Abnormal contractile activity and calcium cycling in cardiac myocytes isolated from dmpk knockout mice

2003 ◽  
Vol 13 (2) ◽  
pp. 139-146 ◽  
Author(s):  
Gurman S. Pall ◽  
Keith J. Johnson ◽  
Godfrey L. Smith
Keyword(s):  
Myotonic Dystrophy ◽  
Ventricular Arrhythmias ◽  
Contractile Activity ◽  
Calcium Cycling ◽  
Gene Encoding ◽  
Ventricular Cardiomyocytes ◽  
Myotonic Dystrophy Protein Kinase ◽  
Intracellular Ca ◽  
Biochemical Measurements

Dysfunction of the gene encoding DMPK (myotonic dystrophy protein kinase) has been implicated in the human neuromuscular disease myotonic dystrophy (DM1). The cardiac features of the disease include progressive conduction defects and ventricular arrhythmias. These defects have been observed in hearts of mice deficient for DMPK function. We have investigated the role of DMPK in the function of ventricular cardiomyocytes using dmpk knockout (KO) mice. A deficit in DMPK caused enhanced basal contractility of single cardiomyocytes and an associated increase in intracellular Ca2+, measured using fura-2. Biochemical measurements indicated hyperphosphorylation of phospholamban (PLB) in KO mice. This suggests increased Ca2+ uptake into the sarcoplasmic reticulum (SR) as the underlying cause of enhanced contractility. This conclusion was supported by the larger amplitude of caffeine-induced Ca2+ release from the SR in KO cardiomyocytes. Concurrent with hyperphosphorylated PLB, the response to isoprenaline was reduced. These observations suggest dmpk has a modulatory role in the control of intracellular Ca2+ concentration in mouse ventricular cardiomyocytes, loss of which may contribute to cardiac dysfunction in DM1.

scholarly journals The role of calcium homeostasis remodeling in inherited cardiac arrhythmia syndromes

2021 ◽  
Author(s):  
Shanna Hamilton ◽  
Roland Veress ◽  
Andriy Belevych ◽  
Dmitry Terentyev
Keyword(s):  
Cardiac Arrhythmia ◽  
Cardiac Death ◽  
Ventricular Arrhythmias ◽  
Polymorphic Ventricular Tachycardia ◽  
Genetic Mutations ◽  
Strong Basis ◽  
Functional Changes ◽  
Intracellular Ca ◽  
Qt Syndrome

AbstractSudden cardiac death due to malignant ventricular arrhythmias remains the major cause of mortality in the postindustrial world. Defective intracellular Ca2+ homeostasis has been well established as a key contributing factor to the enhanced propensity for arrhythmia in acquired cardiac disease, such as heart failure or diabetic cardiomyopathy. More recent advances provide a strong basis to the emerging view that hereditary cardiac arrhythmia syndromes are accompanied by maladaptive remodeling of Ca2+ homeostasis which substantially increases arrhythmic risk. This brief review will focus on functional changes in elements of Ca2+ handling machinery in cardiomyocytes that occur secondary to genetic mutations associated with catecholaminergic polymorphic ventricular tachycardia, and long QT syndrome.

Abstract 191: Deletion or Knockdown of Myotonic Dystrophy Protein Kinase Does Not Affect Cardiac Conduction or Ejection Fraction in Mice

2015 ◽  
Vol 117 (suppl_1) ◽  
Author(s):  
Samuel Carrell ◽  
David Auerbach ◽  
Sanjay Pandey ◽  
Frank Bennett ◽  
Robert Dirksen ◽  
...  
Keyword(s):  
Ejection Fraction ◽  
Myotonic Dystrophy ◽  
Cardiac Conduction ◽  
Nuclear Retention ◽  
Rna Toxicity ◽  
Lv Dysfunction ◽  
Av Conduction ◽  
Myotonic Dystrophy Protein Kinase ◽  
Toxic Rna

