Abstract 066: MEF2-induced Loss of Sarcomeres is Mediated by an Alternative Splice Variant of DMPK

2013 ◽  
Vol 113 (suppl_1) ◽  
Author(s):  
Ies Elzenaar ◽  
Inge van der Made ◽  
Wino J Wijnen ◽  
Elisabeth Ehler ◽  
Leon J De Windt ◽  
...  

The pathology of heart failure is characterized by poorly contracting and dilated ventricles. Although this is associated with lengthening of individual cardiomyocytes and loss of sarcomeres, the mechanism underlying these changes in cardiomyocyte structure remains to be elucidated. We have previously identified the transcription factor myocyte enhancer factor-2 (MEF2) as important trigger for adverse cardiomyocyte remodeling. Here, we use microarray analysis and gain- and loss- of function approaches to identify MEF2 target genes involved in structural remodeling of the cardiomyocyte. Isolated neonatal rat cardiomyocytes infected with adenoviruses expressing MEF2 underwent cellular elongation associated with loss of sarcomeric structure. Microarray analysis revealed myotonic dystrophy protein kinase (DMPK) as MEF2 target gene, which we verified by chromatin immunoprecipitation experiments. siRNA mediated knockdown of DMPK prevented MEF2-induced cardiomyocyte elongation and loss of sarcomeres. Interestingly, RT-PCR analysis of known DMPK splice variants demonstrated a relative increase of the DMPK E isoform in failing mouse hearts. To test the role of this specific splice isoform, we generated adenoviruses expressing DMPK E or a kinase dead mutant DMPK E. Overexpression of wildtype DMPK E, but not of the kinase dead mutant, in cardiomyocytes resulted in severe loss of sarcomeric structure. Moreover, quantitative PCR analysis showed a decrease in mRNA levels for several sarcomeric genes after overexpression of DMPK E. These genes are known targets of the transcription factor serum response factor (SRF) and DMPK is known to phosphorylate SRF. Therefore, we tested the effect of DMPK on SRF activity in luciferase experiments, which demonstrated that DMPK E is an inhibitor of SRF transcriptional activity. Our data indicate that MEF2 induces loss of sarcomeres, which is mediated by at least one specific splice variant of DMPK. Moreover, increased expression of this DMPK splice variant results in a decrease in sarcomeric gene expression, which possibly involves inhibition of SRF transcriptional activity. Together, these results assign a novel function to MEF2 and DMPK in adverse cardiomyocyte remodeling during heart failure development.

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Ies Elzenaar ◽  
Amin Damanafshan ◽  
Inge van der Made ◽  
Yigal M Pinto ◽  
Ralph J van Oort

Background: Heart failure is associated with elongation of cardiomyocytes and loss of sarcomeres. Although the transcription factor myocyte enhancer factor-2 (MEF2) has an important role in this adverse remodeling, the mechanism underlying the structural changes of cardiomyocytes remains to be elucidated. In a screen for MEF2 target genes, we have recently identified myotonic dystrophy protein kinase (DMPK) as a potential mediator of adverse cardiomyocyte remodeling. However, it remains to be determined whether DMPK levels are increased in failing hearts and if DMPK is sufficient to induce structural remodeling of cardiomyocytes. Methods and Results: Since the DMPK gene is subject to extensive alternative splicing, we performed RT-PCR and QPCR analysis of known DMPK splice variants in hearts from mice subjected to transverse aortic constriction (TAC) or sham surgery. This demonstrated a 1.6 fold increase in the DMPK E isoform in failing mouse hearts compared to controls (P<0.05). To test the role of this specific splice isoform, we generated adenoviruses expressing DMPK E or a kinase dead mutant DMPK E. Overexpression of wildtype DMPK E, but not of the kinase dead mutant, in cardiomyocytes resulted in severe loss of sarcomeric structure. Moreover, QPCR analysis showed a decrease in mRNA levels for several sarcomeric genes after overexpression of DMPK E. Since these genes are known targets of the transcription factor serum response factor (SRF) and DMPK is known to phosphorylate SRF, we tested the effect of DMPK E on SRF activity. Luciferase experiments demonstrated that DMPK E is an inhibitor of SRF transcriptional activity. Finally, immunostaining revealed a translocation of SRF from the nucleus to the cytosol upon DMPK E overexpression. Conclusion: Our data indicate that the expression of DMPK E is increased in heart failure. Moreover, increased expression of this DMPK splice variant results in a decrease in sarcomeric gene expression by translocation and inhibition of SRF. Together, these results assign a novel function to DMPK in adverse cardiomyocyte remodeling during heart failure development.


