Heavy Load Exercise Causes Mitochondrial Dysfunction and Increases Mitophagy: 865 Board #126 May 30 2 00 PM - 3 30 PM

PURPOSE: To observe the effect of heavy load exercise on mitochondrial structure and function in skeletal muscle of rats and analyze the change of mitophagy protein of PINK1 and Parkin and related proteins, and to explore the role of PINK1/Parkin pathway in exercise-induced mitochondrial damage in skeletal muscle. METHODS: Male Sprague-Dawley rats were divided into quiet control group (C group, n=8) and exercise group (E group, n=40). Rats in the E group performed a running on a treadmill down a 16°incline at 16m/min for 90 min, and those were further divided into 0h,12h,24h,48h and 72h sub-groups (n=8), and at each time point the soleus muscle was collected under anesthesia. Mitochondrial ultrastructural changes in skeletal muscle were observed by a transmission electron microscope. The content of quatitative enzyme citrate synthase (CS) and the activities of mitochondrial respiratory chain Complex II and IV were measured by ELISA. Protein expression of skeletal muscle cytochrome c oxidease subunit I (COX I),PTEN-induced putative kinase 1 (PINK1) and mitochondrial Parkin,microtubule-associated protein 1 light chain 3 (LC3) were determined by western blot. Mitochondrial co-localization with Parkin,ubiquitin (Ub),p62/Sequestosome 1 (p62) and LC3 was measured by the immunofluorescence double labeling technique. One-way ANOVA was used to evaluate statistical significance. RESULTS: After heavy load exercise, the mitochondrial structure appeared to be abnormal and formed a lot of mitophagosomes; the CS content and Complex II activity significantly decreased, whereas the Complex IV activity and COX I protein level remained unchanged; the expression of PINK1 (E12=2.552±0.141),Parkin (E24=2.535±0.100),Ub (E24=2.501±0.191) ,p62(E12=2.662±0.240) ,LC3 (E12=2.757±0.180) significantly increased (C=1.000, P<0.05 or P<0.01). CONCLUSION: A heavy load exercise may activate the PINK1/Parkin pathway and promote the combination of Ub,p62,LC3 and mitochondria, and result in mitophagy and mitochondrial damage within skeletal muscle. Supported by Natural Science Foundation of China (31471133).