scholarly journals Changes in Thyroid Hormone Signaling Mediate Cardiac Dysfunction in the Tg197 Mouse Model of Arthritis: Potential Therapeutic Implications

2021 ◽  
Vol 10 (23) ◽  
pp. 5512
Author(s):  
Lydia Ntari ◽  
Polyxeni Mantzouratou ◽  
Athanasia Katsaouni ◽  
Constantinos Pantos ◽  
George Kollias ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Mouse Model ◽  
Cardiac Function ◽  
P38 Mapk ◽  
Cardiac Dysfunction ◽  
Systolic Dysfunction ◽  
Calcium Handling ◽  
Hormone Signaling ◽  
Akt Activation ◽  
Cardiac Phenotype

Background Rheumatoid Arthritis (RA) patients show a higher risk of heart failure. The present study investigated possible causes of cardiac dysfunction related to thyroid hormone (TH) signaling in a RA mouse model. Methods A TNF-driven mouse model of RA[TghuTNF (Tg197)] was used. Cardiac function was evaluated by echocardiography. SERCA2a and phospholamban protein levels in left ventricle (LV) tissue, thyroid hormone levels in serum, TH receptors in LV and TH-related kinase signaling pathways were measured. T3 hormone was administered in female Tg197 mice. Results We show LV and atrial dilatation with systolic dysfunction in Tg197 animals, accompanied by downregulated SERCA2a. We suggest an interaction of pro-inflammatory and thyroid hormone signaling indicated by increased p38 MAPK and downregulation of TRβ1 receptor in Tg197 hearts. Interestingly, female Tg197 mice showed a worse cardiac phenotype related to reduced T3 levels and Akt activation. T3 supplementation increased Akt activation, restored SERCA2a expression and improved cardiac function in female Tg197 mice. Conclusions TNF overexpression of Tg197 mice results in cardiac dysfunction via p38 MAPK activation and downregulation of TRβ1. Gender-specific reduction in T3 levels could cause the worse cardiac phenotype observed in female mice, while T3 administration improves cardiac function and calcium handling via modified Akt activation.

Abstract 12153: Impact of a Hybrid Nurse-Led Intervention for the Prevention of Progressive Cardiac Dysfunction in High Risk Individuals: Results From a Pragmatic, Randomized Trial (the NIL-CHF Study)

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Simon Stewart ◽  
Melinda Carrington ◽  
Yih Kai Chan ◽  
Garry Jennings ◽  
Chiew Wong ◽  
...  
Keyword(s):  
High Risk ◽  
Cardiac Function ◽  
Diastolic Dysfunction ◽  
Cardiac Dysfunction ◽  
Systolic Dysfunction ◽  
Cardiac Abnormality ◽  
Coronary Syndrome ◽  
History Of ◽  
Hybrid Program

Background: The natural history of chronic heart failure (CHF) is characterized by initial cardiac insult and/or stressors over time that leaves affected individuals at high risk for progressive cardiac dysfunction and eventual development of the syndrome. Methods: Of a total of 624 subjects at high risk of developing CHF randomized into the NIL-CHF Study comparing a hybrid program of home and clinic-based follow-up (NIL-CHF group) to Standard Care, 454 (73%) underwent serial echocardiography at 1 month post index cardiac hospitalization and at 3 years. At both time points (nil signs/symptoms of CHF at baseline), these were blindly classified as follows: 1) no cardiac abnormality, 2) systolic dysfunction/HFrEF - LVEF ≤ 45% ), 3) diastolic dysfunction/HFpEF as defined by any moderate diastolic dysfunction (with pseudonormalization pattern) or E/E prime ratio ≥ 15, 4) combination of 2 & 3 and 5) other cardiac abnormality (including LVH). Pre-specified criteria were used to determine - i) no change, ii) improvement or iii) deterioration in cardiac function from baseline to 3 years. Results: Mean age was 66±11 years, 71% were male, 70% were hospitalized with an acute coronary syndrome and 62% and 26%, respectively, were being treated for hypertension and diabetes. At baseline 25.2% vs. 28.4% (p=ns), 15.1% vs. 9.1% (p<0.05), 35.1% vs. 32.4% (p=ns) and 34.3% vs. 39.6% had normal cardiac function, HFrEF, HFpEF (13% both HFrEF and HFpEF overall) and LVH (the predominant “other” cardiac abnormality), respectively. At 3 years the proportion of subjects with reversal of pre-existing HFrEF or HFpEF was lower in the NIL-CHF group (23% vs. 16%; p=0.063). Moreover, significantly more NIL-CHF subjects demonstrated any form of cardiac recovery/reversal on echocardiography (39% vs. 25%, p=0.011, 95% CI 1.35, 95% CI 1.04, 1.76). They also demonstrated significantly greater regression to normal LV structure (36% vs. 25%; p=0.047) among those with LVH at baseline. Conclusions: These pre-specified analyses (secondary endpoint) of the recently completed NIL-CHF Study suggests a cardio-protective effect conferred by a long-term, nurse-led, home and clinic-based intervention targeting hospitalized individuals at high risk for developing CHF.

