Dormant 5-lipoxygenase in inflammatory macrophages is triggered by exogenous arachidonic acid

Simona Zarini,Carlos A. Sorgi,Miguel A. Gijón,Nicolas Flamand,Robert C. Murphy,Sarah A. Martin,Rodrigo F. Scandiuzzi,Raphael L. Sanchez,Lucia H. Faccioli,Carlos Guijas

doi:10.1038/s41598-017-11496-3

Abstract

The differentiation of resident tissue macrophages from embryonic precursors and that of inflammatory macrophages from bone marrow cells leads to macrophage heterogeneity. Further plasticity is displayed through their ability to be polarized as subtypes M1 and M2 in a cell culture microenvironment. However, the detailed regulation of eicosanoid production and its involvement in macrophage biology remains unclear. Using a lipidomics approach, we demonstrated that eicosanoid production profiles between bone marrow-derived (BMDM) and peritoneal macrophages differed drastically. In polarized BMDMs, M1 and M2 phenotypes were distinguished by thromboxane B2, prostaglandin (PG) E2, and PGD2 production, in addition to lysophospholipid acyltransferase activity. Although Alox5 expression and the presence of 5-lipoxygenase (5-LO) protein in BMDMs was observed, the absence of leukotrienes production reflected an impairment in 5-LO activity, which could be triggered by addition of exogenous arachidonic acid (AA). The BMDM 5-LO regulatory mechanism was not responsive to PGE2/cAMP pathway modulation; however, treatment to reduce glutathione peroxidase activity increased 5-LO metabolite production after AA stimulation. Understanding the relationship between the eicosanoids pathway and macrophage biology may offer novel strategies for macrophage-associated disease therapy.

Highlights

Mononuclear phagocytes such as monocytes, macrophages, dendritic cells, and their bone marrow progenitors, play a major role in inflammation by eliminating pathogens and producing soluble mediators[1]
The membrane phospholipids comprise a major source of Arachidonic acid (AA) and DHA, and the release of both fatty acids was identified in macrophages
The bone marrow-derived macrophages (BMDMs) production of 5-LO metabolites was absent under these conditions. 5- hydroxyeicosatetraenoic acid (5-HETE) production was demonstrated in BMDMs, at the same level as in non-stimulated macrophages

Summary

Introduction

Mononuclear phagocytes such as monocytes, macrophages, dendritic cells, and their bone marrow progenitors, play a major role in inflammation by eliminating pathogens and producing soluble mediators[1]. The eicosanoid pattern has been demonstrated on macrophage subsets, detailed biochemistry pathway relating to eicosanoid production and function may play specific roles within the larger context of macrophage biology. Lipid mediators such as eicosanoids act as hormone-like factors in biological processes and display diverse functions in the immune system[9]. The data related to the 5-LO pathway in macrophage diversity were inconclusive, in particular with regard to comparison between Res-MAs and Infl-MAs. Compared with well-known features of macrophage metabolism such as glucose consumption and lactate release, fatty acids, vitamins, and iron metabolism, which are dependent on macrophage polarization and tissue specificity[20, 21], the detailed eicosanoid metabolic pathways engaged in macrophage phenotypes (M1 and M2) have remained poorly characterized. An enhanced understanding regarding the role of eicosanoids in the immune system may offer novel opportunities for macrophage-associated disease therapy

Methods

Results

Conclusion