Yang Wang, Yan Zhang, Hongjing Zhang, Dexiang Liu, Zengxun Liu, Xiaojing Cheng, Yi Lu, Jichao Jia, Jintong Liu, Fang Pan
Department of Psychiatry, Shandong University School of Medicine, 44#, Wenhua Xi Road, Jinan, 250012, Shandong, People's Republic of China.
Biol Trace Elem Res. 2014 Jun;159(1-3):410-5. doi: 10.1007/s12011-014-9949-z. Epub 2014 Apr 16.
In this study, the neurotoxicity of Li ion and its effect on the morphologies of Aβ42 molecules were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays, fluorescence (FL), atomic force microscopy (AFM), and circular dichroism (CD) spectroscopy. MTT assays show that Li ion with a dosage level lower than 50 mg/l did not show detectable cytotoxicity on pheochromocytoma (PC12) cells whereas a dosage level higher than 100 mg/l resulted in significant cytotoxicity. The interaction between Aβ42 and Li ion occurs, and the quenching effect of Li ion on the fluorescence emission of AΒ42 is found to be concentration dependent, suggesting that Li ion can bind to the Aβ42 molecules. CD results suggest that a more incompact conformation state will be adopted upon the interaction between Aβ42 and Li ion. According to AFM images, Li ion could induce the formation of the fibrils after incubation for 3 or 5 days. The formation of the oligomer and fibrils originates from the strong interactions between Aβ42 and Li ion. Li ion could accelerate the random coil Aβ42 monomers aggregating into the β-sheet fibrils, which would induce the neurotoxic effect.
在本研究中，通过3-(4,5-二甲基噻唑-2-基)-2,5-二苯基四氮唑溴盐（MTT）法、荧光（FL）、原子力显微镜（AFM）和圆二色（CD）光谱对锂离子的神经毒性及其对Aβ42分子形态的影响进行了评估。MTT法表明，剂量水平低于50mg/l的锂离子对嗜铬细胞瘤（PC12）细胞未显示出可检测到的细胞毒性，而剂量水平高于100mg/l则导致显著的细胞毒性。Aβ42与锂离子之间发生相互作用，且发现锂离子对Aβ42荧光发射的猝灭效应具有浓度依赖性，这表明锂离子可与Aβ42分子结合。CD结果表明，Aβ42与锂离子相互作用后会采用更不紧凑的构象状态。根据AFM图像，锂离子在孵育3天或5天后可诱导纤维形成。寡聚体和纤维的形成源于Aβ42与锂离子之间的强相互作用。锂离子可加速无规卷曲的Aβ42单体聚集成β-折叠纤维，这会诱导神经毒性作用。
