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

Four different cell lines (Hep G2, THP-1, EL 4 6.1, and ECV 304) were grown in a selenium-deficient standard medium (5% fetal calf serum in RPMI 1640 resulting in 5.5 nM selenium of unknown bioavailability) and supplemented with increasing concentration of selenium in the form of sodium selenite, selenomethionine and serum-bound selenium. The activities of two types of glutathione peroxidases (cGPx and PHGPx) were measured to estimate the availability of selenium for selenoprotein synthesis. Only sodium selenite between 1 and 100 nM was found to consistently induce GPx activity in all cell lines, whereas selenomethionine in equal concentrations was practically ineffective. Only THP-1 cells were able to utilize selenium from serum as efficiently as sodium selenite. PHGPx activity similarly responded to selenium supplementation, but was not increased in EL 4 6.1 cells. Our data demonstrate that conventional tissue culture media require selenium supplementation to guarantee adequate selenoprotein biosynthesis in cultured cells. The chemical nature of the selenium compound used for such supplement is as critical for in vitro cultivated cells as for dietary intake.
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PMID:Utilization of selenium from different chemical entities for selenoprotein biosynthesis by mammalian cell lines. 892 68

Differentiation of HL-60 cells by dimethylsulfoxide induces 5-lipoxygenase protein expression, but only low cellular 5-lipoxygenase activity. Similarly, B-lymphocytes express 5-lipoxygenase protein and show activity in cell homogenates but not in intact cells. Here, we demonstrate that suppression of cellular 5-lipoxygenase activity in these cell lines is serum dependent and that the serum effect can be mimicked by selenium. Selenium-dependent inhibition of 5-lipoxygenase activity was also observed in the corresponding cell homogenates or 100,000 x g supernatants when dithiothreitol or glutathione (GSH) was added. The properties of the endogenous selenium-dependent inhibitor, i.e., molecular mass, utilization of GSH and dithiothreitol as substrates, sensitivity to iodacetate, inhibition of 5-lipoxygenase activity in the presence of the GPx-1 inhibitor mercaptosuccinate, suggest that a selenoenzyme with properties of the phospholipid hydroperoxide glutathione peroxidase (GPx-4) is responsible for the 5-lipoxygenase inhibition in BL41-E95-A and immature HL-60 cells. Differentiation of HL-60 cells in the presence of 1,25-dihydroxyvitamin D3 and transforming growth factor-beta (TGF beta) upregulated cellular 5-lipoxygenase activity regardless of whether the cell were grown with or without serum or selenium. Also, 5-lipoxygenase activity in homogenates or 100,000 x g supernatants of 1,25-dihydroxyvitamin D3/TGF beta differentiated HL-60 cells and of human granulocytes was not inhibited by dithiothreitol or GSH. Thus, after 1,25-dihydroxyvitamin D3/TGF beta differentiation, HL-60 cells resemble normal granulocytes with respect to the high 5-lipoxygenase activity in intact cells and to the dithiothreitol effects in broken cell preparations. Combination experiments with 100000 x g supernatants of BL41-E95-A cells and neutrophils revealed that the high 5-lipoxygenase activity of granulocytes is due to stability of the 5-lipoxygenase catalytic activity against selenium-dependent peroxidases, but not to low peroxidase activity. Our data suggest that the capability of mature myeloid cells to release large amounts of leukotrienes after stimulation is due to a peroxidase-insensitive 5-lipoxygenase catalytic activity.
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PMID:Selenium-dependent peroxidases suppress 5-lipoxygenase activity in B-lymphocytes and immature myeloid cells. The presence of peroxidase-insensitive 5-lipoxygenase activity in differentiated myeloid cells. 895 58

