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

Sulfotransferase catalyzed sulfation is important in the regulation of different hormones and the metabolism of hydroxyl containing xenobiotics. In the present investigation, we examined the effects of hyperoxia on aryl sulfotransferase IV in rat lungs in vivo. The enzyme activity of aryl sulfotransferase IV increased 3- to 8-fold in >95% O2 treated rat lungs. However, hyperoxic exposure did not change the mRNA and protein levels of aryl sulfotransferase IV in lungs as revealed by Western blot and RT-PCR. This suggests that oxidative regulation occurs at the level of protein modification. The increase of nonprotein soluble thiol and reduced glutathione (GSH)/oxidized glutathione (GSSG) ratios in treated lung cytosols correlated well with the aryl sulfotransferase IV activity increase. In vitro, rat liver cytosol 2-naphthol sulfation activity was activated by GSH and inactivated by GSSG. Our results suggest that Cys residue chemical modification is responsible for the in vivo and in vitro oxidative regulation. The molecular modeling structure of aryl sulfotransferase IV supports this conclusion. Our gel filtration chromatography results demonstrated that neither GSH nor GSSG treatment changed the existing aryl sulfotransferase IV dimer status in cytosol, suggesting that oxidative regulation of aryl sulfotransferase IV is not caused by dimer-monomer status change.
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PMID:In vivo and in vitro oxidative regulation of rat aryl sulfotransferase IV (AST IV). 1584 21

Peroxiredoxin 6 (Prdx6), a bifunctional 25-kDa protein with both GSH peroxidase and phospholipase A2 activities, is the only mammalian 1-Cys member of the peroxiredoxin superfamily and is expressed in all major organs, with a particularly high level in lung. Prdx6 uses GSH as an electron donor to reduce H2O2 and other hydroperoxides including phospholipid hydroperoxides at approximately 5 micromol/mg protein/min with K1 approximately 3 x 10(6) M(-1) s(-1). Oxidation of the Cys47 to a sulfenic acid during catalysis requires piGST-catalyzed glutathionylation and reduction with GSH to complete the enzymatic cycle. Prdx6 stably overexpressed in cells protected against oxidative stress, whereas antisense treatment resulted in oxidant stress and apoptosis. Adenoviral-mediated overexpression of Prdx6 in mouse lungs protected against the toxicity of hyperoxia, whereas Prdx6-null mice were more sensitive to the effects of hyperoxia or paraquat. We postulate that Prdx6 functions in antioxidant defense mainly by facilitating repair of damaged cell membranes via reduction of peroxidized phospholipids. The PLA2 activity of Prdx6 is Ca2+ independent and maximal at acidic pH. Inhibition of PLA2 activity results in alterations of lung surfactant phospholipid synthesis and turnover. Thus, Prdx6, a unique mammalian peroxiredoxin, is an important antioxidant enzyme and has a major role in lung phospholipid metabolism.
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PMID:Peroxiredoxin 6, a 1-Cys peroxiredoxin, functions in antioxidant defense and lung phospholipid metabolism. 1589 Jun 16

This article describes a metabolite profiling method for evaluating the effect of oxygen exposure on human liver microsomal metabolism of mitomycin C (MC) in the presence of glutathione (GSH) and NADPH under hypoxic (100% helium), limitedly and fully aerobic, and hyperoxic (100% oxygen) conditions. MC and its metabolite(s) were characterized and the relative percentages of these components were estimated at different incubation times using liquid chromatography and quadrupole time-of-flight mass spectrometry. The MC metabolite profiles were confirmed using purified human cytochrome P450 reductase, acidic activation, and UV-Vis detection at 550 nm. In hypoxia, MC was exclusively metabolized into 2,7-diaminomitosene-10-glutathione-S-conjugate (2,7-DAM-10-SG) within 30 min, whereas approximately 5% of this conjugate, 16% of 2,7-diaminomitosene (2,7-DAM), and 77% of MC were observed under a fully aerobic condition at 90 min. Under limitedly aerobic conditions, the relative percentages of the two metabolites in incubations varied greatly depending on the volume ratio of air to liquid. In hyperoxia, 2% of 2,7-DAM-10-SG, 9% of 2,7-DAM, and 86% of MC were obtained at 90 min. The results indicate that oxygen strongly inhibits the in vitro metabolism of MC. These data suggest that GSH may serve a dual function in facilitating the formation of a leucoaziridinomitosene followed by electron rearrangement giving intermediate metabolite 2,7-DAM, and then trapping this intermediate giving rise to 2,7-DAM-10-SG. These findings provide direct evidence for understanding the fate of oxygen-sensitive metabolic deactivation of MC by GSH.
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PMID:Evaluation of the effect of oxygen exposure on human liver microsomal metabolism of mitomycin C in the presence of glutathione using liquid chromatography-quadrupole time of flight mass spectrometry. 1600 24

