Constitutive androstane receptor-mediated changes in bile acid composition contributes to hepatoprotection from lithocholic acid-induced liver injury in mice.
Pharmacological activation of the constitutive androstane receptor (CAR) protects the liver during cholestasis. The current study evaluates how activation of CAR influences genes involved in bile acid biosynthesis as a mechanism of hepatoprotection during bile acid-induced liver injury. CAR activators phenobarbital (PB) and 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP) or corn oil (CO) were administered to C57BL/6 wild-type (WT) and CAR knockout (CAR-null) mice before and during induction of intrahepatic cholestasis using the secondary bile acid, lithocholic acid (LCA). In LCA-treated WT and all the CAR-null groups (excluding controls), histology revealed severe multifocal necrosis. This pathology was absent in WT mice pretreated with PB and TCPOBOP, indicating CAR-dependent hepatoprotection. Decreases in total hepatic bile acids and hepatic monohydroxy, dihydroxy, and trihydroxy bile acids in PB- and TCPOBOP-pretreated WT mice correlated with hepatoprotection. In comparison, concentrations of monohydroxylated and dihydroxylated bile acids were increased in all the treated CAR-null mice compared with CO controls. Along with several other enzymes (Cyp7b1, Cyp27a1, Cyp39a1), Cyp8b1 expression was increased in hepatoprotected mice, which could be suggestive of a shift in the bile acid biosynthesis pathway toward the formation of less toxic bile acids. In CAR-null mice, these changes in gene expression were not different among treatment groups. These results suggest CAR mediates a shift in bile acid biosynthesis toward the formation of less toxic bile acids, as well as a decrease in hepatic bile acid concentrations. We propose that these combined CAR-mediated effects may contribute to the hepatoprotection observed during LCA-induced liver injury.
Beilke
Lisa D
LD
Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, 1703 East Mabel, Tucson, AZ 85721, USA.
Aleksunes
Lauren M
LM
Holland
Ricky D
RD
Besselsen
David G
DG
Beger
Rick D
RD
Klaassen
Curtis D
CD
Cherrington
Nathan J
NJ
D000818:Animals; D001647:Bile Acids and Salts / Q000096:biosynthesis / Q000378:metabolism*; D056486:Chemical and Drug Induced Liver Injury / Q000473:pathology*; D002851:Chromatography, High Pressure Liquid; D000090702:Constitutive Androstane Receptor; D004247:DNA / Q000096:biosynthesis / Q000235:genetics; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D008095:Lithocholic Acid / Q000037:antagonists & inhibitors* / Q000633:toxicity*; D008099:Liver / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D015345:Oligonucleotide Probes; D010634:Phenobarbital / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D012313:RNA / Q000096:biosynthesis / Q000235:genetics; D018160:Receptors, Cytoplasmic and Nuclear / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D000099150:Receptor, Farnesoid X-Activated
D001647:Bile Acids and Salts; D000090702:Constitutive Androstane Receptor; D004247:DNA; D004268:DNA-Binding Proteins; D008095:Lithocholic Acid; D015345:Oligonucleotide Probes; D010634:Phenobarbital; D011725:Pyridines; D012313:RNA; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D000099150:Receptor, Farnesoid X-Activated; C028474:1,4-bis(2-(3,5-dichloropyridyloxy))benzene