NF-κB mediated miR-26a regulation in cardiac fibrosis

Micro-RNAs (miRNAs) are a class of small non-coding RNAs, recently emerged as a post-transcriptional regulator having a key role in various cardiac pathologies. Among them, cardiac fibrosis that occurs as a result from an imbalance of extracellular matrix proteins turnover and is a highly debilitating process that eventually lead to organ dysfunction. An emerging theme on is that miRNAs participate in feedback loop with transcription factors that regulate their transcription. NF-B, a key transcription factor regulator controls a series of gene program in various cardiac diseases through positive and negative feedback mechanism. But, NF-B mediated miRNA regulation in cardiac fibrosis remains obscure. Bioinformatics analysis revealed that miR-26a has targets collagen I and CTGF and possesses putative NF-B binding element in its promoter region. Here, we show that inhibition of NF-B in cardiac fibroblast restores miR-26a expression, attenuating collagen I, and CTGF gene expression in the presence of Ang II, conferring a feedback regulatory mechanism in cardiac fibrosis. The target genes for miR-26a were confirmed using 3-UTR luciferase reporter assays for collagen I and CTGF genes. Using NF-B reporter assays, we determine that miR-26a overexpression inhibits NF-B activity. Finally, we show that miR-26a expression is restored along with the attenuation of collagen I and CTGF genes in cardiac specific IkBa triple mutant transgenic mice (preventing NF-B activation) subjected to 4 weeks transverse aortic banding (TAC), compared to wild type (WT) mice. The data indicate a potential role of miR-26a in cardiac fibrosis and, offer novel therapeutic intervention. J. Cell. Physiol. 228: 14331442, 2013. (c) 2012 Wiley Periodicals, Inc.