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

Abstract

Chawengsub Y, Aggarwal NT, Nithipatikom K, Gauthier KM, Anjaiah S, Hammock BD, Falck JR, Campbell WB. Identification of 15-hydroxy-11,12-epoxyeicosatrienoic acid as a vasoactive 15-lipoxygenase metabolite in rabbit aorta.

Identification of 13-Hydroxy-14,15-epoxyeicosatrienoic Acid as an Acid-stable Endothelium-derived Hyperpolarizing Factor in Rabbit Arteries

“…These 15-LO-I metabolites act on SMCs to open K ϩ channels, hyperpolarize the cell membrane, and induce relaxation. The proposed mediators of this EDHF activity are 11(R),12(S),15(S)-THETA (17) and its possible precursor 15-H-11,12-EETA (15). In this study, acid treatment of aortic incubates eliminated the acid labile allylic epoxyalchohols such as 15-H-11,12-EETA and 11-H-14,15-EETA (15) and allowed characterization of the structure of the acid stable 13-H-14,15-EETA and determination of its actions on SMCs.…”

“…Specifically, we identified the structures of threo-and erythro-13-H-trans-14,15-EETA and demonstrated the vascular functions of the erythro-isomer as an EDHF and an inhibitor of SMC migration. The acidic conditions required for extraction and HPLC converted a portion of the acid labile allylic epoxyalcohols (15-H-11,12-EETA or 11-H-14,15-EETA) to THETAs (15). Prolongation of the exposure to acid assured its complete hydrolysis.…”

“…During the extraction process, the incubation buffer was acidified to pH 3 and incubated for 3 min to hydrolyze the acid-sensitive allylic epoxyalcohols (15-H-11,12-EETA or 11-H-14,15-EETA) to THETAs. This was necessary since an unstable HEETA comigrates with peak A on NP-HPLC (15). When tested for vascular activity, peak A and peak B relaxed phenylephrine preconstricted rabbit aortas in a concentrationdependent manner in the presence of indomethacin (10…”

“…Characteristic of HEETA Metabolites-Because metabolites comigrating with the HEETAs were observed following acidification and extraction, the 12.8 -15.8-min fractions on RP-HPLC may contain acid stable metabolites in addition to the acid sensitive HEETA (15). To test this possibility, peak A and B resolved and collected from NP-HPLC were incubated with 1 N acetic acid for 18 h at room temperature.…”

“…Under normal conditions, rabbit arteries metabolize AA to 15-hydroxyeicosatetraenoic acid (15-HETE), hydroxyepoxyeicosatrienoic acids (HEETAs), and trihydroxyeicosatrienoic acids (THETAs) (11,13,14). 11(R),12(S),15(S)-trihydroxyeicosa-5Z,8Z,13E-trienoic acid (11,12, and its proposed precursor, the unstable 15-H-11,12-EETA function as EDHFs in rabbit aorta and mesenteric arteries (11,(15)(16)(17).…”