ABSTRACT
The pathogenesis of major depressive disorder (MDD) involves lipid metabolism. Our earlier research also revealed that MDD patients had much lower total cholesterol (TC) concentrations than healthy controls (HCs). However, it is still unclear why TC decreased in MDD. Here, based on the Ingenuity Knowledge Base's ingenuity pathway analysis, we found that sodium voltage-gated channel alpha subunit 11A (SCN11A) might serve as a link between low lipid levels and MDD. We analyzed the TC levels and used ELISA kits to measure the levels of SCN11A in the serum from 139 MDD patients, and 65 HCs to confirm this theory and explore the potential involvement of SCN11A in MDD. The findings revealed that TC levels were considerably lower and SCN11A levels were remarkably increased in MDD patients than those in HCs, while they were significantly reversed in drug-treatment MDD patients than in drug-naïve MDD patients. There was no significant difference in SCN11A levels among MDD patients who used single or multiple antidepressants, and selective serotonin reuptake inhibitors or other antidepressants. Pearson correlation analysis showed that the levels of TC and SCN11A were linked with the Hamilton Depression Rating Scales score. A substantial association was also found between TC and SCN11A. Moreover, a discriminative model made up of SCN11A was discovered, which produced an area under a curve of 0.9571 in the training set and 0.9357 in the testing set. Taken together, our findings indicated that SCN11A may serve as a link between low lipid levels and MDD, and showed promise as a candidate biomarker for MDD.
Subject(s)
Cholesterol , Depressive Disorder, Major , Lipid Metabolism , NAV1.9 Voltage-Gated Sodium Channel , Adult , Female , Humans , Male , Antidepressive Agents/therapeutic use , Case-Control Studies , Cholesterol/blood , Depressive Disorder, Major/blood , Depressive Disorder, Major/metabolism , NAV1.9 Voltage-Gated Sodium Channel/blood , NAV1.9 Voltage-Gated Sodium Channel/metabolismABSTRACT
Voltage-gated sodium channel subtypes, Nav1.7, Nav1.8, and Nav1.9 are predominantly expressed in peripheral sensory neurons. Recent genetic studies have revealed that they are involved in pathological pain processing and that the blockade of Nav1.7, Nav1.8, or Nav1.9 will become a promising pharmacotherapy especially for neuropathic pain. A growing number of drug discovery programs have targeted either of the subtypes to obtain a selective inhibitor which can provide pain relief without affecting the cardiovascular and central nervous systems, though none of them has been approved yet. Here we describe the in vitro characteristics of ANP-230, a novel sodium channel blocker under clinical development. Surprisingly, ANP-230 was shown to block three pain-related subtypes, human Nav1.7, Nav1.8, and Nav1.9 with similar potency, but had only low inhibitory activity to human cardiac Nav1.5 channel and rat central Nav channels. The voltage clamp experiments using different step pulse protocols revealed that ANP-230 had a "tonic block" mode of action without state- and use-dependency. In addition, ANP-230 caused a depolarizing shift of the activation curve and decelerated gating kinetics in human Nav1.7-stably expressing cells. The depolarizing shift of activation curve was commonly observed in human Nav1.8-stably expressing cells as well as rat dorsal root ganglion neurons. These data suggested a quite unique mechanism of Nav channel inhibition by ANP-230. Finally, ANP-230 reduced excitability of rat dorsal root ganglion neurons in a concentration dependent manner. Collectively, these promising results indicate that ANP-230 could be a potent drug for neuropathic pain.
Subject(s)
NAV1.7 Voltage-Gated Sodium Channel , NAV1.8 Voltage-Gated Sodium Channel , NAV1.9 Voltage-Gated Sodium Channel , Sodium Channel Blockers , Humans , NAV1.8 Voltage-Gated Sodium Channel/metabolism , NAV1.8 Voltage-Gated Sodium Channel/genetics , Animals , Rats , NAV1.9 Voltage-Gated Sodium Channel/metabolism , NAV1.9 Voltage-Gated Sodium Channel/genetics , NAV1.7 Voltage-Gated Sodium Channel/metabolism , NAV1.7 Voltage-Gated Sodium Channel/genetics , Sodium Channel Blockers/pharmacology , HEK293 Cells , Voltage-Gated Sodium Channel Blockers/pharmacology , Ganglia, Spinal/metabolism , Ganglia, Spinal/drug effects , Ganglia, Spinal/cytologyABSTRACT
Skeletal muscle contraction triggers the exercise pressor reflex (EPR) to regulate the cardiovascular system response to exercise. During muscle contraction, substances are released that generate action potential activity in group III and IV afferents that mediate the EPR. Some of these substances increase afferent activity via G-protein-coupled receptor (GPCR) activation, but the mechanisms are incompletely understood. We were interested in determining if tetrodotoxin-resistant (TTX-R) voltage-dependent sodium channels (NaV) were involved and investigated the effect of a mixture of such compounds (bradykinin, prostaglandin, norepinephrine, and ATP, called muscle metabolites). Using whole cell patch-clamp electrophysiology, we show that the muscle metabolites significantly increased TTX-R NaV currents. The rise time of this enhancement averaged â¼2 min, which suggests the involvement of a diffusible second messenger pathway. The effect of muscle metabolites on the current-voltage relationship, channel activation and inactivation kinetics support NaV1.9 channels as the target for this enhancement. When applied individually at the concentration used in the mixture, only prostaglandin and bradykinin significantly enhanced NaV current, but the sum of these enhancements was <1/3 that observed when the muscle metabolites were applied together. This suggests synergism between the activated GPCRs to enhance NaV1.9 current. When applied at a higher concentration, all four substances could enhance the current, which demonstrates that the GPCRs activated by each metabolite can enhance channel activity. The enhancement of NaV1.9 channel activity is a likely mechanism by which GPCR activation increases action potential activity in afferents generating the EPR.NEW & NOTEWORTHY G-protein-coupled receptor (GPCR) activation increases action potential activity in muscle afferents to produce the exercise pressor reflex (EPR), but the mechanisms are incompletely understood. We provide evidence that NaV1.9 current is synergistically enhanced by application of a mixture of metabolites potentially released during muscle contraction. The enhancement of NaV1.9 current is likely one mechanism by which GPCR activation generates the EPR and the inappropriate activation of the EPR in patients with cardiovascular disease.
