IRE1-JNK在运动致内质网应激-细胞凋亡中的作用机制

The Role of IRE1-JNK in Exercise-Induced Endoplasmic Reticulum Stress-Apoptosis

目的:观察一次大负荷离心运动对大鼠骨骼肌细胞凋亡和内质网应激(ERS)的影响,以及肌醇酶1(inositol requiring enzyme1,IRE1)-应激活化蛋白激酶(c-Jun N-terminal kinase,JNK)通路变化,并通过在体阻断实验,探索IRE1-JNK通路在ERS引起的骨骼肌细胞凋亡中的作用。方法:选取健康8周龄SD雄性大鼠120只,随机分为安静对照组(C组)、运动组(E组)、单纯抑制剂组(Z组)、运动加抑制剂组(EZ组)各30只。根据运动后取材时间点将4组大鼠分别分为0 h组,12 h组,24 h组,48 h组,72 h组。E组、EZ组大鼠进行一次性持续下坡跑,跑速16 m/min,时间90 min,跑台坡度为-16°。Z组与EZ组大鼠,在运动前30 min腹腔注射溶于生理盐水的IRE1抑制剂STF-083010,浓度为2 mg/m L,每只大鼠按15 m L/kg体重注射给药。通过检测Caspase3活性观察骨骼肌细胞凋亡情况;运用Western blot检测GRP78、JNK、IRE1、TRAF2、ASK1蛋白表达。采用双因素方差分析(two-way ANOVA)检测干预因素与时间因素的主效应及交互作用,用事后检验(Post-hoc test)Bonferroni比较组间差异性。结果:1)E组大鼠一次性大负荷离心运动后,比目鱼肌Caspase3活性显著升高(P<0.05),并呈现先升高后下降的趋势,于12 h达到峰值,72 h恢复至C组水平;除72 h外,所选时相EZ组大鼠Caspase3活性均显著高于C组(P<0.05),显著低于E组(P<0.05)。2)与C组、Z组相比,E组大鼠比目鱼肌GRP78蛋白表达均显著升高(P<0.05);与E组相比,EZ组大鼠比目鱼肌GRP78蛋白表达有降低趋势,但无显著性(P>0.05)。3)E组大鼠比目鱼肌IRE1、TRAF2、ASK1、JNK蛋白表达均显著高于Z组(P<0.05),除0 h外,均显著高于C组(P<0.05);EZ组大鼠比目鱼肌IRE1、TRAF2、ASK1、JNK蛋白表达均显著高于C组、Z组(P<0.05),显著低于E组(P<0.05)。结论:大负荷运动后大鼠比目鱼肌发生明显的ERS及细胞凋亡,IRE1抑制剂有效降低大负荷运动后IRE1-JNK通路蛋白表达的升高,并且改善大负荷离心运动后比目鱼肌细胞的凋亡水平,因此大负荷运动引起的细胞凋亡现象与ERS的下游通路IRE1-JNK的激活有关。

Objective:To investigate the effects of a heavy-load eccentric exercise on rat skeletal muscle cell apoptosis and endoplasmic reticulum stress(ERS),and the expression of inositol requiring enzyme1(IRE1)-c-Jun Nterminal kinase(JNK)pathway proteins,and to explore the effects of IRE1-JNK on skeletal muscle cell apoptosis induced by ERS via in vivo inhibition experiments.Methods:One hundred and twenty healthy male SD rats were randomly divided into a non-exercise control group(C),an exercise group(E),an inhibition only group(Z),and an exercise plus inhibition group(EZ),with 30 in each group.Soleus muscle samples were obtained from each of the above-mentioned groups immediately on 12 h,24 h,48 h and 72 h after the exercise.Rats in E and EZ groups underwent a continuous downhill run of a speed of 16 m/min for 90 min and at an incline of 16°.Each rat in Z and EZ groups got an intraperitoneal injection of 2 mg/m L STF-083010 dissolved by physiological saline,with a dose of 15 m L/kg body weight.The apoptosis was observed by detecting Caspase3 activity;and the expression of GRP78,JNK,IRE1,TRAF2 and ASK1 was detected by Western blot.Two-way ANOVA with Post-hoc Bonferroni correction was performed for analyzing the main effect and interaction of the treatment and duration,and for comparing the difference between groups.Results:1)The activity of Caspase3 in group E was significantly increased after one-time heavy-load eccentric exercise(P<0.05),peaked at 12 h,and returned to the baseline level at 72 h.Except at 72 h,the activity of Caspase3 in EZ group was significantly higher than that in C group(P<0.05),and was significantly lower than that in E group(P<0.05).2)Compared with group C and group Z,the expression of GRP78 protein in group E was significantly increased(P<0.05).Compared with group E,the expression of GRP78 protein in EZ group was decreased,but not significantly(P>0.05).3)The expressions of IRE1,TRAF2,ASK1 and JNK in group E were significantly higher than those of group Z(P<0.05);except at 0 h,they were significantly higher in group E than in group C(P<0.05).The expressions of IRE1,TRAF2,ASK1 and JNK protein were significantly higher than those in group C and Z(P<0.05),and were significantly lower than those in group E(P<0.05).Conclusion:A continous heavy-load eccentric exercise caused ERS and apoptosis.IRE1 inhibitor can reduce the expression of the proteins in IRE1-JNK pathway and improve the apoptosis incluced by the exercise.It is speculated that the apoptosis induced by the heavy load exercise may be related to the activation of IRE1-JNK after ERS.