Voltage-gated potassium channels as therapeutic targets

Transforming growth factor-beta 1 enhances discharge activity of cortical neurons

JOURNAL/nrgr/04.03/01300535-202502000-00031/figure1/v/2024-05-28T214302Z/r/image-tiff Transforming growth factor-beta 1 (TGF-β1) has been extensively studied for its pleiotropic effects on central nervous system diseases. The neuroprotective or neurotoxic effects of TGF-β1 in specific brain areas may depend on the pathological process and cell types involved. Voltage-gated sodium channels (VGSCs) are essential ion channels for the generation of action potentials in neurons, and are involved in various neuroexcitation-related diseases. However, the effects of TGF-β1 on the functional properties of VGSCs and firing properties in cortical neurons remain unclear. In this study, we investigated the effects of TGF-β1 on VGSC function and firing properties in primary cortical neurons from mice. We found that TGF-β1 increased VGSC current density in a dose- and time-dependent manner, which was attributable to the upregulation of Nav1.3 expression. Increased VGSC current density and Nav1.3 expression were significantly abolished by preincubation with inhibitors of mitogen-activated protein kinase kinase (PD98059), p38 mitogen-activated protein kinase (SB203580), and Jun NH2-terminal kinase 1/2 inhibitor (SP600125). Interestingly, TGF-β1 significantly increased the firing threshold of action potentials but did not change their firing rate in cortical neurons. These findings suggest that TGF-β1 can increase Nav1.3 expression through activation of the ERK1/2-JNK-MAPK pathway, which leads to a decrease in the firing threshold of action potentials in cortical neurons under pathological conditions. Thus, this contributes to the occurrence and progression of neuroexcitatory-related diseases of the central nervous system.

In situ self-referenced intracellular two-electrode system for enhanced accuracy in single-cell analysis

Since the emergence of single-cell electroanalysis, the two-electrode system has become the predominant electrochemical system for real-time behavioral analysis of single-cell and multicellular populations. However, due to the transmembrane placement of the two electrodes, cellular activities can be interrupted by the transmembrane potentials, and the test results are susceptible to influences from factors such as intracellular solution, membrane, and bulk solution. These limitations impede the advancement of single-cell analysis. Here, we propose a highly miniaturized and integrated in situ self-referenced intracellular two-electrode system (IS-SRITES), wherein both the working and reference electrodes are positioned inside the cell. Additionally, we demonstrated the stability (0.28 mV/h) of the solid-contact in situ Ag/AgCl reference electrode and the ability of the system to conduct standard electrochemical testing in a wide pH range (pH 6.0-8.0). Cell experiments confirmed the non-destructive performance of the electrode system towards cells and its capacity for real-time monitoring of intra- and extracellular pH values. Moreover, through equivalent circuits, finite element simulations, and drug delivery experiments, we illustrated that the IS-SRITES can yield more accurate test results and exhibit enhanced resistance to interference from the extracellular environment. Our proposed system holds the potential to enable the precise detection of intracellular substances and optimize the existing model of the electrode system for intracellular signal detection, thereby spearheading advancements in single-cell analysis.

Voltage-gated potassium channel 1.3: A promising molecular target in multiple disease therapy

Voltage-gated potassium channel 1.3 (Kv1.3) has emerged as a pivotal player in numerous biological processes and pathological conditions, sparking considerable interest as a potential therapeutic target across various diseases. In this review, we present a comprehensive examination of Kv1.3 channels, highlighting their fundamental characteristics and recent advancements in utilizing Kv1.3 inhibitors for treating autoimmune disorders, neuroinflammation, and cancers. Notably, Kv1.3 is prominently expressed in immune cells and implicated in immune responses and inflammation associated with autoimmune diseases and chronic inflammatory conditions. Moreover, its aberrant expression in certain tumors underscores its role in cancer progression. While preclinical studies have demonstrated the efficacy of Kv1.3 inhibitors, their clinical translation remains pending. Molecular imaging techniques offer promising avenues for tracking Kv1.3 inhibitors and assessing their therapeutic efficacy, thereby facilitating their development and clinical application. Challenges and future directions in Kv1.3 inhibitor research are also discussed, emphasizing the significant potential of targeting Kv1.3 as a promising therapeutic strategy across a spectrum of diseases.

Oxidant-induced disruption of vascular K+ channel function: implications for diabetic vasculopathy

Diabetes in humans a chronic metabolic disorder characterised by hyperglycaemia, it is associated with an increased risk of cardiovascular disease, disruptions to metabolism and vascular functions. It is also linked to oxidative stress and its complications. Its role in vascular dysfunctions is generally reported without detailed impact on the molecular mechanisms. Potassium ion channel (K+ channels) are key regulators of vascular tone, and as membrane proteins, are modifiable by oxidant stress associated with diabetes. This review manuscript examined the impact of oxidant stress on vascular K+ channel functions in diabetes, its implication in vascular complications and metabolic and cardiovascular diseases.

Second-generation antipsychotic quetiapine blocks voltage-dependent potassium channels in coronary arterial smooth muscle cells

Voltage-dependent K+ (Kv) channels play an important role in restoring the membrane potential to its resting state, thereby maintaining vascular tone. In this study, native smooth muscle cells from rabbit coronary arteries were used to investigate the inhibitory effect of quetiapine, an atypical antipsychotic agent, on Kv channels. Quetiapine showed a concentration-dependent inhibition of Kv channels, with an IC50 of 47.98 ± 9.46 μM. Although quetiapine (50 μM) did not alter the steady-state activation curve, it caused a negative shift in the steady-state inactivation curve. The application of 1 and 2 Hz train steps in the presence of quetiapine significantly increased the inhibition of Kv current. Moreover, the recovery time constants from inactivation were prolonged in the presence of quetiapine, suggesting that its inhibitory action on Kv channels is use (state)-dependent. The inhibitory effects of quetiapine were not significantly affected by pretreatment with Kv1.5, Kv2.1, and Kv7 subtype inhibitors. Based on these findings, we conclude that quetiapine inhibits Kv channels in both a concentration- and use (state)-dependent manner. Given the physiological significance of Kv channels, caution is advised in the use of quetiapine as an antipsychotic due to its potential side effects on cardiovascular Kv channels.

KCNH5 deletion increases autism susceptibility by regulating neuronal growth through Akt/mTOR signaling pathway

Recent clinical studies have highlighted mutations in the voltage-gated potassium channel Kv10.2 encoded by the KCNH5 gene among individuals with autism spectrum disorder (ASD). Our preliminary study found that Kv10.2 was decreased in the hippocampus of valproic acid (VPA) - induced ASD rats. Nevertheless, it is currently unclear how KCNH5 regulates autism-like features, or becomes a new target for autism treatment. We employed KCNH5 knockout (KCNH5-/-) rats and VPA - induced ASD rats in this study. Then, we used behavioral assessments, combined with electrophysiological recordings and hippocampal brain slice, to elucidate the impact of KCNH5 deletion and environmental factors on neural development and function in rats. We found that KCNH5-/- rats showed early developmental delay, neuronal overdevelopment, and abnormal electroencephalogram (EEG) signals, but did not exhibit autism-like behavior. KCNH5-/- rats exposed to VPA (KCNH5-/--VPA) exhibit even more severe autism-like behaviors and abnormal neuronal development. The absence of KCNH5 excessively enhances the activity of the Protein Kinase B (Akt)/Mechanistic Target of Rapamycin (mTOR) signaling pathway in the hippocampus of rats after exposure to VPA. Overall, our findings underscore the deficiency of KCNH5 increases the susceptibility to autism under environmental exposures, suggesting its potential utility as a target for screening and diagnosis in ASD.

rdHSV-CA8 non-opioid analgesic gene therapy decreases somatosensory neuronal excitability by activating Kv7 voltage-gated potassium channels

Chronic pain is common and inadequately treated, making the development of safe and effective analgesics a high priority. Our previous data indicate that carbonic anhydrase-8 (CA8) expression in dorsal root ganglia (DRG) mediates analgesia via inhibition of neuronal ER inositol trisphosphate receptor-1 (ITPR1) via subsequent decrease in ER calcium release and reduction of cytoplasmic free calcium, essential to the regulation of neuronal excitability. This study tested the hypothesis that novel JDNI8 replication-defective herpes simplex-1 viral vectors (rdHSV) carrying a CA8 transgene (vHCA8) reduce primary afferent neuronal excitability. Whole-cell current clamp recordings in small DRG neurons showed that vHCA8 transduction caused prolongation of their afterhyperpolarization (AHP), an essential regulator of neuronal excitability. This AHP prolongation was completely reversed by the specific Kv7 channel inhibitor XE-991. Voltage clamp recordings indicate an effect via Kv7 channels in vHCA8-infected small DRG neurons. These data demonstrate for the first time that vHCA8 produces Kv7 channel activation, which decreases neuronal excitability in nociceptors. This suppression of excitability may translate in vivo as non-opioid dependent behavioral- or clinical analgesia, if proven behaviorally and clinically.

