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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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2
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Abstract
The carotid body (CB) is a bilateral arterial chemoreceptor located in the carotid artery bifurcation with an essential role in cardiorespiratory homeostasis. It is composed of highly perfused cell clusters, or glomeruli, innervated by sensory fibers. Glomus cells, the most abundant in each glomerulus, are neuron-like multimodal sensory elements able to detect and integrate changes in several physical and chemical parameters of the blood, in particular O2 tension, CO2 and pH, as well as glucose, lactate, or blood flow. Activation of glomus cells (e.g., during hypoxia or hypercapnia) stimulates the afferent fibers which impinge on brainstem neurons to elicit rapid compensatory responses (hyperventilation and sympathetic activation). This chapter presents an updated view of the structural organization of the CB and the mechanisms underlying the chemosensory responses of glomus cells, with special emphasis on the molecular processes responsible for acute O2 sensing. The properties of the glomus cell-sensory fiber synapse as well as the organization of CB output are discussed. The chapter includes the description of recently discovered CB stem cells and progenitor cells, and their role in CB growth during acclimatization to hypoxemia. Finally, the participation of the CB in the mechanisms of disease is briefly discussed.
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Affiliation(s)
- José López-Barneo
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/Consejo Superior de Investigaciones Científicas (CSIC)/Universidad de Sevilla, Seville, Spain; Biomedical Research Center for Neurodegenerative Diseases (CIBERNED), Madrid, Spain.
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3
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Abstract
Oxygen (O2) is essential for life and therefore the supply of sufficient O2 to the tissues is a major physiological challenge. In mammals, a deficit of O2 (hypoxia) triggers rapid cardiorespiratory reflexes (e.g. hyperventilation and increased heart output) that within a few seconds increase the uptake of O2 by the lungs and its distribution throughout the body. The prototypical acute O2-sensing organ is the carotid body (CB), which contains sensory glomus cells expressing O2-regulated ion channels. In response to hypoxia, glomus cells depolarize and release transmitters which activate afferent fibers terminating at the brainstem respiratory and autonomic centers. In this review, we summarize the basic properties of CB chemoreceptor cells and the essential role played by their specialized mitochondria in acute O2 sensing and signaling. We focus on recent data supporting a "mitochondria-to-membrane signaling" model of CB chemosensory transduction. The possibility that the differential expression of specific subunit isoforms and enzymes could allow mitochondria to play a generalized adaptive O2-sensing and signaling role in a wide variety of cells is also discussed.
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Affiliation(s)
- José López-Barneo
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Patricia Ortega-Sáenz
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
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4
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Lactate sensing mechanisms in arterial chemoreceptor cells. Nat Commun 2021; 12:4166. [PMID: 34230483 PMCID: PMC8260783 DOI: 10.1038/s41467-021-24444-7] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 06/08/2021] [Indexed: 12/17/2022] Open
Abstract
Classically considered a by-product of anaerobic metabolism, lactate is now viewed as a fundamental fuel for oxidative phosphorylation in mitochondria, and preferred over glucose by many tissues. Lactate is also a signaling molecule of increasing medical relevance. Lactate levels in the blood can increase in both normal and pathophysiological conditions (e.g., hypoxia, physical exercise, or sepsis), however the manner by which these changes are sensed and induce adaptive responses is unknown. Here we show that the carotid body (CB) is essential for lactate homeostasis and that CB glomus cells, the main oxygen sensing arterial chemoreceptors, are also lactate sensors. Lactate is transported into glomus cells, leading to a rapid increase in the cytosolic NADH/NAD+ ratio. This in turn activates membrane cation channels, leading to cell depolarization, action potential firing, and Ca2+ influx. Lactate also decreases intracellular pH and increases mitochondrial reactive oxygen species production, which further activates glomus cells. Lactate and hypoxia, although sensed by separate mechanisms, share the same final signaling pathway and jointly activate glomus cells to potentiate compensatory cardiorespiratory reflexes. Lactate levels in blood change during hypoxia or exercise, however whether this variable is sensed to evoke adaptive responses is unknown. Here the authors show that oxygen-sensing carotid body cells stimulated by hypoxia are also activated by lactate to potentiate a compensatory ventilatory response.
