大鼠DAI脑细胞凋亡与Phospho-Ser^727 Stat1表达的相关性

目的探讨Stat1是否参与弥漫性轴索损伤（diffuse axonal injury,DAI）后神经细胞凋亡的病理生理过程。方法应用自由落体撞击模型复制大鼠DAI模型,分为正常对照组、假手术组和打击后不同时间组（6、12、24、48、72h,5d和10d）。采用HE染色和镀银染色观察大鼠脑组织的病理改变,用流式细胞检测脑组织中脑细胞的凋亡率,RT-PCR法测定脑组织中bax和bcl-2的表达变化,免疫组织化学法测定脑组织中不同脑区727位丝氨酸磷酸化的信号转导与转录激活子1（Phospho-Ser727 Stat1）的表达情况。结果DAI后HE染色未见脑挫裂伤,镀银染色可见神经轴索扭曲肿胀,个别断端膨大形成轴缩球;损伤组脑细胞的凋亡率和脑组织中bax和bcl-2 cDNA扩增产物的比值24h达到最大值,随后下降;不同脑区Phospho-Ser727 Stat1表达升高,24h达峰后下降,至10d较对照组仍有显著差异;阳性细胞主要是神经元,在不同脑区也有一定量的神经胶质细胞阳性表达。脑组织中Phospho-Ser727 Stat1表达变化与bax和bcl-2的cDNA扩增产物比值的变化具有正相关性,相关系数r为0.921。结论大鼠DAI后Stat1的激活和损伤后脑细胞的凋亡有关,应与损伤后二次打击有关。

The relationship between cell apoptosis and Phospho-Ser727 Stat1 expression in the rat with experimental diffuse axonal injury

Objective To investigate the role of Stat1 in pathological process of nerve cells apoptosis induced by diffuse axonal injury (DAI) on rats. MethodsThe DAI model was established by using an injury model adapted from Marmarou et al. in 1994. All animals were divided into three groups, including control group, mock group and test group sacrificed on 6, 12, 24, 48, 72, 120 and 240 hours post injury (hpi). The paraffin-embedded sections of brain tissue were processed for HE staining and Bielschowsky’s silver method. Cell apoptosis was examined by flow cytometry and the expression of bax and bcl-2 were analyzed by RT-PCR. And Phospho-Ser727 Stat1 expression was examined by immunohistochemistry in different brain regions. ResultsThere was no brain contusion within HE staining, however, waving and enlargement of axons were observed within Bielschowsky’s silver method. The apoptotic rate of brain cells as well as PCR products ratio of bax to bcl-2 was highest at 24 hpi and decreased with time. An up-regulation of Phospho-Ser727 Stat1 at 6 hpi was discernible, and then reached the top at 24 hpi in cortex, cerebellum, brain stem and corpus callosum, and at 12 hpi in hippocampus. This increase was associated with the nerve cells apoptosis, r=0.921. In addition, the Phospho-Ser727 Stat1 positive cells were neurons and glial cells assessed from morphous. ConclusionsOur data indicate that Stat1 may contribute to the apoptosis of DAI on rats. In addition, the expression of Phospho-Ser727 Stat1 in glial cells suggested that glial cells may play an important role in the pathogenic mechanism of DAI.