Nuclear hormone receptor-dependent regulation of hepatic transporters and their role in the adaptive response in cholestasis.

1. Hepatobiliary transport systems are essential for the uptake and excretion of a variety of organic anions including bile acids and bilirubin. Perturbation of this vital liver function can result in pathological conditions such as cholestasis, where the formation of bile at the canaliculus is impaired resulting in the intrahepatic accumulation of toxic bile constituents. 2. Members of the nuclear hormone receptor superfamily are important mediators of the adaptive response during cholestasis controlling the expression of transporters and other proteins with the aim to limit tissue damage. Bile acids are the endogenous ligands for these nuclear hormone receptors and therefore directly participate in the control of their own transport and metabolism. 3. Adaptive events include repression of bile acid uptake and de novo bile acid synthesis as well as a concomitant induction of alternative efflux routes and bile acid detoxification. Importantly, the adaptation also extends to other organs such as intestine and kidney to facilitate elimination of bile acids from the body. 4. This review provides an overview of the transcriptional regulation of bile acid transporting proteins and metabolizing enzymes mediated by nuclear hormone receptors. Furthermore, the complex networks between nuclear hormone receptors and regulated genes are illustrated and implications of targeting these receptors for the treatment of cholestasis are discussed.