RESUMO
BACKGROUND: While calcium is known to play a crucial role in mammalian sperm physiology, how it flows in and out of the male gamete is not completely understood. Herein, we investigated the involvement of Na+/Ca2+ exchangers (NCX) in mammalian sperm capacitation. Using the pig as an animal model, we first confirmed the presence of NCX1 and NCX2 isoforms in the sperm midpiece. Next, we partially or totally blocked Ca2+ outflux (forward transport) via NCX1/NCX2 with different concentrations of SEA0400 (2-[4-[(2,5-difluorophenyl)methoxy]phenoxy]-5-ethoxyaniline; 0, 0.5, 5 and 50 µM) and Ca2+ influx (reverse transport) with SN6 (ethyl 2-[[4-[(4-nitrophenyl)methoxy]phenyl]methyl]-1,3-thiazolidine-4-carboxylate; 0, 0.3, 3 or 30 µM). Sperm were incubated under capacitating conditions for 180 min; after 120 min, progesterone was added to induce the acrosome reaction. At 0, 60, 120, 130, and 180 min, sperm motility, membrane lipid disorder, acrosome integrity, mitochondrial membrane potential (MMP), tyrosine phosphorylation of sperm proteins, and intracellular levels of Ca2+, reactive oxygen species (ROS) and superoxides were evaluated. RESULTS: Partial and complete blockage of Ca2+ outflux and influx via NCX induced a significant reduction of sperm motility after progesterone addition. Early alterations on sperm kinematics were also observed, the effects being more obvious in totally blocked than in partially blocked samples. Decreased sperm motility and kinematics were related to both defective tyrosine phosphorylation and mitochondrial activity, the latter being associated to diminished MMP and ROS levels. As NCX blockage did not affect the lipid disorder of plasma membrane, the impaired acrosome integrity could result from reduced tyrosine phosphorylation. CONCLUSIONS: Inhibition of outflux and influx of Ca2+ triggered similar effects, thus indicating that both forward and reverse Ca2+ transport through NCX exchangers are essential for sperm capacitation.
Assuntos
Cálcio , Trocador de Sódio e Cálcio , Capacitação Espermática , Animais , Masculino , Capacitação Espermática/efeitos dos fármacos , Trocador de Sódio e Cálcio/metabolismo , Trocador de Sódio e Cálcio/efeitos dos fármacos , Cálcio/metabolismo , Suínos , Espermatozoides/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Motilidade dos Espermatozoides/efeitos dos fármacos , Reação Acrossômica/efeitos dos fármacos , Potencial da Membrana Mitocondrial/efeitos dos fármacosRESUMO
BACKGROUND/AIMS: Monensin, an Na ionophore, increases intracellular Na ([Na]i). Alteration of [Na]i influences ion transport through the sarcolemmal membrane. So far, the effects of monensin on ventricular myocytes have not been examined in detail. The main objective of this study was to elucidate the mechanism via which monensin-evoked increases in [Na]i affect the membrane potential and currents in ventricular myocytes of guinea pigs. METHODS: Membrane potentials and currents were measured using the whole-cell patch-clamp technique in single myocytes. The concentration of intracellular Ca ([Ca]i) was evaluated by measuring fluorescence intensity of Fluo-4. RESULTS: Monensin (10-5M) shortened the action potential duration (APD) and reduced the amplitude of the plateau phase. In addition, monensin decreased the sodium current (INa) and shifted the inactivation curve to the hyperpolarized direction. Moreover, it decreased the L-type calcium current (ICa). However, this effect was attenuated by increasing the buffering capacity of [Ca]i. The Na-Ca exchange current (INa-Ca) was activated particularly in the reverse mode. Na-K pump current (INa-K) was also activated. Notably, the inward rectifying K current (IK1) was not affected, and the change in the delayed outward K current (IK) was not evident. CONCLUSION: These results suggest that the monensin-induced shortened APD and reduced amplitude of the plateau phase are primarily due to the decrease in the ICa, the activation of the reverse mode of INa-Ca, and the increased INa-K, and second due to the decreased INa. The IK and the IK1 may not be associated with the abovementioned changes induced by monensin. The elevation of [Na]i can exert multiple influences on electrophysiological phenomena in cardiac myocytes.
Assuntos
Monensin/farmacologia , Miócitos Cardíacos/efeitos dos fármacos , Ionóforos de Sódio/farmacologia , Sódio/metabolismo , Potenciais de Ação/efeitos dos fármacos , Animais , Cálcio/metabolismo , Cardiotônicos/farmacologia , Cátions/metabolismo , Células Cultivadas , Técnicas Eletrofisiológicas Cardíacas , Cobaias , Espaço Intracelular/efeitos dos fármacos , Espaço Intracelular/metabolismo , Masculino , Potenciais da Membrana/efeitos dos fármacos , Microscopia de Fluorescência , Miócitos Cardíacos/metabolismo , Ouabaína/farmacologia , Técnicas de Patch-Clamp , Potássio/metabolismo , Trocador de Sódio e Cálcio/efeitos dos fármacos , ATPase Trocadora de Sódio-Potássio/efeitos dos fármacosRESUMO
The effect of KB-R7943, an inhibitor of the plasmalemmal Na+-Ca2+ exchanger, on mitochondrial Ca2+ transporters was examined with membrane-permeabilized cardiomyocyte-derived H9c2 cells expressing the fluorescent Ca2+ indicator, yellow cameleon 3.1, in the mitochondria. KB-R7943, as well as ruthenium red, inhibited the rise in mitochondrial Ca2+ on increasing the extramitochondrial Ca2+ concentration from 0 nM to 300 nM. CGP-37157, but not KB-R7943, inhibited the decline in mitochondrial Ca2+on return to Ca2+ free extramitochondrial solution. These results indicated that KB-R7943 has inhibitory effects on the mitochondrial Ca2+ uniporter, but not on the mitochondrial Na+-Ca2+ exchanger.
