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Glioblastoma (GBM) is the most common malignant primary brain cancer that, despite recent advances in the understanding of its pathogenesis, remains incurable. GBM contains a subpopulation of cells with stem cell-like properties called cancer stem cells (CSCs). Several studies have demonstrated that CSCs are resistant to conventional chemotherapy and radiation thus representing important targets for novel anti-cancer therapies. Proton sensing receptors expressed by CSCs could represent important factors involved in the adaptation of tumours to the extracellular environment. Accordingly, the expression of acid-sensing ion channels (ASICs), proton-gated sodium channels mainly expressed in the neurons of peripheral (PNS) and central nervous system (CNS), has been demonstrated in several tumours and linked to an increase in cell migration and proliferation. In this paper we report that the ASIC3 isoform, usually absent in the CNS and present in the PNS, is enriched in human GBM CSCs while poorly expressed in the healthy human brain. We propose here a novel therapeutic strategy based on the pharmacological activation of ASIC3, which induces a significant GBM CSCs damage while being non-toxic for neurons. This approach might offer a promising and appealing new translational pathway for the treatment of glioblastoma. [ABSTRACT FROM AUTHOR]

Antiseizure medications (ASMs) play a central role in seizure management, however, unpredictability in the response to treatment persists, even among patients with similar seizure manifestations and clinical backgrounds. An objective biomarker capable of reliably predicting the response to ASMs would profoundly impact epilepsy treatment. Presently, clinicians rely on a trial-and-error approach when selecting ASMs, a time-consuming process that can result in delays in receiving alternative non-pharmacological therapies such as a ketogenetic diet, epilepsy surgery, and neuromodulation therapies. Pharmacogenetic studies investigating the correlation between ASMs and genetic variants regarding their mechanistic targets offer promise in predicting the response to treatment. Sodium channel subunit genes have been extensively studied along with other ion channels and receptors as targets, however, the results have been conflicting, possibly due to methodological disparities including inconsistent definitions of drug response, variations in ASM combinations, and diversity of genetic variants/genes studied. Nonetheless, these studies underscore the potential effect of genetic variants on the mechanism of ASMs and consequently the prediction of treatment response. Recent advances in sequencing technology have led to the generation of large genetic datasets, which may be able to enhance the predictive accuracy of the response to ASMs. [ABSTRACT FROM AUTHOR]

Vincristine-induced peripheral neuropathy is a common side effect of vincristine treatment, which is accompanied by pain and can be dose-limiting. The molecular mechanisms that underlie vincristine-induced pain are not well understood. We have established an animal model to investigate pathophysiological mechanisms of vincristine-induced pain. Our previous studies have shown that the tetrodotoxin-sensitive voltage-gated sodium channel Nav1.6 in medium-diameter dorsal root ganglion (DRG) neurons contributes to the maintenance of vincristine-induced allodynia. In this study, we investigated the effects of vincristine administration on excitability in small-diameter DRG neurons and whether the tetrodotoxin-resistant (TTX-R) Nav1.8 channels contribute to mechanical allodynia. Current-clamp recordings demonstrated that small DRG neurons become hyper-excitable following vincristine treatment, with both reduced current threshold and increased firing frequency. Using voltage-clamp recordings in small DRG neurons, we now show an increase in TTX-R current density and a −7.3 mV hyperpolarizing shift in the half-maximal potential (V1/2) of activation of Nav1.8 channels in vincristine-treated animals, which likely contributes to the hyperexcitability that we observed in these neurons. Notably, vincristine treatment did not enhance excitability of small DRG neurons from Nav1.8 knockout mice, and the development of mechanical allodynia was delayed but not abrogated in these mice. Together, our data suggest that sodium channel Nav1.8 in small DRG neurons contributes to the development of vincristine-induced mechanical allodynia. [ABSTRACT FROM AUTHOR]

Objectives Methods Results Proposed Concept Antidepressants used by patients with bipolar disorder have been associated with destabilization with an increase in mania, depression, and cycling. The most commonly proposed mechanism, that antidepressants ‘overshoot’ their antidepressant effect to create a manic or mixed state, is unlikely since antidepressants have actually been found to be ineffective in treating bipolar depression. Beginning with known bipolar‐specific pathophysiologic abnormalities provides the greatest likelihood of insight.PubMed was queried with ‘bipolar’, ‘sodium’, ‘intracellular sodium’, ‘serotonin 3’, ‘5HT3’, ‘5‐hydroxytryptamine type 3 receptors’, and ‘antidepressant’ either individually or in combination.Pathologic mood states (both mania and depression) are associated with increased intracellular sodium (Na) concentrations that depolarize the resting membrane potential to increase cellular excitability (mania) or cause depolarization block (depression). Stimulation of the serotonin (5HT) receptors depolarizes the post‐synaptic neuron. Stimulation of 5HT3 may be of particular importance since it is coupled to a cation channel that directly depolarizes the membrane. These effects directly impact the physiology of patients with bipolar disorder to alter neuronal excitability in a fashion that worsens both mania and depression.The most consistently observed biological abnormality in individuals going through mania or bipolar depression involves a decline in Na pump activity, with consequent elevation of intracellular Na levels. Antidepressant treatment potentiates this, particularly by activation of 5HT3. This hypothesis can be tested by coadministering a 5HT3 antagonist (e.g., vortioxetine or ondansetron) to achieve blockade of that receptor while treating bipolar depression with a serotoninergic antidepressant. [ABSTRACT FROM AUTHOR]

Cardiac arrhythmia treatment is a clinical challenge necessitating safer and more effective therapies. Recent studies have highlighted the role of the perinexus, an intercalated disc nanodomain enriched in voltage-gated sodium channels including both Na v 1.5 and β1 subunits, adjacent to gap junctions. These findings offer insights into action potential conduction in the heart. A 19-amino acid SCN1B (β1/β1B) mimetic peptide, βadp1, disrupts VGSC beta subunit-mediated adhesion in cardiac perinexii, inducing arrhythmogenic changes. We aimed to explore βadp1's mechanism and develop novel SCN1B mimetic peptides affecting β1-mediated adhesion. Using patch clamp assays in neonatal rat cardiomyocytes and electric cell substrate impedance sensing (ECIS) in β1-expressing cells, we observed βadp1 maintained inhibitory effects for up to 5 h. A shorter peptide (LQLEED) based on the carboxyl-terminus of βadp1 mimicked this inhibitory effect, while dimeric peptides containing repeated LQLEED sequences paradoxically promoted intercellular adhesion over longer time courses. Moreover, we found a link between these peptides and β1-regulated intramembrane proteolysis (RIP) - a signaling pathway effecting gene transcription including that of VGSC subunits. βadp1 increased RIP continuously over 48 h, while dimeric agonists acutely boosted RIP for up to 6 h. In the presence of DAPT, an RIP inhibitor, βadp1's effects on ECIS-measured intercellular adhesion was reduced, suggesting a relationship between RIP and the peptide's inhibitory action. In conclusion, novel SCN1B (β1/β1B) mimetic peptides are reported with the potential to modulate intercellular VGSC β1-mediated adhesion, potentially through β1 RIP. These findings suggest a path towards the development of anti-arrhythmic drugs targeting the perinexus. [Display omitted] • Voltage-gated sodium channel β1 subunit offers novel anti-arrhythmic target. • β1 mimetic peptides increase regulated intramembrane proteolysis (RIP) of β1. • β1 mimetic peptide monomers decrease β1-mediated adhesion. • β1 mimetic peptide dimers stabilize or increase β1-mediated adhesion. [ABSTRACT FROM AUTHOR]

Osteoarthritis (OA) is a highly prevalent joint disease that causes substantial disability, yet effective approaches to disease prevention or to the delay of OA progression are lacking. Emerging evidence has pinpointed ion channels as pivotal mediators in OA pathogenesis and as promising targets for disease-modifying treatments. Preclinical studies have assessed the potential of a variety of ion channel modulators to modify disease pathways involved in cartilage degeneration, synovial inflammation, bone hyperplasia and pain, and to provide symptomatic relief in models of OA. Some of these modulators are currently being evaluated in clinical trials. This review explores the structures and functions of ion channels, including transient receptor potential channels, Piezo channels, voltage-gated sodium channels, voltage-dependent calcium channels, potassium channels, acid-sensing ion channels, chloride channels and the ATP-dependent P2XR channels in the osteoarthritic joint. The discussion spans channel-targeting drug discovery and potential clinical applications, emphasizing opportunities for further research, and underscoring the growing clinical impact of ion channel biology in OA. Ion channels have key functions in chondrocytes, bone cells, immune cells and neurons. Liu and colleagues discuss how these functions might contribute to cartilage degeneration, bone formation inflammation and pain in osteoarthritis, and highlight the therapeutic potential of ion channel modulators. Key points: Ion channels have key functions in the joints and emerge as important contributors to pathogenic processes in osteoarthritis (OA). Dysregulation of mechanical and biochemical stimuli activates ion channels such as TRPV4 and Piezo channels, leading to Ca2+ and Na+ influx, which contributes to cartilage destruction, inflammation and pain in OA. Some ion channels typically associated with peripheral neurons are also expressed in chondrocytes and immune cells, and have a crucial role in the pathophysiology of OA. Exploration of ion channel expression, interactions, and properties in joints, along with development of specific channel agonists and antagonists, has helped to accelerate research on their potential roles in OA. Several ion channel modulators have been recently tested in animal models and patients with OA, with encouraging results. Targeting of ion channels holds promise for the development of new and more effective OA treatment strategies. [ABSTRACT FROM AUTHOR]

