5,6‐Epoxyeicosatrienoic acid‐induced endothelium‐dependent dilation of mouse mesenteric arteries: dependence on TRPV4 channel activity

The TRPV4 channel has been implicated as a mediator of Ca 2+ entry in endothelial cells (ECs) contributing to shear‐ and agonist‐induced vasodilation. Our understanding of the mechanisms that couple extracellular stimulation to TRPV4 activity remains incomplete. 5,6‐Epoxyeicosatrienoic acid (EET), a cytochrome P450 metabolite of arachidonic acid (AA), modulates TRPV4 activity in ECs. Here we examined the functional significance of 5,6‐EET‐TRPV4 signaling in endothelium‐mediated vasodilator responses. In isolated mesenteric arteries from wild‐type (WT) mice, 5,6‐EET‐methyl ester (a stable analog of 5,6‐EET) induced potent endothelium‐dependent dilation (dilation at 10 −5 M of 66±3% in intact and 5±2% in endothelium‐denuded arteries; n=6). The dilations were markedly reduced in TRPV4‐deficient (TRPV4 −/− ) animals (34±4% in intact and 1±3% in denuded; n=5). Using a fura‐2 Ca 2+ assay, 5,6‐EET increased [Ca 2+ ] i in ECs in situ of WT mesenteric arteries (ΔF340/F380 of 0.049±0.002; n=3) whereas only minimal responses were observed in ECs from TRPV4 −/− mice (0.018±0.002; n=3). Using reverse‐phase HPLC, we also examined [ 14 C]‐AA metabolism by mouse aortic ECs. Both WT and TRPV4 −/− ECs metabolize AA into EETs. In conclusion, 5,6‐EET induces vasodilation through a mechanism involving endothelial TRPV4, thus further supporting its potential role in TRPV4 activation and endothelium‐mediated vasodilation.