In neutrophils, 5-hydroxyeicosanoid dehydrogenase (5-HEDH) activity is localised in the microsomal fraction and requires NADP+ as a cofactor to oxidise 5-hydroxy-eicosapentaenoic acid (5-HEPE) to 5-oxo-eicosapentaenoic acid (5-oxo-EPA) (Powell et al. 1995, Patel et al. 2009). Although 5-HEDH activity has been found in a wide range of intact cells and in crude microsome preparations, the enzyme has not yet been purified, its structure is unknown, and the gene that encodes it remains to be identified. Dietary EPA supplementation significantly increases the formation of 5-oxo-EPA that transduces anti-inflammatory actions rather than suppressing production of pro-inflammatory AA metabolites (Cipollina et al. 2014).