Cardiac myocyte intrinsic contractility and calcium handling deficits underlie heart organ dysfunction in murine cancer cachexia

AbstractCachexia is a muscle wasting syndrome occurring in many advanced cancer patients. Cachexia significantly increases cancer morbidity and mortality. Cardiac atrophy and contractility deficits have been observed in patients and in animal models with cancer cachexia, which may contribute to cachexia pathophysiology. However, underlying contributors to decreased in vivo cardiac contractility are not well understood. In this study, we sought to distinguish heart-intrinsic changes from systemic factors contributing to cachexia-associated cardiac dysfunction. We hypothesized that isolated heart and cardiac myocyte functional deficits underlie in vivo contractile dysfunction. To test this hypothesis, isolated heart and cardiac myocyte function was measured in the colon-26 adenocarcinoma murine model of cachexia. Ex vivo perfused hearts from cachectic animals exhibited marked contraction and relaxation deficits during basal and pacing conditions. Isolated myocytes displayed significantly decreased peak contraction and relaxation rates, which was accompanied by decreased peak calcium and decay rates. This study uncovers significant organ and cellular-level functional deficits in cachectic hearts outside of the catabolic in vivo environment, which is explained in part by impaired calcium cycling. These data provide insight into physiological mechanisms of cardiomyopathy in cachexia, which is critical for the ultimate development of effective treatments for patients.

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Na+/Ca2+ exchanger-1 protects against systolic failure in the Akitains2 model of diabetic cardiomyopathy via a CXCR4/NF-κB pathway

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.01198.2011 ◽

2012 ◽

Vol 303 (3) ◽

pp. H353-H367 ◽

Cited By ~ 22

Author(s):

Thomas J. LaRocca ◽

Frank Fabris ◽

Jiqiu Chen ◽

Daniel Benhayon ◽

Shihong Zhang ◽

...

Keyword(s):

Diabetic Cardiomyopathy ◽

Cardiac Myocyte ◽

Calcium Handling ◽

Compensatory Mechanism ◽

Calcium Dependent ◽

Plasmic Reticulum ◽

Diabetic Model

Diabetic cardiomyopathy is characterized, in part, by calcium handling imbalances associated with ventricular dysfunction. The cardiac Na+/Ca2+ exchanger 1 (NCX1) has been implicated as a compensatory mechanism in response to reduced contractility in the heart; however, its role in diabetic cardiomyopathy remains unknown. We aimed to fully characterize the Akitains2 murine model of type 1 diabetes through assessing cardiac function and NCX1 regulation. The CXCL12/CXCR4 chemokine axis is well described in its cardioprotective effects via progenitor cell recruitment postacute myocardial infarction; however, it also functions in regulating calcium dependent processes in the cardiac myocyte. We therefore investigated the potential impact of CXCR4 in diabetic cardiomyopathy. Cardiac performance in the Akitains2 mouse was monitored using echocardiography and in vivo pressure-volume analysis. The Akitains2 mouse is protected against ventricular systolic failure evident at both 5 and 12 mo of age. However, the preserved contractility was associated with a decreased sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA2a)/phospholamban ratio and increased NCX1 content. Direct myocardial injection of adenovirus encoding anti-sense NCX1 significantly decreased NCX1 expression and induced systolic failure in the Akitains2 mouse. CXCL12 and CXCR4 were both upregulated in the Akitains2 heart, along with an increase in IκB-α and NF-κB p65 phosphorylation. We demonstrated that CXCR4 activation upregulates NCX1 expression through a NF-κB-dependent signaling pathway in the cardiac myocyte. In conclusion, the Akitains2 type 1 diabetic model is protected against systolic failure due to increased NCX1 expression. In addition, our studies reveal a novel role of CXCR4 in the diabetic heart by regulating NCX1 expression via a NF-κB-dependent mechanism.

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Remodeling of calcium handling in skeletal muscle through PGC-1α: impact on force, fatigability, and fiber type

AJP Cell Physiology ◽

10.1152/ajpcell.00190.2011 ◽

2012 ◽

Vol 302 (1) ◽

pp. C88-C99 ◽

Cited By ~ 34

Author(s):

Serge Summermatter ◽

Raphael Thurnheer ◽

Gesa Santos ◽

Barbara Mosca ◽

Oliver Baum ◽

...

