title: Cytotoxicity and mutagenicity of dibenzo[a,l]pyrene and (+/-)-dibenzo[a,l]pyrene-11,12-dihydrodiol in V79MZ cells co-expressing either hCYP1A1 or hCYP1B1 together with human glutathione-S-transferase A1.
abstract: We have used V79MZ hamster lung fibroblasts stably transfected with human cytochrome P450-1A1 (hCYP1A1; cell line designated V79MZh1A1) or P450-1B1 (hCYP1B1; cell line designated V79MZh1B1) alone, or in combination with human glutathione-S-transferase (GST) alpha-1 (hGSTA1), in order to examine GST protection against cytotoxicity and mutagenicity of dibenzo[a,l]pyrene (DBP) and the intermediate dihydrodiol metabolite (+/-)-DBP-11,12-dihydrodiol (DBPD). At comparable expression levels of hCYP1A1 and hCYP1B1, both DBP and DBPD were more cytotoxic in V79MZ1A1 (IC(50)=2.7 and 0.7nM, respectively) than in V79MZh1B1 (IC(50)=6.0 and 4.8nM, respectively). In contrast, both DBP and DBPD were two- to four-fold more mutagenic in V79MZh1B1 than in V79MZ1A1. Co-expression of hGSTA1 with hCYP1A1 decreased DBP cytotoxicity two-fold compared to V79MZh1A1 with hCYP1A1 alone, and provided a small, yet still statistically significant, 1.3-fold protection against DBPD. Protection against mutagenicity of these compounds was comparable to that for cytotoxicity in cells expressing hCYP1A1. In V79MZh1B1 cells, co-expression of hGSTA1 conferred up to five-fold protection against DBP cytotoxicity, and up to nine-fold protection against the (+/-)-DBP-dihydrodiol cytotoxicity relative to the cells expressing hCYP1B1 alone. Co-expression of hGSTA1 also reduced mutagenicity of DBP or its dihydrodiol to a lesser extent (1.3-1.8-fold) than the protection against cytotoxicity in cells expressing hCYP1B1. These findings demonstrate that the protective efficacy of hGSTA1 against DBP and DBPD toxicity is variable, depending on the compound or metabolite present, the specific cytochrome P450 isozyme expressed, and the specific cellular damage endpoint examined.
authors.affiliation: Department of Biochemistry, Wake Forest University, School of Medicine, Medical Center Boulevard, 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: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D001580:Benzopyrenes / Q000378:metabolism / Q000633:toxicity*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics* / Q000378:metabolism; D065633:Cytochrome P-450 CYP1B1; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism; D004101:Dihydroxydihydrobenzopyrenes / Q000378:metabolism / Q000633:toxicity*; D005982:Glutathione Transferase / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D009153:Mutagens / Q000378:metabolism / Q000633:toxicity*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection
chemical_list: D001580:Benzopyrenes; D004101:Dihydroxydihydrobenzopyrenes; D009153:Mutagens; D011994:Recombinant Proteins; C071371:dibenzo(a,l)pyrene 11,12-dihydrodiol; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; D019363:Cytochrome P-450 CYP1A1; D065633:Cytochrome P-450 CYP1B1; C484555:GSTA1 protein, human; D005982:Glutathione Transferase; C041517:dibenzo(a,l)pyrene