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Wurm KW, Bartz FM, Schulig L, Bodtke A, Bednarski PJ, Link A. Replacing the oxidation-sensitive triaminoaryl chemotype of problematic K V 7 channel openers: Exploration of a nicotinamide scaffold. Arch Pharm (Weinheim) 2023; 356:e2200473. [PMID: 36395379 DOI: 10.1002/ardp.202200473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 10/13/2022] [Accepted: 10/18/2022] [Indexed: 11/18/2022]
Abstract
KV 7 channel openers have proven their therapeutic value in the treatment of pain as well as epilepsy and, moreover, they hold the potential to expand into additional indications with unmet medical needs. However, the clinically validated but meanwhile discontinued KV 7 channel openers flupirtine and retigabine bear an oxidation-sensitive triaminoraryl scaffold, which is suspected of causing adverse drug reactions via the formation of quinoid oxidation products. Here, we report the design and synthesis of nicotinamide analogs and related compounds that remediate the liability in the chemical structure of flupirtine and retigabine. Optimization of a nicotinamide lead structure yielded analogs with excellent KV 7.2/3 opening activity, as evidenced by EC50 values approaching the single-digit nanomolar range. On the other hand, weighted KV 7.2/3 opening activity data including inactive compounds allowed for the establishment of structure-activity relationships and a plausible binding mode hypothesis verified by docking and molecular dynamics simulations.
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Affiliation(s)
- Konrad W Wurm
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmacy, University of Greifswald, Greifswald, Germany
| | - Frieda-Marie Bartz
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmacy, University of Greifswald, Greifswald, Germany
| | - Lukas Schulig
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmacy, University of Greifswald, Greifswald, Germany
| | - Anja Bodtke
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmacy, University of Greifswald, Greifswald, Germany
| | - Patrick J Bednarski
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmacy, University of Greifswald, Greifswald, Germany
| | - Andreas Link
- Department of Pharmaceutical/Medicinal Chemistry, Institute of Pharmacy, University of Greifswald, Greifswald, Germany
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Wurm KW, Bartz FM, Schulig L, Bodtke A, Bednarski PJ, Link A. Carba Analogues of Flupirtine and Retigabine with Improved Oxidation Resistance and Reduced Risk of Quinoid Metabolite Formation. ChemMedChem 2022; 17:e202200262. [PMID: 35687532 PMCID: PMC9541272 DOI: 10.1002/cmdc.202200262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 06/07/2022] [Indexed: 01/10/2023]
Abstract
The KV7 potassium channel openers flupirtine and retigabine have been valuable options in the therapy of pain and epilepsy. However, as a result of adverse reactions, both drugs are currently no longer in therapeutic use. The flupirtine‐induced liver injury and the retigabine linked tissue discolouration do not appear related at first glance; nevertheless, both events can be attributed to the triaminoaryl scaffold, which is affected by oxidation leading to elusive reactive quinone diimine or azaquinone diimine metabolites. Since the mechanism of action, i. e. KV7 channel opening, seems not to be involved in toxicity, this study aimed to further develop safer replacements for flupirtine and retigabine. In a ligand‐based design strategy, replacing amino substituents of the triaminoaryl core with alkyl substituents led to carba analogues with improved oxidation resistance and negligible risk of quinoid metabolite formation. In addition to these improved safety features, some of the novel analogues exhibited significantly improved KV7.2/3 channel opening activity, indicated by an up to 13‐fold increase in potency and an efficacy of up to 176 % compared to flupirtine, thus being attractive candidates for further development.
