losartan-potassium and Hypertension--Pulmonary

Organ crosstalk pathways represent the next frontier for target-mining in molecular medicine for existing syndromes. Pulmonary hypertension and resistant essential hypertension are syndromes that have been proven elusive in etiology, and frequently refractory to first-line management. Underlying crosstalk mechanisms, not yet considered in these treatments, may hinder outcomes or unlock novel treatments. This review focuses systematically on erythropoietin, a synthesizable molecule, as a mediator of brain-kidney crosstalk. Insights gained from this review will be applied to cardiovascular diseases in a clinician-directed fashion.

Topics: Brain; Endothelins; Erythropoietin; Essential Hypertension; Heart; Humans; Hypertension, Pulmonary; Kidney; Lung; Nitric Oxide; Prostaglandins; Renin-Angiotensin System

Topics: Adaptation, Physiological; Altitude Sickness; Calcium; Chronic Disease; Endothelium, Vascular; Erythropoietin; Heart Failure; Hemodynamics; Humans; Hypertension, Pulmonary; Hypoxia; Muscle, Smooth; Pulmonary Edema; Vascular Diseases; Vascular Remodeling; Vasoconstriction

Numerous uremic patients on hemodialysis have pulmonary hypertension attributable to the presence of arteriovenous fistulas, vascular calcification, and endothelial dysfunction due to alterations in the balance between vasoconstrictive and vasodilatory substances. For these reasons, the effects of recombinant human erythropoietin, a drug widely used in patients on dialysis, on the pulmonary circulation were studied. Some authors maintain that recombinant human erythropoietin has an antihypertensive effect, while others have observed that this hormone induces a reduction in pulmonary arterial pressure due to its vasoactive and stimulatory effects on endothelial and smooth muscle cell precursors.

Topics: Animals; Antihypertensive Agents; Erythropoietin; Humans; Hypertension, Pulmonary; Pulmonary Circulation; Recombinant Proteins; Renal Dialysis

Topics: Animals; Cell Division; DNA-Binding Proteins; Endothelins; Erythropoietin; Humans; Hypertension, Pulmonary; Hypoxia; Hypoxia-Inducible Factor 1; Hypoxia-Inducible Factor 1, alpha Subunit; Muscle, Smooth, Vascular; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nuclear Proteins; Transcription Factors; Vascular Endothelial Growth Factor A

Topics: Acclimatization; Altitude; Animals; Animals, Domestic; Blood Coagulation Factors; Blood Pressure; Blood Viscosity; Blood Volume; Carbon Dioxide; Cardiac Output; Cardiomegaly; Cats; Cattle; Colorado; Coronary Circulation; Dogs; Erythrocyte Count; Erythropoietin; Guinea Pigs; Heart Rate; Humans; Hypertension, Pulmonary; Hypoxia; Indians, South American; Myocardium; Organ Size; Oxygen; Oxygen Consumption; Partial Pressure; Peru; Physical Exertion; Polycythemia; Pulmonary Circulation; Pulmonary Diffusing Capacity; Rabbits; Rats; Vascular Resistance

Polycythemia and pulmonary hypertension are 2 human diseases for which better therapies are needed. Upregulation of hypoxia-inducible factor-2α (HIF-2α) and its target genes, erythropoietin (EPO) and endothelin-1, causes polycythemia and pulmonary hypertension in patients with Chuvash polycythemia who are homozygous for the R200W mutation in the von Hippel Lindau (VHL) gene and in a murine mouse model of Chuvash polycythemia that bears the same homozygous VhlR200W mutation. Moreover, the aged VhlR200W mice developed pulmonary fibrosis, most likely due to the increased expression of Cxcl-12, another Hif-2α target. Patients with mutations in iron regulatory protein 1 (IRP1) also develop polycythemia, and Irp1-knockout (Irp1-KO) mice exhibit polycythemia, pulmonary hypertension, and cardiac fibrosis attributable to translational derepression of Hif-2α, and the resultant high expression of the Hif-2α targets EPO, endothelin-1, and Cxcl-12. In this study, we inactivated Hif-2α with the second-generation allosteric HIF-2α inhibitor MK-6482 in VhlR200W, Irp1-KO, and double-mutant VhlR200W;Irp1-KO mice. MK-6482 treatment decreased EPO production and reversed polycythemia in all 3 mouse models. Drug treatment also decreased right ventricular pressure and mitigated pulmonary hypertension in VhlR200W, Irp1-KO, and VhlR200W;Irp1-KO mice to near normal wild-type levels and normalized the movement of the cardiac interventricular septum in VhlR200Wmice. MK-6482 treatment reduced the increased expression of Cxcl-12, which, in association with CXCR4, mediates fibrocyte influx into the lungs, potentially causing pulmonary fibrosis. Our results suggest that oral intake of MK-6482 could represent a new approach to treatment of patients with polycythemia, pulmonary hypertension, pulmonary fibrosis, and complications caused by elevated expression of HIF-2α.

