Ex vivo DHA supplementation suppresses prostaglandin E2 formation in primary human macrophages

There is evidence that intake of long-chain n-3 polyunsaturated fatty acids (PUFA) is associated with improved prognosis for inflammatory diseases. However, the underlying mechanisms are still subject of ongoing research. For this purpose, we developed an ex vivo n-3 PUFA supplementation strategy to test n-3 PUFA supplementation under controlled conditions in primary human macrophages. Methods and results: Cells were supplemented with docosahexaenoic acid (DHA). Quality parameters to account for possible confounders were established for a reproducible and reliable supplementation. Following supplementation, PUFA pattern of cells was shifted towards a pattern reflecting that of subjects with a high n-3 PUFA status. This was accompanied by a decrease of arachidonic acid-derived oxylipins in a dose- and time-dependent manner in favor of n-3 PUFA ones. Stimulation with LPS resulted in decreased levels of pro-inflammatory prostaglandins in the DHA-supplemented cells, but no changes in cytokines. Conclusion: In vitro supplementation studies with n-3 PUFA need rigorous controls to exclude background formation of oxylipins. By accounting for these possible confounders the desribed ex vivo approach is a promising tool for the mechanistic investigation of n-3 PUFA in primary human immune cells, offering an alternative for intervention studies in humans.