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Kundu D, Dubey VK. Purines and Pyrimidines: Metabolism, Function and Potential as Therapeutic Options in Neurodegenerative Diseases. Curr Protein Pept Sci 2021; 22:170-189. [PMID: 33292151 DOI: 10.2174/1389203721999201208200605] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2020] [Revised: 09/01/2020] [Accepted: 09/25/2020] [Indexed: 11/22/2022]
Abstract
Various neurodegenerative disorders have various molecular origins but some common molecular mechanisms. In the current scenario, there are very few treatment regimens present for advanced neurodegenerative diseases. In this context, there is an urgent need for alternate options in the form of natural compounds with an ameliorating effect on patients. There have been individual scattered experiments trying to identify potential values of various intracellular metabolites. Purines and Pyrimidines, which are vital molecules governing various aspects of cellular biochemical reactions, have been long sought as crucial candidates for the same, but there are still many questions that go unanswered. Some critical functions of these molecules associated with neuromodulation activities have been identified. They are also known to play a role in foetal neurodevelopment, but there is a lacuna in understanding their mechanisms. In this review, we have tried to assemble and identify the importance of purines and pyrimidines, connecting them with the prevalence of neurodegenerative diseases. The leading cause of this class of diseases is protein misfolding and the formation of amyloids. A direct correlation between loss of balance in cellular homeostasis and amyloidosis is yet an unexplored area. This review aims at bringing the current literature available under one umbrella serving as a foundation for further extensive research in this field of drug development in neurodegenerative diseases.
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Affiliation(s)
- Debanjan Kundu
- School of Biochemical Engineering, Indian Institute of Technology BHU, Varanasi, UP - 221005, India
| | - Vikash Kumar Dubey
- School of Biochemical Engineering, Indian Institute of Technology BHU, Varanasi, UP - 221005, India
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2
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Cunha RA. How does adenosine control neuronal dysfunction and neurodegeneration? J Neurochem 2016; 139:1019-1055. [PMID: 27365148 DOI: 10.1111/jnc.13724] [Citation(s) in RCA: 301] [Impact Index Per Article: 37.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 05/23/2016] [Accepted: 06/23/2016] [Indexed: 12/11/2022]
Abstract
The adenosine modulation system mostly operates through inhibitory A1 (A1 R) and facilitatory A2A receptors (A2A R) in the brain. The activity-dependent release of adenosine acts as a brake of excitatory transmission through A1 R, which are enriched in glutamatergic terminals. Adenosine sharpens salience of information encoding in neuronal circuits: high-frequency stimulation triggers ATP release in the 'activated' synapse, which is locally converted by ecto-nucleotidases into adenosine to selectively activate A2A R; A2A R switch off A1 R and CB1 receptors, bolster glutamate release and NMDA receptors to assist increasing synaptic plasticity in the 'activated' synapse; the parallel engagement of the astrocytic syncytium releases adenosine further inhibiting neighboring synapses, thus sharpening the encoded plastic change. Brain insults trigger a large outflow of adenosine and ATP, as a danger signal. A1 R are a hurdle for damage initiation, but they desensitize upon prolonged activation. However, if the insult is near-threshold and/or of short-duration, A1 R trigger preconditioning, which may limit the spread of damage. Brain insults also up-regulate A2A R, probably to bolster adaptive changes, but this heightens brain damage since A2A R blockade affords neuroprotection in models of epilepsy, depression, Alzheimer's, or Parkinson's disease. This initially involves a control of synaptotoxicity by neuronal A2A R, whereas astrocytic and microglia A2A R might control the spread of damage. The A2A R signaling mechanisms are largely unknown since A2A R are pleiotropic, coupling to different G proteins and non-canonical pathways to control the viability of glutamatergic synapses, neuroinflammation, mitochondria function, and cytoskeleton dynamics. Thus, simultaneously bolstering A1 R preconditioning and preventing excessive A2A R function might afford maximal neuroprotection. The main physiological role of the adenosine modulation system is to sharp the salience of information encoding through a combined action of adenosine A2A receptors (A2A R) in the synapse undergoing an alteration of synaptic efficiency with an increased inhibitory action of A1 R in all surrounding synapses. Brain insults trigger an up-regulation of A2A R in an attempt to bolster adaptive plasticity together with adenosine release and A1 R desensitization; this favors synaptotocity (increased A2A R) and decreases the hurdle to undergo degeneration (decreased A1 R). Maximal neuroprotection is expected to result from a combined A2A R blockade and increased A1 R activation. This article is part of a mini review series: "Synaptic Function and Dysfunction in Brain Diseases".