The mRNA levels of three antioxidant genes, Cu/Zn superoxide dismutase (SOD), catalase (CAT) and phospholipid hydroperoxide glutathione peroxidase (GSH-Px), were quantified with real-time qRT-PCR in liver of Atlantic salmon Salmo salar exposed to 80% (normoxia), 105% and 130% O2 saturation for 54 days. The salmon were then translocated and exposed to 90% and 130% O2 saturation for additional 72 days during smoltification. TBARS and vitamin E levels in liver and the levels of oxidized glutathione (GSSG), total glutathione (GSH) and the resulting oxidative stress index (OSI) in blood were quantified as traditional oxidative stress markers. No significant mean normalized expression (MNE) differences of SOD, CAT or GSH-Px were found in liver after hyperoxia exposure at the two sampling times. Significantly decreased OSI was found in smolt exposed to 130% O2 saturation after 126 days (n = 18, P < 0.0001), indicating hyperoxia-induced oxidative stress. No effects were seen on growth, or on the levels of thiobarbituric reactive substances (TBARS) and vitamin E in liver after the exposure experiment. Overall, the mRNA expression of SOD, CAT and GSH-Px in liver related poorly with the hyperoxic exposure regimes, and more knowledge are needed before the expressed levels of these antioxidant genes can be applied as biomarkers of hyperoxia in Atlantic salmon.
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PMID:mRNA expression of antioxidant enzymes (SOD, CAT and GSH-Px) and lipid peroxidative stress in liver of Atlantic salmon (Salmo salar) exposed to hyperoxic water during smoltification. 1610 25

S-Adenosylmethionine (SAM, AdoMet) is the most important methyl donor used for synthesis of nucleic acids, phospholipids, creatine, and polyamines and for methylation of many bioactive molecules. The metabolic response of the lung to oxidative stress of hyperoxia requires increased RNA and protein synthesis for energy metabolism, growth arrest, and antioxidant defense. We studied the production of SAM and other aspects of methionine metabolism in lung epithelial cells exposed to hyperoxia. Human lung epithelial-like (A549) and primary small airway epithelial (SAE) cells were exposed to normoxia (21% O(2)) or hyperoxia (95% O(2)). Cell methionine and S-adenosylmethionine content increased in response to hyperoxia in SAE and A549 cells. Because methionine adenosyl transferase (MAT) is the rate-limiting enzyme of the pathway, we examined the expression of a lung epithelial isoform of MAT 2A in hyperoxia. Western blots revealed a novel MAT 2A isoform expressed in both cell types, with a lower molecular mass than that described in Jurkat cells. Cloning and sequencing of the MAT 2A cDNA revealed one silent nucleotide substitution compared to that expressed in Jurkat. The lower mass of MAT 2A in both lung epithelial cells indicated that the absence of the major posttranslational modification of MAT 2A found in Jurkat. MAT 2A protein progressively increased during hyperoxic exposure in both transformed and primary lung epithelium. Increased flux of (13)C-labeled methionine to S-adenosylhomocysteine (SAH) in A549 demonstrated that SAM's methyl group was utilized, and increased formation of cystathionine indicated that at least part of SAM generated was directed toward cysteine/GSH in the transsulfuration pathway. These results indicate activation of MAT 2A and the transmethylation pathway in the metabolic response to hyperoxia in lung epithelium.
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PMID:Activation of a novel isoform of methionine adenosyl transferase 2A and increased S-adenosylmethionine turnover in lung epithelial cells exposed to hyperoxia. 1641 17

The transcript levels of three genes coding for antioxidants, Cu/Zn superoxide dismutase (SOD), catalase and phospholipid hydroperoxide glutathione peroxidase (GSH-Px), and those of two stress proteins, metallothionein (MT) and CYP1A, were examined with real-time quantitative (q) RT-PCR in hepatic tissue of Atlantic cod exposed to 46% (hypoxia), 76% (normoxia) and 145% (hyperoxia) O(2) saturation (tank outlet). To evaluate the oxidative stress state, the levels of total glutathione (tGSH), reduced glutathione (GSH) and oxidized glutathione (GSSG) and subsequently the oxidative stress index (OSI), were determined in the same tissue samples. The transcript level of GSH-Px was significantly upregulated in fish exposed to hyperoxia, and significantly downregulated in fish exposed to hypoxia, compared to the normoxia group. Significant downregulation was also found for SOD and CYP1A transcriptional levels in fish exposed to hypoxia. The transcript levels of catalase and MT did not change in liver of cod exposed to suboptimal oxygen levels. No significant differences were seen between the groups for tGSH, GSH, GSSG or OSI. Prolonged exposure to unfavourable oxygen saturation levels did not alter the OSI, indicating that the antioxidant glutathione system is maintained at an unchanged level in liver of the examined cod.
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PMID:Effects of hypo- and hyperoxia on transcription levels of five stress genes and the glutathione system in liver of Atlantic cod Gadus morhua. 1685 73

