Arachidonic acid epoxygenase: Structural characterization and quantification of epoxyeicosatrienoates in plasma (original) (raw)
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Epoxyeicosatrienoic acids (EETs): metabolism and biochemical function
Progress in Lipid Research, 2004
Epoxyeicosatrienoic acids (EETs), which are synthesized from arachidonic acid by cytochrome P450 epoxygenases, function primarily as autocrine and paracrine effectors in the cardiovascular system and kidney. They modulate ion transport and gene expression, producing vasorelaxation as well as antiinflammatory and pro-fibrinolytic effects. EETs are incorporated into the sn-2 position of phospholipids and are rapidly mobilized when a cell is treated with a Ca 2+ ionophore, suggesting that they may play a role in phospholipid-mediated signal transduction processes. Soluble epoxide hydrolase (sEH) converts EETs to dihydroxyeicosatrienoic acids (DHETs), and inhibition of sEH is a potential approach for enhancing the biological activity of EETs. EETs also undergo chain-elongation and b-oxidation, and the accumulation of partial b-oxidation products increases when sEH is inhibited. Some functional effects of EETs occur through activation of either the guanine nucleotide binding protein Gas or the Src signal transduction pathways, suggesting that EETs act by binding to membrane receptors. However, other evidence indicates that the modulation of gene expression occurs through an intracellular action of EETs. Because of the diversity of biochemical and functional responses produced by EETs, it is doubtful that a single mechanism or signal transduction pathway can account for all of their actions.
Regiospecific and enantioselective metabolism of 8,9-epoxyeicosatrienoic acid by cyclooxygenase
Biochemical and Biophysical Research Communications, 1992
Arachidonic acid oxygenation by the microsomal cytochrome P-450 system leads to the formation of EETs and HETEs (l-4). EETs have a diversity biological activities (5) including their ability to inhibit arachidonate-induced human platelet aggregation (6). It has been proposed that EETs are involved in the pathophysiology of human disease (7). In support of this proposal it was found that 8(S),9(R)-EET, a major product of rat kidney renal cortex, was a potent renal vasoconstrictor substance (8). During recent studies on the inhibition of human platelet aggregation by 8,9-EET enantiomers, we observed that four metabolites were formed. Two of the metabolites were absent when platelet cyclooxygenase was inhibited with indomethacin or aspirin. 5,6-EET is known to be a substrate for cyclooxygenase where it serves as a precursor for a number of PCs (9-12). However, 8,9-EET is unable to undergo cyclization to an endoperoxide and it has been assumed in the past that it is not metabolized by cyclooxygenase (5,6,13). We report that
Journal of Chromatography B, 2008
Epoxyeicosatrienoic acids (EETs) are cytochrome P450 metabolites of arachidonic acid involved in the regulation of vascular tone. Despite the importance of EETs in a variety of physiological effects, few methods have been developed to quantify them in human blood. This led us to develop a method by GC/MS with negative ion chemical ionization. As EETs are primarily located in phospholipids, red blood cells (RBCs) and plasma phospholipids were hydrolyzed with phospholipase A 2 after a solid phase extraction. Then, EETs were derivatized as pentafluorobenzyl esters, and [ 2 H 8 ]-arachidonic acid was used as internal standard for quantification. EETs were found to be at concentrations of 106 ± 37 ng mL −1 in plasma and 33.4 ± 8.5 ng/10 9 RBCs (mean ± S.D.) in 10 healthy volunteers. Their amount in RBCs was 3-fold that in plasma; both parameters proved to be well correlated.
