101
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Kurpius D, Nolley EP, Dailey ME. Purines induce directed migration and rapid homing of microglia to injured pyramidal neurons in developing hippocampus. Glia 2007; 55:873-84. [PMID: 17405148 DOI: 10.1002/glia.20509] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Traumatic CNS injury activates and mobilizes resident parenchymal microglia (MG), which rapidly accumulate near injured neurons where they transform into phagocytes. The mechanisms underlying this rapid 'homing' in situ are unknown. Using time-lapse confocal imaging in acutely excised neonatal hippocampal slices, we show that rapid accumulation of MG near somata of injured pyramidal neurons in the stratum pyramidale (SP) results from directed migration from tissue regions immediately adjacent to (<200 microm from) the SP. Time-lapse sequences also reveal a 'spreading activation wave' wherein MG situated progressively farther from the SP begin to migrate later and exhibit less directional migration toward the SP. Because purines have been implicated in MG activation and chemotaxis, we tested whether ATP/ADP released from injured pyramidal neurons might account for these patterns of MG behavior. Indeed, application of apyrase, which degrades extracellular ATP/ADP, inhibits MG motility and homing to injured neurons in the SP. Moreover, bath application of exogenous ATP/ADP disrupts MG homing by inducing directional migration toward the slice exterior and away from injured neurons. These results indicate that extracellular ATP/ADP is both necessary and sufficient to induce directional migration and rapid homing of neonatal MG to injured neurons in situ. Rapid, ATP/ADP-dependent MG homing may promote clearance of dead and dying cells and help limit secondary damage during the critical first few hours after neuronal injury.
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Affiliation(s)
- Dana Kurpius
- Department of Biological Sciences, The University of Iowa, Iowa City, Iowa 52242-1324, USA
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102
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Abstract
This review is focused on purinergic neurotransmission, i.e., ATP released from nerves as a transmitter or cotransmitter to act as an extracellular signaling molecule on both pre- and postjunctional membranes at neuroeffector junctions and synapses, as well as acting as a trophic factor during development and regeneration. Emphasis is placed on the physiology and pathophysiology of ATP, but extracellular roles of its breakdown product, adenosine, are also considered because of their intimate interactions. The early history of the involvement of ATP in autonomic and skeletal neuromuscular transmission and in activities in the central nervous system and ganglia is reviewed. Brief background information is given about the identification of receptor subtypes for purines and pyrimidines and about ATP storage, release, and ectoenzymatic breakdown. Evidence that ATP is a cotransmitter in most, if not all, peripheral and central neurons is presented, as well as full accounts of neurotransmission and neuromodulation in autonomic and sensory ganglia and in the brain and spinal cord. There is coverage of neuron-glia interactions and of purinergic neuroeffector transmission to nonmuscular cells. To establish the primitive and widespread nature of purinergic neurotransmission, both the ontogeny and phylogeny of purinergic signaling are considered. Finally, the pathophysiology of purinergic neurotransmission in both peripheral and central nervous systems is reviewed, and speculations are made about future developments.
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Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neurscience Centre, Royal Free and University College Medical School, London, UK.
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103
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Kassa RM, Bentivoglio M, Mariotti R. Changes in the expression of P2X1 and P2X2 purinergic receptors in facial motoneurons after nerve lesions in rodents and correlation with motoneuron degeneration. Neurobiol Dis 2007; 25:121-33. [PMID: 17055278 DOI: 10.1016/j.nbd.2006.08.020] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2006] [Revised: 08/10/2006] [Accepted: 08/30/2006] [Indexed: 01/31/2023] Open
Abstract
Involvement of P2X1 and P2X2 purinergic receptors in motoneuron response to injury was investigated with Western blotting and immunohistochemistry and correlated with motoneuron loss, Bcl-2 expression, nitric oxide synthase induction and glial activation. P2X1 was highly induced in rat facial motoneurons after nerve resection, which causes slowly occurring neurodegeneration. P2X1 induction was lower and less persistent after nerve crush, permissive for fiber regeneration. P2X2 expression was found in nuclei of rat facial motoneurons, with nuclear export in the cytoplasm after nerve resection. P2X1 induction in axotomized facial motoneurons was impaired in superoxide dismutase (SOD)1-G93A-mutant mice, a model of motoneuron disease. The data in rats point to a correlation of P2X1 induction with motoneuron degeneration, which also involves P2X2 intracellular changes, rather than with axon regeneration effort. The data in mice show that the SOD1 mutation interferes with injury-elicited P2X1 induction, suggesting alterations of ATP release from mutant motoneurons after damage.
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Affiliation(s)
- Roman M Kassa
- Department of Morphological and Biomedical Sciences, Faculty of Medicine, Strada Le Grazie 8, 37134 Verona, Italy
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104
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Sperlágh B, Illes P. Purinergic modulation of microglial cell activation. Purinergic Signal 2006; 3:117-27. [PMID: 18404425 PMCID: PMC2096753 DOI: 10.1007/s11302-006-9043-x] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2006] [Accepted: 01/13/2006] [Indexed: 01/10/2023] Open
Abstract
Microglial cells are resident macrophages in the brain and their activation is an important part of the brain immune response and the pathology of the major CNS diseases. Microglial activation is triggered by pathological signals and is characterized by morphological changes, proliferation, phagocytosis and the secretion of various cytokines and inflammatory mediators, which could be both destructive and protective for the nervous tissue. Purines are one of the most important mediators which regulate different aspects of microglial function. They could be released to the extracellular space from neurons, astrocytes and from the microglia itself, upon physiological neuronal activity and in response to pathological stimuli and cellular damage. Microglial activation is regulated by various subtypes of nucleotide (P2X, P2Y) and adenosine (A₁, A(₂A) and A₃) receptors, which control ionic conductances, membrane potential, gene transcription, the production of inflammatory mediators and cell survival. Among them, the role of P2X₇ receptors is especially well delineated, but P2X₄, various P2Y, A₁, A(₂A) and A₃ receptors also powerfully participate in the microglial response. The pathological role of microglial purine receptors has also been demonstrated in disease models; e.g., in ischemia, sclerosis multiplex and neuropathic pain. Due to their upregulation and selective activation under pathological conditions, they provide new avenues in the treatment of neurodegenerative and neuroinflammatory illnesses.
