P3830Carvedilol treatment diminishes spontaneous calcium release and electrical activity in human atrial myocytes

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
V Jimenez-Sabado ◽  
T Lu ◽  
S Casabella ◽  
C Tarifa ◽  
A Herraiz-Martinez ◽  
...  
Keyword(s):  
Electrical Activity ◽  
Adrenergic Receptors ◽  
Calcium Release ◽  
Calcium Waves ◽  
Atrial Myocytes ◽  
Patch Clamp Technique ◽  
Human Atrial Myocytes ◽  
Site Density ◽  
Inward Currents ◽  
Beta 2

Abstract Background Atrial fibrillation (AF) has been associated with an increase in spontaneous calcium release induced electrical activity, which could potentially be reversed by carvedilol, a nonselective beta-blocker that also inhibits the cardiac ryanodine receptor (RyR2). Interestingly the enantiomer R-carvedilol inhibits the RyR2 but not beta-adrenergic receptors, allowing it to effectively prevent calcium release-induced spontaneous electrical activity without inducing bradycardia and hypotension. Purpose The purpose of this study was to determine how carvedilol treatment affects calcium release-induced transient inward currents (ITI) in human atrial myocytes from patients with AF; and to test the effects of R-carvedilol on spontaneous calcium release in order to assess its therapeutical utility. Methods Human atrial myocytes were isolated from patients undergoing cardiac surgery and subjected to patch-clamp technique (n=60) or confocal calcium imaging (n=6). Beta-2 adrenergic receptors were activated with the selective agonist fenoterol (3μM) and 1μM R-carvedilol was used to inhibit spontaneous calcium release events. Results Recordings of calcium release-induced transient inward currents (ITI) revealed that carvedilol treatment reduced the ITI frequency in patients with AF from 2.2±0.4 events/min in untreated patients to 0.59±0.35 events/min (p<0.01), which was even lower than the incidence in patients without AF (1.0±0.1 events/min; p<0.01). To assess the effects of R-carvedilol, myocytes were first simulated with fenoterol. This increased the calcium spark frequency from 23±15 to 960±336 events/s/1000μm2 in 16 cells from 6 patients (p<0.05). This was due to an increase in the spark site density (from 0.50±0.24 to 12.1±2.4 sites/1000μm2, p<0.001) rather than in the firing rate (0.068±0.14 vs. 0.035±0.012 sparks/s in control, p=0.14). Fenoterol also increased the spark duration from 50.9±5.4 to 77.3±4.1ms (p<0.001) without affecting the amplitude. Importantly, fenoterol also induced global calcium release events such as calcium waves and transients (2.8±1.1 vs. 0 events/min in control, p<0.05). When R-carvedilol was added, the effects of fenoterol were abolished, reducing the incidence of calcium sparks to 69±51 events/s/1000μm2 (p<0.05), the spark site density to 1.68±1.04 sites/1000μm2 (p<0.01), the spark duration to 63.4±4.3ms (p<0.05), and calcium waves and transients were reduced to 0.21±0.14 events/min (p<0.05). Conclusions Carvedilol treatment reduces the ITI frequency in patients with AF to levels below that observed at baseline in patients without AF. Furthermore, the non-beta-blocking R-carvedilol enantiomer abolishes spontaneous calcium release events induced by beta-2 adrenergic stimulation in human atrial myocytes, proposing a therapeutical utility for this compound in patients with AF linked to excessive spontaneous calcium release. Acknowledgement/Funding SAF2017-88019; Marato2015-20-30; SGR2017-1769; CIBERCV

P1233Differential effects of five risk variants for atrial fibrillation at the 4q25 region on L-type calcium current and transient inward currents in human atrial myocytes

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
C Tarifa ◽  
A Herraiz-Martinez ◽  
A Llach ◽  
V Jimenez-Sabado ◽  
H Colino ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Calcium Homeostasis ◽  
Calcium Current ◽  
Calcium Release ◽  
Chromosomal Region ◽  
Atrial Myocytes ◽  
Patch Clamp Technique ◽  
Risk Variant ◽  
Risk Variants ◽  
Inward Currents

