Other experimental studies have found that both tobacco smoke and benzopyrene, a compound found in cigarette smoke, increased aortic muscular cell apoptosis and aortic macrophage infiltration and expression of matrix metalloproteinases-2, 9 and 12 and nuclear factor-κB and increased formation of abdominal aortic aneurysms in angiotensin-2 induced hypertension55,56. Here, MMP2 is linked to abdominal aortic aneurysm.