The reaction of arachidonic acid epoxides (epoxyeicosatrienoic acids) with a cytosolic epoxide hydrolase

111

112

Atherosclerosis, in its myriad incarnations the foremost killer disease in the industrialized world, is characterized by aberrant proliferation of vascular smooth muscle (VSM) cells in part as a result of the recruitment of inflammatory cells to the blood vessel wall. The epoxyeicosatrienoic acids are synthesized from arachidonic acid in a reaction catalyzed by the cytochrome P450 system and are vasoactive substances. Metabolism of these compounds by epoxide hydrolases results in the formation of compounds that affect the vasculature in a pleiotropic manner. As an outgrowth of our observations that urea inhibitors of the soluble epoxide hydrolase (sEH) reduce blood pressure in spontaneously hypertensive rats as well as the findings of other investigators that these compounds possess antiinflammatory actions, we have examined the effect of sEH inhibitors on VSM cell proliferation. We now show that the sEH inhibitor 1-cyclohexyl-3-dodecyl urea (CDU) inhibits human VSM cell proliferation in a dose-dependent manner and is associated with a decrease in the level of cyclin D1. In addition, cis-epoxyeicosatrienoic acid mimics the growth-suppressive activity of CDU; there is no evidence of cellular toxicity or apoptosis in CDU-treated cells when incubated with 20 μM CDU for up to 48 h. These results, in light of the antiinflammatory and antihypertensive properties of these compounds that have been demonstrated already, suggest that the urea class of sEH inhibitors may be useful for therapy for diseases such as hypertension and atherosclerosis characterized by exuberant VSM cell proliferation and vascular inflammation

mentioning

confidence: 99%

Inhibitors of soluble epoxide hydrolase attenuate vascular smooth muscle cell proliferation

Davis

Thompson

Howard

et al. 2002

111

112

“…Levels of these molecules are regulated by synthesis, degradation, and membrane incorporation (17,34,35). However, preventing their hydrolysis by inhibiting sEH offers advantages because this greatly enhances the in vivo ) at a 10-fold lower dose is comparable to Gabapentin (100 mg/kg i.p.…”

Section: Discussionmentioning

confidence: 99%

“…epoxide/diol ratio (17,24). A number of biological activities have been attributed to EpFAs; their effects on the functioning of the nervous system are newly described (22,23,34).…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Acute augmentation of epoxygenated fatty acid levels rapidly reduces pain-related behavior in a rat model of type I diabetes

Inceoglu

Wagner

Yang

et al. 2012

The nerve damage occurring as a consequence of glucose toxicity in diabetes leads to neuropathic pain, among other problems. This pain dramatically reduces the quality of life in afflicted patients. The progressive damage to the peripheral nervous system is irreversible although strict control of hyperglycemia may prevent further damage. Current treatments include tricyclic antidepressants, anticonvulsants, and opioids, depending on the severity of the pain state. However, available therapeutics have drawbacks, arguing for the need to better understand the pathophysiology of neuropathic pain and develop novel treatments. Here we demonstrate that stabilization of a class of bioactive lipids, epoxygenated fatty acids (EpFAs), greatly reduces allodynia in rats caused by streptozocin-induced type I diabetes. Inhibitors of the soluble epoxide hydrolase (sEHI) elevated and stabilized the levels of plasma and spinal EpFAs, respectively, and generated dose-dependent antiallodynic effects more potently and efficaciously than gabapentin. In acute experiments, positive modulation of EpFAs did not display differences in insulin sensitivity, glucose tolerance, or insulin secretion, indicating the efficacy of sEHIs are not related to the glycemic status. Quantitative metabolomic analysis of a panel of 26 bioactive lipids demonstrated that sEHI-mediated antiallodynic effects coincided with a selective elevation of the levels of EpFAs in the plasma, and a decrease in degradation products coincided with the dihydroxy fatty acids in the spinal cord. Overall, these results argue that further efforts in understanding the spectrum of effects of EpFAs will yield novel opportunities in treating neuropathic pain.analgesic drug | soluble epoxide hydrolase inhibitor | cytochrome P450 | glucose homeostasis | motor depressant

