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Mammals have approximately 80 genes that encode potassium (K+) channels. They have a wide range of physiological functions, such as modulation of action potential duration and relaxation of smooth muscles. Carvacrol, a compound found in various aromatic plants, has been used traditionally for treating asthma, menstrual spasms, and gastrointestinal disorders. However, its mechanism of action on smooth muscles remains insufficiently understood. This study investigates the role of potassium ion channels in the relaxing effects of carvacrol on isolated rat duodenum smooth muscles. Rats were euthanized and duodenal segments were prepared and placed in an isolated organ bath with Krebs' solution. The segments were equilibrated for 1 h and then treated with chemicals to obtain concentrationresponse curves. The data were evaluated using one-way Analysis of Variance (ANOVA) and Tukey's Honest Significant Difference (Tukey's HSD) test for multiple comparisons. Our findings demonstrate that carvacrol induces a dosedependent relaxation of these muscles. The relaxation effects were significantly reduced in the presence of specific potassium channel inhibitors, including paxilline, UCL1684, linopirdine, barium chloride, and 4-aminopyridine. They were completely blocked by the combination of barium chloride and tetraethylammonium. However, glibenclamide, ruthenium red, and nitroarginine did not alter the relaxing effects of carvacrol. In conclusion: carvacrol relaxes duodenum smooth muscles by opening barium chloride-sensitive Kir2.1 and Kir3.1, as well as tetraethylammoniumsensitive KCa1.1, KCa2.1, KCa2.2, KCa2.3, Kv1.2, Kv1.4, Kv1.5, Kv2.1, Kv2.2, Kv4.1, Kv4.2, Kv4.3, Kv7.1, Kv7.2, Kv7.3, Kv7.4, and Kv7.5 potassium channels. [ABSTRACT FROM AUTHOR]

Arterial hypertension is a highly prevalent chronic disease worldwide, with several etiologies and treatments that may eventually have side effects or result in patients developing tolerance. There is growing interest in traditional medicine and functional foods to isolate biomolecules that could be useful as coadjuvants for treating several aliments. Pitaya, a desert fruit endemic in Mexico, is a rich source of bioactive molecules (betalains and phenolic compounds). In this work, the vasorelaxation properties of pitaya juice concentrate and fraction one were investigated using aortic and mesenteric rings from rats. The incubation of rings with pitaya juice concentrate or fraction one induced significant vasorelaxation, independent of the endothelium, and showed resistance to potassium channel blockers. This vasorelaxation was associated with the transmembrane influx of extracellular calcium through the vascular smooth muscle cells, with an inhibitory effect on the voltage-dependent calcium channel currents. Also, 400 mg/mL of pitaya juice concentrate in spontaneous hypertensive rats reduced their blood pressure for 48 h. Phytochemical analyses showed that the primary compounds in F1 were glycosidic in nature, and could be a complex mixture of disaccharides, dimeric disaccharides, or even tetrasaccharides. The glycosidic compounds found in F1 primarily contributed to vasodilatation, establishing a voltage-dependent calcium channel inhibition as a possible molecular target. [ABSTRACT FROM AUTHOR]

Background and Purpose: Calcitonin gene‐related peptide (CGRP) is a potent vasodilator. While its signalling is assumed to be mediated via increases in cAMP, this study focused on elucidating the actual intracellular signalling pathways involved in CGRP‐induced relaxation of human isolated coronary arteries (HCA). Experimental Approach: HCA were obtained from heart valve donors (27 M, 25 F, age 54 ± 2 years). Concentration–response curves to human α‐CGRP or forskolin were constructed in HCA segments, incubated with different inhibitors of intracellular signalling pathways, and intracellular cAMP levels were measured with and without stimulation. Results: Adenylyl cyclase (AC) inhibitors SQ22536 + DDA and MDL‐12330A, and PKA inhibitors Rp‐8‐Br‐cAMPs and H89, did not inhibit CGRP‐induced relaxation of HCA, nor did the guanylyl cyclase inhibitor ODQ, PKG inhibitor KT5823, EPAC1/2 inhibitor ESI09, potassium channel blockers TRAM‐34 + apamin, iberiotoxin or glibenclamide, or the Gαq inhibitor YM‐254890. Phosphodiesterase inhibitors induced a concentration‐dependent decrease in the response to KCl but did not potentiate relaxation to CGRP. Relaxation to forskolin was not blocked by PKA or AC inhibitors, although AC inhibitors significantly inhibited the increase in cAMP. Inhibition of Gβγ subunits using gallein significantly inhibited the relaxation to CGRP in human coronary arteries. Conclusion: While CGRP signalling is generally assumed to act via cAMP, the CGRP‐induced vasodilation in HCA was not inhibited by targeting this intracellular signalling pathway at different levels. Instead, inhibition of Gβγ subunits did inhibit the relaxation to CGRP, suggesting a different mechanism of CGRP‐induced relaxation than generally believed. [ABSTRACT FROM AUTHOR]

Introduction: The mechanisms leading to the conversion of atrial fibrillation (AF) to sinus rhythm are poorly understood. This study describes the dynamic behavior of electrophysiological parameters and conduction patterns leading to spontaneous and pharmacological AF termination. Methods: Five independent groups of goats were investigated: (1) spontaneous termination of AF, and drug-induced terminations of AF by various potassium channel inhibitors: (2) AP14145, (3) PA-6, (4) XAF-1407, and (5) vernakalant. Biatrial contact mapping was performed during an open chest surgery and intervals with continuous and discrete atrial activity were determined. AF cycle length (AFCL), conduction velocity and path length were calculated for each interval, and the final conduction pattern preceding AF termination was evaluated. Results: AF termination was preceded by a sudden episode of discrete activity both in the presence and absence of an antiarrhythmic drug. This episode was accompanied by substantial increases in AFCL and conduction velocity, resulting in prolongation of path length. In 77% ± 4% of all terminations the conduction pattern preceding AF termination involved medial to lateral conduction along Bachmann's bundle into both atria, followed by anterior to posterior conduction. This finding suggests conduction block in the interatrial septum and/or pulmonary vein area as final step of AF termination. Conclusion: AF termination is preceded by an increased organization of fibrillatory conduction. The termination itself is a sudden process with a critical role for the interplay between spatiotemporal organization and anatomical structure. [ABSTRACT FROM AUTHOR]

Background: The identification of novel toxins from overlooked and taxonomically exceptional species bears potential for various pharmacological applications. The remipede Xibalbanus tulumensis, an underwater cave-dwelling crustacean, is the only crustacean for which a venom system has been described. Its venom contains several xibalbin peptides that have an inhibitor cysteine knot (ICK) scaffold. Results: Our screenings revealed that all tested xibalbin variants particularly inhibit potassium channels. Xib1 and xib13 with their eight-cysteine domain similar to spider knottins also inhibit voltage-gated sodium channels. No activity was noted on calcium channels. Expanding the functional testing, we demonstrate that xib1 and xib13 increase PKA-II and Erk1/2 sensitization signaling in nociceptive neurons, which may initiate pain sensitization. Our phylogenetic analysis suggests that xib13 either originates from the common ancestor of pancrustaceans or earlier while xib1 is more restricted to remipedes. The ten-cysteine scaffolded xib2 emerged from xib1, a result that is supported by our phylogenetic and machine learning-based analyses. Conclusions: Our functional characterization of synthesized variants of xib1, xib2, and xib13 elucidates their potential as inhibitors of potassium channels in mammalian systems. The specific interaction of xib2 with Kv1.6 channels, which are relevant to treating variants of epilepsy, shows potential for further studies. At higher concentrations, xib1 and xib13 activate the kinases PKA-II and ERK1/2 in mammalian sensory neurons, suggesting pain sensitization and potential applications related to pain research and therapy. While tested insect channels suggest that all probably act as neurotoxins, the biological function of xib1, xib2, and xib13 requires further elucidation. A novel finding on their evolutionary origin is the apparent emergence of X. tulumensis-specific xib2 from xib1. Our study is an important cornerstone for future studies to untangle the origin and function of these enigmatic proteins as important components of remipede but also other pancrustacean and arthropod venoms. [ABSTRACT FROM AUTHOR]

A potassium channel blocker 4-AP has been shown to exert pronounced convulsive action to generate burst firings when applied to hippocampal slices. However, it remains unclear how the blockade of potassium channels leads to the generation of burst firings. One possibility is ectopic spiking from the sites different from those for physiological spike initiation at the axon initial segment, as suggested for several experimental models of epileptogenesis in vitro. To test for possible ectopic spiking at the distal axon by 4-AP application, direct recordings from large mossy fiber terminals were made with the loosepatch clamp technique in mouse hippocampal slices. To localize the action of 4-AP on the distal axon, focal perfusion, as well as micro-cut to disconnect soma and distal axons, were adopted. Focal application of 4-AP on the distal portion of mossy fibers reliably induced burst discharges of the mossy fiber terminals. Photochemical blockade of potassium channels at distal axons, by the application of RuBi-4-AP, a visible wavelength blue light-sensitive caged compound, and the illumination of blue light caused robust bursting activity originating from distal axons. Computer simulation suggested that local blockade of axonal potassium channels prolongs the duration of action potentials and thereby causes reverberating spiking activities at distal axons and subsequent antidromic propagation toward the soma. Taken together, it was suggested that local blockade of voltage-dependent potassium channels in distal axons by application of 4-AP is sufficient to cause a hyperexcitable state of hippocampal mossy fiber axons. [ABSTRACT FROM AUTHOR]

