Activin A maintains cerebral cortex neuronal survival and increases voltage-gated Na^+ neuronal current

Activin A, which was first described in 1986, has been shown to maintain hippocampal neuronal survival. Activin A increases intracellular free Ca2＋ via L-type Ca2＋ channels. Our previous study showed that activin A promotes neurite growth of dorsal root ganglia in embryonic chickens and inhibits nitric oxide secretion. The present study demonstrated for the first time that activin A could maintain cerebral cortex neuronal survival in vitro for a long period, and that activin A was shown to increase voltage-gated Na＋ current （/Na） in Neuro-2a cells, which was recorded by patch clamp technique. The present study revealed a novel mechanism for activin A, as well as the influence of activin A on neurons by regulating expressions of vasoactive intestine peptide and inducible nitric oxide synthase.

Functional Expression of Voltage-Gated Sodium Channels Nav1.5 in Human Breast Caner Cell Line MDA-MB-231

Voltage-gated sodium channels （VGSCs） are known to be involved in the initiation and progression of many malignancies, and the different subtypes of VGSCs play important roles in the metastasis cascade of many tumors. This study investigated the functional expression of Nav1.5 and its effect on invasion behavior of human breast cancer cell line MDA-MB-231. The mRNA and protein expression of Nav1.5 was detected by real time PCR, Western Blot and immunofluorescence. The effects of Nav1.5 on cell proliferation, migration and invasion were respectively assessed by MTT and Transwell. The effects of Nav1.5 on the secretion of matrix metalloproteases （MMPs） by MDA-MB-231 were analyzed by RT-PCR. The over-expressed Nav 1.5 was present on the membrane of MDA-MB-231 cells. The invasion ability in vitro and the MMP-9 mRNA expression were respectively decreased to （47.82±0.53）% and （43.97±0.64）% （P〈0.05） respectively in MDA-MB-23 t cells treated with VGSCs specific inhibitor tetrodotoxin （TTX） by blocking Navl.5 activity. It was concluded that Navl.5 functional expression potentiated the invasive behavior of human breast cancer cell line MDA-MB-231 by increasing the secretion of MMP-9.

Do age-associated changes of voltage-gated sodium channel isoforms expressed in the mammalian heart predispose the elderly to atrial fibrillation?

Atrial fibrillation(AF)is the most common cardiac arrhythmia worldwide.The prevalence of the disease increases with age,strongly implying an age-related process underlying the pathology.At a time when people are living longer than ever before,an exponential increase in disease prevalence is predicted worldwide.Hence unraveling the underlying mechanics of the disease is paramount for the development of innovative treatment and prevention strategies.The role of voltage-gated sodium channels is fundamental in cardiac electrophysiology and may provide novel insights into the arrhythmogenesis of AF.Na_v1.5 is the predominant cardiac isoform,responsible for the action potential upstroke.Recent studies have demonstrated that Na_v1.8(an isoform predominantly expressed within the peripheral nervous system)is responsible for cellular arrhythmogenesis through the enhancement of pro-arrhythmogenic currents.Animal studies have shown a decline in Na_v1.5 leading to a diminished action potential upstroke during phase 0.Furthermore,the study of human tissue demonstrates an inverse expression of sodium channel isoforms;reduction of Na_v1.5 and increase of Na_v1.8 in both heart failure and ventricular hypertrophy.This strongly suggests that the expression of voltage-gated sodium channels play a crucial role in the development of arrhythmias in the diseased heart.Targeting aberrant sodium currents has led to novel therapeutic approaches in tackling AF and continues to be an area of emerging research.This review will explore how voltage-gated sodium channels may predispose the elderly heart to AF through the examination of laboratory and clinical based evidence.

