Cross-species comparison of resolvin E and resolvin D biosynthesis: Quantification by liquid chromatography mass spectrometry in fish and human cells exposed to alpha-linolenic acid, eicosapentaenoic acid, and docosahexaenoic acid

Resolvins are lipid mediators essential for resolving inflammatory processes in living organisms. Studies have shown that fish and human cells share enzymatic pathways to produce resolvins E (RvE) and D (RvD) from eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), respectively. However, cross-species comparisons of resolvin production from dietary α-linolenic acid (ALA), an indirect precursor to resolvins as it is the metabolic precursor to EPA and DHA, remain limited. To address this, a liquid chromatography mass spectrometry method was validated for quantifying RvE and RvD released into culture media by salmon head kidney cells and human peripheral blood mononuclear cells exposed to ALA, EPA, and DHA. The assay performance was evaluated using both fish and human cell culture media, demonstrating acceptable results according to international guidelines. Key performance parameters included selectivity, range (0.5–50 ng/mL), linearity (R² = 0.98–0.99), limits of detection (∼0.02–0.09 ng/mL), limits of quantification (∼0.08–0.3 ng/mL), and accuracy (∼97–109 %). The validated method enabled a reliable cross-species comparison and revealed that the DHA → RvD conversion is the predominant pathway in both fish and human cells. In contrast, the EPA → RvE and ALA-indirect pathways (ALA→EPA/DHA → RvE/RvD) contributed minimally in both species. Notably, the study also indicated, the involvement of a retroconversion pathway: DHA → EPA → RvE not being reported yet.