Subject(s)
Bradykinin , Ganglia, Spinal , NAV1.9 Voltage-Gated Sodium Channel/metabolism , Adenosine Triphosphate/metabolism , Bradykinin/pharmacology , Ganglia, Spinal/physiology , Humans , Muscles , Neurons, Afferent/physiology , Norepinephrine/pharmacology , Prostaglandins/metabolism , Prostaglandins/pharmacology , Sodium Channel Blockers/pharmacology , Sodium Channels/metabolism , Tetrodotoxin/pharmacologyABSTRACT
Mesenchyme homeobox protein 2 (MEOX2) is a transcription factor involved in mesoderm differentiation, including development of bones, muscles, vasculature and dermatomes. We have previously identified dysregulation of MEOX2 in fibroblasts from Congenital Insensitivity to Pain patients, and confirmed that btn, the Drosophila homologue of MEOX2, plays a role in nocifensive responses to noxious heat stimuli. To determine the importance of MEOX2 in the mammalian peripheral nervous system, we used a Meox2 heterozygous (Meox2+/- ) mouse model to characterise its function in the sensory nervous system, and more specifically, in nociception. MEOX2 is expressed in the mouse dorsal root ganglia (DRG) and spinal cord, and localises in the nuclei of a subset of sensory neurons. Functional studies of the mouse model, including behavioural, cellular and electrophysiological analyses, showed altered nociception encompassing impaired action potential initiation upon depolarisation. Mechanistically, we noted decreased expression of Scn9a and Scn11a genes encoding Nav 1.7 and Nav 1.9 voltage-gated sodium channels respectively, that are crucial in subthreshold amplification and action potential initiation in nociceptors. Further transcriptomic analyses of Meox2+/- DRG revealed downregulation of a specific subset of genes including those previously associated with pain perception, such as PENK and NPY. Based on these observations, we propose a novel role of MEOX2 in primary afferent nociceptor neurons for the maintenance of a transcriptional programme required for proper perception of acute and inflammatory noxious stimuli.
Subject(s)
Homeodomain Proteins , Nociceptors , Animals , Ganglia, Spinal/metabolism , Homeodomain Proteins/genetics , Homeodomain Proteins/metabolism , Humans , Mesoderm/metabolism , Mice , NAV1.7 Voltage-Gated Sodium Channel/genetics , NAV1.9 Voltage-Gated Sodium Channel/metabolism , Nociceptors/metabolism , Transcription Factors/genetics , Transcription Factors/metabolismABSTRACT
The primary studies have shown that scorpion analgesic peptide N58A has a significant effect on voltage-gated sodium channels (VGSCs) and plays an important role in neuropathic pain. The purpose of this study was to investigate the analgesic effect of N58A on trigeminal neuralgia (TN) and its possible mechanism. The results showed that N58A could significantly increase the threshold of mechanical pain and thermal pain and inhibit the spontaneous asymmetric scratching behavior of rats. Western blotting results showed that N58A could significantly reduce the protein phosphorylation level of ERK1/2, P38, JNK, and ERK5/CREB pathways and the expression of Nav1.8 and Nav1.9 proteins in a dose-dependent manner. The changes in current and kinetic characteristics of Nav1.8 and Nav1.9 channels in TG neurons were detected by the whole-cell patch clamp technique. The results showed that N58A significantly decreased the current density of Nav1.8 and Nav1.9 in model rats, and shifted the activation curve to hyperpolarization and the inactivation curve to depolarization. In conclusion, the analgesic effect of N58A on the chronic constriction injury of the infraorbital (IoN-CCI) model rats may be closely related to the regulation of the MAPK pathway and Nav1.8 and Nav1.9 sodium channels.
