Cardiac responses of rats submitted to postnatal protein restriction

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 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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Co-expression of skeletal and cardiac troponin T decreases mouse cardiac function

AJP Cell Physiology ◽

10.1152/ajpcell.00146.2007 ◽

2008 ◽

Vol 294 (1) ◽

pp. C213-C222 ◽

Cited By ~ 25

Author(s):

Q.-Q. Huang ◽

H. Z. Feng ◽

J. Liu ◽

J. Du ◽

L. B. Stull ◽

...

Keyword(s):

Cardiac Function ◽

Contractile Function ◽

Troponin T ◽

Ex Vivo ◽

Heart Function ◽

Left Ventricular Pressure ◽

Experimental System ◽

Left Ventricular ◽

Negative Effects

In contrast to skeletal muscles that simultaneously express multiple troponin T (TnT) isoforms, normal adult human cardiac muscle contains a single isoform of cardiac TnT. To understand the significance of myocardial TnT homogeneity, we examined the effect of TnT heterogeneity on heart function. Transgenic mouse hearts overexpressing a fast skeletal muscle TnT together with the endogenous cardiac TnT was investigated in vivo and ex vivo as an experimental system of concurrent presence of two classes of TnT in the adult cardiac muscle.This model of myocardial TnT heterogeneity produced pathogenic phenotypes: echocardiograph imaging detected age-progressive reductions of cardiac function; in vivo left ventricular pressure analysis showed decreased myocardial contractility; ex vivo analysis of isolated working heart preparations confirmed an intrinsic decrease of cardiac function in the absence of neurohumoral influence. The transgenic mice also showed chronic myocardial hypertrophy and degeneration. The dominantly negative effects of introducing a fast TnT into the cardiac thin filaments to produce two classes of Ca2+ regulatory units in the adult myocardium suggest that TnT heterogeneity decreases contractile function by disrupting the synchronized action during ventricular contraction that is normally activated as an electrophysiological syncytium.

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Abstract 1856: Transplantation of Bone-marrow Mononuclear Cells into the Infarcted Heart has Favorable Engraftment Compared to Mesenchymal Stem Cells, Skeletal Myoblasts and Fibroblasts

Circulation ◽

10.1161/circ.116.suppl_16.ii_397-a ◽

2007 ◽

Vol 116 (suppl_16) ◽

Author(s):

Koen E van der Bogt ◽

Ahmad Y Sheikh ◽

Sonja Schrepfer ◽

Grant Hoyt ◽

Feng Cao ◽

...

Keyword(s):

Bone Marrow ◽

Cardiac Function ◽

Mononuclear Cells ◽

Bone Marrow Cells ◽

Ex Vivo ◽

Donor Cell ◽

Cell Number ◽

Left Ventricular ◽

Skeletal Myoblasts

Introduction: A comparative analysis of the efficacy of different cell candidates for the treatment of heart disease remains to be described. This study aimed to evaluate the therapeutic efficacy of 4 cell types in a murine model of myocardial infarction. Methods: Bone-marrow cells (MN), mesenchymal cells (MSC), skeletal myoblasts (SkMb) and fibroblasts (Fibro) were isolated from male L2G transgenic mice (FVB background) that express firefly luciferase (Fluc) and green fluorescence protein (GFP). Cells were characterized by flow cytometry, bioluminescence imaging (BLI), and luminometry. Female FVB mice (n=60) underwent LAD ligation and were randomized into 5 groups to intramyocardially receive one cell type (5 × 10 5 ) or PBS. Cell survival was measured in vivo by BLI and ex vivo by TaqMan PCR at week 6. Cardiac function was assessed by echocardiography and invasive hemodynamic measurements at week 6. Results: Fluc expression correlated with cell number in all groups (r 2 >0.93). In vivo BLI revealed donor cell death of MSC, SkMb, and Fibro within 3 weeks after transplantation. By contrast, cardiac signal was still present after 6 weeks in the MN group, as confirmed by PCR (p<0.01). Echocardiography showed significant preservation of fractional shortening in the MN group compared to controls (p<0.05). Measurements of left ventricular end-systolic/diastolic volume revealed the least amount of ventricular dilatation occurred in the MN group (p<0.05). Conclusion: This is the first study to directly compare a variety of cell candidates for myocardial therapy and indicates that MN exhibit a favorable survival pattern, which translates into preservation of cardiac function.

