CNS Exosomes-Mediated Adaptive Immunity in Alzheimer's Disease (AD)

摘要 阿尔茨海默病(AD)仍然是我们社会中最未得到满足的医学挑战之一。在公元后， 此外，神经炎症在AD的发病机制中起着核心作用，这一点已被越来越多地认识到 细胞外淀粉样斑块和过度磷酸化的tau基神经原纤维缠结。虽然这一角色 先天免疫，特别是以小胶质细胞为代表的先天免疫在AD中得到了很好的确立，但对它的了解还远远不够 确定T或B细胞介导的获得性免疫是否以及如何参与AD的发病。 尤其是，是否存在大脑和AD特异性抗原来激活适应性免疫，以及这些抗原是如何 抗原向外周传播的情况仍有待研究。外体(大小40-100 nm)，一种主要的分泌型 细胞外小泡(EV)是从早期向内萌发的腔内小泡(ILV)衍生而来的 在成熟过程中从多个囊泡小体(MVB)释放 内噬菌体。由各种类型的中枢神经系统细胞分泌的EVS和Exosome已经成为一种新的和重要的 细胞间途径在细胞内。外切体介导的分泌也与起始和繁殖有关。 在公元后。虽然外周细胞分泌的外周小体类型特别是免疫和肿瘤细胞会触发 免疫反应、中枢神经系统来源的外切体是否具有免疫原性以及如何具有免疫原性仍未被探索。 通过使用我们最近培育的细胞型特异性ILV/Exosome Report(hCD63-GFPf/f)小鼠，我们 研究表明，星形胶质细胞来源的外切体与水通道蛋白4+(Aqp4+)血管周围终末足/血相关 大脑中的血管。在注射内毒素的血清中也可检测到hCD63-GFP+星形胶质细胞外切体(BUT 非对照组)Glast-Creer+CD63-GFP/+小鼠。令人兴奋的是，外周小体由“反应性”星形胶质细胞(RAE)分泌 在体外和体内都能强烈激活CD4+和CD8+T细胞。基于之前的研究和我们的初步研究 结果：我们提出了以下研究目标：1)确定CNS细胞类型特异性的病理性外排 阿尔茨海默病模型脑外周体及其进入外周循环的研究2)测定AD的抗原性 相关星形胶质外体在体内外激活T细胞中的作用。我们已经产生了大量的 初步数据支持我们的理由，并证明拟议目标的可行性。我们将聘用 小鼠遗传学，病毒注射，免疫组织化学(IHC)分析和体内双光子成像，初级 培养、流式细胞仪和生化方法来研究这两个目的。这个项目的结果将是 测定神经元或星形胶质细胞外切体从脑中排出的变化以及这些外切体进入大脑的情况。 阿尔茨海默病模型的外周循环。此外，我们目前的研究还将调查T细胞如何对“反应性”做出反应 星形胶质外切体。由于反应性星形胶质细胞在包括AD在内的神经退行性疾病中常见， 这将可能揭示T细胞如何参与AD发病的新机制，并有助于确定特定的 脑信号在AD中激活T细胞，从而促进治疗的发展。

Abstract Alzheimer’s disease (AD) remains one of the most unmet medical challenges in our society. In the AD, neuroinflammation has been increasingly recognized to play a central role in the pathogenesis of AD, in addition to extracellular amyloid plaques and hyperphosphorylated tau based neurofibrillary tangles. Although the role of innate immunity especially represented by microglia is well-established in AD, it is far less understood and established about whether and how the T or B cell-mediated adaptive immunity is involved in AD pathogenesis. In particular, whether there are brain- and AD-specific antigens to activate adaptive immunity and how these antigens travel to peripheral remain to be investigated. Exosomes (size 40-100 nm), a major type of secreted extracellular vesicles (EVs), are derived from intraluminal vesicles (ILV) that are budded inwardly from the early endosomal compartment and are released from multiple vesicular bodies (MVB) during the maturation of endosomes. EVs and exosomes secreted from various CNS cell types have emerged as a novel and important intercellular pathway in the. Exosome-mediated secretion has also been implicated in initiation and propagation in AD. Although exosomes secreted from various peripheral cell types especially immune and tumor cells trigger immune responses, whether and how CNS-derived exosomes are immunogenic remains unexplored. By employing cell-type specific ILV/exosome reporter (hCD63-GFPf/f) mice we recently generated, we showed that astroglia-derived exosomes are associated with Aquaporin 4+ (Aqp4+) perivascular end feet/blood vessel in the brain. hCD63-GFP+ astroglial exosomes can also be detected in blood serum of LPS-injected (but not control) Glast-CreER+CD63-GFPf/+ mice. Excitingly, exosomes secreted from “reactive” astroglia (RAEs) strongly activate CD4+ and CD8+ T cells in vitro and in vivo. Based on previous studies and our preliminary results, we propose to investigate the following aims: 1) Determine pathological efflux of CNS cell-type specific exosomes from brain and their entry into peripheral circulation in AD models; 2) Determine antigenicity of AD- relevant astroglial exosomes in activating T cells in vitro and in vivo. We have generated a large amount of preliminary data to support our rationales and to demonstrate feasibility for proposed aims. We will employ mouse genetics, virus injections, immunohistochemical (IHC) analysis and in vivo two-photon imaging, primary cultures, FACS, and biochemical approaches to investigate these two aims. Results from this project will determine the efflux changes of neuron or astroglial exosomes from the brain and these exosomes’ entry into peripheral circulation in AD models. In addition, our current study will investigate how T cells respond to “reactive” astroglial exosomes. As reactive astroglia is commonly observed in neurodegenerative diseases including AD, this will potentially unveil new mechanisms how T cells are involved in AD pathogenesis and help define specific brain signals to activate T cells in AD, which subsequently facilitate the therapeutic development.