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

摘要 慢性重度或酗酒与痴呆症和阿尔茨海默病（AD）风险增加有关， 尽管还没有确定连接疾病病理的机制。AD病理学遵循 脑中促炎性信号传导的时间进展与Aβ沉积、tau纤维形成、突触丧失 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 （p）-tau-181在人类酒精使用障碍（AUD）大脑中的作用，以及在生命早期慢性酒精狂欢后的作用。 Tg-AD小鼠模型。Toll样受体（TLR）促炎信号被认为先于大体病理学 在AD中，这是AUD的显著特征。我们发现年轻人的AUD与AD蛋白有关 在3x-Tg-AD小鼠中，慢性酒精狂欢治疗导致 促炎基因与神经毒性Aβ1-42和p-tau-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传导促进AD神经毒性蛋白病理学。 小胶质细胞已成为AD病理学的介质，有助于Aβ斑块形成，tau蛋白传播， 突触丧失和可能的神经退化小胶质细胞改变表型（例如静息、吞噬、 促炎、修剪或神经毒性）和小胶质细胞活化被认为先于并促进AD 病理人类GWAS以及人类和AD小鼠单核RNA测序（snRNA-seq）具有 发现AD小胶质细胞发生改变，C1 q（促突触修剪）增加，静息状态减少 标记（例如Tmem 119）。在人类AUD大脑中，我们发现静息状态小胶质细胞减少（Tmem 119减少） 促炎性小胶质细胞此外，我们发现体内慢性酒精狂欢持续增加C1 q， 反映AD的促炎细胞因子。因此，我们假设促炎性小胶质细胞活化是通过 慢性重度/酗酒乙醇促进AD Aβ和tau病理学、突触丢失和神经变性。 将在人AD死后脑（Aim 1）和3x-Tg-AD小鼠模型（Aim 2）中检验该假设 以进行性Aβ和tau蛋白病变为特征 凋亡性神经元细胞死亡是AD病理学的一个特征，被认为有助于不可逆的认知衰退。 我们发现酒精过量会增加AD中已知有神经元丢失的大脑区域的神经变性， 前额叶皮层（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，导致凋亡性神经元细胞死亡。我们发现慢性的 酗酒增加HMGB 1-TLR 4信号传导以激活小胶质细胞。促炎性小胶质细胞分泌 我们发现的miRNA let-7 b激活了神经元中的TLR 7。神经元中的Let-7 b-TLR 7信号传导诱导凋亡 通过TNF受体超家族凋亡诱导配体（TRAIL）的神经元细胞死亡。TLR4、HMGB1、let-7 和TRAIL各自与AD病理学有关。然而，AD神经退行性变的联系还没有被证实。 鉴定我们假设慢性酒精狂欢通过增强TRAIL-1促进AD神经退行性变。 介导的凋亡性神经元细胞死亡。这一假设将在人类AD死后脑中进行测试（Aim 1），以及以Aβ诱导的神经元凋亡为特征的5xFAD AD小鼠模型（目的3）。

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.