Keyword(s):

Skeletal Muscle ◽

Calcium Release ◽

Ex Vivo ◽

Fiber Type ◽

Force Production ◽

Calcium Handling ◽

Peroxisome Proliferator ◽

Peroxisome Proliferator Activated Receptor ◽

Calcium Clearance

Regular endurance exercise remodels skeletal muscle, largely through the peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α). PGC-1α promotes fiber type switching and resistance to fatigue. Intracellular calcium levels might play a role in both adaptive phenomena, yet a role for PGC-1α in the adaptation of calcium handling in skeletal muscle remains unknown. Using mice with transgenic overexpression of PGC-1α, we now investigated the effect of PGC-1α on calcium handling in skeletal muscle. We demonstrate that PGC-1α induces a quantitative reduction in calcium release from the sarcoplasmic reticulum by diminishing the expression of calcium-releasing molecules. Concomitantly, maximal muscle force is reduced in vivo and ex vivo. In addition, PGC-1α overexpression delays calcium clearance from the myoplasm by interfering with multiple mechanisms involved in calcium removal, leading to higher myoplasmic calcium levels following contraction. During prolonged muscle activity, the delayed calcium clearance might facilitate force production in mice overexpressing PGC-1α. Our results reveal a novel role of PGC-1α in altering the contractile properties of skeletal muscle by modulating calcium handling. Importantly, our findings indicate PGC-1α to be both down- as well as upstream of calcium signaling in this tissue. Overall, our findings suggest that in the adaptation to chronic exercise, PGC-1α reduces maximal force, increases resistance to fatigue, and drives fiber type switching partly through remodeling of calcium transients, in addition to promoting slow-type myofibrillar protein expression and adequate energy supply.

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Abstract 5572: Endothelial-Selective Deletion of Neuregulin-1 Leads to Impaired Tolerance of Ischemic Injury

Circulation ◽

10.1161/circ.118.suppl_18.s_577-b ◽

2008 ◽

Vol 118 (suppl_18) ◽

Author(s):

Qunhua Huang ◽

April Kalinowski ◽

Kashif Jafri ◽

Monica Palmeri ◽

Raymond R Russell ◽

...

Keyword(s):

Cardiac Function ◽

Glucose Uptake ◽

Cardiac Myocyte ◽

Ex Vivo ◽

Ischemia Reperfusion ◽

Ischemic Injury ◽

Left Ventricular ◽

Neuregulin 1 ◽

Compound C

The neuregulin-1 (NRG)/erbB signaling axis is emerging as an important mediator of endothelial/myocyte crosstalk. We have previously shown that NRG can protect cardiac myocytes from apoptosis induced by hypoxic injury and that endothelial cells can provide this NRG in an ex vivo co-culture model. To extend this observation to an intact animal system, we have generated mice with inducible and endothelial-selective deletion of NRG. We hypothesized that animals with decreased endothelial NRG expression would be more susceptible to ischemic injury. Mice carrying a transgene for tamoxifen-inducible expression of cre recombinase under control of the Tie2 promoter were crossed with those carrying homozygously floxed NRG-1 genes. Serial echocardiographic measurements of cardiac function were performed before, during and after tamoxifen induction. There was no significant decrease in cardiac function following the completion of the induction (NRG knockout) protocol. Hearts from these mice underwent a global ischemia/reperfusion protocol in the Langendorff mode. Both resting and post-ischemic +/−dP/dT and left ventricular developed pressure were impaired in the animals with endothelial selective NRG deletion compared to non-induced transgenics or tamoxifen-induced controls. Hearts from the NRG deleted animals released more CPK and contained significantly more apoptotic nuclei compared to controls after ischemia/reperfusion, supporting the idea that endothelial-derived NRG can protect myocytes against apoptosis in vivo. Another mechanism by which loss of NRG may contribute to cardiac dysfunction in the setting of ischemia is by altering cardiac myocyte glucose uptake. We have shown that adult rat cardiomyocyte glucose uptake is significantly increased in response to NRG and that this response is abrogated partially by wortmannin, but completely by wortmannin plus compound C (an inhibitor of AMP-activated protein kinase), suggesting that both AKT and AMPK dependent pathways of glucose uptake may be activated by NRG in adult myocytes. Thus, we conclude that NRG plays an important role in preservation of cardiac myocyte function in vivo and that this may occur as a result of both protection against apoptosis and enhanced glucose metabolism.

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Cardiac responses of rats submitted to postnatal protein restriction

Applied Physiology Nutrition and Metabolism ◽

10.1139/h2012-017 ◽

2012 ◽

Vol 37 (3) ◽

pp. 455-462 ◽

Cited By ~ 1

Author(s):

Tatiane Moisés Murça ◽

Tatiana Soares dos Reis Magno ◽

Marilda Luz de Andrade De Maria ◽

Carolina Andrade Bragança Capuruço ◽

Deoclécio Alves Chianca ◽

...

Keyword(s):

Cardiac Function ◽

Ex Vivo ◽

Isolated Heart ◽

Left Ventricular ◽

Current Data ◽

Protein Restriction ◽

Fiber Density ◽

Arterial Blood ◽

Male Wistar Rats

Undernutrition during critical stages of development and childhood has important effects on cardiovascular homeostasis. The present study was undertaken to evaluate the in vivo and ex vivo cardiac function of rats submitted to postnatal protein restriction. Male Wistar rats (28 days old) were fed a regular (20%) or low-protein (6%) diet over 5 weeks. After this period, cardiac function was analyzed by echocardiography and isolated heart preparation. Furthermore, the density of cardiac noradrenergic fibers and hematological profile were evaluated. We found that malnourished rats exhibited elevated arterial blood pressure, increased fractional shortening (echocardiography), increased systolic tension, increased ±dT/dt (isolated heart technique), impaired diastolic function characterized by a slight increase in the left ventricular end-diastolic diameter (echocardiography) and decreased diastolic tension (isolated heart technique), and cardiac hypertrophy evidenced by augmentation of the posterior left ventricular wall and discrete hematological changes. In addition, malnourished rats exhibited increased noradrenergic fiber density in their hearts (0.08% ± 0.02% area in control rats vs. 0.17% ± 0.03% area in malnourished rats). Our current data demonstrate that postnatal protein restriction causes cardiac adaptation characterized by an early overworking heart. This is at least in part mediated by an increase in the efferent sympathetic fibers to the heart. These findings provide important information for efforts to prevent and manage the consequences of undernutrition in the human population.

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Abstract 448: The Loss of Rad GTPase Protects Against Infarction-induced Myocardial Remodeling, Scar Formation, and Decompensatory Dilation

Circulation Research ◽

10.1161/res.119.suppl_1.448 ◽

2016 ◽

Vol 119 (suppl_1) ◽

Author(s):

Janet R Manning ◽

Bryana M Levitan ◽

Ayman Haroun ◽

Catherine N Withers ◽

Prabhakara R Nagareddy ◽

...

Keyword(s):

Contractile Function ◽

Ex Vivo ◽

Neutrophil Infiltration ◽

Left Ventricular ◽

Small Gtpase ◽

Calcium Handling ◽

Myocardial Inflammation ◽

Loss Of Function ◽

Ventricular Dilation

Rationale: Myocardial infarction (MI) is a leading cause of death in the U.S. A non-contractile infarct compromises the overall mechanical function of the heart, reducing cardiac output and triggering decompensatory ventricular dilation. Rad GTPase, a member of the small GTPase RGK (Rem, Gem, Kir) family, is a calcium channel blocker that is endogenously expressed in the myocardium. We have previously shown that Rad deletion in mice results in increased Ca 2+ handling and a sustained non-pathological improvement in left ventricular function compared to wildtype. Hypothesis: Rad-ablation attenuates post-ischemic loss of function, resulting in reduced remodeling and improved long-term contractility. Methods and Results: We subjected Rad-deficient mice to ligation of the left anterior descending (LAD) coronary artery, and monitored cardiac function using echocardiography. We found that Rad deletion reduces both mortality and contractile dysfunction after MI, as well as ventricular dilation over five weeks. This improvement is also accompanied by preserved calcium handling in isolated myocytes. Histological and MRI examination of both ex vivo global ischemia and in vivo 24 hour LAD ligated myocardium revealed that initial infarct size is comparable between knockout and wildtype. We found that Rad loss reduced scar development and elongation independent of preserving tissue viability. Investigation of inflammatory pathways to account for this revealed increased expression of the anti-inflammatory protein thrombospondin accompanied by a reduction in neutrophil infiltration into the myocardium after MI. Conclusion: Rad deletion results in reduced cardiac remodeling, diminished myocardial inflammation, and improved contractile function after MI.

