Inflammation, but not recruitment, of adipose tissue macrophages requires signalling through Mac-1 (CD11b/CD18) in diet-induced obesity (DIO).

International audienceCell accumulation is a prerequisite for adipose tissue inflammation. The leukocyte integrin Mac-1 (CD11b/CD18, αMβ2) is a classic adhesion receptor critically regulating inflammatory cell recruitment. Here, we tested the hypothesis that a genetic deficiency and a therapeutic modulation of Mac-1 regulate adipose tissue inflammation in a mouse model of diet-induced obesity (DIO). C57Bl6/J mice genetically deficient (Mac-1(-/-)) or competent for Mac-1 (WT) consumed a high fat diet for 20 weeks. Surprisingly, Mac-1(-/-) mice presented with increased diet-induced weight gain, decreased insulin sensitivity in skeletal muscle and in the liver in insulin-clamps, insulin secretion deficiency and elevated glucose levels in fasting animals, and dyslipidaemia. Unexpectedly, accumulation of adipose tissue macrophages (ATMs) was unaffected, while gene expression indicated less inflamed adipose tissue and macrophages in Mac-1(-/-) mice. In contrast, inflammatory gene expression at distant locations, such as in skeletal muscle, was not changed. Treatment of ATMs with an agonistic anti-Mac-1 antibody, M1/70, induced pro-inflammatory genes in cell culture. In vivo, treatment with M1/70 induced a hyper-inflammatory phenotype with increased expression of IL-6 and MCP-1, whereas accumulation of ATMs did not change. Finally, inhibition of Mac-1's adhesive interaction to CD40L by the peptide inhibitor cM7 did not affect myeloid cell accumulation in adipose tissue. We present the surprising finding that adhesive properties of the leukocyte integrin Mac-1 are not required for macrophage accumulation in adipose tissue. Instead, Mac-1 modulates inflammatory gene expression in macrophages. These findings question the net effect of integrin blockade in cardio-metabolic disease

Binding of CD40L to Mac-1's i-domain involves the EQLKKSKTL motif and mediates leukocyte recruitment and atherosclerosis-but does not affect immunity and thrombosis in mice

Rationale: CD40L figures prominently in chronic inflammatory diseases such as atherosclerosis. However, since CD40L potently regulates immune function and hemostasis by interaction with CD40 receptor and the platelet integrin GPIIb/IIIa, its global inhibition compromises host defense and generated thromboembolic complications in clinical trials. We recently reported that CD40L mediates atherogenesis independently of CD40 and proposed Mac-1 as an alternate receptor. Objective: Here, we molecularly characterized the CD40L-Mac-1 interaction and tested whether its selective inhibition by a small peptide modulates inflammation and atherogenesis in vivo. Methods and Results: CD40L concentration-dependently bound to Mac-1 I-domain in solid phase binding assays, and a high-affinity interaction was revealed by surface-plasmon-resonance analysis. We identified the motif EQLKKSKTL, an exposed loop between the α1 helix and the β-sheet B, on Mac-1 as binding site for CD40L. A linear peptide mimicking this sequence, M7, specifically inhibited the interaction of CD40L and Mac-1. A cyclisized version optimized for in vivo use, cM7, decreased peritoneal inflammation and inflammatory cell recruitment in vivo. Finally, LDLr -/- mice treated with intraperitoneal injections of cM7 developed smaller, less inflamed atherosclerotic lesions featuring characteristics of stability. However, cM7 did not interfere with CD40L-CD40 binding in vitro and CD40L-GPIIb/IIIa-mediated thrombus formation in vivo. Conclusions: We present the novel finding that CD40L binds to the EQLKKSKTL motif on Mac-1 mediating leukocyte recruitment and atherogenesis. Specific inhibition of CD40L-Mac-1 binding may represent an attractive anti-inflammatory treatment strategy for atherosclerosis and other inflammatory conditions, potentially avoiding the unwanted immunologic and thrombotic effects of global inhibition of CD40L.Fil: Wolf, Dennis. Albert-Ludwigs-Universität Freiburg; Alemania. Baker IDI Heart and Diabetes Institute; AustraliaFil: Hohmann, Jan David. Baker IDI Heart and Diabetes Institute; AustraliaFil: Wiedemann, Ansgar. Albert-Ludwigs-Universität Freiburg; AlemaniaFil: Bledzka, Kamila. Cleveland Clinic. Department of Molecular Cardiology; Estados UnidosFil: Blankenbach, Hermann. Albert-Ludwigs-Universität Freiburg; AlemaniaFil: Marchini, Timoteo Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; Argentina. Albert-Ludwigs-Universität Freiburg; AlemaniaFil: Gutte, Katharina. Albert-Ludwigs-Universität Freiburg; AlemaniaFil: Zeschky, Katharina. Albert-Ludwigs-Universität Freiburg; AlemaniaFil: Bassler, Nicole. Baker IDI Heart and Diabetes Institute; AustraliaFil: Hoppe, Natalie. Albert-Ludwigs-Universität Freiburg; AlemaniaFil: Rodriguez, Alexandra Ortiz. Albert-Ludwigs-Universität Freiburg; AlemaniaFil: Herr, Nadine. Albert-Ludwigs-Universität Freiburg; AlemaniaFil: Hilgendorf, Ingo. Albert-Ludwigs-Universität Freiburg; AlemaniaFil: Stachon, Peter. Albert-Ludwigs-Universität Freiburg; AlemaniaFil: Willecke, Florian. Albert-Ludwigs-Universität Freiburg; AlemaniaFil: Duerschmied, Daniel. Albert-Ludwigs-Universität Freiburg; AlemaniaFil: von zur Muhlen, Constantin. Albert-Ludwigs-Universität Freiburg; AlemaniaFil: Soloviev, Dmitry A.. Cleveland Clinic. Department of Molecular Cardiology; Estados UnidosFil: Zhang, Li. University of Maryland; Estados UnidosFil: Bode, Christoph. Albert-Ludwigs-Universität Freiburg; AlemaniaFil: Plow, Edward F.. Cleveland Clinic. Department of Molecular Cardiology; Estados UnidosFil: Libby, Peter. Harvard Medical School; Estados UnidosFil: Peter, Karlheinz. Baker IDI Heart and Diabetes Institute; AustraliaFil: Zirlik, Andreas. Albert-Ludwigs-Universität Freiburg; Alemani

A ligand-specific blockade of the integrin Mac-1 selectively targets pathologic inflammation while maintaining protective host-defense

Integrin-based therapeutics could block inflammatory processes but they also impair host defence, limiting their usefulness. Here the authors report an anti-Mac1 antibody that blocks its interaction with pro-inflammatory ligand CD40L but not other ligands, and show that it can protect against sepsis in mice