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Magnetic resonance-compatible model of isolated working heart from large animal for multimodal assessment of cardiac function, electrophysiology, and metabolism

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00825.2015 ◽

2016 ◽

Vol 310 (10) ◽

pp. H1371-H1380 ◽

Cited By ~ 5

Author(s):

Fanny Vaillant ◽

Julie Magat ◽

Pierre Bour ◽

Jérôme Naulin ◽

David Benoist ◽

...

Keyword(s):

Magnetic Resonance ◽

Cardiac Function ◽

Electromechanical Coupling ◽

Ex Vivo ◽

Simultaneous Recording ◽

Left Ventricular ◽

Homogeneous Distribution ◽

Large Animal ◽

Electrical Pacing

To provide a model close to the human heart, and to study intrinsic cardiac function at the same time as electromechanical coupling, we developed a magnetic resonance (MR)-compatible setup of isolated working perfused pig hearts. Hearts from pigs (40 kg, n = 20) and sheep ( n = 1) were blood perfused ex vivo in the working mode with and without loaded right ventricle (RV), for 80 min. Cardiac function was assessed by measuring left intraventricular pressure and left ventricular (LV) ejection fraction (LVEF), aortic and mitral valve dynamics, and native T1 mapping with MR imaging (1.5 Tesla). Potential myocardial alterations were assessed at the end of ex vivo perfusion from late-Gadolinium enhancement T1 mapping. The ex vivo cardiac function was stable across the 80 min of perfusion. Aortic flow and LV-dP/d tmin were significantly higher ( P < 0.05) in hearts perfused with loaded RV, without differences for heart rate, maximal and minimal LV pressure, LV-dP/d tmax, LVEF, and kinetics of aortic and mitral valves. T1 mapping analysis showed a spatially homogeneous distribution over the LV. Simultaneous recording of hemodynamics, LVEF, and local cardiac electrophysiological signals were then successfully performed at baseline and during electrical pacing protocols without inducing alteration of MR images. Finally, 31P nuclear MR spectroscopy (9.4 T) was also performed in two pig hearts, showing phosphocreatine-to-ATP ratio in accordance with data previously reported in vivo. We demonstrate the feasibility to perfuse isolated pig hearts in the working mode, inside an MR environment, allowing simultaneous assessment of cardiac structure, mechanics, and electrophysiology, illustrating examples of potential applications.

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Endurance exercise attenuates cardiotoxicity induced by androgen deprivation and doxorubicin

Canadian Journal of Physiology and Pharmacology ◽

10.1139/cjpp-2013-0294 ◽

2014 ◽

Vol 92 (5) ◽

pp. 356-362 ◽

Cited By ~ 5

Author(s):

Traci L. Parry ◽

David S. Hydock ◽

Brock T. Jensen ◽

Chia-Ying Lien ◽

Carole M. Schneider ◽

...

Keyword(s):

