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Lohr C. Role of P2Y receptors in astrocyte physiology and pathophysiology. Neuropharmacology 2023; 223:109311. [PMID: 36328064 DOI: 10.1016/j.neuropharm.2022.109311] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 10/24/2022] [Accepted: 10/27/2022] [Indexed: 11/07/2022]
Abstract
Astrocytes are active constituents of the brain that manage ion homeostasis and metabolic support of neurons and directly tune synaptic transmission and plasticity. Astrocytes express all known P2Y receptors. These regulate a multitude of physiological functions such as cell proliferation, Ca2+ signalling, gliotransmitter release and neurovascular coupling. In addition, P2Y receptors are fundamental in the transition of astrocytes into reactive astrocytes, as occurring in many brain disorders such as neurodegenerative diseases, neuroinflammation and epilepsy. This review summarizes the current literature addressing the function of P2Y receptors in astrocytes in the healthy brain as well as in brain diseases.
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Affiliation(s)
- Christian Lohr
- Institute of Cell and Systems Biology of Animals, University of Hamburg, Germany.
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2
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Verkhratsky A, Parpura V, Vardjan N, Zorec R. Physiology of Astroglia. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1175:45-91. [PMID: 31583584 DOI: 10.1007/978-981-13-9913-8_3] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Astrocytes are principal cells responsible for maintaining the brain homeostasis. Additionally, these glial cells are also involved in homocellular (astrocyte-astrocyte) and heterocellular (astrocyte-other cell types) signalling and metabolism. These astroglial functions require an expression of the assortment of molecules, be that transporters or pumps, to maintain ion concentration gradients across the plasmalemma and the membrane of the endoplasmic reticulum. Astrocytes sense and balance their neurochemical environment via variety of transmitter receptors and transporters. As they are electrically non-excitable, astrocytes display intracellular calcium and sodium fluctuations, which are not only used for operative signalling but can also affect metabolism. In this chapter we discuss the molecules that achieve ionic gradients and underlie astrocyte signalling.
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Affiliation(s)
- Alexei Verkhratsky
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, M13 9PT, UK. .,Faculty of Health and Medical Sciences, Center for Basic and Translational Neuroscience, University of Copenhagen, 2200, Copenhagen, Denmark. .,Achucarro Center for Neuroscience, IKERBASQUE, Basque Foundation for Science, 48011, Bilbao, Spain.
| | - Vladimir Parpura
- Department of Neurobiology, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - Nina Vardjan
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia.,Celica Biomedical, Ljubljana, Slovenia
| | - Robert Zorec
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia.,Celica Biomedical, Ljubljana, Slovenia
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3
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Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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4
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Verkhratsky A, Nedergaard M. Physiology of Astroglia. Physiol Rev 2018; 98:239-389. [PMID: 29351512 PMCID: PMC6050349 DOI: 10.1152/physrev.00042.2016] [Citation(s) in RCA: 952] [Impact Index Per Article: 158.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 03/22/2017] [Accepted: 04/27/2017] [Indexed: 02/07/2023] Open
Abstract
Astrocytes are neural cells of ectodermal, neuroepithelial origin that provide for homeostasis and defense of the central nervous system (CNS). Astrocytes are highly heterogeneous in morphological appearance; they express a multitude of receptors, channels, and membrane transporters. This complement underlies their remarkable adaptive plasticity that defines the functional maintenance of the CNS in development and aging. Astrocytes are tightly integrated into neural networks and act within the context of neural tissue; astrocytes control homeostasis of the CNS at all levels of organization from molecular to the whole organ.
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Affiliation(s)
- Alexei Verkhratsky
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
| | - Maiken Nedergaard
- The University of Manchester , Manchester , United Kingdom ; Achúcarro Basque Center for Neuroscience, IKERBASQUE, Basque Foundation for Science , Bilbao , Spain ; Department of Neuroscience, University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain ; Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark ; and Center for Translational Neuromedicine, University of Rochester Medical Center , Rochester, New York
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Verkhratsky A, Burnstock G. Purinergic and glutamatergic receptors on astroglia. ADVANCES IN NEUROBIOLOGY 2014; 11:55-79. [PMID: 25236724 DOI: 10.1007/978-3-319-08894-5_4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Astroglial cells express many neurotransmitter receptors; the receptors to glutamate and ATP being the most abundant. Here, we provide a concise overview on the expression and main properties of astroglial glutamate receptors (ionotropic receptors represented by AMPA and NMDA subtypes) and metabotropic (mainly mGluR5 and mGluR3 subtypes) and purinoceptors (adenosine receptors of A1, A2A, A2B, and A3 types, ionotropic P2X1/5 and P2X7 subtypes, and metabotropic P2Y purinoceptors). We also discuss the role of these receptors in glial physiology and pathophysiology.
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Affiliation(s)
- Alexei Verkhratsky
- Faculty of Life Sciences, School of Biological Sciences, The University of Manchester, 1.124 Stopford Building, Oxford Road, Manchester, M13 9PT, UK,
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6
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Verkhratsky A. Physiology of neuronal–glial networking. Neurochem Int 2010; 57:332-43. [DOI: 10.1016/j.neuint.2010.02.002] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2009] [Revised: 01/05/2010] [Accepted: 02/01/2010] [Indexed: 10/19/2022]
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Burnstock G, Fredholm BB, North RA, Verkhratsky A. The birth and postnatal development of purinergic signalling. Acta Physiol (Oxf) 2010; 199:93-147. [PMID: 20345419 DOI: 10.1111/j.1748-1716.2010.02114.x] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The purinergic signalling system is one of the most ancient and arguably the most widespread intercellular signalling system in living tissues. In this review we present a detailed account of the early developments and current status of purinergic signalling. We summarize the current knowledge on purinoceptors, their distribution and role in signal transduction in various tissues in physiological and pathophysiological conditions.
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Affiliation(s)
- G Burnstock
- Autonomic Neuroscience Centre, Royal Free and University College Medical School, London, UK.
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8
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Verkhrasky A, Krishtal OA, Burnstock G. Purinoceptors on Neuroglia. Mol Neurobiol 2009; 39:190-208. [DOI: 10.1007/s12035-009-8063-2] [Citation(s) in RCA: 154] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2009] [Accepted: 02/24/2009] [Indexed: 02/06/2023]
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9
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Abdipranoto A, Liu GJ, Werry EL, Bennett MR. Mechanisms of secretion of ATP from cortical astrocytes triggered by uridine triphosphate. Neuroreport 2004; 14:2177-81. [PMID: 14625443 DOI: 10.1097/00001756-200312020-00009] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The mechanisms involved in autocrine ATP release from cultured astrocytes isolated from the rat cortex were investigated using an online bioluminescence technique. Astrocytes released ATP in response to application of 10 microM uridine triphosphate, which was blocked by the non-specific purinergic receptor antagonist suramin. Intracellular pathways of the uridine triphosphate-stimulated ATP release were seen to involve inositol triphosphate and calcium with the assistance of the Golgi-complex and cytoskeleton as the release was inhibited by phospholipase C antagonist lithium, endoplasmic reticulum calcium-dependent ATPase inhibitor thapsigargin, F-actin interruptor cytochalasin D and Golgi-complex interruptor brefeldin A. The uridine triphosphate-stimulated ATP release was also potently blocked by exocytosis inhibitor botulinum toxin A and anion transporter blockers furosemide and glibenclamide. These results suggest that calcium-dependent exocytosis and transportation via anion transporters are the predominant secretion mechanisms for uridine triphosphate-stimulated ATP release from cortical astrocytes.
