The Role of Autophagy Regulator HMGB1 in Skeletal Muscle Autophagy After Eccentric Exercise

High mobility group box-1 protein (HMGB1) is an evolutionarily ancient protein, which, as an important non-histone chromosome-binding protein in organism cells, is involved in a variety of important biological processes, including DNA repair, gene transcription, cellular inflammatory response, and autophagy. In this study, we established an eccentric exercise model to observe the effect of HMGB1 on skeletal muscle autophagy and to investigate the underlying molecular mechanisms. Forty-eight male 8-week-old SD rats were randomly divided into control group (C) and exercise group (E). Group E was subjected to a bout of eccentric exercise on a treadmill and sampled soleus at 0 h, 12 h, 24 h, 48 h, and 72 h post-exercise. The speed of the exercise protocol in this study was 16 m/min, the slope was -16(degrees), and the time was 90 min. The ultrastructural changes of skeletal muscle were observed by transmission electron microscopy. The protein expressions of HMGB1, Beclin1, and LC3 were detected by Western Blot. The co-localizations of Beclin1/Bcl-2, Beclin1/HMGB1, and Beclin1/Vps34 were measured by immunofluorescence. The results show that eccentric exercise leads to abnormal changes in the ultrastructure of skeletal muscle, and the protein levels of Beclin1, LC3-II/LC3-I, and the content of HMGB1 in nuclear and cytoplasm were significantly increased at 24 h post-exercise (P < 0.05). The co-localization of Beclin1/Bcl-2 and Beclin1/HMGB1 were increased significantly at 0 h post-exercise and then decreased, while the co-localization of Beclin1/Vps34 showed the highest level at 24 h post-exercise. In conclusion, HMGB1 facilitates the separation of Beclin1 from Bcl-2 and promotes Beclin1 binding to Vps34, which may play an important role in eccentric exercise-induced skeletal muscle autophagy.