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)

We report the isolation of three full-length cDNAs corresponding to the mRNAs of closely related glutathione S-transferase (GST) Pi genes, designated hGSTP1*A, hGSTP1*B, and hGSTP1*C, expressed in normal cells and malignant gliomas. The variant cDNAs result from A --> G and C --> T transitions at nucleotides +313 and +341, respectively. The transitions changed codon 104 from ATC (Ile) in hGSTP1*A to GTC (Val) in hGSTP1*B and hGSTP1*C and changed codon 113 from GCG (Ala) to GTG (Val) in hGSTP1*C. Both amino changes are in the electrophile-binding active site of the GST Pi peptide. Computer modeling of the deduced crystal structures of the encoded peptides showed significant deviations in the interatomic distances of critical electrophile-binding active site amino acids as a consequence of the amino acid changes. The encoded proteins expressed in Escherichia coli and purified by GSH affinity chromatography showed a 3-fold lower Km (CDNB) and a 3-4-fold higher Kcat/Km for the hGSTP1*A encoded protein than the proteins encoded by hGSTP1*B and hGSTP1*C. Analysis of 75 cases showed the relative frequency of hGSTP1*C to be 4-fold higher in malignant gliomas than in normal tissues. These data provide conclusive molecular evidence of allelopolymorphism of the human GST Pi gene locus, resulting in active, functionally different GST Pi proteins, and should facilitate studies of the role of this gene in xenobiotic metabolism, cancer, and other human diseases.
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PMID:Molecular cloning, characterization, and expression in Escherichia coli of full-length cDNAs of three human glutathione S-transferase Pi gene variants. Evidence for differential catalytic activity of the encoded proteins. 909 42

The gene GLCLC encodes the catalytic subunit of gamma-glutamylcysteine synthetase (glutamate-cysteine ligase E.C. 6.3.2.2), the rate limiting enzyme for glutathione synthesis. When HepG2 cells were exposed to the serine/threonine phosphatase inhibitor okadaic acid (OA), increased expression of GLCLC was observed, as was the development of resistance to xenobiotic induced GSH depletion. Okadaic acid is known to activate both NF-kappaB and AP-1 activity. Inhibition of NF-kappaB activity by overexpression of an IkappaB alpha transdominant inhibitor or exposure to the protease inhibitor TLCK did not inhibit the OA mediated increase in GLCLC transcripts. Fibroblasts derived from a mouse containing a c-Jun null mutation exhibited diminished AP-1 binding activity, reduced levels of GLCLC message, and a correspondingly low GSH concentration compared to wild type cells. When the null cells, which express Jun B and Jun D, were exposed to OA, AP-1 binding activity increased, as did expression of GLCLC message. These results indicate that AP-1 transcription factors participate in the regulation of glutathione metabolism.
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PMID:Expression of glutathione and gamma-glutamylcysteine synthetase mRNA is Jun dependent. 917 57

Monofunctional alkylating agents like methyl methanesulfonate (MMS) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) are potent inducers of cellular stress leading to chromosomal aberrations, point mutations, and cell killing. We show that these agents induce a specific cellular stress response program which includes the activation of Jun N-terminal kinases/stress-activated protein kinases (JNK/SAPKs), p38 mitogen-activated protein kinase, and the upstream kinase SEK1/MKK4 and which depends on the reaction mechanism of the alkylating agent in question. Similar to another inducer of cellular stress, UV irradiation, damage of nuclear DNA by alkylation is not involved in the MMS-induced response. However, in contrast to UV and other inducers of the JNK/SAPKs and p38 pathways, activation of growth factor and G-protein-coupled receptors does not play a role in the MMS response. We identified the intracellular glutathione (GSH) level as critical for JNK/SAPK activation by MMS: enhancing the GSH level by pretreatment of the cells with GSH or N-acetylcysteine inhibits, whereas depletion of the cellular GSH pool causes hyperinduction of JNK/SAPK activity by MMS. In light of the JNK/SAPK-dependent induction of c-jun and c-fos transcription, and the Jun/Fos-induced transcription of xenobiotic-metabolizing enzymes, these data provide a potential critical role of JNK/SAPK and p38 in the induction of a cellular defense program against cytotoxic xenobiotics such as MMS.
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PMID:The level of intracellular glutathione is a key regulator for the induction of stress-activated signal transduction pathways including Jun N-terminal protein kinases and p38 kinase by alkylating agents. 923 35

