scholarly journals Cardiomyocyte BRAF and type 1 RAF inhibitors promote cardiomyocyte and cardiac hypertrophy in mice in vivo

2021 ◽  
Author(s):  
Angela Clerk ◽  
Daniel N Meijles ◽  
Michelle A Hardyman ◽  
Stephen J Fuller ◽  
Sonia P Chothani ◽  
...  
Keyword(s):  
Heart Failure ◽  
Cardiac Hypertrophy ◽  
Cardiomyocyte Hypertrophy ◽  
Human Heart Failure ◽  
Endogenous Gene ◽  
Low Concentrations ◽  
Extracellular Signal ◽  
Experimental Type

The extracellular signal-regulated kinase 1/2 (ERK1/2) cascade promotes cardiomyocyte hypertrophy and is cardioprotective, with the three RAF kinases forming a node for signal integration. Our aims were to determine if BRAF is relevant for human heart failure, if BRAF promotes cardiomyocyte hypertrophy, and if Type 1 RAF inhibitors developed for cancer (that paradoxically activate ERK1/2 at low concentrations: the RAF paradox) may have the same effect. BRAF was upregulated in heart samples from patients with heart failure compared with normal controls. We assessed the effects of activated BRAF in the heart using mice with tamoxifen-activated Cre for cardiomyocyte-specific knock-in of the activating V600E mutation into the endogenous gene. We used echocardiography to measure cardiac dimensions/function. Cardiomyocyte BRAFV600E induced cardiac hypertrophy within 10 d, resulting in increased ejection fraction and fractional shortening over 6 weeks. This was associated with increased cardiomyocyte size without significant fibrosis, consistent with compensated hypertrophy. The experimental Type 1 RAF inhibitor, SB590885, and/or encorafenib (a RAF inhibitor used clinically) increased ERK1/2 phosphorylation in cardiomyocytes, and promoted hypertrophy, consistent with a RAF paradox effect. Both promoted cardiac hypertrophy in mouse hearts in vivo, with increased cardiomyocyte size and no overt fibrosis. In conclusion, BRAF potentially plays an important role in human failing hearts, activation of BRAF is sufficient to induce hypertrophy, and Type 1 RAF inhibitors promote hypertrophy via the RAF paradox. Cardiac hypertrophy resulting from these interventions was not associated with pathological features, suggesting that Type 1 RAF inhibitors may be useful to boost cardiomyocyte function.

Cacao Bean Polyphenols Inhibit Cardiac Hypertrophy and Systolic Dysfunction in Pressure Overload-induced Heart Failure Model Mice

Planta Medica ◽  
2020 ◽  
Vol 86 (17) ◽  
pp. 1304-1312
Author(s):  
Nurmila Sari ◽  
Yasufumi Katanasaka ◽  
Hiroki Honda ◽  
Yusuke Miyazaki ◽  
Yoichi Sunagawa ◽  
...  
Keyword(s):  
Heart Failure ◽  
Cardiac Hypertrophy ◽  
Gene Transcription ◽  
Binding Protein ◽  
Systolic Dysfunction ◽  
Pressure Overload ◽  
Left Ventricular ◽  
Cardiomyocyte Hypertrophy ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal

AbstractPathological stresses such as pressure overload and myocardial infarction induce cardiac hypertrophy, which increases the risk of heart failure. Cacao bean polyphenols have recently gained considerable attention for their beneficial effects on cardiovascular diseases. This study investigated the effect of cacao bean polyphenols on the development of cardiac hypertrophy and heart failure. Cardiomyocytes from neonatal rats were pre-treated with cacao bean polyphenols and then stimulated with 30 µM phenylephrine. C57BL/6j male mice were subjected to sham or transverse aortic constriction surgery and then orally administered with vehicle or cacao bean polyphenols. Cardiac hypertrophy and function were examined by echocardiography. In cardiomyocytes, cacao bean polyphenols significantly suppressed phenylephrine-induced cardiomyocyte hypertrophy and hypertrophic gene transcription. Extracellular signal-regulated kinase 1/2 and GATA binding protein 4 phosphorylation induced by phenylephrine was inhibited by cacao bean polyphenols treatment in the cardiomyocytes. Cacao bean polyphenols treatment at 1200 mg/kg significantly ameliorated left ventricular posterior wall thickness, fractional shortening, hypertrophic gene transcription, cardiac hypertrophy, cardiac fibrosis, and extracellular signal-regulated kinase 1/2 phosphorylation induced by pressure overload. In conclusion, these findings suggest that cacao bean polyphenols prevent pressure overload-induced cardiac hypertrophy and systolic dysfunction by inhibiting the extracellular signal-regulated kinase 1/2-GATA binding protein 4 pathway in cardiomyocytes. Thus, cacao bean polyphenols may be useful for heart failure therapy in humans.

