ENDOGENOUS NEURONAL REPAIR MECHANISMS IN SIV-INFECTED MACAQUES

SIV 感染猕猴的内源性神经修复机制

• 批准号: 8172896
• 负责人: Susan V. Westmoreland
• 金额: $ 6.32万
• 依托单位: HARVARD MEDICAL SCHOOL
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-05-01 至 2011-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8172896
• 关键词: Adult; Alzheimer' s Disease; Animal Model; Animals; Anti-Retroviral Agents; Apoptotic; Astrocytes; Binding; Brain; Cessation of life; Chronic; Communication; Computer Retrieval of Information on Scientific Projects Database; Creatine; Dendritic Spines; Development; Disease; Elements; Encephalitis; EphA4 Receptor; Ephrin-B3; Ephrins; Experimental Autoimmune Encephalomyelitis; Funding; Genes; Grant; Growth Associated Protein 43; Growth Cones; HIV encephalitis; Hippocampus (Brain); Inflammatory; Injury; Institution; Ligands; Macaca; Macaca mulatta; Measures; Mediating; Membrane; Messenger RNA; Metabolic; Metabolism; Microglia; Modeling; Monkeys; Multiple Sclerosis; N-acetylaspartate; Natural regeneration; Nerve Growth Factors; Neuronal Plasticity; Neurons; Neuroprotective Agents; Neurotrophic Tyrosine Kinase Receptor Type 1; Pathogenesis; Peripheral; Peripheral Nervous System Diseases; Personal Communication; Phosphotransferases; Presynaptic Terminals; Process; Proteins; Rattus; Recovery; Regulation; Research; Research Personnel; Resources; Role; SIV; Severities; Signal Pathway; Signal Transduction; Source; Spinal Ganglia; Stroke; Synapses; Synaptic Membranes; Synaptic plasticity; Synaptophysin; T-Lymphocyte; Testing; Therapeutic; Time; United States National Institutes of Health; Up-Regulation; Virus; Virus Diseases; antiretroviral therapy; axon growth; axonal guidance; axonal pathfinding; axonal sprouting; cell type; cohort; extracellular; frontal lobe; inhibitor/antagonist; mRNA Stability; macrophage; monocyte; neurotoxic; neurotransmitter release; presynaptic; protein expression; receptor; repaired

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. GAP-43 (neuromodulin) is a component of the presynaptic membrane that is the major protein of axonal growth cones. Its primary functions include axonal growth, axonal pathfinding, synaptic plasticity, and regulating neurotransmitter release. GAP-43 expression has been shown to be up-regulated during development, neuronal plasticity and neuronal death, and it has been used to measure functional axonal recovery in various chronic inflammatory diseases such as multiple sclerosis via the EAE animal model, Alzheimer's disease, and stroke. GAP-43 expression has also been used to test the pathogenesis of antiretroviral-induced peripheral neuropathy and possible effects of neuroprotective drugs in the dorsal root ganglion in rats. The purpose of this study has been to assess neuronal and synaptic damage associated with simian immunodeficiency virus (SIV) encephalitis using markers to evaluate the pre-synaptic terminals (GAP-43 and SYN) and post-synaptic membranes (MAP-2). SIV has been well established as a model for HIV encephalitis (HIVE). It has also been documented that increased severity of SIVE inversely correlates with decreased synaptophysin and MAP-2 expression and with decreased N-acetylaspartate/creatine ratio (NAA/Cr), a marker of neuronal metabolism. Immunohistochemical examination of GAP-43 protein expression in frontal cortex (FC) and hippocampus (HI) was undertaken was evaluated in FC and HI from a cohort of CD8-depleted SIVmac251-infected rhesus with and without combined antiretroviral therapy (CART). We had previously demonstrated that NAA/Cr decline in CD8-depleted SIV-infected macaques is reversed after 28 days of antiretroviral therapy associated with near complete clearance of CD68+ SIV-infected perivascular