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

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Query: EC:1.11.1.9 (glutathione peroxidase)
22,002 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Reactive oxygen metabolites have been implicated in causing epithelial cell injury in colonic inflammation. A model of oxidant injury in intestinal epithelial cells has been developed in which HT-29-18-C1 cells are injured with graded concentrations of hydrogen peroxide and characterised by the MTT test. The MTT test was validated as a cytotoxicity assay and has a similar sensitivity to hydrogen peroxide induced injury as the assay of intracellular adenosine triphosphate. Exposure to a range of hydrogen peroxide concentrations (0.05-20 mM) for varying duration (5-120 min) showed that injury was dependent on time and concentration. The median lethal dose (LD50) for one hour exposure to hydrogen peroxide was approximately 0.1 mM. Injury from hydrogen peroxide was only partially reversible as determined by the MTT test and assay of cellular proliferation by crystal violet staining. There was an exponential loss of hydrogen peroxide when incubated with HT-29-18-C1 cells (t1/2 35 min). Experiments with 0.5 mg/ml aminotriazole and 0.5-2 mM buthionine sulphoximine suggested hydrogen peroxide breakdown was predominantly caused by catalase rather than glutathione peroxidase. Injury resulting from 1 mM hydrogen peroxide could be reduced by either coincubation of cells with 1,10-phenanthroline, an Fe2+ chelator, or preincubation with deferoxamine, and Fe3+ chelator, suggesting the participation of Fe2+ and Fe3+ in hydrogen peroxide induced injury. In conclusion, hydrogen peroxide induces injury in HT-29-18-C1 cells both directly and by generation of the hydroxyl radical.
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PMID:Characterisation of oxidative injury to an intestinal cell line (HT-29) by hydrogen peroxide. 782 76

Small cell lung cancer (SCLC) is treated primarily with combination chemotherapy. Despite high initial response rates, most patients eventually die with drug resistant disease. In some tumours, resistance to multiple chemotherapeutic agents is attributed to overexpression of P-glycoprotein (P-gp). However, this does not appear to be a frequent occurrence in drug resistant SCLC. Increased levels of glutathione (GSH) and related enzymes may play a role in resistance to alkylating agents as well as natural product drugs. We measured levels of GSH, glutathione S-transferase (GST), glutathione reductase (GSH Red), glutathione peroxidase (GSH Px), and gamma-glutamyl transpeptidase (gamma-GT) in a panel of 20 SCLC cell lines. Most of these lines were established from patients treated at this centre. Each cell line had a characteristic and reproducible profile of GSH and related enzyme levels. Immunoblot analysis indicated that the predominant GST in the cell lines was the anionic pi isoenzyme. The relative sensitivity of each of these cell lines to 16 different chemotherapeutic agents was measured using a modified MTT assay. Spearman rank correlation analysis was used to determine the relationships between the relative chemosensitivity of these cell lines and the levels of GSH and related enzymes. The number of positive correlations was no greater than expected by chance alone. Furthermore, there was no correlation with the treatment history of the patients from whom the cell lines were derived. These data suggest that alterations in glutathione metabolism do not play a major role in resistance to chemotherapeutic agents in these human SCLC cell lines.
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PMID:Do glutathione and related enzymes play a role in drug resistance in small cell lung cancer cell lines? 810 44

The role of oxidative stress in mercuric chloride (HgCl2)-induced nephrotoxicity is uncertain and controversial. We demonstrate that I.L.C-PK1 cells, exposed to HgCl2, generate massive amounts of hydrogen peroxide, the latter completely quenched by the hydrogen peroxide scavenger, pyruvate. HgCl2 exerts a dose-dependent cytotoxicity which is attenuated by pyruvate and catalase. Cellular generation of hydrogen peroxide arises, at least in part, from mitochondria since mitochondrial rates of generation of hydrogen peroxide increase in response to HgCl2; HgCl2 also provokes a shift in absorbance spectra in rhodamine 123 loaded-mitochondria and stimulates mitochondrial state 4 respiration. HgCl2, applied for one hour, impairs cellular vitality as demonstrated by the MTT assay, an assay dependent in part on mitochondrial function. HgCl2 impairs function in other organelles such as lysosomes that maintain a transmembrane proton gradient; these latter effects are partially attenuated by pyruvate. We complement these in vitro findings with in vivo evidence demonstrating that HgCl2 stimulates renal generation of hydrogen peroxide. The functional significance of such generation of hydrogen peroxide was evaluated in rats deficient in selenium and vitamin E, a nutrient deficiency that impairs the scavenging of hydrogen peroxide and promotes the toxicity of this oxidant. In these rats serum creatinine values were significantly higher on sequential days following the administration of HgCl2. To probe the renal response to oxidative stress induced by HgCl2, we examined hydrogen peroxide-scavenging enzymes and redox-sensitive genes. Catalase activity was unaltered whereas glutathione peroxidase activity was decreased, effects that may contribute to the net renal generation of hydrogen peroxide. The redox sensitive enzyme, heme oxygenase, was markedly up-regulated in the kidney in response to HgCl2. HgCl2 also induced members of the bcl family, bcl2 and bclx, genes that protect against apoptosis and oxidant injury. In another model of oxidant-induced renal injury, the glycerol model, bcl2 mRNA was not induced at 6 and 24 hours after the administration of glycerol. In summary, we demonstrate that HgCl2 potently stimulates renal generation of hydrogen peroxide in vitro and in vivo and such generation of peroxide contributes to renal dysfunction in vitro and in vivo. We also demonstrate that in response to HgCl2, redox sensitive genes are expressed including heme oxygenase and members of the bcl family.
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PMID:Renal oxidant injury and oxidant response induced by mercury. 887 81

