Sex Differences in Immune Responses to Hypoxic-Ischemic Encephalopathy

 描述（由申请人提供）：围产期缺氧缺血性脑病（HIE）是新生儿死亡和长期残疾的主要原因。迄今为止，没有一种神经保护剂被证明是安全有效的，尽管临床试验显示低温在改善HIE婴儿预后方面的益处。迫切需要针对这种毁灭性疾病进行优化的新疗法。临床上，男性对新生儿缺氧缺血性脑病更敏感;然而，性别差异的机制尚不清楚。先天性免疫应答在HIE的病理生理学中具有重要作用。小胶质细胞的活化是免疫应答的关键启动者，受内源性抑制信号的调节，主要是CX 3CL 1/CX 3CR 1信号通路。近年来的研究发现，正常情况下新生儿脑内小胶质细胞的数量、活化及膜受体表达均存在两性异形。然而，这些基础性别差异如何影响新生儿损伤（如HIE）的反应仍在很大程度上未被探索。我们推测，小胶质细胞在男性和女性新生儿HIE后被差异激活，导致不同的免疫反应和缺血性结局。Rice-Vannucci模型将用于在出生后第10天（P10）的两种性别小鼠中诱导HIE。在目标1中，我们将检验以下假设：由于CX 3CL 1/CX 3CR 1信号传导中的性别二态性，小胶质细胞活化和HIE结局中存在性别差异。本研究将通过对CX 3CL 1/CX 3CR 1信号通路的药理学增强和基因缺失，从机制上研究该通路的调控对HIE的影响。目的二：利用Christmas小鼠（CX 3CR 1gfp/+ CCR 2 rfp/+），研究其中枢和外周免疫反应的性别差异。“圣诞节”小鼠模型使我们能够区分血液来源的巨噬细胞和常驻的小胶质细胞。通过使用“Christmas”小鼠，结合流式细胞术和IHC，我们将能够研究中枢和外周免疫应答的性别差异，并研究每种组分（中枢与外周）在HIE中的作用。这些探索性研究将有助于更好地了解HIE的性别特异性机制，并有助于我们识别和优化儿童治疗干预的生物靶点。

 DESCRIPTION (provided by applicant): Perinatal hypoxic-ischemic encephalopathy (HIE) is a major cause of neonatal death and long-term disability. To date, no individual neuroprotective agent has been proven safe and effective, although clinical trials have shown benefits of hypothermia in improving outcomes in HIE infants. Novel therapies optimized for this devastating disease are urgently needed. Clinically, males are more sensitive to neonatal HIE; however, the mechanisms underlying the sex difference are unknown. The innate immune response has a fundamental role in the pathophysiology of HIE. Microglial activation is the key initiator of the immune response, and is regulated by the endogenous inhibitory signals, primarily CX3CL1/CX3CR1 signaling pathway. Recent studies have found that sexual dimorphism exists in microglia number, activation, and expressed membrane receptors in the neonatal brain under normal conditions. Nevertheless, how these basal sex differences affect the response to a neonatal injury such as HIE remains largely unexplored. We hypothesize that microglia are differentially activated after HIE in male and female neonates, leading to differential immune responses and ischemic outcomes. The Rice-Vannucci model will be used to induce HIE in post-natal day 10 (P10) mice of both sexes. In Aim 1, we will test the hypothesis that sex differences exist in microglial activation and in HIE outcomes due to the sexual dimorphism in CX3CL1/CX3CR1 signaling. Pharmacological enhancement and genetic deletion of CX3CL1/CX3CR1 signaling pathway will be performed to mechanistically study the effect of manipulation of this pathway on HIE. In Aim 2, we will use "Christmas" mouse (CX3CR1gfp/+CCR2rfp/+) to investigate the sexual dimorphism in central and peripheral immune response to HIE. The "Christmas" mouse model allows us to differentiate blood-derived macrophages from resident microglia. By using "Christmas" mice together with flow cytometry and IHC, we will be able to study the sex difference in both the central and peripheral immune response, and investigate the role of each component (central vs. peripheral) in HIE. These exploratory studies will lead to better understanding of sex-specific mechanisms underlying HIE and will help us identify and optimize biological targets for therapeutic intervention in children.