Ho W S V, Zheng X, Zhang D X
Vascular Biology Research Centre, Institute of Cardiovascular and Cell Sciences, St George's University of London, Cranmer Terrace, London, SW17 0RE, UK.
Department of Medicine, Cardiovascular Center, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Br J Pharmacol. 2015 Nov;172(22):5251-64. doi: 10.1111/bph.13312. Epub 2015 Oct 22.
Metabolites of the endocannabinoid, 2-arachidonoylglycerol (2-AG) have been postulated to act as endogenous activators of TRPV4, a Ca(2+) -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.
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 Ca(2+) concentration and single-channel currents were measured in TRPV4-expressing human coronary endothelial cells.
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 Ca(2+) 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.
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.
内源性大麻素2-花生四烯酸甘油酯（2-AG）的代谢产物被认为可作为瞬时受体电位香草酸亚型4（TRPV4）的内源性激活剂，TRPV4是一种Ca(2+) 通透阳离子通道，在内皮依赖性舒张中起关键作用。然而，尚不清楚TRPV4是否参与2-AG的血管作用。
采用大鼠小肠系膜动脉和主动脉的等长张力记录来评估2-AG和合成TRPV4激活剂GSK1016790A（GSK）对血管反应性的影响。在表达TRPV4的人冠状动脉内皮细胞中测量细胞内Ca(2+) 浓度和单通道电流的变化。
在肠系膜动脉中，结构不同的TRPV4拮抗剂HC067047、RN1734和钌红减弱了对2-AG和GSK的内皮依赖性舒张。这些反应被钾通道钙激活抑制剂（蜂毒明肽+蝎毒素）和缝隙连接抑制剂（18α-甘草次酸）抑制。与GSK不同，2-AG引发了不依赖于内皮或TRPV4的显著舒张。通过单酰甘油脂肪酶和环氧化酶抑制2-AG代谢（分别用MAFP和吲哚美辛）导致增强作用，而细胞色素P450和脂氧合酶抑制剂对2-AG舒张无影响。在冠状动脉内皮细胞中，2-AG（加或不加MAFP）诱导细胞内Ca(2+) 浓度升高，且对HC067047敏感。2-AG还增加了外翻膜片中TRPV4通道的开放。然而，在主动脉中，GSK诱导的舒张对HC067047和钌红敏感，而2-AG诱导收缩。
这些数据表明，2-AG可直接激活内皮TRPV4，这部分促成了对2-AG的舒张反应。然而，TRPV4的功能作用高度依赖于血管区域。
