Two-Pore-Domain Potassium (K2P-) Channels: Cardiac Expression Patterns and Disease-Specific Remodelling Processes

Fluoxetine antagonizes the acute response of LPS: Blocks K2P channels

The channels responsible for maintaining resting membrane potential are known as K2P (two-P-domain K+ subunit) channels, a subset of which are known to be blocked by Fluoxetine. In this experiment, the compound's effects on the membrane potential were examined on muscles in larval Drosophila overexpressing a subtype of K2P channel (known in Drosophila as dORKA1 or ORKA1) and compared to larvae without overexpression. The compound was also observed in sequence and/or combination with a form of lipopolysaccharide (LPS) that transiently activates K2P channels. Different concentrations of Fluoxetine were tested, and it was also examined in cocktail with the LPS. At 25 μM Fluoxetine exposure, muscle in control larvae underwent depolarization, while muscles overexpressing K2P channels hyperpolarized; at 50 μM, however, much more variable responses were observed. The LPS caused hyperpolarization in both larval strains, but the effect was more transient in the Canton-S line than in the K2P overexpressors. Finally, LPS continued to cause hyperpolarization even in the presence of Fluoxetine, while Fluoxetine quickly depolarized the muscle during exposure to LPS. The cocktail showed a smaller effect on muscles overexpressing ORKA1 as compared to the controls, indicating that Fluoxetine does not block the ORKA1 subtype. This study is significant because it demonstrates how overexpression of K2P channels alters membrane response to LPS and Fluoxetine exposure.

Associations Between Preoperative Shortness of Breath and Potassium Channels Gene Variations in Women With Breast Cancer

OBJECTIVES

Shortness of breath is a common symptom in patients with cancer. However, the mechanisms that underlie this troublesome symptom are poorly understood. Therefore, this study aimed to determine the prevalence of and associated risk factors for shortness of breath in women prior to breast cancer surgery and identify associations between shortness of breath and polymorphisms for potassium channel genes.

METHODS

Patients were recruited prior to breast cancer surgery and completed a self-report questionnaire on the occurrence of shortness of breath. Genotyping of single nucleotides polymorphism (SNPs) in potassium channel genes was performed using a custom array. Multiple logistic regression analyses were done to identify associations between the occurrence of shortness of breath and SNPs in ten candidate genes.

RESULTS

Of the 398 patients, 11.1% reported shortness of breath. These patients had a lower annual household income, a higher comorbidity burden, and a lower functional status. After controlling for functional status, comorbidity burden, genomic estimates of ancestry and self-reported race and ethnicity, the genetic associations that remained significant in the multiple regression analyses were for potassium voltage-gated channel subfamily D (KCND2) rs12673992, potassium voltage-gated channel modifier subfamily S (KCNS1) rs4499491, and potassium two pore channel subfamily K (KCNK2) rs4411107.

CONCLUSIONS

While these findings warrant replication, they suggest that alterations in potassium channel function may contribute to the occurrence of shortness of breath in women prior to breast cancer surgery.

Circulating Autoantibodies Targeting TREK-1 in Patients With Short-Coupled Ventricular Fibrillation

BACKGROUND

Short-coupled ventricular fibrillation (SCVF) is increasingly being recognized as a distinct primary electrical disorder and cause of otherwise unexplained cardiac arrest. However, the pathophysiology of SCVF remains largely elusive. Despite extensive genetic screening, there is no convincing evidence of a robust monogenic disease gene, thus raising the speculations for alternative pathogeneses. The role of autoimmune mechanisms in SCVF has not been investigated so far. The objective of this study was to screen for circulating autoantibodies in patients with SCVF and assess their role in arrhythmogenesis.

METHODS

This is a prospective, single-center, case-control study enrolling cardiac arrest survivors diagnosed with SCVF or idiopathic ventricular fibrillation (IVF) between 2019 and 2023 at the Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval Inherited Arrhythmia Clinic in Canada. Plasma samples were screened for autoantibodies targeting cardiac ion channels using peptide microarray technology. Identified target autoantibodies were then purified from pooled plasma samples for subsequent cellular electrophysiological studies.