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5
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Iturriaga R, Alcayaga J, Chapleau MW, Somers VK. Carotid body chemoreceptors: physiology, pathology, and implications for health and disease. Physiol Rev 2021; 101:1177-1235. [PMID: 33570461 PMCID: PMC8526340 DOI: 10.1152/physrev.00039.2019] [Citation(s) in RCA: 78] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The carotid body (CB) is the main peripheral chemoreceptor for arterial respiratory gases O2 and CO2 and pH, eliciting reflex ventilatory, cardiovascular, and humoral responses to maintain homeostasis. This review examines the fundamental biology underlying CB chemoreceptor function, its contribution to integrated physiological responses, and its role in maintaining health and potentiating disease. Emphasis is placed on 1) transduction mechanisms in chemoreceptor (type I) cells, highlighting the role played by the hypoxic inhibition of O2-dependent K+ channels and mitochondrial oxidative metabolism, and their modification by intracellular molecules and other ion channels; 2) synaptic mechanisms linking type I cells and petrosal nerve terminals, focusing on the role played by the main proposed transmitters and modulatory gases, and the participation of glial cells in regulation of the chemosensory process; 3) integrated reflex responses to CB activation, emphasizing that the responses differ dramatically depending on the nature of the physiological, pathological, or environmental challenges, and the interactions of the chemoreceptor reflex with other reflexes in optimizing oxygen delivery to the tissues; and 4) the contribution of enhanced CB chemosensory discharge to autonomic and cardiorespiratory pathophysiology in obstructive sleep apnea, congestive heart failure, resistant hypertension, and metabolic diseases and how modulation of enhanced CB reactivity in disease conditions may attenuate pathophysiology.
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Affiliation(s)
- Rodrigo Iturriaga
- Laboratorio de Neurobiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile, and Centro de Excelencia en Biomedicina de Magallanes, Universidad de Magallanes, Punta Arenas, Chile
| | - Julio Alcayaga
- Laboratorio de Fisiología Celular, Facultad de Ciencias, Universidad de Chile, Santiago, Chile
| | - Mark W Chapleau
- Department of Internal Medicine, University of Iowa and Department of Veterans Affairs Medical Center, Iowa City, Iowa
| | - Virend K Somers
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota
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6
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Ortega-Sáenz P, Moreno-Domínguez A, Gao L, López-Barneo J. Molecular Mechanisms of Acute Oxygen Sensing by Arterial Chemoreceptor Cells. Role of Hif2α. Front Physiol 2020; 11:614893. [PMID: 33329066 PMCID: PMC7719705 DOI: 10.3389/fphys.2020.614893] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Accepted: 11/03/2020] [Indexed: 01/28/2023] Open
Abstract
Carotid body glomus cells are multimodal arterial chemoreceptors able to sense and integrate changes in several physical and chemical parameters in the blood. These cells are also essential for O2 homeostasis. Glomus cells are prototypical peripheral O2 sensors necessary to detect hypoxemia and to elicit rapid compensatory responses (hyperventilation and sympathetic activation). The mechanisms underlying acute O2 sensing by glomus cells have been elusive. Using a combination of mouse genetics and single-cell optical and electrophysiological techniques, it has recently been shown that activation of glomus cells by hypoxia relies on the generation of mitochondrial signals (NADH and reactive oxygen species), which modulate membrane ion channels to induce depolarization, Ca2+ influx, and transmitter release. The special sensitivity of glomus cell mitochondria to changes in O2 tension is due to Hif2α-dependent expression of several atypical mitochondrial subunits, which are responsible for an accelerated oxidative metabolism and the strict dependence of mitochondrial complex IV activity on O2 availability. A mitochondrial-to-membrane signaling model of acute O2 sensing has been proposed, which explains existing data and provides a solid foundation for future experimental tests. This model has also unraveled new molecular targets for pharmacological modulation of carotid body activity potentially relevant in the treatment of highly prevalent medical conditions.
