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)

We have previously reported that when garter snakes. Thamnophis sirtalis parietalis, a freeze tolerant species, were exposed to 5 h freezing at -2.5 degrees C organs showed increases in the activities of anti-oxidant enzymes, especially catalase in skeletal muscle. This was interpreted to be an adaptation to deal with the potentially injurious postischemic situation of thawing. The present work analyzes in vitro oxidative inactivation of a possible target of postischemic-induced free radical damage, the secondary anti-oxidant defense glutathione-S transferase, and the protective role of endogenous catalase. Approximately 50% of GST activity from snake muscle homogenates was lost within 2 min after addition of H2O2 plus Fe(II) (0.4-2 mM) in media containing azide whereas addition of iron alone resulted in no damaging effects. The opposing effects of dimethyl sulfoxide and EDTA in modifying this process strongly suggested the involvement of .OH radicals in the GST inactivation. A partial recovery of the activity was promoted by mercaptoethanol, indicating that sulphydryl groups oxidation participate in the mechanism of GST inactivation. Pre-incubation of the reaction media containing H2O2 caused protection of the GST activity only in the absence of azide, indicating that endogenous catalase modulates the extent of oxyradical damage. The protective pre-incubation effect was more efficacious when employing homogenates from lung and liver, organs that have higher catalase activities, as well as homogenates from freezing-exposed muscle (that show an 80% increase in catalase activity, compared with control). The protection against GST inactivation observed in muscle from frozen snakes demonstrates that increased anti-oxidant defenses during freezing exposure can be a key factor in controlling in vitro oxyradical damage. The implications for natural freeze tolerance are discussed.
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PMID:In vitro oxidative inactivation of glutathione S-transferase from a freeze tolerant reptile. 823 86

Female F344 rats received an i.p. injection of iron-dextran (600 mg Fe/kg) and then after 1 week were fed a diet containing 0.02% hexachlorobenzene (HCB) for up to 65 weeks. All rats (8/8) which received HCB after iron overload developed multiple hepatic nodules whereas only 3/8 rats administered HCB alone had nodules (average of one per positive liver). These hyperplastic regions were depleted of iron and were often positive for gamma-glutamyl transpeptidase (GGT) and glutathione S-transferase P (GST-P). Telangiectasis and peliosis were prominent features in the lesions. Short-term experiments (5-15 weeks of iron/HCB treatments) showed that GGT and GST-P were induced early in the neoplastic process but not in discrete focal areas. Iron alone also caused some induction of these enzymes. Some cells with induced GST-P in either short or long term experiments also stained positively for this enzyme in the nucleus. Studies of cytochrome P450 mediated activities showed that at 5 and 15 weeks HCB had induced EROD (an estimate of CYP1A1), PROD (CYP2B1 activity) and BROD activities (CYP2B1 but also other isoenzymes). Under the influence of iron overload EROD was significantly depressed from HCB alone, but not the others or cytochrome P450 reductase. Cytosolic glutathione S-transferase activities were also induced by HCB, but, unlike microsomal EROD, preloading with iron enhanced the effects. In contrast, although cytosolic diaphorase activity was induced by HCB, this response was depressed in combination with iron. Glutathione peroxidase (with H2O2 as substrate) was depressed by both iron and HCB. Clearly, iron overload potentiates the neoplastic process induced by HCB in rats, with both enhancing and depressing effects on various enzyme activities induced by this chemical.
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PMID:Enhancement by iron of hepatic neoplasia in rats caused by hexachlorobenzene. 833 Mar 54

