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:1.6.5.2 (NQO1)
6,196 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Inducibility of oxidative stress in rat liver in vivo by menadione-associated redox cycling activation under redox enzyme modulating conditions was examined by monitoring hepatocyte injury and 8-hydroxydeoxyguanosine (8-OHdG) levels of liver DNA. In addition, the treatment-associated liver tumor initiating activity was assessed in terms of development of gamma-glutamyl-transpeptidase (GGT)- and glutathione S-transferase placental form (GST-P)-positive foci and hyperplastic nodules. With or without following menadione treatment (50 mg/kg, i.g.), redox enzyme modulations of increased cytochrome P450 reductase activity induced by phenobarbital (PB)-Na (100 mg/kg, i.p. for 5 days), inhibition of DT-diaphorase by dicumarol (25 mg/kg, i.p.) and depletion of glutathione by phorone (200 mg/kg, i.p.), with or without further supplement of iron EDTA-Na-Fe(III) (70 mg/kg, i.p.), caused both substantial hepatocyte necrosis and 8-OHdG production in Fischer 344 male rats. Subsequent feeding with a 0.05% PB diet for 64 weeks resulted in slightly increased development of GGT-positive foci but not GST-P positive lesions or hyperplastic nodules, suggesting a lack of tumor-initiating activity of the oxidative DNA damage associated with redox enzyme modulations with or without menadione.
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PMID:Induction of 8-hydroxydeoxyguanosine but not initiation of carcinogenesis by redox enzyme modulations with or without menadione in rat liver. 170 52

In the present study, we investigated Phase I (cytochrome P450; DT-diaphorase, DTD) and Phase II (epoxide hydrolase, EH; glutathione-S-transferases, GSTs) enzymes in normal colon from patients without colorectal adenocarcinoma and in peritumoral and tumoral tissues from patients with colorectal adenocarcinoma. No significant changes in levels of cytochrome P450IIIA4 (the only P450 detectable in this tissue), EH, GSTs and DTD activity were found between normal and peritumoral tissues. In tumoral tissue, compared with peritumoral tissues, we observed significant decreases in cytochrome P450IIIA4 (-50%, P less than 0.002) and EH (-60%, P less than 0.03), no change in DTD activity and significant increases in GST pi (+40%, P less than 0.03) and total GST activity (+30%, P less than 0.01). The numerous changes observed in tumoral tissues suggest that variations in drug-metabolizing enzyme expression in colorectal adenomatous polyps could represent pretumoral markers. Moreover, a better understanding of the expression of these enzymes in tumoral tissues would help us to choose the most appropriate colon tumor cell lines for the testing of new anti-cancer drugs.
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PMID:Drug-metabolizing enzyme expression in human normal, peritumoral and tumoral colorectal tissue samples. 202 56

The level of quinone oxidoreductases (microsomal and cytosolic DT-diaphorase, NADPH-cytochrome P450 reductase and NADH-cytochrome b5 reductase), superoxide dismutase and glutathione-related enzymatic activities in diethylstilbestrol (DES)-induced carcinogenesis in kidney from Syrian golden hamsters are presented. Animals that exhibited two different stages of DES-induced carcinogenesis in kidney--pre- and neoplastic lesions and tumorous lesions (after 6 and 8 months of continuous exposure to DES respectively)--were studied in comparison to kidneys from control animals. A dramatic decrease in microsomal and cytosolic DT-diaphorase activities (13.6 and 37.8% of controls), as well as in glutathione disulphide reductase (39.5%), and less marked in superoxide dismutase (45.6%), NADH cytochrome b5 reductase (61.9%) glutathione transferase (GST) towards 1-chloro-2,4-dinitrobenzene (CDNB) (66.2%) and glutathione peroxidase (GSH-Px) (80%) activities, were observed in kidneys with pre- and neoplastic lesions. NADPH-cytochrome P450 reductase and GST activity towards 4-hydroxy-2,3-trans-nonenal (4-HNE) showed no statistically significant variation at this stage of carcinogenesis. In kidney from animals with tumorous lesions, all the enzymatic activities mentioned above decreased, except for superoxide dismutase, which was increased to 186% of the control activity. GST activity towards 4-HNE again showed no statistically significant variation. These results suggest that if one-electron reduction of diethylstilbestrol-4',4''-quinone (DESQ) occurs, it may play a very important role in the development of DES carcinogenesis (pre- and neoplastic lesions), since at this stage of carcinogenesis the primary defense mechanisms against the oxygen free radicals generated in this way, i.e. SOD activity, is reduced to less than a half of control values. Both cytosolic and microsomal DT-diaphorase activities are unable at this stage of carcinogenesis to promote effectively the two-electron reduction of DESQ, which would avoid the initial formation of superoxide anion. The consequences of these decreases may be an increased steady-state concentration of superoxide anion and hydrogen peroxide, which in the presence of iron might lead to lipid peroxidation. GST activity towards 4-HNE could be responsible for the possible higher steady-state concentration of this lipid peroxidation product during DES treatment. The induction of DT-diaphorase and its protective role in the prevention of the development of pre- and neoplastic lesions in kidney from Syrian golden hamster during DES treatment is also discussed.
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PMID:The levels of quinone reductases, superoxide dismutase and glutathione-related enzymatic activities in diethylstilbestrol-induced carcinogenesis in the kidney of male Syrian golden hamsters. 211 5