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Affiliation(s)
- Konrad W Wurm
- University of Greifswald: Universitat Greifswald, Institute of Pharmacy, GERMANY
| | - Frieda-Marie Bartz
- University of Greifswald: Universitat Greifswald, Institute of Pharmacy, GERMANY
| | - Lukas Schulig
- University of Greifswald: Universitat Greifswald, Institute of Pharmacy, GERMANY
| | - Anja Bodtke
- University of Greifswald: Universitat Greifswald, Institute of Pharmacy, GERMANY
| | - Patrick J Bednarski
- University of Greifswald: Universitat Greifswald, Institute of Pharmacy, GERMANY
| | - Andreas Link
- University of Greifswald, Institute of Pharmacy, F.-L.-Jahn-Str. 17, 17487, Greifswald, GERMANY
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Ramakrishna Y, Manca M, Glowatzki E, Sadeghi SG. Cholinergic Modulation of Membrane Properties of Calyx Terminals in the Vestibular Periphery. Neuroscience 2020; 452:98-110. [PMID: 33197502 DOI: 10.1016/j.neuroscience.2020.10.035] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 10/27/2020] [Accepted: 10/28/2020] [Indexed: 01/10/2023]
Abstract
Vestibular nerve afferents are divided into regular and irregular groups based on the variability of interspike intervals in their resting discharge. Most afferents receive inputs from bouton terminals that contact type II hair cells as well as from calyx terminals that cover the basolateral walls of type I hair cells. Calyces have an abundance of different subtypes of KCNQ (Kv7) potassium channels and muscarinic acetylcholine receptors (mAChRs) and receive cholinergic efferent inputs from neurons in the brainstem. We investigated whether mAChRs affected membrane properties and firing patterns of calyx terminals through modulation of KCNQ channel activity. Patch clamp recordings were performed from calyx terminals in central regions of the cristae of the horizontal and anterior canals in 13-26 day old Sprague-Dawley rats. KCNQ mediated currents were observed as voltage sensitive currents with slow kinetics (activation and deactivation), resulting in spike frequency adaptation so that calyces at best fired a single action potential at the beginning of a depolarizing step. Activation of mAChRs by application of oxotremorine methiodide or inhibition of KCNQ channels by linopirdine dihydrochloride decreased voltage activated currents by ∼30%, decreased first spike latencies by ∼40%, resulted in action potential generation in response to smaller current injections and at lower (i.e., more hyperpolarized) membrane potentials, and increased the number of spikes fired during depolarizing steps. Interestingly, some of the calyces showed spontaneous discharge in the presence of these drugs. Together, these findings suggest that cholinergic efferents can modulate the response properties and encoding of head movements by afferents.
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Affiliation(s)
- Yugandhar Ramakrishna
- Center for Hearing and Deafness, Department of Communicative Disorders and Sciences, State University of New York at Buffalo, Buffalo, NY, United States; Department of Communication Disorders and Sciences, California State University, Northridge, CA, United States
| | - Marco Manca
- Department of Otolaryngology - Head and Neck Surgery, The Center for Hearing and Balance, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Elisabeth Glowatzki
- Department of Otolaryngology - Head and Neck Surgery, The Center for Hearing and Balance, Johns Hopkins University School of Medicine, Baltimore, MD, United States; Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Soroush G Sadeghi
- Center for Hearing and Deafness, Department of Communicative Disorders and Sciences, State University of New York at Buffalo, Buffalo, NY, United States; Neuroscience Program, State University of New York at Buffalo, Buffalo, NY, United States.
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Evans AM. On a Magical Mystery Tour with 8-Bromo-Cyclic ADP-Ribose: From All-or-None Block to Nanojunctions and the Cell-Wide Web. Molecules 2020; 25:E4768. [PMID: 33081414 PMCID: PMC7587525 DOI: 10.3390/molecules25204768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 09/08/2020] [Indexed: 11/16/2022] Open
Abstract
A plethora of cellular functions are controlled by calcium signals, that are greatly coordinated by calcium release from intracellular stores, the principal component of which is the sarco/endooplasmic reticulum (S/ER). In 1997 it was generally accepted that activation of various G protein-coupled receptors facilitated inositol-1,4,5-trisphosphate (IP3) production, activation of IP3 receptors and thus calcium release from S/ER. Adding to this, it was evident that S/ER resident ryanodine receptors (RyRs) could support two opposing cellular functions by delivering either highly localised calcium signals, such as calcium sparks, or by carrying propagating, global calcium waves. Coincidentally, it was reported that RyRs in mammalian cardiac myocytes might be regulated by a novel calcium mobilising messenger, cyclic adenosine diphosphate-ribose (cADPR), that had recently been discovered by HC Lee in sea urchin eggs. A reputedly selective and competitive cADPR antagonist, 8-bromo-cADPR, had been developed and was made available to us. We used 8-bromo-cADPR to further explore our observation that S/ER calcium release via RyRs could mediate two opposing functions, namely pulmonary artery dilation and constriction, in a manner seemingly independent of IP3Rs or calcium influx pathways. Importantly, the work of others had shown that, unlike skeletal and cardiac muscles, smooth muscles might express all three RyR subtypes. If this were the case in our experimental system and cADPR played a role, then 8-bromo-cADPR would surely block one of the opposing RyR-dependent functions identified, or the other, but certainly not both. The latter seemingly implausible scenario was confirmed. How could this be, do cells hold multiple, segregated SR stores that incorporate different RyR subtypes in receipt of spatially segregated signals carried by cADPR? The pharmacological profile of 8-bromo-cADPR action supported not only this, but also indicated that intracellular calcium signals were delivered across intracellular junctions formed by the S/ER. Not just one, at least two. This article retraces the steps along this journey, from the curious pharmacological profile of 8-bromo-cADPR to the discovery of the cell-wide web, a diverse network of cytoplasmic nanocourses demarcated by S/ER nanojunctions, which direct site-specific calcium flux and may thus coordinate the full panoply of cellular processes.