Myotonic dystrophy type 1 (DM1), the most common form of muscular dystrophy in adults, causes dominantly-inherited muscle weakness, defects of cardiac conduction, variable LV dysfunction, and risk of sudden death. The genetic basis is an expanded CTG repeat in the 3’ untranslated region of DMPK. DM1 patients are functionally hemizygous for DMPK protein, due to nuclear retention of mRNA having expanded repeats. The cardiac aspects are attributed to DMPK loss, toxicity of RNA with expanded repeats, or both. Dmpk heterozygous (+/-) and homozygous knockout (-/-) mice were reported to show AV conduction abnormalities resembling DM1 (Berul et al, JCI, 1999). In an effort to reduce RNA toxicity, antisense oligonucleotides (ASOs) targeting DMPK mRNA have recently entered clinical trials. DM1 phenotypes in skeletal muscle were corrected by ASO knockdown of toxic RNA in mice (Wheeler et al, Nature, 2012). While ASOs may have similar potential to mitigate RNA toxicity in the heart, there is risk of aggravated DMPK deficiency. To reexamine the role of DMPK in the conduction system we studied mice with Dmpk gene deletion or ASO knockdown. We obtained ECGs and echocardiograms on Dmpk -/- and +/- mice, compared to WT littermates. The +/- mice were treated with Dmpk-targeting ASOs or saline. Subcutaneous injection of 50 mg/kg/wk ASO was started at age 2 months, then shifted to biweekly injections after 6 weeks. Dmpk expression in hearts of +/- mice was ~50% of WT, and was further reduced by ASOs (84 ± 3% decrease of mRNA, 93 ± 2% decrease of protein, relative to WT). Surface ECGs and echocardiography at 6 and 10 months showed no differences of heart rate, cardiac conduction, or ejection fraction in WT, saline-treated +/-, ASO-treated +/-, or -/- mice. Conscious, unrestrained ECGs obtained at 11-12 months by radiotelemetry showed no differences among WT, saline-treated +/-, ASO-treated +/-, or -/- mice. We conclude that ASOs can induce posttranscriptional silencing of Dmpk in murine hearts. Constitutive absence of DMPK did not impact cardiac conduction or contractility, and the same was true for ASO knockdown to levels <15% of WT. Our data support the idea that cardiac dysfunction in DM1 results mainly from RNA toxicity, which potentially could be prevented or alleviated by ASOs.

The functional role of cardiac T-tubules explored in a model of rat ventricular myocytes

2006 ◽  
Vol 364 (1842) ◽  
pp. 1187-1206 ◽  
Author(s):  
Michal Pásek ◽  
Jiři Šimurda ◽  
Georges Christé
Keyword(s):  
Ventricular Myocytes ◽  
Contractile Activity ◽  
Tubular Lumen ◽  
Current Clamp Mode ◽  
Intracellular Ca ◽  
Ionic Changes ◽  
Access Resistance ◽  
T Tubules ◽  
Tubular Membranes

The morphology of the cardiac transverse-axial tubular system (TATS) has been known for decades, but its function has received little attention. To explore the possible role of this system in the physiological modulation of electrical and contractile activity, we have developed a mathematical model of rat ventricular cardiomyocytes in which the TATS is described as a single compartment. The geometrical characteristics of the TATS, the biophysical characteristics of ion transporters and their distribution between surface and tubular membranes were based on available experimental data. Biophysically realistic values of mean access resistance to the tubular lumen and time constants for ion exchange with the bulk extracellular solution were included. The fraction of membrane in the TATS was set to 56%. The action potentials initiated in current-clamp mode are accompanied by transient K + accumulation and transient Ca 2+ depletion in the TATS lumen. The amplitude of these changes relative to external ion concentrations was studied at steady-state stimulation frequencies of 1–5 Hz. Ca 2+ depletion increased from 7 to 13.1% with stimulation frequency, while K + accumulation decreased from 4.1 to 2.7%. These ionic changes (particularly Ca 2+ depletion) implicated significant decrease of intracellular Ca 2+ load at frequencies natural for rat heart.

scholarly journals Role of cell contractions in cAMP-induced cardiomyocyte atrial natriuretic peptide release