In vivo administration of either 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or methamphetamine (MA) produces damage to the dopaminergic nervous system which may be due in part to the generation of reactive oxygen species (ROS). The resistance of superoxide dismutase (SOD) over-expressing transgenic mice to the effects of both MPTP and MA suggests the involvement of superoxide in the resulting neurotoxicity of both compounds. Superoxide can be converted by SOD to hydrogen peroxide, which itself can cause cellular degeneration by reacting with free iron to produce highly reactive hydroxyl radicals resulting in damage to proteins, nucleic acids and membrane phospholipids. Hydrogen peroxide has also been reported to be produced via inhibition of NADH dehydrogenase by MPP + formed during oxidation of MPTP by MAO-B and by dopamine auto-oxidation following MA-induced dopamine release from synaptic vesicles within nerve terminals. To test whether hydrogen peroxide is an important factor in the toxicity of either of these two neurotoxins, we created clonal PC12 lines expressing elevated levels of the hydrogen peroxide-reducing enzyme glutathione peroxidase (GSHPx). Elevation of GSHPx levels in PC12 was found to diminish the rise in ROS levels and lipid peroxidation resulting from MA but not MPTP treatment. Elevated levels of GSHPx also appeared to prevent decreases in transport-mediated dopamine uptake produced via MA administration as well as to attenuate toxin-induced cell loss as measured by either MTT reduction or LDH release. Our data, therefore, suggest that hydrogen peroxide production likely contributes to MA toxicity in dopaminergic neurons.
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PMID:Elevated expression of glutathione peroxidase in PC12 cells results in protection against methamphetamine but not MPTP toxicity. 919 Oct 89

Various investigations have reported the occurrence in bacterial and mammalian cells of an adaptive response to the toxic effects of oxidants or agents that cause oxidation via redox reactions. In our previous study, it was shown that several cell lines pretreated with a low dose of hydrogen peroxide (H2O2) exhibited an adaptive response to subsequent high doses of adriamycin (ADR), whereas other cell lines did not. Based on the observation that the cell lines utilized differed in their sensitivity towards adriamycin, we undertook the present investigation with the goal of evaluating possible relationships between the levels of antioxidant enzymes and sensitivity towards adriamycin. Another aim was to determine relationships between the inducibility of these enzymes and the occurrence of adaptation. We utilized African Green monkey kidney (V3), human embryo (CLV98), human melanoma (ME18), and Chinese hamster ovary (CHO) cell lines and experimentally developed adriamycin-resistant human melanoma (ME18/RN) and Chinese hamster ovary (CHO/RN) cell sublines. Cytotoxicity was measured by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and trypan blue exclusion. The levels of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) were determined in the same kind of experiment as that revealing the occurrence of adaptation. The rank order established for catalase activities was similar to that for sensitivity towards adriamycin. Aberrant increases in the tested enzymes were demonstrated in experimental groups of all kinds of cells. We conclude that in our cell systems catalase is a major determinant of adriamycin resistance. Whether the occurrence of the adaptive response under study is dependent on the contribution of catalase, itself dependent on the degree of resistance to the drug, is discussed.
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PMID:Studies on adaptation to adriamycin in cells pretreated with hydrogen peroxide. 933 76