The teratogenicity of many xenobiotics is thought to depend at least in part upon their bioactivation by embryonic cytochromes P450, prostaglandin H synthase (PHS) and lipoxygenases (LPOs) to electrophilic and/or free radical reactive intermediates that covalently bind to or oxidize cellular macromolecules such as DNA, protein and lipid, resulting in in utero death or teratogenesis. Using as models the tobacco carcinogens benzo[a]pyrene (B[a]P) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), the anticonvulsant drug phenytoin, structurally related anticonvulsants (e.g. mephenytoin, nirvanol, trimethadione, dimethadione) and the sedative drug thalidomide, we have examined the potential teratologic relevance of free radical-initiated, reactive oxygen species (ROS)-mediated oxidative molecular target damage, genotoxicity (micronucleus formation) and DNA repair in mouse and rabbit models in vivo and in embryo culture, and in vitro using purified enzymes or cultured rat skin fibroblasts. These teratogens were bioactivated by PHS and LPOs to free radical reactive intermediary metabolites, characterized by electron spin resonance spectrometry, that initiated ROS formation, including hydroxyl radicals, which were characterized by salicylate hydroxylation. ROS-initiated oxidation of DNA (8-hydroxy-2'-deoxyguanosine formation), protein (carbonyl formation), glutathione (GSH) and lipid (peroxidation), and embryotoxicity were shown for phenytoin, its major hydroxylated metabolite 5-(p-hydroxyphenyl)-5-phenylhydantoin [HPPH], thalidomide, B[a]P and NNK in vivo and/or in embryo culture, the latter indicating a teratologically critical role for embryonic, as distinct from maternal, processes. DNA oxidation and teratogenicity of phenytoin and thalidomide were reduced by PHS inhibitors. Oxidative macromolecular lesions and teratogenicity also were reduced by the free radical trapping agent phenylbutylnitrone (PBN), and the antioxidants caffeic acid and vitamin E. In embryo culture, addition of superoxide dismutase (SOD) to the medium enhanced embryonic SOD activity, and SOD or catalase blocked the oxidative lesions and embryotoxicity initiated by phenytoin and B[a]P, suggesting a major contribution of ROS, as distinct from covalent binding, to the teratologic mechanism. In in vivo studies, other antioxidative enzymes like GSH peroxidase, GSH reductase and glucose-6-phosphate dehydrogenase (G6PD) were similarly protective. Even untreated G6PD-deficient mice had enhanced embryopathies, indicating a teratological role for endogenous oxidative stress. In cultured fibroblasts, B[a]P, NNK, phenytoin and HPPH initiated DNA oxidation and micronucleus formation, which were inhibited by SOD. Oxidation of DNA may be particularly critical, since transgenic mice with +/- or -/- deficiencies in the p53 tumor suppressor gene, which facilitates DNA repair, are more susceptible to phenytoin and B[a]P teratogenicity. Even p53-deficient mice treated only with normal saline showed enhanced embryopathies, suggesting the teratological importance of endogenous oxidative stress, as observed with G6PD deficiency. These results suggest that oxidative macromolecular damage may play a role in the teratologic mechanism of xenobiotics that are bioactivated to a reactive intermediate, as well in the mechanism of embryopathies occurring in the absence of xenobiotic exposure.
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PMID:Oxidative damage in chemical teratogenesis. 943 60

The present study evaluates the potential of smokeless tobacco to translactationally modify the chemopreventive efficacy of phytic acid and butylated hydroxyanisole (BHA) via modulation of the hepatic xenobiotic detoxication system and antioxidant defense mechanism in the murine system. Phytic acid (1000 mg/kg b.w./day) by gavage while BHA (1% w/w) in diet induced a significant increase in the levels of glutathione-S-transferase (GST), acid soluble sulfhydryl (-SH), cytochrome b5 (Cyt. b5) and cytochrome P-450 (Cyt. P-450) in lactating dams and suckling pups. The hepatic levels of GST and -SH were significantly depressed whereas microsomal Cyt. b5, Cyt. P-450 and MDA levels were elevated in groups treated with smokeless tobacco (50 or 100 mg/kg b.w./day). The data reveals the inhibitory potential of smokeless tobacco on phytic acid-induced GST/GSH system efficiency besides the significant augmentation by smokeless tobacco on phytic acid or BHA-induced microsomal phase I enzymes. The direct or translactational modulation in the levels of xenobiotic detoxication system enzymes suggests the potential of smokeless tobacco to modify the chemopreventive efficacy of phytic acid or BHA.
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PMID:Postnatal effect of smokeless tobacco on phytic acid or the butylated hydroxyanisole-modulated hepatic detoxication system and antioxidant defense mechanism in suckling neonates and lactating mice. 946 4

