骨髓源性单核细胞募集联合GA疫苗治疗实验性阿尔兹海默病的研究

Classical Alzheimer's disease (AD) displays neuropathology that includes amyloid plaques formed by the amyloid β-protein (Aβ) and neurofibrillary tangles, which lead to neuronal and synaptic loss, and the progressive cognitive decline. Bone marrow-derived macrophages (MoBM), are involved in AD pathogenesis, but their precise contributions require elucidation. Recent studies in AD mice have shown that appropriate boosting of peripheral immune responses combined glatiramer acetate (GA) immunization has dramatic beneficial effects. The exact neuroprotective mechanisms of peripheral immunostimulation are not fully understood. One mechanism by which MoBM may eradicate pathological forms of Aβ is by phagocytosis and enzymatic degradation. In vitro preliminary data validated that MoBM increased the clearance of amyloid oligomers (XL-oAβ42) and fibrils (fAβ42). This proposal seeks to elucidate the functional roles of MoBM in removal of Aβ42 oligomers and fibrils, preservation of synapses and cognitive function. In the long term, this project may produce a novel therapeutic approach in which MoBM delivered to brain areas affected by AD remove toxic Aβ assemblies (oligomers and fibrils), thereby preventing disease progression. The studies in this grant will help establish whether the protective phenotype of MoBM is transferable by bone marrow transplantation or by adoptive transfer to the peripheral blood of pre-symptomatic and symptomatic mice. The results could be pivotal to potentially identify new therapeutic targets and modality in AD.

阿尔兹海默病(AD)的特征是β-淀粉样蛋白(Aβ)斑块沉积与神经纤维缠结所导致突触和神经元的大量丢失、以及认知功能的严重障碍。提高和改善记忆是治疗该病的基本策略，而外周骨髓源性单核细胞(MoBM)募集结合醋酸格拉替雷(GA)免疫联合治疗可能给实验性AD减少或清除脑内异常淀粉样斑块、营养和保护突触、改善和提高认知记忆等方面带来根本性的变化。初步的体外数据表明，MoBM可有效的吞噬Aβ寡聚体、保护神经元突触；另一方面，对AD模型动物的研究证实，募集的MoBM结合GA免疫疫苗的联合治疗，则显著提高树突棘数量，以及改善动物的记忆行为。本项目旨在综合应用在体与离体的研究策略，创建一个从形态到功能、从细胞到行为系统相结合的新颖实验平台，遵循“联合免疫调节－突触树突特征－记忆认知行为”的途径，揭阐述MoBM募集联合免疫治疗AD、清除淀粉斑块、拯救突触和改善记忆认知的作用及机制。

阿尔茨海默病(AD)认知能力下降的主要原因，是淀粉样蛋白β蛋白(Aβ42)寡聚体的积累而导致的突触完整性和功能受损。然而Aβ42寡聚体在突触毒性中的确切作用，以及外周先天免疫细胞拯救突触的能力仍然知之甚少。本项目研究了Aβ42纯寡聚体及原纤维对突触和巨噬细胞保护的影响。我们发现皮层神经元更容易受到Aβ42 寡聚体的影响，从而触发额外的神经元突起回缩、功能改变（过多活动和尖峰波形），以及兴奋性突触的丧失。原代小鼠皮质神经元与骨髓来源的巨噬细胞共培养，可保护突触免受 Aβ42 原纤维的侵害；此外，使用醋酸格拉替雷 (GA) 进行免疫激活可进一步保护针对Aβ42寡聚体的伤害。Aβ42原纤维通过巨噬细胞内CD36/EEA1+-早期内体蛋白水解清除，而寡聚体主要通过细胞外MMP-9 酶来降解。GA免疫实验治疗或CD115+-单核细胞移植的APPSWE/PS1E9转基因小鼠的体内研究，以及对内嗅皮层和海马亚结构的前突触和后突触分析，证实了我们对巨噬细胞介导的突触保存的体外研究结果。总之，被激活的巨噬细胞有效清除Aβ42寡聚体并拯救VGluT1/PSD95突触，为巨噬细胞治疗AD提供了良好的实验基础。