Abstract 172: Product of Lipid Oxidation During Inflammation is a New Potent Ligand for β2 Integrin-mediated Macrophage Migration

Abstract

2-(ω-carboxyethyl)pyrrole (CEP) and ethylpyrrole (EP) derivatives of proteins are formed through adduction of end products of docosahexaenoate (DHA) oxidation[[Unable to Display Character: ]] with the ε-amino groups of protein lysyl residues, followed by cyclization and dehydration. Our previous studies demonstrated that EP-modified proteins are present in healthy tissue, while CEP-modified proteins are detected in the tissue during inflammation including inflamed peritoneal wall and atherosclerotic lesions. Potential role of CEP in inflammatory response was evaluated by testing leukocyte recruitment during thioglycollate-induced peritoneal inflammation. We found that injection of anti-CEP antibody dramatically reduced the accumulation of macrophages in the peritoneal cavity at 72 hours, while the earlier accumulation of neutrophils was not affected. Migration of neutrophils was a prerequisite for CEP production in the peritoneum. In vitro adhesion assay revealed strong binding of peritoneal macrophages to CEP, while adhesion to EP was not detected. Moreover, CEP presence in 3D fibrin gel significantly increased migration of macrophages toward MCP-1 gradient. We have previously demonstrated that CEP is ligand for CD36 and TLR2. However, the adhesion of TLR2/CD36-double deficient macrophages to CEP was similar to wild type cells; suggesting that other receptors are involved in CEP-mediated macrophage adhesion/migration. Since αDβ2 and αMβ2 integrins are major macrophage adhesion receptors we tested their ability to bind CEP. Isolated αM and αD I-domains, which are critical for integrin ligand recognition, showed a concentration-dependent binding to immobilized CEP, but not to EP in the biacore assay. Moreover, αDβ2 and αMβ2-transfected but not control HEK293 cells strongly adhered to CEP. This adhesion was significantly inhibited by anti-CEP, anti-β2 and anti-αM (or αD) antibodies, but not by anti-β1 antibody. In summary, we found that CEP-modified proteins drive the migration of macrophages during inflammation by engaging macrophage integrins αMβ2 and αDβ2. Hence, regulation of CEP-mediated adhesion/migration can control the accumulation of macrophages within the site of inflammation and may regulate the development of chronic inflammatory deseases.