Abstract 16629: Endothelial Caveolin-1-trpv4 Regulation of Pulmonary Arterial Pressure and Impairment in Pulmonary Hypertension

Abstract

Background: Pulmonary hypertension (PH) is a degenerative disorder that is characterized by elevated vascular resistance and pulmonary arterial pressure (PAP). Endothelial transient receptor potential vanilloid 4 (TRPV4 EC ) ion channels represent an important Ca 2+ influx signaling mechanism that promotes vasodilation of small pulmonary arteries (PAs). Scaffolding protein caveolin-1 (Cav-1) has been shown to precipitate with TRPV4 channels in pulmonary endothelial cells in culture. Hypothesis: We hypothesized that the endothelial Cav-1-TRPV4 channel signaling in small PAs lowers PAP, and is impaired in PH. Methods: Inducible endothelium-specific KO mice for TRPV4 channel or Cav-1 were used to study the role of Cav-1-TRPV4 signaling in the regulation of resting PAP. Endothelium-specific P2Y2 receptor KO mice were used to test if Cav-1 provides a signaling scaffold for purinergic activation of TRPV4 EC channels. Endothelial Cav-1-TRPV4 signaling was assessed in PAs from two PH mouse models and PH patients. The role of NADPH oxidase (NOX1)- and inducible nitric oxide synthase (iNOS)-mediated peroxynitrite (PN), an oxidant molecule, in impairing Cav-1-TRPV4 signaling in PH was evaluated using NOX1-/- and iNOS-/- mice and pharmacological inhibitors. Results: We show that endothelial Cav-1-TRPV4 signaling in small PAs lowers resting PAP, and protects against the pathogenesis of PH. Endothelial Cav-1 provides a signaling scaffold for the activation of TRPV4 channels by endogenous purinergic receptor signaling. Moreover, TRPV4 EC channel activity and Cav-1-TRPV4 signaling are impaired in small PAs from two mouse models of PH and PH patients. Elevated levels of NOX1 and iNOS enzymes in caveolae resulted in PN formation close to Cav-1 in PH. Elevated PN targeted Cav-1 to lower Cav-1-TRPV4 signaling, thereby contributing to impaired vasodilation and increased PAP. Pharmacological inhibition of NOX1, iNOS, or PN rescued TRPV4 EC channel activity and vasodilation in PH. Conclusion: This study provides novel evidence that endothelial Cav-1-TRPV4 signaling lowers PAP and is impaired in PH. Inhibiting NOX1 or iNOS activity, or lowering endothelial PN levels may represent a novel strategy for restoring TRPV4 EC channel activity, vasodilation, and PAP.