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Affiliation(s)
- Beáta Sperlágh
- Department of Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, 1450, Budapest, Hungary
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105
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Bianco F, Ceruti S, Colombo A, Fumagalli M, Ferrari D, Pizzirani C, Matteoli M, Di Virgilio F, Abbracchio MP, Verderio C. A role for P2X7in microglial proliferation. J Neurochem 2006; 99:745-58. [PMID: 16836656 DOI: 10.1111/j.1471-4159.2006.04101.x] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Microglia, glial cells with an immunocompetent role in the CNS, react to stimuli from the surrounding environment with alterations of their phenotypic response. Amongst other activating signals, the endotoxin lipopolysaccharide (LPS) is widely used as a tool to mimic bacterial infection in the CNS. LPS-activated microglia undergo dramatic changes in cell morphology/activity; in particular, they stop proliferating and differentiate from resting to effector cells. Activated microglia also show modifications of purinoreceptor signalling with a significant decrease in P2X(7) expression. In this study, we demonstrate that the down-regulation of the P2X(7) receptor in activated microglia may play an important role in the antiproliferative effect of LPS. Indeed, chronic blockade of the P2X(7) receptor by antagonists (oxidized ATP, KN62 and Brilliant Blue G), or treatment with the ATP-hydrolase apyrase, severely decreases microglial proliferation, down-regulation of P2X(7) receptor expression by small RNA interference (siRNA) decreases cell proliferation, and the proliferation of P2X(7)-deficient N9 clones and primary microglia, in which P2X(7) expression is down-regulated by siRNA, is unaffected by either LPS or P2X(7) antagonists. Furthermore, flow cytometric analysis indicates that exposure to oxidized ATP or treatment with LPS reversibly decreases cell cycle progression, without increasing the percentage of apoptotic cells. Overall, our data show that the P2X(7) receptor plays an important role in controlling microglial proliferation by supporting cell cycle progression.
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106
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Volonté C, Amadio S, D'Ambrosi N, Colpi M, Burnstock G. P2 receptor web: Complexity and fine-tuning. Pharmacol Ther 2006; 112:264-80. [PMID: 16780954 DOI: 10.1016/j.pharmthera.2005.04.012] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2005] [Accepted: 04/12/2005] [Indexed: 12/25/2022]
Abstract
The present review offers a new perspective on a family of receptors, termed P2 receptors, specific for nucleoside tri- and diphosphates of purines/pyrimidines. We emphasize here that while decoding the inputs of various related extracellular ligands, P2 receptors are a clear example of increasing biological complexity. They are represented by 7 ionotropic P2X and 8 metabotropic P2Y receptors; they have very heterogeneous ligands and binding characteristics, molecular properties, transduction mechanisms, cellular localization and protein-protein interactions. While the reason for this sophistication is unknown, a few compelling issues emerge while looking at such a rich variety. We ask, for instance, why so many different receptor subtypes are necessary for triggering biological properties and functions, and if these receptors are more than the sum of their single entities. A first possibility is that newly synthesized P2 proteins are casually located on the cell surface (stochastic hypothesis). Alternatively, distinct subunits are engaged on different cell phenotypes by genetic control (genetic determinism) and/or selective recruitment under physiopathological conditions and epigenetic stimuli (epigenetic determinism). Nevertheless, an appropriate way to both dissect the vast biological scenario and molecular complexity among P2 receptors and to integrate and upgrade their assortment is to regard them as a "combinatorial receptor web", that is, a dynamic architecture of P2 proteins demonstrating economic efficiency and involving a process of "fine-tuning", a mechanism which endorses the dynamic nature of all biological reactions. In the present analysis, we stimulate a scientific query about what contributes to such a vast P2 receptor sophistication.
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Affiliation(s)
- Cinzia Volonté
- Santa Lucia Foundation/CNR, Via Del Fosso di Fiorano 64, 00143 Roma, Italy.
