Flow-activated endothelial Piezo1-Pannexin1-TRPV4 signaling is impaired in pulmonary hypertension

Abstract

Pulmonary hypertension (PH) is a progressive and debilitating disease, characterized by elevated pulmonary arterial pressure (PAP), increased pulmonary artery (PA) contractility and endothelial cell (EC) dysfunction. Endothelial Ca2+ signals dilate resistance-size PAs (rPAs, ~ 50 μm O.D.) and maintain a low PAP. Impaired endothelial Ca2+ signaling mechanisms contribute to exacerbated rPA contraction and elevated PAP in PH. Studies in systemic arteries show that flow/shear stress (F/SS) activates endothelial Ca2+ signals to cause vasodilation. Although rPAs are a “high-flow” vascular bed, flow-induced endothelial Ca2+ signaling mechanisms have not been investigated in PH. In this regard, we recently showed that Ca2+ influx through endothelial transient receptor potential vanilloid 4 (TRPV4EC) ion channels dilates rPAs and lowers resting PAP (Daneva et al., PNAS, 2021). Moreover, F/SS activates the efflux of adenosine triphosphate (ATP, an endogenous vasodilator) through endothelial Pannexin 1 (Panx1EC) in rPAs (Daneva et al., eLife, 2021). Direct mechanosensitivity of Panx1 has been disputed, suggesting the need for an upstream endothelial mechanosensor that responds to increased flow. In this regard, pulmonary endothelial cells express Piezo1, a well-known mechanosensitive ion channel. Therefore, we hypothesized that endothelial Piezo1 (Piezo1EC)-Panx1EC-TRPV4EC signaling mediates flow-induced dilation (FID) of rPAs and regulates PAP. Cannulated and pressurized (15 mmHg) rPAs from inducible EC-specific Piezo1, Panx1 and TRPV4 mice did not dilate to incremental increases of F/SS (4 - 14 dynes/cm2) in comparison to wildtype mice, providing the first evidence that Piezo1EC-Panx1EC-TRPV4EC signaling is necessary for FID of rPAs. Confocal Ca2+ imaging studies in pressurized rPAs from mice expressing GCaMP8, a calcium biosensor, in ECs showed enhanced TRPV4EC sparklet activity (individual Ca2+ influx signals through TRPV4EC channels) in response to F/SS, demonstrating flow-induced activation of TRPV4EC channels in rPAs. Flow-induced TRPV4EC sparklet activity and FID were reduced in rPAs from a mouse model of PH (Sugen 5416 + chronic hypoxia or Su+CH; 4 weeks; 10% O2) when compared to normoxic control mice, suggesting impaired flow-induced endothelial signaling in PH. Bioluminescence measurements of extracellular ATP concentration showed lower baseline ATP levels in rPAs from Su+CH mice suggesting a decrease in ATP efflux in PH. Importantly, F/SS increased the efflux of ATP in rPAs from normal mice, but not in rPAs from Su+CH mice, indicating that F/SS-Panx1EC signaling is also impaired in PH. Together, these data support the idea that flow-induced Piezo1EC-Panx1EC-TRPV4EC signaling is impaired in PH. Future studies will assess the individual signaling linkages in the flow-induced Piezo1EC-Panx1EC-TRPV4EC signaling axis in PH. R01 HL146914, R01 HL157407, R01 HL167208 to SKS; APS Postdoctoral Fellowship to ZD. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.