IRF5-IRF4 Regulatory Axis: A new Target for Stroke

 描述(由申请人提供)：小胶质细胞激活是启动和维持对脑缺血的先天免疫反应的关键因素。小胶质细胞反应的特征是M1，经典激活(促炎)，或M2，交替激活(抗炎)。这两种不同的小胶质细胞表型可能提供了一种治疗途径，选择性地增强M2和/或抑制M1的激活。卒中后小胶质细胞M1/M2激活的机制尚不清楚。对外周炎症的研究表明，干扰素调节因子5(IRF5)和IRF4是介导巨噬细胞M1/M2极化的关键决定因素。IRF5和IRF4分别通过TLR4-MyD88-IRF5和IL4R-Jmjd3-IRF4途径调节巨噬细胞M1/M2表型。结果表明，这两条途径协同调节M1/M2极化。我们假设，IRF5-IRF4调节轴平衡了TLR4-MyD88-IRF5和IL4R-Jmjd3-IRF4通路，使卒中后小胶质细胞M1/M2极化，并且操纵IRF5-IRF4调节轴提供了抗缺血的神经保护。可诱导条件基因敲除(ICKO)和骨髓嵌合体小鼠模型将被用来研究IRF5-IRF4调节轴在卒中后小胶质细胞或外周血白细胞中的特异性。目的1研究IRF5-IRF4调节轴在脑缺血损伤后小胶质细胞中的作用。在慢性ICKO模型中，IRF5/IRF4在小胶质细胞中选择性丢失，但在外周血白细胞中完整，蛋白过度表达和敲除，小胶质细胞-神经元共培养，我们将测试操纵IRF5-IRF4调节轴是否可以改变小胶质细胞的表型，减少实验性卒中后的缺血性损伤。目的2探讨IRF5-IRF4调节轴在介导脑缺血后损伤中是否起重要作用。将使用骨髓嵌合体和急性IRF5/IRF4 ICKO小鼠模型。AIM 3将检查卒中后IRF5-IRF4调节轴是否存在与年龄相关的差异。IRF5/IRF4 ICKO模型将被用来研究老年小鼠的IRF5/IRF4信号转导。在小胶质细胞/浸润性白细胞中操纵IRF5-IRF4调节轴可能有助于限制缺血性损伤，促进卒中后的组织修复。这项研究具有很高的翻译价值，有望为中风患者的治疗干预找到新的生物学靶点。

 DESCRIPTION (provided by applicant): Microglial activation is a key element in initiating and perpetuating innate immune responses to cerebral ischemia. Microglial responses are characterized as either M1, classical activation (pro-inflammatory), or M2, alternative activation (anti-inflammatory). The two distinct phenotypes of microglia potentially provide a therapeutic avenue that selectively enhances M2 and/or inhibits M1 activation. The mechanism underlying microglial M1/M2 activation after stroke has not been explored. Studies of peripheral inflammation suggested that interferon regulatory factor 5 (IRF5) and IRF4 are key determinants in mediating macrophage M1/M2 polarization. IRF5 and IRF4 function through TLR4- MyD88-IRF5 and IL4R-Jmjd3-IRF4 pathways to regulate macrophage M1/M2 phenotype respectively. It is suggested that the two pathways act synergistically to mediate M1/M2 polarization. We hypothesize that the IRF5-IRF4 regulatory axis balances the TLR4-MyD88-IRF5 and IL4R-Jmjd3-IRF4 pathways to direct microglial M1/M2 polarization after stroke, and that manipulation of the IRF5-IRF4 regulatory axis confers neuroprotection against ischemia. Inducible conditional knockout (ICKO) and a bone marrow chimera mouse model will be utilized to study the IRF5-IRF4 regulatory axis specifically in microglia or in infiltrating peripheral leukocytes afer stroke. Aim 1 will study the role of the IRF5-IRF4 regulatory axis selectively in microglia after ischemic injury. Using a chronic ICKO model in which IRF5/IRF4 is selectively lost in microglia but intact in peripheral leukocytes, protein over-expression and knockdown, and microglia-neuron co- culture, we will test if manipulation of the IRF5-IRF4 regulatory axis can switch microglial phenotype and reduce ischemic injury after experimental stroke. Aim 2 will investigate whether the IRF5-IRF4 regulatory axis in infiltrating peripheral cells plays an important role in mediating post-ischemic brain injury. Bone marrow chimeras and an acute IRF5/IRF4 ICKO mouse model will be employed. Aim 3 will examine if age-related differences exist in the IRF5-IRF4 regulatory axis after stroke. The IRF5/IRF4 ICKO model will be utilized to examine the IRF5/IRF4 signaling in aged mice. Manipulation of the IRF5- IRF4 regulatory axis in microglia/infiltrating leukocytes may help limit ischemic injury and promote tissue repair after stroke. The study has high translational value and will hopefully identify new biological targets for therapeutic intervention for patients with stroke.