ERK1/2对胆红素诱导的海马神经元损伤及NF-κB表达的影响

Effects of ERK 1/2 on bilirubin-induced injury of hippocampal neurons and expression of NF-κB in hippocampal neurons

目的研究细胞外信号调节蛋白激酶(extracellular signal-regulated protein kinase,ERK)1/2对胆红素诱导的大鼠海马神经元核转录因子-κB(nuclear transcription factors,NF-κB)表达的影响,及其对抗胆红素神经元毒性的可能机制。方法将原代培养的海马神经元分为对照组、胆红素组、PD98059(MEK/ERK抑制剂)+胆红素组及芥酸精(erucin,ERN,ERK激活剂)+胆红素组。采用改良噻唑蓝比色法(MTT法)和Annexin V-FITC/PI双染色法,检测各组细胞相对存活率及凋亡率;免疫细胞化学法检测NF-κB p65蛋白表达。结果正常组、ERN+胆红素组、胆红素组、PD98059+胆红素组细胞相对存活率分别为100%、(80.020±8.552)%、(67.546±3.241)%、(50.591±3.981)%,各组比较有统计学差异(P<0.01)。同一时间点各组NF-κB蛋白平均光密度(mean optical density,MOD)值均有统计学差异(P<0.01),对照组最低;胆红素组NF-κB蛋白MOD值在胆红素作用3 h(0.266±0.033)时较高,随时间延长逐渐下降,24 h(0.183±0.021)时最低(P<0.01);PD98059+胆红素组NF-κB蛋白MOD值变化趋势同胆红素组,但MOD值明显下降(P<0.05);与胆红素组相反,ERN+胆红素组MOD值在胆红素作用3 h(0.128±0.028)时较低,随时间延长逐渐升高,24 h(0.305±0.043)时最高(P<0.01)。结论胆红素诱导海马神经元NF-κB表达具有时间依赖性;ERK1/2通路在胆红素诱导的海马神经元损伤过程中起保护作用,可能与ERK1/2通路抑制胆红素诱导的海马神经元NF-κB早期(3～6 h)表达、而促进其晚期(24 h)表达有关。

Objective To investigate the effects of extracellular signal-regulated protein kinase（ERK） 1/2 on the expression of bilirubin-induced nuclear transcription factor-κB（NF-κB） in rat＇s hippocampal neurons,and to discuss the possible mechanism of ERK 1/2 signal pathway on preventing bilirubin neurotoxity in hippocampal neurons.Methods Hippocampal neurons cultured in vitro were randomly divided into a control group,a bilirubin group,a PD98059（MEK/ERK inhibitor） ＋ bilirubin group and an erucin（ERN,ERK activator） ＋ bilirubin group.Modified MTT assay and Annexin V-FITC/PI dual fluorescent staining were employed to detect the relative survival rate and apoptosis rate of hippocampal neurons.Immunocytochemistry was employed to detect the expression of NF-κB p65 protein.Results There were statistical differences among the above four groups in terms of the relative survival rate of hippocampal neurons [100%,（67.546±3.241）%,（50.591±3.981）% and（80.020±8.552）%,P0.01].There were statistical differences among the above four groups in terms of the apoptosis rate of hippocampal neurons[（6.859±1.559）%,（20.729±1.368）%,（28.474±1.710）%,and（13.741±5.150）%,P0.05].At the same time point,there were statistical differences among the above four groups in terms of the mean optical density（MOD） of NF-κB（P0.01）,with the control group having the lowest value.In the bilirubin group,the MOD of NF-κB reached the highest value（0.266±0.033） at 3 h,decreased over time,and reached the lowest value（0.183±0.021） at 24 h（P0.01）.The PD98059＋bilirubin group had a similar trend,yet with a significantly decreased MOD（P0.05）.In the ERN＋bilirubin group,on the contrary,the MOD of NF-κB reached the lowest value（0.128±0.028） at 3 h,increased over time,and reached the highest value（0.305±0.043） at 24 h（P0.01）.Conclusion In hippocampal neurons,bilirubin-induced NF-κB expression is in a time-dependent manner.ERK1/2 signal pathway protects hippocampal neurons from bilirubin-induced injury,and the protection mechanism may be related to the down-regulation of NF-κB early expression（3～6 h） and the up-regulation of NF-κB late expression（24 h）.