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PubMed1982

The inadequacy of the Raney nickel desulfuration method for the structural elucidation of an epoxide-glutathione S-conjugate: desulfuration of phenyloxiran-glutathione S-conjugates to phenyloxiran.

Both of purely separated regioisomers of phenyloxiran-glutathione S-conjugates, conjugate 1 (S-(1-phenyl-2-hydroxyethyl)glutathione) and conjugate 2 (S-(2-phenyl-2-hydroxyethyl)glutathione), afforded phenyloxiran as a common intermediate to the major desulfuration products, phenethyl alcohol and ethylbenzene, and to the minor ones, methylphenylcarbinol and toluene, on the mild treatment with Raney nickel in boiling ethanol. Phenyloxiran formed was hydrogenated to stable phenethyl alcohol and unstable methylphenylcarbinol under the catalytic conditions used, the latter of which was readily deoxygenated to ethylbenzene. The present study indicated that the Raney nickel method, despite of its being recognized to be well established, could not be applicable to the structural assignment of epoxide-glutathione or epoxide-mercapturic acid conjugates.

Chemical Phenomena↗
PubMed1990

Subcellular distribution of N-ethylmaleimide-stimulatable glutathione S-transferase activity in rat liver. Evidence of localization of glutathione S-transferase in peroxisomal membrane.

Subcellular distribution of glutathione S-transferase activity was investigated as stimulated form by N-ethylmaleimide in rat liver. The stimulated glutathione S-transferase activity was localized in mitochondrial and lysosomal fractions besides microsomes. Among N-ethylmaleimide-treated submitochondrial fractions, glutathione S-transferase activity was stimulated only in outer mitochondrial membrane fraction. In lysosomal fraction, it was suggested that glutathione S-transferase activity in peroxisomes, which is immunochemically related to microsomal transferase, was also stimulated, but not in lysosomes.

Animals↗
PubMed1986

Inhibition of cell-mediated cytotoxicity by 2-cyclohexene-1-one: evidence for a role for glutathione and/or glutathione-protein interactions in cytolysis.

In order to explore the role of glutathione in cell-mediated cytotoxicity, we have examined the effect of the sulphydryl-reactive and glutathione-depleting agent 2-cyclohexene-1-one on antibody-dependent cellular cytotoxicity, spontaneous cell-mediated cytotoxicity, and cell-mediated lympholysis by human peripheral blood mononuclear cells. 2-Cyclohexene-1-one significantly inhibited (P less than 0.001) both antibody-dependent and spontaneous cell-mediated cytotoxicity using three different cell-line targets, at three different killer:target cell ratios (10:1, 25:1 and 50:1). Using K-562 cell-line targets, spontaneous cell-mediated cytotoxicity was inhibited by 2-cyclohexene-1-one with an ID50 of 0.71 X 10(-4) M-1.48 X 10(-4) M, while antibody-dependent cellular cytotoxicity was less sensitive to inhibition, and required slightly higher concentrations of 1.48 X 10(-4) M-3.98 X 10(-4) M to achieve 50% inhibition. Similar results were seen with human colon tumour cell-line and Chang liver cell-line cells as targets. Maximal inhibition occurred when 2-cyclohexene-1-one was added to the cytotoxicity assay 60 min prior to, at the start of, or within the first 60 min of a 4-hr assay; inhibition of cytotoxicity occurred with pretreatment of effector cells; and no inhibition of cytotoxicity was observed with pretreatment of target cells. Both the allogeneic mixed leucocyte reaction and cell-mediated lympholysis were also significantly inhibited (P less than 0.001) by 2-cyclohexene-1-one. These studies demonstrate that 2-cyclohexene-1-one is an effective inhibitor of cell-mediated cytotoxicity and suggest that glutathione, specific glutathione-protein interactions, or protein-bound sulphydryl groups are involved in allowing cells to carry out cytolysis.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1994

Sensitive enzymatic cycling assay for glutathione: measurements of glutathione content and its modulation by buthionine sulfoximine in vivo and in vitro in human colon cancer.