scholarly journals ZEB2 regulates a transcriptional network of calcium-handling genes in the injured heart

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
M Gladka ◽  
A De Leeuw ◽  
A Kohela ◽  
B Molenaar ◽  
D Versteeg ◽  
...  
Keyword(s):  
Heart Failure ◽  
Transcription Factor ◽  
Cardiac Function ◽  
Cardiac Dysfunction ◽  
Molecular Mechanisms ◽  
Critical Role ◽  
Calcium Handling ◽  
Funding Source ◽  
Post Injury ◽  
Mesenchymal Transition

Abstract   Intracellular calcium (Ca2+) overload is known to play a critical role in the development of cardiac dysfunction. Despite the remarkable progress in managing the progression of the disease, the development of effective therapies for heart failure (HF) remains challenging. Therefore, it is of great importance to understand the molecular mechanisms that maintain calcium level and contractility in homeostatic conditions. Here we identified a transcription factor ZEB2 that regulates the expression of numerous contractile and calcium-related genes. Zinc finger E-box-binding homeobox2 (ZEB2) is a transcription factor that plays a role during early fetal development and epithelial-to-mesenchymal transition (EMT); however, its function in the heart remains to be determined. Recently, we found that ZEB2 is upregulated in murine cardiomyocytes shortly after an ischemic event, but returns to baseline levels as the disease progresses. Gain- and loss-of-function genetic mouse models revealed the necessity and sufficiency of ZEB2 to maintain proper cardiac function after ischemic injury. We show that cardiomyocyte-specific ZEB2 overexpression (Zeb2 cTG) protected from ischemia-induced diastolic dysfunction and attenuated the structural remodeling of the heart. Moreover, RNA-sequencing of Zeb2 cTG hearts post-injury implicated ZEB2 in the regulation of numerous calcium-handling and contractile-related genes when compared to wildtype mice. Mechanistically, ZEB2 overexpression increased the phosphorylation of phospholamban (PLN) at both serine-16 and threonine-17, implying enhanced activity of the sarcoplasmic reticulum Ca2+-ATPase (SERCA2A), thereby augmenting contractility. Improved cardiac function in ZEB2-overexpressing hearts correlated with higher expression of several sarcomeric proteins like myosin-binding protein C3 (MYBPC3), desmin (DES) and myosin regulatory light chain 2 (MYL2) further contributing to the observed protective phenotype. Furthermore, we observed a decrease in the activity of Ca2+-depended calcineurin/NFAT signaling, which is the main driver of pathological cardiac remodeling. Conversely to Zeb2 cTg mice, loss of ZEB2 from cardiomyocytes perturbed the expression of calcium- and contractile-related proteins and increased the activity of calcineurin/NFAT pathway, exacerbating cardiac dysfunction. Together, we show that ZEB2 is a central regulator of contractile and calcium-handling components, consequently mediating contractility in the mammalian heart. Further mechanistic understanding of the role of ZEB2 in the regulation of calcium homeostasis in cardiomyocytes is a critical step towards the development of improved therapies for various forms of heart failure. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): DR. E. Dekker from Dutch Heart Foundation

scholarly journals Exercise restores dysregulated gene expression in a mouse model of arrhythmogenic cardiomyopathy