Topics: Animals; Basic Helix-Loop-Helix Transcription Factors; Endothelin-1; Erythropoietin; Female; Gene Expression Regulation; Hypertension, Pulmonary; Iron Regulatory Protein 1; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Polycythemia; Sulfones; Von Hippel-Lindau Tumor Suppressor Protein

Topics: Basic Helix-Loop-Helix Transcription Factors; Erythropoietin; Humans; Hypertension, Pulmonary; Polycythemia

The hypoxic response is a stress response triggered by low oxygen tension. Hypoxia-inducible factors (HIFs) play a prominent role in the pathobiology of hypoxia-associated conditions, including pulmonary hypertension (PH) and polycythemia. The c-Jun N-terminal protein kinase (JNK), a stress-activated protein kinase that consists of two ubiquitously expressed isoforms, JNK1 and JNK2, and a tissue-specific isoform, JNK3, has been shown to be activated by hypoxia. However, the physiological role of JNK1 and JNK2 in the hypoxic response remains elusive. Here, using genetic knockout cells and/or mice, we show that JNK2, but not JNK1, up-regulates the expression of HIF-1α and HIF-2α and contributes to hypoxia-induced PH and polycythemia. Knockout or silencing of JNK2, but not JNK1, prevented the accumulation of HIF-1α in hypoxia-treated cells. Loss of JNK2 resulted in a decrease in HIF-1α and HIF-2α mRNA levels under resting conditions and in response to hypoxia. Consequently, hypoxia-treated

Topics: Animals; Basic Helix-Loop-Helix Transcription Factors; Cell Hypoxia; Erythropoiesis; Erythropoietin; Hypertension, Pulmonary; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; JNK Mitogen-Activated Protein Kinases; Mice; Mice, Inbred C57BL; Mice, Knockout; Mitogen-Activated Protein Kinase 8; Mitogen-Activated Protein Kinase 9; Polycythemia; RNA, Messenger; Transcriptional Activation; Up-Regulation

Iron bioavailability has been identified as a factor that influences cellular hypoxia sensing, putatively via an action on the hypoxia-inducible factor (HIF) pathway. We therefore hypothesized that clinical iron deficiency would disturb integrated human responses to hypoxia.. We performed a prospective, controlled, observational study of the effects of iron status on hypoxic pulmonary hypertension. Individuals with absolute iron deficiency (ID) and an iron-replete (IR) control group were exposed to two 6-hour periods of isocapnic hypoxia. The second hypoxic exposure was preceded by i.v. infusion of iron. Pulmonary artery systolic pressure (PASP) was serially assessed with Doppler echocardiography.. Thirteen ID individuals completed the study and were age- and sex-matched with controls. PASP did not differ by group or study day before each hypoxic exposure. During the first 6-hour hypoxic exposure, the rise in PASP was 6.2 mmHg greater in the ID group (absolute rises 16.1 and 10.7 mmHg, respectively; 95% CI for difference, 2.7-9.7 mmHg, P = 0.001). Intravenous iron attenuated the PASP rise in both groups; however, the effect was greater in ID participants than in controls (absolute reductions 11.1 and 6.8 mmHg, respectively; 95% CI for difference in change, -8.3 to -0.3 mmHg, P = 0.035). Serum erythropoietin responses to hypoxia also differed between groups.. Clinical iron deficiency disturbs normal responses to hypoxia, as evidenced by exaggerated hypoxic pulmonary hypertension that is reversed by subsequent iron administration. Disturbed hypoxia sensing and signaling provides a mechanism through which iron deficiency may be detrimental to human health.. ClinicalTrials.gov (NCT01847352).. M.C. Frise is the recipient of a British Heart Foundation Clinical Research Training Fellowship (FS/14/48/30828). K.L. Dorrington is supported by the Dunhill Medical Trust (R178/1110). D.J. Roberts was supported by R&D funding from National Health Service (NHS) Blood and Transplant and a National Institute for Health Research (NIHR) Programme grant (RP-PG-0310-1004). This research was funded by the NIHR Oxford Biomedical Research Centre Programme.