We have measured glutathione content in small tissue samples derived from biopsies of primary and metastatic human colon tumors and from colon cancer cell lines in tissue culture and xenografts in athymic mice. Measurements were performed using an enzymatic cycling assay designed to quantitate extremely low levels of glutathione (GSH) (down to 10(-14) mol) from perchlorate extracts of tissue samples weighing less than 1 mg wet weight. Glutathione was stable in these acid extracts for at least 6 months when stored at -80 degrees C. A survey of normal tissues in mice, rats, and some human tissues showed considerable variation in GSH content of different tissues but generally similar levels were identifiable for the same tissues from different species. The highest GSH level was 56.9 nmol/mg protein in rat liver and the lowest was 1.8 nmol/mg protein in rat skeletal muscle. High GSH levels were also determined in mouse and human liver, while low GSH levels were detected in mouse muscle. Human colon cancer cell lines showed slightly higher GSH levels than did colon cancer tumor samples obtained from biopsies. These studies revealed a marked inter-individual difference in tumor GSH content, as well as a difference in GSH content between tumor deposits at different metastatic sites in the same individual. These results indicate the importance of direct tumor measurements of GSH content in clinical trials designed to modulate tumor glutathione content to try to increase sensitivity to chemotherapy or radiation therapy. Buthionine sulfoximine, an inhibitor of gamma-glutamyl cysteine synthetase, was shown to produce almost complete depletion of GSH in four different human colon cancer cell lines in 24 h. Buthionine sulfoximine was also shown to be capable of producing drastic depletion of GSH in human colon cancer grown as xenografts in athymic animals.

Animals↗
PubMed1993

Glutathione-associated cis-diamminedichloroplatinum(II) metabolism and ATP-dependent efflux from leukemia cells. Molecular characterization of glutathione-platinum complex and its biological significance.

Accumulating evidence suggests a critical role of intracellular glutathione in tumor cell resistance to alkylating agents. The present study provides evidence for the direct interaction between cis-diamminedichloroplatinum(II) (cisplatin) and glutathione (GSH) both in a cell-free system, as well as in L1210 murine leukemia cells. We have isolated the reaction product and identified it by a combination of high performance liquid chromatography and atomic absorption spectroscopy. Stoichiometric analysis showed a 2:1 molar ratio of GSH/cisplatin for the reaction. The molecular mass assessed by mass spectroscopy was 809 Da, corresponding to a GS-platinum chelate complex, bis-(glutathionato)-platinum. The GS-platinum complex was detected in L1210 leukemia cells incubated with 20 microM cisplatin. The intracellular content of the GS-platinum complex reached a maximal level after 12 h, corresponding to about 60% of the intracellular platinum content. Thus, formation of the GS-platinum complex is considered a significant part of the cellular metabolism of cisplatin. The GS-platinum was found to inhibit cell-free protein synthesis in a rabbit reticulocyte lysate system using both chloramphenicol acetyltransferase mRNA and poly(A) mRNA from HL-60 human promyelocytic leukemia cells (IC50 = 190 microM the GS-platinum complex). Elimination of the GS-platinum complex from tumor cells may represent an important mechanism which reduces the intracellular accumulation of the platinum complex. Using plasma membrane vesicles prepared from L1210 cells, the transport of the GS-platinum complex across the plasma membrane was found to be an ATP-dependent process (apparent Km values: 49 microM, ATP; 110 microM, GS-platinum complex). The ATP-dependent transport of the GS-platinum complex was inhibited by vanadate (IC50 = 35 microM) as well as by S-(2,4-dinitrophenyl)-glutathione, leukotriene C4, and GSSG, but not by doxorubicin, daunorubicin, or verapamil. The ATP-dependent glutathione S-conjugate export pump, "GS-X pump" (Ishikawa, T. (1992) Trends Biochem. Sci. 17, 463-468), is suggested to play a role in the elimination of the GS-platinum complex from tumor cells.

Adenosine Triphosphate↗
PubMed1989

Effects of glutathione (GSH and GSSG) and glutathione reductase (GR) on zona-free hamster oocyte ability to decondense human sperm.

