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Zorina-Lichtenwalter K, Ase AR, Verma V, Parra AIM, Komarova S, Khadra A, Séguéla P, Diatchenko L. Characterization of Common Genetic Variants in P2RX7 and Their Contribution to Chronic Pain Conditions. THE JOURNAL OF PAIN 2024; 25:545-556. [PMID: 37742908 DOI: 10.1016/j.jpain.2023.09.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 08/22/2023] [Accepted: 09/19/2023] [Indexed: 09/26/2023]
Abstract
The adenosine triphosphate (ATP)-gated channel P2X7 is encoded by a gene enriched for common nonsynonymous variants. Many of these variants have functional cellular effects, and some have been implicated in chronic pain. In this study, we first systematically characterized all 17 common nonsynonymous variants using whole-cell patch clamp electrophysiology. Then, we analyzed these variants for statistical association with chronic pain phenotypes using both individual P2RX7 variants as predictors and cumulative allele counts of same-direction cellular effect in univariate models. Association and validation analyses were conducted in the Orofacial Pain: Prospective Evaluation and Risk Assessment (OPPERA) cohort (N = 3260) and in the Complex Persistent Pain Conditions (CPPC) cohort (N = 900), respectively. Our results showed an association between allele A of rs7958311 and an increased risk of chronic pelvic pain, with convergent evidence for contribution to fibromyalgia and irritable bowel syndrome, confirmed in a meta-analysis. This allelic variant produced a unique cellular phenotype: a gain-of-function in channel opening, and a loss-of-function in pore opening. A computational study using a 12-state Markov model of ATP binding to the P2X7 receptor suggested that this cellular phenotype arises from an increased ATP binding affinity and an increased open channel conductance combined with a loss of sensitization. Cumulative allele count analysis did not provide additional insights. In conclusion, our results go beyond reproducing association for rs7958311 with chronic pain and suggest that its unique combination of gain-of-function in channel and loss-of-function in pore activity may explain why it is likely the only common P2RX7 variant with contribution to chronic pain. PERSPECTIVE: This study characterizes all common P2RX7 variants using cellular assays and statistical association analyses with chronic pain, with Markov state modeling of the most robustly associated variant.
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Affiliation(s)
- Katerina Zorina-Lichtenwalter
- Faculty of Dental Medicine and Oral Health Sciences, Department of Anesthesia, Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada; Alan Edwards Centre for Research on Pain, Department of Anesthesia, Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada
| | - Ariel R Ase
- Department of Neurology & Neurosurgery, Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada; Montreal Neurological Institute/Hospital, Montreal, QC, Canada; Alan Edwards Centre for Research on Pain, Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada
| | - Vivek Verma
- Faculty of Dental Medicine and Oral Health Sciences, Department of Anesthesia, Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada; Alan Edwards Centre for Research on Pain, Department of Anesthesia, Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada
| | - Arturo I M Parra
- Faculty of Dental Medicine and Oral Health Sciences, Department of Anesthesia, Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada; Alan Edwards Centre for Research on Pain, Department of Anesthesia, Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada
| | - Svetlana Komarova
- Faculty of Dental Medicine and Oral Health Sciences, McGill University, Montreal, QC, Canada
| | - Anmar Khadra
- Department of Physiology, Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada
| | - Philippe Séguéla
- Department of Neurology & Neurosurgery, Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada; Montreal Neurological Institute/Hospital, Montreal, QC, Canada; Alan Edwards Centre for Research on Pain, Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada
| | - Luda Diatchenko
- Faculty of Dental Medicine and Oral Health Sciences, Department of Anesthesia, Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada; Alan Edwards Centre for Research on Pain, Department of Anesthesia, Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada; Faculty of Dental Medicine and Oral Health Sciences, McGill University, Montreal, QC, Canada
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Townsend EA, Guadarrama A, Shi L, Roti Roti E, Denlinger LC. P2X 7 signaling influences the production of pro-resolving and pro-inflammatory lipid mediators in alveolar macrophages derived from individuals with asthma. Am J Physiol Lung Cell Mol Physiol 2023; 325:L399-L410. [PMID: 37581221 PMCID: PMC10639011 DOI: 10.1152/ajplung.00070.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 07/26/2023] [Accepted: 07/27/2023] [Indexed: 08/16/2023] Open
