Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C1260386 (GSH)
 38,102 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

gamma-L-glutamyl-L-cysteinylglycine (GSH) has been shown to inactivate 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and quench DNA crosslink precursors of BCNU. Because of the central role of 2-chloroethyl-nitrosoureas in brain tumor chemotherapy, we investigated the intracellular GSH content and the expression of specific glutathione-S-transferases (GSTs) in three human malignant astrocytoma cell lines (UWR1, UWR2, and UWR3) of varying BCNU resistance to determine the interrelationship of these parameters with brain tumor BCNU resistance. GSH was assayed by ion-exchange high performance liquid chromatography after derivatization with 1-fluoro-2,4 dinitrobenzene. Both bulk and specific GST (acid, near-neutral, and basic) activities were examined using substrates that show high specificities to the different GSTs. Western blot analyses with antisera against GST-alpha, -mu, and -tau subunits were also performed on partially purified GST from the cells of each cell line. The results showed GSH content of 91, 46.5, and 28.3 nmol GSH/mg protein for UWR1, UWR2, and UWR3, respectively. Bulk GST activity (with 1-chloro-2,4-dinitrobenzene as substrate) also correlated with increasing BCNU resistance. Of the three GST classes examined by both substrate specificities and Western blotting, only the expression of the acidic form, GST-tau, correlated significantly with the rank order of BCNU resistance of the cell lines. GST-mu and -alpha were present in only trace amounts in all three cell lines.
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PMID:Glutathione content and glutathione-S-transferase expression in 1,3-bis(2-chloroethyl)-1-nitrosourea-resistant human malignant astrocytoma cell lines. 220 64

In order to study oxidative stress in the lung, we have developed a rat lung slice model with compromised oxidative defences. Lung slices with markedly inhibited glutathione reductase activity (approximately 80% inhibition) were prepared by incubating slices, with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) (100 microM) in an amino acid-rich medium for 45 min at 37 degrees. These lung slices had similar levels of GSH and ATP and polyamine uptake (a marker of alveolar epithelial type I and II cell function) to control rat lung slices. We have utilized these BCNU pretreated slices to study the effects of the herbicide, paraquat, in comparison to those of 2,3-dimethoxy-1,4-naphthoquinone, a potent redox cycler. Paraquat (10-100 microM) caused only minimal changes in the levels of GSH or ATP in control or compromised slices. In contrast, 2,3-dimethoxy-1,4-naphthoquinone caused a decrease in GSH in control slices but a markedly enhanced decrease in both GSH and ATP in compromised slices. Both compounds had only limited effects on putrescine and spermidine uptake in control slices. However, they caused a marked inhibition in compromised slices. Paraquat had little effect on 5-hydroxytryptamine uptake (a marker of endothelial cell function) in either control or compromised slices whereas the quinone inhibited uptake in the compromised slices. Thus, the lack of effect of paraquat on GSH and ATP does not support the involvement of oxidative stress in its toxicity. In contrast, using polyamine uptake, as a functional marker of alveolar epithelial cell damage, suggests a role for redox cycling. As paraquat is known to be accumulated primarily in alveolar type I and II cells (a small fraction of the lung cell population), our data suggest that only a small proportion of pulmonary GSH and ATP is present in alveolar epithelial type I and II cells but that much larger amounts may be present in endothelial cells. These studies highlight the problem of gross tissue measurements in heterogeneous tissues such as the lung.
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PMID:Potentiation of the cell specific toxicity of paraquat by 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). Implications for the heterogeneous distribution of glutathione (GSH) in rat lung. 230 69

Effects of disulfiram (DSF) on freshly isolated hepatocytes were examined. Its effects on the cellular reduced form of glutathione (GSH) were triphasic; GSH decreased instantly after the addition of DSF, returned to subnormal levels within 30 min, and then declined gradually. The initial decrease in GSH after DSF treatment and the subsequent recovery of GSH were accompanied by an increase and decrease in the oxidized form of glutathione (GSSG), respectively. Decreases in cell viability brought about by 0.4 mM of DSF were correlated with the later gradual decrease in GSH. The loss of viability by DSF treatment seemed to appear when the initial GSH levels became lower than approximately 5 nmole/10(6) cells. Hepatocyte toxicity of DSF was potentiated by diethylmaleate (GSH depletor) and inhibited by N-acetylcysteine (GSH biosynthesis precursor). 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), an inhibitor of GSH reductase, inhibited the GSH recovery and potentiated the toxicity. Respiration of hepatocytes was also inhibited by DSF. Free sulfhydryl groups other than GSH showed similar changes to those of GSH. From these results, it seemed that DSF reacted with cellular GSH and other free sulfhydryl groups to form diethyldithiocarbamate and GSSG, GSSG was reduced back to GSH by glutathione reductase, and the decrease in the viability was dependent on the initial loss of GSH.
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PMID:Loss of viability after disulfiram treatment without preceding depletion of intracellular GSH. 239 81