Epithelial Na+ channels (ENaCs) are activated by proteolysis of the α and γ subunits at specific sites flanking embedded inhibitory tracts. To examine the role of α subunit proteolysis in channel activation in vivo, we generated mice lacking the distal furin cleavage site in the α subunit (αF2M mice). On a normal Na+ control diet, no differences in ENaC protein abundance in kidney or distal colon were noted between wild‐type (WT) and αF2M mice. Patch‐clamp analyses revealed similar levels of ENaC activity in kidney tubules, while no physiologically relevant differences in blood chemistry or aldosterone levels were detected. Male αF2M mice did exhibit diminished ENaC activity in the distal colon, as measured by amiloride‐sensitive short‐circuit current (ISC). Following dietary Na+ restriction, WT and αF2M mice had similar natriuretic and colonic ISC responses to amiloride. However, single‐channel activity was significantly lower in kidney tubules from Na+‐restricted αF2M mice compared with WT littermates. ENaC α and γ subunit expression in kidney and distal colon were also enhanced in Na+‐restricted αF2Mvs. WT mice, in association with higher aldosterone levels. These data provide evidence that disrupting α subunit proteolysis impairs ENaC activity in vivo, requiring compensation in response to Na+ restriction. Key points: The epithelial Na+ channel (ENaC) is activated by proteolytic cleavage in vitro, but key questions regarding the role of ENaC proteolysis in terms of whole‐animal physiology remain to be addressed.We studied the in vivo importance of this mechanism by generating a mouse model with a genetic disruption to a key cleavage site in the ENaC's α subunit (αF2M mice).We found that αF2M mice did not exhibit a physiologically relevant phenotype under normal dietary conditions, but have impaired ENaC activation (channel open probability) in the kidney during salt restriction.ENaC function at the organ level was preserved in salt‐restricted αF2M mice, but this was associated with higher aldosterone levels and increased expression of ENaC subunits, suggesting compensation was required to maintain homeostasis.These results provide the first evidence that ENaC α subunit proteolysis is a key regulator of channel activity in vivo. [ABSTRACT FROM AUTHOR]

Since their discovery nearly 30 years ago, fibroblast growth factor homologous factors (FHFs) are now known to control the functionality of excitable tissues through a range of mechanisms. Nervous and cardiac system dysfunctions are caused by loss‐ or gain‐of‐function mutations in FHF genes. The best understood 'canonical' targets for FHF action are voltage‐gated sodium channels, and recent studies have expanded the repertoire of ways that FHFs modulate sodium channel gating. Additional 'non‐canonical' functions of FHFs in excitable and non‐excitable cells, including cancer cells, have been reported over the past dozen years. This review summarizes and evaluates reported canonical and non‐canonical FHF functions. [ABSTRACT FROM AUTHOR]

Tetrodotoxin (TTX) is a potent neurotoxin firstly discovered in the ovary of pufferfish. The genetic basis of voltage-gated sodium channel resistance to TTX has been widely studied, but it remains unclear in the evolution history of voltage-gated sodium channel resistance to TTX in pufferfish with different TTX concentrations. In this study, six scn4aa coding sequences of pufferfish were firstly cloned and sequenced, then used to investigate the adaptive evolution of scn4aa associated with TTX concentration and reconstruct ancestral sequences with seven scn4aa of other fishes. The result of CODEML (codon substitution model) program from the PAML (phylogenetic analysis by maximum likelihood) package shows only in the genus of Takifugu, which contains TTX highly in the liver, under positive selection. The result also indicates that three of four positively selected sites are located in the intracellular regions, which may compensate for normal function. The ancestral sequence reconstruction may suggest that the replacements providing weak toxin resistance might have appeared first in scn4aa, then the genus Takifugu evolved stronger resistance to TTX later. These results contribute to the explanation of the evolutional history of voltage-gated sodium channel resistance to TTX in pufferfish. [ABSTRACT FROM AUTHOR]

Background and Purpose: The voltage‐gated sodium channel isoform NaV1.7 is a high‐interest target for the development of non‐opioid analgesics due to its preferential expression in pain‐sensing neurons. NaV1.7 is also expressed in autonomic neurons, yet its contribution to involuntary visceral reflexes has received limited attention. The small molecule inhibitor ST‐2560 was advanced into pain behaviour and cardiovascular models to understand the pharmacodynamic effects of selective inhibition of NaV1.7. Experimental Approach: Potency of ST‐2560 at NaV1.7 and off‐target ion channels was evaluated by whole‐cell patch‐clamp electrophysiology. Effects on nocifensive reflexes were assessed in non‐human primate (NHP) behavioural models, employing the chemical capsaicin and mechanical stimuli. Cardiovascular parameters were monitored continuously in freely‐moving, telemetered NHPs following administration of vehicle and ST‐2560. Key Results: ST‐2560 is a potent inhibitor (IC50 = 39 nM) of NaV1.7 in primates with ≥1000‐fold selectivity over other isoforms of the human NaV1.x family. Following systemic administration, ST‐2560 (0.1–0.3 mg·kg−1, s.c.) suppressed noxious mechanical‐ and chemical‐evoked reflexes at free plasma concentrations threefold to fivefold above NaV1.7 IC50. ST‐2560 (0.1–1.0 mg·kg−1, s.c.) also produced changes in haemodynamic parameters, most notably a 10‐ to 20‐mmHg reduction in systolic and diastolic arterial blood pressure, at similar exposures. Conclusions and Implications: Acute pharmacological inhibition of NaV1.7 is antinociceptive, but also has the potential to impact the cardiovascular system. Further work is merited to understand the role of NaV1.7 in autonomic ganglia involved in the control of heart rate and blood pressure, and the effect of selective NaV1.7 inhibition on cardiovascular function. [ABSTRACT FROM AUTHOR]

Artificial ion channels that enable high-efficiency ion transport have important implications in nanofluidics and biomedical applications such as drug delivery. Herein, we show a simulation-based chemical design of a biomimetic sodium channel that possesses permeation rate and selectivity potentially higher than those of the state-of-the-art natural vertebrate voltage-gated sodium channels. Importantly, our theoretical findings have undergone empirical testing, aligning well with the Arrhenius law as derived from a diverse range of experimental results. The high-efficiency ion transport is achieved by anchoring the carboxylate functional groups within the channel filter. A key chemical guiding principle underlying the ion channel design is that the freeenergy barrier for the Na+ passage across the channel should be comparable to typical thermal energy at room temperature. With the implementation of the chemical design, we found that the relatively low free-energy barrier can be attributed to the compensation effect of the carboxylate groups to the partially lost oxygen shell of the ion within the ion channel, as well as to the consonant vibration of the ions inside and outside the channel. This mechanistic understanding brings new insight, at the molecular level, into the high-efficiency ion transport across the designed membrane channels. The proof of principle achieved from the simulations will stimulate future experimental confirmation and potential applications of the high-performance artificial channels in nanofluidics and in bioinspired iontronics. [ABSTRACT FROM AUTHOR]

BACKGROUND: Aphis gossypii is a worldwide agricultural pest that causes high levels of economic losses by feeding and transmitting virus diseases. It is usually controlled by chemical insecticides, but this could lead to the selection of resistant populations. Several single nucleotide polymorphisms (SNPs) have been identified associated with insecticide resistance. Monitoring activities to detect the presence of such mutations in field populations can have an important role in insect pest management but, currently, no information on Italian strains is available. RESULTS: The presence of target site mutations conferring resistance to different insecticides was analysed in Italian field collected populations of A. gossypii with an allele specific approach (QSGG, Qualitative Sybr‐Green Genotyping). Primers were designed to detect mutations in genes coding acetylcholinesterase (S431F), nicotinic acetylcholine receptor (R81T) and voltage‐gated sodium channel (M918L and L1014F). S431F was widespread but with high variability across populations. R81T was detected for the first time in Italy but only in two populations. The L1014F mutation (kdr) was not found, while in the samples showing the M918L two different nucleotidic substitutions were detected. Mutant allele frequencies were, respectively, 0.70 (S431), 0.31 (M918) and 0.02 (R81). Further analysis on the voltage‐gated sodium channel gene showed the presence of eight haplotypes and one non‐synonymous mutation in the gene coding region. CONCLUSION: Multiple target‐site mutations were detected within Italian populations. The combinations of genotypes observed in certain locations could affect negatively the control of this pest. Preliminary insights on the genetic structure in the Italian populations of A. gossypii were acquired. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Resistance to insecticides is one of the great challenges that vector control programs must face. The constant use of pyrethroid-type insecticides worldwide has caused selection pressure in populations of the Aedes aegypti vector, which has promoted the emergence of resistant populations. The resistance mechanism to pyrethroid insecticides most studied to date is target-site mutations that desensitize the voltage-gated sodium channel (VGSC) of the insect to the action of pyrethroids. In the present study, susceptibility to the pyrethroid insecticides permethrin, lambda-cyhalothrin, and deltamethrin was evaluated in fourteen populations from the department of Córdoba, Colombia. The CDC bottle bioassay and WHO tube methods were used. Additionally, the frequencies of the F1534C, V1016I, and V410L mutations were determined, and the association of resistance with the tri-locus haplotypes was examined. The results varied between the two techniques used, with resistance to permethrin observed in thirteen of the fourteen populations, resistance to lambda-cyhalothrin in two populations, and susceptibility to deltamethrin in all the populations under study with the CDC method. In contrast, the WHO method showed resistance to the three insecticides evaluated in all populations. The frequencies of the mutated alleles ranged from 0.05–0.43 for 1016I, 0.94–1.0 for 1534C, and 0.01–0.59 for 410L. The triple homozygous mutant CIL haplotype was associated with resistance to all three pyrethroids evaluated with the WHO bioassay, while with the CDC bioassay, it was only associated with resistance to permethrin. This study highlights the importance of implementing systematic monitoring of kdr mutations, allowing resistance management strategies to be dynamically adjusted to achieve effective control of Aedes aegypti. [ABSTRACT FROM AUTHOR]

