Eicosapentaenoic acid is converted via ω-3 epoxygenation to the anti-inflammatory metabolite 12-hydroxy-17,18-epoxyeicosatetraenoic acid.

Eicosapentaenoic acid (EPA) has beneficial effects in many inflammatory disorders. In this study, dietary EPA was converted to 17,18-epoxyeicosatetraenoic acid (17,18-EpETE) by ω-3 epoxygenation in the mouse peritoneal cavity. Mediator lipidomics revealed a series of novel oxygenated metabolites of 17,18-EpETE, and one of the major metabolites, 12-hydroxy-17,18-epoxyeicosatetraenoic acid (12-OH-17,18-EpETE), displayed a potent anti-inflammatory action by limiting neutrophil infiltration in murine zymosan-induced peritonitis. 12-OH-17,18-EpETE inhibited leukotriene B4-induced neutrophil chemotaxis and polarization in vitro in a low nanomolar range (EC50 0.6 nM). The complete structures of two natural isomers were assigned as 12S-OH-17R,18S-EpETE and 12S-OH-17S,18R-EpETE, using chemically synthesized stereoisomers. These natural isomers displayed potent anti-inflammatory action, whereas the unnatural stereoisomers were essentially devoid of activity. These results demonstrate that 17,18-EpETE derived from dietary EPA is converted to a potent bioactive metabolite 12-OH-17,18-EpETE, which may generate an endogenous anti-inflammatory metabolic pathway.