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1.
Am J Physiol Cell Physiol ; 327(3): C557-C570, 2024 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-38985989

RESUMEN

The exchange protein directly activated by cAMP (EPAC) has been implicated in cardiac proarrhythmic signaling pathways including spontaneous diastolic Ca2+ leak from sarcoplasmic reticulum and increased action potential duration (APD) in isolated ventricular cardiomyocytes. The action potential (AP) lengthening following acute EPAC activation is mainly due to a decrease of repolarizing steady-state K+ current (IKSS) but the mechanisms involved remain unknown. This study aimed to assess the role of EPAC1 and EPAC2 in the decrease of IKSS and to investigate the underlying signaling pathways. AP and K+ currents were recorded with the whole cell configuration of the patch-clamp technique in freshly isolated rat ventricular myocytes. EPAC1 and EPAC2 were pharmacologically activated with 8-(4-chlorophenylthio)-2'-O-methyl-cAMP acetoxymethyl ester (8-CPTAM, 10 µmol/L) and inhibited with R-Ce3F4 and ESI-05, respectively. Inhibition of EPAC1 and EPAC2 significantly decreased the effect of 8-CPTAM on APD and IKSS showing that both EPAC isoforms are involved in these effects. Unexpectedly, calmodulin-dependent protein kinase II (CaMKII) inhibition by AIP or KN-93, and Ca2+ chelation by intracellular BAPTA, did not impact the response to 8-CPTAM. However, inhibition of PLC/PKC and nitric oxide synthase (NOS)/PKG pathways partially prevents the 8-CPTAM-dependent decrease of IKSS. Finally, the cumulative inhibition of PKC and PKG blocked the 8-CPTAM effect, suggesting that these two actors work along parallel pathways to regulate IKSS upon EPAC activation. On the basis of such findings, we propose that EPAC1 and EPAC2 are involved in APD lengthening by inhibiting a K+ current via both PLC/PKC and NOS/PKG pathways. This may have pathological implications since EPAC is upregulated in diseases such as cardiac hypertrophy.NEW & NOTEWORHTY Exchange protein directly activated by cAMP (EPAC) proteins modulate ventricular electrophysiology at the cellular level. Both EPAC1 and EPAC2 isoforms participate in this effect. Mechanistically, PLC/PKC and nitric oxide synthase (NO)/PKG pathways are involved in regulating K+ repolarizing current whereas the well-known downstream effector of EPAC, calmodulin-dependent protein kinase II (CaMKII), does not participate. This may have pathological implications since EPAC is upregulated in diseases such as cardiac hypertrophy. Thus, EPAC inhibition may be a new approach to prevent arrhythmias under pathological conditions.


Asunto(s)
Potenciales de Acción , Factores de Intercambio de Guanina Nucleótido , Ventrículos Cardíacos , Miocitos Cardíacos , Proteína Quinasa C , Transducción de Señal , Animales , Factores de Intercambio de Guanina Nucleótido/metabolismo , Miocitos Cardíacos/metabolismo , Miocitos Cardíacos/efectos de los fármacos , Miocitos Cardíacos/enzimología , Proteína Quinasa C/metabolismo , Ratas , Potenciales de Acción/efectos de los fármacos , Ventrículos Cardíacos/metabolismo , Ventrículos Cardíacos/citología , Proteínas Quinasas Dependientes de GMP Cíclico/metabolismo , Óxido Nítrico Sintasa/metabolismo , Óxido Nítrico Sintasa/antagonistas & inhibidores , Fosfolipasas de Tipo C/metabolismo , Fosfolipasas de Tipo C/antagonistas & inhibidores , Masculino , Ratas Wistar , Potasio/metabolismo , AMP Cíclico/metabolismo
2.
Pflugers Arch ; 472(12): 1719-1732, 2020 12.
Artículo en Inglés | MEDLINE | ID: mdl-33047172

RESUMEN

Cardiac fibroblasts play an important role in cardiac matrix turnover and are involved in cardiac fibrosis development. Ca2+ is a driving belt in this phenomenon. This study evaluates the functional expression and contribution of the Ca2+-activated channel TRPM4 in atrial fibroblast phenotype. Molecular and electrophysiological investigations were conducted in human atrial fibroblasts in primary culture and in atrial fibroblasts obtained from wild-type and transgenic mice with disrupted Trpm4 gene (Trpm4-/-). A typical TRPM4 current was recorded on human cells (equal selectivity for Na+ and K+, activation by internal Ca2+, voltage sensitivity, conductance of 23.2 pS, inhibition by 9-phenanthrol (IC50 = 6.1 × 10-6 mol L-1)). Its detection rate was 13% on patches at days 2-4 in culture but raised to 100% on patches at day 28. By the same time, a cell growth was observed. This growth was smaller when cells were maintained in the presence of 9-phenanthrol. Similar cell growth was measured on wild-type mice atrial fibroblasts during culture. However, this growth was minimized on Trpm4-/- mice fibroblasts compared to control animals. In addition, the expression of alpha smooth muscle actin increased during culture of atrial fibroblasts from wild-type mice. This was not observed in Trpm4-/- mice fibroblasts. It is concluded that TRPM4 participates in fibroblast growth and could thus be involved in cardiac fibrosis.


