Aminophylline, a bronchodilator mainly used to treat severe asthma attacks, may induce arrhythmias. Unfortunately, the underlying mechanism is not well understood. We have recently described a significant, on average inhibitory effect of aminophylline on inward rectifier potassium current IK1, known to substantially contribute to arrhythmogenesis, in rat ventricular myocytes at room temperature. This study was aimed to examine whether a similar effect may be observed under clinically relevant conditions. Experiments were performed using the whole cell patch clamp technique at 37°C on enzymatically isolated healthy porcine and failing human ventricular myocytes. The effect of clinically relevant concentrations of aminophylline (10-100 μM) on IK1 did not significantly differ in healthy porcine and failing human ventricular myocytes. IK1 was reversibly inhibited by ∼20 and 30 % in the presence of 30 and 100 μM aminophylline, respectively, at -110 mV; an analogical effect was observed at -50 mV. To separate the impact of IK1 changes on AP configuration, potentially interfering ionic currents were blocked (L-type calcium and delayed rectifier potassium currents). A significant prolongation of AP duration was observed in the presence of 100 μM aminophylline in porcine cardiomyocytes which well agreed with the effect of a specific IK1 inhibitor Ba2+ (10 μM) and with the result of simulations using a porcine ventricular cell model. We conclude that the observed effect of aminophylline on healthy porcine and failing human IK1 might be involved in its proarrhythmic action. To fully understand the underlying mechanism, potential aminophylline impact on other ionic currents should be explored.
- MeSH
- akční potenciály účinky léků MeSH
- aminofylin * farmakologie MeSH
- draslíkové kanály dovnitř usměrňující * metabolismus MeSH
- kardiomyocyty * účinky léků metabolismus MeSH
- lidé MeSH
- metoda terčíkového zámku MeSH
- prasata MeSH
- srdeční komory účinky léků metabolismus MeSH
- srdeční selhání metabolismus farmakoterapie MeSH
- vztah mezi dávkou a účinkem léčiva MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
The combination of aminophylline and salbutamol is frequently used in clinical practice in the treatment of obstructive lung diseases. While the side effects (including arrhythmias) of the individual bronchodilator drugs were well described previously, the side effects of combined treatment are almost unknown. We aimed to study the arrhythmogenic potential of combined aminophylline and salbutamol treatment in vitro. For this purpose, we used the established atomic force microscopy (AFM) model coupled with cardiac organoids derived from human pluripotent stem cells (hPSC-CMs). We focused on the chronotropic, inotropic, and arrhythmogenic effects of salbutamol alone and aminophylline and salbutamol combined treatment. We used a method based on heart rate/beat rate variability (HRV/BRV) analysis to detect arrhythmic events in the hPSC-CM based AFM recordings. Salbutamol and aminophylline had a synergistic chronotropic and inotropic effect compared to the effects of monotherapy. Our main finding was that salbutamol reduced the arrhythmogenic effect of aminophylline, most likely mediated by endothelial nitric oxide synthase activated by beta-2 adrenergic receptors. These findings were replicated and confirmed using hPSC-CM derived from two cell lines (CCTL4 and CCTL12). Data suggest that salbutamol as an add-on therapy may not only deliver a bronchodilator effect but also increase the cardiovascular safety of aminophylline, as salbutamol reduces its arrhythmogenic potential.
- MeSH
- albuterol * farmakologie MeSH
- aminofylin * farmakologie MeSH
- bronchodilatancia farmakologie MeSH
- buněčné linie MeSH
- kardiomyocyty účinky léků metabolismus MeSH
- lidé MeSH
- mikroskopie atomárních sil MeSH
- pluripotentní kmenové buňky účinky léků cytologie MeSH
- srdeční arytmie * farmakoterapie MeSH
- srdeční frekvence účinky léků MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Human induced pluripotent stem cell (iPSC) lines were generated from peripheral blood mononuclear cells (PBMCs) isolated from two related patients diagnosed with either idiopathic ventricular fibrillation or catecholaminergic polymorphic ventricular tachycardia, carrying an unknown variant in the RYR2 gene, c.14201A>G (p.Y4734C) and one healthy related individual. Reprogramming was done using a commercially available Epi5 Reprogramming Kit. The pluripotency of the iPSC lines was verified by the expression of pluripotency markers and by their capacity to differentiate into all three embryonic germ layers in vitro. These iPSC lines are available for functional analysis and in vitro studies of RYR2 channelopathy.
