Lack of neutrophil-derived CRAMP reduces atherosclerosis in mice.

RATIONALE: Neutrophils have been reported to contribute to early atherosclerotic lesion formation. Mechanisms of neutrophil-driven atherosclerosis remain unclear so far. OBJECTIVE: Investigation of the role of the neutrophil granule protein cathelicidin (CRAMP in mouse, LL37 in human) in atherosclerosis. METHODS AND RESULTS: Compared to Apoe(-/-) mice, Cramp(-/-) Apoe(-/-) mice exhibit reduced lesion sizes with lower macrophage numbers. In atherosclerotic aortas, we could detect CRAMP specifically in neutrophils, but not in monocytes or macrophages. By use of intravital microscopy, CRAMP was found to be deposited by activated neutrophils on inflamed endothelium of large arteries. In this location cathelicidins promote adhesion of classical monocytes and neutrophils, but not nonclassical monocytes in a formyl-peptide receptor-dependent manner. CONCLUSIONS: Cathelicidins promote atherosclerosis by enhancement of the recruitment of inflammatory monocytes.