1
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Cleary CM, Browning JL, Armbruster M, Sobrinho CR, Strain ML, Jahanbani S, Soto-Perez J, Hawkins VE, Dulla CG, Olsen ML, Mulkey DK. Kir4.1 channels contribute to astrocyte CO 2/H +-sensitivity and the drive to breathe. Commun Biol 2024; 7:373. [PMID: 38548965 PMCID: PMC10978993 DOI: 10.1038/s42003-024-06065-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 03/18/2024] [Indexed: 04/01/2024] Open
Abstract
Astrocytes in the retrotrapezoid nucleus (RTN) stimulate breathing in response to CO2/H+, however, it is not clear how these cells detect changes in CO2/H+. Considering Kir4.1/5.1 channels are CO2/H+-sensitive and important for several astrocyte-dependent processes, we consider Kir4.1/5.1 a leading candidate CO2/H+ sensor in RTN astrocytes. To address this, we show that RTN astrocytes express Kir4.1 and Kir5.1 transcripts. We also characterized respiratory function in astrocyte-specific inducible Kir4.1 knockout mice (Kir4.1 cKO); these mice breathe normally under room air conditions but show a blunted ventilatory response to high levels of CO2, which could be partly rescued by viral mediated re-expression of Kir4.1 in RTN astrocytes. At the cellular level, astrocytes in slices from astrocyte-specific inducible Kir4.1 knockout mice are less responsive to CO2/H+ and show a diminished capacity for paracrine modulation of respiratory neurons. These results suggest Kir4.1/5.1 channels in RTN astrocytes contribute to respiratory behavior.
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Affiliation(s)
- Colin M Cleary
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT, USA
| | - Jack L Browning
- School of Neuroscience and Genetics, Genomics and Computational Biology, Virginia Tech, Blacksburg, VA, USA
| | - Moritz Armbruster
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Cleyton R Sobrinho
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT, USA
| | - Monica L Strain
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT, USA
| | - Sarvin Jahanbani
- School of Neuroscience and Genetics, Genomics and Computational Biology, Virginia Tech, Blacksburg, VA, USA
| | - Jaseph Soto-Perez
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT, USA
| | - Virginia E Hawkins
- Department of Life Sciences, Manchester Metropolitan University, Manchester, UK
| | - Chris G Dulla
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Michelle L Olsen
- School of Neuroscience and Genetics, Genomics and Computational Biology, Virginia Tech, Blacksburg, VA, USA
| | - Daniel K Mulkey
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT, USA.
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2
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Shigetomi E, Sakai K, Koizumi S. Extracellular ATP/adenosine dynamics in the brain and its role in health and disease. Front Cell Dev Biol 2024; 11:1343653. [PMID: 38304611 PMCID: PMC10830686 DOI: 10.3389/fcell.2023.1343653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Accepted: 12/31/2023] [Indexed: 02/03/2024] Open
Abstract
Extracellular ATP and adenosine are neuromodulators that regulate numerous neuronal functions in the brain. Neuronal activity and brain insults such as ischemic and traumatic injury upregulate these neuromodulators, which exert their effects by activating purinergic receptors. In addition, extracellular ATP/adenosine signaling plays a pivotal role in the pathogenesis of neurological diseases. Virtually every cell type in the brain contributes to the elevation of ATP/adenosine, and various mechanisms underlying this increase have been proposed. Extracellular adenosine is thought to be mainly produced via the degradation of extracellular ATP. However, adenosine is also released from neurons and glia in the brain. Therefore, the regulation of extracellular ATP/adenosine in physiological and pathophysiological conditions is likely far more complex than previously thought. To elucidate the complex mechanisms that regulate extracellular ATP/adenosine levels, accurate methods of assessing their spatiotemporal dynamics are needed. Several novel techniques for acquiring spatiotemporal information on extracellular ATP/adenosine, including fluorescent sensors, have been developed and have started to reveal the mechanisms underlying the release, uptake and degradation of ATP/adenosine. Here, we review methods for analyzing extracellular ATP/adenosine dynamics as well as the current state of knowledge on the spatiotemporal dynamics of ATP/adenosine in the brain. We focus on the mechanisms used by neurons and glia to cooperatively produce the activity-dependent increase in ATP/adenosine and its physiological and pathophysiological significance in the brain.
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Affiliation(s)
- Eiji Shigetomi
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo, Japan
- Yamanashi GLIA Center, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo, Japan
| | - Kent Sakai
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo, Japan
- Yamanashi GLIA Center, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo, Japan
| | - Schuichi Koizumi
- Department of Neuropharmacology, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo, Japan
- Yamanashi GLIA Center, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo, Japan
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3
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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.
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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
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4
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Moreira TS, Mulkey DK, Takakura AC. Update on vascular control of central chemoreceptors. Exp Physiol 2023. [PMID: 38153366 DOI: 10.1113/ep091329] [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: 10/31/2023] [Accepted: 12/11/2023] [Indexed: 12/29/2023]
Abstract
At least four mechanisms have been proposed to elucidate how neurons in the retrotrapezoid (RTN) region sense changes in CO2 /H+ to regulate breathing (i.e., function as respiratory chemosensors). These mechanisms include: (1) intrinsic neuronal sensitivity to H+ mediated by TASK-2 and GPR4; (2) paracrine activation of RTN neurons by CO2 -responsive astrocytes (via a purinergic mechanism); (3) enhanced excitatory synaptic input or disinhibition; and (4) CO2 -induced vascular contraction. Although blood flow can influence tissue CO2 /H+ levels, there is limited understanding of how control of vascular tone in central CO2 chemosensitive regions might contribute to respiratory output. In this review, we focus on recent evidence that CO2 /H+ -induced purinergic-dependent vasoconstriction in the ventral parafacial region near RTN neurons supports respiratory chemoreception. This mechanism appears to be unique to the ventral parafacial region and opposite to other brain regions, including medullary chemosensor regions, where CO2 /H+ elicits vasodilatation. We speculate that this mechanism helps to maintain CO2 /H+ levels in the vicinity of RTN neurons, thereby maintaining the drive to breathe. Important next steps include determining whether disruption of CO2 /H+ vascular reactivity contributes to or can be targeted to improve breathing problems in disease states, such as Parkinson's disease.
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Affiliation(s)
- Thiago S Moreira
- Department of Physiology and Biophysics, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo, Brazil
| | - Daniel K Mulkey
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut, USA
| | - Ana C Takakura
- Department of Pharmacology, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, São Paulo, Brazil
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5
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Butler J, Dale N. X-linked Charcot Marie Tooth mutations alter CO 2 sensitivity of connexin32 hemichannels. Front Cell Neurosci 2023; 17:1330983. [PMID: 38188670 PMCID: PMC10771293 DOI: 10.3389/fncel.2023.1330983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 12/07/2023] [Indexed: 01/09/2024] Open
Abstract
Connexin32 (Cx32) is expressed in myelinating Schwann cells. It forms both reflexive gap junctions, to facilitate transfer of molecules from the outer to the inner myelin layers and hemichannels at the paranode to permit action potential-evoked release of ATP into the extracellular space. Loss of function mutations in Cx32 cause X-linked Charcot Marie Tooth disease (CMTX), a slowly developing peripheral neuropathy. The mechanistic links between Cx32 mutations and CMTX are not well understood. As Cx32 hemichannels can be opened by increases in PCO2, we have examined whether CMTX mutations alter this CO2 sensitivity. By using Ca2+ imaging, dye loading and genetically encoded ATP sensors to measure ATP release, we have found 5 CMTX mutations that abolish the CO2 sensitivity of Cx32 hemichannels (A88D, 111-116 Del, C179Y, E102G, V139M). Others cause a partial loss (L56F, R220Stop, and R15W). Some CMTX mutations have no apparent effect on CO2 sensitivity (R15Q, L9F, G12S, V13L, V84I, W133R). The mutation R15W alters multiple additional aspects of hemichannel function including Ca2+ and ATP permeability. The mutations that abolish CO2 sensitivity are transdominant and abolish CO2 sensitivity of co-expressed Cx32WT. We have shown that Schwannoma RT4 D6P2T cells can release ATP in response to elevated PCO2 via the opening of Cx32. This is consistent with the hypothesis that the CO2 sensitivity of Cx32 may be important for maintenance of healthy myelin. Our data, showing a transdominant effect of certain CMTX mutations on CO2 sensitivity, may need to be taken into account in any future gene therapies for this condition.
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Affiliation(s)
| | - Nicholas Dale
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
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6
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Gałgańska H, Jarmuszkiewicz W, Gałgański Ł. Carbon dioxide and MAPK signalling: towards therapy for inflammation. Cell Commun Signal 2023; 21:280. [PMID: 37817178 PMCID: PMC10566067 DOI: 10.1186/s12964-023-01306-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Accepted: 09/05/2023] [Indexed: 10/12/2023] Open
Abstract
Inflammation, although necessary to fight infections, becomes a threat when it exceeds the capability of the immune system to control it. In addition, inflammation is a cause and/or symptom of many different disorders, including metabolic, neurodegenerative, autoimmune and cardiovascular diseases. Comorbidities and advanced age are typical predictors of more severe cases of seasonal viral infection, with COVID-19 a clear example. The primary importance of mitogen-activated protein kinases (MAPKs) in the course of COVID-19 is evident in the mechanisms by which cells are infected with SARS-CoV-2; the cytokine storm that profoundly worsens a patient's condition; the pathogenesis of diseases, such as diabetes, obesity, and hypertension, that contribute to a worsened prognosis; and post-COVID-19 complications, such as brain fog and thrombosis. An increasing number of reports have revealed that MAPKs are regulated by carbon dioxide (CO2); hence, we reviewed the literature to identify associations between CO2 and MAPKs and possible therapeutic benefits resulting from the elevation of CO2 levels. CO2 regulates key processes leading to and resulting from inflammation, and the therapeutic effects of CO2 (or bicarbonate, HCO3-) have been documented in all of the abovementioned comorbidities and complications of COVID-19 in which MAPKs play roles. The overlapping MAPK and CO2 signalling pathways in the contexts of allergy, apoptosis and cell survival, pulmonary oedema (alveolar fluid resorption), and mechanical ventilation-induced responses in lungs and related to mitochondria are also discussed. Video Abstract.
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Affiliation(s)
- Hanna Gałgańska
- Faculty of Biology, Molecular Biology Techniques Laboratory, Adam Mickiewicz University in Poznan, Uniwersytetu Poznanskiego 6, 61-614, Poznan, Poland
| | - Wieslawa Jarmuszkiewicz
- Faculty of Biology, Department of Bioenergetics, Adam Mickiewicz University in Poznan, Institute of Molecular Biology and Biotechnology, Uniwersytetu Poznanskiego 6, 61-614, Poznan, Poland
| | - Łukasz Gałgański
- Faculty of Biology, Department of Bioenergetics, Adam Mickiewicz University in Poznan, Institute of Molecular Biology and Biotechnology, Uniwersytetu Poznanskiego 6, 61-614, Poznan, Poland.
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7
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Turk AZ, Millwater M, SheikhBahaei S. Whole-brain analysis of CO 2 chemosensitive regions and identification of the retrotrapezoid and medullary raphé nuclei in the common marmoset ( Callithrix jacchus). BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.26.558361. [PMID: 37986845 PMCID: PMC10659419 DOI: 10.1101/2023.09.26.558361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Respiratory chemosensitivity is an important mechanism by which the brain senses changes in blood partial pressure of CO2 (PCO2). It is proposed that special neurons (and astrocytes) in various brainstem regions play key roles as CO2 central respiratory chemosensors in rodents. Although common marmosets (Callithrix jacchus), New-World non-human primates, show similar respiratory responses to elevated inspired CO2 as rodents, the chemosensitive regions in marmoset brain have not been defined yet. Here, we used c-fos immunostainings to identify brain-wide CO2-activated brain regions in common marmosets. In addition, we mapped the location of the retrotrapezoid nucleus (RTN) and raphé nuclei in the marmoset brainstem based on colocalization of CO2-induced c-fos immunoreactivity with Phox2b, and TPH immunostaining, respectively. Our data also indicated that, similar to rodents, marmoset RTN astrocytes express Phox2b and have complex processes that create a meshwork structure at the ventral surface of medulla. Our data highlight some cellular and structural regional similarities in brainstem of the common marmosets and rodents.