Neuroprotective effect of interleukin-6 regulation of voltage-gated Na^+ channels of cortical neurons is time-and dose-dependent

Interleukin-6 has been shown to be involved in nerve injury and nerve regeneration, but the effects of long-term administration of high concentrations of interleukin-6 on neurons in the central nervous system is poorly understood. This study investigated the effects of 24 hour expo-sure of interleukin-6 on cortical neurons at various concentrations （0.1, 1, 5 and 10 ng/mL） and the effects of 10 ng/mL interleukin-6 exposure to cortical neurons for various durations （2, 4, 8, 24 and 48 hours） by studying voltage-gated Na＋ channels using a patch-clamp technique. Volt-age-clamp recording results demonstrated that interleukin-6 suppressed Na＋ currents through its receptor in a time- and dose-dependent manner, but did not alter voltage-dependent activation and inactivation. Current-clamp recording results were consistent with voltage-clamp recording results. Interleukin-6 reduced the action potential amplitude of cortical neurons, but did not change the action potential threshold. The regulation of voltage-gated Na＋channels in rat corti-cal neurons by interleukin-6 is time- and dose-dependent.

Chlorogenic acid alters the voltage-gated potassium channel currents of trigeminal ganglion neurons

Chlorogenic acid（5-caffeoylquinic acid, CGA） is a phenolic compound that is found ubiquitously in plants, fruits and vegetables and is formed via the esterification of caffeic acid and quinic acid. In addition to its notable biological functions against cardiovascular diseases, type-2 diabetes and inflammatory conditions, CGA was recently hypothesized to be an alternative for the treatment of neurological diseases such as Alzheimer＇s disease and neuropathic pain disorders. However, its mechanism of action is unclear.Voltage-gated potassium channel（Kv） is a crucial factor in the electro-physiological processes of sensory neurons. Kv has also been identified as a potential therapeutic target for inflammation and neuropathic pain disorders. In this study, we analysed the effects of CGA on the two main subtypes of Kv in trigeminal ganglion neurons, namely, the IK,Aand IK,Vchannels. Trigeminal ganglion（TRG）neurons were acutely disassociated from the rat TRG, and two different doses of CGA（0.2 and 1 mmol·L21） were applied to the cells.Whole-cell patch-clamp recordings were performed to observe alterations in the activation and inactivation properties of the IK,Aand IK,Vchannels. The results demonstrated that 0.2 mmol·L21CGA decreased the peak current density of IK,A. Both 0.2 mmol·L21and1 mmol·L21CGA also caused a significant reduction in the activation and inactivation thresholds of IK,Aand IK,V. CGA exhibited a strong effect on the activation and inactivation velocities of IK,Aand IK,V. These findings provide novel evidence explaining the biological effects of CGA, especially regarding its neurological effects.

Voltage-gated Sodium Channels and Blockers:An Overview and Where Will They Go?

Voltage-gated sodium(Nav)channels are critical players in the generation and propagation of action potentials by triggering membrane depolarization.Mutations in Nav channels are associated with a variety of channelopathies,which makes them relevant targets for pharmaceutical intervention.Sofar,the cryoelectron microscopic structure of the human Nav 1.2,Nav 1.4,and Nav 1.7 has been reported,which sheds light on the molecular basis of functional mechanism of Nav channels and provides a path toward structure-based drug discovery.In this review,we focus on the recent advances in the structure,molecular mechanism and modulation of Nav channels,and state updated sodium channel blockers for the treatment of pathophysiology disorders and briefly discuss where the blockers may be developed in the future.

Whole-cell recordings of voltage-gated Calcium,Potassium and Sodium currents in acutely isolated hippocampal pyramidal neurons

Objective：To record Calcium, Potassium and Sodium currents in acutely isolated hippocampal pyramidal neurons. Methods：Hippocampal CA3 neurons were freshly isolated by 1 mg protease/3 ml SES and mechanical trituration with polished pipettes of progressively smaller tip diameters. Patch clamp technique in whole-cell mode was employed to record voltage-gated channel currents. Results：The procedure dissociated hippocampal neurons, preserving apical dendrites and several basal dendrites, without impairing the electrical characteristics of the neurons. Whole-cell patch clamp configuration was successfully used to record voltage-gated Ca^2＋ currents, delayed rectifier K^＋ current and voltage-gated Na^＋ currents. Conclusion：Protease combined with mechanical trituration may be used for the dissociation of neurons from rat hippocampus. Voltage-gated channels currents could be recorded using a patch clamp technique.

