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Hyndman TH, Fretwell S, Bowden RS, Coaicetto F, Irons PC, Aleri JW, Kordzakhia N, Page SW, Musk GC, Tuke SJ, Mosing M, Metcalfe SS. The effect of doxapram on survival and APGAR score in newborn puppies delivered by elective caesarean: A randomized controlled trial. J Vet Pharmacol Ther 2023; 46:353-364. [PMID: 37211671 DOI: 10.1111/jvp.13388] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 04/12/2023] [Accepted: 04/30/2023] [Indexed: 05/23/2023]
Abstract
Doxapram is marketed as a respiratory stimulant and is used by some veterinarians to help with neonatal apnoea, especially in puppies delivered by caesarean. There is a lack of consensus as to whether the drug is effective and data on its safety are limited. Doxapram was compared to placebo (saline) in newborn puppies in a randomized, double-blinded clinical trial using two outcome measures: 7-day mortality rate and repeated APGAR score measurements. Higher APGAR scores have been positively correlated with survival and other health outcomes in newborns. Puppies were delivered by caesarean and a baseline APGAR score was measured. This was immediately followed by a randomly allocated intralingual injection of either doxapram or isotonic saline (of the same volume). Injection volumes were determined by the weight of the puppy and each injection was administered within a minute of birth. The mean dose of doxapram administered was 10.65 mg/kg. APGAR scores were measured again at 2, 5, 10 and 20 min. One hundred and seventy-one puppies from 45 elective caesareans were recruited into this study. Five out of 85 puppies died after receiving saline and 7 out of 86 died after receiving doxapram. Adjusting for the baseline APGAR score, the age of the mother and whether the puppy was a brachycephalic breed, there was insufficient evidence to conclude a difference in the odds of 7-day survival for puppies that received doxapram compared to those that received saline (p = .634). Adjusting for the baseline APGAR score, the weight of the mother, the litter size, the mother's parity number, the weight of the puppy and whether the puppy was a brachycephalic breed, there was insufficient evidence to conclude a difference in the probability of a puppy having an APGAR score of ten (the maximum APGAR score) between those that received doxapram compared to those that received saline (p = .631). Being a brachycephalic breed was not associated with an increased odds of 7-day mortality (p = .156) but the effect of the baseline APGAR score on the probability of having an APGAR score of ten was higher for brachycephalic than non-brachycephalic breeds (p = .01). There was insufficient evidence that intralingual doxapram provided an advantage (or disadvantage) compared to intralingual saline when used routinely in puppies delivered by elective caesarean and that were not apnoeic.
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Affiliation(s)
- Timothy H Hyndman
- School of Veterinary Medicine, Murdoch University, Murdoch, Western Australia, Australia
- Harry Butler Institute, Murdoch University, Murdoch, Western Australia, Australia
| | - Shelby Fretwell
- School of Veterinary Medicine, Murdoch University, Murdoch, Western Australia, Australia
- Applecross Veterinary Hospital, Applecross, Western Australia, Australia
| | - Ross S Bowden
- Mathematics and Statistics, Murdoch University, Murdoch, Western Australia, Australia
| | - Flaminia Coaicetto
- School of Veterinary Medicine, Murdoch University, Murdoch, Western Australia, Australia
| | - Peter C Irons
- School of Veterinary Medicine, Murdoch University, Murdoch, Western Australia, Australia
| | - Joshua W Aleri
- School of Veterinary Medicine, Murdoch University, Murdoch, Western Australia, Australia
- Harry Butler Institute, Murdoch University, Murdoch, Western Australia, Australia
| | - Nino Kordzakhia
- School of Mathematical and Physical Sciences, Macquarie University, Macquarie Park, New South Wales, Australia
| | - Stephen W Page
- Advanced Veterinary Therapeutics, Newtown, New South Wales, Australia
| | - Gabrielle C Musk
- School of Veterinary Medicine, Murdoch University, Murdoch, Western Australia, Australia
| | - S Jonathan Tuke
- Mathematics and Statistics, The University of Adelaide, Adelaide, South Australia, Australia
| | - Martina Mosing
- School of Veterinary Medicine, Murdoch University, Murdoch, Western Australia, Australia
| | - Steven S Metcalfe
- Applecross Veterinary Hospital, Applecross, Western Australia, Australia
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2
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Kim D, Hogan JO, White C. TASK inhibition by mild acidosis increases Ca 2+ oscillations to mediate pH sensing in rat carotid body chemoreceptor cells. Am J Physiol Lung Cell Mol Physiol 2023; 324:L259-L270. [PMID: 36692168 PMCID: PMC9970648 DOI: 10.1152/ajplung.00099.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 11/10/2022] [Accepted: 01/14/2023] [Indexed: 01/25/2023] Open
Abstract
Severe levels of acidosis (pH < 6.8) have been shown to cause a sustained rise in cytosolic Ca2+ concentration in carotid body Type 1 (glomus) cells. To understand how physiologically relevant levels of acidosis regulate Ca2+ signaling in glomus cells, we studied the effects of small changes in extracellular pH (pHo) on the kinetics of Ca2+ oscillations. A decrease in pHo from 7.4 to 7.3 (designated mild) and 7.2 (designated moderate) acidosis produced significant increases in the frequency and amplitude of Ca2+ oscillations. These effects of acidosis on Ca2+ oscillations were not blocked by NS383 and amiloride [acid-sensing ion channel (ASIC) inhibitors]. Mild and moderate levels of acidosis, however, caused a small but significant inhibition of two-pore domain acid-sensing K+ channels (TASK) (TASK-1- and TASK-3-like channels) and depolarized the cell by 6-13 mV. Acidosis-induced increase in Ca2+ oscillations was inhibited by nifedipine (1 µM; L-type Cav inhibitor) and by TTA-P2 (20 µM; T-type Cav inhibitor). Mild inhibition of TASK activity by N-[(2,4-difluorophenyl)methyl]-2'-[[[2-(4methoxyphenyl)acetyl]amino]methyl][1,1'-biphenyl]-2-carboxamide (A1899) (0.3 µM) and 1-[1-[6-[[1,1'-biphenyl]-4-ylcarbonyl)-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine-4-yl]-4-piperidinyl]-1-butanon (PK-THPP) (0.1 µM) increased Ca2+ oscillation frequency to levels similar to those observed with mild-moderate acidosis. Mild acidosis (pHo 7.3) and mild hypoxia (∼5%O2) produced similar levels of changes in the kinetics of Ca2+ oscillations. Block of tetraethylammonium (TEA)-sensitive Kv channels did not affect acid-induced increase in Ca2+ oscillations. Our study shows that mild and moderate levels of acidosis increase the frequency and amplitude of Ca2+ oscillations primarily by inhibition of TASK without involving ASICs, and suggests a major role of TASK for signal transduction in response to a physiological change in pHo.