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Affiliation(s)
- Rodrigo A Cunha
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,FMUC-Faculty of Medicine, University of Coimbra, Coimbra, Portugal
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3
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Hernández-González O, Hernández-Flores T, Prieto GA, Pérez-Burgos A, Arias-García MA, Galarraga E, Bargas J. Modulation of Ca2+-currents by sequential and simultaneous activation of adenosine A1 and A 2A receptors in striatal projection neurons. Purinergic Signal 2013; 10:269-81. [PMID: 24014158 PMCID: PMC4040173 DOI: 10.1007/s11302-013-9386-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Accepted: 08/21/2013] [Indexed: 10/26/2022] Open
Abstract
D(1)- and D(2)-types of dopamine receptors are located separately in direct and indirect pathway striatal projection neurons (dSPNs and iSPNs). In comparison, adenosine A(1)-type receptors are located in both neuron classes, and adenosine A(2A)-type receptors show a preferential expression in iSPNs. Due to their importance for neuronal excitability, Ca(2+)-currents have been used as final effectors to see the function of signaling cascades associated with different G protein-coupled receptors. For example, among many other actions, D(1)-type receptors increase, while D(2)-type receptors decrease neuronal excitability by either enhancing or reducing, respectively, CaV1 Ca(2+)-currents. These actions occur separately in dSPNs and iSPNs. In the case of purinergic signaling, the actions of A(1)- and A(2A)-receptors have not been compared observing their actions on Ca(2+)-channels of SPNs as final effectors. Our hypotheses are that modulation of Ca(2+)-currents by A(1)-receptors occurs in both dSPNs and iSPNs. In contrast, iSPNs would exhibit modulation by both A(1)- and A2A-receptors. We demonstrate that A(1)-type receptors reduced Ca(2+)-currents in all SPNs tested. However, A(2A)-type receptors enhanced Ca(2+)-currents only in half tested neurons. Intriguingly, to observe the actions of A(2A)-type receptors, occupation of A(1)-type receptors had to occur first. However, A(1)-receptors decreased Ca(V)2 Ca(2+)-currents, while A(2A)-type receptors enhanced current through Ca(V)1 channels. Because these channels have opposing actions on cell discharge, these differences explain in part why iSPNs may be more excitable than dSPNs. It is demonstrated that intrinsic voltage-gated currents expressed in SPNs are effectors of purinergic signaling that therefore play a role in excitability.
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Affiliation(s)
- O. Hernández-González
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México [UNAM], P.O. Box: 70-253, Mexico City, México 04510
| | - T. Hernández-Flores
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México [UNAM], P.O. Box: 70-253, Mexico City, México 04510
| | - G. A. Prieto
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México [UNAM], P.O. Box: 70-253, Mexico City, México 04510
| | - A. Pérez-Burgos
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México [UNAM], P.O. Box: 70-253, Mexico City, México 04510
| | - M. A. Arias-García
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México [UNAM], P.O. Box: 70-253, Mexico City, México 04510
| | - E. Galarraga
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México [UNAM], P.O. Box: 70-253, Mexico City, México 04510
| | - J. Bargas
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México [UNAM], P.O. Box: 70-253, Mexico City, México 04510
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4
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Dias RB, Rombo DM, Ribeiro JA, Henley JM, Sebastião AM. Adenosine: setting the stage for plasticity. Trends Neurosci 2013; 36:248-57. [PMID: 23332692 DOI: 10.1016/j.tins.2012.12.003] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 10/09/2012] [Accepted: 12/14/2012] [Indexed: 12/19/2022]
Abstract
It is widely accepted that Hebbian forms of plasticity mediate selective modifications in synaptic strength underlying information encoding in response to experience and circuit formation or refinement throughout development. Several complementary forms of homeostatic plasticity coordinate to keep Hebbian plasticity in check, frequently through the actions of conserved regulatory molecules. Recent evidence suggests that this may be the case for adenosine, which is ubiquitous in the brain and is released by both neurons and glial cells via constitutive and activity-dependent mechanisms. Through A1 and A2A receptor activation, adenosine modulates neuronal homeostasis and tunes the ability of synapses to undergo and/or sustain plasticity. Here, we review how adenosine equilibrates neuronal activity and sets the stage for synaptic plasticity.
