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Lactate sensing mechanisms in arterial chemoreceptor cells. Nat Commun 2021; 12:4166. [PMID: 34230483 PMCID: PMC8260783 DOI: 10.1038/s41467-021-24444-7] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 06/08/2021] [Indexed: 12/17/2022] Open
Abstract
Classically considered a by-product of anaerobic metabolism, lactate is now viewed as a fundamental fuel for oxidative phosphorylation in mitochondria, and preferred over glucose by many tissues. Lactate is also a signaling molecule of increasing medical relevance. Lactate levels in the blood can increase in both normal and pathophysiological conditions (e.g., hypoxia, physical exercise, or sepsis), however the manner by which these changes are sensed and induce adaptive responses is unknown. Here we show that the carotid body (CB) is essential for lactate homeostasis and that CB glomus cells, the main oxygen sensing arterial chemoreceptors, are also lactate sensors. Lactate is transported into glomus cells, leading to a rapid increase in the cytosolic NADH/NAD+ ratio. This in turn activates membrane cation channels, leading to cell depolarization, action potential firing, and Ca2+ influx. Lactate also decreases intracellular pH and increases mitochondrial reactive oxygen species production, which further activates glomus cells. Lactate and hypoxia, although sensed by separate mechanisms, share the same final signaling pathway and jointly activate glomus cells to potentiate compensatory cardiorespiratory reflexes. Lactate levels in blood change during hypoxia or exercise, however whether this variable is sensed to evoke adaptive responses is unknown. Here the authors show that oxygen-sensing carotid body cells stimulated by hypoxia are also activated by lactate to potentiate a compensatory ventilatory response.
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Hockman D, Adameyko I, Kaucka M, Barraud P, Otani T, Hunt A, Hartwig AC, Sock E, Waithe D, Franck MCM, Ernfors P, Ehinger S, Howard MJ, Brown N, Reese J, Baker CVH. Striking parallels between carotid body glomus cell and adrenal chromaffin cell development. Dev Biol 2018; 444 Suppl 1:S308-S324. [PMID: 29807017 PMCID: PMC6453021 DOI: 10.1016/j.ydbio.2018.05.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 05/20/2018] [Accepted: 05/20/2018] [Indexed: 12/31/2022]
Abstract
Carotid body glomus cells mediate essential reflex responses to arterial blood hypoxia. They are dopaminergic and secrete growth factors that support dopaminergic neurons, making the carotid body a potential source of patient-specific cells for Parkinson's disease therapy. Like adrenal chromaffin cells, which are also hypoxia-sensitive, glomus cells are neural crest-derived and require the transcription factors Ascl1 and Phox2b; otherwise, their development is little understood at the molecular level. Here, analysis in chicken and mouse reveals further striking molecular parallels, though also some differences, between glomus and adrenal chromaffin cell development. Moreover, histology has long suggested that glomus cell precursors are ‘émigrés’ from neighbouring ganglia/nerves, while multipotent nerve-associated glial cells are now known to make a significant contribution to the adrenal chromaffin cell population in the mouse. We present conditional genetic lineage-tracing data from mice supporting the hypothesis that progenitors expressing the glial marker proteolipid protein 1, presumably located in adjacent ganglia/nerves, also contribute to glomus cells. Finally, we resolve a paradox for the ‘émigré’ hypothesis in the chicken - where the nearest ganglion to the carotid body is the nodose, in which the satellite glia are neural crest-derived, but the neurons are almost entirely placode-derived - by fate-mapping putative nodose neuronal 'émigrés' to the neural crest. Glomus cell precursors express the neuron-specific marker Elavl3/4 (HuC/D). Developing glomus cells express multiple ‘sympathoadrenal' genes. Glomus cell development requires Hand2 and Sox4/11, but not Ret or Tfap2b. Multipotent progenitors with a glial phenotype contribute to glomus cells. Fate-mapping resolves a paradox for the ganglionic 'émigré' hypothesis in birds.
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Affiliation(s)
- Dorit Hockman
- Department of Physiology, Development and Neuroscience, University of Cambridge, Anatomy Building, Downing Street, Cambridge CB2 3DY, United Kingdom; Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Headley Way, Oxford OX3 9DS, United Kingdom; Department of Molecular and Cell Biology, University of Cape Town, Cape Town, South Africa
| | - Igor Adameyko
- Department of Physiology and Pharmacology, Karolinska Institute, S-171 77 Stockholm, Sweden; Center for Brain Research, Medical University Vienna, 1090 Vienna, Austria
| | - Marketa Kaucka
- Department of Physiology and Pharmacology, Karolinska Institute, S-171 77 Stockholm, Sweden
| | - Perrine Barraud
- Department of Physiology, Development and Neuroscience, University of Cambridge, Anatomy Building, Downing Street, Cambridge CB2 3DY, United Kingdom
| | - Tomoki Otani
- Department of Physiology, Development and Neuroscience, University of Cambridge, Anatomy Building, Downing Street, Cambridge CB2 3DY, United Kingdom
| | - Adam Hunt
- Department of Physiology, Development and Neuroscience, University of Cambridge, Anatomy Building, Downing Street, Cambridge CB2 3DY, United Kingdom
| | - Anna C Hartwig
- Institut für Biochemie, Emil-Fischer-Zentrum, Friedrich-Alexander-Universität Erlangen-Nürnberg, Fahrstrasse 17, 91054 Erlangen, Germany
| | - Elisabeth Sock
- Institut für Biochemie, Emil-Fischer-Zentrum, Friedrich-Alexander-Universität Erlangen-Nürnberg, Fahrstrasse 17, 91054 Erlangen, Germany
| | - Dominic Waithe
- Wolfson Imaging Centre, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Headley Way, Oxford OX3 9DS, United Kingdom
| | - Marina C M Franck
- Unit of Molecular Neurobiology, Department of Medical Biochemistry and Biophysics, Karolinska Institute, S-171 77 Stockholm, Sweden
| | - Patrik Ernfors
- Unit of Molecular Neurobiology, Department of Medical Biochemistry and Biophysics, Karolinska Institute, S-171 77 Stockholm, Sweden
| | - Sean Ehinger
- Department of Neurosciences and Program in Neurosciences and Neurodegenerative Diseases, University of Toledo Health Sciences Campus, Toledo, OH 43614, USA
| | - Marthe J Howard
- Department of Neurosciences and Program in Neurosciences and Neurodegenerative Diseases, University of Toledo Health Sciences Campus, Toledo, OH 43614, USA
| | - Naoko Brown
- Depts. of Pediatrics, Cell and Developmental Biology, Vanderbilt University Medical Center, 2215 B Garland Avenue, Nashville, TN 37232, USA
| | - Jeffrey Reese
- Depts. of Pediatrics, Cell and Developmental Biology, Vanderbilt University Medical Center, 2215 B Garland Avenue, Nashville, TN 37232, USA
| | - Clare V H Baker
- Department of Physiology, Development and Neuroscience, University of Cambridge, Anatomy Building, Downing Street, Cambridge CB2 3DY, United Kingdom.
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Hypoxia-regulated catecholamine secretion in chromaffin cells. Cell Tissue Res 2017; 372:433-441. [PMID: 29052004 DOI: 10.1007/s00441-017-2703-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2017] [Accepted: 09/12/2017] [Indexed: 01/21/2023]
Abstract
Adrenal catecholamine (CAT) secretion is a general physiological response of animals to environmental stressors such as hypoxia. This represents an important adaptive mechanism to maintain homeostasis and protect vital organs such as the brain. In adult mammals, CAT secretory responses are triggered by activation of the sympathetic nervous system that supplies cholinergic innervation of adrenomedullary chromaffin cells (AMC) via the splanchnic nerve. In the neonate, the splanchnic innervation of AMC is immature or absent, yet hypoxia stimulates a non-neurogenic CAT secretion that is critical for adaptation to extra-uterine life. This non-neurogenic, hypoxia-sensing mechanism in AMC is gradually lost or suppressed postnatally along a time course that parallels the development of splanchnic innervation. Moreover, denervation of adult AMC results in a gradual return of the direct hypoxia-sensing mechanism. The signaling pathways by which neonatal AMC sense acute hypoxia leading to non-neurogenic CAT secretion and the mechanisms that underlie the re-acquisition of hypoxia-sensing properties by denervated adult AMC, are beginning to be understood. This review will focus on current views concerning the mechanisms responsible for direct acute hypoxia sensing and CAT secretion in perinatal AMC and how they are regulated by innervation during postnatal development. It will also briefly discuss plasticity mechanisms likely to contribute to CAT secretion during exposures to chronic and intermittent hypoxia.
