Perplexity of Plaque Proteinases

Abstract

Cells found in atherosclerotic plaques express matrix metalloproteinases (MMPs). Human atheromata contain a broad array of proteases (Table 1) and their endogenous inhibitors. Altered balance between proteinases and their inhibitors may participate in a number of biological processes important in the clinical manifestations of atherosclerosis.1 For example, matrix remodeling must occur during compensatory enlargement, arterial aneurysm formation, angiogenesis, desquamation of endothelial cells that accompanies superficial erosion, and the weakening of the atherosclerotic plaque’s fibrous cap that presumably renders it prone to rupture and hence thrombosis. View this table: TABLE 1. Examples of the Plethora of Proteinases in Atherosclerotic Plaques See page 2351 In this issue of Arteriosclerosis, Thrombosis, and Vascular Biology , Choudhary et al confirm the presence of MMP gelatinases and highlight the heterogeneity of MMP distribution in human carotid endarterectomy specimens.2 They show differential expression of 2 prototypical MMP gelatinases, MMP-2 and -9. Many normal carotid segments contain more MMP-2 than MMP-9. More complex lesions tended to have more MMP-9 than MMP-2. As normal arteries contain substantial medial pro–MMP-2 (the inactive zymogen form; Figure), this finding is expected.3,4 Likewise, MMP-9 overexpression …