Recent findings suggest that intracellular oxidants are involved in the induction of apoptosis and this type of cell death can be inhibited by various antioxidants. In our accompanying paper, we have shown apoptosis in the villus tip cells of the monkey small intestinal epithelium. The aim of the present study was to evaluate the possible relationship between oxidative stress, antioxidant levels and the apoptotic process in the monkey small intestinal epithelium. Monkey small intestinal epithelial cells were isolated into different fractions consisting of villus, middle and crypt cells. Mitochondrial function was assessed by the reduction of the tetrazolium dye, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), with and without succinate. The extent of lipid peroxidation was assessed by measuring the formation of conjugated diene, depletion of polyunsaturated fatty acids and alpha-tocopherol. Level of antioxidant enzymes like, superoxide dismutase (SOD), catalase, glutathione S-transferase (GST), glutathione peroxidase (GPx) and glutathione reductase were also quantitated in various cell fractions. MTT reduction was significantly decreased in villus cells as compared to the cells from other fractions and this was evident even in presence of the respiratory substrate, succinate. Increased formation of conjugated diene and depletion of polyunsaturated fatty acids were seen in villus and crypt cells as compared to middle fraction cells. The alpha-tocopherol level was decreased in both villus and crypt cells as compared to cells from middle region. Significant decrease of SOD activity was seen in the villus tip cells and a slight decrease was seen in the crypt fractions. Glutathione dependent enzymes like GST, GPx and GSH reductase showed higher activity in the villus fractions. A similar observation was also seen in the catalase activity. This study has shown that although oxidative stress is seen in both villus and crypt cells, decreased mitochondrial function was seen in villus tip cells which may be responsible for apoptotic process in the intestinal epithelium.
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PMID:Apoptotic process in the monkey small intestinal epithelium: 2. Possible role of oxidative stress. 989 35

This study was undertaken to determine whether bioavailable zinc can influence the effects of oxidative stress on cultured human retinal pigment epithelial (RPE) cells. RPE cells were maintained for 7 d in culture medium containing 14 microM total zinc, or in medium containing 0.55 microM total zinc. After 1 week, MTT assays were performed to determine the relative cytotoxicity of H2O2 or paraquat on RPE cells. Conjugated dienes and thiobarbituric acid reactive substances (TBARS) were measured in RPE cells treated with 0, 0.5 mM H2O2, 10 microM FeSO4 + 0.5 mM H2O2 or 10 microM FeSO4 + xanthine/xanthine oxidase for 24 h or paraquat for 7 d. Oxidized proteins were determined by the formation of carbonyl residues. The antioxidants metallothionein, catalase, superoxide dismutase, and glutathione peroxidase were also measured. The MTT assays showed that zinc protected cultured RPE from the toxicity of H2O2 and paraquat. RPE cells in 0.55 microM zinc medium contained higher levels of TBARS, conjugated dienes and protein carbonyls due to the oxidative stresses, compared to cells in 14 microM zinc. Catalase and MT content were reduced in cells cultured in 0.55 microM zinc medium and were reduced additionally when treated with above stresses. Superoxide dismutase activity increased in 0.55 microM zinc medium in response to these stresses. Our results show RPE cells cultured in zinc-reduced medium are more susceptible to oxidative insult.
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PMID:Zinc protects against oxidative damage in cultured human retinal pigment epithelial cells. 1021 60

The cytotoxicity of oxysterols including 7-ketocholesterol, alpha-epoxide, cholestanetriol and 25-hydroxycholesterol and the possible protecting effect of alpha-tocopherol on cholestanetriol and 25-hydroxycholesterol-induced cytotoxicity were investigated in primary cultures of porcine ovarian granulosa cells. Cell viability as determined by % trypan blue staining and mitochondrial function as determined using 3-[4,5-dimethylthiazol-2-yl]-2,5- diphenyltetrazolium bromide (MTT) reduction were decreased significantly after 24 h exposure to 2.5 microM alpha-epoxide, cholestanetriol and 25-hydroxycholesterol. 7-Ketocholesterol (2.5 microM) did not affect cell viability or mitochondrial function under the same culture conditions. The specific activities of catalase and superoxide dismutase, two antioxidant defense enzymes were increased significantly (p < 0.01) following 24 h exposure to 2.5 microM concentrations of cholestanetriol while only superoxide dismutase was increased in 25-hydroxycholesterol-treated cells (p < 0.001). Specific activity of glutathione peroxidase was unchanged relative to control cells. Levels of thiobarbituric acid reactive substances remained unchanged after exposure to 7-ketocholesterol, alpha-epoxide, cholestanetriol, 25-hydroxycholesterol and cholesterol. Administration of 1 microM alpha-tocopherol to the culture medium significantly improved cell viability and restored both superoxide dismutase and catalase activities to control levels in cholestanetriol -treated cells and only superoxide dismutase in 25-hydroxycholesterol-treated cells. These studies suggest that the cytotoxic nature of physiologically relevant concentrations of cholestanetriol and 25-hydroxycholesterol in granulosa cells is in part due to oxidative stress, but it may be reduced in the presence of alpha-tocopherol.
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PMID:Alpha-tocopherol inhibits oxidative stress induced by cholestanetriol and 25-hydroxycholesterol in porcine ovarian granulosa cells. 1039 Nov 43

