Zhang Lijun, Park Jeoung Yun, Zhao Dong, Kwon Hak Cheol, Yang Hyun Ok
Natural Product Research Center, Korea Institute of Science and Technology, Gangneung 25451, Republic of Korea.
Division of Bio-medical Science and Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Republic of Korea.
Biomol Ther (Seoul). 2021 Nov 1;29(6):615-629. doi: 10.4062/biomolther.2021.004.
An active compound, triterpene saponin, astersaponin I (AKNS-2) was isolated from Nakai (AKNS) and the autophagy activation and neuroprotective effect was investigated on and Parkinson's disease (PD) models. The autophagy-regulating effect of AKNS-2 was monitored by analyzing the expression of autophagy-related protein markers in SHSY5Y cells using Western blot and fluorescent protein quenching assays. The neuroprotection of AKNS-2 was tested by using a 1-methyl-4-phenyl-2,3-dihydropyridium ion (MPP)-induced PD model in SH-SY5Y cells and an MPTP-induced PD model in mice. The compound-treated SH-SY5Y cells not only showed enhanced microtubule-associated protein 1A/1B-light chain 3-II (LC3-II) and decreased sequestosome 1 (p62) expression but also showed increased phosphorylated extracellular signal-regulated kinases (p-Erk), phosphorylated AMP-activated protein kinase (p-AMPK) and phosphorylated unc-51-like kinase (p-ULK) and decreased phosphorylated mammalian target of rapamycin (p-mTOR) expression. AKNS-2-activated autophagy could be inhibited by the Erk inhibitor U0126 and by AMPK siRNA. In the MPP-induced PD model, AKNS-2 reversed the reduced cell viability and tyrosine hydroxylase (TH) levels and reduced the induced α-synuclein level. In an MPTP-induced PD model, AKNS-2 improved mice behavioral performance, and it restored dopamine synthesis and TH and α-synuclein expression in mouse brain tissues. Consistently, AKNS-2 also modulated the expressions of autophagy related markers in mouse brain tissue. Thus, AKNS-2 upregulates autophagy by activating the Erk/mTOR and AMPK/mTOR pathways. AKNS-2 exerts its neuroprotective effect through autophagy activation and may serve as a potential candidate for PD therapy.
从紫菀中分离出一种活性化合物——三萜皂苷紫菀皂苷 I（AKNS-2），并在帕金森病（PD）模型上研究了其自噬激活和神经保护作用。通过蛋白质免疫印迹法和荧光蛋白淬灭试验分析SHSY5Y细胞中自噬相关蛋白标志物的表达，监测AKNS-2的自噬调节作用。利用1-甲基-4-苯基-2,3-二氢吡啶离子（MPP）诱导的SH-SY5Y细胞PD模型和MPTP诱导的小鼠PD模型，测试AKNS-2的神经保护作用。用该化合物处理的SH-SY5Y细胞不仅显示微管相关蛋白1A/1B轻链3-II（LC3-II）表达增强、聚集体蛋白1（p62）表达降低，还显示细胞外信号调节激酶（p-Erk）、腺苷酸活化蛋白激酶（p-AMPK）和unc-51样激酶（p-ULK）磷酸化增加以及雷帕霉素哺乳动物靶蛋白（p-mTOR）磷酸化表达降低。AKNS-2激活的自噬可被Erk抑制剂U0126和AMPK小干扰RNA抑制。在MPP诱导的PD模型中，AKNS-2逆转了细胞活力降低和酪氨酸羟化酶（TH）水平降低的情况，并降低了α-突触核蛋白的诱导水平。在MPTP诱导的PD模型中，AKNS-2改善了小鼠的行为表现，并恢复了小鼠脑组织中的多巴胺合成以及TH和α-突触核蛋白的表达。同样，AKNS-2也调节了小鼠脑组织中自噬相关标志物的表达。因此，AKNS-2通过激活Erk/mTOR和AMPK/mTOR途径上调自噬。AKNS-2通过自噬激活发挥其神经保护作用，可能成为PD治疗的潜在候选药物。