The commonly used spice and flavouring agent, rosemary, derived from the leaves of the plant Rosmarinus officinalis L., displays antioxidant properties in foods and in biological systems. Moreover, in animal models rosemary components were found to inhibit the initiation and tumour promotion phases of carcinogenesis. In this work, we studied the mechanisms by which rosemary components block initiation of carcinogenesis by the procarcinogen benzo[a]pyrene (B[a]P) in human bronchial epithelial cells (BEAS-2B). Whole rosemary extract (6 micrograms/ml) or an equivalent concentration of its most potent antioxidant constituents, carnosol or carnosic acid, inhibited DNA adduct formation by 80% after 6 h co-incubation with 1.5 muM B[a]P. Under similar conditions, cytochrome P450 (CYP) 1A1 mRNA expression was 50% lower in the presence of rosemary components, and CYP1A1 activity was inhibited 70-90%. The observed reduction of DNA adduct formation by rosemary components may mostly result from the inhibition of the activation of benzo[a]pyrene to its ultimate metabolites. Carnosol also affected expression of the phase II enzyme glutathione-S-transferase which is known to detoxify the proximate carcinogenic metabolite of B[a]P. Treatment of BEAS-2B cells with carnosol (1 microgram/ml) for 24 h resulted in a 3- to 4-fold induction of GST pi mRNA. Moreover, expression of a second important phase II enzyme, NAD(P)H: quinone reductase, was induced by carnosol in parallel with GST pi. Therefore, rosemary components have the potential to decrease activation and increase detoxification of an important human carcinogen, identifying them as promising candidates for chemopreventive programs.
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PMID:Rosemary components inhibit benzo[a]pyrene-induced genotoxicity in human bronchial cells. 755 54

Biochemical and histochemical studies were conducted in aflatoxin B1-induced liver tumors in adult rainbow trout. Specific activities of the phase I enzymes, ethoxyresorufin-O-deethylase (EROD), microsomal and cytosolic epoxide hydrolase (mEH and cEH), aldehyde dehydrogenase (ALDH) and DT-diaphorase, and the phase II enzymes, gamma-glutamyltransferase (gamma-GT), glutathione transferase (GST) and uridine diphosphoglucuronyl transferase (UDPGT) were measured. Cryostat sections of tumor and surrounding liver from the same cohorts were analyzed immunohistochemically for cytochrome P450IA1 and histochemically for ALDH (benzaldehyde and hexanal), DT-diaphorase, gamma-GT and uridine diphosphoglucuronyl dehydrogenase (UDPGdH). In tumor tissues, the largest biochemical changes were found with benzaldehyde dehydrogenase, where activity increased from undetectable levels to 7.4 nmol/min/mg protein, and gamma-GT, where activity increased 12-fold over controls. Increases in other enzymes ranged from 1.26 to 2.84 times that of control liver, except EROD, which decreased, and cEH and mEH, which were unchanged. Histochemical analyses showed the induction of ALDH, gamma-GT, DT-diaphorase and UDPGdH, and the depression of cytochrome P450IA1 in hepatic neoplasms. In addition, marker enzyme histochemistry of neoplasms revealed heterogeneous populations of hepatocytes and absence of necrotic areas.
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PMID:Biochemical and histochemical properties of hepatic tumors of rainbow trout, Oncorhynchus mykiss. 809 46