Assuntos
Canais de Cálcio/efeitos dos fármacos , Cálcio/metabolismo , Trocador de Sódio e Cálcio/efeitos dos fármacos , Tioureia/análogos & derivados , Animais , Membrana Celular/metabolismo , Células Cultivadas , Clonazepam/análogos & derivados , Clonazepam/farmacologia , Mitocôndrias/metabolismo , Miócitos Cardíacos/efeitos dos fármacos , Ratos , Sódio/metabolismo , Trocador de Sódio e Cálcio/metabolismo , Tiazepinas/farmacologia , Tioureia/farmacologiaRESUMO
Intracellular Na elevation in the heart is a hallmark of pathologies where both acute and chronic metabolic remodelling occurs. Here, we assess whether acute (75 µM ouabain 100 nM blebbistatin) or chronic myocardial Nai load (PLM3SA mouse) are causally linked to metabolic remodelling and whether the failing heart shares a common Na-mediated metabolic 'fingerprint'. Control (PLMWT), transgenic (PLM3SA), ouabain-treated and hypertrophied Langendorff-perfused mouse hearts are studied by 23Na, 31P, 13C NMR followed by 1H-NMR metabolomic profiling. Elevated Nai leads to common adaptive metabolic alterations preceding energetic impairment: a switch from fatty acid to carbohydrate metabolism and changes in steady-state metabolite concentrations (glycolytic, anaplerotic, Krebs cycle intermediates). Inhibition of mitochondrial Na/Ca exchanger by CGP37157 ameliorates the metabolic changes. In silico modelling indicates altered metabolic fluxes (Krebs cycle, fatty acid, carbohydrate, amino acid metabolism). Prevention of Nai overload or inhibition of Na/Camito may be a new approach to ameliorate metabolic dysregulation in heart failure.
Assuntos
Reprogramação Celular/fisiologia , Citoplasma/metabolismo , Insuficiência Cardíaca/metabolismo , Miocárdio/metabolismo , Sódio/metabolismo , Animais , Modelos Animais de Doenças , Metabolismo Energético , Técnicas de Introdução de Genes , Coração , Hipertrofia , Preparação de Coração Isolado , Masculino , Doenças Metabólicas/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Ratos , Ratos Wistar , Sódio/sangue , Trocador de Sódio e Cálcio/efeitos dos fármacos , Tiazepinas/farmacologiaRESUMO
Calcineurin inhibitors (CNIs) are immunosuppressive drugs used to prevent graft rejection after organ transplant. Common side effects include renal magnesium wasting and hypomagnesemia, which may contribute to new-onset diabetes mellitus, and hypercalciuria, which may contribute to post-transplant osteoporosis. Previous work suggested that CNIs reduce the abundance of key divalent cation transport proteins, expressed along the distal convoluted tubule, causing renal magnesium and calcium wasting. It has not been clear, however, whether these effects are specific for the distal convoluted tubule, and whether these represent off-target toxic drug effects, or result from inhibition of calcineurin. The CNI tacrolimus can inhibit calcineurin only when it binds with the immunophilin, FKBP12; we previously generated mice in which FKBP12 could be deleted along the nephron, to test whether calcineurin inhibition is involved, these mice are normal at baseline. Here, we confirmed that tacrolimus-treated control mice developed hypomagnesemia and urinary calcium wasting, with decreased protein and mRNA abundance of key magnesium and calcium transport proteins (NCX-1 and Calbindin-D28k ). However, qPCR also showed decreased mRNA expression of NCX-1 and Calbindin-D28k , and TRPM6. In contrast, KS-FKBP12-/- mice treated with tacrolimus were completely protected from these effects. These results indicate that tacrolimus affects calcium and magnesium transport along the distal convoluted tubule and strongly suggests that inhibition of the phosphatase, calcineurin, is directly involved.
Assuntos
Inibidores de Calcineurina/farmacologia , Cálcio/metabolismo , Hipercalciúria/induzido quimicamente , Túbulos Renais Distais/efeitos dos fármacos , Magnésio/metabolismo , Proteína 1A de Ligação a Tacrolimo/genética , Tacrolimo/farmacologia , Desequilíbrio Hidroeletrolítico/induzido quimicamente , Animais , Calbindina 1/efeitos dos fármacos , Calbindina 1/genética , Calbindina 1/metabolismo , Inibidores de Calcineurina/efeitos adversos , Cálcio/urina , Expressão Gênica , Hipercalciúria/metabolismo , Hipercalciúria/urina , Túbulos Renais Distais/metabolismo , Magnésio/urina , Camundongos , Camundongos Knockout , RNA Mensageiro/efeitos dos fármacos , RNA Mensageiro/metabolismo , Trocador de Sódio e Cálcio/efeitos dos fármacos , Trocador de Sódio e Cálcio/genética , Trocador de Sódio e Cálcio/metabolismo , Canais de Cátion TRPM/efeitos dos fármacos , Canais de Cátion TRPM/genética , Canais de Cátion TRPM/metabolismo , Tacrolimo/efeitos adversos , Proteína 1A de Ligação a Tacrolimo/metabolismo , Desequilíbrio Hidroeletrolítico/metabolismo , Desequilíbrio Hidroeletrolítico/urinaRESUMO
Chronic ethanol (EtOH) exposure can cause intracellular Ca overload by stimulating calcium channel receptors and trigger apoptosis of neurons. NCX3 may play a cytoprotective role in intracellular Ca excretion. In this study, the effect of EtOH on NCX3 was analyzed by observing NCX3 expression in the hippocampus of chronic EtOH-exposed male C57BL/6 mice. Mice were divided into a control group, a 10% EtOH group, and a 20% EtOH group for 30, 60, and 90 days. Behavioral changes were observed using the Morris water maze. The protein and mRNA expressions of NCX3 and their distribution in the hippocampus were observed by western blotting, quantitative PCR, and immunohistochemistry staining. The results showed that EtOH exposure exerted a significant adverse effect on the spatial memory capacity of mice. Increased expression of calpain-1 and cleaved caspase-3 proteins indicated increased apoptosis. The expression of NCX3 in the hippocampus was downregulated after exposure to EtOH (except 10% EtOH for 30 days) and this inhibition was time and dose dependent with EtOH exposure. The level of p-Akt, which is an upstream regulation factor of NCX3, showed a trend similar to that of NCX3 protein. Chronic EtOH exposure reduced the expression of NCX3 in the hippocampus of male C57BL/6 mice, increasing intracellular calcium and apoptosis, resulting in spatial memory impairment in mice.