Topics: Adult; Arterial Pressure; Cardiac Output; Case-Control Studies; Echocardiography, Doppler; Erythropoietin; Female; Hepcidins; Humans; Hypertension, Pulmonary; Hypoxia; Interleukin-6; Iron; Iron Deficiencies; Male; Middle Aged; Oxyhemoglobins; Prospective Studies; Pulmonary Artery; Respiration; Signal Transduction

Upregulation of the erythropoietin (EPO)/EPO receptor (EPOR) system plays a protective role against chronic hypoxia-induced pulmonary hypertension (hypoxic PH) through enhancement of endothelial nitric oxide (NO)-mediated signaling. Genistein (Gen), a phytoestrogen, is considered to ameliorate NO-mediated signaling. We hypothesized that Gen attenuates and prevents hypoxic PH. In vivo, Sprague-Dawley rats raised in a hypobaric chamber were treated with Gen (60 mkg/kg) for 21 days. Pulmonary hemodynamics and vascular remodeling were ameliorated in Gen-treated hypoxic PH rats. Gen also restored cGMP levels and phosphorylated endothelial NO synthase (p-eNOS) at Ser(1177) and p-Akt at Ser(473) expression in the lungs. Additionally, Gen potentiated plasma EPO concentration and EPOR-positive endothelial cell counts. In experiments with hypoxic PH rats' isolated perfused lungs, Gen caused NO- and phosphatidylinositol 3-kinase (PI3K)/Akt-dependent vasodilation that reversed abnormal vasoconstriction. In vitro, a combination of EPO and Gen increased the p-eNOS and the EPOR expression in human umbilical vein endothelial cells under a hypoxic environment. Moreover, Gen potentiated the hypoxic increase in EPO production from human hepatoma cells. We conclude that Gen may be effective for the prevention of hypoxic PH through the improvement of PI3K/Akt-dependent, NO-mediated signaling in association with enhancement of the EPO/EPOR system.

Topics: Animals; Antihypertensive Agents; Blood Pressure; Cell Hypoxia; Cyclic GMP; Drug Evaluation, Preclinical; Erythropoietin; Genistein; Hep G2 Cells; Human Umbilical Vein Endothelial Cells; Humans; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Male; Nitric Oxide; Nitric Oxide Synthase Type III; Phosphorylation; Protein Processing, Post-Translational; Proto-Oncogene Proteins c-akt; Rats; Rats, Sprague-Dawley; Signal Transduction; Vasodilator Agents; Ventricular Pressure

von Hippel-Lindau (VHL) protein is the principal negative regulator of hypoxia sensing mediated by transcription factors. Mutations in exon 3 of the VHL gene lead to Chuvash (VHL(R200W)) and Croatian (VHL(H191D)) polycythemias. Here, we describe an infant of Bangladesh ethnicity with a novel homozygous VHL(D126N) mutation with congenital polycythemia and dramatically elevated erythropoietin (EPO) levels, who developed severe fatal pulmonary hypertension. In contrast to Chuvash polycythemia, erythroid progenitors (BFU-Es) did not reveal a marked EPO hypersensitivity. Further, NF-E2 and RUNX1 transcripts that correlate with BFU-Es EPO hypersensitivity in polycythemic mutations were not elevated.

Topics: Erythropoietin; Humans; Hypertension, Pulmonary; Infant; Male; Mutation, Missense; Polycythemia; Von Hippel-Lindau Tumor Suppressor Protein

