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Felippe ISA, Río RD, Schultz H, Machado BH, Paton JFR. Commonalities and differences in carotid body dysfunction in hypertension and heart failure. J Physiol 2023; 601:5527-5551. [PMID: 37747109 PMCID: PMC10873039 DOI: 10.1113/jp284114] [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: 03/31/2023] [Accepted: 08/29/2023] [Indexed: 09/26/2023] Open
Abstract
Carotid body pathophysiology is associated with many cardiovascular-respiratory-metabolic diseases. This pathophysiology reflects both hyper-sensitivity and hyper-tonicity. From both animal models and human patients, evidence indicates that amelioration of this pathophysiological signalling improves disease states such as a lowering of blood pressure in hypertension, a reduction of breathing disturbances with improved cardiac function in heart failure (HF) and a re-balancing of autonomic activity with lowered sympathetic discharge. Given this, we have reviewed the mechanisms of carotid body hyper-sensitivity and hyper-tonicity across disease models asking whether there is uniqueness related to specific disease states. Our analysis indicates some commonalities and some potential differences, although not all mechanisms have been fully explored across all disease models. One potential commonality is that of hypoperfusion of the carotid body across hypertension and HF, where the excessive sympathetic drive may reduce blood flow in both models and, in addition, lowered cardiac output in HF may potentiate the hypoperfusion state of the carotid body. Other mechanisms are explored that focus on neurotransmitter and signalling pathways intrinsic to the carotid body (e.g. ATP, carbon monoxide) as well as extrinsic molecules carried in the blood (e.g. leptin); there are also transcription factors found in the carotid body endothelium that modulate its activity (Krüppel-like factor 2). The evidence to date fully supports that a better understanding of the mechanisms of carotid body pathophysiology is a fruitful strategy for informing potential new treatment strategies for many cardiovascular, respiratory and metabolic diseases, and this is highly relevant clinically.
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Affiliation(s)
- Igor S. A. Felippe
- Manaaki Manawa – The Centre for Heart Research, Department of Physiology, Faculty of Health & Medical Sciences, University of Auckland, Grafton, Auckland, 1023, New Zealand
| | - Rodrigo Del Río
- Department of Physiology, Laboratory of Cardiorespiratory Control, Pontificia Universidad Católica de Chile, Santiago, Chile
- Centro de Excelencia en Biomedicina de Magallanes (CEBIMA), Universidad de Magallanes, Punta Arenas, Chile
- Mechanisms of Myelin Formation and Repair Laboratory, Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile
- Centro de Envejecimiento y Regeneración (CARE), Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Harold Schultz
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, Nebraska, USA
| | - Benedito H. Machado
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Julian F. R. Paton
- Manaaki Manawa – The Centre for Heart Research, Department of Physiology, Faculty of Health & Medical Sciences, University of Auckland, Grafton, Auckland, 1023, New Zealand
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2
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Seckler JM, Getsy PM, May WJ, Gaston B, Baby SM, Lewis THJ, Bates JN, Lewis SJ. Hypoxia releases S-nitrosocysteine from carotid body glomus cells-relevance to expression of the hypoxic ventilatory response. Front Pharmacol 2023; 14:1250154. [PMID: 37886129 PMCID: PMC10598756 DOI: 10.3389/fphar.2023.1250154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Accepted: 09/13/2023] [Indexed: 10/28/2023] Open
Abstract
We have provided indirect pharmacological evidence that hypoxia may trigger release of the S-nitrosothiol, S-nitroso-L-cysteine (L-CSNO), from primary carotid body glomus cells (PGCs) of rats that then activates chemosensory afferents of the carotid sinus nerve to elicit the hypoxic ventilatory response (HVR). The objective of this study was to provide direct evidence, using our capacitive S-nitrosothiol sensor, that L-CSNO is stored and released from PGCs extracted from male Sprague Dawley rat carotid bodies, and thus further pharmacological evidence for the role of S-nitrosothiols in mediating the HVR. Key findings of this study were that 1) lysates of PGCs contained an S-nitrosothiol with physico-chemical properties similar to L-CSNO rather than S-nitroso-L-glutathione (L-GSNO), 2) exposure of PGCs to a hypoxic challenge caused a significant increase in S-nitrosothiol concentrations in the perfusate to levels approaching 100 fM via mechanisms that required extracellular Ca2+, 3) the dose-dependent increases in minute ventilation elicited by arterial injections of L-CSNO and L-GSNO were likely due to activation of small diameter unmyelinated C-fiber carotid body chemoafferents, 4) L-CSNO, but not L-GSNO, responses were markedly reduced in rats receiving continuous infusion (10 μmol/kg/min, IV) of both S-methyl-L-cysteine (L-SMC) and S-ethyl-L-cysteine (L-SEC), 5) ventilatory responses to hypoxic gas challenge (10% O2, 90% N2) were also due to the activation of small diameter unmyelinated C-fiber carotid body chemoafferents, and 6) the HVR was markedly diminished in rats receiving L-SMC plus L-SEC. This data provides evidence that rat PGCs synthesize an S-nitrosothiol with similar properties to L-CSNO that is released in an extracellular Ca2+-dependent manner by hypoxia.