The main purpose of this study was to determine whether experimental enhancement of oxidative stress by exposure to hyperoxia is an appropriate model for the acceleration of the normal aging process or for establishing a causal association between oxidative stress and aging. Insect tissues are directly exposed to ambient air via the tracheolar invaginations and are thus highly susceptible to oxidative stress under hyperoxic conditions. Amounts of glutathione (GSH), glutathione disulfide (GSSG) and protein mixed disulfides (PrSSG) were compared under normoxic and 100% ambient oxygen in males of two different strains of Drosophila melanogaster (Oregon R (WT) and y w strains). The reason for using two different strains was to preclude the effects of genetic background and to determine whether variations in longevity of the two strains are associated with resistance to oxidative stress. Amounts of GSSG and PrSSG increased, whereas GSH:GSSG ratios declined as a function of age in both strains. Under hyperoxia, y w flies did not exhibit an increase in GSSG amount or a decline in GSH:GSSG ratio, whereas WT flies showed a decline in GSH:GSSG ratio only during the later part of hyperoxic exposure. In neither strain there was a progressive increase in PrSSG amount under hyperoxia. Results indicate that hyperoxia (100% oxygen) neither reproduces nor accelerates the pattern of alterations in glutathione redox state and PrSSG content observed during aging under normoxic conditions, although some other indicators of oxidative stress may be affected.
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PMID:Comparison between the effects of aging and hyperoxia on glutathione redox state and protein mixed disulfides in Drosophila melanogaster. 1701 Oct 21

A dynamic assessment of oxygen status of the arterial blood, activity of antioxidant system enzymes (AOS), succinatedehydrogenase (SDG), mitochondrial alpha-glycero-phosphate-dehydrogenase (alpha-GPDH) and alkaline phosphatase (AP) as well as concentrations of reduced glutathione (GSH) and secondary products of lipid peroxidation reacting with thiobarbituric acid (PLPRTA) has been carried out in patients at the acute stage of ischemic stroke of hemispheric location. Relative hyperoxia as a result of the hyperventilation syndrome was mostly pronounced on day 1 and 3. At the same time, a reduced activity of AOS system and an increase of PLPRTA concentration have been observed from the 1st day after stroke. There were also a decrease of the SDG activity and a marked (2,8 fold) increase of the alpha-GPDH activity as compared to the controls. A decrease of the AP leukocyte activity in the peripheral blood to day 7 after stroke makes possible a prognosis of good functional rehabilitation to the 21st day of the disease. Therefore, the results of the study suggest that the development of oxidative stress in patients with ischemic stroke is caused by tprimary disruption of bioenergetic processes during the reduction of AOS activity.
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PMID:[Oxidative stress and oxygen status in ischemic stroke]. 1731 Jul 94

The aim of this study was to evaluate the effect of 2,5-dihydroxybenzoic acid, a salicylate derived from Acetyl salicylic acid (ASA) and vitamin A (vit A) on Na(+), K(+) ATPase enzyme and GSH levels in brain of rats exposed to hyperoxia (Hyp) as oxidant protocol. Rats were treated as follow: group I (control), group II (Hyp), group III (Hyp, ASA), group IV (vit A), group V (Hyp, vit A), group VI (Hyp, vit A, ASA). Vit A was given 5 days before and during Hyp, aspirin at the end of Hyp. Na(+),K(+) ATPase and total ATPase activity was significantly increased in group V. Levels of GSH showed a significant increase in group III, besides, levels of 2,5-dihydroxybenzoic acid as salicylate in plasma were significantly increased in group II. These results elucidate differences in the biochemical response of animal towards intake of various types of antioxidant substances, with increased GSH and salicylate in hyperoxia.
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PMID:Assessment of antioxidant effect of 2,5-dihydroxybenzoic acid and vitamin a in brains of rats with induced hyperoxia. 1740 73

Redox imbalance has been implicated in the pathogenesis of many acute and chronic lung diseases. The b-Zip transcription factor Nrf2 acts via an antioxidant/electrophilic response element to regulate antioxidants and maintain cellular redox homeostasis. Our previous studies have shown that Nrf2-deficient mice (Nrf2(-/-)) show reduced pulmonary expression of several antioxidant enzymes, which renders them highly susceptible to hyperoxia-induced lung injury. To better understand the physiologic significance of Nrf2-induced redox signaling, we have used primary cells isolated from the lungs of Nrf2(+/+) and Nrf2(-/-) mice. Our studies were focused on type II cells because these cells are constantly exposed to the oxidant environment and play key roles in host defense, injury, and repair processes. Using this system, we now report that an Nrf2 deficiency leads to defects in type II cell proliferation and greatly enhances the cells' sensitivity to oxidant-induced cell death. These defects were closely associated with high levels of reactive oxygen species (ROS) and redox imbalance in Nrf2(-/-) cells. Glutathione (GSH) supplementation rescued these phenotypic defects associated with the Nrf2 deficiency. Intriguingly, although the antioxidant N-acetyl-cysteine drastically squelched ROS levels, it was unable to counteract growth arrest in Nrf2(-/-) cells. Moreover, despite their elevated levels of ROS, Nrf2(-/-) type II cells were viable and, like their wild-type counterparts, exhibited normal differentiation characteristics. Our data suggest that dysfunctional Nrf2-regulated GSH-induced signaling is associated with deregulation of type II cell proliferation, which contributes to abnormal injury and repair and leads to respiratory impairment.
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PMID:Deficiency in Nrf2-GSH signaling impairs type II cell growth and enhances sensitivity to oxidants. 2876 65


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