Zastaprazan (JAQBO®) is a next-generation potassium-competitive acid blocker being developed by Onconic Therapeutics, a subsidiary of Jeil Pharmaceutical, for the treatment of acid-related diseases. Zastaprazan binds directly to proton pumps in a competitive manner to reduce gastric acid secretion, allowing for a quick onset of action. On 24 April 2024, zastaprazan received approval in South Korea for the treatment of erosive gastroesophageal reflux disease (GERD). Zastaprazan is also undergoing phase III development for the treatment of gastric ulcer and for the prevention of non-steroidal anti-inflammatory drug (NSAID)-induced peptic ulcer. This article summarizes the milestones in the development of zastaprazan leading to this first approval for erosive GERD. [ABSTRACT FROM AUTHOR]

Introduction: Febrile neutropenia (FN) is an oncologic emergency requiring immediate empiric antibiotic therapy. Although carboplatin plus etoposide combination chemotherapy is associated with a relatively high frequency of FN, the risk factors are unclear. Hence, this retrospective study aimed to identify predictive markers of carboplatin/etoposide-induced FN. Methods: We conducted a retrospective cohort analysis of patients with previously untreated small-cell lung cancer (SCLC) who received combination chemotherapy with carboplatin (area under the concentration curve: 5 mg/mL·min, day 1) and etoposide (80 or 100 mg/m2, days 1–3) between July 2007 and June 2022. FN was assessed during the 21 days after initiation of carboplatin and etoposide therapy according to the Japanese Society of Medical Oncology's definition. Fisher's exact test for categorical variables and Mann-Whitney U test for continuous variables were used to compare the two groups. Statistical significance was set at p values <0.05. Explanatory variables with p values <0.05 in the univariate analysis were included in the multivariate logistic regression analysis. Results: Among the 176 eligible patients, the incidence of FN during the first cycle of chemotherapy was 25.0% (44/176). Multivariate analysis revealed that co-administration of proton pump inhibitors (PPIs) or potassium-competitive acid blockers (PCABs) and body mass index (BMI) were significantly associated with FN (p = 0.0035 and 0.0011, respectively). Patients with both co-administration of PPIs or PCABs and a BMI ≤22.509 kg/m2 presented with significantly higher frequencies of FN compared with the other patients (13/24 [54.2%] vs. 31/152 [20.4%] patients; odds ratio: 4.56, 95% confidence interval: 1.70–12.48; p = 0.00147). Conclusion: Patients who received carboplatin plus etoposide for SCLC with co-administration of PPIs or PCABs and a BMI ≤22.509 kg/m2 more frequently present with FN than those without the two factors. [ABSTRACT FROM AUTHOR]

Pseudohyperaldosteronism (PHA) is characterized by hypertension, hypokalemia, and a decrease in plasma renin and aldosterone levels. It can be caused by several causes, but the most frequent is due to excess intake of licorice. The effect is mediated by the active metabolite of licorice, glycyrrhetinic acid (GA), which acts by blocking the 11-hydroxysteroid dehydrogenase type 2 and binding to the mineralocorticoid receptor (MR) as an agonist. The management of licorice-induced PHA depends on several individual factors, such as age, gender, comorbidities, duration and amount of licorice intake, and metabolism. The clinical picture usually reverts upon licorice withdrawal, but sometimes mineralocorticoid-like effects can be critical and persist for several weeks, requiring treatment with MR blockers and potassium supplements. Through this case series of licorice-induced PHA, we aim to increase awareness about exogenous PHA, and the possible risk associated with excess intake of licorice. An accurate history is mandatory in patients with hypertension and hypokalemia to avoid unnecessary testing. GA is a component of several products, such as candies, breath fresheners, beverages, tobacco, cosmetics, and laxatives. In recent years, the mechanisms of action of licorice and its active compounds have been better elucidated, suggesting its benefits in several clinical settings. Nevertheless, licorice should still be consumed with caution, considering that licorice-induced PHA is still an underestimated condition, and its intake should be avoided in patients with increased risk of licorice toxicity due to concomitant comorbidities or interfering drugs. [ABSTRACT FROM AUTHOR]

The effects of pomegranate juice (PJ) and its components on uterine smooth muscle are unknown. Hence, this study unequivocally demonstrates that pomegranate juice (PJ) significantly impacts myometrial function, providing crucial insights into its relaxant properties and their potential therapeutic applications for uterine-related disorders. Rat uterine smooth muscle horn strips were suspended in Krebs solution organ baths. Contractions were measured isometrically using a transducer (AD instrument Australia). The effects of PJ were evaluated on contractile activity elicited by potassium chloride (KCl 60 Mm) depolarization. Inhibitors of nitric oxide (L-NAME 3 X 10−4), guanylate cyclase (methylene blue 1 X 10−5), and Prostaglandin I2 (indomethacin 3 X 10−5), as well as Potassium Channels blockers, were determined. The juice at concentrations from 1.5–5 mg/ml significantly decreased the rat uterine horn contraction induced by KCl. The NO, cGMP, and PGI2 inhibitors did not block the relaxation response. Furthermore, the PGI2 inhibitor significantly enhanced the relaxation effects; K+ channel blockers had no inhibitory effects on the relaxation responses. Contrarily, GLIB improved considerably relaxation. Research suggests pomegranate juice's active ingredient may reduce uterine contractions and treat uterotonic disorders, potentially preventing preterm birth and dysmenorrhea. Further research is needed to determine its mechanism of action. Code: AEC-013 [ABSTRACT FROM AUTHOR]

Background: Proton-pump inhibitors (PPIs) and potassium-competitive acid blockers (P-CABs) are recommended for erosive esophagitis (EE), with good safety and tolerance. However, it is unclear which is the best treatment option for EE. Objectives: This study aimed to evaluate the comparative efficacy of P-CABs and PPIs for healing EE patients, seeking an appropriate treatment choice in the 4- or 8-week treatment and standard or double dose. Design: A systematic review and network meta-analysis. Data sources and methods: Relevant databases were searched to collect randomized controlled trials of PPIs and P-CABs in the treatment of EE up to 31 May 2023. Studies on standard or double-dose PPIs or P-CABs which were published in English and assessed 4- or 8-week healing effects in EE were included. A network meta-analysis was performed to evaluate the efficacy of the treatments under the frequentist framework. Sensitivity and subgroup analyses of patients with different baseline EE were also conducted. Results: In all, 34 studies involving 25,054 patients and 9 PPIs, 6 P-CABs, or placebo treatment interventions were included. The pooled 4-week healing rate was significantly statistically lower than the pooled 8-week healing rate for most treatments. Besides, the higher healing rate of double-dose treatment than standard-dose treatment was not observed in the initial treatment of most drugs. The main analysis only included studies conducted for both patients with and without severe EE at baseline, and the proportion of severe EE included in the study was >10%, Keverprazan 20 mg qd ranked best with a surface under the cumulative ranking curve (SUCRA) value of 84.7, followed by Ilaprazole 10 mg qd with a SUCRA value of 82.0, for the healing rate at 8 weeks. Sensitivity analysis showed that the results were robust. Subgroup analysis showed that most P-CABs had higher healing rates than PPIs, particularly for patients with severe EE. And the healing rate of Keverprazan 20 mg qd at 8 weeks ranked best in the subgroup without or with severe EE at baseline. Conclusion: This study showed that an 8-week treatment seemed more effective than the 4-week treatment for healing EE patients. The healing effect of Keverprazan (20 mg qd) ranked best in 8-week treatment, for both severe and non-severe EE patients. Trial registration: The study protocol was registered with INPLASY (registration number INPLASY2023120053). Plain language summary: A review and network meta-analysis of different medications for treating erosive esophagitis: potassium-competitive acid blockers and proton-pump inhibitors Why was the study done? Proton-pump inhibitors (PPIs) and potassium-competitive acid blockers (P-CABs) are commonly used to treat Erosive esophagitis (EE) due to their good safety and tolerance. This study aimed to compare the effectiveness of P-CABs and PPIs in healing EE patients. We wanted to determine the best treatment choice in terms of the duration of treatment (4 or 8 weeks) and the dosage (standard or double-dose). What did the researchers do? The researchers searched relevant databases for randomized controlled trials that studied the use of PPIs and P-CABs in treating EE up until May 31, 2023. They included studies that evaluated the healing effects of standard or double-dose PPIs or P-CABs over a period of 4 or 8 weeks. A network meta-analysis was performed to compare the effectiveness of these treatments. They also conducted sensitivity analysis and subgroup analysis to examine the effects on patients with different levels of EE. What did the researchers find? The results showed that the healing rate after 4 weeks of treatment was significantly lower than the healing rate after 8 weeks for most treatments. Additionally, the higher healing rate observed with double-dose treatment compared to standard-dose treatment was not seen in the initial treatment of most drugs. In the main analysis, which included studies with patients both with and without severe EE at the beginning, Keverprazan 20mg qd was ranked as the most effective treatment with a healing rate of 84.7, followed by Ilaprazole 10mg qd with a healing rate of 82.0 at 8 weeks. The results were robust in sensitivity analysis. Subgroup analysis showed that most P-CABs had higher healing rates than PPIs, especially for patients with severe EE. What do the findings mean? Treating EE patients for 8 weeks was more effective than treating them for 4 weeks. Keverprazan (20mg once a day) with the 8-week treatment is the optimal method. [ABSTRACT FROM AUTHOR]