Abstract Background An increasing number of single nucleotide polymorphisms (SNPs) at the chromosomal region 4q25 have been associated with risk of atrial fibrillation (AF) and we have recently reported that carriers of the rs13143308 risk variant have an increased incidence of spontaneous calcium release-induce transient inward currents (ITI). However, it is not known if different 4q25 variants have similar effects. Purpose This study aimed to compare the effects of five SNPs at 4q25 on L-type calcium current (ICa) and ITI frequency, features that are altered in patients with AF. Methods To avoid confounding effects of AF on calcium homeostasis, atrial samples from 63 patients without AF were genotyped and divided into groups according to the genotype of the SNPs rs1448818, rs6817105, rs13143308, rs6843082, rs3853443 ordered according to their location and identified by the three last digits + an R for risk or N for normal variants. ICa density and ITI frequency were measured with perforated patch clamp technique in atrial myocytes from these patients. Results Three SNPs 818, 308 and 443 segregated independently of the genotype at the other loci. The 105 and 082 loci always co-segregated with 308 but never together. The ICa density was smaller in carriers of 818R and 443N variants (−1.6±0.3pA/pF, p=0.01) or 818N and 443R variants (−1.6±0.4pA/pF, p=0.02) than in patients with 818N and 443N variants (−3.2±0.4pA/pF), independently of the genotype at 105, 308 and 082 (these loci did not affect ICa). In contrast, to this, the ITI frequency was increased only in myocytes from patients carrying 105R, 308R and 082N (1.4±0.2events/min, p<0.001) or 105N, 308R and 082R (1.6±0.5events/min, p=0.002) when compared to patients with 105N, 308N and 082N (0.36±0.09events/min) independently of the genotypes at 818 and 443, or when compared to patients without risk at any of the five loci (0.55±0.30events/min). The table shows schematically the qualitative effects of the different risk variants. Risk variant rs1448818C rs6817105C rs13143308T rs6843082T rs3853445C ICa Decreased Unchanged Unchanged Unchanged Decreased ITI Unchanged Increased Increased Increased Unchanged Conclusion Different SNPs at the chromosomal region 4q25 are associated with differential pathological changes in intracellular calcium homeostasis. Risk variants at rs1448818 or rs3853445 cause loss of ICa without affecting ITI frequency while a risk variant at rs13143308 elevates the ITI frequency without affecting ICa. These findings afford a framework for stratification of pharmacological therapy based on the functional effects of the 4q25 risk variants Acknowledgement/Funding SAF2017-88019; Marato2015-20-30; SGR2017-1769; CIBERCV

Transmembrane chloride currents in human atrial myocytes

1996 ◽  
Vol 270 (2) ◽  
pp. C500-C507 ◽  
Author(s):  
G. R. Li ◽  
J. Feng ◽  
Z. Wang ◽  
S. Nattel
Keyword(s):  
Membrane Conductance ◽  
Cell Swelling ◽  
Disulfonic Acid ◽  
Atrial Myocytes ◽  
Patch Clamp Technique ◽  
Chloride Currents ◽  
Whole Cell ◽  
Human Atrial Myocytes ◽  
Cyclic Monophosphate ◽  
Whole Cell Patch Clamp

The present study was designed to evaluate the presence of basal, swelling-induced, and cAMP-dependent Cl- currents in human atrial myocytes studied with the whole cell patch-clamp technique. Under basal conditions, a small outwardly rectifying background conductance was noted that reversed close to 0 mV and was not altered by Cl- replacement. Isoproterenol (1 microM), forskolin (3 microM), and 8-bromoadenosine 3',5'-cyclic monophosphate (50 microM) did not increase membrane conductance, even when responsiveness to isoproterenol was confirmed by an increase in Ca2+ current and when perforated-patch techniques (nystatin) were used. Exposure to hyposmotic solutions increased cell volume and induced a whole cell conductance that showed outward rectification, was inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (100 microM), and responded to changes in Cl- gradient in a fashion consistent with a Cl(-)-selective conductance, with estimated relative permeabilities of 1, 0.25, and 0.07 for Cl-, methanesulfonate, and aspartate, respectively. The results suggest that human atrial cells lack basal and adenosine 3',5'-cyclic monophosphate-dependent Cl- current but manifest a substantial Cl- conductance in the presence of cell swelling.

