IRF5-IRF4 Regulatory Axis: A new Target for Stroke

 描述（由申请人提供）：小胶质细胞活化是启动和维持对脑缺血的先天免疫应答的关键因素。小胶质细胞反应的特征为M1，经典激活（促炎），或M2，替代激活（抗炎）。小胶质细胞的两种不同表型可能提供选择性增强M2和/或抑制M1活化的治疗途径。卒中后小胶质细胞M1/M2激活的机制尚未研究。外周炎症的研究表明，干扰素调节因子5（IRF 5）和IRF 4是介导巨噬细胞M1/M2极化的关键决定因素。IRF 5和IRF 4分别通过TLR 4-MyD 88-IRF 5和IL 4 R-Jmjd 3-IRF 4途径调节巨噬细胞M1/M2表型。这表明，这两个途径协同作用，介导M1/M2极化。我们假设IRF 5-IRF 4调节轴平衡TLR 4-MyD 88-IRF 5和IL 4 R-Jmjd 3-IRF 4通路以指导中风后小胶质细胞M1/M2极化，并且IRF 5-IRF 4调节轴的操纵赋予针对缺血的神经保护。 诱导条件性基因敲除（ICKO）和骨髓嵌合体小鼠模型将用于研究IRF 5-IRF 4调节轴，特别是在小胶质细胞或浸润性外周血白细胞中风后。目的1选择性研究IRF 5-IRF 4调节轴在小胶质细胞缺血损伤中的作用。使用其中IRF 5/IRF 4在小胶质细胞中选择性丢失但在外周白细胞中完整的慢性ICKO模型、蛋白质过表达和敲低以及小胶质细胞-神经元共培养，我们将测试IRF 5-IRF 4调节轴的操纵是否可以转换小胶质细胞表型并减少实验性中风后的缺血性损伤。目的2探讨浸润的外周血细胞中的IRF 5-IRF 4调节轴是否在介导缺血后脑损伤中发挥重要作用。将采用骨髓嵌合体和急性IRF 5/IRF 4 ICKO小鼠模型。目的3将检查卒中后IRF 5-IRF 4调节轴是否存在年龄相关差异。IRF 5/IRF 4 ICKO模型将用于检查老年小鼠中的IRF 5/IRF 4信号传导。在小胶质细胞/浸润性白细胞中操纵IRF 5-IRF 4调节轴可能有助于限制缺血性损伤并促进卒中后的组织修复。该研究具有很高的转化价值，有望为脑卒中患者的治疗干预确定新的生物靶点。

 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.