Instituto de Neurociencias de Castilla y León, Universidad de Salamanca, Spain.
J Alzheimers Dis. 2018;65(4):1109-1124. doi: 10.3233/JAD-180332.
Amyloid-β (Aβ) peptides, Aβ40, Aβ42, and recently Aβ25 - 35, have been directly implicated in the pathogenesis of Alzheimer's disease (AD). We have previously shown that all three peptides decrease neuronal viability, but Aβ40 also promotes synaptic disassembling. In this work, we have studied the effects of these peptides on astrocytes in primary culture and found that the three Aβ peptides were internalized by astrocytes and significantly decreased astrocyte viability, while increasing ROS production. Aβ peptide internalization is temperature-dependent, a fact that supports the idea that Aβ peptides are actively endocytosed by astrocytes. However, inhibiting caveolae formation by methyl-beta-cyclodextrin or by silencing caveolin-1 with RNA interference did not prevent Aβ endocytosis, which suggests that Aβ peptides do not use caveolae to enter astrocytes. Conversely, inhibition of clathrin-coated vesicle formation by chlorpromazine or by silencing clathrin with RNA interference significantly decreased Aβ internalization and partially reverted the decrease of astrocyte viability caused by the presence of Aβ. These results suggest that Aβ is endocytosed by clathrin-coated vesicles in astrocytes. Aβ-loaded astrocytes, when co-incubated with non-treated astrocytes in separate wells but with the same incubation medium, promoted cell death in non-treated astrocytes; a fact that was associated with the presence of Aβ inside previously unloaded astrocytes. This phenomenon was inhibited by the presence of chlorpromazine in the co-incubation medium. These results suggest that astrocyte may perform Aβ transcytosis, a process that could play a role in the clearance of Aβ peptides from the brain to cerebrospinal fluid.
淀粉样蛋白-β（Aβ）肽，Aβ40、Aβ42，最近还有 Aβ25-35，直接参与阿尔茨海默病（AD）的发病机制。我们之前已经表明，这三种肽都降低神经元活力，但 Aβ40 还促进突触解体。在这项工作中，我们研究了这些肽对原代培养星形胶质细胞的影响，发现这三种 Aβ 肽被星形胶质细胞内化，并显著降低星形胶质细胞活力，同时增加 ROS 产生。Aβ 肽内化是温度依赖性的，这一事实支持 Aβ 肽被星形胶质细胞主动内吞的观点。然而，用甲基-β-环糊精抑制小窝形成或用 RNA 干扰沉默窖蛋白-1并不能阻止 Aβ 内吞，这表明 Aβ 肽不使用小窝进入星形胶质细胞。相反，用氯丙嗪抑制网格蛋白包被小泡形成或用 RNA 干扰沉默网格蛋白则显著减少 Aβ 内化，并部分逆转 Aβ 存在引起的星形胶质细胞活力下降。这些结果表明 Aβ 被星形胶质细胞中的网格蛋白包被小泡内吞。用 Aβ 负载的星形胶质细胞，在与未处理的星形胶质细胞分别在不同孔中共同孵育，但使用相同的孵育培养基时，会促进未处理的星形胶质细胞死亡；这一事实与之前未负载的星形胶质细胞内存在 Aβ 有关。在共同孵育培养基中加入氯丙嗪可抑制这一现象。这些结果表明星形胶质细胞可能进行 Aβ 转胞吞作用，这一过程可能在 Aβ 肽从大脑清除到脑脊液中发挥作用。
