Computational modelling of the initiation and development of spontaneous intracellular Ca 2+ waves in ventricular myocytes

2010 ◽  
Vol 368 (1925) ◽  
pp. 3953-3965 ◽  
Author(s):  
Pan Li ◽  
Wenjie Wei ◽  
Xing Cai ◽  
Christian Soeller ◽  
Mark B. Cannell ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Membrane Potential ◽  
Ryanodine Receptor ◽  
Computational Modelling ◽  
Confocal Imaging ◽  
Polymorphic Ventricular Tachycardia ◽  
Quantitative Prediction ◽  
Sensitivity Factor ◽  
Intracellular Ca ◽  
Receptor Clusters

Intracellular Ca 2+ dynamics provides excitation–contraction coupling in cardiac myocytes. Under pathological conditions, spontaneous Ca 2+ release events can lead to intracellular Ca 2+ travelling waves, which can break, giving transitory or persistent intracellular re-entrant Ca 2+ scroll waves. Intracellular Ca 2+ waves can trigger cellular delayed after-depolarizations of membrane potential, which if they occur in a cluster of a few hundred neighbouring myocytes may lead to cardiac arrhythmia. Quantitative prediction of the initiation and propagation of intracellular Ca 2+ waves requires the dynamics of Ca 2+ -induced Ca 2+ release, and the intracellular spatial distribution of Ca 2+ release units (CRUs). The spatial distribution of ryanodine receptor clusters within a few sarcomeres was reconstructed directly from confocal imaging measurements. It was then embedded into a three-dimensional ventricular cell model, with a resting membrane potential and simple stochastic Ca 2+ -induced Ca 2+ release dynamics. Isotropic global Ca 2+ wave propagation can be produced within the anisotropic intracellular architecture, by isotropic local Ca 2+ diffusion, and the branching Z-disc structure providing inter Z-disc pathways for Ca 2+ propagation. The branching Z-disc provides a broader spatial distribution of ryanodine receptor clusters across Z-discs, which reduces the likelihood of wave initiation by spontaneous Ca 2+ releases. Intracellular Ca 2+ dynamics during catecholaminergic polymorphic ventricular tachycardia (CPVT) was simulated phenomenologically by increasing the Ca 2+ sensitivity factor of the CRU, which results in an increased rate of Ca 2+ release events. Flecainide has been shown to prevent arrhythmias in a murine model of CPVT and in patients. The modelled actions of flecainide on the time course of Ca 2+ release events prevented the initiation of Ca 2+ waves.

Intramitochondrial [Ca2+] and membrane potential in ventricular myocytes exposed to anoxia-reoxygenation

1998 ◽  
Vol 275 (2) ◽  
pp. H484-H494 ◽  
Author(s):  
T. J. Delcamp ◽  
C. Dales ◽  
L. Ralenkotter ◽  
P. S. Cole ◽  
R. W. Hadley
Keyword(s):  
Membrane Potential ◽  
Guinea Pig ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Membrane ◽  
Cell Injury ◽  
Ventricular Myocytes ◽  
Confocal Imaging ◽  
Mitochondrial Depolarization ◽  
Intracellular Ca ◽  
A Cell

The aim of this study was to investigate the role of mitochondrial ionic homeostasis in promoting reoxygenation-induced hypercontracture in cardiac muscle. Mitochondrial membrane potential and intramitochondrial Ca2+ concentration ([Ca2+]) were measured using confocal imaging in guinea pig ventricular myocytes exposed to anoxia and reoxygenation. Anoxia produced a variable, but often profound, mitochondrial depolarization. Some cells mounted a recovery of their mitochondrial membrane potential during reoxygenation; the depolarization was sustained in other cells. Recovery of the mitochondrial membrane potential seemed essential to avoid reoxygenation-induced hypercontracture. Reoxygenation also caused a sizable elevation in intramitochondrial [Ca2+], the amplitude of which was correlated with the likelihood of a cell undergoing hypercontracture. A sustained Ca2+load analogous to that seen during reoxygenation was imposed on cardiac mitochondria through permeabilization of the plasma membrane. Elevation of intracellular [Ca2+] to 800 nM caused a substantial mitochondrial depolarization. We propose that the conditions seen in guinea pig ventricular myocytes during reoxygenation are well suited to produce Ca2+-dependent mitochondrial depolarization, which may play a significant role in promoting irreversible cell injury.

scholarly journals Loss of dysferlin or myoferlin results in differential defects in excitation–contraction coupling in mouse skeletal muscle

