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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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Lazarov NE, Atanasova DY. Mechanisms of Chemosensory Transduction in the Carotid Body. ADVANCES IN ANATOMY, EMBRYOLOGY, AND CELL BIOLOGY 2023; 237:49-62. [PMID: 37946077 DOI: 10.1007/978-3-031-44757-0_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2023]
Abstract
The mammalian carotid body (CB) is a polymodal chemoreceptor, which is activated by blood-borne stimuli, most notably hypoxia, hypercapnia and acidosis, thus ensuring an appropriate cellular response to changes in physical and chemical parameters of the blood. The glomus cells are considered the CB chemosensory cells and the initial site of chemoreceptor transduction. However, the molecular mechanisms by which they detect changes in blood chemical levels and how these changes lead to transmitter release are not yet well understood. Chemotransduction mechanisms are by far best described for oxygen and acid/carbon dioxide sensing. A few testable hypotheses have been postulated including a direct interaction of oxygen with ion channels in the glomus cells (membrane hypothesis), an indirect interface by a reversible ligand like a heme (metabolic hypothesis), or even a functional interaction between putative oxygen sensors (chemosome hypothesis) or the interaction of lactate with a highly expressed in the CB atypical olfactory receptor, Olfr78, (endocrine model). It is also suggested that sensory transduction in the CB is uniquely dependent on the actions and interactions of gaseous transmitters. Apparently, oxygen sensing does not utilize a single mechanism, and later observations have given strong support to a unified membrane model of chemotransduction.
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Affiliation(s)
- Nikolai E Lazarov
- Department of Anatomy and Histology, Faculty of Medicine, Medical University of Sofia, Sofia, Bulgaria.
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3
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Gao L, Ortega-Sáenz P, Moreno-Domínguez A, López-Barneo J. Mitochondrial Redox Signaling in O 2-Sensing Chemoreceptor Cells. Antioxid Redox Signal 2022; 37:274-289. [PMID: 35044243 DOI: 10.1089/ars.2021.0255] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Significance: Acute responses to hypoxia are essential for the survival of mammals. The carotid body (CB), the main arterial chemoreceptor, contains glomus cells with oxygen (O2)-sensitive K+ channels, which are inhibited during hypoxia to trigger adaptive cardiorespiratory reflexes. Recent Advances: In this review, recent advances in molecular mechanisms of acute O2 sensing in CB glomus cells are discussed, with a special focus on the signaling role of mitochondria through regulating cellular redox status. These advances have been achieved thanks to the use of genetically engineered redox-sensitive green fluorescent protein (roGFP) probes, which allowed us to monitor rapid changes in ROS production in real time in different subcellular compartments during hypoxia. This methodology was used in combination with conditional knockout mice models, pharmacological approaches, and transcriptomic studies. We have proposed a mitochondria-to-membrane signaling model of acute O2 sensing in which H2O2 released in the mitochondrial intermembrane space serves as a signaling molecule to inhibit K+ channels on the plasma membrane. Critical Issues: Changes in mitochondrial reactive oxygen species (ROS) production during acute hypoxia are highly compartmentalized in the submitochondrial regions. The use of redox-sensitive probes targeted to specific compartments is essential to fully understand the role of mitochondrial ROS in acute O2 sensing. Future Directions: Further studies are needed to specify the ROS and to characterize the target(s) of ROS in chemoreceptor cells during acute hypoxia. These data may also contribute to a more complete understanding of the implication of ROS in acute responses to hypoxia in O2-sensing cells in other organs. Antioxid. Redox Signal. 37, 274-289.
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Affiliation(s)
- 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
| | - 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.,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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4
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Blum K, Brodie MS, Pandey SC, Cadet JL, Gupta A, Elman I, Thanos PK, Gondre-Lewis MC, Baron D, Kazmi S, Bowirrat A, Febo M, Badgaiyan RD, Braverman ER, Dennen CA, Gold MS. Researching Mitigation of Alcohol Binge Drinking in Polydrug Abuse: KCNK13 and RASGRF2 Gene(s) Risk Polymorphisms Coupled with Genetic Addiction Risk Severity (GARS) Guiding Precision Pro-Dopamine Regulation. J Pers Med 2022; 12:jpm12061009. [PMID: 35743793 PMCID: PMC9224860 DOI: 10.3390/jpm12061009] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 06/12/2022] [Accepted: 06/16/2022] [Indexed: 11/22/2022] Open
Abstract
Excessive alcohol intake, e.g., binge drinking, is a serious and mounting public health problem in the United States and throughout the world. Hence the need for novel insights into the underlying neurobiology that may help improve prevention and therapeutic strategies. Therefore, our group employed a darkness-induced alcohol intake protocol to define the reward deficiency domains of alcohol and other substance use disorders in terms of reward pathways' reduced dopamine signaling and its restoration via specifically-designed therapeutic compounds. It has been determined that KCNK13 and RASGRF2 genes, respectively, code for potassium two pore domain channel subfamily K member 13 and Ras-specific guanine nucleotide-releasing factor 2, and both genes have important dopamine-related functions pertaining to alcohol binge drinking. We present a hypothesis that identification of KCNK13 and RASGRF2 genes' risk polymorphism, coupled with genetic addiction risk score (GARS)-guided precision pro-dopamine regulation, will mitigate binge alcohol drinking. Accordingly, we review published reports on the benefits of this unique approach and provide data on favorable outcomes for both binge-drinking animals and drunk drivers, including reductions in alcohol intake and prevention of relapse to drinking behavior. Since driving under the influence of alcohol often leads to incarceration rather than rehabilitation, there is converging evidence to support the utilization of GARS with or without KCNK13 and RASGRF2 risk polymorphism in the legal arena, whereby the argument that "determinism" overrides the "free will" account may be a plausible defense strategy. Obviously, this type of research is tantamount to helping resolve a major problem related to polydrug abuse.
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Affiliation(s)
- Kenneth Blum
- The Kenneth Blum Behavioral & Neurogenetic Institute, Austin, TX 78701, USA; (E.R.B.); (C.A.D.)
- Division of Addiction Research & Education, Center for Psychiatry, Medicine & Primary Care (Office of Provost), Western University Health Sciences, Pomona, CA 91766, USA; (D.B.); (M.F.)
- Institute of Psychology, ELTE Eötvös Loránd University, Egyetem tér 1-3, 1053 Budapest, Hungary
- Department of Psychiatry, School of Medicine, University of Vermont, Burlington, VT 05405, USA
- Department of Psychiatry, Wright State University Boonshoft School of Medicine and Dayton VA Medical Centre, Dayton, OH 45324, USA
- Correspondence:
| | - Mark S. Brodie
- Center for Alcohol Research in Epigenetics, Departments of Physiology and Biophysics, and Psychiatry, University of Illinois at Chicago, Chicago, IL 60612, USA; (M.S.B.); (S.C.P.)
| | - Subhash C. Pandey
- Center for Alcohol Research in Epigenetics, Departments of Physiology and Biophysics, and Psychiatry, University of Illinois at Chicago, Chicago, IL 60612, USA; (M.S.B.); (S.C.P.)
| | - Jean Lud Cadet
- Molecular Neuropsychiatry Research Branch, National Institute on Drug Abuse, National Institutes of Health, Bethesda, MD 20892, USA;
| | - Ashim Gupta
- Future Biologics, Lawrenceville, GA 30043, USA;
| | - Igor Elman
- Center for Pain and the Brain (P.A.I.N Group), Department of Anesthesiology, Critical Care & Pain Medicine, Boston Children’s Hospital, Boston, MA 02115, USA;
| | - Panayotis K. Thanos
- Behavioral Neuropharmacology and Neuroimaging Laboratory on Addictions, Clinical Research Institute on Addictions, Department of Pharmacology and Toxicology, Jacobs School of Medicine and Biosciences, State University of New York at Buffalo, Buffalo, NY 14203, USA;
- Department of Psychology, State University of New York at Buffalo, Buffalo, NY 14203, USA
| | - Marjorie C. Gondre-Lewis
- Neuropsychopharmacology Laboratory, Department of Anatomy, Howard University College of Medicine, Washington, DC 20059, USA;
| | - David Baron
- Division of Addiction Research & Education, Center for Psychiatry, Medicine & Primary Care (Office of Provost), Western University Health Sciences, Pomona, CA 91766, USA; (D.B.); (M.F.)
| | - Shan Kazmi
- College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, Pomona, CA 91766, USA;
| | - Abdalla Bowirrat
- Department of Molecular Biology and Adelson School of Medicine, Ariel University, Ariel 40700, Israel;
| | - Marcelo Febo
- Division of Addiction Research & Education, Center for Psychiatry, Medicine & Primary Care (Office of Provost), Western University Health Sciences, Pomona, CA 91766, USA; (D.B.); (M.F.)
| | - Rajendra D. Badgaiyan
- Department of Psychiatry, South Texas Veteran Health Care System, Audie L. Murphy Memorial VA Hospital, Long School of Medicine, University of Texas Medical Center, San Antonio, TX 78229, USA;
| | - Eric R. Braverman
- The Kenneth Blum Behavioral & Neurogenetic Institute, Austin, TX 78701, USA; (E.R.B.); (C.A.D.)