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Affiliation(s)
- Andrea Abdipranoto
- Department of Physiology and Institute for Biomedical Research, University of Sydney, Australia
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10
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Burnstock G, Knight GE. Cellular Distribution and Functions of P2 Receptor Subtypes in Different Systems. INTERNATIONAL REVIEW OF CYTOLOGY 2004; 240:31-304. [PMID: 15548415 DOI: 10.1016/s0074-7696(04)40002-3] [Citation(s) in RCA: 581] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
This review is aimed at providing readers with a comprehensive reference article about the distribution and function of P2 receptors in all the organs, tissues, and cells in the body. Each section provides an account of the early history of purinergic signaling in the organ?cell up to 1994, then summarizes subsequent evidence for the presence of P2X and P2Y receptor subtype mRNA and proteins as well as functional data, all fully referenced. A section is included describing the plasticity of expression of P2 receptors during development and aging as well as in various pathophysiological conditions. Finally, there is some discussion of possible future developments in the purinergic signaling field.
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Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Institute, Royal Free and University College Medical School, London NW3 2PF, United Kingdom
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11
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Bennett GC, Ford APDW, Smith JAM, Emmett CJ, Webb TE, Boarder MR. P2Y receptor regulation of cultured rat cerebral cortical cells: calcium responses and mRNA expression in neurons and glia. Br J Pharmacol 2003; 139:279-88. [PMID: 12770933 PMCID: PMC1573842 DOI: 10.1038/sj.bjp.0705242] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1 We have investigated increases in cytosolic Ca(2+) in response to nucleotides in mixed rat cerebrocortical cultures (neurons and glia in similar numbers) and in essentially neuron-free glial cultures. 2 In both cultures, the agonist-response profile was 2-methylthioADP(2MeSADP)>2-methylthioATP(2MeSATP)>ADP>ATP>adenosine 5'-O-(3-thiotriphosphate), consistent with a P2Y(1) receptor. The maximal responses to 2MeSADP, 2MeSATP and ADP were identical, but that to ATP was higher. 3 Suramin, pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid, reactive blue 2 (RB2), and adenosine biphosphate (A3P5P) were antagonists with apparent pA(2) values of 5.5 for suramin, 6.4 for RB2, and 4.7 for A3P5P. 4 Single cell imaging divided the cells from the mixed neuronal-glial cultures into two populations: responsive (neurons) and unresponsive (glial cells) to high [K(+)]. The response of cells to nucleotides was almost exclusively limited to those not responsive to high K(+). 5 In the presence of extracellular Mn(2+), the response of the mixed cultures to 30 mM K(+) and 20 micro M Bay K 8644 was attenuated. However, when 2MeSADP was added there was no reduction in response in cultures previously loaded with Mn(2+). This further indicated that the 2MeSADP response was not in the neurons. 6 Reverse transcriptase-polymerase chain reaction studies detected transcripts for P2Y(1), P2Y(4) and P2Y(6) in RNA preparations from embryonic rat cortex, and from both mixed and glial cultures. P2Y(2) transcripts were not detected in the embryonic cortex. 7 Based on this and previous work, it is proposed that the principal P2Y influences in the brain are on cytosolic Ca(2+) in glial cells and presynaptic sites on neurons.
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Affiliation(s)
- Gillian C Bennett
- Neurobiology Unit, Roche Bioscience, 3401 Hillview Avenue, Palo Alto, CA 94304, U.S.A
| | - Anthony P D W Ford
- Neurobiology Unit, Roche Bioscience, 3401 Hillview Avenue, Palo Alto, CA 94304, U.S.A
| | - Jacqueline A M Smith
- Neurobiology Unit, Roche Bioscience, 3401 Hillview Avenue, Palo Alto, CA 94304, U.S.A
| | - Caroline J Emmett
- Neurobiology Unit, Roche Bioscience, 3401 Hillview Avenue, Palo Alto, CA 94304, U.S.A
| | - Tania E Webb
- Cell Signalling Laboratory, School of Pharmacy, The Hawthorn Building, De Montfort University, Leicester LE1 9BH, UK
| | - Michael R Boarder
- Neurobiology Unit, Roche Bioscience, 3401 Hillview Avenue, Palo Alto, CA 94304, U.S.A
- Cell Signalling Laboratory, School of Pharmacy, The Hawthorn Building, De Montfort University, Leicester LE1 9BH, UK
- Author for correspondence:
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12
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James G, Butt AM. P2Y and P2X purinoceptor mediated Ca2+ signalling in glial cell pathology in the central nervous system. Eur J Pharmacol 2002; 447:247-60. [PMID: 12151016 DOI: 10.1016/s0014-2999(02)01756-9] [Citation(s) in RCA: 181] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Activation of purinoceptors by extracellular ATP is an important component of the glial response to injury in the central nervous system (CNS). ATP has been shown to evoke raised cytosolic [Ca(2+)] in astrocytes, oligodendrocytes, and microglia, the three major glial cell types in the CNS. Glial cells express a heterogenous collection of metabotropic P2Y and ionotropic P2X purinoceptors, which respectively mobilise Ca(2+) from intracellular stores and trigger Ca(2+) influx across the plasmalemma. It is likely that different receptors have distinct roles in glial cell physiology and pathology. Our studies on optic nerve glia in situ indicate that P2Y(1) and P2Y(2/4) receptors are activated at low ATP concentrations, suggesting they are the predominant purinoceptors mediating physiological Ca(2+) signalling. Glia also express P2X(1) and P2X(3) purinoceptors, which mediate fast, rapidly desensitising current and may also be important in signalling. At high concentrations, such as occur in CNS injury, ATP induces large and prolonged increases in glial [Ca(2+)](i) with a primary role for P2Y purinoceptors and inositol trisphosphate (IP(3))-dependent release of Ca(2+) from intracellular stores. In addition, we found that high concentrations of ATP activated a significant P2X component that did not desensitise or saturate and was dependent on extracellular Ca(2+). These are characteristic properties of the P2X(7) subtype, and we provide in situ evidence that application of the P2X(7) receptor agonist benzoyl-benzoyl ATP (BzATP) evokes raised [Ca(2+)](i) in optic nerve glia, and that the dye YO-PRO-1, which passes through pore-forming P2X(7) receptors, is taken up by astrocytes, oligodendrocytes and microglia. Glia also express P2X(2) and P2X(4) receptors that are also pore-forming in the presence of sustained high ATP concentrations and which may also be important in the glial injury response. There is evidence that activation of P2 purinoceptors is a key step in triggering reactive changes in glial cells, including expression of immediate early genes, induction of extracellular signal regulated kinase and cyclooxygenase-2, synthesis of phospholipase A(2), release of arachidonic acid, production of prostaglandins and release of interleukins. We show that the ATP-mediated increase in glial [Ca(2+)](i) is potentiated by arachidonic acid and reduced by the inhibition of phospholipase A(2) inhibition. Together, the results implicate ATP as a primary signalling molecule in glial cells and indicate specific roles for P2Y and P2X purinoceptors in glial cell pathology.