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Gao L, Bonilla-Henao V, García-Flores P, Arias-Mayenco I, Ortega-Sáenz P, López-Barneo J. Gene expression analyses reveal metabolic specifications in acute O 2 -sensing chemoreceptor cells. J Physiol 2017; 595:6091-6120. [PMID: 28718507 DOI: 10.1113/jp274684] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Accepted: 07/03/2017] [Indexed: 01/05/2023] Open
Abstract
KEY POINTS Glomus cells in the carotid body (CB) and chromaffin cells in the adrenal medulla (AM) are essential for reflex cardiorespiratory adaptation to hypoxia. However, the mechanisms whereby these cells detect changes in O2 tension are poorly understood. The metabolic properties of acute O2 -sensing cells have been investigated by comparing the transcriptomes of CB and AM cells, which are O2 -sensitive, with superior cervical ganglion neurons, which are practically O2 -insensitive. In O2 -sensitive cells, we found a characteristic prolyl hydroxylase 3 down-regulation and hypoxia inducible factor 2α up-regulation, as well as overexpression of genes coding for three atypical mitochondrial electron transport subunits and pyruvate carboxylase, an enzyme that replenishes tricarboxylic acid cycle intermediates. In agreement with this observation, the inhibition of succinate dehydrogenase impairs CB acute O2 sensing. The responsiveness of peripheral chemoreceptor cells to acute hypoxia depends on a 'signature metabolic profile'. ABSTRACT Acute O2 sensing is a fundamental property of cells in the peripheral chemoreceptors, e.g. glomus cells in the carotid body (CB) and chromaffin cells in the adrenal medulla (AM), and is necessary for adaptation to hypoxia. These cells contain O2 -sensitive ion channels, which mediate membrane depolarization and transmitter release upon exposure to hypoxia. However, the mechanisms underlying the detection of changes in O2 tension by cells are still poorly understood. Recently, we suggested that CB glomus cells have specific metabolic features that favour the accumulation of reduced quinone and the production of mitochondrial NADH and reactive oxygen species during hypoxia. These signals alter membrane ion channel activity. To investigate the metabolic profile characteristic of acute O2 -sensing cells, we used adult mice to compare the transcriptomes of three cell types derived from common sympathoadrenal progenitors, but exhibiting variable responsiveness to acute hypoxia: CB and AM cells, which are O2 -sensitive (glomus cells > chromaffin cells), and superior cervical ganglion neurons, which are practically O2 -insensitive. In the O2 -sensitive cells, we found a characteristic mRNA expression pattern of prolyl hydroxylase 3/hypoxia inducible factor 2α and up-regulation of several genes, in particular three atypical mitochondrial electron transport subunits and some ion channels. In addition, we found that pyruvate carboxylase, an enzyme fundamental to tricarboxylic acid cycle anaplerosis, is overexpressed in CB glomus cells. We also observed that the inhibition of succinate dehydrogenase impairs CB acute O2 sensing. Our data suggest that responsiveness to acute hypoxia depends on a 'signature metabolic profile' in chemoreceptor cells.
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Affiliation(s)
- Lin Gao
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Victoria Bonilla-Henao
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Paula García-Flores
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Ignacio Arias-Mayenco
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Patricia Ortega-Sáenz
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - José López-Barneo
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
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Fernández-Agüera MC, Gao L, González-Rodríguez P, Pintado CO, Arias-Mayenco I, García-Flores P, García-Pergañeda A, Pascual A, Ortega-Sáenz P, López-Barneo J. Oxygen Sensing by Arterial Chemoreceptors Depends on Mitochondrial Complex I Signaling. Cell Metab 2015; 22:825-37. [PMID: 26437605 DOI: 10.1016/j.cmet.2015.09.004] [Citation(s) in RCA: 140] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2015] [Revised: 07/17/2015] [Accepted: 09/08/2015] [Indexed: 12/30/2022]
Abstract
O2 sensing is essential for mammalian homeostasis. Peripheral chemoreceptors such as the carotid body (CB) contain cells with O2-sensitive K(+) channels, which are inhibited by hypoxia to trigger fast adaptive cardiorespiratory reflexes. How variations of O2 tension (PO2) are detected and the mechanisms whereby these changes are conveyed to membrane ion channels have remained elusive. We have studied acute O2 sensing in conditional knockout mice lacking mitochondrial complex I (MCI) genes. We inactivated Ndufs2, which encodes a protein that participates in ubiquinone binding. Ndufs2-null mice lose the hyperventilatory response to hypoxia, although they respond to hypercapnia. Ndufs2-deficient CB cells have normal functions and ATP content but are insensitive to changes in PO2. Our data suggest that chemoreceptor cells have a specialized succinate-dependent metabolism that induces an MCI state during hypoxia, characterized by the production of reactive oxygen species and accumulation of reduced pyridine nucleotides, which signal neighboring K(+) channels.
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Affiliation(s)
- M Carmen Fernández-Agüera
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Campus Hospital Universitario Virgen del Rocío, Avenida Manuel Siurot, s/n, 41013 Seville, Spain; Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Avenida Sánchez Pizjuan, 4, 41009 Seville, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Campus Hospital Universitario Virgen del Rocío, Avenida Manuel Siurot, s/n, 41013 Seville, Spain
| | - Lin Gao
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Campus Hospital Universitario Virgen del Rocío, Avenida Manuel Siurot, s/n, 41013 Seville, Spain; Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Avenida Sánchez Pizjuan, 4, 41009 Seville, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Campus Hospital Universitario Virgen del Rocío, Avenida Manuel Siurot, s/n, 41013 Seville, Spain
| | - Patricia González-Rodríguez
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Campus Hospital Universitario Virgen del Rocío, Avenida Manuel Siurot, s/n, 41013 Seville, Spain; Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Avenida Sánchez Pizjuan, 4, 41009 Seville, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Campus Hospital Universitario Virgen del Rocío, Avenida Manuel Siurot, s/n, 41013 Seville, Spain
| | - C Oscar Pintado
- Centro de Producción y Experimentación Animal, Universidad de Sevilla, Calle San Fernando, 4, 41004 Seville, Spain
| | - Ignacio Arias-Mayenco
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Campus Hospital Universitario Virgen del Rocío, Avenida Manuel Siurot, s/n, 41013 Seville, Spain; Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Avenida Sánchez Pizjuan, 4, 41009 Seville, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Campus Hospital Universitario Virgen del Rocío, Avenida Manuel Siurot, s/n, 41013 Seville, Spain
| | - Paula García-Flores
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Campus Hospital Universitario Virgen del Rocío, Avenida Manuel Siurot, s/n, 41013 Seville, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Campus Hospital Universitario Virgen del Rocío, Avenida Manuel Siurot, s/n, 41013 Seville, Spain
| | - Antonio García-Pergañeda
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Campus Hospital Universitario Virgen del Rocío, Avenida Manuel Siurot, s/n, 41013 Seville, Spain
| | - Alberto Pascual
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Campus Hospital Universitario Virgen del Rocío, Avenida Manuel Siurot, s/n, 41013 Seville, Spain
| | - Patricia Ortega-Sáenz
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Campus Hospital Universitario Virgen del Rocío, Avenida Manuel Siurot, s/n, 41013 Seville, Spain; Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Avenida Sánchez Pizjuan, 4, 41009 Seville, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Campus Hospital Universitario Virgen del Rocío, Avenida Manuel Siurot, s/n, 41013 Seville, Spain
| | - José López-Barneo
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Campus Hospital Universitario Virgen del Rocío, Avenida Manuel Siurot, s/n, 41013 Seville, Spain; Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Avenida Sánchez Pizjuan, 4, 41009 Seville, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Campus Hospital Universitario Virgen del Rocío, Avenida Manuel Siurot, s/n, 41013 Seville, Spain.
