title: Inhibition of aryl hydrocarbon receptor transactivation and DNA adduct formation by CYP1 isoform-selective metabolic deactivation of benzo[a]pyrene.
abstract: Benzo[a]pyrene (BaP), a polyaromatic hydrocarbon produced by the combustion of cigarettes and coke ovens, is a known procarcinogen. BaP activates the aryl hydrocarbon receptor (AhR) and induces the expression of a battery of genes, including CYP1A1, which metabolize BaP to toxic compounds. The possible role of CYP1 enzymes in mediating BaP detoxification or metabolic activation remains to be elucidated. In this study, we assessed the effects of CYP1 enzymes (CYP1A1, CYP1A2 and CYP1B1) on BaP-induced AhR transactivation and DNA adduct formation in HEK293 cells and HepG2 cells. Transfection of CYP1A1 and CYP1B1, but not CYP1A2, suppressed BaP-induced activation of AhR. Expression of CYP1A1 and CYP1A2, but not CYP1B1, inhibited DNA adduct formation in BaP-treated HepG2 cells. These results indicate that CYP1A1 and CYP1B1 play a role in deactivation of BaP on AhR and that CYP1A1 and CYP1A2 are involved in BaP detoxification by suppressing DNA adduct formation. BaP treatment did not induce DNA adduct formation in HEK293 cells, even after transfection of CYP1 enzymes, suggesting that expression of CYP1 enzymes is not sufficient for DNA adduct formation. Lower expression of epoxide hydrolase and higher expression of glutathione S-transferase P1 (GSTP1) and GSTM1/M2 were observed in HEK293 cells compared with HepG2 cells. Dynamic expression of CYP1A1, CYP1A2 and CYP1B1 along with expression of other enzymes such as epoxide hydrolase and phase II enzymes may determine the detoxification or metabolic activation of BaP.
authors: Division of Biochemistry, Department of Biomedical Sciences, Nihon University School of Medicine, 30-1 Oyaguchi-kamicho, Itabashi-ku, Tokyo 173-8610, Japan.
authors: Kaori
authors: K
authors: Endo
authors: Shigeyuki
authors: S
authors: Uno
authors: Taiichiro
authors: T
authors: Seki
authors: Toyohiko
authors: T
authors: Ariga
authors: Yoshiaki
authors: Y
authors: Kusumi
authors: Masako
authors: M
authors: Mitsumata
authors: Sachiko
authors: S
authors: Yamada
authors: Makoto
authors: M
authors: Makishima
mesh_terms: D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism; D001564:Benzo(a)pyrene / Q000378:metabolism* / Q000494:pharmacology*; D015153:Blotting, Western; D002273:Carcinogens / Q000378:metabolism* / Q000494:pharmacology*; D002460:Cell Line; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism; D065633:Cytochrome P-450 CYP1B1; D065607:Cytochrome P-450 Enzyme Inhibitors; D018736:DNA Adducts / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors; D051549:Glutathione S-Transferase pi / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D018336:Receptors, Aryl Hydrocarbon / Q000037:antagonists & inhibitors* / Q000235:genetics*; D015533:Transcriptional Activation / Q000187:drug effects*
chemical_list: D001189:Aryl Hydrocarbon Hydroxylases; D001564:Benzo(a)pyrene; D002273:Carcinogens; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2; D065633:Cytochrome P-450 CYP1B1; D065607:Cytochrome P-450 Enzyme Inhibitors; D018736:DNA Adducts; D004791:Enzyme Inhibitors; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase; D007527:Isoenzymes; D018336:Receptors, Aryl Hydrocarbon; C585496:CYP1B1 protein, human