1
|
Demir EA, Gonder O. Ticagrelor-Related Dyspnea Beyond Adenosine: Insights into Retrotrapezoid Hyperactivity. Respir Physiol Neurobiol 2024; 331:104349. [PMID: 39293566 DOI: 10.1016/j.resp.2024.104349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2024] [Accepted: 09/10/2024] [Indexed: 09/20/2024]
Abstract
Ticagrelor, a P2Y12 receptor antagonist, has been demonstrated to induce dyspnea, which is not associated with cardiac or pulmonary alterations, or metabolic disturbances. The attribution of ticagrelor-related dyspnea to excess adenosine has been widely proposed, yet is not supported by experimental data. In this paper, we put forth a novel hypothesis that the hyperactivity of the retrotrapezoid nucleus, a group of ventral medullary neurons involved in respiratory modulation, is the underlying cause of ticagrelor-related dyspnea. This hypothesis offers a theoretical resolution to the discrepancies and controversies present in previous theories.
Collapse
Affiliation(s)
- Enver Ahmet Demir
- Department of Cardiology, Ankara Etlik City Hospital, Ankara, Türkiye.
| | - Okan Gonder
- Department of Cardiology, Ankara Etlik City Hospital, Ankara, Türkiye
| |
Collapse
|
2
|
Lino-Alvarado A, Maia OAC, Oliveira MA, Takakura AC, Tavares-Lima W, Moriya HT, Moreira TS. Central and peripheral mechanisms underlying respiratory deficits in a mouse model of accelerated senescence. Pflugers Arch 2024:10.1007/s00424-024-03006-y. [PMID: 39150501 DOI: 10.1007/s00424-024-03006-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2024] [Revised: 07/24/2024] [Accepted: 08/06/2024] [Indexed: 08/17/2024]
Abstract
Aging invariably decreases sensory and motor stimuli and affects several neuronal systems and their connectivity to key brain regions, including those involved in breathing. Nevertheless, further investigation is needed to fully comprehend the link between senescence and respiratory function. Here, we investigate whether a mouse model of accelerated senescence could develop central and peripheral respiratory abnormalities. Adult male Senescence Accelerated Mouse Prone 8 (SAMP8) and the control SAMR1 mice (10 months old) were used. Ventilatory parameters were assessed by whole-body plethysmography, and measurements of respiratory input impedance were performed. SAMP8 mice exhibited a reduction in the density of neurokinin-1 receptor immunoreactivity in the entire ventral respiratory column. Physiological experiments showed that SAMP8 mice exhibited a decreased tachypneic response to hypoxia (FiO2 = 0.08; 10 min) or hypercapnia (FiCO2 = 0.07; 10 min). Additionally, the ventilatory response to hypercapnia increased further due to higher tidal volume. Measurements of respiratory mechanics in SAMP8 mice showed decreased static compliance (Cstat), inspiratory capacity (IC), resistance (Rn), and elastance (H) at different ages (3, 6, and 10 months old). SAMP8 mice also have a decrease in contractile response to methacholine compared to SAMR1. In conclusion, our findings indicate that SAMP8 mice display a loss of the NK1-expressing neurons in the respiratory brainstem centers, along with impairments in both central and peripheral respiratory mechanisms. These observations suggest a potential impact on breathing in a senescence animal model.
Collapse
Affiliation(s)
| | - Octavio A C Maia
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of Sao Paulo, Sao Paulo, SP, Brazil
| | - Maria Aparecida Oliveira
- Deptartment of Pharmacology, Institute of Biomedical Science, University of Sao Paulo, Sao Paulo, SP, Brazil
| | - Ana C Takakura
- Deptartment of Pharmacology, Institute of Biomedical Science, University of Sao Paulo, Sao Paulo, SP, Brazil
| | - Wothan Tavares-Lima
- Deptartment of Pharmacology, Institute of Biomedical Science, University of Sao Paulo, Sao Paulo, SP, Brazil
| | - Henrique T Moriya
- Biomedical Engineering Laboratory, University of Sao Paulo, Sao Paulo, SP, Brazil
| | - Thiago S Moreira
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of Sao Paulo, Sao Paulo, SP, Brazil.
| |
Collapse
|
3
|
Furdui A, da Silveira Scarpellini C, Montandon G. Anatomical distribution of µ-opioid receptors, neurokinin-1 receptors, and vesicular glutamate transporter 2 in the mouse brainstem respiratory network. J Neurophysiol 2024; 132:108-129. [PMID: 38748514 DOI: 10.1152/jn.00478.2023] [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: 12/21/2023] [Revised: 05/08/2024] [Accepted: 05/12/2024] [Indexed: 07/03/2024] Open
Abstract
µ-Opioid receptors (MORs) are responsible for mediating both the analgesic and respiratory effects of opioid drugs. By binding to MORs in brainstem regions involved in controlling breathing, opioids produce respiratory depressive effects characterized by slow and shallow breathing, with potential cardiorespiratory arrest and death during overdose. To better understand the mechanisms underlying opioid-induced respiratory depression, thorough knowledge of the regions and cellular subpopulations that may be vulnerable to modulation by opioid drugs is needed. Using in situ hybridization, we determined the distribution and coexpression of Oprm1 (gene encoding MORs) mRNA with glutamatergic (Vglut2) and neurokinin-1 receptor (Tacr1) mRNA in medullary and pontine regions involved in breathing control and modulation. We found that >50% of cells expressed Oprm1 mRNA in the preBötzinger complex (preBötC), nucleus tractus solitarius (NTS), nucleus ambiguus (NA), postinspiratory complex (PiCo), locus coeruleus (LC), Kölliker-Fuse nucleus (KF), and the lateral and medial parabrachial nuclei (LBPN and MPBN, respectively). Among Tacr1 mRNA-expressing cells, >50% coexpressed Oprm1 mRNA in the preBötC, NTS, NA, Bötzinger complex (BötC), PiCo, LC, raphe magnus nucleus, KF, LPBN, and MPBN, whereas among Vglut2 mRNA-expressing cells, >50% coexpressed Oprm1 mRNA in the preBötC, NTS, NA, BötC, PiCo, LC, KF, LPBN, and MPBN. Taken together, our study provides a comprehensive map of the distribution and coexpression of Oprm1, Tacr1, and Vglut2 mRNA in brainstem regions that control and modulate breathing and identifies Tacr1 and Vglut2 mRNA-expressing cells as subpopulations with potential vulnerability to modulation by opioid drugs.NEW & NOTEWORTHY Opioid drugs can cause serious respiratory side-effects by binding to µ-opioid receptors (MORs) in brainstem regions that control breathing. To better understand the regions and their cellular subpopulations that may be vulnerable to modulation by opioids, we provide a comprehensive map of Oprm1 (gene encoding MORs) mRNA expression throughout brainstem regions that control and modulate breathing. Notably, we identify glutamatergic and neurokinin-1 receptor-expressing cells as potentially vulnerable to modulation by opioid drugs and worthy of further investigation using targeted approaches.
Collapse
Affiliation(s)
- Andreea Furdui
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Ontario, Canada
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | | | - Gaspard Montandon
- Keenan Research Centre for Biomedical Science, St. Michael's Hospital, Toronto, Ontario, Canada
- Institute of Medical Science, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
- Division of Respirology, Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| |
Collapse
|
4
|
Cardani S, Janes TA, Betzner W, Pagliardini S. Knockdown of PHOX2B in the retrotrapezoid nucleus reduces the central CO 2 chemoreflex in rats. eLife 2024; 13:RP94653. [PMID: 38727716 PMCID: PMC11087052 DOI: 10.7554/elife.94653] [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] [Indexed: 05/12/2024] Open
Abstract
PHOX2B is a transcription factor essential for the development of different classes of neurons in the central and peripheral nervous system. Heterozygous mutations in the PHOX2B coding region are responsible for the occurrence of Congenital Central Hypoventilation Syndrome (CCHS), a rare neurological disorder characterised by inadequate chemosensitivity and life-threatening sleep-related hypoventilation. Animal studies suggest that chemoreflex defects are caused in part by the improper development or function of PHOX2B expressing neurons in the retrotrapezoid nucleus (RTN), a central hub for CO2 chemosensitivity. Although the function of PHOX2B in rodents during development is well established, its role in the adult respiratory network remains unknown. In this study, we investigated whether reduction in PHOX2B expression in chemosensitive neuromedin-B (NMB) expressing neurons in the RTN altered respiratory function. Four weeks following local RTN injection of a lentiviral vector expressing the short hairpin RNA (shRNA) targeting Phox2b mRNA, a reduction of PHOX2B expression was observed in Nmb neurons compared to both naive rats and rats injected with the non-target shRNA. PHOX2B knockdown did not affect breathing in room air or under hypoxia, but ventilation was significantly impaired during hypercapnia. PHOX2B knockdown did not alter Nmb expression but it was associated with reduced expression of both Task2 and Gpr4, two CO2/pH sensors in the RTN. We conclude that PHOX2B in the adult brain has an important role in CO2 chemoreception and reduced PHOX2B expression in CCHS beyond the developmental period may contribute to the impaired central chemoreflex function.
Collapse
Affiliation(s)
- Silvia Cardani
- Department of Physiology, Faculty of Medicine and Dentistry, University of AlbertaEdmontonCanada
- Women and Children’s Health Research Institute, University of AlbertaEdmontonCanada
| | - Tara A Janes
- Department of Physiology, Faculty of Medicine and Dentistry, University of AlbertaEdmontonCanada
- Women and Children’s Health Research Institute, University of AlbertaEdmontonCanada
| | - William Betzner
- Department of Physiology, Faculty of Medicine and Dentistry, University of AlbertaEdmontonCanada
| | - Silvia Pagliardini
- Department of Physiology, Faculty of Medicine and Dentistry, University of AlbertaEdmontonCanada
- Women and Children’s Health Research Institute, University of AlbertaEdmontonCanada
- Neuroscience and Mental Health Institute, University of AlbertaEdmontonCanada
| |
Collapse
|
5
|
Janes TA, Cardani S, Saini JK, Pagliardini S. Etonogestrel promotes respiratory recovery in an in vivo rat model of central chemoreflex impairment. Acta Physiol (Oxf) 2024; 240:e14093. [PMID: 38258900 DOI: 10.1111/apha.14093] [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: 08/08/2023] [Revised: 10/11/2023] [Accepted: 01/01/2024] [Indexed: 01/24/2024]
Abstract
AIM The central CO2 chemoreflex is a vital component of respiratory control networks, providing excitatory drive during resting conditions and challenges to blood gas homeostasis. The retrotrapezoid nucleus is a crucial hub for CO2 chemosensitivity; its ablation or inhibition attenuates CO2 chemoreflexes and diminishes restful breathing. Similar phenotypes characterize certain hypoventilation syndromes, suggesting underlying retrotrapezoid nucleus impairment in these disorders. Progesterone stimulates restful breathing and CO2 chemoreflexes. However, its mechanisms and sites of actions remain unknown and the experimental use of synthetic progestins in patients and animal models have been met with mixed respiratory outcomes. METHODS We investigated whether acute or chronic administration of the progestinic drug, etonogestrel, could rescue respiratory chemoreflexes following selective lesion of the retrotrapezoid nucleus with saporin toxin. Adult female Sprague Dawley rats were grouped based on lesion size determined by the number of surviving chemosensitive neurons, and ventilatory responses were measured by whole body plethysmography. RESULTS Ventilatory responses to hypercapnia (but not hypoxia) were compromised in a lesion-dependent manner. Chronic etonogestrel treatment improved CO2 chemosensitivity selectively in rats with moderate lesion, suggesting that a residual number of chemosensitive neurons are required for etonogestrel-induced CO2 chemoreflex recovery. CONCLUSION This study provides new evidence for the use of progestins as respiratory stimulants under conditions of central hypoventilation and provides a new testable model for assessing the mechanism of action of progestins in the respiratory network.
