1
|
Torres-Rodríguez O, Rivera-Escobales Y, Castillo-Ocampo Y, Velazquez B, Colón M, Porter JT. Purinergic P2X7 receptor-mediated inflammation precedes PTSD-related behaviors in rats. Brain Behav Immun 2023; 110:107-118. [PMID: 36822379 PMCID: PMC10106407 DOI: 10.1016/j.bbi.2023.02.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 01/25/2023] [Accepted: 02/18/2023] [Indexed: 02/23/2023] Open
Abstract
Clinical evidence has linked increased peripheral pro-inflammatory cytokines with post-traumatic stress disorder (PTSD) symptoms. However, whether inflammation contributes to or is a consequence of PTSD is still unclear. Previous research shows that stress can activate purinergic P2X7 receptors (P2X7Rs) on microglia to induce inflammation and behavioral changes. In this investigation, we examined whether P2X7Rs contribute to the development of PTSD-like behaviors induced by single prolonged stress (SPS) exposure in rats. Consistent with the literature, exposing adult male and female rats to SPS produced a PTSD-like phenotype of impaired fear extinction and extinction of cue-induced center avoidance one week after exposure. Next, we examined if inflammation precedes the behavioral manifestations. Three days after SPS exposure, increased inflammatory cytokines were found in the blood and hippocampal microglia showed increased expression of the P2X7R, IL-1β, and TNF-α, suggesting increased peripheral and central inflammation before the onset of impaired fear extinction. In addition, SPS-exposed animals with impaired fear extinction recall also had more Iba1-positive microglia expressing the P2X7R in the ventral hippocampus. To determine whether P2X7Rs contribute to the PTSD-related behaviors induced by SPS exposure, we gave ICV infusions of the P2X7R antagonist, A-438079, for one week starting the day of SPS exposure. Blocking P2X7Rs prevented the SPS-induced impaired fear extinction and extinction of cue-induced center avoidance in male and female rats, suggesting that SPS activates P2X7Rs which increase inflammation to produce a PTSD-like phenotype.
Collapse
Affiliation(s)
- Orlando Torres-Rodríguez
- Dept of Basic Sciences, Ponce Research Institute, Ponce Health Sciences University, Ponce, Puerto Rico, 00732
| | - Yesenia Rivera-Escobales
- Dept of Basic Sciences, Ponce Research Institute, Ponce Health Sciences University, Ponce, Puerto Rico, 00732
| | - Yesenia Castillo-Ocampo
- Dept of Basic Sciences, Ponce Research Institute, Ponce Health Sciences University, Ponce, Puerto Rico, 00732
| | - Bethzaly Velazquez
- Dept of Basic Sciences, Ponce Research Institute, Ponce Health Sciences University, Ponce, Puerto Rico, 00732
| | - María Colón
- Dept of Basic Sciences, Ponce Research Institute, Ponce Health Sciences University, Ponce, Puerto Rico, 00732
| | - James T Porter
- Dept of Basic Sciences, Ponce Research Institute, Ponce Health Sciences University, Ponce, Puerto Rico, 00732.
| |
Collapse
|
2
|
Zhang Y, Yin HY, Rubini P, Illes P, Tang Y. ATP indirectly stimulates hippocampal CA1 and CA3 pyramidal neurons via the activation of neighboring P2X7 receptor-bearing astrocytes and NG2 glial cells, respectively. Front Pharmacol 2022; 13:944541. [PMID: 35935830 PMCID: PMC9355480 DOI: 10.3389/fphar.2022.944541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Accepted: 06/29/2022] [Indexed: 11/24/2022] Open
Abstract
There is ongoing dispute on the question whether CNS neurons possess ATP-sensitive P2X7 receptors (Rs) or whether only non-neuronal cells bear this receptor-type and indirectly signal to the neighboring neurons. We genetically deleted P2X7Rs specifically in astrocytes, oligodendrocytes and microglia, and then recorded current responses in neurons to the prototypic agonist of this receptor, dibenzoyl-ATP (Bz-ATP). These experiments were made in brain slice preparations taken from the indicated variants of the P2X7R KO animals. In hippocampal CA3, but not CA1 pyramidal neurons, the deletion of oligodendrocytic (NG2 glial) P2X7Rs abolished the Bz-ATP-induced current responses. In contrast to the Bz-ATP-induced currents in CA3 pyramidal neurons, current amplitudes evoked by the ionotropic glutamate/GABAAR agonists AMPA/muscimol were not inhibited at all. Whereas in the CA3 area NG2 glia appeared to mediate the P2X7R-mediated stimulation of pyramidal neurons, in the CA1 area, astrocytic P2X7Rs had a somewhat similar effect. This was shown by recording the frequencies and amplitudes of spontaneous excitatory currents (sPSCs) in brain slice preparations. Bz-ATP increased the sPSC frequency in CA1, but not CA3 pyramidal neurons without altering the amplitude, indicating a P2X7R-mediated increase of the neuronal input. Micro-injection of the selective astrocytic toxin L-α-aminoadipate into both hippocampi, or the in vitro application of the GABAAR antagonistic gabazine, completely blocked the frequency increases of sPSCs. Hence, CA1 and CA3 pyramidal neurons of the mouse did not possess P2X7Rs, but were indirectly modulated by astrocytic and oligodendrocytic P2X7Rs, respectively.
