Mitogen-activated protein kinases (MAPKs) (ERK1/2, JNK, and p38) are upregulated in diabetic cardiomyopathy (DCM). Dual-specific phosphatase-1 (DUSP-1) has been reported to regulate the activity of MAPKs in cardiac hypertrophy; however, the role of DUSP-1 in regulating MAPKs activity in DCM is not known. MicroRNAs have been reported to regulate the expression of several genes in hypertrophied failing hearts. However, little is known about the microRNAs regulating DUSP-1 expression in diabetes-related cardiac hypertrophy. In the present study, we investigated the role of DUSP-1 and miR-200c in diabetes-induced cardiac hypertrophy. DCM was induced in Wistar rats by low-dose Streptozotocin high-fat diet for 12 weeks. Cardiac expression of ERK, p-38, JNK, DUSP-1, miR-200c, and hypertrophy markers (ANP and β-MHC) was studied in DCM in control rats and in high-glucose (HG)-treated rat neonatal cardiomyocytes. miR-200c inhibition was performed to validate DUSP-1 as target. A significant increase in phosphorylated ERK, p38, and JNK was observed in DCM model and in HG-treated cardiomyocytes (p < 0.05). Expression of DUSP-1 was significantly decreased in diabetes group and in HG-treated cardiomyocytes (p < 0.05). Increased expression of miR-200c was observed in DCM model and in HG-treated cardiomyocytes (p < 0.05). Inhibition of miR-200c induces the expression of the DUSP-1 causing decreased expression of phosphorylated ERK, p38, and JNK and attenuated cardiomyocyte hypertrophy in HG-treated cardiomyocytes. miR-200c plays a role in diabetes-associated cardiac hypertrophy by modulating expression of DUSP-1.
Methylation-mediated silencing of the DUSP-1 promoter does not appear to be associated with reduced expression, indicating the involvement of other factors in specific suppression of DUSP-1 in diabetes-associated cardiac hypertrophy.
Myocardin (MYOCD), a cardiac specific transcriptional co-activator is up-regulated in heart failure (HF). Up-regulation of MYOCD expression has been proposed to be an important adaptive response in cardiac remodelling. However, molecular mechanisms contributing to increased cardiac MYOCD expression in HF are not known. The goal of this study was to identify microRNA(s) regulating cardiac MYOCD expression and to study the effect of cardiac modulation of MYOCD specific miRNA in an animal model of HF. miRNA(s) targeting MYOCD were identified using
in silico
approach and validated by 3’-UTR luciferase reporter assay. Cardiac expression of miRNA was measured in endomyocardial biopsies from idiopathic DCM (IDCM) patients, renal artery ligation rat model of HF (RAL) and in Ang II treated cardiomyocytes by real-time PCR. miRNA-33a, miRNA-33b, miRNA-139 and miRNA-542 were identified with MYOCD as putative target. Cardiac expression of miRNA-33a and miRNA-33b was significantly decreased, whereas expression of miRNA-139 and miRNA-542 was not altered in IDCM. miRNA-33a expression was also decreased in RAL and in Ang II treated cardiomyocytes. Luciferase assay confirmed MYOCD as target gene for miRNA-33a. miRNA-33a overexpression significantly decreased expression of MYOCD, ANP and fibrotic genes in Ang II treated cardiomyocytes. Cardiac specific delivery of miRNA-33a, using a homing peptide conjugated siRNA, attenuated cardiac hypertrophy and fibrosis, decreased expression of ANP, β-MHC and fibrotic genes and ameliorated the impaired diastolic dysfunction in RAL. Our results provide the first evidence that miRNA-33a regulates MYOCD expression and cardiac specific augmentation of miRNA-33a attenuated cardiac remodelling and partially restored left ventricular function. Our results suggest miR-33a as a potential therapeutic target in reversal of cardiac remodelling and improvement in heart function in HF.
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