51
|
Purinergic modulation of frog electroretinographic responses: The role of the ionotropic receptor P2X7. Vis Neurosci 2018; 34:E015. [PMID: 28965497 DOI: 10.1017/s0952523817000128] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The contribution of the purinergic receptors P2X7 (P2X7Rs) to the electroretinographic (ERG) responses was studied by testing the effects of the selective P2X7R antagonist A438079 and the selective P2X7R agonist Bz-ATP on the electroretinograms obtained in perfused frog (Rana ridibunda) eyecup preparations under a variety of stimulation conditions. The P2X7R blockade by 200 µM A438079 diminished the amplitude of the photoreceptor components: the a-wave and the pharmacologically isolated mass receptor potential. In the pure rod-driven and pure cone-driven responses, the amplitude of the postreceptoral ON (b-wave) and OFF (d-wave) components was also diminished. The OFF responses were affected to a greater extent compared to the ON responses. In the mixed rod- and cone-driven responses, obtained in the mesopic intensity range, the b-wave amplitude was increased, while the d-wave amplitude was decreased. The amplitude of the oscillatory potentials was diminished. The relative amplitude changes produced by the P2X7R blockade were greater in the dark-adapted compared to the light-adapted eyes. The application of 100 µM Bz-ATP produced small effects opposite to those of the antagonist, while a prolonged (>20 min) treatment with 1 mM Bz-ATP resulted in a significant amplitude reduction or even abolishment of b- and d-waves. Our results show that endogenous ATP through its P2X7Rs exerts significant, mostly potentiating effects on the ERG photoreceptor and postreceptoral responses. There is a clear ON/OFF asymmetry of the effects on the ERG postreceptoral responses favoring OFF responses: they are always strongly potentiated, while the ON responses are either less potentiated (in the rod-driven and most of the cone-driven responses) or even inhibited (in the mixed rod- and cone-driven responses). The overstimulation of P2X7Rs can produce acute pathological changes, that is, a decrease or abolishment of the ERG responses.
Collapse
|
52
|
Savio LEB, de Andrade Mello P, da Silva CG, Coutinho-Silva R. The P2X7 Receptor in Inflammatory Diseases: Angel or Demon? Front Pharmacol 2018; 9:52. [PMID: 29467654 PMCID: PMC5808178 DOI: 10.3389/fphar.2018.00052] [Citation(s) in RCA: 293] [Impact Index Per Article: 48.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 01/15/2018] [Indexed: 12/13/2022] Open
Abstract
Under physiological conditions, adenosine triphosphate (ATP) is present at low levels in the extracellular milieu, being massively released by stressed or dying cells. Once outside the cells, ATP and related nucleotides/nucleoside generated by ectonucleotidases mediate a high evolutionary conserved signaling system: the purinergic signaling, which is involved in a variety of pathological conditions, including inflammatory diseases. Extracellular ATP has been considered an endogenous adjuvant that can initiate inflammation by acting as a danger signal through the activation of purinergic type 2 receptors-P2 receptors (P2Y G-protein coupled receptors and P2X ligand-gated ion channels). Among the P2 receptors, the P2X7 receptor is the most extensively studied from an immunological perspective, being involved in both innate and adaptive immune responses. P2X7 receptor activation induces large-scale ATP release via its intrinsic ability to form a membrane pore or in association with pannexin hemichannels, boosting purinergic signaling. ATP acting via P2X7 receptor is the second signal to the inflammasome activation, inducing both maturation and release of pro-inflammatory cytokines, such as IL-1β and IL-18, and the production of reactive nitrogen and oxygen species. Furthermore, the P2X7 receptor is involved in caspases activation, as well as in apoptosis induction. During adaptive immune response, P2X7 receptor modulates the balance between the generation of T helper type 17 (Th17) and T regulatory (Treg) lymphocytes. Therefore, this receptor is involved in several inflammatory pathological conditions. In infectious diseases and cancer, P2X7 receptor can have different and contrasting effects, being an angel or a demon depending on its level of activation, cell studied, type of pathogen, and severity of infection. In neuroinflammatory and neurodegenerative diseases, P2X7 upregulation and function appears to contribute to disease progression. In this review, we deeply discuss P2X7 receptor dual function and its pharmacological modulation in the context of different pathologies, and we also highlight the P2X7 receptor as a potential target to treat inflammatory related diseases.
Collapse
Affiliation(s)
- Luiz E B Savio
- Laboratory of Immunophysiology, Biophysics Institute Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Paola de Andrade Mello
- Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Harvard University, Boston, MA, United States
| | - Cleide Gonçalves da Silva
- Division of Vascular Surgery, Department of Surgery, Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
| | - Robson Coutinho-Silva
- Laboratory of Immunophysiology, Biophysics Institute Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| |
Collapse
|
53
|
Teixeira JM, Parada CA, Tambeli CH. A cyclic pathway of P2 × 7, bradykinin, and dopamine receptor activation induces a sustained articular hyperalgesia in the knee joint of rats. Inflamm Res 2017; 67:301-314. [PMID: 29260240 DOI: 10.1007/s00011-017-1122-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 11/27/2017] [Accepted: 11/29/2017] [Indexed: 12/27/2022] Open
Abstract
OBJECTIVE We investigated whether: (1) P2 × 7 receptor activation by its agonist (BzATP) induces articular hyperalgesia in the rat's knee joint via inflammatory mechanisms and (2) activation of P2 × 7 receptors by endogenous ATP contributes to the articular hyperalgesia induced by bradykinin, TNF-α, IL-1β, CINC-1, PGE2, and dopamine. METHODS The articular hyperalgesia was quantified using the rat knee joint incapacitation test. The knee joint inflammation, characterized by the concentration of pro-inflammatory cytokines and by neutrophil migration, was quantified in the synovial lavage fluid by ELISA and myeloperoxidase enzyme activity assay, respectively. RESULTS BzATP induced a dose-dependent articular hyperalgesia in the rat's knee joint that was significantly reduced by the selective antagonists for P2 × 7, bradykinin B1 or B2 receptors, β1 or β2 adrenoceptors, and by pre-treatment with Indomethacin. BzATP induced a local increase of TNF-α, IL-1β, IL-6, and CINC-1 concentration and neutrophil migration into the knee joint. The co-administration of the selective P2 × 7 receptor antagonist A-740003 significantly reduced the articular hyperalgesia induced by bradykinin and dopamine, but not by TNF-α, IL-1β, CINC-1, and PGE2. CONCLUSIONS P2 × 7 receptor activation induces articular hyperalgesia mediated by the previous inflammatory mediator release. P2 × 7 receptor-induced articular hyperalgesia is sustained by the involvement of this purinergic receptor in bradykinin and dopamine-induced hyperalgesia in the knee joint.
Collapse
Affiliation(s)
- Juliana Maia Teixeira
- Department of Structural and Functional Biology, Institute of Biology, State University of Campinas, UNICAMP, Rua Monteiro Lobato, 255, Campinas, SP, CEP 13083-862, Brazil
| | - Carlos Amílcar Parada
- Department of Structural and Functional Biology, Institute of Biology, State University of Campinas, UNICAMP, Rua Monteiro Lobato, 255, Campinas, SP, CEP 13083-862, Brazil
| | - Cláudia Herrera Tambeli
- Department of Structural and Functional Biology, Institute of Biology, State University of Campinas, UNICAMP, Rua Monteiro Lobato, 255, Campinas, SP, CEP 13083-862, Brazil.
| |
Collapse
|
54
|
Site-Specific Regulation of P2X7 Receptor Function in Microglia Gates Morphine Analgesic Tolerance. J Neurosci 2017; 37:10154-10172. [PMID: 28924009 DOI: 10.1523/jneurosci.0852-17.2017] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Revised: 09/03/2017] [Indexed: 01/12/2023] Open
Abstract
Tolerance to the analgesic effects of opioids is a major problem in chronic pain management. Microglia are implicated in opioid tolerance, but the core mechanisms regulating their response to opioids remain obscure. By selectively ablating microglia in the spinal cord using a saporin-conjugated antibody to Mac1, we demonstrate a causal role for microglia in the development, but not maintenance, of morphine tolerance in male rats. Increased P2X7 receptor (P2X7R) activity is a cardinal feature of microglial activation, and in this study we found that morphine potentiates P2X7R-mediated Ca2+ responses in resident spinal microglia acutely isolated from morphine tolerant rats. The increased P2X7R function was blocked in cultured microglia by PP2, a Src family protein tyrosine kinase inhibitor. We identified Src family kinase activation mediated by μ-receptors as a key mechanistic step required for morphine potentiation of P2X7R function. Furthermore, we show by site-directed mutagenesis that tyrosine (Y382-384) within the P2X7R C-terminus is differentially modulated by repeated morphine treatment and has no bearing on normal P2X7R function. Intrathecal administration of a palmitoylated peptide corresponding to the Y382-384 site suppressed morphine-induced microglial reactivity and preserved the antinociceptive effects of morphine in male rats. Thus, site-specific regulation of P2X7R function mediated by Y382-384 is a novel cellular determinant of the microglial response to morphine that critically underlies the development of morphine analgesic tolerance.SIGNIFICANCE STATEMENT Controlling pain is one of the most difficult challenges in medicine and its management is a requirement of a large diversity of illnesses. Although morphine and other opioids offer dramatic and impressive relief of pain, their impact is truncated by loss of efficacy (analgesic tolerance). Understanding why this occurs and how to prevent it are of critical importance in improving pain therapies. We uncovered a novel site (Y382-384) within the P2X7 receptor that can be targeted to blunt the development of morphine analgesic tolerance, without affecting normal P2X7 receptor function. Our findings provide a critical missing mechanistic piece, site-specific modulation by Y382-384, that unifies P2X7R function to the activation of spinal microglia and the development of morphine tolerance.
Collapse
|
55
|
Abdelrahman A, Namasivayam V, Hinz S, Schiedel AC, Köse M, Burton M, El-Tayeb A, Gillard M, Bajorath J, de Ryck M, Müller CE. Characterization of P2X4 receptor agonists and antagonists by calcium influx and radioligand binding studies. Biochem Pharmacol 2017; 125:41-54. [DOI: 10.1016/j.bcp.2016.11.016] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 11/15/2016] [Indexed: 10/20/2022]
|
56
|
Rat P, Olivier E, Tanter C, Wakx A, Dutot M. A fast and reproducible cell- and 96-well plate-based method for the evaluation of P2X7 receptor activation using YO-PRO-1 fluorescent dye. J Biol Methods 2017; 4:e64. [PMID: 31453224 PMCID: PMC6708926 DOI: 10.14440/jbm.2017.136] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 12/14/2016] [Accepted: 12/14/2016] [Indexed: 02/06/2023] Open
Abstract
The YO-PRO-1 assay provides a quantitative estimation of P2X7 receptor activation. P2X7 receptor is associated to pathological conditions including infectious, inflammatory, neurological, musculoskeletal disorders, pain and cancer. Most primary cells and cell lines from diverse origin may be used thanks to the ubiquitous distribution of P2X7 receptor. To study the activation of P2X7 receptor by chemicals or biological agents, we established a microplate-based cytometry protocol to accurately and rapidly quantify the activation of P2X7 receptor that leads to the formation of large pores in cell membranes. The YO-PRO-1 assay is based on the ability of cells to incorporate and bind YO-PRO-1 dye to DNA after activation of P2X7 receptor through pore formation. Cells are seeded in 96-well plates and incubated with the compound being tested for the appropriate time. The microplate is then incubated for 10 min with YO-PRO-1 staining solution. After the 10 min staining time, fluorescence signal is read using a microplate reader in 1 min. This procedure is easier and requires less handling steps than flow cytometry. 96-well plate based YO-PRO-1 assay is a reproducible and fast method to study both P2X7 receptor activation by toxic agents at subnecrotic concentrations and P2X7 receptor inhibition by antagonists.
Collapse
Affiliation(s)
- Patrice Rat
- UMR 8638 CNRS COMETE, Université Paris Descartes, Sorbonne Paris Cité, Faculté de Pharmacie, 4 avenue de l'Observatoire, 75006 Paris, France
| | - Elodie Olivier
- UMR 8638 CNRS COMETE, Université Paris Descartes, Sorbonne Paris Cité, Faculté de Pharmacie, 4 avenue de l'Observatoire, 75006 Paris, France.,Soliance-Givaudan, Route de Bazancourt, 51110 Pomacle, France
| | - Caroline Tanter
- Recherche et Développement, Laboratoire d'Evaluation Physiologique, Yslab, 2 rue Félix Le Dantec, 29000 Quimper, France
| | - Anaïs Wakx
- UMR 8638 CNRS COMETE, Université Paris Descartes, Sorbonne Paris Cité, Faculté de Pharmacie, 4 avenue de l'Observatoire, 75006 Paris, France
| | - Mélody Dutot
- UMR 8638 CNRS COMETE, Université Paris Descartes, Sorbonne Paris Cité, Faculté de Pharmacie, 4 avenue de l'Observatoire, 75006 Paris, France.,Recherche et Développement, Laboratoire d'Evaluation Physiologique, Yslab, 2 rue Félix Le Dantec, 29000 Quimper, France
| |
Collapse
|
57
|
Fujiwara M, Ohbori K, Ohishi A, Nishida K, Uozumi Y, Nagasawa K. Species Difference in Sensitivity of Human and Mouse P2X7 Receptors to Inhibitory Effects of Divalent Metal Cations. Biol Pharm Bull 2017; 40:375-380. [DOI: 10.1248/bpb.b16-00887] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Makiko Fujiwara
- Department of Environmental Biochemistry, Kyoto Pharmaceutical University
| | - Kenshi Ohbori
- Department of Environmental Biochemistry, Kyoto Pharmaceutical University
| | - Akihiro Ohishi
- Department of Environmental Biochemistry, Kyoto Pharmaceutical University
| | - Kentaro Nishida
- Department of Environmental Biochemistry, Kyoto Pharmaceutical University
| | | | - Kazuki Nagasawa
- Department of Environmental Biochemistry, Kyoto Pharmaceutical University
| |
Collapse
|
58
|
Abstract
The P2X7 receptor is a trimeric ion channel gated by extracellular adenosine 5'-triphosphate. The receptor is present on an increasing number of different cells types including stem, blood, glial, neural, ocular, bone, dental, exocrine, endothelial, muscle, renal and skin cells. The P2X7 receptor induces various downstream events in a cell-specific manner, including inflammatory molecule release, cell proliferation and death, metabolic events, and phagocytosis. As such this receptor plays important roles in heath and disease. Increasing knowledge about the P2X7 receptor has been gained from studies of, but not limited to, protein chemistry including cloning, site-directed mutagenesis, crystal structures and atomic modeling, as well as from studies of primary tissues and transgenic mice. This chapter focuses on the P2X7 receptor itself. This includes the P2RX7 gene and its products including splice and polymorphic variants. This chapter also reviews modulators of P2X7 receptor activation and inhibition, as well as the transcriptional regulation of the P2RX7 gene via its promoter and enhancer regions, and by microRNA and long-coding RNA. Furthermore, this chapter discusses the post-translational modification of the P2X7 receptor by N-linked glycosylation, adenosine 5'-diphosphate ribosylation and palmitoylation. Finally, this chapter reviews interaction partners of the P2X7 receptor, and its cellular localisation and trafficking within cells.
