RESUMO
BKCa channels (large-conductance Ca2+-activated K+ channels) play a critical role in regulating vascular tone and blood pressure. These channels are present in the smooth muscle cells of blood vessels and are activated by voltage and increased intracellular Ca2+ concentration. More recently, the expression and activity of BKCa have been proposed to be relevant in endothelial cells, too, specifically in human umbilical vein endothelial cells (HUVECs), the more studied cell type in the fetoplacental circulation. The role of BKCa in endothelial cells is not well understood, but in HUVECs or placental endothelium, these channels could be crucial for vascular tone regulation during pregnancy as part of endothelium-derived hyperpolarization (EDH), a key mechanism for an organ that lacks nervous system innervation like the placenta.In this review, we will discuss the evidence about the role of BKCa (and other Ca2+-activated K+ channels) in HUVECs and the placenta to propose a physiological mechanism for fetoplacental vascular regulation and a pathophysiological role of BKCa, mainly associated with pregnancy pathologies that present maternal hypertension and/or placental hypoxia, like preeclampsia.
Assuntos
Canais de Potássio Ativados por Cálcio de Condutância Alta , Canais de Potássio Cálcio-Ativados , Feminino , Humanos , Gravidez , Células Endoteliais da Veia Umbilical Humana , Placenta/metabolismo , Miócitos de Músculo Liso/metabolismo , Canais de Potássio Cálcio-Ativados/metabolismoRESUMO
BACKGROUND AND PURPOSE: CaV 3.1-3 currents differentially contribute to neuronal firing patterns. CaV 3 are regulated by G protein-coupled receptors (GPCRs) activity, but information about CaV 3 as targets of the constitutive activity of GPCRs is scarce. We investigate the impact of D5 recpetor constitutive activity, a GPCR with high levels of basal activity, on CaV 3 functionality. D5 recpetor and CaV 3 are expressed in the hippocampus and have been independently linked to pathophysiological states associated with epilepsy. EXPERIMENTAL APPROACH: Our study models were HEK293T cells heterologously expressing D1 or D5 receptor and CaV 3.1-3, and mouse brain slices containing the hippocampus. We used chlorpromazine (D1 /D5 inverse agonist) and a D5 receptor mutant lacking constitutive activity as experimental tools. We measured CaV 3 currents and excitability parameters using the patch-clamp technique. We completed our study with computational modelling and imaging technique. KEY RESULTS: We found a higher sensitivity to TTA-P2 (CaV 3 blocker) in CA1 pyramidal neurons obtained from chlorpromazine-treated animals compared with vehicle-treated animals. We found that CaV 3.2 and CaV 3.3-but not CaV 3.1-are targets of D5 receptor constitutive activity in HEK293T cells. Finally, we found an increased firing rate in CA1 pyramidal neurons from chlorpromazine-treated animals in comparison with vehicle-treated animals. Similar changes in firing rate were observed on a neuronal model with controlled CaV 3 currents levels. CONCLUSIONS AND IMPLICATIONS: Native hippocampal CaV 3 and recombinant CaV 3.2-3 are sensitive to D5 receptor constitutive activity. Manipulation of D5 receptor constitutive activity could be a valuable strategy to control neuronal excitability, especially in exacerbated conditions such as epilepsy.
Assuntos
Dopamina , Receptores de Dopamina D1 , Animais , Humanos , Camundongos , Clorpromazina/farmacologia , Agonismo Inverso de Drogas , Células HEK293 , Hipocampo/metabolismo , Neurônios/metabolismo , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D5/metabolismo , Canais de Potássio Cálcio-Ativados/metabolismoRESUMO
Population aging, as well as the handling of age-associated diseases, is a worldwide increasing concern. Among them, Alzheimer's disease stands out as the major cause of dementia culminating in full dependence on other people for basic functions. However, despite numerous efforts, in the last decades, there was no new approved therapeutic drug for the treatment of the disease. Calcium-activated potassium channels have emerged as a potential tool for neuronal protection by modulating intracellular calcium signaling. Their subcellular localization is determinant of their functional effects. When located on the plasma membrane of neuronal cells, they can modulate synaptic function, while their activation at the inner mitochondrial membrane has a neuroprotective potential via the attenuation of mitochondrial reactive oxygen species in conditions of oxidative stress. Here we review the dual role of these channels in the aging phenotype and Alzheimer's disease pathology and discuss their potential use as a therapeutic tool.