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Affiliation(s)
- Ariana Z. Turk
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, 20892 MD, USA
| | - Marissa Millwater
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, 20892 MD, USA
| | - Shahriar SheikhBahaei
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, 20892 MD, USA
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8
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Gonye EC, Bayliss DA. Criteria for central respiratory chemoreceptors: experimental evidence supporting current candidate cell groups. Front Physiol 2023; 14:1241662. [PMID: 37719465 PMCID: PMC10502317 DOI: 10.3389/fphys.2023.1241662] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2023] [Accepted: 08/16/2023] [Indexed: 09/19/2023] Open
Abstract
An interoceptive homeostatic system monitors levels of CO2/H+ and provides a proportionate drive to respiratory control networks that adjust lung ventilation to maintain physiologically appropriate levels of CO2 and rapidly regulate tissue acid-base balance. It has long been suspected that the sensory cells responsible for the major CNS contribution to this so-called respiratory CO2/H+ chemoreception are located in the brainstem-but there is still substantial debate in the field as to which specific cells subserve the sensory function. Indeed, at the present time, several cell types have been championed as potential respiratory chemoreceptors, including neurons and astrocytes. In this review, we advance a set of criteria that are necessary and sufficient for definitive acceptance of any cell type as a respiratory chemoreceptor. We examine the extant evidence supporting consideration of the different putative chemoreceptor candidate cell types in the context of these criteria and also note for each where the criteria have not yet been fulfilled. By enumerating these specific criteria we hope to provide a useful heuristic that can be employed both to evaluate the various existing respiratory chemoreceptor candidates, and also to focus effort on specific experimental tests that can satisfy the remaining requirements for definitive acceptance.
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Affiliation(s)
- Elizabeth C. Gonye
- Department of Pharmacology, University of Virginia, Charlottesville, VA, United States
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9
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Severs LJ, Bush NE, Quina LA, Hidalgo-Andrade S, Burgraff NJ, Dashevskiy T, Shih AY, Baertsch NA, Ramirez JM. Purinergic signaling mediates neuroglial interactions to modulate sighs. Nat Commun 2023; 14:5300. [PMID: 37652903 PMCID: PMC10471608 DOI: 10.1038/s41467-023-40812-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 08/10/2023] [Indexed: 09/02/2023] Open
Abstract
Sighs prevent the collapse of alveoli in the lungs, initiate arousal under hypoxic conditions, and are an expression of sadness and relief. Sighs are periodically superimposed on normal breaths, known as eupnea. Implicated in the generation of these rhythmic behaviors is the preBötzinger complex (preBötC). Our experimental evidence suggests that purinergic signaling is necessary to generate spontaneous and hypoxia-induced sighs in a mouse model. Our results demonstrate that driving calcium increases in astrocytes through pharmacological methods robustly increases sigh, but not eupnea, frequency. Calcium imaging of preBötC slices corroborates this finding with an increase in astrocytic calcium upon application of sigh modulators, increasing intracellular calcium through g-protein signaling. Moreover, photo-activation of preBötC astrocytes is sufficient to elicit sigh activity, and this response is blocked with purinergic antagonists. We conclude that sighs are modulated through neuron-glia coupling in the preBötC network, where the distinct modulatory responses of neurons and glia allow for both rhythms to be independently regulated.
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Affiliation(s)
- Liza J Severs
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, 98101, USA.
- Department of Physiology and Biophysics, University of Washington, Seattle, WA, 98195, USA.
| | - Nicholas E Bush
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, 98101, USA
| | - Lely A Quina
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, 98101, USA
| | - Skyler Hidalgo-Andrade
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, 98101, USA
| | - Nicholas J Burgraff
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, 98101, USA
| | - Tatiana Dashevskiy
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, 98101, USA
| | - Andy Y Shih
- Center for Developmental Biology and Regenerative Medicine, Seattle Children's Research Institute, Seattle, WA, 98101, USA
- Department of Pediatrics, University of Washington School of Medicine, Seattle, WA, 98195, USA
- Department of Bioengineering, University of Washington, Seattle, WA, 98195, USA
| | - Nathan A Baertsch
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, 98101, USA
- Department of Pediatrics, University of Washington School of Medicine, Seattle, WA, 98195, USA
| | - Jan-Marino Ramirez
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, 98101, USA.
- Department of Physiology and Biophysics, University of Washington, Seattle, WA, 98195, USA.
- Department of Pediatrics, University of Washington School of Medicine, Seattle, WA, 98195, USA.
- Department of Neurological Surgery, University of Washington School of Medicine, Seattle, WA, 98195, USA.
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10
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Li K, Gonye EC, Stornetta RL, Bayliss CB, Yi G, Stornetta DS, Baca SM, Abbott SB, Guyenet PG, Bayliss DA. The astrocytic Na + -HCO 3 - cotransporter, NBCe1, is dispensable for respiratory chemosensitivity. J Physiol 2023; 601:3667-3686. [PMID: 37384821 PMCID: PMC10528273 DOI: 10.1113/jp284960] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2023] [Accepted: 06/02/2023] [Indexed: 07/01/2023] Open
Abstract
The interoceptive homeostatic mechanism that controls breathing, blood gases and acid-base balance in response to changes in CO2 /H+ is exquisitely sensitive, with convergent roles proposed for chemosensory brainstem neurons in the retrotrapezoid nucleus (RTN) and their supporting glial cells. For astrocytes, a central role for NBCe1, a Na+ -HCO3 - cotransporter encoded by Slc4a4, has been envisaged in multiple mechanistic models (i.e. underlying enhanced CO2 -induced local extracellular acidification or purinergic signalling). We tested these NBCe1-centric models by using conditional knockout mice in which Slc4a4 was deleted from astrocytes. In GFAP-Cre;Slc4a4fl/fl mice we found diminished expression of Slc4a4 in RTN astrocytes by comparison to control littermates, and a concomitant reduction in NBCe1-mediated current. Despite disrupted NBCe1 function in RTN-adjacent astrocytes from these conditional knockout mice, CO2 -induced activation of RTN neurons or astrocytes in vitro and in vivo, and CO2 -stimulated breathing, were indistinguishable from NBCe1-intact littermates; hypoxia-stimulated breathing and sighs were likewise unaffected. We obtained a more widespread deletion of NBCe1 in brainstem astrocytes by using tamoxifen-treated Aldh1l1-Cre/ERT2;Slc4a4fl/fl mice. Again, there was no difference in effects of CO2 or hypoxia on breathing or on neuron/astrocyte activation in NBCe1-deleted mice. These data indicate that astrocytic NBCe1 is not required for the respiratory responses to these chemoreceptor stimuli in mice, and that any physiologically relevant astrocytic contributions must involve NBCe1-independent mechanisms. KEY POINTS: The electrogenic NBCe1 transporter is proposed to mediate local astrocytic CO2 /H+ sensing that enables excitatory modulation of nearby retrotrapezoid nucleus (RTN) neurons to support chemosensory control of breathing. We used two different Cre mouse lines for cell-specific and/or temporally regulated deletion of the NBCe1 gene (Slc4a4) in astrocytes to test this hypothesis. In both mouse lines, Slc4a4 was depleted from RTN-associated astrocytes but CO2 -induced Fos expression (i.e. cell activation) in RTN neurons and local astrocytes was intact. Likewise, respiratory chemoreflexes evoked by changes in CO2 or O2 were unaffected by loss of astrocytic Slc4a4. These data do not support the previously proposed role for NBCe1 in respiratory chemosensitivity mediated by astrocytes.
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Affiliation(s)
- Keyong Li
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA, 22908
| | - Elizabeth C. Gonye
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA, 22908
| | - Ruth L. Stornetta
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA, 22908
| | | | - Grace Yi
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA, 22908
| | - Daniel S. Stornetta
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA, 22908
| | - Serapio M. Baca
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA, 22908
| | - Stephen B.G. Abbott
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA, 22908
| | - Patrice G. Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA, 22908
| | - Douglas A. Bayliss
- Department of Pharmacology, University of Virginia, Charlottesville, VA, USA, 22908
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11
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Martínez-Mendoza ML, Rodríguez-Arzate CA, Gómez-González GB, Rosas-Arellano A, Martínez-Torres A. Morphological characteristics of astrocytes of the fastigial nucleus. Heliyon 2023; 9:e18006. [PMID: 37483700 PMCID: PMC10362242 DOI: 10.1016/j.heliyon.2023.e18006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 05/08/2023] [Accepted: 07/05/2023] [Indexed: 07/25/2023] Open
Abstract
Astrocytes are a diverse and morphologically complex class of glial cells restricted to the central nervous system which have been implicated in the modulation of neuronal activity. The cerebellum is involved in planning movements and motor learning. Within the cerebellum three deep cerebellar nuclei (dentate, interposed and fastigial) provide the sole neuronal output. The fastigial nucleus participates in saccadic and vestibular function, and recent evidence disclosed neuronal projections to cognitive, affective, and motor areas. However, thus far there are no reliable descriptions of the distribution and morphological classifications of astrocytes in this nucleus. This work aims to describe the characteristics of astrocytes of the fastigial nucleus based on the expression of GFP in a transgenic mouse model.
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Affiliation(s)
- Marianne Lizeth Martínez-Mendoza
- Instituto de Neurobiología, Universidad Nacional Autónoma de México, Departamento de Neurobiología Celular y Molecular, Laboratorio de Neurobiología Molecular y Celular, Juriquilla, Querétaro, 76230, Mexico
| | - Cynthia Alejandra Rodríguez-Arzate
- Instituto de Neurobiología, Universidad Nacional Autónoma de México, Departamento de Neurobiología Celular y Molecular, Laboratorio de Neurobiología Molecular y Celular, Juriquilla, Querétaro, 76230, Mexico
| | - Gabriela B. Gómez-González
- Instituto de Neurobiología, Universidad Nacional Autónoma de México, Departamento de Neurobiología Celular y Molecular, Laboratorio de Neurobiología Molecular y Celular, Juriquilla, Querétaro, 76230, Mexico
| | - Abraham Rosas-Arellano
- Unidad de Imagenología, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510. Ciudad de México, Mexico
| | - Ataúlfo Martínez-Torres
- Instituto de Neurobiología, Universidad Nacional Autónoma de México, Departamento de Neurobiología Celular y Molecular, Laboratorio de Neurobiología Molecular y Celular, Juriquilla, Querétaro, 76230, Mexico
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12
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Fabbri R, Spennato D, Conte G, Konstantoulaki A, Lazzarini C, Saracino E, Nicchia GP, Frigeri A, Zamboni R, Spray DC, Benfenati V. The emerging science of Glioception: Contribution of glia in sensing, transduction, circuit integration of interoception. Pharmacol Ther 2023; 245:108403. [PMID: 37024060 DOI: 10.1016/j.pharmthera.2023.108403] [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: 10/13/2022] [Revised: 03/29/2023] [Accepted: 03/30/2023] [Indexed: 04/08/2023]
Abstract
Interoception is the process by which the nervous system regulates internal functions to achieve homeostasis. The role of neurons in interoception has received considerable recent attention, but glial cells also contribute. Glial cells can sense and transduce signals including osmotic, chemical, and mechanical status of extracellular milieu. Their ability to dynamically communicate "listening" and "talking" to neurons is necessary to monitor and regulate homeostasis and information integration in the nervous system. This review introduces the concept of "Glioception" and focuses on the process by which glial cells sense, interpret and integrate information about the inner state of the organism. Glial cells are ideally positioned to act as sensors and integrators of diverse interoceptive signals and can trigger regulatory responses via modulation of the activity of neuronal networks, both in physiological and pathological conditions. We believe that understanding and manipulating glioceptive processes and underlying molecular mechanisms provide a key path to develop new therapies for the prevention and alleviation of devastating interoceptive dysfunctions, among which pain is emphasized here with more focused details.