Collapse
Affiliation(s)
- Ronald Sluyter
- School of Biological Sciences, University of Wollongong, Wollongong, NSW, 2522, Australia. .,Centre for Medical and Molecular Bioscience, University of Wollongong, Wollongong, NSW, 2522, Australia. .,Illawarra Health and Medical Research Institute, Wollongong, NSW, 2522, Australia.
| |
Collapse
|
59
|
Zhang PA, Xu QY, Xue L, Zheng H, Yan J, Xiao Y, Xu GY. Neonatal Maternal Deprivation Enhances Presynaptic P2X7 Receptor Transmission in Insular Cortex in an Adult Rat Model of Visceral Hypersensitivity. CNS Neurosci Ther 2016; 23:145-154. [PMID: 27976523 DOI: 10.1111/cns.12663] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2016] [Revised: 10/06/2016] [Accepted: 11/11/2016] [Indexed: 12/12/2022] Open
Abstract
AIMS Insular cortex (IC) is involved in processing the information of pain. The aim of this study was to investigate roles and mechanisms of P2X7 receptors (P2X7Rs) in IC in development of visceral hypersensitivity of adult rats with neonatal maternal deprivation (NMD). METHODS Visceral hypersensitivity was quantified by abdominal withdrawal reflex threshold to colorectal distension (CRD). Expression of P2X7Rs was determined by qPCR and Western blot. Synaptic transmission in IC was recorded by patch-clamp recording. RESULTS The expression of P2X7Rs and glutamatergic neurotransmission in IC was significantly increased in NMD rats when compared with age-matched controls. Application of BzATP (P2X7R agonist) enhanced the frequency of spontaneous excitatory postsynaptic currents (sEPSC) and miniature excitatory postsynaptic currents (mEPSC) in IC slices of control rats. Application of BBG (P2X7R antagonist) suppressed the frequencies of sEPSC and mEPSC in IC slices of NMD rats. Microinjection of BzATP into right IC significantly decreased CRD threshold in control rats while microinjection of BBG or A438079 into right IC greatly increased CRD threshold in NMD rats. CONCLUSION Data suggested that the enhanced activities of P2X7Rs in IC, likely through a presynaptic mechanism, contributed to visceral hypersensitivity of adult rats with NMD.
Collapse
Affiliation(s)
- Ping-An Zhang
- Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases, Laboratory of Translational Pain Medicine, Institute of Neuroscience, Soochow University, Suzhou, China
| | - Qi-Ya Xu
- Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases, Laboratory of Translational Pain Medicine, Institute of Neuroscience, Soochow University, Suzhou, China
| | - Lu Xue
- Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases, Laboratory of Translational Pain Medicine, Institute of Neuroscience, Soochow University, Suzhou, China
| | - Hang Zheng
- Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases, Laboratory of Translational Pain Medicine, Institute of Neuroscience, Soochow University, Suzhou, China
| | - Jun Yan
- The Second Affiliated Hospital of Soochow University, Suzhou, China
| | - Ying Xiao
- Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases, Laboratory of Translational Pain Medicine, Institute of Neuroscience, Soochow University, Suzhou, China.,Chengdu Radio and TV University, Chengdu, China
| | - Guang-Yin Xu
- Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases, Laboratory of Translational Pain Medicine, Institute of Neuroscience, Soochow University, Suzhou, China
| |
Collapse
|
60
|
Lim JC, Lu W, Beckel JM, Mitchell CH. Neuronal Release of Cytokine IL-3 Triggered by Mechanosensitive Autostimulation of the P2X7 Receptor Is Neuroprotective. Front Cell Neurosci 2016; 10:270. [PMID: 27932954 PMCID: PMC5120082 DOI: 10.3389/fncel.2016.00270] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 11/07/2016] [Indexed: 12/05/2022] Open
Abstract
Mechanical strain due to increased pressure or swelling activates inflammatory responses in many neural systems. As cytokines and chemokine messengers lead to both pro-inflammatory and neuroprotective actions, understanding the signaling patterns triggered by mechanical stress may help improve overall outcomes. While cytokine signaling in neural systems is often associated with glial cells like astrocytes and microglia, the contribution of neurons themselves to the cytokine response is underappreciated and has bearing on any balanced response. Mechanical stretch of isolated neurons was previously shown to trigger ATP release through pannexin hemichannels and autostimulation of P2X7 receptors (P2X7Rs) on the neural membrane. Given that P2X7Rs are linked to cytokine activation in other cells, this study investigates the link between neuronal stretch and cytokine release through a P2X7-dependent pathway. Cytokine assays showed application of a 4% strain to isolated rat retinal ganglion cells (RGCs) released multiple cytokines. The P2X7R agonist BzATP also released multiple cytokines; Interleukin 3 (IL-3), TNF-α, CXCL9, VEGF, L-selectin, IL-4, GM-CSF, IL-10, IL-1Rα, MIP and CCL20 were released by both stimuli, with the release of IL-3 greatest with either stimuli. Stretch-dependent IL-3 release was confirmed with ELISA and blocked by P2X7R antagonists A438079 and Brilliant Blue G (BBG), implicating autostimulation of the P2X7R in stretch-dependent IL-3 release. Neuronal IL-3 release triggered by BzATP required extracellular calcium. The IL-3Rα receptor was expressed on RGCs but not astrocytes, and both IL-3Rα and IL-3 itself were predominantly expressed in the retinal ganglion cell layer of adult retinal sections, implying autostimulation of receptors by released IL-3. While the number of surviving ganglion cells decreased with time in culture, the addition of IL-3 protected against this loss of neurons. Expression of mRNA for IL-3 and IL-3Rα increased in rat retinas stretched with moderate intraocular pressure (IOP) elevation; BBG blocked the rise in IL-3, implicating a role for the P2X7R in transcriptional regulation in vivo. In summary, mechanical stretch triggers release of cytokines from neurons that can convey neuroprotection. The enhancement of these signals in vivo implicates P2X7R-mediated IL-3 signaling as an endogenous pathway that could minimize damage following neuronal exposure to chronic mechanical strain.
Collapse
Affiliation(s)
- Jason C Lim
- Department of Anatomy and Cell Biology, University of Pennsylvania Philadelphia, PA, USA
| | - Wennan Lu
- Department of Anatomy and Cell Biology, University of Pennsylvania Philadelphia, PA, USA
| | - Jonathan M Beckel
- Department of Pharmacology and Chemical Biology, University of Pittsburgh Pittsburgh, PA, USA
| | - Claire H Mitchell
- Department of Anatomy and Cell Biology, University of PennsylvaniaPhiladelphia, PA, USA; Department of Physiology, University of PennsylvaniaPhiladelphia, PA, USA; Department of Ophthalmology, University of PennsylvaniaPhiladelphia, PA, USA
| |
Collapse
|
61
|
Brilliant Blue Dyes in Daily Food: How Could Purinergic System Be Affected? INTERNATIONAL JOURNAL OF FOOD SCIENCE 2016; 2016:7548498. [PMID: 27833914 PMCID: PMC5090090 DOI: 10.1155/2016/7548498] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 08/28/2016] [Indexed: 11/21/2022]
Abstract
Dyes were first obtained from the extraction of plant sources in the Neolithic period to produce dyed clothes. At the beginning of the 19th century, synthetic dyes were produced to color clothes on a large scale. Other applications for synthetic dyes include the pharmaceutical and food industries, which are important interference factors in our lives and health. Herein, we analyzed the possible implications of some dyes that are already described as antagonists of purinergic receptors, including special Brilliant Blue G and its derivative FD&C Blue No. 1. Purinergic receptor family is widely expressed in the body and is critical to relate to much cellular homeostasis maintenance as well as inflammation and cell death. In this review, we discuss previous studies and show purinergic signaling as an important issue to be aware of in food additives development and their correlations with the physiological functions.
Collapse
|
62
|
Bhattacharya A, Biber K. The microglial ATP-gated ion channel P2X7 as a CNS drug target. Glia 2016; 64:1772-87. [PMID: 27219534 DOI: 10.1002/glia.23001] [Citation(s) in RCA: 156] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Revised: 04/17/2016] [Accepted: 04/18/2016] [Indexed: 12/14/2022]
Abstract
Based on promising preclinical evidence, microglial P2X7 has increasingly being recognized as a target for therapeutic intervention in neurological and psychiatric diseases. However, despite this knowledge no P2X7-related drug has yet entered clinical trials with respect to CNS diseases. We here discuss the current literature on P2X7 being a drug target and identify unsolved issues and still open questions that have hampered the development of P2X7 dependent therapeutic approaches for CNS diseases. It is concluded here that the lack of brain penetrating P2X7 antagonists is a major obstacle in the field and that central P2X7 is a yet untested clinical drug target. In the CNS, microglial P2X7 activation causes neuroinflammation, which in turn plays a role in various CNS disorders. This has resulted in a surge of brain penetrant P2X7 antagonists. P2X7 is a viable, clinically untested CNS drug target. GLIA 2016;64:1772-1787.
Collapse
Affiliation(s)
- Anindya Bhattacharya
- LLC. Neuroscience Drug Discovery, Janssen Research & Development, 3210 Merryfield Row, San Diego, California
| | - Knut Biber
- Department of Psychiatry and Psychotherapy, University Hospital Freiburg, Hauptstrasse 5, Freiburg, Germany.,Department of Neuroscience, University Medical Center Groningen, University of Groningen, Ant. Deusinglaan 1, AV Groningen, The Netherlands
| |
Collapse
|
63
|
Mac Nair CE, Schlamp CL, Montgomery AD, Shestopalov VI, Nickells RW. Retinal glial responses to optic nerve crush are attenuated in Bax-deficient mice and modulated by purinergic signaling pathways. J Neuroinflammation 2016; 13:93. [PMID: 27126275 PMCID: PMC4850653 DOI: 10.1186/s12974-016-0558-y] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2015] [Accepted: 04/20/2016] [Indexed: 01/14/2023] Open
Abstract
Background Retinal ganglion cell (RGC) soma death is a consequence of optic nerve damage, including in optic neuropathies like glaucoma. The activation of the innate immune network in the retina after nerve damage has been linked to RGC pathology. Since the eye is immune privileged, innate immune functions are the responsibility of the glia, specifically the microglia, astrocytes, and Müller cells that populate the retina. Glial activation, leading to the production of inflammatory cytokines, is a hallmark feature of retinal injury resulting from optic nerve damage and purported to elicit secondary degeneration of RGC somas. Methods A mouse model of optic nerve crush (ONC) was used to study retinal glial activation responses. RGC apoptosis was blocked using Bax-deficient mice. Glial activation responses were monitored by quantitative PCR and immunofluorescent labeling in retinal sections of activation markers. ATP signaling pathways were interrogated using P2X receptor agonists and antagonists and Pannexin 1 (Panx1)-deficient mice with RGC-specific deletion. Results ONC induced activation of both macroglia and microglia in the retina, and both these responses were dramatically muted if RGC death was blocked by deletion of the Bax gene. Macroglial, but not microglial, activation was modulated by purinergic receptor activation. Release of ATP after optic nerve damage was not mediated by PANX1 channels in RGCs. Conclusions RGC death in response to ONC plays a principal stimulatory role in the retinal glial activation response. Electronic supplementary material The online version of this article (doi:10.1186/s12974-016-0558-y) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Caitlin E Mac Nair
- Department of Ophthalmology and Visual Sciences, University of Wisconsin, 571A Medical Sciences-1300 University Ave, Madison, WI, 53706, USA.,Cellular and Molecular Pathology Graduate Program, University of Wisconsin-Madison, 3170-10K/L MFCB, 1685 Highland Avenue, Madison, WI, 53705, USA
| | - Cassandra L Schlamp
- Department of Ophthalmology and Visual Sciences, University of Wisconsin, 571A Medical Sciences-1300 University Ave, Madison, WI, 53706, USA
| | - Angela D Montgomery
- Department of Ophthalmology and Visual Sciences, University of Wisconsin, 571A Medical Sciences-1300 University Ave, Madison, WI, 53706, USA
| | - Valery I Shestopalov
- Department of Ophthalmology, University of Miami Miller School of Medicine, 900 N.W. 17th Street, Miami, FL, 33136, USA.,Department of Cell Biology and Anatomy, University of Miami Miller School of Medicine, 900 N.W. 17th Street, Miami, FL, 33136, USA
| | - Robert W Nickells
- Department of Ophthalmology and Visual Sciences, University of Wisconsin, 571A Medical Sciences-1300 University Ave, Madison, WI, 53706, USA.
| |
Collapse
|
64
|
Conductance of P2X4 purinergic receptor is determined by conformational equilibrium in the transmembrane region. Proc Natl Acad Sci U S A 2016; 113:4741-6. [PMID: 27071117 DOI: 10.1073/pnas.1600519113] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ligand-gated ion channels are partially activated by their ligands, resulting in currents lower than the currents evoked by the physiological full agonists. In the case of P2X purinergic receptors, a cation-selective pore in the transmembrane region expands upon ATP binding to the extracellular ATP-binding site, and the currents evoked by α,β-methylene ATP are lower than the currents evoked by ATP. However, the mechanism underlying the partial activation of the P2X receptors is unknown although the crystal structures of zebrafish P2X4 receptor in the apo and ATP-bound states are available. Here, we observed the NMR signals from M339 and M351, which were introduced in the transmembrane region, and the endogenous alanine and methionine residues of the zebrafish P2X4 purinergic receptor in the apo, ATP-bound, and α,β-methylene ATP-bound states. Our NMR analyses revealed that, in the α,β-methylene ATP-bound state, M339, M351, and the residues that connect the ATP-binding site and the transmembrane region, M325 and A330, exist in conformational equilibrium between closed and open conformations, with slower exchange rates than the chemical shift difference (<100 s(-1)), suggesting that the small population of the open conformation causes the partial activation in this state. Our NMR analyses also revealed that the transmembrane region adopts the open conformation in the state bound to the inhibitor trinitrophenyl-ATP, and thus the antagonism is due to the closure of ion pathways, except for the pore in the transmembrane region: i.e., the lateral cation access in the extracellular region.