Assuntos
Envelhecimento/metabolismo , Doença de Alzheimer/metabolismo , Inflamação/metabolismo , Mitocôndrias/metabolismo , Neurônios/metabolismo , Canais de Potássio Cálcio-Ativados/metabolismo , Envelhecimento/patologia , Doença de Alzheimer/tratamento farmacológico , Doença de Alzheimer/patologia , Doença de Alzheimer/terapia , Animais , Cálcio/metabolismo , Sinalização do Cálcio/efeitos dos fármacos , Sinalização do Cálcio/genética , Morte Celular/genética , Humanos , Memória/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Estresse Oxidativo/genética , Canais de Potássio Cálcio-Ativados/agonistas , Canais de Potássio Cálcio-Ativados/antagonistas & inibidores , Espécies Reativas de Oxigênio/metabolismoRESUMO
Although leaves of Anchietea salutaris are used in Brazilian traditional medicine, there is no available data in the literature proving its efficacy and safety. Thus, the aim of the study was to perform a meticulous botanical, phytochemical, toxicological, and pharmacological investigation of A. salutaris in Wistar rats. At first, a morphoanatomical characterization of Anchietea pyrifolia leaves and stems was performed. Then, a purified infusion (ethanol-soluble fraction obtained from A. pyrifolia [ESAP]) was obtained followed by its chemical profile elucidation. Furthermore, an acute toxicity test was performed, and the acute and prolonged diuretic and hypotensive effects were also evaluated in Wistar rats. Finally, the vasodilatory responses of ESAP in mesenteric vascular beds were investigated. The main secondary metabolites identified from ESAP were O-glycosylated flavonoids, chlorogenic acids, and phenylpropanoic acid derivatives. ESAP did not promote any toxic effects in female rats nor increased urinary excretion in male rats after a single exposure. However, ESAP significantly reduced renal elimination of sodium, potassium, and chloride after prolonged treatment. An ESAP highest dose promoted significant acute hypotension without affecting blood pressure levels after prolonged use. Furthermore, its cardiovascular effects seem to be related with the calcium-activated potassium channel activation in resistance vessels.
Assuntos
Anti-Hipertensivos/administração & dosagem , Hipertensão/tratamento farmacológico , Extratos Vegetais/administração & dosagem , Violaceae/química , Animais , Anti-Hipertensivos/efeitos adversos , Anti-Hipertensivos/química , Pressão Sanguínea/efeitos dos fármacos , Brasil , Diuréticos/administração & dosagem , Diuréticos/efeitos adversos , Diuréticos/química , Feminino , Humanos , Hipertensão/genética , Hipertensão/metabolismo , Hipertensão/fisiopatologia , Masculino , Extratos Vegetais/efeitos adversos , Extratos Vegetais/química , Folhas de Planta/química , Canais de Potássio Cálcio-Ativados/genética , Canais de Potássio Cálcio-Ativados/metabolismo , Ratos WistarRESUMO
Cadmium is an environmental pollutant closely linked with cardiovascular diseases that seems to involve endothelium dysfunction and reduced nitric oxide (NO) bioavailability. Knowing that NO causes dilatation through the activation of potassium channels and Na+/K+-ATPase, we aimed to determine whether acute cadmium administration (10 µM) alters the participation of K+ channels, voltage-activated calcium channel, and Na+/K+-ATPase activity in vascular function of isolated aortic rings of rats. Cadmium did not modify the acetylcholine-induced relaxation. After L-NAME addition, the relaxation induced by acetylcholine was abolished in presence or absence of cadmium, suggesting that acutely, this metal did not change NO release. However, tetraethylammonium (a nonselective K+ channels blocker) reduced acetylcholine-induced relaxation but this effect was lower in the preparations with cadmium, suggesting a decrease of K+ channels function in acetylcholine response after cadmium incubation. Apamin (a selective blocker of small Ca2+-activated K+ channels-SKCa), iberiotoxin (a selective blocker of large-conductance Ca2+-activated K+ channels-BKCa), and verapamil (a blocker of calcium channel) reduced the endothelium-dependent relaxation only in the absence of cadmium. Finally, cadmium decreases Na+/K+-ATPase activity. Our results provide evidence that the cadmium acute incubation unaffected the calcium-activated potassium channels (SKCa and BKCa) and voltage-calcium channels on the acetylcholine vasodilatation. In addition, acute cadmium incubation seems to reduce the Na+/K+-ATPase activity.