2000 ◽  
Vol 278 (1) ◽  
pp. H117-H125 ◽  
Author(s):  
D. J. Church ◽  
M. C. Rebsamen ◽  
D. Morabito ◽  
V. van der Bent ◽  
M. B. Vallotton ◽  
...  
Keyword(s):  
Atrial Natriuretic Peptide ◽  
Natriuretic Peptide ◽  
Contractile Activity ◽  
Fold Increase ◽  
Prostaglandin E ◽  
Ventricular Cardiomyocytes ◽  
Peptide Release ◽  
Butanedione Monoxime ◽  
Atrial Natriuretic

Incubation of spontaneously beating ventricular cardiomyocytes from neonatal rats with prostaglandin E2 (0.1 μM) or forskolin (0.1 μM) simultaneously increased the rate of cellular contraction and atrial natriuretic peptide (ANP) secretion. Both responses were maximal within 10–20 min of application and were accompanied by three- to fourfold increases in cAMP formation. By contrast, a higher regimen of forskolin (10 μM) promoted a 20- to 30-fold increase in basal cAMP production, which was accompanied by the abolition of contractile activity and ANP release. Low regimens of forskolin (0.1 μM) doubled the occurrence of cytosolic Ca2+ transients associated with monolayer contraction, whereas higher regimens of forskolin (10 μM) completely suppressed Ca2+transients. Moreover, in quiescent cultures that were pretreated with ryanodine, tetrodotoxin, nifedipine, or butanedione monoxime, prostaglandin E2 (0.1 μM) and forskolin (0.1 μM) failed to elicit significant ANP secretion, suggesting that cAMP-elevating agents promote ANP secretion to a great extent via an increase in cellular contraction frequency in ventricular cardiomyocytes.

scholarly journals Role of Myotonic Dystrophy Protein Kinase (DMPK) in Glucose Homeostasis and Muscle Insulin Action

PLoS ONE ◽  
2007 ◽  
Vol 2 (11) ◽  
pp. e1134 ◽  
Author(s):  
Esther Llagostera ◽  
Daniele Catalucci ◽  
Luc Marti ◽  
Marc Liesa ◽  
Marta Camps ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Myotonic Dystrophy ◽  
Glucose Homeostasis ◽  
Insulin Action ◽  
Myotonic Dystrophy Protein Kinase ◽  
Muscle Insulin Action

RESEARCH THE VALUE OF THE COMBINATION OF T WAVE ALTERNANS AND NT-PROBNT IN PREDICTING SUDDEN CARDIAC DEATH

2012 ◽  
pp. 74-83
Author(s):  
Anh Tien Hoang ◽  
Nhat Quang Nguyen
Keyword(s):  
Myocardial Infarction ◽  
Sudden Cardiac Death ◽  
Cardiac Death ◽  
Ventricular Arrhythmias ◽  
Healthy Person ◽  
Treadmill Test ◽  
T Wave ◽  
T Wave Alternans

Background: Decades of research now link TWA with inducible and spontaneous clinical ventricular arrhythmias. This bench-to-bedside foundation makes TWA, NT-ProBNP a very plausible index of susceptibility to ventricular arrythmia, and motivates the need to define optimal combination of TWA and NT-ProBNP in predicting ventricular arrythmia in myocardial infarction patients. We research this study with 2 targets: 1. To evaluate the role of TWA in predicting sudden cardiac death in myocardial infarction patients. 2. To evaluate the role of NT-ProBNP in predicting sudden cardiac death in myocardial infarction patients 3. Evaluate the role of the combined NT-ProBNP and TWA in predicting sudden cardiac death in myocardial infarction patients. Methods: Prospective study with follow up the mortality in 2 years: 71 chronic myocardial infarction patients admitted to hospital from 5/2009 to 5/20011 and 50 healthy person was done treadmill test to caculate TWA; ECG, echocardiography, NT-ProBNP. Results: Cut-off point of NT-ProBNP in predicting sudden cardiac death is 3168 pg/ml; AUC = 0,86 (95% CI: 0,72 - 0,91); Cut-off point of TWA in predicting sudden cardiac death is 107 µV; AUC = 0,81 (95% CI: 0,69 - 0,87); NT-ProBNP can predict sudden cardiac death with OR= 7,26 (p<0,01); TWA can predict sudden cardiac death with OR= 8,45 (p<0,01). The combined NT-ProBNP and TWA in predicting ventricular arrythmia in heart failure patients: OR= 17,91 (p<0,001). Conclusions: The combined NT-ProBNP and TWA have the best predict value of sudden cardiac death in myocardial infarction patients, compare to NT-ProBNP or TWA alone

