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1.
Nat Commun ; 11(1): 4368, 2020 08 31.
Artigo em Inglês | MEDLINE | ID: mdl-32868758

RESUMO

Increased extracellular sodium activates Th17 cells, which provide protection from bacterial and fungal infections. Whilst high salt diets have been shown to worsen autoimmune disease, the immunological consequences of clinical salt depletion are unknown. Here, we investigate immunity in patients with inherited salt-losing tubulopathies (SLT). Forty-seven genotyped SLT patients (with Bartter, Gitelman or EAST Syndromes) are recruited. Clinical features of dysregulated immunity are recorded with a standardised questionnaire and immunological investigations of IL-17 responsiveness undertaken. The effects of altering extracellular ionic concentrations on immune responses are then assessed. Patients are hypokalaemic and hypomagnesaemic, with reduced interstitial sodium stores determined by 23Na-magnetic resonance imaging. SLT patients report increased mucosal infections and allergic disease compared to age-matched controls. Aligned with their clinical phenotype, SLT patients have an increased ratio of Th2:Th17 cells. SLT Th17 and Tc17 polarisation is reduced in vitro, yet STAT1 and STAT3 phosphorylation and calcium flux following T cell activation are unaffected. In control cells, the addition of extracellular sodium (+40 mM), potassium (+2 mM), or magnesium (+1 mM) reduces Th2:Th17 ratio and augments Th17 polarisation. Our results thus show that the ionic environment typical in SLT impairs IL-17 immunity, but the intracellular pathways that mediate salt-driven Th17 polarisation are intact and in vitro IL-17 responses can be reinvigorated by increasing extracellular sodium concentration. Whether better correction of extracellular ions can rescue the immunophenotype in vivo in SLT patients remains unknown.


Assuntos
Síndromes de Imunodeficiência/etiologia , Interleucina-17/metabolismo , Túbulos Renais Distais/patologia , Adolescente , Adulto , Idoso de 80 Anos ou mais , Animais , Pré-Escolar , Doença Crônica , Estudos de Coortes , Feminino , Doenças Genéticas Inatas , Humanos , Magnésio/metabolismo , Masculino , Pessoa de Meia-Idade , Potássio/metabolismo , Sais/metabolismo , Sais/uso terapêutico , Sódio/metabolismo , Cloreto de Sódio/metabolismo , Cloreto de Sódio na Dieta/uso terapêutico , Células Th17/metabolismo , Células Th2/metabolismo , Adulto Jovem
2.
PLoS Biol ; 18(9): e3000873, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32966273

RESUMO

The inhibitory axonless olfactory bulb granule cells form reciprocal dendrodendritic synapses with mitral and tufted cells via large spines, mediating recurrent and lateral inhibition. As a case in point for dendritic transmitter release, rat granule cell dendrites are highly excitable, featuring local Na+ spine spikes and global Ca2+- and Na+-spikes. To investigate the transition from local to global signaling, we performed holographic, simultaneous 2-photon uncaging of glutamate at up to 12 granule cell spines, along with whole-cell recording and dendritic 2-photon Ca2+ imaging in acute juvenile rat brain slices. Coactivation of less than 10 reciprocal spines was sufficient to generate diverse regenerative signals that included regional dendritic Ca2+-spikes and dendritic Na+-spikes (D-spikes). Global Na+-spikes could be triggered in one third of granule cells. Individual spines and dendritic segments sensed the respective signal transitions as increments in Ca2+ entry. Dendritic integration as monitored by the somatic membrane potential was mostly linear until a threshold number of spines was activated, at which often D-spikes along with supralinear summation set in. As to the mechanisms supporting active integration, NMDA receptors (NMDARs) strongly contributed to all aspects of supralinearity, followed by dendritic voltage-gated Na+- and Ca2+-channels, whereas local Na+ spine spikes, as well as morphological variables, barely mattered. Because of the low numbers of coactive spines required to trigger dendritic Ca2+ signals and thus possibly lateral release of GABA onto mitral and tufted cells, we predict that thresholds for granule cell-mediated bulbar lateral inhibition are low. Moreover, D-spikes could provide a plausible substrate for granule cell-mediated gamma oscillations.


Assuntos
Potenciais de Ação , Sinalização do Cálcio , Dendritos/metabolismo , Bulbo Olfatório/metabolismo , Sódio/metabolismo , Animais , Cálcio/metabolismo , Feminino , Holografia , Técnicas In Vitro , Masculino , Ratos Wistar , Receptores de N-Metil-D-Aspartato/metabolismo
3.
Rev Med Suisse ; 16(701): 1450-1455, 2020 Aug 05.
Artigo em Francês | MEDLINE | ID: mdl-32833367

RESUMO

The Covid 19 pandemic remains a serious public health problem until effective drugs and/or vaccines are available. Can we explain why so many people remain asymptomatic but nevertheless highly contagious explaining the speed with which the pandemic has spread around the world? Can we explain why the acute respiratory distress syndrome (ARDS) appears late but can so quickly have a fatal outcome? In the lung, mucociliary clearance (CMC) and alveolar clearance (CA) depend on the transport of sodium through the plasma membrane of epithelial cells. This transport is mediated by a highly selective sodium channel (Epithelial Sodium Channel = ENaC) which could be a key element in the pulmonary pathophysiology of SARS-CoV-2 infection.