Background: Pyrethroid chemicals are one of the main acaricides used against ticks. Resistance to these chemicals has been reported to be associated with mutations in the voltage-gated sodium channel (VGSC) gene of the Rhipicephalus microplus. This study investigates R. microplus resistance to pyrethroids in Guangxi region of China, marking one of the first research efforts in this area. The findings are intended to provide vital baseline for the effective implementation of localized tick control strategies. Methods: From March to July 2021, 447 R. microplus tick samples were collected from five prefecture-level cities in Guangxi. Allele-specific polymerase chain reaction (AS-PCR) was used to amplify segments C190A and G215T of the domain II S4-5 linker and T2134A of domain III S6 in the VGSC, to detect nucleotide mutations associated with resistance to pyrethroid acaricides. Subsequent analyses were conducted to ascertain the prevalence, types of mutations, and genotypic distributions within the sampled populations. Results: Mutations within VGSC gene were identified across all five studied populations of R. microplus, although the mutation rates remained generally low. Specifically, the most prevalent mutation was C190A, observed in 4.9% of the samples (22/447), followed by G215T at 4.0% (18/447), and T2134A at 1.3% (6/447). The distribution of mutations across three critical sites of the VGSC gene revealed four distinct mutation types: C190A, G215T, C190A + G215T, and T2134A. Notably, the single mutation C190A had the highest mutation frequency, accounting for 4.3%, and the C190A + G215T combination had the lowest, at only 0.7%. The analysis further identified seven genotypic combinations, with the wild-type combination C/C + G/G + T/T predominating at a frequency of 90.4%. Subsequently, the C/A + G/G + T/T combination was observed at a frequency of 4.3%, whereas the C/C + T/T + T/T combination exhibited the lowest frequency (0.2%). Additionally, no instances of simultaneous mutations at all three sites were detected. Geographical differences in mutation types were apparent. Both samples from Hechi to Chongzuo cities exhibited the same three mutation types; however, C190A was the most prevalent in Hechi, while G215T dominated in Chongzuo. In contrast, samples from Beihai to Guilin each exhibited only one mutation type: G215T occurred in 12.5% (4/32) of Beihai samples, and C190A in 7.5% (4/53) of Guilin samples. Conclusions: These findings underscore the relatively low frequency of VGSC gene mutations in R. microplus associated with pyrethroid resistance in the Guangxi, China. Moreover, the variation in mutation types and genotypic distributions across different locales highlights the need for regionalized strategies in monitoring and managing pyrethroid resistance in tick populations. This molecular surveillance is crucial for informing targeted control measures and mitigating the risk of widespread resistance emergence. [ABSTRACT FROM AUTHOR]

Objective Methods Results Interpretation Developmental and epileptic encephalopathies (DEEs) can result from dominant, gain of function variants of neuronal ion channels. More than 450 de novo missense variants of the sodium channel gene SCN8A have been identified in individuals with DEE.We studied a mouse model carrying the patient Scn8a variant p.Asn1768Asp. An AAV‐PHP.eB virus carrying an allele‐specific single guide RNA (sgRNA) was administered by intracerebroventricular injection. Cas9 was provided by an inherited transgene.Allele‐specific disruption of the reading frame of the pathogenic transcript generated out‐of‐frame indels in 1/4 to 1/3 of transcripts throughout the brain. This editing efficiency was sufficient to rescue lethality and seizures. Neuronal hyperexcitability was reduced in cells expressing the virus.The data demonstrate efficient allele‐specific editing of a dominant missense variant and support the feasibility of allele‐specific therapy for DEE epilepsy. ANN NEUROL 2024 [ABSTRACT FROM AUTHOR]

Na4Fe3(PO4)2P2O7 is regarded as the most promising polyanionic cathode for sodium‐ion batteries (SIBs) due to its superior structural stability, cost‐effectiveness, and environmental benignity. However, the low operating voltage inevitably weakens its competitiveness in energy density. Previous works have tried to enhance its operating voltage by Mn doping, which draws on the design idea of LiFexMn1‐xPO4 cathode for lithium‐ion batteries, but with little success. In this context, uncovering the role of Mn substitution in Na4Fe3‐xMnx(PO4)2P2O7 (NFMxPP) cathode is urgently needed. This work discloses the effect of Mn contents on the structure, sodium storage property, and reaction mechanism of NFMxPP cathode for the first time. Introducing a moderate amount of Mn (0.6 ≤ x ≤ 1.2) into NFMxPP can weaken the Fe–O bonding interaction, thus leading to the full utilization of Mn3+/Mn2+ redox couple. As the representative, NFM1.2PP cathode exhibited a high operating voltage of ≈3.3 V with a reversible capacity of 109.2 mAh g−1. Note that a Hard carbon||NFM1.2PP full battery manifests considerably high‐capacity retention of 92.3% over 1600 cycles. It is believed that an understanding of the role of Mn substitution in this work will promote the practical application of high voltage NFMxPP cathodes for SIBs. [ABSTRACT FROM AUTHOR]

It is well recognized that changes in the extracellular concentration of calcium ions influence the excitability of neurons, yet what mechanism(s) mediate these effects is still a matter of debate. Using patch‐clamp recordings from rat hippocampal CA1 pyramidal neurons, we examined the contribution of G‐proteins and intracellular calcium‐dependent signaling mechanisms to changes in intrinsic excitability evoked by altering the extracellular calcium concentration from physiological (1.2 mM) to a commonly used experimental (2 mM) level. We find that the inhibitory effect on intrinsic excitability of calcium ions is mainly expressed as an increased threshold for action potential firing (with no significant effect on resting membrane potential) that is not blocked by either the G‐protein inhibitor GDPβS or the calcium chelator BAPTA. Our results therefore argue that in the concentration range studied, G‐protein coupled calcium‐sensing receptors, non‐selective cation conductances, and intracellular calcium signaling pathways are not involved in mediating the effect of extracellular calcium ions on intrinsic excitability. Analysis of the derivative of the action potential, dV/dt versus membrane potential, indicates a current shift towards more depolarized membrane potentials at the higher calcium concentration. Our results are thus consistent with a mechanism in which extracellular calcium ions act directly on the voltage‐gated sodium channels by neutralizing negative charges on the extracellular surface of these channels to modulate the threshold for action potential activation. [ABSTRACT FROM AUTHOR]

Botulinum neurotoxins (BoNTs), produced by Clostridium botulinum, have been used for the treatment of various central and peripheral neurological conditions. Recent studies have suggested that BoNTs may also have a beneficial effect on pain conditions. It has been hypothesized that one of the mechanisms underlying BoNTs' analgesic effects is the inhibition of pain-related receptors' transmission to the neuronal cell membrane. BoNT application disrupts the integration of synaptic vesicles with the cellular membrane, which is responsible for transporting various receptors, including pain receptors such as TRP channels, calcium channels, sodium channels, purinergic receptors, neurokinin-1 receptors, and glutamate receptors. BoNT also modulates the opioidergic system and the GABAergic system, both of which are involved in the pain process. Understanding the cellular and molecular mechanisms underlying these effects can provide valuable insights for the development of novel therapeutic approaches for pain management. This review aims to summarize the experimental evidence of the analgesic functions of BoNTs and discuss the cellular and molecular mechanisms by which they can act on pain conditions by inhibiting the transmission of pain-related receptors. [ABSTRACT FROM AUTHOR]

