Jinnouchi Y, Sano H, Nagai R, Hakamata H, Kodama T, Suzuki H, Yoshida M, Ueda S, Horiuchi S
Department of Biochemistry, Kumamoto University School of Medicine, Kumamoto, 860-0811, Japan.
J Biochem. 1998 Jun;123(6):1208-17. doi: 10.1093/oxfordjournals.jbchem.a022062.
It was shown that proteins modified with advanced glycation end products (AGE) are effectively endocytosed by macrophages or macrophage-derived cells in vitro, and immunohistochemical studies involving anti-AGE antibodies demonstrated the accumulation of AGE-modified proteins (AGE-proteins) in macrophage-derived foam cells in human atherosclerotic lesions in situ, suggesting the involvement of AGE-modified LDL in the atherogenic process in vivo. To examine this suggestion, LDL was modified with glycolaldehyde, a highly reactive intermediate of the Maillard reaction. Physicochemically, glycolaldehyde-modified LDL (GA-LDL) was characterized by increases in negative charge, fluorescence intensity, and reactivity to anti-AGE antibodies, properties highly similar to those of AGE-proteins. The cellular interaction of GA-LDL with mouse peritoneal macrophages showed that GA-LDL was specifically recognized and endocytosed, followed by lysosomal degradation. The endocytic uptake of GA-LDL by these cells was competitively inhibited by acetylated LDL (acetyl-LDL), and the endocytic degradation of acetyl-LDL was also competed for by GA-LDL. Furthermore, incubation of GA-LDL with these macrophages and Chinese hamster ovary cells overexpressing the macrophage scavenger receptor (MSR), but not with peritoneal macrophages from MSR-knockout mice, led to the intracellular accumulation of cholesteryl esters (CE). These results raised the possibility that AGE-modified LDL, if available in situ, is taken up by macrophages mainly via MSR and then contributes to foam cell formation in early atherosclerotic lesions.
研究表明，晚期糖基化终产物（AGE）修饰的蛋白质在体外能被巨噬细胞或巨噬细胞衍生细胞有效内吞，涉及抗AGE抗体的免疫组织化学研究表明，AGE修饰的蛋白质（AGE蛋白）在人动脉粥样硬化病变原位的巨噬细胞衍生泡沫细胞中积聚，这表明AGE修饰的低密度脂蛋白（LDL）参与了体内动脉粥样硬化形成过程。为验证这一推测，用乙二醛（美拉德反应的一种高反应性中间体）修饰LDL。从物理化学性质来看，乙二醛修饰的LDL（GA-LDL）的特点是负电荷增加、荧光强度增加以及对抗AGE抗体的反应性增加，这些特性与AGE蛋白的特性高度相似。GA-LDL与小鼠腹腔巨噬细胞的细胞相互作用表明，GA-LDL被特异性识别并内吞，随后被溶酶体降解。这些细胞对GA-LDL的内吞摄取被乙酰化LDL（乙酰-LDL）竞争性抑制，而乙酰-LDL的内吞降解也受到GA-LDL的竞争。此外，将GA-LDL与这些巨噬细胞以及过表达巨噬细胞清道夫受体（MSR）的中国仓鼠卵巢细胞共同孵育，而非与MSR基因敲除小鼠的腹腔巨噬细胞共同孵育，会导致细胞内胆固醇酯（CE）的积累。这些结果增加了一种可能性，即如果原位存在AGE修饰的LDL，它主要通过MSR被巨噬细胞摄取，然后在早期动脉粥样硬化病变中促进泡沫细胞的形成。