Assuntos
Betacoronavirus/patogenicidade , Infecções por Coronavirus/metabolismo , Modelos Biológicos , Pneumonia Viral/metabolismo , Sódio/metabolismo , Infecções por Coronavirus/virologia , Humanos , Transporte de Íons , Pandemias , Pneumonia Viral/virologia
4.
Nat Commun ; 11(1): 4337, 2020 08 28.
Artigo em Inglês | MEDLINE | ID: mdl-32859897

RESUMO

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/farmacologia
5.
Nat Commun ; 11(1): 4222, 2020 08 24.
Artigo em Inglês | MEDLINE | ID: mdl-32839436

RESUMO

Our understanding of Na+ homeostasis has recently been reshaped by the notion of skin as a depot for Na+ accumulation in multiple cardiovascular diseases and risk factors. The proposed water-independent nature of tissue Na+ could induce local pathogenic changes, but lacks firm demonstration. Here, we show that tissue Na+ excess upon high Na+ intake is a systemic, rather than skin-specific, phenomenon reflecting architectural changes, i.e. a shift in the extracellular-to-intracellular compartments, due to a reduction of the intracellular or accumulation of water-paralleled Na+ in the extracellular space. We also demonstrate that this accumulation is unlikely to justify the observed development of experimental hypertension if it were water-independent. Finally, we show that this isotonic skin Na+ excess, reflecting subclinical oedema, occurs in hypertensive patients and in association with aging. The implications of our findings, questioning previous assumptions but also reinforcing the importance of tissue Na+ excess, are both mechanistic and clinical.


Assuntos
Edema/metabolismo , Homeostase/fisiologia , Sódio/metabolismo , Equilíbrio Hidroeletrolítico/fisiologia , Envelhecimento/metabolismo , Animais , Edema/diagnóstico , Feminino , Humanos , Hipertensão/diagnóstico , Hipertensão/metabolismo , Hipertensão/fisiopatologia , Fígado/metabolismo , Pulmão/metabolismo , Masculino , Miocárdio/metabolismo , Especificidade de Órgãos , Concentração Osmolar , Potássio/metabolismo , Ratos Endogâmicos WKY , Pele/metabolismo , Fatores de Transcrição/metabolismo
6.
PLoS One ; 15(8): e0237347, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32785272

RESUMO

Here we examine a class of neurons that have been recently explored, the somatosensory neuronal subclass of cold thermosensors. We create a mathematical model of a cold sensing neuron that has been formulated to understand the variety of ionic channels involved. In particular this model showcases the role of TRPM8 and voltage gated potassium channels in setting the temperature dependent activation and inactivation threshold level. Bifurcation analysis of the model demonstrates that a Hodgkin-Huxley type model with additional TRPM8 channels is sufficient to replicate observable experimental features of when different threshold level cold thermosensors turn on. Additionally, our analysis gives insight into what is happening at the temperature levels at which these neurons shut off and the role sodium and leak currents may have in this. This type of model construction and analysis provides a framework moving forward that will help tackle less well understood neuronal classes and their important ionic channels.


Assuntos
Temperatura Baixa , Modelos Neurológicos , Canais de Cátion TRPM/metabolismo , Termorreceptores/fisiologia , Sensação Térmica/fisiologia , Animais , Potenciais da Membrana/fisiologia , Potássio/metabolismo , Sódio/metabolismo
7.
Nature ; 583(7816): 421-424, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32641825