Subject(s)
Analgesics/pharmacology , Peptides/pharmacology , Scorpion Venoms/chemistry , Trigeminal Neuralgia/drug therapy , Analgesics/administration & dosage , Analgesics/isolation & purification , Animals , Disease Models, Animal , Dose-Response Relationship, Drug , Female , MAP Kinase Signaling System/drug effects , NAV1.8 Voltage-Gated Sodium Channel/drug effects , NAV1.8 Voltage-Gated Sodium Channel/metabolism , NAV1.9 Voltage-Gated Sodium Channel/drug effects , NAV1.9 Voltage-Gated Sodium Channel/metabolism , Pain/drug therapy , Patch-Clamp Techniques , Peptides/administration & dosage , Peptides/isolation & purification , Rats , Rats, Sprague-Dawley , Scorpions , Tetrodotoxin/pharmacologyABSTRACT
The aim of the present study was to observe the changes of TTX-R, Nav1.8, and Nav1.9 Na+ currents in MSU-induced gouty arthritis mice, and to explore the possibility of Nav1.8 and Nav1.9 channels as potential targets for gout pain treatment. Acute gouty arthritis was induced by monosodium urate (MSU) in mice. Swelling degree was evaluated by measuring the circumference of the ankle joint. Mechanical allodynia was assessed by applying the electronic von Frey. Na+ currents were recorded by patch-clamp techniques in acute isolated dorsal root ganglion (DRG) neurons. MSU treatment significantly increased the swelling degree of ankle joint and decreased the mechanical pain threshold. The amplitude of TTX-R Na+ current was significantly increased and reached its peak on the 4th day after injection of MSU. For TTX-R Na+ channel subunits, Nav1.8 current density was significantly increased, but Nav1.9 current density was markedly decreased after MSU treatment. MSU treatment shifted the steady-state activation curves of TTX-R Na+ channel, Nav1.8 and Nav1.9 channels, and the inactivation curves of TTX-R Na+ channel and Nav1.8 channels to the depolarizing direction, but did not affect the inactivation curve of Nav1.9 channel. Compared with the normal group, the recovery of Nav1.8 channel was faster, while that of Nav1.9 channel was slower. The recovery of TTX-R Na+ channel remained unchanged after MSU treatment. Additionally, MSU treatment increased DRG neurons excitability by reducing action potential threshold. Nav1.8 channel, not Nav1.9 channel, may be involved in MSU-induced gout pain by increasing nerve excitability.
Subject(s)
Arthritis, Gouty/chemically induced , Arthritis, Gouty/metabolism , NAV1.8 Voltage-Gated Sodium Channel/metabolism , NAV1.9 Voltage-Gated Sodium Channel/metabolism , Uric Acid/toxicity , Animals , Arthritis, Gouty/pathology , Ganglia, Spinal/drug effects , Ganglia, Spinal/metabolism , Ganglia, Spinal/pathology , Hyperalgesia/chemically induced , Hyperalgesia/metabolism , Hyperalgesia/pathology , Male , Mice , Mice, Inbred ICR , Sodium Channel Blockers/pharmacologyABSTRACT
Mutations in the genes encoding for voltage-gated sodium channels cause profound sensory disturbances and other symptoms dependent on the distribution of a particular channel subtype in different organs. Humans with the gain-of-function mutation p.Leu811Pro in SCN11A (encoding for the voltage-gated Nav1.9 channel) exhibit congenital insensitivity to pain, pruritus, self-inflicted injuries, slow healing wounds, muscle weakness, Charcot-like arthropathies, and intestinal dysmotility. As already shown, knock-in mice (Scn11a+/L799P) carrying the orthologous mutation p.Leu799Pro replicate reduced pain sensitivity and show frequent tissue lesions. In the present study we explored whether Scn11a+/L799P mice develop also pruritus, muscle weakness, and changes in gastrointestinal transit time. Furthermore, we analyzed morphological and functional differences in nerves, skeletal muscle, joints and small intestine from Scn11a+/L799P and Scn11a+/+ wild type mice. Compared to Scn11a+/+ mice, Scn11a+/L799P mice showed enhanced scratching bouts before skin lesions developed, indicating pruritus. Scn11a+/L799P mice exhibited reduced grip strength, but no disturbances in motor coordination. Skeletal muscle fiber types and joint architecture were unaltered in Scn11a+/L799P mice. Their gastrointestinal transit time was unaltered. The small intestine from Scn11a+/L799P showed a small shift towards less frequent peristaltic movements. Similar proportions of lumbar dorsal root ganglion neurons from Scn11a+/L799P and Scn11a+/+ mice were calcitonin gene-related peptide (CGRP-) positive, but isolated sciatic nerves from Scn11a+/L799P mice exhibited a significant reduction of the capsaicin-evoked release of CGRP indicating reduced neurogenic inflammation. These data indicate important Nav1.9 channel functions in several organs in both humans and mice. They support the pathophysiological relevance of increased basal activity of Nav1.9 channels for sensory abnormalities (pain and itch) and suggest resulting malfunctions of the motor system and of the gastrointestinal tract. Scn11a+/L799P mice are suitable to investigate the role of Nav1.9, and to explore the pathophysiological changes and mechanisms which develop as a consequence of Nav1.9 hyperactivity.
