151
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Bartlett R, Stokes L, Curtis SJ, Curtis BL, Sluyter R. Probenecid directly impairs activation of the canine P2X7 receptor. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2017; 36:736-744. [PMID: 29200326 DOI: 10.1080/15257770.2017.1391395] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The current study aimed to determine if probenecid could directly impair the canine P2X7 receptor, a ligand-gated cation channel activated by extracellular adenosine 5'-triphosphate (ATP). Patch clamp measurements demonstrated that probenecid impairs ATP-induced inward currents in HEK-293 cells expressing canine P2X7. Flow cytometric measurements of ethidium+ uptake into HEK-293 cells expressing canine P2X7 showed that probenecid impairs ATP-induced pore formation in a concentration-dependent manner, with a half maximal inhibitory concentration of 158 µM. Finally, ELISA measurements revealed that probenecid impairs ATP-induced interleukin-1β release in dog blood. In conclusion, this study reveals that probenecid can directly impair canine P2X7 activation.
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Affiliation(s)
- Rachael Bartlett
- a School of Biological Sciences, University of Wollongong , Wollongong , NSW , Australia.,b Centre for Medical and Molecular Bioscience, University of Wollongong , Wollongong , NSW , Australia.,c Illawarra Health and Medical Research Institute , Wollongong , NSW , Australia
| | - Leanne Stokes
- d School of Pharmacy, University of East Anglia , Norwich , United Kingdom
| | - Stephen J Curtis
- e Albion Park Veterinary Hospital , Albion Park , NSW , Australia
| | - Belinda L Curtis
- e Albion Park Veterinary Hospital , Albion Park , NSW , Australia
| | - Ronald Sluyter
- a School of Biological Sciences, University of Wollongong , Wollongong , NSW , Australia.,b Centre for Medical and Molecular Bioscience, University of Wollongong , Wollongong , NSW , Australia.,c Illawarra Health and Medical Research Institute , Wollongong , NSW , Australia
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152
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Willebrords J, Maes M, Crespo Yanguas S, Vinken M. Inhibitors of connexin and pannexin channels as potential therapeutics. Pharmacol Ther 2017; 180:144-160. [PMID: 28720428 PMCID: PMC5802387 DOI: 10.1016/j.pharmthera.2017.07.001] [Citation(s) in RCA: 106] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
While gap junctions support the exchange of a number of molecules between neighboring cells, connexin hemichannels provide communication between the cytosol and the extracellular environment of an individual cell. The latter equally holds true for channels composed of pannexin proteins, which display an architecture reminiscent of connexin hemichannels. In physiological conditions, gap junctions are usually open, while connexin hemichannels and, to a lesser extent, pannexin channels are typically closed, yet they can be activated by a number of pathological triggers. Several agents are available to inhibit channels built up by connexin and pannexin proteins, including alcoholic substances, glycyrrhetinic acid, anesthetics and fatty acids. These compounds not always strictly distinguish between gap junctions, connexin hemichannels and pannexin channels, and may have effects on other targets as well. An exception lies with mimetic peptides, which reproduce specific amino acid sequences in connexin or pannexin primary protein structure. In this paper, a state-of-the-art overview is provided on inhibitors of cellular channels consisting of connexins and pannexins with specific focus on their mode-of-action and therapeutic potential.
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Affiliation(s)
- Joost Willebrords
- Department of In Vitro Toxicology and Dermato-cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Laarbeeklaan 103, Brussels, Belgium
| | - Michaël Maes
- Department of In Vitro Toxicology and Dermato-cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Laarbeeklaan 103, Brussels, Belgium
| | - Sara Crespo Yanguas
- Department of In Vitro Toxicology and Dermato-cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Laarbeeklaan 103, Brussels, Belgium
| | - Mathieu Vinken
- Department of In Vitro Toxicology and Dermato-cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Laarbeeklaan 103, Brussels, Belgium.
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153
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Horton SM, Luna Lopez C, Blevins E, Howarth H, Weisberg J, Shestopalov VI, Makarenkova HP, Shah SB. Pannexin 1 Modulates Axonal Growth in Mouse Peripheral Nerves. Front Cell Neurosci 2017; 11:365. [PMID: 29213230 PMCID: PMC5702652 DOI: 10.3389/fncel.2017.00365] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Accepted: 11/06/2017] [Indexed: 01/29/2023] Open
Abstract
The pannexin family of channels consists of three members—pannexin-1 (Panx1), pannexin-2 (Panx2), and pannexin-3 (Panx3) that enable the exchange of metabolites and signaling molecules between intracellular and extracellular compartments. Pannexin-mediated release of intracellular ATP into the extracellular space has been tied to a number of cellular activities, primarily through the activity of type P2 purinergic receptors. Previous work indicates that the opening of Panx1 channels and activation of purinergic receptors by extracellular ATP may cause inflammation and apoptosis. In the CNS (central nervous system) and PNS (peripheral nervous system), coupled pannexin, and P2 functions have been linked to peripheral sensitization (pain) pathways. Purinergic pathways are also essential for other critical processes in the PNS, including myelination and neurite outgrowth. However, whether such pathways are pannexin-dependent remains to be determined. In this study, we use a Panx1 knockout mouse model and pharmacological inhibitors of the Panx1 and the ATP-mediated signaling pathway to fill gaps in our understanding of Panx1 localization in peripheral nerves, roles for Panx1 in axonal outgrowth and myelination, and neurite extension. Our data show that Panx1 is localized to axonal, myelin, and vascular compartments of the peripheral nerves. Knockout of Panx1 gene significantly increased axonal caliber in vivo and axonal growth rate in cultured dorsal root ganglia (DRG) neurons. Furthermore, genetic knockout of Panx1 or inhibition of components of purinergic signaling, by treatment with probenecid and apyrase, resulted in denser axonal outgrowth from cultured DRG explants compared to untreated wild-types. Our findings suggest that Panx1 regulates axonal growth in the peripheral nervous system.
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Affiliation(s)
- Steven M Horton
- Department of Orthopaedic Surgery, University of California, San Diego, La Jolla, CA, United States
| | - Carlos Luna Lopez
- Department of Orthopaedic Surgery, University of California, San Diego, La Jolla, CA, United States
| | - Elisabeth Blevins
- Department of Orthopaedic Surgery, University of California, San Diego, La Jolla, CA, United States.,Research Service, Veterans Affairs San Diego Healthcare System, San Diego, La Jolla, CA, United States
| | - Holly Howarth
- Department of Bioengineering, University of California, San Diego, La Jolla, CA, United States
| | - Jake Weisberg
- Department of Orthopaedic Surgery, University of California, San Diego, La Jolla, CA, United States
| | | | - Helen P Makarenkova
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA, United States
| | - Sameer B Shah
- Department of Orthopaedic Surgery, University of California, San Diego, La Jolla, CA, United States.,Research Service, Veterans Affairs San Diego Healthcare System, San Diego, La Jolla, CA, United States.,Department of Bioengineering, University of California, San Diego, La Jolla, CA, United States
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154
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Barros-Barbosa AR, Oliveira Â, Lobo MG, Cordeiro JM, Correia-de-Sá P. Under stressful conditions activation of the ionotropic P2X7 receptor differentially regulates GABA and glutamate release from nerve terminals of the rat cerebral cortex. Neurochem Int 2017; 112:81-95. [PMID: 29154812 DOI: 10.1016/j.neuint.2017.11.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 11/08/2017] [Accepted: 11/10/2017] [Indexed: 01/08/2023]
Abstract
γ-Aminobutyric acid (GABA) and glutamate (Glu) are the main inhibitory and excitatory neurotransmitters in the central nervous system (CNS), respectively. Fine tuning regulation of extracellular levels of these amino acids is essential for normal brain activity. Recently, we showed that neocortical nerve terminals from patients with epilepsy express higher amounts of the non-desensitizing ionotropic P2X7 receptor. Once activated by ATP released from neuronal cells, the P2X7 receptor unbalances GABAergic vs. glutamatergic neurotransmission by differentially interfering with GABA and Glu uptake. Here, we investigated if activation of the P2X7 receptor also affects [3H]GABA and [14C]Glu release measured synchronously from isolated nerve terminals (synaptosomes) of the rat cerebral cortex. Data show that activation of the P2X7 receptor consistently increases [14C]Glu over [3H]GABA release from cortical nerve terminals, but the GABA/Glu ratio depends on extracellular Ca2+ concentrations. While the P2X7-induced [3H]GABA release is operated by a Ca2+-dependent pathway when external Ca2+ is available, this mechanism shifts towards the reversal of the GAT1 transporter in low Ca2+ conditions. A different scenario is verified regarding [14C]Glu outflow triggered by the P2X7 receptor, since the amino acid seems to be consistently released through the recruitment of connexin-containing hemichannels upon P2X7 activation, both in the absence and in the presence of external Ca2+. Data from this study add valuable information suggesting that ATP, via P2X7 activation, not only interferes with the high-affinity uptake of GABA and Glu but actually favors the release of these amino acids through distinct molecular mechanisms amenable to differential therapeutic control.
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Affiliation(s)
- Aurora R Barros-Barbosa
- Laboratório de Farmacologia e Neurobiologia, Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto (UP), Porto, Portugal; Center for Drug Discovery and Innovative Medicines (MedInUP), Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto (UP), Porto, Portugal
| | - Ângela Oliveira
- Laboratório de Farmacologia e Neurobiologia, Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto (UP), Porto, Portugal; Center for Drug Discovery and Innovative Medicines (MedInUP), Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto (UP), Porto, Portugal
| | - M Graça Lobo
- Laboratório de Farmacologia e Neurobiologia, Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto (UP), Porto, Portugal; Center for Drug Discovery and Innovative Medicines (MedInUP), Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto (UP), Porto, Portugal
| | - J Miguel Cordeiro
- Laboratório de Farmacologia e Neurobiologia, Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto (UP), Porto, Portugal; Center for Drug Discovery and Innovative Medicines (MedInUP), Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto (UP), Porto, Portugal
| | - Paulo Correia-de-Sá
- Laboratório de Farmacologia e Neurobiologia, Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto (UP), Porto, Portugal; Center for Drug Discovery and Innovative Medicines (MedInUP), Instituto de Ciências Biomédicas de Abel Salazar (ICBAS), Universidade do Porto (UP), Porto, Portugal.
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155
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Beltrán-Castillo S, Olivares MJ, Contreras RA, Zúñiga G, Llona I, von Bernhardi R, Eugenín JL. D-serine released by astrocytes in brainstem regulates breathing response to CO 2 levels. Nat Commun 2017; 8:838. [PMID: 29018191 PMCID: PMC5635109 DOI: 10.1038/s41467-017-00960-3] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Accepted: 08/09/2017] [Indexed: 11/17/2022] Open
Abstract
Central chemoreception is essential for adjusting breathing to physiological demands, and for maintaining CO2 and pH homeostasis in the brain. CO2-induced ATP release from brainstem astrocytes stimulates breathing. NMDA receptor (NMDAR) antagonism reduces the CO2-induced hyperventilation by unknown mechanisms. Here we show that astrocytes in the mouse caudal medullary brainstem can synthesize, store, and release d-serine, an agonist for the glycine-binding site of the NMDAR, in response to elevated CO2 levels. We show that systemic and raphe nucleus d-serine administration to awake, unrestrained mice increases the respiratory frequency. Application of d-serine to brainstem slices also increases respiratory frequency, which was prevented by NMDAR blockade. Inhibition of d-serine synthesis, enzymatic degradation of d-serine, or the sodium fluoroacetate-induced impairment of astrocyte functions decrease the basal respiratory frequency and the CO2-induced respiratory response in vivo and in vitro. Our findings suggest that astrocytic release of d-serine may account for the glutamatergic contribution to central chemoreception. Astrocytes are involved in chemoreception in brainstem areas that regulate breathing rhythm, and astrocytes are known to release d-serine. Here the authors show that astrocyte release of d-serine contributes to CO2 sensing and breathing in brainstem slices, and in vivo in awake unrestrained mice.
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Affiliation(s)
- S Beltrán-Castillo
- Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, USACH, Santiago, 9170022, Chile
| | - M J Olivares
- Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, USACH, Santiago, 9170022, Chile
| | - R A Contreras
- Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, USACH, Santiago, 9170022, Chile
| | - G Zúñiga
- Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, USACH, Santiago, 9170022, Chile
| | - I Llona
- Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, USACH, Santiago, 9170022, Chile
| | - R von Bernhardi
- Departamento de Neurología, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, 8330024, Chile.
| | - J L Eugenín
- Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, USACH, Santiago, 9170022, Chile.