Collapse
Affiliation(s)
- Ying Zhang
- School of Acupuncture and Tuina, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Hai-Yan Yin
- School of Acupuncture and Tuina, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Patrizia Rubini
- School of Acupuncture and Tuina, Chengdu University of Traditional Chinese Medicine, Chengdu, China
- International Collaborative Center on Big Science Plan for Purinergic Signaling, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Peter Illes
- School of Acupuncture and Tuina, Chengdu University of Traditional Chinese Medicine, Chengdu, China
- International Collaborative Center on Big Science Plan for Purinergic Signaling, Chengdu University of Traditional Chinese Medicine, Chengdu, China
- Rudolf Boehm Institute for Pharmacology and Toxicology, University of Leipzig, Leipzig, Germany
- *Correspondence: Peter Illes, ; Yong Tang,
| | - Yong Tang
- School of Acupuncture and Tuina, Chengdu University of Traditional Chinese Medicine, Chengdu, China
- International Collaborative Center on Big Science Plan for Purinergic Signaling, Chengdu University of Traditional Chinese Medicine, Chengdu, China
- Key Laboratory of Sichuan Province for Acupuncture and Chronobiology, Chengdu University of Traditional Chinese Medicine, Chengdu, China
- *Correspondence: Peter Illes, ; Yong Tang,
| |
Collapse
|
3
|
Hua SQ, Hu JL, Zou FL, Liu JP, Luo HL, Hu DX, Wu LD, Zhang WJ. P2X7 receptor in inflammation and pain. Brain Res Bull 2022; 187:199-209. [PMID: 35850190 DOI: 10.1016/j.brainresbull.2022.07.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 06/15/2022] [Accepted: 07/13/2022] [Indexed: 11/02/2022]
Abstract
Different studies have confirmed P2X7 receptor-mediated inflammatory mediators play a key role in the development of pain. P2X7 receptor activation can induce the development of pain by mediating the release of inflammatory mediators. In view of the fact that P2X7 receptor is expressed in the nervous system and immune system, it is closely related to the stability and maintenance of the nervous system function. ATP activates P2X7 receptor, opens non-selective cation channels, activates multiple intracellular signaling, releases multiple inflammatory cytokines, and induces pain. At present, the role of P2X7 receptor in inflammatory response and pain has been widely recognized and affirmed. Therefore, in this paper, we discussed the pathological mechanism of P2X7 receptor-mediated inflammation and pain, focused on the internal relationship between P2X7 receptor and pain. Moreover, we also described the effects of some antagonists on pain relief by inhibiting the activities of P2X7 receptor. Thus, targeting to inhibit activation of P2X7 receptor is expected to become another potential target for the relief of pain.
Collapse
Affiliation(s)
- Shi-Qi Hua
- Nanchang University, Nanchang City 343000, Jiangxi Province, China
| | - Jia-Ling Hu
- Emergency Department, The Second Affiliated Hospital, Nanchang University, Nanchang City 343000, Jiangxi Province, China
| | - Fei-Long Zou
- Gastrointestinal Surgery, The Second Affiliated Hospital, Nanchang University, Nanchang City 343000, Jiangxi Province, China
| | - Ji-Peng Liu
- Gastrointestinal Surgery, The Second Affiliated Hospital, Nanchang University, Nanchang City 343000, Jiangxi Province, China
| | - Hong-Liang Luo
- Gastrointestinal Surgery, The Second Affiliated Hospital, Nanchang University, Nanchang City 343000, Jiangxi Province, China
| | - Dong-Xia Hu
- Department of Rehabilitation Medicine, The Second Affiliated Hospital, Nanchang University, Nanchang City 343000, Jiangxi Province, China.
| | - Li-Dong Wu
- Emergency Department, The Second Affiliated Hospital, Nanchang University, Nanchang City 343000, Jiangxi Province, China.
| | - Wen-Jun Zhang
- Department of Rehabilitation Medicine, The Second Affiliated Hospital, Nanchang University, Nanchang City 343000, Jiangxi Province, China.
| |
Collapse
|
4
|
NMDA and P2X7 Receptors Require Pannexin 1 Activation to Initiate and Maintain Nociceptive Signaling in the Spinal Cord of Neuropathic Rats. Int J Mol Sci 2022; 23:ijms23126705. [PMID: 35743148 PMCID: PMC9223805 DOI: 10.3390/ijms23126705] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 06/13/2022] [Accepted: 06/14/2022] [Indexed: 02/01/2023] Open
Abstract
Pannexin 1 (Panx1) is involved in the spinal central sensitization process in rats with neuropathic pain, but its interaction with well-known, pain-related, ligand-dependent receptors, such as NMDA receptors (NMDAR) and P2X7 purinoceptors (P2X7R), remains largely unexplored. Here, we studied whether NMDAR- and P2X7R-dependent nociceptive signaling in neuropathic rats require the activation of Panx1 channels to generate spinal central sensitization, as assessed by behavioral (mechanical hyperalgesia) and electrophysiological (C-reflex wind-up potentiation) indexes. Administration of either a selective NMDAR agonist i.t. (NMDA, 2 mM) or a P2X7R agonist (BzATP, 150 μM) significantly increased both the mechanical hyperalgesia and the C-reflex wind-up potentiation, effects that were rapidly reversed (minutes) by i.t. administration of a selective pannexin 1 antagonist (10panx peptide, 300 μM), with the scores even reaching values of rats without neuropathy. Accordingly, 300 μM 10panx completely prevented the effects of NMDA and BzATP administered 1 h later, on mechanical hyperalgesia and C-reflex wind-up potentiation. Confocal immunofluorescence imaging revealed coexpression of Panx1 with NeuN protein in intrinsic dorsal horn neurons of neuropathic rats. The results indicate that both NMDAR- and P2X7R-mediated increases in mechanical hyperalgesia and C-reflex wind-up potentiation require neuronal Panx1 channel activation to initiate and maintain nociceptive signaling in neuropathic rats.
