losartan-potassium and Hyperoxia

Erythropoietin (Epo) was once considered to be a regulator of erythropoiesis by controlling the apoptosis, proliferation and differentiation of erythroid precursor cells over an extended period of time. However, the expression of Epo and Epo receptor (Epo-R) occurs in the brain and retina in addition to the kidney. These expression behaviors lead to physiological effects in addition to hematocrit elevation. In this review we discuss the protective effect of Epo on retinal cells.

Topics: Animals; Cell Survival; Erythropoietin; Humans; Hyperoxia; Hypoxia; Retinal Degeneration

Hypoxia is the natural trigger for endogenous EPO production but recently the use of intermittent hyperoxia to stimulate EPO has been postulated and this phenomenon has been called the "normobaric oxygen paradox" (NOP). The "NOP" is a mechanism by which oxygen regulates the expression of the Hypoxia Inducible Factor 1 alpha (HIF-1α). The HIF-1α-depending gene regulation is responsible for many different genetic expressions including EPO and VEGF. It has been proposed that relative changes of oxygen availability rather than steady state hypoxic or hyperoxic conditions, play an important role in HIF transcriptional effects. According to this hypothesis, the cell interprets the return to normoxia after a hyperoxic event as an oxygen shortage, and induces HIF-1-regulated gene synthesis, including EPO. Being both a hormone and a cytokine, the actual actions of EPO are complex; its clinical utility has been postulated for neuroprotection and cardioprotection. The precise level of inspired oxygen and the exact timeframe for its iterative administration are not totally known. N-Acetyl-L-Cysteine (NAC) supplementation has been shown to help. All the reported data demonstrate how hyperoxic and hypoxic states can potentially be manipulated if oxygen is been considered as a multifaceted molecule more than just a gas.

Topics: Erythropoietin; Humans; Hyperoxia; Oxygen

Perinatal hypoxic-ischemic encephalopathy can be a devastating complication of childbirth. Herein, the authors review the pathophysiology of hypoxic-ischemic encephalopathy and the current status of neuroprotective strategies to ameliorate the injury centering on four themes: (1) monitoring in the perinatal period, (2) rapid identification of affected neonates to allow timely institution of therapy, (3) preconditioning therapy (a therapeutic that reduces the brain vulnerability) before hypoxic-ischemic encephalopathy, and (4) prompt institution of postinsult therapies to ameliorate the evolving injury. Recent clinical trials have demonstrated the significant benefit for hypothermic therapy in the postnatal period; furthermore, there is accumulating preclinical evidence that adjunctive therapies can enhance hypothermic neuroprotection. Advances in the understanding of preconditioning may lead to the administration of neuroprotective agents earlier during childbirth. Although most of these neuroprotective strategies have not yet entered clinical practice, there is a significant hope that further developments will enhance hypothermic neuroprotection.

Topics: Adrenergic alpha-Agonists; Animals; Anti-Inflammatory Agents; Anticonvulsants; Antioxidants; Apoptosis; Erythropoietin; Female; Free Radical Scavengers; Humans; Hyperoxia; Hypocapnia; Hypoxia-Ischemia, Brain; Inflammation; Ischemic Preconditioning; Neuroprotective Agents; Neurotoxins; Pregnancy; Prenatal Diagnosis; Receptors, N-Methyl-D-Aspartate; Seizures

The history of retinopathy of prematurity (ROP) gives a prime example of how dangerous the uncontrolled introduction of a new medical treatment--particularly in the field of neonatology--may be. The most important risk factors for the development of ROP are the immaturity of premature infants as well as uncontrolled and/or inadequate treatment with oxygen. In comparison to the fetus, the premature infant is exposed to a nonphysiologically high oxygen concentration. This hyperoxia leads to formation of aggressive oxygen radicals on the one hand and, on the other hand, to temporarily reduced production of growth factors such as vascular endothelial growth factor and erythropoietin, which both play an important role in the pathogenesis of ROP. The most important measure to prevent ROP is restrictive and carefully monitored oxygen treatment. Medical treatment to prevent ROP includes injection of D-penicillamine and retinol, but the available data are still limited, particularly with regard to the long-term effects of this treatment. A higher oxygenation in prethreshold ROP does not lead to recovery of ocular findings, but it increases the incidence of pulmonary complications. A reduction of light intensity in neonatal intensive care units proved not to be efficient for preventing ROP. To avoid blindness, standardized screening of the risk group is needed.

Topics: Erythrocyte Transfusion; Erythropoietin; Gestational Age; Humans; Hyperoxia; Infant, Newborn; Iron Overload; Mass Screening; Oxygen Inhalation Therapy; Recombinant Proteins; Referral and Consultation; Retinopathy of Prematurity; Risk Factors

Recent findings suggest that besides renal tissue hypoxia, relative decrements in tissue oxygenation, using a transition of the breathing mixture from hyperoxic to normoxic, can also stimulate erythropoietin (EPO) production. To further clarify the importance of the relative change in tissue oxygenation on plasma EPO concentration [EPO], we investigated the effect of a consecutive hyperoxic and hypoxic breathing intervention. Eighteen healthy male subjects were assigned to either IHH (N = 10) or CON (N = 8) group. The IHH group breathed pure oxygen (F(i)O(2) ~ 1.0) for 1 h, followed by a 1-h period of breathing a hypoxic gas mixture (F(i)O(2) ~ 0.15). The CON group breathed a normoxic gas mixture (F(i)O(2) ~ 0.21) for the same duration (2 h). Blood samples were taken just before, after 60 min, and immediately after the 2-h exposure period. Thereafter, samples were taken at 3, 5, 8, 24, 32, and 48 h after the exposure. During the breathing interventions, subjects remained in supine position. There were significant increases in absolute [EPO] within groups at 8 and 32 h in the CON and at 32 h only in the IHH group. No significant differences in absolute [EPO] were observed between groups following the intervention. Relative (∆[EPO]) levels were significantly lower in the IHH than in the CON group, 5 and 8 h following exposure. The tested protocol of consecutive hyperoxic-hypoxic gas mixture breathing did not induce [EPO] synthesis stimulation. Moreover, the transient attenuation in ∆[EPO] in the IHH group was most likely due to a hyperoxic suppression. Hence, our findings provide further evidence against the "normobaric O(2) paradox" theory.

Topics: Acute Disease; Adult; Erythropoietin; Humans; Hyperoxia; Hypoxia; Male; Models, Theoretical; Nitrogen; Oxygen; Oxygen Consumption; Respiration; Time Factors; Young Adult

Previous studies in healthy subjects have shown an increase in erythropoietin (EPO) production after administration of N-acetyl-cysteine (NAC). These authors hypothesized that NAC increases intracellular reduced glutathione, decreasing reactive oxygen species and enabling EPO production. We investigated if EPO production could be stimulated with a single dose of NAC, after 90 min of pure oxygen breathing. Thirty-eight healthy volunteers were randomized into either the control (C) group or the NAC group, which received 600 mg NAC PO dissolved in a glass of orange juice, 60 min before breathing 15 L/min of 100% normobaric oxygen. Orange juice was administered to both groups. Blood samples for EPO measurement were taken at T0, before the orange juice administration, and T1, T2, T3 and T4, respectively, 8, 24, 32 and 48 h after the orange juice. The EPO concentrations of the NAC group decreased significantly at T1, followed by a significant increase compared to baseline, which was obvious until T4. The EPO concentrations of the C group did not show any significant variations. In this study, a significant increase of EPO production was observed after a short-term hyperoxic stimulus only when preceded with the administration of a single dose of NAC.

