Beschreibung:
<jats:sec><jats:title>Introduction</jats:title><jats:p>The ubiquitously expressed calcium channel transient receptor potential vanilloid subtype 4 (TRPV4) has been implicated in various endothelial functions. Specifically, TRPV4 activation triggers endothelial barrier failure. In the lung, TRPV4‐mediated pulmonary edema formation has been reported in response to various triggers including acid aspiration and positive pressure ventilation. Thus, TRPV4 is a promising target for preventing or treating lung injury, but its ubiquitous expression requires investigating potential off‐target effects during therapeutic modulation.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>The present study is working toward this aim by comparing TRPV4 expression and function in human endothelial cells from five different vascular beds: pulmonary (HPMEC), cerebral (HCMEC) and adipose (HAMEC) microvascular as well as pulmonary artery (HPAEC) and coronary artery (HCAEC). Response to the TRPV4 agonist GSK1016790A was assessed by ratiometric Fura‐2 imaging of intracellular calcium concentration [Ca<jats:sup>2+</jats:sup>]<jats:sub>i</jats:sub>, measuring transendothelial electrical resistance (TEER), and fluorescence imaging of cytoskeletal actin and VE‐cadherin. TRPV4 protein expression was densitometrically quantified by Western blot, normalized to GAPDH for comparison between the five cell types.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Agonist treatment increased [Ca<jats:sup>2+</jats:sup>]<jats:sub>i</jats:sub> and decreased TEER in all endothelial cell types studied, while vehicle (dimethylsulfoxide) had no effect. Interestingly, there was strong inverse correlation between the [Ca<jats:sup>2+</jats:sup>]<jats:sub>i</jats:sub> response and decrease in TEER amongst the three microvascular cell types, HPMEC, HAMEC and HCMEC, with the [Ca<jats:sup>2+</jats:sup>]<jats:sub>i</jats:sub> and reduction of TEER increasing in the order HPMEC < HAMEC < HCMEC. This effect was corroborated by fluorescence imaging that showed TRPV4 agonism caused intercellular adherens junctions to become disrupted and gaps to form within the endothelial monolayer. In some cases, endothelial cells significantly contracted and became rounded, losing surface VE‐cadherin and forming actin stress fibers. The degree of this effect varied between microvascular cells, again in the increasing order HPMEC < HAMEC < HCMEC. Furthermore, these observations correlated with quantification of Western blot showing HCMECs had highest expression of TRPV4 protein. Notably, while macrovascular HPAECs and HCAECs showed quantitatively similar responses as microvascular endothelial cells, they did not fit the linear regression between [Ca<jats:sup>2+</jats:sup>]<jats:sub>i</jats:sub> and TEER response.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>These results demonstrate quantitative heterogeneity in endothelial TRPV4 function in different vascular beds, and identify TRPV4 as a major regulator of microvascular endothelial cell permeability, while confirming the established differences in barrier function between micro‐ and macrovascular endothelial cells.</jats:p><jats:p><jats:bold>Support or Funding Information</jats:bold></jats:p><jats:p>Canadian Institutes of Health Research (CIHR)</jats:p><jats:p>Ontario Research Fund (ORF)</jats:p></jats:sec>