The Pentameric Ligand-Gated Ion Channel Family: A New Member of the Voltage Gated Ion Channel Superfamily?

In this report we present seven lines of bioinformatic evidence supporting the conclusion that the Pentameric Ligand-gated Ion Channel (pLIC) Family is a member of the Voltage-gated Ion Channel (VIC) Superfamily. In our approach, we used the Transporter Classification Database (TCDB) as a reference and applied a series of bioinformatic methods to search for similarities between the pLIC family and members of the VIC superfamily. These include: (1) sequence similarity, (2) compatibility of topology and hydropathy profiles, (3) shared domains, (4) conserved motifs, (5) similarity of Hidden Markov Model profiles between families, (6) common 3D structural folds, and (7) clustering analysis of all families. Furthermore, sequence and structural comparisons as well as the identification of a 3-TMS repeat unit in the VIC superfamily suggests that the sixth transmembrane segment evolved into a re-entrant loop. This evidence suggests that the voltage-sensor domain and the channel domain have a common origin. The classification of the pLIC family within the VIC superfamily sheds light onto the topological origins of this family and its evolution, which will facilitate experimental verification and further research into this superfamily by the scientific community.

MultiToxPred 1.0: a novel comprehensive tool for predicting 27 classes of protein toxins using an ensemble machine learning approach

Protein toxins are defense mechanisms and adaptations found in various organisms and microorganisms, and their use in scientific research as therapeutic candidates is gaining relevance due to their effectiveness and specificity against cellular targets. However, discovering these toxins is time-consuming and expensive. In silico tools, particularly those based on machine learning and deep learning, have emerged as valuable resources to address this challenge. Existing tools primarily focus on binary classification, determining whether a protein is a toxin or not, and occasionally identifying specific types of toxins. For the first time, we propose a novel approach capable of classifying protein toxins into 27 distinct categories based on their mode of action within cells. To accomplish this, we assessed multiple machine learning techniques and found that an ensemble model incorporating the Light Gradient Boosting Machine and Quadratic Discriminant Analysis algorithms exhibited the best performance. During the tenfold cross-validation on the training dataset, our model exhibited notable metrics: 0.840 accuracy, 0.827 F1 score, 0.836 precision, 0.840 sensitivity, and 0.989 AUC. In the testing stage, using an independent dataset, the model achieved 0.846 accuracy, 0.838 F1 score, 0.847 precision, 0.849 sensitivity, and 0.991 AUC. These results present a powerful next-generation tool called MultiToxPred 1.0, accessible through a web application. We believe that MultiToxPred 1.0 has the potential to become an indispensable resource for researchers, facilitating the efficient identification of protein toxins. By leveraging this tool, scientists can accelerate their search for these toxins and advance their understanding of their therapeutic potential.

The scorpion toxin BeKm-1 blocks hERG cardiac potassium channels using an indispensable arginine residue

BeKm-1 is a peptide toxin from scorpion venom that blocks the pore of the potassium channel hERG (Kv11.1) in the human heart. Although individual protein structures have been resolved, the structure of the complex between hERG and BeKm-1 is unknown. Here, we used molecular dynamics and ensemble docking, guided by previous double-mutant cycle analysis data, to obtain an in silico model of the hERG-BeKm-1 complex. Adding to the previous mutagenesis study of BeKm-1, our model uncovers the key role of residue Arg20, which forms three interactions (a salt bridge and hydrogen bonds) with the channel vestibule simultaneously. Replacement of this residue even by lysine weakens the interactions significantly. In accordance, the recombinantly produced BeKm-1R20K mutant exhibited dramatically decreased activity on hERG. Our model may be useful for future drug design attempts.

The binding and mechanism of a positive allosteric modulator of Kv3 channels

Small-molecule modulators of diverse voltage-gated K+ (Kv) channels may help treat a wide range of neurological disorders. However, developing effective modulators requires understanding of their mechanism of action. We apply an orthogonal approach to elucidate the mechanism of action of an imidazolidinedione derivative (AUT5), a highly selective positive allosteric modulator of Kv3.1 and Kv3.2 channels. AUT5 modulation involves positive cooperativity and preferential stabilization of the open state. The cryo-EM structure of the Kv3.1/AUT5 complex at a resolution of 2.5 Å reveals four equivalent AUT5 binding sites at the extracellular inter-subunit interface between the voltage-sensing and pore domains of the channel's tetrameric assembly. Furthermore, we show that the unique extracellular turret regions of Kv3.1 and Kv3.2 essentially govern the selective positive modulation by AUT5. High-resolution apo and bound structures of Kv3.1 demonstrate how AUT5 binding promotes turret rearrangements and interactions with the voltage-sensing domain to favor the open conformation.

Cholesterol modulates the structural dynamics of the paddle motif loop of KvAP voltage sensor

KvAP is a prokaryotic Kv channel, which has been widely used as a model system to understand voltage- and lipid-dependent gating mechanisms. In phospholipid membranes, the KvAP-VSD adopts the activated/'Up' conformation, whereas the presence of non-phospholipids in membranes favours the structural transition to resting/'Down' state. The S3b-S4 paddle motif loop of KvAP-VSD is functionally important as this participates in protein-protein interactions and is the target for animal toxins. In this study, we have monitored the modulatory role of cholesterol - the physiologically-relevant non-phospholipid - on the organization and dynamics of the S3b-S4 loop of the isolated KvAP-VSD in membranes by site-directed fluorescence approaches using the environmental sensitivity of 7-nitrobenz-2-oxa-1,3-diazol-4-yl-ethylenediamine (NBD) fluorescence. Our results show that cholesterol alters the dynamic nature (rotational and hydration dynamics) of S3b-S4 loop in a segmental fashion, i.e., the residues 110 to 114 and 115 to 117 behave differently in the presence of cholesterol, which is accompanied by considerable change in conformational heterogeneity. Further, quantitative depth measurements using the parallax quenching method reveal that the sensor loop is located at the shallow interfacial region of cholesterol-containing membranes, suggesting that the sensor loop organization is not directly correlated with S4 helix movement. Our results clearly show that cholesterol-induced changes in bilayer properties may not be the predominant factor for the sensor loop's altered structural dynamics, but can be attributed to the conformational change of the KvAP-VSD in cholesterol-containing membranes. Overall, these results are relevant for gating mechanisms, particularly the lipid-dependent gating, of Kv channels in membranes.

Informatic challenges and advances in illuminating the druggable proteome

The understudied members of the druggable proteomes offer promising prospects for drug discovery efforts. While large-scale initiatives have generated valuable functional information on understudied members of the druggable gene families, translating this information into actionable knowledge for drug discovery requires specialized informatics tools and resources. Here, we review the unique informatics challenges and advances in annotating understudied members of the druggable proteome. We demonstrate the application of statistical evolutionary inference tools, knowledge graph mining approaches, and protein language models in illuminating understudied protein kinases, pseudokinases, and ion channels.

