Differential interactions of antiretroviral agents with LXR, ER and GR nuclear receptors: potential contributing factors to adverse events.

BACKGROUND AND PURPOSE: Antiretroviral (ARV) drugs activate pregnane X receptors and constitutive androstane receptors, increasing the risk of drug interactions due to altered drug metabolism and disposition. The closely related liver X receptors (LXRα/ß), oestrogen receptors (ERα/ß) and glucocorticoid receptor (GR) regulate many endogenous processes such as lipid/cholesterol homeostasis, cellular differentiation and inflammation. However, ARV drug activation of these nuclear receptors has not been thoroughly investigated. EXPERIMENTAL APPROACH: The ability of an ARV drug library to activate LXRα/ß, ERα/ß and GR was assessed using a combined in silico and in vitro approach encompassing computational docking and molecular descriptor filtering, cell-free time-resolved fluorescence resonance energy transfer co-activator assays to assess direct binding to ligand-binding domains (LBDs), cell-based reporter assays and target gene expression. KEY RESULTS: Direct LBD interactions with LXRα and/or LXRß were predicted in silico and confirmed in vitro for darunavir, efavirenz, flavopiridol, maraviroc and tipranavir. Likewise, efavirenz was also predicted and confirmed as a ligand of ERα-LBD. Interestingly, atazanavir and ritonavir also activated LXRα/ß in reporter assays, while tipranavir enhanced transcriptional activity of ERα. Effects on ER and LXR target gene expression were confirmed for efavirenz and tipranavir. CONCLUSIONS AND IMPLICATIONS: There was good agreement between in silico predictions and in vitro results. However, some nuclear receptor interactions identified in vitro were probably due to allosteric effects or nuclear receptor cross-talk, rather than direct LBD binding. This study indicates that some of the adverse effects associated with ARV use may be mediated through 'off-target' effects involving nuclear receptor activation.

Rational targeting of peroxisome proliferating activated receptor subtypes.

Peroxisome-Proliferating Activating Receptors (PPARs) have long been established as validated targets for therapeutic intervention in several important disease states, including type II diabetes and dyslipidemia. More recently, evidence has implicated novel regulatory roles for PPARs in cancer, inflammation and neurodegeneration. Although current PPAR targeting treatments exist, most are associated with undesirable and potentially life-threatening side effects. Consequent from these observations is a significant research effort into PPAR modulator drug discovery and design. In this review, the progress of PPAR modulator design over the past several years will be highlighted. Particular focus on how detailed structural information and virtual screening techniques can aid in the rational design and development of tailored next generation PPAR drug therapeutics will be discussed.