1
|
Oyama M, Watanabe S, Iwai T, Tanabe M. Selective inhibition of A-fiber-mediated excitatory transmission underlies the analgesic effects of KCNQ channel opening in the spinal dorsal horn. Neuropharmacology 2024; 254:109994. [PMID: 38750803 DOI: 10.1016/j.neuropharm.2024.109994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2024] [Revised: 04/11/2024] [Accepted: 05/10/2024] [Indexed: 05/18/2024]
Abstract
Neuronal voltage-gated KCNQ (Kv7) channels, expressed centrally and peripherally, mediate low-threshold and non-inactivating M-currents responsible for the control of tonic excitability of mammalian neurons. Pharmacological opening of KCNQ channels has been reported to generate analgesic effects in animal models of neuropathic pain. Here, we examined the possible involvement of central KCNQ channels in the analgesic effects of retigabine, a KCNQ channel opener. Behaviorally, intraperitoneally applied retigabine exerted analgesic effects on thermal and mechanical hypersensitivity in male mice developing neuropathic pain after partial sciatic nerve ligation, which was antagonized by the KCNQ channel blocker XE991 preadministered intraperitoneally and intrathecally. Intrathecally applied retigabine also exerted analgesic effects that were inhibited by intrathecally injected XE991. We then explored the synaptic mechanisms underlying the analgesic effects of retigabine in the spinal dorsal horn. Whole-cell recordings were made from dorsal horn neurons in spinal slices with attached dorsal roots from adult male mice developing neuropathic pain, and the effects of retigabine on miniature and afferent-evoked postsynaptic currents were examined. Retigabine reduced the amplitude of A-fiber-mediated EPSCs without affecting C-fiber-mediated excitatory synaptic transmission. A-fiber-mediated EPSCs remained unaltered by retigabine in the presence of XE991, consistently with the behavioral findings. The frequency and amplitude of mEPSCs were not affected by retigabine. Thus, opening of KCNQ channels in the central terminals of primary afferent A-fibers inhibits excitatory synaptic transmission in the spinal dorsal horn, most likely contributing to the analgesic effect of retigabine.
Collapse
Affiliation(s)
- Misa Oyama
- Laboratory of Pharmacology, School of Pharmaceutical Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan; Medicinal Research Laboratories, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan
| | - Shun Watanabe
- Laboratory of Pharmacology, School of Pharmaceutical Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan; Medicinal Research Laboratories, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan
| | - Takashi Iwai
- Laboratory of Pharmacology, School of Pharmaceutical Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan; Medicinal Research Laboratories, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan
| | - Mitsuo Tanabe
- Laboratory of Pharmacology, School of Pharmaceutical Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan; Medicinal Research Laboratories, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan.
| |
Collapse
|
2
|
Zhuang GZ, Goins WF, Kandel MB, Marzulli M, Zhang M, Glorioso JC, Kang Y, Levitt AE, Sarantopoulos KD, Levitt RC. Disease-modifying rdHSV-CA8* non-opioid analgesic gene therapy treats chronic osteoarthritis pain by activating Kv7 voltage-gated potassium channels. Front Mol Neurosci 2024; 17:1416148. [PMID: 39086927 PMCID: PMC11289847 DOI: 10.3389/fnmol.2024.1416148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2024] [Accepted: 06/13/2024] [Indexed: 08/02/2024] Open
Abstract
Chronic pain is common in our population, and most of these patients are inadequately treated, making the development of safer analgesics a high priority. Knee osteoarthritis (OA) is a primary cause of chronic pain and disability worldwide, and lower extremity OA is a major contributor to loss of quality-adjusted life-years. In this study we tested the hypothesis that a novel JDNI8 replication-defective herpes simplex-1 viral vector (rdHSV) incorporating a modified carbonic anhydrase-8 transgene (CA8*) produces analgesia and treats monoiodoacetate-induced (MIA) chronic knee pain due to OA. We observed transduction of lumbar DRG sensory neurons with these viral constructs (vHCA8*) (~40% of advillin-positive cells and ~ 50% of TrkA-positive cells colocalized with V5-positive cells) using the intra-articular (IA) knee joint (KJ) route of administration. vHCA8* inhibited chronic mechanical OA knee pain induced by MIA was dose- and time-dependent. Mechanical thresholds returned to Baseline by D17 after IA KJ vHCA8* treatment, and exceeded Baseline (analgesia) through D65, whereas negative controls failed to reach Baseline responses. Weight-bearing and automated voluntary wheel running were improved by vHCA8*, but not negative controls. Kv7 voltage-gated potassium channel-specific inhibitor XE-991 reversed vHCA8*-induced analgesia. Using IHC, IA KJ of vHCA8* activated DRG Kv7 channels via dephosphorylation, but negative controls failed to impact Kv7 channels. XE-991 stimulated Kv7.2-7.5 and Kv7.3 phosphorylation using western blotting of differentiated SH-SY5Y cells, which was inhibited by vHCA8* but not by negative controls. The observed prolonged dose-dependent therapeutic effects of IA KJ administration of vHCA8* on MIA-induced chronic KJ pain due to OA is consistent with the specific activation of Kv7 channels in small DRG sensory neurons. Together, these data demonstrate for the first-time local IA KJ administration of vHCA8* produces opioid-independent analgesia in this MIA-induced OA chronic pain model, supporting further therapeutic development.