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Livermore S, Zhou Y, Pan J, Yeger H, Nurse CA, Cutz E. Pulmonary neuroepithelial bodies are polymodal airway sensors: Evidence for CO2/H+ sensing. Am J Physiol Lung Cell Mol Physiol 2015; 308:L807-15. [DOI: 10.1152/ajplung.00208.2014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 01/26/2015] [Indexed: 12/24/2022] Open
Abstract
Pulmonary neuroepithelial bodies (NEB) in mammalian lungs are thought to function as airway O2 sensors that release serotonin (5-HT) in response to hypoxia. Direct evidence that NEB cells also respond to airway hypercapnia/acidosis (CO2/H+) is presently lacking. We tested the effects of CO2/H+ alone or in combination with hypoxia on 5-HT release from intact NEB cells in a neonatal hamster lung slice model. For the detection of 5-HT release we used carbon fiber amperometry. Fluorescence Ca2+ imaging method was used to assess CO2/H+-evoked changes in intracellular Ca2+. Exposure to 10 and 20% CO2 or pH 6.8–7.2 evoked significant release of 5-HT with a distinct rise in intracellular Ca2+ in hamster NEBs. This secretory response was dependent on the voltage-gated entry of extracellular Ca2+. Moreover, the combined effects of hypercapnia and hypoxia were additive. Critically, an inhibitor of carbonic anhydrase (CA), acetazolamide, suppressed CO2/H+-mediated 5-HT release. The expression of mRNAs for various CA isotypes, including CAII, was identified in NEB cells from human lung, and protein expression was confirmed by immunohistochemistry using a specific anti-CAII antibody on sections of human and hamster lung. Taken together our findings provide strong evidence for CO2/H+ sensing by NEB cells and support their role as polymodal airway sensors with as yet to be defined functions under normal and disease conditions.
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Affiliation(s)
- S. Livermore
- Division of Pathology, Department of Paediatric Laboratory Medicine, The Research Institute, The Hospital for Sick Children and Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; and
| | - Y. Zhou
- Division of Pathology, Department of Paediatric Laboratory Medicine, The Research Institute, The Hospital for Sick Children and Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; and
| | - J. Pan
- Division of Pathology, Department of Paediatric Laboratory Medicine, The Research Institute, The Hospital for Sick Children and Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; and
| | - H. Yeger
- Division of Pathology, Department of Paediatric Laboratory Medicine, The Research Institute, The Hospital for Sick Children and Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; and
| | - C. A. Nurse
- Department of Biology, McMaster University, Hamilton, Ontario, Canada
| | - E. Cutz
- Division of Pathology, Department of Paediatric Laboratory Medicine, The Research Institute, The Hospital for Sick Children and Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; and
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Salman S, Buttigieg J, Nurse CA. Ontogeny of O2 and CO2//H+ chemosensitivity in adrenal chromaffin cells: role of innervation. ACTA ACUST UNITED AC 2014; 217:673-81. [PMID: 24574383 DOI: 10.1242/jeb.086165] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The adrenal medulla plays a key role in the physiological responses of developing and mature mammals by releasing catecholamines (CAT) during stress. In rodents and humans, the innervation of CAT-producing, adrenomedullary chromaffin cells (AMCs) is immature or absent during early postnatal life, when these cells possess 'direct' hypoxia- and CO2/H(+)-chemosensing mechanisms. During asphyxial stressors at birth, these mechanisms contribute to a CAT surge that is critical for adaptation to extra-uterine life. These direct chemosensing mechanisms regress postnatally, in parallel with maturation of splanchnic innervation. Here, we review the evidence that neurotransmitters released from the splanchnic nerve during innervation activate signaling cascades that ultimately cause regression of direct AMC chemosensitivity to hypoxia and hypercapnia. In particular, we consider the roles of cholinergic and opioid receptor signaling, given that splanchnic nerves release acetylcholine and opiate peptides onto their respective postsynaptic nicotinic and opioid receptors on AMCs. Recent in vivo and in vitro studies in the rat suggest that interactions involving α7 nicotinic acetylcholine receptors (nAChRs), the hypoxia inducible factor (HIF)-2α signaling pathway, protein kinases and ATP-sensitive K(+) (KATP) channels contribute to the selective suppression of hypoxic chemosensitivity. In contrast, interactions involving μ- and/or δ-opiod receptor signaling pathways contribute to the suppression of both hypoxic and hypercapnic chemosensitivity, via regulation of the expression of KATP channels and carbonic anhydrase (CA I and II), respectively. These data suggest that the ontogeny of O2 and CO2/H(+) chemosensitivity in chromaffin cells can be regulated by the tonic release of presynaptic neurotransmitters.
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Affiliation(s)
- Shaima Salman
- Department of Biology, McMaster University, Hamilton, ON, Canada, L8S 4K1
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8
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Salman S, Holloway AC, Nurse CA. Chronic opioids regulate KATP channel subunit Kir6.2 and carbonic anhydrase I and II expression in rat adrenal chromaffin cells via HIF-2α and protein kinase A. Am J Physiol Cell Physiol 2014; 307:C266-77. [PMID: 24898587 DOI: 10.1152/ajpcell.00135.2014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
At birth, asphyxial stressors such as hypoxia and hypercapnia are important physiological stimuli for adrenal catecholamine release that is critical for the proper transition to extrauterine life. We recently showed that chronic opioids blunt chemosensitivity of neonatal rat adrenomedullary chromaffin cells (AMCs) to hypoxia and hypercapnia. This blunting was attributable to increased ATP-sensitive K(+) (KATP) channel and decreased carbonic anhydrase (CA) I and II expression, respectively, and involved μ- and δ-opioid receptor signaling pathways. To address underlying molecular mechanisms, we first exposed an O2- and CO2-sensitive, immortalized rat chromaffin cell line (MAH cells) to combined μ {[d-Arg(2),Ly(4)]dermorphin-(1-4)-amide}- and δ ([d-Pen(2),5,P-Cl-Phe(4)]enkephalin)-opioid agonists (2 μM) for ∼7 days. Western blot and quantitative real-time PCR analysis revealed that chronic opioids increased KATP channel subunit Kir6.2 and decreased CAII expression; both effects were blocked by naloxone and were absent in hypoxia-inducible factor (HIF)-2α-deficient MAH cells. Chronic opioids also stimulated HIF-2α accumulation along a time course similar to Kir6.2. Chromatin immunoprecipitation assays on opioid-treated cells revealed the binding of HIF-2α to a hypoxia response element in the promoter region of the Kir6.2 gene. The opioid-induced regulation of Kir6.2 and CAII was dependent on protein kinase A, but not protein kinase C or calmodulin kinase, activity. Interestingly, a similar pattern of HIF-2α, Kir6.2, and CAII regulation (including downregulation of CAI) was replicated in chromaffin tissue obtained from rat pups born to dams exposed to morphine throughout gestation. Collectively, these data reveal novel mechanisms by which chronic opioids blunt asphyxial chemosensitivity in AMCs, thereby contributing to abnormal arousal responses in the offspring of opiate-addicted mothers.
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Affiliation(s)
- Shaima Salman
- Department of Biology, McMaster University, Hamilton, Ontario, Canada; and
| | - Alison C Holloway
- Division of Reproductive Biology, Department of Obstetrics and Gynecology Division of Reproductive Biology, McMaster University, Hamilton, Ontario, Canada
| | - Colin A Nurse
- Department of Biology, McMaster University, Hamilton, Ontario, Canada; and
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Jyoti S, Tandon S. Hypocapnia leads to enhanced expression of pluripotency and meso-endodermal differentiation genes in mouse embryonic stem cells. Exp Cell Res 2014; 322:389-401. [PMID: 24560741 DOI: 10.1016/j.yexcr.2014.02.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 01/15/2014] [Accepted: 02/07/2014] [Indexed: 11/18/2022]
Abstract
The efficient utilization of embryonic stem cells for applications like cell based therapy, transplantation and drug discovery largely depends upon the culturing conditions of these cells. In this report, we have analyzed gene, protein expression and morphological changes of embryonic stem cells when subjected to lowered CO2 levels i.e. hypocapnia. We studied the quantitative expression of pluripotent genes, Oct3/4, Nanog and Sox2 and genes involved in the differentiation to the three lineages, under varying CO2 levels. Enhanced expression of these genes was seen at cultures maintained at 1.5% CO2 as compared to those maintained at 5% CO2. The cells exposed to hypocapnic conditions when subjected to immunocytochemical analysis stained positive for Oct-3/4, Nanog and Sox2 transcription factors. Flow cytometry and western blot further showed that the pluripotent proteins in the 1.5% CO2 maintained cultures have higher levels of expression as compared to the ES cells at 5% CO2. In addition, there was enhanced differentiation particularly towards the mesodermal and endodermal lineages at cultures maintained and differentiated at 1.5% CO2 at all the time periods analyzed i.e. day 10 (5+5d), 12 (5+7d) and day 15 (5+10d). These results, which we feel are the first of their kind, indicate that lowered CO2 levels seem to be preferred for the maintenance of pluripotency and the subsequent differentiation.
