Lack of Neutrophil-Derived CRAMP Reduces Atherosclerosis in Mice

Abstract

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. Key Words: atherosclerosis Ⅲ monocyte recruitment Ⅲ neutrophil A therosclerosis is a chronic inflammation of the arterial vessel wall with relatively well-defined roles for leukocytes such as macrophages and lymphocytes. 1,2 Recent studies, however, have revealed that neutrophils infiltrate atherosclerotic lesions at various time points, 3-5 and depletion studies provide evidence for a proatherogenic role of neutrophils. 5,6 Nevertheless, mechanistic insights into how neutrophils promote early atherosclerotic lesion formation remain elusive. Neutrophils contain granules with more than 300 different proteins that undergo limited exocytosis on neutrophil extravasation. 7 Some of these proteins are able to activate and recruit immune cells and thus have been coined alarmins. 8 Cathelicidins (CRAMP in mouse, LL37 in humans) residing in neutrophil secondary granules were shown to potently activate and recruit monocytes and macrophages, 9,10 thus fulfilling alarmin criteria. Because cathelicidins were identified in atherosclerotic lesions, 11 we investigated their role in a mouse model of atherosclerosis. Conclusions: Editorial, see p 1036 In This Issue, see p 1035 MethodsDetailed Methods are provided in the Online Supplement. Plaque StudiesCramp Ϫ/Ϫ mice 12 were crossed with Apoe Ϫ/Ϫ mice. Atherosclerotic lesion size as well as lesional neutrophil and macrophage content were assessed by histology and immunohistochemistry. Intravital MicroscopyLeukocyte adhesion to the carotid artery was studied by intravital fluorescence microscopy as described previously. 5 ResultsTo investigate the role of CRAMP in early atherosclerotic lesion formation, we fed Apoe Ϫ/Ϫ and CrampOriginal received January 29, 2012; revision received February 15, 2012; accepted February 27, 2012. In January 2012, the average time from submission to first decision for all original research papers submitted to Circulation Research was 13.88 days.Brief UltraRapid Communications are designed to be a format for manuscripts that are of outstanding interest to the readership, report definitive observations, but have a relatively narrow scope.

Peptidylarginine deiminase inhibition is immunomodulatory and vasculoprotective in murine lupus

“…Indeed, both DNase and Cl-amidine similarly prolonged time to carotid artery thrombosis induced by endothelial injury while significantly reducing the density of NETs in these thrombi. In this model, neutrophils undergoing NET formation were especially captured in the vicinity of the endothelium, which is interesting given the observation that endothelial activation can promote NET formation (76) as well as the recent evidence that NETs invade the endothelium and promote vascular damage in atherosclerosis (53,80). We propose that the NET-dependent prothrombotic phenotype observed here has implications not only for the characteristic hypercoagulability of lupus patients (51), but also for patients with other inflammatory diseases characterized by enhanced NET formation, such ANCAassociated small vessel vasculitis, in which thrombosis is a wellrecognized complication of active disease (54,81).…”

“…for neutrophils undergoing NET formation in vascular tissue (47,50,53,54), and indeed, cells and cell remnants staining positive for either marker were less likely to be captured in the thrombi of DNase-treated mice ( Figure 7B). Further, not only did DNase treatment change the content of the thrombi, but time to vessel occlusion was also significantly delayed by DNase (quantified in Figure 7C, with representative flow tracings in Figure 7D).…”

Annexin A1 Counteracts Chemokine-Induced Arterial Myeloid Cell Recruitment

“…These data are in striking contrast to the previously reported lesion phenotype of mice lacking the neutrophil-borne FPR2 ligand CRAMP (Cathelicidin-related Antimicrobial Peptide). 7 Thus, we hypothesized that resolution-inducing FPR2 ligands may hold an important role during early atherosclerosis and consequently studied the development of atherosclerosis in mice lacking the proresolving FPR2 ligand AnxA1. Apoe …”

Changing world of neutrophils

“…Moreover, the neutrophil granule protein cathelicidin LL37 was reported to promote adhesion of monocytes to the vessel wall [31].…”