Structural Insights and Influence of Terahertz Waves in Midinfrared Region on Kv1.2 Channel Selectivity Filter

Potassium ion channels are the structural basis for excitation transmission, heartbeat, and other biological processes. The selectivity filter is a critical structural component of potassium ion channels, whose structure is crucial to realizing their function. As biomolecules vibrate and rotate at frequencies in the terahertz band, potassium ion channels are sensitive to terahertz waves. Therefore, it is worthwhile to investigate how the terahertz wave influences the selectivity filter of the potassium channels. In this study, we investigate the structure of the selectivity filter of Kv1.2 potassium ion channels using molecular dynamics simulations. The effect of an electric field on the channel has been examined at four different resonant frequencies of the carbonyl group in SF: 36.75 37.06, 37.68, and 38.2 THz. As indicated by the results, 376GLY appears to be the critical residue in the selectivity filter of the Kv1.2 channel. Its dihedral angle torsion is detrimental to the channel structural stability and the transmembrane movement of potassium ions. 36.75 THz is the resonance frequency of the carbonyl group of 376GLY. Among all four frequencies explored, the applied terahertz electric field of this frequency has the most significant impact on the channel structure, negatively impacting the channel stability and reducing the ion permeability by 20.2% compared to the absence of fields. In this study, we simulate that terahertz waves in the mid-infrared frequency region can significantly alter the structure and function of potassium ion channels and that the effects of terahertz waves differ greatly based on frequency.

Proteome landscape and interactome of voltage-gated potassium channel 1.6 (Kv1.6) of the murine ophthalmic artery and neuroretina

The voltage-gated potassium channel 1.6 (Kv1.6) plays a vital role in ocular neurovascular beds and exerts its modulatory functions via interaction with other proteins. However, the interactome and their potential roles remain unknown. Here, the global proteome landscape of the ophthalmic artery (OA) and neuroretina was mapped, followed by the determination of Kv1.6 interactome and validation of its functionality and cellular localization. Microfluorimetric analysis of intracellular [K+] and Western blot validated the native functionality and cellular expression of the recombinant Kv1.6 channel protein. A total of 54, 9 and 28 Kv1.6-interacting proteins were identified in the mouse OA and, retina of mouse and rat, respectively. The Kv1.6-protein partners in the OA, namely actin cytoplasmic 2, alpha-2-macroglobulin and apolipoprotein A-I, were implicated in the maintenance of blood vessel integrity by regulating integrin-mediated adhesion to extracellular matrix and Ca2+ flux. Many retinal protein interactors, particularly the ADP/ATP translocase 2 and cytoskeleton protein tubulin, were involved in endoplasmic reticulum stress response and cell viability. Three common interactors were found in all samples comprising heat shock cognate 71 kDa protein, Ig heavy constant gamma 1 and Kv1.6 channel. This foremost in-depth investigation enriched and identified the elusive Kv1.6 channel and, elucidated its complex interactome.

Voltage-gated potassium channels control extended access cocaine seeking: a role for nucleus accumbens astrocytes

Dopaminergic signaling in the nucleus accumbens shell (NAc) regulates neuronal activity relevant to reward-related learning, including cocaine-associated behaviors. Although astrocytes respond to dopamine and cocaine with structural changes, the impact of dopamine and cocaine on astrocyte functional plasticity has not been widely studied. Specifically, behavioral implications of voltage-gated channel activity in the canonically non-excitable astrocytes are not known. We characterized potassium channel function in NAc astrocytes following exposure to exogenous dopamine or cocaine self-administration training under short (2 h/day) and extended (6 h/day) access schedules. Electrophysiological, Ca2+ imaging, mRNA, and mass spectrometry tools were used for molecular characterization. Behavioral effects were examined after NAc-targeted microinjections of channel antagonists and astroglial toxins. Exogenous dopamine increased activity of currents mediated by voltage-gated (Kv7) channels in NAc astrocytes. This was associated with a ~5-fold increase in expression of Kcnq2 transcript level in homogenized NAc micropunches. Matrix-assisted laser desorption/ionization mass spectrometry revealed increased NAc dopamine levels in extended access, relative to short access, rats. Kv7 inhibition selectively increased frequency and amplitude of astrocyte intracellular Ca2+ transients in NAc of extended access rats. Inhibition of Kv7 channels in the NAc attenuated cocaine-seeking in extended access rats only, an effect that was occluded by microinjection of the astrocyte metabolic poison, fluorocitrate. These results suggest that voltage-gated K+ channel signaling in NAc astrocytes is behaviorally relevant, support Kv7-mediated regulation of astrocyte Ca2+ signals, and propose novel mechanisms of neuroglial interactions relevant to drug use.

Enhancement of K+ channel permeation by selective terahertz excitation

The optical excitation effects offer an opportunity to gain insights into the structure and the function of K+ channel, contributing to the prediction of possible targets for drug design and precision therapy. Although there has been increasing research attention on the modulation of ion permeation in K+ channel by terahertz electromagnetic (THz-EM) stimuli, little exploration has been conducted regarding the dependence of ion permeation on frequencies. By using two-dimensional (2D) infrared excitation spectrum calculation for the K+ channel, we have discovered that the frequency of 53.60 THz serves as an optimal excitation modulation mode. This mode leads to an almost twofold enhancement in the rate of K+ ion permeation and a tenfold increase in selectivity efficiency. These improvements can be attributed to the coupling mode matching of the excited properties of CO groups in the K+ channel. Our findings propose a promising application of terahertz technology to improve the performance of ion channels, nanomembrane sieves, nanodevices, as well as neural therapy.

A small-molecule activation mechanism that directly opens the KCNQ2 channel

Pharmacological activation of voltage-gated ion channels by ligands serves as the basis for therapy and mainly involves a classic gating mechanism that augments the native voltage-dependent open probability. Through structure-based virtual screening, we identified a new scaffold compound, Ebio1, serving as a potent and subtype-selective activator for the voltage-gated potassium channel KCNQ2 and featuring a new activation mechanism. Single-channel patch-clamp, cryogenic-electron microscopy and molecular dynamic simulations, along with chemical derivatives, reveal that Ebio1 engages the KCNQ2 activation by generating an extended channel gate with a larger conductance at the saturating voltage (+50 mV). This mechanism is different from the previously observed activation mechanism of ligands on voltage-gated ion channels. Ebio1 caused S6 helices from residues S303 and F305 to perform a twist-to-open movement, which was sufficient to open the KCNQ2 gate. Overall, our findings provide mechanistic insights into the activation of KCNQ2 channel by Ebio1 and lend support for KCNQ-related drug development.

Research Status, Synthesis and Clinical Application of Antiepileptic Drugs

According to the 2017 ILAE's official definition, epilepsy is a slow brain disease state characterized by recurrent episodes. Due to information released by ILAE in 2017, it can be divided into four types, including focal epilepsy, generalized epilepsy, combined generalized, and focal epilepsy, and unknown epilepsy. Since 1989, 24 new antiepileptic drugs have been approved to treat different types of epilepsy. Besides, there are a variety of antiepileptic medications under clinical monitoring. These novel antiepileptic drugs have plenty of advantages. Over the past 33 years, there have been many antiepileptic drugs on the mearket, but no one has been found that can completely cure epilepsy. In this paper, the mentioned drugs were classified according to their targets, and the essential information, and clinical studies of each drug were described. The structure-activity relationship of different chemical structures was summarized. This paper provides help for the follow-up research on epilepsy drugs.

Voltage-gated potassium channels KCNQs: Structures, mechanisms, and modulations

KCNQ (Kv7) channels are voltage-gated, phosphatidylinositol 4,5-bisphosphate- (PIP2-) modulated potassium channels that play essential roles in regulating the activity of neurons and cardiac myocytes. Hundreds of mutations in KCNQ channels are closely related to various cardiac and neurological disorders, such as long QT syndrome, epilepsy, and deafness, which makes KCNQ channels important drug targets. During the past several years, the application of single-particle cryo-electron microscopy (cryo-EM) technique in the structure determination of KCNQ channels has greatly advanced our understanding of their molecular mechanisms. In this review, we summarize the currently available structures of KCNQ channels, analyze their special voltage gating mechanism, and discuss their activation mechanisms by both the endogenous membrane lipid and the exogenous synthetic ligands. These structural studies of KCNQ channels will guide the development of drugs targeting KCNQ channels.