Effects of reduced glutathione (GSH), oxidized glutathione (GSSG), or glutathione reductase (GR) supply were studied on the ability of hamster oocytes to be fertilized by human sperm. Zona-free oocytes were pretreated with these compounds prior to sperm insemination. Oocyte pretreatment with high concentrations of GSH or GSSG (50 or 100 mM, 30 min) significantly increased the penetrated oocyte rate (PR). Polyspermy was not increased except when high concentrations of GSH (100 mM) were used. Incubation of oocytes with GR (1 or 10 IU/ml) prior to sperm insemination induced increasing dose-dependent PR. Polyspermy increased significantly with 10 mM GR in oocyte incubation medium. Oocyte incubation for 30 min with the sulfhydryl blocking agent iodoacetamide (1 mM) led to a drastic decrease in oocyte penetration and in polyspermy. Our results demonstrate an original way to increase the efficacy of human-hamster heterospecific fertilization. Various hypotheses are discussed explaining these observations which open new investigations for heterospecific and homospecific in vitro fertilization.

Animals↗
PubMed1996

Differential redox regulation by glutathione of glutathione reductase and CuZn-superoxide dismutase gene expression in Pinus sylvestris L. needles.

Glutathione reductase (GR; EC 1.6.4.2) and superoxide dismutase (SOD; EC 1.15.1.1) are two well-known enzymes involved in the scavenging of reactive oxygen intermediates. However, little is known about the regulation of Gor and Sod genes in plant cells. To obtain information about hypothetical redox regulatory mechanisms controlling Gor and Sod gene expression we artificially enhanced the levels of reduced and oxidized forms of glutathione (GSH and GSSG) in Pinus sylvestris L. needles. Scots pine shoots were placed for 12 h in beakers containing 5 mM GSH, 5 mM GSSG or water. Increased levels of both GSSG and GSH were observed in the GSSG-treated needles after 3 h. In contrast, only the GSH level was increased by the GSH treatment. Thus, the GSH/GSSG ratio increased up to 15-fold during the GSH treatment and decreased approximately two-fold during the GSSG treatment. The GR activity was significantly higher (60%) when GSSG was applied, without any apparent change in the amount and isoform population of GR or accumulation of Gor gene transcripts. This indicates that the GR activity increased per se in the GSSG treatment. The level of cytosolic CuZn-Sod transcripts was decreased significantly by the GSH treatment without any change in enzyme activity. The chloroplastic CuZn-Sod gene generally showed a more stable transcript level in the different treatments. However, a similarity between the cytosolic and chloroplastic levels of CuZn-Sod transcripts could be observed in different treatments. This suggests that the redox state of glutathione plays an important role in the in vivo regulation of CuZn-Sod gene expression in plants.

Amino Acid Sequence↗
PubMed1986

Electron transfer between reduced methyl viologen and oxidized glutathione: a new assay of Saccharomyces cerevisiae glutathione reductase.

Pure glutathione reductase from Saccharomyces cerevisiae catalyzed under anaerobic conditions the enzymatic reduction of GSSG using electrochemically reduced methyl viologen as electron donor. The new assay was completely dependent on the amount of active enzyme present, and involved the formation of 1 mol GSH per mole of reduced methyl viologen consumed. The enzyme followed a standard Michaelis-Menten kinetics; a Km = 230 microM for reduced methyl viologen and a turnover number of 969 mumol GSSG reduced per minute per micromole enzyme were determined. The enzymatic activity seemed to depend on the redox potential, showing half-maximal activity at -0.407 V. The enzyme was quite specific: the activity using reduced benzyl viologen as electron donor was just 1.5% of that obtained with reduced methyl viologen at the same concentration and potential. Glutathione reductase was totally inactivated after a brief anaerobic exposure with reduced methyl viologen in the absence of GSSG; a partial reactivation was observed following addition of glutathione disulfide. No inhibition of the methyl viologen-dependent activity was observed in the presence of 2',5'-ADP or 2'-P-5'-ADP-ribose, two NADP(H) analogs, at concentrations which drastically inhibited the NADPH-dependent activity, thus suggesting that the reduced viologen does not interact with the pyridine nucleotide-binding site.

Adenosine Diphosphate↗
PubMed1989

Glutathione and glutathione S-transferases in a human plasma cell line resistant to melphalan.

