Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, 303 East Chicago Avenue, Chicago, IL 60611, USA.
Mol Neurodegener. 2013 Jan 14;8:2. doi: 10.1186/1750-1326-8-2.
Although the mechanism of neuron loss in Alzheimer's disease (AD) is enigmatic, it is associated with cerebral accumulation of Aβ42. The 5XFAD mouse model of amyloid deposition expresses five familial AD (FAD) mutations that are additive in driving Aβ42 overproduction. 5XFAD mice exhibit intraneuronal Aβ42 accumulation at 1.5 months, amyloid deposition at 2 months, and memory deficits by 4 months of age.
Here, we demonstrate by unbiased stereology that statistically significant neuron loss occurs by 9 months of age in 5XFAD mice. We validated two Aβ42-selective antibodies by immunostaining 5XFAD; BACE1-/- bigenic brain sections and then used these antibodies to show that intraneuronal Aβ42 and amyloid deposition develop in the same regions where neuron loss is observed in 5XFAD brain. In 5XFAD neuronal soma, intraneuronal Aβ42 accumulates in puncta that co-label for Transferrin receptor and LAMP-1, indicating endosomal and lysosomal localization, respectively. In addition, in young 5XFAD brains, we observed activated Caspase-3 in the soma and proximal dendrites of intraneuronal Aβ42-labeled neurons. In older 5XFAD brains, we found activated Caspase-3-positive punctate accumulations that co-localize with the neuronal marker class III β-tubulin, suggesting neuron loss by apoptosis.
Together, our results indicate a temporal sequence of intraneuronal Aβ42 accumulation, Caspase-3 activation, and neuron loss that implies a potential apoptotic mechanism of neuron death in the 5XFAD mouse.
尽管阿尔茨海默病（AD）中神经元丧失的机制尚不清楚，但它与大脑中 Aβ42 的积累有关。淀粉样蛋白沉积的 5XFAD 小鼠模型表达了五个家族性 AD（FAD）突变，这些突变在驱动 Aβ42 过度产生方面具有加性。5XFAD 小鼠在 1.5 个月时表现出神经元内 Aβ42 积累，在 2 个月时出现淀粉样蛋白沉积，在 4 个月时出现记忆缺陷。
在这里，我们通过无偏立体学证明，5XFAD 小鼠在 9 个月时发生了统计学上显著的神经元丧失。我们通过免疫染色 5XFAD；BACE1-/-双基因脑切片验证了两种 Aβ42 选择性抗体，然后使用这些抗体表明，神经元内 Aβ42 和淀粉样蛋白沉积在 5XFAD 脑观察到神经元丧失的相同区域发展。在 5XFAD 神经元胞体中，神经元内 Aβ42 聚集在标记物 Transferrin receptor 和 LAMP-1 的斑点中，分别表示内体和溶酶体定位。此外，在年轻的 5XFAD 脑中，我们观察到 Caspase-3 在神经元内 Aβ42 标记神经元的胞体和近端树突中被激活。在年龄较大的 5XFAD 脑中，我们发现激活的 Caspase-3 阳性点状聚集物与神经元标志物 III 类 β-微管蛋白共定位，提示通过细胞凋亡导致神经元丧失。
总之，我们的结果表明神经元内 Aβ42 积累、Caspase-3 激活和神经元丧失的时间顺序表明 5XFAD 小鼠中神经元死亡存在潜在的凋亡机制。
