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Query: UNIPROT:P36969 (phospholipid hydroperoxide glutathione peroxidase)
 344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We report a transient adaptation to the oxidative stress of hydrogen peroxide (H2O2) exposure in several mammalian cell lines: Chinese hamster ovary fibroblast (CHO) cells, HA-1 cells (a defined CHO subclone), C3H 10T1/2 cells (embryonic mouse fibroblasts), V79 cells (Chinese hamster lung fibroblasts), and Clone 9 liver cells (rat liver epithelial cells). Up to 40-fold adaptive increases in resistance to H2O2 challenge occurred following pretreatment with relatively low H2O2 "priming" doses, from as little as 1.9% cell viability for untreated cells to as much as 76.5% viability for H2O2 pretreated cells. Detailed studies with HA-1 cells revealed the following pattern of responses to H2O2: very low H2O2 concentrations of 0.1 to 0.5 mumol/10(7) cells (3 to 15 microM) stimulated cell growth by 25 to 45%; low H2O2 concentrations of 2-5 mumol/10(7) cells (120 to 150 microM) induced a temporary growth-arrest, a lengthening of cell cycle from 18 h to approximately 26 h, and marked adaptive increases in H2O2 resistance; intermediate H2O2 concentrations of 9 to 14 mumol/10(7) cells (250 to 400 microM) caused permanent growth-arrest (i.e., permanent loss of replicative or divisional competence) with no evidence of necrosis; high H2O2 concentrations of 30 mumol/10(7) cells or greater (> or = 1 mM) caused an apoptotic-like necrotic cell death and destruction. The adaptive response to low H2O2 concentrations of 2-5 mumol/10(7) (120 to 150 microM) was maximal 18 h after pretreatment of HA-1 cells, declined thereafter toward baseline sensitivity, and was observed with both 7-day fix and stain procedures and clonogenic viability assays. Transient adaptation following H2O2 pretreatment of 4.15 mumol/10(7) (150 microM) involved the de novo synthesis of at least 20 proteins and was blocked by the translation inhibitor, cycloheximide. During the 18-h adaptation in HA-1 cells proteins were synthesized in three phases; early (0-4 h), middle (4-8 h), and late (8-15 h). No H2O2 response proteins were synthesized beyond 18 h after pretreatment, by which time adaptation had already maximized. Selective translational inhibition of the early, middle, or late proteins revealed that all three sets were necessary for a maximal adaptive increase in H2O2 resistance. Northern blot and enzyme activity analyses revealed no significant increases in transcription or translation of the classical antioxidant enzymes catalase, glutathione peroxidase, phospholipid hydroperoxide glutathione peroxidase, Cu, Zn superoxide dismutase, or Mn superoxide dismutase in H2O2-adapted HA-1 cells.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Transient adaptation of oxidative stress in mammalian cells. 772 66

Murine leukemia L1210 cells rendered deficient in glutathione peroxidase (GPX) and phospholipid hydroperoxide glutathione peroxidase (PHGPX) by Se deprivation (L.Se(-) cells) were found to be more sensitive to tert-butyl hydroperoxide (t-BuOOH) cytotoxicity than Se-replete controls (L.Se(+) cells). Human K562 cells, which express PHGPX, but not GPX, were also more sensitive to t-BuOOH in the Se-deficient (K.Se(-)) than Se-satisfied (K.Se(+)) condition. In examining the metabolic basis for selenoperoxidase-dependent resistance, we found that glucose-replete Se(-) cells reduce t-BuOOH to t-butanol far more slowly than Se(+) cells, the ratio of the first-order rate constants approximating that of the GPX activities (L1210 cells) or PHGPX activities (K562 cells). Monitoring peroxide-induced changes in GSH and GSSG gave consistent results; e.g., glucose-depleted L.Se(+) cells exhibited a first order loss of GSH that was substantially faster than that of glucose-depleted L.Se(-) cells. Under the conditions used, peroxide-induced conversion of GSH to GSSG could be stoichiometrically reversed by resupplying D-glucose, indicating that no significant lysis or GSSG efflux and/or interchange had taken place. The apparent first-order rate constant for GSH decay increased progressively for L1210 cells expressing a range of GPX activities from approximately 5% to 100%, demonstrating that peroxide detoxification is strictly dependent on enzyme content. The initial rate of 14CO2 release from D-[1-14C]glucose supplied in the medium was much greater for L.Se(+) or K.Se(+) cells than for their respective Se(-) counterparts, consistent with greater hexose monophosphate shunt activity in the former. These results highlight the importance of selenoperoxidase action in the glutathione cycle as a means by which tumor cells cope with hydroperoxide stress.
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PMID:Selenoperoxidase-dependent glutathione cycle activity in peroxide-challenged leukemia cells. 777 66

