Role Of Voltage-gated Sodium Channels Research Articles

Analgesic effect of Botulinum toxin in neuropathic pain is sodium channel independent

Botulinum neurotoxin type A BoNT/A is used off-label as a third line therapy for neuropathic pain. However, the mechanism of action remains unclear. In recent years, the role of voltage-gated sodium channels (Nav) in neuropathic pain became evident and it was suggested that block of sodium channels by BoNT/A would contribute to its analgesic effect.We assessed sodium channel function in the presence of BoNT/A in heterologously expressed Nav1.7, Nav1.3, and the neuronal cell line ND7/23 by high throughput automated and manual patch-clamp. We used both the full protein and the isolated catalytic light chain LC/A for acute or long-term extracellular or intracellular exposure. To assess the toxin's effect in a human cellular system, we differentiated induced pluripotent stem cells (iPSC) into sensory neurons from a healthy control and a patient suffering from a hereditary neuropathic pain syndrome (inherited erythromelalgia) carrying the Nav1.7/p.Q875E-mutation and carried out multielectrode-array measurements.Both BoNT/A and the isolated catalytic light chain LC/A showed limited effects in heterologous expression systems and the neuronal cell line ND7/23. Spontaneous activity in iPSC derived sensory neurons remained unaltered upon BoNT/A exposure both in neurons from the healthy control and the mutation carrying patient.BoNT/A may not specifically be beneficial in pain syndromes linked to sodium channel variants. The favorable effects of BoNT/A in neuropathic pain are likely based on mechanisms other than sodium channel blockage and new approaches to understand BoNT/A's therapeutic effects are necessary.

Role of voltage-gated sodium channels in axonal signal propagation of trigeminal ganglion neurons after infraorbital nerve entrapment

Chronic pain arising from peripheral nerve injuries represents a significant clinical challenge because even the most efficacious anticonvulsant drug treatments are limited by their side effects profile. We investigated pain behavior, changes in axonal signal conduction and excitability of trigeminal neurons, and expression of voltage-gated sodium channels (NaVs) in the infraorbital nerve and trigeminal ganglion (TG) after infraorbital nerve entrapment (IoNE). Compared to Sham, IoNE rats had increased A- and C-fiber compound action potentials (CAPs) and Aδ component of A-CAP area from fibers innervating the vibrissal pad. After IoNE, A- and C-fiber CAPs were more sensitive to blockade by tetrodotoxin (TTX), and those fibers that were TTX-resistant were more sensitive to blockade by the NaV1.8 selective blocker, A-803467. Although NaV1.7 blocker, ICA-121431 alone, did not affect Aδ-fiber signal propagation, cumulative application with A-803467 and 4,9-anhydro-TTX significantly reduced the Aδ-fiber CAP in IoNE rats. In patch clamp recordings from small- and medium-sized TG neurons, IoNE resulted in reduced action potential (AP) depolarizing current threshold, hyperpolarized AP voltage threshold, increased AP duration, and a more depolarized membrane potential. While the transcripts of most NaVs were reduced in the ipsilateral TG after IoNE, NaV1.3, NaV1.7, and NaV1.8 mRNAs, and NaV1.8 protein, were significantly increased in the nerve. Altogether, our data suggest that axonal redistribution of NaV1.8, and to a lesser extent NaV1.3, and NaV1.7 contributes to enhanced nociceptive signal propagation in peripheral nerve after IoNE.

