Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0242706 (hyperoxia)
 5,219 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Erythropoietin (Ep) levels in spent culture media of a Hep G2 human hepatoblastoma cell line were measured by radioimmunoassay (RIA), fetal mouse liver erythroid colony formation (FMLC), and the exhypoxic polycythemic mouse assay (EHPCMA). The Hep G2 cells at high density produced approximately 700 mU/ml Ep when measured with the RIA. On the other hand, the Ep levels when assayed in EHPCMA and FMLC were 50 and 2,600 mU/ml, respectively. The bioactivity in FMLC was completely neutralized by an antibody to purified human recombinant Ep, indicating that the erythropoietic activity in the Hep G2 spent culture medium was immunologically equivalent to Ep. Ep levels in the medium from low-density Hep G2 cells in 5% O2 and 1% O2 were 2.5- and 4-fold greater, respectively, than that of 20% O2. In contrast, hyperoxia (40% O2) significantly inhibited Ep production. A significant increase in Ep secretion was also observed when the cells were incubated with cobaltous chloride (2 X 10(-6) -2.5 X 10(-4) M). Tunicamycin (0.5 micrograms/ml), which inhibits N-linked glycosylation, significantly reduced the enhancement of Ep secretion induced by hypoxia (1% O2) without affecting cell growth. Forskolin and cholera toxin, each of which increased the levels of cyclic AMP in the Hep G2 cells by 40-fold, produced a significant (P less than 0.05) further increase in Ep secretion in the presence of hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Enhanced erythropoietin secretion in hepatoblastoma cells in response to hypoxia. 255 19

Exposure to high concentrations of oxygen can result in tissue damage, particularly in the lung. Lung pathology induced by hyperoxia includes changes in lung cell populations and morphology. Presumably, alterations in gene expression underlie some of these cellular changes. In order to better understand the molecular basis of these events, a cDNA library was constructed from the mRNA of the lungs of a hyperoxia-exposed rabbit and differentially screened for clones corresponding to hyperoxia-induced messages. This approach has led to the isolation of four clones, three of which are presented in this communication. One clone corresponds to a message whose steady state levels were induced 6-fold and encodes the tissue inhibitor of metalloproteinases, a protein that plays a key role in the regulation of connective tissue turnover in some cells and potentiates erythroid development in others.
 ...
PMID:Hyperoxic exposure alters gene expression in the lung. Induction of the tissue inhibitor of metalloproteinases mRNA and other mRNAs. 270 56

The effect of hypoxia and changes in erythropoiesis on the absorption of 59Fe3+ from in situ tied-off duodenal segments was studied in the mouse. Hypoxia led to an increase in mucosal uptake within 6 h, whilst mucosal transfer was unaffected for about 20 h, suggesting independent regulation of these two processes. Hypoxia (3 d) stimulated erythropoiesis and resulted in a 2-3-fold increase in the total mucosal uptake of 59Fe. Conversely, hyperoxia (100% O2) caused a decrease in reticulocyte counts and the total mucosal uptake. The changes in the transfer of 59Fe from the mucosa to the body were more marked than changes in uptake in both hypoxia and hyperoxia. Mice subjected to subtotal nephrectomy showed a normal increase in the total mucosal uptake of 59Fe3+ following hypoxic exposure, despite the absence of any changes in the reticulocyte count. Obliteration of the erythroid tissue of animals by splenectomy and 89Sr treatment was accompanied by a marked decrease in the transfer of 59Fe from mucosa to the carcass. However, exposure of splenectomized 89Sr-treated mice to hypoxia resulted in an increase in the total mucosal uptake and carcass transfer of 59Fe, without any change in erythropoiesis. These results indicate that hypoxia enhances mucosal iron uptake by a mechanism which is independent of stimulated erythropoiesis, but that changes in the rate of erythropoiesis have an additional effect, particularly on the transfer phase of iron absorption.
 ...
PMID:In vivo studies on the relationship between intestinal iron (Fe3+) absorption, hypoxia and erythropoiesis in the mouse. 335 97