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Grants
- 01/A/S/07453 Biotechnology and Biological Sciences Research Council
- WT046374 , WT056423, WT070772, WT074434, WT081195AIA, WT212923, WT093147 Wellcome Trust
- PG/10/95/28657 British Heart Foundation
- FS/03/033/15432, FS/05/050, PG/05/128/19884, RG/12/14/29885, PG/10/95/28657 British Heart Foundation
- RG/12/14/29885 British Heart Foundation
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Affiliation(s)
- A Mark Evans
- Centre for Discovery Brain Sciences and Cardiovascular Science, Edinburgh Medical School, Hugh Robson Building, University of Edinburgh, Edinburgh EH8 9XD, UK
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Abstract
Voltage-gated potassium channels of the KV7 family are expressed in many tissues. The physiological importance of KV7 channels is evident from specific forms of disorders linked to dysfunctional KV7 channels, including variants of epilepsy, cardiac arrhythmia and hearing impairment. Thus, understanding how KV7 channels are regulated in the body is of great interest. This Mini Review focuses on the effects of polyunsaturated fatty acids (PUFAs) on KV7 channel activity and possible underlying mechanisms of action. By summarizing reported effects of PUFAs on KV7 channels and native KV7-mediated currents, we conclude that the generally observed effect is a PUFA-induced increase in current amplitude. The increase in current is commonly associated with a shift in the voltage-dependence of channel opening and in some cases with increased maximum conductance. Auxiliary KCNE subunits, which associate with KV7 channels in certain tissues, may influence PUFA effects, though findings are conflicting. Both direct and indirect activating PUFA effects have been described, direct effects having been most extensively studied on KV7.1. The negative charge of the PUFA head-group has been identified as critical for electrostatic interaction with conserved positively charged amino acids in transmembrane segments 4 and 6. Additionally, the localization of double bonds in the PUFA tail tunes the apparent affinity of PUFAs to KV7.1. Indirect effects include those mediated by PUFA metabolites. Indirect inhibitory effects involve KV7 channel degradation and re-distribution from lipid rafts. Understanding how PUFAs regulate KV7 channels may provide insight into physiological regulation of KV7 channels and bring forth new therapeutic strategies.
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Affiliation(s)
- Johan E Larsson
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Damon J A Frampton
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Sara I Liin
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
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Bock C, Surur AS, Beirow K, Kindermann MK, Schulig L, Bodtke A, Bednarski PJ, Link A. Sulfide Analogues of Flupirtine and Retigabine with Nanomolar K V 7.2/K V 7.3 Channel Opening Activity. ChemMedChem 2019; 14:952-964. [PMID: 30861620 DOI: 10.1002/cmdc.201900112] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Indexed: 12/18/2022]
Abstract
The potassium channel openers flupirtine and retigabine have proven to be valuable analgesics or antiepileptics. Their recent withdrawal due to occasional hepatotoxicity and tissue discoloration, respectively, leaves a therapeutic niche unfilled. Metabolic oxidation of both drugs gives rise to the formation of electrophilic quinones. These elusive, highly reactive metabolites may induce liver injury in the case of flupirtine and blue tissue discoloration after prolonged intake of retigabine. We examined which structural features can be altered to avoid the detrimental oxidation of the aromatic ring and shift oxidation toward the formation of more benign metabolites. Structure-activity relationship studies were performed to evaluate the KV 7.2/3 channel opening activity of 45 derivatives. Sulfide analogues were identified that are devoid of the risk of quinone formation, but possess potent KV 7.2/3 opening activity. For example, flupirtine analogue 3-(3,5-difluorophenyl)-N-(6-(isobutylthio)-2-(pyrrolidin-1-yl)pyridin-3-yl)propanamide (48) has 100-fold enhanced activity (EC50 =1.4 nm), a vastly improved toxicity/activity ratio, and the same efficacy as retigabine in vitro.