- MeSH
- buněčná diferenciace MeSH
- buněčné linie MeSH
- dospělí MeSH
- fibrilace komor * genetika MeSH
- indukované pluripotentní kmenové buňky * metabolismus MeSH
- komorová tachykardie * genetika metabolismus MeSH
- lidé MeSH
- ryanodinový receptor vápníkového kanálu * genetika metabolismus MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
The sarcolemmal Ca2+ efflux pathways, Na+-Ca2+-exchanger (NCX) and Ca2+-ATPase (PMCA), play a crucial role in the regulation of intracellular Ca2+ load and Ca2+ transient in cardiomyocytes. The distribution of these pathways between the t-tubular and surface membrane of ventricular cardiomyocytes varies between species and is not clear in human. Moreover, several studies suggest that this distribution changes during the development and heart diseases. However, the consequences of NCX and PMCA redistribution in human ventricular cardiomyocytes have not yet been elucidated. In this study, we aimed to address this point by using a mathematical model of the human ventricular myocyte incorporating t-tubules, dyadic spaces, and subsarcolemmal spaces. Effects of various combinations of t-tubular fractions of NCX and PMCA were explored, using values between 0.2 and 1 as reported in animal experiments under normal and pathological conditions. Small variations in the action potential duration (≤ 2%), but significant changes in the peak value of cytosolic Ca2+ transient (up to 17%) were observed at stimulation frequencies corresponding to the human heart rate at rest and during activity. The analysis of model results revealed that the changes in Ca2+ transient induced by redistribution of NCX and PMCA were mainly caused by alterations in Ca2+ concentrations in the subsarcolemmal spaces and cytosol during the diastolic phase of the stimulation cycle. The results suggest that redistribution of both transporters between the t-tubular and surface membranes contributes to changes in contractility in human ventricular cardiomyocytes during their development and heart disease and may promote arrhythmogenesis.
- MeSH
- akční potenciály MeSH
- biologické modely MeSH
- buněčná membrána metabolismus MeSH
- kardiomyocyty * metabolismus MeSH
- lidé MeSH
- modely kardiovaskulární MeSH
- pumpa pro výměnu sodíku a vápníku * metabolismus MeSH
- sarkolema * metabolismus MeSH
- srdeční komory * metabolismus MeSH
- vápník * metabolismus MeSH
- vápníková signalizace MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Traditionally, aborted cardiac arrest (ACA) due to documented ventricular fibrillation (VF) in the absence of structural heart disease has been termed idiopathic VF. By careful evaluation, a specific etiology can be found in a substantial proportion of patients. The aim of this survey was to assess the yield of an advanced diagnostic work-up to reveal a causative etiology in a real-life clinical setting. Patients from the University Hospital Brno's ACA database were analyzed (514 patients in total). Forty-six patients (31 males) fulfilled the inclusion criteria, which were: (1) absence of structural pathology on echocardiography; (2) absence of coronary artery disease; and (3) absence of reversible cause of ACA. The diagnostic work-up consisted in cardiac magnetic resonance imaging, stress testing, sodium channel blocker challenge, and genetic testing according to the availability of the method and patient compliance. A specific disease was found in 17 individuals (37.0%), although at least one diagnostic step was refused by 13 patients (28.3%). True idiopathic VF was confirmed in 7 patients (15.2%), for whom the entire diagnostic work-up did not reveal any specific pathology. Our real-life survey shows that, even with an incomplete diagnostic work-up (due to the unavailability of a particular method or variable patient compliance), a specific diagnosis can be identified in more than one third of the cases of "idiopathic" VF, which can thus enable targeted treatment and family screening.
