractile factor released from hypoxic endothelial cells. This contractile mediator is distinct from ET.

Topics: Animals; Endothelin Receptor Antagonists; Endothelin-1; Endothelins; Endothelium, Vascular; Hypoxia; In Vitro Techniques; Male; Pulmonary Artery; Pulmonary Valve; Swine; Time Factors; Vasoconstriction

The effect of hypoxic shock on the ability of endothelin (ET) receptors to interact with the cAMP second messenger system was assessed in rat pulmonary arteries. Whole pieces of tissue were dissected from the pulmonary arterial system of control and hypoxic (10% O2, 14 days) rats, incubated, where appropriate, with ET-1 (0.1 microM), and the levels of intracellular cAMP measured. Maintenance of rats under hypoxic conditions significantly reduced the basal cAMP levels in all of the arterial branches with the exception of the pulmonary resistance vessels, in which no change was observed. Incubation of the main and first branch extralobar pulmonary arteries from control rats with ET-1 resulted in a consistent decrease in the levels of intracellular cAMP. The ETA receptor antagonist FR139317 partially blocked this ET-1-mediated inhibition of cAMP accumulation in the main extralobar artery. In contrast, ET-1 caused a threefold increase in the levels of this cyclic nucleotide in the pulmonary resistance vessels from the normoxic rat. No ET-1-mediated reduction in intracellular cAMP levels was observed in any of the vessels isolated from hypoxic animals. All vessels showed ligand-activated increases in cAMP production. These results suggest differential modulation of cAMP in the different pulmonary arteries, either by direct activation through Gi and Gs or indirectly via a uncharacterized cross-talk mechanism.

Topics: Animals; Azepines; Chronic Disease; Cyclic AMP; Endothelin Receptor Antagonists; Endothelin-1; Hypoxia; Indoles; Male; Pulmonary Artery; Rats; Rats, Wistar; Signal Transduction

We previously showed that CI-1020, an endothelin (ET)-A-selective receptor antagonist, dose-dependently blocked acute hypoxic pulmonary hypertension (PH) in rats. In this study we show that CI-1020 can reverse existing PH and prevent progression of right ventricular hypertrophy (RVH) in rats exposed to chronic hypoxia. Male Sprague-Dawley rats were exposed to 20 days of hypoxia (10% O2) with CI-1020 treatment (20 or 40 mg/kg/day) starting on day 10. On day 20 of hypoxia, the rats were instrumented under anesthesia with a pulmonary artery cannula and allowed to recover to consciousness before measurement of mean pulmonary arterial pressure (MPAP). Blood samples were then collected for plasma ET-1 measurements, the rats killed, and their hearts dissected, dried, and weighed. RV/LV + septum ratio (g/g) was used as an index of RVH (RVHi). Normoxic rats and rats exposed to hypoxia for only 10 days were also evaluated as controls. Normoxic rats had MPAPs of 13 +/- 1 mm Hg, plasma ET-1 levels of 2.1 +/- 0.1 pg/ml, and an average RVHi of 0.29 +/- 0.03. Rats exposed to 10 or 20 days of hypoxia had MPAPs of 33 +/- 2 and 44 +/- 0 mm Hg, plasma ET-1 levels of 4.2 +/- 0.8 and 4.6 +/- 0.8 pg/ml, and average RVHis of 0.47 +/- 0.05 and 0.52 +/- 0.03, respectively. In comparison, rats treated with CI-1020 had MPAPs that were 37% (20 mg/kg/day) and 44% (40 mg/kg/day) lower than untreated 20-day hypoxic rats. Furthermore, rats dosed with 40 mg/kg/day of CI-1020 had MPAPs that were significantly lower (24%) than control 10-day hypoxic rats, indicating a significant reversal of PH. Along with this reversal in PH, their average RVHi was 23% lower (p < 0.05) relative to untreated 20-day hypoxic rats.

Topics: Animals; Blood Pressure; Cardiomegaly; Chronic Disease; Dioxoles; Endothelin Receptor Antagonists; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Male; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A

Our study was designed to elucidate the effects of tetramethylpyrazine (TMP), a Chinese medicine, on plasma endothelin-1 (ET-1) levels in dogs with acute pulmonary alveolar hypoxia. Anesthetized dogs were used under artificial ventilation with room air or a hypoxic gas mixture (10% O2 and 90% N2) (n = 10) for 60 min. Effects of TMP (80 mg/kg) were studied by i.v. injection of TMP before exposure to hypoxia (n = 8). Mean pulmonary arterial pressure (PAPm), systemic arterial pressure (SAPm), right atrial pressure (RAP), pulmonary capillary wedge pressure (PCWP), cardiac output (CO), and heart rate (HR) were measured. The pulmonary vascular resistance (PVR) was calculated by the equation of (PAPm-PCWP) x 8/CO. Plasma ET-1 levels were determined in the abdominal aorta and pulmonary artery by RIA. The effects of TMP on PAP and plasma ET-1 level were evaluated by using percent increase in PAPm and the change of Da-pET (delta ET) before and after hypoxia. Both PAPm and PVR were significantly elevated 5 min after acute hypoxia over a period of 60 min, whereas CO and PCWP did not change. Plasma ET-1 levels in the abdominal aorta and Da-pET showed a significant increase. Administration of TMP significantly decreased the hypoxia-induced increase in the PAPm, PVR, and delta ET. These results suggest that TMP could be a useful therapeutic agent in the treatment of pulmonary hypertension induced by acute hypoxia through decrease of plasma ET-1 levels.