Collapse
|
65
|
Pollatzek E, Hitzel N, Ott D, Raisl K, Reuter B, Gerstberger R. Functional expression of P2 purinoceptors in a primary neuroglial cell culture of the rat arcuate nucleus. Neuroscience 2016; 327:95-114. [PMID: 27072848 DOI: 10.1016/j.neuroscience.2016.04.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 04/06/2016] [Accepted: 04/06/2016] [Indexed: 12/22/2022]
Abstract
The arcuate nucleus (ARC) plays an important role in the hypothalamic control of energy homeostasis. Expression of various purinoceptor subtypes in the rat ARC and physiological studies suggest a modulatory function of P2 receptors within the neuroglial ARC circuitry. A differentiated mixed neuronal and glial microculture was therefore established from postnatal rat ARC, revealing neuronal expression of ARC-specific transmitters involved in food intake regulation (neuropeptide Y (NPY), proopiomelanocortin (POMC), tyrosine hydroxylase (TH)). Some NPYergic neurons cosynthesized TH, while POMC and TH expression proved to be mutually exclusive. Stimulation with the general purinoceptor agonists 2-methylthioadenosine-5'triphosphate (2-MeSATP) and ATP but not the P2X1/P2X3 receptor subtype agonist α,β-methyleneadenosine-5'triphosphate (α,β-meATP) induced intracellular calcium signals in ARC neurons and astrocytes. Some 5-10% each of 2-MeSATP responsive neurons expressed POMC, NYP or TH. Supporting the calcium imaging data, radioligand binding studies to hypothalamic membranes showed high affinity for 2-MeSATP, ATP but not α,β-meATP to displace [α-(35)S]deoxyadenosine-5'thiotriphosphate ([(35)S]dATPαS) from P2 receptors. Repetitive superfusion with equimolar 2-MeSATP allowed categorization of ARC cells into groups with a high or low (LDD) degree of purinoceptor desensitization, the latter allowing further receptor characterization. Calcium imaging experiments performed at 37°C vs. room temperature showed further reduction of desensitization. Agonist-mediated intracellular calcium signals were suppressed in all LDD neurons but only 25% of astrocytes in the absence of extracellular calcium, suggestive of metabotropic P2Y receptor expression in the majority of ARC astrocytes. The highly P2Y1-selective receptor agonists MRS2365 and 2-methylthioadenosine-5'diphosphate (2-MeSADP) activated 75-85% of all 2-MeSATP-responsive ARC astrocytes. Taking into consideration the high potency to dose-dependently stimulate ARC cells of the LDD group, the high affinity for rat P2X(1-3) and low affinity for rat P2X4, P2X7 and P2Y receptor subtypes except P2Y1 and P2Y13, the agonist 2-MeSATP primarily acted upon P2X2 and P2Y1 purinoceptors to trigger intracellular calcium signaling in ARC neurons and astrocytes.
Collapse
Affiliation(s)
- Eric Pollatzek
- Institut für Veterinär-Physiologie und -Biochemie, Justus-Liebig-Universität Giessen, Frankfurter Strasse 100, D-35392 Giessen, Deutschland.
| | - Norma Hitzel
- Institut für Veterinär-Physiologie und -Biochemie, Justus-Liebig-Universität Giessen, Frankfurter Strasse 100, D-35392 Giessen, Deutschland.
| | - Daniela Ott
- Institut für Veterinär-Physiologie und -Biochemie, Justus-Liebig-Universität Giessen, Frankfurter Strasse 100, D-35392 Giessen, Deutschland.
| | - Katrin Raisl
- Institut für Veterinär-Physiologie und -Biochemie, Justus-Liebig-Universität Giessen, Frankfurter Strasse 100, D-35392 Giessen, Deutschland.
| | - Bärbel Reuter
- Institut für Veterinär-Physiologie und -Biochemie, Justus-Liebig-Universität Giessen, Frankfurter Strasse 100, D-35392 Giessen, Deutschland.
| | - Rüdiger Gerstberger
- Institut für Veterinär-Physiologie und -Biochemie, Justus-Liebig-Universität Giessen, Frankfurter Strasse 100, D-35392 Giessen, Deutschland.
| |
Collapse
|
66
|
Marichal N, Fabbiani G, Trujillo-Cenóz O, Russo RE. Purinergic signalling in a latent stem cell niche of the rat spinal cord. Purinergic Signal 2016; 12:331-41. [PMID: 26988236 DOI: 10.1007/s11302-016-9507-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 03/07/2016] [Indexed: 01/11/2023] Open
Abstract
The ependyma of the spinal cord harbours stem cells which are activated by traumatic spinal cord injury. Progenitor-like cells in the central canal (CC) are organized in spatial domains. The cells lining the lateral aspects combine characteristics of ependymocytes and radial glia (RG) whereas in the dorsal and ventral poles, CC-contacting cells have the morphological phenotype of RG and display complex electrophysiological phenotypes. The signals that may affect these progenitors are little understood. Because ATP is massively released after spinal cord injury, we hypothesized that purinergic signalling plays a part in this spinal stem cell niche. We combined immunohistochemistry, in vitro patch-clamp whole-cell recordings and Ca(2+) imaging to explore the effects of purinergic agonists on ependymal progenitor-like cells in the neonatal (P1-P6) rat spinal cord. Prolonged focal application of a high concentration of ATP (1 mM) induced a slow inward current. Equimolar concentrations of BzATP generated larger currents that reversed close to 0 mV, had a linear current-voltage relationship and were blocked by Brilliant Blue G, suggesting the presence of functional P2X7 receptors. Immunohistochemistry showed that P2X7 receptors were expressed around the CC and the processes of RG. BzATP also generated Ca(2+) waves in RG that were triggered by Ca(2+) influx and propagated via Ca(2+) release from internal stores through activation of ryanodine receptors. We speculate that the intracellular Ca(2+) signalling triggered by P2X7 receptor activation may be an epigenetic mechanism to modulate the behaviour of progenitors in response to ATP released after injury.
Collapse
Affiliation(s)
- Nicolás Marichal
- Neurofisiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, Avenida Italia 3318, CP 11600, Montevideo, Uruguay
- Adult Neurogenesis and Cellular Reprogramming, Institute of Physiological Chemistry, Johannes Gutenberg University, Hanns-Dieter-Husch-Weg 19, Mainz, 55128, Germany
| | - Gabriela Fabbiani
- Neurofisiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, Avenida Italia 3318, CP 11600, Montevideo, Uruguay
| | - Omar Trujillo-Cenóz
- Neurofisiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, Avenida Italia 3318, CP 11600, Montevideo, Uruguay
| | - Raúl E Russo
- Neurofisiología Celular y Molecular, Instituto de Investigaciones Biológicas Clemente Estable, Avenida Italia 3318, CP 11600, Montevideo, Uruguay.
| |
Collapse
|
67
|
Mahaut-Smith MP, Taylor KA, Evans RJ. Calcium Signalling through Ligand-Gated Ion Channels such as P2X1 Receptors in the Platelet and other Non-Excitable Cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 898:305-29. [PMID: 27161234 DOI: 10.1007/978-3-319-26974-0_13] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Ligand-gated ion channels on the cell surface are directly activated by the binding of an agonist to their extracellular domain and often referred to as ionotropic receptors. P2X receptors are ligand-gated non-selective cation channels with significant permeability to Ca(2+) whose principal physiological agonist is ATP. This chapter focuses on the mechanisms by which P2X1 receptors, a ubiquitously expressed member of the family of ATP-gated channels, can contribute to cellular responses in non-excitable cells. Much of the detailed information on the contribution of P2X1 to Ca(2+) signalling and downstream functional events has been derived from the platelet. The underlying primary P2X1-generated signalling event in non-excitable cells is principally due to Ca(2+) influx, although Na(+) entry will also occur along with membrane depolarization. P2X1 receptor stimulation can lead to additional Ca(2+) mobilization via a range of routes such as amplification of G-protein-coupled receptor-dependent Ca(2+) responses. This chapter also considers the mechanism by which cells generate extracellular ATP for autocrine or paracrine activation of P2X1 receptors. For example cytosolic ATP efflux can result from opening of pannexin anion-permeable channels or following damage to the cell membrane. Alternatively, ATP stored in specialised secretory vesicles can undergo quantal release via the process of exocytosis. Examples of physiological or pathophysiological roles of P2X1-dependent signalling in non-excitable cells are also discussed, such as thrombosis and immune responses.
Collapse
Affiliation(s)
- Martyn P Mahaut-Smith
- Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester, LE1 9HN, UK.
| | - Kirk A Taylor
- Department of Biomedical and Forensic Sciences, Anglia Ruskin University, Cambridge, UK
| | - Richard J Evans
- Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester, LE1 9HN, UK
| |
Collapse
|
68
|
Maynard JP, Lee JS, Sohn BH, Yu X, Lopez-Terrada D, Finegold MJ, Goss JA, Thevananther S. P2X3 purinergic receptor overexpression is associated with poor recurrence-free survival in hepatocellular carcinoma patients. Oncotarget 2015; 6:41162-79. [PMID: 26517690 PMCID: PMC4747397 DOI: 10.18632/oncotarget.6240] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Accepted: 09/17/2015] [Indexed: 01/01/2023] Open
Abstract
UNLABELLED P2 purinergic receptors are overexpressed in certain cancer tissues, but the pathophysiologic relevance of purinergic signaling in hepatocellular carcinoma (HCC) remains unknown. To examine the role of P2 purinergic signaling in the pathogenesis of HCC and characterize extracellular nucleotide effects on HCC cell proliferation, two independent HCC patient cohorts were analyzed for P2 purinergic receptor expression, and nucleotide treated HCC cell lines were evaluated for effects on proliferation and cell cycle progression. Our studies suggest that multiple P2 purinergic receptor isoforms are overexpressed in liver tumors, as compared to uninvolved liver, and dysregulation of P2 purinergic receptor expression is apparent in HCC cell lines, as compared to human primary hepatocytes. High P2X3 purinergic receptor expression is associated with poor recurrence-free survival (RFS), while high P2Y13 expression is associated with improved RFS. Extracellular nucleotide treatment alone is sufficient to induce cell cycle progression, via activation of JNK signaling, and extracellular ATP-mediated activation of P2X3 receptors promotes proliferation in HCC cells. CONCLUSION Our analysis of HCC patient livers and HCC cells in vitro identifies a novel role for dysregulation of P2 purinergic signaling in the induction of hyper-proliferative HCC phenotype and identifies P2X3 purinergic receptors as potential new targets for therapy.
Collapse
MESH Headings
- Adenosine Triphosphate/pharmacology
- Adolescent
- Adult
- Aged
- Blotting, Western
- Carcinoma, Hepatocellular/complications
- Carcinoma, Hepatocellular/genetics
- Carcinoma, Hepatocellular/metabolism
- Cell Cycle/drug effects
- Cell Cycle/genetics
- Cell Line, Tumor
- Cell Proliferation/drug effects
- Cell Proliferation/genetics
- Cells, Cultured
- Cohort Studies
- Disease-Free Survival
- Female
- Gene Expression Regulation, Neoplastic
- Hepatitis C/complications
- Hepatitis C/genetics
- Hepatitis C/metabolism
- Humans
- Immunohistochemistry
- Liver Neoplasms/complications
- Liver Neoplasms/genetics
- Liver Neoplasms/metabolism
- Male
- Middle Aged
- Neoplasm Recurrence, Local
- Receptors, Purinergic P2X3/genetics
- Receptors, Purinergic P2X3/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Young Adult
Collapse
Affiliation(s)
- Janielle P. Maynard
- Department of Pediatrics, Division of Gastroenterology, Hepatology and Nutrition, Texas Children's Liver Center, Houston, TX, USA
- Program in Translational Biology and Molecular Medicine, Baylor College of Medicine, Houston, TX, USA
| | - Ju-Seog Lee
- Department of Systems Biology, UT MD Anderson Cancer Center, Houston, TX, USA
| | - Bo Hwa Sohn
- Department of Systems Biology, UT MD Anderson Cancer Center, Houston, TX, USA
| | - Xiaoying Yu
- Department of Medicine, Division of Gastroenterology, Baylor College of Medicine, Houston, TX, USA
| | - Dolores Lopez-Terrada
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX, USA
| | - Milton J. Finegold
- Program in Translational Biology and Molecular Medicine, Baylor College of Medicine, Houston, TX, USA
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX, USA
| | - John A. Goss
- Program in Translational Biology and Molecular Medicine, Baylor College of Medicine, Houston, TX, USA
- Department of Surgery, Baylor College of Medicine, Houston, TX, USA
| | - Sundararajah Thevananther
- Department of Pediatrics, Division of Gastroenterology, Hepatology and Nutrition, Texas Children's Liver Center, Houston, TX, USA
- Program in Translational Biology and Molecular Medicine, Baylor College of Medicine, Houston, TX, USA
| |
Collapse
|
69
|
Feng JF, Gao XF, Pu YY, Burnstock G, Xiang Z, He C. P2X7 receptors and Fyn kinase mediate ATP-induced oligodendrocyte progenitor cell migration. Purinergic Signal 2015; 11:361-9. [PMID: 26099359 DOI: 10.1007/s11302-015-9458-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 06/12/2015] [Indexed: 12/19/2022] Open
Abstract
Recruitment of oligodendrocyte precursor cells (OPCs) to the lesions is the most important event for remyelination after central nervous system (CNS) injury or in demyelinating diseases. However, the underlying molecular mechanism is not fully understood. In the present study, we found high concentrations of ATP could increase the number of migrating OPCs in vitro, while after pretreatment with oxidized ATP (a P2X7 receptor antagonist), the promotive effect was attenuated. The promotive effect of 2'(3')-O-(4-benzoylbenzoyl) adenosine 5'-triphosphate (BzATP) (a P2X7 receptor agonist) was more potent than ATP. After incubation with BzATP, the activity of Fyn, one member of the Src family of kinases, was enhanced. Moreover, the interaction between P2X7 and Fyn was identified by co-immunoprecipitation. After blocking the activity of Fyn or down-regulating the expression of Fyn, the migration of OPCs induced by BzATP was inhibited. These data indicate that P2X7 receptors/Fyn may mediate ATP-induced OPC migration under pathological conditions.