Assuntos
Depressores do Sistema Nervoso Central/toxicidade , Etanol/toxicidade , Hipocampo/efeitos dos fármacos , Trocador de Sódio e Cálcio/efeitos dos fármacos , Trocador de Sódio e Cálcio/metabolismo , Animais , Hipocampo/metabolismo , Aprendizagem/efeitos dos fármacos , Masculino , Memória/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos C57BLAssuntos
Canais de Cálcio/metabolismo , Mitocôndrias Cardíacas/metabolismo , Infarto do Miocárdio/metabolismo , Animais , Antiarrítmicos/uso terapêutico , Cálcio/sangue , Canais de Cálcio/efeitos dos fármacos , Humanos , Camundongos , Mitocôndrias Cardíacas/fisiologia , Infarto do Miocárdio/tratamento farmacológico , Infarto do Miocárdio/fisiopatologia , Miócitos Cardíacos/química , Miócitos Cardíacos/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Trocador de Sódio e Cálcio/antagonistas & inibidores , Trocador de Sódio e Cálcio/efeitos dos fármacos , Trocador de Sódio e Cálcio/uso terapêuticoRESUMO
BACKGROUND: Long QT syndrome mutations in the SCN5A gene are associated with an enhanced late sodium current (INa,L) which may lead to pro-arrhythmic action potential prolongation and intracellular calcium dysregulation. We here investigated the dynamic relation between INa,L, intracellular sodium ([Na+]i) and calcium ([Ca2+]i) homeostasis and pro-arrhythmic events in the setting of a SCN5A mutation. METHODS AND RESULTS: Wild-type (WT) and Scn5a1798insD/+ (MUT) mice (age 3-5â¯months) carrying the murine homolog of the SCN5A-1795insD mutation on two distinct genetic backgrounds (FVB/N and 129P2) were studied. [Na+]i, [Ca2+]i and Ca2+ transient amplitude were significantly increased in 129P2-MUT myocytes as compared to WT, but not in FVB/N-MUT. Accordingly, INa,L wassignificantly more enhanced in 129P2-MUT than in FVB/N-MUT myocytes, consistent with a dose-dependent correlation. Quantitative RT-PCR analysis revealed intrinsic differences in mRNA expression levels of the sodium/potassium pump, the sodium/hydrogen exchanger, and sodiumcalcium exchanger between the two mouse strains. The rate of increase in [Na+]i, [Ca2+]i and Ca2+ transient amplitude following the application of the Na+/K+-ATPase inhibitor ouabain was significantly greater in 129P2-MUT than in 129P2-WT myocytes and was normalized by the INa,L inhibitor ranolazine. Furthermore, ranolazine decreased the incidence of pro-arrhythmic calcium after-transients elicited in 129P2-MUT myocytes. CONCLUSIONS: In this study we established a causal link between the magnitude of INa,L, extent of Na+ and Ca2+ dysregulation, and incidence of pro-arrhythmic events in murine Scn5a1798insD/+ myocytes. Furthermore, our findings provide mechanistic insight into the anti-arrhythmic potential of pharmacological inhibition of INa,L in patients with LQT3 syndrome.
Assuntos
Arritmias Cardíacas/genética , Arritmias Cardíacas/fisiopatologia , Cálcio/fisiologia , Líquido Intracelular/fisiologia , Canal de Sódio Disparado por Voltagem NAV1.5/fisiologia , Sódio/fisiologia , Animais , Arritmias Cardíacas/etiologia , Células Cultivadas , Líquido Intracelular/efeitos dos fármacos , Camundongos , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/fisiologia , Bloqueadores dos Canais de Sódio/farmacologia , Bloqueadores dos Canais de Sódio/uso terapêutico , Trocador de Sódio e Cálcio/efeitos dos fármacos , Trocador de Sódio e Cálcio/fisiologiaRESUMO
We have previously demonstrated that methylene blue (MB) counteracts the effects of hydrogen sulfide (H2S) cardiotoxicity by improving cardiomyocyte contractility and intracellular Ca2+ homeostasis disrupted by H2S poisoning. In vivo, MB restores cardiac contractility severely depressed by sulfide and protects against arrhythmias, ranging from bundle branch block to ventricular tachycardia or fibrillation. To dissect the cellular mechanisms by which MB reduces arrhythmogenesis and improves bioenergetics in myocytes intoxicated with H2S, we evaluated the effects of H2S on resting membrane potential (Em), action potential (AP), Na+/Ca2+ exchange current (INaCa), depolarization-activated K+ currents and ATP levels in adult mouse cardiac myocytes and determined whether MB could counteract the toxic effects of H2S on myocyte electrophysiology and ATP. Exposure to toxic concentrations of H2S (100 µM) significantly depolarized Em, reduced AP amplitude, prolonged AP duration at 90% repolarization (APD90), suppressed INaCa and depolarization-activated K+ currents, and reduced ATP levels in adult mouse cardiac myocytes. Treating cardiomyocytes with MB (20 µg/ml) 3 min after H2S exposure restored Em, APD90, INaCa, depolarization-activated K+ currents, and ATP levels toward normal. MB improved mitochondrial membrane potential (∆ψm) and oxygen consumption rate in myocytes in which Complex I was blocked by rotenone. We conclude that MB ameliorated H2S-induced cardiomyocyte toxicity at multiple levels: (1) reversing excitation-contraction coupling defects (Ca2+ homeostasis and L-type Ca2+ channels); (2) reducing risks of arrhythmias (Em, APD, INaCa and depolarization-activated K+ currents); and (3) improving cellular bioenergetics (ATP, ∆ψm).
