Destabilizing Role of Cathepsin S in Murine Atherosclerotic Plaques

Abstract

Objective-Lysosomal proteinases have been implicated in a number of pathologies associated with extracellular matrix breakdown. Therefore, we investigated the possibility that the lysosomal proteinase cathepsin S may be involved in atherosclerotic plaque destabilization. Methods and Results-Atherosclerotic plaques in the brachiocephalic arteries of fat-fed apolipoprotein E/cathepsin S double knockout mice had 73% fewer acute plaque ruptures (Pϭ0.026) and were 46% smaller (Pϭ0.025) than those in age-, strain-, and sex-matched apolipoprotein E single knockout controls. When the incidence of acute plaque rupture was normalized for plaque size, the reduction in the double knockouts was 72% (Pϭ0.039). The number of buried fibrous layers, indicative of an unstable plaque phenotype, was reduced by 67% in the double knockouts (Pϭ0.008). The cysteine proteinase inhibitor, egg white cystatin, was biotinylated and used as an active-site-directed probe for cathepsins. Biotinylated cystatin selectively detected cathepsin S in extracts of human carotid atherosclerotic plaque. Active cathepsin S was detectable in extracts of human atherosclerotic plaque but not in nondiseased carotid arteries. Active cathepsins were especially prominent in macrophages in the shoulder regions of plaques, areas considered to be vulnerable to rupture. Cathepsin S protein colocalized with regions of elastin degradation in human coronary plaques. Conclusion-These data provide direct evidence that an endogenous proteinase, cathepsin S, plays an important role in atherosclerotic plaque destabilization and rupture. Key Words: atherosclerosis Ⅲ plaque Ⅲ pathology Ⅲ cathepsin T he highly thrombogenic gruel in the core of an atherosclerotic plaque is luminally covered by a fibrous cap, weakening of which leads to plaque rupture and thrombus formation. Macrophages and T cells accumulate at sites of plaque disruption. 1 Degradation of collagen by macrophagederived matrix metalloproteinases has been reported, 2 but less is known of other classes of proteinase, which may be released by activated macrophages.The lysosomal cathepsins have been implicated in the development and progression of atherosclerosis. Increased levels of cathepsins F, K, and S are present in atherosclerotic lesions, 3,4 whereas levels of the major extracellular inhibitor of cysteine proteinases, cystatin C, are decreased. 5 In humans, an association has been shown between a genetically determined decrease in cystatin C levels and the severity of coronary artery disease. 6 Cathepsin S/low-density lipoprotein (LDL) receptor double knockout mice have impaired atherogenesis when compared with LDL receptor single knockout controls. 7 Grading of atherosclerosis in the aortic arch showed that there was a delay in lesion progression in the double knockouts. For example, 12 weeks of feeding atherogenic diet to the double knockouts resulted in an average lesion severity similar to that seen in single knockout controls after just 8 weeks of feeding, and 26 weeks of atherogenic diet feeding in the ...

Interrelated Cathepsin S-Lowering and LDL Subclass Profile Improvements Induced by Atorvastatin in the Plasma of Stable Angina Patients

“…As to the CTSS-mediated effects observed in the setting of atherogenesis, the CTSS mRNA and protein levels are increased in human and animal atheromas, but not in non-atherosclerotic arteries 3,4) . CTSS is synthesized by macrophages, smooth muscle cells and endothelial cells 5) and, when released extracellularly, it exerts elastolytic and collagenolytic effects, leading to elastic lamina degradation 6,7) , plaque rupture 8) and necrotic core development 7) . Some studies have reported higher concentrations of CTSS in the plasma of patients with cardiovascular disease 9,10) .…”

Role of Cathepsin K, L and S in Blood Vessel Remodeling

“…The atheroprotective effect of cathepsin S deficiency was also confirmed by experiments with apolipoprotein Edeficient mice lacking this protease. (Rodgers et al, 2006). Atherosclerotic lesions in brachiocephalic arteries of apolipoprotein E-deficient and cathepsin S double deficient mice were significantly smaller and had fewer acute plaque ruptures.…”

“…The use of cathepsin and MMP inhibitors revealed that cathepsins had significantly greater contribution to elastolytic activity of atherosclerotic lesions extracts. Cathepsin K and S immunoreactivities were mostly localized in the fibrous cap region that suggested their important role in plaque destabilization (Sukhova et al, 1998;Rodgers et al, 2006). In addition, smooth muscle cells cultured with IFN- or interleukin-1 secreted active cathepsin S and showed significantly increased ability to degrade elastin.…”

“…These mice also had a lower number of buried fibrous caps, which are believed to be a marker of unstable atherosclerotic plaques. The fibrous caps in plaques of double knockout mice were also thicker compared to cathepsin S-expressing mice that most likely rendered higher stability to those plaques (Rodgers et al, 2006). Recently, the role of cathepsin S in atherosclerosis was investigated in chimeric low density lipoprotein receptor-deficient mice lacking this protease in leukocytes ).…”

“…These results instigated a series of studies on the involvement of cathepsin K, L and S in the development of cardiovascular diseases based on animal models of atherosclerosis and abdominal aortic aneurysm www.intechopen.com formation (Lutgens et al, 2007;Lafarge et al, 2010;Liu et al, 2004). The lack of these proteases resulted in a plaque size reduction and delay of plaque progression as well as in reduced level of medial elastin degradation and smooth muscle cell transmigration from the media to the intima (Lutgens et al, 2006a;Rodgers et al, 2006;Samokhin et al, 2008;Sukhova et al, 2003). These results were corroborated by in vitro experiments that revealed the differences in collageno-and elastolytic activities of smooth muscle cells and macrophages from mice expressing and lacking these cathepsins.…”