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Affiliation(s)
- James M. Seckler
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States
| | - Paulina M. Getsy
- Departments of Pediatrics, Case Western Reserve University, Cleveland, OH, United States
| | - Walter J. May
- Department of Pediatrics, University of Virginia, Charlottesville, Virginia, United States
| | - Benjamin Gaston
- Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN, United States
| | | | - Tristan H. J. Lewis
- Departments of Pediatrics, Case Western Reserve University, Cleveland, OH, United States
| | - James N. Bates
- Department of Anesthesia, University of Iowa, Iowa City, IA, United States
| | - Stephen J. Lewis
- Departments of Pediatrics, Case Western Reserve University, Cleveland, OH, United States
- Departments of Pharmacology, Case Western Reserve University, Cleveland, OH, United States
- Functional Electrical Stimulation Center, Case Western Reserve University, Cleveland, OH, United States
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3
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Lazarov NE, Atanasova DY. Neurochemical Anatomy of the Mammalian Carotid Body. ADVANCES IN ANATOMY, EMBRYOLOGY, AND CELL BIOLOGY 2023; 237:63-103. [PMID: 37946078 DOI: 10.1007/978-3-031-44757-0_6] [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
Carotid body (CB) glomus cells in most mammals, including humans, contain a broad diversity of classical neurotransmitters, neuropeptides and gaseous signaling molecules as well as their cognate receptors. Among them, acetylcholine, adenosine triphosphate and dopamine have been proposed to be the main excitatory transmitters in the mammalian CB, although subsequently dopamine has been considered an inhibitory neuromodulator in almost all mammalian species except the rabbit. In addition, co-existence of biogenic amines and neuropeptides has been reported in the glomus cells, thus suggesting that they store and release more than one transmitter in response to natural stimuli. Furthermore, certain metabolic and transmitter-degrading enzymes are involved in the chemotransduction and chemotransmission in various mammals. However, the presence of the corresponding biosynthetic enzyme for some transmitter candidates has not been confirmed, and neuroactive substances like serotonin, gamma-aminobutyric acid and adenosine, neuropeptides including opioids, substance P and endothelin, and gaseous molecules such as nitric oxide have been shown to modulate the chemosensory process through direct actions on glomus cells and/or by producing tonic effects on CB blood vessels. It is likely that the fine balance between excitatory and inhibitory transmitters and their complex interactions might play a more important than suggested role in CB plasticity.
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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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4
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Bock JM, Vungarala S, Karim S, Somers VK. Obstructive Sleep Apnea as a Cardiovascular Risk Factor-Beyond CPAP. Can J Cardiol 2021; 37:756-765. [PMID: 33610689 DOI: 10.1016/j.cjca.2021.01.027] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 01/28/2021] [Accepted: 01/31/2021] [Indexed: 12/14/2022] Open
Abstract
Patients with obstructive sleep apnea (OSA) experience repetitive partial or complete airway collapse during sleep resulting in nocturnal hypoxia-normoxia cycling, and are at increased cardiovascular risk. The number of apneas and hypopneas indexed per hour of sleep (apnea-hypopnea index) along with the associated intermittent hypoxia predict the increased cardiovascular risk; thus, their attenuation or prevention are objectives of OSA therapy. Continuous positive airway pressure (CPAP) is the gold standard treatment for OSA and, when effective, mitigates the apnea-hypopnea index and hypoxemia. As such, it is reasonable to expect CPAP would decrease cardiovascular risk. However, 3 recent randomized clinical trials of CPAP vs usual care did not show any significant effects of CPAP in attenuating incident cardiovascular events in patients with OSA. In this review, we discuss these studies in addition to potential complementary therapeutic options to CPAP (eg, neurostimulation) and conclude with suggested therapeutic targets for future interventional studies (eg, the autonomic nervous system). Although these areas of research are exciting, they have yet to be tested to any similar degree of rigour as CPAP.
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Affiliation(s)
- Joshua M Bock
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota, USA
| | - Soumya Vungarala
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota, USA
| | - Shahid Karim
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota, USA
| | - Virend K Somers
- Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota, USA.
