Abstract:

Alzheimer's disease (AD) is considered to be closely associated with the fibrillar aggregation of amyloid-β protein (Aβ). Therefore, development of efficient inhibitors against Aβ fibrillization is one of the strategies to combat AD. Previous studies have found the inhibition effect of transthyretin (TTR) on Aβ fibrillization through hydrophobic interactions, but it only showed high inhibitory potency at quite high concentrations (150 μg·ml^-1). To elevate the potency of TTR on inhibiting Aβ aggregation, this work used the basification method by modifying TTR with ethylenediamine via its reaction with the carboxyl groups on the protein surface. The TTR basification could increase the electrostatic interactions between basified TTR (TTR-B) and the negatively charged Aβ. Studies have shown that TTR-B3 with the highest degree of modification (on average 38.9% of the carboxyl groups on TTR per molecule are converted to amino groups) has a significantly improved ability to inhibit Aβ aggregation. The potency of TTR-B3 was much more efficient than native TTR. TTR-B3 alleviated the toxicity of Aβ aggregates and increased the cultured cell viability from 78% to >90% at 15 μg·ml^-1, which was only 10% of native TTR. As compared to basified human serum albumin (HSA-BF), TTR-B3 also worked at significantly lower dosages. TTR-B3 extended the same lifespan of AD nematodes at 75% of HSA-BF, and completely scavenged Aβ plaques in AD nematodes at 45% of HSA-BF. The results indicated that TTR-B3 is a highly effective inhibitor of Aβ aggregation.

Key words: Alzheimer's disease, protein, amyloid-?β protein, transthyretin, aggregation, biomedical engineering

摘要：

阿尔茨海默症与淀粉样β蛋白（amyloid-β protein，Aβ）的纤维化聚集有关，因此开发高效的抗Aβ聚集的抑制剂是防治阿尔茨海默症的策略之一。研究发现，甲状腺素运载蛋白（transthyretin，TTR）可通过疏水作用抑制Aβ单体之间的聚集，但抑制作用需要较高蛋白浓度（150 μg·ml^-1）。为了提高TTR抑制Aβ聚集的作用，本研究利用乙二胺修饰TTR表面的羧基，生成碱化甲状腺素运载蛋白（TTR-B），以增加其与带负电荷的Aβ之间的静电相互作用。研究表明，修饰度最高的TTR-B3（平均每分子TTR上38.9%的羧基被转换成氨基）对Aβ聚集的抑制能力显著提高，在较低的浓度下（15 μg·ml^-1）即可有效缓解Aβ对细胞的毒性（使细胞活性从78%提高至>90%），浓度仅为TTR的10%。与碱化人血清白蛋白（HSA-BF）相比，TTR-B3用量为HSA-BF的75%时即可使AD线虫延长相同的寿命，在HSA-BF用量的45%时即可完全清除AD线虫体内的Aβ斑块。结果表明TTR-B3是一种高效的Aβ聚集抑制剂。

关键词: 阿尔茨海默症, 蛋白质, 淀粉样β蛋白, 甲状腺素运载蛋白, 聚集, 生物医学工程