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
David Y. Barefield ◽  
Jordan J. Sell ◽  
Ibrahim Tahtah ◽  
Samuel D. Kearns ◽  
Elizabeth M. McNally ◽  
...  
Keyword(s):  
Ryanodine Receptor ◽  
Calcium Binding ◽  
Physiological Role ◽  
Muscle Disease ◽  
Calcium Handling ◽  
Membrane Repair ◽  
Tubule Formation ◽  
Ec Coupling ◽  
Associated Proteins ◽  
Receptor Clusters

AbstractMuscular dystrophies are disorders characterized by progressive muscle loss and weakness that are both genotypically and phenotypically heterogenous. Progression of muscle disease arises from impaired regeneration, plasma membrane instability, defective membrane repair, and calcium mishandling. The ferlin protein family, including dysferlin and myoferlin, are calcium-binding, membrane-associated proteins that regulate membrane fusion, trafficking, and tubule formation. Mice lacking dysferlin (Dysf), myoferlin (Myof), and both dysferlin and myoferlin (Fer) on an isogenic inbred 129 background were previously demonstrated that loss of both dysferlin and myoferlin resulted in more severe muscle disease than loss of either gene alone. Furthermore, Fer mice had disordered triad organization with visibly malformed transverse tubules and sarcoplasmic reticulum, suggesting distinct roles of dysferlin and myoferlin. To assess the physiological role of disorganized triads, we now assessed excitation contraction (EC) coupling in these models. We identified differential abnormalities in EC coupling and ryanodine receptor disruption in flexor digitorum brevis myofibers isolated from ferlin mutant mice. We found that loss of dysferlin alone preserved sensitivity for EC coupling and was associated with larger ryanodine receptor clusters compared to wildtype myofibers. Loss of myoferlin alone or together with a loss of dysferlin reduced sensitivity for EC coupling, and produced disorganized and smaller ryanodine receptor cluster size compared to wildtype myofibers. These data reveal impaired EC coupling in Myof and Fer myofibers and slightly potentiated EC coupling in Dysf myofibers. Despite high homology, dysferlin and myoferlin have differential roles in regulating sarcotubular formation and maintenance resulting in unique impairments in calcium handling properties.

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.

Regulation of intracellular calcium in N1E-115 neuroblastoma cells: the role of Na+/Ca2+exchange

2002 ◽  
Vol 282 (5) ◽  
pp. C1000-C1008 ◽  
Author(s):  
Kara L. Kopper ◽  
Joseph S. Adorante
Keyword(s):  
Membrane Potential ◽  
Intracellular Calcium ◽  
Normal Cell ◽  
Buffer Capacity ◽  
Neuroblastoma Cells ◽  
Fold Increase ◽  
Scorpion Venom ◽  
Reverse Mode ◽  
Intracellular Ca

In fura 2-loaded N1E-115 cells, regulation of intracellular Ca2+ concentration ([Ca2+]i) following a Ca2+ load induced by 1 μM thapsigargin and 10 μM carbonylcyanide p-trifluoromethyoxyphenylhydrazone (FCCP) was Na+ dependent and inhibited by 5 mM Ni2+. In cells with normal intracellular Na+ concentration ([Na+]i), removal of bath Na+, which should result in reversal of Na+/Ca2+exchange, did not increase [Ca2+]i unless cell Ca2+ buffer capacity was reduced. When N1E-115 cells were Na+ loaded using 100 μM veratridine and 4 μg/ml scorpion venom, the rate of the reverse mode of the Na+/Ca2+ exchanger was apparently enhanced, since an ∼4- to 6-fold increase in [Ca2+]ioccurred despite normal cell Ca2+ buffering. In SBFI-loaded cells, we were able to demonstrate forward operation of the Na+/Ca2+ exchanger (net efflux of Ca2+) by observing increases (∼ 6 mM) in [Na+]i. These Ni2+ (5 mM)-inhibited increases in [Na+]i could only be observed when a continuous ionomycin-induced influx of Ca2+ occurred. The voltage-sensitive dye bis-(1,3-diethylthiobarbituric acid) trimethine oxonol was used to measure changes in membrane potential. Ionomycin (1 μM) depolarized N1E-115 cells (∼25 mV). This depolarization was Na+dependent and blocked by 5 mM Ni2+ and 250–500 μM benzamil. These data provide evidence for the presence of an electrogenic Na+/Ca2+ exchanger that is capable of regulating [Ca2+]i after release of Ca2+ from cell stores.

