海马活化素βA亚基基因表达与神经元对抗兴奋性损害内源性保护效应的关系

背景自从发现活化素可促进鸡视网膜神经细胞存活以来,活化素在神经系统的研究受到关注.近年发现,缺血、缺氧等多种脑损伤模型的海马组织活化素βAmRNA表达上调,但癫痫活动后活化素βA mRNA表达的变化有待研究.目的观察小鼠毛果芸香碱(pilocarpine,C)致惊后不同时间海马活化素βAmRNA的表达,探讨其作用机制.设计以实验动物为研究对象,随机对照的实验研究.单位一所大学医院的神经内科和一所大学神经病学研究所.材料实验于2001-11/2002-07在复旦大学附属华山医院神经病学研究所及上海医学院病理室完成.选择8～10周龄健康雄性C57BL/6小鼠168只,体质量20～25g,由中国科学院上海实验动物中心提供.干预实验组小鼠腹腔注射PC350mg/kg(10 g/L),并于注射PC前30min皮下注射东莨菪碱1 mg/kg,以拮抗其外周胆碱能反应.注射PC后呈连续的肌阵挛或全身强直阵挛发作并持续1h为癫痫持续状态(statusepilepticus,E)模型鼠.成模后即刻腹腔注射安定(4mg/kg)终止发作,未成模鼠(NSE)于注射PC 1.5 h后亦注射相同剂量的安定.对照组小鼠用生理盐水代替毛果芸香碱腹腔注射,余同实验组.SE鼠、NSE鼠及对照组鼠按致模后时间随机分为0,,3,,24,8h 6小组,每小组6只(原位杂交分析中无NSE组及0 h点).主要观察指标应用RT-PCR观察SE成模鼠与NSE鼠不同时间海马活化素βAmRNA的表达;应用原位杂交观察SE后不同时间小鼠海马活化素βA mRNA表达的分布.结果NSE鼠与对照组鼠海马活化素βAmRNA的表达各时间点间无明显变化;SE开始时(0 h)活化素βA mRNA(0.49±0.11)有一过性显著将低,至SE1 h时(0.73±0.12)迅速回升至对照水平(0.74±0.13).活化素βAmRNA继续增高, h达(0.97±0.24),h达(1.34±0.19),并维持至近24 h(0.98±0.17),此后于48 h(0.83±0.09)下降至略高于对照水平.与对照组相比,,6,4h增高有显著差异(t=2.668,.289,2.916,＜0.001～0.05).活化素βA mRNA表达明显上调的部位最早于SE后3h出现于海马CA2与DG区, h后CA3区亦见明显表达,24 h后仅CA2,A3区有表达,8 h后仅CA2区可见少量阳性细胞.结论PC诱导的SE能明显上调海马活化素βAmRNA的表达,而NSE对之无明显上调作用;活化素βA mRNA表达的上调很可能是神经元对抗兴奋性损害的一种内源性保护效应.

Relationship between the hippocampal activin beta-A subgene expression and the endogenous protective effects of neurons on antagonizing excitatory injury

BACKGROUND: Since the discovery of the fact that activin can promote the survival of retinal neurocyte in chicken,the effects of activin in nervous system receives recognition. As discovered recently,hippocampal activin βA mRNA expression up-regulates in multiple brain injury animal models including ischemia and hypoxia; however,the change of activin βA mRNA expression after epilepsy is waiting for investigation.OBJECTIVE: To observe hippocampal activin βA mRNA expression at different time point after pilocarpine (PC) -induced epilepsy in mouse to explore its mechanism.DESIGN: A randomized controlled experimental study based on the experimental animals.SETTING: Department of neurology in a university affiliated hospital and the institute of neurology in a university.MATERIALS: The study was conducted in the Institute of Neurology of Huashan Hospital Affiliated to Fudan University and the Department of Pathology of Shanghai Medical College between November 2001 and July 2002. Totally 168 eight to ten-week old healthy male C57BL/6 mice with a body mass between 20 g and 25 g were obtained from Shanghai Experimental Animal Center,Chinese Academy of Science.INTERVENTIONS: 350 mg/kg(10 g/L) of PC was injected into the abdominal cavity in the mice of study group,in which 1 mg/kg of scopolamine (SC) was injected at 30 minutes before the injection of PC to antagonize its peripheral cholinergic reaction. Status epilepticus(SE) model mouse was the mouse with continuous mgoelonus or generalized seizure of rigid clonus that lasted for 1 hour after the injection of PC. Valium(4 mg/kg) was immediately injected after the modeling to terminate seizure. Same dose of Valium was injected into non-SE(NSE) mice after 1.5 hours of PC injection. Saline was used to replace PC to inject into mice of control group,and the rest disposals of control group were as same as that of study group. SE mice,NSE mice and control mice were randomly divided into six subgroups including 0hour,1 hour,3 hours,6 hours,24 hours and 48 hours subgroups according to the time point after modeling with 6 mice of each subgroup(mice of NSE group and subgroups of 0 hour time point were not included into analysis of hybridization in situ).MAIN OUTCOME MEASURES: Hippocampal activin βA mRNA expression of different time point in SE mice and NSE mice were observed by RT-PCR; the distribution of hippocampal activin βA mRNA expression at different time points in mice were observed by hybridization in situ.RESULTS: There was no significant change of hippocampal activin βA mRNA expression at different time point in mice of NSE group and control group. In SE group,activin βA mRNA(0.49 ± 0. 11) had a transient significant decrease at the beginning(0 hour),which rapidly returned to control level(0. 74 ±0. 13) at 1 hour(0.73 ±0. 12) . Activin βA mRNA continuously increased and reached (0.97 ±0. 24) at 3 hours,(1.34 ±0. 19) at 6 hours,maintained (0.98 ±0. 17) until 24 hours,and decreased to (0. 83 ± 0.09) at 48 hours afterwards,which was slightly higher than control level. Compared with control group,the increases at 3 hours,6 hours and 24hours were significant( t = 2. 668,6. 289,2. 916,P ＜ 0. 001 - 0. 05). The significant up-regulation of activin βA mRNA expression was occurred earliest in hippocampal CA2 and DG regions at 3 hours after SE,and the significant expressions also could be seen in CA3 region after 6 hours. There were expressions in only CA2 and CA3 regions after 24 hours,while there were very few positive cells in CA2 region after 48 hours.CONCLUSION: PC-induced SE could significantly up-regulate hippocampal activin βA mRNA expression,while NSE has no such up-regulative effect. The up-regulation of hippocampal activin βA mRNA expression might be an endogenous protective effect of neuron on antagonizing excitatory injury.