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Affiliation(s)
- Saras Jyoti
- Department of Biotechnology and Bioinformatics, Jaypee University of Information Technology, Waknaghat 173234, India
| | - Simran Tandon
- Department of Biotechnology and Bioinformatics, Jaypee University of Information Technology, Waknaghat 173234, India.
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10
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Salman S, Buttigieg J, Zhang M, Nurse CA. Chronic exposure of neonatal rat adrenomedullary chromaffin cells to opioids in vitro blunts both hypoxia and hypercapnia chemosensitivity. J Physiol 2012; 591:515-29. [PMID: 23148319 DOI: 10.1113/jphysiol.2012.243477] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
At birth, rat adrenomedullary chromaffin cells (AMCs) respond directly to asphyxial stressors such as hypoxia and hypercapnia by triggering catecholamine secretion, which is critical for proper transition to extrauterine life. These non-neurogenic responses are suppressed postnatally in parallel with the development of splanchnic innervation, and reappear following denervation of the adult adrenal gland. To test whether neural factors released from the splanchnic nerve may regulate AMC chemosensitivity, we previously showed that nicotinic agonists in utero and in vitro suppressed hypoxia, but not hypercapnia, sensitivity. Here, we considered the potential role of opiate peptides which are also released from the splanchnic nerve and act via postsynaptic μ-, δ- and -opioid receptors. Treatment of neonatal rat AMC cultures for ∼1 week with μ- and/or δ- (but not ) opioid agonists (2 μm) led to a marked suppression of both hypoxia and hypercapnia sensitivity, as measured by K(+) current inhibition and membrane depolarization; co-incubation with naloxone prevented the effects of combined opioids. The suppression of hypoxia sensitivity was attributable to upregulation of K(ATP) current density and the K(ATP) channel subunit Kir6.2, and was reversed by the K(ATP) channel blocker, glibenclamide. By contrast, suppression of hypercapnia sensitivity was associated with down-regulation of two key mediators of CO(2) sensing, i.e. carbonic anhydrase I and II. Collectively, these studies point to a novel role for opioid receptor signalling in the developmental regulation of chromaffin cell chemosensitivity, and suggest that prenatal exposure to opioid drugs could lead to impaired arousal responses in the neonate.
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Affiliation(s)
- Shaima Salman
- Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada
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Developmental Regulation of Glucosensing in Rat Adrenomedullary Chromaffin Cells: Potential Role of the KATP Channel. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 758:191-8. [DOI: 10.1007/978-94-007-4584-1_27] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
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12
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Functional and transcriptional induction of aquaporin-1 gene by hypoxia; analysis of promoter and role of Hif-1α. PLoS One 2011; 6:e28385. [PMID: 22174795 PMCID: PMC3233559 DOI: 10.1371/journal.pone.0028385] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Accepted: 11/07/2011] [Indexed: 01/11/2023] Open
Abstract
Aquaporin-1 (AQP1) is a water channel that is highly expressed in tissues with rapid O2 transport. It has been reported that this protein contributes to gas permeation (CO2, NO and O2) through the plasma membrane. We show that hypoxia increases Aqp1 mRNA and protein levels in tissues, namely mouse brain and lung, and in cultured cells, the 9L glioma cell line. Stopped-flow light-scattering experiments confirmed an increase in the water permeability of 9L cells exposed to hypoxia, supporting the view that hypoxic Aqp1 up-regulation has a functional role. To investigate the molecular mechanisms underlying this regulatory process, transcriptional regulation was studied by transient transfections of mouse endothelial cells with a 1297 bp 5′ proximal Aqp1 promoter-luciferase construct. Incubation in hypoxia produced a dose- and time-dependent induction of luciferase activity that was also obtained after treatments with hypoxia mimetics (DMOG and CoCl2) and by overexpressing stabilized mutated forms of HIF-1α. Single mutations or full deletions of the three putative HIF binding domains present in the Aqp1 promoter partially reduced its responsiveness to hypoxia, and transfection with Hif-1α siRNA decreased the in vitro hypoxia induction of Aqp1 mRNA and protein levels. Our results indicate that HIF-1α participates in the hypoxic induction of AQP1. However, we also demonstrate that the activation of Aqp1 promoter by hypoxia is complex and multifactorial and suggest that besides HIF-1α other transcription factors might contribute to this regulatory process. These data provide a conceptual framework to support future research on the involvement of AQP1 in a range of pathophysiological conditions, including edema, tumor growth, and respiratory diseases.
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Livermore S, Piskuric NA, Buttigieg J, Zhang M, Nurse CA. Low glucose sensitivity and polymodal chemosensing in neonatal rat adrenomedullary chromaffin cells. Am J Physiol Cell Physiol 2011; 301:C1104-15. [DOI: 10.1152/ajpcell.00170.2011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Glucose is the primary metabolic fuel in mammalian fetuses, yet mammals are incapable of endogenous glucose production until several hours after birth. Thus, when the maternal supply of glucose ceases at birth there is a transient hypoglycemia that elicits a counterregulatory surge in circulating catecholamines. Because the innervation of adrenomedullary chromaffin cells (AMCs) is immature at birth, we hypothesized that neonatal AMCs act as direct glucosensors, a property that could complement their previously established roles as hypoxia and acid hypercapnia sensors. During perforated-patch, whole cell recordings, low glucose depolarized and/or excited a subpopulation of neonatal AMCs; in addition, aglycemia (0 mM glucose) caused inhibition of outward K+ current, blunted by the simultaneous activation of glibenclamide-sensitive KATP channels. Some cells were excited by each of the three metabolic stimuli, i.e., aglycemia, hypoxia (Po2 ∼30 mmHg), and isohydric hypercapnia (10% CO2; pH = 7.4). Using carbon fiber amperometry, aglycemia and hypoglycemia (3 mM glucose) induced robust catecholamine secretion that was sensitive to nickel (50 μM and 2 mM) and the L-type Ca2+ channel blocker nifedipine (10 μM), suggesting involvement of both T-type and L-type voltage-gated Ca2+ channels. Fura-2 measurements of intracellular Ca2+ ([Ca2+] i) revealed that ∼42% of neonatal AMCs responded to aglycemia with a significant rise in [Ca2+] i. Approximately 40% of these cells responded to hypoxia, whereas ∼25% cells responded to both aglycemia and hypoxia. These data suggest that together with hypoxia and acid hypercapnia, low glucose is another important metabolic stimulus that contributes to the vital asphyxia-induced catecholamine surge from AMCs at birth.
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Affiliation(s)
- S. Livermore
- Department of Biology, McMaster University, Hamilton, Ontario, Canada; and
| | - N. A. Piskuric
- Department of Biology, McMaster University, Hamilton, Ontario, Canada; and
| | - J. Buttigieg
- Department of Biology, McMaster University, Hamilton, Ontario, Canada; and
- Department of Biology, University of Regina, Regina, Saskatchewan, Canada
| | - M. Zhang
- Department of Biology, McMaster University, Hamilton, Ontario, Canada; and
| | - C. A. Nurse
- Department of Biology, McMaster University, Hamilton, Ontario, Canada; and
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Developmental and stress-induced remodeling of cell–cell communication in the adrenal medullary tissue. Cell Mol Neurobiol 2011; 30:1425-31. [PMID: 21061165 DOI: 10.1007/s10571-010-9583-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Accepted: 09/02/2010] [Indexed: 12/27/2022]
Abstract
The adrenal medullary tissue contributes to maintain body homeostasis in reaction to stressful environmental changes via the release of catecholamines into the blood circulation in response to splanchnic nerve activation. Accordingly, chromaffin cell stimulus-secretion coupling undergoes temporally restricted periods of anatomo- functional remodeling in response to prevailing hormonal requirements of the organism. The postnatal development of the adrenal medulla and response to stress are remarkable physiological situations in which the stimulus- secretion coupling is critically affected. Catecholamine secretion from rat chromaffin cells is under a dual control involving an incoming initial command arising from the sympathetic nervous system that releases acetylcholine at the splanchnic nerve terminal-chromaffin cell synapses and a local gap junction-mediated intercellular communication. Interestingly, these two communication pathways are functionally interconnected within the gland and exhibit coordinated plasticity mechanisms. This article reviews the physiological and molecular evidence that the adrenal medullary tissue displays anatomical and functional adaptative remodeling of cell–cell communications upon physiological (postnatal development) and/or physiopathological (stress) situations associated with specific needs in circulating catecholamine levels.