We report the development of a melphalan-resistant HS-Sultan human plasma cell line. The melphalan-resistant [MEL(R)] cell line was 16.7-fold more resistant to melphalan in vitro than the parent cell line [MEL(S)]. The wild type and MEL(R) HS-Sultan cell lines formed localized plasmacytomas when injected into nude mice. A dose-response effect of melphalan against the drug-sensitive plasmacytomas was present in vivo. A dose of 10 mg/kg of melphalan, which caused a 90% regression of MEL(S) plasmacytomas, had no effect on the MEL(R) plasmacytomas in vivo. In contrast to previous reports, there was no increase in the levels of glutathione (GSH) in the MEL(S) and MEL(R) plasmacytomas, suggesting that the association of elevated glutathione levels and melphalan resistance may not be common to all drug-resistant lines. In the MEL(R) plasmacytomas, there was a 1.5-fold induction of a pi type glutathione S-transferase (GST) as evidenced by isoelectric focusing (IEF) and Western blotting. This GST isoenzyme was purified and, although immunochemically similar to the pi type isoenzymes induced in other drug-resistant cell lines, was noted to have different functional characteristics. These data suggest that, depending on cell type and the drug studied, functionally different GST isoenzymes may be induced and they could be of importance in the development of drug resistance.

Animals↗
PubMed1994

Effect of carbamate thioester derivatives of methyl- and 2-chloroethyl isocyanate on glutathione levels and glutathione reductase activity in isolated rat hepatocytes.

The present study examined the effects of S-(N-methylcarbamoyl)glutathione (SMG), S-(N-methylcarbamoyl)-L-cysteine (L-SMC) and some analogs of these S-linked conjugates of methyl isocyanate (MIC) on the activity of glutathione reductase (GR) in freshly isolated rat hepatocytes and on the levels of reduced and oxidized glutathione (GSH and GSSG) in exposed cells. Both SMG and its monoethyl ester (0.5 mM) were found to inhibit GR weakly, although L-SMC proved to be an effective inhibitor of the enzyme (60 +/- 4% activity remaining after a 4-hr incubation at 0.5 mM). The cysteine adduct (SCC) of 2-chloroethyl isocyanate (CEIC) was a strong inhibitor of GR (27 +/- 1% activity remaining after a 1-hr incubation at 0.1 mM) and was essentially equipotent with the antitumor agent N,N'-bis(2-chloroethyl)-N-nitrosourea (BCNU). L-SMC depleted intracellular GSH in a time- and concentration-dependent manner up to 2 hr of incubation, beyond which time GSH levels began to recover. Exposure of cells to the enantiomeric conjugate, D-SMC, led to a similar concentration- and time-dependent inhibition of GR and fall in intracellular GSH, but in this case the depletion of GSH was extensive and was sustained throughout the 5-hr incubation period. Only a small amount (less than 10%) of the GSH that was lost from cells exposed to SMC was recovered in the medium, indicating that SMC did not cause efflux of GSH (most of the free cysteine released during breakdown of SMC was recovered in the medium). Experiments with hepatocytes exposed for 5 hr to SCC (0.1 mM) demonstrated that GSSG levels were elevated by 32 +/- 5% relative to controls. Collectively, these results indicate that carbamate thioester conjugates of MIC and CEIC inhibit GR, probably via release of the free isocyanate at the cell surface, which then penetrates the hepatocyte. The inhibitory effects of the isocyanates on GR, coupled with their propensity to react spontaneously with GSH, combine to deplete significantly intracellular stores of GSH.

Animals↗
PubMed1996

The role of the oxidative state of glutathione and glutathione-related enzymes in anemia of hemodialysis patients.

OBJECTIVE: To investigate the oxidative state of glutathione and glutathione peroxidase (GSH-Px), glutathione reductase (GSSG-R), and glucose-6-phosphate dehydrogenase (G-6-PD) levels in patients with chronic renal failure (CRF) and controls. RESULTS: Erythrocyte GSH levels of patients were decreased, but GSSG was not significantly different from that of controls. Also, plasma GSH levels were not different, although GSSG was increased. GSSG/GSH ratios in erythrocyte and plasma were significantly higher in CRF patients. Erythrocyte GSSG-R activity was high, but G-6-PD and GPX were low. CONCLUSIONS: The findings suggest that: 1. Low GSH is related to decreased G-6-PD activities. 2. The reduction of peroxides with GPX are decreased by low GSH and low GPX activity. 3. GSSG may react with hemoglobin and causes protein aggregation in erythrocytes. These alterations cause hemolysis and could play a role in the pathogenesis of anemia in hemodialyzed patients.