The ability of allylamine (AA) administration to produce vascular lesions resembling atherosclerotic disease in animals, has been linked to metabolism of AA to the toxic aldehyde acrolein (ACR) by a semicarbazide-sensitive amine oxidase (SSAO) found in plasma and in vascular smooth muscle. Here, we have assessed the cytotoxicity of AA and ACR towards cultured human umbilical vein endothelial cells (HUVEC). After 20h treatment, 50 microM AA alone had no effect and 100 microM AA produced a modest reduction in cell viability. However, both concentrations produced considerable cell death when incubated with HUVEC in the presence of human umbilical artery homogenate as a source of human vascular SSAO activity. The cytotoxic actions of 50 microM AA were not altered by coincubation with 100 microM pargyline (an inhibitor of monoamine oxidase, MAO) but were completely prevented by 100 microM semicarbazide (SSAO inhibitor) and propargylamine (MAO/SSAO inhibitor). ACR at 50 and 100 microM was considerably cytotoxic, but had little effect at 5 and 10 microM. Since SSAO can also metabolize the biogenic aliphatic amine methylamine to formaldehyde (FA), effects of this aldehyde upon HUVEC were also studied. 50 microM FA did not significantly alter HUVEC viability whereas 200 microM FA produced a small but significant reduction in viability. However, 200 microM FA (but not 50 microM FA) was highly cytotoxic in HUVEC pretreated for 24h with the glutathione (GSH) synthesis inhibitor, D.L-buthionine sulphoximine (200 microM). These results suggest that endothelial integrity or function in blood vessels could be affected by these aliphatic aldehydes as environmental pollutants, dietary contaminants, and possible products of metabolic pathways, including those involving the action of SSAO upon biogenic and xenobiotic aliphatic amines. The availability of GSH-dependent mechanisms for metabolizing these aldehydes may have an important protective influence.
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PMID:[Effect of activity of semicarbazide-sensitive aminooxidases and cellular glutathione on the cytotoxic effect of allylamine, acrolein, and formaldehyde in human cultured endothelial cells]. 950 71

1. In this study we have compared freshly cut and cultured precision-cut rat liver slices produced by the Krumdieck and Brendel-Vitron tissue slicers. 2. No significant differences were observed in levels of protein, potassium, total glutathione (i.e. GSH and GSSG), reduced glutathione (GSH) and cytochrome P450 and activities of 7-ethoxyresorufin O-deethylase and 7-benzoxyresorufin O-debenzylase in freshly cut rat liver slices produced by the two tissue slicers. However, levels of oxidized glutathione (GSSG) were significantly greater in liver slices produced with the Brendel-Vitron tissue slicer. 3. Precision-cut rat liver slices produced with both tissue slicers were cultured for 0 (i.e. a 1-h preincubation), 24 and 72 h in a dynamic organ culture system in an atmosphere of either 95% 02/5% CO2 or 95% air/5% CO2. 4. Apart from small differences in glutathione levels in 0 and 24 h cultured liver slices, no significant differences were observed in the parameters measured between liver slices prepared with both tissue slicers and cultured in both gas phases. 5. With liver slices produced by both tissue slicers 50 microM sodium arsenite produced a greater induction of heat shock protein 70 levels in slices cultured for 24 h in a high oxygen than in an air atmosphere. 6. These results suggest that both tissue slicers can readily produce precision-cut liver slices for studies of xenobiotic metabolism and toxicity. However, the data suggest that for any given application of precision-cut tissue slices it is desirable to establish optimal culture conditions
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PMID:Use of precision-cut rat liver slices for studies of xenobiotic metabolism and toxicity: comparison of the Krumdieck and Brendel tissue slicers. 960

