Peroxynitrite‐induced Reversible Impairment of Endothelial TRPV4 Channel Function in Obesity

Abstract

Obesity‐induced endothelial dysfunction contributes to the development of cardiovascular abnormalities. Although endothelial Ca2+ signaling is well‐known to regulate endothelium‐dependent vasodilation in small arteries, whether endothelial Ca2+ signaling mechanisms are impaired in obesity remains unknown. We recently showed that unitary Ca2+ influx through TRPV4 (transient receptor potential vanilloid 4) channels, termed TRPV4 Ca2+ sparklets, elicits vasodilation through the activation of Ca2+‐sensitive K+ (IK and SK) channels. A kinase anchoring protein 150 (AKAP150), which can anchor protein kinase A and protein kinase C (PKA and PKC), is a key regulator of TRPV4 sparklet activity. In this study, we determined whether obesity impairs AKAP150‐TRPV4 regulation of endothelial Ca2+ signaling. In the novel endothelium‐specific AKAP150−/− mice, systolic blood pressures were significantly elevated and endothelium‐dependent vasodilation of third‐order mesenteric arteries (MAs) was considerably attenuated. TRPV4 channel activity and vascular function were determined in MAs from C57BL/6J mice fed with normal (10% kcal) or high fat diet (60% kcal) for 12 weeks. While vasodilation to a selective TRPV4 channel agonist GSK1016790A (GSK101, 3–30 nM) was impaired in obese mice, dilatory response to an IK/SK channel activator (NS309, 1 mM) was not altered, suggesting inhibition of TRPV4 channel function, but not downstream signaling and endothelial‐smooth muscle communication in obesity. In fluo‐4‐loaded en face MAs from obese mice, TRPV4 sparklet activity (as NPO; N is the number of channels at a site and PO is open state probability) in response to 10 nM GSK101 was diminished by 2‐fold. TRPV4 expression at both the mRNA and protein levels was unaltered, suggesting impaired channel regulation rather than expression in obesity. Peroxynitrite (PN) has been implicated in endothelial dysfunction in obesity and other disorders, although the mechanisms for PN‐induced endothelial dysfunction remain unknown. PN scavenger (uric acid, 200 mM) rescued impaired TRPV4 sparklet activity and vasodilation in obese mice. We, therefore, hypothesized that PN impairs AKAP150‐TRPV4 regulation of endothelial Ca2+ signaling in obesity. Exogenous PN (1 mM) markedly decreased TRPV4 activity and vasodilation by 3‐fold in normal MAs, which was prevented by uric acid pretreatment. Moreover, obese MAs showed higher 3‐nitrotyrosine levels (protein nitration product of PN) predominantly at myoendothelial projections (MEPs), where majority of TRPV4 sparklet activity occurs and AKAP150 expression is concentrated. Collectively, obesity‐induced increase in PN may lead to nitrotyrosine formation on AKAP150, thereby reversibly impairing TRPV4 sparklet activity and vasodilation.Support or Funding InformationThis study was supported by grants from the National Institutes of Health to S.K.S. (HL121484 and R56HL138496, S.K.S.) and University of Virginia School of Medicine and Robert M. Berne Cardiovascular Research Center startup funds.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.