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Affiliation(s)
- Christian Bock
- Institute of Pharmacy, University of Greifswald, Friedrich-Ludwig-Jahn-Str. 17, 17489, Greifswald, Germany
| | - Abdrrahman S Surur
- Institute of Pharmacy, University of Greifswald, Friedrich-Ludwig-Jahn-Str. 17, 17489, Greifswald, Germany
| | - Kristin Beirow
- Institute of Pharmacy, University of Greifswald, Friedrich-Ludwig-Jahn-Str. 17, 17489, Greifswald, Germany
| | - Markus K Kindermann
- Institute of Pharmacy, University of Greifswald, Friedrich-Ludwig-Jahn-Str. 17, 17489, Greifswald, Germany
| | - Lukas Schulig
- Institute of Pharmacy, University of Greifswald, Friedrich-Ludwig-Jahn-Str. 17, 17489, Greifswald, Germany
| | - Anja Bodtke
- Institute of Pharmacy, University of Greifswald, Friedrich-Ludwig-Jahn-Str. 17, 17489, Greifswald, Germany
| | - Patrick J Bednarski
- Institute of Pharmacy, University of Greifswald, Friedrich-Ludwig-Jahn-Str. 17, 17489, Greifswald, Germany
| | - Andreas Link
- Institute of Pharmacy, University of Greifswald, Friedrich-Ludwig-Jahn-Str. 17, 17489, Greifswald, Germany
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7
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Du C, Li J, Shao Z, Mwangi J, Xu R, Tian H, Mo G, Lai R, Yang S. Centipede KCNQ Inhibitor SsTx Also Targets K V1.3. Toxins (Basel) 2019; 11:toxins11020076. [PMID: 30717088 PMCID: PMC6409716 DOI: 10.3390/toxins11020076] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Revised: 01/25/2019] [Accepted: 01/27/2019] [Indexed: 12/19/2022] Open
Abstract
It was recently discovered that Ssm Spooky Toxin (SsTx) with 53 residues serves as a key killer factor in red-headed centipede’s venom arsenal, due to its potent blockage of the widely expressed KCNQ channels to simultaneously and efficiently disrupt cardiovascular, respiratory, muscular, and nervous systems, suggesting that SsTx is a basic compound for centipedes’ defense and predation. Here, we show that SsTx also inhibits KV1.3 channel, which would amplify the broad-spectrum disruptive effect of blocking KV7 channels. Interestingly, residue R12 in SsTx extends into the selectivity filter to block KV7.4, however, residue K11 in SsTx replaces this ploy when toxin binds on KV1.3. Both SsTx and its mutant SsTx_R12A inhibit cytokines production in T cells without affecting the level of KV1.3 expression. The results further suggest that SsTx is a key molecule for defense and predation in the centipedes’ venoms and it evolves efficient strategy to disturb multiple physiological targets.
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Affiliation(s)
- Canwei Du
- College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China.
| | - Jiameng Li
- College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China.
| | - Zicheng Shao
- College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China.
| | - James Mwangi
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences/Yunnan Province, Kunming Institute of Zoology, Kunming 650223, Yunnan, China.
- University of Chinese Academy of Sciences, Beijing 100009, China.
| | - Runjia Xu
- College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China.
| | - Huiwen Tian
- College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China.
| | - Guoxiang Mo
- College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China.
| | - Ren Lai
- College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China.
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences/Yunnan Province, Kunming Institute of Zoology, Kunming 650223, Yunnan, China.
- Sino-African Joint Research Center, Chinese Academy of Science, Wuhan 430074, Hubei, China.
| | - Shilong Yang
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences/Yunnan Province, Kunming Institute of Zoology, Kunming 650223, Yunnan, China.
- Sino-African Joint Research Center, Chinese Academy of Science, Wuhan 430074, Hubei, China.