Background: Sand flies serve as crucial vectors in various medical and veterinary diseases. Sand fly-borne diseases pose a significant public health burden globally, as the causative agents can infect a diverse range of hosts, leading to severe consequences such as leishmaniasis and sand fly fever. Additionally, the widespread use of insecticides for agricultural purposes and mosquito control is not specifically targeted at sand flies, potentially leading to resistance development. We investigated sand fly species, their potential role as vectors of various parasitic agents, and insecticide resistance in the endemic regions of Natawi and Sadao districts in Songkhla, Thailand. Methods: Sand flies were collected using CDC light traps. The collected sand flies were then identified to species level using molecular techniques. Subsequent analyses included the detection of pathogens and the identification of pyrethroid resistance mutations within the voltage-sensitive sodium channel (Vgsc) domain IIS6 gene, followed by sequence analysis. Results: The study identified nine sand fly species belonging to the genera Phlebotomus and Sergentomyia. The DNA of Sergentomyia khawi was the only species found to test positive for one sample of Leishmania orientalis in Sadao district. This finding represents the first detection of L. orientalis in Thailand. Moreover, three samples of Leishmania martiniquensis and four samples of Trypanosoma sp. were found in the Natawi district. No I1011M, L1014F/S, V1016G, or F1020S mutations were detected in Vgsc gene. Conclusions: The results of this study provide valuable information on sand fly species and the continuous circulation of Leishmania spp. and Trypanosoma spp. in Songkhla, southern Thailand. Moreover, the development of geo-spatial information on vectors, parasites, and insecticide resistance in sand flies has the potential to provide well-informed risk assessments and evidence-based guidance for targeted vector control in Thailand. These results can serve as a foundation for integrating the One Health approach, which is crucial for disease control, considering the diverse ecological interactions among human and/or animal reservoir hosts, parasites, and sand fly vectors. [ABSTRACT FROM AUTHOR]

Background: Pyrethroid resistance is one of the major threats for effectiveness of insecticide-treated bed nets (ITNs) in malaria vector control. Genotyping of mutations in the voltage gated sodium channel (VGSC) gene is widely used to easily assess the evolution and spread of pyrethroid target-site resistance among malaria vectors. L1014F and L1014S substitutions are the most common and best characterized VGSC mutations in major African malaria vector species of the Anopheles gambiae complex. Recently, an additional substitution involved in pyrethroid resistance, i.e. V402L, has been detected in Anopheles coluzzii from West Africa lacking any other resistance alleles at locus 1014. The evolution of target-site resistance mutations L1014F/S and V402L was monitored in An. coluzzii and Anopheles arabiensis specimens from a Burkina Faso village over a 10-year range after the massive ITN scale-up started in 2010. Methods: Anopheles coluzzii (N = 300) and An. arabiensis (N = 362) specimens collected both indoors and outdoors by different methods (pyrethrum spray catch, sticky resting box and human landing collections) in 2011, 2015 and 2020 at Goden village were genotyped by TaqMan assays and sequencing for the three target site resistance mutations; allele frequencies were statistically investigated over the years. Results: A divergent trend in resistant allele frequencies was observed in the two species: 1014F decreased in An. coluzzii (from 0.76 to 0.52) but increased in An. arabiensis (from 0.18 to 0.70); 1014S occurred only in An. arabiensis and slightly decreased over time (from 0.33 to 0.23); 402L increased in An. coluzzii (from 0.15 to 0.48) and was found for the first time in one An. arabiensis specimen. In 2020 the co-occurrence of different resistance alleles reached 43% in An. coluzzii (alleles 410L and 1014F) and 32% in An. arabiensis (alleles 1014F and 1014S). Conclusions: Overall, an increasing level of target-site resistance was observed among the populations with only 1% of the two malaria vector species being wild type at both loci, 1014 and 402, in 2020. This, together with the co-occurrence of different mutations in the same specimens, calls for future investigations on the possible synergism between resistance alleles and their phenotype to implement local tailored intervention strategies. [ABSTRACT FROM AUTHOR]

The open-channel block of N-methyl-D-aspartate receptors (NMDARs) and their calcium-dependent desensitization (CDD) represent conventional mechanisms of glutamatergic synapse regulation. In neurotrauma, neurodegeneration, and neuropathic pain the clinical benefits of cure with memantine, ketamine, Mg2+, and some tricyclic antidepressants are often attributed to NMDAR open-channel block, while possible involvement of NMDAR CDD in the therapy is not well established. Here the effects of selective high-affinity sodium-calcium exchanger (NCX) isoform 1 inhibitor, SEA0400, on NMDA-activated whole-cell currents and their block by amitriptyline, desipramine and clomipramine recorded by patchclamp technique in cortical neurons of primary culture were studied. We demonstrated that in the presence of extracellular Ca2+, 50 nM SEA0400 caused a reversible decrease of the steady-state amplitude of NMDAR currents, whereas loading neurons with BAPTA or the removal of extracellular Ca2+ abolished the effect. The decrease did not exceed 30% of the amplitude and did not depend on membrane voltage. The external Mg2+ block and 50 nM SEA0400 inhibition of currents were additive, suggesting their independent modes of action. In the presence of Ca2+ SEA0400 speeded up the decay of NMDAR currents to the steady state determined by CDD. The measured IC50 value of 27 nM for SEA0400-induced inhibition coincides with that for NCX1. Presumably, SEA0400 effects are induced by an enhancement of NMDAR CDD through the inhibition of Ca2+ extrusion by NCX1. SEA0400, in addition, at nanomolar concentrations could interfere with Ca2+-dependent effect of tricyclic antidepressants. In the presence of 50 nM SEA0400, the IC50s for NMDAR inhibition by amitriptyline and desipramine increased by about 20 folds, as the Ca2+-dependent NMDAR inhibition disappeared. This observation highlights NCX1 involvement in amitriptyline and desipramine effects on NMDARs and unmasks competitive relationships between SEA0400 and these antidepressants. Neither amitriptyline nor desipramine could affect NCX3. The open-channel block of NMDARs by these substances was not affected by SEA0400. In agreement, SEA0400 did not change the IC50 for clomipramine, which acts as a pure NMDAR open-channel blocker. Thus, NCX seems to represent a promising molecular target to treat neurological disorders, because of the ability to modulate NMDARs by decreasing the open probability through the enhancement of their CDD. [ABSTRACT FROM AUTHOR]

Ovarian granulosa cells are essential to gonadotrophin-regulated estrogen production, female cycle maintenance and fertility. The epithelial Na+ channel (ENaC) is associated with female fertility; however, whether and how it plays a role in ovarian cell function(s) remained unexplored. Here, we report patch-clamp and Na+ imaging detection of ENaC expression and channel activity in both human and mouse ovarian granulosa cells, which are promoted by pituitary gonadotrophins, follicle stimulating hormone (FSH) or luteinizing hormone (LH). Cre-recombinase- and CRISPR-Cas9-based granulosa-specific knockout of ENaC α subunit (Scnn1a) in mice resulted in failed estrogen elevation at early estrus, reduced number of corpus luteum, abnormally extended estrus phase, reduced litter size and subfertility in adult female mice. Further analysis using technologies including RNA sequencing and Ca2+ imaging revealed that pharmacological inhibition, shRNA-based knockdown or the knockout of ENaC diminished spontaneous or stimulated Ca2+ oscillations, lowered the capacity of intracellular Ca2+ stores and impaired FSH/LH-stimulated transcriptome changes for estrogen production in mouse and/or human granulosa cells. Together, these results have revealed a previously undefined role of ENaC in modulating gonadotrophin signaling in granulosa cells for estrogen homeostasis and thus female fertility. [ABSTRACT FROM AUTHOR]

Electrical signaling is essential for all fast processes in biology, but its molecular mechanisms have been uncertain. This review article focuses on studies of bacterial sodium channels in order to home in on the essential molecular and chemical mechanisms underlying transmembrane ion conductance and voltage-dependent gating without the overlay of complex protein interactions and regulatory mechanisms in mammalian sodium channels. This minimalist approach has yielded a nearly complete picture of sodium channel function at the atomic level that are mostly conserved in mammalian sodium channels, including sodium selectivity and conductance, voltage sensing and activation, electromechanical coupling to pore opening and closing, slow inactivation, and pathogenic dysfunction in a debilitating channelopathy. Future studies of nature's simplest sodium channels may continue to yield key insights into the fundamental molecular and chemical principles of their function and further elucidate the chemical basis of electrical signaling. [Display omitted] In this review, Catterall et al. describe how electrical signals are generated in excitable cells by voltage-gated sodium channels. The authors highlight fundamental molecular and chemical mechanisms that have arisen in evolution that are crucial to improve our understanding of sodium channel diseases and to develop improved therapies. [ABSTRACT FROM AUTHOR]

Voltage-gated sodium (Na v) and calcium (Ca v) channels are responsible for the initiation of electrical signals. They have long been targeted for the treatment of various diseases. The mounting number of cryoelectron microscopy (cryo-EM) structures for diverse subtypes of Na v and Ca v channels from multiple organisms necessitates a generic residue numbering system to establish the structure-function relationship and to aid rational drug design or optimization. Here we suggest a structure-based residue numbering scheme, centering around the most conserved residues on each of the functional segments. We elaborate the generic numbers through illustrative examples, focusing on representative drug-binding sites of eukaryotic Na v and Ca v channels. We also extend the numbering scheme to compare common disease mutations among different Na v subtypes. Application of the generic residue numbering scheme affords immediate insights into hotspots for pathogenic mutations and critical loci for drug binding and will facilitate drug discovery targeting Na v and Ca v channels. In this perspective, Xueqin Jin et al. propose a uniform residue numbering scheme for conserved segments in Na v and Ca v channels across species and subtypes. This structure-based scheme will advance structural pharmacology by identifying common mutations and druggable sites, thereby facilitating targeted therapies. [ABSTRACT FROM AUTHOR]

