title: Induction of cytochromes P-450 1A1 and 1B1 by motorcycle exhaust particulate in human breast cancer MCF-7 cells.
abstract: The effects of motorcycle exhaust particulate (MEP) on cytochrome P-450-dependent monooxygenases were determined using MCF-7 human breast cancer cells treated with organic extracts of MEP. Treatment with MEP extract produced concentration- and time-dependent increases of monooxygenase activity in S9 fractions. Treatment with 50 microg/ml MEP extract for 24 h increased benzo[a]pyrene hydroxylase and 7-ethoxycoumarin, 7-ethoxyresorufin, and methoxyresorufin O-dealkylases activities in S9. Treatments with 1 and 10 microg/ml MEP extract for 24 h markedly enhanced catabolism of 17beta-estradiol in MCF-7 cells. Cotreatment of the cells with 2 microM alpha-naphthoflavone, a cytochrome P-450 inhibitor and arylhydrocarbon receptor antagonist, blocked the increase of benzo[a]pyrene hydroxylase activity induced by treatment with MEP extract alone. Immunoblot analyses of S9 proteins using a mouse monoclonal antibody 1-12-3 against rat cytochrome P-450 1A1 and a rabbit polyclonal antibody against human cytochrome P-450 1B1 revealed that MEP extract induced proteins immunorelated to cytochromes P-450 1A1 and 1B1. RNA blot analysis of total RNA using human cytochrome P-450 (CYP)1A1 3'-end and human CYP1B1 RT-PCR product cDNA probes showed that MEP extract increased the levels of cytochromes P-450 1A1 and 1B1 mRNA hybridizable to the respective cDNA probes. Treatment with 10 micro M benzo[a]pyrene, a component of MEP extract, for 24 h induced catalytic activity, protein, and mRNA of cytochromes P-450 1A1 and 1B1 in MCF-7 cells. Treatment with MEP extract increased cytochromes P-450 1A1 and 1B1 proteins and mRNA levels in NCI-H322 human lung carcinoma and CL5 human lung adenocarcinoma cells. The extract also increased cytochrome P-450 1A1, but not cytochrome P-450 1B1, protein, and mRNA, in HepG2 human hepatoma cells. The present findings demonstrate that MEP extract has the ability to induce cytochromes P-450 1A1 and 1B1 in the estrogen-responsive MCF-7 cells. Induction of the carcinogen- and estrogen-metabolizing cytochromes P-450 1A1 and 1B1 may be an important factor to consider in assessing the potential health effects associated with human exposure to MEP.
authors.affiliation: Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Taiwan, Republic of China.
authors.forename: Hui-Wu
authors.initials: HW
authors.lastname: Wang
authors.forename: Fong-Wen
authors.initials: FW
authors.lastname: Chen
authors.forename: Tzuu-Huei
authors.initials: TH
authors.lastname: Ueng
mesh_terms: D000393:Air Pollutants / Q000633:toxicity*; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000096:biosynthesis* / Q000235:genetics; D001943:Breast Neoplasms / Q000201:enzymology* / Q000473:pathology; D002470:Cell Survival / Q000187:drug effects; D019363:Cytochrome P-450 CYP1A1 / Q000096:biosynthesis* / Q000235:genetics; D065633:Cytochrome P-450 CYP1B1; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004790:Enzyme Induction; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000201:enzymology / Q000473:pathology; D009049:Motorcycles; D012313:RNA / Q000032:analysis; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D001335:Vehicle Emissions / Q000633:toxicity*
chemical_list: D000393:Air Pollutants; D004338:Drug Combinations; D012333:RNA, Messenger; D001335:Vehicle Emissions; D012313:RNA; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; C585498:Cyp1b1 protein, mouse; C585499:Cyp1b1 protein, rat; D019363:Cytochrome P-450 CYP1A1; D065633:Cytochrome P-450 CYP1B1