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At least 811 records · Page 45Linked to original sources
PubMed1995

Glutathione peroxidase and phospholipid hydroperoxide glutathione peroxidase are differentially regulated in rats by dietary selenium.

Phospholipid hydroperoxide glutathione peroxidase (PHGPX) and classical glutathione peroxidase (GPX1) are encoded by separate genes with only about 40% amino acid and nucleic acid sequence identity. To determine the response of tissue PHGPX expression to dietary Se level and to compare these responses with those for GPX1, weanling male rats were fed amino acid diets containing from 2 (-Se) to 130 (+Se) microgram Se/kg diet or a torula diet containing 5 and 190 micrograms Se/kg diet as Na2SeO3 for 28 d. Tissues were analyzed for PHGPX and GPX1 activity and mRNA. There was no effect of Se on growth. In -Se rats, GPX1 activity was reduced to 1% in liver and 4-9% in heart, kidney and lung compared with +Se rats; PHGPX activity was reduced only to 25-50% in these four tissues. The Se response curves indicated that the dietary Se requirement to reach plateau liver PHGPX activity was half that required for plateau GPX activity. In -Se rats, liver and heart GPX1 mRNA levels were reduced to 6 and 12%, respectively, whereas PHGPX mRNA was not significantly affected by Se deficiency. Notably, 65 micrograms Se/kg diet resulted in plateau liver GPX1 mRNA levels but not plateau GPX activity. Testis had the lowest GPX activity and GPX1 mRNA of all tissues examined, but had 15-fold higher PHGPX activity and 45-fold higher PHGPX mRNA levels when compared with liver. There was no significant effect of dietary Se on testis GPX1 and PHGPX mRNA levels. This study demonstrates that these two selenoperoxidases are differentially regulated by dietary Se.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Glutathione S-transferase activity, sulfhydryl group and glutathione levels, and DNA cross-linking activity with chlorambucil in chronic lymphocytic leukemia.

Glutathione (GSH) levels and glutathione S-transferase (GST) activities were measured in the leukemia cells of 12 patients with chronic lymphocytic leukemia. Both were correlated with prior clinical exposure to alkylating agents and with DNA cross-link formation by chlorambucil in these cells in vitro. No correlation was observed between prior exposure to alkylating agents and GSH level or GST activity. An inverse correlation was observed between GST activity and cross-linking by chlorambucil, which was enhanced if both GST activity and GSH level were related to cross-linking. These findings suggest that the combination of GST and GSH protects the DNA of leukemia cells from chlorambucil, but the role of this combination in clinical resistance remains to be determined.

Adult↗
PubMed1992

Site-directed mutagenesis of amino acid residues involved in the glutathione binding of human glutathione S-transferase P1-1.

The four residues of human glutathione S-transferase P1-1 whose counterparts were indicated by X-ray crystallography to reside in the GSH-binding site of pig glutathione S-transferase P1-1 were individually replaced with threonine or alanine by site-directed mutagenesis to obtain mutants R13T, K44T, Q51A, and Q64A. The kinetic parameters, susceptibilities to an inhibitor, S-hexyl-GSH, and affinities for GSH-Sepharose of the latter were compared with those of the wild-type enzyme, and pKa of the thiol group of GSH bound in R13T was shown to be equivalent to that in the wild type. From the results, Lys44, Gln51, and Gln64 were deduced to contribute to the binding of GSH. On the other hand, Arg13 seems to be essential for the enzymatic activity as mainly involved in the construction of a proper structure of the active site.

Amino Acid Sequence↗
PubMed1981

An enzymatic assay of reduced glutathione using glutathione S-aryltransferase with o-dinitrobenzene as a substrate.

A simple and sensitive enzymatic assay method for the determination of reduced glutathione (GSH) has been developed using glutathione S-aryltransferase with o-dinitrobenzene as a substrate. o-Dinitrobenzene is a good substrate for the enzyme and has low spontaneous reactivity with GSH at neutral pH. GSH can be determined by colorimetrically measuring nitrite released upon the enzymatic conjugation of GSH and o-dinitrobenzene by using a diazo-coupling method with N-(1-naphthyl)ethylenediamine dihydrochloride. This method is capable of quantitating 1 to 40 nmol of GSH, and can be applied to physiological samples containing deproteinizing reagents.

