title: Monocyte chemoattractant protein-1/CC chemokine ligand 2 enhances apoptotic cell removal by macrophages through Rac1 activation.
abstract: Apoptotic cell removal (efferocytosis) is an essential process in the regulation of inflammation and tissue repair. We have shown that monocyte chemoattractant protein-1/CC chemokine ligand 2 (MCP-1/CCL2) enhances efferocytosis by alveolar macrophages in murine bacterial pneumonia. However, the mechanism by which MCP-1 exerts this effect remains to be determined. Here we explored that hypothesis that MCP-1 enhances efferocytosis through a Rac1/phosphatidylinositol 3-kinase (PI3-kinase)-dependent mechanism. We assessed phagocytosis of apoptotic cells by MCP-1 treated murine macrophages in vitro and in vivo. Rac activity in macrophages was measured using a Rac pull down assay and an ELISA based assay (GLISA). The downstream Rac1 activation pathway was studied using a specific Rac1 inhibitor and PI3-kinase inhibitor in in vitro assays. MCP-1 enhanced efferocytosis of apoptotic cells by murine alveolar macrophages (AMs), peritoneal macrophages (PMs), the J774 macrophage cell line (J774s) in vitro, and murine AMs in vivo. Rac1 activation was demonstrated in these cell lines. The effect of MCP-1 on efferocytosis was completely negated by the Rac1 inhibitor and PI3-kinase inhibitor. We demonstrated that MCP-1 enhances efferocytosis in a Rac1-PI3 kinase-dependent manner. Therefore, MCP-1-Rac1-PI3K interaction plays a critical role in resolution of acute lung inflammation.
authors.affiliation: Department of Clinical Medicine, Institute of Tropical Medicine, Nagasaki University, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Tanaka
authors.forename: Mayumi
authors.initials: M
authors.lastname: Terada
authors.forename: Koya
authors.initials: K
authors.lastname: Ariyoshi
authors.forename: Konosuke
authors.initials: K
authors.lastname: Morimoto
mesh_terms: D000818:Animals; D017209:Apoptosis; D018932:Chemokine CCL2 / Q000378:metabolism* / Q000494:pharmacology; D004789:Enzyme Activation; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000201:enzymology / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008813:Mice, Inbred ICR; D009479:Neuropeptides / Q000096:biosynthesis*; D010587:Phagocytosis; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011014:Pneumonia / Q000276:immunology*; D054390:Receptors, CCR2 / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D015854:Up-Regulation; D020744:rac GTP-Binding Proteins / Q000096:biosynthesis*; D020830:rac1 GTP-Binding Protein
chemical_list: C491768:Ccl2 protein, mouse; C515335:Ccr2 protein, mouse; D018932:Chemokine CCL2; D009479:Neuropeptides; C484602:Rac1 protein, mouse; D054390:Receptors, CCR2; D011994:Recombinant Proteins; D019869:Phosphatidylinositol 3-Kinases; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein