Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.5.1.18 (glutathione S-transferase)
22,582 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The proximal tubule is a frequent target for nephrotoxic compounds due to it's ability to transport and accumulate xenobiotics and their metabolites, as well as by the presence of an organ-selective set of biotransformation enzymes. The aim of the present study was to characterize the activities of different biotransformation enzymes during primary culturing of rat proximal tubular cells (PT cells). Specific marker substrates for determining cytochrome P450 (CYP450) activity of primary cultured PT cells include 7-ethoxyresorufin (CYP1A1), caffeine (CYP1A), testosterone (CY2B/C, CYP3A), tolbutamide (CYP2C) and dextromethorphan (CYP2D1). Activities of the CYP450 isoenzymes decreased considerably during culture with the greatest loss in activity within 24 h of culture. In addition, expression of CYP450 apoprotein, including CYP1A, CYP2C, CYP2D, CYP2E and CYP4A, was detected in microsomes from freshly isolated PT cells by immunoblotting using specific antibodies. CYP2B and CYP3A apoprotein could not be detected. Activity of the phase II biotransformation enzymes GST, GGT, beta-lyase and UGT was determined with 1-chloro-2,4-dinitrobenzene, L-glutamic acid gamma-(7-amido-4-methyl-coumarin), S-(1,1,2,2-tetrafluoroethyl)-L-cysteine and 1-naphthol, respectively, as marker substrates. Activity of the phase II enzymes remained more stable and, in contrast to CYP450 activity, significant activity was still expressed after 1 week of PT cell culture. Thus, despite the obvious advantages of PT cells as an in-vitro model for studies of biotransformation mediated toxicity, the strong time dependency of especially phase I and, to a lesser extent, phase II biotransformation activities confers limitations to their application.
...
PMID:Characterization of biotransformation enzyme activities in primary rat proximal tubular cells. 1131 Dec 12

Glutathione conjugation has been identified as an important detoxication reaction. However, several glutathione-dependent bioactivation reactions have been identified. Current knowledge on the mechanisms and the possible biological importance of these reactions is discussed in this article. Vicinal dihaloalkanes are transformed by glutathione S-transferase-catalyzed reactions to mutagenic and nephrotoxic S-(2-haloethyl) glutathione S-conjugates. Electrophilic episulphonium ions are the ultimate reactive intermediates formed and interact with nucleic acids. Several polychlorinated alkenes are bioactivated in a complex, glutathione-dependent pathway. The first step is hepatic glutathione S-conjugate formation followed by cleavage to the corresponding cysteine S-conjugates, and, after translocation to the kidney, metabolism by renal cystein conjugate beta-lyase. Beta-Lyase-dependent metabolism of halovinyl cysteine S-conjugates yields electrophilic thioketenes, whose covalent binding to cellular macromolecules is likely to be responsible for the observed nephrotoxicity of the parent compounds. Finally, hepatic glutathione conjugate formation with hydroquinones and aminophenols yields conjugates that are directed to gamma-glutamyltransferase-rich tissues, such as the kidney, where they cause alkylation or redox cycling reactions, or both, that cause organ-selective damage.
...
PMID:Chemical-induced nephrotoxicity mediated by glutathione S-conjugate formation. 1168 55

