Microglial and macrophage PGE2 signaling in post-stroke inflammation

描述(申请人提供)：中风是一个多阶段的过程，最初的缺血期之后是继发性损伤和中风后炎症的修复，并在一段较长的时间内展开。由于针对神经保护和脑血流的策略的有效时间窗口很窄，卒中后炎症反应代表了卒中演变的一个可翻译的阶段，在这个阶段，干预可能会促进功能恢复。在卒中后，髓系细胞，特别是驻留的小胶质细胞和浸润性巨噬细胞，发挥着重要和有益的功能，包括清除有毒碎片，形成生长和抗炎因子；然而，这些细胞也可以产生有毒的活性氧、细胞因子和蛋白酶。因此，小胶质细胞和巨噬细胞在中风后可能有有益的但也有毒性的影响。在最近对PGE2EP2受体在小胶质细胞和巨噬细胞中的体内功能的研究中，我们已经确定，细胞特异性地去除髓系EP2信号在体内是显著有益的，可以减少毒性炎症，增强免疫细胞的运输和有毒物质的清除，并导致在先天性免疫炎症模型中营养因子的阐述。由于卒中后早期炎症阶段表现出许多先天免疫反应的特征，我们假设卒中后、小胶质细胞和巨噬细胞EP2信号将呈现类似的特征，在这种情况下切除髓系细胞中的EP2将通过促进有毒碎片的吞噬和产生有益的营养因子而具有显著和有益的效果。在这项提案中，我们将使用一种经过验证的条件基因敲除遗传方法来选择性地消融巨噬细胞和小胶质细胞中的EP2，以及验证这些假设的药理学策略。我们将测试卒中后炎性EP2信号失活是否可以增强和加速功能恢复。建议的研究将有助于促进我们对卒中后小胶质-巨噬细胞生物学的理解，并验证针对卒中后EP2信号通路的新方法。

DESCRIPTION (provided by applicant): Stroke is a multiphasic process, and the initial ischemic phase is followed by secondary injury and repair from post-stroke inflammation that unfolds over an extended time period. Because strategies targeting neuroprotection and cerebral blood flow have a narrow time window of efficacy, the post-stroke inflammatory response represents a translationally accessible phase in stroke evolution where intervention may improve functional recovery. Myeloid-lineage cells, notably resident microglia and infiltrating macrophages, perform important and beneficial functions after stroke, including clearance of toxic debris and elaboration of growth and anti-inflammatory factors; however, these cells also can produce toxic reactive oxygen species, cytokines, and proteases. Therefore, microglia and macrophages can have beneficial but also toxic effects after stroke. In recent studies examining the in vivo function of the PGE2 EP2 receptor in microglia and macrophages, we have determined that cell-specific ablation of myeloid-lineage EP2 signaling is significantly beneficial in vivo, and reduces toxic inflammation, enhances immune cell trafficking and clearance of toxic substances, and leads to elaboration of trophic factors in models of innate immune inflammation. Because the early post-stroke inflammatory phase exhibits many of the characteristics of an innate immune response, we hypothesize that post-stroke, microglia and macrophage EP2 signaling will assume similar characteristics, and ablation of EP2 in myeloid cells in this setting will have significant and beneficial effects by enhancing phagocytosis of toxic debris and generating beneficial trophic factors. In this proposal, we will use a validated conditional knockout genetic approach to selectively ablate EP2 in macrophages and microglia as well as pharmacological strategies to test these hypotheses. We will test whether functional recovery can be enhanced and accelerated with inactivation of inflammatory EP2 signaling post stroke. The proposed studies should help advance our understanding of microglial-macrophage biology post-stroke, and validate new approaches targeting EP2 signaling pathway after stroke.