Department of Biochemical Engineering, Key Laboratory of Systems Bioengineering of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, PR China.
Department of Chemical and Biological Engineering, University of Alabama, Tuscaloosa, AL, USA.
J Inorg Biochem. 2017 Dec;177:183-189. doi: 10.1016/j.jinorgbio.2017.09.015. Epub 2017 Sep 22.
Interactions of Zn with amyloid β-protein (Aβ) and the subsequent induction of Aβ aggregation have been implicated in the pathogenesis of Alzheimer's disease (AD). The development of small-compound inhibitors against Zn-mediated Aβ aggregation is therefore greatly desired. In this study, brazilin was used to inhibit Zn-mediated Aβ aggregation and alleviate its cytotoxicity. The binding properties of brazilin and Zn were first probed using Fourier transform infrared (FTIR) spectroscopy and isothermal titration calorimetry (ITC) assays. Both the FTIR and ITC results have shown that brazilin is able to bind Zn in a physiologically suitable range of concentrations. The dissociation constant (K) between brazilin and Zn was about 46.0±6.8μM, which makes brazilin a potential drug model for the chelation of free Zn. Moreover, the higher affinity of brazilin for Aβ (K=2.5±1.6μM) than that of Zn (K=6.2±0. 9μM), enables brazilin to sequester Zn from the Aβ-Zn complex. In addition, the inhibitory effects of brazilin on Zn-mediated Aβ aggregation were examined using the Thioflavin T fluorescence assay, transmission electron microscopy and cytotoxicity assays. It was found that brazilin showed remarkable inhibitory capability against Zn-induced aggregation of Aβ. Furthermore, the Zn-mediated cytotoxicity of Aβ was also largely mitigated under the influence of brazilin. This study therefore provides further insights into the role of Zn in the Aβ aggregation pathway, indicating potential new strategies for the design of small compounds with therapeutic potential for AD.
锌与淀粉样β蛋白（Aβ）的相互作用以及随后诱导的 Aβ聚集被认为与阿尔茨海默病（AD）的发病机制有关。因此，非常希望开发针对锌介导的 Aβ聚集的小分子抑制剂。在这项研究中，巴西苏木素被用于抑制锌介导的 Aβ聚集并减轻其细胞毒性。首先使用傅里叶变换红外（FTIR）光谱和等温热力学滴定（ITC）测定法探测巴西苏木素与锌的结合特性。FTIR 和 ITC 的结果均表明，巴西苏木素能够在生理适宜的浓度范围内与锌结合。巴西苏木素与锌之间的离解常数（K）约为 46.0±6.8μM，这使巴西苏木素成为游离锌螯合的潜在药物模型。此外，巴西苏木素与 Aβ（K=2.5±1.6μM）的亲和力高于锌（K=6.2±0.9μM），使巴西苏木素能够从 Aβ-Zn 复合物中夺取锌。此外，还使用噻唑蓝 T 荧光测定法、透射电子显微镜和细胞毒性测定法检查了巴西苏木素对锌介导的 Aβ聚集的抑制作用。结果发现，巴西苏木素对锌诱导的 Aβ聚集表现出显著的抑制能力。此外，在巴西苏木素的影响下，锌介导的 Aβ细胞毒性也大大减轻。因此，这项研究进一步深入了解了锌在 Aβ聚集途径中的作用，为设计具有治疗 AD 潜力的小分子化合物提供了新的策略。
