Abstract
The aim of the present study is to establish the mechanism associated with the proliferation of PASMCs under ANG II stimulation. The results showed that treatment of PASMCs with ANG II induces an increase in cell proliferation and 100 nM was the optimum concentration for maximum increase in proliferation of the cells. Pretreatment of the cells with AT1, but not AT2, receptor antagonist inhibited ANG II induced cell proliferation. Pretreatment with pharmacological and genetic inhibitors of sphingomyelinase (SMase) and sphingosine kinase (SPHK) prevented ANG II-induced cell proliferation. ANG II has also been shown to induce SMase activity, SPHK phosphorylation and S1P production. In addition, ANG II caused an increase in proMMP-2 expression and activation, ERK1/2 phosphorylation and NADPH oxidase activation. Upon inhibition of MMP-2, SMase activity and S1P level were curbed leading to inhibition of cell proliferation. SPHK was phosphorylated by ERK1/2 during ET-1 stimulation of the cells. ANG II-induced ERK1/2 phosphorylation and proMMP-2 expression and activation in the cells were abrogated upon inhibition of NADPH oxidase activity. Overall, NADPH oxidase plays an important role in proMMP-2 expression and activation and that MMP-2 mediated SMC proliferation occurs through the involvement of Spm-Cer-S1P signaling axis under ANG II stimulation of PASMCs.