Does Microglial Activation Influence Propagation of Alpha-synuclein Pathology

 描述（由申请方提供）：α-突触核蛋白（α-syn）聚集体的神经元间传播被认为有助于帕金森病（PD）的发病机制，并构成α-syn神经病理学常规进展模式的基础。这一假设表明，聚集的α-syn从一个神经元转移到另一个神经元，在那里它播种了进一步的α-syn聚集。然而，目前尚不清楚小胶质细胞如何影响这一过程，以及炎症时发生的特定小胶质细胞激活状态如何影响α-syn转移。为了填补这一空白，我们开发了一种独特的小鼠模型，使我们能够监测神经元之间的α-syn朊病毒样传播。我们的体内范例涉及将胚胎中脑神经元移植到过表达人α- syn的小鼠纹状体中，并允许操纵小胶质细胞（即消融或特异性激活）。在这个新模型中， 在移植的小鼠细胞（最初没有人α-syn）内的人α-syn的量用作α-syn转移的读出。基于我们的初步数据，我们假设在正常条件下，小胶质细胞从细胞外空间摄取α-syn，导致神经元之间的α-syn转移减少。我们还假设脂多糖处理后α-syn在小胶质细胞中积累，因为脂多糖激活的小胶质细胞具有降低的蛋白水解能力，而白细胞介素4诱导的小胶质细胞有效地减少细胞外α-syn的池，从而减轻α-syn从神经元到神经元的转移。将追求两个具体目标来检验该假设：1）确定小胶质细胞的缺乏如何影响α-syn的神经元至神经元转移;和2）确定脂多糖诱导的与白细胞介素4诱导的活化小胶质细胞的存在如何影响α-syn的神经元至神经元转移速率。首先，我们将使用我们独特的细胞间转移体内模型监测小胶质细胞的缺失是否导致不同程度的α-syn细胞间转移。其次，我们将评估在不同小胶质细胞表型的背景下α-syn向移植神经元的转移，脂多糖或白细胞介素4注射将用于刺激这些差异表型。我们的方法是创新的，因为它允许我们评估两个因素（炎症和α-syn传播）之间的相互作用，这两个因素都被认为在单个动物模型中的PD发病机制中起关键作用，我们可以使用无偏的，自动化的和定量的神经病理学指标来定义结果。我们预测，小胶质细胞的缺乏将转化为α-syn的神经元-神经元转移的增加，并且小胶质细胞活化的性质将影响小胶质细胞内α-syn的积累。最终，拟议的研究将产生一种创新和有效的α-syn病理传播模型，有可能促进基于调节炎症治疗的疾病修饰疗法的开发。

 DESCRIPTION (provided by applicant): Neuron-to-neuron propagation of α-synuclein (α-syn) aggregates is thought to contribute to the pathogenesis of Parkinson's disease (PD) and underlie the stereotypical progression pattern of α-syn neuropathology. This postulate suggests that aggregated α-syn transfers from one neuron to another where it seeds further α-syn aggregation. However, it is not known how microglia influence this process, and how specific microglia activation states that occur upon inflammation affect α-syn transfer. To fill this gap i knowledge we developed a unique mouse model that allows us to monitor α-syn prion-like propagation between neurons. Our in vivo paradigm involves transplantation of embryonic midbrain neurons into the striatum of a mouse overexpressing human α- syn and allows the manipulation of microglia (i.e. ablation or specific activation). In this novel model, the presence of human α-syn within the grafted mouse cells (initially devoid of human α-syn) is used as a read-out for α-syn transfer. Based on our preliminary data we hypothesize that under normal conditions, microglia take up α-syn from the extracellular space, resulting in reduced α-syn transfer from neuron to neuron. We also hypothesize that α-syn accumulates in microglia following lipopolysaccharide treatment, as lipopolysaccharide -activated microglia have reduced proteolytic capacity whereas Interleukin 4-induced microglia effectively reduce the pool of extracellular α-syn, and thereby mitigate α-syn transfer from neuron to neuron. Two specific aims will be pursued to test this hypothesis: 1) Determine how the absence of microglia affects neuron-to-neuron transfer of α-syn; and 2) Determine how the presence of lipopolysaccharide-induced vs Interleukin 4-induced activated microglia affects the rate of neuron-to-neuron transfer of α-syn. First, we will monitor if the absence of microglia results in a different degre of α-syn cell-to-cell transfer using our unique in vivo model of cell-to-cell transfer. Second, we wil assess the transfer of α-syn into grafted neurons in the context of distinct microglial phenotypes lipopolysaccharide or Interleukin 4 injection will be used to stimulate these differential phenotypes. Our approach is innovative because it allows us to assess the interaction between two factors (inflammation and α-syn propagation) both considered to play key roles in PD pathogenesis in a single animal model, and we can define outcomes using unbiased, automated and quantitative measures of neuropathology. We predict that the absence of microglia will translate to increased neuron-to-neuron transfer of α-syn and that the nature of microglial activation will affect the accumulation of α-syn within microglia. Ultimately, the proposed research will result in an innovative and valid model of α-syn pathology propagation with the potential to facilitate the development of disease-modifying therapies based on treatments that modulate inflammation.