The development of tools to monitor the right ventricle in pulmonary arterial hypertension (PAH) is of clinical importance. PAH is associated with pathologic expression of the transcription factor hypoxia-inducible factor (HIF)-1α, which induces glycolytic metabolism and mobilization of proangiogenic progenitor (CD34(+)CD133(+)) cells. We hypothesized that PAH cardiac myocytes have a HIF-related switch to glycolytic metabolism that can be detected with fasting 2-deoxy-2-[(18)F]fluoro-d-glucose positron emission tomography (FDG-PET) and that glucose uptake is informative for cardiac function.. Six healthy control subjects and 14 patients with PAH underwent fasting FDG-PET and echocardiogram. Blood CD34(+)CD133(+) cells and erythropoietin were measured as indicators of HIF activation. Twelve subjects in the PAH cohort underwent repeat studies 1 year later to determine if changes in FDG uptake were related to changes in echocardiographic parameters or to measures of HIF activation.. FDG uptake in the right ventricle was higher in patients with PAH than in healthy control subjects and correlated with echocardiographic measures of cardiac dysfunction and circulating CD34(+)CD133(+) cells but not erythropoietin. Among patients with PAH, FDG uptake was lower in those receiving β-adrenergic receptor blockers. Changes in FDG uptake over time were related to changes in echocardiographic parameters and CD34(+)CD133(+) cell numbers. Immunohistochemistry of explanted PAH hearts of patients undergoing transplantation revealed that HIF-1α was present in myocyte nuclei but was weakly detectable in control hearts.. PAH hearts have pathologic glycolytic metabolism that is quantitatively related to cardiac dysfunction over time, suggesting that metabolic imaging may be useful in therapeutic monitoring of patients.

Topics: Adrenergic beta-1 Receptor Antagonists; Adult; Antigens, CD; Cell Hypoxia; Echocardiography; Erythropoietin; Familial Primary Pulmonary Hypertension; Female; Fluorodeoxyglucose F18; Glucose; Heart Ventricles; Humans; Hypertension, Pulmonary; Hypoxia-Inducible Factor 1, alpha Subunit; Male; Middle Aged; Monitoring, Physiologic; Neovascularization, Pathologic; Positron-Emission Tomography; Reproducibility of Results; Ventricular Dysfunction, Right

The central pathway for oxygen-dependent control of red cell mass is the prolyl hydroxylase domain protein (PHD):hypoxia inducible factor (HIF) pathway. PHD site specifically prolyl hydroxylates the transcription factor HIF-α, thereby targeting the latter for degradation. Under hypoxia, this modification is attenuated, allowing stabilized HIF-α to activate target genes, including that for erythropoietin (EPO). Studies employing genetically modified mice point to Hif-2α, one of two main Hif-α isoforms, as being the critical regulator of Epo in the adult mouse. More recently, erythrocytosis patients with heterozygous point mutations in the HIF2A gene have been identified; whether these mutations were polymorphisms unrelated to the phenotype could not be ruled out. In the present report, we characterize a mouse line bearing a G536W missense mutation in the Hif2a gene that corresponds to the first such human mutation identified (G537W). We obtained mice bearing both heterozygous and homozygous mutations at this locus. We find that these mice display, in a mutation dose-dependent manner, erythrocytosis and pulmonary hypertension with a high degree of penetrance. These findings firmly establish missense mutations in HIF-2α as a cause of erythrocytosis, highlight the importance of this HIF-α isoform in erythropoiesis, and point to physiologic consequences of HIF-2α dysregulation.

Topics: Animals; Basic Helix-Loop-Helix Transcription Factors; Blood Gas Analysis; Cells, Cultured; Disease Models, Animal; Endothelin-1; Erythropoiesis; Erythropoietin; Gene Expression; Gene Knock-In Techniques; Genetic Association Studies; Humans; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Kidney; Lung; Mice; Mice, Inbred C57BL; Mutagenesis; Mutation, Missense; Polycythemia; Proto-Oncogene Proteins c-sis; Respiratory Rate; RNA, Messenger; Up-Regulation; Vascular Endothelial Growth Factor A

Iron regulatory proteins (Irps) 1 and 2 posttranscriptionally control the expression of transcripts that contain iron-responsive element (IRE) sequences, including ferritin, ferroportin, transferrin receptor, and hypoxia-inducible factor 2α (HIF2α). We report here that mice with targeted deletion of Irp1 developed pulmonary hypertension and polycythemia that was exacerbated by a low-iron diet. Hematocrits increased to 65% in iron-starved mice, and many polycythemic mice died of abdominal hemorrhages. Irp1 deletion enhanced HIF2α protein expression in kidneys of Irp1(-/-) mice, which led to increased erythropoietin (EPO) expression, polycythemia, and concomitant tissue iron deficiency. Increased HIF2α expression in pulmonary endothelial cells induced high expression of endothelin-1, likely contributing to the pulmonary hypertension of Irp1(-/-) mice. Our results reveal why anemia is an early physiological consequence of iron deficiency, highlight the physiological significance of Irp1 in regulating erythropoiesis and iron distribution, and provide important insights into the molecular pathogenesis of pulmonary hypertension.

