Abstract
Alternative (M2)-polarized macrophages possess high capacities to produce specialized proresolving mediators (SPM; i.e., resolvins, protectins, and maresins) that play key roles in resolution of inflammation and tissue regeneration. Vacuolar (H+)-ATPase (V-ATPase) is fundamental in inflammatory cytokine trafficking and secretion and was implicated in macrophage polarization toward the M2 phenotype, but its role in SPM production and lipid mediator biosynthesis in general is elusive. In this study, we show that V-ATPase activity is required for the induction of SPM-biosynthetic pathways in human M2-like monocyte-derived macrophages (MDM) and consequently for resolution of inflammation. Blockade of V-ATPase by archazolid during IL-4-induced human M2 polarization abrogated 15-lipoxygenase-1 expression and prevented the related biosynthesis of SPM in response to pathogenic Escherichia coli, assessed by targeted liquid chromatography-tandem mass spectrometry-based metabololipidomics. In classically activated proinflammatory M1-like MDM, however, the biosynthetic machinery for lipid mediator formation was independent of V-ATPase activity. Targeting V-ATPase in M2 influenced neither IL-4-triggered JAK/STAT6 nor the mTOR complex 1 signaling but strongly suppressed the ERK-1/2 pathway. Accordingly, the ERK-1/2 pathway contributes to 15-lipoxygenase-1 expression and SPM formation in M2-like MDM. Targeting V-ATPase in vivo delayed resolution of zymosan-induced murine peritonitis accompanied by decreased SPM levels without affecting proinflammatory leukotrienes or PGs. Together, our data propose that V-ATPase regulates 15-lipoxygenase-1 expression and consequent SPM biosynthesis involving ERK-1/2 during M2 polarization, implying a crucial role for V-ATPase in the resolution of inflammation.