scholarly journals Atrial Fibrillation Is Associated With Increased Spontaneous Calcium Release From the Sarcoplasmic Reticulum in Human Atrial Myocytes

Circulation ◽  
2004 ◽  
Vol 110 (11) ◽  
pp. 1358-1363 ◽  
Author(s):  
Leif Hove-Madsen ◽  
Anna Llach ◽  
Antoni Bayes-Genís ◽  
Santiago Roura ◽  
Enrique Rodriguez Font ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Sarcoplasmic Reticulum ◽  
Calcium Release ◽  
Atrial Myocytes ◽  
Human Atrial Myocytes

An increase of late sodium current induces delayed afterdepolarizations and sustained triggered activity in atrial myocytes

2008 ◽  
Vol 294 (5) ◽  
pp. H2031-H2039 ◽  
Author(s):  
Yejia Song ◽  
John C. Shryock ◽  
Luiz Belardinelli
Keyword(s):  
Calcium Release ◽  
Sodium Current ◽  
Calcium Overload ◽  
Atrial Myocytes ◽  
Patch Clamp Technique ◽  
Calcium Release Channel ◽  
Release Channel ◽  
Triggered Activity ◽  
Pipette Solution ◽  
Delayed Afterdepolarizations

This study determined the role of a slowly inactivating component of sodium current ( INa), late INa, to induce delayed afterdepolarizations (DADs) and triggered activity. We hypothesized that an increase of late INa may induce not only early afterdepolarizations (EADs), but also intracellular calcium overload and DADs. Guinea pig atrial myocytes were studied using the whole cell patch-clamp technique. Anemone toxin II (ATX-II) (5–10 nmol/l) was used to enhance late INa. Ranolazine (10 μmol/l) and TTX (2 μmol/l) were applied to block ATX-II-induced late INa. ATX-II prolonged action potential duration and induced EADs. In the continuous presence of ATX-II, following the appearance of EADs, both DADs and sustained triggered activity occurred. Triggered activity was abolished and DADs were reduced by either ranolazine or TTX. Consistent with induction of DADs, ATX-II induced the transient inward current ( ITI). The amplitude of ITI was significantly reduced by ranolazine. ATX-II induced only EADs, but no DADs, in the presence of the sodium-calcium exchange inhibitor KB-R7943 or the sarcoplasmic reticulum calcium release channel inhibitor ryanodine, or when the calcium chelator EGTA or BAPTA was included in the pipette solution. In conclusion, an increase of late INa, in addition to inducing EADs, can cause cellular calcium overload and induce DADs and sustained triggered activity in atrial myocytes. The data reveal that an increase of late INa is a novel mechanism for initiation of atrial arrhythmic activity.

Regulation of alpha 1-, beta 1-, and beta 2-adrenergic receptors in rat heart by norepinephrine

1996 ◽  
Vol 271 (5) ◽  
pp. H1762-H1768 ◽  
Author(s):  
M. Zhao ◽  
H. K. Hagler ◽  
K. H. Muntz
Keyword(s):  
Adrenergic Receptors ◽  
Ventricular Myocytes ◽  
Plasma Catecholamine ◽  
Elevated Plasma ◽  
Atrial Myocytes ◽  
Rat Hearts ◽  
Chronic Infusion ◽  
Beta 2 ◽  
Set Up ◽  
Tissue Compartments