Abstract MP217: Nuclease-deficient Cas9 Transcription Factors Restore Krueppel-like Factor 15 Expression In Stressed Mouse And Human Cardiomyocytes

2021 ◽  
Vol 129 (Suppl_1) ◽  
Author(s):  
Eric Schoger ◽  
Kim Rosa ◽  
Cheila Rocha ◽  
Mareike Jassyk ◽  
Shirin Doroudgar ◽  
...  
Keyword(s):  
Heart Failure ◽  
Specific Inhibitor ◽  
Induced Pluripotent Stem Cell ◽  
Cardiomyocyte Hypertrophy ◽  
Endogenous Gene ◽  
Human Cardiomyocytes ◽  
Post Surgery ◽  
Stressed Mouse ◽  
Heart Failure Progression

Transcriptional changes in cardiomyocytes drive heart failure progression, however, precise control over endogenous gene expression remains challenging. The expression of Krueppel-like factor 15 ( KLF15 ), an evolutionary conserved nuclear and cardiomyocyte specific inhibitor of WNT/CTNNB1 signalling in the heart, is lost upon cardiac remodelling, and accompanied by aberrantly active WNT/CTNNB1 resulting in heart failure progression. We investigated KLF15 expression dynamics employing CRISPR/Cas9-based tools in mouse cardiomyocytes in vivo and in human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CM) under the hypothesis that re-establishment of KLF15 levels in myocardial stress conditions prevents heart failure progression. Using a mouse model expressing enzymatically inactive Cas9 (dCas9) fused to transcriptional activators (VPR) under Myh6 -promoter control, we activated Klf15 in a murine pressure overload model by transverse aortic constriction. Delivery of Klf15 gRNAs targeted to the Klf15 promoter region via AAV9 induced Klf15 expression sufficiently to re-normalize Klf15 expression to transcript levels comparable to sham surgery hearts. This was accompanied by reduced decrease of fractional shortening as well as reduced cardiomyocyte hypertrophy in stressed Klf15 re-activated hearts compared to non-trageted (NT) gRNA hearts (n=3-8 per group, echo data from 4 and 8 weeks post-surgery). We achieved titratable KLF15 activation in dCas9VPR transgenic hiPSC-CM by selection of single and multiple gRNAs (n=3-4 replicates) and used these cells to generate human engineered myocardium by combining hiPSC-CM and fibroblasts which we subjected to isometric contractions in order to induce mechanical stress, which resulted in KLF15 expressional decrease in line with our in vivo data. This transcriptional loss was rescued in CRISPR/dCas9VPR hiPSC-CM targeted to the KLF15 locus compared to controls (n=6-9/2/4 tissues per group/casting sessions/differentiations). Additionally, TGFB1 induced cardiomyocyte stress resulted in decreased KLF15 expression levels in 2D hiPSC-CM cultures which were rescued by dCas9VPR- KLF15 targeting (n=3 experiments). In conclusion, we report controllable gene activity by CRISPR/dCas9VPR to restore the loss of KLF15 in stressed mouse and human cardiomyocytes. We furthermore evaluate the potential to gain full control over gene dose titratability with these models to validate and define novel therapeutic targets for the prevention of heart failure progression.