In the present study, we studied the signal transduction mechanism that is involved in the expression of c-Jun protein evident after exposure of rat liver epithelial RL34 cells to the major end product of oxidized fatty acid metabolism, 4-hydroxy-2-nonenal (HNE). HNE treatment of the cells resulted in depletion of intracellular glutathione (GSH) and in the formation of protein-bound HNE in plasma membrane. In addition, HNE strongly induced intracellular peroxide production, suggesting that HNE exerted oxidative stress on the cells. Potent expression of c-Jun occurred within 30 min of HNE treatment, which was accompanied by a time-dependent increase in activator protein-1 (AP-1) DNA binding activity. We found that HNE caused an immediate increase in tyrosine phosphorylation in RL34 cells. In addition, HNE strongly induced phosphorylation of c-Jun N-terminal kinases (JNK) and p38 mitogen-activated protein kinases and also moderately induced phosphorylation of extracellular signal-regulated kinases. The phosphorylation of JNK was accompanied by a rapid and transient increase in JNK and p38 activities, whereas changes in the activity of extracellular signal-regulated kinase were scarcely observed. GSH depletion by L-buthionine-S, R-sulfoximine, a specific inhibitor of GSH biosynthesis, only slightly enhanced peroxide production and JNK activation, suggesting that HNE exerted these effects independent of GSH depletion. This and the findings that (i) HNE strongly induced intracellular peroxide production, (ii) HNE-induced JNK activation was inhibited by pretreatment of the cells with a thiol antioxidant, N-acetylcysteine, and (iii) H2O2 significantly activated JNK support the hypothesis that pro-oxidants play a crucial role in the HNE-induced activation of stress signaling pathways. In addition, we found that, among the inhibitors of tyrosine kinases, cyclooxygenase, and Ca2+ influx, only quercetin exerted a significant inhibitory effect on HNE-induced JNK activation. In light of the JNK-dependent induction of c-jun transcription and the AP-1-induced transcription of xenobiotic-metabolizing enzymes, these data may show a potential critical role for JNK in the induction of a cellular defense program against toxic products generated from lipid peroxidation.
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PMID:Activation of stress signaling pathways by the end product of lipid peroxidation. 4-hydroxy-2-nonenal is a potential inducer of intracellular peroxide production. 989 Sep 86

Humans ingest about 1 g of flavonoids daily in their diet, and they are increasingly being associated with cytoprotective antitumour properties. The mechanism(s) responsible for these effects have not yet been elucidated but may involve interaction with xenobiotic metabolising enzymes to alter the metabolic activation of potential carcinogens. We have investigated the effect of the flavonoids, quercetin (Q), myricetin (M) and epicatechin (E) on the growth, morphology and enzyme activities of MCF7 human breast cancer cells. Of the three flavonoids studied only Q caused a decrease in cell protein content and decreased the reduction of MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium). It also inhibited protein, DNA and RNA synthesis to the greatest extent. Q and M increased intracellular reduced glutathione (GSH) content, and Q altered the morphology of the cells after 24 h exposure to 25 microM. E and Q inhibited the O-deethylation of ethoxyresorufin (EROD) catalysed by cytochrome P450 CYPIA. In contrast, M increased the EROD reaction 2-fold. Q increased the activity of DT-diaphorase, NADPH cytochrome c reductase and glutathione reductase, while E increased only NADPH cytochrome c reductase activity. The effects on enzyme activities in vitro suggest that there is not only the potential for flavonoids to alter metabolic activation of carcinogens but also of therapeutically administered drugs in vivo. We are at present investigating the synergy between anti-cancer drugs and flavonoids in terms of anti-tumour efficacy.
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PMID:The effect of the flavonoids, quercetin, myricetin and epicatechin on the growth and enzyme activities of MCF7 human breast cancer cells. 992 Apr 63

Oxidants play a key role in disease processes, particularly in the detrimental mechanisms leading to tissue damage in certain forms of acute lung injury. A number of mediators contribute to the pathologic response in ARDS, SIRS or hyperoxia-induced pulmonary damage. One of the most important detrimental factors is the generation and activation of highly reactive oxygen species which are leading factors implicated in the process of tissue damage. N-acetylcysteine (NAC) is a free radical scavenger and might access the endothelial cell thus increasing intracellular glutathione (GSH) stores. Different studies have demonstrated that NAC might be a promising compound either for the prevention or the treatment of acute lung damages such as ARDS. However, the true beneficial effect so far reported in several clinical and experimental studies contrasts with some contradictory and intriguing aspects, probably because the significance of a direct in vivo antioxidative effect of this compound remains to be established in humans. Thus, the mode of action of NAC may not be the same in different pathologies and clinical situations. More research into the mechanisms of action of this unique xenobiotic substance may offer a clue for elucidating these controversies.
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PMID:[Therapeutic use of N-acetylcysteine in acute lung diseases]. 1009 Dec 58


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