Inducers of Phase II enzymes, already consumed by humans as food additives, medicines or as constituents of vegetables, can prevent experimental carcinogenesis. Since protection is neither carcinogen- nor organ-specific, clinical trials are already underway to establish the efficacy of 'anticarcinogenic enzyme inducers' (i.e. oltipraz). However, efficient and cost-effective assays to establish the dose wherein a putative anticarcinogen can raise Phase II enzyme levels are lacking. We tested the proposal that serum Phase II enzyme activities would be dependent on relative tissue levels by measuring quinone reductase and glutathione S-transferase activities in sera of mice treated with dietary 2(3)-tert-butyl-4-hydroxyanisole (BHA) or dimethyl fumarate. Serum activities were significantly elevated in animals with increased tissue specific activities of these Phase II enzymes. Increasing concentrations of BHA in the diet from 0.05-0.5% increased hepatic specific activities of both QR and GST from two to six-fold, and increases in serum activities were well correlated to increases observed in the liver (r2 > or = 0.95). There was no evidence for an elevation of serum alanine aminotransferase levels. Thus, in the absence of serological evidence for hepatocellular damage, increased serum Phase II enzyme activities can be correlated to tissue levels. Our results suggest that similar assays tailored to human sera will not only be useful in the execution of chemoprevention trials, but also to assess the role that Phase II enzyme induction plays in the prevention of cancer by fruits and vegetables.
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PMID:Elevation of serum phase II enzymes by anticarcinogenic enzyme inducers: markers for a chemoprotected state? 826 10

Female F344 rats received an i.p. injection of iron-dextran (600 mg Fe/kg) and then after 1 week were fed a diet containing 0.02% hexachlorobenzene (HCB) for up to 65 weeks. All rats (8/8) which received HCB after iron overload developed multiple hepatic nodules whereas only 3/8 rats administered HCB alone had nodules (average of one per positive liver). These hyperplastic regions were depleted of iron and were often positive for gamma-glutamyl transpeptidase (GGT) and glutathione S-transferase P (GST-P). Telangiectasis and peliosis were prominent features in the lesions. Short-term experiments (5-15 weeks of iron/HCB treatments) showed that GGT and GST-P were induced early in the neoplastic process but not in discrete focal areas. Iron alone also caused some induction of these enzymes. Some cells with induced GST-P in either short or long term experiments also stained positively for this enzyme in the nucleus. Studies of cytochrome P450 mediated activities showed that at 5 and 15 weeks HCB had induced EROD (an estimate of CYP1A1), PROD (CYP2B1 activity) and BROD activities (CYP2B1 but also other isoenzymes). Under the influence of iron overload EROD was significantly depressed from HCB alone, but not the others or cytochrome P450 reductase. Cytosolic glutathione S-transferase activities were also induced by HCB, but, unlike microsomal EROD, preloading with iron enhanced the effects. In contrast, although cytosolic diaphorase activity was induced by HCB, this response was depressed in combination with iron. Glutathione peroxidase (with H2O2 as substrate) was depressed by both iron and HCB. Clearly, iron overload potentiates the neoplastic process induced by HCB in rats, with both enhancing and depressing effects on various enzyme activities induced by this chemical.
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PMID:Enhancement by iron of hepatic neoplasia in rats caused by hexachlorobenzene. 833 Mar 54

Antiestrogens are thought to exert most of their beneficial effects in breast cancer by antagonizing the actions of estrogen. We report here that antiestrogens also stimulate the expression of quinone reductase (QR) [NAD(P)H:quinone oxidoreductase, EC 1.6.99.2], which may provide protective effects against the toxicity and mutagenicity caused by quinones. QR is up-regulated by low concentrations of antiestrogens (trans-hydroxytamoxifen, tamoxifen, and ICI182,780) in estrogen receptor (ER)-containing breast cancer cells, and this increase is suppressed by estrogen via an ER-dependent mechanism. Since regulation of the QR gene, as well as other genes involved in detoxification such as the glutathione S-transferase Ya subunit (GST Ya) gene, is known to be mediated by an electrophile/antioxidant response element (EpRE/ARE), we examined the effects of antiestrogens on a 41-bp electrophile responsive region derived from the GST Ya gene. Transfection of this EpRE-containing region into ER-negative breast cancer cells in the presence or absence of an expression vector for the human ER, as well as mutagenesis studies, revealed that the EpRE-containing construct was activated by antiestrogen to the same extent as by tert-butylhydroquinone (TBHQ), a known activator of EpREs; however, only the stimulation by antiestrogen, and not TBHQ, required ER and was repressed by estradiol, although activation by both inducers mapped to the same 10-bp EpRE consensus sequence. Thus, there appear to be two pathways for QR induction, one that is activated by electrophile inducers such as TBHQ and is ER independent, and a second that is antiestrogen regulated and ER dependent; both pathways act through the EpRE. The anticancer action of antiestrogens may thus derive not only from the already well-known repression of estrogen-stimulated activities but also from the activation of detoxifying enzymes, such as QR, that may contribute to the beneficial antioxidant activity of antiestrogens.
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PMID:The quinone reductase gene: a unique estrogen receptor-regulated gene that is activated by antiestrogens. 912 38

