Role of phospholipase C and diacylglyceride lipase pathway in arachidonic acid release and acetylcholine-induced vascular relaxation in rabbit aorta

• Published in: American journal of physiology. Heart and circulatory physiology 2006-01, Vol.290 (1), p.H37-H45
• Main Authors: Tang, Xin, Edwards, Erik M, Holmes, BlyB, Falck, John R, Campbell, William B
• Format: Article
• Language: English
• Subjects: Acetylcholine - pharmacology; Animals; Aorta, Thoracic - drug effects; Aorta, Thoracic - physiology; Arachidonic Acid - secretion; Arachidonic Acids - pharmacology; Carbamates - pharmacology; Cells, Cultured; Cyclohexanones - pharmacology; Diazomethane - analogs & derivatives; Diazomethane - pharmacology; Endothelium, Vascular - cytology; Endothelium, Vascular - drug effects; Estrenes - pharmacology; In Vitro Techniques; Indomethacin - pharmacology; Isoenzymes - biosynthesis; Lipoprotein Lipase - physiology; Methacholine Chloride - pharmacology; Nitroarginine - pharmacology; Phospholipases A - biosynthesis; Phospholipases A2; Pyrrolidinones - pharmacology; Rabbits; Type C Phospholipases - antagonists & inhibitors; Type C Phospholipases - biosynthesis; Type C Phospholipases - physiology; Vasodilation - drug effects
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.00491.2005

1 Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin; and 2 Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas Submitted 12 May 2005 ; accepted in final form 11 July 2005 ACh stimulates arachidonic acid (AA) release from membrane phospholipids of vascular endothelial cells (ECs). In rabbit aorta, AA is metabolized through the 15-lipoxygenase pathway to form vasodilatory eicosanoids 15-hydroxy-11,12-epoxyeicosatrienoic acid (HEETA) and 11,12,15-trihydroxyeicosatrienoic acid (THETA). AA is released from phosphatidylcholine (PC) and phosphatidylethanolamine (PE) by phospholipase A 2 (PLA 2 ), or from phosphatidylinositol (PI) by phospholipase C (PLC) pathway. The diacylglycerol (DAG) lipase can convert DAG into 2-arachidonoylglycerol from which free AA can be released by monoacylglycerol (MAG) lipase or fatty acid amidohydrolase (FAAH). We used specific inhibitors to determine the involvement of the PLC pathway in ACh-induced AA release. In rabbit aortic rings precontracted by phenylephrine, ACh induced relaxation in the presence of indomethacin and N -nitro- L -arginine ( L -NNA). These relaxations were blocked by the PLC inhibitor U-73122, DAG lipase inhibitor RHC-80267, and MAG lipase/FAAH inhibitor URB-532. Cultured rabbit aortic ECs were labeled with [ 14 C]AA and stimulated with methacholine (10 –5 M). Free [ 14 C]AA was released by methacholine. Methacholine decreased the [ 14 C]AA content of PI, DAG, and MAG fractions but not PC or PE fractions. Methacholine-induced release of [ 14 C]AA was blocked by U-73122, RHC-80267, and URB-532 but not by U-73343, an inactive analog of U-73122. The data suggested that ACh activates PLC, DAG lipase, and MAG lipase pathway to release AA from membrane lipids. This pathway is important in regulating vasodilatory eicosanoid synthesis and vascular relaxation in rabbit aorta. endothelium-dependent hyperpolarizing factor; phospholipid; monoacylglycerol lipase; trihydroxyeicosatrienoic acid; hydroxyepoxyeicosatrienoic acid Address for reprint requests and other correspondence: W. B. Campbell, Dept. of Pharmacology and Toxicology, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226 (e-mail: wbcamp{at}mcw.edu )