MiR-146a targets Fos expression in human cardiac cells.

Xavier Palomer,Cristina Rodríguez,Francisco Vidal,Tung O Chan,Arthur M Feldman,Gaia Botteri,Mercy M Davidson,Emma Barroso,Manuel Vázquez-Carrera,Eva Capdevila-Busquets,José Martínez-González

doi:10.1242/dmm.020768

Abstract

ABSTRACTmiR-146a is a microRNA whose transcript levels are induced in the heart upon activation of NF-κB, a transcription factor induced by pro-inflammatory molecules (such as TNF-α) that is strongly related to the pathogenesis of cardiac disorders. The main goal of this study consisted of studying new roles of miR-146a in cardiac pathological processes caused by the pro-inflammatory cytokine TNF-α. Our results demonstrate that miR-146a transcript levels were sharply increased in cardiac ventricular tissue of transgenic mice with specific overexpression of TNF-α in the heart, and also in a cardiomyocyte cell line of human origin (AC16) exposed to TNF-α. Among all the in silico predicted miR-146a target genes, Fos mRNA and protein levels notably decreased after TNF-α treatment or miR-146a overexpression. These changes correlated with a diminution in the DNA-binding activity of AP-1, the Fos-containing transcription factor complex. Interestingly, AP-1 inhibition was accompanied by a reduction in matrix metalloproteinase (MMP)-9 mRNA levels in human cardiac cells. The specific regulation of this MMP by miR-146a was further confirmed at the secretion and enzymatic activity levels, as well as after anti-miR-mediated miR-146a inhibition. The results reported here demonstrate that Fos is a direct target of miR-146a activity and that downregulation of the Fos–AP-1 pathway by miR-146a has the capacity to inhibit MMP-9 activity. Given that MMP-9 is an AP-1 target gene involved in cardiac remodeling, myocardial dysfunction and progression of heart failure, these findings suggest that miR-146a might be a new and promising therapeutic tool for treating cardiac disorders associated with enhanced inflammation in the heart.

Highlights

They find a huge increase in miR-146a levels in the heart of transgenic mice with cardiac-specific overexpression of tumor necrosis factor-α (TNF-α) and in human cardiac AC16 cells exposed to TNF-α
The authors demonstrate that Fos is a direct target of miR-146a activity: overexpression of the latter results in a notable decrease in both Fos mRNA and protein levels, which correlated with a diminution in the DNA-binding activity of activator protein-1 (AP-1), the Foscontaining transcription factor complex
The results reported here demonstrate that Fos is a direct target of miR-146a activity and that downregulation of the Fos–AP-1 pathway by miR-146a has the capacity to inhibit matrix metalloproteinase (MMP)-9 activity

Summary

Introduction

Received March 2015; Accepted June 2015 chemokines such as interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-α (TNF-α) (Palomer et al, 2013a,b) These pro-inflammatory mediators, which are transcriptionally regulated by the ubiquitous and inducible nuclear factor-κB (NF-κB), exert their pleiotropic autocrine effects via downstream activation of activator protein-1 (AP-1) and NF-κB itself, thereby contributing to myocardial inflammation, dilated cardiomyopathy, cardiac hypertrophy and heart failure (Gupta et al, 2008; Palomer et al, 2013a,b). Myocardial injury caused by these pathologies leads to myocyte function failure, fibrosis and ensuing ventricular remodeling, which can eventually trigger heart failure In this regard, TNF-α production is enhanced in the heart of spontaneously hypertensive rats and in the failing human heart; this contributes to cardiac remodeling and malfunction, thereby speeding up heart failure progression (Bergman et al, 1999). It is not surprising that pharmacological inhibition of TNF-α activity improves myocardial function during heart failure (Isic et al, 2008)

Objectives

Methods

Results

Discussion

Conclusion