Dataset Information

Regulation of Myofilament Contractile Function in Human Donor and Failing Hearts.

ABSTRACT: Heart failure (HF) often includes changes in myocardial contractile function. This study addressed the myofibrillar basis for contractile dysfunction in failing human myocardium. Regulation of contractile properties was measured in cardiac myocyte preparations isolated from frozen, left ventricular mid-wall biopsies of donor (n = 7) and failing human hearts (n = 8). Permeabilized cardiac myocyte preparations were attached between a force transducer and a position motor, and both the Ca2+ dependence and sarcomere length (SL) dependence of force, rate of force, loaded shortening, and power output were measured at 15 ± 1°C. The myocyte preparation size was similar between groups (donor: length 148 ± 10 ?m, width 21 ± 2 ?m, n = 13; HF: length 131 ± 9 ?m, width 23 ± 1 ?m, n = 16). The maximal Ca2+-activated isometric force was also similar between groups (donor: 47 ± 4 kN?m-2; HF: 44 ± 5 kN?m-2), which implicates that previously reported force declines in multi-cellular preparations reflect, at least in part, tissue remodeling. Maximal force development rates were also similar between groups (donor: k tr = 0.60 ± 0.05 s-1; HF: k tr = 0.55 ± 0.04 s-1), and both groups exhibited similar Ca2+ activation dependence of k tr values. Human cardiac myocyte preparations exhibited a Ca2+ activation dependence of loaded shortening and power output. The peak power output normalized to isometric force (PNPO) decreased by ?12% from maximal Ca2+ to half-maximal Ca2+ activations in both groups. Interestingly, the SL dependence of PNPO was diminished in failing myocyte preparations. During sub-maximal Ca2+ activation, a reduction in SL from ?2.25 to ?1.95 ?m caused a ?26% decline in PNPO in donor myocytes but only an ?11% change in failing myocytes. These results suggest that altered length-dependent regulation of myofilament function impairs ventricular performance in failing human hearts.

SUBMITTER: McDonald KS

PROVIDER: S-EPMC7261867 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Regulation of Myofilament Contractile Function in Human Donor and Failing Hearts.

McDonald Kerry S KS Hanft Laurin M LM Robinett Joel C JC Guglin Maya M Campbell Kenneth S KS

Frontiers in physiology 20200525

Heart failure (HF) often includes changes in myocardial contractile function. This study addressed the myofibrillar basis for contractile dysfunction in failing human myocardium. Regulation of contractile properties was measured in cardiac myocyte preparations isolated from frozen, left ventricular mid-wall biopsies of donor (<i>n</i> = 7) and failing human hearts (<i>n</i> = 8). Permeabilized cardiac myocyte preparations were attached between a force transducer and a position motor, and both th ...[more]

PMID: 32523542

Similar Datasets

Project description:Sudden cardiac death (SCD) from ventricular tachycardia/fibrillation (VT/VF) is a leading cause of death, but current therapies are limited. Despite extensive research on drugs targeting sarcolemmal ion channels, none have proven sufficiently effective for preventing SCD. Sarcoplasmic ryanodine receptor 2 (RyR2) Ca2+ release channels, the downstream effectors of sarcolemmal ion channels, are underexplored in this context. Recent evidence implicates reactive oxygen species (ROS)-mediated oxidation and hyperactivity of RyR2s in the pathophysiology of SCD. We tested the hypothesis that RyR2 inhibition of failing arrhythmogenic hearts reduces sarcoplasmic Ca2+ leak and repolarization lability, mitigates VT/VF/SCD and improves contractile function. We used a guinea pig model that replicates key clinical aspects of human nonischemic HF, such as a prolonged QT interval, a high prevalence of spontaneous arrhythmic SCD, and profound Ca2+ leak via a hyperactive RyR2. HF animals were randomized to receive dantrolene (DS) or placebo in early or chronic HF. We assessed the incidence of VT/VF and SCD (primary outcome), ECG heart rate and QT variability, echocardiographic left ventricular (LV) structure and function, immunohistochemical LV fibrosis, and sarcoplasmic RyR2 oxidation. DS treatment prevented VT/VF and SCD by decreasing dispersion of repolarization and ventricular arrhythmias. Compared to placebo, DS lowered resting heart rate, preserved chronotropic competency during transient β-adrenergic challenge, and improved heart rate variability and cardiac function. Inhibition of RyR2 hyperactivity with dantrolene mitigates the vicious cycle of sarcoplasmic Ca2+ leak-induced increases in diastolic Ca2+ and ROS-mediated RyR2 oxidation, thereby reducing repolarization lability and protecting against VT/VF/SCD. Moreover, the consequent increase in sarcoplasmic Ca2+ load improves contractile function. These potentially life-saving effects of RyR2 inhibition warrant further investigation, such as clinical studies of repurposing dantrolene as a potential new therapy for heart failure and/or SCD.

Project description:Backgroundβ1AR (beta-1 adrenergic receptor) and β2AR (beta-2 adrenergic receptor)-mediated cyclic adenosine monophosphate signaling has distinct effects on cardiac function and heart failure progression. However, the mechanism regulating spatial localization and functional compartmentation of cardiac β-ARs remains elusive. Emerging evidence suggests that microtubule-dependent trafficking of mRNP (messenger ribonucleoprotein) and localized protein translation modulates protein compartmentation in cardiomyocytes. We hypothesized that β-AR compartmentation in cardiomyocytes is accomplished by selective trafficking of its mRNAs and localized translation.MethodsThe localization pattern of β-AR mRNA was investigated using single molecule fluorescence in situ hybridization and subcellular nanobiopsy in rat cardiomyocytes. The role of microtubule on β-AR mRNA localization was studied using vinblastine, and its effect on receptor localization and function was evaluated with immunofluorescent and high-throughput Förster resonance energy transfer microscopy. An mRNA protein co-detection assay identified plausible β-AR translation sites in cardiomyocytes. The mechanism by which β-AR mRNA is redistributed post-heart failure was elucidated by single molecule fluorescence in situ hybridization, nanobiopsy, and high-throughput Förster resonance energy transfer microscopy on 16 weeks post-myocardial infarction and detubulated cardiomyocytes.Resultsβ1AR and β2AR mRNAs show differential localization in cardiomyocytes, with β1AR found in the perinuclear region and β2AR showing diffuse distribution throughout the cell. Disruption of microtubules induces a shift of β2AR transcripts toward the perinuclear region. The close proximity between β2AR transcripts and translated proteins suggests that the translation process occurs in specialized, precisely defined cellular compartments. Redistribution of β2AR transcripts is microtubule-dependent, as microtubule depolymerization markedly reduces the number of functional receptors on the membrane. In failing hearts, both β1AR and β2AR mRNAs are redistributed toward the cell periphery, similar to what is seen in cardiomyocytes undergoing drug-induced detubulation. This suggests that t-tubule remodeling contributes to β-AR mRNA redistribution and impaired β2AR function in failing hearts.ConclusionsAsymmetrical microtubule-dependent trafficking dictates differential β1AR and β2AR localization in healthy cardiomyocyte microtubules, underlying the distinctive compartmentation of the 2 β-ARs on the plasma membrane. The localization pattern is altered post-myocardial infarction, resulting from transverse tubule remodeling, leading to distorted β2AR-mediated cyclic adenosine monophosphate signaling.

Dataset Information

Regulation of Myofilament Contractile Function in Human Donor and Failing Hearts.

Publications

Regulation of Myofilament Contractile Function in Human Donor and Failing Hearts.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets