title: Molecular mechanism of the aryl hydrocarbon receptor activation by the fungicide iprodione in rainbow trout (Oncorhynchus mykiss) hepatocytes.
abstract: The dicarboximide fungicide iprodione (Ip) causes oxidative damage as a result of the production of free oxygen radicals, and induces cytochrome P4501A3 (CYP1A3) in cultured rainbow trout hepatocytes. The aim of this study was to characterise some of the molecular mechanisms by means of which Ip activates the aryl hydrocarbon receptor (AhR) and subsequently induces the CYP1A3 gene in rainbow trout (Oncorhynchus mykiss). The study was performed using primary hepatocytes and transfected HepG2 cells with a reporter construct, in which luciferase gene expression is under the transcriptional control of a multimerised xenobiotic response elements (4XREs), or a 2.3 Kb DNA fragment (corresponding to the trout CYP1A3 gene promoter). Ip exposure increased rainbow trout hepatocyte CYP1A3 mRNA over time and increased the expression of reporter gene in HepG2, thus suggesting that Ip induces the CYP1A3 gene by activating the AhR. Genistein, a tyrosine kinase inhibitor, efficiently inhibited the Ip-mediated induction of the CYP1A3 gene as demonstrated by mRNA level decrease and the impaired activation of the luciferase reporter gene constructs. Staurosporine, an inhibitor of protein kinase C, also suppressed the induction by Ip. When the AhR antagonist alpha-naphthoflavone was added to the cultures, Ip-mediated CYP1A3 induction was suppressed. These findings are consistent with a mechanism of Ip-mediated CYP1A3 gene induction that involves the activation of the AhR complex via phosphorylation-dephosphorylation reactions.
authors.affiliation: Department of Pharmacology, Chemotherapy and Medical Toxicology E. Trabucchi, University of Milan, Via Vanvitelli 32, 20129 Milan, Italy. tossicol@unimi.it
authors.forename: Michela
authors.initials: M
authors.lastname: Ferraris
authors.forename: Adriano
authors.initials: A
authors.lastname: Flora
authors.forename: Enzo
authors.initials: E
authors.lastname: Chiesara
authors.forename: Diego
authors.initials: D
authors.lastname: Fornasari
authors.forename: Helen
authors.initials: H
authors.lastname: Lucchetti
authors.forename: Laura
authors.initials: L
authors.lastname: Marabini
authors.forename: Silvia
authors.initials: S
authors.lastname: Frigerio
authors.forename: Sonia
authors.initials: S
authors.lastname: Radice
mesh_terms: D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000633:toxicity; D000704:Analysis of Variance; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics; D015152:Blotting, Northern; D002478:Cells, Cultured; D005659:Fungicides, Industrial / Q000378:metabolism* / Q000633:toxicity; D005786:Gene Expression Regulation / Q000187:drug effects*; D017930:Genes, Reporter / Q000235:genetics; D019833:Genistein / Q000494:pharmacology; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D006827:Hydantoins / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000633:toxicity; D008156:Luciferases / Q000378:metabolism; D017686:Oncorhynchus mykiss / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D018336:Receptors, Aryl Hydrocarbon / Q000378:metabolism*; D019311:Staurosporine / Q000494:pharmacology; D018675:Toxicity Tests; D015533:Transcriptional Activation
chemical_list: D005659:Fungicides, Industrial; D006827:Hydantoins; D018336:Receptors, Aryl Hydrocarbon; D000620:Aminoimidazole Carboxamide; D019833:Genistein; D008156:Luciferases; D001189:Aryl Hydrocarbon Hydroxylases; C106496:cytochrome P-450 CYP1A3 (rainbow trout); D019311:Staurosporine; C033148:iprodione