Assuntos
Trifosfato de Adenosina/metabolismo , Arritmias Cardíacas/induzido quimicamente , Arritmias Cardíacas/prevenção & controle , Metabolismo Energético/efeitos dos fármacos , Sulfeto de Hidrogênio/toxicidade , Canais Iônicos/efeitos dos fármacos , Azul de Metileno/farmacologia , Miócitos Cardíacos/efeitos dos fármacos , Potenciais de Ação , Animais , Arritmias Cardíacas/metabolismo , Arritmias Cardíacas/fisiopatologia , Canais de Cálcio Tipo L/efeitos dos fármacos , Canais de Cálcio Tipo L/metabolismo , Sinalização do Cálcio/efeitos dos fármacos , Frequência Cardíaca/efeitos dos fármacos , Canais Iônicos/metabolismo , Potencial da Membrana Mitocondrial/efeitos dos fármacos , Camundongos , Mitocôndrias Cardíacas/efeitos dos fármacos , Mitocôndrias Cardíacas/metabolismo , Contração Miocárdica/efeitos dos fármacos , Miócitos Cardíacos/metabolismo , Consumo de Oxigênio/efeitos dos fármacos , Canais de Potássio de Abertura Dependente da Tensão da Membrana/efeitos dos fármacos , Canais de Potássio de Abertura Dependente da Tensão da Membrana/metabolismo , Trocador de Sódio e Cálcio/efeitos dos fármacos , Trocador de Sódio e Cálcio/metabolismoRESUMO
BACKGROUND: The cardiac sodium/calcium (Na+/Ca2+) exchanger (NCX) contributes to diastolic depolarization in cardiac pacemaker cells. Increased NCX activity has been found in heart failure and atrial fibrillation. The influence of increased NCX activity on resting heart rate, beta-adrenergic-mediated increase in heart rate, and cardiac conduction properties is unknown. OBJECTIVE: The purpose of this study was to investigate the influence of NCX overexpression in a homozygous transgenic whole-heart mouse model (NCX-OE) on sinus and AV nodal function. METHODS: Langendorff-perfused, beating whole hearts of NCX-OE and the corresponding wild-type (WT) were studied ± isoproterenol (ISO; 0.2 µM). Epicardial ECG, AV nodal Wenckebach cycle length (AVN-WCL), and retrograde AVN-WCL were obtained. RESULTS: At baseline, basal heart rate was unaltered between NCX-OE and WT (WT: cycle length [CL] 177.6 ± 40.0 ms, no. of hearts [n] = 20; NCX-OE: CL 185.9 ± 30.5 ms, n = 18; P = .21). In the presence of ISO, NCX-OE exhibited a significantly higher heart rate compared to WT (WT: CL 133.4 ± 13.4 ms, n = 20; NCX-OE: CL 117.7 ± 14.2 ms, n = 18; P <.001). ISO led to a significant shortening of the anterograde and retrograde AVN-WCL without differences between NCX-OE and WT. CONCLUSION: This study is the first to demonstrate that increased NCX activity enhances beta-adrenergic increase of heart rate. Mechanistically, increased NCX inward mode activity may promote acceleration of diastolic depolarization in sinus nodal pacemaker cells, thus enhancing chronotropy in NCX-OE. These findings suggest a novel potential therapeutic target for heart rate control in the presence of increased NCX activity, such as heart failure.
Assuntos
Insuficiência Cardíaca/tratamento farmacológico , Frequência Cardíaca/fisiologia , Isoproterenol/farmacologia , Contração Miocárdica/fisiologia , Miócitos Cardíacos/patologia , Nó Sinoatrial/fisiopatologia , Trocador de Sódio e Cálcio/biossíntese , Agonistas Adrenérgicos beta/farmacologia , Animais , Cálcio/metabolismo , Modelos Animais de Doenças , Insuficiência Cardíaca/metabolismo , Camundongos , Camundongos Transgênicos , Miócitos Cardíacos/metabolismo , Nó Sinoatrial/metabolismo , Trocador de Sódio e Cálcio/efeitos dos fármacosRESUMO
The quintessential property of developing cardiomyocytes is their ability to beat spontaneously. The mechanisms underlying spontaneous beating in developing cardiomyocytes are thought to resemble those of adult heart, but have not been directly tested. Contributions of sarcoplasmic and mitochondrial Ca(2+)-signaling vs. If-channel in initiating spontaneous beating were tested in human induced Pluripotent Stem cell-derived cardiomyocytes (hiPS-CM) and rat Neonatal cardiomyocytes (rN-CM). Whole-cell and perforated-patch voltage-clamping and 2-D confocal imaging showed: (1) both cell types beat spontaneously (60-140/min, at 24°C); (2) holding potentials between -70 and 0mV had no significant effects on spontaneous pacing, but suppressed action potential formation; (3) spontaneous pacing at -50mV activated cytosolic Ca(2+)-transients, accompanied by in-phase inward current oscillations that were suppressed by Na(+)-Ca(2+)-exchanger (NCX)- and ryanodine receptor (RyR2)-blockers, but not by Ca(2+)- and If-channels blockers; (4) spreading fluorescence images of cytosolic Ca(2+)-transients emanated repeatedly from preferred central cellular locations during spontaneous beating; (5) mitochondrial un-coupler, FCCP at non-depolarizing concentrations (â¼50nM), reversibly suppressed spontaneous pacing; (6) genetically encoded mitochondrial Ca(2+)-biosensor (mitycam-E31Q) detected regionally diverse, and FCCP-sensitive mitochondrial Ca(2+)-uptake and release signals activating during INCX oscillations; (7) If-channel was absent in rN-CM, but activated only negative to -80mV in hiPS-CM; nevertheless blockers of If-channel failed to alter spontaneous pacing.