Gain-of-function mutations in the KCNT1 gene, which encodes the sodium-activated potassium channel known as SLACK, are associated with the rare but devastating developmental and epileptic encephalopathy known as epilepsy of infancy with migrating focal seizures (EIMFS). The design of small molecule inhibitors of SLACK channels represents a potential therapeutic approach to the treatment of EIMFS, other childhood epilepsies, and developmental disorders. Herein, we describe a hit optimization effort centered on a xanthine SLACK inhibitor (8) discovered via a high-throughput screen. Across three distinct regions of the chemotype, we synthesized 58 new analogs and tested each one in a whole-cell automated patch-clamp assay to develop structure–activity relationships for inhibition of SLACK channels. We further evaluated selected analogs for their selectivity versus a variety of other ion channels and for their activity versus clinically relevant SLACK mutants. Selectivity within the series was quite good, including versus hERG. Analog 80 (VU0948578) was a potent inhibitor of WT, A934T, and G288S SLACK, with IC50 values between 0.59 and 0.71 µM across these variants. VU0948578 represents a useful in vitro tool compound from a chemotype that is distinct from previously reported small molecule inhibitors of SLACK channels. [ABSTRACT FROM AUTHOR]

The article explores the ongoing debate surrounding the mechanism of KATP channel closure in pancreatic β-cells. Some researchers believe that mitochondria play a crucial role in producing ATP to close the channels, while others argue that glycolytic ATP is responsible. The article presents conflicting experimental evidence from various studies and acknowledges the limitations of these studies. It also discusses the physiological differences between β-cells and heart cells, which further complicate the interpretation of the data. The article concludes by emphasizing the need for further research to determine the true mechanism of KATP channel closure in β-cells. Additionally, the authors critique a study that proposed a model involving pyruvate kinase activity and ATP production, suggesting that alternative pathways and direct evidence need to be considered. They propose that more research is necessary to fully understand the role of glycolysis in KATP channel closure in β-cells. [Extracted from the article]

Background: Schisandra chinensis (S. chinensis) is a drug commonly used in the clinical treatment of cardiovascular diseases in Traditional Chinese Medicine. However, the specific components and mechanisms of its action are still unclear. We screened six kinds of lignans from S. chinensis with high content and found that schisandrol A and schisantherin A had a strong vasorelaxant effect. The purpose of this study was to investigate the relaxation and underlying mechanism of schisandrol A in the isolated thoracic aorta of rats. Materials and Methods: Isolated rat endothelium-intact and endothelium-removed thoracic aorta strips were pre-constricted with phenylephrine (PE), and the relaxation of schisandrol A on the strips was observed. Then, the mechanism was explored by pre-incubating the strips with nitric oxide synthetase inhibitor Nɷ-nitro-l-arginine methyl ester (L-NAME), cyclooxygenase inhibitor (indomethacin), potassium channel blockers 4-aminopyridine (4-AP), barium chloride (BaCl2), tetraethylamine (TEA), and glibenclamide, respectively, and changing the calcium concentration in the bath. In addition, expressions of endothelial nitric oxide synthetase (eNOS) mRNA and protein in rat thoracic aorta were detected. Results: Schisandrol A induced both endothelium-dependent and endothelium-independent relaxation of isolated thoracic aorta strips of rats, and the mechanism might be related to promoting the synthesis of NO, inhibiting Ca2+ release from the sarcoplasmic reticulum, and blocking the Ca2+ channels. Conclusion: These discoveries may provide a theoretical basis for the traditional application of S. chinensis to treat cardiovascular disease. [ABSTRACT FROM AUTHOR]

In the realm of cardiac research, the control of spiral waves and turbulent states has been a persistent focus for scholars. Among various avenues of investigation, the modulation of ion currents represents a crucial direction. It has been proved that the methods involving combined control of currents are superior to singular approaches. While previous studies have proposed some combination strategies, further reinforcement and supplementation are required, particularly in the context of controlling arrhythmias through the combined regulation of two potassium ion currents. This study employs the Luo–Rudy phase I cardiac model, modulating the maximum conductance of the time-dependent potassium current and the time-independent potassium current, to investigate the effects of this combined modulation on spiral waves and turbulent states. Numerical simulation results indicate that, compared to modulating a single current, combining reductions in the conductance of two potassium ion currents can rapidly control spiral waves and turbulent states in a short duration. This implies that employing blockers for both potassium ion currents concurrently represents a more efficient control strategy. The control outcomes of this study represent a novel and effective combination for antiarrhythmic interventions, offering potential avenues for new antiarrhythmic drug targets. [ABSTRACT FROM AUTHOR]

Gastroesophageal reflux disease (GERD) is a chronic disorder characterized by the reflux of gastric contents into the esophagus, leading to symptoms and potential long-term complications such as Barrett esophagus and esophageal adenocarcinoma. Currently, there are various medical, endoscopic, and surgical therapeutic strategies for GERD. However, proton pump inhibitors (PPIs), which effectively suppress acid secretion but require daily administration, remain the mainstay of treatment. Noncontinuous therapy for GERD includes on-demand and different variations of intermittent administration of antireflux medication. Attributes that make an antireflux medication a good candidate for noncontinuous therapy for GERD include potent acid suppression, rapid effect, durability of antisecretory effect, and flexibility of administration. Noncontinuous therapy for GERD is appealing to patients because it is convenient, reduces cost, and alleviates concerns about complications of long-term PPI use. Patients with nonerosive esophageal reflux disease or low-grade erosive esophagitis who have episodic heartburn are probably best suited for such treatment. Although PPIs have been shown to be efficacious as on-demand or intermittent therapy for GERD, their usefulness as on-demand treatment for episodic heartburn has been limited by their slow maximal effect on intragastric acid secretion. In contrast, potassium-competitive acid blockers (P-CABs) demonstrate the pharmacokinetic and pharmacodynamic characteristics that make this class of drugs a good candidate for noncontinuous treatment of GERD. Early studies using P-CABs for noncontinuous treatment of GERD have demonstrated promising results. Future studies are needed to further establish the value of P-CABs for such a therapeutic approach. This article reviews the current evidence on the use of PPIs and P-CABs in noncontinuous therapy for GERD. [ABSTRACT FROM AUTHOR]

Tetraethylammonium (TEA), a quaternary ammonium compound, is a wellknown blocker of potassium channels belonging to various subfamilies, such as KV1-3, KCa1, 2 and prokaryotic KcsA. In many cases, TEA acts from the extracellular side by open pore blockade. TEA can also block transient receptor potential (TRP) cation channels, such as TRPM7, in a voltagedependent manner. In human T lymphocytes, intracellular (cytosolic) TEA and its analog TMA (tetramethylammonium) inhibit TRPM7 channel currents in the outward but not inward direction. By contrast, intracellular Mg2+, protons and polyamines inhibit both outward and inward current components equally. Likewise, the majority of available pharmacological tools inhibit TRPM7 channels in a voltage-independent manner. Since TRPM7 is a steeply outwardly rectifying conductance, voltage-dependent blockers can be useful for studying the cellular functions of this channel. TRPM7 protein is endogenously expressed in diverse cell lines, including HEK, HeLa, CHO, RBL and Jurkat. Using patch-clamp electrophysiology, we found that incubating HEK293 and Jurkat T cells overnight in the presence of 20 mM TEA-Cl, resulted in the nearly complete blockade of whole-cell TRPM7 outward current, measured at breakin. By contrast, the inward current was unchanged in TEA-loaded cells. The blockade was fully reversible after washout of intracellular solution in whole-cell but not in perforated-patch recording configurations. Overnight incubation with 20 mM TMA-Cl resulted in a more modest blockade of the outward TRPM7 current. Internal 129 mM TMA and TEA eliminated most of the outward current. TEA uptake in transfected HEK293 cells led to blockade of recombinant murine TRPM7 and the Mg2+ and pH insensitive Ser1107Arg variant. Unexpectedly, Tris-HCl, a widely used pH buffer, could similarly be loaded into Jurkat and HEK cells, and preferentially blocked outward TRPM7 currents. 20 mM and 129 mM Tris in the internal solution blocked TRPM7 current in outward but not inward direction. Voltage-dependent channel blockade by TEA, TMA and Tris loading will be useful for studying the properties and functions of TRPM7- mediated ion transport in intact cells. [ABSTRACT FROM AUTHOR]

