Prevention of CaCl 2 -induced aortic inflammation and subsequent aneurysm formation by the CCL3–CCR5 axis

Inflammatory mediators such as cytokines and chemokines are crucially involved in the development of abdominal aortic aneurysm (AAA). Here we report that CaCl 2 application into abdominal aorta induces AAA with intra-aortic infiltration of macrophages as well as enhanced expression of chemokine (C-C motif) ligand 3 (CCL3) and MMP-9. Moreover, infiltrating macrophages express C-C chemokine receptor 5 (CCR5, a specific receptor for CCL3) and MMP-9. Both Ccl3 −/− mice and Ccr5 −/− but not Ccr1 −/− mice exhibit exaggerated CaCl 2 -inducced AAA with augmented macrophage infiltration and MMP-9 expression. Similar observations are also obtained on an angiotensin II-induced AAA model. Immunoneutralization of CCL3 mimics the phenotypes observed in CaCl 2 -treated Ccl3 −/− mice. On the contrary, CCL3 treatment attenuates CaCl 2 -induced AAA in both wild-type and Ccl3 −/− mice. Consistently, we find that the CCL3–CCR5 axis suppresses PMA-induced enhancement of MMP-9 expression in macrophages. Thus, CCL3 can be effective to prevent the development of CaCl 2 -induced AAA by suppressing MMP-9 expression.