Abstract
Few new therapeutics exist to target airway inflammation in mild-to-moderate asthma. Alveolar macrophages regulate airway inflammation by producing proresolving eicosanoids. We hypothesized that stimulation of the purinergic receptor P2X7 in macrophages from individuals with asthma produces eicosanoids associated with airway inflammation and resolution, and that these responses are predicted, in part, by P2X7 pore function. Study subjects were recruited in an Institutional Review Board (IRB)-approved study. Alveolar macrophages were recovered from bronchoalveolar lavage fluid following bronchoscopy. Purinergic receptor classification was performed using flow cytometry and fluorescent cell assay. Macrophages were stimulated in vitro and eicosanoids were measured via ELISA or enzyme immunoassay (EIA) in the presence and absence of P2X7-specific agonist [2'(3')-O-(4-Benzoylbenzoyl)adenosine-5'-triphosphate tri(triethylammonium) salt (Bz-ATP)] and antagonist (AZD9056). Functional P2X7 pore status was confirmed in a live cell assay using P2X7-specific agonists and antagonists. Alveolar macrophages produced increased quantities of the oxylipins lipoxin A4 (LXA4), resolvin D1 (RvD1), and 15(S)-hydroxyeicosatetraenoic acid (15(S)-HETE) following stimulation with Bz-ATP compared with vehicle controls, responses that were attenuated in the presence of the P2X7-selective antagonist, AZD9056. LXA4 and RvD1 production was greatest at 1 h, whereas 15(S)-HETE was maximally produced 24 h. Prostaglandin E-2 and resolvin E1 were minimally produced by P2X7 activation, indicating differential signaling pathways involved in eicosanoid production in alveolar macrophages derived from individuals with asthma. The early production of the proresolving eicosanoids, LXA4 and resolvin D1, is regulated by P2X7, whereas generation of the proinflammatory eicosanoid, 15(S)-HETE, is only partially regulated through P2X7 signaling and reaches maximal production after the peak in proresolving eicosanoids.NEW & NOTEWORTHY Alveolar macrophages obtained from individuals with asthma produce soluble lipid mediators in response to P2X7 purinergic receptor signaling. Proinflammatory mediators may contribute to asthma exacerbations but proresolving mediators may help with resolution of asthma loss of control. These specialized proresolving lipid mediators may serve as future potential therapeutics for asthma exacerbation resolution and recovery.
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Affiliation(s)
- Elizabeth A Townsend
- Department of Anesthesiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States
| | - Arturo Guadarrama
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States
| | - Lei Shi
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States
| | - Elon Roti Roti
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States
| | - Loren C Denlinger
- Division of Allergy, Pulmonary and Critical Care Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, United States
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Li H, Cvejic E, Gu B, Vollmer-Conna U, Hickie I, Wakefield D, Davenport T, Wiley J, Lloyd AR. Regulation of the Acute Sickness Response by the P2RX7 Receptor. J Infect Dis 2021; 224:914-920. [PMID: 33471105 DOI: 10.1093/infdis/jiab027] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 01/14/2021] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND The acute sickness response to infection is a stereotyped set of illness manifestations initiated by proinflammatory signals in the periphery but mediated centrally. P2RX7 is a highly polymorphic gene encoding an ATP-gated cationic pore, widely expressed on immune cells and the brain, and regulating the NLRP3 inflammasome, as well as diverse neural functions. METHODS Associations between P2RX7 genotype, pore activity, and illness manifestations were examined in a cohort with acute viral and bacterial infections (n = 484). Genotyping of 12 P2RX7 function-modifying single-nucleotide polymorphisms (SNPs) was used to identify haplotypes and diplotypes. Leucocyte pore activity was measured by uptake of the fluorescent dye, YO-PRO-1, and by ATP-induced interleukin-1β (IL-1β) release. Associations were sought with scores describing the symptom domains, or endophenotypes, derived from principal components analysis. RESULTS Among the 12 SNPs, a 4-SNP haplotype block with 5 variants was found in 99.5% of the subjects. These haplotypes and diplotypes were closely associated with variations in pore activity and IL-1β production. Homozygous diplotypes were associated with overall illness severity as well as fatigue, pain, and mood disturbances. CONCLUSIONS P2RX7 signaling plays a significant role in the acute sickness response to infection, likely acting in both the immune system and the brain.
