Investigation of Basal Forebrain Degeneration in HIV-Associated Neurocognitive Disorder

项目摘要/摘要 尽管联合抗逆转录病毒疗法问世已近25年，但高达50%的艾滋病毒携带者 在他们的一生中会经历某种程度的认知障碍。这些与艾滋病毒相关的神经学 紊乱(手)是通过各种神经毒性效应导致的，由艾滋病毒渗透到中枢 神经系统(CNS)。虽然手的神经病理多年来一直被理解，但具体的 手部个体认知功能障碍的机制尚不清楚。免费的HIV病毒蛋白是 已知具有独立的神经毒性作用。在这些分子中，膜蛋白gp120是已知的 促进导致中枢神经系统区域神经元简化/凋亡的广泛细胞事件 对更高的认知功能至关重要。了解gp120如何引起这些影响对未来至关重要。 为艾滋病毒携带者开发治疗方法。在手部的老鼠模型中，结构性地表达 在中枢神经系统中的gp120(Gp120tg)，我们的实验室已经确定gp120扰乱了神经营养素前体的加工和 上调p75NTR，一种促凋亡的前神经营养素受体。我们最近的研究还表明，树突 由于gp120驱动的神经营养因子受体的破坏，脊柱简化或丢失的风险增加。 环境。P75NTR在这一效应中的核心作用是通过部分挽救生化、组织学、 当p75NTR被移除时，老年gp120tg小鼠的行为异常。然而，失去了一个脆弱的人 基底前脑高表达p75NTR及其受体的胆碱能神经元群 在多种神经退行性疾病中观察到变性可能更好地解释认知障碍 手而不是广泛的突触丢失。这方面的初步数据表明，年龄较大的gp120tg小鼠已经受到了损害 消除条件性恐惧，这是一种依赖于BFCN诚信的行为。我假设gp120表达驱动 通过破坏局部神经营养环境的机制使这些BFCNs退化。 为了证实gp120的表达是否扰乱了前脑中神经营养素的处理，我将牺牲年龄 Gp120转基因小鼠(和对照组)，并评估前脑神经生长因子(ProNGF)和 NGF，以及催化其转化的两种蛋白酶(目标1a)。从这些小组，我也将部分 前脑和BFCNs标记物评估胆碱能细胞群及BFCN的测量 复杂性(目标1b)。来自BFCN靶区的突触体将决定是否表达 Gp120tg小鼠胆碱能神经支配减少(目标1c)。最后，我将评估前脑的萎缩。 在这个模型中，灰质密度和隔海马束完整性(BFCN纤维)通过磁场 磁共振(MR)成像方法(目标2)。我推测，衰老的gp120tg小鼠的前脑会发生变化。 神经营养环境，这将与BFCN数量/复杂性和前脑减少相对应 灰质密度/隔海马束完整性。在整个拟议的培训期间，我将获得以下方面的专业知识 体视学和磁共振成像，在神经退行性疾病领域具有很高的翻译价值。

PROJECT SUMMARY/ABSTRACT Despite nearly 25 years since the advent of combined antiretroviral therapy, up to 50% of people living with HIV will experience some degree of cognitive impairment in their lifetimes. These HIV-associated neurological disorders (HAND) are driven through a variety of neurotoxic effects resulting from HIV infiltration of the central nervous system (CNS). While the neuropathology of HAND has been understood for years, the specific mechanisms underpinning cognitive dysfunction in HAND individuals remain unclear. Free HIV viral proteins are known to possess independent neurotoxic effects. Of these molecules, the envelope protein gp120, is known to facilitate a wide range of cellular events which result in simplification / apoptosis of neurons in CNS regions critical for higher cognitive function. Understanding how gp120 may elicit these effects is critical for the future development of therapeutics for those living with HIV. In a mouse model of HAND which constitutively expresses gp120 in the CNS (gp120tg), our lab has established that gp120 perturbs pro-neurotrophin processing and upregulates p75NTR, a pro-apoptotic proneurotrophin receptor. Our recent work has also shown that dendritic spines are at increased risk for simplification or loss due to gp120-driven disruption of the neurotrophin-receptor environment. A central role for p75NTR in this effect is supported by partial rescue of biochemical, histological, and behavioral abnormalities in older gp120tg mice when p75NTR is removed. However, loss of a vulnerable population of cholinergic neurons in the basal forebrain (BFCNs) which highly express p75NTR and whose degeneration is observed in multiple neurodegenerative diseases may better explain cognitive impairments in HAND than broad synapse loss. Preliminary data in this direction indicates that older gp120tg mice have impaired extinction of conditioned fear, a behavior dependent on BFCN integrity. I hypothesize gp120 expression drives degeneration of these BFCNs through a mechanism involving disruption of the local neurotrophic environment. To confirm whether gp120 expression disrupts neurotrophin processing in the forebrain, I will sacrifice aged gp120 transgenic mice (and controls) and assess forebrain expression of pro nerve growth factor (proNGF) and NGF, as well as two proteases which catalyze their conversion (Aim 1a). From these groups, I will also section the forebrain and immunostain for BFCNs markers to assess cholinergic cell population and measures of BFCN complexity (Aim 1b). Synaptosomes from BFCN-targeted regions will determine if expression of markers of cholinergic innervation are decreased in gp120tg mice (Aim 1c). Finally, I will assess decrements in forebrain gray matter density and septohippocampal tract integrity (BFCN fibers) in this model through a magnetic resonance (MR) imaging approach (aim 2). I hypothesize that aged gp120tg mice will display an altered forebrain neurotrophic environment, which will correspond with reduced BFCN count / complexity and decreased forebrain gray matter density / septohippocampal tract integrity. Throughout the proposed training, I will gain expertise in stereology and MR imaging, which have high translational value in the field of neurodegenerative diseases.