title: Ortho-aminoazotoluene activates mouse constitutive androstane receptor (mCAR) and increases expression of mCAR target genes.
abstract: 2'-3-dimethyl-4-aminoazobenzene (ortho-aminoazotoluene, OAT) is an azo dye and a rodent carcinogen that has been evaluated by the International Agency for Research on Cancer (IARC) as a possible (class 2B) human carcinogen. Its mechanism of action remains unclear. We examined the role of the xenobiotic receptor Constitutive Androstane Receptor (CAR, NR1I3) as a mediator of the effects of OAT. We found that OAT increases mouse CAR (mCAR) transactivation in a dose-dependent manner. This effect is specific because another closely related azo dye, 3'-methyl-4-dimethyl-aminoazobenzene (3'MeDAB), did not activate mCAR. Real-time Q-PCR analysis in wild-type C57BL/6 mice revealed that OAT induces the hepatic mRNA expression of the following CAR target genes: Cyp2b10, Cyp2c29, Cyp3a11, Ugt1a1, Mrp4, Mrp2 and c-Myc. CAR-null (Car(-/-)) mice showed no increased expression of these genes following OAT treatment, demonstrating that CAR is required for their OAT dependent induction. The OAT-induced CAR-dependent increase of Cyp2b10 and c-Myc expression was confirmed by Western blotting. Immunohistochemistry analysis of wild-type and Car(-/-) livers showed that OAT did not acutely induce hepatocyte proliferation, but at much later time points showed an unexpected CAR-dependent proliferative response. These studies demonstrate that mCAR is an OAT xenosensor, and indicate that at least some of the biological effects of this compound are mediated by this nuclear receptor.
authors.affiliation: Department of Molecular and Cellular Biology, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA. maria.smetanina@gmail.com
authors.forename: Mariya A
authors.initials: MA
authors.lastname: Smetanina
authors.forename: Mariya Y
authors.initials: MY
authors.lastname: Pakharukova
authors.forename: Svitlana M
authors.initials: SM
authors.lastname: Kurinna
authors.forename: Bingning
authors.initials: B
authors.lastname: Dong
authors.forename: Juan P
authors.initials: JP
authors.lastname: Hernandez
authors.forename: David D
authors.initials: DD
authors.lastname: Moore
authors.forename: Tatyana I
authors.initials: TI
authors.lastname: Merkulova
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics; D049109:Cell Proliferation / Q000187:drug effects; D000090702:Constitutive Androstane Receptor; D000072467:Cytochrome P450 Family 2; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D018160:Receptors, Cytoplasmic and Nuclear / Q000187:drug effects* / Q000502:physiology; D013250:Steroid Hydroxylases / Q000235:genetics; D009762:o-Aminoazotoluene / Q000633:toxicity*
chemical_list: D000090702:Constitutive Androstane Receptor; C000716327:NR1I3 protein, human; C000716328:Nr1i3 protein, mouse; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; C101679:Cyp2b10 protein, mouse; D000072467:Cytochrome P450 Family 2; D009762:o-Aminoazotoluene