title: Clearance of apoptotic cells by macrophages induces regulatory phenotype and involves stimulation of CD36 and platelet-activating factor receptor.
abstract: Phagocytosis of apoptotic cells (efferocytosis) induces macrophage differentiation towards a regulatory phenotype (IL-10(high)/IL-12p40(low)). CD36 is involved in the recognition of apoptotic cells (AC), and we have shown that the platelet-activating factor receptor (PAFR) is also involved. Here, we investigated the contribution of PAFR and CD36 to efferocytosis and to the establishment of a regulatory macrophage phenotype. Mice bone marrow-derived macrophages were cocultured with apoptotic thymocytes, and the phagocytic index was determined. Blockage of PAFR with antagonists or CD36 with specific antibodies inhibited the phagocytosis of AC (~70-80%). Using immunoprecipitation and confocal microscopy, we showed that efferocytosis increased the CD36 and PAFR colocalisation in the macrophage plasma membrane; PAFR and CD36 coimmunoprecipitated with flotillin-1, a constitutive lipid raft protein, and disruption of these membrane microdomains by methyl-β-cyclodextrin reduced AC phagocytosis. Efferocytosis induced a pattern of cytokine production, IL-10(high)/IL-12p40(low), that is, characteristic of a regulatory phenotype. LPS potentiated the efferocytosis-induced production of IL-10, and this was prevented by blocking PAFR or CD36. It can be concluded that phagocytosis of apoptotic cells engages CD36 and PAFR, possibly in lipid rafts, and this is required for optimal efferocytosis and the establishment of the macrophage regulatory phenotype.
authors.affiliation: Department of Immunology, Biomedical Sciences Institute, University of São Paulo, Avenue Professor Lineu Prestes 1730, ICB IV, Sala 140/146, 05508-000 São Paulo, SP, Brazil.
authors.forename: Matheus
authors.initials: M
authors.lastname: Ferracini
authors.affiliation: Department of Immunology, Biomedical Sciences Institute, University of São Paulo, Avenue Professor Lineu Prestes 1730, ICB IV, Sala 140/146, 05508-000 São Paulo, SP, Brazil ; Institute of Cardiovascular and Medical Sciences, British Heart Foundation Glasgow Cardiovascular Research Centre, University of Glasgow, Glasgow G12 8TA, UK.
authors.forename: Francisco J O
authors.initials: FJ
authors.lastname: Rios
authors.affiliation: Department of Immunology, Biomedical Sciences Institute, University of São Paulo, Avenue Professor Lineu Prestes 1730, ICB IV, Sala 140/146, 05508-000 São Paulo, SP, Brazil.
authors.forename: Mateus
authors.initials: M
authors.lastname: Pecenin
authors.affiliation: Department of Immunology, Biomedical Sciences Institute, University of São Paulo, Avenue Professor Lineu Prestes 1730, ICB IV, Sala 140/146, 05508-000 São Paulo, SP, Brazil.
authors.forename: Sonia
authors.initials: S
authors.lastname: Jancar
mesh_terms: D000818:Animals; D017209:Apoptosis; D018955:CD36 Antigens / Q000502:physiology*; D016753:Interleukin-10 / Q000502:physiology; D053762:Interleukin-12 Subunit p40 / Q000502:physiology; D008264:Macrophages / Q000276:immunology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010587:Phagocytosis; D010641:Phenotype; D010980:Platelet Membrane Glycoproteins / Q000502:physiology*; D043562:Receptors, G-Protein-Coupled / Q000502:physiology*
chemical_list: D018955:CD36 Antigens; D053762:Interleukin-12 Subunit p40; D010980:Platelet Membrane Glycoproteins; D043562:Receptors, G-Protein-Coupled; C039351:platelet activating factor receptor; D016753:Interleukin-10