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Affiliation(s)
- Hui Li
- Viral Immunology Systems Program, Kirby Institute, University of New South Wales, Sydney, Australia
| | - Erin Cvejic
- Department of Human Behaviour, School of Psychiatry, University of New South Wales, Sydney, Australia
| | - Ben Gu
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Ute Vollmer-Conna
- Department of Human Behaviour, School of Psychiatry, University of New South Wales, Sydney, Australia
| | - Ian Hickie
- Brain and Mind Centre, University of Sydney, Sydney, Australia
| | - Denis Wakefield
- School of Medical Sciences, University of New South Wales, Sydney, Australia
| | | | - James Wiley
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
| | - Andrew R Lloyd
- Viral Immunology Systems Program, Kirby Institute, University of New South Wales, Sydney, Australia
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Wei L, Syed Mortadza SA, Yan J, Zhang L, Wang L, Yin Y, Li C, Chalon S, Emond P, Belzung C, Li D, Lu C, Roger S, Jiang LH. ATP-activated P2X7 receptor in the pathophysiology of mood disorders and as an emerging target for the development of novel antidepressant therapeutics. Neurosci Biobehav Rev 2018; 87:192-205. [PMID: 29453990 DOI: 10.1016/j.neubiorev.2018.02.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Revised: 02/01/2018] [Accepted: 02/08/2018] [Indexed: 12/11/2022]
Abstract
Mood disorders are a group of psychiatric conditions that represent leading global disease burdens. Increasing evidence from clinical and preclinical studies supports that innate immune system dysfunction plays an important part in the pathophysiology of mood disorders. P2X7 receptor, belonging to the ligand-gated ion channel P2X subfamily of purinergic P2 receptors for extracellular ATP, is highly expressed in immune cells including microglia in the central nervous system (CNS) and has a vital role in mediating innate immune response. The P2X7 receptor is also important in neuron-glia signalling in the CNS. The gene encoding human P2X7 receptor is located in a locus of susceptibility to mood disorders. In this review, we will discuss the recent progress in understanding the role of the P2X7 receptor in the pathogenesis and development of mood disorders and in discovering CNS-penetrable P2X7 antagonists for potential uses in in vivo imaging to monitor brain inflammation and antidepressant therapeutics.
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Affiliation(s)
- Linyu Wei
- Sino-UK Joint Laboratory of Brain Function and Injury of Henan Province, Xinxiang Medical University, China; School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, United Kingdom
| | - Sharifah A Syed Mortadza
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, United Kingdom; Faculty of Medicine and Health Science, University Putra Malaysia, Selangor, Malaysia
| | - Jing Yan
- Sino-UK Joint Laboratory of Brain Function and Injury of Henan Province, Xinxiang Medical University, China
| | - Libin Zhang
- Sino-UK Joint Laboratory of Brain Function and Injury of Henan Province, Xinxiang Medical University, China
| | - Lu Wang
- Sino-UK Joint Laboratory of Brain Function and Injury of Henan Province, Xinxiang Medical University, China
| | - Yaling Yin
- Sino-UK Joint Laboratory of Brain Function and Injury of Henan Province, Xinxiang Medical University, China
| | - Chaokun Li
- Sino-UK Joint Laboratory of Brain Function and Injury of Henan Province, Xinxiang Medical University, China
| | - Sylvie Chalon
- Inserm UMR 1253, iBrain, Université de Tours, Tours, France
| | - Patrick Emond
- Inserm UMR 1253, iBrain, Université de Tours, Tours, France; CHRU de Tours, Service de Médecine Nucléaire In Vitro, Tours, France
| | | | - Dongliang Li
- Sino-UK Joint Laboratory of Brain Function and Injury of Henan Province, Xinxiang Medical University, China; Key Laboratory for the Brain Research of Henan Province, Xinxiang Medical University, China
| | - Chengbiao Lu
- Sino-UK Joint Laboratory of Brain Function and Injury of Henan Province, Xinxiang Medical University, China; Key Laboratory for the Brain Research of Henan Province, Xinxiang Medical University, China
| | - Sebastien Roger
- Inserm UMR1069, Nutrition, Croissance et Cancer, Université de Tours, France; Institut Universitaire de France, Paris Cedex 05, France
| | - Lin-Hua Jiang
- Sino-UK Joint Laboratory of Brain Function and Injury of Henan Province, Xinxiang Medical University, China; School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, United Kingdom; Institut Universitaire de France, Paris Cedex 05, France.