The effects of enhanced late INa, a persistent component of the Na+ channel current, on the intracellular ion dynamics and the automaticity of the pulmonary vein cardiomyocytes were studied with fluorescent microscopy. Anemonia viridis toxin II (ATX- II), an enhancer of late INa, caused increases in the basal Na+ and Ca2+ concentrations, increases in the number of Ca2+ sparks and Ca2+ waves, and the generation of repetitive Ca2+ transients. These phenomena were inhibited by eleclazine, a blocker of the late INa; SEA0400, an inhibitor of the Na+/Ca2+ exchanger (NCX); H89, a protein kinase A (PKA) inhibitor; and KN-93, a Ca2+/calmodulin-dependent protein kinase II (CaMKII) inhibitor. These results suggest that enhancement of late INa in the pulmonary vein cardiomyocytes causes disturbance of the intracellular ion environment through activation of the NCX and Ca2+-dependent enzymes. Such mechanisms are probably involved in the ectopic electrical activity of the pulmonary vein myocardium. [ABSTRACT FROM AUTHOR]

Slow brain rhythms, for example during slow-wave sleep or pathological conditions like seizures and spreading depolarization, can be accompanied by oscillations in extracellular potassium concentration. Such slow brain rhythms typically have a lower frequency than tonic action-potential firing. They are assumed to arise from network-level mechanisms, involving synaptic interactions and delays, or from intrinsically bursting neurons. Neuronal burst generation is commonly attributed to ion channels with slow kinetics. Here, we explore an alternative mechanism generically available to all neurons with class I excitability. It is based on the interplay of fast-spiking voltage dynamics with a one-dimensional slow dynamics of the extracellular potassium concentration, mediated by the activity of the Na+/K+-ATPase. We use bifurcation analysis of the complete system as well as the slow-fast method to reveal that this coupling suffices to generate a hysteresis loop organized around a bistable region that emerges from a saddle-node loop bifurcation–a common feature of class I excitable neurons. Depending on the strength of the Na+/K+-ATPase, bursts are generated from pump-induced shearing the bifurcation structure, spiking is tonic, or cells are silenced via depolarization block. We suggest that transitions between these dynamics can result from disturbances in extracellular potassium regulation, such as glial malfunction or hypoxia affecting the Na+/K+-ATPase activity. The identified minimal mechanistic model outlining the sodium-potassium pump's generic contribution to burst dynamics can, therefore, contribute to a better mechanistic understanding of pathologies such as epilepsy syndromes and, potentially, inform therapeutic strategies. Author summary: The brain can produce slow rhythms, such as those observed during sleep or epilepsy. These rhythms are much slower than the neuronal electrical signals, and their origins are still under debate. Mechanisms discussed so far are often based on the connection delays in neural networks or on neuronal ion channels with particularly slow kinetics. We show that neurons with specific spiking dynamics–allowing them to fire at arbitrarily low frequencies (so-called class I neurons) can produce slow rhythmic patterns without requiring synaptic connectivity or special ion channels. In these cells, slow rhythmic activity arises from the interplay of slow changes in extracellular potassium concentration and the cell's voltage dynamics, mediated by the Na+/K+-ATPase pump. The latter, found in all neurons, regulates the concentrations of sodium and potassium ions across the cell membrane. The core mechanism is not idiosyncratic, rather mathematical analysis shows under which conditions slow rhythmic activity can arise generically from the pump-based coupling in a broad class of neurons. We demonstrate that the pump is relevant for the creation of different firing patterns, some of which have been associated with pathologies of the brain. A better mechanistic understanding of these complex, concentration-dependent dynamics can therefore be relevant for therapeutic approaches. [ABSTRACT FROM AUTHOR]

Background: Vector control based on indoor residual spraying (IRS) is one of the main components of the visceral leishmaniasis (VL) elimination programme in India. Dichlorodiphenyltrichloroethane (DDT) was used for IRS until 2015 and was later replaced by the synthetic pyrethroid alpha-cypermethrin. Both classes of insecticides share the same target site, the voltage-gated sodium channel (Vgsc). As high levels of resistance to DDT have been documented in the local sand fly vector, Phlebotomus argentipes, it is possible that mutations in the Vgsc gene could provide resistance to alpha-cypermethrin, affecting current IRS pyrethroid-based vector control. Methods: This study aimed to compare frequencies of knockdown resistance (kdr) mutations in Vgsc between two sprayed and two unsprayed villages in Bihar state, India, which had the highest VL burden of the four endemic states. Across four villages, 350 female P. argentipes were collected as part of a 2019 molecular xenomonitoring study. DNA was extracted and used for sequence analysis of the IIS6 fragment of the Vgsc gene to assess the presence of kdr mutations. Results: Mutations were identified at various positions, most frequently at codon 1014, a common site known to be associated with insecticide resistance in mosquitoes and sand flies. Significant inter-village variation was observed, with sand flies from Dharampur, an unsprayed village, showing a significantly higher proportion of wild-type alleles (55.8%) compared with the three other villages (8.5–14.3%). The allele differences observed across the four villages may result from selection pressure caused by previous exposure to DDT. Conclusions: While DDT resistance has been reported in Bihar, P. argentipes is still susceptible to pyrethroids. However, the presence of kdr mutations in sand flies could present a threat to IRS used for VL control in endemic villages in India. Continuous surveillance of vector bionomics and insecticide resistance, using bioassays and target genotyping, is required to inform India's vector control strategies and to ensure the VL elimination target is reached and sustained. [ABSTRACT FROM AUTHOR]

Intrinsic plasticity, a fundamental process enabling neurons to modify their intrinsic properties, plays a crucial role in shaping neuronal input‐output function and is implicated in various neurological and psychiatric disorders. Despite its importance, the underlying molecular mechanisms of intrinsic plasticity remain poorly understood. In this study, a new ubiquitin ligase adaptor, protein tyrosine phosphatase receptor type N (PTPRN), is identified as a regulator of intrinsic neuronal excitability in the context of temporal lobe epilepsy. PTPRN recruits the NEDD4 Like E3 Ubiquitin Protein Ligase (NEDD4L) to NaV1.2 sodium channels, facilitating NEDD4L‐mediated ubiquitination, and endocytosis of NaV1.2. Knockout of PTPRN in hippocampal granule cells leads to augmented NaV1.2‐mediated sodium currents and higher intrinsic excitability, resulting in increased seizure susceptibility in transgenic mice. Conversely, adeno‐associated virus‐mediated delivery of PTPRN in the dentate gyrus region decreases intrinsic excitability and reduces seizure susceptibility. Moreover, the present findings indicate that PTPRN exerts a selective modulation effect on voltage‐gated sodium channels. Collectively, PTPRN plays a significant role in regulating intrinsic excitability and seizure susceptibility, suggesting a potential strategy for precise modulation of NaV1.2 channels' function. [ABSTRACT FROM AUTHOR]

Aim: In rodent models of nephrotic syndrome (NS), edema formation was prevented by blockade of the epithelial sodium channel ENaC with amiloride. However, apart from case reports, there is no evidence favoring ENaC blockade in patients with NS. Methods: The monocentric randomized controlled AMILOR study investigated the antiedematous effect of amiloride (starting dose 5 mg/day, max. 15 mg/day) in comparison to standard therapy with the loop diuretic furosemide (40 mg/day, max. 120 mg/day) over 16 days. Overhydration (OH) was measured by bioimpedance spectroscopy (BCM, Fresenius). Depending on the OH response, diuretic dose was adjusted on days 2, 5, 8 and 12, and if necessary, hydrochlorothiazide (HCT) was added from d8 (12.5 mg/day, max. 25 mg/day). The primary endpoint was the decrease in OH on d8. The study was terminated prematurely due to insufficient recruitment and a low statistical power due to a low actual effect size. Results: Median baseline OH was +26.4 (interquartile range 15.5–35.1)% extracellular water (ECW) in the amiloride arm and + 27.9 (24.1–29.4)% ECW in the furosemide arm and decreased by 1.95 (0.80–6.40) and 5.15 (0.90–8.30)% ECW after 8 days, respectively, and by 10.10 (1.30–14.40) and 7.40 (2.80–10.10)% ECW after 16 days, respectively. OH decrease on d8 and d16 was not significantly different between both arms. Conclusion: The AMILOR study is the first randomized controlled pilot study suggesting a similar antiedematous effect as furosemide. Further studies are required to better define the role of amiloride in NS (EudraCT 2019‐002607‐18). [ABSTRACT FROM AUTHOR]