Topics: Anesthesia, General; Animals; Blood Pressure; Dogs; Drugs, Chinese Herbal; Endothelin-1; Hemodynamics; Hypoxia; Lung Diseases; Pulmonary Alveoli; Pulmonary Circulation; Pyrazines; Vascular Resistance; Vasodilator Agents

1. We examined the endothelin (ET) receptors mediating contractions to ET-1, ET-3 and sarafotoxin S6c (SX6c) in rat pulmonary resistance arteries by use of peptide and non-peptide ET receptor antagonists. Changes induced by pulmonary hypertension were examined in the chronically hypoxic rat. The effect of the mixed ET(A)/ET(B) receptor antagonist SB 209670 on endothelin-mediated contraction was also examined in human pulmonary resistance arteries. 2. In rat vessels, the order of potency for the endothelin agonists was SX6c = ET-3 > ET-1 (pEC50 values in control rats: 9.12+/-0.10, 8.76+/-0.14 and 8.12+/-0.04, respectively). Maximum contractions induced by ET-3 and ET-1 were increased in vessels from chronically hypoxic rats. 3. The ET(A) receptor antagonist FR 139317 (1 microM) had no effect on the potency of ET-1 in any vessel studied but abolished the increased response to ET-1 in the chronically hypoxic vessels. The ET(A) receptor antagonist BMS 182874 (1 microM) increased the potency of ET-1 in control rat vessels without effecting potency in the pulmonary hypertensive rat vessels. 4. Bosentan (non-peptide mixed ET(A)/ET(B) receptor antagonist) increased the potency of ET-1 in control rat vessels but was without effect in the pulmonary hypertensive rat vessels. Bosentan (1 microM) inhibited responses to SX6c in control and chronically hypoxic rat vessels with pKb values of 5.84 and 6.11, respectively. The ET(B) receptor antagonist BQ-788 (1 microM) did not inhibit responses to ET-1 in any vessel tested but did inhibit responses to both SX6c and ET-3 (pKb values in control and chronically hypoxic rat vessels respectively: SX6c 7.15 and 7.22; ET-3: 6.68 and 6.89). BQ-788 (1 microM) added with BMS 182874 (10 microM) did not inhibit responses to ET-1 in control vessels but caused a significant inhibition of responses to ET-1 in chronically hypoxic preparations. 5. SB 209670 inhibited responses to ET-1 in both control and chronically hypoxic vessels with pKb values of 7.36 and 7.39, respectively. SB 209670 (0.1 and 1 microM) virtually abolished responses to ET-1 in the human pulmonary resistance artery. 6. In conclusion, in rat pulmonary resistance arteries, vasoconstrictions induced by ET-1, SX6c and ET-3 are mediated predominantly by activation of an ET(B)-like receptor. However, lack of effect of some antagonists on ET-1 induced vasoconstriction suggests that ET-1 stimulates an atypical ET(B) receptor. The increase in potency of ET-1 in the presence of s

Topics: Animals; Chronic Disease; Endothelin Receptor Antagonists; Endothelin-1; Endothelin-3; Humans; Hypoxia; In Vitro Techniques; Indans; Male; Muscle Contraction; Pulmonary Artery; Rats; Rats, Wistar; Receptors, Endothelin; Vascular Resistance; Vasoconstriction

Elevated levels of the potent vasoactive peptide endothelin (ET), have been found in pathophysiological conditions associated with pulmonary hypertension. In this study, we have investigated the effects of the ETA receptor antagonist, BMS-182874, on hypoxic pulmonary hypertension in pigs.. Pigs were subjected to acute, intermittent 15-min periods of hypoxia (FiO2 0.1). Following a first hypoxia establishing hypoxic baseline values, vehicle or BMS-182874 (10 or 30 mg/kg) was administered i.v. before a second hypoxic period. In separate groups of animals, the effects of the nitric oxide synthase inhibitor N omega-nitro-L-arginine (L-NNA) in combination with BMS-182874 (10 mg) during repeated hypoxia were investigated. The ET-1-blocking properties of BMS-182874 were studied in vivo by infusion of ET-1 during normoxia and in vitro using isolated porcine pulmonary arteries.. The hypoxia-evoked increase in mean pulmonary artery pressure was reduced by administration of BMS-182874 (10 mg/kg i.v.; from 42 +/- 8 to 34 +/- 4 mmHg, P < 0.05 and 30 mg/kg i.v.; from 38 +/- 4 to 30 +/- 5 mmHg, P < 0.05). In addition, BMS-182874 at 30 mg/kg reduced the pulmonary vascular resistance during hypoxia (from 7.4 +/- 1.5 to 5.3 +/- 1.1 mmHg.min.l-1 P < 0.05). The hemodynamic response to repeated hypoxia was reproducible in control animals and unaffected by the cyclo-oxygenase inhibitor diclophenac (3 mg/kg). Infusion of L-NNA alone resulted in an augmented pulmonary vasoconstriction during hypoxia; pulmonary arterial pressure from 35 +/- 6 to 43 +/- 9 mmHg; P < 0.05 and vascular resistance from 7.2 +/- 1.1 to 9.9 +/- 1.8 mmHg.min.l-1; P < 0.05. L-NNA in combination with BMS-182874 (10 mg/kg) resulted in a hypoxic pulmonary vasoconstriction of similar magnitude as hypoxic baseline. In addition, BMS-182874 reduced the hemodynamic response to ET-1 in normoxic pigs and competitively antagonized the vasoconstrictor effect of ET-1 in isolated porcine pulmonary arteries.. The non-peptide, selective ETA receptor antagonist, BMS-182874, reduces hypoxic pulmonary vasoconstriction in pigs. The reduction in pulmonary vascular response to hypoxia following BMS-182874 is at least partly independent of nitric oxide.

