Enhanced basal contractility but reduced excitation-contraction coupling efficiency and β-adrenergic reserve of hearts with increased Cav1.2 activity

Cardiac remodeling during heart failure development induces a significant increase in the activity of the L-type Ca2+ channel (Cav1.2). However, the effects of enhanced Cav1.2 activity on myocyte excitation-contraction (E-C) coupling, cardiac contractility, and its regulation by the β-adrenergic system are not clear. To recapitulate the increased Cav1.2 activity, a double transgenic (DTG) mouse model overexpressing the Cavβ2a subunit in a cardiac-specific and inducible manner was established. We studied cardiac (in vivo) and myocyte (in vitro) contractility at baseline and upon β-adrenergic stimulation. E-C coupling efficiency was evaluated in isolated myocytes as well. The following results were found: 1) in DTG myocytes, L-type Ca2+ current ( ICa,L) density, myocyte fractional shortening (FS), peak Ca2+ transients, and sarcoplasmic reticulum (SR) Ca2+ content (caffeine-induced Ca2+ transient peak) were significantly increased (by 100.8%, 48.8%, 49.8%, and 46.8%, respectively); and 2) cardiac contractility evaluated with echocardiography [ejection fraction (EF) and (FS)] and invasive intra-left ventricular pressure (maximum dP/d t and −dP/d t) measurements were significantly greater in DTG mice than in control mice. However, 1) the cardiac contractility (EF, FS, dP/d t, and −dP/d t)-enhancing effect of the β-adrenergic agonist isoproterenol (2 μg/g body wt ip) was significantly reduced in DTG mice, which could be attributed to the loss of β-adrenergic stimulation on contraction, Ca2+ transients, ICa,L, and SR Ca2+ content in DTG myocytes; and 2) E-C couplng efficiency was significantly lower in DTG myocytes. In conclusion, increasing Cav1.2 activity by promoting its high-activity mode enhances cardiac contractility but decreases E-C coupling efficiency and the adrenergic reserve of the heart.

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β-blockade abolishes the augmented cardiac tPA release induced by transactivation of heterodimerised bradykinin receptor-2 and β2-adrenergic receptor in vivo

Thrombosis and Haemostasis ◽

10.1160/th14-01-0059 ◽

2014 ◽

Vol 112 (11) ◽

pp. 951-959 ◽

Cited By ~ 1

Author(s):

Morten Eriksen ◽

Arnfinn Ilebekk ◽

Alessandro Cataliotti ◽

Cathrine Rein Carlson ◽

Torstein Lyberg ◽

...

Keyword(s):

Adrenergic Receptor ◽

Sympathetic Nerves ◽

Ventricular Myocardium ◽

Left Ventricular ◽

Left Ventricular Myocardium ◽

Adrenergic Stimulation ◽

Β2 Adrenergic Receptor ◽

Β Blocker

SummaryBradykinin (BK) receptor-2 (B2R) and β2-adrenergic receptor (β2AR) have been shown to form heterodimers in vitro. However, in vivo proofs of the functional effects of B2R-β2AR heterodimerisation are missing. Both BK and adrenergic stimulation are known inducers of tPA release. Our goal was to demonstrate the existence of B2R-β2AR heterodimerisation in myocardium and to define its functional effect on cardiac release of tPA in vivo. We further investigated the effects of a non-selective β-blocker on this receptor interplay. To investigate functional effects of B2R-β2AR heterodimerisation (i. e. BK transactivation of β2AR) in vivo, we induced serial electrical stimulation of cardiac sympathetic nerves (SS) in normal pigs that underwent concomitant BK infusion. Both SS and BK alone induced increases in cardiac tPA release. Importantly, despite B2R desensitisation, simultaneous BK infusion and SS (BK+SS) was characterised by 2.3 ± 0.3-fold enhanced tPA release compared to SS alone. When β-blockade (propranolol) was introduced prior to BK+SS, tPA release was inhibited. A persistent B2R-β2AR heterodimer was confirmed in BK-stimulated and nonstimulated left ventricular myocardium by immunoprecipitation studies and under non-reducing gel conditions. All together, these results strongly suggest BK transactivation of β2AR leading to enhanced β2AR-mediated release of tPA. Importantly, non-selective β-blockade inhibits both SS-induced release of tPA and the functional effects of B2R-β2AR heterodimerisation in vivo, which may have important clinical implications.