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Affiliation(s)
- Raquel B Dias
- Institute of Pharmacology and Neurosciences, Faculty of Medicine, University of Lisbon, Lisbon, Portugal
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5
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Sebastião AM, Ribeiro JA. Tuning and fine-tuning of synapses with adenosine. Curr Neuropharmacol 2010; 7:180-94. [PMID: 20190960 PMCID: PMC2769002 DOI: 10.2174/157015909789152128] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2009] [Revised: 04/21/2009] [Accepted: 04/28/2009] [Indexed: 12/03/2022] Open
Abstract
The ‘omnipresence’ of adenosine in all nervous system cells (neurons and glia) together with the intensive release of adenosine following insults, makes adenosine as a sort of ‘maestro’ of synapses leading to the homeostatic coordination of brain function. Besides direct actions of adenosine on the neurosecretory mechanisms, where adenosine operates to tune neurotransmitter release, receptor-receptor interactions as well as interplays between adenosine receptors and transporters occur as part of the adenosine’s attempt to fine tuning synaptic transmission. This review will focus on the different ways adenosine can use to trigger or brake the action of several neurotransmitters and neuromodulators. Adenosine receptors cross talk with other G protein coupled receptors (GPCRs), with ionotropic receptors and with receptor kinases. Most of these interactions occur through A2A receptors, which in spite their low density in some brain areas, such as the hippocampus, may function as metamodulators. Tonic adenosine A2A receptor activity is a required step to allow synaptic actions of neurotrophic factors, namely upon synaptic transmission at both pre- and post-synaptic level as well as upon synaptic plasticity and neuronal survival. The implications of these interactions in normal brain functioning and in neurologic and psychiatric dysfunction will be discussed.
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Affiliation(s)
- A M Sebastião
- Institute of Pharmacology and Neurosciences, Faculty of Medicine and Unit of Neurosciences, Institute of Molecular Medicine, University of Lisbon, Lisboa, Portugal.
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6
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Piccinin S, Di Angelantonio S, Piccioni A, Volpini R, Cristalli G, Fredholm BB, Limatola C, Eusebi F, Ragozzino D. CX3CL1-induced modulation at CA1 synapses reveals multiple mechanisms of EPSC modulation involving adenosine receptor subtypes. J Neuroimmunol 2010; 224:85-92. [PMID: 20570369 DOI: 10.1016/j.jneuroim.2010.05.012] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Accepted: 05/04/2010] [Indexed: 11/18/2022]
Abstract
We characterized the role of adenosine receptor (AR) subtypes in the modulation of glutamatergic neurotransmission by the chemokine fractalkine (CX3CL1) in mouse hippocampal CA1 neurons. CX(3)CL1 causes a reversible depression of excitatory postsynaptic current (EPSC), which is abolished by the A(3)R antagonist MRS1523, but not by A(1)R (DPCPX) or A(2A)R (SCH58261) antagonists. Consistently, CX3CL1-induced EPSC depression is absent in slices from A(3)R(-/-) but not A(1)R(-/-) or A(2A)R(-/-) mice. Further, A(3)R stimulation causes similar EPSC depression. In cultured neurons, CX3CL1-induced depression of AMPA current shows A(1)R-A(3)R pharmacology. We conclude that glutamatergic depression induced by released adenosine requires the stimulation of different ARs.