Collapse
Affiliation(s)
- Tara A Janes
- Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
- Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Silvia Cardani
- Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
- Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Jasmeen K Saini
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Silvia Pagliardini
- Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
- Women and Children's Health Research Institute, University of Alberta, Edmonton, Alberta, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| |
Collapse
|
6
|
Souza GMPR, Abbott SBG. Loss-of-function of chemoreceptor neurons in the retrotrapezoid nucleus: What have we learned from it? Respir Physiol Neurobiol 2024; 322:104217. [PMID: 38237884 PMCID: PMC10922619 DOI: 10.1016/j.resp.2024.104217] [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: 10/14/2023] [Revised: 01/11/2024] [Accepted: 01/13/2024] [Indexed: 01/23/2024]
Abstract
Central respiratory chemoreceptors are cells in the brain that regulate breathing in relation to arterial pH and PCO2. Neurons located at the retrotrapezoid nucleus (RTN) have been hypothesized to be central chemoreceptors and/or to be part of the neural network that drives the central respiratory chemoreflex. The inhibition or ablation of RTN chemoreceptor neurons has offered important insights into the role of these cells on central respiratory chemoreception and the neural control of breathing over almost 60 years since the original identification of acid-sensitive properties of this ventral medullary site. Here, we discuss the current definition of chemoreceptor neurons in the RTN and describe how this definition has evolved over time. We then summarize the results of studies that use loss-of-function approaches to evaluate the effects of disrupting the function of RTN neurons on respiration. These studies offer evidence that RTN neurons are indispensable for the central respiratory chemoreflex in mammals and exert a tonic drive to breathe at rest. Moreover, RTN has an interdependent relationship with oxygen sensing mechanisms for the maintenance of the neural drive to breathe and blood gas homeostasis. Collectively, RTN neurons are a genetically-defined group of putative central respiratory chemoreceptors that generate CO2-dependent drive that supports eupneic breathing and stimulates the hypercapnic ventilatory reflex.
Collapse
|
7
|
SheikhBahaei S, Marina N, Rajani V, Kasparov S, Funk GD, Smith JC, Gourine AV. Contributions of carotid bodies, retrotrapezoid nucleus neurons and preBötzinger complex astrocytes to the CO 2 -sensitive drive for breathing. J Physiol 2024; 602:223-240. [PMID: 37742121 PMCID: PMC10841148 DOI: 10.1113/jp283534] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 09/06/2023] [Indexed: 09/25/2023] Open
Abstract
Current models of respiratory CO2 chemosensitivity are centred around the function of a specific population of neurons residing in the medullary retrotrapezoid nucleus (RTN). However, there is significant evidence suggesting that chemosensitive neurons exist in other brainstem areas, including the rhythm-generating region of the medulla oblongata - the preBötzinger complex (preBötC). There is also evidence that astrocytes, non-neuronal brain cells, contribute to central CO2 chemosensitivity. In this study, we reevaluated the relative contributions of the RTN neurons, the preBötC astrocytes, and the carotid body chemoreceptors in mediating the respiratory responses to CO2 in experimental animals (adult laboratory rats). To block astroglial signalling via exocytotic release of transmitters, preBötC astrocytes were targeted to express the tetanus toxin light chain (TeLC). Bilateral expression of TeLC in preBötC astrocytes was associated with ∼20% and ∼30% reduction of the respiratory response to CO2 in conscious and anaesthetized animals, respectively. Carotid body denervation reduced the CO2 respiratory response by ∼25%. Bilateral inhibition of RTN neurons transduced to express Gi-coupled designer receptors exclusively activated by designer drug (DREADDGi ) by application of clozapine-N-oxide reduced the CO2 response by ∼20% and ∼40% in conscious and anaesthetized rats, respectively. Combined blockade of astroglial signalling in the preBötC, inhibition of RTN neurons and carotid body denervation reduced the CO2 -induced respiratory response by ∼70%. These data further support the hypothesis that the CO2 -sensitive drive to breathe requires inputs from the peripheral chemoreceptors and several central chemoreceptor sites. At the preBötC level, astrocytes modulate the activity of the respiratory network in response to CO2 , either by relaying chemosensory information (i.e. they act as CO2 sensors) or by enhancing the preBötC network excitability to chemosensory inputs. KEY POINTS: This study reevaluated the roles played by the carotid bodies, neurons of the retrotrapezoid nucleus (RTN) and astrocytes of the preBötC in mediating the CO2 -sensitive drive to breathe. The data obtained show that disruption of preBötC astroglial signalling, blockade of inputs from the peripheral chemoreceptors or inhibition of RTN neurons similarly reduce the respiratory response to hypercapnia. These data provide further support for the hypothesis that the CO2 -sensitive drive to breathe is mediated by the inputs from the peripheral chemoreceptors and several central chemoreceptor sites.
Collapse
Affiliation(s)
- Shahriar SheikhBahaei
- Centre for Cardiovascular and Metabolic Neuroscience, Research Department of Neuroscience Physiology and Pharmacology, University College London, London WC1E 6BT, UK
- Cellular and Systems Neurobiology Section, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, 20892 MD, USA
- present address: Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, 20892 MD, USA
| | - Nephtali Marina
- Centre for Cardiovascular and Metabolic Neuroscience, Research Department of Neuroscience Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Vishaal Rajani
- Department of Physiology, Neuroscience & Mental Health Institute, Women and Children’s Health Research Institute, University of Alberta, T6G 2E1, Canada
- present address: Division of Biomedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL A1B 3V6, Canada
| | - Sergey Kasparov
- Department of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, UK
| | - Gregory D. Funk
- Department of Physiology, Neuroscience & Mental Health Institute, Women and Children’s Health Research Institute, University of Alberta, T6G 2E1, Canada
| | - Jeffrey C. Smith
- Cellular and Systems Neurobiology Section, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, 20892 MD, USA
| | - Alexander V. Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Research Department of Neuroscience Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| |
Collapse
|
8
|
Javaheri S, Badr MS. Central sleep apnea: pathophysiologic classification. Sleep 2023; 46:zsac113. [PMID: 35551411 PMCID: PMC9995798 DOI: 10.1093/sleep/zsac113] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Revised: 05/05/2022] [Indexed: 11/14/2022] Open
Abstract
Central sleep apnea is not a single disorder; it can present as an isolated disorder or as a part of other clinical syndromes. In some conditions, such as heart failure, central apneic events are due to transient inhibition of ventilatory motor output during sleep, owing to the overlapping influences of sleep and hypocapnia. Specifically, the sleep state is associated with removal of wakefulness drive to breathe; thus, rendering ventilatory motor output dependent on the metabolic ventilatory control system, principally PaCO2. Accordingly, central apnea occurs when PaCO2 is reduced below the "apneic threshold". Our understanding of the pathophysiology of central sleep apnea has evolved appreciably over the past decade; accordingly, in disorders such as heart failure, central apnea is viewed as a form of breathing instability, manifesting as recurrent cycles of apnea/hypopnea, alternating with hyperpnea. In other words, ventilatory control operates as a negative-feedback closed-loop system to maintain homeostasis of blood gas tensions within a relatively narrow physiologic range, principally PaCO2. Therefore, many authors have adopted the engineering concept of "loop gain" (LG) as a measure of ventilatory instability and susceptibility to central apnea. Increased LG promotes breathing instabilities in a number of medical disorders. In some other conditions, such as with use of opioids, central apnea occurs due to inhibition of rhythm generation within the brainstem. This review will address the pathogenesis, pathophysiologic classification, and the multitude of clinical conditions that are associated with central apnea, and highlight areas of uncertainty.
Collapse
Affiliation(s)
- Shahrokh Javaheri
- Division of Pulmonary and Sleep Medicine, Bethesda North Hospital, Cincinnati, OH, USA
- Division of Pulmonary Critical Care and Sleep Medicine, University of Cincinnati, Cincinnati, OH, USA
- Division of Cardiology, Department of Medicine, Ohio State University, Columbus, OH, USA
| | - M Safwan Badr
- Department of Internal Medicine, Liborio Tranchida, MD, Endowed Professor of Medicine, Wayne State University School of Medicine, University Health Center, Detroit, MI, USA
| |
Collapse
|
9
|
Tian Y, Geng D, Wang Y, Shi L, Yu H, He W, Zhu Y, Jun S, Fu C, Wang X, Zhang X, Yuan F, Wang S. Contribution of retrotrapezoid nucleus neurons to CO 2 -amplified cardiorespiratory activity in spontaneously hypertensive rats. J Physiol 2020; 599:1115-1130. [PMID: 33347681 DOI: 10.1113/jp280246] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 12/04/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS This study demonstrates that both CO2 -induced respiratory and cardiovascular responses are augmented in spontaneously hypertensive rats (SHRs). Genetic ablation of the retrotrapezoid nucleus (RTN) neurons depresses enhanced hypercapnic ventilatory response and eliminates CO2 -stimulated increase in arterial pressure and heart rate in SHRs. SHRs have a high protein level of pH-sensitive channels in the RTN, including the TASK-2 channel, Kv12.1 channel and acid-sensing ion channel 3. The inhibition of putative TASK-2 channel activity by clofilium diminishes amplified hypercapnic ventilatory and cardiovascular responses, and reduces the number of CO2 -activated RTN neurons in SHRs. These results indicate that RTN neurons contribute to enhanced CO2 -stimulated respiratory and cardiovascular responses in SHRs. ABSTRACT The respiratory regulation of cardiovascular activity is essential for maintaining an efficient ventilation and perfusion ratio. Activation of central respiratory chemoreceptors not only elicits a ventilatory response but also regulates sympathetic nerve activity and arterial blood pressure (ABP). The retrotrapezoid nucleus (RTN) is the most completely characterized cluster of central respiratory chemoreceptors. We hypothesize that RTN neurons contribute to augmented CO2 -stimulated respiratory and cardiovascular responses in adult spontaneously hypertensive rats (SHRs). Our findings indicate that SHRs exhibit more enhanced hypercapnic cardiorespiratory responses than age-matched normotensive Wistar-Kyoto rats. Genetic ablation of RTN neurons notably depresses an enhanced hypercapnic ventilatory response (HCVR) and eliminates a CO2 -stimulated greater increase in ABP and heart rate in SHRs. In addition, SHRs have a higher protein level of pH-sensitive channels in the RTN, including TASK-2 channels, Kv12.1 channels and acid-sensing ion channel 3. Administration of clofilium (i.p.), an unselective inhibitor of TASK-2 channels, not only significantly reduces the enhanced HCVR but also inhibits CO2 -amplified increases in ABP and heart rate in SHRs. Moreover, clofilium significantly decreases the number of CO2 -activated RTN neurons in SHRs. Taken together, we suggest that RTN neurons play an important role in enhanced hypercapnic ventilatory and cardiovascular responses in SHRs and the putative mechanism involved is associated with TASK-2 channel activity in the RTN.
Collapse
Affiliation(s)
- Yanming Tian
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei, 050017, China
| | - Danyang Geng
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei, 050017, China
| | - Yakun Wang
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei, 050017, China
| | - Luo Shi
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei, 050017, China
| | - Hongxiao Yu
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei, 050017, China
| | - Wei He
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei, 050017, China
| | - Yufang Zhu
- School of Nursing, Hebei Medical University, Shijiazhuang, Hebei, 050000, China
| | - Shirui Jun
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei, 050017, China
| | - Congrui Fu
- School of Nursing, Hebei Medical University, Shijiazhuang, Hebei, 050000, China
| | - Xin Wang
- Physiology Laboratory of Teaching Experiment Center, Hebei Medical University, Shijiazhuang, Hebei, 050000, China
| | - Xiangjian Zhang
- Hebei Key Laboratory of Vascular Homeostasis and Hebei Collaborative Innovation Center for Cardio-cerebrovascular Disease, Shijiazhuang, Hebei, 050000, China
| | - Fang Yuan
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei, 050017, China
| | - Sheng Wang
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei, 050017, China.,Hebei Key Laboratory of Neurophysiology, Shijiazhuang, Hebei, 050017, China
| |
Collapse
|
10
|
Moreira TS, Sobrinho CR, Falquetto B, Oliveira LM, Lima JD, Mulkey DK, Takakura AC. The retrotrapezoid nucleus and the neuromodulation of breathing. J Neurophysiol 2020; 125:699-719. [PMID: 33427575 DOI: 10.1152/jn.00497.2020] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Breathing is regulated by a host of arousal and sleep-wake state-dependent neuromodulators to maintain respiratory homeostasis. Modulators such as acetylcholine, norepinephrine, histamine, serotonin (5-HT), adenosine triphosphate (ATP), substance P, somatostatin, bombesin, orexin, and leptin can serve complementary or off-setting functions depending on the target cell type and signaling mechanisms engaged. Abnormalities in any of these modulatory mechanisms can destabilize breathing, suggesting that modulatory mechanisms are not overly redundant but rather work in concert to maintain stable respiratory output. The present review focuses on the modulation of a specific cluster of neurons located in the ventral medullary surface, named retrotrapezoid nucleus, that are activated by changes in tissue CO2/H+ and regulate several aspects of breathing, including inspiration and active expiration.