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107
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Visentin S, Nuccio CD, Bellenchi GC. Different patterns of Ca²⁺ signals are induced by low compared to high concentrations of P2Y agonists in microglia. Purinergic Signal 2006; 2:605-17. [PMID: 18404463 PMCID: PMC2096653 DOI: 10.1007/s11302-006-9023-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2005] [Revised: 06/19/2006] [Accepted: 06/19/2006] [Indexed: 01/26/2023] Open
Abstract
Brain-resident macrophages (microglia) are key cellular elements in the preservation of tissue integrity. On the other hand, they can also contribute to the development of pathological events by causing an extensive and inappropriate inflammatory response. A growing number of reports indicate the involvement of nucleotides in the control of microglial functions. With this study on P2Y receptors in rat microglia, we want to contribute to the definition of their expression profile and to the characterisation of their signalling mechanisms leading to Ca2+ movements. Endogenous nucleotides, when applied at a concentration of 100 μM, elicited robust Ca2+ transients, thanks to a panel of metabotropic receptors comprising mainly P2Y2, P2Y6 and P2Y12 subtypes. The involvement of P2Y12 receptors in Ca2+ responses induced by adenine nucleotides was confirmed by the pharmacological and pertussis toxin sensitivity of the response induced by adenosine diphosphate (ADP). Beside the G protein involved, Gi and Gq respectively, adenine and uracil nucleotides differed also for induction by the latter of a capacitative Ca2+ plateau. Moreover, when applied at low (sub-micromolar) concentrations with a long-lasting challenge, uracil nucleotides elicited oscillatory Ca2+ changes with low frequency of occurrence (≤ 1 min−), sometimes superimposed to an extracellular Ca2+-dependent sustained Ca2+ rise. We conclude that different patterns of Ca2+ transients are induced by low (i.e., oscillatory Ca2+ activity) compared to high (i.e., fast release followed by sustained raise) concentrations of nucleotides, which can suggest different roles played by receptor stimulation depending not only on the type but also on the concentration of nucleotides.
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Affiliation(s)
- S Visentin
- Department of Cell Biology and Neuroscience, Section of Degenerative and Inflammatory Neurological Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161, Rome, Italy,
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108
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Abbracchio MP, Burnstock G, Boeynaems JM, Barnard EA, Boyer JL, Kennedy C, Knight GE, Fumagalli M, Gachet C, Jacobson KA, Weisman GA. International Union of Pharmacology LVIII: update on the P2Y G protein-coupled nucleotide receptors: from molecular mechanisms and pathophysiology to therapy. Pharmacol Rev 2006; 58:281-341. [PMID: 16968944 PMCID: PMC3471216 DOI: 10.1124/pr.58.3.3] [Citation(s) in RCA: 987] [Impact Index Per Article: 54.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
There have been many advances in our knowledge about different aspects of P2Y receptor signaling since the last review published by our International Union of Pharmacology subcommittee. More receptor subtypes have been cloned and characterized and most orphan receptors de-orphanized, so that it is now possible to provide a basis for a future subdivision of P2Y receptor subtypes. More is known about the functional elements of the P2Y receptor molecules and the signaling pathways involved, including interactions with ion channels. There have been substantial developments in the design of selective agonists and antagonists to some of the P2Y receptor subtypes. There are new findings about the mechanisms underlying nucleotide release and ectoenzymatic nucleotide breakdown. Interactions between P2Y receptors and receptors to other signaling molecules have been explored as well as P2Y-mediated control of gene transcription. The distribution and roles of P2Y receptor subtypes in many different cell types are better understood and P2Y receptor-related compounds are being explored for therapeutic purposes. These and other advances are discussed in the present review.
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Affiliation(s)
- Maria P Abbracchio
- Department of Pharmacological Sciences, University of Milan, Milan, Italy
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109
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Kurpius D, Wilson N, Fuller L, Hoffman A, Dailey ME. Early activation, motility, and homing of neonatal microglia to injured neurons does not require protein synthesis. Glia 2006; 54:58-70. [PMID: 16715500 DOI: 10.1002/glia.20355] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Neuronal injury in CNS tissues induces a rapid activation and mobilization of resident microglia (MG). It is widely assumed that changes in gene expression drive the morphological transformation of MG and regulate their mobilization during activation. Here, we used acutely excised neonatal rat brain slices to test whether the morphological transformation and homing of MG to injured neurons requires gene expression and de novo protein synthesis. Traumatic injury during excision of live brain tissue slices induces a rapid and transient translocation of a transcription factor, NF-kappaB, to nuclei in MG. This is followed within 4-8 h by an increase in immunolabeling for cell adhesion molecules and lysosomal proteins, accompanied by changes in cell morphology. Application of anisomycin, a protein synthesis inhibitor, prevents the increase in immunolabeling for markers of MG activation but not the morphological transformation. Confocal time-lapse imaging in live tissue slices indicates that MG cell motility (branch extension and retraction) and locomotion are unaffected by anisomycin at early postinjury time-points (<4 h), while at later time-points (4-8 h postinjury) MG locomotion but not motility is inhibited. Thus, activated MG rapidly localize to injured pyramidal neuron cell bodies by 4-h postinjury, even in the presence of anisomycin. Moreover, this early MG activation and homing to injured neurons is unaffected in tissue slices from beta2 integrin deficient mice. These results indicate that gene activation and new protein synthesis coincide with, but are not necessary for, the rapid morphological transformation and early migration-dependent homing of activated MG to injured neurons in CNS tissues.
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Affiliation(s)
- Dana Kurpius
- Department of Biological Sciences, The University of Iowa, Iowa City, 52242, USA
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110
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Färber K, Kettenmann H. Purinergic signaling and microglia. Pflugers Arch 2006; 452:615-21. [PMID: 16791619 DOI: 10.1007/s00424-006-0064-7] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2006] [Accepted: 03/06/2006] [Indexed: 11/25/2022]
Abstract
Microglial cells are considered as the pathologic sensors of the brain. In this paper, we review mechanisms of purinergic signaling in microglia. As ATP is not only considered as a physiological signaling substance but is also elevated in pathology, it is not surprising that microglia express a variety of P2X, P2Y and adenosin receptors. As a rapid physiological event, ATP triggers a cationic conductance, increases the potassium conductance and also elicits a calcium response. As a long-term effect, purinergic receptor activation is linked to the movement of microglial processes and, in the context of pathology, to chemotaxis. The purinoreceptors also modulate the release of substances from microglia, such as cytokines, nitric oxide, or superoxide, which are important in the context of a pathologic response.