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A Novel Ex Vivo Heart Model for the Assessment of Cardiac Pacing Systems

Journal of Biomechanical Engineering ◽

10.1115/1.2049312 ◽

2005 ◽

Vol 127 (6) ◽

pp. 894-898 ◽

Cited By ~ 12

Author(s):

Timothy G. Laske ◽

Nicholas D. Skadsberg ◽

Paul A. Iaizzo

Keyword(s):

Ex Vivo ◽

Isolated Heart ◽

Cardiac Pacing ◽

P Wave ◽

Tissue Interface ◽

The Right ◽

Endocardial Pacing ◽

The Impact ◽

Heart Apparatus

Background: Advances in endocardial device design have been limited by the inability to visualize the device-tissue interface. The purpose of this study was to assess the validity of an isolated heart approach, which allows direct ex vivo intracardiac visualization, as a research tool for studying endocardial pacing systems. Method of approach: Endocardial pacing leads were implanted in the right atria and ventricles of intact swine (n=8) under fluoroscopic guidance. After collection of pacing and sensing performance parameters, the hearts were excised with the leads intact and reanimated on the isolated heart apparatus, and parameters again recorded. Results: Atrial ex vivo parameters significantly decreased compared with in vivo measurements: P-wave amplitudes by 39%, slew rates by 61%, and pacing impedances by 42% (p<0.05 for each). Similarly, several ventricular ex vivo parameters decreased: R-wave amplitudes by 39%, slew rates by 62%, and pacing impedances by 31%. In contrast, both atrial (4.4±2.8 vs 3.3±2.8V; p=ns) and ventricular thresholds increased (1.2±0.7 vs 0.6±0.1V; p<0.05 for all). Three distinct phenomena were observed at the lead-tissue interface. Normal implants (70%) demonstrated minimal tissue distortion and resulted in elevated impedance and threshold values. Three implants (13%) resulted in severe tissue distortion and/or tissue wrapping and were associated with highly elevated pacing parameters. Tissue coring occurred in four implants (17%) where the lead would spin freely in the tissue after overtorquing of the lead. Conclusions: The utility of the isolated heart approach was demonstrated as a tool for the design and assessment of the performance of endocardial pacing systems. Specifically, the ability to visualize device-heart interactions allows new insights into the impact of product design and clinical factors on lead performance and successful implantation.

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1178Unsuspected role of the cardiac PKA type I in excitation-contraction coupling and in heart failure development

European Heart Journal ◽

10.1093/eurheartj/ehz748.0020 ◽

2019 ◽

Vol 40 (Supplement_1) ◽

Author(s):

M Gandon-Renard ◽

I Bedioune ◽

S Karam ◽

A Varin ◽

P Lechene ◽

...

Keyword(s):