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Affiliation(s)
- Donghee Kim
- Department of Physiology and Biophysics, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, United States
| | - James O Hogan
- Department of Physiology and Biophysics, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, United States
| | - Carl White
- Department of Physiology and Biophysics, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, United States
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3
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Cooper RL, Krall RM. Hyperpolarization Induced by Lipopolysaccharides but Not by Chloroform Is Inhibited by Doxapram, an Inhibitor of Two-P-Domain K + Channel (K2P). Int J Mol Sci 2022; 23:ijms232415787. [PMID: 36555429 PMCID: PMC9779748 DOI: 10.3390/ijms232415787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 11/20/2022] [Accepted: 11/24/2022] [Indexed: 12/15/2022] Open
Abstract
Bacterial septicemia is commonly induced by Gram-negative bacteria. The immune response is triggered in part by the secretion of bacterial endotoxin lipopolysaccharide (LPS). LPS induces the subsequent release of inflammatory cytokines which can result in pathological conditions. There is no known blocker to the receptors of LPS. The Drosophila larval muscle is an amendable model to rapidly screen various compounds that affect membrane potential and synaptic transmission such as LPS. LPS induces a rapid hyperpolarization in the body wall muscles and depolarization of motor neurons. These actions are blocked by the compound doxapram (10 mM), which is known to inhibit a subtype of the two-P-domain K+ channel (K2P channels). However, the K2P channel blocker PK-THPP had no effect on the Drosophila larval muscle at 1 and 10 mM. These channels are activated by chloroform, which also induces a rapid hyperpolarization of these muscles, but the channels are not blocked by doxapram. Likewise, chloroform does not block the depolarization induced by doxapram. LPS blocks the postsynaptic glutamate receptors on Drosophila muscle. Pre-exposure to doxapram reduces the LPS block of these ionotropic glutamate receptors. Given that the larval Drosophila body wall muscles are depolarized by doxapram and hyperpolarized by chloroform, they offer a model to begin pharmacological profiling of the K2P subtype channels with the potential of identifying blockers for the receptors to mitigate the actions of the Gram-negative endotoxin LPS.
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Affiliation(s)
- Robin L. Cooper
- Department of Biology, University of Kentucky, Lexington, KY 40506-0225, USA
- Correspondence:
| | - Rebecca M. Krall
- Department of STEM Education, University of Kentucky, Lexington, KY 40506-0001, USA
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Holmes AP, Swiderska A, Nathanael D, Aldossary HS, Ray CJ, Coney AM, Kumar P. Are Multiple Mitochondrial Related Signalling Pathways Involved in Carotid Body Oxygen Sensing? Front Physiol 2022; 13:908617. [PMID: 35711317 PMCID: PMC9194093 DOI: 10.3389/fphys.2022.908617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 05/09/2022] [Indexed: 11/13/2022] Open
Abstract
It is generally acknowledged that the carotid body (CB) type I cell mitochondria are unique, being inhibited by relatively small falls in PaO2 well above those known to inhibit electron transport in other cell types. This feature is suggested to allow for the CB to function as an acute O2 sensor, being stimulated and activating systemic protective reflexes before the metabolism of other cells becomes compromised. What is less clear is precisely how a fall in mitochondrial activity links to type I cell depolarisation, a process that is required for initiation of the chemotransduction cascade and post-synaptic action potential generation. Multiple mitochondrial/metabolic signalling mechanisms have been proposed including local generation of mitochondrial reactive oxygen species (mitoROS), a change in mitochondrial/cellular redox status, a fall in MgATP and an increase in lactate. Although each mechanism is based on compelling experimental evidence, they are all not without question. The current review aims to explore the importance of each of these signalling pathways in mediating the overall CB response to hypoxia. We suggest that there is unlikely to be a single mechanism, but instead multiple mitochondrial related signalling pathways are recruited at different PaO2s during hypoxia. Furthermore, it still remains to be determined if mitochondrial signalling acts independently or in partnership with extra-mitochondrial O2-sensors.