Asunto(s)
Fibrosis Endomiocárdica/metabolismo , Miofibroblastos/metabolismo , Canales Catiónicos TRPM/metabolismo , Potenciales de Acción , Anciano , Animales , Calcio/metabolismo , Proliferación Celular , Células Cultivadas , Femenino , Humanos , Masculino , Ratones , Miocardio/citología , Miofibroblastos/efectos de los fármacos , Miofibroblastos/fisiología , Fenantrenos
3.
BMC Med Genet ; 18(1): 31, 2017 03 18.
Artículo en Inglés | MEDLINE | ID: mdl-28315637

RESUMEN

BACKGROUND: Long QT syndrome (LQTS) is an inherited arrhythmic disorder characterized by prolongation of the QT interval, a risk of syncope, and sudden death. There are already a number of causal genes in LQTS, but not all LQTS patients have an identified mutation, which suggests LQTS unknown genes. METHODS: A cohort of 178 LQTS patients, with no mutations in the 3 major LQTS genes (KCNQ1, KCNH2, and SCN5A), was screened for mutations in the transient potential melastatin 4 gene (TRPM4). RESULTS: Four TRPM4 variants (2.2% of the cohort) were found to change highly conserved amino-acids and were either very rare or absent from control populations. Therefore, these four TRPM4 variants were predicted to be disease causing. Furthermore, no mutations were found in the DNA of these TRPM4 variant carriers in any of the 13 major long QT syndrome genes. Two of these variants were further studied by electrophysiology (p.Val441Met and p.Arg499Pro). Both variants showed a classical TRPM4 outward rectifying current, but the current was reduced by 61 and 90% respectively, compared to wild type TRPM4 current. CONCLUSIONS: This study supports the view that TRPM4 could account for a small percentage of LQTS patients. TRPM4 contribution to the QT interval might be multifactorial by modulating whole cell current but also, as shown in Trpm4-/- mice, by modulating cardiomyocyte proliferation. TRPM4 enlarges the subgroup of LQT genes (KCNJ2 in Andersen syndrome and CACNA1C in Timothy syndrome) known to increase the QT interval through a more complex pleiotropic effect than merely action potential alteration.


Asunto(s)
Sustitución de Aminoácidos , Síndrome de QT Prolongado/genética , Síndrome de QT Prolongado/fisiopatología , Canales Catiónicos TRPM/genética , Adolescente , Adulto , Anciano , Niño , Preescolar , Femenino , Humanos , Lactante , Masculino , Persona de Mediana Edad , Adulto Joven
4.
J Physiol ; 594(2): 295-306, 2016 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-26548780

RESUMEN

KEY POINTS: The transient receptor potential melastatin 4 (TRPM4) inhibitor 9-phenanthrol reduces action potential duration in rabbit Purkinje fibres but not in ventricle. TRPM4-like single channel activity is observed in isolated rabbit Purkinje cells but not in ventricular cells. The TRPM4-like current develops during the notch and early repolarization phases of the action potential in Purkinje cells. ABSTRACT: Transient receptor potential melastatin 4 (TRPM4) Ca(2+)-activated non-selective cation channel activity has been recorded in cardiomyocytes and sinus node cells from mammals. In addition, TRPM4 gene mutations are associated with human diseases of cardiac conduction, suggesting that TRPM4 plays a role in this aspect of cardiac function. Here we evaluate the TRPM4 contribution to cardiac electrophysiology of Purkinje fibres. Ventricular strips with Purkinje fibres were isolated from rabbit hearts. Intracellular microelectrodes recorded Purkinje fibre activity and the TRPM4 inhibitor 9-phenanthrol was applied to unmask potential TRPM4 contributions to the action potential. 9-Phenanthrol reduced action potential duration measured at the point of 50 and 90% repolarization with an EC50 of 32.8 and 36.1×10(-6) mol l(-1), respectively, but did not modulate ventricular action potentials. Inside-out patch-clamp recordings were used to monitor TRPM4 activity in isolated Purkinje cells. TRPM4-like single channel activity (conductance = 23.8 pS; equal permeability for Na(+) and K(+); sensitivity to voltage, Ca(2+) and 9-phenanthrol) was observed in 43% of patches from Purkinje cells but not from ventricular cells (0/16). Action potential clamp experiments performed in the whole-cell configuration revealed a transient inward 9-phenanthrol-sensitive current (peak density = -0.65 ± 0.15 pA pF(-1); n = 5) during the plateau phases of the Purkinje fibre action potential. These results show that TRPM4 influences action potential characteristics in rabbit Purkinje fibres and thus could modulate cardiac conduction and be involved in triggering arrhythmias.


Asunto(s)
Potenciales de Acción , Miocitos Cardíacos/metabolismo , Ramos Subendocárdicos/metabolismo , Canales Catiónicos TRPM/metabolismo , Animales , Calcio/metabolismo , Células Cultivadas , Femenino , Miocitos Cardíacos/fisiología , Potasio/metabolismo , Ramos Subendocárdicos/citología , Ramos Subendocárdicos/fisiología , Conejos , Sodio/metabolismo
5.
Am J Physiol Regul Integr Comp Physiol ; 307(12): R1493-501, 2014 Dec 15.
Artículo en Inglés | MEDLINE | ID: mdl-25377479

RESUMEN

Cardiomyocyte contraction depends on rapid changes in intracellular Ca(2+). In mammals, Ca(2+) influx as L-type Ca(2+) current (ICa) triggers the release of Ca(2+) from sarcoplasmic reticulum (SR) and Ca(2+)-induced Ca(2+) release (CICR) is critical for excitation-contraction coupling. In fish, the relative contribution of external and internal Ca(2+) is unclear. Here, we characterized the role of ICa to trigger SR Ca(2+) release in rainbow trout ventricular myocytes using ICa regulation by Ca(2+) as an index of CICR. ICa was recorded with a slow (EGTA) or fast (BAPTA) Ca(2+) chelator in control and isoproterenol conditions. In the absence of ß-adrenergic stimulation, the rate of ICa inactivation was not significantly different in EGTA and BAPTA (27.1 ± 1.8 vs. 30.3 ± 2.4 ms), whereas with isoproterenol (1 µM), inactivation was significantly faster with EGTA (11.6 ± 1.7 vs. 27.3 ± 1.6 ms). When barium was the charge carrier, inactivation was significantly slower in both conditions (61.9 ± 6.1 vs. 68.0 ± 8.7 ms, control, isoproterenol). Quantification revealed that without isoproterenol, only 39% of ICa inactivation was due to Ca(2+), while with isoproterenol, inactivation was Ca(2+)-dependent (∼65%) and highly reliant on SR Ca(2+) (∼46%). Thus, SR Ca(2+) is not released in basal conditions, and ICa is the main trigger of contraction, whereas during a stress response, SR Ca(2+) is an important source of cytosolic Ca(2+). This was not attributed to differences in SR Ca(2+) load because caffeine-induced transients were not different in both conditions. Therefore, Ca(2+) stored in SR of trout cardiomyocytes may act as a safety mechanism, allowing greater contraction when higher contractility is required, such as stress or exercise.