2006 ◽  
Vol 291 (1) ◽  
pp. E128-E136 ◽  
Author(s):  
Kristen E. Govoni ◽  
Seong Keun Lee ◽  
Robert B. Chadwick ◽  
Hongrun Yu ◽  
Yuji Kasukawa ◽  
...  

Growth hormone (GH) is important in the development and maintenance of bone; however, the IGF-dependent and -independent molecular pathways involved remain to be established. We used microarray analysis to evaluate GH signaling pathways in 4-wk-old GH-deficient mice following a single injection of GH (4 mg/kg body wt) or PBS ( n = 6/group) at 6 or 24 h after treatment. Six thousand one hundred sixty genes were differentially expressed at P ≤ 0.05, and 17% of these genes were identified at both time points. Several of the genes differentially expressed were expressed sequence tags, and the remaining genes fell into 49 Gene Ontology categories. For subsequent studies, we focused on T-box (Tbx)3, a novel transcription factor, which increased more than twofold at both time points. Real-time RT-PCR analysis determined that pretreatment with IGF-binding protein-4 did not block GH-induced Tbx3 expression in vitro. Pretreatment with TNF-α blocked GH-induced Tbx3 expression. Tbx3 expression increased during osteoblast differentiation and following BMP-7 and Wnt3a treatment ( P ≤ 0.05). Blocking Tbx3 expression by small interfering RNA decreased cell number and [3H]Thymidine incorporation ( P < 0.01). In conclusion, 1) GH caused acute changes in several novel genes, suggesting that many GH-induced signaling pathways and target genes remain to be discovered; 2) because Tbx3 expression is regulated in osteoblasts and blockage of Tbx3 expression decreased cell number and DNA synthesis, we propose that Tbx3 is an important determinant of osteoblast cell number.


2004 ◽  
Vol 180 (2) ◽  
pp. 325-335 ◽  
Author(s):  
◽  
R Pineiro ◽  
MJ Iglesias ◽  
O Gualillo ◽  
PA Kelly ◽  
...  

The use of GH to treat heart failure has received considerable attention in recent years. Although the mechanisms of its beneficial effects are unknown, it has been implicated in the regulation of apoptosis in several cell types, and cardiomyocyte apoptosis is known to occur in heart failure. We therefore decided to investigate whether GH protects cardiomyocytes from apoptosis. Preliminary experiments confirmed the expression of the GH receptor (GHR) gene in primary cultures of neonatal rat cardiomyocytes (PC), the specific binding of GH by HL-1 cardiomyocytes, and the GH-induced activation of GHR and its classical downstream effectors in the latter. That GH prevented the apoptosis of PC cells deprived of serum for 48 h was shown by DNA electrophoresis and by Hoechst staining assays in which GH reduced the percentage of cells undergoing apoptosis. Similarly, the TUNEL-evaluated pro-apoptotic effect of cytosine arabinoside (AraC) on HL-1 cells was almost totally prevented by pre-treatment with GH. Fluorescence-activated cell sorter (FACS) analysis showed apoptosis in 9.7% of HL-1 cells growing in normal medium, 21.1% of those treated with AraC and 13.9% of those treated with AraC+GH, and that GH increased the percentage of AraC-treated cells in the S/G(2)/M phase from 36.9% to 52.8%. GH did not modify IGF-I mRNA levels or IGF-I secretion in HL-1 cells treated with AraC, and the protection afforded by GH against AraC-induced apoptosis in HL-1 cells was not affected by the presence of anti-IGF-I antibodies, but was largely abolished by the calcineurin-inhibiting combination cyclosporin+FK506. GH also reduced AraC-induced phosphorylation of mitogen-activated protein kinase p38 (MAPK p38) in HL-1 cells. In summary, GH protects PC and HL-1 cells from apoptosis. This effect is not mediated by IGF-I and may involve MAPK p38 as well as calcineurin.