Nitric oxide (NO) and reactive oxygen species (ROS) are crucial elements in cytokine-mediated beta-cell destruction. In insulin-producing RINm5F cells, overexpression of cytoprotective enzymes provides significant protection against the synergistic toxicity of NO and ROS. We therefore examined whether overexpression of catalase (Cat), glutathione peroxidase (Gpx), and Cu/Zn superoxide dismutase (SOD) can provide protection for bioengineered RINm5F cells against cytokine-mediated toxicity. A 72-h exposure of RINm5F control cells to interleukin-1beta (IL-1beta) alone or a combination of IL-1beta, tumor necrosis factor-alpha, and gamma-interferon resulted in a time- and concentration-dependent decrease of cell viability in the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) cytotoxicity assay. Although IL-1beta alone caused only a moderate reduction of viability in the range of 25%, the cytokine mixture induced a significant loss of viability of >75%. This increased toxicity of the cytokine mixture compared with that of IL-1beta alone could be explained by a higher rate of NO generation within the early 24-48 h incubation period that would favor the toxic synergism of NO and oxygen free radicals. Overexpression of Cat, Gpx, and Cu/Zn SOD protected against toxicity of the cytokine mixture but not against that of IL-1beta alone. The reduction of cytokine-mediated toxicity was evident also because of an increased proliferation rate and a drastic decrease in the cell death rate. The improved antioxidant defense status did not prevent the activation of iNOS after cytokine exposure. However, RINm5F cells overexpressing cytoprotective enzymes showed a significantly lower level of ROS-damaged protein residues. Thus, protection through Cat, Gpx, and Cu/Zn SOD overexpression was apparently because of an inactivation of ROS generated in the signal cascades of the cytokines. Overexpression of cytoprotective enzymes thus represents a feasible strategy to protect insulin-producing cells against cytokine-mediated cytotoxicity.
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PMID:Protection of insulin-producing RINm5F cells against cytokine-mediated toxicity through overexpression of antioxidant enzymes. 1090 68

It has been reported that several cis-unsaturated fatty acids (c-UFAs) could increase doxorubicin (DOX) accumulation in cancer cells and hence elevate its cytotoxicity. However, some researchers showed that c-UFA pretreatment did not affect its cytotoxicity in special cell lines. It is possible that the different results occurred due to different cellular characteristics. We hypothesized that c-UFA treatment might modulate the activities of some antioxidant enzymes to affect the resistance of cells to DOX. In the present study, we examined how c-UFA pretreatment affected DOX cytotoxicity on mouse leukemia cell line, P388, and its resistant subline, P388/DOX, which we found to have significantly higher glutathione peroxidase (GPx) activity as well as P-glycoprotein (p-gp) overexpression. We chose two c-UFAs, gamma-linolenic acid (GLA) (18:3n-6) and docosahexaenoic acid (DHA) (22:6n-3). Cytotoxicity was measured by MTT (3-(4.5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and trypan blue exclusion assays. DOX accumulation and p-gp expression were measured by flow cytometry. The activities of catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), and GPx were determined for both cell lines with and without treatment with GLA or DHA. Significant DOX accumulation occurred in both cell lines with GLA or DHA pretreatment, but without any change in p-gp expression in either cell line. Sensitivity to DOX cytotoxicity was improved by GLA or DHA pretreatment in P388/DOX in which only SOD activity was significantly increased, but not in the parental cell line P388 in which both SOD and CAT were significantly increased by the pretreatment. However, combined pretreatment of GLA or DHA with antioxidants, pyrrolidinedithiocarbamate (PDTC) or Vitamin C, could sensitize not only P388/DOX but also P388 cells to DOX. We conclude that the effects of c-UFA pretreatment on the sensitivity of cancer cells to DOX not only depend on the change in drug accumulation but also the change in the levels of antioxidant enzyme activities, and suggest that combined administration of c-UFAs, antioxidants, and DOX may be more effective in treating leukemia.
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PMID:Effects of cis-unsaturated fatty acids on doxorubicin sensitivity in P388/DOX resistant and P388 parental cell lines. 1095 54


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