Induction of CYP1A1 and CYP1B1 by benzo(k)fluoranthene and benzo(a)pyrene in T-47D human breast cancer cells: roles of PAH interactions and PAH metabolites |
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Authors: | Spink David C Wu Susan J Spink Barbara C Hussain Mirza M Vakharia Dilip D Pentecost Brian T Kaminsky Laurence S |
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Affiliation: | Wadsworth Center, New York State Department of Health, Albany, NY 12201-0509, USA. spink@wadsworth.org |
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Abstract: | The interactions of polycyclic aromatic hydrocarbons (PAH) and cytochromes P450 (CYP) are complex; PAHs are enzyme inducers, substrates, and inhibitors. In T-47D breast cancer cells, exposure to 0.1 to 1 microM benzo(k)fluoranthene (BKF) induced CYP1A1/1B1-catalyzed 17beta-estradiol (E(2)) metabolism, whereas BKF levels greater than 1 muM inhibited E(2) metabolism. Time course studies showed that induction of CYP1-catalyzed E(2) metabolism persisted after the disappearance of BKF or co-exposed benzo(a)pyrene, suggesting that BKF metabolites retaining Ah receptor agonist activity were responsible for prolonged CYP1 induction. BKF metabolites were shown, through the use of ethoxyresorufin O-deethylase and CYP1A1-promoter-luciferase reporter assays to induce CYP1A1/1B1 in T-47D cells. Metabolites formed by oxidation at the C-2/C-3 region of BKF had potencies for CYP1 induction exceeding those of BKF, whereas C-8/C-9 oxidative metabolites were somewhat less potent than BKF. The activities of expressed human CYP1A1 and 1B1 with BKF as substrate were investigated by use of HPLC with fluorescence detection, and by GC/MS. The results showed that both enzymes efficiently catalyzed the formation of 3-, 8-, and 9-OHBKF from BKF. These studies indicate that the inductive effects of PAH metabolites as potent CYP1 inducers are likely to be additional important factors in PAH-CYP interactions that affect metabolism and bioactivation of other PAHs, ultimately modulating PAH toxicity and carcinogenicity. |
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Keywords: | AhR, aryl hydrocarbon receptor BAP, benzo[a]pyrene BKF, benzo[k]fluoranthene BAA, benz[a]anthracene BAA-3,4-diol, benz[a]anthracene-trans-3,4-dihydrodiol BKF-2,3-diol, benzo[k]fluoranthene-trans-2,3-dihydrodiol BKF-8,9-diol, benzo[k]fluoranthene-trans-8,9-dihydrodiol CYP or P450, cytochrome P450 DBAHA-5,6-diol, dibenz[a,h]anthracene-cis-5,6-dihydrodiol DMEM, Dulbecco's modified Eagle's medium DMSO, dimethyl sulfoxide E2, 17β-estradiol EROD, ethoxyresorufin O-deethylase GC/MS, gas chromatography/mass spectrometry HPLC, high-performance liquid chromatography 3-, 8-, and 9-OHBKF, 3-, 8-, and 9-hydroxybenzo[k]fluoranthene 2- and 4-MeOE2, 2- and 4-methoxyestradiol PAH, polycyclic aromatic hydrocarbon TCDD, 2,3,7,8-tetrachlorodibenzo-p-dioxin TMS, trimethylsilyl |
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