Role for enhanced faecal excretion of bile acid in hydroxysteroid sulfotransferase-mediated protection against lithocholic acid-induced liver toxicity.
The efficient clearance of toxic bile acids such as lithocholic acid (LCA) requires drug-metabolizing enzymes. We therefore assessed the influence of pregnenolone 16alpha-carbonitrile (PCN) treatment on LCA-induced hepatotoxicity and disposition of LCA metabolites using female farnesoid X receptor (FXR)-null and wild-type mice. Marked decreases in serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities, and hepatic tauroLCA (TLCA) concentrations were found in LCA-fed wild-type mice co-treated with PCN. Whereas induction of Cyp3a and hydroxysteroid sulfotransferase (Sult2a) proteins was observed in FXR-null and wild-type mice, clear increases in biliary 3alpha-sulfated TLCA but not total 6alpha-hydroxy LCA (taurohyodeoxycholic acid and hyodeoxycholic acid) were only observed in PCN-treated wild-type mice. Biliary 3alpha-sulfated TLCA output rate was increased 7.2-fold, but accounts for only 4.2% of total bile acid output rate in LCA and PCN-co-treated wild-type mice. Total 3alpha-sulfated LCA (LCA and TLCA) was, however, the most abundant bile acid component in faeces suggesting that efficient faecal excretion of biliary 3alpha-sulfated TLCA through escape from enterohepatic circulation. FXR-null mice, which have constitutively high levels of the Sult2a protein, were fed a diet supplemented with 1% LCA and 0.4% dehydroepiandrosterone (DHEA), a typical Sult2a substrate/inhibitor. The faecal total 3alpha-sulfated bile acid excretion was reduced to 62% of FXR-null mice fed only the LCA diet. Hepatic TLCA concentration and serum AST activity were significantly higher in FXR-null mice fed DHEA and LCA diet than in FXR-null mice fed the LCA diet or DHEA diet. These results suggest that hepatic formation of 3alpha-sulfated TLCA is a crucial factor for protection against LCA-induced hepatotoxicity.
Miyata
M
M
Division of Drug Metabolism and Molecular Toxicology, Tohoku University, Graduate School of Pharmaceutical Sciences, Aramaki, Sendai, Japan. miyata@mail.pharm.tohoku.ac.jp
Watase
H
H
Hori
W
W
Shimada
M
M
Nagata
K
K
Gonzalez
F J
FJ
Yamazoe
Y
Y
D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics; D005243:Feces; D008095:Lithocholic Acid / Q000378:metabolism* / Q000633:toxicity; D008099:Liver / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011285:Pregnenolone Carbonitrile / Q000494:pharmacology; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics; D015238:Sulfotransferases / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics; D000099150:Receptor, Farnesoid X-Activated
D004268:DNA-Binding Proteins; D008095:Lithocholic Acid; D011285:Pregnenolone Carbonitrile; D018160:Receptors, Cytoplasmic and Nuclear; D015238:Sulfotransferases; D014157:Transcription Factors; D000099150:Receptor, Farnesoid X-Activated; C028152:alcohol sulfotransferase