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Bock JM, Hanson BE, Asama TF, Feider AJ, Hanada S, Aldrich AW, Dyken ME, Casey DP. Acute inorganic nitrate supplementation and the hypoxic ventilatory response in patients with obstructive sleep apnea. J Appl Physiol (1985) 2021; 130:87-95. [PMID: 33211592 DOI: 10.1152/japplphysiol.00696.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Patients with obstructive sleep apnea (OSA) have increased cardiovascular disease risk largely attributable to hypertension. Heightened peripheral chemoreflex sensitivity (i.e., exaggerated responsiveness to hypoxia) facilitates hypertension in these patients. Nitric oxide blunts the peripheral chemoreflex, and patients with OSA have reduced nitric oxide bioavailability. We therefore investigated the dose-dependent effects of acute inorganic nitrate supplementation (beetroot juice), an exogenous nitric oxide source, on blood pressure and cardiopulmonary responses to hypoxia in patients with OSA using a randomized, double-blind, placebo-controlled crossover design. Fourteen patients with OSA (53 ± 10 yr, 29.2 ± 5.8 kg/m2, apnea-hypopnea index = 17.8 ± 8.1, 43%F) completed three visits. Resting brachial blood pressure and cardiopulmonary responses to inspiratory hypoxia were measured before, and 2 h after, acute inorganic nitrate supplementation [∼0.10 mmol (placebo), 4.03 mmol (low dose), and 8.06 mmol (high dose)]. Placebo increased neither plasma [nitrate] (30 ± 52 to 52 ± 23 μM, P = 0.26) nor [nitrite] (266 ± 153 to 277 ± 164 nM, P = 0.21); however, both increased following low (29 ± 17 to 175 ± 42 μM, 220 ± 137 to 514 ± 352 nM) and high doses (26 ± 11 to 292 ± 90 μM, 248 ± 155 to 738 ± 427 nM, respectively, P < 0.01 for all). Following placebo, systolic blood pressure increased (120 ± 9 to 128 ± 10 mmHg, P < 0.05), whereas no changes were observed following low (121 ± 11 to 123 ± 8 mmHg, P = 0.19) or high doses (124 ± 13 to 124 ± 9 mmHg, P = 0.96). The peak ventilatory response to hypoxia increased following placebo (3.1 ± 1.2 to 4.4 ± 2.6 L/min, P < 0.01) but not low (4.4 ± 2.4 to 5.4 ± 3.4 L/min, P = 0.11) or high doses (4.3 ± 2.3 to 4.8 ± 2.7 L/min, P = 0.42). Inorganic nitrate did not change the heart rate responses to hypoxia (beverage-by-time P = 0.64). Acute inorganic nitrate supplementation appears to blunt an early-morning rise in systolic blood pressure potentially through suppression of peripheral chemoreflex sensitivity in patients with OSA.NEW & NOTEWORTHY The present study is the first to examine the acute effects of inorganic nitrate supplementation on resting blood pressure and cardiopulmonary responses to hypoxia (e.g., peripheral chemoreflex sensitivity) in patients with obstructive sleep apnea (OSA). Our data indicate inorganic nitrate supplementation attenuates an early-morning rise in systolic blood pressure potentially attributable to blunted peripheral chemoreflex sensitivity. These data show proof-of-concept that inorganic nitrate supplementation could reduce the risk of cardiovascular disease in patients with OSA.
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Affiliation(s)
- Joshua M Bock
- Department of Physical Therapy & Rehabilitation Science, University of Iowa, Iowa City, Iowa
| | - Brady E Hanson
- Department of Physical Therapy & Rehabilitation Science, University of Iowa, Iowa City, Iowa
| | - Thomas F Asama
- Department of Physical Therapy & Rehabilitation Science, University of Iowa, Iowa City, Iowa
| | - Andrew J Feider
- Department of Anesthesia, University of Iowa, Iowa City, Iowa
| | - Satoshi Hanada
- Department of Anesthesia, University of Iowa, Iowa City, Iowa
| | - Aric W Aldrich
- Department of Anesthesia, University of Iowa, Iowa City, Iowa
| | - Mark Eric Dyken
- Department of Neurology, Carver College of Medicine, University of Iowa, Iowa City, Iowa
| | - Darren P Casey
- Department of Physical Therapy & Rehabilitation Science, University of Iowa, Iowa City, Iowa.,Abboud Cardiovascular Research Center, University of Iowa, Iowa City, Iowa.,Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa
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Brognara F, Felippe ISA, Salgado HC, Paton JFR. Autonomic innervation of the carotid body as a determinant of its sensitivity: implications for cardiovascular physiology and pathology. Cardiovasc Res 2020; 117:1015-1032. [PMID: 32832979 DOI: 10.1093/cvr/cvaa250] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 07/01/2020] [Accepted: 08/18/2020] [Indexed: 12/14/2022] Open
Abstract
The motivation for this review comes from the emerging complexity of the autonomic innervation of the carotid body (CB) and its putative role in regulating chemoreceptor sensitivity. With the carotid bodies as a potential therapeutic target for numerous cardiorespiratory and metabolic diseases, an understanding of the neural control of its circulation is most relevant. Since nerve fibres track blood vessels and receive autonomic innervation, we initiate our review by describing the origins of arterial feed to the CB and its unique vascular architecture and blood flow. Arterial feed(s) vary amongst species and, unequivocally, the arterial blood supply is relatively high to this organ. The vasculature appears to form separate circuits inside the CB with one having arterial venous anastomoses. Both sympathetic and parasympathetic nerves are present with postganglionic neurons located within the CB or close to it in the form of paraganglia. Their role in arterial vascular resistance control is described as is how CB blood flow relates to carotid sinus afferent activity. We discuss non-vascular targets of autonomic nerves, their possible role in controlling glomus cell activity, and how certain transmitters may relate to function. We propose that the autonomic nerves sub-serving the CB provide a rapid mechanism to tune the gain of peripheral chemoreflex sensitivity based on alterations in blood flow and oxygen delivery, and might provide future therapeutic targets. However, there remain a number of unknowns regarding these mechanisms that require further research that is discussed.