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Affiliation(s)
- Katrin Färber
- Cellular Neuroscience, Max-Delbrueck-Center for Molecular Medicine, Robert-Rössle-Strasse 10, 13092, Berlin, Germany
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111
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Abbracchio MP, Ceruti S. Roles of P2 receptors in glial cells: focus on astrocytes. Purinergic Signal 2006; 2:595-604. [PMID: 18404462 PMCID: PMC2096663 DOI: 10.1007/s11302-006-9016-0] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2005] [Revised: 05/15/2006] [Accepted: 05/15/2006] [Indexed: 11/30/2022] Open
Abstract
Central nervous system glial cells release and respond to nucleotides under both physiological and pathological conditions, suggesting that these molecules play key roles in both normal brain function and in repair after damage. In particular, ATP released from astrocytes activates P2 receptors on astrocytes and other brain cells, allowing a form of homotypic and heterotypic signalling, which also involves microglia, neurons and oligodendrocytes. Multiple P2X and P2Y receptors are expressed by both astrocytes and microglia; however, these receptors are differentially recruited by nucleotides, depending upon specific pathophysiological conditions, and also mediate the long-term trophic changes of these cells during inflammatory gliosis. In astrocytes, P2-receptor-induced gliosis occurs via activation of the extracellular-regulated kinases (ERK) and protein kinase B/Akt pathways and involves induction of inflammatory and anti-inflammatory genes, cyclins, adhesion and antiapoptotic molecules. While astrocytic P2Y1 and P2Y2,4 are primarily involved in short-term calcium-dependent signalling, multiple P2 receptor subtypes seem to cooperate to astrocytic long-term changes. Conversely, in microglia, exposure to inflammatory and immunological stimuli results in differential functional changes of distinct P2 receptors, suggesting highly specific roles in acquisition of the activated phenotype. We believe that nucleotide-induced activation of astrocytes and microglia may originally start as a defence mechanism to protect neurons from cytotoxic and ischaemic insults; dysregulation of this process in chronic inflammatory diseases eventually results in neuronal cell damage and loss. On this basis, full elucidation of the specific roles of P2 receptors in these cells may help exploit the beneficial neuroprotective features of activated glia while attenuating their harmful properties and thus provide the basis for novel neuroprotective strategies that specifically target the purinergic system.
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Affiliation(s)
- Maria P Abbracchio
- Laboratory of Molecular and Cellular Pharmacology of Purinergic Transmission, Department of Pharmacological Sciences, University of Milan, Via Balzaretti 9, 20133, Milano, Italy,
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112
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Scrivens M, Dickenson JM. Functional expression of the P2Y14 receptor in human neutrophils. Eur J Pharmacol 2006; 543:166-73. [PMID: 16820147 DOI: 10.1016/j.ejphar.2006.05.037] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2006] [Revised: 05/16/2006] [Accepted: 05/19/2006] [Indexed: 11/18/2022]
Abstract
Previous studies using quantitative reverse transcriptase polymerase chain reaction (RT-PCR) analysis have shown that the P2Y(14) receptor is expressed at high levels in human neutrophils. Therefore the primary aim of this study was to determine whether the P2Y(14) receptor is functionally expressed in human neutrophils. In agreement with previous studies RT-PCR analysis detected the expression of P2Y(14) receptor mRNA in human neutrophils. UDP-glucose (IC(50)=1 microM) induced a small but significant inhibition (circa 30%) of forskolin-stimulated cAMP accumulation suggesting functional coupling of endogenously expressed P2Y(14) receptors to the inhibition of adenylyl cyclase activity in human neutrophils. In contrast, the other putative P2Y(14) receptor agonists UDP-galactose and UDP-glucuronic acid (at concentrations up to 100 microM) had no significant effect, whereas 100 microM UDP-N-acetylglucosamine-induced a small but significant inhibition of forskolin-stimulated cAMP accumulation (20% inhibition). UDP-galactose, UDP-glucuronic acid and UDP-N-acetylglucosamine behaved as partial agonists by blocking UDP-glucose mediated inhibition of forskolin-induced cAMP accumulation. Treatment of neutrophils with pertussis toxin (G(i/o) blocker) abolished the inhibitory effects of UDP-glucose on forskolin-stimulated cAMP accumulation. UDP-glucose (100 microM) also induced a modest increase in extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation, whereas the other sugar nucleotides had no effect on ERK1/2 activation. Finally, UDP-glucose and related sugar nucleotides had no significant effect on N-formyl-methionyl-leucyl-phenylalanine-induced elastase release from neutrophils. In summary, although we have shown that the P2Y(14) receptor is functionally expressed in human neutrophils (coupling to inhibition of forskolin-induced cAMP and ERK1/2 activation) it does not modulate neutrophil degranulation (assessed by monitoring elastase release). Clearly further studies are required in order to establish the functional role of the P2Y(14) receptor expressed in human neutrophils.
