丙酮酸盐拮抗β-淀粉样蛋白寡聚体神经毒性的保护作用与机制研究

Recent progress in the field of Alzheimer's disease (AD) has provided evidence that Aβ oligomers cause the inhibition of synaptic transmission preceding neuronal cell death. Aβ oligomers inhibit long-term potentiation (LTP), a classic experimental paradigm for memory and synaptic plasticity. Therapeutic strategies developed to interfere with Aβ oligomers deposition and clearance have shown initial benefit in AD patients and rodent models. .Pyruvate, an intermediate metabolite of the glycolysis cycle, is a cell protective agent and administration of pyruvate protects neurons against the neurotoxicity of hydrogen peroxide in vitro and Aβ-induced neuronal death. However, whether pyruvate works protectively against the suppression of the synaptic transmission induced by Aβ oligomers is unknown. .This study will use the slice culture system to investigate the effects of pyruvate on the Aβ oligomer-induced inhibition of LTP, and use AD pathological model to investigate the effects of pyruvate on the Aβ oligomer -induced neurodegeneration and cognitive impairement. We propose that pyruvate could prevent the Aβ oligomer-induced inhibition of LTP (in the short term of AD) by the re-autophosphorylation of CaMKⅡ through PP2A inactivation, and pyruvate also could reduce neurodegenneration (in the long term of AD) induced by Aβ oligomer and improve the congnitive function through preservation of the NAD+ levels and ATP levels. The reduction of ROS production is considered to be the upstream mechanism of this observed pyruvate protection. Accordingly, pyruvate may be clinically applied to the the early stage of Alzheimer's disease patients who suffered from amnesia in which synaptic function will be mainly compromised with minimum neuronal cell loss. Considering the low cost and small degree of side effects of pyruvate, its application as a neuroprotective drug is expectted to achieve an excellent cost performance in clinical practice of AD.

阿尔茨海默病（AD）是一种神经退行性疾病，以进行性记忆减退和认知功能障碍为主要临床症状，但AD的病因和发病机制复杂,目前AD的确切病因尚不清楚,研究表明在AD出现神经变性前的早期记忆功能障碍中，可溶性β-淀粉样蛋白(Aβ)寡聚体发挥了重要的作用，已成为治疗AD的热门靶点。本研究拟用海马组织切片培养体外模拟AD环境和建立大鼠AD模型两种实验手段，明确丙酮酸盐对Aβ寡聚体所诱导的神经突触传递抑制的保护作用，以及明确丙酮酸盐可以降低AD大鼠的神经细胞死亡率和改善认知功能障碍，探讨丙酮酸盐神经保护作用的可能机制。首次提出丙酮酸盐可通过抗氧化作用抑制磷酸酯酶2A（PP2A）活化,间接增加磷酸化Ca2+/钙调蛋白依赖性蛋白激酶Ⅱ（CaMKⅡ）水平，从而发挥丙酮酸盐的神经保护作用。研究结果对进一步明确丙酮酸盐改善AD患者认知功能障碍的本质具有重要意义，有助于在基础理论和临床治疗AD中取得新突破。

阿尔茨海默病（AD）是一种神经退行性疾病，以进行性记忆减退和认知功能障碍为主要临床症状，但AD的病因和发病机制复杂,目前AD的确切病因尚不清楚,研究表明在AD出现神经变性前的早期记忆功能障碍中，可溶性β-淀粉样蛋白(Aβ)寡聚体发挥了重要的作用，已成为治疗AD的热门靶点。外源性的丙酮酸盐（Pyruvate）在体内转化为丙酮酸根阴离子和（或）丙酮酸起作用。丙酮酸是体内糖酵解的中间产物，位于无氧酵解和有氧氧化代谢交接处，属α-酮酸，是三大营养物质代谢的枢纽，其分子量小，可通过血脑屏障，经单羧酸转运体自由进出细胞和线粒体，为丙酮酸盐在体内作用提供保障。丙酮酸盐不仅可作为三羧酸循环的底物产生腺苷三磷酸（ATP）为组织正常生理结构功能的维持提供能量，还可作为细胞保护剂，保护神经细胞拮抗谷氨酸盐所致的神经毒性作用，对酒精诱导的神经细胞损伤具有保护作用，改善严重低血糖所致的神经细胞死亡和认知功能障碍,保护神经细胞拮抗β-淀粉样蛋白所致的神经细胞死亡（neuronal cell death,in vitro）。本研究拟用海马组织切片培养体外模拟AD环境和建立大鼠AD模型两种实验手段，明确丙酮酸盐对Aβ寡聚体所诱导的神经突触传递抑制的保护作用，以及明确丙酮酸盐可以降低AD大鼠的神经细胞死亡率并改善认知功能障碍，探讨丙酮酸盐神经保护作用的可能机制。我们的研究结果证明丙酮酸盐能够改善AD大鼠的认知功能障碍，可能通过逆转Aβ寡聚体诱导的LTP的抑制及拮抗Aβ寡聚体诱导的海马神经细胞死亡来发挥其神经保护作用： ①丙酮酸盐可能通过抑制PP2A活化间接增加磷酸化CaMKⅡ水平，来阻止Aβ寡聚体诱导的LTP抑制，从而改善认知功能障碍（学习和记忆的损害）；②丙酮酸盐可能通过降低PARP的活性及维持细胞内NAD+水平，来拮抗Aβ寡聚体诱导的海马神经细胞死亡，从而延缓AD进展；③丙酮酸盐的抗氧化作用可能是丙酮酸盐神经保护作用的上游机制。我们的研究结果对进一步明确丙酮酸盐提高AD患者认知功能的本质具有重要意义，为AD的防治提供了新的思路及有益的实验数据。