- MeSH
- dospělí MeSH
- echokardiografie MeSH
- fibrilace komor * diagnóza MeSH
- genetické testování metody MeSH
- lidé středního věku MeSH
- lidé MeSH
- magnetická rezonanční tomografie metody MeSH
- senioři MeSH
- zátěžový test MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- senioři MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- MeSH
- Brugadův syndrom * patofyziologie genetika diagnóza terapie MeSH
- lidé MeSH
- modely nemocí na zvířatech * MeSH
- myši MeSH
- napěťově řízený sodíkový kanál, typ 5 genetika MeSH
- sodíkové kanály genetika MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- myši MeSH
- zvířata MeSH
- Publikační typ
- komentáře MeSH
- úvodníky MeSH
- Publikační typ
- abstrakt z konference MeSH
Sildenafil (Viagra), the first approved and widely used oral drug for the treatment of erectile dysfunction, was occasionally associated with life-threatening ventricular arrhythmias in patients. Since inward rectifier potassium current (IK1) may considerably contribute to this arrhythmogenesis, we investigated the effect of sildenafil on the human Kir2.1 and Kir2.2, the prevailing subunits forming the ventricular IK1 channels. Experiments were performed by the whole-cell patch clamp technique at 37°C using Chinese hamster ovary cells transiently expressing the human Kir2.1 and Kir2.2 channels. Changes of both the inward and outward current components (at -110 and -50 mV, respectively) were tested to be able to consider the physiological relevance of the sildenafil effect (changes at -110 and -50 mV did not significantly differ, results at -50 mV are listed below). A significant Kir2.1 inhibition was observed at all applied sildenafil concentrations (16.1% ± 3.7%, 20.0% ± 2.6%, and 15.0% ± 3.0% at 0.1, 1, and 10 μM, respectively). The inhibitory effect of 0.1 μM sildenafil was potentiated by the presence of a low concentration of Ba2+ (0.1 μM) which induced only a slight Kir2.1 inhibition by 5.95% ± 0.75% alone (the combined effect was 35.5% ± 3.4%). The subtherapeutic and therapeutic sildenafil concentrations (0.1 and 1 μM) caused a dual effect on Kir2.2 channels whereas a significant Kir2.2 activation was observed at the supratherapeutic sildenafil concentration (10 μM: 34.1% ± 5.6%). All effects were fully reversible. This is the first study demonstrating that sildenafil at clinically relevant concentrations inhibits both the inward and outward current components of the main human ventricular IK1 subunit Kir2.1. This inhibitory effect was significantly potentiated by a low concentration of environmental contaminant Ba2+ in agreement with recently reported data on rat ventricular IK1 which additionally showed a significant repolarization delay. Considering the similar subunit composition of the human and rat ventricular IK1 channels, the observed effects might contribute to sildenafil-associated arrhythmogenesis in clinical practice.
- Publikační typ
- časopisecké články MeSH
The transverse-axial tubular system (tubular system) of cardiomyocytes plays a key role in excitation-contraction coupling. To determine the area of the tubular membrane in relation to the area of the surface membrane, indirect measurements through the determination of membrane capacitances are currently used in addition to microscopic methods. Unlike existing electrophysiological methods based on an irreversible procedure (osmotic shock), the proposed new approach uses a reversible short-term intermittent increase in the electrical resistance of the extracellular medium. The resulting increase in the lumen resistance of the tubular system makes it possible to determine separate capacitances of the tubular and surface membranes. Based on the analysis of the time course of the capacitive current, computational relations were derived to quantify the elements of the electrical equivalent circuit of the measured cardiomyocyte including both capacitances. The exposition to isotonic low-conductivity sucrose solution is reversible which is the main advantage of the proposed approach allowing repetitive measurements on the same cell under control and sucrose solutions. Experiments on rat ventricular cardiomyocytes (n = 20) resulted in the surface and tubular capacitance values implying the fraction of tubular capacitance/area of 0.327 ± 0.018. We conclude that the newly proposed method provides results comparable to the data obtained by the currently used detubulation method and, in addition, by being reversible, allows repeated evaluation of surface and tubular membrane parameters on the same cell.
- MeSH
- biologický transport * fyziologie MeSH
- buněčná membrána fyziologie MeSH
- iontové kanály řízené ligandy fyziologie MeSH
- lidé MeSH
- membránové transportní proteiny MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- přehledy MeSH