RESULTS

Fourteen patients with SCVF (n=4 [29% of patients] female patients; median age, 45 years [interquartile range: 36, 59]; n=14 [100% of patients] non-Hispanic White) and 19 patients with idiopathic ventricular fibrillation (n=8 [42%] female patients; median age, 49 years [38, 57]; n=19 [100%] non-Hispanic White) were enrolled in the study and compared with 38 (n=20 [53%] female subjects; median age, 45 years [29, 66]; n=36 [95%] non-Hispanic White) sex-, age- and ethnicity-matched healthy controls. During the study period, 11 (79%) SCVF probands experienced ventricular fibrillation recurrence after a median of 4.3 months (interquartile range, 0.3-20.7). Autoantibodies targeting cardiac TREK-1 (TWIK [tandem of pore-domains in a weakly inward rectifying potassium channel]-related potassium channel 1 were identified in 7 (50%) patients with SCVF (P=0.049). Patch clamp experiments demonstrated channel-activating properties of anti-TREK-1 autoantibodies that are antagonized by quinidine in both HEK293 cells and human induced pluripotent stem cell-derived cardiomyocytes.

CONCLUSIONS

Patients with SCVF harbor circulating autoantibodies against the cardiac TREK-1 channel. Anti-TREK-1 autoantibodies not only present the first reported biomarker for SCVF, but our functional studies also suggest a direct implication in the arrhythmogenesis of SCVF.

The effects of doxapram and its potential interactions with K2P channels in experimental model preparations

The channels commonly responsible for maintaining cell resting membrane potentials are referred to as K2P (two-P-domain K+ subunit) channels. These K+ ion channels generally remain open but can be modulated by their local environment. These channels are classified based on pharmacology, pH sensitivity, mechanical stretch, and ionic permeability. Little is known about the physiological nature of these K2P channels in invertebrates. Acidic conditions depolarize neurons and muscle fibers, which may be caused by K2P channels given that one subtype can be blocked by acidic conditions. Doxapram is used clinically as a respiratory aid known to block acid-sensitive K2P channels; thus, the effects of doxapram on the muscle fibers and synaptic transmission in larval Drosophila and crawfish were monitored. A dose-dependent response was observed via depolarization of the larval Drosophila muscle and an increase in evoked synaptic transmission, but doxapram blocked the production of action potentials in the crawfish motor neuron and had a minor effect on the resting membrane potential of the crawfish muscle. This indicates that the nerve and muscle tissues in larval Drosophila and crawfish likely express different K2P channel subtypes. Since these organisms serve as physiological models for neurobiology and physiology, it would be of interest to further investigate what types of K2P channel are expressed in these tissues. (212 words).

SARS-CoV-2 ORF 3a-mediated currents are inhibited by antiarrhythmic drugs

AIMS

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been linked to cardiovascular complications, notably cardiac arrhythmias. The open reading frame (ORF) 3a of the coronavirus genome encodes for a transmembrane protein that can function as an ion channel. The aim of this study was to investigate the role of the SARS-CoV-2 ORF 3a protein in COVID-19-associated arrhythmias and its potential as a pharmacological target.

METHODS AND RESULTS

Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) and cultured human fibroblasts were infected with SARS-CoV-2. Subsequent immunoblotting assays revealed the expression of ORF 3a protein in hiPSC-CM but not in fibroblasts. After intracytoplasmic injection of RNA encoding ORF 3a proteins into Xenopus laevis oocytes, macroscopic outward currents could be measured. While class I, II, and IV antiarrhythmic drugs showed minor effects on ORF 3a-mediated currents, a robust inhibition was detected after application of class III antiarrhythmics. The strongest effects were observed with dofetilide and amiodarone. Finally, molecular docking simulations and mutagenesis studies identified key amino acid residues involved in drug binding.

CONCLUSION

Class III antiarrhythmic drugs are potential inhibitors of ORF 3a-mediated currents, offering new options for the treatment of COVID-19-related cardiac complications.

