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Chemerin Peptides Promote Phagocytosis in a ChemR23- and Syk-Dependent Manner

Jenna L. Cash, Annabel R. Christian and David R. Greaves
11/30/2013
The Journal of Immunology

Chemerin peptides represent a recently identified component of the endogenous anti-inflammatory network that act via the G protein-coupled receptor ChemR23. The role of the chemerin peptide/ChemR23 pathway in phagocytosis, the clearance of apoptotic cells (efferocytosis), and the resolution of inflammation is unknown. In this article, we report that low picomolar concentrations of the chemerin peptide chemerin15 (C15) enhance macrophage (MF) phagocytosis of microbial particles and apoptotic cells by up to 360% in vitro. These prophagocytic effects of C15 are significantly impaired in ChemR232/2 MFs and are associated with increased actin polymerization and localization of F-actin to the phagocytic cup. Importantly, pharmacological inhibition of Syk activity completely abrogates the prophagocytic activities of C15 and associated changes in actin polymerization and phagocytic cup formation, suggesting that C15 promotes phagocytosis by facilitating phagocytic cup development in a Sykdependent manner. During peritoneal inflammation, C15 administration (8 pg/mouse) enhances microbial particle clearance and apoptotic neutrophil ingestion by MFs in wild-type but not ChemR232/2 mice, such that levels of apoptotic and necrotic cells at the inflammatory site are profoundly reduced. In contrast, neutralization of endogenous chemerin species during peritoneal inflammation significantly impairs MF ingestion of apoptotic neutrophils and zymosan. Our data identify a key role of the chemerin peptide/ChemR23 axis in the efficient clearance of foreign material, efferocytosis, and, hence, the resolution of inflammation. Manipulation of the chemerin peptide/ChemR23 axis may represent a novel therapeutic approach for the treatment of inflammatory pathologies, especially if failure to efficiently clear phagocytic targets has been implicated in their pathogenesis.