Analysis of Dihydropyridine and Ryanodine Receptor Clusters in Healthy and Failing Human Cardiac Myocytes

2008 ◽  
Vol 17 ◽  
pp. S232
Author(s):  
David Crossman ◽  
Christian Soeller ◽  
Peter Ruygrok ◽  
Mark Cannell
Keyword(s):  
Cardiac Myocytes ◽  
Ryanodine Receptor ◽  
Receptor Clusters

Fluid pressure modulates L-type Ca2+ channel via enhancement of Ca2+-induced Ca2+ release in rat ventricular myocytes

2008 ◽  
Vol 294 (4) ◽  
pp. C966-C976 ◽  
Author(s):  
Sunwoo Lee ◽  
Joon-Chul Kim ◽  
Yuhua Li ◽  
Min-Jeong Son ◽  
Sun-Hee Woo
Keyword(s):  
Ventricular Myocytes ◽  
Fluid Pressure ◽  
Inhibitory Effect ◽  
Cellular Mechanism ◽  
Confocal Imaging ◽  
Rat Ventricular Myocytes ◽  
Whole Cell Patch Clamp ◽  
Current Voltage ◽  
Intracellular Ca ◽  
High Concentrations

This study examines whether fluid pressure (FP) modulates the L-type Ca2+ channel in cardiomyocytes and investigates the underlying cellular mechanism(s) involved. A flow of pressurized (∼16 dyn/cm2) fluid, identical to that bathing the myocytes, was applied onto single rat ventricular myocytes using a microperfusion method. The Ca2+ current ( ICa) and cytosolic Ca2+ signals were measured using a whole cell patch-clamp and confocal imaging, respectively. It was found that the FP reversibly suppressed ICa (by 25%) without altering the current-voltage relationships, and it accelerated the inactivation of ICa. The level of ICa suppression by FP depended on the level and duration of pressure. The Ba2+ current through the Ca2+ channel was only slightly decreased by the FP (5%), suggesting an indirect inhibition of the Ca2+ channel during FP stimulation. The cytosolic Ca2+ transients and the basal Ca2+ in field-stimulated ventricular myocytes were significantly increased by the FP. The effects of the FP on the ICa and on the Ca2+ transient were resistant to the stretch-activated channel inhibitors, GsMTx-4 and streptomycin. Dialysis of myocytes with high concentrations of BAPTA, the Ca2+ buffer, eliminated the FP-induced acceleration of ICa inactivation and reduced the inhibitory effect of the FP on ICa by ≈80%. Ryanodine and thapsigargin, abolishing sarcoplasmic reticulum Ca2+ release, eliminated the accelerating effect of FP on the ICa inactivation, and they reduced the inhibitory effect of FP on the ICa. These results suggest that the fluid pressure indirectly suppresses the Ca2+ channel by enhancing the Ca2+-induced intracellular Ca2+ release in rat ventricular myocytes.

Abstract 1079: Prevention of Fatal Arrhythmia in a Catecholaminergic Polymorphic Ventricular Tachycardia Mouse Model Carrying Calsequestrin-2 Mutation

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Hiroko Wakimoto ◽  
Ronny Alcalai ◽  
Lei Song ◽  
Michael Arad ◽  
Christine E Seidman ◽  
...  
Keyword(s):  
Ventricular Tachycardia ◽  
Mouse Model ◽  
Peak Height ◽  
Mutant Mice ◽  
Catecholaminergic Polymorphic Ventricular Tachycardia ◽  
Polymorphic Ventricular Tachycardia ◽  
Study Drug Administration ◽  
Intracellular Ca

