褪黑素对肺炎链球菌溶血素致大鼠脑损伤细胞凋亡的影响

目的 探讨褪黑素(MT)对肺炎链球菌溶血素(PLY)致脑损伤细胞凋亡的影响.方法 幼鼠84只随机分成3组:9 g·L-1盐水组(NS组)28只,颈内动脉注射9 g·L-1盐水；PLY组28只,颈内动脉注射0.2 mL(7 μg)PLY; MT组28只,腹腔注射(1 g·L-1)MT 10 ng·kg-1,15 min后颈内动脉注射0.2 mL(7μg)PLY.每组按照注射后不同的时间点(24 h、48 h)分为2个亚组.预定时间点处死动物,制备脑组织标本.干湿质量法测定其脑组织含水量( BWC),甲酰胺法测定伊文思兰(EB)水平,免疫组织化学技术测定凋亡诱导因子(AIF)表达,原位末端标记法检测细胞凋亡.结果　HE染色光镜下可见PLY组血管间隙增宽,大脑皮质炎性细胞浸润,胶质细胞和神经无细胞有不同程度肿胀、空泡变性.NS组无上述病理变化.MT组大鼠脑组织改变较PLY组轻.PLY组各时间点脑组织BWC水平、EB水平、AIF水平明显增加,24h高于48 h,差异有统计学意义.PLY组各时间点凋亡细胞数明显增加,48 h高于24h,差异有统计学意义.各时间点PLY组与对照组比较均有统计学差异.予以MT干扰后各时间点脑组织各指标以及凋亡细胞数均降低,与PLY组比较,差异有统计学意义.结论　MT能够降低AIF表达,减少神经细胞凋亡,保护脑组织.

Intervention of Melatonin on Apoptosis in Brain Injury Induced by Pneumolysin of Rats

Objective To explore the intervention of melatonin(MT) on the apoptosis of nervous cells in infectious brain injury model of rats induced by pneumolysin(PLY). Methods A total of 84 infant rats were randomly divided into 3 groups:NS group(n=28),isopyknic normal saline was given to each rat via the left internal carotid;PLY groups(n=28),0.2 mL(7 μg)PLY was injected;MT group(n=28),1 g·L-1 MT 10 mg·kg-1 was administered via intraperitoneal injection before 15 min PLY injection.Each group was divided into 2 subgroups:24 h group and 48 h group.Rats were decapitated at different time points and brain tissue samples were prepared.By measuring both wet and dry weight,the brain water content(BWC) was recorded.The Evan′s blue(EB) content of brain tissue was measured by the formamide method.The expression of apoptosis-inducing factor(AIF) protein was studied by immunohistochemistry.The apoptosis of nervous cells was examined by terminadeoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay technique. Results After the HE dying and observation by light-microscopy,compared with NS group,in PLY group,the clearance around vessels became broader and inflammatory cells infiltrated out of vessels.Neurons and gliacytes became swelled and vacuolar degeneration occurred.These changes were not discovered in NS group.In MT group,these changes were not as serious in PLY group.Compared with NS group,the levels of BWC,EB content,and AIF were all higher in PLY groups at different time points.At 24 h,the levels of BWC,EB content,and AIF were all higher than those at 48 h.The differences were significant.Compared with NS group,the number of apoptosis was all higher in PLY group at different time points.The differencse were significant.At 48 h,it was higher than that of 24 h.After the application of MT,the levels of BWC,EB content,AIF and the number of apoptosis in the brain tissue were lower than those in PLY group at each time point. Conclusions MT has the protective effect on the infectious brain injury,and melatonin can inhibit the expression of AIF and reduce the apoptosis of nervous cells.