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

 描述(申请人提供)：在AD中可能存在γ-分泌酶的双重作用。γ-分泌酶对APP的裂解是AD和淀粉样蛋白在脑内堆积的关键。因此，γ-分泌酶多年来一直是AD治疗和γ-分泌酶抑制剂(GSI)开发的靶点。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Aü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信号通路而损害有益的小胶质细胞活性，我们试图开发一类新的类黄酮类GSI，它可以减少γ-APP的切割，同时将其对小胶质细胞吞噬活性的潜在负面影响降至最低。最理想的情况是，我们将寻求做前者，同时促进后者。关于Diosmin促进抗淀粉样变性APP处理和小胶质细胞吞噬Aç的功效，我们最近发现，用Diosmin治疗Tg2576小鼠显著减少了大脑中A？40，42种物质，从而减少了A？基于这一发现，其代谢物Diosmetin成为我们初步研究的重点。这些结果表明，Diosmin/Diosmetin不仅通过抑制γ-APP的切割来降低A？，通过调节GSK3？的激活来减少过度磷酸化的tau，而且还能促进小胶质细胞的吞噬表型转换。在这项建议中，在3xTg-AD小鼠发生AD样病理之前(预防性治疗组)或之后(治疗组)，将口服黄酮类-地奥司明。未经处理的非转基因窝产仔组将与转基因处理组进行比较。给4月龄和6月龄3xTg-AD小鼠灌胃地奥司明，为期6个月。目的1，我们将在几个年龄段处死这些小鼠，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)。在这项研究中，我们计划评估两个时间点，比较地奥司明和对照。两组将根据他们在对抗认知障碍和减少AD样病理(包括脑淀粉样沉积和tau过度磷酸化/NFT)方面的效果进行比较。众所周知，AD伴随着促炎小胶质细胞反应的上调，表现为小胶质细胞产生的趋化因子增加。此外，我们的初步数据显示，Diosmin的代谢物Diosmetin通过下调小胶质细胞CD40信号并促进老年Aü肽的小胶质细胞吞噬而诱导抗炎表型。因此，在目标2中，我们将验证这样的假设，即Diosmin治疗保留了从年轻和老年3xTg-AD小鼠分离的原代小胶质细胞的促炎表型。这些研究可能为在不久的将来使用地奥明饮食补充剂进行AD的临床试验奠定基础。

 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.