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Affiliation(s)
- Andrew P. Holmes
- School of Biomedical Sciences, Institute of Clinical Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Agnieszka Swiderska
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Demitris Nathanael
- School of Biomedical Sciences, Institute of Clinical Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Hayyaf S. Aldossary
- School of Biomedical Sciences, Institute of Clinical Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
- College of Medicine, Basic Medical Sciences, King Saud bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia
| | - Clare J. Ray
- School of Biomedical Sciences, Institute of Clinical Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Andrew M. Coney
- School of Biomedical Sciences, Institute of Clinical Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Prem Kumar
- School of Biomedical Sciences, Institute of Clinical Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
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Ochoa SV, Otero L, Aristizabal-Pachon AF, Hinostroza F, Carvacho I, Torres YP. Hypoxic Regulation of the Large-Conductance, Calcium and Voltage-Activated Potassium Channel, BK. Front Physiol 2022; 12:780206. [PMID: 35002762 PMCID: PMC8727448 DOI: 10.3389/fphys.2021.780206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 11/15/2021] [Indexed: 11/15/2022] Open
Abstract
Hypoxia is a condition characterized by a reduction of cellular oxygen levels derived from alterations in oxygen balance. Hypoxic events trigger changes in cell-signaling cascades, oxidative stress, activation of pro-inflammatory molecules, and growth factors, influencing the activity of various ion channel families and leading to diverse cardiovascular diseases such as myocardial infarction, ischemic stroke, and hypertension. The large-conductance, calcium and voltage-activated potassium channel (BK) has a central role in the mechanism of oxygen (O2) sensing and its activity has been related to the hypoxic response. BK channels are ubiquitously expressed, and they are composed by the pore-forming α subunit and the regulatory subunits β (β1–β4), γ (γ1–γ4), and LINGO1. The modification of biophysical properties of BK channels by β subunits underly a myriad of physiological function of these proteins. Hypoxia induces tissue-specific modifications of BK channel α and β subunits expression. Moreover, hypoxia modifies channel activation kinetics and voltage and/or calcium dependence. The reported effects on the BK channel properties are associated with events such as the increase of reactive oxygen species (ROS) production, increases of intracellular Calcium ([Ca2+]i), the regulation by Hypoxia-inducible factor 1α (HIF-1α), and the interaction with hemeproteins. Bronchial asthma, chronic obstructive pulmonary diseases (COPD), and obstructive sleep apnea (OSA), among others, can provoke hypoxia. Untreated OSA patients showed a decrease in BK-β1 subunit mRNA levels and high arterial tension. Treatment with continuous positive airway pressure (CPAP) upregulated β1 subunit mRNA level, decreased arterial pressures, and improved endothelial function coupled with a reduction in morbidity and mortality associated with OSA. These reports suggest that the BK channel has a role in the response involved in hypoxia-associated hypertension derived from OSA. Thus, this review aims to describe the mechanisms involved in the BK channel activation after a hypoxic stimulus and their relationship with disorders like OSA. A deep understanding of the molecular mechanism involved in hypoxic response may help in the therapeutic approaches to treat the pathological processes associated with diseases involving cellular hypoxia.
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Affiliation(s)
- Sara V Ochoa
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, Colombia.,Semillero de Investigación, Biofísica y Fisiología de Canales Iónicos, Pontificia Universidad Javeriana, Bogotá, Colombia
| | - Liliana Otero
- Center of Dental Research Dentistry Faculty, Pontificia Universidad Javeriana, Bogotá, Colombia
| | | | - Fernando Hinostroza
- Department of Biology and Chemistry, Faculty of Basic Sciences, Universidad Católica del Maule, Talca, Chile.,Centro de Investigación de Estudios Avanzados del Maule, CIEAM, Vicerrectoría de Investigación y Postgrado, Universidad Católica del Maule, Talca, Chile.,Facultad de Ciencias de la Salud, Centro de Investigación en Neuropsicología y Neurociencias Cognitivas, Universidad Católica del Maule, Talca, Chile
| | - Ingrid Carvacho
- Department of Biology and Chemistry, Faculty of Basic Sciences, Universidad Católica del Maule, Talca, Chile
| | - Yolima P Torres
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, Colombia.,Semillero de Investigación, Biofísica y Fisiología de Canales Iónicos, Pontificia Universidad Javeriana, Bogotá, Colombia
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6
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OUP accepted manuscript. Cardiovasc Res 2022; 118:1613-1614. [DOI: 10.1093/cvr/cvac044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 03/14/2022] [Indexed: 11/14/2022] Open
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7
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Wiedmann F, Beyersdorf C, Zhou XB, Kraft M, Paasche A, Jávorszky N, Rinné S, Sutanto H, Büscher A, Foerster KI, Blank A, El-Battrawy I, Li X, Lang S, Tochtermann U, Kremer J, Arif R, Karck M, Decher N, van Loon G, Akin I, Borggrefe M, Kallenberger S, Heijman J, Haefeli WE, Katus HA, Schmidt C. Treatment of atrial fibrillation with doxapram: TASK-1 potassium channel inhibition as a novel pharmacological strategy. Cardiovasc Res 2021; 118:1728-1741. [PMID: 34028533 DOI: 10.1093/cvr/cvab177] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2020] [Indexed: 12/20/2022] Open
Abstract
AIMS TASK-1 (K2P3.1) two-pore domain potassium channels are atrial-specific and significantly upregulated in atrial fibrillation (AF) patients, contributing to AF-related electrical remodelling. Inhibition of TASK-1 in cardiomyocytes of AF patients was shown to counteract AF-related action potential duration shortening. Doxapram was identified as a potent inhibitor of the TASK-1 channel. In the present study, we investigated the antiarrhythmic efficacy of doxapram in a porcine model of AF. METHODS AND RESULTS Doxapram successfully cardioverted pigs with artificially induced episodes of AF. We established a porcine model of persistent AF in domestic pigs via intermittent atrial burst stimulation using implanted pacemakers. All pigs underwent catheter-based electrophysiological investigations prior to and after 14 d of doxapram treatment. Pigs in the treatment group received intravenous administration of doxapram once per day. In doxapram-treated AF pigs, the AF burden was significantly reduced. After 14 d of treatment with doxapram, TASK-1 currents were still similar to values of sinus rhythm animals. Doxapram significantly suppressed AF episodes and normalized cellular electrophysiology by inhibition of the TASK-1 channel. Patch-clamp experiments on human atrial cardiomyocytes, isolated from patients with and without AF could reproduce the TASK-1 inhibitory effect of doxapram. CONCLUSIONS Repurposing doxapram might yield a promising new antiarrhythmic drug to treat AF in patients. TRANSLATIONAL PERSPECTIVE Pharmacological suppression of atrial TASK 1 potassium currents prolongs atrial refractoriness with no effects on ventricular repolarization, resulting in atrial-specific class III antiarrhythmic effects. In our preclinical pilot study the respiratory stimulant doxapram was successfully administered for cardioversion of acute AF as well as rhythm control of persistent AF in a clinically relevant porcine animal model.
