Microglia responses to CNS injury: targeting p38 MAPK signaling

 描述(申请人提供)：小胶质细胞是大脑中常驻的组织髓样细胞。成人小胶质细胞的急性分离和分子图谱已经明确地确定了小胶质细胞特有的基因表达谱，这在其他巨噬细胞群或中枢神经系统中的其他细胞中没有发现。作为一种分子和功能独特的细胞群体，小胶质细胞表现出非凡的能力来观察大脑，并迅速对侮辱或组织损伤做出一系列反应。这些协调的反应通常会导致对伤害的保护，但可能会功能失调，加剧甚至导致神经疾病。当单核细胞在疾病或损伤后被招募到大脑时，就会出现一层额外的复杂性。作为一个功能不同的群体，新招募的单核/巨噬细胞在疾病进展中的作用与小胶质细胞不同。小胶质细胞/巨噬细胞中最典型的通路之一是p38MAPK通路，这是一个在应激反应中非常重要的信号通路。在上一个资助阶段，我们记录了p38α亚型在小胶质细胞促炎细胞因子产生中的重要性，并发现抑制p38α可以防止导致随后的神经元/突触损伤的炎症反应。在两种弥漫性创伤性脑损伤(TBI)小鼠模型中，我们发现髓系细胞中p38α基因的缺失与小胶质细胞激活减少、前庭运动障碍、认知障碍和突触蛋白丢失的挽救有关。我们的数据证明了p38α在调节巨噬细胞/小胶质细胞的关键功能中的重要性，而巨噬细胞/小胶质细胞因脑损伤而改变，这为进一步的机制和翻译研究提供了强有力的先例。我们现在已经开发出一种特殊的小分子p38α抑制剂(称为MW150)，即中枢神经系统渗透剂，具有药物样特性，在非常高的剂量下没有不良反应。MW150是一种新型试剂，对未来的治疗开发具有很高的翻译相关性。作为未来发展的基础，我们现在建议机械地解决如何靶向p38α以改善脑损伤后的结果。为此，我们需要回答：1)什么时候可以靶向p38α；即，脑损伤后的最佳治疗窗口是什么？2)p38α可以在哪里以及如何靶向；即，除了小胶质细胞(浸润性巨噬细胞、星形胶质细胞、内皮细胞)外，p38α还存在于其他类型的炎症细胞中吗？ 对脑外伤后的神经炎性反应有何贡献？我们的研究将提供关于损伤诱导的多种细胞类型中依赖p38α的炎症反应如何协同和串扰驱动神经损伤的关键机制信息。我们将测试这一假设，即在中枢神经系统损伤后，在适当的治疗窗口和适当的细胞类型中抑制p38α信号可以导致选择性的、有益的结果。我们的目标是：1.建立我们的小分子P38A抑制剂疗效的创伤后治疗窗口。目的2.明确P38A在颅脑损伤中驻留小胶质细胞和浸润巨噬细胞中的作用。目的3.确定其他CNS炎性细胞类型(星形胶质细胞和内皮细胞)中的p38α如何参与损伤诱导的反应。

 DESCRIPTION (provided by applicant): Microglia are the resident tissue myeloid cell in the brain. Acute isolation and molecular profiling of adult microglia have clearly identified a microglia-specific gene expression profile not found in other macrophage populations, or other cells in the CNS. As a molecular and functionally unique population of cells, microglia exhibit a remarkable ability to survey the brain and rapidly undergo a spectrum of responses to insults or tissue damage. These coordinated responses normally result in protection against injury, but can be dysfunctional and exacerbate or even cause neurological disease. An added layer of complexity occurs when monocytes are recruited to the brain following disease or injury. As a functionally distinct population, newly recruited monocytes/macrophages make different contributions to disease progression compared to microglia. One of the top canonical pathways in microglia/macrophages is the p38 MAPK pathway, a well-established signaling pathway important in stress responses. In the last funding period, we documented the importance of the p38alpha isoform in microglia proinflammatory cytokine production, and found that suppression of p38alpha can prevent the inflammatory response that causes subsequent neuronal/synaptic damage. In two mouse models of diffuse traumatic brain injury (TBI), we found that deletion of p38alpha in myeloid cells was associated with decreased microglia activation, and a rescue of vestibulomotor deficits, cognitive impairments and synaptic protein loss. Our data demonstrating the importance of p38alpha in regulating key functions of macrophages/microglia that are altered by a brain injury provides a strong precedent for further mechanistic and translational studies. We have now developed an exceptionally specific small molecule p38alpha inhibitor (termed MW150), that is CNS- penetrant, has drug-like properties, and no adverse effects at very high doses. MW150 is a novel reagent with high translational relevance for future therapeutic development. As a foundation for future development, we now propose to address mechanistically how to target p38alpha to improve outcomes following a TBI. To this end we need to answer: 1) When can p38alpha be targeted; i.e., what is the optimal therapeutic window after TBI? 2) Where and how can p38alpha be targeted; i.e., does p38alpha in other inflammatory cell types besides microglia (infiltrating macrophages, astrocytes, endothelial cells) contribute to neuroinflammatory responses after TBI? Our studies will provide key mechanistic information about how injury-induced, p38alpha-dependent inflammatory responses in multiple cell types synergize and cross-talk to drive neurologic impairments. We will test the hypothesis that suppression of p38alpha signaling in appropriate therapeutic windows and appropriate cell types after CNS injury can lead to selective, beneficial outcomes. Our aims are: Aim 1. Establish the post-injury therapeutic window for efficacy of our small molecule p38a inhibitor. Aim 2. Define the contribution of p38a in resident microglia versus infiltrating macrophages to TBI-induced impairments. Aim 3. Determine how p38alpha in other CNS inflammatory cell types (astrocytes and endothelial cells) contributes to injury-induced responses.