macrophages from the brain. We hypothesized that part of the cause of the normalization of NAA in treated macaques was reversal of presynaptic membrane loss that would be represented by increased synaptophysin. We also hypothesized that GAP-43 would be upregulated as a repair mechanism with CART. We demonstrate here that although synaptophysin loss is not reversed in this time frame with CART, GAP-43 is upreglulated, but the upregulation occurs with initial SIV infection and is not augmented with CART. Increased GAP-43 represents an endogenous repair mechanism that occurs with initial injury and may serve as a potential marker of repair in the SIV model. We have also demonstrated that microglia and infiltrating macrophages activated during SIV-infection express the axonal guidance molecule ephrin B3. Ephrin B3 is a ligand for EphA4 and EphB3 and is involved in synapse and dendritic spine formation. It mediates demonstrated anti-apoptotic activity in neurons, but also functions as an inhibitor of axonal growth, a mechanism to maintain axonal stability. Although ephrin B3 can regulate axonal sprouting through repulsion, its action has been associated with induction of GAP-43. The discovery of ephrin B3 in macrophages and microglia in the brain was not unanticipated. Ephrin B3 and its receptors are expressed in peripheral T cells and monocytes/macrophages. This may provide a mechanism whereby macrophages and microglia could modulate neuron and astrocyte function, as both cell types express the ephrin B3 receptors, EphA4 and EphB3. Despite the documented significant improvement in neuronal metabolism with short-term CART evidenced by normalization of NAA/Cr in the treated animals, there was no significant difference in GAP-43 expression between SIV-infected untreated monkeys and those that received CART. We speculate that there is ongoing injury (and attempts at repair) that continues to induce GAP-43 expression despite the marked reduction in brain virus burden that is observed in the animals that received CART in this study. We observe a mismatch in marked reduction of brain virus burden with CART, but persistent levels of microglial activation and TNFa, a neurotoxic factor, in the treated animals (L. Annamalai personal communication). The mismatch in parameters of improvement, neuronal metabolism and GAP-43/ephrin B3, may also reflect differences in the time course of metabolic improvement, compared with the time course of induction and suppression of factors that promote neuroadaptive processes. GAP-43 mRNA is induced by nerve growth factor (NGF), which is dependent on Mst3b, a neuron-specific kinase central to regulation of axonal outgrowth. The role of ephrins as factors that can promote or hinder neuronal repair mechanisms is controversial, but it is clear that ephrins are involved in the intricate communication of neurons with astrocytes and microglia. We propose a model in which microglia activated by virus infection (and ephrin B3 expression) stimulate astrocytes to secrete NGF, which binds TrkA receptors on neurons, thus inducing neuroprotective signaling cascades that result in the induction and increased mRNA stability of GAP-43. Other ephrins in addition to ephrin B3 and their receptors are likely to be involved in this multicellular activation and signaling pathway. Therapeutic modulation of these extracellular axonal growth molecules, their receptors, or downstream signaling elements may augment axonal sprouting and regeneration in the adult CNS. The adult SIV-infected macaque model will be useful for exploring additional genes and ephrins that are associated with synaptic plasticity as well as for further characterization of endogenous neuroregenerative potential.