Inorganic arsenicals are important environmental toxicants and carcinogens in humans. In mammals, including humans, inorganic arsenicals often undergo methylation, forming compounds such as dimethyarsinic acid (DMA). Recent evidence indicates DMA is a complete carcinogen in rodents while evidence for inorganic arsenicals as carcinogens in rodents remains equivocal. Thus, we studied the molecular mechanisms of in vitro cytolethality of DMA compared to that of the trivalent inorganic arsenical, sodium arsenite, using a rat liver epithelial cell line (TRL 1215). Arsenite was very cytotoxic in these cells (LC(50) = 35 microM after 48 h of exposure). With arsenite exposure, most dead cells showed histological and biochemical evidence of necrosis. Arsenite cytotoxicity increased markedly when cellular GSH was depleted with the glutathione synthase inhibitor, L-buthionine-[S,R]-sulfoximine (BSO). In contrast, DMA was nearly 3 orders of magnitude less cytotoxic (LC(50) = 1.5 mM) although evidence showed the predominating form of death was apoptosis. Surprisingly, GSH depletion actually decreased DMA-induced apoptosis. A glutathione scavenger, diethyl maleate (DEM), and a glutathione reductase inhibitor, carmustine, also prevented DMA-induced apoptosis. These data indicate that DMA requires intracellular GSH to induce apoptosis. Ethacrynic acid (EA), an inhibitor of glutathione S-transferase (GST) that catalyzes GSH-substrate conjugation, acivicin, an inhibitor of gamma-glutamyltranspeptidase (GGT) which catalyzes the initial breakdown of GSH-substrate conjugates, and aminooxyacetic acid (AOAA), an inhibitor of beta-lyase which catalyzes the final breakdown of GSH-substrate conjugates, all were effective in suppressing DMA-induced apoptosis. These findings indicate that DMA likely is conjugated in some form with GSH, and that it is this conjugate that induces apoptosis during subsequent metabolic reactions.
...
PMID:A major human arsenic metabolite, dimethylarsinic acid, requires reduced glutathione to induce apoptosis. 1201 83

The S3 ribosomal protein of Drosophila melanogaster possesses various DNA repair activities, including the capacity to incise at apurinic/apyrimidinic (AP) sites and 8-oxo-7,8-dihydroguanine (8-oxoG) residues. We have recently hypothesized that this multifunctional protein may improve the efficiency of DNA base excision repair (BER) in mammalian cells. We have investigated the effect of pure GST-tagged Drosophila S3 on BER of different endogenous lesions performed by human and mouse cell extracts. Drosophila S3 significantly accelerated the BER of 8-oxoG (initiated by the bifunctional glycosylase OGG1). The stimulating effect was linked to the capacity of S3 to remove the 8-oxoG lesion and cleave the resulting AP site, rather than acceleration of downstream steps of the BER pathway (e.g., removal of 3' blocking fragments). No stimulating effect was observed on the BER of uracil, natural AP sites, and beta-lyase-cleaved AP sites. Heterologous expression of Drosophila S3 may be used to enhance 8-oxoG repair in human cells.
...
PMID:Drosophila S3 ribosomal protein accelerates repair of 8-oxoguanine performed by human and mouse cell extracts. 1287 13

Inorganic arsenicals are clearly toxicants and carcinogens in humans. In mammals, including humans, inorganic arsenic often undergoes methylation, forming compounds such as monomethylarsonic acid (MMAs(V)) and dimethylarsinic acid (DMAs(V)). However, much less information is available on the in vitro toxic potential or mechanisms of these methylated arsenicals, especially MMAs(V). We studied the molecular mechanisms of in vitro cytolethality of MMAs(V) using a rat liver epithelial cell line (TRL 1215). MMAs(V) was not cytotoxic in TRL 1215 cells even at concentrations exceeding 10 mM, but it became weakly cytotoxic and induced both necrotic and apoptotic cell death when cellular reduced glutathione (GSH) was depleted with the glutathione synthase inhibitor, l-buthionine-[S,R]-sulfoximine (BSO), or the glutathione reductase inhibitor, carmustine. Similar results were observed in the other mammalian cells, such as human skin TIG-112 cells, chimpanzee skin CRT-1609 cells, and mouse metallothionein (MT) positive and MT negative embryonic cells. Ethacrynic acid (EA), an inhibitor of glutathione S-transferase (GST) that catalyses GSH-substrate conjugation, also enhanced the cytolethality of MMAs(V), but aminooxyacetic acid (AOAA), an inhibitor of beta-lyase that catalyses the final breakdown of GSH-substrate conjugates, had no effect. Both the cellular GSH levels and the cellular GST activity were increased by the exposure to MMAs(V) in TRL 1215 cells. On the other hand, the addition of exogenous extracellular GSH enhanced the cytolethality of MMAs(V), although cellular GSH levels actually prevented the cytolethality of combined MMAs(V) and exogenous GSH. These findings indicate that human arsenic metabolite MMAs(V) is not a highly toxic compound in mammalian cells, and the level of cellular GSH is critical to its eventual toxic effects.
...
PMID:Cellular glutathione prevents cytolethality of monomethylarsonic acid. 1499 80

