聚集体自噬在运动性骨骼肌损伤中的特征

Characterization of aggrephagy in exercise-induced muscle damage

背景:一次大负荷离心运动会诱导骨骼肌损伤、内质网应激、错误折叠蛋白增多,聚集体自噬作为蛋白质质量控制的途径之一,在损伤修复过程中应当发挥一定的作用。目的:探讨一次大负荷离心运动诱导骨骼肌损伤恢复过程中聚集体自噬的激活程度,分析聚集体自噬在运动诱导骨骼肌损伤中的作用,以完善运动诱导骨骼肌损伤的蛋白降解途径。方法:将64只成年雄性SD大鼠(购自北京维通利华实验技术有限公司)随机分为安静对照组(n=8)和运动组(n=56),运动组又按运动后时相分为0,3,6,12,24,48,72h组,每组8只。运动组大鼠进行一次跑台下坡跑运动(-16°,16 m/min,90 min),分别在运动后的相应时刻取比目鱼肌,使用透视电子显微镜观察损伤发生程度,采用Western Blot方法检测比目鱼肌难溶蛋白聚集体自噬相关蛋白组蛋白去乙酰化酶6和微管相关蛋白1轻链3Ⅱ/Ⅰ的蛋白表达。实验获得北京体育大学运动科学实验伦理委员会批准(2016030A)。结果与结论:(1)透射电镜显示一次大负荷离心运动后,大鼠比目鱼肌出现一过性的肌节紊乱、变宽,Z线呈水波状、断裂直至消失,线粒体肿胀、分布不均、结构不清,其中运动后12h损伤最为严重,于运动后72h完全恢复;(2)Western Blot检测显示,一次性离心运动后即刻组蛋白去乙酰化酶6显著增高,运动后6 h达到峰值,之后逐渐降低,运动后72 h恢复到对照组水平;一次性离心运动后3 h的微管相关蛋白1轻链3Ⅱ/Ⅰ显著升高,运动后12h达到峰值,之后显著降低,运动后72 h恢复到对照组水平;(3)结果表明,一次大负荷离心运动后一过性发生聚集体自噬,在清除错误折叠蛋白、维持细胞环境稳定和骨骼肌损伤恢复中发挥着重要作用。

BACKGROUND:A high-intensity eccentric exercise may lead to skeletal muscle damage,endoplasmic reticulum stress,increasing misfolded proteins.Aggrephagy works as an effective way of controlling quality of proteins and plays an important role in damage repair.OBJECTIVE:To discover the activation degree of aggrephagy in the damage repair process after an overload eccentric exercise,and to discuss the role of aggrephagy in the exercise-induced muscle damage,which is supplementary to the protein degradation pathway in skeletal muscle damage.METHODS:Sixty-four male adult Sprague Dawley rats were randomly divided into a static control group(n=8) and seven exercise groups according to post-exercise time(0,3,6,12,24,48 and 72 hours,eight rats in each).Damage models were established by downhill running(-16°,16 m/min,90 minutes).Subsequently,the histological changes of the rat soleus muscle was observed under an electron microscope and protein expressions of histone deacetylase 6 and microtubule-associated protein 1 light chain 3Ⅱ/Ⅰ related to aggrephagy were detected using western bot assay.RESULTS AND CONCLUSION:(1) Under the transmission electron microscope,the rat soleus muscle was disordered and widened and appeared to have transient sarcomere,the Z line was water wave-like,broken and disappeared,and the mitochondria were swollen and unevenly distributed with an unclear structure after high-intensity eccentric exercise.The model rats suffered severest muscle damage at 12 hours and recovered completely at 72 hours after high-intensity eccentric exercise.(2) After one-time eccentric exercise,the expression of histone deacetylase 6 had a transient increase.The histone deacetylase 6 expression reached the peak at 6 hours,then gradually reduced and recovered at 72 hours after exercise.The microtubule-associated protein 1 light chain 3Ⅱ/Ⅰ expression was significantly increased at 3 hours after exercise,reached the peak at 12 hours,then reduced significantly and recovered at 72 hours after exercise.All these findings indicate that aggrephagy transiently happens and exerts important roles in the clearance of misfolded proteins,maintenance of cellular environmental homeostasis and recovery of skeletal muscle damage.