Snake Venom: A Promising Source of Neurotoxins Targeting Voltage-Gated Potassium Channels

The venom derived from various sources of snakes represents a vast collection of predominantly protein-based toxins that exhibit a wide range of biological actions, including but not limited to inflammation, pain, cytotoxicity, cardiotoxicity, and neurotoxicity. The venom of a particular snake species is composed of several toxins, while the venoms of around 600 venomous snake species collectively encompass a substantial reservoir of pharmacologically intriguing compounds. Despite extensive research efforts, a significant portion of snake venoms remains uncharacterized. Recent findings have demonstrated the potential application of neurotoxins derived from snake venom in selectively targeting voltage-gated potassium channels (Kv). These neurotoxins include BPTI-Kunitz polypeptides, PLA2 neurotoxins, CRISPs, SVSPs, and various others. This study provides a comprehensive analysis of the existing literature on the significance of Kv channels in various tissues, highlighting their crucial role as proteins susceptible to modulation by diverse snake venoms. These toxins have demonstrated potential as valuable pharmacological resources and research tools for investigating the structural and functional characteristics of Kv channels.

Information integration during bioelectric regulation of morphogenesis of the embryonic frog brain

Spatiotemporal patterns of cellular resting potential regulate several aspects of development. One key aspect of the bioelectric code is that transcriptional and morphogenetic states are determined not by local, single-cell, voltage levels but by specific distributions of voltage across cell sheets. We constructed and analyzed a minimal dynamical model of collective gene expression in cells based on inputs of multicellular voltage patterns. Causal integration analysis revealed a higher-order mechanism by which information about the voltage pattern was spatiotemporally integrated into gene activity, as well as a division of labor among and between the bioelectric and genetic components. We tested and confirmed predictions of this model in a system in which bioelectric control of morphogenesis regulates gene expression and organogenesis: the embryonic brain of the frog Xenopus laevis. This study demonstrates that machine learning and computational integration approaches can advance our understanding of the information-processing underlying morphogenetic decision-making, with a potential for other applications in developmental biology and regenerative medicine.

Low glycemic index diet restrains epileptogenesis in a gender-specific fashion

Dietary restriction, such as low glycemic index diet (LGID), have been successfully used to treat drug-resistant epilepsy. However, if such diet could also counteract antiepileptogenesis is still unclear. Here, we investigated whether the administration of LGID during the latent pre-epileptic period, prevents or delays the appearance of the overt epileptic phenotype. To this aim, we used the Synapsin II knockout (SynIIKO) mouse, a model of temporal lobe epilepsy in which seizures manifest 2-3 months after birth, offering a temporal window in which LGID may affect epileptogenesis. Pregnant SynIIKO mice were fed with either LGID or standard diet during gestation and lactation. Both diets were maintained in weaned mice up to 5 months of age. LGID delayed the seizure onset and induced a reduction of seizures severity only in female SynIIKO mice. In parallel with the epileptic phenotype, high-density multielectrode array recordings revealed a reduction of frequency, amplitude, duration, velocity of propagation and spread of interictal events by LGID in the hippocampus of SynIIKO females, but not mutant males, confirming the gender-specific effect. ELISA-based analysis revealed that LGID increased cortico-hippocampal allopregnanolone (ALLO) levels only in females, while it was unable to affect ALLO plasma concentrations in either sex. The results indicate that the gender-specific interference of LGID with the epileptogenic process can be ascribed to a gender-specific increase in cortical ALLO, a neurosteroid known to strengthen GABAergic transmission. The study highlights the possibility of developing a personalized gender-based therapy for temporal lobe epilepsy.

Conotoxin Prediction: New Features to Increase Prediction Accuracy

Conotoxins are toxic, disulfide-bond-rich peptides from cone snail venom that target a wide range of receptors and ion channels with multiple pathophysiological effects. Conotoxins have extraordinary potential for medical therapeutics that include cancer, microbial infections, epilepsy, autoimmune diseases, neurological conditions, and cardiovascular disorders. Despite the potential for these compounds in novel therapeutic treatment development, the process of identifying and characterizing the toxicities of conotoxins is difficult, costly, and time-consuming. This challenge requires a series of diverse, complex, and labor-intensive biological, toxicological, and analytical techniques for effective characterization. While recent attempts, using machine learning based solely on primary amino acid sequences to predict biological toxins (e.g., conotoxins and animal venoms), have improved toxin identification, these methods are limited due to peptide conformational flexibility and the high frequency of cysteines present in toxin sequences. This results in an enumerable set of disulfide-bridged foldamers with different conformations of the same primary amino acid sequence that affect function and toxicity levels. Consequently, a given peptide may be toxic when its cysteine residues form a particular disulfide-bond pattern, while alternative bonding patterns (isoforms) or its reduced form (free cysteines with no disulfide bridges) may have little or no toxicological effects. Similarly, the same disulfide-bond pattern may be possible for other peptide sequences and result in different conformations that all exhibit varying toxicities to the same receptor or to different receptors. We present here new features, when combined with primary sequence features to train machine learning algorithms to predict conotoxins, that significantly increase prediction accuracy.

Inhibitory effects of N-methyl-D-aspartate (NMDA) and α1-adrenergic receptor antagonist ifenprodil on human Kv1.5 channel

Ifenprodil has been known to reduce cardiac contractility and cerebral vasodilation by antagonizing α1-adrenergic and N-methyl D-aspartate receptor-mediated intracellular signals. This study aimed to investigate the direct effect of ifenprodil on the human voltage-gated Kv1.5 channel (hKv1.5) by using a Xenopus oocyte expression system and a two-microelectrode voltage clamp technique. The amplitudes of hKv1.5 currents, including peak and steady state, were suppressed in a concentration-dependent manner (IC50; 43.1 and 35.5 μM, respectively) after 6 min of ifenprodil treatment. However, these effects were  ~ 80% reversed by washout, suggesting that ifenprodil directly inhibited the hKv1.5 independent of membrane receptors or intracellular signals. The inhibition rate of steady state showed voltage dependence, wherein the rates increased according to test voltage depolarization. Ifenprodil reduced the time constants of hKv1.5 inactivation but has higher effects on activation. hKv1.5 inhibition by ifenprodil showed use dependency because the drug more rapidly reduced the current at the higher activation frequencies, and subsequent reduction in frequency after high activation frequency caused a partial channel block relief. Therefore, ifenprodil directly blocked the hKv1.5 in an open state and accelerated the time course of the channel inactivation, which provided a biophysical mechanism for the hKv1.5 blocking effects of ifenprodil.

Kalium 3.0 is a comprehensive depository of natural, artificial, and labeled polypeptides acting on potassium channels

Here, we introduce the third release of Kalium database (http://kaliumdb.org/), a manually curated comprehensive depository that accumulates data on polypeptide ligands of potassium channels. The major goal of this amplitudinous update is to summarize findings for natural polypeptide ligands of K+ channels, as well as data for the artificial derivatives of these substances obtained over the decades of exploration. We manually analyzed more than 700 original manuscripts and systematized the information on mutagenesis, production of radio- and fluorescently labeled derivatives, and the molecular pharmacology of K+ channel ligands. As a result, data on more than 1200 substances were processed and added enriching the database content fivefold. We also included the electrophysiological data obtained on the understudied and neglected K+ channels including the heteromeric and concatenated channels. We associated target channels in Kalium with corresponding entries in the official database of the International Union of Basic and Clinical Pharmacology. Kalium was supplemented with an adaptive Statistics page, where users are able to obtain actual data output. Several other improvements were introduced, such as a color code to distinguish the range of ligand activity concentrations and advanced tools for filtration and sorting. Kalium is a fully open-access database, crosslinked to other databases of interest. It can be utilized as a convenient resource containing ample up-to-date information about polypeptide ligands of K+ channels.

Ligand activation mechanisms of human KCNQ2 channel

The human voltage-gated potassium channel KCNQ2/KCNQ3 carries the neuronal M-current, which helps to stabilize the membrane potential. KCNQ2 can be activated by analgesics and antiepileptic drugs but their activation mechanisms remain unclear. Here we report cryo-electron microscopy (cryo-EM) structures of human KCNQ2-CaM in complex with three activators, namely the antiepileptic drug cannabidiol (CBD), the lipid phosphatidylinositol 4,5-bisphosphate (PIP2), and HN37 (pynegabine), an antiepileptic drug in the clinical trial, in an either closed or open conformation. The activator-bound structures, along with electrophysiology analyses, reveal the binding modes of two CBD, one PIP2, and two HN37 molecules in each KCNQ2 subunit, and elucidate their activation mechanisms on the KCNQ2 channel. These structures may guide the development of antiepileptic drugs and analgesics that target KCNQ2.