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Affiliation(s)
- Michelle Scrivens
- School of Biomedical and Natural Sciences, Nottingham Trent University, Clifton Lane, Nottingham, NG11 8NS, UK
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113
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Integration of P2Y receptor-activated signal transduction pathways in G protein-dependent signalling networks. Purinergic Signal 2006; 2:451-69. [PMID: 18404483 PMCID: PMC2254474 DOI: 10.1007/s11302-006-9008-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2005] [Accepted: 03/17/2006] [Indexed: 12/21/2022] Open
Abstract
The role of nucleotides in intracellular energy provision and nucleic acid synthesis has been known for a long time. In the past decade, evidence has been presented that, in addition to these functions, nucleotides are also autocrine and paracrine messenger molecules that initiate and regulate a large number of biological processes. The actions of extracellular nucleotides are mediated by ionotropic P2X and metabotropic P2Y receptors, while hydrolysis by ecto-enzymes modulates the initial signal. An increasing number of studies have been performed to obtain information on the signal transduction pathways activated by nucleotide receptors. The development of specific and stable purinergic receptor agonists and antagonists with therapeutical potential largely contributed to the identification of receptors responsible for nucleotide-activated pathways. This article reviews the signal transduction pathways activated by P2Y receptors, the involved second messenger systems, GTPases and protein kinases, as well as recent findings concerning P2Y receptor signalling in C6 glioma cells. Besides vertical signal transduction, lateral cross-talks with pathways activated by other G protein-coupled receptors and growth factor receptors are discussed.
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114
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Robson SC, Sévigny J, Zimmermann H. The E-NTPDase family of ectonucleotidases: Structure function relationships and pathophysiological significance. Purinergic Signal 2006; 2:409-30. [PMID: 18404480 PMCID: PMC2254478 DOI: 10.1007/s11302-006-9003-5] [Citation(s) in RCA: 712] [Impact Index Per Article: 39.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Accepted: 01/23/2006] [Indexed: 12/17/2022] Open
Abstract
Ectonucleotidases are ectoenzymes that hydrolyze extracellular nucleotides to the respective nucleosides. Within the past decade, ectonucleotidases belonging to several enzyme families have been discovered, cloned and characterized. In this article, we specifically address the cell surface-located members of the ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase/CD39) family (NTPDase1,2,3, and 8). The molecular identification of individual NTPDase subtypes, genetic engineering, mutational analyses, and the generation of subtype-specific antibodies have resulted in considerable insights into enzyme structure and function. These advances also allow definition of physiological and patho-physiological implications of NTPDases in a considerable variety of tissues. Biological actions of NTPDases are a consequence (at least in part) of the regulated phosphohydrolytic activity on extracellular nucleotides and consequent effects on P2-receptor signaling. It further appears that the spatial and temporal expression of NTPDases by various cell types within the vasculature, the nervous tissues and other tissues impacts on several patho-physiological processes. Examples include acute effects on cellular metabolism, adhesion, activation and migration with other protracted impacts upon developmental responses, inclusive of cellular proliferation, differentiation and apoptosis, as seen with atherosclerosis, degenerative neurological diseases and immune rejection of transplanted organs and cells. Future clinical applications are expected to involve the development of new therapeutic strategies for transplantation and various inflammatory cardiovascular, gastrointestinal and neurological diseases.
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Affiliation(s)
- Simon C. Robson
- Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts USA
| | - Jean Sévigny
- Centre de Recherche en Rhumatologie et Immunologie, Université Laval, Québec, Québec Canada
| | - Herbert Zimmermann
- Institut fuer Zellbiologie und Neurowissenschaft, Biozentrum der J.W. Goethe-Universitaet, Marie-Curie-Str. 9, D-60439 Frankfurt am Main, Germany
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115
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Rappold PM, Lynd-Balta E, Joseph SA. P2X7 receptor immunoreactive profile confined to resting and activated microglia in the epileptic brain. Brain Res 2006; 1089:171-8. [PMID: 16635480 DOI: 10.1016/j.brainres.2006.03.040] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2005] [Revised: 02/24/2006] [Accepted: 03/01/2006] [Indexed: 11/19/2022]
Abstract
The purpose of this study was to identify the CNS cellular constituent immunoreactive for specific P2X7 receptor antiserum in the kainate-induced seizure and non-seizure rat brain. Analysis of P2X7 immunocytochemistry (ICC) revealed small immunoreactive cells with processes showing distinct morphological changes as seizures progressed in time. These morphological changes were reminiscent of reactive glia during CNS injury. In order to determine the identity of this non-neuronal cellular constituent, we employed dual ICC techniques using sequential antibody incubations and reacted the sections with contrasting chromagens. Specific glial markers tested in the series included Iba1 (microglia), COX-1 (microglia), and GFAP (astroglia). Results of this study revealed distinct colocalization when sections immunostained for P2X7 were dual immunostained with antisera specific for microglia (Iba1, COX-1). In contrast, no colocalization was evident when sections were dual immunostained with P2X7 and GFAP, an astrocytic marker. In the latter experiment, dual ICC revealed two distinct cell populations with contrasting color demonstrating a population of distinct GFAP immunopositive cells and a population of distinct P2X7 immunopositive cells. We conclude that P2X7 antiserum used in this study is specific for and identifies microglia in rat and that there exists a timeline of progressive changes in microglia morphology that can be demonstrated following kainate-induced seizures. In addition, the morphological changes in microglia following seizure induction that can be identified with P2X7 antisera or with antisera specific for microglia suggest a neuroinflammatory milieu in areas of CNS seizure activity.
