Mechanisms of neurodegeneration by a fibrinogen-containing protein complex during traumatic brain injury

项目摘要 该应用程序解决与血管认知障碍(VCI)相关的问题。特别是，它的目的是定义 血管-星形胶质细胞功能连接导致炎症后认知功能减退的机制 病理，例如创伤性脑损伤(TBI)。已知血管通透性增加参与了 神经血管网络的病理改变，如纤维蛋白原(Fg)和细胞Pron蛋白积聚 (PrPC)导致神经元功能障碍和变性。然而，引发这些影响的关键因素并不是 为人所知。我们的初步数据表明，脑损伤导致血液中纤维蛋白原水平升高，称为高纤维蛋白原血症。 (HFG)，并增加脑血管对蛋白质的通透性，主要是通过空泡穿胞作用。这一影响导致了 血管-星形胶质细胞界面FG沉积增加，FG和PrPC复合体形成增加，导致 在血管-星形胶质细胞中，物理解偶联和星形胶质细胞激活通过 神经营养酪氨酸受体蛋白B(TrkB)的过度表达与活性氧(ROS)的形成 这些效应与小鼠神经元变性和短时记忆(STM)减少有关 TBI。重要的是，用针对小凹病毒膜蛋白小窝蛋白-1(Cav-1)的siRNA治疗小鼠的情况有所改善 脑损伤引起的记忆减退。基于这些数据，我们提出了一个新的假说，即脑损伤介导的 炎症可增加血中Fg水平，Fg通过与内皮细胞ICAM-1结合激活空泡蛋白 跨细胞作用导致FG沉积增加，形成FG-PrPC复合体，从而导致星形胶质细胞 激活、血管-星形胶质细胞解偶联和随后的神经元变性(通过TrkB-ROS途径)导致 在STM减少方面。这一令人信服的假说提供了血管功能障碍和神经元之间的关键联系。 在各种脑血管病变中，变性导致认知功能障碍。目前的研究 应该揭示之前未知的血管-星形胶质细胞解偶联的基本机制(更改 功能和物理连接)导致脑损伤后神经元变性和记忆减退。这个 假说将以三个特定的目标进行检验：(1)定义HFG介导的空泡蛋白 颅脑损伤时，跨细胞作用可促进FG沉积和FG-PrPC复合体在脑血管外间隙形成。(2) 血管-星形胶质细胞界面FG-PrPC复合体的形成是否导致血管-星形胶质细胞 颅脑损伤时STM的解偶联和神经元变性导致STM减少。(3)确定小窝是否缩小 血管内皮细胞的形成和FG-PrPC复合体的形成可以改善神经元变性和STM 在TBI期间减少。颅脑损伤致血管-星形胶质细胞解偶联和记忆障碍的具体机制 即VCI，将使用培养的内皮细胞和星形胶质细胞以及C57BL/6J野生型和转基因HFG进行研究 老鼠。FG-PrPC复合体和ROS形成、TrkB水平、星形胶质细胞激活和神经元变性 Neun的评估将通过免疫组织化学和Western印迹进行评估。STM将由NOVICE进行评估 物体识别试验、巴恩斯迷宫和Y迷宫试验。

Project Summary This application addresses problems related to vascular cognition impairment (VCI). Particularly it aims to define mechanisms of vasculo-astrocyte functional connectivity that results in cognitive decline after inflammatory pathologies, e.g. traumatic brain injury (TBI). It is known that increased vascular permeability is involved in pathological alterations in neurovascular network such as accumulation of fibrinogen (Fg) and cellular prion protein (PrPC) leading to neuronal dysfunction and degeneration. However, critical factors that initiate these effects are not known. Our preliminary data indicated that TBI-induced an increase in blood level of Fg, called hyperfibrinogenemia (HFg), and enhanced cerebrovascular permeability to proteins mainly via caveolar transcytosis. This effect caused a greater deposition of Fg and increased formation of Fg and PrPC complex in vasculo-astrocyte interface, resulting in vasculo-astrocyte physical uncoupling and astrocyte activation leading to neuronal degeneration via overexpression of neurotrophic tyrosine receptor kinase B (TrkB) and formation of reactive oxygen species (ROS). These effects were associated with neuronal degeneration and reduction in short-term memory (STM) in mice after TBI. Importantly, treatment of mice with siRNA against caveolae membrane protein caveolin-1 (Cav-1) ameliorated TBI-induced memory reduction. Based on these data, we propose a novel hypothesis that TBI-mediated inflammation increases the blood level of Fg, which via binding to endothelial ICAM-1 activates caveolar protein transcytosis resulting in enhanced Fg deposition and formation of Fg-PrPC complex, which cause astrocyte activation, vasculo-astrocyte uncoupling and subsequent neuronal degeneration (via TrkB-ROS pathway) resulting in STM reduction. This compelling hypothesis provides the crucial link between vascular dysfunction and neuronal degeneration leading to cognition impairment during various cerebrovascular pathologies. The present study should reveal the fundamental, previously unknown mechanism for vasculo-astrocyte uncoupling (altered functional and physical connectivity) leading to neuronal degeneration and memory reduction after TBI. The hypothesis will be tested with three specific aims: (1) To define whether the HFg-mediated caveolar protein transcytosis enhances Fg deposition and Fg-PrPC complex formation in brain extravascular space during TBI. (2) To define whether the Fg-PrPC complex formation in vasculo-astrocyte interface causes vasculo-astrocyte uncoupling and neuronal degeneration leading to reduction in STM during TBI. (3) To define if diminishing caveolae formation in vascular endothelium and Fg-PrPC complex formation can ameliorate neuronal degeneration and STM reduction during TBI. Specific mechanisms of TBI-induced vasculo-astrocyte uncoupling and memory impairment, i.e. VCI, will be studied using cultured endothelial cells and astrocytes, and C57BL/6J wild type and transgenic HFg mice. Fg-PrPC complex and ROS formations, levels of TrkB, astrocyte activation, and neuronal degeneration assessed by NeuN will be evaluated by immunohistochemistry and Western blot. STM will be assessed by novel object recognition test, Barnes maze and Y-maze tests.