星型胶质细胞溶酶体介导的β淀粉样蛋白降解在阿尔海默茨病中的作用

Astrocyte lysosome can degrade and clear Aβ. Regulation of lysosome degradation ability is one of the method for Alzheimer's Disease (AD) therapy. Our previews data have shown that degradation of Aβ decreases in the old wild-type astrocyte and astrocyte of AD transgenic mice. Moreover,astrocyte lysosome can release its contents under pathological conditions, for example ischemia. The purpose of this study was to further determine the role and mechanism of astrocyte lysosome in the process of Aβ degradation and release. We will use live-cell imaging technology together with immunocytochemistry and electronic microscope method to study whether the accumulation of oligmer Aβ (a more toxic form of Aβ) increases in the old and AD astrocyte lysosome; whether activation of GSK-3 and PKA will change the PH of astrocyte lysosome, and then affect the degradation of Aβ and oligmer Aβ; We will also observe whether Aβ can be release to extracellular together with lysosome under ischemia stimulation. This process will reduce the duration of Aβ in astrocyte lysosome, decrease the degradation of Aβ and increase the toxicity of Aβ to neurons. The project will analyze the role of astrocyte in the pathogenesis of AD, and will help us to find out new ideas and methods for therapeutic treatment of AD.

星形胶质细胞溶酶体可以对Aβ进行降解和清除，溶酶体功能的调节被认为是阿尔茨海默病(AD)治疗的一种潜在途径。我们前期的研究发现AD和老年小鼠星形胶质细胞溶酶体降解Aβ的能力显著下降。星形胶质细胞溶酶体还可以在缺血缺氧等刺激下释放其内容物。本项目在此基础上，重点探明星形胶质细胞溶酶体在Aβ降解及释放中的作用及机制。本课题拟采用活细胞成像结合免疫细胞化学、电镜等方法（1）研究AD及老年小鼠星形胶质细胞溶酶体内是否形成毒性更大的寡聚体Aβ；（2）探讨改变细胞PH值对星形胶质细胞溶酶体内Aβ及寡聚体Aβ含量的影响以及GSK-3和PKA信号通路在此过程中的作用。（3）分析在缺血缺氧等刺激下，溶酶体内聚集的Aβ是否随溶酶体的释放而释放，从而减少Aβ在溶酶体内的时间，降低Aβ降解，促进Aβ发挥神经毒性。本项目阐明星形胶质溶酶体在AD发病中的作用，为AD的临床治疗和研究提供理论基础。

星形胶质细胞溶酶体可以对Aβ进行降解和清除，因此溶酶体功能的调节被认为是阿尔茨海默病(AD)治疗的一种潜在途径。我们研究发现星形胶质细胞具有吞噬并降解Aβ的功能，该功能与星形胶质细胞溶酶体密切相关，因为星形胶质细胞内吞Aβ后定位于溶酶体。Aβ42处理后可使溶酶体变酸，溶酶体体积变大、数目减少。而溶酶体内的酸性环境对Aβ的吞噬与降解至关重要：实验发现质子泵抑制剂Bafilomycin A1使溶酶体数目减少，使Aβ在细胞内聚集，无法被溶酶体有效降解；而NH4Cl及Forskolin加速Aβ的内吞和在细胞内的降解。Aβ的清除还与钙离子及谷氨酸相关，1 μM Ionomycin和5 mM谷氨酸刺激在48 min内不会影响星形胶质细胞膜的完整性，可升高星形胶质细胞溶酶体在细胞内钙离子浓度和神经兴奋性毒性并促进内吞的Aβ释放到细胞外，该过程证明是依赖囊泡膜相关蛋白Vamp7的。此外，我们还筛选到调节溶酶体稳态基因TMEM175。根据实验结果我们提出星形胶质细胞溶酶体是以“kiss and run”方式将Aβ释放到细胞外。项目研究成果对AD的治疗提供了新理论指导及途径。