Microglia Activation and TLR-induced Neurodegeneration by Alcohol Promotes Progression of Alzheimer Pathology

摘要 长期大量饮酒或酗酒与痴呆症和阿尔茨海默病(AD)风险增加有关， 尽管与疾病病理有关的机制尚未确定。AD病理学遵循的是 Aβ沉积、tau原纤维形成、突触丢失、 神经退化和认知能力下降。我们发现AD病理蛋白Aβ1-42和磷酸化增加 (P)-tau-181在人类酒精使用障碍(AUD)脑中和慢性酗酒后早期生命中的3倍-tau-181 TG-AD小鼠模型。Toll样受体(TLR)促炎症信号被认为先于大体病理 在AD中，并且是AUD的一个显著特征。我们发现年轻人的AUD与AD蛋白有关 在3x-TG-AD小鼠中积聚和慢性酗酒治疗导致持续上调 促炎基因与神经毒性A tau-1-42和p-β-181蛋白水平密切相关。因此，我们 假设乙醇通过增强促炎信号来促进AD神经毒性蛋白的病理改变。 小胶质细胞是AD病理的中介细胞，参与了Aβ斑块的形成、tau的增殖、 突触丢失，可能还有神经变性。小胶质细胞改变表型(如静息、吞噬、 促炎、修剪或神经毒性)和小胶质细胞激活被认为是AD的先兆和促进因素 病理学。人GWAS以及人和AD小鼠的单核RNA测序(SnRNA-seq) 发现AD小胶质细胞改变，增加了C1q(突触前修剪)和减少了静息状态 标记(例如Tem119)。在人的AUD脑中，我们发现静息状态的小胶质细胞减少(减少的Tem119) 有促炎的小胶质细胞。此外，我们还发现，体内长期酗酒会持续增加C1q和 促炎细胞因子反映AD。因此，我们假设促炎性小胶质细胞激活是通过 长期大量饮酒会促进AD Aβ和tau病理、突触丢失和神经变性。 这一假设将在人类AD死后脑(AIM 1)和3x-TG-AD小鼠模型(AIM 2)中进行验证 这是以进行性Aβ和tau病理为特征的。 神经细胞凋亡是阿尔茨海默病的一个病理特征，被认为是导致不可逆转的认知功能下降的原因之一。 我们发现，酗酒会增加AD中已知神经元丢失的脑区的神经变性，例如 前额叶皮质(PFC)和海马体。我们的研究涉及促炎性Toll样受体(TLR) 激活和小胶质细胞与神经元的相互作用，导致神经细胞的凋亡。我们发现慢性 酗酒会增加HMGB1-TLR4信号，从而激活小胶质细胞。促炎小胶质细胞分泌 我们发现的miRNA let-7b可以激活神经元中的TLR7。神经元中的let-7b-TLR7信号诱导细胞凋亡 肿瘤坏死因子受体超家族凋亡诱导配体(TRAIL)介导的神经细胞死亡。TLR4、HMGB1、LET-7 和TRAIL都与AD的病理有牵连。然而，阿尔茨海默病与神经退行性变之间的联系并不是 已确认身份。我们假设长期酗酒通过增强TRAIL促进AD神经退行性变- 介导的神经细胞凋亡。这一假说将在人类AD死后脑(AIM)中得到验证 1)，以及5xFAD小鼠模型(Aim 3)，该模型以Aβ诱导的神经元凋亡为特征。

Abstract Chronic heavy or binge alcohol use is associated with dementia and increased risk for Alzheimer's disease (AD), though mechanisms connecting the disease pathologies have not been identified. AD pathology follows a temporal progression of proinflammatory signaling in brain with Aβ deposition, tau fibril formation, synapse loss, neurodegeneration, and cognitive decline. We find increased AD pathology proteins Aβ1-42 and phosphorylated (p)-tau-181 in human alcohol use disorder (AUD) brain and after chronic binge ethanol during early life in the 3x- Tg-AD mouse model. Toll-like Receptor (TLR) proinflammatory signaling is thought to precede gross pathology in AD, and is a prominent feature of AUD. We find AUD in young individuals is associated with AD protein accumulation, and chronic binge ethanol treatment in 3x-Tg-AD mice causes persistent upregulation of proinflammatory genes that correlated strongly with levels of neurotoxic Aβ1-42 and p-tau-181 protein. Thus, we hypothesize ethanol promotes AD neurotoxic protein pathology by enhancing proinflammatory signaling. Microglia have emerged as mediators of AD pathology, contributing to Aβ plaque formation, tau propagation, synapse loss and possibly neurodegeneration. Microglial change phenotype (e.g. resting, phagocytic, proinflammatory, pruning, or neurotoxic) and microglial activation is thought to precede and promote AD pathology. Human GWAS as well as human and AD mouse single nuclei RNA sequencing (snRNA-seq) have identified AD microglia as altered, having increased C1q (pro-synaptic pruning) and reduced resting state markers (e.g. Tmem119). In human AUD brain, we find reduced resting state microglia (reduced Tmem119) with proinflammatory microglia. Further, we find chronic binge ethanol in vivo persistently increases C1q and proinflammatory cytokines mirroring AD. Thus, we hypothesize proinflammatory microglial activation by chronic heavy/binge ethanol promotes AD Aβ and tau pathology, synapse loss and neurodegeneration. This hypothesis will be tested in human AD post-mortem brain (Aim 1), and the 3x-Tg-AD mouse model (Aim 2) that features progressive Aβ and tau pathology. Apoptotic neuronal cell death is a feature of AD pathology thought to contribute to irreversible cognitive decline. We find binge ethanol increases neurodegeneration in brain regions known to have neuronal loss in AD such as prefrontal cortex (PFC) and hippocampus. Our studies implicate proinflammatory Toll-like Receptor (TLR) activation and microglial to neuronal interactions that lead to apoptotic neuronal cell death. We find chronic binge ethanol increases HMGB1-TLR4 signaling to activate microglia. Proinflammatory microglia secrete the miRNA let-7b that we found activates TLR7 in neurons. Let-7b-TLR7 signaling in neurons induces apoptotic neuronal cell death via the TNF-receptor superfamily apoptosis-inducing ligand (TRAIL). TLR4, HMGB1, let-7 and TRAIL have each been implicated in AD pathology. However, a link in AD neurodegeneration has not been identified. We hypothesize chronic binge ethanol promotes AD neurodegeneration by enhancing TRAIL- mediated apoptotic neuronal cell death. This hypothesis will be tested in human AD post-mortem brain (Aim 1), and the 5xFAD AD mouse model (Aim 3) that features Aβ-induced apoptotic neuronal death.