Department of Chemistry, School of Chemistry and Molecular Engineering, East China Normal University, Dongchuan Road 500, Shanghai, 200241, China; College of Biological, Chemical Sciences and Engineering, Jiaxing University, Jiahang Road 118, Jiaxing, 314001, China.
State Key Laboratory of Precision Spectroscopy, East China Normal University, North Zhongshan Road 3663, Shanghai, 200062, China.
Free Radic Biol Med. 2019 May 1;135:125-131. doi: 10.1016/j.freeradbiomed.2019.02.030. Epub 2019 Mar 5.
In the amyloid plaques, a signature of AD, abnormally high Cu concentrations are found bound to Aβ. Most of previous studies reported that Cu-Aβ could contribute to oxidative stress, as HO and •OH are catalytically generated by Cu-Aβ with the assistance of biological reductant, with only one recent report stated that free O is also generated in the Cu-Aβ catalyzed processes, where an indirect technique was applied. To comprehensively investigate the free radicals produced during this Cu-Aβ-mediated process with a biological reductant, DNA-cleavage assay, an indirect method, and two direct methods including electron paramagnetic resonance (EPR) spectroscopy and transient absorption spectroscopy (TAS), both having qualitative and quantitative power, were employed in this work. All the experimental results obtained from the three methods demonstrated that Cu-Aβ in the biological reducing environment was not only able to catalyze the production of HO and •OH, but also to generate free O. The results further indicated that O was the precursor of HO and •OH. It is also important to note that the results obtained from EPR spectroscopy and TAS provided direct evidence for the presence of O and •OH. By virtue of the direct techniques, we also found that the longest peptide fragments of Aβ, Aβ, and Aβ produced the least radicals with a lowest rate. More interestingly, the fibrillar forms of Aβ generated less O and •OH compared with oligomeric and monomeric forms.
在淀粉样斑块中，发现 AD 的特征是异常高浓度的 Cu 与 Aβ 结合。大多数先前的研究报告称，Cu-Aβ 可能导致氧化应激，因为 HO 和 •OH 在生物还原剂的协助下被 Cu-Aβ 催化生成，只有最近的一份报告称，在 Cu-Aβ 催化的过程中也会产生游离的 O，其中应用了间接技术。为了全面研究 Cu-Aβ 介导的生物还原剂过程中产生的自由基，采用 DNA 切割测定法（间接方法）和电子顺磁共振（EPR）光谱和瞬态吸收光谱（TAS）两种直接方法（具有定性和定量能力）。所有三种方法的实验结果均表明，在生物还原环境中，Cu-Aβ不仅能够催化 HO 和 •OH 的生成，而且还能够生成游离的 O。结果进一步表明，O 是 HO 和 •OH 的前体。同样重要的是要注意，EPR 光谱和 TAS 的结果为 O 和 •OH 的存在提供了直接证据。借助直接技术，我们还发现 Aβ 的最长肽片段 Aβ 和 Aβ 产生的自由基最少，速率最低。更有趣的是，与寡聚体和单体形式相比，纤维形式的 Aβ 产生的 O 和 •OH 较少。