The Effect of Calcium Ions on Resting Membrane Potential

Regulating membrane potential is key to cellular function. For many animal cells, resting membrane potential is predominantly driven by a family of K2P (two-pore domain) potassium channels. These channels are commonly referred to as leak channels, as their presence results in the membrane being permeable to K+ ions. These channels, along with various pumps and exchangers, keep the cell resting membrane potential (Rp) relatively close to potassium's equilibrium potential (EK); however, in many cells, the resting membrane potential is more depolarized than the EK due to a small Na+ ion leak. Raising [Ca2+]O (extracellular Ca2+ concentration) can result in hyperpolarization of the membrane potential from the resting state. The mechanism for this hyperpolarization likely lies in the blockage of a Na+ leak channel (NALCN) and/or voltage-gated Na+ channels. The effects may also be connected to calcium-activated potassium channels. Using Drosophila melanogaster, we here illustrate that changing [Ca2+]O from 0.5 to 3 mM hyperpolarizes the muscle. Replacing NaCl with LiCl or choline chloride still led to hyperpolarization when increasing [Ca2+]O. Replacing CaCl2 with BaCl2 results in depolarization. K2P channel overexpression in the larval muscle greatly reduces the effects of [Ca2+]O on cell membrane potential, likely because potential is heavily driven by the EK in these muscles. These experiments provide an understanding of the mechanisms behind neuronal hypo-excitability during hypercalcemia, as well as the effects of altered expression of K2P channels on membrane potential.

The principles and promising future of sonogenetics for precision medicine

Sonogenetics is an emerging medical technology that uses acoustic waves to control cells through sonosensitive mediators (SSMs) that are genetically encoded, thus remotely and non-invasively modulating specific molecular events and/or biomolecular functions. Sonogenetics has opened new opportunities for targeted spatiotemporal manipulation in the field of gene and cell-based therapies due to its inherent advantages, such as its noninvasive nature, high level of safety, and deep tissue penetration. Sonogenetics holds impressive potential in a wide range of applications, from tumor immunotherapy and mitigation of Parkinsonian symptoms to the modulation of neural reward pathway, and restoration of vision. This review provides a detailed overview of the mechanisms and classifications of established sonogenetics systems and summarizes their applications in disease treatment and management. The review concludes by highlighting the challenges that hinder the further progress of sonogenetics, paving the way for future advances.

Evolution of two-pore domain potassium channels and their gene expression in zebrafish embryos

BACKGROUND

The two-pore domain potassium (K2P) channels are a major type of potassium channels that maintain the cell membrane potential by conducting passive potassium leak currents independent of voltage change. They play prominent roles in multiple physiological processes, including neuromodulation, perception of pain, breathing and mood control, and response to volatile anesthetics. Mutations in K2P channels have been linked to many human diseases, such as neuronal and cardiovascular disorders and cancers. Significant progress has been made to understand their protein structures, physiological functions, and pharmacological modifiers. However, their expression and function during embryonic development remain largely unknown.

RESULTS

We employed the zebrafish model and identified 23 k2p genes using BLAST search and gene cloning. We first analyzed vertebrate K2P channel evolution by phylogenetic and syntenic analyses. Our data revealed that the six subtypes of the K2P genes have already evolved in invertebrates long before the emergence of vertebrates. Moreover, the vertebrate K2P gene number increased, most likely due to two whole-genome duplications. Furthermore, we examined zebrafish k2p gene expression during early embryogenesis by in situ hybridization. Each subgroup's genes showed similar but distinct gene expression domains with some exceptions. Most of them were expressed in neural tissues consistent with their known function of neural excitability regulation. However, a few k2p genes were expressed temporarily in specific tissues or organs, suggesting that these K2P channels may be needed for embryonic development.

CONCLUSIONS

Our phylogenetic and developmental analyses of K2P channels shed light on their evolutionary history and potential roles during embryogenesis related to their physiological functions and human channelopathies.

Real-time prognostic biomarkers for predicting in-hospital mortality and cardiac complications in COVID-19 patients

