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:2.5.1.18 (glutathione S-transferase)
22,582 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Zerumbone (ZER), a sesquiterpene compound occurring in tropical ginger Zingiber zerumbet Smith, has been implicated as one of the promising chemopreventive agents against colon and skin cancer. In the present study, we investigated the phase II detoxification enzymes induction of ZER using a cultured rat normal liver epithelial cell line. Exposure of RL34 cells to ZER resulted in the significant induction of glutathione S-transferase, while the reduced analogues of ZER (alpha-humulene and 8-hydroxy-alpha-humulene) did not show any inducing effect. Therefore, the electrophilic property, characterized by the reactivity with intracellular nucleophiles including protein sulfhydryls as well as low molecular weight thiols, at the 8-position alpha,beta-unsaturated carbonyl group plays an important role in the induction of phase II enzymes. ZER induced nuclear localization of the transcription factor Nrf2 that binds to antioxidant response element (ARE) of the phase II enzyme genes, suggesting that ZER is a potential activator of the Nrf2/ARE-dependent detoxification pathway. This is consistent with the observation that ZER potentiated the gene expression of several Nrf2/ARE-dependent phase II enzyme genes, including gamma-glutamylcysteine synthetase, glutathione peroxidase, and hemeoxygenase-1. The present study also implied the antioxidant role of this detoxification system activation by ZER in the neutralization of lipid peroxidation in hepatocytes, providing a new insight for cancer prevention.
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PMID:Zerumbone, a tropical ginger sesquiterpene, activates phase II drug metabolizing enzymes. 1530 56

The proinflammatory effects of particulate pollutants, including diesel exhaust particles (DEP), are related to their content of redox cycling chemicals and their ability to generate oxidative stress in the respiratory tract. An antioxidant defense pathway, which involves phase II enzyme expression, protects against the pro-oxidative and proinflammatory effects of DEP. The expression of enzymes, including heme oxygenase-1 (HO-1) and GST, is dependent on the activity of a genetic antioxidant response element in their promoters. In this study we investigated the mechanism by which redox cycling organic chemicals, prepared from DEP, induce phase II enzyme expression as a protective response. We demonstrate that aromatic and polar DEP fractions, which are enriched in polycyclic aromatic hydrocarbons and quinones, respectively, induce the expression of HO-1, GST, and other phase II enzymes in macrophages and epithelial cells. We show that HO-1 expression is mediated through accumulation of the bZIP transcription factor, Nrf2, in the nucleus, and that Nrf2 gene targeting significantly weakens this response. Nrf2 accumulation and subsequent activation of the antioxidant response element is regulated by the proteasomal degradation of Nrf2. This pathway is sensitive to pro-oxidative and electrophilic DEP chemicals and is also activated by ambient ultrafine particles. We propose that Nrf2-mediated phase II enzyme expression protects against the proinflammatory effects of particulate pollutants in the setting of allergic inflammation and asthma.
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PMID:Nrf2 is a key transcription factor that regulates antioxidant defense in macrophages and epithelial cells: protecting against the proinflammatory and oxidizing effects of diesel exhaust chemicals. 1532 12

The tripeptide glutathione (GSH) represents the major brain thiol and is essential for prevention of oxidative stress. Using monochlorobimane to label intracellular GSH in a glutathione S-transferase catalyzed reaction we have examined the kinetics of GSH metabolism including its rate of conjugation, total GSH content, synthesis, and efflux in astrocyte cultures under basal conditions and after induction of antioxidant response element (ARE)-mediated gene expression by the transcription factor Nrf2. In the presence of a cerebral spinal fluid-like salt solution astrocytes could not synthesize detectable levels of GSH. Addition of GSH precursors, cystine, glutamate, and glycine, rapidly restored GSH synthesis. Astrocytes were able to use either glutamate or glutamine as precursors equally for GSH synthesis. Using the small molecule chemical inducer tert-butylhydroqunione (tBHQ) we report that induction of ARE-mediated gene expression is associated with a coordinated increase in GSH content and synthesis rate with little effect on the rate of GSH conjugation or efflux. Consistent with the effect of the inducer, adenovirus-mediated overexpression of the transcription factor Nrf2 that mediates tBHQ's effects also increased GSH content, confirming that GSH metabolism can be regulated by the Nrf2 pathway.
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PMID:Coordinate regulation of glutathione metabolism in astrocytes by Nrf2. 1558 88