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Ortega-Sáenz P, Levitsky KL, Marcos-Almaraz MT, Bonilla-Henao V, Pascual A, López-Barneo J. Carotid body chemosensory responses in mice deficient of TASK channels. ACTA ACUST UNITED AC 2010; 135:379-92. [PMID: 20351062 PMCID: PMC2847918 DOI: 10.1085/jgp.200910302] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Background K+ channels of the TASK family are believed to participate in sensory transduction by chemoreceptor (glomus) cells of the carotid body (CB). However, studies on the systemic CB-mediated ventilatory response to hypoxia and hypercapnia in TASK1- and/or TASK3-deficient mice have yielded conflicting results. We have characterized the glomus cell phenotype of TASK-null mice and studied the responses of individual cells to hypoxia and other chemical stimuli. CB morphology and glomus cell size were normal in wild-type as well as in TASK1−/− or double TASK1/3−/− mice. Patch-clamped TASK1/3-null glomus cells had significantly higher membrane resistance and less hyperpolarized resting potential than their wild-type counterpart. These electrical parameters were practically normal in TASK1−/− cells. Sensitivity of background currents to changes of extracellular pH was drastically diminished in TASK1/3-null cells. In contrast with these observations, responsiveness to hypoxia or hypercapnia of either TASK1−/− or double TASK1/3−/− cells, as estimated by the amperometric measurement of catecholamine release, was apparently normal. TASK1/3 knockout cells showed an enhanced secretory rate in basal (normoxic) conditions compatible with their increased excitability. Responsiveness to hypoxia of TASK1/3-null cells was maintained after pharmacological blockade of maxi-K+ channels. These data in the TASK-null mouse model indicate that TASK3 channels contribute to the background K+ current in glomus cells and to their sensitivity to external pH. They also suggest that, although TASK1 channels might be dispensable for O2/CO2 sensing in mouse CB cells, TASK3 channels (or TASK1/3 heteromers) could mediate hypoxic depolarization of normal glomus cells. The ability of TASK1/3−/− glomus cells to maintain a powerful response to hypoxia even after blockade of maxi-K+ channels, suggests the existence of multiple sensor and/or effector mechanisms, which could confer upon the cells a high adaptability to maintain their chemosensory function.
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Affiliation(s)
- Patricia Ortega-Sáenz
- Instituto de Biomedicina de Sevilla (IBIS), Hospital Universitario Virgen del Rocío, Consejo Superior de Investigaciones Cientificas, Universidad de Sevilla, Sevilla, Spain
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16
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The locus coeruleus and central chemosensitivity. Respir Physiol Neurobiol 2010; 173:264-73. [PMID: 20435170 DOI: 10.1016/j.resp.2010.04.024] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2010] [Revised: 04/23/2010] [Accepted: 04/24/2010] [Indexed: 11/21/2022]
Abstract
The locus coeruleus (LC) lies in the dorsal pons and supplies noradrenergic (NA) input to many regions of the brain, including respiratory control areas. The LC may provide tonic input for basal respiratory drive and is involved in central chemosensitivity since focal acidosis of the region stimulates ventilation and ablation reduces CO(2)-induced increased ventilation. The output of LC is modulated by both serotonergic and glutamatergic inputs. A large percentage of LC neurons are intrinsically activated by hypercapnia. This percentage and the magnitude of their response are highest in young neonates and decrease dramatically after postnatal day P10. The cellular bases for intrinsic chemosensitivity of LC neurons are comprised of multiple factors, primary among them being reduced extracellular and intracellular pH, which inhibit inwardly rectifying and voltage-gated K(+) channels, and activate L-type Ca(2+) channels. Activation of K(Ca) channels in LC neurons may limit their ultimate response to hypercapnia. Finally, the LC mediates central chemosensitivity and contains pH-sensitive neurons in amphibians, suggesting that the LC has a long-standing phylogenetic role in respiratory control.
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Qin Z, Lewis JE, Perry SF. Zebrafish (Danio rerio) gill neuroepithelial cells are sensitive chemoreceptors for environmental CO2. J Physiol 2010; 588:861-72. [PMID: 20051495 DOI: 10.1113/jphysiol.2009.184739] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Adult zebrafish exhibit hyperventilatory responses to absolute environmental CO(2) levels as low as 0.13% ( mmHg), more than an order of magnitude lower than the typical arterial levels (40 mmHg) monitored by the mammalian carotid body. The sensory basis underlying the ability of fish to detect and respond to low ambient CO(2) levels is not clear. Here, we show that the neuroepithelial cells (NECs) of the zebrafish gill, known to sense O(2) levels, also respond to low levels of CO(2). An electrophysiological characterization of this response using both current and voltage clamp protocols revealed that for increasing CO(2) levels, a background K(+) channel was inhibited, resulting in a partial pressure-dependent depolarization of the NEC. To elucidate the signalling pathway underlying K(+) channel inhibition, we used immunocytochemistry to show that these NECs express carbonic anhydrase (CA), an enzyme involved in CO(2) sensing in the mammalian carotid body. Further, the NEC response to CO(2) (magnitude of membrane depolarization and time required to achieve maximal response), under conditions of constant pH, was reduced by 50% by the CA-inhibitor acetazolamide. This suggests that the CO(2) detection mechanism involves an intracellular sensor that is responsive to the rate of acidification associated with the hydration of CO(2) and which does not require a change of extracellular pH. Because some cells that were responsive to increasing also responded to hypoxia with membrane depolarization, the present results demonstrate that a subset of the NECs in the zebrafish gill are bimodal sensors of CO(2) and O(2).
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Affiliation(s)
- Z Qin
- Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, ON, Canada
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18
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Nurse CA, Buttigieg J, Brown S, Holloway AC. Regulation of Oxygen Sensitivity in Adrenal Chromaffin Cells. Ann N Y Acad Sci 2009; 1177:132-9. [DOI: 10.1111/j.1749-6632.2009.05031.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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19
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Pascual A, Romero-Ruiz A, Lopez-Barneo J. Differential proteomic analysis of adrenal gland during postnatal development. Proteomics 2009; 9:2946-54. [PMID: 19415653 DOI: 10.1002/pmic.200800748] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The adrenal glands (AGs) are endocrine organs essential for life. They undergo a fetal to adult developmental maturation process, occurring in rats during the first postnatal month. The molecular modifications underlying these ontogenic changes are essentially unknown. Here we report the results of a comparative proteomic analysis performed on neonatal (Postnatal day 3) versus adult (Postnatal day 30) AGs, searching for proteins with a relative higher abundance at each age. We have identified a subset of proteins with relevant expression in each developmental period using 2-DE and DIGE analysis. The identified proteins belong to several functional categories, including proliferation/differentiation, cell metabolism, and steroid biosynthesis. To study if the changes in the proteome are correlated with changes at the mRNA level, we have randomly selected several proteins with differential expression and measured their relative mRNA levels using quantitative RT-PCR. Cell-cycle regulating proteins (retinoblastoma binding protein 9 and prohibitin) with contrasting effects on proliferation are expressed differentially in neonatal and adult AG. Progesterone metabolizing enzymes, up-regulated in the neonatal gland, might contribute to the hyporesponsiveness of the adrenal cortex characteristic of this developmental period. We have also observed in the adult gland a marked up-regulation of enzymes involved in NAD(P)H production, thus providing the reducing power necessary for steroid hormone biosynthesis.
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Affiliation(s)
- Alberto Pascual
- Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Sevilla, Spain.