该副本是利用众多研究子项目之一 由NIH/NCRR资助的中心赠款提供的资源。子弹和 调查员（PI）可能已经从其他NIH来源获得了主要资金， 因此可以在其他清晰的条目中代表。列出的机构是 对于中心，这不一定是调查员的机构。 GAP-43（NeuroModulin）是突触前膜的组成部分，该膜是轴突生长锥的主要蛋白质。它的主要功能包括轴突生长，轴突探路，突触可塑性和调节神经递质释放。 GAP-43表达已被证明在发育，神经元可塑性和神经元死亡过程中被上调，并且已用于测量各种慢性炎症性疾病（例如通过EAE动物模型，阿尔茨海默氏病）和中风等各种慢性炎性疾病的功能性轴突恢复。 GAP-43表达也已用于测试抗逆转录病毒诱导的周围神经病的发病机理，以及神经保护药物在大鼠背根神经节中的可能作用。 这项研究的目的是使用标记物评估与猿猴免疫缺陷病毒（SIV）脑炎相关的神经元和突触损伤，以评估突触前末端（GAP-43和SYN）和突触后膜（MAP-2）。 SIV已成为HIV脑炎（Hive）的模型已被良好确立。还可以证明，Sive的严重程度增加与突触素和MAP-2表达的降低以及N-乙酰天冬氨酸/肌酸的降低（NAA/CR）（神经元代谢的标志）。在FC中评估了额叶皮层（FC）中GAP-43蛋白表达的免疫组织化学检查和HIAPPOCAMPUS（HI）的免疫组织化学检查，并在FC中评估了CD8耗尽的SIVMAC251感染的瑞斯斯的同类，具有和没有合并的抗逆转录病毒治疗（CART）。 我们先前曾证明，在与大脑几乎完全清除CD68+ SIV感染的脑血管周围巨噬细胞的抗逆转录病毒疗法28天后，CD8缺失的SIV感染的猕猴的NAA/CR下降逆转。 我们假设在处理过的猕猴中NAA归一化的部分原因是突触前膜损失的逆转，这将由突触的增加所代表。我们还假设GAP-43将被上调为带有购物车的修复机制。 我们在这里证明，尽管在用购物车的时间范围内，突触蛋白损失并未逆转，但GAP-43已上调，但上调是随着初始SIV感染而发生的，并且不会随CART增强。 增加的GAP-43代表了一种内源性修复机制，该机制在初始损伤中发生，并且可以作为SIV模型修复的潜在标志。 我们还证明，在SIV感染期间激活的小胶质细胞和浸润巨噬细胞表达轴突引导分子ephrin B3。 Ephrin B3是Epha4和Ephb3的配体，参与突触和树突状脊柱形成。 它介导了神经元中的抗凋亡活性，但也起着轴突生长的抑制剂的作用，这是一种维持轴突稳定性的机制。尽管ephrin B3可以通过排斥来调节轴突发芽，但其作用与GAP-43的诱导有关。 在巨噬细胞和大脑中的小胶质细胞中发现了Ephrin B3的发现并非意外。 ephrin B3及其受体在外周T细胞和单核细胞/巨噬细胞中表达。这可能提供一种机制，巨噬细胞和小胶质细胞可以调节神经元和星形胶质细胞功能，因为两种细胞类型都表达Ephrin B3受体Epha4和Ephb3。 尽管有记录的神经元代谢有显着改善，而在治疗的动物中NAA/CR的标准化证明了短期推车，但SIV感染的未经处理的猴子与接收到的手推车之间的GAP-43表达没有显着差异。 我们推测，尽管脑病毒负担显着减轻了，但在本研究中接受购物车的动物中观察到，尽管脑病毒负担显着减轻，但仍在继续诱导GAP-43表达。 我们观察到与手推车显着减轻了脑病毒负担的不匹配，但是在处理过的动物中，小胶质激活和神经毒性因子的持续水平（L. annamalai个人交流）。 与促进神经适应过程的因素的诱导时间和抑制相比，改善，神经元代谢和GAP-43/Ephrin B3参数的不匹配也可能反映了代谢改善的时间过程的差异。 GAP-43 mRNA是由神经生长因子（NGF）诱导的，该因子取决于MST3B，MST3B是一种神经元特异性激酶，是轴突生长调节的中心。 以弗所作为可以促进或阻碍神经元修复机制的因素的作用是有争议的，但是很明显，埃弗林与星形胶质细胞和小胶质细胞的神经元进行了复杂的交流。 我们提出了一个模型，其中通过病毒感染激活的小胶质细胞（和Ephrin B3表达）刺激星形胶质细胞分泌NGF，该模型结合了神经元上TRKA受体的NGF，从而导致神经保护信号传导级联，从而导致GAP-43的诱导和增加的mRNA稳定性。 除ephrin B3及其受体外，其他以弗林蛋白可能参与了这种多细胞激活和信号传导途径。 这些细胞外轴突生长分子，其受体或下游信号传导元件的治疗调节可能会增强成年中枢神经系统的轴突发芽和再生。 成年SIV感染的猕猴模型将有助于探索与突触可塑性相关的其他基因和ephrins以及内源性神经加续潜能的进一步表征。