Sepsis and the Systemic Cytokine Storm in Aging and Alzheimer Disease Models

摘要 严重感染和脓毒症加速了美国老年人的认知能力下降，特别是那些早期 阿尔茨海默病（AD）。已知脓毒症会诱导全身性炎症性“细胞因子风暴”， 时间然而，这种反应往往持续感染后，即使在患者中解决。我们假设这 全身性细胞因子风暴可能影响症状前AD患者和 没有认知缺陷的老年人在临床前AD模型中，淀粉样蛋白和tau蛋白的增加 和病理学受全身炎症的影响。关于脓毒症的认知能力下降知之甚少 没有早期AD的幸存者，称为脓毒症相关脑病（SAE），以及这是否与 淀粉样蛋白和tau神经病理学的发展。我们的总体假设是脓毒症和CCI诱导 独特的局部和全身免疫反应，直接影响小鼠AD和SAE相关 病理我们假设，在早期或前驱AD，脓毒症将特别加剧大脑健康 淀粉样蛋白和tau神经病理学恶化，而在认知正常的老年人中，SAE结局 会因衰老而恶化我们将使用4个具体目标来测试这些假设。目标1）我们将 评估年龄是否在驱动脓毒症诱导的神经退行性变和认知丧失中起关键作用 (SAE)在野生型小鼠中。在这里，我们建议采用一个可存活的盲肠结扎和穿孔模型， 在6个月（mo）的年轻和18个月的老年成年C57 BL/6中，每日慢性应激（CLP+DCS）的多微生物脓毒症 (B6)混合性别小鼠在脓毒症后4或8周将小鼠安乐死，以进行炎症和神经病理学检查。 评估，其中将包括神经元死亡和脑炎症变化的分析。同时空间 转录组学和蛋白质组学分析（NanoString GeoMx™）将允许评估大脑区域特异性 对外周细胞因子风暴的反应改变。将分析血浆中的炎性细胞因子， 选择报警器。小鼠还将在其脓毒性损伤后进行认知评估。目标2：我们将 评价CLP+ DCS诱导的全身性炎症是否改变Aβ沉积。在这里我们将使用两个APP 转基因小鼠模型-快速进展的TgCRND 8小鼠和缓慢进展的Tg.PrP HuAβ（APPsi） 小鼠-评估系统性细胞因子风暴如何调节淀粉样蛋白沉积。在目标3）中，我们将评估是否 全身性炎症加剧了tau病理学。我们将评估脓毒症是否诱导AD中的tau病理学， PS19小鼠的相关脑区。最后，在目标4）中，我们将测试是否预防性操作 在选定的动物模型中，免疫系统改变SAE或AD相关的病理。使用AAV-directed 我们将测试是否抑制IL-10全身或在大脑中减弱 神经病理/行为结果。其他小鼠将在败血症期间口服二甲双胍，因为可能 神经保护这项研究将提供一个机制的理解脓毒症引起的病理，以及 有和没有既存AD的老年人之间的差异。

ABSTRACT Severe infection and sepsis accelerate cognitive decline in older Americans, especially those with incipient Alzheimer's disease (AD). Sepsis is known to induce a systemic inflammatory `cytokine storm', which wanes with time. However, this response often persists even after infection resolution in patients. We hypothesize that this systemic cytokine storm can potentially affect brain neuropathology in both pre-symptomatic AD patients and in older adults with no known cognitive deficits. In preclinical AD models, both amyloid and tau protein accretion and pathology are influenced by systemic inflammation. Less is known about the cognitive decline in sepsis survivors without incipient AD, known as sepsis-associated encephalopathy (SAE), and whether this is related to development of amyloid and tau neuropathology. Our overarching hypothesis is that sepsis and CCI induce unique local and systemic immunological responses that directly influence murine AD- and SAE-related pathology. We hypothesize that in incipient or prodromal AD, sepsis would specifically exacerbate brain health by exacerbating amyloid and tau neuropathology, while in cognitively normal older individuals, SAE outcomes would be exacerbated by aging pathways. We will test these hypotheses using 4 specific aims. In Aim 1) we will evaluate whether age plays a critical role in driving sepsis-induced neurodegeneration and loss of cognition (SAE) in wild-type mice. Here we propose to employ a survivable cecal ligation and puncture model of polymicrobial sepsis with daily chronic stress (CLP+DCS) in 6 month (mo) young and 18 mo older adult C57BL/6 (B6) mixed sex mice. Mice will be euthanized at 4 or 8 weeks post-sepsis for inflammatory and neuropathologic evaluation, which will include analysis of neuronal death, and brain inflammatory changes. Simultaneous spatial transcriptomic and proteomic profiling (NanoString GeoMx™) will allow assessment of brain region-specific alterations in response to the peripheral cytokine storm. Plasma will be analyzed for inflammatory cytokines and selected alarmins. Mice will also undergo cognitive assessment following their septic insult. In Aim 2) we will evaluate whether CLP+DCS-induced systemic inflammation alters Aβ deposition. Here we will use two APP transgenic mouse models – the fast progressing TgCRND8 mice and the slow progressing Tg.PrP HuAβ (APPsi) mice - to assess how systemic cytokine storm modulates amyloid deposition. In Aim 3) we will evaluate whether systemic inflammation exacerbates tau pathology. We will assess whether sepsis induces tau pathology in AD- relevant brain areas in the PS19 mice. Finally, in Aim 4) we will test whether prophylactic manipulation of the immune system alters SAE or AD-associated pathologies in selected animal models. Using an AAV-directed decoy sIL-10R, we will test whether suppressing IL-10 systemically or in the brain attenuates neuropathologic/behavioral outcomes. Additional mice will receive metformin orally during sepsis as it may be neuroprotective. This study will provide a mechanistic under-standing of sepsis-induced pathology, as well as differences in older adults with and without pre-existing AD.