RESUMO

The suprachiasmatic nucleus (SCN) serves as the body's master circadian clock that adaptively coordinates changes in physiology and behaviour in anticipation of changing requirements throughout the 24-h day-night cycle1-4. For example, the SCN opposes overnight adipsia by driving water intake before sleep5,6, and by driving the secretion of anti-diuretic hormone7,8 and lowering body temperature9,10 to reduce water loss during sleep11. These responses can also be driven by central osmo-sodium sensors to oppose an unscheduled rise in osmolality during the active phase12-16. However, it is unknown whether osmo-sodium sensors require clock-output networks to drive homeostatic responses. Here we show that a systemic salt injection (hypertonic saline) given at Zeitgeber time 19-a time at which SCNVP (vasopressin) neurons are inactive-excited SCNVP neurons and decreased non-shivering thermogenesis (NST) and body temperature. The effects of hypertonic saline on NST and body temperature were prevented by chemogenetic inhibition of SCNVP neurons and mimicked by optogenetic stimulation of SCNVP neurons in vivo. Combined anatomical and electrophysiological experiments revealed that osmo-sodium-sensing organum vasculosum lamina terminalis (OVLT) neurons expressing glutamic acid decarboxylase (OVLTGAD) relay this information to SCNVP neurons via an excitatory effect of γ-aminobutyric acid (GABA). Optogenetic activation of OVLTGAD neuron axon terminals excited SCNVP neurons in vitro and mimicked the effects of hypertonic saline on NST and body temperature in vivo. Furthermore, chemogenetic inhibition of OVLTGAD neurons blunted the effects of systemic hypertonic saline on NST and body temperature. Finally, we show that hypertonic saline significantly phase-advanced the circadian locomotor activity onset of mice. This effect was mimicked by optogenetic activation of the OVLTGAD→ SCNVP pathway and was prevented by chemogenetic inhibition of OVLTGAD neurons. Collectively, our findings provide demonstration that clock time can be regulated by non-photic physiologically relevant cues, and that such cues can drive unscheduled homeostatic responses via clock-output networks.


Assuntos
Relógios Circadianos/fisiologia , Vias Neurais , Neurônios/metabolismo , Sódio/metabolismo , Núcleo Supraquiasmático/fisiologia , Ácido gama-Aminobutírico/metabolismo , Animais , Temperatura Corporal/efeitos dos fármacos , Temperatura Corporal/fisiologia , Relógios Circadianos/efeitos dos fármacos , Ritmo Circadiano/efeitos dos fármacos , Ritmo Circadiano/fisiologia , Ingestão de Líquidos/efeitos dos fármacos , Glutamato Descarboxilase/metabolismo , Locomoção/efeitos dos fármacos , Locomoção/fisiologia , Masculino , Camundongos , Vias Neurais/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Optogenética , Organum Vasculosum/citologia , Organum Vasculosum/efeitos dos fármacos , Organum Vasculosum/enzimologia , Organum Vasculosum/fisiologia , Concentração Osmolar , Solução Salina Hipertônica/administração & dosagem , Solução Salina Hipertônica/metabolismo , Solução Salina Hipertônica/farmacologia , Sódio/administração & dosagem , Sódio/farmacologia , Núcleo Supraquiasmático/citologia , Núcleo Supraquiasmático/efeitos dos fármacos , Vasopressinas/metabolismo
8.
Proc Natl Acad Sci U S A ; 117(32): 19599-19603, 2020 08 11.
Artigo em Inglês | MEDLINE | ID: mdl-32719136

RESUMO

We have used recent measurements of mammalian cone light responses and voltage-gated currents to calculate cone ATP utilization and compare it to that of rods. The largest expenditure of ATP results from ion transport, particularly from removal of Na+ entering outer segment light-dependent channels and inner segment hyperpolarization-activated cyclic nucleotide-gated channels, and from ATP-dependent pumping of Ca2+ entering voltage-gated channels at the synaptic terminal. Single cones expend nearly twice as much energy as single rods in darkness, largely because they make more synapses with second-order retinal cells and thus must extrude more Ca2+ In daylight, cone ATP utilization per cell remains high because cones never remain saturated and must continue to export Na+ and synaptic Ca2+ even in bright illumination. In mouse and human retina, rods greatly outnumber cones and consume more energy overall even in background light. In primates, however, the high density of cones in the fovea produces a pronounced peak of ATP utilization, which becomes particularly prominent in daylight and may make this part of the retina especially sensitive to changes in energy availability.


Assuntos
Retina/metabolismo , Células Fotorreceptoras Retinianas Cones/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Cálcio/metabolismo , GMP Cíclico/metabolismo , Canais de Cátion Regulados por Nucleotídeos Cíclicos/metabolismo , Fóvea Central/citologia , Fóvea Central/metabolismo , Humanos , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/metabolismo , Ativação do Canal Iônico , Luz , Camundongos , Terminações Pré-Sinápticas/metabolismo , Retina/citologia , Células Fotorreceptoras Retinianas Bastonetes/metabolismo , Sódio/metabolismo
9.
PLoS One ; 15(6): e0235360, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32603346

