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Mediators of antihypertensive actions of docosahexaenoic acid (DHA) are largely unknown. The omega-3 epoxide of DHA, 19, 20-EDP (epoxy docosapentaenoic acid), is metabolized by soluble epoxide hydrolase (sEH), which also metabolizes the anti-inflammatory and antihypertensive arachidonic acid epoxides, epoxyeicosatrienoic acids (EETs). Based in part on plasma levels of EDPs after a DHA-rich diet, we hypothesized that 19, 20-EDP contributes to the antihypertensive actions of DHA in angiotensin-II (Ang-II)–dependent hypertension. Treatment individually with 19, 20-EDP and a potent sEH inhibitor TPPU (1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea) significantly lowered blood pressure (BP) as compared with Ang-II–infused animals. The largest reduction in BP was obtained with the combination of 19, 20-EDP and TPPU, which was more efficacious than the combination of 14, 15-EET and TPPU. Oxylipin profiling revealed that 19, 20-EDP and 14, 15-EET infusion affected not only most metabolites of the P450 pathway but also renal levels of prostaglandin-E2. Our findings suggest that 19, 20-EDP is a mediator of the antihypertensive effects of DHA in Ang-II–dependent hypertension. It seems that 19, 20-EDP requires metabolic stabilization with a sEH inhibitor to be most effective in lowering BP, although both TPPU and 19, 20-EDP are so effective on their own that demonstrating additive or synergistic interactions is difficult.

Two hundred and seventy-one compounds including benzoylureas, arylureas and related compounds were assayed using recombinant murine soluble epoxide hydrolase (MsEH) produced from a baculovirus expression system. Among all the insect growth regulators assayed, 18 benzoylphenylurea congeners showed weak activity against MsEH. Newly synthesized cyclohexylphenylurea, 1-benzyl-3-phenylurea, and 1,3-dibenzylurea analogues were rather potent. The introduction of a methyl group at the para-position of the phenyl ring of cyclohexylphenylurea enhanced the activity 6-fold, though similar substituent effects were not seen for any of the benzoylphenylureas. The activities of these compounds, including several previously reported compounds, such as dicyclohexylurea, diphenylurea, and their related analogues (Morisseau et al., Proc. Natl. Acad. Sci., 1999, 96, 8849), were quantitatively analyzed using comparative molecular field analysis (CoMFA), a three-dimensional quantitative structure–activity relationship (3-D QSAR) method. Both steric and electrostatic factors contributing to variations in the activity were visualized using CoMFA. CoMFA results showed that one side of the cyclohexylurea moiety having a trans-amide conformation (A-ring moiety) is surrounded by large sterically unfavorable fields, while the other side of A-ring moiety and the other cyclohexyl group (B-ring moiety) is encompassed by sterically favored fields. Electrostatically negative fields were scattered around the entire molecule, and a positive field surrounds the carbon of the carbonyl group. Hydrophobic fields were visualized using Kellogg's hydropathic interaction (HINT) in conjunction with CoMFA. Hydrophobically favorable fields appeared beside the 4- and 4′-carbon atoms of the cyclohexyl groups, and hydrophobically unfavorable fields surrounded the urea bridge. The addition of the molecular hydrophobicity, it> /it>, to CoMFA did not improve the correlation significantly. The ligand-binding interactions shown by X-ray crystallographic data were rationalized using the results of the CoMFA and HINT analyses, and the essential physicochemical parameters for the design of new MsEH inhibitors were disclosed.