Collapse
Affiliation(s)
- Gerald Z. Zhuang
- Department of Anesthesiology, Perioperative Medicine and Pain Management, University of Miami Miller School of Medicine, Miami, FL, United States
| | - William F. Goins
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Munal B. Kandel
- Department of Anesthesiology, Perioperative Medicine and Pain Management, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Marco Marzulli
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Mingdi Zhang
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Joseph C. Glorioso
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Yuan Kang
- Department of Anesthesiology, Perioperative Medicine and Pain Management, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Alexandra E. Levitt
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Konstantinos D. Sarantopoulos
- Department of Anesthesiology, Perioperative Medicine and Pain Management, University of Miami Miller School of Medicine, Miami, FL, United States
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Roy C. Levitt
- Department of Anesthesiology, Perioperative Medicine and Pain Management, University of Miami Miller School of Medicine, Miami, FL, United States
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, United States
- John T. MacDonald Foundation Department of Human Genetics, University of Miami Miller School of Medicine, Miami, FL, United States
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL, United States
| |
Collapse
|
3
|
Kandel MB, Zhuang GZ, Goins WF, Marzulli M, Zhang M, Glorioso JC, Kang Y, Levitt AE, Kwok WM, Levitt RC, Sarantopoulos KD. rdHSV-CA8 non-opioid analgesic gene therapy decreases somatosensory neuronal excitability by activating Kv7 voltage-gated potassium channels. Front Mol Neurosci 2024; 17:1398839. [PMID: 38783904 PMCID: PMC11112096 DOI: 10.3389/fnmol.2024.1398839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2024] [Accepted: 04/18/2024] [Indexed: 05/25/2024] Open
Abstract
Chronic pain is common and inadequately treated, making the development of safe and effective analgesics a high priority. Our previous data indicate that carbonic anhydrase-8 (CA8) expression in dorsal root ganglia (DRG) mediates analgesia via inhibition of neuronal ER inositol trisphosphate receptor-1 (ITPR1) via subsequent decrease in ER calcium release and reduction of cytoplasmic free calcium, essential to the regulation of neuronal excitability. This study tested the hypothesis that novel JDNI8 replication-defective herpes simplex-1 viral vectors (rdHSV) carrying a CA8 transgene (vHCA8) reduce primary afferent neuronal excitability. Whole-cell current clamp recordings in small DRG neurons showed that vHCA8 transduction caused prolongation of their afterhyperpolarization (AHP), an essential regulator of neuronal excitability. This AHP prolongation was completely reversed by the specific Kv7 channel inhibitor XE-991. Voltage clamp recordings indicate an effect via Kv7 channels in vHCA8-infected small DRG neurons. These data demonstrate for the first time that vHCA8 produces Kv7 channel activation, which decreases neuronal excitability in nociceptors. This suppression of excitability may translate in vivo as non-opioid dependent behavioral- or clinical analgesia, if proven behaviorally and clinically.