The role of ion channels in the relationship between the immune system and cancer

The immune system is capable of identifying and eliminating cancer, a complicated illness marked by unchecked cellular proliferation. The significance of ion channels in the complex interaction between the immune system and cancer has been clarified by recent studies. Ion channels, which are proteins that control ion flow across cell membranes, have variety of physiological purposes, such as regulating immune cell activity and tumor development. Immune cell surfaces contain ion channels, which have been identified to control immune cell activation, motility, and effector activities. The regulation of immune responses against cancer cells has been linked to a number of ion channels, including potassium, calcium, and chloride channels. As an example, potassium channels are essential for regulating T cell activation and proliferation, which are vital for anti-tumor immunity. Calcium channels play a crucial role when immune cells produce cytotoxic chemicals in order to eliminate cancer cells. Chloride channels also affect immune cell infiltration and invasion into malignancies. Additionally, tumor cells' own expressed ion channels have an impact on their behavior and in the interaction with the immune system. The proliferation, resistance to apoptosis, and immune evasion of cancer cells may all be impacted by changes in ion channel expression and function. Ion channels may also affect the tumor microenvironment by controlling angiogenesis, inflammatory responses, and immune cell infiltration. Ion channel function in the interaction between the immune system and cancer has important implications for cancer treatment. A possible method to improve anti-tumor immune responses and stop tumor development is to target certain ion channels. Small compounds and antibodies are among the ion channel modulators under investigation as possible immunotherapeutics. The complex interaction between ion channels, the immune system, and cancer highlights the significance of these channels for tumor immunity. The development of novel therapeutic strategies for the treatment of cancer will be made possible by unraveling the processes by which ion channels control immune responses and tumor activity. Hence, the main driving idea of the present chapter is trying to understand the possible function of ion channels in the complex crosstalk between cancer and immunoresponse. To this aim, after giving a brief journey of ion channels throughout the history, a classification of the main ion channels involved in cancer disease will be discussed. Finally, the last paragraph will focus on more recently advancements in the use of biomaterials as therapeutic strategy for cancer treatment. The hope is that future research will take advantage of the promising combination of ion channels, immunomodulation and biomaterials filed to provide better solutions in the treatment of cancer disease.

Effects of Nitro-Oxidative Stress on Biomolecules: Part 1-Non-Reactive Molecular Dynamics Simulations

Plasma medicine, or the biomedical application of cold atmospheric plasma (CAP), is an expanding field within plasma research. CAP has demonstrated remarkable versatility in diverse biological applications, including cancer treatment, wound healing, microorganism inactivation, and skin disease therapy. However, the precise mechanisms underlying the effects of CAP remain incompletely understood. The therapeutic effects of CAP are largely attributed to the generation of reactive oxygen and nitrogen species (RONS), which play a crucial role in the biological responses induced by CAP. Specifically, RONS produced during CAP treatment have the ability to chemically modify cell membranes and membrane proteins, causing nitro-oxidative stress, thereby leading to changes in membrane permeability and disruption of cellular processes. To gain atomic-level insights into these interactions, non-reactive molecular dynamics (MD) simulations have emerged as a valuable tool. These simulations facilitate the examination of larger-scale system dynamics, including protein-protein and protein-membrane interactions. In this comprehensive review, we focus on the applications of non-reactive MD simulations in studying the effects of CAP on cellular components and interactions at the atomic level, providing a detailed overview of the potential of CAP in medicine. We also review the results of other MD studies that are not related to plasma medicine but explore the effects of nitro-oxidative stress on cellular components and are therefore important for a broader understanding of the underlying processes.

Potassium channels in behavioral brain disorders. Molecular mechanisms and therapeutic potential: A narrative review

Potassium channels (K+-channels) selectively control the passive flow of potassium ions across biological membranes and thereby also regulate membrane excitability. Genetic variants affecting many of the human K+-channels are well known causes of Mendelian disorders within cardiology, neurology, and endocrinology. K+-channels are also primary targets of many natural toxins from poisonous organisms and drugs used within cardiology and metabolism. As genetic tools are improving and larger clinical samples are being investigated, the spectrum of clinical phenotypes implicated in K+-channels dysfunction is rapidly expanding, notably within immunology, neurosciences, and metabolism. K+-channels that previously were considered to be expressed in only a few organs and to have discrete physiological functions, have recently been found in multiple tissues and with new, unexpected functions. The pleiotropic functions and patterns of expression of K+-channels may provide additional therapeutic opportunities, along with new emerging challenges from off-target effects. Here we review the functions and therapeutic potential of K+-channels, with an emphasis on the nervous system, roles in neuropsychiatric disorders and their involvement in other organ systems and diseases.

The role of ion channels in T cell function and disease

T lymphocytes (T cells) are an important sub-group of cells in our immune system responsible for cell-mediated adaptive responses and maintaining immune homeostasis. Abnormalities in T cell function, lead the way to the persistence of infection, impaired immunosurveillance, lack of suppression of cancer growth, and autoimmune diseases. Ion channels play a critical role in the regulation of T cell signaling and cellular function and are often overlooked and understudied. Little is known about the ion "channelome" and the interaction of ion channels in immune cells. This review aims to summarize the published data on the impact of ion channels on T cell function and disease. The importance of ion channels in health and disease plus the fact they are easily accessible by virtue of being expressed on the surface of plasma membranes makes them excellent drug targets.

Of Seven New K+ Channel Inhibitor Peptides of Centruroides bonito, α-KTx 2.24 Has a Picomolar Affinity for Kv1.2

Seven new peptides denominated CboK1 to CboK7 were isolated from the venom of the Mexican scorpion Centruroides bonito and their primary structures were determined. The molecular weights ranged between 3760.4 Da and 4357.9 Da, containing 32 to 39 amino acid residues with three putative disulfide bridges. The comparison of amino acid sequences with known potassium scorpion toxins (KTx) and phylogenetic analysis revealed that CboK1 (α-KTx 10.5) and CboK2 (α-KTx 10.6) belong to the α-KTx 10.x subfamily, whereas CboK3 (α-KTx 2.22), CboK4 (α-KTx 2.23), CboK6 (α-KTx 2.21), and CboK7 (α-KTx 2.24) bear > 95% amino acid similarity with members of the α-KTx 2.x subfamily, and CboK5 is identical to Ce3 toxin (α-KTx 2.10). Electrophysiological assays demonstrated that except CboK1, all six other peptides blocked the Kv1.2 channel with Kd values in the picomolar range (24-763 pM) and inhibited the Kv1.3 channel with comparatively less potency (Kd values between 20-171 nM). CboK3 and CboK4 inhibited less than 10% and CboK7 inhibited about 42% of Kv1.1 currents at 100 nM concentration. Among all, CboK7 showed out-standing affinity for Kv1.2 (Kd = 24 pM), as well as high selectivity over Kv1.3 (850-fold) and Kv1.1 (~6000-fold). These characteristics of CboK7 may provide a framework for developing tools to treat Kv1.2-related channelopathies.

Permeability enhancement of Kv1.2 potassium channel by a terahertz electromagnetic field

As biomolecules vibrate and rotate in the terahertz band, the biological effects of terahertz electromagnetic fields have drawn considerable attention from the physiological and medical communities. Ion channels are the basis of biological electrical signals, so studying the effect of terahertz electromagnetic fields on ion channels is significant. In this paper, the effect of a terahertz electromagnetic field with three different frequencies, 6, 15, and 25 THz, on the Kv1.2 potassium ion channel was investigated by molecular dynamics simulations. The results show that an electromagnetic field with a 15 THz frequency can significantly enhance the permeability of the Kv1.2 potassium ion channel, which is 1.7 times higher than without an applied electric field. By analyzing the behavior of water molecules, it is found that the electromagnetic field with the 15 THz frequency shortens the duration of frozen and relaxation processes when potassium ions pass through the channel, increases the proportion of the direct knock-on mode, and, thus, enhances the permeability of the Kv1.2 potassium ion channel.

