Adenovirus-mediated gene transfer of cGMP-dependent protein kinase increases the sensitivity of cultured vascular smooth muscle cells to the antiproliferative and pro-apoptotic effects of nitric oxide cGMP

Studies in vitro have underestimated the importance of cGMP-dependent prote in kinase (PKG) in the modulation of vascular smooth muscle cell (SMC) prol iferation and apoptosis in vivo, This is attributable, in part, to a rapid decline in PKG levels as vascular SMC are passaged in culture, We used a re combinant adenovirus encoding PKG (Ad.PKG) to augment kinase activity in cu ltured rat pulmonary artery SMC (RPaSMC), Incubation of Ad.PKG-infected RPa SMC (multiplicity of infection = 200) with 8-Br-cGMP decreased serum-stimul ated DNA synthesis by 85% and cell proliferation at day 5 by 74%. The effec t of 8-Br-cGMP on DNA synthesis in Ad.PKG-infected RPaSMC was blocked by KT 5823 (PKG inhibitor), but not by KT5720 (cAMP-dependent protein kinase inhi bitor). A nitric oxide (NO) donor compound, S-nitrosoglutathione, at concen trations as low as 100 nM, inhibited DNA synthesis in Ad.PKG-infected RPaSM C, but not in uninfected cells or in cells infected with a control adenovir us. In addition, 8-Br-cGMP and S-nitrosoglutathione induced apoptosis in se rum-deprived RPaSMC infected with Ad.PKG, but not in uninfected cells or in cells infected with a control adenovirus, These results demonstrate that m odulation of PKG levels in vascular SMC can alter the sensitivity of these cells to NO and cGMP, Moreover, these observations suggest an important rol e for PKG in the regulation of vascular SMC proliferation and apoptosis by NO and cGMP.