The modifying effects of dietary administration of D,L-alpha-difluoromethylornithine (DFMO) during initiation or postinitiation phase on the hepatocarcinogenesis initiated by diethylnitrosamine (DEN) were investigated in male F344 rats. A total of 129 animals were divided into seven groups. Groups 1-5 were given the drinking water containing 40 ppm DEN for 5 weeks, starting at 7 weeks of age. Groups 2 and 3 were fed the diets mixed with 500 and 1000 ppm DFMO, respectively, for 7 weeks, starting at 6 weeks of age. Groups 4 and 5 were given the diets containing 500 and 1000 ppm DFMO, respectively, starting 1 week after DEN exposure and maintained on these diets until the end of the study (Week 32). Rats in group 6 were fed the DFMO diet (1000 ppm) alone during the experiment. Group 7 served as an untreated control. At the end of the study, the incidences of liver cell foci (resistant iron accumulation or positive for glutathione S-transferase placental form) and hepatocellular neoplasms along with polyamine levels in the liver were measured. Also, morphometric analysis of silver-stained nucleolar organizer regions proteins as cell proliferation activity in liver cells was performed. The mean incidences and areas of foci in rats given DEN and DFMO in groups 2-5 were significantly lower than those of group 1 (P < 0.01). The frequencies of liver cell tumors in group 3 (50%), 4 (24%), and 5 (45%) were significantly reduced compared to that of group 1 (100%) (P < 0.01). The multiplicities of neoplasms in group 2 (1.15/rat), 3 (0.65/rat), 4 (0.35/rat), and 5 (0.95/rat) were significantly smaller than that of group 1 (3.34/rat) (P < 0.001). Although the polyamine levels of liver tissues among the groups showed no clear differences among the groups, the number and area of silver-stained nucleolar organizer regions proteins/nucleus in rats given DEN and DFMO (groups 2-5) were significantly lower than those of group 1. These results indicate that the feeding of DFMO during the initiation or postinitiation stage clearly inhibited DEN-induced rat hepatocarcinogenesis and that such inhibition may be due to alteration in cell proliferation activity caused by DFMO.
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PMID:Chemopreventive effects of dietary D,L-alpha-difluoromethylornithine, an ornithine decarboxylase inhibitor, on initiation and postinitiation stages of diethylnitrosamine-induced rat hepatocarcinogenesis. 835 15

To clarify the mechanism of oxidative stress in skeletal muscle atrophied by immobilization, we investigated the change of antioxidant enzyme activities in a typical slow red muscle, the soleus. Atrophied soleus muscles were collected from male Wistar rats (16 weeks old), one ankle joint of which had been immobilized in the fully extended position for 7 days. Also, soleus muscles were collected from intact age-matched rats as control. The activities of Mn-containing superoxide dismutase (Mn-SOD), Cu,Zn-containing superoxide dismutase (Cu,Zn-SOD), Se-dependent glutathione peroxidase (Se-GSHPx), glutathione S-transferase (GST), catalase, and glutathione reductase (GSSGRx) were measured. The activities of Cu,Zn-SOD, GST, and GSSGRx were significantly higher in atrophied muscles, while the others were unchanged. Increased Cu,Zn-SOD and unchanged Mn-SOD levels might reflect increased generation of superoxide anions in the cytoplasm rather than in the mitochondria. Owing to the enhancement of Cu,Zn-SOD and the unaltered Se-GSHPx and catalase activities, hydrogen peroxide is thought to be increased in the cytoplasm. Because there is also an increase of iron in the microsomes of atrophied muscles, the production of hydroxyl radicals, the most aggressive of radicals, might consequently be elevated.
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PMID:Antioxidant enzyme systems in skeletal muscle atrophied by immobilization. 843 91

The modifying effect of dietary protocatechuic acid (PCA) given during the initiation phase or the postinitiation phase on liver carcinogenesis induced by diethylnitrosamine (DEN) was studied in male F344 rats. At 6 weeks of age, rats were divided into experimental and control groups and fed the diets containing 500 and 1000 ppm PCA or the basal diet. At 7 weeks of age, all animals except PCA alone and control groups were given DEN at 40 ppm in the drinking water for 5 weeks to induce liver cell neoplasms. Seven days after the DEN exposure, groups of animals fed the PCA diets and continued on these diets until the end of the study. All animals were necropsied during the 37 weeks after the start of the experiment in order to determine the incidences of preneoplastic liver cell foci and neoplasms. Hepatic ornithine decarboxylase activity was also measured in all animals at the termination of the study. Dietary PCA administered at both doses during the initiation phase significantly inhibited the incidence of altered hepatocellular foci resistant for iron accumulation or those positive for glutathione S-transferase placental form and the liver cell tumor incidence and multiplicity. Similarly, the numbers of liver cell foci and neoplasms and tumor multiplicity were significantly reduced in groups fed the PCA diets at the postinitiation stage of carcinogenesis. Hepatic ornithine decarboxylase activity was reduced in DEN-treated animals fed the PCA diets compared to those given DEN alone. Although the precise mechanisms of PCA-induced inhibition of hepatocarcinogenesis remain to be elucidate, it is likely that the inhibitory effects during the initiation and postinitiation phases may be due to alteration in hepatic ornithine decarboxylase activity under the present experimental condition.
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PMID:Chemoprevention of diethylnitrosamine-induced hepatocarcinogenesis by a simple phenolic acid protocatechuic acid in rats. 850 18

