Sex Differences in Immune Responses to Hypoxic-Ischemic Encephalopathy

 描述(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。到目前为止，还没有单独的神经保护剂被证明是安全和有效的，尽管临床试验表明低温在改善HIE婴儿预后方面有好处。迫切需要针对这种毁灭性疾病进行优化的新疗法。在临床上，男性对新生儿HIE更敏感；然而，性别差异背后的机制尚不清楚。先天免疫反应在HIE的病理生理学中起着基础性作用。小胶质细胞的激活是免疫应答的关键启动者，受内源性抑制信号的调控，主要是CX3CL1/CX3CR1信号通路。最近的研究发现，在正常情况下，新生儿脑内小胶质细胞的数量、激活和膜受体的表达存在性别二型性。然而，这些基本的性别差异如何影响对新生儿损伤(如HIE)的反应仍在很大程度上尚不清楚。我们假设，在男性和女性新生儿HIE后，小胶质细胞被不同地激活，导致不同的免疫反应和缺血结果。采用莱斯-万努奇模型，建立出生后第10天(P10)雌雄小鼠缺氧缺血性脑病模型。在目标1中，我们将检验这一假设，即由于CX3CL1/CX3CR1信号的性别二型性，在小胶质细胞激活和HIE结局中存在性别差异。通过对CX3CL1/CX3CR1信号通路的药理增强和基因缺失，从机制上研究该通路对HIE的影响。在目标2中，我们将使用“圣诞节”小鼠(CX3CR1gfp/+CCR2rfp/+)来研究HIE中枢和外周免疫反应中的性别二型性。“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“圣诞节”小鼠，结合流式细胞仪和免疫组化，我们将能够研究中枢和外周免疫反应中的性别差异，并调查每个组成部分(中枢和外周)在HIE中的作用。这些探索性研究将有助于更好地理解HIE的性别特异性机制，并将帮助我们确定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.