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Tiwari MN, Mohan S, Biala Y, Yaari Y. Differential contributions of Ca 2+ -activated K + channels and Na + /K + -ATPases to the generation of the slow afterhyperpolarization in CA1 pyramidal cells. Hippocampus 2018; 28:338-357. [PMID: 29431274 PMCID: PMC5947627 DOI: 10.1002/hipo.22836] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Revised: 12/17/2017] [Accepted: 02/05/2018] [Indexed: 12/13/2022]
Abstract
In many types of CNS neurons, repetitive spiking produces a slow afterhyperpolarization (sAHP), providing sustained, intrinsically generated negative feedback to neuronal excitation. Changes in the sAHP have been implicated in learning behaviors, in cognitive decline in aging, and in epileptogenesis. Despite its importance in brain function, the mechanisms generating the sAHP are still controversial. Here we have addressed the roles of M-type K+ current (IM ), Ca2+ -gated K+ currents (ICa(K) 's) and Na+ /K+ -ATPases (NKAs) current to sAHP generation in adult rat CA1 pyramidal cells maintained at near-physiological temperature (35 °C). No evidence for IM contribution to the sAHP was found in these neurons. Both ICa(K) 's and NKA current contributed to sAHP generation, the latter being the predominant generator of the sAHP, particularly when evoked with short trains of spikes. Of the different NKA isoenzymes, α1 -NKA played the key role, endowing the sAHP a steep voltage-dependence. Thus normal and pathological changes in α1 -NKA expression or function may affect cognitive processes by modulating the inhibitory efficacy of the sAHP.
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Affiliation(s)
- Manindra Nath Tiwari
- Department of Medical Neurobiology; Institute for Medical Research Israel‐CanadaThe Hebrew University‐Hadassah School of MedicineJerusalem91120Israel
| | - Sandesh Mohan
- Department of Medical Neurobiology; Institute for Medical Research Israel‐CanadaThe Hebrew University‐Hadassah School of MedicineJerusalem91120Israel
| | - Yoav Biala
- Department of Medical Neurobiology; Institute for Medical Research Israel‐CanadaThe Hebrew University‐Hadassah School of MedicineJerusalem91120Israel
| | - Yoel Yaari
- Department of Medical Neurobiology; Institute for Medical Research Israel‐CanadaThe Hebrew University‐Hadassah School of MedicineJerusalem91120Israel
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9
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Peiris M, Hockley JR, Reed DE, Smith ESJ, Bulmer DC, Blackshaw LA. Peripheral K V7 channels regulate visceral sensory function in mouse and human colon. Mol Pain 2018; 13:1744806917709371. [PMID: 28566000 PMCID: PMC5456027 DOI: 10.1177/1744806917709371] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Background Chronic visceral pain is a defining symptom of many gastrointestinal disorders. The KV7 family (KV7.1–KV7.5) of voltage-gated potassium channels mediates the M current that regulates excitability in peripheral sensory nociceptors and central pain pathways. Here, we use a combination of immunohistochemistry, gut-nerve electrophysiological recordings in both mouse and human tissues, and single-cell qualitative real-time polymerase chain reaction of gut-projecting sensory neurons, to investigate the contribution of peripheral KV7 channels to visceral nociception. Results Immunohistochemical staining of mouse colon revealed labelling of KV7 subtypes (KV7.3 and KV7.5) with CGRP around intrinsic enteric neurons of the myenteric plexuses and within extrinsic sensory fibres along mesenteric blood vessels. Treatment with the KV7 opener retigabine almost completely abolished visceral afferent firing evoked by the algogen bradykinin, in agreement with significant co-expression of mRNA transcripts by single-cell qualitative real-time polymerase chain reaction for KCNQ subtypes and the B2 bradykinin receptor in retrogradely labelled extrinsic sensory neurons from the colon. Retigabine also attenuated responses to mechanical stimulation of the bowel following noxious distension (0–80 mmHg) in a concentration-dependent manner, whereas the KV7 blocker XE991 potentiated such responses. In human bowel tissues, KV7.3 and KV7.5 were expressed in neuronal varicosities co-labelled with synaptophysin and CGRP, and retigabine inhibited bradykinin-induced afferent activation in afferent recordings from human colon. Conclusions We show that KV7 channels contribute to the sensitivity of visceral sensory neurons to noxious chemical and mechanical stimuli in both mouse and human gut tissues. As such, peripherally restricted KV7 openers may represent a viable therapeutic modality for the treatment of gastrointestinal pathologies.
