TRPV4 (Transient Receptor Potential Vanilloid 4) Mediates Endothelium-Dependent Contractions in the Aortas of Hypertensive Mice

Abstract

The role of TRPV4 (transient receptor potential vanilloid 4) in regulating vascular contraction in hypertensive mice is poorly established. We tested the hypothesis that TRPV4 regulates endothelium-dependent contractions in aortas from hypertensive mice through the activation of cytosolic cPLA (phospholipase A) and COX2 (cyclooxygenase 2) and identified the possible endothelium-derived contracting factor generated by COX2. Using myography, we demonstrated that GSK1016790A (a TRPV4 agonist) and acetylcholine (ACh) trigger endothelium-dependent contractions in aortas from hypertensive mice, and the contractions were abolished with TRPV4 deletion. PLA assay and Western blotting showed that cPLA activity was higher in salt-induced hypertension and HC067047 or a Ca chelator inhibited cPLA activity. Contractions induced by TRPV4 and ACh were inhibited by the cPLA inhibitor or removal of extracellular Ca COX2 expression was enhanced in the endothelium from hypertensive mice and contractions induced by TRPV4 or ACh were inhibited by the COX2 inhibitor. Enzyme immunoassay showed that the release of prostaglandin F (PGF) was increased in hypertensive mice. GSK1016790A or ACh triggered the release of PGF and this was inhibited by HC067047, the cPLA inhibitor, and COX2 inhibitor. GSK1016790A, ACh, and PGF induced contractions were significantly reduced by S18886 in salt-induced hypertensive mice. The present study demonstrates that PGF generated by COX2 in the endothelium is the most likely endothelium-derived contracting factor underlying endothelium-dependent, TRPV4-mediated contraction in hypertensive mice. This contraction involved increased intracellular Ca concentrations and cPLA activity. These results suggested an important role of TRPV4 in endothelium-dependent contraction in mice during hypertension.

TRPV4 activates cytosolic phospholipase A2 via Ca2+‐dependent PKC/ERK1/2 signalling in controlling hypertensive contraction

“…It is reported that endothelial cPLA 2 contributes to L‐NAME‐induced hypertension . In line with this notion, we have shown that TRPV4‐mediated cPLA 2 activation contributes to endothelium‐dependent contraction in hypertensive mice . However, the underlying mechanism by which TRPV4 regulates cPLA 2 activity in hypertension has not been defined.…”

“…We next determined the role of PKCα and ERK1/2 in TRPV4‐mediated cPLA 2 activity. In the previous study, we have demonstrated that stimulation of TRPV4 increases the phosphorylation of cPLA 2 and PLA 2 activity in hypertensive mice . In the present study, we found that inhibition of PKCα and ERK1/2 decreased the TRPV4‐induced phosphorylation of cPLA 2 and PLA 2 activity.…”

“…Consistent with this finding, we also found that ACh‐mediated phosphorylation of cPLA 2 and PLA 2 activity was inhibited by blocking of PKCα and ERK1/2. PGF 2α is involved in TRPV4‐dependent contractions in aortae from hypertensive mice . PGF 2α is the most likely EDCF candidate induced by TRPV4/cPLA 2 signalling .…”

“…After 60 minutes of equilibration at baseline tension, 60 mmol/L KCl (the NaCl in Krebs solution was substituted with an equimolar amount of KCl) was applied to confirm the contractility of the artery, washed in Krebs solution, and finally allowed to equilibrate for 30 minutes. The bath solution was modified Krebs solution …”

“…Thus, cPLA 2 is considered the rate‐limiting enzyme in AA release. AA can be subsequently metabolized by COX and most of the downstream products of COX pathway are considered as EDCFs . Release of these metabolites by endothelial cells is crucial for the control the vascular tone.…”