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Affiliation(s)
- Felix Wiedmann
- Department of Cardiology, University of Heidelberg, Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany.,HCR, Heidelberg Center for Heart Rhythm Disorders, University of Heidelberg, Heidelberg, Germany
| | - Christoph Beyersdorf
- Department of Cardiology, University of Heidelberg, Heidelberg, Germany.,HCR, Heidelberg Center for Heart Rhythm Disorders, University of Heidelberg, Heidelberg, Germany
| | - Xiao-Bo Zhou
- DZHK (German Center for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany.,First Department of Medicine, University Medical Center Mannheim, Mannheim, Germany
| | - Manuel Kraft
- Department of Cardiology, University of Heidelberg, Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany.,HCR, Heidelberg Center for Heart Rhythm Disorders, University of Heidelberg, Heidelberg, Germany
| | - Amelie Paasche
- Department of Cardiology, University of Heidelberg, Heidelberg, Germany.,HCR, Heidelberg Center for Heart Rhythm Disorders, University of Heidelberg, Heidelberg, Germany
| | - Natasa Jávorszky
- Department of Cardiology, University of Heidelberg, Heidelberg, Germany.,HCR, Heidelberg Center for Heart Rhythm Disorders, University of Heidelberg, Heidelberg, Germany
| | - Susanne Rinné
- Institute for Physiology and Pathophysiology, Vegetative Physiology and Marburg Center for Mind, Brain and Behavior MCMBB, University of Marburg, Marburg, Germany
| | - Henry Sutanto
- Cardiovascular Research Institute Maastricht, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Antonius Büscher
- Department of Cardiology, University of Heidelberg, Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany.,HCR, Heidelberg Center for Heart Rhythm Disorders, University of Heidelberg, Heidelberg, Germany
| | - Kathrin I Foerster
- Department of Clinical Pharmacology and Pharmacoepidemiology, University Hospital Heidelberg, Heidelberg, Germany
| | - Antje Blank
- Department of Clinical Pharmacology and Pharmacoepidemiology, University Hospital Heidelberg, Heidelberg, Germany
| | - Ibrahim El-Battrawy
- DZHK (German Center for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany.,First Department of Medicine, University Medical Center Mannheim, Mannheim, Germany
| | - Xin Li
- First Department of Medicine, University Medical Center Mannheim, Mannheim, Germany
| | - Siegfried Lang
- DZHK (German Center for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany.,First Department of Medicine, University Medical Center Mannheim, Mannheim, Germany
| | - Ursula Tochtermann
- Department of Cardiac Surgery, University Hospital Heidelberg, Heidelberg, Germany
| | - Jamila Kremer
- Department of Cardiac Surgery, University Hospital Heidelberg, Heidelberg, Germany
| | - Rawa Arif
- Department of Cardiac Surgery, University Hospital Heidelberg, Heidelberg, Germany
| | - Matthias Karck
- Department of Cardiac Surgery, University Hospital Heidelberg, Heidelberg, Germany
| | - Niels Decher
- Institute for Physiology and Pathophysiology, Vegetative Physiology and Marburg Center for Mind, Brain and Behavior MCMBB, University of Marburg, Marburg, Germany
| | - Gunther van Loon
- Department of Large Animal Internal Medicine, Equine Cardioteam, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium
| | - Ibrahim Akin
- DZHK (German Center for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany.,First Department of Medicine, University Medical Center Mannheim, Mannheim, Germany
| | - Martin Borggrefe
- DZHK (German Center for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany.,First Department of Medicine, University Medical Center Mannheim, Mannheim, Germany
| | - Stefan Kallenberger
- Digital Health Center, Berlin Institute of Health (BIH) and Charité, Berlin, Germany and Health Data Science Unit, University Hospital Heidelberg, Heidelberg, Germany
| | - Jordi Heijman
- Cardiovascular Research Institute Maastricht, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Walter E Haefeli
- Department of Clinical Pharmacology and Pharmacoepidemiology, University Hospital Heidelberg, Heidelberg, Germany
| | - Hugo A Katus
- Department of Cardiology, University of Heidelberg, Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany.,HCR, Heidelberg Center for Heart Rhythm Disorders, University of Heidelberg, Heidelberg, Germany
| | - Constanze Schmidt
- Department of Cardiology, University of Heidelberg, Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany.,HCR, Heidelberg Center for Heart Rhythm Disorders, University of Heidelberg, Heidelberg, Germany
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The effects of doxapram on time to tracheal extubation and early recovery in young morbidly obese patients scheduled for bariatric surgery: A randomised controlled trial. Eur J Anaesthesiol 2021; 37:457-465. [PMID: 31842026 DOI: 10.1097/eja.0000000000001144] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