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156
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Exploration of inclusion complexes of probenecid with α and β-cyclodextrins: Enhancing the utility of the drug. J Mol Struct 2017. [DOI: 10.1016/j.molstruc.2017.05.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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157
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Murana E, Pagani F, Basilico B, Sundukova M, Batti L, Di Angelantonio S, Cortese B, Grimaldi A, Francioso A, Heppenstall P, Bregestovski P, Limatola C, Ragozzino D. ATP release during cell swelling activates a Ca 2+-dependent Cl - current by autocrine mechanism in mouse hippocampal microglia. Sci Rep 2017. [PMID: 28646166 PMCID: PMC5482828 DOI: 10.1038/s41598-017-04452-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Microglia cells, resident immune cells of the brain, survey brain parenchyma by dynamically extending and retracting their processes. Cl− channels, activated in the cellular response to stretch/swelling, take part in several functions deeply connected with microglia physiology, including cell shape changes, proliferation, differentiation and migration. However, the molecular identity and functional properties of these Cl− channels are largely unknown. We investigated the properties of swelling-activated currents in microglial from acute hippocampal slices of Cx3cr1+/GFP mice by whole-cell patch-clamp and imaging techniques. The exposure of cells to a mild hypotonic medium, caused an outward rectifying current, developing in 5–10 minutes and reverting upon stimulus washout. This current, required for microglia ability to extend processes towards a damage signal, was carried mainly by Cl− ions and dependent on intracellular Ca2+. Moreover, it involved swelling-induced ATP release. We identified a purine-dependent mechanism, likely constituting an amplification pathway of current activation: under hypotonic conditions, ATP release triggered the Ca2+-dependent activation of anionic channels by autocrine purine receptors stimulation. Our study on native microglia describes for the first time the functional properties of stretch/swelling-activated currents, representing a key element in microglia ability to monitor the brain parenchyma.
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Affiliation(s)
- E Murana
- Department of Physiology and Pharmacology, Sapienza University, Rome, Italy
| | - F Pagani
- Istituto Italiano di Tecnologia, CLNS@Sapienza, Rome, Italy.
| | - B Basilico
- Department of Physiology and Pharmacology, Sapienza University, Rome, Italy
| | - M Sundukova
- Mouse Biology Unit, EMBL, Monterotondo, Italy
| | - L Batti
- Mouse Biology Unit, EMBL, Monterotondo, Italy
| | - S Di Angelantonio
- Department of Physiology and Pharmacology, Sapienza University, Rome, Italy.,Istituto Italiano di Tecnologia, CLNS@Sapienza, Rome, Italy
| | - B Cortese
- CNR NANOTEC - Istituto di Nanotecnologia, Department of Physics, University Sapienza, Rome, Italy
| | - A Grimaldi
- Istituto Italiano di Tecnologia, CLNS@Sapienza, Rome, Italy
| | - A Francioso
- Department of Biochemistry, "Sapienza" University of Rome, Rome, Italy
| | | | - P Bregestovski
- Aix Marseille University, Inserm, INS, Institut de Neurosciences des Systèmes, Marseille, France
| | - C Limatola
- IRCCS Neuromed, Via Atinese, Pozzilli, Italy.,Pasteur Institute - Department of Physiology and Pharmacology, Sapienza University, Rome, Italy
| | - D Ragozzino
- Department of Physiology and Pharmacology, Sapienza University, Rome, Italy.,IRCCS Neuromed, Via Atinese, Pozzilli, Italy
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158
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Abstract
Many people avidly consume foods and drinks containing caffeine, despite its bitter taste. Here, we review what is known about caffeine as a bitter taste stimulus. Topics include caffeine's action on the canonical bitter taste receptor pathway and caffeine's action on noncanonical receptor-dependent and -independent pathways in taste cells. Two conclusions are that (1) caffeine is a poor prototypical bitter taste stimulus because it acts on bitter taste receptor-independent pathways, and (2) caffeinated products most likely stimulate "taste" receptors in nongustatory cells. This review is relevant for taste researchers, manufacturers of caffeinated products, and caffeine consumers.
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Affiliation(s)
- Rachel L Poole
- Monell Chemical Senses Center, Philadelphia, Pennsylvania
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159
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Whyte-Fagundes P, Siu R, Brown C, Zoidl G. Pannexins in vision, hearing, olfaction and taste. Neurosci Lett 2017; 695:32-39. [PMID: 28495272 DOI: 10.1016/j.neulet.2017.05.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 04/06/2017] [Accepted: 05/05/2017] [Indexed: 12/25/2022]
Abstract
In mammals, the pannexin gene family consists of three members (Panx1, 2, 3), which represent a class of integral membrane channel proteins sharing some structural features with chordate gap junction proteins, the connexins. Since their discovery in the early 21st century, pannexin expression has been detected throughout the vertebrate body including eye, ear, nose and tongue, making the investigation of the roles of this new class of channel protein in health and disease very appealing. The localization in sensory organs, coupled with unique channel properties and associations with major signaling pathways make Panx1, and its relative's, significant contributors for fundamental functions in sensory perception. Until recently, cell-based studies were at the forefront of pannexin research. Lately, the availability of mice with genetic ablation of pannexins opened new avenues for testing pannexin functions and behavioural phenotyping. Although we are only at the beginning of understanding the roles of pannexins in health and disease, this review summarizes recent advances in elucidating the various emerging roles pannexins play in sensory systems, with an emphasis on unresolved conflicts.
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Affiliation(s)
- Paige Whyte-Fagundes
- Graduate Program In Biology, Faculty of Science, York University, Toronto, ON, Canada
| | - Ryan Siu
- Graduate Program In Biology, Faculty of Science, York University, Toronto, ON, Canada
| | - Cherie Brown
- Graduate Program In Biology, Faculty of Science, York University, Toronto, ON, Canada
| | - Georg Zoidl
- Department of Biology, Faculty of Science, York University, Toronto, ON, Canada; Center for Vision Research, York University, Toronto, ON, Canada.
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160
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Xu J, Chen L, Li L. Pannexin hemichannels: A novel promising therapy target for oxidative stress related diseases. J Cell Physiol 2017; 233:2075-2090. [PMID: 28295275 DOI: 10.1002/jcp.25906] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 03/09/2017] [Indexed: 12/16/2022]
Abstract
Pannexins, which contain three subtypes: pannexin-1, -2, and -3, are vertebrate glycoproteins that form non-junctional plasma membrane intracellular hemichannels via oligomerization. Oxidative stress refers to an imbalance of the generation and elimination of reactive oxygen species (ROS). Studies have shown that elevated ROS levels are pivotal in the development of a variety of diseases. Recent studies indicate that the occurrence of these oxidative stress related diseases is associated with pannexin hemichannels. It is also reported that pannexins regulate the production of ROS which in turn may increase the opening of pannexin hemichannels. In this paper, we review recent researches about the important role of pannexin hemichannels in oxidative stress related diseases. Thus, pannexin hemichannels, novel therapeutic targets, hold promise in managing oxidative stress related diseases such as the tumor, inflammatory bowel diseases (IBD), pulmonary fibrosis, chronic obstructive pulmonary disease (COPD), cardiovascular disease, insulin resistance (IR), and neural degeneration diseases.
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Affiliation(s)
- Jin Xu
- Learning Key Laboratory for Pharmacoproteomics, Institute of Pharmacy and Pharmacology, University of South China, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang, P. R. China
| | - Linxi Chen
- Learning Key Laboratory for Pharmacoproteomics, Institute of Pharmacy and Pharmacology, University of South China, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang, P. R. China
| | - Lanfang Li
- Learning Key Laboratory for Pharmacoproteomics, Institute of Pharmacy and Pharmacology, University of South China, Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, Hengyang, P. R. China
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161
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Petes C, Wynick C, Guzzo C, Mehta D, Logan S, Banfield BW, Basta S, Cooper A, Gee K. IL-27 enhances LPS-induced IL-1β in human monocytes and murine macrophages. J Leukoc Biol 2017; 102:83-94. [PMID: 28377398 DOI: 10.1189/jlb.3a0316-098r] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 02/17/2017] [Accepted: 03/16/2017] [Indexed: 11/24/2022] Open
Abstract
IL-27 bridges innate and adaptive immunity by modulating cytokine production from myeloid cells and regulating Th cell differentiation. During bacterial infection, TLR4 triggering by LPS induces IL-27 production by monocytes and macrophages. We have previously shown that IL-27 can prime monocytes for LPS responsiveness by enhancing TLR4 expression and intracellular signaling. If unregulated, this could result in damaging inflammation, whereas on the other hand, this may also provide greater responses by inflammatory processes induced in response to bacterial pathogens. A key process in fine-tuning inflammatory responses is activation of the inflammasome, which ultimately results in IL-1β production. Herein, we investigated the molecular mechanisms by which IL-27 modulates LPS-induced IL-1β secretion in monocytes and macrophages. We found that when delivered simultaneously with LPS, IL-27 augments activation of caspase-1 and subsequent release of IL-1β. Furthermore, we determined that IL-27 primes cells for enhanced IL-1β production by up-regulating surface expression of TLR4 and P2X purinoceptor 7 (P2X7) for enhanced LPS and ATP signaling, respectively. These findings provide new evidence that IL-27 plays an important role in the proinflammatory capacity of monocytes and macrophages via enhancing IL-1β secretion levels triggered by dual LPS-ATP stimulation.
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Affiliation(s)
- Carlene Petes
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Christopher Wynick
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Christina Guzzo
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada.,Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA; and
| | - Divya Mehta
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Sarah Logan
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Bruce W Banfield
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Sameh Basta
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Andrea Cooper
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom
| | - Katrina Gee
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada;
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162
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Kim Y, Davidson JO, Green CR, Nicholson LFB, O'Carroll SJ, Zhang J. Connexins and Pannexins in cerebral ischemia. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:224-236. [PMID: 28347700 DOI: 10.1016/j.bbamem.2017.03.018] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 02/24/2017] [Accepted: 03/22/2017] [Indexed: 12/12/2022]
Abstract
A common cause of mortality and long-term adult disability, cerebral ischemia or brain ischemia imposes a significant health and financial burden on communities worldwide. Cerebral ischemia is a condition that arises from a sudden loss of blood flow and consequent failure to meet the high metabolic demands of the brain. The lack of blood flow initiates a sequelae of cell death mechanisms, including the activation of the inflammatory pathway, which can ultimately result in irreversible brain tissue damage. In particular, Connexins and Pannexins are non-selective channels with a large pore that have shown to play time-dependent roles in the perpetuation of ischaemic injury. This review highlights the roles of Connexin and Pannexin channels in cell death mechanisms as a promising therapeutic target in cerebral ischemia, and in particular connexin hemichannels which may contribute most of the ATP release as a result of ischemia as well as during reperfusion. This article is part of a Special Issue entitled: Gap Junction Proteins edited by Jean Claude Herve.
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Affiliation(s)
- Yeri Kim
- Department of Ophthalmology, Faculty of Medical and Health Sciences, University of Auckland
| | - Joanne O Davidson
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland
| | - Colin R Green
- Department of Ophthalmology, Faculty of Medical and Health Sciences, University of Auckland
| | - Louise F B Nicholson
- Centre for Brain Research, Faculty of Medical and Health Sciences, University of Auckland
| | - Simon J O'Carroll
- Centre for Brain Research, Faculty of Medical and Health Sciences, University of Auckland
| | - Jie Zhang
- Department of Ophthalmology, Faculty of Medical and Health Sciences, University of Auckland.
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163
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Bigiani A. Calcium Homeostasis Modulator 1-Like Currents in Rat Fungiform Taste Cells Expressing Amiloride-Sensitive Sodium Currents. Chem Senses 2017; 42:343-359. [DOI: 10.1093/chemse/bjx013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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164
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Wu JQ, Zhang SS, Gao H, Qi Z, Zhou CJ, Ji WW, Liu Y, Chen Y, Li Q, Li X, Wang H. Experimental and Theoretical Studies on Rhodium-Catalyzed Coupling of Benzamides with 2,2-Difluorovinyl Tosylate: Diverse Synthesis of Fluorinated Heterocycles. J Am Chem Soc 2017; 139:3537-3545. [DOI: 10.1021/jacs.7b00118] [Citation(s) in RCA: 202] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Jia-Qiang Wu
- School
of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Shang-Shi Zhang
- School
of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Hui Gao
- School
of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Zisong Qi
- Dalian
Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Chu-Jun Zhou
- School
of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Wei-Wei Ji
- School
of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Yao Liu
- School
of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Yunyun Chen
- School
of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Qingjiang Li
- School
of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Xingwei Li
- Dalian
Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Honggen Wang
- School
of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
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165
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Ohbuchi T, Do BH, Koizumi H, Takeuchi S, Ueta Y, Suzuki H. Possible contribution of pannexin-1 to capsaicin-induced ATP release in rat nasal columnar epithelial cells. Channels (Austin) 2017; 11:273-280. [PMID: 28631948 PMCID: PMC5555260 DOI: 10.1080/19336950.2017.1293209] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Current evidence indicates that transient receptor potential (TRP) channel activity involves a relationship between opening of pannexin-1 and release of ATP into the extracellular space. We examined the effects of agonists of thermosensitive TRP channels (TRPM8, TRPA1, TRPV1, and TRPV2) on ATP release from rat nasal mucosa, and measured ciliary beat frequency (CBF) using digital high-speed video imaging. Single-cell patch clamping from dissociated rat nasal columnar epithelial cells was performed to confirm the relationship between pannexin-1 and TRP. We demonstrated that ATP release and CBF were significantly potentiated by the heat-sensitive TRPV1 agonist capsaicin (10 μM), but not by other TRP agonists. Capsaicin-induced ATP release and CBF increase were significantly inhibited by the pannexin-1 blockers carbenoxolone (10 μM) and probenecid (300 μM). In addition, the voltage step-evoked currents in the presence of capsaicin were inhibited by the pannexin-1 blockers in single-cell patch clamping. Our results suggest the participation of TRPV1 and pannexin-1 in the physiologic functions of rat nasal mucosa.