Topics: Animals; Antihypertensive Agents; Dansyl Compounds; Drug Synergism; Endothelin Receptor Antagonists; Endothelin-1; Hypertension, Pulmonary; Hypoxia; In Vitro Techniques; Nitric Oxide Synthase; Nitroarginine; Pulmonary Artery; Swine

Topics: Animals; Chronic Disease; Endothelin-1; Endothelins; Endothelium, Vascular; Hemodynamics; Hypertension, Pulmonary; Hypoxia; Lung; Male; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Protein Precursors; Rats

The objective of this study was to determine the influence of chinonin on acute hypoxic pulmonary vasoconstriction (HPV) in Sprague-Dawley (SD) rats and investigate its mechanism. Sixty-five SD rats were divided into five groups at random: six in the control group; six in the hypoxia group; 13 in the group of hypoxia with chinonin; 20 in the group of endothelin-1 (ET-1) with chinonin and 20 in the group of platelet activating factor (PAF) with chinonin. Their mean pulmonary arterial pressures (mPAP) were measured and the concentration of molondialdehyde (MDA) in plasma and the activity of phospholipase A2 (PLA2) of the lung tissues were detected. The PAF and ET-1 levels of plasma and lung homogenates were detected in the control and hypoxia groups. There was evidence of an increase in mPAP, MDA, PAF and ET-1 in the plasma, and activity of PLA2, PAF and ET-1 of the lung tissues when the rats inhaled a 10% mixture of oxygen in nitrogen. It appeared that chinonin may have been inhibiting the action of ET-1 and PAF. Chinonin could have prevented an increase in MPAP caused by hypoxia and inhibited the action of ET-1 and PAF. But chinonin had no influence on the increase in MDA in the plasma and the PLA2 activity of the lungs when hypoxia occurred. Chinonin can reduce HPV, but does not influence normal mPAP. It may do this by blocking the action of ET-1 and/or PAF or others. The definite mechanism needs to be studied further.

Topics: Animals; Anti-Inflammatory Agents; Endothelin-1; Female; Free Radical Scavengers; Glycosides; Hypoxia; Male; Malondialdehyde; Phospholipases A; Phospholipases A2; Plant Extracts; Platelet Activating Factor; Pulmonary Circulation; Rats; Rats, Sprague-Dawley; Vasoconstriction; Xanthenes; Xanthones

This study investigated the mechanisms that may contribute to the hypoxic pulmonary vasoconstriction and compared the effects of hypoxia on pulmonary and systemic vascular beds. Six anesthetized spontaneously breathing pigs inhaled a hypoxic mixture (10% O2 in air) in control conditions and after pre-treatment with Indomethacin (3 mg kg(-1) i.v.) to block the cyclooxygenase pathway. During hypoxia, the Indomethacin pre-treated pigs were given Cromakalim (80 microg kg(-1) i.v.) to activate K+(ATP) channels. Bosentan (5 mg kg(-1) i.v.) was administered to block endothelin-1 receptors and then during hypoxia Cromakalim was administered as before. In all experimental conditions we recorded breathing pattern and vascular parameters: mean systemic and pulmonary arterial pressures; systemic and pulmonary vascular resistances; cardiac output; and heart rate. Vascular and respiratory responses to hypoxia were determined when PaO2 was reduced to 50 +/- 5 mmHg. The main finding was that in spontaneously breathing pigs, hypoxia induces pulmonary vasoconstriction and an increase in mean systemic arterial pressure, which are cyclooxygenase-independent. A role of endothelin-1 appears in both vascular districts, but pulmonary vasoconstriction may also be due to ET-1-dependent inhibition of K+(ATP) channels.

Topics: Adenosine Triphosphate; Animals; Antihypertensive Agents; Blood Pressure; Bosentan; Cardiac Output; Cromakalim; Cyclooxygenase Inhibitors; Endothelin-1; Female; Heart Rate; Hypoxia; Indomethacin; Male; Potassium Channels; Pulmonary Artery; Pulmonary Ventilation; Sulfonamides; Swine; Vascular Resistance; Vasoconstriction

When pulmonary hypertension occurs in the face of hypoxia there is remodeling of all three layers of the pulmonary vessels, but in particular, there is an increase in number of adventitial fibroblasts. Hypoxia causes vasoconstriction in the pulmonary circulation and vasodilation in the systemic circulation. We hypothesized that there are fundamental differences in oxygen sensing and cell signaling between systemic and pulmonary artery cells in response to hypoxia. Here, we determined the effect of hypoxia either alone or in combination with known growth factors such as serum, endothelin-1 (ET-1), and platelet-derived growth factor (PDGF) on the proliferative responses of bovine pulmonary artery and mesenteric artery fibroblasts. Fibroblasts were obtained from primary cultures. Growth was assessed by [3H]thymidine incorporation. Inositol 1,4,5-triphosphate (IP3) generation was measured using a competitive binding assay. Hypoxia alone increased proliferation of pulmonary artery fibroblasts (611 +/- 24%), but not in those from the mesentery. Furthermore, hypoxia had the effect of increasing the replicative response of pulmonary fibroblasts to serum and PDGF, but no change was observed in the mesenteric cells. ET-1 had no effect on growth of either cell type. PDGF gave rise to a significant elevation in IP3 production under hypoxic conditions in the pulmonary artery cells (234%), but not in the mesenteric cells. ET-1 caused no change in IP3 production in any cell type. These data suggest that hypoxia sensitizes pulmonary artery fibroblasts to the proliferative effect of mitogens through a pathway that is not present, or is present but repressed, in the mesenteric cells.

Topics: Analysis of Variance; Animals; Blood; Cattle; Cell Communication; Cell Division; Cells, Cultured; Elastic Tissue; Endothelin-1; Fibroblasts; Hypertension, Pulmonary; Hypoxia; Inositol 1,4,5-Trisphosphate; Mesenteric Arteries; Mitogens; Platelet-Derived Growth Factor; Pulmonary Artery; Radiopharmaceuticals; Thymidine; Tritium; Vasoconstriction; Vasodilation

The immediate effect on the pulmonary circulation of reoxygenation with either room air or 100% O2 was studied in newborn piglets. Hypoxemia was induced by ventilation with 8% O2 until base excess was <-20 mmol/L or mean arterial blood pressure was <20 mm Hg. Reoxygenation was performed with either room air (n = 9) or 100% O2 (n = 9). Mean pulmonary artery pressure increased during hypoxemia (p = 0.012). After 5 min of reoxygenation, pulmonary artery pressure increased further from 24 +/- 2 mm Hg at the end of hypoxemia to 35 +/- 3 mm Hg (p = 0.0077 versus baseline) in the room air group and from 27 +/- 3 mm Hg at the end of hypoxemia to 30 +/- 2 mm Hg (p = 0.011 versus baseline) in the O2 group (NS between groups). Pulmonary vascular resistance index increased (p = 0.0005) during hypoxemia. During early reoxygenation pulmonary vascular resistance index decreased rapidly to values comparable to baseline within 5 min of reoxygenation in both groups (NS between groups). Plasma endothelin-1 (ET-1) decreased during hypoxemia from 1.5 +/- 0.1 ng/L at baseline to 1.2 +/- 0.1 ng/L at the end of hypoxemia (p = 0.003). After 30 min of reoxygenation plasma ET-1 increased to 1.8 +/- 0.3 and 1.5 +/- 0.2 ng/L in the room air and O2 groups, respectively (p = 0.0077 in each group versus end hypoxemia; NS between groups). We conclude that hypoxemic pulmonary hypertension and plasma ET-1 normalizes as quickly when reoxygenation is performed with room air as with 100% O2 in this hypoxia model with newborn piglets.

