The statin class of HMG-CoA reductase inhibitors demonstrate differential activation of the nuclear receptors PXR, CAR and FXR, as well as their downstream target genes

The therapeutic class of HMG-CoA reductase inhibitors, the statins are central agents in the treatment of hypercholesterolaemia and the associated conditions of cardiovascular disease, obesity and metabolic syndrome. Although statin therapy is generally considered safe, a number of known adverse effects do occur, most commonly treatment-associated muscular pain. In vitro evidence also supports the potential for drug--drug interactions involving this class of agents, and to examine this a ligand-binding assay was used to determine the ability of six clinically used statins for their ability to directly activate the nuclear receptors pregnane X-receptor (PXR), farnesoid X-receptor (FXR) and constitutive androstane receptor (CAR), demonstrating a relative activation of PXR > FXR > CAR. Using reporter gene constructs, we demonstrated that this order of activation is mirrored at the transcriptional activation level, with PXR-mediated gene activation being pre-eminent. Finally, we described a novel regulatory loop, whereby activation of FXR by statins increases PXR reporter gene expression, potentially enhancing PXR-mediated responses. Delineating the molecular interactions of statins with nuclear receptors is an important step in understanding the full biological consequences of statin exposure. This demonstration of their ability to directly activate nuclear receptors, leading to nuclear receptor cross-talk, has important potential implications for their use within a polypharmacy paradigm.