In Vivo Cardiac‐specific Adenylyl Cyclase 4 gene delivery protects against Klotho deficiency‐induced heart failure

Abstract

Background and Objective Heart failure is the leading cause of death in the world. Adenylyl cyclase, that catalyzes the formation of cAMP from ATP, regulates many aspects of cardiac physiology and pathology. Klotho deficiency causes heart failure in Kotho-hypomorphic mutant (KL (-/-)) mice. The objective of this study was to investigate whether in vivo cardiac-specific adenylyl cyclase type 4 (AC4) gene expression protects against Klotho deficiency- induced heart failure. Methods and Results We found that Klotho deficiency-induced heart failure was accompanied by AC4 reduction. Next, we constructed a rAAV vector in which the truncated αMHC promoter drives the expression of AC4 (AAV2/9-αMHC-AC4). The AAV viral particles were then administered intravenously via the tail vein and the mice were sacrificed at 7 weeks after gene delivery. Interestingly, cardiac-specific AC4 gene delivery increased left ventricular fractional shortening, ejection fraction, stroke volume, and left ventricular end-diastolic volume, suggesting that cardiac-specific AC4 gene delivery protected against Klotho deficiency-induced heart dysfunction. Meanwhile, cardiac-specific AC4 gene delivery also decreased heart weight to body weight ratio and cardiomyocyte cross-section area, suggesting that cardiac-specific AC4 gene expression protected against Klotho deficiency-induced cardiac hypertrophy. Cardiac-specific AC4 gene delivery also alleviated Klotho deficiency-induced cardiac fibrosis and calcification. Furthermore, cardiac-specific AC4 gene delivery attenuated cardiomyocyte apoptotic cell death and mitochondrial dysfunction. Mechanistically, AAV2/9-αMHC-AC4 increased cardiomyocytic cAMP levels and so regulated PKA-PLN-SERCA2 signal pathway, which are critical in modulating calcium flux, mitochondrial function. Conclusion Cardiac-specific AC4 gene delivery protected against Klotho deficiency-induced heart failure through increasing cardiomyocytic cAMP levels, which alleviated PKA-dependent mitochondrial dysfunction and apoptotic cell death. AC4 could be a potential therapeutic target for heart failure associated with Klotho deficiency in aging or chronic kidney disease.