Exposure of iron-loaded C57BL/10ScSn mice to the polychlorinated biphenyls (PCBs) mixture Aroclor 1254 in the diet (0.01%) for 5 weeks caused massive hepatic porphyria far greater than occurred with PCBs alone. This regime eventually causes hepatocellular carcinoma. Hepatic microsomal ethoxy-, pentoxy-, and benzyloxyresorufin dealkylase activities (respectively EROD, PROD, and BROD) catalyzed primarily by cytochrome P4501A1 and 2B isoenzymes were markedly induced after 2 weeks of diet (when no porphyria had developed) but showed little effect of iron. EROD activity in the nuclear membrane was also induced by the PCBs as was CYP1A1 protein when shown by immunoblotting. Nuclear dealkylase activities of PCBs-treated mice were considerably less than microsomal activities but were stimulated by iron pretreatment. The mechanism of the iron-enhanced toxicity may be due to oxidative damage associated with chronic induction of CYP1A1 isoforms. Lucigenin-enhanced chemiluminescence (CL) by microsomes and nuclear membranes was used as a method to estimate their potential to form reactive oxygen species. Despite CL being induced by PCBs it was less with microsomes from iron-treated mice. In a comparison of a variety of inducers of microsomal cytochrome P450 there was no correlation between inducer, uroporphyrogenic agent, and intensity of CL. On the other hand, cytosolic glutathione S-transferase (GST) activities with 1-chloro-2,4-dinitrobenzene and 1,2-dichloro-4-nitrobenzene (DCNB) as substrates, were also induced by the PCBs mixture, the induction with DCNB being synergistically potentiated by iron pretreatment. Complementary results were observed by immunocytochemistry using anti alpha-GST antibody. In contrast, total glutathione peroxidase activity and selenium-dependent glutathione peroxidase activity were depressed by PCBs but particularly in mice also administered iron. The results illustrate that PCBs not only induce CYP1A1 in microsomes but also in the nuclear membrane, which may be of significance in the mechanism of the iron-enhanced carcinogenicity of these chemicals. The iron-enhanced induction of GST with accompanying depletion of glutathione peroxidase provides evidence for oxidative processes induced in vivo by the PCBs.
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PMID:Modulation by iron of hepatic microsomal and nuclear cytochrome P450, and cytosolic glutathione S-transferase and peroxidase in C57BL/10ScSn mice induced with polychlorinated biphenyls (Aroclor 1254). 856 Apr 83

An iron chelate, ferric nitrilotriacetate (Fe-NTA), induces acute renal proximal tubular necrosis, a consequence of free radical-mediated oxidative tissue damage, that eventually leads to a high incidence of renal adenocarcinoma in rodents. In the present study, we investigated the free radical-induced oxidative stress response in this carcinogenesis model, focusing on the expression of glutathione S-transferases (GSTs) which catalyze the conjugation of reactive chemicals with glutathione and play an important role in protecting cells. A single intraperitoneal Fe-NTA treatment (15 mg Fe/kg body weight) induced a rapid oxidative stress, which was monitored by the accumulation of lipid peroxidation products and the loss of sulfhydryl contents in the kidneys, resulting in a 30% reduction of GST activity 1 h after an Fe-NTA treatment. The enzyme activity returned to the control level after 16 h. The immunoblot analysis of GST isozymes demonstrated that the level of alpha-class GSTs (GST-Ya and GST-Yc) and pi-class GST (GST-Yp), major GST isozymes constitutively produced in the kidney, decreased immediately within 1 h of the Fe-NTA treatment. The onset of the recovery of GST-Yp protein levels was detected 3 h after the Fe-NTA treatment. The enhanced production of GST-Yp in gene expression was evident in the drastic elevation of mRNA levels and these increases coincided with a substantial rise in the GST activity and protein levels. The alpha-class GSTs were not inducible by treatment with Fe-NTA. The immunohistochemical analysis demonstrated that the expression of GST-Yp was strongly induced in the regenerating proximal tubular cells. A steady accumulation of GST-Yp protein was observed in the subacute toxicity experiments with multiple injections of Fe-NTA. These results suggest that the enhanced expression of GST-Yp is important in mediating cell repairs or increasing the resistance to subsequent injury.
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PMID:Oxidative stress response in iron-induced renal carcinogenesis: acute nephrotoxicity mediates the enhanced expression of glutathione S-transferase Yp isozyme. 861 33

