1
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Christie IN, Theparambil SM, Braga A, Doronin M, Hosford PS, Brazhe A, Mascarenhas A, Nizari S, Hadjihambi A, Wells JA, Hobbs A, Semyanov A, Abramov AY, Angelova PR, Gourine AV. Astrocytes produce nitric oxide via nitrite reduction in mitochondria to regulate cerebral blood flow during brain hypoxia. Cell Rep 2023; 42:113514. [PMID: 38041814 PMCID: PMC7615749 DOI: 10.1016/j.celrep.2023.113514] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 10/17/2023] [Accepted: 11/14/2023] [Indexed: 12/04/2023] Open
Abstract
During hypoxia, increases in cerebral blood flow maintain brain oxygen delivery. Here, we describe a mechanism of brain oxygen sensing that mediates the dilation of intraparenchymal cerebral blood vessels in response to reductions in oxygen supply. In vitro and in vivo experiments conducted in rodent models show that during hypoxia, cortical astrocytes produce the potent vasodilator nitric oxide (NO) via nitrite reduction in mitochondria. Inhibition of mitochondrial respiration mimics, but also occludes, the effect of hypoxia on NO production in astrocytes. Astrocytes display high expression of the molybdenum-cofactor-containing mitochondrial enzyme sulfite oxidase, which can catalyze nitrite reduction in hypoxia. Replacement of molybdenum with tungsten or knockdown of sulfite oxidase expression in astrocytes blocks hypoxia-induced NO production by these glial cells and reduces the cerebrovascular response to hypoxia. These data identify astrocyte mitochondria as brain oxygen sensors that regulate cerebral blood flow during hypoxia via release of nitric oxide.
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Affiliation(s)
- Isabel N Christie
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London WC1E 6BT, UK
| | - Shefeeq M Theparambil
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London WC1E 6BT, UK.
| | - Alice Braga
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London WC1E 6BT, UK
| | - Maxim Doronin
- College of Medicine, Jiaxing University, Jiaxing 314001, China
| | - Patrick S Hosford
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London WC1E 6BT, UK
| | - Alexey Brazhe
- Department of Molecular Neurobiology, Institute of Bioorganic Chemistry, Moscow 117997, Russian Federation; Faculty of Biology, Lomonosov Moscow State University, Moscow 119234, Russian Federation
| | - Alexander Mascarenhas
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London WC1E 6BT, UK
| | - Shereen Nizari
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London WC1E 6BT, UK; Centre for Advanced Biomedical Imaging, Division of Medicine, University College London, London WC1E 6BT, UK
| | - Anna Hadjihambi
- The Roger Williams Institute of Hepatology, Foundation for Liver Research, and Faculty of Life Sciences and Medicine, King's College London, London SE5 9NT, UK
| | - Jack A Wells
- Centre for Advanced Biomedical Imaging, Division of Medicine, University College London, London WC1E 6BT, UK
| | - Adrian Hobbs
- William Harvey Research Institute, Barts and The London School of Medicine, Queen Mary University of London, London EC1M 6BQ, UK
| | - Alexey Semyanov
- College of Medicine, Jiaxing University, Jiaxing 314001, China; Department of Molecular Neurobiology, Institute of Bioorganic Chemistry, Moscow 117997, Russian Federation
| | - Andrey Y Abramov
- Department of Clinical and Movement Neurosciences, Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Plamena R Angelova
- Department of Clinical and Movement Neurosciences, Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Alexander V Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London WC1E 6BT, UK.
