TY - JOUR T1 - Mode of PPARγ Activation by Luteolin JF - Molecular Pharmacology JO - Mol Pharmacol DO - 10.1124/mol.111.076216 SP - mol.111.076216 AU - Ana C. Puhl AU - Amanda Bernardes AU - Rodrigo L. Silveira AU - Jing Yuan AU - Jessica L. O. Campos AU - Daniel M. Saidemberg AU - Mario S. Palma AU - Aleksandra Cvoro AU - Stephen D. Ayers AU - Paul Webb AU - Peter S. Reinach AU - Munir S. Skaf AU - Igor Polikarpov Y1 - 2012/03/05 UR - http://molpharm.aspetjournals.org/content/early/2012/03/05/mol.111.076216.abstract N2 - Peroxisome proliferator-activated receptor γ (PPARγ) is a target for treatment of type II diabetes and other conditions. PPARγ full agonists, like thiazolidinediones (TZDs), are effective insulin sensitizers and anti-inflammatories but their use is limited by adverse side effects. Luteolin is flavonoid with anti-inflammatory actions that binds PPARγ but, unlike TZDs, does not promote adipocyte differentiation. However, previous reports variously suggested that luteolin is a PPARγ agonist or an antagonist. We show that luteolin exhibits weak partial agonist/antagonist activity in transfections, inhibits several PPARγ target genes in 3T3-L1 cells (LPL, ORL1 and CBPα) and PPARγ-dependent adipogenesis but activates GLUT4 similarly to rosiglitazone implying gene-specific partial agonism. The crystal structure of the PPARγ ligand binding domain (LBD) reveals that luteolin occupies buried ligand binding pocket (LBP) but binds an inactive PPARγ LBD conformer and occupies a space near the β-sheet region far from activation helix (H12) consistent with partial agonist/antagonist actions. A single myristic acid molecule simultaneously binds the LBP, suggesting that luteolin may cooperate with other ligands to bind PPARγ, and molecular dynamics simulations show that luteolin and myristic acid cooperate to stabilize the Ω-loop between H2’ and 3 and β-sheet region. Interestingly, luteolin strongly suppresses hypertonicity-induced release of the pro-inflammatory IL-8 from human corneal epithelial cells (HCEC) and reverses reductions in transepithelial electrical resistance (TEER). This effect is PPARγ dependent. We propose that activities of luteolin are related to its singular binding mode, that anti-inflammatory activity does not require H12 stabilization and that our structure can be useful in developing safe selective PPARγ modulators. ER -