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Franco R, Lillo A, Rivas-Santisteban R, Reyes-Resina I, Navarro G. Microglial Adenosine Receptors: From Preconditioning to Modulating the M1/M2 Balance in Activated Cells. Cells 2021; 10:1124. [PMID: 34066933 PMCID: PMC8148598 DOI: 10.3390/cells10051124] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 04/19/2021] [Accepted: 05/01/2021] [Indexed: 12/14/2022] Open
Abstract
Neuronal survival depends on the glia, that is, on the astroglial and microglial support. Neurons die and microglia are activated not only in neurodegenerative diseases but also in physiological aging. Activated microglia, once considered harmful, express two main phenotypes: the pro-inflammatory or M1, and the neuroprotective or M2. When neuroinflammation, i.e., microglial activation occurs, it is important to achieve a good M1/M2 balance, i.e., at some point M1 microglia must be skewed into M2 cells to impede chronic inflammation and to afford neuronal survival. G protein-coupled receptors in general and adenosine receptors in particular are potential targets for increasing the number of M2 cells. This article describes the mechanisms underlying microglial activation and analyzes whether these cells exposed to a first damaging event may be ready to be preconditioned to better react to exposure to more damaging events. Adenosine receptors are relevant due to their participation in preconditioning. They can also be overexpressed in activated microglial cells. The potential of adenosine receptors and complexes formed by adenosine receptors and cannabinoids as therapeutic targets to provide microglia-mediated neuroprotection is here discussed.
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Affiliation(s)
- Rafael Franco
- CiberNed, Network Research Center, Neurodegenerative Diseases, Spanish National Health Institute Carlos III, 28034 Madrid, Spain;
- Department of Biochemistry and Molecular Biomedicine, University of Barcelona, 08028 Barcelona, Spain
| | - Alejandro Lillo
- Department of Biochemistry and Physiology, Faculty of Pharmacy and Food Science, University of Barcelona, 08028 Barcelona, Spain;
| | - Rafael Rivas-Santisteban
- CiberNed, Network Research Center, Neurodegenerative Diseases, Spanish National Health Institute Carlos III, 28034 Madrid, Spain;
- Department of Biochemistry and Molecular Biomedicine, University of Barcelona, 08028 Barcelona, Spain
| | - Irene Reyes-Resina
- CiberNed, Network Research Center, Neurodegenerative Diseases, Spanish National Health Institute Carlos III, 28034 Madrid, Spain;
- Department of Biochemistry and Molecular Biomedicine, University of Barcelona, 08028 Barcelona, Spain
| | - Gemma Navarro
- CiberNed, Network Research Center, Neurodegenerative Diseases, Spanish National Health Institute Carlos III, 28034 Madrid, Spain;
- Department of Biochemistry and Physiology, Faculty of Pharmacy and Food Science, University of Barcelona, 08028 Barcelona, Spain;
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Franco R, Rivas-Santisteban R, Lillo J, Camps J, Navarro G, Reyes-Resina I. 5-Hydroxytryptamine, Glutamate, and ATP: Much More Than Neurotransmitters. Front Cell Dev Biol 2021; 9:667815. [PMID: 33937270 PMCID: PMC8083958 DOI: 10.3389/fcell.2021.667815] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Accepted: 03/17/2021] [Indexed: 01/08/2023] Open
Abstract
5-hydroxytryptamine (5-HT) is derived from the essential amino acid L-tryptophan. Although the compound has been studied extensively for its neuronal handling and synaptic actions, serotonin 5-HT receptors can be found extra-synaptically and not only in neurons but in many types of mammalian cells, inside and outside the central nervous system (CNS). In sharp contrast, glutamate (Glu) and ATP are better known as metabolism-related molecules, but they also are neurotransmitters, and their receptors are expressed on almost any type of cell inside and outside the nervous system. Whereas 5-hydroxytryptamine and Glu are key regulators of the immune system, ATP actions are more general. 5-hydroxytryptamine, ATP and Glu act through both G protein-coupled receptors (GPCRs), and ionotropic receptors, i.e., ligand gated ion channels. These are the three examples of neurotransmitters whose actions as holistic regulatory molecules are briefly put into perspective here.
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Affiliation(s)
- Rafael Franco
- Department Biochemistry and Molecular Biomedicine, School of Biology, University of Barcelona, Barcelona, Spain,Centro de Investigación en Red, Enfermedades Neurodegenerativas (CIberNed), Instituto de Salud Carlos III, Madrid, Spain,*Correspondence: Rafael Franco, ;
| | - Rafael Rivas-Santisteban
- Department Biochemistry and Molecular Biomedicine, School of Biology, University of Barcelona, Barcelona, Spain,Centro de Investigación en Red, Enfermedades Neurodegenerativas (CIberNed), Instituto de Salud Carlos III, Madrid, Spain
| | - Jaume Lillo
- Department Biochemistry and Molecular Biomedicine, School of Biology, University of Barcelona, Barcelona, Spain,Centro de Investigación en Red, Enfermedades Neurodegenerativas (CIberNed), Instituto de Salud Carlos III, Madrid, Spain
| | - Jordi Camps
- Department Biochemistry and Molecular Biomedicine, School of Biology, University of Barcelona, Barcelona, Spain
| | - Gemma Navarro
- Centro de Investigación en Red, Enfermedades Neurodegenerativas (CIberNed), Instituto de Salud Carlos III, Madrid, Spain,Department of Biochemistry and Physiology, School of Pharmacy, University of Barcelona, Barcelona, Spain
| | - Irene Reyes-Resina
- Department Biochemistry and Molecular Biomedicine, School of Biology, University of Barcelona, Barcelona, Spain,Irene Reyes-Resina,
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