Abstract 16798: MicroRNA 142-5p Targets Myocardial Hypertrophy and Cytokine Response

Abstract

Background: p300 is a dose-dependent and limiting regulator of cardiac hypertrophy. p300 regulates hypertrophy by controlling the expression of specific microRNAs. Objective: To dissect the role of miR142 during hypertrophic growth and to verify its targets. Methods and Results: In mice with myocardial overexpression (OE) of p300 (p300tg) and in acute myocardial ischemia, we observed altered expression of microRNAs miR142-5p and -3p (miR142). Induction of myocyte hypertrophy in vitro and in vivo were associated with downregulation of miR142. Induction of miR142 by serum was sensitive to inhibitors of ERK/MAPK and JNK signaling pathways, establishing an inverse relationship between hypertrophic signaling and miR142 levels. Adenovirus-mediated OE of p300 in NRVM caused a steep reduction in miR142, while siRNA-mediated KD of p300 significantly upregulated miR142. Thus, p300 is both necessary and sufficient for miR142 downregulation. MiR142 altered the expression of many sarcomeric proteins including Tni2, Tnt2, Myh3 and Mlc1. MiR142 directly inhibited the translation of ACTN4 through a conserved 3’UTR binding site. MiR142 potently repressed multiple components of the NF-κB, TNF-α and interleukin signaling pathways and abrogated the upregulation of iNOS mRNA and NO production in myocytes exposed to cytokines. We identified IL6st/gp130 as a direct target of miR142 through paired 3’UTR 142-5p and -3p binding sites, implicating miR142 in myocyte survival signalling. Lentiviral transduction of miR142 confirmed the same gene targets in myocardium in vivo, associated with development of systolic dysfunction and extensive apoptosis at 2 months. Finally, miR142 inhibited the expression of p300 both in vitro and in vivo, through a miR142-5p 3’UTR binding site. Altered immune response gene expression in p300tg mice was restored to near-wt levels by miR142 OE, indicating that p300 and miR142 are mutually inhibitory. Conclusion: MiR142 is a potent inhibitor of myocardial cytokine signaling through repression of IL6st/gp130 expression. Induction of hypertrophy involves the MAPK-activated, p300-mediated inhibition of miR142, which removes a block to sarcomeric protein expression, gp130-mediated survival signaling, and sustained expression of p300.