Asunto(s)
Señalización del Calcio , Calcio/metabolismo , Contracción Miocárdica , Miocitos Cardíacos/metabolismo , Oncorhynchus mykiss/metabolismo , Retículo Sarcoplasmático/metabolismo , Agonistas Adrenérgicos beta/farmacología , Animales , Quelantes del Calcio/farmacología , Señalización del Calcio/efectos de los fármacos , Ácido Egtácico/análogos & derivados , Ácido Egtácico/farmacología , Acoplamiento Excitación-Contracción , Contracción Miocárdica/efectos de los fármacos , Miocitos Cardíacos/efectos de los fármacos , Canal Liberador de Calcio Receptor de Rianodina/metabolismo , Retículo Sarcoplasmático/efectos de los fármacos , Factores de Tiempo
6.
J Cardiovasc Pharmacol ; 64(2): 134-41, 2014 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-24662493

RESUMEN

OBJECTIVE: To assess the electrophysiological impact of aldosterone during myocardial ischemia-reperfusion. METHODS: We used an in vitro model of "border zone" using rabbit right ventricle and standard microelectrodes. RESULTS: Aldosterone (10 and 100 nmol/L) shortened ischemic action potential [action potential duration at 90% of repolarization (APD90), from 55 ± 3 to 39 ± 1 ms and 36 ± 3 ms, respectively, P < 0.05] and induced resting membrane potential (RMP) hyperpolarization in the nonischemic zone (from -83 ± 1 to -93 ± 7 mV and -94 ± 3 mV, respectively, P < 0.05) and in the ischemic zone during reperfusion (from -81 ± 2 to -88 ± 2 mV and -91 ± 2 mV, respectively, P < 0.05). Bimakalim, an ATP-sensitive potassium (K(ATP)) channel opener, also induced RMP hyperpolarization and APD90 shortening. Aldosterone (10 and 100 nmol/L) increased APD90 dispersion between ischemic and nonischemic zones (from 96 ± 3 to 117 ± 5 ms and 131 ± 6 ms, respectively, P < 0.05) and reperfusion-induced severe premature ventricular contraction occurrence (from 18% to 67% and 75%, respectively, P < 0.05). Adding glibenclamide, a nonspecific K(ATP) antagonist, to aldosterone superfusion abolished these effects different to sodium 5-hydroxydecanoate, a mitochondrial-K(ATP) antagonist. CONCLUSIONS: In this in vitro rabbit model of border zone, aldosterone induced RMP hyperpolarization and decreased ischemic APD90 evoking the modulation of K currents. Glibenclamide prevented these effects different to 5-hydroxydecanoate, suggesting that sarcolemmal-K(ATP) channels may be involved in this context.


Asunto(s)
Aldosterona/metabolismo , Ventrículos Cardíacos/metabolismo , Canales KATP/metabolismo , Sarcolema/metabolismo , Potenciales de Acción/efectos de los fármacos , Aldosterona/farmacología , Animales , Benzopiranos/farmacología , Dihidropiridinas/farmacología , Modelos Animales de Enfermedad , Femenino , Gliburida/farmacología , Ventrículos Cardíacos/efectos de los fármacos , Ventrículos Cardíacos/fisiopatología , Técnicas In Vitro , Canales KATP/agonistas , Canales KATP/antagonistas & inhibidores , Masculino , Daño por Reperfusión Miocárdica/metabolismo , Daño por Reperfusión Miocárdica/fisiopatología , Perfusión , Conejos
7.
J Mol Cell Cardiol ; 57: 96-105, 2013 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-23376036

RESUMEN

Sympathetic stimulation is an important modulator of cardiac function via the classic cAMP-dependent signaling pathway, PKA. Recently, this paradigm has been challenged by the discovery of a family of guanine nucleotide exchange proteins directly activated by cAMP (Epac), acting in parallel to the classic signaling pathway. In cardiac myocytes, Epac activation is known to modulate Ca(2+) cycling yet their actions on cardiac ionic currents remain poorly characterized. This study attempts to address this paucity of information using the patch clamp technique to record action potential (AP) and ionic currents on rat ventricular myocytes. Epac was selectively activated by 8-CPT-AM (acetoxymethyl ester form of 8-CPT). AP amplitude, maximum depolarization rate and resting membrane amplitude were unaltered by 8-CPT-AM, strongly suggesting that Na(+) current and inward rectifier K(+) current are not regulated by Epac. In contrast, AP duration was significantly increased by 8-CPT-AM (prolongation of duration at 50% and 90% of repolarization by 41±10% and 43±8% respectively, n=11). L-type Ca(2+) current density was unaltered by 8-CPT-AM (n=16) so this cannot explain the action potential lengthening. However, the steady state component of K(+) current was significantly inhibited by 8-CPT-AM (-38±6%, n=15), while the transient outward K(+) current was unaffected by 8-CPT-AM. These effects were PKA-independent since they were observed in the presence of PKA inhibitor KT5720. Isoprenaline (100nM) induced a significant prolongation of AP duration, even in the presence of KT5720. This study provides the first evidence that the cAMP-binding protein Epac critically modulates cardiac AP duration by decreasing steady state K(+) current. These observations may be relevant to diseases in which Epac is upregulated, like cardiac hypertrophy.


