A quantitative comparison of dibenzo[a,l]pyrene-DNA adduct formation by recombinant human cytochrome P450 microsomes.
Dibenzo[a,l]pyrene (DB[a,l]P), an extremely potent environmental carcinogen, is metabolically activated in mammalian cells and microsomes through the fjord-region dihydrodiol, trans-DB[a,l]P-11, 12-diol, to syn- and anti-DB[a,l]P-11,12-diol-13,14-epoxides (syn- and anti-DB[a,l]PDEs). The role of seven individual recombinant human cytochrome P450s (1A1, 1A2, 1B1, 2B6, 2C9, 2E1, and 3A4) in the metabolic activation of DB[a,l]P and formation of DNA adducts was examined by using (32)P postlabeling, thin-layer chromatography, and high-pressure liquid chromatography. We found that, in the presence of epoxide hydrolase, only P450 1A1 and P450 1B1 catalyzed the formation of DB[a,l]PDE-DNA adducts and several unidentified polar adducts. Human P450 1A1 catalyzed the formation of DB[a, l]PDE-DNA adducts and unidentified polar adducts at rates threefold and 17-fold greater than did human P450 1B1 (256 fmol/h/nmol P450 versus 90 fmol/h/nmol P450 and 132 fmol/h/nmol P450 versus 8 fmol/h/nmol P450, respectively). P450 1A1 DNA adducts were derived from both anti- and syn-DB[a,l]PDE at rates of 73 fmol/h/nmol P450 and 51 fmol/h/nmol P450, respectively. P450 1B1 produced adducts derived from anti-DB[a,l]PDE at a rate of 82 fmol/h/nmol, whereas only a small number of adducts were derived from syn-DB[a,l]PDE (0.4 fmol/h/nmol). These results demonstrated the potential of human P450 1A1 and P450 1B1 to contribute to the metabolic activation and carcinogenicity of DB[a,l]P and provided additional evidence that human P450 1A1 and 1B1 differ in their stereospecific activation of DB[a,l]P. Mol. Carcinog. 26:74-82, 1999. Published 1999 Wiley-Liss, Inc.
King
L C
LC
Biochemistry and Pathobiology Branch, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA.
Adams
L
L
Allison
J
J
Kohan
M J
MJ
Nelson
G
G
Desai
D
D
Amin
S
S
Ross
J A
JA
D000818:Animals; D001580:Benzopyrenes / Q000378:metabolism*; D001711:Biotransformation; D002273:Carcinogens / Q000378:metabolism*; D002417:Cattle; D002474:Cell-Free System; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000494:pharmacology*; D018736:DNA Adducts / Q000032:analysis / Q000096:biosynthesis / Q000378:metabolism*; D018076:DNA, Complementary / Q000378:metabolism; D004851:Epoxide Hydrolases / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D008861:Microsomes / Q000378:metabolism*; D020033:Protein Isoforms; D011994:Recombinant Proteins / Q000494:pharmacology; D013950:Thymus Gland / Q000378:metabolism; D013997:Time Factors
D001580:Benzopyrenes; D002273:Carcinogens; D018736:DNA Adducts; D018076:DNA, Complementary; D020033:Protein Isoforms; D011994:Recombinant Proteins; D003577:Cytochrome P-450 Enzyme System; D004851:Epoxide Hydrolases; C041517:dibenzo(a,l)pyrene