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Affiliation(s)
- Roberta Fabbri
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Via P. Gobetti 101, I-40129 Bologna, Italy; Department of Electrical, Electronic, and Information Engineering "Guglielmo Marconi", University of Bologna, viale del Risorgimento 2, 40136 Bologna, Italy.
| | - Diletta Spennato
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Via P. Gobetti 101, I-40129 Bologna, Italy; Department of Bioscience, Biotechnologies and Biopharmaceutics, Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, BA, Italy
| | - Giorgia Conte
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Via P. Gobetti 101, I-40129 Bologna, Italy
| | - Aikaterini Konstantoulaki
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Via P. Gobetti 101, I-40129 Bologna, Italy; Department of Chemistry "Giacomo Ciamician", University of Bologna, Via Selmi, 2, 40126 Bologna, BO, Italy
| | - Chiara Lazzarini
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Via P. Gobetti 101, I-40129 Bologna, Italy
| | - Emanuela Saracino
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Via P. Gobetti 101, I-40129 Bologna, Italy
| | - Grazia Paola Nicchia
- School of Medicine, Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari "Aldo Moro", Bari, BA, Italy; Department of Bioscience, Biotechnologies and Biopharmaceutics, Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, BA, Italy
| | - Antonio Frigeri
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA; Department of Bioscience, Biotechnologies and Biopharmaceutics, Centre of Excellence in Comparative Genomics, University of Bari "Aldo Moro", Bari, BA, Italy
| | - Roberto Zamboni
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Via P. Gobetti 101, I-40129 Bologna, Italy
| | - David C Spray
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Valentina Benfenati
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Via P. Gobetti 101, I-40129 Bologna, Italy.
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13
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Dale N, Butler J, Dospinescu VM, Nijjar S. Channel-mediated ATP release in the nervous system. Neuropharmacology 2023; 227:109435. [PMID: 36690324 DOI: 10.1016/j.neuropharm.2023.109435] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 01/10/2023] [Accepted: 01/19/2023] [Indexed: 01/21/2023]
Abstract
ATP is well established as a transmitter and modulator in the peripheral and central nervous system. While conventional exocytotic release of ATP at synapses occurs, this transmitter is unusual in also being released into the extracellular space via large-pored plasma membrane channels. This review considers the channels that are known to be permeable to ATP and some of the functions of channel-mediated ATP release. While the possibility of ATP release via channels mediating volume transmission has been known for some time, localised ATP release via channels at specialised synapses made by taste cells to the afferent nerve has recently been documented in taste buds. This raises the prospect that "channel synapses" may occur in other contexts. However, volume transmission and channel synapses are not necessarily mutually exclusive. We suggest that certain glial cells in the brain stem and hypothalamus, which possess long processes and are known to release ATP, may be candidates for both modes of ATP release -channel-mediated volume transmission in the region of their somata and more localised transmission possibly via either conventional or channel synapses from their processes at distal targets. Finally, we consider the different characteristics of vesicular and channel synapses and suggest that channel synapses may be advantageous in requiring less energy than their conventional vesicular counterparts. This article is part of the Special Issue on "Purinergic Signaling: 50 years".
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Affiliation(s)
- Nicholas Dale
- School of Life Sciences, University of Warwick, Coventry, CV4, AL, UK.
| | - Jack Butler
- School of Life Sciences, University of Warwick, Coventry, CV4, AL, UK
| | | | - Sarbjit Nijjar
- School of Life Sciences, University of Warwick, Coventry, CV4, AL, UK
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14
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Krohn F, Novello M, van der Giessen RS, De Zeeuw CI, Pel JJM, Bosman LWJ. The integrated brain network that controls respiration. eLife 2023; 12:83654. [PMID: 36884287 PMCID: PMC9995121 DOI: 10.7554/elife.83654] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Accepted: 01/29/2023] [Indexed: 03/09/2023] Open
Abstract
Respiration is a brain function on which our lives essentially depend. Control of respiration ensures that the frequency and depth of breathing adapt continuously to metabolic needs. In addition, the respiratory control network of the brain has to organize muscular synergies that integrate ventilation with posture and body movement. Finally, respiration is coupled to cardiovascular function and emotion. Here, we argue that the brain can handle this all by integrating a brainstem central pattern generator circuit in a larger network that also comprises the cerebellum. Although currently not generally recognized as a respiratory control center, the cerebellum is well known for its coordinating and modulating role in motor behavior, as well as for its role in the autonomic nervous system. In this review, we discuss the role of brain regions involved in the control of respiration, and their anatomical and functional interactions. We discuss how sensory feedback can result in adaptation of respiration, and how these mechanisms can be compromised by various neurological and psychological disorders. Finally, we demonstrate how the respiratory pattern generators are part of a larger and integrated network of respiratory brain regions.
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Affiliation(s)
- Friedrich Krohn
- Department of Neuroscience, Erasmus MC, Rotterdam, Netherlands
| | - Manuele Novello
- Department of Neuroscience, Erasmus MC, Rotterdam, Netherlands
| | | | - Chris I De Zeeuw
- Department of Neuroscience, Erasmus MC, Rotterdam, Netherlands.,Netherlands Institute for Neuroscience, Royal Academy of Arts and Sciences, Amsterdam, Netherlands
| | - Johan J M Pel
- Department of Neuroscience, Erasmus MC, Rotterdam, Netherlands
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15
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López-Sundh AE, Escribano-Palomino E, Feito-Rodríguez M, Tenorio J, Brizzi ME, Krasnovska Zayets K, Servera-Negra G, de Lucas-Laguna R. Keratitis-ichthyosis-deafness syndrome with lethal p.Ala88Val variant and severe hypercalcemia. Am J Med Genet A 2023; 191:253-258. [PMID: 36286624 DOI: 10.1002/ajmg.a.63005] [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: 03/27/2022] [Revised: 07/03/2022] [Accepted: 08/27/2022] [Indexed: 12/14/2022]
Abstract
Keratitis-ichthyosis-deafness (KID) syndrome is a rare genetic disease caused by pathogenic variants in connexin 26 (gene GJB2), which is part of the transmembrane channels of the epithelia. Connexin 26 is expressed mainly in the cornea, the sensory epithelium of the inner ear, and in the skin keratinocytes, which are the three main target organs in KID syndrome. Approximately a dozen pathogenic variants have been described to date, including some lethal forms. Patients with lethal pathogenic variants present with severe symptoms from birth and die from sepsis during the first year of life. We present a premature female patient with KID syndrome carrying the lethal p.Ala88Val pathogenic variant in GJB2. In addition to the respiratory distress associated with this variant, our patient presented severe hypercalcemia of unexplained origin refractory to treatment. This abnormality has not been reported earlier in other patients with KID syndrome with the same variant.
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Affiliation(s)
| | | | | | - Jair Tenorio
- CIBERER, Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, Madrid, Spain.,Institute of Medical and Molecular Genetics (INGEMM)-IdiPAZ, Hospital Universitario La Paz-UAMs, Madrid, Spain.,ITHACA, European Reference Network on Rare Congenital Malformations and Rare Intellectual Disability, Paris, France
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16
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Martínez-Gallego I, Pérez-Rodríguez M, Coatl-Cuaya H, Flores G, Rodríguez-Moreno A. Adenosine and Astrocytes Determine the Developmental Dynamics of Spike Timing-Dependent Plasticity in the Somatosensory Cortex. J Neurosci 2022; 42:6038-6052. [PMID: 35768208 PMCID: PMC9351642 DOI: 10.1523/jneurosci.0115-22.2022] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 04/18/2022] [Accepted: 05/18/2022] [Indexed: 02/05/2023] Open
Abstract
During development, critical periods of synaptic plasticity facilitate the reordering and refinement of neural connections, allowing the definitive synaptic circuits responsible for correct adult physiology to be established. The L4-L2/3 synapses in the somatosensory cortex (S1) exhibit a presynaptic form of spike timing-dependent long-term depression (t-LTD) that probably fulfills a role in synaptic refinement. This t-LTD persists until the fourth postnatal week in mice, disappearing thereafter. When we investigated the mechanisms underlying this maturation-related loss of t-LTD in either sex mouse slices, we found that it could be completely recovered by antagonizing adenosine type 1 receptors. By contrast, an agonist of A1R impeded the induction of t-LTD at P13-27. Furthermore, we found that the adenosine that mediated the loss of t-LTD at the end of the fourth week of development is most probably supplied by astrocytes. At more mature stages (P38-60), we found that the protocol used to induce t-LTD provokes t-LTP. We characterized the mechanisms underlying the induction of this form of LTP, and we found it to be expressed presynaptically, as witnessed by paired-pulse and coefficient of variation analysis. In addition, this form of presynaptic t-LTP requires the activation of NMDARs and mGlu1Rs, and the entry of Ca2+ into the postsynaptic neuron through L-type voltage-dependent Ca2+ channels. Nitric oxide is also required for t-LTP as a messenger in the postsynaptic neuron as are the adenosine and glutamate that are released in association with astrocyte signaling. These results provide direct evidence of the mechanisms that close the window of plasticity associated with t-LTD and that drive the switch in synaptic transmission from t-LTD to t-LTP at L4-L2/3 synapses, in which astrocytes play a central role.SIGNIFICANCE STATEMENT During development, critical periods of plasticity facilitate the reordering and refining of neural connections, allowing correct adult physiology to be established. The L4-L2/3 synapses in the somatosensory cortex exhibit a presynaptic form plasticity (LTD) that probably fulfills a role in synaptic refinement. It is present until the fourth postnatal week in mice, disappearing thereafter. The mechanisms that are responsible for this loss of plasticity are not clear. We describe here these mechanisms and those involved in the switch from LTD to LTP observed as the brain matures. Defining these events responsible for closing (and opening) plasticity windows may be important for brain repair, sensorial recovery, the treatment of neurodevelopmental disorders, and for educational policy.
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Affiliation(s)
- Irene Martínez-Gallego
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, ES-41013 Seville, Spain
| | - Mikel Pérez-Rodríguez
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, ES-41013 Seville, Spain
| | - Heriberto Coatl-Cuaya
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, ES-41013 Seville, Spain
| | - Gonzalo Flores
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Puebla CP 72570, México
| | - Antonio Rodríguez-Moreno
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, ES-41013 Seville, Spain
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17
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Gourine AV, Dale N. Brain H + /CO 2 sensing and control by glial cells. Glia 2022; 70:1520-1535. [PMID: 35102601 DOI: 10.1002/glia.24152] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 01/11/2022] [Accepted: 01/17/2022] [Indexed: 01/04/2023]
Abstract
Maintenance of constant brain pH is critically important to support the activity of individual neurons, effective communication within the neuronal circuits, and, thus, efficient processing of information by the brain. This review article focuses on how glial cells detect and respond to changes in brain tissue pH and concentration of CO2 , and then trigger systemic and local adaptive mechanisms that ensure a stable milieu for the operation of brain circuits. We give a detailed account of the cellular and molecular mechanisms underlying sensitivity of glial cells to H+ and CO2 and discuss the role of glial chemosensitivity and signaling in operation of three key mechanisms that work in concert to keep the brain pH constant. We discuss evidence suggesting that astrocytes and marginal glial cells of the brainstem are critically important for central respiratory CO2 chemoreception-a fundamental physiological mechanism that regulates breathing in accord with changes in blood and brain pH and partial pressure of CO2 in order to maintain systemic pH homeostasis. We review evidence suggesting that astrocytes are also responsible for the maintenance of local brain tissue extracellular pH in conditions of variable acid loads associated with changes in the neuronal activity and metabolism, and discuss potential role of these glial cells in mediating the effects of CO2 on cerebral vasculature.
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Affiliation(s)
- Alexander V Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Nicholas Dale
- School of Life Sciences, University of Warwick, Coventry, UK
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18
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Hosford PS, Wells JA, Nizari S, Christie IN, Theparambil SM, Castro PA, Hadjihambi A, Barros LF, Ruminot I, Lythgoe MF, Gourine AV. CO 2 signaling mediates neurovascular coupling in the cerebral cortex. Nat Commun 2022; 13:2125. [PMID: 35440557 PMCID: PMC9019094 DOI: 10.1038/s41467-022-29622-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 03/23/2022] [Indexed: 11/24/2022] Open
Abstract
Neurovascular coupling is a fundamental brain mechanism that regulates local cerebral blood flow (CBF) in response to changes in neuronal activity. Functional imaging techniques are commonly used to record these changes in CBF as a proxy of neuronal activity to study the human brain. However, the mechanisms of neurovascular coupling remain incompletely understood. Here we show in experimental animal models (laboratory rats and mice) that the neuronal activity-dependent increases in local CBF in the somatosensory cortex are prevented by saturation of the CO2-sensitive vasodilatory brain mechanism with surplus of exogenous CO2 or disruption of brain CO2/HCO3- transport by genetic knockdown of electrogenic sodium-bicarbonate cotransporter 1 (NBCe1) expression in astrocytes. A systematic review of the literature data shows that CO2 and increased neuronal activity recruit the same vasodilatory signaling pathways. These results and analysis suggest that CO2 mediates signaling between neurons and the cerebral vasculature to regulate brain blood flow in accord with changes in the neuronal activity.