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Affiliation(s)
- Fernanda Brognara
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, 85 Park Road, Grafton Auckland 1023, New Zealand.,Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Igor S A Felippe
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, 85 Park Road, Grafton Auckland 1023, New Zealand
| | - Helio C Salgado
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Julian F R Paton
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, 85 Park Road, Grafton Auckland 1023, New Zealand
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Muñoz P, Ardiles ÁO, Pérez-Espinosa B, Núñez-Espinosa C, Paula-Lima A, González-Billault C, Espinosa-Parrilla Y. Redox modifications in synaptic components as biomarkers of cognitive status, in brain aging and disease. Mech Ageing Dev 2020; 189:111250. [PMID: 32433996 DOI: 10.1016/j.mad.2020.111250] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 03/05/2020] [Accepted: 04/10/2020] [Indexed: 02/06/2023]
Abstract
Aging is a natural process that includes several changes that gradually make organisms degenerate and die. Harman's theory proposes that aging is a consequence of the progressive accumulation of oxidative modifications mediated by reactive oxygen/nitrogen species, which plays an essential role in the development and progression of many neurodegenerative diseases. This review will focus on how abnormal redox modifications induced by age impair the functionality of neuronal redox-sensitive proteins involved in axonal elongation and guidance, synaptic plasticity, and intercellular communication. We will discuss post-transcriptional regulation of gene expression by microRNAs as a mechanism that controls the neuronal redox state. Finally, we will discuss how some brain-permeant antioxidants from the diet have a beneficial effect on cognition. Taken together, the evidence revised here indicates that oxidative-driven modifications of specific proteins and changes in microRNA expression may be useful biomarkers for aging and neurodegenerative diseases. Also, some specific antioxidant therapies have undoubtedly beneficial neuroprotective effects when administered in the correct doses, in the ideal formulation combination, and during the appropriate therapeutic window. The use of some antioxidants is, therefore, still poorly explored for the treatment of neurodegenerative diseases such as Alzheimer's disease.
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Affiliation(s)
- Pablo Muñoz
- Department of Pathology and Physiology, Medical School, Faculty of Medicine, Universidad de Valparaíso, Valparaíso, Chile; Translational Neurology Center, Faculty of Medicine, Universidad de Valparaíso, Valparaíso, Chile; Biomedical Research Center, Universidad de Valparaíso, Valparaíso, Chile; Thematic Task Force on Healthy Aging, CUECH Research Network.
| | - Álvaro O Ardiles
- Department of Pathology and Physiology, Medical School, Faculty of Medicine, Universidad de Valparaíso, Valparaíso, Chile; Translational Neurology Center, Faculty of Medicine, Universidad de Valparaíso, Valparaíso, Chile; Thematic Task Force on Healthy Aging, CUECH Research Network; Interdisciplinary Center of Neuroscience of Valparaíso, Universidad de Valparaíso, Valparaíso, Chile; Interdisciplinary Center for Health Studies, Universidad de Valparaíso, Valparaíso, Chile
| | - Boris Pérez-Espinosa
- Thematic Task Force on Healthy Aging, CUECH Research Network; Laboratorio biología de la Reproduccion, Departamento Biomédico, Facultad Ciencias de la Salud, Universidad de Antofagasta, Antofagasta, Chile
| | - Cristian Núñez-Espinosa
- Thematic Task Force on Healthy Aging, CUECH Research Network; School of Medicine, Universidad de Magallanes, Punta Arenas, Chile
| | - Andrea Paula-Lima
- Thematic Task Force on Healthy Aging, CUECH Research Network; Institute for Research in Dental Sciences, Faculty of Dentistry; Universidad de Chile, Santiago, Chile; Biomedical Neuroscience Institute (BNI) and Department of Neuroscience, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Christian González-Billault
- Thematic Task Force on Healthy Aging, CUECH Research Network; Laboratory of Cell and Neuronal Dynamics, Department of Biology, Faculty of Sciences, Universidad de Chile, Santiago, Chile; FONDAP Geroscience Center for Brain Health and Metabolism, Santiago, Chile; Buck Institute for Research on Aging, Novato, CA, USA.
| | - Yolanda Espinosa-Parrilla
- Thematic Task Force on Healthy Aging, CUECH Research Network; School of Medicine, Universidad de Magallanes, Punta Arenas, Chile; Laboratory of Molecular Medicine - LMM, Center for Education, Healthcare and Investigation - CADI, University of Magallanes, Punta Arenas, Chile.