Assuntos
Sinalização do Cálcio/fisiologia , Frequência Cardíaca/fisiologia , Mitocôndrias Cardíacas/fisiologia , Miócitos Cardíacos/fisiologia , Animais , Bloqueadores dos Canais de Cálcio/farmacologia , Sinalização do Cálcio/efeitos dos fármacos , Linhagem Celular , Células Cultivadas , Humanos , Camundongos , Modelos Animais , Miócitos Cardíacos/citologia , Técnicas de Patch-Clamp , Ratos , Canal de Liberação de Cálcio do Receptor de Rianodina/efeitos dos fármacos , Canal de Liberação de Cálcio do Receptor de Rianodina/fisiologia , Trocador de Sódio e Cálcio/antagonistas & inibidores , Trocador de Sódio e Cálcio/efeitos dos fármacos , Trocador de Sódio e Cálcio/fisiologiaRESUMO
BACKGROUND: Fibroblast growth factor (FGF)-23 is a key regulator of phosphate homeostasis. Higher FGF-23 levels are correlated with poor outcomes in cardiovascular diseases. FGF-23 can produce cardiac hypertrophy and increase intracellular calcium, which can change cardiac electrical activity. However, it is not clear whether FGF-23 possesses arrhythmogenic potential through calcium dysregulation. Therefore, the purposes of this study were to evaluate the electrophysiological effects of FGF-23 and identify the underlying mechanisms. METHODS: Patch clamp, confocal microscope with Fluo-4 fluorescence, and Western blot analyses were used to evaluate the electrophysiological characteristics, calcium homeostasis and calcium regulatory proteins in HL-1 atrial myocytes with and without FGF-23 (10 and 25 ng/mL) incubation for 24 h. RESULTS: FGF-23 (25 ng/mL) increased L-type calcium currents, calcium transient and sarcoplasmic reticulum Ca(2+) contents in HL-1 cells. FGF-23 (25 ng/mL)-treated cells (n = 14) had greater incidences (57%, 17% and 15%, P < 0·05) of delayed afterdepolarizations than control (n = 12) and FGF-23 (10 ng/mL)-treated cells (n = 13). Compared with control cells, FGF-23 (25 ng/mL)-treated cells (n = 14) exhibited increased phosphorylation of calcium/calmodulin-dependent protein kinase IIδ and phospholamban (PLB) at threonine 17 but had similar phosphorylation extents of PLB at serine 16, total PLB and sarcoplasmic reticulum Ca(2+) -ATPase protein. Moreover, the FGF receptor inhibitor (PD173074, 10 nM), calmodulin inhibitor (W7, 5 µM) and phospholipase C inhibitor (U73122, 1 µM) attenuated the effects of FGF-23 on calcium/calmodulin-dependent protein kinase II phosphorylation. CONCLUSIONS: FGF-23 increases HL-1 cells arrhythmogenesis with calcium dysregulation through modulating calcium-handling proteins.
Assuntos
Cálcio/metabolismo , Fatores de Crescimento de Fibroblastos/fisiologia , Homeostase/fisiologia , Potenciais de Ação/efeitos dos fármacos , Arritmias Cardíacas/fisiopatologia , Proteínas de Ligação ao Cálcio/efeitos dos fármacos , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/antagonistas & inibidores , Células Cultivadas , Relação Dose-Resposta a Droga , Estrenos/farmacologia , Fator de Crescimento de Fibroblastos 23 , Fatores de Crescimento de Fibroblastos/farmacologia , Átrios do Coração/metabolismo , Homeostase/efeitos dos fármacos , Humanos , Miócitos Cardíacos/metabolismo , Técnicas de Patch-Clamp , Inibidores de Proteínas Quinases/farmacologia , Pirimidinas/farmacologia , Pirrolidinonas/farmacologia , Trocador de Sódio e Cálcio/efeitos dos fármacos , Sulfonamidas/farmacologiaRESUMO
Considerable electrophysiological and pharmacological evidence has long suggested an important role for acetylcholine in the regulation of rapid-eye-movement (REM) sleep. For example, injection of the cholinergic agonist carbachol into the dorsomedial pons produces an REM sleep-like state with muscle atonia and cortical activation, both of which are cardinal features of REM sleep. Located within this region of the pons is the sublaterodorsal nucleus (SLD), a structure thought to be both necessary and sufficient for generating REM sleep muscle atonia. Subsets of glutamatergic SLD neurons potently contribute to motor inhibition during REM sleep through descending projections to motor-related glycinergic/GABAergic neurons in the spinal cord and ventromedial medulla. Prior electrophysiological and pharmacological studies examining the effects of acetylcholine on SLD neurons have, however, produced conflicting results. In the present study, we sought to clarify how acetylcholine influences the activity of spinally projecting SLD (SLDsp) neurons. We used retrograde tracing in combination with patch-clamp recordings and recorded pre- and postsynaptic effects of carbachol on SLDsp neurons. Carbachol acted presynaptically by increasing the frequency of glutamatergic miniature excitatory postsynaptic currents. We also found that carbachol directly excited SLDsp neurons by activating an Na(+)-Ca(2+) exchanger. Both pre- and postsynaptic effects were mediated by co-activation of M1 and M3 muscarinic receptors. These observations suggest that acetylcholine produces synergistic, excitatory pre- and postsynaptic responses on SLDsp neurons that, in turn, probably serve to promote muscle atonia during REM sleep.
