5-lipoxygenase-dependent biosynthesis of novel 20:4 n-3 metabolites with anti-inflammatory activity.

5-lipoxygenase (5-LO) catalyzes the conversion of arachidonic acid (AA) into pro-inflammatory leukotrienes. N-3 PUFA like eicosapentaenoic acid are subject to a similar metabolism and are precursors of pro-resolving mediators. Stearidonic acid (18:4 n-3, SDA) is a plant source of n-3 PUFA that is elongated to 20:4 n-3, an analogue of AA. However, no 5-LO metabolites of 20:4 n-3 have been reported. In this study, control and 5-LO-expressing HEK293 cells were stimulated in the presence of 20:4 n-3. Metabolites were characterized by LC-MS/MS and their anti-inflammatory properties assessed using AA-induced autocrine neutrophil stimulation and leukotriene B4 -mediated chemotaxis. 8‑hydroxy‑9,11,14,17-eicosatetraenoic acid (Δ17 -8-HETE) and 8,15-dihydroxy-9,11,13,17-eicosatetraenoic acid (Δ17 -8,15-diHETE) were identified as novel metabolites. Δ17 -8,15-diHETE production was inhibited by the leukotriene A4 hydrolase inhibitor SC 57461A. Autocrine neutrophil leukotriene stimulation and neutrophil chemotaxis, both BLT1-dependent processes, were inhibited by Δ17 -8,15-diHETE at low nM concentrations. These data support an anti-inflammatory role for Δ17 -8,15-diHETE, a novel 5-LO product.