OBJECTIVETo examine whether calcineurin/NFAT signaling pathway mediates endothelin-1 (ET-1)-induced proliferation of pulmonary artery smooth muscle cells (PASMCs) by regulating phosphodiesterase-5 (PDE5) and the effect of the selective calcineurin inhibitor cyclosporine A and PDE5 inhibitor sildenafil on ET-1-induced PASMC proliferation.

METHODSPASMCs were treated with ET-1 to stimulate their proliferation with or without prior treatment of the cells with CsA or sildenafil. Calcineurin activity in the cells was measured using a calcineurin activity assay kit, PDE5 expression examined using immunoblotting, and cGMP level detected using a cGMP direct immunoassay kit. PASMC proliferation following the treatments was determined using [(3)H]thymidine incorporation assay.

RESULTSET-1 caused a 2.05-fold increase in the cellular calcineurin activity, a 1.80-fold increase in PDE5 expression, and a 3.20-fold increase in the DNA synthesis rate, and reduced the cGMP level by 67%. Pretreatment of the cells with Cyclosporine blocked the effects of ET-1, and PDE5 inhibition by sildenafil pretreatment also abolished ET-1-induced reduction of cGMP level in the cells. Both Cyclosporine and sildenafil suppressed ET-1-stimulated PASMC proliferation.

CONCLUSIONActivation of calcineurin/NFAT signaling pathway mediates ET-1-induced PASMC proliferation by stimulating PDE5 expression, which further degrades cGMP. Both Cyclosporine and sildenafil can suppress ET-1-stimulated PASMC proliferation in vitro.