Graduate School of Biomedical Engineering, UNSW Sydney, Sydney, New South Wales, Australia; Vascular Biology Research Centre, Department of Surgery, Westmead Hospital, Westmead, New South Wales, Australia; The University of Sydney, Westmead Clinical School, Westmead, New South Wales, Australia.
Graduate School of Biomedical Engineering, UNSW Sydney, Sydney, New South Wales, Australia.
J Biol Chem. 2021 Jan-Jun;296:100520. doi: 10.1016/j.jbc.2021.100520. Epub 2021 Mar 5.
The retention of low-density lipoprotein (LDL) is a key process in the pathogenesis of atherosclerosis and largely mediated via smooth-muscle cell-derived extracellular proteoglycans including the glycosaminoglycan chains. Macrophages can also internalize lipids via complexes with proteoglycans. However, the role of polarized macrophage-derived proteoglycans in binding LDL is unknown and important to advance our understanding of the pathogenesis of atherosclerosis. We therefore examined the identity of proteoglycans, including the pendent glycosaminoglycans, produced by polarized macrophages to gain insight into the molecular basis for LDL binding. Using the quartz crystal microbalance with dissipation monitoring technique, we established that classically activated macrophage (M1)- and alternatively activated macrophage (M2)-derived proteoglycans bind LDL via both the protein core and heparan sulfate (HS) in vitro. Among the proteoglycans secreted by macrophages, we found perlecan was the major protein core that bound LDL. In addition, we identified perlecan in the necrotic core as well as the fibrous cap of advanced human atherosclerotic lesions in the same regions as HS and colocalized with M2 macrophages, suggesting a functional role in lipid retention in vivo. These findings suggest that macrophages may contribute to LDL retention in the plaque by the production of proteoglycans; however, their contribution likely depends on both their phenotype within the plaque and the presence of enzymes, such as heparanase, that alter the secreted protein structure.
低密度脂蛋白 (LDL) 的保留是动脉粥样硬化发病机制的关键过程，主要通过平滑肌细胞衍生的细胞外蛋白聚糖介导，包括糖胺聚糖链。巨噬细胞也可以通过与蛋白聚糖的复合物内化脂质。然而，极化的巨噬细胞衍生的蛋白聚糖在与 LDL 结合中的作用尚不清楚，这对于深入了解动脉粥样硬化的发病机制很重要。因此，我们研究了极化的巨噬细胞产生的蛋白聚糖的特性，包括其连接的糖胺聚糖，以深入了解 LDL 结合的分子基础。我们使用石英晶体微天平结合耗散监测技术，在体外证实了经典激活的巨噬细胞 (M1) 和替代激活的巨噬细胞 (M2) 衍生的蛋白聚糖通过蛋白核心和硫酸乙酰肝素 (HS) 与 LDL 结合。在巨噬细胞分泌的蛋白聚糖中，我们发现连接蛋白是与 LDL 结合的主要蛋白核心。此外，我们在人动脉粥样硬化病变的坏死核心和纤维帽中发现了连接蛋白，与 HS 位于同一区域，并与 M2 巨噬细胞共定位，表明其在体内脂质保留中具有功能作用。这些发现表明，巨噬细胞可能通过产生蛋白聚糖来促进斑块中 LDL 的保留；然而，它们的贡献可能取决于斑块内的表型以及改变分泌蛋白结构的酶（如硫酸乙酰肝素酶）的存在。
