Injuriousness of glycochenodeoxycholate and taurochenodeoxycholate to cultured hepatocytes

Abstract

Among bile acids whose levels increase greatly during hepatic failure, glycocholate (GC), taurocholate (TC), glycochenodeoxycholate (GCDC), and taurochenodeoxycholate (TCDC) are potentially hepatotoxic. Most bioartificial liver systems utilize isolated or cultured hepatocytes, and therefore the injuriousness of these bile acids might constitute a clinical drawback. To assess the possible hepatocellular injuriousness of these bile acids, changes in gluconeogenesis, ureagenesis, alanine aminotransferase (ALT) in medium, DNA contents, and morphological changes in hepatocytes were analyzed. The measurements were made 1, 3, and 5 days after cultured hepatocytes were exposed to the bile acids. The concentration of each bile acid was 2 mM, which is lower than their reported critical micelle concentrations (CMCs). TCDC and GCDC showed significantly high elevation of ALT, significantly low gluconeogenesis and ureagenesis activities, and low DNA contents. They also caused serious injury to hepatocytes on morphological study. TCDC showed heavier hepatocyte toxicity than did GCDC. Although the DNA contents in the GCDC group were relatively preserved throughout the experimental period, marked necrosis and deformity of hepatocytes were observed, whereas GC and TC were not seen to cause any injury to hepatocytes. The CMCs of TCDC and GCDC were reported to be 2.5 mM. However, our experiment showed that 2 mM of TCDC or GCDC has strong toxicity to hepatocytes. This raises the possibility that the CMCs of TCDC and GCDC could be 2 mM or even lower. In the clinical use of a bioartificial liver, removal of elevated TCDC and GCDC must be considered. Even if the levels of individual bile acids are lower than these CMCs, their cumulative hepatotoxic effect must be considered and requires further investigation.