Subject(s)
Gain of Function Mutation , Muscle Weakness/genetics , NAV1.9 Voltage-Gated Sodium Channel/genetics , Pruritus/genetics , Animals , Calcitonin Gene-Related Peptide/metabolism , Female , Gastrointestinal Transit , Hand Strength , Intestine, Small/metabolism , Intestine, Small/pathology , Male , Mice , Mice, Inbred C57BL , Movement , Muscle, Skeletal/metabolism , Muscle, Skeletal/pathology , NAV1.9 Voltage-Gated Sodium Channel/metabolism , Sciatic Nerve/metabolism , Sciatic Nerve/pathologyABSTRACT
The sodium channels Nav1.7, Nav1.8 and Nav1.9 are critical for pain perception in peripheral nociceptors. Loss of function of Nav1.7 leads to congenital insensitivity to pain in humans. Here we show that the spider peptide toxin called HpTx1, first identified as an inhibitor of Kv4.2, restores nociception in Nav1.7 knockout (Nav1.7-KO) mice by enhancing the excitability of dorsal root ganglion neurons. HpTx1 inhibits Nav1.7 and activates Nav1.9 but does not affect Nav1.8. This toxin produces pain in wild-type (WT) and Nav1.7-KO mice, and attenuates nociception in Nav1.9-KO mice, but has no effect in Nav1.8-KO mice. These data indicate that HpTx1-induced hypersensitivity is mediated by Nav1.9 activation and offers pharmacological insight into the relationship of the three Nav channels in pain signalling.
Subject(s)
Hyperalgesia/chemically induced , Hyperalgesia/metabolism , Ion Channel Gating , NAV1.7 Voltage-Gated Sodium Channel/metabolism , NAV1.9 Voltage-Gated Sodium Channel/metabolism , Peptides/adverse effects , Spider Venoms/adverse effects , Amino Acid Sequence , Animals , Female , Ganglia, Spinal/pathology , Humans , Hyperalgesia/complications , Male , Mice, Knockout , NAV1.7 Voltage-Gated Sodium Channel/chemistry , NAV1.8 Voltage-Gated Sodium Channel/metabolism , NAV1.9 Voltage-Gated Sodium Channel/chemistry , Neurons/drug effects , Neurons/pathology , Pain/complications , Pain/physiopathology , RatsSubject(s)
Headache Disorders, Secondary/etiology , Nitric Oxide/toxicity , Substance-Related Disorders/complications , Headache/chemically induced , Headache/metabolism , Headache Disorders, Secondary/chemically induced , Headache Disorders, Secondary/metabolism , Humans , NAV1.9 Voltage-Gated Sodium Channel/drug effects , NAV1.9 Voltage-Gated Sodium Channel/metabolism , Nitric Oxide/pharmacology , Prescription Drugs/adverse effects , Signal Transduction/drug effects , Substance-Related Disorders/metabolismABSTRACT
Genetic and functional studies have confirmed an important role for the voltage-gated sodium channel Nav1.9 in human pain disorders. However, low functional expression of Nav1.9 in heterologous systems (e.g. in human embryonic kidney 293 (HEK293) cells) has hampered studies of its biophysical and pharmacological properties and the development of high-throughput assays for drug development targeting this channel. The mechanistic basis for the low level of Nav1.9 currents in heterologous expression systems is not understood. Here, we implemented a multidisciplinary approach to investigate the mechanisms that govern functional Nav1.9 expression. Recombinant expression of a series of Nav1.9-Nav1.7 C-terminal chimeras in HEK293 cells identified a 49-amino-acid-long motif in the C terminus of the two channels that regulates expression levels of these chimeras. We confirmed the critical role of this motif in the context of a full-length channel chimera, Nav1.9-Ct49aaNav1.7, which displayed significantly increased current density in HEK293 cells while largely retaining the characteristic Nav1.9-gating properties. High-resolution live microscopy indicated that the newly identified C-terminal motif dramatically increases the number of channels on the plasma membrane of HEK293 cells. Molecular modeling results suggested that this motif is exposed on the cytoplasmic face of the folded C terminus, where it might interact with other channel partners. These findings reveal that a 49-residue-long motif in Nav1.9 regulates channel trafficking to the plasma membrane.