PINNED: identifying characteristics of druggable human proteins using an interpretable neural network

The identification of human proteins that are amenable to pharmacologic modulation without significant off-target effects remains an important unsolved challenge. Computational methods have been devised to identify features which distinguish between "druggable" and "undruggable" proteins, finding that protein sequence, tissue and cellular localization, biological role, and position in the protein-protein interaction network are all important discriminant factors. However, many prior efforts to automate the assessment of protein druggability suffer from low performance or poor interpretability. We developed a neural network-based machine learning model capable of generating druggability sub-scores based on each of four distinct categories, combining them to form an overall druggability score. The model achieves an excellent performance in separating drugged and undrugged proteins in the human proteome, with an area under the receiver operating characteristic (AUC) of 0.95. Our use of multiple sub-scores allows the assessment of potential protein targets of interest based on distinct contributors to druggability, leading to a more interpretable and holistic model to identify novel targets.

Identification and Venom Characterization of Two Scorpions from the State of Chihuahua Mexico: Chihuahuanus coahuliae and Chihuahuanus crassimannus

Chihuahua is the largest state in Mexico. The ecosystem of this region is composed of large area of bushes, forests, and grasslands, which allows for a specific diversity of fauna; among them are interesting species of non-lethal scorpions. Most of the Chihuahuan scorpions have been previously morphologically and molecularly described; however, this manuscript could be the first to describe the composition of those venoms. This work aimed at the collection of two scorpion species from the region of Jiménez (Southwest of the State of Chihuahua), which belong to the species Chihuahuanus cohauilae and Chihuahuanus crassimanus; the two species were taxonomically and molecularly identified using a 16S DNA marker. Reverse-phase high-performance liquid chromatography (RP-HPLC) of C. coahuilae and C. crassimanus venoms allowed the identification of three fractions lethal to mice. Additionally, three fractions of each scorpion displayed an effect on house crickets. In the end, three new fractions from the venom of C. coahuilae were positive for antimicrobial activity, although none from C. crassimanus venom displayed growth inhibition. Despite being a preliminary study, the venom biochemical analysis of these two uncharacterized scorpion species opens the opportunity to find new molecules with potential applications in the biomedical and biotechnological fields.

Discovery and Biomimetic Semisynthesis of Spirophyllines A-D from Uncaria rhynchophylla

Spirophyllines A-D (1-4), four new spirooxindole alkaloids all characterized by the spiro[pyrrolidin-3,3'-oxindole] core and a rare isoxazolidine ring, were isolated from Uncaria rhynchophylla. Their structures were determined by spectroscopic methods and confirmed by X-ray crystallography. Based on the biomimetic semisynthesis strategy, compounds 1-8 were synthesized in three steps via the key reactions of 1,3-dipolar cycloaddition and Krapcho decarboxylation from corynoxeine. Interestingly, compound 3 showed moderate inhibitory activity against the Kv1.5 potassium channel (IC50 = 9.1 μM).

Genetic deletion of Kvβ2 (AKR6) causes loss of muscle function and increased inflammation in mice

The voltage-gated potassium channels (Kv) are complex ion channels with distinct roles in neurotransmission, electrical conductivity of the heart, and smooth and striated muscle functions. Previously, we demonstrated that deletion of Kvβ2 in mice results in decreased Pax7 protein levels, hindlimb muscles and body weights, and fiber type switching. In the present study, we tested the hypothesis that Kvβ2 regulates skeletal muscle function in mice. The young and old Kvβ2 knockout (KO) and wildtype (WT) mice were utilized to test the aging phenotype and skeletal muscle function. Consistent with our previous finding, we found a significant reduction in hindlimb skeletal muscles mass and body weight in young Kvβ2 KO mice, which was also significantly reduced in old Kvβ2 KO mice compared with age-matched WT mice. Forelimb grip strength, and the hindleg extensor digitorum longus (EDL) muscles force-frequency relations were significantly decreased in young and old Kvβ2 KO mice compared to age-matched WT mice. Analysis of transmission electron microscopy images of EDL muscles in young mice revealed a significant reduction in the sarcomere length for Kvβ2 KO vs. WT. Hematoxylin and eosin-stained tibialis anterior muscles cryosections displayed a significant decrease in the number of medium (2,000-4,000 µm²) and largest (>4,000 µm²) myofibers area in young Kvβ2 KO vs. WT mice. We also found a significant increase in fibrotic tissue area in young Kvβ2 KO mice compared with age-matched WT mice. Analysis of RNA Seq data of the gastrocnemius muscles (GAS) identified significant increase in genes involved in skeletal muscle development, proliferation and cell fate determination, atrophy, energy metabolism, muscle plasticity, inflammation, and a decrease in circadian core clock genes in young Kvβ2 KO vs. WT mice. Several genes were significantly upregulated (384 genes) and downregulated (40 genes) in young Kvβ2 KO mice compared to age-matched WT mice. Further, RT-qPCR analysis of the GAS muscles displayed a significant increase in pro-inflammatory marker Il6 expression in young Kvβ2 KO mice compared to age-matched WT mice. Overall, the present study shows that deletion of Kvβ2 leads to decreased muscles strength and increased inflammation.

Synthesis and applications of mirror-image proteins

The homochirality of biomolecules in nature, such as DNA, RNA, peptides and proteins, has played a critical role in establishing and sustaining life on Earth. This chiral bias has also given synthetic chemists the opportunity to generate molecules with inverted chirality, unlocking valuable new properties and applications. Advances in the field of chemical protein synthesis have underpinned the generation of numerous 'mirror-image' proteins (those comprised entirely of D-amino acids instead of canonical L-amino acids), which cannot be accessed using recombinant expression technologies. This Review seeks to highlight recent work on synthetic mirror-image proteins, with a focus on modern synthetic strategies that have been leveraged to access these complex biomolecules as well as their applications in protein crystallography, drug discovery and the creation of mirror-image life.

Recent Advances in Computer-Aided Structure-Based Drug Design on Ion Channels

Ion channels play important roles in fundamental biological processes, such as electric signaling in cells, muscle contraction, hormone secretion, and regulation of the immune response. Targeting ion channels with drugs represents a treatment option for neurological and cardiovascular diseases, muscular degradation disorders, and pathologies related to disturbed pain sensation. While there are more than 300 different ion channels in the human organism, drugs have been developed only for some of them and currently available drugs lack selectivity. Computational approaches are an indispensable tool for drug discovery and can speed up, especially, the early development stages of lead identification and optimization. The number of molecular structures of ion channels has considerably increased over the last ten years, providing new opportunities for structure-based drug development. This review summarizes important knowledge about ion channel classification, structure, mechanisms, and pathology with the main focus on recent developments in the field of computer-aided, structure-based drug design on ion channels. We highlight studies that link structural data with modeling and chemoinformatic approaches for the identification and characterization of new molecules targeting ion channels. These approaches hold great potential to advance research on ion channel drugs in the future.

Anxiolytic, Analgesic and Anti-Inflammatory Effects of Peptides Hmg 1b-2 and Hmg 1b-4 from the Sea Anemone Heteractis magnifica

Acid-sensing ion channels (ASICs) have been known as sensors of a local pH change within both physiological and pathological conditions. ASIC-targeting peptide toxins could be potent molecular tools for ASIC-manipulating in vitro, and for pathology treatment in animal test studies. Two sea anemone toxins, native Hmg 1b-2 and recombinant Hmg 1b-4, both related to APETx-like peptides, inhibited the transient current component of human ASIC3-Δ20 expressed in Xenopus laevis oocytes, but only Hmg 1b-2 inhibited the rat ASIC3 transient current. The Hmg 1b-4 action on rASIC3 as a potentiator was confirmed once again. Both peptides are non-toxic molecules for rodents. In open field and elevated plus maze tests, Hmg 1b-2 had more of an excitatory effect and Hmg 1b-4 had more of an anxiolytic effect on mouse behavior. The analgesic activity of peptides was similar and comparable to diclofenac activity in an acid-induced muscle pain model. In models of acute local inflammation induced by λ-carrageenan or complete Freund's adjuvant, Hmg 1b-4 had more pronounced and statistically significant anti-inflammatory effects than Hmg 1b-2. It exceeded the effect of diclofenac and, at a dose of 0.1 mg/kg, reduced the volume of the paw almost to the initial volume. Our data highlight the importance of a comprehensive study of novel ASIC-targeting ligands, and in particular, peptide toxins, and present the slightly different biological activity of the two similar toxins.