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Barberà-Cremades M, Gómez AI, Baroja-Mazo A, Martínez-Alarcón L, Martínez CM, de Torre-Minguela C, Pelegrín P. P2X7 Receptor Induces Tumor Necrosis Factor-α Converting Enzyme Activation and Release to Boost TNF-α Production. Front Immunol 2017; 8:862. [PMID: 28791020 PMCID: PMC5523084 DOI: 10.3389/fimmu.2017.00862] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 07/07/2017] [Indexed: 01/15/2023] Open
Abstract
Tumor necrosis factor (TNF)-α is a major pro-inflammatory cytokine produced in response to toll-like receptor stimulation. TNF-α release is controlled by the activity of TNF-α converting enzyme (TACE) that cut membrane-bound TNF-α to shed its ectodomain as a soluble cytokine. The purinergic receptor P2X ligand-gated ion channel 7 (P2X7) is activated in response to elevated concentrations of extracellular ATP and induces different pro-inflammatory pathways in macrophages to establish an inflammatory response. P2X7 receptor promotes the activation of the inflammasome and the release of interleukin-1β, the production of inflammatory lipids, and the generation of reactive oxygen species. In this study, we analyzed the mechanism of P2X7 receptor responsible of TNF-α release after priming macrophages with LPS doses ≤100 ng/ml. We found that P2X7 receptor increases the extracellular activity of TACE through the release of the mature form of TACE in exosomes. This effect was blocked using P2X7 receptor inhibitors or in macrophages obtained from P2X7 receptor-deficient mice. Elevation of intracellular Ca2+ and p38 mitogen-activated protein kinase after P2X7 receptor activation were involved in the release of TACE, which was able to process TNF-α on nearby expressing cells. Finally, we observed an increase of TNF-α in the peritoneal lavage of mice treated with LPS and ATP. In conclusion, P2X7 receptor induces the release of TACE in exosomes to the extracellular compartment that could amplify the pro-inflammatory signal associated to this receptor. These results are important for the development of therapeutics targeting P2X7 receptor.
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Affiliation(s)
- Maria Barberà-Cremades
- Biomedical Research Institute of Murcia (IMIB-Arrixaca), Clinical University Hospital Virgen de la Arrixaca, Murcia, Spain
| | - Ana I Gómez
- Biomedical Research Institute of Murcia (IMIB-Arrixaca), Clinical University Hospital Virgen de la Arrixaca, Murcia, Spain
| | - Alberto Baroja-Mazo
- Biomedical Research Institute of Murcia (IMIB-Arrixaca), Clinical University Hospital Virgen de la Arrixaca, Murcia, Spain
| | - Laura Martínez-Alarcón
- Biomedical Research Institute of Murcia (IMIB-Arrixaca), Clinical University Hospital Virgen de la Arrixaca, Murcia, Spain
| | - Carlos M Martínez
- Biomedical Research Institute of Murcia (IMIB-Arrixaca), Clinical University Hospital Virgen de la Arrixaca, Murcia, Spain
| | - Carlos de Torre-Minguela
- Biomedical Research Institute of Murcia (IMIB-Arrixaca), Clinical University Hospital Virgen de la Arrixaca, Murcia, Spain
| | - Pablo Pelegrín
- Biomedical Research Institute of Murcia (IMIB-Arrixaca), Clinical University Hospital Virgen de la Arrixaca, Murcia, Spain
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Monif M, Reid CA, Powell KL, Drummond KJ, O'Brien TJ, Williams DA. Interleukin-1β has trophic effects in microglia and its release is mediated by P2X7R pore. J Neuroinflammation 2016; 13:173. [PMID: 27364756 PMCID: PMC4929731 DOI: 10.1186/s12974-016-0621-8] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Accepted: 06/10/2016] [Indexed: 11/21/2022] Open