2019 ◽  
Vol 116 (6) ◽  
pp. 1199-1213 ◽  
Author(s):  
Sirisha M Cheedipudi ◽  
Jinzhu Hu ◽  
Siyang Fan ◽  
Ping Yuan ◽  
Jennifer Karmouch ◽  
...  
Keyword(s):  
Gene Expression ◽  
Mouse Model ◽  
Cardiac Function ◽  
Cardiac Dysfunction ◽  
Treadmill Exercise ◽  
Arrhythmogenic Cardiomyopathy ◽  
Transcript Levels ◽  
Myocardial Apoptosis ◽  
Genes Encoding ◽  
Canonical Wnt

Abstract Aims Arrhythmogenic cardiomyopathy (ACM) is a myocardial disease caused mainly by mutations in genes encoding desmosome proteins ACM patients present with ventricular arrhythmias, cardiac dysfunction, sudden cardiac death, and a subset with fibro-fatty infiltration of the right ventricle predominantly. Endurance exercise is thought to exacerbate cardiac dysfunction and arrhythmias in ACM. The objective was to determine the effects of treadmill exercise on cardiac phenotype, including myocyte gene expression in myocyte-specific desmoplakin (Dsp) haplo-insufficient (Myh6-Cre:DspW/F) mice. Methods and results Three months old sex-matched wild-type (WT) and Myh6-Cre:DspW/F mice with normal cardiac function, as assessed by echocardiography, were randomized to regular activity or 60 min of daily treadmill exercise (5.5 kJ work per run). Cardiac myocyte gene expression, cardiac function, arrhythmias, and myocardial histology, including apoptosis, were analysed prior to and after 3 months of routine activity or treadmill exercise. Fifty-seven and 781 genes were differentially expressed in 3- and 6-month-old Myh6-Cre:DspW/F cardiac myocytes, compared to the corresponding WT myocytes, respectively. Genes encoding secreted proteins (secretome), including inhibitors of the canonical WNT pathway, were among the most up-regulated genes. The differentially expressed genes (DEGs) predicted activation of epithelial–mesenchymal transition (EMT) and inflammation, and suppression of oxidative phosphorylation pathways in the Myh6-Cre:DspW/F myocytes. Treadmill exercise restored transcript levels of two-third (492/781) of the DEGs and the corresponding dysregulated transcriptional and biological pathways, including EMT, inflammation, and secreted inhibitors of the canonical WNT. The changes were associated with reduced myocardial apoptosis and eccentric cardiac hypertrophy without changes in cardiac function. Conclusion Treadmill exercise restored transcript levels of the majority of dysregulated genes in cardiac myocytes, reduced myocardial apoptosis, and induced eccentric cardiac hypertrophy without affecting cardiac dysfunction in a mouse model of ACM. The findings suggest that treadmill exercise has potential beneficial effects in a subset of cardiac phenotypes in ACM.

Abstract 50: Therapeutic Silencing of miRNA-652 Restores Cardiac Function and Attenuates Pathological Remodeling in a Mouse Model of Pressure Overload

2014 ◽  
Vol 115 (suppl_1) ◽  
Author(s):  
Bianca C Bernardo ◽  
Sally S Nguyen ◽  
Catherine E Winbanks ◽  
Xiao-Ming Gao ◽  
Esther J Boey ◽  
...  
Keyword(s):  
Heart Failure ◽  
Mouse Model ◽  
Cardiac Function ◽  
Cardiac Dysfunction ◽  
Heart Function ◽  
Pressure Overload ◽  
Post Treatment ◽  
Locked Nucleic Acid ◽  
Luciferase Assay ◽  
Sham Operation

