Expression and function of claudins in hepatocytes.

Tight junctions of hepatocytes play crucial roles in the barrier to keep bile in bile canaliculi away from the blood circulation, which we call the blood-biliary barrier. Tight junction proteins of hepatocytes are regulated by various cytokines and growth factors via distinct signal transduction pathways. To investigate changes in expression and function of tight junction proteins including claudins via signal transduction pathways in hepatocytes during EMT induced by TGF-β, we examined effects of TGF-β on expression and localization of the integral tight junction proteins, claudin-1, -2, and occludin, as well as the fence function by using primary cultures of adult rat hepatocytes.