Inflammation in atheroma: implications for plaque rupture and platelet-collagen interaction

Atherosclerosis is an inflammatory reaction to accumulated extracellular lipid in the arterial intima. Evidence from pathological studies indicate that there is constant deposition and lysis of fibrin within the atherosclerotic arterial wall. In patients with stable peripheral atherosclerosis, the functional severity of the disease is associated with circulating fibrinogen and degradation of cross-linked fibrin reflecting procoagulant activity in the blood-vessel wall interface, or in the wall itself. In atheromas the fibrinolytic activity is connected to macrophages, which can assemble in the plasminogen-plasmin system and generate plasmin-mediated pericellular proteolysis in tissues with inflammation. Plasmin capable of activating collagenase may therefore be a candidate for plaque rupture. The nature of the exposed vascular tissue, the inflammatory state, tissue-factor dependent thrombin generation and the degree of matrix degradation regulate platelet reactivity. Little is yet known about platelet adhesive functions in proteolyzed collagens that are the underlying substrate where platelets deposit during plaque rupture, the triggering event for thrombosis. Research in these areas is likely to improve the understanding of the thrombogenicity of atheromas when the tissue is suddenly exposed to blood.