| | - Catherine A. Dennen
- The Kenneth Blum Behavioral & Neurogenetic Institute, Austin, TX 78701, USA; (E.R.B.); (C.A.D.)
| | - Mark S. Gold
- Department of Psychiatry, Washington University School of Medicine, St. Louis, MO 63110, USA;
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5
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Hawrysh PJ, Myrka AM, Buck LT. Review: A history and perspective of mitochondria in the context of anoxia tolerance. Comp Biochem Physiol B Biochem Mol Biol 2022; 260:110733. [PMID: 35288242 DOI: 10.1016/j.cbpb.2022.110733] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 03/07/2022] [Accepted: 03/07/2022] [Indexed: 01/01/2023]
Abstract
Symbiosis is found throughout nature, but perhaps nowhere is it more fundamental than mitochondria in all eukaryotes. Since mitochondria were discovered and mechanisms of oxygen reduction characterized, an understanding gradually emerged that these organelles were involved not just in the combustion of oxygen, but also in the sensing of oxygen. While multiple hypotheses exist to explain the mitochondrial involvement in oxygen sensing, key elements are developing that include potassium channels and reactive oxygen species. To understand how mitochondria contribute to oxygen sensing, it is informative to study a model system which is naturally adapted to survive extended periods without oxygen. Amongst air-breathing vertebrates, the most highly adapted are western painted turtles (Chrysemys picta bellii), which overwinter in ice-covered and anoxic water bodies. Through research of this animal, it was postulated that metabolic rate depression is key to anoxic survival and that mitochondrial regulation is a key aspect. When faced with anoxia, excitatory neurotransmitter receptors in turtle brain are inhibited through mitochondrial calcium release, termed "channel arrest". Simultaneously, inhibitory GABAergic signalling contributes to the "synaptic arrest" of excitatory action potential firing through a pathway dependent on mitochondrial depression of ROS generation. While many pathways are implicated in mitochondrial oxygen sensing in turtles, such as those of adenosine, ATP turnover, and gaseous transmitters, an apparent point of intersection is the mitochondria. In this review we will explore how an organelle that was critical for organismal complexity in an oxygenated world has also become a potentially important oxygen sensor.
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Affiliation(s)
- Peter John Hawrysh
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada
| | - Alexander Morley Myrka
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada
| | - Leslie Thomas Buck
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada; Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3G5, Canada.
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6
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Argent LP, Bose A, Paton JFR. Intra-carotid body inter-cellular communication. J R Soc N Z 2022. [DOI: 10.1080/03036758.2022.2079681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Liam P. Argent
- Manaaki Manawa – the Centre for Heart Research, Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Aabharika Bose
- Manaaki Manawa – the Centre for Heart Research, Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Julian F. R. Paton
- Manaaki Manawa – the Centre for Heart Research, Department of Physiology, University of Auckland, Auckland, New Zealand
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7
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Rakoczy RJ, Schiebrel CM, Wyatt CN. Acute Oxygen-Sensing via Mitochondria-Generated Temperature Transients in Rat Carotid Body Type I Cells. Front Physiol 2022; 13:874039. [PMID: 35510145 PMCID: PMC9060449 DOI: 10.3389/fphys.2022.874039] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 03/28/2022] [Indexed: 12/28/2022] Open
Abstract
The Carotid Bodies (CB) are peripheral chemoreceptors that detect changes in arterial oxygenation and, via afferent inputs to the brainstem, correct the pattern of breathing to restore blood gas homeostasis. Herein, preliminary evidence is presented supporting a novel oxygen-sensing hypothesis which suggests CB Type I cell “hypoxic signaling” may in part be mediated by mitochondria-generated thermal transients in TASK-channel-containing microdomains. Distances were measured between antibody-labeled mitochondria and TASK-potassium channels in primary rat CB Type I cells. Sub-micron distance measurements (TASK-1: 0.33 ± 0.04 µm, n = 47 vs TASK-3: 0.32 ± 0.03 µm, n = 54) provided evidence for CB Type I cell oxygen-sensing microdomains. A temperature-sensitive dye (ERthermAC) indicated that inhibition of mitochondrial activity in isolated cells caused a rapid and reversible inhibition of mitochondrial thermogenesis and thus temperature in these microdomains. Whole-cell perforated-patch current-clamp electrophysiological recordings demonstrated sensitivity of resting membrane potential (Vm) to temperature: lowering bath temperature from 37°C to 24°C induced consistent and reversible depolarizations (Vm at 37°C: 48.4 ± 4.11 mV vs 24°C: 31.0 ± 5.69 mV; n = 5; p < 0.01). These data suggest that hypoxic inhibition of mitochondrial thermogenesis may play an important role in oxygen chemotransduction in the CB. A reduction in temperature within cellular microdomains will inhibit plasma membrane ion channels, influence the balance of cellular phosphorylation–dephosphorylation, and may extend the half-life of reactive oxygen species. The characterization of a thermosensory chemotransduction mechanism, that may also be used by other oxygen-sensitive cell types and may impact multiple other chemotransduction mechanisms is critical if we are to fully understand how the CBs, and potentially other oxygen-sensitive cells, respond to hypoxia.
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8
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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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9
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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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10
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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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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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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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13
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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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14
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Hydroxycobalamin Reveals the Involvement of Hydrogen Sulfide in the Hypoxic Responses of Rat Carotid Body Chemoreceptor Cells. Antioxidants (Basel) 2019; 8:antiox8030062. [PMID: 30871199 PMCID: PMC6466535 DOI: 10.3390/antiox8030062] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 03/01/2019] [Accepted: 03/09/2019] [Indexed: 12/28/2022] Open
Abstract
Carotid body (CB) chemoreceptor cells sense arterial blood PO2, generating a neurosecretory response proportional to the intensity of hypoxia. Hydrogen sulfide (H2S) is a physiological gaseous messenger that is proposed to act as an oxygen sensor in CBs, although this concept remains controversial. In the present study we have used the H2S scavenger and vitamin B12 analog hydroxycobalamin (Cbl) as a new tool to investigate the involvement of endogenous H2S in CB oxygen sensing. We observed that the slow-release sulfide donor GYY4137 elicited catecholamine release from isolated whole carotid bodies, and that Cbl prevented this response. Cbl also abolished the rise in [Ca2+]i evoked by 50 µM NaHS in enzymatically dispersed CB glomus cells. Moreover, Cbl markedly inhibited the catecholamine release and [Ca2+]i rise caused by hypoxia in isolated CBs and dispersed glomus cells, respectively, whereas it did not alter these responses when they were evoked by high [K+]e. The L-type Ca2+ channel blocker nifedipine slightly inhibited the rise in CB chemoreceptor cells [Ca2+]i elicited by sulfide, whilst causing a somewhat larger attenuation of the hypoxia-induced Ca2+ signal. We conclude that Cbl is a useful and specific tool for studying the function of H2S in cells. Based on its effects on the CB chemoreceptor cells we propose that endogenous H2S is an amplifier of the hypoxic transduction cascade which acts mainly by stimulating non-L-type Ca2+ channels.
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15
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da Silva MP, Moraes DJA, Bonagamba LGH, Mecawi ADS, Varanda WA, Machado BH. Hyperexcitability and plasticity induced by sustained hypoxia on rectus abdominis motoneurons. J Physiol 2019; 597:1935-1956. [PMID: 30747446 DOI: 10.1113/jp277030] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Accepted: 02/06/2019] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Acute hypoxia induces active expiration in rectus abdominis (RA) muscles in conscious freely moving rats, although its overall contribution is smaller than in internal oblique (IO) muscles. Tonically active and silent RA motoneurons were identified in in vitro preparations of rat spinal cords. Sustained hypoxia (SH) increased the synaptic strength and induced morphological changes in tonically active RA motoneurons. Expiratory RA motoneurons were recorded in the in situ preparation and SH enhanced both the excitability and the synaptic transmission in those firing during the stage 2 expiration. The present study contributes to a better understanding of the mechanisms involved in SH recruitment of RA motoneurons to induce active expiration in rats. ABSTRACT Rectus abdominis (RA) motoneurons translate the complex respiratory brainstem inputs into effective muscle contractions. Despite their fundamental role in respiration, their functional and morphological properties are not fully understood. In the present study, we investigated for the first time the contribution of RA muscle to active expiration and characterized RA motoneurons regarding their electrical, molecular and morphological profiles in control rats and in rats submitted to sustained hypoxia (SH), which induces chronic recruitment of abdominal muscles. Electromyographic experiments in conscious freely moving control rats and SH rats showed that RA contributes to active expiration induced by acute hypoxia, although its contribution is smaller than in internal oblique muscles. in vitro whole-cell patch clamp recordings from RA motoneurons revealed two populations of cells: tonically active and silent. SH induced hyperexcitability in the tonically active cells by changing their action potential properties, and EPSCs. Three-dimensional morphological reconstructions of these cells showed that SH increased the dendritic complexity, stimulated the appearance of dendrite spines, and increased the somatic area and volume. Physiologically identified RA motoneurons, firing in two distinct phases of expiration, were recorded in the brainstem-spinal cord in situ preparation of rats. SH increased the firing frequency and EPSCs of neurons firing during stage 2 expiration. Taken together, our results show that RA motoneurons reconfigure their biophysical properties, morphology and synaptic strength to produce an appropriate expiratory drive in response to SH in rats.