Collapse
Affiliation(s)
- Thiago S Moreira
- Department of Physiology and Biophysics, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| | - Cleyton R Sobrinho
- Department of Physiology and Biophysics, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| | - Barbara Falquetto
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| | - Luiz M Oliveira
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| | - Janayna D Lima
- Department of Physiology and Biophysics, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| | - Daniel K Mulkey
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut
| | - Ana C Takakura
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo (USP), São Paulo, Brazil
| |
Collapse
|
11
|
Souza GMPR, Stornetta RL, Stornetta DS, Abbott SBG, Guyenet PG. Contribution of the Retrotrapezoid Nucleus and Carotid Bodies to Hypercapnia- and Hypoxia-induced Arousal from Sleep. J Neurosci 2019; 39:9725-9737. [PMID: 31641048 PMCID: PMC6891059 DOI: 10.1523/jneurosci.1268-19.2019] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 09/03/2019] [Accepted: 10/16/2019] [Indexed: 11/21/2022] Open
Abstract
The combination of hypoxia and hypercapnia during sleep produces arousal, which helps restore breathing and normalizes blood gases. Hypercapnia and hypoxia produce arousal in mammals by activating central (pH-sensitive) and peripheral (primarily O2-sensitive) chemoreceptors. The relevant chemoreceptors and the neuronal circuits responsible for arousal are largely unknown. Here we examined the contribution of two lower brainstem nuclei that could be implicated in CO2 and hypoxia-induced arousal: the retrotrapezoid nucleus (RTN), a CO2-responsive nucleus, which mediates the central respiratory chemoreflex; and the C1 neurons, which are hypoxia activated and produce arousal and blood pressure increases when directly stimulated. Additionally, we assessed the contribution of the carotid bodies (CBs), the main peripheral chemoreceptors in mammals, to hypoxia and CO2-induced arousal. In unanesthetized male rats, we tested whether ablation of the RTN, CBs, or C1 neurons affects arousal from sleep and respiratory responses to hypercapnia or hypoxia. The sleep-wake pattern was monitored by EEG and neck EMG recordings and breathing by whole-body plethysmography. The latency to arousal in response to hypoxia or hypercapnia was determined along with changes in ventilation coincident with the arousal. RTN lesions impaired CO2-induced arousal but had no effect on hypoxia-induced arousal. CB ablation impaired arousal to hypoxia and, to a lesser extent, hypercapnia. C1 neuron ablation had no effect on arousal. Thus, the RTN contributes to CO2-induced arousal, whereas the CBs contribute to both hypoxia and CO2-induced arousal. Asphyxia-induced arousal likely requires the combined activation of RTN, CBs and other central chemoreceptors.SIGNIFICANCE STATEMENT Hypercapnia and hypoxia during sleep elicit arousal, which facilitates airway clearing in the case of obstruction and reinstates normal breathing in the case of hypoventilation or apnea. Arousal can also be detrimental to health by interrupting sleep. We sought to clarify how CO2 and hypoxia cause arousal. We show that the retrotrapezoid nucleus, a brainstem nucleus that mediates the effect of brain acidification on breathing, also contributes to arousal elicited by CO2 but not hypoxia. We also show that the carotid bodies contribute predominantly to hypoxia-induced arousal. Lesions of the retrotrapezoid nucleus or carotid bodies attenuate, but do not eliminate, arousal to CO2 or hypoxia; therefore, we conclude that these structures are not the sole trigger of CO2 or hypoxia-induced arousal.
Collapse
Affiliation(s)
- George M P R Souza
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908
| | - Ruth L Stornetta
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908
| | - Daniel S Stornetta
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908
| | - Stephen B G Abbott
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908
| | - Patrice G Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908
| |
Collapse
|
12
|
Souza GMPR, Kanbar R, Stornetta DS, Abbott SBG, Stornetta RL, Guyenet PG. Breathing regulation and blood gas homeostasis after near complete lesions of the retrotrapezoid nucleus in adult rats. J Physiol 2019; 596:2521-2545. [PMID: 29667182 DOI: 10.1113/jp275866] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 04/04/2018] [Indexed: 12/16/2022] Open
Abstract
KEY POINTS The retrotrapezoid nucleus (RTN) drives breathing proportionally to brain PCO2 but its role during various states of vigilance needs clarification. Under normoxia, RTN lesions increased the arterial PCO2 set-point, lowered the PO2 set-point and reduced alveolar ventilation relative to CO2 production. Tidal volume was reduced and breathing frequency increased to a comparable degree during wake, slow-wave sleep and REM sleep. RTN lesions did not produce apnoeas or disordered breathing during sleep. RTN lesions in rats virtually eliminated the central respiratory chemoreflex (CRC) while preserving the cardiorespiratory responses to hypoxia; the relationship between CRC and number of surviving RTN Nmb neurons was an inverse exponential. The CRC does not function without the RTN. In the quasi-complete absence of the RTN and CRC, alveolar ventilation is reduced despite an increased drive to breathe from the carotid bodies. ABSTRACT The retrotrapezoid nucleus (RTN) is one of several CNS nuclei that contribute, in various capacities (e.g. CO2 detection, neuronal modulation) to the central respiratory chemoreflex (CRC). Here we test how important the RTN is to PCO2 homeostasis and breathing during sleep or wake. RTN Nmb-positive neurons were killed with targeted microinjections of substance P-saporin conjugate in adult rats. Under normoxia, rats with large RTN lesions (92 ± 4% cell loss) had normal blood pressure and arterial pH but were hypoxic (-8 mmHg PaO2 ) and hypercapnic (+10 mmHg ). In resting conditions, minute volume (VE ) was normal but breathing frequency (fR ) was elevated and tidal volume (VT ) reduced. Resting O2 consumption and CO2 production were normal. The hypercapnic ventilatory reflex in 65% FiO2 had an inverse exponential relationship with the number of surviving RTN neurons and was decreased by up to 92%. The hypoxic ventilatory reflex (HVR; FiO2 21-10%) persisted after RTN lesions, hypoxia-induced sighing was normal and hypoxia-induced hypotension was reduced. In rats with RTN lesions, breathing was lowest during slow-wave sleep, especially under hyperoxia, but apnoeas and sleep-disordered breathing were not observed. In conclusion, near complete RTN destruction in rats virtually eliminates the CRC but the HVR persists and sighing and the state dependence of breathing are unchanged. Under normoxia, RTN lesions cause no change in VE but alveolar ventilation is reduced by at least 21%, probably because of increased physiological dead volume. RTN lesions do not cause sleep apnoea during slow-wave sleep, even under hyperoxia.
Collapse
Affiliation(s)
- George M P R Souza
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA
| | - Roy Kanbar
- Department of Pharmaceutical Sciences, Lebanese American University, Beyrouth, Lebanon
| | - Daniel S Stornetta
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA
| | - Stephen B G Abbott
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA
| | - Ruth L Stornetta
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA
| | - Patrice G Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA
| |
Collapse
|
13
|
Bruce RM, Jolley C, White MJ. Control of exercise hyperpnoea: Contributions from thin-fibre skeletal muscle afferents. Exp Physiol 2019; 104:1605-1621. [PMID: 31429500 DOI: 10.1113/ep087649] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 08/16/2019] [Indexed: 12/16/2022]
Abstract
NEW FINDINGS What is the topic of this review? In this review, we examine the evidence for control mechanisms underlying exercise hyperpnoea, giving attention to the feedback from thin-fibre skeletal muscle afferents, and highlight the frequently conflicting findings and difficulties encountered by researchers using a variety of experimental models. What advances does it highlight? There has been a recent resurgence of interest in the role of skeletal muscle afferent involvement, not only as a mechanism of healthy exercise hyperpnoea but also in the manifestation of breathlessness and exercise intolerance in chronic disease. ABSTRACT The ventilatory response to dynamic submaximal exercise is immediate and proportional to metabolic rate, which maintains isocapnia. How these respiratory responses are controlled remains poorly understood, given that the most tightly controlled variable (arterial partial pressure of CO2 /H+ ) provides no error signal for arterial chemoreceptors to trigger reflex increases in ventilation. This review discusses evidence for different postulated control mechanisms, with a focus on the feedback from group III/IV skeletal muscle mechanosensitive and metabosensitive afferents. This concept is attractive, because the stimulation of muscle mechanoreceptors might account for the immediate increase in ventilation at the onset of exercise, and signals from metaboreceptors might be proportional to metabolic rate. A variety of experimental models have been used to establish the contribution of thin-fibre muscle afferents in ventilatory control during exercise, with equivocal results. The inhibition of afferent feedback via the application of lumbar intrathecal fentanyl during exercise suppresses ventilation, which provides the most compelling supportive evidence to date. However, stimulation of afferent feedback at rest has no consistent effect on respiratory output. However, evidence is emerging for synergistic interactions between muscle afferent feedback and other stimulatory inputs to the central respiratory neuronal pool. These seemingly hyperadditive effects might explain the conflicting findings encountered when using different experimental models. We also discuss the increasing evidence that patients with certain chronic diseases exhibit exaggerated muscle afferent activation during exercise, resulting in enhanced cardiorespiratory responses. This might provide a neural link between the well-established limb muscle dysfunction and the associated exercise intolerance and exertional dyspnoea, which might offer therapeutic targets for these patients.
Collapse
Affiliation(s)
- Richard M Bruce
- Centre for Human and Applied Physiological Sciences, School of Basic and Medical Sciences, King's College London, London, UK
| | - Caroline Jolley
- Centre for Human and Applied Physiological Sciences, School of Basic and Medical Sciences, King's College London, London, UK
| | - Michael J White
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
| |
Collapse
|
14
|
Relationship with excessive daytime sleepiness and serum substance P levels in OSAS patients and the effect of PAP treatment. Sleep Biol Rhythms 2019. [DOI: 10.1007/s41105-019-00217-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
15
|
Zhuang J, Zang N, Ye C, Xu F. Lethal avian influenza A (H5N1) virus replicates in pontomedullary chemosensitive neurons and depresses hypercapnic ventilatory response in mice. Am J Physiol Lung Cell Mol Physiol 2019; 316:L525-L536. [PMID: 30628490 PMCID: PMC6459289 DOI: 10.1152/ajplung.00324.2018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 12/04/2018] [Accepted: 12/29/2018] [Indexed: 01/09/2023] Open
Abstract
The highly pathogenic H5N1 (HK483) viral infection causes a depressed hypercapnic ventilatory response (dHCVR, 20%↓) at 2 days postinfection (dpi) and death at 7 dpi in mice, but the relevant mechanisms are not fully understood. Glomus cells in the carotid body and catecholaminergic neurons in locus coeruleus (LC), neurokinin 1 receptor (NK1R)-expressing neurons in the retrotrapezoid nucleus (RTN), and serotonergic neurons in the raphe are chemosensitive and responsible for HCVR. We asked whether the dHCVR became worse over the infection period with viral replication in these cells/neurons. Mice intranasally inoculated with saline or the HK483 virus were exposed to hypercapnia for 5 min at 0, 2, 4, or 6 dpi, followed by immunohistochemistry to determine the expression of nucleoprotein of H5N1 influenza A (NP) alone and coupled with 1) tyrosine hydroxylase (TH) in the carotid body and LC, 2) NK1R in the RTN, and 3) tryptophan hydroxylase (TPH) in the raphe. HK483 viral infection blunted HCVR by ∼20, 50, and 65% at 2, 4, and 6 dpi. The NP was observed in the pontomedullary respiratory-related nuclei (but not in the carotid body) at 4 and 6 dpi, especially in 20% of RTN NK1R, 35% of LC TH, and ∼10% raphe TPH neurons. The infection significantly reduced the local NK1R or TPH immunoreactivity and population of neurons expressing NK1R or TPH. We conclude that the HK483 virus infects the pontomedullary respiratory nuclei, particularly chemosensitive neurons in the RTN, LC, and raphe, contributing to the severe depression of HCVR and respiratory failure at 6 dpi. NEW & NOTEWORTHY The H5N1 virus infection is lethal due to respiratory failure, but the relevant mechanisms remain unclear. In this study, we demonstrated a gradual diminution of hypercapnic ventilatory response to a degree, leading to respiratory failure over a 6-day infection. Death was associated with viral replication in the pontomedullary respiratory-related nuclei, especially the central chemosensitive neurons. These results not only provide insight into the mechanisms of the lethality of H5N1 viral infection but also offer clues in the development of corresponding treatments to minimize and prevent respiratory failure.
