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内质网应激(endoplasmic reticulum stress,ERS)是细胞对环境改变的适应性反应,但过度ERS可诱导细胞凋亡。C/EBP同源蛋白(C/EBP homologous protein,CHOP)是ERS相关凋亡途径中重要的信号分子。本实验旨在探讨CHOP介导的ERS相关凋亡途径在大鼠腹主动脉狭窄致高血压心肌肥厚发生、发展中的作用。健康雄性Wistar大鼠85只,随机分为模型组(n=45)和对照组(n=40),模型组行腹主动脉狭窄术,对照组仅分离腹主动脉不行狭窄术,分别于术后1d、3d、7d、14d、28d时观察各组血流动力学变化,测定全心重/体重比(HW/BW)和左心室重/体重比(LVW/BW),RT-PCR技术检测左心室心肌组织ERS相关分子葡萄糖调节蛋白78(glucose-regulated protein78,GRP78)、钙网蛋白(calreticulin,CRT)和CHOPmRNA表达变化,Western blot分析GRP78、CRT、CHOP,以及凋亡相关蛋白Bax和Bcl-2表达变化。结果显示,腹主动脉狭窄可诱导大鼠心肌肥厚,与对照组比较,术后7d模型组大鼠血压升高,心功能代偿性增加,HW/BW和LVW/BW显著增加。模型组内质网分子伴侣CRTmRNA表达于术后1d即发生显著上调,较对照组增加136%(P<0.01),而蛋白在术后7d开始出现显著变化,较对照组升高69.2%(P<0.01);GRP78基因和蛋白表达均于术后7d显著增加,分别较对照组增加20%和186%(均P<0.01),在此后观察期间内CRT和GRP78mRNA和蛋白均持续高水平表达。相关分析显示左心室内压最大上升速率(+dp/dtmax)分别与CRT蛋白表达(r=0.780,P<0.01)和GRP78蛋白表达(r=0.694,P<0.01)显著正相关。长期ERS(14d)可触发CHOP凋亡途径,模型组大鼠心肌组织CHOP mRNA和蛋白表达均于术后14d显著上调,分别较对照组增加22.2%和76.0%(均P<0.01),同时促凋亡蛋白Bax表达增加(较对照组增加41.1%,P<0.01),而抗凋亡蛋白Bcl-2表达降低(较对照组降低25.5%,P<0.01);相关分析显示CHOP蛋白表达与Bax表达正相关(r=0.654,P<0.01),而与Bcl-2表达负相关(r=–0.671,P<0.01)。上述结果提示腹主动脉狭窄早期即可诱导内质网分子伴侣表达变化,触发ERS,长期ERS诱导心肌细胞凋亡,CHOP介导的ERS相关凋亡途径可能参与了心肌肥厚过程,推测心肌细胞凋亡参与了心肌肥厚及失代偿的调节,决定肥厚心肌失代偿的进程。
Endoplasmic reticulum stress (ERS) is an adaptive response of cells to environmental changes, but excessive ERS can induce apoptosis. C / EBP homologous protein (CHOP) is an important signaling molecule in ERS-related apoptotic pathway. This experiment aimed to investigate the role of CHOP-mediated ERS-related apoptosis in the occurrence and development of hypertensive cardiac hypertrophy induced by abdominal aortic stenosis in rats. A total of 85 healthy male Wistar rats were randomly divided into model group (n = 45) and control group (n = 40). The model group received abdominal aortic stenosis. The control group was only separated from the abdominal aorta without stenosis. The hemodynamic changes were observed on the 1st, 3rd, 7th, 14th and 28th day after operation, and the ratio of total heart weight to body weight (HW / BW) and left ventricular weight to body weight (LVW / BW) The expressions of GRP78, calreticulin (CRT) and CHOP mRNA in left ventricular myocardium were detected by Western blot. The expressions of GRP78, CRT, CHOP and apoptosis-related proteins Bax and Bcl- -2 expression changes. The results showed that abdominal aorta stenosis can induce cardiac hypertrophy in rats. Compared with the control group, the blood pressure, the compensatory increase of cardiac function, and the increase of HW / BW and LVW / BW in the model group at 7 days after operation were significantly increased. The expression of endoplasmic reticulum chaperone CRT mRNA in model group significantly increased at 1 day after operation, which was 136% higher than that in control group (P <0.01), while the protein began to show significant changes at 7 days after operation, which was 69.2% higher than that in control group <0.01). The expression of GRP78 mRNA and protein both increased significantly at 7 days after operation and increased by 20% and 186% respectively compared with the control group (all P <0.01). Correlation analysis showed that the maximum rate of increase of left ventricular pressure (+ dp / dtmax) was positively correlated with CRT protein expression (r = 0.780, P <0.01) and GRP78 protein expression (r = 0.694, P <0.01). Long-term ERS (14d) could trigger the CHOP apoptotic pathway. CHOP mRNA and protein expression in myocardium of model group were significantly increased 14 days after operation, which increased by 22.2% and 76.0% respectively compared with control group (all P <0.01) (P <0.01), while the expression of Bcl-2 was decreased (25.5% compared with the control group, P <0.01). The correlation analysis showed that the expression of CHOP protein was positively correlated with Bax (R = 0.654, P <0.01), but negatively correlated with Bcl-2 expression (r = -0.671, P <0.01). The above results suggest that endoplasmic reticulum chaperone expression can be induced in the early stage of abdominal aortic stenosis, trigger ERS, long-term ERS-induced cardiomyocyte apoptosis, CHOP mediated ERS-related apoptotic pathway may be involved in cardiac hypertrophy, speculated that myocardial apoptosis Death participated in the regulation of cardiac hypertrophy and decompensation, determine the process of hypertrophy of cardiac decompensation.