Lipid mediators generated by the cytochrome P450—Epoxide hydrolase pathway

The cytochrome P450 (CYP) soluble epoxide hydrolase (sEH) pathway generates a large number of biologically active epoxides and diols from a range of ω-3 and ω-6 polyunsaturated fatty acids (PUFAs). While epoxides of arachidonic acid or epoxyeicosatrienoic acids are probably the best studied of these mediators, epoxides of linoleic acid as well as the fish oils; docosahexaenoic acid and eicosapentaenoic acid have also been attributed signaling actions. Cell and tissue levels of the PUFA epoxides are largely determined by the sEH and in many cases inflammation and chronic diseases, e.g., cardiovascular disease, diabetes and Alzheimer's disease, have been associated with increased sEH expression and the accelerated conversion of PUFA epoxides to their corresponding diols. In low concentrations, the diols act to influence stem and progenitor cells as well as brown adipose tissue but in high concentrations, they tend to have pro-inflammatory and cytotoxic effects that promote disease progression. This review outlines some of the actions to the PUFA epoxides and diols in physiology and pathophysiology as well as the beneficial effects associates with sEH inhibition.