Identification of 15-hydroxy-11,12-epoxyeicosatrienoic acid as a vasoactive 15-lipoxygenase metabolite in rabbit aorta

Yuttana Chawengsub, Nitin T. Aggarwal, Kasem Nithipatikom, Kathryn M. Gauthier, Siddam Anjaiah, Bruce D. Hammock, John R. Falck, William B. Campbell

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Abstract

Arachidonic acid (AA) causes endothelium-dependent smooth muscle hyperpolarizations and relaxations that are mediated by a 15-lipoxygenase-I (15-LO-I) metabolite, 11,12,15-trihydroxyeicosatrienoic acid (11,12,15-THETA). We propose that AA is metabolized sequentially by 15-LO-I and hydroperoxide isomerase to an unidentified hydroxyepoxyeicosatrienoic acid (HEETA), which is hydrolyzed by a soluble epoxide hydrolase (sEH) to 11,12,15-THETA. After incubation of aorta with 14C-labeled AA, metabolites were extracted and the HEETAs were resolved by performing HPLC. Mass spectrometric analyses identified 15-Hydroxy-11,12-epoxyeicosatrienoic acid (15-H-11,12-EETA). Incubation of aortic incubates with methanol and acetic acid trapped the acidsensitive 15-H-11,12-EETA as methoxydihydroxyeicosatrienoic acids (MDHEs) (367 m/z, M-H). Pretreatment of the aortic tissue with the sEH inhibitor 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA; 10-6 M) increased the formation of 15-H-11,12-EETA, measured as MDHEs. Thus 15-H-11,12-EETA is an acid- and sEH-sensitive precursor of 11,12,15-THETA. Aortic homogenates and endothelial cells contain a 57-kDa protein corresponding to the rabbit sEH. In preconstricted aortic rings, AA (10-7-10-4 M) and acetylcholine (10-9-10-6 M) caused concentration-related relaxations that were enhanced by pretreatment with AUDA. These enhanced relaxations were inhibited by increasing extracellular [K+] from 4.8 to 20 mM. AA (3 × 10-6 M) induced cell membrane hyperpolarization (from -31.0 ± 1 to -46.8 ± 2 mV) in aortic strips with an intact endothelium, which was enhanced by AUDA. These results indicate that 15-H-11,12-EETA is produced by the aorta, hydrolyzed by sEH to 11,12,15-THETA, and mediates relaxations by membrane hyperpolarization. 15-H-11,12-EETA represents an endothelium-derived hyperpolarizing factor.

Original languageEnglish (US)
Pages (from-to)H1348-H1356
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume294
Issue number3
DOIs
StatePublished - Mar 1 2008

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Keywords

  • 15-lipoxygenase
  • Arachidonic acid
  • Endothelial cells
  • Endothelium-derived hyperpolarizing factor

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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