(±)5(6) eet

5(6)-EET is a fully racemic version of the enantiomeric forms biosynthesized from arachidonic acid by cytochrome P450 enzymes. In solution, 5(6)-EET degrades into 5,6-DiHET and 5(6)-δ-lactone, which can be converted to 5(6)-DiHET and quantified by GC-MS. In neuroendocrine cells, such as the anterior pituitary and pancreatic islets, 5(6)-EET has been implicated in the mobilization of calcium and hormone secretion. 5(6)-EET is an inhibitor of T-type voltage-gated calcium channels (Cav3) that inhibits isoforms Cav3.1, Cav3.2 (IC50 = 0.54 μM), and Cav3.3 and decreases nifedipine-resistant phenylephrine-induced vasoconstriction in isolated mouse mesenteric arteries via Cav3.2 blockade when used at a concentration of 3 μM. In addition, it is a substrate of COX-1 and COX-2, as measured by oxygen consumption and product formation assays when used at a concentration of 50 μM. (±)5(6)-EET is provided as a mixture of the free acid and lactone.

(±)14(15)-EET is a metabolite of arachidonic acid that is formed via epoxidation of arachidonic acid by cytochrome P450.[1],[2] It prevents increases in leukotriene B4, ICAM-1, and chemokine (C-C motif) ligand 1 (CCL2) induced by oxidized LDL in primary rat pulmonary artery endothelial cells (RPAECs) when used at a concentration of 1 μM.[3] (±)14(15)-EET induces dilation of preconstricted isolated canine coronary arterioles (EC50 = 0.2 pM).[4] It reduces myocardial infarct size as a percentage of the area at risk in a canine model of ischemia-reperfusion injury induced by left anterior descending coronary artery (LAD) occlusion when administered at a dose of 0.128 mg kg prior to occlusion or reperfusion.[5] Reference:[1]. Chacos, N., Falck, J.R., Wixtrom, C., et al. Novel epoxides formed during the liver cytochrome P-450 oxidation of arachidonic acid. Biochem. Biophys. Res. Commun. 104(3), 916-922 (1982).[2]. Oliw, E.H., Guengerich, F.P., and Oates, J.A. Oxygenation of arachidonic acid by hepatic monooxygenases. Isolation and metabolism of four epoxide intermediates. J. Biol. Chem. 257(7), 3771-3781 (1982).[3]. Jiang, J.-X., Zhang, S.-J., Xiong, Y.-K., et al. EETs attenuate ox-LDL-induced LTB4 production and activity by inhibiting p38 MAPK phosphorylation and 5-LO BLT1 receptor expression in rat pulmonary arterial endothelial cells. PLoS One 10(6), e0128278 (2015).[4]. Oltman, C.L., Weintraub, N.L., VanRollins, M., et al. Epoxyeicosatrienoic acids and dihydroxyeicosatrienoic acids are potent vasodilators in the canine coronary microcirculation. Circ. Res. 83(9), 932-939 (1998).[5]. Nithipatikom, K., Moore, J.M., Isbell, M.A., et al. Epoxyeicosatrienoic acids in cardioprotection: Ischemic versus reperfusion injury. Am. J. Physiol. Heart Circ. Physiol. 291(2), H537-H542 (2006).

(±)11(12)-EET is a fully racemic version of the R S enantiomeric forms biosynthesized from arachidonic acid by cytochrome P450 enzymes.[1][2][3] A higher proportion of 11(R),12(S)-EET is produced by the CYP450 isoforms CYP2C23 and CYP2C24, while CYP2B2 produces a higher proportion of 11(S),12(R)-EET.[3] 11(12)-EET has been shown, along with 8(9)-EET, to play a role in the recovery of depleted calcium pools in cultured smooth muscle cells.[4] It also inhibits basolateral 18-pS potassium channels in the renal cortical collecting duct at a concentration of 100 nM.[5] 11(12)-EET (50 μg kg per day) increases adhesion of isolated peripheral blood leukocytes in a chamber coated with P-selectin and ICAM-1 but does not affect choroidal neovascularization size following laser photocoagulation.[6] It also has anti-inflammatory, angiogenic, and cardioprotective properties.[7]

5,6-DiHET lactone is a lactonized form of 5,6-EET and 5,6-DiHET. In solution, 5(6)-EET degrades into 5(6)-DiHET and 5(6)-δ-lactone, which can be converted to 5(6)-DiHET and quantified by GC-MS. 5,6-DiHET potently induces vasodilation of isolated canine coronary arterioles, with 41% and 100% inhibition occurring at 0.01 and 100 pM, respectively. It also induces vasodilation in isolated human microvessels and increases intracellular calcium levels in a dose-dependent manner, an effect that can be blocked by the nitric oxide scavenger [L-NAME].

5(6)-DiHET is a racemic compound synthesized through the action of epoxide hydrolases on 5(6)-EET, encompassing both enantiomeric forms. It serves as a quantitative marker for 5(6)-EET, facilitating its measurement by utilizing the compound's conversion to 5(6)-δ-lactone in solution. Additionally, 5(6)-DiHET activates large-conductance calcium-activated potassium (KCa1.1/BK) channels in rat small coronary artery smooth muscle cells, supporting its biological significance in vascular regulation. It also acts as a substrate for sheep seminal vesicle COX, leading to the in vitro production of 5,6-dihydroxy prostaglandin E1 and F1α metabolites. Notably, its levels diminish in the plasma of rats subjected to a high-fat diet, indicating a potential role in the pathophysiology of hyperlipidemia.