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)

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.
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PMID: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. 1582 14

The human alpha class glutathione S-transferases (GSTs) consist of 5 genes, hGSTA1-hGSTA5, and 7 pseudogenes on chromosome 6p12.1-6p12.2. hGSTA1-hGSTA4 have been well characterized as proteins, but hGSTA5 has not been detected as a gene product. hGSTA1-1 (and to a lesser extent hGSTA2-2) catalyzes the GSH-dependent detoxification of carcinogenic metabolites of environmental pollutants and tobacco smoke (e.g., polycyclic aromatic hydrocarbon diolepoxides) and several alkylating chemotherapeutic agents and has peroxidase activity toward fatty acid hydroperoxides (FA-OOH) and phosphatidyl FA-OOH. hGSTA3-3 has high activity for the GSH-dependent Delta(5)-Delta(4) isomerization of steroids, and hGSTA4-4 has high activity for the GSH conjugation of 4-hydroxynonenal. hGSTA4 is expressed in many tissues; hGSTA1-1 and hGSTA2-2 are expressed at high levels in liver, intestine, kidney, adrenal gland, and testis; and hGSTA3 is expressed in steroidogenic tissues. Functional, allelic, single nucleotide polymorphisms occur in an SP1-binding element of hGSTA1 and in the coding regions of hGSTA2 and hGSTA3. The main effects of these polymorphisms are the low hepatic expression of hGSTA1 in individuals homozygous for hGSTA1*B and the low specific activity of the hGSTA2E-2E variant toward FA-OOH. These properties suggest that alpha class GSTs will be involved in susceptibility to diseases with an environmental component (such as cancer, asthma, and cardiovascular disease) and in response to chemotherapy. Although hGSTM1, hGSTT1, and hGSTP1 have been associated with such diseases (on the basis of genetic polymorphisms as indicators of expression), alpha class GSTs have been little studied in this respect. Nevertheless, hGSTA1*B has been associated with increased susceptibility to colorectal cancer and with increased efficacy of chemotherapy for breast cancer. Methods for identification and quantitation of human alpha class GST protein, mRNA, and genotype are reviewed, and the potential for GST-alpha in plasma to be used as a marker for hepatic expression and induction is discussed.
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PMID:Human alpha class glutathione S-transferases: genetic polymorphism, expression, and susceptibility to disease. 1639 77

The mitochondrial environment is rich in reactive oxygen species (ROS) that may ultimately peroxidize membrane proteins and generate unsaturated aldehydes such as 4-hydroxy-2-nonenal (4HNE). We had previously demonstrated the presence of hGSTA4-4, an efficient catalyst of 4HNE detoxification, in human liver mitochondria to the exclusion of the cytosol. In the present study, GSH-affinity chromatography was used in conjunction with biochemical and proteomic analysis to determine the presence of additional cytosolic glutathione S-transferases (GSTs) in human hepatic mitochondria. HPLC-subunit analysis of GSH affinity-purified liver mitochondrial proteins indicated the presence of several potential mitochondrial GST isoforms. Electrospray ionization-mass spectrometry analysis of eluted mitochondrial GST subunits yielded molecular masses similar to those of hGSTP1, hGSTA1 and hGSTA2. Octagonal matrix-assisted laser desorption/ionization time of flight mass spectrometry and proteomics analysis using MS-FIT confirmed the presence of these three GST subunits in mitochondria, and HPLC analysis indicated that the relative contents of the mitochondrial GST subunits were hGSTA1>hGSTA2>hGSTP1. The mitochondrial localization of the alpha and pi class GST subunits was consistent with immunoblotting analysis of purified mitochondrial GST. Enzymatic studies using GSH-purified mitochondrial GST fractions demonstrated the presence of significant GST activity using the nonspecific GST substrate 1-chloro-2,4-dinitrobenzene (CDNB), as well as 4HNE, delta(5)-androstene-3,17-dione (ADI), and cumene hydroperoxide (CuOOH). Interestingly, the specific mitochondrial GST activities toward 4HNE, a highly toxic alpha,beta-unsaturated aldehyde produced during the breakdown of membrane lipids, exceeded that observed in liver cytosol. These observations are suggestive of a role of GST in protecting against mitochondrial injury during the secondary phase of oxidative stress, or modulation of 4HNE-mediated mitochondrial signaling pathways. However, other properties of mitochondrial GST, such as conjugation of environmental chemicals and binding of lipophilic non-substrate xenobiotics and endogenous compounds, remain to be investigated.
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PMID:Several glutathione S-transferase isozymes that protect against oxidative injury are expressed in human liver mitochondria. 1661 95

