title: Sunlight Irradiation of Highly Brominated Polyphenyl Ethers Generates Polybenzofuran Products That Alter Dioxin-responsive mRNA Expression in Chicken Hepatocytes.
abstract: We report on two highly brominated polyphenyl ether flame retardants, tetradecabromo-1,4- diphenoxybenzene (TeDB-DiPhOBz) and 2,2',3,3',4,4',5,5',6,6'-decabromodiphenyl ether (BDE-209), that formed photolytic degradation products in tetrahydrofuran (THF)/hexane solvent after 21 days of natural sunlight irradiation (SI). These degradation products of SI-TeDB-DiPhOBz and SI-BDE-209 included the numerous polybrominated homologue groups of polybenzofurans and dibenzofurans, respectively. Formation of similar polybenzofuran and dibenzofuran products was also observed following a 3 month exposure of the solid powder forms of TeDB-DiPhOBz and BDE-209 to natural SI. These resulting degradation product mixtures were administered to chicken embryonic hepatocytes (CEH) to determine effects on mRNA expression levels of 27 dioxin-responsive genes. For the solvent-based SI study, equivalent concentrations of 1 or 25 μM of SI-TeDB-DiPhOBz or 1 or 10 μM of SI-BDE-209 resulted in gene expression profiles that were similar to those of the most potent dioxin-like compound, 2,3,7,8-tetrachlorodibenzo-p-dioxin. In addition, a concentration-dependent induction of CYP1A4 and CYP1A5 mRNA was observed following exposure to SI-TeDB-DiPhOBz and SI-BDE-209. Based on ECthreshold values for CYP1A4/5 mRNA expression, relative potency (ReP) values were 1 × 10(-6) and 1 × 10(-5) for SI-TeDB-DiPhOBz and SI-BDE-209, respectively. The SI TeDB-DiPhOBz and BDE-209 powder degradation product mixture also significantly induced CYP1A4 mRNA levels in CEH. Our findings clearly show that the environmental stability of TeDB-DiPhOBz and BDE-209, and possibly other highly brominated polyphenyl ethers, is of great concern from a dioxin-like degradation products and toxicity perspective.
authors: Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, National Wildlife Research Centre, Carleton University , Ottawa, Ontario K1A 0H3, Canada.|Department of Chemistry, Carleton University , Ottawa, Ontario K1S 5B6, Canada.
authors: Guanyong
authors: G
authors: Su
authors: Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, National Wildlife Research Centre, Carleton University , Ottawa, Ontario K1A 0H3, Canada.|Department of Chemistry, Carleton University , Ottawa, Ontario K1S 5B6, Canada.
authors: Robert J
authors: RJ
authors: Letcher
authors: Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, National Wildlife Research Centre, Carleton University , Ottawa, Ontario K1A 0H3, Canada.
authors: Doug
authors: D
authors: Crump
authors: Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, National Wildlife Research Centre, Carleton University , Ottawa, Ontario K1A 0H3, Canada.|Centre for Advanced Research in Environmental Genomics, Department of Biology, University of Ottawa , Ottawa, Ontario K1N 6N5, Canada.
authors: Reza
authors: R
authors: Farmahin
authors: Department of Veterinary Biomedical Sciences and Toxicology Centre, University of Saskatchewan , Saskatoon, Saskatchewan S7N 5B3, Canada.|Department of Zoology and Center for Integrative Toxicology, Michigan State University , East Lansing, Michigan 48824, United States.
authors: John P
authors: JP
authors: Giesy
authors: Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, National Wildlife Research Centre, Carleton University , Ottawa, Ontario K1A 0H3, Canada.|Centre for Advanced Research in Environmental Genomics, Department of Biology, University of Ottawa , Ottawa, Ontario K1N 6N5, Canada.
authors: Sean W
authors: SW
authors: Kennedy
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics / Q000378:metabolism; D030161:Avian Proteins / Q000235:genetics / Q000378:metabolism; D001572:Benzofurans / Q000633:toxicity*; D002642:Chick Embryo; D002645:Chickens; D002853:Chromatography, Liquid; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D055768:Halogenated Diphenyl Ethers / Q000528:radiation effects*; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D007477:Ions; D013058:Mass Spectrometry; D010782:Photolysis / Q000187:drug effects / Q000528:radiation effects; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018336:Receptors, Aryl Hydrocarbon / Q000378:metabolism; D013472:Sunlight; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D030161:Avian Proteins; D001572:Benzofurans; D055768:Halogenated Diphenyl Ethers; D007477:Ions; D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D001189:Aryl Hydrocarbon Hydroxylases; C416342:CYP1A4 protein, Gallus gallus; C108015:cytochrome P-450 CYP1A5; C105430:benzofuran