title: Inflammatory mediators accelerate metabolism of benzo[a]pyrene in rat alveolar type II cells: the role of enhanced cytochrome P450 1B1 expression.
abstract: Long-term deregulated inflammation represents one of the key factors contributing to lung cancer etiology. Previously, we have observed that tumor necrosis factor-α (TNF-α), a major pro-inflammatory cytokine, enhances genotoxicity of benzo[a]pyrene (B[a]P), a highly carcinogenic polycyclic aromatic hydrocarbon, in rat lung epithelial RLE-6TN cells, a model of alveolar type II cells. Therefore, we analyzed B[a]P metabolism in RLE-6TN cells under inflammatory conditions, simulated using either recombinant TNF-α, or a mixture of inflammatory mediators derived from activated alveolar macrophage cell line. Inflammatory conditions significantly accelerated BaP metabolism, as evidenced by decreased levels of both parent B[a]P and its metabolites. TNF-α altered production of the metabolites associated with dihydrodiol-epoxide and radical cation pathways of B[a]P metabolism, especially B[a]P-dihydrodiols, and B[a]P-diones. We then evaluated the role of cytochrome P450 1B1 (CYP1B1), which is strongly up-regulated in cells treated with B[a]P under inflammatory conditions, in the observed effects. The siRNA-mediated CYP1B1 knock-down increased levels of B[a]P and reduced formation of stable DNA adducts, thus confirming the essential role of CYP1B1 in B[a]P metabolism under inflammatory conditions. TNF-α also reduced expression of aldo-keto reductase 1C14, which may compete with CYP1B1 for B[a]P-7,8-dihydrodiol and divert it from the formation of ultimate B[a]P dihydrodiol epoxide. Together, the present data suggests that the CYP1B1-catalyzed metabolism of polycyclic aromatic hydrocarbons might contribute to their enhanced bioactivation and genotoxic effects under inflammatory conditions.
authors.affiliation: Department of Cytokinetics, Institute of Biophysics AS CR, 61265 Brno, Czech Republic.
authors.forename: Lenka
authors.initials: L
authors.lastname: Smerdová
authors.forename: Jiří
authors.initials: J
authors.lastname: Neča
authors.forename: Jana
authors.initials: J
authors.lastname: Svobodová
authors.forename: Jan
authors.initials: J
authors.lastname: Topinka
authors.forename: Jana
authors.initials: J
authors.lastname: Schmuczerová
authors.forename: Alois
authors.initials: A
authors.lastname: Kozubík
authors.forename: Miroslav
authors.initials: M
authors.lastname: Machala
authors.forename: Jan
authors.initials: J
authors.lastname: Vondráček
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000096:biosynthesis / Q000235:genetics; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000096:biosynthesis* / Q000235:genetics; D001564:Benzo(a)pyrene / Q000378:metabolism*; D015153:Blotting, Western; D002460:Cell Line; D017077:Culture Media, Conditioned; D065633:Cytochrome P-450 CYP1B1; D016207:Cytokines / Q000378:metabolism; D018736:DNA Adducts; D018836:Inflammation Mediators / Q000494:pharmacology*; D050837:Oxidoreductases Acting on Aldehyde or Oxo Group Donors / Q000096:biosynthesis / Q000235:genetics; D011650:Pulmonary Alveoli / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D034741:RNA, Small Interfering; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D053719:Tandem Mass Spectrometry; D014162:Transfection
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D017077:Culture Media, Conditioned; D016207:Cytokines; D018736:DNA Adducts; D018836:Inflammation Mediators; D034741:RNA, Small Interfering; D001564:Benzo(a)pyrene; C095122:multidrug resistance protein 3; D001189:Aryl Hydrocarbon Hydroxylases; C585499:Cyp1b1 protein, rat; D065633:Cytochrome P-450 CYP1B1; C560506:AKR1C15 protein, rat; D050837:Oxidoreductases Acting on Aldehyde or Oxo Group Donors
keywords: CYP1B1; DNA adducts; Inflammation; Metabolism; Polycyclic aromatic hydrocarbons