Regulation of the major histocompatibility complex class I mRNA expression by bile acids in cultured human hepatoma cells.

We investigated the effect of bile acids on major histocompatibility complex (MHC) class I gene expression in the cultured human hepatoma cell HepG2. Not only chenodeoxycholic acid, but its stereoisomer ursodeoxycholic acid as well, increased steady state level of MHC class I mRNA. When various bile acids were studied, inducibility of MHC class I mRNA was closely associated with the hydrophobicity of the corresponding bile acids. Pretreatment of the cells with a protein kinase C (PKC) inhibitor H7 suppressed induction of MHC class I mRNA by those bile acids. Furthermore, treatment of the cells with chenodeoxycholic acid significantly induced translocation of PKC from cytosol to membrane. In summary, our data strongly indicate up-regulatory effect of bile acids on MHC class I mRNA expression, most probably via activation of PKC-dependent pathway.