Impairment of endothelial Pannexin1-TRPV4 signaling and flow-induced vasodilation in obesity-induced pulmonary hypertension

Abstract

Obesity is a highly prevalent and debilitating disease that significantly contributes to the development of other pathologies, such as pulmonary hypertension (PH). However, the mechanisms triggering obesity-induced PH (OiPH) are currently unknown. Endothelial cell (EC) Ca 2+ signals dilate small pulmonary arteries (PAs) and maintain a low resting pulmonary arterial pressure (PAP). Impairment of endothelial Ca 2+ signaling mechanisms is a crucial contributor to elevated PAP in PH. Although PAs are a “high-flow” vascular bed, flow-induced endothelial Ca 2+ signaling mechanisms have not been investigated in OiPH. In this regard, we recently showed that Ca 2+ influx through endothelial transient receptor potential vanilloid 4 (TRPV4 EC ) ion channels dilates PAs and lowers resting PAP (Daneva et al., PNAS, 2021). Moreover, flow/shear stress (F/SS) activates the efflux of adenosine triphosphate (ATP) through endothelial Pannexin 1 (Panx1 EC ) in PAs. Panx1 EC -effluxed ATP, in turn, stimulates endothelial purinergic P2Y2 receptor (P2Y2R EC ) to increase TRPV4 EC channel activity (Daneva et al., eLife, 2021). Therefore, I hypothesized that impaired Panx1 EC -P2Y2R EC -TRPV4 EC signaling axis reduces flow-induced dilation of PAs and elevates PAP in OiPH. Right ventricular systolic pressure, an indicator of PAP, was significantly higher in mice exposed to a high-fat diet (HFD, 60%, 24 weeks) compared to normal chow-fed mice, confirming OiPH in these mice. F/SS (4–15 dynes/cm 2 )-induced dilation was drastically reduced in small PAs (~ 50 μm), cannulated at both ends and pressurized to 15 mm Hg, from HFD mice, possibly indicating impaired flow-induced endothelial signaling in OiPH. Confocal Ca 2+ imaging studies in fluo-4-loaded PAs showed that the baseline and agonist (GSK1016790A)-induced activity of TRPV4 EC sparklets (unitary Ca 2+ influx signals through TRPV4 EC channels) is reduced in HFD mice compared to normal mice, confirming a decrease in TRPV4 EC channel activity in OiPH. F/SS (4–15 dynes/cm 2 ) resulted in increased activity of TRPV4 EC sparklets in PAs from normal mice, but not in PAs from HFD mice, suggesting that flow-induced TRPV4 EC activity is reduced in OiPH. Bioluminescence measurements of extracellular ATP concentration showed lower baseline ATP levels in PAs from HFD mice than normal mice. Importantly, F/SS (4 – 15 dynes/cm 2 ) increased ATP efflux in PAs from normal mice, but not in PAs from HFD mice, indicating that flow-Panx1 EC signaling is also impaired in OiPH. Together, these data support the idea that flow-induced Panx1 EC -TRPV4 EC signaling is impaired in OiPH. Targeting the individual elements of this pathway may provide novel therapies in OiPH. Future studies will assess the signaling linkages of the flow-Panx1 EC -P2Y2R EC -TRPV4 EC signaling axis in OiPH. R01 HL142808, R01 HL146914, R01 HL157407 to Dr. S.K. Sonkusare; APS Postdoctoral Fellowship Award to Dr. Z. Daneva This is the full abstract presented at the American Physiology Summit 2023 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.