RESUMO
Myocyte Enhancer Factor 2 (MEF2) mediates cardiac remodelling in heart failure (HF) and is also a target of ß-adrenergic signalling, a front-line treatment for HF. We identified global gene transcription networks involved in HF with and without ß-blocker treatment. Experimental HF by transverse aortic constriction (TAC) in a MEF2 "sensor" mouse model (6 weeks) was followed by four weeks of ß-blockade with Atenolol (AT) or Solvent (Sol) treatment. Transcriptome analysis (RNA-seq) from left ventricular RNA samples and MEF2A depleted cardiomyocytes was performed. AT treatment resulted in an overall improvement in cardiac function of TAC mice and repression of MEF2 activity. RNA-seq identified 65 differentially expressed genes (DEGs) due to TAC treatment with enriched GO clusters including the inflammatory system, cell migration and apoptosis. These genes were mapped against DEGs in cardiomyocytes in which MEF2A expression was suppressed. Of the 65 TAC mediated DEGs, AT reversed the expression of 28 mRNAs. Rarres2 was identified as a novel MEF2 target gene that is upregulated with TAC in vivo and isoproterenol treatment in vitro which may have implications in cardiomyocyte apoptosis and hypertrophy. These studies identify a cohort of genes with vast potential for disease diagnosis and therapeutic intervention in heart failure.
Assuntos
Antagonistas Adrenérgicos beta/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Insuficiência Cardíaca/genética , Fatores de Transcrição MEF2/genética , Transcriptoma , Antagonistas Adrenérgicos beta/uso terapêutico , Animais , Apoptose/efeitos dos fármacos , Apoptose/genética , Cardiomegalia , Biologia Computacional/métodos , Modelos Animais de Doenças , Perfilação da Expressão Gênica , Insuficiência Cardíaca/tratamento farmacológico , Insuficiência Cardíaca/patologia , Insuficiência Cardíaca/fisiopatologia , Fatores de Transcrição MEF2/metabolismo , Camundongos , Miócitos Cardíacos/metabolismoRESUMO
Transforming growth factor beta (TGF-beta) is a multifunctional cytokine capable of regulating diverse cellular processes. In this study we investigated the effect of autocrine TGF-beta signaling on tumor necrosis factor (TNF) alpha-induced cell death. We abrogated the TGF-beta autocrine loop by overexpression of a truncated TGF-beta type II receptor in MCF-7 breast carcinoma cells and found that this generated resistance to TNF-alpha-induced cytotoxicity. To elucidate the molecular basis of the influence of TGF-beta on TNF-alpha-induced cytotoxicity, we evaluated the expression levels or activities of proteins involved in TNF-alpha signal transduction or the regulation of apoptosis in general in TGF-beta-responsive and TGF-beta-nonresponsive MCF-7 cells. We observed no significant difference in the expression of TNF-alpha receptors or the TNF receptor-associated death domain protein. In addition, downstream activation of nuclear factor kappaB by TNF-alpha was not altered in cells that had lost TGF-beta responsiveness. Analysis of members of the Bcl-2 family of apoptosis-regulatory proteins revealed that Bcl-X(L) and Bax expression levels were not changed by disruption of TGF-beta signaling. In contrast, the TGF-beta-nonresponsive cells expressed much higher levels of Bcl-2 protein and mRNA than did cells with an intact TGF-beta autocrine loop. Furthermore, restoration of a TGF-beta signal to MCF-7 cells that had spontaneously acquired resistance to TGF-beta caused a reduction in Bcl-2 protein expression. Taken together, our data indicate that loss of autocrine TGF-beta signaling results in enhanced resistance to TNF-alpha-mediated cell death and that this is likely to be mediated by derepression of Bcl-2 expression.