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Affiliation(s)
- Patricia Ortega-Sáenz
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Alejandro Moreno-Domínguez
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain
| | - Lin Gao
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - José López-Barneo
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
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7
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Kim D, Hogan JO, White C. Ca 2+ oscillations in rat carotid body type 1 cells in normoxia and hypoxia. Am J Physiol Cell Physiol 2020; 318:C430-C438. [PMID: 31913694 DOI: 10.1152/ajpcell.00442.2019] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We studied the mechanisms by which carotid body glomus (type 1) cells produce spontaneous Ca2+ oscillations in normoxia and hypoxia. In cells perfused with normoxic solution at 37°C, we observed relatively uniform, low-frequency Ca2+ oscillations in >60% of cells, with each cell showing its own intrinsic frequency and amplitude. The mean frequency and amplitude of Ca2+ oscillations were 0.6 ± 0.1 Hz and 180 ± 42 nM, respectively. The duration of each Ca2+ oscillation ranged from 14 to 26 s (mean of ∼20 s). Inhibition of inositol (1,4,5)-trisphosphate receptor and store-operated Ca2+ entry (SOCE) using 2-APB abolished Ca2+ oscillations. Inhibition of endoplasmic reticulum Ca2+-ATPase (SERCA) using thapsigargin abolished Ca2+ oscillations. ML-9, an inhibitor of STIM1 translocation, also strongly reduced Ca2+ oscillations. Inhibitors of L- and T-type Ca2+ channels (Cav; verapamil>nifedipine>TTA-P2) markedly reduced the frequency of Ca2+ oscillations. Thus, Ca2+ oscillations observed in normoxia were caused by cyclical Ca2+ fluxes at the ER, which was supported by Ca2+ influx via Ca2+ channels. Hypoxia (2-5% O2) increased the frequency and amplitude of Ca2+ oscillations, and Cav inhibitors (verapamil>nifedipine>>TTA-P2) reduced these effects of hypoxia. Our study shows that Ca2+ oscillations represent the basic Ca2+ signaling mechanism in normoxia and hypoxia in CB glomus cells.
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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
| | - James O Hogan
- Department of Physiology and Biophysics, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois
| | - Carl White
- Department of Physiology and Biophysics, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois
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8
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Luo Q, Wang X, Liu R, Qiao H, Wang P, Jiang C, Zhang Q, Cao Y, Yu H, Qu L. alpha1A-adrenoceptor is involved in norepinephrine-induced proliferation of pulmonary artery smooth muscle cells via CaMKII signaling. J Cell Biochem 2018; 120:9345-9355. [PMID: 30520144 DOI: 10.1002/jcb.28210] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 11/15/2018] [Indexed: 12/13/2022]
Abstract
Pulmonary arterial hypertension (PAH) is a progressive disease of the pulmonary vasculature characterized by excessive proliferation of pulmonary artery smooth muscle cells (PASMCs). Some studies have demonstrated the sympathetic nervous system is activated in PAH and norepinephrine (NE) released is closely linked with its activation. However, the subtypes of adrenoreceptor (AR) and the downstream molecular cascades which are involved in the proliferation of PASMCs are still unclear. In this study, adult male Wistar rats were exposed to chronic hypoxia and PASMCs were cultured in hypoxic condition. Significant upregulation of α1A -AR was identified by Western blot analysis or immunofluorescence in all of the pulmonary arteries, lung tissues, and cell hypoxic models. Western blot analysis, flow cytometry, and immunofluorescence were applied to detect the roles of α1A -AR in NE mediated proliferation of PASMCs. We revealed 5-methylurapidil (5-MU) reversed NE-induced upregulation of PCNA, CyclinA and CyclinE, more cells from G0 /G1 phase to G2 /M+S phase, enhancement of the microtubule formation. In addition, we found calcium/calmodulin(CaM)-dependent protein kinase type II (CaMKII) pathway was involved in α1A -AR-mediated cell proliferation. [Ca2+ ]i measurements showed that an increase of [Ca2+ ]i caused by NE or/and hypoxia could be blocked by 5-MU in PASMCs. Western blot analysis results demonstrated the augmentation of CaMKII phosphorylation level was caused by hypoxia or NE in pulmonary arteries, lung tissues, and PASMCs. KN62 attenuated NE-induced proliferation of PASMCs under normoxia and hypoxia. In conclusion, those results suggested NE which stimulated α1A -AR-mediated the proliferation of PASMCs, which may be via the CaMKII pathway, and it could be used as a novel treatment strategy in PAH.
