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1.
Nature ; 586(7829): 457-462, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32999458

RESUMO

TASK2 (also known as KCNK5) channels generate pH-gated leak-type K+ currents to control cellular electrical excitability1-3. TASK2 is involved in the regulation of breathing by chemosensory neurons of the retrotrapezoid nucleus in the brainstem4-6 and pH homeostasis by kidney proximal tubule cells7,8. These roles depend on channel activation by intracellular and extracellular alkalization3,8,9, but the mechanistic basis for TASK2 gating by pH is unknown. Here we present cryo-electron microscopy structures of Mus musculus TASK2 in lipid nanodiscs in open and closed conformations. We identify two gates, distinct from previously observed K+ channel gates, controlled by stimuli on either side of the membrane. Intracellular gating involves lysine protonation on inner helices and the formation of a protein seal between the cytoplasm and the channel. Extracellular gating involves arginine protonation on the channel surface and correlated conformational changes that displace the K+-selectivity filter to render it nonconductive. These results explain how internal and external protons control intracellular and selectivity filter gates to modulate TASK2 activity.


Assuntos
Microscopia Crioeletrônica , Ativação do Canal Iônico , Canais de Potássio de Domínios Poros em Tandem/química , Canais de Potássio de Domínios Poros em Tandem/ultraestrutura , Potássio/metabolismo , Animais , Concentração de Íons de Hidrogênio , Camundongos , Modelos Moleculares , Canais de Potássio de Domínios Poros em Tandem/metabolismo , Domínios Proteicos , Relação Estrutura-Atividade
2.
Nat Commun ; 11(1): 5168, 2020 10 14.
Artigo em Inglês | MEDLINE | ID: mdl-33057011

RESUMO

The potassium ion (K+) channel plays a fundamental role in controlling K+ permeation across the cell membrane and regulating cellular excitabilities. Mutations in the transmembrane pore reportedly affect the gating transitions of K+ channels, and are associated with the onset of neural disorders. However, due to the lack of structural and dynamic insights into the functions of K+ channels, the structural mechanism by which these mutations cause K+ channel dysfunctions remains elusive. Here, we used nuclear magnetic resonance spectroscopy to investigate the structural mechanism underlying the decreased K+-permeation caused by disease-related mutations, using the prokaryotic K+ channel KcsA. We demonstrated that the conformational equilibrium in the transmembrane region is shifted toward the non-conductive state with the closed intracellular K+-gate in the disease-related mutant. We also demonstrated that this equilibrium shift is attributable to the additional steric contacts in the open-conductive structure, which are evoked by the increased side-chain bulkiness of the residues lining the transmembrane helix. Our results suggest that the alteration in the conformational equilibrium of the intracellular K+-gate is one of the fundamental mechanisms underlying the dysfunctions of K+ channels caused by disease-related mutations.


Assuntos
Proteínas de Bactérias/metabolismo , Ativação do Canal Iônico/genética , Canais de Potássio/metabolismo , Potássio/metabolismo , Alanina/genética , Ataxia/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/isolamento & purificação , Epilepsia/genética , Humanos , Síndrome do QT Longo/genética , Espectroscopia de Ressonância Magnética , Simulação de Dinâmica Molecular , Mutação de Sentido Incorreto , Canais de Potássio/genética , Canais de Potássio/isolamento & purificação , Conformação Proteica em alfa-Hélice/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificação , Proteínas Recombinantes/metabolismo , Streptomyces lividans , Valina/genética
3.
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
4.
PLoS One ; 15(9): e0238447, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32881909

RESUMO

BACKGROUND: Polyamines are involved in a wide variety of biological processes including a marked effect on the structure and function of DNA. During our study on the interaction of polyamines with DNA, we found that K+ enhanced in vitro gene expression in the presence of polyamine more strongly than Na+. Thus, we sought to clarify the physico-chemical mechanism underlying this marked difference between the effects of K+ and Na+. PRINCIPAL FINDINGS: It was found that K+ enhanced gene expression in the presence of spermidine, SPD(3+), much more strongly than Na+, through in vitro experiments with a Luciferase assay on cell extracts. Single-DNA observation by fluorescence microscopy showed that Na+ prevents the folding transition of DNA into a compact state more strongly than K+. 1H NMR measurement revealed that Na+ inhibits the binding of SPD to DNA more strongly than K+. Thus, SPD binds to DNA more favorably in K+-rich medium than in Na+-rich medium, which leads to favorable conditions for RNA polymerase to access DNA by decreasing the negative charge. CONCLUSION AND SIGNIFICANCE: We found that Na+ and K+ exhibit markedly different effects through competitive binding with a cationic polyamine, SPD, to DNA, which causes a large difference in the higher-order structure of genomic DNA. It is concluded that the larger favorable effect of Na+ than K+ on in vitro gene expression observed in this study is well attributable to the significant difference between Na+ and K+ on the competitive binding inducing conformational transition of DNA.