Topics: Acetylcysteine; Adult; Erythropoietin; Exercise Test; Female; Humans; Hyperoxia; Male; Middle Aged; Oxygen; Oxygen Consumption; Respiratory Function Tests; Time Factors; Young Adult

Erythropoietin (EPO) controls red cell production. Hypoxaemia, reduced blood oxygen-carrying capacity and increased affinity of haemoglobin (Hb) for oxygen are the primary stimuli for EPO secretion. The effect of hyperoxaemia (arterial oxygen tension (Pa,O2) > 13.3 kPa) on EPO secretion has not been thoroughly studied and is not fully understood. The primary purpose of this study was to evaluate EPO production in patients with acute respiratory failure as well as to determine the effect of hyperoxaemia on EPO secretion in patients with and without anaemia. A prospective clinical study was carried out in a 14-bed general (medical and surgical) intensive care unit in a university hospital. Twenty-one patients with acute or acute on chronic respiratory failure, requiring mechanical ventilation, were included in this study. The patients were divided into two groups; group I comprised patients who developed anaemia, and group II patients who did not. EPO levels and haematological parameters were measured in venous blood under three oxygenation conditions: hypoxaemia, hyperoxaemia and normoxaemia. All patients exhibited high EPO levels during hypoxaemia (mean value 108.7 +/- 27 mU.mL-1 (+/- SD)). During hyperoxaemia, EPO levels decreased in both groups (mean value 21.6 +/- 15.2 mU.mL-1 in group I, 36.8 +/- 19 mU.mL-1 in group II). During normoxaemia, EPO levels increased again in group I patients, but in group II patients EPO production remained stable. In conclusion, hyperoxaemia inhibits erythropoietin secretion in spite of anaemia and low arterial oxygen tension. Hyperoxaemia may be a contributing factor to anaemia in intensive care unit patients under oxygen therapy.

Topics: Adult; Aged; Analysis of Variance; Anemia; Blood Gas Analysis; Erythropoietin; Female; Humans; Hyperoxia; Linear Models; Lung Diseases, Obstructive; Male; Middle Aged; Monitoring, Physiologic; Prospective Studies; Pulmonary Gas Exchange; Respiration, Artificial; Respiratory Insufficiency; Sensitivity and Specificity

Aquatic hypoxia is both a naturally-occurring and anthropogenically-generated event. Fish species have evolved different adaptations to cope with hypoxic environments, including gill modifications and air breathing. However, little is known about the molecular mechanisms involved in the respiration of embryonic and larval fishes during critical windows of development. We assessed expression of the genes hif-1α, fih-1, nhe1, epo, gr and il8 using the developing tropical gar as a piscine model during three developmental periods (fertilization to hatch, 1 to 6 days post hatch (dph) and 7 to 12 dph) when exposed to normoxia (~7.43 mg/L DO), hypoxia (~2.5 mg/L DO) or hyperoxia (~9.15 mg/L DO). All genes had higher expression when fish were exposed to either hypoxia or hyperoxia during the first two developmental periods. However, fish continuously exposed to hypoxia had increased expression of the six genes by hatching and 6 dph, and by 12 dph only hif-1α still had increased expression. The middle developmental period was the most hypoxia-sensitive, coinciding with several changes in physiology and morphology. The oldest larvae were the most resilient to gene expression change, with little variation in expression of the six genes compared. This study is the first to relate the molecular response of an air-breathing fish to oxygen availability to developmental critical windows and contributes to our understanding of some molecular responses of developing fish to changes in oxygen availability.

Topics: Animals; Aquaculture; Erythropoietin; Female; Fish Diseases; Fish Proteins; Fishes; Gene Expression Regulation, Developmental; Hyperoxia; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Interleukin-8; Male; Receptors, Glucocorticoid; Respiratory Physiological Phenomena; Sodium-Hydrogen Exchanger 1

Anemia of prematurity is common in extremely preterm neonates, and oxygen exposure may participate to anemia by inhibiting erythropoietin secretion. We aimed to determine whether hyperoxia exerts an independent role in the occurrence of the anemia of prematurity.. Sprague-Dawley pups were exposed to 80% oxygen or room air from days 3 to 10 of life. Main outcome was the difference in hemoglobin and circulating erythropoietin levels in animals exposed to hyperoxia at 10 days of life. We performed a complete blood count analysis using fluorescent laser flow cytometry and measured circulating erythropoietin levels using ELISA.. We found lower hemoglobin in the hyperoxia group, compared to the normoxia group, both in males (70 ± 3 versus 78 ± 2 g/l) and in females (71 ± 2 versus 81 ± 3 g/l) at 10 days of life. Reticulocyte count was not increased in the hyperoxia group. Circulating erythropoietin levels were lower at 10 days of life in the animals exposed to hyperoxia, both in males (33 ± 7 versus 73 ± 6 pg/ml) and in females (37 ± 5 versus 66 ± 3 pg/ml), but were similar at 28 days of life.. Neonatal exposure to hyperoxia decreases hematopoiesis in rats.. Mechanisms leading to anemia of prematurity are not well known and their study in humans is complicated due to multiple confounders. This study shows for the first time that exposure to high concentrations of oxygen in the neonatal period decreases hematopoiesis in rats, providing insight on the pathophysiological mechanisms of the anemia of prematurity. This research paves the way for future therapeutic developments aiming to reduce the burden of anemia of prematurity and the necessity of red blood cell transfusions in extremely preterm neonates.

Topics: Animals; Animals, Newborn; Erythropoietin; Female; Humans; Hyperoxia; Infant, Newborn; Infant, Premature, Diseases; Male; Oxygen; Rats; Rats, Sprague-Dawley

The aim of the present study is to investigate the protection effects of bone marrow mesenchymal stem cells (MSCs) in combination with EPO against hyperoxia-induced bronchopulmonary dysplasia (BPD) injury in neonatal mice. BPD model was prepared by continuous high oxygen exposure, 1×106 bone marrow MSCs and 5000U/kg recombinant human erythropoietin (EPO) were injected respectively. Results showed that administration of MSCs, EPO especially MSCs+EPO significant attenuated hyperoxia-induced lung damage with a decrease of fibrosis, radical alveolar counts and inhibition of the occurrence of epithelial-mesenchymal transition (EMT). Furthermore, MSCs+EPO co-treatment more significantly suppressed the levels of transforming growth factor-β1(TGF-β1) than MSCs or EPO alone. Collectively, these results suggested that MSCs, EPO in particular MSCs+EPO co-treatment could promote lung repair in hyperoxia-induced alveoli dysplasia injury via inhibition of TGF-β1 signaling pathway to further suppress EMT process and may be a promising therapeutic strategy.