The potential effects of dietary glutathione on the metabolism of peroxidized lipid ingested in the diet were studied using everted sacs of rat small intestine and peroxidized methyl linoleate. Peroxidized methyl linoleate was added to the luminal side, and the appearance of thiobarbituric acid-reactive (TBA-reactive) material on the contraluminal side was measured. Incubation with N,N,bis(2-chloroethyl)-N-nitrosourea (BCNU) under conditions in which it inhibits the glutathione disulfide reductase/glutathione peroxidase system increased the appearance of TBA-reactive material, indicating that at least a portion of the TBA-reactive material passing through the epithelium is peroxide in nature. Adding glutathione (GSH) to the luminal side substantially decreased the appearance of TBA-reactive material on the contraluminal side, either without or with BCNU treatment. Inhibition of GSH transport and control experiments with GSH, peroxidized methyl linoleate and purified brush border membranes showed that this decrease was due primarily to uptake of luminal GSH and its use to support intracellular GSH-dependent reactions. Thus, the results indicate that exogenous GSH, which can exist in certain diets, can be taken up by the small intestine and used to protect against absorption of lipid peroxidation products.
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PMID:Use of exogenous glutathione for metabolism of peroxidized methyl linoleate in rat small intestine. 239 17

Although both direct and glutathione S-transferase (GST)-catalyzed interactions between many electrophiles and GSH generally result in inactivation of the former, there are several reports of compounds whose electrophilic, alkylating, and cytotoxic activities are potentiated by GSH. This study investigates the effects of direct in vitro interaction between GSH and BCNU at physiological pH (7.2) and temperature (37 degrees C) and how this affects the cytotoxic and DNA cross-linking activity of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) in target human malignant brain tumor cells. The kinetics and dose-response relationship of this interaction were determined by measuring residual GSH and residual BCNU-cytotoxicity in aGSH/BCNU mixture over a 45-min period and at varying BCNU concentrations. The results demonstrate that reaction of BCNU with four times its molar concentration of GSH for 45 min significantly inactivates BCNU, as expressed by a 32% decrease in induction of cellular DNA cross-linking, a 21% increase in DNA synthesis, and a 15% increase in clonogenic survival of human brain tumor cells compared to incubates of BCNU alone. Equine liver (EL)-GST increased the inactivation of BCNU only slightly (insignificant at p = 0.05). These results suggest that, in contrast to agents such as the alkyl-N-nitro-N'-nitrosoguanidines which become more potent alkylators after reacting with GSH, the 2-chloroethylnitrosoureas (CENUs) undergo inactivation by GSH. We propose that such interactions between GSH and the CENUs may constitute an important aspect of CENU metabolism and provide a potential means by which brain tumor cells can circumvent CENU toxicity and exhibit resistance to this class of agents.
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PMID:Decreased DNA interstrand cross-linking and cytotoxicity induced in human brain tumor cells by 1,3-bis(2-chloroethyl)-1-nitrosourea after in vitro reaction with glutathione. 255 96

A mechanistic study was performed to elucidate the biochemical events connected with the cocarcinogenic effect of sulfur dioxide (SO2). Glutathione S-sulfonate (GSSO3H), a competitive inhibitor of the glutathione S-transferases, forms in lung cells exposed in culture to sulfite, the hydrated form of SO2. Changes in glutathione status (total GSH) were also observed during a 1-h exposure. Some cells were pretreated with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) to inhibit glutathione reductase. In human lung cells GSSO3H formed in a concentration-dependent manner, while glutathione (GSH) increased and glutathione disulfide (GSSG) decreased as the extracellular sulfite concentration was increased from 0 to 20 mM. The ratio of GSH/GSSG increased greater than 5-fold and the GSH/GSSO3H ratio decreased to 10 with increasing sulfite concentration. GSSO3H formed in rat lung cells exposed to sulfite, with no detectable effect on GSH and GSSG. GSSO3H also formed from cellular GSH mixed disulfides. GSSO3H formed rapidly, reaching its maximum value in 15 min. The viability of both cell types was unaffected except at 20 mM sulfite. GSSO3H incubated with human lung cells did not affect cellular viability. BCNU inhibited cellular GSSO3H reductase to the same extent as GSSG reductase. These results indicate that GSSO3H is formed in cells exposed to sulfite, and could be the active metabolite of sulfite responsible for the cocarcinogenic effect of SO2 by inhibiting conjugation of electrophiles by GSH.
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PMID:Effects of sulfite on glutathione S-sulfonate and the glutathione status of lung cells. 273 75

The teratogenicity of phenytoin may be mediated through a reactive electrophilic and/or free radical intermediate which, if not detoxified, may interact with fetal cellular macromolecules and initiate teratologic effects. Glutathione (GSH) maintains cellular physiological processes and detoxifies xenobiotic reactive intermediates. The role of GSH in protection against phenytoin embryopathy was studied by altering GSH homeostasis using 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), an inhibitor of glutathione reductase. BCNU was administered to pregnant CD-1 mice on gestational day 12, in doses ranging from 10 to 50 mg/kg i.p., with or without phenytoin, 55 or 65 mg/kg i.p., given 4 and 24 hr after BCNU. BCNU alone in doses of 10, 25 or 50 mg/kg resulted in a dose-related increase in the incidence of resorptions, cleft palates and postpartum death (P less than .05), and in lowered fetal weight (P less than .05). Fetuses exposed to 50 mg/kg of BCNU had an array of gross abnormalities, and this dose was not used in subsequent studies. BCNU, 25 mg/kg, inhibited GSH reductase activity by 23% in the placenta (P less than .05) and by 30% in the embryo (P less than .05) at 4 hr after treatment. Embryonic, but not placental GSH reductase activity remained significantly inhibited at 24 hr after BCNU. A BCNU dose-related increase in the incidence of resorptions (P less than .0001) and postpartum death (P less than .05) was seen in groups treated with both BCNU and 65 mg/kg of phenytoin, compared to controls treated with either chemical alone.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Modulation of embryonic glutathione reductase and phenytoin teratogenicity by 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). 274 6