Collapse
|
5
|
Francistiová L, Vörös K, Lovász Z, Dinnyés A, Kobolák J. Detection and Functional Evaluation of the P2X7 Receptor in hiPSC Derived Neurons and Microglia-Like Cells. Front Mol Neurosci 2022; 14:793769. [PMID: 35095416 PMCID: PMC8791009 DOI: 10.3389/fnmol.2021.793769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Accepted: 12/07/2021] [Indexed: 11/22/2022] Open
Abstract
A large body of evidence suggests the involvement of the ATP-gated purinergic receptor P2X7 (P2X7R) in neurodegenerative diseases, including Alzheimer's disease. While it is well-described to be present and functional on microglia cells contributing to inflammatory responses, some reports suggest a neuronal expression of the receptor as well. Here, we present experimental results showing P2X7 receptors to be expressed on human hiPSC-derived microglia-like cells, hiPSC-derived neuronal progenitors and hiPSC-derived matured neuronal cells. By applying cell surface protein detection assays, we show that P2X7R is not localized on the cell membrane, despite being detected in neuronal cells and thus may not be available for directly mediating neurotoxicity. On hiPSC-derived microglia-like cells, a clear membranous expression was detected. Additionally, we have not observed differences in P2X7R functions between control and familial Alzheimer's disease patient-derived neuronal cells. Functional assays employing a P2X7R antagonist JNJ 47965567 confirm these findings by showing P2X7R-dependent modulation of microglia-like cells viability upon treatment with P2X7R agonists ATP and BzATP, while the same effect was absent from neuronal cells. Since the majority of P2X7R research was done on rodent models, our work on human hiPSC-derived cells presents a valuable contribution to the field, extending the work on animal models to the human cellular system and toward clinical translation.
Collapse
Affiliation(s)
- Linda Francistiová
- Biotalentum Ltd., Gödöllő, Hungary
- Department of Physiology and Animal Health, Institute of Physiology and Animal Health, Hungarian University of Agriculture and Life Sciences, Gödöllő, Hungary
| | - Kinga Vörös
- Biotalentum Ltd., Gödöllő, Hungary
- Department of Physiology and Animal Health, Institute of Physiology and Animal Health, Hungarian University of Agriculture and Life Sciences, Gödöllő, Hungary
| | | | - András Dinnyés
- Biotalentum Ltd., Gödöllő, Hungary
- Department of Physiology and Animal Health, Institute of Physiology and Animal Health, Hungarian University of Agriculture and Life Sciences, Gödöllő, Hungary
- HCEMM-USZ Stem Cell Research Group, Hungarian Centre of Excellence for Molecular Medicine, Szeged, Hungary
- Department of Cell Biology and Molecular Medicine, University of Szeged, Szeged, Hungary
- College of Life Sciences, Sichuan University, Chengdu, China
| | | |
Collapse
|
6
|
Wu YY, Zhang HL, Lu X, Du H, Li YC, Zhang PA, Xu GY. Targeting GATA1 and p2x7r Locus Binding in Spinal Astrocytes Suppresses Chronic Visceral Pain by Promoting DNA Demethylation. Neurosci Bull 2021; 38:359-372. [PMID: 34890016 PMCID: PMC9068853 DOI: 10.1007/s12264-021-00799-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Accepted: 09/04/2021] [Indexed: 11/26/2022] Open
Abstract
Irritable bowel syndrome is a gastrointestinal disorder of unknown etiology characterized by widespread, chronic abdominal pain associated with altered bowel movements. Increasing amounts of evidence indicate that injury and inflammation during the neonatal period have long-term effects on tissue structure and function in the adult that may predispose to gastrointestinal diseases. In this study we aimed to investigate how the epigenetic regulation of DNA demethylation of the p2x7r locus guided by the transcription factor GATA binding protein 1 (GATA1) in spinal astrocytes affects chronic visceral pain in adult rats with neonatal colonic inflammation (NCI). The spinal GATA1 targeting to DNA demethylation of p2x7r locus in these rats was assessed by assessing GATA1 function with luciferase assay, chromatin immunoprecipitation, patch clamp, and interference in vitro and in vivo. In addition, a decoy oligodeoxynucleotide was designed and applied to determine the influence of GATA1 on the DNA methylation of a p2x7r CpG island. We showed that NCI caused the induction of GATA1, Ten-eleven translocation 3 (TET3), and purinergic receptors (P2X7Rs) in astrocytes of the spinal dorsal horn, and demonstrated that inhibiting these molecules markedly increased the pain threshold, inhibited the activation of astrocytes, and decreased the spinal sEPSC frequency. NCI also markedly demethylated the p2x7r locus in a manner dependent on the enhancement of both a GATA1–TET3 physical interaction and GATA1 binding at the p2x7r promoter. Importantly, we showed that demethylation of the p2x7r locus (and the attendant increase in P2X7R expression) was reversed upon knockdown of GATA1 or TET3 expression, and demonstrated that a decoy oligodeoxynucleotide that selectively blocked the GATA1 binding site increased the methylation of a CpG island in the p2x7r promoter. These results demonstrate that chronic visceral pain is mediated synergistically by GATA1 and TET3 via a DNA-demethylation mechanism that controls p2x7r transcription in spinal dorsal horn astrocytes, and provide a potential therapeutic strategy by targeting GATA1 and p2x7r locus binding.
Collapse
Affiliation(s)
- Yan-Yan Wu
- Jiangsu Key Laboratory of Neuropsychiatric Diseases, Institute of Neuroscience, Soochow University, Suzhou, 215123, China
| | - Hai-Long Zhang
- Jiangsu Key Laboratory of Neuropsychiatric Diseases, Institute of Neuroscience, Soochow University, Suzhou, 215123, China
| | - Xiaomin Lu
- Department of Oncology, The Affiliated Haian Hospital of Nantong University, Nantong, 226600, China
| | - Han Du
- Jiangsu Key Laboratory of Neuropsychiatric Diseases, Institute of Neuroscience, Soochow University, Suzhou, 215123, China
| | - Yong-Chang Li
- Jiangsu Key Laboratory of Neuropsychiatric Diseases, Institute of Neuroscience, Soochow University, Suzhou, 215123, China
| | - Ping-An Zhang
- Jiangsu Key Laboratory of Neuropsychiatric Diseases, Institute of Neuroscience, Soochow University, Suzhou, 215123, China.