Assuntos
Expressão Gênica/efeitos dos fármacos , Potássio/metabolismo , Sódio/metabolismo , Fenômenos Bioquímicos , DNA/metabolismo , Poliaminas/metabolismo , Poliaminas/farmacologia , Espermidina/farmacologia , Espermina/farmacologia
5.
Plant Mol Biol ; 104(4-5): 397-410, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32803476

RESUMO

KEY MESSAGE: Enhanced bioactive JA (JA-Ile) accumulation in OsJAZ9 overexpressing rice helps plants tolerate K deficiency. Potassium (K) represents up to 10% of the plant's total dry biomass, and its deficiency makes plants highly susceptible to both abiotic and biotic stresses. K shortage results in the inhibition of root and shoots growth, but the underlying mechanism of this response is unclear. Our RNA-Seq and qPCR analysis suggested leading roles for JA pathway genes under K deficiency in rice. Notably, K deficiency and JA application produced similar phenotypic and transcriptional responses. Here, we integrated molecular, physiological and morphological studies to analyze the role of OsJAZ9 in JA homeostasis and K deficiency responses. We raised OsJAZ9 over-expression, knockdown, transcriptional reporter, translational reporter and C-terminal deleted translational reporter lines in rice to establish the role of JA signaling in K ion homeostasis. JA profiling revealed significantly increased JA-Ile levels in OsJAZ9 OE lines under K deficiency. Furthermore, we established that OsJAZ9 overexpression and knockdown result in K deficiency tolerance and sensitivity, respectively, by modulating various K transporters and root system architecture. Our data provide evidence on the crucial roles of OsJAZ9 for improving K deficiency tolerance in rice by altering JA levels and JA responses.


Assuntos
Ciclopentanos/metabolismo , Oryza/metabolismo , Oxilipinas/metabolismo , Proteínas de Plantas/metabolismo , Potássio/metabolismo , Regulação da Expressão Gênica de Plantas , Homeostase , Isoleucina/análogos & derivados , Isoleucina/metabolismo , Oryza/efeitos dos fármacos , Oryza/genética , Proteínas de Plantas/genética , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , Plantas Geneticamente Modificadas , Potássio/farmacologia
6.
J Biosci Bioeng ; 130(5): 520-524, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32830038

RESUMO

To clarify the physiological factors associated with the development of tomato leaf marginal necrosis associated with potassium deficiency, tomato leaf blades prior to development of the symptoms were collected, and profiles of water-soluble metabolites were analyzed using gas chromatography-mass spectrometry. Multivariate analysis was conducted to screen for a component that was related to potassium deficiency-induced leaf necrosis among the 60 metabolites detected in tomato leaves. Polyamines, sugars, and branched amino acids were ranked highly. Putrescine was most strongly and negatively correlated with potassium concentration and exhibited an exponential response, regardless of the site or plant body. In addition to putrescine, glucose, xylose and l-isoleucine are known to play important roles in stress response and ion balance control, and it is thought that changes in metabolite profiles are linked to tomato leaf marginal necrosis associated with a decrease in endogenous potassium concentration. These findings will be useful for cultivation management to mitigate this physiological disorder of tomato.


Assuntos
Cromatografia Gasosa-Espectrometria de Massas , Lycopersicon esculentum/citologia , Lycopersicon esculentum/metabolismo , Metabolômica , Folhas de Planta/citologia , Folhas de Planta/metabolismo , Potássio/metabolismo , Necrose/metabolismo
7.
PLoS One ; 15(8): e0236246, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32804956

RESUMO

K+ is an essential nutrient for plant growth and is responsible for many important physiological processes. K+ deficiency leads to crop yield losses, and overexpression of K+ transporter genes has been proven to be an effective way to resolve this problem. However, current research on the overexpression of K+ transporter genes is limited to plant sources. TrkH is a bacterial K+ transporter whose function generally depends on the regulation of TrkA. To date, whether TrkH can improve K+ uptake in eukaryotic organisms is still unknown. In this study, a novel MbtrkH gene was cloned from marine microbial metagenomic DNA. Functional complementation and K+-depletion analyses revealed that MbTrkH functions in K+ uptake in the K+-deficient yeast strain CY162. Moreover, K+-depletion assays revealed that MbtrkH overexpression improves plant K+ uptake. K+ hydroponic culture experiments showed that, compared with WT tobacco lines, MbtrkH transgenic tobacco lines had significantly greater fresh weights, dry weights and K+ contents. These results indicate that MbTrkH promotes K+ uptake independently of TrkA in eukaryotes and provide a new strategy for improving K+-use efficiency in plants.