Collapse
Affiliation(s)
- Jianguo Zhuang
- Pathophysiology Program, Lovelace Respiratory Research Institute , Albuquerque, New Mexico
| | - Na Zang
- Pathophysiology Program, Lovelace Respiratory Research Institute , Albuquerque, New Mexico
| | - Chunyan Ye
- Pathophysiology Program, Lovelace Respiratory Research Institute , Albuquerque, New Mexico
| | - Fadi Xu
- Pathophysiology Program, Lovelace Respiratory Research Institute , Albuquerque, New Mexico
| |
Collapse
|
16
|
Zoccal DB, Silva JN, Barnett WH, Lemes EV, Falquetto B, Colombari E, Molkov YI, Moreira TS, Takakura AC. Interaction between the retrotrapezoid nucleus and the parafacial respiratory group to regulate active expiration and sympathetic activity in rats. Am J Physiol Lung Cell Mol Physiol 2018; 315:L891-L909. [PMID: 30188747 DOI: 10.1152/ajplung.00011.2018] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The retrotrapezoid nucleus (RTN) contains chemosensitive cells that distribute CO2-dependent excitatory drive to the respiratory network. This drive facilitates the function of the respiratory central pattern generator (rCPG) and increases sympathetic activity. It is also evidenced that during hypercapnia, the late-expiratory (late-E) oscillator in the parafacial respiratory group (pFRG) is activated and determines the emergence of active expiration. However, it remains unclear the microcircuitry responsible for the distribution of the excitatory signals to the pFRG and the rCPG in conditions of high CO2. Herein, we hypothesized that excitatory inputs from chemosensitive neurons in the RTN are necessary for the activation of late-E neurons in the pFRG. Using the decerebrated in situ rat preparation, we found that lesions of neurokinin-1 receptor-expressing neurons in the RTN region with substance P-saporin conjugate suppressed the late-E activity in abdominal nerves (AbNs) and sympathetic nerves (SNs) and attenuated the increase in phrenic nerve (PN) activity induced by hypercapnia. On the other hand, kynurenic acid (100 mM) injections in the pFRG eliminated the late-E activity in AbN and thoracic SN but did not modify PN response during hypercapnia. Iontophoretic injections of retrograde tracer into the pFRG of adult rats revealed labeled phox2b-expressing neurons within the RTN. Our findings are supported by mathematical modeling of chemosensitive and late-E populations within the RTN and pFRG regions as two separate but interacting populations in a way that the activation of the pFRG late-E neurons during hypercapnia require glutamatergic inputs from the RTN neurons that intrinsically detect changes in CO2/pH.
Collapse
Affiliation(s)
- Daniel B Zoccal
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University , São Paulo , Brazil
| | - Josiane N Silva
- Department of Pharmacology, Institute of Biomedical Science, University of São Paulo , São Paulo , Brazil
| | - William H Barnett
- Deptartment of Mathematics and Statistics, Georgia State University , Atlanta, Georgia
| | - Eduardo V Lemes
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University , São Paulo , Brazil
| | - Barbara Falquetto
- Department of Pharmacology, Institute of Biomedical Science, University of São Paulo , São Paulo , Brazil
| | - Eduardo Colombari
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University , São Paulo , Brazil
| | - Yaroslav I Molkov
- Deptartment of Mathematics and Statistics, Georgia State University , Atlanta, Georgia.,Neuroscience Institute, Georgia State University , Atlanta, Georgia
| | - Thiago S Moreira
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of São Paulo , São Paulo , Brazil
| | - Ana C Takakura
- Department of Pharmacology, Institute of Biomedical Science, University of São Paulo , São Paulo , Brazil
| |
Collapse
|
17
|
Iadarola MJ, Sapio MR, Wang X, Carrero H, Virata-Theimer ML, Sarnovsky R, Mannes AJ, FitzGerald DJ. Analgesia by Deletion of Spinal Neurokinin 1 Receptor Expressing Neurons Using a Bioengineered Substance P-Pseudomonas Exotoxin Conjugate. Mol Pain 2018; 13:1744806917727657. [PMID: 28814145 PMCID: PMC5574484 DOI: 10.1177/1744806917727657] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Cell deletion approaches to pain directed at either the primary nociceptive afferents or
second-order neurons are highly effective analgesic manipulations. Second-order spinal
neurons expressing the neurokinin 1 (NK1) receptor are required for the perception of many
types of pain. To delete NK1+ neurons for the purpose of pain control, we generated a
toxin–peptide conjugate using DTNB-derivatized (Cys0) substance P (SP) and a
N-terminally truncated Pseudomonas exotoxin (PE35) that retains the endosome-release and
ADP-ribosylation enzymatic domains but with only one free sulfhydryl side chain for
conjugation. This allowed generation of a one-to-one product linked by a disulfide bond
(SP-PE35). In vitro, Chinese hamster ovary cells stably transfected with the NK1 receptor
exhibited specific cytotoxicity when exposed to SP-PE35
(IC50 = 5 × 10−11 M), whereas the conjugate was nontoxic to NK2
and NK3 receptor-bearing cell lines. In vivo studies showed that, after infusion into the
spinal subarachnoid space, the toxin was extremely effective in deleting NK1
receptor-expressing cells from the dorsal horn of the spinal cord. The specific cell
deletion robustly attenuated thermal and mechanical pain sensations and inflammatory
hyperalgesia but did not affect motoric capabilities. NK1 receptor cell deletion and
antinociception occurred without obvious lesion of non–receptor-expressing cells or
apparent reorganization of primary afferent innervation. These data demonstrate the
extraordinary selectivity and broad-spectrum antinociceptive efficacy of this
ligand-directed protein therapeutic acting via receptor-mediated endocytosis. The loss of
multiple pain modalities including heat and mechanical pinch, transduced by different
populations of primary afferents, shows that spinal NK1 receptor-expressing neurons are
critical points of convergence in the nociceptive transmission circuit. We further suggest
that therapeutic end points can be effectively and safely achieved when SP-PE35 is locally
infused, thereby producing a regionally defined analgesia.
Collapse
Affiliation(s)
- Michael J Iadarola
- Department of Perioperative Medicine, Clinical Center, National Institutes of Health, Bethesda, MD 20892
| | | | - Xunde Wang
- Biotherapy Section, Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892
| | - Hector Carrero
- Pain and Neurosensory Mechanisms Branch, National Institutes of Dental and Craniofacial
| | - Maria Luisa Virata-Theimer
- Biotherapy Section, Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892
| | - Robert Sarnovsky
- Biotherapy Section, Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892
| | - Andrew J Mannes
- Department of Perioperative Medicine, Clinical Center, National Institutes of Health, Bethesda, MD 20892
| | - David J FitzGerald
- Biotherapy Section, Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892
| |
Collapse
|
18
|
Huckstepp RTR, Cardoza KP, Henderson LE, Feldman JL. Distinct parafacial regions in control of breathing in adult rats. PLoS One 2018; 13:e0201485. [PMID: 30096151 PMCID: PMC6086409 DOI: 10.1371/journal.pone.0201485] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 07/15/2018] [Indexed: 11/29/2022] Open
Abstract
Recently, based on functional differences, we subdivided neurons juxtaposed to the facial nucleus into two distinct populations, the parafacial ventral and lateral regions, i.e., pFV and pFL. Little is known about the composition of these regions, i.e., are they homogenous or heterogeneous populations? Here, we manipulated their excitability in spontaneously breathing vagotomized urethane anesthetized adult rats to further characterize their role in breathing. In the pFL, disinhibition or excitation decreased breathing frequency (f) with a concomitant increase of tidal volume (VT), and induced active expiration; in contrast, reducing excitation had no effect. This result is congruent with pFL neurons constituting a conditional expiratory oscillator comprised of a functionally homogeneous set of excitatory neurons that are tonically suppressed at rest. In the pFV, disinhibition increased f with a presumptive reflexive decrease in VT; excitation increased f, VT and sigh rate; reducing excitation decreased VT with a presumptive reflexive increase in f. Therefore, the pFV, has multiple functional roles that require further parcellation. Interestingly, while hyperpolarization of the pFV reduces ongoing expiratory activity, no perturbation of pFV excitability induced active expiration. Thus, while the pFV can affect ongoing expiratory activity, presumably generated by the pFL, it does not appear capable of directly inducing active expiration. We conclude that the pFL contains neurons that can initiate, modulate, and sustain active expiration, whereas the pFV contains subpopulations of neurons that differentially affect various aspects of breathing pattern, including but not limited to modulation of ongoing expiratory activity.
Collapse
Affiliation(s)
- Robert T. R. Huckstepp
- Department of Neurobiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Kathryn P. Cardoza
- Department of Neurobiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Lauren E. Henderson
- Department of Neurobiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Jack L. Feldman
- Department of Neurobiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail:
| |
Collapse
|
19
|
Bright FM, Vink R, Byard RW. The potential role of substance P in brainstem homeostatic control in the pathogenesis of sudden infant death syndrome (SIDS). Neuropeptides 2018; 70:1-8. [PMID: 29908886 DOI: 10.1016/j.npep.2018.02.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 02/25/2018] [Accepted: 02/25/2018] [Indexed: 12/30/2022]
Abstract
Victims of sudden infant death syndrome (SIDS) are believed to have an underlying dysfunction in medullary homeostatic control that impairs critical responses to life threatening challenges such as hypoxia, hypercarbia and asphyxia, often during a sleep period. This failure is thought to result from abnormalities in a network of neural pathways in the medulla oblongata that control respiration, chemosensitivity, autonomic function and arousal. Studies have mainly focused on the role of serotonin, 5-hydroxytyptamine (5HT), although the neuropeptide substance P (SP) has also been shown to play an integral role in the modulation of medullary homeostatic function, often in conjunction with 5-HT. Actions of SP include regulation of respiratory rhythm generation, integration of cardiovascular control, modulation of the baroreceptor reflex and mediation of the chemoreceptor reflex in response to hypoxia. Abnormalities in SP neurotransmission may, therefore, also play a significant role in homeostatic dysfunction of the neurotransmitter network in SIDS. This review focuses on the pathways within the medulla involving SP and its tachykinin NK1 receptor, their potential relationship with the medullary 5-HT system, and possible involvement in the pathogenesis of SIDS.
Collapse
Affiliation(s)
- Fiona M Bright
- Discipline of Anatomy and Pathology, Adelaide Medical School, University of Adelaide, SA, Australia.
| | - Robert Vink
- Sansom Institute for Health Research, University of South Australia, Adelaide, SA, Australia
| | - Roger W Byard
- Discipline of Anatomy and Pathology, Adelaide Medical School, University of Adelaide, SA, Australia
| |
Collapse
|
20
|
Stojanovska V, Miller SL, Hooper SB, Polglase GR. The Consequences of Preterm Birth and Chorioamnionitis on Brainstem Respiratory Centers: Implications for Neurochemical Development and Altered Functions by Inflammation and Prostaglandins. Front Cell Neurosci 2018; 12:26. [PMID: 29449803 PMCID: PMC5799271 DOI: 10.3389/fncel.2018.00026] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 01/17/2018] [Indexed: 11/16/2022] Open
Abstract
Preterm birth is a major cause for neonatal morbidity and mortality, and is frequently associated with adverse neurological outcomes. The transition from intrauterine to extrauterine life at birth is particularly challenging for preterm infants. The main physiological driver for extrauterine transition is the establishment of spontaneous breathing. However, preterm infants have difficulty clearing lung liquid, have insufficient surfactant levels, and underdeveloped lungs. Further, preterm infants have an underdeveloped brainstem, resulting in reduced respiratory drive. These factors facilitate the increased requirement for respiratory support. A principal cause of preterm birth is intrauterine infection/inflammation (chorioamnionitis), and infants with chorioamnionitis have an increased risk and severity of neurological damage, but also demonstrate impaired autoresuscitation capacity and prevalent apnoeic episodes. The brainstem contains vital respiratory centers which provide the neural drive for breathing, but the impact of preterm birth and/or chorioamnionitis on this brain region is not well understood. The aim of this review is to provide an overview of the role and function of the brainstem respiratory centers, and to highlight the proposed mechanisms of how preterm birth and chorioamnionitis may affect central respiratory functions.
Collapse
Affiliation(s)
- Vanesa Stojanovska
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia
| | - Suzanne L Miller
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia.,Department of Obstetrics and Gynaecology, Monash University and Hudson Institute of Medical Research, Melbourne, VIC, Australia
| | - Stuart B Hooper
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia.,Department of Obstetrics and Gynaecology, Monash University and Hudson Institute of Medical Research, Melbourne, VIC, Australia
| | - Graeme R Polglase
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia.,Department of Obstetrics and Gynaecology, Monash University and Hudson Institute of Medical Research, Melbourne, VIC, Australia
| |
Collapse
|
21
|
Korsak A, Sheikhbahaei S, Machhada A, Gourine AV, Huckstepp RTR. The Role Of Parafacial Neurons In The Control Of Breathing During Exercise. Sci Rep 2018; 8:400. [PMID: 29321559 PMCID: PMC5762684 DOI: 10.1038/s41598-017-17412-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 11/24/2017] [Indexed: 02/07/2023] Open
Abstract
Neuronal cell groups residing within the retrotrapezoid nucleus (RTN) and C1 area of the rostral ventrolateral medulla oblongata contribute to the maintenance of resting respiratory activity and arterial blood pressure, and play an important role in the development of cardiorespiratory responses to metabolic challenges (such as hypercapnia and hypoxia). In rats, acute silencing of neurons within the parafacial region which includes the RTN and the rostral aspect of the C1 circuit (pFRTN/C1), transduced to express HM4D (Gi-coupled) receptors, was found to dramatically reduce exercise capacity (by 60%), determined by an intensity controlled treadmill running test. In a model of simulated exercise (electrical stimulation of the sciatic or femoral nerve in urethane anaesthetised spontaneously breathing rats) silencing of the pFRTN/C1 neurons had no effect on cardiovascular changes, but significantly reduced the respiratory response during steady state exercise. These results identify a neuronal cell group in the lower brainstem which is critically important for the development of the respiratory response to exercise and, determines exercise capacity.
