State Key Laboratory of Natural Medicines, China Pharmaceutical University, 210009, Nanjing, Jiangsu, China.
Jiangsu Key Laboratory of Metabolic Disease, China Pharmaceutical University, 210009, Nanjing, Jiangsu, China.
Theranostics. 2018 Jul 30;8(15):4262-4278. doi: 10.7150/thno.26164. eCollection 2018.
It has been reported that peroxisome proliferator activated receptor γ (PPARγ) level decreases significantly in the brains of Alzheimer's disease (AD) patients and mice models, while the mechanism is unclear. This study aims to unravel the mechanism that amyloid β (Aβ) decreases PPARγ and attempted to discover lead compound that preserves PPARγ. In APP/PS1 transgenic mice and Aβ treated microglia, the interaction between HSP90 and PPARγ were analyzed by western blot. Using a PPRE (PPARγ responsive element) containing reporter cell line, compounds that activate PPARγ activity were identified. After genetic ablation or pharmacological inhibition of potential target pathways, the target of jujuboside A (JuA) was discovered through Axl/HSP90β. After oral administration or intrathecal injection, the anti-AD activity of JuA was evaluated by Morris water maze (MWM) test and object recognition test. Soluble Aβ42 levels and plaque numbers after JuA treatment were detected by thioflavin S staining, and the activation of microglia was assayed by immunofluorescence staining against Iba-1. We found that Aβ stress decreased heat shock protein 90 β (HSP90β), subsequently reduced the abundance of PPARγ, and down-regulated Aβ clearance-related genes in BV2 cells and primary microglia. We identified that JuA stimulated the expression of HSP90β, strengthened the interaction between HSP90β and PPARγ, preserved PPARγ levels, and thus effectively promoted the clearance of Aβ42. We demonstrated that JuA increased HSP90β expression through Axl/ERK pathway. JuA significantly ameliorated cognitive deficiency in APP/PS1 transgenic mice, meanwhile, JuA significantly reduced the soluble Aβ42 levels and plaque numbers in the brain. Notably, the therapeutic effects of JuA were dampened by R428, an Axl inhibitor. This study suggests that the up-regulation of HSP90β by JuA through Axl is a potential therapeutic strategy to facilitate Aβ42 clearance and ameliorate cognitive deficiency in AD.
据报道，阿尔茨海默病（AD）患者和小鼠模型的大脑中过氧化物酶体增殖物激活受体γ（PPARγ）水平显著降低，但其机制尚不清楚。本研究旨在揭示淀粉样蛋白β（Aβ）降低 PPARγ的机制，并试图发现保留 PPARγ的先导化合物。在 APP/PS1 转基因小鼠和 Aβ处理的小胶质细胞中，通过 Western blot 分析 HSP90 与 PPARγ 的相互作用。使用含有 PPRE（PPARγ 反应元件）的报告细胞系，鉴定激活 PPARγ 活性的化合物。在遗传敲除或药理学抑制潜在靶途径后，通过 Axl/HSP90β 发现了 Jujuboside A（JuA）的靶标。通过 Morris 水迷宫（MWM）试验和物体识别试验评价 JuA 的抗 AD 活性，通过硫黄素 S 染色检测 JuA 处理后可溶性 Aβ42 水平和斑块数量，通过免疫荧光染色检测 Iba-1 检测小胶质细胞的激活。我们发现 Aβ 应激降低了热休克蛋白 90β（HSP90β），随后降低了 BV2 细胞和原代小胶质细胞中 PPARγ 的丰度，并下调了与 Aβ 清除相关的基因。我们确定 JuA 刺激 HSP90β 的表达，增强 HSP90β 与 PPARγ 的相互作用，维持 PPARγ 水平，从而有效促进 Aβ42 的清除。我们证明 JuA 通过 Axl/ERK 途径增加 HSP90β 的表达。JuA 显著改善 APP/PS1 转基因小鼠的认知缺陷，同时，JuA 显著降低了大脑中可溶性 Aβ42 水平和斑块数量。值得注意的是，Axl 抑制剂 R428 削弱了 JuA 的治疗效果。本研究表明，JuA 通过 Axl 上调 HSP90β 是促进 Aβ42 清除和改善 AD 认知缺陷的潜在治疗策略。