Assuntos
Organismos Aquáticos/genética , Potássio/metabolismo , Saccharomyces cerevisiae/metabolismo , Água do Mar/microbiologia , Tabaco/metabolismo , Clonagem Molecular , Metagenoma , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo , Canais de Potássio/genética , Canais de Potássio/metabolismo , Saccharomyces cerevisiae/genética , Tabaco/genética
8.
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
9.
Ecotoxicol Environ Saf ; 205: 111163, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32836159

RESUMO

Arthrobacter sp. JQ-1 can completely degrade 500 mg/L of DEHP within 3 days. The minimum inhibitory concentrations (MICs) of Cu2+ could reach 1.56 mM, however, 5.0 mg/L Cu2+ apparently inhibited DEHP degradation and bacterial growth. Consequently, JQ-1 was exposed to the DEHP-copper environment to verify the toxicity mechanism based on the physiological responses of cellular multiple interfaces (cellular surface, membrane and intracellular characteristics). The results showed the combination of 500 mg/L DEHP and 5.0 mg/L Cu2+ significantly decreased cell surface hydrophobicity (CSH) and the absolute value of zeta potential, which implied the bioavailability of DEHP was decreased. The cellular surface changes were mainly due to the interaction between Cu2+ and some functional groups (CH2, CH3, aromatic rings, and amide). The weakened proton-motive force (PMF) across the plasma membrane may interfere the formation and utilization of energy, which is not conducive to the repair process of cellular damages. In this study, Non-invasive micro-test technology (NMT) was applied to the research of combined toxicity of DEHP and heavy metal ions for the first time. DEHP-copper intensified K+ efflux and Ca2+ influx across the plasma membrane, which disturbed ion homeostasis of K+ and Ca2+ and might induce apoptosis and further inhibit DEHP degradation. The decline of intracellular esterase activity indicated that the metabolic capacity is apparently restrained. This study enhances our understanding of cellular different interface processes responding to combined pollutants.


Assuntos
Arthrobacter/efeitos dos fármacos , Cobre/toxicidade , Dietilexilftalato/toxicidade , Poluentes do Solo/toxicidade , Arthrobacter/metabolismo , Arthrobacter/ultraestrutura , Biodegradação Ambiental , Cálcio/metabolismo , Cobre/metabolismo , Dietilexilftalato/metabolismo , Sinergismo Farmacológico , Potássio/metabolismo , Solo/química , Microbiologia do Solo , Poluentes do Solo/metabolismo
10.
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
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.
PLoS One ; 15(7): e0232860, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32645001

RESUMO

Limited information is available that seed biopriming with plant growth-promoting Enterobacter spp. play a prominent role to enhance vegetative growth of plants. Contrary to Enterobacter cloacae, Enterobacter hormaechei is a less-studied counterpart despite its vast potential in plant growth-promotion mainly through the inorganic phosphorus (P) and potassium (K) solubilization abilities. To this end, 18 locally isolated bacterial pure cultures were screened and three strains showed high P- and K-solubilizing capabilities. Light microscopy, biochemical tests and 16S rRNA gene sequencing revealed that strains 15a1 and 40a were closely related to Enterobacter hormaechei while strain 38 was closely related to Enterobacter cloacae (Accession number: MN294583; MN294585; MN294584). All Enterobacter spp. shared common plant growth-promoting traits, namely nitrogen (N2) fixation, indole-3-acetic acid production and siderophore production. The strains 38 and 40a were able to produce gibberellic acid, while only strain 38 was able to secrete exopolysaccharide on agar. Under in vitro germination assay of okra (Abelmoschus esculentus) seeds, Enterobacter spp. significantly improved overall germination parameters and vigor index (19.6%) of seedlings. The efficacy of root colonization of Enterobacter spp. on the pre-treated seedling root tips was confirmed using Scanning Electron Microscopy (SEM). The pot experiment of bioprimed seeds of okra seedling showed significant improvement of the plant growth (> 28%) which corresponded to the increase of P and K uptakes (> 89%) as compared to the uninoculated control plants. The leaf surface area and the SPAD chlorophyll index of bioprimed plants were increased by up to 29% and 9% respectively. This report revealed that the under-explored species of P- and K-solubilizing Enterobacter hormaechei sp. with multiple plant beneficial traits presents a great potential sustainable approach for enhancement of soil fertility and P and K uptakes of plants.