Tramadol, an analgesic classified as an "atypical opioid", exhibits both opioid and non-opioid mechanisms of action. This study aimed to explore these mechanisms, specifically the opioid-, cannabinoid-, nitric oxide-, and potassium channel-based mechanisms, which contribute to the peripheral antinociception effect of tramadol, in an experimental rat model. The nociceptive threshold was determined using paw pressure withdrawal. To examine the mechanisms of action, several substances were administered intraplantarly: naloxone, a non-selective opioid antagonist (50 µg/paw); AM251 (80 µg/paw) and AM630 (100 µg/paw) as the selective antagonists for types 1 and 2 cannabinoid receptors, respectively; nitric oxide synthase inhibitors L-NOArg, L-NIO, L-NPA, and L-NIL (24 µg/paw); and the enzyme inhibitors of guanylatocyclase and phosphodiesterase of cGMP, ODQ, and zaprinast. Additionally, potassium channel blockers glibenclamide, tetraethylammonium, dequalinium, and paxillin were used. The results showed that opioid and cannabinoid receptor antagonists did not reverse tramadol's effects. L-NOarg, L-NIO, and L-NPA partially reversed antinociception, while ODQ completely reversed, and zaprinast enhanced tramadol's antinociception effect. Notably, glibenclamide blocked tramadol's antinociception in a dose-dependent manner. These findings suggest that tramadol's peripheral antinociception effect is likely mediated by the nitrergic pathway and sensitive ATP potassium channels, rather than the opioid and cannabinoid pathways. [ABSTRACT FROM AUTHOR]

Aim: Inositol 1,4,5‐trisphosphate receptors (IP3Rs) are intracellular Ca2+‐release channels with crucial roles in cell function. Current IP3R inhibitors suffer from off‐target effects and poor selectivity towards the three distinct IP3R subtypes. We developed a novel peptide inhibitor of IP3Rs and determined its effect on connexin‐43 (Cx43) hemichannels, which are co‐activated by IP3R stimulation. Methods: IP3RPEP6 was developed by in silico molecular docking studies and characterized by on‐nucleus patch‐clamp experiments of IP3R2 channels and carbachol‐induced IP3‐mediated Ca2+ responses in IP3R1, 2 or 3 expressing cells, triple IP3R KO cells and astrocytes. Cx43 hemichannels were studied by patch‐clamp and ATP‐release approaches, and by inhibition with Gap19 peptide. IP3RPEP6 interactions with IP3Rs were verified by co‐immunoprecipitation and affinity pull‐down assays. Results: IP3RPEP6 concentration‐dependently reduced the open probability of IP3R2 channels and competitively inhibited IP3Rs in an IC50 order of IP3R2 (~3.9 μM) < IP3R3 (~4.3 μM) < IP3R1 (~9.0 μM), without affecting Cx43 hemichannels or ryanodine receptors. IP3RPEP6 co‐immunoprecipitated with IP3R2 but not with IP3R1; interaction with IP3R3 varied between cell types. The IC50 of IP3RPEP6 inhibition of carbachol‐induced Ca2+ responses decreased with increasing cellular Cx43 expression. Moreover, Gap19‐inhibition of Cx43 hemichannels significantly reduced the amplitude of the IP3‐Ca2+ responses and strongly increased the EC50 of these responses. Finally, we identified palmitoyl‐8G‐IP3RPEP6 as a membrane‐permeable IP3RPEP6 version allowing extracellular application of the IP3R‐inhibiting peptide. Conclusion: IP3RPEP6 inhibits IP3R2/R3 at concentrations that have limited effects on IP3R1. IP3R activation triggers hemichannel opening, which strongly affects the amplitude and concentration‐dependence of IP3‐triggered Ca2+ responses. [ABSTRACT FROM AUTHOR]

Malaria, leishmaniasis, and African trypanosomiasis are protozoan diseases that constitute major global health problems, especially in developing countries; however, the development of drug resistance coupled with the toxicity of current treatments has hindered their management. The involvement of certain enzymes (dihydrofolate reductase [DHFR]) or proteins (potassium channels) in the pathogenesis of these protozoan diseases is undeniable. In this study, a series of three DHFR inhibitors (6-5 fused heterocyclic derivatives X, Y, and Z) and one K+ channel blocker (E4031) were screened for their inhibitory effects on Leishmania donovani, Plasmodium falciparum, and Trypanosoma brucei. A resazurin assay was used to assess the antitrypanosomal and antileishmanial activities of the test compounds, whereas the antiplasmodial activity was evaluated through the SYBR Green I test. Moreover, the cytotoxicities of the test compounds were evaluated in Vero, Raw 264.7, and HepG-2 cells using a resazurin-based test, while their pharmacokinetic properties were predicted using the online tool, pkCSM. As a result, compound Y exhibited selective (selectivity index range: from 2.69 to >61.4; Vero, Raw 264.7, and HepG-2 cells) and broad-spectrum antiprotozoal activity against L. donovani promastigotes (IC50: 12.4 µM), amastigotes (IC50: 4.28 µM), P. falciparum (IC50: 0.028 µM), and T. brucei brucei (IC50: 0.81 µM). In addition, compound X inhibited the growth of P. falciparum (IC50: 0.0052 µM) and T. brucei brucei (IC50: 6.49 µM). In silico screening of the active antiprotozoal compounds revealed positive drug likeness scores, as none of the criteria for Lipinski's rule were violated by these compounds. However, in-depth pharmacokinetic and mechanistic studies are warranted to support the discovery of novel antiprotozoal agents against malaria, leishmaniasis, and African trypanosomiasis by repurposing K+ channel blockers and DHFR inhibitors. [ABSTRACT FROM AUTHOR]

The taiep rat is a tubulin mutant with an early hypomyelination followed by progressive demyelination of the central nervous system due to a point mutation in the Tubb4a gene. It shows clinical, radiological, and pathological signs like those of the human leukodystrophy hypomyelination with atrophy of the basal ganglia and cerebellum (H-ABC). Taiep rats had tremor, ataxia, immobility episodes, epilepsy, and paralysis; the acronym of these signs given the name to this autosomal recessive trait. The aim of this study was to analyze the characteristics of somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) in adult taiep rats and in a patient suffering from H-ABC. Additionally, we evaluated the effects of 4-aminopyridine (4-AP) on sensory responses and locomotion and finally, we compared myelin loss in the spinal cord of adult taiep and wild type (WT) rats using immunostaining. Our results showed delayed SSEPs in the upper and the absence of them in the lower extremities in a human patient. In taiep rats SSEPs had a delayed second negative evoked responses and were more susceptible to delayed responses with iterative stimulation with respect to WT. MEPs were produced by bipolar stimulation of the primary motor cortex generating a direct wave in WT rats followed by several indirect waves, but taiep rats had fused MEPs. Importantly, taiep SSEPs improved after systemic administration of 4-AP, a potassium channel blocker, and this drug induced an increase in the horizontal displacement measured in a novelty-induced locomotor test. In taiep subjects have a significant decrease in the immunostaining of myelin in the anterior and ventral funiculi of the lumbar spinal cord with respect to WT rats. In conclusion, evoked potentials are useful to evaluate myelin alterations in a leukodystrophy, which improved after systemic administration of 4-AP. Our results have a translational value because our findings have implications in future medical trials for H-ABC patients or with other leukodystrophies. [ABSTRACT FROM AUTHOR]

Critical care physicians are commonly faced with patients exhibiting atrial fibrillation (AF), a cardiac arrhythmia with multifaceted origins. Recent investigations shed light on the heterogeneity among AF patients by uncovering unique AF phenotypes, characterized by differing treatment strategies and clinical outcomes. In this retrospective study encompassing 9401 AF patients in an intensive care cohort, we sought to identify differences in average treatment effects (ATEs) across different patient groups. We extract data from the MIMIC-III database, use hierarchical agglomerative clustering to identify patients' phenotypes, and assign them to treatment groups based on their initial drug administration during AF episodes. The treatment options examined included beta blockers (BBs), potassium channel blockers (PCBs), calcium channel blockers (CCBs), and magnesium sulfate (MgS). Utilizing multiple imputation and inverse probability of treatment weighting, we estimate ATEs related to rhythm control, rate control, and mortality, approximated as hourly and daily rates (%/h, %/d). Our analysis unveiled four distinctive AF phenotypes: (1) postoperative hypertensive, (2) non-cardiovascular mutlimorbid, (3) cardiovascular multimorbid, and (4) valvulopathy atrial dilation. PCBs showed the highest cardioversion rates across phenotypes, ranging from 11.6%/h (9.35–13.3) to 7.69%/h (5.80–9.22). While CCBs demonstrated the highest effectiveness in controlling ventricular rates within the overall patient cohort, PCBs and MgS outperformed them in specific phenotypes. PCBs exhibited the most favorable mortality outcomes overall, except for the non-cardiovascular multimorbid cluster, where BBs displayed a lower mortality rate of 1.33%/d [1.04–1.93] compared to PCBs' 1.68%/d [1.10–2.24]. The results of this study underscore the significant diversity in ATEs among individuals with AF and suggest that phenotype-based classification could be a valuable tool for physicians, providing personalized insights to inform clinical decision making. [ABSTRACT FROM AUTHOR]