Transcription factor Nrf2 regulates gene expression of drug metabolizing enzymes such as glutathione S-transferase via the antioxidant response element, ARE. Aldose reductase (AR), a member of the aldo-keto reductase (AKR) superfamily, metabolizes various endogenous and exogenous aldehydes. The AR gene 5'-flanking region contains a multiple stress response region (MSRR) composed of two putative AREs (ARE1 and ARE2), an AP1 site, and a tonicity response element (TonE). As this region is highly conserved among species, we examined the involvement of Nrf2 in transcriptional regulation of the AR gene. beta-Naphthoflavone, an Nrf2 activator, elevated the level of AR mRNA in HepG2 cells and increased the promoter activity of the mouse AR (AKR1B3) gene. The promoter activity of the AKR1B3 gene, containing MSRR, was also augmented by overexpression of Nrf2. Deletion and mutation analyses indicated that both ARE1 and the AP1 site were essential for the responsiveness to Nrf2, while ARE2 was nonfunctional. The presence of an ARE1 binding protein complex was revealed by electrophoretic mobility shift assay. These findings indicate that Nrf2 regulates the AKR1B3 promoter activity via ARE1 and the AP1 site.
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PMID:Transcription factor Nrf2 regulates promoter activity of mouse aldose reductase (AKR1B3) gene. 1565 94

Exposure of cells to a wide variety of chemoprotective compounds confers resistance to a broad set of carcinogens. For a subset of the chemoprotective compounds, protection is generated by an increase in the abundance of phase 2 detoxification enzymes such as glutathione S-transferases (GSTs). Transcription factor Nrf2, which is sequestered in the cytoplasm by Keap1 (Kelch-like ECH-associated protein-1) under unstimulated conditions, regulates the induction of phase 2 enzymes. In this study, to explore the role of the proteasome in the detoxification response, we tested the effect of proteasome inhibitors such as MG132, clasto-lactacystin beta-lactone, and lactacystin on the induction of GST isozymes and found that these inhibitors selectively induced the class Pi GST isozyme (GST P1). Down-regulation of the proteasome by antisense oligonucleotides or RNA interference indeed resulted in significant up-regulation of GST P1, suggesting that a decline in the proteasome activity could be directly or indirectly linked to the induction of GST P1. From the functional analysis of various deletion constructs of the upstream regulatory region of the GST P1 promoter, GST P1 enhancer I was identified as the response element for proteasome inhibition. Overexpression of the wild-type and dominant-negative forms of Nrf2 and Keap1 had little effect on the induction of GST P1 not only by the proteasome inhibitor, but also by phase 2-inducing isothiocyanate, suggesting that there may be a process of GST P1 induction distinct from other phase 2 gene induction mechanisms. Because GST P1 is highly and specifically induced during early hepatocarcinogenesis as well as in hepatocellular carcinoma cells, these data may provide a potential critical role for the proteasome in the induction of a cellular defense program associated with carcinogenesis.
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PMID:Selective induction of the tumor marker glutathione S-transferase P1 by proteasome inhibitors. 1586 7