Collapse
Affiliation(s)
- Munal B. Kandel
- Department of Anesthesiology, Perioperative Medicine and Pain Management, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Gerald Z. Zhuang
- Department of Anesthesiology, Perioperative Medicine and Pain Management, University of Miami Miller School of Medicine, Miami, FL, United States
| | - William F. Goins
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Marco Marzulli
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Mingdi Zhang
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Joseph C. Glorioso
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Yuan Kang
- Department of Anesthesiology, Perioperative Medicine and Pain Management, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Alexandra E. Levitt
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Wai-Meng Kwok
- Department of Anesthesiology and Department of Pharmacology & Toxicology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Roy C. Levitt
- Department of Anesthesiology, Perioperative Medicine and Pain Management, University of Miami Miller School of Medicine, Miami, FL, United States
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, United States
- John T. MacDonald Foundation Department of Human Genetics, University of Miami Miller School of Medicine, Miami, FL, United States
- John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL, United States
| | - Konstantinos D. Sarantopoulos
- Department of Anesthesiology, Perioperative Medicine and Pain Management, University of Miami Miller School of Medicine, Miami, FL, United States
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, United States
| |
Collapse
|
4
|
Nagaraja S, Tewari SG, Reifman J. Identification of key factors driving inflammation-induced sensitization of muscle sensory neurons. Front Neurosci 2023; 17:1147437. [PMID: 37250415 PMCID: PMC10213456 DOI: 10.3389/fnins.2023.1147437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 04/24/2023] [Indexed: 05/31/2023] Open
Abstract
Sensory neurons embedded in muscle tissue that initiate pain sensations, i.e., nociceptors, are temporarily sensitized by inflammatory mediators during musculoskeletal trauma. These neurons transduce peripheral noxious stimuli into an electrical signal [i.e., an action potential (AP)] and, when sensitized, demonstrate lower activation thresholds and a heightened AP response. We still do not understand the relative contributions of the various transmembrane proteins and intracellular signaling processes that drive the inflammation-induced hyperexcitability of nociceptors. In this study, we used computational analysis to identify key proteins that could regulate the inflammation-induced increase in the magnitude of AP firing in mechanosensitive muscle nociceptors. First, we extended a previously validated model of a mechanosensitive mouse muscle nociceptor to incorporate two inflammation-activated G protein-coupled receptor (GPCR) signaling pathways and validated the model simulations of inflammation-induced nociceptor sensitization using literature data. Then, by performing global sensitivity analyses that simulated thousands of inflammation-induced nociceptor sensitization scenarios, we identified three ion channels and four molecular processes (from the 17 modeled transmembrane proteins and 28 intracellular signaling components) as potential regulators of the inflammation-induced increase in AP firing in response to mechanical forces. Moreover, we found that simulating single knockouts of transient receptor potential ankyrin 1 (TRPA1) and reducing the rates of Gαq-coupled receptor phosphorylation and Gαq subunit activation considerably altered the excitability of nociceptors (i.e., each modification increased or decreased the inflammation-induced fold change in the number of triggered APs compared to when all channels were present). These results suggest that altering the expression of TRPA1 or the concentration of intracellular Gαq might regulate the inflammation-induced increase in AP response of mechanosensitive muscle nociceptors.
Collapse
Affiliation(s)
- Sridevi Nagaraja
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Development Command, Fort Detrick, MD, United States
- The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, MD, United States
| | - Shivendra G. Tewari
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Development Command, Fort Detrick, MD, United States
- The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, MD, United States
| | - Jaques Reifman
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Development Command, Fort Detrick, MD, United States
| |
Collapse
|
5
|
Roza C, Bernal L. Electrophysiological characterization of ectopic spontaneous discharge in axotomized and intact fibers upon nerve transection: a role in spontaneous pain? Pflugers Arch 2022; 474:387-396. [PMID: 35088129 DOI: 10.1007/s00424-021-02655-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 12/13/2021] [Accepted: 12/14/2021] [Indexed: 12/14/2022]
Abstract
Many patients experience positive symptoms after traumatic nerve injury. Despite the increasing number of experimental studies in models of peripheral neuropathy and the knowledge acquired, most of these patients lack an effective treatment for their chronic pain. One possible explanation might be that most of the preclinical studies focused on the development of mechanical or thermal allodynia/hyperalgesia, neglecting that most of the patients with peripheral neuropathies complain mostly about spontaneous forms of pains. Here, we summarize the aberrant electrophysiological behavior of peripheral nerve fibers recorded in experimental models, the underlying pathophysiological mechanisms, and their relationship with the symptoms reported by patients. Upon nerve section, axotomized but also intact fibers develop ectopic spontaneous activity. Most interestingly, a proportion of axotomized fibers might present receptive fields in the skin far beyond the site of damage, indicative of a functional cross talk between neuromatose and intact fibers. All these features can be linked with some of the symptoms that neuropathic patients experience. Furthermore, we spotlight the consequence of primary afferents with different patterns of spontaneous discharge on the neural code and its relationship with chronic pain states. With this article, readers will be able to understand the pathophysiological mechanisms that might underlie some of the symptoms that experience neuropathic patients, with a special focus on spontaneous pain.