Topics: Acid-Base Equilibrium; Animals; Animals, Newborn; Disease Models, Animal; Endothelin-1; Hemodynamics; Humans; Hypoxia; Infant, Newborn; Oxygen; Oxygen Inhalation Therapy; Pulmonary Circulation; Swine

It has been proposed that endothelin-1 (ET-1), a potent endogenous vasoactive peptide, may play an important role in the regulation of pulmonary blood flow. The purpose of the present study was to characterize the effects of ET-1 and a nonpeptide mixed ET(A) and ET(B) receptor antagonist, SB 209670, in isolated segments of the canine pulmonary artery and to examine the effects of SB 209670 in a canine model of acute hypoxia-induced pulmonary hypertension. In isolated segments of the pulmonary artery, SB 209670 (3-300 nM) produced a concentration-dependent antagonism of contraction elicited by ET-1 (pA2 = 8.9; slope = 0.9) and had no effect on phenylephrine responses. In addition, SB 209670 antagonized the small, endothelium-dependent relaxation induced by sarafotoxin 6c in phenylephrine (10 microM)-precontracted vessels (pKB = 8.6). In anesthetized dogs, the driving pressure across the pulmonary circulation increased approximately 100% during the hypoxic period (area under the curve [AUC] = 267.1 +/- 25.3 mm Hg x min). SB 209670 treatment (3 and 30 microg/kg/min i.v.) reduced pulmonary vascular resistance and produced a profound dose-related inhibition of hypoxia-induced pulmonary hypertension (AUC = 158.3 +/- 22.7 mm Hg x min and 50.1 +/- 4.9 mm Hg x min, respectively). None of the other hemodynamic or arterial blood gas parameters differed significantly in the vehicle and treatment groups. In addition, SB 209670 produced a significant reversal of hypoxia-induced pulmonary hypertension (AUC = 267.1 +/- 25.3 mm Hg x min vs. 167.8 +/- 23.4 mm Hg x min) when administered at the plateau of the hypoxic response. It was found that SB 209670 administration significantly elevated plasma levels of ET-1-LI (> or = 25-fold). These results suggest that ET-1 is an important mediator of hypoxia-induced pulmonary hypertension in the dog and that SB 209670, a potent and selective mixed ET(A) and ET(B)receptor antagonist in the pulmonary circulation, may represent an important therapeutic approach to the treatment of pulmonary hypertension.

Topics: Animals; Blood Pressure; Dogs; Endothelin Receptor Antagonists; Endothelin-1; Heart Rate; Hypertension, Pulmonary; Hypoxia; In Vitro Techniques; Indans; Male; Muscle Contraction; Muscle, Smooth, Vascular; Phenylephrine; Pulmonary Artery; Vasoconstrictor Agents; Viper Venoms

There is accumulating evidence from in vitro studies suggesting that the genes of endothelin-1, PDGF, and VEGF are, like the erythropoietin gene, regulated by oxygen tension and by divalent cations. Hypoxia-induced stimulation of, such as endothelin-1, PDGF or VEGF might be involved in the pathogenesis of acute or chronic renal failure, and in renal "inflammatory" diseases (glomerulonephritis, vasculitis, allograft rejection). Hypoxia (8% O2) for six hours caused a 55-fold/1.6-fold increase of renal erythropoietin/endothelin-1 gene expression, whereas endothelin-3, PDGF-A, PDGF-B, and VEGF gene expression was unchanged. Carbon monoxide (0.1%) treatment for six hours stimulated renal erythropoietin gene expression 140-fold; however, endothelin-1, endothelin-3, PDGF-A, PDGF-B, and VEGF gene expression was not affected. Finally, cobalt treatment (60 mg/kg CoCl2) increased only renal erythropoietin/PDGF-B gene expression 5-fold/1.65-fold. These findings suggest that hypoxia is a rather weak stimulus for renal endothelin-1 gene expression, and that renal PDGF and VEGF gene expression in vivo is not sensitive to tissue hypoxia, in contrast to cell culture experiments. The in vivo regulation of endothelin-1, PDGF, and VEGF differs substantially from that of erythropoietin, suggesting that the basic gene regulatory mechanisms may not be the same.

Topics: Animals; Endothelial Growth Factors; Endothelin-1; Endothelin-3; Erythropoietin; Gene Expression; Growth Substances; Hypoxia; Kidney; Kidney Diseases; Lymphokines; Male; Platelet-Derived Growth Factor; Rats; Rats, Sprague-Dawley; RNA, Messenger; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors

