Investigation of Basal Forebrain Degeneration in HIV-Associated Neurocognitive Disorder

项目总结/摘要 尽管联合抗逆转录病毒疗法问世近25年来，高达50%的艾滋病毒感染者 在他们的一生中都会经历一定程度的认知障碍。这些与艾滋病相关的神经系统疾病 HAND是通过由HIV浸润中枢神经系统引起的各种神经毒性作用驱动的。 神经系统（CNS）。虽然HAND的神经病理学已经被理解多年，但具体的神经病理学研究仍然存在。 支持HAND个体认知功能障碍的机制仍不清楚。游离的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，已知包膜蛋白gp 120 促进广泛的细胞事件，导致CNS区域神经元的简化/凋亡 对高级认知功能至关重要了解gp 120如何引发这些效应对未来至关重要。 为艾滋病毒感染者开发治疗方法。在组成性表达HAND的小鼠模型中， gp 120在中枢神经系统（gp 120 tg），我们的实验室已经确定，gp 120扰乱前神经营养素加工， 上调p75 NTR，一种促凋亡的前神经营养因子受体。我们最近的研究还表明， 由于GP 120驱动的神经营养素受体的破坏 环境p75 NTR在这种作用中的中心作用得到了生化，组织学， 以及去除p75 NTR后老年gp 120 tg小鼠的行为异常。然而，失去一个脆弱的 基底前脑（BFCN）中高度表达p75 NTR的胆碱能神经元群体， 在多种神经退行性疾病中观察到的退化可能更好地解释了 手比宽突触损失。这方面的初步数据表明，年龄较大的gp 120 tg小鼠 消除条件性恐惧，一种依赖于BFCN完整性的行为。我假设gp 120表达驱动 这些BFCN通过涉及破坏局部神经营养环境的机制而退化。 为了证实gp 120的表达是否破坏了前脑中神经营养素的加工，我将处死老年人， gp 120转基因小鼠（和对照），并评估前神经生长因子（proNGF）的前脑表达， NGF，以及催化其转化的两种蛋白酶（目的1a）。从这些群体中，我也将部分 前脑和BFCN标记物免疫染色以评估胆碱能细胞群和BFCN测量 复杂性（目标1b）。来自BFCN靶向区域的突触体将决定BFCN靶向区域的标记物的表达， gp 120 tg小鼠的胆碱能神经支配减少（Aim 1c）。最后，我将评估前脑的 灰质密度和隔海马束完整性（BFCN纤维）在这个模型中，通过磁 磁共振（MR）成像方法（目的2）。我假设年老的gp 120 tg小鼠的前脑会发生改变， 神经营养环境，这将对应于BFCN计数/复杂性降低和前脑 灰质密度/隔海马束完整性。在整个拟议的培训中，我将获得以下方面的专业知识： 体视学和MR成像，在神经退行性疾病领域具有很高的转化价值。

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.