Pathogenesis of Early- Versus Late-Stage Alcohol-Mediated White Matter Degeneration

长期大量饮酒或酗酒会损害大脑的结构和功能完整性。 乙醇的神经毒性和退行性作用在整个生命周期中以白色物质（WM）为目标，导致 髓鞘、受损的髓鞘维持和轴突变性。由于WM完整性对许多CNS至关重要， 功能，更好地了解乙醇如何发挥其对WM的不利影响，以防止或 修复相关的神经行为和认知缺陷。少突胶质细胞功能障碍是 WM变性，因为少突胶质细胞负责合成和维持髓鞘。髓鞘被 需要支持和保护轴突，并确保有效的神经元传导性。我们假设酒精- 涉及WM的相关脑变性（ARBD）可分为：1）早期，可逆阶段， 主要与髓鞘丢失相关，并由氧化应激、炎症和神经毒性神经酰胺介导 通过髓鞘分解和脂质代谢失调的积累;和2）后期阶段， 通过PI 3 K-Akt-mTOR-mTORC受损的胰岛素/IGF-1信号传导。后者的后果包括： 成熟的少突胶质细胞和致密的髓鞘，少突胶质细胞成熟受损，轴突损伤， 进一步进行性失调的鞘脂代谢与神经酰胺积累和硫苷脂消耗。 我们预计，禁欲将足以补救早期阶段的WM ARBD，而积极 干预措施，如胰岛素增敏剂治疗，将需要扭转WM损伤持续了很长时间， 大量酒精暴露的时期。然而，ARBD的早期和晚期都可能对神经酰胺产生反应， 抑制剂，如myriocin。目的1将描述的结构，生物化学和分子病理学的特点， 在已建立的慢性乙醇暴露大鼠模型中观察到早期WM ARBD。目标2将利用大鼠模型 和人类死后大脑来评估受损的胰岛素/IGF-1信号通过PI 3 K-Akt-mTOR的作用 以及mTORC 1与mTORC 2作为少突胶质细胞功能障碍和鞘脂代谢改变的驱动因素 在WM ARBD的后期阶段。目的3将评估禁欲，神经酰胺抑制剂， 胰岛素增敏剂治疗少突胶质细胞功能障碍和相关髓鞘改变 在WM ARBD的早期与晚期阶段中的鞘脂组成。此外，一个新的子目标将决定 乙醇诱导的CNS WM髓鞘鞘脂异常的程度及其对 可以在外周血单核细胞（PBMC）中检测治疗。我们的基本假设是 通过使用定量免疫组织化学，电子显微镜，多重ELISA， mRNA研究和基质辅助激光解吸/电离成像质谱法。研究计划 是新颖的，机械的，稳健的，透明的，包括两性，人类验证研究， 根据ARBD分期进行分层治疗，以及潜在监测ARBD相关 WM生化病理学和对非侵入性PBMC测定治疗的反应。

Chronic heavy or binge alcohol consumption damages the structural and functional integrity of the brain. Ethanol’s neurotoxic and degenerative effects target white matter (WM) across the lifespan, resulting in loss of myelin, impaired myelin maintenance, and degeneration of axons. Since WM integrity is critical to many CNS functions, better understanding of how ethanol exerts its adverse effects on WM is needed to prevent or remediate the associated neurobehavioral and cognitive deficits. Oligodendrocyte dysfunction is at the core of WM degeneration since oligodendroglia are responsible for synthesizing and maintaining myelin. Myelin is needed to support and protect axons and ensure efficient neuronal conductivity. We hypothesize that alcohol- related brain degeneration (ARBD) involving WM could be divided into: 1) an early, reversible stage that is mainly associated with myelin loss and mediated by oxidative stress, inflammation, and neurotoxic ceramide accumulation via myelin breakdown and dysregulation of lipid metabolism; and 2) a later stage marked by impaired insulin/IGF-1 signaling through PI3K-Akt-mTOR-mTORC. Consequences of the latter include loss of mature oligodendrocytes and compact myelin, impaired maturation of oligodendroglia, axonal damage, and further progressive dysregulated sphingolipid metabolism with ceramide accumulation and sulfatide depletion. We anticipate that abstinence will be sufficient to remediate early stages of WM ARBD, whereas active interventions, such as insulin sensitizer treatments, will be required to reverse WM damage sustained by long periods of heavy alcohol exposure. However, both early and late stages of ARBD will likely respond to ceramide inhibitors such as myriocin. Aim 1 will characterize the structural, biochemical and molecular pathologies of early-stage WM ARBD in an established rat model of chronic ethanol exposure. Aim 2 will utilize a rat model and human postmortem brains to assess the roles of impaired insulin/IGF-1 signaling through PI3K-Akt-mTOR and mTORC1 versus mTORC2 as drivers of oligodendrocyte dysfunction and altered sphingolipid metabolism in the later stages of WM ARBD. Aim 3 will evaluate the effectiveness of abstinence, ceramide inhibitor, and insulin sensitizer treatments in remediating oligodendrocyte dysfunction and associated alterations in myelin sphingolipid composition in early versus late stages of WM ARBD. In addition, a novel sub-aim will determine the degree to which ethanol-induced CNS WM myelin sphingolipid abnormalities and their responses to treatment can be detected in peripheral blood mononuclear cells (PBMCs). Our underlying hypotheses are addressed through the use of quantitative immunohistochemistry, electron microscopy, multiplex ELISAs, mRNA studies, and Matrix-assisted laser desorption/ionization-imaging mass spectrometry. The research plan is novel, mechanistic, robust, transparent, and inclusive of both sexes, human validation studies, prospects for stratifying treatment according to ARBD stage, and approaches for potentially monitoring ARBD-associated WM biochemical pathology and responses to treatment with non-invasive PBMC assays.