Figure 4

Rosiglitazone (RSG) also increases protein kinase G (PKG) activity and phosphorylated vasodilator-stimulated phosphoprotein (VASP) at serine 239, resulting in the reduction of vascular smooth muscle cell (VSMC) viability. (a) Phosphorylation of VASP (a substrate of PKG) at serine 239 reflects PKG activity and inhibits VSMC proliferation. Western blot analysis showed that RSG treatment increased VASP phosphorylation, which was reversed by PKG inhibitor, suggesting that RSG increased PKG activity. Moreover, GW9662, a peroxisome proliferator-activated receptor (PPAR)-γ antagonist, reversed the increased phosphorylation of VASP induced by RSG. These results suggest that the effect of RSG on PKG activity is mediated through a PPARγ-dependent mechanism. Arrow indicates the phosphorylated form of VASP at serine 239. The right panel indicates the quantitative graph of the western blot analysis in the left upper panel. V, vehicle, pVASP 239, phospho-VASP at serine 239. (b, c) Quantitative graphs of bromodeoxyuridine (BrdU) incorporation assay for VSMC proliferation and cell counting for VSMC viability. RSG treatment reduced the increased proliferation and viability of VSMCs induced by platelet-derived growth factor (PDGF) treatment. This effect was reversed by PKG inhibitor, suggesting that the effect of RSG on VSMC viability was also regulated by PKG activation. *P<0.05 vs vehicle+PDGF. **P<0.05 vs PDGF+RSG, n=4.