Two enzymatic mechanisms have been proposed for the metabolism of hydroperoxy-phospholipids: i) the combined action of phospholipase A2 and glutathione peroxidase, and/or ii) direct enzymatic reduction. The latter reaction may be catalyzed by selenium-dependent phospholipid hydroperoxide glutathione peroxidase and/or by glutathione S-transferase alpha. To study the pathway of this reaction, we used human hepatoma HepG2 cells into which was incorporated labeled, hydroperoxy-phospholipids. The major product of incorporated l-palmitoyl-2-(13-hydroperoxy-cis-9, trans-11-octadecadienoyl)-L-3-phosphatidylcholine was the corresponding hydroxy-phospholipid with no hydroxy- or hydroperoxy-fatty acids. The contributions to reduction of hydroperoxy-phospholipids in HepG2 cells from glutathione S-transferase Al and phospholipid hydroperoxide glutathione peroxidase were calculated to be 0.5% and 99.5%, respectively. Increasing selenium in the cell culture medium led to increases in selenium-dependent phospholipid hydroperoxide glutathione peroxidase activity but not in glutathione S-transferase alpha. This increase in the selenium-dependent enzyme was paralleled by a concomitant increase in the extent of reduction of the incorporated hydroperoxy-phospholipid. We conclude that the main metabolic fate of hydroperoxy-phospholipids in HepG2 cells is by direct reduction to hydroxy-phospholipids by phospholipid hydroperoxide glutathione peroxidase but also by glutathione S-transferase alpha, and that phospholipase A2/selenium-dependent glutathione peroxidase does not play a significant role in the reduction.
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PMID:Metabolism of hydroperoxy-phospholipids in human hepatoma HepG2 cells. 897 87

Selenium is an essential nutrient and synthesis of selenoproteins is affected by limited selenium supply. During selenium deficiency there is a differential regulation of selenoprotein synthesis and gene expression; for example, there is a decrease in abundance of mRNA for cytosolic glutathione peroxidase (cGSH-Px) and a preservation of mRNA for phospholipid-hydroperoxide glutathione peroxidase (PHGSH-Px). This difference is not due to an alteration in the rate of transcription but might reflect differences in translation. The aim of the present work was to assess the role of cGSH-Px and PHGSH-Px 3' untranslated regions (UTRs) in the regulation of selenoprotein mRNA stability and translation by using H4-II-E-C3 cells transfected with different constructs containing a type I iodothyronine deiodinase-coding region linked to different selenoprotein mRNA 3' UTRs. Translational efficiency results showed that the efficiency of the 3' UTRs in permitting selenocysteine incorporation is similar in selenium-replete conditions but, when selenium is limiting, the 3' UTR of cGSH-Px is less efficient than the 3' UTR of PHGSH-Px. The results suggest that the 3' UTR of these selenoprotein mRNA species influences their extent of translation when selenium levels are low. The different sensitivity of the 3' UTRs to selenium deficiency can explain the differential effect that selenium deficiency has on cGSH-Px and PHGSH-Px activity and mRNA levels, stability and translation. This might be partly responsible for channelling selenium for synthesis of PHGSH-Px rather than cGSH-Px.
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PMID:Role of the 3' untranslated region in the regulation of cytosolic glutathione peroxidase and phospholipid-hydroperoxide glutathione peroxidase gene expression by selenium supply. 900 77

Selenium-dependent cellular glutathione peroxidase (GPX1) overexpressing [GPX1(+)] mice were derived by microinjecting a 5.3-kb cloned entire mouse GPX1 genomic DNA into fertilized eggs. The objective of this study was to determine the effect of GPX1 overexpression and dietary selenium on the expression of selenoperoxidases and the status of lipid peroxidation of these transgenic animals. An experiment with a 2 x 2 factorial arrangement of treatments with 15 GPX1(+) and 15 control mice (2 mo old) was conducted for 8 wk. Ten mice of each group (half males and females) were fed a Se-deficient, Torula yeast basal diet (0.02 mg Se/kg, no supplemental vitamin E) and five mice (three males and two females) were fed the basal diet supplemented with 0.51 mg Se/kg as Na2SeO3. The GPX1(+) mice had greater GPX1 activities (one- to sixfold, P < 0.0001) than the control mice at both levels of dietary selenium in all tissues except for liver, in which such difference (100%, P < 0.05) was observed only in Se-deficient mice. The GPX1 mRNA level in kidney and in lung of the Se-deficient GPX1(+) mice was 81% and 7.5-fold greater (P < 0.003) than the respective control level. Overexpression of GPX1 did not alter phospholipid hydroperoxide glutathione peroxidase (GPX4) activities and mRNA levels or glutathione S-transferase (GST) activities in most of the tissues, plasma glutathione peroxidase (GPX3) activity or plasma Se concentrations. No differences in lipid peroxidation in kidney, lung or intestine were observed between the Se-deficient GPX1(+) and control mice. In conclusion, the overexpression of the GPX1 gene in these mice was tissue specific and did not affect the expression of GPX3, GPX4 or GST and plasma Se levels; dietary Se appeared to affect the GPX1 overexpression at its mRNA level.
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PMID:Overexpression of cellular glutathione peroxidase does not affect expression of plasma glutathione peroxidase or phospholipid hydroperoxide glutathione peroxidase in mice offered diets adequate or deficient in selenium. 916 85