scholarly journals Thyroid Hormone Increases TGF-β1 in Cardiomyocytes Cultures Independently of Angiotensin II Type 1 and Type 2 Receptors

2010 ◽  
Vol 2010 ◽  
pp. 1-7 ◽  
Author(s):  
Gabriela Placoná Diniz ◽  
Marcela Sorelli Carneiro-Ramos ◽  
Maria Luiza Morais Barreto-Chaves
Keyword(s):  
Angiotensin Ii ◽  
Cardiac Hypertrophy ◽  
Transforming Growth Factor ◽  
Cardiac Fibroblasts ◽  
Angiotensin Ii Receptors ◽  
Cardiomyocyte Hypertrophy ◽  
Tgf Β1

TH-induced cardiac hypertrophyin vivois accompanied by increased cardiac Transforming Growth Factor-β1 (TGF-β1) levels, which is mediated by Angiotensin II type 1 receptors (AT1R) and type 2 receptors (AT2R). However, the possible involvement of this factor in TH-induced cardiac hypertrophy is unknown. In this study we evaluated whether TH is able to modulate TGF-β1 in isolated cardiac, as well as the possible contribution of AT1R and AT2R in this response. The cardiac fibroblasts treated withT3did not show alteration on TGF-β1 expression. However, cardiomyocytes treated withT3presented an increase in TGF-β1 expression, as well as an increase in protein synthesis. The AT1R blockade prevented theT3-induced cardiomyocyte hypertrophy, while the AT2R blockage attenuated this response. TheT3-induced increase on TGF-β1 expression in cardiomyocytes was not changed by the use of AT1R and AT2R blockers. These results indicate that Angiotensin II receptors are not implicated inT3-induced increase on TGF-βexpression and suggest that the trophic effects exerted byT3on cardiomyocytes are not dependent on the higher TGF-β1 levels, since the AT1R and AT2R blockers were able to attenuate theT3-induced cardiomyocyte hypertrophy but were not able to attenuate the increase on TGF-β1 levels promoted byT3.

scholarly journals Hispidulin Attenuates Cardiac Hypertrophy by Improving Mitochondrial Dysfunction

2020 ◽  
Vol 7 ◽  
Author(s):  
Yan Wang ◽  
Zengshuo Xie ◽  
Nan Jiang ◽  
Zexuan Wu ◽  
Ruicong Xue ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Heart Failure ◽  
Cardiac Hypertrophy ◽  
Mitochondrial Function ◽  
Specific Inhibitor ◽  
Cardiomyocyte Hypertrophy ◽  
Mitochondrial Morphology ◽  
Protective Effects

Cardiac hypertrophy is a pathophysiological response to harmful stimuli. The continued presence of cardiac hypertrophy will ultimately develop into heart failure. The mitochondrion is the primary organelle of energy production, and its dysfunction plays a crucial role in the progressive development of heart failure from cardiac hypertrophy. Hispidulin, a natural flavonoid, has been substantiated to improve energy metabolism and inhibit oxidative stress. However, how hispidulin regulates cardiac hypertrophy and its underlying mechanism remains unknown. We found that hispidulin significantly inhibited pressure overload-induced cardiac hypertrophy and improved cardiac function in vivo and blocked phenylephrine (PE)-induced cardiomyocyte hypertrophy in vitro. We further proved that hispidulin remarkably improved mitochondrial function, manifested by increased electron transport chain (ETC) subunits expression, elevated ATP production, increased oxygen consumption rates (OCR), normalized mitochondrial morphology, and reduced oxidative stress. Furthermore, we discovered that Sirt1, a well-recognized regulator of mitochondrial function, might be a target of hispidulin, as evidenced by its upregulation after hispidulin treatment. Cotreatment with EX527 (a Sirt1-specific inhibitor) and hispidulin nearly completely abolished the antihypertrophic and protective effects of hispidulin on mitochondrial function, providing further evidence that Sirt1 could be the pivotal downstream effector of hispidulin in regulating cardiac hypertrophy.

