Indole-3-carbinol (I-3-C), a normal dietary constituent, has been shown to decrease chemical carcinogenesis in experimental animals. N-nitrosodimethylamine (NDMA) requires metabolic oxidation in order to express its hepatotoxic, mutagenic and carcinogenic potential. Our results show that treatment of mice by gavage with I-3-C decreases the covalent binding of (14C)NDMA metabolites to DNA or protein up to 90% with no change in the rate of NDMA demethylation of cytochrome P-450 levels. We found that ethanol or methylene chloride extracts of livers from mice treated with I-3-C decreased the covalent binding of NDMA metabolites to DNA and protein in liver cell fractions from untreated mice. In order to explain these observations, we developed the hypothesis that treatment of mice with I-3-C gives rise to lipophilic nucleophiles that protect tissue macromolecules from electrophilic attack by a scavenging mechanism. To test this hypothesis, we developed a procedure to assign a relative value of nucleophilicity to chemicals or chemical mixtures, such as tissue extracts. The nucleophilic index value (NIV) for liver tissue extracts is inversely proportional to the rate of covalent binding of MDMA metabolites to DNA and protein, and independent of the rate of NDMA demethylation.
The Specific Aims of this project are: a) to find the I-3-C dose regimen to maximize tissue NIV; b) to correlate NIV with indices of hepatotoxicity and DNA damage; c) to fractionate solvent extracts of livers from I-3-C treated mice in order to purify and identify the active nucleophilic material(s), using the HPLC separation techniques in parallel with liquid scintillation counting and high resolution mass spectrometry compound identification procedures; d0 to establish the mechanism of protection by I-3-C. The objectives of this research plan are a) to establish and validate a model system which uses the NIV of the liver to predict biochemical and functional susceptibility of the liver to damage from the hepatotoxic and caracinogenic chemical NDMA; b) to identify the chemical species and the mechanisms involved in the I-3-C protection from molecular and cellular damage. This project offers a predictive model for tissue susceptibility to, and a molecular basis for dietary protection from certain environmental toxic and mutagenic/carcinogenic insults.
|Liu, R M; Nebert, D W; Shertzer, H G (1993) Menadione toxicity in two mouse liver established cell lines having striking genetic differences in quinone reductase activity and glutathione concentrations. Toxicol Appl Pharmacol 122:101-7|
|Liu, R M; Sainsbury, M; Tabor, M W et al. (1993) Mechanisms of protection from menadione toxicity by 5,10-dihydroindeno[1,2,-b]indole in a sensitive and resistant mouse hepatocyte line. Biochem Pharmacol 46:1491-9|
|Liang, H C; Shertzer, H G; Nebert, D W (1992) ""Oxidative stress"" response in liver of an untreated newborn mouse having a 1.2-centimorgan deletion on chromosome 7. Biochem Biophys Res Commun 182:1160-5|
|Shertzer, H G; Lastbom, L; Sainsbury, M et al. (1992) Menadione-mediated membrane fluidity alterations and oxidative damage in rat hepatocytes. Biochem Pharmacol 43:2135-41|
|Shertzer, H G; Bannenberg, G L; Moldeus, P (1992) Evaluation of iron binding and peroxide-mediated toxicity in rat hepatocytes. Biochem Pharmacol 44:1367-73|
|Shertzer, H G; Bannenberg, G L; Rundgren, M et al. (1991) Relationship of membrane fluidity, chemoprotection, and the intrinsic toxicity of butylated hydroxytoluene. Biochem Pharmacol 42:1587-93|
|Shertzer, H G; Sainsbury, M (1991) Intrinsic acute toxicity and hepatic enzyme inducing properties of the chemoprotectants indole-3-carbinol and 5,10-dihydroindeno[1,2-b]indole in mice. Food Chem Toxicol 29:237-42|
|Shertzer, H G; Sainsbury, M; Graupner, P R et al. (1991) Mechanisms of chemical mediated cytotoxicity and chemoprotection in isolated rat hepatocytes. Chem Biol Interact 78:123-41|
|Tabor, M W; Coats, E; Sainsbury, M et al. (1991) Antioxidation potential of indole compounds--structure activity studies. Adv Exp Med Biol 283:833-6|
|Shertzer, H G; Sainsbury, M (1991) Chemoprotective and hepatic enzyme induction properties of indole and indenoindole antioxidants in rats. Food Chem Toxicol 29:391-400|
Showing the most recent 10 out of 22 publications