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

Circ Res. 2011 Nov 11;109(11):1269-79. doi: 10.1161/CIRCRESAHA.111.247684. Epub 2011 Oct 13.


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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Animals
  • Atherosclerosis / genetics
  • Atherosclerosis / metabolism*
  • Atherosclerosis / prevention & control
  • Bleeding Time
  • Blood Coagulation / drug effects
  • Blood Coagulation / physiology
  • CD40 Ligand / metabolism*
  • CHO Cells
  • Cells, Cultured
  • Chemotaxis, Leukocyte / physiology*
  • Cricetinae
  • Humans
  • Macrophage-1 Antigen / metabolism*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Models, Molecular
  • Peptide Fragments / pharmacology
  • Peptide Fragments / therapeutic use
  • Peptides, Cyclic / pharmacology
  • Peritonitis / blood
  • Peritonitis / prevention & control
  • Protein Conformation
  • Protein Interaction Mapping
  • Protein Structure, Tertiary
  • Receptors, LDL / deficiency
  • Recombinant Fusion Proteins / physiology
  • Surface Plasmon Resonance
  • Thrombosis / etiology*


  • Macrophage-1 Antigen
  • Peptide Fragments
  • Peptides, Cyclic
  • Receptors, LDL
  • Recombinant Fusion Proteins
  • CD40 Ligand