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a familial arrhythmia syndrome caused by mutations in the ryanodine receptor (RyR2) or calsequestrin-2 (CASQ2) genes and characterized by exercise or emotional stress-induced sudden death. Beta-adrenergic blockers are only partially effective and other agents have not been widely tested. Recent studies have shown that CPVT is mediated by increased Ca 2+ leak through the RyR2 channel. Our aim was to determine whether agents that inhibit intracellular Ca 2+ leak can effectively prevent CPVT. Methods: The efficacy of intraperitoneal (IP) propranolol (1mcg/g), Mg 2+ (0.002mEq/g), verapamil (8 mcg/g) and diltiazem (8 mcg/g) were tested both in vivo and in vitro using CASQ2 mutant mouse CPVT model. In vivo studies included ambulatory ECG recordings at rest and following epinephrine stress (0.4 mcg/g IP) at baseline and after study drug administration. Experiments for each drug were performed on separate days to avoid confounding effects. In vitro studies included intracellular Ca 2+ transient analysis on isolated cardiomyocytes from mutant mice with and without epinephrine (5.5 μM). Results: All 4 drugs restored sinus rhythm and reduced the frequency of VT episodes induced by epinephrine in CASQ2 mutant mice. Only verapamil completely prevented epinephrine-induced VT in 87% of the mice (p<0.01). Cardiomyocyte studies in basal conditions revealed that Mg 2+ and verapamil inhibited sarcomere contraction and normalized the prolonged Ca 2+ reuptake period in CASQ2 mutants, but did not decrease baseline Ca 2+ peak height. Epinephrine-stressed mutant myocytes had increased diastolic Ca 2+ levels, lower Ca 2+ peak height and spontaneous SR Ca 2+ release events that were partially prevented by verapamil and Mg 2+ . Verapamil was more effective than Mg 2+ in reducing the frequency of spontaneous Ca 2+ releases induced by epinephrine. Conclusions: All 4 agents can inhibit ventricular arrhythmia in CPVT mouse model; however verapamil appears most effective in preventing arrhythmia in vivo and in modifying intracellular abnormal calcium handling. Calcium antagonists might have therapeutic value in CPVT and other RyR2-mediated arrhythmias and should be considered for human clinical studies.

Junctophilin-2  physically interacts with ryanodine receptor type 2 for peripheral coupling of mouse cardiomyocytes

2020 ◽  
Author(s):  
Tianxia Luo ◽  
Ningning Yan ◽  
Mengru Xu ◽  
Fengjuan Dong ◽  
Qian Liang ◽  
...  
Keyword(s):  
Ryanodine Receptor ◽  
Bioinformatic Analysis ◽  
Cardiac Contraction ◽  
Receptor Type ◽  
Immunofluorescent Staining ◽  
Physical Interaction ◽  
C Terminus ◽  
Confocal Immunofluorescence ◽  
Intracellular Ca

Abstract Background: Ryanodine receptor type 2 (RyR2) mediate Ca 2+ release from the endoplasmic and sarcoplasmic reticulum (ER and SR), which is involved in the peripheral coupling of mouse cardiomyocytes, and thereby plays an important role in cardiac contraction. Junctophilin-2 (JPH2, JP2) is anchored to the plasma membrane (PM) and membranes of the ER and SR, and modulates intracellular Ca 2+ handling through regulation of RyR2. However, the potential RyR2 binding region of JPH2 is poorly understood. Methods: The interaction of JPH2 with RyR2 was studied using LC-MS/MS , bioinformatic analysis,co-immunoprecipitation studies in cardiac SR vesicles. GST-pull down analysis was performed to investigate the physical interaction between RyR2 and JPH2 fragments. Immunofluorescent staining was carried out to determine the colocalization of RyR2 and JPH2 in isolated mouse cardiomyocytes. Ion Optix photometry system was used to measure the levels of intracellular Ca 2+ transients in cardiomyocytes isolated from JPH2 knock down mice. Results: We report that (i) JPH2 interacts with RyR2 and (ii) the C terminus of the JPH2 protein can pull down RyR2 receptors. Confocal immunofluorescence imaging indicated that the majority of JPH2 and RyR2 proteins were colocalized near Z-lines. A decrease in the levels of JPH2 expression reduced the amplitude of Ca 2+ transients in cardiomyocytes. Conclusions: This study suggests that the C terminus domain of JPH2 is required for interactions with RyR2 in the context of peripheral coupling of mouse cardiomyocytes, which provide a molecular mechanism for looking for Ca 2+ - related diseases prevention strategies.

Distribution and Activation of Intracellular Ca2+ Stores in Cultured Olfactory Bulb Neurons

1997 ◽  
Vol 78 (4) ◽  
pp. 2176-2185 ◽  
Author(s):  
Greg C. Carlson ◽  
Melissa L. Slawecki ◽  
Eric Lancaster ◽  
Asaf Keller
Keyword(s):  
Olfactory Bulb ◽  
Ryanodine Receptor ◽  
Acid Decarboxylase ◽  
Cultured Neurons ◽  
Local Pressure ◽  
Intracellular Release ◽  
Intracellular Ca ◽  
Almost All ◽  
Olfactory Bulb Neurons

