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Amorim MR, Wang X, Aung O, Bevans-Fonti S, Anokye-Danso F, Ribeiro C, Escobar J, Freire C, Pho H, Dergacheva O, Branco LGS, Ahima RS, Mendelowitz D, Polotsky VY. Leptin signaling in the dorsomedial hypothalamus couples breathing and metabolism in obesity. Cell Rep 2023; 42:113512. [PMID: 38039129 PMCID: PMC10804286 DOI: 10.1016/j.celrep.2023.113512] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2023] [Revised: 10/25/2023] [Accepted: 11/14/2023] [Indexed: 12/03/2023] Open
Abstract
Mismatch between CO2 production (Vco2) and respiration underlies the pathogenesis of obesity hypoventilation. Leptin-mediated CNS pathways stimulate both metabolism and breathing, but interactions between these functions remain elusive. We hypothesized that LEPRb+ neurons of the dorsomedial hypothalamus (DMH) regulate metabolism and breathing in obesity. In diet-induced obese LeprbCre mice, chemogenetic activation of LEPRb+ DMH neurons increases minute ventilation (Ve) during sleep, the hypercapnic ventilatory response, Vco2, and Ve/Vco2, indicating that breathing is stimulated out of proportion to metabolism. The effects of chemogenetic activation are abolished by a serotonin blocker. Optogenetic stimulation of the LEPRb+ DMH neurons evokes excitatory postsynaptic currents in downstream serotonergic neurons of the dorsal raphe (DR). Administration of retrograde AAV harboring Cre-dependent caspase to the DR deletes LEPRb+ DMH neurons and abolishes metabolic and respiratory responses to leptin. These findings indicate that LEPRb+ DMH neurons match breathing to metabolism through serotonergic pathways to prevent obesity-induced hypoventilation.
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Affiliation(s)
- Mateus R Amorim
- Department of Medicine, Johns Hopkins University, Baltimore, MD 21224, USA; Department of Anesthesiology and Critical Care Medicine, George Washington University, Washington, DC 20037, USA.
| | - Xin Wang
- Department of Pharmacology and Physiology, George Washington University, Washington, DC 20037, USA
| | - O Aung
- Department of Medicine, Johns Hopkins University, Baltimore, MD 21224, USA
| | - Shannon Bevans-Fonti
- Department of Medicine, Johns Hopkins University, Baltimore, MD 21224, USA; Department of Anesthesiology and Critical Care Medicine, George Washington University, Washington, DC 20037, USA
| | | | - Caitlin Ribeiro
- Department of Pharmacology and Physiology, George Washington University, Washington, DC 20037, USA
| | - Joan Escobar
- Department of Pharmacology and Physiology, George Washington University, Washington, DC 20037, USA
| | - Carla Freire
- Department of Medicine, Johns Hopkins University, Baltimore, MD 21224, USA
| | - Huy Pho
- Department of Medicine, Johns Hopkins University, Baltimore, MD 21224, USA
| | - Olga Dergacheva
- Department of Pharmacology and Physiology, George Washington University, Washington, DC 20037, USA
| | - Luiz G S Branco
- University of São Paulo, Ribeirão Preto, São Paulo 14040-904, Brazil
| | - Rexford S Ahima
- Department of Medicine, Johns Hopkins University, Baltimore, MD 21224, USA
| | - David Mendelowitz
- Department of Pharmacology and Physiology, George Washington University, Washington, DC 20037, USA
| | - Vsevolod Y Polotsky
- Department of Medicine, Johns Hopkins University, Baltimore, MD 21224, USA; Department of Anesthesiology and Critical Care Medicine, George Washington University, Washington, DC 20037, USA; Department of Pharmacology and Physiology, George Washington University, Washington, DC 20037, USA.