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MESH Headings
- Adenosine A1 Receptor Antagonists
- Adenosine A2 Receptor Antagonists
- Adenosine A3 Receptor Antagonists
- Animals
- CA1 Region, Hippocampal/immunology
- CA1 Region, Hippocampal/metabolism
- CA1 Region, Hippocampal/ultrastructure
- Cells, Cultured
- Chemokine CX3CL1/physiology
- Excitatory Postsynaptic Potentials/genetics
- Excitatory Postsynaptic Potentials/immunology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Neural Inhibition/genetics
- Neural Inhibition/immunology
- Organ Culture Techniques
- Patch-Clamp Techniques
- Presynaptic Terminals/immunology
- Presynaptic Terminals/metabolism
- Receptor, Adenosine A1/deficiency
- Receptor, Adenosine A1/physiology
- Receptor, Adenosine A3/deficiency
- Receptor, Adenosine A3/physiology
- Receptors, Adenosine A2/deficiency
- Receptors, Adenosine A2/physiology
- Receptors, Purinergic P1/deficiency
- Receptors, Purinergic P1/genetics
- Receptors, Purinergic P1/physiology
- Synaptic Transmission/genetics
- Synaptic Transmission/immunology
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Affiliation(s)
- S Piccinin
- Istituto Pasteur-Fondazione Cenci Bolognetti & Dipartimento di Fisiologia e Farmacologia Sapienza Università di Roma, Piazzale A. Moro 5, 00185 Rome, Italy
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7
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Lauro C, Cipriani R, Catalano M, Trettel F, Chece G, Brusadin V, Antonilli L, van Rooijen N, Eusebi F, Fredholm BB, Limatola C. Adenosine A1 receptors and microglial cells mediate CX3CL1-induced protection of hippocampal neurons against Glu-induced death. Neuropsychopharmacology 2010; 35:1550-9. [PMID: 20200508 PMCID: PMC3055460 DOI: 10.1038/npp.2010.26] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Fractalkine/CX3CL1 is a neuron-associated chemokine, which modulates microglia-induced neurotoxicity activating the specific and unique receptor CX3CR1. CX3CL1/CX3CR1 interaction modulates the release of cytokines from microglia, reducing the level of tumor necrosis factor-alpha, interleukin-1-beta, and nitric oxide and induces the production of neurotrophic substances, both in vivo and in vitro. We have recently shown that blocking adenosine A(1) receptors (A(1)R) with the specific antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) abolishes CX3CL1-mediated rescue of neuronal excitotoxic death and that CX3CL1 induces the release of adenosine from microglia. In this study, we show that the presence of extracellular adenosine is mandatory for the neurotrophic effect of CX3CL1 as reducing adenosine levels in hippocampal cultures, by adenosine deaminase treatment, strongly impairs CX3CL1-mediated neuroprotection. Furthermore, we confirm the predominant role of microglia in mediating the neuronal effects of CX3CL1, because the selective depletion of microglia from hippocampal cultures treated with clodronate-filled liposomes causes the complete loss of effect of CX3CL1. We also show that hippocampal neurons obtained from A(1)R(-/-) mice are not protected by CX3CL1 whereas A(2A)R(-/-) neurons are. The requirement of functional A(1)R for neuroprotection is not unique for CX3CL1 as A(1)R(-/-) hippocampal neurons are not rescued from Glu-induced cell death by other neurotrophins such as brain-derived neurotrophic factor and erythropoietin, which are fully active on wt neurons.
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Affiliation(s)
- Clotilde Lauro
- Istituto Pasteur, Fondazione Cenci Bolognetti, Rome, Italy,Centro di Eccellenza BEMM, Rome, Italy,Dipartimento di Fisiologia e Farmacologia, Università Sapienza, Rome, Italy
| | - Raffaela Cipriani
- Istituto Pasteur, Fondazione Cenci Bolognetti, Rome, Italy,Centro di Eccellenza BEMM, Rome, Italy,Dipartimento di Fisiologia e Farmacologia, Università Sapienza, Rome, Italy
| | - Myriam Catalano
- Istituto Pasteur, Fondazione Cenci Bolognetti, Rome, Italy,Centro di Eccellenza BEMM, Rome, Italy,Dipartimento di Fisiologia e Farmacologia, Università Sapienza, Rome, Italy
| | - Flavia Trettel
- Istituto Pasteur, Fondazione Cenci Bolognetti, Rome, Italy,Centro di Eccellenza BEMM, Rome, Italy,Dipartimento di Fisiologia e Farmacologia, Università Sapienza, Rome, Italy
