Piezo1, a stretch-activated calcium permeable channel is a sensor of mechanical stress present in endothelial cells (ECs) and vascular smooth muscle cells (SMCs). Our previous studies have shown that endothelial Piezo1 contributes to intrapulmonary artery (IPA) relaxation in mice. The present study was undertaken to investigate the implication of Piezo1 in both rat ECs and SMCs in pulmonary hypertension (PH).

Chronically hypoxic rats, an animal model of PH, were exposed to chronic hypoxia (CH, −50% O₂ for 1 weeks), whereas normoxic rats were housed in normoxic condition (NX). NX or CH IPA tone variation induced by YODA1 was quantified by myograph. Intracellular calcium concentration ([Ca2+]i) was determined with Cal520-AM probes. Protein levels of endothelial nitric oxide synthase (eNOS), phosphorylated eNOS (peNOS), Akt and pAkt were quantified by Western blot analysis.

Immunofluorescence labeling and patch-clamp revealed the presence of Piezo1 in both ECs and SMCs. In IPAs, YODA1 induced a contraction in NX condition. By contrast, YODA1 induced an endothelium and nitric oxide-dependent relaxation in CH IPAs. Activation of Piezo1 channels by its agonist YODA1 increased [Ca2+]i. However, the [Ca2+]i increase in ECs was greater in CH as compared to NX condition. In addition, CH condition increased level of eNOS proteins as compared to NX condition and YODA1 induced a phosphorylation of Akt (Ser 473) and eNOS (Ser 1177) in NX and CH conditions.

The present study thus demonstrates that endothelial Piezo1 contributes to intrapulmonary vascular relaxation by controlling endothelial [Ca2+]i and Akt-eNOS- pathway activation that could counteract PH.