Hospitalized patients with Coronavirus disease 2019 (COVID-19) are highly susceptible to in-hospital mortality and cardiac complications such as atrial arrhythmias (AA). However, the utilization of biomarkers such as potassium, B-type natriuretic peptide, albumin, and others for diagnosis or the prediction of in-hospital mortality and cardiac complications has not been well established. The study aims to investigate whether biomarkers can be utilized to predict mortality and cardiac complications among hospitalized COVID-19 patients. Data were collected from 6,927 hospitalized COVID-19 patients from March 1, 2020, to March 31, 2021 at one quaternary (Henry Ford Health) and five community hospital registries (Trinity Health Systems). A multivariable logistic regression prediction model was derived using a random sample of 70% for derivation and 30% for validation. Serum values, demographic variables, and comorbidities were used as input predictors. The primary outcome was in-hospital mortality, and the secondary outcome was onset of AA. The associations between predictor variables and outcomes are presented as odds ratio (OR) with 95% confidence intervals (CIs). Discrimination was assessed using area under ROC curve (AUC). Calibration was assessed using Brier score. The model predicted in-hospital mortality with an AUC of 90% [95% CI: 88%, 92%]. In addition, potassium showed promise as an independent prognostic biomarker that predicted both in-hospital mortality, with an AUC of 71.51% [95% Cl: 69.51%, 73.50%], and AA with AUC of 63.6% [95% Cl: 58.86%, 68.34%]. Within the test cohort, an increase of 1 mEq/L potassium was associated with an in-hospital mortality risk of 1.40 [95% CI: 1.14, 1.73] and a risk of new onset of AA of 1.55 [95% CI: 1.25, 1.93]. This cross-sectional study suggests that biomarkers can be used as prognostic variables for in-hospital mortality and onset of AA among hospitalized COVID-19 patients.

Physiological role of potassium channels in mammalian germ cell differentiation, maturation, and capacitation

BACKGROUND

Ion channels are essential for differentiation and maturation of germ cells, and even for fertilization in mammals. Different types of potassium channels have been identified, which are grouped into voltage-gated channels (Kv), ligand-gated channels (Kligand ), inwardly rectifying channels (Kir ), and tandem pore domain channels (K2P ).

MATERIAL-METHODS

The present review includes recent findings on the role of potassium channels in sperm physiology of mammals.

RESULTS-DISCUSSION

While most studies conducted thus far have been focused on the physiological role of voltage- (Kv1, Kv3, and Kv7) and calcium-gated channels (SLO1 and SLO3) during sperm capacitation, especially in humans and rodents, little data about the types of potassium channels present in the plasma membrane of differentiating germ cells exist. In spite of this, recent evidence suggests that the content and regulation mechanisms of these channels vary throughout spermatogenesis. Potassium channels are also essential for the regulation of sperm cell volume during epididymal maturation and for preventing premature membrane hyperpolarization. It is important to highlight that the nature, biochemical properties, localization, and regulation mechanisms of potassium channels are species-specific. In effect, while SLO3 is the main potassium channel involved in the K+ current during sperm capacitation in rodents, different potassium channels are implicated in the K+ outflow and, thus, plasma membrane hyperpolarization during sperm capacitation in other mammalian species, such as humans and pigs.

CONCLUSIONS

Potassium conductance is essential for male fertility, not only during sperm capacitation but throughout the spermiogenesis and epididymal maturation.

Up-regulated expression of two-pore domain K+ channels, KCNK1 and KCNK2, is involved in the proliferation and migration of pulmonary arterial smooth muscle cells in pulmonary arterial hypertension

Background

Pulmonary arterial hypertension (PAH) is a severe and rare disease in the cardiopulmonary system. Its pathogenesis involves vascular remodeling of the pulmonary artery, which results in progressive increases in pulmonary arterial pressure. Chronically increased pulmonary arterial pressure causes right ventricular hypertrophy and subsequent right heart failure. Pulmonary vascular remodeling is attributed to the excessive proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs), which are induced by enhanced Ca2+ signaling following the up-/down-regulation of ion channel expression.

Objectives

In the present study, the functional expression of two-pore domain potassium KCNK channels was investigated in PASMCs from idiopathic PAH (IPAH) patients and experimental pulmonary hypertensive (PH) animals.

Results

In IPAH-PASMCs, the expression of KCNK1/TWIK1 and KCNK2/TREK1 channels was up-regulated, whereas that of KCNK3/TASK1 and KCNK6/TWIK2 channels was down-regulated. The similar up-regulated expression of KCNK1 and KCNK2 channels was observed in the pulmonary arterial smooth muscles of monocrotaline-induced PH rats, Sugen 5416/hypoxia-induced PH rats, and hypoxia-induced PH mice. The facilitated proliferation of IPAH-PASMCs was suppressed by the KCNK channel blockers, quinine and tetrapentylammonium. The migration of IPAH-PASMCs was also suppressed by these channel blockers. Furthermore, increases in the proliferation and migration were inhibited by the siRNA knockdown of KCNK1 or KCNK2 channels. The siRNA knockdown also caused membrane depolarization and subsequent decrease in cytosolic [Ca2+]. The phosphorylated level of c-Jun N-terminal kinase (JNK) was elevated in IPAH-PASMCs compared to normal-PASMCs. The increased phosphorylation was significantly reduced by the siRNA knockdown of KCNK1 or KCNK2 channels.