Collapse
Affiliation(s)
- Carolina Roza
- Dpto. Biología de Sistemas, Edificio de Medicina Universidad de Alcalá, 28871, Alcalá de Henares, Madrid, Spain.
| | | |
Collapse
|
6
|
Wang J, Liu Y, Hu F, Yang J, Guo X, Hou X, Ju C, Wang K. Activation of Neuronal Voltage-Gated Potassium Kv7/KCNQ/M-Current by a Novel Channel Opener SCR2682 for Alleviation of Chronic Pain. J Pharmacol Exp Ther 2021; 377:20-28. [DOI: 10.1124/jpet.120.000357] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 01/06/2021] [Indexed: 12/20/2022] Open
|
7
|
Bernal L, Cisneros E, Roza C. Activation of the regeneration-associated gene STAT3 and functional changes in intact nociceptors after peripheral nerve damage in mice. Eur J Pain 2021; 25:886-901. [PMID: 33345380 DOI: 10.1002/ejp.1718] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 12/16/2020] [Indexed: 12/13/2022]
Abstract
BACKGROUND In the context of neuropathic pain, the contribution of regeneration to the development of positive symptoms is not completely understood. Several efforts have been done to described changes in axotomized neurons, however, there is scarce data on changes occurring in intact neurons, despite experimental evidence of functional changes. To address this issue, we analysed by immunohistochemistry the presence of phosphorylated signal transducer and activator of transcription 3 (pSTAT3), an accepted marker of regeneration, within DRGs where axotomized neurons were retrogradely labelled following peripheral nerve injury. Likewise, we have characterized abnormal electrophysiological properties in intact fibres after partial nerve injury. METHODS/RESULTS We showed that induction of pSTAT3 in sensory neurons was similar after partial or total transection of the sciatic nerve and to the same extent within axotomized and non-axotomized neurons. We also examined pSTAT3 presence on non-peptidergic and peptidergic nociceptors. Whereas the percentage of neurons marked by IB4 decrease after injury, the proportion of CGRP neurons did not change, but its expression switched from small- to large-diameter neurons. Besides, the percentage of CGRP+ neurons expressing pSTAT3 increased significantly 2.5-folds after axotomy, preferentially in neurons with large diameters. Electrophysiological recordings showed that after nerve damage, most of the neurons with ectopic spontaneous activity (39/46) were non-axotomized C-fibres with functional receptive fields in the skin far beyond the site of damage. CONCLUSIONS Neuronal regeneration after nerve injury, likely triggered from the site of injury, may explain the abnormal functional properties gained by intact neurons, reinforcing their role in neuropathic pain. SIGNIFICANCE Positive symptoms in patients with peripheral neuropathies correlate to abnormal functioning of different subpopulations of primary afferents. Peripheral nerve damage triggers regenerating programs in the cell bodies of axotomized but also in non-axotomized nociceptors which is in turn, develop abnormal spontaneous and evoked discharges. Therefore, intact nociceptors have a significant role in the development of neuropathic pain due to their hyperexcitable peripheral terminals. Therapeutical targets should focus on inhibiting peripheral hyperexcitability in an attempt to limit peripheral and central sensitization.
Collapse
Affiliation(s)
- Laura Bernal
- Department of System's Biology, Medical School, University of Alcala, Alcalá de Henares, Spain
| | - Elsa Cisneros
- Department of System's Biology, Medical School, University of Alcala, Alcalá de Henares, Spain.,Health Sciences School, Centro Universitario Internacional de Madrid (CUNIMAD), Madrid, Spain.,Health Sciences School, Universidad Internacional de La Rioja (UNIR), Logroño, Spain
| | - Carolina Roza
- Department of System's Biology, Medical School, University of Alcala, Alcalá de Henares, Spain
| |
Collapse
|
8
|
Changes in expression of Kv7.5 and Kv7.2 channels in dorsal root ganglion neurons in the streptozotocin rat model of painful diabetic neuropathy. Neurosci Lett 2020; 736:135277. [PMID: 32739272 DOI: 10.1016/j.neulet.2020.135277] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 07/21/2020] [Accepted: 07/22/2020] [Indexed: 11/21/2022]
Abstract
Diabetic peripheral neuropathic pain (DPNP), the most debilitating complication of diabetes mellitus, is resistant to current therapy. The pathogenesis of DPNP is still elusive, but several mechanisms have been proposed including abnormal hyperexcitability of dorsal root ganglion (DRG) neurons. The underlying molecular mechanisms of such aberrant hyperexcitability are incompletely understood. Using the streptozotocin (STZ) rat model of DPNP, we have recently provided evidence implicating neuronal Kv7 channels that normally exert a powerful stabilizing influence on neuronal excitability, in the abnormal hyperexcitability of DRG neurons and in pain hypersensitivity associated with DPNP. In the present immunohistochemical study, we sought to determine whether Kv7.2 and/or Kv7.5 channel expression is altered in DRG neurons in STZ rats. We found 35 days post-STZ: (1) a significant decrease in Kv7.5-immunoreactivity in small (<30 μm) DRG neurons (both IB4 positive and IB4 negative) and medium-sized (30-40 μm) neurons, and (2) a significant increase in Kv7.2-immunoreactivity in small (<30 μm) neurons, and a non-significant increase in medium/large neurons. The decrease in Kv7.5 channel expression in small and medium-sized DRG neurons in STZ rats is likely to contribute to the mechanisms of hyperexcitability of these neurons and thereby to the resulting pain hypersensitivity associated with DPNP. The upregulation of Kv7.2 subunit in small DRG neurons may be an activity dependent compensatory mechanism to limit STZ-induced hyperexcitability of DRG neurons and the associated pain hypersensitivity. The findings support the notion that Kv7 channels may represent a novel target for DPNP treatment.