Hexachlorobutadiene (HCBD) is a potent nephrotoxin in rodents that can cause degeneration, necrosis and regeneration in renal tubular epithelial cells. Its toxicity is due to its conjugation by glutathione (GSH) to form glutathione S-conjugate, by the enzyme glutathione S-transferase and finally to the related cysteine-conjugate. This metabolite is then actively taken up by kidney and cleared in the renal tubular epithelial cells, rich in beta-lyase, to a reactive thiol derivative that covalently binds to the macromolecules. In this study, different groups of 28-day male Wistar albino (W/A) rats were dosed daily with 25 mg/kg HCBD for 2, 3, 4 and 7 days; control group dosed with corn oil. Data showed that in the 2- and 3-day treated groups there was substantial necrosis to the straight portion of the proximal tubules (pars recta or S3 segment), rich in glutamine transaminase K (GTK/beta-lyase). In the 4-day treated group, the renal proximal tubules had regenerated and showed a basophilic appearance. In animals treated for 7 days, it was observed that the kidney appeared to have returned to normal and had become resistant to further doses of HCBD. To define the time for the kidney to regain susceptibility to HCBD, 18- and 25-day studies with both low (25 mg/kg) and high (100 mg/kg) doses of HCBD (following two initial doses of 25 mg/kg) were performed. In the 18-day study, histopathological examination of the kidneys in animals of this group and also animals in the 25-day study, which received two further doses of HCBD, showed that the severity of kidney damage is much less than in the 2-day treated animals, a clear indication that the tubular cells were still resistant to the low dose of HCBD. Concentration of blood urea nitrogen, as a marker of kidney damage, in these two groups also confirmed the results. In animals re-exposed to the high dose of HCBD, data showed that the susceptibility to HCBD was starting to return.
...
PMID:Development of resistance against hexachlorobutadiene in the proximal tubules of young male rat. 1501 8

One of the dose-limiting toxicities of cisplatin is nephrotoxicity. Renal toxicity is localized to quiescent proximal tubule cells, where the formation of DNA-adducts cannot account for the dose-limiting toxicity. Our earlier results have shown that a glutathione conjugate of cisplatin is metabolized to a nephrotoxicant via gamma-glutamyl transpeptidase (GGT) and a cysteine S-conjugate beta-lyase. The present study was designed to evaluate the potential role of glutathione S-transferase Pi (GSTP) in the initial steps of the bioactivation of cisplatin. Wild-type mice and mice deficient in both murine GSTP genes (GstP1/P2) were treated with cisplatin. Toxicity in both male and female mice was evaluated 5 days after treatment and renal damage was most severe in wild-type male mice. Wild-type males have approximately 10-fold higher levels of GSTP expression in the liver than females, suggesting that hepatic GSTP in the wild-type males contributed to the formation of the nephrotoxic platinum-glutathione conjugate. In GstP1/P2 null mice the gender difference in toxicity was eliminated. Our data show that GSTP expression is a determinant in cisplatin-induced nephrotoxicity and its levels contribute to sex-dependent differences.
...
PMID:Role of glutathione S-transferase Pi in cisplatin-induced nephrotoxicity. 1881 70

