Begg Malcolm, Mo Fong-Ming, Offertaler László, Bátkai Sándor, Pacher Pál, Razdan Raj K, Lovinger David M, Kunos George
Laboratories of Physiologic Studies and of Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, Bethesda, Maryland 20892, USA.
J Biol Chem. 2003 Nov 14;278(46):46188-94. doi: 10.1074/jbc.M307258200. Epub 2003 Sep 2.
The cannabinoid analog "abnormal cannabidiol" (abn-cbd) causes endothelium-dependent vasodilation in rat isolated mesenteric arteries through a G protein-coupled receptor distinct from CB1 or CB2. We examined the actions of abn-cbd on the electrophysiology of human umbilical vein endothelial cells (HUVEC), using the whole cell version of the patch clamp technique. Voltage steps produced noninactivating outward currents, which were abolished by iberiotoxin or by chelation of intracellular calcium. The presence of a BKCa channel in HUVEC was documented by reverse transcriptase-PCR. Abn-cbd concentration dependently potentiated the outward current produced by a single voltage step. This potentiation was abolished by the cannabidiol analog O-1918 or by pertussis toxin but was unaffected by CB1 or CB2 antagonists. HU-210, a CB1/CB2 receptor agonist, had no effect on the outward current. Clamping [Ca2+]i did not prevent abn-cbd-induced increases in outward current. cGMP potentiated the outward current, and abn-cbd increased the cellular levels of cGMP. The increase in outward current produced by abn-cbd was blocked by KT-5823, an inhibitor of protein kinase G, or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one (ODQ), an inhibitor of soluble guanylate cyclase. We conclude that a Ca2+-activated K+ current in HUVEC is potentiated by activation of a Gi/Go-coupled receptor distinct from CB1 or CB2, which signals through cGMP and protein kinase G to increase channel availability or the sensitivity of the channel to voltage and/or Ca2+. Because iberiotoxin also inhibited abn-cbd-induced relaxation of intact, but not of endothelium-denuded, rat mesenteric artery segments, modulation of endothelial BKCa channels may underlie the mesenteric vasodilator action of abn-cbd.
大麻素类似物“异常大麻二酚”（abn-cbd）通过一种不同于CB1或CB2的G蛋白偶联受体，在大鼠离体肠系膜动脉中引起内皮依赖性血管舒张。我们使用膜片钳技术的全细胞模式，研究了abn-cbd对人脐静脉内皮细胞（HUVEC）电生理学的作用。电压阶跃产生了非失活外向电流，该电流被iberiotoxin或细胞内钙螯合剂消除。通过逆转录聚合酶链反应（RT-PCR）证实了HUVEC中存在大电导钙激活钾通道（BKCa通道）。abn-cbd浓度依赖性地增强了单个电压阶跃产生的外向电流。这种增强作用被大麻二酚类似物O-1918或百日咳毒素消除，但不受CB1或CB2拮抗剂的影响。CB1/CB2受体激动剂HU-210对外向电流无影响。钳制细胞内钙离子浓度（[Ca2+]i）并不能阻止abn-cbd引起的外向电流增加。环磷酸鸟苷（cGMP）增强了外向电流，而abn-cbd增加了细胞内cGMP水平。abn-cbd产生的外向电流增加被蛋白激酶G抑制剂KT-5823或可溶性鸟苷酸环化酶抑制剂1H-[1,2,4]恶二唑并[4,3-a]喹喔啉-1-酮（ODQ）阻断。我们得出结论，HUVEC中的钙激活钾电流通过一种不同于CB1或CB2的Gi/Go偶联受体激活而增强，该受体通过cGMP和蛋白激酶G信号传导，以增加通道的可利用性或通道对电压和/或钙离子的敏感性。由于iberiotoxin也抑制abn-cbd诱导的完整大鼠肠系膜动脉段（而非内皮剥脱的动脉段）的舒张，内皮BKCa通道的调节可能是abn-cbd肠系膜血管舒张作用的基础。