Collapse
Affiliation(s)
- Alla Korsak
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, WC1E 6BT, United Kingdom
| | - Shahriar Sheikhbahaei
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, WC1E 6BT, United Kingdom
| | - Asif Machhada
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, WC1E 6BT, United Kingdom
| | - Alexander V Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, WC1E 6BT, United Kingdom.
| | - Robert T R Huckstepp
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, WC1E 6BT, United Kingdom. .,School of Life Sciences, University of Warwick, Coventry, CV4 7AL, United Kingdom.
| |
Collapse
|
22
|
Guyenet PG, Bayliss DA, Stornetta RL, Kanbar R, Shi Y, Holloway BB, Souza GMPR, Basting TM, Abbott SBG, Wenker IC. Interdependent feedback regulation of breathing by the carotid bodies and the retrotrapezoid nucleus. J Physiol 2017; 596:3029-3042. [PMID: 29168167 DOI: 10.1113/jp274357] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 11/02/2017] [Indexed: 12/13/2022] Open
Abstract
The retrotrapezoid nucleus (RTN) regulates breathing in a CO2 - and state-dependent manner. RTN neurons are glutamatergic and innervate principally the respiratory pattern generator; they regulate multiple aspects of breathing, including active expiration, and maintain breathing automaticity during non-REM sleep. RTN neurons encode arterial PCO2 /pH via cell-autonomous and paracrine mechanisms, and via input from other CO2 -responsive neurons. In short, RTN neurons are a pivotal structure for breathing automaticity and arterial PCO2 homeostasis. The carotid bodies stimulate the respiratory pattern generator directly and indirectly by activating RTN via a neuronal projection originating within the solitary tract nucleus. The indirect pathway operates under normo- or hypercapnic conditions; under respiratory alkalosis (e.g. hypoxia) RTN neurons are silent and the excitatory input from the carotid bodies is suppressed. Also, silencing RTN neurons optogenetically quickly triggers a compensatory increase in carotid body activity. Thus, in conscious mammals, breathing is subject to a dual and interdependent feedback regulation by chemoreceptors. Depending on the circumstance, the activity of the carotid bodies and that of RTN vary in the same or the opposite directions, producing additive or countervailing effects on breathing. These interactions are mediated either via changes in blood gases or by brainstem neuronal connections, but their ultimate effect is invariably to minimize arterial PCO2 fluctuations. We discuss the potential relevance of this dual chemoreceptor feedback to cardiorespiratory abnormalities present in diseases in which the carotid bodies are hyperactive at rest, e.g. essential hypertension, obstructive sleep apnoea and heart failure.
Collapse
Affiliation(s)
- Patrice G Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Douglas A Bayliss
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Ruth L Stornetta
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Roy Kanbar
- Department of Pharmaceutical Sciences, Lebanese American University, Beyrouth, Lebanon
| | - Yingtang Shi
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Benjamin B Holloway
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - George M P R Souza
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Tyler M Basting
- Department of Pharmacology & Experimental Therapeutics, Louisiana State University, New Orleans, Louisiana 70112, USA
| | - Stephen B G Abbott
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Ian C Wenker
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| |
Collapse
|
23
|
Nalcn Is a "Leak" Sodium Channel That Regulates Excitability of Brainstem Chemosensory Neurons and Breathing. J Neurosci 2017; 36:8174-87. [PMID: 27488637 DOI: 10.1523/jneurosci.1096-16.2016] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 06/15/2016] [Indexed: 01/01/2023] Open
Abstract
UNLABELLED The activity of background potassium and sodium channels determines neuronal excitability, but physiological roles for "leak" Na(+) channels in specific mammalian neurons have not been established. Here, we show that a leak Na(+) channel, Nalcn, is expressed in the CO2/H(+)-sensitive neurons of the mouse retrotrapezoid nucleus (RTN) that regulate breathing. In RTN neurons, Nalcn expression correlated with higher action potential discharge over a more alkalized range of activity; shRNA-mediated depletion of Nalcn hyperpolarized RTN neurons, and reduced leak Na(+) current and firing rate. Nalcn depletion also decreased RTN neuron activation by the neuropeptide, substance P, without affecting pH-sensitive background K(+) currents or activation by a cotransmitter, serotonin. In vivo, RTN-specific knockdown of Nalcn reduced CO2-evoked neuronal activation and breathing; hypoxic hyperventilation was unchanged. Thus, Nalcn regulates RTN neuronal excitability and stimulation by CO2, independent of direct pH sensing, potentially contributing to respiratory effects of Nalcn mutations; transmitter modulation of Nalcn may underlie state-dependent changes in breathing and respiratory chemosensitivity. SIGNIFICANCE STATEMENT Breathing is an essential, enduring rhythmic motor activity orchestrated by dedicated brainstem circuits that require tonic excitatory drive for their persistent function. A major source of drive is from a group of CO2/H(+)-sensitive neurons in the retrotrapezoid nucleus (RTN), whose ongoing activity is critical for breathing. The ionic mechanisms that support spontaneous activity of RTN neurons are unknown. We show here that Nalcn, a unique channel that generates "leak" sodium currents, regulates excitability and neuromodulation of RTN neurons and CO2-stimulated breathing. Thus, this work defines a specific function for this enigmatic channel in an important physiological context.
Collapse
|
24
|
Fu C, Xue J, Wang R, Chen J, Ma L, Liu Y, Wang X, Guo F, Zhang Y, Zhang X, Wang S. Chemosensitive Phox2b-expressing neurons are crucial for hypercapnic ventilatory response in the nucleus tractus solitarius. J Physiol 2017; 595:4973-4989. [PMID: 28488367 DOI: 10.1113/jp274437] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 05/04/2017] [Indexed: 02/03/2023] Open
Abstract
KEY POINTS Central hypercapnic hypoventilation is highly prevalent in children suffering from congenital central hypoventilation syndrome (CCHS). Mutations of the gene for paired-like homeobox 2b (Phox2b) are aetiologically associated with CCHS and Phox2b is present in central components of respiratory chemoreflex, such as the nucleus tractus solitarius (NTS). Injection of the neurotoxin substance P-saporin into NTS destroys Phox2b-expressing neurons. Impaired hypercapnic ventilatory response caused by this neurotoxin is attributable to a loss of CO2 -sensitive Phox2b-expressing NTS neurons. A subgroup of Phox2b-expressing neurons exhibits intrinsic chemosensitivity. A background K+ channel-like current is partially responsible for such chemosensitivity in Phox2b-expressing neurons. The present study helps us better understand the mechanism of respiratory deficits in CCHS and potentially locates a brainstem site for development of precise clinical intervention. ABSTRACT The nucleus tractus solitarius (NTS) neurons have been considered to function as central respiratory chemoreceptors. However, the common molecular marker defined for these neurons remains unknown. The present study investigated whether paired-like homeobox 2b (Phox2b)-expressing NTS neurons are recruited in hypercapnic ventilatory response (HCVR) and whether these neurons exhibit intrinsic chemosensitivity. HCVR was assessed using whole body plethysmography and neuronal chemosensitivity was examined by patch clamp recordings in brainstem slices or dissociated neurons from Phox2b-EGFP transgenic mice. Injection of the neurotoxin substance P-saporin (SSP-SAP) into NTS destroyed Phox2b-expressing neurons. Minute ventilation and tidal volume were both reduced by 13% during exposure to 8% CO2 in inspired air when ∼13% of the Phox2b-expressing neurons were eliminated. However, a loss of ∼18% of these neurons was associated with considerable decreases in minute ventilation by ≥18% and in tidal volume by≥22% when challenged by ≥4% CO2 . In both cases, breathing frequency was unaffected. Most CO2 -activated neurons were immunoreactive to Phox2b. In brainstem slices, ∼43% of Phox2b-expressing neurons from Phox2b-EGFP mice displayed a sustained or transient increase in firing rate during physiological acidification (pH 7.0 or 8% CO2 ). Such a response was also present in dissociated neurons in favour of an intrinsic property. In voltage clamp recordings, a background K+ channel-like current was found in a subgroup of Phox2b-expressing neurons. Thus, the respiratory deficits caused by injection of SSP-SAP into the NTS are attributable to proportional lesions of CO2 /H+ -sensitive Phox2b-expressing neurons.
Collapse
Affiliation(s)
- Congrui Fu
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Jinyu Xue
- Department of Respiration, Hebei Chest Hospital, Shijiazhuang, Hebei, China
| | - Ri Wang
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Jinting Chen
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Lan Ma
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Yixian Liu
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Xuejiao Wang
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Fang Guo
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Yi Zhang
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Xiangjian Zhang
- Department of Neurology, Second Hospital of Hebei Medical University, Shijiazhuang, Hebei, China.,Hebei Key Laboratory of Vascular Homeostasis and Hebei Collaborative Innovation Center for Cardio-cerebrovascular Disease, Shijiazhuang, Hebei, China
| | - Sheng Wang
- Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei, China.,Hebei Key Laboratory of Vascular Homeostasis and Hebei Collaborative Innovation Center for Cardio-cerebrovascular Disease, Shijiazhuang, Hebei, China
| |
Collapse
|
25
|
Wojciechowski P, Szereda-Przestaszewska M, Lipkowski AW. Cardiorespiratory activity of C-terminal pentapeptide of substance P in anaesthetized rats. Respir Physiol Neurobiol 2016; 233:7-13. [DOI: 10.1016/j.resp.2016.07.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 07/20/2016] [Accepted: 07/21/2016] [Indexed: 12/19/2022]
|
26
|
Moreira TS, Takakura AC, Czeisler C, Otero JJ. Respiratory and autonomic dysfunction in congenital central hypoventilation syndrome. J Neurophysiol 2016; 116:742-52. [PMID: 27226447 PMCID: PMC6208311 DOI: 10.1152/jn.00026.2016] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Accepted: 05/25/2016] [Indexed: 12/22/2022] Open
Abstract
The developmental lineage of the PHOX2B-expressing neurons in the retrotrapezoid nucleus (RTN) has been extensively studied. These cells are thought to function as central respiratory chemoreceptors, i.e., the mechanism by which brain Pco2 regulates breathing. The molecular and cellular basis of central respiratory chemoreception is based on the detection of CO2 via intrinsic proton receptors (TASK-2, GPR4) as well as synaptic input from peripheral chemoreceptors and other brain regions. Murine models of congenital central hypoventilation syndrome designed with PHOX2B mutations have suggested RTN neuron agenesis. In this review, we examine, through human and experimental animal models, how a restricted number of neurons that express the transcription factor PHOX2B play a crucial role in the control of breathing and autonomic regulation.