Sea anemones are an important source of bioactive compounds with potential pharmacological applications. Their toxins are produced and stored in organelles called nematocysts and act on specific targets, including voltage-gated ion channels. To date, sea anemone toxins have demonstrated effects on voltage-gated sodium and potassium channels, facilitating investigations into the structure and function of these proteins. In this study, we evaluated the effect of Bunodeopsis globulifera sea anemone crude extract, and of a low molecular weight fraction, on voltage-gated sodium and calcium channels within the murine nervous system. Notably, the crude extract led to a significant reduction in total sodium current, while also triggering calcium-dependent glutamate release. Furthermore, the low molecular weight fraction, in particular, enhanced total calcium currents and current density. These findings underscore the existence of sea anemone toxins with diverse mechanisms of action beyond those previously documented. [ABSTRACT FROM AUTHOR]

SCN2A -related disorders secondary to altered function in the voltage-gated sodium channel Nav1.2 are rare, with clinically heterogeneous expressions that include epilepsy, autism and multiple severe to profound impairments and other conditions. To advance understanding of the clinical phenotypes and their relationship to channel function, 81 patients (36 female, 44%, median age 5.4 years) with 69 unique SCN2A variants were systematically phenotyped and their Nav1.2 channel function systematically assessed. Participants were recruited through the FamileSCN2A Foundation. Primary phenotype (epilepsy of neonatal onset, n = 27; infant onset, n = 18; and later onset n = 24; and autism without seizures, n = 12) was strongly correlated with a non-seizure severity index (P = 0.002), which was based on presence of severe impairments in gross motor, fine motor, communication abilities, gastrostomy tube dependence and diagnosis of cortical visual impairment and scoliosis. Non-seizure severity was greatest in the neonatal-onset group and least in the autism group (P = 0.002). Children with the lowest severity indices were still severely impaired, as reflected by an average Vineland Adaptive Behavior composite score of 49.5 (>3 standard deviations below the norm-referenced mean of the test). Epileptic spasms were significantly more common in infant-onset (67%) than in neonatal (22%) or later-onset (29%) epilepsy (P = 0.007). Primary phenotype was also strongly correlated with variant function (P < 0.0001); gain-of-function and mixed function variants predominated in neonatal-onset epilepsy, shifting to moderate loss of function in infant-onset epilepsy and to severe and complete loss of function in later-onset epilepsy and autism groups. Exploratory cluster analysis identified five groups, representing: (i) primarily later-onset epilepsy with moderate loss-of-function variants and low severity indices; (ii) mostly infant-onset epilepsy with moderate loss-of-function variants but higher severity indices; and (iii) late-onset and autism only, with the lowest severity indices (mostly zero) and severe/complete loss-of-function variants. Two exclusively neonatal clusters were distinguished from each other largely on non-seizure severity scores and secondarily on variant function. The relationship between primary phenotype and variant function emphasizes the role of developmental factors in the differential clinical expression of SCN2A variants based on their effects on Nav1.2 channel function. The non-seizure severity of SCN2A disorders depends on a combination of the age at seizure onset (primary phenotype) and variant function. As precision therapies for SCN2A -related disorders advance towards clinical trials, knowledge of the relationship between variant function and clinical disease expression will be valuable for identifying appropriate patients for these trials and in selecting efficient clinical outcomes. [ABSTRACT FROM AUTHOR]

Objective: Scorpion α-neurotoxins (ɑ-NaTx) inhibit the inactivation of voltage-gated sodium channels (Nav) with variable efficiency between organisms and channel isoforms. Based on our previous results, we hypothesized that the derivative of the ɑ-NaTx called BeM9 with two amino acid residues substituted with glycine (A4G and Y17G; BeM9GG) should be more selective for the mammalian channels. Surprisingly, BeM9GG lost its activity on the cardiac isoform Nav1.5. We provide a possible explanation of this effect, taking into account the published structures of ɑ-NaTx–Nav complexes. Methods: We produced BeM9GG in Escherichia coli as a fusion protein with thioredoxin, which was cleaved by cyanogen bromide. We purified BeM9GG using chromatography and measured its activity on Nav isoforms expressed in Xenopus laevis oocytes by the two-electrode voltage clamp technique. We performed computer modeling of ɑ-NaTx–Nav complexes to figure out the peculiarities of toxin interactions with Nav1.5. Results and Discussion: Using electrophysiology, we tested BeM9GG on Nav, and unexpectedly observed compromised activity on Nav1.5. We compared the structures of available ɑ-NaTx–Nav complexes to explain this effect. In case of Nav1.5 the toxin-binding site is immersed deeper in the membrane. We explain this by sequence variations in two positions of the voltage-sensing domain IV of Nav: in Nav1.5 corresponding residues have shorter side chains, permitting the toxin to sit deeper. At the same time, residue Y17 in BeM9, which is missing in BeM9GG, interacts with the hydrophobic core of the membrane and may play a significant role in its activity against Nav1.5. Conclusions: The role of the membrane in ɑ-NaTx interactions with Nav has been overlooked. It is especially important in case of Nav1.5, where the tripartite toxin–ion channel– membrane complex is formed. Our study will be of help for the future design of selective Nav ligands. [ABSTRACT FROM AUTHOR]

The adverse outcome pathway (AOP) framework serves as a practical tool for organising scientific knowledge that can be used to infer cause–effect relationships between stressor events and toxicity outcomes in intact organisms. However, a major challenge in the broader application of the AOP concept within regulatory toxicology is the development of a robust AOPs that can withstand peer review and acceptance. This is mainly due to the considerable amount of work required to substantiate the modular units of a complete AOP, which can take years from inception to completion. The methodology used here consisted of an initial assessment of a single chemical hazard using the Integrated Approach to Testing and Assessment (IATA) framework. An evidence‐based approach was then used to gather empirical evidence combining systematic literature review methods with expert knowledge to ensure the effectiveness of the AOP development methodology. The structured framework used assured transparency, objectivity and comprehensiveness, and included expert knowledge elicitation for the evaluation of key event relationships (KERs). This stepwise approach led to the development of an AOP that begins with binding of chemicals to Voltage Gate Sodium Channels (VGSC/Nav) during mammalian development leading to adverse consequences in neurodevelopment evidenced as deficits in cognitive functions. Disruption of the formation of precise neural circuits by alterations in VGSC kinetics during the perinatal stages of brain development may also underlie neurodevelopmental disorders. Gaps in our understanding include the specific critical developmental windows and the quantitative relationship of binding to VGSC and subsequent disruption and cognitive function. Despite the limited quantitative information at all KER levels, regulatory applications of this AOP for DNT assessment have been identified. [ABSTRACT FROM AUTHOR]

Crotalphine is an analgesic peptide identified from the venom of the South American rattlesnake Crotalus durissus terrificus. Although its antinociceptive effect is well documented, its direct mechanisms of action are still unclear. The aim of the present work was to study the action of the crotalid peptide on the NaV1.7 channel subtype, a genetically validated pain target. To this purpose, the effects of crotalphine were evaluated on the NaV1.7 component of the tetrodotoxin-sensitive Na+ current in the dorsal root ganglion neurons of adult mice, using the whole-cell patch-clamp configuration, and on cell viability, using propidium iodide fluorescence and trypan blue assays. The results show that 18.7 µM of peptide inhibited 50% of the Na+ current. The blocking effect occurred without any marked change in the current activation and inactivation kinetics, but it was more important as the membrane potential was more positive. In addition, crotalphine induced an increase in the leakage current amplitude of approximately 150% and led to a maximal 31% decrease in cell viability at a high 50 µM concentration. Taken together, these results point out, for the first time, the effectiveness of crotalphine in acting on the NaV1.7 channel subtype, which may be an additional target contributing to the peptide analgesic properties and, also, although less efficiently, on a second cell plasma membrane component, leading to cell loss. [ABSTRACT FROM AUTHOR]

Olfactory perception is an important physiological function for human well-being and health. Loss of olfaction, or anosmia, caused by viral infections such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has received considerable attention, especially in persistent cases that take a long time to recover. This review discusses the integration of different components of the olfactory epithelium to serve as a structural and functional unit and explores how they are affected during viral infections, leading to the development of olfactory dysfunction. The review mainly focused on the role of receptors mediating the disruption of olfactory signal transduction pathways such as angiotensin converting enzyme 2 (ACE2), transmembrane protease serine type 2 (TMPRSS2), neuropilin 1 (NRP1), basigin (CD147), olfactory, transient receptor potential vanilloid 1 (TRPV1), purinergic, and interferon gamma receptors. Furthermore, the compromised function of the epithelial sodium channel (ENaC) induced by SARS-CoV-2 infection and its contribution to olfactory dysfunction are also discussed. Collectively, this review provides fundamental information about the many types of receptors that may modulate olfaction and participate in olfactory dysfunction. It will help to understand the underlying pathophysiology of virus-induced anosmia, which may help in finding and designing effective therapies targeting molecules involved in viral invasion and olfaction. To the best of our knowledge, this is the only review that covered all the receptors potentially involved in, or mediating, the disruption of olfactory signal transduction pathways during COVID-19 infection. This wide and complex spectrum of receptors that mediates the pathophysiology of olfactory dysfunction reflects the many ways in which anosmia can be therapeutically managed. [ABSTRACT FROM AUTHOR]