RESUMO

The sodium (Na+)-chloride cotransporter (NCC) expressed in the distal convoluted tubule (DCT) is a key molecule regulating urinary Na+ and potassium (K+) excretion. We previously reported that high-K+ load rapidly dephosphorylated NCC and promoted urinary K+ excretion in mouse kidneys. This effect was inhibited by calcineurin (CaN) and calmodulin inhibitors. However, the detailed mechanism through which high-K+ signal results in CaN activation remains unknown. We used Flp-In NCC HEK293 cells and mice to evaluate NCC phosphorylation. We analyzed intracellular Ca2+ concentration ([Ca2+]in) using live cell Ca2+ imaging in HEK293 cells. We confirmed that high-K+-induced NCC dephosphorylation was not observed without CaN using Flp-In NCC HEK29 cells. Extracellular Ca2+ reduction with a Ca2+ chelator inhibited high-K+-induced increase in [Ca2+]in and NCC dephosphorylation. We focused on Na+/Ca2+ exchanger (NCX) 1, a bidirectional regulator of cytosolic Ca2+ expressed in DCT. We identified that NCX1 suppression with a specific inhibitor (SEA0400) or siRNA knockdown inhibited K+-induced increase in [Ca2+]in and NCC dephosphorylation. In a mouse study, SEA0400 treatment inhibited K+-induced NCC dephosphorylation. SEA0400 reduced urinary K+ excretion and induced hyperkalemia. Here, we identified NCX1 as a key molecule in urinary K+ excretion promoted by CaN activation and NCC dephosphorylation in response to K+ load.


Assuntos
Hiperpotassemia/metabolismo , Potássio , Trocador de Sódio e Cálcio , Compostos de Anilina/farmacologia , Animais , Células HEK293 , Humanos , Túbulos Renais Distais/metabolismo , Camundongos , Éteres Fenílicos/farmacologia , Fosforilação/efeitos dos fármacos , Potássio/metabolismo , Potássio/urina , Sódio/metabolismo , Trocador de Sódio e Cálcio/antagonistas & inibidores , Trocador de Sódio e Cálcio/metabolismo
10.
Am J Physiol Renal Physiol ; 319(2): F323-F334, 2020 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-32628540

RESUMO

We investigated the regulation of Na+ and K+ excretion and the epithelial Na+ channel (ENaC) in mice lacking the gene for aldosterone synthase (AS) using clearance methods to assess excretion and electrophysiology and Western blot analysis to test for ENaC activity and processing. After 1 day of dietary Na+ restriction, AS-/- mice lost more Na+ in the urine than AS+/+ mice did. After 1 wk on this diet, both genotypes strongly reduced urinary Na+ excretion, but creatinine clearance decreased only in AS-/- mice. Only AS+/+ animals exhibited increased ENaC function, assessed as amiloride-sensitive whole cell currents in collecting ducts or cleavage of αENaC and γENaC in Western blots. To assess the role of aldosterone in the excretion of a K+ load, animals were fasted overnight and refed with high-K+ or low-K+ diets for 5 h. Both AS+/+ and AS-/- mice excreted a large amount of K+ during this period. In both phenotypes the excretion was benzamil sensitive, indicating increased K+ secretion coupled to ENaC-dependent Na+ reabsorption. However, the increase in plasma K+ under these conditions was much larger in AS-/- animals than in AS+/+ animals. In both groups, cleavage of αENaC and γENaC increased. However, Na+ current measured ex vivo in connecting tubules was enhanced only in AS+/+ mice. We conclude that in the absence of aldosterone, mice can conserve Na+ without ENaC activation but at the expense of diminished glomerular filtration rate. Excretion of a K+ load can be accomplished through aldosterone-independent upregulation of ENaC, but aldosterone is required to excrete the excess K+ without hyperkalemia.


Assuntos
Citocromo P-450 CYP11B2/metabolismo , Canais Epiteliais de Sódio/metabolismo , Potássio/metabolismo , Sódio na Dieta/metabolismo , Sódio/metabolismo , Animais , Canais Epiteliais de Sódio/genética , Túbulos Renais Coletores/metabolismo , Camundongos , Natriurese/fisiologia
11.
Aquat Toxicol ; 226: 105561, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32688145

RESUMO

In the aquatic environment, metals are present as mixtures, therefore studies on mixture toxicity are crucial to thoroughly understand their toxic effects on aquatic organisms. Common carp (Cyprinus carpio) were used to assess the effects of short-term Cu(II) and Cd(II) mixtures, using a fixed concentration of one of the metals, representing 25 % of its individual 96h-LC50 (concentration lethal for 50 % of the population) combined with a variable concentration of the other metal corresponding to 10, 25 or 50 % of its 96h-LC50, and vice versa. Our results showed a fast Cu and Cd bioaccumulation, with the percentage of increase in the order gill > liver > carcass. An inhibitory effect of Cu on Cd uptake was observed; higher Cu concentrations at fixed Cd levels resulted in a decreased accumulation of Cd. The presence of the two metal ions resulted in losses of total Na, K and Ca. Fish tried to compensate for the Na loss through the induction of the genes coding for Na+/K+-ATPase and H+-ATPase. Additionally, a counterintuitive induction of the gene encoding the high affinity copper transporter (CTR1) occurred, while a downregulation was expected to prevent further metal ion uptake. An induction of defensive mechanisms, both metal ion binding protein and anti-oxidant defences, was observed. Despite the metal accumulation and electrolyte loss, the low mortality suggest that common carp is able to cope with these metal levels, at least during a one-week exposure.


