The inhibitory effects of m-nisoldipine on the 5-hydroxytryptamine-induced proliferation of pulmonary artery smooth muscle cells via Ca2+ antagonism and antioxidant mechanisms

The excessive proliferation of pulmonary artery smooth muscle cells (PASMCs) plays a critical role in the development of pulmonary arterial hypertension. Recent studies indicate that Ca(2+) and reactive oxygen species are critically involved in the process of smooth muscle cell proliferation stimulated by mitogens, such as 5-hydroxytryptamine (5-HT). Because m-nisoldipine, a Ca(2+) channel blocker of the dihydropyridine class, possesses some calcium antagonistic and antioxidant properties, we investigated the effect of m-nisoldipine on PASMC proliferation. The results indicated that m-nisoldipine inhibited 5-HT-induced PASMC proliferation, evaluated by BrdU incorporation and the MTT assay, and this effect was associated with a decreased expression of proliferating cell nuclear antigen (PCNA). Flow cytometry analysis showed that m-nisoldipine blocked 5-HT-induced cell-cycle progression by arresting the cells in the G(0)/G(1) phase. Next, the production of reactive oxygen species and the levels of [Ca(2+)](i) in PASMCs were measured by laser scanning confocal microscopy; m-nisoldipine pretreatment attenuated the [Ca(2+)](i) elevation and the production of reactive oxygen species induced by 5-HT. In addition, m-nisoldipine significantly decreased the 5-HT-induced activation of extracellular signal-regulated kinase (ERK1/2) and c-Jun N-terminal kinase (JNK) and the subsequent c-fos and c-jun mRNA expression. Meanwhile, results also showed that N-acetylcysteine (a reactive oxygen species scavenger) suppressed the proliferation and the ERK1/2 and JNK activation induced by 5-HT. In summary, this study demonstrated that m-nisoldipine effectively suppressed the 5-HT-induced PASMC proliferation, ERK1/2 and JNK activation and subsequent c-fos and c-jun mRNA expression, all of which might be associated with the Ca(2+) antagonistic and antioxidant properties of m-nisoldipine.