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1.
Proc Natl Acad Sci U S A ; 116(43): 21874-21881, 2019 10 22.
Artigo em Inglês | MEDLINE | ID: mdl-31591206

RESUMO

Junctophilin proteins maintain close contacts between the endoplasmic/sarcoplasmic reticulum (ER/SR) and the plasma membrane in many types of cells, as typified by junctophilin-2 (JPH2), which is necessary for the formation of the cardiac dyad. Here, we report that JPH2 is the most abundant junctophilin isotype in native smooth muscle cells (SMCs) isolated from cerebral arteries and that acute knockdown diminishes the area of sites of interaction between the SR and plasma membrane. Superresolution microscopy revealed nanometer-scale colocalization of JPH2 clusters with type 2 ryanodine receptor (RyR2) clusters near the cell surface. Knockdown of JPH2 had no effect on the frequency, amplitude, or kinetics of spontaneous Ca2+ sparks generated by transient release of Ca2+ from the SR through RyR2s, but it did nearly abolish Ca2+ spark-activated, large-conductance, Ca2+-activated K+ (BK) channel currents. We also found that JPH2 knockdown was associated with hypercontractility of intact cerebral arteries. We conclude that JPH2 maintains functional coupling between RyR2s and BK channels and is critically important for cerebral arterial function.


Assuntos
Artérias Cerebrais/fisiologia , Proteínas de Membrana/fisiologia , Contração Muscular/fisiologia , Músculo Liso Vascular/fisiologia , Canal de Liberação de Cálcio do Receptor de Rianodina/fisiologia , Animais , Artérias Cerebrais/citologia , Técnicas de Silenciamento de Genes , Masculino , Proteínas de Membrana/genética , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Nanopartículas , Canais de Potássio Cálcio-Ativados/fisiologia , Transdução de Sinais
2.
Toxins (Basel) ; 11(4)2019 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-30939844

RESUMO

Russell's viper (Daboia russelii) venom causes a range of clinical effects in humans. Hypotension is an uncommon but severe complication of Russell's viper envenoming. The mechanism(s) responsible for this effect are unclear. In this study, we examined the cardiovascular effects of Sri Lankan D. russelii venom in anaesthetised rats and in isolated mesenteric arteries. D. russelii venom (100 µg/kg, i.v.) caused a 45 ± 8% decrease in blood pressure within 10 min of administration in anaesthetised (100 µg/kg ketamine/xylazine 10:1 ratio, i.p.) rats. Venom (1 ng/mL⁻1 µg/mL) caused concentration-dependent relaxation (EC50 = 145.4 ± 63.6 ng/mL, Rmax = 92 ± 2%) in U46619 pre-contracted rat small mesenteric arteries mounted in a myograph. Vasorelaxant potency of venom was unchanged in the presence of the nitric oxide synthase inhibitor, L-NAME (100 µM), or removal of the endothelium. In the presence of high K⁺ (30 mM), the vasorelaxant response to venom was abolished. Similarly, blocking voltage-dependent (Kv: 4-aminopryidine; 1000 µM) and Ca2+-activated (KCa: tetraethylammonium (TEA; 1000 µM); SKCa: apamin (0.1 µM); IKCa: TRAM-34 (1 µM); BKCa; iberiotoxin (0.1 µM)) K⁺ channels markedly attenuated venom-induced relaxation. Responses were unchanged in the presence of the ATP-sensitive K⁺ channel blocker glibenclamide (10 µM), or H1 receptor antagonist, mepyramine (0.1 µM). Venom-induced vasorelaxtion was also markedly decreased in the presence of the transient receptor potential cation channel subfamily V member 4 (TRPV4) antagonist, RN-1734 (10 µM). In conclusion, D. russelii-venom-induced hypotension in rodents may be due to activation of Kv and KCa channels, leading to vasorelaxation predominantly via an endothelium-independent mechanism. Further investigation is required to identify the toxin(s) responsible for this effect.


Assuntos
Artérias Mesentéricas/efeitos dos fármacos , Canais de Potássio Cálcio-Ativados/fisiologia , Canais de Potássio de Abertura Dependente da Tensão da Membrana/fisiologia , Víbora de Russell , Vasodilatação/efeitos dos fármacos , Vasodilatadores/farmacologia , Venenos de Víboras/farmacologia , Animais , Masculino , Artérias Mesentéricas/fisiologia , Ratos Sprague-Dawley
3.
Biol Res ; 51(1): 38, 2018 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-30290763

RESUMO

BACKGROUND: Hydrogen sulfide has been shown to improve the quality of oocytes destined for in vitro fertilization. Although hydrogen sulfide is capable of modulating ion channel activity in somatic cells, the role of hydrogen sulfide in gametes and embryos remains unknown. Our observations confirmed the hypothesis that the KATP and L-type Ca2+ ion channels play roles in porcine oocyte ageing and revealed a plausible contribution of hydrogen sulfide to the modulation of ion channel activity. RESULTS: We confirmed the benefits of the activation and suppression of the KATP and L-type Ca2+ ion channels, respectively, for the preservation of oocyte quality. CONCLUSIONS: Our experiments identified hydrogen sulfide as promoting the desired ion channel activity, with the capacity to protect porcine oocytes against cell death. Further experiments are needed to determine the exact mechanism of hydrogen sulfide in gametes and embryos.


