Circular RNAs (circRNAs) participate in regulating gene expression in diverse biological and pathological processes. The present study aimed to investigate the mechanism underlying the modulation of circRNA_000203 on expressions of fibrosis-associated genes in cardiac fibroblasts. CircRNA_000203 was shown upregulated in the diabetic mouse myocardium and in Ang-II-induced mouse cardiac fibroblasts. Enforced-expression of circRNA_000203 could increase expressions of Col1a2, Col3a1 and α-SMA in mouse cardiac fibroblasts. RNA pull-down and RT-qPCR assay indicated that circRNA_000203 could specifically sponge miR-26b-5p. Dual luciferase reporter assay revealed that miR-26b-5p interacted with 3′UTRs of Col1a2 and CTGF, and circ_000203 could block the interactions of miR-26b-5p and 3′UTRs of Col1a2 and CTGF. Transfection of miR-26b-5p could post-transcriptionaly inhibit expressions of Col1a2 and CTGF, accompanied with the suppressions of Col3a1 and α-SMA in cardiac fibroblasts. Additionally, over-expression of circRNA_000203 could eliminate the anti-fibrosis effect of miR-26b-5p in cardiac fibroblasts. Together, our results reveal that suppressing the function of miR-26b-5p contributes to the pro-fibrosis effect of circRNA_000203 in cardiac fibroblasts.

The molecular mechanisms underlying anthracyclines-induced cardiotoxicity have not been well elucidated. MiRNAs were revealed dysregulated in the myocardium and plasma of rats received Dox treatment. MicroRNA-34a-5p (miR-34a-5p) was verified increased in the myocardium and plasma of Dox-treated rats, but was reversed in rats received Dox plus DEX treatments. Human miR-34a-5p was also observed increased in the plasma of patients with diffuse large B-cell lymphoma after 9- and 16-week epirubicin therapy. Up-regulation of miR-34a-5p was observed in Dox-induced rat cardiomyocyte H9c2 cells. MiR-34a-5p could augment Bax expression, but inhibited Bcl-2 expression, along with the increases of the activated caspase-3 and mitochondrial potentials in H9C2 cells. MiR-34a-5p was verified to modulate Sirt1 expression post-transcriptionally. In parallel to Sirt1 siRNA, miR-34a-5p could enhance p66shc expression, accompanied by increases of Bax and the activated caspase-3 and a decrease of Bcl-2 in H9c2 cells. Moreover, enforced expression of Sirt1 alleviated Dox-induced apoptosis of H9c2 cells, with suppressing levels of p66shc, Bax, the activated caspase-3 and miR-34a-5p, and enhancing Bcl-2 expression. Therefore, miR-34a-5p enhances cardiomyocyte apoptosis by targeting Sirt1, activation of miR-34a-5p/Sirt1/p66shc pathway contributes to Dox-induced cardiotoxicity, and blockage of this pathway represents a potential cardioprotective effect against anthracyclines.

The role of microRNA-214-3p (miR-214-3p) in cardiac fibrosis was not well illustrated. The present study aimed to investigate the expression and potential target of miR-214-3p in angiotensin II (Ang-II)-induced cardiac fibrosis. MiR-214-3p was markedly decreased in the fibrotic myocardium of a mouse Ang-II infusion model, but was upregulated in Ang-II-treated mouse myofibroblasts. Cardiac fibrosis was shown attenuated in Ang-II-infused mice received tail vein injection of miR-214-3p agomir. Consistently, miR-214-3p inhibited the expression of Col1a1 and Col3a1 in mouse myofibroblasts in vitro. MiR-214-3p could bind the 3′-UTRs of enhancer of zeste homolog 1 (EZH1) and −2, and suppressed EZH1 and −2 expressions at the transcriptional level. Functionally, miR-214-3p mimic, in parallel to EZH1 siRNA and EZH2 siRNA, could enhance peroxisome proliferator-activated receptor-γ (PPAR-γ) expression and inhibited the expression of Col1a1 and Col3a1 in myofibroblasts. In addition, enforced expression of EZH1 and −2, and knockdown of PPAR-γ resulted in the increase of Col1a1 and Col3a1 in myofibroblasts. Moreover, the NF-κB signal pathway was verified to mediate Ang-II-induced miR-214-3p expression in myofibroblasts. Taken together, our results revealed that EZH1 and −2 were novel targets of miR-214-3p, and miR-214-3p might be one potential miRNA for the prevention of cardiac fibrosis.