Collapse
Affiliation(s)
- Thiago S Moreira
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil;
| | - Ana C Takakura
- Department of Pharmacology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil; and
| | - Catherine Czeisler
- The Ohio State University, College of Medicine, Department of Pathology, Division of Neuropathology, Columbus, Ohio
| | - Jose J Otero
- The Ohio State University, College of Medicine, Department of Pathology, Division of Neuropathology, Columbus, Ohio
| |
Collapse
|
27
|
Huckstepp RT, Henderson LE, Cardoza KP, Feldman JL. Interactions between respiratory oscillators in adult rats. eLife 2016; 5. [PMID: 27300271 PMCID: PMC4907693 DOI: 10.7554/elife.14203] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 04/27/2016] [Indexed: 01/20/2023] Open
Abstract
Breathing in mammals is hypothesized to result from the interaction of two distinct oscillators: the preBötzinger Complex (preBötC) driving inspiration and the lateral parafacial region (pFL) driving active expiration. To understand the interactions between these oscillators, we independently altered their excitability in spontaneously breathing vagotomized urethane-anesthetized adult rats. Hyperpolarizing preBötC neurons decreased inspiratory activity and initiated active expiration, ultimately progressing to apnea, i.e., cessation of both inspiration and active expiration. Depolarizing pFL neurons produced active expiration at rest, but not when inspiratory activity was suppressed by hyperpolarizing preBötC neurons. We conclude that in anesthetized adult rats active expiration is driven by the pFL but requires an additional form of network excitation, i.e., ongoing rhythmic preBötC activity sufficient to drive inspiratory motor output or increased chemosensory drive. The organization of this coupled oscillator system, which is essential for life, may have implications for other neural networks that contain multiple rhythm/pattern generators. DOI:http://dx.doi.org/10.7554/eLife.14203.001 Mammals breathe air into and out of their lungs to absorb oxygen into the body and to remove carbon dioxide. The rhythm of breathing is most likely controlled by two groups of neurons in a part of the brain called the brain stem. One group called the preBötzinger Complex drives breathing in (inspiration), and normally, breathing out (expiration) occurs when the muscles responsible for inspiration relax. The other group of neurons – known as the lateral parafacial region – controls extra muscles that allow us to increase our breathing when we need to, such as during exercise. Huckstepp et al. set out to determine how these two groups of neurons interact with one another in anesthetized rats to produce a reliable and efficient pattern of breathing. The experiments provide further evidence that inspiration is mainly driven by the preBötzinger Complex. Whilst activity from the lateral parafacial region is needed to cause the rats to breathe out more forcefully than normal, a second low level of activity from another source is also required. This source could either be the preBötzinger Complex, or some unknown neurons that change their activity in response to the levels of oxygen and carbon dioxide in the blood or fluid of the brain. Further investigation is required to identify how these interactions go awry in diseases that affect breathing, such as sleep apneas. DOI:http://dx.doi.org/10.7554/eLife.14203.002
Collapse
Affiliation(s)
- Robert Tr Huckstepp
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, United States
| | - Lauren E Henderson
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, United States
| | - Kathryn P Cardoza
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, United States
| | - Jack L Feldman
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, United States
| |
Collapse
|
28
|
Takakura AC, Moreira TS. The retrotrapezoid nucleus as a central brainstem area for central and peripheral chemoreceptor interactions. Exp Physiol 2016; 101:455-6. [DOI: 10.1113/ep085615] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Ana C. Takakura
- Department of Pharmacology; Institute of Biomedical Science, University of São Paulo (USP) 05508-000; São Paulo SP Brazil
| | - Thiago S. Moreira
- Department of Physiology and Biophysics; Institute of Biomedical Science, University of São Paulo (USP) 05508-000; São Paulo SP Brazil
| |
Collapse
|
29
|
Silva JN, Tanabe FM, Moreira TS, Takakura AC. Neuroanatomical and physiological evidence that the retrotrapezoid nucleus/parafacial region regulates expiration in adult rats. Respir Physiol Neurobiol 2016; 227:9-22. [PMID: 26900003 DOI: 10.1016/j.resp.2016.02.005] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 02/11/2016] [Accepted: 02/11/2016] [Indexed: 01/09/2023]
Abstract
The rostroventrolateral medulla contains two functional neuronal populations: (1) the parafacial respiratory group (pFRG) neurons and (2) the chemosensitive retrotrapezoid nucleus (RTN) neurons. Using anatomical and physiological techniques, we investigated the role of the RTN/pFRG in CO2-induced active expiration (AE) in urethane-anesthetized rats. Anterograde tracing using biotinylated dextran amine (BDA) revealed dense neuronal projections emanating from the RTN/pFRG to the caudal ventral respiratory group (cVRG), 60% of which contained vesicular glutamate transporter-2. The minority (16%) of the RTN projections to the cVRG emanated from Phox2b positive neurons. Hypercapnia (10% CO2) increased DiaEMG and elicited AbdEMG activity. Bilateral injections of muscimol (2mM) into the RTN/pFRG reduced the activation of DiaEMG (23±4%) and abolished AE-induced by chemoreflex stimulation. Taken together, these results support the presence of direct excitatory projections from RTN/pFRG neurons to cVRG expiratory premotor neurons, playing a role in the generation/modulation of AE.
Collapse
Affiliation(s)
- Josiane N Silva
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo (USP), 05508-000 São Paulo, SP, Brazil
| | - Fabiola M Tanabe
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo (USP), 05508-000 São Paulo, SP, Brazil
| | - Thiago S Moreira
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of São Paulo (USP), 05508-000 São Paulo, SP, Brazil
| | - Ana C Takakura
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo (USP), 05508-000 São Paulo, SP, Brazil.
| |
Collapse
|
30
|
Role of Astrocytes in Central Respiratory Chemoreception. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 949:109-145. [PMID: 27714687 DOI: 10.1007/978-3-319-40764-7_6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Astrocytes perform various homeostatic functions in the nervous system beyond that of a supportive or metabolic role for neurons. A growing body of evidence indicates that astrocytes are crucial for central respiratory chemoreception. This review presents a classical overview of respiratory central chemoreception and the new evidence for astrocytes as brainstem sensors in the respiratory response to hypercapnia. We review properties of astrocytes for chemosensory function and for modulation of the respiratory network. We propose that astrocytes not only mediate between CO2/H+ levels and motor responses, but they also allow for two emergent functions: (1) Amplifying the responses of intrinsic chemosensitive neurons through feedforward signaling via gliotransmitters and; (2) Recruiting non-intrinsically chemosensitive cells thanks to volume spreading of signals (calcium waves and gliotransmitters) to regions distant from the CO2/H+ sensitive domains. Thus, astrocytes may both increase the intensity of the neuron responses at the chemosensitive sites and recruit of a greater number of respiratory neurons to participate in the response to hypercapnia.
Collapse
|
31
|
Ikeda K, Takahashi M, Sato S, Igarashi H, Ishizuka T, Yawo H, Arata S, Southard-Smith EM, Kawakami K, Onimaru H. A Phox2b BAC Transgenic Rat Line Useful for Understanding Respiratory Rhythm Generator Neural Circuitry. PLoS One 2015; 10:e0132475. [PMID: 26147470 PMCID: PMC4492506 DOI: 10.1371/journal.pone.0132475] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Accepted: 06/15/2015] [Indexed: 11/21/2022] Open
Abstract
The key role of the respiratory neural center is respiratory rhythm generation to maintain homeostasis through the control of arterial blood pCO2/pH and pO2 levels. The neuronal network responsible for respiratory rhythm generation in neonatal rat resides in the ventral side of the medulla and is composed of two groups; the parafacial respiratory group (pFRG) and the pre-Bötzinger complex group (preBötC). The pFRG partially overlaps in the retrotrapezoid nucleus (RTN), which was originally identified in adult cats and rats. Part of the pre-inspiratory (Pre-I) neurons in the RTN/pFRG serves as central chemoreceptor neurons and the CO2 sensitive Pre-I neurons express homeobox gene Phox2b. Phox2b encodes a transcription factor and is essential for the development of the sensory-motor visceral circuits. Mutations in human PHOX2B cause congenital hypoventilation syndrome, which is characterized by blunted ventilatory response to hypercapnia. Here we describe the generation of a novel transgenic (Tg) rat harboring fluorescently labeled Pre-I neurons in the RTN/pFRG. In addition, the Tg rat showed fluorescent signals in autonomic enteric neurons and carotid bodies. Because the Tg rat expresses inducible Cre recombinase in PHOX2B-positive cells during development, it is a potentially powerful tool for dissecting the entire picture of the respiratory neural network during development and for identifying the CO2/O2 sensor molecules in the adult central and peripheral nervous systems.
Collapse
Affiliation(s)
- Keiko Ikeda
- Division of Biology, Hyogo College of Medicine, Nishinomiya, Hyogo, Japan
- Division of Biology, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan
- * E-mail:
| | - Masanori Takahashi
- Division of Biology, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan
| | - Shigeru Sato
- Division of Biology, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan
| | - Hiroyuki Igarashi
- Department of Physiology, and Pharmacology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
| | - Toru Ishizuka
- Department of Developmental Biology and Neuroscience, Tohoku University Graduate School of Life Sciences and JST/CREST, Sendai, Miyagi, Japan
| | - Hiromu Yawo
- Department of Physiology, and Pharmacology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
- Department of Developmental Biology and Neuroscience, Tohoku University Graduate School of Life Sciences and JST/CREST, Sendai, Miyagi, Japan
| | - Satoru Arata
- Center for Biotechnology, Showa University, Shinagawa, Tokyo, Japan
| | - E. Michelle Southard-Smith
- Division of Genetic Medicine, Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Kiyoshi Kawakami
- Division of Biology, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Tochigi, Japan
| | - Hiroshi Onimaru
- Department of Physiology, Showa University School of Medicine, Shinagawa, Tokyo, Japan
| |
Collapse
|
32
|
Ruffault PL, D'Autréaux F, Hayes JA, Nomaksteinsky M, Autran S, Fujiyama T, Hoshino M, Hägglund M, Kiehn O, Brunet JF, Fortin G, Goridis C. The retrotrapezoid nucleus neurons expressing Atoh1 and Phox2b are essential for the respiratory response to CO₂. eLife 2015; 4. [PMID: 25866925 PMCID: PMC4429526 DOI: 10.7554/elife.07051] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Accepted: 04/09/2015] [Indexed: 01/08/2023] Open
Abstract
Maintaining constant CO2 and H+ concentrations in the arterial blood is critical for life. The principal mechanism through which this is achieved in mammals is the respiratory chemoreflex whose circuitry is still elusive. A candidate element of this circuitry is the retrotrapezoid nucleus (RTN), a collection of neurons at the ventral medullary surface that are activated by increased CO2 or low pH and project to the respiratory rhythm generator. Here, we use intersectional genetic strategies to lesion the RTN neurons defined by Atoh1 and Phox2b expression and to block or activate their synaptic output. Photostimulation of these neurons entrains the respiratory rhythm. Conversely, abrogating expression of Atoh1 or Phox2b or glutamatergic transmission in these cells curtails the phrenic nerve response to low pH in embryonic preparations and abolishes the respiratory chemoreflex in behaving animals. Thus, the RTN neurons expressing Atoh1 and Phox2b are a necessary component of the chemoreflex circuitry. DOI:http://dx.doi.org/10.7554/eLife.07051.001 An adult at rest will typically breathe in and out up to 20 times per minute, inhaling oxygen and exhaling carbon dioxide in a process that, for the most part, occurs automatically. While we can choose to override this process and exert voluntary control over our breathing, we cannot suppress it indefinitely. Attempting to do so will ultimately trigger a reflex that forces us to start breathing again. This reflex is mostly a response to the rise of carbon dioxide (CO2) in the blood, which lowers the pH of the blood. This rise in CO2 is toxic and triggers an increase in breathing so that the excess CO2 is exhaled. The majority of the sensors that detect CO2 are in the brainstem, which is at the junction of the brain and the spinal cord. However, the precise location of these sensors is not clear. Ruffault et al. now argue that the sensors are in a region called the ‘retrotrapezoid nucleus’, and that they can be identified by the presence of two proteins, Atoh1 and Phox2b. In the brains of foetal mice, Ruffault et al. recorded cells in the retrotrapezoid nucleus and found that they fired in a rhythmic pattern, as would be expected for cells that control breathing. Moreover, the firing rate of these cells increased when the pH was lowered. Ruffault et al. then created genetically modified mice with mutations in genes for Atoh1 or Phox2b. The retrotrapezoid nucleus was either absent or abnormal in these mutant mice. Moreover, new-born pups with these mutations were not able to increase their breathing when the level of CO2 in their blood rose. These results shed light on the respiratory distress experienced by patients with a rare disorder called congenital central hypoventilation syndrome (CCHS) that is caused by mutations in Phox2b. More commonly, unstable or irregular breathing is seen in human infants that are born prematurely, and sometimes in infants born at full term. In the light of the new findings by Ruffault et al., it is possible that abnormal development or immaturity of the retrotrapezoid nucleus is the cause. DOI:http://dx.doi.org/10.7554/eLife.07051.002
Collapse
Affiliation(s)
- Pierre-Louis Ruffault
- Université Paris-Saclay, Université Paris-Sud, CNRS, UMR 9197, Institut des Neurosciences Paris-Saclay, Gif-sur-Yvette, France
| | - Fabien D'Autréaux
- Institut de Biologie de l'École Normale Supérieure, Inserm U1024, and CNRS UMR 8197, Paris, France
| | - John A Hayes
- Université Paris-Saclay, Université Paris-Sud, CNRS, UMR 9197, Institut des Neurosciences Paris-Saclay, Gif-sur-Yvette, France
| | - Marc Nomaksteinsky
- Institut de Biologie de l'École Normale Supérieure, Inserm U1024, and CNRS UMR 8197, Paris, France
| | - Sandra Autran
- Université Paris-Saclay, Université Paris-Sud, CNRS, UMR 9197, Institut des Neurosciences Paris-Saclay, Gif-sur-Yvette, France
| | - Tomoyuki Fujiyama
- Department of Biochemistry and Cellular Biology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Mikio Hoshino
- Department of Biochemistry and Cellular Biology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Martin Hägglund
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Ole Kiehn
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Jean-François Brunet
- Institut de Biologie de l'École Normale Supérieure, Inserm U1024, and CNRS UMR 8197, Paris, France
| | - Gilles Fortin
- Université Paris-Saclay, Université Paris-Sud, CNRS, UMR 9197, Institut des Neurosciences Paris-Saclay, Gif-sur-Yvette, France
| | - Christo Goridis
- Institut de Biologie de l'École Normale Supérieure, Inserm U1024, and CNRS UMR 8197, Paris, France
| |
Collapse
|
33
|
Abstract
Contiguous brain regions associated with a given behavior are increasingly being divided into subregions associated with distinct aspects of that behavior. Using recently developed neuronal hyperpolarizing technologies, we functionally dissect the parafacial region in the medulla, which contains key elements of the central pattern generator for breathing that are important in central CO2-chemoreception and for gating active expiration. By transfecting different populations of neighboring neurons with allatostatin or HM4D Gi/o-coupled receptors, we analyzed the effect of their hyperpolarization on respiration in spontaneously breathing vagotomized urethane-anesthetized rats. We identify two functionally separate parafacial nuclei: ventral (pFV) and lateral (pFL). Disinhibition of the pFL with bicuculline and strychnine led to active expiration. Hyperpolarizing pFL neurons had no effect on breathing at rest, or changes in inspiratory activity induced by hypoxia and hypercapnia; however, hyperpolarizing pFL neurons attenuated active expiration when it was induced by hypercapnia, hypoxia, or disinhibition of the pFL. In contrast, hyperpolarizing pFV neurons affected breathing at rest by decreasing inspiratory-related activity, attenuating the hypoxia- and hypercapnia-induced increase in inspiratory activity, and when present, reducing expiratory-related abdominal activity. Together with previous observations, we conclude that the pFV provides a generic excitatory drive to breathe, even at rest, whereas the pFL is a conditional oscillator quiet at rest that, when activated, e.g., during exercise, drives active expiration.