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Hypotensive mechanism of [Leu13]motilin in dogs in vivo and in vitro

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y98-138 ◽

1998 ◽

Vol 76 (12) ◽

pp. 1103-1109 ◽

Cited By ~ 6

Author(s):

Takeshi Iwai ◽

Hiroyuki Nakamura ◽

Hisanori Takanashi ◽

Kenji Yogo ◽

Ken-Ichi Ozaki ◽

...

Keyword(s):

Mesenteric Artery ◽

Left Ventricular Pressure ◽

Left Ventricular ◽

Gastric Antrum ◽

Ventricular Pressure ◽

High Dose ◽

Aortic Blood Flow ◽

Arterial Blood

The effects of [Leu13]motilin were examined in vivo after its intravenous administration into anesthetized dogs and in vitro with isolated preparations of canine mesenteric artery. [Leu13]Motilin (0.1-10 nmol·kg-1, i.v.) induced both strong and clustered phasic contractions in the gastric antrum and duodenum. At doses of over 1 nmol·kg-1, [Leu13]motilin also produced transient decreases in arterial blood pressure, left ventricular pressure, maximum rate of rise of left ventricular pressure, and total peripheral resistance, and an increase in aortic blood flow and heart rate. A selective motilin antagonist, GM-109 (Phe-cyclo[Lys-Tyr(3-tBu)-betaAla]betatrifluoroacetate), completely abolished the gastric antrum and duodenal motor responses induced by [Leu13]motilin. In contrast, hypotension induced by [Leu13]motilin (1 nmol·kg-1) was unchanged in the presence of GM-109. In isolated mesenteric artery preparations precontracted with U-46619 (10-7 M), [Leu13]motilin (10-8-10-5 M) induced an endothelium-dependent relaxation, and this was inhibited by a pretreatment with Nomega-nitro-L-arginine, a competitive inhibitor of NO synthase (10-4 M). A high dose (10-4 M) of GM-109 slightly decreased [Leu13]motilin-induced relaxation, and shifted the concentration-response curve of [Leu13]motilin to the right. However, the pA2 value (4.09) of GM-109 for [Leu13]motilin in the present study was conspicuously lower than that previously demonstrated in the rabbit duodenum (7.37). These results suggest that [Leu13]motilin induces hypotension via the endothelial NO-dependent relaxation mechanism and not through the receptor type that causes upper gastrointestinal contractions.Key words: motilin, gastrointestinal motility, hypotension, hemodynamics, anesthetized dog, mesenteric artery, endothelium, nitric oxide.

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Slowing of cardiomyocyte Ca2+ release and contraction during heart failure progression in postinfarction mice

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.01009.2008 ◽

2009 ◽

Vol 296 (4) ◽

pp. H1069-H1079 ◽

Cited By ~ 32

Author(s):

Halvor K. Mørk ◽

Ivar Sjaastad ◽

Ole M. Sejersted ◽

William E. Louch

Keyword(s):