Collapse
Affiliation(s)
- Ji-Feng Feng
- Institute of Neuroscience and Key Laboratory of Molecular Neurobiology of Ministry of Education, Neuroscience Research Center of Changzheng Hospital, Second Military Medical University, Shanghai, China
| | | | | | | | | | | |
Collapse
|
70
|
Chadet S, Ivanes F, Benoist L, Salmon-Gandonnière C, Guibon R, Velge-Roussel F, Babuty D, Baron C, Roger S, Angoulvant D. Hypoxia/Reoxygenation Inhibits P2Y11 Receptor Expression and Its Immunosuppressive Activity in Human Dendritic Cells. THE JOURNAL OF IMMUNOLOGY 2015; 195:651-60. [PMID: 26078273 DOI: 10.4049/jimmunol.1500197] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 05/17/2015] [Indexed: 12/20/2022]
Abstract
High concentrations of extracellular ATP (eATP) resulting from cell damage may be found during an ischemia/reperfusion (I/R) episode at the site of injury. eATP activates purinergic receptors in dendritic cells (DCs) and may inhibit inflammation. This immunosuppressive activity could be of interest in the field of I/R, which is an inflammatory condition involved in myocardial infarction, stroke, and solid organ transplantation. However, the specific purinergic receptor responsible for this effect remains to be identified. In this study, we report that eATP induced maturation of human monocyte-derived DCs. Additionally, eATP inhibited IL-12 production whereas IL-10 levels remained unchanged in activated DCs. These effects were prevented by the P2Y11R antagonist NF340. Interestingly, a 5-h hypoxia prevented the effects of eATP on cytokine production whereas a 1-h hypoxia did not affect the eATP-mediated decrease of IL-12 and IL-6. We showed a time-dependent downregulation of P2Y11R at both mRNA and protein levels that was prevented by knocking down hypoxia-inducible factor-1α. In this study, we showed an immunosuppressive role of P2Y11R in human DCs. Additionally, we demonstrated that the time-dependent downregulation of P2Y11R by hypoxia orientates DCs toward a proinflammatory phenotype that may be involved in post-I/R injuries as observed after organ transplantation.
Collapse
Affiliation(s)
- Stéphanie Chadet
- EA 4245 Cellules Dendritiques, Immunomodulation et Greffes, Université François-Rabelais de Tours, 37032 Tours, France
| | - Fabrice Ivanes
- EA 4245 Cellules Dendritiques, Immunomodulation et Greffes, Université François-Rabelais de Tours, 37032 Tours, France; Service de Cardiologie, Hôpital Trousseau, Centre Hospitalier Régional Universitaire de Tours, 37044 Tours, France
| | - Lauriane Benoist
- EA 4245 Cellules Dendritiques, Immunomodulation et Greffes, Université François-Rabelais de Tours, 37032 Tours, France
| | - Charlotte Salmon-Gandonnière
- Service de Néphrologie et d'Immunologie Clinique, Centre Hospitalier Régional Universitaire de Tours, 37000 Tours, France
| | - Roseline Guibon
- EA 4245 Cellules Dendritiques, Immunomodulation et Greffes, Université François-Rabelais de Tours, 37032 Tours, France
| | - Florence Velge-Roussel
- EA 4245 Cellules Dendritiques, Immunomodulation et Greffes, Université François-Rabelais de Tours, 37032 Tours, France; Fédération Hospitalo-Universitaire SUPPORT Tours, Poitiers, Limoges, Université François-Rabelais de Tours, 37032 Tours, France; and
| | - Dominique Babuty
- EA 4245 Cellules Dendritiques, Immunomodulation et Greffes, Université François-Rabelais de Tours, 37032 Tours, France; Service de Cardiologie, Hôpital Trousseau, Centre Hospitalier Régional Universitaire de Tours, 37044 Tours, France
| | - Christophe Baron
- EA 4245 Cellules Dendritiques, Immunomodulation et Greffes, Université François-Rabelais de Tours, 37032 Tours, France; Service de Néphrologie et d'Immunologie Clinique, Centre Hospitalier Régional Universitaire de Tours, 37000 Tours, France; Fédération Hospitalo-Universitaire SUPPORT Tours, Poitiers, Limoges, Université François-Rabelais de Tours, 37032 Tours, France; and
| | - Sébastien Roger
- UMR INSERM 1069, "Nutrition, Croissance et Cancer," Université François-Rabelais de Tours, 37032 Tours, France
| | - Denis Angoulvant
- EA 4245 Cellules Dendritiques, Immunomodulation et Greffes, Université François-Rabelais de Tours, 37032 Tours, France; Service de Cardiologie, Hôpital Trousseau, Centre Hospitalier Régional Universitaire de Tours, 37044 Tours, France; Fédération Hospitalo-Universitaire SUPPORT Tours, Poitiers, Limoges, Université François-Rabelais de Tours, 37032 Tours, France; and
| |
Collapse
|
71
|
Sophocleous RA, Mullany PRF, Winter KM, Marks DC, Sluyter R. Propensity of red blood cells to undergo P2X7 receptor-mediated phosphatidylserine exposure does not alter during in vivo or ex vivo aging. Transfusion 2015; 55:1946-54. [PMID: 25823581 DOI: 10.1111/trf.13101] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Revised: 02/13/2015] [Accepted: 02/13/2015] [Indexed: 12/20/2022]
Abstract
BACKGROUND Phosphatidylserine (PS) exposure facilitates the removal of red blood cells (RBCs) from the circulation, potentially contributing to the loss of stored RBCs after transfusion, as well as senescent RBCs. Activation of the P2X7 receptor by extracellular adenosine 5'-triphosphate (ATP) can induce PS exposure on freshly isolated human RBCs, but whether this process occurs in stored RBCs or changes during RBC aging is unknown. STUDY DESIGN AND METHODS RBCs were processed and stored according to Australian blood banking guidelines. PS exposure was determined by annexin V binding and flow cytometry. Efficacy of P2X antagonists was assessed by flow cytometric measurements of ATP-induced ethidium+ uptake in RPMI 8226 cells. Osmotic fragility was assessed by lysis in hypotonic saline. RBCs were fractionated by discontinuous density centrifugation. RESULTS ATP (1 mmol/L) induced PS exposure on RBCs stored for less than 1 week. This process was near-completely inhibited by the P2X7 antagonists A438079 and AZ10606120 and the P2X1/P2X7 antagonist MRS2159 but not the P2X1 antagonist NF499. ATP-induced PS exposure on RBCs was not dependent on K+, Na+, or Cl- fluxes. ATP did not alter the osmotic fragility of stored RBCs. ATP-induced PS exposure was similar between RBCs of different densities. ATP-induced PS exposure was also similar between RBCs stored for less than 1 week or for 6 weeks. CONCLUSION The propensity of RBCs to undergo P2X7-mediated PS exposure does not alter during in vivo and ex vivo aging. Thus, P2X7 activation is unlikely to be involved in the removal of senescent RBCs or stored RBCs after transfusion.
Collapse
Affiliation(s)
- Reece A Sophocleous
- School of Biological Sciences.,Centre for Medical and Molecular Bioscience, University of Wollongong.,Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia
| | - Phillip R F Mullany
- School of Biological Sciences.,Centre for Medical and Molecular Bioscience, University of Wollongong.,Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia
| | - Kelly M Winter
- Research and Development, Australian Red Cross Blood Service, Sydney, NSW, Australia
| | - Denese C Marks
- Research and Development, Australian Red Cross Blood Service, Sydney, NSW, Australia
| | - Ronald Sluyter
- School of Biological Sciences.,Centre for Medical and Molecular Bioscience, University of Wollongong.,Illawarra Health and Medical Research Institute, Wollongong, NSW, Australia
| |
Collapse
|
72
|
Jindrichova M, Bhattacharya A, Rupert M, Skopek P, Obsil T, Zemkova H. Functional characterization of mutants in the transmembrane domains of the rat P2X7 receptor that regulate pore conductivity and agonist sensitivity. J Neurochem 2015; 133:815-27. [PMID: 25712548 DOI: 10.1111/jnc.13078] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Revised: 02/11/2015] [Accepted: 02/17/2015] [Indexed: 11/30/2022]
Abstract
In the sustained presence of agonist, the opening of P2X7R channel is followed by pore dilatation, which causes an increase in its permeability to larger organic cations, accompanied by receptor sensitization. To explore the molecular mechanisms by which the conductivity and sensitivity are increased, we analyzed the electrophysiological properties and YO-PRO-1 uptake of selected alanine mutants in the first and second transmembrane domains of the rat P2X7R. Substitution of residues Y40, F43, G338, and D352 with alanine reduced membrane trafficking, and the D352A was practically non-functional. The Y40A and F43A mutants that were expressed in the membrane lacked pore dilation ability. Moreover, the Y40A and Y40F displayed desensitization, whereas the Y40W partially recovered receptor function. The G338A/S mutations favored the open state of the channel and displayed instantaneous permeability to larger organic cations. The G338P was non-functional. The L341A and G345A displayed normal trafficking, current amplitude, and sensitization, but both mutations resulted in a decreased pore formation and dye uptake. These results showed that the increase in P2X7R conductivity and sensitivity is critically dependent on residues Y40 and F43 in the TM1 domain and that the region located at the intersection of TM2 helices controls the rate of large pore opening. We investigated the mechanism of the proapoptotic receptor P2X7R's large pore opening and its sensitization. We found that aromatic residues in the upper part of the first transmembrane domain (TM1) are critical for both the P2X7R channel pore opening and receptor sensitization, and residues located at or below the intersection of the second transmembrane domains (TM2) control the rate of pore opening. These findings identify new residues involved in pore formation of P2X7R.
Collapse
Affiliation(s)
- Marie Jindrichova
- Department of Cellular and Molecular Neuroendocrinology, Institute of Physiology of the Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Anirban Bhattacharya
- Department of Cellular and Molecular Neuroendocrinology, Institute of Physiology of the Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Marian Rupert
- Department of Cellular and Molecular Neuroendocrinology, Institute of Physiology of the Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Petr Skopek
- Department of Cellular and Molecular Neuroendocrinology, Institute of Physiology of the Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Tomas Obsil
- Department of Physical and Macromolecular Chemistry, Faculty of Science, Charles University, Prague, Czech Republic
| | - Hana Zemkova
- Department of Cellular and Molecular Neuroendocrinology, Institute of Physiology of the Academy of Sciences of the Czech Republic, Prague, Czech Republic
| |
Collapse
|
73
|
Monette MM, Evans DL, Krunkosky T, Camus A, Jaso-Friedmann L. Nonspecific cytotoxic cell antimicrobial protein (NCAMP-1): a novel alarmin ligand identified in zebrafish. PLoS One 2015; 10:e0116576. [PMID: 25689842 PMCID: PMC4331361 DOI: 10.1371/journal.pone.0116576] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2014] [Accepted: 12/10/2014] [Indexed: 01/13/2023] Open
Abstract
Cells from the coelomic cavity of adult zebrafish (zf) were used to study the alarmin-like activities of nonspecific cytotoxic cell antimicrobial protein-1 (NCAMP-1). Immunohistochemistry studies using polyclonal anti-NCAMP-1 identified constitutive NCAMP-1 in epithelial cells of the zf anterior kidney, in liver parenchyma and in the lamina propria of the intestine. NCAMP-1 was also located in the cytosol of mononuclear cells in these tissues. Cytosolic NCAMP-1 was detected in a diverse population of coelomic cells (CC) using confocal microscopy and polyclonal anti-NCAMP-1 staining. Large mononuclear and heterophil-like CC had intracellular NCAMP-1. These studies indicated that NCAMP-1 is constitutively found in epithelial cells and in ZFCC. To establish a relationship between NCAMP-1 and the alarmin functions of ATP, a stimulation-secretion model was initiated using zf coelomic cells (ZFCC). ZFCCs treated with the alarmin ATP secreted NCAMP-1 into culture supernatants. Treatment of ZFCC with either ATP or NCAMP-1 activated purinergic receptor induced pore formation detected by the ZFCC uptake of the dye YO-PRO-1. ATP induced YO-PRO-1 uptake was inhibited by antagonists oxidized-ATP, KN62, or CBB. These antagonists did not compete with NCAMP-1 induced YO-PRO-1 uptake. Binding of ZFCC by both ATP and NCAMP-1 produced an influx of Ca2+. Combined treatment of ZFCC with ATP and NCAMP-1 increased target cell cytotoxicity. Individually NCAMP-1 or ATP treatment did not produce target cell damage. Similar to ATP, NCAMP-1 activates cellular pore formation, calcium influx and cytotoxicity.
