Nonsteroidal antiâinflammatory drugs interfere with the metabolism of arachidonic acid to proinflammatory prostaglandins and leukotrienes by targeting cyclooxygenases (COXs), 5âlipoxygenase (LOX), or the 5âLOXâactivating protein (FLAP). These and related enzymes act in conjunction with marked crosstalk within a complex lipid mediator (LM) network where also specialized proresolving LMs (SPMs) are formed. Here, we present how prominent LM pathways can be differentially modulated in human proinflammatory M1 and proresolving M2 macrophage phenotypes that, upon exposure to Escherichia coli, produce either abundant prostaglandins and leukotrienes (M1) or SPMs (M2). Targeted liquid chromatographyâtandem mass spectrometryâbased metabololipidomics was applied to analyze and quantify the specific LM profiles. Besides expected onâtarget actions, we found that: 1) COX or 15âLOXâ1 inhibitors elevate inflammatory leukotriene levels, 2) FLAP and 5âLOX inhibitors reduce leukotrienes in M1 but less so in M2 macrophages, 3) zileuton blocks resolutionâinitiating SPM biosynthesis, whereas FLAP inhibition increases SPM levels, and 4) that the 15âLOXâ1 inhibitor 3887 suppresses SPM formation in M2 macrophages. Conclusively, interference with discrete LM biosynthetic enzymes in different macrophage phenotypes considerably affects the LM metabolomes with potential consequences for inflammationâresolution pharmacotherapy. Our data may allow better appraisal of the therapeutic potential of these drugs to intervene with inflammatory disorders.âWerner, M., Jordan, P. M., Romp, E., Czapka, A., Rao, Z., Kretzer, C., Koeberle, A., Garscha, U., Pace, S., Claesson, H.âE., Serhan, C. N., Werz, O., Gerstmeier, J. Targeting biosynthetic networks of the proinflammatory and proresolving lipid metabolome. FASEB J. 33, 6140â6153 (2019). http://www.fasebj.org