Inflammatory bowel disease (IBD) is characterized by dysregulated intestinal inflammation, yet endogenous lipid-mediated mechanisms that restrain inflammatory responses remain incompletely understood. Oxylipins generated by arachidonate 15-lipoxygenase (ALOX15) have been implicated in intestinal inflammation; however, their functional roles and underlying signaling mechanisms are controversial. Here, we investigated the temporal regulation and anti-inflammatory actions of ALOX15-derived oxylipins in experimental colitis and macrophages. In a dextran sulfate sodium-induced murine colitis model, colonic expression of Alox15 and levels of its downstream oxylipins, including 12-hydroxyeicosatetraenoic acid (12-HETE) and 13-hydroxyoctadecadienoic acid (13-HODE), were increased during the early and middle phases of colitis and declined at later stages. Both intestinal epithelial cells and lamina propria immune cells contributed to Alox15 expression. Functional analyses revealed that 12-HETE and 13-HODE suppressed lipopolysaccharide (LPS)-induced production of tumor necrosis factor-α and interleukin-6 in RAW264.7 macrophages without affecting cell viability or epithelial barrier permeability. Mechanistically, both oxylipins attenuated inflammatory signaling through inhibition of NF-κB, p38, and ERK pathways. Pharmacological analyses demonstrated that these anti-inflammatory effects were mediated via Gαq-dependent G protein-coupled receptor signaling and downstream activation of phospholipase C and protein kinase C. Notably, 12-HETE required Ca2+-dependent conventional PKCs, whereas 13-HODE selectively involved PKCε. Together, our findings identify ALOX15-derived oxylipins as endogenous regulators that attenuate macrophage inflammatory signaling via a Gαq-PLC-PKC pathway, providing mechanistic insight into lipid-mediated control of intestinal inflammation.
Hilman et al. (Wed,) studied this question.