- Center for Translational Medicine, The Affiliated Zhangjiagang Hospital of Soochow University, Suzhou, 215600, China.
| | - Guang-Yin Xu
- Jiangsu Key Laboratory of Neuropsychiatric Diseases, Institute of Neuroscience, Soochow University, Suzhou, 215123, China.
- Center for Translational Medicine, The Affiliated Zhangjiagang Hospital of Soochow University, Suzhou, 215600, China.
| |
Collapse
|
7
|
Zhao YF, Tang Y, Illes P. Astrocytic and Oligodendrocytic P2X7 Receptors Determine Neuronal Functions in the CNS. Front Mol Neurosci 2021; 14:641570. [PMID: 33642994 PMCID: PMC7906075 DOI: 10.3389/fnmol.2021.641570] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 01/19/2021] [Indexed: 12/20/2022] Open
Abstract
P2X7 receptors are members of the ATP-gated cationic channel family with a preferential localization at the microglial cells, the resident macrophages of the brain. However, these receptors are also present at neuroglia (astrocytes, oligodendrocytes) although at a considerably lower density. They mediate necrosis/apoptosis by the release of pro-inflammatory cytokines/chemokines, reactive oxygen species (ROS) as well as the excitotoxic (glio)transmitters glutamate and ATP. Besides mediating cell damage i.e., superimposed upon chronic neurodegenerative processes in Alzheimer’s Disease, Parkinson’s Disease, multiple sclerosis, and amyotrophic lateral sclerosis, they may also participate in neuroglial signaling to neurons under conditions of high ATP concentrations during any other form of neuroinflammation/neurodegeneration. It is a pertinent open question whether P2X7Rs are localized on neurons, or whether only neuroglia/microglia possess this receptor-type causing indirect effects by releasing the above-mentioned signaling molecules. We suggest as based on molecular biology and functional evidence that neurons are devoid of P2X7Rs although the existence of neuronal P2X7Rs cannot be excluded with absolute certainty.
Collapse
Affiliation(s)
- Ya-Fei Zhao
- School of Acupuncture and Tuina, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Yong Tang
- School of Acupuncture and Tuina, Chengdu University of Traditional Chinese Medicine, Chengdu, China.,International Collaborative Center on Big Science Plan for Purine Signaling, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Peter Illes
- School of Acupuncture and Tuina, Chengdu University of Traditional Chinese Medicine, Chengdu, China.,International Collaborative Center on Big Science Plan for Purine Signaling, Chengdu University of Traditional Chinese Medicine, Chengdu, China.,Rudolf Boehm Institute for Pharmacology and Toxicology, University of Leipzig, Leipzig, Germany
| |
Collapse
|
8
|
Marotta G, Basagni F, Rosini M, Minarini A. Memantine Derivatives as Multitarget Agents in Alzheimer's Disease. Molecules 2020; 25:molecules25174005. [PMID: 32887400 PMCID: PMC7504780 DOI: 10.3390/molecules25174005] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 08/31/2020] [Accepted: 09/01/2020] [Indexed: 12/24/2022] Open
Abstract
Memantine (3,5-dimethyladamantan-1-amine) is an orally active, noncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonist approved for treatment of moderate-to-severe Alzheimer’s disease (AD), a neurodegenerative condition characterized by a progressive cognitive decline. Unfortunately, memantine as well as the other class of drugs licensed for AD treatment acting as acetylcholinesterase inhibitors (AChEIs), provide only symptomatic relief. Thus, the urgent need in AD drug development is for disease-modifying therapies that may require approaching targets from more than one path at once or multiple targets simultaneously. Indeed, increasing evidence suggests that the modulation of a single neurotransmitter system represents a reductive approach to face the complexity of AD. Memantine is viewed as a privileged NMDAR-directed structure, and therefore, represents the driving motif in the design of a variety of multi-target directed ligands (MTDLs). In this review, we present selected examples of small molecules recently designed as MTDLs to contrast AD, by combining in a single entity the amantadine core of memantine with the pharmacophoric features of known neuroprotectants, such as antioxidant agents, AChEIs and Aβ-aggregation inhibitors.
Collapse
|
9
|
Boks MP, He Y, Schubart CD, Gastel WV, Elkrief L, Huguet G, Eijk KV, Vinkers CH, Kahn RS, Paus T, Conrod P, Hol EM, de Witte LD. Cannabinoids and psychotic symptoms: A potential role for a genetic variant in the P2X purinoceptor 7 (P2RX7) gene. Brain Behav Immun 2020; 88:573-581. [PMID: 32330591 DOI: 10.1016/j.bbi.2020.04.051] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 04/07/2020] [Accepted: 04/20/2020] [Indexed: 12/17/2022] Open
Abstract
To investigate the biological mechanisms underlying the higher risk for psychosis in those that use cannabis, we conducted a genome-wide environment-interaction study (GWEIS). In a sample of individuals without a psychiatric disorder (N = 1262), we analyzed the interactions between regular cannabis use and genotype with psychotic-like experiences (PLE) as outcome. PLE were measured using the Community Assessment of Psychic Experiences (CAPE). The sample was enriched for those at the extremes of both cannabis use and PLE to increase power. A single nucleotide polymorphism in the P2RX7 gene (rs7958311) was associated with risk for a high level of psychotic experiences in regular cannabis users (p = 1.10 x10-7) and in those with high levels of lifetime cannabis use (p = 4.5 × 10-6). This interaction was replicated in individuals with high levels of lifetime cannabis use in the IMAGEN cohort (N = 1217, p = 0.020). Functional relevance of P2RX7 in cannabis users was suggested by in vitro experiments on activated monocytes. Exposure of these cells to tetrahydrocannabinol (THC) or cannabidiol (CBD) reduced the immunological response of the P2X7 receptor, which was dependent on the identified genetic variant. P2RX7 variants have been implicated in psychiatric disorders before and the P2X7 receptor is involved in pathways relevant to psychosis, such as neurotransmission, synaptic plasticity and immune regulation. We conclude that P2RX7 plays a role in vulnerability to develop psychotic symptoms when using cannabis and point to a new pathway that can potentially be targeted by newly developed P2X7 antagonists.