The signaling complex around voltage-gated sodium (Nav) channels includes accessory proteins and kinases crucial for regulating neuronal firing. Previous studies showed that one such kinase, WEE1—critical to the cell cycle—selectively modulates Nav1.2 channel activity through the accessory protein fibroblast growth factor 14 (FGF14). Here, we tested whether WEE1 exhibits crosstalk with the AKT/GSK3 kinase pathway for coordinated regulation of FGF14/Nav1.2 channel complex assembly and function. Using the in-cell split luciferase complementation assay (LCA), we found that the WEE1 inhibitor II and GSK3 inhibitor XIII reduce the FGF14/Nav1.2 complex formation, while the AKT inhibitor triciribine increases it. However, combining WEE1 inhibitor II with either one of the other two inhibitors abolished its effect on the FGF14/Nav1.2 complex formation. Whole-cell voltage-clamp recordings of sodium currents (INa) in HEK293 cells co-expressing Nav1.2 channels and FGF14-GFP showed that WEE1 inhibitor II significantly suppresses peak INa density, both alone and in the presence of triciribine or GSK3 inhibitor XIII, despite the latter inhibitor's opposite effects on INa. Additionally, WEE1 inhibitor II slowed the tau of fast inactivation and caused depolarizing shifts in the voltage dependence of activation and inactivation. These phenotypes either prevailed or were additive when combined with triciribine but were outcompeted when both WEE1 inhibitor II and GSK3 inhibitor XIII were present. Concerted regulation by WEE1 inhibitor II, triciribine, and GSK3 inhibitor XIII was also observed in long-term inactivation and use dependency of Nav1.2 currents. Overall, these findings suggest a complex role for WEE1 kinase—in concert with the AKT/GSK3 pathway—in regulating the Nav1.2 channelosome. [ABSTRACT FROM AUTHOR]

The synergistic effect of crystal and amorphous phases boosts the sodium ion transport kinetics in NVP, mitigates volume deformations during cycling, achieve a high capacity of 82 mAh/g at 10 C. [Display omitted] • A homogeneous hybridization of crystalline and amorphous phases in Na 3 V 2 (PO 4) 3 /C was achieved through a straightforward design. • The inclusion of the amorphous phase indirectly enhances the proportion of active Na2 sites. • In-situ formation of high-speed sodium-ion diffusion channels in amorphous phases enhances diffusion kinetics, the biphasic synergy provided an impressive capacity of 114 mAh/g at 0.2 C and a rate performance 82 mAh/g at 10 C. Na 3 V 2 (PO 4) 3 (NVP) has attracted considerable attention as a promising cathode material for sodium-ion batteries (SIBs). But its insufficient electronic conductivity, limited capacities, and fragile structure hinder its extended application, particularly in scenarios involving rapid charging and prolonged cycling. A hybrid cathode material has been developed to integrate both amorphous and crystalline phases, with the objective of improving the rate performance and Na storage capacity by leveraging bi-phase coordination. Consequently, the combination of amorphous and crystalline phases enhanced the kinetics of Na-ion diffusion, resulting in a 1–2 orders of magnitude enhancement in diffusion dynamics. Furthermore, the existence of amorphous states has been demonstrated to elevate the active Na2 site content, resulting in an increased reversible capacity. This assertion is substantiated by evidence derived from solid-state nuclear magnetic resonance (ss-NMR) and electrochemical characteristics. The innovative bi-phase collaborative material provides a specific capacity of 114 mAh/g at 0.2 C, exceptional rate performance of 82 mAh/g at 10 C, and remarkable long-term cycle stability, retaining 95 mAh/g at 5 C even after 300 cycles. In conclusion, the homogeneous hybridization of amorphous and crystalline phases presents itself as a promising and effective strategy for improving Na-ion storage capacity of cathodes in SIBs. [ABSTRACT FROM AUTHOR]

Homeostatic plasticity maintains the stability of functional brain networks. The axon initial segment (AIS), where action potentials start, undergoes dynamic adjustment to exert powerful control over neuronal firing properties in response to network activity changes. However, it is poorly understood whether this plasticity involves direct synaptic input to the AIS. Here, we show that changes of GABAergic synaptic input from chandelier cells (ChCs) drive homeostatic tuning of the AIS of principal neurons (PNs) in the prelimbic (PL) region, while those from parvalbumin-positive basket cells do not. This tuning is evident in AIS morphology, voltage-gated sodium channel expression, and PN excitability. Moreover, the impact of this homeostatic plasticity can be reflected in animal behavior. Social behavior, inversely linked to PL PN activity, shows time-dependent alterations tightly coupled to changes in AIS plasticity and PN excitability. Thus, AIS-originated homeostatic plasticity in PNs may counteract deficits elicited by imbalanced ChC presynaptic input at cellular and behavioral levels. [ABSTRACT FROM AUTHOR]

The dispanins are a family of transmembrane proteins with diverse and often unclear physiological functions. Many dispanins are expressed in the central nervous system, where they are involved in the development and maturation of synapses, the regulation of neurotransmitter release, and interactions with ion channels, including AMPA receptors. The roles of dispanins expressed in the peripheral nervous system are not as clear. Recently, a family of neurotoxins isolated from Australian stinging trees were shown to target dispanins in the periphery to modulate the function of voltage-gated sodium channels. This positions dispanins as an inherently druggable class of transmembrane proteins that may be targeted for the treatment of dispanin-associated neurological disease. The dispanins are a family of 15 transmembrane proteins that have diverse and often unclear physiological functions. Many dispanins, including synapse differentiation induced gene 1 (SynDIG1), proline-rich transmembrane protein 1 (PRRT1)/SynDIG4, and PRRT2, are expressed in the central nervous system (CNS), where they are involved in the development of synapses, regulation of neurotransmitter release, and interactions with ion channels, including AMPA receptors (AMPARs). Others, including transmembrane protein 233 (TMEM233) and trafficking regulator of GLUT4-1 (TRARG1), are expressed in the peripheral nervous system (PNS); however, the function of these dispanins is less clear. Recently, a family of neurotoxins isolated from the giant Australian stinging tree was shown to target TMEM233 to modulate the function of voltage-gated sodium (Na V) channels, suggesting that the dispanins are inherently druggable. Here, we review current knowledge about the structure and function of the dispanins, in particular TMEM233 and its two most closely related homologs PRRT2 and TRARG1, which may be drug targets involved in neurological disease. [ABSTRACT FROM AUTHOR]

BACKGROUND: Voltage‐dependent anion‐selective channels (VDACs) serve as pore proteins within the mitochondrial membrane, aiding in the regulation of cell life and cell death. Although the occurrence of cell death is crucial for defense against virus infection, the function played by VDAC in Bombyx mori, in response to the influence of Bombyx mori nucleopolyhedrovirus (BmNPV), remains unclear. RESULTS: BmVDAC was found to be relatively highly expressed both during embryonic development, and in the Malpighian tubule and midgut. Additionally, the expression levels of BmVDAC were found to be different among silkworm strains with varying levels of resistance to BmNPV, strongly suggesting a connection between BmVDAC and virus infection. To gain further insight into the function of BmVDAC in BmNPV, we employed RNA interference (RNAi) to silence and overexpress it by pIZT/V5‐His‐mCherry. The results revealed that BmVDAC is instrumental in developing the resistance of host cells to BmNPV infection in BmN cell‐line cells, which was further validated as likely to be associated with initiating programmed cell death (PCD). Furthermore, we evaluated the function of BmVDAC in another insect, Spodoptera exigua. Knockdown of the BmVDAC homolog in S. exigua, SeVDAC, made the larvae more sensitive to BmNPV. CONCLUSION: We have substantiated the pivotal role of BmVDAC in conferring resistance against BmNPV infection, primarily associated with the initiation of PCD. The findings of this study shine new light on the molecular mechanisms governing the silkworm's response to BmNPV infection, thereby supporting innovative approaches for pest biocontrol. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Loss-, gain-of-function and mixed variants in SCN1A (Nav1.1 voltage-gated sodium channel) have been associated with a spectrum of neurologic disorders with different severity and drug-responsiveness. Most SCN1A variants are heterozygous changes occurring de novo or dominantly inherited; recessive inheritance has been reported in a few cases. Here, we report a family in which the biallelic inheritance of two novel SCN1A variants, N935Y and H1393Q, occurs in two siblings presenting with drug-responsive developmental and epileptic encephalopathy and born to heterozygous asymptomatic parents. To assess the genotype–phenotype correlation and support the treatment choice, HEK 293 cells were transfected with different combinations of the SCN1A WT and mutant cDNAs, and the resulting sodium currents were recorded through whole-cell patch-clamp. Functional studies showed that the N935Y and H1393Q channels and their combinations with the WT (WT + N935Y and WT + H1393Q) had current densities and biophysical properties comparable with those of their respective control conditions. This explains the asymptomatic condition of the probands' parents. The co-expression of the N935Y + H1393Q channels, mimicking the recessive inheritance of the two variants in siblings, showed ~20% reduced current amplitude compared with WT and with parental channels. This mild loss of Nav1.1 function may contribute in part to the disease pathogenesis, although other mechanisms may be involved. [ABSTRACT FROM AUTHOR]

