Sleep Disruption and Alzheimer's Disease Pathology

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ABSTRACT (Parent R01 Abstract) Alzheimer’s disease (AD) is a disease of aging. AD is the most common form of dementia, afflicting more than 5 million Americans aged 65 and older. By 2050 it is estimated that more than 14 million Americans will suffer this disease, and that its direct financial impact will exceed $1.1 trillion. AD is particularly burdensome because it impairs memory; it worsens with time; and there is no cure. Sleep disruption in AD is highly prevalent, and changes in sleep architecture and circadian rhythmicity that result in excessive daytime sleepiness and nighttime insomnia are well documented. Less well known is the impact of sleep or circadian disruption on the etiology of the disease. Sleep facilitates Aβ clearance from brain, and sleep disruption increases Aβ in cerebrospinal fluid. Aβ pathology impairs core clock genes and exacerbates neuroinflammation. Collectively, these data suggest that sleep and circadian disruption induce responses that feed forward and contribute to or exacerbate AD pathology and accelerate disease progression. However, to our knowledge definitive studies to determine the extent to which sleep disruption per se contributes to AD pathology have not been conducted. We will use mice expressing an inducible mutant amyloid precursor protein (APP) transgene to temporally dissociate sleep disruption and mutant APP expression from subsequent Aβ deposition and AD-like pathology. Specifically, we will: 1) determine how chronic sleep disruption of transgenic mice alters the course of pathology induced by expression of mutant APP; 2) determine if sleep disruption accelerates AD onset; and 3) target a key mediator of innate immune activation and determine effects on responses to sleep disruption and/or mutant APP expression. Outcome measures for each aim include assessments of cognitive performance; synaptic plasticity; differential gene expression; glial activation; cytokine production; neuroinflammatory signaling; and proteinopathy. Our multidisciplinary research team has demonstrated expertise and possesses all requisite skills to successfully complete the proposed project. Successful completion of this project will have a sustained impact on the field because we will elucidate the extent to which, and potential mechanisms by which, chronic sleep disruption alters the progression of AD-like pathology. (Administrative Supplement) The INCLUDE project focuses on critical health and quality-of-life needs for individuals with Down syndrome. Links between AD and DS are well-documented, but mechanisms underlying them are little understood. NIA is prioritizing research that aims “to understand the molecular mechanism(s) underlying the interplay between aging and neurodegeneration in DS”. A strong candidate for the DS-AD link is the triplication of the Amyloid Precursor Protein (APP) and Regulator of calcineurin1 (RCAN1) genes in trisomy 21. The cleavage product of APP, Aβ, is a defining histopathological marker of AD and promotes sleep dysfunction, whereas RCAN1 affects circadian function and promotes AD-related pathology. This administrative supplement focuses on sleep disruption, APP and RCAN1 as mechanistic DS-AD links. Our preliminary data demonstrate that genetic manipulation to restore Rcan1 to normal levels ameliorates sleep disturbances in a DS model. The research proposed in this supplement is significant because the role of APP overexpression in promoting DS-related sleep or cognitive abnormalities has not been investigated.