Identification of 13-hydroxy-14,15-epoxyeicosatrienoic acid as an acid-stable endothelium-derived hyperpolarizing factor in rabbit arteries.
Arachidonic acid (AA) is metabolized by endothelial 15-lipoxygenase (15-LO) to several vasodilatory eicosanoids such as 11,12,15-trihydroxyeicosatrienoic acid (11,12,15-THETA) and its proposed unstable precursor 15-hydroxy-11,12-epoxyeicosatrienoic acid (15-H-11,12-EETA). In the present study, the acid-stable 13-hydroxy-trans-14,15-epoxy-eicosatrienoic acid (13-H-14,15-EETA) was identified and its vascular activities characterized. Rabbit aorta, mesenteric arteries, and the combination of 15-LO and cytochrome P450 2J2 converted AA to two distinct HEETA metabolites. The HEETA metabolites were resistant to acidic hydrolysis but were hydrolyzed by recombinant sEH to a more polar metabolite identified by mass spectrometry as 13,14,15-THETA. Mass spectrometric analyses and HPLC comigration identified the HEETAs as threo- and erythro-diastereomers of 13-H-trans-14,15-EETA. Erythro- and threo-diastereomers of 13-H-trans-14,15-EETA relaxed endothelium-denuded rabbit small mesenteric arteries with maximum relaxations of 22.6 +/- 6.0% and 8.6 +/- 4.3%, respectively. Apamin (10(-7) m) inhibited the relaxations to the erythro-isomer (maximum relaxation = 1.2 +/- 5.6%) and increasing [K(+)](o) from 4.6 to 30 mm blocked relaxations to both isomers. In cell-attached patches of mesenteric arterial smooth muscle cells (SMCs), erythro-13-H-trans-14,15-EETA (1-3 x 10(-6) m) increased mean open time of small conductance K(+) channels (13-14 pS) from 0.0007 +/- 0.0007 to 0.0053 +/- 0.0042. This activation was inhibited by apamin. The erythro, but not the threo, isomer blocked angiotensin II-stimulated aortic SMC migration. These studies demonstrate that 13-H-14,15-EETAs induces vascular relaxation via K(+) channel activation to cause SMC hyperpolarization. Thus, 13-H-14,15-EETA represents a new endothelial factor.
Chawengsub
Yuttana
Y
Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
Gauthier
Kathryn M
KM
Nithipatikom
Kasem
K
Hammock
Bruce D
BD
Falck
John R
JR
Narsimhaswamy
Dubasi
D
Campbell
William B
WB
D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D000143:Acids / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D001158:Arteries / Q000737:chemistry / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D011817:Rabbits; D014665:Vasodilator Agents / Q000737:chemistry / Q000378:metabolism*
D000143:Acids; D014665:Vasodilator Agents; D016718:Arachidonic Acid; D015126:8,11,14-Eicosatrienoic Acid