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Affiliation(s)
- Toyoaki Ohbuchi
- Department of Otorhinolaryngology-Head and Neck Surgery, University of Occupational and Environmental Health, Kitakyushu, Japan,CONTACT Toyoaki Ohbuchi Department of Otorhinolaryngology-Head and Neck surgery, School of Medicine, University of Occupational and Environmental Health, 1–1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan
| | - Ba Hung Do
- Department of Otorhinolaryngology-Head and Neck Surgery, University of Occupational and Environmental Health, Kitakyushu, Japan
| | - Hiroki Koizumi
- Department of Otorhinolaryngology-Head and Neck Surgery, University of Occupational and Environmental Health, Kitakyushu, Japan
| | - Shoko Takeuchi
- Department of Otorhinolaryngology-Head and Neck Surgery, University of Occupational and Environmental Health, Kitakyushu, Japan
| | - Yoichi Ueta
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan
| | - Hideaki Suzuki
- Department of Otorhinolaryngology-Head and Neck Surgery, University of Occupational and Environmental Health, Kitakyushu, Japan
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166
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Burma NE, Bonin RP, Leduc-Pessah H, Baimel C, Cairncross ZF, Mousseau M, Shankara JV, Stemkowski PL, Baimoukhametova D, Bains JS, Antle MC, Zamponi GW, Cahill CM, Borgland SL, De Koninck Y, Trang T. Blocking microglial pannexin-1 channels alleviates morphine withdrawal in rodents. Nat Med 2017; 23:355-360. [PMID: 28134928 DOI: 10.1038/nm.4281] [Citation(s) in RCA: 112] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 01/08/2017] [Indexed: 12/18/2022]
Abstract
Opiates are essential for treating pain, but termination of opiate therapy can cause a debilitating withdrawal syndrome in chronic users. To alleviate or avoid the aversive symptoms of withdrawal, many of these individuals continue to use opiates. Withdrawal is therefore a key determinant of opiate use in dependent individuals, yet its underlying mechanisms are poorly understood and effective therapies are lacking. Here, we identify the pannexin-1 (Panx1) channel as a therapeutic target in opiate withdrawal. We show that withdrawal from morphine induces long-term synaptic facilitation in lamina I and II neurons within the rodent spinal dorsal horn, a principal site of action for opiate analgesia. Genetic ablation of Panx1 in microglia abolished the spinal synaptic facilitation and ameliorated the sequelae of morphine withdrawal. Panx1 is unique in its permeability to molecules up to 1 kDa in size and its release of ATP. We show that Panx1 activation drives ATP release from microglia during morphine withdrawal and that degrading endogenous spinal ATP by administering apyrase produces a reduction in withdrawal behaviors. Conversely, we found that pharmacological inhibition of ATP breakdown exacerbates withdrawal. Treatment with a Panx1-blocking peptide (10panx) or the clinically used broad-spectrum Panx1 blockers, mefloquine or probenecid, suppressed ATP release and reduced withdrawal severity. Our results demonstrate that Panx1-mediated ATP release from microglia is required for morphine withdrawal in rodents and that blocking Panx1 alleviates the severity of withdrawal without affecting opiate analgesia.
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Affiliation(s)
- Nicole E Burma
- Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Robert P Bonin
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada
| | - Heather Leduc-Pessah
- Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Corey Baimel
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Zoe F Cairncross
- Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Michael Mousseau
- Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | | | - Patrick L Stemkowski
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Dinara Baimoukhametova
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Jaideep S Bains
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Michael C Antle
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Department of Psychology, University of Calgary, Calgary, Alberta, Canada
| | - Gerald W Zamponi
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Catherine M Cahill
- Department of Anesthesiology and Perioperative Care, University of California Irvine, Irvine, California, USA
| | - Stephanie L Borgland
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Yves De Koninck
- Department of Psychiatry and Neuroscience, Institut Universitaire en santé mentale de Québec, Université Laval, Ville de Québec, Québec, Canada
| | - Tuan Trang
- Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
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167
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Calabró V, Piotrkowski B, Fischerman L, Vazquez Prieto MA, Galleano M, Fraga CG. Modifications in nitric oxide and superoxide anion metabolism induced by fructose overload in rat heart are prevented by (-)-epicatechin. Food Funct 2017; 7:1876-83. [PMID: 26960258 DOI: 10.1039/c6fo00048g] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Fructose overload promotes functional and metabolic derangements in humans and in animal experimental models. Evidence suggests that dietary flavonoids have the ability to prevent/attenuate the development of metabolic diseases. In this work we investigated the effects of (-)-epicatechin on the modifications induced by fructose overload in the rat heart in terms of nitric oxide and superoxide metabolism. Male Sprague Dawley rats received 10% (w/v) fructose in the drinking water for 8 weeks, with or without (-)-epicatechin (20 mg per kg body weight per day) in the rat chow diet. These conditions of fructose overload did not lead to overt manifestations of heart hypertrophy or tissue remodeling. However, biochemical and molecular changes were observed and could represent the onset of functional alterations. (-)-Epicatechin prevented a compromised NO bioavailability and the development of oxidative stress produced by fructose overload essentially acting on superoxide anion metabolism. In this line, the increase in superoxide anion production, the overexpression of NOX2 subunit p47phox and of NOX4, the decrease in superoxide dismutase activity, and the higher oxidized/reduced glutathione ratio installed by fructose overload were absent in the rats receiving (-)-epicatechin. These results support the hypothesis that diets rich in (-)-epicatechin could prevent the onset and progression of heart dysfunctions associated with metabolic alterations.
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Affiliation(s)
- Valeria Calabró
- Physical Chemistry-Institute of Biochemistry and Molecular Medicine (IBIMOL) School of Pharmacy and Biochemistry, University of Buenos Aires-National Council of Scientific and Technological Research (CONICET), Argentina
| | - Barbara Piotrkowski
- Physical Chemistry-Institute of Biochemistry and Molecular Medicine (IBIMOL) School of Pharmacy and Biochemistry, University of Buenos Aires-National Council of Scientific and Technological Research (CONICET), Argentina
| | - Laura Fischerman
- Physical Chemistry-Institute of Biochemistry and Molecular Medicine (IBIMOL) School of Pharmacy and Biochemistry, University of Buenos Aires-National Council of Scientific and Technological Research (CONICET), Argentina
| | - Marcela A Vazquez Prieto
- Department of Pathology, School of Medicine, National University of Cuyo and Institute of Medicine and Experimental Biology-CONICET, Mendoza, Argentina.
| | - Monica Galleano
- Physical Chemistry-Institute of Biochemistry and Molecular Medicine (IBIMOL) School of Pharmacy and Biochemistry, University of Buenos Aires-National Council of Scientific and Technological Research (CONICET), Argentina
| | - Cesar G Fraga
- Physical Chemistry-Institute of Biochemistry and Molecular Medicine (IBIMOL) School of Pharmacy and Biochemistry, University of Buenos Aires-National Council of Scientific and Technological Research (CONICET), Argentina
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168
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Hainz N, Wolf S, Tschernig T, Meier C. Probenecid Application Prevents Clinical Symptoms and Inflammation in Experimental Autoimmune Encephalomyelitis. Inflammation 2016; 39:123-128. [PMID: 26276126 DOI: 10.1007/s10753-015-0230-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system. Neurological impairments are caused by axonal damage due to demyelination and neuroinflammation within the central nervous system. T cells mediate the neuroinflammation. The activation of T cells is induced by the release of adenosine triphosphate and involves purinergic receptors as well as pannexin (Panx) proteins. As Panx1 is expressed on T cells, we here propose that application of probenecid, a known Panx inhibitor, will prevent the onset of clinical symptoms in a mouse model of MS, the experimental autoimmune encephalomyelitis (EAE) model. EAE-induced mice received daily injections of probenecid. Disease scores, T cell numbers, and microglia activation were compared between experimental groups. Probenecid treatment resulted in lower disease scores as compared to EAE animals. Probenecid-treated animals also displayed fewer inflammatory lesions. Microglia activation was not altered by treatment. In conclusion, probenecid prevented the onset of EAE.
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Affiliation(s)
- Nadine Hainz
- Department of Anatomy and Cell Biology, Saarland University, Building 61, 66421, Homburg, Saar, Germany
| | - Sandra Wolf
- Department of Anatomy and Cell Biology, Saarland University, Building 61, 66421, Homburg, Saar, Germany
| | - Thomas Tschernig
- Department of Anatomy and Cell Biology, Saarland University, Building 61, 66421, Homburg, Saar, Germany
| | - Carola Meier
- Department of Anatomy and Cell Biology, Saarland University, Building 61, 66421, Homburg, Saar, Germany.
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169
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Huang H, Zhang X, Yu C, Li X, Zhang Y, Wang W. Highly Regio- and Stereoselective Synthesis of Z and E Enol Esters by an Amine-Catalyzed Conjugate Addition–Rearrangement Reaction of Ynals with Carboxylic Acids. ACS Catal 2016. [DOI: 10.1021/acscatal.6b02206] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- He Huang
- Department of Chemistry & Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
| | - Xinshuai Zhang
- Department of Chemistry & Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
| | - Chenguang Yu
- Department of Chemistry & Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
| | - Xiangmin Li
- Department of Chemistry & Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
- State Key Laboratory of Bioengineering Reactor, Shanghai Key Laboratory of New Drug Design, Shanghai Key Laboratory of Chemical Biology, and School of Pharmacy, East China University of Science & Technology, Shanghai 200237, People’s Republic of China
| | - Yueteng Zhang
- Department of Chemistry & Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
| | - Wei Wang
- Department of Chemistry & Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
- State Key Laboratory of Bioengineering Reactor, Shanghai Key Laboratory of New Drug Design, Shanghai Key Laboratory of Chemical Biology, and School of Pharmacy, East China University of Science & Technology, Shanghai 200237, People’s Republic of China
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170
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The earliest neuronal responses to hypoxia in the neocortical circuit are glutamate-dependent. Neurobiol Dis 2016; 95:158-67. [PMID: 27443966 DOI: 10.1016/j.nbd.2016.07.019] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 07/11/2016] [Accepted: 07/17/2016] [Indexed: 11/23/2022] Open
Abstract
Soon after exposure to hypoxia or ischemia, neurons in cortical tissues undergo massive anoxic depolarization (AD). This precipitous event is preceded by more subtle neuronal changes, including enhanced excitatory and inhibitory synaptic transmitter release. Here, we have used patch-in-slice techniques to identify the earliest effects of acute hypoxia on the synaptic and intrinsic properties of Layer 5 neurons, to determine their time course and to evaluate the role of glutamate receptors in their generation. Coronal slices of mouse somatosensory cortex were maintained at 36°C in an interface chamber and challenged with episodes of hypoxia. In recordings with cell-attached electrodes, the open probability of Ca(2+)-dependent BK channels began to increase within seconds of hypoxia onset, indicating a sharp rise in [Ca(2+)]i just beneath the membrane. By using a high concentration of K(+) in the pipette, we simultaneously monitored the membrane potential and showed that the [Ca(2+)]i rise was not associated with membrane depolarization. The earliest hypoxia-induced synaptic disturbance was a marked increase in the frequency of sPSCs, which also began soon after the removal of oxygen and long before AD. This synaptic effect was accompanied by depletion of the readily releasable transmitter pools, as demonstrated by a decreased response to hyperosmotic solutions. The early [Ca(2+)]i rise, the early increase in transmitter release and the subsequent AD itself were all prevented by bathing in a cocktail containing blockers of ionotropic glutamate receptors. We found no evidence for involvement of pannexin hemichannels or TRPM7 channels in the early responses to hypoxia in this experimental preparation. Our data indicate that the earliest cellular consequences of cortical hypoxia are triggered by activation of glutamate-gated channels.