Subject(s)
Cell Membrane/metabolism , NAV1.9 Voltage-Gated Sodium Channel/chemistry , NAV1.9 Voltage-Gated Sodium Channel/metabolism , Amino Acid Motifs , Amino Acid Sequence , Cytosol/metabolism , Green Fluorescent Proteins/metabolism , HEK293 Cells , Humans , Ion Channel Gating , Kinetics , NAV1.7 Voltage-Gated Sodium Channel/chemistry , NAV1.7 Voltage-Gated Sodium Channel/metabolism , Protein Domains , Protein Transport , Structure-Activity RelationshipABSTRACT
Previous studies have found that increased expression of Nav1.9 and protein kinase C (PKC) contributes to pain hypersensitivity in a couple of inflammatory pain models. Here we want to observe if PKC can regulate the expression of Nav1.9 in dorsal root ganglion (DRG) in rheumatoid arthritis (RA) pain model. A chronic knee joint inflammation model was produced by intra-articular injection of the complete Freund's adjuvant (CFA) in rats. Nociceptive behaviors including mechanical, cold, and heat hyperalgesia were examined. The expression of Nav1.9 and PKCα in DRG was detected by a quantitative polymerase chain reaction, Western blot, and immunofluorescence. The in vitro and in vivo effects of a PKC activator (phorbol 12-myristate 13-acetate [PMA]) and a PKC inhibitor (GF-109203X) on the expression of Nav1.9 were examined. Moreover, the effects of PKC modulators on nociceptive behaviors were studied. Increased mechanical, heat, and cold sensitivity was observed 3 to 14 days after CFA injection. Parallel increases in messenger RNA and protein expression of Nav1.9 and PKCα were found. Immunofluorescence experiments found that Nav1.9 was preferentially colocalized with IB4+DRG neurons in RA rats. In cultured DRG neurons, PMA increased Nav1.9 expression while GF-109203X prevented the effect of PMA. PMA increased Nav1.9 expression in naïve rats while GF-109203X decreased Nav1.9 expression in RA rats. In naïve rats, PMA caused mechanical and cold hyperalgesia. On the other hand, GF-109203X attenuated mechanical and cold hyperalgesia in RA-pain model. Nav1.9 might be upregulated by PKCα in DRG, which contributes to pain hypersensitivity in CFA-induced chronic knee joint inflammation model of RA pain.
Subject(s)
Arthritis, Experimental/complications , Ganglia, Spinal/pathology , Inflammation/complications , NAV1.9 Voltage-Gated Sodium Channel/metabolism , Nociceptors/pathology , Pain/pathology , Protein Kinase C-alpha/metabolism , Animals , Arthritis, Experimental/chemically induced , Arthritis, Experimental/metabolism , Arthritis, Experimental/pathology , Behavior, Animal , Disease Models, Animal , Freund's Adjuvant/toxicity , Ganglia, Spinal/metabolism , Inflammation/chemically induced , Inflammation/metabolism , Inflammation/pathology , Male , Nociceptors/metabolism , Pain/etiology , Pain/metabolism , Rats , Rats, Sprague-DawleyABSTRACT
Inflammatory monocyte and macrophage subset accumulation during the inflammatory response that drives atherosclerosis can exacerbate the extent of atherosclerosis. It has been demonstrated that voltage-gated sodium channels (VGSCs) can regulate cell bioactivities in monocytes/macrophages. We hypothesized that blockade of mononuclear phagocyte VGSCs was atheroprotective through monocyte/macrophage subset modulation and macrophage proliferation suppression in atherosclerotic lesions. In this experimental study, when VGSCs were knocked down with RNA interference plasmid transfection in mouse peripheral blood monocytes and monocyte-macrophage lineage RAW264.7 cells in vitro, the biological characteristics of proliferation, phagocytosis, and migration in RAW264.7 cells declined. In addition, suppression of LPS-induced M1 polarization and facilitation of IL-4-induced M2 polarization were also observed. In an in vivo study, ApoE knockout (ApoE-/-) mice were fed a standard chow diet (CD) or a western diet (WD). After feeding with phenytoin (PHT), no significant differences were detected in plasma lipids, and the anti-inflammatory phenotypes of both monocytes and macrophages were elevated and proinflammatory phenotypes declined. The local proliferation of macrophages was also distinctly suppressed, along with a significant reduction in atheromatous plaques. In conclusion, blockade of VGSCs in the mononuclear phagocyte system reduced atherosclerotic lesions, which may occur through altering monocyte/macrophage subsets and suppressing macrophage proliferation in atherosclerotic plaques. Blockage of VGSCs may play an important role in cardiovascular protection.