Cardiac Function ◽

Endurance Exercise ◽

Cardiac Dysfunction ◽

Ex Vivo ◽

Left Ventricular ◽

Androgen Deprivation ◽

Maximal Rate ◽

Sprague Dawley ◽

Developed Pressure

Doxorubicin (DOX) is associated with cardiac dysfunction and irreversible testicular damage. Androgen deprivation therapy (ADT) is administered prior to DOX treatment to preserve testicular function. However, ADT may exacerbate DOX-induced cardiac dysfunction. Exercise is cardioprotective, but the effects of exercise on cardiac function during combined ADT and DOX treatment are currently unknown. In this study, male Sprague–Dawley rats were randomly assigned to experimental groups: control (CON), ADT, DOX, or ADT+DOX. Animals received ADT or control implants on days 1 and 29 of the 56-day protocol. Animals remained sedentary (SED) or engaged in treadmill endurance exercise (TM) beginning on day 1. On day 15, the animals received DOX at 1 mg·(kg body mass)–1·d–1 by intraperitoneal injection for 10 consecutive days, or an equivalent volume of saline. On day 57, cardiac function was assessed in vivo and ex vivo. Animals treated with DOX alone, or with combined ADT+DOX, showed significant (P < 0.05) reductions in left ventricular developed pressure (–21% and –27%), maximal rate of pressure development (–29% and –32%), and maximal rate of pressure decline (25% and 31%), respectively when compared with the sedentary control animals. Endurance exercise training attenuated (P > 0.05) cardiac dysfunction associated with combined ADT+DOX treatment, indicating that exercise during simultaneous ADT+DOX treatment is cardioprotective.

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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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Abstract 293: Inhibition of Nitric Oxide Synthase Decreases Myocardial Injury Following Hemorrhagic Shock and Resuscitation in Rat Model

Circulation ◽

10.1161/circ.130.suppl_2.293 ◽

2014 ◽

Vol 130 (suppl_2) ◽

Author(s):

Mona Soliman

Keyword(s):

Nitric Oxide ◽

Nitric Oxide Synthase ◽

Hemorrhagic Shock ◽

Contractile Function ◽

Ex Vivo ◽

Left Ventricular ◽

Arterial Blood ◽

Myocardial Contractile ◽

Oxide Synthase

Resuscitation following hemorrhagic shock result in myocardial contractile dysfunction and injury. We examined the protective effects of non-selective inhibitor of nitric oxide synthase N(G)-nitro-L-arginine methylester (L-NAME) on myocardial contractile function in the isolated perfused hearts, after ex vivo as well as in vivo treatment with L-NAME and resuscitation following one hour of hemorrhagic shock.Male Sprague Dawley rats (300-350 gm) were assigned to 2 sets of experimental protocols: ex vivo and in vivo treatment and resuscitation. Each set has 3 experimental groups (n= 6 per group): normotensive (N), hemorrhagic shock and resuscitation (HS-R) and hemorrhagic shock rats treated with L-NAME and resuscitated (HS- L-NAME-R). Rats were hemorrhaged over 60 min to reach a mean arterial blood pressure of 40 mmHg. In the ex vivo group, hearts were harvested and ex vivo treated and resuscitated by perfused in the Langendorff System. In the L-NAME treated group, L-NAME was added for the first 5 min . Cardiac function was measured Left ventricular generated pressure and +dP/dt were calculated. In the in vivo group, rats were treated with L-NAME intra-arterially after 60 min hemorrhagic shock. Resuscitation was performed in vivo by the reinfusion of the shed blood for 30 min to restore normo-tension. Inhibition of nitric oxide synthase using L-NAME before resuscitation in ex vivo treated and resuscitated isolated hearts and in in vivo treated and resuscitated rats following hemorrhagic shock improved myocardial contractile function. Left ventricular generated pressure and + dP/dt max was significantly higher in L-NAME treated rats compared to the untreated group.Treatment with L-NAME improved left ventricular generated pressure following hemorrhagic shock in the ex vivo as well as the in vivo treated and resuscitated rats. The results indicate that L-NAME protects the myocardium against dysfunction by inhibiting NOS.

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Computational Investigation of Transmural Differences in Left Ventricular Contractility

Journal of Biomechanical Engineering ◽

10.1115/1.4034558 ◽

2016 ◽

Vol 138 (11) ◽

Cited By ~ 6

Author(s):

Hua Wang ◽

Xiaoyan Zhang ◽

Shauna M. Dorsey ◽

Jeremy R. McGarvey ◽

Kenneth S. Campbell ◽

...