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20
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Fernández-Morales JC, Cortés-Gil L, García AG, de Diego AMG. Differences in the quantal release of catecholamines in chromaffin cells of rat embryos and their mothers. Am J Physiol Cell Physiol 2009; 297:C407-18. [DOI: 10.1152/ajpcell.00086.2009] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Studies on the bulk catecholamine release from fetal and neonatal rat adrenals, adrenal slices, or isolated chromaffin cells stimulated with high K+, hypoxia, hypercapnia, or acidosis are available. However, a study analyzing the kinetics of quantal secretion is lacking. We report here such a study in which we compare the quantal release of catecholamines from immature rat embryo chromaffin cells (ECCs) and their mothers' (MCCs). Cell challenging with a strong depolarizing stimulus (75 mM K+) caused spike bursts having the following characteristics. ECCs released more multispike events and wave envelopes than MCCs. This, together with narrower single-spike events, a faster decay, and a threefold smaller quantal size suggest a faster secretory machinery in ECCs. Furthermore, with a milder stimulus (25 mM K+) enhanced Ca2+ entry by L-type Ca2+ channel activator BAY K 8644 did not change the kinetic parameters of single spikes in ECCs; in contrast, augmentation of Ca2+ entry increased spike amplitude and width, quantal size, and decay time in MCCs. This suggests that in mature MCCs, the last exocytotic steps are more tightly regulated than in immature ECCs. Finally, we found that quantal secretion was fully controlled by L-type voltage-dependent Ca2+ channels (VDCCs) in ECCs, whereas both L- and non-L VDCCs (N and PQ) contributed equally to secretion control in MCCs. Our results have the following physiological, pharmacological, and clinical relevance: 1) they may help to better understand the regulation of adrenal catecholamine release in response to stress during fetal life and delivery; 2) if clinically used, L-type Ca2+ channel blockers may augment the incidence of sudden infant death syndrome (SIDS); and 3) so-called Ca2+ promotors or activators of Ca2+ entry through L-type VDCCs may be useful to secure a healthy catecholamine surge upon violent stress during fetal life, at birth, or to prevent the SIDS in neonates at risk.
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Chronic nicotine blunts hypoxic sensitivity in perinatal rat adrenal chromaffin cells via upregulation of KATP channels: role of alpha7 nicotinic acetylcholine receptor and hypoxia-inducible factor-2alpha. J Neurosci 2009; 29:7137-47. [PMID: 19494136 DOI: 10.1523/jneurosci.0544-09.2009] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Fetal nicotine exposure blunts hypoxia-induced catecholamine secretion from neonatal adrenomedullary chromaffin cells (AMCs), providing a link between maternal smoking, abnormal arousal responses, and risk of sudden infant death syndrome. Here, we show that the mechanism is attributable to upregulation of K(ATP) channels via stimulation of alpha7 nicotinic ACh receptors (AChRs). These K(ATP) channels open during hypoxia, thereby suppressing membrane excitability. After in utero exposure to chronic nicotine, neonatal AMCs show a blunted hypoxic sensitivity as determined by inhibition of outward K(+) current, membrane depolarization, rise in cytosolic Ca(2+), and catecholamine secretion. However, hypoxic sensitivity could be unmasked in nicotine-exposed AMCs when glibenclamide, a blocker of K(ATP) channels, was present. Both K(ATP) current density and K(ATP) channel subunit (Kir 6.2) expression were significantly enhanced in nicotine-exposed cells relative to controls. The entire sequence could be reproduced in culture by exposing neonatal rat AMCs or immortalized fetal chromaffin (MAH) cells to nicotine for approximately 1 week, and was prevented by coincubation with selective blockers of alpha7 nicotinic AChRs. Additionally, coincubation with inhibitors of protein kinase C and CaM kinase, but not protein kinase A, prevented the effects of chronic nicotine in vitro. Interestingly, chronic nicotine failed to blunt hypoxia-evoked responses in MAH cells bearing short hairpin knockdown (>90%) of the transcription factor, hypoxia-inducible factor-2alpha (HIF-2alpha), suggesting involvement of the HIF pathway. The therapeutic potential of K(ATP) channel blockers was validated in experiments in which hypoxia-induced neonatal mortality in nicotine-exposed pups was significantly reduced after pretreatment with glibenclamide.
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Branco LGS, Moreira TS, Guyenet PG, Lalley PM, Kawai A, Putnam RW, Chamberlin NL, Saper CB, Gourine AV, Kanamaru M, Homma I. Commentaries on Viewpoint: Central chemoreception is a complex system function that involves multiple brain stem sites. J Appl Physiol (1985) 2009; 106:1467-70. [PMID: 19336680 DOI: 10.1152/japplphysiol.00057.2009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Conrad SC, Nichols NL, Ritucci NA, Dean JB, Putnam RW. Development of chemosensitivity in neurons from the nucleus tractus solitarii (NTS) of neonatal rats. Respir Physiol Neurobiol 2009; 166:4-12. [PMID: 19056522 PMCID: PMC2683148 DOI: 10.1016/j.resp.2008.11.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2008] [Revised: 11/07/2008] [Accepted: 11/07/2008] [Indexed: 11/16/2022]
Abstract
We studied the development of chemosensitivity during the neonatal period in rat nucleus tractus solitarii (NTS) neurons. We determined the percentage of neurons activated by hypercapnia (15% CO(2)) and assessed the magnitude of the response by calculating the chemosensitivity index (CI). There were no differences in the percentage of neurons that were inhibited (9%) or activated (44.8%) by hypercapnia or in the magnitude of the activated response (CI 164+/-4.9%) in NTS neurons from neonatal rats of all ages. To assess the degree of intrinsic chemosensitivity in these neurons we used chemical synaptic block medium and the gap junction blocker carbenoxolone. Chemical synaptic block medium slightly decreased basal firing rate but did not affect the percentage of NTS neurons that responded to hypercapnia at any neonatal age. However, in neonates aged
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Affiliation(s)
- Susan C. Conrad
- Department of Neuroscience, Cell Biology and Physiology, Wright State University School of Medicine, 3640 Colonel Glenn Highway, Dayton, OH 45435
| | - Nicole L. Nichols
- Department of Neuroscience, Cell Biology and Physiology, Wright State University School of Medicine, 3640 Colonel Glenn Highway, Dayton, OH 45435
| | - Nick A. Ritucci
- Department of Neuroscience, Cell Biology and Physiology, Wright State University School of Medicine, 3640 Colonel Glenn Highway, Dayton, OH 45435
| | - Jay B. Dean
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, 12901 Bruce B. Downs Boulevard, Tampa, FL 33612
| | - Robert W. Putnam
- Department of Neuroscience, Cell Biology and Physiology, Wright State University School of Medicine, 3640 Colonel Glenn Highway, Dayton, OH 45435
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Levitsky KL, López-Barneo J. Developmental change of T-type Ca2+ channel expression and its role in rat chromaffin cell responsiveness to acute hypoxia. J Physiol 2009; 587:1917-29. [PMID: 19273573 DOI: 10.1113/jphysiol.2009.168989] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Neonatal chromaffin cells of the adrenal medulla (AM) are intrinsic chemoreceptors that secrete catecholamines in response to hypoxia, thus contributing to fetal adaptation to extrauterine life. In most mammals studied, oxygen sensitivity of AM cells disappears a few days after birth, possibly due to innervation of the adrenal gland by the cholinergic fibres of the splanchnic nerve (approximately postnatal day 7 in the rat). The mechanisms underlying these homeostatic changes in chromaffin cells are unknown. Low voltage-activated, T-type, Ca(2+) channels regulate cell excitability and their expression is up-regulated by hypoxia. Hence, we hypothesized that these channels contribute to the developmental changes in the chemoreceptive properties of AM chromaffin cells. Using electrophysiological, immunocytochemical and molecular biology methodologies we show here that neonatal AM chromaffin cells express T-type Ca(2+) channels (of alpha1H or Ca(v)3.2 sub-type) and that the function of these channels is necessary for catecholamine release in response to acute hypoxia. T-type Ca(2+) channel expression, as well as chromaffin cell responsiveness to hypoxia, decrease with postnatal maturation. Adult chromaffin cell sensitivity to hypoxia reappears after AM denervation in parallel with the recruitment of T-type Ca(2+) channels. These observations indicate that T-type Ca(2+) channels are essential for the acute response of chromaffin cells to hypoxia and help explain the disappearance of O(2) sensitivity in adult AM chromaffin cells. Our results may also be relevant for understanding the pathogenesis of disorders associated with chronic hypoxia or maternal nicotine consumption.