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171
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Abstract
Pannexin (Panx) is a gene family encoding gap junction proteins in vertebrates. So far, three isoforms (Panx1, 2 and 3) have been identified. All of three Panx isoforms express in the cochlea with distinct expression patterns. Panx1 expresses in the cochlea extensively, including the spiral limbus, the organ of Corti, and the cochlear lateral wall, whereas Panx2 and Panx3 restrict to the basal cells of the stria vascularis in the lateral wall and the cochlear bony structure, respectively. However, there is no pannexin expression in auditory sensory hair cells. Recent studies demonstrated that like connexin gap junction gene, Panx1 deficiency causes hearing loss. Panx1 channels dominate ATP release in the cochlea. Deletion of Panx1 abolishes ATP release in the cochlea and reduces endocochlear potential (EP), auditory receptor current/potential, and active cochlear amplification. Panx1 deficiency in the cochlea also activates caspase-3 cell apoptotic pathway leading to cell degeneration. These new findings suggest that pannexins have a critical role in the cochlea in regard to hearing. However, detailed information about pannexin function in the cochlea and Panx mutation induced hearing loss still remain largely undetermined. Further studies are required.
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Affiliation(s)
- Hong-Bo Zhao
- Department of Otolaryngology, University of Kentucky Medical Center, 800 Rose Street, Lexington, KY, 40536, USA.
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172
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Abstract
Communication among cells via direct cell-cell contact by connexin gap junctions, or between cell and extracellular environment via pannexin channels or connexin hemichannels, is a key factor in cell function and tissue homeostasis. Upon malignant transformation in different cancer types, the dysregulation of these connexin and pannexin channels and their effect in cellular communication, can either enhance or suppress tumorigenesis and metastasis. In this review, we will highlight the latest reports on the role of the well characterized connexin family and its ability to form gap junctions and hemichannels in cancer. We will also introduce the more recently discovered family of pannexin channels and our current knowledge about their involvement in cancer progression.
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Affiliation(s)
- Jean X Jiang
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX, 78229, USA
| | - Silvia Penuela
- Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario, N6A5C1, Canada.
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173
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Jian Z, Ding S, Deng H, Wang J, Yi W, Wang L, Zhu S, Gu L, Xiong X. Probenecid protects against oxygen-glucose deprivation injury in primary astrocytes by regulating inflammasome activity. Brain Res 2016; 1643:123-9. [PMID: 27154322 DOI: 10.1016/j.brainres.2016.05.002] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 04/18/2016] [Accepted: 05/02/2016] [Indexed: 01/21/2023]
Abstract
Inflammation is extremely important in the development of cerebral ischemia/reperfusion injury. Pannexin 1 (Panx1) channel has been reported to activate inflammasome in astrocytes and be involved in ischemic injury, but this damage effect is reversed by a Panx1 inhibitor-probenecid. However, the mechanism of probenecid protects against cerebral ischemia/reperfusion injury remains unclear. In present study, we hypothesized that probenecid protected astrocytes from ischemia/reperfusion injury in vitro by modulating the inflammasome. Primary cultured neocortical astrocytes were exposed to oxygen-glucose deprivation/reoxygenation (OGD/RX) and probenecid was added in this model. Viability and nuclear morphology of astrocytes, production of reactive oxygen species (ROS), protein expressions of NLRP3 (NOD-like receptor protein 3), caspase-1, and AQP4 (Aquaporins 4), as well as release of cellular HMGB1 and IL-1β were observed to evaluate the effect and mechanisms of probenecid on OGD/reoxygenated astrocytes. Probenecid did not affect cell viability at concentrations of 1, 5, 10, and 100μM but induced significant astrocytes death at 500μM. Probenecid inhibited cell death and ROS generation in astrocytes subjected to 6h of OGD and 24h of reoxygenation. The expression levels of NLRP3, caspase-1, and AQP4 increased after 6h of OGD, but probenecid treatment attenuated this increase. Moreover, the extracellular release of IL-1β and HMGB1 from OGD/reoxygenated astrocytes increased significantly. However, treatment by probenecid resulted in substantial reduction of these proteins levels in extracellular space. In conclusion, The Panx1 inhibitor, probenecid, which was administered before OGD, provided protective effects on the OGD/reoxygenation model of cultured astrocytes by modulating inflammasome activity and downregulating AQP4 expression.
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Affiliation(s)
- Zhihong Jian
- Department of Neurosurgery, Renmin Hospital of Wuhan University, Hubei, China
| | - Shuai Ding
- Department of Anesthesia, the First Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang, China
| | - Hongping Deng
- Cardiovascular Surgery, Renmin Hospital of Wuhan University, Hubei, China
| | - Jun Wang
- Department of Neurosurgery, Renmin Hospital of Wuhan University, Hubei, China
| | - Wei Yi
- Department of Neurosurgery, Renmin Hospital of Wuhan University, Hubei, China
| | - Lei Wang
- Department of Neurosurgery, Renmin Hospital of Wuhan University, Hubei, China
| | - Shengmei Zhu
- Department of Anesthesia, the First Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang, China
| | - Lijuan Gu
- Central laboratory, Renmin Hospital of Wuhan University, Hubei, China.
| | - Xiaoxing Xiong
- Department of Neurosurgery, Renmin Hospital of Wuhan University, Hubei, China; Central laboratory, Renmin Hospital of Wuhan University, Hubei, China.
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174
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Wu D, Li L, Chen L. A new perspective of mechanosensitive pannexin-1 channels in cancer metastasis: clues for the treatment of other stress-induced diseases. Acta Biochim Biophys Sin (Shanghai) 2016; 48:487-9. [PMID: 27025600 DOI: 10.1093/abbs/gmw018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Di Wu
- Institute of Pharmacy and Pharmacology, University of South China, Hengyang 421001, China
| | - Lanfang Li
- Institute of Pharmacy and Pharmacology, University of South China, Hengyang 421001, China
| | - Linxi Chen
- Institute of Pharmacy and Pharmacology, University of South China, Hengyang 421001, China
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175
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P2X7-pannexin-1 and amyloid β-induced oxysterol input in human retinal cell: Role in age-related macular degeneration? Biochimie 2016; 127:70-8. [PMID: 27109381 DOI: 10.1016/j.biochi.2016.04.014] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 04/15/2016] [Indexed: 02/07/2023]
Abstract
Age-related macular degeneration (AMD) is the most common cause of severe vision loss worldwide. Amyloid β involvement in degenerative diseases such as AMD is well known and its toxicity has been related to P2X7 receptor-pannexin-1. Recently, oxysterols (oxidized derivatives of cholesterol) have been implicated in AMD pathogenesis. The aim of our study was to highlight amyloid β/oxysterols relationship and to describe P2X7 receptor-pannexin-1 role in oxysterols toxicity. Using retinal epithelial cells, we first quantified sterols levels after amyloid β incubation and second we investigated the cytotoxic effects induced by oxysterols. For the first time, our results showed that amyloid β induced oxysterols formation in human retinal pigmented epithelial cells. We showed that oxysterol toxicity is mediated by P2X7 receptor activation. This activation was dependent on pannexin-1 with 25-hydroxycholesterol whereas P2X7 receptor signaling pathway was pannexin-1-independent for 7-ketocholesterol. Taken together our data suggest a pivotal role of P2X7 receptor-pannexin-1 in oxysterols toxicity in retinal cells which could be an important target to develop new treatments for AMD.
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176
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Shao Q, Lindstrom K, Shi R, Kelly J, Schroeder A, Juusola J, Levine KL, Esseltine JL, Penuela S, Jackson MF, Laird DW. A Germline Variant in the PANX1 Gene Has Reduced Channel Function and Is Associated with Multisystem Dysfunction. J Biol Chem 2016; 291:12432-12443. [PMID: 27129271 DOI: 10.1074/jbc.m116.717934] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Indexed: 12/20/2022] Open
Abstract
Pannexin1 (PANX1) is probably best understood as an ATP release channel involved in paracrine signaling. Given its ubiquitous expression, PANX1 pathogenic variants would be expected to lead to disorders involving multiple organ systems. Using whole exome sequencing, we discovered the first patient with a homozygous PANX1 variant (c.650G→A) resulting in an arginine to histidine substitution at position 217 (p.Arg217His). The 17-year-old female has intellectual disability, sensorineural hearing loss requiring bilateral cochlear implants, skeletal defects, including kyphoscoliosis, and primary ovarian failure. Her consanguineous parents are each heterozygous for this variant but are not affected by the multiorgan syndromes noted in the proband. Expression of the p.Arg217His mutant in HeLa, N2A, HEK293T, and Ad293 cells revealed normal PANX1 glycosylation and cell surface trafficking. Dye uptake, ATP release, and electrophysiological measurements revealed p.Arg217His to be a loss-of-function variant. Co-expression of the mutant with wild-type PANX1 suggested the mutant was not dominant-negative to PANX1 channel function. Collectively, we demonstrate a PANX1 missense change associated with human disease in the first report of a "PANX1-related disorder."
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Affiliation(s)
- Qing Shao
- Department of Anatomy and Cell Biology, The University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Kristin Lindstrom
- Division of Genetics and Metabolism, Phoenix Children's Hospital, Phoenix, Arizona 85016
| | - Ruoyang Shi
- Department of Pharmacology and Therapeutics, University of Manitoba, Winnipeg, Manitoba R3E 0Z3, Canada,; Kleysen Institute for Advanced Medicine, Health Sciences Centre, Winnipeg, Manitoba R3E 0Z3, Canada
| | - John Kelly
- Department of Anatomy and Cell Biology, The University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Audrey Schroeder
- Division of Genetics, University of Rochester Medical Center, Rochester, New York 14642
| | | | | | - Jessica L Esseltine
- Department of Anatomy and Cell Biology, The University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Silvia Penuela
- Department of Anatomy and Cell Biology, The University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Michael F Jackson
- Department of Pharmacology and Therapeutics, University of Manitoba, Winnipeg, Manitoba R3E 0Z3, Canada,; Kleysen Institute for Advanced Medicine, Health Sciences Centre, Winnipeg, Manitoba R3E 0Z3, Canada
| | - Dale W Laird
- Department of Anatomy and Cell Biology, The University of Western Ontario, London, Ontario N6A 5C1, Canada.
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177
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Abstract
Pannexin channels are newly discovered ATP release channels expressed throughout the body. Pannexin 1 (Panx1) channels have become of great interest as they appear to participate in a multitude of signalling cascades, including regulation of vascular function. Although numerous Panx1 pharmacological inhibitors have been discovered, these inhibitors are not specific for Panx1 and have additional effects on other proteins. Therefore, molecular tools, such as RNA interference and knockout animals, are needed to demonstrate the role of pannexins in various cellular functions. This review focuses on the known roles of Panx1 related to purinergic signalling in the vasculature focusing on post-translational modifications and channel gating mechanisms that may participate in the regulated release of ATP.
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178
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Dahl G. ATP release through pannexon channels. Philos Trans R Soc Lond B Biol Sci 2016; 370:rstb.2014.0191. [PMID: 26009770 DOI: 10.1098/rstb.2014.0191] [Citation(s) in RCA: 170] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Extracellular adenosine triphosphate (ATP) serves as a signal for diverse physiological functions, including spread of calcium waves between astrocytes, control of vascular oxygen supply and control of ciliary beat in the airways. ATP can be released from cells by various mechanisms. This review focuses on channel-mediated ATP release and its main enabler, Pannexin1 (Panx1). Six subunits of Panx1 form a plasma membrane channel termed 'pannexon'. Depending on the mode of stimulation, the pannexon has large conductance (500 pS) and unselective permeability to molecules less than 1.5 kD or is a small (50 pS), chloride-selective channel. Most physiological and pathological stimuli induce the large channel conformation, whereas the small conformation so far has only been observed with exclusive voltage activation of the channel. The interaction between pannexons and ATP is intimate. The pannexon is not only the conduit for ATP, permitting ATP efflux from cells down its concentration gradient, but the pannexon is also modulated by ATP. The channel can be activated by ATP through both ionotropic P2X as well as metabotropic P2Y purinergic receptors. In the absence of a control mechanism, this positive feedback loop would lead to cell death owing to the linkage of purinergic receptors with apoptotic processes. A control mechanism preventing excessive activation of the purinergic receptors is provided by ATP binding (with low affinity) to the Panx1 protein and gating the channel shut.