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2
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Martins Sá RW, Theparambil SM, Dos Santos KM, Christie IN, Marina N, Cardoso BV, Hosford PS, Antunes VR. Salt-loading promotes extracellular ATP release mediated by glial cells in the hypothalamic paraventricular nucleus of rats. Mol Cell Neurosci 2023; 124:103806. [PMID: 36592801 DOI: 10.1016/j.mcn.2022.103806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Revised: 12/21/2022] [Accepted: 12/28/2022] [Indexed: 01/01/2023] Open
Abstract
Previously, we have shown that purinergic signalling is involved in the control of hyperosmotic-induced sympathoexcitation at the level of the PVN, via activation of P2X receptors. However, the source(s) of ATP that drives osmotically-induced increases in sympathetic outflow remained undetermined. Here, we tested the two competing hypotheses that either (1) higher extracellular ATP in PVN during salt loading (SL) is a result of a failure of ectonucleotidases to metabolize ATP; and/or (2) SL can stimulate PVN astrocytes to release ATP. Rats were salt loaded with a 2 % NaCl solution replacing drinking water up to 4 days, an experimental model known to cause a gradual increase in blood pressure and plasma osmolarity. Immunohistochemical assessment of glial-fibrillary acidic protein (GFAP) revealed increased glial cell reactivity in the PVN of rats after 4 days of high salt exposure. ATP and adenosine release measurements via biosensors in hypothalamic slices showed that baseline ATP release was increased 17-fold in the PVN while adenosine remained unchanged. Disruption of Ca2+-dependent vesicular release mechanisms in PVN astrocytes by virally-driven expression of a dominant-negative SNARE protein decreased the release of ATP. The activity of ectonucleotidases quantified in vitro by production of adenosine from ATP was increased in SL group. Our results showed that SL stimulates the release of ATP in the PVN, at least in part, from glial cells by a vesicle-mediated route and likely contributes to the neural control of circulation during osmotic challenges.
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Affiliation(s)
- Renato W Martins Sá
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - Shefeeq M Theparambil
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Karoline Martins Dos Santos
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - Isabel N Christie
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Nephtali Marina
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Barbara V Cardoso
- Department of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, UK
| | - Patrick S Hosford
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK.
| | - Vagner R Antunes
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil.
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3
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Christie IN, Windsor R, Mutsaerts HJMM, Tillin T, Sudre CH, Hughes AD, Golay X, Gourine AV, Hosford PS. Cerebral perfusion in untreated, controlled, and uncontrolled hypertension. J Cereb Blood Flow Metab 2022; 42:2188-2190. [PMID: 36113055 PMCID: PMC7613835 DOI: 10.1177/0271678x221124644] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 06/09/2022] [Accepted: 07/08/2022] [Indexed: 12/14/2022]
Abstract
This study evaluated the association between systemic arterial blood pressure and cerebral perfusion in 740 participants of the UK's largest tri-ethnic study with measurements of cerebral blood flow (CBF) performed using arterial spin labelling MRI. A significant negative correlation between blood pressure, age and CBF was observed across the patient cohort. The lowest CBF values were recorded in the group of patients with hypertension that were prescribed with anti-hypertensive drugs, but uncontrolled on medication. These findings confirm that hypertension is associated with reduced cerebral perfusion and highlight the importance of blood pressure control for the benefit of maintaining brain blood flow.
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Affiliation(s)
- Isabel N Christie
- Centre for Cardiovascular and Metabolic Neuroscience,
Neuroscience, Physiology and Pharmacology, University College London, London,
UK
| | - Rowan Windsor
- Centre for Cardiovascular and Metabolic Neuroscience,
Neuroscience, Physiology and Pharmacology, University College London, London,
UK
| | - Henk JMM Mutsaerts
- Department of Radiology and Nuclear Medicine, Amsterdam
University Medical Center, Amsterdam, The Netherlands
| | - Therese Tillin
- MRC Unit for Lifelong Health & Ageing, Population Science
& Experimental Medicine, Faculty of Population Health Sciences, University
College London, London, UK
| | - Carole H Sudre
- MRC Unit for Lifelong Health & Ageing, Population Science
& Experimental Medicine, Faculty of Population Health Sciences, University
College London, London, UK
| | - Alun D Hughes
- Institute of Cardiovascular Science, Population Science &
Experimental Medicine, Faculty of Population Health Sciences, University College
London, London, UK
| | - Xavier Golay
- Queen Square 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
| | - Patrick S Hosford
- Centre for Cardiovascular and Metabolic Neuroscience,
Neuroscience, Physiology and Pharmacology, University College London, London,
UK
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4
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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5
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Yu Y, Payne C, Marina N, Korsak A, Southern P, García‐Prieto A, Christie IN, Baker RR, Fisher EMC, Wells JA, Kalber TL, Pankhurst QA, Gourine AV, Lythgoe MF. Remote and Selective Control of Astrocytes by Magnetomechanical Stimulation. Adv Sci (Weinh) 2022; 9:e2104194. [PMID: 34927381 PMCID: PMC8867145 DOI: 10.1002/advs.202104194] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 11/15/2021] [Indexed: 05/06/2023]
Abstract
Astrocytes play crucial and diverse roles in brain health and disease. The ability to selectively control astrocytes provides a valuable tool for understanding their function and has the therapeutic potential to correct dysfunction. Existing technologies such as optogenetics and chemogenetics require the introduction of foreign proteins, which adds a layer of complication and hinders their clinical translation. A novel technique, magnetomechanical stimulation (MMS), that enables remote and selective control of astrocytes without genetic modification is described here. MMS exploits the mechanosensitivity of astrocytes and triggers mechanogated Ca2+ and adenosine triphosphate (ATP) signaling by applying a magnetic field to antibody-functionalized magnetic particles that are targeted to astrocytes. Using purpose-built magnetic devices, the mechanosensory threshold of astrocytes is determined, a sub-micrometer particle for effective MMS is identified, the in vivo fate of the particles is established, and cardiovascular responses are induced in rats after particles are delivered to specific brainstem astrocytes. By eliminating the need for device implantation and genetic modification, MMS is a method for controlling astroglial activity with an improved prospect for clinical application than existing technologies.