Assuntos
Bioacumulação/efeitos dos fármacos , Cádmio/toxicidade , Carpas/metabolismo , Cobre/toxicidade , Homeostase/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Animais , Cádmio/metabolismo , Carpas/genética , Cobre/metabolismo , Transportador de Cobre 1/genética , Transportador de Cobre 1/metabolismo , Eletrólitos/metabolismo , Brânquias/efeitos dos fármacos , Brânquias/metabolismo , Transporte de Íons , Dose Letal Mediana , Potássio/metabolismo , Sódio/metabolismo , ATPase Trocadora de Sódio-Potássio/metabolismo , Poluentes Químicos da Água/metabolismo
12.
Am J Physiol Heart Circ Physiol ; 319(2): H396-H409, 2020 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-32678707

RESUMO

Myocardial ischemia leads to conduction slowing, cell-to-cell uncoupling, and arrhythmias. We previously demonstrated that varying perfusate sodium (Na+) and calcium (Ca2+) attenuates conduction slowing and arrhythmias during simulated ischemia with continuous perfusion. Cardioprotection was selectively associated with widening of the perinexus, a gap junction adjacent nanodomain important to ephaptic coupling. It is unknown whether perfusate composition affects the perinexus or ischemic conduction during nonsimulated ischemia, when coronary flow is reduced or halted. We hypothesized that altering preischemic perfusate composition could facilitate perinexal expansion and attenuate conduction slowing during global ischemia. To test this hypothesis, ex vivo guinea pig hearts (n = 49) were Langendorff perfused with 145 or 153 mM Na+ and 1.25 or 2.0 mM Ca2+ and optically mapped during 30 min of no-flow ischemia. Altering Na+ and Ca2+ did not substantially affect baseline conduction. Increasing Na+ and decreasing Ca2+ both lowered pacing thresholds, whereas increasing Ca2+ narrowed perinexal width (Wp). A least squares mean estimate revealed that reduced perfusate Na+ and Ca2+ resulted in the most severe conduction slowing during ischemia. Increasing Na+ alone modestly attenuated conduction slowing, yet significantly delayed the median time to conduction block (10 to 16 min). Increasing both Na+ and Ca2+ selectively widened Wp during ischemia (22.7 vs. 15.7 nm) and attenuated conduction slowing to the greatest extent. Neither repolarization nor levels of total or phosphorylated connexin43 correlated with conduction slowing or block. Thus, perfusate-dependent widening of the perinexus preserved ischemic conduction and may be an adaptive response to ischemic stress.NEW & NOTEWORTHY Conduction slowing during acute ischemia creates an arrhythmogenic substrate. We have shown that extracellular ionic concentrations can alter conduction by modulating ephaptic coupling. Here, we demonstrate increased extracellular sodium and calcium significantly attenuate conduction slowing during no-flow ischemia. This effect was associated with selective widening of the perinexus, an intercalated disc nanodomain and putative cardiac ephapse. These findings suggest that acute changes in ephaptic coupling may serve as an adaptive response to ischemic stress.


Assuntos
Bradicardia/prevenção & controle , Cálcio/metabolismo , Bloqueio Cardíaco/prevenção & controle , Sistema de Condução Cardíaco/metabolismo , Frequência Cardíaca , Isquemia Miocárdica/metabolismo , Sódio/metabolismo , Potenciais de Ação , Animais , Bradicardia/etiologia , Bradicardia/metabolismo , Bradicardia/fisiopatologia , Circulação Coronária , Modelos Animais de Doenças , Cobaias , Bloqueio Cardíaco/etiologia , Bloqueio Cardíaco/metabolismo , Bloqueio Cardíaco/fisiopatologia , Preparação de Coração Isolado , Masculino , Isquemia Miocárdica/complicações , Isquemia Miocárdica/fisiopatologia , Transdução de Sinais , Fatores de Tempo
13.
J Pharmacol Sci ; 143(4): 325-329, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32487451

RESUMO

The effects of class I antiarrhythmic drugs on the automaticity of isolated guinea pig pulmonary vein myocardia were investigated using microelectrode and voltage clamp methods. All of the drugs examined reduced the maximum rate of rise of automatic action potentials. The firing frequency and rate of diastolic depolarization were decreased by aprindine, flecainide and propafenone, but not by cibenzoline, disopyramide and pilsicainide, which correlated with blockade of the sodium current component induced by ramp depolarization mimicking the diastolic depolarization. In conclusion, class I antiarrhythmic drugs which block the diastolic sodium current component inhibit the automaticity of the pulmonary vein myocardium.