Assuntos
Canais de Cálcio/fisiologia , Senescência Celular/fisiologia , Sulfeto de Hidrogênio/farmacologia , Oócitos/efeitos dos fármacos , Canais de Potássio Cálcio-Ativados/fisiologia , Trifosfato de Adenosina , Animais , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio/efeitos dos fármacos , Feminino , Minoxidil/farmacologia , Oócitos/metabolismo , Fenótipo , Canais de Potássio Cálcio-Ativados/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Suínos , Verapamil/farmacologia
4.
Yakugaku Zasshi ; 138(10): 1271-1275, 2018.
Artigo em Japonês | MEDLINE | ID: mdl-30270271

RESUMO

 Skeletal muscle atrophy reduces quality of life and increases mortality. However, there are few available drugs for the treatment of muscle atrophy. Recently, cell signaling pathways involved in skeletal muscle atrophy or hypertrophy have been determined. To develop drugs for skeletal muscle atrophy, we have studied compounds which modulate pathways of myogenic differentiation, a pivotal step for the maintenance of skeletal muscle mass. First, we examined a K+ channel opener on myogenic differentiation, since hyperpolarization is a trigger for skeletal muscle differentiation. 5,6-Dichloro-1-ethyl-1,3-dihydro-2H-benzimidazol-2-one (DCEBIO), an opener of the small/intermediate conductance Ca2+ activated K+ (SKCa/IKCa) channels, increases myogenic differentiation in C2C12 mouse skeletal myoblasts. This effect was inhibited by TRAM-34, an IKCa channel blocker. This suggests that K+ channels in skeletal muscle stem cells are potential targets for an anti-muscle atrophy drug. Next, we searched for drugs which prevent sepsis-induced muscle atrophy. Lipopolysaccharide (LPS), an inducer of sepsis, attenuates myogenic differentiation in C2C12 myoblasts. LPS also increases the protein expression of myostatin and activates NFκB during differentiation. The TLR4 signal inhibitor TAK-242, and an anti-TNFα neutralizing antibody, reduce these inflammatory responses. Our data suggest that LPS inhibits myogenic differentiation via the NFκB/TNFα pathway. This pathway may be involved in the development of muscle wasting caused by sepsis.


Assuntos
Benzimidazóis/farmacologia , Benzimidazóis/uso terapêutico , Diferenciação Celular/genética , Descoberta de Drogas , Desenvolvimento Muscular/genética , Desenvolvimento Muscular/fisiologia , Músculo Esquelético , Atrofia Muscular/tratamento farmacológico , Atrofia Muscular/etiologia , Canais de Potássio Cálcio-Ativados/metabolismo , Animais , Diferenciação Celular/efeitos dos fármacos , Expressão Gênica , Humanos , Lipopolissacarídeos/efeitos adversos , Camundongos , Atrofia Muscular/genética , Mioblastos/citologia , Mioblastos/fisiologia , Miostatina/genética , Miostatina/metabolismo , NF-kappa B/metabolismo , Canais de Potássio Cálcio-Ativados/fisiologia , Sepse/complicações , Transdução de Sinais/fisiologia , Fator de Necrose Tumoral alfa/metabolismo
5.
PLoS Comput Biol ; 14(7): e1006293, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-30020934

RESUMO

Bladder small DRG neurons, which are putative nociceptors pivotal to urinary bladder function, express more than a dozen different ionic membrane mechanisms: ion channels, pumps and exchangers. Small-conductance Ca2+-activated K+ (SKCa) channels which were earlier thought to be gated solely by intracellular Ca2+ concentration ([Ca]i) have recently been shown to exhibit inward rectification with respect to membrane potential. The effect of SKCa inward rectification on the excitability of these neurons is unknown. Furthermore, studies on the role of KCa channels in repetitive firing and their contributions to different types of afterhyperpolarization (AHP) in these neurons are lacking. In order to study these phenomena, we first constructed and validated a biophysically detailed single compartment model of bladder small DRG neuron soma constrained by physiological data. The model includes twenty-two major known membrane mechanisms along with intracellular Ca2+ dynamics comprising Ca2+ diffusion, cytoplasmic buffering, and endoplasmic reticulum (ER) and mitochondrial mechanisms. Using modelling studies, we show that inward rectification of SKCa is an important parameter regulating neuronal repetitive firing and that its absence reduces action potential (AP) firing frequency. We also show that SKCa is more potent in reducing AP spiking than the large-conductance KCa channel (BKCa) in these neurons. Moreover, BKCa was found to contribute to the fast AHP (fAHP) and SKCa to the medium-duration (mAHP) and slow AHP (sAHP). We also report that the slow inactivating A-type K+ channel (slow KA) current in these neurons is composed of 2 components: an initial fast inactivating (time constant ∼ 25-100 ms) and a slow inactivating (time constant ∼ 200-800 ms) current. We discuss the implications of our findings, and how our detailed model can help further our understanding of the role of C-fibre afferents in the physiology of urinary bladder as well as in certain disorders.


