Publications

• Identification of 13-hydroxy-14,15-epoxyeicosatrienoic acid as an acid-stable endothelium-derived hyperpolarizing factor in rabbit arteries.

  Chawengsub Y., Gauthier K.M., Nithipatikom K., Hammock B.D., Falck J.R., Narsimhaswamy D., Campbell W.B.

  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 ... >> More

  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. << Less

  J. Biol. Chem. 284:31280-31290(2009) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Cytochrome P450-dependent transformations of 15R- and 15S-hydroperoxyeicosatetraenoic acids: stereoselective formation of epoxy alcohol products.

  Chang M.S., Boeglin W.E., Guengerich F.P., Brash A.R.

  Although there are many reports of epoxy alcohol synthesis from lipoxygenase products (fatty acid hydroperoxides) in mammalian tissues, there are no well-defined examples of the stereoselective synthesis of individual epoxy alcohol diastereomers. An earlier report on the metabolism of 15S-hydroper ... >> More

  Although there are many reports of epoxy alcohol synthesis from lipoxygenase products (fatty acid hydroperoxides) in mammalian tissues, there are no well-defined examples of the stereoselective synthesis of individual epoxy alcohol diastereomers. An earlier report on the metabolism of 15S-hydroperoxyeicosatetraenoic acid (15S-HPETE) in rat liver microsomes suggested such a specific reaction [Weiss, R. H., et al. (1987) Arch. Biochem. Biophys. 252, 334-338]. To characterize this reaction further, we set out to determine the precise structures and mechanism of biosynthesis of the epoxy alcohol products. We compared the products formed from 15R- and 15S-HPETE by hematin (a nonenzymatic reaction), by liver microsomes isolated from control and phenobarbital-treated rats, and by purified cytochrome P450 2B1. Eight epoxy alcohol isomers were identified by mass spectrometry and 1H NMR. In the hematin reaction, the major products are four epoxy alcohols with the epoxide in the trans configuration, diastereomers are formed in similar amounts, and the 15-HPETE enantiomers give indistinguishable patterns of products. By contrast, the liver microsomes and P450 2B1 enzyme form predominantly single diastereomers, and the configuration of the epoxide is dependent on the stereochemistry of the substrate. The main product formed from 15S-HPETE is 11S-hydroxy-14S,15S-trans-epoxyeicosa-5Z,8Z,12E-trienoic acid, and the amounts increase upon phenobarbital induction. The main products from 15R-HPETE are 11-hydroxy-14S,15R-epoxyeicosa-5Z,8Z,12E-t rienoic acid from microsomes from control rats and 13-hydroxy-14S,15R-cis-epoxyeicosa-5,8,11-trienoic acid in microsomes from phenobarbital-induced rats. The P450 2B1 enzyme gave products similar to those from the phenobarbital-induced microsomes. Analysis of an incubation using the 18O-labeled 15S-HPETE substrate demonstrated 97.6% retention of both hydroperoxy oxygens in the major product with progressively lower 18O retentions in the minor products (74-32%), possibly reflecting degrees of enzymatic control of these reactions. These results establish a precedent for the stereoselective synthesis of epoxy alcohols by mammalian cytochrome P450s. << Less

  Biochemistry 35:464-471(1996) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.