(a) Proteinase inhibitors predominate in the quiescent vessel, while net proteolysis degrades the media and causes aneurysmal rupture during atherosclerosis. EC, endothelial cell; SMC, smooth muscle cell; Mφ, macrophage; EL, elastic lamina. (b) Inflammatory cells produce plasminogen (Plg) activators that activate plasmin, which degrades fibrin, laminin, and fibronectin. By activating zymogen pro-MMPs, plasmin orchestrates degradation of collagen and elastin, leading to complete destruction of all vessel wall matrix components.