Assuntos
Fenômenos Biofísicos , Simulação por Computador , Gânglios Espinais/citologia , Neurônios/fisiologia , Bexiga Urinária/inervação , Potenciais de Ação/fisiologia , Animais , Cálcio/metabolismo , Corantes/metabolismo , Citoplasma/metabolismo , Retículo Endoplasmático/metabolismo , Humanos , Receptores de Inositol 1,4,5-Trifosfato/metabolismo , Potenciais da Membrana/fisiologia , Mitocôndrias/metabolismo , ATPases Transportadoras de Cálcio da Membrana Plasmática/metabolismo , Canais de Potássio Cálcio-Ativados/fisiologia , Canal de Liberação de Cálcio do Receptor de Rianodina/metabolismo , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/metabolismo , Canais de Sódio/fisiologia
6.
Brain Behav Immun ; 73: 584-595, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-29981425

RESUMO

Recent studies described a critical role for microglia in amyotrophic lateral sclerosis (ALS), where these CNS-resident immune cells participate in the establishment of an inflammatory microenvironment that contributes to motor neuron degeneration. Understanding the mechanisms leading to microglia activation in ALS could help to identify specific molecular pathways which could be targeted to reduce or delay motor neuron degeneration and muscle paralysis in patients. The intermediate-conductance calcium-activated potassium channel KCa3.1 has been reported to modulate the "pro-inflammatory" phenotype of microglia in different pathological conditions. We here investigated the effects of blocking KCa3.1 activity in the hSOD1G93AALS mouse model, which recapitulates many features of the human disease. We report that treatment of hSOD1G93A mice with a selective KCa3.1 inhibitor, 1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole (TRAM-34), attenuates the "pro-inflammatory" phenotype of microglia in the spinal cord, reduces motor neuron death, delays onset of muscle weakness, and increases survival. Specifically, inhibition of KCa3.1 channels slowed muscle denervation, decreased the expression of the fetal acetylcholine receptor γ subunit and reduced neuromuscular junction damage. Taken together, these results demonstrate a key role for KCa3.1 in driving a pro-inflammatory microglia phenotype in ALS.


Assuntos
Microglia/fisiologia , Neurônios Motores/fisiologia , Canais de Potássio Cálcio-Ativados/fisiologia , Esclerose Amiotrófica Lateral/patologia , Animais , Morte Celular , Modelos Animais de Doenças , Progressão da Doença , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Microglia/metabolismo , Fenótipo , Canais de Potássio Cálcio-Ativados/antagonistas & inibidores , Canais de Potássio Cálcio-Ativados/metabolismo , Pirazóis/farmacologia , Medula Espinal/patologia , Superóxido Dismutase/genética , Superóxido Dismutase/metabolismo , Superóxido Dismutase/fisiologia
7.
J Physiol ; 596(23): 5891-5906, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-29869786

RESUMO

KEY POINTS: Gestational hypoxia represses ten-eleven translocation methylcytosine dioxygenase 1 (TET1) expression in uterine arteries, which is recovered by inhibiting endogenous miR-210. Inhibition of miR-210 rescues BKCa channel expression and current in uterine arteries of pregnant animals acclimatized to high altitude hypoxia in a TET-dependent manner. miR-210 blockade restores BKCa channel-mediated relaxations and attenuates pressure-dependent myogenic tone in uterine arteries of pregnant animals acclimatized to high altitude. ABSTRACT: Gestational hypoxia at high altitude has profound adverse effects on the uteroplacental circulation, and is associated with increased incidence of preeclampsia and fetal intrauterine growth restriction. Previous studies demonstrated that suppression of large-conductance Ca2+ -activated K+ (BKCa ) channel function played a critical role in the maladaptation of uteroplacental circulation caused by gestational hypoxia. Yet, the mechanisms underlying gestational hypoxia-induced BKCa channel repression remain undetermined. The present study investigated a causal role of microRNA-210 (miR-210) in hypoxia-mediated repression of BKCa channel expression and function in uterine arteries using a sheep model. The results revealed that gestational hypoxia significantly decreased ten-eleven translocation methylcytosine dioxygenase 1 (TET1) expression in uterine arteries, which was recovered by inhibiting endogenous miR-210 with miR-210 locked nucleic acid (miR-210-LNA). Of importance, miR-210-LNA restored BKCa channel ß1 subunit expression in uterine arteries, which was blocked by a competitive TET inhibitor, fumarate, thus functionally linking miR-210 to the TET1-BKCa channel cascade. In addition, miR-210-LNA reversed hypoxia-mediated suppression of BKCa channel function and rescued the effect of steroid hormones in upregulating BKCa channel expression and function in uterine arteries, which were also ablated by fumarate. Collectively, the present study demonstrates a causative effect of miR-210 in the downregulation of TET1 and subsequent repression of BKCa channel expression and function, providing a novel mechanistic insight into the regulation of BKCa channel function and the molecular basis underlying the maladaptation of uterine vascular function in gestational hypoxia.


Assuntos
Doença da Altitude/fisiopatologia , MicroRNAs , Canais de Potássio Cálcio-Ativados/fisiologia , Artéria Uterina/fisiologia , Animais , Feminino , Oxigenases de Função Mista/fisiologia , Gravidez , Proteínas Proto-Oncogênicas/fisiologia , Ovinos
8.
Proc Natl Acad Sci U S A ; 115(9): E2095-E2104, 2018 02 27.
Artigo em Inglês | MEDLINE | ID: mdl-29439202

RESUMO

During a critical developmental period, cochlear inner hair cells (IHCs) exhibit sensory-independent activity, featuring action potentials in which Ca2+ ions play a fundamental role in driving both spiking and glutamate release onto synapses with afferent auditory neurons. This spontaneous activity is controlled by a cholinergic input to the IHC, activating a specialized nicotinic receptor with high Ca2+ permeability, and coupled to the activation of hyperpolarizing SK channels. The mechanisms underlying distinct excitatory and inhibitory Ca2+ roles within a small, compact IHC are unknown. Making use of Ca2+ imaging, afferent auditory bouton recordings, and electron microscopy, the present work shows that unusually high intracellular Ca2+ buffering and "subsynaptic" cisterns provide efficient compartmentalization and tight control of cholinergic Ca2+ signals. Thus, synaptic efferent Ca2+ spillover and cross-talk are prevented, and the cholinergic input preserves its inhibitory signature to ensure normal development of the auditory system.


