A flavonoid gamma-secretase modulator (GSM) reduces beta-amyloid and tau pathologies in the AD mice

 性状（由申请人提供）：γ-分泌酶在AD中可能具有双重作用。γ-分泌酶对APP的切割是AD发病机制和脑中淀粉样蛋白积聚的关键。因此，多年来，γ-分泌酶一直是AD疗法和γ-分泌酶抑制剂（GSI）开发的目标。最近的研究表明，影响γ-分泌酶活性的早老素突变可能会损害小胶质细胞对ApoA的吞噬作用，并促进淀粉样蛋白的积累。由于GSI可能通过抑制Notch信号通路损害有益的小胶质细胞活性，我们寻求开发一类新的类黄酮GSI，其可以减少γ-APP切割，同时最小化其对小胶质细胞吞噬活性的潜在负面影响。最理想的情况是，我们将寻求在促进后者的同时做到前者。关于地奥司明促进抗淀粉样蛋白生成APP加工和小胶质细胞吞噬AAPs的功效，我们最近表明，用地奥司明治疗Tg 2576小鼠显著减少脑A β 40，42种类，从而降低AAPs沉积。基于这一发现，其代谢产物薯蓣皂苷成为我们的重点进行了初步研究。这些结果表明，地奥司明/diosmetin不仅通过抑制γ-APP切割减少AAPs，通过调节GSK 3 β活化减少过度磷酸化tau，而且还增强小胶质细胞吞噬表型转换。在本提案中，将在AD样病理学发展之前（预防性治疗组）或之后（治疗性治疗组）对3XTg-AD小鼠经口给予类黄酮-地奥司明。将未处理的非转基因同窝仔组与转基因处理组进行比较。将对4月龄和6月龄的3XTg-AD小鼠经口给予地奥司明6个月。目的1，我们将在几个年龄处死这些小鼠，以检查组织学和生化终点，并将病理变化与认知障碍的改善相关联（由NCAAM资助）。在本研究中，我们计划评价两个时间点，比较地奥司明与对照品。将通过其对抗认知障碍和减少AD样病理学（包括脑β-淀粉样蛋白沉积和tau过度磷酸化/NFT）的作用对各组进行比较。已知AD伴随促炎性小胶质细胞反应的上调，表现为小胶质细胞增加的趋化因子产生。此外，我们的初步数据表明，地奥司明的代谢产物，diosmetin通过下调小胶质细胞CD 40信号传导和由此促进小胶质细胞对老化的ARAP 10肽的吞噬作用诱导抗炎表型。因此，在目的2中，我们将检验地奥司明治疗保留从年轻和老年3XTg-AD小鼠分离的原代小胶质细胞中的促炎表型的假设。这些研究可为不久的将来进行地奥司明饮食补充的AD临床试验奠定基础。

 DESCRIPTION (provided by applicant): There may be a dual role of γ-secretase in AD. The cleavage of APP by γ-secretase is key in the pathogenesis of AD and amyloid accumulation in the brain. As such, γ-secretase has been targeted for years for development of AD therapies and γ-secretase inhibitors (GSIs). Most recently it was shown that a mutation in presenilin affecting γ-secretase activity may impair microglial phagocytosis of Aß and promote amyloid accumulation. Because GSIs may impair salutary microglia activity via inhibition of Notch signaling pathway, we seek to develop a new class of flavonoids GSIs that can reduce γ-APP cleavage yet minimize their potential negative effect on microglia phagocytosis activity. Optimally we would seek to do the former while promoting the latter. Turning to diosmin's efficacy as promoting both anti-amyloidogenic APP processing and microglial phagocytosis of Aß, we have recently shown that the treatment of Tg2576 mice with diosmin markedly reduces cerebral Aß40,42 species and consequently lowers Aß deposits. Based on this finding, its diosmetin metabolite becaome our focus on preliminary studies. These results indicate that diosmin/diosmetin not only reduces Aß by inhibiting γ-APP cleavage and decreases hyperphosphorylated tau by modulating GSK3ß activation, but also enhances microglial phagocytotic phenotype switching. In this proposal, flavonoid-diosmin will be orally administered to 3XTg-AD mice before (prophylactic treatment group) or after (therapeutic treatment group) development of AD-like pathology. Groups of untreated non-transgenic littermates will be compared to the transgenic treatment groups. Oral administration of diosmin to 3XTg-AD mice at 4 and 6 months of age will be performed for 6 months. Aim 1, we will sacrifice these mice at several ages to examine histological and biochemical endpoints and correlate pathological changes with improvement of cognitive impairment (funded by NCAAM). In this study, we plan to evaluate two time points comparing diosmin to control. Groups will be compared by their effects on opposing cognitive impairment and reducing AD-like pathology, including cerebral ß-amyloid deposits and tau hyperphosphorylation/NFT. AD is known to be accompanied by up-regulation of pro-inflammatory microglial responses manifested as the increased chemokine production by microglia. In addition, our preliminary data show that diosmin's metabolite, diosmetin induces anti-inflammatory phenotype through down-regulation of microglial CD40 signaling and resultant promotion of microglial phagocytosis of the aged Aß peptide. Thus in Aim 2, we will test the hypothesis that diosmin treatment preserves the pro-inflammatory phenotype in primary microglia isolated from young and aged 3XTg-AD mice. These studies could lay the foundation for AD clinical trials with diosmin diet supplementation in the near future.