The Role Of Autophagy Regulator HMGB1 In Skeletal Muscle Autophagy After Exercise

Objective: High mobility group box protein B1(HMGB1)is an evolutionary ancient protein.It is an important non-histone chromosome binding protein in the body’s cells and participates in many important organisms.Scientific processes,including DNA repair,gene transcription,cellular inflammatory response,autophagy,etc.In this study,one-time high-load eccentric exercise was used as an intervention method to observe skeletal muscle autophagy at different phases after exercise,and to explore the effect and molecular mechanism of HMGB1 as an autophagy regulator on skeletal muscle autophagy after heavy load exercise.Methods: Forty-eight male 8-week-old SD rats were randomly divided into a control group(C)and an exercise group(E).Group E was subjected to a one-time high-load centrifugal exercise.The exercise components were divided into the post-exercise group(E0),the 12 h group(E12),the 24 h group(E24),the 48 h group(E48),and the 72 h group(E72),8 in each group.After the intervention,the soleus muscles of rats were detected at the corresponding time points.Observe the ultrastructural changes of skeletal muscle in each group with transmission electron microscope;use Western Blot method to detect the protein expression of HMGB1,Beclin1,and LC3 in skeletal muscle;use immunofluorescence double staining technique to detect the Co-localization.Results:(1)After the heavy-load eccentric exercise,abnormal changes in the ultrastructure of skeletal muscle occur,the sarcomere shortens,the M line is blurred or even disappeared,the Z band is distorted or even broken,and more autophagosomes appeared.(2)Within 72 hours after one-time heavy exercise,the expression of Beclin1,LC3II/LC3 I,and HMGB1 proteins in skeletal muscle increased and then decreased;24 hours after exercise,Beclin1 protein expression and LC3II/LC3 I in skeletal muscle It was significantly higher than the quiet control group(P<0.05,P<0.01),and the nuclear HMGB1 protein content was significantly higher in 24 h and 48 h after exercise than in the quiet control group(P<0.01,P<0.05).(3)The co-localization of Beclin1/Bcl-2 increased significantly after exercise,showing a trend of increasing first and then decreasing,and then returning to a quiet level 72 hours after exercise.The co-localization of Beclin1/HMGB1 peaks immediately after exercise,and it tends to rise first,then decrease,and then gradually return to a quiet state.Beclin1/Vps34 significantly increased co-localization after exercise,peaked at24 hours after exercise,tended to rise first and then decreased,and returned to a quiet level 72 hours after exercise.Conclusion:(1)HMGB1 may play an important role in rat skeletal muscle autophagy caused by one-time high-load eccentric exercise.(2)After one-time heavy exercise,HMGB1 may promote the separation of Beclin1 from Bcl-2 and promote Beclin1 binding to Vps34 to induce skeletal muscle autophagy.