Collapse
Affiliation(s)
- Margaret Mariscal Monette
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America
| | - Donald Lee Evans
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America
| | - Thomas Krunkosky
- Department of Veterinary Biosciences and Diagnostic Imaging, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America
| | - Alvin Camus
- Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America
| | - Liliana Jaso-Friedmann
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America
- * E-mail:
| |
Collapse
|
74
|
Bartlett R, Stokes L, Sluyter R. The P2X7 receptor channel: recent developments and the use of P2X7 antagonists in models of disease. Pharmacol Rev 2015; 66:638-75. [PMID: 24928329 DOI: 10.1124/pr.113.008003] [Citation(s) in RCA: 316] [Impact Index Per Article: 35.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The P2X7 receptor is a trimeric ATP-gated cation channel found predominantly, but not exclusively, on immune cells. P2X7 activation results in a number of downstream events, including the release of proinflammatory mediators and cell death and proliferation. As such, P2X7 plays important roles in various inflammatory, immune, neurologic and musculoskeletal disorders. This review focuses on the use of P2X7 antagonists in rodent models of neurologic disease and injury, inflammation, and musculoskeletal and other disorders. The cloning and characterization of human, rat, mouse, guinea pig, dog, and Rhesus macaque P2X7, as well as recent observations regarding the gating and permeability of P2X7, are discussed. Furthermore, this review discusses polymorphic and splice variants of P2X7, as well as the generation and use of P2X7 knockout mice. Recent evidence for emerging signaling pathways downstream of P2X7 activation and the growing list of negative and positive modulators of P2X7 activation and expression are also described. In addition, the use of P2X7 antagonists in numerous rodent models of disease is extensively summarized. Finally, the use of P2X7 antagonists in clinical trials in humans and future directions exploring P2X7 as a therapeutic target are described.
Collapse
Affiliation(s)
- Rachael Bartlett
- School of Biological Sciences, University of Wollongong, New South Wales, Australia and Illawarra Health and Medical Research Institute, Wollongong, New South Wales, Australia (R.B., R.S.); and Health Innovations Research Institute, School of Medical Sciences, RMIT University, Bundoora, Victoria, Australia (L.S.)
| | - Leanne Stokes
- School of Biological Sciences, University of Wollongong, New South Wales, Australia and Illawarra Health and Medical Research Institute, Wollongong, New South Wales, Australia (R.B., R.S.); and Health Innovations Research Institute, School of Medical Sciences, RMIT University, Bundoora, Victoria, Australia (L.S.)
| | - Ronald Sluyter
- School of Biological Sciences, University of Wollongong, New South Wales, Australia and Illawarra Health and Medical Research Institute, Wollongong, New South Wales, Australia (R.B., R.S.); and Health Innovations Research Institute, School of Medical Sciences, RMIT University, Bundoora, Victoria, Australia (L.S.)
| |
Collapse
|
75
|
Purinergic P2X receptors: structural models and analysis of ligand-target interaction. Eur J Med Chem 2014; 89:561-80. [PMID: 25462266 DOI: 10.1016/j.ejmech.2014.10.071] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 10/07/2014] [Accepted: 10/24/2014] [Indexed: 01/04/2023]
Abstract
The purinergic P2X receptors are ligand-gated cation channels activated by the endogenous ligand ATP. They assemble as homo- or heterotrimers from seven cloned subtypes (P2X1-7) and all trimer subunits present a common topology consisting in intracellular N- and C- termini, two transmembrane domains and a large extracellular domain. These membrane proteins are present in virtually all mammalian tissues and regulate a large variety of responses in physio- and pathological conditions. The development of ligands that selectively activate or block specific P2X receptor subtypes hence represents a promising strategy to obtain novel pharmacological tools for the treatment of pain, cancer, inflammation, and neurological, cardiovascular, and endocrine diseases. The publication of the crystal structures of zebrafish P2X4 receptor in inactive and ATP-bound active forms provided structural data for the analysis of the receptor structure, the interpretation of mutagenesis data, and the depiction of ligand binding and receptor activation mechanism. In addition, the availability of ATP-competitive ligands presenting selectivity for P2X receptor subtypes supports the design of new potent and selective ligands with possibly improved pharmacokinetic profiles, with the final aim to obtain new drugs. This study describes molecular modelling studies performed to develop structural models of the human and rat P2X receptors in inactive and active states. These models allowed to analyse the role of some non-conserved residues at ATP binding site and to study the receptor interaction with some non-specific or subtype selective agonists and antagonists.
Collapse
|
76
|
Teixeira JM, de Oliveira-Fusaro MCG, Parada CA, Tambeli CH. Peripheral P2X7 receptor-induced mechanical hyperalgesia is mediated by bradykinin. Neuroscience 2014; 277:163-73. [PMID: 24997266 DOI: 10.1016/j.neuroscience.2014.06.057] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Revised: 06/23/2014] [Accepted: 06/26/2014] [Indexed: 12/12/2022]
Abstract
P2X7 receptors play an important role in inflammatory hyperalgesia, but the mechanisms involved in their hyperalgesic role are not completely understood. In this study, we hypothesized that P2X7 receptor activation induces mechanical hyperalgesia via the inflammatory mediators bradykinin, sympathomimetic amines, prostaglandin E2 (PGE2), and pro-inflammatory cytokines and via neutrophil migration in rats. We found that 2'(3')-O-(4-benzoylbenzoyl)adenosine 5'-triphosphate triethylammonium salt (BzATP), the most potent P2X7 receptor agonist available, induced a dose-dependent mechanical hyperalgesia that was blocked by the P2X7 receptor-selective antagonist A-438079 but unaffected by the P2X1,3,2/3 receptor antagonist TNP-ATP. These findings confirm that, although BzATP also acts at both P2X1 and P2X3 receptors, BzATP-induced hyperalgesia was mediated only by P2X7 receptor activation. Co-administration of selective antagonists of bradykinin B1 (Des-Arg(8)-Leu(9)-BK (DALBK)) or B2 receptors (bradyzide), β1 (atenolol) or β2 adrenoceptors (ICI 118,551), or local pre-treatment with the cyclooxygenase inhibitor indomethacin or the nonspecific selectin inhibitor fucoidan each significantly reduced BzATP-induced mechanical hyperalgesia in the rat hind paw. BzATP also induced the release of the pro-inflammatory cytokines tumor necrosis factor α (TNF-α), interleukin (IL)-1β, IL-6 and cytokine-induced neutrophil chemoattractant-1 (CINC-1), an effect that was significantly reduced by A-438079. Co-administration of DALBK or bradyzide with BzATP significantly reduced BzATP-induced IL-1β and CINC-1 release. These results indicate that peripheral P2X7 receptor activation induces mechanical hyperalgesia via inflammatory mediators, especially bradykinin, which may contribute to pro-inflammatory cytokine release. These pro-inflammatory cytokines in turn may mediate the contributions of PGE2, sympathomimetic amines and neutrophil migration to the mechanical hyperalgesia induced by local P2X7 receptor activation.
Collapse
Affiliation(s)
- J M Teixeira
- Department of Structural and Functional Biology, Institute of Biology, State University of Campinas - UNICAMP, Rua Monteiro Lobato, 255, Campinas, SP CEP 13083-862, Brazil
| | - M C G de Oliveira-Fusaro
- Faculty of Applied Sciences, State University of Campinas - UNICAMP, Rua Pedro Zaccaria, 1300, Limeira, SP CEP 13484-350, Brazil
| | - C A Parada
- Department of Structural and Functional Biology, Institute of Biology, State University of Campinas - UNICAMP, Rua Monteiro Lobato, 255, Campinas, SP CEP 13083-862, Brazil
| | - C H Tambeli
- Department of Structural and Functional Biology, Institute of Biology, State University of Campinas - UNICAMP, Rua Monteiro Lobato, 255, Campinas, SP CEP 13083-862, Brazil.
| |
Collapse
|
77
|
Rubini P, Pagel G, Mehri S, Marquardt P, Riedel T, Illes P. Functional P2X7 receptors at cultured hippocampal astrocytes but not neurons. Naunyn Schmiedebergs Arch Pharmacol 2014; 387:943-54. [DOI: 10.1007/s00210-014-1005-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Accepted: 06/05/2014] [Indexed: 02/02/2023]
|
78
|
Glaser T, de Oliveira SLB, Cheffer A, Beco R, Martins P, Fornazari M, Lameu C, Junior HMC, Coutinho-Silva R, Ulrich H. Modulation of mouse embryonic stem cell proliferation and neural differentiation by the P2X7 receptor. PLoS One 2014; 9:e96281. [PMID: 24798220 PMCID: PMC4010452 DOI: 10.1371/journal.pone.0096281] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 04/04/2014] [Indexed: 12/31/2022] Open
Abstract
Background Novel developmental functions have been attributed to the P2X7 receptor (P2X7R) including proliferation stimulation and neural differentiation. Mouse embryonic stem cells (ESC), induced with retinoic acid to neural differentiation, closely assemble processes occurring during neuroectodermal development of the early embryo. Principal Findings P2X7R expression together with the pluripotency marker Oct-4 was highest in undifferentiated ESC. In undifferentiated cells, the P2X7R agonist Bz-ATP accelerated cell cycle entry, which was blocked by the specific P2X7R inhibitor KN-62. ESC induced to neural differentiation with retinoic acid, reduced Oct-4 and P2X7R expression. P2X7R receptor-promoted intracellular calcium fluxes were obtained at lower Bz-ATP ligand concentrations in undifferentiated and in neural-differentiated cells compared to other studies. The presence of KN-62 led to increased number of cells expressing SSEA-1, Dcx and β3-tubulin, as well as the number of SSEA-1 and β3-tubulin-double-positive cells confirming that onset of neuroectodermal differentiation and neuronal fate determination depends on suppression of P2X7R activity. Moreover, an increase in the number of Ki-67 positive cells in conditions of P2X7R inhibition indicates rescue of progenitors into the cell cycle, augmenting the number of neuroblasts and consequently neurogenesis. Conclusions In embryonic cells, P2X7R expression and activity is upregulated, maintaining proliferation, while upon induction to neural differentiation P2X7 receptor expression and activity needs to be suppressed.
Collapse
Affiliation(s)
- Talita Glaser
- Departamento de Bioquímica; Instituto de Química, Universidade de São Paulo, São Paulo, Brasil
| | | | - Arquimedes Cheffer
- Departamento de Bioquímica; Instituto de Química, Universidade de São Paulo, São Paulo, Brasil
| | - Renata Beco
- Departamento de Bioquímica; Instituto de Química, Universidade de São Paulo, São Paulo, Brasil
| | - Patrícia Martins
- Departamento de Bioquímica; Instituto de Química, Universidade de São Paulo, São Paulo, Brasil
| | - Maynara Fornazari
- Departamento de Bioquímica; Instituto de Química, Universidade de São Paulo, São Paulo, Brasil
| | - Claudiana Lameu
- Departamento de Bioquímica; Instituto de Química, Universidade de São Paulo, São Paulo, Brasil
| | - Helio Miranda Costa Junior
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro - UFRJ, Rio de Janeiro, RJ, Brazil
| | - Robson Coutinho-Silva
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro - UFRJ, Rio de Janeiro, RJ, Brazil
| | - Henning Ulrich
- Departamento de Bioquímica; Instituto de Química, Universidade de São Paulo, São Paulo, Brasil
- * E-mail:
| |
Collapse
|
79
|
Kojima S, Negishi Y, Tsukimoto M, Takenouchi T, Kitani H, Takeda K. Purinergic signaling via P2X7 receptor mediates IL-1β production in Kupffer cells exposed to silica nanoparticle. Toxicology 2014; 321:13-20. [PMID: 24685903 DOI: 10.1016/j.tox.2014.03.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 03/20/2014] [Accepted: 03/21/2014] [Indexed: 12/20/2022]
Abstract
There is extensive evidence that nanoparticles (NPs) cause adverse effects in multiple organs, including liver, though the mechanisms involved remain to be fully established. Kupffer cells are macrophages resident in the liver, and play important roles in liver inflammation induced by various toxic agents, including lipopolysaccharide (LPS). Interleukin-1 (IL-1) family members IL-1α,β are released from LPS-primed macrophages exposed to NPs, including silica NPs (SNPs), via activation of nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 inflammasomes. Here, we investigated the mechanism of production of IL-1β via activation of inflammasomes in mouse Kupffer cell line KUP5, focusing on the role of purinergic signaling via P2X7 receptor. IL-1β production by LPS-primed KUP5 cells exposed to SNPs was increased dose-dependently, and was greatest in response to SNPs with a diameter of 30 nm (SNP30), as compared with 70-nm and 300-nm SNPs (SNP70 and SNP300). ATP release was also highest in cells exposed to SNP30. Treatment of LPS-primed KUP5 cells with ATP also induced a high level of IL-1β production, similar to that induced by SNP30. IL-1β production was significantly inhibited by apyrase (an ecto-nucleotidase) and A438079 (a P2X7 antagonist/ATP-release inhibitor). Production of reactive oxygen species (ROS) was confirmed in cells exposed to SNP30. In conclusion, ATP released from P2X7 receptor in response to stimulation of KUP5 cells with SNP30 induces ROS production via cell-membrane NADPH oxidase. The ROS causes activation of inflammasomes, leading to caspase-1-dependent processing of IL-1β.