The mechanisms by which acute alveolar hypoxia induces pulmonary vasoconstriction remain unclear. We investigated whether endothelin-1 (ET-1) could be detected in plasma during pulmonary alveolar hypoxia without systemic hypoxemia (one-lung hypoxia) and whether the levels could be related to hemodynamic status in humans.. Thirteen adult patients with primary lung carcinoma were studied prior to surgery. Anesthesia was induced with fentanyl, diazepam, and pancuronium iv. Differential lung ventilation was performed for 40 min. The right lung was ventilated with a mixture of 6% O2, 5% CO2, and 89% N2 and the left lung ventilated with 100% O2. Blood gas values, hemodynamic parameters, and plasma ET-1 levels were measured.. Mean pulmonary artery pressure increased from 13.0 +/- 3.5 to 17.2 +/- 3.2 mm Hg (P < 0.01) after 20 min of one-lung hypoxia. The plasma ET-1 levels in arterial blood and wedged right pulmonary arterial blood increased from 1.69 +/- 0.61 to 2.13 +/- 0.48 pg/ml (P < 0.01) and from 1.75 +/- 0.47 to 2.26 +/- 0.40 pg/ml (P < 0.001), respectively, after 40 min of one-lung hypoxia. At baseline and after 40 min of one-lung hypoxia, there was a significant correlation between the mean pulmonary artery pressure and arterial plasma ET-1 levels (r = 0.650, P < 0.01) in the wedged pulmonary arterial plasma levels (r = 0.484, P < 0.05). The increase in plasma ET-1 levels in arterial blood and in the wedged pulmonary arterial blood of the hypoxic lung occurred slowly.. We concluded that ET-1 may a supporting, but not a primary, role in human hypoxic pulmonary vasoconstriction.

Topics: Aged; Anesthesia; Blood Pressure; Carbon Dioxide; Endothelin-1; Female; Humans; Hypoxia; Lung Neoplasms; Male; Middle Aged; Oxygen; Pneumonectomy; Pulmonary Alveoli; Pulmonary Artery; Respiration, Artificial; Vascular Resistance

Pigs were subjected to acute, intermittent hypoxia (fraction of inhaled O2 0.1, n = 10). The increase in mean pulmonary artery pressure during hypoxia was not altered after i.v. administration of the selective endothelin ETB receptor antagonist BQ-788 (N-cis-2,6-dimethylpiperidinocarbonyl-L-gamma-methylleucyl-D -1- methoxycarbonyltryptophanyl-D-norleucine) (1 mg). However, the vasodilatory effect of endothelin-1 (25 ng/kg per min) infused into the pulmonary artery during hypoxia was attenuated by BQ-788. The present results suggest that the pulmonary vasodilator effect of exogenously administered endothelin-1 during acute hypoxia is mediated by endothelin ETB receptors in the pig. Furthermore, endothelin ETB receptor antagonism with BQ-788 does not influence the pulmonary vascular response to acute hypoxia.

Topics: Analysis of Variance; Animals; Blood Pressure; Dose-Response Relationship, Drug; Endothelin Receptor Antagonists; Endothelin-1; Hypoxia; Injections, Intravenous; Oligopeptides; Piperidines; Pulmonary Artery; Pulmonary Wedge Pressure; Rats; Receptor, Endothelin B; Swine; Vascular Resistance; Vasodilation

Exposure to chronic hypobaric hypoxia in the newborn piglet causes pulmonary hypertension and structural abnormalities in the intrapulmonary arteries that resemble those seen in babies with pulmonary hypertension of the newborn. To investigate whether the density and subtype of endothelin (ET) receptors in intrapulmonary arteries were altered by exposure to chronic hypobaric hypoxia (50.8 kPa) and changed on recovery, (125)I-labeled ET-1 binding was studied using an in vitro autoradiographic technique on 67 piglets. Plasma ET was measured in 116 control, hypoxic, and recovery animals. In piglets exposed to hypoxia from birth, plasma ET was greater than normal for age (P < 0.05), and the binding density of ET-1 was increased in elastic arteries, muscular arteries, and veins due to an increase in the density of ET(A) binding (P < 0.05 for all vessel types). On recovery, plasma ET level became normal after 6 days. After 1 day of recovery, the binding density of ET-1 and ET(A) was normal in elastic arteries but was greater than normal in muscular arteries even after 6 days (P < 0.05). Exposure to hypoxia from 3 to 6 or from 14 to 17 days did not alter the plasma ET or the binding density in muscular arteries, but the density of binding of ET-1, ET(A), and ET(B) in elastic pulmonary arteries decreased (P < 0.05). On recovery, it returned to normal by 6 days. In summary, the increases in plasma ET and ET-1 and ET(A) binding density suggest a role for ET in the pathogenesis of hypoxic pulmonary hypertension in the newborn period. An initial normal period of adaptation is protective.

Topics: Aging; Animals; Animals, Newborn; Binding Sites; Blood Vessels; Bronchi; Endothelin-1; Hypoxia; Muscle, Smooth; Pulmonary Circulation; Receptors, Endothelin; Reference Values; Swine

Gastric microcirculatory disturbances are involved in the pathogenesis of stress ulcers; however, vasomodulators causing this process are not fully understood. This study was conducted to investigate the role of endothelin 1 (ET-1), a potent vasoconstrictive peptide, in stress ulcers in critically ill patients.. Using sandwich enzyme immunoassay, we measured ET-1 content in plasma and the gastric mucosa of 16 critically ill patients with traumatic head injury on admission and of 11 healthy subjects. Gastric mucosal samples were obtained endoscopically. When gastric drainage contained occult blood, endoscopic examination was performed again, and ET-1 concentrations in injured and adjacent normal mucosa were compared.. Plasma and mucosal ET-1 concentrations were significantly higher in critically ill patients on admission (6.1 +/- 0.6 pg/ml and 13.8 +/- 1.6 ng/g, respectively) compared with values in control subjects (2.7 +/- 0.4 pg/ml and 8.2 +/- 0.5 ng/g, respectively) (p < 0.01). The mucosal ET-1 concentration tended to be elevated in patients who had experienced hypoxia compared with those who had not (p = 0.07). In five patients who were again examined endoscopically, the ET-1 concentration in the injured mucosa was significantly higher than that in adjacent mucosa (19.2 +/- 3.2 and 10.1 +/- 1.6 ng/g, respectively; p < 0.05).. These results suggest that endogenous ET-1 plays an important role in the local pathogenesis of stress ulcers, especially those caused by hypoxia.