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Affiliation(s)
- Melina P da Silva
- School of Medicine of Ribeirão Preto, Department of Physiology, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Davi José A Moraes
- School of Medicine of Ribeirão Preto, Department of Physiology, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Leni G H Bonagamba
- School of Medicine of Ribeirão Preto, Department of Physiology, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - André de Souza Mecawi
- Paulista School of Medicine, Department of Biophysics, Federal University of São Paulo, São Paulo, Brazil
| | - Wamberto A Varanda
- School of Medicine of Ribeirão Preto, Department of Physiology, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Benedito H Machado
- School of Medicine of Ribeirão Preto, Department of Physiology, University of São Paulo, Ribeirão Preto, SP, Brazil
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16
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Lindsey BG, Nuding SC, Segers LS, Morris KF. Carotid Bodies and the Integrated Cardiorespiratory Response to Hypoxia. Physiology (Bethesda) 2019; 33:281-297. [PMID: 29897299 DOI: 10.1152/physiol.00014.2018] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Advances in our understanding of brain mechanisms for the hypoxic ventilatory response, coordinated changes in blood pressure, and the long-term consequences of chronic intermittent hypoxia as in sleep apnea, such as hypertension and heart failure, are giving impetus to the search for therapies to "erase" dysfunctional memories distributed in the carotid bodies and central nervous system. We review current network models, open questions, sex differences, and implications for translational research.
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Affiliation(s)
- Bruce G Lindsey
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Sarah C Nuding
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Lauren S Segers
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
| | - Kendall F Morris
- Department of Molecular Pharmacology and Physiology, Morsani College of Medicine, University of South Florida , Tampa, Florida
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17
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Abstract
Respiratory chemoreceptors in vertebrates are specialized cells that detect chemical changes in the environment or arterial blood supply and initiate autonomic responses, such as hyperventilation or changes in heart rate, to improve O2 uptake and delivery to tissues. These chemoreceptors are sensitive to changes in O2, CO2 and/or H+. In fish and mammals, respiratory chemoreceptors may be additionally sensitive to ammonia, hypoglycemia, and numerous other stimuli. Thus, chemoreceptors that affect respiration respond to different types of stimuli (or modalities) and are considered to be "polymodal". This review discusses the polymodal nature of respiratory chemoreceptors in vertebrates with a particular emphasis on chemoreceptors of the carotid body and pulmonary epithelium in mammals, and on neuroepithelial cells in water- and air-breathing fish. A major goal will be to examine the evidence for putative polymodal chemoreceptors in fish within the context of studies on mammalian models, for which polymodal chemoreceptors are well described, in order to improve our understanding of the evolution of polymodal chemoreceptors in vertebrates, and to aid in future studies that aim to identify putative receptors in air- and water-breathing fish.
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18
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Pulgar-Sepúlveda R, Varas R, Iturriaga R, Del Rio R, Ortiz FC. Carotid Body Type-I Cells Under Chronic Sustained Hypoxia: Focus on Metabolism and Membrane Excitability. Front Physiol 2018; 9:1282. [PMID: 30283346 PMCID: PMC6157308 DOI: 10.3389/fphys.2018.01282] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 08/24/2018] [Indexed: 12/23/2022] Open
Abstract
Chronic sustained hypoxia (CSH) evokes ventilatory acclimatization characterized by a progressive hyperventilation due to a potentiation of the carotid body (CB) chemosensory response to hypoxia. The transduction of the hypoxic stimulus in the CB begins with the inhibition of K+ currents in the chemosensory (type-I) cells, which in turn leads to membrane depolarization, Ca2+ entry and the subsequent release of one- or more-excitatory neurotransmitters. Several studies have shown that CSH modifies both the level of transmitters and chemoreceptor cell metabolism within the CB. Most of these studies have been focused on the role played by such putative transmitters and modulators of CB chemoreception, but less is known about the effect of CSH on metabolism and membrane excitability of type-I cells. In this mini-review, we will examine the effects of CSH on the ion channels activity and excitability of type-I cell, with a particular focus on the effects of CSH on the TASK-like background K+ channel. We propose that changes on TASK-like channel activity induced by CSH may contribute to explain the potentiation of CB chemosensory activity.
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Affiliation(s)
- Raúl Pulgar-Sepúlveda
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile
| | - Rodrigo Varas
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile
- Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Talca, Chile
| | - Rodrigo Iturriaga
- Laboratorio de Neurobiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Rodrigo Del Rio
- Laboratory of Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
- Centro de Envejecimiento y Regeneración, Pontificia Universidad Católica de Chile, Santiago, Chile
- Centro de Excelencia en Biomedicina de Magallanes, Universidad de Magallanes, Punta Arenas, Chile
| | - Fernando C. Ortiz
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile
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19
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O'Donohoe PB, Huskens N, Turner PJ, Pandit JJ, Buckler KJ. A1899, PK-THPP, ML365, and Doxapram inhibit endogenous TASK channels and excite calcium signaling in carotid body type-1 cells. Physiol Rep 2018; 6:e13876. [PMID: 30284397 PMCID: PMC6170881 DOI: 10.14814/phy2.13876] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 08/24/2018] [Indexed: 01/10/2023] Open
Abstract
Sensing of hypoxia and acidosis in arterial chemoreceptors is thought to be mediated through the inhibition of TASK and possibly other (e.g., BKCa ) potassium channels which leads to membrane depolarization, voltage-gated Ca-entry, and neurosecretion. Here, we investigate the effects of pharmacological inhibitors on TASK channel activity and [Ca2+ ]i -signaling in isolated neonatal rat type-1 cells. PK-THPP inhibited TASK channel activity in cell attached patches by up to 90% (at 400 nmol/L). A1899 inhibited TASK channel activity by 35% at 400 nmol/L. PK-THPP, A1899 and Ml 365 all evoked a rapid increase in type-1 cell [Ca2+ ]i . These [Ca2+ ]i responses were abolished in Ca2+ -free solution and greatly attenuated by Ni2+ (2 mM) suggesting that depolarization and voltage-gated Ca2+ -entry mediated the rise in [Ca2+ ]i. Doxapram (50 μmol/L), a respiratory stimulant, also inhibited type-1 cell TASK channel activity and increased [Ca2+ ]i. . We also tested the effects of combined inhibition of BKCa and TASK channels. TEA (5 mmol/L) slightly increased [Ca2+ ]i in the presence of PK-THPP and A1899. Paxilline (300 nM) and iberiotoxin (50 nmol/L) also slightly increased [Ca2+ ]i in the presence of A1899 but not in the presence of PK-THPP. In general [Ca2+ ]i responses to TASK inhibitors, alone or in combination with BKCa inhibitors, were smaller than the [Ca2+ ]i responses evoked by hypoxia. These data confirm that TASK channel inhibition is capable of evoking membrane depolarization and robust voltage-gated Ca2+ -entry but suggest that this, even with concomitant inhibition of BKCa channels, may be insufficient to account fully for the [Ca2+ ]i -response to hypoxia.
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Affiliation(s)
- Peadar B. O'Donohoe
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUnited Kingdom
- Nuffield Department of AnaestheticsOxford University HospitalsOxfordUnited Kingdom
| | - Nicky Huskens
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUnited Kingdom
| | - Philip J. Turner
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUnited Kingdom
| | - Jaideep J. Pandit
- Nuffield Department of AnaestheticsOxford University HospitalsOxfordUnited Kingdom
| | - Keith J. Buckler
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUnited Kingdom
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20
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Gao L, Ortega-Sáenz P, López-Barneo J. Acute oxygen sensing-Role of metabolic specifications in peripheral chemoreceptor cells. Respir Physiol Neurobiol 2018; 265:100-111. [PMID: 30172779 DOI: 10.1016/j.resp.2018.08.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Revised: 08/17/2018] [Accepted: 08/29/2018] [Indexed: 12/30/2022]
Abstract
Acute oxygen sensing is essential for humans under hypoxic environments or pathologic conditions. This is achieved by the carotid body (CB), the key arterial chemoreceptor, along with other peripheral chemoreceptor organs, such as the adrenal medulla (AM). Although it is widely accepted that inhibition of K+ channels in the plasma membrane of CB cells during acute hypoxia results in the activation of cardiorespiratory reflexes, the molecular mechanisms by which the hypoxic signal is detected to modulate ion channel activity are not fully understood. Using conditional knockout mice lacking mitochondrial complex I (MCI) subunit NDUFS2, we have found that MCI generates reactive oxygen species and pyridine nucleotides, which signal K+ channels during acute hypoxia. Comparing the transcriptomes from CB and AM, which are O2-sensitive, with superior cervical ganglion, which is practically O2-insensitive, we have found that CB and AM contain unique metabolic gene expression profiles. The "signature metabolic profile" and their biophysical characteristics could be essential for acute O2 sensing by 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), Madrid, 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), Madrid, 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), Madrid, Spain.