Assuntos
Abelmoschus/crescimento & desenvolvimento , Enterobacter/fisiologia , Fósforo/metabolismo , Potássio/metabolismo , Sementes/microbiologia , Abelmoschus/classificação , Abelmoschus/metabolismo , Abelmoschus/microbiologia , Contenção de Riscos Biológicos , Enterobacter/isolamento & purificação , Germinação , Tipagem Molecular , Desenvolvimento Vegetal , RNA Ribossômico 16S , Plântula/crescimento & desenvolvimento , Sementes/crescimento & desenvolvimento
13.
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
14.
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
15.
PLoS One ; 15(7): e0236634, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32706842

RESUMO

Potassium (K) input is essential for the improvement of soil fertility in agricultural systems. However, organic amendment may differ from mineral K fertilization with respect to modifying the soil K transformation among different fractions, affecting soil K availability. We conducted a 60-day lab incubation experiment to evaluate the response of soil K dynamics and availability in various fractions with a view to simulating crop residue return and chemical K fertilization in an Anthrosol of northwest China. The tested soil was divided into two main groups, no K fertilization (K0) and K fertilization (K1), each of which was subjected to four straw addition regimes: no straw addition (Control), wheat straw addition (WS), maize straw addition (MS), and both wheat straw and maize straw addition (WS+MS). Soil K levels in the available (AK) and non-exchangeable (NEK) fractions were both significantly increased after K addition, following the order of K>WS>MS. Fertilizer K was the most efficient K source, demonstrating a 72.9% efficiency in increasing soil AK, while wheat and maize straw exhibited efficiencies of 47.1% and 39.3%, respectively. Furthermore, K fertilization and wheat and maize straw addition increased the soil AK in a cumulative manner when used in combination. The mobility factor (MF) and reduced partition index (IR) of soil K were used to quantitate the comprehensive soil K mobility and stability, respectively. Positive relationships were observed between the MF and all relatively available fractions of soil K, whereas the IR value of soil K correlated negatively with both MF and all available fractions of soil K. In conclusion, straw amendment could be inferior to mineral K fertilization in improving soil K availability when they were almost equal in the net K input. Crop straw return coupled with K fertilization can be a promising strategy for improving both soil K availability and cycling in soil-plant systems.


Assuntos
Agricultura , Potássio/química , Solo/química , Triticum/metabolismo , Zea mays/metabolismo , China , Fertilizantes/análise , Potássio/metabolismo , Análise de Componente Principal , Triticum/química , Zea mays/química
16.
Proc Natl Acad Sci U S A ; 117(28): 16626-16637, 2020 07 14.
Artigo em Inglês | MEDLINE | ID: mdl-32601236

RESUMO

Neuronal activity leads to an increase in local cerebral blood flow (CBF) to allow adequate supply of oxygen and nutrients to active neurons, a process termed neurovascular coupling (NVC). We have previously shown that capillary endothelial cell (cEC) inwardly rectifying K+ (Kir) channels can sense neuronally evoked increases in interstitial K+ and induce rapid and robust dilations of upstream parenchymal arterioles, suggesting a key role of cECs in NVC. The requirements of this signal conduction remain elusive. Here, we utilize mathematical modeling to investigate how small outward currents in stimulated cECs can elicit physiologically relevant spread of vasodilatory signals within the highly interconnected brain microvascular network to increase local CBF. Our model shows that the Kir channel can act as an "on-off" switch in cECs to hyperpolarize the cell membrane as extracellular K+ increases. A local hyperpolarization can be amplified by the voltage-dependent activation of Kir in neighboring cECs. Sufficient Kir density enables robust amplification of the hyperpolarizing stimulus and produces responses that resemble action potentials in excitable cells. This Kir-mediated excitability can remain localized in the stimulated region or regeneratively propagate over significant distances in the microvascular network, thus dramatically increasing the efficacy of K+ for eliciting local hyperemia. Modeling results show how changes in cEC transmembrane current densities and gap junctional resistances can affect K+-mediated NVC and suggest a key role for Kir as a sensor of neuronal activity and an amplifier of retrograde electrical signaling in the cerebral vasculature.