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Affiliation(s)
- Gerhard Dahl
- School of Medicine, University of Miami, 1600 NW 10th Avenue, Miami, FL 33136, USA
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179
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Riding A, Pullar CE. ATP Release and P2 Y Receptor Signaling are Essential for Keratinocyte Galvanotaxis. J Cell Physiol 2016; 231:181-91. [PMID: 26058714 DOI: 10.1002/jcp.25070] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Accepted: 06/05/2015] [Indexed: 01/06/2023]
Abstract
Repair to damaged tissue requires directional cell migration to heal the wound. Immediately upon wounding an electrical guidance cue is created with the cathode of the electric field (EF) located at the center of the wound. Previous research has demonstrated directional migration of keratinocytes toward the cathode when an EF of physiological strength (100-150 mV/mm) is applied in vitro, but the "sensor" by which keratinocytes sense the EF remains elusive. Here we use a customized chamber design to facilitate the application of a direct current (DC) EF of physiological strength (100 mV/mm) to keratinocytes whilst pharmacologically modulating the activation of both connexin hemichannels and purinergic receptors to determine their role in EF-mediated directional keratinocyte migration, galvanotaxis. In addition, keratinocytes were exposed to DiSCAC2 (3) dye to visualize membrane potential changes within the cell upon exposure to the applied DC EF. Here we unveil ATP-medicated mechanisms that underpin the initiation of keratinocyte galvanotaxis. The application of a DC EF of 100 mV/mm releases ATP via hemichannels activating a subset of purinergic P2 Y receptors, locally, to initiate the directional migration of keratinocytes toward the cathode in vitro, the center of the wound in vivo. The delineation of the mechanisms underpinning galvanotaxis extends our understanding of this endogenous cue and will facilitate the optimization and wider use of EF devices for chronic wound treatment. J. Cell. Physiol. 230: 181-191, 2016. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Aimie Riding
- Department of Cell Physiology and Pharmacology, University of Leicester, Leicester, UK
| | - Christine E Pullar
- Department of Cell Physiology and Pharmacology, University of Leicester, Leicester, UK
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180
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Yang D, He Y, Muñoz-Planillo R, Liu Q, Núñez G. Caspase-11 Requires the Pannexin-1 Channel and the Purinergic P2X7 Pore to Mediate Pyroptosis and Endotoxic Shock. Immunity 2015; 43:923-32. [PMID: 26572062 DOI: 10.1016/j.immuni.2015.10.009] [Citation(s) in RCA: 401] [Impact Index Per Article: 44.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Revised: 07/31/2015] [Accepted: 10/07/2015] [Indexed: 12/16/2022]
Abstract
The noncanonical inflammasome induced by intracellular lipopolysaccharide (LPS) leads to caspase-11-dependent pyroptosis, which is critical for induction of endotoxic shock in mice. However, the signaling pathway downstream of caspase-11 is unknown. We found that cytosolic LPS stimulation induced caspase-11-dependent cleavage of the pannexin-1 channel followed up by ATP release, which in turn activated the purinergic P2X7 receptor to mediate cytotoxicity. In the absence of P2X7 or pannexin-1, pyroptosis induced by cytosolic LPS was abrogated. Cleavage of pannexin-1 required the catalytic activity of caspase-11 and was essential for ATP release and P2X7-mediated pyroptosis. Priming the caspase-11 pathway in vivo with LPS or Toll-like receptor-3 (TLR3) agonist resulted in high mortality in wild-type mice after secondary LPS challenge, but not in Casp11(-/-), Panx1(-/-), or P2x7(-/-) mice. These results reveal a critical role for pannexin-1 and P2X7 downstream of caspase-11 for pyroptosis and susceptibility to sepsis induced by the noncanonical inflammasome.
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Affiliation(s)
- Dahai Yang
- Department of Pathology and Comprehensive Cancer Center, University of Michigan, Ann Arbor, MI 48109, USA; State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Yuan He
- Department of Pathology and Comprehensive Cancer Center, University of Michigan, Ann Arbor, MI 48109, USA
| | - Raul Muñoz-Planillo
- Department of Pathology and Comprehensive Cancer Center, University of Michigan, Ann Arbor, MI 48109, USA
| | - Qin Liu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China.
| | - Gabriel Núñez
- Department of Pathology and Comprehensive Cancer Center, University of Michigan, Ann Arbor, MI 48109, USA.
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181
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Wang SP, Chen FY, Dong LX, Zhang YQ, Chen HY, Qiao K, Wang KJ. A novel innexin2 forming membrane hemichannel exhibits immune responses and cell apoptosis in Scylla paramamosain. FISH & SHELLFISH IMMUNOLOGY 2015; 47:485-499. [PMID: 26384843 DOI: 10.1016/j.fsi.2015.09.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Revised: 09/06/2015] [Accepted: 09/14/2015] [Indexed: 06/05/2023]
Abstract
Innexins are a class of transmembrane proteins that are important for embryonic development, morphogenesis and electrical synapse formation. In the present study, a novel innexin2 gene from Scylla paramamosain was named Sp-inx2 and characterized. The complete cDNA and genomic DNA sequences of Sp-inx2 were revealed. Sp-inx2 mRNA transcripts were distributed in various tissues of S. paramamosain and were most abundant in the hemocytes. The Sp-inx2 was significantly upregulated in hemocyte, gill and hepatopancreas tissues with the challenge of either Vibrio alginolyticus, Vibrio parahaemolyticus or lipopolysaccharides (LPSs) when analyzed at 3 and 6 h using quantitative real-time PCR, suggesting that it could activate an immune response against the challenge of LPSs or Vibrio species. Using the chemical inhibitors carbenoxolone and probenecid, the absorption of the fluorescent dye Lucifer yellow decreased in the primary cultured hemocytes of crabs, thus confirming that hemichannels composed of Sp-inx2 existed in the crab hemocytes. With LPS stimulation, the level of mRNA transcripts and protein expression of Sp-inx2 in the same cultured hemocytes gradually increased from 6 to 48 h, while the activity of hemichannels was down-regulated at 6 and 12 h, demonstrating that LPSs could modulate the absorption activity of hemichannels in addition to its upregulation of Sp-inx2 gene expression. Furthermore, the dye uptake rate in HeLa cells in which Sp-inx2 was ectopically expressed increased dramatically but the increase was significantly down-regulated with the addition of 50 μg mL(-1) LPS, suggesting that the LPS stimulation could effectively reduce the activity of hemichannels. Interestingly, with the ectopic expression of Sp-inx2 in HeLa and EPC cells, apoptosis spontaneously occurred in both cultured cell lines when detected using TUNEL assay. In summary, a new Sp-inx2 gene was first characterized in a marine animal S. paramamosain and it had a function associated with immune response and cell apoptosis.
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Affiliation(s)
- Shu-Ping Wang
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian, PR China
| | - Fang-Yi Chen
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian, PR China; Fujian Collaborative Innovation Center for Exploitation and Utilization of Marine Biological Resources, Xiamen University, Xiamen, Fujian, PR China; Fujian Engineering Laboratory of Marine Bioproducts and Technology, Xiamen University, Xiamen, Fujian, PR China
| | - Li-Xia Dong
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian, PR China
| | - Ya-Qun Zhang
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian, PR China
| | - Hui-Yun Chen
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian, PR China; Fujian Collaborative Innovation Center for Exploitation and Utilization of Marine Biological Resources, Xiamen University, Xiamen, Fujian, PR China; Fujian Engineering Laboratory of Marine Bioproducts and Technology, Xiamen University, Xiamen, Fujian, PR China
| | - Kun Qiao
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian, PR China
| | - Ke-Jian Wang
- State Key Laboratory of Marine Environmental Science, College of Ocean & Earth Science, Xiamen University, Xiamen, Fujian, PR China; Fujian Collaborative Innovation Center for Exploitation and Utilization of Marine Biological Resources, Xiamen University, Xiamen, Fujian, PR China; Fujian Engineering Laboratory of Marine Bioproducts and Technology, Xiamen University, Xiamen, Fujian, PR China.
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182
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Abstract
Inflammasomes are high molecular weight complexes that sense and react to injury and infection. Their activation induces caspase-1 activation and release of interleukin-1β, a pro-inflammatory cytokine involved in both acute and chronic inflammatory responses. There is increasing evidence that inflammasomes, particularly the NLRP3 inflammasome, act as guardians against noninfectious material. Inappropriate activation of the NLRP3 inflammasome contributes to the progression of many noncommunicable diseases such as gout, type II diabetes, and Alzheimer's disease. Inhibiting the inflammasome may significantly reduce damaging inflammation and is therefore regarded as a therapeutic target. Currently approved inhibitors of interleukin-1β are rilonacept, canakinumab, and anakinra. However, these proteins do not possess ideal pharmacokinetic properties and are unlikely to easily cross the blood-brain barrier. Because inflammation can contribute to neurological disorders, this review focuses on the development of small-molecule inhibitors of the NLRP3 inflammasome.
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Affiliation(s)
- Alex G Baldwin
- Manchester Pharmacy School, Faculty of Medical and Human Sciences, The University of Manchester , Stopford Building, Oxford Road, Manchester M13 9PT, U.K
| | - David Brough
- Faculty of Life Sciences, The University of Manchester , AV Hill Building, Oxford Road, Manchester M13 9PT, U.K
| | - Sally Freeman
- Manchester Pharmacy School, Faculty of Medical and Human Sciences, The University of Manchester , Stopford Building, Oxford Road, Manchester M13 9PT, U.K
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183
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Wei R, Wang J, Xu Y, Yin B, He F, Du Y, Peng G, Luo B. Probenecid protects against cerebral ischemia/reperfusion injury by inhibiting lysosomal and inflammatory damage in rats. Neuroscience 2015; 301:168-77. [PMID: 26047730 DOI: 10.1016/j.neuroscience.2015.05.070] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 05/14/2015] [Accepted: 05/28/2015] [Indexed: 10/23/2022]
Abstract
Probenecid has been used for decades to treat gout, and recent studies have revealed it is also a specific inhibitor of the pannexin-1 channel. It has been reported that the pannexin-1 channel is involved in ischemic injury. Here, we investigated the neuroprotective effect and the possible mechanisms of action of probenecid in global cerebral ischemia/reperfusion (I/R) injury in rats. Twenty minutes of transient global cerebral I/R injury was induced using the four-vessel occlusion (4-VO) method in male Sprague-Dawley rats. Different doses of probenecid were administered intravenously, intraperitoneally, or by gavage before or after reperfusion. Probenecid via all three routes protected against CA1 neuronal death when given before reperfusion. This protective effect continued when probenecid was given at 2h after reperfusion, but not at 6h. Interestingly, the protective effect regained if probenecid was given continuously for 7days after reperfusion. The release of cathepsin B and overexpression of calpain-1 after reperfusion were inhibited, while the upregulation of Hsp70 was strengthened by probenecid pre-treatment. Furthermore, the activation and proliferation of microglia and astrocytes after I/R injury were suppressed by continuous given for 7days, but only partly by a single dose at 6h of reperfusion. Thus, our data indicate that probenecid protects against transient global cerebral I/R injury probably by inhibiting calpain-cathepsin pathway and the inflammatory reaction.
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Affiliation(s)
- R Wei
- The Brain Medical Center and the Collaborative Innovation Center for Brain Science, Department of Neurology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China
| | - J Wang
- Department of Neurology, The First Affiliated Hospital, Anhui Medical University, Hefei 230022, China
| | - Y Xu
- The Brain Medical Center and the Collaborative Innovation Center for Brain Science, Department of Neurology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China
| | - B Yin
- Department of Neurology, Renmin Hospital, Wuhan University, Wuhan 430000, China
| | - F He
- The Brain Medical Center and the Collaborative Innovation Center for Brain Science, Department of Neurology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China
| | - Y Du
- The Brain Medical Center and the Collaborative Innovation Center for Brain Science, Department of Neurology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China
| | - G Peng
- The Brain Medical Center and the Collaborative Innovation Center for Brain Science, Department of Neurology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China
| | - B Luo
- The Brain Medical Center and the Collaborative Innovation Center for Brain Science, Department of Neurology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China.
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184
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Pannexin 1 is required for full activation of insulin-stimulated glucose uptake in adipocytes. Mol Metab 2015; 4:610-8. [PMID: 26413467 PMCID: PMC4563021 DOI: 10.1016/j.molmet.2015.06.009] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Accepted: 06/27/2015] [Indexed: 02/08/2023] Open
Abstract
Objective Defective glucose uptake in adipocytes leads to impaired metabolic homeostasis and insulin resistance, hallmarks of type 2 diabetes. Extracellular ATP-derived nucleotides and nucleosides are important regulators of adipocyte function, but the pathway for controlled ATP release from adipocytes is unknown. Here, we investigated whether Pannexin 1 (Panx1) channels control ATP release from adipocytes and contribute to metabolic homeostasis. Methods We assessed Panx1 functionality in cultured 3T3-L1 adipocytes and in adipocytes isolated from murine white adipose tissue by measuring ATP release in response to known activators of Panx1 channels. Glucose uptake in cultured 3T3-L1 adipocytes was measured in the presence of Panx1 pharmacologic inhibitors and in adipocytes isolated from white adipose tissue from wildtype (WT) or adipocyte-specific Panx1 knockout (AdipPanx1 KO) mice generated in our laboratory. We performed in vivo glucose uptake studies in chow fed WT and AdipPanx1 KO mice and assessed insulin resistance in WT and AdipPanx1 KO mice fed a high fat diet for 12 weeks. Panx1 channel function was assessed in response to insulin by performing electrophysiologic recordings in a heterologous expression system. Finally, we measured Panx1 mRNA in human visceral adipose tissue samples by qRT-PCR and compared expression levels with glucose levels and HOMA-IR measurements in patients. Results Our data show that adipocytes express functional Pannexin 1 (Panx1) channels that can be activated to release ATP. Pharmacologic inhibition or selective genetic deletion of Panx1 from adipocytes decreased insulin-induced glucose uptake in vitro and in vivo and exacerbated diet-induced insulin resistance in mice. Further, we identify insulin as a novel activator of Panx1 channels. In obese humans Panx1 expression in adipose tissue is increased and correlates with the degree of insulin resistance. Conclusions We show that Panx1 channel activity regulates insulin-stimulated glucose uptake in adipocytes and thus contributes to control of metabolic homeostasis. Adipocytes express Pannexin 1 channels that can be activated to release ATP. Inhibition of Pannexin 1 decreased insulin-induced glucose uptake in adipocytes. Adipocyte Pannexin 1 knockout mice are more insulin resistant on high fat diet. We identify insulin as a novel activator of Pannexin 1 channels. Pannexin 1 expression in human adipose tissue correlates with insulin resistance.