Assuntos
Antiarrítmicos/farmacologia , Veias Pulmonares/efeitos dos fármacos , Potenciais de Ação/efeitos dos fármacos , Animais , Antiarrítmicos/classificação , Cobaias , Técnicas In Vitro , Microeletrodos , Técnicas de Patch-Clamp , Veias Pulmonares/metabolismo , Sódio/metabolismo
14.
Nature ; 583(7815): 314-318, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32499654

RESUMO

Light-driven sodium pumps actively transport small cations across cellular membranes1. These pumps are used by microorganisms to convert light into membrane potential and have become useful optogenetic tools with applications in neuroscience. Although the resting state structures of the prototypical sodium pump Krokinobacter eikastus rhodopsin 2 (KR2) have been solved2,3, it is unclear how structural alterations over time allow sodium to be translocated against a concentration gradient. Here, using the Swiss X-ray Free Electron Laser4, we have collected serial crystallographic data at ten pump-probe delays from femtoseconds to milliseconds. High-resolution structural snapshots throughout the KR2 photocycle show how retinal isomerization is completed on the femtosecond timescale and changes the local structure of the binding pocket in the early nanoseconds. Subsequent rearrangements and deprotonation of the retinal Schiff base open an electrostatic gate in microseconds. Structural and spectroscopic data, in combination with quantum chemical calculations, indicate that a sodium ion binds transiently close to the retinal within one millisecond. In the last structural intermediate, at 20 milliseconds after activation, we identified a potential second sodium-binding site close to the extracellular exit. These results provide direct molecular insight into the dynamics of active cation transport across biological membranes.


Assuntos
Flavobacteriaceae/química , Rodopsinas Microbianas/química , Rodopsinas Microbianas/efeitos da radiação , ATPase Trocadora de Sódio-Potássio/química , ATPase Trocadora de Sódio-Potássio/efeitos da radiação , Sítios de Ligação , Cristalografia , Elétrons , Transporte de Íons , Isomerismo , Lasers , Prótons , Teoria Quântica , Retinaldeído/química , Retinaldeído/metabolismo , Bases de Schiff/química , Sódio/metabolismo , Análise Espectral , Eletricidade Estática , Fatores de Tempo
15.
PLoS Biol ; 18(6): e3000722, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32569301

RESUMO

Inflammation and infection can trigger local tissue Na+ accumulation. This Na+-rich environment boosts proinflammatory activation of monocyte/macrophage-like cells (MΦs) and their antimicrobial activity. Enhanced Na+-driven MΦ function requires the osmoprotective transcription factor nuclear factor of activated T cells 5 (NFAT5), which augments nitric oxide (NO) production and contributes to increased autophagy. However, the mechanism of Na+ sensing in MΦs remained unclear. High extracellular Na+ levels (high salt [HS]) trigger a substantial Na+ influx and Ca2+ loss. Here, we show that the Na+/Ca2+ exchanger 1 (NCX1, also known as solute carrier family 8 member A1 [SLC8A1]) plays a critical role in HS-triggered Na+ influx, concomitant Ca2+ efflux, and subsequent augmented NFAT5 accumulation. Moreover, interfering with NCX1 activity impairs HS-boosted inflammatory signaling, infection-triggered autolysosome formation, and subsequent antibacterial activity. Taken together, this demonstrates that NCX1 is able to sense Na+ and is required for amplifying inflammatory and antimicrobial MΦ responses upon HS exposure. Manipulating NCX1 offers a new strategy to regulate MΦ function.


Assuntos
Macrófagos/metabolismo , Trocador de Sódio e Cálcio/metabolismo , Sódio/metabolismo , Processamento Alternativo/genética , Animais , Cálcio/metabolismo , Espaço Extracelular/metabolismo , Inativação Gênica/efeitos dos fármacos , Ativação do Canal Iônico/efeitos dos fármacos , Íons , Lipopolissacarídeos/farmacologia , Macrófagos/efeitos dos fármacos , Camundongos , Óxido Nítrico/biossíntese , Células RAW 264.7 , Cloreto de Sódio/farmacologia
16.
Eur J Pharmacol ; 882: 173237, 2020 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-32525005

RESUMO

Pirfenidone (PFD), a pyridone compound, is well recognized as an antifibrotic agent tailored for the treatment of idiopathic pulmonary fibrosis. Recently, through its anti-inflammatory and anti-oxidant effects, PFD based clinical trial has also been launched for the treatment of coronavirus disease (COVID-19). To what extent this drug can perturb membrane ion currents remains largely unknown. Herein, the exposure to PFD was observed to depress the amplitude of hyperpolarization-activated cation current (Ih) in combination with a considerable slowing in the activation time of the current in pituitary GH3 cells. In the continued presence of ivabradine or zatebradine, subsequent application of PFD decreased Ih amplitude further. The presence of PFD resulted in a leftward shift in Ih activation curve without changes in the gating charge. The addition of this compound also led to a reduction in area of voltage-dependent hysteresis evoked by long-lasting inverted triangular (downsloping and upsloping) ramp pulse. Neither the amplitude of M-type nor erg-mediated K+ current was altered by its presence. In whole-cell potential recordings, addition of PFD reduced the firing frequency, and this effect was accompanied by the depression in the amplitude of sag voltage elicited by hyperpolarizing current stimulus. Overall, this study highlights evidence that PFD is capable of perturbing specific ionic currents, revealing a potential additional impact on functional activities of different excitable cells.