Assuntos
Neurônios/metabolismo , Acoplamento Neurovascular , Canais de Potássio Corretores do Fluxo de Internalização/metabolismo , Potássio/metabolismo , Animais , Encéfalo/irrigação sanguínea , Encéfalo/metabolismo , Circulação Cerebrovascular , Células Endoteliais/química , Células Endoteliais/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Modelos Biológicos , Neurônios/química , Potássio/química , Canais de Potássio Corretores do Fluxo de Internalização/química , Canais de Potássio Corretores do Fluxo de Internalização/genética , Transdução de Sinais , Canais de Cátion TRPV/química , Canais de Cátion TRPV/genética , Canais de Cátion TRPV/metabolismo
17.
Arch Microbiol ; 202(9): 2461-2470, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32607724

RESUMO

The present study was aimed to study the effect of bacteria inhabiting in buffalo dung on nutritional properties of soil and plant. Three beneficial bacteria Proteus mirabilis, Pseudomonas aeruginosa, and Enterobacter xiangfangensis were isolated from buffalo dung to evaluate for their effects individually as well as in consortium. The combined effect of P. mirabilis and P. aeruginosa showed a significant enhancement in different biological parameters of Foeniculum vulgare such as primary branch (99.32%), secondary branch (98.32%), number of umbels (87.62%), number of umbellets (99.85%), number of seeds (104.94%), grain yield (62.38%), biological yield (35.99%), and harvest index (19.48%). Consortium of these potent bacteria also enhanced proximate constituents such as total ash (49.79%), ether extract (63.06%), crude fibre (48.91%), moisture content (33.40%), dry matter (31.45%), acid insoluble ash (33.20%), and crude protein (40.73%). A highly significant correlation (p ≤ 0.01) was found between nitrogen (r = 0.97), phosphorous (r = 0.95), and potassium (r = 0.97) contents of soil. This research enhances the knowledge of the effect of plant growth-promoting bacteria on nutrient properties of soil and fennel which deliver a new index for healthier use in organic agricultural practices.


Assuntos
Fenômenos Fisiológicos Bacterianos , Fezes/microbiologia , Foeniculum/microbiologia , Microbiologia do Solo , Animais , Búfalos , Nitrogênio/análise , Nitrogênio/metabolismo , Nutrientes/análise , Nutrientes/metabolismo , Desenvolvimento Vegetal , Potássio/análise , Potássio/metabolismo , Sementes/química , Solo/química
18.
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
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.
Am J Physiol Gastrointest Liver Physiol ; 319(2): G142-G150, 2020 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-32567323

RESUMO

Transepithelial K+ absorption requires apical K+ uptake and basolateral K+ exit. In the colon, apical H+-K+-ATPase mediates cellular K+ uptake, and it has been suggested that electroneutral basolateral K+ exit reflects K+-Cl- cotransporter-1 (KCC1) operating in parallel with K+ and Cl- channels. The present study was designed to identify basolateral transporter(s) responsible for K+ exit in rat distal colon. Active K+ absorption was determined by measuring 86Rb+ (K+ surrogate) fluxes across colonic epithelia under voltage-clamp conditions. With zero Cl- in the mucosal solution, net K+ absorption was reduced by 38%, indicating that K+ absorption was partially Cl--dependent. Serosal addition of DIOA (KCC1 inhibitor) or Ba2+ (nonspecific K+ channel blocker) inhibited net K+ absorption by 21% or 61%, respectively, suggesting that both KCC1 and K+ channels contribute to basolateral K+ exit. Clotrimazole and TRAM34 (IK channel blockers) added serosally inhibited net K+ absorption, pointing to the involvement of IK channels in basolateral K+ exit. GaTx2 (CLC2 blocker) added serosally also inhibited net K+ absorption, suggesting that CLC2-mediated Cl- exit accompanies IK channel-mediated K+ exit across the basolateral membrane. Net K+ absorption was not inhibited by serosal addition of either IbTX (BK channel blocker), apamin (SK channel blocker), chromanol 293B (KV7 channel blocker), or CFTRinh172 (CFTR blocker). Immunofluorescence studies confirmed basolateral membrane colocalization of CLC2-like proteins and Na+-K+-ATPase α-subunits. We conclude that active K+ absorption in rat distal colon involves electroneutral basolateral K+ exit, which may reflect IK and CLC2 channels operating in parallel.NEW & NOTEWORTHY This study demonstrates that during active electroneutral K+ absorption in rat distal colon, K+ exit across the basolateral membrane mainly reflects intermediate conductance K+ channels operating in conjunction with chloride channel 2, with a smaller, but significant, contribution from K+-Cl- cotransporter-1 (KCC1) activity.


Assuntos
Canais de Cloreto/metabolismo , Colo/fisiologia , Mucosa Intestinal/metabolismo , Canais de Potássio/metabolismo , Potássio/metabolismo , Animais , Canais de Cloreto/genética , Cloretos/metabolismo , Feminino , Transporte de Íons , Masculino , Técnicas de Patch-Clamp , Canais de Potássio/genética , Transporte Proteico , Ratos , Ratos Sprague-Dawley
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