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Affiliation(s)
- Yichao Yu
- Centre for Advanced Biomedical ImagingDivision of MedicineUniversity College London72 Huntley StreetLondonWC1E 6DDUK
| | - Christopher Payne
- Centre for Advanced Biomedical ImagingDivision of MedicineUniversity College London72 Huntley StreetLondonWC1E 6DDUK
| | - Nephtali Marina
- Centre for Cardiovascular and Metabolic NeuroscienceResearch Department of Neuroscience, Physiology and PharmacologyUniversity College LondonGower StreetLondonWC1E 6BTUK
| | - Alla Korsak
- Centre for Cardiovascular and Metabolic NeuroscienceResearch Department of Neuroscience, Physiology and PharmacologyUniversity College LondonGower StreetLondonWC1E 6BTUK
| | - Paul Southern
- Healthcare Biomagnetics LaboratoryUniversity College London21 Albemarle StreetLondonW1S 4BSUK
| | - Ana García‐Prieto
- Healthcare Biomagnetics LaboratoryUniversity College London21 Albemarle StreetLondonW1S 4BSUK
- Departamento Física Aplicada IUniversidad del País VascoBilbao48013Spain
| | - Isabel N. Christie
- Centre for Cardiovascular and Metabolic NeuroscienceResearch Department of Neuroscience, Physiology and PharmacologyUniversity College LondonGower StreetLondonWC1E 6BTUK
| | - Rebecca R. Baker
- Centre for Advanced Biomedical ImagingDivision of MedicineUniversity College London72 Huntley StreetLondonWC1E 6DDUK
| | - Elizabeth M. C. Fisher
- Department of Neuromuscular DiseasesQueen Square Institute of NeurologyUniversity College LondonQueen SquareLondonWC1N 3BGUK
| | - Jack A. Wells
- Centre for Advanced Biomedical ImagingDivision of MedicineUniversity College London72 Huntley StreetLondonWC1E 6DDUK
| | - Tammy L. Kalber
- Centre for Advanced Biomedical ImagingDivision of MedicineUniversity College London72 Huntley StreetLondonWC1E 6DDUK
| | - Quentin A. Pankhurst
- Healthcare Biomagnetics LaboratoryUniversity College London21 Albemarle StreetLondonW1S 4BSUK
| | - Alexander V. Gourine
- Centre for Cardiovascular and Metabolic NeuroscienceResearch Department of Neuroscience, Physiology and PharmacologyUniversity College LondonGower StreetLondonWC1E 6BTUK
| | - Mark F. Lythgoe
- Centre for Advanced Biomedical ImagingDivision of MedicineUniversity College London72 Huntley StreetLondonWC1E 6DDUK
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6
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Nizari S, Basalay M, Chapman P, Korte N, Korsak A, Christie IN, Theparambil SM, Davidson SM, Reimann F, Trapp S, Yellon DM, Gourine AV. Glucagon-like peptide-1 (GLP-1) receptor activation dilates cerebral arterioles, increases cerebral blood flow, and mediates remote (pre)conditioning neuroprotection against ischaemic stroke. Basic Res Cardiol 2021; 116:32. [PMID: 33942194 PMCID: PMC8093159 DOI: 10.1007/s00395-021-00873-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 04/22/2021] [Indexed: 12/12/2022]
Abstract
Stroke remains one of the most common causes of death and disability worldwide. Several preclinical studies demonstrated that the brain can be effectively protected against ischaemic stroke by two seemingly distinct treatments: remote ischaemic conditioning (RIC), involving cycles of ischaemia/reperfusion applied to a peripheral organ or tissue, or by systemic administration of glucagon-like-peptide-1 (GLP-1) receptor (GLP-1R) agonists. The mechanisms underlying RIC- and GLP-1-induced neuroprotection are not completely understood. In this study, we tested the hypothesis that GLP-1 mediates neuroprotection induced by RIC and investigated the effect of GLP-1R activation on cerebral blood vessels, as a potential mechanism of GLP-1-induced protection against ischaemic stroke. A rat model of ischaemic stroke (90 min of middle cerebral artery occlusion followed by 24-h reperfusion) was used. RIC was induced by 4 cycles of 5 min left hind limb ischaemia interleaved with 5-min reperfusion periods. RIC markedly (by ~ 80%) reduced the cerebral infarct size and improved the neurological score. The neuroprotection established by RIC was abolished by systemic blockade of