Tetrafluoroethylcysteine (TFEC), a metabolite of the industrial gas tetrafluoroethylene, can cause both nephrotoxicity and limited hepatotoxicity in animal models, and this is associated with the covalent modification of specific intramitochondrial proteins including heat shock protein 60 (HSP60), mitochondrial HSP70 (mtHSP70), aspartate aminotransferase (AST), aconitase, and alpha-ketoglutarate dehydrogenase (alphaKGDH). Using the murine TAMH cell line as a useful in vitro model for TFEC toxicity, we demonstrate a rapid and sustained induction of Nrf2, a member of the "cap-and-collar" transcription factor family, following exposure to cytotoxic concentrations of TFEC. A functional correlate was also established with the rapid translocation of cytosolic Nrf2 into the nucleus. In addition, transcriptional and translational upregulation of known Nrf2 regulated genes including glutamate cysteine ligase (GCL), both catalytic and modulatory subunits, heme oxygenase-1, and glutathione S-transferase (GST) isoforms were detected. While Nrf2 activation is often linked to perturbation of cellular thiol status and/or oxidative stress, we were unable to detect any significant depletion of cellular glutathione or oxidation of mitochondrial membrane cardiolipin or increases in reactive oxygen species (ROS). These data suggest Nrf2 activation is likely independent of classical oxidative stress or, at best, a result of a transient, low-level redox stress. Moreover, supporting evidence indicates an early endoplasmic reticular (ER) stress response after TFEC treatment, with a time-dependent upregulation of the ER responsive genes gadd34, gadd45, gadd153, and ndr1 . These findings suggest an alternative pathway for Nrf2 activation, i.e., Nrf2 phosphorylation through ER-mediated protein kinases such as PKR-like endoplasmic reticular kinase (PERK). Overall, the results implicate a role for Nrf2 in the cellular response to TFEC toxicity and suggest a previously unrecognized role for the ER in this model of mitochondrially initiated cytotoxicity.
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PMID:Nrf2 activation involves an oxidative-stress independent pathway in tetrafluoroethylcysteine-induced cytotoxicity. 1590 13

One of the rational and effective strategies for chemoprevention is the blockade of DNA damage caused by carcinogenic insult. This can be achieved either by reducing the formation of reactive carcinogenic species or stimulating their detoxification. A wide spectrum of xenobiotic metabolizing enzymes catalyze both phase I (oxidation and reduction) and phase II biotransformation (conjugation) reactions involved in carcinogen activation and/or deactivation. Several antioxidant-response element (ARE)-regulated gene products such as glutathione S-transferase, NAD(P)H:quinone oxidoreductase 1, UDP-glucuronosyltransferase, gamma-glutamate cysteine ligase, and hemeoxygenase-1 are known to mediate detoxification and/or to exert antioxidant functions thereby protecting cells from genotoxic damage. The transcription of ARE-driven genes is regulated, at least in part, by nuclear transcription factor erythroid 2p45 (NF-E2)-related factor 2 (Nrf2), which is sequestered in cytoplasm by Kelch-like ECH-associated protein 1 (Keap1). Exposure of cells to ARE inducers results in the dissociation of Nrf2 from Keap1 and facilitates translocation of Nrf2 to the nucleus, where it heterodimerizes with small Maf protein, and binds to ARE, eventually resulting in the transcriptional regulation of target genes. The Nrf2-Keap1-ARE signaling pathway can be modulated by several upstream kinases including phosphatidylinositol 3-kinase, protein kinase C, and mitogen-activated protein kinases. Selected Nrf2-Keap1-ARE activators, such as oltipraz, anethole dithiolethione, sulforaphane, 6-methylsulphinylhexyl isothiocyanate, curcumin, caffeic acid phenethyl ester, 4'-bromoflavone, etc. are potential chemopreventive agents. This mini-review will focus on a chemopreventive strategy directed towards protection of DNA and other important cellular molecules by inducing de novo synthesis of phase II detoxifying or antioxidant genes via the Nrf2-ARE core signaling pathway.
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PMID:Nrf2 as a novel molecular target for chemoprevention. 1591 68