Selective inhibition of gamma aminobutyric acid release from mouse hippocampal interneurone subtypes by the volatile anaesthetic isoflurane

BackgroundThe cellular and molecular mechanisms by which general anaesthesia occurs is poorly understood. Hippocampal interneurone subpopulations, which are critical regulators of cognitive function, have diverse neurophysiological and synaptic properties, but their responses to anaesthetics are unclear. MethodsWe used live-cell imaging of fluorescent biosensors expressed in mouse hippocampal neurones to delineate interneurone subtype-specific effects of isoflurane on synaptic vesicle exocytosis. The role of voltage-gated sodium channel (Nav) subtype expression in determining isoflurane sensitivity was probed by overexpression or knockdown of specific Nav subtypes in identified interneurones. ResultsClinically relevant concentrations of isoflurane differentially inhibited synaptic vesicle exocytosis: to 83.1% (11.7%) of control in parvalbumin-expressing interneurones, and to 58.6% (13.3%) and 64.5% (8.5%) of control in somatostatin-expressing interneurones and glutamatergic neurones, respectively. The relative expression of Nav1.1 (associated with lower sensitivity) and Nav1.6 (associated with higher sensitivity) determined the sensitivity of exocytosis to isoflurane. ConclusionsIsoflurane inhibits synaptic vesicle exocytosis from hippocampal glutamatergic neurones and GABAergic interneurones in a cell-type-specific manner depending on their expression of voltage-gated sodium channel subtypes.

Role of voltage-gated sodium channels in endothelial functions: Are they new vascular mechanosensors?

Voltage-gated sodium (Na V ) channels are the hallmarks of excitable cells and involved in the cardiac excitation-contraction coupling. They are made of a pore-forming α subunit encoding by 9 genes (SCN1A–5A and 8A–11A) associated with β auxiliary subunits (SCN1B–4B genes). Interestingly, Na V channels are also expressed in non-excitable cells such as endothelial cells (EC) but their role is still not yet totally understood. The aim of our study is to explore the role of Na V channels: – in proliferation and migration of EC, key process of vascular remodeling; – as new vascular mechanosensor since Na V channels have been shown to be sensitive to mechanical forces in cardiomyocytes and EC are constitutively exposed to physical forces created by blood flow, especially to shear stress. Proliferation and migration of Human Umbilical Vein Endothelial Cells (HUVEC) were studied using the live-cell imaging system IncuCyte S3 and shear stress using the Ibidi pump system. Blocking Na V activity using the selective inhibitor tetrodotoxin inhibited significantly proliferation and migration of HUVEC. Exposition of HUVEC to a laminar shear stress (20 dynes/cm 2 ) for 4 days induced a cell orientation in the flow direction and activated the atheroprotective signaling pathway (KLF2, eNOS, CYP1B1). Moreover, shear stress led to a profound transcriptional remodeling of different subunits of Na V channels on HUVEC with a down-regulation for the cardiac SCN5A by 5-fold and up-regulation for SCN8A, SCN9A, SCN1B and SCN3B. Since SCN3B is strongly upregulated by shear stress (9-fold), overexpression and silencing of this protein are currently under process in order to better understand the involvement of this transmembrane protein belong to Ig-CAM family in EC functions and its regulation. Our data highlight the contribution of Na V channels in EC functions and suggest a new role of SCN3B as a potential vascular mechanotransductor.

PAR2, Keratinocytes, and Cathepsin S Mediate the Sensory Effects of Ciguatoxins Responsible for Ciguatera Poisoning

Ciguatera fish poisoning is caused by the consumption of fish contaminated with ciguatoxins (CTXs). The most distressing symptoms are cutaneous sensory disturbances, including cold dysesthesia and itch. CTXs are neurotoxins known to activate voltage-gated sodium channels, but no specific treatment exists. Peptidergic neurons have been critically involved in ciguatera fish poisoning sensory disturbances. Protease-activated receptor-2 (PAR2) is an itch- and pain-related G protein‒coupled receptor whose activation leads to a calcium-dependent neuropeptide release. In this study, we studied the role of voltage-gated sodium channels, PAR2, and the PAR2 agonist cathepsin S in the cytosolic calcium increase and subsequent release of the neuropeptide substance P elicited by Pacific CTX-2 (P-CTX-2) in rat sensory neurons and human epidermal keratinocytes. In sensory neurons, the P-CTX-2‒evoked calcium response was driven by voltage-gated sodium channels and PAR2-dependent mechanisms. In keratinocytes, P-CTX-2 also induced voltage-gated sodium channels and PAR2-dependent marked calcium response. In the cocultured cells, P-CTX-2 significantly increased cathepsin S activity, and cathepsin S and PAR2 antagonists almost abolished P-CTX-2‒elicited substance P release. Keratinocytes synergistically favored the induced substance P release. Our results demonstrate that the sensory effects of CTXs involve the cathepsin S-PAR2 pathway and are potentiated by their direct action on nonexcitable keratinocytes through the same pathway.

