School of Chinese Medicine, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong Special Administrative Region.
School of Chinese Medicine, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong Special Administrative Region; Brain Research Centre, School of Chinese Medicine, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong Special Administrative Region.
Brain Behav Immun. 2019 Nov;82:264-278. doi: 10.1016/j.bbi.2019.08.194. Epub 2019 Aug 30.
Isorhynchophylline (IRN) has been demonstrated to have distinct anti-Alzheimer's disease (AD) activity in several animal models of AD. In this study, we aimed at evaluating the preventive effect of IRN on the cognitive deficits and amyloid pathology in TgCRND8 mice. Male TgCRND8 mice were administered with IRN (20 or 40 mg/kg) by oral gavage daily for 4 months, followed by assessing the spatial learning and memory functions with the Radial Arm Maze (RAM) test. Brain tissues were determined immunohistochemically or biochemically for changes in amyloid pathology, tau hyperphosphorylation and neuroinflammation. Our results revealed that IRN (40 mg/kg) significantly ameliorated cognitive deficits in TgCRND8 mice. In addition, IRN (40 mg/kg) markedly reduced the levels of Aβ, Aβ and tumor necrosis factor (TNF-α), interleukin 6 (IL-6) and IL-1β, and modulated the amyloid precursor protein (APP) processing and phosphorylation by altering the protein expressions of β-site APP cleaving enzyme-1 (BACE-1), phosphorylated APP (Thr668), presenilin-1 (PS-1) and anterior pharynx-defective-1 (APH-1), as well as insulin degrading enzyme (IDE), a major Aβ-degrading enzyme. IRN was also found to inhibit the phosphorylation of tau at the sites of Thr205 and Ser396. Immunofluorescence showed that IRN reduced the Aβ deposition, and suppressed the activation of microglia (Iba-1) and astrocytes (GFAP) in the cerebral cortex and hippocampus of TgCRND8 mice. Furthermore, IRN was able to attenuate the ratios of p-c-Jun/c-Jun and p-JNK/JNK in the brains of TgCRND8 mice. IRN also showed marked inhibitory effect on JNK signaling pathway in the Aβ-treated rat primary hippocampus neurons. We conclude that IRN improves cognitive impairment in TgCRND8 transgenic mice via reducing Aβ generation and deposition, tau hyperphosphorylation and neuroinflammation through inhibiting the activation of JNK signaling pathway, and has good potential for further development into pharmacological treatment for AD.
异钩藤碱（IRN）在几种 AD 动物模型中表现出明显的抗 AD 活性。在这项研究中，我们旨在评估 IRN 对 TgCRND8 小鼠认知缺陷和淀粉样蛋白病理学的预防作用。雄性 TgCRND8 小鼠通过口服灌胃每天给予 IRN（20 或 40mg/kg），持续 4 个月，然后用放射臂迷宫（RAM）测试评估空间学习和记忆功能。通过免疫组织化学或生物化学方法测定脑组织中淀粉样蛋白病理学、tau 过度磷酸化和神经炎症的变化。我们的结果表明，IRN（40mg/kg）可显著改善 TgCRND8 小鼠的认知缺陷。此外，IRN（40mg/kg）显著降低了 Aβ、Aβ 和肿瘤坏死因子（TNF-α）、白细胞介素 6（IL-6）和白细胞介素 1β（IL-1β）的水平，并通过改变β-位点 APP 切割酶-1（BACE-1）、磷酸化 APP（Thr668）、早老素-1（PS-1）和前咽缺陷-1（APH-1）以及胰岛素降解酶（IDE）的蛋白表达，调节 APP 加工和磷酸化，IDE 是主要的 Aβ 降解酶。IRN 还被发现抑制 tau 在 Thr205 和 Ser396 位点的磷酸化。免疫荧光显示，IRN 减少了 Aβ 的沉积，并抑制了 TgCRND8 小鼠大脑皮层和海马区小胶质细胞（Iba-1）和星形胶质细胞（GFAP）的激活。此外，IRN 能够降低 TgCRND8 小鼠大脑中 p-c-Jun/c-Jun 和 p-JNK/JNK 的比值。IRN 对 Aβ 处理的大鼠原代海马神经元 JNK 信号通路也表现出明显的抑制作用。我们的结论是，IRN 通过抑制 JNK 信号通路的激活，减少 Aβ 的产生和沉积、tau 的过度磷酸化和神经炎症，改善 TgCRND8 转基因小鼠的认知障碍，具有进一步开发为 AD 药物治疗的良好潜力。