Thymine hydroperoxide (5-hydroperoxymethyluracil), a model compound representing products of oxidative damage to DNA, is a substrate for glutathione peroxidase and some isoforms of glutathione transferase. In this paper, we show that selenium-dependent human phospholipid hydroperoxide glutathione peroxidase (Se-PHGPx) exhibits about four orders of magnitude higher activity on thymine hydroperoxide than that of other human enzymes such as selenium-dependent glutathione peroxidase and various representatives of glutathione transferases. The results indicate that Se-PHGPx may be an important enzyme in repairing oxidatively damaged DNA.
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PMID:Reduction of thymine hydroperoxide by phospholipid hydroperoxide glutathione peroxidase and glutathione transferases. 923 31

Selenium-dependent cellular glutathione peroxidase (GPX1) knockout [GPX1(-)] mice were derived from 129/SVJ x C57BL/6 hybrid mice by microinjecting C57BL/6 blastocysts with recombinant embryonic stem cells carrying a target mutation in the GPX1 gene. Experiment 1 was conducted to determine the effects of the GPX1 knockout on the susceptibility of mice to dietary vitamin E and Se deficiency and on the expression of the Se-dependent plasma glutathione peroxidase (GPX3) and phospholipid hydroperoxide glutathione peroxidase (GPX4), and the Se-independent glutathione S-transferase (GST). Eleven GPX1(-) and 11 control mice (5 wk old, six males and five females) were fed a Se-deficient, Torula yeast basal diet (0.02 mg Se/kg, no supplemental vitamin E) or the basal diet supplemented with 0.5 mg Se/kg (as Na2SeO3) for 13 wk. Experiment 2 was conducted to determine the effect of the GPX1 knockout on the total Se concentration in the liver of Se-adequate mice. Six GPX1(-) and four control mice (5 wk old, half males and females) were fed the basal diet supplemented with 0.2 mg Se/kg and 15 mg of all-rac-alpha-tocopheryl acetate/kg for 5 wk. There was no difference in body weight gain or apparent susceptibility to dietary vitamin E and Se deficiency between the GPX1(-) and control mice. Knockout of GPX1 resulted in almost complete abolishment of GPX1 activity in various tissues, but had no effect on the GPX3 or GPX4 mRNA level and activity or the GST activity in several tissues at either level of dietary Se. The liver total Se concentration in the Se-adequate GPX1(-) mice was only 42% of that in the controls (P < 0. 0001). These results indicate that GPX1 is expressed independently of GPX3 or GPX4 and represents approximately 60% of the total hepatic Se in Se-adequate mice.
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PMID:Cellular glutathione peroxidase knockout mice express normal levels of selenium-dependent plasma and phospholipid hydroperoxide glutathione peroxidases in various tissues. 923 36

We recently isolated stable transfectants expressing human phospholipid hydroperoxide glutathione peroxidase (PHGPx) from the cells of guinea pig cell line 104C1 (Biochem. Biophys. Res. Commun. 219, 486-491, 1996). Among them, one transfectant, designated 104C1/O4C, expressed high glutathione peroxidase activity toward dilinoleoyl phosphatidylcholine hydroperoxide (PCOOH); and another one, 104C1/O2D, moderate activity. In the present study, we investigated the effect of selenium on the PHGPx activity and on the lipid hydroperoxide-mediated cell injury in the transfectants to clarify further the action of PHGPx in preventing oxidative injury of the cells. When transfectant 104C1/O2D cells were cultured in the medium added with 250 nM selenium, glutathione peroxidase activity toward PCOOH increased 8-fold. Western blot analysis also revealed an increase in the amount of protein immunoreactive against anti-rat PHGPx antibody in this transfectant. Lipid hydroperoxide-mediated cell injury to the transfectant 104C1/O2D was significantly suppressed in accordance with the increase in the enzyme activity when the cells were cultured in the medium added with selenium. On the contrary, neither glutathione peroxidase activity toward PCOOH nor susceptibility to the injury was affected by selenium addition to the medium of the parental 104C1 cells, which have no selenium-dependent glutathione peroxidase. These results clearly support our previous conclusion that expression of PHGPx is responsible for the protection of host cells from lipid hydroperoxide-mediated injury.
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PMID:Effect of selenium on human phospholipid hydroperoxide glutathione peroxidase expression and host cell susceptibility to lipid hydroperoxide-mediated injury. 928 63