The Role of Voltage-Gated Sodium Channel 1.8 in the Effect of Atropine on Heart Rate: Evidence From a Retrospective Clinical Study and Mouse Model.

Atropine is commonly used to counter the effects of the parasympathetic neurotransmitter acetylcholine on heart rate in clinical practice, such as in the perioperative period; however, individual differences in the response to atropine are huge. The association between SCN10A/voltage-gated sodium channel 1.8 (NaV1.8) and cardiac conduction has been demonstrated; however, the exact role of SCN10A/NaV1.8 in the heart rate response to atropine remains unclear. To identify the role of SCN10A variants that influence the heart rate responses to atropine, we carried out a retrospective study in 1,005 Han Chinese subjects. Our results showed that rs6795970 was associated with the heart rate response to atropine. The heart rate responses to atropine and methoctramine in NaV1.8 knockout mice were lower, whereas the heart rate response to isoproterenol was like those in wild type mice. Furthermore, we observed that the NaV1.8 blocker A-803467 alleviated the heart rate response to atropine in wild type mice. The retrospective study revealed a previously unknown role of NaV1.8 in controlling the heart rate response to atropine, as shown by the animal study, a speculative mechanism that may involve the cardiac muscarinic acetylcholine receptor M2.

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. Nav1.5 is the predominant cardiac isoform, responsible for the action potential upstroke. Recent studies have demonstrated that Nav1.8 (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 Nav1.5 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 Nav1.5 and increase of Nav1.8 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.

Detection of the role of voltage-gated sodium channels in the mechanism of anticonvulsant action of Gabapentin in chicks (in-vivo)

Background:Because of the fact that the mechanism of anticonvulsant action of Gabapentin is not yet clear, so the aim of our present study was to determine whether the voltage-gated sodium channels (VGSC) may be correlate with its mechanism. To achieve this goal, Cypermethrin was chosen as a (convulsion inducer) resulting from its prolongs the opening of (VGSC) in order to interfere with Gabapentin .
 Method:The experiment animals were divided into four groups. The first group was treated with a single dose of Cypermethrin (1000 mg / kg, orally), while the second and third group were treated with a single dose of Gabapentin (100 mg / kg, orally)15 or 30 minutes before the Cypermethrin treatment respectively. The fourth group was treated with Gabapentin alone in a dose of (100 mg / kg, orally) .After the end of treatment of the chicks were transferred to the cages to be monitored individually and recorded percentages of appearance of nervous signs and the percentage of each mortality and protection against mortality.
 Results: Chicks treated with Cypermethrin alone (1000 mg / kg, orally)showed nervous signs which included the jerking movements of the leg and wings (clonic convulsion) and whole body tremors accompanied with opisthotonos at percentages (80%, 100%,60%) respectively that end with death at (100%) , but the pretreatment of chicks with Gabapentin (100 mg / kg, orally) resulted in time-dependent protection against Cypermethrin-induced nervous signs and mortality,which representing by significantly decrease in the percentage of each clonic convulsion,whole body tremors and mortality to (0%, 20% and 20%) respectively and accompanied by significant increase the percentage of protection of chicks against mortality to (80%) in the group that pretreatment with Gabapentin 30 minute before administration of Cypermethrin compared with control group (Cypermethrin alone).
 We conclude from our results that recorded for the first time the Gabapentin provided protection to chicks against Cypermethrin-induced nervous signs and mortality , this result may be related to effect of Gabapentin on (VGSC). Thus, the currently study will open the way to use Cypermethrin as a model in scientific research that detect the mechanisms of action of anticonvulsant drugs .

