Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.5.1.18 (glutathione S-transferase)
 22,582 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Specific oxidative metabolites of valproic acid (VPA) have been associated with the clinically defined toxicity of the drug. To investigate the role of enzymatic detoxification in clinical toxicity, we compared activities of five antioxidant enzymes in 15 patients with a serious adverse experience (SAE) related to VPA therapy, to enzyme activities measured in 35 patients with good clinical tolerance of VPA, and 50 healthy, age-matched subjects. These enzymes included glutathione peroxidase (GSH-Px), glutathione reductase (GSSG-R), glutathione transferase, superoxide dismutase, and catalase in erythrocytes; and GSH-Px in plasma. We also determined levels of Se, Cu, and Zn, trace elemental cofactors for these enzymes, in plasma from each individual. In patients with a VPA-associated SAE, GSH-Px was significantly depressed and GSSG-R was significantly elevated relative to values for the other groups. Selenium and zinc concentrations were lower in SAE patients than in controls. These findings may indicate a role for selenium dependent antioxidant activity in individual susceptibility to an SAE related to VPA therapy.
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PMID:Altered antioxidant enzyme activities in children with a serious adverse experience related to valproic acid therapy. 976 95

Oxyradicals are involved in multiple mutational events and can contribute to the conversion of healthy cells to cancer cells. Glutathione (GSH) and the GSH-replenishing enzymes keep the antioxidant status of normal cells at a level where they can avert oxyradical derived mutations. The aim of this study was to determine whether in cancer cells the GSH-replenishing, GSH antioxidant and GSH-depleting enzymes were not at appropriate levels and therefore not able to protect cancer cells adequately against oxyradical-induced mutations. Cancer of the oesophagus was chosen since it is the most common gastrointestinal malignancy in South African Blacks. Biopsies and blood from 31 patients with cancer of the oesophagus and 29 non-cancer patients were assessed for these enzymes. The mean activity of the antioxidant and depleting enzyme GSH-peroxidase was elevated significantly by twofold in the cancer tissue compared to normal tissue. However, the activity of the replenishing enzyme GSSG-reductase and the level of the depleting enzyme GSH-s-transferase P1-isoenzyme were significantly reduced by 23% and 33% respectively. As in a previous paper we found that GSH was depleted and gamma-glutamine transpeptidase was diminished in oesophageal cancer. There can be two reasons for GSH depletion. Firstly, elevated GSH-peroxidase will use more GSH in an attempt to cope with the excessive production of oxyradicals as revealed by elevated lipid peroxidation; this was, as shown by us before, elevated sixfold in oesophageal cancer. Secondly, if little replenishment of GSH occurred the level of GSH would become lower. This was confirmed by our findings that the activities of the replenishing enzymes were significantly diminished in oesophageal cancer tissue. Contrary to what was expected, the other depleting enzyme GSH-s-transferase P1 was not elevated in cancer tissue but was significantly lower. However, in the blood of the same patients it was significantly elevated. An explanation for this phenomenon is that, although the production of GST-P1 was enhanced in cancer, it did not show because it was rapidly extruded into the blood by an unknown mechanism operational only in cancer cells.
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PMID:Glutathione-linked enzymes in benign and malignant oesophageal tissue. 1038 74

Both sorbitol accumulation-linked osmotic stress and "pseudohypoxia" [increase in NADH/NAD+, similar to that in hypoxic tissues, and attributed to increased sorbitol dehydrogenase (1-iditol:NAD+ 5-oxidoreductase; EC 1.1.1.14; SDH) activity] have been invoked among the mechanisms underlying oxidative injury in target tissues for diabetic complications. We used the specific SDH inhibitor SDI-157 [2-methyl-4(4-N,N-dimethylaminosulfonyl-1-piperazino)pyrimid ine] to evaluate the role of osmotic stress versus "pseudohypoxia" in oxidative stress occurring in diabetic precataractous lens. Control and diabetic rats were treated with or without SDI-157 (100 mg/kg/day for 3 weeks). Lens malondialdehyde (MDA) plus 4-hydroxyalkenals (4-HA), MDA, GSH, and ascorbate levels, as well as the GSSG/GSH ratios, were similar in SDI-treated and untreated control rats, thus indicating that SDI-157 was not a prooxidant. Intralenticular osmotic stress, manifested by sorbitol levels, was more severe in SDI-treated diabetic rats (38.2+/-6.8 vs 21.2+/-3.5 micromol/g in untreated diabetic and 0.758+/-0.222 micromol/g in control rats, P<0.01 for both), while the decrease in the free cytosolic NAD+/NADH ratio was partially prevented (120+/-16 vs 88+/-11 in untreated diabetic rats and 143+/-13 in controls, P<0.01 for both). GSH and ascorbate levels were decreased, while MDA plus 4-HA and MDA levels were increased in diabetic rats versus controls; both antioxidant depletion and lipid aldehyde accumulation were exacerbated by SDI treatment. Superoxide dismutase (superoxide:superoxide oxidoreductase; EC 1.15.1.1), GSSG reductase (NAD[P]H:oxidized-glutathione oxidoreductase; EC 1.6.4.2), GSH transferase (glutathione S-transferase; EC 2.5.1.18), GSH peroxidase (glutathione:hydrogen-peroxide oxidoreductase; EC 1.11.1.9), and cytoplasmic NADH oxidase activities were increased in diabetic rats versus controls, and all the enzymes but GSH peroxidase were up-regulated further by SDI. In conclusion, sorbitol accumulation and osmotic stress generated oxidative stress in diabetic lens, whereas the contribution of "pseudohypoxia" was minor. SDIs provide a valuable tool for exploring mechanisms of oxidative injury in sites of diabetic complications.
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PMID:Interaction between osmotic and oxidative stress in diabetic precataractous lens: studies with a sorbitol dehydrogenase inhibitor. 1059 Nov 49

