Nuclear Receptors CAR and PXR in Metabolism and Elimination of Drugs

The metabolism and elimination of drugs is mainly mediated by various cytochrome P450 (CYP) enzymes, conjugative enzymes, transporters, and efflux proteins. Members of these gene families are up-regulated at transcriptional level by drug exposure, thus leading to induction of drug metabolism and elimination. There is compelling evidence that this induction is controlled by two drug-activated nuclear receptors, constitutive androstane receptor (CAR), and pregnane X receptor (PXR). This mini-review summarizes the current knowledge of CAR and PXR, their DNA and ligand binding preferences, expression patterns and polymorphisms, mechanisms of activation, and target genes.