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Affiliation(s)
- Qian Luo
- Department of Physiology, College of Basic Medical Sciences, Harbin Medical University-Daqing, Daqing, China
| | - Xiaoyan Wang
- Department of Physiology, College of Basic Medical Sciences, Harbin Medical University-Daqing, Daqing, China
| | - Ruxia Liu
- Department of Physiology, College of Basic Medical Sciences, Harbin Medical University-Daqing, Daqing, China
| | - Hui Qiao
- Department of Physiology, College of Basic Medical Sciences, Harbin Medical University-Daqing, Daqing, China.,Department of Gastroenterology, Daqing Oilfield General Hospital, Daqing, China
| | - Peng Wang
- Department of Physiology, College of Basic Medical Sciences, Harbin Medical University-Daqing, Daqing, China
| | - Chao Jiang
- Department of Physiology, College of Basic Medical Sciences, Harbin Medical University-Daqing, Daqing, China
| | - Qianlong Zhang
- Department of Physiology, College of Basic Medical Sciences, Harbin Medical University-Daqing, Daqing, China
| | - Yonggang Cao
- Department of Pharmacology, College of Basic Medical Sciences, Harbin Medical University-Daqing, Daqing, China
| | - Hang Yu
- Department of Physiology, College of Basic Medical Sciences, Harbin Medical University-Daqing, Daqing, China
| | - Lihui Qu
- Department of Physiology, College of Basic Medical Sciences, Harbin Medical University-Daqing, Daqing, China
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9
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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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10
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López‐Barneo J. All for one - O 2 -sensitive K + channels that mediate carotid body activation. J Physiol 2018; 596:2951-2952. [PMID: 29271487 PMCID: PMC6068221 DOI: 10.1113/jp275591] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Affiliation(s)
- José López‐Barneo
- Instituto de Biomedicina de Sevilla (IBiS)Hospital Universitario Virgen del Rocío/CSIC/Universidad de SevillaSpain
- Departamento de Fisiología Médica y Biofísica, Facultad de MedicinaUniversidad de SevillaSpain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED)Spain
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11
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Holmes AP, Ray CJ, Coney AM, Kumar P. Is Carotid Body Physiological O 2 Sensitivity Determined by a Unique Mitochondrial Phenotype? Front Physiol 2018; 9:562. [PMID: 29867584 PMCID: PMC5964187 DOI: 10.3389/fphys.2018.00562] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 04/30/2018] [Indexed: 12/12/2022] Open
Abstract
The mammalian carotid body (CB) is the primary arterial chemoreceptor that responds to acute hypoxia, initiating systemic protective reflex responses that act to maintain O2 delivery to the brain and vital organs. The CB is unique in that it is stimulated at O2 levels above those that begin to impact on the metabolism of most other cell types. Whilst a large proportion of the CB chemotransduction cascade is well defined, the identity of the O2 sensor remains highly controversial. This short review evaluates whether the mitochondria can adequately function as acute O2 sensors in the CB. We consider the similarities between mitochondrial poisons and hypoxic stimuli in their ability to activate the CB chemotransduction cascade and initiate rapid cardiorespiratory reflexes. We evaluate whether the mitochondria are required for the CB to respond to hypoxia. We also discuss if the CB mitochondria are different to those located in other non-O2 sensitive cells, and what might cause them to have an unusually low O2 binding affinity. In particular we look at the potential roles of competitive inhibitors of mitochondrial complex IV such as nitric oxide in establishing mitochondrial and CB O2-sensitivity. Finally, we discuss novel signaling mechanisms proposed to take place within and downstream of mitochondria that link mitochondrial metabolism with cellular depolarization.
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Affiliation(s)
| | | | | | - Prem Kumar
- Institute of Clinical Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
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12
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López-Barneo J. Oxygen sensing and stem cell activation in the hypoxic carotid body. Cell Tissue Res 2018; 372:417-425. [PMID: 29368257 DOI: 10.1007/s00441-017-2783-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2017] [Accepted: 12/22/2017] [Indexed: 12/15/2022]
Abstract
The carotid body (CB) is the major arterial chemoreceptor responsible for the detection of acute decreases in O2 tension (hypoxia) in arterial blood that trigger hyperventilation and sympathetic activation. The CB contains O2-sensitive glomus (chief) cells, which respond to hypoxia with the release of transmitters to activate sensory nerve fibers impinging upon the brain respiratory and autonomic centers. During exposure to sustained hypoxia (for weeks or months), the CB grows several-fold in size, a response associated with acclimatization to high altitude or to medical conditions presenting hypoxemia. Here, I briefly present recent advances on the mechanisms underlying glomus cell sensitivity to hypoxia, in particular the role of mitochondrial complex I in acute oxygen sensing. I also summarize the properties of adult CB stem cells and of glomus cell-stem cell synapses, which contribute to CB hypertrophy in chronic hypoxia. A note on the relationship between hypoxic CB growth and tumorigenesis is included. Finally, the medical implications of CB pathophysiology are discussed.
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Affiliation(s)
- José López-Barneo
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Avenida Manuel Siurot s/n, 41013, Seville, Spain. .,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Sevilla, Spain. .,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain.