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8
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Atanasova DY, Dandov AD, Dimitrov ND, Lazarov NE. Histochemical and immunohistochemical localization of nitrergic structures in the carotid body of spontaneously hypertensive rats. Acta Histochem 2020; 122:151500. [PMID: 31918956 DOI: 10.1016/j.acthis.2019.151500] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 11/25/2019] [Accepted: 12/12/2019] [Indexed: 12/11/2022]
Abstract
The carotid body (CB) is a multipurpose metabolic sensor that acts to initiate cardiorespiratory reflex adjustments to maintain homeostasis of blood-borne chemicals. Emerging evidence suggests that nitric oxide increases the CB chemosensory activity and this enhanced peripheral chemoreflex sensitivity contributes to sympathoexcitation and consequent pathology. The aim of this study was to examine by means of NADPH-diaphorase histochemistry and nitric oxide synthase (NOS) immunohistochemistry the presence and distribution of nitrergic structures in the CB of spontaneously hypertensive rats (SHRs) and to compare their expression patterns to that of age-matched normotensive Wistar rats (NWRs). Histochemistry revealed that the chemosensory glomus cells were NADPH-d-negative but were encircled by fine positive varicosities, which were also dispersed in the stroma around the glomeruli. The NADPH-d-reactive fibers showed the same distributional pattern in the CB of SHRs, however their staining activity was weaker when compared with NWRs. Thin periglomerular, intraglomerular and perivascular varicose fibers, but not glomus or sustentacular cells in the hypertensive CB, constitutively expressed two isoforms of NOS, nNOS and eNOS. In addition, clusters of glomus cells and blood vessels in the CB of SHRs exhibited moderate immunoreactivity for the third known NOS isoenzyme, iNOS. The present study demonstrates that in the hypertensive CB nNOS and eNOS protein expression shows statistically significant down-regulation whereas iNOS expression is up-regulated in the glomic tissue compared to normotensive controls. Our results suggest that impaired NO synthesis could contribute to elevated blood pressure in rats via an increase in chemoexcitation and sympathetic nerve activity in the CB.
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Affiliation(s)
- Dimitrinka Y Atanasova
- Institute of Neurobiology, Bulgarian Academy of Sciences, Sofia, Bulgaria; Department of Anatomy, Faculty of Medicine, Trakia University, Stara Zagora, Bulgaria.
| | - Angel D Dandov
- Department of Anatomy and Histology, Medical University of Sofia, Sofia, Bulgaria.
| | - Nikolay D Dimitrov
- Department of Anatomy, Faculty of Medicine, Trakia University, Stara Zagora, Bulgaria.
| | - Nikolai E Lazarov
- Institute of Neurobiology, Bulgarian Academy of Sciences, Sofia, Bulgaria; Department of Anatomy and Histology, Medical University of Sofia, Sofia, Bulgaria.
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Genetically determined enlargement of carotid body evaluated using computed angiotomography. Respir Physiol Neurobiol 2018; 254:10-15. [PMID: 29627490 DOI: 10.1016/j.resp.2018.04.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Revised: 03/30/2018] [Accepted: 04/04/2018] [Indexed: 11/21/2022]
Abstract
It has recently been established that carotid bodies play a significant role in the regulation of activities of the cardiovascular system as well as in the pathogenesis of arterial hypertension, heart failure and diabetes. Aim of study was to determinate the influence of polymorphisms within genes of the renin-angiotensin-aldosterone system (RAAS) on the volume of the carotid bodies (CB) in patients with hypertension (HTA). The study group consisted of 77 patients with HTA. All patients were genotyped for single-nucleotide polymorphisms of genes coding for: angiotensinogen: rs4762, rs5049, rs5051 and rs699; angiotensin-converting enzyme: rs4343; angiotensin receptor type 1 gene (AGTR1): rs5182 and rs5186; and the aldosterone synthase: rs1799998. The estimation of volumes of CB (VrCB+lCB) was based on computed tomography angiography. Among individuals with essential hypertension certain relationships were documented between rs5182 and rs5186 polymorphisms of AGTR1 gene and rs1799998 polymorphism of CYP11B2 gene on one hand and the volume of carotid bodies on one other. Patients carrying the C alleles within the rs5182 and rs5186 of AGTR1 gene was associated with higher values of VrCB+lCB. The carriage of the T allele in the rs5182 locus of the AGTR1 gene determine lower values of VrCB+lCB. In summary, in patients with HTA a higher volume of CB may be resulted from the presence of specific genotypes in RAAS.
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10
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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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11
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Nunes AR, Holmes AP, Conde SV, Gauda EB, Monteiro EC. Revisiting cAMP signaling in the carotid body. Front Physiol 2014; 5:406. [PMID: 25389406 PMCID: PMC4211388 DOI: 10.3389/fphys.2014.00406] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 10/01/2014] [Indexed: 12/25/2022] Open
Abstract
Chronic carotid body (CB) activation is now recognized as being essential in the development of hypertension and promoting insulin resistance; thus, it is imperative to characterize the chemotransduction mechanisms of this organ in order to modulate its activity and improve patient outcomes. For several years, and although controversial, cyclic adenosine monophosphate (cAMP) was considered an important player in initiating the activation of the CB. However, its relevance was partially displaced in the 90s by the emerging role of the mitochondria and molecules such as AMP-activated protein kinase and O2-sensitive K+ channels. Neurotransmitters/neuromodulators binding to metabotropic receptors are essential to chemotransmission in the CB, and cAMP is central to this process. cAMP also contributes to raise intracellular Ca2+ levels, and is intimately related to the cellular energetic status (AMP/ATP ratio). Furthermore, cAMP signaling is a target of multiple current pharmacological agents used in clinical practice. This review (1) provides an outline on the classical view of the cAMP-signaling pathway in the CB that originally supported its role in the O2/CO2 sensing mechanism, (2) presents recent evidence on CB cAMP neuromodulation and (3) discusses how CB activity is affected by current clinical therapies that modify cAMP-signaling, namely dopaminergic drugs, caffeine (modulation of A2A/A2B receptors) and roflumilast (PDE4 inhibitors). cAMP is key to any process that involves metabotropic receptors and the intracellular pathways involved in CB disease states are likely to involve this classical second messenger. Research examining the potential modification of cAMP levels and/or interactions with molecules associated with CB hyperactivity is currently in its beginning and this review will open doors for future explorations.
