Article date: November 2015
By: W S V Ho, X Zheng, D X Zhang in Volume 172, Issue 22, pages 5251-5264
Background and Purpose
Metabolites of the endocannabinoid, 2‐arachidonoylglycerol (2‐AG) have been postulated to act as endogenous activators of TRPV4, a Ca2+‐permeable cation channel that plays a critical role in endothelium‐dependent relaxation. However, it is unclear if TRPV4 contributes to the vascular actions of 2‐AG.
Experimental Approach
Isometric tension recording of rat small mesenteric arteries and aortae were used to assess the effect of 2‐AG and the synthetic TRPV4 activator, GSK1016790A (GSK) on vascular reactivity. Changes in intracellular Ca2+ concentration and single‐channel currents were measured in TRPV4‐expressing human coronary endothelial cells.
Key Results
In mesenteric arteries, endothelium‐dependent relaxation to both 2‐AG and GSK was attenuated by structurally distinct TRPV4 antagonists, HC067047, RN1734 and ruthenium red. The responses were inhibited by KCa inhibitors (apamin + charybdotoxin) and a gap junction inhibitor (18α‐glycyrrhetinic acid). In contrast to GSK, 2‐AG elicited considerable relaxation independently of the endothelium or TRPV4. Inhibition of 2‐AG metabolism via monoacylglycerol lipase and COX (by MAFP and indomethacin) caused potentiation, while cytochrome P450 and lipoxygenase inhibitors had no effect on 2‐AG relaxation. In coronary endothelial cells, 2‐AG (with and without MAFP) induced HC067047‐sensitive increases in intracellular Ca2+ concentration. 2‐AG also increased TRPV4 channel opening in inside‐out patches. However, in aortae, GSK induced a relaxation sensitive to HC067047 and ruthenium red, whereas 2‐AG induced contractions.
Conclusions and Implications
These data suggest that 2‐AG can directly activate endothelial TRPV4, which partly contributes to the relaxant response to 2‐AG. However, the functional role of TRPV4 is highly dependent on the vascular region.
DOI: 10.1111/bph.13312
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