A yeast mutant (LT06) was isolated that showed no growth on iron-limited medium but normal growth on iron-replete medium. A gene cloned from a genomic yeast library complemented the defect, allowing growth on low iron medium. Allelic segregation analysis demonstrated that the cloned gene was the normal allele rather than a high copy suppressor. A disruption mutant was nonviable, indicating that the gene was essential. Sequence analysis and functional assays indicated that the cloned gene was identical to ERG25, a gene that codes for methyl sterol oxidase. Incubation of LT06 in low iron medium resulted in marked changes in lipid metabolism, including the accumulation of fatty acids, triglycerides, methyl sterols, and other sterol precursors. A human homologue of ERG25 was cloned, sequenced, and mapped to human chromosome 4q32-34. Analysis of the data base with both ERG25 and the human homologue resulted in the identification of a putative set of metal binding motifs with similarity to that seen in a family of membrane desaturases-hydroxylases. Western analysis using antibodies to an Erg25-GST fusion protein detected two proteins of 34 and 75 kDa. Both proteins are membrane bound and contain one N-glycosyl unit. Immunofluorescence data suggest that the proteins are present in the endoplasmic reticulum and plasma membrane. Although ERG25 transcripts are not iron regulated, there is a large increase in the concentration of transcript in the mutant LT06 grown in low iron medium. These results suggest that the enzyme is regulated not by iron but by an end product of the ergosterol pathway.
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PMID:Characterization of yeast methyl sterol oxidase (ERG25) and identification of a human homologue. 866 58

Liver damage induced by a variety of agents including hepatocarcinogens, alcohol, and virus induces proliferation of oval cells. In this study, iron overloading of the liver is used as a means of inducing liver damage over an extended period to ascertain whether it promotes the appearance of oval cells. Rats were fed a 2% carbonyl-iron-supplemented diet for 3 or 6 months. Extensive iron deposits appeared periportally in hepatocytes and some Kupffer cells. Iron deposition was less pronounced pericentrally. Small oval-like cells, morphologically and immunocytochemically similar to CDE-derived oval cells, were identified and quantified. They first emerged periportally and subsequently in small tracts or foci nearer central regions and stained positively for alpha-fetoprotein, pi-class glutathione S-transferase, and the embryonic form of pyruvate kinase. They contained very few iron deposits and were classified as iron free. The major difference between CDE- and iron-overload-derived oval cells was that the latter were negative for transferrin. This study shows that cellular changes occurring in iron-overloaded rat liver are similar to those observed in rats placed on a hepatocarcinogenic diet and in rats chronically exposed to alcohol.
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PMID:Chronic iron overload in rats induces oval cells in the liver. 870 79

cDNAs encoding the full-length sequence for tryptophan hydroxylase, and deletion mutants consisting of the regulatory (amino acids 1-98) or catalytic (amino acids 99-444) domains of the enzyme, were cloned and expressed as glutathione S-transferase fusion proteins in E. coli. The recombinant fusion proteins could be purified to near homogeneity within minutes by affinity chromatography on glutathione-agarose. The full-length enzyme and the catalytic core expressed very high levels of tryptophan hydroxylase activity. The regulatory domain was devoid of activity. The full-length enzyme and the catalytic core, while adsorbed to glutathione-agarose beads, obeyed Michaelis-Menten kinetics, and the kinetic properties of each recombinant enzyme for cofactor and substrate compared very closely to native, brain tryptophan hydroxylase. Both active forms of the glutathione S-transferase-tryptophan hydroxylase fusion proteins had strict requirements for ferrous iron in catalysis and expressed much higher levels of activity (Vmax) than the brain enzyme. Analysis of full-length tryptophan hydroxylase and the catalytic core by molecular sieve chromatography under nondenaturing conditions revealed that each fusion protein behaved as a tetrameric species. These results indicate that a truncated tryptophan hydroxylase, consisting of amino acids 99-444 of the full-length enzyme, contains the sequence motifs needed for subunit assembly. Both wild-type tryptophan hydroxylase and the catalytic core are expressed as apoenzymes which are converted to holoenzymes by exogenous iron. The tryptophan hydroxylase catalytic core is also as active as the full-length enzyme, suggesting the possibility that the regulatory domain exerts a suppressive effect on the catalytic core of tryptophan hydroxylase.
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PMID:Expression and deletion mutagenesis of tryptophan hydroxylase fusion proteins: delineation of the enzyme catalytic core. 875 96


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