MeCP2 regulation of cardiac fibroblast proliferation and fibrosis by down-regulation of DUSP5

Highlights

• MeCP2 modifications impact on the development of cardiac fibrosis.

• DUSP5 is decreased in neonatal rat cardiac fibroblasts proliferation.

• MeCP2 inhibits DUSP5 expression in neonatal rat cardiac fibroblasts activation.

• MeCP2 and DUSP5 may serve as possible therapeutic targets for cardiac fibrosis.

Abstract

Cardiac fibrosis is a complex pathological process that includes the abnormal proliferation of cardiac fibroblasts and deposition of the extracellular matrix (ECM) proteins and collagens. Methyl-CpG-binding protein 2 (MeCP2) is a multifunctional nuclear protein, and plays a key role in the fibrotic diseases. However, the potential role of MeCP2 in cardiac fibrosis remains unclear. We report that MeCP2 modulates cardiac fibrosis via down-regulation of dual-specificity phosphatase 5 (DUSP5), a nuclear phosphatase that negatively regulates prohypertrophic signaling by ERK1/2. MeCP2 is a critical participant in the epigenetic silencing of regulatory genes. Here, we found that down-regulation of DUSP5 in cardiac fibrosis is associated with MeCP2 over-expression. Treatment of cardiac fibroblasts with MeCP2-siRNA blocked proliferation. Knockdown of MeCP2 elevated DUSP5 expression in activated cardiac fibroblasts. Moreover, we investigated the effect of DUSP5 on the ERK1/2 activation. Our results demonstrated that MeCP2 modulates DUSP5 mediated activation of ERK1/2 in cardiac fibrosis. Taken together, these results indicated that MeCP2 acts as a key regulator of pathological cardiac fibrosis, promotes cardiac fibroblasts proliferation and fibrosis by down-regulation of DUSP5.

Introduction

Cardiac fibrosis is an important pathological feature of cardiac remodeling in heart diseases [1], [2]. The abnormal proliferation of cardiac fibroblasts and deposition of the extracellular matrix (ECM) proteins and collagens results in the development of cardiac fibrosis, which then adversely affects the performance of the heart [3], [4]. Increased fibrosis and subsequent cardiac dysfunction can cause heart failure, arrhythmia, and even sudden death [5], [6]. Over the past decade, a wide variety of growth factors have been found to be able to regulate cell proliferation and ECM synthesis, and thus have the potential to be involved in cardiac fibrosis [7], [8]. Recent studies showed that the synthesis of collagen can be selectively induced by transforming growth factor-β1 (TGF-β1) [9], [10], [11]. The extracellular regulated protein kinases1/2 (ERK1/2) signaling pathway has long been recognized as the intracellular signal transduction enzymes, which are critically involved in regulating proliferation [12], [13], [14]. Specific dephosphorylation of MAPKs on phosphoserine/phosphothreonine and phosphotyrosine residues is mediated by dual-specificity phosphatases (DUSPs), a family of cysteine-dependent protein tyrosine phosphatases [15]. DUSP5, a nuclear phosphatase, negatively regulates prohypertrophic signaling by ERK1/2 [16]. However, the molecular mechanisms of DUSP5 in cardiac fibrosis, is not completely understood.

The methyl-CpG-binding protein 2 (MeCP2) is a member of a family of proteins that specifically bind to methylated DNA sequences in the genome [17]. The protein encoded by the MeCP2 gene contains a methyl-CpG-binding domain (MBD), which binds to symmetrically methylated cytosine, and a transcriptional repression domain (TRD), which interacts with co-repressor proteins, such as histone deacetylases (HDACs) and mSin3a [18], [19]. MeCP2 has been characterized as a transcription repressor, acting by binding to the methylated sequences of its target gene promoter and recruiting transcriptional repressors to silence gene expression [20]. A recent study has shown that MeCP2 plays a key role in fibrosis diseases [21]. Furthermore, MeCP2 was found to be up-regulated in differentiated cardiomyocytes [22]. What is more, over-expression of MeCP2 in the mouse heart leads to embryonic lethality with cardiac septum hypertrophy [23]. However, the role of MeCP2 in cardiac fibrosis remains unclear. Supporting our hypothesis, we found that MeCP2 modulates DUSP5 mediated activation of ERK1/2 in cardiac fibrosis. These results further support MeCP2 acts as a key regulator of pathological cardiac fibrosis, promotes cardiac fibroblasts proliferation and fibrosis by down-regulation of DUSP5.