1. Polarization of Macrophages toward M2 Phenotype Is Favored by Reduction in iPLA2β (Group VIA Phospholipase A2).
- Author
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Ashley JW, Hancock WD, Nelson AJ, Bone RN, Tse HM, Wohltmann M, Turk J, and Ramanadham S
- Subjects
- Animals, Cyclooxygenase 2 genetics, Cyclooxygenase 2 immunology, Female, Group VI Phospholipases A2 genetics, Humans, Inflammation genetics, Inflammation immunology, Macrophages enzymology, Macrophages immunology, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, NADPH Oxidase 4, NADPH Oxidases genetics, NADPH Oxidases immunology, Cell Polarity, Group VI Phospholipases A2 immunology, Inflammation enzymology, Macrophages cytology
- Abstract
Macrophages are important in innate and adaptive immunity. Macrophage participation in inflammation or tissue repair is directed by various extracellular signals and mediated by multiple intracellular pathways. Activation of group VIA phospholipase A
2 (iPLA2 β) causes accumulation of arachidonic acid, lysophospholipids, and eicosanoids that can promote inflammation and pathologic states. We examined the role of iPLA2 β in peritoneal macrophage immune function by comparing wild type (WT) and iPLA2 β-/- mouse macrophages. Compared with WT, iPLA2 β-/- macrophages exhibited reduced proinflammatory M1 markers when classically activated. In contrast, anti-inflammatory M2 markers were elevated under naïve conditions and induced to higher levels by alternative activation in iPLA2 β-/- macrophages compared with WT. Induction of eicosanoid (12-lipoxygenase (12-LO) and cyclooxygenase 2 (COX2))- and reactive oxygen species (NADPH oxidase 4 (NOX4))-generating enzymes by classical activation pathways was also blunted in iPLA2 β-/- macrophages compared with WT. The effects of inhibitors of iPLA2 β, COX2, or 12-LO to reduce M1 polarization were greater than those to enhance M2 polarization. Certain lipids (lysophosphatidylcholine, lysophosphatidic acid, and prostaglandin E2 ) recapitulated M1 phenotype in iPLA2 β-/- macrophages, but none tested promoted M2 phenotype. These findings suggest that (a) lipids generated by iPLA2 β and subsequently oxidized by cyclooxygenase and 12-LO favor macrophage inflammatory M1 polarization, and (b) the absence of iPLA2 β promotes macrophage M2 polarization. Reducing macrophage iPLA2 β activity and thereby attenuating macrophage M1 polarization might cause a shift from an inflammatory to a recovery/repair milieu., (© 2016 by The American Society for Biochemistry and Molecular Biology, Inc.)- Published
- 2016
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