Collapse
Affiliation(s)
- Marco P Boks
- Department of Psychiatry, UMC Utrecht Brain Center, University Medical Centre Utrecht, Utrecht University, The Netherlands
| | - Yujie He
- Department of Psychiatry, UMC Utrecht Brain Center, University Medical Centre Utrecht, Utrecht University, The Netherlands
| | - Chris D Schubart
- Department of Psychiatry, Tergooi Hospital, Blaricum, The Netherlands
| | | | - Laurent Elkrief
- Department of Medicine, Université de Montréal, Montreal, Quebec, Canada
| | - Guillaume Huguet
- Department of Pediatrics, Université de Montréal, Montreal, Quebec, Canada; Center Hospitalier Universitaire Sainte-Justine Research Center, Montreal, Quebec, Canada
| | - Kristel van Eijk
- Department of Neurology and Neurosurgery, UMC Utrecht Brain Center, Utrecht University, The Netherlands
| | - Christiaan H Vinkers
- Department of Psychiatry, Amsterdam UMC (location VUmc), Amsterdam, The Netherlands; Department of Anatomy and Neurosciences, Amsterdam UMC (location VUmc), Amsterdam, The Netherlands
| | - René S Kahn
- Department of Psychiatry, UMC Utrecht Brain Center, University Medical Centre Utrecht, Utrecht University, The Netherlands; Department of psychiatry, Icahn School of Medicine at Mount Sinai, New York City, USA
| | - Tomás Paus
- Bloorview Research Institute, Holland Bloorview Kids Rehabilitation Hospital and Departments of Psychology and Psychiatry, University of Toronto, Toronto, Ontario, Canada
| | - Patricia Conrod
- Center Hospitalier Universitaire Sainte-Justine Research Center, Montreal, Quebec, Canada; Department of Psychiatry, University of Montreal, Montréal, QC, Canada
| | - Elly M Hol
- Department of Translational Neuroscience, UMC Utrecht Brain Center, Utrecht University, The Netherlands; Neuroimmunology Research Group, Netherlands Institute for Neuroscience, An Institute of the Royal Netherlands Academy of Arts and Sciences, Amsterdam, Netherlands
| | - Lot D de Witte
- Department of Psychiatry, UMC Utrecht Brain Center, University Medical Centre Utrecht, Utrecht University, The Netherlands; Department of psychiatry, Icahn School of Medicine at Mount Sinai, New York City, USA.
| |
Collapse
|
10
|
Munoz FM, Patel PA, Gao X, Mei Y, Xia J, Gilels S, Hu H. Reactive oxygen species play a role in P2X7 receptor-mediated IL-6 production in spinal astrocytes. Purinergic Signal 2020; 16:97-107. [PMID: 32146607 DOI: 10.1007/s11302-020-09691-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Accepted: 02/11/2020] [Indexed: 01/29/2023] Open
Abstract
Astrocytes mediate a remarkable variety of cellular functions, including gliotransmitter release. Under pathological conditions, high concentrations of the purinergic receptor agonist adenosine triphosphate (ATP) are released into the extracellular space leading to the activation of the purinergic P2X7 receptor, which in turn can initiate signaling cascades. It is well-established that reactive oxygen species (ROS) increase in macrophages and microglia following P2X7 receptor activation. However, direct evidence that activation of P2X7 receptor leads to ROS production in astrocytes is lacking to date. While it is known that P2X7R activation induces cytokine production, the mechanism involved in this process is unclear. In the present study, we demonstrated that P2X7 receptor activation induced ROS production in spinal astrocytes in a concentration-dependent manner. We also found that P2X7R-mediated ROS production is at least partially through NADPH oxidase. In addition, our ELISA data show that P2X7R-induced IL-6 release was dependent on NADPH oxidase-mediated production of ROS. Collectively, these results reveal that activation of the P2X7 receptor on spinal astrocytes increases ROS production through NADPH oxidase, subsequently leading to IL-6 release. Our results reveal a role of ROS in the P2X7 signaling pathway in mouse spinal cord astrocytes and may indicate a potential mechanism for the astrocytic P2X7 receptor in chronic pain.
Collapse
Affiliation(s)
- Frances M Munoz
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Priya A Patel
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Xinghua Gao
- Department of Pharmacology of Chinese Materia Medica, China Pharmaceutical University, Nanjing, China
| | - Yixiao Mei
- Department of Anesthesiology, Rutgers New Jersey Medical School, 185 S. Orange Ave., Newark, NJ, 07103, USA
| | - Jingsheng Xia
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Sofia Gilels
- Department of Anesthesiology, Rutgers New Jersey Medical School, 185 S. Orange Ave., Newark, NJ, 07103, USA
| | - Huijuan Hu
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA, USA. .,Department of Anesthesiology, Rutgers New Jersey Medical School, 185 S. Orange Ave., Newark, NJ, 07103, USA.
| |
Collapse
|
11
|
Domercq M, Matute C. Targeting P2X4 and P2X7 receptors in multiple sclerosis. Curr Opin Pharmacol 2019; 47:119-125. [PMID: 31015145 DOI: 10.1016/j.coph.2019.03.010] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 03/18/2019] [Accepted: 03/19/2019] [Indexed: 12/25/2022]
Abstract
Multiple sclerosis (MS) is a chronic disease of the central nervous system characterized by massive infiltration of immune cells, demyelination, and axonal loss. However, spontaneous myelin repair can occur during the course of the disease. A major component of this regenerative process is a robust innate immune response consisting of infiltrating macrophages and brain microgliosis. Therefore, specifically targeting myeloid cells could be an attractive therapeutic approach. Purinergic receptors control not only immune cell function together with the activation of microglia and astrocytes, but also neuronal and oligodendroglial survival in the pathology. Thus, targeting these receptors can modulate a whole variety of responses. In this review, we will summarize recent findings highlighting the potential of P2X4 and P2X7 as therapeutic targets for MS.
