Peroxynitrite Impairs Caveolin‐1‐TRPV4 Channel Signaling in Pulmonary Hypertension

Abstract

The endothelium is an important regulator of vascular resistance and overall pulmonary arterial pressure (PAP). Endothelial dysfunction in small, resistance pulmonary arteries (PAs) leads to impaired vasodilation, increased PAP, and the development of pulmonary hypertension (PH). However, the mechanisms leading to endothelial dysfunction in PH remain unknown. We recently identified endothelial TRPV4 (transient receptor potential vanilloid 4‐TRPV4EC) channels as important regulators of endothelium‐dependent vasodilation in small PAs, and showed that localized Ca2+ influx events through TRPV4EC channels activate an endothelial nitric oxide (eNOS)‐dependent vasodilatory pathway. Furthermore, inducible endothelium‐specific TRPV4 knockout (TRPV4EC−/−) mice have impaired vasodilation and elevated PAP, revealing TRPV4EC channels as critical regulators of resting PAP. However, the signaling pathways that regulate TRPV4EC channels and how they may be impaired in PH remain unknown. Caveolin‐1 (Cav‐1EC) is an important structural protein that is known to associate with TRPV4 channels in cultured endothelial cells, and global Cav‐1−/− mice were shown to have high PAP. We, therefore, hypothesized that impairment in Cav‐1EC‐TRPV4EC signaling regulation contributes to endothelial dysfunction in PH. PH was induced using a three week‐chronic hypoxia (CH) model. TRPV4EC channel function was studied using high‐speed Ca2+ imaging, which records Ca2+ influx events through TRPV4EC channels (TRPV4EC sparklets) in the intact endothelium of small PAs. Pressure myography in small PAs was used to determine the functional outcome of TRPV4EC channel signaling. Right ventricular systolic pressure (RVSP) was measured as an indicator of PAP. In normal PAs, Cav‐1EC anchoring of protein kinase C (PKC) increased TRPV4EC sparklet activity and TRPV4EC‐‐dependent vasodilation. However, in CH, decreased Cav‐1EC‐PKC localization resulted in impaired TRPV4EC sparklet activity and endotheliumdependent vasodilation. Elevated peroxynitrite (PN) levels have been shown to contribute to the development of PH. PN levels, as indicated by nitrotyrosine staining, were elevated in PAs from CH mice. PN scavenger, FeTPPS, rescued TRPV4EC sparklet activity and vasodilation in PAs obtained from CH mice. Furthermore, acute injection of FeTPPS significantly lowered PAP in CH mice. Exogenous PN significantly decreased TRPV4EC sparklet activity and vasodilation in control mice but had no effect on PAs from inducible Cav‐1EC−/− mice, indicating that the effect of PN on TRPV4EC channel activity is Cav‐1EC‐dependent. Our results support the idea that elevated PN levels in PH impairs Cav‐1EC‐PKC‐dependent potentiation of TRPV4EC channel activity. Inhibition of TRPV4EC channel activity by PN contributes to impaired vasodilation and elevated PAP observed in PH.Support or Funding Information17PRE33660762, HL138496This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.