title: Protective efficacy of hGSTM1-1 against B[a]P and (+)- or (-)-B[a]P-7,8-dihydrodiol cytotoxicity, mutagenicity, and macromolecular adducts in V79 cells coexpressing hCYP1A1.
abstract: Transgenic cell lines were constructed to study the dynamics of competition between activation versus detoxification of benzo[a]pyrene (B[a]P) or B[a]P-7,8-dihydrodiol metabolites. Stably transfected V79MZ cells expressing human cytochrome P4501A1 (hCYP1A1) alone or in combination with human glutathione-S-transferase M1 (hGSTM1) were used to determine how effectively this GST isozyme protects against cytotoxic, genotoxic, and mutagenic effects of B[a]P or the enantiomeric dihydrodiol metabolites (+)-benzo[a]pyrene-7,8-dihydrodiol ((+)-B[a]P-7,8-diol) and (-)-benzo[a]pyrene-7,8-dihydrodiol ((-)-B[a]P-7,8-diol). Expression of hGSTM1 in the presence of hCYP1A1 conferred significant 8.5-fold protection against B[a]P-induced cytotoxicity, but protection against cytotoxicity of either B[a]P-7,8-diol enantiomer was not significant. Mutagenicity of B[a]P at the hprt locus was dose and time dependent in cells that expressed hCYP1A1. Mutagenicity of B[a]P was reduced by 21-32% and mutagenicity induced by the B[a]P-7,8-diols was reduced 20-58% in cells further modified to coexpress hGSTM1-1 compared to cells expressing hCYP1A1 alone. Expression of hGSTM1-1 reduced adducts in total cellular macromolecules by twofold, in good correlation with the reduction in B[a]P mutagenicity. These results indicate that while hGSTM1-1 effectively protects against hCYP1A1-mediated cytotoxicity of B[a]P, a significant fraction of the mutagenicity that results from activation of B[a]P and its 7,8-dihydrodiol metabolites by hCYP1A1 is derived from B[a]P metabolites that are not detoxified by hGSTM1.
authors.affiliation: Department of Cancer Biology, Comrprehensive Cancer Center, Wake Forest University, Winston-Salem, NC 27157, USA.
authors.forename: Mary E
authors.initials: ME
authors.lastname: Kushman
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Kabler
authors.forename: Sarfaraz
authors.initials: S
authors.lastname: Ahmad
authors.forename: Johannes
authors.initials: J
authors.lastname: Doehmer
authors.forename: Charles S
authors.initials: CS
authors.lastname: Morrow
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Townsend
mesh_terms: D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide / Q000378:metabolism*; D000818:Animals; D001564:Benzo(a)pyrene / Q000493:pharmacokinetics / Q000633:toxicity*; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000187:drug effects / Q000235:genetics; D018736:DNA Adducts / Q000378:metabolism*; D004101:Dihydroxydihydrobenzopyrenes / Q000493:pharmacokinetics / Q000633:toxicity*; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D008658:Inactivation, Metabolic; D009152:Mutagenicity Tests; D009153:Mutagens / Q000493:pharmacokinetics / Q000633:toxicity*; D009154:Mutation; D013237:Stereoisomerism; D014162:Transfection
chemical_list: D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; D001564:Benzo(a)pyrene; D019363:Cytochrome P-450 CYP1A1; D004247:DNA; D018736:DNA Adducts; D004101:Dihydroxydihydrobenzopyrenes; D005982:Glutathione Transferase; D007041:Hypoxanthine Phosphoribosyltransferase; D009153:Mutagens; C043931:benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide-DNA; C017228:benzo(a)pyrene 7,8-dihydrodiol