Everolimus-Incorporated Therapy Reduces Myocardial Hypertrophy in Recipients of Heart Transplantation

A new miRNA regulator, miR-672, reduces cardiac hypertrophy by inhibiting JUN expression

Cardiac hypertrophy is one of the initial symptoms of many heart diseases. We found that miR-672-5p may participate in the regulation of heart disease development in mouse, but the association between miR-672-5p and cardiac hypertrophy remains unclear. In the present study, we found that the abundance of miR-672-5p decreased in hypertrophic cardiomyocytes induced by phenylephrine, angiotensin II (Ang II) and insulin-like growth factor 1. Putative target genes of miR-672-5p were identified using four pipelines, miRWalk, miRanda, RNA22 and Targetscan, and a total of 834 genes were predicted by all four pipelines. Among these target genes, 98 were associated with the development of heart disease. PPI networks showed that the Jun proto-oncogene product (JUN), a subunit of the AP-1 transcription factor, had the highest node degree, and it was defined as the hub gene of the PPI networks. Luciferase assays showed that miR-672-5p bound to the 3' UTR of the JUN gene and decreased luciferase activity, indicating that JUN is a target of miR-672-5p. Finally, we found that increasing the abundance of miR-672-5p in cardiomyocytes controlled the relative cell area in Ang II-stimulated hypertrophic cardiomyocytes. Correspondingly, the abundance of JUN, a target of miR-672-5p, was decreased in hypertrophic cardiomyocytes on both mRNA and protein levels, implying that miR-672-5p had suppressive effects on cardiac hypertrophy through regulating the expression of Jun in cardiomyocytes.

Autophagy modulation: a potential therapeutic approach in cardiac hypertrophy

Autophagy is an evolutionarily conserved process used by the cell to degrade cytoplasmic contents for quality control, survival for temporal energy crisis, and catabolism and recycling. Rapidly increasing evidence has revealed an important pathogenic role of altered activity of the autophagosome-lysosome pathway (ALP) in cardiac hypertrophy and heart failure. Although an early study suggested that cardiac autophagy is increased and that this increase is maladaptive to the heart subject to pressure overload, more recent reports have overwhelmingly supported that myocardial ALP insufficiency results from chronic pressure overload and contributes to maladaptive cardiac remodeling and heart failure. This review examines multiple lines of preclinical evidence derived from recent studies regarding the role of autophagic dysfunction in pressure-overloaded hearts, attempts to reconcile the discrepancies, and proposes that resuming or improving ALP flux through coordinated enhancement of both the formation and the removal of autophagosomes would benefit the treatment of cardiac hypertrophy and heart failure resulting from chronic pressure overload.

microRNA-10a Targets T-box 5 to Inhibit the Development of Cardiac Hypertrophy

The mechanism of cardiac hypertrophy involving microRNAs (miRNAs) is attracting increasing attention. Our study aimed to investigate the role of miR-10a in cardiac hypertrophy development and the underlying regulatory mechanism.Transverse abdominal aortic constriction (TAAC) surgery was performed to establish a cardiac hypertrophy rat model, and angiotensin II (AngII) was used to induce cardiac hypertrophy in cultured neonatal rat cardiomyocytes. Expression of T-box 5 (TBX5) and miR-10a was altered by cell transfection of siRNA or miRNA mimic/inhibitor. Leucine incorporation assay, histological and cytological examination, quantitative real-time PCR (qRT-PCR), and Western blot were performed to detect the effects of miR-10a and TBX5 on cardiac hypertrophy. Dual-luciferase reporter assay was conducted to verify the regulation of TBX5 by miR-10a.miR-10a was down-regulated, and TBX5 was up-regulated in the rat model and AngII-stimulated cardiomyocytes. miR-10a inhibited TBX5 expression by directly targeting the binding site in Tbx5 3'UTR. Overexpression of miR-10a in AngII-treated cardiomyocytes decreased relative cell area, and significantly reduced the mRNA levels of natriuretic peptide A (Nppa), myosin heavy chain 7 cardiac muscle beta (Myh7), and leucine incorporation (P < 0.01 or P < 0.001). Knockdown of Tbx5 had similar effects on AngII-induced cardiomyocytes.Our findings indicate that miR-10a may inhibit cardiac hypertrophy via targeting Tbx5. Thus, miR-10a provides promising therapeutic strategies for the treatment of cardiac hypertrophy.