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Affiliation(s)
- Greg James
- Centre for Neuroscience Research, GKT Guy's Campus, King's College London, Hodgkin Building, SE1 1UL, London, UK
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James G, Butt AM. P2X and P2Y purinoreceptors mediate ATP-evoked calcium signalling in optic nerve glia in situ. Cell Calcium 2001; 30:251-9. [PMID: 11587549 DOI: 10.1054/ceca.2001.0232] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
It is known that ATP acts as an extracellular messenger mediating Ca2+ signalling in glial cells. Here, the mechanisms involved in the ATP-evoked increase in glial [Ca2+]i were studied in situ, in the acutely isolated rat optic nerve. ATP and agonists for P2X (a,b-metATP) and P2Y (2MeSATP) purinoreceptors triggered raised glial [Ca2+]i, and there was no significant difference between cells identified morphologically as astrocytes and oligodendrocytes. Dose-response curves indicated that P2Y receptors were activated at nanomolar concentrations, whereas P2X purinoreceptors were only activated above 10 microM. The rank order of potency for several agonists indicated optic nerve glia expressed heterogeneous purinoreceptors, with P2Y1< or = P2Y2/4< or = P2X. The ATP evoked increase in [Ca2+]i was reversibly blocked by the P2X/Y purinoreceptor antagonist suramin (100 microM) and markedly reduced by thapsigargin (10 microM), which blocks IP3-dependent release of Ca2+ from intracellular stores. Removal of extracellular Ca2+ reduced the ATP evoked increase in [Ca2+]i and completely blocked its recovery, indicating that refilling of intracellular stores was ultimately dependent on Ca2+ influx from the extracellular milieu. The results implicate ATP as an important signal in CNS white matter astrocytes and oligodendrocytes in situ, and indicate that metabotropic P2Y purinoreceptors mobilize intracellular Ca2+ at physiological concentrations of ATP, whereas ionotropic P2X purinoreceptors induce Ca2+ influx across the plasmalemma only at high concentrations of ATP, such as occur following CNS injury.
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Affiliation(s)
- G James
- Neural Damage & Repair Research Group, Centre for Neuroscience Research, King's College London, London, London, UK
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14
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Lacza Z, Káldi K, Kövecs K, Görlach C, Nagy Z, Sándor P, Benyó Z, Wahl M. Involvement of prostanoid release in the mediation of UTP-induced cerebrovascular contraction in the rat. Brain Res 2001; 896:169-74. [PMID: 11277988 DOI: 10.1016/s0006-8993(01)02083-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The interaction between uridine-5'-triphosphate (UTP) and prostanoids was studied in isolated rat middle cerebral arteries (MCAs). The strong contractions in MCA segments induced by UTP were weakened significantly by indomethacin and more markedly by the thromboxane receptor antagonist ICI 192605. Thromboxane A(2) (TXA(2)) release by MCAs was below the detection limit of the chemiluminescence enzyme immunoassay, but increased TXA(2) formation was detected in basilar arteries in the presence of UTP. Prostacyclin (PGI(2)) formation by MCAs also increased in the presence of UTP. These results suggest that UTP stimulates the release of both TXA(2) and PGI(2) from the rat MCA but the vascular effect of TXA(2) is dominant.
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Affiliation(s)
- Z Lacza
- Department of Physiology, Ludwig-Maximilians University, Munich, Germany
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15
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Bolego C, Centemeri C, Abbracchio MP, Ceruti S, Cattabeni F, Jacobson KA, Puglisi L, Rovati GE, Burnstock G, Nicosia S. Two Distinct P2Y Receptors Are Involved in Purine- and Pyrimidine-Evoked Ca 2+ Elevation in Mammalian Brain Astrocytic Cultures. Drug Dev Res 2001; 52:122-132. [PMID: 38239931 PMCID: PMC10794909 DOI: 10.1002/ddr.1106] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
ATP and 2-methyl-thio-ATP (2-Me-SATP) increase cytosolic calcium concentrations ([Ca2+]i) in rat striatal astrocytes (Centemeri et al. [1997] Br J Pharmacol 121:1700-1706). The aim of the present study was to: (1) characterize pyrimidine-induced [Ca2+]i increases in the same experimental system, and (2) try to identify the multiple P2Y receptor subtypes mediating Ca2+ mobilization. UDP and UTP triggered a concentration-dependent [Ca2+]i elevation (EC50s = 0.58 μM ± 0.4 and 31 μM ± 6, respectively).Pyrimidine-evoked [Ca2+]i elevation was solely due to mobilization from intracellular stores, because: (1) removing calcium from extracellular medium or (2) blocking its influx with Ni2+ did not modify UTP responses; (3) the store-depleting agent thapsigargin completely abolished UTP-evoked [Ca2+]i increments. Guanosine-5'-O-(2-thiodiphosphate) partially inhibited the UTP response, whereas pertussis toxin (PTx) had no effect. The phospholipase C inhibitor U-73122 significantly reduced the UTP-evoked [Ca2+]i rise. Computer-assisted analysis indicated that the UTP and UDP responses are mediated by a single receptor, while ATP and 2-Me-SATP interact with two distinct receptors. The selective P2Y1 receptor antagonist MRS2179 abolished the ATP higher potency component. Sequential challenges with the same nucleotides resulted in almost complete homologous desensitization. Pre-exposure to UTP lowered the subsequent responses to either ATP or 2-Me-SATP. Maximally active concentrations of UTP and ATP were not additive. In conclusion, [Ca2+]i elevation in astrocytes by purines and pyrimidines is mediated by two distinct P2Y receptors, likely the P2Y1 and P2Y6 subtypes.
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Affiliation(s)
- Chiara Bolego
- Department of Pharmacological Sciences, University of Milan, Milan, Italy
| | - Carlo Centemeri
- Department of Pharmacological Sciences, University of Milan, Milan, Italy
| | | | - Stefania Ceruti
- Department of Pharmacological Sciences, University of Milan, Milan, Italy
| | - Flaminio Cattabeni
- Department of Pharmacological Sciences, University of Milan, Milan, Italy
| | - Kenneth A. Jacobson
- Molecular Recognition Section, Laboratory of Bioorganic Chemistry, NIDDK, NIH, Bethesda, Maryland
| | - Lina Puglisi
- Department of Pharmacological Sciences, University of Milan, Milan, Italy
| | - Gian Enrico Rovati
- Department of Pharmacological Sciences, University of Milan, Milan, Italy
| | - Geoffrey Burnstock
- Autonomic Neuroscience Institute, Royal Free Hospital, School of Medicine, London, United Kingdom
| | - Simonetta Nicosia
- Department of Pharmacological Sciences, University of Milan, Milan, Italy
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16
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Lenz G, Gottfried C, Luo Z, Avruch J, Rodnight R, Nie WJ, Kang Y, Neary JT. P(2Y) purinoceptor subtypes recruit different mek activators in astrocytes. Br J Pharmacol 2000; 129:927-36. [PMID: 10696092 PMCID: PMC1571921 DOI: 10.1038/sj.bjp.0703138] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/1999] [Revised: 12/03/1999] [Accepted: 12/07/1999] [Indexed: 11/09/2022] Open
Abstract
Extracellular ATP can function as a glial trophic factor as well as a neuronal transmitter. In astrocytes, mitogenic signalling by ATP is mediated by metabotropic P(2Y) receptors that are linked to the extracellular signal regulated protein kinase (Erk) cascade, but the types of P(2Y) receptors expressed in astrocytes have not been defined and it is not known whether all P(2Y) receptor subtypes are coupled to Erk by identical or distinct signalling pathways. We found that the P(2Y) receptor agonists ATP, ADP, UTP and 2-methylthioATP (2MeSATP) activated Erk and its upstream activator MAP/Erk kinase (Mek). cRaf-1, the first kinase in the Erk cascade, was activated by 2MeSATP, ADP and UTP but, surprisingly, cRaf-1 was not stimulated by ATP. Furthermore, ATP did not activate B-Raf, the major isoform of Raf in the brain, nor other Mek activators such as Mek kinase 1 (MekK1) and MekK2/3. Reverse transcriptase-polymerase chain reaction (RT - PCR) studies using primer pairs for cloned rat P(2Y) receptors revealed that rat cortical astrocytes express P(2Y(1)), a receptor subtype stimulated by ATP and ADP and their 2MeS analogues, as well as P(2Y(2)) and P(2Y(4)), subtypes in rats for which ATP and UTP are equipotent. Transcripts for P(2Y(6)), a pyrimidine-preferring receptor, were not detected. ATP did not increase cyclic AMP levels, suggesting that P(2Y(11)), an ATP-preferring receptor, is not expressed or is not linked to adenylyl cyclase in rat cortical astrocytes. These signal transduction and RT - PCR experiments reveal differences in the activation of cRaf-1 by P(2Y) receptor agonists that are inconsistent with properties of the P(2Y(1)), P(2Y(2)) and P(2Y(4)) receptors shown to be expressed in astrocytes, i.e. ATP=UTP; ATP=2MeSATP, ADP. This suggests that the properties of the native P(2Y) receptors coupled to the Erk cascade differ from the recombinant P(2Y) receptors or that astrocytes express novel purine-preferring and pyrimidine-preferring receptors coupled to the ERK cascade.
