NKCC1 inhibition reduces periaxonal swelling, increases white matter sparing, and improves neurological recovery after contusive SCI.

Ultrastructural studies of contusive spinal cord injury (SCI) in mammals have shown that the most prominent acute changes in white matter are periaxonal swelling and separation of myelin away from their axon, axonal swelling, and axonal spheroid formation. However, the underlying cellular and molecular mechanisms that cause periaxonal swelling and the functional consequences are poorly understood. We hypothesized that periaxonal swelling and loss of connectivity between the axo-myelinic interface impedes neurological recovery by disrupting conduction velocity, and glial to axonal trophic support resulting in axonal swelling and spheroid formation. Utilizing in vivo longitudinal imaging of Thy1YFP+ axons and myelin labeled with Nile red, we reveal that periaxonal swelling significantly increases acutely following a contusive SCI (T13, 30 kdyn, IH Impactor) versus baseline recordings (laminectomy only) and often precedes axonal spheroid formation. In addition, using longitudinal imaging to determine the fate of myelinated fibers acutely after SCI, we show that ∼73% of myelinated fibers present with periaxonal swelling at 1 h post SCI and âˆ¼ 51% of those fibers transition to axonal spheroids by 4 h post SCI. Next, we assessed whether cation-chloride cotransporters present within the internode contributed to periaxonal swelling and whether their modulation would increase white matter sparing and improve neurological recovery following a moderate contusive SCI (T9, 50 kdyn). Mechanistically, activation of the cation-chloride cotransporter KCC2 did not improve neurological recovery and acute axonal survival, but did improve chronic tissue sparing. In distinction, the NKKC1 antagonist bumetanide improved neurological recovery, tissue sparing, and axonal survival, in part through preventing periaxonal swelling and disruption of the axo-myelinic interface. Collectively, these data reveal a novel neuroprotective target to prevent periaxonal swelling and improve neurological recovery after SCI.

Efficacy of bumetanide in animal models of ischemic stroke: a systematic review and meta-analysis.

This meta-analysis aimed to describe the efficacy of bumetanide in improving infarct volume, brain edema, and behavioral outcomes in animal models of cerebral ischemia. Embase, PubMed and Web of Science databases were searched from their inception to February 2024 (INPLASY:202430023). Data on the animal species, stroke model, drug dose, time of treatment, method of administration, study quality, and outcomes were extracted and pooled in a meta-analysis. The combined standardized mean difference (SMD) or mean difference (MD) estimates and 95% confidence intervals (CIs) were calculated using random- or fixed-effects models. Thirteen eligible studies involving >200 animals fulfilled the inclusion criteria and were included in this meta-analysis. Meta-analyses demonstrated that bumetanide treatment significantly reduced cerebral infarct volume (SMD: -0.42; 95% CI: -0.75, -0.09; p < 0.01; n = 186 animals) and consistently relieved brain edema (SMD: -1.39; 95% CI: -2.06, -0.72; p < 0.01; n = 64 animals). Subgroup analyses demonstrated that bumetanide treatment reduced infarct volume in transient but not permanent cerebral ischemia models. When administered after the stroke, it was more effective than treatment initiation before the stroke. Eight studies assessed the effect of bumetanide on behavioral function and the results showed that bumetanide treatment significantly improved neurobehavioral deficits (SMD: -2.35; 95% CI: -2.72, -1.97; p < 0.01; n = 250 animals). We conclude that bumetanide appears to be effective in reducing infarct volume and brain edema and improving behavioral recovery in animal models of cerebral ischemia. This mechanism needs to be confirmed through further investigation.

Heterogeneous brain distribution of bumetanide following systemic administration in rats.

Bumetanide is used widely as a tool and off-label treatment to inhibit the Na-K-2Cl cotransporter NKCC1 in the brain and thereby to normalize intra-neuronal chloride levels in several brain disorders. However, following systemic administration, bumetanide only poorly penetrates into the brain parenchyma and does not reach levels sufficient to inhibit NKCC1. The low brain penetration is a consequence of both the high ionization rate and plasma protein binding, which restrict brain entry by passive diffusion, and of brain efflux transport. In previous studies, bumetanide was determined in the whole brain or a few brain regions, such as the hippocampus. However, the blood-brain barrier and its efflux transporters are heterogeneous across brain regions, so it cannot be excluded that bumetanide reaches sufficiently high brain levels for NKCC1 inhibition in some discrete brain areas. Here, bumetanide was determined in 14 brain regions following i.v. administration of 10 mg/kg in rats. Because bumetanide is much more rapidly eliminated by rats than humans, its metabolism was reduced by pretreatment with piperonyl butoxide. Significant, up to 5-fold differences in regional bumetanide levels were determined with the highest levels in the midbrain and olfactory bulb and the lowest levels in the striatum and amygdala. Brain:plasma ratios ranged between 0.004 (amygdala) and 0.022 (olfactory bulb). Regional brain levels were significantly correlated with local cerebral blood flow. However, regional bumetanide levels were far below the IC50 (2.4 µM) determined previously for rat NKCC1. Thus, these data further substantiate that the reported effects of bumetanide in rodent models of brain disorders are not related to NKCC1 inhibition in the brain.