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Affiliation(s)
- P M Rappold
- Department of Neurosurgery, Box 670, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
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116
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Invited Lectures : Overviews Purinergic signalling: past, present and future. Purinergic Signal 2006; 2:1-324. [PMID: 18404494 PMCID: PMC2096525 DOI: 10.1007/s11302-006-9006-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/02/2006] [Indexed: 12/11/2022] Open
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117
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Franke H, Krügel U, Illes P. P2 receptors and neuronal injury. Pflugers Arch 2006; 452:622-44. [PMID: 16645849 DOI: 10.1007/s00424-006-0071-8] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2006] [Accepted: 03/09/2006] [Indexed: 02/08/2023]
Abstract
Extracellular adenosine 5'-triphosphate (ATP) was proposed to be an activity-dependent signaling molecule that regulates glia-glia and glia-neuron communications. ATP is a neurotransmitter of its own right and, in addition, a cotransmitter of other classical transmitters such as glutamate or GABA. The effects of ATP are mediated by two receptor families belonging either to the P2X (ligand-gated cationic channels) or P2Y (G protein-coupled receptors) types. P2X receptors are responsible for rapid synaptic responses, whereas P2Y receptors mediate slow synaptic responses and other types of purinergic signaling involved in neuronal damage/regeneration. ATP may act at pre- and postsynaptic sites and therefore, it may participate in the phenomena of long-term potentiation and long-term depression of excitatory synaptic transmission. The release of ATP into the extracellular space, e.g., by exocytosis, membrane transporters, and connexin hemichannels, is a widespread physiological process. However, ATP may also leave cells through their plasma membrane damaged by inflammation, ischemia, and mechanical injury. Functional responses to the activation of multiple P2 receptors were found in neurons and glial cells under normal and pathophysiological conditions. P2 receptor-activation could either be a cause or a consequence of neuronal cell death/glial activation and may be related to detrimental and/or beneficial effects. The present review aims at demonstrating that purinergic mechanisms correlate with the etiopathology of brain insults, especially because of the massive extracellular release of ATP, adenosine, and other neurotransmitters after brain injury. We will focus in this review on the most important P2 receptor-mediated neurodegenerative and neuroprotective processes and their beneficial modulation by possible therapeutic manipulations.
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Affiliation(s)
- Heike Franke
- Rudolf-Boehm Institute of Pharmacology and Toxicology, University of Leipzig, Härtelstrasse 16-18, 04107, Leipzig, Germany.
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118
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Zimmermann H. Nucleotide signaling in nervous system development. Pflugers Arch 2006; 452:573-88. [PMID: 16639549 DOI: 10.1007/s00424-006-0067-4] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2006] [Accepted: 03/06/2006] [Indexed: 11/24/2022]
Abstract
The development of the nervous system requires complex series of cellular programming and intercellular communication events that lead from the early neural induction to the formation of a highly structured central and peripheral nervous system. Neurogenesis continuously takes place also in select regions of the adult mammalian brain. During the past years, a multiplicity of cellular control mechanisms has been identified, ranging from differential transcriptional mediators to inducers or inhibitors of cell specification or neurite outgrowth. While the identification of transcription factors typical for the stage-specific progression has been a topic of key interest for many years, less is known concerning the potential multiplicity of relevant intercellular signaling pathways and the fine tuning of epigenetic gene regulation. Nucleotide receptors can induce a multiplicity of cellular signaling pathways and are involved in multiple molecular interactions, thus opening the possibility of cross talk between several signaling pathways, including growth factors, cytokines, and extracellular matrix components. An increasing number of studies provides evidence for a role of nucleotide signaling in nervous system development. This includes progenitor cell proliferation, cell migration, neuronal and glial cellular interaction and differentiation, and synaptic network formation.
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Affiliation(s)
- Herbert Zimmermann
- Institut fuer Zellbiologie und Neurowissenschaft, Biozentrum der J.W. Goethe-Universitaet, Max-von-Lane-Str. 9, 60438, Frankfurt am Main, Germany.
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119
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Abstract
The concept of a purinergic signaling system, using purine nucleotides and nucleosides as extracellular messengers, was first proposed over 30 years ago. After a brief introduction and update of purinoceptor subtypes, this article focuses on the diverse pathophysiological roles of purines and pyrimidines as signaling molecules. These molecules mediate short-term (acute) signaling functions in neurotransmission, mechanosensory transduction, secretion and vasodilatation, and long-term (chronic) signaling functions in cell proliferation, differentiation, and death involved in development and regeneration. Plasticity of purinoceptor expression in pathological conditions is frequently observed, including an increase in the purinergic component of autonomic cotransmission. Recent advances in therapies using purinergic-related drugs in a wide range of pathological conditions will be addressed with speculation on future developments in the field.
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Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Centre, Royal Free and University College Medical School, London NW3 2PF, UK.
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120
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Van Nassauw L, Costagliola A, Van Op den Bosch J, Cecio A, Vanderwinden JM, Burnstock G, Timmermans JP. Region-specific distribution of the P2Y4 receptor in enteric glial cells and interstitial cells of Cajal within the guinea-pig gastrointestinal tract. Auton Neurosci 2006; 126-127:299-306. [PMID: 16616701 DOI: 10.1016/j.autneu.2006.02.018] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2005] [Revised: 02/16/2006] [Accepted: 02/27/2006] [Indexed: 01/01/2023]
Abstract
Although there is pharmacological evidence to assume that the P2Y4 receptor is a regulator of epithelial ion transport, no detailed data about its distribution within the gut are available. Therefore, this study, using whole mounts and cryosections, aimed to reveal the expression pattern of P2Y4 along the entire guinea-pig gastrointestinal tract. P2Y4 immunoreactivity was absent from enteric neurons but present in enteric glial cells of the stomach, small and large intestine. In the esophagus, P2Y4 appeared to be exclusively located within striated muscle cells. P2Y4 showed also a region dependency regarding its presence in different subpopulations of interstitial cells of Cajal: in myenteric interstitial cells of Cajal in the stomach and ileum; in some intramuscular interstitial cells in the stomach and cecum; in some deep muscular plexus interstitial cells in the ileum; and in some submucosal surface interstitial cells in the colon. These results and the knowledge that P2Y4 activation causes intracellular Ca2+ recruitment led us to suggest that P2Y4 in enteric glia plays a modulatory role in intercellular Ca2+ waves, while P2Y4 in interstitial cells of Cajal modulates intracellular Ca2+ oscillations.