Abstract
Background Enhanced expression of the purinergic P2X7 receptor (P2X7R) occurs in several neuroinflammatory conditions where increased microglial activation is a co-existing feature. P2X7 receptors can function either as a cation channel or, upon continued stimulation, a large pore. P2X7R-over-expression alone is sufficient to drive microglial activation and proliferation in a process that is P2X7R pore dependent, although the biological signaling pathway through which this occurs remains unclear. Once activated, microglia are known to release a number of bioactive substances that include the proinflammatory cytokine interleukin-1β (IL-1β). Previous studies have linked P2X7R stimulation to the processing and release of IL-1β, but whether the channel or pore state of P2X7R is predominant in driving IL-1β release is unknown and is a major aim of this study. In addition, we will determine whether IL-1β has trophic effects on surrounding microglia. Methods Electron microscopy and immunohistochemistry were used to delineate the sub-cellular localization of P2X7R and IL-1β in primary hippocampal rat cultures. FM1-43 fluorescent dye and confocal microscopy were used to quantify vesicular exocytosis from microglia expressing the pore-forming P2X7R versus a non-pore-forming point mutant, P2X7RG345Y. IL-1β in culture was quantified with an enzyme-linked immunosorbent assay (ELISA). IL-1β intracellular processing was blocked with inhibition of caspase 1 (with a synthetic peptide antagonist), and its extracellular form was neutralized with an IL-1β neutralizing antibody. Microglial activation and proliferation was quantified immunohistochemically with confocal microscopy. Results P2X7R and IL-1β were co-localized in lysosomes. Vesicular exocytosis was higher in microglia expressing the pore-forming P2X7R compared to those expressing the non-pore-forming mutant. There was increased IL-1β in cultures expressing the pore-forming P2X7R, and this proinflammatory cytokine was found to mediate the trophic effects of P2X7R pore in microglia. Inhibition of IL-1β production and function resulted in a significant decrease in P2X7R-mediated microglial activation and proliferation. Conclusions IL-1β is a mediator of microglial activation and proliferation, and its release/production is P2X7R pore dependent. Blockade of P2X7R pore could serve as a therapeutic target in alleviating the degree of inflammation seen in neurodegenerative and neoplastic conditions. Electronic supplementary material The online version of this article (doi:10.1186/s12974-016-0621-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Mastura Monif
- Department of Physiology, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Melbourne, Victoria, 3010, Australia.,The Department of Neurology, The Royal Melbourne Hospital, Parkville, Victoria, 3052, Australia
| | - Christopher A Reid
- Howard Florey Institute, The University of Melbourne, Melbourne, Victoria, 3010, Australia
| | - Kim L Powell
- Department of Medicine, Royal Melbourne Hospital, The University of Melbourne, Melbourne, Victoria, 3010, Australia
| | - Katherine J Drummond
- Department of Surgery, Royal Melbourne Hospital, The University of Melbourne, Melbourne, Victoria, 3010, Australia
| | - Terrence J O'Brien
- Department of Medicine, Royal Melbourne Hospital, The University of Melbourne, Melbourne, Victoria, 3010, Australia
| | - David A Williams
- Department of Physiology, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Melbourne, Victoria, 3010, Australia.