The reduced glutathione (GSH)/oxidized glutathione (GSSG) redox state is thought to function in signaling of detoxification gene expression, but also appears to be tightly regulated in cells under normal conditions. Thus it is not clear that the magnitude of change in response to physiologic stimuli is sufficient for a role in redox signaling under nontoxicologic conditions. The purpose of this study was to determine the change in 2GSH/GSSG redox during signaling of differentiation and increased detoxification enzyme activity in HT29 cells. We measured GSH, GSSG, cell volume, and cell pH, and we used the Nernst equation to determine the changes in redox potential Eh of the 2GSH/GSSG pool in response to the differentiating agent, sodium butyrate, and the detoxification enzyme inducer, benzyl isothiocyanate. Sodium butyrate caused a 60-mV oxidation (from -260 to -200 mV), an oxidation sufficient for a 100-fold change in protein dithiols:disulfide ratio. Benzyl isothiocyanate caused a 16-mV oxidation in control cells but a 40-mV oxidation (to -160 mV) in differentiated cells. Changes in GSH and mRNA for glutamate:cysteine ligase did not correlate with Eh; however, correlations were seen between Eh and glutathione S-transferase (GST) and nicotinamide adenine dinucleotide phosphate (NADPH):quinone reductase activities (N:QR). These results show that 2GSH/GSSG redox changes in response to physiologic stimuli such as differentiation and enzyme inducers are of a sufficient magnitude to control the activity of redox-sensitive proteins. This suggests that physiologic modulation of the 2GSH/GSSG redox poise could provide a fundamental parameter for the control of cell phenotype.
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PMID:Glutathione redox potential in response to differentiation and enzyme inducers. 1064 13

Redox cycling metabolism of diquat catalyzes generation of reactive oxygen species, and diquat-induced acute hepatic necrosis in male Fischer 344 (F344) rats has been studied as a model of oxidant mechanisms of cell killing in vivo. At equal doses of diquat, female F344 rats sustained less hepatic damage than did male rats, as estimated by plasma alanine aminotransferase (ALT) activities after 6 h. Biliary efflux of glutathione disulfide (GSSG) was greater in male than in female rats at each dose of diquat, but even comparable rates of GSSG excretion were associated with less hepatic injury in female rats. Hepatic activities of superoxide dismutase (SOD) and glutathione peroxidase (GPX) were similar in the two genders, and activities of glutathione reductase (GR) and glutathione S-transferase-alpha (GST-alpha) activities were higher in the male rats. Previous studies in male rats have implicated formation of 2,4-dinitrophenylhydrazine (DNPH)-reactive "protein carbonyls" and related iron chelate-catalyzed redox reactions as mechanisms critical to diquat-induced acute cell death in vivo. However, diquat-treated female rats showed higher levels of DNPH-reactive proteins in livers and in bile than did males, both at identical doses of diquat and at doses that produced similar elevations in plasma ALT activities. In female rats, fragmentation of hepatic deoxyribonucleic acids (DNA) was increased by doses of diquat that did not increase plasma ALT activities, and increased fragmentation was observed prior to elevation of plasma ALT activities. In the present studies, hepatic necrosis was most closely associated with DNA fragmentation, although additional studies are needed to determine the mechanisms responsible for and the pathophysiological consequences of the fragmentation.
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PMID:Sex differences in diquat-induced hepatic necrosis and DNA fragmentation in Fischer 344 rats. 1074 47