Animals↗
PubMed1989

A comparison of glutathione reductase and glutathione peroxidase activities in patients with rheumatoid arthritis and healthy adults.

A 30% increase in erythrocyte glutathione peroxidase (GP) activity was found in patients with rheumatoid arthritis when compared with healthy controls (p = 0.001) whereas the increase in glutathione reductase (GR) was statistically insignificant. No correlation was found between the activities of the enzymes and the erythrocyte sedimentation rate (ESR). The enzyme activities were independent of age, sex, or type of drug treatment of the patients. A possible interpretation of the results is presented.

Adult↗
PubMed2005

Genotoxicity of 4-hydroxy-2-nonenal in human colon tumor cells is associated with cellular levels of glutathione and the modulation of glutathione S-transferase A4 expression by butyrate.

The cellular production of 4-hydroxy-2-nonenal (HNE), a product of endogenous lipid peroxidation, constitutes a genotoxic risk factor for carcinogenesis. Our previous studies have shown that human HT29 colon cells developed resistance toward HNE injury after treatment with butyrate, a diet-associated gut fermentation product. This resistance was attributed to the induction of certain glutathione S-transferases (hGSTP1-1, hGSTM2-2, and hGSTA1-1) and also for the tripeptide glutathione (GSH) synthesizing enzymes. In the present study, we have investigated in HT29 cells whether hGSTA4-4, which has a high substrate specificity for HNE, was also inducible by butyrate and, thus, could contribute to the previously observed chemoresistance. In addition, we investigated if cellular depletion of GSH by L-buthionine-S,R-sulfoximine (BSO) enhances chemosensitivity to HNE injury in HT29 cells. Incubation of HT29 cells with butyrate (2-4 mM) significantly elicited a 1.8 to 3-fold upregulation of steady state hGSTA4 mRNA over 8-24 h after treatment. Moreover, 4 mM butyrate tended to increase hGSTA4-4 protein concentrations. Incubation with 100 microM BSO decreased cellular GSH levels by 77% without significant changes in cell viability. Associated with this was a 2-fold higher level of HNE-induced DNA damage as measured by the comet assay. Collectively, the results of this study and our previous work indicate that the genotoxicity of HNE is highly dependent on cellular GSH status and those GSTs that contribute toward HNE conjugation, including hGSTA4-4. Since HNE contributes to colon carcinogenesis, the favorable modulation of the GSH/GST system by butyrate may contribute to chemoprevention and reduction of the risks.

Aldehydes↗
PubMed2002

Visualization of the compartmentalization of glutathione and protein-glutathione mixed disulfides in cultured cells.

Fluorescence microscopy of A549 cells stained with a glutathione (L-gamma-glutamyl-L-cysteinylglycine, GSH)-specific polyclonal antibody displayed uniform staining of the peri-nuclear cytosol, with the nuclear region apparently lacking GSH staining. This discontinuous staining was confirmed in other cell types and also corroborated in A549 cells stained with the thiol-reactive dye mercury orange. The selectivity of antibody binding was confirmed by buthionine sulfoximine (BSO)-dependent inhibition of GSH synthesis. However, confocal visualization of antibody-stained A549 cells in the z-plane revealed the majority of the peri-nuclear staining intensity in the upper half of the cell to be associated with mitochondria, as confirmed by double staining for cytochrome oxidase. Integration of the confocal signals from the nuclear and cytosolic regions halfway down the z-plane showed that the GSH concentrations of these compartments are close to equilibrium. Confirmation of the relatively high levels of mitochondrial glutathione was provided in cells treated with BSO and visualized in z-section, revealing the mitochondrial GSH content of these cells to be well preserved in apposition to near-complete depletion of cytosolic/nuclear GSH. Localized gradients within the cytosolic compartment were also visible, particularly in the z-plane. The antibody also provided initial visualization of the compartmentalization of protein-GSH mixed disulfides formed in A549 cells exposed to diamide. Discontinuous staining was again evident, with heavy staining in membrane blebs and in the nuclear region. Using FACS analysis of anti-GSH antibody-stained Jurkat T lymphocytes, we also demonstrated population variations in the cellular compliment of GSH and protein-GSH mixed disulfides, formed in response to diamide. In addition, we showed cell-cycle variation in GSH content of the cells, with the highest levels of GSH associated with the G2/M mitotic phase of the cell cycle, using double staining with propidium iodide. Similar FACS analyses performed in isolated mitochondria presented a considerable variation in GSH content within mitochondria of uniform granularity from the same preparation.