| | - Giuseppina Chece
- Istituto Pasteur, Fondazione Cenci Bolognetti, Rome, Italy,Centro di Eccellenza BEMM, Rome, Italy,Dipartimento di Fisiologia e Farmacologia, Università Sapienza, Rome, Italy
| | - Valentina Brusadin
- Dipartimento di Fisiologia e Farmacologia, Università Sapienza, Rome, Italy
| | - Letizia Antonilli
- Dipartimento di Fisiologia e Farmacologia, Università Sapienza, Rome, Italy
| | - Nico van Rooijen
- Department of Molecular Cell Biology, Free University Medical Center, Amsterdam, The Netherlands
| | - Fabrizio Eusebi
- Istituto Pasteur, Fondazione Cenci Bolognetti, Rome, Italy,Centro di Eccellenza BEMM, Rome, Italy,Dipartimento di Fisiologia e Farmacologia, Università Sapienza, Rome, Italy,IRCSS NeuroMed, Pozzilli, Italy
| | - Bertil B Fredholm
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Cristina Limatola
- Istituto Pasteur, Fondazione Cenci Bolognetti, Rome, Italy,Centro di Eccellenza BEMM, Rome, Italy,Dipartimento di Fisiologia e Farmacologia, Università Sapienza, Rome, Italy,IRCSS NeuroMed, Pozzilli, Italy,Dipartimento di Fisiologia e Farmacologia, Università di Roma Sapienza, Piazzale Aldo Moro, 5, Rome 00185, Italy. Tel: +39 06 49690243; Fax: +39 06 49910851; E-mail:
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8
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Yang K, Lei G, Jackson MF, MacDonald JF. The Involvement of PACAP/VIP System in the Synaptic Transmission in the Hippocampus. J Mol Neurosci 2010; 42:319-26. [DOI: 10.1007/s12031-010-9372-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Accepted: 04/12/2010] [Indexed: 11/24/2022]
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9
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Serpa A, Ribeiro JA, Sebastião AM. Cannabinoid CB1 and adenosine A1 receptors independently inhibit hippocampal synaptic transmission. Eur J Pharmacol 2009; 623:41-6. [DOI: 10.1016/j.ejphar.2009.09.020] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2009] [Revised: 08/23/2009] [Accepted: 09/08/2009] [Indexed: 10/20/2022]
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10
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Yang K, Trepanier CH, Li H, Beazely MA, Lerner EA, Jackson MF, MacDonald JF. Vasoactive intestinal peptide acts via multiple signal pathways to regulate hippocampal NMDA receptors and synaptic transmission. Hippocampus 2009; 19:779-89. [PMID: 19173226 DOI: 10.1002/hipo.20559] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Vasoactive intestinal peptide (VIP) is a 28-amino acid peptide, which belongs to a superfamily of structurally related peptide hormones including pituitary adenylate cyclase-activating polypeptide (PACAP). Although several studies have identified the involvement of PACAP in learning and memory, little work has been done to investigate such a role for VIP. At least three receptors for VIP have been identified including the PACAP receptor (PAC1-R) and the two VIP receptors (VPAC receptors). VIP can activate the PAC1-R only if it is used at relatively high concentrations (e.g., 100 nM); however, at lower concentrations (e.g., 1 nM) it is selective for the VPAC receptors. Our lab has showed that PAC1-R activation signals through PKC/CAKbeta/Src pathway to regulate NMDA receptors; however, there is little known about the potential regulation of NMDA receptors by VPAC receptors. Our studies demonstrated that application of 1 nM VIP enhanced NMDA currents by stimulating the VPAC receptors as the effect was blocked by VPAC receptor antagonist [Ac-Tyr(1), D-Phe(2)]GRF (1-29). This enhancement of NMDA currents was blocked by both Rp-cAMPS and PKI(14-22) (they are highly specific PKA inhibitors), but not by the specific PKC inhibitor, bisindolylmaleimide I. In addition, the VIP-induced enhancement of NMDA currents was accentuated by inhibition of phosphodiesterase 4, which inhibits the degradation of cAMP. This regulation of NMDA receptors also required the scaffolding protein AKAP. In contrast, the potentiation induced by high concentration of VIP (e.g., 100 nM) was mediated by PAC1-R as well as by Src kinase. Overall, these results show that VIP can regulate NMDA receptors through different receptors and signaling pathways.