Collapse
|
9
|
Smith PA. K + Channels in Primary Afferents and Their Role in Nerve Injury-Induced Pain. Front Cell Neurosci 2020; 14:566418. [PMID: 33093824 PMCID: PMC7528628 DOI: 10.3389/fncel.2020.566418] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 08/21/2020] [Indexed: 12/12/2022] Open
Abstract
Sensory abnormalities generated by nerve injury, peripheral neuropathy or disease are often expressed as neuropathic pain. This type of pain is frequently resistant to therapeutic intervention and may be intractable. Numerous studies have revealed the importance of enduring increases in primary afferent excitability and persistent spontaneous activity in the onset and maintenance of peripherally induced neuropathic pain. Some of this activity results from modulation, increased activity and /or expression of voltage-gated Na+ channels and hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. K+ channels expressed in dorsal root ganglia (DRG) include delayed rectifiers (Kv1.1, 1.2), A-channels (Kv1.4, 3.3, 3.4, 4.1, 4.2, and 4.3), KCNQ or M-channels (Kv7.2, 7.3, 7.4, and 7.5), ATP-sensitive channels (KIR6.2), Ca2+-activated K+ channels (KCa1.1, 2.1, 2.2, 2.3, and 3.1), Na+-activated K+ channels (KCa4.1 and 4.2) and two pore domain leak channels (K2p; TWIK related channels). Function of all K+ channel types is reduced via a multiplicity of processes leading to altered expression and/or post-translational modification. This also increases excitability of DRG cell bodies and nociceptive free nerve endings, alters axonal conduction and increases neurotransmitter release from primary afferent terminals in the spinal dorsal horn. Correlation of these cellular changes with behavioral studies provides almost indisputable evidence for K+ channel dysfunction in the onset and maintenance of neuropathic pain. This idea is underlined by the observation that selective impairment of just one subtype of DRG K+ channel can produce signs of pain in vivo. Whilst it is established that various mediators, including cytokines and growth factors bring about injury-induced changes in DRG function and excitability, evidence presently available points to a seminal role for interleukin 1β (IL-1β) in control of K+ channel function. Despite the current state of knowledge, attempts to target K+ channels for therapeutic pain management have met with limited success. This situation may change with the advent of personalized medicine. Identification of specific sensory abnormalities and genetic profiling of individual patients may predict therapeutic benefit of K+ channel activators.
Collapse
Affiliation(s)
- Peter A. Smith
- Department of Pharmacology and Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| |
Collapse
|
10
|
Bernal L, Cisneros E, García-Magro N, Roza C. Immunostaining in whole-mount lipid-cleared peripheral nerves and dorsal root ganglia after neuropathy in mice. Sci Rep 2019; 9:8374. [PMID: 31182787 PMCID: PMC6558043 DOI: 10.1038/s41598-019-44897-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Accepted: 05/23/2019] [Indexed: 12/31/2022] Open
Abstract
Immunohistochemical characterization of primary afferent fibers (intact or after nerve damage) is traditionally performed in thin sections from dorsal root ganglia (DRGs) or in teased fibers, as light scattering in whole-mounts compromises visualization. These procedures are time-consuming, require specific equipment and advanced experimental skills. Lipid-clearing techniques are increasing in popularity, but they have never been used for the peripheral nervous system. We established a modified, inexpensive clearing method based on lipid-removal protocols to make transparent peripheral nerve tissue (inCLARITY). We compared retrograde-labeling and free-floating immunostaining with cryo-sections. Confocal microscopy on whole-mount transparent DRGs showed neurons marked with retrograde tracers applied to experimental neuromas (Retrobeads, Fluoro-ruby, Fluoro-emerald, DiI, and Fluoro-gold). After immunostaining with calcitonin gene-related peptide (peptidergic) or isolectin IB4 (non-peptidergic), nociceptors were visualized. Immunostaining in transparent whole-mount nerves allows simultaneous evaluation of the axotomized branches containing the neuroma and neighboring intact branches as they can be mounted preserving their anatomical disposition and fiber integrity. The goal of our study was to optimize CLARITY for its application in peripheral nerve tissues. The protocol is compatible with the use of retrograde tracers and improves immunostaining outcomes when compared to classical cryo-sectioning, as lack of lipids maximizes antibody penetration within the tissue.