Motor Neuron Disease Associated with Voltage-Gated Potassium Channel Antibodies

Introduction: Antibodies to voltage-gated potassium channels have been implicated in causing a host of peripheral and central nervous system disorders. However, the presence of these antibodies has not been previously associated with motor neuropathy. We describe the first case of acquired motor neuron disease associated with voltage-gated potas-sium channel antibodies. Case Report: The patient is an 81-year-old female who developed signs and symptoms of an idiopathic motor neuron disease. The patient was found to have increased antibodies to voltage-gated potassium chan-nels in the absence of a known metastatic or autoimmune process. Magnetic resonance imaging of the cervical spine demonstrated increased signal in the anterior horn regions of the cervical and upper thoracic spinal cord on T2-weighted imaging. The patient’s disease progression was refractory to both intravenous immunoglobulin and ster-oid therapy. Conclusion: Voltage-gated potassium channels may be causal or simply associated with motor neuron disease;this relationship needs to be elucidated. Testing for these antibodies may be warranted in cases of idiopathic rapidly progressing motor neuron disease.

Molecular Docking Studies on Anticonvulsant Enaminones Inhibiting Voltage-Gated Sodium Channels

Epilepsy is described as the most common chronic brain disorder. A typical symptom of epilepsy results in uncontrolled convulsions caused by temporary excessive neuronal discharges. Although several new anticon-vulsants have been introduced, some types of seizures have still not been adequately controlled with these new and current therapies. There is an urgent need to develop new anticonvulsant drugs to control the many different types of seizures. Many studies have shown that the epilepsies involve more than one mechanism and therefore may be responsible for the various types of observed seizures. Recently reported studies have shown that a group of newly synthesized 6 Hz active anticonvulsant fluorinated N-benzamide enaminones exhibited selective inhibitions of voltage-gated sodium (Nav) channels. Nav channels are responsible for the initial inward currents during the depolarization phases of the action potential in excitable cells. The activation and opening of Nav channels result in the initial phases of action potentials. We hypothesize that there is an essential pharmacophore model for the interactions between these enaminones and the active sites of Nav channels. The research reported here is focused on molecular docking studies of the interactions that occur between the fluorinated N-benzamide enaminones and the Nav channels. These studies may open an avenue for designing anticonvulsant drugs by inhibiting Nav channels.

Isoprenylated Flavonoids as Cav3.1 Low Voltage-Gated Ca^(2+)Channel Inhibitors from Salvia digitaloides

Saldigones A-C(1,3,4),three new isoprenylated flavonoids with diverse flavanone,pterocarpan,and isoflavanone architec-tures,were characterized from the roots of Salvia digitaloides,together with a known isoprenylated flavanone(2).Notably,it’s the first report of isoprenylated flavonoids from Salvia species.The structures of these isolates were elucidated by extensive spectroscopic analysis.All of the compounds were evaluated for their activities on Cav3.1 low voltage-gated Ca^(2+)channel(LVGCC),of which 2 strongly and dose-dependently inhibited Cav3.1 peak current.

Frequency Switches at Transition Temperature in Voltage-Gated Ion Channel Dynamics of Neural Oscillators

Understanding of the mechanisms of neural phase transitions is crucial for clarifying cognitive processes in the brain. We investigate a neural oscillator that undergoes different bifurcation transitions from the big saddle homoclinic orbit type to the saddle node on an invariant circle type, and the saddle node on an invariant circle type to the small saddle homoclinic orbit type. The bifurcation transitions are accompanied by an increase in thermodynamic temperature that affects the voltage-gated ion channel in the neural oscillator. We show that nonlinear and thermodynamical mechanisms are responsible for different switches of the frequency in the neural oscillator. We report a dynamical role of the phase response curve in switches of the frequency, in terms of slopes of frequency-temperature curve at each bifurcation transition. Adopting the transition state theory of voltagegated ion channel dynamics, we confirm that switches of the frequency occur in the first-order phase transition temperature states and exhibit different features of their potential energy derivatives in the ion channel. Each bifurcation transition also creates a discontinuity in the Arrhenius plot used to compute the time constant of the ion channel.

