Increase of NAD(P)H:quinone reductase by dietary antioxidants: possible role in protection against carcinogenesis and toxicity.

Abstract

2(3)tert-Butyl4hydroxyanisole (BHA) is one of several widely used antioxidant food additives that protect against chemical carcinogenesis and toxicity. The present report concerns the enhancement of dicoumarolinhibited NAD(P)HL quinone reductase [NAD(P)H dehydrogenase (quinone); NAD(P)H:(quinone acceptor) oxidoreductase, EC 1.6.99.21 activity in mouse tissues in response to dietary administration of BHA. Cytosolic quinone reductase specific activity was increased significantly in 10 of 15 tissues examined from BHA-fed mice. The greatest proportionate increase, to 10 times control levels, was observed in liver. BHA also increased the quinone reductase activities of kidney, lung, and the mucosa of the upper small intestine severalfold. The increases of quinone reductase activities in liver and digestive tissues in response to BHA were comparable to the increases previously observed in glutathione S-transferase (EC 2.5.1.18) and epoxide hydratase (EC 3.3.2.3) activities. Quinones are among the toxic products of oxidative metabolism of aromatic hydrocarbons. NAD(P)H:quinone reductase exhibits broad specificity for structurally diverse hydrophobic quinones an may facilitate the microsomal metabolism of quinones to readily excreted conjugates. The protectie effects of BHA appear to be due, at least in part, to the ability of this antioxidant to increase the activities in rodent tissues of several enzymes involved in the nonoxidative metabolism of a wide variety of xenobiotics.The widely used antioxidant food additive 2(3)-tert-butyl-4-hydroxyanisole (BHA) has a number of interesting and potentially important pharmacological properties. BHA Administration of BHA to mice has little or no effect on numerous other monooxygenase activities of hepatic microsomes (11,15,17), although ring hydroxylation of aniline is markedly enhanced (11). Liver microsomes from BHA-fed mice also produce altered patterns of metabolites from benzo[a]pyrene in vitro. Lam and Wattenberg (18) observed decreased epoxidation and increased formation of 3-hydroxybenzo[a]pyrene relative to controls, and these changes were accompanied by a 50% decrease in the binding of metabolites to DNA (19,20).The NADH-and NADPH-linked quinone oxidoreductase here called quinone reductase has also been designated variously as menadione reductase, DT-diaphorase, NAD(P)H dehydrogenase, and vitamin K reductase (21). Recent studies have shown that rat liver cytosol azoreductase activity for methyl red also reflects the action of quinone reductase (22, 23). Unusual features of this flavoprotein enzyme include: (i) comparable reaction with NADH and NADPH (24-26); (ti) potent and specific inhibition, in competition with reduced nicotinamide nucleotides, by dicoumarol and related vitamin K antagonists (24, 27); (iii) reversible stimulation of activity of the soluble cytosolic quinone reductase by serum albumin, neutral phospholipids, and a number of detergents (24,26,27); and (iv) broad specificity for a variety of hydrophobic quinones, including benzoquinones, na...

Dietary Supplementation of Curcumin Enhances Antioxidant and Phase II Metabolizing Enzymes in ddY Male Mice: Possible Role in Protection against Chemical Carcinogenesis and Toxicity

“…The changes in absorbance were recorded at 340 nm and enzyme activity was calculated as nmol CDNB conjugate formed/min./mg protein using a molar extinction coefficient of 9.6 ¿ 10 3 M/cm. Quinone reductase activity was determined by the method of Benson et al (1980), as described by Iqbal et al (1999), using 2,6 dichlorophenol-indophenol as an electron acceptor. The assay system consisted of 2.0 ml Tris-HCl buffer (0.025 M, pH 7.4), 0.7 ml BSA (1.0 mg/ml), 0.02 ml Tween-20 (1.0%), 0.1 ml FAD (150 mM), 0.02 ml NADPH (0.1 mM), 0.05 ml 2,6-dichlorophenol indophenol (2.4 mM), 0.01 ml and 0.025 ml of renal and hepatic cytosolic fraction (10%w/v), respectively, in a total volume of 3.0 ml.…”

Potent induction of total cellular GSH and NQO1 as well as mitochondrial GSH by 3H-1,2-dithiole-3-thione in SH-SY5Y neuroblastoma cells and primary human neurons: Protection against neurocytotoxicity elicited by dopamine, 6-hydroxydopamine, 4-hydroxy-2-nonenal, or hydrogen peroxide

“…Cellular NQO1 activity was measured according to the procedures described previously (Benson et al, 1980). Briefly, the reaction mix contained in 50 mM Tris-HCl, pH 7.5, 0.08% Triton X-100,0.25 mM NADPH, and 80 μM of 2,6-dichloroindophenol (DCIP) in the presence or absence of 60 μM dicumarol.…”

Induction of DT-diaphorase by 1,2-dithiole-3-thiones in human tumour and normal cells and effect on anti-tumour activity of bioreductive agents

“…The enzyme is found in all eukaryotes and is present at varying levels in most tissues (Benson et al, 1980;Belinsky and Jaiswal, 1993). DT-diaphorase is located mainly in the cytosol, but 5-10% is membrane bound in mitochondria, microsomes and Golgi apparatus (Riley and Workman, 1992).…”

“…Several DT-diaphorases have been identified in humans (Jaiswal et al, 1990;Jaiswal, 1991), but the NQO, gene has been most extensively studied and appears to be most important for activation of bioreductive anti-tumour agents (Jaiswal, 1991;Riley and Workman, 1992;Belinsky and Jaiswal, 1993). Enzyme levels have been shown to be relatively high in mouse and/or human stomach, bladder, intestine, colon and kidney, but are usually low in liver, lung and haematopoietic cells (Benson et al, 1980;Schlager and Powis, 1990;Smitskamp-Wilms et al, 1995). DT-diaphorase activity is higher in some tumour cells than in the corresponding normal cells, with elevated levels of enzyme activity having been observed in human liver, colon, breast and lung tumour cells (Schlager and Powis, 1990;Malkinson et al, 1992;Belinsky and Jaiswal, 1993;Smitskamp-Wilms et al, 1995).…”