丰富环境对大鼠缺血再灌注后星形胶质细胞A1/A2表型转换和认知功能的影响

Effects of enriched environment on A1/A2 phenotype conversion of astrocytes and cognitive function in rats after ischemia reperfusion

目的:探究丰富环境对大鼠缺血再灌注(ischemia-reperfusion,I/R)后星形胶质细胞A1/A2表型转换和认知功能的影响。方法:选用42只成年雄性SD大鼠,体重(220±20)g,接受大脑中动脉闭塞(middle cerebral artery occlusion,MCAO)手术,2h后拔出线栓实现再灌注。术后3天,将造模成功的30只大鼠随机分为标准环境组(standard environment,SE)和丰富环境组(enriched environment,EE),另选用10只大鼠作为假手术组(sham)。EE组饲养于丰富环境笼子中,其余两组饲养于标准环境中。21天后,使用Bederson评分和m Nss评分检测各组大鼠的神经功能缺损情况,使用Morris水迷宫对大鼠的认知功能进行检测;随后使用蛋白质印迹分析星形胶质细胞标志物胶质纤维酸性蛋白(GFAP)的激活情况;实时PCR和ELISA对A1型星形胶质细胞标志物(C3)和A2型星形胶质细胞标志物(S100A10)的表达情况进行检测;苏木素-伊红(HE)染色观察梗死周围皮层组织病理学变化;TUNEL染色检测细胞凋亡情况。结果:与SE组相比,EE组GFAP的蛋白表达量显著减少(P<0.05)。EE组A1型星形胶质标志物C3的表达量显著低于SE组(P<0.05),而A2型星形胶质标志物S100A10的表达量则显著高于SE组(P<0.05)。与这一结果相对应,在EE组中,A1星形胶质细胞分泌的细胞因子TNF-α显著低于SE组(P<0.05),A2星形胶质细胞分泌的细胞因子BDNF显著高于SE组(P<0.05)。TUNEL染色和HE染色显示,EE组细胞凋亡和损伤情况更少(P<0.05)。此外,EE组大鼠的神经功能缺血情况较轻,包括Bederson评分和m Nss评分的显著差异(P<0.01);与SE组相比,EE组的大鼠有着更好的认知功能,表现为水迷宫实验中的潜伏期更短(P<0.05),在目标象限的停留时间更长(P<0.01),穿越平台的次数更多(P<0.05)。结论:丰富环境可以抑制星形胶质细胞的激活,同时引导已激活的星形胶质细胞转化为神经保护的A2型,抑制其转化为神经毒性的A1型,从而改善大鼠缺血性卒中后的认知功能。

Objective:To explore the effect of enriched environment on the A1/A2 phenotype conversion of astrocytes and cognitive function in rats after ischemia-reperfusion(I/R)in rats.Method:Forty two adult male SD rats(weight 220±20g)were selected for middle cerebral artery occlusion(MCAO)surgery,followed by reperfusion 2 hours later.Three days after operation,30 rats were randomly divided into standard environment group(n=15)and enriched environment group(n=15),and 10 rats were selected as sham operation group.The enriched environment group was raised in the enriched environment cag es,and the other two groups were raised in the standard environment.After 21 days,the Bederson score and mNss score were used to detect the behavioral changes of rats in each group,and the Morris water maze was used to detect the cognitive function of rats.Subsequently,western blot analysis was used to analyze the activation of glial fibrillary acidic protein(GFAP),a marker of astrocytes.Real-time PCR and ELISA detect the expression of A1 type astrocyte marker(C3)and A2 type astrocyte marker(S100A10).Hematoxylin eosin(HE)staining was used to observe the pathological changes of cortex around the infarction.TUNEL staining was used to detect apoptosis.Result:Compared with SE group,the expression of GFAP protein in EE group decreased significantly(P<0.05).The expression level of the A1 type astrocyte marker C3 in EE group was significantly lower than that in SE group(P<0.05),while the expression of A2 type astrocyte marker S100A10 was significantly higher than that in SE group(P<0.05).Correspondingly to this result,in the EE group,the secretion of the cytokine TNF-αby A1 astrocytes was significantly lower than in the SE group(P<0.05),and the secretion of the cytokine BDNF by A2 astrocytes was significantly higher than in the SE group(P<0.05).TUNEL and HE staining showed that the apoptosis and damage of cells in EE group were less(P<0.05).In addition,the neurological ischemia in the EE group was less severe,including significant differences in the Bederson score and mNss score(P<0.01).Compared with the SE group,the rats in the EE group had better cognitive function,characterized by shorter latency(P<0.05),longer residence time in the target quadrant(P<0.01),and more times of crossing the platform(P<0.05)in the water maze experiment.Conclusion:The enriched environment can inhibit the activation of astrocytes,promote the conversion of activated astrocytes to neuroprotective type A2 and inhibit their conversion into neurotoxic type A1,resulting in improving cognitive function after ischemic stroke in rats.