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The TGF-b superfamily cytokine GDF15 is a CCN2-regulated autocrine/paracrine factor in the heart

ABSTRACT: Growth differentiating factor (GDF)15 is a TGFβ superfamily cytokine and a reported biomarker of heart failure. Myocardial expression of GDF15 is increased in heart failure. Yet, the mechanisms that control synthesis and release of GDF15 as well as the autocrine/paracrine functions of GDF15 on fibroblast function is lacking. Thus, the aim of this study was to investigate signaling pathways and functions of GDF15 in cardiac fibroblasts. Cardiac fibroblasts and cardiac myocytes were isolated from adult C57/BL6 mice, maintained in primary culture and stimulated with recombinant (r)GDF15 or recombinant (r)CCN2. Short-term stimulation (30 minutes) of cardiac fibroblasts demonstrated a GDF15-induced activation of several intracellular signaling pathways including a concentration-dependent increase of phospho-Smad3(Ser423/425) (p<0.05, n=3), phospho-AKT(Ser473) (p<0.05, n=3) and phospho-IκBα(Ser32/36) (p<0.05, n=3) levels. However, rGDF15 did not phosphorylate Smad3(Ser423/425) or IκBα(Ser32/36) in cardiac myocyte. Cardiac fibroblasts exposed to rGDF15 for 48 hours displayed differentiation towards myofibroblasts reflected by increased levels of the differentiation marker α-smooth muscle actin (SMA) similar to cardiac fibroblasts stimulated with TGFβ. The effect of GDF15 on α-SMA was dose-dependent ranging from 500 nM - 20 nM rGDF15 (p<0.05, n=3). Differentiation towards a myofibroblast phenotype in the presence of GDF15 was also supported by higher matrix metalloproteinase (MMP) enzyme activity in the cell culture medium (6±1 fold increase, n=3, p<0.05) and increased expression and release of MMP-3, 9 and 13. Immunoreactive GDF15 was predominantly found in cardiac myocytes. Recombinant CCN2 substantially induced GDF15 expression in cardiac myocytes, but not in cardiac fibroblasts. In conclusion, our data demonstrate that GDF15 is a paracrine factor in myocardial tissue and specifically regulated by CCN2 in cardiac myocytes. GDF15 has similar effects as TGFβ on fibroblasts by activation of intracellular signaling pathways and differentiation to a myofibroblasts phenotype.