Topics: Adult; Critical Illness; Endothelin-1; Female; Gastric Mucosa; Humans; Hypoxia; Male; Middle Aged; Prospective Studies; Stomach Ulcer; Time Factors

Exposure to hypoxia is associated with increased pulmonary artery pressure and plasma endothelin (ET-1) levels and with selective enhancement of ET-1 peptide and messenger RNA (mRNA) and endothelin-A (ET-A) receptor mRNA in rat lung. Our study tested the hypothesis that A-127722, an orally active antagonist of the ET-A receptor, can prevent hypoxia-induced pulmonary hypertension and vascular remodeling in the rat. Pretreatment with A-127722 (3, 10, and 30 mg/kg/day in drinking water for 2 days) caused dose-dependent inhibition of the pulmonary vasoconstrictor response to short-term hypoxia (10% O2, 90 min). Long-term A-127722 treatment (10 mg/kg/day in drinking water for 2 weeks) instituted 48 h before hypoxic exposure attenuated the subsequent development of pulmonary hypertension, the associated right atrial hypertrophy, and pulmonary vascular remodeling. Institution of A-127722 treatment (10 mg/kg/day in drinking water for 4 weeks) after 2 weeks of hypoxia retarded the progression of established hypoxia-induced pulmonary hypertension and right atrial hypertrophy and reversed the pulmonary vascular remodeling despite continuing hypoxic exposure. These findings support the hypothesis that endogenous ET-1 plays a major role in hypoxic pulmonary vasoconstriction/hypertension, right heart hypertrophy, and pulmonary vascular remodeling and suggest that ET-A receptor blockers may be useful in the treatment and prevention of hypoxic pulmonary hypertension in humans.

Topics: Animals; Atrasentan; Blood Pressure; Cardiomegaly; Endothelin Receptor Antagonists; Endothelin-1; Heart Rate; Hypertension, Pulmonary; Hypoxia; Male; Pulmonary Artery; Pyrrolidines; Rats; Receptor, Endothelin A

Endothelin (ET)-1, a potent vasoconstrictor and mitogen, acts through ETA and ETB receptors and may be involved in the pathogenesis of persistent pulmonary hypertension of the newborn. We hypothesized that hypoxia-induced pulmonary hypertension in the newborn is associated with increased ET-1 release and modified ET receptor characteristics leading to vasoconstriction and vascular remodeling. Therefore, we studied 1-day-old piglets exposed for 3 or 14 days to hypoxia (fraction of inspired O2 = 0.10) or normoxia (controls). ET-1 circulating levels in pulmonary artery and vein were measured. Pulmonary vascular reactivity to ET-1 was evaluated using isolated-perfused lungs. ET binding characteristics were examined in microsomes from pulmonary arteries (down to 100 microns). ET-1 circulating levels are low and are not altered by hypoxia. The magnitude of the initial dilator response to ET-1 decreases after 3 days of hypoxia (P < 0.05), whereas the number of ETB receptors is reduced by 40% in the pulmonary arteries (P < 0.05). ETA receptors are predominant (65-90%) in pulmonary arteries. ETA receptors decrease by 50% after 14 days of exposure to hypoxia (P < 0.05), whereas the constrictor response to ET-1 remains unchanged. The fact that the reduction in vasodilator response parallels the decrease in ETB receptors suggests a decrease in receptor expression. We speculate that the maintenance of the vasoconstrictor response to ET-1 despite a reduction in the number of binding sites is likely due to receptor occupancy. In conclusion, in the newborn piglet pulmonary vasculature, ETA and ETB receptors may be affected differently by hypoxia.

Topics: Animals; Animals, Newborn; Down-Regulation; Endothelin-1; Hypertension, Pulmonary; Hypoxia; In Vitro Techniques; Microsomes; Pulmonary Artery; Pulmonary Circulation; Pulmonary Veins; Receptor, Endothelin A; Receptor, Endothelin B; Receptors, Endothelin; Reference Values; Swine; Vasoconstriction; Vasodilation

Topics: Animals; Endothelin-1; Fluorescent Dyes; Hypoxia; Kidney; Kinetics; Luminescent Measurements; Male; Microcirculation; Oximetry; Oxygen; Rats; Rats, Sprague-Dawley; Tissue Distribution

Significant elevations in endothelin (ET)-1 levels accompany many diseases, but the underlying regulatory mechanisms are unclear. To investigate the in vivo regulation of human preproendothelin-1 (PPET-1), we examined the activity of the PPET-1 promoter in transgenic mice exposed to hypoxia. Mice expressing one of three PPET-1 promoter-luciferase (PPET-1/LUC) reporter transgenes (approximately 2.5 kb, 138 bp, or none of the 5'-flanking sequences of the PPET-1 gene) were generated. LUC expression was reduced in mice with a truncated 138-bp PPET-1 promoter. Exposure of mice bearing the 2.5-kb PPET-1/LUC transgene to hypoxia (10% O2 for 24 h) increased LUC expression sixfold in pulmonary tissue but only twofold in other tissues. In situ hybridization revealed the strongest transgene expression in the pulmonary vasculature and bronchiolar epithelium. These data are consistent with the hypothesis that hypoxic induction of the PPET-1 gene leads to increased pulmonary production of ET-1 in diseases associated with low O2 tension.

Topics: Animals; Cattle; Cells, Cultured; Endothelin-1; Endothelins; Endothelium, Vascular; Genes, Reporter; Humans; Hypoxia; Luciferases; Lung; Mice; Mice, Transgenic; Promoter Regions, Genetic; Protein Precursors; Pulmonary Artery; Recombinant Fusion Proteins; RNA, Messenger; Transcription, Genetic; Transfection

To determine the possible adverse effects of human cross-linked hemoglobin in endotoxemia.. Prospective, controlled, laboratory trial.. Animal research laboratory.. New Zealand white rabbits.. Conscious rabbits received intravenous infusions of either lipopolysaccharide (LPS) alone (10 micrograms/kg, Escherichia coli 0111:B4), human hemoglobin cross-linked between the alpha chains (alpha alpha Hb, 0.7 g/kg), or both LPS and alpha alpha Hb. The cardiovascular effects of alpha alpha Hb and LPS as single agents or administered together were then studied in anesthetized rabbits.. Mortality in conscious animals that received alpha alpha Hb followed by LPS 4 hrs later (n = 5), or LPS and alpha alpha Hb at the same time (n = 6) was 60% and 67%, respectively. In anesthetized animals, infusion of both LPS and alpha alpha Hb (n = 6) resulted in hypoxia, lactic acidosis, ventricular arrhythmias, and decreased myocardial contractility and left ventricular pressure. In contrast, anesthetized rabbits that received alpha alpha Hb (n = 5) or LPS (n = 5) alone did not develop hypoxia, acidosis, alteration in myocardial contractility, or arrhythmias. Furthermore, death did not occur in any of the conscious animals that received either LPS (n = 7) or alpha alpha Hb (n = 4) as single agents.. In an animal model of nonlethal endotoxemia, infusion of alpha alpha Hb significantly increases mortality. Our data suggest that mortality may be due to the acute increased cardiopulmonary toxicity of alpha alpha Hb in animals with underlying endotoxemia.

