Age-related repetitive element dysregulation, neuroinflammation and Alzheimer's disease

项目摘要 越来越多的证据将转座/重复元件（RE）转录本与阿尔茨海默病（AD）联系起来，但 其潜在机制和疾病相关性尚不清楚。在这个项目中，我们将测试假设， RE与AD相关的机制是年龄依赖性的、整体RE转录物增加，其导致年龄/AD- 相关的神经炎症我们的理论基础是：1）衰老是AD的关键危险因素; 2）RE转录本来源于 基因组中结构/逆转录病毒序列的RE转录物随着年龄的增长而逐渐积累; 3）RE转录物是 易于形成双链RNA（dsRNA）和/或互补DNA（cDNA），这两者都可以引起 神经炎症（病理学之前的脑老化/AD的主要驱动因素）; 4）老化和AD也是 与表观遗传控制中的损伤有关（例如，低甲基化，这可以促进RE转录） 和质量控制系统，如自噬，降解RE转录本（这可能增强RE衍生的 cDNA/dsRNA积累）。新出现的数据甚至表明，RE衍生的dsRNA/cDNA可以通过 细胞外囊泡（EV），在AD中观察到的病理学的一个潜在的非细胞自主解释。 这些观察结果表明一种与AD的年龄依赖性高度一致的模型， 与年龄相关的RE转录物增加导致RE衍生的dsRNA/cDNA，其驱动神经炎症和AD。 为了支持这一观点，我们的初步数据显示，AD患者的RE转录本是低甲基化的， 与病理学之前的神经炎症相关，并抑制人RE转录本的积累 星形胶质细胞/神经元可以减少炎症。我们还在AD患者的循环EV中发现了RE的证据。 基于这些观察结果，我们建议（目标1）确定是否与年龄而非病理相关的RE 通过对现有的RNA-seq进行大量的生物信息学分析， 数据，探测人类/AD大脑中的RE，并分析全局甲基化（全基因组亚硫酸氢盐测序） 在相同的大脑中，以及来自大脑老化纵向研究的>100名受试者的样本中， 神经炎症和AD。与此同时（目标2），我们将使用患者来源的星形胶质细胞和神经元来测试 临床上可转化的治疗的功效（例如，甲基化/自噬激活剂），减少RE衍生的 dsRNA和cDNA抑制年龄/AD相关的神经炎症，我们将确定RE可能导致 通过与细胞dsRNA和cDNA传感器（PKR和cGAS）结合来抑制神经炎症。最后（目标3），我们将 确定RE转录物是否诱导老年/AD样神经炎症并在年轻星形胶质细胞的EV中积累 以及这些EV传播的RE转录物是否在其他细胞中引起炎症/毒性。我们也 将使用现有样本（如上所述）确定EV中的RE是否与全身性 炎症、神经炎症和AD。这些研究是专门设计来扩展我们的 正在进行的，国家免疫局资助的试点项目，产生多组学数据的可再生能源在老龄化/AD，并提供一个平台， 未来的诊断学或治疗学。

PROJECT SUMMARY Growing evidence links transposable/repetitive element (RE) transcripts with Alzheimer’s disease (AD), but the underlying mechanisms and disease relevance are unclear. In this project, we will test the hypothesis that the mechanism linking RE with AD is an age-dependent, global RE transcript increase that causes age/AD- related neuroinflammation. Our rationale is that: 1) aging is the key risk factor for AD; 2) RE transcripts derived from structural/retroviral sequences in the genome accumulate progressively with aging; 3) RE transcripts are prone to form double-stranded RNA (dsRNA) and/or complementary DNA (cDNA), both of which can cause neuroinflammation (a major driver of brain aging/AD that precedes pathology); 4) aging and AD are also linked with impairments in epigenetic control (e.g., hypo-methylation, which could facilitate RE transcription) and quality control systems like autophagy that degrade RE transcripts (which could potentiate RE-derived cDNA/dsRNA accumulation). Emerging data even suggest that RE-derived dsRNAs/cDNAs could spread via extracellular vesicles (EVs), a potential non-cell-autonomous explanation for the pathology observed in AD. These observations suggest a model that is highly consistent with the age-dependence of AD, in which global, age-related RE transcript increases lead to RE-derived dsRNAs/cDNAs that drive neuroinflammation and AD. In support of this idea, our preliminary data show that RE transcripts are hypomethylated in AD patients and correlate with neuroinflammation prior to pathology, and that inhibiting RE transcript buildup in human astrocytes/neurons may reduce inflammation. We also find evidence of RE in circulating EVs from AD patients. Based on these observations, we propose to (Aim 1) determine if age- rather than pathology-related RE transcript dysregulation links RE with AD by performing a large bioinformatics analysis of existing RNA-seq data, probing for RE in human/AD brains, and profiling global methylation (whole-genome bisulfite sequencing) in the same brains, as well as in samples from >100 subjects from a longitudinal study on brain aging, neuroinflammation and AD. In parallel (Aim 2), we will use patient-derived astrocytes and neurons to test the efficacy of clinically translatable treatments (e.g., methylation/autophagy activators) that reduce RE-derived dsRNAs and cDNAs for inhibiting age/AD-related neuroinflammation, and we will identify RE that may cause neuroinflammation by binding to cellular dsRNA and cDNA sensors (PKR and cGAS). Finally (Aim 3), we will determine if RE transcripts induce aged/AD-like neuroinflammation and accumulate in EVs in young astrocytes and neurons, and whether these EV-borne RE transcripts cause inflammation/toxicity in other cells. We also will use existing samples (as described above) to determine if RE in EVs are related to markers of systemic inflammation, neuroinflammation and AD in humans. These studies are specifically designed to extend on our ongoing, NIA-funded pilot projects, generate multi-omics data on RE in aging/AD, and to provide a platform for future diagnostics or therapeutics in this context.