Collapse
Affiliation(s)
- María Domercq
- Department of Neurosciences, University of the Basque Country, Achucarro Basque Center for Neuroscience-UPV/EHU, Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), 48940 Leioa, Spain
| | - C Matute
- Department of Neurosciences, University of the Basque Country, Achucarro Basque Center for Neuroscience-UPV/EHU, Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), 48940 Leioa, Spain.
| |
Collapse
|
12
|
Guan S, Shen Y, Ge H, Xiong W, He L, Liu L, Yin C, Wei X, Gao Y. Dihydromyricetin Alleviates Diabetic Neuropathic Pain and Depression Comorbidity Symptoms by Inhibiting P2X 7 Receptor. Front Psychiatry 2019; 10:770. [PMID: 31681052 PMCID: PMC6813736 DOI: 10.3389/fpsyt.2019.00770] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Accepted: 09/24/2019] [Indexed: 12/12/2022] Open
Abstract
Diabetic neuropathic pain (DNP) and major depressive disorder (MDD) are common complications of diabetes mellitus and mutually affect each other. As a member of the ATP-gated ion channel family, P2X7 receptor is associated with the transduction of pain signal and the onset of depression. The aim of this study was to investigate the effects of dihydromyricetin (DHM) on rats with comorbid DNP and MDD. After the comorbid model was established, rat behavior changes were monitored by measuring the mechanical withdrawal threshold, thermal withdrawal latency, sugar water preference, immobility time in the forced-swim test, and open-field test parameters. The expressions of P2X7 receptor in the dorsal root ganglia (DRGs), spinal cord, and hippocampus were assessed by quantitative real-time PCR, Western blotting, and double immunofluorescence. We found that hyperalgesia, allodynia, and depressive behaviors of rats with comorbid DNP and MDD were relieved by treatment with DHM or application of a short-hairpin RNA for P2X7 receptor. The expression levels of P2X7, phosphorylated extracellular signal-regulated kinase 1/2, tumor necrosis factor α, and interleukin 1ß were increased in the DRGs, spinal cord, and hippocampus of rats in the model group but restored after DHM or P2X7 short-hairpin RNA treatment. In conclusion, P2X7 receptor in the DRGs, spinal cord, and hippocampus participates in the transduction of DNP and MDD signals. DHM seems to relieve comorbid DNP and MDD by reducing the expression of P2X7 receptor in the DRGs, spinal cord, and hippocampus and may be an effective new drug for the treatment of patients with both DNP and MDD.
Collapse
Affiliation(s)
- Shu Guan
- Department of Physiology, Basic Medical College, Nanchang University, Nanchang, China
| | - Yulin Shen
- Department of Physiology, Basic Medical College, Nanchang University, Nanchang, China.,Sport Biological Centre, China Institute of Sport Science, Beijing, China
| | - Huixiang Ge
- Department of Physiology, Basic Medical College, Nanchang University, Nanchang, China
| | - Wei Xiong
- Department of Preventive Dentistry, Affiliated Stomatological Hospital of Nanchang University, Nanchang, China
| | - Lingkun He
- Department of Preventive Dentistry, Affiliated Stomatological Hospital of Nanchang University, Nanchang, China
| | - Lijuan Liu
- Department of Preventive Dentistry, Affiliated Stomatological Hospital of Nanchang University, Nanchang, China
| | - Cancan Yin
- Department of Preventive Dentistry, Affiliated Stomatological Hospital of Nanchang University, Nanchang, China
| | - Xingyu Wei
- Basic Medical College of Grade 2017, Nanchang University, Nanchang, China
| | - Yun Gao
- Department of Physiology, Basic Medical College, Nanchang University, Nanchang, China.,Jiangxi Provincial Key Laboratory of Autonomic Nervous Function and Disease, Nanchang University, Nanchang, China
| |
Collapse
|
13
|
Su WJ, Zhang T, Jiang CL, Wang W. Clemastine Alleviates Depressive-Like Behavior Through Reversing the Imbalance of Microglia-Related Pro-inflammatory State in Mouse Hippocampus. Front Cell Neurosci 2018; 12:412. [PMID: 30483062 PMCID: PMC6243034 DOI: 10.3389/fncel.2018.00412] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 10/22/2018] [Indexed: 12/20/2022] Open
Abstract
Backgrounds: Abundant reports indicate that neuroinflammatory signaling contributes to behavioral complications associated with depression and may be related to treatment response. The glial cells, especially microglia and astrocytes in brain regions of hippocampus and medial prefrontal cortex (mPFC), are major components of CNS innate immunity. Moreover, purinergic receptor P2X, ligand-gated ion channel 7 (P2X7R) was recently reckoned as a pivotal regulator in central immune system. Besides, it was pointed out that clemastine, a first-generation histamine receptor H1 (HRH1) antagonist with considerable safety profile and pharmacological effect, may suppress immune activation through modulating P2X7R. Herein, we investigated the potential anti-neuroinflammatory effects of clemastine on chronic unpredictable mild stress (CUMS)-induced depressive-like behavior in a mouse model. Methods: Male BALB/c mice were subjected to CUMS for 4 weeks, some of them were injected with clemastine fumarate solution. After the stress procedure, behavioral tests including Sucrose Preference Tests (SPTs), Tail Suspension Tests (TSTs) and locomotor activities were performed to evaluate depressive-like phenotype. Subsequently, expression of cytokines and microglia-related inflammatory biomarkers were assessed. Results: In the present research, we found that clemastine significantly reversed both the declination of SPT percentage and the extension of TST immobility durations in depression mouse model without affecting locomotor activity. Also, we observed that clemastine regulated the imbalance of pro-inflammatory cytokines including interleukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) in the hippocampus and serum of depressive-like mice. Additionally, clemastine significantly suppressed microglial M1-like activation specifically in the hippocampus, and also improved hippocampal astrocytic loss. Furthermore, clemastine downregulated hippocampal P2X7R without interfering with the expression of HRH1. Conclusion: As a safe and efficient anti-allergic agent, clemastine could impressively alleviate stress-related depressive-like phenotype in mice. Further evidence supported that it was because of the potential function of clemastine in modulating the expression of P2X7 receptor possibly independent of HRH1, therefore suppressing the microglial M1-like activation and pro-inflammatory cytokines release in brain regions of hippocampus rather than mPFC.