Introduction: Targeting microRNAs differentially regulated in settings of stress and protection could represent a new approach for the treatment of heart failure. miR-652 expression increased in hearts of a cardiac stress mouse model and was downregulated in a model of cardiac protection. Aim: To assess the therapeutic potential of silencing miR-652 in a mouse model with established pathological hypertrophy and cardiac dysfunction due to pressure overload. Methods: Mice were subjected to a sham operation (n=10) or transverse aortic constriction (TAC, n=14) for 4 weeks to induce hypertrophy and cardiac dysfunction. Mice were subcutaneously administered a locked nucleic acid (LNA)-antimiR-652 or LNA-control. Cardiac function was assessed by echocardiography before and 8 weeks post treatment, followed by molecular and histological analyses. Results: Expression of miR-652 increased in hearts subjected to pressure overload compared to sham operated mice (2.9 fold, n=3-5, P<0.05), but was silenced in hearts of mice administered LNA-antimiR-652 (95% decrease, n=3-7, P<0.05). In mice subjected to pressure overload, inhibition of miR-652 improved cardiac function (29±1% at 4 weeks post TAC compared to 35±1% post treatment, n=7, P<0.001) and attenuated cardiac hypertrophy. Functional and morphologic improvements in hearts of treated mice were associated with reduced cardiac fibrosis, apoptosis, cardiomyocyte size; decreased B-type natriuretic peptide gene expression; and preserved angiogenesis (all P<0.05, n=4-7/group). Mechanistically, we identified Jagged1, a Notch1 ligand, as a direct target of miR-652 by luciferase assay. Jagged1 and Notch1 mRNA were upregulated in hearts of TAC treated mice (1.2-1.7 fold, n=7, P<0.05). Importantly, chronic knockdown of miR-652 was not associated with any notable toxicity in other tissues. Conclusion: Therapeutic silencing of miR-652 protects the heart against pathological cardiac remodeling and improves heart function via mechanisms that are associated with preserved angiogenesis, decreased fibrosis and upregulation of a miR-652 target, Jagged1. These studies provide the first evidence that targeted inhibition of miR-652 could represent an attractive approach for the treatment of heart failure.

Abstract 5356: Brca1 Is An Essential Regulator Of Cardiac Function

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Praphulla C Shukla ◽  
Krishna K Singh ◽  
Fina Lovren ◽  
Yi Pan ◽  
Guilin Wang ◽  
...  
Keyword(s):  
Cardiac Function ◽  
Cardiac Dysfunction ◽  
Systolic Dysfunction ◽  
Genotoxic Stress ◽  
Neonatal Rat ◽  
Physical Interaction ◽  
Loss Of Function ◽  
Gain Of Function ◽  
P53 Expression

INTRODUCTION: Preservation of structure and function of the myocardium is critically dependent upon improving the survival of existing cardiomyocytes (CM), through strategies that limit CM apoptosis and DNA damage. BRCA1 is a tumor suppressor gene which functions to promote DNA repair, and protect cells against oxidative and genotoxic stress. We hypothesized that BRCA1 is a novel cellular target to limit CM apoptosis, and prevent aberrant cardiac remodeling. METHODS AND RESULTS: Experimental MI in mice caused a profound 16-fold upregulation in BRCA1 expression, which peaked at 72 hours (p<0.01). In vitro gain-of-function experiments demonstrated that Ad-BRCA1 overexpression protected neonatal rat CM against doxorubicin- and H 2 O 2 -induced apoptosis, as assessed by FACS (p<0.01) and activated caspase-3. Ad-BRCA1-expressing CM exhibited a profound reduction in p53 expression in response to doxorubicin and H 2 O 2 . Co-immunoprecipitation studies demonstrated a distinct physical interaction of BRCA1 with p53. Inhibition of p53, with pifithrin-alpha, blocked doxorubicin-induced CM apoptosis in a manner similar to BRCA1, but BRCA1-overexpressing CM, when treated with doxorubicin did not show further reduction with pifithrin-alpha, indicating an essential requirement of BRCA1 to modulate p53. In vivo gain-of-function studies demonstrated that systemic Ad-BRCA1 delivery completely prevented doxorubicin-induced cardiac dysfunction in mice (echocardiography, p<0.01). In vivo loss-of-function studies were performed in CM -specific BRCA1-KO mice (developed using Cre-lox P technology), which demonstrated marked cardiac dysfunction and mortality in response to doxorubicin administration (p< 0.01 vs. WT + Dox). CONCLUSIONS: We report for the first time an essential role of BRCA1 to limit CM apoptosis, and improve cardiac function in response to genotoxic and oxidative stress. Heart specific deletion of BRCA1 promotes severe systolic dysfunction, and limits survival. In addition to the immediate implications for cardiovascular repair, these data may have ramifications for individuals with BRCA1 mutations or cancer syndromes, particularly in the setting of adjuvant chemotherapy.