Selenium is an essential component in the two antioxidant enzymes glutathione peroxidase (GSH-Px) and phospholipid hydroperoxide glutathione peroxidase (PLGSH-Px). Free oxygen radicals are involved in the inflammatory process seen in rheumatoid arthritis (RA) and are generated mainly through the phagocytic activity of the polymorphonuclear leucocytes. Several experimental studies indicate that selenium is important to the functioning of the immune system and to the inflammatory process. A low selenium status among patients with RA has been reported from areas with both high and low natural selenium intake. The reduction in the serum level is approx. 10%. This reduction is related to the clinical disease activity in arthritis patients in both cross-sectional and longitudinal studies, and selenium concentrations have been found to fluctuate during the disease. Reduced selenium concentrations have been reported in red blood cells, too, and concentrations have been found to be slightly reduced in the polymorphonuclear leucocytes. Studies do not agree on the activity of GSH-Px among RA patients. Thus activity levels have been reported to range from low to high. Those studies that have focused on the subgroup of patients with high persistent disease activity have reported reduced GSH-Px activities in both serum, red blood cells and polymorphonuclear leucocytes. Selenium supplementation using organic selenium compounds in doses of around 250 microgram/day increases the selenium concentration in serum and red blood cells considerably. However, supplementation is not reflected in the selenium level in polymorphonuclear leucocytes from RA patients as opposed to healthy subjects, in whom the level of selenium in polymorphonuclear leucocytes increases. Selenium supplementation increased GSH-Px activity in serum, red blood cells and platelets from RA patients, but in the polymorphonuclear leucocytes the increase was not sufficient to reach the levels of the controls. This apparent lack of de novo synthesis of GSH-Px in polymorphonuclear leucocytes from RA patients may be explained by their inability to increase their selenium content in spite of high levels of available extracellular selenium. this may be in accordance with the lack of anti-arthritic effect of selenium supplementation in controlled clinical studies among RA patients. Several experimental studies have reported inhibition of GSH-Px by antirheumatic drugs, in particular gold. In addition, gold has been found to reduce selenium in rat plasma. These interactions can, however, be modified by increasing the amount of selenium in the feed. Among RA patients there is no clear evidence of an interaction between gold, selenium and GSH-Px.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Selenium and the selenium-dependent glutathione peroxidase in rheumatoid arthritis. 792 58

A new technique, high-performance liquid chromatography with reductive mode electrochemical detection on a mercury drop (HPLC-EC), has been used for analyzing lipid hydroperoxide (LOOH) formation in photooxidatively stressed L1210 leukemia cells. Highly specific and sensitive for peroxides (detection limits < 0.5 pmol for cholesterol hydroperoxides and < 50 pmol for phospholipid hydroperoxides), this approach allows different classes of LOOH to be separated and determined in minimally damaged cells. L1210 cells in serum-containing growth medium were irradiated in the presence of merocyanine 540 (MC540), a lipophilic photosensitizing dye. Lipid extracts from cells exposed to a light fluence of 0.11 J/cm2 (which reduced clonally assessed survival by 30%) showed 12-15 well-defined peaks in HPLC-EC. None of these peaks was observed when cells were irradiated without MC540 or when dye/light-treated samples were reduced with triphenylphosphine prior to analysis. Three peaks of relatively low retention time (< 12 min) were assigned to the following species by virtue of comigration with authentic standards: 3 beta-hydroxy-5 alpha-cholest-6-ene-5-hydroperoxide (5 alpha-OOH), 3 beta-hydroxycholest-4-ene-6 beta-hydroperoxide (6 beta-OOH), and 3 beta-hydroxycholest-5-ene-7 alpha/7 beta-hydroperoxide (7 alpha/7 beta-OOH). Formation of 5 alpha-OOH and 6 beta-OOH (single oxygen adducts) was confirmed by subjecting [14C]cholesterol-labeled cells to relatively high levels of photooxidation and analyzing extracted lipids by HPLC with radiochemical detection. Material represented in a major peak at 18-22 min on HPLC-EC was isolated in relatively large amounts by semipreparative HPLC and shown to contain phospholipid hydroperoxides (predominantly phosphatidylcholine species, PCOOH) according to the following criteria: (i) decay of 18-22 min peak during Ca2+/phospholipase A2 treatment, with reciprocal appearance of fatty acid hydroperoxides; (ii) reduction of peroxide during treatment with reduced glutathione and phospholipid hydroperoxide glutathione peroxidase, but not glutathione peroxidase; and (iii) comigration with PCOOH standards in thin-layer chromatography. HPLC-EC analysis revealed quantifiable amounts of PCOOH and ChOOH at a light fluence that clonally inactivated < 10% of the cells, which allows for the possibility that photoperoxidative damage plays a causal role in cell killing.
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PMID:Characterization of lipid hydroperoxides generated by photodynamic treatment of leukemia cells. 796 65

