Proinflammatory eicosanoids (prostaglandins and leukotrienes) and specialized pro-resolving mediators (SPM) are temporally regulated during infections. Here we show that human macrophage phenotypes biosynthesize unique lipid mediator signatures when exposed to pathogenic bacteria. E. coli and S. aureus each stimulate predominantly proinflammatory 5-lipoxygenase (LOX) and cyclooxygenase pathways (i.e., leukotriene B4 and prostaglandin E2) in M1 macrophages. These pathogens stimulate M2 macrophages to produce SPMs including resolvin D2 (RvD2), RvD5, and maresin-1. E. coli activates M2 macrophages to translocate 5-LOX and 15-LOX-1 to different subcellular locales in a Ca2+-dependent manner. Neither attenuated nor non-pathogenic E. coli mobilize Ca2+ or activate LOXs, rather these bacteria stimulate prostaglandin production. RvD5 is more potent than leukotriene B4 at enhancing macrophage phagocytosis. These results indicate that M1 and M2 macrophages respond to pathogenic bacteria differently, producing either leukotrienes or resolvins that further distinguish inflammatory or pro-resolving phenotypes.

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Resolution of acute inflammation is an active process governed by specialized pro-resolving mediators (SPM) including resolvin D2 (RvD2) that activates a cell surface G protein–coupled receptor (GPCR), GPR18/DRV2. Here, we investigated RvD2-DRV2-dependent resolution mechanisms using DRV2-deficient mice (DRV2-KO). In polymicrobial sepsis initiated by cecal ligation and puncture (CLP), RvD2 (~2.7 nmol/mouse) significantly increased survival (>50%) of wild-type (WT), reduced hypothermia and bacterial titers compared to vehicle-treated CLP mice that succumbed at 48h. Protection by RvD2 was abolished in DRV2-KO mice. Mass spectrometry-based lipid mediator metabololipidomics demonstrated that DRV2-KO infectious exudates gave higher pro-inflammatory leukotriene (LT) B4 and pro-coagulating thromboxane (TX) B2, as well as lower SPM, including RvD1 and RvD3, compared to WT. RvD2-DRV2-initiated intracellular signals were investigated using mass cytometry (CyTOF) which demonstrated that RvD2 enhanced phosphorylation of CREB, ERK1/2 and STAT3 that were absent in DRV2-KO macrophages. Monitored by real-time imaging, RvD2-DRV2 interaction significantly enhanced phagocytosis of live E. coli, an action dependent on PKA and STAT3 in macrophages. Taken together, we identified an RvD2-DRV2 axis that activates intracellular signaling pathways that increase phagocytosis-mediated bacterial clearance, survival and organ protection. Moreover, these results provide evidence for RvD2-DRV2 and their downstream pathways in pathophysiology of infectious inflammation.