Heart Failure ◽

Ex Vivo ◽

Cardiac Contractility ◽

Cardiac Contraction ◽

Type I ◽

Excitation Contraction Coupling ◽

Contraction Coupling ◽

Contraction And Relaxation

Abstract The cAMP-dependent protein kinase (PKA) consists of two regulatory (R) and two catalytic (C) subunits and comprises two subtypes, PKAI and PKAII, defined by the nature of their regulatory subunits, RIα and RIIα respectively. Whereas PKAII is thought to play a key role in β-adrenergic (β-AR) regulation of cardiac contractility, the function of PKAI is unclear. To address this question, we generated mice with cardiomyocyte-specific and conditional invalidation of the RIα subunit of PKA. Tamoxifen injection in 8 weeks-old mice resulted in a >70% decrease in RIα protein without modification of other PKA subunits, which was associated with ∼2-fold increased basal PKA activity in RIα-KO mice (p<0.05, N=6/group). This translated into enhanced cardiac contraction and relaxation, as observed in vivo by increased fractional shortening and E-wave velocity (p<0.05, N=10/group) and ex vivo by increased LV pressure and maximal rate of contraction and relaxation (p<0.05, N=9/group). L-type Ca2+ current density was increased in ventricular myocytes from RIα-KO, and β-AR stimulation was decreased by ∼50% (p<0.05, n=38 cells for WT, and, n=40 for RIα-KO). Consistently, Ca2+ transients amplitude and relaxation kinetics were increased, along with increased occurrence of Ca2+ sparks and waves (p<0.05, n=44 cells for WT, and, n=50 for RIα KO). Phosphorylation of Ca2+ channels (CaV1.2), PLB, RyR2 and cMyBP-C at PKA sites was increased >2-fold (p<0.05, N=6/group) in RIα KO without modification of total protein expression. With age, these mice developed a congestive heart failure (HF) phenotype with massive hypertrophy and fibrosis which eventually led to death in 50% of RIα-KO mice at 50 weeks (versus 0% in WT, p<0.01). These results reveal a previously unsuspected role of PKA type I in cardiac excitation-contraction coupling and HF.

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β3-Adrenoceptor activation relieves oxidative inhibition of the cardiac Na+-K+ pump in hyperglycemia induced by insulin receptor blockade

AJP Cell Physiology ◽

10.1152/ajpcell.00071.2015 ◽

2015 ◽

Vol 309 (5) ◽

pp. C286-C295 ◽

Cited By ~ 17

Author(s):

Keyvan Karimi Galougahi ◽

Chia-Chi Liu ◽

Alvaro Garcia ◽

Natasha A. Fry ◽

Elisha J. Hamilton ◽

...

Keyword(s):

Oxidative Stress ◽

Nadph Oxidase ◽

Insulin Receptor ◽

Cardiac Myocytes ◽

Cardiac Myocyte ◽

Ex Vivo ◽

Pump Current ◽

Cardiovascular Complications ◽

Oxidative Modification

Dysregulated nitric oxide (NO)- and superoxide (O2·−)-dependent signaling contributes to the pathobiology of diabetes-induced cardiovascular complications. We examined if stimulation of β3-adrenergic receptors (β3-ARs), coupled to endothelial NO synthase (eNOS) activation, relieves oxidative inhibition of eNOS and the Na+-K+ pump induced by hyperglycemia. Hyperglycemia was established in male New Zealand White rabbits by infusion of the insulin receptor antagonist S961 for 7 days. Hyperglycemia increased tissue and blood indexes of oxidative stress. It induced glutathionylation of the Na+-K+ pump β1-subunit in cardiac myocytes, an oxidative modification causing pump inhibition, and reduced the electrogenic pump current in voltage-clamped myocytes. Hyperglycemia also increased glutathionylation of eNOS, which causes its uncoupling, and increased coimmunoprecipitation of cytosolic p47 phox and membranous p22 phox NADPH oxidase subunits, consistent with NADPH oxidase activation. Blocking translocation of p47 phox to p22 phox with the gp91ds-tat peptide in cardiac myocytes ex vivo abolished the hyperglycemia-induced increase in glutathionylation of the Na+-K+ pump β1-subunit and decrease in pump current. In vivo treatment with the β3-AR agonist CL316243 for 3 days eliminated the increase in indexes of oxidative stress, decreased coimmunoprecipitation of p22 phox with p47 phox, abolished the hyperglycemia-induced increase in glutathionylation of eNOS and the Na+-K+ pump β1-subunit, and abolished the decrease in pump current. CL316243 also increased coimmunoprecipitation of glutaredoxin-1 with the Na+-K+ pump β1-subunit, which may reflect facilitation of deglutathionylation. In vivo β3-AR activation relieves oxidative inhibition of key cardiac myocyte proteins in hyperglycemia and may be effective in targeting the deleterious cardiac effects of diabetes.

