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      Elastin- and Collagen-Rich Human Carotid Plaques Have Increased Levels of the Cysteine Protease Inhibitor Cystatin C

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          Background: Cystatin C is a major inhibitor of the elastin- and collagen-degrading cysteine proteases and may therefore have an important role in preserving atherosclerotic plaque stability. In this study we analyzed the associations between human carotid plaque cystatin C expression and the plaque content of collagen and elastin. Methods: Thirty-one plaques were removed by endarterectomy and homogenized. Cystatin C levels were analyzed by densitometry of Western blots and elastin and collagen levels were determined colorimetrically. Results: The plaque content of cystatin C correlated with total elastin (r = 0.58, p = 0.001) and collagen (r = 0.50, p = 0.004), as well as with cross-linked forms of elastin (r = 0.42, p = 0.022) and collagen (r = 0.52, p = 0.003). Immunohistochemical analysis demonstrated that cystatin C colocalized with elastin and collagen. No correlation was seen between cystatin C and the amount of degraded elastin or collagen in plaques. Conclusion: The positive correlation between cystatin C levels and collagen and elastin levels in plaques supports the notion that cystatin C plays an important role in maintaining atherosclerotic plaque stability.

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          Most cited references 19

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          A simplified method for the analysis of hydroxyproline in biological tissues.

          A critical study of the different steps involved in previous procedure for hydroxyproline assay allows the direct measurement of collagen content in tissue' homogenates without losing the advantages of the method. The procedure is based on alkaline hydrolysis of the tissue homogenate and subsequent determination of the free hydroxyproline in hydrolyzates. Chloramine-T was used to oxidize the free hydroxyproline for the production of a pyrrole. The addition of Ehrlich's reagent resulted in the formation of a chromophore that can be measured at 550 nm. Optimal assay conditions were determined using tissue homogenate and purified acid soluble collagen along with standard hydroxyproline. Critical parameters such as the amount of chloramine-T, sodium hydroxide, p-dimethylaminobenzaldehyde, pH of the reaction buffer, and length of oxidation time were examined to obtain satisfactory results. The method has been applied to samples of tissue homogenate and purified acid soluble collagen, with recovery of added hydroxyproline of 101 +/- 6.5 and 104 +/- 6.0 (SD) percent, respectively. The method is highly sensitive and reproducible when used to measure the imino acid in tissue homogenates. The modified hydroxyproline assay presented in this communication will be useful for routine measurement of collagen content in extracts of various tissue specimens. In addition, the modified method can be used for batch processing of column fractions to monitor the collagen concentrations during purification.
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            Dual role of matrix metalloproteinases (matrixins) in intimal thickening and atherosclerotic plaque rupture.

            Intimal thickening, the accumulation of cells and extracellular matrix within the inner vessel wall, is a physiological response to mechanical injury, increased wall stress, or chemical insult (e.g., atherosclerosis). If excessive, it can lead to the obstruction of blood flow and tissue ischemia. Together with expansive or constrictive remodeling, the extent of intimal expansion determines final lumen size and vessel wall thickness. Plaque rupture represents a failure of intimal remodeling, where the fibrous cap overlying an atheromatous core of lipid undergoes catastrophic mechanical breakdown. Plaque rupture promotes coronary thrombosis and myocardial infarction, the most prevalent cause of premature death in advanced societies. The matrix metalloproteinases (MMPs) can act together to degrade the major components of the vascular extracellular matrix. All cells present in the normal and diseased blood vessel wall upregulate and activate MMPs in a multistep fashion driven in part by soluble cytokines and cell-cell interactions. Activation of MMP proforms requires other MMPs or other classes of protease. MMP activation contributes to intimal growth and vessel wall remodeling in response to injury, most notably by promoting migration of vascular smooth muscle cells. A broader spectrum and/or higher level of MMP activation, especially associated with inflammation, could contribute to pathological matrix destruction and plaque rupture. Inhibiting the activity of specific MMPs or preventing their upregulation could ameliorate intimal thickening and prevent myocardial infarction.
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              Differential expression of bone matrix regulatory proteins in human atherosclerotic plaques.

              In the present study, we examined the expression of regulators of bone formation and osteoclastogenesis in human atherosclerosis because accumulating evidence suggests that atherosclerotic calcification shares features with bone calcification. The most striking finding of this study was the constitutive immunoreactivity of matrix Gla protein, osteocalcin, and bone sialoprotein in nondiseased aortas and the absence of bone morphogenetic protein (BMP)-2, BMP-4, osteopontin, and osteonectin in nondiseased aortas and early atherosclerotic lesions. When atherosclerotic plaques demonstrated calcification or bone formation, BMP-2, BMP-4, osteopontin, and osteonectin were upregulated. Interestingly, this upregulation was associated with a sustained immunoreactivity of matrix Gla protein, osteocalcin, and bone sialoprotein. The 2 modulators of osteoclastogenesis (osteoprotegerin [OPG] and its ligand, OPGL) were present in the nondiseased vessel wall and in early atherosclerotic lesions. In advanced calcified lesions, OPG was present in bone structures, whereas OPGL was only present in the extracellular matrix surrounding calcium deposits. The observed expression patterns suggest a tight regulation of the expression of bone matrix regulatory proteins during human atherogenesis. The expression pattern of both OPG and OPGL during atherogenesis might suggest a regulatory role of these proteins not only in osteoclastogenesis but also in atherosclerotic calcification.

                Author and article information

                J Vasc Res
                Journal of Vascular Research
                S. Karger AG
                August 2008
                28 March 2008
                : 45
                : 5
                : 395-401
                aDepartment of Clinical Sciences, Experimental Cardiovascular Research Unit, Lund University and bDepartments of Cardiology and Internal Medicine, Malmö University Hospital, Malmö, and cDepartment of Cardiology, Lund University Hospital and dLund Stem Cell Centre, Lund University, Lund, Sweden; eCardiovascular Institute of Lisbon, Lisbon, Portugal
                121474 J Vasc Res 2008;45:395–401
                © 2008 S. Karger AG, Basel

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                Page count
                Figures: 2, Tables: 2, References: 24, Pages: 7
                Research Paper


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