内质网应激反应在严重烧伤大鼠心肌细胞凋亡中的作用

目的内质网应激反应(endoplasmic reticulum stress,ERS)介导的凋亡是真核细胞重要凋亡途径之一,通过观察严重烧伤大鼠心肌ERS不同通路蛋白表达变化,探讨其在心肌细胞凋亡中的可能作用。方法雄性7周龄Wistar大鼠64只,体重200～220 g;随机分为两组,每组32只。实验组大鼠背部制备30%体表面积Ⅲ度烫伤;对照组制备假伤模型。伤后1、4、7、14 d两组各处死8只大鼠取心肌组织,透射电镜观察心肌超微结构变化,TUNEL法检测心肌细胞凋亡,Western blot检测ERS相关蛋白,如葡萄糖调节蛋白78(glucose regulated protein 78,GRP 78)、C/EBP同源蛋白(C/EBP-homologous protein,CHOP)、半胱氨酸天冬氨酸蛋白酶12(Caspase 12)剪切体表达变化。结果大鼠均存活至实验结束。透射电镜观察示实验组大鼠心肌细胞呈凋亡改变。伤后各时间点实验组心肌细胞凋亡指数均明显高于对照组(P<0.05),伤后1、4、7 d凋亡指数逐渐升高,14 d时下降,各时间点间比较差异均有统计学意义(P<0.05)。实验组心肌细胞GRP78、CHOP及Caspase 12剪切体蛋白表达持续升高,其中各时间点GRP 78及Caspase 12剪切体表达均较对照组显著升高,差异有统计学意义(P<0.05);除伤后1 d外,其余各时间点实验组CHOP蛋白表达均较对照组升高(P<0.05)。结论严重烧伤后大鼠心肌发生ERS,其中CHOP、Caspase 12介导的凋亡通路活化,ERS可能是心肌细胞凋亡的途径之一。

Role of endoplasmic reticulum stress during myocardial apoptosis in rats with severe burn injury

Objective Endoplasmic reticulum stress(ERS) mediated apoptosis is one of the eukaryotic cellular apoptotic pathways,to investigate the potential role of ERS during myocardium apoptosis in rats with severe burn injury. Methods Sixty-four 7-week-old male Wistar rats,weighing 200-220 g,were randomly divided into 2 groups.Thirty percentage of total body surface area full-thickness thermal injury was produced in 32 rats of burn group,while sham burn was produced in 32 rats of control group.The heart tissues were harvested from 8 rats in each group at 1,4,7,and 14 days after burn to observe the changes of myocardium ultrastructure with transmission electron microscope(TEM).Myocardium apoptosis was detected with TUNEL assay.The expressions of glucose regulated protein 78(GRP 78),C/EBP-homologous protein(CHOP),and cleaved Caspase 12 in different pathways of ERS were analysed with Western blot. Results All rats survived during the experiment.Apoptotic changes of cardiomyocytes were observed in burn group,and the apoptosis index in burn group was significantly higher than that in control group at each time point(P < 0.05),and it reached peak at 7 days after burn injury(P < 0.05).The expressions of myocardial GRP 78,CHOP,and cleaved Caspase 12 showed persistent elevation in burn group.The expressions of GRP 78 and cleaved Caspase 12 in burn group were significantly higher than those in control group at each time point(P < 0.05),while the expression of CHOP was higher than that in control group at the other time points(P < 0.05) except 1st day after burn injury.Conclusion ERS and CHOP,Caspase 12 mediated apoptotic pathway are activated in myocardium after severe burn injury,and this may be one pathway of myocardium apoptosis.