scholarly journals LCZ696 Ameliorates Oxidative Stress and Pressure Overload-Induced Pathological Cardiac Remodeling by Regulating the Sirt3/MnSOD Pathway

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Shi Peng ◽  
Xiao-feng Lu ◽  
Yi-ding Qi ◽  
Jing Li ◽  
Juan Xu ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Heart Failure ◽  
Cardiac Hypertrophy ◽  
Pressure Overload ◽  
Neonatal Rat ◽  
Cardiomyocyte Hypertrophy ◽  
Rat Cardiomyocytes ◽  
Pathological Cardiac Hypertrophy

Aims. We aimed to investigate whether LCZ696 protects against pathological cardiac hypertrophy by regulating the Sirt3/MnSOD pathway. Methods. In vivo, we established a transverse aortic constriction animal model to establish pressure overload-induced heart failure. Subsequently, the mice were given LCZ696 by oral gavage for 4 weeks. After that, the mice underwent transthoracic echocardiography before they were sacrificed. In vitro, we introduced phenylephrine to prime neonatal rat cardiomyocytes and small-interfering RNA to knock down Sirt3 expression. Results. Pathological hypertrophic stimuli caused cardiac hypertrophy and fibrosis and reduced the expression levels of Sirt3 and MnSOD. LCZ696 alleviated the accumulation of oxidative reactive oxygen species (ROS) and cardiomyocyte apoptosis. Furthermore, Sirt3 deficiency abolished the protective effect of LCZ696 on cardiomyocyte hypertrophy, indicating that LCZ696 induced the upregulation of MnSOD and phosphorylation of AMPK through a Sirt3-dependent pathway. Conclusions. LCZ696 may mitigate myocardium oxidative stress and apoptosis in pressure overload-induced heart failure by regulating the Sirt3/MnSOD pathway.

scholarly journals Cardiac Overexpression of Myotrophin Triggers Myocardial Hypertrophy and Heart Failure in Transgenic Mice

2004 ◽  
Vol 279 (19) ◽  
pp. 20422-20434 ◽  
Author(s):  
Sagartirtha Sarkar ◽  
Douglas W. Leaman ◽  
Sudhiranjan Gupta ◽  
Parames Sil ◽  
David Young ◽  
...  
Keyword(s):  
Heart Failure ◽  
Transgenic Mice ◽  
Cardiac Hypertrophy ◽  
Gene Clusters ◽  
The United States ◽  
Cellular Interaction ◽  
Marker Genes ◽  
Human Heart Failure

Cardiac hypertrophy and heart failure remain leading causes of death in the United States. Many studies have suggested that, under stress, myocardium releases factors triggering protein synthesis and stimulating myocyte growth. We identified and cloned myotrophin, a 12-kDa protein from hypertrophied human and rat hearts. Myotrophin (whose gene is localized on human chromosome 7q33) stimulates myocyte growth and participates in cellular interaction that initiates cardiac hypertrophyin vitro. In this report, we present data on the pathophysiological significance of myotrophinin vivo, showing the effects of overexpression of cardio-specific myotrophin in transgenic mice in which cardiac hypertrophy occurred by 4 weeks of age and progressed to heart failure by 9-12 months. This hypertrophy was associated with increased expression of proto-oncogenes, hypertrophy marker genes, growth factors, and cytokines, with symptoms that mimicked those of human cardiomyopathy, functionally and morphologically. This model provided a unique opportunity to analyze gene clusters that are differentially up-regulated during initiation of hypertrophyversustransition of hypertrophy to heart failure. Importantly, changes in gene expression observed during initiation of hypertrophy were significantly different from those seen during its transition to heart failure. Our data show that overexpression of myotrophin results in initiation of cardiac hypertrophy that progresses to heart failure, similar to changes in human heart failure. Knowledge of the changes that take place as a result of overexpression of myotrophin at both the cellular and molecular levels will suggest novel strategies for treatment to prevent hypertrophy and its progression to heart failure.