Topics: Animals; Basic Helix-Loop-Helix Transcription Factors; Diet; Endothelial Cells; Endothelin-1; Erythropoietin; Gastrointestinal Hemorrhage; Gene Deletion; Hematopoiesis, Extramedullary; Hypertension, Pulmonary; Iron; Iron Regulatory Protein 1; Iron Regulatory Protein 2; Longevity; Mice; Models, Biological; Nerve Degeneration; Organ Specificity; Polycythemia; Protein Biosynthesis; Transcriptional Activation

Erythropoietin (EPO) has long been utilized for the treatment of renal anemia. The erythropoietin receptor (EPOR) is also expressed in the cardiovascular and central nervous systems in addition to an erythroid lineage, to provide an organoprotective role against several types of cellular stress. Pulmonary hypertension (PH) is a poor prognostic disease caused by primary and secondary pulmonary vascular injury. We observed the effects of EPO derivatives on monocrotaline-induced PH in rats on the supposition that EPO may protect small arteries from injury. Asialoerythropoietin (AEPO) lacks sialic acids in the termini of carbohydrate chains that results in rapid clearance from blood. Carbamyl-erythropoietin (CEPO) interacts with EPOR/βc heterodimers, but not with EPOR homodimers expressed in erythroid cells. Monocrotaline-injected rats were treated with continuous intravenous injection of 2500 ng/kg/day of EPO, AEPO, or CEPO for 21 days, and lung histology, cardiac function, and mRNA expression in the lungs were examined. Wall thickening of small arteries in the lungs and PH were improved by administration of EPO, but not by its non-hematopoietic derivatives, AEPO, or CEPO. Erythropoietin administration increased mRNA expression of the anti-apoptotic molecule, Bcl-xL, and maintained expression of the CD31 antigen. We conclude that lungs may express EPOR homoreceptors, but not heteroreceptors. Adequate serum erythropoietin levels may be essential for pulmonary protective effects.

Topics: Animals; Asialoglycoproteins; Disease Models, Animal; Erythropoietin; Hypertension, Pulmonary; Male; Monocrotaline; Neuroprotective Agents; Rats; Rats, Wistar; Receptors, Erythropoietin; RNA, Messenger; Treatment Outcome

This study sought to understand the prevalence and clinical relevance of iron deficiency in patients with idiopathic pulmonary arterial hypertension (IPAH).. Iron availability influences the pulmonary vascular response to hypoxia in humans and may be significant in the pathogenesis of IPAH.. Iron deficiency, defined by raised levels of soluble transferrin receptor (sTfR), was investigated in 98 patients with IPAH. Hepcidin and erythropoietin (EPO) levels were also measured. The effect of bone morphogenetic protein (BMP) receptor knockdown on BMP-6-stimulated hepcidin production was assessed in human hepatoma HepG2 cells. Relationships between sTfR and exercise capacity, functional class, and all-cause mortality were analyzed.. Circulating sTfR levels were raised in 63% of IPAH patients, indicating significant iron deficiency. Consistent with this, iron, ferritin, and transferrin saturation levels were reduced and red cell distribution width increased, without overt anemia. Hepcidin correlated inversely with sTfR and positively with increasing ferritin. Hepcidin was inappropriately raised in IPAH independent of the inflammatory marker interleukin-6. EPO levels were also raised and correlated inversely with hepcidin. BMP receptor-type 2 (BMPR2) knockdown in HepG2 cells increased BMP-6-stimulated hepcidin expression. sTfR increased with World Health Organization functional class (p < 0.05), correlated negatively with exercise capacity (p = 0.027), and values >28.1 nmol/l independently predicted survival (p = 0.011).. Iron deficiency is common in IPAH patients and associated with disease severity and poor clinical outcome. Inappropriately raised hepcidin levels, which impair iron absorption from the gut, may be a factor.