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Affiliation(s)
- Guido Lenz
- Department of Biophysics, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Carmem Gottfried
- Department of Biochemistry, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Zhijun Luo
- Diabetes Unit Medical Services, Massachusetts General Hospital, Boston, Massachusetts, U.S.A
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, U.S.A
- Department of Medicine, Harvard Medical School, Boston, Massachusetts, U.S.A
| | - Joseph Avruch
- Diabetes Unit Medical Services, Massachusetts General Hospital, Boston, Massachusetts, U.S.A
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, U.S.A
- Department of Medicine, Harvard Medical School, Boston, Massachusetts, U.S.A
| | - Richard Rodnight
- Department of Biochemistry, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Wie-Jia Nie
- Research Service, Veterans Affairs Medical Center, Miami, Florida, U.S.A
| | - Yuan Kang
- Research Service, Veterans Affairs Medical Center, Miami, Florida, U.S.A
| | - Joseph T Neary
- Research Service, Veterans Affairs Medical Center, Miami, Florida, U.S.A
- Department of Pathology, University of Miami, School of Medicine, Miami, Florida, U.S.A
- Department of Biochemistry & Molecular Biology, University of Miami, School of Medicine, Miami, Florida, U.S.A
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17
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Mitogenic signaling by ATP/P2Y purinergic receptors in astrocytes: involvement of a calcium-independent protein kinase C, extracellular signal-regulated protein kinase pathway distinct from the phosphatidylinositol-specific phospholipase C/calcium pathway. J Neurosci 1999. [PMID: 10341225 DOI: 10.1523/jneurosci.19-11-04211.1999] [Citation(s) in RCA: 158] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Activation of ATP/P2Y purinergic receptors stimulates proliferation of astrocytes, but the mitogenic signaling pathway linked to these G-protein-coupled receptors is unknown. We have investigated the role of extracellular signal-regulated protein kinase (ERK) in P2Y receptor-stimulated mitogenic signaling as well as the pathway that couples P2Y receptors to ERK. Downregulation of protein kinase C (PKC) in primary cultures of rat cerebral cortical astrocytes greatly reduced the ability of extracellular ATP to stimulate ERK. Because occupancy of P2Y receptors also leads to inositol phosphate formation, calcium mobilization, and PKC activation, we explored the possibility that signaling from P2Y receptors to ERK is mediated by a phosphatidylinositol-specific phospholipase C (PI-PLC)/calcium pathway. However, neither inhibition of PI-PLC nor chelation of calcium significantly reduced ATP-stimulated ERK activity. Moreover, a preferential inhibitor of calcium-dependent PKC isoforms, Gö 6976, was significantly less effective in blocking ATP-stimulated ERK activity than GF102903X, an inhibitor of both calcium-dependent and -independent PKC isoforms. Furthermore, ATP stimulated a rapid translocation of PKCdelta, a calcium-independent PKC isoform, but not PKCgamma, a calcium-dependent PKC isoform. ATP also stimulated a rapid increase in choline, and inhibition of phosphatidylcholine hydrolysis blocked ATP-evoked ERK activation. These results indicate that P2Y receptors in astrocytes are coupled independently to PI-PLC/calcium and ERK pathways and suggest that signaling from P2Y receptors to ERK involves a calcium-independent PKC isoform and hydrolysis of phosphatidylcholine by phospholipase D. In addition, we found that inhibition of ERK activation blocked extracellular ATP-stimulated DNA synthesis, thereby indicating that the ERK pathway mediates mitogenic signaling by P2Y receptors.
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18
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Langley D, Pearce B. Pyrimidine nucleotide-stimulated thromboxane A2 release from cultured glia. Cell Mol Neurobiol 1998; 18:477-86. [PMID: 9777248 DOI: 10.1023/a:1026323208437] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
1. Uridine triphosphate (UTP), uridine diphosphate (UDP), cytidine triphosphate (CTP), and deoxythymidine triphosphate (TTP) caused concentration-dependent increases in the release of thromboxane A2 (TXA2) from cultured glia prepared from the newborn rat cerebral cortex. Although each of the pyrimidine nucleotides displayed similar potencies, CTP and TTP were considerably less effective than either UTP or UDP. The purine nucleotide ATP was equally as potent as the pyrimidine nucleotides but was marginally less effective than either UTP or UDP. 2. The ability of UTP, UDP, TTP, and CTP to promote TXA2 release from cultured glia was inhibited in a concentration-dependent manner by suramin and was markedly reduced when incubations were performed either in Ca(2+)-free medium or on cultures which had been maintained in serum-free growth medium for 4 days prior to experimentation. 3. Challenges with UTP and UDP in combination were found to elicit a response which was no different from the effects of these nucleotides alone; in addition, their effects were reversed by the phospholipase A2 inhibitor ONO-RS-082. A slight reduction in UTP- and UDP-stimulated TXA2 release was observed in cultures grown in the presence of leucine methyl ester, a treatment reported to limit microglial survival. 4. These results suggest that glia are targets for extracellular pyrimidine nucleotides and that their ability to release eicosanoids from these cells may be important in the brain's response to damage.
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Affiliation(s)
- D Langley
- Department of Pharmacology, School of Pharmacy, London, UK
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19
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Idestrup CP, Salter MW. P2Y and P2U receptors differentially release intracellular Ca2+ via the phospholipase c/inositol 1,4,5-triphosphate pathway in astrocytes from the dorsal spinal cord. Neuroscience 1998; 86:913-23. [PMID: 9692727 DOI: 10.1016/s0306-4522(98)00128-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
In astrocytes, raising intracellular Ca2+ concentration is a principal mechanism for transducing extracellular signals following activation of cell-surface receptors. Receptors that may be activated by purine nucleotides, P2 receptors, are known to be expressed by astrocytes from dorsal spinal cord; these astrocytes express two distinct subtypes of P2 receptor, P2Y and P2U. A main goal of the present study was to determine the intracellular signalling pathways mediating the Ca2+ responses produced by stimulating these receptors. Experiments were done using cultured astrocytes from rat dorsal spinal cord. Ca2+ responses were evoked by 2-methylthio-ATP or UTP, nucleotides previously shown to selectively activate P2Y and P2U receptors, respectively, in these cells. P2Y- and P2U-evoked Ca2+ responses were found not to depend upon extracellular Ca2+ and were blocked by thapsigargin, a Ca2+-ATPase inhibitor known to deplete inositol 1,4,5-triphosphate-sensitive Ca2+ stores. Intracellular application of the inositol 1,4,5-triphosphate-sensitive receptor antagonist, heparin, or of the G-protein inhibitor guanosine 5'-O-(2-thiodiphosphate), blocked the P2Y- and P2U-evoked Ca2+ responses. Moreover, the responses were prevented by the phospholipase C inhibitor, U-73122, but were unaffected by the inactive analogue, U-73343. These results indicate that P2Y and P2U receptors on dorsal spinal astrocytes are linked via G-protein coupling to release of intracellular Ca2+ via the phospholipase C/inositol 1,4,5-triphosphate pathway. When we assessed the releasable pools of intracellular Ca2+, by repeated agonist applications in zero extracellular Ca2+, we found that the pool accessed by activating P2U receptors was only a subpool of that accessed by activating P2Y receptors. This implies that there are separable inositol 1,4,5-triphosphate-releasable pools of Ca2+ in dorsal spinal astrocytes and that these may be differentially released by activating distinct metabotropic P2 receptors. This differential release of Ca2+ may be important for physiological as well as pathophysiological events occurring within the spinal cord.
