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

项目摘要 本申请解决了与血管性认知障碍（VCI）相关的问题。特别是，它旨在定义 炎症后导致认知能力下降的血管-星形胶质细胞功能连接机制 病理学，例如创伤性脑损伤（TBI）。已知增加的血管渗透性涉及 神经血管网络的病理改变，如纤维蛋白原（Fg）和细胞朊蛋白的积累 （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 知道的我们的初步数据表明，TBI诱导血液中纤维蛋白原水平的增加，称为高纤维蛋白原血症 (HFg)主要通过胞吞作用增强脑血管对蛋白质的通透性。这种影响导致 血管-星形胶质细胞界面Fg沉积增加，Fg和PrPC复合物形成增加， 在血管-星形胶质细胞物理解偶联和星形胶质细胞活化中， 神经营养酪氨酸受体激酶B（Trk B）的过表达和活性氧（ROS）的形成。 这些效应与神经元变性和短期记忆（STM）的减少有关。 创伤性脑损伤重要的是，用针对小窝膜蛋白caveolin-1（Cav-1）的siRNA治疗小鼠， 创伤性脑损伤导致的记忆减退。基于这些数据，我们提出了一个新的假设，即TBI介导的 炎症增加Fg的血液水平，Fg通过与内皮细胞ICAM-1结合激活小窝蛋白 转胞吞作用导致Fg沉积和Fg-PrPC复合物的形成增强，这导致星形胶质细胞 活化、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）， 在STM减少。这一令人信服的假设提供了血管功能障碍和神经元损伤之间的关键联系。 在各种脑血管病理过程中导致认知障碍的变性。本研究 应该揭示基本的，以前未知的机制，血管星形胶质细胞解偶联（改变 功能和物理连接），导致TBI后神经元变性和记忆力下降。的 我们将以三个特定的目标来检验这一假设：（1）确定HFg介导的小窝蛋白是否 转胞吞作用增强TBI期间脑血管外空间中Fg沉积和Fg-PrPC复合物形成。（二） 明确血管-星形胶质细胞界面Fg-PrPC复合物的形成是否会导致血管-星形胶质细胞 解偶联和神经元变性导致TBI期间STM减少。(3)为了确定减少的小凹是否 Fg-PrPC复合物的形成可改善神经元变性和STM TBI期间减少。TBI诱导的血管-星形胶质细胞解偶联和记忆障碍的具体机制， 即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来研究VCI 小鼠Fg-PrPC复合物和ROS形成、TrkB水平、星形胶质细胞活化和神经元变性 将通过免疫组织化学和蛋白质印迹来评价通过NeuN评估的细胞。STM将通过小说进行评估 物体识别测试、巴恩斯迷宫和Y-迷宫测试。

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.