LXRβ经SIRT1去乙酰化调控阿尔茨海默病转基因小鼠海马神经发生的作用与机制研究

Abnormal neurogenesis induced by depletion of f radial glia like cells (RGLs) in the dentate gyrus of hippocampus is considered to be a key factor related to dysfunction of learning and memory in the Alzheimer's disease (AD).Our previous study has demonstrated that loss of LXRβ inhibited adult hippocampus neurogenesis, whereas the number of RGLs in the dentate gyrus was increased in the AD mice pretreatment with LXR　agonist.These indicate that LXRβ is propbably involved in the maintaining the number of RGLs in the hippocampal dentate gyrus of AD mice, and thereby contributed to continuous hippocampus neurogenesis.Whether the modulating roles of LXRβ in the RGLs maintaining and continuous neurogenesis are related to the balance of resting and activation of RGLs , and the underlying mechanism has not been well explored.In the present study, the modulating roles of LXRβ involved in the the balance of resting and activation of RGLs in the AD mice hippocampus will be investigated with LXRβ knockout and AD double transgenic mice.SIRT1 lentivirus infection will be used to detect the effect of LXRβ deacetylation on the modulation of hippocampus neurogenesis and RGLs maintaing in the AD mice. A chromatin precipitation will be used to detect LXRβ modulation the Hes1 and Ngn2 transcription regulation of SIRT1 downstream. The effect of LXRβ deacetylation on the expression of P27 Kip1 and Ngn2 will be detected in the cultured hippcampal neural stem cell . It will clarify the underlying mechanism of LXRβ in the regulation of continued adult hippocampal neurogenesis in the AD mice, and therefore provide a theoretical basis for self-repair strategy to treat AD.

成年海马齿回放射状胶质细胞样（RGLs）神经干细胞耗竭而导致的异常神经发生是阿尔茨海默病（AD）学习记忆功能受损的关键因素。我们前期研究发现LXRβ敲除抑制海马神经发生，LXR激动剂持续增加AD小鼠海马齿回RGLs的数量，提示LXRβ具有维持AD小鼠海马内RGLs数量，促进海马持续神经发生的作用，这一作用是否通过有效调控RGLs激活与静息之间的平衡而实现，其分子机制如何？目前尚不清楚。本课题采用LXRβ敲除与双转基因AD小鼠杂交，分析LXRβ对AD小鼠海马齿回RGLs激活与静息之间平衡的调控。SIRT1慢病毒感染检测LXRβ去乙酰化对AD小鼠海马神经发生及RGLs维持的调控；采用染色质免疫沉淀技术检测LXRβ对SIRT1下游Hes1与Ngn2的转录调节及LXRβ去乙酰化对P27（Kip1） 和Ngn2的调节，阐明LXRβ调控AD小鼠海马持续神经发生的机制，为自修复策略治疗AD提供理论依据。

成年海马齿回放射状胶质细胞样（RGLs）神经干细胞耗竭而导致的异常神经发生是阿尔茨海默病（AD）学习记忆功能受损的关键因素。肝脏X受体β（ LXRβ）调控齿回放射状胶质细胞（RGC）的发育与分化，是决定生后与成年海马神经发生的重要核转录因子，而其对RGC的调控机制目前仍不清楚。本研究旨在分析LXRβ调控RGC分化与Sirt1通路的相关性，明确LXRβ调控RGC分化及海马神经发生的主要途径，阐明内源性LXRβ激活促进AD转基因小鼠海马齿回神经发生的机制。我们发现与野生型小鼠相比较， LXRβ 基因敲除小鼠在海马齿回发育的关键期内RGC的形成、增殖及分化为齿回颗粒神经元均受到显著抑制，并导致生后及成年海马齿回神经发生的抑制。离体实验显示LXR激动剂激活内源性LXRβ内源性LXRβ，促进RGC的增殖及向神经元方向分化，并抑制其向星形胶质细胞分化。LXR激动剂处理AD小鼠一周，则可观察到内源性LXRβ激活促进RGC的维持和分化，进而促进AD转基因小鼠海马齿回神经发生。与此同时，采用白藜芦醇处理成年小鼠，通过激活Sirt1亦可明显促进新生及成年海马齿回神经发生；LPS处理小鼠导致海马齿回神经发生受到抑制，而白藜芦醇则翻转这一效应。对分裂模式进一步进行分析显示激活Sirt1通过影响RGC中Hes1通路而介导RGC的维持，并通过促进对称分裂模式而调节RGC在静息与激活之间的平衡；从而维持成年海马齿回干细胞的数量，确保持续海马神经发生。在LXRβ 基因敲除小鼠海马中亦检测到Notch1/Hes1信号通路的下调，Notch1阻断剂可拮抗LXR激动剂对海马神经发生的促进效应；提示LXRβ与Sirt1通过Notch1/Hes1信号通路的调节；而参与AD小鼠中海马神经发生的促进作用。研究结果对理解RGC在AD小鼠海马神经发生中的作用以及LXRβ 通过对RGC的调节作用而促进海马齿回神经发生的的分子机制和信号转导途径提供新的证据，为AD治疗提供新的实验依据。