Repurposing FDA-approved agonists of HCAR2 as novel therapeutics for Alzheimer's Disease

阿尔茨海默病是一种毁灭性的神经退行性疾病，目前尚无有效的治疗方法 治疗。饮食中烟酸摄入量低会增加认知脆弱的风险，烟酸缺乏会导致 神经退行性变。相反，烟酸摄入量越高，认知能力就越强。 降低认知衰退和阿尔茨海默病的风险。烟酸在大脑中的作用与其他组织不同 用作代谢底物，但主要通过激活HCAR2(Gpr109a)发挥作用， 小胶质细胞选择性地在脑中表达的一种gpcr。 NIASPAN®是FDA批准的烟酸配方，用于临床治疗血脂异常。最近，它已经 富马酸单甲酯(MMF)是富马酸二甲酯(DMF)的生物活性代谢物，是一种 HCAR2激动剂。Tecfidera®是FDA批准的DMF配方，临床用于治疗多发性硬化症 (毫秒)。用烟酸或DMF激活HCAR2可诱导帕金森病、中风和 MS模特。烟酸治疗改善了帕金森病患者的临床结果，并且有一个正在进行的临床试验 试验(NCT03808961)。烟酸治疗多发性硬化症小鼠模型，诱导保护性小胶质细胞表型。这个 这些激动剂在AD或其动物模型中的作用尚未被研究。我们假设激动剂 HCAR2对阿尔茨海默病有治疗作用。 我们提供了初步证据，在AD脑中，小胶质细胞强烈地诱导了HCAR2的表达。 5xFAD患者Hcar2基因失活增加斑块负担并加速认知损害 老鼠模型。相反，NIASPAN®治疗减少了斑块负担和神经元病理，表明 药物激活HCAR2是治疗AD的一种可行策略。 我们将研究FDA批准的HCAR2、Niaspan®和Tecfidera®激动剂的声誉潜力 对于临床前水平的阿尔茨海默病采用5xFAD小鼠模型。 目的1)评价FDA批准的药物的疗效和药理作用靶点 Niaspan®和Tecfidera®在5xFAD淀粉样变性小鼠模型中的应用 治疗5xFAD小鼠的有效治疗策略。我们将在早期和早期使用HCAR2激动剂治疗小鼠 疾病晚期和不同时期。药物疗效将通过一组表型进行评估 和行为读数。将进行药代动力学和药效学研究。我们将建立 HCAR2激动剂是否仅由小胶质细胞HCAR2选择性和诱导性产生作用 使用Cx3cr1CreERT2；Hcar2fl/fl；5xFAD小鼠灭活。 目的2)分析Niaspan®和Tecfidera®对阿尔茨海默病患者小胶质细胞转录谱的影响 我们将通过RNA-seq分析来确定Niaspan®和Tecfidera®对小胶质细胞转录组的影响 用Aβ1-42聚集体激活培养的小胶质细胞，并用这些药物处理。原代小鼠小胶质细胞 将对人类多能干细胞(HPSC)来源的小胶质细胞进行分析，以确定 Niaspan®和Tecfidera®在人类和小鼠小胶质细胞之间具有可比性。我们将在中国进行一项比较 表达高、低水平Hcar2的5xFAD小鼠小胶质细胞亚群的活体分析 使用MRFP-Report专线使用Niaspan®和Tecfidera®进行治疗。这些研究将确定目标基因和 小胶质细胞中HCAR2激活调节的通路，这些通路减弱了HCAR2在AD中的神经保护作用 允许对潜在机制进行剖析。

Alzheimer’s disease (AD) is a devastating neurodegenerative disease for which there are no effective treatments. Low dietary niacin intake increases the risk of cognitive frailty and niacin deficiency leads to neurodegeneration. Conversely, higher niacin intake is associated with improved cognitive performance, reduced risk of cognitive decline and AD. Niacin actions in the brain are distinct from other tissues where it is not used as a metabolic substrate, but exerts its actions principally through its ability to activate HCAR2 (GPR109A), a GPCR that is expressed in the brain selectively by microglia. Niaspan® is the FDA approved formulation of niacin and is used clinically to treat dyslipidemia. Recenty, it has been appreciated that monomethyl fumarate (MMF), the bioactive metabolite of dimethyl fumarate (DMF) is an agonist of HCAR2. Tecfidera® is the FDA-approved formulation of DMF used clinically to treat multiple sclerosis (MS). HCAR2 activation with niacin or DMF elicits neuroprotective effects in Parkinson's disease, stroke, and MS models. Niacin treatment of Parkinson’s patients improved clinical outcomes and there is an ongoing clinical trial (NCT03808961). Niacin treatment of a murine model of MS, induces a protective microglial phenotype. The effect of these agonists has not been investigated in AD or its animal models. We hypothesize that agonists of HCAR2 are of therapeutic utility in AD. We provide preliminary evidence there is a robust induction of HCAR2 expression by microglia in the AD brain. Genetic inactivation of Hcar2 increases plaque burden and accelerates cognitive impairment in 5xFAD AD mouse model. Conversely, Niaspan® treatment reduced plaque burden and neuronal pathology, suggesting that pharmacological activation of HCAR2 is a viable therapeutic strategy for AD. We will study the repuporsing potential of the FDA-approved agonists of HCAR2, Niaspan® and Tecfidera® for AD in the preclinical level using the 5xFAD mouse model of AD. Aim 1) Evaluate the therapeutic efficacy and pharmacological target of the FDA-approved drugs Niaspan® and Tecfidera® in the 5xFAD amyloidogenic mouse model We propose to establish an optimal effective therapeutic strategy for treatment of 5xFAD mice. We will treat mice with HCAR2 agonists at early and late disease stages and for diferent periods of time. Drug efficacy will be evaluated by a battery of phenotypic and behavioral readouts. Pharmacokinetic and pharmacodynamic studies will be performed. We will establish whether the effects HCAR2 agonists arise exclusively from microglial HCAR2 by its selective and inducible inactivation using Cx3cr1CreERT2;Hcar2fl/fl;5xFAD mice. Aim 2) Analyze microglial transcriptomic profiles induced by Niaspan® and Tecfidera® in AD We will determine the effect of Niaspan® and Tecfidera® on the microglial transcriptome by RNA-seq analysis of cultured microglia activated with Aβ1-42 aggregates and treated with these drugs. Both primary murine microglia and human pluripotent stem cells (hPSC)-derived microglia will be analyzed to establish if the actions of Niaspan® and Tecfidera® are comparable between human and murine microglia. We will carry out a parallel in vivo analysis of microglial subpopulations expressing high and low levels of Hcar2 isolated from 5xFAD mice treated with Niaspan® and Tecfidera® using an mRFP-reporter line. These studies will identify target genes and pathways modulated by HCAR2 activation in microglia which subserve its neuroprotective effects in AD, and allow the dissection of underlying mechanisms.