Asunto(s)
Potenciales de Acción/efectos de los fármacos , AMP Cíclico/análogos & derivados , Factores de Intercambio de Guanina Nucleótido/fisiología , Miocitos Cardíacos/fisiología , Potasio/metabolismo , Agonistas Adrenérgicos beta/farmacología , Animales , Señalización del Calcio , Carbazoles/farmacología , Células Cultivadas , AMP Cíclico/farmacología , Proteínas Quinasas Dependientes de AMP Cíclico/antagonistas & inhibidores , Evaluación Preclínica de Medicamentos , Factores de Intercambio de Guanina Nucleótido/agonistas , Ventrículos Cardíacos/citología , Isoproterenol/farmacología , Masculino , Miocitos Cardíacos/efectos de los fármacos , Pirroles/farmacología , Ratas , Ratas Wistar
8.
Front Physiol ; 14: 1120336, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-36909224

RESUMEN

Introduction: Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and is associated with increased mortality and morbidity. The Exchange Protein directly Activated by cAMP (EPAC), has been implicated in pro-arrhythmic signaling pathways in the atria, but the underlying mechanisms remain unknown. Methods: In this study, we investigated the involvement of EPAC1 and EPAC2 isoforms in the genesis of AF in wild type (WT) mice and knockout (KO) mice for EPAC1 or EPAC2. We also employed EPAC pharmacological modulators to selectively activate EPAC proteins (8-CPT-AM; 10 µM), or inhibit either EPAC1 (AM-001; 20 µM) or EPAC2 (ESI-05; 25 µM). Transesophageal stimulation was used to characterize the induction of AF in vivo in mice. Optical mapping experiments were performed on isolated mouse atria and cellular electrophysiology was examined by whole-cell patch-clamp technique. Results: In wild type mice, we found 8-CPT-AM slightly increased AF susceptibility and that this was blocked by the EPAC1 inhibitor AM-001 but not the EPAC2 inhibitor ESI-05. Consistent with this, in EPAC1 KO mice, occurrence of AF was observed in 3/12 (vs. 4/10 WT littermates) and 4/10 in EPAC2 KO (vs. 5/10 WT littermates). In wild type animals, optical mapping experiments revealed that 8-CPT-AM perfusion increased action potential duration even in the presence of AM-001 or ESI-05. Interestingly, 8-CPT-AM perfusion decreased conduction velocity, an effect blunted by AM-001 but not ESI-05. Patch-clamp experiments demonstrated action potential prolongation after 8-CPT-AM perfusion in both wild type and EPAC1 KO mice and this effect was partially prevented by AM-001 in WT. Conclusion: Together, these results indicate that EPAC1 and EPAC2 signaling pathways differentially alter atrial electrophysiology but only the EPAC1 isoform is involved in the genesis of AF. Selective blockade of EPAC1 with AM-001 prevents AF in mice.

9.
Adv Exp Med Biol ; 704: 147-71, 2011.
Artículo en Inglés | MEDLINE | ID: mdl-21290294

RESUMEN

Transient Receptor Potential (TRP) proteins are non-selective cationic channels with a consistent Ca(2+)-permeability, except for TRPM4 and TRPM5 that are not permeable to this ion. However, Ca(2+) is a major regulator of their activity since both channels are activated by a rise in internal Ca(2+). Thus TRPM4 and TRPM5 are responsible for most of the Ca(2+)-activated non-selective cationic currents (NSC(Ca)) recorded in a large variety of tissues. Their activation induces cell-membrane depolarization that modifies the driving force for ions as well as activity of voltage gated channels and thereby strongly impacts cell physiology. In the last few years, the ubiquitously expressed TRPM4 channel has been implicated in insulin secretion, the immune response, constriction of cerebral arteries, the activity of inspiratory neurons and cardiac dysfunction. Conversely, TRPM5 whose expression is more restricted, has until now been mainly implicated in taste transduction.


Asunto(s)
Canales Catiónicos TRPM/fisiología , Animales , Biofisica , Señalización del Calcio , Humanos , Transporte Iónico , Conformación Proteica , Canales Catiónicos TRPM/química , Canales Catiónicos TRPM/efectos de los fármacos
10.
Cells ; 10(3)2021 03 12.
Artículo en Inglés | MEDLINE | ID: mdl-33809210

RESUMEN

Aldosterone plays a major role in atrial structural and electrical remodeling, in particular through Ca2+-transient perturbations and shortening of the action potential. The Ca2+-activated non-selective cation channel Transient Receptor Potential Melastatin 4 (TRPM4) participates in atrial action potential. The aim of our study was to elucidate the interactions between aldosterone and TRPM4 in atrial remodeling and arrhythmias susceptibility. Hyperaldosteronemia, combined with a high salt diet, was induced in mice by subcutaneously implanted osmotic pumps during 4 weeks, delivering aldosterone or physiological serum for control animals. The experiments were conducted in wild type animals (Trpm4+/+) as well as Trpm4 knock-out animals (Trpm4-/-). The atrial diameter measured by echocardiography was higher in Trpm4-/- compared to Trpm4+/+ animals, and hyperaldosteronemia-salt produced a dilatation in both groups. Action potentials duration and triggered arrhythmias were measured using intracellular microelectrodes on the isolated left atrium. Hyperaldosteronemia-salt prolong action potential in Trpm4-/- mice but had no effect on Trpm4+/+ mice. In the control group (no aldosterone-salt treatment), no triggered arrythmias were recorded in Trpm4+/+ mice, but a high level was detected in Trpm4-/- mice. Hyperaldosteronemia-salt enhanced the occurrence of arrhythmias (early as well as delayed-afterdepolarization) in Trpm4+/+ mice but decreased it in Trpm4-/- animals. Atrial connexin43 immunolabelling indicated their disorganization at the intercalated disks and a redistribution at the lateral side induced by hyperaldosteronemia-salt but also by Trpm4 disruption. In addition, hyperaldosteronemia-salt produced pronounced atrial endothelial thickening in both groups. Altogether, our results indicated that hyperaldosteronemia-salt and TRPM4 participate in atrial electrical and structural remodeling. It appears that TRPM4 is involved in aldosterone-induced atrial action potential shortening. In addition, TRPM4 may promote aldosterone-induced atrial arrhythmias, however, the underlying mechanisms remain to be explored.


