Department of Rehabilitation Medicine, The Third Affiliated Hospital, Sun Yat-sen University, 600 Tianhe Road, Guangzhou, Guangdong, China.
Guangdong Provincial Key Laboratory of Laboratory Animals, Guangdong Laboratory Animals Monitoring Institute, Guangzhou, 510663, Guangdong, China.
Mol Brain. 2020 Oct 7;13(1):135. doi: 10.1186/s13041-020-00659-5.
Cerebral microinfarcts (MIs) lead to progressive cognitive impairments in the elderly, and there is currently no effective preventative strategy due to uncertainty about the underlying pathogenic mechanisms. One possibility is the dysfunction of GABAergic transmission and ensuing excitotoxicity. Dysfunction of GABAergic transmission induces excitotoxicity, which contributes to stroke pathology, but the mechanism has kept unknown. The secreted leucine-rich repeat (LRR) family protein slit homologue 2 (Slit2) upregulates GABAergic activity and protects against global cerebral ischemia, but the neuroprotective efficacy of Slit2 against MIs has not been examined.
Middle-aged Wild type (WT) and Slit2-Tg mice were divided into sham and MI treatment groups. MIs were induced in parietal cortex by laser-evoked arteriole occlusion. Spatial memory was then compared between sham and MI groups using the Morris water maze (MWM) task. In addition, neuronal activity, blood brain barrier (BBB) permeability, and glymphatic clearance in peri-infarct areas were compared using two-photon imaging, while GABAergic transmission, microglial activation, neuronal loss, and altered cortical connectivity were compared by immunofluorescent staining or western blotting.
Microinfarcts increased the amplitude and frequency of spontaneous intracellular Ca signals, reduced neuronal survival and connectivity within parietal cortex, decreased the number of GABAergic interneurons and expression of vesicular GABA transporter (VGAT), induced neuroinflammation, and impaired both glymphatic clearance and spatial memory. Alternatively, Slit2 overexpression attenuated dysfunctional neuronal Ca signaling, protected against neuronal death in the peri-infarct area as well as loss of parietal cortex connectivity, increased GABAergic interneuron number and VGAT expression, attenuated neuroinflammation, and improved both glymphatic clearance and spatial memory.
Our results strongly suggest that overexpression of Slit2 protected against the dysfunction in MIs, which is a potential therapeutic target for cognition impairment in the elderly.
脑微梗死（MIs）可导致老年人进行性认知障碍，由于对潜在发病机制的不确定性，目前尚无有效的预防策略。一种可能性是 GABA 能传递功能障碍和随之而来的兴奋性毒性。GABA 能传递功能障碍诱导兴奋性毒性，从而导致中风病理，但机制尚不清楚。分泌的富含亮氨酸重复序列（LRR）家族蛋白 Slit 同源物 2（Slit2）上调 GABA 能活性并防止全脑缺血，但 Slit2 对 MIs 的神经保护作用尚未得到检验。
中年野生型（WT）和 Slit2-Tg 小鼠分为假手术和 MI 治疗组。通过激光诱导的小动脉闭塞在顶叶皮层诱导 MIs。然后使用 Morris 水迷宫（MWM）任务比较 sham 和 MI 组之间的空间记忆。此外，通过双光子成像比较梗死周围区域的神经元活动、血脑屏障（BBB）通透性和糖质清除率，通过免疫荧光染色或 Western blot 比较 GABA 能传递、小胶质细胞激活、神经元丢失和皮质连接改变。
微梗死增加了顶叶皮层自发细胞内 Ca 信号的幅度和频率，减少了神经元的存活和连接，减少了 GABA 能中间神经元的数量和囊泡 GABA 转运体（VGAT）的表达，诱导了神经炎症，并损害了糖质清除和空间记忆。相反，Slit2 过表达减弱了功能障碍性神经元 Ca 信号，防止了梗死周围区域神经元死亡以及顶叶皮层连接丧失，增加了 GABA 能中间神经元数量和 VGAT 表达，减弱了神经炎症，并改善了糖质清除和空间记忆。
我们的结果强烈表明，Slit2 的过表达可防止 MIs 功能障碍，这可能是治疗老年人认知障碍的潜在靶点。