The role of microRNA-214-3p (miR-214-3p) in cardiac hypertrophy was not well illustrated. The present study aimed to investigate the expression and potential target of miR-214-3p in angiotensin II (Ang-II)-induced mouse cardiac hypertrophy. In mice with either Ang-II infusion or transverse aortic constriction (TAC) model, miR-214-3p expression was markedly decreased in the hypertrophic myocardium. Down-regulation of miR-214-3p was observed in the myocardium of patients with cardiac hypertrophy. Expression of miR-214-3p was upregulated in Ang-II-induced hypertrophic neonatal mouse ventricular cardiomyocytes. Cardiac hypertrophy was attenuated in Ang-II-infused mice by tail vein injection of miR-214-3p. Moreover, miR-214-3p inhibited the expression of atrial natriuretic peptide (ANP) and β-myosin heavy chain (MHC) in Ang-II-treated mouse cardiomyocytes in vitro. Myocyte-specific enhancer factor 2C (MEF2C), which was increased in Ang-II-induced hypertrophic mouse myocardium and cardiomyocytes, was identified as a target gene of miR-214-3p. Functionally, miR-214-3p mimic, consistent with MEF2C siRNA, inhibited cell size increase and protein expression of ANP and β-MHC in Ang-II-treated mouse cardiomyocytes. The NF-κB signal pathway was verified to mediate Ang-II-induced miR-214-3p expression in cardiomyocytes. Taken together, our results revealed that MEF2C is a novel target of miR-214-3p, and attenuation of miR-214-3p expression may contribute to MEF2Cexpressionin cardiac hypertrophy.

No abstract

MicroRNA-199a-5p (miR-199a-5p) and -3p are enriched in the myocardium, but it is unknown whether miR-199a-5p and -3p are co-expressed in cardiac remodeling and what roles they have in cardiac hypertrophy and fibrosis. We show that miR-199a-5p and -3p are co-upregulated in the mouse and human myocardium with cardiac remodeling and in Ang-II-treated neonatal mouse ventricular cardiomyocytes (NMVCs) and cardiac fibroblasts (CFs). miR-199a-5p and -3p could aggravate cardiac hypertrophy and fibrosis in vivo and in vitro . PPAR gamma coactivator 1 alpha (Ppargc1a) and sirtuin 1 (Sirt1) were identified as target genes to mediate miR-199a-5p in promoting both cardiac hypertrophy and fibrosis. However, miR-199a-3p aggravated cardiac hypertrophy and fibrosis through targeting RB transcriptional corepressor 1 (Rb1) and Smad1, respectively. Serum response factor and nuclear factor κB p65 participated in the upregulation of miR-199a-5p and -3p in Ang-II-treated NMVCs and mouse CFs, and could be conversely elevated by miR-199a-5p and -3p. Together, Ppargc1a and Sirt1, Rb1 and Smad1 mediated the pathological effect of miR-199a-5p and -3p by promoting cardiac hypertrophy and fibrosis, respectively. This study suggests a possible new strategy for cardiac remodeling therapy by inhibiting miR-199a-5p and -3p.

The role of microRNA-92b-3p (miR-92b-3p) in cardiac hypertrophy was not well illustrated. The present study aimed to investigate the expression and potential target of miR-92b-3p in angiotensin II (Ang-II)-induced mouse cardiac hypertrophy. MiR-92b-3p was markedly decreased in the myocardium of Ang-II-infused mice and of patients with cardiac hypertrophy. However, miR-92b-3p expression was revealed increased in Ang-II-induced neonatal mouse cardiomyocytes. Cardiac hypertrophy was shown attenuated in Ang-II-infused mice received tail vein injection of miR-92b-3p mimic. Moreover, miR-92b-3p inhibited the expression of atrial natriuretic peptide (ANP), skeletal muscle α-actin (ACTA1) and β-myosin heavy chain (MHC) in Ang-II-induced mouse cardiomyocytes in vitro. Myocyte-specific enhancer factor 2D (MEF2D), which was increased in Ang-II-induced mouse hypertrophic myocardium and cardiomyocytes, was identified as a target gene of miR-92b-3p. Functionally, miR-92b-3p mimic, consistent with MEF2D siRNA, inhibited cell size increase and protein expression of ANP, ACTA1 and β-MHC in Ang-II-treated mouse cardiomyocytes. Taken together, we demonstrated that MEF2D is a novel target of miR-92b-3p, and attenuation of miR-92b-3p expression may contribute to the increase of MEF2D in cardiac hypertrophy.