Conclusion

Collectively, these findings indicate that the up-regulated expression of KCNK1 and KCNK2 channels facilitates the proliferation and migration of PASMCs via enhanced Ca2+ signaling and JNK signaling pathway, which is associated with vascular remodeling in PAH.

Rapid weather changes are associated with daily hospital visitors for atrial fibrillation accompanied by abnormal ECG repolarization: a case-crossover study

BACKGROUND

Atrial fibrillation (AF) is highly prevalent in the population, yet the factors contributing to AF events in susceptible individuals remain partially understood. The potential relationship between meteorological factors and AF, particularly with abnormal electrocardiograph (ECG) repolarization, has not been adequately studied. This case-crossover study aims to investigate the association between meteorological factors and daily hospital visits for AF with abnormal ECG repolarization in Shanghai, China.

METHODS

The study cohort comprised 10,325 patients with ECG-confirmed AF who sought treatment at Shanghai Sixth People's Hospital between 2015 and 2018. Meteorological and air pollutant concentration data were matched with the patient records. Using a case-crossover design, we analyzed the association between meteorological factors and the daily count of hospital visitors for AF with abnormal ECG repolarization at our AF center. Lag analysis models were applied to examine the temporal relationship between meteorological factors and AF events.

RESULTS

The analysis revealed statistically significant associations between AF occurrence and specific meteorological factors. AF events were significantly associated with average atmospheric pressure (lag 0 day, OR 0.9901, 95% CI 0.9825-0.9977, P < 0.05), average temperature (lag 1 day, OR 0.9890, 95% CI 0.9789-0.9992, P < 0.05), daily pressure range (lag 7 days, OR 1.0195, 95% CI 1.0079-1.0312, P < 0.01), and daily temperature range (lag 5 days, OR 1.0208, 95% CI 1.0087-1.0331, P < 0.01). Moreover, a significant correlation was observed between daily pressure range and daily temperature range with AF patients, particularly those with abnormal ECG repolarization, as evident in the case-crossover analysis.

CONCLUSION

This study highlights a significant correlation between meteorological factors and daily hospital visits for AF accompanied by abnormal ECG repolarization in Shanghai, China. In addition, AF patients with abnormal ECG repolarization were found to be more vulnerable to rapid daily changes in pressure and temperature compared to AF patients without such repolarization abnormalities.

Activation of neurokinin-III receptors modulates human atrial TASK-1 currents

RATIONALE

The neurokinin-III receptor was recently shown to regulate atrial cardiomyocyte excitability by inhibiting atrial background potassium currents. TASK-1 (hK2P3.1) two-pore-domain potassium channels, which are expressed atrial-specifically in the human heart, contribute significantly to atrial background potassium currents. As TASK-1 channels are regulated by a variety of intracellular signalling cascades, they represent a promising candidate for mediating the electrophysiological effects of the Gq-coupled neurokinin-III receptor.

OBJECTIVE

To investigate whether TASK-1 channels mediate the neurokinin-III receptor activation induced effects on atrial electrophysiology.

METHODS AND RESULTS

In Xenopus laevis oocytes, heterologously expressing neurokinin-III receptor and TASK-1, administration of the endogenous neurokinin-III receptor ligands substance P or neurokinin B resulted in a strong TASK-1 current inhibition. This could be reproduced by application of the high affinity neurokinin-III receptor agonist senktide. Moreover, preincubation with the neurokinin-III receptor antagonist osanetant blunted the effect of senktide. Mutagenesis studies employing TASK-1 channel constructs which lack either protein kinase C (PKC) phosphorylation sites or the domain which is regulating the diacyl glycerol (DAG) sensitivity domain of TASK-1 revealed a protein kinase C independent mechanism of TASK-1 current inhibition: upon neurokinin-III receptor activation TASK-1 channels are blocked in a DAG-dependent fashion. Finally, effects of senktide on atrial TASK-1 currents could be reproduced in patch-clamp measurements, performed on isolated human atrial cardiomyocytes.