Collapse
Affiliation(s)
- Wen-Jun Su
- Department of Stress Medicine, Faculty of Psychology and Mental Health, Second Military Medical University, Shanghai, China
| | - Ting Zhang
- Department of Stress Medicine, Faculty of Psychology and Mental Health, Second Military Medical University, Shanghai, China.,Department of Navy Aviation Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai, China
| | - Chun-Lei Jiang
- Department of Stress Medicine, Faculty of Psychology and Mental Health, Second Military Medical University, Shanghai, China
| | - Wei Wang
- Department of Stress Medicine, Faculty of Psychology and Mental Health, Second Military Medical University, Shanghai, China
| |
Collapse
|
14
|
Khan MT, Liu J, Nerlich J, Tang Y, Franke H, Illes P. Regulation of P2X7 receptor function of neural progenitor cells in the hippocampal subgranular zone by neuronal activity in the dentate gyrus. Neuropharmacology 2018; 140:139-149. [PMID: 30092245 DOI: 10.1016/j.neuropharm.2018.08.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Revised: 07/09/2018] [Accepted: 08/02/2018] [Indexed: 12/25/2022]
Abstract
P2X7 receptors (Rs) mediate apoptosis/necrosis in neuronal and non-neuronal systems. Patch-clamp recordings from dentate gyrus (DG) granule cells in acutely prepared hippocampal slices of mice showed that incubation with 4-aminopyridine (4-AP) causes an excitability increase. This led to an enhanced sensitivity of P2X7Rs of the underlying subgranular zone neural progenitor cells (NPCs) towards dibenzoyl-ATP (Bz-ATP). The glutamatergic agonists NMDA and AMPA, as well as the purinergic agonist ATP also increased the Bz-ATP-induced current amplitudes (IBzATP). Tetrodotoxin as well as the standard antiepileptic drugs phenytoin, valproic acid and gabapentin counteracted the effect of 4-AP, most likely by decreasing the firing rate and/or action potential duration of DG granule cells and in consequence the release of ATP/glutamate onto NPCs. Experiments with organotypic hippocampal slice cultures confirmed these results also under conditions when 4-AP was applied for longer time periods and at much lower concentrations than used in acute slices. It was concluded that pathological firing modelled by 4-AP might trigger a sensitivity increase of P2X7Rs leading to necrosis/apoptosis of NPCs with the subsequent decrease of NPC, and in consequence, granule cell number. Hence, supersensitive P2X7Rs may exert a beneficial counter-regulatory effect by reducing the chances for the evolution of chronic temporal lobe epilepsy by ectopically located granule cells.
Collapse
Affiliation(s)
- Muhammad Tahir Khan
- Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Universität Leipzig, 04107, Leipzig, Germany
| | - Juan Liu
- Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Universität Leipzig, 04107, Leipzig, Germany; Acupuncture and Tuina School, Chengdu University of TCM, 610075, Chengdu, China
| | - Jana Nerlich
- Carl-Ludwig-Institut für Physiologie, Universität Leipzig, 04103, Leipzig, Germany
| | - Yong Tang
- Acupuncture and Tuina School, Chengdu University of TCM, 610075, Chengdu, China
| | - Heike Franke
- Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Universität Leipzig, 04107, Leipzig, Germany
| | - Peter Illes
- Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Universität Leipzig, 04107, Leipzig, Germany; Acupuncture and Tuina School, Chengdu University of TCM, 610075, Chengdu, China.
| |
Collapse
|
15
|
Merighi A. The histology, physiology, neurochemistry and circuitry of the substantia gelatinosa Rolandi (lamina II) in mammalian spinal cord. Prog Neurobiol 2018; 169:91-134. [PMID: 29981393 DOI: 10.1016/j.pneurobio.2018.06.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Revised: 06/07/2018] [Accepted: 06/30/2018] [Indexed: 02/06/2023]
Abstract
The substantia gelatinosa Rolandi (SGR) was first described about two centuries ago. In the following decades an enormous amount of information has permitted us to understand - at least in part - its role in the initial processing of pain and itch. Here, I will first provide a comprehensive picture of the histology, physiology, and neurochemistry of the normal SGR. Then, I will analytically discuss the SGR circuits that have been directly demonstrated or deductively envisaged in the course of the intensive research on this area of the spinal cord, with particular emphasis on the pathways connecting the primary afferent fibers and the intrinsic neurons. The perspective existence of neurochemically-defined sets of primary afferent neurons giving rise to these circuits will be also discussed, with the proposition that a cross-talk between different subsets of peptidergic fibers may be the structural and functional substrate of additional gating mechanisms in SGR. Finally, I highlight the role played by slow acting high molecular weight modulators in these gating mechanisms.