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Affiliation(s)
- Kai Yang
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
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11
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Rahman A. The role of adenosine in Alzheimer's disease. Curr Neuropharmacol 2009; 7:207-16. [PMID: 20190962 PMCID: PMC2769004 DOI: 10.2174/157015909789152119] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2009] [Revised: 05/15/2009] [Accepted: 05/27/2009] [Indexed: 12/20/2022] Open
Abstract
Alzheimer's disease (AD) is a neurodegenerative disorder of the central nervous system manifested by cognitive and memory deterioration, a variety of neuropsychiatric symptoms, behavioral disturbances, and progressive impairment of daily life activities. Current pharmacotherapies are restricted to symptomatic interventions but do not prevent progressive neuronal degeneration. Therefore, new therapeutic strategies are needed to intervene with these progressive pathological processes. In the past several years adenosine, a ubiquitously released purine ribonucleoside, has become important for its neuromodulating capability and its emerging positive experimental effects in neurodegenerative diseases. Recent research suggests that adenosine receptors play important roles in the modulation of cognitive function. The present paper attempts to review published reports and data from different studies showing the evidence of a relationship between adenosinergic function and AD-related cognitive deficits. Epidemiological studies have found an association between coffee (a nonselective adenosine receptor antagonist) consumption and improved cognitive function in AD patients and in the elderly. Long-term administration of caffeine in transgenic animal models showed a reduced amyloid burden in brain with better cognitive performance. Antagonists of adenosine A2A receptors mimic these beneficial effects of caffeine on cognitive function. Neuronal cell cultures with amyloid beta in the presence of an A2A receptor antagonist completely prevented amyloid beta-induced neurotoxicity. These findings suggest that the adenosinergic system constitutes a new therapeutic target for AD, and caffeine and A2A receptor antagonists may have promise to manage cognitive dysfunction in AD.
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Affiliation(s)
- Anisur Rahman
- Legacy Research, R.S Dow Neurobiology Laboratories, 1225 NE 2nd Avenue, Portland OR 97232, USA.
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12
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Abstract
The adenosine receptors (ARs) in the nervous system act as a kind of "go-between" to regulate the release of neurotransmitters (this includes all known neurotransmitters) and the action of neuromodulators (e.g., neuropeptides, neurotrophic factors). Receptor-receptor interactions and AR-transporter interplay occur as part of the adenosine's attempt to control synaptic transmission. A(2A)ARs are more abundant in the striatum and A(1)ARs in the hippocampus, but both receptors interfere with the efficiency and plasticity-regulated synaptic transmission in most brain areas. The omnipresence of adenosine and A(2A) and A(1) ARs in all nervous system cells (neurons and glia), together with the intensive release of adenosine following insults, makes adenosine a kind of "maestro" of the tripartite synapse in the homeostatic coordination of the brain function. Under physiological conditions, both A(2A) and A(1) ARs play an important role in sleep and arousal, cognition, memory and learning, whereas under pathological conditions (e.g., Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, stroke, epilepsy, drug addiction, pain, schizophrenia, depression), ARs operate a time/circumstance window where in some circumstances A(1)AR agonists may predominate as early neuroprotectors, and in other circumstances A(2A)AR antagonists may alter the outcomes of some of the pathological deficiencies. In some circumstances, and depending on the therapeutic window, the use of A(2A)AR agonists may be initially beneficial; however, at later time points, the use of A(2A)AR antagonists proved beneficial in several pathologies. Since selective ligands for A(1) and A(2A) ARs are now entering clinical trials, the time has come to determine the role of these receptors in neurological and psychiatric diseases and identify therapies that will alter the outcomes of these diseases, therefore providing a hopeful future for the patients who suffer from these diseases.
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Affiliation(s)
- Ana M Sebastião
- Institute of Pharmacology and Neurosciences, Institute of Molecular Medicine, University of Lisbon, 1649-028 Lisbon, Portugal.