Collapse
Affiliation(s)
- Shuji Kojima
- Department of Radiation Biosciences, Faculty of Pharmaceutical Sciences, Tokyo University of Science (TUS), 2641 Yamazaki, Noda-shi, Chiba 278-8510, Japan.
| | - Yusuke Negishi
- Department of Radiation Biosciences, Faculty of Pharmaceutical Sciences, Tokyo University of Science (TUS), 2641 Yamazaki, Noda-shi, Chiba 278-8510, Japan
| | - Mitsutoshi Tsukimoto
- Department of Radiation Biosciences, Faculty of Pharmaceutical Sciences, Tokyo University of Science (TUS), 2641 Yamazaki, Noda-shi, Chiba 278-8510, Japan
| | - Takato Takenouchi
- Transgenic Animal Research Center, National Institute of Agrobiological Sciences, Ohwashi 1-2, Tsuuba, Ibaraki 305-8634, Japan
| | - Hiroshi Kitani
- Transgenic Animal Research Center, National Institute of Agrobiological Sciences, Ohwashi 1-2, Tsuuba, Ibaraki 305-8634, Japan
| | - Ken Takeda
- Department of Hygienic Chemistry, Faculty of Pharmaceutical Sciences, Tokyo University of Science (TUS), 2641 Yamazaki, Noda-shi, Chiba 278-8510, Japan
| |
Collapse
|
80
|
Shoji KF, Sáez PJ, Harcha PA, Aguila HL, Sáez JC. Pannexin1 channels act downstream of P2X 7 receptors in ATP-induced murine T-cell death. Channels (Austin) 2014; 8:142-56. [PMID: 24590064 DOI: 10.4161/chan.28122] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Death of murine T cells induced by extracellular ATP is mainly triggered by activation of purinergic P2X 7 receptors (P2X 7Rs). However, a link between P2X 7Rs and pannexin1 (Panx1) channels, which are non-selective, has been recently demonstrated in other cell types. In this work, we characterized the expression and cellular distribution of pannexin family members (Panxs 1, 2 and 3) in isolated T cells. Panx1 was the main pannexin family member clearly detected in both helper (CD4+) and cytotoxic (CD8+) T cells, whereas low levels of Panx2 were found in both T-cell subsets. Using pharmacological and genetic approaches, Panx1 channels were found to mediate most ATP-induced ethidium uptake since this was drastically reduced by Panx1 channel blockers (10Panx1, Probenecid and low carbenoxolone concentration) and absent in T cells derived from Panx1-/- mice. Moreover, electrophysiological measurements in wild-type CD4+ cells treated with ATP unitary current events and pharmacological sensitivity compatible with Panx1 channels were found. In addition, ATP release from T cells treated with 4Br-A23187, a calcium ionophore, was completely blocked with inhibitors of both connexin hemichannels and Panx1 channels. Panx1 channel blockers drastically reduced the ATP-induced T-cell mortality, indicating that Panx1 channels mediate the ATP-induced T-cell death. However, mortality was not reduced in T cells of Panx1-/- mice, in which levels of P2X 7Rs and ATP-induced intracellular free Ca2+ responses were enhanced suggesting that P2X 7Rs take over Panx1 channels lose-function in mediating the onset of cell death induced by extracellular ATP.
Collapse
Affiliation(s)
- Kenji F Shoji
- Departamento de Fisiología; Pontificia Universidad Católica de Chile; Santiago, Chile
| | - Pablo J Sáez
- Departamento de Fisiología; Pontificia Universidad Católica de Chile; Santiago, Chile
| | - Paloma A Harcha
- Departamento de Fisiología; Pontificia Universidad Católica de Chile; Santiago, Chile
| | - Hector L Aguila
- Department of Immunology; University of Connecticut Health Center; Farmington, CT USA
| | - Juan C Sáez
- Departamento de Fisiología; Pontificia Universidad Católica de Chile; Santiago, Chile; Instituto Milenio; Centro Interdisciplinario de Neurociencias de Valparaíso; Valparaíso, Chile
| |
Collapse
|
81
|
Hashioka S, Wang YF, Little JP, Choi HB, Klegeris A, McGeer PL, McLarnon JG. Purinergic responses of calcium-dependent signaling pathways in cultured adult human astrocytes. BMC Neurosci 2014; 15:18. [PMID: 24447580 PMCID: PMC3903030 DOI: 10.1186/1471-2202-15-18] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Accepted: 01/15/2014] [Indexed: 12/18/2022] Open
Abstract
Background The properties of Ca2+ signaling mediated by purinergic receptors are intrinsically linked with functional activity of astrocytes. At present little is known concerning Ca2+-dependent purinergic responses in adult human astrocytes. This work has examined effects of purinergic stimulation to alter levels of intracellular Ca2+ in adult human astrocytes. Ca2+-sensitive spectrofluorometry was carried out to determine mobilization of intracellular Ca2+ following adenosine triphosphate (ATP) or 3′-O-(4-benzoyl)benzoyl-ATP (Bz-ATP) stimulation of adult human astrocytes. In some experiments pharmacological modulation of Ca2+ pathways was applied to help elucidate mechanisms of Ca2+ signaling. RT-PCR was also performed to confirm human astrocyte expression of specific purinoceptors which were indicated from imaging studies. Results The endogenous P2 receptor agonist ATP (at 100 μM or 1 mM) applied in physiological saline solution (PSS) evoked a rapid increase of [Ca2+]i to a peak amplitude with the decay phase of response exhibiting two components. The two phases of decay consisted of an initial rapid component which was followed by a secondary slower component. In the presence of Ca2+-free solution, the secondary phase of decay was absent indicating this prolonged component was due to influx of Ca2+. This prolonged phase of decay was also attenuated with the store-operated channel (SOC) inhibitor gadolinium (at 2 μM) added to standard PSS, suggesting this component was mediated by SOC activation. These results are consistent with ATP activation of P2Y receptor (P2YR) in adult human astrocytes leading to respective rapid [Ca2+]i mobilization from intracellular stores followed by Ca2+ entry through SOC. An agonist for P2X7 receptor (P2X7R), BzATP induced a very different response compared with ATP whereby BzATP (at 300 μM) elicited a slowly rising increase in [Ca2+]i to a plateau level which was sustained in duration. The BzATP-induced increase in [Ca2+]i was not enhanced with lipopolysaccharide pre-treatment of cells as previously found for P2X7R mediated response in human microglia. RT-PCR analysis showed that adult human astrocytes in vitro constitutively express mRNA for P2Y1R, P2Y2R and P2X7R. Conclusion These results suggest that activation of metabotropic P2YR (P2Y1R and/or P2Y2R) and ionotropic P2X7R could mediate purinergic responses in adult human astrocytes.
Collapse
Affiliation(s)
- Sadayuki Hashioka
- Kinsmen Laboratory of Neurological Research, Department of Psychiatry, The University of British Columbia, Vancouver, BC Canada.
| | | | | | | | | | | | | |
Collapse
|
82
|
Hausmann R, Bahrenberg G, Kuhlmann D, Schumacher M, Braam U, Bieler D, Schlusche I, Schmalzing G. A hydrophobic residue in position 15 of the rP2X3 receptor slows desensitization and reveals properties beneficial for pharmacological analysis and high-throughput screening. Neuropharmacology 2014; 79:603-15. [PMID: 24452010 DOI: 10.1016/j.neuropharm.2014.01.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Revised: 12/24/2013] [Accepted: 01/09/2014] [Indexed: 11/19/2022]
Abstract
The homotrimeric P2X3 subtype, one of the seven members of the ATP-gated P2X receptor family, plays a role in sensory neurotransmission, including nociception. To overcome the bias resulting from fast desensitization of the P2X3 receptor in dose-response analyses, a non-desensitizing P2X2-X3 receptor chimera has been repeatedly used as a surrogate for the P2X3 receptor for functional analysis. Here, we show that only three of the P2X2-specific amino acid residues of the P2X2-X3 chimera, (19)P(21)V(22)I, are needed to confer a slowly desensitizing phenotype to the P2X3 receptor. The strongest delay in desensitization of the P2X3 receptor by a single residue was observed when (15)Ser was replaced by Val or another hydrophobic residue. Pharmacologically, the S(15)V-rP2X3 mutant behaved similarly to the wt-P2X3 receptor. Analysis of the S(15)V-rP2X3 receptor in 1321N1 astrocytoma cells by a common calcium-imaging-based assay showed 10-fold higher calcium transients relative to those of the wt-rP2X3 receptor. The S(15)V-rP2X3 cell line enabled reliable analysis of antagonistic potencies and correctly reported the mechanism of action of the P2X3 receptor antagonists A-317491 and TNP-ATP by a calcium-imaging assay. Together, these data suggest that the S(15)V-rP2X3 mutant may be suitable not only for automated fluorescence-based screening of molecule libraries for identification of lead compounds but also for facilitated pharmacological characterization of specific P2X3 receptor ligands. We suggest that the mechanism of desensitization of the P2X3 receptor may involve the movement of an N-terminal inactivation particle, in analogy to the "hinged-lid" or "ball and chain" mechanisms of voltage-gated NaV and Shaker KV channels, respectively.
Collapse
Affiliation(s)
- Ralf Hausmann
- Department of Molecular Pharmacology, Medical Faculty of the RWTH Aachen University, Wendlingweg 2, 52074 Aachen, Germany.
| | - Gregor Bahrenberg
- Grünenthal GmbH, Global Drug Discovery, Department of Molecular Pharmacology, Zieglerstrasse 6, 52078 Aachen, Germany
| | - Daniel Kuhlmann
- Department of Molecular Pharmacology, Medical Faculty of the RWTH Aachen University, Wendlingweg 2, 52074 Aachen, Germany
| | - Michaela Schumacher
- Department of Molecular Pharmacology, Medical Faculty of the RWTH Aachen University, Wendlingweg 2, 52074 Aachen, Germany
| | - Ursula Braam
- Department of Molecular Pharmacology, Medical Faculty of the RWTH Aachen University, Wendlingweg 2, 52074 Aachen, Germany
| | - Dagmar Bieler
- Grünenthal GmbH, Global Drug Discovery, Department of Molecular Pharmacology, Zieglerstrasse 6, 52078 Aachen, Germany
| | - Ilka Schlusche
- Grünenthal GmbH, Global Drug Discovery, Department of Molecular Pharmacology, Zieglerstrasse 6, 52078 Aachen, Germany
| | - Günther Schmalzing
- Department of Molecular Pharmacology, Medical Faculty of the RWTH Aachen University, Wendlingweg 2, 52074 Aachen, Germany
| |
Collapse
|
83
|
Jaso-Friedmann L, Leary JH, Camus AC, Evans DL. The teleost acute-phase inflammatory response and caspase activation by a novel alarmin-like ligand. J Leukoc Biol 2014; 95:785-796. [PMID: 24399841 DOI: 10.1189/jlb.0313171] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Revised: 10/23/2013] [Accepted: 12/13/2013] [Indexed: 12/15/2022] Open
Abstract
This study tested the hypothesis that NCAMP-1 has alarmin-like properties and activates the caspase-1-binding site in cells of the teleost bone marrow (equivalent). In mammals, alarmins have been studied extensively; however, in teleosts, little is known about their identity and functions. Similar to alarmins, NCAMP-1 has a broad spectrum of bacteriolytic activity. NCAMP-1 is constitutively present in CF serum, and levels were increased following infection with Edwardsiella ictaluri Binding to AK cells was determined with rNCAMP-1 and an anti-His-tag antibody. In vitro treatment of AK (bone marrow equivalent) or spleen cells with rNCAMP-1 increased the IL-1β message three- to fivefold at 3 h, 6 h, and 9 h post-treatment. The association of NCAMP-1 with the activities of alarmin ATP and the acute inflammatory response was demonstrated by NCAMP-1-induced P2X7R pore opening and YO-PRO-1 cellular influx. The association of NCAMP-1 binding with inflammasome activation was demonstrated by NCAMP-1 activation of the caspase-1-binding site for tetrapeptide Z-YVAD-FMK. In competition assays, this tetrapeptide competitively inhibited subsequent binding by the pan-caspase substrate tripeptide FAM-VAD-FMK. Lymphocyte-like cells from the spleen were 16%+, and epithelial cells were also positive for NCAMP-1. IHC staining and confocal microscopy confirmed the cytosolic existence of NCAMP-1 in lymphoreticular tissue and IL-1β in AK cells. CF T cell lines G14D and 28S.3 expressed NCAMP-1 in the cytosol and in storage granules. These studies strongly suggested that NCAMP-1 is an alarmin-like ligand with similar but distinct activities to those of ATP and HMGB-1.
Collapse
Affiliation(s)
| | | | - A C Camus
- Pathology, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
| | | |
Collapse
|
84
|
Purinergic receptor P2X₇: a novel target for anti-inflammatory therapy. Bioorg Med Chem 2013; 22:54-88. [PMID: 24314880 DOI: 10.1016/j.bmc.2013.10.054] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Accepted: 10/31/2013] [Indexed: 12/31/2022]
Abstract
Purinergic receptors, also known as purinoceptors, are ligand gated membrane ion channels involved in many cellular functions. Among all identified purinergic receptors, P2X₇ subform is unique since it induces the caspase activity, cytokine secretion, and apoptosis. The distribution of P2X₇ receptors, and the need of high concentration of ATP required to activate this receptor exhibited its ability to function as 'danger' sensor associated with tissue inflammation and damage. Further, the modulation of other signalling pathways associated with P2X₇ has also been proposed to play an important role in the control of macrophage functions and inflammatory responses, especially towards lipopolysaccharides. Experimentally, researchers have also observed the decreased severity of inflammatory responses in P2X₇ receptor expressing gene (P2RX₇) knockout (KO) phenotypes. Therefore, newly developed potent antagonists of P2X₇ receptor would serve as novel therapeutic agents to combat various inflammatory conditions. In this review article, we tried to explore various aspects of P2X₇ receptors including therapeutic potential, and recent discoveries and developments of P2X₇ receptor antagonists.
