Peroxisome Proliferator-Activated Receptor Ligands Stimulate Endothelial Nitric Oxide Production Through Distinct Peroxisome Proliferator-Activated Receptor –Dependent Mechanisms

Objective—We recently reported that the peroxisome proliferator-activated receptor (PPAR ) ligands 15-deoxyprostaglandin J2 (15d-PGJ2) and ciglitazone increased cultured endothelial cell nitric oxide (NO) release without increasing the expression of endothelial nitric oxide synthase (eNOS). The current study was designed to characterize further the molecular mechanisms underlying PPAR -ligand–stimulated increases in endothelial cell NO production. Methods and Results—Treating human umbilical vein endothelial cells (HUVEC) with PPAR ligands (10 mol/L 15d-PGJ2, ciglitazone, or rosiglitazone) for 24 hours increased NOS activity and NO release. In selected studies, HUVEC were treated with PPAR ligands and with the PPAR antagonist GW9662 (2 mol/L), which fully inhibited stimulation of a luciferase reporter gene, or with small interfering RNA to PPAR , which reduced HUVEC PPAR expression. Treatment with either small interfering RNA to PPAR or GW9662 inhibited 15d-PGJ2-, ciglitazone-, and rosiglitazone-induced increases in endothelial cell NO release. Rosiglitazone and 15d-PGJ2, but not ciglitazone, increased heat shock protein 90-eNOS interaction and eNOS ser phosphorylation. The heat shock protein 90 inhibitor geldanamycin attenuated 15d-PGJ2and rosiglitazone-stimulated NOS activity and NO production. Conclusions—These findings further clarify mechanisms involved in PPAR -stimulated endothelial cell NO release and emphasize that individual ligands exert their effects through distinct PPAR -dependent mechanisms. (Arterioscler Thromb Vasc Biol. 2005;25:1810-1816.)