Myocardial Infarction ◽

Heart Failure ◽

Contractile Function ◽

Cardiac Contractility ◽

Posterior Wall ◽

Left Ventricular ◽

Shortening Velocity ◽

Transient Time

Deterioration of cardiac contractility during congestive heart failure (CHF) is believed to involve decreased function of individual cardiomyocytes and may include reductions in contraction magnitude and/or kinetics. We examined the progression of in vivo and in vitro alterations in contractile function in CHF mice and investigated underlying alterations in Ca2+ homeostasis. Following induction of myocardial infarction (MI), mice with CHF were examined at early (1 wk post-MI) and chronic (10 wk post-MI) stages of disease development. Sham-operated mice served as controls. Global and local left ventricle function were assessed by echocardiography in sedated animals (∼2% isoflurane). Excitation-contraction coupling was examined in cardiomyocytes isolated from the viable septum. CHF progression between 1 and 10 wk post-MI resulted in increased mortality, development of hypertrophy, and deterioration of global left ventricular function. Local function in the noninfarcted myocardium also declined, as posterior wall shortening velocity was reduced in chronic CHF (1.2 ± 0.1 vs. 1.9 ± 0.2 cm/s in sham). Parallel alterations occurred in isolated cardiomyocytes since contraction and Ca2+ transient time to peak values were prolonged in chronic CHF (115 ± 6 and 158 ± 11% sham values, respectively). Surprisingly, contraction and Ca2+ transient magnitudes in CHF were larger than sham values at both time points, resulting from increased sarcoplasmic reticulum Ca2+ content and greater Ca2+ influx via L-type channels. We conclude that, in mice with CHF following myocardial infarction, declining myocardial function involves slowing of cardiomyocyte contraction without reduction in contraction magnitude. Corresponding alterations in Ca2+ transients suggest that slowing of Ca2+ release is a critical mediator of CHF progression.

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Cardiac fibroblasts acquire properties of matrifibrocytes in vitro and in mice with pressure overload-induced congestive heart failure

European Heart Journal ◽

10.1093/ehjci/ehaa946.3741 ◽

2020 ◽

Vol 41 (Supplement_2) ◽

Author(s):

K.M Herum ◽

G Gilles ◽

A Romaine ◽

A.O Melleby ◽

G Christensen ◽

...

Keyword(s):

Heart Failure ◽

Congestive Heart Failure ◽

Cardiac Fibroblasts ◽

Pressure Overload ◽

Left Ventricular Pressure ◽

Left Ventricular ◽

Funding Source ◽

High Stiffness

Abstract Introduction Activation of cardiac fibroblasts (CFB) is a key step in development of fibrosis in the heart. It was recently shown that, in addition to the well-studied myofibroblast (myoFB) phenotype, activated cardiac fibroblasts can adopt a newly defined matrifibrocyte phenotype, characterized by expression of extracellular matrix (ECM) genes associated with bone, cartilage and tendon development. However, it is unknown whether matrifibrocytes exists in the pressure-overloaded fibrotic and failing heart, and whether substrate stiffness drives differentiation. Hypothesis Matrifibrocyte differentiation occurs in vitro during culturing of primary cardiac fibroblasts, and in vivo in response to left ventricular pressure overload. Methods Left ventricular pressure overload induced by o-ring aortic banding (ORAB) induced cardiac phenotypes of concentric hypertrophic remodelling and congestive heart failure. Primary CFB from adult mice were cultured on plastic or soft polyacrylamide hydrogels (4.5 kPa) for various times. mRNA expression of phenotypic markers were measured by RT-PCR. Presence of smooth muscle α-actin (SMA) fibers was determined by immunocytochemistry. Results ECM genes normally expressed in bone and cartilage (COMP, CILP-2, OPG and SCX) were upregulated in hypertrophic left ventricles of mice with congestive heart failure. The myoFB marker acta2 was increased 2 weeks after ORAB, returned to baseline at 4 weeks and increased again at 20 weeks when the left ventricle was dilating and failing, indicating that the myoFB phenotype is not permanent. In vitro, primary CFB upregulated bone/cartilage-associated ECM genes after 12 days of culturing on plastic. Acta2 mRNA and SMA protein levels peaked after 9 days in culture whereafter they declined, indicating a shift in phenotype. Culturing primary CFB on soft (4.5 kPa) hydrogels delayed, but did not prevent, myoFB differentiation while expression of bone/cartilage ECM genes was absent or low, indicating that high stiffness is a driver of the matrifibrocyte phenotype. Blockers of mechanotransduction, SB431542 (TGFβRI inhibitor), Y27623 (ROCK inhibitor) and cyclosporine A (calcineurin inhibitor), completely inhibited myoFB differentiation but upregulated several matrifibrocyte markers, indicating that distinct signaling pathways regulate myoFB and matrifibrocyte differentiation. Removing inhibitors re-induced myofibroblast markers in cells on plastic but not on soft gels consistent with high stiffness promoting myofibroblast differentiation. Conclusion Primary cardiac fibroblasts acquire characteristics of matrifibrocytes in vitro when cultured for long time on plastic and in vivo in left ventricles of mice with pressure overload-induced congestive heart failure. Funding Acknowledgement Type of funding source: Public grant(s) – EU funding. Main funding source(s): Marie Sklodowska-Curie Individual Fellowship

