基于Aβ靶点的抗阿尔茨海默症——天然玉蕊醇型三萜的发现及作用机制研究

Alzheimer's disease was probably caused by multiple reason, but the same characteristic of pathology suggest that the different cause of disease has the similar mechanism of action which all related with Aβ peptides, the main constituent of amyloid plaques, and Aβ peptides were considered to be the key link in the development and progress of AD. Therefor, it has important meaning and bright perspective to find effective medicine to cure AD based on Aβ target. Aβ25-35 was the main active fragment of Aβ and its toxic effect had been certified by a great quantity of study.In previous research, barrigenol triterpene had notable activities on improving the learning and memory ability of mice with Alzheimer's disease induced by Aβ25-35. Based on this, the current study was designed to searching Aβ deposition and neurotoxicity inhibitor from plant of sapindace in barrigenol triterpene of AD cell model induced by Aβ25-35 on PC-12 and SH-SY5Y, and established the structure-activity relationship between hydroxyl groups, acyl groups and sugar substitution of barrigenol triterpene with activities of improving the learning and memory ability. Our study will provide strong evidence and new thread and method to find more active and specific anti-Alzheimer's disease agents.

阿尔茨海默症（AD）是一种多病因的疾病，但相同的病理特点提示不同病因具有相似的作用机制，这些机制都与Aβ有关，认为Aβ是AD发生、发展的中心环节。因此以Aβ为切入点，寻找有效的防治AD的药物有着重要的意义和光明的前景。Aβ25-35是Aβ的主要活性片段，其毒性作用已被大量研究所证实。前期工作中发现，玉蕊醇型三萜类化合物对Aβ25-35所致小鼠学习记忆障碍有显著改善作用。本课题通过对含有玉蕊醇型三萜的无患子科植物进行系统分离和结构鉴定，采用Aβ25-35作用于PC12和SH-SY5Y细胞，构建有效、合理、快速的AD细胞模型，对以Aβ为靶点的玉蕊醇型三萜进行抑制Aβ聚集或神经毒性研究，并初步提出相关分子作用机制。继而建立玉蕊醇型三萜类化合物羟基、酰基或糖取代等模式与改善学习记忆活性的构效关系，为发现活性更高、特异性更强的抗阿尔茨海默症药物提供新的思路、方法和理论依据。

阿尔茨海默症（AD）是一种多病因的疾病，但相同的病理特点提示不同病因具有相似的作用机制，这些机制都与Aβ有关，认为Aβ是AD发生、发展的中心环节。因此以Aβ为切入点，寻找有效的防治AD的药物有着重要的意义和光明的前景。我们前期工作中发现，玉蕊醇型三萜类化合物对Aβ25-35所致小鼠学习记忆障碍有显著改善作用。本课题在前期研究基础上，采用活性筛选的方法对富含有玉蕊醇型三萜的无患子科植物文冠果活性部位进行系统分离和结构鉴定，从中分离得到24个玉蕊醇型三萜类成分，其中3个为未见文献报道的新化合物。采用H2O2和Aβ25-35作用于SH-SY5Y细胞，建立神经细胞损伤模型进行快速的体外活性筛选，以此构建了玉蕊醇型三萜类化合物羟基、酰基或糖取代等模式与神经保护作用的构效关系，结果表明，16-deoxybarringtogenol C型玉蕊醇型三萜对神经损伤的保护作用显著强于R1-barrigenol 型玉蕊醇型三萜。对于16- deoxybarringtogenol C型玉蕊醇型三萜随着连糖数量增多和糖上当归酰基的取代，活性增强。采用Y迷宫、新物体辨别、Morris水迷宫和被动回避实验进一步对活性较强的单体类成分XS-1, XS-6, XS-7和XS-8进行Aβ1-42诱导的AD模型小鼠学习记忆障碍改善作用研究。结果表明四种单体成分均具有改善AD小鼠学习记忆障碍的作用，其中XS-8活性最强，药效高于阳性对照药多奈哌齐。对其分子作用机制进行初步地探讨显示，XS-8可能是通过抑制Aβ过度激活小胶质细胞，进而抑制炎症因子释放，对抗氧化应激损伤，最终发挥神经保护作用，改善Aβ致痴呆小鼠学习记忆障碍。玉蕊醇型三萜XS-8有望成为潜在的抗阿尔茨海默症候选药物。本项目对玉蕊醇型三萜抗阿尔茨海默症的研究，为发现活性更高、特异性更强的抗阿尔茨海默症候选药物提供新的思路、基础和理论依据。