Doxycycline inducible expression of SERCA2a improves calcium handling and reverts cardiac dysfunction in pressure overload-induced cardiac hypertrophy

2004 ◽  
Vol 287 (5) ◽  
pp. H2164-H2172 ◽  
Author(s):  
Jorge Suarez ◽  
Bernd Gloss ◽  
Darrell D. Belke ◽  
Ying Hu ◽  
Brian Scott ◽  
...  
Keyword(s):  
Cardiac Function ◽  
Cardiac Myocytes ◽  
Cardiac Dysfunction ◽  
Pressure Overload ◽  
Calcium Transient ◽  
Calcium Handling ◽  
Calcium Loading ◽  
Plasmic Reticulum ◽  
Constitutive Overexpression ◽  
Rate Of Decline

Delayed cardiac relaxation in failing hearts has been attributed to reduced activity and/or expression of sarco(endo)plasmic reticulum Ca2+-ATPase 2a (SERCA2a). Although constitutive overexpression of SERCA2a has proven effective in preventing cardiac dysfunction, it is unclear whether increasing SERCA2a expression in hearts with preexisting hypertrophy will be therapeutic. To test this hypothesis, we generated a binary transgenic (BTG) system that allows tetracycline-inducible, cardiac-specific SERCA2a expression. In this system (tet-on SERCA2a), a FLAG-tagged SERCA2a transgene is expressed in the presence of doxycycline (Dox) but not in the absence of Dox (2.3-fold more mRNA, 45% more SERCA2a protein). Calcium transients measured in isolated cardiac myocytes from nonbanded Dox-treated BTG mice showed an accelerated calcium decline and an increased systolic Ca2+ peak. Sarcoplasmic reticulum (SR) calcium loading was increased by 45% in BTG mice. In the presence of pressure overload (aortic banding), echocardiographic analysis revealed that expression of SERCA2a-FLAG caused an improvement in fractional shortening. SERCA2a-FLAG expression alleviated the resultant cardiac dysfunction. This was illustrated by an increase in the rate of decline of the calcium transient. Cell shortening and SR calcium loading were also improved in cardiac myocytes isolated from banded BTG mice after SERCA2a overexpression. In conclusion, we generated a novel transgenic mouse that conditionally overexpresses SERCA2a. This model is suitable for both long- and short-term studies of the effects of controlled SERCA2a expression on cardiac function. In addition, inducible overexpression of SERCA2a improved cardiac function and calcium handling in mice with established contractile dysfunction.

scholarly journals Human amyloidogenic light chain proteins result in cardiac dysfunction, cell death, and early mortality in zebrafish

2013 ◽  
Vol 305 (1) ◽  
pp. H95-H103 ◽  
Author(s):  
Shikha Mishra ◽  
Jian Guan ◽  
Eva Plovie ◽  
David C. Seldin ◽  
Lawreen H. Connors ◽  
...  
Keyword(s):  
Cell Death ◽  
Cardiac Function ◽  
P38 Mapk ◽  
Light Chain ◽  
Cardiac Dysfunction ◽  
Cardiac Amyloidosis ◽  
Model System ◽  
In Vivo Model ◽  
Zebrafish Model