Collapse
Affiliation(s)
- L Bernal
- Department of System's Biology, Medical School, University of Alcala, Alcalá de Henares, 28871, Madrid, Spain
| | - E Cisneros
- Department of System's Biology, Medical School, University of Alcala, Alcalá de Henares, 28871, Madrid, Spain.,Centro Universitario Internacional de Madrid (CUNIMAD), Madrid, Spain
| | - N García-Magro
- Department of Anatomy, Histology and Neuroscience, Medical School, Autonoma University of Madrid, 28029, Madrid, Spain
| | - C Roza
- Department of System's Biology, Medical School, University of Alcala, Alcalá de Henares, 28871, Madrid, Spain.
| |
Collapse
|
11
|
Surur AS, Bock C, Beirow K, Wurm K, Schulig L, Kindermann MK, Siegmund W, Bednarski PJ, Link A. Flupirtine and retigabine as templates for ligand-based drug design of KV7.2/3 activators. Org Biomol Chem 2019; 17:4512-4522. [DOI: 10.1039/c9ob00511k] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Puzzling stability: molecular jigsaw pieces of residues characterized in light of activity, lipophilicity, stability against oxidation, and hepatotoxicity were combined to yield flupirtine analogue 25b.
Collapse
Affiliation(s)
- Abdrrahman S. Surur
- Pharmaceutical and Medicinal Chemistry
- Institute of Pharmacy
- University of Greifswald
- 17487 Greifswald
- Germany
| | - Christian Bock
- Pharmaceutical and Medicinal Chemistry
- Institute of Pharmacy
- University of Greifswald
- 17487 Greifswald
- Germany
| | - Kristin Beirow
- Pharmaceutical and Medicinal Chemistry
- Institute of Pharmacy
- University of Greifswald
- 17487 Greifswald
- Germany
| | - Konrad Wurm
- Pharmaceutical and Medicinal Chemistry
- Institute of Pharmacy
- University of Greifswald
- 17487 Greifswald
- Germany
| | - Lukas Schulig
- Pharmaceutical and Medicinal Chemistry
- Institute of Pharmacy
- University of Greifswald
- 17487 Greifswald
- Germany
| | - Markus K. Kindermann
- Pharmaceutical and Medicinal Chemistry
- Institute of Pharmacy
- University of Greifswald
- 17487 Greifswald
- Germany
| | - Werner Siegmund
- Center of Drug Absorption and Transport (C_DAT) Greifswald
- Germany
| | - Patrick J. Bednarski
- Pharmaceutical and Medicinal Chemistry
- Institute of Pharmacy
- University of Greifswald
- 17487 Greifswald
- Germany
| | - Andreas Link
- Pharmaceutical and Medicinal Chemistry
- Institute of Pharmacy
- University of Greifswald
- 17487 Greifswald
- Germany
| |
Collapse
|
12
|
Du X, Gao H, Jaffe D, Zhang H, Gamper N. M-type K + channels in peripheral nociceptive pathways. Br J Pharmacol 2018; 175:2158-2172. [PMID: 28800673 PMCID: PMC5980636 DOI: 10.1111/bph.13978] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 07/17/2017] [Accepted: 08/03/2017] [Indexed: 12/22/2022] Open
Abstract
Pathological pain is a hyperexcitability disorder. Since the excitability of a neuron is set and controlled by a complement of ion channels it expresses, in order to understand and treat pain, we need to develop a mechanistic insight into the key ion channels controlling excitability within the mammalian pain pathways and how these ion channels are regulated and modulated in various physiological and pathophysiological settings. In this review, we will discuss the emerging data on the expression in pain pathways, functional role and modulation of a family of voltage-gated K+ channels called 'M channels' (KCNQ, Kv 7). M channels are increasingly recognized as important players in controlling pain signalling, especially within the peripheral somatosensory system. We will also discuss the therapeutic potential of M channels as analgesic drug targets. LINKED ARTICLES This article is part of a themed section on Recent Advances in Targeting Ion Channels to Treat Chronic Pain. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.12/issuetoc/.
