Mechanisms of Neurodegeneration & Neuroprotection in EAE

描述（由申请人提供）：多发性硬化症（MS）是一种中枢神经系统（CNS）脱髓鞘和退行性疾病。大多数MS患者经历复发-缓解症状，随后是疾病的继发进展期（24）。免疫调节疗法在复发-缓解期部分改变了MS的病程;然而，疾病的继发性进展期仍然对此类治疗具有耐药性（25）。这种二分法的一个可能的解释是，在疾病的第二阶段，CNS对髓鞘和轴突都造成了不可逆的损伤，这种损伤再也不能通过代偿机制来纠正。最近的几项研究表明，轴突损伤存在于MS及其动物模型实验性自身免疫性脑脊髓炎（EAE）中，并可能导致固定的神经功能缺损（26，27）。因此，改善轴突损伤的策略可以预防MS中的慢性残疾。Wlds小鼠是一种自发发生的突变体，具有针对几种形式的轴突损伤的保护的独特表型。该模型中的神经保护机制目前尚不清楚，但可能与Ube 4 b/Nmnat嵌合基因的功能有关（28）。我们已经发现，WId小鼠具有减弱的EAE过程，并且具有比野生型小鼠更少的轴突损伤和脱髓鞘。此外，我们发现这些小鼠在EAE期间CNS中CD 200的表达增加，与CNS中巨噬细胞/小胶质细胞的积累减少相关。已知CD 200在神经元上表达，并且其受体CD 200 R的连接抑制巨噬细胞/小胶质细胞活化。在中枢神经系统中增加CD 200的表达可能促进EAE和MS的神经保护作用。在这个修订的资助申请中，我们的目标是2倍。首先，我们将探讨CD 200在减轻CNS中的免疫应答和神经病理学中的作用。大胶质细胞/小胶质细胞被认为是轴突损伤和脱髓鞘的主要介质。下调其激活的策略，特别是在中枢神经系统中，可以预防慢性残疾。通过CD 200激活CD 200 R是一种这样的策略。在这个目标中，我们将更详细地研究CD 200表达的动力学和分布在中枢神经系统中的幼稚野生型小鼠和野生型小鼠，以及在EAE。我们将探讨CD 200 R结扎对体外小胶质细胞和巨噬细胞活化的影响，以及对小胶质细胞诱导的神经毒性模型的影响。最后，我们将研究CD 200 CD 200 R通路激活在EAE的效应（慢性）以及引发阶段的影响。我们的第二个目标集中在理解Wlds嵌合基因和底物如CD 200的关系。基于我们最近的初步结果，这表明减少泛素化的CD 200在Wld脊髓，我们假设，Wld基因发挥其作用，通过改变泛素蛋白酶体途径（UPS）降解某些底物，导致神经保护表型。UPS的改变是几种神经退行性疾病/模型的原因。我们将探讨嵌合蛋白和CD 200之间的关系。此外，我们将试图确定其他底物的改变泛素化，可能发挥作用的轴突保护WLDS模型。最后，我们将探讨抑制UPS可能减少炎症介导的轴突病的可能性。我们预计，最终目标的结果可能会为我们提供基础，为未来的研究UPS途径在EAE轴突保护中的作用，并可能在MS。

DESCRIPTION (provided by applicant): Multiple sclerosis (MS) is a demyelinating and degenerative disease of the central nervous system (CNS). The majority of MS patients experience relapsing-remitting symptoms, followed by a secondary progressive phase of disease (24). Immunomodulatory therapies partially alter the disease course of MS during the relapsing-remitting phase; however the secondary progressive phase of the disease remains resistant to such treatments (25). A possible explanation for this dichotomy is that in the secondary phase of disease, the CNS has sustained irreversible damage to both myelin and axons, which can no longer be corrected by compensatory mechanisms. Several studies have recently shown that axonal damage is present in both MS and its animal model experimental autoimmune encephalomyelitis (EAE) and may contribute to fixed neurological deficits (26, 27). Thus, strategies that ameliorate axon damage may prevent chronic disability in MS. The Wlds mouse is a spontaneously occurring mutant with the unique phenotype of protection against several forms of axonal injury. The mechanisms of neuroprotection in this model is currently unknown, however likely relates to the function of the Ube4b/Nmnat chimeric gene (28). We have found that WId mice have an attenuated course of EAE, and have less axonal damage and demyelination than wild-type mice. In addition, we have found that these mice have increased expression of CD200 in the CNS during EAE, correlating with decreased accumulation of macrophages/microglia in the CNS. CD200 is known to be expressed on neurons, and ligation of its receptor CD200R is inhibitory for macrophage/microglial activation. Increased expression of CD200 in the CNS may promote neuroprotection in EAE and potentially in MS. In this revised grant application, our goals are 2 fold. Firstly, we will explore the role of CD200 in attenuating the immune response and neuropathology in the CNS. Macrophages/microglia have been implicated as the primary mediators of axonal damage and demyelination. Strategies to down-regulate their activation, particularly in the CNS may prevent chronic disability. Activation of CD200R by CD200 is 1 such strategy. In this Aim, we will study in more detail the dynamics and distribution of CD200 expression in the CNS in naive Wlds and wild-type mice, as well as during EAE. We will explore the effects of CD200R ligation on microglia and macrophage activation in vitro, and on a model of microglia-induced neurotoxicity. And lastly we will study the effects of CD200 CD200R pathway activation during the effector (chronic) as well as priming stages of EAE. Our second goal focuses on understanding the relationship of the Wlds chimeric gene and substrates such as CD200. Based on our recent preliminary results, which demonstrate decreased ubiquitination of CD200 in Wld spinal cord, we hypothesize that the Wld gene exerts its effects by altering the ubiquitin proteasome pathway (UPS) degradation of certain substrates, leading to the neuroprotective phenotype. Alterations in the UPS are responsible for several neurodegenerative diseases/models. We will explore the relationship between the chimeric protein and CD200. In addition, we will attempt to identify other substrates subject to altered ubiquitination that may play a role in axon protection in the Wlds model. Lastly, we will explore the possibility that inhibition of the UPS may reduce inflammation-mediated axonopathy. We anticipate that results from this final Aim may provide us with the basis for future studies in the role of the UPS pathway in axon-protection in EAE, and potentially in MS.