1999 ◽  
Vol 276 (6) ◽  
pp. H2013-H2019 ◽  
Author(s):  
Gordana Nikcevic ◽  
Maria C. Heidkamp ◽  
Merja Perhonen ◽  
Brenda Russell

Mechanical inactivity depresses protein expression in cardiac muscle tissue and results in atrophy. We explore the mechanical transduction mechanism in spontaneously beating neonatal rat cardiomyocytes expressing the α-myosin heavy chain (α-MyHC) isoform by interfering with cross-bridge function [2,3-butanedione monoxime (BDM), 7.5 mM] without affecting cell calcium. The polysome content and α-MyHC mRNA levels in fractions from a sucrose gradient were analyzed. BDM treatment blocked translation at initiation (162 ± 12% in the nonpolysomal RNA fraction and 43 ± 6% in the polysomal fraction, relative to control as 100%; P < 0.05). There was an increase in α-MyHC mRNA from the nonpolysomal fraction (120.5 ± 7.7%; P < 0.05 compared with control) with no significant change in the heavy polysomes. In situ hybridization of α-MyHC mRNA was used to estimate message abundance as a function of the distance from the nucleus. The mRNA was dispersed through the cytoplasm in spontaneously beating cells as well as in BDM-treated cells (no significant difference). We conclude that direct inhibition of contractile machinery, but not calcium, regulates initiation of α-MyHC mRNA translation. However, calcium, not pure mechanical signals, appears to be important for message localization.


2021 ◽  
Vol 129 (Suppl_1) ◽  
Author(s):  
Masahiko Umei ◽  
Hiroshi Akazawa ◽  
Akiko Saga-Kamo ◽  
Hiroki Yagi ◽  
Qing Liu ◽  
...  

Introduction: Short-chain fatty acids (SCFA) are one of the gut microbial metabolites that can influence host health and disease. We previously reported that gut dysbiosis is associated with heart failure, and that the proportion of butyrate-producing bacteria is decreased in the gut of patients with heart failure. Purpose: We investigated the molecular mechanism of butyrate in the development of cardiac hypertrophy. Methods and Results: Single-cell transcriptome analysis and co-expression network analysis revealed that G protein-coupled receptors for short-chain fatty acid receptors were not expressed in cardiomyocytes and that Olfr78 was expressed in vascular smooth muscle cells in the heart. On the other hand, treatment with butyrate inhibited ET1-induced and isoproterenol (ISO)-induced hypertrophic growth in cultured neonatal rat cardiomyocytes. Moreover, butyrate increased the acetylation levels of histone H3, suggesting the inhibitory effect of butyrate on HDAC. In addition, butyrate caused the degradation of HDAC2 and up-regulation of Inpp5f, encoding inositol polyphosphate-5-phosphatase f, leading to a significant decrease in the phosphorylation levels of Akt and glycogen synthase kinase 3β (GSK3β). Finally, intraperitoneal injection of butyrate inhibited ISO-induced cardiac hypertrophy in mice. These results suggest that butyrate protects against hypertrophic responses via suppression of the Akt-GSK3β pathway through HDAC inhibition. Conclusion: In the heart, there were no known short-chain fatty acid receptors in cardiomyocytes. However, butyrate was shown to have an epigenetic mechanism in suppressing effect on cardiomyocyte hypertrophy via suppression of HDAC2-Akt-GSK3β axis. Our results uncover a potential link between dysbiosis of intestinal microbiota and the development of cardiac hypertrophy.


Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Yoshiaki Ohyama ◽  
Toru Tanaka ◽  
Takehisa Shimizu ◽  
Hiroshi Doi ◽  
Norimichi Koitabashi ◽  
...  

Backgroud: Recent studies demonstrated non-hematopoietical effects of Erythropoietin (Epo) and its receptor (EpoR) in a variety of tissues including cardiovascular system. Epo treatment improves cardiac function in patients with heart failure and reduces infarct size after ischemia/reperfusion injury in the heart. However, little attention has been paid for the endogenous regulatory mechanisms regulating EpoR expression. In this study, we hypothesize that B-type natriuretic peptide upregulates EpoR gene expression in failing heart. Methods and Results: Wister rats underwent transverse aortic constriction surgery to induce hypertrophy. RT-PCR analyses of those rats showed that EpoR mRNA levels were increased in the left ventricle and positively correlated with the levels of BNP mRNA (n=10, r=0.67, p<0.05). Next we examined the expression of EpoR in human failing heart by using autopsy specimens and found that EpoR mRNA levels were significantly elevated in patients with dilated cardiomyopathy compared with those in normal heart. Immunohistochemistry of endomyocardial biopsy specimens of failing heart (n=54) showed that EpoR mRNA levels were correlated with severity of cardiac dysfunction estimated by diameter of cardiac chambers, pathomorphology, serum BNP concentration and functional class of New York Heart Association. Interestingly, stimulation of cultured neonatal rat cardiac myocytes with BNP, but not with hypertrophic reagents including endothelin I, angiotensin II and norepinephrine, significantly increased the EpoR mRNA levels in a time-dependent manner. Overexpression of cGMP-dependent protein kinase (PKG) increased EpoR transcript in cultured cardiac myocytes. BNP-induced EpoR expression was abrogated in the presence of KT5823, a specific inhibitor for PKG. Conclusion: These results suggest a role for BNP in mediating an induction of EpoR expression in failing myocardium and indicate that the cardiac EpoR gene is a target of cGMP/PKG signaling.


Biomolecules ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1667
Author(s):  
Jian-Hong Lin ◽  
Kun-Ta Yang ◽  
Pei-Ching Ting ◽  
Yu-Po Luo ◽  
Ding-Jyun Lin ◽  
...  

Myocardial ischemia/reperfusion (I/R) injury has been associated with ferroptosis, which is characterized by an iron-dependent accumulation of lipid peroxide to lethal levels. Gossypol acetic acid (GAA), a natural product taken from the seeds of cotton plants, prevents oxidative stress. However, the effects of GAA on myocardial I/R-induced ferroptosis remain unclear. This study investigated the ability of GAA to attenuate I/R-induced ferroptosis in cardiomyocytes along with the underlying mechanisms in a well-established rat model of myocardial I/R and isolated neonatal rat cardiomyocytes. H9c2 cells and cardiomyocytes were treated with the ferroptosis inducers erastin, RSL3, and Fe-SP. GAA could protect H9c2 cells against ferroptotic cell death caused by these ferroptosis inducers by decreasing the production of malondialdehyde and reactive oxygen species, chelating iron content, and downregulating mRNA levels of Ptgs2. GAA could prevent oxygen-glucose deprivation/reperfusion-induced cell death and lipid peroxidation in the cardiomyocytes. Moreover, GAA significantly attenuated myocardial infarct size, reduced lipid peroxidation, decreased the mRNA levels of the ferroptosis markers Ptgs2 and Acsl4, decreased the protein levels of ACSL4 and NRF2, and increased the protein levels of GPX4 in I/R-induced ex vivo rat hearts. Thus, GAA may play a cytoprotectant role in ferroptosis-induced cardiomyocyte death and myocardial I/R-induced ferroptotic cell death.


2018 ◽  
Vol 115 (1) ◽  
pp. 71-82 ◽  
Author(s):  
Andrea Grund ◽  
Malgorzata Szaroszyk ◽  
Janina K Döppner ◽  
Mona Malek Mohammadi ◽  
Badder Kattih ◽  
...  

