Transcriptional Dysfunction in Dentate Gyrus Cell Types: Roles of Retinoic Acid Responsive Genes in Protection Against Alzheimer's Disease Pathogenesis

项目摘要/摘要 海马齿状回(DG)的过度兴奋性与早期学习障碍有关 阿尔茨海默病(AD)。AD早期DG回路内出现的因果上行信号机制 发病机制尚不清楚。衰老的线粒体自由基理论提出 线粒体通过产生过量的活性氧物种(ROS)，导致氧化损伤 蛋白质、类脂和DNA？这一过程称为氧化应激(OS)。抗氧化剂通常会中和 这一过程通过清除多余的ROS，从而防止OS。抗氧化剂全反式维甲酸 视黄醇的活性形式全反式维甲酸(ATRA)在清除ROS和转录调控ROS方面具有双重作用。 突触/神经元蛋白通过其作为维甲酸受体(RAR)激动剂的功能。最近的证据来自 由于内环境平衡崩溃，啮齿动物表现出海马ATRA水平随年龄的下降 肝脏-脑轴的位置。我们认为DG中ATRA耗竭是AD发病机制中的早期事件， 导致过量的ROS诱导的损伤、线粒体功能障碍和整个RAR的占有率降低 DG细胞类型、加速淀粉样变性、网络过度兴奋和认知功能障碍。支持这一点 科学前提下，对人类海马区转录数据的二次分析导致我们发现了大量的 阿尔茨海默病患者脑组织中OS和RAR敏感基因的数量异常。在公元20年的初步研究中 小鼠模型，慢性用全反式维甲酸治疗行为正常化，防止异常抑制的形成 DG中的电路，并对包括RAR和OS敏感基因在内的许多通路进行标准化 DG。因此，我们的中心假设是全反式维甲酸的耗竭会导致氧化应激和血管紧张素转换酶 DG细胞类型中RAR敏感基因的转录调控，可加速或延迟 通过双向操纵DG ATRA水平。使用创新的多学科方法， 独一无二地结合了依赖DG的学习范例、单细胞转录和细胞/突触 在两个AD小鼠模型中的分析，我们将确定ATRA水平的双向操作如何改变 RAR敏感基因在不同类型DG细胞中的转录控制和影响DG依赖的学习和 细胞/突触功能。SA1测试了DG特异性反转学习受损伴随的假设 由于DG细胞类型中RAR敏感基因转录受损，OS和线粒体增加 两种AD小鼠模型的功能障碍。SA2测试了这样的假设：反向学习成绩、OS水平、 在两个AD小鼠模型中，DG细胞类型中RAR敏感基因的表达依赖于饮食中的视黄醇摄入量。 最后，SA3在两只AD小鼠身上验证了DG回路功能依赖于饮食中视黄醇摄入量的假设 模特们。该项目的成功完成将揭示DG相关学习障碍的新机制 在AD中发现新的AD生物标志物，在特定的细胞类型中指示ATRA缺乏。确定角色 视黄醇在预防AD方面的应用将使知识从长凳上迅速传播到床边。

PROJECT SUMMARY / ABSTRACT Hyperexcitability of the hippocampal dentate gyrus (DG) is associated with impaired learning in early stages of Alzheimer’s disease (AD). Causal upstream signaling mechanisms occurring within DG circuits early in AD pathogenesis remain poorly understood. The Mitochondrial Free Radical Theory of Aging proposes that mitochondria, through the production of excess reactive oxygen species (ROS), cause oxidative damage to proteins, lipids, and DNA ¾ a process termed oxidative stress (OS). Antioxidants (AOs) normally counteract this process by scavenging excess ROS, thereby preventing OS. The antioxidant all-trans retinoic acid (ATRA), the active form of retinol, has a dual role in ROS scavenging and transcriptional control of synaptic/neuronal proteins via its function as a retinoic acid receptor (RAR) agonist. Recent evidence from rodents has demonstrated an age-dependent decline in hippocampal ATRA levels due to homeostatic collapse of the liver-brain axis. We propose that ATRA depletion in the DG is an early event in AD pathogenesis, leading to excess ROS-induced damage, mitochondrial dysfunction, and reduced occupancy of RARs across DG cell types, accelerating amyloidosis, network hyperexcitability, and cognitive dysfunction. Bolstering this scientific premise, secondary analyses of human hippocampal transcriptomic data led us to discover a large number of OS- and RAR-sensitive genes dysregulated in AD brains. In preliminary studies from the J20 AD mouse model, chronic treatment with ATRA normalized behavior, prevented the formation of aberrant inhibitory circuits in the DG, and normalized a number of pathways that included RAR- and OS-sensitive genes in the DG. Therefore, our central hypothesis is that ATRA depletion induces oxidative stress and loss of transcriptional control of RAR-sensitive genes in DG cell types, which can be accelerated or delayed by bidirectionally manipulating DG ATRA levels. Using an innovative multidisciplinary approach that uniquely combines DG-dependent learning paradigms, single cell transcriptomics, and cellular/synaptic analysis in two AD mouse models, we will determine how bidirectional manipulation of ATRA levels alters transcriptional control of RAR-sensitive genes across DG cell types and impacts DG-dependent learning and cellular/synaptic function. SA1 tests the hypothesis that impaired DG-specific reversal learning is accompanied by impaired transcription of RAR-sensitive genes in DG cell types, increased OS, and mitochondrial dysfunction in two AD mouse models. SA2 tests the hypothesis that reversal learning performance, OS levels, and RAR-sensitive gene expression in DG cell types depend on dietary retinol intake in two AD mouse models. Finally, SA3 tests the hypothesis that DG circuit function depends on dietary retinol intake in two AD mouse models. Successful completion of this project will reveal novel mechanisms of DG-related learning impairments in AD and discover new AD biomarkers in specific cell types indicative of ATRA deficiency. Determining roles of retinol in protection against AD will enable rapid dissemination of knowledge from bench to bedside.