The Investigation Of The Protective Effect Of Exercise Preconditioning On Keap1-Nrf2-ARE Signal Transduction Pathway In Exhausted Rats

ObjectiveIn order to research the exercise preconditioning(EP)on cardiac function parameters such as myocardial injury and cardiac systolic function,we investigate the exhausted rats.The effect of EP on the expression of the correlation factor to transcription factors E2(Nrf2)and Kelch-like epichlorohydrin-related protein-1(Keap1)in myocardium of exhausted rats was discussed.The intervention effects of antioxidant enzymes such as downstream catalase(CAT),glutathione(GSH),and superoxide dismutase(SOD)were also considered.Methods1.The 60 male SD rats were randomly divided into 4 groups(n=15):The control group(C),the exhaustion(EE)group,the short-term exercise preconditioning(SE)group and the long-term exercise preconditioning(LE)group.Group C did not exercise.The EE group swam to exhaustion at one time(reference to the Thomas standard).The SE group(referred to the Lennon method)performed intermittent swimming every day,swimming for 15 minutes,resting for 5 minutes,repeating for 3 times and for 3 days.The LE group(referred to the Margonato method)underwent intermittent swimming every day for 3 weeks,and the exercise was similar to the short-term adaptation group.After the end of the last exercise preconditioning,the swimming preconditioning group took the next day swimming to exhaustion.The C group was in a quiet state,while the exhaustive group drawn immediately after exhaustive force.2.HBFP staining was applied to observe the changes of myocardial ischemia and hypoxia.3.The serum levels of NT-proBNP,cTnI,ROS,GSH,SOD and CAT in rats were detected by enzyme immunoassay.4.The Millar pressure volume catheter was used to examine the parameters of cardiac function:Heart rate,left ventricular end systolic pressure,left ventricular end-diastolic pressure,left ventricular end-systolic volume,left ventricular end-diastolic volume,heart rate,ejection fraction,relation curve slope of left ventricular end systolic volume,Tau value,relation curve slope of left ventricular end diastolic pressure volume.5.Western blot was used to detect the expression levels of Nrf2 and Keap1 proteins in the myocardium.Results1.HBFP staining of myocardial tissue in rats showed that:The ventricular structure of group C rats was approximately normal.Myocardial fiber structure was relatively clear and was evenly stained.Each cell was arranged in regular order and the nucleus was ovoid.It was located in the center of the cell without obvious deviation.In group EE,the central muscle fibers showed various forms.The staining was uneven and the cell arrangement was irregular.The myocardial structure of group SE and group LE was more regular than that of group EE.Group EE showed large red staining,and red staining area of SE group decreased significantly,while red staining area of LE group was the smallest.2.Contents of cTnI and NT-proBNP in rats: The levels of cTnI and NT-proBNP in EE group,SE group and LE group were significantly higher than those in control group,which was statistically significant(P<0.05).Compared with the EE group,the serum cTnI and NT-proBNP levels of group SE and group LE were significantly lower than that of group EE(P<0.05).There was no statistical difference between the SE group and the LE group(P>0.05).3.Cardiac function parameters of rats: Compared with the C group,the HR,Pes,EF and ESPVR in the EE group decreased significantly,but the values of Ped,Ves,Ved,SV and Tau increased with statistical significance(P<0.05).The EDPVR phase was not statistically significant(P>0.05).Compared with group SE,group HR,Pes,EF increased significantly,Ped,SV and Tau values decreased compared with group EE with statistical difference(P<0.05).ESPVR,EDPVR,Ves and Ved were not statistically different(P>0.05)(EE).Compared with group LE,group HR and Pes increased,while Ped and Tau decreased.There was statistical significance(P<0.05).There were no significant differences in ESPVR,EDPVR,Ves,Ved,SV and EF(P>0.05)between the two groups(EE).4.Contents of ROS,GSH,SOD and CAT in rats: Compared with the C group,the content of ROS in EE group,SE group and LE group increased significantly(P<0.05).There was no statistically significant difference in ROS content between the SE group and the LE group(P>0.05).The contents of CAT,GSH and SOD in group EE,group SE and group LE were lower than those in group C(P<0.05),which were statistically significant.Compared with the EE group,the contents of CAT,GSH and SOD in the LE group were relatively higher(P<0.05).There was no significant difference between the SE group and the EE group(P>0.05).5.Expression of Nrf2 and Keap1 proteins in myocardium of rats: Compared with the C group,the expression of Nrf2 protein in EE group,SE group and LE group increased.There was statistical significance(P<0.05).Compared with the EE group,the expression of Nrf2 protein in the SE group and the LE group increased significantly with statistical significance(P<0.05).Compared with group SE and group LE,the expression of Nrf2 protein in LE group increased.Compared with the C group,the expression of Keap1 protein in the EE group,SE group and LE group decreased and there was statistical significance(P<0.05).Compared with the EE group,the expression of Keap1 protein in SE group and LE group decreased,which was statistically significant.There was no statistical difference in the expression of Keap1 protein between the SE group and the LE group(P>0.05).Conclusion1.Exhaustion of high intensity exercise can cause oxidative level rises,large amounts of oxygen free radicals,resulting in myocardial cell injury.2.Exercise preconditioning could regulate Nrf2/keap1 downstream by stimulating myocardial Nrf2/Keap-1,GSH,SOD,HO-1 expression,thereby enhancing myocardial antioxidant capacity.3.Short exercise preconditioning and long-term exercise preconditioning improves myocardial antioxidant to protect the myocardium,and exercise preconditioning was more obvious for a long time.