从Trem2介导小胶质细胞清除Aβ的角度探讨当归芍药散对阿尔兹海默病的作用机制

It’s widely accepted that β-amyloid protein (Aβ) is the key factor of Alzheimer’s disease (AD), clearance of Aβ is important to treatment of AD. Research has shown that regulating the microglial phenotypes to induce M2 phenotype could promote Aβ clearance by phagocytosis. In addition, Trem2 could up-regulate expression of some anti-inflammatory factors related to M2 phenotype. The pathogenesis of dementia in Chinese medicine was considered as deficiency in origin and excess in superficiality. Meanwhile, Danggui-Shaoyao-San (DSS) is capable of supplement insufficiency and reducing excessiveness. DSS was found to improve cognitive dysfunction of patients and model animals of AD. Our previous research found that DSS could reduce the content of Aβ in the brain of model mouse, and up-regulate the expression of Trem2 in BV2 cells. Therefore, we hypothesized that Trem2 could play a critical role in regulating the microglial phenotypes. And DSS could treat AD by promoting the capability of Aβ clearance and relieving the neuro-inflammation caused by Aβ which are basing on the microglial phenotypes transferring to M2 phenotype by up-regulating the expression of Trem2. Moreover, we will explore the pharmacological mechanism of DSS on AD treatment in vitro and vivo which is innovative on ideas and details and will prove the scientificity and reasonability of Traditional Chinese herbal compound prescriptions to some extent.

β淀粉样蛋白（Aβ）是阿尔兹海默病（AD）发生的核心病理因素，清除Aβ是治疗AD的重要途径。研究表明调控小胶质细胞活化状态，促进其向M2型转化，能够促进Aβ的吞噬清除，而Trem2能够上调M2型小胶质细胞相关的抗炎因子。痴呆病机为本虚标实，当归芍药散（DSS）具有补本虚、祛标实特点，研究发现DSS能改善AD患者和动物的认知功能。本项目前期研究发现DSS能减少AD动物脑内Aβ含量，并上调小鼠小胶质细胞上Trem2蛋白表达水平。故我们推测Trem2可能是调控小胶质细胞活化状态的关键因子，DSS可能通过上调Trem2表达，促进小胶质细胞活化状态向M2型转化，从而增强对Aβ的吞噬清除作用，同时减轻由Aβ导致的神经炎症反应，干预AD的发生发展。本项目拟在前期工作基础上，通过体内外实验，探讨DSS抗AD的药理作用机制，在研究思路和内容上均有创新性，为中药复方组方的科学性和合理性提供一定的实验依据。

研究背景：目前研究认为，清除β淀粉样蛋白（Aβ）是治疗阿尔兹海默病（AD）的重要途径，调控小胶质细胞活化状态向M2型转化，能够促进Aβ的吞噬清除，而Trem2能够上调M2型小胶质细胞相关的抗炎因子。我们前期研究表明当归芍药散（DSS）能够改善APP/PS1小鼠的学习记忆能力，减少小鼠脑内Aβ42的表达及淀粉样斑块的沉积，同时DSS含药血清能够上调BV2细胞上Trem2蛋白表达水平。故我们推测Trem2可能是调控小胶质细胞活化状态的关键因子，DSS可能通过上调Trem2表达，促进小胶质细胞向M2型转化，从而增强对Aβ的吞噬清除作用，同时减轻神经炎症反应，干预AD的发生发展。.研究内容：本研究证明了DSS改善APP/PS1小鼠学习记忆的能力。观察了Trem2对小胶质细胞功能活化状态及Aβ吞噬作用的影响；并应用APP/PS1 小鼠模型及BV2细胞模型，验证了DSS清除Aβ治疗AD的作用靶点。.研究结果：DSS改善了APP/PS1小鼠的学习记忆能力，促进小胶质细胞在Aβ斑块周围聚集，减少APP/PS1小鼠脑内Aβ含量并减轻Aβ斑块沉积。在体内及体外实验中，DSS均可上调Trem2蛋白及mRNA表达水平，促进M2型小胶质细胞标志物Arg1、IL-10的mRNA表达水平，抑制M1型小胶质细胞标志物iNOS、TNF-α的表达，并下调促炎因子（IL-1β、TNF-α、IL-6）的mRNA表达水平，减轻神经炎症反应。定向诱导BV2细胞后，M2型小胶质细胞中Trem2高表达；过表达Trem2可下调iNOS蛋白表达水平、同时上调Arg1蛋白表达水平。体外实验中，DSS含药血清可促进BV2细胞的增殖；Trem2基因沉默后，Arg1、IL-10的mRNA表达水平显著降低，同时BV2细胞对Aβ的吞噬清除作用减弱，而DSS含药血清干预后可改善BV2细胞对Aβ的清除作用。 .结论及意义：Trem2可能是调控小胶质细胞活化状态进而促进Aβ吞噬清除的关键因子。DSS可能是通过上调Trem2的表达，促进小胶质细胞活化状态向M2型转变，从而增强了小胶质细胞对Aβ的吞噬清除作用，同时减轻由Aβ导致的神经炎症反应，最终起到积极干预AD的作用。为传统中药复方组方的科学性和合理性提供新的实验依据，并为治疗AD药物的研发提供新的思路。