Role of Voltage-Gated Sodium Channels in the Mechanism of Ether-Induced Unconsciousness

Despite continuous clinical use for more than 170 years, the mechanism of general anesthetics has not been completely characterized. In this review, we focus on the role of voltage-gated sodium channels in the sedative-hypnotic actions of halogenated ethers, describing the history of anesthetic mechanisms research, the basic neurobiology and pharmacology of voltage-gated sodium channels, and the evidence for a mechanistic interaction between halogenated ethers and sodium channels in the induction of unconsciousness. We conclude with a more integrative perspective of how voltage-gated sodium channels might provide a critical link between molecular actions of the halogenated ethers and the more distributed network-level effects associated with the anesthetized state across species.

Voltage-gated Sodium Channels in Sensory Information Processing.

Objective & Background: Voltage-gated sodium channels (VGSCs) and potassium channels are critical in the generation of action potentials in the nervous system. VGSCs and potassium channels play important roles in the five fundamental senses of vision, audition, olfaction, taste and touch. Dysfunctional VGSCs are associated with clinical sensory symptoms, such as hyperpselaphesia, parosphresia, and so on. Conclusion: This short review highlights the recent advances in the study of VGSCs in sensory information processing and discusses the potential role of VGSCs to serve as pharmacological targets for the treatment of sensory system diseases.

The Role of Voltage-Gated Sodium Channels in Pain Signaling.

Acute pain signaling has a key protective role and is highly evolutionarily conserved. Chronic pain, however, is maladaptive, occurring as a consequence of injury and disease, and is associated with sensitization of the somatosensory nervous system. Primary sensory neurons are involved in both of these processes, and the recent advances in understanding sensory transduction and human genetics are the focus of this review. Voltage-gated sodium channels (VGSCs) are important determinants of sensory neuron excitability: they are essential for the initial transduction of sensory stimuli, the electrogenesis of the action potential, and neurotransmitter release from sensory neuron terminals. Nav1.1, Nav1.6, Nav1.7, Nav1.8, and Nav1.9 are all expressed by adult sensory neurons. The biophysical characteristics of these channels, as well as their unique expression patterns within subtypes of sensory neurons, define their functional role in pain signaling. Changes in the expression of VGSCs, as well as posttranslational modifications, contribute to the sensitization of sensory neurons in chronic pain states. Furthermore, gene variants in Nav1.7, Nav1.8, and Nav1.9 have now been linked to human Mendelian pain disorders and more recently to common pain disorders such as small-fiber neuropathy. Chronic pain affects one in five of the general population. Given the poor efficacy of current analgesics, the selective expression of particular VGSCs in sensory neurons makes these attractive targets for drug discovery. The increasing availability of gene sequencing, combined with structural modeling and electrophysiological analysis of gene variants, also provides the opportunity to better target existing therapies in a personalized manner.

The Emerging Role of Voltage-Gated Sodium Channels in Tumor Biology.

Voltage-gated sodium channels (VGSCs) are transmembrane proteins which function as gates that control the flux of ions across the cell membrane. They are key ion channels for action potentials in excitable tissues and have important physiological functions. Abnormal function of VGSCs will lead to dysfunction of the body and trigger a variety of diseases. Various studies have demonstrated the participation of VGSCs in the progression of different tumors, such as prostate cancer, cervical cancer, breast cancer, and others, linking VGSC to the invasive capacity of tumor cells. However, it is still unclear whether the VGSC regulate the malignant biological behavior of tumors. Therefore, this paper systematically addresses the latest research progress on VGSCs subunits and tumors and the underlying mechanisms, and it summarizes the potential of VGSCs subunits to serve as potential targets for tumor diagnosis and treatment.

Evaluation of the antinociceptive activities of several sodium channel blockers using veratrine test in mice.