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Affiliation(s)
- Konstantin L Levitsky
- Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío, Universidad de Sevilla, Sevilla, Spain
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25
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Nichols NL, Mulkey DK, Wilkinson KA, Powell FL, Dean JB, Putnam RW. Characterization of the chemosensitive response of individual solitary complex neurons from adult rats. Am J Physiol Regul Integr Comp Physiol 2009; 296:R763-73. [PMID: 19144749 DOI: 10.1152/ajpregu.90769.2008] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We studied the CO(2)/H(+)-chemosensitive responses of individual solitary complex (SC) neurons from adult rats by simultaneously measuring the intracellular pH (pH(i)) and electrical responses to hypercapnic acidosis (HA). SC neurons were recorded using the blind whole cell patch-clamp technique and loading the soma with the pH-sensitive dye pyranine through the patch pipette. We found that SC neurons from adult rats have a lower steady-state pH(i) than SC neurons from neonatal rats. In the presence of chemical and electrical synaptic blockade, adult SC neurons have firing rate responses to HA (percentage of neurons activated or inhibited and the magnitude of response as determined by the chemosensitivity index) that are similar to SC neurons from neonatal rats. They also have a typical response to isohydric hypercapnia, including decreased DeltapH(i), followed by pH(i) recovery, and increased firing rate. Thus, the chemosensitive response of SC neurons from adults is similar to the chemosensitive response of SC neurons from neonatal rats. Because our findings for adults are similar to previously reported values for neurons from neonatal rats, we conclude that intrinsic chemosensitivity is established early in development for SC neurons and is maintained throughout adulthood.
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Affiliation(s)
- Nicole L Nichols
- Dept. of Neuroscience, Cell Biology and Physiology, Wright State Univ., Boonshoft School of Medicine, Dayton, OH 45435, USA
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Buttigieg J, Brown ST, Lowe M, Zhang M, Nurse CA. Functional mitochondria are required for O2but not CO2sensing in immortalized adrenomedullary chromaffin cells. Am J Physiol Cell Physiol 2008; 294:C945-56. [DOI: 10.1152/ajpcell.00495.2007] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Catecholamine (CAT) release from adrenomedullary chromaffin cells (AMC) in response to stressors such as low O2(hypoxia) and elevated CO2/H+is critical during adaptation of the newborn to extrauterine life. Using a surrogate model based on a v -myc immortalized adrenal chromaffin cell line (i.e., MAH cells), combined with genetic perturbation of mitochondrial function, we tested the hypothesis that functional mitochondria are required for O2sensing. Wild-type MAH cells responded to both hypoxia and increased CO2(hypercapnia) with K+current inhibition and membrane depolarization. Additionally, these stimuli caused a rise in cytosolic Ca2+and CAT secretion, determined by fura-2 spectrofluorimetry and carbon fiber amperometry, respectively. In contrast, mitochondria-deficient (ρ0) MAH cells were hypoxia insensitive, although responses to hypercapnia and expression of several markers, including carbonic anhydrase II, remained intact. Rotenone (1 μM), a mitochondrial complex I blocker known to mimic and occlude the effects of hypoxia in primary AMC, was effective in wild-type but not ρ0MAH cells. These data demonstrate that functional mitochondria are involved in hypoxia-sensing by adrenal chromaffin cells. We also show for the first time that, like their neonatal chromaffin cell counterparts, MAH cells are CO2sensors; however, this property is independent of functional mitochondria.
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Buttigieg J, Brown S, Zhang M, Lowe M, Holloway AC, Nurse CA. Chronic nicotine in utero selectively suppresses hypoxic sensitivity in neonatal rat adrenal chromaffin cells. FASEB J 2007; 22:1317-26. [PMID: 18070822 DOI: 10.1096/fj.07-9194com] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Nicotine in cigarette smoke has been linked to several deleterious side effects on the offspring of smoking mothers, including impaired development of the sympathoadrenal system, abnormal arousal reflexes, and sudden infant death syndrome. Catecholamine (CA) release from adrenomedullary chromaffin cells (AMCs) in response to asphyxial stressors, e.g., low O(2) (hypoxia) and elevated CO(2) (hypercapnia), is critical for adaptation to extrauterine life and occurs before splanchnic innervation. Here, we investigated the effects of prenatal nicotine bitartrate exposure on the ability of neonatal (P0) rat AMCs to respond appropriately to asphyxial stressors. Control AMCs isolated from pups born to saline-treated dams displayed typical responses to hypoxia and hypercapnia, including inhibition of outward K(+) current, membrane depolarization, increased cytosolic calcium, and CA secretion. In contrast, P0 AMCs from pups born to nicotine-treated dams showed a marked suppression or loss of hypoxic sensitivity, although hypercapnic sensitivity and the expression of CO(2) markers (i.e., carbonic anhydrase I and II) appeared normal. Moreover, isolated saline-treated P0 AMCs lost their hypoxic sensitivity when grown in culture for approximately 1 wk in the presence of a subsaturating concentration of nicotine base (50 microM), and this effect was abolished by the nicotinic acetylcholine receptor (nAChR) blocker mecamylamine (100 microM). Taken together, these data suggest that the adverse effects of maternal smoking on sympathoadrenal function in the offspring are due in part to a loss or suppression of acute hypoxic sensitivity in adrenal chromaffin cells, triggered by the direct action of nicotine on endogenous nicotinic acetylcholine receptors.
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Affiliation(s)
- Josef Buttigieg
- Department of Biology, McMaster University, 1280 Main St. West, Hamilton, Ontario, Canada L8S 4K1
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García-Fernández M, Ortega-Sáenz P, Castellano A, López-Barneo J. Mechanisms of low-glucose sensitivity in carotid body glomus cells. Diabetes 2007; 56:2893-900. [PMID: 17827405 DOI: 10.2337/db07-0122] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Glucose sensing is essential for the adaptive counterregulatory responses to hypoglycemia. We investigated the mechanisms underlying carotid body (CB) glomus cells activation by low glucose. RESEARCH DESIGN/METHODS AND RESULTS Removal of extracellular glucose elicited a cell secretory response, abolished by blockade of plasma membrane Ca(2+) channels, and a reversible increase in cytosolic Ca(2+) concentration. These data indicated that glucopenia induces transmembrane Ca(2+) influx and transmitter secretion. In patch-clamped glomus cells, exposure to low glucose resulted in inhibition of macroscopic outward K(+) currents and in the generation of a depolarizing receptor potential (DRP). The DRP was abolished upon removal of extracellular Na(+). The membrane-permeable 1-oleoyl-2-acetyl-sn-glycerol induced inward currents of similar characteristics as the current triggered by glucose deficiency. The functional and pharmacological analyses suggest that low glucose activates background cationic Na(+)-permeant channels, possibly of the transient receptor potential C subtype. Rotenone, a drug that occludes glomus cell sensitivity to hypoxia, did not abolish responsiveness to low glucose. The association of Glut2 and glucokinase, characteristic of some high glucose-sensing cells, did not seem to be needed for low glucose detection. CONCLUSIONS Altogether, these data support the view that the CB is a multimodal chemoreceptor with a physiological role in glucose homeostasis.