Endogenous lipid peroxidation (LPO)-derived aldehydes accumulate in human skin after photoexposure and contribute to the development of skin cytotoxicity and cancer. This study employed LC-ESI-MS and HPLC-UV-DAD techniques to investigate the effect of UVB radiation on the biotransformation and detoxification of the prototype aldehyde 4-hydroxy-2-trans-nonenal (HNE) using the human keratinocyte cell line (NCTC 2544). In parallel we followed the keratinocytes' cytotoxic response to HNE through morphological analysis and cell viability assay. In UVB-unstressed keratinocytes, even a supraphysiological dose of the aldehyde (200 microM) was rapidly and completely cleared in metabolized form (free and GSH-conjugated metabolites) from the cell, with no signs of cytotoxicity. By contrast, UVB preexposure already at 1 MED (50 mJ/cm2, the minimal erythemal dose in humans) markedly impaired HNE metabolism. After 2 h of incubation, the relative amount of GSH-conjugated adducts dose-dependently dropped from 44% (unirradiated cells) to 22% at 3 MED as a consequence of UVB-induced GSH depletion (no impairment of GST A4.4 nor of G6PD activities was observed). The levels of free metabolites, 1,4-dihydroxy-trans-nonene (DHN) and 4-hydroxy-trans-2-nonenoic acid (HNA), were modified (+30% DHN, -22% HNA) only at 3 MED, in parallel to the AR and ALDH enzyme activity modulation. In addition, a dose-dependent increase of unmodified HNE was found in the extracellular medium, paralleled by a significant fraction of the HNE-incubated dose not recovered at the intra- or extracellular level. The impairment of HNE metabolism paralleled a dramatic cytotoxic response. These results provide a reasonable explanation for the massive accumulation of carbonyl toxins in human skin in vivo after photoexposure and shed light on the detrimental effects of UVB radiation in the presence of unmetabolized LPO metabolites.
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PMID:Effects of UVB radiation on 4-hydroxy-2-trans-nonenal metabolism and toxicity in human keratinocytes. 1730 72

cis-6-(2-Acetylvinylthio)purine (cAVTP) and trans-6-(2-acetylvinylthio)guanine (tAVTG) are thiopurine prodrugs provisionally inactivated by an alpha,beta-unsaturated substituent on the sulfur of the parental thiopurines 6-mercaptopurine (6-MP) and 6-thioguanine (6-TG). The active thiopurines are liberated intracellularly by glutathione (GSH) in reactions catalyzed by glutathione transferases (GSTs) (EC 2.5.1.18). Catalytic activities of 13 human GSTs representing seven distinct classes of soluble GSTs have been determined. The bioactivation of cAVTP and tAVTG occurs via a transient addition of GSH to the activated double bond of the S-substituent of the prodrug, followed by elimination of the thiopurine. The first of these consecutive reactions is rate-limiting for thiopurine release, but GST-activation of this first addition is shifting the rate limitation to the subsequent elimination. Highly active GSTs reveal the transient intermediate, which is detectable by UV spectroscopy and HPLC analysis. LC/MS analysis of the reaction products demonstrates that the primary GSH conjugate, 4-glutathionylbuten-2-one, can react with a second GSH molecule to form the 4-(bis-glutathionyl)butan-2-one. GST M1-1 and GST A4-4 were the most efficient enzymes with tAVTG, and GST M1-1 and GST M2-2 had highest activity with cAVTP. The highly efficient GST M1-1 is polymorphic and is absent in approximately half of the human population. GST P1-1, which is overexpressed in many cancer cells, had no detectable activity with cAVTP and only minor activity with tAVTG. Other GST-activated prodrugs have targeted GST P1-1-expressing cancer cells. Tumors expressing high levels of GST M1-1 or GST A4-4 can be predicted to be particularly vulnerable to chemotherapy with cAVTP or tAVTG.
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PMID:Human glutathione transferases catalyzing the bioactivation of anticancer thiopurine prodrugs. 1743 63