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13
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Kang D, Wang J, Hogan JO, Kim D. TASK-1 (K2P3) and TASK-3 (K2P9) in Rabbit Carotid Body Glomus Cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1071:35-41. [DOI: 10.1007/978-3-319-91137-3_4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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14
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Wang J, Kim D. Activation of voltage-dependent K + channels strongly limits hypoxia-induced elevation of [Ca 2+ ] i in rat carotid body glomus cells. J Physiol 2017; 596:3119-3136. [PMID: 29160573 DOI: 10.1113/jp275275] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 11/10/2017] [Indexed: 01/01/2023] Open
Abstract
KEY POINTS We studied the role of the large-conductance Ca2+ -activated K+ channel (BK) and voltage-dependent K+ channels (Kv) on [Ca2+ ]i responses to a wide range of hypoxia at different resting cell membrane potential (Em ). BK/Kv were mostly closed at rest in normoxia. BK/Kv became basally active when cells were depolarized by elevated [KCl]o (>12 mm). Regardless of whether BK/Kv were closed or basally open, hypoxia-induced elevation of [Ca2+ ]i was enhanced 2- to 3-fold by inhibitors of BK/Kv. Hypoxia-induced elevation of [Ca2+ ]i was enhanced ∼2-fold by an inhibitor of Kv2, a major Kv in rat glomus cells. Hypoxia did not inhibit BK in inside-out patches. Our study supports a scheme in which activation of BK/Kv strongly limits the magnitude of hypoxia-induced [Ca2+ ]i rise, with Kv having a much greater effect than BK. ABSTRACT Large-conductance KCa (BK) and other voltage-dependent K+ channels (Kv) are highly expressed in carotid body (CB) glomus cells, but their role in hypoxia-induced excitation is still not well defined and remains controversial. We addressed this issue by studying the effects of inhibitors of BK (IBTX) and BK/Kv (TEA/4-AP) on [Ca2+ ]i responses to a wide range of hypoxia at different levels of resting cell membrane potential (Em ). IBTX and TEA/4-AP did not affect the basal [Ca2+ ]i in isolated glomus cells bathed in 5 mm KClo , but elicited transient increases in [Ca2+ ]i in cells that were moderately depolarized (11-20 mV) by elevation of [KCl]o (12-20 mm). Thus, BK and Kv were mostly closed at rest and activated by depolarization. Four different levels of hypoxia (mild, moderate, severe, anoxia) were used to produce a wide range of [Ca2+ ]i elevation (0-700 nm). IBTX did not affect the rise in [Ca2+ ]i , but TEA/4-AP strongly (∼3-fold) enhanced [Ca2+ ]i rise by moderate and severe levels of hypoxia. Guangxitoxin, a Kv2 blocker, inhibited the whole-cell current by ∼50%, and enhanced 2-fold the [Ca2+ ]i rise elicited by moderate and severe levels of hypoxia. Anoxia did not directly affect BK, but activated BK via depolarization. Our findings do not support the view that hypoxia inhibits BK/Kv to initiate or maintain the hypoxic response. Rather, our results show that BK/Kv are activated as glomus cells depolarize in response to hypoxia, which then limits the rise in [Ca2+ ]i . Inhibition of Kv may provide a mechanism to enhance the chemosensory activity of the CB and ventilation.
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Affiliation(s)
- Jiaju Wang
- Department of Physiology and Biophysics, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA
| | - Donghee Kim
- Department of Physiology and Biophysics, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA
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Wang J, Hogan JO, Wang R, White C, Kim D. Role of cystathionine-γ-lyase in hypoxia-induced changes in TASK activity, intracellular [Ca 2+] and ventilation in mice. Respir Physiol Neurobiol 2017; 246:98-106. [PMID: 28851593 DOI: 10.1016/j.resp.2017.08.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Revised: 08/09/2017] [Accepted: 08/15/2017] [Indexed: 10/19/2022]
Abstract
Cystathionine-γ-lyase (CSE) is a multifunctional enzyme, and hydrogen sulfide (H2S) is one of its products. CSE and H2S have recently been proposed to be critical signaling molecules in hypoxia-induced excitation of carotid body (CB) glomus cells and the chemosensory response. Because the role of H2S in arterial chemoreception is still debated, we further examined the role of CSE by studying the effects of hypoxia on TASK K+ channel activity, cell depolarization, [Ca2+]i and ventilation using CSE+/+ and CSE-/- mice. As predicted, hypoxia reduced TASK activity and depolarized glomus cells isolated from CSE+/+ mice. These effects of hypoxia were not significantly altered in glomus cells from CSE-/- mice. Basal [Ca2+]i and hypoxia-induced elevation of [Ca2+] were also not significantly different in glomus cells from CSE+/+ and CSE-/- mice. In whole-body plethysmography, hypoxia (10%O2) increased minute ventilation in both CSE+/+ and CSE-/- mice equally well, and no significant differences were found in either males or females when adjusted by body weight. Together, these results show that deletion of the CSE gene has no effects on hypoxia-induced changes in TASK, cell depolarization, [Ca2+]i and ventilation, and therefore do not support the idea that CSE/H2S signaling is important for CB chemoreceptor activity in mice.