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21
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Rakoczy RJ, Wyatt CN. Acute oxygen sensing by the carotid body: a rattlebag of molecular mechanisms. J Physiol 2018; 596:2969-2976. [PMID: 29214644 PMCID: PMC6068253 DOI: 10.1113/jp274351] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 11/27/2017] [Indexed: 12/14/2022] Open
Abstract
The molecular underpinnings of the oxygen sensitivity of the carotid body Type I cells are becoming better defined as research begins to identify potential interactions between previously separate theories. Nevertheless, the field of oxygen chemoreception still presents the general observer with a bewildering array of potential signalling pathways by which a fall in oxygen levels might initiate Type I cell activation. The purpose of this brief review is to address five of the current oxygen sensing hypotheses: the lactate-Olfr 78 hypothesis of oxygen chemotransduction; the role mitochondrial ATP and metabolism may have in chemotransduction; the AMP-activated protein kinase hypothesis and its current role in oxygen sensing by the carotid body; reactive oxygen species as key transducers in the oxygen sensing cascade; and the mechanisms by which H2 S, reactive oxygen species and haem oxygenase may integrate to provide a rapid oxygen sensing transduction system. Over the previous 15 years several lines of research into acute hypoxic chemotransduction mechanisms have focused on the integration of mitochondrial and membrane signalling. This review places an emphasis on the subplasmalemmal-mitochondrial microenvironment in Type I cells and how theories of acute oxygen sensing are increasingly dependent on functional interaction within this microenvironment.
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Affiliation(s)
- Ryan J. Rakoczy
- Department of Neuroscience, Cell Biology, and PhysiologyWright State University3640 Colonel Glenn HwyDaytonOH45435USA
| | - Christopher N. Wyatt
- Department of Neuroscience, Cell Biology, and PhysiologyWright State University3640 Colonel Glenn HwyDaytonOH45435USA
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22
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Song MS, Park SM, Park JS, Byun JH, Jin HJ, Seo SH, Ryu PD, Lee SY. Kv3.1 and Kv3.4, Are Involved in Cancer Cell Migration and Invasion. Int J Mol Sci 2018; 19:ijms19041061. [PMID: 29614836 PMCID: PMC5979479 DOI: 10.3390/ijms19041061] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2018] [Revised: 03/13/2018] [Accepted: 03/31/2018] [Indexed: 12/27/2022] Open
Abstract
Voltage-gated potassium (Kv) channels, including Kv3.1 and Kv3.4, are known as oxygen sensors, and their function in hypoxia has been well investigated. However, the relationship between Kv channels and tumor hypoxia has yet to be investigated. This study demonstrates that Kv3.1 and Kv3.4 are tumor hypoxia-related Kv channels involved in cancer cell migration and invasion. Kv3.1 and Kv3.4 protein expression in A549 and MDA-MB-231 cells increased in a cell density-dependent manner, and the pattern was similar to the expression patterns of hypoxia-inducible factor-1α (HIF-1α) and reactive oxygen species (ROS) according to cell density, whereas Kv3.3 protein expression did not change in A549 cells with an increase in cell density. The Kv3.1 and Kv3.4 blocker blood depressing substance (BDS) did not affect cell proliferation; instead, BDS inhibited cell migration and invasion. We found that BDS inhibited intracellular pH regulation and extracellular signal-regulated kinase (ERK) activation in A549 cells cultured at a high density, potentially resulting in BDS-induced inhibition of cell migration and invasion. Our data suggest that Kv3.1 and Kv3.4 might be new therapeutic targets for cancer metastasis.
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Affiliation(s)
- Min Seok Song
- Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul 08826, Korea.
| | - Su Min Park
- Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul 08826, Korea.
| | - Jeong Seok Park
- Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul 08826, Korea.
| | - Jin Ho Byun
- Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul 08826, Korea.
| | - Hee Jung Jin
- Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul 08826, Korea.
| | - Seung Hyun Seo
- Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul 08826, Korea.
| | - Pan Dong Ryu
- Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul 08826, Korea.
| | - So Yeong Lee
- Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul 08826, Korea.
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Role of acid-sensing ion channels in hypoxia- and hypercapnia-induced ventilatory responses. PLoS One 2018; 13:e0192724. [PMID: 29474404 PMCID: PMC5825021 DOI: 10.1371/journal.pone.0192724] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Accepted: 01/29/2018] [Indexed: 12/13/2022] Open
Abstract
Previous reports indicate roles for acid-sensing ion channels (ASICs) in both peripheral and central chemoreception, but the contributions of ASICs to ventilatory drive in conscious, unrestrained animals remain largely unknown. We tested the hypotheses that ASICs contribute to hypoxic- and hypercapnic-ventilatory responses. Blood samples taken from conscious, unrestrained mice chronically instrumented with femoral artery catheters were used to assess arterial O2, CO2, and pH levels during exposure to inspired gas mixtures designed to cause isocapnic hypoxemia or hypercapnia. Whole-body plethysmography was used to monitor ventilatory parameters in conscious, unrestrained ASIC1, ASIC2, or ASIC3 knockout (-/-) and wild-type (WT) mice at baseline, during isocapnic hypoxemia and during hypercapnia. Hypercapnia increased respiratory frequency, tidal volume, and minute ventilation in all groups of mice, but there were no differences between ASIC1-/-, ASIC2-/-, or ASIC3-/- and WT. Isocapnic hypoxemia also increased respiratory frequency, tidal volume, and minute ventilation in all groups of mice. Minute ventilation in ASIC2-/- mice during isocapnic hypoxemia was significantly lower compared to WT, but there were no differences in the responses to isocapnic hypoxemia between ASIC1-/- or ASIC3-/- compared to WT. Surprisingly, these findings show that loss of individual ASIC subunits does not substantially alter hypercapnic or hypoxic ventilatory responses.
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Muñoz-Cabello AM, Torres-Torrelo H, Arias-Mayenco I, Ortega-Sáenz P, López-Barneo J. Monitoring Functional Responses to Hypoxia in Single Carotid Body Cells. Methods Mol Biol 2018; 1742:125-137. [PMID: 29330796 DOI: 10.1007/978-1-4939-7665-2_12] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The carotid body is the main arterial chemoreceptor in mammals that mediates the cardiorespiratory reflexes activated by acute hypoxia. Here we describe the protocols followed in our laboratory to study responsiveness to hypoxia of single, enzymatically dispersed, glomus cells monitored by microfluorimetry and the patch-clamp technique.
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Affiliation(s)
- Ana María Muñoz-Cabello
- 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, Madrid, Spain.
| | - Hortensia Torres-Torrelo
- 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, Madrid, Spain
| | - Ignacio Arias-Mayenco
- 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, 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, 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, Madrid, Spain.
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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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26
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Zachar PC, Pan W, Jonz MG. Characterization of ion channels and O 2 sensitivity in gill neuroepithelial cells of the anoxia-tolerant goldfish ( Carassius auratus). J Neurophysiol 2017; 118:3014-3023. [PMID: 28904098 DOI: 10.1152/jn.00237.2017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Revised: 09/07/2017] [Accepted: 09/07/2017] [Indexed: 01/10/2023] Open
Abstract
The neuroepithelial cell (NEC) of the fish gill is an important model for O2 sensing in vertebrates; however, a complete picture of the chemosensory mechanisms in NECs is lacking, and O2 chemoreception in vertebrates that are tolerant to anoxia has not yet been explored. Using whole cell patch-clamp recording, we characterized four types of ion channels in NECs isolated from the anoxia-tolerant goldfish. A Ca2+-dependent K+ current (IKCa) peaked at ~20 mV, was potentiated by increased intracellular Ca2+, and was reduced by 100 μM Cd2+ A voltage-dependent inward current in Ba2+ solution, with peak at 0 mV, confirmed the presence of Ca2+ channels. A voltage-dependent K+ current (IKV) was inhibited by 20 mM tetraethylammonium and 5 mM 4-aminopyridine, revealing a background K+ current (IKB) with open rectification. Mean resting membrane potential of -45.2 ± 11.6 mV did not change upon administration of hypoxia (Po2 = 11 mmHg), nor were any of the K+ currents sensitive to changes in Po2 during whole cell recording. By contrast, when the membrane and cytosol were left undisturbed during fura-2 or FM 1-43 imaging experiments, hypoxia increased intracellular Ca2+ concentration and initiated synaptic vesicle activity. 100 μM Cd2+ and 50 μM nifedipine eliminated uptake of FM 1-43. We conclude that Ca2+ influx via L-type Ca2+ channels is correlated with vesicular activity during hypoxic stimulation. In addition, we suggest that expression of IKCa in gill NECs is species specific and, in goldfish, may contribute to an attenuated response to acute hypoxia.NEW & NOTEWORTHY This study provides the first physiological characterization of oxygen chemoreceptors from an anoxia-tolerant vertebrate. Neuroepithelial cells (NECs) from the gills of goldfish displayed L-type Ca2+ channels and three types of K+ channels, one of which was dependent upon intracellular Ca2+ Although membrane currents were not inhibited by hypoxia during patch-clamp recording, this study is the first to show that NECs with an undisturbed cytosol responded to hypoxia with increased intracellular Ca2+ and synaptic vesicle activity.