BACKGROUND Bariatric surgery is a well established treatment of the obese. Postoperative respiratory failure and airway obstruction after bariatric surgery can often be attributed to the residual depressant effects of anaesthetics, sedatives and opioids. Peri-operative management of morbidly obese patients is still a concern for operating room professionals. OBJECTIVE The evaluation of the effects of doxapram on the outcomes of general anaesthesia following bariatric surgical procedures in the morbidly obese. DESIGN A single-blind randomised controlled trial with two parallel arms. SETTING A tertiary care teaching hospital, Tehran, Iran, from 2017 to 2018. PARTICIPANTS In total, 100 patients (69 women) with at least class two obesity were included in two groups of equal sizes and underwent bariatric surgery. MAIN OUTCOME MEASURES The primary outcome was the time from the administration of doxapram to tracheal extubation. Secondary outcomes included vital signs and variables including peak expiratory flow rate, time to return to spontaneous breathing, time to eye-opening and hand-squeezing on the commands, and time to recovery. INTERVENTIONS Both groups underwent general anaesthesia. The intervention group received a single dose of doxapram 1 mg kg ideal body weight, immediately after reversal of neuromuscular blockade and after discontinuation of all anaesthetics. RESULTS Doxapram decreased time to extubation, time to eye-opening and hand-squeezing, shortened recovery time and lowered end-tidal CO2 significantly (all P < 0.001). Moreover, it increased peak expiratory flow rate, oxygen saturation, temperature, heart rate and blood pressure (all P < 0.001). The two groups were similar in the bispectral index and mean arterial pressure (both P > 0.05). None of our participants had complications attributable to doxapram. CONCLUSION The postoperative use of doxapram improves peak expiratory flow rate, and decreases respiratory complications of anaesthesia during recovery in the morbidly obese undergoing bariatric surgery. Doxapram is well tolerated in young ASA physical status classes 1 to 2 morbidly obese patients; however, the anaesthesiologist should cautiously evaluate the vital signs for at least half an hour following the administration of doxapram. REGISTRATION Iranian Registry of Clinical Trials (IRCT) http://www.irct.ir/ number IRCT2017060712203N9.
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9
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Kraft M, Büscher A, Wiedmann F, L’hoste Y, Haefeli WE, Frey N, Katus HA, Schmidt C. Current Drug Treatment Strategies for Atrial Fibrillation and TASK-1 Inhibition as an Emerging Novel Therapy Option. Front Pharmacol 2021; 12:638445. [PMID: 33897427 PMCID: PMC8058608 DOI: 10.3389/fphar.2021.638445] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Accepted: 01/21/2021] [Indexed: 12/19/2022] Open
Abstract
Atrial fibrillation (AF) is the most common sustained arrhythmia with a prevalence of up to 4% and an upwards trend due to demographic changes. It is associated with an increase in mortality and stroke incidences. While stroke risk can be significantly reduced through anticoagulant therapy, adequate treatment of other AF related symptoms remains an unmet medical need in many cases. Two main treatment strategies are available: rate control that modulates ventricular heart rate and prevents tachymyopathy as well as rhythm control that aims to restore and sustain sinus rhythm. Rate control can be achieved through drugs or ablation of the atrioventricular node, rendering the patient pacemaker-dependent. For rhythm control electrical cardioversion and pharmacological cardioversion can be used. While electrical cardioversion requires fasting and sedation of the patient, antiarrhythmic drugs have other limitations. Most antiarrhythmic drugs carry a risk for pro-arrhythmic effects and are contraindicated in patients with structural heart diseases. Furthermore, catheter ablation of pulmonary veins can be performed with its risk of intraprocedural complications and varying success. In recent years TASK-1 has been introduced as a new target for AF therapy. Upregulation of TASK-1 in AF patients contributes to prolongation of the action potential duration. In a porcine model of AF, TASK-1 inhibition by gene therapy or pharmacological compounds induced cardioversion to sinus rhythm. The DOxapram Conversion TO Sinus rhythm (DOCTOS)-Trial will reveal whether doxapram, a potent TASK-1 inhibitor, can be used for acute cardioversion of persistent and paroxysmal AF in patients, potentially leading to a new treatment option for AF.