GLP-1R with a specific antagonist Exendin(9-39). In the cerebral cortex of GLP-1R reporter mice, ~ 70% of cortical arterioles displayed GLP-1R expression. In acute brain slices of the rat cerebral cortex, activation of GLP-1R with an agonist Exendin-4 had a strong dilatory effect on cortical arterioles and effectively reversed arteriolar constrictions induced by metabolite lactate or oxygen and glucose deprivation, as an ex vivo model of ischaemic stroke. In anaesthetised rats, Exendin-4 induced lasting increases in brain tissue PO2, indicative of increased cerebral blood flow. These results demonstrate that neuroprotection against ischaemic stroke established by remote ischaemic conditioning is mediated by a mechanism involving GLP-1R signalling. Potent dilatory effect of GLP-1R activation on cortical arterioles suggests that the neuroprotection in this model is mediated via modulation of cerebral blood flow and improved brain perfusion.
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Affiliation(s)
- Shereen Nizari
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Marina Basalay
- The Hatter Cardiovascular Institute, University College London, London, WC1E 6HX, UK
| | - Philippa Chapman
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Nils Korte
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Alla Korsak
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Isabel N Christie
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Shefeeq M Theparambil
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Sean M Davidson
- The Hatter Cardiovascular Institute, University College London, London, WC1E 6HX, UK
| | - Frank Reimann
- Wellcome Trust/MRC Institute of Metabolic Science, University of Cambridge, Cambridge, UK
| | - Stefan Trapp
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
| | - Derek M Yellon
- The Hatter Cardiovascular Institute, University College London, London, WC1E 6HX, UK
| | - Alexander V Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
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7
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Hosford PS, Wells JA, Christie IN, Lythgoe MF, Millar J, Gourine AV. Electrochemical carbon fiber-based technique for simultaneous recordings of brain tissue PO 2, pH, and extracellular field potentials. Biosens Bioelectron X 2019; 3:100034. [PMID: 32685919 PMCID: PMC7357830 DOI: 10.1016/j.biosx.2020.100034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 01/04/2020] [Accepted: 01/17/2020] [Indexed: 04/25/2023]
Abstract
A method for simultaneous electrochemical detection of brain tissue PO2 (PtO2) and pH changes together with neuronal activity using a modified form of fast cyclic voltammetry with carbon fiber electrodes is described. This technique has been developed for in vivo applications and recordings from discrete brain nuclei in experimental animals. The small size of the carbon fiber electrode (⌀7 μm, length <100 μm) ensures minimal disruption of the brain tissue and allows recordings from small brain areas. Sample rate (up to 4 Hz) is sufficient to resolve rapid changes in PtO2 and pH that follow changes in neuronal activity and metabolism. Rapid switching between current and voltage recordings allows combined electrochemical detection and monitoring of extracellular action potentials. For simultaneous electrochemical detection of PtO2 and pH, two consecutive trapezoidal voltage ramps are applied with double differential-subtraction of the background current. This enables changes in current caused by protons and oxygen to be detected separately with minimal interference between the two. The profile of PtO2 changes evoked by increases in local neuronal activity recorded using the described technique was very similar to that of blood-oxygen-level-dependent responses recorded using fMRI. This voltammetric technique can be combined with fMRI and brain vessel imaging to study the metabolic mechanisms underlying neurovascular coupling response with much greater spatial and temporal resolution than is currently possible.