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MESH Headings
- Adenosine Triphosphate/analogs & derivatives
- Adenosine Triphosphate/pharmacology
- Animals
- Astrocytes/cytology
- Astrocytes/drug effects
- Astrocytes/physiology
- Calcium/metabolism
- Calcium Channels/chemistry
- Calcium Channels/physiology
- Cells, Cultured
- Embryo, Mammalian
- Estrenes/pharmacology
- GTP-Binding Proteins/antagonists & inhibitors
- Guanosine Diphosphate/analogs & derivatives
- Guanosine Diphosphate/pharmacology
- Heparin/analogs & derivatives
- Heparin/pharmacology
- Inositol 1,4,5-Trisphosphate/metabolism
- Inositol 1,4,5-Trisphosphate Receptors
- Phosphodiesterase Inhibitors/pharmacology
- Pyrrolidinones/pharmacology
- Rats
- Rats, Wistar
- Receptors, Cytoplasmic and Nuclear/chemistry
- Receptors, Cytoplasmic and Nuclear/physiology
- Receptors, Purinergic P2/physiology
- Receptors, Purinergic P2Y2
- Signal Transduction
- Spinal Cord/cytology
- Spinal Cord/physiology
- Thionucleotides/pharmacology
- Type C Phospholipases/metabolism
- Uridine Triphosphate/pharmacology
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Affiliation(s)
- C P Idestrup
- Hospital for Sick Children, Department of Physiology, University of Toronto, Ontario, Canada
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20
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Abstract
ATP-induced arachidonic acid (AA) release was studied in [3H]AA-prelabeled cultured astrocytes. To characterize the P2 purinoceptor-mediated effect of ATP, the subtype-specific agonists 2-methylthio ATP (2-MeSATP) and UTP were compared. ATP, UTP, or 2-MeSATP induced a dose-dependent increase of [3H]AA release, with EC50 values of 22.7 microM, 29.4 microM, and 1.68 microM, respectively; alpha,beta-methyleneATP and adenosine had no effect. The order of potency was ATP = UTP > or = 2-MeSATP, indicating that ATP interacted with both P2Y1 and P2Y2 receptors to mediate AA release in astrocytes. The effect of ATP, UTP, or 2-MeSATP was markedly inhibited by pretreatment of cells with pertussis toxin. Ca2+ ionophore-A23187 and PKC activator-TPA mimicked the effects of these three agonists to stimulate AA release. ATP, UTP, and 2-MeSATP induced a rapidly initial rise of [Ca2+]i and a sustained [Ca2+]i increase. The AA release was blocked in the external Ca2+ free in condition the sustained [Ca2+]i increase was abolished. Both A23187- and TPA-induced AA release were also blocked in this condition. Furthermore, inorganic Ca2+ channel blocker Co2+ inhibited ATP, UTP, or 2-MeSATP induced AA release as well. Long-term (24 h) treatment of cells with TPA resulted in an attenuation of three agonists, TPA or A23187 response. Similarly, ATP or TPA promoted AA release was inhibited by the mitogen-activated protein kinase (MAPK) cascade inhibitor PD 98059. ATP, TPA, or A23187 induced an increase in the activity and tyrosine phosphorylation of p42 MAPK, as well as a molecular weight shift, consistent with phosphorylation, of cytosolic phospholipase A2 (cPLA2). ATP- and TPA-stimulated activation of p42 MAPK activity and tyrosine phosphorylation were inhibited by long-term TPA treatment, while A23187-stimulated effects were completely blocked. Furthermore, tyrosine phosphorylation and activation of p42 MAPK and mobility shift of cPLA2 induced by A23187 were reversed in the absence of external Ca2+, suggesting the involvement of PKCalpha in MAPK activation and mobility shift of cPLA2. Taken together, ATP-stimulated AA release was secondary to the activation of P2Y1 and P2Y2 receptors/PLC pathway. Ca2+ and PKC interact to regulate this response. Elevation of intracellular Ca2+, the mechanism involving extracellular Ca2+ influx, might act partly through PKCalpha activation and in turn MAPK might be activated, leading to cPLA2 phosphorylation and AA release.
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Affiliation(s)
- W C Chen
- Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei
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21
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Abstract
Glial cells respond to various electrical, mechanical, and chemical stimuli, including neurotransmitters, neuromodulators, and hormones, with an increase in intracellular Ca2+ concentration ([Ca2+]i). The increases exhibit a variety of temporal and spatial patterns. These [Ca2+]i responses result from the coordinated activity of a number of molecular cascades responsible for Ca2+ movement into or out of the cytoplasm either by way of the extracellular space or intracellular stores. Transplasmalemmal Ca2+ movements may be controlled by several types of voltage- and ligand-gated Ca(2+)-permeable channels as well as Ca2+ pumps and a Na+/Ca2+ exchanger. In addition, glial cells express various metabotropic receptors coupled to intracellular Ca2+ stores through the intracellular messenger inositol 1,4,5-triphosphate. The interplay of different molecular cascades enables the development of agonist-specific patterns of Ca2+ responses. Such agonist specificity may provide a means for intracellular and intercellular information coding. Calcium signals can traverse gap junctions between glial cells without decrement. These waves can serve as a substrate for integration of glial activity. By controlling gap junction conductance, Ca2+ waves may define the limits of functional glial networks. Neuronal activity can trigger [Ca2+]i signals in apposed glial cells, and moreover, there is some evidence that glial [Ca2+]i waves can affect neurons. Glial Ca2+ signaling can be regarded as a form of glial excitability.
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Affiliation(s)
- A Verkhratsky
- Department of Cellular Neurosciences, Max-Delbrück Center for Molecular Medicine, Berlin-Buch, Germany
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22
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Reetz G, Wiesinger H, Reiser G. ATP-induced oscillations of cytosolic Ca2+ activity in cultured astrocytes from rat brain are modulated by medium osmolarity indicating a control of [Ca2+]i oscillations by cell volume. Neurochem Res 1997; 22:621-8. [PMID: 9131642 DOI: 10.1023/a:1022430305491] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Oscillations of cytosolic Ca2+ activity ([Ca2+]i) induced by stimulation with ATP in rat astrocytes in primary cultures were analysed. Astrocytes, prepared from the brains of newborn rats, loaded with the fluorescent Ca2+ indicator fura-2/AM, were continuously stimulated with ATP (10 microM). ATP caused a large initial [Ca2+]i peak, followed by regular [Ca2+]i oscillations (frequencies 1-5/min). Astrocytes were identified by glial fibrillary acidic protein staining of cells after [Ca2+]i recording. The oscillations were reversibly blocked by the P2 purinoceptor antagonist suramin (30 microM). Influx of extracellular Ca2+ and mobilization of Ca2+ from intracellular stores both contributed to the oscillations. The effects of hypertonic and hypotonic superfusion medium on ATP-induced [Ca2+]i oscillations were examined. Hypertonic medium (430 mOsm) reversibly suppressed the ATP-induced oscillations. Hypotonic medium (250 mOsm), in spite of having heterogeneous effects, most frequently induced a rise in [Ca2+]i or reversibly increased the frequency of the oscillations. Thus, a change in cell volume might be closely connected with [Ca2+]i oscillations in astrocytes indicating that [Ca2+]i oscillations in glial cells play an important role in regulatory volume regulation in the brain.
