Role of Protein Kinase A in the Proliferation of Cultured Human Arterial SMC Induced by Ox LDL and N LDL

Recent studies suggested that the oxidative modified low density lipoprotein (Ox LDL) existing in the atherosclerotic lesions was associated with the atherosclerogenesis. In previous study it was found that Ox LDL had strikingly stimulating effects on DNA synthesis and proliferation of cultured human arterial smooth muscle cells (SMC). In order to evaluate the role of protein kinase A in the proliferation of SMC induced by Ox LDL and N LDL, a specific activator, dbcAMP, and a specific inhibitor, RPS 20 of a 20 peptide from rabbit muscle for protein kinase A (PKA) were used to activate and inhibit PKA activity in SMC, and then the effects of PKA activator and inhibitor on the Ox LDL and N LDL mediated SMC growth were observed. The results indicated that dbcAMP had stimulating effects on the proliferation of the cultured human SMC both in N LDL and Ox LDL groups exposing the cells to dbc AMP ranging from 0 25 1 mmol/L. At the dose of 1 mmol/L dbcAMP, the cells in N LDL and Ox LDL groups were increased 23% and 19% respectively ( P 0 05 and P 0 05). When the cells exposed to RPS 20 at the dose of 2 μg/ml,the SMC growth in N LDL and Ox LDL groups were decreased 23 8% and 20% respectively ( P 0 05 and P 0 05). These results suggested that the proliferation of cultured human SMC induced by N LDL and Ox LDL might be involved partly in PKA signal transduction pathway.