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

创伤性脑损伤期间含纤维蛋白原的蛋白质复合物引起神经退行性变的机制

• 批准号: 10027325
• 负责人: DAVID LOMINADZE
• 金额: $ 33.86万
• 依托单位: UNIVERSITY OF SOUTH FLORIDA
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-05-01 至 2023-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10027325
• 关键词: Mechanisms; neurodegeneration; fibrinogen; containing; protein

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.

项目概要 该应用程序解决了与血管认知障碍（VCI）相关的问题。它特别旨在定义 血管星形胶质细胞功能连接导致炎症后认知能力下降的机制 病理学，例如创伤性脑损伤（TBI）。众所周知，血管通透性增加与 神经血管网络的病理改变，例如纤维蛋白原 (Fg) 和细胞朊病毒蛋白的积累 (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 已知。我们的初步数据表明，TBI 会导致血液中 Fg 水平升高，称为高纤维蛋白原血症 (HFg)，并主要通过小凹转胞吞作用增强脑血管对蛋白质的通透性。这种效应造成了 血管-星形胶质细胞界面中 Fg 的沉积量增加，Fg 和 PrPC 复合物的形成增加，从而导致 在血管星形胶质细胞中，物理解偶联和星形胶质细胞激活导致神经元变性 神经营养性酪氨酸受体激酶 B (TrkB) 的过度表达和活性氧 (ROS) 的形成。 这些影响与小鼠的神经元变性和短期记忆（STM）减少有关。 创伤性脑损伤。重要的是，用针对小凹膜蛋白 Caveolin-1 (Cav-1) 的 siRNA 治疗小鼠，病情得到改善 TBI 引起的记忆力减退。基于这些数据，我们提出了一个新的假设，即 TBI 介导的 炎症会增加 Fg 的血液水平，Fg 通过与内皮 ICAM-1 结合激活小凹蛋白 转胞吞作用导致 Fg 沉积增强并形成 Fg-PrPC 复合物，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） 减少STM。这一令人信服的假设提供了血管功能障碍和神经元之间的关键联系 退化导致各种脑血管病理期间的认知障碍。目前的研究 应该揭示血管星形胶质细胞解偶联的基本的、以前未知的机制（改变 功能和物理连接）导致 TBI 后神经元退化和记忆力下降。这 假设将通过三个具体目标进行检验：（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。 (2) 确定血管-星形胶质细胞界面中 Fg-PrPC 复合物的形成是否导致血管-星形胶质细胞 解偶联和神经元变性导致 TBI 期间 STM 减少。 (3) 定义是否减少小窝 血管内皮细胞的形成和 Fg-PrPC 复合物的形成可以改善神经元变性和 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 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 复合物和 ROS 形成、TrkB 水平、星形胶质细胞激活和神经元变性 NeuN 评估的结果将通过免疫组织化学和蛋白质印迹进行评估。 STM将通过小说进行评估 物体识别测试、Barnes 迷宫和 Y 迷宫测试。