Role Of CaMKⅡδ In The Regulation Of Cardiomyocyte Apoptosis In Hypertension Induced By Aerobic Exercise

Purposes:Hypertension is the main risk factor of cardiovascular disease.Longterm hypertension can lead to hypertensive heart disease,promote cardiomyocyte apoptosis and aggravate the development of heart failure.Calcium/calmodulindependent protein kinase Ⅱδ(CaMKⅡδ)plays an important role in cardiomyocyte apoptosis and mediates apoptosis.In the present study,the role of ox-CaMKⅡδ in the regulation of cardiomyocyte apoptosis in hypertension induced by aerobic exercise was studied.Method:Twelve-week-old male spontaneously hypertensive rats(SHR)and Wistar-Kyoto male rats(WKY)were selected and randomly divided into normal control group(WKY-SED),normal aerobic exercise group(WKY-EX),hypertensive control group(SHR-SED)and hypertensive aerobic exercise group(SHR-EX).After 12 weeks of treadmill exercise(slope 0°,20m/min,60min/d,5d/w),the blood pressure of the tail artery of each group was measured.The Millar pressure-volume system was used to measure the heart function of the rats in vivo.HE staining was used to observe the morphology of cardiomyocytes.Analysis of myocardial collagen volume fraction(CVF%)was measured by Masson staining.Detection of caspase 3 activity and TUNEL staining were used to observe the apoptosis of cardiac myocytes.Western Blot measures the protein expression of CaMKⅡδ,ox-CaMKⅡδ,IκBα,NF-κB P65,HSP70,Bax and Bcl-2 in rat myocardial tissue.Results:1.Basic indicators:The systolic blood pressure in the WKY-EX group was significantly lower than that in the WKY-SED group(P<0.05).The heart rate and blood pressure of the SHR-SED group were significantly higher than those of the WKY-SED group(P<0.05).The heart rate,systolic blood pressure and diastolic blood pressure of the SHR-EX group were significantly lower than those of the SHE-SED group(P<0.05).2.Heart function:Compared with the WKY-SED group,the maximum rising rate of left ventricular pressure(+dp/dtmax)and the absolute value of the maximum decreasing rate of ventricular pressure(-dp/dtmax)were significantly increased(P<0.05).Compared with the WKY-SED group,+dp/dtmax and the absolute values of-dp/dtmax decreased significantly in SHR-SED group(P<0.01).After 12 weeks of aerobic exercise,+dp/dtmax and the absolute values of-dp/dtmax in the SHREX group increased significantly(P<0.05).Compared with WKY-SED group,ventricular end-systolic pressure(ESP),end-diastolic pressure(EDP)and isovolumic relaxation constant(Tau)increased significantly in SHR-SED group(P<0.01).After 12 weeks of aerobic exercise,ESP,EDP and effective arterial elasticity(Ea)decreased significantly(P<0.01)in SHR-EX group.Compared with WKY-SED group,slope Ees of end-systolic pressure-volume relationship curve(ESPVR),stroke volume(SV)and ejection fraction(EF)in WKY-EX group increased significantly(P<0.05),while SV,EF and Ees decreased significantly in SHR-SED group(P<0.01).After 12 weeks of aerobic exercise,EF and Ees in SHR-EX group increased significantly(P<0.05),and SV increased significantly(P<0.01),and Tau decreased significantly(P<0.05).3.Heart morphology:Myocardial cells in the WKY-SED group were arranged neatly.Cardiomyocytes in WKY-EX group were arranged densely.Compared with the WKYSED group,the cardiomyocytes in the SHR-SED group were sparsely arranged,and the myocardial fibers were bifurcated and broken.Compared with SHR-SED group,the arrangement of myocardial cells in SHR-EX group was orderly and dense.Compared with the WKY-SED group,the collagen fibers in the SHR-SED group were excessively proliferated and the CVF%increased significantly(P<0.01);compared with the SHR-SED group,the myocardial tissue fibrosis in the SHR-EX group was reduced,and the CVF%decreased significantly(P<0.01).4.Cardiomyocyte apoptosis:Compared with the WKY-SED group,the myocardial caspase 3 of rats in the WKYEX group was significantly decreased(P<0.05),and the myocardial caspase 3 of the rats in the SHR-SED group was significantly increased(P<0.05),and the number of TUNEL-positive particles was significantly increased in the SHR-SED group(P<0.01).Compared with the SHR-SED group,the number of myocardial caspase 3 in the SHREX group was significantly reduced(P<0.05),and the number of TUNEL-positive particles was significantly reduced(P<0.01).5.Western Blot:Compared with WKYSED group,there was no significant difference in ox-CaMKⅡδ protein in WKY-EX group,but the expression of HSP70 and IκBα protein were significantly increased(P<0.01)and the expression of NF-κB P65 and Bax protein were significantly decreased(P<0.05).The expression of Bcl-2 protein was significantly increased(P<0.05),and the ratio of Bax/Bcl-2 was significantly decreased(P<0.05).Compared with WKY-SED group,the expression of ox-CaMKⅡδ protein in SHR-SED group was significantly increased(P<0.01).The expression of IκBα and Bcl-2 protein decreased significantly(P<0.01).The expression of HSP70 protein decreased significantly(P<0.05).The expression of NF-κB P65 and Bax protein increased significantly(P<0.05).The ratio of Bax/Bcl-2 increased significantly(P<0.01).The expression of ox-CaMKⅡδ protein in SHR-EX group was significantly lower than that in SHR-SED group(P<0.05).The expression of IκBα and Bcl-2 protein were significantly increased(P<0.05).The expression of HSP70 protein were significantly increased(P<0.01).The expression of NF-κB P65 and Bax protein were significantly decreased(P<0.05).The ratio of Bax/Bcl-2 was significantly decreased(P<0.01).Conclusion:Aerobic exercise inhibits cardiomyocyte apoptosis by downregulating SHR myocardium ox-CaMKⅡδ,while activating anti-apoptosis-related signal pathways to improve cardiac function,which may be one of the mechanisms of exercise-induced heart remodeling in hypertension.