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Affiliation(s)
- Patrick S Hosford
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK.
| | - Jack A Wells
- UCL Centre for Advanced Biomedical Imaging, Division of Medicine, University College London, London, UK
| | - Shereen Nizari
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Isabel N Christie
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Shefeeq M Theparambil
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Pablo A Castro
- Centro de Estudios Científicos (CECs) & Universidad San Sebastián, Valdivia, Chile
- Universidad Austral de Chile, Valdivia, Chile
| | - Anna Hadjihambi
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - L Felipe Barros
- Centro de Estudios Científicos (CECs) & Universidad San Sebastián, Valdivia, Chile
| | - Iván Ruminot
- Centro de Estudios Científicos (CECs) & Universidad San Sebastián, Valdivia, Chile.
| | - Mark F Lythgoe
- UCL Centre for Advanced Biomedical Imaging, Division of Medicine, University College London, London, UK
| | - Alexander V Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK.
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19
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Toledo C, Ortolani D, Ortiz FC, Marcus NJ, Del Rio R. Potential Role of the Retrotrapezoid Nucleus in Mediating Cardio-Respiratory Dysfunction in Heart Failure With Preserved Ejection Fraction. Front Physiol 2022; 13:863963. [PMID: 35492622 PMCID: PMC9039230 DOI: 10.3389/fphys.2022.863963] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Accepted: 03/29/2022] [Indexed: 01/15/2023] Open
Abstract
A strong association between chemoreflex hypersensitivity, disordered breathing, and elevated sympathetic activity has been shown in experimental and human heart failure (HF). The contribution of chemoreflex hypersensitivity in HF pathophysiology is incompletely understood. There is ample evidence that increased peripheral chemoreflex drive in HF with reduced ejection fraction (HFrEF; EF<40%) leads to pathophysiological changes in autonomic and cardio-respiratory control, but less is known about the neural mechanisms mediating cardio-respiratory disturbances in HF with preserved EF (HFpEF; EF>50%). Importantly, it has been shown that activation of the central chemoreflex worsens autonomic dysfunction in experimental HFpEF, an effect mediated in part by the activation of C1 catecholaminergic neurons neighboring the retrotrapezoid nucleus (RTN), an important region for central chemoreflex control of respiratory and autonomic function. Accordingly, the main purpose of this brief review is to discuss the possible role played by activation of central chemoreflex pathways on autonomic function and its potential role in precipitating disordered breathing in HFpEF. Improving understanding of the contribution of the central chemoreflex to the pathophysiology of HFpEF may help in development of novel interventions intended to improve cardio-respiratory outcomes in HFpEF.
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Affiliation(s)
- Camilo Toledo
- Laboratory Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
- Centro de Excelencia en Biomedicina de Magallanes (CEBIMA), Universidad de Magallanes, Punta Arenas, Chile
| | - Domiziana Ortolani
- Laboratory Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Fernando C. Ortiz
- Mechanisms of Myelin Formation and Repair Laboratory, Facultad de Ciencias de Salud, Instituto de Ciencias Biomédicas, Universidad Autónoma de Chile, Santiago, Chile
| | - Noah J. Marcus
- Department of Physiology and Pharmacology, Des Moines University, Des Moines, IA, United States
| | - Rodrigo Del Rio
- Laboratory Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
- Centro de Excelencia en Biomedicina de Magallanes (CEBIMA), Universidad de Magallanes, Punta Arenas, Chile
- Centro de Envejecimiento y Regeneración (CARE), Pontificia Universidad Católica de Chile, Santiago, Chile
- *Correspondence: Rodrigo Del Rio,
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20
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Brotherton DH, Savva CG, Ragan TJ, Dale N, Cameron AD. Conformational changes and CO 2-induced channel gating in connexin26. Structure 2022; 30:697-706.e4. [PMID: 35276081 PMCID: PMC9592558 DOI: 10.1016/j.str.2022.02.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Revised: 01/24/2022] [Accepted: 02/14/2022] [Indexed: 12/22/2022]
Abstract
Connexins form large-pore channels that function either as dodecameric gap junctions or hexameric hemichannels to allow the regulated movement of small molecules and ions across cell membranes. Opening or closing of the channels is controlled by a variety of stimuli, and dysregulation leads to multiple diseases. An increase in the partial pressure of carbon dioxide (PCO2) has been shown to cause connexin26 (Cx26) gap junctions to close. Here, we use cryoelectron microscopy (cryo-EM) to determine the structure of human Cx26 gap junctions under increasing levels of PCO2. We show a correlation between the level of PCO2 and the size of the aperture of the pore, governed by the N-terminal helices that line the pore. This indicates that CO2 alone is sufficient to cause conformational changes in the protein. Analysis of the conformational states shows that movements at the N terminus are linked to both subunit rotation and flexing of the transmembrane helices. High-resolution cryo-EM structures of connexin26 at varying levels of PCO2 CO2 alone causes conformational changes in the protein under stable pH conditions The N-terminal helices regulate the aperture of the pore KID syndrome mutations affecting CO2 sensitivity map to flexion points of structure
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Affiliation(s)
- Deborah H Brotherton
- School of Life Sciences, University of Warwick, Gibbet Hill Road, CV4 7AL Coventry, UK
| | - Christos G Savva
- Leicester Institute of Structural and Chemical Biology, Department of Molecular and Cell Biology, University of Leicester, Lancaster Road, LE1 7HB Leicester, UK
| | - Timothy J Ragan
- Leicester Institute of Structural and Chemical Biology, Department of Molecular and Cell Biology, University of Leicester, Lancaster Road, LE1 7HB Leicester, UK
| | - Nicholas Dale
- School of Life Sciences, University of Warwick, Gibbet Hill Road, CV4 7AL Coventry, UK.
| | - Alexander D Cameron
- School of Life Sciences, University of Warwick, Gibbet Hill Road, CV4 7AL Coventry, UK.
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21
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Blake LI, Cann MJ. Carbon Dioxide and the Carbamate Post-Translational Modification. Front Mol Biosci 2022; 9:825706. [PMID: 35300111 PMCID: PMC8920986 DOI: 10.3389/fmolb.2022.825706] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 02/03/2022] [Indexed: 01/10/2023] Open
Abstract
Carbon dioxide is essential for life. It is at the beginning of every life process as a substrate of photosynthesis. It is at the end of every life process as the product of post-mortem decay. Therefore, it is not surprising that this gas regulates such diverse processes as cellular chemical reactions, transport, maintenance of the cellular environment, and behaviour. Carbon dioxide is a strategically important research target relevant to crop responses to environmental change, insect vector-borne disease and public health. However, we know little of carbon dioxide’s direct interactions with the cell. The carbamate post-translational modification, mediated by the nucleophilic attack by carbon dioxide on N-terminal α-amino groups or the lysine ɛ-amino groups, is one mechanism by which carbon dioxide might alter protein function to form part of a sensing and signalling mechanism. We detail known protein carbamates, including the history of their discovery. Further, we describe recent studies on new techniques to isolate this problematic post-translational modification.
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22
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Turk AZ, Bishop M, Adeck A, SheikhBahaei S. Astrocytic modulation of central pattern generating motor circuits. Glia 2022; 70:1506-1519. [PMID: 35212422 DOI: 10.1002/glia.24162] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 02/08/2022] [Accepted: 02/09/2022] [Indexed: 12/26/2022]
Abstract
Central pattern generators (CPGs) generate the rhythmic and coordinated neural features necessary for the proper conduction of complex behaviors. In particular, CPGs are crucial for complex motor behaviors such as locomotion, mastication, respiration, and vocal production. While the importance of these networks in modulating behavior is evident, the mechanisms driving these CPGs are still not fully understood. On the other hand, accumulating evidence suggests that astrocytes have a significant role in regulating the function of some of these CPGs. Here, we review the location, function, and role of astrocytes in locomotion, respiration, and mastication CPGs and propose that, similarly, astrocytes may also play a significant role in the vocalization CPG.
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Affiliation(s)
- Ariana Z Turk
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Mitchell Bishop
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Afuh Adeck
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, Maryland, USA
| | - Shahriar SheikhBahaei
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, Maryland, USA
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Mulkey DK, Olsen ML, Ou M, Cleary CM, Du G. Putative Roles of Astrocytes in General Anesthesia. Curr Neuropharmacol 2022; 20:5-15. [PMID: 33588730 PMCID: PMC9199541 DOI: 10.2174/1570159x19666210215120755] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 01/29/2021] [Accepted: 02/06/2021] [Indexed: 02/08/2023] Open
Abstract
General anesthetics are a mainstay of modern medicine, and although much progress has been made towards identifying molecular targets of anesthetics and neural networks contributing to endpoints of general anesthesia, our understanding of how anesthetics work remains unclear. Reducing this knowledge gap is of fundamental importance to prevent unwanted and life-threatening side-effects associated with general anesthesia. General anesthetics are chemically diverse, yet they all have similar behavioral endpoints, and so for decades, research has sought to identify a single underlying mechanism to explain how anesthetics work. However, this effort has given way to the 'multiple target hypothesis' as it has become clear that anesthetics target many cellular proteins, including GABAA receptors, glutamate receptors, voltage-independent K+ channels, and voltagedependent K+, Ca2+ and Na+ channels, to name a few. Yet, despite evidence that astrocytes are capable of modulating multiple aspects of neural function and express many anesthetic target proteins, they have been largely ignored as potential targets of anesthesia. The purpose of this brief review is to highlight the effects of anesthetic on astrocyte processes and identify potential roles of astrocytes in behavioral endpoints of anesthesia (hypnosis, amnesia, analgesia, and immobilization).
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Affiliation(s)
- Daniel K. Mulkey
- Department of Physiology and Neurobiology, University of Connecticut, StorrsCT, USA;,Address correspondence to this author at the Department of Physiology and Neurobiology, University of Connecticut, Storrs CT, USA; E-mail:
| | | | | | - Colin M. Cleary
- Department of Physiology and Neurobiology, University of Connecticut, StorrsCT, USA
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24
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Abstract
Brain PCO2 is sensed primarily via changes in [H+]. Small pH changes are detected in the medulla oblongata and trigger breathing adjustments that help maintain arterial PCO2 constant. Larger perturbations of brain CO2/H+, possibly also sensed elsewhere in the CNS, elicit arousal, dyspnea, and stress, and cause additional breathing modifications. The retrotrapezoid nucleus (RTN), a rostral medullary cluster of glutamatergic neurons identified by coexpression of Phoxb and Nmb transcripts, is the lynchpin of the central respiratory chemoreflex. RTN regulates breathing frequency, inspiratory amplitude, and active expiration. It is exquisitely responsive to acidosis in vivo and maintains breathing autorhythmicity during quiet waking, slow-wave sleep, and anesthesia. The RTN response to [H+] is partly an intrinsic neuronal property mediated by proton sensors TASK-2 and GPR4 and partly a paracrine effect mediated by astrocytes and the vasculature. The RTN also receives myriad excitatory or inhibitory synaptic inputs including from [H+]-responsive neurons (e.g., serotonergic). RTN is silenced by moderate hypoxia. RTN inactivity (periodic or sustained) contributes to periodic breathing and, likely, to central sleep apnea. RTN development relies on transcription factors Egr2, Phox2b, Lbx1, and Atoh1. PHOX2B mutations cause congenital central hypoventilation syndrome; they impair RTN development and consequently the central respiratory chemoreflex.