Previous studies suggest that the desensitization and downregulation of beta 1-adrenergic receptors (beta 1-AR) in the failing heart are the result of the elevated plasma catecholamine levels associated with this disease. To examine norepinephrine (NE)-induced regulation of cardiac adrenergic receptors, rats were infused with l-NE (200 micrograms.kg-1.h-1 for 7 days) or vehicle (0.001 N HCl) by implantation of osmotic minipumps. The technique of coverslip autoradiography was used to quantify alpha 1-adrenergic receptors (alpha 1-AR), beta 1-AR, and beta 2-AR in different tissue compartments of rat hearts. For measurement of beta-AR binding, sections were incubated with 70 pM [125I]iodocyanopindolol (ICYP) alone or in the presence of 5 microM dl-propranolol or 5 x 10(-7) M CGP-20712A (a beta 1-antagonist) and then set up for autoradiography. [3H]prazosin (1 nM) with or without phentolamine was used to study alpha-AR binding. Chronic infusion of NE induced a greater downregulation of beta 2-AR compared with beta 1-AR in all regions studied, including atrial and ventricular myocytes, coronary arterioles, and connective tissue. An 18% loss of beta 1-AR was seen only in atrial myocytes; beta 1-AR density actually increased 28% in ventricular myocytes following NE infusion. There was a 15% decrease in alpha 1-AR in ventricular myocytes, whereas no change in alpha 1-AR density was seen in myocardial arterioles. Our study demonstrates that beta 2-AR are more susceptible to NE-induced downregulation than beta 1-AR. Thus other mechanisms may be involved in the selective downregulation of beta 1-AR in certain forms of heart failure.

scholarly journals Transverse tubules are a common feature in large mammalian atrial myocytes including human

2011 ◽  
Vol 301 (5) ◽  
pp. H1996-H2005 ◽  
Author(s):  
M. A. Richards ◽  
J. D. Clarke ◽  
P. Saravanan ◽  
N. Voigt ◽  
D. Dobrev ◽  
...  
Keyword(s):  
Calcium Release ◽  
Surface Membrane ◽  
Atrial Myocytes ◽  
Close Coupling ◽  
Human Atrial Myocytes ◽  
Temporal Properties ◽  
Ventricular Cells ◽  
T Tubules ◽  
Spatio Temporal ◽  
Cellular Dysfunction

Transverse (t) tubules are surface membrane invaginations that are present in all mammalian cardiac ventricular cells. The apposition of L-type Ca2+ channels on t tubules with the sarcoplasmic reticulum (SR) constitutes a “calcium release unit” and allows close coupling of excitation to the rise in systolic Ca2+. T tubules are virtually absent in the atria of small mammals, and therefore Ca2+ release from the SR occurs initially at the periphery of the cell and then propagates into the interior. Recent work has, however, shown the occurrence of t tubules in atrial myocytes from sheep. As in the ventricle, Ca2+ release in these cells occurs simultaneously in central and peripheral regions. T tubules in both the atria and the ventricle are lost in disease, contributing to cellular dysfunction. The aim of this study was to determine if the occurrence of t tubules in the atrium is restricted to sheep or is a more general property of larger mammals including humans. In atrial tissue sections from human, horse, cow, and sheep, membranes were labeled using wheat germ agglutinin. As previously shown in sheep, extensive t-tubule networks were present in horse, cow, and human atrial myocytes. Analysis shows half the volume of the cell lies within 0.64 ± 0.03, 0.77 ± 0.03, 0.84 ± 0.03, and 1.56 ± 0.19 μm of t-tubule membrane in horse, cow, sheep, and human atrial myocytes, respectively. The presence of t tubules in the human atria may play an important role in determining the spatio-temporal properties of the systolic Ca2+ transient and how this is perturbed in disease.

Inhibition of metabolism abolishes transient outward current in rabbit atrial myocytes

1994 ◽  
Vol 266 (1) ◽  
pp. H182-H190 ◽  
Author(s):  
A. Ogbaghebriel ◽  
A. Shrier
Keyword(s):  
Steady State ◽  
Patch Clamp ◽  
Potassium Current ◽  
Outward Current ◽  
Transient Outward Current ◽  
Atrial Myocytes ◽  
Patch Clamp Technique ◽  
Outward Currents ◽  
Inward Currents ◽  
Inhibition Of Metabolism

