Compensatory induction of liver efflux transporters in response to ANIT-induced liver injury is impaired in FXR-null mice.
Alpha-naphthyl isothiocyanate (ANIT) is a hepatotoxicant that produces acute intrahepatic cholestasis in rodents. Farnesoid X receptor (FXR) and pregnane X receptor (PXR) are two major bile acid sensors in liver. The purpose of this study was to characterize the regulation of hepatic transporters by FXR and PXR during ANIT-induced liver injury. Wild-type, FXR-null, and PXR-null mice were administered ANIT (75 mg/kg, po) and evaluated 48 h later for hepatotoxicity and messenger RNA (mRNA) expression of basolateral uptake (sodium taurocholate-cotransporting polypeptide, organic anion transporting polypeptide [Oatp] 1a1, Oatp1a4, Oatp1b2) and efflux transporters (organic solute transporter [Ost] alpha, Ostbeta, multidrug resistance-associated protein [Mrp] 3, Mrp4), as well as canalicular transporters (bile salt export pump [Bsep], Mrp2, multidrug resistance protein 2 [Mdr2], ATPase, class I, type 8B, member 1 [Atp8b1]). Livers from wild-type and PXR-null mice had comparable multifocal necrosis 48 h after ANIT. However, ANIT-treated FXR-null mice have fewer and smaller necrotic foci than wild-type mice but had scattered single-cell hepatocyte necrosis throughout the liver. Serum alanine transaminase, alkaline phosphatase (ALP), and direct bilirubin were increased in all genotypes, with higher ALP levels in FXR-null mice. Serum and liver unconjugated bile acids were higher in ANIT-treated FXR-null mice than the other two genotypes. ANIT induced mRNA expression of Mdr2, Bsep, and Atp8b1 in wild-type and PXR-null mice but failed to upregulate these genes in FXR-null mice. mRNA expression of uptake transporters declined in livers of all genotypes following ANIT treatment. ANIT increased Ostbeta and Mrp3 mRNA in livers of wild-type and PXR-null mice but did not alter Ostbeta mRNA in FXR-null mice. In conclusion, FXR deficiency enhances susceptibility of mice to ANIT-induced liver injury, likely a result of impaired induction of hepatobiliary efflux transporters and subsequent hepatic accumulation of unconjugated bile acids.
Cui
Yue J
YJ
Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
Aleksunes
Lauren M
LM
Tanaka
Yuji
Y
Goedken
Michael J
MJ
Klaassen
Curtis D
CD
D015058:1-Naphthylisothiocyanate / Q000633:toxicity*; D000410:Alanine Transaminase / Q000097:blood; D000818:Animals; D001219:Aspartate Aminotransferases / Q000097:blood; D001647:Bile Acids and Salts / Q000097:blood / Q000378:metabolism; D015415:Biomarkers; D021121:Branched DNA Signal Amplification Assay; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D056486:Chemical and Drug Induced Liver Injury / Q000235:genetics* / Q000378:metabolism*; D002780:Cholestasis, Intrahepatic / Q000139:chemically induced / Q000235:genetics; D005455:Fluorescent Antibody Technique; D007555:Isoxazoles / Q000494:pharmacology; D008099:Liver / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D000077297:Pregnane X Receptor; D012313:RNA / Q000096:biosynthesis / Q000235:genetics; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists / Q000235:genetics*; D011987:Receptors, Steroid / Q000235:genetics; D000099150:Receptor, Farnesoid X-Activated
D015058:1-Naphthylisothiocyanate; D000410:Alanine Transaminase; D001219:Aspartate Aminotransferases; D001647:Bile Acids and Salts; D015415:Biomarkers; D002352:Carrier Proteins; D007555:Isoxazoles; D000077297:Pregnane X Receptor; D012313:RNA; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D000099150:Receptor, Farnesoid X-Activated; C412815:GW 4064