Potassium Ion Channels in Glioma: From Basic Knowledge into Therapeutic Applications

Ion channels, specifically those controlling the flux of potassium across cell membranes, have recently been shown to exhibit an important role in the pathophysiology of glioma, the most common primary central nervous system tumor with a poor prognosis. Potassium channels are grouped into four subfamilies differing by their domain structure, gating mechanisms, and functions. Pertinent literature indicates the vital functions of potassium channels in many aspects of glioma carcinogenesis, including proliferation, migration, and apoptosis. The dysfunction of potassium channels can result in pro-proliferative signals that are highly related to calcium signaling as well. Moreover, this dysfunction can feed into migration and metastasis, most likely by increasing the osmotic pressure of cells allowing the cells to initiate the "escape" and "invasion" of capillaries. Reducing the expression or channel blockage has shown efficacy in reducing the proliferation and infiltration of glioma cells as well as inducing apoptosis, priming several approaches to target potassium channels in gliomas pharmacologically. This review summarizes the current knowledge on potassium channels, their contribution to oncogenic transformations in glioma, and the existing perspectives on utilizing them as potential targets for therapy.

Neuron-oligodendrocyte potassium shuttling at nodes of Ranvier protects against inflammatory demyelination

Multiple sclerosis (MS) is a progressive inflammatory demyelinating disease of the CNS. Increasing evidence suggests that vulnerable neurons in MS exhibit fatal metabolic exhaustion over time, a phenomenon hypothesized to be caused by chronic hyperexcitability. Axonal Kv7 (outward-rectifying) and oligodendroglial Kir4.1 (inward-rectifying) potassium channels have important roles in regulating neuronal excitability at and around the nodes of Ranvier. Here, we studied the spatial and functional relationship between neuronal Kv7 and oligodendroglial Kir4.1 channels and assessed the transcriptional and functional signatures of cortical and retinal projection neurons under physiological and inflammatory demyelinating conditions. We found that both channels became dysregulated in MS and experimental autoimmune encephalomyelitis (EAE), with Kir4.1 channels being chronically downregulated and Kv7 channel subunits being transiently upregulated during inflammatory demyelination. Further, we observed that pharmacological Kv7 channel opening with retigabine reduced neuronal hyperexcitability in human and EAE neurons, improved clinical EAE signs, and rescued neuronal pathology in oligodendrocyte-Kir4.1-deficient (OL-Kir4.1-deficient) mice. In summary, our findings indicate that neuron-OL compensatory interactions promoted resilience through Kv7 and Kir4.1 channels and identify pharmacological activation of nodal Kv7 channels as a neuroprotective strategy against inflammatory demyelination.

Structure Elucidation of Two Intriguing Neo-Debromoaplysiatoxin Derivatives from Marine Cyanobacterium Lyngbya sp. Showing Strong Inhibition of Kv1.5 Potassium Channel and Differential Cytotoxicity

Two aplysiatoxin derivatives, neo-debromoaplysiatoxin I (1) and neo-debromoaplysiatoxin J (2), were isolated from marine cyanobacterium Lyngbya sp. collected from the South China Sea. Their structures including absolute configurations were assigned by spectroscopic analysis, in combination with GIAO NMR shift calculation and DP4+ analysis. Structures of neo-debromoaplysiatoxin I and neo-debromoaplysiatoxin J contained a decahydro-5H-pyrano [2,3,4-de] chromen-5-one 6/6/6 ring skeleton and an intriguing peroxide bridge group, respectively, which are unprecedented structure scaffold and motif in aplysiatoxins. Two compounds displayed comparable inhibitory activities against Kv1.5 K⁺ channel with IC₅₀ values of 2.59 ± 0.37 μM (1) and 1.64 ± 0.15 μM (2); however, they presented differential cytotoxic effects. It is worth noting that neo-debromoaplysiatoxin J, containing a peroxide bridge, showed remarkable cytotoxicity against four cancer cell lines including SW480, SGC7901, LoVo and PC-9 compared to the human normal cell line.

Whole-exome sequencing and electrophysiological study reveal a novel loss-of-function mutation of KCNA10 in epinephrine provoked long QT syndrome with familial history of sudden cardiac death

Congenital long QT syndrome (LQTS) is one type of inherited fatal cardiac arrhythmia that may lead to sudden cardiac death (SCD). Mutations in more than 16 genes have been reported to be associated with LQTS, whereas the genetic causes of about 20% of cases remain unknown. In the present study, we investigated a four-generation pedigree with familial history of syncope and SCD. The proband was a 33-year-old young woman who experienced 3 episodes of syncope when walking at night. The electrocardiogram revealed a markedly epinephrine-provoked prolonged QT interval (QT = 468 ms, QTc = 651 ms) but no obvious arrhythmia in the resting state. Three family members have died of suspected SCD. Whole-exome sequencing and bioinformatic analysis based on pedigree revealed that a novel missense mutation KCNA10 (c.1397G＞A/Arg466Gln) was the potential genetic lesion. Sanger sequencing was performed to confirm the whole-exome sequencing results. This mutation resulted in the K_V1.8 channel amino acid residue 466 changing from arginine to glutamine, and the electrophysiological experiments verified it as a loss-of-function mutation of K_V1.8, which reduced the K⁺ currents of K_V1.8 and might result in the prolonged QT interval. These findings suggested that KCNA10 (c.1397G＞A) mutation was possibly pathogenic in this enrolled LQTS family, and may provide a new potential genetic target for diagnosis and counseling of stress-related LQTS families as well as the postmortem diagnosis of SCD.

The in vitro anticancer effects of FS48 from salivary glands of Xenopsylla cheopis on NCI-H460 cells via its blockage of voltage-gated K+ channels

Voltage-gated K⁺ (K_v) channels play a role in the cellular processes of various cancer cells, including lung cancer cells. We previously identified and reported a salivary protein from the Xenopsylla cheopis, FS48, which exhibited inhibitory activity against K_v1.1-1.3 channels when assayed in HEK 293T cells. However, whether FS48 has an inhibitory effect on cancer cells expressing Kv channels is unclear. The present study aims to reveal the effects of FS48 on the K_v channels and the NCI-H460 human lung cancer cells through patch clamp, MTT, wound healing, transwell, gelatinase zymography, qRT-PCR and WB assays. The results demonstrated that FS48 can be effective in suppressing the K_v currents, migration, and invasion of NCI-H460 cells in a dose-dependent manner, despite the failure to inhibit the proliferation. Moreover, the expression of K_v1.1 and K_v1.3 mRNA and protein were found to be significantly reduced. Finally, FS48 decreases the mRNA level of MMP-9 while increasing TIMP-1 mRNA level. The present study highlights for the first time that blood-sucking arthropod saliva-derived protein can inhibit the physiological activities of tumour cells via the Kv channels. Furthermore, FS48 can be taken as a hit compound against the tumour cells expressing K_v channels.

Antioxidant, anti-inflammatory and analgesic activity of Mimosa acutistipula (Mart.) Benth

ETHNOPHARMACOLOGICAL RELEVANCE

Medicinal plants belonging to the genus Mimosa, such as Mimosa tenuiflora, M. caesalpinifolia, and M. verrucosa are known for their popular use for asthma, bronchitis and fever. Ethnopharmacological studies report that Mimosa acutistipula is used to treat alopecia and pharyngitis, conditions that can be related to oxidative stress, inflammatory processes and painful limitations. However, there is no studies on its efficacy and mechanism of action.

AIM OF THE STUDY

To elucidate the antioxidant, anti-inflammatory, analgesic and antipyretic activity of M. acutistipula leaves.