Topics: Actins; Adult; Antimicrobial Cationic Peptides; Bone Morphogenetic Protein 6; Bone Morphogenetic Proteins; Erythropoietin; Familial Primary Pulmonary Hypertension; Female; Ferritins; Growth Differentiation Factor 15; Hep G2 Cells; Hepcidins; Humans; Hypertension, Pulmonary; Interleukin-1; Iron; Iron Deficiencies; Liver; Male; Middle Aged; Receptors, Transferrin

Patients with refractory anemia with ring sideroblasts and thrombocytosis (RARS-T) are difficult to treat because the cytoreductive treatment might be beneficial for the thrombocytosis component but harmful for the RARS component. As lenalidomide has shown to be efficacious in both myelodysplastic syndromes and myeloproliferative neoplasms, we have treated 2 RARS-T patients, who were transfusion dependent, with lenalidomide. We report the results of lenalidomide treatment in these patients and show that lenalidomide has clinical activity in this rare disorder. Both patients became transfusion independent, and 1 of the patients attained indeed a complete molecular remission.

Topics: Aged, 80 and over; Anabolic Agents; Anemia, Refractory; Anemia, Sideroblastic; Antineoplastic Agents; Erythropoietin; Humans; Hypertension, Pulmonary; Janus Kinase 2; Lenalidomide; Male; Middle Aged; Mutation; Pulmonary Embolism; Pyridoxine; Reverse Transcriptase Polymerase Chain Reaction; Thalidomide; Thrombocytosis; Vitamin B Complex

To investigate the effect of polycythemia on hypoxia induced pulmonary hypertension and pulmonary vascular remodeling in rats.. The healthy female Sprague-Dawley rats were randomly divided into 3 groups: normoxia control group (C group), hypoxia group (H group), hypoxia + different doses of human recombine hemopoietin (rEPO) group. All rats in hyoxia groups were exposed to hypoxia, 8 hours every day, for 21 days. The rEPO groups were injected sc with different doses of rEPO (300 U/kg, 600 U/kg, 900 U/kg, 1200 U/kg) thrice weekly. Blood samples were taken for the measurement of RBC, Hb, Hct, plasma EPO concentration, whole blood/plasma viscosities, the animals were then catheterized to record mean pulmonary arterial pressure (mPAP) and demised to calculate the ratio [RV/(LV+S)]. Percentage of vascular wall thickness and muscularization of non-muscular pulmonary arteriole were examined microscopically.. (1) As the dosage of exogenous rEPO increased, blood concentration of EPO increased correspondingly, as RBC, Hb, Hct and whole blood/plasma viscosities increased in various degrees. (2) There was positive correlation between whole blood viscosity and Hct at both high and low shears and linear correlation between mPAP and whole blood viscosity at high shear. (3) The degree of pulmonary hypertension, reflected by mPAP increased in accordance to rEPO dosage increment. However, the extent of pulmonary vascular remodeling alleviated somehow as the rEPO dose increased and so did right ventricular hypertrophy.. Polycythemia induced by exogenous EPO increases the blood viscosity and the pulmonary vascular resistance, which contributes to the formation of hypoxia induced pulmonary hypertension.

Topics: Animals; Erythropoietin; Female; Hypertension, Pulmonary; Hypoxia; Polycythemia; Pulmonary Artery; Random Allocation; Rats; Rats, Sprague-Dawley

Erythropoietin (EPO) mobilises endothelial progenitor cells and promotes neovascularisation in heart failure. The present authors studied the effects of EPO on pulmonary vascular and cardiac remodelling in a model for flow-associated pulmonary arterial hypertension (PAH). PAH was induced in adult male Wistar rats by the injection of monocrotaline combined with an abdominal aortocaval shunt 1 week later (PAH or experimental group). Immediately afterwards, rats were randomised into those who received treatment with EPO (PAH+EPO group) and controls. Pulmonary and systemic haemodynamics, and right ventricular and pulmonary vascular remodelling were evaluated 3 weeks later. Vascular occlusion of the intra-acinar pulmonary vessels (13.4+/-0.7 versus 16.7+/-1.3% in PAH+EPO and PAH, respectively) and medial wall thickness of the pre-acinar arteries (wall-to-lumen ratio 0.13+/-0.01 versus 0.17+/-0.01 in PAH+EPO and PAH, respectively) decreased after treatment with EPO. Moreover, right ventricular capillary density was increased by therapy (2,322+/-61 versus 2,100+/-63 capillaries x mm(-2) in PAH+EPO and PAH, respectively). Increased mean pulmonary arterial pressure and decreased right ventricular contractility in the model were not altered by EPO treatment. In this rat model of flow-associated pulmonary arterial hypertension, erythropoietin treatment beneficially affected pulmonary vascular and cardiac remodelling. These histopathological effects were not accompanied by significantly improved haemodynamics.

