Amyloid-β42 protofibrils are internalized by microglia more extensively than monomers.
Amyloid-β42 protofibrils are internalized by microglia more extensively than monomers.
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DOI：
10.1016/j.brainres.2016.08.016
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发表时间：
2016-10-01
期刊：
影响因子：
2.9
通讯作者：
Nichols MR
中科院分区：
文献类型：
--
作者：
Gouwens LK;Makoni NJ;Rogers VA;Nichols MR
阿尔茨海默病（AD）的一个病理标志是受影响的脑中淀粉样蛋白-β肽（Aβ）的积累。虽然Aβ蓄积有许多有害作用，但人们普遍认为，对聚集的Aβ的持续炎症反应有助于AD中的进行性神经变性，小胶质细胞在此过程中发挥重要作用。我们的实验室和其他实验室已经表明，Aβ的小可溶性聚集体激活小胶质细胞介导的炎症反应。反应的一个组成部分涉及细胞外Aβ的内化，并且该过程可能对Aβ结构非常敏感。在这项研究中，我们使用荧光标记的Aβ分析了小胶质细胞内化Aβ42单体和原纤维的倾向。两种Aβ42物质均通过Alexa Fluor 488四氟苯基酯（AF 488-TFP）的氨基键直接标记，然后通过色谱法单独分离。Aβ42原纤维在标记后保留了它们的大小和形态学特性，但与原纤维相比，单体具有高得多的标记化学计量。与AF 488-A β 42单体相比，原代鼠小胶质细胞迅速且大量内化AF 488-A β 42原纤维。小胶质细胞对原纤维的内化具有时间和浓度依赖性，并与肿瘤坏死因子α的分泌相对应。在竞争研究中，通过免疫染色检测到的未标记Aβ42原纤维内化并没有减少AF 488-原纤维摄取。发现内化的AF 488-Aβ42原纤维广泛分散在细胞质中，有一些溶酶体积累，但很少降解。这些研究强调了小胶质细胞在内化过程中对Aβ结构的敏感性，并强调了它们对可溶性Aβ原纤维的亲和力。
One pathological hallmark of Alzheimer’s disease (AD) is the accumulation of amyloid-β peptide (Aβ) in the affected brain. While there are numerous deleterious effects of Aβ accumulation, there is general agreement that a sustained inflammatory response to aggregated Aβ contributes to progressive neurodegeneration in AD and microglial cells play a significant role in this process. Our laboratory and others have shown that small soluble aggregates of Aβ activate a microglia-mediated inflammatory response. One component of the response involves internalization of extracellular Aβ, and this process is likely very sensitive to Aβ structure. In this study we analyzed the proclivity of microglia for internalization of Aβ42 monomers and protofibrils using fluorescently-labeled Aβ. Both Aβ42 species were labeled directly via amino linkage with an Alexa Fluor 488 tetrafluorophenyl ester (AF488-TFP) and then isolated individually by chromatography. Aβ42 protofibrils retained their size and morphological properties after labeling but monomers had a much higher stoichiometry of labeling compared to protofibrils. Primary murine microglia internalized AF488-Aβ42 protofibrils rapidly and in significant amounts compared to AF488-Aβ42 monomers. Microglial internalization of protofibrils was dependent on time and concentration, and corresponded with tumor necrosis factor α secretion. In competition studies, unlabeled Aβ42 protofibril internalization, detected by immunostaining, did not diminish AF488-protofibril uptake. Internalized AF488-Aβ42 protofibrils were found widely dispersed in the cytosol with some lysosomal accumulation but little degradation. These studies highlight the sensitivity that microglia exhibit to Aβ structure in the internalization process and emphasize their affinity for soluble Aβ protofibrils.