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Affiliation(s)
- Patrice G Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, VA, United States.
| | - Douglas A Bayliss
- Department of Pharmacology, University of Virginia, Charlottesville, VA, United States
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25
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Guyenet PG, Stornetta RL. Rostral ventrolateral medulla, retropontine region and autonomic regulations. Auton Neurosci 2021; 237:102922. [PMID: 34814098 DOI: 10.1016/j.autneu.2021.102922] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 11/08/2021] [Accepted: 11/15/2021] [Indexed: 12/17/2022]
Abstract
The rostral half of the ventrolateral medulla (RVLM) and adjacent ventrolateral retropontine region (henceforth RVLMRP) have been divided into various sectors by neuroscientists interested in breathing or autonomic regulations. The RVLMRP regulates respiration, glycemia, vigilance and inflammation, in addition to blood pressure. It contains interoceptors that respond to acidification, hypoxia and intracranial pressure and its rostral end contains the retrotrapezoid nucleus (RTN) which is the main central respiratory chemoreceptor. Acid detection by the RTN is an intrinsic property of the principal neurons that is enhanced by paracrine influences from surrounding astrocytes and CO2-dependent vascular constriction. RTN mediates the hypercapnic ventilatory response via complex projections to the respiratory pattern generator (CPG). The RVLM contributes to autonomic response patterns via differential recruitment of several subtypes of adrenergic (C1) and non-adrenergic neurons that directly innervate sympathetic and parasympathetic preganglionic neurons. The RVLM also innervates many brainstem and hypothalamic nuclei that contribute, albeit less directly, to autonomic responses. All lower brainstem noradrenergic clusters including the locus coeruleus are among these targets. Sympathetic tone to the circulatory system is regulated by subsets of presympathetic RVLM neurons whose activity is continuously restrained by the baroreceptors and modulated by the respiratory CPG. The inhibitory input from baroreceptors and the excitatory input from the respiratory CPG originate from neurons located in or close to the rhythm generating region of the respiratory CPG (preBötzinger complex).
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Affiliation(s)
- Patrice G Guyenet
- University of Virginia School of Medicine, Department of Pharmacology, 1340 Jefferson Park Avenue, Charlottesville, VA 22908-0735, USA.
| | - Ruth L Stornetta
- University of Virginia School of Medicine, Department of Pharmacology, 1340 Jefferson Park Avenue, Charlottesville, VA 22908-0735, USA.
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26
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Patodia S, Somani A, Thom M. Review: Neuropathology findings in autonomic brain regions in SUDEP and future research directions. Auton Neurosci 2021; 235:102862. [PMID: 34411885 PMCID: PMC8455454 DOI: 10.1016/j.autneu.2021.102862] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 07/16/2021] [Accepted: 07/24/2021] [Indexed: 12/21/2022]
Abstract
Autonomic dysfunction is implicated from clinical, neuroimaging and experimental studies in sudden and unexpected death in epilepsy (SUDEP). Neuropathological analysis in SUDEP series enable exploration of acquired, seizure-related cellular adaptations in autonomic and brainstem autonomic centres of relevance to dysfunction in the peri-ictal period. Alterations in SUDEP compared to control groups have been identified in the ventrolateral medulla, amygdala, hippocampus and central autonomic regions. These involve neuropeptidergic, serotonergic and adenosine systems, as well as specific regional astroglial and microglial populations, as potential neuronal modulators, orchestrating autonomic dysfunction. Future research studies need to extend to clinically and genetically characterized epilepsies, to explore if common or distinct pathways of autonomic dysfunction mediate SUDEP. The ultimate objective of SUDEP research is the identification of disease biomarkers for at risk patients, to improve post-mortem recognition and disease categorisation, but ultimately, for exposing potential treatment targets of pharmacologically modifiable and reversible cellular alterations.
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Affiliation(s)
- Smriti Patodia
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK
| | - Alyma Somani
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK
| | - Maria Thom
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK.
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27
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Gourine AV, Spyer KM. Geoff Burnstock, purinergic signalling, and chemosensory control of breathing. Auton Neurosci 2021; 235:102839. [PMID: 34198056 DOI: 10.1016/j.autneu.2021.102839] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 06/11/2021] [Accepted: 06/20/2021] [Indexed: 12/14/2022]
Abstract
This article is the authors' contribution to the tribute issue in honour of Geoffrey Burnstock, the founder of this journal and the field of purinergic signalling. We give a brief account of the results of experimental studies which at the beginning received valuable input from Geoff, who both directly and indirectly influenced our research undertaken over the last two decades. Research into the mechanisms controlling breathing identified ATP as the common mediator of the central and peripheral chemosensory transduction. Studies of the sources and mechanisms of chemosensory ATP release in the CNS suggested that this signalling pathway is universally engaged in conditions of increased metabolic demand by brain glial cells - astrocytes. Astrocytes appear to function as versatile CNS metabolic sensors that detect changes in brain tissue pH, CO2, oxygen, and cerebral perfusion pressure. Experimental studies on various aspects of astrocyte biology generated data indicating that the function of these omnipresent glial cells and communication between astrocytes and neurons are governed by purinergic signalling, - first discovered by Geoff Burnstock in the 70's and researched through his entire scientific career.
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Affiliation(s)
- Alexander V Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
| | - K Michael Spyer
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
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28
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King DR, Sedovy MW, Leng X, Xue J, Lamouille S, Koval M, Isakson BE, Johnstone SR. Mechanisms of Connexin Regulating Peptides. Int J Mol Sci 2021; 22:ijms221910186. [PMID: 34638526 PMCID: PMC8507914 DOI: 10.3390/ijms221910186] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 09/16/2021] [Accepted: 09/17/2021] [Indexed: 12/22/2022] Open
Abstract
Gap junctions (GJ) and connexins play integral roles in cellular physiology and have been found to be involved in multiple pathophysiological states from cancer to cardiovascular disease. Studies over the last 60 years have demonstrated the utility of altering GJ signaling pathways in experimental models, which has led to them being attractive targets for therapeutic intervention. A number of different mechanisms have been proposed to regulate GJ signaling, including channel blocking, enhancing channel open state, and disrupting protein-protein interactions. The primary mechanism for this has been through the design of numerous peptides as therapeutics, that are either currently in early development or are in various stages of clinical trials. Despite over 25 years of research into connexin targeting peptides, the overall mechanisms of action are still poorly understood. In this overview, we discuss published connexin targeting peptides, their reported mechanisms of action, and the potential for these molecules in the treatment of disease.
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Affiliation(s)
- D. Ryan King
- Fralin Biomedical Research Institute at Virginia Tech Carilion School of Medicine, Virginia Tech, Roanoke, VA 24016, USA; (D.R.K.); (M.W.S.); (X.L.); (S.L.)
| | - Meghan W. Sedovy
- Fralin Biomedical Research Institute at Virginia Tech Carilion School of Medicine, Virginia Tech, Roanoke, VA 24016, USA; (D.R.K.); (M.W.S.); (X.L.); (S.L.)
- Translational Biology, Medicine, and Health Graduate Program, Virginia Tech, Blacksburg, VA 24061, USA
| | - Xinyan Leng
- Fralin Biomedical Research Institute at Virginia Tech Carilion School of Medicine, Virginia Tech, Roanoke, VA 24016, USA; (D.R.K.); (M.W.S.); (X.L.); (S.L.)
| | - Jianxiang Xue
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; (J.X.); (B.E.I.)
| | - Samy Lamouille
- Fralin Biomedical Research Institute at Virginia Tech Carilion School of Medicine, Virginia Tech, Roanoke, VA 24016, USA; (D.R.K.); (M.W.S.); (X.L.); (S.L.)
- Center for Vascular and Heart Research, Virginia Tech, Roanoke, VA 24016, USA
| | - Michael Koval
- Department of Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA;
| | - Brant E. Isakson
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; (J.X.); (B.E.I.)
- Department of Molecular Physiology and Biophysics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Scott R. Johnstone
- Fralin Biomedical Research Institute at Virginia Tech Carilion School of Medicine, Virginia Tech, Roanoke, VA 24016, USA; (D.R.K.); (M.W.S.); (X.L.); (S.L.)
- Center for Vascular and Heart Research, Virginia Tech, Roanoke, VA 24016, USA
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24060, USA
- Correspondence:
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29
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Montalant A, Carlsen EMM, Perrier J. Role of astrocytes in rhythmic motor activity. Physiol Rep 2021; 9:e15029. [PMID: 34558208 PMCID: PMC8461027 DOI: 10.14814/phy2.15029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Revised: 08/11/2021] [Accepted: 08/13/2021] [Indexed: 01/14/2023] Open
Abstract
Rhythmic motor activities such as breathing, locomotion, tremor, or mastication are organized by groups of interconnected neurons. Most synapses in the central nervous system are in close apposition with processes belonging to astrocytes. Neurotransmitters released from neurons bind to receptors expressed by astrocytes, activating a signaling pathway that leads to an increase in calcium concentration and the release of gliotransmitters that eventually modulate synaptic transmission. It is therefore likely that the activation of astrocytes impacts motor control. Here we review recent studies demonstrating that astrocytes inhibit, modulate, or trigger motor rhythmic behaviors.
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Affiliation(s)
- Alexia Montalant
- Department of NeuroscienceFaculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Eva M. M. Carlsen
- Department of NeuroscienceFaculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Jean‐François Perrier
- Department of NeuroscienceFaculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
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30
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Baloğlu E, Mairbäurl H. In Search of a Sensor: How Does CO 2 Regulate Alveolar Ion Transport? Am J Respir Cell Mol Biol 2021; 65:571-572. [PMID: 34348088 PMCID: PMC8641802 DOI: 10.1165/rcmb.2021-0270ed] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Affiliation(s)
- Emel Baloğlu
- Acibadem Mehmet Ali Aydinlar University School of Medicine, Department of Pharmacology , Istanbul, Turkey
| | - Heimo Mairbäurl
- University Hospital Heidelberg, 27178, Translational Pneumology and Translational Lung Research Center Heidelberg (TLRC) German Center for Lung Research (DZL) Im Neuenheimer Feld 156, Heidelberg, Germany;
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31
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Astrocytic contribution to glutamate-related central respiratory chemoreception in vertebrates. Respir Physiol Neurobiol 2021; 294:103744. [PMID: 34302992 DOI: 10.1016/j.resp.2021.103744] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 07/01/2021] [Accepted: 07/18/2021] [Indexed: 12/24/2022]
Abstract
Central respiratory chemoreceptors play a key role in the respiratory homeostasis by sensing CO2 and H+ in brain and activating the respiratory neural network. This ability of specific brain regions to respond to acidosis and hypercapnia is based on neuronal and glial mechanisms. Several decades ago, glutamatergic transmission was proposed to be involved as a main mechanism in central chemoreception. However, a complete identification of mechanism has been elusive. At the rostral medulla, chemosensitive neurons of the retrotrapezoid nucleus (RTN) are glutamatergic and they are stimulated by ATP released by RTN astrocytes in response to hypercapnia. In addition, recent findings show that caudal medullary astrocytes in brainstem can also contribute as CO2 and H+ sensors that release D-serine and glutamate, both gliotransmitters able to activate the respiratory neural network. In this review, we describe the mammalian astrocytic glutamatergic contribution to the central respiratory chemoreception trying to trace in vertebrates the emergence of several components involved in this process.
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32
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CO 2-Sensitive Connexin Hemichannels in Neurons and Glia: Three Different Modes of Signalling? Int J Mol Sci 2021; 22:ijms22147254. [PMID: 34298872 PMCID: PMC8304244 DOI: 10.3390/ijms22147254] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 06/29/2021] [Accepted: 07/01/2021] [Indexed: 01/28/2023] Open
Abstract
Connexins can assemble into either gap junctions (between two cells) or hemichannels (from one cell to the extracellular space) and mediate cell-to-cell signalling. A subset of connexins (Cx26, Cx30, Cx32) are directly sensitive to CO2 and fluctuations in the level within a physiological range affect their open probability, and thus, change cell conductance. These connexins are primarily found on astrocytes or oligodendrocytes, where increased CO2 leads to ATP release, which acts on P2X and P2Y receptors of neighbouring neurons and changes excitability. CO2-sensitive hemichannels are also found on developing cortical neurons, where they play a role in producing spontaneous neuronal activity. It is plausible that the transient opening of hemichannels allows cation influx, leading to depolarisation. Recently, we have shown that dopaminergic neurons in the substantia nigra and GABAergic neurons in the VTA also express Cx26 hemichannels. An increase in the level of CO2 results in hemichannel opening, increasing whole-cell conductance, and decreasing neuronal excitability. We found that the expression of Cx26 in the dopaminergic neurons in the substantia nigra at P7-10 is transferred to glial cells by P17-21, displaying a shift from being inhibitory (to neuronal activity) in young mice, to potentially excitatory (via ATP release). Thus, Cx26 hemichannels could have three modes of signalling (release of ATP, excitatory flickering open and shut and inhibitory shunting) depending on where they are expressed (neurons or glia) and the stage of development.