Assuntos
Carbacol/farmacologia , Neurônios Colinérgicos/efeitos dos fármacos , Neurônios Motores/efeitos dos fármacos , Agonistas Muscarínicos/farmacologia , Ponte/efeitos dos fármacos , Medula Espinal/efeitos dos fármacos , Acetilcolina/metabolismo , Animais , Neurônios Colinérgicos/metabolismo , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Feminino , Ácido Glutâmico/metabolismo , Técnicas In Vitro , Masculino , Camundongos Endogâmicos C57BL , Potenciais Pós-Sinápticos em Miniatura/efeitos dos fármacos , Neurônios Motores/metabolismo , Inibição Neural/efeitos dos fármacos , Vias Neurais/efeitos dos fármacos , Vias Neurais/metabolismo , Ponte/metabolismo , Terminações Pré-Sinápticas/efeitos dos fármacos , Terminações Pré-Sinápticas/metabolismo , Receptor Muscarínico M1/agonistas , Receptor Muscarínico M1/metabolismo , Receptor Muscarínico M3/agonistas , Receptor Muscarínico M3/metabolismo , Transdução de Sinais/efeitos dos fármacos , Sono REM/efeitos dos fármacos , Trocador de Sódio e Cálcio/efeitos dos fármacos , Trocador de Sódio e Cálcio/metabolismo , Medula Espinal/metabolismo , Fatores de TempoRESUMO
Ginkgo biloba has been used for medical purposes for centuries in traditional Chinese medicine. Ginkgo biloba extract 50 (GBE50) is a new standardized GBE product that matches the standardized German product as EGb761. This paper is aimed at studying the cardio-protection effects of GBE50 Salvia miltiorrhiza on myocardial function, area at risk, myocardial ultra-structure, and expression of calcium handling proteins in rat ischemic myocardium. Myocardium ischemia was induced by the left anterior descending (LAD) coronary artery occlusion and myocardial function was recorded by a transducer advanced into the left ventricle on a computer system. In vitro myocardial infarction was measured by 2,3,5-triphenyltetrazolium chloride (TTC) and Evans blue staining of heart sections. Morphological change was evaluated by electric microscopy and Western blotting was used for protein expression. Hemodynamic experiments in vivo showed that postischemic cardiac contractile function was reduced in ischemic rats. Salvia miltiorrhiza (7.5 g/kg/d×7) and Ginkgo biloba extract 50 (GBE50) (100 mg/kg/d×7) improved post-schemic cardiac diastolic dysfunction while not affecting the systolic function. In hearts of GBE50 group and Salvia miltiorrhiza (SM) group, the area at risk was significantly reduced and myocardial structure was better-preserved. Moreover, Naâº-Ca²âº exchanger (NCX) expression increase and sarcoplasmic reticulum Ca²âº-ATPase 2 (SERCA2), LTCC, and ryanodine receptor 2 (RyR2) expression decreases were smaller than those in ischemia group. There was a significant difference between the GBE50 and ischemia group in NCX expression. GBE50 could improve recovery in contractile function and prevent myocardium from ischemia damage, which may be caused by attenuating the abnormal expression of NCX.
Assuntos
Cardiotônicos/farmacologia , Ginkgo biloba , Coração/efeitos dos fármacos , Infarto do Miocárdio , Fitoterapia/métodos , Extratos Vegetais/farmacologia , Salvia miltiorrhiza , Função Ventricular Esquerda/efeitos dos fármacos , Animais , Canais de Cálcio Tipo L/efeitos dos fármacos , Canais de Cálcio Tipo L/metabolismo , Frequência Cardíaca/efeitos dos fármacos , Masculino , Microscopia Eletrônica , Contração Miocárdica/efeitos dos fármacos , Traumatismo por Reperfusão Miocárdica , Miocárdio/ultraestrutura , Ratos , Canal de Liberação de Cálcio do Receptor de Rianodina/efeitos dos fármacos , Canal de Liberação de Cálcio do Receptor de Rianodina/metabolismo , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/efeitos dos fármacos , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/metabolismo , Trocador de Sódio e Cálcio/efeitos dos fármacos , Trocador de Sódio e Cálcio/metabolismoRESUMO
The treatment of heart failure (HF) is challenging and morbidity and mortality are high. The goal of this study was to determine if inhibition of the late Na(+) current with ranolazine during early hypertensive heart disease might slow or stop disease progression. Spontaneously hypertensive rats (aged 7 mo) were subjected to echocardiographic study and then fed either control chow (CON) or chow containing 0.5% ranolazine (RAN) for 3 mo. Animals were then restudied, and each heart was removed for measurements of t-tubule organization and Ca(2+) transients using confocal microscopy of the intact heart. RAN halted left ventricular hypertrophy as determined from both echocardiographic and cell dimension (length but not width) measurements. RAN reduced the number of myocytes with t-tubule disruption and the proportion of myocytes with defects in intracellular Ca(2+) cycling. RAN also prevented the slowing of the rate of restitution of Ca(2+) release and the increased vulnerability to rate-induced Ca(2+) alternans. Differences between CON- and RAN-treated animals were not a result of different expression levels of voltage-dependent Ca(2+) channel 1.2, sarco(endo)plasmic reticulum Ca(2+)-ATPase 2a, ryanodine receptor type 2, Na(+)/Ca(2+) exchanger-1, or voltage-gated Na(+) channel 1.5. Furthermore, myocytes with defective Ca(2+) transients in CON rats showed improved Ca(2+) cycling immediately upon acute exposure to RAN. Increased late Na(+) current likely plays a role in the progression of cardiac hypertrophy, a key pathological step in the development of HF. Early, chronic inhibition of this current slows both hypertrophy and development of ultrastructural and physiological defects associated with the progression to HF.