Animals↗
PubMed1996

Effects of diallyl sulfide and diallyl disulfide on cisplatin-induced changes in glutathione and glutathione-S-transferase activity.

The effects of diallyl sulfide (DAS) and diallyl disulfide (DADS) on cisplatin-induced changes in glutathione (GSH) and glutathione-S-transferase (GST) activity in rat liver and kidney was investigated. Cisplatin treatment significantly (p < 0.05) decreased GSH and GST activity in both liver and kidney. DADS treatment significantly (p < 0.05) enhanced GSH and GST activity in rat liver and kidney. Furthermore, DADS treatment reversed the effect of cisplatin on GSH and GST activity both in liver and kidney. Administration of DADS with cisplatin could enhance GSH and GST activity and lower cisplatin-induced nephrotoxicity.

Allyl Compounds↗
PubMed2001

Relationship between cytocidal activity and glutathione-S-transferase inhibition using doxorubicin coupled to stereoisomers of glutathione with different substrate specificity.

To determine the cytotoxic mode of action of a glutathione (GSH)--doxorubicin (DXR) conjugate, which exhibited potent cytotoxicity against various multidrug-resistant as well as DXR-sensitive cell lines, the molecular interaction between covalent GSH--DXR conjugates and glutathione-S-transferase (GST), a possible molecular target of the conjugates, was investigated. The following four GSH molecules with stereoisomeric forms were prepared: L-Glu--L-Cys--Gly (LL-GSH), D-Glu--L-Cys--Gly (DL-GSH), L-Glu--D-Cys--Gly (LD-GSH) and D-Glu--D-Cys--Gly (DD-GSH). The enzymic activity of GST against each GSH stereoisomer was 88, 38, 8 and 4 nmol/mg/min, respectively, suggesting that the L-form cysteine residue in the molecule was an important substrate of GST. Addition of DXR conjugated with each isomer (10 microM) to a GSH-containing GST assay mixture inhibited the GST activity to 32% for LL-GSH--XR, 16% for DL-GSH-DXR and 61% for LD-GSH-DXR as compared with the solvent control. Moreover, IC50 values for these conjugates were 30, 20 and 250 nM, respectively. The cytocidal activity of each conjugate corresponded to the substrate specificity of GST activity for the GSH isomer. These conjugates bound to the GST molecule, and the binding ability was 0.746, 0.627 and 0.462 mol/mol of GST for LL-GSH--XR, DL-GSH-DXR and LD-GSH--XR, respectively. These findings suggested that GSH--DXR interacted with the substrate-binding site of the GST molecule and inhibition of GST activity exhibited potent cytotoxicity.

Animals↗
PubMed1994

Comparison of plasma reduced glutathione and oxidized glutathione with lung and liver tissue oxidant and antioxidant activity during acute inflammation.

We determined whether plasma levels of reduced glutathione (GSH) and oxidized glutathione (GSSG) accurately reflect the tissue GSH and GSSG levels in lung and liver during a progressive acute inflammation-induced increased oxidant activity. We also determined whether plasma GSH also reflected other antioxidant defenses. Male Wistar rats (n = 38) were given intraperitoneal zymosan (.75 mg/g body weight) producing an acute progressive peritonitis and generalized inflammation. Animals were resuscitated then killed at 4 or 24 h. Plasma and tissue levels of GSH, GSSG, vitamin C, alpha-tocopherol, and catalase were measured. Conjugated dienes and malondialdehyde were used as tissue markers of lipid peroxidation. We found lung and liver tissue GSH to be decreased significantly at 4 h while GSSG was increased. Lipid peroxidation was also present in the lung. At 24 h, GSH remained decreased in liver and GSSG remained increased in lung along with the lipid peroxides conjugated dienes and malondialdehyde. In addition, overall antioxidant defenses were decreased in both lung and liver. Plasma GSH remained decreased at 24 h corresponding with the decrease in liver GSH as well as the decrease in other plasma and tissue antioxidants. However, plasma GSSG levels were not significantly increased, at any time point, indicating plasma GSSG does not accurately reflect tissue oxidant activity.