Transglutaminase activity in rat islet homogenates was increased after preincubation of the islets at high glucose concentration, and severely decreased after preincubation in the presence of either 1,2-bis(2-chloroethyl)-1-nitrosurea or 2-cyclohexene-1-one. The stimulatory action of glucose was still observed when the islets were preincubated in the absence or extracellular Ca2+. The enzymic activity was decreased by NAD+ or NADP+ but not NADH or NADPH, and inhibited by GSSG more than by GSH. These findings suggest that the glucose-induced activation of transglutaminase may be related to induction of a more reduced redox state with subsequent change in thiol-disulfide balance.
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PMID:Glucose-induced activation of transglutaminase in pancreatic islets. 287 59

Reduced glutathione (GSH) and activities of several glutathione-related enzymes were measured in two 9L rat brain tumor cell lines with differing sensitivities to both 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and nitrogen mustard. GSH, measured by a specific high-performance liquid chromatographic method, was found to be approximately twice as high in 9L cells sensitive to BCNU but resistant to nitrogen mustard. The nitrogen mustard resistant cell line was also found to have 2.5-fold more bulk glutathione transferase activity and approximately 3-fold more gamma-glutamyl transpeptidase activity. Glutathione reductase activity, protein thiol, and total protein content were similar in the two cell lines. Pretreatment of 9L cells with 50 microM buthionine sulfoximine for 24 h to deplete GSH only slightly potentiated BCNU cytotoxicity in a clonogenic assay whereas that of nitrogen mustard was markedly potentiated in both cell lines. Similarly, buthionine sulfoximine pretreatment had little effect on the induction of sister chromatid exchanges by BCNU, but significantly increased the number of sister chromatid exchanges induced by nitrogen mustard in both cell lines. Depleting GSH also had no significant effect on the cytotoxicity of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea and 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea to 9L cells. Pretreatment of 9L cells with 1 mM GSH significantly protected against nitrogen mustard cytotoxicity. Moreover, nitrogen mustard incubated with GSH and glutathione transferase was 4-fold less cytotoxic than nitrogen mustard incubated with GSH alone. Incubation of BCNU with GSH alone or with glutathione transferase had no effect on BCNU cytotoxicity. These results indicate that elevated GSH and glutathione transferase activity is one mechanism of cellular resistance to nitrogen mustard in the 9L cell line, but it does not correlate with resistance to BCNU or other clinically important nitrosoureas.
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PMID:Glutathione and related enzymes in rat brain tumor cell resistance to 1,3-bis(2-chloroethyl)-1-nitrosourea and nitrogen mustard. 288 34

1-(2-Chloroethyl)-1-nitrosoureas (CNUs) are alkylating agents that also possess carbamoylating activity, depending on the chemical nature of the substituent at N-3. Although effects on a variety of enzymes, including inhibition of glutathione reductase (GS-R) have been attributed to carbamoylation, the biological significance is still not well understood. This deficiency is due at least in part to the analytical method that has been used to measure carbamoylation:in-vitro reaction with the omega-amino group of lysine. Reaction of CNUs with glutathione (GSH) offers a better estimation of carbamoylating potential in vitro. The decrease in free thiol groups during incubation of GSH with various CNUs can be followed using the thiol reagent 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB). With this test, carbamoylating potential relative to that of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) as 100% was 94% for 1-(2-chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea (MeCCNU), 86% for 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU), 16% for 1-(2-chloroethyl)-3-(2-hydroxyethyl)-1-nitrosourea (HECNU) and 6% for chlorozotocin (CLZ). Various carbamoylated and alkylated GSH derivatives, such as S-(2-chloroethylcarbamoyl)-, S-(2-hydroxyethylcarbamoyl)-, S-(cyclohexylcarbamoyl)-, S-(4-methylcyclohexylcarbamoyl)- and S-(2-hydroxyethyl)glutathione, are formed on incubation of GSH with CNUs. High-performance liquid chromatography (HPLC) revealed that, in comparison to carbamoylated compounds, alkylated GSH derivatives are formed in only low yields (less than 3%). Formation of carbamoylated products during incubation correlated with the decrease in free thiol groups. Concentrations achieving 50% GS-R inhibition in vitro were 0.16 mM for BCNU and 1.9 mM for HECNU.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A method to determine the carbamoylating potential of 1-(2-chloroethyl)-1-nitrosoureas. 296 Jun 14


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