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13
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St Hilaire C, Carroll SH, Chen H, Ravid K. Mechanisms of induction of adenosine receptor genes and its functional significance. J Cell Physiol 2008; 218:35-44. [PMID: 18767039 DOI: 10.1002/jcp.21579] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Adenosine is a metabolite generated and released from cells, particularly under injury or stress. It elicits protective or damaging responses via signaling through the adenosine receptors, including the adenylyl cyclase inhibitory A(1) and A(3), and the adenylyl cyclase stimulatory A(2A) and A(2B). Multiple adenosine receptor types, including stimulatory and inhibitory, can be found in the same cell, suggesting that a careful balance of adenosine receptor expression in a particular cell is necessary for a specific adenosine-induced response. This balance could be controlled by differential expression of the adenosine receptor genes under different stimuli. Here, we have reviewed an array of studies that have characterized basal or induced expression of the adenosine receptors and common as well as distinct mechanisms of effect, in hopes that ongoing studies on this topic will further elucidate detailed mechanisms of adenosine receptor regulation, leading to potential therapeutic applications.
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Affiliation(s)
- Cynthia St Hilaire
- Department of Biochemistry and Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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14
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Cunha-Reis D, Ribeiro JA, Sebastião AM. A1 and A2A receptor activation by endogenous adenosine is required for VIP enhancement of K+-evoked [3H]-GABA release from rat hippocampal nerve terminals. Neurosci Lett 2008; 430:207-12. [DOI: 10.1016/j.neulet.2007.10.037] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2007] [Revised: 10/10/2007] [Accepted: 10/30/2007] [Indexed: 11/28/2022]
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15
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Boison D. The adenosine kinase hypothesis of epileptogenesis. Prog Neurobiol 2007; 84:249-62. [PMID: 18249058 DOI: 10.1016/j.pneurobio.2007.12.002] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2007] [Revised: 11/02/2007] [Accepted: 12/05/2007] [Indexed: 02/07/2023]
Abstract
Current therapies for epilepsy are largely symptomatic and do not affect the underlying mechanisms of disease progression, i.e. epileptogenesis. Given the large percentage of pharmacoresistant chronic epilepsies, novel approaches are needed to understand and modify the underlying pathogenetic mechanisms. Although different types of brain injury (e.g. status epilepticus, traumatic brain injury, stroke) can trigger epileptogenesis, astrogliosis appears to be a homotypic response and hallmark of epilepsy. Indeed, recent findings indicate that epilepsy might be a disease of astrocyte dysfunction. This review focuses on the inhibitory neuromodulator and endogenous anticonvulsant adenosine, which is largely regulated by astrocytes and its key metabolic enzyme adenosine kinase (ADK). Recent findings support the "ADK hypothesis of epileptogenesis": (i) Mouse models of epileptogenesis suggest a sequence of events leading from initial downregulation of ADK and elevation of ambient adenosine as an acute protective response, to changes in astrocytic adenosine receptor expression, to astrocyte proliferation and hypertrophy (i.e. astrogliosis), to consequential overexpression of ADK, reduced adenosine and - finally - to spontaneous focal seizure activity restricted to regions of astrogliotic overexpression of ADK. (ii) Transgenic mice overexpressing ADK display increased sensitivity to brain injury and seizures. (iii) Inhibition of ADK prevents seizures in a mouse model of pharmacoresistant epilepsy. (iv) Intrahippocampal implants of stem cells engineered to lack ADK prevent epileptogenesis. Thus, ADK emerges both as a diagnostic marker to predict, as well as a prime therapeutic target to prevent, epileptogenesis.
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Affiliation(s)
- Detlev Boison
- R.S. Dow Neurobiology Laboratories, Legacy Research, Portland, OR 97232, USA.
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Adenosine as a neuromodulator in neurological diseases. Curr Opin Pharmacol 2007; 8:2-7. [PMID: 17942368 DOI: 10.1016/j.coph.2007.09.002] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2007] [Accepted: 09/10/2007] [Indexed: 12/20/2022]
Abstract
Adenosine is a modulator of brain function uniquely positioned to integrate excitatory and inhibitory neurotransmission. The past few years brought a wealth of new data fostering our understanding of how the adenosine system is involved in the pathogenesis of neurological diseases. Thus, dysregulation of the adenosine system is implicated in epileptogenesis and cell therapies have been developed to locally augment adenosine in an approach to prevent seizures. While activation of inhibitory adenosine A(1) receptors is beneficial in epilepsy, chronic pain and cerebral ischemia, inhibition of facilitatory A(2A) receptors has profound neuroprotective effects, which are currently exploited in clinical trials in Parkinson's disease. A new era of adenosine-based therapies has begun, with the prospect to cover a wide range of neurological diseases.
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