Short-Term Regulation of Fc γ R-Mediated Phagocytosis by TLRs in Macrophages: Participation of 5-Lipoxygenase Products

Mediators Inflamm. 2017:2017:2086840. doi: 10.1155/2017/2086840. Epub 2017 Aug 15.

Abstract

TLRs recognize a broad spectrum of microorganism molecules, triggering a variety of cellular responses. Among them, phagocytosis is a critical process for host defense. Leukotrienes (LTs), lipid mediators produced from 5-lipoxygenase (5-LO) enzyme, increase FcγR-mediated phagocytosis. Here, we evaluated the participation of TLR2, TLR3, TLR4, and TLR9 in FcγR-mediated phagocytosis and whether this process is modulated by LTs. Rat alveolar macrophages (AMs), murine bone marrow-derived macrophages (BMDMs), and peritoneal macrophages (PMs) treated with TLR2, TLR3, and TLR4 agonists, but not TLR9, enhanced IgG-opsonized sheep red blood cell (IgG-sRBC) phagocytosis. Pretreatment of AMs or BMDMs with drugs that block LT synthesis impaired the phagocytosis promoted by TLR ligands, and TLR potentiation was also abrogated in PMs and BMDMs from 5-LO-/- mice. LTB4 production induced by IgG engagement was amplified by TLR ligands, while cys-LTs were amplified by activation of TLR2 and TLR4, but not by TLR3. We also noted higher ERK1/2 phosphorylation in IgG-RBC-challenged cells when preincubated with TLR agonists. Furthermore, ERK1/2 inhibition by PD98059 reduced the phagocytic activity evoked by TLR agonists. Together, these data indicate that TLR2, TLR3, and TLR4 ligands, but not TLR9, amplify IgG-mediated phagocytosis by a mechanism which requires LT production and ERK-1/2 pathway activation.

MeSH terms

  • Animals
  • Arachidonate 5-Lipoxygenase / genetics
  • Arachidonate 5-Lipoxygenase / metabolism*
  • Erythrocytes / drug effects*
  • Erythrocytes / metabolism*
  • Flavonoids / pharmacology
  • Immunoblotting
  • Leukotrienes / metabolism
  • Macrophages, Alveolar / metabolism
  • Male
  • Mice
  • Mice, Knockout
  • Phagocytosis / drug effects
  • Phagocytosis / genetics
  • Phagocytosis / physiology
  • Phosphorylation / drug effects
  • Phosphorylation / genetics
  • Rats
  • Rats, Wistar
  • Sheep
  • Toll-Like Receptor 2 / genetics
  • Toll-Like Receptor 2 / metabolism
  • Toll-Like Receptor 3 / genetics
  • Toll-Like Receptor 3 / metabolism
  • Toll-Like Receptor 4 / genetics
  • Toll-Like Receptor 4 / metabolism

Substances

  • Flavonoids
  • Leukotrienes
  • TLR3 protein, mouse
  • Tlr2 protein, mouse
  • Toll-Like Receptor 2
  • Toll-Like Receptor 3
  • Toll-Like Receptor 4
  • Arachidonate 5-Lipoxygenase
  • 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one