Assuntos
Sinalização do Cálcio , Cálcio/metabolismo , Cóclea/fisiologia , Células Ciliadas Auditivas Internas/citologia , Sinapses/fisiologia , Acetilcolina/farmacologia , Potenciais de Ação , Animais , Vias Auditivas/fisiologia , Estimulação Elétrica , Feminino , Ácido Glutâmico/metabolismo , Audição , Masculino , Camundongos , Neurônios/fisiologia , Técnicas de Patch-Clamp , Canais de Potássio Cálcio-Ativados/fisiologia , Ratos , Ratos Sprague-Dawley , Receptores Nicotínicos/fisiologia , Transdução de Sinais
9.
Curr Neuropharmacol ; 16(5): 608-617, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-28875832

RESUMO

BACKGROUND: The KCa3.1 channel is the intermediate-conductance member of the Ca2+- activated K channel superfamily. It is widely expressed in excitable and non-excitable cells, where it plays a major role in a number of cell functions. This paper aims at illustrating the main structural, biophysical and modulatory properties of the KCa3.1 channel, and providing an account of experimental data on its role in volume regulation and Ca2+ signals. METHODS: Research and online content related to the structure, structure/function relationship, and physiological role of the KCa3.1 channel are reviewed. RESULTS: Expressed in excitable and non-excitable cells, the KCa3.1 channel is voltage independent, its opening being exclusively gated by the binding of intracellular Ca2+ to calmodulin, a Ca2+- binding protein constitutively associated with the C-terminus of each KCa3.1 channel α subunit. The KCa3.1 channel activates upon high affinity Ca2+ binding, and in highly coordinated fashion giving steep Hill functions and relatively low EC50 values (100-350 nM). This high Ca2+ sensitivity is physiologically modulated by closely associated kinases and phosphatases. The KCa3.1 channel is normally activated by global Ca2+ signals as resulting from Ca2+ released from intracellular stores, or by the refilling influx through store operated Ca2+ channels, but cases of strict functional coupling with Ca2+-selective channels are also found. KCa3.1 channels are highly expressed in many types of cells, where they play major roles in cell migration and death. The control of these complex cellular processes is achieved by KCa3.1 channel regulation of the driving force for Ca2+ entry from the extracellular medium, and by mediating the K+ efflux required for cell volume control. CONCLUSION: Much work remains to be done to fully understand the structure/function relationship of the KCa3.1 channels. Hopefully, this effort will provide the basis for a beneficial modulation of channel activity under pathological conditions.


Assuntos
Cálcio/metabolismo , Ativação do Canal Iônico/fisiologia , Canais de Potássio Cálcio-Ativados/fisiologia , Animais , Calmodulina/metabolismo , Simulação de Dinâmica Molecular , Canais de Potássio Cálcio-Ativados/química , Ligação Proteica , Estrutura Terciária de Proteína
10.
Microcirculation ; 25(2)2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29117630

RESUMO

OBJECTIVE: Electrical signaling along the endothelium underlies spreading vasodilation and blood flow control. We use mathematical modeling to determine the electrical properties of the endothelium and gain insight into the biophysical determinants of electrical conduction. METHODS: Electrical conduction data along endothelial tubes (40 µm wide, 2.5 mm long) isolated from mouse skeletal muscle resistance arteries were analyzed using cable equations and a multicellular computational model. RESULTS: Responses to intracellular current injection attenuate with an axial length constant (λ) of 1.2-1.4 mm. Data were fitted to estimate the axial (ra ; 10.7 MΩ/mm) and membrane (rm ; 14.5 MΩ∙mm) resistivities, EC membrane resistance (Rm ; 12 GΩ), and EC-EC coupling resistance (Rgj ; 4.5 MΩ) and predict that stimulation of ≥30 neighboring ECs is required to elicit 1 mV of hyperpolarization at distance = 2.5 mm. Opening Ca2+ -activated K+ channels (KCa ) along the endothelium reduced λ by up to 55%. CONCLUSIONS: High Rm makes the endothelium sensitive to electrical stimuli and able to conduct these signals effectively. Whereas the activation of a group of ECs is required to initiate physiologically relevant hyperpolarization, this requirement is increased by myoendothelial coupling and KCa activation along the endothelium inhibits conduction by dissipating electrical signals.


