Mechanisms of TRPV4 channel activation in human arteriolar endothelial cells: A structure‐activity study with arachidonic acid and analogs
Authors: Zinkevich Natalya S , Gutterman David D , Zhang David X 
Published: June 2021

Previous studies from our group indicated that arachidonic acid (AA) induces dilation of human coronary arterioles (HCAs) through the activation of endothelial TRPV4 channels followed by the release of vasodilator factors or endothelial hyperpolarization. In addition, TRPV4‐mediated vasodilatory response to flow is augmented in HCAs from subjects with coronary artery disease (CAD), a condition associated with a change of vasodilators from nitric oxide to hydrogen peroxide. However, the mechanisms of TRPV4 activation by AA and its role in the regulation of TRPV4 function under normal conditions remain to be elucidated. In this study, we examined the structure‐activity relationships of AA and its congeners in human adipose arterioles from subjects without CAD (non‐CAD). Adipose arterioles (~150 μm ID), isolated from non‐CAD human subjects, were cannulated and pressurized at 60 mmHg for videomicroscopic measurement of vessel diameters. In adipose arterioles pre‐constricted with endothelin‐1, AA (10−11 to 10−6 M) elicited a potent concentration‐dependent dilation (maximal dilation: 84±3%, logEC50: −8.2, n=6), and this response was largely blocked by HC‐067047 (10−6 M), a TRPV4 antagonist (17±3%, n=6). Compared with AA (C20:4ω6), vasodilator effect of AA analog homo‐γ‐linolenic acid (HGLA, C20:3ω6; 10−11 to 10−6 M) was less potent (maximal dilation: 44±8%, logEC50: −7.2, n=6) but the dilation was also largely abolished by HC‐067047 (6±3%, n=4). These HC067047‐inhibitable vasodilator effects of AA and HGLA were similar as those in HCAs from CAD subjects shown previously (maximal dilation: 84±5% and 40±5%, logEC50: −8.3 and −6.8, n=5 and 3, respectively). In adipose arterioles, another AA analog 5,8,11,14‐eicosatetraynoic acid (ETYA, 10−11 to 10−6 M) demonstrated greatly reduced response (maximal dilation: 19±3%, logEC50: −7.1, n=3), which was eliminated by HC‐067047 (5±2%, n=3). Pretreatment of adipose arterioles with ETYA (10−5 M) decreased vasodilation responses to AA (25±2%, n=5). Vessel denudation markedly reduced vasodilatory responses to AA (10−11 to 10−6 M) (maximal dilation: 33±5%, n=4) as well as to HGLA (10−11 to 10−6 M) (maximal dilation: 13±3%, n=4), confirming the endothelium‐dependent effects of AA and analogs. The dilation to the smooth muscle relaxant sodium nitroprusside (10−10 to 10−4 M) was not affected by HC‐067047 (maximal dilation: 100±0% vs. 99.8±1%, n=2). Together, these data provide evidence that AA activates endothelial TRPV4 to induce comparable dilation in non‐CAD human arterioles. AA congeners also activate TRPV4 channels, however, but they exhibit reduced vasodilatory responses and can antagonize arachidonic‐acid‐induced TRPV4‐mediated vasodilation, suggesting a potential role of specific cis‐double bonds and/or their position for AA‐induced TRPV4 activation. Future studies will examine whether the mechanisms of TRPV4 activation involve potential binding of AA to the channel protein or indirect effect through AA metabolites.Support or Funding InformationThis work was supported by R01‐HL 096647This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.