Ciguatoxins (CTXs) are neurotoxins responsible for ciguatera poisoning (CP), which affects more than 50,000 people worldwide annually. The development of analytical methods to prevent CP is a pressing global issue, and the N2a assay is one of the most promising methods for detecting CTXs. CTXs are highly toxic, and an action level of 0.01 μg CTX1B equivalent (eq)/kg in fish has been proposed. It is desirable to further increase the detection sensitivity of CTXs in the N2a assay to detect such low concentrations reliably. The opening of voltage-gated sodium channels (NaV channels) and blocking of voltage-gated potassium channels (KV channels) are thought to be involved in the toxicity of CTXs. Therefore, in this study, we developed an assay that could detect CTXs with higher sensitivity than conventional N2a assays, using KV channel inhibitors as sensitizing reagents for N2a cells. The addition of the KV channel inhibitors 4-aminopyridine and tetraethylammonium chloride to N2a cells, in addition to the traditional sensitizing reagents ouabain and veratridine, increased the sensitivity of N2a cells to CTXs by up to approximately 4-fold. This is also the first study to demonstrate the influence of KV channels on the toxicity of CTXs in a cell-based assay. [ABSTRACT FROM AUTHOR]

Glutamate is a major excitatory neurotransmitter that mediates neuronal damage in acute and chronic brain disorders. The effect and mechanism of phillygenin, a natural compound with neuroprotective potential, on glutamate release in isolated nerve terminals (synaptosomes) prepared from the rat cerebral cortex were examined. In this study, 4-aminopyridine (4-AP), a potassium channel blocker, was utilized to induce the release of glutamate, which was subsequently quantified via a fluorometric assay. Our findings revealed that phillygenin reduced 4-AP-induced glutamate release, and this inhibitory effect was reversed by removing extracellular Ca2+ or inhibiting vesicular transport with bafilomycin A1. However, exposure to the glutamate transporter inhibitor dl-threo-beta-benzyl-oxyaspartate (dl-TOBA) did not influence the inhibitory effect. Moreover, phillygenin did not change the synaptosomal membrane potential but lowered the 4-AP-triggered increase in intrasynaptosomal Ca2+ concentration ([Ca2+]i). Antagonizing Cav2.2 (N-type) calcium channels blocked the inhibition of glutamate release by phillygenin, whereas pretreatment with the mitochondrial Na+/Ca2+ exchanger inhibitor, CGP37157 or the ryanodine receptor inhibitor, dantrolene, both of which block intracellular Ca2+ release, had no effect. The effect of phillygenin on glutamate release triggered by 4-AP was completely abolished when MAPK/ERK inhibitors were applied. Furthermore, phillygenin attenuated the phosphorylation of ERK1/2 and its major presynaptic target, synapsin I, a protein associated with synaptic vesicles. These data collectively suggest that phillygenin mediates the inhibition of evoked glutamate release from synaptosomes primarily by reducing the influx of Ca2+ through Cav2.2 calcium channels, thereby subsequently suppressing the MAPK/ERK/synapsin I signaling cascade. [ABSTRACT FROM AUTHOR]

Introduction: Proton pump inhibitor (PPI) is the mainstay therapy for the maintenance of healed erosive esophagitis (EE). It is unknown whether potassium‐competitive acid blockers (PCABs) are more efficacious and safer than PPIs. Methods: Only randomized controlled trials (RCTs) comparing PCABs to PPIs in the maintenance of healing rates of endoscopically proven healed EE and indexed in MEDLINE, EMBASE, and CENTRAL until 3 February 2024, were included. A fixed‐effects model meta‐analysis was performed to pool primary efficacy outcome (maintenance of healing rates at week 24) and safety data (any treatment‐emergent adverse event or TEAE). The risk of bias was assessed using Cochrane's Risk of Bias 2 (RoB2) tool. Results: Four RCTs with a total of 2554 patients were eligible for inclusion. All trials were of low risk of bias. Compared to lansoprazole 15 mg, the maintenance rates of healed EE at week 24 were significantly higher with vonoprazan 10 mg (RR 1.13; 95% CI 1.07–1.19) and vonoprazan 20 mg (RR 1.15; 95% CI 1.10–1.21). Likewise, compared to lansoprazole 15 mg, any TEAEs were significantly greater with vonoprazan 20 mg (RR 1.10; 95% CI 1.01–1.20) but not vonoprazan 10 mg. Conclusion: Vonoprazan 10 and 20 mg were superior to lansoprazole 15 mg in the maintenance of the healing of EE. Any TEAEs were greater with vonoprazan 20 mg. [ABSTRACT FROM AUTHOR]

The Kv4.2 potassiumchannel plays established roles in neuronal excitability, while also being implicated in plasticity. Current means to study the roles of Kv4.2 are limited, motivating us to design a genetically encoded membrane tethered Heteropodatoxin-2 (MetaPoda). We find that MetaPoda is an ultrapotent and selective gating-modifier of Kv4.2. We narrow its site of contact with the channel to two adjacent residues within the voltage sensitive domain (VSD) and, with docking simulations, suggest that the toxin binds the VSD from within the membrane. We also show that MetaPoda does not require an external linker of the channel for its activity. In neurons (obtained from female and male rat neonates), MetaPoda specifically, and potently, inhibits all Kv4 currents, leaving all other A-type currents unaffected. Inhibition of Kv4 in hippocampal neurons does not promote excessive excitability, as is expected from a simple potassium channel blocker. We do find that MetaPoda’s prolonged expression (1 week) increases expression levels of the immediate early gene cFos and prevents potentiation. These findings argue for a major role of Kv4.2 in facilitating plasticity of hippocampal neurons. Lastly, we show that our engineering strategy is suitable for the swift engineering of another potent Kv4.2-selective membrane-tethered toxin, Phrixotoxin-1, denoted MetaPhix. Together, we provide two uniquely potent genetic tools to study Kv4.2 in neuronal excitability and plasticity. [ABSTRACT FROM AUTHOR]

The compound 3,4‐diaminopyridine (3,4‐AP), a derivative of 4‐aminopyridine (4‐AP), is used in the symptomatic treatment of fatigue in multiple sclerosis as well as Lambert–Eaton myasthenia syndrome whereas the parent compound 4‐AP is used as an acetylcholine‐releasing drug, in serum, saliva, and urine. 4‐AP is an experimental drug that may reduce symptoms in some people with multiple sclerosis, particularly those who are more sensitive to heat. The carbon nanotubes (CNTs) have inside cavity tethering on the surface upon functionalization and adsorption on the walls of CNTs, which provides extra ability to carry pharmaceutical agents through multiple ways. Due to these benefits, this communication will discuss the comparative changes in geometry, electronic properties, and shielding parameters of 4‐AP and 3,4‐AP absorbed C56H16. The DFT/B3LYP/6–31G (d, p) method is used for the first time to report electronic structure and interaction parameters on the CNT surface. The same level theory is used to discuss the thermodynamic stability of CNT‐4‐AP/3,4‐AP. The calculated UV spectra of CNT are compared with UV spectra of CNT‐4‐AP and 3,4‐AP by using the same level theory in a water solvent, which provides a better comprehension of CNT as a drug delivery system after absorption of the 4‐AP and 3,4‐AP in the human body. The nature and strength of interactions have been discussed with the help of AIM analysis, and the frontier orbital highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) gap, chemical softness, and chemical hardness have been calculated to understand its complete chemical properties. The characters of the frontier molecular orbitals are discussed and analyzed by comparing the DOS spectra of CNT with CNT‐4‐AP/3,4‐AP. [ABSTRACT FROM AUTHOR]

Natural compounds, known for diverse pharmacological properties, have attracted attention as potential sources for hypertension treatment. Previous studies have revealed the hypotensive effect and vascular relaxation of prunetin, a natural compound derived from Prunus yedoensis. However, the potential blood pressure-lowering and vasorelaxant effects of sakuranetin, another representative compound found in plants belonging to the genus Prunus, have remained unexplored. We aimed to fill this gap by investigating the hypotensive and vasorelaxant effects of sakuranetin in rats. Results indicated that sakuranetin, particularly in the sakuranetin 20 mg/kg group, led to significant reductions in systolic blood pressure (SBP) and diastolic blood pressure (DBP) by −14.53 ± 5.64% and −19.83 ± 6.56% at 4 h after administration. In the sakuranetin 50 mg/kg group, the SBP and DBP decreased by −13.27 ± 6.86% and −16.62 ± 10.01% at 2 h and by −21.61 ± 4.49% and −30.45 ± 5.21% at 4 h after administration. In addition, we identified the vasorelaxant effects of sakuranetin, attributing its mechanisms to the inhibition of calcium influx and the modulation of angiotensin II. Considering its hypotensive and vasorelaxant effects, sakuranetin could potentially serve as an antihypertensive agent. However, further research is required to evaluate the safety and long-term efficacy. [ABSTRACT FROM AUTHOR]

Stimulation of the calcium‐sensing receptor (CaSR) induces both vasoconstrictions and vasorelaxations but underlying cellular processes remain unclear. This study investigates expression and effect of stimulating the CaSR by increasing external Ca2+ concentration ([Ca2+]o) on contractility of rat mesenteric arteries. Immunofluorescence studies showed expression of the CaSR in perivascular nerves, vascular smooth muscle cells (VSMCs), and vascular endothelium cells. Using wire myography, increasing [Ca2+]o from 1 to 10 mM induced vasorelaxations which were inhibited by the calcilytic Calhex‐231 and partially dependent on a functional endothelium. [Ca2+]o‐induced vasorelaxations were reduced by endothelial NO synthase (eNOS, L‐NAME) and large conductance Ca2+‐activated K+ channels (BKCa, iberiotoxin), with their inhibitory action requiring a functional endothelium. [Ca2+]o‐induced vasorelaxations were also markedly inhibited by an ATP‐dependent K+ channel (KATP) blocker (PNU37883), which did not require a functional endothelium to produce its inhibitory action. Inhibitor studies also suggested contributory roles for inward rectifying K+ channels (Kir), Kv7 channels, and small conductance Ca2+‐activated K+ channels (SKCa) on [Ca2+]o‐induced vasorelaxations. These findings indicate that stimulation of the CaSR mediates vasorelaxations involving multiple pathways, including an endothelium‐dependent pathway involving NO production and activation of BKCa channels and an endothelium‐independent pathway involving stimulation of KATP channels. [ABSTRACT FROM AUTHOR]

