高胆红素血症新生大鼠脑组织激活素A、caspase-3表达的研究

Expressions of activin A and caspase-3 in brain tissue of neonatal rats with hyperbilirubinemia

目的探讨高胆红素血症新生大鼠脑损伤后内源性激活素A（ACTA），caspase-3表达的变化。方法将100只SD大鼠按随机数字表法分为正常对照组（C组,n=10），实验1组（T1组，n=30），实验2组（T2组，n=30）和实验3组（T3组，n=30），各实验组建立高胆红素血症动物模型（T1组注射胆红素50μg／g，T2组100μg／g，T3组200μg／g），于造模后0、4、8、12、24h采集标本，各组检测血清胆红素浓度、脑组织胆红素含量、脑组织含水量，观察脑组织病理改变及用免疫组织化学法检测脑组织中ACTA、caspase-3的表达。结果T1组血清胆红素浓度于造模后8h、12h显著高于C组（P〈0．05），T1组脑组织胆红素含量、脑组织含水量及ACTA、caspase-3表达于造模后各时间点与C组比较均无统计学意义（P〉0．05）。T2、T3组血清胆红素浓度、脑组织胆红素含量、脑组织含水量及ACTA、caspase-3表达于造模后各时间点均显著高于C组（P〈0．01）。脑组织胆红素含量与脑组织含水量及ACTA、caspase-3表达均呈正相关（r=0．876，P〈0.01；r=0.886，P〈0．01；r=0．900，P〈0．01）。C组、T1组大脑皮质、海马区神经元排列整齐，结构完整；T2、T3组神经元数量减少，结构紊乱，可见胆红素沉积。T2、T3组造模后4hACTA蛋白表达开始上调，12h达高峰，保持高表达状态至24h：阳性反应主要位于细胞浆和突起．细胞核不着色。T2、T3组造模后4h caspase-3蛋白表达开始上调，24h达高峰：阳性反应主要位于细胞核。结论高胆红素血症新生大鼠脑损伤后可诱导ACTA，caspase-3表达的增加，提示二者在高胆红素血症新生大鼠脑损伤的病理过程中可能发挥重要作用。

Objective To investigate the expressions of activin A （ACT A） and caspase-3 in different severity of brain injuries of neonatal rats with hyperbilirubinemia. Methods Totally 100 7-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 according to the increased bilirubin injected intmperitoneally （T1, 50 μg/g; T2, 100 μg/g; T3, 200 μg/g）. The specimens were collected at each time point （0, 4, 8, 12, 24 h） after the bilirubin injection. 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. And we observed the pathological changes of brain tissue and the expressions of ACT A and caspase-3 by immunohistochemistry staining. Results The serum bilirubin content of T1 group was increased obviously at 8, 12 h compared with that in control group （P〈0.05）. There was no significant difference in the brain bilirubin content, the brain edema and the expressions of ACT A and caspase-3 between T1 group and control group （P〉0.05）. The bilirubin contents in the brain and serum, the brain edema and the expressions of ACT A and caspase-3 of T2, T3 groups were increased respectively at each time points after the bilirubin injection （P〈0.01 vs control）. There were positive relations between the brain bilirubin content and the brain edema, the expressions of ACT 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 control and T1 groups had complete structure and lined up in order. The neurons of T2 and T3 groups shrank obviously, and normal structure and arrangement disappeared. In T2, T3 groups, the expression of ACT A began at 8 h, reached a peak at 12 h and was still in high level until 24 h after the bilirubin injection, while the expression of caspase-3 began at 4 h and peaked at 24 h after the bilirubin injection. The caspase-3 and ACT A positive cells were mostly located in cerebral cortex and hippocampus. Conclusions The expressions of ACT A and caspase-3 are increased and dynamic in different severity of brain injury in neonatal rats with hyperbilirubinemia. It indicates that both of them may play important roles in pathogenic procedure of brain injury in neonatal rats caused by hyperbilirubinemia.