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Affiliation(s)
- Patrick S. Hosford
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London, UK
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
- Corresponding author. William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK.
| | - Jack A. Wells
- Centre for Advanced Biomedical Imaging, Department of Medicine, University College London, London, UK
| | - Isabel N. Christie
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London, UK
| | - Mark F. Lythgoe
- Centre for Advanced Biomedical Imaging, Department of Medicine, University College London, London, UK
| | - Julian Millar
- Department of Medical Education, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Alexander V. Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London, UK
- Corresponding author. Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London, UK.
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8
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Hosford PS, Christie IN, Niranjan A, Aziz Q, Anderson N, Ang R, Lythgoe MF, Wells JA, Tinker A, Gourine AV. A critical role for the ATP-sensitive potassium channel subunit K IR6.1 in the control of cerebral blood flow. J Cereb Blood Flow Metab 2019; 39:2089-2095. [PMID: 29862863 PMCID: PMC6775590 DOI: 10.1177/0271678x18780602] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 04/20/2018] [Accepted: 05/01/2018] [Indexed: 12/19/2022]
Abstract
KIR6.1 (KCNJ8) is a subunit of ATP sensitive potassium channel (KATP) that plays an important role in the control of peripheral vascular tone and is highly expressed in brain contractile cells (vascular smooth muscle cells and pericytes). This study determined the effect of global deletion of the KIR6.1 subunit on cerebral blood flow, neurovascular coupling and cerebral oxygenation in mice. In KIR6.1 deficient mice resting cerebral blood flow and brain parenchymal partial pressure of oxygen (PO2) were found to be markedly lower compared to that in their wildtype littermates. However, cortical blood oxygen level dependent responses triggered by visual stimuli were not affected in conditions of KIR6.1 deficiency. These data suggest that KATP channels containing KIR6.1 subunit are critically important for the maintenance of normal cerebral perfusion and parenchymal PO2 but play no significant role in the mechanisms underlying functional changes in brain blood flow.
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Affiliation(s)
- Patrick S Hosford
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, London, UK
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & Pharmacology, University College London, London, UK
| | - Isabel N Christie
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & Pharmacology, University College London, London, UK
- UCL Centre for Advanced Biomedical Imaging, Division of Medicine, University College London, London, UK
| | - Arun Niranjan
- UCL Centre for Advanced Biomedical Imaging, Division of Medicine, University College London, London, UK
| | - Qadeer Aziz
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, London, UK
| | - Naomi Anderson
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, London, UK
| | - Richard Ang
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & Pharmacology, University College London, London, UK
| | - Mark F Lythgoe
- UCL Centre for Advanced Biomedical Imaging, Division of Medicine, University College London, London, UK
| | - Jack A Wells
- UCL Centre for Advanced Biomedical Imaging, Division of Medicine, University College London, London, UK
| | - Andrew Tinker
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, London, UK
| | - Alexander V Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & Pharmacology, University College London, London, UK
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9
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Hosford PS, Mosienko V, Kishi K, Jurisic G, Seuwen K, Kinzel B, Ludwig MG, Wells JA, Christie IN, Koolen L, Abdala AP, Liu BH, Gourine AV, Teschemacher AG, Kasparov S. CNS distribution, signalling properties and central effects of G-protein coupled receptor 4. Neuropharmacology 2018; 138:381-392. [PMID: 29894771 PMCID: PMC6063991 DOI: 10.1016/j.neuropharm.2018.06.007] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 06/04/2018] [Accepted: 06/05/2018] [Indexed: 12/14/2022]
Abstract