Background: The present study aimed to investigate whether levcromakalim, a KATP channel opener, induces migraine attacks in people with migraine pre-treated with erenumab, a monoclonal CGRP receptor antibody. Methods: In this double-blind, placebo-controlled, two-way cross-over study, adults with migraine without aura received a subcutaneous injection of 140 mg of erenumab on day 1. Subsequently, they were randomized to receive a 20-minute infusion of 0.05 mg/ml levcromakalim or placebo on two experimental days separated by at least one week (between days 8 and 21). The primary endpoint was the difference in the incidence of migraine attacks between levcromakalim and placebo during the 12-hour post-infusion period. Results: In total, 16 participants completed the study. During the 12-hour observation period, 14 (88%) of 16 participants experienced migraine attacks after levcromakalim, compared to two (12%) after placebo (p < 0.001). The area under the curve for median headache intensity was greater after levcromakalim than placebo (p < 0.001). Levcromakalim elicited dilation of the superficial temporal artery during the first hour after infusion, a response absent following placebo (p < 0.001). Conclusions: The induction of migraine attacks via opening of KATP channels appears independent of CGRP receptor activation. [ABSTRACT FROM AUTHOR]

The leukotrienes, lipid mediators, have a role in gastric damage induced by ethanol. Here, the gastroprotective effect of montelukast, an antagonist of the leukotriene receptor, and the involvement of the NO-cGMP-K ATP channel pathway, were evaluated in gastric damage induced by ethanol in rats. For this, l -arginine, l -NAME, methylene blue (guanylate cyclase inhibitor), sildenafil, diazoxide, or glibenclamide (ATP-sensitive potassium channel blocker) were administered 30 min before montelukast (0.1, 1, 10, and 20 mg/kg, by mouth [p.o.]). After 1 h, to induce gastric damage, the rats received absolute ethanol (4 mL/kg, p.o.), and then microscopic, macroscopic, and pro-inflammatory parameters (TNF-α and IL-1β) were assessed. Results obtained here revealed that montelukast significantly attenuated the macroscopic and microscopic lesions induced by ethanol. Montelukast also reduced IL-1β and TNF-α levels. It was also observed that NOS inhibitor (l -NAME), methylene blue, and glibenclamide inhibited the effects of montelukast in the stomach. Moreover, the NO precursor (l -arginine), the PDE-5 inhibitor (sildenafil), and a potassium channel opener (diazoxide) before montelukast produced gastroprotective effects. In conclusion, the effect of montelukast against gastric lesions induced by ethanol is mediated, at least in part, through the pathway of the NO-cGMP-K ATP channel. • Montelukast produced a gastroprotective effect in ethanol-induced gastric damage. • The NO-cGMP-K ATP channels pathway has an involvement in the effect of montelukast. • Montelukast attenuated TNF-α and IL-1β levels in ethanol-induced gastric damage. • Montelukast attenuated TNF-α through the NO-cGMP-K ATP channels pathway. [ABSTRACT FROM AUTHOR]

Modulation of mitochondrial K channels represents a pharmacological strategy to promote cardioprotective effects. Isothiocyanates emerge as molecules capable of releasing hydrogen sulfide (H2S), an endogenous pleiotropic gasotransmitter responsible for anti-ischemic cardioprotective effects also through the involvement of mitoK channels. Erucin (ERU) is a natural isothiocyanate resulting from the enzymatic hydrolysis of glucosinolates (GSLs) present in Eruca sativa Mill. seeds, an edible plant of the Brassicaceae family. In this experimental work, the specific involvement of mitoKATP channels in the cardioprotective effect induced by ERU was evaluated in detail. An in vivo preclinical model of acute myocardial infarction was reproduced in rats to evaluate the cardioprotective effect of ERU. Diazoxide was used as a reference compound for the modulation of potassium fluxes and 5-hydroxydecanoic acid (5HD) as a selective blocker of KATP channels. Specific investigations on isolated cardiac mitochondria were carried out to evaluate the involvement of mitoKATP channels. The results obtained showed ERU cardioprotective effects against ischemia/reperfusion (I/R) damage through the involvement of mitoKATP channels and the consequent depolarizing effect, which in turn reduced calcium entry and preserved mitochondrial integrity. [ABSTRACT FROM AUTHOR]

Background: Cancer-associated fibroblasts (CAFs), the predominant stromal cell of tumor microenvironment (TME), play an important role in tumor progression and immunoregulation by remodeling extracellular matrix (ECM) and secreting cytokines. However, little is known about the details of the underlying mechanism in bladder cancer. Methods: Bioinformatics analysis was performed to analyze the prognostic value of CAFs and CXCL12 using GEO, TCGA and SRA databases. The effects of CXCL12 on bladder cancer progression were investigated through in vitro and in vivo assays. The biological mechanism of the effect of CXCL12 on PDL1 were investigated using western blotting, immunoprecipitation, RT-PCR, immunofluorescence, mass spectrometry, protein stability, and flow cytometry. Results: The results demonstrated that CAFs-derived CXCL12 promoted cancer cell migration and invasion and upregulated PDL1. Mechanistically, upon binding to its specific receptor, CXCL12 activated the downstream JAK2/STAT3 pathway and rapidly up-regulated the expression of deubiquitinase CYLD. CYLD deubiquitinated P62 causing P62 accumulation, which in turn inhibited the autophagic degradation of PDL1. In vivo experiments demonstrated that blocking CXCL12 inhibited tumor growth, reduced tumor PDL1 expression and increased immune cell infiltration. Conclusions: This study revealed a novel mechanism for the role of CXCL12 in P62-mediated PDL1 autophagic regulation. Combined application of CXCL12 receptor blocker and PD1/PDL1 blocker can more effectively inhibit PDL1 expression and enhance antitumor immune response. Targeting CAFs-derived CXCL12 may provide an effective strategy for immunotherapy in bladder cancer. [ABSTRACT FROM AUTHOR]

Locked azobenzenes (LAB) derivatives are recognized as photoswitchable potassium ion channel blockers. Here we report the effect of tetraethyl ammonium ion (TEA) substituent and KcsA K+‐ion channel protein environment on the thermodynamic stability and vertical excitation energy of locked azobenzene. The complete active space self‐consistent field (CASSCF and state‐averaged CASSCF, SA2‐CAS) with complete active space perturbation theory (state‐averaged CASPT2, SA2‐CASPT2) and our own n‐layered integrated molecular orbital and molecular mechanics—mechanical embedding (ONIOM‐ME) followed by electronic embedding (ONIOM‐EE) methods were employed for the study. The Z‐isomer of LAB is thermodynamically more stable as compared to E‐isomer. The substitution of tetraethyl ammonium ion does not influence the thermodynamic stability. On the other hand, the thermodynamic stability is reversed in the protein environment. Furthermore, the vertical excitation energies (VEE) and geometrical parameters show that the photochemistry of LAB is unaffected by para‐substituted TEA. However, geometrical changes imposed by the protein on the confined LAB‐TEA decreases the VEE. [ABSTRACT FROM AUTHOR]

Pheochromocytomas/paragangliomas (PPGLs) are neuroendocrine tumours, mostly resulting from mutations in predisposing genes. Mutations of succinate dehydrogenase (SDH) subunit B (SDHB) are associated with high probability of metastatic disease. Since bioelectrical properties and signalling in cancer are an emerging field, we investigated the metabolic, functional and electrophysiological characteristics in human succinate dehydrogenase subunit B (SDHB)-deficient pheochromocytoma cells. These cells exhibited reduced SDH function with elevated succinate-to-fumarate ratio and reduced intracellular ATP levels. The analysis of membrane passive properties revealed a more hyperpolarized membrane potential and a lower cell capacitance of SDHB-deficient cells compared to the parental ones. These bioelectrical changes were associated with reduced proliferation and adhesion capacity of SDHB-deficient cells. Only in SDHB-deficient cells, we also observed an increased amplitude of potassium currents suggesting an activation of ATP-sensitive potassium channels (KATP). Indeed, exposure of the SDHB-deficient cells to glibenclamide, a specific KATP inhibitor, or to ATP caused normalization of potassium current features and altered proliferation and adhesion. In this work, we show for the first time that reduced intracellular ATP levels in SDHB-deficient chromaffin cells impaired cell bioelectrical properties, which, in turn, are associated with an increased cell aggressiveness. Moreover, we first ever demonstrated that glibenclamide not only reduced the outward potassium currents in SDHB-deficient cells but increased their growth capacity, reduced their ability to migrate and shifted their phenotype towards one more similar to that of parental one. [ABSTRACT FROM AUTHOR]