Topics: Animals; Bronchopulmonary Dysplasia; Cells, Cultured; Combined Modality Therapy; Disease Models, Animal; Epithelial-Mesenchymal Transition; Erythropoietin; Female; Fibrosis; Humans; Hyperoxia; Mesenchymal Stem Cell Transplantation; Mice; Mice, Inbred C57BL; Pulmonary Alveoli; Recombinant Proteins; Signal Transduction; Transforming Growth Factor beta1

Hypoxia induces angiogenesis while hyperoxia promotes vasoregression in the retina. We investigated herein the effect of prolonged hyperoxia on retinal angiogenesis and the underlying mechanism in an oxygen-induced retinopathy (OIR) model.. Vascular morphology was quantified in whole-mount retina from the mice subjected to the conventional OIR model (c-OIR) or the OIR model with prolonged hyperoxia (p-OIR). Expressions of genes related to angiogenesis were determined by real-time PCR.. p-OIR retinas showed few intraretinal neovascular tufts at the border of avascular zones, lacking preretinal neovascularization, whereas c-OIR retinas had numerous preretinal neovascularizations. p-OIR retinas demonstrated outgrowth of capillaries in the deep layers despite persistent hyperoxia and possess a larger avascular zone compared with the c-OIR retinas. The capillaries in the p-OIR retinas were well-formed in contrast to those in the c-OIR retinas. p-OIR retinas expressed significantly higher TNFα (∼4 fold) than c-OIR retinas. The expression of vascular endothelial growth factor, Erythropoietin, Angiopoietin 1 and 2 remained unchanged.. Our data demonstrate that TNFα transcription is increased in hyperoxia-promoted retinal angiogenesis, implicating it, in association with low VEGF levels, as a possible proponent in retinal angiogenesis under hyperoxia.

Topics: Angiopoietin-1; Angiopoietin-2; Animals; Erythropoietin; Fluorescent Antibody Technique; Gene Expression Regulation; Hyperoxia; Hypoxia; Mice, Inbred C57BL; Retinal Neovascularization; Reverse Transcriptase Polymerase Chain Reaction; Transcription, Genetic; Tumor Necrosis Factor-alpha; Up-Regulation; Vascular Endothelial Growth Factor A

Cerebral white and grey matter injury is the leading cause of an adverse neurodevelopmental outcome in prematurely born infants. High oxygen concentrations have been shown to contribute to the pathogenesis of neonatal brain damage. Here, we focused on motor-cognitive outcome up to the adolescent and adult age in an experimental model of preterm brain injury. In search of the putative mechanisms of action we evaluated oligodendrocyte degeneration, myelination, and modulation of synaptic plasticity-related molecules. A single dose of erythropoietin (20,000 IU/kg) at the onset of hyperoxia (24 hours, 80% oxygen) in 6-day-old Wistar rats improved long-lasting neurocognitive development up to the adolescent and adult stage. Analysis of white matter structures revealed a reduction of acute oligodendrocyte degeneration. However, erythropoietin did not influence hypomyelination occurring a few days after injury or long-term microstructural white matter abnormalities detected in adult animals. Erythropoietin administration reverted hyperoxia-induced reduction of neuronal plasticity-related mRNA expression up to four months after injury. Thus, our findings highlight the importance of erythropoietin as a neuroregenerative treatment option in neonatal brain injury, leading to improved memory function in adolescent and adult rats which may be linked to increased neuronal network connectivity.

Topics: Animals; Animals, Newborn; Behavior, Animal; Brain Injuries; Cell Survival; Cognition; Diffusion Tensor Imaging; Disease Models, Animal; Down-Regulation; Erythropoietin; Hyperoxia; Immunohistochemistry; Microscopy, Confocal; Mitochondria; Myelin Basic Protein; Neuregulin-1; Neuronal Plasticity; Neuropilin-1; Neuroprotective Agents; Oligodendroglia; Rats; Rats, Wistar; Synaptophysin; White Matter

Adult animals that have been perinatally exposed to oxygen-rich atmospheres (hyperoxia), recalling those used for oxygen therapy in infants, exhibit a loss of hypoxic pulmonary vasoconstriction, whereas vasoconstriction elicited by depolarizing agents is maintained. Loss of pulmonary hypoxic vasoconstriction is not linked to alterations in oxygen-sensitive K(+) currents in pulmonary artery smooth muscle cells. Loss of hypoxic vasoconstriction is associated with early postnatal oxidative damage and corrected by an antioxidant diet. Perinatal hyperoxia damages carotid body chemoreceptor cell function and the antioxidant diet does not reverse it. The hypoxia-elicited increase in erythropoietin plasma levels is not affected by perinatal hyperoxia. The potential clinical significance of the findings in clinical situations such as pneumonia, chronic obstructive pulmonary disease or general anaesthesia is considered.. Adult mammalians possess three cell systems that are activated by acute bodily hypoxia: pulmonary artery smooth muscle cells (PASMC), carotid body chemoreceptor cells (CBCC) and erythropoietin (EPO)-producing cells. In rats, chronic perinatal hyperoxia causes permanent carotid body (CB) atrophy and functional alterations of surviving CBCC. There are no studies on PASMC or EPO-producing cells. Our aim is to define possible long-lasting functional changes in PASMC or EPO-producing cells (measured as EPO plasma levels) and, further, to analyse CBCC functional alterations. We used 3- to 4-month-old rats born and reared in a normal atmosphere or exposed to perinatal hyperoxia (55-60% O2 for the last 5-6 days of pregnancy and 4 weeks after birth). Perinatal hyperoxia causes an almost complete loss of hypoxic pulmonary vasoconstriction (HPV), which was correlated with lung oxidative status in early postnatal life and prevented by antioxidant supplementation in the diet. O2 -sensitivity of K(+) currents in the PASMC of hyperoxic animals is normal, indicating that their inhibition is not sufficient to trigger HPV. Perinatal hyperoxia also abrogated responses elicited by hypoxia on catecholamine and cAMP metabolism in the CB. An increase in EPO plasma levels elicited by hypoxia was identical in hyperoxic and control animals, implying a normal functioning of EPO-producing cells. The loss of HPV observed in adult rats and caused by perinatal hyperoxia, comparable to oxygen therapy in premature infants, might represent a previously unrecognized complication of such a medical intervention capable of aggravating medical conditions such as regional pneumonias, atelectases or general anaesthesia in adult life.

Topics: Animals; Antioxidants; Carotid Body; Erythropoietin; Female; Hyperoxia; Hypoxia; Pregnancy; Pulmonary Artery; Rats, Wistar; Vasoconstriction

Activation of hypoxia-inducible factor (HIF) can prevent oxygen-induced retinopathy in rodents. Here we demonstrate that dimethyloxaloylglycine (DMOG)-induced retinovascular protection is dependent on hepatic HIF-1 because mice deficient in liver-specific HIF-1α experience hyperoxia-induced damage even with DMOG treatment, whereas DMOG-treated wild-type mice have 50% less avascular retina (P < 0.0001). Hepatic HIF stabilization protects retinal function because DMOG normalizes the b-wave on electroretinography in wild-type mice. The localization of DMOG action to the liver is further supported by evidence that i) mRNA and protein erythropoietin levels within liver and serum increased in DMOG-treated wild-type animals but are reduced by 60% in liver-specific HIF-1α knockout mice treated with DMOG, ii) triple-positive (Sca1/cKit/VEGFR2), bone-marrow-derived endothelial precursor cells increased twofold in DMOG-treated wild-type mice (P < 0.001) but are unchanged in hepatic HIF-1α knockout mice in response to DMOG, and iii) hepatic luminescence in the luciferase oxygen-dependent degradation domain mouse was induced by subcutaneous and intraperitoneal DMOG. These findings uncover a novel endocrine mechanism for retinovascular protection. Activating HIF in visceral organs such as the liver may be a simple strategy to protect capillary beds in the retina and in other peripheral tissues.

