TRPC channels contribute to endothelial dysfunction in pulmonary arterial hypertension.

BACKGROUND-: Pulmonary arterial hypertension (PAH) is a rare, fatal, and progressive pulmonary vascular disease. Pulmonary endothelial cell dysfunction is a hallmark of PAH, defined by excessive proliferation and dysregulated angiogenesis, along with imbalanced production and release of vasoactive substances, growth factors, and mediators of coagulation and inflammation. Intracellular calcium (Ca2+) variations are essential in these processes. Among the various channels involved in Ca2+ homeostasis, transient receptor potential canonical channels (TRPC1 to 7) are known to be essential for endothelial cells of various origins, but their role in PAH remains unknown. RESULTS-: We found that four TRPC channels (TRPC1, TRPC3, TRPC4, and TRPC6) were expressed in human pulmonary endothelial cells (hPECs) from control and PAH patients. By knocking down each of these channels in hPECs isolated from PAH patients (PAH-hPECs), we found that TRPC1 and TRPC4 are involved in store-operated Ca2+ entry (SOCE). We showed that TRPC1 and TRPC3 are essential for PAH-hPECs proliferation and that TRPC3, TRPC4, and TRPC6 are important for mitogenic crosstalk in the PAH-hPECs medium. Moreover, we showed that none of the TRPC channels is involved in the migration or in vitro tubulogenesis of PAH-hPECs. Finally, we found that TRPC1 knockdown induces changes in the mRNA expression of several genes described to be crucial for endothelial cell homeostasis. CONCLUSIONS-: These data demonstrate that TRPC channels, especially TRPC1, are essential for maintaining the hPECs function in PAH, indicating that TRPC channels are central and represent interesting candidates for reducing endothelial dysfunction in PAH.