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Affiliation(s)
- Madusha Peiris
- 1 Centre for Neuroscience and Trauma, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - James Rf Hockley
- 2 Department of Pharmacology, University of Cambridge, Cambridge, UK
| | - David E Reed
- 3 GI Diseases Research Unit, Queen's University, Kingston, ON, Canada
| | | | - David C Bulmer
- 1 Centre for Neuroscience and Trauma, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - L Ashley Blackshaw
- 1 Centre for Neuroscience and Trauma, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
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10
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Lemmerhirt CJ, Rombach M, Bodtke A, Bednarski PJ, Link A. Oxidation potentials of N-modified derivatives of the analgesic flupirtine linked to potassium KV 7 channel opening activity but not hepatocyte toxicity. ChemMedChem 2014; 10:368-79. [PMID: 25392984 DOI: 10.1002/cmdc.201402442] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Indexed: 12/30/2022]
Abstract
Openers of neuronal voltage-gated potassium channels (KV ) are of interest as therapeutic agents for treating pain (flupirtine) and epilepsy (retigabine). In an effort to better understand the mechanisms of action and toxicity of flupirtine, we synthesized nine novel analogues with varying redox behavior. Flupirtine can be oxidatively metabolized into azaquinone diimines; thus, the oxidation potentials of flupirtine and its analogues were measured by cyclic voltammetry. KV 7.2/3 (KCNQ2/3) opening activity was determined by an established assay with HEK293 cells overexpressing these channels. A link was found between the oxidation potentials of the compounds and their EC50 values for potassium channel opening activity. On the other hand, no correlation was observed between oxidation potentials and cytotoxicity in cultures of transgenic mouse hepatocytes (TAMH). These results support the idea that oxidative metabolites of flupirtine contribute to the mechanism of action, similar to what was recently proposed for acetaminophen (paracetamol), but not to hepatotoxicity.
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Affiliation(s)
- Christian J Lemmerhirt
- Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy, Ernst Moritz Arndt University, Friedrich-Ludwig-Jahn-Str. 17, 17487 Greifswald (Germany)
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11
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Hedegaard ER, Nielsen BD, Kun A, Hughes AD, Krøigaard C, Mogensen S, Matchkov VV, Fröbert O, Simonsen U. KV 7 channels are involved in hypoxia-induced vasodilatation of porcine coronary arteries. Br J Pharmacol 2014; 171:69-82. [PMID: 24111896 DOI: 10.1111/bph.12424] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 07/08/2013] [Accepted: 09/04/2013] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND AND PURPOSE Hypoxia causes vasodilatation of coronary arteries, but the underlying mechanisms are poorly understood. We hypothesized that hypoxia reduces intracellular Ca(2+) concentration ([Ca(2+)](i)) by opening of K channels and release of H₂S. EXPERIMENTAL APPROACH Porcine coronary arteries without endothelium were mounted for measurement of isometric tension and [Ca(2+)](i), and the expression of voltage-gated K channels K(V)7 channels (encoded by KCNQ genes) and large-conductance calcium-activated K channels (K(Ca)1.1) was examined. Voltage clamp assessed the role of K(V)7 channels in hypoxia. KEY RESULTS Gradual reduction of oxygen concentration from 95 to 1% dilated the precontracted coronary arteries and this was associated with reduced [Ca(2+)](i) in PGF(2α) (10 μM)-contracted arteries whereas no fall in [Ca(2+)](i) was observed in 30 mM K-contracted arteries. Blockers of ATP-sensitive voltage-gated potassium channels and K(Ca)1.1 inhibited hypoxia-induced dilatation in PGF2α -contracted arteries; this inhibition was more marked in the presence of the K(v)7 channel blockers, XE991 and linopirdine, while a K(V)7.1 blocker, failed to change hypoxic vasodilatation. XE991 also inhibited H₂S- and adenosine-induced vasodilatation. PCR revealed the expression of K(V)7.1, K(V)7.4, K(V)7.5 and K(Ca)1.1 channels, and K(Ca)1.1, K(V)7.4 and K(V)7.5 were also identified by immunoblotting. Voltage clamp studies showed the XE991-sensitive current was more marked in hypoxic conditions. CONCLUSION The K(V)7.4 and K(V)7.5 channels, which we identified in the coronary arteries, appear to have a major role in hypoxia-induced vasodilatation. The voltage clamp results further support the involvement of K(V)7 channels in this vasodilatation. Activation of these K(V)7 channels may be induced by H₂S and adenosine.
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Affiliation(s)
- E R Hedegaard
- Department of Biomedicine, Pulmonary and Cardiovascular Pharmacology, University of Aarhus, Aarhus, Denmark
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