Endothelium-derived 2-arachidonylglycerol: an intermediate in vasodilatory eicosanoid release in bovine coronary arteries.
Acetylcholine stimulates the release of endothelium-derived arachidonic acid (AA) metabolites including prostacyclin and epoxyeicosatrienoic acids (EETs), which relax coronary arteries. However, mechanisms of endothelial cell (EC) AA activation remain undefined. We propose that 2-arachidonylglycerol (2-AG) plays an important role in this pathway. An AA metabolite isolated from bovine coronary ECs was identified as 2-AG by mass spectrometry. In ECs pretreated with the fatty acid amidohydrolase inhibitor diazomethylarachidonyl ketone (DAK; 20 micromol/l), methacholine (10 micromol/l)-stimulated 2-AG release was blocked by the phospholipase C inhibitor U-73122 (10 micromol/l) or the diacylglycerol lipase inhibitor RHC-80267 (40 micromol/l). In U-46619-preconstricted bovine coronary arterial rings, 2-AG relaxations averaging 100% at 10 micromol/l were inhibited by endothelium removal, by DAK, by the hydrolase inhibitor methyl arachidonylfluorophosphate (10 micromol/l), by the cyclooxygenase inhibitor indomethacin (10 micromol/l), but not by the CB1 cannabinoid receptor antagonist SR-141716 (1 micromol/l). The cytochrome P-450 inhibitor SKF-525a (10 micromol/l) and the 14,15-epoxyeicosa-5Z-enoic acid EET antagonist (14,15-EEZE; 10 micromol/l) further attenuated the indomethacin-resistant relaxations. The nonhydrolyzable 2-AG analogs noladin ether, 2-AG amide, and 14,15-EET glycerol amide did not induce relaxation. N-nitro-L-arginine-resistant relaxations to methacholine were also inhibited by U-73122, RHC-80267, and DAK. 14,15-EET glycerol ester increased opening of large-conductance K(+) channels 12-fold in cell-attached patches of isolated smooth muscle cells and induced relaxations averaging 95%. These results suggest that methacholine stimulates EC 2-AG production through phospholipase C and diacylglycerol lipase activation. 2-AG is further hydrolyzed to AA, which is metabolized to vasoactive eicosanoids. These studies reveal a role for 2-AG in EC AA release and the regulation of coronary tone.
Gauthier
Kathryn M
KM
Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA. kgauth@mcw.edu <kgauth@mcw.edu>
Baewer
David V
DV
Hittner
Sarah
S
Hillard
Cecilia J
CJ
Nithipatikom
Kasem
K
Reddy
D Sudarshan
DS
Falck
J R
JR
Campbell
William B
WB
D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D000818:Animals; D016718:Arachidonic Acid / Q000493:pharmacokinetics*; D001095:Arachidonic Acids / Q000378:metabolism*; D002250:Carbon Radioisotopes; D002417:Cattle; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000166:cytology / Q000502:physiology*; D063388:Endocannabinoids; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D005989:Glycerides / Q000378:metabolism*; D006893:Hydroxyeicosatetraenoic Acids / Q000378:metabolism; D014664:Vasodilation / Q000502:physiology*
C107016:14,15-dihydroxyeicosatrienoic acid; D001095:Arachidonic Acids; D002250:Carbon Radioisotopes; D063388:Endocannabinoids; D005989:Glycerides; D006893:Hydroxyeicosatetraenoic Acids; D016718:Arachidonic Acid; C046782:14,15-epoxy-5,8,11-eicosatrienoic acid; C094503:glyceryl 2-arachidonate; D015126:8,11,14-Eicosatrienoic Acid