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Affiliation(s)
- G Reetz
- Institut für Neurobiochemie Medizinische Fakultät der Otto-von-Guericke-Universität Magdeburg, Germany
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23
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Mateo J, Miras-Portugal MT, Castro E. Co-existence of P2Y-and PPADS-insensitive P2U-purinoceptors in endothelial cells from adrenal medulla. Br J Pharmacol 1996; 119:1223-32. [PMID: 8937727 PMCID: PMC1915897 DOI: 10.1111/j.1476-5381.1996.tb16026.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
1. We have studied the effects of purinoceptor stimulation on Ca2+ signals in bovine adrenomedullary endothelial cells. [Ca2+]i was determined with the fluorescent probe fura-2 both in population samples and in single, isolated, endothelial cells in primary culture and after subculturing. 2. In endothelial cells, maintained in culture for more than one passage, several purinoceptor agonists elicited clear [Ca2+]i transient peaks that remained in the absence of extracellular Ca2+. Adenosine 5'-triphosphate (ATP) and uridine 5'-triphosphate (UTP) were equipotently active, with EC50 values of 8.5 +/- 0.9 microM and 6.9 +/- 1.5 microM, respectively, whereas 2-methylthioadenosine 5'-triphosphate (2MeSATP), adenosine 5'-(alpha, beta-methylene)triphosphate (alpha, beta-MeATP) and adenosine(5')tetraphospho(5')adenosine (Ap4A) were basically inactive. Adenosine 5'-O-(2-thiodiphosphate) (ADP beta S) was a weak agonist. The apparent potency order was UTP = ATP > ADP beta S >> 2MeSATP > alpha, beta-MeATP. 3. Cross-desensitization experiments revealed that UTP or ATP, added sequentially at concentrations of maximal effect, could completely abolish the [Ca2+]i response to the second agonist. ADP beta S exerted only a partial desensitization of the response to maximal ATP, in accordance with its lower potency in raising [Ca2+]i. 4. The effect on [Ca2+]i of 100 microM ATP in subcultured cells was reduced by only 25% with 100 microM suramin pretreatment and was negligibly affected by exposure to 10 microM pyridoxalphosphate-6-azophenyl-2', 4'-disulphonic acid (PPADS). The concentration-effect curve for ATP was not significantly affected by PPADS, but was displaced to the right by a factor of 6.5 by 100 microM suramin. 5. In primary cultures, clear [Ca2+]i responses were elicited by 2MeSATP. Suramin totally and selectively blocked 2MeSATP responses, whereas UTP-evoked [Ca2+]i transients were mainly unaffected by suramin or PPADS. Over 80% of cells tested showed responses to both 2MeSATP and UTP. The [Ca2+]i response to UTP was not desensitized in the presence of 2MeSATP. 6. ATP and UTP stimulated the release of preloaded [3H]-arachidonic acid ([3H]-AA), both in the presence and in the absence of extracellular Ca2+, by approximately 135% with respect to basal levels. Suramin and PPADS enhanced, rather than inhibited, the [3H]-AA releasing effect of ATP by 2.5 times. Suramin also potentiated the effect of the calcium ionophore A23187. 7. These results indicate that endothelial cells from adrenomedullary capillaries co-express both P2Y- and P2U-purinoceptors. P2Y-purinoceptors are lost in culture with the first passage of the cells. The P2U-purinoceptor subtype present in these cells is insensitive to PPADS and thus similar to that found in aortic endothelial cells.
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Affiliation(s)
- J Mateo
- Departamento de Bioquímica y Biología Molecular IV, Universidad Complutense de Madrid, Spain
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24
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King BF, Neary JT, Zhu Q, Wang S, Norenberg MD, Burnstock G. P2 purinoceptors in rat cortical astrocytes: expression, calcium-imaging and signalling studies. Neuroscience 1996; 74:1187-96. [PMID: 8895885 DOI: 10.1016/0306-4522(96)00209-6] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Extracellular ATP is known to activate intracellular enzymes in astrocytes via P2 purinoceptors that appear to play important physiological and pathological roles in these supporting brain cells. In this study, major P2 purinoceptor subtypes on astrocytes of neonatal rat cerebral cortices were identified in receptor expression experiments, when astrocytic messenger RNA was injected into Xenopus oocytes and recombinant P2 purinoceptors were characterized pharmacologically. In messenger RNA-injected oocytes, ATP evoked inward chloride currents (ICl,Ca) typical of stimulating metabotropic receptors that release intracellular Ca2+. Half-maximal activation with ATP occurred at 40 nM: the Hill coefficient was 0.5, which indicated that ATP stimulated two subtypes of P2 purinoceptor. UTP and 2-methylthioATP were the most active (and equipotent) of a series of nucleotides activating recombinant P2 purinoceptors. These results indicated that the two P2 purinoceptors expressed by astrocytic messenger RNA were of P2U and P2Y subtypes. Responses to ATP were antagonized by the P2 purinoceptor antagonist (suramin) but not by the P1 purinoceptor blocker (sulphophenyltheophylline). Findings in expression studies were confirmed in assays of intracellular signalling systems using primary cultures of rat astrocytes. UTP and 2-methylthioATP stimulated mitogen-activated protein kinase to the same extent as ATP, although UTP was less potent than either ATP or 2-methylthioATP. Both UTP and ATP increased intracellular Ca2+ (as measured by fura-2/AM luminescence) which, in cross-desensitization experiments, indicated the involvement of two subtypes of P2 purinoceptors. In conclusion, rat cortical astrocytes express two major subtypes (P2U and P2Y) of metabotropic ATP receptor which, when activated, raise intracellular Ca2+ and also stimulate mitogen-activated protein kinase.
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Affiliation(s)
- B F King
- Department of Anatomy and Developmental Biology, University College London, U.K
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25
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Chen CC, Chen WC. ATP-evoked inositol phosphates formation through activation of P2U purinergic receptors in cultured astrocytes: regulation by PKC subtypes alpha, delta, and theta. Glia 1996; 17:63-71. [PMID: 8723843 DOI: 10.1002/(sici)1098-1136(199605)17:1<63::aid-glia6>3.0.co;2-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
ATP-induced phosphoinositide (PI) hydrolysis was studied in cultured astrocytes. To characterize the P2 purinergic receptor-mediated effects of ATP, the subtype-specific agonists 2-methylthio ATP (2-MeSATP), UTP, and alpha, beta-methylene ATP were compared. ATP, UTP, or 2-MeSATP induced a dose-dependent increase of inositol phosphates (IP) accumulation; alpha, beta-methylene ATP and adenosine had no effect. The order of potency was ATP > or = UTP >> 2-MeSATP. Cross-desensitization experiments indicated that ATP interacted with both P2U and P2Y receptors. P2U was the predominant P2 receptor in mediating PI hydrolysis in astrocytes. The effect of ATP, UTP, or 2-MeSATP was markedly inhibited by pretreatment of cells with pertussis toxin (PTX), indicating that both P2U and P2Y receptors coupled to phospholipase C through PTX-sensitive G protein. Short-term (10 min) treatment of cells with 1 microM TPA attenuated ATP, UTP, and 2-MeSATP-induced PI breakdown; however, long-term (24 h) pretreatment resulted in marked potentiation of both ATP and UTP, and restoration of 2-MeSATP responses. In a further analysis of the effect of TPA, 10 min and 1.5 h pretreatment attenuated ATP-and UTP-induced PI breakdown, but this inhibitory action was lost after 3 h of treatment. Both 6 and 24 h pretreatments resulted in a potentiation. Western blot analysis showed translocation of protein kinase C (PKC) alpha, -delta, and -theta from the cytosol to the membrane following 10 min and 1.5 h treatments, and restoration to basal levels in the membrane fraction was seen after 3 h of treatment. On the other hand, partial and complete down-regulation of these three isoforms was seen after 6 and 24 h of treatment, respectively. PKC eta was translocated but not down-regulated by TPA. These results suggested that PKC alpha, -delta, and -theta, not -eta may exert tonic inhibition on P2U receptor-mediated PI turnover in unstimulated astrocytes.