Collapse
|
85
|
Salas E, Carrasquero LMG, Olivos-Oré LA, Bustillo D, Artalejo AR, Miras-Portugal MT, Delicado EG. Purinergic P2X7 receptors mediate cell death in mouse cerebellar astrocytes in culture. J Pharmacol Exp Ther 2013; 347:802-15. [PMID: 24101734 DOI: 10.1124/jpet.113.209452] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The brain distribution and functional role of glial P2X7 receptors are broader and more complex than initially anticipated. We characterized P2X7 receptors from cerebellar astrocytes at the molecular, immunocytochemical, biophysical, and cell physiologic levels. Mouse cerebellar astrocytes in culture express mRNA coding for P2X7 receptors, which is translated into P2X7 receptor protein as proven by Western blot analysis and immunocytochemistry. Fura-2 imaging showed cytosolic calcium responses to ATP and the synthetic analog 3'-O-(4-benzoyl)benzoyl-ATP (BzATP) exhibited two components, namely an initial transient and metabotropic component followed by a sustained one that depended on extracellular calcium. This latter component, which was absent in astrocytes from P2X7 receptor knockout mice (P2X7 KO), was modulated by extracellular Mg(2+), and was sensitive to Brilliant Blue G (BBG) and 3-(5-(2,3-dichlorophenyl)-1H-tetrazol-1-yl)methyl pyridine (A438079) antagonism. BzATP also elicited inwardly directed nondesensitizing whole-cell ionic currents that were reduced by extracellular Mg(2+) and P2X7 antagonists (BBG and calmidazolium). In contrast to that previously reported in rat cerebellar astrocytes, sustained BzATP application induced a gradual increase in membrane permeability to large cations, such as N-methyl-d-glucamine and 4-[3-methyl-2(3H)-benzoxazolylidene)-methyl]-1-[3-(triethylammonio)propyl]diiodide, which ultimately led to the death of mouse astrocytes. Cerebellar astrocyte cell death was prevented by BBG but not by calmidazolium, removal of extracellular calcium, or treatment with the caspase-3 inhibitor, benzyloxycarbonyl-Asp(OMe)-Glu(OMe)-Val-Asp(OMe)-fluoromethylketone, thus suggesting a necrotic-type mechanism of cell death. Since this cellular response was not observed in astrocytes from P2X7 KO mice, this study suggests that stimulation of P2X7 receptor may convey a cell death signal to cerebellar astrocytes in a species-specific manner.
Collapse
Affiliation(s)
- Elvira Salas
- Department of Biochemistry, Faculty of Medicine, University of Costa Rica, San José, Costa Rica (E.S.); Departments of Biochemistry (L.M.G.C., M.T.M.-P., E.G.D.) and Toxicology and Pharmacology (L.A.O., D.B., A.R.A.), Faculty of Veterinary Medicine, Complutense University of Madrid, Madrid, Spain; and Neurochemistry Research Institute, Complutense University of Madrid, Madrid, Spain (L.A.O., D.B., A.R.A., M.T.M.P., E.G.D.)
| | | | | | | | | | | | | |
Collapse
|
86
|
Receptor-independent effects of 2'(3')-O-(4-benzoylbenzoyl)ATP triethylammonium salt on cytosolic pH. Purinergic Signal 2013; 9:687-93. [PMID: 23689980 DOI: 10.1007/s11302-013-9365-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Accepted: 04/23/2013] [Indexed: 10/26/2022] Open
Abstract
The effect of the relatively potent P2X7 receptor agonist 2'(3')-O-(4-benzoylbenzoyl)adenosine 5'-triphosphate triethylammonium salt (BzATP-TEA) on cytosolic pH (pHi) was studied using MC3T3-E1 osteoblast-like cells, which endogenously express P2X7 receptors. pHi was measured fluorimetrically using the pH-sensitive dye 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. BzATP-TEA (0.3-1.5 mM) elicited fast-onset alkalinization responses. In contrast, adenosine 5'-triphosphate disodium salt (5 mM) failed to reproduce the BzATP-TEA-induced responses, indicating a P2 receptor-independent mechanism. We speculated that triethylamine, which is present in solutions of BzATP-TEA, permeates the plasma membrane, and is protonated intracellularly, leading to an increase in pHi. Consistent with this hypothesis, triethylammonium (TEA) chloride mimicked the effects of BzATP-TEA on pHi. Moreover, measurements using a Cytosensor microphysiometer revealed that TEA chloride transiently suppressed proton efflux from cells, whereas washout of TEA transiently enhanced proton efflux. BzATP-TEA also elicited a sustained increase in proton efflux that was blocked specifically by the P2X7 antagonist A-438079. Taken together, we conclude that BzATP-TEA-induced alkalinization is unrelated to P2X7 activation, but is due to the presence of TEA. This effect may confound assessment of the outcomes of P2X7 activation by BzATP-TEA in other systems. Thus, control experiments using TEA chloride are recommended to distinguish between receptor-mediated and nonspecific effects of this widely used agonist. We performed such a control and confirmed that BzATP-TEA, but not TEA chloride, caused the elevation of cytosolic free Ca(2+) in MC3T3-E1 cells, ruling out the possibility that receptor-independent effects on pHi underlie BzATP-TEA-induced Ca(2+) signaling.
Collapse
|
87
|
Lambertucci C, Sundukova M, Kachare DD, Panmand DS, Dal Ben D, Buccioni M, Marucci G, Marchenkova A, Thomas A, Nistri A, Cristalli G, Volpini R. Evaluation of adenine as scaffold for the development of novel P2X3 receptor antagonists. Eur J Med Chem 2013; 65:41-50. [PMID: 23688699 DOI: 10.1016/j.ejmech.2013.04.037] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Revised: 04/15/2013] [Accepted: 04/16/2013] [Indexed: 11/29/2022]
Abstract
Ligands that selectively block P2X3 receptors localized on nociceptive sensory fibres may be useful for the treatment of chronic pain conditions including neuropathic pain, migraine, and inflammatory pain. With the aim at exploring the suitability of adenine moiety as a scaffold for the development of antagonists of this receptor, a series of 9-benzyl-2-aminoadenine derivatives were designed and synthesized. These new compounds were functionally evaluated at rat or human P2X3 receptors expressed in human embryonic kidney (HEK) cells and on native P2X3 receptors from mouse trigeminal ganglion sensory neurons using patch clamp recording under voltage clamp configuration. The new molecules behaved as P2X3 antagonists, as they rapidly and reversibly inhibited (IC50 in the low micromolar range) the membrane currents induced via P2X3 receptor activation by the full agonist α,β-methyleneATP. Introduction of a small lipophilic methyl substituent at the 6-amino group enhanced the activity, in comparison to the corresponding unsubstituted derivative, resulting in the 9-(5-iodo-2-isopropyl-4-methoxybenzyl)-N(6)-methyl-9H-purine-2,6-diamine (24), which appears to be a good antagonist on recombinant and native P2X3 receptors with IC50 = 1.74 ± 0.21 μM.
Collapse
Affiliation(s)
- Catia Lambertucci
- School of Pharmacy, Medicinal Chemistry Unit, University of Camerino, Via S. Agostino, 1, 62032 Camerino, MC, Italy
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
88
|
ATP induces NO production in hippocampal neurons by P2X(7) receptor activation independent of glutamate signaling. PLoS One 2013; 8:e57626. [PMID: 23472093 PMCID: PMC3589399 DOI: 10.1371/journal.pone.0057626] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Accepted: 01/27/2013] [Indexed: 12/31/2022] Open
Abstract
To assess the putative role of adenosine triphosphate (ATP) upon nitric oxide (NO) production in the hippocampus, we used as a model both rat hippocampal slices and isolated hippocampal neurons in culture, lacking glial cells. In hippocampal slices, additions of exogenous ATP or 2′(3′)-O-(4-Benzoylbenzoyl) ATP (Bz-ATP) elicited concentration-dependent NO production, which increased linearly within the first 15 min and plateaued thereafter; agonist EC50 values were 50 and 15 µM, respectively. The NO increase evoked by ATP was antagonized in a concentration-dependent manner by Coomassie brilliant blue G (BBG) or by Nω-propyl-L-arginine, suggesting the involvement of P2X7Rs and neuronal NOS, respectively. The ATP induced NO production was independent of N-methyl-D-aspartic acid (NMDA) receptor activity as effects were not alleviated by DL-2-Amino-5-phosphonopentanoic acid (APV), but antagonized by BBG. In sum, exogenous ATP elicited NO production in hippocampal neurons independently of NMDA receptor activity.
Collapse
|
89
|
He YQ, Chen J, Lu XJ, Shi YH. Characterization of P2X7R and its function in the macrophages of ayu, Plecoglossus altivelis. PLoS One 2013; 8:e57505. [PMID: 23437395 PMCID: PMC3578793 DOI: 10.1371/journal.pone.0057505] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Accepted: 01/22/2013] [Indexed: 11/18/2022] Open
Abstract
P2X purinoceptor 7 (P2X7R), an ATP-gated ion channel, plays an important role during the innate immune response in mammals. However, relatively little is known about the role of P2X7R in the fish immune system. Here, we cloned a cDNA sequence encoding ayu (Plecoglossus altivelis) P2X7R (aP2X7R). The predicted protein was composed of 574 amino acid residues with a P2X family signature, two transmembrane domains, and a long C-terminal. aP2X7R transcripts were mainly distributed in ayu immune tissues and significantly increased in all tested tissues and in macrophages after Listonella anguillarum infection. The aP2X7R protein was upregulated significantly in macrophages upon bacterial challenge. An antibody against the ectodomain of aP2X7R (aEPAb) and an antagonist (oATP) were used to block aP2X7R. aP2X7R siRNA was also used to knockdown the receptor expression in ayu macrophages. Cell death induced by ATP was significantly inhibited in ayu macrophages after aEPAb, oATP, or siRNA treatment. Moreover, aP2X7R ablation also resulted in suppression of phagocytic activity and ATP-induced bacterial killing in ayu macrophages. Our results indicated that aP2X7R was upregulated after infection and mediated cell death, phagocytosis, and bacterial killing of ayu macrophages.
Collapse
Affiliation(s)
- Yu-Qing He
- School of Marine Sciences, Ningbo University, Ningbo, China
| | - Jiong Chen
- School of Marine Sciences, Ningbo University, Ningbo, China
- * E-mail:
| | - Xin-Jiang Lu
- School of Marine Sciences, Ningbo University, Ningbo, China
| | - Yu-Hong Shi
- School of Marine Sciences, Ningbo University, Ningbo, China
| |
Collapse
|
90
|
Foster JG, Carter E, Kilty I, MacKenzie AB, Ward SG. Mitochondrial superoxide generation enhances P2X7R-mediated loss of cell surface CD62L on naive human CD4+ T lymphocytes. THE JOURNAL OF IMMUNOLOGY 2013; 190:1551-9. [PMID: 23319734 DOI: 10.4049/jimmunol.1201510] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Migration of naive CD4(+) T lymphocytes into lymphoid tissue is essential for their activation and subsequent roles in adaptive immunity. The adhesion molecule L-selectin (CD62L), critical for this process, is highly expressed on naive CD4(+) T lymphocytes and is downregulated upon T lymphocyte activation. We demonstrate protein expression of P2X7R on naive CD4(+) T lymphocytes and show functional channel activity in whole-cell patch clamp recordings. CD62L downregulation occurs rapidly in response to extracellular ATP, a process that is blocked by selective antagonists of P2X7R. This loss of surface CD62L expression was not associated with externalization of phosphatidylserine. While investigating the mechanisms for this process, we revealed that pharmacological modulation of mitochondrial complex I or III, but not inhibition of NADPH oxidase, enhanced P2X7R-dependent CD62L downregulation by increasing ATP potency. Enhanced superoxide generation in the mitochondria of rotenone- and antimycin A-treated cells was observed and may contribute to the enhanced sensitivity of P2X7R to ATP. P2X7R-dependent exposure of phosphatidylserine was also revealed by preincubation with mitochondrial uncouplers prior to ATP treatment. This may present a novel mechanism whereby P2X7R-dependent phosphatidylserine exposure occurs only when cells have enhanced mitochondrial reactive oxygen species generation. The clearance of apoptotic cells may therefore be enhanced by this mechanism which requires functional P2X7R expression.
Collapse
Affiliation(s)
- John G Foster
- Department of Pharmacy and Pharmacology, University of Bath, Bath BA2 7AY, United Kingdom
| | | | | | | | | |
Collapse
|
91
|
Haanes KA, Schwab A, Novak I. The P2X7 receptor supports both life and death in fibrogenic pancreatic stellate cells. PLoS One 2012; 7:e51164. [PMID: 23284663 PMCID: PMC3524122 DOI: 10.1371/journal.pone.0051164] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 10/30/2012] [Indexed: 12/29/2022] Open
Abstract
The pancreatic stellate cells (PSCs) have complex roles in pancreas, including tissue repair and fibrosis. PSCs surround ATP releasing exocrine cells, but little is known about purinergic receptors and their function in PSCs. Our aim was to resolve whether PSCs express the multifunctional P2X7 receptor and elucidate how it regulates PSC viability. The number of PSCs isolated from wild type (WT) mice was 50% higher than those from the Pfizer P2X7 receptor knock out (KO) mice. The P2X7 receptor protein and mRNA of all known isoforms were expressed in WT PSCs, while KO PSCs only expressed truncated versions of the receptor. In culture, the proliferation rate of the KO PSCs was significantly lower. Inclusion of apyrase reduced the proliferation rate in both WT and KO PSCs, indicating importance of endogenous ATP. Exogenous ATP had a two-sided effect. Proliferation of both WT and KO cells was stimulated with ATP in a concentration-dependent manner with a maximum effect at 100 µM. At high ATP concentration (5 mM), WT PSCs, but not the KO PSCs died. The intracellular Ca2+ signals and proliferation rate induced by micromolar ATP concentrations were inhibited by the allosteric P2X7 receptor inhibitor az10606120. The P2X7 receptor-pore inhibitor A438079 partially prevented cell death induced by millimolar ATP concentrations. This study shows that ATP and P2X7 receptors are important regulators of PSC proliferation and death, and therefore might be potential targets for treatments of pancreatic fibrosis and cancer.