Assuntos
Acetanilidas/farmacologia , Sinalização do Cálcio/efeitos dos fármacos , Hipertensão/tratamento farmacológico , Miócitos Cardíacos/efeitos dos fármacos , Piperazinas/farmacologia , Bloqueadores dos Canais de Sódio/farmacologia , Canais de Sódio/efeitos dos fármacos , Sódio/metabolismo , Animais , Canais de Cálcio Tipo L/efeitos dos fármacos , Canais de Cálcio Tipo L/metabolismo , Modelos Animais de Doenças , Progressão da Doença , Relação Dose-Resposta a Droga , Insuficiência Cardíaca/etiologia , Insuficiência Cardíaca/metabolismo , Insuficiência Cardíaca/fisiopatologia , Insuficiência Cardíaca/prevenção & controle , Hipertensão/complicações , Hipertensão/diagnóstico por imagem , Hipertensão/metabolismo , Hipertensão/fisiopatologia , Hipertrofia Ventricular Esquerda/etiologia , Hipertrofia Ventricular Esquerda/metabolismo , Hipertrofia Ventricular Esquerda/fisiopatologia , Hipertrofia Ventricular Esquerda/prevenção & controle , Masculino , Miócitos Cardíacos/metabolismo , Canal de Sódio Disparado por Voltagem NAV1.5/efeitos dos fármacos , Canal de Sódio Disparado por Voltagem NAV1.5/metabolismo , Ranolazina , Ratos , Ratos Endogâmicos SHR , Canal de Liberação de Cálcio do Receptor de Rianodina/efeitos dos fármacos , Canal de Liberação de Cálcio do Receptor de Rianodina/metabolismo , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/metabolismo , Canais de Sódio/metabolismo , Trocador de Sódio e Cálcio/efeitos dos fármacos , Trocador de Sódio e Cálcio/metabolismo , Fatores de Tempo , UltrassonografiaAssuntos
Angina Pectoris/tratamento farmacológico , Angina Pectoris/fisiopatologia , Cálcio/sangue , Doença da Artéria Coronariana/tratamento farmacológico , Doença da Artéria Coronariana/fisiopatologia , Hipercalcemia/tratamento farmacológico , Hipercalcemia/fisiopatologia , Isquemia Miocárdica/tratamento farmacológico , Isquemia Miocárdica/fisiopatologia , Canais de Sódio/fisiologia , Trocador de Sódio e Cálcio/fisiologia , Acetanilidas/uso terapêutico , Antagonistas Adrenérgicos beta/uso terapêutico , Angina Pectoris/diagnóstico , Fibrilação Atrial/diagnóstico , Fibrilação Atrial/tratamento farmacológico , Fibrilação Atrial/fisiopatologia , Benzazepinas/uso terapêutico , Bloqueadores dos Canais de Cálcio/uso terapêutico , Fármacos Cardiovasculares/uso terapêutico , Doença da Artéria Coronariana/diagnóstico , Eletrocardiografia/efeitos dos fármacos , Endotélio Vascular/fisiopatologia , Insuficiência Cardíaca Diastólica/diagnóstico , Insuficiência Cardíaca Diastólica/tratamento farmacológico , Insuficiência Cardíaca Diastólica/fisiopatologia , Humanos , Hipercalcemia/diagnóstico , Ivabradina , Isquemia Miocárdica/diagnóstico , Nitratos/uso terapêutico , Piperazinas/uso terapêutico , Ranolazina , Sódio/metabolismo , Canais de Sódio/efeitos dos fármacos , Trocador de Sódio e Cálcio/efeitos dos fármacosRESUMO
BACKGROUND: Epidemiological studies revealed significantly lower mortality rates in cancer patients receiving cardiac glycosides, which turned on interest in the anticancer properties of these drugs. However, cardiac glycosides have also been shown to stimulate cell growth in several cell types. In the present investigation we analyzed the pro-death and pro-survival properties of ouabain in the human lymphoma derived cell line U937. METHODS: ROS, intracellular Ca++, cell cycle were evaluated by loading the cells with fluorescent probes under cytofluorimetry. Cell counts and evaluation of trypan blue-excluding cells were performed under optic microscope. Protein detection was done by specific antibodies after protein separation from cellular lysates by SDS-PAGE and transfer blot. RESULTS: High doses of ouabain cause ROS generation, elevation of [Ca++]i and death of lymphoma derived U937 cells. Lower doses of OUA activate a survival pathway in which plays a role the Na+/Ca++-exchanger (NCX), active in the Ca++ influx mode rather than in the Ca++ efflux mode. Also p38 MAPK plays a pro-survival role. However, the activation of this MAPK does not appear to depend on NCX. CONCLUSION: This investigation shows that the cardiac glycoside OUA is cytotoxic also for the lymphoma derived cell line U937 and that can activate a survival pathway in which are involved NCX and p38 MAPK. These molecules can represent potential targets of combined therapy.
Assuntos
Cálcio/metabolismo , Ouabaína/administração & dosagem , Espécies Reativas de Oxigênio/metabolismo , Trocador de Sódio e Cálcio , Morte Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Citometria de Fluxo , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Linfoma/genética , Linfoma/metabolismo , Trocador de Sódio e Cálcio/efeitos dos fármacos , Trocador de Sódio e Cálcio/metabolismo , Células U937 , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
The late Na current is of pathophysiological importance for the heart. Ranolazine is an innovative anti-ischemic and antianginal agent that inhibits the late Na current, thereby reducing the Na-dependent Ca-overload, which improves diastolic tone and oxygen handling during myocardial ischemia. In addition, ranolazine seems to exert beneficial effects on diastolic cardiac function. Moreover, there are experimental and clinical data about its antiarrhythmic properties. A beneficial atrial selectivity of ranolazine has been suggested that may be helpful for the treatment of atrial fibrillation. The purpose of this review article is to discuss possible future clinical indications based on novel experimental and preclinical results and the significance of the available data.