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185
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Furlow PW, Zhang S, Soong TD, Halberg N, Goodarzi H, Mangrum C, Wu YG, Elemento O, Tavazoie SF. Mechanosensitive pannexin-1 channels mediate microvascular metastatic cell survival. Nat Cell Biol 2015; 17:943-52. [PMID: 26098574 PMCID: PMC5310712 DOI: 10.1038/ncb3194] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Accepted: 05/21/2015] [Indexed: 02/07/2023]
Abstract
During metastatic progression, circulating cancer cells become lodged within the microvasculature of end organs, where most die from mechanical deformation. Although this phenomenon was first described over a half-century ago, the mechanisms enabling certain cells to survive this metastasis-suppressive barrier remain unknown. By applying whole-transcriptome RNA-sequencing technology to isogenic cancer cells of differing metastatic capacities, we identified a mutation encoding a truncated form of the pannexin-1 (PANX1) channel, PANX1(1-89), as recurrently enriched in highly metastatic breast cancer cells. PANX1(1-89) functions to permit metastatic cell survival during traumatic deformation in the microvasculature by augmenting ATP release from mechanosensitive PANX1 channels activated by membrane stretch. PANX1-mediated ATP release acts as an autocrine suppressor of deformation-induced apoptosis through P2Y-purinergic receptors. Finally, small-molecule therapeutic inhibition of PANX1 channels is found to reduce the efficiency of breast cancer metastasis. These data suggest a molecular basis for metastatic cell survival on microvasculature-induced biomechanical trauma.
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MESH Headings
- Adenosine Triphosphate/metabolism
- Animals
- Breast Neoplasms/blood supply
- Breast Neoplasms/genetics
- Breast Neoplasms/metabolism
- Cell Line, Tumor
- Cell Survival/drug effects
- Cell Survival/genetics
- Cells, Cultured
- Connexins/antagonists & inhibitors
- Connexins/genetics
- Connexins/metabolism
- Gene Expression Regulation, Neoplastic
- HEK293 Cells
- Humans
- Immunoblotting
- Interleukin Receptor Common gamma Subunit/genetics
- Interleukin Receptor Common gamma Subunit/metabolism
- Mice, Inbred NOD
- Mice, Knockout
- Mice, SCID
- Microscopy, Confocal
- Mutation
- Neoplasm Metastasis
- Neovascularization, Pathologic/genetics
- Neovascularization, Pathologic/metabolism
- Neovascularization, Pathologic/prevention & control
- Nerve Tissue Proteins/antagonists & inhibitors
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/metabolism
- Oligonucleotide Array Sequence Analysis
- RNA Interference
- Small Molecule Libraries/pharmacology
- Stress, Mechanical
- Transcriptome
- Transplantation, Heterologous
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Affiliation(s)
- Paul W. Furlow
- Laboratory of Systems Cancer Biology, Rockefeller University, 1230 York Avenue, New York, New York 10065, USA
| | - Steven Zhang
- Laboratory of Systems Cancer Biology, Rockefeller University, 1230 York Avenue, New York, New York 10065, USA
| | - T. David Soong
- Department of Physiology and Biophysics, Weill Cornell Medical College
| | - Nils Halberg
- Laboratory of Systems Cancer Biology, Rockefeller University, 1230 York Avenue, New York, New York 10065, USA
| | - Hani Goodarzi
- Laboratory of Systems Cancer Biology, Rockefeller University, 1230 York Avenue, New York, New York 10065, USA
| | - Creed Mangrum
- Laboratory of Systems Cancer Biology, Rockefeller University, 1230 York Avenue, New York, New York 10065, USA
| | - Y. Gloria Wu
- Laboratory of Systems Cancer Biology, Rockefeller University, 1230 York Avenue, New York, New York 10065, USA
| | - Olivier Elemento
- Department of Physiology and Biophysics, Weill Cornell Medical College
| | - Sohail F. Tavazoie
- Laboratory of Systems Cancer Biology, Rockefeller University, 1230 York Avenue, New York, New York 10065, USA
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186
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Vandenbeuch A, Anderson CB, Kinnamon SC. Mice Lacking Pannexin 1 Release ATP and Respond Normally to All Taste Qualities. Chem Senses 2015; 40:461-7. [PMID: 26136251 DOI: 10.1093/chemse/bjv034] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Adenosine triphosphate (ATP) is required for the transmission of all taste qualities from taste cells to afferent nerve fibers. ATP is released from Type II taste cells by a nonvesicular mechanism and activates purinergic receptors containing P2X2 and P2X3 on nerve fibers. Several ATP release channels are expressed in taste cells including CALHM1, Pannexin 1, Connexin 30, and Connexin 43, but whether all are involved in ATP release is not clear. We have used a global Pannexin 1 knock out (Panx1 KO) mouse in a series of in vitro and in vivo experiments. Our results confirm that Panx1 channels are absent in taste buds of the knockout mice and that other known ATP release channels are not upregulated. Using a luciferin/luciferase assay, we show that circumvallate taste buds from Panx1 KO mice normally release ATP upon taste stimulation compared with wild type (WT) mice. Gustatory nerve recordings in response to various tastants applied to the tongue and brief-access behavioral testing with SC45647 also show no difference between Panx1 KO and WT. These results confirm that Panx1 is not required for the taste evoked release of ATP or for neural and behavioral responses to taste stimuli.
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Affiliation(s)
- Aurelie Vandenbeuch
- Department of Otolaryngology, University of Colorado School of Medicine, Aurora, CO, USA and Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine, Aurora, CO, USA
| | - Catherine B Anderson
- Department of Otolaryngology, University of Colorado School of Medicine, Aurora, CO, USA and Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine, Aurora, CO, USA
| | - Sue C Kinnamon
- Department of Otolaryngology, University of Colorado School of Medicine, Aurora, CO, USA and Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine, Aurora, CO, USA
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187
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Liu X, Wang C, Fujita T, Malmstrom HS, Nedergaard M, Ren YF, Dirksen RT. External Dentin Stimulation Induces ATP Release in Human Teeth. J Dent Res 2015; 94:1259-66. [PMID: 26130258 DOI: 10.1177/0022034515592858] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
ATP is involved in neurosensory processing, including nociceptive transduction. Thus, ATP signaling may participate in dentin hypersensitivity and dental pain. In this study, we investigated whether pannexins, which can form mechanosensitive ATP-permeable channels, are present in human dental pulp. We also assessed the existence and functional activity of ecto-ATPase for extracellular ATP degradation. We further tested if ATP is released from dental pulp upon dentin mechanical or thermal stimulation that induces dentin hypersensitivity and dental pain and if pannexin or pannexin/gap junction channel blockers reduce stimulation-dependent ATP release. Using immunofluorescence staining, we demonstrated immunoreactivity of pannexin 1 and 2 in odontoblasts and their processes extending into the dentin tubules. Using enzymatic histochemistry staining, we also demonstrated functional ecto-ATPase activity within the odontoblast layer, subodontoblast layer, dental pulp nerve bundles, and blood vessels. Using an ATP bioluminescence assay, we found that mechanical or cold stimulation to the exposed dentin induced ATP release in an in vitro human tooth perfusion model. We further demonstrated that blocking pannexin/gap junction channels with probenecid or carbenoxolone significantly reduced external dentin stimulation-induced ATP release. Our results provide evidence for the existence of functional machinery required for ATP release and degradation in human dental pulp and that pannexin channels are involved in external dentin stimulation-induced ATP release. These findings support a plausible role for ATP signaling in dentin hypersensitivity and dental pain.
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Affiliation(s)
- X Liu
- Division of General Dentistry, Eastman Institute for Oral Health, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - C Wang
- Department of Neurosurgery, Qilu Hospital, Shandong University, Jinan, China
| | - T Fujita
- Center for Translational Neuromedicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - H S Malmstrom
- Division of General Dentistry, Eastman Institute for Oral Health, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - M Nedergaard
- Center for Translational Neuromedicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Y F Ren
- Division of General Dentistry, Eastman Institute for Oral Health, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - R T Dirksen
- Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
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188
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Tordoff MG, Aleman TR, Ellis HT, Ohmoto M, Matsumoto I, Shestopalov VI, Mitchell CH, Foskett JK, Poole RL. Normal Taste Acceptance and Preference of PANX1 Knockout Mice. Chem Senses 2015; 40:453-9. [PMID: 25987548 DOI: 10.1093/chemse/bjv025] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Taste compounds detected by G protein-coupled receptors on the apical surface of Type 2 taste cells initiate an intracellular molecular cascade culminating in the release of ATP. It has been suggested that this ATP release is accomplished by pannexin 1 (PANX1). However, we report here that PANX1 knockout mice do not differ from wild-type controls in response to representative taste solutions, measured using 5-s brief-access tests or 48-h two-bottle choice tests. This implies that PANX1 is unnecessary for taste detection and consequently that ATP release from Type 2 taste cells does not require PANX1.
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Affiliation(s)
- Michael G Tordoff
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA,
| | - Tiffany R Aleman
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA
| | - Hillary T Ellis
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA
| | - Makoto Ohmoto
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA
| | - Ichiro Matsumoto
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA
| | - Val I Shestopalov
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, FL 33136, USA
| | - Claire H Mitchell
- Department of Anatomy and Cell Biology, University of Pennsylvania, 240 South 40th Street, PA 19104, USA, and
| | - J Kevin Foskett
- Department of Physiology, University of Pennsylvania, 415 Curie Boulevard, Philadelphia, PA 19104, USA
| | - Rachel L Poole
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA
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189
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Freitas-Andrade M, Naus CC. Astrocytes in neuroprotection and neurodegeneration: The role of connexin43 and pannexin1. Neuroscience 2015; 323:207-21. [PMID: 25913636 DOI: 10.1016/j.neuroscience.2015.04.035] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2015] [Revised: 04/13/2015] [Accepted: 04/15/2015] [Indexed: 12/26/2022]
Abstract
The World Health Organization has predicted that by 2040 neurodegenerative diseases will overtake cancer to become the world's second leading cause of death after cardiovascular disease. This has sparked the development of several European and American brain research initiatives focusing on elucidating the underlying cellular and molecular mechanisms of neurodegenerative diseases. Connexin (Cx) and pannexin (Panx) membrane channel proteins are conduits through which neuronal, glial, and vascular tissues interact. In the brain, this interaction is highly critical for homeostasis and brain repair after injury. Understanding the molecular mechanisms by which these membrane channels function, in health and disease, might be particularly influential in establishing conceptual frameworks to develop new therapeutics against Cx and Panx channels. This review focuses on current insights and emerging concepts, particularly the impact of connexin43 and pannexin1, under neuroprotective and neurodegenerative conditions within the context of astrocytes.
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Affiliation(s)
- M Freitas-Andrade
- Department of Cellular and Physiological Sciences, The Life Science Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - C C Naus
- Department of Cellular and Physiological Sciences, The Life Science Institute, University of British Columbia, Vancouver, British Columbia, Canada.
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190
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Orellana JA, Moraga-Amaro R, Díaz-Galarce R, Rojas S, Maturana CJ, Stehberg J, Sáez JC. Restraint stress increases hemichannel activity in hippocampal glial cells and neurons. Front Cell Neurosci 2015; 9:102. [PMID: 25883550 PMCID: PMC4382970 DOI: 10.3389/fncel.2015.00102] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 03/09/2015] [Indexed: 12/21/2022] Open
Abstract
Stress affects brain areas involved in learning and emotional responses, which may contribute in the development of cognitive deficits associated with major depression. These effects have been linked to glial cell activation, glutamate release and changes in neuronal plasticity and survival including atrophy of hippocampal apical dendrites, loss of synapses and neuronal death. Under neuro-inflammatory conditions, we recently unveiled a sequential activation of glial cells that release ATP and glutamate via hemichannels inducing neuronal death due to activation of neuronal NMDA/P2X7 receptors and pannexin1 hemichannels. In the present work, we studied if stress-induced glia activation is associated to changes in hemichannel activity. To this end, we compared hemichannel activity of brain cells after acute or chronic restraint stress in mice. Dye uptake experiments in hippocampal slices revealed that acute stress induces opening of both Cx43 and Panx1 hemichannels in astrocytes, which were further increased by chronic stress; whereas enhanced Panx1 hemichannel activity was detected in microglia and neurons after acute/chronic and chronic stress, respectively. Moreover, inhibition of NMDA/P2X7 receptors reduced the chronic stress-induced hemichannel opening, whereas blockade of Cx43 and Panx1 hemichannels fully reduced ATP and glutamate release in hippocampal slices from stressed mice. Thus, we propose that gliotransmitter release through hemichannels may participate in the pathogenesis of stress-associated psychiatric disorders and possibly depression.
