Smoking Increases Proteolytic Activity in the Human Abdominal Aorta

Abstract

To determine the mechanism of smoking on the development of abdominal aortic aneurysms, the authors evaluated the proteolytic activity and quantity of matrix metalloproteinase enzymes in human aortic tissue. Abdominal aortic specimens of normal caliber were harvested from 13 organ donors, eight of whom had a history of smoking. Tissue samples were snap frozen in liquid nitrogen, pulverized, resuspended in a protein isolation buffer, and centrifuged to obtain the protein fraction. Gelatin substrate zymography was performed to determine proteolytic activity. Western immunoblotting using monoclonal antibodies directed against matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) was also performed. A significant increase in proteolytic activity was noted on zymography at 68 kilodaltons (kDa) in samples from smoking patients. Proteolytic activity at 96 kDa was not different between smokers and nonsmokers. No differences in the quantity of MMP-2 or MMP-9 were noted on immunoblots between the smoking and nonsmoking groups. These data establish a link between smoking and increased proteolytic activity in the human aortic wall and implicate smoking in the etiology of aortic aneurysms.