Assuntos
Endotélio Vascular/fisiologia , Microvasos/fisiologia , Modelos Biológicos , Transdução de Sinais/fisiologia , Animais , Potenciais da Membrana/fisiologia , Camundongos , Músculo Esquelético/irrigação sanguínea , Canais de Potássio Cálcio-Ativados/fisiologia , Fluxo Sanguíneo Regional , Transmissão Sináptica , Vasodilatação
11.
PLoS One ; 12(8): e0183124, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28817716

RESUMO

The roles of nitric oxide (NO), endothelium-derived hyperpolarizing factors (EDHF), and calcium-activated K+ (KCa) channels in diabetes-associated endothelial dysfunction of small renal arteries are not clear. The present study investigated acetylcholine (ACh)-induced vasorelaxation of renal arcuate arteries from obese Zucker (OZ) rats at different diabetes durations, and the relative contribution of NO, EDHF, and KCa channels to the endothelial dysfunction. OZ rats of 7 weeks (prediabetic stage), 12 weeks (early diabetic stage), and 20 weeks (late diabetic stage), and time-matched lean control rats, were studied. Segments of arcuate arteries (130 to 180 µm) were isolated, cannulated and pressurized. Vascular endothelial functions were tested using ACh-induced vasodilation. Our experiments demonstrated: (1) ACh-elicited vasodilation was impaired in OZ rats of 20 weeks, but not in rats of 7 and 12 weeks; (2) inhibition of NO or EDHF (contributed by epoxyeicosatrienoic acids [EETs]) production significantly decreased ACh-induced vasodilation in both lean and OZ rats of 20 weeks. The reduction of ACh-induced vasodilation by inhibition of NO or EDHF formation was less in OZ rats, as compared to lean rats; and (3) inhibition of KCa channels markedly reduced ACh-induced vasodilation in lean control rats, but not in OZ rats of 20 weeks. Our observations indicated that endothelium-dependent vasodilation in renal arcuate arteries is impaired in diabetes mellitus; NO and EDHF, mainly EETs, dominate the ACh-induced vasodilation in renal arcuate arteries; the contribution of NO and EETs is impaired in diabetic rats; KCa channels are involved in ACh-induced vasodilation; and the activity of KCa channels is downregulated in diabetes mellitus.


Assuntos
Artérias/fisiopatologia , Fatores Biológicos/fisiologia , Endotélio Vascular/fisiopatologia , Rim/irrigação sanguínea , Óxido Nítrico/fisiologia , Obesidade/fisiopatologia , Canais de Potássio Cálcio-Ativados/fisiologia , Animais , Estudos de Casos e Controles , Masculino , Ratos , Ratos Zucker
12.
J Cardiovasc Pharmacol ; 70(5): 314-328, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28777255

RESUMO

Both big (BKCa) and small (SKCa) conductance Ca-sensitive K channels are present in mammalian cardiac cell mitochondria (m). We used pharmacological agonists and antagonists of BKCa and SKCa channels to examine the importance of endogenous opening of these channels and the relative contribution of either or both of these channels to protect against contractile dysfunction and reduce infarct size after ischemia reperfusion (IR) injury through a mitochondrial protective mechanism. After global cardiac IR injury of ex vivo perfused Guinea pig hearts, we found the following: both agonists NS1619 (for BKCa) and DCEB (for SKCa) improved contractility; BKCa antagonist paxilline (PAX) alone or with SKCa antagonist NS8593 worsened contractility and enhanced infarct size; both antagonists PAX and NS8593 obliterated protection by their respective agonists; BKCa and SKCa antagonists did not block protection afforded by SKCa and BKCa agonists, respectively; and all protective effects by the agonists were blocked by scavenging superoxide anions (O2) with Mn(III) tetrakis (4-benzoic acid) porphyrin (TBAP). Contractile function was inversely associated with global infarct size. In in vivo rats, infusion of NS8593, PAX, or both antagonists enhanced regional infarct size while infusion of either NS1619 or DCEB reduced infarct size. In cardiac mitochondria isolated from ex vivo hearts after IR, combined SKCa and BKCa agonists improved respiratory control index and Ca retention capacity compared with IR alone, whereas the combined antagonists did not alter respiratory control index but worsened Ca retention capacity. Although the differential protective bioenergetics effects of endogenous or exogenous BKCa and SKCa channel opening remain unclear, each channel likely responds to different sensing Ca concentrations and voltage gradients over time during oxidative stress-induced injury to individually or together protect cardiac mitochondria and myocytes.


Assuntos
Cardiotônicos/farmacologia , Mitocôndrias Cardíacas/fisiologia , Miócitos Cardíacos/fisiologia , Canais de Potássio Cálcio-Ativados/agonistas , Canais de Potássio Cálcio-Ativados/fisiologia , 1-Naftilamina/análogos & derivados , 1-Naftilamina/farmacologia , Animais , Benzimidazóis/farmacologia , Feminino , Cobaias , Masculino , Mitocôndrias Cardíacas/efeitos dos fármacos , Miócitos Cardíacos/efeitos dos fármacos , Canais de Potássio Cálcio-Ativados/antagonistas & inibidores , Ratos , Ratos Sprague-Dawley
13.
Int J Cardiol ; 241: 351-357, 2017 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-28487150