A range of potential chemoprotective agents, most of them natural dietary constituents, has been examined for ability to modulate both phase I (cytochrome P450 1A1, 1A2, 2B1/2, 2C11, 2E1, 3A, 4A) and phase II drug metabolizing enzymes (glutathione S-transferases, in particular subunits Yc2 and P, aflatoxin B1-aldehyde reductase and quinone reductase) in rat liver. In addition to assays of total enzyme activity and Western blots for individual isozymes, the ability of microsomes to metabolize aflatoxin B1, and of cytosols to conjugate aflatoxin B1 (AFB1)-epoxide to GSH and to produce AFB1-dialcohol, were measured. Induction of gamma-glutamyl transpeptidase activity was examined by histochemistry. Differing patterns of induction were observed, reflecting differences in the control of expression of the individual enzymes studied. Of the compounds examined, butylated hydroxytoluene, ethoxyquin, indole-3-carbinol and phenethyl isothiocyanate were the most potent bifunctional agents (inducing both phase I and II activities). Oltipraz, while only weakly inducing CYP1A2 and 2B1/2, was a potent inducer of phase II enzymes. Caffeic acid, garlic oil, sinigrin and propyl gallate all showed some ability to induce phase II enzymes. 4-Methyl catechol, alpha-tocopherol and red wine decreased certain phase I enzyme activities, while inducing total GST activity. Butylated hydroxytoluene, ethoxyquin, garlic oil and indole-3-carbinol induced gamma glutamyltranspeptidase in periportal hepatocytes. Particularly because of their ability to induce the detoxifying activities of glutathione S-transferase Yc2 and aldehyde reductase, butylated hydroxytoluene, ethoxyquin, indole-3-carbinol, oltipraz, phenethyl isothiocyanate and sinigrin will be effective blocking agents in rodents, if administered prior to AFB1. While these studies indicate the relative contributions of phase I and II metabolism in the overall protective effect in rat, care should be taken that a similar balance is achieved in man, and that relevant enzymes or iso forms are induced.
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PMID:Mechanism of action of dietary chemoprotective agents in rat liver: induction of phase I and II drug metabolizing enzymes and aflatoxin B1 metabolism. 932 68

Maintenance of cellular homeostasis is a critical survival trait when cells are exposed to electrophilic chemicals. Because conjugation and elimination of these toxins is dependent upon sequential and coordinated metabolic pathways, acquired resistance through a gradual adaptive response would rarely be expected to be the consequence of changes in one gene product. Human HT29 colon cancer cells chronically exposed to EA have acquired resistance to the drug. Commensurate with resistance, EA is more effectively conjugated to GSH and effluxed from the resistant cells. Using directed and random (differential display) approaches, a number of detoxification and/or protective gene products have been shown to be expressed at elevated levels. These include gamma-GCS (approximately 3-fold), GST-pi (approximately 3-fold), MRP (approximately 3-fold), NQO1 (approximately 3-fold), DDH (20-fold), and SSP 3521, a transcriptional regulator (approximately 3-fold). Multiple mechanisms contribute to these increases, including enhanced transcriptional rate and prolonged mRNA and protein half lives. Further indications for the involvement of transcriptional regulators is found in HL60 adriamycin-resistant cells which overexpress MRP, GST-pi and gamma-GCS and also have 15-20-fold more DNA-dependent protein kinase. It is possible that this enzyme serves as an early stress response gene which may activate downstream transcription factors. Intriguingly, the catalytic subunit of DNA-dependent protein kinase has a high avidity for [35S]azidophenacyl-GSH. High levels of GSH conjugates indicate cell stress and it would seem reasonable to speculate that DNA-dependent protein kinase may serve as a receiver and transmitter of signals which contribute to drug resistance and maintain cell viability.
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PMID:Coordinate changes in expression of protective genes in drug-resistant cells. 967 55


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