Alzheimer's disease pathogenesis and the desynchronization of cortico-limbic circadian rhythms

最近的研究建立了阿尔茨海默病(AD)和脑电活动中断之间的明确联系 昼夜节律计时系统然而，这种关系的机制基础并不清楚。 已确认身份。有趣的是，如果我们试图解构这种关系并将其置于 阿尔茨海默病对认知的深刻影响，几个想法开始成为焦点。第一，数据 到目前为止，已经揭示了皮质-边缘回路中的昼夜节律调节复杂的行为状态， 包括认知。第二，AD对这些相同回路的功能可塑性有显著影响。这些 观察提出了一个有趣的问题：阿尔茨海默病的认知缺陷是否部分源于 大脑皮质-边缘环路的昼夜节律失调？作为对这一想法的初步审查，我们 建议检验以下假设：阿尔茨海默病早期到中期的认知缺陷部分是由 整个系统的皮质-边缘昼夜节律计时系统的保真度崩溃。为了检验这一假设，我们 已经组装了一套创新的转基因小鼠模型和最先进的成像方法，将 允许我们描述和操纵疾病进展过程中的昼夜节律。在目标1中， 淀粉样蛋白β肽(Aβ)对基于细胞和电路的时间保持能力的保真度的影响将是 检查过了。在实验中，我们将使用基于细胞培养的图谱方法来测试β寡聚体对 从SCN分离的神经元的细胞自主昼夜节律能力 生物钟)、大脑皮层和海马体。在实验中1B脑片外植体成像将用于测试 Aβ对基于电路的昼夜节律产生的影响。在目标2中，我们建议配置时钟计时和 钟控基因在5XFAD小鼠AD模型中的表达在实验中2a，颅窗成像(通过 多光子显微镜)在额叶皮质和海马区的时钟计时将被用来产生 时钟相位、节奏幅度和振荡器同步的蜂窝级和系统级配置文件 阿尔茨海默病的病程。这项研究将得到基于免疫荧光的时钟基因的补充 分析(Exp.2b)和转录剖析(Exp.2C)。在目标3中，我们将测试疾病的影响 5XFAD模式中的进展具有时钟门控(Exp.3A)和活动诱发(Exp.3b)蜂窝信令， 以及树突棘的形成。在目标4中，我们将测试边缘皮质的去同步化 振荡器是阿尔茨海默病5XFAD小鼠模型认知缺陷的基础。实现这一目标的关键是测试 时钟增强剂PF-670462是否触发皮质边缘振荡器的再同步 如果是这样的话，这种效应是否构成了PF-670462增强认知能力的基础。如果我们的 基本假设得到验证，这些数据将为新的调查路线提供重要的起点 (以及潜在的新的治疗干预措施)旨在进一步了解机制关系 (在细胞、系统和遗传学水平上)昼夜节律和AD发病机制之间的关系。

Recent work has established a clear connection between Alzheimer’s disease (AD) and the disruption of the circadian timing system. However, the mechanistic underpinnings of this relationship have not been clearly identified. Interestingly, if we attempt to deconstruct this relationship and place it within the context of the profound effects that Alzheimer’s disease has on cognition, several ideas begin to come into focus. First, data to date has revealed that circadian timing within cortico-limbic circuits modulates complex behavioral states, including cognition. Second, AD has marked effects on functional plasticity of these same circuits. These observations raise an interesting question: could the cognitive deficits in AD result, in part, from the dysregulation of circadian timing within cortico-limbic circuits? As an initial examination of this idea, we propose to test the following hypothesis: The cognitive deficits during early- to mid-stage of AD results in part from a systems-wide breakdown in the fidelity of the cortico-limbic circadian timing systems. To test this hypothesis, we have assembled an innovative set of transgenic mouse models and state-of-the-art imaging methods that will allow us to both profile and manipulate circadian timing over the course of disease progression. In Aim 1, the effects of amyloid β peptide (Aβ) on the fidelity of cellular-and circuit-based time-keeping capacity will be examined. In Exp. 1A, we will use a cell-culture based profiling approach to test the effects of Aβ oligomer on the cell autonomous circadian timekeeping capacity of neurons isolated from the SCN (the locus of the master circadian clock), the cortex and the hippocampus. In Exp. 1B brain slice explant imaging will be used to test the effects of Aβ on circuit-based circadian rhythm generation. In Aim 2 we propose to profile clock timing and clock-gated gene expression in the 5XFAD mouse model of AD. In Exp. 2A, cranial window imaging (via multiphoton microscopy) of clock timing in the frontal cortex and the hippocampus will be used to generate a cellular- and systems-level profile of clock phasing, rhythm amplitude and oscillator synchrony over the course of the AD-like pathology. This study will be complemented by immunofluorescence-based clock gene profiling (Exp. 2B) and by transcriptomic profiling (Exp. 2C). In Aim 3, we will test the effects that disease progression in the 5XFAD model has on clock-gated (Exp. 3A) and activity-evoked (Exp. 3B) cellular signaling, as well as on dendritic spine formation. In Aim 4 we will test whether the desynchronization of cortico-limbic oscillators underlies the cognitive deficits in the 5XFAD mouse model of AD. Key to this aim will be to test whether the clock enhancing compound PF-670462 triggers the resynchronization of cortico-limbic oscillator populations, and if so, whether this effect underlies the capacity of PF-670462 to augment cognition. If our underlying hypothesis is validated, these data will provide an important starting point for new lines of inquiry (and potentially new therapeutic interventions) designed to further understand the mechanistic relationships (at a cellular, systems, and genetics level) between circadian timing and AD pathogenesis.