Heart Failure Treatment By Reestablishing Ventricular Kv4.3-CaMKⅡ Unite

Objective To investigate the role of Kv4.3-CaMKII unit in the disturbance of calcium homeostasis and cardiac dysfunction during heart failure in order to explore a new and effective method for heart failure treatment.Methods In HEK293 cells transfected with Kv4.3 and CaMKII,cardiomyocytes and heart tissue,immunoprecipitation and FRET were performed to confirm the formation of Kv4.3-CaMKII units.6-8 weeks C57BL6 mice were used to perform severe thoracic aortic ligation for establishing heart failure model induced by pressure overload.AAV-Kv4.3(HF + Kv4.3),AAV-Kv4.2(HF + Kv4.2)and AAV-GFP(HF)were injected into the jugular vein at one week after heart failure surgery.After four weeks of virus expressing,echocardiography was conducted to evaluate systolic and diastolic cardiac functions.The primary cardiomyocytes were isolated for recording Ito currents.Calcium transients and the sarcromere length were measured to evaluate systolic and diastolic function of single cardiomyocyte and the calcium transportion.The expression levels of calcium regulating proteins were measured by Western Blot,including CaMKⅡ,p-CaMKⅡ,PLB,p-PLB(Thr17),p-PLB(Ser16)and SERCA2a.Cardiac fibrosis was evaluated by PSR staining.Results Stable Kv4.3-CaMKII units existed in HEK293 cells,mouse left ventricular cardiomyocytes and heart tissue.Four weeks after virus injection,Kv4.3,Kv4.2 and GFP were stably expressed in mouse heart.Compared with HF+Kv4.2 and HF groups,cardiac functions of HF+Kv4.3 group were significantly improved as evidenced by the higher EF value,lower E/A and E/Em ratios.The heart weight/body weight and lung weight/body weight ratios of HF+Kv4.3 mice were significantly lower than those of the other two groups.There was no significant difference in Ito current between HF+Kv4.3 group and HF+Kv4.2 groups.The systolic and diastolic functions of single cardiomyocyte in HF+Kv4.3 group were better than those in the other two groups.Western Blot showed that CaMKII expression level in HF+Kv4.3 mice was similar to that in HF+Kv4.2 and HF groups,but the expression levels of p-CaMKII and p-PLB(Thr17)were significantly decreased,and p-PLB(Ser16)level was significantly increased and SERCA2a had no difference among three groups.The above results suggest that Kv4.3 binds to CaMKII and inhibits its activity,reducing the excessive phosphorylation of calcium regulating proteins and ultimately improving the systolic and diastolic functions of heart failure mice.Compared with HF+Kv4.2 and HF groups,the interstitial fibrosis of HF+Kv4.3 group was significantly attenuated.Conclusion Reestablishing Kv4.3-CaMKII unit in heart failure mice can significantly improve cardiac functions,which is expected to provide new insights for the treatment of heart failure.