Acute Disease↗
PubMed2006

Crystallization and preliminary X-ray crystallographic analysis of a highly stable mutant V107A of glutathione transferase from Anopheles dirus in complex with glutathione.

An engineered mutant V107A of the dimeric glutathione transferase enzyme from Anopheles dirus (adgstD4-4) was cocrystallized with glutathione substrate using the hanging-drop vapour-diffusion method. The crystal diffracted to 2.47 A resolution in space group P3(2)21 (unit-cell parameters a = b = 49.4, c = 272.4 A). Although the crystal morphology differed from that previously obtained for the wild-type enzyme, the crystal packing was the same. At 318 K, the engineered mutant showed an enzyme stability that was increased by about 32-fold, while possessing a similar catalytic function to the wild type. Structural determination will provide valuable understanding of the role of Val107. This residue is in the dimeric interface and appears to contribute towards enhancing the physical properties of the entire protein.

Amino Acid Sequence↗
PubMed2005

E6* oncoprotein expression of human papillomavirus type-16 determines different ultraviolet sensitivity related to glutathione and glutathione peroxidase antioxidant defence.

Clinical observations of non-melanoma skin cancer in immunocompromised patients, such as organ transplant recipients, suggest co-operative effects of human papillomavirus (HPV) and ultraviolet (UV) radiation. The aim of the present study is to evaluate UV sensitivity and DNA damage formation according to antioxidant status in HPV16-infected keratinocytes. We used SKv cell lines, infected with HPV16 and well characterized for their proliferative and tumorigenic capacities. We showed that SKv cell lines presented various E6* (a truncated form of E6) RNA levels. We demonstrated that the higher oncoprotein RNA expression level was associated with a higher resistance to solar-simulated radiation, more specifically to UVB radiation and to hydrogen peroxide. Moreover, this high resistance was associated with a low oxidative DNA damage formation after UV radiation and was related to high glutathione content and glutathione peroxidase activities. Therefore, the results of our study suggest that E6* levels could modulate the glutathione/glutathione peroxidase pathway providing a mechanism to protect HPV-infected keratinocytes against an environmental oxidative stress, such as UV radiation.

Antioxidants↗
PubMed1999

Low glutathione and glutathione S-transferase levels in Barrett's esophagus as compared to normal esophageal epithelium.

Patients with Barrett's esophagus, wherein squamous epithelium has been replaced by columnar epithelium, have an increased risk for developing esophageal adenocarcinoma as compared to the general population. Glutathione S-transferase (GST), a family of detoxification enzymes consisting of class alpha, mu, pi, and theta isoforms, is involved in detoxification of carcinogens and low levels of these enzymes correlated with high cancer risk. We have now compared GST enzyme activity, GST isoenzyme composition and glutathione (GSH) content of Barrett's mucosa with that of adjacent normal squamous epithelium. Biopsy specimens of 98 patients with Barrett's esophagus were taken from both Barrett's and adjacent normal squamous epithelium. GST enzyme activity towards 1-chloro-2,4-dinitrobenzene was measured, and GST isoenzyme levels were determined by densitometrical analyses of western blots after immunodetection with monoclonal antibodies. Total GSH content was determined by high-performance liquid chromatography after conjugation with monobromobimane. Wilcoxon's signed rank test and Spearman correlation analyses were used for statistical evaluation. As compared with adjacent normal squamous epithelium, GST enzyme activity in Barrett's epithelium was reduced by 35%, and GST mu, GST pi and GSH levels were reduced by 24%, 30%, and 63%, respectively. However, the minor GST alpha and GST theta levels were higher in Barrett's epithelium (by 625% and 33%, respectively). High levels of GSH and GSTs in general are correlated with protection against cellular or cytogenetic damage. The observed reduction in GSTs and GSH in Barrett's epithelium may therefore contribute to the increased cancer risk in this tissue.

Adult↗
PubMedDate not supplied

Glutathione concentrations and glutathione S-transferase activity in human colonic neoplasms.