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Chronic Red Bull Consumption during Adolescence: Effect on Mesocortical and Mesolimbic Dopamine Transmission and Cardiovascular System in Adult Rats

Pharmaceuticals ◽

10.3390/ph14070609 ◽

2021 ◽

Vol 14 (7) ◽

pp. 609

Author(s):

Romina Vargiu ◽

Francesca Broccia ◽

Carla Lobina ◽

Daniele Lecca ◽

Alessandro Capra ◽

...

Keyword(s):

Papillary Muscle ◽

Drugs Of Abuse ◽

Cardiac Contractility ◽

Left Ventricular ◽

Nucleus Accumbens Shell ◽

Adult Rats ◽

Dopamine Transmission ◽

Red Bull

Energy drinks are very popular nonalcoholic beverages among adolescents and young adults for their stimulant effects. Our study aimed to investigate the effect of repeated intraoral Red Bull (RB) infusion on dopamine transmission in the nucleus accumbens shell and core and in the medial prefrontal cortex and on cardiac contractility in adult rats exposed to chronic RB consumption. Rats were subjected to 4 weeks of RB voluntary consumption from adolescence to adulthood. Monitoring of in vivo dopamine was carried out by brain microdialysis. In vitro cardiac contractility was studied on biomechanical properties of isolated left-ventricular papillary muscle. The main finding of the study was that, in treated animals, RB increased shell dopamine via a nonadaptive mechanism, a pattern similar to that of drugs of abuse. No changes in isometric and isotonic mechanical parameters were associated with chronic RB consumption. However, a prolonged time to peak tension and half-time of relaxation and a slower peak rate of tension fall were observed in RB-treated rats. It is likely that RB treatment affects left-ventricular papillary muscle contraction. The neurochemical results here obtained can explain the addictive properties of RB, while the cardiovascular investigation findings suggest a hidden papillary contractility impairment.

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Hemodynamic and electromechanical effects of paraquat in rat heart

10.1101/2020.06.01.127464 ◽

2020 ◽

Author(s):

Chih-Chuan Lin ◽

Kuang-Hung Hsu ◽

Gwo-Jyh Chang

Keyword(s):

Ventricular Myocytes ◽

Cardiac Contractility ◽

Left Ventricular ◽

Qtc Interval ◽

Dependent Manner ◽

Concentration Dependent Manner ◽

Isolated Hearts ◽

Dose Dependent

AbstractParaquat (PQ) is a highly lethal herbicide. Ingestion of large quantities of PQ usually results in cardiovascular collapse and eventually death. However, the mechanism of acute PQ poisoning induced cardiotoxicity is poorly understood. Therefore, the purpose of the present study was to aim to investigate the mechanisms of PQ induced cardiotoxicity by examining the effects of PQ on hemodynamics in vivo, as well as in vitro on isolated hearts and ventricular myocytes in rats. Intravenous administration of PQ (100 or 180 mg/kg) in anesthetized rats induced dose-dependent decreases in heart rate, blood pressure, and cardiac contractility (left ventricular [LV] dP/dtmax). Furthermore, it prolonged the rate-corrected QT (QTc) interval. In Langendorff-perfused isolated hearts, PQ (33 or 60 μM) decreased LV pressure and contractility (LV dP/dtmax in isolated ventricular myocytes), PQ (10–60 μM) decreased the amplitude of Ca2+ transients and cell shortening in a concentration-dependent manner. Patch-clamp experiments demonstrated that PQ decreased the amplitude and availability of the transient outward K+ channel (Ito) and altered its gating kinetics. These results suggest that PQ-induced cardiotoxicity results mainly from diminished Ca2+ transients and inhibited K+ channels, which lead to the suppression of LV contractile force and prolongation of the QTc interval.

