Astrocytes, one of the most resilient cells in the brain, transform into reactive astrocytes in response to toxic proteins such as amyloid beta (Aβ) in Alzheimer’s disease (AD). However, reactive astrocyte-mediated non-cell autonomous neuropathological mechanism is not fully understood yet. We aimed our study to find out whether Aβ-induced proteotoxic stress affects the expression of autophagy genes and the modulation of autophagic flux in astrocytes, and if yes, how Aβ-induced autophagy-associated genes are involved Aβ clearance in astrocytes of animal model of AD. Whole RNA sequencing (RNA-seq) was performed to detect gene expression patterns in Aβ-treated human astrocytes in a time-dependent manner. To verify the role of astrocytic autophagy in an AD mouse model, we developed AAVs expressing shRNAs for MAP1LC3B/LC3B (LC3B) and Sequestosome1 (SQSTM1) based on AAV-R-CREon vector, which is a Cre recombinase-dependent gene-silencing system. Also, the effect of astrocyte-specific overexpression of LC3B on the neuropathology in AD (APP/PS1) mice was determined. Neuropathological alterations of AD mice with astrocytic autophagy dysfunction were observed by confocal microscopy and transmission electron microscope (TEM). Behavioral changes of mice were examined through novel object recognition test (NOR) and novel object place recognition test (NOPR). Here, we show that astrocytes, unlike neurons, undergo plastic changes in autophagic processes to remove Aβ. Aβ transiently induces expression of LC3B gene and turns on a prolonged transcription of SQSTM1 gene. The Aβ-induced astrocytic autophagy accelerates urea cycle and putrescine degradation pathway. Pharmacological inhibition of autophagy exacerbates mitochondrial dysfunction and oxidative stress in astrocytes. Astrocyte-specific knockdown of LC3B and SQSTM1 significantly increases Aβ plaque formation and GFAP-positive astrocytes in APP/PS1 mice, along with a significant reduction of neuronal marker and cognitive function. In contrast, astrocyte-specific overexpression of LC3B reduced Aβ aggregates in the brain of APP/PS1 mice. An increase of LC3B and SQSTM1 protein is found in astrocytes of the hippocampus in AD patients. Taken together, our data indicates that Aβ-induced astrocytic autophagic plasticity is an important cellular event to modulate Aβ clearance and maintain cognitive function in AD mice.

中文翻译：

---

星形胶质细胞自噬可塑性调节阿尔茨海默病中的 Aβ 清除和认知功能


星形胶质细胞是大脑中最具弹性的细胞之一，它会转变为反应性星形胶质细胞，以响应阿尔茨海默病 (AD) 中的淀粉样蛋白 (Aβ) 等有毒蛋白质。然而，反应性星形胶质细胞介导的非细胞自主神经病理机制尚未完全了解。我们的研究目的是找出 Aβ 诱导的蛋白毒性应激是否影响星形胶质细胞中自噬基因的表达和自噬通量的调节，如果是的话，Aβ 诱导的自噬相关基因如何参与动物模型星形胶质细胞中的 Aβ 清除。广告。全RNA测序（RNA-seq）以时间依赖性方式检测Aβ处理的人星形胶质细胞中的基因表达模式。为了验证星形胶质细胞自噬在 AD 小鼠模型中的作用，我们基于 AAV-R-CREon 载体（一种 Cre 重组酶依赖性基因沉默系统）开发了表达 MAP1LC3B/LC3B (LC3B) 和 Sequestosome1 (SQSTM1) shRNA 的 AAV 。此外，还确定了星形胶质细胞特异性过度表达 LC3B 对 AD (APP/PS1) 小鼠神经病理学的影响。通过共聚焦显微镜和透射电子显微镜（TEM）观察星形细胞自噬功能障碍的 AD 小鼠的神经病理学改变。通过新物体识别测试（NOR）和新物体位置识别测试（NOPR）检查小鼠的行为变化。在这里，我们发现星形胶质细胞与神经元不同，在自噬过程中经历塑性变化以去除 Aβ。 Aβ 短暂诱导 LC3B 基因表达，并开启 SQSTM1 基因的延长转录。 Aβ 诱导的星形细胞自噬加速尿素循环和腐胺降解途径。自噬的药理抑制会加剧星形胶质细胞的线粒体功能障碍和氧化应激。 星形胶质细胞特异性敲除 LC3B 和 SQSTM1 显着增加 APP/PS1 小鼠中 Aβ 斑块形成​​和 GFAP 阳性星形胶质细胞，同时神经元标记物和认知功能显着降低。相比之下，星形胶质细胞特异性过度表达 LC3B 会减少 APP/PS1 小鼠大脑中的 Aβ 聚集。 AD 患者海马星形胶质细胞中发现 LC3B 和 SQSTM1 蛋白增加。综上所述，我们的数据表明，Aβ 诱导的星形细胞自噬可塑性是调节 Aβ 清除和维持 AD 小鼠认知功能的重要细胞事件。