米诺环素介导小胶质细胞形态转换减轻缺血性脑卒中早期脑损伤的机制研究

目的 观察大鼠缺血性脑损伤早期的病理生理特点,探讨米诺环素在缺血性脑损伤早期的神经保护效应及可能机制.方法 线栓法制备大鼠缺血性脑损伤(middle cerebral artery occlusion,MCAO)模型,在MCAO 6、24 h分别给予米诺环素腹腔注射,通过TTC染色观察脑梗死面积,TUNEL染色及尼氏染色检测神经元凋亡情况;免疫荧光染色了解小胶质细胞形态变化以及Western blot检测凋亡通路NF-κB表达情况.使用Morris水迷宫检测手术28 d后大鼠学习记忆能力.结果 米诺环素减少MCAO 6 h后大鼠脑梗死面积[(43.0±5.3)cm3 vs (36.0±6.8)cm3, P<0.01],减少脑神经元凋亡数量并促进M2型(神经保护型)小胶质细胞增殖,MCAO 24 h后米诺环素治疗不能改善脑梗死以及神经元细胞凋亡(P>0.05).米诺环素显著减少MCAO 6 h诱导的凋亡信号通路蛋白NF-κB的表达(P<0.01).MCAO 28 d后大鼠学习记忆能力较假手术组显著降低;米诺环素显著改善MCAO后学习记忆能力(P<0.05),而MCAO 24 h后米诺环素不能改善大鼠神经功能障碍,差异无统计学意义(P>0.05).结论 米诺环素能促进缺血性脑卒中早期活化小胶质细胞向M2型转化并抑制凋亡信号通路,减轻脑缺血诱导的神经炎症及细胞凋亡,改善大鼠学习记忆功能.

Minocycline conducted microglia phenotype transformation attenuates early brain injury in rats after ischemia stroke

Objective To investigate the early pathophysical characteristics of ischemic brain injury in rats, and explore the neuroprotective effects on the injury and possible involved molecular mechanisms.Methods Middle cerebral artery occlusion (MCAO) was performed in rats using a nylon suture to establish rat model of ischemic brain injury.In 6 and 24 h after MCAO, minocycline was injected intraperitoneally.Triphenyl tetrazolium chloride (TTC) staining was used to detect the infarct volume, and Tunel staining and Nissl staining were used to observe the apoptotic neurons.Immunohistochemical assay was used to detect microglial phenotype, and Western blot assay was employed to detect the expression of apoptosis pathway protein NF-κB.Morris water maze test was adopted to exam the long-term learning memory after MCAO and minocycline administration in 28 d after surgery.Results Minocycline administration significantly reduced brain infarct volume in 6 h after MCAO (43.0±5.3 vs 36.0±6.8 cm3, P<0.01), decreased the apoptotic cerebral neurons and promoted M2 microglia proliferation.However, minocycline given in 24 h after MCAO had no protective effect on infarct volume and neuron apoptosis (P>0.05).In addition, minocycline decreased NF-κB protein expression in 6 h after MCAO (P<0.01).The learning and memory abilities were obviously lower in the rats after 28 d of MCAO, which could be notably improved by minocycline treatment (P<0.01).But such neuroprotective effects were not observed in the rats treated 24 h after MCAO (P>0.05).Conclusion Minocycline improves memory deficits induced by early ischemic stroke via M2 microglial transformation and suppression of apoptosis signal pathway, and attenuates cerebral ischemia-induced neurological inflammation and apoptosis, so as to improve learning and memory function in rats.