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Affiliation(s)
- Peter C Zachar
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | - Wen Pan
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | - Michael G Jonz
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
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Chang AJ. Acute oxygen sensing by the carotid body: from mitochondria to plasma membrane. J Appl Physiol (1985) 2017; 123:1335-1343. [PMID: 28819004 DOI: 10.1152/japplphysiol.00398.2017] [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: 05/02/2017] [Revised: 08/11/2017] [Accepted: 08/12/2017] [Indexed: 12/12/2022] Open
Abstract
Maintaining oxygen homeostasis is crucial to the survival of animals. Mammals respond acutely to changes in blood oxygen levels by modulating cardiopulmonary function. The major sensor of blood oxygen that regulates breathing is the carotid body (CB), a small chemosensory organ located at the carotid bifurcation. When arterial blood oxygen levels drop in hypoxia, neuroendocrine cells in the CB called glomus cells are activated to signal to afferent nerves that project to the brain stem. The mechanism by which hypoxia stimulates CB sensory activity has been the subject of many studies over the past 90 years. Two discrete models emerged that argue for the seat of oxygen sensing to lie either in the plasma membrane or mitochondria of CB cells. Recent studies are bridging the gap between these models by identifying hypoxic signals generated by changes in mitochondrial function in the CB that can be sensed by plasma membrane proteins on glomus cells. The CB is important for physiological adaptation to hypoxia, and its dysfunction contributes to sympathetic hyperactivity in common conditions such as sleep-disordered breathing, chronic heart failure, and insulin resistance. Understanding the basic mechanism of oxygen sensing in the CB could allow us to develop strategies to target this organ for therapy. In this short review, I will describe two historical models of CB oxygen sensing and new findings that are integrating these models.
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Affiliation(s)
- Andy J Chang
- Department of Physiology and Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California
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28
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Hockman D, Burns AJ, Schlosser G, Gates KP, Jevans B, Mongera A, Fisher S, Unlu G, Knapik EW, Kaufman CK, Mosimann C, Zon LI, Lancman JJ, Dong PDS, Lickert H, Tucker AS, Baker CVH. Evolution of the hypoxia-sensitive cells involved in amniote respiratory reflexes. eLife 2017; 6:e21231. [PMID: 28387645 PMCID: PMC5438250 DOI: 10.7554/elife.21231] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2016] [Accepted: 04/07/2017] [Indexed: 01/01/2023] Open
Abstract
The evolutionary origins of the hypoxia-sensitive cells that trigger amniote respiratory reflexes - carotid body glomus cells, and 'pulmonary neuroendocrine cells' (PNECs) - are obscure. Homology has been proposed between glomus cells, which are neural crest-derived, and the hypoxia-sensitive 'neuroepithelial cells' (NECs) of fish gills, whose embryonic origin is unknown. NECs have also been likened to PNECs, which differentiate in situ within lung airway epithelia. Using genetic lineage-tracing and neural crest-deficient mutants in zebrafish, and physical fate-mapping in frog and lamprey, we find that NECs are not neural crest-derived, but endoderm-derived, like PNECs, whose endodermal origin we confirm. We discover neural crest-derived catecholaminergic cells associated with zebrafish pharyngeal arch blood vessels, and propose a new model for amniote hypoxia-sensitive cell evolution: endoderm-derived NECs were retained as PNECs, while the carotid body evolved via the aggregation of neural crest-derived catecholaminergic (chromaffin) cells already associated with blood vessels in anamniote pharyngeal arches.
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Affiliation(s)
- Dorit Hockman
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
- Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
- Department of Molecular and Cell Biology, University of Cape Town, Cape Town, South Africa
| | - Alan J Burns
- Stem Cells and Regenerative Medicine, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
- Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Gerhard Schlosser
- School of Natural Sciences, National University of Ireland, Galway, Ireland
| | - Keith P Gates
- Human Genetics Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, United States
| | - Benjamin Jevans
- Stem Cells and Regenerative Medicine, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
| | - Alessandro Mongera
- Department of Genetics, Max-Planck Institut für Entwicklungsbiologie, Tübingen, Germany
| | - Shannon Fisher
- Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, United States
| | - Gokhan Unlu
- Division of Genetic Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, United States
| | - Ela W Knapik
- Division of Genetic Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, United States
| | - Charles K Kaufman
- Children’s Hospital Boston, Howard Hughes Medical Institute, Harvard Medical School, Boston, United States
| | - Christian Mosimann
- Children’s Hospital Boston, Howard Hughes Medical Institute, Harvard Medical School, Boston, United States
| | - Leonard I Zon
- Children’s Hospital Boston, Howard Hughes Medical Institute, Harvard Medical School, Boston, United States
| | - Joseph J Lancman
- Human Genetics Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, United States
| | - P Duc S Dong
- Human Genetics Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, United States
| | - Heiko Lickert
- Institute of Diabetes and Regeneration Research, Helmholtz Zentrum München, Neuherberg, Germany
| | - Abigail S Tucker
- Department of Craniofacial Development and Stem Cell Biology, King’s College London, London, United Kingdom
| | - Clare V H Baker
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
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29
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Syeda F, Holmes AP, Yu TY, Tull S, Kuhlmann SM, Pavlovic D, Betney D, Riley G, Kucera JP, Jousset F, de Groot JR, Rohr S, Brown NA, Fabritz L, Kirchhof P. PITX2 Modulates Atrial Membrane Potential and the Antiarrhythmic Effects of Sodium-Channel Blockers. J Am Coll Cardiol 2016; 68:1881-1894. [PMID: 27765191 PMCID: PMC5075046 DOI: 10.1016/j.jacc.2016.07.766] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 07/05/2016] [Accepted: 07/20/2016] [Indexed: 12/19/2022]
Abstract
BACKGROUND Antiarrhythmic drugs are widely used to treat patients with atrial fibrillation (AF), but the mechanisms conveying their variable effectiveness are not known. Recent data suggested that paired like homeodomain-2 transcription factor (PITX2) might play an important role in regulating gene expression and electrical function of the adult left atrium (LA). OBJECTIVES After determining LA PITX2 expression in AF patients requiring rhythm control therapy, the authors assessed the effects of Pitx2c on LA electrophysiology and the effect of antiarrhythmic drugs. METHODS LA PITX2 messenger ribonucleic acid (mRNA) levels were measured in 95 patients undergoing thoracoscopic AF ablation. The effects of flecainide, a sodium (Na+)-channel blocker, and d,l-sotalol, a potassium channel blocker, were studied in littermate mice with normal and reduced Pitx2c mRNA by electrophysiological study, optical mapping, and patch clamp studies. PITX2-dependent mechanisms of antiarrhythmic drug action were studied in human embryonic kidney (HEK) cells expressing human Na channels and by modeling human action potentials. RESULTS Flecainide 1 μmol/l was more effective in suppressing atrial arrhythmias in atria with reduced Pitx2c mRNA levels (Pitx2c+/-). Resting membrane potential was more depolarized in Pitx2c+/- atria, and TWIK-related acid-sensitive K+ channel 2 (TASK-2) gene and protein expression were decreased. This resulted in enhanced post-repolarization refractoriness and more effective Na-channel inhibition. Defined holding potentials eliminated differences in flecainide's effects between wild-type and Pitx2c+/- atrial cardiomyocytes. More positive holding potentials replicated the increased effectiveness of flecainide in blocking human Nav1.5 channels in HEK293 cells. Computer modeling reproduced an enhanced effectiveness of Na-channel block when resting membrane potential was slightly depolarized. CONCLUSIONS PITX2 mRNA modulates atrial resting membrane potential and thereby alters the effectiveness of Na-channel blockers. PITX2 and ion channels regulating the resting membrane potential may provide novel targets for antiarrhythmic drug development and companion therapeutics in AF.
