Author + information
- Zhao Di and
- Zhao Zhuo
Growing evidence shows that protein kinase D (PKD) plays an important role in the cardiovascular diseases including cardiac hypertrophy, while the mechanisms are not clear.
This study tested our hypothesis that PKD might be involved in cardiac hypertrophy by negatively regulating autophagy using the technique of PKD knockdown by siRNA both in vivo and in vitro. Cardiac hypertrophy was induced in 8-week old C57BL/6 male mice by transverse aortic constriction (TAC) surgery. TAC mice were then divided into five groups receiving the treatments of vehicle (DMSO), control siRNA, an autophagy inducer rapamycin (1 mg/kg/day), PKD siRNA (0.6 mg/kg/day, intravenous injection), and PKD siRNA+3-methyladenine (3-MA, an autophagy inhibitor, 10 mg/kg/day), respectively.
Four weeks after TAC surgery, echocardiographic study, the gene expression for biomarkers of cardiac hypertrophy, hematoxylin and eosin (HE) staining, and Masson's staining showed mice with TAC had significantly hypertrophy and remodeling compared with sham animals. Four weeks of PKD-siRNA or rapamycin treatment significantly ameliorated the cardiac hypertrophy and dysfunction, while 3-MA inhibited the protective effects of PKD siRNA. Moreover, both PKD siRNA and rapamycin increased cardiac autophagic activity determined by electron micrographic study and the related AKT/mTOR/p70S6k signaling pathway measured with Western blot analysis.
These in vivo findings were consistent with the in vitro studies in cultured neonatal rat cardiomyocytes showing that PKD siRNA inhibited phenylephrine (PE)-induced hypertrophy associated with the increased intracellular autophagy and the related AKT/mTOR/p70S6k signaling pathway. In summary, both in vivo and in vitro studies have demonstrated that PKD is involved in the development of cardiac hypertrophy by inhibiting cardiac autophagy via AKT/mTOR pathway.