An important role of voltage-gated sodium channels (VGSCs) in many different pain states has been established in animal models and humans wherein sodium channel blockers partially ameliorate pain. However, behavioral tests for screening analgesics that exhibit pharmacologic action by acting on VGSCs are rarely reported, and there are no studies on antinociception using veratrine as a nociceptive agent. The aim of the present study was to examine the amount of nociceptive behavior evoked by subcutaneous administration of veratrine into the hind paw and investigate whether veratrine can be used as a VGSC agonist to test the pharmacological properties of candidate analgesics via sodium channel blockade. We report for the first time that intraplantar injection of veratrine produced a reproducible nociceptive response in mice. Furthermore, several sodium channel blockers, namely carbamazepine, valproate, mexiletine, and the selective Nav1.7 inhibitor PF-04856264, but not flecainide or pilsicainide, reduced veratrine-induced nociception. In contrast, calcium channel blockers gabapentin and ethosuximide did not change veratrine-induced nociception. The veratrine test in mice might be a useful tool, at least in part, to evaluate the potential analgesic effect of sodium channel blockers.

Abnormal changes in voltage-gated sodium channels subtypes NaV1.1, NaV1.2, NaV1.3, NaV1.6 and CaM/CaMKII pathway in low-grade astrocytoma

Epileptic seizures are the main clinical manifestation of low-grade astrocytoma. Voltage-gated sodium channels (VGSCs) play a crucial role in epilepsy. Until now, the role of VGSCs and the relationships between calmodulin (CaM)/CaM-dependent protein kinase II (CaMKII) and VGSCs in low-grade astrocytoma have not been demonstrated. In our study, the protein expression of NaV1.3, NaV1.6 and CaM was significantly increased in the tumor compared to control tissue, while the level of p-CaMKII/CaMKII was significantly decreased in the tumor group as determined by Western Blotting and immunohistochemistry. Furthermore, double-labeling immunofluorescence results showed that NaV1.3/NaV1.6 and CaM co-localization was significantly increased in the tumor group compared to control tissue. This study represents the first evidence of the abnormal changes in VGSCs subtypes and CaM/CaMKII pathway in human brain low-grade astrocytoma, providing new potential targets for molecular therapies of this disease.

Preemptive application of QX-314 attenuates trigeminal neuropathic mechanical allodynia in rats.

The aim of the present study was to examine the effects of preemptive analgesia on the development of trigeminal neuropathic pain. For this purpose, mechanical allodynia was evaluated in male Sprague-Dawley rats using chronic constriction injury of the infraorbital nerve (CCI-ION) and perineural application of 2% QX-314 to the infraorbital nerve. CCI-ION produced severe mechanical allodynia, which was maintained until postoperative day (POD) 30. An immediate single application of 2% QX-314 to the infraorbital nerve following CCI-ION significantly reduced neuropathic mechanical allodynia. Immediate double application of QX-314 produced a greater attenuation of mechanical allodynia than a single application of QX-314. Immediate double application of 2% QX-314 reduced the CCI-ION-induced upregulation of GFAP and p-p38 expression in the trigeminal ganglion. The upregulated p-p38 expression was co-localized with NeuN, a neuronal cell marker. We also investigated the role of voltage-gated sodium channels (Navs) in the antinociception produced by preemptive application of QX-314 through analysis of the changes in Nav expression in the trigeminal ganglion following CCI-ION. Preemptive application of QX-314 significantly reduced the upregulation of Nav1.3, 1.7, and 1.9 produced by CCI-ION. These results suggest that long-lasting blockade of the transmission of pain signaling inhibits the development of neuropathic pain through the regulation of Nav isoform expression in the trigeminal ganglion. Importantly, these results provide a potential preemptive therapeutic strategy for the treatment of neuropathic pain after nerve injury.