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Affiliation(s)
- Fahima Syeda
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Andrew P Holmes
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Ting Y Yu
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom; Physical Sciences of Imaging in the Biomedical Sciences, School of Chemistry, University of Birmingham, Birmingham, United Kingdom
| | - Samantha Tull
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | | | - Davor Pavlovic
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Daniel Betney
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Genna Riley
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Jan P Kucera
- Department of Physiology, University of Bern, Bern, Switzerland
| | - Florian Jousset
- Department of Physiology, University of Bern, Bern, Switzerland
| | - Joris R de Groot
- Heart Center, Department of Cardiology, Academisch Medisch Centrum, Amsterdam, the Netherlands
| | - Stephan Rohr
- Department of Physiology, University of Bern, Bern, Switzerland
| | - Nigel A Brown
- St. George's Hospital Medical School, University of London, London, United Kingdom
| | - Larissa Fabritz
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom; Department of Cardiovascular Medicine, University Hospital Muenster, Muenster, Germany; Atrial Fibrillation NETwork, Muenster, Germany; University Hospitals Birmingham NHS Foundation Trust, Birmingham, United Kingdom
| | - Paulus Kirchhof
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom; Department of Cardiovascular Medicine, University Hospital Muenster, Muenster, Germany; Atrial Fibrillation NETwork, Muenster, Germany; University Hospitals Birmingham NHS Foundation Trust, Birmingham, United Kingdom; Sandwell and West Birmingham Hospitals NHS Trust, Birmingham, United Kingdom.
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30
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Evans AM, Mahmoud AD, Moral-Sanz J, Hartmann S. The emerging role of AMPK in the regulation of breathing and oxygen supply. Biochem J 2016; 473:2561-72. [PMID: 27574022 PMCID: PMC5003690 DOI: 10.1042/bcj20160002] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 04/20/2016] [Accepted: 05/03/2016] [Indexed: 01/25/2023]
Abstract
Regulation of breathing is critical to our capacity to accommodate deficits in oxygen availability and demand during, for example, sleep and ascent to altitude. It is generally accepted that a fall in arterial oxygen increases afferent discharge from the carotid bodies to the brainstem and thus delivers increased ventilatory drive, which restores oxygen supply and protects against hypoventilation and apnoea. However, the precise molecular mechanisms involved remain unclear. We recently identified as critical to this process the AMP-activated protein kinase (AMPK), which is key to the cell-autonomous regulation of metabolic homoeostasis. This observation is significant for many reasons, not least because recent studies suggest that the gene for the AMPK-α1 catalytic subunit has been subjected to natural selection in high-altitude populations. It would appear, therefore, that evolutionary pressures have led to AMPK being utilized to regulate oxygen delivery and thus energy supply to the body in the short, medium and longer term. Contrary to current consensus, however, our findings suggest that AMPK regulates ventilation at the level of the caudal brainstem, even when afferent input responses from the carotid body are normal. We therefore hypothesize that AMPK integrates local hypoxic stress at defined loci within the brainstem respiratory network with an index of peripheral hypoxic status, namely afferent chemosensory inputs. Allied to this, AMPK is critical to the control of hypoxic pulmonary vasoconstriction and thus ventilation-perfusion matching at the lungs and may also determine oxygen supply to the foetus by, for example, modulating utero-placental blood flow.
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Affiliation(s)
- A Mark Evans
- Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, Hugh Robson Building, University of Edinburgh, Edinburgh EH8 9XD, U.K.
| | - Amira D Mahmoud
- Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, Hugh Robson Building, University of Edinburgh, Edinburgh EH8 9XD, U.K
| | - Javier Moral-Sanz
- Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, Hugh Robson Building, University of Edinburgh, Edinburgh EH8 9XD, U.K
| | - Sandy Hartmann
- Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, Hugh Robson Building, University of Edinburgh, Edinburgh EH8 9XD, U.K
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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: 42] [Impact Index Per Article: 5.3] [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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32
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Oxygen-sensing by arterial chemoreceptors: Mechanisms and medical translation. Mol Aspects Med 2016; 47-48:90-108. [DOI: 10.1016/j.mam.2015.12.002] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Accepted: 12/01/2015] [Indexed: 12/30/2022]
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López-Barneo J, González-Rodríguez P, Gao L, Fernández-Agüera MC, Pardal R, Ortega-Sáenz P. Oxygen sensing by the carotid body: mechanisms and role in adaptation to hypoxia. Am J Physiol Cell Physiol 2016; 310:C629-42. [PMID: 26764048 DOI: 10.1152/ajpcell.00265.2015] [Citation(s) in RCA: 89] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Oxygen (O2) is fundamental for cell and whole-body homeostasis. Our understanding of the adaptive processes that take place in response to a lack of O2(hypoxia) has progressed significantly in recent years. The carotid body (CB) is the main arterial chemoreceptor that mediates the acute cardiorespiratory reflexes (hyperventilation and sympathetic activation) triggered by hypoxia. The CB is composed of clusters of cells (glomeruli) in close contact with blood vessels and nerve fibers. Glomus cells, the O2-sensitive elements in the CB, are neuron-like cells that contain O2-sensitive K(+)channels, which are inhibited by hypoxia. This leads to cell depolarization, Ca(2+)entry, and the release of transmitters to activate sensory fibers terminating at the respiratory center. The mechanism whereby O2modulates K(+)channels has remained elusive, although several appealing hypotheses have been postulated. Recent data suggest that mitochondria complex I signaling to membrane K(+)channels plays a fundamental role in acute O2sensing. CB activation during exposure to low Po2is also necessary for acclimatization to chronic hypoxia. CB growth during sustained hypoxia depends on the activation of a resident population of stem cells, which are also activated by transmitters released from the O2-sensitive glomus cells. These advances should foster further studies on the role of CB dysfunction in the pathogenesis of highly prevalent human diseases.
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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, Universidad de Sevilla, Seville, Spain; and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Patricia González-Rodríguez
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío, CSIC, Universidad de Sevilla, Seville, Spain; Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Seville, Spain; and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, 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, Universidad de Sevilla, Seville, Spain; and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - M Carmen Fernández-Agüera
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío, CSIC, Universidad de Sevilla, Seville, Spain; Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Seville, Spain; and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Ricardo Pardal
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío, CSIC, Universidad de Sevilla, Seville, Spain; Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Seville, Spain; and 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, Universidad de Sevilla, Seville, Spain; and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
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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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Chang AJ, Ortega FE, Riegler J, Madison DV, Krasnow MA. Oxygen regulation of breathing through an olfactory receptor activated by lactate. Nature 2015; 527:240-4. [PMID: 26560302 PMCID: PMC4765808 DOI: 10.1038/nature15721] [Citation(s) in RCA: 205] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 08/28/2015] [Indexed: 12/25/2022]
Abstract
Animals have evolved homeostatic responses to changes in oxygen availability that act on different time scales. Although the hypoxia-inducible factor (HIF) transcriptional pathway that controls long term responses to low oxygen (hypoxia) has been established1, the pathway that mediates acute responses to hypoxia in mammals is not well understood. Here we show that the olfactory receptor Olfr78 is highly and selectively expressed in oxygen-sensitive glomus cells of the carotid body, a chemosensory organ at the carotid artery bifurcation that monitors blood oxygen and stimulates breathing within seconds when oxygen declines2. Olfr78 mutants fail to increase ventilation in hypoxia but respond normally to hypercapnia. Glomus cells are present in normal numbers and appear structurally intact, but hypoxia-induced carotid body activity is diminished. Lactate, a metabolite that rapidly accumulates in hypoxia and induces hyperventilation3–6, activates Olfr78 in heterologous expression experiments, induces calcium transients in glomus cells, and stimulates carotid sinus nerve activity through Olfr78. We propose that in addition to its role in olfaction, Olfr78 acts as a hypoxia sensor in the breathing circuit by sensing lactate produced when oxygen levels decline.
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Affiliation(s)
- Andy J Chang
- Department of Biochemistry, Stanford University School of Medicine and Howard Hughes Medical Institute, Stanford, California 94305-5307, USA
| | - Fabian E Ortega
- Department of Biochemistry, Stanford University School of Medicine and Howard Hughes Medical Institute, Stanford, California 94305-5307, USA
| | - Johannes Riegler
- Department of Medicine, Stanford University School of Medicine, Stanford, California 94305, USA
| | - Daniel V Madison
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California 94305, USA
| | - Mark A Krasnow
- Department of Biochemistry, Stanford University School of Medicine and Howard Hughes Medical Institute, Stanford, California 94305-5307, USA
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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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Yokoyama T, Nakamuta N, Kusakabe T, Yamamoto Y. Serotonin-mediated modulation of hypoxia-induced intracellular calcium responses in glomus cells isolated from rat carotid body. Neurosci Lett 2015; 597:149-53. [PMID: 25937361 DOI: 10.1016/j.neulet.2015.04.044] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Revised: 04/17/2015] [Accepted: 04/27/2015] [Indexed: 11/19/2022]
Abstract
In the present study, we examined serotonin (5-HT)-induced intracellular Ca(2+) ([Ca(2+)]i) responses to hypoxia in glomus cells isolated from carotid body (CB) of the rat. 5-HT did not induce any [Ca(2+)]i responses in clustered glomus cells during normoxia (21% O2), whereas, the perfusion of hypoxic solution (1% O2) induced repetitive increases in [Ca(2+)]i in the same specimens. The frequency and magnitude of hypoxia-induced [Ca(2+)]i changes observed in the glomus cells were enhanced in the presence of 5-HT, and this response was inhibited by the 5-HT2 receptor antagonist, ketanserin. Furthermore, RT-PCR analysis detected the expression of 5-HT1A, 5-HT1B, 5-HT1D, 5-HT1F, 5-HT2A, 5-HT2B, 5-HT3A, and 5-HT3B receptor mRNAs in extracts of the CB. These results suggest that 5-HT increases hypoxia-induced [Ca(2+)]i responses in glomus cells. 5-HT may elevate hypoxic responses in glomus cells in order to increase chemosensory activity of the CB.
