title: A novel activity of microsomal epoxide hydrolase: metabolism of the endocannabinoid 2-arachidonoylglycerol.
abstract: Microsomal epoxide hydrolase (EPHX1, EC 3.3.2.9) is a highly abundant α/β-hydrolase enzyme that is known for its catalytical epoxide hydrolase activity. A wide range of EPHX1 functions have been demonstrated including xenobiotic metabolism; however, characterization of its endogenous substrates is limited. In this study, we present evidence that EPHX1 metabolizes the abundant endocannabinoid 2-arachidonoylglycerol (2-AG) to free arachidonic acid (AA) and glycerol. The EPHX1 metabolism of 2-AG was demonstrated using commercially available EPHX1 microsomes as well as PC-3 cells overexpressing EPHX1. Conversely, EPHX1 siRNA markedly reduced the EPHX1 expression and 2-AG metabolism in HepG2 cells and LNCaP cells. A selective EPHX1 inhibitor, 10-hydroxystearamide, inhibited 2-AG metabolism and hydrolysis of a well-known EPHX1 substrate, cis-stilbene oxide. Among the inhibitors studied, a serine hydrolase inhibitor, methoxy-arachidonyl fluorophosphate, was the most potent inhibitor of 2-AG metabolism by EPHX1 microsomes. These results demonstrate that 2-AG is an endogenous substrate for EPHX1, a potential role of EPHX1 in the endocannabinoid signaling and a new AA biosynthetic pathway.
authors: Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI 53226.
authors: Kasem
authors: K
authors: Nithipatikom
authors: Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI 53226.
authors: Michael P
authors: MP
authors: Endsley
authors: Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI 53226.
authors: Adam W
authors: AW
authors: Pfeiffer
authors: Departments of Biochemistry and Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390.
authors: John R
authors: JR
authors: Falck
authors: Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI 53226.
authors: William B
authors: WB
authors: Campbell
mesh_terms: D001095:Arachidonic Acids / Q000378:metabolism*; D063388:Endocannabinoids / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004851:Epoxide Hydrolases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005989:Glycerides / Q000378:metabolism*; D056945:Hep G2 Cells; D006801:Humans; D008861:Microsomes / Q000201:enzymology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
chemical_list: D001095:Arachidonic Acids; D063388:Endocannabinoids; D004791:Enzyme Inhibitors; D005989:Glycerides; C094503:glyceryl 2-arachidonate; D004851:Epoxide Hydrolases; C522330:EPHX1 protein, human
keywords: anandamide; arachidonic acid; prostate carcinoma cells