Topics: Acidosis, Lactic; Animals; Arrhythmias, Cardiac; Cross-Linking Reagents; Drug Administration Schedule; Endothelin-1; Endotoxemia; Escherichia coli; Hemodynamics; Hemoglobin A; Humans; Hypoxia; Leukopenia; Lipopolysaccharides; Male; Myocardial Contraction; Rabbits

This study investigated the effects of the nonpeptide endothelin (ET) receptor antagonist, SB 217242, against ET-1-induced pulmonary pressor responses and in a model of hypoxia-induced pulmonary hypertension in the guinea pig. In guinea pig isolated pulmonary artery rings, SB 217242 (3-300 nM) produced a concentration-dependent inhibition of ET-1-induced contractions, with a pA2 of 8.1. SB 217242 (1 or 3 mg/kg i.v.) elicited a dose-related inhibition of ET-1-induced increases in pulmonary artery and airway insufflation pressure responses in anesthetized guinea pigs. Chronic exposure to hypoxia (9% O2 for 0-14 days) produced a time-dependent increase in mean pulmonary artery pressure. After a 10-day exposure to hypoxia there was about a 100% elevation in pulmonary artery pressure, and right ventricular mass and plasma irET levels increased 3-fold compared with normoxic animals. SB 217242, administered by continuous intraperitoneal infusion via mini osmotic pump (0.36, 3.6 or 10.8 mg/day), significantly reduced (by about 50%) hypoxia-induced pulmonary artery pressure increases at all three doses used. The hypoxia-induced right ventricular hypertrophy was significantly attenuated by the 3.6 and 10.8 mg/day doses. Based on hematocrit, hemoglobin and red blood cell counts, SB 217242 did not affect the normal physiological erythropoietic response to hypoxia. There were no appreciable differences in the maximum contractile effects of ET-1 or the potency of SB 217242 (pKB values, 8.3 and 8.0, respectively) versus ET-1-induced responses in isolated pulmonary arteries from hypoxic versus normoxic guinea pigs. However, there was a marked reduction in endothelium-dependent relaxation of precontracted pulmonary artery isolated from hypoxic compared with normoxic animals. The results of the present study provide further preclinical evidence for a pathophysiological role of ET-1 and the potential therapeutic utility of ET receptor antagonists, such as SB 217242, in pulmonary hypertension.

Topics: Animals; Blood Pressure; Carboxylic Acids; Endothelin Receptor Antagonists; Endothelin-1; Guinea Pigs; Hypoxia; In Vitro Techniques; Indans; Male; Pulmonary Artery

To determine whether mRNA for endothelin-1 was present and changed in the lungs of rats exposed to chronic hypoxia.. cRNA probes for rat ET-1 and c-fos were labelled by in vitro transcription with digoxigenin-UTP for in situ hybridization. Endothelin-1 like immunoreactivity (ET-1-LI) in plasma as well as in lung homogenate was measured by radioimmunoassay.. The vascular endothelial cells of pulmonary arteries and the bronchiolar epithelial cells were strongly positive for the ET-1 probe. The perivascular and peribronchiolar smooth muscle were positive for the c-fos probe, primarily. There was little expression of ET-1 and c-fos in the rat lungs in controls. There was significant increase of ET-1-LI levels in rats exposed to hypoxia for 3 weeks, the concentration ET-1-LI in venous samples was 3.85 +/- 1.52 ng/L (P < 0.05 as compared with the control groups), in arterial sample was 4.72 +/- 1.66 ng/L (P < 0.05) and in lung was 2.06 +/- 0.68 ng/g wet lung weight (P < 0.05).. Chronic hypoxia elevated the mean pulmonary arterial pressure, caused vessel remodelling and the right ventricular hypertrophy. These changes were accompanied by an increase of ET-1 in plasma and lung homogenate. The expression and production of ET-1 were localized to endothelium and airway epithelium in the lungs.

Topics: Animals; Endothelin-1; Gene Expression; Hypertension, Pulmonary; Hypoxia; Lung; Male; Proto-Oncogene Proteins c-fos; Rats; Rats, Wistar; RNA, Messenger

To investigate the impact of nitric oxide on endothelin-1 (ET-1) mRNA expression in pulmonary artery endothelial cells and pulmonary artery smooth muscle cells of chronic hypoxic rats.. In situ hybridization was performed on lung sections from 40 chronic hypoxic rats treated either with L-Arginine (L-Arg) or N omega-nitro-L-arginine methyl ester (L-NAME) by using cRNA probe for ET-1.. Most intrapulmonary arteries had 1%-50% of the endothelial cells expressing ET-1 mRNA in both one-week and two-week hypoxic rats (75% +/- 3% and 71% +/- 6%, respectively), which was significantly inhibited by L-Arg but augmented by L-NAME administration. Most pulmonary artery smooth muscle cells showed no ET-1 mRNA signals in both one-week and two-week hypoxic rats (85% +/- 6% and 98% +/- 2%, respectively). However, L-NAME increased ET-1 mRNA expression in pulmonary artery smooth muscle cells of hypoxic rats.. Nitric oxide inhibited ET gene expression in both pulmonary artery endothelial cells and smooth muscle cells of rats exposed to chronic hypoxia.