Asunto(s)
Arritmias Cardíacas/metabolismo , Función del Atrio Izquierdo , Remodelación Atrial , Atrios Cardíacos/metabolismo , Frecuencia Cardíaca , Canales Catiónicos TRPM/metabolismo , Potenciales de Acción , Aldosterona , Animales , Arritmias Cardíacas/inducido químicamente , Arritmias Cardíacas/genética , Arritmias Cardíacas/fisiopatología , Conexina 43/metabolismo , Modelos Animales de Enfermedad , Atrios Cardíacos/fisiopatología , Masculino , Ratones Endogámicos C57BL , Ratones Noqueados , Cloruro de Sodio Dietético , Canales Catiónicos TRPM/genética , Factores de Tiempo
11.
Sci Transl Med ; 13(603)2021 07 21.
Artículo en Inglés | MEDLINE | ID: mdl-34290058

RESUMEN

The emergence and spread of Plasmodium falciparum resistance to first-line antimalarials creates an imperative to identify and develop potent preclinical candidates with distinct modes of action. Here, we report the identification of MMV688533, an acylguanidine that was developed following a whole-cell screen with compounds known to hit high-value targets in human cells. MMV688533 displays fast parasite clearance in vitro and is not cross-resistant with known antimalarials. In a P. falciparum NSG mouse model, MMV688533 displays a long-lasting pharmacokinetic profile and excellent safety. Selection studies reveal a low propensity for resistance, with modest loss of potency mediated by point mutations in PfACG1 and PfEHD. These proteins are implicated in intracellular trafficking, lipid utilization, and endocytosis, suggesting interference with these pathways as a potential mode of action. This preclinical candidate may offer the potential for a single low-dose cure for malaria.


Asunto(s)
Antimaláricos , Malaria Falciparum , Malaria , Parásitos , Animales , Antimaláricos/farmacología , Antimaláricos/uso terapéutico , Endocitosis , Malaria/tratamiento farmacológico , Malaria Falciparum/tratamiento farmacológico , Plasmodium falciparum
12.
Prog Biophys Mol Biol ; 96(1-3): 305-20, 2008.
Artículo en Inglés | MEDLINE | ID: mdl-17869329

RESUMEN

Heart rate is an essential determinant of cardiac performance. In rat ventricular myocytes, a sudden increase in rate yields to a prolongation of the action potential duration (APD). The mechanism underlying this prolongation is controversial: it has been proposed that the longer APD is due to either: (1) a decrease in K+ currents only or (2) an increase in Ca2+ current only. The aim of this study was to quantitatively investigate the contribution of Ca2+ and K+ currents in the adaptation of APD to pacing rate. Simulation using a mathematical model of ventricular rat cardiac cell model [Pandit, S.V., Clark, R.B., Giles, W.R., Demir, S.S., 2001. A mathematical model of action potential heterogeneity in adult rat left ventricular myocytes. Biophys. J. 81, 3029-3051] predicted a role in the prolongation of APD for K+ currents only. In patch clamp experiments, increasing the pacing rate leads to a significant increase in APD in both control and detubulated myocytes, although it was more marked in control than detubulated myocytes. Supporting the model prediction, we observed that increasing stimulation frequency leads to a decrease in K+ currents in voltage clamped rat ventricular myocytes (square and action potential waveforms), and to a similar extent in both cell types. We have also observed that frequency-dependent facilitation of Ca2+ current occurred in control cells but not in detubulated cells (square and action potential waveforms). From these experiments, we calculated that the relative contribution of Ca2+ and K+ currents to the longer APD following an increase in pacing rate is approximately 65% and approximately 35%, respectively. Therefore, in contrast to the model prediction, Ca2+ current has a significant role in the adaptation of APD to pacing rate. Finally, we have introduced a simplistic modification to the Pandit's model to account for the frequency-dependent facilitation of Ca2+ current.


Asunto(s)
Potenciales de Acción/fisiología , Adaptación Fisiológica , Frecuencia Cardíaca/fisiología , Miocitos Cardíacos/fisiología , Animales , Calcio/metabolismo , Ventrículos Cardíacos/citología , Humanos , Potasio/metabolismo , Ratas , Ratas Wistar , Función Ventricular
13.
Nat Rev Cardiol ; 16(6): 344-360, 2019 06.
Artículo en Inglés | MEDLINE | ID: mdl-30664669

RESUMEN

Transient receptor potential (TRP) channels are nonselective cationic channels that are generally Ca2+ permeable and have a heterogeneous expression in the heart. In the myocardium, TRP channels participate in several physiological functions, such as modulation of action potential waveform, pacemaking, conduction, inotropy, lusitropy, Ca2+ and Mg2+ handling, store-operated Ca2+ entry, embryonic development, mitochondrial function and adaptive remodelling. Moreover, TRP channels are also involved in various pathological mechanisms, such as arrhythmias, ischaemia-reperfusion injuries, Ca2+-handling defects, fibrosis, maladaptive remodelling, inherited cardiopathies and cell death. In this Review, we present the current knowledge of the roles of TRP channels in different cardiac regions (sinus node, atria, ventricles and Purkinje fibres) and cells types (cardiomyocytes and fibroblasts) and discuss their contribution to pathophysiological mechanisms, which will help to identify the best candidates for new therapeutic targets among the cardiac TRP family.