RESUMO

BACKGROUND: Opening of mitochondrial calcium-activated potassium channels (BKCa) reduces infarct size after myocardial ischemia/reperfusion injury (I/R). It is unknown if targeting BKCa-channels improves cardiac performance in the long-term after I/R. METHODS: Experiments were conducted in compliance with institutional and national guidelines in C57BL/6 mice (n=7-8/group). Animals were randomized into two groups. Preconditioning was induced by intraperitoneal application of NS1619 (NS, 1µg/g bw) 10min before ischemia, control animals (Con) received the vehicle. All animals underwent 45min of myocardial ischemia and four weeks of reperfusion. Transthoracal Echocardiography (TTE) was conducted one and four weeks after ischemia (TTEW1/TTEW4) and additionally a cardiac MRI was done in week four. At the end of experiments the infarction scar was determined by AZAN staining. RESULTS: TTE revealed that NS1619 improved ejection fraction one week (Con: 36±4%, NS: 45±4%; P<0.05) and four weeks after I/R (Con: 33±11%, NS: 46±8%; P<0.05). Preconditioning with NS1619 reduced end-diastolic volume at both time points (TTEW1: Con: 60±12µl, NS: 45±8µl; TTEW4: Con: 82±31µl, NS: 44±8µl; each P<0.05) and increased fractional shortening after four weeks (TTEW4: Con: 12±6%, NS: 24±8%; P<0.05). MRI-analysis after four weeks confirmed the echocardiographic results. NS1619 increased ejection fraction by 45% (MRI: Con: 29±6%, NS: 42±9%; P<0.05 vs. Con) and reduced end-diastolic and -systolic volume (EDV, ESV) compared to control (MRI: EDV: Con: 110±19µl, NS: 88±16µl; ESV: Con: 79±19µl, NS: 53±18µl; each P<0.05). Preconditioning reduced infarction scar after four weeks by 25% (Con: 12±3%, NS: 9±2%; P<0.05). CONCLUSIONS: Preconditioning by opening of BKCa-channels with NS1619 improves cardiac performance after four weeks of reperfusion and reduces myocardial infarction scar.


Assuntos
Oclusão Coronária/diagnóstico por imagem , Oclusão Coronária/fisiopatologia , Canais de Potássio Cálcio-Ativados/fisiologia , Função Ventricular Esquerda/fisiologia , Animais , Benzimidazóis/farmacologia , Benzimidazóis/uso terapêutico , Oclusão Coronária/tratamento farmacológico , Ecocardiografia/tendências , Eletrocardiografia/tendências , Ativação do Canal Iônico/efeitos dos fármacos , Ativação do Canal Iônico/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Canais de Potássio Cálcio-Ativados/agonistas , Distribuição Aleatória , Fatores de Tempo , Função Ventricular Esquerda/efeitos dos fármacos
14.
J Physiol ; 595(7): 2285-2297, 2017 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-27902841

RESUMO

KEY POINTS: A mathematical model of a small conductance Ca2+ -activated potassium (SK) channel was developed and incorporated into a physiologically detailed ventricular myocyte model. Ca2+ -sensitive K+ currents promote negative intracellular Ca2+ to membrane voltage (CAi2+ → Vm ) coupling. Increase of Ca2+ -sensitive K+ currents can be responsible for electromechanically discordant alternans and quasiperiodic oscillations at the cellular level. At the tissue level, Turing-type instability can occur when Ca2+ -sensitive K+ currents are increased. ABSTRACT: Cardiac alternans is a precursor to life-threatening arrhythmias. Alternans can be caused by instability of the membrane voltage (Vm ), instability of the intracellular Ca2+ ( Ca i2+) cycling, or both. Vm dynamics and Ca i2+ dynamics are coupled via Ca2+ -sensitive currents. In cardiac myocytes, there are several Ca2+ -sensitive potassium (K+ ) currents such as the slowly activating delayed rectifier current (IKs ) and the small conductance Ca2+ -activated potassium (SK) current (ISK ). However, the role of these currents in the development of arrhythmias is not well understood. In this study, we investigated how these currents affect voltage and Ca2+ alternans using a physiologically detailed computational model of the ventricular myocyte and mathematical analysis. We define the coupling between Vm and Ca i2+ cycling dynamics ( Ca i2+→Vm coupling) as positive (negative) when a larger Ca2+ transient at a given beat prolongs (shortens) the action potential duration (APD) of that beat. While positive coupling predominates at baseline, increasing IKs and ISK promote negative Ca i2+→Vm coupling at the cellular level. Specifically, when alternans is Ca2+ -driven, electromechanically (APD-Ca2+ ) concordant alternans becomes electromechanically discordant alternans as IKs or ISK increase. These cellular level dynamics lead to different types of spatially discordant alternans in tissue. These findings help to shed light on the underlying mechanisms of cardiac alternans especially when the relative strength of these currents becomes larger under pathological conditions or drug administrations.


Assuntos
Cálcio/fisiologia , Canais de Potássio Cálcio-Ativados/fisiologia , Modelos Biológicos , Miócitos Cardíacos/fisiologia
15.
Front Med ; 10(3): 250-7, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27376950

RESUMO

Alternative splicing plays a fundamental role in the development and physiological function of the inner ear. Inner-ear-specific gene splicing is necessary to establish the identity and maintain the function of the inner ear. For example, exon 68 of Cadherin 23 (Cdh23) gene is subject to inner-ear-specific alternative splicing, and as a result, Cdh23(+ 68) is only expressed in inner ear hair cells. Alternative splicing along the tonotopic axis of the cochlea contributes to frequency tuning, particularly in lower vertebrates, such as chickens and turtles. Differential splicing of Kcnma1, which encodes for the α subunit of the Ca(2+)-activated K(+) channel (BK channel), has been suggested to affect the channel gating properties and is important for frequency tuning. Consequently, deficits in alternative splicing have been shown to cause hearing loss, as we can observe in Bronx Waltzer (bv) mice and Sfswap mutant mice. Despite the advances in this field, the regulation of alternative splicing in the inner ear remains elusive. Further investigation is also needed to clarify the mechanism of hearing loss caused by alternative splicing deficits.