Topics: Amino Acids, Dicarboxylic; Animals; Erythropoietin; Hyperoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Liver; Mice; Mice, Knockout; Oxygen; Retinal Diseases

Erythropoiesis is affected during deep saturation dives. The mechanism should be related to a downregulation of serum Erythropoietin (s-EPO) concentration or to a toxic effect of the hyperbaric hyperoxia. We evaluated s-EPO and other haematological parameters in 6 scuba divers before, during and after a 14-days guinness saturation dive (8-10 m). Athletes were breathing air at 1.8-2 ATA, under the control of a team of physicians. Serum parameters were measured before diving (T0) and: 7 days (T1), 14 days (T2) after the beginning of the dive and 2 h (T3) and 24 h (T4) after resurfacing. Hgb, and many other haematological parameters did not change whereas Ht, s-EPO, the ratio between s-EPO predicted and that observed and reticulocytes (absolute, percent) declined progressively from T0 to T3. At T4 a significant rise in s-EPO was observed. Hgb did not vary but erythropoiesis seemed to be affected as s-EPO and reticulocyte counts showed. All these changes were statistically significant. The experiment, conducted in realistic conditions of dive length, oxygen concentration and pressure, allows us to formulate some hypotheses about the role of prolonged hyperbarism on erythropoiesis. The s-EPO rise, 24 h after resurfacing, is clearly documented and related to the "Normobaric Oxygen Paradox". This evidence suggests interesting hypotheses for new clinical applications such as modulation of s-EPO production and Hgb content triggered by appropriate O₂ administration in pre-surgical patients or in some anemic disease.

Topics: Adult; Atmospheric Pressure; Biomarkers; Diving; Erythropoiesis; Erythropoietin; Female; Healthy Volunteers; Hemoglobins; Humans; Hyperoxia; Male; Middle Aged

To study the effect of systemic hypoxia-inducible factor prolyl hydroxylase inhibition (HIF PHDi) in the rat 50/10 oxygen-induced retinopathy (OIR) model.. Oxygen-induced retinopathy was created with the rat 50/10 OIR model. OIR animals received intraperitoneal injections of dimethyloxalylglycine (DMOG, 200 μg/g), an antagonist of α-ketoglutarate cofactor and inhibitor for HIF PHD, on postnatal day (P)3, P5, and P7. Control animals received intraperitoneal injections of PBS. On P14 and P21, animals were humanely killed and the effect on vascular obliteration, tortuosity, and neovascularization quantified. To analyze HIF and erythropoietin, rats at P5 were injected with DMOG (200 μg/g). Western blot or ELISA measured the levels of HIF-1 and Epo protein. Epo mRNA was measured by quantitative PCR.. Alternating hyperoxia and hypoxia in untreated rats led to peripheral vascular obliteration on day P14 and P21. Rats that were treated with systemic DMOG by intraperitoneal injections had 3 times less ischemia and greater peripheral vascularity (P = 0.001) than control animals treated with PBS injections. Neovascularization similarly decreased by a factor of 3 (P = 0.0002). Intraperitoneal DMOG administration increased the levels of HIF and Epo in the liver and brain. Serum Epo also increased 6-fold (P = 0.0016). Systemic DMOG had no adverse effect on growth of rats treated with oxygen.. One of the many controversies in the study of retinopathy of prematurity is whether hyperoxia or alternating hyperoxia and hypoxia creates the disease phenotype in humans. We have previously demonstrated that PHDi prevents OIR in mice exposed to 5 days of sustained 75% oxygen followed by 5 days of 21% oxygen. The 50/10 rat experiments demonstrate that PHDi is also effective in a 24-hour alternating hyperoxia-hypoxia model. The rat OIR model further validates the therapeutic value of HIF PHDi to prevent retinopathy of prematurity because it reduces oxygen-induced vascular obliteration and retinovascular growth attenuation in prolonged and/or alternating hyperoxia.

Topics: Amino Acids, Dicarboxylic; Animals; Animals, Newborn; Blotting, Western; Disease Models, Animal; Enzyme-Linked Immunosorbent Assay; Erythropoietin; Hyperoxia; Hypoxia-Inducible Factor 1; Injections, Intraperitoneal; Neovascularization, Pathologic; Oxygen; Procollagen-Proline Dioxygenase; Rats; Retinal Diseases; Retinal Vessels

The partial pressure of oxygen in the brain parenchyma is tightly controlled, and normal brain function is delicately sensitive to continuous and controlled oxygen delivery. The objective of this study was to determine brain angiogenic adaptive changes during chronic normobaric hyperoxia and hypercapnia in mice. Four-month-old C56BL/6 J mice were kept in a normobaric chamber at 50 % O2 and 2.5 % CO2 for up to 3 weeks. Normoxic littermates were kept adjacent to the chamber and maintained on the same schedule. Physiological variables were measured at time points throughout the 3 weeks or when the mice were sacrificed. Freshly collected or fixed brain specimens were analyzed by Western blot analysis and immunohistochemistry (IHC). We found significant accumulation of hypoxia-inducible factors 1α and 2α (HIF-1α and HIF-2α) and increased expression of erythropoietin (EPO), cyclooxygenase-2 (COX-2), and angiopoietin-2 (Ang-2) in hyperoxia and hypercapnia. Conversely, vascular endothelial growth factor (VEGF), and VEGF receptor-2 (KDR/Flk-1), peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α), and prolyl hydroxylase-2 (PHD-2) expressions were decreased in hyperoxia and hypercapnia. Capillary density was significantly diminished by the end of the 3rd week of hyperoxia and hypercapnia as compared to control. We conclude that HIF-independent mechanisms contribute to brain capillary density modulation that is continuously adjusted in accordance with tissue oxygen tension.

Topics: Angiopoietin-2; Animals; Basic Helix-Loop-Helix Transcription Factors; Blood Gas Analysis; Cerebral Cortex; Cyclooxygenase 2; Erythropoietin; Hypercapnia; Hyperoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Hypoxia-Inducible Factor-Proline Dioxygenases; Male; Mice; Mice, Inbred C57BL; Microvessels; Neovascularization, Pathologic; Oxygen; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; Transcription Factors; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor Receptor-2

Based on a report of a marked increase in the erythropoietin concentration ([EPO]) a few hours after the cessation of a single 2-h session of O(2) breathing, short periods of O(2) administration have been advocated as a therapy for anaemia. Accordingly, the purpose of the present study was to evaluate this theory by investigating the effect of 10 daily short-term exposures to normobaric O(2) over a 2-week period on the plasma [EPO] in healthy individuals.. Twenty men were assigned to either an experimental (NBO(2)) or to a control (AIR) group. The NBO(2) group breathed 100% normobaric O(2) for 2 h every weekday over a 2-week period. The AIR group breathed air within the same time protocol. Blood samples were collected at the pre-, mid- and post-intervention periods to determine [EPO].. [EPO] of the NBO(2) group was significantly lower than that of the AIR group during the mid- and post-periods (P < 0·001). [EPO] of the NBO(2) group showed a slight, albeit statistically nonsignificant, decrease during the mid (∼11%)- and post (∼16%)-periods.. Daily short-term exposures to normobaric hyperoxia do not increase the [EPO] in healthy individuals. The increased O(2) tension suppresses [EPO]. Hence, administration of pure O(2) to enhance erythropoiesis is not warranted.