Subject(s)
Atherosclerosis/prevention & control , Macrophage Activation , Macrophages/metabolism , Monocytes/metabolism , NAV1.4 Voltage-Gated Sodium Channel/metabolism , NAV1.9 Voltage-Gated Sodium Channel/metabolism , Animals , Atherosclerosis/genetics , Atherosclerosis/metabolism , Atherosclerosis/pathology , Cell Proliferation , Disease Models, Animal , Down-Regulation , Macrophages/pathology , Male , Mice , Mice, Inbred C57BL , Mice, Knockout, ApoE , Monocytes/pathology , NAV1.4 Voltage-Gated Sodium Channel/genetics , NAV1.9 Voltage-Gated Sodium Channel/genetics , Phagocytosis , Plaque, Atherosclerotic , RAW 264.7 Cells , RNA Interference , Signal TransductionABSTRACT
Medication-overuse headaches (MOH) occur with both over-the-counter and pain-relief medicines, including paracetamol, opioids and combination analgesics. The mechanisms that lead to MOH are still uncertain. Here, we show that abnormal activation of Nav1.9 channels by Nitric Oxide (NO) is responsible for MOH induced by triptan migraine medicine. Deletion of the Scn11a gene in MOH mice abrogates NO-mediated symptoms, including cephalic and extracephalic allodynia, photophobia and phonophobia. NO strongly activates Nav1.9 in dural afferent neurons from MOH but not normal mice. Abnormal activation of Nav1.9 triggers CGRP secretion, causing artery dilatation and degranulation of mast cells. In turn, released mast cell mediators potentiates Nav1.9 in meningeal nociceptors, exacerbating inflammation and pain signal. Analysis of signaling networks indicates that PKA is downregulated in trigeminal neurons from MOH mice, relieving its inhibitory action on NO-Nav1.9 coupling. Thus, anomalous activation of Nav1.9 channels by NO, as a result of chronic medication, promotes MOH.
Subject(s)
Headache Disorders, Secondary/pathology , Migraine Disorders/pathology , NAV1.9 Voltage-Gated Sodium Channel/metabolism , Neurons, Afferent/metabolism , Nitric Oxide/metabolism , Tryptamines/adverse effects , Animals , Calcitonin Gene-Related Peptide/metabolism , Cell Degranulation/physiology , Cells, Cultured , Female , Headache Disorders, Secondary/chemically induced , Hyperalgesia/physiopathology , Male , Mast Cells/pathology , Mice , Mice, Inbred C57BL , Mice, Knockout , NAV1.9 Voltage-Gated Sodium Channel/genetics , Neurons, Afferent/drug effects , Nociceptors/physiology , Pain/physiopathology , Prescription Drug Overuse/adverse effectsSubject(s)
Cholesterol/physiology , Inflammation/complications , Pain/etiology , Animals , Cholesterol/deficiency , Cholesterol/pharmacology , Humans , Inflammation/metabolism , NAV1.9 Voltage-Gated Sodium Channel/metabolism , NAV1.9 Voltage-Gated Sodium Channel/physiology , Nociceptors/drug effects , Nociceptors/metabolism , Pain/metabolism , Pain Perception/drug effectsABSTRACT
Itch (pruritis) and pain represent two distinct sensory modalities; yet both have evolved to alert us to potentially harmful external stimuli. Compared with pain, our understanding of itch is still nascent. Here, we report a new clinical case of debilitating itch and altered pain perception resulting from the heterozygous de novo p.L811P gain-of-function mutation in NaV1.9, a voltage-gated sodium (NaV) channel subtype that relays sensory information from the periphery to the spine. To investigate the role of NaV1.9 in itch, we developed a mouse line in which the channel is N-terminally tagged with a fluorescent protein, thereby enabling the reliable identification and biophysical characterization of NaV1.9-expressing neurons. We also assessed NaV1.9 involvement in itch by using a newly created NaV1.9-/- and NaV1.9L799P/WT mouse model. We found that NaV1.9 is expressed in a subset of nonmyelinated, nonpeptidergic small-diameter dorsal root ganglia (DRGs). In WT DRGs, but not those of NaV1.9-/- mice, pruritogens altered action potential parameters and NaV channel gating properties. Additionally, NaV1.9-/- mice exhibited a strong reduction in acute scratching behavior in response to pruritogens, whereas NaV1.9L799P/WT mice displayed increased spontaneous scratching. Altogether, our data suggest an important contribution of NaV1.9 to itch signaling.
Subject(s)
Ganglia, Spinal , Mutation , NAV1.9 Voltage-Gated Sodium Channel , Neurons , Pruritus , Signal Transduction , Animals , Disease Models, Animal , Ganglia, Spinal/metabolism , Ganglia, Spinal/pathology , Humans , Male , Mice , Mice, Knockout , NAV1.9 Voltage-Gated Sodium Channel/genetics , NAV1.9 Voltage-Gated Sodium Channel/metabolism , Neurons/metabolism , Neurons/pathology , Pruritus/genetics , Pruritus/metabolism , Pruritus/pathologyABSTRACT
BACKGROUND: Oxaliplatin-induced cold allodynia is a frequent complication appearing in patients treated with this anti-tumor drug. Since, there are no clear algorithms to overcome this painful condition effectively, it is important to establish novel strategies for its treatment. AIM: In this study, the ability of pregabalin and ambroxol, used as single drugs or in combinations administered in a time-shifted manner to attenuate cold allodynia was assessed in the mouse cold plate test. The hot plate test was additionally used to assess antinociceptive properties of ambroxol in the acute, thermally-induced pain model. Locomotor activity and motor coordination of mice were also evaluated. In silico studies were undertaken to predict potential binding of ambroxol to sodium channel (Nav) subtypes whose overexpression is implicated in the development of oxaliplatin-induced neuropathic pain. KEY FINDINGS: A hyperadditive antiallodynic effect of combined sub-analgesic ambroxol and pregabalin was demonstrated in oxaliplatin-treated mice. This effect was particularly strong when these drugs were given 4â¯h apart. Both drugs used in combination reduced animals' locomotor activity, but they did not impair motor coordination in the rotarod test. Ambroxol did not show antinociceptive properties in the hot plate test. The molecular docking studies predicted that in mice ambroxol might bind to Nav1.6 and Nav1.9 rather than Nav1.7 and Nav1.8. SIGNIFICANCE: Time-shifted co-administration of sub-analgesic doses of ambroxol and pregabalin effectively attenuates oxaliplatin-induced cold allodynia. Molecular docking model predicts preferential binding of ambroxol to mouse Nav1.6, Nav1.9 channels. This mechanism, if confirmed in vitro, might explain pharmacological activities observed in vivo.
