Effects of vesnarinone on nitric oxide synthesis in rat cardiac myocytes.

OBJECTIVE The purpose of this study was to investigate the effects of vesnarinone on nitric oxide (NO) synthesis in cardiac myocytes. METHODS We measured the accumulation of nitrite, a stable oxidation product of NO synthase (iNOS) protein in cultured neonatal rat cardiac myocytes. RESULTS Incubation of the cultures with interleukin-1 beta (IL-1 beta; 10 ng/ml) and tumor necrosis factor alpha (TNF alpha; 10 ng/ml) caused a marked increase in nitrite production. Although vesnarinone by itself showed no effect on nitrite accumulation, it enhanced cytokine-induced nitrite production by cardiac myocytes in a dose-dependent manner. The effect of vesnarinone was completely abolished in the presence of NG-monomethyl-L-arginine or actinomycin D. The vesnarinone-induced nitrite production was accompanied by increased iNOS protein expression. In the presence of dibutyryl-cAMP, cytokine-induced nitrite accumulation was further increased, but the stimulatory effect on vesnarinone on nitrite accumulation was diminished. The effect of vesnarinone was also inhibited by Rp-8-Br-cAMPS, a competitive inhibitor of protein kinase A, in a dose-dependent manner. CONCLUSIONS These findings indicate that vesnarinone increases NO synthesis in cytokine-stimulated cardiac myocytes, at least partially through a cAMP-dependent pathway.