Topics: Adult; Case-Control Studies; Erythropoiesis; Erythropoietin; Humans; Hyperbaric Oxygenation; Hyperoxia; Male; Oxygen; Time Factors; Young Adult

Normal brain function is dependent on continuous and controlled oxygen delivery. Chronic moderate hypoxia leads to angiogenesis, suggesting a modulatory role for oxygen in determining capillary density. The objective of this study was to determine physiologic and brain angiogenic adaptational changes during chronic moderate normobaric hyperoxia in mice. Four-month old C56BL/6J mice were kept in a normobaric chamber at 50% O(2) for up to 3 weeks. Normoxic littermates were kept in the same room outside the chamber. Freshly collected or fixed brain specimens were analyzed by RT-PCR, Western blot analysis and immunohistochemistry. Results show accumulation of hypoxia inducible factors 1 and 2α (HIF-1 and 2α), and increased expression of erythropoietin (EPO), cyclooxygenase-2 (COX-2) and angiopoietin-2 (Ang-2). Conversely, vascular endothelial growth factor (VEGF), and VEGF receptor-2 (KDR/Flk-1), Peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α) and prolylhydroxylase-2 (PHD-2) expressions were decreased. VEGF mRNA level was diminished but there was no change in HIF-1α mRNA and von Hippel Lindau E3 ubiquitin ligase (VHL) protein expression. Microvascular density was significantly diminished by the end of the 3rd week of hyperoxia. Overall, our results are: (1) increased expression of the potent neuroprotective molecule, EPO; (2) diminished expression of the potent angiogenic factor, VEGF; and (3) decreased microvascular density. We can, therefore, conclude that brain microvascular density can be controlled by HIF-independent mechanisms, and that brain capillary density is a continuously adjusted variable with tissue oxygen availability as one of the controlling modulators.

Topics: Angiopoietin-2; Animals; Basic Helix-Loop-Helix Transcription Factors; Body Weight; Cerebral Cortex; Cyclooxygenase 2; Disease Models, Animal; Erythropoietin; Gene Expression Regulation; Hematocrit; Hyperoxia; Hypoxia-Inducible Factor 1; Male; Mice; Mice, Inbred C57BL; Microvessels; Oxygen; RNA, Messenger; Time Factors; Vascular Endothelial Growth Factor A

The purpose of the present study was to evaluate the 'normobaric oxygen paradox' theory by investigating the effect of a 2-h normobaric O(2) exposure on the concentration of plasma erythropoietin (EPO).. Ten healthy males were studied twice in a single-blinded counterbalanced crossover study protocol. On one occasion they breathed air (NOR) and on the other 100% normobaric O(2) (HYPER). Blood samples were collected Pre, Mid and Post exposure; and thereafter, 3, 5, 8, 24, 32, 48, 72 and 96 h, and 1 and 2 weeks after the exposure to determine EPO concentration.. The concentration of plasma erythropoietin increased markedly 8 and 32 h after the NOR exposure (approx. 58% and approx. 52%, respectively, P ≤ 0.05) as a consequence of its natural diurnal variation. Conversely, the O(2) breathing was followed by approx. 36% decrement of EPO 3 h after the exposure (P ≤ 0.05). Moreover, EPO concentration was significantly lower in HYPER than in the NOR condition 3, 5 and 8 h after the breathing intervention (P ≤ 0.05).. In contrast to the 'normobaric oxygen paradox' theory, the present results indicate that a short period of normobaric O(2) breathing does not increase the EPO concentration in aerobically fit healthy males. Increased O(2) tension suppresses the EPO concentration 3 and 5 h after the exposure; thereafter EPO seems to change in a manner consistent with natural diurnal variation.

Topics: Adult; Cross-Over Studies; Erythropoietin; Humans; Hyperoxia; Male; Oxygen; Single-Blind Method; Young Adult

Oxygen toxicity contributes to the pathogenesis of adverse neurological outcome in survivors of preterm birth in clinical studies. In infant rodent brains, hyperoxia triggers widespread apoptotic neurodegeneration, induces pro-inflammatory cytokines and inhibits growth factor signaling cascades. Since a tissue-protective effect has been observed for recombinant erythropoietin (rEpo), we hypothesized that rEpo would influence hyperoxia-induced oxidative stress in the developing rat brain. The aim of this study was to investigate the level of glutathione (reduced and oxidized), lipid peroxidation and the expression of heme oxygenase-1 (HO-1) and acetylcholinesterase (AChE) after hyperoxia and rEpo treatment. Six-day-old Wistar rats were exposed to 80% oxygen for 2-48 h and received 20,000 IU/kg rEpo intraperitoneally (i.p.). Sex-matched littermates kept under room air and injected with normal saline or rEpo served as controls. Treatment with rEpo significantly reduced hyperoxia-induced upregulation of oxidized glutathione (GSSG) and malondialdehyde, a product of lipid breakdown, whereas reduced glutathione (GSH) was upregulated by rEpo. In parallel, hyperoxia-treated immature rat brains revealed rEpo-suppressible upregulation of synaptic AChE-S as well as of the stress-inducible AChE-R variant, together predicting rEpo-protected cholinergic signaling and restrained inflammatory reactions. Furthermore, treatment with rEpo induced upregulation of HO-1 on mRNA, protein and activity level in the developing rat brain. Our results suggest that rEpo generates its protective effect against oxygen toxicity by a reduction of diverse oxidative stress parameters and by limiting the stressor-inducible changes in both HO-1 and cholinergic functions.

Topics: Analysis of Variance; Animals; Animals, Newborn; Blotting, Western; Brain; Erythropoietin; Female; Glutathione; Heme Oxygenase-1; Hyperoxia; Lipid Peroxidation; Male; Oxidative Stress; Random Allocation; Rats; Rats, Wistar; Recombinant Proteins; Reverse Transcriptase Polymerase Chain Reaction; Time Factors

To study the effect of recombinant human erythropoietin (rhEPO) on apoptosis following hyperoxic lung injury in neonatal rats.. Ninety-six neonatal Sprague-Dawley rats were randomly divided into four groups: air-exposed control, air-exposed rhEPO-treated, hyperoxia-exposed placebo (95% oxygen), and hyperoxia-exposed rhEPO-treated. rhEPO (800 U/kg) was administered 2, 4, and 6 days after air or hyperoxia exposure. The rats were sacrificed 3, 7 and 14 days after air or hyperoxia exposure for the assessment of lung histological changes by hematoxylin and eosin staining (n=8 each time point). p-JNK levels were measured by Western blot. Lung cell apoptosis was evaluated by TUNEL assay.. Compared with the air-exposed control group, inflammatory cell infiltration was found at 3 days and increased obviously at 7 days, and widening of the alveolar septa was observed, the number of alveoli decreased and normal alveolarization disappeared at 14 days after hyperoxia exposure in the hyperoxia-exposed placebo group. rhEPO treatment alleviated significantly the hyeroxia-induced alterations in lung pathology. P-JNK protein levels and the number of apoptosis cells decreased significantly in the hyperoxia-exposed rhEPO-treated compared with those in the hyperoxia-exposed placebo group.. rhEPO may reduce apoptosis and thus provide a protective effect against hyperoxic lung injury in neonatal rats. JNK signal pathway may be involved in the protective mechanism.

