Role of inflammasomes in Alzheimer's Disease

项目概要/摘要 神经炎症是阿尔茨海默病（AD）的重要组成部分。然而，分子 炎症调节AD进展的机制尚未确定。我们发现β-淀粉样蛋白 1-42激活NLRP 3炎性小体，AD患者一致具有激活NLRP 3炎性小体的证据， 大脑中的炎性小体为了测试NLRP 3炎性小体在AD中的作用，我们饲养了APP/PS 1小鼠（一只 基于淀粉样蛋白的AD鼠模型）转化为NLRP 3、ASC或半胱天冬酶-1科斯（构成 NLRP 3炎性小体），并观察到这些小鼠完全免受许多AD特征的影响 包括学习/记忆缺陷和长时程增强的异常。 NLRP 3炎性小体调节IL-1 β和IL-18的表达，这两种高度促炎细胞因子 在小胶质细胞中大量产生;此外，星形胶质细胞强表达pro-IL-18。IL-1 β是 淀粉样斑块周围的小胶质细胞丰富，可引起发热，急性期强烈 反应、脓毒症综合征和焦萎细胞死亡。IL-18是IL-1超家族的成员。不像IL- 1 β，IL-18不激活NF-κ B或具有致热原活性。尚不清楚IL-1 β或IL-18 在炎性小体缺陷型APP/PS1小鼠中，减少是保护性表型的原因。我们 产生了IL-18 KO/APP/PS1小鼠，令人惊讶的是，这些小鼠发展出致命的癫痫发作障碍， 被左乙拉西坦治疗完全逆转。正如流行病学研究所表明的那样， 几乎三分之二的AD患者在疾病过程中的某个时候会癫痫发作。 在目的1中，我们将研究炎症体依赖性焦凋亡在小胶质细胞中的作用， 使用转基因小鼠研究AD的发病机制，其中炎性小体已被特异性地从 APP/PS1背景下的小胶质细胞。我们还将测试Gasdermin D缺陷的APP/PS1小鼠（a 半胱天冬酶-1底物和焦亡的最终效应分子）。在目标2中，我们将检查IL-18是否 抵消IL-1 β在AD相关癫痫发作中的促癫痫作用。我们将使用遗传学方法 （在其他AD小鼠模型中删除IL-18）以及药理学方法（IL-1 β功能丧失 方法），并评估动物的癫痫发作。在目标3中，我们将确定 IL-18降低神经元网络活性和调节突触传递。我们将识别 通过进行形态学和免疫组织化学研究， 电生理学研究以及使用免疫组织化学的生化分析。我们将特别 使用floxed IL-18转基因小鼠系检查小胶质细胞IL-18的作用。成功完成这些 目的阐明炎性小体产生的细胞因子在AD中的作用，并可能导致新的翻译， 旨在专门阻止驱动AD的炎症的方法，以及机械靶向 影响AD患者生活质量的癫痫发作。

PROJECT SUMMARY/ABSTRACT Neuroinflammation is an important component of Alzheimer's disease (AD). However, the molecular mechanism by which inflammation modulates AD progression is not defined. We discovered that beta-amyloid 1-42 activates NLRP3 inflammasomes and that AD patients uniformly have evidence of activated inflammasomes in their brains. To test the role of NLRP3 inflammasomes in AD, we bred APP/PS1 mice (an amyloid-based murine model of AD) into NLRP3, ASC, or caspase-1 KOs (the three proteins comprising the NLRP3 inflammasome) and observed that these mice were completely protected from numerous AD features including learning/memory deficits and abnormalities in long-term potentiation. NLRP3 inflammasomes regulate the expression of IL-1beta and IL-18, two highly proinflammatory cytokines abundantly produced in microglial cells; in addition, astrocytes are strong expresses of pro-IL-18. IL-1beta is abundant in microglial cells on the periphery of amyloid plaques and can cause fever, a strong acute phase response, sepsis syndrome, and pyroptotic cell death. IL-18 is a member of the IL1 superfamily. Unlike IL- 1beta, IL-18 does not activate NF-kappaB or have pyrogenic activity. It is unknown if IL-1beta or IL-18 reduction was responsible for the protective phenotype in inflammasome-deficient APP/PS1 mice. We generated IL-18KO/APP/PS1 mice and, surprisingly, these mice developed a lethal seizure disorder, which was completely reversed by levetiracetam therapy. This is highly relevant as epidemiologic studies suggest that almost two-thirds of AD patients have seizures at some point during the course of their disease. In Aim 1, we will examine the role of inflammasome-dependent pyroptosis in microglial cells in the pathogenesis of AD using transgenic mice in which the inflammasome has been specifically deleted from microglial cells on an APP/PS1 background. We will also test APP/PS1 mice deficient for Gasdermin D (a caspase-1 substrate and the final effector molecule of pyroptosis). In Aim 2, we will examine if IL-18 counterbalances the proepileptic effects of IL-1beta in AD-related seizures. We will use a genetic approach (deleting IL-18 in other AD mouse models) as well as a pharmacological approach (an IL-1beta loss-of-function approach) in IL-18KO/APP/PS1 mice and assess animals for seizures. In Aim 3, we will determine the role of IL-18 in reducing neuronal network activity and modulating synaptic transmission. We will identify the types of synapses that are dysregulated in IL-18KO/APP/PS1 mice by performing morphological and electrophysiological studies as well as biochemical analysis using immunohistochemistry. We will specifically examine the role of microglial IL-18 using a floxed IL-18 transgenic mouse line. Successful completion of these Aims will elucidate the role of inflammasome-generated cytokines in AD, and could result in novel translational approaches designed to specifically halt the inflammation that drives AD, as well as mechanistically target seizures that affect the quality of life of AD patients.