星形胶质细胞alpha7胆碱能受体调控内源性Cryab抑制β-淀粉样蛋白聚集的研究

Astrocytic alpha7 nicotinic receptors inhibit βamyloid aggregation via upregulation endogenous Cryab The aggregation of β-amyloid (Aβ) play an important role in the pathogenesis of Alzheimer's disease (AD). Astrocytes can significantly inhibit the aggregation of Aβ. However, the mechanism is unknown. B-crystallin (Cryab), one astrocytic endogenous protein, has been shown to inhibit Aβ aggregation. In our previous studies, we found the activation of astrocytic alpha7 nicotinic receptors (nAChRs) can significantly enhance the ability of astrocytes to inhibit Aβaggregation. However, the underline mechanism is still unknown. Our recently preliminary data showed that the activation of astrocytic alpha7 nAChRs can induce the upregulations of intracellular Calcium as well as Cryab. Furthermore, the upregulations of Cryab is dependent on the level of Calcium and the activity of Calmodulin (CaM). Based on our preliminary data, we hypothesized that the activation of astrocytic alpha7 nAChRs can firstly induce increased Calcium and CaM activity, then induce the upregulation of Cryab. The increased Cryab enhance the inhibition of Aβ aggregation. Our hypothesis will be tested in several transgenic animal and cell culture models by using Cryab SiRNA and gene transfection techniques. Our project will provide new ideas and therapeutic targets for AD treatment.

β-淀粉样蛋白（Aβ）聚集是阿尔茨海默病(AD)核心发病机制，星形胶质细胞能够抑制Aβ的聚集，但机制不详。星形胶质细胞内源性B-晶状体蛋白（Cryab）能够阻止Aβ聚集。我们发现，激活星形胶质细胞a7胆碱能受体（a7nAChRs）能够显著增强星形胶质细胞对Aβ聚集的抑制，但具体调控机制不清楚。在预实验中发现：a7nAChRs的激活引起细胞内钙增加和Cryab上调，而且Cryab上调依赖于细胞内钙水平升高和钙调蛋白（CaM）活性增强。因此，我们推测"激活星形胶质细胞的a7 nAChRs，引起细胞内钙水平和CaM升高，从而上调Cryab，促进Cryab对Aβ蛋白聚集的抑制"是星形胶质细胞a7nAChRs抑制Aβ聚集的新机制。本课题拟制备a7nAChRs敲除、AD动物模型和星形胶质细胞，应用siRNA，Cryab转染等技术，从整体-细胞层次证明我们的假说。本研究将为AD的防治提供新的思路和靶点。

β-淀粉样蛋白（Aβ）聚集是阿尔茨海默病(AD)核心发病机制，星形胶质细胞能够抑制 Aβ的聚集，但机制不详。星形胶质细胞内源性 B-晶状体蛋白（Cryab）能够阻止 Aβ聚集。我们前期研究初步发现，激活星形胶质细胞α7 胆碱能受体（α7 nAChRs）能够显著增强星形胶质细胞对Aβ聚集的抑制，但具体调控机制不清楚。.在本研究中，我们首先在原代星型胶质细胞培养模型上，观察到应用不同α7 nAChRs激动剂（尼古丁、PNU 、S24795）激活星型胶质细胞α7 nAChRs能够有效的抑制Aβ的聚集。我们的研究进一步证实星型胶质细胞α7 nAChRs抑制A的聚集的效应可能与α7 nAChRs上调细胞内的钙调蛋白（CaM）和Cryab蛋白水平有关。基于上述结果，我们推测激活星形胶质细胞α7 nAChRs通过上调细胞内CaM和Cryab蛋白水平，从而抑制了Aβ的聚集。.其次，我们想确定哪些细胞内信号通路参与了星形胶质细胞α7 nAChRs抑制Aβ聚集的功能。我们的研究结果发现激活星形胶质细胞α7 nAChRs能够显著地上调PI3K-Akt信号通路的磷酸化水平，提示PI3K-Akt信号通路可能参与了α7 nAChRs抑制Aβ聚集的功能。我们进一步研究发现，阻断星型胶质细胞PI3K-Akt信号通路能够显著抑制α7 nAChRs激动剂（尼古丁、PNU 、S24795）对星型胶质细胞Cryab蛋白水平的上调作用；PI3K-Akt信号通路被阻断时，能够显著抑制α7 nAChRs激动剂（尼古丁、PNU 、S24795）促进星型胶质细胞降解Aβ聚集的作用。. 综上所述，尼古丁、PNU以及S24795通过激活星形胶质细胞α7 nAChRs上调内源性Cryab从而抑制Aβ集聚；PI3K/Akt信号通路可能是参与了星形胶质细胞α7 nAChRs上调内源性Cryab和而抑制Aβ集聚的重要生理功能。该项目研究结果为进一步研究Cryab蛋白可能是治疗AD的一个潜在靶点提供了一定的基础。