Differential responses of PPARα, PPARδ, and PPARγ reporter cell lines to selective PPAR synthetic ligands

To characterize the specificity of synthetic compounds for peroxisome proliferator-activated receptors (PPARs), three stable cell lines expressing the ligand binding domain (LBD) of human PPARα, PPARδ, or PPARγ fused to the yeast GAL4 DNA binding domain (DBD) were developed. These reporter cell lines were generated by a two-step transfection procedure. First, a stable cell line, HG5LN, expressing the reporter gene was developed. These cells were then transfected with the different receptor genes. With the help of the three PPAR reporter cell lines, we assessed the selectivity and activity of PPAR agonists GW7647, WY-14-643, L-165041, GW501516, BRL49653, ciglitazone, and pioglitazone. GW7647, L-165041, and BRL49653 were the most potent and selective agonists for hPPARα, hPPARδ, and hPPARγ, respectively. Two PPAR antagonists, GW9662 and BADGE, were also tested. GW9662 was a selective PPARγ antagonist, whereas BADGE was a low-affinity PPAR ligand. Furthermore, GW9662 was a full antagonist on PPARγ and PPARδ, whereas it showed partial agonism on PPARα. We conclude that our stable models allow specific and sensitive measurement of PPAR ligand activities and are a high-throughput, cell-based screening tool for identifying and characterizing PPAR ligands.