Adolescent↗
PubMed1997

The glutathione conjugate of ethacrynic acid can bind to human pi class glutathione transferase P1-1 in two different modes.

The diuretic drug ethacrynic acid, an inhibitor of pi class glutathione S-transferase, has been tested in clinical trials as an adjuvant in chemotherapy. We recently solved the crystal structure of this enzyme in complex with ethacrynic acid and its glutathione conjugate. Here we present a new structure of the ethacrynic-glutathione conjugate complex. In this structure the ethacrynic moiety of the complex is shown to bind in a completely different orientation to that previously observed. Thus there are at least two binding modes possible, an observation of great importance to the design of second generation inhibitors of the enzyme.

Binding Sites↗
PubMed1990

Role of the charged groups of glutathione disulfide in the catalysis of glutathione reductase: crystallographic and kinetic studies with synthetic analogues.

Six analogues of glutathione disulfide were synthesized. All of them involved the abolishment of charges, either by amidation of carboxylates or by removal of amino groups. Four of these analogues could be bound to crystalline oxidized glutathione reductase, and their binding modes could be established by X-ray analyses at 2.4-A resolution. All six analogues were catalytically processed; the kinetic parameters were determined. The two analogues that did not bind in the crystals had by far the poorest catalytic efficiencies. Kinetic parameters together with X-ray data show the influence of each charged group on binding and catalytic rate. Data analysis indicates that the enzyme avoids processing of incorrect substrates in two ways: First, it reduces their binding strengths and/or enforces displacement of catalytically important substrate parts. Furthermore, it forms a fragile cluster of bound substrate and catalytically competent residues, which is unbalanced by incorrect parts of the substrate such that catalysis is prevented. A scouting microcalorimetric study using glutathione disulfide yielded a binding enthalpy of -103 (+/- 10) kJ/mol at 25 degrees C and a heat capacity change of -8 (+/- 1) kJ.mol-1.K-1. The study showed that it is feasible to measure these parameters as a function of substrate modification.

Catalysis↗
PubMed2002

Nitration/S-nitrosation of proteins by peroxynitrite-treatment and subsequent modification by glutathione S-transferase and glutathione peroxidase.

In various peroxynitrite (PN)-treated proteins, the formations of stable 3-nitrotyrosine (nitration) and labile S-nitrosocysteine (S-nitrosation) were observed by employing rapid Western blot in 6 h. The steps of SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and membrane-blotting were performed at 4 degrees C. It was noted that the intensity of immunoreactive bands specific for anti-nitrotyrosine was stronger than that specific for anti-S-nitrosocysteine. Additionally, the intensity was in the manner of a dose-dependency of PN. Nitration/S-nitrosation were formed in the following treated proteins, including bovine serum albumin (BSA), DNase-1, ceruloplasmin, catalase and hemoglobin (Hb). The incubation of PN-pretreated hemoglobin with 1 mM reduced glutathione (GSH) did not change immunoreactivity significantly. However, the addition of glutathione S-transferase (GST) or glutathione peroxidase (GPX) to the above incubation mixture, resulted in decreased immunoreactivity, suggesting GSH may form a transition complex with PN-pretreated hemoglobin and/or partially reduce/modify the treated hemoglobin, thereby increasing the accessibility for the subsequent modification by GST or GPX. Such decreased immunoreactivity indicates that nitrotyrosine and S-nitrosocysteine of treated hemoglobin was, indeed, further modified via (a) converting -NO2 to -NH2 in tyrosine residues, (b) denitrating -NO2 directly/indirectly in tyrosine residues, and/or (c) changing -S-NO to -SH in cysteine residues, or denitrosation. The findings imply similar enzymatic modifications of proteins may also occur in vivo, and therefore play a pivotal role in the NO-related cellular signaling cascade(s).

Animals↗
PubMed2001

Microsomal glutathione S-transferase A1-1 with glutathione peroxidase activity from sheep liver: molecular cloning, expression and characterization.