This study was designed to (1) evaluate retinal lipid peroxidation in early diabetes by the method specific for free malondialdehyde and 4-hydroxyalkenals, (2) identify impaired antioxidative defense mechanisms and (3) assess if enhanced retinal oxidative stress in diabetes is prevented by the potent antioxidant, DL-alpha-lipoic acid. The groups included control and streptozotocin-diabetic rats treated with or without DL-alpha-lipoic acid (100 mg kg(-1) day(-1), i.p., for 6 weeks). All parameters were measured in individual retinae. 4-Hydroxyalkenal concentration was increased in diabetic rats (2.63+/-0.60 vs. 1.44+/-0.30 nmol/mg soluble protein in controls, P<0.01), and this increase was prevented by DL-alpha-lipoic acid (1.20+/-0.88, P<0.01 vs. untreated diabetic group). Malondialdehyde, reduced glutathione (GSH) and oxidized glutathione (GSSG) concentrations were similar among the groups. Superoxide dismutase, glutathione peroxidase (GSHPx), glutathione reductase (GSSGRed) and glutathione transferase (GSHTrans) activities were decreased in diabetic rats vs. controls. Quinone reductase was upregulated in diabetic rats, whereas catalase and cytoplasmic NADH oxidase activities were unchanged. DL-alpha-Lipoic acid prevented changes in superoxide dismutase and quinone reductase activities induced by diabetes without affecting the enzymes of glutathione metabolism. In conclusion, accumulation of 4-hydroxyalkenals is an early marker of oxidative stress in the diabetic retina. Increased lipid peroxidation occurs in the absence of GSH depletion, and is prevented by DL-alpha-lipoic acid.
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PMID:Early changes in lipid peroxidation and antioxidative defense in diabetic rat retina: effect of DL-alpha-lipoic acid. 1085 58

Comparison of Hirosaki hairless rat (HHR) and Sprague-Dawley (SD) rat liver glutathione transferase (GST) subunits by HPLC revealed differences in subunit 3; a new peak was detected in HHR GSTs and this was tentatively named X. By chromatofocusing, the HHR GST form composed of peak X and SD rat GST 3-3 were eluted at pH 8.8 and 9.1 respectively. The former was more sensitive to the SH reagent N-ethylmaleimide (NEM) than the latter. GSSG treatment of peak X resulted in a shift of retention time (peak Y) by HPLC analysis. However, such conversion was not observed for the SD rat GST 3-3 following GSSG or dithiothreitol (DTT) treatment. Peak Y exhibited m/z values of 26091.9 and 26125.4 by matrix-assisted laser-desorption ionization-time-of-flight MS, higher than those of peak X by 304-307, equivalent to the molecular-mass value of GSH. On treatment with DTT, peak Y was converted into peak X, with release of a substance with HPLC-characteristics of GSH. This substance was confirmed to be GSH by liquid chromatography/MS. These results thus indicated peak Y to be a glutathionylated form of peak X. Quantification revealed the release of 4 nmol of GSH from 0.12 mg of the peak Y protein, corresponding to 4.8 nmol (M(r) 25000). The nucleotide sequence of HHR GST subunit 3 cDNA proved identical to that reported for pGTA/C44, possessing asparagine and cysteine as the 198th and 199th amino acid residues, respectively, corresponding to lysine and serine in subunit 3 of the SD rat. Thus peak X appeared to be the product of HHR GST subunit 3 cDNA. Treatment with N-(4-dimethylamino-3,5-dinitrophenyl)maleimide, a coloured analogue of NEM, followed by trypsin-treatment and sequencing of labelled peptides, identified the reactive cysteine residue of HHR GST subunit 3 to be located at position 199. Unlike SD rat GST 3-3, HHR GST 3-3 was not activated by treatment with xanthine and xanthine oxidase. These results suggest polymorphism of the rat GST subunit 3 gene with individual gene product variation in sensitivity to oxidative stress.
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PMID:Polymorphism of the glutathione transferase subunit 3 in Sprague-Dawley rats involves a reactive cysteine residue. 1094 54