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33
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Caldwell HG, Smith KJ, Lewis NCS, Hoiland RL, Willie CK, Lucas SJE, Stembridge M, Burgess KR, MacLeod DB, Ainslie PN. Regulation of cerebral blood flow by arterial PCO 2 independent of metabolic acidosis at 5050 m. J Physiol 2021; 599:3513-3530. [PMID: 34047356 DOI: 10.1113/jp281446] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Accepted: 05/21/2021] [Indexed: 12/23/2022] Open
Abstract
KEY POINTS We investigated the influence of arterial PCO2 (PaCO2 ) with and without experimentally altered pH on cerebral blood flow (CBF) regulation at sea level and with acclimatization to 5050 m. At sea level and high altitude, we assessed stepwise alterations in PaCO2 following metabolic acidosis (via 2 days of oral acetazolamide; ACZ) with and without acute restoration of pH (via intravenous sodium bicarbonate; ACZ+HCO3 - ). Total resting CBF was unchanged between trials at each altitude even though arterial pH and [HCO3 - ] (i.e. buffering capacity) were effectively altered. The cerebrovascular responses to changes in arterial [H+ ]/pH were consistent with the altered relationship between PaCO2 and [H+ ]/pH following ACZ at high altitude (i.e. leftward x-intercept shifts). Absolute cerebral blood velocity (CBV) and the sensitivity of CBV to PaCO2 was unchanged between trials at high altitude, indicating that CBF is acutely regulated by PaCO2 rather than arterial pH. ABSTRACT Alterations in acid-base balance with progressive acclimatization to high altitude have been well-established. However, how respiratory alkalosis and the resultant metabolic compensation interact to regulate cerebral blood flow (CBF) is uncertain. We addressed this via three separate experimental trials at sea level and following partial acclimatization (14 to 20 days) at 5050 m; involving: (1) resting acid-base balance (control); (2) following metabolic acidosis via 2 days of oral acetazolamide at 250 mg every 8 h (ACZ; pH: Δ -0.07 ± 0.04 and base excess: Δ -5.7 ± 1.9 mEq⋅l-1 , trial effects: P < 0.001 and P < 0.001, respectively); and (3) after acute normalization of arterial acidosis via intravenous sodium bicarbonate (ACZ + HCO3 - ; pH: Δ -0.01 ± 0.04 and base excess: Δ -1.5 ± 2.1 mEq⋅l-1 , trial effects: P = 1.000 and P = 0.052, respectively). Within each trial, we utilized transcranial Doppler ultrasound to assess the cerebral blood velocity (CBV) response to stepwise alterations in arterial PCO2 (PaCO2 ), i.e. cerebrovascular CO2 reactivity. Resting CBF (via Duplex ultrasound) was unaltered between trials within each altitude, indicating that respiratory compensation (i.e. Δ -3.4 ± 2.3 mmHg PaCO2 , trial effect: P < 0.001) was sufficient to offset any elevations in CBF induced via the ACZ-mediated metabolic acidosis. Between trials at high altitude, we observed consistent leftward shifts in both the PaCO2 -pH and CBV-pH responses across the CO2 reactivity tests with experimentally reduced arterial pH via ACZ. When indexed against PaCO2 - rather than pH - the absolute CBV and sensitivity of CBV-PaCO2 was unchanged between trials at high altitude. Taken together, following acclimatization, CO2 -mediated changes in cerebrovascular tone rather than arterial [H+ ]/pH is integral to CBF regulation at high altitude.
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Affiliation(s)
- Hannah G Caldwell
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Kurt J Smith
- Integrative Physiology Laboratory, Department of Kinesiology and Nutrition, University of Illinois Chicago, Chicago, Illinois, USA
| | - Nia C S Lewis
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Ryan L Hoiland
- Department of Anesthesiology, Pharmacology and Therapeutics, Vancouver General Hospital, West 12th Avenue, University of British Columbia, Vancouver, British Columbia, Canada.,Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Christopher K Willie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Samuel J E Lucas
- Department of Physiology, University of Otago, Dunedin, New Zealand.,School of Sport, Exercise and Rehabilitation Sciences & Centre for Human Brain Health, University of Birmingham, Birmingham, UK
| | - Michael Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
| | - Keith R Burgess
- Peninsula Sleep Clinic, Sydney, New South Wales, Australia.,Department of Medicine, University of Sydney, Sydney, New South Wales, Australia
| | - David B MacLeod
- Human Pharmacology and Physiology Lab, Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
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34
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Cleary CM, Milla BM, Kuo FS, James S, Flynn WF, Robson P, Mulkey DK. Somatostatin-expressing parafacial neurons are CO 2/H + sensitive and regulate baseline breathing. eLife 2021; 10:e60317. [PMID: 34013884 PMCID: PMC8169115 DOI: 10.7554/elife.60317] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 05/19/2021] [Indexed: 01/16/2023] Open
Abstract
Glutamatergic neurons in the retrotrapezoid nucleus (RTN) function as respiratory chemoreceptors by regulating breathing in response to tissue CO2/H+. The RTN and greater parafacial region may also function as a chemosensing network composed of CO2/H+-sensitive excitatory and inhibitory synaptic interactions. In the context of disease, we showed that loss of inhibitory neural activity in a mouse model of Dravet syndrome disinhibited RTN chemoreceptors and destabilized breathing (Kuo et al., 2019). Despite this, contributions of parafacial inhibitory neurons to control of breathing are unknown, and synaptic properties of RTN neurons have not been characterized. Here, we show the parafacial region contains a limited diversity of inhibitory neurons including somatostatin (Sst)-, parvalbumin (Pvalb)-, and cholecystokinin (Cck)-expressing neurons. Of these, Sst-expressing interneurons appear uniquely inhibited by CO2/H+. We also show RTN chemoreceptors receive inhibitory input that is withdrawn in a CO2/H+-dependent manner, and chemogenetic suppression of Sst+ parafacial neurons, but not Pvalb+ or Cck+ neurons, increases baseline breathing. These results suggest Sst-expressing parafacial neurons contribute to RTN chemoreception and respiratory activity.
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Affiliation(s)
- Colin M Cleary
- Department of Physiology and Neurobiology, University of ConnecticutStorrsUnited States
| | - Brenda M Milla
- Department of Physiology and Neurobiology, University of ConnecticutStorrsUnited States
| | - Fu-Shan Kuo
- Department of Physiology and Neurobiology, University of ConnecticutStorrsUnited States
| | - Shaun James
- Department of Physiology and Neurobiology, University of ConnecticutStorrsUnited States
| | - William F Flynn
- The Jackson Laboratory for Genomic MedicineFarmingtonUnited States
| | - Paul Robson
- The Jackson Laboratory for Genomic MedicineFarmingtonUnited States
- Institute for Systems Genomics, University of ConnecticutFarmingtonUnited States
| | - Daniel K Mulkey
- Department of Physiology and Neurobiology, University of ConnecticutStorrsUnited States
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35
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Dale N. Biological insights from the direct measurement of purine release. Biochem Pharmacol 2021; 187:114416. [PMID: 33444569 DOI: 10.1016/j.bcp.2021.114416] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 01/05/2021] [Accepted: 01/07/2021] [Indexed: 12/23/2022]
Abstract
Although purinergic signalling has been a well-established and accepted mechanism of chemical communication for many years, it remains important to measure the extracellular concentration of ATP and adenosine in real time. In this review I summarize the reasons why such measurements are still needed, how they provide additional mechanistic insight and give an overview of the techniques currently available to make spatially localised measurements of ATP and adenosine in real time. To illustrate the impact of direct real-time measurements, I explore CO2 and nutrient sensing in the medulla oblongata and hypothalamus. In both of these examples, the sensing involves hemichannel mediated ATP release from glial cells. For CO2 the hemichannels involved, connexin26, are directly CO2-sensitive. This mechanism contributes to the chemosensory control of breathing. In the hypothamalus, specialised glial cells, tanycytes, directly contact the cerebrospinal fluid in the 3rd ventricle and sense nutrients via sweet and umami taste receptors. Nutrient sensing by tanycytes is likely to contribute to the control of body weight as their selective stimulation alters food intake. To illustrate the importance of direct adenosine measurements, I consider the complex and multiple mechanisms of activity-dependent adenosine release in different brain regions. This activity dependent release of adenosine is likely to mediate important feedback regulation and may also be involved in controlling the sleep-wake state. I finish by briefly considering the potential of whole blood purine measurements in clinical practice.
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Affiliation(s)
- Nicholas Dale
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK.
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Dale N. CO 2 sensing by connexin26 and its role in the control of breathing. Interface Focus 2021; 11:20200029. [PMID: 33633831 DOI: 10.1098/rsfs.2020.0029] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/09/2020] [Indexed: 12/14/2022] Open
Abstract
Breathing is essential to provide the O2 required for metabolism and to remove its inevitable CO2 by-product. The rate and depth of breathing is controlled to regulate the excretion of CO2 to maintain the pH of arterial blood at physiological values. A widespread consensus is that chemosensory cells in the carotid body and brainstem measure blood and tissue pH and adjust the rate of breathing to ensure its homeostatic regulation. In this review, I shall consider the evidence that underlies this consensus and highlight historical data indicating that direct sensing of CO2 also plays a significant role in the regulation of breathing. I shall then review work from my laboratory that provides a molecular mechanism for the direct detection of CO2 via the gap junction protein connexin26 (Cx26) and demonstrates the contribution of this mechanism to the chemosensory regulation of breathing. As there are many pathological mutations of Cx26 in humans, I shall discuss which of these alter the CO2 sensitivity of Cx26 and the extent to which these mutations could affect human breathing. I finish by discussing the evolution of the CO2 sensitivity of Cx26 and its link to the evolution of amniotes.
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Affiliation(s)
- Nicholas Dale
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK
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Acosta ML, Mat Nor MN, Guo CX, Mugisho OO, Coutinho FP, Rupenthal ID, Green CR. Connexin therapeutics: blocking connexin hemichannel pores is distinct from blocking pannexin channels or gap junctions. Neural Regen Res 2021; 16:482-488. [PMID: 32985469 PMCID: PMC7996017 DOI: 10.4103/1673-5374.290097] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Compounds that block the function of connexin and pannexin protein channels have been suggested to be valuable therapeutics for a range of diseases. Some of these compounds are now in clinical trials, but for many of them, the literature is inconclusive about the molecular effect on the tissue, despite evidence of functional recovery. Blocking the different channel types has distinct physiological and pathological implications and this review describes current knowledge of connexin and pannexin protein channels, their function as channels and possible mechanisms of the channel block effect for the latest therapeutic compounds. We summarize the evidence implicating pannexins and connexins in disease, considering their homeostatic versus pathological roles, their contribution to excesive ATP release linked to disease onset and progression.