The major function of the erythrocyte is to transport oxygen from the lungs to the other tissues, a function ensured by the glycoprotein hormone erythropoietin which couples red cell production to long term tissue oxygen requirements. Tissue hypoxia is the only physiological mechanism for increasing erythropoietin production but there are a variety of mechanisms for its down regulation including hyperoxia, increased catabolism by an expanded erythroid progenitor cell pool, blood hyperviscosity independently of its oxygen content, renal disease and the cytokines produced in inflammatory, infectious and neoplastic disorders. Erythropoietin lack results in severe and often transfusion-dependent anemia but if bone marrow function is otherwise normal, recombinant human erythropoietin therapy can restore the red cell mass and alleviate the transfusion need. However, elevation of the red cell mass by recombinant human erythropoietin is associated with a reduction in plasma volume and in some patients, hypertension is induced. Elevation of the red cell mass is also associated with a reduction in cerebral blood flow. When used to gradually elevate the hematocrit to 36% in anemic patients, recombinant human erythropoietin therapy is usually uneventful. However, when the normal hematocrit level is exceeded, the risk for thrombotic events increases since blood viscosity varies exponentially with the hematocrit. Increasing the hematocrit by autologous blood transfusions can enhance athletic performance in fit individuals and recombinant human erythropoietin administration is an obvious surrogate for autologous blood transfusions. However, paradoxically, its effects are the opposite of those of endurance training, namely a change in red cell mass without an increase in the total blood volume. Thus, the use of recombinant human erythropoietin as a performance-enhancing agent is dangerous, particularly in the less fit athlete, and probably of little benefit in the highly conditioned one. Differences in the carbohydrate content of native and recombinant human erythropoietin are identifiable by isoelectric focusing, providing a direct means for detecting erythropoietin abuse using urine specimens; a panel of surrogate blood markers of enhanced erythropoiesis such as soluble transferrin receptors, serum erythropoietin, reticulocyte hematocrit and percent macrocytes provide an indirect means for this purpose. Timing of surveillance is, of course, critical due to biological limitations on the physical presence of the hormone. However, education about its dangers may prove to be the most valuable solution to abuse of recombinant human erythropoietin for competitive advantage.
 ...
PMID:Erythropoietin use and abuse: When physiology and pharmacology collide. 1195 Jan 39

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.
 ...
PMID:Enhanced hypoxia-stimulated erythropoietin production in mice with depression of erythropoiesis induced by hyperoxia. 1271 14

Nuclear factor erythroid 2-related factor (Nrf2) confers protection against cell death induced by hyperoxia and other proapoptotic stimuli. Because phosphoinositide-3-kinase (PI3K)/Akt signaling promotes cell survival, the significance of this pathway in mediating reactive oxygen species (ROS)-dependent hyperoxia-induced Nrf2 activation was investigated in the murine pulmonary epithelial cell line, C10. Inhibition of the PI3K pathway markedly attenuated hyperoxia-induced Nrf2 translocation and ARE (antioxidant response element)-mediated transcription. Consistent with this, hyperoxia markedly stimulated the activation of PI3K pathway, while an NADPH oxidase inhibitor and an antioxidant prevented such activation. The inhibition of Akt activity using a pharmacological inhibitor markedly attenuated Nrf2 translocation and ARE-driven expression. Moreover, overexpression of a dominant-negative Akt mutant attenuated the transcription, whereas a constitutively active mutant stimulated it. These results suggest that PI3K/Akt signaling regulates Nrf2 activation by hyperoxia. Inhibition of the PI3K pathway prevented hyperoxia-stimulated Akt and ERK1/2 kinase activation, which is critical for Nrf2-mediated transcription. Likewise, the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, AG1478, blocked hyperoxia-stimulated Akt and ERK1/2 phosphorylation, Nrf2 nuclear accumulation, and ARE-driven transcription. Consistent with this result, an NADPH oxidase inhibitor blocked hyperoxia- stimulated EGFR phosphorylation, which was correlated with the attenuation of Akt and ERK activation. Collectively, our data suggest that EGFR-PI3K signaling through Akt and ERK kinases regulates ROS-dependent, hyperoxia-induced Nrf2 activation in pulmonary epithelial cells.
 ...
PMID:Hyperoxia stimulates an Nrf2-ARE transcriptional response via ROS-EGFR-PI3K-Akt/ERK MAP kinase signaling in pulmonary epithelial cells. 1648 36

Nuclear factor, erythroid 2 related factor 2 (Nrf2) belongs to the Cap'n'collar/basic region leucine zipper (CNC-bZIP) transcription factor family, and is activated by diverse oxidants, pro-oxidants, antioxidants, and chemopreventive agents. After phosphorylation and dissociation from the cytoplasmic inhibitor, Kelch-like ECH-associated protein 1 (Keap1), Nrf2 translocates to the nucleus and binds to an antioxidant response element (ARE). Through transcriptional induction of ARE-bearing genes that encode antioxidant-detoxifying proteins, Nrf2 activates cellular rescue pathways against oxidative injury, inflammation/immunity, apoptosis, and carcinogenesis. ARE-driven genes include direct antioxidants (e.g., GPx), thiol metabolism-associated detoxifying enzymes (e.g., GSTs), stress-response genes (e.g., HO-1), and others (e.g., PSMB5). Application of nrf2 germ-line mutant mice elucidated protective roles for Nrf2 in various models of human disorders in the liver, lung, kidney, brain, and circulation. In the lung, deficiency of nrf2 augmented injury caused by bleomycin and environmental oxidants including hyperoxia, diesel exhaust particles, and cigarette smoke. Microarray analyses of lungs from nrf2-deficient and -sufficient mice identified Nrf2-dependent genes that might be critical in pulmonary protection. Observations from these studies highlight the importance of the Nrf2-antioxidant pathway and may provide new therapeutic strategies for acute respiratory distress syndrome, idiopathic pulmonary fibrosis, cancer, and emphysema in which oxidative stress is implicated.
 ...
PMID:Nrf2 defends the lung from oxidative stress. 1648 40