The effects of fish oil and corn oil diets on diethylnitrosamine initiation/phenobarbital promotion of hepatic enzyme-altered foci in female Sprague-Dawley rats were investigated. Groups of 12 rats were initiated with diethylnitrosamine (15 mg/kg) at 24 h of age. After weaning, they received diets containing either 13.5% fish oil plus 1. 5% corn oil or 15% corn oil for 24 weeks. Rats fed fish oil had significantly greater liver weight, relative liver weight, spleen weight, and relative spleen weight than rats fed corn oil (p < 0.05). Hepatic phospholipid fatty-acid profile was significantly affected by the type of dietary lipid. The rats fed fish oil had significantly greater hepatic phospholipid 20:5 and 22:6 than rats fed corn oil; in contrast, the rats fed corn oil had significantly greater hepatic phospholipid 18:2 and 20:4 than rats fed fish oil (p < 0.05). Rats fed fish oil had significantly lower hepatic vitamin E and PGE(2) content but significantly greater hepatic lipid peroxidation than rats fed corn oil (p < 0.05). The hepatic levels of antioxidant enzymes (GSH reductase and GST) were significantly greater in rats fed fish oil than in rats fed corn oil (p < 0.05). Except for PGST-positive foci (foci area/tissue area), all the other foci parameters (GGT-positive foci area/tissue area, GGT-positive foci no./cm(2), GGT-positive foci no./cm(3), PGST-positive foci no. /cm(2), and PGST-positive foci no./cm(3)) measured in the fish oil group were 10-30% of those in the corn oil group (p < 0.05). Analyses of Pearson correlation coefficient revealed a positive correlation between hepatic GGT- or PGST-positive foci number (no. /cm(2)) and PGE(2) content (r = 0.66, P = 0.01; r = 0.56, P = 0.02, respectively) but a negative correlation between GGT- and PGST-positive foci (no./cm(2)) and lipid peroxidation (r = -0.8, P = 0.0006; r = -0.58, P = 0.01, respectively), GSH/(GSH + GSSG) ratio (r = -0.61, P = 0.05; r = -0.4, P = 0.14, respectively), GSH reductase (r = -0.75, P = 0.002; r = -0.53, P = 0.02, respectively), and GST activities (r = -0.65, P = 0.01; r = -0.44, P = 0.07, respectively). Similar correlation between foci number (no./cm(3)) and PGE(2), lipid peroxidation, GSH/(GSH + GSSG) ratio, GSH reductase, and GST activities were obtained. The results of this study show that dietary fish oil significantly inhibited hepatic enzyme-altered foci formation compared with corn oil in rats. These results suggest that the possible mechanisms involved in this process are the stimulation of hepatic detoxification system, changes in membrane composition, inhibition of PGE(2) synthesis, the enhancement of GSH-related antioxidant capacity, and the enhancement of lipid peroxidation by fish oil.
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PMID:Comparison of the effect of fish oil and corn oil on chemical-induced hepatic enzyme-altered foci in rats. 1099 28

The mechanisms by which acute administration of methapyrilene, an H(1)-receptor antihistamine causes periportal necrosis to rats are unknown. This study investigated the role of the hepato-biliary system in methapyrilene hepatotoxicity following daily administration of 150 mg/kg per day over 3 consecutive days. Biliary metabolites of methapyrilene were tentatively identified. In male Han Wistar rats administration of methapyrilene significantly increased hepatic reduced glutathione (GSH) to 140% of control levels 24 h following the last dose. There were no significant changes in the activities of glutathione-related enzymes, glutathione peroxidase (GPx) and reductase (GSH), glutathione S-transferase (GST), and gamma-glutamyl cysteine synthetase (gamma-GCS) over 3 days of methapyrilene administration. Methapyrilene treatment resulted in no significant increase in excretion of biliary oxidized glutathione (GSSG), a sensitive marker of oxidative stress in vivo, following the third dose. [3H]Methapyrilene-derived radioactivity was detected in bile, to a greater extent than in feces, indicating that methapyrilene and/or metabolites underwent enterohepatic recirculation. Cannulation and exteriorization of the bile duct (to interrupt enterohepatic recirculation) afforded some protection against the hepatotoxicity, assessed by clinical chemistry and histopathology. Liquid chromatography-mass spectrometry (LC-MS) analysis of bile indicated the presence of unmetabolized methapyrilene, methapyrilene O-glucuronide and desmethyl methapyrilene O-glucuronide. These data demonstrate that acute methapyrilene hepatotoxicity in vivo is not a consequence of GSH depletion, or oxidative stress, but that enterohepatic recirculation of biliary metabolites may be important. Progressive exposure to non-oxidizing, reactive metabolic intermediates may be responsible for hepatotoxicity.
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PMID:Methapyrilene hepatotoxicity is associated with increased hepatic glutathione, the formation of glucuronide conjugates, and enterohepatic recirculation. 1113 66

It has been proposed that oxidative stress develops in tumors, with important consequences for growth and progression. To investigate this hypothesis, we measured low m.w. thiols, disulfides, protein-mixed disulfides and a pool of major anti-oxidant enzymes in renal-cortex as well as renal-cell carcinoma (RCC) specimens at stages I-II and III. Our data showed (i) a significant increase in the levels of total intracellular glutathione at both tumor stages (levels were 2.6-2.8 fold higher than those in the normal renal cortex), (ii) a marked lowering of the GSH/GSSG ratio in stage I-II accompanied by a significant decrease of many GSH-dependent enzymes (i.e., GPX, GST, GGT, GR) and (iii) unchanged GSH/GSSG ratio and GSH-dependent enzyme activity in stage III with respect to normal renal cortex. These results indicate that relevant variations exist in the glutathione antioxidant system in the different stages of RCC and support the hypothesis that oxidative stress plays an important role in RCC growth and progression.
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PMID:Altered glutathione anti-oxidant metabolism during tumor progression in human renal-cell carcinoma. 1114 20


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