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Affiliation(s)
- Monica L Acosta
- School of Optometry and Vision Science; New Zealand National Eye Centre, University of Auckland; Centre for Brain Research, Faculty of Medical and Health Sciences, The University of Auckland; Brain Research New Zealand-Rangahau Roro Aotearoa, Auckland, New Zealand
| | - Mohd N Mat Nor
- School of Optometry and Vision Science, University of Auckland, Auckland, New Zealand; Faculty of Medicine, Universiti Sultan Zainal Abidin, Terengganu, Malaysia
| | - Cindy X Guo
- School of Optometry and Vision Science, University of Auckland, Auckland, New Zealand
| | - Odunayo O Mugisho
- Department of Ophthalmology, University of Auckland; Buchanan Ocular Therapeutics Unit, Department of Ophthalmology; New Zealand National Eye Centre, University of Auckland, Auckland, New Zealand
| | - Frazer P Coutinho
- Department of Ophthalmology, University of Auckland, Auckland, New Zealand
| | - Ilva D Rupenthal
- Department of Ophthalmology, University of Auckland; Buchanan Ocular Therapeutics Unit, Department of Ophthalmology; New Zealand National Eye Centre, University of Auckland, Auckland, New Zealand
| | - Colin R Green
- Department of Ophthalmology; New Zealand National Eye Centre, University of Auckland, Auckland, New Zealand
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Turovsky EA, Braga A, Yu Y, Esteras N, Korsak A, Theparambil SM, Hadjihambi A, Hosford PS, Teschemacher AG, Marina N, Lythgoe MF, Haydon PG, Gourine AV. Mechanosensory Signaling in Astrocytes. J Neurosci 2020; 40:9364-9371. [PMID: 33122390 PMCID: PMC7724146 DOI: 10.1523/jneurosci.1249-20.2020] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 08/20/2020] [Accepted: 09/16/2020] [Indexed: 02/07/2023] Open
Abstract
Mechanosensitivity is a well-known feature of astrocytes, however, its underlying mechanisms and functional significance remain unclear. There is evidence that astrocytes are acutely sensitive to decreases in cerebral perfusion pressure and may function as intracranial baroreceptors, tuned to monitor brain blood flow. This study investigated the mechanosensory signaling in brainstem astrocytes, as these cells reside alongside the cardiovascular control circuits and mediate increases in blood pressure and heart rate induced by falls in brain perfusion. It was found that mechanical stimulation-evoked Ca2+ responses in astrocytes of the rat brainstem were blocked by (1) antagonists of connexin channels, connexin 43 (Cx43) blocking peptide Gap26, or Cx43 gene knock-down; (2) antagonists of TRPV4 channels; (3) antagonist of P2Y1 receptors for ATP; and (4) inhibitors of phospholipase C or IP3 receptors. Proximity ligation assay demonstrated interaction between TRPV4 and Cx43 channels in astrocytes. Dye loading experiments showed that mechanical stimulation increased open probability of carboxyfluorescein-permeable membrane channels. These data suggest that mechanosensory Ca2+ responses in astrocytes are mediated by interaction between TRPV4 and Cx43 channels, leading to Cx43-mediated release of ATP which propagates/amplifies Ca2+ signals via P2Y1 receptors and Ca2+ recruitment from the intracellular stores. In astrocyte-specific Cx43 knock-out mice the magnitude of heart rate responses to acute increases in intracranial pressure was not affected by Cx43 deficiency. However, these animals displayed lower heart rates at different levels of cerebral perfusion, supporting the hypothesis of connexin hemichannel-mediated release of signaling molecules by astrocytes having an excitatory action on the CNS sympathetic control circuits.SIGNIFICANCE STATEMENT There is evidence suggesting that astrocytes may function as intracranial baroreceptors that play an important role in the control of systemic and cerebral circulation. To function as intracranial baroreceptors, astrocytes must possess a specialized membrane mechanism that makes them exquisitely sensitive to mechanical stimuli. This study shows that opening of connexin 43 (Cx43) hemichannels leading to the release of ATP is the key central event underlying mechanosensory Ca2+ responses in astrocytes. This astroglial mechanism plays an important role in the autonomic control of heart rate. These data add to the growing body of evidence suggesting that astrocytes function as versatile surveyors of the CNS metabolic milieu, tuned to detect conditions of potential metabolic threat, such as hypoxia, hypercapnia, and reduced perfusion.
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Affiliation(s)
- Egor A Turovsky
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London WC1E 6BT, United Kingdom
| | - Alice Braga
- Department of Neuroscience, Tufts Neuroscience Institute, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Yichao Yu
- UCL Centre for Advanced Biomedical Imaging, Division of Medicine, University College London, London WC1E 6DD, United Kingdom
| | - Noemi Esteras
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London WC1N 3BG, United Kingdom
| | - Alla Korsak
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London WC1E 6BT, United Kingdom
| | - Shefeeq M Theparambil
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London WC1E 6BT, United Kingdom
| | - Anna Hadjihambi
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London WC1E 6BT, United Kingdom
- Department of Biomedical Sciences, University of Lausanne, Lausanne 1005, Switzerland
| | - Patrick S Hosford
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London WC1E 6BT, United Kingdom
| | - Anja G Teschemacher
- Physiology, Pharmacology, and Neuroscience, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Nephtali Marina
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London WC1E 6BT, United Kingdom
| | - Mark F Lythgoe
- UCL Centre for Advanced Biomedical Imaging, Division of Medicine, University College London, London WC1E 6DD, United Kingdom
| | - Philip G Haydon
- Department of Neuroscience, Tufts Neuroscience Institute, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Alexander V Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London WC1E 6BT, United Kingdom
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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.
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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
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Blockade of Glial Connexin 43 Hemichannels Reduces Food Intake. Cells 2020; 9:cells9112387. [PMID: 33142723 PMCID: PMC7693394 DOI: 10.3390/cells9112387] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 10/20/2020] [Accepted: 10/26/2020] [Indexed: 12/16/2022] Open
Abstract
The metabolic syndrome, which comprises obesity and diabetes, is a major public health problem and the awareness of energy homeostasis control remains an important worldwide issue. The energy balance is finely regulated by the central nervous system (CNS), notably through neuronal networks, located in the hypothalamus and the dorsal vagal complex (DVC), which integrate nutritional, humoral and nervous information from the periphery. The glial cells’ contribution to these processes emerged few year ago. However, its underlying mechanism remains unclear. Glial connexin 43 hemichannels (Cx43 HCs) enable direct exchange with the extracellular space and can regulate neuronal network activity. In the present study, we sought to determine the possible involvement of glial Cx43 HCs in energy balance regulation. We here show that Cx43 is strongly expressed in the hypothalamus and DVC and is associated with glial cells. Remarkably, we observed a close apposition of Cx43 with synaptic elements in both the hypothalamus and DVC. Moreover, the expression of hypothalamic Cx43 mRNA and protein is modulated in response to fasting and diet-induced obesity. Functionally, we found that Cx43 HCs are largely open in the arcuate nucleus (ARC) from acute mice hypothalamic slices under basal condition, and significantly inhibited by TAT-GAP19, a mimetic peptide that specifically blocks Cx43 HCs activity. Moreover, intracerebroventricular (i.c.v.) TAT-GAP19 injection strongly decreased food intake, without further alteration of glycaemia, energy expenditures or locomotor activity. Using the immediate early gene c-Fos expression, we found that i.c.v. TAT-GAP19 injection induced neuronal activation in hypothalamic and brainstem nuclei dedicated to food intake regulation. Altogether, these results suggest a tonic delivery of orexigenic molecules associated with glial Cx43 HCs activity and a possible modulation of this tonus during fasting and obesity.
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Nijjar S, Maddison D, Meigh L, de Wolf E, Rodgers T, Cann MJ, Dale N. Opposing modulation of Cx26 gap junctions and hemichannels by CO 2. J Physiol 2020; 599:103-118. [PMID: 33022747 DOI: 10.1113/jp280747] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Accepted: 10/02/2020] [Indexed: 01/21/2023] Open
Abstract
KEY POINTS A moderate increase in P C O 2 (55 mmHg) closes Cx26 gap junctions. This effect of CO2 is independent of changes in intra- or extracellular pH. The CO2 -dependent closing effect depends on the same residues (K125 and R104) that are required for the CO2 -dependent opening of Cx26 hemichannels. Pathological mutations of Cx26 abolish the CO2 -dependent closing of the gap junction. Elastic network modelling suggests that the effect of CO2 on Cx26 hemichannels and gap junctions is mediated through changes in the lowest entropy state of the protein. ABSTRACT Cx26 hemichannels open in response to moderate elevations of CO2 ( P C O 2 55 mmHg) via a carbamylation reaction that depends on residues K125 and R104. Here we investigate the action of CO2 on Cx26 gap junctions. Using a dye transfer assay, we found that an elevated P C O 2 of 55 mmHg greatly delayed the permeation of a fluorescent glucose analogue (NBDG) between HeLa cells coupled by Cx26 gap junctions. However, the mutations K125R or R104A abolished this effect of CO2 . Whole cell recordings demonstrated that elevated CO2 reduced the Cx26 gap junction conductance (median reduction 66.7%, 95% CI, 50.5-100.0%) but had no effect on Cx26K125R or Cx31 gap junctions. CO2 can cause intracellular acidification. Using 30 mm propionate, we found that acidification in the absence of a change in P C O 2 caused a median reduction in the gap junction conductance of 41.7% (95% CI, 26.6-53.7%). This effect of propionate was unaffected by the K125R mutation (median reduction 48.1%, 95% CI, 28.0-86.3%). pH-dependent and CO2 -dependent closure of the gap junction are thus mechanistically independent. Mutations of Cx26 associated with the keratitis ichthyosis deafness syndrome (N14K, A40V and A88V), in combination with the mutation M151L, also abolished the CO2 -dependent gap junction closure. Elastic network modelling suggests that the lowest entropy state when CO2 is bound is the closed configuration for the gap junction but the open state for the hemichannel. The opposing actions of CO2 on Cx26 gap junctions and hemichannels thus depend on the same residues and presumed carbamylation reaction.
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Affiliation(s)
- Sarbjit Nijjar
- School of Life Sciences, University of Warwick, Coventry, UK
| | - Daniel Maddison
- School of Life Sciences, University of Warwick, Coventry, UK
| | - Louise Meigh
- School of Life Sciences, University of Warwick, Coventry, UK
| | | | - Thomas Rodgers
- School of Chemical Engineering and Analytical Science, University of Manchester, Manchester, UK
| | - Martin J Cann
- Department of Biosciences, Durham University, Durham, UK
| | - Nicholas Dale
- School of Life Sciences, University of Warwick, Coventry, UK
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Theparambil SM, Hosford PS, Ruminot I, Kopach O, Reynolds JR, Sandoval PY, Rusakov DA, Barros LF, Gourine AV. Astrocytes regulate brain extracellular pH via a neuronal activity-dependent bicarbonate shuttle. Nat Commun 2020; 11:5073. [PMID: 33033238 PMCID: PMC7545092 DOI: 10.1038/s41467-020-18756-3] [Citation(s) in RCA: 67] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 09/09/2020] [Indexed: 12/19/2022] Open
Abstract
Brain cells continuously produce and release protons into the extracellular space, with the rate of acid production corresponding to the levels of neuronal activity and metabolism. Efficient buffering and removal of excess H+ is essential for brain function, not least because all the electrogenic and biochemical machinery of synaptic transmission is highly sensitive to changes in pH. Here, we describe an astroglial mechanism that contributes to the protection of the brain milieu from acidification. In vivo and in vitro experiments conducted in rodent models show that at least one third of all astrocytes release bicarbonate to buffer extracellular H+ loads associated with increases in neuronal activity. The underlying signalling mechanism involves activity-dependent release of ATP triggering bicarbonate secretion by astrocytes via activation of metabotropic P2Y1 receptors, recruitment of phospholipase C, release of Ca2+ from the internal stores, and facilitated outward HCO3- transport by the electrogenic sodium bicarbonate cotransporter 1, NBCe1. These results show that astrocytes maintain local brain extracellular pH homeostasis via a neuronal activity-dependent release of bicarbonate. The data provide evidence of another important metabolic housekeeping function of these glial cells.
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Affiliation(s)
- Shefeeq M Theparambil
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Patrick S Hosford
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Iván Ruminot
- Centro de Estudios Científicos (CECs), Valdivia, Chile
| | - Olga Kopach
- Institute of Neurology, University College London, London, UK
| | | | | | | | | | - Alexander V Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK.
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43
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Real-time measurement of adenosine and ATP release in the central nervous system. Purinergic Signal 2020; 17:109-115. [PMID: 33025425 PMCID: PMC7954901 DOI: 10.1007/s11302-020-09733-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 09/13/2020] [Indexed: 11/12/2022] Open
Abstract
This brief review recounts how, stimulated by the work of Geoff Burnstock, I developed biosensors that allowed direct real-time measurement of ATP and adenosine during neural function. The initial impetus to create an adenosine biosensor came from trying to understand how ATP and adenosine-modulated motor pattern generation in the frog embryo spinal cord. Early biosensor measurements demonstrated slow accumulation of adenosine during motor activity. Subsequent application of these biosensors characterized real-time release of adenosine in in vitro models of brain ischaemia, and this line of work has recently led to clinical measurements of whole blood purine levels in patients undergoing carotid artery surgery or stroke. In parallel, the wish to understand the role of ATP signalling in the chemosensory regulation of breathing stimulated the development of ATP biosensors. This revealed that release of ATP from the chemosensory areas of the medulla oblongata preceded adaptive changes in breathing, triggered adaptive changes in breathing via activation of P2 receptors, and ultimately led to the discovery of connexin26 as a channel that mediates CO2-gated release of ATP from cells.
