Contribution of TRPC channels in human and experimental pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is due to progressive distal pulmonary artery (PA) obstruction leading to right ventricular hypertrophy and failure. Exacerbated store-operated Ca entry (SOCE) contributes to PAH pathogenesis, mediating human PA smooth muscle cells (hPASMCs) abnormalities. The transient receptor potential canonical channels (TRPC family) are Ca-permeable channels contributing to SOCE in different cell types, including PASMCs. However, the properties, signaling pathways, and contribution to Ca signaling of each TRPC isoform are unclear in human PAH. We studied the impact of TRPC knockdown on control and PAH-hPASMCs function. we analyzed the consequences of pharmacological TRPC inhibition using the experimental model of pulmonary hypertension (PH) induced by monocrotaline (MCT)-exposure. Compared to control-hPASMCs cells, in PAH-hPASMCs, we found a decreased TRPC4 expression, overexpression of TRPC3 and TRPC6, and unchanged TRPC1 expression. Using the siRNA strategy, we found that the knockdown of TRPC1-C3-C4-C6 reduced the SOCE and the proliferation rate of PAH-hPASMCs. Only TRPC1 knockdown decreased the migration capacity of PAH-hPASMCs. After PAH-hPASMCs exposure to the apoptosis inducer staurosporine, TRPC1-C3-C4-C6 knockdown increased the percentage of apoptotic cells, suggesting that these channels promote apoptosis resistance. Only TRPC3 function contributed to exacerbated calcineurin activity. In the MCT-PH rats' model, only TRPC3 protein expression was increased in lungs compared to control rats, and "curative" administration of a TRPC3 inhibitor attenuated PH development in rats. These results suggest that TRPC channels contribute to PAH-hPASMCs dysfunctions, including SOCE, proliferation, migration, apoptosis resistance, and could be considered as therapeutic targets in PAH.