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Affiliation(s)
- Ana R Nunes
- CEDOC, Chronic Diseases Research Center, NOVA Medical School/Faculdade de Ciências Médicas, Universidade Nova de Lisboa Lisboa, Portugal
| | - Andrew P Holmes
- School of Clinical and Experimental Medicine, University of Birmingham Birmingham, UK
| | - Sílvia V Conde
- CEDOC, Chronic Diseases Research Center, NOVA Medical School/Faculdade de Ciências Médicas, Universidade Nova de Lisboa Lisboa, Portugal
| | - Estelle B Gauda
- Neonatology Research Laboratories, Department of Pediatrics, Johns Hopkins Medical Institutions, Johns Hopkins University Baltimore, MD, USA
| | - Emília C Monteiro
- CEDOC, Chronic Diseases Research Center, NOVA Medical School/Faculdade de Ciências Médicas, Universidade Nova de Lisboa Lisboa, Portugal
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Gonzalez C, Conde SV, Gallego-Martín T, Olea E, Gonzalez-Obeso E, Ramirez M, Yubero S, Agapito MT, Gomez-Niñno A, Obeso A, Rigual R, Rocher A. Fernando de Castro and the discovery of the arterial chemoreceptors. Front Neuroanat 2014; 8:25. [PMID: 24860435 PMCID: PMC4026738 DOI: 10.3389/fnana.2014.00025] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 04/03/2014] [Indexed: 01/27/2023] Open
Abstract
When de Castro entered the carotid body (CB) field, the organ was considered to be a small autonomic ganglion, a gland, a glomus or glomerulus, or a paraganglion. In his 1928 paper, de Castro concluded: “In sum, the Glomus caroticum is innervated by centripetal fibers, whose trophic centers are located in the sensory ganglia of the glossopharyngeal, and not by centrifugal [efferent] or secretomotor fibers as is the case for glands; these are precisely the facts which lead to suppose that the Glomus caroticum is a sensory organ.” A few pages down, de Castro wrote: “The Glomus represents an organ with multiple receptors furnished with specialized receptor cells like those of other sensory organs [taste buds?]…As a plausible hypothesis we propose that the Glomus caroticum represents a sensory organ, at present the only one in its kind, dedicated to capture certain qualitative variations in the composition of blood, a function that, possibly by a reflex mechanism would have an effect on the functional activity of other organs… Therefore, the sensory fiber would not be directly stimulated by blood, but via the intermediation of the epithelial cells of the organ, which, as their structure suggests, possess a secretory function which would participate in the stimulation of the centripetal fibers.” In our article we will recreate the experiments that allowed Fernando de Castro to reach this first conclusion. Also, we will scrutinize the natural endowments and the scientific knowledge that drove de Castro to make the triple hypotheses: the CB as chemoreceptor (variations in blood composition), as a secondary sensory receptor which functioning involves a chemical synapse, and as a center, origin of systemic reflexes. After a brief account of the systemic reflex effects resulting from the CB stimulation, we will complete our article with a general view of the cellular-molecular mechanisms currently thought to be involved in the functioning of this arterial chemoreceptor.
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Affiliation(s)
- Constancio Gonzalez
- Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid Valladolid, España ; CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Facultad de Medicina, Universidad de Valladolid Valladolid, España
| | - Silvia V Conde
- Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid Valladolid, España ; CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Facultad de Medicina, Universidad de Valladolid Valladolid, España
| | - Teresa Gallego-Martín
- Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid Valladolid, España ; CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Facultad de Medicina, Universidad de Valladolid Valladolid, España
| | - Elena Olea
- Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid Valladolid, España ; CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Facultad de Medicina, Universidad de Valladolid Valladolid, España
| | - Elvira Gonzalez-Obeso
- Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid Valladolid, España ; CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Facultad de Medicina, Universidad de Valladolid Valladolid, España
| | - Maria Ramirez
- Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid Valladolid, España ; CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Facultad de Medicina, Universidad de Valladolid Valladolid, España
| | - Sara Yubero
- Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid Valladolid, España ; CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Facultad de Medicina, Universidad de Valladolid Valladolid, España
| | - Maria T Agapito
- Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid Valladolid, España ; CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Facultad de Medicina, Universidad de Valladolid Valladolid, España
| | - Angela Gomez-Niñno
- Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid Valladolid, España ; CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Facultad de Medicina, Universidad de Valladolid Valladolid, España
| | - Ana Obeso
- Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid Valladolid, España ; CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Facultad de Medicina, Universidad de Valladolid Valladolid, España
| | - Ricardo Rigual
- Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid Valladolid, España ; CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Facultad de Medicina, Universidad de Valladolid Valladolid, España
| | - Asunción Rocher
- Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética Molecular, Consejo Superior de Investigaciones Científicas, Universidad de Valladolid Valladolid, España ; CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Facultad de Medicina, Universidad de Valladolid Valladolid, España
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Abstract
Mammalian carotid bodies are the main peripheral arterial chemoreceptors, strategically located at the bifurcation of the common carotid artery. When stimulated these receptors initiate compensatory respiratory and cardiovascular reflexes to maintain homeostasis. Thus, in response to low oxygen (hypoxia) or increased CO2/H(+) (acid hypercapnia), chemoreceptor type I cells depolarize and release excitatory neurotransmitters, such as ATP, which stimulate postsynaptic P2X2/3 receptors on afferent nerve terminals. The afferent discharge is shaped by autocrine and paracrine mechanisms involving both excitatory and inhibitory neuromodulators such as adenosine, serotonin (5-HT), GABA and dopamine. Recent evidence suggests that paracrine activation of P2Y2 receptors on adjacent glia-like type II cells may help boost the ATP signal via the opening of pannexin-1 channels. The presence of an inhibitory efferent innervation, mediated by release of nitric oxide, provides additional control of the afferent discharge. The broad array of neuromodulators and their receptors appears to endow the carotid body with a remarkable plasticity, most apparent during natural and pathophysiological conditions associated with chronic sustained and intermittent hypoxia.
