Do EPA and DHA serve as precursors to specialized pro-resolving mediators?

The metabolic conversion of omega-3 polyunsaturated fatty acids into highly active signaling molecules is a cornerstone of modern inflammatory biology. Rather than acting as passive barriers to inflammation, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) serve as direct substrates for the enzymatic synthesis of specialized pro-resolving mediators (SPMs).

Biosynthetic pathways of SPMs

• Substrate specificity: EPA is converted via the 5-lipoxygenase (5-LOX) and cyclooxygenase-2 (COX-2) pathways into E-series resolvins (RvE1–RvE3). DHA undergoes lipoxygenation by 15-LOX and 12-LOX to yield D-series resolvins (RvD1–RvD6), protectins (such as PD1), and maresins (MaR1 and MaR2).
• Enzymatic regulation: This stereospecific biosynthesis occurs rapidly at the site of inflammation, mediated by transcellular biosynthesis between interacting endothelial cells and leukocytes.

Cellular mechanisms of resolution

• Active orchestration: SPMs bind to specific G-protein coupled receptors (GPCRs), such as ChemR23 and ALX/FPR2, to actively initiate the resolution phase of inflammation rather than merely blocking initial inflammatory cascades.
• Leukocyte trafficking and efferocytosis: SPMs halt further neutrophil infiltration into inflamed tissues and downregulate pro-inflammatory cytokines. Simultaneously, they stimulate macrophage phagocytosis of apoptotic neutrophils and cellular debris (efferocytosis) to prevent secondary necrosis and promote tissue repair.
• Macrophage polarization: Exposure to SPMs shifts macrophage phenotypes from the pro-inflammatory M1 state toward the pro-resolving, tissue-regenerative M2-like phenotype.

Clinical considerations

• Translation to clinical endpoints: While the biochemical pathways and cellular actions of SPMs are robustly characterized in vitro and in animal models, human trials evaluating the precise correlation between EPA/DHA dietary intake, systemic SPM concentrations, and localized clinical resolution are still developing, partly due to the transient nature and low circulating concentrations of these mediators.

Bottom line

• EPA and DHA are established biosynthetic precursors to resolvins, protectins, and maresins. These specialized pro-resolving mediators actively resolve inflammation by limiting neutrophil infiltration, enhancing efferocytosis, and promoting tissue repair to restore homeostasis.