P1618A polymethoxy flavonoid, Nobiletin, Has a therapeutic potency against the development of heart failure through NBP1 activation

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
Y Sunagawa ◽  
M Funamoto ◽  
K Shimizu ◽  
S Shimizu ◽  
Y Katanasaka ◽  
...  
Keyword(s):  
Heart Failure ◽  
Cardiac Hypertrophy ◽  
Natural Compound ◽  
Binding Protein ◽  
Systolic Dysfunction ◽  
Myocardial Cell ◽  
Cardiomyocyte Hypertrophy ◽  
Target Molecule ◽  
Cell Hypertrophy

Abstract Introduction Maladaptive hypertrophy is being recognized as a critical event during the development of heart failure. The control of cardiac hypertrophy may be one of the therapeutic strategy for heart failure therapy. In our previous study, we screened natural compound library and found that a natural compound, Nobiletin, could inhibit cardiomyocyte hypertrophy in culture. Nobiletin has various useful effects such as anti-cancer, anti-inflammation, and anti-oxidant and may be applicable to pharmacological therapy for heart failure. Hypothesis We thought that nobiletin might prevent the development of heart failure in vivo and investigated the target molecule of Nobiletin in the heart. Methods and results In primary cardiomyocytes, Nobiletin significantly inhibited phenylephrine (PE)-induced hypertrophic responses such as increases in cell size and hypertrophic gene transcription, such as ANF and BNP. C57BL6 mice were subjected to sham or transarotic constriction (TAC). Oral administrations of Nobiletin (20 mg/kg/day) or vehicle were repeated for 8 weeks. Nobiletin treatment significantly prevented TAC-induced increases in PWT and systolic dysfunction. Nobiletin also suppressed TAC-induced myocardial cell hypertrophy, perivascular fibrosis, and hypertrophic gene transcriptions. To investigate the target molecule of Nobiletin, Nobiletin-binding proteins were purified from rat heart using biotin-conjugated Nobiletin. We identified 162 novel binding protein of Nobiletin by LC/MS-MS. One of them, Nobiletin-binding protein 1 (NBP1) related to cellular metabolic pathway. Pulldown assay demonstrated that biotin-conjugated Nobiletin, but not biotin, directly interacted with recombinant NBP1. In vitro enzyme assay showed that Nobiletin enhanced NBP1 activity. Although NBP1 knockdown could not affect PE-induced hypertrophic response gene transcriptions and cardiomyocyte hypertrophy, NBP1 knockdown failed to exhibit Nobiletin-mediated anti-hypertrophic effects. NBP1-KO mice and WT mice were subjected to sham or TAC and randomly divided into two groups: Nobiletin (20 mg/kg/day) and vehicle. After 8 weeks, Nobiletin significantly improved TAC-induced cardiac hypertrophy and systolic dysfunction in WT mice but not in NBP1-KO mice. Nobiletin also prevented TAC-induced increases in HW/BW rate, myocardial cell hypertrophy, and mRNA levels of ANF and β-MHC in WT mice but not in NBP1-KO mice. Conclusions In this study, we demonstrate that Nobiletin inhibits cardiomyocyte hypertrophy and the development of heart failure in vivo. NBP1 activity is required to exhibit therapeutic potency of Nobiletin for heart failure. These finding suggest that a natural compound, nobiletin, might be a candidate for heart failure agent in human. Acknowledgement/Funding This work was supported by JSPS KAKENHI Grant.

scholarly journals Betulinic Acid Protects DOX-Triggered Cardiomyocyte Hypertrophy Response through the GATA-4/Calcineurin/NFAT Pathway

Molecules ◽  
2020 ◽  
Vol 26 (1) ◽  
pp. 53
Author(s):  
Jung Joo Yoon ◽  
Chan Ok Son ◽  
Hye Yoom Kim ◽  
Byung Hyuk Han ◽  
Yun Jung Lee ◽  
...  
Keyword(s):  
Heart Failure ◽  
Cardiac Hypertrophy ◽  
Natriuretic Peptide ◽  
Betulinic Acid ◽  
Cardiomyocyte Hypertrophy ◽  
Ros Generation ◽  
H9c2 Cells ◽  
Myosin Light Chain 2 ◽  
Cardiovascular Morbidity And Mortality