MATERIALS AND METHODS

Phytochemical profile of M. acutistipula extracts was evaluated by several reaction-specific methods. Secondary metabolites such as tannins, phenols and flavonoids were quantified with colorimetric assays. In vitro antioxidant potential was evaluated using DPPH and ABTS + as free radical scavenging tests, FRAP and phosphomolybdenum as oxide-reduction assays, and anti-hemolytic for lipid peroxidation evaluation. In vivo anti-inflammatory evaluation was performed by paw edema, and peritonitis induced by carrageenan. Analgesic effect and its possible mechanisms were determined by acetic acid-induced abdominal writhing and the formalin test. Antipyretic activity was evaluated by yeast-induced fever.

RESULTS

Cyclohexane, chloroform, ethyl acetate and methanol extracts of leaves had presence of tannins, flavonoids, phenol, alkaloids, terpenes (except methanolic extract), and saponins (only for methanolic and chloroformic extracts). In phenols, flavonoids and tannins quantification, methanolic and ethyl acetate extract had higher amounts of this phytocompounds. Ethyl acetate extract, due to its more expressive quantity of phenols and flavonoids, was chosen for carrying out the in vivo tests. Due to the relationship between oxidative stress and inflammation, antioxidant tests were performed, showing that ethyl acetate extract had a high total antioxidant activity (70.18%), moderate activity in DPPH radical scavenging, and a moderate ABTS + radical inhibition (33.61%), and FRAP assay (112.32 μg Fe²⁺/g). M. acutistipula showed anti-inflammatory activity, with 54.43% of reduction in paw edema (50 mg/kg) when compared to the vehicle. In peritonitis test, a reduction in the concentration of NO could be seen, which is highly involved in the anti-inflammatory activity and is responsible for the increase in permeability. In the analgesic evaluation, most significant results in writhing test were seen at 100 mg/kg, with a 34.7% reduction of writhing. A dual mechanism of action was confirmed with the formalin test, both neurogenic and inflammatory pain were reduced, with a mechanism via opioid route. In the antipyretic test, results were significantly decreased at all concentrations tested.

CONCLUSION

M. acutistipula leaves ethyl acetate extract showed expressive concentrations of phenolic compounds and antioxidant activity. It also exhibited anti-inflammatory and analgesic activity, besides its antipyretic effect. Thus, these results provide information regarding its popular use and might help future therapeutics involving this specimen.

Proceedings of the First Pediatric Coma and Disorders of Consciousness Symposium by the Curing Coma Campaign, Pediatric Neurocritical Care Research Group, and NINDS: Gearing for Success in Coma Advancements for Children and Neonates

This proceedings article presents the scope of pediatric coma and disorders of consciousness based on presentations and discussions at the First Pediatric Disorders of Consciousness Care and Research symposium held on September 14th, 2021. Herein we review the current state of pediatric coma care and research opportunities as well as shared experiences from seasoned researchers and clinicians. Salient current challenges and opportunities in pediatric and neonatal coma care and research were identified through the contributions of the presenters, who were Jose I. Suarez, MD, Nina F. Schor, MD, PhD, Beth S. Slomine, PhD Erika Molteni, PhD, and Jan-Marino Ramirez, PhD, and moderated by Varina L. Boerwinkle, MD, with overview by Mark Wainwright, MD, and subsequent audience discussion. The program, executively planned by Varina L. Boerwinkle, MD, Mark Wainwright, MD, and Michelle Elena Schober, MD, drove the identification and development of priorities for the pediatric neurocritical care community.

Pimozide Increases a Delayed Rectifier K+ Conductance in Chicken Embryo Vestibular Hair Cells

Pimozide is a conventional antipsychotic drug largely used in the therapy for schizophrenia and Tourette's syndrome. Pimozide is assumed to inhibit synaptic transmission at the CNS by acting as a dopaminergic D₂ receptor antagonist. Moreover, pimozide has been shown to block voltage-gated Ca²⁺ and K⁺ channels in different cells. Despite its widespread clinical use, pimozide can cause several adverse effects, including extrapyramidal symptoms and cardiac arrhythmias. Dizziness and loss of balance are among the most common side effects of pimozide. By using the patch-clamp whole-cell technique, we investigated the effect of pimozide [3 μM] on K⁺ channels expressed by chicken embryo vestibular type-II hair cells. We found that pimozide slightly blocks a transient outward rectifying A-type K⁺ current but substantially increases a delayed outward rectifying K⁺ current. The net result was a significant hyperpolarization of type-II hair cells at rest and a strong reduction of their response to depolarizing stimuli. Our findings are consistent with an inhibitory effect of pimozide on the afferent synaptic transmission by type-II hair cells. Moreover, they provide an additional key to understanding the beneficial/collateral pharmacological effects of pimozide. The finding that pimozide can act as a K⁺ channel opener provides a new perspective for the use of this drug.

In-situ and amplification-free imaging of hERG ion channels at single-cell level using a unique core-molecule-shell-secondary antibody SERS nanoprobe

Research on ion channels and their monoclonal antibodies plays a critical role in drug development and disease diagnosis. The current ion channel researches are often not conducted in the microenvironment for cells survival, which restricts the mechanism study of the links between the cell structure and the ion channel function. In this work, we synthesized gold core-4-mercaptobenzonitrile-sliver shell-goat anti-rabbit immunoglobulin G (Au@4-MBN@Ag@IgG) nanoparticles as surface-enhanced Raman scattering (SERS) nanoprobes for investigating the human ether-a-go-go related gene (hERG) potassium ion channel in cell membranes. This is the first attempt to study ion channels using SERS. Due to the unique core-molecule-shell structure and the silver shell of nanoprobes, strong and stable SERS signal was obtained. With the help of antibodies, the Au@4-MBN@Ag@IgG nanoprobes were captured by hERG antibodies and then bonded with hERG ion channels based on the sandwich immune response. The reporter molecule, 4-MBN, displayed a strong and sharp characteristic peak at 2233 cm^-1 in the Raman silent region. The intensity of this peak denoted the concentration of antibodies and the expression of ion channel proteins. We successfully applied this amplification-free method for in-situ imaging the distribution of the hERG ion channel on the transfected HEK293 cell surface at the single-cell level. This hERG ion channel profiling strategy promises a maneuverable tool for ion channel research.

Antidiabetic omarigliptin dilates rabbit aorta by activating voltage-dependent K+ channels and the sarco/endoplasmic reticulum Ca2+ -ATPase pump

We investigated the vasodilatory effect of omarigliptin, an oral antidiabetic drug in the dipeptidyl peptidase-4 inhibitor class, and its related mechanisms using phenylephrine (Phe)-induced pre-contracted aortic rings. Omarigliptin dilated aortic rings pre-constricted with Phe in a dose-dependent manner. Pretreatment with the voltage-dependent K⁺ channel inhibitor 4-aminopyridine significantly attenuated the vasodilatory effect of omarigliptin, whereas pretreatment with the inwardly rectifying K⁺ channel inhibitor Ba²⁺ , ATP-sensitive K⁺ channel inhibitor glibenclamide, and large-conductance Ca²⁺ -activated K⁺ channel inhibitor paxilline did not alter its vasodilation. Pretreatment with the sarco/endoplasmic reticulum Ca²⁺ -ATPase (SERCA) pump inhibitors thapsigargin and cyclopiazonic acid significantly reduced the vasodilatory effect of omarigliptin. Neither cAMP/PKA-related signaling pathway inhibitors nor cGMP/PKG-related signaling pathway inhibitors modulated the vasodilatory effect of omarigliptin. Removal of endothelium did not diminish the vasodilatory effect of omarigliptin. Furthermore, pretreatment with the nitric oxide synthase inhibitor L-NAME or small-conductance Ca²⁺ -activated K⁺ channel inhibitor apamin, together with the intermediate-conductance Ca²⁺ -activated K⁺ channel inhibitor TRAM-34, did not influence the vasodilatory effect of omarigliptin. In conclusion, omarigliptin induced vasodilation in rabbit aortic smooth muscle by activating voltage-dependent K⁺ channels and the SERCA pump independently of other K⁺ channels, cAMP/PKA- and cGMP/PKG-related signaling pathways, and the endothelium.