Assuntos
Cádmio/farmacologia , Metais Pesados/farmacologia , Canais de Potássio Cálcio-Ativados/metabolismo , ATPase Trocadora de Sódio-Potássio/metabolismo , Animais , Apamina/farmacologia , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Potássio/metabolismo , Ratos , Verapamil/farmacologiaRESUMO
Antimalarials have demonstrated beneficial effects in Systemic Lupus Erithematosus and Rheumatoid Arthritis. However, the mechanisms and the molecular players targeted by these drugs remain obscure. Although hydroxychloroquine (HCQ) is a known ion channel inhibitor, this property has not been linked to its anti-inflammatory effects. We aimed to study whether HCQ inhibits pro-inflammatory ion channels. Electrophysiology experiments demonstrated that HCQ inhibited Ca++-activated K+ conductance in THP-1 macrophages in a dose-dependent manner. In macrophages, ATP-induced K+ efflux plays a key role in activating the NLRP3 inflammasome. ATP-induced IL-1beta secretion was controlled by the KCa1.1 inhibitor iberiotoxin. NS1619 and NS309 (KCa1.1 and KCa3.1 activators respectively) induced the secretion of IL-1beta. This effect was inhibited by HCQ and also by iberiotoxin and clotrimazol (KCa3.1 inhibitor), arguing against off-target effect. In vitro, HCQ inhibited IL-1beta and caspase 1 activation induced by ATP in a dose-dependent manner. HCQ impaired K+ efflux induced by ATP. In vivo, HCQ inhibited caspase 1-dependent ATP-induced neutrophil recruitment. Our results show that HCQ inhibits Ca++-activated K+ channels. This effect may lead to impaired inflammasome activation. These results are the basis for i) a novel anti-inflammatory mechanism for HCQ and ii) a new strategy to target pro-rheumatic Ca++-activated K+ channels.
Assuntos
Hidroxicloroquina/farmacologia , Inflamassomos/metabolismo , Ativação do Canal Iônico/efeitos dos fármacos , Canais de Potássio Cálcio-Ativados/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Biomarcadores , Caspase 1/genética , Caspase 1/metabolismo , Humanos , CamundongosRESUMO
The effect of 3ß-hidroxihop-22(29)ene (3-BHO) on insulin and glucagon-like peptide 1 (GLP-1) secretion as well as the mechanism of action of the compound in pancreatic islet on glucose homeostasis was investigated. The data from in vivo treatment show that 3-BHO significantly reduces the hyperglycemia by increasing the insulin and GLP-1 secretion, as well as by accumulating hepatic glycogen in hyperglycemic rats. In rat pancreatic ß-cell, 3-BHO stimulates the glucose uptake, insulin vesicles translocation to the plasma membrane and thus the insulin secretion through the involvement of potassium channels (ATP- and Ca(2+)-dependent K(+) channels) and calcium channels (L-type voltage-dependent calcium channels (L-VDCC)). Furthermore, this study also provides evidence for a crosstalk between intracellular high calcium concentration, PKA and PKC in the signal transduction of 3-BHO to stimulate insulin secretion. In conclusion, 3-BHO diminishes glycaemia, stimulates GLP-1 secretion and potentiates insulin secretion and increase hepatic glycogen content. Moreover, this triterpene modulates calcium influx characterizing ATP-K(+), Ca(2+)-K(+) and L-VDCC channels-dependent pathways as well as PKA and PKC activity in pancreatic islets underlying the signaling of 3-BHO for the secretory activity and contribution on glucose homeostasis.