Assuntos
Acetanilidas/uso terapêutico , Arritmias Cardíacas/tratamento farmacológico , Inibidores Enzimáticos/uso terapêutico , Insuficiência Cardíaca Diastólica/tratamento farmacológico , Piperazinas/uso terapêutico , Potenciais de Ação/efeitos dos fármacos , Antiarrítmicos/uso terapêutico , Fibrilação Atrial/tratamento farmacológico , Cálcio/metabolismo , Fármacos Cardiovasculares/uso terapêutico , Cátions/metabolismo , Diástole/efeitos dos fármacos , Insuficiência Cardíaca/tratamento farmacológico , Humanos , Contração Miocárdica/efeitos dos fármacos , Canal de Sódio Disparado por Voltagem NAV1.5/efeitos dos fármacos , Ranolazina , Sódio/metabolismo , Trocador de Sódio e Cálcio/efeitos dos fármacosRESUMO
The mechanisms by which NaCl raises blood pressure (BP) in hypertension are unresolved, but much evidence indicates that endogenous ouabain is involved. In rodents, arterial smooth muscle cell (ASMC) Na(+) pumps with an α(2)-catalytic subunit (ouabain EC(50) ≤1.0 nM) are crucial for some hypertension models, even though ≈80% of ASMC Na(+) pumps have an α(1)-subunit (ouabain EC(50) ≈ 5 µM). Human α(1)-Na(+) pumps, however, have high ouabain affinity (EC(50) ≈ 10-20 nM). We used immunoblotting, immunocytochemistry, and Ca(2+) imaging (fura-2) to examine the expression, distribution, and function of Na(+) pump α-subunit isoforms in human arteries and primary cultured human ASMCs (hASMCs). hASMCs express α(1)- and α(2)-Na(+) pumps. Further, α(2)-, but not α(1)-, pumps are confined to plasma membrane microdomains adjacent to sarcoplasmic reticulum (SR), where they colocalize with Na/Ca exchanger-1 (NCX1) and C-type transient receptor potential-6 (receptor-operated channels, ROCs). Prolonged inhibition (72 h) with 100 nM ouabain (blocks nearly all α(1)- and α(2)-pumps) was toxic to most cultured hASMCs. Treatment with 10 nM ouabain (72 h), however, increased NCX1 and sarco(endo)plasmic reticulum Ca(2+)-ATPase expression and augmented ATP (10 µM)-induced SR Ca(2+) release in 0 Ca(2+), ouabain-free media, and Ca(2+) influx after external Ca(2+) restoration. The latter was likely mediated primarily by ROCs and store-operated Ca(2+) channels. These hASMC protein expression and Ca(2+) signaling changes are comparable with previous observations on myocytes isolated from arteries of many rat hypertension models. We conclude that the same structurally and functionally coupled mechanisms (α(2)-Na(+) pumps, NCX1, ROCs, and the SR) regulate Ca(2+) homeostasis and signaling in hASMCs and rodent ASMCs. These ouabain/endogenous ouabain-modulated mechanisms underlie the whole body autoregulation associated with increased vascular resistance and elevation of BP in human, salt-sensitive hypertension.
Assuntos
Sinalização do Cálcio/efeitos dos fármacos , Músculo Liso Vascular/efeitos dos fármacos , Miócitos de Músculo Liso/efeitos dos fármacos , Ouabaína/farmacologia , Cloreto de Sódio/farmacologia , Trocador de Sódio e Cálcio/efeitos dos fármacos , Resistência Vascular/efeitos dos fármacos , Adolescente , Adulto , Idoso , Animais , Pressão Sanguínea/efeitos dos fármacos , Western Blotting , Cardenolídeos/metabolismo , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Forma Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Relação Dose-Resposta a Droga , Feminino , Homeostase , Humanos , Hipertensão/induzido quimicamente , Hipertensão/metabolismo , Hipertensão/fisiopatologia , Imuno-Histoquímica , Receptores de Inositol 1,4,5-Trifosfato/efeitos dos fármacos , Receptores de Inositol 1,4,5-Trifosfato/metabolismo , Masculino , Artéria Torácica Interna/efeitos dos fármacos , Artéria Torácica Interna/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Microscopia de Fluorescência , Pessoa de Meia-Idade , Músculo Liso Vascular/metabolismo , Músculo Liso Vascular/fisiopatologia , Miócitos de Músculo Liso/metabolismo , Ratos , Saponinas/metabolismo , Retículo Sarcoplasmático/efeitos dos fármacos , Retículo Sarcoplasmático/metabolismo , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/metabolismo , Cloreto de Sódio/toxicidade , Trocador de Sódio e Cálcio/metabolismo , ATPase Trocadora de Sódio-Potássio/antagonistas & inibidores , ATPase Trocadora de Sódio-Potássio/metabolismo , Canais de Cátion TRPC/efeitos dos fármacos , Canais de Cátion TRPC/metabolismo , Fatores de Tempo , Regulação para Cima , Adulto JovemRESUMO
Pharmacologic modification of cellular calcium handling recently moved into focus as an alternative for prevention and treatment of ventricular tachyarrhythmias. Calcium overload and spontaneous calcium release from the sarcoplasmatic reticulum are regarded as possible initiations of early and delayed afterdepolarization thereby triggering ventricular arrhythmias. In chronic heart failure, calcium overload is more likely to occur compared with healthy hearts, which is one explantation for the increased vulnerability in this condition. L-type calcium channel, sodium-calcium-exchanger (NCX), and ryanodine receptor are crucial for calcium homeostasis and therefore represent potential targets for antiarrhythmic drug therapy. Experimental studies have proven beneficial effects for all these three mechanisms in prevention and suppression of tachyarrhythmias. However, clinical data is mainly available for the L-type calcium channel inhibitor verapamil. Therefore, it is still a long way to clinical employment of drugs modifying cellular calcium handling for antiarrhythmic therapy.