Role of the Voltage-Gated Proton Channel Hv1 in Nervous Systems

Hv1 is the only voltage-gated proton-selective channel in mammalian cells.It contains a conserved voltage-sensor domain,shared by a large class of voltage-gated ion channels,but lacks a pore domain.Its primary role is to extrude protons from the cytoplasm upon pH reduction and membrane depolarization.The best-known function of Hv1 is the regulation of cytosolic pH and the nicotinamide adenine dinucleotide phosphate oxidase-dependent production of reactive oxygen species.Accumulating evidence indicates that Hv1 is expressed in nervous systems,in addition to immune cells and others.Here,we summarize the molecular properties,distribution,and physiological functions of Hv1 in the peripheral and central nervous systems.We describe the recently discovered functions of Hv1 in various neurological diseases,including brain or spinal cord injury,ischemic stroke,demyelinating diseases,and pain.We also summarize the current advances in the discovery and application of Hv1-targeted small molecules in neurological diseases.Finally,we discuss the current limitations of our understanding of Hv1 and suggest future research directions.

Expression and Role of Voltage-Gated Sodium Channels in Human Dorsal Root Ganglion Neurons with Special Focus on Nav1.7,Species Differences, and Regulation by Paclitaxel

Voltage-gated sodium channels （Navs） play an important role in human pain sensation. However, the expression and role of Nav subtypes in native human sensory neurons are unclear. To address this issue, we obtained human dorsal root ganglion （hDRG） tissues from healthy donors. PCR analysis of seven DRG-expressed Nav subtypes revealed that the hDRG has higher expression of Navl.7 （,-~ 50% of total Nav expression） and lower expres- sion of Navl.8 （~ 12%）, whereas the mouse DRG has higher expression of Nav 1.8 （- 45%） and lower expression of Navl.7 （- 18%）. To mimic Nav regulation in chronic pain, we treated hDRG neurons in primary cultures with paclitaxel （0.1-1 μmol/L） for 24 h. Paclitaxel increased the Navl.7 but not Navl.8 expression and also increased the transient Na＋ currents and action potential firing frequency in small-diameter （〈50 ~tm） hDRG neurons. Thus, the hDRG provides a translational model in which to study ＂human pain in a dish＂ and test new pain therapeutics.

Exploring the obscure profiles of pharmacological binding sites on voltage-gated sodium channels by BmK neurotoxins

Diverse subtypes of voltage-gated sodium channels(VGSCs)have been found throughout tissues of the brain,muscles and the heart.Neurotoxins extracted from the venom of the Asian scorpion Buthus martensi Karsch(BmK)act as sodium channel-specific modulators and have therefore been widely used to study VGSCs.α-type neurotoxins,named BmK I,BmKαIV and BmK abT,bind to receptor site-3 on VGSCs and can strongly prolong the inactivation phase of VGSCs.In contrast,β-type neurotoxins,named BmK AS,BmK AS-1,BmK IT and BmK IT2,occupy receptor site-4 on VGSCs and can suppress peak currents and hyperpolarize the activation kinetics of sodium channels.Accumulating evidence from binding assays of scorpion neurotoxins on VGSCs,however,indicate that pharmacological sensitivity of VGSC subtypes to different modulators is much more complex than that suggested by the simpleα-type and β-type neurotoxin distinction.Exploring the mechanisms of possible dynamic interactions between site 3-/4-specific modulators and region-and/or speciesspecific subtypes of VGSCs would therefore greatly expand our understanding of the physiological and pharmacological properties of diverse VGSCs.In this review,we discuss the pharmacological and structural diversity of VGSCs as revealed by studies exploring the binding properties and cross-competitive binding of site 3-or site 4-specific modulators in VGSC subtypes in synaptosomes from distinct tissues of diverse species.