Topics: Animals; Erythropoietin; Gene Expression Regulation; Heart Ventricles; Hypertension, Pulmonary; Male; Monocrotaline; Neovascularization, Pathologic; Pulmonary Circulation; Rats; Rats, Wistar; Stem Cells; Time Factors; Vascular Endothelial Growth Factor A; Ventricular Remodeling

Recent studies have suggested that endogenous erythropoietin (Epo) plays an important role in the mobilization of bone marrow-derived endothelial progenitor cells (EPCs). However, it remains to be elucidated whether the Epo system exerts protective effects on pulmonary hypertension (PH), a fatal disorder encountered in cardiovascular medicine.. A mouse model of hypoxia-induced PH was used for study. We evaluated right ventricular systolic pressure, right ventricular hypertrophy, and pulmonary vascular remodeling in mice lacking the Epo receptor (EpoR) in nonerythroid lineages (EpoR(-/-) rescued mice) after 3 weeks of exposure to hypoxia. Those mice lack EpoR in the cardiovascular system but not in the hematopoietic system. The development of PH and pulmonary vascular remodeling were accelerated in EpoR(-/-) rescued mice compared with wild-type mice. The mobilization of EPCs and their recruitment to the pulmonary endothelium were significantly impaired in EpoR(-/-) rescued mice. By contrast, reconstitution of the bone marrow with wild-type bone marrow cells ameliorated PH in the EpoR(-/-) rescued mice. Hypoxia enhanced the expression of EpoR on pulmonary endothelial cells in wild-type but not EpoR(-/-) rescued mice. Finally, hypoxia activated endothelial nitric oxide synthase in the lungs in wild-type mice but not in EpoR(-/-) rescued mice.. These results indicate that the endogenous Epo/EpoR system plays an important role in the recruitment of EPCs and prevents the development of PH during chronic hypoxia in mice in vivo, suggesting the therapeutic importance of the system for the treatment of PH.

Topics: Animals; Bone Marrow Transplantation; Cell Movement; Cells, Cultured; Chronic Disease; Endothelial Cells; Endothelium; Endothelium, Vascular; Enzyme Activation; Erythroid Precursor Cells; Erythropoietin; GATA1 Transcription Factor; Heart Failure; Hematopoietic Stem Cells; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Lung; Male; Mice; Mice, Knockout; Mice, Transgenic; Muscle, Smooth, Vascular; Nitric Oxide Synthase Type III; Organ Specificity; Radiation Chimera; Receptor, TIE-2; Receptors, Erythropoietin; Systole; Ventricular Dysfunction, Right

Acute alveolar hypoxia causes pulmonary vasoconstriction that matches lung perfusion to ventilation to optimize gas exchange. Chronic alveolar hypoxia induces pulmonary hypertension, characterized by increased muscularization of the pulmonary vasculature and right ventricular hypertrophy. Elevated erythropoietin (EPO) plasma levels increase hematocrit and blood viscosity and may affect structure and function of the pulmonary circulation. To differentiate between the direct effects of hypoxia and those linked to a hypoxia-induced increase in EPO/hematocrit levels, we investigated the lung vasculature in transgenic mice constitutively over-expressing EPO (termed tg6) upon exposure to normoxia and chronic hypoxia. Despite increased hematocrit levels (approximately 0.86),tg6 mice kept in normoxia did not develop selective right ventricular hypertrophy. The portion of vessels with a diameter of 51-95 microm and >155 microm was increased whereas the portion of small vessels (30-50 microm) was decreased. Pulmonary vascular resistance and the strength of hypoxic vasoconstriction measured in isolated perfused lungs were decreased. Vasoconstrictions induced by the thromboxane mimetic U46619 tended to be reduced. After chronic hypoxia (FiO2 = 0.10, 21 days), vascular resistance and vasoconstrictor responses to acute hypoxia and U46619 were reduced in tg6 mice compared to wildtype controls. Chronic hypoxia increased the degree of pulmonary vascular muscularization in wildtype but not in tg6 mice that already exhibited less muscularization in normoxia. In conclusion, congenital over-expression of EPO exerts an "anti-pulmonary hypertensive" effect, both structurally and functionally, particularly obvious upon chronic hypoxia.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Aspirin; Blood Pressure; Blood Vessels; Blood Viscosity; Cyclooxygenase Inhibitors; Erythropoietin; Hematocrit; Hypertension, Pulmonary; Hypertrophy, Left Ventricular; Hypertrophy, Right Ventricular; Hypoxia; Lung; Mice; Mice, Inbred C57BL; Mice, Transgenic; Muscle, Smooth, Vascular; Nitric Oxide Synthase; omega-N-Methylarginine; Up-Regulation; Vascular Resistance; Vasoconstriction; Vasoconstrictor Agents