A 25 kDa subunit of glutathione S-transferase (GST) from sheep liver microsomes (microsomal GSTA1-1) with a significant selenium-independent glutathione peroxidase activity has been isolated and characterized. Several analytical criteria, including EDTA stripping, protease protection assay and extraction with alkaline Na(2)CO(3), indicate that the microsomal GSTA1-1 is associated with the inner microsomal membrane. The specific cDNA nucleotide sequence reveals that the enzyme is made up of 222 amino acid residues and shares approx. 73-83% sequence similarity to Alpha-class GSTs from different species. The molecular mass, as determined by electrospray mass ionization, is 25611.3 Da. The enzyme is distinct from the previously reported rat liver microsomal GST in both amino acid sequence and catalytic properties [Morgenstern, Guthenberg and DePierre (1982) Eur. J. Biochem. 128, 243-248]. The microsomal GSTA1-1 differs from the sheep liver cytosolic GSTs, reported previously from this laboratory, in its substrate specificity profile and molecular mass [Reddy, Burgess, Gong, Massaro and Tu (1983) Arch. Biochem. Biophys. 224, 87-101]. In addition to catalysing the conjugation of 4-hydroxynonenal with GSH, the enzyme also exhibits significant glutathione peroxidase activity towards physiologically relevant fatty acid hydroperoxides, such as linoleic and arachidonic acid hydroperoxides, as well as phosphatidylcholine hydroperoxide, but not with H(2)O(2). Thus the microsomal GSTA1-1 isoenzyme might have an important role in the protection of biological membranes against oxidative damage.

Amino Acid Sequence↗
PubMed1995

Markedly decreased expression of glutathione S-transferase pi gene in human cancer cell lines resistant to buthionine sulfoximine, an inhibitor of cellular glutathione synthesis.

Buthionine sulfoximine (BSO) is a synthetic amino acid that irreversibly inhibits an enzyme, gamma-glutamylcysteine synthetase (gamma-GCS), which is a critical step in glutathione biosynthesis. We isolated three BSO-resistant sublines, KB/BSO1, KB/BSO2, and KB/BSO3, from human epidermoid cancer KB cells. These cell lines showed 10-to 13-fold higher resistance to BSO, respectively, and had collateral sensitivity to cisplatin, ethacrynic acid, and alkylating agents such as melphalan and nitrosourea. Cellular levels of glutathione S-transferase pi (GST-pi) and its mRNA in BSO-resistant cell lines were less than 10% of the parental cells. Nuclear run-on assay showed that the transcriptional activity of GST-pi was decreased in BSO-resistant cells, and transient transfection of GST-pi promoter-chloramphenicol acetyltransferase constructs revealed that the sequences between -130 and -80 base pairs of the 5'-flanking region wer at least partially responsible for the decreased expression of the GST-pi gene. By contrast, gamma-GCS mRNA levels were 3-to 5-fold higher in resistant cell lines than in KB cells, and the gamma-GCS gene was found to be amplified in the BSO-resistant cells lines. GST-pi mRNA levels appeared to be inversely correlated with gamma-GCS mRNA levels in BSO-resistant cells. We further established the transfectants, KB/BSO3-pi1 and KB/ BSO2-pi2, that overexpressed GST-pi, from KB/BSO3, after introducing a GST-pi expression plasmid. These two transfectants had similar levels in gamma-GCS mRNA, drug sensitivity to alkylating agents, and glutathione content at those of KB cells. These findings suggest that the cellular levels of GST-pi and gamma-GCS might be co-regulated in these novel BSO-resistant cells.

Blotting, Southern↗
PubMed2002

Protective effects of S-allylcysteine on hepatic glutathione and glutathione-dependent enzymes during hamster cheek pouch carcinogenesis.

The effects of S-allylcysteine (SAC) on hepatic lipid peroxidation and antioxidant status during 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch carcinogenesis (HBP) were investigated in male Syrian hamsters. Enhanced lipid peroxidation in the liver of tumour-bearing animals was accompanied by significant decreases in the activities of glutathione peroxidase (GPx) and glutathione S-transferase (GST) and a reduction in reduced glutathione (GSH) levels. Administration of SAC significantly decreased the formation of lipid peroxides and enhanced the levels of antioxidants and detoxifying enzymes. We suggest that the elevation of hepatic GSH and GSH-dependent enzymes by SAC may play a key role in preventing cancer development in the hamster cheek pouch.

9,10-Dimethyl-1,2-benzanthracene↗