Cardiac hypertrophy is a major risk factor for heart failure and leads to cardiovascular morbidity and mortality. Doxorubicin (DOX) is regarded as one of the most potent anthracycline antibiotic agents; however, its clinical usage has some limitations because it has serious cardiotoxic side effects such as dilated cardiomyopathy and congestive heart failure. Betulinic acid (BA) is a pentacyclic-cyclic lupane-type triterpene that has been reported to have anti-bacterial, anti-inflammatory, anti-vascular neogenesis, and anti-fibrotic effects. However, there is no study about its direct effect on DOX induced cardiac hypertrophy and apoptosis. The present study aims to investigate the effect of BA on DOX-induced cardiomyocyte hypertrophy and apoptosis in vitro in H9c2 cells. The H9c2 cells were stimulated with DOX (1 µM) in the presence or absence of BA (0.1–1 μM) and incubated for 24 h. The results of the present study indicated that DOX induces the increase cell surface area and the upregulation of hypertrophy markers including atrial natriuretic peptide (ANP), B-type natriuretic peptide (BNP), beta-myosin heavy chain (β-MHC), and Myosin Light Chain-2 (MLC2) in H9c2 cells. However, the pathological hypertrophic responses were downregulated after BA treatment. Moreover, phosphorylation of JNK, ERK, and p38 in DOX treated H9c2 cells was blocked by BA. As a result of measuring the change in ROS generation using DCF-DA, BA significantly inhibited DOX-induced the production of intracellular reactive oxygen species (ROS) when BA was treated at a concentration of over 0.1 µM. DOX-induced activation of GATA-4 and calcineurin/NFAT-3 signaling pathway were remarkably improved by pre-treating of BA to H9c2 cells. In addition, BA treatment significantly reduced DOX-induced cell apoptosis and protein expression levels of Bax and cleaved caspase-3/-9, while the expression of Bcl-2 was increased by BA. Therefore, BA can be a potential treatment for cardiomyocyte hypertrophy and apoptosis that lead to sudden heart failure.

scholarly journals Empagliflozin improves endothelial and cardiomyocyte function in human heart failure with preserved ejection fraction via reduced pro-inflammatory-oxidative pathways and protein kinase Gα oxidation

2020 ◽  
Author(s):  
Detmar Kolijn ◽  
Steffen Pabel ◽  
Yanna Tian ◽  
Mária Lódi ◽  
Melissa Herwig ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Heart Failure ◽  
Ejection Fraction ◽  
Linear Regression Analysis ◽  
Lipid Peroxide ◽  
Dependent Manner ◽  
Preserved Ejection Fraction ◽  
Human Heart Failure ◽  
Stress Dependent

Abstract Aims Sodium-glucose-cotransporter-2 inhibitors showed favourable cardiovascular outcomes, but the underlying mechanisms are still elusive. This study investigated the mechanisms of empagliflozin in human and murine heart failure with preserved ejection fraction (HFpEF). Methods and results The acute mechanisms of empagliflozin were investigated in human myocardium from patients with HFpEF and murine ZDF obese rats, which were treated in vivo. As shown with immunoblots and ELISA, empagliflozin significantly suppressed increased levels of ICAM-1, VCAM-1, TNF-α, and IL-6 in human and murine HFpEF myocardium and attenuated pathological oxidative parameters (H2O2, 3-nitrotyrosine, GSH, lipid peroxide) in both cardiomyocyte cytosol and mitochondria in addition to improved endothelial vasorelaxation. In HFpEF, we found higher oxidative stress-dependent activation of eNOS leading to PKGIα oxidation. Interestingly, immunofluorescence imaging and electron microscopy revealed that oxidized PKG1α in HFpEF appeared as dimers/polymers localized to the outer-membrane of the cardiomyocyte. Empagliflozin reduced oxidative stress/eNOS-dependent PKGIα oxidation and polymerization resulting in a higher fraction of PKGIα monomers, which translocated back to the cytosol. Consequently, diminished NO levels, sGC activity, cGMP concentration, and PKGIα activity in HFpEF increased upon empagliflozin leading to improved phosphorylation of myofilament proteins. In skinned HFpEF cardiomyocytes, empagliflozin improved cardiomyocyte stiffness in an anti-oxidative/PKGIα-dependent manner. Monovariate linear regression analysis confirmed the correlation of oxidative stress and PKGIα polymerization with increased cardiomyocyte stiffness and diastolic dysfunction of the HFpEF patients. Conclusion Empagliflozin reduces inflammatory and oxidative stress in HFpEF and thereby improves the NO–sGC–cGMP–cascade and PKGIα activity via reduced PKGIα oxidation and polymerization leading to less pathological cardiomyocyte stiffness.