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Affiliation(s)
- Luc Van Nassauw
- Laboratory of Cell Biology and Histology, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium
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121
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Xiang Z, Chen M, Ping J, Dunn P, Lv J, Jiao B, Burnstock G. Microglial morphology and its transformation after challenge by extracellular ATP in vitro. J Neurosci Res 2006; 83:91-101. [PMID: 16323207 DOI: 10.1002/jnr.20709] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The novel morphological characteristics of N9 microglial cells and primary cultured rat microglial cells were examined using the bitotin-IB4 and streptavidin-FITC system. Numerous fine, long processes of both microglial cell preparations formed a network, beginning after 30 min in culture. Dye coupling studies did not show communication between neighbouring cells via the processes in normal conditions. The network of microglial cell processes was well formed into a 'resting state' by 16-24 hr after re-plating. After being challenged by 3 mM ATP the microglial cells were activated, became amoeboid-like cells within 2 hr and finally floated in the culture medium. The complicated network of processes did not retract to the microglial cell body. Flow cytometry analysis showed that the majority of these floating cells were alive and could recover to the resting state after ATP was removed from the culture medium.
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Affiliation(s)
- Zhenghua Xiang
- Department of Biochemistry and Molecular Biology, Second Military Medical University Shanghai, People's Republic of China
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122
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Witting A, Chen L, Cudaback E, Straiker A, Walter L, Rickman B, Möller T, Brosnan C, Stella N. Experimental autoimmune encephalomyelitis disrupts endocannabinoid-mediated neuroprotection. Proc Natl Acad Sci U S A 2006; 103:6362-7. [PMID: 16571660 PMCID: PMC1458883 DOI: 10.1073/pnas.0510418103] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Focal cerebral ischemia and traumatic brain injury induce an escalating amount of cell death because of harmful mediators diffusing from the original lesion site. Evidence suggests that healthy cells surrounding these lesions attempt to protect themselves by producing endocannabinoids (eCBs) and activating cannabinoid receptors, the molecular target for marijuana-derived compounds. Indeed, activation of cannabinoid receptors reduces the production and diffusion of harmful mediators. Here, we provide evidence that an exception to this pattern is found in experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis. We show that cell damage induced by EAE does not lead to increase in eCBs, even though cannabinoid receptors are functional because synthetic cannabinoid agonists are known to confine EAE-induced lesions. This lack of eCB increase is likely due to IFN-gamma, which is released by primed T cells invading the CNS. We show that IFN-gamma disrupts the functionality of purinergic P2X7 receptors, a key step controlling eCB production by microglia, the main source of eCBs in brain. Accordingly, induction of EAE in P2X7-/- mice results in even lower eCB levels and more pronounced cell damage than in wild-type mice. Our data suggest that the high level of CNS IFN-gamma associated with EAE disrupts eCB-mediated neuroprotection while maintaining functional cannabinoid receptors, thus providing additional support for the use of cannabinoid-based medicine to treat multiple sclerosis.
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Affiliation(s)
| | - Lanfen Chen
- Department of Pathology, F-520, Albert Einstein College of Medicine, Bronx, NY 10461
| | | | | | | | | | - Thomas Möller
- **Neurology
- Department of Pathology, F-520, Albert Einstein College of Medicine, Bronx, NY 10461
| | | | - Nephi Stella
- Departments of *Pharmacology
- Psychiatry and Behavioral Sciences, and
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA 98195; and
- To whom correspondence should be sent at the * address. E-mail:
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123
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Amadio S, Tramini G, Martorana A, Viscomi MT, Sancesario G, Bernardi G, Volonté C. Oligodendrocytes express P2Y12 metabotropic receptor in adult rat brain. Neuroscience 2006; 141:1171-80. [PMID: 16831517 DOI: 10.1016/j.neuroscience.2006.05.058] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2006] [Revised: 05/23/2006] [Accepted: 05/25/2006] [Indexed: 10/24/2022]
Abstract
In the CNS, nucleotide receptors termed P2 receptors are identified on neurons and glial cells, mediating neuron-neuron, glia-glia and glia-neuron communication. In the present work, we qualify in vivo in the adult rat CNS the cellular/subcellular distribution of P2Y12 receptor protein in cerebral cortex, white matter and subcortical nuclei (striatum and substantia nigra), by means of immunofluorescence-confocal, electron microscopy and Western blot analysis. P2Y12 receptor immunoreactivity colocalizes neither with markers such as neuronal nuclei, neurofilament light chain, calbindin and tyrosine hydroxylase, nor with glial fibrillary acidic protein and isolectin B4, but with myelin basic protein and the oligodendrocyte marker RIP, in both cell bodies and processes, indicating therefore oligodendrocyte localization. Electron microscopy identifies P2Y12 receptors in both the perikaryon and under the plasmalemma of oligodendrocyte cell bodies and radiating processes, until the paranodal region of fibers. By Western blot analysis, P2Y12 receptor shows a specific band of 42-44 kDa, matching the molecular mass predicted from amino acid sequencing. Since in platelets P2Y12 receptor is known to regulate adhesion/activation and thrombus growth/stability, from our results we could speculate by analogy that, in oligodendrocytes, P2Y12 receptor signaling might contribute to the migration and adhesion of the glial processes to axons to be myelinated.