Voltage-gated potassium channel Kvl.3 in rabbit ciliary epithelium regulates the membrane potential via coupling intracellular calcium

Background The cell layer of the ciliary epithelium is responsible for aqueous humor secretion and maintenance. Ion channels play an important role in these processes. The main aim of this study was to determine whether the well-characterized members of the Kvl family （Kv1.3） contribute to the Kv currents in ciliary epithelium. Methods New Zealand White rabbits were maintained in a 12 hours light/dark cycle. Ciliary epithelium samples were isolated from the rabbits. We used Western blotting and immunocytochemistry to identify the expression and location of a voltage-gated potassium channel Kvl.3 in ciliary body epithelium. Membrane potential change after adding of Kvl.3 inhibitor margatoxin （MgTX） was observed with a fluorescence method. Results Western blotting and immunocytochemical studies showed that the Kv1.3 protein expressed in pigment ciliary epithelium and nonpigment ciliary epithelium, however it seemed to express more in the apical membrane of the nonpigmented epithelial cells. One nmol/L margatoxin, a specific inhibitor of Kv1.3 channels caused depolarization of the cultured nonpigmented epithelium （NPE） membrane potential. The cytosolic calcium increased after NPE cell depolarization, this increase of cytosolic calcium was partially blocked by 12.5 μmol/L dantrolene and 10 μmol/L nifedipine. These observations suggest that Kv1.3 channels modulate ciliary epithelium potential and effect calcium dependent mechanisms. Conclusion Kv1.3 channels contribute to K＋ efflux at the membrane of rabbit ciliary epithelium.

Expressions of voltage-gated K^＋ channel 2.1 and 2.2 in rat bladder with detrusor hyperreflexia

Background Voltage-gated K^＋ channel （Kv） plays a critical role in the modulation of detrusor contraction. This study was conducted to investigate the expressions of Kv2.1 and Kv2.2 in rat bladder with detrusor hyperreflexia （DH）. Methods Thirty adult female Sprague-Dawley rats （200-220 g） were randomly divided into the control group and the experimental group. The experimental group was subjected to spinal cord injury （SCI）. In the controls, the surgical procedure was identical with the exception that dura and spinal cord were transected. Four weeks after SCI, in vivo cystometry and mechanical pulling tests of isolated detrusor strips were performed, mRNA was extracted from the detrusors of normal and DH rats for the detection of expression of Kv2.1 and Kv2.2 by RT-PCR. Differences in expression between normal and overactive detrusors were identified by gel imaging. Results Fourteen rats in the experimental group exhibited uninhibited bladder contraction （〉8 cmH20） before voiding after SCI. One rat died from infection. The frequency of DH in the experimental group was significantly different from that in the control group with or without treatment with 4-aminopyridine （4-AP） （P 〈0.05）, while the amplitude of DH did not change markedly. The rates of variation of the automatic contractile frequency and amplitude were （66.8±12.4）% and （42.6±12.6）% respectively in the control group, and （38.4±9.8）% and （28.0±4.6）% respectively in the DH group. 4-AP increased the automatic contractile frequency apart from the automatic contractile amplitude in both the control and DH groups （P 〈0.05）. 4-AP increased the rate of variation of the automatic contractile frequency more markedly in the control group than in the DH group （P 〈0.05）. Significant expression of Kv2.2 was not detected in bladders in the control group. Compared to the mRNA levels of 13-actin, the mRNA level of Kv2.1 was 1.26±K）.12 in the control group and 0.66±0.08 in the DH group. SCI significantly reduced the mRNA level of Kv2.1 in rat bladders with DH （P 〈0.05）. Conclusions Our study showed that the mRNA level of Kv2.1 decreased significantly in rat bladder with DH, which was one of the important pathogenetic mechanisms for DH, and suggested that Kv2.1 might be one of the therapeutic targets for bladder overactivity.

Theoretical and simulation studies on voltage-gated sodium channels

Voltage-gated sodium （Nav） channels are indispensable membrane elements for the generation and propagation of electric signals in excitable cells. The successes in the crystallographic studies on prokaryotic Nay chan- nels in recent years greatly promote the mechanistic investigation of these proteins and their eukaryotic counterparts. In this paper, we mainly review the pro- gress in computational studies, especially the simula- tion studies, on these proteins in the past years.