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Affiliation(s)
- C C Chen
- Institute of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan
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26
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Abstract
Microfluorimetric techniques were used to measure changes in intracellular calcium in astrocytes cultured from the forebrain of the adult rat. Application of ATP consistently raised intracellular calcium. The response persisted in the absence of extracellular calcium, but then quickly declined upon repeated agonist application. Thapsigargin abolished responses to nucleotides following depletion of the endoplasmic reticular calcium stores. Calcium release was inhibited by caffeine, but was dramatically increased through inositol phosphate receptor sensitization by the sulphydryl reagent thimerosal. Responses to repeated nucleotide applications resulted in a gradual decline of peak calcium concentrations, suggesting a (post)receptor-mediated desensitization or gradual depletion of the internal calcium stores. Subsequent application of ionomycin suggested intracellular calcium depletion as the relevant mechanism. Depletion of the internal calcium stores with ATP, ionomycin or thapsigargin failed to reveal a calcium influx pathway. These results suggest that the capacitative mechanism of calcium entry does not operate in response to nucleotide receptor activation in these cells, and that the immediate refilling of the internal calcium stores is primarily determined by re-uptake of cytosolic calcium into the endoplasmic reticulum. A complete refilling of this calcium store by extracellular calcium may be a much slower process. Control of these signal transduction pathways is crucial to the maintenance of the calcium/energy homeostasis of the adult astrocyte in the central nervous system.
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Affiliation(s)
- S Peuchen
- Department of Neurochemistry, Institute of Neurology, London, UK
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27
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Czubayko U, Reiser G. P2U nucleotide receptor activation in rat glial cell line induces [Ca2+]i oscillations which depend on cytosolic pH. Glia 1996; 16:108-16. [PMID: 8929898 DOI: 10.1002/(sici)1098-1136(199602)16:2<108::aid-glia3>3.0.co;2-#] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
In single rat glioma cells, the signal transduction process activated by the UTP sensitive purinergic nucleotide receptor was studied by determining [Ca2+]i by Fura-2 fluorescence and measuring pH by BCECF fluorescence to elucidate the control of [Ca2+]i oscillations by intracellular pH. Addition of UTP for long time periods (some min) causes a [Ca2+]i response composed of i) an initial large peak and a following sustained increase (160 s duration), and ii) subsequent regular [Ca2+]i oscillations (amplitude 107 nM, frequency 1.5 oscillations per min). The maintenance of the [Ca2+]i oscillations depends on the continued presence of agonist. The oscillations are abolished by reducing extracellular Ca2+ concentration. The interaction of UTP receptors and bradykinin receptors during the [Ca2+]i oscillations was investigated because previous studies have already shown that the peptide causes comparable [Ca2+]i oscillations. During [Ca2+]i oscillations induced by UTP or bradykinin, long-term admission of both hormones (400-500 s) causes a large initial response superimposed on regular [Ca2+]i oscillations. Short pulses (12 s) of the second agonist given in any phase of the oscillations induce large [Ca2+]i peaks. In both cases, the following oscillations are not disturbed. The influence of cytosolic pH was studied by alkalinizing pHi by application of NH4Cl. [Ca2+]i oscillations stop after addition of NH4Cl. Recovery of NH4Cl-induced alkalinization is reduced by furosemide. To the same degree, the interruption of [Ca2+]i oscillations is significantly prolonged in the presence of furosemide. Thus cytosolic alkalinization suppresses hormone-induced [Ca2+]i oscillations in rat glioma cells. The understanding of the molecular mechanism of this interference of pH should provide an important contribution for unravelling the function of cytosolic pH in cellular signal transduction.
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Affiliation(s)
- U Czubayko
- Institut fur Neurobiochemie der Otto-von-Guericke-Universitat Magdeburg, Germany
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28
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Neary JT, Rathbone MP, Cattabeni F, Abbracchio MP, Burnstock G. Trophic actions of extracellular nucleotides and nucleosides on glial and neuronal cells. Trends Neurosci 1996; 19:13-8. [PMID: 8787135 DOI: 10.1016/0166-2236(96)81861-3] [Citation(s) in RCA: 359] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In addition to their well-established roles as neurotransmitters and neuromodulators, growing evidence suggests that nucleotides and nucleosides might also act as trophic factors in both the central and peripheral nervous systems. Specific extracellular receptor subtypes for these compounds are expressed on neurons, glial and endothelial cells, where they mediate strikingly different effects. These range from induction of cell differentiation and apoptosis, mitogenesis and morphogenetic changes, to stimulation of synthesis or release, or both, of cytokines and neurotrophic factors, both under physiological and pathological conditions. Nucleotides and nucleosides might be involved in the regulation of development and plasticity of the nervous system, and in the pathophysiology of neurodegenerative disorders. Receptors for nucleotides and nucleosides could represent a novel target for the development of therapeutic strategies to treat incurable diseases of the nervous system, including trauma- and ischemia-associated neurodegeneration, demyelinating and aging-associated cognitive disorders.