Hyperkalemia, especially chronic elevated potassium, is a common problem in patients with certain diseases. Although dietary changes and diuretics can have an impact, many people will require additional therapy with potassium binders which may allow patients to maximize their current disease medications. [ABSTRACT FROM AUTHOR]

Ezetimibe is a lipid-lowering agent that selectively inhibits cholesterol absorption by binding to the Niemann–Pick C1-like 1 (NPC1L1) protein. Although it is well known that administration of ezetimibe in hypercholesterolemia patients reduces the risk of cardiovascular events through attenuation of atherosclerosis, studies on the direct effect of ezetimibe on vascular function are not sufficient. The aim of the present study was to investigate the vascular effects of ezetimibe in rat mesenteric arteries. In the present study, 12-week-old male Sprague Dawley rats were used. After the rats were sacrificed, the second branches of the mesenteric arteries were isolated and cut into 2–3 mm segments and mounted in a multi-wire myography system to measure isometric tension. Ezetimibe reduced vasoconstriction induced by U46619 (500 nM) in endothelium-intact and endothelium-denuded arteries. Ezetimibe-induced vasodilation was not affected by the endothelial nitric oxide synthase (eNOS) inhibitor Nω-Nitro-L-arginine (L-NNA, 300 μM) or the non-selective potassium channel blocker, tetraethylammonium (TEA, 10 mM). Moreover, ezetimibe also completely blocked the contraction induced by an increase in external calcium concentration. Ezetimibe significantly reduced vascular contraction induced by L-type Ca2+ channel activator (Bay K 8644, 30 nM). Treatment with ezetimibe decreased the phosphorylation level of 20 kDa myosin light chain (MLC20) in vascular smooth muscle cells. In the present study, we found that ezetimibe has a significant vasodilatory effect in rat mesenteric resistance arteries. These results suggest that ezetimibe may have beneficial cardiovascular effects beyond its cholesterol-lowering properties. [ABSTRACT FROM AUTHOR]

Recent advances in immuno-oncology have opened up new and impressive treatment options for cancer. Notwithstanding, overcoming the limitations of the current FDA-approved therapies with monoclonal antibodies (mAbs) that block the PD-1/PD-L1 pathway continues to lead to the testing of multiple approaches and optimizations. Recently, a series of macrocyclic peptides have been developed that exhibit binding strengths to PD-L1 ranging from sub-micromolar to micromolar. In this study, we present the most potent non-antibody-based PD-1/PD-L1 interaction inhibitor reported to date. The structural and biological characterization of this macrocyclic PD-L1 targeting peptide provides the rationale for inhibition of both PD-1/PD-L1 and CD80/PD-L1 complexes. The IC50 and EC50 values obtained in PD-L1 binding assays indicate that the pAC65 peptide has potency equivalent to the current FDA-approved mAbs and may have similar activity to the BMS986189 peptide, which entered the clinical trial and has favorable safety and pharmacokinetic data. The data presented here delineate the generation of similar peptides with improved biological activities and applications not only in the field of cancer immunotherapy but also in other disorders related to the immune system. [ABSTRACT FROM AUTHOR]

Objective(s): The present research aimed to identify the functional effects and underlying mechanisms of metformin on the rat thoracic aorta. Materials and Methods: Thoracic aorta segments of Wistar Albino rats were put in the chambers of an isolated tissue bath system. The resting tone was adjusted to 1 g. Following the equilibration time, potassium chloride or phenylephrine was used to contract the vascular segments. The vessel segments were cumulatively treated with metformin (10-7-10-3 M) when a steady contraction was achieved. The described experimental approach was repeated after incubations with signaling pathway inhibitors and selective blockers of potassium channels to identify the effect mechanisms of metformin. Results: Metformin had a potent vasorelaxant effect in a concentration-dependent way (P<0.001). After the endothelium was removed, the vasorelaxant effect level of metformin was significantly reduced. The level of vasorelaxant effect of metformin was increased by the maintenance of perivascular adipose tissue. Following administrations of L-NAME, methylene blue, compound C, BIM-I, and potassium channel blockers, the level of vasodilatory action of metformin was significantly reduced (P<0.001). Conclusion: According to the results of this investigation, metformin significantly relaxes the thoracic aorta segments of rats. Metformin-mediated vasorelaxation involves the activation of numerous subtypes of potassium channels, including BKCa, IKCa, Kv, Kir, and K2p channels, as well as endothelium-dependent processes, including AMPK and eNOS/NO/sGS signaling pathways. Moreover, metformin-induced vasorelaxation is mediated through PVAT activation and the PKC signaling pathway. [ABSTRACT FROM AUTHOR]

Salvia hispanica L., commonly known as chía, and its seeds have been used since ancient times to prepare different beverages. Due to its nutritional content, it is considered a dietary ingredient and has been reported with many health benefits. Chia seed components are helpful in cardiovascular disease (CVD) by reducing blood pressure, platelet aggregation, cholesterol, and oxidation. Still, its vasodilator effects on the vascular system were not reported yet. The hexanic (HESh), dichloromethanic (DESh), and methanolic (MESh) extracts obtained from chía seeds were evaluated on an aortic ring ex-vivo experimental model. The vasorelaxant efficacy and mechanism of action were determined. Also, phytochemical data was obtained through 13C NMR-based dereplication. The MESh extract showed the highest efficacy (Emax = 87%), and its effect was partially endothelium-dependent. The mechanism of action was determined experimentally, and the vasorelaxant curves were modified in the presence of L-NAME, ODQ, and potassium channel blockers. MESh caused a relaxing effect on KCl 80 mM-induced contraction and was less potent than nifedipine. The CaCl2-induced contraction was significantly decreased compared with the control curve. Phytochemical analysis of MESh suggests the presence of mannitol, previously reported as a vasodilator on aortic rings. Our findings suggest NO-cGMP pathway participation as a vasodilator mechanism of action of S. hispanica seeds; this effect can be attributed, in part, to the mannitol presence. S. hispanica could be used in future research focused on antihypertensive therapies. [ABSTRACT FROM AUTHOR]

Simple Summary: This was a study into how doxapram (a therapeutic compound with the capacity to block K2p channel function), pH, and the interactions between the two affect cardiac function in larval Drosophila, with resulting insight into mammalian cardiac function and general physiology. Two-P-domain K+ (K2p) channels are responsible for maintaining the resting membrane potential. K2p channels have varied expression in healthy tissue, but they also change in cancerous or diseased states. The correlation and causation as regards the alteration of K2p channel expression are still being investigated. The compound doxapram seems to block K2p channels and depolarize cells. Using Drosophila, the increased expression of the ORK1 K2p channel in cardiac and skeletal muscle was investigated. The heart rate in larval Drosophila is very sensitive to pH, and since doxapram blocks a subset of the K2p channels that are known to be acid-sensitive, it was postulated that doxapram would affect heart rate. A pH change from 7.1 to 6.5 increased the rate, while that from 7.1 to 7.5 decreased the rate. An amount of 0.1 mM of doxapram had no effect, but 0.5 of mM depressed Drosophila heart rates within five minutes. Exposure to 5 mM of doxapram immediately decreased the rate. Lipopolysaccharides (LPSs) from Gram-negative bacteria acutely increased the rate. LPSs activate K2p channels in the skeletal muscle of larvae and are blocked by doxapram. LPSs slightly reduce depression in the rate induced by doxapram. The overexpression of K2p channels in the heart and skeletal muscle depressed the heart rate and heightened pH sensitivity. At larval neuromuscular junctions, the overexpression in skeletal muscle increases the frequency of spontaneous quantal events and produces a more negative resting membrane potential. [ABSTRACT FROM AUTHOR]

KCNH2 loss-of-function mutations cause long QT syndrome type 2 (LQT2), an inherited cardiac disorder associated with life-threatening ventricular arrhythmia. Through whole-exome sequencing, we discovered a novel AGCGACAC deletion (S981fs) in the hERG gene of an LQT2 patient. Using a heterologous expression system and patch clamping, we found that the mutant K channel had reduced cell surface expression and lower current amplitude compared to the wild type. However, functional expression was restored by lowering temperature and using potassium channel inhibitors or openers (E4031, cisapride, nicorandil). Co-immunoprecipitation experiments confirmed the assembly of mutant proteins with wild-type hERG. Confocal imaging showed decreased hERG distribution on the cell membrane in cells expressing S981fs. Notably, treatment with G418 significantly increased hERG current in wild-type/S981fs heterozygotes. In conclusion, our study identifies a novel hERG mutation leading to impaired Kv11.1 function due to trafficking and nonsense-mediated RNA decay defects. These findings shed light on the mechanisms underlying LQT2 and offer potential therapeutic avenues. [ABSTRACT FROM AUTHOR]