Asunto(s)
Fibroblastos/metabolismo , Cardiopatías/metabolismo , Miocitos Cardíacos/metabolismo , Ramos Subendocárdicos/metabolismo , Nodo Sinoatrial/metabolismo , Canales de Potencial de Receptor Transitorio/metabolismo , Potenciales de Acción , Animales , Fármacos Cardiovasculares/uso terapéutico , Fibroblastos/efectos de los fármacos , Cardiopatías/tratamiento farmacológico , Cardiopatías/fisiopatología , Humanos , Terapia Molecular Dirigida , Miocitos Cardíacos/efectos de los fármacos , Ramos Subendocárdicos/efectos de los fármacos , Ramos Subendocárdicos/fisiopatología , Transducción de Señal , Nodo Sinoatrial/efectos de los fármacos , Nodo Sinoatrial/fisiopatología , Canales de Potencial de Receptor Transitorio/efectos de los fármacos
14.
Anesth Analg ; 106(2): 365-70, table of contents, 2008 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-18227286

RESUMEN

BACKGROUND: Etomidate and ketamine are used during induction of anesthesia in high-risk patients. However, their effects on action potential (AP) variables and ischemia/reperfusion-induced arrhythmias and conduction blocks are unknown. METHODS: Guinea pig right ventricular muscle strips were mounted in a 5-mL double chamber bath with the strips separated into two zones by an impermeable latex membrane. One-half (normal zone) was exposed to normal perfusate while the other half (altered zone) was exposed to hypoxia, hyperkalemia, acidosis, and lack of glucose. AP variables were recorded continuously in the normal and altered zones. Spontaneous arrhythmias and conduction blocks were noted. Etomidate (10(-7), 10(-6), and 10(-5) M) and ketamine (10(-6), 10(-5), and 10(-4) M) were superfused into the bath throughout the experiment and the electrophysiologic effects compared with the control group. RESULTS: We found that under control conditions, etomidate and ketamine did not modify resting membrane potential, maximal upstroke velocity, AP amplitude, or AP duration at 90% of repolarization (APD90). Ketamine (10(-4) M), but not weaker concentrations and none of the concentration of etomidate, reversed the ischemia-induced shortening of APD90 and APD dispersion. Etomidate and ketamine did not modify the occurrence of conduction block during simulated ischemia. In contrast, ketamine (25% at 10(-6) M, 13% at 10(-5) M, and 13% at 10(-4) M vs 90% in the control group, P < 0.05) but not etomidate (38% at 10(-7) M, 63% at 10(-6) M, and 63% at 10(-5) M vs 90% in the control group, NS) decreased the incidence of reperfusion-induced spontaneous arrhythmias. CONCLUSIONS: In guinea pig myocardium, our data suggest that ketamine, in clinically relevant concentrations, decreases ischemia-induced AP shortening and spontaneous reperfusion-induced ventricular arrhythmias. Further study is required to precisely determine the effect of etomidate on reperfusion-induced arrhythmias.


Asunto(s)
Potenciales de Acción/efectos de los fármacos , Etomidato/farmacología , Ketamina/farmacología , Daño por Reperfusión Miocárdica/tratamiento farmacológico , Miocardio , Potenciales de Acción/fisiología , Animales , Electrofisiología , Etomidato/uso terapéutico , Femenino , Cobayas , Técnicas In Vitro , Ketamina/química , Ketamina/uso terapéutico , Masculino , Daño por Reperfusión Miocárdica/fisiopatología
15.
Prog Biophys Mol Biol ; 91(1-2): 1-82, 2006.
Artículo en Inglés | MEDLINE | ID: mdl-16503439

RESUMEN

Calcium is a ubiquitous second messenger which plays key roles in numerous physiological functions. In cardiac myocytes, Ca2+ crosses the plasma membrane via specialized voltage-gated Ca2+ channels which have two main functions: (i) carrying depolarizing current by allowing positively charged Ca2+ ions to move into the cell; (ii) triggering Ca2+ release from the sarcoplasmic reticulum. Recently, it has been suggested than Ca2+ channels also participate in excitation-transcription coupling. The purpose of this review is to discuss the physiological roles of Ca2+ currents in cardiac myocytes. Next, we describe local regulation of Ca2+ channels by cyclic nucleotides. We also provide an overview of recent studies investigating the structure-function relationship of Ca2+ channels in cardiac myocytes using heterologous system expression and transgenic mice, with descriptions of the recently discovered Ca2+ channels alpha(1D) and alpha(1E). We finally discuss the potential involvement of Ca2+ currents in cardiac pathologies, such as diseases with autoimmune components, and cardiac remodeling.


