AUTHOR=Cui Kui , Ardell Christopher L. , Podolnikova Nataly P. , Yakubenko Valentin P. 

TITLE=Distinct Migratory Properties of M1, M2, and Resident Macrophages Are Regulated by αDβ2 and αMβ2 Integrin-Mediated Adhesion

JOURNAL=Frontiers in Immunology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2018.02650

DOI=10.3389/fimmu.2018.02650

ISSN=1664-3224

ABSTRACT=<p>Chronic inflammation is essential mechanism during the development of cardiovascular and metabolic diseases. The outcome of diseases depends on the balance between the migration/accumulation of pro-inflammatory (M1) and anti-inflammatory (M2) macrophages in damaged tissue. The mechanism of macrophage migration and subsequent accumulation is still not fully understood. Currently, the amoeboid adhesion-independent motility is considered essential for leukocyte migration in the three-dimensional environment. We challenge this hypothesis by studying the contribution of leukocyte adhesive receptors, integrins α<sub>M</sub>β<sub>2</sub>, and α<sub>D</sub>β<sub>2</sub>, to three-dimensional migration of M1-polarized, M2-polarized, and resident macrophages. Both integrins have a moderate expression on M2 macrophages, while α<sub>D</sub>β<sub>2</sub> is upregulated on M1 and α<sub>M</sub>β<sub>2</sub> demonstrates high expression on resident macrophages. The level of integrin expression determines its contribution to macrophage migration. Namely, intermediate expression supports macrophage migration, while a high integrin density inhibits it. Using <italic>in vitro</italic> three-dimensional migration and <italic>in vivo</italic> tracking of adoptively-transferred fluorescently-labeled macrophages during the resolution of inflammation, we found that strong adhesion of M1-activated macrophages translates to weak 3D migration, while moderate adhesion of M2-activated macrophages generates dynamic motility. Reduced migration of M1 macrophages depends on the high expression of α<sub>D</sub>β<sub>2</sub>, since α<sub>D</sub>-deficiency decreased M1 macrophage adhesion and improved migration in fibrin matrix and peritoneal tissue. Similarly, the high expression of α<sub>M</sub>β<sub>2</sub> on resident macrophages prevents their amoeboid migration, which is markedly increased in α<sub>M</sub>-deficient macrophages. In contrast, α<sub>D</sub>- and α<sub>M</sub>-knockouts decrease the migration of M2 macrophages, demonstrating that moderate integrin expression supports cell motility. The results were confirmed in a diet-induced diabetes model. α<sub>D</sub> deficiency prevents the retention of inflammatory macrophages in adipose tissue and improves metabolic parameters, while α<sub>M</sub> deficiency does not affect macrophage accumulation. Summarizing, β<sub>2</sub> integrin-mediated adhesion may inhibit amoeboid and mesenchymal macrophage migration or support mesenchymal migration in tissue, and, therefore, represents an important target to control inflammation.</p>