Protective response of the Ah receptor to ANIT-induced biliary epithelial cell toxicity in see-through medaka.
The adaptive role of the aryl hydrocarbon receptor (Ah receptor or AHR) in protecting against disease-related conditions remains unclear in nonmammalian models, particularly teleosts. Therefore, this study focused on the potential role of AHR in response to biliary epithelial cell toxicity and hepatobiliary alteration in medaka. See-through medaka (STII strain) were exposed for 96 h using the biliary toxicant alpha-naphthylisothiocyanate (ANIT) as a reagent, and fish were evaluated daily using histological and ultrastructural analysis, and by imaging directly through the body wall of living fish. Brightfield and transmission electron microscopy showed that a single ANIT dose (40 mg/kg) specifically induced swelling and apoptosis of bile preductular epithelial cells (BPDECs) as early as 6 h after initial exposure. Following ANIT-induced BPDEC toxicity, in vivo imaging of STII medaka showed significant gallbladder discoloration from 48-72 h. Collectively, these pathologic data suggested that ANIT exposure resulted in acute hepatobiliary changes, lasting < 96 h following initial exposure. We then tested the potential role of AHR in response to ANIT-induced hepatobiliary alteration. Overall, we demonstrated that (1) transient AHR activation and cytochrome P450 1A (CYP1A) induction in livers occurred during ANIT-induced hepatobiliary impairment, (2) pretreatment with an AHR agonist partially protected against acute hepatobiliary alteration, and (3) using a luciferase-based reporter assay, the bile pigment bilirubin weakly activated mouse AHR and binding to medaka-specific CYP1A promoter, resulting in AHR element-driven transcription. Given that bile acids and pigments are present in mammalian and fish liver, these studies collectively suggest that bile-induced AHR activation may be conserved between teleosts and rodents.
Volz
David C
DC
Integrated Toxicology Program and Nicholas School of the Environment and Earth Sciences, Duke University, Durham, North Carolina 27708.
Kullman
Seth W
SW
Howarth
Deanna L
DL
Hardman
Ron C
RC
Hinton
David E
DE
D015058:1-Naphthylisothiocyanate / Q000633:toxicity*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001653:Bile Ducts, Intrahepatic / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D001663:Bilirubin / Q000494:pharmacology; D045744:Cell Line, Tumor; D002780:Cholestasis, Intrahepatic / Q000378:metabolism / Q000517:prevention & control*; D003001:Cloning, Molecular; D019363:Cytochrome P-450 CYP1A1 / Q000096:biosynthesis / Q000235:genetics; D004195:Disease Models, Animal; D004336:Drug Antagonism; D004790:Enzyme Induction; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D005704:Gallbladder / Q000187:drug effects / Q000473:pathology; D015870:Gene Expression / Q000187:drug effects; D007274:Injections, Intraperitoneal; D008099:Liver / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D009990:Oryzias / Q000502:physiology*; D010858:Pigmentation / Q000235:genetics; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D018336:Receptors, Aryl Hydrocarbon / Q000819:agonists* / Q000187:drug effects / Q000378:metabolism*
D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D015058:1-Naphthylisothiocyanate; D019363:Cytochrome P-450 CYP1A1; D001663:Bilirubin