Oxidative modification of human low-density lipoprotein (LDL) is thought to play an important role in the development of atherosclerosis. LDL oxidizability is believed to be strongly influenced by factors such as (a) content of preexisting lipid hydroperoxides (LOOHs) and (b) content of endogenous antioxidants such as alpha-tocopherol and beta-carotene. The purpose of this study was to examine the prooxidant role of preexisting LDL-LOOHs, using a recently developed method for ultrasensitive and selective LOOH analysis: high-performance liquid chromatography with mercury drop electrochemical detection (HPLC-EC). Exceedingly low detection limits for LDL-LOOHs have been achieved by HPLC-EC, e.g., approximately 100 fmol for cholesteryl ester hydroperoxide (CEOOH). This sensitivity has allowed us to monitor LDL-LOOHs at levels that are undetectable by most other methods. Fresh LDL prepared with the utmost care to prevent autoxidation was found to contain small, yet significant amounts of CEOOH, 6-12 pmol/mg protein. Our data suggest that these peroxides could not have arisen during LDL isolation or sample work-up for HPLC-EC. Incubation with GSH and phospholipid hydroperoxide glutathione peroxidase resulted in nearly complete reduction of the CEOOH. This LDL was found to be much more resistant to Cu(2+)-induced peroxidation than starting material, exhibiting a lag period that was at least six times greater. We have also determined that LDL becomes progressively more susceptible to Cu(2+)-induced lipid peroxidation (as evidenced by a shortened lag) when it is preloaded with increasing amounts of photochemically generated LOOHs. Taken together, these results provide strong support for the idea that preexisting LOOHs in LDL are important determinants of its overall oxidizability.
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PMID:Involvement of preexisting lipid hydroperoxides in Cu(2+)-stimulated oxidation of low-density lipoprotein. 798 64

The involvement of Se enzymes in the protection against the oxidative stress induced by adriamycin (ADR) in rat heart has been studied in animals fed for 10 weeks at three different levels of Se content (low = 0.02 ppm; normal = 0.5 ppm; high = 1.0 ppm) and receiving a weekly injection of 3 mg/kg ADR for 4 weeks. ECG (QaT duration) and contractility of isolated atria were measured. The high-Se diet showed a significant protection on both parameters. To assess the hypothesis that an increase of specific activity of antioxidant Se enzymes may account for the cardioprotective effect of selenium, glutathione peroxidase (GPX), and phospholipid hydroperoxide glutathione peroxidase (PHGPX) were tested. The assays were performed on ventricles isolated from treated rats. At the end of the experimental period, GPX (cytosolic enzyme) did not show any significant difference between controls and ADR-treated at any level of Se content, thus excluding its involvement in the cardioprotection observed in high-Se ADR-treated animals. PHGPX, which is present both in cytosol and in the cell membrane, showed a trend to increase its activity in the presence of ADR treatment only in the membrane fraction; however, the statistical significance was reached only in the low-Se group (+100%). This observation suggests that membrane PHGPX might be involved in the cellular mechanism of adaptation of the heart to the toxic effects of ADR; however, the behavior of these enzymes does not seem to account for the significant protection of selenium supplementation both on ECG and on contractile indices of ADR cardiotoxicity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Protective effect of dietary selenium supplementation on delayed cardiotoxicity of adriamycin in rat: is PHGPX but not GPX involved? 800 24

A human cDNA that encodes a polypeptide that has 94% deduced amino-acid sequence identity to porcine phospholipid hydroperoxide glutathione peroxidase was cloned from a testis library. The sequence shows preservation of the UGA selenocysteine codon, putative active-site Trp and Glu residues and a Tyr residue that is phosphorylated in the porcine protein. The 3'-UTR shows some conservation of sequences implicated in the insertion of selenocysteine at an opal codon in human glutathione peroxidase-1.
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PMID:Cloning and sequencing of the cDNA encoding a human testis phospholipid hydroperoxide glutathione peroxidase. 803 23