Assuntos
Membrana Celular/efeitos dos fármacos , Infecções por Coronavirus/tratamento farmacológico , Pneumonia Viral/tratamento farmacológico , Piridonas/farmacologia , Animais , Betacoronavirus/metabolismo , Cátions/metabolismo , Linhagem Celular Tumoral , Membrana Celular/metabolismo , Infecções por Coronavirus/virologia , Humanos , Canais Iônicos/efeitos dos fármacos , Canais Iônicos/metabolismo , Transporte de Íons/efeitos dos fármacos , Potenciais da Membrana/efeitos dos fármacos , Pandemias , Pneumonia Viral/virologia , Potássio/metabolismo , Piridonas/uso terapêutico , Ratos , Sódio/metabolismo
17.
Plant Mol Biol ; 103(4-5): 545-560, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32504260

RESUMO

KEY MESSAGE: OsGTγ-2, a trihelix transcription factor, is a positive regulator of rice responses to salt stress by regulating the expression of ion transporters. Salinity stress seriously restricts rice growth and yield. Trihelix transcription factors (GT factors) specifically bind to GT elements and play a diverse role in plant morphological development and responses to abiotic stresses. In our previous study, we found that the GT-1 element (GAAAAA) is a key element in the salinity-induced OsRAV2 promoter. Here, we identified a rice OsGTγ family member, OsGTγ-2, which directly interacted with the GT-1 element in the OsRAV2 promoter. OsGTγ-2 specifically targeted the nucleus, was mainly expressed in roots, sheathes, stems and seeds, and was induced by salinity, osmotic and oxidative stresses and abscisic acid (ABA). The seed germination rate, seedling growth and survival rate under salinity stress was improved in OsGTγ-2 overexpressing lines (PZmUbi::OsGTγ-2). In contrast, CRISPR/Cas9-mediated OsGTγ-2 knockout lines (osgtγ-2) showed salt-hypersensitive phenotypes. In response to salt stress, different Na+ and K+ acclamation patterns were observed in PZmUbi::OsGTγ-2 lines and osgtγ-2 plants were observed. The molecular mechanism of OsGTγ-2 in rice salt adaptation was also investigated. Several major genes responsible for ion transporting, such as the OsHKT2; 1, OsHKT1; 3 and OsNHX1 were transcriptionally regulated by OsGTγ-2. A subsequent yeast one-hybrid assay and EMSA indicated that OsGTγ-2 directly interacted with the promoters of OsHKT2; 1, OsNHX1 and OsHKT1; 3. Taken together, these results suggest that OsGTγ-2 is an important positive regulator involved in rice responses to salt stress and suggest a potential role for OsGTγ-2 in regulating salinity adaptation in rice.


Assuntos
Aclimatação/fisiologia , Proteínas de Ligação a DNA/metabolismo , Oryza/fisiologia , Estresse Salino/fisiologia , Tolerância ao Sal/genética , Fatores de Transcrição/metabolismo , Ácido Abscísico/metabolismo , Aclimatação/genética , Adaptação Fisiológica , Sistemas CRISPR-Cas , Proteínas de Transporte de Cátions/metabolismo , Proteínas de Ligação a DNA/genética , Regulação da Expressão Gênica de Plantas , Oryza/genética , Oryza/crescimento & desenvolvimento , Desenvolvimento Vegetal , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Raízes de Plantas/metabolismo , Salinidade , Plântula/genética , Sementes/metabolismo , Sódio/metabolismo , Trocadores de Sódio-Hidrogênio/metabolismo , Estresse Fisiológico/genética , Simportadores/metabolismo , Fatores de Transcrição/genética
18.
Obesity (Silver Spring) ; 28(7): 1292-1300, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32568462