Topics: Animals; Animals, Newborn; Apoptosis; Bronchopulmonary Dysplasia; Erythropoietin; Female; Humans; Hyperoxia; Infant, Newborn; JNK Mitogen-Activated Protein Kinases; Lung; Male; Rats; Rats, Sprague-Dawley; Recombinant Proteins

Acclimatization to hypoxic exposure relies on an elevated ventilation and erythropoietic activity. We recently proposed that erythropoietin (Epo) links both responses: apart from red blood cell production, cerebral and plasma Epo interact with the central and peripheral respiratory centers. Knowing that women cope better than men with reduced oxygen supply (as observed at high altitude), we analyzed the hypoxic ventilatory response in Epo-overexpressing transgenic male and female mice with high Epo levels in brain and plasma (Tg6) or in wild-type animals injected with recombinant human Epo (rhEpo). Exposure to moderate and severe hypoxia as well as to hyperoxia and injection of domperidone, a potent peripheral ventilatory stimulant, revealed that the presence of transgenic or rhEpo extensively increased the hypoxic ventilatory response in female mice compared with their corresponding male siblings. Alterations of catecholamines in the brain stem's respiratory centers were also sex dependent. In a proof-of-concept study, human volunteers were intravenously injected with 5,000 units rhEpo and subsequently exposed to 10% oxygen. Compared with men, the hypoxic ventilatory response was significantly increased in women. We conclude that Epo exerts a sex-dependent impact on hypoxic ventilation improving the response in female mice and in women that most probably involves sexual hormones. Our data provides an explanation as to why women are less susceptible to hypoxia-associated syndromes than men.

Topics: Adaptation, Physiological; Adult; Animals; Brain Stem; Catecholamines; Disease Models, Animal; Domperidone; Dopamine Antagonists; Erythropoietin; Female; Humans; Hyperoxia; Hypoxia; Injections, Intravenous; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Pulmonary Ventilation; Recombinant Proteins; Respiratory Mechanics; Sex Factors; Young Adult

Oxygen toxicity appears to contribute to the pathogenesis of adverse neurological outcome in survivors of preterm birth. In infant rodent brains, hyperoxia triggers widespread apoptotic neurodegeneration, induces proinflammatory cytokines and inhibits growth factor signaling cascades. Since a tissue-protective effect has been observed for recombinant erythropoietin (rEpo), we hypothesized that rEpo would influence the expression of proinflammatory cytokines and matrix metalloproteinase (MMP)-2 and MMP-9. Six-day-old Wistar rats were exposed to 80% oxygen for 2-48 h and received 20,000 IU rEpo i.p. Sex-matched littermates kept in room air and injected with normal saline or rEpo served as controls. Treatment with rEpo significantly reduced hyperoxia-induced upregulation of the proinflammatory cytokines IL-1beta and IL-18 in infant rodent brains on the mRNA and protein levels. In parallel, gelatin zymography in hyperoxia-treated immature rat brains revealed an upregulation of active MMP-2 which was reduced by concomitant rEpo treatment. Furthermore, hyperoxia induced upregulation of MMP-9 following 12 h of oxygen exposure and this was attenuated by rEpo treatment. Our results suggest that rEpo generates its protective effect against oxygen toxicity through a reduction of proinflammatory mediator levels.

Topics: Analysis of Variance; Animals; Animals, Newborn; Blotting, Western; Brain; Cell Death; Erythropoietin; Hyperoxia; Interleukin-18; Interleukin-1beta; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; Oxygen; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction

Bronchopulmonary dysplasia (BPD) is a multifactorial disease resulting from the impact of injury (including oxygen toxicity, barotrauma, volutrauma, and infection) on the immature lung. Oxygen toxicity is thought to be a major contributing factor in the pathogenesis in BPD. Previous animal studies have shown that exposure to hyperoxia in the neonatal period causes lung structural changes that are similar to the histology seen in human infants with BPD. Erythropoietin (EPO) has pleiotropic actions including antioxidant, anti-apoptotic, anti-inflammatory and angiogenic effects. Animal experiments reveal that EPO may have protective effects on hyperoxic lung injury, but the mechanisms remain unknown. The aim of the study was to evaluate the anti-inflammatory effects and understand mechanism of action of EPO on the hyperoxia-induced BPD in newborn rats.. Several litters of Wistar pups were pooled together within 12 hours after birth and randomly divided into four groups: I. air-exposed control group, II. air-exposed human recombinant erythropoietin (rhEPO)-treated group, III. hyperoxia-exposed placebo group and IV. hyperoxia-exposed rhEPO-treated group . Group III and IV rats were exposed to 85% oxygen. Group II and IV rats received rhEPO (1200 IU/kg) subcutaneously on postnatal days 0 and 2. Group I and III received 0.9% saline in the same way. Pups from each group were sacrificed on days 3, 7, and 14. Blood hemoglobin concentration, hematocrit and platelet count were determined by blood cell analyzer. Total protein content in bronchoalveolar lavage fluid (BALF) and myeloperoxidase (MPO) were measured by biochemical assay. Changes of monocyte chemoattractant protein-1 (MCP-1) and cytokine-induced neutrophil chemoattractant-1 (CINC-1) mRNA expressions were measured by RT-PCR.. In group III, there were a few inflammatory cells infiltrations in interstitium on day 3 and inflammatory response worsened on day 7. Alveolar and capillary hypoplasia and interstitial fibrosis were evident on day 14. The pathological changes were ameliorated greatly in group IV and the survival was prolonged. There were no abnormal raises of hemoglobin concentration, hematocrit and platelet count in group IV compared with group I. Total protein concentration in BALF was measured as a marker for capillary leakage. MPO is a major constituent of neutrophil cytoplasmic granules and its activity therefore is a direct measure of neutrophil presence and an indirect indicator of lung injury. Total protein concentration and MPO in BALF were greatly depressed in group IV compared with group III, P<0.05, P<0.001. The upregulation of genes of CINC-1 and MCP-1 was closely related with lung inflammation caused by oxidative stress. MCP-1 and CINC-1 mRNA expression were detected and it was found that their changes were in line with the degree of lung inflammation. MCP-1 and CINC-1 mRNA expression increased in group III compared with group I especially on day 7, P<0.01 or <0.001. The changes of MCP-1 and CINC-1 mRNA were positively correlated with changes of MPO in BALF covering all groups on days 3, 7 and 14, respectively (r = 0.391, P<0.05; r = 0.701, P<0.01; r = 0.600, P<0.01; r = 0.471, P<0.01; r = 0.789, P<0.01; r = 0.588, P<0.01).. EPO could significantly reduce the lung inflammatory cell infiltration, and capillary endothelial cell injury in hyperoxic lung injury in newborn rats. The mechanism may be related with the inhibition of MCP-1 and CINC-1 gene expression by EPO.

Topics: Animals; Animals, Newborn; Chemokine CCL2; Disease Models, Animal; Erythropoietin; Female; Hyperoxia; Lung; Lung Injury; Male; Rats; Rats, Wistar; Recombinant Proteins

The developing nervous system is sensitive to supraphysiological oxygen concentrations. Recent studies showed that exposure to hyperoxia in infant rats leads to extensive apoptotic degeneration in the cortex and white matter of the developing brain. A wide variety of experimental studies have shown that erythropoietin exerts a remarkable neuroprotection in both cell cultures and in animal models of nervous system disorders. In the present study, we investigated the effect of erythropoietin against hyperoxia-induced neurodegeneration in the developing brain. Eighteen Wistar rat pups were divided into three groups: control group, hyperoxia+saline-treated group and hyperoxia+erythropoietin-treated group. Hyperoxia groups were exposed to 80% oxygen (n=12) in a plexiglas chamber in which the oxygen concentration was monitored twice daily from birth until postnatal day 5. Hyperoxia exposure was 24h/day for 5 days. The hyperoxia+erythropoietin group received an intraperitoneal injection of recombinant human erythropoietin at a dose of 1000U/(kgday). At postnatal day 5, all animals were sacrificed. Neuronal cell death and apoptosis were evaluated. Histopathological examination showed that erythropoietin significantly diminished apoptosis in the CA1 region and dentate gyrus of hippocampus and parietal cortex in hyperoxia+erythropoietin-treated group. Regarding the safety profile of erythropoietin in premature and mature infants, this agent may be potentially beneficial in preventing hyperoxic brain injury.