The complete amino acid sequence of the selenoprotein phospholipid-hydroperoxide glutathione peroxidase (PHGPX) from pig heart has been deduced from the corresponding genomic DNA, the cDNA covering the coding region, and by sequencing the N terminus of the protein. The maximum length of the peptide chain derived from the cDNA amounts to 170 amino acid residues. By protein sequencing the N-terminal residues methionine and cysteine of the deduced sequence were found to be cleaved. The molecular mass of 19,671 Da obtained by laser desorption mass spectroscopy, however, significantly exceeds the mean molecular mass of 19,257.09 calculated for the sequence 3-170 of PHGPX, thus indicating posttranscriptional modification. In contrast to glutathione peroxidase (GPX) the coding area of the PHGPX gene is composed of seven exons. Only the amino acid sequences encoded by the third and fifth exon are highly homologous to GPX sequences. The amino acid residues selenocysteine, tryptophan, and glutamine forming the catalytic site in bovine GPX are conserved in homologous positions of PHGPX, whereas the arginine residues presumed to bind GSH in GPX are not. Gaps in the PHGPX sequence correspond to subunit interaction sites of the tetrameric GPX. The data suggest an identical catalytic mechanism of the selenoperoxidases, a less stringent substrate specificity of PHGPX, and explain the monomeric nature of PHGPX. As in other selenoproteins, the selenocysteine residue of PHGPX is encoded by UGA. The 3'-untranslated region (UTR) of the PHGPX shows a limited consensus with that of GPX and 5'-deiodinase, where it was shown to be responsible for the decoding of UGA as selenocysteine. The 3'-UTR of PHGPX can form a stem/loop as in other mammalian selenoprotein genes. The 5'-UTR and the first intron of the PHGPX gene contain a variety of putative regulatory elements indicating hormonal control.
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PMID:Phospholipid-hydroperoxide glutathione peroxidase. Genomic DNA, cDNA, and deduced amino acid sequence. 812 51

We hypothesize that the differential susceptibility to photic injury among different strains of rat retinas may depend on the levels of phospholipid hydroperoxide glutathione peroxidase (PHGPX) activity, one of the endogenous antioxidant enzymes in the retina. The retinas of four inbred strains of albino rat (Fischer, Wistar, Buffalo and Lewis) were analyzed for glutathione peroxidase activity using H2O2, cumene hydroperoxide, and phospholipid hydroperoxide as assay substrates. In all four strains of rat, PHGPX was observed only in the high salt extract of the retina, while peroxidases determined by H2O2 or cumene hydroperoxide were observed mainly in the low salt extract. PHGPX was highest (66.7 mU/mg) in the most light-resistant Fischer strain and lowest in the most light-sensitive Lewis strain (31.9 mU/mg), while the activity levels in the moderately light-sensitive Buffalo and Wistar strains were 46.6 and 38.5 mU/mg, respectively. In contrast, there was no significant difference in peroxidases determined by H2O2 or cumene hydroperoxide among the four strains. These observations suggested that, in rat retina, the membrane-associated PHGPX may have an important role in the defense against light-induced free radical damage.
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PMID:Correlation of phospholipid hydroperoxide glutathione peroxidase activity to the sensitivity of rat retinas to photic injury. 813 90

The reaction of phospholipid hydroperoxide glutathione peroxidase (PHGPx) and Ebselen with phospholipid and cholesterylester hydroperoxides associated with HDLox and LDLox was investigated using specific HPLC assays for the hydroperoxides of phosphatidylcholine (PCOOH) and cholesteryllinolate (Ch18:2-OOH) and for cholesteryllinolate hydroxides (Ch18:2-OH). HDLox and LDLox were formed from the corresponding isolated native lipoproteins by controlled and limited oxidation initiated by aqueous peroxyl radicals. Incubation of HDLox or LDLox in the presence of PHGPx/GSH or Ebselen/GSH resulted in rapid degradation of both classes of lipid hydroperoxides, with equimolar amounts of Ch18:2-OH formed from Ch18:2-OOH. No pronounced differences were observed between PCOOH and Ch18:2-OOH in terms of substrate specificity, whereas HDLox-associated PCOOH and Ch18:2-OOH appeared to be slightly better substrates for PHGPx/GSH as compared to those in LDLox. Also, Ch18:2-OOH associated with HDLox but not LDLox were reduced by Ebselen or GSH alone. These in vitro findings indicate that the enzymatic PHGPx/GSH and the nonenzymatic Ebselen/GSH systems can efficiently reduce hydroperoxides of phospholipids and cholesterylesters associated with intact lipoproteins.
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PMID:Reduction of HDL- and LDL-associated cholesterylester and phospholipid hydroperoxides by phospholipid hydroperoxide glutathione peroxidase and Ebselen (PZ 51). 813 30


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