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Hypercapnia: An Aggravating Factor in Asthma. J Clin Med 2020; 9:jcm9103207. [PMID: 33027886 PMCID: PMC7599850 DOI: 10.3390/jcm9103207] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2020] [Revised: 10/01/2020] [Accepted: 10/02/2020] [Indexed: 02/06/2023] Open
Abstract
Asthma is a common chronic respiratory disorder with relatively good outcomes in the majority of patients with appropriate maintenance therapy. However, in a small minority, patients can experience severe asthma with respiratory failure and hypercapnia, necessitating intensive care unit admission. Hypercapnia occurs due to alveolar hypoventilation and insufficient removal of carbon dioxide (CO2) from the blood. Although mild hypercapnia is generally well tolerated in patients with asthma, there is accumulating evidence that elevated levels of CO2 can act as a gaso-signaling molecule, triggering deleterious effects in various organs such as the lung, skeletal muscles and the innate immune system. Here, we review recent advances on pathophysiological response to hypercapnia and discuss potential detrimental effects of hypercapnia in patients with asthma.
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45
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Serova OV, Gantsova EA, Deyev IE, Petrenko AG. The Value of pH Sensors in Maintaining Homeostasis of the Nervous System. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2020. [DOI: 10.1134/s1068162020040196] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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46
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van de Wiel J, Meigh L, Bhandare A, Cook J, Nijjar S, Huckstepp R, Dale N. Connexin26 mediates CO 2-dependent regulation of breathing via glial cells of the medulla oblongata. Commun Biol 2020; 3:521. [PMID: 32958814 PMCID: PMC7505967 DOI: 10.1038/s42003-020-01248-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 08/21/2020] [Indexed: 01/12/2023] Open
Abstract
Breathing is highly sensitive to the PCO2 of arterial blood. Although CO2 is detected via the proxy of pH, CO2 acting directly via Cx26 may also contribute to the regulation of breathing. Here we exploit our knowledge of the structural motif of CO2-binding to Cx26 to devise a dominant negative subunit (Cx26DN) that removes the CO2-sensitivity from endogenously expressed wild type Cx26. Expression of Cx26DN in glial cells of a circumscribed region of the mouse medulla - the caudal parapyramidal area - reduced the adaptive change in tidal volume and minute ventilation by approximately 30% at 6% inspired CO2. As central chemosensors mediate about 70% of the total response to hypercapnia, CO2-sensing via Cx26 in the caudal parapyramidal area contributed about 45% of the centrally-mediated ventilatory response to CO2. Our data unequivocally link the direct sensing of CO2 to the chemosensory control of breathing and demonstrates that CO2-binding to Cx26 is a key transduction step in this fundamental process.
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Affiliation(s)
| | - Louise Meigh
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
| | - Amol Bhandare
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
| | - Jonathan Cook
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
| | - Sarbjit Nijjar
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
| | - Robert Huckstepp
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
| | - Nicholas Dale
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK.
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Astrocyte-mediated switch in spike timing-dependent plasticity during hippocampal development. Nat Commun 2020; 11:4388. [PMID: 32873805 PMCID: PMC7463247 DOI: 10.1038/s41467-020-18024-4] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 07/31/2020] [Indexed: 01/31/2023] Open
Abstract
Presynaptic spike timing-dependent long-term depression (t-LTD) at hippocampal CA3-CA1 synapses is evident until the 3rd postnatal week in mice, disappearing during the 4th week. At more mature stages, we found that the protocol that induced t-LTD induced t-LTP. We characterized this form of t-LTP and the mechanisms involved in its induction, as well as that driving this switch from t-LTD to t-LTP. We found that this t-LTP is expressed presynaptically at CA3-CA1 synapses, as witnessed by coefficient of variation, number of failures, paired-pulse ratio and miniature responses analysis. Additionally, this form of presynaptic t-LTP does not require NMDARs but the activation of mGluRs and the entry of Ca2+ into the postsynaptic neuron through L-type voltage-dependent Ca2+ channels and the release of Ca2+ from intracellular stores. Nitric oxide is also required as a messenger from the postsynaptic neuron. Crucially, the release of adenosine and glutamate by astrocytes is required for t-LTP induction and for the switch from t-LTD to t-LTP. Thus, we have discovered a developmental switch of synaptic transmission from t-LTD to t-LTP at hippocampal CA3-CA1 synapses in which astrocytes play a central role and revealed a form of presynaptic LTP and the rules for its induction. Presynaptic spike timing-dependent long-term depression at hippocampal CA3-CA1 synapses is evident until the third postnatal week in mice. The authors show that maturation beyond four weeks is associated with a switch to long-term potentiation in which astrocytes play a central role.
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48
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Hill E, Dale N, Wall MJ. Moderate Changes in CO 2 Modulate the Firing of Neurons in the VTA and Substantia Nigra. iScience 2020; 23:101343. [PMID: 32683315 PMCID: PMC7371905 DOI: 10.1016/j.isci.2020.101343] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 04/30/2020] [Accepted: 07/01/2020] [Indexed: 12/21/2022] Open
Abstract
The substantia nigra (SN) and ventral tegmental area (VTA) are vital for the control of movement, goal-directed behavior, and encoding reward. Here we show that the firing of specific neuronal subtypes in these nuclei can be modulated by physiological changes in the partial pressure of carbon dioxide (PCO2). The resting conductance of substantia nigra dopaminergic neurons in young animals (postnatal days 7-10) and GABAergic neurons in the VTA is modulated by changes in the level of CO2. We provide several lines of evidence that this CO2-sensitive conductance results from connexin 26 (Cx26) hemichannel expression. Since the levels of PCO2 in the blood will vary depending on physiological activity and pathology, this suggests that changes in PCO2 could potentially modulate motor activity, reward behavior, and wakefulness.
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Affiliation(s)
- Emily Hill
- School of Life Sciences, University of Warwick, Gibbet Hill, Coventry CV4 7AL, UK.
| | - Nicholas Dale
- School of Life Sciences, University of Warwick, Gibbet Hill, Coventry CV4 7AL, UK
| | - Mark J Wall
- School of Life Sciences, University of Warwick, Gibbet Hill, Coventry CV4 7AL, UK.
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Pérez-Rodríguez M, Arroyo-García LE, Prius-Mengual J, Andrade-Talavera Y, Armengol JA, Pérez-Villegas EM, Duque-Feria P, Flores G, Rodríguez-Moreno A. Adenosine Receptor-Mediated Developmental Loss of Spike Timing-Dependent Depression in the Hippocampus. Cereb Cortex 2020; 29:3266-3281. [PMID: 30169759 PMCID: PMC6644873 DOI: 10.1093/cercor/bhy194] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 06/18/2018] [Accepted: 07/20/2018] [Indexed: 02/04/2023] Open
Abstract
Critical periods of synaptic plasticity facilitate the reordering and refining of neural connections during development, allowing the definitive synaptic circuits responsible for correct adult physiology to be established. Presynaptic spike timing-dependent long-term depression (t-LTD) exists in the hippocampus, which depends on the activation of NMDARs and that probably fulfills a role in synaptic refinement. This t-LTD is present until the third postnatal week in mice, disappearing in the fourth week of postnatal development. We were interested in the mechanisms underlying this maturation related loss of t-LTD and we found that at CA3–CA1 synapses, presynaptic NMDA receptors (pre-NMDARs) are tonically active between P13 and P21, mediating an increase in glutamate release during this critical period of plasticity. Conversely, at the end of this critical period (P22–P30) and coinciding with the loss of t-LTD, these pre-NMDARs are no longer tonically active. Using immunogold electron microscopy, we demonstrated the existence of pre-NMDARs at Schaffer collateral synaptic boutons, where a decrease in the number of pre-NMDARs during development coincides with the loss of both tonic pre-NMDAR activation and t-LTD. Interestingly, this t-LTD can be completely recovered by antagonizing adenosine type 1 receptors (A1R), which also recovers the tonic activation of pre-NMDARs at P22–P30. By contrast, the induction of t-LTD was prevented at P13–P21 by an agonist of A1R, as was tonic pre-NMDAR activation. Furthermore, we found that the adenosine that mediated the loss of t-LTD during the fourth week of development is supplied by astrocytes. These results provide direct evidence for the mechanism that closes the window of plasticity associated with t-LTD, revealing novel events probably involved in synaptic remodeling during development.
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Affiliation(s)
- Mikel Pérez-Rodríguez
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, Seville, Spain
| | - Luis E Arroyo-García
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, Seville, Spain.,Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, 72570 Puebla, Mexico
| | - José Prius-Mengual
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, Seville, Spain
| | - Yuniesky Andrade-Talavera
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, Seville, Spain
| | - José A Armengol
- Human Anatomy and Embryology Unit, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, Seville, Spain
| | - Eva M Pérez-Villegas
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, Seville, Spain
| | - Paloma Duque-Feria
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, Seville, Spain
| | - Gonzalo Flores
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, 72570 Puebla, Mexico
| | - Antonio Rodríguez-Moreno
- Laboratory of Cellular Neuroscience and Plasticity, Department of Physiology, Anatomy and Cell Biology, Universidad Pablo de Olavide, Seville, Spain
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Maia OAC, Malheiros-Lima MR, Oliveira MA, Castro CL, Moriya HT, Tavares-de-Lima W, Takakura AC, Moreira TS. Pilocarpine-induced status epilepticus reduces chemosensory control of breathing. Brain Res Bull 2020; 161:98-105. [PMID: 32433938 DOI: 10.1016/j.brainresbull.2020.05.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 04/27/2020] [Accepted: 05/02/2020] [Indexed: 12/14/2022]
Abstract
One of the possible causes of death in epilepsy is breathing disorders, especially apneas, which lead to an increase in CO2 levels (hypercapnia) and/or a decrease in O2 levels in arterial blood (hypoxemia). The respiratory neurons located in the ventral brainstem respiratory column are the main groups responsible for controlling breathing. Recent data from our group demonstrated respiratory changes in two experimental models of epilepsy, i.e. audiogenic epilepsy, and amygdala rapid kindling. Here, we aimed to evaluate respiratory changes in the classic model of temporal lobe epilepsy induced by intra-hippocampal injection of pilocarpine. Adult Wistar rats with stainless-steel cannulas implanted in the hippocampus region were used. The animals were submitted to pilocarpine injection (2.4 mg/μL, N = 12-15) or saline (N = 9) into the hippocampus. The respiratory parameters analyzed by whole-body plethysmography were respiratory rate (fR), tidal volume (VT) and ventilation (VE). Respiratory mechanics such as Newtonian airway resistance (Rn), viscance of the pulmonary parenchyma (G) and the elastance of the pulmonary parenchyma (H) were also investigated. No changes in baseline breathing were detected 15 or 30 days after pilocarpine-induced status epilepticus (SE). However, 30 days after pilocarpine-induced SE, a significant reduction in VE was observed during hypercapnic (7% CO2) stimulation, without affecting the hypoxia (8% O2) ventilatory response. We also did not observe changes in respiratory mechanics. The present results suggest that the impairment of the hypercapnia ventilatory response in pilocarpine-induced SE could be related to a presumable degeneration of brainstem respiratory neurons but not to peripheral mechanisms.
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Affiliation(s)
- Octávio A C Maia
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of Sao Paulo, 1524 Prof Lineu Prestes Av 05508-000, Sao Paulo, SP, Brazil
| | - Milene R Malheiros-Lima
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of Sao Paulo, 1524 Prof Lineu Prestes Av 05508-000, Sao Paulo, SP, Brazil
| | - Maria A Oliveira
- Department of Pharmacology, Institute of Biomedical Science, University of Sao Paulo, Sao Paulo, SP, Brazil
| | - Claudio L Castro
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of Sao Paulo, 1524 Prof Lineu Prestes Av 05508-000, Sao Paulo, SP, Brazil
| | - Henrique T Moriya
- Department of Engineering of Control and Telecommunication, University of Sao Paulo, Sao Paulo, SP, Brazil
| | - Wothan Tavares-de-Lima
- Department of Pharmacology, Institute of Biomedical Science, University of Sao Paulo, Sao Paulo, SP, Brazil
| | - Ana C Takakura
- Department of Pharmacology, Institute of Biomedical Science, University of Sao Paulo, Sao Paulo, SP, Brazil
| | - Thiago S Moreira
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of Sao Paulo, 1524 Prof Lineu Prestes Av 05508-000, Sao Paulo, SP, Brazil.
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