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Affiliation(s)
- Takuya Yokoyama
- Laboratory of Veterinary Anatomy and Cell Biology, Faculty of Agriculture, Iwate University, Morioka, Japan; Department of Basic Veterinary Science, United Graduate School of Veterinary Science, Gifu University, Gifu, Japan
| | - Nobuaki Nakamuta
- Laboratory of Veterinary Anatomy and Cell Biology, Faculty of Agriculture, Iwate University, Morioka, Japan; Department of Basic Veterinary Science, United Graduate School of Veterinary Science, Gifu University, Gifu, Japan
| | - Tatsumi Kusakabe
- Laboratory for Anatomy and Physiology, Department of Sport and Medical Science, Kokushikan University, Tama, Japan
| | - Yoshio Yamamoto
- Laboratory of Veterinary Anatomy and Cell Biology, Faculty of Agriculture, Iwate University, Morioka, Japan; Department of Basic Veterinary Science, United Graduate School of Veterinary Science, Gifu University, Gifu, Japan.
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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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Pye RL, Dunn EJ, Ricker EM, Jurcsisn JG, Barr BL, Wyatt CN. Acutely Administered Leptin Increases [Ca2+] i and BK Ca Currents But Does Not Alter Chemosensory Behavior in Rat Carotid Body Type I Cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 860:61-7. [PMID: 26303468 DOI: 10.1007/978-3-319-18440-1_8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Obesity related pathologies are the health care crisis of our generation. The fat cell derived adipokine leptin has been shown to be a central stimulant of respiration. Very high levels of leptin, however, are associated with the depressed ventilatory phenotype observed in obesity hypoventilation syndrome. Leptin receptors have been identified on carotid body type I cells but how their activation might influence the physiology of these cells is not known.The acute application of leptin evoked calcium signaling responses in isolated type I cells. Cells increased their Fura 2 ratio by 0.074 ± 0.010 ratio units (n = 39, P < 0.001). Leptin also increased the peak membrane currents in 6 of 9 cells increasing the peak macroscopic currents at +10 mV by 61 ± 14 % (p < 0.02). Leptin administered in the presence of the selective BK(Ca) channel inhibitor Paxilline (0.5 μM) failed to increase membrane currents (n = 5). Interestingly, leptin did not significantly alter the resting membrane potential of isolated type I cells (n = 9) and anoxic/acidic depolarizations were unaffected by leptin (n = 7, n = 6).These data suggest that leptin receptors are functional in type I cells but that their acute activation does not alter chemosensory properties. Future studies will use chronic models of leptin dysregulation.
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Affiliation(s)
- Richard L Pye
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, 3640 Colonel Glenn Hwy, Dayton, OH, 45435, USA
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41
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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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42
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Shin DH, Lin H, Zheng H, Kim KS, Kim JY, Chun YS, Park JW, Nam JH, Kim WK, Zhang YH, Kim SJ. HIF-1α-mediated upregulation of TASK-2 K⁺ channels augments Ca²⁺ signaling in mouse B cells under hypoxia. THE JOURNAL OF IMMUNOLOGY 2014; 193:4924-33. [PMID: 25305321 DOI: 10.4049/jimmunol.1301829] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The general consensus is that immune cells are exposed to physiological hypoxia in vivo (PhyO2, 2-5% P(O2)). However, functional studies of B cells in hypoxic conditions are sparse. Recently, we reported the expression in mouse B cells of TASK-2, a member of pH-sensitive two-pore domain K(+) channels with background activity. In this study, we investigated the response of K(+) channels to sustained PhyO2 (sustained hypoxia [SH], 3% P(O2) for 24 h) in WEHI-231 mouse B cells. SH induced voltage-independent background K(+) conductance (SH-K(bg)) and hyperpolarized the membrane potential. The pH sensitivity and the single-channel conductance of SH-K(bg) were consistent with those of TASK-2. Immunoblotting assay results showed that SH significantly increased plasma membrane expressions of TASK-2. Conversely, SH failed to induce any current following small interfering (si)TASK-2 transfection. Similar hypoxic upregulation of TASK-2 was also observed in splenic primary B cells. Mechanistically, upregulation of TASK-2 by SH was prevented by si hypoxia-inducible factor-1α (HIF-1α) transfection or by YC-1, a pharmacological HIF-1α inhibitor. In addition, TASK-2 current was increased in WEHI-231 cells overexpressed with O2-resistant HIF-1α. Importantly, [Ca(2+)]c increment in response to BCR stimulation was significantly higher in SH-exposed B cells, which was abolished by high K(+)-induced depolarization or by siTASK-2 transfection. The data demonstrate that TASK-2 is upregulated under hypoxia via HIF-1α-dependent manner in B cells. This is functionally important in maintaining the negative membrane potential and providing electrical driving force to control Ca(2+) influx.
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Affiliation(s)
- Dong Hoon Shin
- Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; Division of Natural Medical Sciences, College of Health Science, Chosun University, Gwangju 501-759, Republic of Korea
| | - Haiyue Lin
- Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea
| | - Haifeng Zheng
- Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea
| | - Kyung Su Kim
- Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea
| | - Jin Young Kim
- Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea
| | - Yang Sook Chun
- Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea
| | - Jong Wan Park
- Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; Department of Pharmacology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; and
| | - Joo Hyun Nam
- Channelopathy Research Center, Dongguk University College of Medicine, Goyang 410-773, Republic of Korea
| | - Woo Kyung Kim
- Channelopathy Research Center, Dongguk University College of Medicine, Goyang 410-773, Republic of Korea
| | - Yin Hua Zhang
- Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea
| | - Sung Joon Kim
- Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea;
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Prabhakar NR, Peers C. Gasotransmitter regulation of ion channels: a key step in O2 sensing by the carotid body. Physiology (Bethesda) 2014; 29:49-57. [PMID: 24382871 PMCID: PMC3929115 DOI: 10.1152/physiol.00034.2013] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Carotid bodies detect hypoxia in arterial blood, translating this stimulus into physiological responses via the CNS. It is long established that ion channels are critical to this process. More recent evidence indicates that gasotransmitters exert powerful influences on O2 sensing by the carotid body. Here, we review current understanding of hypoxia-dependent production of gasotransmitters, how they regulate ion channels in the carotid body, and how this impacts carotid body function.
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Affiliation(s)
- Nanduri R Prabhakar
- Institute for Integrative Physiology and Center for Systems Biology of O2 Sensing, Biological Sciences Division, University of Chicago, Chicago, Illinois; and
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44
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Kang D, Wang J, Hogan JO, Vennekens R, Freichel M, White C, Kim D. Increase in cytosolic Ca2+ produced by hypoxia and other depolarizing stimuli activates a non-selective cation channel in chemoreceptor cells of rat carotid body. J Physiol 2014; 592:1975-92. [PMID: 24591572 DOI: 10.1113/jphysiol.2013.266957] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The current model of O2 sensing by carotid body chemoreceptor (glomus) cells is that hypoxia inhibits the outward K(+) current and causes cell depolarization, Ca(2+) influx via voltage-dependent Ca(2+) channels and a rise in intracellular [Ca(2+)] ([Ca(2+)]i). Here we show that hypoxia (<5% O2), in addition to inhibiting the two-pore domain K(+) channels TASK-1/3 (TASK), indirectly activates an ∼20 pS channel in isolated glomus cells. The 20 pS channel was permeable to K(+), Na(+) and Cs(+) but not to Cl(-) or Ca(2+). The 20 pS channel was not sensitive to voltage. Inhibition of TASK by external acid, depolarization of glomus cells with high external KCl (20 mm) or opening of the Ca(2+) channel with FPL64176 activated the 20 pS channel when 1 mm Ca(2+) was present in the external solution. Ca(2+) (10 μm) applied to the cytosolic side of inside-out patches activated the 20 pS channel. The threshold [Ca(2+)]i for activation of the 20 pS channel in cell-attached patches was ∼200 nm. The reversal potential of the 20 pS channel was estimated to be -28 mV. Our results reveal a sequential mechanism in which hypoxia (<5% O2) first inhibits the K(+) conductance and then activates a Na(+)-permeable, non-selective cation channel via depolarization-induced rise in [Ca(2+)]i. Our results suggest that inhibition of K(+) efflux and stimulation of Na(+) influx both contribute to the depolarization of glomus cells during moderate to severe hypoxia.