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DREADD technology reveals major impact of Gq signalling on cardiac electrophysiology

Cardiovascular Research ◽

10.1093/cvr/cvy251 ◽

2018 ◽

Vol 115 (6) ◽

pp. 1052-1066 ◽

Cited By ~ 6

Author(s):

Elisabeth Kaiser ◽

Qinghai Tian ◽

Michael Wagner ◽

Monika Barth ◽

Wenying Xian ◽

...

Keyword(s):

Cardiac Function ◽

Cardiac Electrophysiology ◽

Striated Muscle ◽

Ex Vivo ◽

Isolated Heart ◽

Phosphorylation Site ◽

Muscle Creatine Kinase ◽

Electrophysiological Properties ◽

Transgenic Mouse Line

Abstract Aims Signalling via Gq-coupled receptors is of profound importance in many cardiac diseases such as hypertrophy and arrhythmia. Nevertheless, owing to their widespread expression and the inability to selectively stimulate such receptors in vivo, their relevance for cardiac function is not well understood. We here use DREADD technology to understand the role of Gq-coupled signalling in vivo in cardiac function. Methods and results We generated a novel transgenic mouse line that expresses a Gq-coupled DREADD (Dq) in striated muscle under the control of the muscle creatine kinase promotor. In vivo injection of the DREADD agonist clozapine-N-oxide (CNO) resulted in a dose-dependent, rapid mortality of the animals. In vivo electrocardiogram data revealed severe cardiac arrhythmias including lack of P waves, atrioventricular block, and ventricular tachycardia. Following Dq activation, electrophysiological malfunction of the heart could be recapitulated in the isolated heart ex vivo. Individual ventricular and atrial myocytes displayed a positive inotropic response and arrhythmogenic events in the absence of altered action potentials. Ventricular tissue sections revealed a strong co-localization of Dq with the principal cardiac connexin CX43. Western blot analysis with phosphor-specific antibodies revealed strong phosphorylation of a PKC-dependent CX43 phosphorylation site following CNO application in vivo. Conclusion Activation of Gq-coupled signalling has a major impact on impulse generation, impulse propagation, and coordinated impulse delivery in the heart. Thus, Gq-coupled signalling does not only modulate the myocytes’ Ca2+ handling but also directly alters the heart’s electrophysiological properties such as intercellular communication. This study greatly advances our understanding of the plethora of modulatory influences of Gq signalling on the heart in vivo.

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Cardiac Optical Mapping in Situ in Swine Models: A View of the Current Situation

Medicina ◽

10.3390/medicina56110620 ◽

2020 ◽

Vol 56 (11) ◽

pp. 620

Author(s):

Irma Martišienė ◽

Regina Mačianskienė ◽

Rimantas Benetis ◽

Jonas Jurevičius

Keyword(s):

Electrical Activity ◽

Optical Mapping ◽

Ex Vivo ◽

Isolated Heart ◽

Spatiotemporal Resolution ◽

Electrophysiological Properties ◽

Promising Tool ◽

Large Animals

Optical mapping is recognized as a promising tool for the registration of electrical activity in the heart. Most cardiac optical mapping experiments are performed in ex vivo isolated heart models. However, the electrophysiological properties of the heart are highly influenced by the autonomic nervous system as well as humoral regulation; therefore, in vivo investigations of heart activity in large animals are definitely preferred. Furthermore, such investigations can be considered the last step before clinical application. Recently, two comprehensive studies have examined optical mapping approaches for pig hearts in situ (in vivo), likely advancing the methodological capacity to perform complex electrophysiological investigations of the heart. Both studies had the same aim, i.e., to develop high-spatiotemporal-resolution optical mapping suitable for registration of electrical activity of pig heart in situ, but the methods chosen were different. In this brief review, we analyse and compare the results of recent studies and discuss their translational potential for in situ cardiac optical mapping applications in large animals. We focus on the modes of blood circulation that are employed, the use of different voltage-sensitive dyes and their loading procedures, and ways of eliminating contraction artefacts. Finally, we evaluate the possible scenarios for optical mapping (OM) application in large animals in situ and infer which scenario is optimal.

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