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Reversal of cardiac myocyte dysfunction as a unique mechanism of rescue by P2X4 receptors in cardiomyopathy

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.01316.2008 ◽

2009 ◽

Vol 296 (4) ◽

pp. H1089-H1095 ◽

Cited By ~ 14

Author(s):

Jian-Bing Shen ◽

Robin Shutt ◽

Mariela Agosto ◽

Achilles Pappano ◽

Bruce T. Liang

Keyword(s):

Heart Failure ◽

Cardiac Myocyte ◽

Left Ventricular ◽

Similar Data ◽

Heart Failure Progression ◽

P2x4 Receptors ◽

Unique Mechanism ◽

Fractional Shortening

Binary cardiac transgenic (Tg) overexpression of P2X4 receptors (P2X4R) improved the survival of the cardiomyopathic calsequestrin (CSQ) mice. Here we studied the mechanism of rescue using binary P2X4R/CSQ Tg and CSQ Tg mice as models. Cellular and intact heart properties were determined by simultaneous sarcomere shortening (SS) and Ca2+ transients in vitro and echocardiography in vivo. Similar to a delay in death, binary mice exhibited a slowed heart failure progression with a greater left ventricular (LV) fractional shortening (FS) and thickness and a concomitant lesser degree of LV dilatation in both systole and diastole at 8 or 12 wk. By 16 wk, binary hearts showed similarly depressed FS and thinned out LV and equal enlargement of LV as did 12-wk-old CSQ hearts. Binary cardiac myocytes showed higher peak basal cell shortening (CS) and SS as well as greater basal rates of shortening and relaxation than did the CSQ myocytes at either 8 or 12 wk. Similar data were obtained in comparing the Ca2+ transient. At 16 wk, binary myocytes were like the 12-wk-old CSQ myocytes with equally depressed CS, SS, and Ca2+ transient. CSQ myocytes were longer than myocytes from wild-type and binary mice at 12 wk of age. At 16 wk, the binary myocyte length increased to that of the 12-wk-old CSQ myocyte, parallel to LV dilatation. The data suggest a unique mechanism, which involves a reversal of cardiac myocyte dysfunction and a delay in heart failure progression. It represents an example of targeting the abnormal failing myocyte in treating heart failure.

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Overexpression of Cyclic Adenosine Monophosphate Effluent Protein MRP4 Induces an Altered Response to β-Adrenergic Stimulation in the Senescent Rat Heart

Anesthesiology ◽

10.1097/aln.0000000000000526 ◽

2015 ◽

Vol 122 (2) ◽

pp. 334-342 ◽

Cited By ~ 7

Author(s):

Aude Carillion ◽

Sarah Feldman ◽

Cheng Jiang ◽

Fabrice Atassi ◽

Na Na ◽

...

Keyword(s):

Positive Inotropic Effect ◽

Cyclic Adenosine Monophosphate ◽

Calcium Transient ◽

Adenosine Monophosphate ◽

Left Ventricular ◽

Inotropic Effect ◽

Inotropic Response ◽

Adrenergic Stimulation

Abstract Background: In the senescent heart, the positive inotropic response to β-adrenoceptor stimulation is reduced, partly by dysregulation of β1- and β3-adrenoceptors. The multidrug resistance protein 4 (MRP4) takes part in the control of intracellular cyclic adenosine monophosphate concentration by controlling its efflux but the role of MRP4 in the β-adrenergic dysfunction of the senescent heart remains unknown. Methods: The β-adrenergic responses to isoproterenol were investigated in vivo (stress echocardiography) and in vitro (isolated cardiomyocyte by Ionoptix® with sarcomere shortening and calcium transient) in young (3 months old) and senescent (24 months old) rats pretreated or not with MK571, a specific MRP4 inhibitor. MRP4 was quantified in left ventricular homogenates by Western blotting. Data are mean ± SD expressed as percent of baseline value. Results: The positive inotropic effect of isoproterenol was reduced in senescent rats in vivo (left ventricular shortening fraction 120 ± 16% vs. 158 ± 20%, P < 0.001, n = 16 rats) and in vitro (sarcomere shortening 129 ± 37% vs. 148 ± 35%, P = 0.004, n = 41 or 43 cells) as compared to young rats. MRP4 expression increased 3.6-fold in senescent compared to young rat myocardium (P = 0.012, n = 8 rats per group). In senescent rats, inhibition of MRP4 by MK571 restored the positive inotropic effect of isoproterenol in vivo (143 ± 11%, n = 8 rats). In vitro in senescent cardiomyocytes pretreated with MK571, both sarcomere shortening (161 ± 45% vs. 129 ± 37%, P = 0.007, n = 41 cells per group) and calcium transient amplitude (132 ± 25% vs. 113 ± 27%, P = 0.007) increased significantly. Conclusion: MRP4 overexpression contributes to the reduction of the positive inotropic response to β-adrenoceptor stimulation in the senescent heart.