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Affiliation(s)
- Colin A Nurse
- Department of Biology, McMaster University, 1280 Main St. West, Hamilton, Ontario, L8S 4K1, Canada
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Retamal MA. Connexin and Pannexin hemichannels are regulated by redox potential. Front Physiol 2014; 5:80. [PMID: 24611056 PMCID: PMC3933782 DOI: 10.3389/fphys.2014.00080] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Accepted: 02/08/2014] [Indexed: 01/28/2023] Open
Abstract
Connexins (Cxs) and Pannexins (Panxs) are two non-related protein families, having both the property to form hemichannels at the plasma membrane. There are 21 genes coding for different Cx based proteins and only 3 for Panx. Under physiological conditions, these hemichannels (Cxs and Panxs) present a low open probability, but when open, they allow the release of signaling molecules to the extracellular space. However, under pathological conditions, these hemichannels increase their open probability, inducing important lysis of metabolites, and ionic imbalance, which in turn induce the massive entry of Ca+2 to the cell. Actually, it is well recognized that Cxs and Panxs based channels play an important role in several diseases and -in many cases- this is associated with an aberrant hemichannel opening. Hemichannel opening and closing are controlled by a plethora of signaling including changes of the voltage plasma membrane, protein-protein interactions, and several posttranslational modifications, including protein cleavage, phosphorylation, glycosylation, hydroxylation and S-nitrosylation, among others. In particular, it has been recently shown that the cellular redox status modulates the opening/closing and permeability of at least Cx43, Cx46, and Panx1 hemichannels. Thus, for example, the gaseous transmitter nitric oxide (NO) can induce the S-nitrosylation of these proteins modulating in turn several of their properties. The reason is that the redox status of a cell is fundamental to set their response to the environment and also plays an important role in several pathologies. In this review, I will discuss how NO and other molecules associated with redox signaling modulate Cxs and Panx hemichannels properties.
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Affiliation(s)
- Mauricio A Retamal
- Facultad de Medicina Clínica Alemana, Centro de Fisiología Celular e Integrativa, Universidad del Desarrollo Santiago, Chile
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Abstract
The pannexins (Panxs) are a family of chordate proteins homologous to the invertebrate gap junction forming proteins named innexins. Three distinct Panx paralogs (Panx1, Panx2, and Panx3) are shared among the major vertebrate phyla, but they appear to have suppressed (or even lost) their ability to directly couple adjacent cells. Connecting the intracellular and extracellular compartments is now widely accepted as Panx's primary function, facilitating the passive movement of ions and small molecules along electrochemical gradients. The tissue distribution of the Panxs ranges from pervasive to very restricted, depending on the paralog, and are often cell type-specific and/or developmentally regulated within any given tissue. In recent years, Panxs have been implicated in an assortment of physiological and pathophysiological processes, particularly with respect to ATP signaling and inflammation, and they are now considered to be a major player in extracellular purinergic communication. The following is a comprehensive review of the Panx literature, exploring the historical events leading up to their discovery, outlining our current understanding of their biochemistry, and describing the importance of these proteins in health and disease.