scholarly journals CXCR4 Cardiac Specific Knockout Mice Develop a Progressive Cardiomyopathy

2019 ◽  
Vol 20 (9) ◽  
pp. 2267 ◽  
Author(s):  
Thomas J. LaRocca ◽  
Perry Altman ◽  
Andrew A. Jarrah ◽  
Ron Gordon ◽  
Edward Wang ◽  
...  
Keyword(s):  
Heart Failure ◽  
Cardiac Hypertrophy ◽  
Cardiac Myocytes ◽  
Knockout Mice ◽  
Cardiac Dysfunction ◽  
Left Ventricular ◽  
Subsequent Increase ◽  
Transition Electron Microscopy ◽  
Cardiac Phenotype

Activation of multiple pathways is associated with cardiac hypertrophy and heart failure. We previously published that CXCR4 negatively regulates β-adrenergic receptor (β-AR) signaling and ultimately limits β-adrenergic diastolic (Ca2+) accumulation in cardiac myocytes. In isolated adult rat cardiac myocytes; CXCL12 treatment prevented isoproterenol-induced hypertrophy and interrupted the calcineurin/NFAT pathway. Moreover; cardiac specific CXCR4 knockout mice show significant hypertrophy and develop cardiac dysfunction in response to chronic catecholamine exposure in an isoproterenol-induced (ISO) heart failure model. We set this study to determine the structural and functional consequences of CXCR4 myocardial knockout in the absence of exogenous stress. Cardiac phenotype and function were examined using (1) gated cardiac magnetic resonance imaging (MRI); (2) terminal cardiac catheterization with in vivo hemodynamics; (3) histological analysis of left ventricular (LV) cardiomyocyte dimension; fibrosis; and; (4) transition electron microscopy at 2-; 6- and 12-months of age to determine the regulatory role of CXCR4 in cardiomyopathy. Cardiomyocyte specific-CXCR4 knockout (CXCR4 cKO) mice demonstrate a progressive cardiac dysfunction leading to cardiac failure by 12-months of age. Histological assessments of CXCR4 cKO at 6-months of age revealed significant tissue fibrosis in knockout mice versus wild-type. The expression of atrial naturietic factor (ANF); a marker of cardiac hypertrophy; was also increased with a subsequent increase in gross heart weights. Furthermore, there were derangements in both the number and the size of the mitochondria within CXCR4 cKO hearts. Moreover, CXCR4 cKO mice were more sensitive to catocholamines, their response to β-AR agonist challenge via acute isoproterenol (ISO) infusion demonstrated a greater increase in ejection fraction, dp/dtmax, and contractility index. Interestingly, prior to ISO infusion, there were significant differences in baseline hemodynamics between the CXCR4 cKO compared to littermate controls. However, upon administering ISO, the CXCR4 cKO responded in a robust manner overcoming the baseline hemodynamic deficits reaching WT values supporting our previous data that CXCR4 negatively regulates β-AR signaling. This further supports that, in the absence of the physiologic negative modulation, there is an overactivation of down-stream pathways, which contribute to the development and progression of contractile dysfunction. Our results demonstrated that CXCR4 plays a non-developmental role in regulating cardiac function and that CXCR4 cKO mice develop a progressive cardiomyopathy leading to clinical heart failure.

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