Assuntos
Processamento Alternativo , Caderinas/genética , Cóclea/fisiologia , Células Ciliadas Auditivas Internas/metabolismo , Canais de Potássio Cálcio-Ativados/genética , Animais , Caderinas/fisiologia , Galinhas , Perda Auditiva/genética , Humanos , Masculino , Camundongos , Canais de Potássio Cálcio-Ativados/fisiologia , Tartarugas
16.
Am J Physiol Regul Integr Comp Physiol ; 310(11): R1081-7, 2016 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-27053645

RESUMO

Nitric oxide (NO) increases cutaneous blood flow; however, the underpinning mechanism(s) remains to be elucidated. We hypothesized that the cutaneous blood flow response during intradermal administration of sodium nitroprusside (SNP, a NO donor) is regulated by calcium-activated potassium (KCa) channels and cyclooxygenase (COX) in young adults. We also hypothesized that these contributions are diminished in older adults given that aging can downregulate KCa channels and reduce COX-derived vasodilator prostanoids. In 10 young (23 ± 5 yr) and 10 older (54 ± 4 yr) adults, cutaneous vascular conductance (CVC) was measured at four forearm skin sites infused with 1) Ringer (Control), 2) 50 mM tetraethylammonium (TEA), a nonspecific KCa channel blocker, 3) 10 mM ketorolac, a nonspecific COX inhibitor, or 4) 50 mM TEA + 10 mM ketorolac via intradermal microdialysis. All skin sites were coinfused with incremental doses of SNP (0.005, 0.05, 0.5, 5, and 50 mM each for 25 min). During SNP administration, CVC was similar at the ketorolac site (0.005-50 mM, all P > 0.05) relative to Control, but lower at the TEA and TEA + ketorolac sites (0.005-0.05 mM, all P < 0.05) in young adults. In older adults, ketorolac increased CVC relative to Control during 0.005-0.05 mM SNP administration (all P < 0.05), but this increase was not observed when TEA was coadministered (all P > 0.05). Furthermore, TEA alone did not modulate CVC during any concentration of SNP administration in older adults (all P > 0.05). We show that during low-dose NO administration (e.g., 0.005-0.05 mM), KCa channels contribute to cutaneous blood flow regulation in young adults; however, in older adults, COX inhibition increases cutaneous blood flow through a KCa channel-dependent mechanism.


Assuntos
Envelhecimento/fisiologia , Velocidade do Fluxo Sanguíneo/fisiologia , Óxido Nítrico/administração & dosagem , Canais de Potássio Cálcio-Ativados/fisiologia , Prostaglandina-Endoperóxido Sintases/metabolismo , Fenômenos Fisiológicos da Pele/efeitos dos fármacos , Adulto , Envelhecimento/efeitos dos fármacos , Velocidade do Fluxo Sanguíneo/efeitos dos fármacos , Relação Dose-Resposta a Droga , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Canais de Potássio Cálcio-Ativados/efeitos dos fármacos , Prostaglandina-Endoperóxido Sintases/efeitos dos fármacos , Vasodilatação/efeitos dos fármacos , Vasodilatação/fisiologia , Vasodilatadores/administração & dosagem
17.
Yakugaku Zasshi ; 136(3): 479-83, 2016.
Artigo em Japonês | MEDLINE | ID: mdl-26935090

RESUMO

Potassium ion (K(+)) channels play an important role in the modulation of calcium ion (Ca(2+)) signaling via control of the membrane potential. In T-lymphocytes, the voltage-gated K(+) channel, KV1.3, and the intermediate-conductance Ca(2+)-activated K(+) channel, KCa3.1, predominantly contribute to K(+) conductance, and are responsible for cell proliferation, differentiation, apoptosis and infiltration. Inflammatory bowel disease (IBD), including ulcerative colitis and Crohn's disease, afflicts more than 0.1% of the population worldwide. In the chemically-induced IBD model mouse, an increase in KCa3.1 activity was observed in mesenteric lymph node CD4(+) T-lymphocytes, concomitant with an upregulation of KCa3.1 and a positive KCa3.1 regulator, NDPK-B. Pharmacological blockade of the KCa3.1 K(+) channel by TRAM-34 and/or ICA17043 elicited 1) a significant decrease in IBD severity, as assessed by diarrhea, visible fecal blood, inflammation and crypt damage of the colon; and 2) restoration of the expression levels of KCa3.1 and Th1 cytokines in CD4(+) T-lymphocytes in the IBD model. Recent studies have indicated the impact of K2P5.1 upregulation in T lymphocytes on the pathogenesis of autoimmune diseases such as rheumatoid arthritis and multiple sclerosis. The K2P5.1 K(+) channel is therefore highlighted as a potent therapeutic target in managing the pathogenesis of autoimmune diseases. Alternatively, pre-mRNA splicing of ion channels is associated with the development and progression of various diseases, including autoimmune diseases. Therefore, mRNA-splicing mechanisms underlying the transcriptional regulation of K2P5.1 K(+) channels may be a new strategic therapeutic target for autoimmune and inflammatory diseases.


