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Query: UMLS:C0242706 (hyperoxia)
 5,219 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hyperoxia activates superoxide dismutase (SOD) while inactivating catalase and glutathione peroxidase in polymorphonuclear leucocytes (PMN) and alveolar marcophages (AM) obtained from guinea-pigs exposed to 85% oxygen for 90 h. The influence of these altered enzyme activities on the rate of oxygen consumption and release of superoxide anion (O--2) and hydrogen peroxide (H2O2) was investigated. By 18 h O--2 released from resting PMN increased two-fold and remained elevated through the entire periods of the study, whereas H2O2 release and oxygen consumption at the same time points remained normal. At 66 h PMN phagocytizing opsonized zymosan particles released additional quantities of O--2 and H2O2 and consumed significantly more oxygen compared to the usual increase noted at earlier time points. Although oxygen consumption was almost two-fold higher in AM than PMN, phagocytizing AM released three-fold less O--2 and five-fold less H2O2 than did PMN. Furthermore, AM of animals exposed to hyperoxia no longer exhibited enhanced O--2 production upon exposure to opsonized zymosan. Hydrogen peroxide release progressively decreased at rest but progressively increased during phagocytosis of opsonized zymosan during the 90 h exposure to hyperoxia. No changes in oxygen consumption of AM occurred during hyperoxia. The divergent oxidative responses in PMN and AM of guinea-pigs exposed to hyperoxia suggest different biochemical adaptive mechanisms.
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PMID:Effect of hyperoxia on superoxide anion and hydrogen peroxide production of polymorphonuclear leucocytes and alveolar macrophages. 19 22

To evaluate the regulation of endothelial cell Cu,Zn-SOD, we have exposed bovine pulmonary artery endothelial cells in culture to hyperoxia and hypoxia, second messengers or related agonists, hormones, free radical generating systems, endotoxin, and cytokines and have measured Cu,Zn-SOD protein of these cells by an ELISA developed in our laboratory. Control preconfluent and confluent cells in room air contained 196 +/- 18 ng Cu,Zn-SOD/10(6) cells. A23187 (0.33 microM), forskolin (10 microM), isobutylmethylxanthine (0.1 mM), dexamethasone (1 microM), triiodothyronine (1 microM) and retinoic acid (1 microM) failed to alter this level of Cu,Zn-SOD. Exposure to anoxia and hyperoxia both elevated the level approximately 1.5-2.0-fold over 20% oxygen-exposed controls at 48-72 hr. Similarly, exposures to glucose oxidase (0.0075 units/ml), menadione (12.5 microM), xanthine-xanthine oxidase (10 microM, 0.03 units/ml) and H2O2 (0.0005%) increased the level up to two-threefold over controls at 24-48 hr. Lipopolysaccharide, TGF beta 1, TNF alpha, and Il-1 also increased levels of cellular Cu,Zn-SOD, but only in proliferating cells. Il-2, Il-4, interferon-gamma, and GM-CSF had no effect on Cu,Zn-SOD. All treatments that elevated SOD resulted in inhibition of cellular growth, but decreased growth of cells at confluence alone was not associated with increased Cu,Zn-SOD. We propose from these studies that Cu,Zn-SOD of endothelial cells is not under conventional second messenger or hormonal regulation, but that up-regulation of the enzyme is associated with (and perhaps stimulated by) free-radical or oxidant production that also may be influenced by availability of certain cytokines under replicating conditions.
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PMID:Regulation of Cu,Zn-superoxide dismutase in bovine pulmonary artery endothelial cells. 133 80

Oxygen free radicals and hydroperoxides have been postulated to play a causal role in the aging process, implying that antioxidant enzymes may act as longevity determinants. Catalase (H2O2:H2O2 oxidoreductase; EC1.11.1.6) is the sole enzyme involved in the elimination of H2O2 in Drosophila melanogaster; glutathione peroxidase being absent. A genomic fragment containing the Drosophila catalase gene was used to construct transgenic Drosophila lines by means of P element-mediated transformation. Enhanced levels of catalase (up to 80%) did not prolong the life span of flies, nor did they provide improved protection against oxidative stress induced by hyperoxia or paraquat treatment. However, enhanced resistance to hydrogen peroxide was observed in the overexpressors.
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PMID:The effects of catalase gene overexpression on life span and resistance to oxidative stress in transgenic Drosophila melanogaster. 137 30

According to the free radical theory of aging, loss of cellular function during aging is a consequence of accumulating subcellular damage inflicted by activated oxygen species. In cells, the deleterious effects of activated oxygen species may become manifest when the balance between radical formation and destruction (removal) is disturbed creating a situation denoted as 'oxidative stress'. Cell culture systems are especially useful to study the effects of oxidative stress, in terms of both toxicity and cellular adaptive responses. A better understanding of such processes may be pertinent to fully comprehend the cellular aging process. This article reviews three model systems for oxidative stress: extracellular sources of O2-. and H2O2, and normobaric hyperoxia (elevated ambient oxygen). Methodological and practical aspects of these exposure models are discussed, as well as their prominent effects as observed in cultures of Chinese hamster cell lines. Since chronic exposure models are to be preferred, it is argued that normobaric hyperoxia is a particularly relevant oxidative stress model for in vitro cellular aging studies.
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PMID:Cell culture models for oxidative stress: superoxide and hydrogen peroxide versus normobaric hyperoxia. 138 81

The effect of hyperoxia (1-14 days, 85% O2) on rat alveolar macrophage and alveolar type II cell oxidant and antioxidant characteristics was investigated. Unstimulated control macrophages (2 h ex vivo) released hydrogen peroxide at a rate of 3.5 +/- 1.3 nmol/min mg protein-1, which was a cyanide-sensitive process. H2O2 release from alveolar macrophages decreased slightly but not significantly after 1 day in hyperoxia and increased significantly after 3 days (180%, p less than .05) and 14 days (380%, p less than .01). When H2O2 release was expressed as nmol from total macrophages per animal, the increase after 14 days in hyperoxia was 760%. H2O2 generation by hyperoxic macrophages was cyanide resistant, indicating the involvement of active NADPH oxidase. In both control and hyperoxic macrophages H2O2 release could be significantly stimulated with phorbol myristate acetate (PMA). Comparisons of H2O2 release by freshly isolated alveolar macrophages and alveolar type II cells must be cautiously interpreted because some cell functions may change during the isolation procedure. Freshly isolated (6 h ex vivo) control alveolar type II cells were found to generate H2O2 at a rate of 0.26 +/- 0.05 nmol/min mg protein-1. In type II cells H2O2 release, calculated as nmol/mg protein, decreased during the first 7 days of hyperoxia to 10% (p less than .01) of the control value and then returned back up to the control level after 14 days. A similar decrease was observed if H2O2 release was calculated as nmol/cell number. H2O2 release from control and hyperoxic type II cells was cyanide sensitive. The decrease in H2O2 release in type II cells was associated with cell membrane injury (as assessed by electron microscopy), while biochemical markers of cellular injury (trypan blue exclusion and cellular high-energy phosphates ATP, ADP) were unchanged. The ability of type II cells to scavenge extracellular H2O2 did not change in acute hyperoxia, but it increased significantly during the second week in hyperoxia. These results indicate that macrophages but not type II cells are stimulated to produce H2O2 during prolonged exposure to hyperoxia.
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PMID:Hydrogen peroxide release from alveolar macrophages and alveolar type II cells during adaptation to hyperoxia in vivo. 139 11

A significant decrease in blood haemoglobin, reduced glutathione and protein in lung and liver, without any change in blood reduced glutathione, was observed in rats exposed to 80% oxygen. Hydrogen peroxide induced erythrocyte haemolysis was significantly increased following exposure to hyperoxia. The lungs of rats exposed to hyperoxia showed perivascular edema. Simultaneous treatment with antioxidants, vitamin A, C, or E, protected the animals against oxygen toxicity.
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PMID:Biochemical and pathological changes in response to hyperoxia and protection by antioxidants in rats. 150 90

The conversion of xanthine dehydrogenase (XDH) to xanthine oxidase (XO) and the reaction of XO-derived partially reduced oxygen species (PROS) have been suggested to be important in diverse mechanisms of tissue pathophysiology, including oxygen toxicity. Bovine aortic endothelial cells expressed variable amounts of XDH and XO activity in culture. Xanthine dehydrogenase plus xanthine oxidase specific activity increased in dividing cells, peaked after achieving confluency, and decreased in postconfluent cells. Exposure of BAEC to hyperoxia (95% O2; 5% CO2) for 0-48 h caused no change in cell protein or DNA when compared to normoxic controls. Cell XDH+XO activity decreased 98% after 48 h of 95% O2 exposure and decreased 68% after 48 h normoxia. During hyperoxia, the percentage of cell XDH+XO in the XO form increased to 100%, but was unchanged in air controls. Cell catalase activity was unaffected by hyperoxia and lactate dehydrogenase activity was minimally elevated. Hyperoxia resulted in enhanced cell detachment from monolayers, which increased 112% compared to controls. Release of DNA and preincorporated [8-14C]adenine was also used to assess hyperoxic cell injury and did not significantly change in exposed cells. Pretreatment of cells with allopurinol for 1 h inhibited XDH+XO activity 100%, which could be reversed after oxidation of cell lysates with potassium ferricyanide (K3Fe(CN)6). After 48 h of culture in air with allopurinol, cell XDH+XO activity was enhanced when assayed after reversal of inhibition with K3Fe(CN)6, and cell detachment was decreased. In contrast, allopurinol treatment of cells 1 h prior to and during 48 h of hyperoxic exposure did not reduce cell damage. After K3Fe(CN)6 oxidation, XDH+XO activity was undetectable in hyperoxic cell lysates. Thus, XO-derived PROS did not contribute to cell injury or inactivation of XDH+XO during hyperoxia. It is concluded that endogenous cell XO was not a significant source of reactive oxygen species during hyperoxia and contributes only minimally to net cell production of O2- and H2O2 during normoxia.
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PMID:The contribution of vascular endothelial xanthine dehydrogenase/oxidase to oxygen-mediated cell injury. 156 25