Trichloroethylene (TCE) is a suspected renal carcinogen. TCE-associated renal genotoxicity occurs predominantly through glutathione S-transferase (GST) conjugation and bioactivation by renal cysteine beta-lyase (CCBL1). We conducted a case-control study in Central Europe (1,097 cases and 1,476 controls) specifically designed to assess risk associated with occupational exposure to TCE through analysis of detailed job histories. All jobs were coded for organic/chlorinated solvent and TCE exposure (ever/never) as well as the frequency and intensity of exposure based on detailed occupational questionnaires, specialized questionnaires, and expert assessments. Increased risk was observed among subjects ever TCE exposed [odds ratio (OR) = 1.63; 95% confidence interval (95% CI), 1.04-2.54]. Exposure-response trends were observed among subjects above and below the median exposure [average intensity (OR = 1.38; 95% CI, 0.81-2.35; OR = 2.34; 95% CI, 1.05-5.21; P(trend) = 0.02)]. A significant association was found among TCE-exposed subjects with at least one intact GSTT1 allele (active genotype; OR = 1.88; 95% CI, 1.06-3.33) but not among subjects with two deleted alleles (null genotype; OR = 0.93; 95% CI, 0.35-2.44; P(interaction) = 0.18). Similar associations for all exposure metrics including average intensity were observed among GSTT1-active subjects (OR = 1.56; 95% CI, 0.79-3.10; OR = 2.77; 95% CI, 1.01-7.58; P(trend) = 0.02) but not among GSTT1 nulls (OR = 0.81; 95% CI, 0.24-2.72; OR = 1.16; 95% CI, 0.27-5.04; P(trend) = 1.00; P(interaction) = 0.34). Further evidence of heterogeneity was seen among TCE-exposed subjects with >or=1 minor allele of several CCBL1-tagging single nucleotide polymorphisms: rs2293968, rs2280841, rs2259043, and rs941960. These findings provide the strongest evidence to date that TCE exposure is associated with increased renal cancer risk, particularly among individuals carrying polymorphisms in genes that are important in the reductive metabolism of this chemical, and provides biological plausibility of the association in humans.
...
PMID:Occupational trichloroethylene exposure and renal carcinoma risk: evidence of genetic susceptibility by reductive metabolism gene variants. 2066 6

Kidney cells were isolated from rat kidney cortex and maintained in short-term monolayer cultures. A number of important parameters were studied in order to establish the usefulness of these cells for toxicity studies. Despite morphological differences between the cultured cells and similar cells in vivo, many relevant enzyme systems remained present and functional. Intracellular glutathione levels were stable up to 5 days in culture. The glutathione S-transferase activity during culture remained stable although at a lower level than in freshly isolated cells. Whereas rat kidney cytosol contained subunits 4, 7, 2 and 1, 3- and 5-day-old cultures contained glutathione transferase subunits 7, 2 and a small amount of subunit 1. Cytochrome P-450, although measurable in microsomes from freshly isolated cells, could not be determined after 1 day in culture. Organic anion transporters on the basolateral side and gamma-glutamyl transpeptidase on the apical side were present. Through cytotoxicity studies, beta-lyase activity could be demonstrated in the culture. Hence this monolayer culture system, which can be used in combination with filters, seems to be suitable for studying various mechanisms of nephrotoxicity.
...
PMID:Use of monolayers of primary rat kidney cortex cells for nephrotoxicity studies. 2070 91

This study investigated the effect of protein malnutrition on metabolism and toxicity of cisplatin (CP), 5-fluorouracil (FU) and mitomycin C (MMC) in rat stomach. Weanling male Wistar rats received a normal (24%) or low (2.5%) protein diet for 28 days and were allocated into: normally-fed control, protein-malnourished control (PM), 3 normally-fed drug-treated groups and 3 protein-malnourished drug-treated groups (PM-CP, PM-FU and PM-MMC). Cisplatin and MMC were injected intraperitoneally (8 mg/kg on day 26 and 1 mg/kg/day for 7 days, respectively). 5-Fluorouracil was given orally (50 mg/kg/day for 5 days). Compared with normally-fed counterparts, PM-CP rats exhibited higher glutathione S-transferase, aminopeptidase N and cysteine S-conjugate beta-lyase (CCBL) and lower gamma-glutamyltransferase activities, PM-FU rats exhibited decreased dihydropyrimidine dehydrogenase and cytochrome P450 1A1/2 activities and PM-MMC rats showed higher quinone reductase and depleted xanthine oxidase activities. Protein-malnourished drug-treated groups exhibited exacerbated gastrotoxicity, relative to normally-fed counterparts, manifested by lower mucus levels, higher permeability and histopathological deterioration, along with increased oxidative stress in PM-CP rats and exaggerated prostaglandin E2 production in PM-MMC rats. Conclusively, protein malnutrition alters CP, FU and MMC metabolism in rat stomach by enhancing CCBL pathway for CP activation, delaying FU elimination and activating two-electron reduction of MMC, potentiating their gastrotoxicity.
...
PMID:Effect of protein malnutrition on the metabolism and toxicity of cisplatin, 5-fluorouracil and mitomycin C in rat stomach. 2345 48


1

---