RESUMO

OBJECTIVE: Lipedema is characterized by pain, fatigue, and excessive adipose tissue and sodium accumulation of the lower extremities. This case-control study aims to determine whether sodium or vascular dysfunction is present in the central nervous system. METHODS: Brain magnetic resonance imaging was performed at 3 T in patients with lipedema (n = 15) and control (n = 18) participants matched for sex, age, race, and BMI. Standard anatomical imaging and intracranial angiography were applied to evaluate brain volume and vasculopathy, respectively; arterial spin labeling and sodium magnetic resonance imaging were applied to quantify cerebral blood flow (CBF) (milliliters per 100 grams of tissue/minute) and brain tissue sodium content (millimoles per liter), respectively. A Mann-Whitney U test (significance criteria P < 0.05) was applied to evaluate group differences. RESULTS: No differences in tissue volume, white matter hyperintensities, intracranial vasculopathy, or tissue sodium content were observed between groups. Gray matter CBF was elevated (P = 0.03) in patients with lipedema (57.2 ± 9.6 mL per 100 g/min) versus control participants (49.8 ± 9.1 mL per 100 g/min). CONCLUSIONS: Findings provide evidence that brain sodium and tissue fractions are similar between patients with lipedema and control participants and that patients with lipedema do not exhibit abnormal radiological indicators of intracranial vasculopathy or ischemic injury. Potential explanations for elevated CBF are discussed in the context of the growing literature on lipedema symptomatology and vascular dysfunction.


Assuntos
Encéfalo/irrigação sanguínea , Encéfalo/metabolismo , Circulação Cerebrovascular/fisiologia , Lipedema/metabolismo , Lipedema/fisiopatologia , Sódio/metabolismo , Tecido Adiposo/metabolismo , Tecido Adiposo/patologia , Adulto , Encéfalo/diagnóstico por imagem , Encéfalo/patologia , Química Encefálica/fisiologia , Estudos de Casos e Controles , Feminino , Humanos , Lipedema/diagnóstico , Lipedema/psicologia , Imagem por Ressonância Magnética/métodos , Pessoa de Meia-Idade , Neuroimagem/métodos , Sódio/análise
19.
J Environ Sci Health B ; 55(8): 749-755, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32558613

RESUMO

This study assessed the hematological, enzymatic and osmoregulatory responses of silver catfish (Rhamdia quelen) exposed to sublethal concentrations (1.125 and 3.750 µg/L) of a commercial thiamethoxam-containing insecticide used on rice crops. Groups of 6 fish per tank (in triplicate, n = 3, total 54 fish) were exposed for up to 96 h to different concentrations of the compound. After this period, fish were placed in clean water for 48 h. Two fish from each tank (6 per treatment) that had been exposed to the insecticide for 24 h were anesthetized with eugenol and blood was collected to evaluate hematological and biochemical parameters. Blood, liver and muscle were collected for determination of metabolic parameters, plasma cortisol, Cl-, Na+ and K+ levels and H+-ATPase and Na+/K+-ATPase activity in the gill. H+-ATPase activity was higher in fish exposed to 1.125 µg/L insecticide at 24 h compared to control (0.0 µg/L). Differences in cortisol levels were evidenced throughout the experimental period. These results indicated that exposure to the insecticide changed the hematological, biochemical and metabolic profile of the animals, suggesting concern about environmental safety. Therefore, we discourage the use of this pesticide in areas that come into contact with water bodies inhabited by fish.


Assuntos
Peixes-Gato/fisiologia , Inseticidas/toxicidade , Tiametoxam/toxicidade , Adenosina Trifosfatases/metabolismo , Animais , Peixes-Gato/sangue , Ecotoxicologia/métodos , Brânquias/efeitos dos fármacos , Brânquias/metabolismo , Hidrocortisona/sangue , Fígado/efeitos dos fármacos , Músculos/efeitos dos fármacos , Músculos/metabolismo , Potássio/metabolismo , Sódio/metabolismo , Testes de Toxicidade Aguda , Poluentes Químicos da Água/toxicidade
20.
Arch Biochem Biophys ; 689: 108436, 2020 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-32492375

RESUMO

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels belong to the superfamily of voltage-gated potassium (Kv) and cyclic nucleotide-gated (CNG) channels. HCN channels contain the glycine-tyrosine-glycine (GYG) sequence that forms part of the selectivity filter, a similar structure than some potassium channels; however, they permeate both sodium and potassium, giving rise to an inward current. Yet a second amino acid sequence, leucine-cysteine-isoleucine (LCI), next to GYG, is well-preserved in all HCNs but not in the selective potassium channels. In this study we used site-directed mutagenesis and electrophysiology in frog oocytes to determine whether the LCI sequence affects the kinetics of HCN2 currents. Permeability and voltage dependence were evaluated, and we found a role of LCI in the gating mechanism combined with changes in ion permeability. The I residue resulted critical to this function.


Assuntos
Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/metabolismo , Proteínas de Xenopus/metabolismo , Xenopus/metabolismo , Sequência de Aminoácidos , Animais , Células Cultivadas , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/química , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/genética , Ativação do Canal Iônico , Potenciais da Membrana , Mutagênese Sítio-Dirigida , Oócitos/metabolismo , Permeabilidade , Potássio/metabolismo , Sódio/metabolismo , Xenopus/genética , Proteínas de Xenopus/química , Proteínas de Xenopus/genética
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