Assuntos
Doenças Autoimunes/etiologia , Doenças Inflamatórias Intestinais/etiologia , Canais de Potássio Cálcio-Ativados/fisiologia , Linfócitos T/imunologia , Animais , Doenças Autoimunes/terapia , Sinalização do Cálcio/fisiologia , Modelos Animais de Doenças , Humanos , Doenças Inflamatórias Intestinais/terapia , Potenciais da Membrana/fisiologia , Camundongos , Terapia de Alvo Molecular , Canais de Potássio Cálcio-Ativados/genética , Processamento de RNA , RNA Mensageiro/genética , Transcrição Genética
18.
Acta Pharmacol Sin ; 37(1): 82-97, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26725737

RESUMO

The proper expression and function of the cardiac pacemaker is a critical feature of heart physiology. The sinoatrial node (SAN) in human right atrium generates an electrical stimulation approximately 70 times per minute, which propagates from a conductive network to the myocardium leading to chamber contractions during the systoles. Although the SAN and other nodal conductive structures were identified more than a century ago, the mechanisms involved in the generation of cardiac automaticity remain highly debated. In this short review, we survey the current data related to the development of the human cardiac conduction system and the various mechanisms that have been proposed to underlie the pacemaker activity. We also present the human embryonic stem cell-derived cardiomyocyte system, which is used as a model for studying the pacemaker. Finally, we describe our latest characterization of the previously unrecognized role of the SK4 Ca(2+)-activated K(+) channel conductance in pacemaker cells. By exquisitely balancing the inward currents during the diastolic depolarization, the SK4 channels appear to play a crucial role in human cardiac automaticity.


Assuntos
Canais de Potássio Ativados por Cálcio de Condutância Intermediária/fisiologia , Canais de Potássio Cálcio-Ativados/fisiologia , Nó Sinoatrial/fisiologia , Relógios Biológicos , Células-Tronco Embrionárias Humanas/citologia , Células-Tronco Embrionárias Humanas/fisiologia , Humanos , Miócitos Cardíacos/citologia , Miócitos Cardíacos/fisiologia
19.
Zhonghua Nan Ke Xue ; 22(9): 838-842, 2016 Sep.
Artigo em Chinês | MEDLINE | ID: mdl-29071884

RESUMO

The contractile and diastolic function of smooth muscle cells (SMCs) is closely related to penile erection and erectile dysfunction (ED). In addition to nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S), sulfur dioxide (SO2), estrogen receptor (ER), P2Y receptor, perivascular tissue (PVT), and calcium activated potassium channel (Kca) are found to be involved in the relaxation of SMCs. This review updates the mechanisms of the relaxation of SMCs and its relationship with ED.


Assuntos
Disfunção Erétil/etiologia , Miócitos de Músculo Liso/fisiologia , Ereção Peniana/fisiologia , Monóxido de Carbono/fisiologia , Disfunção Erétil/fisiopatologia , Humanos , Sulfeto de Hidrogênio/metabolismo , Masculino , Contração Muscular , Músculo Liso , Óxido Nítrico/fisiologia , Canais de Potássio Cálcio-Ativados/fisiologia , Receptores Estrogênicos/fisiologia , Receptores Purinérgicos P2Y/fisiologia , Dióxido de Enxofre/metabolismo
20.
J Comput Neurosci ; 39(3): 329-47, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26497496

RESUMO

Synaptic modifications induced at one synapse are accompanied by hetero-synaptic changes at neighboring sites. In addition, it is suggested that the mechanism of spatial association of synaptic plasticity is based on intracellular calcium signaling that is mainly regulated by two types of receptors of endoplasmic reticulum calcium store: the ryanodine receptor (RyR) and the inositol triphosphate receptor (IP3R). However, it is not clear how these types of receptors regulate intracellular calcium flux and contribute to the outcome of calcium-dependent synaptic change. To understand the relation between the synaptic association and store-regulated calcium dynamics, we focused on the function of RyR calcium regulation and simulated its behavior by using a computational neuron model. As a result, we observed that RyR-regulated calcium release depended on spike timings of pre- and postsynaptic neurons. From the induction site of calcium release, the chain activation of RyRs occurred, and spike-like calcium increase propagated along the dendrite. For calcium signaling, the propagated calcium increase did not tend to attenuate; these characteristics came from an all-or-none behavior of RyR-sensitive calcium store. Considering the role of calcium dependent synaptic plasticity, the results suggest that RyR-regulated calcium propagation induces a similar change at the synapses. However, according to the dependence of RyR calcium regulation on the model parameters, whether the chain activation of RyRs occurred, sensitively depended on spatial expression of RyR and nominal fluctuation of calcium flux. Therefore, calcium regulation of RyR helps initiate rather than relay calcium propagation.


Assuntos
Sinalização do Cálcio/fisiologia , Simulação por Computador , Modelos Neurológicos , Plasticidade Neuronal/fisiologia , Canal de Liberação de Cálcio do Receptor de Rianodina/fisiologia , Animais , Cálcio/metabolismo , Compartimento Celular , Citoplasma/metabolismo , Canais de Potássio de Retificação Tardia/fisiologia , Retículo Endoplasmático/metabolismo , Humanos , Líquido Intracelular/metabolismo , Neurônios/ultraestrutura , Potássio/metabolismo , Canais de Potássio Cálcio-Ativados/fisiologia , Canais de Potássio de Domínios Poros em Tandem/fisiologia , Sódio/metabolismo , Canais de Sódio Disparados por Voltagem/fisiologia
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