Application of near infra-red laser light increases current threshold in optic nerve consistent with increased Na+-dependent transport.

Increases in the current threshold occur in optic nerve axons with the application of infra-red laser light, whose mechanism is only partly understood. In isolated rat optic nerve, laser light was applied near the site of electrical stimulation, via a flexible fibre optic. Paired applications of light produced increases in threshold that were reduced on the second application, the response recovering with increasing delays, with a time constant of 24 s. 3-min duration single applications of laser light gave rise to a rapid increase in threshold followed by a fade, whose time-constant was between 40 and 50 s. After-effects were sometimes apparent following the light application, where the resting threshold was reduced. The increase in threshold was partially blocked by 38.6 mM Li+ in combination with 5  µ M bumetanide, a manoeuvre increasing refractoriness and consistent with axonal depolarization. Assessing the effect of laser light on the nerve input resistance ruled out a previously suggested fall in myelin resistance as contributing to threshold changes. These data appear consistent with an axonal membrane potential that partly relies on temperature-dependent electroneutral Na+ influx, and where fade in the response to the laser may be caused by a gradually diminishing Na+ pump-induced hyperpolarization, in response to falling intracellular [Na+].

Crossover randomized controlled trial of bumetanide to rescue an attack of exercise induced hand weakness in hypokalaemic periodic paralysis.

The aim of this study was to establish whether bumetanide can abort an acute attack of weakness in patients with HypoPP. This was a randomised, double-blind, cross-over, placebo-controlled phase II clinical trial. Focal attack of weakness was induced by isometric exercise of ADM followed by rest (McManis protocol). Participants had two study visits and received either placebo or 2 mg bumetanide at attack onset (defined as 40 % decrement in the abductor digiti minimi CMAP amplitude from peak). CMAP measurements assessed attack severity and duration. Nine participants completed both visits. CMAP percentage of peak amplitudes in the bumetanide (40.6 %) versus placebo (34.9 %) group at 1hr following treatment did not differ significantly (estimated effect difference 5.9 % (95 % CI: (-5.7 %; 17.5 %), p = 0.27, primary outcome). CMAP amplitudes assessed by the area under the curve for early (0-2hr post-treatment) and late (2-4 h post-treatment) efficacy were not statistically different between bumetanide and placebo (early effect estimate 0.043, p = 0.3; late effect estimate 0.085, p = 0.1). Two participants recovered from the attack following bumetanide intake; none recovered following placebo. Bumetanide was well tolerated but not efficacious to rescue a focal attack in an immobilised hand in the majority of patients, although data supports further studies of this agent.

Bumetanide in autism spectrum disorder / Bumetanida no transtorno do espectro autista / Bumetanida en el trastorno del espectro autista

Objectives: This study aimed to make a bibliographic update on the already published data on bumetanide, addressing the main information on its use in Autism Spectrum Disorder (ASD). Methods: This was an integrative narrative review in which the following databases were used: Web of Science, MEDLINE, ScienceDirect, and Scielo. The descriptors used were: Autism Spectrum Disorder, Autistic Disorder and Bumetanide. It was considered only articles published in English and French. Original articles, randomized clinical trials, case reports, and review articles were included. Results: The results show that the use of bumetanide alters regions of the brain linked to the positive development of language, improvement of visual contact, improvement in social interactions, among others. Studies are also concerned about the safety and efficacy of bumetanide in ASD since several adverse effects have been reported. The most frequent were hypokalemia, polyuria, and loss of appetite. Conclusion: Bumetanide has proven as effective in improving some important symptoms in ASD, especially linked to language and social interaction, however, studies with larger groups of patients and with longer treatment and observation time are needed to confirm the efficacy and clarify the safety profile in use for people with ASD.