Assuntos
Canais de Cálcio Tipo L/metabolismo , Peptídeo 1 Semelhante ao Glucagon/sangue , Insulina/metabolismo , Ilhotas Pancreáticas/efeitos dos fármacos , Canais KATP/metabolismo , Canais de Potássio Cálcio-Ativados/metabolismo , Triterpenos/farmacologia , Animais , Transporte Biológico , Cálcio/metabolismo , Canais de Cálcio Tipo L/genética , Proteínas Quinases Dependentes de AMP Cíclico/genética , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Regulação da Expressão Gênica , Peptídeo 1 Semelhante ao Glucagon/genética , Glucose/metabolismo , Teste de Tolerância a Glucose , Glicogênio/metabolismo , Homeostase/genética , Humanos , Insulina/sangue , Secreção de Insulina , Ilhotas Pancreáticas/citologia , Ilhotas Pancreáticas/metabolismo , Canais KATP/genética , Masculino , Canais de Potássio Cálcio-Ativados/genética , Proteína Quinase C/genética , Proteína Quinase C/metabolismo , Ratos , Ratos Wistar , Transdução de Sinais , Técnicas de Cultura de TecidosAssuntos
Animais , Humanos , Fatores Biológicos/metabolismo , Endotélio Vascular/fisiologia , Pressão Sanguínea/fisiologia , Endotélio Vascular/metabolismo , Endotélio Vascular/fisiopatologia , Músculo Liso Vascular/metabolismo , Músculo Liso Vascular/fisiologia , Músculo Liso Vascular/fisiopatologia , Canais de Potássio Cálcio-Ativados/metabolismoRESUMO
Chondrocytes, the only cell in cartilage, are subjected to hyperosmotic challenges continuously since extracellular osmolarity in articular cartilage increases in response to mechanical loads during joint movement. Hyperosmolarity can affect membrane transport, and it is possible that load modulates matrix synthesis through alterations in intracellular composition. In the present study, the effects of hyperosmotic challenges were evaluated using the whole-cell patch clamp technique, whole cell mode on freshly isolated human and bovine articular chondrocytes. In human chondrocytes, hypertonicity induced the activation of outward Ca(2+)-sensitive K(+) currents, which were inhibited by iberiotoxin and TEA-Cl. The current induced by hypertonic switching (osmolarity from 300 to 400 mOsm/l) caused cell hyperpolarization (from -39 mV to -70 mV) with a reversal potential of -96 ± 7 mV. These results suggest a role for Ca(2+)-activated K(+) channels in human articular chondrocytes, leading to hyperpolarization as a consequence of K(+) efflux through these channels. These channels could have a role in the articular chondrocyte's response to a hyperosmotic challenge and matrix metabolism regulation by load.
Assuntos
Cartilagem Articular/citologia , Condrócitos/metabolismo , Canais de Potássio Cálcio-Ativados/química , Canais de Potássio Cálcio-Ativados/metabolismo , Animais , Bovinos , Eletrofisiologia , Humanos , Líquido Intracelular/fisiologia , Potenciais da Membrana/efeitos dos fármacos , Concentração Osmolar , Técnicas de Patch-Clamp/métodos , Peptídeos/antagonistas & inibidores , Peptídeos/farmacologiaRESUMO
The high conductance voltage- and Ca(2+)-activated K(+) channel is one of the most broadly expressed channels in mammals. This channel is named BK for 'big K' because of its single-channel conductance that can be as large as 250 pS in 100 mm symmetrical K(+). BK channels increase their activity by membrane depolarization or an increase in cytosolic Ca(2+). One of the key features that defines the behaviour of BK channels is that neither Ca(2+) nor voltage is strictly necessary for channel activation. This and several other observations led to the idea that both Ca(2+) and voltage increase the open probability by an allosteric mechanism. In this type of mechanism, the processes of voltage sensor displacement, Ca(2+) binding and pore opening are independent equilibria that interact allosterically with each other. These allosteric interactions in BK channels reside in the structural characteristics of the BK channel in the sense that voltage and Ca(2+) sensors and the pore need to be contained in different structures or 'modules'. Through electrophysiological, mutagenesis, biochemical and fluorescence studies these modules have been identified and, more important, some of the interactions between them have been unveiled. In this review, we have covered the main advances achieved during the last few years in the elucidation of the structure of the BK channel and how this is related with its function as an allosteric protein.