Objective To explore the effects of an aerobic exercise of different durations on the binding capacity of NF-E2-related factor 2(Nrf2)/Kelch-like ECH-associated protein-1(Keap1) in skeletal muscle of mice.Methods Thirty C57BL/6J mice were divided into a control(0h) group,an acute exercise for 3 hours (3h) group and an acute exercise for 6 hours(6h) group.The mice ran on treadmill at the speed of 15 m/min for different durations.The mice were sacrificed immediately after exercise and collected skeletal muscles of legs.The high quality fluorescence assay was done to detect the reactive oxygen species(ROS) level in the skeletal muscles of mice.The binding capacity of Nrf2/Keap1 was detected using co-immunoprecipitation.The expression of Nrf2 and Keap1 was analyzed using the Western blotting.Result Compared with group 0h,the Nrf2/Keap1 binding capacity in skeletal muscles of group 3h and 6h decreased significantly(P＜0.05),but the total Nrf2 in skeletal muscles increased significantly(P＜0.05).No significant differences were observed in the expression of total Keapl.The expression of Nrf2 protein of group 3h and 6h increased significantly compared with 0h,with that of group 6h significantly higher than group 3h(P＜0.05).The ROS level in skeletal muscles of group 6h increased significantly compared with group 0h(P＜0.05).Conclusion The effect of acute aerobic exercise on Nrf2/Keap1 binding capacity in skeletal muscle of mice depends on its duration.

BACKGROUND:Mitochondrial reactive oxygen bursts have been shown to play a key role in skeletal muscle ischemia-reperfusion injury.3-Nitro-N-methylsalicylamide(3-NNMS)can effectively reduce the electron transport rate and has a potential protective effect on limb ischemia-reperfusion injury,but there is no clear research and clinical application. OBJECTIVE:To investigate the protective effect of 3-NNMS on the skeletal muscle after limb ischemia-reperfusion injury in rats and its mechanism. METHODS:Forty healthy 8-week-old Sprague-Dawley rats were randomly divided into control group,0,25 and 125 μg/mL 3-NNMS groups,with 10 rats in each group.Animal models of limb ischemia-reperfusion injury were prepared in the latter three groups.3-NNMS was injected into the injury site 30 minutes before reperfusion.The animals were sacrificed 2 hours after reperfusion.Blood from the apical part of the heart,and the tissue of the rectus femoris muscle of the right lower limb were taken for testing.The pathological morphology of the rectus femoris muscle was detected by hematoxylin-eosin staining.Serum levels of creatine kinase found in the skeletal muscle(CK-MM),lactate dehydrogenase,and myeloperoxidase were detected using ELISA;the levels of nuclear factor κB,tumor necrosis factor α,interleukin 1β,cyclooxygenase 2,malondialdehyde,reactive oxygen species,superoxide dismutase,catalase and glutathione peroxidase in the rectus femoris muscle were measured;and adenosine triphosphate(ATP)level,ATPase activity,and mitochondrial respiratory control rate were tested. RESULTS AND CONCLUSION:Compared with the control group,the model rats with ischemia-reperfusion injury had increased serum levels of CK-MM,lactate dehydrogenase,and myeloperoxidase,increased levels of nuclear factor κB,tumor necrosis factor α,interleukin 1β,cyclooxygenase 2,malondialdehyde and reactive oxygen species in the rectus femoris muscle,decreased levels of catalase and glutathione peroxidase in the rectus femoris muscle,and reduced ATPase activity and mitochondrial respiratory control rate.Moreover,cell morphology was irregular,inflammatory cell infiltration was obvious,and the cells were swollen in rats after ischemia-reperfusion injury.Compared with the 0 μg/mL group,the serum CK-MM and lactate dehydrogenase levels decreased,the levels of nuclear factor κB and cyclooxygenase 2 in the rectus femoris muscle decreased,reactive oxygen species level decreased,and superoxide dismutase activity increased in the 25 μg/mL group;cell morphology was more regular,inflammatory cell infiltration was lighter,and cell swelling was alleviated.Compared with the 0 μg/mL group,the 125 μg/mL group had a reduction in the serum levels of CK-MM,lactate dehydrogenase,and myeloperoxidase and the levels of nuclear factor κB,tumor necrosis factor α,cyclooxygenase 2,malondialdehyde and reactive oxygen species in the rectus femoris muscle,as well as an increase in the levels of superoxide dismutase and glutathione peroxidase in the rectus femoris muscle,and mitochondrial respiratory control rate.Moreover,the cells were arranged neatly,the outline was clear and complete,and the inflammatory cell infiltration was light.To conclude,3-NNMS can alleviate the functional impairment of the skeletal muscle caused by limb ischemia-reperfusion,and its mechanism of action may be through improving mitochondrial function,reducing reactive oxygen species production,decreasing oxidative stress and inflammatory response,and thus reducing tissue damage and repairing skeletal muscle function.