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Affiliation(s)
- Jiaju Wang
- Department of Physiology and Biophysics, Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, United States
| | - James O Hogan
- Department of Physiology and Biophysics, Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, United States
| | - Rui Wang
- Cardiovascular and Metabolic Research Unit, Laurentian University, Sudbury, Canada
| | - Carl White
- Department of Physiology and Biophysics, Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, United States
| | - Donghee Kim
- Department of Physiology and Biophysics, Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, United States.
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Gao L, Bonilla-Henao V, García-Flores P, Arias-Mayenco I, Ortega-Sáenz P, López-Barneo J. Gene expression analyses reveal metabolic specifications in acute O 2 -sensing chemoreceptor cells. J Physiol 2017; 595:6091-6120. [PMID: 28718507 DOI: 10.1113/jp274684] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Accepted: 07/03/2017] [Indexed: 01/05/2023] Open
Abstract
KEY POINTS Glomus cells in the carotid body (CB) and chromaffin cells in the adrenal medulla (AM) are essential for reflex cardiorespiratory adaptation to hypoxia. However, the mechanisms whereby these cells detect changes in O2 tension are poorly understood. The metabolic properties of acute O2 -sensing cells have been investigated by comparing the transcriptomes of CB and AM cells, which are O2 -sensitive, with superior cervical ganglion neurons, which are practically O2 -insensitive. In O2 -sensitive cells, we found a characteristic prolyl hydroxylase 3 down-regulation and hypoxia inducible factor 2α up-regulation, as well as overexpression of genes coding for three atypical mitochondrial electron transport subunits and pyruvate carboxylase, an enzyme that replenishes tricarboxylic acid cycle intermediates. In agreement with this observation, the inhibition of succinate dehydrogenase impairs CB acute O2 sensing. The responsiveness of peripheral chemoreceptor cells to acute hypoxia depends on a 'signature metabolic profile'. ABSTRACT Acute O2 sensing is a fundamental property of cells in the peripheral chemoreceptors, e.g. glomus cells in the carotid body (CB) and chromaffin cells in the adrenal medulla (AM), and is necessary for adaptation to hypoxia. These cells contain O2 -sensitive ion channels, which mediate membrane depolarization and transmitter release upon exposure to hypoxia. However, the mechanisms underlying the detection of changes in O2 tension by cells are still poorly understood. Recently, we suggested that CB glomus cells have specific metabolic features that favour the accumulation of reduced quinone and the production of mitochondrial NADH and reactive oxygen species during hypoxia. These signals alter membrane ion channel activity. To investigate the metabolic profile characteristic of acute O2 -sensing cells, we used adult mice to compare the transcriptomes of three cell types derived from common sympathoadrenal progenitors, but exhibiting variable responsiveness to acute hypoxia: CB and AM cells, which are O2 -sensitive (glomus cells > chromaffin cells), and superior cervical ganglion neurons, which are practically O2 -insensitive. In the O2 -sensitive cells, we found a characteristic mRNA expression pattern of prolyl hydroxylase 3/hypoxia inducible factor 2α and up-regulation of several genes, in particular three atypical mitochondrial electron transport subunits and some ion channels. In addition, we found that pyruvate carboxylase, an enzyme fundamental to tricarboxylic acid cycle anaplerosis, is overexpressed in CB glomus cells. We also observed that the inhibition of succinate dehydrogenase impairs CB acute O2 sensing. Our data suggest that responsiveness to acute hypoxia depends on a 'signature metabolic profile' in chemoreceptor cells.
