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Papers In Press, published online ahead of print September 1, 2005
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* Vascular Biology Program, Department of Surgery, Children's Hospital, Boston, MA 02115
Division of Endocrinology and Metabolism, Department of Medicine, University of California, San Diego, La Jolla, CA 92093
Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115
The online version of this article (available at http://www.jlr.org) contains an additional figure
Published, JLR Papers in Press, July 1, 2005. DOI 10.1194/jlr.M500241-JLR200
1 To whom correspondence should be addressed. e-mail: karen.moulton{at}childrens.harvard.edu
Retention of lipoproteins to proteoglycans in the subendothelial matrix (SEM) is an early event in atherosclerosis. We recently reported that collagen XVIII and its proteolytically released fragment endostatin (ES) are differentially depleted in blood vessels affected by atherosclerosis. Loss of collagen XVIII/ES in atherosclerosis-prone mice enhanced plaque neovascularization and increased the vascular permeability to lipids by distinct mechanisms. Impaired endothelial barrier function increased the influx of lipoproteins across the endothelium; however, we hypothesized that enhanced retention might be a second mechanism leading to the increased lipid content in atheromas lacking collagen XVIII. We now demonstrate a novel property of ES that binds both the matrix proteoglycan biglycan and LDL and interferes with LDL retention to biglycan and to SEM. A peptide encompassing the
coil in the ES crystal structure mediates the major blocking effect of ES on LDL retention. ES inhibits the macrophage uptake of biglycan-associated LDL indirectly by interfering with LDL retention to biglycan, but it has no direct effect on the macrophage uptake of native or modified lipoproteins.
Thus, loss of ES in advanced atheromas enhances lipoprotein retention in SEM. Our data reveal a third protective role of this vascular basement membrane component during atherosclerosis.
Abbreviations: Bmax, maximum density of binding sites in matrix; ES, endostatin; GAG, glycosaminoglycan; HBS, HEPES-buffered saline; HUVEC, human umbilical vein endothelial cells; Kd, dissociation constant; OxLDL, oxidized low density lipoprotein; SEM, subendothelial matrix
Supplementary key words low density lipoprotein extracellular matrix vascular basement membrane proteoglycans collagen XVIII
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