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Affiliation(s)
- Dawon Kang
- 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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45
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Clanton TL, Hogan MC, Gladden LB. Regulation of cellular gas exchange, oxygen sensing, and metabolic control. Compr Physiol 2013; 3:1135-90. [PMID: 23897683 DOI: 10.1002/cphy.c120030] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cells must continuously monitor and couple their metabolic requirements for ATP utilization with their ability to take up O2 for mitochondrial respiration. When O2 uptake and delivery move out of homeostasis, cells have elaborate and diverse sensing and response systems to compensate. In this review, we explore the biophysics of O2 and gas diffusion in the cell, how intracellular O2 is regulated, how intracellular O2 levels are sensed and how sensing systems impact mitochondrial respiration and shifts in metabolic pathways. Particular attention is paid to how O2 affects the redox state of the cell, as well as the NO, H2S, and CO concentrations. We also explore how these agents can affect various aspects of gas exchange and activate acute signaling pathways that promote survival. Two kinds of challenges to gas exchange are also discussed in detail: when insufficient O2 is available for respiration (hypoxia) and when metabolic requirements test the limits of gas exchange (exercising skeletal muscle). This review also focuses on responses to acute hypoxia in the context of the original "unifying theory of hypoxia tolerance" as expressed by Hochachka and colleagues. It includes discourse on the regulation of mitochondrial electron transport, metabolic suppression, shifts in metabolic pathways, and recruitment of cell survival pathways preventing collapse of membrane potential and nuclear apoptosis. Regarding exercise, the issues discussed relate to the O2 sensitivity of metabolic rate, O2 kinetics in exercise, and influences of available O2 on glycolysis and lactate production.
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Affiliation(s)
- T L Clanton
- Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida, USA.
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46
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Turner PJ, Buckler KJ. Oxygen and mitochondrial inhibitors modulate both monomeric and heteromeric TASK-1 and TASK-3 channels in mouse carotid body type-1 cells. J Physiol 2013; 591:5977-98. [PMID: 24042502 DOI: 10.1113/jphysiol.2013.262022] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In rat arterial chemoreceptors, background potassium channels play an important role in maintaining resting membrane potential and promoting depolarization and excitation in response to hypoxia or acidosis. It has been suggested that these channels are a heterodimer of TASK-1 and TASK-3 based on their similarity to heterologously expressed TASK-1/3 fusion proteins. In this study, we sought to confirm the identity of these channels through germline ablation of Task-1 (Kcnk3) and Task-3 (Kcnk9) in mice. Background K-channels were abundant in carotid body type-1 cells from wild-type mice and comparable to those previously described in rat type-1 cells with a main conductance state of 33 pS. This channel was absent from both Task-1(-/-) and Task-3(-/-) cells. In its place we observed a larger (38 pS) K(+)-channel in Task-1(-/-) cells and a smaller (18 pS) K(+)-channel in Task-3(-/-) cells. None of these channels were observed in Task-1(-/-)/Task-3(-/-) double knock-out mice. We therefore conclude that the predominant background K-channel in wild-type mice is a TASK-1/TASK-3 heterodimer, whereas that in Task-1(-/-) mice is TASK-3 and, conversely, that in Task-3(-/-) mice is TASK-1. All three forms of TASK channel in type-1 cells were inhibited by hypoxia, cyanide and the uncoupler FCCP, but the greatest sensitivity was seen in TASK-1 and TASK-1/TASK-3 channels. In summary, the background K-channel in type-1 cells is predominantly a TASK-1/TASK-3 heterodimer. Although both TASK-1 and TASK-3 are able to couple to the oxygen and metabolism sensing pathways present in type-1 cells, channels containing TASK-1 appear to be more sensitive.
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Affiliation(s)
- Philip J Turner
- K. J. Buckler: Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK.
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47
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Buckler KJ, Turner PJ. Oxygen sensitivity of mitochondrial function in rat arterial chemoreceptor cells. J Physiol 2013; 591:3549-63. [PMID: 23671162 PMCID: PMC3731613 DOI: 10.1113/jphysiol.2013.257741] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The mechanism of oxygen sensing in arterial chemoreceptors is unknown but has often been linked to mitochondrial function. A common criticism of this hypothesis is that mitochondrial function is insensitive to physiological levels of hypoxia. Here we investigate the effects of hypoxia (down to 0.5% O2) on mitochondrial function in neonatal rat type-1 cells. The oxygen sensitivity of mitochondrial [NADH] was assessed by monitoring autofluorescence and increased in hypoxia with a P50 of 15 mm Hg (1 mm Hg = 133.3 Pa) in normal Tyrode or 46 mm Hg in Ca(2+)-free Tyrode. Hypoxia also depolarised mitochondrial membrane potential (m, measured using rhodamine 123) with a P50 of 3.1, 3.3 and 2.8 mm Hg in normal Tyrode, Ca(2+)-free Tyrode and Tyrode containing the Ca(2+) channel antagonist Ni(2+), respectively. In the presence of oligomycin and low carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP; 75 nm) m is maintained by electron transport working against an artificial proton leak. Under these conditions hypoxia depolarised m/inhibited electron transport with a P50 of 5.4 mm Hg. The effects of hypoxia upon cytochrome oxidase activity were investigated using rotenone, myxothiazol, antimycin A, oligomycin, ascorbate and the electron donor tetramethyl-p-phenylenediamine. Under these conditions m is maintained by complex IV activity alone. Hypoxia inhibited cytochrome oxidase activity (depolarised m) with a P50 of 2.6 mm Hg. In contrast hypoxia had little or no effect upon NADH (P50 = 0.3 mm Hg), electron transport or cytochrome oxidase activity in sympathetic neurons. In summary, type-1 cell mitochondria display extraordinary oxygen sensitivity commensurate with a role in oxygen sensing. The reasons for this highly unusual behaviour are as yet unexplained.
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Affiliation(s)
- Keith J Buckler
- Department of Physiology, Anatomy & Genetics, Parks Road, Oxford, UK.
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48
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Roy A, Derakhshan F, Wilson RJA. Stress peptide PACAP engages multiple signaling pathways within the carotid body to initiate excitatory responses in respiratory and sympathetic chemosensory afferents. Am J Physiol Regul Integr Comp Physiol 2013; 304:R1070-84. [PMID: 23594614 DOI: 10.1152/ajpregu.00465.2012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Consistent with a critical role in respiratory and autonomic stress responses, the carotid bodies are strongly excited by pituitary adenylate cyclase-activating polypeptide (PACAP), a neuropeptide implicated in stress responses throughout the sympathetic nervous system. PACAP excites isolated carotid body glomus cells via activation of PAC1 receptors, with one study suggesting PAC1-induced excitation is due entirely to protein kinase A (PKA)-mediated inhibition of TASK channels. However, in other systems, PAC1 is known to be coupled to multiple intracellular signaling pathways, including PKA, phospholipase C (PLC), phospholipase D (PLD), and protein kinase C (PKC), that trigger multiple downstream effectors including increased Ca²⁺ mobilization, inhibition of various K⁺ channels, and activation of nonselective cation channels. This study tests if non-PKA/TASK channel signaling helps mediate the stimulatory effects of PACAP on the carotid body. Using an ex vivo arterially perfused rat carotid body preparation, we show that PACAP-38 stimulates carotid sinus nerve activity in a biphasic manner (peak response, falling to plateau). PKA blocker H-89 only reduced the plateau response (~41%), whereas the TASK-1-like K⁺ channel blocker/transient receptor potential vanilloid 1 channel agonist anandamide only inhibited the peak response (~48%), suggesting involvement of additional pathways. The PLD blocker CAY10594 significantly inhibited both peak and plateau responses. The PLC blocker U73122 decimated both peak and plateau responses. Brefeldin A, a blocker of Epac (cAMP-activated guanine exchange factor, reported to link Gs-coupled receptors with PLC/PLD), also reduced both phases of the response, as did blocking signaling downstream of PLC/PLD with the PKC inhibitors chelerythrine chloride and GF109203X. Suggesting the involvement of non-TASK ion channels in the effects of PACAP, the A-type K⁺ channel blocker 4-aminopyridine, and the putative transient receptor potential channel (TRPC)/T-type calcium channel blocker SKF96365 each significantly inhibited the peak and steady-state responses. These data suggest the stimulatory effect of PACAP-38 on carotid body sensory activity is mediated through multiple signaling pathways: the PLC-PKC pathways predominates, with TRPC and/or T-type channel activation and Kv channel inactivation; only partial involvement is attributable to PKA and PLD activation.
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Affiliation(s)
- Arijit Roy
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada
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49
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Numata T, Ogawa N, Takahashi N, Mori Y. TRP channels as sensors of oxygen availability. Pflugers Arch 2013; 465:1075-85. [DOI: 10.1007/s00424-013-1237-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 01/31/2013] [Accepted: 01/31/2013] [Indexed: 11/28/2022]
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50
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Ortiz FC, Del Rio R, Ebensperger G, Reyes VR, Alcayaga J, Varas R, Iturriaga R. Inhibition of rat carotid body glomus cells TASK-like channels by acute hypoxia is enhanced by chronic intermittent hypoxia. Respir Physiol Neurobiol 2013; 185:600-7. [DOI: 10.1016/j.resp.2012.11.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Revised: 11/26/2012] [Accepted: 11/27/2012] [Indexed: 01/19/2023]
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