Journal of Biological Chemistry, 2005
The cytochrome P450 arachidonic acid epoxygenase metabolites, the epoxyeicosatrienoic acids (EETs) are powerful, nonregioselective, stimulators of cell proliferation. In this study we compared the ability of the four EETs (5,6-, 8,9-, 11,12-, and 14,15-EETs) to regulate endothelial cell proliferation in vitro and angiogenesis in vivo and determined the molecular mechanism by which EETs control these events. Inhibition of the epoxygenase blocked serum-induced endothelial cell proliferation, and exogenously added EETs rescued cell proliferation from epoxygenase inhibition. Studies with selective ERK, p38 MAPK, or PI3K inhibitors revealed that whereas activation of p38 MAPK is required for the proliferative responses to 8,9-and 11,12-EET, activation of PI3K is necessary for the cell proliferation induced by 5,6-and 14,15-EET. Among the four EETs, only 5,6-and 8,9-EET are capable of promoting endothelial cell migration and the formation of capillary-like structures, events that are dependent on EET-mediated activation of ERK and PI3K. Using subcutaneous sponge models, we showed that 5,6-and 8,9-EET are pro-angiogenic in mice and that their neo-vascularization effects are enhanced by the co-administration of an inhibitor of EET enzymatic hydration, presumably because of reduced EET metabolism and inactivation. These studies identify 5,6-and 8,9-EET as powerful and selective angiogenic lipids, provide a functional link between the EET proliferative chemotactic properties and their angiogenic activity, and suggest a physiological role for them in angiogenesis and de novo vascularization.
The role of epoxyeicosatrienoic acids in the cardiovascular system
British journal of clinical pharmacology, 2015
There is increasing evidence suggesting that epoxyeicosatrienoic acids (EETs) play an important role in cardio-protective mechanisms. These include regulating vascular tone, modulating inflammatory responses, improving cardiomyocyte function, and reducing ischaemic damage, resulting in attenuation of animal models of cardiovascular risk factors. This review discusses the current knowledge on the role of EETs in endothelium-dependent control of vascular tone in the healthy and in subjects with cardiovascular risk factors, and considers the pharmacological potential of targeting this pathway.
Hypolipidemic Effect of Ethyl all-cis-5,8,11,14,17-Icosapentaenoate (EPA-E) in Rats
The Japanese Journal of Pharmacology, 1992
We examined the effect of ethyl all-cis-5,8,11,14,17-icosapentaenoate (EPA-E) with high purity on circulating lipids in rats under several experimental conditions. In normolipidemic rats, EPA E decreased the lipids in a dose-dependent manner. Clofibrate (100 mg/kg/day) was more potent in lowering the lipids than EPA-E (1000 mg/kg/day). In high cholesterol diet-fed rats, EPA-E (300 mg/kg/day) decreased the total cholesterol. However, clofibrate (300 mg/kg/day) had little effect on the total cholesterol. In hypertriglycemic rats induced by corn oil, EPA-E (300 mg/kg/day) or clofi brate (100 mg/kg/day) reduced the rise of triglycerides. EPA-E (300 mg/kg/day), clinofibrate (100 mg/kg/day) or clofibrate (300 mg/kg/day) caused a significant reduction in the lipids induced by the in jection of Triton WR-1339. Furthermore, EPA-E (300 mg/kg/day) or clinofibrate (100 mg/kg/day) de creased the elevation of lipids produced by feeding the rats a casein-rich diet. These results show that EPA-E possesses potent inhibitory activity on experimental hyperlipidemia induced either exogenously or endogenously.
AJP: Heart and Circulatory Physiology, 2005
Epoxyeicosatrienoic acids (EETs) are metabolized by soluble epoxide hydrolase (sEH) to form dihydroxyeicosatrienoic acids (DHETs) and are putative endothelium-derived hyperpolarizing factors (EDHFs). EDHFs modulate microvascular tone; however, the chemical identity of EDHF in the human coronary microcirculation is not known. We examined the capacity of EETs, DHETs, and sEH inhibition to affect vasomotor tone in isolated human coronary arterioles (HCAs). HCAs from right atrial appendages were prepared for videomicroscopy and immunohistochemistry. In vessels preconstricted with endothelin-1, three EET regioisomers (8,9-, 11,12-, and 14,15-EET) each induced a concentration-dependent dilation that was sensitive to blockade of large-conductance Ca 2+activated K + (BK Ca ) channels by iberio-toxin. EET-induced dilation was not altered by endothelial denudation. 8,9-, 11,12-, and 14,15-DHET also dilated HCA via activation of BK Ca channels. Dilation was less with 8,9-and 14,15-DHET but was similar with 11,12-DHET, compared with the corresponding EETs. Immunohistochemistry revealed prominent expression of cytochrome P-450