Microglia responses to CNS injury: targeting p38 MAPK signaling

 描述（由申请人提供）：小胶质细胞是脑中的常驻组织髓样细胞。成人小胶质细胞的急性分离和分子分析已经清楚地确定了在其他巨噬细胞群体或CNS中的其他细胞中未发现的小胶质细胞特异性基因表达谱。作为一种分子和功能独特的细胞群体，小胶质细胞表现出显着的能力，调查大脑和迅速经历一系列的反应，侮辱或组织损伤。这些协调的反应通常会导致保护免受伤害，但可能会功能失调，加剧甚至导致神经系统疾病。当单核细胞在疾病或损伤后被招募到大脑时，会出现额外的复杂性。作为功能上不同的群体，新募集的单核细胞/巨噬细胞与小胶质细胞相比对疾病进展做出不同的贡献。小胶质细胞/巨噬细胞中的顶级经典途径之一是p38 MAPK途径，这是一种在应激反应中重要的成熟信号传导途径。在上一个资助期，我们记录了p38 α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p38 α可以预防导致随后神经元/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p38 α的缺失与小胶质细胞活化减少，以及前庭功能障碍，认知障碍和突触蛋白丢失的拯救有关。我们的数据表明p38 α在调节脑损伤改变的巨噬细胞/小胶质细胞的关键功能中的重要性，为进一步的机制和翻译研究提供了强有力的先例。我们现在已经开发了一种非常特异的小分子p38 α抑制剂（称为MW 150），即CNS渗透剂，具有药物样性质，并且在非常高的剂量下没有副作用。MW 150是一种具有高度翻译相关性的新型试剂，可用于未来的治疗开发。作为未来发展的基础，我们现在建议机械地解决如何靶向p38 α以改善TBI后的结果。为此，我们需要回答：1）何时可以靶向p38 α;即，创伤性脑损伤后的最佳治疗窗是什么？2)p38 α在哪里以及如何被靶向;即，p38 α在除小胶质细胞外的其他炎性细胞类型（浸润性巨噬细胞、星形胶质细胞、内皮细胞）中是否 TBI后的神经炎症反应？我们的研究将提供关于损伤诱导的p38 α依赖性炎症反应如何在多种细胞类型中协同作用和相互作用以驱动神经损伤的关键机制信息。我们将检验这一假设，即在CNS损伤后适当的治疗窗和适当的细胞类型中抑制p38 α信号传导可以导致选择性的有益结果。我们的目标是：目标1。为我们的小分子p38 a抑制剂的疗效建立损伤后治疗窗口。目标2.定义p38 a在驻留小胶质细胞与浸润巨噬细胞中对TBI诱导的损伤的贡献。目标3.确定其他CNS炎症细胞类型（星形胶质细胞和内皮细胞）中的p38 α如何促进损伤诱导的反应。

 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.