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.