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Affiliation(s)
- Juan A Orellana
- Departamento de Neurología, Escuela de Medicina, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Rodrigo Moraga-Amaro
- Laboratorio de Neurobiología, Centro de Investigaciones Biomédicas, Facultad de Ciencias Biológicas and Facultad de Medicina, Universidad Andres Bello Santiago, Chile
| | - Raúl Díaz-Galarce
- Laboratorio de Neurobiología, Centro de Investigaciones Biomédicas, Facultad de Ciencias Biológicas and Facultad de Medicina, Universidad Andres Bello Santiago, Chile
| | - Sebastián Rojas
- Laboratorio de Neurobiología, Centro de Investigaciones Biomédicas, Facultad de Ciencias Biológicas and Facultad de Medicina, Universidad Andres Bello Santiago, Chile
| | - Carola J Maturana
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Jimmy Stehberg
- Laboratorio de Neurobiología, Centro de Investigaciones Biomédicas, Facultad de Ciencias Biológicas and Facultad de Medicina, Universidad Andres Bello Santiago, Chile
| | - Juan C Sáez
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile Santiago, Chile ; Instituto Milenio, Centro Interdisciplinario de Neurociencias de Valparaíso Santiago, Chile
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191
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Sandow N, Kim S, Raue C, Päsler D, Klaft ZJ, Antonio LL, Hollnagel JO, Kovacs R, Kann O, Horn P, Vajkoczy P, Holtkamp M, Meencke HJ, Cavalheiro EA, Pragst F, Gabriel S, Lehmann TN, Heinemann U. Drug resistance in cortical and hippocampal slices from resected tissue of epilepsy patients: no significant impact of p-glycoprotein and multidrug resistance-associated proteins. Front Neurol 2015; 6:30. [PMID: 25741317 PMCID: PMC4332373 DOI: 10.3389/fneur.2015.00030] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 02/03/2015] [Indexed: 01/16/2023] Open
Abstract
Drug resistant patients undergoing epilepsy surgery have a good chance to become sensitive to anticonvulsant medication, suggesting that the resected brain tissue is responsible for drug resistance. Here, we address the question whether P-glycoprotein (Pgp) and multidrug resistance-associated proteins (MRPs) expressed in the resected tissue contribute to drug resistance in vitro. Effects of anti-epileptic drugs [carbamazepine (CBZ), sodium valproate, phenytoin] and two unspecific inhibitors of Pgp and MRPs [verapamil (VPM) and probenecid (PBN)] on seizure-like events (SLEs) induced in slices from 35 hippocampal and 35 temporal cortex specimens of altogether 51 patients (161 slices) were studied. Although in slice preparations the blood brain barrier is not functional, we found that SLEs predominantly persisted in the presence of anticonvulsant drugs (90%) and also in the presence of VPM and PBN (86%). Following subsequent co-administration of anti-epileptic drugs and drug transport inhibitors, SLEs continued in 63% of 143 slices. Drug sensitivity in slices was recognized either as transition to recurrent epileptiform transients (30%) or as suppression (7%), particularly by perfusion with CBZ in PBN containing solutions (43, 9%). Summarizing responses to co-administration from more than one slice per patient revealed that suppression of seizure-like activity in all slices was only observed in 7% of patients. Patients whose tissue was completely or partially sensitive (65%) presented with higher seizure frequencies than those with resistant tissue (35%). However, corresponding subgroups of patients do not differ with respect to expression rates of drug transporters. Our results imply that parenchymal MRPs and Pgp are not responsible for drug resistance in resected tissue.
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Affiliation(s)
- Nora Sandow
- Institute of Neurophysiology, Charité Universitätsmedizin Berlin , Berlin , Germany ; Department of Neurosurgery, Charité Universitätsmedizin Berlin , Berlin , Germany
| | - Simon Kim
- Institute of Neurophysiology, Charité Universitätsmedizin Berlin , Berlin , Germany
| | - Claudia Raue
- Institute of Neurophysiology, Charité Universitätsmedizin Berlin , Berlin , Germany
| | - Dennis Päsler
- Institute of Neurophysiology, Charité Universitätsmedizin Berlin , Berlin , Germany
| | - Zin-Juan Klaft
- Institute of Neurophysiology, Charité Universitätsmedizin Berlin , Berlin , Germany
| | - Leandro Leite Antonio
- Institute of Neurophysiology, Charité Universitätsmedizin Berlin , Berlin , Germany ; Laboratorio de Neurologia Experimental, Universidade Federal de São Paulo-Escola Paulista de Medicina , São Paulo , Brazil
| | - Jan Oliver Hollnagel
- Institute of Neurophysiology, Charité Universitätsmedizin Berlin , Berlin , Germany
| | - Richard Kovacs
- Institute of Neurophysiology, Charité Universitätsmedizin Berlin , Berlin , Germany
| | - Oliver Kann
- Institute of Neurophysiology, Charité Universitätsmedizin Berlin , Berlin , Germany ; Institute of Physiology and Pathophysiology, University of Heidelberg , Heidelberg , Germany
| | - Peter Horn
- Department of Neurosurgery, Charité Universitätsmedizin Berlin , Berlin , Germany
| | - Peter Vajkoczy
- Department of Neurosurgery, Charité Universitätsmedizin Berlin , Berlin , Germany
| | - Martin Holtkamp
- Epilepsy Center of Berlin-Brandenburg, Ev. Krankenhaus Königin Elisabeth Herzberge , Berlin , Germany
| | - Heinz-Joachim Meencke
- Epilepsy Center of Berlin-Brandenburg, Ev. Krankenhaus Königin Elisabeth Herzberge , Berlin , Germany
| | - Esper A Cavalheiro
- Laboratorio de Neurologia Experimental, Universidade Federal de São Paulo-Escola Paulista de Medicina , São Paulo , Brazil
| | - Fritz Pragst
- Institute of Forensic Medicine - Forensic Toxicology, Charité Universitätsmedizin Berlin , Berlin , Germany
| | - Siegrun Gabriel
- Institute of Neurophysiology, Charité Universitätsmedizin Berlin , Berlin , Germany
| | | | - Uwe Heinemann
- Institute of Neurophysiology, Charité Universitätsmedizin Berlin , Berlin , Germany
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192
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Billaud M, Chiu YH, Lohman AW, Parpaite T, Butcher JT, Mutchler SM, DeLalio LJ, Artamonov MV, Sandilos JK, Best AK, Somlyo AV, Thompson RJ, Le TH, Ravichandran KS, Bayliss DA, Isakson BE. A molecular signature in the pannexin1 intracellular loop confers channel activation by the α1 adrenoreceptor in smooth muscle cells. Sci Signal 2015; 8:ra17. [PMID: 25690012 DOI: 10.1126/scisignal.2005824] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Both purinergic signaling through nucleotides such as ATP (adenosine 5'-triphosphate) and noradrenergic signaling through molecules such as norepinephrine regulate vascular tone and blood pressure. Pannexin1 (Panx1), which forms large-pore, ATP-releasing channels, is present in vascular smooth muscle cells in peripheral blood vessels and participates in noradrenergic responses. Using pharmacological approaches and mice conditionally lacking Panx1 in smooth muscle cells, we found that Panx1 contributed to vasoconstriction mediated by the α1 adrenoreceptor (α1AR), whereas vasoconstriction in response to serotonin or endothelin-1 was independent of Panx1. Analysis of the Panx1-deficient mice showed that Panx1 contributed to blood pressure regulation especially during the night cycle when sympathetic nervous activity is highest. Using mimetic peptides and site-directed mutagenesis, we identified a specific amino acid sequence in the Panx1 intracellular loop that is essential for activation by α1AR signaling. Collectively, these data describe a specific link between noradrenergic and purinergic signaling in blood pressure homeostasis.
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Affiliation(s)
- Marie Billaud
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA. Department of Molecular Physiology and Biophysics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Yu-Hsin Chiu
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Alexander W Lohman
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA. Department of Molecular Physiology and Biophysics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Thibaud Parpaite
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Joshua T Butcher
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Stephanie M Mutchler
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Leon J DeLalio
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA. Department of Molecular Physiology and Biophysics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Mykhaylo V Artamonov
- Department of Molecular Physiology and Biophysics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Joanna K Sandilos
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Angela K Best
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Avril V Somlyo
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA. Department of Molecular Physiology and Biophysics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Roger J Thompson
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Thu H Le
- Department of Medicine, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Kodi S Ravichandran
- Center for Cell Clearance, University of Virginia, Charlottesville, VA 22908, USA. Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA 22908, USA. Beirne B. Carter Center for Immunology Research, University of Virginia, Charlottesville, VA 22908, USA
| | - Douglas A Bayliss
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Brant E Isakson
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA. Department of Molecular Physiology and Biophysics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
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193
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Boassa D, Nguyen P, Hu J, Ellisman MH, Sosinsky GE. Pannexin2 oligomers localize in the membranes of endosomal vesicles in mammalian cells while Pannexin1 channels traffic to the plasma membrane. Front Cell Neurosci 2015; 8:468. [PMID: 25698922 PMCID: PMC4313697 DOI: 10.3389/fncel.2014.00468] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Accepted: 12/27/2014] [Indexed: 12/13/2022] Open
Abstract
Pannexin2 (Panx2) is the largest of three members of the pannexin proteins. Pannexins are topologically related to connexins and innexins, but serve different functional roles than forming gap junctions. We previously showed that pannexins form oligomeric channels but unlike connexins and innexins, they form only single membrane channels. High levels of Panx2 mRNA and protein in the Central Nervous System (CNS) have been documented. Whereas Pannexin1 (Panx1) is fairly ubiquitous and Pannexin3 (Panx3) is found in skin and connective tissue, both are fully glycosylated, traffic to the plasma membrane and have functions correlated with extracellular ATP release. Here, we describe trafficking and subcellular localizations of exogenous Panx2 and Panx1 protein expression in MDCK, HeLa, and HEK 293T cells as well as endogenous Panx1 and Panx2 patterns in the CNS. Panx2 was found in intracellular localizations, was partially N-glycosylated, and localizations were non-overlapping with Panx1. Confocal images of hippocampal sections immunolabeled for the astrocytic protein GFAP, Panx1 and Panx2 demonstrated that the two isoforms, Panx1 and Panx2, localized at different subcellular compartments in both astrocytes and neurons. Using recombinant fusions of Panx2 with appended genetic tags developed for correlated light and electron microscopy and then expressed in different cell lines, we determined that Panx2 is localized in the membrane of intracellular vesicles and not in the endoplasmic reticulum as initially indicated by calnexin colocalization experiments. Dual immunofluorescence imaging with protein markers for specific vesicle compartments showed that Panx2 vesicles are early endosomal in origin. In electron tomographic volumes, cross-sections of these vesicles displayed fine structural details and close proximity to actin filaments. Thus, pannexins expressed at different subcellular compartments likely exert distinct functional roles, particularly in the nervous system.
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Affiliation(s)
- Daniela Boassa
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California San Diego, La Jolla, CA, USA
| | - Phuong Nguyen
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California San Diego, La Jolla, CA, USA
| | - Junru Hu
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California San Diego, La Jolla, CA, USA
| | - Mark H Ellisman
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California San Diego, La Jolla, CA, USA ; Department of Neurosciences, University of California San Diego, La Jolla, CA, USA
| | - Gina E Sosinsky
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California San Diego, La Jolla, CA, USA ; Department of Neurosciences, University of California San Diego, La Jolla, CA, USA
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194
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Pannexin-1-mediated ATP release from area CA3 drives mGlu5-dependent neuronal oscillations. Neuropharmacology 2015; 93:219-28. [PMID: 25645390 DOI: 10.1016/j.neuropharm.2015.01.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Revised: 01/12/2015] [Accepted: 01/15/2015] [Indexed: 02/08/2023]
Abstract
The activation of Group I metabotropic glutamate receptors (GI mGluRs) in the hippocampus results in the appearance of persistent bursts of synchronised neuronal activity. In response to other stimuli, such activity is known to cause the release of the purines ATP and its neuroactive metabolite, adenosine. We have thus investigated the potential release and role of the purines during GI mGluR-induced oscillations in rat hippocampal areas CA3 and CA1 using pharmacological techniques and microelectrode biosensors for ATP and adenosine. The GI mGluR agonist DHPG induced both persistent oscillations in neuronal activity and the release of adenosine in areas CA1 and CA3. In contrast, the DHPG-induced release of ATP was only observed in area CA3. Whilst adenosine acting at adenosine A1 receptors suppressed DHPG-induced burst activity, the activation of mGlu5 and P2Y1 ATP receptors were necessary for the induction of DHPG-induced oscillations. Selective inhibition of pannexin-1 hemichannels with a low concentration of carbenoxolone (10 μM) or probenecid (1 mM) did not affect adenosine release in area CA3, but prevented both ATP release in area CA3 and DHPG-induced bursting. These data reveal key aspects of GI mGluR-dependent neuronal activity that are subject to bidirectional regulation by ATP and adenosine in the initiation and pacing of burst firing, respectively, and which have implications for the role of GI mGluRs in seizure activity and neurodevelopmental disorders.