Systemic amyloid light-chain (AL) amyloidosis is associated with rapidly progressive and fatal cardiomyopathy resulting from the direct cardiotoxic effects of circulating AL light chain (AL-LC) proteins and the indirect effects of AL fibril tissue infiltration. Cardiac amyloidosis is resistant to standard heart failure therapies, and, to date, there are limited treatment options for these patients. The mechanisms underlying the development of cardiac amyloidosis and AL-LC cardiotoxicity are largely unknown, and their study has been limited by the lack of a suitable in vivo model system. Here, we establish an in vivo zebrafish model of human AL-LC-induced cardiotoxicity. AL-LC isolated from AL cardiomyopathy patients or control nonamyloidogenic LC protein isolated from multiple myeloma patients (Con-LC) was directly injected into the circulation of zebrafish at 48 h postfertilization. AL-LC injection resulted in impaired cardiac function, pericardial edema, and increased cell death relative to Con-LC, culminating in compromised survival with 100% mortality within 2 wk, independent of AL fibril deposition. Prior work has implicated noncanonical p38 MAPK activation in the pathogenesis of AL-LC-induced cardiotoxicity, and p38 MAPK inhibition via SB-203580 rescued AL-LC-induced cardiac dysfunction and cell death and attenuated mortality in zebrafish. This in vivo zebrafish model of AL-LC cardiotoxicity demonstrates that antagonism of p38 MAPK within the AL-LC cardiotoxic signaling response may serve to improve cardiac function and mortality in AL cardiomyopathy. Furthermore, this in vivo model system will allow for further study of the molecular underpinnings of AL cardiotoxicity and identification of novel therapeutic strategies.

Abstract 365: Ponatinib Triggers Cardiac Inflammation by STAT-3 Dependent Immune Checkpoint Blockade

2020 ◽  
Vol 127 (Suppl_1) ◽  
Author(s):  
Anand P Singh ◽  
Tousif Sultan ◽  
Prachi Umbarkar ◽  
Qinkun Zhang ◽  
Hind Lal
Keyword(s):  
Adverse Events ◽  
Mouse Model ◽  
Cardiac Function ◽  
Immune Cells ◽  
Cardiac Dysfunction ◽  
Kinase Inhibitor ◽  
Immune Checkpoint Blockade ◽  
Immune Checkpoints ◽  
Myocardial Inflammation ◽  
Cardiac Inflammation

Background: Ponatinib is a potent anticancer tyrosine kinase inhibitor (TKI) with considerable cardiotoxicity. The manifestation of cardiovascular adverse events, including fatal myocardial infarction and congestive heart failure, has hampered its clinical use. Therefore, a better understanding of the mechanism by which ponatinib exerts cardiotoxicity is urgently warranted to efficiently counteract treatment-related adversities. Methods: Wild type C57BL/6, comorbidity mouse model ApoE -/- , and pressure overload (PO) mouse model were used to investigate the cardiotoxic mechanism of ponatinib. Echocardiography was performed to assess cardiac function. Flow cytometry analysis was performed to assess the dynamics of inflammation. Results: We observed that high-fat diet (HFD) fed ApoE -/- mice develop cardiac dysfunction within 2 weeks of ponatinib treatment. An unbiased RNA-Seq analysis revealed significant upregulation of inflammatory genes (CCR1, CCR5, CCL6, CCL8, CCL9, CXCL4) in ponatinib treated hearts. Since ApoE -/- background, and HFD are known confounder of inflammation signal, we validated this observation in naïve C57BL/6 mice. Despite the lack of cardiac dysfunction in ponatinib treated naïve C57BL/6 mice, comprehensive immune profiling depicted upregulation of myocardial inflammation as evident by infiltrated immune cells (CD45 + TNFα + , CD45 + CD11b + F4/80 + Ly6C + CCR2 + , CD45 + Gal1 + ). Interestingly, we also demonstrated the downregulation of immune checkpoints over T cells (TCRαβ + CTLA4 + , TCRαβ + PD1 + ) in ponatinib treated hearts. Next, in the PO mouse model, ponatinib treated mice showed significant cardiac dysfunction with myocardial inflammation as reflected by increased frequencies of inflammatory parameters (TNFα + , IL1β + , IL6 + , MCP1 + , CXCL9 + ). Mechanistically, we demonstrated that ponatinib potentially suppresses PD-L1 expression over cardiomyocytes via inhibition of STAT3, subsequently leading to immune cells mediated myocardial inflammation. Conclusions: These findings uncover a novel mechanism of ponatinib induced cardiac inflammation leading to adverse cardiac function. It also suggests that strategies to attenuate inflammation may be an effective therapy to prevent ponatinib induced cardiac adverse events.