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Affiliation(s)
- Manuel Kraft
- Department of Cardiology, University of Heidelberg, Heidelberg, Germany
- DZHK (German Center for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
- HCR, Heidelberg Center for Heart Rhythm Disorders, University of Heidelberg, Heidelberg, Germany
| | - Antonius Büscher
- Clinic for Cardiology II: Electrophysiology, University Hospital Münster, Münster, Germany
| | - Felix Wiedmann
- Department of Cardiology, University of Heidelberg, Heidelberg, Germany
- DZHK (German Center for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
- HCR, Heidelberg Center for Heart Rhythm Disorders, University of Heidelberg, Heidelberg, Germany
| | - Yannick L’hoste
- Department of Cardiology, University of Heidelberg, Heidelberg, Germany
- HCR, Heidelberg Center for Heart Rhythm Disorders, University of Heidelberg, Heidelberg, Germany
| | - Walter E. Haefeli
- Department of Clinical Pharmacology and Pharmacoepidemiology, University of Heidelberg, Heidelberg, Germany
| | - Norbert Frey
- Department of Cardiology, University of Heidelberg, Heidelberg, Germany
- DZHK (German Center for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
- HCR, Heidelberg Center for Heart Rhythm Disorders, University of Heidelberg, Heidelberg, Germany
| | - Hugo A. Katus
- Department of Cardiology, University of Heidelberg, Heidelberg, Germany
- DZHK (German Center for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
- HCR, Heidelberg Center for Heart Rhythm Disorders, University of Heidelberg, Heidelberg, Germany
| | - Constanze Schmidt
- Department of Cardiology, University of Heidelberg, Heidelberg, Germany
- DZHK (German Center for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany
- HCR, Heidelberg Center for Heart Rhythm Disorders, University of Heidelberg, Heidelberg, Germany
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10
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Wiedmann F, Beyersdorf C, Zhou XB, Kraft M, Foerster KI, El-Battrawy I, Lang S, Borggrefe M, Haefeli WE, Frey N, Schmidt C. The Experimental TASK-1 Potassium Channel Inhibitor A293 Can Be Employed for Rhythm Control of Persistent Atrial Fibrillation in a Translational Large Animal Model. Front Physiol 2021; 11:629421. [PMID: 33551849 PMCID: PMC7858671 DOI: 10.3389/fphys.2020.629421] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Accepted: 12/30/2020] [Indexed: 12/19/2022] Open
Abstract
Background Upregulation of the two-pore-domain potassium channel TASK-1 (hK2P3.1) was recently described in patients suffering from atrial fibrillation (AF) and resulted in shortening of the atrial action potential. In the human heart, TASK-1 channels facilitate repolarization and are specifically expressed in the atria. In the present study, we tested the antiarrhythmic effects of the experimental ion channel inhibitor A293 that is highly affine for TASK-1 in a porcine large animal model of persistent AF. Methods Persistent AF was induced in German landrace pigs by right atrial burst stimulation via implanted pacemakers using a biofeedback algorithm over 14 days. Electrophysiological and echocardiographic investigations were performed before and after the pharmacological treatment period. A293 was intravenously administered once per day. After a treatment period of 14 days, atrial cardiomyocytes were isolated for patch clamp measurements of currents and atrial action potentials. Hemodynamic consequences of TASK-1 inhibition were measured upon acute A293 treatment. Results In animals with persistent AF, the A293 treatment significantly reduced the AF burden (6.5% vs. 95%; P < 0.001). Intracardiac electrophysiological investigations showed that the atrial effective refractory period was prolonged in A293 treated study animals, whereas, the QRS width, QT interval, and ventricular effective refractory periods remained unchanged. A293 treatment reduced the upregulation of the TASK-1 current as well as the shortening of the action potential duration caused by AF. No central nervous side effects were observed. A mild but significant increase in pulmonary artery pressure was observed upon acute TASK-1 inhibition. Conclusion Pharmacological inhibition of atrial TASK-1 currents exerts in vivo antiarrhythmic effects that can be employed for rhythm control in a porcine model of persistent AF. Care has to be taken as TASK-1 inhibition may increase pulmonary artery pressure levels.
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Affiliation(s)
- Felix Wiedmann
- Department of Cardiology, Heidelberg University, Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg University, Heidelberg, Germany.,HCR, Heidelberg Center for Heart Rhythm Disorders, Heidelberg University, Heidelberg, Germany
| | - Christoph Beyersdorf
- Department of Cardiology, Heidelberg University, Heidelberg, Germany.,HCR, Heidelberg Center for Heart Rhythm Disorders, Heidelberg University, Heidelberg, Germany
| | - Xiao-Bo Zhou
- DZHK (German Center for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg University, Heidelberg, Germany.,First Department of Medicine, University Medical Center, Mannheim University, Mannheim, Germany
| | - Manuel Kraft
- Department of Cardiology, Heidelberg University, Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg University, Heidelberg, Germany.,HCR, Heidelberg Center for Heart Rhythm Disorders, Heidelberg University, Heidelberg, Germany
| | - Kathrin I Foerster
- Department of Clinical Pharmacology and Pharmacoepidemiology, Heidelberg University, Heidelberg, Germany
| | - Ibrahim El-Battrawy
- DZHK (German Center for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg University, Heidelberg, Germany.,First Department of Medicine, University Medical Center, Mannheim University, Mannheim, Germany
| | - Siegfried Lang
- DZHK (German Center for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg University, Heidelberg, Germany.,First Department of Medicine, University Medical Center, Mannheim University, Mannheim, Germany
| | - Martin Borggrefe
- DZHK (German Center for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg University, Heidelberg, Germany.,First Department of Medicine, University Medical Center, Mannheim University, Mannheim, Germany
| | - Walter E Haefeli
- Department of Clinical Pharmacology and Pharmacoepidemiology, Heidelberg University, Heidelberg, Germany
| | - Norbert Frey
- Department of Cardiology, Heidelberg University, Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg University, Heidelberg, Germany.,HCR, Heidelberg Center for Heart Rhythm Disorders, Heidelberg University, Heidelberg, Germany
| | - Constanze Schmidt
- Department of Cardiology, Heidelberg University, Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Heidelberg/Mannheim, Heidelberg University, Heidelberg, Germany.,HCR, Heidelberg Center for Heart Rhythm Disorders, Heidelberg University, Heidelberg, Germany
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11
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Competitive Interactions between Halothane and Isoflurane at the Carotid Body and TASK Channels. Anesthesiology 2020; 133:1046-1059. [DOI: 10.1097/aln.0000000000003520] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Background
The degree to which different volatile anesthetics depress carotid body hypoxic response relates to their ability to activate TASK potassium channels. Most commonly, volatile anesthetic pairs act additively at their molecular targets. We examined whether this applied to carotid body TASK channels.
Methods
We studied halothane and isoflurane effects on hypoxia-evoked rise in intracellular calcium (Ca2+i, using the indicator Indo-1) in isolated neonatal rat glomus cells, and TASK single-channel activity (patch clamping) in native glomus cells and HEK293 cell line cells transiently expressing TASK-1.
