Apolipoprotein E and immunometabolism in Alzheimer's disease

摘要：慢性神经炎症和代谢障碍是神经退行性疾病的特征， 包括阿尔茨海默病(AD)。已知的最早的AD生物标志物之一是一种改变的模式 大脑中的局部葡萄糖代谢。载脂蛋白E(ApoE)ε4等位基因携带者表现为 从小大脑葡萄糖代谢改变的模式，并患有显著增加的风险 收购AD的可能性。同时，ε4的个体也被认为具有不适应和有害的 神经炎性表型，ε4小胶质细胞中的促炎信号增加。另外，这是很好的- 证实小胶质细胞炎症表型是由精确的代谢重新编程驱动的，与亲- 炎性细胞因子的产生需要增加有氧糖酵解--这种现象被称为 ‘免疫代谢’。这项建议旨在调查ε4的神经炎性表型 小胶质细胞可能是由ε4‘S对糖代谢的影响所驱动的。目标1将调查 糖酵解原基因表达增强驱动神经炎性ε4转录的假说 通过利用靶向单细胞RNA测序的能力来询问基因表达的表型 一组预先选择的代谢、神经炎性和疾病相关基因，结果在 蛋白质和翻译后水平。目标2将解决ε4小胶质细胞表现出增加的假设 由于中枢碳代谢的潜在损害而导致的促炎表型。我们将使用STRATE 用13C-葡萄糖示踪剂测定ε2、ε3和ε4的代谢通量的同位素分解代谢组学 原代小胶质细胞对促炎和抗炎治疗有反应。我们会将氧化反应 对这些处理作出反应的磷酸化和糖酵解活性。这些新陈代谢指标将会是 通过同时评估细胞因子释放和吞噬活性，与小胶质细胞功能的读数相关联。目标3 将评估靶向关键代谢节点以重新编程ε4炎症反应的效果。我们 假设药物抑制或病毒过度表达的特定代谢酶在 我们的初步数据显示，受载脂蛋白E基因干扰，ε4小胶质细胞将重新平衡细胞因子的产生 改善β-淀粉样蛋白的吞噬功能。我们这次研究的最终目标是：(1)了解 APOE基因如何影响小胶质细胞对炎症刺激的代谢反应，(2)决定 代谢基因表达的改变是否会驱动有利于神经炎症和 增加AD风险，以及(3)确定APOE基因改变的免疫代谢途径可能代表 治疗神经退行性疾病的靶向途径。这一建议融合了创新 转录和代谢组技术与小胶质细胞的功能读数相结合，以统一我们对 ε4‘S风险的两个主要方面：代谢功能障碍和慢性神经炎。以这两个目标为目标 在开发成功的治疗AD的疗法方面，这些方面可能拥有更大的希望。

Summary: Chronic neuroinflammation and metabolic dysfunction characterize neurodegenerative diseases, including Alzheimer's disease (AD). One of the earliest known biomarkers of AD is an altered pattern of regional glucose metabolism in the brain. Carriers of the ε4 allele of apolipoprotein E (APOE) exhibit this pattern of altered cerebral glucose metabolism from a young age and suffer from a dramatically increased risk of acquiring AD. Meanwhile, ε4 individuals are also considered to have a maladaptive and detrimental neuroinflammatory phenotype, with increased pro-inflammatory signaling in ε4 microglia. Additionally, it is well- established that microglial inflammatory phenotypes are driven by precise metabolic reprogramming, with pro- inflammatory cytokine production requiring increased aerobic glycolysis – a phenomenon known as `immunometabolism'. This proposal aims to investigate whether the neuroinflammatory phenotype in ε4 microglia could be intrinsically driven by ε4’s effects on glucose metabolism. Aim 1 will investigate the hypothesis that enhanced pro-glycolytic gene expression drives neuroinflammatory ε4 transcriptional phenotypes by leveraging the power of targeted single-cell RNA sequencing to interrogate gene expression of a panel of pre-selected metabolic, neuroinflammatory, and disease-associated genes, with results validated at the protein and post-translational level. Aim 2 will address the hypothesis that ε4 microglia show an increased pro-inflammatory phenotype due to underlying impairments in central carbon metabolism. We will use Stable Isotope Resolved Metabolomics (SIRM) with a 13C-glucose tracer to measure metabolic flux in ε2, ε3, and ε4 primary microglia responding to pro- and anti-inflammatory treatments. We will compare oxidative phosphorylation and glycolytic activity in response to these treatments. These metabolic measures will then be linked to readouts of microglial function by assessing cytokine release and phagocytic activity in parallel. Aim 3 will evaluate the efficacy of targeting key metabolic nodes to reprogram the ε4 inflammatory response. We hypothesize that pharmacological inhibition or viral overexpression of specific metabolic enzymes identified in our preliminary data as being perturbed by APOE genotype will rebalance cytokine production in ε4 microglia and improve phagocytosis of amyloid beta peptide. Our ultimate goals for this research are to: (1) understand how APOE genotype influences the metabolic response to inflammatory stimuli in microglia, (2) determine whether altered metabolic gene expression drives a transcriptional profile that favors neuroinflammation and increased AD risk, and (3) identify immunometabolic pathways altered by APOE genotype that could represent avenues to target in the treatment of neurodegenerative disease. This proposal integrates innovative transcriptomic and metabolomic techniques with functional readouts of microglia to unify our understanding of two major facets of ε4’s risk: metabolic dysfunction and chronic neuroinflammation. Targeting both of these aspects in tandem may hold greater promise in developing successful therapeutics for the treatment of AD.