Collapse
Affiliation(s)
- Adalberto Merighi
- Department of Veterinary Sciences, University of Turin, Largo Paolo Braccini 2, I-10095 Grugliasco (TO), Italy.
| |
Collapse
|
16
|
Amadio S, Parisi C, Piras E, Fabbrizio P, Apolloni S, Montilli C, Luchetti S, Ruggieri S, Gasperini C, Laghi-Pasini F, Battistini L, Volonté C. Modulation of P2X7 Receptor during Inflammation in Multiple Sclerosis. Front Immunol 2017; 8:1529. [PMID: 29187851 PMCID: PMC5694754 DOI: 10.3389/fimmu.2017.01529] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 10/27/2017] [Indexed: 11/18/2022] Open
Abstract
Multiple sclerosis (MS) is characterized by macrophage accumulation and inflammatory infiltrates into the CNS contributing to demyelination. Because purinergic P2X7 receptor (P2X7R) is known to be abundantly expressed on cells of the hematopoietic lineage and of the nervous system, we further investigated its phenotypic expression in MS and experimental autoimmune encephalomyelitis conditions. By quantitative reverse transcription polymerase chain reaction and flow cytometry, we analyzed the P2X7R expression in human mononuclear cells of peripheral blood from stable and acute relapsing-remitting MS phases. Human monocytes were also challenged in vitro with pro-inflammatory stimuli such as the lipopolysaccharide, or the P2X7R preferential agonist 2′(3′)-O-(4 Benzoylbenzoyl)adenosine 5′-triphosphate, before evaluating P2X7R protein expression. Finally, by immunohistochemistry and immunofluorescence confocal analysis, we investigated the P2X7R expression in frontal cortex from secondary progressive MS cases. We demonstrated that P2X7R is present and inhibited on peripheral monocytes isolated from MS donors during the acute phase of the disease, moreover it is down-regulated in human monocytes after pro-inflammatory stimulation in vitro. P2X7R is instead up-regulated on astrocytes in the parenchyma of frontal cortex from secondary progressive MS patients, concomitantly with monocyte chemoattractant protein-1 chemokine, while totally absent from microglia/macrophages or oligodendrocytes, despite the occurrence of inflammatory conditions. Our results suggest that inhibition of P2X7R on monocytes and up-regulation in astrocytes might contribute to sustain inflammatory mechanisms in MS. By acquiring further knowledge about P2X7R dynamics and identifying P2X7R as a potential marker for the disease, we expect to gain insights into the molecular pathways of MS.
Collapse
Affiliation(s)
- Susanna Amadio
- Cellular Neurobiology Unit, Santa Lucia Foundation, Rome, Italy
| | - Chiara Parisi
- Institute of Cell Biology and Neurobiology, Consiglio Nazionale Delle Ricerche (CNR), Rome, Italy
| | - Eleonora Piras
- Neuroimmunology Unit, Santa Lucia Foundation, Rome, Italy
| | - Paola Fabbrizio
- Cellular Neurobiology Unit, Santa Lucia Foundation, Rome, Italy.,Institute of Cell Biology and Neurobiology, Consiglio Nazionale Delle Ricerche (CNR), Rome, Italy
| | - Savina Apolloni
- Cellular Neurobiology Unit, Santa Lucia Foundation, Rome, Italy
| | - Cinzia Montilli
- Department of Medical Sciences, Surgery and Neurosciences, University of Siena, Siena, Italy
| | - Sabina Luchetti
- Neuroimmunology Research Group, Netherlands Institute for Neuroscience, Amsterdam, Netherlands
| | - Serena Ruggieri
- Neurology Unit "Lancisi", San Camillo Forlanini Hospital, Rome, Italy.,Department of Neurology and Psychiatry, University of Rome "Sapienza", Rome, Italy
| | - Claudio Gasperini
- Neurology Unit "Lancisi", San Camillo Forlanini Hospital, Rome, Italy
| | - Franco Laghi-Pasini
- Department of Medical Sciences, Surgery and Neurosciences, University of Siena, Siena, Italy
| | | | - Cinzia Volonté
- Cellular Neurobiology Unit, Santa Lucia Foundation, Rome, Italy.,Institute of Cell Biology and Neurobiology, Consiglio Nazionale Delle Ricerche (CNR), Rome, Italy
| |
Collapse
|
17
|
Neuronal P2X7 Receptors Revisited: Do They Really Exist? J Neurosci 2017; 37:7049-7062. [PMID: 28747388 DOI: 10.1523/jneurosci.3103-16.2017] [Citation(s) in RCA: 123] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 05/22/2017] [Accepted: 05/24/2017] [Indexed: 12/13/2022] Open
Abstract
P2X7 receptors (Rs) constitute a subclass of ATP-sensitive ionotropic receptors (P2X1-P2X7). P2X7Rs have many distinguishing features, mostly based on their long intracellular C terminus regulating trafficking to the cell membrane, protein-protein interactions, and post-translational modification. Their C-terminal tail is especially important in enabling the transition from the nonselective ion channel mode to a membrane pore allowing the passage of large molecules. There is an ongoing dispute on the existence of neuronal P2X7Rs with consequences for our knowledge on their involvement in neuroinflammation, aggravating stroke, temporal lobe epilepsy, neuropathic pain, and various neurodegenerative diseases. Whereas early results appeared to support the operation of P2X7Rs at neurons, more recently glial P2X7Rs are increasingly considered as indirect causes of neuronal effects. Specific tools for P2X7Rs are of limited value because of the poor selectivity of agonists, and the inherent failure of antibodies to differentiate between the large number of active and inactive splice variants, or gain-of-function and loss-of-function small nucleotide polymorphisms of the receptor. Unfortunately, the available P2RX7 knock-out mice generated by pharmaceutical companies possess certain splice variants, which evade inactivation. In view of the recently discovered bidirectional dialogue between astrocytes and neurons (and even microglia and neurons), we offer an alternative explanation for previous data, which assumedly support the existence of P2X7Rs at neurons. We think that the unbiased reader will follow our argumentation on astrocytic or microglial P2X7Rs being the primary targets of pathologically high extracellular ATP concentrations, although a neuronal localization of these receptors cannot be fully excluded either.
Collapse
|