Expression Of Activin A And Caspase-3 In Brain Tissue Of Neonatal Rats With Hyperbilirubinemia

Objective Hyperbilirubinemia is the most common disease during neonatal period, which leads to neonatal death or induces central nervous system injury.Activin A (ACT A)is a sort of sugar proteinic hormone.The latest research shows that ACT A participates in hypoxic-ischemic brain damage(HIBD),and the exogenous ACT A can protect the brain tissue of neonatal rats with hypoxic-ischemic brain damage. Caspase-3 is the key enzyme in the process of apoptosis.The method of this research adopts animal experiment,it investigates the expression of ACT A and Caspase-3 in different severity of brain injuries of neonatal rats with hyperbilirubinemia.It aims to provide experimental gist to the pathogenesis of central nervous system injury and the valid prevention and cure measure for further study of hyperbilirubinemia.Methods Totally 100 seven-day-old SD rats were randomly assigned to the normal control group(n=10)and the experiment group(n=90).The rats of experiment group were medially subdivided into 3 groups:T1,T2,and T3 groups(30 for each) according to the increased bilirubin injected intraperitoneally.The specimens were collected at each time point(0,4,8,12,24 hours)after the bilirubin injection.Observe the behavior disorder of every group at each time point.The bilirubin contents in the brain and serum were measured and the degree of the brain edema was assessed by wet/dry weight ratios of the brain tissue.Brain tissues were fixed in 4% paraformaldehyde at certain time point for a certain period,then anhydrated in gradient ethanol,luciditied in xylene,embed in paraffin.Observe the pathology changes of brain tissue with H&E staining and the expression of ACT A and Caspase-3 by immunohistochemistry staining under light microscope.All data were expressed as mean±standard variance((?)±s).All statistical analyses were completed by the package of SPSS13.0.Results The serum bilirubin content of T1 group increased obviously at 8h,12h than those in C group(P＜0.05).There was no significant difference in the brain bilirubin content,the brain edema and the expression of activin A and Caspase-3 between T1 group and C group(P＞0.05).The bilirubin contents in the brain and serum,the brain edema and the expression of activin A and Caspase-3 of T2,T3 group increased respectively at each time points after the bilirubin injection(P＜0.01,vs C). There was positive relation between the brain bilirubin content and the brain edema, the expression of activin A and Caspase-3(r=0.876,P＜0.01;r=0.886,P＜0.01; r=0.900,P＜0.01).The neurons of C group had complete structure and lined up in order.The neurons of T2,T3 group shrank obviously,and normal structure and arrangement disappeared.In T2,T3 group,the expression of activin A began at 8h, reached a peak at 12h and was still in high level until 24h after the bilirubin injection, while the expression of Caspase-3 began at 4h and peaked at 24h after the bilirubin injection.The positive cells of activin A and Caspase-3 mostly located in cerebral cortex and hippocampus.Positive reaction of activin A localized mainly in cytoplasm,axon and dendron,nonstaining in nucleus.Positive reaction of Caspase-3 localized mainly in nucleus,and also in cytoplasm,axon and dendron.Conclusions1.There are different severity of brain injury and behavior disorder in neonatal rats with hyperbilirubinemia.And there is positive relation between the severity and the brain bilirubin content.2.The expression of Caspase-3 increases dynamically in neonatal rats with hyperbilirubinemia.It indicates the bilirubin in brain tissue induces apoptosis.3.The expression of ACT A increases in neonatal rats with hyperbilirubinemia.It indicates that ACT A may play an important role in pathogenic procedure of brain injury in neonatal rats caused by hyperbilirubinemia.ACT A may be used as a sensitive index in hyperbilirubinemia and brain injury.