Compensatory induction of liver efflux transporters in response to ANIT-induced liver injury is impaired in FXR-null mice

Toxicol Sci. 2009 Jul;110(1):47-60. doi: 10.1093/toxsci/kfp094. Epub 2009 Apr 30.

Abstract

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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • 1-Naphthylisothiocyanate / toxicity*
  • Alanine Transaminase / blood
  • Animals
  • Aspartate Aminotransferases / blood
  • Bile Acids and Salts / blood
  • Bile Acids and Salts / metabolism
  • Biomarkers
  • Branched DNA Signal Amplification Assay
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Chemical and Drug Induced Liver Injury / genetics*
  • Chemical and Drug Induced Liver Injury / metabolism*
  • Cholestasis, Intrahepatic / chemically induced
  • Cholestasis, Intrahepatic / genetics
  • Fluorescent Antibody Technique
  • Isoxazoles / pharmacology
  • Liver / metabolism*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Pregnane X Receptor
  • RNA / biosynthesis
  • RNA / genetics
  • Receptors, Cytoplasmic and Nuclear / agonists
  • Receptors, Cytoplasmic and Nuclear / genetics*
  • Receptors, Steroid / genetics

Substances

  • Bile Acids and Salts
  • Biomarkers
  • Carrier Proteins
  • Isoxazoles
  • Pregnane X Receptor
  • Receptors, Cytoplasmic and Nuclear
  • Receptors, Steroid
  • farnesoid X-activated receptor
  • 1-Naphthylisothiocyanate
  • RNA
  • Aspartate Aminotransferases
  • Alanine Transaminase
  • GW 4064