Abstract 463: Linoleate Epoxides, Epomes, Are Potent Anti-inflammatory Fatty Acid Epoxides and Nearly Equivalent to Arachidonate-derived Epetres

Background: Epoxides of arachidonic acid (EpETrEs, also commonly EETs) are potent anti-inflammatory lipid mediators and are associated with hypotensive and protective vascular actions. Marine omega-3 versions (epoxides of eicosapentaenoic and docosahexaenoic acids) have similar action. Surprisingly, none of these epoxides are as abundant in tissues or in plasma as epoxides of linoleic acid (EpOMEs) are. EpOMEs are up to one-hundred times more abundant than EpETrEs. Hence, EpOMEs could exert physiologic effects even with potency two-orders of magnitude higher, provided they have comparable efficacy. Few studies consider EpOMEs when assessing outcomes. Objective: To compare the potency and efficacy of EpOMEs to EpETrEs in a model of inflammation relevant to vascular disease, the RAW 264.7 macrophage. Approach and results: The suppression of inflammatory cytokines (IL-6 and TNFa) in RAW 264.7 macrophages responding to LPS treatment (500 nM, 24 hrs.) was measured in the presence of 1 hour pretreatment with 9(10)-EpOME and 11(12)-EpETrE over 4-orders of magnitude (0.03 nM to 100 nM). The resulting dose-response curves were used to estimate potency (IC 50 ), and efficacy (suppression as percent of maximal LPS activation). Least-square-mean and 95% CIs are reported. The IC 50 for suppression of cytokines by EpOME and EpETrE were not different, regardless of cytokine, yielding an estimate of 4.2 [2.6, 6.8] nM and indicating that EpOMEs are equipotent to EpETrEs in cytokine suppression. While EpOMEs had the same effectiveness in suppressing IL-6 to 59% [54, 64] of max, they were not as effective in suppressing TNFa, to 83% [80, 86] of max versus 78% [75, 81] for EpETrEs (p<0.01). Conclusions: Given their great abundance in tissue and plasma, linoleate epoxides would need to be more than 100 times less potent than arachidonate epoxides to be physiologically irrelevant. Here, we find they are equipotent for suppression of two pro-inflammatory cytokines, with moderately lower efficacy for one cytokine, TNFa. We find little reason to ignore linoleate-derived EpOMEs and conclude they are a physiologically relevant pool of epoxides whose levels should be measured along with EpETrE and other epoxides when estimating overall epoxide effects.