Carlson, Greg C., Melissa L. Slawecki, Eric Lancaster, and Asaf Keller. Distribution and activation of intracellular Ca2+ stores in cultured olfactory bulb neurons. J. Neurophysiol. 78: 2176–2185, 1997. The presence and distribution of intracellular Ca2+ release pathways in olfactory bulb neurons were studied in dissociated cell cultures. Histochemical techniques and imaging of Ca2+ fluxes were used to identify two major intracellular Ca2+ release mechanisms: inositol 1,4,5-triphosphate receptor (IP3R)-mediated release, and ryanodine receptor-mediated release. Cultured neurons were identified by immunocytochemistry for the neuron-specificmarker β-tubulin III. Morphometric analyses and immunocytochemistry for glutamic acid-decarboxylase revealed a heterogeneous population of cultured neurons with phenotypes corresponding to both projection (mitral/tufted) and intrinsic (periglomerular/granule) neurons of the in vivo olfactory bulb. Immunocytochemistry for the IP3R, and labeling with fluorescent-tagged ryanodine, revealed that, irrespective of cell type, almost all cultured neurons express IP3R and ryanodine binding sites in both somata and dendrites. Functional imaging revealed that intracellular Ca2+ fluxes can be generated in the absence of external Ca2+, using agonists specific to each of the intracellular release pathways. Local pressure application of glutamate or quisqualate evoked Ca2+ fluxes in both somata and dendrites in nominally Ca2+ free extracellular solutions, suggesting the presence of IP3-dependent Ca2+ release. These fluxes were blocked by preincubation with thapsigargin and persisted in the presence of the glutamate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione. Local application of caffeine, a ryanodine receptor agonist, also evoked intracellular Ca2+ fluxes in the absence of extracellular Ca2+. These Ca2+ fluxes were suppressed by preincubation with ryanodine. In all neurons, both IP3- and ryanodine-dependent release pathways coexisted, suggesting that they interact to modulate intracellular Ca2+ concentrations.

scholarly journals The arrhythmogenic N53I variant subtly changes the structure and dynamics in the calmodulin N-terminal domain, altering its interaction with the cardiac ryanodine receptor

2020 ◽  
Vol 295 (22) ◽  
pp. 7620-7634
Author(s):  
Christian Holt ◽  
Louise Hamborg ◽  
Kelvin Lau ◽  
Malene Brohus ◽  
Anders Bundgaard Sørensen ◽  
...  
Keyword(s):  
Ventricular Tachycardia ◽  
Ryanodine Receptor ◽  
Hydrophobic Surface ◽  
Catecholaminergic Polymorphic Ventricular Tachycardia ◽  
Polymorphic Ventricular Tachycardia ◽  
Open Probability ◽  
Calmodulin Binding ◽  
Terminal Domain ◽  
Genes Encoding ◽  
Cardiac Ryanodine Receptor

Mutations in the genes encoding the highly conserved Ca2+-sensing protein calmodulin (CaM) cause severe cardiac arrhythmias, including catecholaminergic polymorphic ventricular tachycardia or long QT syndrome and sudden cardiac death. Most of the identified arrhythmogenic mutations reside in the C-terminal domain of CaM and mostly affect Ca2+-coordinating residues. One exception is the catecholaminergic polymorphic ventricular tachycardia–causing N53I substitution, which resides in the N-terminal domain (N-domain). It does not affect Ca2+ coordination and has only a minor impact on binding affinity toward Ca2+ and on other biophysical properties. Nevertheless, the N53I substitution dramatically affects CaM's ability to reduce the open probability of the cardiac ryanodine receptor (RyR2) while having no effect on the regulation of the plasmalemmal voltage-gated Ca2+ channel, Cav1.2. To gain more insight into the molecular disease mechanism of this mutant, we used NMR to investigate the structures and dynamics of both apo- and Ca2+-bound CaM-N53I in solution. We also solved the crystal structures of WT and N53I CaM in complex with the primary calmodulin-binding domain (CaMBD2) from RyR2 at 1.84–2.13 Å resolutions. We found that all structures of the arrhythmogenic CaM-N53I variant are highly similar to those of WT CaM. However, we noted that the N53I substitution exposes an additional hydrophobic surface and that the intramolecular dynamics of the protein are significantly altered such that they destabilize the CaM N-domain. We conclude that the N53I-induced changes alter the interaction of the CaM N-domain with RyR2 and thereby likely cause the arrhythmogenic phenotype of this mutation.

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