大脑皮层梗死后血脑屏障LRP1和glymphatic系统受损介导丘脑Aβ沉积导致认知障碍

Post-stroke cognitive impairment was associated with the secondary damage in the thalamus. The underlying mechanisms remain unclear and Aβ deposition was considered to be the key factor involved in the post-stroke cognitive impairment. Our previous studies confirmed that Aβ deposition was the significant pathologic feature in the secondary thalamic damage after cerebral cortex infarction, and interventions ameliorating this damage could improve cognitive function, which indicated that Aβ deposition in the thalamus might be related with post-stroke cognitive impairment. However, it is unclear how Aβ accumulation is triggered and regulated in the thalamus following cerebral infarction. Currently, the dysfunction of blood-brain barrier LRP1 and glymphatic system are identified as the primary mechanism of Aβ deposition in the brain. Our preliminary experiment also observed that the blood-brain barrier LRP1 and glymphatic system were impaired in the thalamus after cortical infarction. It remains unclear whether the dysfunction of blood-brain barrier LRP1 and glymphatic system mediated Aβ deposition in the thalamus and led to post-stroke cognitive impairment. To address these issues, the present project is firstly designed to confirm that the dysfunction of blood-brain barrier LRP1 and glymphatic system are existed in the thalamus using the cortical infarction model in hypertensive rats. Further, by means of regulating the gene expression of LRP1 and AQP4, we wish to investigate the roles of the dysfunction of blood-brain barrier LRP1 and glymphatic system in Aβ deposition in the thalamus secondary to cerebral cortex infarction and their relationship with post-stroke cognitive impairment. Findings from the present proposal would help to elucidate the potential mechanism underlying post-stroke cognitive impairment and provide new strategies for the prophylaxis and treatment of post-stroke cognitive impairment.

脑梗死后认知障碍与远离缺血灶的丘脑继发损害有关，其机制不明，Aβ沉积被认为是关键因素。我们前期研究证实，Aβ沉积也是大脑皮层梗死后丘脑继发损害的重要病理特征，减轻丘脑继发损害可改善认知功能，提示丘脑Aβ沉积与脑梗死后认知障碍有关。然而导致脑梗死后丘脑Aβ沉积的机制未明。目前发现血脑屏障LRP1和glymphatic系统受损是脑内Aβ沉积的主要机制，预实验也观察到脑梗死后丘脑血脑屏障LRP1和glymphatic系统受损，其是否也介导了丘脑Aβ沉积并导致脑梗死后认知障碍尚不明确。本项目拟采用高血压大鼠建立大脑皮层梗死模型，证实丘脑血脑屏障LRP1及glymphatic系统受损；进而通过调控LRP1和AQP4基因表达为切入点，探讨大脑皮层梗死后血脑屏障LRP1和glymphatic系统受损在丘脑Aβ沉积中的作用及其与脑梗死后认知障碍的关系，以揭示其发生机制，为脑梗死后认知障的防治提供新策略。

前期研究表明，脑梗死后丘脑Aβ沉积可能与脑梗死后认知障碍有关，但其机制尚不清楚。目前证实血脑屏障LRP1和glymphatic系统受损是脑内Aβ沉积的主要因素，其是否介导丘脑Aβ沉积并导致脑梗死后认知障碍尚不明确。本项目基于高血压大鼠建立MCAO模型，观察脑梗死后认知功能、丘脑Aβ沉积和LRP1及glymphatic系统受损情况，然后通过上调LRP1和AQP4基因表达，探讨血脑屏障LRP1和glymphatic系统受损在丘脑Aβ沉积中的作用及其与脑梗死后认知障碍的关系。研究发现：（1）MCAO后出现认知功能损害：Morris水迷宫结果显示，与假手术组相比，MCAO后4周的逃避潜伏期明显延长、跨越目标平台次数及目标象限停留时间均明显减少。（2）同侧丘脑出现神经元丢失、Aβ沉积等继发性损害：免疫组化染色结果显示，与假手术组相比，MCAO术后1周和4周NeuN+细胞数量显著减少；假手术组未见Aβ染色，与假手术组相比，MCAO术后1周和4周可见大量 Aβ3-16染色呈散点状弥漫沉积。（3）同侧丘脑出现LRP1和glymphatic系统受损：Western Blot结果显示，与假手术组相比，MCAO术后1周和4周LRP1表达逐渐下降；免疫荧光染色结果显示，与假手术组相比，MCAO术后第4周出现星形胶质细胞AQP4极性紊乱。（4）同侧丘脑Aβ沉积及神经元丢失与认知功能损害相关：Spearman 相关分析结果显示，同侧丘脑NeuN+细胞数量和Aβ含量与逃避潜伏期、跨越目标平台次数及目标象限停留时间存在相关。（5）上调LRP1和AQP4基因表达减轻同侧丘脑神经元丢失及Aβ沉积：免疫组化染色结果显示，与MCAO组相比，上调LRP1和AQP4基因表达后同侧丘脑NeuN+细胞数量增多；与MCAO组相比，上调LRP1和AQP4基因表达后同侧丘脑Aβ+细胞数量减少。（6）上调LRP1和AQP4基因表达改善脑梗死后认知障碍：Morris水迷宫结果显示，与MCAO组相比，上调LRP1和AQP4基因表达后第4周逃避潜伏期时间缩短。本研究拓展了脑梗死丘脑Aβ沉积及认知障碍的发生机制，为卒中后认知障碍的防治提供了新策略，具有潜在临床意义。