Int J Biol Sci 2017; 13(1):22-31. doi:10.7150/ijbs.16298 This issue Cite
1. Department of Pharmacology (State-Province Key Laboratories of Biomedicine-Pharmaceutics of China, Key Laboratory of Cardiovascular Research, Ministry of Education), College of Pharmacy, Harbin Medical University, Harbin, Heilongjiang 150081, P. R. China.
2. Department of Cardiology (Key Laboratory of Myocardial Ischemia, Ministry of Education), The 2nd Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150081, P. R. China
3. Northern Translational Medicine Research and Cooperation Center, Heilongjiang Academy of Medical Sciences, Harbin Medical University, Harbin, Heilongjiang 150081, P. R. China.
* These authors contributed equally to this work.
Background: MicroRNAs (miRNAs) have been emerged as important regulator in a multiple of cardiovascular disease, including arrhythmia, cardiac hypertrophy and fibrosis, and myocardial infarction. The aim of this study was to investigate whether miRNA let-7a has antihypertrophic effects in angiotensin II (AngII)-induced cardiac hypertrophy.
Methods: Neonatal rat ventricular myocytes (NRVMs) were exposed to AngII for 36 h as a cellular model of hypertrophy; subcutaneous injection of AngII for 2 weeks was used to establish a mouse model of cardiac hypertrophy in vivo study. Cell surface area (CSA) was measured by immunofluorescence cytochemistry; expression of hypertrophy-related genes ANP, BNP, β-MHC was detected by Real-time PCR; luciferase activity assay was performed to confirm the miRNA's binding site in the calmodulin (CaM) gene; CaM protein was detected by Western blot; the hypertrophy parameters were measured by echocardiographic assessment.
Results: The expression of let-7a was decreased in AngII-induced cardiac hypertrophy in vitro and in vivo. Overexpression of let-7a attenuated AngII-induced increase of cell surface area and repressed the increased mRNA levels of ANP, BNP and β-MHC. Dual-luciferase reporter assay showed that let-7a could bind to the 3'UTR of CaM 1 gene. Let-7a downregulated the expression of CaM protein. In vivo, let-7a produced inhibitory effects on cardiac hypertrophy, including the downregulation of cross-sectional area of cardiomyocytes in mouse heart, the reduction of IVSD and LVPWD, the suppression of hypertrophy marker genes ANP, BNP, β-MHC mRNA level, and the downregulation of CaM protein level.
Conclusions: let-7a possesses a prominent anti-hypertrophic property by targeting CaM genes. The findings provide new insight into molecular mechanism of cardiac hypertrophy.
Keywords: Cardiac hypertrophy, miRNA, let-7a, angiotensin Ⅱ, calmodulin.