Topics: Animals; Animals, Newborn; Apoptosis; Brain; Brain Diseases; Dentate Gyrus; DNA Fragmentation; Enzyme-Linked Immunosorbent Assay; Erythropoietin; Hippocampus; Hyperoxia; Image Processing, Computer-Assisted; Immunohistochemistry; In Situ Nick-End Labeling; Neuroprotective Agents; Oxygen; Parietal Lobe; Rats; Rats, Wistar; Recombinant Proteins

Oxygen toxicity has been identified as a risk factor for adverse neurological outcome in survivors of preterm birth. In infant rodent brains, hyperoxia induces disseminated apoptotic neurodegeneration. Because a tissue-protective effect has been observed for recombinant erythropoietin (rEpo), widely used in neonatal medicine for its hematopoietic effect, we examined the effect of rEpo on hyperoxia-induced brain damage.. Six-day-old C57Bl/6 mice or Wistar rats were exposed to hyperoxia (80% O(2)) or normoxia for 24 hours and received rEpo or normal saline injections intraperitoneally. The amount of degenerating cells in their brains was determined by DeOlmos cupric silver staining. Changes of their brain proteome were determined through two-dimensional electrophoresis and mass spectrometry. Western blot, enzyme activity assays and real-time polymerase chain reaction were performed for further analysis of candidate proteins.. Systemic treatment with 20,000 IE/kg rEpo significantly reduced hyperoxia-induced apoptosis and caspase-2, -3, and -8 activity in the brains of infant rodents. In parallel, rEpo inhibited most brain proteome changes observed in infant mice when hyperoxia was applied exclusively. Furthermore, brain proteome changes after a single systemic rEpo treatment point toward a number of mechanisms through which rEpo may generate its protective effect against oxygen toxicity. These include reduction of oxidative stress and restoration of hyperoxia-induced increased levels of proapoptotic factors, as well as decreased levels of neurotrophins.. These findings are highly relevant from a clinical perspective because oxygen administration to neonates is often inevitable, and rEpo may serve as an adjunctive neuroprotective therapy.

Topics: Animals; Apoptosis; Asphyxia Neonatorum; Brain; Caspases; Cell Death; Disease Models, Animal; Erythropoietin; Humans; Hyperoxia; Infant, Newborn; Mice; Mice, Inbred C57BL; Nerve Degeneration; Neurons; Neuroprotective Agents; Oxidative Stress; Oxygen; Oxygen Inhalation Therapy; Proteome; Rats; Rats, Wistar

To investigate the inheritance of susceptibility to oxygen-induced retinopathy in the rat with the use of formal backcross analysis.. Neonatal offspring of inbred albino Fischer 344 (F344) and pigmented Dark Agouti (DA) crosses and F1xF344 and F1xDA backcrosses were exposed to alternating 24-hour cycles of hyperoxia (80% oxygen in air) and normoxia (21% oxygen in air) for 14 days. Retinal avascular area was analyzed by staining with Griffonia simplicifolia isolectin B4, a marker of vascular endothelial cells. Expression of erythropoietin (EPO) mRNA in retinas was quantified by real-time reverse-transcription polymerase chain reaction.. Oxygen-exposed offspring of two F344xDA F1 crosses showed retinal avascular areas and ocular and coat pigmentation that were similar to those of the DA strain. Mean retinal avascular area was 73%. Offspring of two DAxF1 backcrosses were similar to F344xDA F1 pups, with pigmented eyes and coats and a mean retinal avascular area of 76%. In contrast, offspring of two F344xF1 backcrosses exhibited a range of eye and coat pigmentation. Mean retinal avascular area of pigmented offspring of the F344xF1 backcrosses was 71% (P < 0.001 compared with F344 rats). Mean avascular area of albino offspring of the F344xF1 backcrosses was 27% (P > 0.05 compared with F344 rats). The normalized expression of EPO mRNA was 3.01 +/- 1.00 in retinas from pigmented F344xF1 backcross offspring compared with 1.31 +/- 0.69 for albino offspring (P < 0.001).. Segregation of the susceptibility trait to oxygen-induced retinopathy in the DA and F344 rat strains is associated with pigmentation and erythropoietin expression and can be modeled using an autosomal dominant pattern of inheritance.

Topics: Animals; Animals, Newborn; Disease Models, Animal; Endothelium, Vascular; Erythropoietin; Female; Genetic Predisposition to Disease; Humans; Hyperoxia; Inbreeding; Infant, Newborn; Oxygen; Pedigree; Plant Lectins; Rats; Rats, Inbred F344; Retina; Retinal Vessels; Retinopathy of Prematurity; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Skin Pigmentation

This study was done to determine whether recombinant human erythropoietin (rhEPO) treatment could attenuate hyperoxia-induced lung injury, and if so, whether this protective effect is mediated by the down-modulation of inflammation in neonatal rats. Newborn Sprague Dawley rat pups were subjected to 14 days of hyperoxia (>95% oxygen) within 10 hr after birth. Treatment with rhEPO significantly attenuated the mortality and reduced body weight gain caused by hyperoxia. With rhEPO treatment, given 3 unit/gm intraperitoneally at 4th, 5th, and 6th postnatal day, hyperoxia- induced alterations in lung pathology such as decreased radial alveolar count, increased mean linear intercept, and fibrosis were significantly improved, and the inflammatory changes such as myeloperoxidase activity and tumor necrosis factor-alpha expression were also significantly attenuated. In summary, rhEPO treatment significantly attenuated hyperoxia-induced lung injury by down-modulating the inflammatory responses in neonatal rats.

Topics: Animals; Animals, Newborn; Cytoprotection; Disease Models, Animal; Erythropoietin; Female; Hyperoxia; Inflammation; Lung; Peroxidase; Rats; Rats, Sprague-Dawley; Recombinant Proteins; Survival Rate; Tumor Necrosis Factor-alpha

Renal (peritubular) tissue hypoxia is a well-known physiological trigger for erythropoietin (EPO) production. We investigated the effect of rebound relative hypoxia after hyperoxia obtained under normo- and hyperbaric oxygen breathing conditions. A group of 16 healthy volunteers were investigated before and after a period of breathing 100% normobaric oxygen for 2 h and a period of breathing 100% oxygen at 2.5 ATA for 90 min (hyperbaric oxygen). Serum EPO concentration was measured using a radioimmunoassay at various time points during 24-36 h. A 60% increase (P < 0.001) in serum EPO was observed 36 h after normobaric oxygen. In contrast, a 53% decrease in serum EPO was observed at 24 h after hyperbaric oxygen. Those changes were not related to the circadian rhythm of serum EPO of the subjects. These results indicate that a sudden and sustained decrease in tissue oxygen tension, even above hypoxia thresholds (e.g., after a period of normobaric oxygen breathing), may act as a trigger for EPO serum level. This EPO trigger, the "normobaric oxygen paradox," does not appear to be present after hyperbaric oxygen breathing.