Objetivo: O objetivo deste trabalho foi fazer uma atualização bibliográfica sobre os dados já publicados da bumetanida, abordando as principais informações sobre seu uso no Transtorno do Espectro Autista (TEA). Metodologia: Foi realizada uma revisão do tipo narrativa integrativa, da qual foram utilizadas as bases de dados: Web of Science, MEDLINE, ScienceDirect e Scielo, com a utilização dos seguintes descritores: Autism Spectrum Disorder, Autistic Disorder e Bumetanide. Foram considerados apenas artigos publicados nas línguas inglesa e francesa. Foram incluídos artigos originais, ensaios clínicos randomizados e relatos de caso. Foram excluídos artigos de revisão. Resultados: Os resultados mostram que o uso da bumetanida altera regiões do cérebro ligadas ao desenvolvimento positivo da linguagem, melhora do contato visual, melhora nas interações sociais, entre outros. Os estudos também se preocupam em relacionar a segurança e a eficácia da bumetanida no TEA, do qual foram relatados diversos efeitos adversos, sendo os mais frequentes a hipocalemia, a poliúria e a perda de apetite. Conclusão: A bumetanida mostrou ser eficaz na melhoria de alguns importantes sintomas no TEA, especialmente ligados à linguagem e interação social, entretanto, estudos com grupos maiores de pacientes e com maior tempo de tratamento e observação são necessários para confirmar a eficácia e esclarecer o perfil de segurança no uso para pessoas com TEA.

: Este estudio tuvo como objetivo realizar una actualización bibliográfica sobre los datos ya publicados sobre la bumetanida, abordando la principal información sobre su uso en el Trastorno del Espectro Autista (TEA). Métodos: Se trata de una revisión narrativa integradora en la que se utilizaron las siguientes bases de datos: Web of Science, MEDLINE, ScienceDirect y Scielo. Los descriptores utilizados fueron: Trastorno del Espectro Autista, Trastorno Autista y Bumetanida. Se consideraron sólo los artículos publicados en inglés y francés. Se incluyeron artículos originales, ensayos clínicos aleatorios, informes de casos y artículos de revisión. Resultados: Los resultados muestran que el uso de la bumetanida altera regiones del cerebro relacionadas con el desarrollo positivo del lenguaje, la mejora del contacto visual, la mejora de las interacciones sociales, entre otros. Los estudios también se preocupan por la seguridad y eficacia de la bumetanida en el TEA, ya que se han reportado varios efectos adversos. Los más frecuentes fueron la hipocalemia, la poliuria y la pérdida de apetito. Conclusiones: La bumetanida ha demostrado ser eficaz en la mejora de algunos síntomas importantes en el TEA, especialmente vinculados al lenguaje y la interacción social, sin embargo, se necesitan estudios con grupos más grandes de pacientes y con mayor tiempo de tratamiento y observación para confirmar la eficacia y aclarar el perfil de seguridad en el uso para personas con TEA.

Pharmacological Suppression of rat distal colon chloride secretion requires two blockers

Rat distal colon epithelium is frequently employed to assess the effect of natural and synthetic chemicals on chloride secretion. Inhibition of chloride secretion is often reported as the loop diuretic-sensitive portion of short-circuit current (Isc). The present work challenges the hypothesis that a loop diuretic alone is able to fully abolish chloride secretion. Isolated mucosa preparations were mounted in an Ussing chamber. The effects on short-circuit current of replacement of normal Ringer by a low (2.5 mmol/L) Cl solution and of blockers of basolateral Na, K, 2 Cl symport (bumetanide), apical Cl channels (diphenylamine-2-carboxylate, DPC), and anion exchange (4-acetamido-4-isothiocyanatostilbene-2,2-disulfonic acid, SITS) alone and combined were assessed. Low Cl reversibly decreased Isc by 76%. In normal Ringer, bumetanide decreased Isc by 65%. SITS also had a significant effect at the serosal side, but not at the apical side, where DPC caused a 40% decrease. Chloride replacement, bumetanide and DPC, but not SITS, increased epithelial resistivity. Combined blockade of Na, K, 2 Cl symport and apical Cl channels, of Na, K, 2 Cl symport and anion antiport, or of anion antiport and apical Cl channels was needed to achieve reduction of short circuit current to the same extent seen with chloride replacement. Present results indicate that Isc of the unstimulated epithelium is mostly due to chloride secretion, and at least two blockers are required to abolish it. This fact should be taken into account in studies of chloride secretion-stimulating agents. (AU)

Insuficiencia cardíaca y diuréticos: una relación controvertida / Cardiac insufficiency and diuretics: a controversy relationship

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