Abstract Aims Chronic heart failure is becoming increasingly prevalent and is still associated with a high mortality rate. Myocardial hypertrophy and fibrosis drive cardiac remodelling and heart failure, but they are not sufficiently inhibited by current treatment strategies. Furthermore, despite increasing knowledge on cardiomyocyte intracellular signalling proteins inducing pathological hypertrophy, therapeutic approaches to target these molecules are currently unavailable. In this study, we aimed to establish and test a therapeutic tool to counteract the 22 kDa calcium and integrin binding protein (CIB) 1, which we have previously identified as nodal regulator of pathological cardiac hypertrophy and as activator of the maladaptive calcineurin/NFAT axis. Methods and results Among three different sequences, we selected a shRNA construct (shCIB1) to specifically down-regulate CIB1 by 50% upon adenoviral overexpression in neonatal rat cardiomyocytes (NRCM), and upon overexpression by an adeno-associated-virus (AAV) 9 vector in mouse hearts. Overexpression of shCIB1 in NRCM markedly reduced cellular growth, improved contractility of bioartificial cardiac tissue and reduced calcineurin/NFAT activation in response to hypertrophic stimulation. In mice, administration of AAV-shCIB1 strongly ameliorated eccentric cardiac hypertrophy and cardiac dysfunction during 2 weeks of pressure overload by transverse aortic constriction (TAC). Ultrastructural and molecular analyses revealed markedly reduced myocardial fibrosis, inhibition of hypertrophy associated gene expression and calcineurin/NFAT as well as ERK MAP kinase activation after TAC in AAV-shCIB1 vs. AAV-shControl treated mice. During long-term exposure to pressure overload for 10 weeks, AAV-shCIB1 treatment maintained its anti-hypertrophic and anti-fibrotic effects, but cardiac function was no longer improved vs. AAV-shControl treatment, most likely resulting from a reduction in myocardial angiogenesis upon downregulation of CIB1. Conclusions Inhibition of CIB1 by a shRNA-mediated gene therapy potently inhibits pathological cardiac hypertrophy and fibrosis during pressure overload. While cardiac function is initially improved by shCIB1, this cannot be kept up during persisting overload.


Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Susanna Cooper ◽  
Zoe Haines ◽  
Viridiana Alcantara Alonso ◽  
Joshua J Cull ◽  
Feroz Ahmad ◽  
...  

Introduction: Epidermal growth factor (EGF) receptors (EGFRs: ERBB1-4) are activated by a family of ligands (e.g. EGF, Hb-EGF, EREG, TGFa), signaling through ERK1/2 and Akt to promote cell division and cancer. Antibody-based inhibition of ERBB2 in breast cancer can cause heart failure, but the role of other receptors and EGFR ligands in the heart, and potential cardiotoxicity of generic EGFR inhibitors is unclear. Hypothesis: We hypothesize that EGFR ligands play an important role in cardiac adaptation to hypertension, acting through EGFRs to promote adaptive remodelling. Methods & Results: EGF ligand/receptor mRNA expression was assessed in human failing hearts and normal controls (n=12/8). EGFRs were expressed at similar levels, but ligand expression differed with significant up- or downregulation of EGF/Hb-EGF vs EREG/TGFa, respectively, in failing hearts (p<0.05). EGF potently activated ERK1/2 and Akt (assessed by immunoblotting) in neonatal rat cardiomyocytes, leading to hypertrophy (p<0.05, n=4). The anti-cancer drug afatinib inhibits EGFRs. To assess the role of EGF signaling in cardiac adaptation to hypertension in vivo , C57Bl/6J mice (n=6) were treated with 0.8 mg/kg/d angiotensin II (AngII; 7d) ± 0.45 mg/kg/d afatinib. AngII promoted cardiac hypertrophy with increased left ventricular (LV) wall thickness (WT) and decreased LV internal diameter (ID; assessed by echocardiography). Afatinib enhanced AngII-induced hypertrophy with significantly increased WT:ID ratios (1.30-fold and 1.54-fold in diastole and systole, respectively; p<0.05) but inhibited AngII-induced increases in Nppb mRNA expression and cardiomyocyte cross-sectional area (208.80±9.78 vs 161.10±3.87μm 2 ; p<0.05). In contrast, Col1a1 mRNA expression was enhanced by afatinib, along with interstitial and perivascular fibrosis (3.21±0.38 vs 5.61±0.46, 0.98±0.06 vs 1.45±0.18 % area; p<0.05). Conclusion: EGFR signaling is modulated in human heart failure, promotes cardiomyocyte hypertrophy and is required for cardiac adaptation to hypertension. Since EGFR inhibition in hypertension prevents adaptive cardiomyocyte hypertrophy whilst promoting fibrosis, EGFR inhibitors are likely to cause cardiac dysfunction and be cardiotoxic in hypertensive patients.


