Ablation of Endothelial TRPV4 Channels Alters the Dynamic Ca2+ Signaling Profile in Mouse Carotid Arteries.

Stuart J Mcfarland,David S Weber,Mark S Taylor,Chung-Sik Choi,Mike T Lin

doi:10.3390/ijms21062179

Stuart J Mcfarland, David S Weber + Show 3 more

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https://doi.org/10.3390/ijms21062179

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Abstract

Transient receptor potential vanilloid 4 channels (TRPV4) are pivotal regulators of vascular homeostasis. Altered TRPV4 signaling has recently been implicated in various cardiovascular diseases, including hypertension and atherosclerosis. These versatile nonselective cation channels increase endothelial Ca2+ influx in response to various stimuli including shear stress and G protein-coupled receptor (GPCR) activation. Recent findings suggest TRPV4 channels produce localized Ca2+ transients at the endothelial cell plasma membrane that may allow targeted effector recruitment and promote large-scale Ca2+ events via release from internal stores (endoplasmic reticulum). However, the specific impact of TRPV4 channels on Ca2+ signaling in the intact arterial intima remains unknown. In the current study, we employ an endothelium-specific TRPV4 knockout mouse model (ecTRPV4−/−) to identify and characterize TRPV4-dependent endothelial Ca2+ dynamics. We find that carotid arteries from both ecTRPV4−/− and WT mice exhibit a range of basal and acetylcholine (ACh)-induced Ca2+ dynamics, similar in net frequency. Analysis of discrete Ca2+ event parameters (amplitude, duration, and spread) and event composite values reveals that while ecTRPV4−/− artery endothelium predominantly produces large Ca2+ events comparable to and in excess of those produced by WT endothelium, they are deficient in a particular population of small events, under both basal and ACh-stimulated conditions. These findings support the concept that TRPV4 channels are responsible for generating a distinct population of focal Ca2+ transients in the intact arterial endothelium, likely underlying their essential role in vascular homeostasis.

Highlights

Dynamic Ca2+ signals direct many aspects of endothelial function and vascular homeostasis
In order to determine the specific impact of Transient receptor potential vanilloid 4 channels (TRPV4) ablation on the dynamic endothelial Ca2+ signaling profile, we assessed the intima of opened carotid artery segments loaded with the Ca2+ indicator Fluo-4
The ecTRPV4−/− artery endothelium exhibited a similar number of Ca2+ signal origination sites and events as WT artery endothelium, both basally and after 10 nM ACh stimulation (Figure 2b)

Summary

Introduction

Dynamic Ca2+ signals direct many aspects of endothelial function and vascular homeostasis They control the degree and specificity of many responses from vasodilation to permeability and inflammation. As key contributors to endothelial Ca2+ influx, type 4 vanilloid transient receptor potential (TRPV4) channels have emerged as crucial regulators of endothelial function and as pivotal players in the development of cardiovascular disease [4,5,6,7,8]. These nonselective cation channels are versatile environmental detectors, integrating various chemical and physical stimuli, including receptor agonist second messengers (e.g., arachidonic acid metabolites), temperature, and shear stress to affect a range of Ca2+-dependent pathways [2,9,10,11,12,13,14]. Endothelial hyperpolarization may enhance TRPV4 Ca2+ influx, allowing widespread expansion of Ca2+ dynamics (i.e., through Ca2+-induced Ca2+ release from IP3Rs) [15,16]

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