Genetic Variants of Potassium Voltage-gated Channel Subfamily J Member 11 in Gestational Diabetes Mellitus:A Case-control Study

Objective::To investigate the association of rs5210 in potassium voltage-gated channel subfamily J member 11(KCNJ11)with gestational diabetes mellitus(GDM).Methods::Six hundred and thirty-two uncorrelated pregnancy females were recruited in Tongji hospital from October 2017 to June 2018,in which 241 pregnant women were identified as GDM,and 391 were non-GDM.All the pregnant women recruited in this study their peripheral venous blood of 5 mL were withdrawn,and DNA in the blood was extracted.rs5210 in KCNJ11 were genotyped using TaqMan Assays and genotype models were analyzed using logistic regression analyses.Results::After adjusting age and body mass index,the variant genotypes of rs5210 in genotype models were as follows:P for dominant model was 0.945,(odd ratio:0.987,95%confidence intervals(CI):0.681-1.430);P for recessive model:0.556,(odd ratio:1.217,95%CI:0.633-2.343)and P for addictive model was 0.098(genotype AA vs.GG),(odds ratio:1.435,95%CI:0.936-2.201).Weight-gain during pregnancy and total cholesterol were significantly different in recessive model(P=0.015,P=0.022,respectively)of all participants.Conclusion::No significant association between gene susceptibility of rs5210 in KCNJ11 and GDM occurrence in Chinese pregnant women.But the variant of rs5210 was associated with weight-gain during pregnancy and total cholesterol blood levels.However,more cases are needed in genetic study to check its susceptibility with GDM occurrence in Chinese women.

Distribution and Functional Characteristics of Voltage-Gated Sodium Channels in Immature Cochlear Hair Cells

Voltage-gated sodium channels(VGSCs)are transiently expressed in cochlear hair cells before hearing onset and play an indispensable role in shaping spontaneous activity.In this study,we showed that Na^+currents shaped the spontaneous action potentials in developing mouse inner hair cells(IHCs)by decreasing the time required for the membrane potential to reach the action-potential threshold.In immature IHCs,we identified 9 known VGSC subtypes(Navl.la-l.9ot),among which Navl.7a was the most highly expressed subtype and the main contributor to Na+currents in developing hair cells.Electrophysiological recordings of two cochlea-specific Navi.7 variants(CbmNavl.7a and CbmNavl.7b)revealed a novel loss-of-function mutation(C934R)at the extracellular linker between segments 5 and 6 of domain II.In addition,post-transcriptional modification events,such as alternative splicing and RNA editing,amended the gating properties and kinetic features of CbmNavl.7a(C934).These results provide molecular and functional characteristics of VGSCs in mammalian IHCs and their contributions to spontaneous physiological activity during cochlear maturation.

The Effect of Peony and Licorice Decoction on the Voltage-Gated Sodium Channel Subtype 1.4 Based on Standard Decoction

Objective:The objective of this study is to investigate the inhibitory effect of peony and licorice decoction and its compatibility components on the Nav1.4 voltage-gated sodium channels(VGSCs).Materials and Methods:Writhing test was carried out with ICR mice.Paeonia lactiflora and Glycyrrhiza uralensis group were administrated 0.2 ml of solution of freeze-dried powder dissolved in normal saline with the concentration of 2.94 mg/ml,1.47 mg/ml,and 0.74 mg/ml using intragastric administration,respectively.Peony and licorice decoction groups were administrated 0.2 ml of solution of freeze-dried powder dissolved in normal saline with the concentration of 5.89 mg/ml,2.94 mg/ml,and 1.47 mg/ml using intragastric administration,respectively.For electrophysiology studies,each freeze-dried powder was dissolved in DMSO to make 10 mg/ml and 50 mg/ml stock solutions.The electrophysiological recordings were obtained under visual control of a microscope.For UPLC analysis,the freeze-dried powder was dissolved in methanol and then determines the contents of the nine marker compounds.Results:The effect of G.uralensis on incubation period and writhing frequency was significantly better than that of peony and licorice decoction group and P.lactiflora group.The inhibition rate of 50 mg/ml water extracts of the three samples was significantly higher than that of the 10 mg/ml group.Moreover,the water extract of G.uralensis at 50 mg/ml had the strongest inhibitory effect on I_(Nav) 1.4 of the three.Conclusion:The possible mechanism of peony and licorice decoction in relieving spasm and pain is most likely by inhibiting Voltage-Gated Sodium Channel Subtype 1.4.