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Affiliation(s)
- Lin Gao
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Victoria Bonilla-Henao
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Paula García-Flores
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Ignacio Arias-Mayenco
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Patricia Ortega-Sáenz
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - José López-Barneo
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
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Wang J, Hogan JO, Kim D. Voltage- and receptor-mediated activation of a non-selective cation channel in rat carotid body glomus cells. Respir Physiol Neurobiol 2016; 237:13-21. [PMID: 28013061 DOI: 10.1016/j.resp.2016.12.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 11/16/2016] [Accepted: 12/08/2016] [Indexed: 10/20/2022]
Abstract
A recent study showed that hypoxia activates a Ca2+-sensitive, Na+-permeable non-selective cation channel (NSC) in carotid body glomus cells. We studied the effects of mitochondrial inhibitors that increase Ca2+ influx via Ca2+ channel (Cav), and receptor agonists that release Ca2+ from endoplasmic reticulum (ER) on NSC. Mitochondrial inhibitors (NaCN, FCCP, H2S, NO) elevated [Ca2+]i and activated NSC. Angiotensin II and acetylcholine that elevate [Ca2+]i via the Gq-IP3 pathway activated NSC. However, endothelin-1 (Gq) and 5-HT (Gq) showed little or no effect on [Ca2+]i and did not activate NSC. Adenosine (Gs) caused a weak rise in [Ca2+]i but did not activate NSC. Dopamine (Gs) and γ-aminobytyric acid (Gi) were ineffective in raising [Ca2+]i and failed to activate NSC. Store-operated Ca2+ entry (SOCE) produced by depletion of Ca2+ stores with cyclopiazonic acid activated NSC. Our results show that Ca2+ entry via Cav, ER Ca2+ release and SOCE can activate NSC. Thus, NSC contributes to both voltage- and receptor-mediated excitation of glomus cells.
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Affiliation(s)
- Jiaju Wang
- Department of Physiology and Biophysics, Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, USA
| | - James O Hogan
- Department of Physiology and Biophysics, Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, USA
| | - Donghee Kim
- Department of Physiology and Biophysics, Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, USA.
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Wilson RJA, Teppema LJ. Integration of Central and Peripheral Respiratory Chemoreflexes. Compr Physiol 2016; 6:1005-41. [PMID: 27065173 DOI: 10.1002/cphy.c140040] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
A debate has raged since the discovery of central and peripheral respiratory chemoreceptors as to whether the reflexes they mediate combine in an additive (i.e., no interaction), hypoadditive or hyperadditive manner. Here we critically review pertinent literature related to O2 and CO2 sensing from the perspective of system integration and summarize many of the studies on which these seemingly opposing views are based. Despite the intensity and quality of this debate, we have yet to reach consensus, either within or between species. In reviewing this literature, we are struck by the merits of the approaches and preparations that have been brought to bear on this question. This suggests that either the nature of combination is not important to system responses, contrary to what has long been supposed, or that the nature of the combination is more malleable than previously assumed, changing depending on physiological state and/or respiratory requirement.
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Affiliation(s)
- Richard J A Wilson
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute and Alberta Children Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Luc J Teppema
- Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands
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Buckler KJ, Turner PJ. Functional Properties of Mitochondria in the Type-1 Cell and Their Role in Oxygen Sensing. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 860:69-80. [PMID: 26303469 DOI: 10.1007/978-3-319-18440-1_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
The identity of the oxygen sensor in arterial chemoreceptors has been the subject of much speculation. One of the oldest hypotheses is that oxygen is sensed through oxidative phosphorylation. There is a wealth of data demonstrating that arterial chemoreceptors are excited by inhibitors of oxidative phosphorylation. These compounds mimic the effects of hypoxia inhibiting TASK1/3 potassium channels causing membrane depolarisation calcium influx and neurosecretion. The TASK channels of Type-I cells are also sensitive to cytosolic MgATP. The existence of a metabolic signalling pathway in Type-1 cells is thus established; the contentious issue is whether this pathway is also used for acute oxygen sensing. The main criticism is that because cytochrome oxidase has a high affinity for oxygen (P50 ≈ 0.2 mmHg) mitochondrial metabolism should be insensitive to physiological hypoxia. This argument is however predicated on the assumption that chemoreceptor mitochondria are analogous to those of other tissues. We have however obtained new evidence to support the hypothesis that type-1 cell mitochondria are not like those of other cells in that they have an unusually low affinity for oxygen (Mills E, Jobsis FF, J Neurophysiol 35(4):405-428, 1972; Duchen MR, Biscoe TJ, J Physiol 450:13-31, 1992a). Our data confirm that mitochondrial membrane potential, NADH, electron transport and cytochrome oxidase activity in the Type-1 cell are all highly sensitive to hypoxia. These observations not only provide exceptionally strong support for the metabolic hypothesis but also reveal an unknown side of mitochondrial behaviour.