Hydrogen peroxide production in organotypic cultures of fetal and newborn rat lung cells has been investigated using an ultrastructural histochemical method, in which the quantity and location of an electron-dense reaction product derived from the interaction of cerium chloride and hydrogen peroxide was detected. Hydrogen peroxide was present in fetal cell cultures exposed to hyperoxia (50% oxygen) compared to controls maintained in 10% oxygen. This increase could be limited by incubation of cultures with ascorbic acid and preincubation with dexamethasone. On the other hand, in newborn rat lung cell cultures, less hydrogen peroxide was identified in cultures including those exposed to hyperoxia (50% oxygen).
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PMID:An ultrastructural study of hydrogen peroxide production by cultured fetal and neonatal rat lung cells exposed to hyperoxia. 161 92

Toxicity to the central nervous system (CNS) by hyperbaric oxygen (HBO) presumably relates to increased production of reactive oxygen species. The sites of generation of reactive oxygen species during HBO, however, have not been fully characterized in the brain. We investigated the relationship between regional generation of hydrogen peroxide (H2O2) in the brain in the presence of an irreversible inhibitor of catalase, aminotriazole (ATZ), and protection from CNS O2 toxicity by a monoamine oxidase (MAO) inhibitor, pargyline. At 6 ATA of oxygen, pargyline significantly protected rats from CNS O2 toxicity whereas ATZ enhanced O2 toxicity. In animals pretreated with ATZ, HBO inactivated 21-40% more catalase than air exposure in the six brain regions studied. Because ATZ-mediated inactivation of catalase was H2O2 dependent, the decrease in catalase activity during hyperoxia was proportional to the intracellular production of H2O2. Pargyline, administered 30 min before HBO, inhibited MAO by greater than 90%, prevented ATZ inhibition of catalase activity during HBO, and reversed the augmentation of CNS O2 toxicity by ATZ. These findings indicate that H2O2 generated by MAO during hyperoxia is important to the pathogenesis of CNS O2 toxicity in rats.
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PMID:Prevention of H2O2 generation by monoamine oxidase protects against CNS O2 toxicity. 175 1

The ability of niacin to relieve the growth-inhibiting effect of hyperoxia on Escherichia coli can be attributed to the dioxygen sensitivity of quinolinate synthetase. The activity of this enzyme within E. coli was diminished by exposure of the cells to 4.2 atm O2, while the activity in extracts was rapidly decreased by 0.2 atm O2. Neither catalase nor superoxide dismutase afforded detectable protection against the inactivating effect of O2, indicating that H2O2 and O2- were not significant intermediates in this process. Nevertheless, H2O2 at 1.0 mM did inactivate quinolinate synthetase, even under anaerobic conditions and in the absence of catalatic activity which might have generated O2. Addition of paraquat to aerobic cultures of E. coli caused an inactivation of quinolinate synthetase, which may be explained in terms of an increase in the production of H2O2. The O2-dependent inactivation of quinolinate synthetase in extracts was gradually reversed during anaerobic incubation and this reactivation was blocked by alpha, alpha'-dipyridyl or by 1,10-phenanthroline. The sequence of the quinolinate synthetase "A" protein contains a--cys-w-x-cys-y-z-cys--sequence, which is characteristic of (Fe-S)4-containing proteins. This sequence, together with the effect of the Fe(II)-chelating agents, suggests that the O2-sensitive site of quinolinate synthetase is an iron-sulfur cluster which is essential for the dehydration reaction catalyzed by the A protein.
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PMID:Quinolinate synthetase: the oxygen-sensitive site of de novo NAD(P)+ biosynthesis. 184 9


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