Information on the distribution and biology of the G-protein coupled receptor 4 (GPR4) in the brain is limited. It is currently thought that GPR4 couples to Gs proteins and may mediate central respiratory sensitivity to CO2. Using a knock-in mouse model, abundant GPR4 expression was detected in the cerebrovascular endothelium and neurones of dorsal raphe, retro-trapezoidal nucleus locus coeruleus and lateral septum. A similar distribution was confirmed using RNAscope in situ hybridisation. In HEK293 cells, overexpressing GPR4, it was highly constitutively active at neutral pH with little further increase in cAMP towards acidic pH. The GPR4 antagonist NE 52-QQ57 effectively blocked GPR4-mediated cAMP accumulation (IC50 26.8 nM in HEK293 cells). In HUVEC which natively express GPR4, physiological acidification (pH 7.4-7.0) resulted in a cAMP increase by ∼55% which was completely prevented by 1 μM NE 52-QQ57. The main extracellular organic acid, l-lactic acid (LL; 1-10 mM), suppressed pH dependent activation of GPR4 in HEK293 and HUVEC cells, suggesting allosteric negative modulation. In unanaesthetised mice and rats, NE 52-QQ57 (20 mg kg-1) reduced ventilatory response to 5 and 10% CO2. In anaesthetised rats, systemic administration of NE 52-QQ57 (up to 20 mg kg-1) had no effect on hemodynamics, cerebral blood flow and blood oxygen level dependent responses. Central administration of NE 52-QQ57 (1 mM) in vagotomised anaesthetised rats did not affect CO2-induced respiratory responses. Our results indicate that GPR4 is expressed by multiple neuronal populations and endothelium and that its pH sensitivity is affected by level of expression and LL. NE 52-QQ57 blunts hypercapnic response to CO2 but this effect is absent under anaesthesia, possibly due to the inhibitory effect of LL on GPR4.
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Affiliation(s)
- P S Hosford
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, WC1E 6BT, UK
| | - V Mosienko
- Physiology, Pharmacology and Neuroscience, University of Bristol, BS8 1TD, UK
| | - K Kishi
- Physiology, Pharmacology and Neuroscience, University of Bristol, BS8 1TD, UK
| | - G Jurisic
- Novartis Institutes for Biomedical Research, CH-4002 Basel, Switzerland
| | - K Seuwen
- Novartis Institutes for Biomedical Research, CH-4002 Basel, Switzerland
| | - B Kinzel
- Novartis Institutes for Biomedical Research, CH-4002 Basel, Switzerland
| | - M G Ludwig
- Novartis Institutes for Biomedical Research, CH-4002 Basel, Switzerland
| | - J A Wells
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, WC1E 6BT, UK
| | - I N Christie
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, WC1E 6BT, UK
| | - L Koolen
- Physiology, Pharmacology and Neuroscience, University of Bristol, BS8 1TD, UK
| | - A P Abdala
- Physiology, Pharmacology and Neuroscience, University of Bristol, BS8 1TD, UK
| | - B H Liu
- Physiology, Pharmacology and Neuroscience, University of Bristol, BS8 1TD, UK
| | - A V Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, WC1E 6BT, UK
| | - A G Teschemacher
- Physiology, Pharmacology and Neuroscience, University of Bristol, BS8 1TD, UK.
| | - S Kasparov
- Physiology, Pharmacology and Neuroscience, University of Bristol, BS8 1TD, UK; Baltic Federal University, Kaliningrad 236041, Russian Federation.
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Marina N, Turovsky E, Christie IN, Hosford PS, Hadjihambi A, Korsak A, Ang R, Mastitskaya S, Sheikhbahaei S, Theparambil SM, Gourine AV. Brain metabolic sensing and metabolic signaling at the level of an astrocyte. Glia 2018; 66:1185-1199. [PMID: 29274121 PMCID: PMC5947829 DOI: 10.1002/glia.23283] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 10/04/2017] [Accepted: 11/29/2017] [Indexed: 12/18/2022]
Abstract
Astrocytes support neuronal function by providing essential structural and nutritional support, neurotransmitter trafficking and recycling and may also contribute to brain information processing. In this article we review published results and report new data suggesting that astrocytes function as versatile metabolic sensors of central nervous system (CNS) milieu and play an important role in the maintenance of brain metabolic homeostasis. We discuss anatomical and functional features of astrocytes that allow them to detect and respond to changes in the brain parenchymal levels of metabolic substrates (oxygen and glucose), and metabolic waste products (carbon dioxide). We report data suggesting that astrocytes are also sensitive to circulating endocrine signals-hormones like ghrelin, glucagon-like peptide-1 and leptin, that have a major impact on the CNS mechanisms controlling food intake and energy balance. We discuss signaling mechanisms that mediate communication between astrocytes and neurons and consider how these mechanisms are recruited by astrocytes activated in response to various metabolic challenges. We review experimental data suggesting that astrocytes modulate the activities of the respiratory and autonomic neuronal networks that ensure adaptive changes in breathing and sympathetic drive in order to support the physiological and behavioral demands of the organism in ever-changing environmental conditions. Finally, we discuss evidence suggesting that altered astroglial function may contribute to the pathogenesis of disparate neurological, respiratory and cardiovascular disorders such as Rett syndrome and systemic arterial hypertension.