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Impaired Cardiac Contractility Response to Hemodynamic Stress in S100A1-Deficient Mice

Molecular and Cellular Biology ◽

10.1128/mcb.22.8.2821-2829.2002 ◽

2002 ◽

Vol 22 (8) ◽

pp. 2821-2829 ◽

Cited By ~ 89

Author(s):

Xiao-Jun Du ◽

Timothy J. Cole ◽

Nora Tenis ◽

Xiao-Ming Gao ◽

Frank Köntgen ◽

...

Keyword(s):

Cardiac Contractility ◽

Pressure Overload ◽

Left Ventricular ◽

Ventricular Contractility ◽

Adrenergic Stimulation ◽

Protein Levels ◽

Hemodynamic Stress ◽

Gene Coding ◽

Ef Hand

ABSTRACT Ca2+ signaling plays a central role in cardiac contractility and adaptation to increased hemodynamic demand. We have generated mice with a targeted deletion of the S100A1 gene coding for the major cardiac isoform of the large multigenic S100 family of EF hand Ca2+-binding proteins. S100A1−/− mice have normal cardiac function under baseline conditions but have significantly reduced contraction rate and relaxation rate responses to β-adrenergic stimulation that are associated with a reduced Ca2+ sensitivity. In S100A1−/− mice, basal left-ventricular contractility deteriorated following 3-week pressure overload by thoracic aorta constriction despite a normal adaptive hypertrophy. Surprisingly, heterozygotes also had an impaired response to acute β-adrenergic stimulation but maintained normal contractility in response to chronic pressure overload that coincided with S100A1 upregulation to wild-type levels. In contrast to other genetic models with impaired cardiac contractility, loss of S100A1 did not lead to cardiac hypertrophy or dilation in aged mice. The data demonstrate that high S100A1 protein levels are essential for the cardiac reserve and adaptation to acute and chronic hemodynamic stress in vivo.

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Recapitulating aortic valve disease hemodynamics with a highly tunable bio-inspired soft robotic aortic sleeve

10.21203/rs.3.rs-713582/v1 ◽

2021 ◽

Author(s):

Luca Rosalia ◽

Caglar Ozturk ◽

Yiling Fan ◽

Jaume Coll-Font ◽

Shi Chen ◽

...

Keyword(s):

Aortic Valve ◽

Pressure Overload ◽

Left Ventricular Pressure ◽

Flow Patterns ◽

Left Ventricular ◽

Patient Specific ◽

Congenital Defects ◽

Lumped Parameter

Abstract Existing models of aortic stenosis (AS) are limited to inducing left ventricular pressure overload. As they have reduced control over the severity of aortic constriction, the clinical relevance of these models is largely hindered by their inability to mimic AS hemodynamics and recapitulate flow patterns associated with congenital valve defects, responsible for the accelerated onset and progression of AS. Here we report the development of a highly tunable bio-inspired soft robotic tool that enables the recapitulation of AS in a porcine model, in which customization of actuation patterns allows hemodynamic mimicry of AS and congenital aortic valve defects. In vitro and computational tools including lumped-parameter, finite element, and computational fluid dynamics platforms were developed to predict the hemodynamics induced by the bio-inspired soft robotic sleeve. The controllability of our in vivo model and its ability to replicate flow patterns of AS and congenital defects were demonstrated in swine through echocardiography, left ventricular catheterization, and magnetic resonance imaging. This work supports the use of soft robotics to simulate human physiology and disease, while paving the way towards the development of patient-specific models of AS and congenital defects that can guide clinical decisions to improve the management and treatment of these patients.

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