Zhou Li, Liu Jianxu, Dong Dong, Wei Chunsheng, Wang Rui
Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology 130 Meilong Road, Shanghai 200237, China.
Am J Transl Res. 2017 Jan 15;9(1):184-196. eCollection 2017.
Imbalance of Aβ production and Aβ removal leads to Aβ accumulation. Aβ degrading enzyme (including neprilysin-NEP, endothelin converting enzyme-ECE) as a therapeutic strategy for lowering brain Aβ deposition has attracted increasing attention. In this study, we investigated alteration of age and region-dependent in APP/PS1 double transgenic mice (3, 6, 9, 12 months) and their age-matched wild type mice including the ability of spatial memory, Aβ deposits, the protein expression, location and activity of NEP and ECE. Our data demonstrated that, as compared with wild type mice, APP/PS1 mice displayed significant cognitive deficit at 9 month revealed by obviously longer in the latency and distance to find the platform and shorter in time spent and swimming distance in the target quadrant. Aβ and Aβ levels exhibited a significant increase with age in the cerebral cortex and hippocampus of APP/PS1 mice after 6 month, compared with their age-matched wild type mice. And Aβ levels were significantly higher than Aβ levels in the same age of APP/PS1 mice. Furthermore, NEP protein and activity displayed a marked decrease with age in the cerebral cortex and hippocampus of APP/PS1 mice older than 6 month. Slightly different from NEP, ECE protein was up-regulated with age, while ECE activity showed a significantly decrease with age in cortex and hippocampus of APP/PS1 mice older than 6 month. Double immunofluorescence staining also demonstrated that ECE and NEP highly colocalized in cytoplasmic and membrane, and ECE immunoreactivity tended to increase with age in APP/PS1 mice, especially 12 month APP/PS1 mice. Correlation analysis showed the negative correlation between enzyme (NEP or ECE) activity and Aβ levels in the cerebral cortex and hippocampus of APP/PS1 mice, which was correlated with Aβ accumulation. These results indicate NEP rather than ECE plays more important role in resisting Aβ accumulation. The compensatory upregulation of NEP and ECE could balance Aβ metabolism and protect neuronal functions in infant and juvenile mice. These evidence might provide some clues for the treatment of Alzheimer's disease.
淀粉样前体蛋白（Aβ）生成与清除的失衡会导致Aβ聚集。作为降低脑内Aβ沉积的一种治疗策略，Aβ降解酶（包括中性内肽酶-NEP、内皮素转化酶-ECE）已引起越来越多的关注。在本研究中，我们调查了APP/PS1双转基因小鼠（3、6、9、12个月龄）及其年龄匹配的野生型小鼠年龄和区域依赖性的变化，包括空间记忆能力、Aβ沉积、NEP和ECE的蛋白表达、定位及活性。我们的数据表明，与野生型小鼠相比，APP/PS1小鼠在9个月龄时表现出明显的认知缺陷，表现为找到平台的潜伏期和距离明显延长，以及在目标象限花费的时间和游泳距离缩短。与年龄匹配的野生型小鼠相比，6个月龄后APP/PS1小鼠大脑皮质和海马中的Aβ及Aβ水平随年龄显著增加。并且在相同年龄的APP/PS1小鼠中，Aβ水平显著高于Aβ水平。此外，6个月龄以上的APP/PS1小鼠大脑皮质和海马中的NEP蛋白及活性随年龄显著降低。与NEP略有不同，ECE蛋白随年龄上调，而在6个月龄以上的APP/PS1小鼠的皮质和海马中，ECE活性随年龄显著降低。双重免疫荧光染色还表明，ECE和NEP在细胞质和细胞膜中高度共定位，并且在APP/PS1小鼠中，尤其是12个月龄的APP/PS1小鼠中，ECE免疫反应性倾向于随年龄增加。相关性分析表明，APP/PS1小鼠大脑皮质和海马中酶（NEP或ECE）活性与Aβ水平呈负相关，这与Aβ聚集相关。这些结果表明，NEP而非ECE在抵抗Aβ聚集中发挥更重要的作用。NEP和ECE的代偿性上调可以平衡Aβ代谢并保护幼年小鼠的神经元功能。这些证据可能为阿尔茨海默病的治疗提供一些线索。