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195
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Davidson J, Green C, Bennet L, Gunn A. Battle of the hemichannels – Connexins and Pannexins in ischemic brain injury. Int J Dev Neurosci 2014; 45:66-74. [DOI: 10.1016/j.ijdevneu.2014.12.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Revised: 12/19/2014] [Accepted: 12/19/2014] [Indexed: 12/20/2022] Open
Affiliation(s)
- J.O. Davidson
- Department of PhysiologyThe University of AucklandAucklandNew Zealand
| | - C.R. Green
- Department of OphthalmologyThe University of AucklandAucklandNew Zealand
| | - L. Bennet
- Department of PhysiologyThe University of AucklandAucklandNew Zealand
| | - A.J. Gunn
- Department of PhysiologyThe University of AucklandAucklandNew Zealand
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196
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Probenecid as a sensitizer of bisphosphonate-mediated effects in breast cancer cells. Mol Cancer 2014; 13:265. [PMID: 25496233 PMCID: PMC4295226 DOI: 10.1186/1476-4598-13-265] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 11/27/2014] [Indexed: 12/17/2022] Open
Abstract
Background Anti-resorptive bisphosphonates (BP) are used for the treatment of osteoporosis and bone metastases. Clinical studies indicated a benefit in survival and tumor relapse in subpopulations of breast cancer patients receiving zoledronic acid, thus stimulating the debate about its anti-tumor activity. Amino-bisphosphonates in nM concentrations inhibit farnesyl pyrophosphate synthase leading to accumulation of isopentenyl pyrophosphate (IPP) and the ATP/pyrophosphate adduct ApppI, which induces apoptosis in osteoclasts. For anti-tumor effects μM concentrations are needed and a sensitizer for bisphosphonate effects would be beneficial in clinical anti-tumor applications. We hypothesized that enhancing intracellular pyrophosphate accumulation via inhibition of probenecid-sensitive channels and transporters would sensitize tumor cells for bisphosphonates anti-tumor efficacy. Method MDA-MB-231, T47D and MCF-7 breast cancer cells were treated with BP (zoledronic acid, risedronate, ibandronate, alendronate) and the pyrophosphate channel inhibitors probenecid and novobiocin. We determined cell viability and caspase 3/7 activity (apoptosis), accumulation of IPP and ApppI, expression of ANKH, PANX1, ABCC1, SLC22A11, and the zoledronic acid target gene and tumor-suppressor KLF2. Results Treatment of MDA-MB-231 with BP induced caspase 3/7 activity, with zoledronic acid being the most effective. In MCF-7 and T47D either BP markedly suppressed cell viability with only minor effects on apoptosis. Co-treatment with probenecid enhanced BP effects on cell viability, IPP/ApppI accumulation as measurable in MCF-7 and T47D cells, caspase 3/7 activity and target gene expression. Novobiocin co-treatment of MDA-MB-231 yielded identical results on viability and apoptosis compared to probenecid, rendering SLC22A family members as candidate modulators of BP effects, whereas no such evidence was found for ANKH, ABCC1 and PANX1. Conclusions In summary, we demonstrate effects of various bisphosphonates on caspase 3/7 activity, cell viability and expression of tumor suppressor genes in breast cancer cells. Blocking probenecid and novobiocin-sensitive channels and transporters enhances BP anti-tumor effects and renders SLC22A family members as good candidates as BP modulators. Further studies will have to unravel if treatment with such BP-sensitizers translates into preclinical and clinical efficacy. Electronic supplementary material The online version of this article (doi:10.1186/1476-4598-13-265) contains supplementary material, which is available to authorized users.
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197
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Orellana JA, Busso D, Ramírez G, Campos M, Rigotti A, Eugenín J, von Bernhardi R. Prenatal nicotine exposure enhances Cx43 and Panx1 unopposed channel activity in brain cells of adult offspring mice fed a high-fat/cholesterol diet. Front Cell Neurosci 2014; 8:403. [PMID: 25520621 PMCID: PMC4251442 DOI: 10.3389/fncel.2014.00403] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Accepted: 11/08/2014] [Indexed: 01/06/2023] Open
Abstract
Nicotine, the most important neuroteratogen of tobacco smoke, can reproduce brain and cognitive disturbances per se when administered prenatally. However, it is still unknown if paracrine signaling among brain cells participates in prenatal nicotine-induced brain impairment of adult offspring. Paracrine signaling is partly mediated by unopposed channels formed by connexins hemichannels (HCs) and pannexins serving as aqueous pores permeable to ions and small signaling molecules, allowing exchange between the intra- and extracellular milieus. Our aim was to address whether prenatal nicotine exposure changes the activity of those channels in adult mice offspring under control conditions or subjected to a second challenge during young ages: high-fat/cholesterol (HFC) diet. To induce prenatal exposure to nicotine, osmotic minipumps were implanted in CF1 pregnant mice at gestational day 5 to deliver nicotine bitartrate or saline (control) solutions. After weaning, offspring of nicotine-treated or untreated pregnant mice were fed ad libitum with chow or HFC diets for 8 weeks. The functional state of connexin 43 (Cx43) and pannexin 1 (Panx1) unopposed channels was evaluated by dye uptake experiments in hippocampal slices from 11-week-old mice. We found that prenatal nicotine increased the opening of Cx43 HCs in astrocytes, and Panx1 channels in microglia and neurons only if offspring mice were fed with HFC diet. Blockade of inducible nitric oxide synthase (iNOS), cyclooxygenase 2 (COX2) and prostaglandin E receptor 1 (EP1), ionotropic ATP receptor type 7 (P2X7) and NMDA receptors, showed differential inhibition of prenatal nicotine-induced channel opening in glial cells and neurons. Importantly, inhibition of the above mentioned enzymes and receptors, or blockade of Cx43 and Panx1 unopposed channels greatly reduced adenosine triphosphate (ATP) and glutamate release from hippocampal slices of prenatally nicotine-exposed offspring. We propose that unregulated gliotransmitter release through Cx43 and Panx1 unopposed channels may participate in brain alterations observed in offspring of mothers exposed to tobacco smoke during pregnancy.
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Affiliation(s)
- Juan A Orellana
- Departamento de Neurología, Escuela de Medicina, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Dolores Busso
- Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile Santiago, Chile ; Centro de Nutrición Molecular y Enfermedades Crónicas, Escuela de Medicina, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Gigliola Ramírez
- Departamento de Neurología, Escuela de Medicina, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Marlys Campos
- Laboratorio de Sistemas Neurales, Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile Santiago, Chile
| | - Attilio Rigotti
- Departamento de Nutrición, Diabetes y Metabolismo, Escuela de Medicina, Pontificia Universidad Católica de Chile Santiago, Chile ; Centro de Nutrición Molecular y Enfermedades Crónicas, Escuela de Medicina, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Jaime Eugenín
- Laboratorio de Sistemas Neurales, Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile Santiago, Chile
| | - Rommy von Bernhardi
- Departamento de Neurología, Escuela de Medicina, Pontificia Universidad Católica de Chile Santiago, Chile
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198
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Mondal P, Trigun SK. Pannexin1 as a novel cerebral target in pathogenesis of hepatic encephalopathy. Metab Brain Dis 2014; 29:1007-15. [PMID: 24807590 DOI: 10.1007/s11011-014-9556-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Accepted: 04/28/2014] [Indexed: 12/11/2022]
Abstract
Hepatic encephalopathy (HE) represents a nervous system disorder caused due to liver dysfunction. HE is broadly classified as acute/overt and moderate-minimal HE. Since HE syndrome severely affects quality of life of the patients and it may be life threatening, it is important to develop effective therapeutic strategy against HE. Mainly ammonia neurotoxicity is considered accountable for HE. Increased level of ammonia in the brain activates glutamate-NMDA (N-methyl-D-aspartate) receptor (NMDAR) pathway leading to Ca(2+) influx, energy deficit and oxidative stress in the post synaptic neurons. Moreover, NMDAR blockage has been found to be a poor therapeutic option, as this neurotransmitter receptor plays important role in maintaining normal neurophysiology of the brain. Thus, searching new molecular players in HE pathogenesis is of current concern. There is an evolving concept about roles of the trans-membrane channels in the pathogenesis of a number of neurological complications. Pannexin1 (Panx1) is one of them and has been described to be implicated in stroke, epilepsy and ischemia. Importantly, the pathogenesis of these complications relates to some extent with NMDAR over activation. Thus, it is speculated that HE pathogenesis might also involve Panx1. Indeed, some recent observations in the animal models of HE provide support to this argument. Since opening of Panx1 channel is mostly associated with the neuronal dysfunctions, down regulation of this channel could serve as a relevant therapeutic strategy without producing any serious side effects. In the review article an attempt has been made to summarize the current information on implication of Panx1 in the brain disorders and its prospects for being examined as pharmacological target in HE pathogenesis.
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Affiliation(s)
- Papia Mondal
- Biochemistry Section Centre of Advanced Study in Zoology, Banaras Hindu university, Varanasi, 221005, India
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199
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Differential regulation of cone calcium signals by different horizontal cell feedback mechanisms in the mouse retina. J Neurosci 2014; 34:11826-43. [PMID: 25164677 DOI: 10.1523/jneurosci.0272-14.2014] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Controlling neurotransmitter release by modulating the presynaptic calcium level is a key mechanism to ensure reliable signal transmission from one neuron to the next. In this study, we investigated how the glutamatergic output of cone photoreceptors (cones) in the mouse retina is shaped by different feedback mechanisms from postsynaptic GABAergic horizontal cells (HCs) using a combination of two-photon calcium imaging and pharmacology at the level of individual cone axon terminals. We provide evidence that hemichannel-mediated (putative ephaptic) feedback sets the cone output gain by defining the basal calcium level, a mechanism that may be crucial for adapting cones to the ambient light level. In contrast, pH-mediated feedback did not modulate the cone basal calcium level but affected the size and shape of light-evoked cone calcium signals in a contrast-dependent way: low-contrast light responses were amplified, whereas high-contrast light responses were reduced. Finally, we provide functional evidence that GABA shapes light-evoked calcium signals in cones. Because we could not localize ionotropic GABA receptors on cone axon terminals using electron microscopy, we suggest that GABA may act through GABA autoreceptors on HCs, thereby possibly modulating hemichannel- and/or pH-mediated feedback. Together, our results suggest that at the cone synapse, hemichannel-mediated (ephaptic) and pH-mediated feedback fulfill distinct functions to adjust the output of cones to changing ambient light levels and stimulus contrasts and that the efficacy of these feedback mechanisms is likely modulated by GABA release in the outer retina.
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200
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Activation of neuronal NMDA receptors triggers transient ATP-mediated microglial process outgrowth. J Neurosci 2014; 34:10511-27. [PMID: 25100586 DOI: 10.1523/jneurosci.0405-14.2014] [Citation(s) in RCA: 193] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Microglia are morphologically dynamic cells that rapidly extend their processes in response to various stimuli including extracellular ATP. In this study, we tested the hypothesis that stimulation of neuronal NMDARs trigger ATP release leading to communication with microglia. We used acute mouse hippocampal brain slices and two-photon laser scanning microscopy to study microglial dynamics and developed a novel protocol for fixation and immunolabeling of microglia processes. Similar to direct topical ATP application in vivo, short multiple applications of NMDA triggered transient microglia process outgrowth that was reversible and repeatable indicating that this was not due to excitotoxic damage. Stimulation of NMDAR was required as NMDAR antagonists, but not blockers of AMPA/kainate receptors or voltage-gated sodium channels, prevented microglial outgrowth. We report that ATP release, secondary to NMDAR activation, was the key mediator of this neuron-microglia communication as both blocking purinergic receptors and inhibiting hydrolysis of ATP to prevent locally generated gradients abolished outgrowth. Pharmacological and genetic analyses showed that the NMDA-triggered microglia process extension was independent of Pannexin 1, the ATP releasing channels, ATP release from astrocytes via connexins, and nitric oxide generation. Finally, using whole-cell patch clamping we demonstrate that activation of dendritic NMDAR on single neurons is sufficient to trigger microglia process outgrowth. Our results suggest that dendritic neuronal NMDAR activation triggers ATP release via a Pannexin 1-independent manner that induces outgrowth of microglia processes. This represents a novel uncharacterized form of neuron-microglial communication mediated by ATP.
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