Subject(s)
Ambroxol/administration & dosage , Analgesics/administration & dosage , Cold Temperature , Hyperalgesia/prevention & control , NAV1.6 Voltage-Gated Sodium Channel/drug effects , NAV1.9 Voltage-Gated Sodium Channel/drug effects , Oxaliplatin , Pain Threshold/drug effects , Pregabalin/administration & dosage , Ambroxol/metabolism , Analgesics/metabolism , Animals , Behavior, Animal/drug effects , Binding Sites , Disease Models, Animal , Dose-Response Relationship, Drug , Drug Administration Schedule , Drug Therapy, Combination , Hyperalgesia/chemically induced , Hyperalgesia/metabolism , Hyperalgesia/physiopathology , Male , Mice , Molecular Docking Simulation , Motor Activity/drug effects , NAV1.6 Voltage-Gated Sodium Channel/metabolism , NAV1.9 Voltage-Gated Sodium Channel/metabolism , Protein Binding , Rotarod Performance Test , Signal Transduction/drug effects , Time FactorsABSTRACT
Damage-sensing nociceptors in the skin provide an indispensable protective function thanks to their specialized ability to detect and transmit hot temperatures that would block or inflict irreversible damage in other mammalian neurons. Here we show that the exceptional capacity of skin C-fiber nociceptors to encode noxiously hot temperatures depends on two tetrodotoxin (TTX)-resistant sodium channel α-subunits: NaV1.8 and NaV1.9. We demonstrate that NaV1.9, which is commonly considered an amplifier of subthreshold depolarizations at 20°C, undergoes a large gain of function when temperatures rise to the pain threshold. We also show that this gain of function renders NaV1.9 capable of generating action potentials with a clear inflection point and positive overshoot. In the skin, heat-resistant nociceptors appear as two distinct types with unique and possibly specialized features: one is blocked by TTX and relies on NaV1.9, and the second type is insensitive to TTX and composed of both NaV1.8 and NaV1.9. Independent of rapidly gated TTX-sensitive NaV channels that form the action potential at pain threshold, NaV1.8 is required in all heat-resistant nociceptors to encode temperatures higher than â¼46°C, whereas NaV1.9 is crucial for shaping the action potential upstroke and keeping the NaV1.8 voltage threshold within reach.
Subject(s)
Hot Temperature , NAV1.8 Voltage-Gated Sodium Channel/metabolism , NAV1.9 Voltage-Gated Sodium Channel/metabolism , Nociceptors/metabolism , Action Potentials , Animals , Cell Line , Evolution, Molecular , In Vitro Techniques , Mice, Inbred C57BL , Pain Threshold , Patch-Clamp Techniques , SkinABSTRACT
The exercise pressor reflex (EPR) is activated by muscle contractions to increase heart rate and blood pressure during exercise. While this reflex is beneficial in healthy individuals, the reflex activity is exaggerated in patients with cardiovascular disease, which is associated with increased mortality. Group III and IV afferents mediate the EPR and have been shown to express both tetrodotoxin-sensitive (TTX-S, NaV1.6, and NaV1.7) and -resistant (TTX-R, NaV1.8, and NaV1.9) voltage-gated sodium (NaV) channels, but NaV1.9 current has not yet been demonstrated. Using a F--containing internal solution, we found a NaV current in muscle afferent neurons that activates at around -70 mV with slow activation and inactivation kinetics, as expected from NaV1.9 current. However, this current ran down with time, which resulted, at least in part, from increased steady-state inactivation since it was slowed by both holding potential hyperpolarization and a depolarized shift of the gating properties. We further show that, following NaV1.9 current rundown (internal F-), application of the NaV1.8 channel blocker A803467 inhibited significantly more TTX-R current than we had previously observed (internal Cl-), which suggests that NaV1.9 current did not rundown with that internal solution. Using immunohistochemistry, we found that the majority of group IV somata and axons were NaV1.9 positive. The majority of small diameter myelinated afferent somata (putative group III) were also NaV1.9 positive, but myelinated muscle afferent axons were rarely labeled. The presence of NaV1.9 channels in muscle afferents supports a role for these channels in activation and maintenance of the EPR. NEW & NOTEWORTHY Small diameter muscle afferents signal pain and muscle activity levels. The muscle activity signals drive the cardiovascular system to increase muscle blood flow, but these signals can become exaggerated in cardiovascular disease to exacerbate cardiac damage. The voltage-dependent sodium channel NaV1.9 plays a unique role in controlling afferent excitability. We show that NaV1.9 channels are expressed in muscle afferents, which supports these channels as a target for drug development to control hyperactivity of these neurons.
