The Effect Of Exercise Preconditioning On Acute Skeletal Muscle Inflammation And The Regulatory Effect Of GCN2 Pathway

Objective The intervention of sports injury,especially the acute phase of injury,is getting more and more attention in the field of sports medicine research.Exercise preconditioning may inhibit acute muscle injury.Studies have shown that GCN2 is involved in the regulation of inflammation,but its molecular mechanism is currently unclear.In this study,mice were pre-adapted to swimming for 8 weeks,and then a model of acute skeletal muscle inflammation was induced through lipopolysaccharide(LPS)to provide a theoretical basis for the prevention of acute injury of skeletal muscle.Methods 8-week-old male C57 BL / 6J mice were randomly divided into C57 control group(C57,n = 10),C57 injection LPS group(C57L,n = 10),C57 exercise group(C57 E,n = 10),and C57 injection of LPS Exercise group(C57 EL,n = 10).The mice in the exercise group performed swimming for 8 weeks,and the mice in the quiet group were routinely reared in an SPF barrier.Twenty-four hours after the mice completed their last exercise,mice in the LPS group were injected intraperitoneally with LPS(10 ug / g),and mice in the control group were injected with the same amount of normal saline,and samples were taken 6 hours later.The inflammatory cell infiltration in mice was detected by HE staining,and the expression of gastrocnemius related proteins in mice was detected by Western blot.Results(1)Effect of exercise preconditioning on the weight of C57 mice induced by LPS: After 8 weeks of aerobic exercise,compared with the quiet group,the mice in the C57 exercise group lost some weight but did not show significant statistical differences(P>0.05);Compared with the control group,LPS injection resulted in a significant reduction in body weight of the mice(P<0.05);compared with the C57 LPS group,the C57 LPS exercise group had a significant weight loss(P<0.05).(2)Effect of preconditioning on skeletal muscle morphology: HE staining observations revealed that the cytoplasm of skeletal muscle of C57 mice was stained pink,with regular cell morphology,tight arrangement,clear outline,and muscle cell nuclei stained blue-violet.Multiple nuclei were located on the edge of muscle cells,with good muscle membrane integrity and no inflammatory cell infiltration.C57 L group muscle cross section showed that muscle cell morphology blurred and swelled with a large number of multinuclear inflammatory cells infiltration.Compared with the C57 L group,the C57 EL group had better integrity of skeletal muscle cells,with slight swelling,hypertrophy,and less inflammatory cell infiltration.(3)Effects of exercise preconditioning on gastrocnemius inflammatory factors in C57mice: In the quiet group,the NF-κB phosphorylation level and IL-6 protein level in the LPS administration group were significantly higher than those in the normal saline group(P<0.05),IL-10 protein level decreased and the difference was significant(P<0.05),and there was no significant difference in IL-12 protein expression(P>0.05);compared with the quiet group,NF-κB phosphorylation level and IL-6 protein level reduced significantly(P<0.05),and IL-10 and IL-12 protein expressions increased significantly(P<0.05).Compared with LPS group,The levels of NF-κB phosphorylation and IL-6 protein decreased significantly(P<0.05),and the expression of IL-10 and IL-12 proteins increased significantly(P<0.05).(4)Effect of exercise preconditioning on the expression level of GCN2 signaling pathway in gastrocnemius muscle of C57 mice: In the quiet group,there was no significant statistical difference in GCN2 protein expression between the LPS administration group and the normal saline group(P>0.05),but an upward trend showed;e IF2α phosphorylation level and ATF4 protein expression level increased significantly(P<0.05);compared with the quiet group,GCN2,e IF2α phosphorylation and ATF4 protein levels in the gastrocnemius muscle of mice after 8-week exercise preconditioning decreased but not significantly(P>0.05);compared with the LPS group,the levels of phosphorylation of GCN2 and e IF2α decreased significantly in the LPS exercise group(P<0.05),and the expression of ATF4 protein decreased but the difference was not significant(P>0.05).Conclusion(1)Intraperitoneal injection of LPS can cause skeletal muscle inflammation,which is manifested by weight loss in mice and infiltration of skeletal muscle inflammatory cells.The inflammatory response may be related to the NF-κB inflammation pathway and the downstream proinflammatory factor IL-6;(2)8-week exercise preconditioning can reduce the degree of weight loss in mice,reduce the degree of skeletal muscle inflammatory cell infiltration,inhibit the NF-κB inflammation pathway to reduce acute inflammation,and activate anti-inflammatory factors to play a role;(3)GCN2 may be activated by LPS to participate in acute inflammation of skeletal muscle.Preconditioning for 8 weeks may inhibit the expression of GCN2 protein in mouse skeletal muscle induced by LPS,and then inhibit the e IF2α / ATF4 pathway.Exercise preconditioning may affect LPS-induced acute skeletal muscle inflammation through the GCN2 pathway.