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Affiliation(s)
- María García-Fernández
- Laboratorio de Investigaciones Biomédicas, Departamento de Fisiología Médica y Biofísica, Hospital Universitario Virgen del Rocío, Universidad de Sevilla, Sevilla, Spain
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Vause C, Bowen E, Spierings E, Durham P. Effect of carbon dioxide on calcitonin gene-related peptide secretion from trigeminal neurons. Headache 2007; 47:1385-97. [PMID: 18052948 PMCID: PMC3138149 DOI: 10.1111/j.1526-4610.2007.00850.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVE The goal of this study was to determine whether the physiological effects of carbon dioxide (CO(2)) involve regulation of CGRP secretion from trigeminal sensory neurons. BACKGROUND The neuropeptide calcitonin gene-related peptide (CGRP) is implicated in the pathophysiology of allergic rhinosinusitis and migraine. Recent clinical evidence supports the use of noninhaled intranasal delivery of 100% CO(2) for treatment of these diseases. Patients report 2 distinct physiological events: first, a short duration stinging or burning sensation within the nasal mucosa, and second, alleviation of primary symptoms. METHODS Primary cultures of rat trigeminal ganglia were utilized to investigate the effects of CO(2) on CGRP release stimulated by a depolarizing stimulus (KCl), capsaicin, nitric oxide, and/or protons. The amount of CGRP secreted into the culture media was determined using a CGRP-specific radioimmunoassay. Intracellular pH and calcium levels were measured in cultured trigeminal neurons in response to CO(2) and stimulatory agents using fluorescent imaging techniques. RESULTS Incubation of primary trigeminal ganglia cultures at pH 6.0 or 5.5 was shown to significantly stimulate CGRP release. Similarly, CO(2) treatment of cultures caused a time-dependent acidification of the media, achieving pH values of 5.5-6 that stimulated CGRP secretion. In addition, KCl, capsaicin, and a nitric oxide donor also caused a significant increase in CGRP release. Interestingly, CO(2) treatment of cultures under isohydric conditions, which prevents extracellular acidification while allowing changes in PCO(2) values, significantly repressed the stimulatory effects of KCl, capsaicin, and nitric oxide on CGRP secretion. We found that CO(2) treatment under isohydric conditions resulted in a decrease in intracellular pH and inhibition of the KCl- and capsaicin-mediated increases in intracellular calcium. CONCLUSIONS Results from this study provide the first evidence of a unique regulatory mechanism by which CO(2) inhibits sensory nerve activation, and subsequent neuropeptide release. Furthermore, the observed inhibitory effect of CO(2) on CGRP secretion likely involves modulation of calcium channel activity and changes in intracellular pH.
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Affiliation(s)
- Carrie Vause
- Missouri State University-Biology, Department of Biology, Springfield, MO 65897, USA
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García-Fernández M, Mejías R, López-Barneo J. Developmental changes of chromaffin cell secretory response to hypoxia studied in thin adrenal slices. Pflugers Arch 2006; 454:93-100. [PMID: 17165070 DOI: 10.1007/s00424-006-0186-y] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2006] [Revised: 10/16/2006] [Accepted: 11/30/2006] [Indexed: 11/30/2022]
Abstract
Adrenomedullary chromaffin (AMC) cells are sensitive to hypoxia in the newborn, but whether this property is lost during postnatal maturation is a matter of controversy. We have developed a rat adrenal slice preparation that allows the study of neonatal and adult AMC cell sensitivity to hypoxia in almost optimal physiological conditions. Responses to secretagogues can be quantitatively and noninvasively monitored in intact cells by amperometry. We have found hypoxia "responsive" (R) and "non-responsive" AMC cells in both neonatal (P0-P8) and juvenile/adult (P12-P60) adrenal glands. However, in the neonate, the proportion of R cells and the magnitude of the response to hypoxia were larger than in the adult. This developmental change of hypoxia responsiveness did not seem to depend on a decrease of the AMC cell's excitability. Spontaneous secretory activity in slices from adult rats was even increased with respect to neonatal animals. The analysis of the secretory events suggests that changes in spike frequency, rather than in vesicle size, account for the increased basal secretion rate in adult AMC cells. Thus, we report a major, but not complete, loss of direct hypoxia sensitivity in adult AMC cells. The adrenal slice appears to be a valuable technique to study acute O(2) sensing and its modifications in pathophysiological states.
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Affiliation(s)
- María García-Fernández
- Laboratorio de Investigaciones Biomédicas, Edificio de Laboratorios, Hospital Universitario Virgen del Rocío, Avenida Manuel Siurot s/n, 41013 Seville, Spain
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Kumar GK, Rai V, Sharma SD, Ramakrishnan DP, Peng YJ, Souvannakitti D, Prabhakar NR. Chronic intermittent hypoxia induces hypoxia-evoked catecholamine efflux in adult rat adrenal medulla via oxidative stress. J Physiol 2006; 575:229-39. [PMID: 16777938 PMCID: PMC1819426 DOI: 10.1113/jphysiol.2006.112524] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Chronic intermittent hypoxia (CIH) augments physiological responses to low partial pressures of O2 in the arterial blood. Adrenal medullae from adult rats, however, are insensitive to direct effects of acute hypoxia. In the present study, we examined whether CIH induces hypoxic sensitivity in the adult rat adrenal medulla and, if so, by what mechanism(s). Experiments were performed on adult male rats exposed to CIH (15 s of 5% O2 followed by 5 min of 21% O2; 9 episodes h(-1); 8 h d(-1); for 3 or 10 days) or to comparable, cumulative durations of continuous hypoxia (CH; 4 h of 7% O2 followed by 20 h of 21% O2 for 1 or 10 days). Noradrenaline (NA) and adrenaline (ADR) effluxes were monitored from ex vivo adrenal medullae. In adrenal medullae of rats exposed to CIH, acute hypoxia evoked robust NA and ADR effluxes, whereas these responses were absent in control rats or in those exposed to CH for 1 or 10 days. Hypercapnia (10% CO2; either acidic, pH 6.8, or isohydric, pH 7.4) was ineffective in eliciting catecholamine (CA) efflux from control, CIH or CH rats. Nicotine (100 microM) evoked NA and ADR effluxes in control rats, and this response was abolished in CIH but not in CH rats. Systemic administration of 2-deoxyglucose depleted ADR content in control rats, and CIH attenuated this response, indicating downregulation of neurally regulated CA secretion. Cytosolic and mitochondrial aconitase enzyme activities decreased in CIH adrenal medullae, suggesting increased generation of superoxide anions. Systemic administration of antioxidants reversed the effect of CIH on the adrenal medulla. Rats exposed to CIH exhibited increased blood pressures and elevated plasma CA, and antioxidants abolished these responses. These observations demonstrate that CIH induces hypoxic sensing in the adult rat adrenal medulla via mechanisms involving increased generation of superoxide anions and suggest that hypoxia-evoked CA efflux from the adrenal medulla contributes, in part, to elevated blood pressure and plasma CA.
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Affiliation(s)
- Ganesh K Kumar
- Department of Biochemistry, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-4935, USA.
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Rico AJ, Prieto-Lloret J, Gonzalez C, Rigual R. Hypoxia and acidosis increase the secretion of catecholamines in the neonatal rat adrenal medulla: an in vitro study. Am J Physiol Cell Physiol 2005; 289:C1417-25. [PMID: 16093283 DOI: 10.1152/ajpcell.00023.2005] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hypoxia elicits catecholamine (CA) secretion from the adrenal medulla (AM) in perinatal animals by acting directly on chromaffin cells. However, whether innervation of the AM, which in the rat occurs in the second postnatal week, suppresses this direct hypoxic response is the subject of debate. Opioid peptides have been proposed as mediators of this suppression. To resolve these controversies, we have compared CA-secretory responses with high external concentrations of K+ ([K+]e) and hypoxia in the AM of neonatal (1- to 2-day-old) and juvenile (14- or 15- and 30-day-old) rats subjected to superfusion in vitro. In addition, we studied the effect of hypercapnic acidosis on the CA-secretory responses in the AM during postnatal development and the possible interaction between acidic and hypoxic stimuli. Responses to high [K+]e were comparable at all ages, but responses to hypoxia and hypercapnic acidosis were maximal in neonatal animals. Suppression of the hypoxic response in the rat AM was not mediated by opioids, because their agonists did not affect the hypoxic CA response. The association of hypercapnic acidosis and hypoxia, mimicking the episodes of asphyxia occurring during delivery, generates a more than additive secretory response in the neonatal rat AM. Our data confirm the loss of the direct sensitivity to hypoxia of the AM in the initial weeks of life and demonstrate a direct response of neonatal AM to hypercapnic acidosis. The synergistic effect of hypoxia and acidosis would explain the CA outburst crucial for adaptation to extrauterine life observed in naturally delivered mammals.
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Affiliation(s)
- A J Rico
- Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética Molecular (IBGM Universidad de Valladolid, Consejo Superior de Investigaciones Científicas, Facultad de Medicina, Calle Ramón y Cajal, 47005 Valladolid, Spain
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