ORGANISM(S): Mus musculus

PROVIDER: GSE55252 | GEO | 2017/02/19

SECONDARY ACCESSION(S): PRJNA239002

REPOSITORIES: GEO

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Project description:Introduction: We have reported that iPSC-cardiac myocytes from patients with arrhythmogenic cardiomyopathy (ACM) mount an intense innate immune response under basal conditions in vitro. In addition, blocking innate immune signaling via NFκB prevents disease in a mouse model of ACM (Dsg2mut/mut mice). Here, we defined the relative pathogenic roles of immune signaling in cardiac myocytes vs. infiltrating inflammatory cells in Dsg2mut/mut mice. Methods: To define the role of immune signaling in cardiac myocytes, we bred Dsg2mut/mut mice with mice with cardiac myocyte-specific expression of a dominant-negative form of IκBα (DN-IκBα), which prevents nuclear translocation and, thereby, activation of NFκB signaling only in cardiac myocytes. To define the role of inflammatory cells in ACM, we focused on cells expressing C-C motif chemokine receptor-2 (CCR2+ cells), known to mediate adverse cardiac remodeling and fibrosis. We bred Dsg2mut/mut mice with germline deletion of Ccr2 mice (Ccr2-/- mice). We compared phenotypes in Dsg2mut/mut mice with double-mutant Dsg2mut/mut X DN-IκB and Dsg2mut/mut X Ccr2-/- lines. Results: Dsg2mut/mut mice develop marked myocardial fibrosis, reduced LV ejection fraction (EF) and many PVCs. These disease features were all normalized in Dsg2mut/mut X DN-IκB mice. Hearts of Dsg2mut/mut and Dsg2mut/mut X DN-IκB mice contained equal numbers of CD68+ macrophages, but Dsg2mut/mut hearts had many more CCR2+ cells. Cardiac myocyte expression of Tlr4 which activates NFκB, was increased in Dsg2mut/mut mice but not in Dsg2mut/mut X Ccr2-/- mice. Dsg2mut/mut X Ccr2-/- mice showed greatly reduced myocardial fibrosis and PVCs but LV EF was markedly depressed. This suggested that contractile dysfunction in ACM is due not only to loss of muscle but to immune signaling in viable cardiac myocytes as well. To test this hypothesis, we treated Dsg2mut/mut and Dsg2mut/mut X Ccr2-/- mice with the NFκB inhibitor Bay 11-7082. Before treatment, LV EFs were significantly reduced in both groups. Untreated Dsg2mut/mut mice had ongoing deterioration of LV function, whereas treated Dsg2mut/mut mice showed no further disease progression and actually had some improvement in contractile function. However, LV function in treated Dsg2mut/mut X Ccr2-/- mice was virtually normalized. Conclusions: NFκB signaling in cardiac myocytes drives myocardial injury, LV dysfunction and arrhythmias in Dsg2mut/mut mice. It also mobilizes CCR2+ cells to the heart, where they promote myocardial injury and arrhythmias. CCR2+ cells alter gene expression in cardiac myocytes. LV dysfunction in Dsg2mut/mut mice is caused not only by muscle loss but also by negative inotropic effects of inflammation mediated by NFκB in viable cardiac myocytes. These results have obvious implications for ACM patients and suggest that anti-inflammatory therapy may be beneficial even in patients with established disease.

Project description:This a model from the article: Electrophysiological modeling of fibroblasts and their interaction with myocytes. Sachse FB, Moreno AP, Abildskov JA. Ann Biomed Eng. year volume page 17999190 , Abstract: Experimental studies have shown that cardiac fibroblasts are electrically inexcitable, but can contribute to electrophysiology of myocardium in various manners. The aim of this computational study was to give insights in the electrophysiological role of fibroblasts and their interaction with myocytes. We developed a mathematical model of fibroblasts based on data from whole-cell patch clamp and polymerase chain reaction (PCR) studies. The fibroblast model was applied together with models of ventricular myocytes to assess effects of heterogeneous intercellular electrical coupling. We investigated the modulation of action potentials of a single myocyte varying the number of coupled fibroblasts and intercellular resistance. Coupling to fibroblasts had only a minor impact on the myocyte's resting and peak transmembrane voltage, but led to significant changes of action potential duration and upstroke velocity. We examined the impact of fibroblasts on conduction in one-dimensional strands of myocytes. Coupled fibroblasts reduced conduction and upstroke velocity. We studied electrical bridging between ventricular myocytes via fibroblast insets for various coupling resistors. The simulations showed significant conduction delays up to 20.3 ms. In summary, the simulations support strongly the hypothesis that coupling of fibroblasts to myocytes modulates electrophysiology of cardiac cells and tissues. This model was taken from the CellML repository and automatically converted to SBML. The original model was: sachse, moreno, abildskov.(2008) - version05 The original CellML model was created by: Lloyd, Catherine, May c.lloyd@auckland.ac.nz The University of Auckland Auckland Bioengineering Institute This model originates from BioModels Database: A Database of Annotated Published Models (http://www.ebi.ac.uk/biomodels/). It is copyright (c) 2005-2011 The BioModels.net Team. To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information. In summary, you are entitled to use this encoded model in absolutely any manner you deem suitable, verbatim, or with modification, alone or embedded it in a larger context, redistribute it, commercially or not, in a restricted way or not.. To cite BioModels Database, please use: Li C, Donizelli M, Rodriguez N, Dharuri H, Endler L, Chelliah V, Li L, He E, Henry A, Stefan MI, Snoep JL, Hucka M, Le Novère N, Laibe C (2010) BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. BMC Syst Biol., 4:92.

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The TGF-b superfamily cytokine GDF15 is a CCN2-regulated autocrine/paracrine factor in the heart

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