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Affiliation(s)
- Stephen R Bond
- Genome Technology Branch, Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health Bethesda, MD, USA ; Department of Cellular and Physiological Science, Life Sciences Institute, University of British Columbia Vancouver, BC, Canada
| | - Christian C Naus
- Department of Cellular and Physiological Science, Life Sciences Institute, University of British Columbia Vancouver, BC, Canada
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Lowe M, Park SJ, Nurse CA, Campanucci VA. Purinergic stimulation of carotid body efferent glossopharyngeal neurones increases intracellular Ca2+ and nitric oxide production. Exp Physiol 2013; 98:1199-212. [PMID: 23525247 DOI: 10.1113/expphysiol.2013.072058] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The mammalian carotid body (CB) is a peripheral chemosensory organ that controls ventilation and is innervated by both afferent and efferent nerve fibres. The afferent pathway is stimulated by chemoexcitants, such as hypoxia, hypercapnia and acidosis. The efferent pathway causes inhibition of the sensory discharge via release of NO that originates mainly from neuronal nitric oxide synthase (nNOS)-positive autonomic neurones within the glossopharyngeal nerve (GPN). Recent studies in the rat indicate that these inhibitory GPN neurones and their processes express purinergic P2X receptors and can be activated by ATP, a key excitatory CB neurotransmitter. Here we tested the hypothesis that purinergic agonists stimulate a rise in [Ca(2+)]i, leading to nNOS activation and NO production in isolated GPN neurones, using the fluorescent probes fura-2 and 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM DA), respectively. ATP caused a dose-dependent increase in [Ca(2+)]i in GPN neurones (EC50 ≈ 1.92 μm) that was markedly inhibited by a combination of 100 μm suramin (a non-specific P2X blocker) and 100 nm Brilliant Blue G (a selective P2X7 blocker). ATP also stimulated NO production in GPN neurones, as revealed by an increase in DAF fluorescence; this NO signal was inhibited by purinergic blockers, chelators of extracellular Ca(2+), the nNOS inhibitor l-NAME and the NO scavenger carboxy-PTIO. The P2X2/3 and P2X7 agonists α,β,-methylene ATP and benzoyl ATP mimicked the effects of ATP. Taken together, these data indicate that ATP may contribute to negative feedback inhibition of CB sensory discharge via purinergic stimulation of NO production in efferent fibres.
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Affiliation(s)
- Michael Lowe
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
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Piskuric NA, Nurse CA. Expanding role of ATP as a versatile messenger at carotid and aortic body chemoreceptors. J Physiol 2012; 591:415-22. [PMID: 23165772 DOI: 10.1113/jphysiol.2012.234377] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
In mammals, peripheral arterial chemoreceptors monitor blood chemicals (e.g. O(2), CO(2), H(+), glucose) and maintain homeostasis via initiation of respiratory and cardiovascular reflexes. Whereas chemoreceptors in the carotid bodies (CBs), located bilaterally at the carotid bifurcation, control primarily respiratory functions, those in the more diffusely distributed aortic bodies (ABs) are thought to regulate mainly cardiovascular functions. Functionally, CBs sense partial pressure of O(2) ( ), whereas ABs are considered sensors of O(2) content. How these organs, with essentially a similar complement of chemoreceptor cells, differentially process these two different types of signals remains enigmatic. Here, we review evidence that implicates ATP as a central mediator during information processing in the CB. Recent data allow an integrative view concerning its interactions at purinergic P2X and P2Y receptors within the chemosensory complex that contains elements of a 'quadripartite synapse'. We also discuss recent studies on the cellular physiology of ABs located near the aortic arch, as well as immunohistochemical evidence suggesting the presence of pathways for P2X receptor signalling. Finally, we present a hypothetical 'quadripartite model' to explain how ATP, released from red blood cells during hypoxia, could contribute to the ability of ABs to sense O(2) content.
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Affiliation(s)
- Nikol A Piskuric
- Department of Biology, McMaster University, 1280 Main St West, Hamilton, Ontario L8S 4K1, Canada
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Kumar P, Peers C. Foreword. Respir Physiol Neurobiol 2012; 184:115-6. [DOI: 10.1016/j.resp.2012.07.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 07/23/2012] [Indexed: 10/28/2022]
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Zhang M, Piskuric NA, Vollmer C, Nurse CA. P2Y2 receptor activation opens pannexin-1 channels in rat carotid body type II cells: potential role in amplifying the neurotransmitter ATP. J Physiol 2012; 590:4335-50. [PMID: 22733659 DOI: 10.1113/jphysiol.2012.236265] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Signal processing in the carotid body (CB) is initiated at receptor glomus (or type I) cells which depolarize and release the excitatory neurotransmitter ATP during chemoexcitation by hypoxia and acid hypercapnia. Glomus cell clusters (GCs) occur in intimate association with glia-like type II cells which express purinergic P2Y2 receptors (P2Y2Rs) but their function is unclear. Here we immunolocalize the gap junction-like protein channel pannexin-1 (Panx-1) in type II cells and show Panx-1 mRNA expression in the rat CB. As expected, type II cell activation within or near isolated GCs by P2Y2R agonists, ATP and UTP (100 μm), induced a rise in intracellular [Ca(2+)]. Moreover in perforated-patch whole cell recordings from type II cells, these agonists caused a prolonged depolarization and a concentration-dependent, delayed opening of non-selective ion channels that was prevented by Panx-1 blockers, carbenoxolone (5 μm) and 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid (DIDS; 10 μm). Because Panx-1 channels serve as conduits for ATP release, we hypothesized that paracrine, type II cell P2Y2R activation leads to ATP-induced ATP release. In proof-of-principle experiments we used co-cultured chemoafferent petrosal neurones (PNs), which express P2X2/3 purinoceptors, as sensitive biosensors of ATP released from type II cells. In several cases, UTP activation of type II cells within or near GCs led to depolarization or increased firing in nearby PNs, and the effect was reversibly abolished by the selective P2X2/3 receptor blocker, pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS; 10 μm). We propose that CB type II cells may function as ATP amplifiers during chemotransduction via paracrine activation of P2Y2Rs and Panx-1 channels.
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Affiliation(s)
- Min Zhang
- Department of Biology, McMaster University, 1280 Main St. West, Hamilton, Ontario L8S 4K1, Canada
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