Results
Halothane (5%) depressed glomus cell Ca2+i hypoxic response (mean ± SD, 94 ± 4% depression; P < 0.001 vs. control). Isoflurane (5%) had a less pronounced effect (53 ± 10% depression; P < 0.001 vs. halothane). A mix of 3% isoflurane/1.5% halothane depressed cell Ca2+i response (51 ± 17% depression) to a lesser degree than 1.5% halothane alone (79 ± 15%; P = 0.001), but similar to 3% isoflurane alone (44 ± 22%; P = 0.224), indicating subadditivity. Halothane and isoflurane increased glomus cell TASK-1/TASK-3 activity, but mixes had a lesser effect than that seen with halothane alone: 4% halothane/4% isoflurane yielded channel open probabilities 127 ± 55% above control, versus 226 ± 12% for 4% halothane alone (P = 0.009). Finally, in HEK293 cell line cells, progressively adding isoflurane (1.5 to 5%) to halothane (2.5%) reduced TASK-1 channel activity from 120 ± 38% above control, to 88 ± 48% (P = 0.034).
Conclusions
In all three experimental models, the effects of isoflurane and halothane combinations were quantitatively consistent with the modeling of weak and strong agonists competing at a common receptor on the TASK channel.
Editor’s Perspective
What We Already Know about This Topic
What This Article Tells Us That Is New
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12
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Mathie A, Veale EL, Cunningham KP, Holden RG, Wright PD. Two-Pore Domain Potassium Channels as Drug Targets: Anesthesia and Beyond. Annu Rev Pharmacol Toxicol 2020; 61:401-420. [PMID: 32679007 DOI: 10.1146/annurev-pharmtox-030920-111536] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Two-pore domain potassium (K2P) channels stabilize the resting membrane potential of both excitable and nonexcitable cells and, as such, are important regulators of cell activity. There are many conditions where pharmacological regulation of K2P channel activity would be of therapeutic benefit, including, but not limited to, atrial fibrillation, respiratory depression, pulmonary hypertension, neuropathic pain, migraine, depression, and some forms of cancer. Up until now, few if any selective pharmacological regulators of K2P channels have been available. However, recent publications of solved structures with small-molecule activators and inhibitors bound to TREK-1, TREK-2, and TASK-1 K2P channels have given insight into the pharmacophore requirements for compound binding to these sites. Together with the increasing availability of a number of novel, active, small-molecule compounds from K2P channel screening programs, these advances have opened up the possibility of rational activator and inhibitor design to selectively target K2P channels.
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Affiliation(s)
- Alistair Mathie
- Medway School of Pharmacy, University of Greenwich and University of Kent, Kent ME4 4TB, United Kingdom;
| | - Emma L Veale
- Medway School of Pharmacy, University of Greenwich and University of Kent, Kent ME4 4TB, United Kingdom;
| | - Kevin P Cunningham
- Wolfson Centre for Age-Related Diseases, King's College London, London SE1 1UL, United Kingdom
| | - Robyn G Holden
- Medway School of Pharmacy, University of Greenwich and University of Kent, Kent ME4 4TB, United Kingdom;
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Imam MZ, Kuo A, Smith MT. Countering opioid-induced respiratory depression by non-opioids that are respiratory stimulants. F1000Res 2020; 9. [PMID: 32089833 PMCID: PMC7008602 DOI: 10.12688/f1000research.21738.1] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 02/03/2020] [Indexed: 12/13/2022] Open
Abstract
Strong opioid analgesics are the mainstay of therapy for the relief of moderate to severe acute nociceptive pain that may occur post-operatively or following major trauma, as well as for the management of chronic cancer-related pain. Opioid-related adverse effects include nausea and vomiting, sedation, respiratory depression, constipation, tolerance, and addiction/abuse liability. Of these, respiratory depression is of the most concern to clinicians owing to the potential for fatal consequences. In the broader community, opioid overdose due to either prescription or illicit opioids or co-administration with central nervous system depressants may evoke respiratory depression. To address this problem, there is ongoing interest in the identification of non-opioid respiratory stimulants to reverse opioid-induced respiratory depression but without reversing opioid analgesia. Promising compound classes evaluated to date include those that act on a diverse array of receptors including 5-hydroxytryptamine, D
1-dopamine, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), N-methyl-D-aspartate (NMDA) receptor antagonists, and nicotinic acetylcholine as well as phosphodiesterase inhibitors and molecules that act on potassium channels on oxygen-sensing cells in the carotid body. The aim of this article is to review recent advances in the development potential of these compounds for countering opioid-induced respiratory depression.