Collapse
Affiliation(s)
- Xiaona Du
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of EducationHebei Medical UniversityShijiazhuangChina
- The Key Laboratory of New Drug Pharmacology and ToxicologyShijiazhuangHebei ProvinceChina
| | - Haixia Gao
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of EducationHebei Medical UniversityShijiazhuangChina
- The Key Laboratory of New Drug Pharmacology and ToxicologyShijiazhuangHebei ProvinceChina
- School of Biomedical Sciences, Faculty of Biological SciencesUniversity of LeedsLeedsUK
| | - David Jaffe
- Department of Biology, UTSA Neurosciences InstituteUniversity of Texas at San AntonioSan AntonioTXUSA
| | - Hailin Zhang
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of EducationHebei Medical UniversityShijiazhuangChina
- The Key Laboratory of New Drug Pharmacology and ToxicologyShijiazhuangHebei ProvinceChina
| | - Nikita Gamper
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of EducationHebei Medical UniversityShijiazhuangChina
- The Key Laboratory of New Drug Pharmacology and ToxicologyShijiazhuangHebei ProvinceChina
- School of Biomedical Sciences, Faculty of Biological SciencesUniversity of LeedsLeedsUK
| |
Collapse
|
13
|
Ling J, Erol F, Gu JG. Role of KCNQ2 channels in orofacial cold sensitivity: KCNQ2 upregulation in trigeminal ganglion neurons after infraorbital nerve chronic constrictive injury. Neurosci Lett 2018; 664:84-90. [PMID: 29133175 PMCID: PMC5817018 DOI: 10.1016/j.neulet.2017.11.026] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Revised: 11/08/2017] [Accepted: 11/09/2017] [Indexed: 11/17/2022]
Abstract
Sensitivity to cooling temperatures often becomes heightened in orofacial regions leading to orofacial cold allodynia/hyperalgesia after chronic trigeminal nerve injury. KCNQ2 channels are involved in controlling excitability of primary afferent neurons and thereby regulate sensory functions under both physiological and pathological conditions. In the present study, we sought to determine whether KCNQ2 channels in trigeminal nerves are involved in regulating orofacial operant behavioral responses to cooling stimulation. We also sought to examine whether chronic trigeminal nerve injury may alter KCNQ2 channel expression in trigeminal ganglions. Using the orofacial operant tests, animals show cold allodynia/hyperalgesia in orofacial regions following infraorbital nerve chronic constrictive injury (ION-CCI), which could be alleviated by subcutaneous administration of retigabine, a KCNQ2 activator. In contrast, subcutaneous administration of the KCNQ2 inhibitor XE991 directly elicits cold allodynia/hyperalgesia in sham animals. Using immunostaining, we show that KCNQ2 channels are primarily expressed in small-sized TG neurons. Interestingly, KCNQ2 channel expression becomes significantly upregulated in TG neurons following the ION-CCI. Our results suggest that KCNQ2 channels are involved in regulating orofacial cold sensitivity. Upregulation of KCNQ2 channels may be a compensatory change in attempting to limit injury-induced trigeminal hyperexcitability.
Collapse
Affiliation(s)
- Jennifer Ling
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, United States
| | - Ferhat Erol
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, United States
| | - Jianguo G Gu
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, United States.
| |
Collapse
|
14
|
Barkai O, Goldstein RH, Caspi Y, Katz B, Lev S, Binshtok AM. The Role of Kv7/M Potassium Channels in Controlling Ectopic Firing in Nociceptors. Front Mol Neurosci 2017; 10:181. [PMID: 28659757 PMCID: PMC5468463 DOI: 10.3389/fnmol.2017.00181] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Accepted: 05/24/2017] [Indexed: 11/13/2022] Open
Abstract
Peripheral nociceptive neurons encode and convey injury-inducing stimuli toward the central nervous system. In normal conditions, tight control of nociceptive resting potential prevents their spontaneous activation. However, in many pathological conditions the control of membrane potential is disrupted, leading to ectopic, stimulus-unrelated firing of nociceptive neurons, which is correlated to spontaneous pain. We have investigated the role of KV7/M channels in stabilizing membrane potential and impeding spontaneous firing of nociceptive neurons. These channels generate low voltage-activating, noninactivating M-type K+ currents (M-current, IM ), which control neuronal excitability. Using perforated-patch recordings from cultured, rat nociceptor-like dorsal root ganglion neurons, we show that inhibition of M-current leads to depolarization of nociceptive neurons and generation of repetitive firing. To assess to what extent the M-current, acting at the nociceptive terminals, is able to stabilize terminals' membrane potential, thus preventing their ectopic activation, in normal and pathological conditions, we built a multi-compartment computational model of a pseudo-unipolar unmyelinated nociceptive neuron with a realistic terminal tree. The modeled terminal tree was based on the in vivo structure of nociceptive peripheral terminal, which we assessed by in vivo multiphoton imaging of GFP-expressing nociceptive neuronal terminals innervating mice hind paw. By modifying the conductance of the KV7/M channels at the modeled terminal tree (terminal gKV7/M) we have found that 40% of the terminal gKV7/M conductance is sufficient to prevent spontaneous firing, while ~75% of terminal gKV7/M is sufficient to inhibit stimulus induced activation of nociceptive neurons. Moreover, we showed that terminal M-current reduces susceptibility of nociceptive neurons to a small fluctuations of membrane potentials. Furthermore, we simulated how the interaction between terminal persistent sodium current and M-current affects the excitability of the neurons. We demonstrated that terminal M-current in nociceptive neurons impeded spontaneous firing even when terminal Na(V)1.9 channels conductance was substantially increased. On the other hand, when terminal gKV7/M was decreased, nociceptive neurons fire spontaneously after slight increase in terminal Na(V)1.9 conductance. Our results emphasize the pivotal role of M-current in stabilizing membrane potential and hereby in controlling nociceptive spontaneous firing, in normal and pathological conditions.