Dynamic wrinkle reduction continues to challenge aesthetic dermatology, predominantly addressed through Botulinumtoxin (Botox) injections. Despite Botox's robust efficacy with up to an 80% reduction in wrinkle visibility within just one week, its invasive administration and specific mechanism of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex inhibition prompt the exploration of safer, non-invasive alternatives. This review critically assesses recent innovations in non-invasive effects, with a focus on peptides and botanical extracts that exhibit a diverse array of mechanisms including SNARE complex inhibition, modulation of calcium and sodium channels, and interactions with acetylcholine receptors, contributing to their effectiveness in muscle relaxation on dynamic wrinkle approaches. Noteworthy peptides such as Argireline and SYN-Ake replicate the neuromodulatory effects of Botox, achieving up to a 52% reduction in wrinkles within four weeks without injections. Moreover, botanical extracts meet the rising demand for clean beauty solutions by enhancing skin elasticity and health through gentle yet potent mechanisms. However, the main concern with peptides is their low absorption rate, with only six clinical validations regarding Botox-like peptide anti-wrinkle efficacy available. These advancements not only deepen our understanding of cosmetic dermatology but also significantly influence market dynamics and consumer behavior, underscoring their pivotal role in redefining the future landscape of anti-aging effects. [ABSTRACT FROM AUTHOR]

The epithelial Na+ channel (ENaC) emerged early in vertebrates and has played a role in Na+ and fluid homeostasis throughout vertebrate evolution. We previously showed that proteolytic activation of the channel evolved at the water-to-land transition of vertebrates. Sensitivity to extracellular Na+, known as Na+ self-inhibition, reduces ENaC function when Na+ concentrations are high and is a distinctive feature of the channel. A fourth ENaC subunit, δ, emerged in jawed fishes from an α subunit gene duplication. Here, we analyzed 849 α and δ subunit sequences and found that a key Asp in a postulated Na+ binding site was nearly always present in the α subunit, but frequently lost in the δ subunit (e.g. human). Analysis of site evolution and codon substitution rates provide evidence that the ancestral α subunit had the site and that purifying selection for the site relaxed in the δ subunit after its divergence from the α subunit, coinciding with a loss of δ subunit expression in renal tissues. We also show that the proposed Na+ binding site in the α subunit is a bona fide site by conferring novel function to channels comprising human δ subunits. Together, our findings provide evidence that ENaC Na+ self-inhibition improves fitness through its role in Na+ homeostasis in vertebrates. [ABSTRACT FROM AUTHOR]

Sodium and potassium channels, especially Nav1.5 and Kir2.1, play key roles in the formation of action potentials in cardiomyocytes. These channels interact with, and are regulated by, synapse‐associated protein 97 (SAP97). However, the regulatory role of SAP97 in myocyte remains incompletely understood. Here, we investigate the function of SAP97 phosphorylation in the regulation of Nav1.5 and Kir2.1 channel complexes and the upstream regulation of SAP97. We found that SAP97 is phosphorylated by casein kinase II (CK2) in vitro. In addition, transfection of casein kinase 2 interacting protein‐1 (CKIP‐1) into cardiomyocytes to drive CK2 from the nucleus to the cytoplasm, increased SAP97 phosphorylation and Nav1.5 and Kir2.1 current activity. These findings demonstrated that CKIP‐1 modulates the subcellular translocation of CK2, which regulates Nav1.5 and Kir2.1 channel complex formation and activity in cardiomyocytes. [ABSTRACT FROM AUTHOR]

Prostaglandin E2 (PGE2) is a major contributor to inflammatory pain hyperalgesia, however, the extent to which it modulates the activity of nociceptive axons is incompletely understood. We developed and characterized a microfluidic cell culture model to investigate sensitisation of the axons of dorsal root ganglia neurons. We show that application of PGE2 to fluidically isolated axons leads to sensitisation of their responses to depolarising stimuli. Interestingly the application of PGE2 to the DRG axons elicited a direct and persistent spiking activity propagated to the soma. Both the persistent activity and the membrane depolarisation in the axons are abolished by the EP4 receptor inhibitor and a blocker of cAMP synthesis. Further investigated into the mechanisms of the spiking activity showed that the PGE2 evoked depolarisation was inhibited by Nav1.8 sodium channel blockers but was refractory to the application of TTX or zatebradine. Interestingly, the depolarisation of axons was blocked by blocking ANO1 channels with T16Ainh-A01. We further show that PGE2-elicited axonal responses are altered by the changes in chloride gradient within the axons following treatment with bumetanide a Na-K-2Cl cotransporter NKCC1 inhibitor, but not by VU01240551 an inhibitor of potassium-chloride transporter KCC2. Our data demonstrate a novel role for PGE2/EP4/cAMP pathway which culminates in a sustained depolarisation of sensory axons mediated by a chloride current through ANO1 channels. Therefore, using a microfluidic culture model, we provide evidence for a potential dual function of PGE2 in inflammatory pain: it sensitises depolarisation-evoked responses in nociceptive axons and directly triggers action potentials by activating ANO1 and Nav1.8 channels. [ABSTRACT FROM AUTHOR]

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

The airway epithelium plays a pivotal role in regulating mucosal immunity and inflammation. Epithelial barrier function, homeostasis of luminal fluid, and mucociliary clearance are major components of mucosal defense mechanisms. The epithelial sodium channel (ENaC) is one of the key players in controlling airway fluid volume and composition, and characteristic cytokines cause ENaC and barrier dysfunctions following pulmonary infections or allergic reactions. Given the limited understanding of the requisite duration and magnitude of cytokines to affect ENaC and barrier function, available treatment options for restoring normal ENaC activity are limited. Previous studies have demonstrated that distinct amino acids can modulate epithelial ion channel activities and barrier function in intestines and airways. Here, we have investigated the time- and concentration-dependent effect of representative cytokines for Th1- (IFN-γ and TNF-α), Th2- (IL-4 and IL-13), and Treg-mediated (TGF-β1) immune responses on ENaC activity and barrier function in human bronchial epithelial cells. When cells were exposed to Th1 and Treg cytokines, ENaC activity decreased gradually while barrier function remained largely unaffected. In contrast, Th2 cytokines had an immediate and profound inhibitory effect on ENaC activity that was subsequently followed by epithelial barrier disruption. These functional changes were associated with decreased membrane protein expression of α-, β-, and γ-ENaC, and decreased mRNA levels of β- and γ-ENaC. A proprietary blend of amino acids was developed based on their ability to prevent Th2 cytokine-induced ENaC dysfunction. Exposure to the select amino acids reversed the inhibitory effect of IL-13 on ENaC activity by increasing mRNA levels of β- and γ-ENaC, and protein expression of γ-ENaC. This study indicates the beneficial effect of select amino acids on ENaC activity in an in vitro setting of Th2-mediated inflammation suggesting these amino acids as a novel therapeutic approach for correcting this condition. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs) are considered as a beneficial complement to lithium‐ion batteries for large‐scale energy storage systems because of the abundant sodium resources. However, the relatively large ionic radius of Na+ inevitably results in a huge volume change and sluggish electrochemical reaction kinetics, which put forward higher requirements for electrode materials. Among the reported cathode materials for SIBs, the manganese hexacyanoferrate (MnHCF) with the merits of large channels for fast sodium ion transport, high theoretical capacity and low cost has attracted extensive attention. In this review, the recent achievements of MnHCF for SIBs are focused. The key challenges of MnHCF limiting the practical application include the interstitial water, vacancies, low electronic conductivity, and the Jahn‐Teller effect. Subsequently, the mainstream strategies to boost the sodium storage performance of MnHCF are summarized (such as structure regulation, surface coating, hybridization with carbon materials, and element substitution). Finally, the potential research directions are also proposed to promote the practical application of MnHCF for SIBs. This review is expected to provide a whole insight into exploring MnHCF cathode materials for SIBs. [ABSTRACT FROM AUTHOR]

Constructing powerful anode/cathode interphases by modulate ion solvation structure is the principle of electrolyte design. However, the methodological and theoretical design principles of electrolyte/solvation structure and their effect on electrochemical performance are still vague. Here, we propose a cationic weakly coordinating-intervention strategy for modulating the Na+ solvation sheathes and constructing robust anode/cathode interphases in sodium-metal batteries. Unlike the local highly concentrated electrolytes, 1,2-difluorobenzene can weakly coordinate with Na+ thus transforming the solvation structure into Na+-anion-incorporated structures and strengthening anode/cathode interphases formation by combining with salt decomposition. Furthermore, the correlations between the electrode interface properties and solvation structure are revealed, which can be tuned by the weakly coordination. Ultimately, the modulated electrolyte achieves 97.5% Coulombic efficiency for 600 cycles in Na‖Cu cells at 1 mA cm−2 and a beneficial lifetime (2500 h) in Na‖Na cells. Meanwhile, Na‖PB cells have achieved long-term operation at 4.8 V, along with operation at wide temperatures. Here, authors propose a weakly coordinating-intervention strategy to modulate the Na+ solvation sheath and construct a robust interphase in sodium-metal batteries. Correlation between electrode interface properties and solvation structure is also stated. [ABSTRACT FROM AUTHOR]