以HRD1为靶点研究淫羊藿苷抗阿尔茨海默病的作用

Pathogenesis of Alzheimer’s disease (AD) is still fully unknown, and the ideal treatment drugs for AD are unavailable yet. Recently, it is found that endoplasmic reticulum associated degradation (ERAD) is involved in the pathogenesis of AD. The unfolded amyloid precursor protein (APP) in brain is degraded by ERAD pathway, resulting in decreased generation of β-amyloid (Aβ). Among of them, HRD1 is the key ubiquitin ligase in the ERAD pathway. Deficit of HRD1-mediated ERAD in cerebral cortex maybe leads to AD pathogenesis. Our previous research has demonstrated that icariin suppresses neuronal apoptosis through promoting the expression of HRD1, but the underlying mechanisms are still unknown. Therefore, this project is designed to investigate the effect of icariin on learning and memory function of APP/PS1 mice and APP-Aβ pathway in brain, and analyze the correlation between the abovementioned effect and HRD1 level. Meanwhile, injured neuron models insulted by the endogenous and exogenous oxidative stressors are applied to investigate the effect of icariin on oxidative stress by regulating HRD1 expression. Injured neuron models induced by Aβ or siRNA-Hrd1 are applied to investigate the effect of HRD1 on both APP and Aβ contents, as well as the intervention effect of icariin on them. This project is aimed to provide the theoretical evidence for AD treatment with icariin, and lay the foundation for the new strategies to AD treatment based on regulating ERAD pathway.

阿尔茨海默病(AD)的发病机制未完全明了，且无理想的治疗药物。近年来发现内质网关联降解(ERAD)参与AD发病，脑中未折叠的淀粉样前体蛋白(APP)经ERAD途经降解，从而使Aβ产生减少，其中HRD1是该途经关键的泛素连接酶。大脑皮层如果缺乏HRD1-ERAD途经则可导致AD发病。前期研究发现淫羊藿苷通过促进HRD1表达抑制神经元凋亡，但机制不清。因此，本项目首先观察淫羊藿苷对APP/PS1转基因小鼠学习记忆功能及大脑组织APP-Aβ途经的影响，并分析该作用与脑内HRD1含量的关系；同时，采用内源性和外源性氧化应激因子诱导神经元损伤模型，研究淫羊藿苷调节HRD1表达发挥抗氧化应激损伤的作用；以Aβ及siRNA-Hrd1所致神经元损伤模型，观察HRD1对APP和Aβ量的影响以及淫羊藿苷的干预作用。本项目旨在为淫羊藿苷用于AD治疗提供理论依据，并为基于调节ERAD通路的AD治疗新策略奠定基础。

阿尔茨海默病（AD）的发病机制未完全明了，且无理想的治疗药物。内质网应激及内质网关联降解（ERAD）参与AD发病，HRD1是该途经关键的E3泛素连接酶。大脑若缺乏HRD1-ERAD途经则可导致AD发病。前期研究发现淫羊藿苷通过促进HRD1表达抑制神经元凋亡，但机制不清。本项目首先采用APP/PS1转基因小鼠观察淫羊藿苷的效应指标并分析机制；再通过氧化应激因子诱导神经元损伤模型，观察淫羊藿苷抗氧化应激损伤的作用及机制；进而通过基因操作手段观察淫羊藿苷对HRD1及其互作蛋白的影响。本研究结果表明淫羊藿苷明显改善APP/PS1小鼠学习记忆能力，抑制APP-Aβ的剪切途径，通过ERAD途径增加APP的降解；整体动物及细胞实验结果均提示淫羊藿苷通过抑制PERK/eIF2α信号通路，减轻内质网应激的发生；在蛋白互作实验中发现，HRD1与NF-κB p65结合，而NF-κB p65又与去泛素化酶（USP22）结合。在LPS诱导的炎症过程中，淫羊藿苷提高USP22的表达水平，减少细胞核内NF-κB p65的含量，从而降低炎症因子IL-6的含量及基因表达水平。综上所述，淫羊藿苷抗AD的作用机制涉及到以下方面：抑制APP-Aβ剪切途径，增加APP的降解，抑制内质网应激的PERK/eIF2α信号通路，通过抑制NF-κB p65的核转位而减轻炎症反应。因而，本研究为淫羊藿苷用于AD的防治提供了理论依据。