GDNF对阿尔茨海默病小胶质细胞的活性调控及抗炎机制研究

Alzheimer's disease (AD) is the most common progressive neurodegenerative disease and a leading cause of dementia in the elderly. Neuroinflammation resulting from activation of microglia stimulated by abnormal deposition of β-amyloid is the core pathological mechanism of AD. Activated microglia plays a pivotal role in the inflammatory response in AD and is a potential treatment target. It is critical for inhibiting AD progression to attenuate the neuroinflammtion and improve the phagocytosis by regluating microglial activation. It is reported that astroglia play a negative regulatory role in acute and chronic neuroinflammation mediated by microglia. However, the association between astroglia and microglia in AD is still unclear. Moreover, our co-culture of astroglia with microglia has resulted in inhibiting the release of inflammatory mediators in AD model. And the mechanism of astroglial effect on micrglia-mediated neuroinflammation in AD should be elucidated. Astrocytes have similar traits with enteric glial cells. Our previous studies have confirmed that GDNF from enteric glial cells could inhibit the intestinal inflammation. According to our previous studiers and other reports, we hypothesize that astroytes-derived GDNF may regulate the microglial activity and inhibit the neuroinflammation in AD. This study aims to explore the effect of GDNF on anti-inflammation and increasing microglial phagocytosis in vitro and in vivo, and detect the anti-inflammatory pathways for further mechanism. And GDNF is expected to become a novel drug for AD.

调控小胶质细胞活性，以抑制其介导的过度炎症反应和增加其吞噬Aβ蛋白的能力，是治疗阿尔茨海默病（AD）的关键环节。在小胶质细胞介导的神经系统急性和慢性炎症中，星形胶质细胞起负调控作用，但AD中这两种细胞之间的联系尚不清楚。为此，我们将两者共培养，发现AD中星形胶质细胞能抑制小胶质细胞释放炎性介质，但星形胶质细胞发挥此效应的机制有待阐明。星形胶质细胞与肠胶质细胞的结构和功能相似，我们前期发现肠胶质细胞分泌的胶质细胞源性神经营养因子（GDNF）可减少炎症介质的释放，抑制肠道炎症反应。我们推测星形胶质细胞通过分泌GDNF调控小胶质细胞活性，补充GDNF可抑制AD炎症反应。本研究拟从体外、体内探讨GDNF对AD模型炎症反应及小胶质细胞吞噬功能的影响，并通过高通量分析技术寻找GDNF调控AD中小胶质细胞介导的炎症反应的关键信号通路。为AD发病机制的研究提供思路，为以GDNF为靶点的新药研发提供依据。

阿尔茨海默病（AD）是与增龄密切相关的神经退行性疾病。虽然AD发病机制尚未完全清楚，但神经炎症是学界公认的AD核心病理机制，有效调节神经炎症反应是治疗AD的关键环节。在AD神经炎症反应中，小胶质细胞扮演重要角色，调控小胶质细胞活性从而抑制其介导的过度炎症反应可能阻滞AD病情进展。本项目1）基于mRNA转录组测序分析技术，成功寻找到Hippo/YAP信号通路在AD模型炎症反应中发挥作用。在Aβ诱导的BV2小胶质细胞/原代小胶质细胞的炎症反应中，YAP的激动剂和抑制剂分别可以降低和增加促炎症因子 (TNFα、IL1b和IL12b)的表达。同时，YAP基因过表达和RNA干扰分别降低和增加了Aβ诱导的BV2细胞促炎症因子的表达。我们的研究表明，Hippo/YAP（传统观点认为其与细胞生长和器官再生相关）是小胶质细胞介导AD炎症反应的关键信号通路。同时我们还将使用小胶质细胞YAP基因特异性敲除小鼠进行体内机制的深入研究。2）近年研究发现星形胶质细胞分泌的GDNF可以下调小胶质细胞介导的多种急性和慢性炎症。本项目使用GDNF干预Aβ激活的BV2小胶质细胞，发现促炎症因子表达下降，且与GDNF呈剂量依赖性；而在YAP基因干扰的BV2小胶质细胞中，GDNF干预效果不明显。我们上述研究从细胞层面表明，GDNF通过Hippo/YAP信号通路下调小胶质细胞的炎性反应。3）我们成功构建了GDNF腺病毒载体，研究GDNF对APP/PS1 AD转基因小鼠的行为学及分子生物学等方面的影响，结果表明了GDNF可以降低AD转基因小鼠脑组织的炎性因子表达，改善其认知能力。本项目成功发现小胶质细胞介导AD炎症反应的一条关键信号通路（Hippo/YAP），为GDNF治疗AD提供了新思路，具有良好的临床转化前景。