Topics: Blood Gas Monitoring, Transcutaneous; Erythropoietin; Female; Humans; Hyperbaric Oxygenation; Hyperoxia; Hypoxia; Male; Oxygen; Time Factors

A reduction in haemoglobin concentration is consistently reported after deep saturation dives. This may be due to a downregulation of erythropoietin (EPO) concentration or to a toxic effect of the hyperoxia associated with the dives resulting in an increased destruction rate of erythrocytes. In this study haemoglobin concentration, blood cell counts, serum ferritin, bilirubin, haptoglobin and EPO concentrations were measured before, during and after a 19 day saturation dive to 240 m. The partial pressure of oxygen (PO(2)) was 35-70 kPa during the 7 day compression and bottom phase, and 30-50 kPa during the 12 day decompression phase. There was a reduction in EPO concentration from 8.4+/-1.4 (mean +/- 1SD) to 6.3 +/- 1.9 U.L(-1) on Dive day 2. On Dive days 7 and 17 EPO concentrations were not significantly different from baseline despite the continued exposure to hyperoxia. Immediately after the dive and return to a normoxic environment there was an increase in the EPO concencentration to 14.5 +/- 4.7 U.L(-1). Haemoglobin concentration, erythrocyte and reticulocyte counts were decreased at the end of the dive, and there was an increase in serum ferritin. There were no changes in bilirubin or haptoglobin concentrations indicative of haemolysis. It appears that the change in PO(2), rather than the sustained exposure to a hyperoxic environment, induces the changes in the EPO concentrations and erythropoietic activity.

Topics: Adult; Bilirubin; Blood Cell Count; Diving; Erythropoietin; Ferritins; Haptoglobins; Hemoglobins; Humans; Hyperoxia; Male; Middle Aged

Topics: Adult; Circadian Rhythm; Erythropoietin; Humans; Hypercapnia; Hyperoxia; Hypoventilation; Hypoxia; Male; Middle Aged; Sleep Apnea, Obstructive; Syndrome

An HLF (HIF-1alpha-like factor)/HIF-2alpha-knockout mouse is embryonic lethal, preventing investigation of HLF function in adult mice. To investigate the role of HLF in adult pathological angiogenesis, we generated HLF-knockdown (HLF(kd/kd)) mice by inserting a neomycin gene sandwiched between two loxP sequences into exon 1 of the HLF gene. HLF(kd/kd) mice expressing 80-20% reduction, depending on the tissue, in wild-type HLF mRNA were fertile and apparently normal. Hyperoxia-normoxia treatment, used as a murine model of retinopathy of prematurity (ROP), induced neovascularization in wild-type mice, but not in HLF(kd/kd) mice, whereas prolonged normoxia following hyperoxic treatment caused degeneration of retinal neural layers in HLF(kd/kd) mice due to poor vascularization. Cre-mediated removal of the inserted gene recovered normal HLF expression and retinal neovascularization in HLF(kd/kd) mice. Expression levels of various angiogenic factors revealed that only erythropoietin (Epo) gene expression was significantly affected, in parallel with HLF expression. Together with the results from intraperitoneal injection of Epo into HLF(kd/kd) mouse, this suggests that Epo is one of the target genes of HLF responsible for experimental ROP.

Topics: Animals; Antibodies; Basic Helix-Loop-Helix Transcription Factors; Disease Models, Animal; Electroretinography; Erythropoietin; Female; Gene Expression Regulation; Gene Targeting; Genetic Vectors; Helix-Loop-Helix Motifs; Humans; Hyperoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Immunohistochemistry; In Situ Nick-End Labeling; Infant, Newborn; Integrases; Mice; Mice, Knockout; Retina; Retinal Neovascularization; Retinopathy of Prematurity; RNA, Messenger; Tissue Distribution; Trans-Activators; Transcription Factors; Vimentin; Viral Proteins

Current evidence suggests that a modulatory action on O(2)-dependent EPO secretion is exerted by the erythroid/precursor cell population in the erythropoietic organs through a negative feedback system. The hypothesis is based on studies of stimulated-EPO secretion performed in mice in whom the erythropoietic rates were either enhanced or depressed in the presence of normal plasma EPO half-lives. Since erythropoietic depression was elicited by cyclophosphamide administration, which could have altered EPO production directly, the aim of the present investigation was to estimate hypoxia-stimulated EPO secretion in a mouse model of functional depressed erythropoiesis induced by exposure to normobaric hyperoxia. Females CF#1 mice aged 70 d were divided into control (C) and experimental (E) groups. The former was maintained in plastic cages in a normal environment, while the latter was placed in an environment of 60% O(2)/40% N(2) in an 85-dm(3) atmospheric chamber with air flow of 1 L/min. Erythropoiesis was evaluated by either 24-h RBC-(59)Fe uptake or iron kinetics performed 3 h after IV injection of a tracer dose of (59)Fe. Both indexes of the red cell production rate were significantly depressed in E mice. Plasma disappearance of exogenous EPO in C mice, as well as in E mice exposed to hyperoxia for 4 d, was estimated by injecting (125)I-rHuEPO intravenously. Linear regression analysis indicated that neither the differences between the slopes of both curves nor the Y-intercepts were significant. Hypobaric hypoxemia was used as stimulus for EPO production. Plasma immuno-EPO titer after a 4-h exposure to hypobaric air was 73% higher in mice with hyperoxia-induced hypoerythropoiesis than in control mice with normal erythropoiesis. Data support the concept that the rate of erythropoiesis, perhaps through the number of the erythroid progenitor/precursor cell population, modulates O(2)-dependent EPO secretion.

Topics: Animals; Bone Marrow; Enzyme-Linked Immunosorbent Assay; Erythrocytes; Erythropoiesis; Erythropoietin; Female; Hematocrit; Hyperoxia; Hypoxia; Iron Radioisotopes; Linear Models; Mice; Models, Animal; Regression Analysis; Spleen

Iron is an important catalyst for free oxygen radicals and lipid peroxidation reactions which may play a role in the pathogenesis of several diseases in premature infants. During the early neonatal period, extracellular iron is available in excessive amounts. We hypothesized that administration of erythropoietin (EPO) mobilizes iron from plasma and inhibits iron-catalyzed reactions. To evaluate this hypothesis, recombinant human EPO (rhEPO) was administered s.c. to premature rabbits delivered at 29-d gestation: one group was kept in room air (RA) and the other in a 100% oxygen environment. Within each group, the animals were randomized to receive placebo or rhEPO at 400 or at 800 U/kg on d 0 and 2 of life. On d 3 or 4, plasma iron and iron saturation of transferrin were assessed. Lipid peroxidation was analyzed in plasma and bronchoalveolar lavage fluid (BAL). Nonsedimentable protein (NSP) and phospholipid content were measured in BAL. Erythropoiesis was evaluated in liver and bone marrow. Treatment with rhEPO decreased plasma iron, decreased iron saturation of transferrin, increased reticulocytes, and increased erythropoiesis in liver and bone marrow in both RA and hyperoxia group. Oxygen exposure increased NSP in BAL and decreased the ability of BAL to inhibit lipid peroxidation as measured by malondialdehyde (MDA) generation compared with RA exposure. In O2-exposed animals, EPO treatment increased the ability of both plasma (EPO 800) and BAL (EPO 400 and 800) to inhibit lipid peroxidation and decreased NSP in BAL (EPO 400). In addition, rhEPO treatment decreased alveolar thickening and proteinaceous exudate in the hyperoxia group. We propose that by stimulating erythropoiesis, rhEPO mobilizes non-heme iron and decreases oxidant injury that depends on the availability of transient metal.

Topics: Animals; Animals, Newborn; Antioxidants; Catalysis; Disease Models, Animal; Drug Evaluation, Preclinical; Erythropoiesis; Erythropoietin; Free Radicals; Gestational Age; Humans; Hyperoxia; Infant, Newborn; Infant, Premature, Diseases; Iron; Lung Diseases; Oxidative Stress; Rabbits; Recombinant Proteins