Riccardin C: A natural product that functions as a liver X receptor (LXR)α agonist and an LXRβ antagonist

Liver X receptors (LXRs) α and β share considerable sequence homology and several functions, respond to the same endogenous and synthetic ligands, and play critical roles in maintaining lipid homeostasis. In this study, liverwort-derived riccardin C (RC) and F (RF) were identified as an LXRα agonist/LXRβ antagonist and an LXRα antagonist, respectively. RC and RF bound to LXRs, but had different abilities to recruit a coactivator and thereby induce transactivation. Despite its unique subtype-selective activity, RC enhanced ABCA1 and ABCG1 expression and cellular cholesterol efflux in THP-1 cells. RC may provide a novel tool for identifying subtype-function and drug development.