The role of voltage-gated sodium channels in modality-specific pain pathways

The role of voltage-gated sodium channels in modality-specific pain pathways

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 Nav1.7 (~50% of total Nav expression) and lower expression of Nav1.8 (~12%), whereas the mouse DRG has higher expression of Nav1.8 (~45%) and lower expression of Nav1.7 (~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 Nav1.7 but not Nav1.8 expression and also increased the transient Na+ currents and action potential firing frequency in small-diameter (<50 μm) hDRG neurons. Thus, the hDRG provides a translational model in which to study “human pain in a dish” and test new pain therapeutics.

Voltage-gated sodium channels and pain-related disorders.

Voltage-gated sodium channels (VGSCs) are heteromeric transmembrane protein complexes. Nine homologous members, SCN1A-11A, make up the VGSC gene family. Sodium channel isoforms display a wide range of kinetic properties endowing different neuronal typeswith distinctly varied firing properties. Among the VGSCs isoforms, Nav1.7, Nav1.8 and Nav1.9 are preferentially expressed in the peripheral nervous system. These isoforms are known to be crucial in the conduction of nociceptive stimuli with mutations in these channels thought to be the underlying cause of a variety of heritable pain disorders. This review provides an overview of the current literature concerning the role of VGSCs in the generation of pain and heritable pain disorders.

Engineering Highly Potent and Selective Microproteins against Nav1.7 Sodium Channel for Treatment of Pain

The prominent role of voltage-gated sodium channel 1.7 (Nav1.7) in nociception was revealed by remarkable human clinical and genetic evidence. Development of potent and subtype-selective inhibitors of this ion channel is crucial for obtaining therapeutically useful analgesic compounds. Microproteins isolated from animal venoms have been identified as promising therapeutic leads for ion channels, because they naturally evolved to be potent ion channel blockers. Here, we report the engineering of highly potent and selective inhibitors of the Nav1.7 channel based on tarantula ceratotoxin-1 (CcoTx1). We utilized a combination of directed evolution, saturation mutagenesis, chemical modification, and rational drug design to obtain higher potency and selectivity to the Nav1.7 channel. The resulting microproteins are highly potent (IC50 to Nav1.7 of 2.5 nm) and selective. We achieved 80- and 20-fold selectivity over the closely related Nav1.2 and Nav1.6 channels, respectively, and the IC50 on skeletal (Nav1.4) and cardiac (Nav1.5) sodium channels is above 3000 nm The lead molecules have the potential for future clinical development as novel therapeutics in the treatment of pain.

Colonic Hypersensitivity and Sensitization of Voltage-gated Sodium Channels in Primary Sensory Neurons in Rats with Diabetes.

Background/AimsPatients with long-standing diabetes often demonstrate intestinal dysfunction and abdominal pain. However, the pathophysiology of abdominal pain in diabetic patients remains elusive. The purpose of study was to determine roles of voltage-gated sodium channels in dorsal root ganglion (DRG) in colonic hypersensitivity of rats with diabetes.MethodsDiabetic models were induced by a single intraperitoneal injection of streptozotocin (STZ; 65 mg/kg) in adult female rats, while the control rats received citrate buffer only. Behavioral responses to colorectal distention were used to determine colonic sensitivity in rats. Colon projection DRG neurons labeled with DiI were acutely dissociated for measuring excitability and sodium channel currents by whole-cell patch clamp recordings. Western blot analysis was employed to measure the expression of NaV1.7 and NaV1.8 of colon DRGs.ResultsSTZ injection produced a significantly lower distention threshold than control rats in responding to colorectal distention. STZ injection also depolarized the resting membrane potentials, hyperpolarized action potential threshold, decreased rheobase and increased frequency of action potentials evoked by 2 and 3 times rheobase and ramp current stimulation. Furthermore, STZ injection enhanced neuronal sodium current densities of DRG neurons innervating the colon. STZ injection also led to a significant upregulation of NaV1.7 and NaV1.8 expression in colon DRGs compared with age and sex-matched control rats.ConclusionsOur results suggest that enhanced neuronal excitability following STZ injection, which may be mediated by upregulation of NaV1.7 and NaV1.8 expression in DRGs, may play an important role in colonic hypersensitivity in rats with diabetes.