Collapse
|
34
|
Abstract
Lung ventilation fluctuates widely with behavior but arterial PCO2 remains stable. Under normal conditions, the chemoreflexes contribute to PaCO2 stability by producing small corrective cardiorespiratory adjustments mediated by lower brainstem circuits. Carotid body (CB) information reaches the respiratory pattern generator (RPG) via nucleus solitarius (NTS) glutamatergic neurons which also target rostral ventrolateral medulla (RVLM) presympathetic neurons thereby raising sympathetic nerve activity (SNA). Chemoreceptors also regulate presympathetic neurons and cardiovagal preganglionic neurons indirectly via inputs from the RPG. Secondary effects of chemoreceptors on the autonomic outflows result from changes in lung stretch afferent and baroreceptor activity. Central respiratory chemosensitivity is caused by direct effects of acid on neurons and indirect effects of CO2 via astrocytes. Central respiratory chemoreceptors are not definitively identified but the retrotrapezoid nucleus (RTN) is a particularly strong candidate. The absence of RTN likely causes severe central apneas in congenital central hypoventilation syndrome. Like other stressors, intense chemosensory stimuli produce arousal and activate circuits that are wake- or attention-promoting. Such pathways (e.g., locus coeruleus, raphe, and orexin system) modulate the chemoreflexes in a state-dependent manner and their activation by strong chemosensory stimuli intensifies these reflexes. In essential hypertension, obstructive sleep apnea and congestive heart failure, chronically elevated CB afferent activity contributes to raising SNA but breathing is unchanged or becomes periodic (severe CHF). Extreme CNS hypoxia produces a stereotyped cardiorespiratory response (gasping, increased SNA). The effects of these various pathologies on brainstem cardiorespiratory networks are discussed, special consideration being given to the interactions between central and peripheral chemoreflexes.
Collapse
Affiliation(s)
- Patrice G Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia
| |
Collapse
|
35
|
Reyes EP, Cerpa V, Corvalán L, Retamal MA. Cxs and Panx- hemichannels in peripheral and central chemosensing in mammals. Front Cell Neurosci 2014; 8:123. [PMID: 24847209 PMCID: PMC4023181 DOI: 10.3389/fncel.2014.00123] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 04/18/2014] [Indexed: 01/08/2023] Open
Abstract
Connexins (Cxs) and Pannexins (Panx) form hemichannels at the plasma membrane of animals. Despite their low open probability under physiological conditions, these hemichannels release signaling molecules (i.e., ATP, Glutamate, PGE2) to the extracellular space, thus subserving several important physiological processes. Oxygen and CO2 sensing are fundamental to the normal functioning of vertebrate organisms. Fluctuations in blood PO2, PCO2 and pH are sensed at the carotid bifurcations of adult mammals by glomus cells of the carotid bodies. Likewise, changes in pH and/or PCO2 of cerebrospinal fluid are sensed by central chemoreceptors, a group of specialized neurones distributed in the ventrolateral medulla (VLM), raphe nuclei, and some other brainstem areas. After many years of research, the molecular mechanisms involved in chemosensing process are not completely understood. This manuscript will review data regarding relationships between chemosensitive cells and the expression of channels formed by Cxs and Panx, with special emphasis on hemichannels.
Collapse
Affiliation(s)
- Edison Pablo Reyes
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo Santiago, Chile ; Dirección de Investigación, Universidad Autónoma de Chile Santiago, Chile
| | - Verónica Cerpa
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo Santiago, Chile
| | - Liliana Corvalán
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo Santiago, Chile
| | - Mauricio Antonio Retamal
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo Santiago, Chile
| |
Collapse
|
36
|
Takakura AC, Barna BF, Cruz JC, Colombari E, Moreira TS. Phox2b-expressing retrotrapezoid neurons and the integration of central and peripheral chemosensory control of breathing in conscious rats. Exp Physiol 2014; 99:571-85. [DOI: 10.1113/expphysiol.2013.076752] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Ana C. Takakura
- Department of Pharmacology; Institute of Biomedical Science; University of São Paulo (USP); 05508-000 São Paulo SP Brazil
| | - Bárbara F. Barna
- Department of Physiology and Biophysics; Institute of Biomedical Science; University of São Paulo (USP); 05508-000 São Paulo SP Brazil
| | - Josiane C. Cruz
- Department of Biothechnology; Biotechnology Center; Federal University of Paraiba (UFPB); 58051-900 João Pessoa PB Brazil
| | - Eduardo Colombari
- Department of Physiology and Pathology; School of Dentistry, São Paulo State University (UNESP); 14801-903 Araraquara SP Brazil
| | - Thiago S. Moreira
- Department of Physiology and Biophysics; Institute of Biomedical Science; University of São Paulo (USP); 05508-000 São Paulo SP Brazil
| |
Collapse
|
37
|
Substance P differentially modulates firing rate of solitary complex (SC) neurons from control and chronic hypoxia-adapted adult rats. PLoS One 2014; 9:e88161. [PMID: 24516602 PMCID: PMC3917864 DOI: 10.1371/journal.pone.0088161] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Accepted: 01/03/2014] [Indexed: 11/19/2022] Open
Abstract
NK1 receptors, which bind substance P, are present in the majority of brainstem regions that contain CO2/H(+)-sensitive neurons that play a role in central chemosensitivity. However, the effect of substance P on the chemosensitive response of neurons from these regions has not been studied. Hypoxia increases substance P release from peripheral afferents that terminate in the caudal nucleus tractus solitarius (NTS). Here we studied the effect of substance P on the chemosensitive responses of solitary complex (SC: NTS and dorsal motor nucleus) neurons from control and chronic hypoxia-adapted (CHx) adult rats. We simultaneously measured intracellular pH and electrical responses to hypercapnic acidosis in SC neurons from control and CHx adult rats using the blind whole cell patch clamp technique and fluorescence imaging microscopy. Substance P significantly increased the basal firing rate in SC neurons from control and CHx rats, although the increase was smaller in CHx rats. However, substance P did not affect the chemosensitive response of SC neurons from either group of rats. In conclusion, we found that substance P plays a role in modulating the basal firing rate of SC neurons but the magnitude of the effect is smaller for SC neurons from CHx adult rats, implying that NK1 receptors may be down regulated in CHx adult rats. Substance P does not appear to play a role in modulating the firing rate response to hypercapnic acidosis of SC neurons from either control or CHx adult rats.
Collapse
|
38
|
Gilabert-Oriol R, Weng A, Mallinckrodt BV, Melzig MF, Fuchs H, Thakur M. Immunotoxins constructed with ribosome-inactivating proteins and their enhancers: a lethal cocktail with tumor specific efficacy. Curr Pharm Des 2014; 20:6584-643. [PMID: 25341935 PMCID: PMC4296666 DOI: 10.2174/1381612820666140826153913] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Accepted: 08/05/2014] [Indexed: 11/30/2022]
Abstract
The term ribosome-inactivating protein (RIP) is used to denominate proteins mostly of plant origin, which have N-glycosidase enzymatic activity leading to a complete destruction of the ribosomal function. The discovery of the RIPs was almost a century ago, but their usage has seen transition only in the last four decades. With the advent of antibody therapy, the RIPs have been a subject of extensive research especially in targeted tumor therapies, which is the primary focus of this review. In the present work we enumerate 250 RIPs, which have been identified so far. An attempt has been made to identify all the RIPs that have been used for the construction of immunotoxins, which are conjugates or fusion proteins of an antibody or ligand with a toxin. The data from 1960 onwards is reviewed in this paper and an extensive list of more than 450 immunotoxins is reported. The clinical reach of tumor-targeted toxins has been identified and detailed in the work as well. While there is a lot of potential that RIPs embrace for targeted tumor therapies, the success in preclinical and clinical evaluations has been limited mainly because of their inability to escape the endo/lysosomal degradation. Various strategies that can increase the efficacy and lower the required dose for targeted toxins have been compiled in this article. It is plausible that with the advancements in platform technologies or improved endosomal escape the usage of tumor targeted RIPs would see the daylight of clinical success.
Collapse
Affiliation(s)
| | | | | | | | | | - Mayank Thakur
- Institut fur Laboratoriumsmedizin, Klinische Chemie und Pathobiochemie, Charite - Universitatsmedizin Berlin, Campus Virchow-Klinikum (Forum 4), Augustenburger Platz 1, D-13353 Berlin, Germany.
| |
Collapse
|
39
|
Guyenet PG, Abbott SBG, Stornetta RL. The respiratory chemoreception conundrum: light at the end of the tunnel? Brain Res 2013; 1511:126-37. [PMID: 23088963 PMCID: PMC3570739 DOI: 10.1016/j.brainres.2012.10.028] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 10/10/2012] [Accepted: 10/14/2012] [Indexed: 11/29/2022]
Abstract
Arterial PCO₂ is tightly regulated via changes in breathing. A rise in PCO₂ activates the carotid bodies and exerts additional effects on neurons located within the CNS, causing an increase in lung ventilation. Central respiratory chemoreception refers to the component of this homeostatic reflex that is triggered by activation of receptors located within the brain (central chemoreceptors). Throughout the body, CO₂ generally operates via the proxy of pH. Since countless proteins, ion channels and neurons display some degree of pH-sensitivity, the notion that central respiratory chemoreception could rely on a few specialized neurons seems a priori counter-intuitive. Yet, two types of neurons currently stand out as critically important for breathing regulation by CO₂: the retrotrapezoid nucleus (RTN) and the raphe. RTN neurons are glutamatergic, strongly activated by hypercapnia in vivo and by CO₂ or protons in slices. These neurons target selectively the pontomedullary regions implicated in generating the respiratory rhythm and pattern. Their response to CO₂ seems to involve both cell-autonomous and paracrine effects of CO₂, the latter presumably mediated by the surrounding glia. The specific connections that these excitatory neurons establish with the rest of the breathing network are likely to be the main explanation of their importance to respiratory chemoreception. Serotonergic neurons have a powerful stimulatory effect on breathing, they facilitate the chemoreflexes and a subset of them likely function as CO₂ sensors. Opto- and pharmacogenetic methods have played an important role in assessing the contribution of RTN and serotonergic neurons as well as glial cells to respiration. These particular experiments are emphasized here for thematic reasons although the current perception of the importance of the RTN and serotonergic cells to respiratory chemoreception also relies on many other types of evidence. A small portion of this evidence is presented as background. This article is part of a Special Issue entitled Optogenetics (7th BRES).