CONCLUSIONS

Heterologously expressed human TASK-1 channels are inhibited by neurokinin-III receptor activation in a DAG dependent fashion. Patch-clamp measurements, performed on human atrial cardiomyocytes suggest that the atrial-specific effects of neurokinin-III receptor activation on cardiac excitability are predominantly mediated via TASK-1 currents.

Physiological and pathophysiological roles of the KCNK3 potassium channel in the pulmonary circulation and the heart

Potassium channel subfamily K member 3 (KCNK3), encoded by the KCNK3 gene, is part of the two-pore domain potassium channel family, constitutively active at resting membrane potentials in excitable cells, including smooth muscle and cardiac cells. Several physiological and pharmacological mediators, such as intracellular signalling pathways, extracellular pH, hypoxia and anaesthetics, regulate KCNK3 channel function. Recent studies show that modulation of KCNK3 channel expression and function strongly influences pulmonary vascular cell and cardiomyocyte function. The altered activity of KCNK3 in pathological situations such as atrial fibrillation, pulmonary arterial hypertension and right ventricular dysfunction demonstrates the crucial role of KCNK3 in cardiovascular homeostasis. Furthermore, loss of function variants of KCNK3 have been identified in patients suffering from pulmonary arterial hypertension and atrial fibrillation. This review focuses on current knowledge of the role of the KCNK3 channel in pulmonary circulation and the heart, in healthy and pathological conditions.

Cloxyquin activates hTRESK by allosteric modulation of the selectivity filter

The TWIK-related spinal cord K⁺ channel (TRESK, K_2P18.1) is a K_2P channel contributing to the maintenance of membrane potentials in various cells. Recently, physiological TRESK function was identified as a key player in T-cell differentiation rendering the channel a new pharmacological target for treatment of autoimmune diseases. The channel activator cloxyquin represents a promising lead compound for the development of a new class of immunomodulators. Identification of cloxyquin binding site and characterization of the molecular activation mechanism can foster the future drug development. Here, we identify the cloxyquin binding site at the M2/M4 interface by mutational scan and analyze the molecular mechanism of action by protein modeling as well as in silico and in vitro electrophysiology using different permeating ion species (K⁺ / Rb⁺). In combination with kinetic analyses of channel inactivation, our results suggest that cloxyquin allosterically stabilizes the inner selectivity filter facilitating the conduction process subsequently activating hTRESK.

Chinese herbal medicine for the treatment of cardiovascular diseases ─ targeting cardiac ion channels

Cardiovascular disease (CVD) remains the leading cause of morbidity and mortality, imposing an increasing global health burden. Cardiac ion channels (voltage-gated Na_V, Ca_V, K_Vs, and others) synergistically shape the cardiac action potential (AP) and control the heartbeat. Dysfunction of these channels, due to genetic mutations, transcriptional or post-translational modifications, may disturb the AP and lead to arrhythmia, a major risk for CVD patients. Although there are five classes of anti-arrhythmic drugs available, they can have varying levels of efficacies and side effects on patients, possibly due to the complex pathogenesis of arrhythmias. As an alternative treatment option, Chinese herbal remedies have shown promise in regulating cardiac ion channels and providing anti-arrhythmic effects. In this review, we first discuss the role of cardiac ion channels in maintaining normal heart function and the pathogenesis of CVD, then summarize the classification of Chinese herbal compounds, and elaborate detailed mechanisms of their efficacy in regulating cardiac ion channels and in alleviating arrhythmia and CVD. We also address current limitations and opportunities for developing new anti-CVD drugs based on Chinese herbal medicines.