2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
C Fernandez ◽  
J Rysa ◽  
J Nilsson ◽  
G Engstrom ◽  
M Orho-Melander ◽  
...  

Abstract Background Hypertension is the leading cause for the development of heart failure (HF). Increased hemodynamic load, including mechanical stretch and neurohumoral factors, is able to trigger hypertrophic growth of cardiac myocytes. Although hypertensive HF is prevalent, there is no useful biomarker to identify HF due to chronic hypertension. Aims To identify plasma markers associated with incidence of hypertensive HF. Methods Circulating levels of 149 proteins were measured by proximity extension assay at baseline examination in 4469 individuals from the Malmö Diet and Cancer study. Protein levels were compared to stretch-activated gene expression changes in cultured neonatal rat ventricular myocytes (NRVM) in response to 1, 4, 12, 24 or 48 hours of cyclic mechanical stretch. Association between plasma proteins level and HF incidence and hypertension was studied using respectively Cox proportional hazards model and binary logistic regressions. Results After Bonferroni correction, 44 circulating proteins were significantly differentially expressed in individuals who developed HF during follow-up versus controls (P<3.4E-4). Out of these, 5 proteins (Interleukin-6 (IL-6), Growth Differentiation Factor-15 (GDF15), Interleukin-1 Receptor-Like-1 (ST2), Plasminogen Activator Urokinase Receptor (U-PAR), Transforming Growth Factor-α (TGF-α)), corresponding mRNA levels were upregulated by mechanical stretch in NRVM at all time points (P<0.05). Similar upregulation for the 5 proteins was shown in hypertensive versus normotensive individuals (P≤8.05E-4). In a model with all 5 proteins entered simultaneously, GDF15 and IL-6 were predictive of incident HF after adjustment for age, sex and NT-BNP levels (205 events; hazard ratio [HR] per SD increment of protein: HR=1.29, CI=1.05–1.58, P=0.013 and HR=1.16, CI=1.02–1.33, P=0.028). Using the same model, IL-6 but not GDF15 associated with hypertension (Odds ratio [OR] per SD increment of IL-6: OR=1.18, CI=1.09–1.27, P=3.3E-5). In hypertensive individuals GDF15 and IL-6 were individually predictive of future HF after adjustment for age, sex, NT-BNP levels, smoking, BMI and diabetes (183 events; HR=1.36, CI=1.16–1.60, P=1.64E-4 and HR=1.21, CI=1.05–1.40, P=0.008). Furthermore, in these hypertensive individuals, GDF15 and IL-6 were predictive of HF in a model with IL-6, GDF15, ST2 and TGF-α entered simultaneously after adjustment for age, sex and NT-BNP levels (176 events; HR=1.36, CI=1.13–1.64, P=0.001 and HR=1.16, CI=1.01–1.34, P=0.041). Conclusions Circulating levels of IL-6 and GDF15 might be used as NT-BNP independent biomarkers for HF development in hypertensive patients. Acknowledgement/Funding Påhlsson, Crafoord, Lundström, Åke Wiberg, Royal Physiographic Society and the Swedish Foundation for Strategic Research for IRC15-0067


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