Modulation of drug metabolizing enzymes, leading to facilitated elimination of carcinogens represents a successful strategy for cancer chemoprevention. Nitric oxide-donating aspirin (NO-ASA) is a promising agent for the prevention of colon and other cancers. We studied the effect of NO-ASA on drug metabolizing enzymes in HT-29 human colon adenocarcinoma and Hepa 1c1c7 mouse liver adenocarcinoma cells and in Min mice treated with NO-ASA for 3 weeks. In these cell lines, NO-ASA induced the activity and expression of NAD(P)H:quinone oxireductase (NQO) and glutathione S-transferase (GST). Compared with untreated Min mice, NO-ASA increased in the liver the activity (nmol/min/mg; mean+/-SEM for all) of NQO (85+/-6 versus 128+/-11, P<0.05) and GST (2560+/-233 versus 4254+/-608, P<0.005) and also in the intestine but not in the kidney; the expression of NQO1 and GST P1-1 was also increased. NO-ASA had only a marginal effect on P450 1A1 and P450 2E1, two phase I enzymes. The release of NO from NO-ASA, determined with a selective microelectrode was paralleled by the induction of NQO1 and abrogated by NO scavengers; an exogenous NO donor also induced the expression of NQO1. NO-ASA induced concentration-dependently the translocation of Nrf2 into the nucleus as documented by immunofluorescence and immunoblotting; this paralleled the induction of NQO1 and GST P1-1. Thus NO-ASA induces phase II enzymes, at least in part, through the action of NO that it releases and by modulating the Keap1-Nrf2 pathway; this effect may be part of its mechanism of action against colon and other cancers.
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PMID:NO-donating aspirin induces phase II enzymes in vitro and in vivo. 1626 95

Placental glutathione S-transferase (GST-P), a member of glutathione S-transferase, is known for its specific expression during rat hepatocarcinogenesis and has been used as a reliable tumor marker for experimental rat hepatocarcinogenesis. To explain the molecular mechanism underlying its specific expression concomitant with the malignant transformation, we have analyzed the regulatory element of the GST-P gene and the transcription factor that binds to this element. From the extensive analyses by the establishment of the transgenic rat lines having various regions of GST-P gene, we could identify the GPE1 as an essential enhancer element for specific GST-P expression. Next, we examined the transcription factor that binds and activates the GPE1, specifically in the early stage of hepatocarcinogenesis and in the hepatoma. Electrophoresis gel mobility shift assay, reporter transfection analysis, and the chromatin immunoprecipitation analysis indicate that the Nrf2/MafK heterodimer binds and activates GPE1 element in preneoplastic lesions and hepatomas but not in the normal liver cells. In this chapter, we describe details of the transgenic rat analyses and the identification of a factor responsible for the specific expression of the GST-P gene and discuss a possible molecular scenario for malignant transformation and tumor marker gene expression.
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PMID:Regulation of GST-P gene expression during hepatocarcinogenesis. 1639 78

We investigated the cytoprotective mechanisms of flunarizine in cisplatin-induced death of auditory cells. Concomitant with an increase in viability, treatment with flunarizine resulted in a marked dissociation of Nrf2/Keap1 and subsequent intranuclear translocation of Nrf2, which was mediated by PI3K-Akt signaling. Overexpression of Nrf2 protected cells from cisplatin along with transcriptional activation of ARE to generate heme oxygenase-1 (HO-1). Pretreatment with flunarizine predominantly increased the transcriptional activity of HO-1 among Nrf2-driven transcripts, including HO-1, NQO1, GCLC, GCLM, GST micro-1, and GSTA4. Furthermore, both pharmacological inhibition and siRNA transfection of HO-1 completely abolished the flunarizine-mediated protection of HEI-OC1 cells and the primary rat (P2) organ of Corti explants from cisplatin. These results suggest that Nrf2-driven transcriptional activation of ARE through PI3K-Akt signaling augments the generation of HO-1, which may be a critically important determinant in cellular response toward cisplatin and the cytoprotective effect of flunarizine against cisplatin.
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PMID:Flunarizine induces Nrf2-mediated transcriptional activation of heme oxygenase-1 in protection of auditory cells from cisplatin. 1648 34


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