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Affiliation(s)
- Mohammad Zafar Imam
- School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia
| | - Andy Kuo
- School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia
| | - Maree T Smith
- School of Biomedical Sciences, Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia
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14
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Cunningham KP, MacIntyre DE, Mathie A, Veale EL. Effects of the ventilatory stimulant, doxapram on human TASK-3 (KCNK9, K2P9.1) channels and TASK-1 (KCNK3, K2P3.1) channels. Acta Physiol (Oxf) 2020; 228:e13361. [PMID: 31423744 PMCID: PMC7003846 DOI: 10.1111/apha.13361] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 08/14/2019] [Accepted: 08/15/2019] [Indexed: 01/16/2023]
Abstract
AIMS The mode of action by which doxapram acts as a respiratory stimulant in humans is controversial. Studies in rodent models, have shown that doxapram is a more potent and selective inhibitor of TASK-1 and TASK-1/TASK-3 heterodimer channels, than TASK-3. Here we investigate the direct effect of doxapram and chirally separated, individual positive and negative enantiomers of the compound, on both human and mouse, homodimeric and heterodimeric variants of TASK-1 and TASK-3. METHODS Whole-cell patch clamp electrophysiology on tsA201 cells was used to assess the potency of doxapram on cloned human or mouse TASK-1, TASK-3 and TASK-2 channels. Mutations of amino acids in the pore-lining region of TASK-3 channels were introduced using site-directed mutagenesis. RESULTS Doxapram was an equipotent inhibitor of human TASK-1 and TASK-3 channels, compared with mouse channel variants, where it was more selective for TASK-1 and heterodimers of TASK-1 and TASK-3. The effect of doxapram could be attenuated by either the removal of the C-terminus of human TASK-3 channels or mutations of particular hydrophobic residues in the pore-lining region. These mutations, however, did not alter the effect of a known extracellular inhibitor of TASK-3, zinc. The positive enantiomer of doxapram, GAL-054, was a more potent antagonist of TASK channels, than doxapram, whereas the negative enantiomer, GAL-053, had little inhibitory effect. CONCLUSION These data show that in contrast to rodent channels, doxapram is a potent inhibitor of both TASK-1 and TASK-3 human channels, providing further understanding of the pharmacological profile of doxapram in humans and informing the development of new therapeutic agents.
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Affiliation(s)
- Kevin P. Cunningham
- Medway School of PharmacyUniversity of Greenwich and University of KentChatham MaritimeUK
| | - D. Euan MacIntyre
- Department of Drug DiscoveryGalleon Pharmaceuticals, IncHorshamPennsylvania
| | - Alistair Mathie
- Medway School of PharmacyUniversity of Greenwich and University of KentChatham MaritimeUK
| | - Emma L. Veale
- Medway School of PharmacyUniversity of Greenwich and University of KentChatham MaritimeUK
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15
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Reversing Neuromuscular Blockade: Not Just the Diaphragm, but Carotid Body Function Too. Anesthesiology 2019; 131:453-455. [DOI: 10.1097/aln.0000000000002814] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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16
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Raju M, Pandit JJ. Re-awakening the carotid bodies after anaesthesia: managing hypnotic and neuromuscular blocking agents. Anaesthesia 2019; 75:301-304. [PMID: 31421004 DOI: 10.1111/anae.14789] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/29/2019] [Indexed: 12/11/2022]
Affiliation(s)
- M Raju
- Nuffield Department of Anaesthesia, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - J J Pandit
- Nuffield Department of Anaesthesia, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
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17
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O'Donohoe PB, Turner PJ, Huskens N, Buckler KJ, Pandit JJ. Influence of propofol on isolated neonatal rat carotid body glomus cell response to hypoxia and hypercapnia. Respir Physiol Neurobiol 2018; 260:17-27. [PMID: 30389452 PMCID: PMC6336315 DOI: 10.1016/j.resp.2018.10.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Revised: 10/14/2018] [Accepted: 10/29/2018] [Indexed: 11/06/2022]
Abstract
The intravenous anaesthetic propofol acts directly on carotid body glomus cells to inhibit their response to hypoxia. Propofol acts via novel mechanisms, as we excluded action via its known target receptors (nicotinic, GABA-ergic, or K+ channel). Inhibition of the hypoxic response is clinically relevant in anaesthesia.
In humans the intravenous anaesthetic propofol depresses ventilatory responses to hypoxia and CO2. Animal studies suggest that this may in part be due to inhibition of synaptic transmission between chemoreceptor glomus cells of the carotid body and the afferent carotid sinus nerve. It is however unknown if propofol can also act directly on the glomus cell. Here we report that propofol can indeed inhibit intracellular Ca2+ responses to hypoxia and hypercapnia in isolated rat glomus cells. Neither this propofol effect, nor the glomus cell response to hypoxia in the absence of propofol, were influenced by GABA receptor activation (using GABA, muscimol and baclofen) or inhibition (using bicuculline and 5-aminovaleric acid). Suggesting that these effects of propofol are not mediated through GABA receptors. Propofol inhibited calcium responses to nicotine in glomus cells but the nicotinic antagonists vecuronium and methyllycaconitine did not inhibit calcium responses to hypoxia. TASK channel activity was not altered by propofol. The glomus cell Ca2+ response to depolarisation with 30 mM K+ was however modestly inhibited by propofol. In summary we conclude that propofol does have a direct effect upon hypoxia signalling in isolated type-1 cells and that this may be partially due to its ability to inhibit voltage gated Ca2+v channels. We also note that propofol has the capacity to supress glomus cell excitation via nicotinic receptors and may therefore also interfere with paracrine/autocrine cholinergic signalling in the intact organ. The effects of propofol on chemoreceptor function are however clearly complex and require further investigation.
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Affiliation(s)
- Peadar B O'Donohoe
- Department of Physiology, Anatomy & Genetics, Parks Road, University of Oxford, Oxford, OX1 3PT, UK; Nuffield Department of Anaesthetics, Oxford University Hospitals NHS Trust, Oxford, OX3 9DU, UK
| | - Philip J Turner
- Department of Physiology, Anatomy & Genetics, Parks Road, University of Oxford, Oxford, OX1 3PT, UK
| | - Nicky Huskens
- Department of Physiology, Anatomy & Genetics, Parks Road, University of Oxford, Oxford, OX1 3PT, UK
| | - Keith J Buckler
- Department of Physiology, Anatomy & Genetics, Parks Road, University of Oxford, Oxford, OX1 3PT, UK
| | - Jaideep J Pandit
- Nuffield Department of Anaesthetics, Oxford University Hospitals NHS Trust, Oxford, OX3 9DU, UK.
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