内质网应激相关因子 CCAAT／增强子结合蛋白同源蛋白在蛛网膜下腔出血后早期脑损伤中的作用

摘要

目的：探讨内质网应激相关因子CCAAT／增强子结合蛋白同源蛋白（ CHOP）的表达及其在蛛网膜下腔出血（ SAH）后早期脑损伤（ EBI）中的作用。方法选取健康雄性SD大鼠78只，采用随机数字表法将其分为空白对照组（6只）、假手术组（36只）与SAH组（36只）。将假手术组和SAH组分别于1、6、12、24、48、72 h，采用简单随机抽样法选取6只大鼠处死。比较各组不同时间点光镜及电镜下大鼠海马神经元形态改变、 CHOP相对表达水平、海马神经元凋亡细胞水平及神经行为学评分。结果3组大鼠6、12、24、48 h时CHOP相对表达水平比较，差异均有统计学意义（ P＜0.05）；其中SAH组大鼠6、12、24、48 h时CHOP相对表达水平均高于空白对照组和假手术组（P＜0.05）。空白对照组和假手术组大鼠不同时间点 CHOP相对表达水平比较，差异无统计学意义（P＞0.05）。空白对照组与假手术组仅有极少数海马神经元凋亡细胞； SAH组1 h海马神经元未见明显凋亡改变； SAH组6、12 h海马神经元凋亡细胞较前增多，部分散在的海马神经元凋亡细胞的细胞核呈棕褐色； SAH组24 h海马神经元凋亡细胞明显增多； SAH组48 h海马神经元凋亡细胞逐渐减少，72 h可见少量海马神经元凋亡细胞。3组大鼠6、12、24、48 h时海马神经元凋亡细胞水平比较，差异均有统计学意义（ P＜0.05）；其中SAH组大鼠6、12、24、48 h时海马神经元凋亡细胞水平均高于空白对照组和假手术组（ P＜0.01）。空白对照组和假手术组大鼠不同时间点海马神经元凋亡细胞水平比较，差异无统计学意义（P＞0.05）。空白对照组、假手术组及SAH组大鼠实验前神经行为学评分比较，差异无统计学意义（P＞0.05）。3组大鼠6、12、24、48 h时神经行为学评分比较，差异均有统计学意义（P＜0.05）；其中SAH组大鼠6、12、24、48 h时神经行为学评分均低于空白对照组和假手术组（ P＜0.01）。空白对照组和假手术组大鼠不同时间点神经行为学评分比较，差异无统计学意义（ P＞0.05）。 SAH组CHOP相对表达水平与海马神经元凋亡细胞水平呈正相关（r＝0.933， P＜0.01）。结论 SAH后早期CHOP表达增高，海马神经元凋亡细胞增多，神经行为学评分降低，提示CHOP在SAH后内质网应激诱导的细胞凋亡中发挥重要作用。%Objective To investigate the effects of endoplasmic reticulum stress factor -induced transcriptional factor CHOP on early brain injury ( EBI) after subarachnoid hemorrhage ( SAH) .Methods A total of 78 healthy male Sprague -Dawley rats were selected and randomly assigned into control group (n=6), sham operation group (n=36) and SAH group (n=36) .At 1, 6, 12, 24, 48 and 72 h, we selected 6 rats from both sham operation group and SAH group using simple random sampling method and killed these rats .Comparison was made in the morphological change of hippocampal neurons , the relative expression level of CHOP , the apoptosis level of hippocampal neuron cells and the score of neuroethology observed under light microscope and electron microscope among the three groups at different time points .Results In each group , the relevant expression levels of CHOP at 6, 12, 24 and 48 h were significantly different (P<0.05) .SAH group was higher (P<0.05) than control group and sham operation group in the relative expression level of CHOP at 6, 12, 24 and 48 h.No significant difference (P>0.05) was noted between control group and sham group in the relevant expression level of CHOP at different time points.In control group and sham operation group , very few apoptotic hippocampal neuron cells were observed; in SAH group , no obvious apoptosis of hippocampal neuron cells was observed at 1 h; in SAH group, the apoptotic hippocampal neuron cells increased at 6 and 12 h than before , and the karyons of some scattered apoptotic hippocampal neuron cells took on the color of sepia; in SAH group , apoptotic hippocampal neuron cells increased notably at 24 h and decreased gradually at 48 h, and a small number of apoptotic hippocampal neuron cells were observed at 72 h.In each group , the apoptosis levels of hippocampal neuron cells at 6, 12, 24 and 48 h were significantly different ( P<0.05) .SAH group was higher ( P<0.01) than control group and the sham operation group in the apoptosis level of hippocampal neuron cells at 6, 12, 24 and 48 h.No significant difference ( P>0.05) was noted between control group and sham group in the apoptosis level of hippocampal neuron cells at different time points.No significant difference (P>0.05) was noted among the three groups in the score of neuroethology before intervention .In each group, the scores of neuroethology at 6, 12, 24 and 48 h were significantly different (P<0.05) .SAH group was lower (P<0.01) than control group and sham operation group in the score of neuroethology at 6, 12, 24 and 48 h.No significant difference (P>0.05) was noted between control group and sham group in the score of neuroethology at different time points .In SHA group, the expression level of CHOP was positively correlated with the apoptosis level of hippocampal neuron cells ( r=0.933, P<0.01 ) .Conclusion At the early stage following SAH , the expression of CHOP increases , the apoptotic hippocampal neuron cells increase , and the score of neuroethology decreases .It suggests that CHOP plays an important role in cell apoptosis induced by endoplasmic reticulum stress after SAH .