4968Increased Gao expression underlies cardiac dysfunction and lethal arrhythmias accompanied with abnormal Ca2+ handling

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
H Inazumi ◽  
K Kuwahara ◽  
Y Kuwabara ◽  
Y Nakagawa ◽  
H Kinoshita ◽  
...  
Keyword(s):  
Heart Failure ◽  
Cardiac Function ◽  
Knockout Mice ◽  
Cardiac Dysfunction ◽  
Troponin T ◽  
Systolic Dysfunction ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Electrical Stability ◽  
Normal Cardiac Function

Abstract Background We previously demonstrated that a transcriptional repressor, neuron restrictive silencer factor (NRSF), maintains normal cardiac function and electrical stability. Transgenic mice expressing a dominant-negative mutant of NRSF in their hearts (dnNRSF-Tg) exhibit systolic dysfunction with cardiac dilation and premature death due to lethal arrhythmias like human dilated cardiomyopathy (DCM). Underlining mechanisms remain to be elucidated, however. Purpose We studied underling mechanisms by which NRSF maintains normal cardiac function to identify novel therapeutic targets for heart failure. Methods and results We generated cardiac-specific NRSF knockout mice (NRSFcKO) and confirmed that cardiac phenotypes of NRSFcKO are similar to those of dnNRSF-Tg. cDNA microarray analysis revealed that cardiac gene expression of GNAO1 that encodes Gαo, a member of inhibitory G protein Gαi family, is increased in both dnNRSF-Tg and NRSFcKO ventricles. We confirmed that GNAO1 is a direct target of NRSF through ChIP-seq analysis, reporter assay and electrophoretic mobility shift assay. In dnNRSF-Tg, pharmacological inhibition of Gαo with pertussis toxin improved systolic dysfunction and knockdown of Gαo by crossing with GNAO1 knockout mice improved not only systolic function but also frequency of ventricular arrhythmias and survival rates. Electrophysiological and biochemical analysis in ventricular myocytes obtained from dnNRSF-Tg demonstrated that genetic reduction of Gαo ameliorated abnormalities in Ca2+ handling, which include increased current density in surface sarcolemmal L-type Ca2+ channel, reduced content of sarcoplasmic reticulum Ca2+ and lowered peak of Ca2+ transient. Furthermore, genetic reduction of Gαo attenuated increased phosphorylation levels of CAMKII in dnNRSF-Tg ventricles, which presumably underlies the improvement in Ca2+ handling. In addition, we identified increased Gαo expression in ventricles of heart failure model mice induced by transverse aortic constriction and cardiac troponin T mutant DCM model mice, in both of which, genetic reduction of Gαo ameliorated cardiac dysfunction. Figure 1 Conclusions We found that increased expression of Gαo, induced by attenuation of NRSF-mediated repression, plays a crucial role in the progression of cardiac dysfunction and lethal arrhythmias by evoking Ca2+ handling abnormality. These data demonstrate that Gαo is a potential therapeutic target for heart failure.

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