“…Although uniformly expressed in the liver, high expression of sEH is highly localized in other tissues including vascular endothelium, some smooth muscle, and the proximal tubule (3,4). Epoxy fatty acids generated by cytochrome P450 epoxygenases are endogenous substrates for the sEH C-terminal domain (5), with critical roles in the regulation of cardiovascular, renal, and inflammatory biology (6)(7)(8)(9). The hydrolysis of epoxy fatty acids modulates their intracellular fate (10,11) and biological activity (9,12,13).…”

mentioning

confidence: 99%

The soluble epoxide hydrolase encoded by EPXH2 is a bifunctional enzyme with novel lipid phosphate phosphatase activity

Newman

Morisseau

Harris

et al. 2003

191

180

The gene EPXH2 encodes for the soluble epoxide hydrolase (sEH), an enzyme involved in the regulation of cardiovascular and renal physiology containing two distinct domains connected via a proline-rich linker. The C-terminal domain containing the EH catalytic activity has been well studied. In contrast, a function for the N-terminal domain, which has high homology to the haloacid dehalogenase family of phosphatases, has not been definitively reported. In this study we describe the N-terminal domain as a functional phosphatase unaffected by a number of classic phosphatase inhibitors. Assuming a functional association between these catalytic activities, dihydroxy lipid phosphates were rationalized as potential endogenous substrates. A series of phosphorylated hydroxy lipids were therefore synthesized and found to be excellent substrates for the human sEH. The best substrate tested was the monophosphate of dihydroxy stearic acid (threo-9͞ 10-phosphonoxy-hydroxy-octadecanoic acid) with K m ‫؍‬ 21 ؎ 0.3 M, VMax ‫؍‬ 338 ؎ 12 nmol⅐min ؊1 ⅐mg ؊1 , and kcat ‫؍‬ 0.35 ؎ 0.01 s ؊1 . Therefore dihydroxy lipid phosphates are possible candidates for the endogenous substrates of the sEH N-terminal domain, which would represent a novel branch of fatty acid metabolism with potential signaling functions.T he soluble epoxide hydrolase (sEH), first described in 1972(1), is an ubiquitous enzyme in vertebrates that transforms epoxides to their corresponding diols (2). Although uniformly expressed in the liver, high expression of sEH is highly localized in other tissues including vascular endothelium, some smooth muscle, and the proximal tubule (3, 4). Epoxy fatty acids generated by cytochrome P450 epoxygenases are endogenous substrates for the sEH C-terminal domain (5), with critical roles in the regulation of cardiovascular, renal, and inflammatory biology (6-9). The hydrolysis of epoxy fatty acids modulates their intracellular fate (10, 11) and biological activity (9,12,13). In vivo, the pharmacological blockade of epoxide hydrolysis attenuates hypertension (4, 14), whereas the deletion of this gene reduces blood pressure in male mice to female levels (15).The sEH is a homodimer with a monomeric unit of 62.5 kDa (2) whose primary structure suggests that the EPXH2 gene was produced by the fusion of two primordial dehalogenase genes (16,17). This gene fusion hypothesis was recently supported by a 2.8-Å resolution x-ray crystal structure of the mouse enzyme (18). The C-terminal sEH domain has high homology to haloalkane dehalogenase, whereas the N-terminal domain is similar to haloacid dehalogenase (HAD). Although analysis of the sEH crystal structure revealed that the conserved HAD-like catalytic residues were properly oriented for catalysis, no dehalogenase activity was detected (18). However, the amino-terminal catalytic DXDX(T͞V) motif of HAD has been used to describe an enzyme class that includes numerous phosphatases (19)(20)(21).It can be argued that gene fusion events are driven by evolution, leading to the physical linkage of f...