The aflatoxin B(1)-8,9-epoxide (AFBO) is hepatocarcinogenic intermediate of aflatoxin B(1) (AFB(1)) and is detoxified by glutathione S-transferases (GSTs). In this study, we investigated whether sulforaphane (SFN) could increase the rate of conjugation between AFBO and glutathione (GSH) as well as which of the GST isozymes were involved in the conjugation reaction. The conjugation potential was inhibited dose dependently with curcumin, an inhibitor of GSTs. SFN induced the expression of GST A3, GST A4, GST M1, GST P1, and GST T1 in alpha mouse line (AML) 12 cells. The cells treated with SFN (10 microM) for 12 h showed a 35-fold increase in conjugation potential of AFBO with GSH compared with the vehicle-treated cell. The conjugation potential was blocked partially by transfection of cells with siRNAs against each of the GST isozymes. The activity of GST A3 had the strongest effect on the conjugation potential. SFN treatment also increased total GST activity detected with 1-chloro-2,4-dinitrobenzene (CDNB) up to 4.3-fold. The induction fold was much lower than that detected with AFBO. These results suggest that the chemopreventive effect of SFN on the decomposition of AFBO is related to the upregulation of several GST isozymes genes. The increase of GST activity by SFN was extremely specific toward the conjugation reaction of AFBO compared with CDNB. Therefore, this system for detecting GST activity seems to be an excellent method for screening chemopreventive compounds toward AFB(1) toxicity.
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PMID:Sulforaphane induces glutathione S-transferase isozymes which detoxify aflatoxin B(1)-8,9-epoxide in AML 12 cells. 2081 11

4-Hydroxy-2-trans-nonenal (HNE) is a lipid peroxidation product that contributes to the pathophysiology of several diseases with components of oxidative stress. The electrophilic nature of HNE results in covalent adduct formation with proteins, fatty acids and DNA. However, it remains unclear whether enzymes that metabolize HNE avoid inactivation by it. Glutathione transferase A4-4 (GST A4-4) plays a significant role in the elimination of HNE by conjugating it with glutathione (GSH), with catalytic activity toward HNE that is dramatically higher than the homologous GST A1-1 or distantly related GSTs. To determine whether enzymes that metabolize HNE resist its covalent adduction, the rates of adduction of these GST isoforms were compared and the functional effects of adduction on catalytic properties were determined. Although GST A4-4 and GST A1-1 have striking structural similarity, GST A4-4 was insensitive to adduction by HNE under conditions that yield modest adduction of GST A1-1 and extensive adduction of GST P1-1. Furthermore, adduction of GST P1-1 by HNE eliminated its activity toward the substrates 1-chloro-2,4-dinitrobenzene (CDNB) and toward HNE itself. HNE effects on GST A4-4 and A1-1 were less significant. The results indicate that enzymes that metabolize HNE may have evolved structurally to resist covalent adduction by it.
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PMID:Glutathione transferase A4-4 resists adduction by 4-hydroxynonenal. 2083 86

4-Hydroxynonenal (HNE) is an end product of lipoperoxidation with antiproliferative and proapoptotic properties in various tumors. Here we report a greater sensitivity to HNE in PC3 and LNCaP cells compared to DU145 cells. In contrast to PC3 and LNCaP cells, HNE-treated DU145 cells showed a smaller reduction in growth and did not undergo apoptosis. In DU145 cells, HNE did not induce ROS production and DNA damage and generated a lower amount of HNE-protein adducts. DU145 cells had a greater GSH and GST A4 content and GSH/GST-mediated HNE detoxification. Nuclear factor erythroid 2-related factor-2 (Nrf2) is a regulator of the antioxidant response. Nrf2 protein content and nuclear accumulation were higher in DU145 cells compared to PC3 and LNCaP cells, whereas the expression of KEAP1, the main negative regulator of Nrf2 activity, was lower. Inhibition of Nrf2 expression with specific siRNA resulted in a reduction in GST A4 expression and GS-HNE formation, indicating that Nrf2 controls HNE metabolism. In addition, Nrf2 knockdown sensitized DU145 cells to HNE-mediated antiproliferative and proapoptotic activity. In conclusion, we demonstrated that increased Nrf2 activity resulted in a reduction in HNE sensitivity in prostate cancer cells, suggesting a potential mechanism of resistance to pro-oxidant therapy.
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PMID:Nuclear factor erythroid 2-related factor-2 activity controls 4-hydroxynonenal metabolism and activity in prostate cancer cells. 2181 20


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