The soluble epoxide hydrolase (sEH) plays a significant role in the biosynthesis of inf lammation mediators as well as xenobiotic transformations. Herein, we report the discovery of substituted ureas and carbamates as potent inhibitors of sEH. Some of these selective, competitive tight-binding inhibitors with nanomolar K i values interacted stoi-chiometrically with the homogenous recombinant murine and human sEHs. These inhibitors enhance cytotoxicity of trans-stilbene oxide, which is active as the epoxide, but reduce cytotoxicity of leukotoxin, which is activated by epoxide hydrolase to its toxic diol. They also reduce toxicity of leukotoxin in vivo in mice and prevent symptoms suggestive of acute respiratory distress syndrome. These potent inhibitors may be valuable tools for testing hypotheses of involvement of diol and epoxide lipids in chemical mediation in vitro or in vivo systems. Epoxide hydrolases (EH; E.C.220.127.116.11) catalyze the hydrolysis of epoxides or arene oxides to their corresponding diols by the addition of water (1). In mammals, the hepatic microsomal and soluble epoxide hydrolase forms are known to complement each other in detoxifying a wide array of mutagenic, toxic, and carcinogenic, xenobiotic epoxides (2, 3). Soluble EH (sEH) is also involved in the metabolism of arachidonic (4) and linoleic (5) acid epoxides. Arachidonate epoxides and diols are ele-vated in association with pregnancy-induced hypertension and modulate vascular permeability in the heart and kidneys (6). Diols derived from epoxy-linoleate (leukotoxin) perturb mem-brane permeability and calcium homeostasis (5), resulting in inflammation modulated by nitric oxide synthase and endo-thelin-1 (7, 8). Micromolar concentrations of leukotoxin re-ported in association with inflammation and hypoxia (9) depress mitochondrial respiration in vitro (10) and cause mammalian cardiopulmonary toxicity in vivo (7, 11, 12). Leu-kotoxin toxicity presents symptoms suggestive of multiple organ failure and acute respiratory distress syndrome (9). In both cellular and organismal models, leukotoxin-mediated toxicity depends on epoxide hydrolysis (5). The bioactivity of these epoxide hydrolysis products and their association with inflammation suggest that inhibition of vicinal-dihydroxylipid biosynthesis may have therapeutic value, making sEH a promising pharmacological target. Pre-viously described selective sEH inhibitors, substituted chal-cone oxides (as compound 1 in Table 1), and phenylglycidols (13, 14) are epoxides that are hydrolyzed slowly by the target enzyme. Inhibition stems from an electronically stabilized covalent intermediate that results in low turnover and transient inhibition (15). Moreover, these compounds are relatively unstable, particularly in the presence of glutathione (13), making them of limited use in vivo. We describe herein the discovery of new potent and stable inhibitors of soluble EH and their application to both in vitro and in vivo models.
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