Tissue concentrations of glutathione (GSH) and the activity of glutathione S-transferases (GST) are relevant to the inactivation of a variety of xenobiotics including carcinogens and anti-neoplastic drugs. In this study, GSH concentrations and GST activity were determined in 25 adenomatous polyps removed at colonoscopy, and in cancer and uninvolved 'normal' mucosa from 58 operative specimens containing colon cancer. We also examined the relationship between GSH concentrations, GST activity and rates of cell proliferation as assessed by flow cytometry. Concentrations of GSH were significantly higher in adenomas (P = 0.001) and cancer (P = 0.001) than in uninvolved mucosa while GST activity was significantly higher in cancer (P = 0.007). There was a positive relationship between GSH concentrations and GST activity in adenomas (P = 0.001) but not in uninvolved mucosa (P = 0.06) or cancer (P = 0.4). Concentrations of GSH and GST activity were independent of results from flow cytometry. The higher concentrations of GSH in colonic neoplasms and the raised activity of GST in cancer may contribute to their resistance to anti-neoplastic drugs.

Adenoma↗
PubMed2006

The multidrug resistance protein 1 (Mrp1), but not Mrp5, mediates export of glutathione and glutathione disulfide from brain astrocytes.

Astrocytes play an important role in the glutathione (GSH) metabolism of the brain. To test for an involvement of multidrug resistance protein (Mrp) 1 and 5 in the release of GSH and glutathione disulfide (GSSG) from astrocytes, we used astrocyte cultures from wild-type, Mrp1-deficient [Mrp1(-/-)] and Mrp5-deficient [Mrp5(-/-)] mice. During incubation of wild-type or Mrp5(-/-) astrocytes, GSH accumulated in the medium at a rate of about 3 nmol/(h.mg), whereas the export of GSH from Mrp1(-/-) astrocytes was only one-third of that. In addition, Mrp1(-/-) astrocytes had a 50% higher specific GSH content than wild-type or Mrp5(-/-) cells. The presence of 50 microm of the Mrp inhibitor MK571 inhibited the rate of GSH release from wild-type and Mrp5(-/-) astrocytes by 60%, but stimulated at the low concentration of 1 microm GSH release by 40%. In contrast, both concentrations of MK571 did not affect GSH export from Mrp1(-/-) astrocytes. Moreover, in contrast to wild-type and Mrp5(-/-) cells, GSSG export during H(2)O(2) stress was not observed for Mrp1(-/-) astrocytes. These data demonstrate that in astrocytes Mrp1 mediates 60% of the GSH export, that Mrp1 is exclusively responsible for GSSG export and that Mrp5 does not contribute to these transport processes.

Animals↗
PubMed1985

Glutathione peroxidase activity and reduced glutathione content in erythrocytes of patients with chronic renal failure.

Erythrocytes from 18 patients with chronic renal failure (CRF) and 10 healthy subjects were examined with respect to glutathione peroxidase (GSH-Px) activity and reduced glutathione (GSH) contents. The activity of GSH-Px and GSH content were found to be lower in RBC from CRF patients as compared with normal RBC. These reduced levels of GSH and GSH-Px in the red cells of uraemic patients may predispose the cells to oxidative damage.

Adult↗
PubMed1989

Changes in catalase, glutathione peroxidase and glutathione-S-transferase activities in the liver of newts exposed to 2-methyl-4-chlorophenoxyacetic acid (MCPA).

Activities of catalase, glutathione peroxidase (GSH-Px) and glutathione-S-transferase (GST) were measured in livers of the crested newt (Urodele Amphibian) after 16 days of percutaneous exposure to the herbicide Agroxone 3, a commercial formulation of 2-methyl-4-chlorophenoxyacetic acid (MCPA) containing 25% MCPA as sodium salt and 75% wetting and dispersing ingredients. Animals of both sexes were exposed to 800 p.p.m. of the active ingredient. There was a three-fold increase in catalase and a clear enhancement of GSH-Px in the MCPA-exposed animals of both sexes. A sex-dependent effect of MCPA was observed on GST activity, which increased significantly in female newts only. Similar liver enzyme changes were observed in female newts, and not in males, given the hypolipidaemic drug clofibrate (13 mg/animal/day, by gavage, for 8 days), which is structurally related to phenoxyherbicides. These findings indicate that the crested newt is sensitive to the hepatic effects of the peroxisome proliferators.

2-Methyl-4-chlorophenoxyacetic Acid↗