Topics: Animals; Chronic Disease; Endothelin-1; Gene Expression; Hypoxia; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide; Pulmonary Artery; Rats; Rats, Wistar; RNA, Messenger

We have previously shown that high altitude pulmonary edema-susceptible subjects (HAPE-S) have an accentuated pulmonary vascular response to hypoxia. In this study, we investigated the relationship between plasma endothelin-1 (ET-1) levels and the acute hypoxic pulmonary vascular response in HAPE-S and control subjects. In six HAPE-S and seven healthy subjects, we evaluated acceleration time/right ventricular ejection time (AcT/RVET) using Doppler echocardiography, and measured plasma ET-1 levels by radioimmunoassay (RIA) before and after 5 minutes of breathing 10% oxygen. The HAPE-S showed a significantly increased pulmonary vascular response to hypoxia compared with healthy subjects. However, no statistically significant changes of plasma ET-1 levels were observed before and after hypoxia in both groups. We conclude that the increased pulmonary vascular response to acute hypoxia in HAPE-S may not be related to ET-1 release.

Topics: Acute Disease; Adult; Altitude Sickness; Case-Control Studies; Endothelin-1; Female; Humans; Hypoxia; Male; Middle Aged; Pulmonary Circulation; Pulmonary Edema

The role of endothelin (ET)-1 in pulmonary arterial pressure (Ppa) homeostasis and hypoxia-induced pulmonary hypertension was examined. ET-1 was chronically infused (2 and 4 pmol.kg-1.min-1) into the pulmonary circulation of male Sprague-Dawley rats for 3, 7, and 14 days while they were exposed to normoxia or hypobaric hypoxia (inspired O2 fraction 10%). The role of endogenous ET was examined by infusion of ET antiserum (ET-AS; 0.25 and 0.5 microliter.rat-1.h-1; cross-reacting with ET-1, -2, and -3) or the ETA-receptor blocker BQ-123 (10 pmol.kg-1.min-1). ET-1 (4 pmol) increased Ppa at 3 and 7 days in normoxia and hypoxia and was ineffective at 14 days, probably from ETA-receptor downregulation. BQ-123 blunted the hypoxic Ppa rise at all times, confirming a role for ETA receptors. ET-AS (0.5 microliter) was mostly ineffective but exacerbated hypoxic Ppa at 14 days, in contrast to BQ-123, suggesting that a different ET receptor could be involved. ET-1 infusion (2 pmol) caused right ventricular hypertrophy (RVH) in normoxia and exacerbated RVH in hypoxia, whereas BQ-123 and ET-AS (0.25 microliter) reduced hypoxic RVH. In conclusion, endogenous ET-1 plays a role in hypoxia-induced pulmonary hypertension and RVH by augmenting the level of hypoxic response. ET-1 also affects hematocrit and may reduce blood levels of the vasodilator calcitonin gene-related peptide.

Topics: Animals; Blood Pressure; Calcitonin Gene-Related Peptide; Chronic Disease; Endothelin Receptor Antagonists; Endothelin-1; Hematocrit; Hypoxia; Immune Sera; Longitudinal Studies; Lung; Male; Myocardium; Organ Size; Peptides, Cyclic; Pulmonary Circulation; Rats; Rats, Sprague-Dawley; Reference Values

Topics: Adaptation, Physiological; Animals; Atrial Natriuretic Factor; Carotid Body; Cyclic AMP; Endothelin-1; Endothelins; Hypoxia; Inositol 1,4,5-Trisphosphate; Male; Mammals; Nitric Oxide; Rabbits; Rats; Second Messenger Systems

This study is aimed to investigate the effects of L-arginine, a precursor of the formation of nitric oxide, on acute hypoxic pulmonary hypertension in vivo and on production of endothelin-1 both in vivo and in cultured endothelial cells. In mechanically ventilated anesthetized dogs (n = 7), L-arginine (0.5 g/kg) reduced the mean pulmonary arterial pressure and femoral arterial pressure during hypoxic ventilation and its action lasted for about 30 minutes. Meanwhile, plasma endothelin-1 in the pulmonary and femoral artery had no remarkable change. In cultured endothelial cells from umbilical veins, different concentrations of L-arginine had no influence on endothelin-1 level of culture medium in 4 or 24 hours after the addition of L-arginine. These results indicate that L arginine can decrease the pulmonary arterial pressure during acute hypoxia, which may be associated with the increase of nitric oxide production.

Topics: Animals; Arginine; Blood Pressure; Cells, Cultured; Dogs; Endothelin-1; Endothelium, Vascular; Female; Humans; Hypertension, Pulmonary; Hypoxia; Male

The aim of the present study was to determine whether mRNA for endothelin-1 (ET-1) was present and changed in the lungs of rats exposed to chronic hypoxia, cRNA probes for rat ET-1 and c-fos were labelled by in vitro transcription with digoxigenin-UTP for in situ hybridization. Endothelin-1 like immunoactivity (ET-1-LI) in plasma as well as in lung homogenate was measured by radio-immunoassay. The results showed that the vascular endothelia cells of pulmonary artelics and the bronchiolar epithelial cells were strongly positive for the ET-1 probe. The perivascular and peribronchiolar smooth muscle were positive for the c-fos probe primarily. Whereas, there were little expression of ET-1 and c-fos in the rat lungs in controls. There were significant increase of ET-1-LI levels in rats exposed to hypoxia for 3 weeks, the concentration in venous samples was 3.85 +/- 1.52ng/L (P < 0.05 as compared with the control groups), in arterial sample was 4.72 +/- 1.66ng/L (P < 0.05) and in lung tissue was 2.06 +/- 0.68ng/g wet lung weight (P < 0.05). It is suggested that chronic hypoxia elevated the mean pulmonary arterial pressure, caused vessel remodelling and right ventricular hypertrophy. These changes were accompanied by an increase of ET-1 in plasma and lung homogenate. The expression and production of ET-1 were localized to endothelium and airway epithelium in the lungs.

Topics: Animals; Endothelin-1; Hypertension, Pulmonary; Hypoxia; Lung; Male; Proto-Oncogene Proteins c-fos; Rats; Rats, Wistar; RNA, Messenger