Pulmonary vascular remodeling during chronic hypoxia may be the result of either oxygen deprivation or erythrocytosis. To separate experimentally the effects of hypoxia and erythrocytosis, we analyzed transgenic mice that constitutively overexpress the human erythropoietin gene in an oxygen-independent manner. These mice are characterized by polycythemia but have normal blood pressure, heart rate, and cardiac output. In transgenic mice, pulmonary artery pressure (PAP) was increased in vivo but was reduced in blood-free perfused lungs. The thromboxane receptor agonist U46619 caused a smaller rise in PAP in isolated transgenic lungs than in lungs from wild-type mice. The transgenic pulmonary vasculature was characterized by elevated prostacyclin production, stronger endothelial nitric oxide synthase expression, and reduced pulmonary vascular smooth muscle thickness. The fact that transgenic polycythemic mice have marked pulmonary hypertension in vivo but not in vitro suggests that their pulmonary hypertension is due to the increased blood viscosity, thus supporting an independent role of polycythemia in the development of pulmonary hypertension. In addition, our findings indicate that the lungs of transgenic animals adapt to the high PAP by elevated synthesis of vasodilators and reduced vascular smooth muscle thickness that tend to reduce vascular tone and vascular responsiveness.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Analysis of Variance; Animals; Blood Viscosity; Erythropoietin; Hypertension, Pulmonary; Hypoxia; Immunohistochemistry; Lung; Mice; Mice, Transgenic; Muscle, Smooth, Vascular; Polycythemia; Pulmonary Artery; Vasoconstrictor Agents

Topics: Adult; Aged; Aged, 80 and over; Aortic Valve Insufficiency; Aortic Valve Stenosis; Cardiac Surgical Procedures; Christianity; Coronary Artery Bypass; Erythropoietin; Female; Heart Septal Defects, Atrial; Humans; Hypertension, Pulmonary; Middle Aged; Mitral Valve Insufficiency; Myocardial Infarction; Pulmonary Valve Stenosis; Religion and Medicine; Rheumatic Heart Disease; Tricuspid Valve Insufficiency

In two rat strains (H and M) with differing susceptibilities to chronic hypoxia we examined the role of polycythemia in the differing hypoxic pulmonary hemodynamic responses. We hypothesized that augmentation of hematocrit (Hct) during hypoxia in the resistant M strain would render cardiopulmonary responses similar to those obtained in the susceptible H strain. Administration of human recombinant erythropoietin (EPO) in doses of 100, 250 and 500 U.kg-1 s.c. thrice weekly for three weeks raised Hct similarly in both strains indicating that normoxic rats had similar sensitivities to EPO. In rats exposed to hypobaric hypoxia (0.5 atm) for 21 days, EPO (500 U.kg-1 thrice weekly) significantly increased Hct and whole blood viscosity as expected. Surprisingly, right ventricular (RV) to body weight (BW) ratio as an index of right ventricular hypertrophy (RVH) and RV peak systolic pressure did not increase in EPO-injected rats of either strain compared to hypoxic controls. Among hypoxic animals, Hct correlated highly with viscosity but not with RV/BW. We conclude, contrary to our hypothesis, that polycythemia does not appear to be responsible for the strain difference in RVH and pulmonary hypertension.

Topics: Animals; Erythropoietin; Hematocrit; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Polycythemia; Pulmonary Circulation; Rats; Rats, Sprague-Dawley; Species Specificity

Topics: Adult; Budd-Chiari Syndrome; Dyspnea; Erythropoietin; Hepatomegaly; Humans; Hypertension, Pulmonary; Kidney Diseases, Cystic; Male; Polycythemia

Topics: Blood Cell Count; Blood Volume Determination; Child; Child, Preschool; Erythropoietin; Female; Hematocrit; Hemoglobins; Humans; Hypertension, Pulmonary; Male; Polycythemia