Subject(s)
Axons/physiology , NAV1.9 Voltage-Gated Sodium Channel/metabolism , Neurons, Afferent/physiology , Reflex, Stretch/physiology , Action Potentials/physiology , Aniline Compounds/pharmacology , Animals , Furans/pharmacology , Ganglia, Spinal/diagnostic imaging , Ganglia, Spinal/physiology , Immunohistochemistry , Male , Microscopy, Fluorescence , Muscle Contraction/physiology , Muscle, Skeletal/diagnostic imaging , Muscle, Skeletal/physiology , Normal Distribution , Patch-Clamp Techniques , Rats , Rats, Sprague-Dawley , Sodium Channel Blockers/pharmacologyABSTRACT
Many veterans of Operation Desert Storm (ODS) struggle with the chronic pain of Gulf War Illness (GWI). Exposure to insecticides and pyridostigmine bromide (PB) have been implicated in the etiology of this multisymptom disease. We examined the influence of 3 (DEET (N,N-diethyl-meta-toluamide), permethrin, chlorpyrifos) or 4â¯GW agents (DEET, permethrin, chlorpyrifos, pyridostigmine bromide (PB)) on the post-exposure ambulatory and resting behaviors of rats. In three independent studies, rats that were exposed to all 4 agents consistently developed both immediate and delayed ambulatory deficits that persisted at least 16â¯weeks after exposures had ceased. Rats exposed to a 3 agent protocol (PB excluded) did not develop any ambulatory deficits. Cellular and molecular studies on nociceptors harvested from 16WP (weeks post-exposure) rats indicated that vascular nociceptor Nav1.9 mediated currents were chronically potentiated following the 4 agent protocol but not following the 3 agent protocol. Muscarinic linkages to muscle nociceptor TRPA1 were also potentiated in the 4 agent but not the 3 agent, PB excluded, protocol. Although Kv7 activity changes diverged from the behavioral data, a Kv7 opener, retigabine, transiently reversed ambulation deficits. We concluded that PB played a critical role in the development of pain-like signs in a GWI rat model and that shifts in Nav1.9 and TRPA1 activity were critical to the expression of these pain behaviors.
Subject(s)
Behavior, Animal , Ganglia, Spinal/metabolism , Muscle, Skeletal/innervation , NAV1.9 Voltage-Gated Sodium Channel/metabolism , Pain Perception , Persian Gulf Syndrome/metabolism , Persian Gulf Syndrome/psychology , Pyridostigmine Bromide , TRPA1 Cation Channel/metabolism , Adaptation, Physiological , Animals , Chlorpyrifos , DEET , Disease Models, Animal , Ganglia, Spinal/physiopathology , KCNQ Potassium Channels/metabolism , Male , Pain Threshold , Permethrin , Persian Gulf Syndrome/chemically induced , Persian Gulf Syndrome/physiopathology , Rats, Sprague-Dawley , Receptors, Muscarinic/metabolism , Signal Transduction , Time FactorsABSTRACT
The aim of the present study was to identify whether the sodium voltage-gated channel alpha subunit 9 (SCN9A) gene modification is a potential treatment for diarrheapredominant irritable bowel syndrome (DIBS), via regulating the Na+ channel and the expression of nerve growth factor (NGF). The recombinant adenovirus vector of the SCN9A gene was established, and rat colon cells were isolated for SCN9A gene modification. All subjects were divided into four groups: i) The SCN9Amodified (DIBS rat model implanted with SCN9Amodified colon cells), ii) negative control (NC; DIBS rat model implanted with colon cells without SCN9A gene modification), iii) blank (DIBS rat model without any treatment) and iv) normal (normal rats without any treatment). Western blotting and reverse transcriptionquantitative polymerase chain reaction were used to detect the protein and mRNA expression levels of SCN9A, NGF and voltage gated sodium channels (Nav)1.8 and Nav1.9 in rat colon tissues. Compared with the normal group, the rats in the SCN9A, NC and blank groups had significantly elevated mRNA and protein expression levels of NGF, SCN9A, Nav1.8 and Nav1.9. The rats in the SCN9A group demonstrated significantly increased mRNA and protein expression levels of NGF, SCN9A, Nav1.8 and Nav1.9 compared with the NC group and the blank group (all P<0.05). SCN9A gene modification can promote the expression of Nav1.8 and Nav1.9 channels, in addition to NGF which may provide a novel therapeutic basis for treating of DIBS.