Various rat and human tissues and cell lines naturally exposed to endogenous or exogenous oxidative stress were examined for their pattern of selenoprotein transcripts. Selenoprotein P mRNA was mainly expressed in rat kidney, testis, liver and lung. In testis, a high phospholipid hydroperoxide glutathione peroxidase (PHGPx) but only a weak cytosolic glutathione peroxidase (cGPx) signal was obtained. In kidney, spleen, heart, liver and lung cGPx mRNA levels were higher than those of PHGPx and for both only weak signals were obtained with brain mRNA. The Northern blot results concerning the tissue distribution of cGPx in the rat were fully supported by activity measurements. None of the human tissues revealed a PHGPx mRNA signal, whereas selenoprotein P transcripts were present in all human tissues with the highest abundance in heart, liver, and lung, tissues which also exhibited strong cGPx signals. The gastrointestinal glutathione peroxidase (GPx-GI) was only expressed in human liver and colon liver. Liver, the organ that showed the broadest repertoire of selenoproteins, has to cope with reactive oxygen intermediates produced during detoxification reactions. Human cell lines of the myeloic system that may be exposed to oxidative stress during inflammatory processes showed distinct cGPx signals: epithelial cells showed low cGPx signals. Similar cGPx mRNA levels were found in normal human thyroid tissue and thyroid carcinoma cells. Among the human cell lines selenoprotein P expression was detected in HepG2 and HTh74 thyroid cells. Our data confirm the necessity of getting specific information on distinct tissue- and cell-specific patterns of selenoprotein expression as endpoints of selenium supply and biological function of the selenoprotein family. Analysis of total selenium contents of tissues or body fluids only provides integrative information on the global selenium status of individuals.
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PMID:Expression of selenoproteins in various rat and human tissues and cell lines. 928 88

Selenoprotein biosynthesis may not only be affected by the availability of selenium and the transcription rate of pertinent genes but also by the activity of components of the selenocysteine incorporation complex, SelA, B, C, or D. Incorporation of selenocysteine into selenoproteins requires a complex co-translational mechanism guaranteeing the correct recoding of the termination codon TGA as selenocysteine codon. A particular tRNA(Ser)(Sec) is enzymatically transformed by selenophosphate into tRNA(Sec) which recognizes the UGA codon by means of a specific elongation factor (SelB) and a peculiar mRNA secondary structure. Selenophosphate is formed from selenide and ATP by the SelD gene product, selenophosphate synthase (SelD). To further elucidate the biological role of phospholipid hydroperoxide GPx (PHG-Px), we transformed cells with a heterologous (pig) PHGPx gene and/or an additional (human) SelD gene and studied the behaviour of these cells under selenium depletion and repletion. Transfection of the endothelial cell line ECV 304 with either PHGPx cDNA or SelD cDNA did not result in a substantial increase of PHGPx activities, independent of selenium supply. However, cells co-transfected with both, PHGPx and SelD cDNA, expressed significantly higher PHGPx activity. This effect was much more pronounced under selenium limiting conditions. The enhanced PHGPx activity correlated with two functional parameters, increased capability to reduce hydroperoxides and less sensitivity against H2O2-induced cytotoxicity. Thus, the ECV cells, stably transfected with PHGPx and SelD cDNA, provide a model to specifically investigate the role of PHGPx in endothelial cell function.
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PMID:Determinants of PHGPx expression in a cultured endothelial cell line. 931 7


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