Discovery of new liver X receptor agonists by pharmacophore modeling and shape-based virtual screening

Abstract

Agonists of liver X receptors (LXR) α and β are important regulators of cholesterol metabolism, but agonism of the LXRα subtype appears to cause hepatic lipogenesis, suggesting LXRβ-selective activators are attractive new lipid lowering drugs. In this work, pharmacophore modeling and shape-based virtual screening were combined to predict new LXRβ-selective ligands. Out of the 10 predicted compounds, three displayed significant LXR activity. Two activated both LXR subtypes. The third compound activated LXRβ 1.8-fold over LXRα.

Figure 1

Pharmacophore models that showed a significant enrichment of highly LXRβ-selective compounds. The models are named after the X-ray crystal structure protein data bank code from which they were originally derived. Blue spheres illustrate hydrophobic features. Green arrows represent hydrogen bond acceptors. Brown spheres represent aromatic interactions with indicated direction. The gray spheres signify so-called exclusion volumes that represent the space occupied by the protein. Model 1pc6 consists of two hydrophobic features, one hydrogen bond acceptor, an aromatic interaction, and 31 exclusion volumes. Model 1pqc consists of three hydrophobic features, one hydrogen bond acceptor, and 458 exclusion volumes. Model 3fal consists of three hydrophobic features, one hydrogen bond acceptor, and 514 exclusion volumes.

Figure 2

ROCS shape query derived from a low energy 3D conformation generated in Omega of the LXRβ-selective ligand 1.The green spheres illustrate ROCS ring features, and the red spheres illustrate hydrogen bond acceptors.

Chart 1. 10 Virtual Hits Selected for Biological Testinga

Figure 3

Effect of compounds 2–11 and LXR agonist GW3965 on LXRα- and LXRβ-luciferase activity in HEK293 cells. HEK293 cells were transiently transfected with hLXREx3TK-Luc as a reporter plasmid, pCMV-hLXR-α or pCMV-hLXR-β as expression vectors, and GFP as internal transfection control. Cells were treated with the indicated compounds. LXR agonist GW3965 was used as the positive control and DMSO as the negative control. At the end of the incubation period, the cells were lysed and assayed for luciferase activities. The results are expressed as relative luciferase activity (fold difference compared to solvent control). All values are means ± SEM (n = 3, each in quadruplicate) vs control, *p < 0.05, **p < 0.01, and ***p < 0.001.