Flavonoids as Modulators of Potassium Channels

Potassium channels are widely distributed integral proteins responsible for the effective and selective transport of K+ ions through the biological membranes. According to the existing structural and mechanistic differences, they are divided into several groups. All of them are considered important molecular drug targets due to their physiological roles, including the regulation of membrane potential or cell signaling. One of the recent trends in molecular pharmacology is the evaluation of the therapeutic potential of natural compounds and their derivatives, which can exhibit high specificity and effectiveness. Among the pharmaceuticals of plant origin, which are potassium channel modulators, flavonoids appear as a powerful group of biologically active substances. It is caused by their well-documented anti-oxidative, anti-inflammatory, anti-mutagenic, anti-carcinogenic, and antidiabetic effects on human health. Here, we focus on presenting the current state of knowledge about the possibilities of modulation of particular types of potassium channels by different flavonoids. Additionally, the biological meaning of the flavonoid-mediated changes in the activity of K+ channels will be outlined. Finally, novel promising directions for further research in this area will be proposed.

Electrical Remodelling in Cardiac Disease

The human heart responds to various diseases with structural, mechanical, and electrical remodelling processes [...].

Progress on role of ion channels of cardiac fibroblasts in fibrosis

Cardiac fibrosis is defined as excessive deposition of extracellular matrix (ECM) in pathological conditions. Cardiac fibroblasts (CFs) activated by injury or inflammation differentiate into myofibroblasts (MFs) with secretory and contractile functions. In the fibrotic heart, MFs produce ECM which is composed mainly of collagen and is initially involved in maintaining tissue integrity. However, persistent fibrosis disrupts the coordination of excitatory contractile coupling, leading to systolic and diastolic dysfunction, and ultimately heart failure. Numerous studies have demonstrated that both voltage- and non-voltage-gated ion channels alter intracellular ion levels and cellular activity, contributing to myofibroblast proliferation, contraction, and secretory function. However, an effective treatment strategy for myocardial fibrosis has not been established. Therefore, this review describes the progress made in research related to transient receptor potential (TRP) channels, Piezo1, Ca²⁺ release-activated Ca²⁺ (CRAC) channels, voltage-gated Ca²⁺ channels (VGCCs), sodium channels, and potassium channels in myocardial fibroblasts with the aim of providing new ideas for treating myocardial fibrosis.

Advances in the Understanding of Two-Pore Domain TASK Potassium Channels and Their Potential as Therapeutic Targets

TWIK-related acid-sensitive K⁺ (TASK) channels, including TASK-1, TASK-3, and TASK-5, are important members of the two-pore domain potassium (K_2P) channel family. TASK-5 is not functionally expressed in the recombinant system. TASK channels are very sensitive to changes in extracellular pH and are active during all membrane potential periods. They are similar to other K_2P channels in that they can create and use background-leaked potassium currents to stabilize resting membrane conductance and repolarize the action potential of excitable cells. TASK channels are expressed in both the nervous system and peripheral tissues, including excitable and non-excitable cells, and are widely engaged in pathophysiological phenomena, such as respiratory stimulation, pulmonary hypertension, arrhythmia, aldosterone secretion, cancers, anesthesia, neurological disorders, glucose homeostasis, and visual sensitivity. Therefore, they are important targets for innovative drug development. In this review, we emphasized the recent advances in our understanding of the biophysical properties, gating profiles, and biological roles of TASK channels. Given the different localization ranges and biologically relevant functions of TASK-1 and TASK-3 channels, the development of compounds that selectively target TASK-1 and TASK-3 channels is also summarized based on data reported in the literature.

Research Progress on Natural Products’ Therapeutic Effects on Atrial Fibrillation by Regulating Ion Channels

Antiarrhythmic drugs (AADs) have a therapeutic effect on atrial fibrillation (AF) by regulating the function of ion channels. However, several adverse effects and high recurrence rates after drug withdrawal seriously affect patients’ medication compliance and clinical prognosis. Thus, safer and more effective drugs are urgently needed. Active components extracted from natural products are potential choices for AF therapy. Natural products like Panax notoginseng (Burk.) F.H. Chen, Sophora flavescens Ait., Stephania tetrandra S. Moore., Pueraria lobata (Willd.) Ohwi var. thomsonii (Benth.) Vaniot der Maesen., and Coptis chinensis Franch. have a long history in the treatment of arrhythmia, myocardial infarction, stroke, and heart failure in China. Based on the classification of chemical structures, this article discussed the natural product components’ therapeutic effects on atrial fibrillation by regulating ion channels, connexins, and expression of related genes, in order to provide a reference for development of therapeutic drugs for atrial fibrillation.