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.