Asunto(s)
Canales de Calcio/fisiología , Señalización del Calcio/fisiología , Calcio/metabolismo , Activación del Canal Iónico/fisiología , Potenciales de la Membrana/fisiología , Miocitos Cardíacos/fisiología , Animales , Humanos
16.
J Cardiovasc Pharmacol Ther ; 22(6): 564-573, 2017 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-28381122

RESUMEN

BACKGROUND AND PURPOSE: Cardioprotection against ischemia-reperfusion (I/R) damages remains a major concern during prehospital management of acute myocardial infarction. Noble gases have shown beneficial effects in preconditioning studies. Because emergency proceedings in the context of myocardial infarction require postconditioning strategies, we evaluated the effects of argon in such protocols on mammalian cardiac tissue. EXPERIMENTAL APPROACHES: In rat, cardiac I/R was induced in vivo by transient coronary artery ligature and cardiac functions were evaluated by magnetic resonance imaging. Hypoxia-reoxygenation (H/R)-induced arrhythmias were evaluated in vitro using intracellular microelectrodes on both rat-isolated ventricle and a model of border zone in guinea pig ventricle. Hypoxia-reoxygenation loss of contractile force was assessed in human atrial appendages. In those models, postconditioning was induced by 5 minutes application of argon at the time of reperfusion. KEY RESULTS: In the in vivo model, I/R produced left ventricular ejection fraction decrease (24%) and wall motion score increase (36%) which was prevented when argon was applied in postconditioning. In vitro, argon postconditioning abolished H/R-induced arrhythmias such as early after depolarizations, conduction blocks, and reentries. Recovery of contractile force in human atrial appendages after H/R was enhanced in the argon group, increasing from 51% ± 2% in the nonconditioned group to 83% ± 7% in the argon-treated group ( P < .001). This effect of argon was abolished in the presence of wortmannin and PD98059 which inhibit prosurvival phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt) and MEK/extracellular receptor kinase 1/2 (ERK 1/2), respectively, or in the presence of the mitochondrial permeability transition pore opener atractyloside, suggesting the involvement of the reperfusion injury salvage kinase pathway. CONCLUSION AND IMPLICATIONS: Argon has strong cardioprotective properties when applied in conditions of postconditioning and thus appears as a potential therapeutic tool in I/R situations.


Asunto(s)
Argón/administración & dosificación , Poscondicionamiento Isquémico/métodos , Daño por Reperfusión Miocárdica/prevención & control , Reperfusión Miocárdica/métodos , Animales , Apéndice Atrial/efectos de los fármacos , Apéndice Atrial/fisiopatología , Cobayas , Humanos , Masculino , Daño por Reperfusión Miocárdica/fisiopatología , Técnicas de Cultivo de Órganos , Ratas , Ratas Wistar
17.
Circ Res ; 95(1): e1-7, 2004 Jul 09.
Artículo en Inglés | MEDLINE | ID: mdl-15192026

RESUMEN

We have characterized modulation of ICa by Ca2+ at the t-tubules (ie, in control cells) and surface sarcolemma (ie, in detubulated cells) of cardiac ventricular myocytes, using the whole-cell patch clamp technique to record ICa. ICa inactivation was significantly slower in detubulated cells than in control cells (27.1+/-7.8 ms, n=22, versus 16.4+/-7.9 ms, n=22; P<0.05). In atrial myocytes, which lack t-tubules, ICa inactivation was not changed by the treatment used to produce detubulation. In the presence of ryanodine or BAPTA, or when Ba2+ was used as the charge carrier, the rate of inactivation was not significantly different in control and detubulated cells. Frequency-dependent facilitation occurred in control cells but not in detubulated cells, and was abolished by ryanodine. These results suggest that Ca2+ released from the SR has a greater effect on ICa in the t-tubules than at the surface sarcolemma. This does not appear to be due to differences in local Ca2+ release from the SR, because the gain of Ca2+ release was not significantly different in control and detubulated cells. These data suggest that the t-tubules are a key site for the regulation of transsarcolemmal Ca2+ flux by Ca2+ release from the SR; this could play a role in altered Ca2+ homeostasis in pathological conditions. The full text of this article is available online at http://circres.ahajournals.org.


Asunto(s)
Canales de Calcio Tipo L/metabolismo , Calcio/metabolismo , Membrana Celular/metabolismo , Miocitos Cardíacos/fisiología , Retículo Sarcoplasmático/metabolismo , Animales , Células Cultivadas , Conductividad Eléctrica , Ventrículos Cardíacos/citología , Miocitos Cardíacos/metabolismo , Técnicas de Placa-Clamp , Ratas , Ratas Wistar
18.
Eur J Pharmacol ; 532(3): 279-89, 2006 Feb 27.
Artículo en Inglés | MEDLINE | ID: mdl-16480976

RESUMEN

To evaluate class III effects of clinically relevant concentrations of dofetilide (5 and 10 nmol/l) and the effects of extracellular potassium [K+]o modulation of arrhythmias onset at the level of the "border zone," we used a previously reported in vitro model whereby normoxic and ischemic/reperfused zones were studied. Guinea-pig right ventricular strips (driven at 1 Hz at 36.5+/-0.5 degrees C) were superfused with Tyrode's solution in oxygenated (HCO3- 25 mmol/l, K+ 4 mmol/l, pH 7.35+/-0.05, glucose 5.5 mmol/l: normal zone) and ischemia-simulating conditions (HCO3- 9 mmol/l, pH 6.90+/-0.05, no oxygen and no glucose: altered zone) having either [K+]o 4 (n=20), 8 (n=20) or 12 (n=20) mmol/l. Action potentials in normal and altered zones were recorded simultaneously during 30 min of simulated-ischemia and after 30 min of reperfusion with oxygenated Tyrode's solution. Each preparation served as control for successive phases of dofetilide studies (at 5 and 10 nmol/l) and action potential values were normalized to those present at the beginning of the experiment. During simulated-ischemia, the higher the [K+]o the worse were action potential changes, although full recovery was seen upon 30 min of reperfusion in all [K+]o groups. A high incidence of ischemia/reperfusion arrhythmias was observed in 4 and 12 mmol/l [K+]o groups as opposed to a low incidence of arrhythmias in 8 mmol/l [K+]o group. Dofetilide at 5 and 10 nmol/l with all [K+]o explored: (i) exhibited class III effects, (ii) was effective (or neutral) against ventricular arrhythmias during both simulated-ischemia and reperfusion, and (iii) did not globally increase the dispersion of action potential durations between normal and altered zones. Different arrhythmogenic mechanisms are involved in this model at different [K+]o with 8 mmol/l providing relative protection. Class III effects of dofetilide are evident in the normal zone when in the ischemic-like zone [K+]o ranges from 4 to 12 mmol/l. Thus dofetilide did not increase dispersion of repolarization and had either an antiarrhythmic or a neutral effect during ischemia/reperfusion.