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Affiliation(s)
- Nephtali Marina
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
- Research Department of Metabolism and Experimental Therapeutics, Division of MedicineUniversity College LondonLondonWC1E 6JJUnited Kingdom
| | - Egor Turovsky
- Laboratory of Intracellular SignallingInstitute of Cell Biophysics, Russian Academy of SciencesPushchinoRussia
| | - Isabel N Christie
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
| | - Patrick S Hosford
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
| | - Anna Hadjihambi
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
| | - Alla Korsak
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
| | - Richard Ang
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
| | - Svetlana Mastitskaya
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
| | - Shahriar Sheikhbahaei
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
| | - Shefeeq M Theparambil
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
| | - Alexander V Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology & PharmacologyUniversity College LondonLondonWC1E 6BTUnited Kingdom
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11
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Niranjan A, Christie IN, Solomon SG, Wells JA, Lythgoe MF. fMRI mapping of the visual system in the mouse brain with interleaved snapshot GE-EPI. Neuroimage 2016; 139:337-345. [PMID: 27296012 PMCID: PMC4988789 DOI: 10.1016/j.neuroimage.2016.06.015] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 06/01/2016] [Accepted: 06/09/2016] [Indexed: 12/01/2022] Open
Abstract
The use of functional magnetic resonance imaging (fMRI) in mice is increasingly prevalent, providing a means to non-invasively characterise functional abnormalities associated with genetic models of human diseases. The predominant stimulus used in task-based fMRI in the mouse is electrical stimulation of the paw. Task-based fMRI in mice using visual stimuli remains underexplored, despite visual stimuli being common in human fMRI studies. In this study, we map the mouse brain visual system with BOLD measurements at 9.4T using flashing light stimuli with medetomidine anaesthesia. BOLD responses were observed in the lateral geniculate nucleus, the superior colliculus and the primary visual area of the cortex, and were modulated by the flashing frequency, diffuse vs focussed light and stimulus context. Negative BOLD responses were measured in the visual cortex at 10Hz flashing frequency; but turned positive below 5Hz. In addition, the use of interleaved snapshot GE-EPI improved fMRI image quality without diminishing the temporal contrast-noise-ratio. Taken together, this work demonstrates a novel methodological protocol in which the mouse brain visual system can be non-invasively investigated using BOLD fMRI.
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Affiliation(s)
- Arun Niranjan
- UCL Centre for Advanced Biomedical Imaging, Division of Medicine and Institute of Child Health, University College London, London, UK
| | - Isabel N Christie
- UCL Centre for Advanced Biomedical Imaging, Division of Medicine and Institute of Child Health, University College London, London, UK; Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London, UK
| | - Samuel G Solomon
- Department of Experimental Psychology, University College London, London, UK
| | - Jack A Wells
- UCL Centre for Advanced Biomedical Imaging, Division of Medicine and Institute of Child Health, University College London, London, UK
| | - Mark F Lythgoe
- UCL Centre for Advanced Biomedical Imaging, Division of Medicine and Institute of Child Health, University College London, London, UK
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12
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Christie IN, Wells JA, Southern P, Marina N, Kasparov S, Gourine AV, Lythgoe MF. fMRI response to blue light delivery in the naïve brain: Implications for combined optogenetic fMRI studies. Neuroimage 2013; 66:634-41. [DOI: 10.1016/j.neuroimage.2012.10.074] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Revised: 10/17/2012] [Accepted: 10/26/2012] [Indexed: 12/30/2022] Open
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