Overexpression of Complement in the Brain and HIV Neuropathogenesis

描述（由申请人提供）：在多种神经退行性疾病中，补体成分在脑中升高，但其对神经发病机制的作用尚不清楚。最近的研究表明，C1 q和C3参与发育过程中的突触重塑，并介导疾病过程中某些特定形式的突触损伤。与这些发现一致，我们已经证明：a）在HIV-1相关痴呆期间，大脑中的C3升高; B）在感染嵌合HIV-1的小鼠中; c）在暴露于HIV-1的原代人类和小鼠星形胶质细胞中培养。我们的初步数据还表明，HIV-1诱导C3在星形胶质细胞间接通过NF-：B依赖性途径，与白细胞介素6（IL-6）的生产。基于在正常脑发育过程中突触重塑需要C3的发现，我们假设在HIV感染期间脑中C3过表达启动异位突触重塑和神经发病机制。在本申请中，我们提出了探索性研究，以测试这一假设在两个特定的目的：1。我们将确定完整的HIV-1和达特在星形胶质细胞中诱导C3的机制，重点是HIV-1诱导的IL-6作为介体的潜在作用。2.我们将确定一种HIV-1相关的神经发病机制的小鼠模型，该模型最适合于研究脑中HIV-1或达特对C3和IL-6的诱导作用以及活化补体在突触中的沉积。建议的探索性研究应建立的概念基础和实验工具，详细调查的作用，补体及其潜在的诱导剂HIV和IL-6在HIV介导的神经发病机制。这些研究将包括在培养的原代星形胶质细胞中进行HIV和达特的实验，并将评估三种现有的HIV神经发病机制的小动物模型，包括将HIV-1感染的同系星形胶质细胞移植到小鼠脑中，将表达塔特的同系星形胶质细胞移植到小鼠脑中，以及通过嵌合HIV-1直接感染小鼠。每个系统将采用野生型、C3敲除和IL-6敲除小鼠。该项目涉及的研究学科包括逆转录病毒学、分子生物学、神经生物学、神经病理学和动物研究。该项目旨在解决日益严重的艾滋病毒相关神经认知障碍的公共卫生问题。如果成功的话，在这项工作中表征的小动物模型可以用于指定用于对抗补体和IL-6在大脑中的潜在神经退行性作用的治疗的转化研究。公共卫生相关性：HIV-1感染仍是一种全球性流行病。令人不安的是，在美国，新感染的发生率被低估了，而且近年来在纽约，这一比率实际上正在上升。因此，这一祸害仍然是一个严重的公共卫生挑战。本申请针对的是一种在HIV-1感染者中持续存在的疾病，即神经认知障碍。神经系统功能障碍可由直接的细胞死亡引起，但最近的研究也表明HIV-1感染的大脑中神经元功能障碍的重要性。这种应用程序的重点是突触消除的机制，通常发生在发育中的大脑，但可能在HIV-1感染期间被颠覆。该途径需要补体成分C3的表达，这是一种在HIV-1感染期间在大脑中升高的血清蛋白，如图所示。提出了对脑中数量最多的原代星形胶质细胞中过表达机制的研究。为了了解这一过程在大脑中的影响，将研究三种HIV-1神经发病机制的小鼠模型，以了解C3表达和突触消除的显着性，这是神经变性的明确途径。如果成功，这种开发应用将提供重要的线索，以对抗HIV-1感染期间发生的神经元功能障碍的新的生理相关途径。

DESCRIPTION (provided by applicant): Complement components are elevated in the brain in a variety of neurodegenerative disorders but their contribution to neuropathogenesis is unknown. Recent studies indicate that C1q and C3 contribute to synaptic remodeling during development and mediate some specific forms of synaptic damage during disease. Consistent with these findings, we have shown that C3 is elevated a) in the brain during HIV-1-associated dementia; b) in mice infected with chimeric HIV-1; and c) in primary human and mouse astrocytes exposed to HIV-1 in culture. Our preliminary data also indicate that HIV-1 induces C3 in astrocytes indirectly through a NF-:B dependent pathway that correlates with production of interleukin 6 (IL-6). Based on the finding that synaptic remodeling during normal brain development requires C3, we hypothesize that C3 overexpression in the brain during HIV infection initiates ectopic synaptic remodeling and neuropathogenesis. In this application, we propose exploratory studies toward testing this hypothesis in two Specific Aims: 1. We will determine the mechanism of C3 induction in astrocytes by intact HIV-1 and Tat with focus on the potential role of HIV-1-induced IL-6 as a mediator. 2. We will identify a mouse model of HIV-1-associated neuropathogenesis that is most suitable for study of C3 and IL-6 induction by HIV-1 or Tat in the brain and the deposition of activated complement in synapses. The proposed exploratory studies should establish the conceptual basis and experimental tools for detailed investigation of the role of complement and its potential inducers HIV and IL-6 in HIV mediated neuropathogenesis. The studies will include experiments with HIV and Tat in primary astrocytes in culture and will evaluate three existing small animal models of HIV neuropathogenesis including transplant of HIV-1-infected syngeneic astrocytes into the mouse brain, transplant of Tat-expressing syngeneic astrocytes into the mouse brain, and direct infection of mice by chimeric HIV-1. Each system will employ wildtype, C3 knockout, and IL-6 knockout mice. Research disciplines involved in this project include retrovirology, molecular biology, neurobiology, neuropathology, and animal studies. The project addresses the growing public health problem of HIV-associated neurocognitive disorders. If successful, the small animal models characterized in this work may be employed for translational research on treatments designated to counter the potential neurodegenerative actions of complement and IL-6 in the brain. PUBLIC HEALTH RELEVANCE: HIV-1 infection continues as a world-wide pandemic. It is disturbing to learn that the incidence of new infections has been under-estimated in the United States and the rate is actually increasing over recent years in New York. Thus this scourge remains a serious Public Health challenge. This application addresses one disorder that persists among HIV-1-infected people, neurocognitive disorders. Nervous system dysfunction can arise from outright cell death, but recent studies also indicate the importance of neuronal functional impairment in the HIV-1- infected brain. This application focuses upon a mechanism of synapse elimination that normally takes place in the developing brain, but may be subverted during HIV-1 infection. This route entails expression of complement component C3, a serum protein found elevated in the brain during HIV-1 infection, as shown here. Proposed are studies on the mechanism of overexpression in primary astrocytes, the most numerous cell in the brain. Turning to understand the impact of this process in the brain, three mouse models of HIV-1 neuropathogenesis will be investigated for the salience of C3 expression and synaptic elimination, a clear path to neurodegeneration. If successful, this developmental application will provide significant leads to counter a new, physiologically relevant pathway of functional impairment of neurons that occurs during HIV-1 infection.