title: Automated dose-response analysis and comparative toxicogenomic evaluation of the hepatic effects elicited by TCDD, TCDF, and PCB126 in C57BL/6 mice.
abstract: The toxic equivalency factor (TEF) approach recommended by the World Health Organization is used to quantify dioxin-like exposure concentrations for mixtures of polychlorinated dibenzo-dioxins, -furans, and polychlorinated biphenyls (PCBs), including 2,3,7,8-tetrachlorodibenzofuran (TCDF) and 3,3',4,4',5-pentachlorobiphenyl (PCB126) relative to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Whole-genome microarrays were used to evaluate the hepatic gene expression potency of TCDF and PCB126 relative to TCDD with complementary histopathology, tissue level analysis, and ethoxyresorufin-O-deethylase (EROD) assay results. Immature ovariectomized C57BL/6 mice were gavaged with 0.001, 0.01, 0.03, 0.1, 0.3, 1, 3, 10, 30, 100, and 300 μg/kg TCDD and TEF-adjusted doses (TEF for TCDF and PCB126 is 0.1) of TCDF or PCB126 (1, 3, 10, 30, 100, 300, 1000, and 3000 μg/kg of TCDF or PCB126) or sesame oil vehicle and sacrificed 24 h post dose. In general, TCDD, TCDF, and PCB126 tissue levels, as well as histopathological effects, were comparable when comparing TEF-adjusted doses. Automated dose-response modeling (ToxResponse Modeler) of the microarray data identified 210 TCDF and 40 PCB126 genes that exhibited sigmoidal dose-response curves with comparable slopes when compared with TCDD. These similar responses were used to calculate a median TCDF gene expression relative potency (REP) of 0.06 and a median PCB126 gene expression REP of 0.02. REPs of 0.02 were also calculated for EROD induction for both compounds. Collectively, these data suggest that differences in the ability of the liganded aryl hydrocarbon receptor:AhR nuclear translocator complex to elicit differential hepatic gene expression, in addition to pharmacokinetic differences between ligands, influence their potency in immature ovariectomized C57BL/6 mice.
authors: Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, Michigan 48824, USA.
authors: Anna K
authors: AK
authors: Kopec
authors: Lyle D
authors: LD
authors: Burgoon
authors: Daher
authors: D
authors: Ibrahim-Aibo
authors: Ashley R
authors: AR
authors: Burg
authors: Andrea W
authors: AW
authors: Lee
authors: Colleen
authors: C
authors: Tashiro
authors: Dave
authors: D
authors: Potter
authors: Bonnie
authors: B
authors: Sharratt
authors: Jack R
authors: JR
authors: Harkema
authors: J Craig
authors: JC
authors: Rowlands
authors: Robert A
authors: RA
authors: Budinsky
authors: Timothy R
authors: TR
authors: Zacharewski
mesh_terms: D000818:Animals; D001572:Benzofurans / Q000493:pharmacokinetics / Q000633:toxicity*; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004785:Environmental Pollutants / Q000493:pharmacokinetics / Q000633:toxicity*; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D008024:Ligands; D008099:Liver / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D020411:Oligonucleotide Array Sequence Analysis; D009929:Organ Size / Q000187:drug effects; D010052:Ovariectomy; D011078:Polychlorinated Biphenyls / Q000493:pharmacokinetics / Q000633:toxicity*; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity*; D012333:RNA, Messenger / Q000378:metabolism; D043922:Toxicogenetics
chemical_list: D001572:Benzofurans; D004785:Environmental Pollutants; D008024:Ligands; D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D011078:Polychlorinated Biphenyls; D019363:Cytochrome P-450 CYP1A1; C023035:3,4,5,3',4'-pentachlorobiphenyl; C014211:2,3,7,8-tetrachlorodibenzofuran