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Affiliation(s)
- Keith J Buckler
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford, OX1 3PT, UK,
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Carotid body oxygen sensing and adaptation to hypoxia. Pflugers Arch 2015; 468:59-70. [DOI: 10.1007/s00424-015-1734-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 09/01/2015] [Accepted: 09/04/2015] [Indexed: 10/23/2022]
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TASK channels in arterial chemoreceptors and their role in oxygen and acid sensing. Pflugers Arch 2015; 467:1013-25. [PMID: 25623783 PMCID: PMC4428840 DOI: 10.1007/s00424-015-1689-1] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Revised: 01/06/2015] [Accepted: 01/07/2015] [Indexed: 01/05/2023]
Abstract
Arterial chemoreceptors play a vital role in cardiorespiratory control by providing the brain with information regarding blood oxygen, carbon dioxide, and pH. The main chemoreceptor, the carotid body, is composed of sensory (type 1) cells which respond to hypoxia or acidosis with a depolarising receptor potential which in turn activates voltage-gated calcium entry, neurosecretion and excitation of adjacent afferent nerves. The receptor potential is generated by inhibition of Twik-related acid-sensitive K(+) channel 1 and 3 (TASK1/TASK3) heterodimeric channels which normally maintain the cells' resting membrane potential. These channels are thought to be directly inhibited by acidosis. Oxygen sensitivity, however, probably derives from a metabolic signalling pathway. The carotid body, isolated type 1 cells, and all forms of TASK channel found in the type 1 cell, are highly sensitive to inhibitors of mitochondrial metabolism. Moreover, type1 cell TASK channels are activated by millimolar levels of MgATP. In addition to their role in the transduction of chemostimuli, type 1 cell TASK channels have also been implicated in the modulation of chemoreceptor function by a number of neurocrine/paracrine signalling molecules including adenosine, GABA, and serotonin. They may also be instrumental in mediating the depression of the acute hypoxic ventilatory response that occurs with some general anaesthetics. Modulation of TASK channel activity is therefore a key mechanism by which the excitability of chemoreceptors can be controlled. This is not only of physiological importance but may also offer a therapeutic strategy for the treatment of cardiorespiratory disorders that are associated with chemoreceptor dysfunction.
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Kim D, Kang D. Role of K₂p channels in stimulus-secretion coupling. Pflugers Arch 2014; 467:1001-11. [PMID: 25476848 DOI: 10.1007/s00424-014-1663-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 11/26/2014] [Accepted: 11/28/2014] [Indexed: 11/30/2022]
Abstract
Two-pore domain K(+) (K2P) channels are involved in a variety of physiological processes by virtue of their high basal activity and sensitivity to various biological stimuli. One of these processes is secretion of hormones and transmitters in response to stimuli such as hypoxia, acidosis, and receptor agonists. The rise in intracellular [Ca(2+)] ([Ca(2+)]i) that is critical for the secretory event can be achieved by several mechanisms: (a) inhibition of resting (background) K(+) channels, (b) activation of Na(+)/Ca(2+)-permeable channels, and (c) release of Ca(2+) from intracellular stores. Here, we discuss the role of TASK and TREK in stimulus-secretion mechanisms in carotid body chemoreceptor cells and adrenal medullary/cortical cells. Studies show that stimuli such as hypoxia and acidosis cause cell depolarization and transmitter/hormone secretion by inhibition of TASK or TREK. Subsequent elevation of [Ca(2+)]i produced by opening of voltage-dependent Ca(2+) channels then activates a Na(+)-permeable cation channel, presumably to help sustain the depolarization and [Ca(2+)]i. Agonists such as angiotensin II may elevate [Ca(2+)]i via multiple mechanisms involving both inhibition of TASK/TREK and Ca(2+) release from internal stores to cause aldosterone secretion. Thus, inhibition of resting (background) K(+) channels and subsequent activation of voltage-gated Ca(2+) channels and Na(+)-permeable non-selective cation channels may be a common ionic mechanism that lead to hormone and transmitter secretion.
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Affiliation(s)
- Donghee Kim
- Department of Physiology and Biophysics, Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL, 60064, USA,
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