Myocardial Noncompaction

2018 ◽  
Vol 69 (8) ◽  
pp. 2209-2212
Author(s):  
Alexandru Radu Mihailovici ◽  
Vlad Padureanu ◽  
Carmen Valeria Albu ◽  
Venera Cristina Dinescu ◽  
Mihai Cristian Pirlog ◽  
...  
Keyword(s):  
Ventricular Arrhythmias ◽  
Specific Treatment ◽  
Left Ventricular ◽  
Left Ventricular Noncompaction ◽  
Ventricular Noncompaction ◽  
Genetic Transmission ◽  
Asymptomatic Patients ◽  
Increased Risk ◽  
Patients With Heart Failure

Left ventricular noncompaction is a primary cardiomyopathy with genetic transmission in the vast majority of autosomal dominant cases. It is characterized by the presence of excessive myocardial trabecularities that generally affect the left ventricle. In diagnosing this condition, echocardiography is the gold standard, although this method involves an increased risk of overdiagnosis and underdiagnosis. There are also uncertain cases where echocardiography is inconclusive, a multimodal approach is needed, correlating echocardiographic results with those obtained by magnetic resonance imaging. The clinical picture may range from asymptomatic patients to patients with heart failure, supraventricular or ventricular arrhythmias, thromboembolic events and even sudden cardiac death. There is no specific treatment of left ventricular noncompaction, but the treatment is aimed at preventing and treating the complications of the disease. We will present the case of a young patient with left ventricular noncompactioncardiomyopathy and highlight the essential role of transthoracic echocardiography in diagnosing this rare heart disease.

scholarly journals The Role of Mitochondria in Carcinogenesis

2021 ◽  
Vol 22 (10) ◽  
pp. 5100
Author(s):  
Paulina Kozakiewicz ◽  
Ludmiła Grzybowska-Szatkowska ◽  
Marzanna Ciesielka ◽  
Jolanta Rzymowska
Keyword(s):  
Prostate Cancer ◽  
Mitochondrial Dna ◽  
Nuclear Dna ◽  
Dna Polymorphisms ◽  
Gene Encoding ◽  
Dna Mutations ◽  
Nadh Ubiquinone Oxidoreductase ◽  
Gene Coi ◽  
The Impact

The mitochondria are essential for normal cell functioning. Changes in mitochondrial DNA (mtDNA) may affect the occurrence of some chronic diseases and cancer. This process is complex and not entirely understood. The assignment to a particular mitochondrial haplogroup may be a factor that either contributes to cancer development or reduces its likelihood. Mutations in mtDNA occurring via an increase in reactive oxygen species may favour the occurrence of further changes both in mitochondrial and nuclear DNA. Mitochondrial DNA mutations in postmitotic cells are not inherited, but may play a role both in initiation and progression of cancer. One of the first discovered polymorphisms associated with cancer was in the gene NADH-ubiquinone oxidoreductase chain 3 (mt-ND3) and it was typical of haplogroup N. In prostate cancer, these mutations and polymorphisms involve a gene encoding subunit I of respiratory complex IV cytochrome c oxidase subunit 1 gene (COI). At present, a growing number of studies also address the impact of mtDNA polymorphisms on prognosis in cancer patients. Some of the mitochondrial DNA polymorphisms occur in both chronic disease and cancer, for instance polymorphism G5913A characteristic of prostate cancer and hypertension.

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