5-Lipoxygenase contributes to PPARγ activation in macrophages in response to apoptotic cells

• Published in: Cellular signalling 2013-12, Vol.25 (12), p.2762-2768
• Main Authors: von Knethen, Andreas, Sha, Lisa K., Kuchler, Laura, Heeg, Annika K., Fuhrmann, Dominik, Heide, Heinrich, Wittig, Ilka, Maier, Thorsten J., Steinhilber, Dieter, Brüne, Bernhard
• Format: Article
• Language: English
• Subjects: 5-Lipoxygenase; Activation; Alternative activation; Animals; Apoptosis; Arachidonate 5-Lipoxygenase - immunology; Arachidonate 5-Lipoxygenase - metabolism; Cell Line; Cellular; Efferocytosis; Gene expression; Humans; Inhibitors; Jurkat Cells; Lipids; Macrophages; Macrophages - immunology; Membrane Microdomains - immunology; Mice; PPAR gamma - immunology; Protein Transport; Rafts; Reactive Oxygen Species - immunology; Sepsis
• ISSN: 0898-6568; 1873-3913
• DOI: 10.1016/j.cellsig.2013.08.045

Macrophage polarization to an anti-inflammatory phenotype upon contact with apoptotic cells is a contributing hallmark to immune suppression during the late phase of sepsis. Although the peroxisome proliferator-activated receptor γ (PPARγ) supports this macrophage phenotype switch, it remains elusive how apoptotic cells activate PPARγ. Assuming that a molecule causing PPARγ activation in macrophages originates in the cell membrane of apoptotic cells we analyzed lipid rafts from apoptotic, necrotic, and living human Jurkat T cells which showed the presence of 5-lipoxygenase (5-LO) in lipid rafts of apoptotic cells only. Incubating macrophages with lipid rafts of apoptotic, but not necrotic or living cells, induced PPAR responsive element (PPRE)-driven mRuby reporter gene expression in RAW 264.7 macrophages stably transduced with a 4xPPRE containing vector. Experiments with lipid rafts of apoptotic murine EL4 T cells revealed similar results. To verify the involvement of 5-LO in activating PPARγ in macrophages, Jurkat T cells were incubated with the 5-LO inhibitor MK-866 prior to induction of apoptosis, which failed to induce mRuby expression. Similar results were obtained with lipid rafts of apoptotic EL4 T cells preexposed to the 5-LO inhibitors zileuton and CJ-13610. Interestingly, Jurkat T cells overexpressing 5-LO failed to activate PPARγ in macrophages, while their 5-LO overexpressing apoptotic counterparts did. Our results suggest that during apoptosis 5-LO gets associated with lipid rafts and synthesizes ligands that in turn stimulate PPARγ in macrophages. •In apoptotic cells 5-lipoxygenase associates to lipid rafts.•Lipid rafts of apoptotic cells activate PPARγ in macrophages.•5-Lipoxygenase overexpression in apoptotic cells is insufficient to activate PPARγ.•5-Lipoxygenase inhibitors block PPARγ activation in macrophages.•Reactive oxygen species contribute to 5-lipoxygenase translocation and activation.