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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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Retamal MA, Fernandez-Olivares A, Stehberg J. Over-activated hemichannels: A possible therapeutic target for human diseases. Biochim Biophys Acta Mol Basis Dis 2021; 1867:166232. [PMID: 34363932 DOI: 10.1016/j.bbadis.2021.166232] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 07/21/2021] [Accepted: 07/26/2021] [Indexed: 12/14/2022]
Abstract
In our body, all the cells are constantly sharing chemical and electrical information with other cells. This intercellular communication allows them to respond in a concerted way to changes in the extracellular milieu. Connexins are transmembrane proteins that have the particularity of forming two types of channels; hemichannels and gap junction channels. Under normal conditions, hemichannels allow the controlled release of signaling molecules to the extracellular milieu. However, under certain pathological conditions, over-activated hemichannels can induce and/or exacerbate symptoms. In the last decade, great efforts have been put into developing new tools that can modulate these over-activated hemichannels. Small molecules, antibodies and mimetic peptides have shown a potential for the treatment of human diseases. In this review, we summarize recent findings in the field of hemichannel modulation via specific tools, and how these tools could improve patient outcome in certain pathological conditions.
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Affiliation(s)
- Mauricio A Retamal
- Universidad del Desarrollo, Programa de Comunicación Celular en Cáncer, Santiago, Chile; Universidad del Desarrollo, Centro de Fisiología Celular e Integrativa, Santiago, Chile.
| | | | - Jimmy Stehberg
- Laboratorio de Neurobiología, Instituto de Ciencias Biomédicas, Facultad de medicina y Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile
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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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Michenkova M, Taki S, Blosser MC, Hwang HJ, Kowatz T, Moss FJ, Occhipinti R, Qin X, Sen S, Shinn E, Wang D, Zeise BS, Zhao P, Malmstadt N, Vahedi-Faridi A, Tajkhorshid E, Boron WF. Carbon dioxide transport across membranes. Interface Focus 2021; 11:20200090. [PMID: 33633837 PMCID: PMC7898146 DOI: 10.1098/rsfs.2020.0090] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/04/2021] [Indexed: 12/30/2022] Open
Abstract
Carbon dioxide (CO2) movement across cellular membranes is passive and governed by Fick's law of diffusion. Until recently, we believed that gases cross biological membranes exclusively by dissolving in and then diffusing through membrane lipid. However, the observation that some membranes are CO2 impermeable led to the discovery of a gas molecule moving through a channel; namely, CO2 diffusion through aquaporin-1 (AQP1). Later work demonstrated CO2 diffusion through rhesus (Rh) proteins and NH3 diffusion through both AQPs and Rh proteins. The tetrameric AQPs exhibit differential selectivity for CO2 versus NH3 versus H2O, reflecting physico-chemical differences among the small molecules as well as among the hydrophilic monomeric pores and hydrophobic central pores of various AQPs. Preliminary work suggests that NH3 moves through the monomeric pores of AQP1, whereas CO2 moves through both monomeric and central pores. Initial work on AQP5 indicates that it is possible to create a metal-binding site on the central pore's extracellular face, thereby blocking CO2 movement. The trimeric Rh proteins have monomers with hydrophilic pores surrounding a hydrophobic central pore. Preliminary work on the bacterial Rh homologue AmtB suggests that gas can diffuse through the central pore and three sets of interfacial clefts between monomers. Finally, initial work indicates that CO2 diffuses through the electrogenic Na/HCO3 cotransporter NBCe1. At least in some cells, CO2-permeable proteins could provide important pathways for transmembrane CO2 movements. Such pathways could be amenable to cellular regulation and could become valuable drug targets.
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Affiliation(s)
- Marie Michenkova
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Sara Taki
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Matthew C. Blosser
- Mork Family Department of Chemical Engineering & Materials Science, University of Southern California, Los Angeles, CA, USA
| | - Hyea J. Hwang
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Thomas Kowatz
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Fraser. J. Moss
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Rossana Occhipinti
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Xue Qin
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Soumyo Sen
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Eric Shinn
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Dengke Wang
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Brian S. Zeise
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Pan Zhao
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Noah Malmstadt
- Mork Family Department of Chemical Engineering & Materials Science, University of Southern California, Los Angeles, CA, USA
| | - Ardeschir Vahedi-Faridi
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Emad Tajkhorshid
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Walter F. Boron
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH, USA
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH, USA
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Linthwaite VL, Cummins E, Cann MJ. Carbon dioxide detection in biological systems. Interface Focus 2021. [DOI: 10.1098/rsfs.2021.0001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
| | - Eoin Cummins
- UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
| | - Martin J. Cann
- Department of Biosciences, Durham University, South Road, Durham DH1 3LE, UK
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