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Affiliation(s)
- S Amadio
- Santa Lucia Foundation/CNR, Via del Fosso di Fiorano 64, 00143 Rome, Italy
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124
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Sak K, Illes P. Neuronal and glial cell lines as model systems for studying P2Y receptor pharmacology. Neurochem Int 2005; 47:401-12. [PMID: 16081187 DOI: 10.1016/j.neuint.2005.05.012] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2005] [Accepted: 05/31/2005] [Indexed: 11/18/2022]
Abstract
Investigation of the role of extracellular nucleotides in nervous system has been one of the main topics of the P2Y receptor research throughout the years. In parallel to numerous studies on primary culture systems, various neuronal and non-neuronal cell lines have been used to model in vitro the processes mediated by extracellular nucleotides. In this review article, a survey of expression profiles of G protein-coupled P2Y receptor subtypes in nervous-system-derived cell lines is presented, by analysing the receptor expression at the mRNA, protein, and functional level. The variability of receptor expression profiles in established cell lines is further discussed, bringing forward some general properties for neuronal and glial malignant cell lines.
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Affiliation(s)
- Katrin Sak
- Rudolf-Boehm Institute of Pharmacology and Toxicology, and Interdisciplinary Center for Clinical Research, Medical Faculty, University of Leipzig, D-04107 Leipzig, Germany.
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125
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Light AR, Wu Y, Hughen RW, Guthrie PB. Purinergic receptors activating rapid intracellular Ca increases in microglia. ACTA ACUST UNITED AC 2005; 2:125-138. [PMID: 16652167 PMCID: PMC1424667 DOI: 10.1017/s1740925x05000323] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We provide both molecular and pharmacological evidence that the metabotropic, purinergic, P2Y(6), P2Y(12) and P2Y(13) receptors and the ionotropic P2X(4) receptor contribute strongly to the rapid calcium response caused by ATP and its analogues in mouse microglia. Real-time PCR demonstrates that the most prevalent P2 receptor in microglia is P2Y(6) followed, in order, by P2X(4), P2Y(12), and P2X(7) = P2Y(13). Only very small quantities of mRNA for P2Y(1), P2Y(2), P2Y(4), P2Y(14), P2X(3) and P2X(5) were found. Dose-response curves of the rapid calcium response gave a potency order of: 2MeSADP>ADP=UDP=IDP=UTP>ATP>BzATP, whereas A2P4 had little effect. Pertussis toxin partially blocked responses to 2MeSADP, ADP and UDP. The P2X(4) antagonist suramin, but not PPADS, significantly blocked responses to ATP. These data indicate that P2Y(6), P2Y(12), P2Y(13) and P2X receptors mediate much of the rapid calcium responses and shape changes in microglia to low concentrations of ATP, presumably at least partly because ATP is rapidly hydrolyzed to ADP. Expression of P2Y(6), P2Y(12) and P2Y(13) receptors appears to be largely glial in the brain, so that peripheral immune cells and CNS microglia share these receptors. Thus, purinergic, metabotropic, P2Y(6), P2Y(12), P2Y(13) and P2X(4) receptors might share a role in the activation and recruitment of microglia in the brain and spinal cord by widely varying stimuli that cause the release of ATP, including infection, injury and degeneration in the CNS, and peripheral tissue injury and inflammation which is signaled via nerve signaling to the spinal cord.
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Affiliation(s)
- Alan R. Light
- Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA
- Please address correspondence to: Alan R. Light, Department of Anesthesiology, University of Utah, 3C444 SOM, 3oN. 1900 E, Salt Lake City, UT 84132-2304, USA, phone: +1 801 581 6393, fax: +1 801 581 4367,
| | - Ying Wu
- Oral Biology Program, School of Dentistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27510, USA
| | - Ronald W. Hughen
- Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA
| | - Peter B. Guthrie
- Scientific Review Administrator, Center for Scientific Review, National Institutes of Health, 6701 Rockledge Drive, Room 4142 Msc 7850, Bethesda, MD 20892-7850, USA
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126
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Ferrari D, la Sala A, Panther E, Norgauer J, Di Virgilio F, Idzko M. Activation of human eosinophils via P2 receptors: novel findings and future perspectives. J Leukoc Biol 2005; 79:7-15. [PMID: 16244111 DOI: 10.1189/jlb.0505286] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
A growing body of information indicates that release of intracellular nucleotides represents an important way to modulate several cell pathways in physiological or pathological conditions. Nucleotides released as a consequence of cell damage, cell stress, bacterial infection, or other noxious stimuli signal at a class of plasma membrane receptors--P2 receptors--activating diverse intracellular pathways in many tissues and organs. For example, nucleotides secreted in the airway system control chloride/liquid secretion, goblet cell degranulation, and ciliary beat frequency. Several studies indicate that nucleotides play a role in airway diseases through their action on multiple cell types, including mast cells, dendritic cells, neurons, and eosinophils. Recent work by us and other groups led to the identification and characterization of P2 receptors expressed by human eosinophils. In this review, we will summarize recent developments in this field and put forward a hypothesis about the role of P2 receptors in pathophysiological conditions where eosinophils are major players.
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Affiliation(s)
- Davide Ferrari
- Department of Experimental and Diagnostic Medicine, Interdisciplinary Center for the Study of Inflammation, University of Ferrara, Ferrara, Italy.
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