Keyword(s):

Myocardial Contractility ◽

Ex Vivo ◽

Experimental Studies ◽

Contractile Force ◽

Left Ventricular ◽

Lv Function ◽

Fe Model ◽

Myocardial Layers ◽

Best Fit

Myocardial contractility of the left ventricle (LV) plays an essential role in maintaining normal pump function. A recent ex vivo experimental study showed that cardiomyocyte force generation varies across the three myocardial layers of the LV wall. However, the in vivo distribution of myocardial contractile force is still unclear. The current study was designed to investigate the in vivo transmural distribution of myocardial contractility using a noninvasive computational approach. For this purpose, four cases with different transmural distributions of maximum isometric tension (Tmax) and/or reference sarcomere length (lR) were tested with animal-specific finite element (FE) models, in combination with magnetic resonance imaging (MRI), pressure catheterization, and numerical optimization. Results of the current study showed that the best fit with in vivo MRI-derived deformation was obtained when Tmax assumed different values in the subendocardium, midmyocardium, and subepicardium with transmurally varying lR. These results are consistent with recent ex vivo experimental studies, which showed that the midmyocardium produces more contractile force than the other transmural layers. The systolic strain calculated from the best-fit FE model was in good agreement with MRI data. Therefore, the proposed noninvasive approach has the capability to predict the transmural distribution of myocardial contractility. Moreover, FE models with a nonuniform distribution of myocardial contractility could provide a better representation of LV function and be used to investigate the effects of transmural changes due to heart disease.

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Abstract 314: BRaf Plays a Major Role in Gene Expression in Cardiomyocytes in Mouse Hearts in vivo

Circulation Research ◽

10.1161/res.121.suppl_1.314 ◽

2017 ◽

Vol 121 (suppl_1) ◽

Author(s):

Michelle A Hardyman ◽

Stephen J Fuller ◽

Daniel N Meijles ◽

Kerry A Rostron ◽

Sam J Leonard ◽

...

Keyword(s):

Gene Expression ◽

Cardiac Hypertrophy ◽

Cardiac Function ◽

Left Ventricular ◽

Braf Mutations ◽

Gene Markers ◽

Lv Mass ◽

Cardiac Volumes

Introduction: Raf kinases lie upstream of ERK1/2 with BRaf being the most highly expressed and having the highest basal activity. V600E BRaf mutations constitutively activate ERK1/2 and are common in cancer. The role of BRaf in the adult heart is yet to be established. ERK1/2 regulate cardiomyocyte gene expression, promoting cardiac hypertrophy and cardioprotection, but effects of ERK1/2 may depend on signal strength. Hypothesis: Our hypotheses are that BRaf is critical in regulating ERK1/2 signaling in cardiomyocytes and, whilst moderate ERK1/2 activity is beneficial, excessive ERK1/2 activity is detrimental to the heart. Methods: We generated heterozygote mice for tamoxifen- (Tam-) inducible cardiomyocyte-specific knockin of V600E in the endogenous BRaf gene. Mice (12 wks) received 2 injections of Tam or vehicle on consecutive days (n=4-10 per group). Kinase activities and mRNA expression were assessed by immunoblotting and qPCR. Echocardiography was performed (Vevo2100). M-mode images (short axis view) were analyzed; data for each mouse were normalized to the mean of 2 baseline controls. Results: V600E knockin did not affect overall BRaf or cRaf levels in mouse hearts, but significantly increased ERK1/2 activities within 48 h (1.51±0.05 fold). Concurrently, mRNAs for hypertrophic gene markers including BNP and immediate early genes (IEGs) increased signficantly. At 72 h, expression of BNP, Fosl1, Myc, Ereg and CTGF increased further, other IEGs (Jun, Fos, Egr1, Atf3) declined, and ANF was upregulated. In contrast, expression of α and β myosin heavy chain mRNAs was substantially downregulated (0.46/0.41±0.05 relative to controls). Within 72 h, left ventricular (LV) mass and diastolic LV wall thickness had increased (1.23±0.05 relative to controls), but cardiac function was severely compromised with significant decreases in ejection fraction and cardiac output (0.53/0.68±0.09 relative to controls) associated with increased LV internal diameters and cardiac volumes. Conclusions: Endogenous cardiomyocyte BRaf is sufficient to activate ERK1/2 in mouse hearts and induce cardiac hypertrophy associated with dynamic temporal changes in gene expression. However, excessive activation of ERK1/2 in isolation is detrimental to cardiac function.

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