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Affiliation(s)
- J T Neary
- Dept of Pathology, University of Miami School of Medicine, FL, USA
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29
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Ho C, Hicks J, Salter MW. A novel P2-purinoceptor expressed by a subpopulation of astrocytes from the dorsal spinal cord of the rat. Br J Pharmacol 1995; 116:2909-18. [PMID: 8680724 PMCID: PMC1909233 DOI: 10.1111/j.1476-5381.1995.tb15944.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
1. Astrocytes from the dorsal spinal cord express P2-purinoceptors which, when stimulated, produce a rise in the intracellular level of free Ca2+ ([Ca2+]i). Previously we have found that the P2Y class of receptor is expressed by nearly all astrocytes from the dorsal horn. To determine whether other metabotropic P2-purinoceptor classes are also present, in this study we investigated the effects of UTP. 2. Application of UTP (1-500 microM, 5-20 s) produced a transient rise in [Ca2+]i in a subpopulation of astrocytes. The magnitude of the peak increase in [Ca2+]i was dependent upon UTP concentration and the EC50 was found to be 5.2 +/- 0.2 microM. Ca2+ responses were maximum at 100 microM UTP. 3. The rise in [Ca2+]i in response to UTP was not affected by removal of extracellular Ca2+. On the other hand, application of the sarcoplasmic-endoplasmic reticulum Ca(2+)-ATPase inhibitor, thapsigargin, abolished responses to UTP. These findings indicate that UTP stimulates the release of Ca2+ from a thapsigargin-sensitive intracellular pool. 4. The Ca2+ response to UTP was unaffected by treatment with pertussis toxin, suggesting that UTP responses may be mediated via a pertussis toxin-insensitive G protein. 5. While all cells tested (n = 52) responded to the P2Y-purinoceptor agonist, 2-methylthio-ATP, only a subpopulation of astrocytes (n = 67/93) was responsive to UTP. The presence of UTP-sensitive and UTP-insensitive cells requires the existence of two discrete types of receptor. One receptor, expressed by UTP-insensitive cells, appears to be activated selectively by 2-methylthio-ATP. 6. To investigate whether UTP and 2-methylthio-ATP activate a common type of receptor in UTP-responsive cells, a cross-desensitization strategy was used. Desensitization with prolonged exposure to a high concentration of 2-methylthio-ATP failed to affect responses to UTP and vice versa, indicating that receptors activated by UTP are distinct from those activated by 2-methylthio-ATP. 7. The P2-purinoceptor antagonist, suramin (100 microM), blocked Ca2+ responses to UTP and to 2-methylthio-ATP. 8. Pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), has been reported to block responses mediated by P2X- and P2Y-purinoceptors in other systems and therefore we investigated its effects on responses to 2-methylthio-ATP and to UTP. PPADS was found to block Ca2+ responses to 2-methylthio-ATP in a concentration-dependent manner with an IC50 of 0.92 +/- 0.1 microM. PPADS also blocked UTP-evoked responses and the IC50 was 7.2 +/- 1.9 microM. At a concentration of 10 microM, PPADS produced a rightward shift in the dose-response curve for UTP and did not affect the maximum response. 9. Calcium responses evoked by the muscarinic agonist, carbachol, were unaffected either by suramin (100 microM) or by PPADS (50 microM). 10. The present results indicate the presence of a novel class of metabotropic P2U-purinoceptor in dorsal spinal astrocytes. In contrast to P2Y-purinoceptors, the P2U-purinoceptor is expressed only by a subpopulation of astrocytes and its sensitivity to suramin and PPADS distinguish this receptor from P2U-purinoceptors found in other tissues.
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Affiliation(s)
- C Ho
- Division of Neuroscience, Hospital for Sick Children, University of Toronto, Canada
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30
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Di Marzo V. Arachidonic acid and eicosanoids as targets and effectors in second messenger interactions. Prostaglandins Leukot Essent Fatty Acids 1995; 53:239-54. [PMID: 8577777 DOI: 10.1016/0952-3278(95)90123-x] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- V Di Marzo
- Istituto per la Chimica di Molecole di Interesse Biologico, C.N.R., Naples, Italy
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31
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Strohmeier GR, Reppert SM, Lencer WI, Madara JL. The A2b adenosine receptor mediates cAMP responses to adenosine receptor agonists in human intestinal epithelia. J Biol Chem 1995; 270:2387-94. [PMID: 7836474 DOI: 10.1074/jbc.270.5.2387] [Citation(s) in RCA: 189] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Adenosine is thought to be a major effector in immunological stimulation of Cl- secretion in intestinal epithelia. Previous studies indicate that both apical and basolateral domains of intestinal epithelial cells possess functionally defined adenosine receptors. However, it is unclear whether the same receptor subclass is expressed, what the receptor subclass(es) is, or how the receptors signal the Cl- secretory response. We now characterize the intestinal epithelial adenosine receptor subtype using the model epithelium, T84. Both apical and basolateral adenosine receptor agonist response profiles revealed a hierarchy (ED50) of 5'-(N-ethylcarboxamido)adenosine > adenosine > CGS-21680. Similarly inhibition studies revealed identical ID50 hierarchies for apical and basolateral antagonism by xanthine amine congener > 1,3-diethyl-8-phenylxanthine > aminophylline. Analyses of both agonist and antagonist pharmacological hierarchies in Chinese hamster ovary cells stably expressing the A2b receptor revealed these same hierarchies. Northern blots performed on RNA extracted from polarized T84 monolayers demonstrated no detectable message for A1 or A2a adenosine receptor, but strong hybridization was detected for the A2b adenosine receptor. Subsequent Northern blots of RNA prepared from human alimentary tract revealed that A2b adenosine receptor message was heavily expressed throughout the colon, in the appendix, and more modestly expressed in the small intestine (ileum). Analyses of cAMP generation in T84 cells in response to adenosine indicated that the basolateral A2b receptor elicits Cl- secretion through this signaling pathway. Stimulation of Cl- secretion through the apical A2b receptor exhibited relatively small but significant increases in cAMP compared with basolateral stimulation. The protein kinase A inhibitor H-89, used at concentrations that did not affect short circuit current responses to the Ca(2+)-mediated agonist carbachol, effectively inhibited short circuit current elicited by either apical or basolateral adenosine. These data suggest that the major intestinal epithelial adenosine receptor is the A2b subclass, which is positively coupled to adenylate cyclase. Such observations have potentially important implications for the treatment of diarrheal diseases.
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Affiliation(s)
- G R Strohmeier
- Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts 02115
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32
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Abstract
There is now wide acceptance that ATP and other nucleotides are ubiquitous extracellular chemical messengers. ATP and diadenosine polyphosphates can be released from synaptosomes. They act on a large and diverse family of P2 purinoceptors, four of which have been cloned. This receptor family can be divided into two distinct classes: ligand-gated ion channels for P2X receptors and G protein-coupled receptors for P2Y, P2U, P2T and P2D receptors. The P2Y, P2U and P2D receptors have a fairly wide tissue distribution, while the P2X receptor is mainly found in neurons and muscles and the P2T and P2Z receptors confined to platelets and immune cells, respectively. Inositol phosphate and calcium signalling appear to be the predominant mechanisms for transducing the G-protein linked P2 receptor signals. Multiple P2 receptors are expressed by neurons and glia in the CNS and also in neuroendocrine cells. ATP and other nucleotides may therefore have important roles not only as a neurotransmitter but also as a neuroendocrine regulatory messenger.
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Affiliation(s)
- Z P Chen
- Department of Medicine, University of Bristol, Bristol Royal Infirmary, UK
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Pearce B, Langley D. Purine- and pyrimidine-stimulated phosphoinositide breakdown and intracellular calcium mobilisation in astrocytes. Brain Res 1994; 660:329-32. [PMID: 7820701 DOI: 10.1016/0006-8993(94)91307-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Phosphoinositide breakdown in cultured cortical astrocytes was assessed by measuring the accumulation of [3H]inositol phosphates (IP's) following incubations with various purines and pyrimidines. Dose-response relationships gave the following order of potency: 2-methylthioadenosine triphosphate (2-MeSATP) > uridine 5'-triphosphate (UTP) > ATP = ADP > inosine 5' triphosphate (ITP). However, 2-MeSATP and UTP were only half as effective as either ATP or ADP in stimulating [3H]IP production. Astrocytes were also challenged with combined additions of maximally effective concentrations of agonists. Responses to ADP plus UTP and 2-MeSATP plus UTP were essentially additive whilst ATP plus UTP evoked a response which was only partially additive. ATP-stimulated [3H]IP accumulation was markedly reduced in the presence of 2-MeSATP suggesting that the latter may be a partial agonist at these receptors. We also examined the ability of ATP and UTP to increase intracellular Ca2+ concentrations in these cells. Greater than 90% of all cells tested responded to ATP with a release from internal Ca2+ stores but less than half of these responded similarly when challenged with UTP. Our results indicate that astrocytes possess both P2Y-purinoceptors and a population of receptors which are also coupled to phosphoinositide metabolism and intracellular Ca2+ mobilisation but recognise ATP and the pyrimidine nucleotide UTP.
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Affiliation(s)
- B Pearce
- Department of Pharmacology, School of Pharmacy, London, UK
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