Background-Matrix metalloproteinase-9 (MMP-9) is involved in atherosclerosis and elevated MMP-9 activity has been found in unstable plaques, suggesting a crucial role in plaque rupture. This study aims to assess the effect of MMP-9 on plaque stability in apolipoprotein E-deficient mice at different stages of plaque progression. Methods and Results-Atherosclerotic lesions were elicited in carotid arteries by perivascular collar placement. MMP-9 overexpression in intermediate or advanced plaques was effected by intraluminal incubation with an adenovirus (Ad.MMP-9). A subset was coincubated with Ad.TIMP-1. Mock virus served as a control. Plaques were analyzed histologically. In intermediate lesions, MMP-9 overexpression induced outward remodeling, as shown by a 30% increase in media size (pϭ0.03). In both intermediate and advanced lesions, prevalence of vulnerable plaque morphology tended to be increased. Half of MMP-9 -treated lesions displayed intraplaque hemorrhage, whereas in controls and the Ad.MMP-9/Ad.TIMP-1 group this was 8% and 16%, respectively (pϭ0.007). Colocalization with neovessels may point to neo-angiogenesis as a source for intraplaque hemorrhage. Conclusion-These data show a differential effect of MMP-9 at various stages of plaque progression and suggest that lesion-targeted MMP-9 inhibition might be a valuable therapeutic modality in stabilizing advanced plaques, but not at earlier stages of lesion progression. Key Words: adenovirus Ⅲ atherosclerosis Ⅲ metalloproteinases Ⅲ remodeling Ⅲ vulnerable plaque M atrix metalloproteinase (MMP) family members are enzymes with activity against extracellular matrix (ECM) constituents and are linked to atherosclerosis and plaque rupture. Because plaque disruption is a frequent cause of acute coronary syndromes 1,2,3 and MMPs are believed to degrade the ECM in the fibrous cap, 4,5 these enzymes might prove to be relevant targets for therapeutic intervention.However, the evidence that links these proteases to plaque destabilization is largely based on retrospective observations. Elevated MMP levels, among which is MMP-9, were found in unstable areas in carotid endarterectomy specimens. 6,7 Several promoter polymorphisms are correlated to coronary artery disease and to lesion complexity. 8,9 Also, elevated MMP-9 plasma levels can be detected in patients with acute coronary syndromes. 10,11 Taken together, this suggests that MMP-9 is causally involved in plaque destabilization, although the underlying mechanism remains unclear. One report showed that MMP-9 overexpression leads to thrombosis by stimulating release of matrix-bound tissue factor in balloon-injured coronaries. 12 Conversely, targeted gene disruption of MMP-9 in mice impaired smooth muscle cell (SMC) migration and led to collagen accumulation. 13 In vitro, MMP-9 deficiency impaired the contracting capacity of collagen, indicating that MMP-9 not only is important for SMC migration and matrix degradation but also plays a role in ECM organization. 13 Notwithstanding these observations, direct evidence fo...

Objective-Although IL-18 has been implicated in atherosclerotic lesion development, little is known about its role in advanced atherosclerotic plaques. This study aims to assess the effect of IL-18 overexpression on the stability of preexisting plaques. Methods and Results-Atherosclerotic lesions were elicited in carotid arteries of apolipoprotein E (apoE)-deficient mice (nϭ32) by placement of a perivascular collar. Overexpression of IL-18 was effected by intravenous injection of an adenoviral vector 5 weeks after surgery. Two weeks after transduction, lesions were analyzed histologically with regard to plaque morphology and composition or by real-time polymerase chain reaction. No difference in plaque size was detected between groups. In the Ad.IL-18 -treated group, 62% of lesions displayed a vulnerable morphology or even intraplaque hemorrhage as compared with only 24% in the controls (Pϭ0.037). In agreement, IL-18 overexpression reduced intimal collagen by 44% (PϽ0.003) and cap-to-core ratio by 41% (PϽ0.002). Although IL-18 did not affect the expression of collagen synthesis-related genes, it was found to enhance the collagenolytic activity of vascular smooth muscle cells in vitro, suggesting that the low collagen content is attributable to matrix degradation rather than to decreased synthesis. Key Words: atherosclerosis Ⅲ vulnerable plaque Ⅲ adenovirus Ⅲ IL-18 Ⅲ collagen N umerous reports have indicated that inflammatory processes play a pivotal role throughout plaque development, as well as in plaque rupture and thrombosis. 1,2 One of the proinflammatory mediators that has received considerable attention in this regard is IL-18. It is an IL-1 family member 3 and induces interferon (IFN)-␥, a known proatherogenic mediator, 4,5 in macrophages and in smooth muscle cells, but not in endothelial cells. 6 Binding to the IL-18 receptor results in enhanced secretion of many cytokines and proteins causally involved in atherosclerosis, among which are IL-6, IL-8, intercellular adhesion molecule-1, and various matrix metalloproteinases (MMPs). 6 IL-18 and its receptor are expressed in human atheroma-associated endothelial cells, vascular smooth muscle cells (VSMCs), and macrophages, and their expression is enhanced on stimulation with IL-1␤ and tumor necrosis factor-␣. 6 In mouse models, IL-18 enhanced aortic atherogenesis in apolipoprotein E (apoE)-deficient mice through release of IFN-␥. 7 Conversely, IL-18 deficiency and IL-18 binding protein attenuated lesion development and progression, and it was suggested to promote plaque stability during initial lesion formation. 8,9 Although the role of IL-18 in atherogenesis is wellestablished, its effect at later stages of plaque development and on plaque stability is less well-investigated. Epidemiological studies in humans pointed to a destabilizing role for IL-18 in more advanced stages of plaque development. IL-18 serum levels have been found to correlate to cardiovascular morbidity and mortality in patients with coronary heart disease. 10 -13 In addition, Mallat et a...

The contribution of the hemostatic system in the development of cardiovascular disease (CVD) in patients with type 2 diabetes is not completely defined. The aim of this study was to elucidate associations of hemostatic factors with the development of CVD in patients with type 2 diabetes. Patients with type 2 diabetes without CVD (n ¼ 113), with CVD (n ¼ 94), and controls without CVD (n ¼ 100) were enrolled in this study. Several hemostatic markers were measured. A disturbed hemostatic balance in patients with type 2 diabetes was observed as illustrated by hypofibrinolysis and increased levels of von Willebrand factor (vWF) and plasminogen-activator inhibitor 1 (PAI-1). Patients with type 2 diabetes with CVD have more thrombin generation compared to patients without CVD. This hemostatic imbalance might contribute to the development of CVD in patients with type 2 diabetes.