西洋参茎叶总皂苷通过抑制内质网应激相关细胞凋亡减轻大鼠急性心肌梗死后心室重构

 目的： 研究西洋参茎叶总皂苷 (Panax quinquefolium saponin, PQS)对大鼠急性心肌梗死(AMI)后心室重构的作用及其机制。方法： 健康雄性SD大鼠90只，随机分为假手术 (sham) 组、AMI组、牛磺酸 (300 mg·kg-1·d-1) 组及PQS (50、100和200 mg·kg-1·d-1) 组 (n=15)。结扎大鼠左冠状动脉前降支复制AMI模型。术后第2天开始，各用药组用饮用水10 mL·kg-1·d-1溶解药物灌胃，sham组及AMI组予等量饮用水灌胃。术后4周，超声心动图检测左室结构及功能变化；TTC染色法测定心肌梗死范围；比色法测定非梗死区心肌组织羟脯氨酸含量；TUNEL法检测非梗死区心肌细胞凋亡率，Western blotting检测内质网应激分子葡萄糖调节蛋白78 (GRP78)、钙网蛋白 (CRT)、C/EBP同源蛋白 (CHOP) 及凋亡相关蛋白Bcl-2、Bax的表达。结果： 与AMI组比较，PQS低、中、高剂量组左室收缩末期内径分别降低17.2%、20.3%和38.8%,左室舒张末期内径分别降低8.9%、9.0%和17.2%,左室收缩末期容积分别降低31.4%、38.5%和66.9%左室舒张末期容积分别降低18.2%、18.8%和34.2%,射血分数分别升高44.9%、60.1%和118.0%,左室短轴缩短率分别升高55.4%、71.0%和148.0%，梗死范围分别降低4.6%、39.5%和55.8% (均P<0.05)；非梗死区心肌组织羟脯氨酸含量分别降低34.5%、35.9%和48.7% (P<0.01)。与AMI组比较，PQS 200 mg·kg-1·d-1组心肌细胞凋亡率降低27.3% (P<0.05)，GRP78和CRT蛋白表达分别降低79.9%和80.8% (P<0.01)，CHOP和Bax分别降低42.5%和53.1% (P<0.01)，Bcl-2表达升高1.1倍 (P<0.01)；上述保护作用的程度与内质网应激抑制剂牛磺酸相近 (P>0.05)。Spearman相关分析发现CHOP蛋白表达与心肌细胞凋亡率显著正相关 (r=0.797, P<0.01)。结论： PQS剂量依赖性减轻大鼠心肌梗死后心室重构，其机制与抑制CHOP介导的内质网应激凋亡通路有关。

Panax quinquefolium saponin attenuates ventricular remodeling in rats after myocardial infarction by inhibiting CHOP-mediated endoplasmic reticulum stress-related apoptosis

AIM: To observe the effect of Panax quinquefolium saponin (PQS) on ventricular remodeling after myocardial infarction in rats, and investigate mechanism from the aspect of endoplasmic reticulum stress-related apoptosis. METHODS: 90 healthy male SD rats were randomly divided into 6 groups, the sham group, the Acute myocardial infarction (AMI) group, the Taurine 300 mg/kg/d group, the 50 mg/kg/d, 100 mg/kg/d and 200 mg/kg/d PQS groups (n = 15). AMI models were produced by ligating the left coronary arteries in SD rats. Rats in each treatment group were gavaged with drugs dissolved in water (10 ml/kg/d), and rats of the sham group and the AMI group received an equivalent volume of vehicle (water) daily continuing for 4 weeks after MI. After 4 weeks, the heart structure and function paraments were measured by Echocardiography, the infartion size was measured by triphenyltetrazolium chloride staining, the hydroxyproline level of noninfarcted myocardium was determinated through colorimetric method, the apoptotis index of noninfarction cardiac myocytes were examined by Terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling (TUNEL) assay, and the expression of CRT, GRP78, CHOP, Bax, Bcl-2 protein were detected by western blotting. RESULTS: Compared with the sham rats，both the left ventricular end-diastolic and end-systolic dimension increased by 1.60 times and 41.30% respectively (P < 0.05), both the left ventricular end-diastolic and end-systolic volume increased by 7.95 times and 1.15 times respectively (P < 0.05), the thickness of left ventricular end-diastolic and end-systolic anterior wall decreased by 92.17% and 87.51% respectively (P < 0.05), the left ventricular ejection factor and fractional shortening decreased by 64.12% and 72.12% respectively (P < 0.05); AMI group rats shows obvious infarction (infarction size 31.98% ±5.87%); the hydroxyproline level of noninfarcted myocardium increased by 2.04 times (P < 0.05). Compared with the AMI rats，the left ventricular end-systolic dimension of PQS (50mg/kg/d, 100mg/kg/d, 200mg/kg/d) groups rats decreased by 17.2%, 20.3% and 38.8% respectively (P < 0.05), and left ventricular end-diastolic dimension decreased by 8.91%, 8.95% and 17.2% respectively (P < 0.05), the left ventricular end-systolic volume decreased by 31.42%, 38.52% and 66.97% respectively (P < 0.05), the left ventricular end-diastolic volume decreased by 18.21%, 18.84% and 34.24% respectively (P < 0.05), the left ventricular ejection factor increased by 44.9%, 60.1% and 118% respectively (P < 0.05), the fractional shortening increased by 55.4%, 70.99% and 148% respectively (P < 0.05); The infarction size decreased by 4.6%, 39.5% and 55.8% respectively (P < 0.05); The noninfarcted myocardial hydroxyproline level decreased by 34.51%, 35.88% and 48.70% respectively (P < 0.01). PQS can significantly reduce myocardial apoptosis and endoplasmic reticulum stress response in rats after myocardial infarction. Compared with the AMI rats，PQS (200 mg/kg/d) decreased the cardiac myocytes apoptosis index by 27.3% (P < 0.05); it increased the protein expression of Bcl-2 by 114%, and decreased that of Bax by 53.14% (P < 0.05), that of GRP78 by 79.90% (P < 0.01), that of CRT by 80.84% (P < 0.01), and that of CHOP by 42.45% (P < 0.01)．The above mentioned protective effect extent in PQS group and Taurine (endoplasmic reticulum stress inhibitor) was similar (P> 0.05). The Spearman correlation analysis revealed that CHOP expression showed significant positive correlation with apoptosis index (r = 0.797, P < 0.01). CONCLUSION: Panax quinquefolium saponin attenuated ventricular remodeling in rats, the underlying mechanisim maybe associated with inhibiting CHOP-mediated endoplasmic reticulum stress-related cardiomyocyte apoptosis.