1 Department of Psychiatry and Behavioral Neurosciences, Morsani College of Medicine, University of South Florida, Tampa, FL, USA.
2 Departments of Biomedical Sciences and Pathology, Saitama Medical Center and Saitama Medical University, Kawagoe, Saitama, Japan.
Cell Transplant. 2018 Mar;27(3):438-455. doi: 10.1177/0963689718759473. Epub 2018 Mar 21.
Alzheimer's disease (AD) is an age-related disorder that affects cognition. Our previous studies showed that the neuroprotective fragment of amyloid procurer protein (APP) metabolite, soluble APPα (sAPPα), interferes with β-site APP-cleaving enzyme 1 (BACE1, β-secretase) cleavage and reduces amyloid-β (Aβ) generation. In an attempt to identify approaches to restore sAPPα levels, we found that human cord blood serum (CBS) significantly promotes sAPPα production compared with adult blood serum (ABS) and aged blood serum (AgBS) in Chinese hamster ovary cells stably expressing wild-type human APP. Interestingly, CBS selectively mediated the α-secretase cleavage of human neuron-specific recombinant APP in a cell-free system independent of tumor necrosis factor-α converting enzyme (TACE; a disintegrin and metalloproteinase domain-containing protein 17 [ADAM17]) and ADAM. Subsequently, using 3-step chromatographic separation techniques (i.e., diethylaminoethanol, size-exclusion, and ion-exchange chromatography), we purified and ultimately identified a CBS-specific fraction with enhanced α-secretase catalytic activity (termed αCBSF) and found that αCBSF has more than 3,000-fold increased α-secretase catalytic activity compared with the original pooled CBS. Furthermore, intracerebroventricular injection of αCBSF markedly increased cerebral sAPPα levels together with significant decreases in cerebral Aβ production and abnormal tau (Thr) phosphorylation compared with the AgBS fraction with enhanced α-secretase activity (AgBSF) treatment in triple transgenic Alzheimer's disease (3xTg-AD) mice. Moreover, AgBSF administered intraperitoneally to transgenic mice with five familial Alzheimer's disease mutations (5XFAD) via an osmotic mini pump for 6 weeks (wk) ameliorated β-amyloid plaques and reversed cognitive impairment measures. Together, our results propose the necessity for further study aimed at identification and characterization of α-secretase in CBS for novel and effective AD therapy.
阿尔茨海默病（AD）是一种与年龄相关的疾病，影响认知。我们之前的研究表明，淀粉样前体蛋白（APP）代谢物的神经保护片段可溶性 APPα（sAPPα）干扰β-位点 APP 切割酶 1（BACE1，β-分泌酶）的切割，减少淀粉样-β（Aβ）的产生。为了寻找恢复 sAPPα 水平的方法，我们发现与成人血清（ABS）和老年血清（AgBS）相比，人脐血清（CBS）显著促进中国仓鼠卵巢细胞中稳定表达野生型人 APP 时 sAPPα 的产生。有趣的是，CBS 以 TNF-α 转化酶（TACE；解整合素和金属蛋白酶域蛋白 17 [ADAM17]）和 ADAM 独立的方式在无细胞系统中选择性介导人神经元特异性重组 APP 的 α-分泌酶切割。随后，我们使用 3 步色谱分离技术（即二乙氨基乙醇、分子筛和离子交换色谱），纯化并最终鉴定出具有增强的 α-分泌酶催化活性的 CBS 特异性部分（称为αCBSF），并发现与原始混合 CBS 相比，αCBSF 的 α-分泌酶催化活性增加了 3000 多倍。此外，与增强 α-分泌酶活性的 AgBS 部分（AgBSF）处理相比，脑室内注射αCBSF 可显著增加大脑 sAPPα 水平，同时显著降低大脑 Aβ 产生和异常 tau（Thr）磷酸化。此外，通过渗透微型泵向携带 5 种家族性阿尔茨海默病突变（5XFAD）的转基因小鼠腹腔内给予 AgBSF 6 周（wk）可改善β-淀粉样斑块并逆转认知障碍指标。总之，我们的结果表明有必要进一步研究 CBS 中的 α-分泌酶，以寻找针对 AD 的新型有效治疗方法。
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