Indeed, MMP-9/TIMP-1 imbalance has been observed in sputum of patients with cystic fibrosis [17] and in abdominal aortic aneurysm [19]; where the high level of HNE promotes a large MMP-9 activation either directly or by the proteolysis of TIMP-1, its natural inhibitor. Here, TIMP1 is linked to abdominal aortic aneurysm.