Asunto(s)
Antiarrítmicos/farmacología , Corazón/efectos de los fármacos , Miocardio/metabolismo , Fenetilaminas/farmacología , Bloqueadores de los Canales de Potasio/farmacología , Potasio/metabolismo , Sulfonamidas/farmacología , Potenciales de Acción , Animales , Antiarrítmicos/uso terapéutico , Arritmias Cardíacas/metabolismo , Arritmias Cardíacas/prevención & control , Relación Dosis-Respuesta a Droga , Cobayas , Ventrículos Cardíacos , Hiperpotasemia/tratamiento farmacológico , Hiperpotasemia/metabolismo , Técnicas In Vitro , Cinética , Modelos Animales , Daño por Reperfusión Miocárdica/tratamiento farmacológico , Daño por Reperfusión Miocárdica/metabolismo , Fenetilaminas/uso terapéutico , Bloqueadores de los Canales de Potasio/uso terapéutico , Sulfonamidas/uso terapéutico
19.
Eur J Pharmacol ; 518(2-3): 165-74, 2005 Aug 22.
Artículo en Inglés | MEDLINE | ID: mdl-16083874

RESUMEN

There are few investigations on azimilide effects during ischemia/reperfusion. We have therefore investigated low concentrations of azimilide (0.1 and 0.5 micromol/l) versus Controls on action potential parameters and occurrence of repetitive responses during simulated ischemia and reperfusion. An in vitro model of "border zone" in guinea-pig ventricular myocardium (n=30) was used. Azimilide 0.5 micromol/l lengthened action potential duration in normoxic but not in ischemic-like conditions. Therefore an increased dispersion of action potential duration at 90% of repolarization during simulated ischemia in presence of azimilide was seen. Upon reperfusion, both normal and reperfused myocardium showed azimilide-induced action potential duration increase. There was a neutral effect on the occurrence of arrhythmias during simulated ischemia; however azimilide showed significant (P=0.033) antiarrhythmic properties following reperfusion. To mimic I(Kr) and I(Ks) blocking properties of azimilide we further used dofetilide 10 nmol/l with HMR 1556 1 nmol/l (N=9), which was accompanied by less severe shortening (P<0.05) of action potential duration at 90% of repolarization at 30 min of ischemic-like conditions (-43+/-9%), as compared with azimilide 0.5 micromol/l (-64+/-5%) but similar to what seen with azimilide 0.1 micromol/l (-53+/-5%) and Controls (-52+/-6%). During reperfusion, 2/9 (22%) preparations had sustained activities, which was less than what observed in Controls (5/10, 50%) and with azimilide 0.5 micromol/l (0/10, 0%), although not statistically different (respectively, P=0.35 and P=0.21). Lack versus homogenous class III effects of azimilide in respectively simulated ischemia and reperfusion may explain its different efficacy on arrhythmias, although prevention of reperfusion arrhythmias calls for other than just its I(Kr) and I(Ks) blocking properties.


Asunto(s)
Potenciales de Acción/efectos de los fármacos , Ventrículos Cardíacos/efectos de los fármacos , Imidazolidinas/farmacología , Daño por Reperfusión Miocárdica/fisiopatología , Piperazinas/farmacología , Animales , Antiarrítmicos/farmacología , Arritmias Cardíacas/etiología , Arritmias Cardíacas/fisiopatología , Arritmias Cardíacas/prevención & control , Cromanos/farmacología , Relación Dosis-Respuesta a Droga , Femenino , Cobayas , Ventrículos Cardíacos/fisiopatología , Hidantoínas , Técnicas In Vitro , Masculino , Isquemia Miocárdica/complicaciones , Isquemia Miocárdica/fisiopatología , Daño por Reperfusión Miocárdica/complicaciones , Fenetilaminas/farmacología , Bloqueadores de los Canales de Potasio/farmacología , Sulfonamidas/farmacología , Factores de Tiempo
20.
Cardiovasc Res ; 108(1): 21-30, 2015 Oct 01.
Artículo en Inglés | MEDLINE | ID: mdl-26272755

RESUMEN

TRPM4 forms a non-selective cation channel activated by internal Ca(2+). Its functional expression was demonstrated in cardiomyocytes of several mammalian species including humans, but the channel is also present in many other tissues. The recent characterization of the TRPM4 inhibitor 9-phenanthrol, and the availability of transgenic mice have helped to clarify the role of TRPM4 in cardiac electrical activity, including diastolic depolarization from the sino-atrial node cells in mouse, rat, and rabbit, as well as action potential duration in mouse cardiomyocytes. In rat and mouse, pharmacological inhibition of TRPM4 prevents cardiac ischaemia-reperfusion injuries and decreases the occurrence of arrhythmias. Several studies have identified TRPM4 mutations in patients with inherited cardiac diseases including conduction blocks and Brugada syndrome. This review identifies TRPM4 as a significant actor in cardiac electrophysiology.


Asunto(s)
Corazón/fisiología , Canales Catiónicos TRPM/fisiología , Potenciales de Acción , Animales , Calcio/metabolismo , Diástole/fisiología , Humanos , ARN Mensajero/análisis , Canales Catiónicos TRPM/genética
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