神经细胞自噬与Aβ沉积在运动训练改善脑梗死大鼠认知障碍中的作用及机制

Cognitive impairment is a major sequela in stroke. It is demonstrate that physical exercise could improve post-stroke cognitive impairment(PSCI) in recent clinical researches, but the underlying mechanism is not clear. Lately，Aβ, a well-known neuronal toxin in Alzheimer's disease (AD), has been shown to accumulate in ischemic brain. In our previous study, we found that physical exercise promoted IGF-1 expression and reduced autophagosomes accumulation in cerebral ischemia，in addition, inhibition of autophagosomes accumulation by 3-MA contributed to reduce Aβ deposits. Furthermore, physical exercise decreased Aβdeposition and improved cognitive function in spontaneous hypertensive rats (SHR). Therefore, we propose that reduction of autophagosomes accumulation by IGF-1 up-regulation may involve in exercise-induced Aβ burden decreasing and cognitive function improvement. Male SHR subjected to transient focal cerebral ischemia by left transient middle cerebral artery occlusion are used in this experiment. All animals in exercise group submitted to the running wheel exercise were placed into a programmable, motorized wheel apparatus. Cognitive function is tested by Morris water maze. The expression of autophagy, Aβ, IGF-1 and the role of PI3K/Akt/mTOR pathway are detected by immunofluorescence staining, RT-PCR, westernblot , Elisa and RNAi in cerebrospinal fluid and brain tissue. The results may contribute to further understand the pathogenesis and optimize rehabilitative therapy of PSCI in clinical medicine.

认知障碍是脑卒中常见表现之一，近来发现，运动训练能改善脑卒中后认知障碍（PSCI），但机制未明。有实验报道，脑梗死后可见脑内淀粉样蛋白（Aβ）异常聚积，而Aβ对神经细胞的毒性众所周知，它是Alzheimer 病的元凶。我们前期实验发现：①运动训练可促进脑梗死后胰岛素样生长因子（IGF-1）表达，减少自噬体过量聚集；②抑制自噬体聚集可减少Aβ沉积；③运动训练可减少高血压大鼠脑内Aβ沉积，改善其认知功能。据此假设，运动训练改善脑梗死后认知障碍可能与其促进IGF-1表达，调节神经细胞自噬，减少Aβ沉积有关。本研究采用转基因自发性高血压大鼠建立tMCAO运动训练模型，以水迷宫、免疫荧光、RT-PCR、western blot、Elisa、RNAi等方法检测大鼠行为学、自噬、Aβ、IGF-1表达及PI3K/Akt/mTOR通路变化。研究结果对深入了解PSCI发病机制及进一步优化其治疗策略有重要意义。

脑卒中后认知障碍严重影响患者的生存质量，目前其发病机制仍不清楚，且无确切有效的治疗手段。近来研究表明，脑卒中后脑内可见Aβ沉积，Aβ沉积形成老年斑是阿尔兹海默病（Alzheimer's disease，AD）的特征性病理改变。以往的研究认为，自噬参与Aβ的生成、转运及清除，脑卒中后异常的自噬体聚集，可能参与Aβ的沉积。我们前期的研究发现，运动训练可抑制自噬，并促进脑卒中大鼠神经功能恢复。本项目在前期研究基础上，采用自发性高血压大鼠tMCAO模型，并采用3-MA侧脑室注射抑制自噬，研究运动训练对脑卒中大鼠认知功能的影响，及神经自噬和Aβ沉积在运动训练改善脑卒中后认知障碍中的作用及机制。. 研究结果发现：（1）脑卒中导致SHR出现认知功能障碍；（2）SHR脑卒中后梗死边缘区出现自噬聚集及Aβ沉积；（3）运动训练可改善脑卒中SHR认知功能障碍，并抑制自噬减少Aβ沉积；（4）采用3-MA抑制SHR脑卒中后自噬可减少Aβ沉积，改善认知功能障碍；（5）运动训练可能通过PI3K/Akt/mTOR信号通路抑制自噬减少Aβ沉积；（6）检测自噬相关蛋白及Aβ生成相关蛋白（APP、BACE1及PS-1）结果发现运动训练通过抑制自噬减少Aβ生成关键酶BACE1，抑制Aβ生成。. 研究结果表明运动训练可能通过激活PI3K/Akt/mTOR信号通路抑制自噬减少Aβ生成，改善脑卒中大鼠认知功能障碍。研究结果为我们在临床上运用运动训练作为认知障碍的康复治疗手段提供理论基础与科学依据，并对深入了解 PSCI的发病机制及进一步优化其治疗策略具有重要意义。