Increased oxidative stress is associated with perinatal asphyxia and respiratory distress in the newborn period. Induction of nuclear factor erythroid 2 p45-related factor (Nrf2) has been shown to decrease oxidative stress through the regulation of specific gene pathways. We hypothesized that Nrf2 attenuates mortality and alveolar growth inhibition in newborn mice exposed to hyperoxia. Nrf2(+/+) and Nrf2(-/-) newborn mice were exposed to hyperoxia at 24 h. Survival was significantly less in Nrf2(-/-) mice exposed to 72 h of hyperoxia and returned to room air (P < 0.0001) and in Nrf2(-/-) mice exposed to hyperoxia for 8 continuous days (P < 0.005). To determine the response of Nrf2 target genes to hyperoxia, glutathione peroxidase 2 (Gpx2) and NAD(P)H:quinone oxidoreductase (NQO1) expression was measured from lung of newborn mice using real-time PCR. In the Nrf2(+/+) mice, significant induction of lung Gpx2 and NQO1 above room air controls was found with hyperoxia. In contrast, Nrf2(-/-) mice had minimal induction of lung Gpx2 and NQO1 with hyperoxia. Expression of p21 and IL-6, genes not regulated by Nrf2, were also measured. IL-6 expression in Nrf2(-/-) lung was markedly induced by 72 h of hyperoxia in contrast to the Nrf2(+/+) mice. p21 was induced in both Nrf2(+/+) and Nrf2(-/-) lung by hyperoxia. Mean linear intercept (MLI) and mean chord length (MCL) were significantly increased in 14-day-old Nrf2(-/-) mice previously exposed to hyperoxia compared with Nrf2(+/+) mice. The percentage of surfactant protein C (Sp-c(+)) type 2 alveolar cells in 14-day-old Nrf2(-/-) mice exposed to neonatal hyperoxia was also significantly less than Nrf2(+/+) mice (P < 0.02). In summary, these findings indicate that Nrf2 increases survival in newborn mice exposed to hyperoxia and that Nrf2 may help attenuate alveolar growth inhibition caused by hyperoxia exposure.
 ...
PMID:Nrf2 increases survival and attenuates alveolar growth inhibition in neonatal mice exposed to hyperoxia. 1915 Nov 8

For nearly 100 y, pediatricians have regularly used oxygen to treat neonatal and childhood diseases. During this time, it has become clear that oxygen is toxic and that overzealous use can lead to significant morbidity. As we have learned more about the appropriate clinical indications for oxygen therapy, studies at the bench have begun to elucidate the molecular mechanisms by which cells respond to hyperoxia. In this review, we discuss transcription factors whose activity is regulated by oxygen, including nuclear factor, erythroid 2-related factor 2 (Nrf2), activator protein 1 (AP-1), p53, nuclear factor kappaB (NF-kappaB), signal transducers and activators of transcription protein (STAT), and ccat/enhancer binding protein (CEBP). Special attention is paid to the mechanisms by which hyperoxia affects these transcription factors in the lung. Finally, we identify downstream targets of these transcription factors, with a focus on heme oxygenase-1. A better understanding of how oxygen affects various signaling pathways could lead to interventions aimed at preventing hyperoxic injury.
 ...
PMID:Manipulation of gene expression by oxygen: a primer from bedside to bench. 1928 38

Nuclear factor-erythroid 2 related factor 2 (Nrf2) is a ubiquitous master transcription factor that regulates antioxidant response elements (AREs)-mediated expression of antioxidant enzyme and cytoprotective proteins. In the unstressed condition, Kelch-like ECH-associated protein 1 (Keap1) suppresses cellular Nrf2 in cytoplasm and drives its proteasomal degradation. Nrf2 can be activated by diverse stimuli including oxidants, pro-oxidants, antioxidants, and chemopreventive agents. Nrf2 induces cellular rescue pathways against oxidative injury, abnormal inflammatory and immune responses, apoptosis, and carcinogenesis. Application of Nrf2 germ-line mutant mice has identified an extensive range of protective roles for Nrf2 in experimental models of human disorders in the liver, gastrointestinal tract, airway, kidney, brain, circulation, and immune or nerve system. In the lung, lack of Nrf2 exacerbated toxicity caused by multiple oxidative insults including supplemental respiratory therapy (e.g., hyperoxia, mechanical ventilation), cigarette smoke, allergen, virus, bacterial endotoxin and other inflammatory agents (e.g., carrageenin), environmental pollution (e.g., particles), and a fibrotic agent bleomycin. Microarray analyses and bioinformatic studies elucidated functional AREs and Nrf2-directed genes that are critical components of signaling mechanisms in pulmonary protection by Nrf2. Association of loss of function with promoter polymorphisms in NRF2 or somatic and epigenetic mutations in KEAP1 and NRF2 has been found in cohorts of patients with acute lung injury/acute respiratory distress syndrome or lung cancer, which further supports the role for NRF2 in these lung diseases. In the current review, we address the role of Nrf2 in airways based on emerging evidence from experimental oxidative disease models and human studies.
 ...
PMID:Nrf2 protects against airway disorders. 1964 63


1 2 3 Next >>