Peroxisome proliferator-activated receptor (PPAR)-γ expression in human vascular smooth muscle cells: inhibition of growth, migration, and c-fos expression by the peroxisome proliferator-activated receptor (PPAR)-γ activator troglitazone

This study was conducted to determine whether cultured human coronary artery and aorta vascular smooth muscle (VSM) cells express the nuclear transcription factor peroxisome proliferator-activated receptor-γ (PPARγ); whether the thiazolidinedione troglitazone, a ligand for PPARγ, would inhibit c-fos expression by these cells; and whether troglitazone would inhibit proliferation and migration induced in these cells by mitogenic growth factors. Using immunoblotting and reverse-transcriptase polymerase chain reaction (RT-PCR) techniques, we show that both human aorta and coronary artery VSM cell lines expressed PPARγ protein and mRNA for both PPARγ isoforms, PPARγ1 and PPARγ2. Immunocytochemical staining localized the PPARγ protein primarily within the nucleus. Troglitazone inhibited basic fibroblast growth factor and platelet-derived growth factor-BB induced DNA synthesis in a dose-dependent manner and downregulated the growth-factor–induced expression of c-fos. Troglitazone also inhibited the migration of coronary artery VSM cells along a platelet-derived growth factor-BB concentration gradient. These findings demonstrate for the first time the expression and nuclear localization of PPARγ in human coronary artery and aorta VSM cells. The data also suggest that the downregulation of c-fos expression, growth-factor–induced proliferation, and migration by VSM may, in part, be mediated by activation of the PPARγ receptor.