Collapse
Affiliation(s)
| | - Albrecht Schwab
- Institut für Physiologie II, Universität Münster, Münster, Germany
| | - Ivana Novak
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
- * E-mail:
| |
Collapse
|
92
|
P2X7 receptor activation induces reactive oxygen species formation in erythroid cells. Purinergic Signal 2012; 9:101-12. [PMID: 23014887 DOI: 10.1007/s11302-012-9335-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Accepted: 09/12/2012] [Indexed: 10/27/2022] Open
Abstract
The presence of P2X7 on erythroid cells is well established, but its physiological role remains unclear. The current study aimed to determine if P2X7 activation induces reactive oxygen species (ROS) formation in murine erythroleukaemia (MEL) cells, a commonly used erythroid cell line. ATP induced ROS formation in a time- and concentration-dependent fashion. The most potent P2X7 agonist, 2'(3')-O-(4-benzoylbenzoyl)ATP, but not UTP or ADP, also induced ROS formation. The P2X7 antagonist, A-438079, impaired ATP-induced ROS formation. The ROS scavenger, N-acetyl-L-cysteine, and the ROS inhibitor, diphenyleneiodonium, also impaired P2X7-induced ROS formation, but use of enzyme-specific ROS inhibitors failed to identify the intracellular source of P2X7-induced ROS formation. P2X7-induced ROS formation was impaired partly by physiological concentrations of Ca(2+) and Mg(2+) and almost completely in cells in N-methyl-D-glucamine chloride medium. The p38 MAPK inhibitors SB202190 and SB203580, and the caspase inhibitor Z-VAD-FMK, but not N-acetyl-L-cysteine, impaired P2X7-induced MEL cell apoptosis. ATP also stimulated p38 MAPK and caspase activation, both of which could be impaired by A-438079. In conclusion, these findings indicate that P2X7 activation induces ROS formation in MEL cells and that this process may be involved in events downstream of P2X7 activation, other than apoptosis, in erythroid cells.
Collapse
|
93
|
Nishida K, Nakatani T, Ohishi A, Okuda H, Higashi Y, Matsuo T, Fujimoto S, Nagasawa K. Mitochondrial dysfunction is involved in P2X7 receptor-mediated neuronal cell death. J Neurochem 2012; 122:1118-28. [PMID: 22774935 DOI: 10.1111/j.1471-4159.2012.07868.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
P2X7 receptor (P2X7R) is known to be a 'death receptor' in immune cells, but its functional expression in non-immune cells such as neurons is controversial. Here, we examined the involvement of P2X7R activation and mitochondrial dysfunction in ATP-induced neuronal death in cultured cortical neurons. In P2X7R- and pannexin-1-expressing neuron cultures, 5 or more mM ATP or 0.1 or more mM BzATP induced neuronal death including apoptosis, and cell death was prevented by oxATP, P2X7R-selective antagonists. ATP-treated neurons exhibited Ca(2+) entry and YO-PRO-1 uptake, the former being inhibited by oxATP and A438079, and the latter by oxATP and carbenoxolone, while P2X7R antagonism with oxATP, but not pannexin-1 blocking with carbenoxolone, prevented the ATP-induced neuronal death. The ATP treatment induced reactive oxygen species generation through activation of NADPH oxidase and activated poly(ADP-ribose) polymerase, but both of them made no or negligible contribution to the neuronal death. Rhodamine123 efflux from neuronal mitochondria was increased by the ATP-treatment and was inhibited by oxATP, and a mitochondrial permeability transition pore inhibitor, cyclosporine A, significantly decreased the ATP-induced neuronal death. In ATP-treated neurons, the cleavage of pro-caspase-3 was increased, and caspase inhibitors, Q-VD-OPh and Z-DEVD-FMK, inhibited the neuronal death. The cleavage of apoptosis-inducing factor was increased, and calpain inhibitors, MDL28170 and PD151746, inhibited the neuronal death. These findings suggested that P2X7R was functionally expressed by cortical neuron cultures, and its activation-triggered Ca(2+) entry and mitochondrial dysfunction played important roles in the ATP-induced neuronal death.
Collapse
Affiliation(s)
- Kentaro Nishida
- Department of Environmental Biochemistry, Kyoto Pharmaceutical University, Kyoto, Japan
| | | | | | | | | | | | | | | |
Collapse
|
94
|
Ito G, Suekawa Y, Watanabe M, Takahashi K, Inubushi T, Murasaki K, Hirose N, Hiyama S, Uchida T, Tanne K. P2X7receptor in the trigeminal sensory nuclear complex contributes to tactile allodynia/hyperalgesia following trigeminal nerve injury. Eur J Pain 2012; 17:185-99. [DOI: 10.1002/j.1532-2149.2012.00174.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/01/2012] [Indexed: 12/29/2022]
Affiliation(s)
- G. Ito
- Department of Orthodontics and Craniofacial Developmental Biology; Hiroshima University Graduate School of Biomedical Sciences; Japan
| | - Y. Suekawa
- Department of Orthodontics and Craniofacial Developmental Biology; Hiroshima University Graduate School of Biomedical Sciences; Japan
| | - M. Watanabe
- Department of Oral Biology; Division of Molecular Medical Science; Hiroshima University Graduate School of Biomedical Science; Japan
| | - K. Takahashi
- Department of Orthodontics and Craniofacial Developmental Biology; Hiroshima University Graduate School of Biomedical Sciences; Japan
| | - T. Inubushi
- Department of Orthodontics and Craniofacial Developmental Biology; Hiroshima University Graduate School of Biomedical Sciences; Japan
| | - K. Murasaki
- Department of Orthodontics and Craniofacial Developmental Biology; Hiroshima University Graduate School of Biomedical Sciences; Japan
| | - N. Hirose
- Department of Orthodontics and Craniofacial Developmental Biology; Hiroshima University Graduate School of Biomedical Sciences; Japan
| | - S. Hiyama
- Department of Oral Biology; Division of Molecular Medical Science; Hiroshima University Graduate School of Biomedical Science; Japan
| | - T. Uchida
- Department of Oral Biology; Division of Molecular Medical Science; Hiroshima University Graduate School of Biomedical Science; Japan
| | - K. Tanne
- Department of Orthodontics and Craniofacial Developmental Biology; Hiroshima University Graduate School of Biomedical Sciences; Japan
| |
Collapse
|
95
|
Hattori M, Gouaux E. Molecular mechanism of ATP binding and ion channel activation in P2X receptors. Nature 2012; 485:207-12. [PMID: 22535247 DOI: 10.1038/nature11010] [Citation(s) in RCA: 412] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Accepted: 03/04/2012] [Indexed: 11/09/2022]
Abstract
P2X receptors are trimeric ATP-activated ion channels permeable to Na+, K+ and Ca2+. The seven P2X receptor subtypes are implicated in physiological processes that include modulation of synaptic transmission, contraction of smooth muscle, secretion of chemical transmitters and regulation of immune responses. Despite the importance of P2X receptors in cellular physiology, the three-dimensional composition of the ATP-binding site, the structural mechanism of ATP-dependent ion channel gating and the architecture of the open ion channel pore are unknown. Here we report the crystal structure of the zebrafish P2X4 receptor in complex with ATP and a new structure of the apo receptor. The agonist-bound structure reveals a previously unseen ATP-binding motif and an open ion channel pore. ATP binding induces cleft closure of the nucleotide-binding pocket, flexing of the lower body β-sheet and a radial expansion of the extracellular vestibule. The structural widening of the extracellular vestibule is directly coupled to the opening of the ion channel pore by way of an iris-like expansion of the transmembrane helices. The structural delineation of the ATP-binding site and the ion channel pore, together with the conformational changes associated with ion channel gating, will stimulate development of new pharmacological agents.
Collapse
Affiliation(s)
- Motoyuki Hattori
- Vollum Institute, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239, USA
| | | |
Collapse
|
96
|
Namovic MT, Jarvis MF, Donnelly‐Roberts D. High Throughput Functional Assays for P2X Receptors. ACTA ACUST UNITED AC 2012; Chapter 9:Unit 9.15.. [DOI: 10.1002/0471141755.ph0915s57] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Marian T. Namovic
- Global Pharmaceutical Research and Development, Abbott Laboratories Abbott Park Illinois
| | - Michael F. Jarvis
- Global Pharmaceutical Research and Development, Abbott Laboratories Abbott Park Illinois
| | - Diana Donnelly‐Roberts
- Global Pharmaceutical Research and Development, Abbott Laboratories Abbott Park Illinois
| |
Collapse
|
97
|
Chu K, Yin B, Wang J, Peng G, Liang H, Xu Z, Du Y, Fang M, Xia Q, Luo B. Inhibition of P2X7 receptor ameliorates transient global cerebral ischemia/reperfusion injury via modulating inflammatory responses in the rat hippocampus. J Neuroinflammation 2012; 9:69. [PMID: 22513224 PMCID: PMC3418181 DOI: 10.1186/1742-2094-9-69] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2011] [Accepted: 04/18/2012] [Indexed: 01/05/2023] Open
Abstract
Background Neuroinflammation plays an important role in cerebral ischemia/reperfusion (I/R) injury. The P2X7 receptor (P2X7R) has been reported to be involved in the inflammatory response of many central nervous system diseases. However, the role of P2X7Rs in transient global cerebral I/R injury remains unclear. The purpose of this study is to determine the effects of inhibiting the P2X7R in a rat model of transient global cerebral I/R injury, and then to explore the association between the P2X7R and neuroinflammation after transient global cerebral I/R injury. Methods Immediately after infusion with the P2X7R antagonists Brilliant blue G (BBG), adenosine 5′-triphosphate-2′,3′-dialdehyde (OxATP) or A-438079, 20 minutes of transient global cerebral I/R was induced using the four-vessel occlusion (4-VO) method in rats. Survival rate was calculated, neuronal death in the hippocampal CA1 region was observed using H & E staining, and DNA cleavage was observed by deoxynucleotidyl transferase-mediated UTP nick end labeling TUNEL). In addition, behavioral deficits were measured using the Morris water maze, and RT-PCR and immunohistochemical staining were performed to measure the expression of IL-1β, TNF-α and IL-6, and to identify activated microglia and astrocytes. Results The P2X7R antagonists protected against transient global cerebral I/R injury in a dosage-dependent manner. A high dosage of BBG (10 μg) and A-0438079 (3 μg), and a low dosage of OxATP (1 μg) significantly increased survival rates, reduced I/R-induced learning memory deficit, and reduced I/R-induced neuronal death, DNA cleavage, and glial activation and inflammatory cytokine overexpression in the hippocampus. Conclusions Our study indicates that inhibiting P2X7Rs protects against transient global cerebral I/R injury by reducing the I/R-induced inflammatory response, which suggests inhibition of P2X7Rs may be a promising therapeutic strategy for clinical treatment of transient global cerebral I/R injury.
Collapse
Affiliation(s)
- Ketan Chu
- Department of Neurology, First Affiliated Hospital, Zhejiang University School of Medicine, 76 Qingchun Road, Hangzhou 310003, China
| | | | | | | | | | | | | | | | | | | |
Collapse
|
98
|
Niforatos W, Jarvis MF. Electrophysiological characterization of recombinant and native P2X receptors. ACTA ACUST UNITED AC 2012; Chapter 11:Unit 11.9. [PMID: 22294117 DOI: 10.1002/0471141755.ph1109s26] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
ATP acts as a fast neurotransmitter by activating a family of ligand-gated ion channels, the P2X receptors. Functional homomeric P2X(3) and heteromeric P2X(2/3) receptors are highly localized on primary sensory afferent neurons that transmit nociceptive sensory information. Activation of these P2X(3)-containing channels may provide a specific mechanism whereby ATP, released via synaptic transmission or by cellular injury, elicits pain. The experimental procedures described in this unit are useful for the electorphysiological characterization of P2X receptors. In addition, these protocols provide methods for the evaluation of ligands that interact with P2X receptors that are either natively expressed on excitable cells or cloned and expressed in heterologous cell systems. These methods are derived from standard electrophysiological principles and procedures that are applicable to a wide variety of ligand-gated ion channels. Specific attention is given here to the reliable electrophysiological measurement of both quickly (P2X(3)) and more slowly (P2X(2) and P2X(2/3)) desensitizing receptors.
Collapse
|
99
|
Grol MW, Zelner I, Dixon SJ. P2X₇-mediated calcium influx triggers a sustained, PI3K-dependent increase in metabolic acid production by osteoblast-like cells. Am J Physiol Endocrinol Metab 2012; 302:E561-75. [PMID: 22185840 DOI: 10.1152/ajpendo.00209.2011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The P2X₇ receptor is an ATP-gated cation channel expressed by a number of cell types, including osteoblasts. Genetically modified mice with loss of P2X₇ function exhibit altered bone formation. Moreover, activation of P2X₇ in vitro stimulates osteoblast differentiation and matrix mineralization, although the underlying mechanisms remain unclear. Because osteogenesis is associated with enhanced cellular metabolism, our goal was to characterize the effects of nucleotides on metabolic acid production (proton efflux) by osteoblasts. The P2X₇ agonist 2',3'-O-(4-benzoylbenzoyl)ATP (BzATP; 300 μM) induced dynamic membrane blebbing in MC3T3-E1 osteoblast-like cells (consistent with activation of P2X₇ receptors) but did not induce cell death. Using a Cytosensor microphysiometer, we found that 9-min exposure to BzATP (300 μM) caused a dramatic increase in proton efflux from MC3T3-E1 cells (∼2-fold), which was sustained for at least 1 h. In contrast, ATP or UTP (100 μM), which activate P2 receptors other than P2X₇, failed to elicit a sustained increase in proton efflux. Specific P2X₇ receptor antagonists A 438079 and A 740003 inhibited the sustained phase of the BzATP-induced response. Extracellular Ca²⁺ was required during P2X₇ receptor stimulation for initiation of sustained proton efflux, and removal of extracellular glucose within the sustained phase abolished the elevation elicited by BzATP. In addition, inhibition of phosphatidylinositol 3-kinase blocked the maintenance but not initiation of the sustained phase. Taken together, we conclude that brief activation of P2X₇ receptors on osteoblast-like cells triggers a dramatic, Ca²⁺-dependent stimulation of metabolic acid production. This increase in proton efflux is sustained and dependent on glucose and phosphatidylinositol 3-kinase activity.
Collapse
Affiliation(s)
- Matthew W Grol
- Dept. of Anatomy and Cell Biology, Schulich School of Medicine & Dentistry, Univ. of Western Ontario, London, ON, Canada
| | | | | |
Collapse
|
100
|
|