Gout is the most common inflammatory arthritis associated with interleukin-1β (IL-1β) accumulation during exacerbation. In this study, we aimed to clarify whether potassium channel antagonists attenuate local inflammation in mice with monosodium urate (MSU)-induced gout.Methods: We cultured human macrophage THP-1 cells and evaluated the molecular levels of both IL-1β and potassium channels stimulated with MSU and/or potassium channel antagonists. Acute gout models were generated in IL-1β luciferase transgenic male mice using synovium-like subcutaneous air pouches with MSU injection. Their luciferase activities were monitored following potassium channel blocker treatment using the IVIS Spectrum CT imaging system. The lavages and tissues were extracted from their air pouches, followed by cell counting and pathological analysis.Results: MSU stimulation increased the gene expression levels of pro-IL-1β, P2x7r and Kv1.3, whereas the expression of Kcnq1 was decreased in phorbol 12-myristate 13-acetate-induced THP-1 cells. Both high and low concentrations of the P2x7 receptor inhibitor adenosine 5′-triphosphate (ATP) derivative periodate oxidized ATP (oATP) decreased the production of IL-1β in the supernatant of THP-1 cells. The sixth hour was the peak time of IL-1β luciferase activity after MSU intervention in vivo. oATP ameliorated the synovial IL-1β luciferase activity, reduced inflammatory cell infiltration and alleviated the erosive damage in the cartilage.Conclusion: The anti-inflammatory properties of potassium channel inhibitors, especially of oATP, might point to new strategies for local anti-inflammatory therapy for acute gout. [ABSTRACT FROM AUTHOR]

Methadone is a chiral synthetic opioid primarily used to treat heroin and prescription-opioid addiction: the (R)-enantiomer (Levomethadone) activates the µ-opioid receptor more potently than the (S)-enantiomer, which is a more potent blocker of the hERG potassium channels, resulting in QTc prolongation. The purpose of this retrospective study was to assess the effect of methadone on the QTc interval and to investigate the benefits of Levomethadone. The electrocardiograms of 165 patients taking methadone at various dosages and for different periods of time were examined: the QTc value was manually measured and then adjusted using Bazett's formula. Data analysis revealed a linear association between the dosage of methadone and QTc length; no correlation was found between the QTc value and gender, age, or duration of therapy. In total, 14% of the sample (23 patients) showed a prolongation of the QTc interval (>470 ms in males and >480 ms in females); 10 of the 23 patients with QTc elongation underwent a change of therapy from Methadone to Levomethadone—in 90% of these patients, a normalization in the QTc length was established. This study confirmed the role of methadone, specifically its dosage, in QTc prolongation and the efficiency of Levomethadone as an adequate therapeutic substitute in these circumstances. This study validates the importance of careful electrocardiographic monitoring in methadone-treated patients. [ABSTRACT FROM AUTHOR]

When screening new drugs to treat retinal diseases, ex vivo electroretinography (ERG) potentially combines the experimental throughput of its traditional in vivo counterpart, with greater mechanistic insight and reproducible delivery. To date, this technique was used in experiments with open loop superfusion and lasting up to a few hours. Here, we present a compact apparatus that provides continuous and simultaneous recordings of the scotopic a-waves from four mouse retinas for much longer durations. Crucially, each retina can be incubated at 37 °C in only 2 mL of static medium, enabling the testing of very expensive drugs or nano devices. Light sensitivity and response kinetics of these preparations remain in the physiological range throughout incubation, displaying only very slow drifts. As an example application, we showed that barium, a potassium channel blocker used to abolish the glial component of the ERG, displayed no overt side effects on photoreceptors over several hours. In another example, we fully regenerated a partially bleached retina using a minimal quantity of 9-cis-retinal. Finally, we demonstrated that including antibiotic in the incubation medium extends physiological light responses to over one day. This system represents a necessary stepping stone towards the goal of combining ERG recordings with organotypically cultured retinas. [ABSTRACT FROM AUTHOR]

Aedes aegypti (Ae. aegypti) saliva induces a variety of anti-inflammatory and immunomodulatory activities. Interestingly, although it is known that mosquito bites cause allergic reactions in sensitised hosts, the primary exposure of humans to Ae. aegypti does not evoke significant itching. Whether active components in the saliva of Ae. aegypti can counteract the normal itch reaction to injury produced by a histaminergic or non-histaminergic pathway in vertebrate hosts is unknown. This study investigated the effects of Ae. aegypti mosquito salivary gland extract (SGE) on sensitive reactions such as itching and associated skin inflammation. Acute pruritus and plasma extravasation were induced in mice by the intradermal injection of either compound 48/80 (C48/80), the Mas-related G protein-coupled receptor (Mrgpr) agonist chloroquine (CQ), or the transient receptor potential ankyrin 1 (TRPA1) agonist allyl isothiocyanate (AITC). The i.d. co-injection of Ae. aegypti SGE inhibited itching, plasma extravasation, and neutrophil influx evoked by C48/80, but it did not significantly affect mast cell degranulation in situ or in vitro. Additionally, SGE partially reduced CQ- and AITC-induced pruritus in vivo, suggesting that SGE affects pruriceptive nerve firing independently of the histaminergic pathway. Activation of TRPA1 significantly increased intracellular Ca2+ in TRPA-1-transfected HEK293t lineage, which was attenuated by SGE addition. We showed for the first time that Ae. aegypti SGE exerts anti-pruriceptive effects, which are partially regulated by the histamine-independent itch TRPA1 pathway. Thus, SGE may possess bioactive molecules with therapeutic potential for treating nonhistaminergic itch. [ABSTRACT FROM AUTHOR]

Reactions of pial arteries to exogenous hydrogen sulfide exposure and assessment of the contribution of KATP and BKCa channels to H2S-mediated dilation was studied in rats of different ages. Intravital microphotography in Sprague-Dawley rats aged 4 and 18 months was used to study the reactions of pial arteries of various diameters to the exposure of exogenous hydrogen sulfide donor solution—sodium hydrosulfide (NaHS, 30 µM), as well as their change with the preliminary use of potassium channel blockers: KATP (glibenclamide, 10 µM) and BKCa (tetraethyl ammonium, 2 mM). It was found that inhibition of H2S-mediated dilation of pial arteries and increase in constrictor responses to exogenous hydrogen sulfide exposure are taking place in rats with age. Age-related changes in H2S-induced dilatory response of the pial arteries in rats depend on the size of the vessels. With age, there is a decrease in the number of dilations of pial arteries with a diameter of more than 20 µm. At the same time, aging does not affect the dilatation of smaller arteries. These disorders are probably associated with changes in the processes caused by the activation of potassium channels. It was found that aging is accompanied by the increasing of KATP-channels contribution to the implementation of H2S-mediated dilation in pial arteries with diameters less than 40 µm. BKCa-channels contribution to the dilatation decreases with age. In 18-months-old rats, these channels barely participate in H2S-mediated dilation in arteries with diameters more than 20 µm. [ABSTRACT FROM AUTHOR]

Objective: To investigate the role of Ca2+-activated small conductance SK3 potassium channels in Cu-Aβ complex-induced microglial activation and the downstream signaling pathway. Methods: The Cu-Aβ complex-induced release of tumor necrosis factor-α (TNF-α) and hydrogen peroxide (H2O2) in cell culture supernatants were detected using ELISA and the Amplex Red reagent. The levels of mRNA and protein of potassium channels as well as phosphorylation levels of related signaling molecules were detected by qPCR and Western blot. Results: (1) The experimental results of pretreatment with different ion channel blockers or potassium channel blockers of different subtypes showed that SK3 channels may mediate microglial activation caused by Cu-Aβ complex. (2) The results of qPCR and Western blot detection showed that Cu-Aβ complex could upregulate SK3 mRNA and protein expression in microglia. (3) The application of SK3-siRNA to knock down SK3 expression showed that the downregulation of SK3 expression significantly inhibited microglial activation caused by Cu-Aβ complex. (4) The experimental results of Western blot detection showed that PI3K/Akt signaling and ERK signaling were involved in microglial activation caused by Cu-Aβ complex. (5) The results of experiments using specific blockers of signaling molecules further showed that SK3 channels may lie upstream of the PI3K/Akt-ERK signaling pathway during the microglial activation induced by the Cu-Aβ complex. Conclusions: SK3 channels mediate microglial inflammatory responses induced by Cu-Aβ complex through the downstream PI3K/Akt-ERK signaling pathway [ABSTRACT FROM AUTHOR]

Background/Aim: Networks of glioma cells are linked to small groups of pacemaker cells in which levels of calcium ions pulse periodically, driving a signal through the network that causes tumor growth. Using inhibitors, one study blocked the activity of the Ca2+ activated potassium-channel protein KCa3.1 in in vitro models and mice, preventing the proliferation of glioma cells and tumor expansion. Marked reduction of tumor cell viability occurred within the entire network, as well as reduced tumor growth in mice and extended animal survival. Materials and Methods: KCa3.1 is encoded by the gene potassium calcium-activated channel subfamily N member 4 (KCNN4) on the chromosomal location 19q13.31. We used the Cancer Genome Atlas (TCGA) to evaluate the effect of KCNN4 on human glioma survival in the TCGA Lower Grade Glioma (LGG) dataset. Results: In humans, KCNN4 is prognostic in glioma; high expression is unfavorable. In addition, KCNN4 copy number variations are prognostic. Increased masked copy number segments are unfavorable in lower grade glioma. KCNN4 is lost in gliomas with the 1p 19q co-deletion, which may explain in part the comparatively favorable prognosis of 1p 19q co-deletion tumors. Conclusion: Our finding of increased KCNN4 expression related to poor survival in human lower grade glioma suggests that developing novel therapies, such as KCa3.1-inhibiting drugs, might be worthwhile. [ABSTRACT FROM AUTHOR]