Outward currents were measured in single rabbit atrial myocytes using the whole cell configuration of the patch-clamp technique in the presence of tetrodotoxin (5–10 microM) and MnCl2 (2 mM) to block inward currents. Depolarizing voltage-clamp steps from a holding potential of -80 mV elicited a predominant 4-aminopyridine (4-AP)-sensitive transient outward current (Ito). Inhibitors of oxidative metabolism, 2,4-dinitrophenol (DNP; 100 microM) and cyanide (3 mM) abolished Ito and caused a large increase in the steady-state outward current. This steady-state outward current was inhibited by glibenclamide (5 microM), a blocker of the ATP-regulated potassium current (IKATP). In the presence of DNP, glibenclamide (5 microM) not only inhibited IKATP but also partially restored Ito. Absence of ATP from the pipette produced effects on outward currents similar to those induced by DNP or cyanide. We conclude that metabolic inhibition abolishes Ito in rabbit atrial myocytes and suggest that ATP may be required for the activation of the channel.

scholarly journals The 4q25 variant rs13143308T links risk of atrial fibrillation to defective calcium homoeostasis

2018 ◽  
Vol 115 (3) ◽  
pp. 578-589 ◽  
Author(s):  
Adela Herraiz-Martínez ◽  
Anna Llach ◽  
Carmen Tarifa ◽  
Jorge Gandía ◽  
Verónica Jiménez-Sabado ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Electrical Activity ◽  
Calcium Release ◽  
Nucleotide Polymorphisms ◽  
Risk Variant ◽  
Spontaneous Electrical Activity ◽  
Risk Variants ◽  
Calcium Loading ◽  
Inward Currents ◽  
Confocal Calcium Imaging

Abstract Aims Single nucleotide polymorphisms on chromosome 4q25 have been associated with risk of atrial fibrillation (AF) but the exiguous knowledge of the mechanistic links between these risk variants and underlying electrophysiological alterations hampers their clinical utility. Here, we tested the hypothesis that 4q25 risk variants cause alterations in the intracellular calcium homoeostasis that predispose to spontaneous electrical activity. Methods and results Western blotting, confocal calcium imaging, and patch-clamp techniques were used to identify mechanisms linking the 4q25 risk variants rs2200733T and rs13143308T to defects in the calcium homoeostasis in human atrial myocytes. Our findings revealed that the rs13143308T variant was more frequent in patients with AF and that myocytes from carriers of this variant had a significantly higher density of calcium sparks (14.1 ± 4.5 vs. 3.1 ± 1.3 events/min, P = 0.02), frequency of transient inward currents (ITI) (1.33 ± 0.24 vs. 0.26 ± 0.09 events/min, P < 0.001) and incidence of spontaneous membrane depolarizations (1.22 ± 0.26 vs. 0.56 ± 0.17 events/min, P = 0.001) than myocytes from patients with the normal rs13143308G variant. These alterations were linked to higher sarcoplasmic reticulum calcium loading (10.2 ± 1.4 vs. 7.3 ± 0.5 amol/pF, P = 0.01), SERCA2 expression (1.37 ± 0.13 fold, P = 0.03), and RyR2 phosphorylation at ser2808 (0.67 ± 0.08 vs. 0.47 ± 0.03, P = 0.01) but not at ser2814 (0.28 ± 0.14 vs. 0.31 ± 0.14, P = 0.61) in patients carrying the rs13143308T risk variant. Furthermore, the presence of a risk variant or AF independently increased the ITI frequency and the increase in the ITI frequency observed in carriers of the risk variants was exacerbated in those with AF. By contrast, the presence of a risk variant did not affect the amplitude or properties of the L-type calcium current in patients with or without AF. Conclusions Here, we identify the 4q25 variant rs13143308T as a genetic risk marker for AF, specifically associated with excessive calcium release and spontaneous electrical activity linked to increased SERCA2 expression and RyR2 phosphorylation.

The proarrhythmic antihistaminic drug terfenadine increases spontaneous calcium release in human atrial myocytes

2006 ◽  
Vol 553 (1-3) ◽  
pp. 215-221 ◽  
Author(s):  
Leif Hove-Madsen ◽  
Anna Llach ◽  
Cristina E. Molina ◽  
Cristina Prat-Vidal ◽  
Jordi Farré ◽  
...  
Keyword(s):  
Calcium Release ◽  
Atrial Myocytes ◽  
Human Atrial Myocytes ◽  
Antihistaminic Drug
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