Collapse
Affiliation(s)
- Omer Barkai
- Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, Hadassah School of Medicine, The Hebrew University-Hadassah School of MedicineJerusalem, Israel.,The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of JerusalemJerusalem, Israel
| | - Robert H Goldstein
- Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, Hadassah School of Medicine, The Hebrew University-Hadassah School of MedicineJerusalem, Israel.,The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of JerusalemJerusalem, Israel
| | - Yaki Caspi
- Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, Hadassah School of Medicine, The Hebrew University-Hadassah School of MedicineJerusalem, Israel.,The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of JerusalemJerusalem, Israel
| | - Ben Katz
- Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, Hadassah School of Medicine, The Hebrew University-Hadassah School of MedicineJerusalem, Israel.,The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of JerusalemJerusalem, Israel
| | - Shaya Lev
- Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, Hadassah School of Medicine, The Hebrew University-Hadassah School of MedicineJerusalem, Israel.,The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of JerusalemJerusalem, Israel
| | - Alexander M Binshtok
- Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, Hadassah School of Medicine, The Hebrew University-Hadassah School of MedicineJerusalem, Israel.,The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of JerusalemJerusalem, Israel
| |
Collapse
|
15
|
Bernal L, Lopez-Garcia JA, Roza C. Spontaneous activity in C-fibres after partial damage to the saphenous nerve in mice: Effects of retigabine. Eur J Pain 2016; 20:1335-45. [PMID: 27061852 DOI: 10.1002/ejp.858] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/17/2015] [Indexed: 12/13/2022]
Abstract
BACKGROUND Spontaneous pain is the most devastating positive symptom in neuropathic pain patients. Recent data show a direct relationship between spontaneous discharges in C-fibres and spontaneous pain in neuropathic patients. Unfortunately, to date there is a lack of experimental animal models for drug testing. METHODS We recorded afferent fibres from a new experimental model in vitro. The preparation contains a neuroma formed in a peripheral branch of the saphenous nerve together with the undamaged branches, which maintain intact terminals in a skin flap. RESULTS Fibres with stable rates of ectopic spontaneous discharges were found among axotomized (5 A- and 18 C-fibres, mean discharge 0.48 ± 0.08 Hz) and 'putative intact' fibres (12 C-fibres, mean discharge 0.28 ± 0.08 Hz). A proportion (~9%) of axotomized fibres had mechanical receptive fields in the skin far beyond the site of injury. Collision experiments demonstrated that action potentials evoked from neuroma and skin travelled by the same fibre, indicating functional cross-talk between neuromatose and putative intact fibres. Retigabine, the specific Kv7 channel opener, depressed spontaneous discharges by 70% in 15/18 units tested. In contrast, responses to mechanical stimulation of the skin were unaltered by retigabine. CONCLUSIONS Partial damage to a peripheral nerve may increase the incidence of spontaneous activity in C-fibres. Retigabine reduced spontaneous activity but not stimulus-evoked activity, suggesting an important role for ion channels in the control of spontaneous pain and demonstrating the utility of the model for the testing of compounds in clinically relevant variables. WHAT DOES THIS STUDY ADD?: Our in vitro experimental model of peripheral neuropathy allows for pharmacological characterization of spontaneously active fibres. Using this model, we show that retigabine inhibits aberrant spontaneous discharges without altering physiological responses in primary afferents.
Collapse
Affiliation(s)
- L Bernal
- Dpto. Biología de Sistemas, Edificio de Medicina Universidad de Alcalá, Alcalá de Henares, Madrid, Spain
| | - J A Lopez-Garcia
- Dpto. Biología de Sistemas, Edificio de Medicina Universidad de Alcalá, Alcalá de Henares, Madrid, Spain
| | - C Roza
- Dpto. Biología de Sistemas, Edificio de Medicina Universidad de Alcalá, Alcalá de Henares, Madrid, Spain
| |
Collapse
|