Collapse
Affiliation(s)
- Patrice G Guyenet
- Department of Pharmacology, University of Virginia, 1300 Jefferson Park Ave, Charlottesville, VA 22908, USA.
| | | | | |
Collapse
|
40
|
Takakura AC, Moreira TS, De Paula PM, Menani JV, Colombari E. Control of breathing and blood pressure by parafacial neurons in conscious rats. Exp Physiol 2012; 98:304-15. [DOI: 10.1113/expphysiol.2012.065128] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
41
|
Mouradian GC, Forster HV, Hodges MR. Acute and chronic effects of carotid body denervation on ventilation and chemoreflexes in three rat strains. J Physiol 2012; 590:3335-47. [PMID: 22615434 DOI: 10.1113/jphysiol.2012.234658] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Brown Norway (BN) rats have a relatively specific deficit in CO2 sensitivity. This deficit could be due to an abnormally weak carotid body contribution to CO2 sensitivity. Accordingly, we tested the hypothesis that CBD would have less of an effect on eupnoeic breathing and CO2 sensitivity in the BN rats compared to other rat strains.We measured ventilation and blood gases at rest (eupnoea) and during hypoxia (FIO2 =0.12) or hypercapnia (FICO2 =0.07) before and up to 23 days after bilateral or Sham CBD in BN, Sprague–Dawley (SD) and Dahl Salt-Sensitive (SS) rats. In all three rat strains, CBD elicited eupnoeic hypoventilation (PaCO2 +8.7–11.0 mmHg) 1–2 days post-CBD (P <0.05), and attenuated ventilatory responses to hypoxia (P <0.05) and venous sodium cyanide (NaCN; P<0.05), while sham CBD had no effect on resting breathing, blood gases or chemoreflexes (P >0.05). In contrast, CBD had no effect on CO2 sensitivity (˙VE/PaCO2) in all strains (P>0.05). Eupnoeic PaCO2 returned to pre-CBD values within 15–23 days post-CBD. Thus, the effects of CBD in rats (1) further support an important role for the carotid bodies in eupnoeic blood gas regulation, (2) suggest that the carotid bodies are not a major determinant of CO2 sensitivity in rats, and (3) may not support the concept of an interaction among the peripheral and central chemoreceptors in rats.
Collapse
Affiliation(s)
- Gary C Mouradian
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | | | | |
Collapse
|
42
|
Abstract
Central chemoreception traditionally refers to a change in ventilation attributable to changes in CO2/H(+) detected within the brain. Interest in central chemoreception has grown substantially since the previous Handbook of Physiology published in 1986. Initially, central chemoreception was localized to areas on the ventral medullary surface, a hypothesis complemented by the recent identification of neurons with specific phenotypes near one of these areas as putative chemoreceptor cells. However, there is substantial evidence that many sites participate in central chemoreception some located at a distance from the ventral medulla. Functionally, central chemoreception, via the sensing of brain interstitial fluid H(+), serves to detect and integrate information on (i) alveolar ventilation (arterial PCO2), (ii) brain blood flow and metabolism, and (iii) acid-base balance, and, in response, can affect breathing, airway resistance, blood pressure (sympathetic tone), and arousal. In addition, central chemoreception provides a tonic "drive" (source of excitation) at the normal, baseline PCO2 level that maintains a degree of functional connectivity among brainstem respiratory neurons necessary to produce eupneic breathing. Central chemoreception responds to small variations in PCO2 to regulate normal gas exchange and to large changes in PCO2 to minimize acid-base changes. Central chemoreceptor sites vary in function with sex and with development. From an evolutionary perspective, central chemoreception grew out of the demands posed by air versus water breathing, homeothermy, sleep, optimization of the work of breathing with the "ideal" arterial PCO2, and the maintenance of the appropriate pH at 37°C for optimal protein structure and function.
Collapse
Affiliation(s)
- Eugene Nattie
- Dartmouth Medical School, Department of Physiology, Lebanon, New Hampshire, USA.
| | | |
Collapse
|
43
|
Abstract
Central chemoreception traditionally refers to a change in ventilation attributable to changes in CO2/H(+) detected within the brain. Interest in central chemoreception has grown substantially since the previous Handbook of Physiology published in 1986. Initially, central chemoreception was localized to areas on the ventral medullary surface, a hypothesis complemented by the recent identification of neurons with specific phenotypes near one of these areas as putative chemoreceptor cells. However, there is substantial evidence that many sites participate in central chemoreception some located at a distance from the ventral medulla. Functionally, central chemoreception, via the sensing of brain interstitial fluid H(+), serves to detect and integrate information on (i) alveolar ventilation (arterial PCO2), (ii) brain blood flow and metabolism, and (iii) acid-base balance, and, in response, can affect breathing, airway resistance, blood pressure (sympathetic tone), and arousal. In addition, central chemoreception provides a tonic "drive" (source of excitation) at the normal, baseline PCO2 level that maintains a degree of functional connectivity among brainstem respiratory neurons necessary to produce eupneic breathing. Central chemoreception responds to small variations in PCO2 to regulate normal gas exchange and to large changes in PCO2 to minimize acid-base changes. Central chemoreceptor sites vary in function with sex and with development. From an evolutionary perspective, central chemoreception grew out of the demands posed by air versus water breathing, homeothermy, sleep, optimization of the work of breathing with the "ideal" arterial PCO2, and the maintenance of the appropriate pH at 37°C for optimal protein structure and function.
Collapse
Affiliation(s)
- Eugene Nattie
- Dartmouth Medical School, Department of Physiology, Lebanon, New Hampshire, USA.
| | | |
Collapse
|
44
|
Spirovski D, Li Q, Pilowsky PM. Brainstem galanin-synthesizing neurons are differentially activated by chemoreceptor stimuli and represent a subpopulation of respiratory neurons. J Comp Neurol 2011; 520:154-73. [DOI: 10.1002/cne.22723] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
|
45
|
Wilkinson KA, Fu Z, Powell FL. Ventilatory effects of substance P-saporin lesions in the nucleus tractus solitarii of chronically hypoxic rats. Am J Physiol Regul Integr Comp Physiol 2011; 301:R343-50. [PMID: 21593425 PMCID: PMC3154706 DOI: 10.1152/ajpregu.00375.2010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Accepted: 05/16/2011] [Indexed: 01/09/2023]
Abstract
During ventilatory acclimatization to hypoxia (VAH), time-dependent increases in ventilation lower Pco(2) levels, and this persists on return to normoxia. We hypothesized that plasticity in the caudal nucleus tractus solitarii (NTS) contributes to VAH, as the NTS receives the first synapse from the carotid body chemoreceptor afferents and also contains CO(2)-sensitive neurons. We lesioned cells in the caudal NTS containing the neurokinin-1 receptor by microinjecting the neurotoxin saporin conjugated to substance P and measured ventilatory responses in awake, unrestrained rats 18 days later. Lesions did not affect hypoxic or hypercapnic ventilatory responses in normoxic control rats, in contrast to published reports for similar lesions in other central chemosensitive areas. Also, lesions did not affect the hypercapnic ventilatory response in chronically hypoxic rats (inspired Po(2) = 90 Torr for 7 days). These results suggest functional differences between central chemoreceptor sites. However, lesions significantly increased ventilation in normoxia or acute hypoxia in chronically hypoxic rats. Hence, chronic hypoxia increases an inhibitory effect of neurokinin-1 receptor neurons in the NTS on ventilatory drive, indicating that these neurons contribute to plasticity during chronic hypoxia, although such plasticity does not explain VAH.
Collapse
Affiliation(s)
- Katherine A Wilkinson
- Division of Physiology, Department of Medicine, University of California, San Diego, USA.
| | | | | |
Collapse
|
46
|
Abstract
A subset of preBötzinger Complex (preBötC) neurokinin 1 receptor (NK1R) and somatostatin peptide (SST)-expressing neurons are necessary for breathing in adult rats, in vivo. Their developmental origins and relationship to other preBötC glutamatergic neurons are unknown. Here we show, in mice, that the "core" of preBötC SST(+)/NK1R(+)/SST 2a receptor(+) (SST2aR) neurons, are derived from Dbx1-expressing progenitors. We also show that Dbx1-derived neurons heterogeneously coexpress NK1R and SST2aR within and beyond the borders of preBötC. More striking, we find that nearly all non-catecholaminergic glutamatergic neurons of the ventrolateral medulla (VLM) are also Dbx1 derived. PreBötC SST(+) neurons are born between E9.5 and E11.5 in the same proportion as non-SST-expressing neurons. Additionally, preBötC Dbx1 neurons are respiratory modulated and show an early inspiratory phase of firing in rhythmically active slice preparations. Loss of Dbx1 eliminates all glutamatergic neurons from the respiratory VLM including preBötC NK1R(+)/SST(+) neurons. Dbx1 mutant mice do not express any spontaneous respiratory behaviors in vivo. Moreover, they do not generate rhythmic inspiratory activity in isolated en bloc preparations even after acidic or serotonergic stimulation. These data indicate that preBötC core neurons represent a subset of a larger, more heterogeneous population of VLM Dbx1-derived neurons. These data indicate that Dbx1-derived neurons are essential for the expression and, we hypothesize, are responsible for the generation of respiratory behavior both in vitro and in vivo.
Collapse
|
47
|
Goridis C, Dubreuil V, Thoby-Brisson M, Fortin G, Brunet JF. Phox2b, congenital central hypoventilation syndrome and the control of respiration. Semin Cell Dev Biol 2010; 21:814-22. [DOI: 10.1016/j.semcdb.2010.07.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2010] [Accepted: 07/25/2010] [Indexed: 10/19/2022]
|
48
|
Abstract
By definition central respiratory chemoreceptors (CRCs) are cells that are sensitive to changes in brain PCO(2) or pH and contribute to the stimulation of breathing elicited by hypercapnia or metabolic acidosis. CO(2) most likely works by lowering pH. The pertinent proton receptors have not been identified and may be ion channels. CRCs are probably neurons but may also include acid-sensitive glia and vascular cells that communicate with neurons via paracrine mechanisms. Retrotrapezoid nucleus (RTN) neurons are the most completely characterized CRCs. Their high sensitivity to CO(2) in vivo presumably relies on their intrinsic acid sensitivity, excitatory inputs from the carotid bodies and brain regions such as raphe and hypothalamus, and facilitating influences from neighboring astrocytes. RTN neurons are necessary for the respiratory network to respond to CO(2) during the perinatal period and under anesthesia. In conscious adults, RTN neurons contribute to an unknown degree to the pH-dependent regulation of breathing rate, inspiratory, and expiratory activity. The abnormal prenatal development of RTN neurons probably contributes to the congenital central hypoventilation syndrome. Other CRCs presumably exist, but the supportive evidence is less complete. The proposed locations of these CRCs are the medullary raphe, the nucleus tractus solitarius, the ventrolateral medulla, the fastigial nucleus, and the hypothalamus. Several wake-promoting systems (serotonergic and catecholaminergic neurons, orexinergic neurons) are also putative CRCs. Their contribution to central respiratory chemoreception may be behavior dependent or vary according to the state of vigilance.
Collapse
Affiliation(s)
- Patrice G Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908, USA.
| | | | | |
Collapse
|
49
|
Abstract
Research in animal models implicates the retrotrapezoid nucleus (RTN) as a critical central chemoreceptor located in the brain stem. In rodents, RTN neurons co-express the tachykinin receptor NK1R and the transcription factor PHOX2B. In humans, PHOX2B mutations, which expand a polyalanine tract in the protein, cause congenital central hypoventilation syndrome. Mice with analogous Phox2B mutations model this phenotype and lack PHOX2B immunoreactivity in their RTNs. We evaluated PHOX2B immunoreactivity in sections of the caudal pons and medulla of 17 human fetuses and infants. The transcription factor was detected in brain stem nuclei that correspond to established sites of murine PHOX2B expression, including the RTN. The putative human RTN is located ventral to the facial nucleus and lateral to the superior olivary nucleus at the level of the pontomedullary junction.
Collapse
Affiliation(s)
- Erin Rudzinski
- Department of Laboratories, Seattle Children's Hospital, Seattle, WA, USA
| | | |
Collapse
|
50
|
de Carvalho D, Bícego KC, de Castro OW, da Silva GS, Garcia-Cairasco N, Gargaglioni LH. Role of neurokinin-1 expressing neurons in the locus coeruleus on ventilatory and cardiovascular responses to hypercapnia. Respir Physiol Neurobiol 2010; 172:24-31. [DOI: 10.1016/j.resp.2010.04.016] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Revised: 04/04/2010] [Accepted: 04/08/2010] [Indexed: 10/19/2022]
|