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The P2X7 receptor: a key player in immune-mediated bone loss? ScientificWorldJournal 2014; 2014:954530. [PMID: 24574936 PMCID: PMC3915485 DOI: 10.1155/2014/954530] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Accepted: 10/29/2013] [Indexed: 12/20/2022] Open
Abstract
Inflammatory diseases are often multiorganic diseases with manifestations not related directly to the primary affected organ. They are often complicated by a generalized bone loss that subsequently leads to osteoporosis and bone fractures. The exact mechanism for the accompanying bone loss is not understood in full detail, but factors such as glucocorticoid treatment, immobilization, malnutrition, and insufficient intake of vitamin D play a role. However, it has become evident that the inflammatory process itself is involved and the resulting bone loss is termed immune-mediated bone loss. It stems from an increase in bone resorption and the pro-inflammatory cytokines tumor necrosis factor alpha and interleukin 1 beta and has been shown to not only mediate the inflammatory response but also to strongly stimulate bone degradation. The purinergic P2X7 receptor is central in the processing of these two cytokines and in the initiation of the inflammatory response, and it is a key molecule in the regulation of both bone formation and bone resorption. The aim of this review is therefore to provide evidence-based novel hypotheses of the role of ATP-mediated purinergic signalling via the P2X7 receptor in immune-mediated bone loss and -osteoporosis.
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8
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Gavala ML, Liu YP, Lenertz LY, Zeng L, Blanchette JB, Guadarrama AG, Denlinger LC, Bertics PJ, Smith JA. Nucleotide receptor P2RX7 stimulation enhances LPS-induced interferon-β production in murine macrophages. J Leukoc Biol 2013; 94:759-68. [PMID: 23911869 PMCID: PMC3774844 DOI: 10.1189/jlb.0712351] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Revised: 05/22/2013] [Accepted: 06/27/2013] [Indexed: 12/22/2022] Open
Abstract
Stimulation of P2RX(7) with extracellular ATP potentiates numerous LPS-induced proinflammatory events, including cytokine induction in macrophages, but the molecular mechanisms underlying this process are not well defined. Although P2RX(7) ligation has been proposed to activate several transcription factors, many of the LPS-induced mediators affected by P2RX(7) activation are not induced by P2RX(7) agonists alone, suggesting a complementary role for P2RX(7) in transcriptional regulation. Type I IFN production, whose expression is tightly controlled by multiple transcription factors that form an enhanceosome, is critical for resistance against LPS-containing bacteria. The effect of purinergic receptor signaling on LPS-dependent type I IFN is unknown and would be of great relevance to a diverse array of inflammatory conditions. The present study demonstrates that stimulation of macrophages with P2RX(7) agonists substantially enhances LPS-induced IFN-β expression, and this enhancement is ablated in macrophages that do not express functional P2RX(7) or when the MAPK MEK1/2 pathways are inhibited. Potentiation of LPS-induced IFN-β expression following P2RX(7) stimulation is likely transcriptionally regulated, as this enhancement is observed at the IFN-β promoter level. Furthermore, P2RX(7) stimulation is able to increase the phosphorylation and subsequent IFN-β promoter occupancy of IRF-3, a transcription factor that is critical for IFN-β transcription by TLR agonists. This newly discovered role for P2RX(7) in IFN regulation may have implications in antimicrobial defense, which has been linked to P2RX(7) activation in other studies.
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Affiliation(s)
- M L Gavala
- 2.University of Wisconsin School of Medicine and Public Health, 600 Highland Ave., CSC H4/472, Madison, WI 53792-9988, USA.
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9
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Wickert LE, Blanchette JB, Waldschmidt NV, Bertics PJ, Denu JM, Denlinger LC, Lenertz LY. The C-terminus of human nucleotide receptor P2X7 is critical for receptor oligomerization and N-linked glycosylation. PLoS One 2013; 8:e63789. [PMID: 23691096 PMCID: PMC3653848 DOI: 10.1371/journal.pone.0063789] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2012] [Accepted: 04/11/2013] [Indexed: 11/21/2022] Open
Abstract
Background The P2X7 receptor binds extracellular ATP to mediate numerous inflammatory responses and is considered a potential biomarker and therapeutic target for diverse inflammatory and neurological diseases. P2X7 contains many single nucleotide polymorphisms, including several mutations located within its intracellular C-terminal trafficking domain. Mutations within the trafficking domain result in attenuated receptor activity and cell surface presentation, but the mechanisms by which amino acid changes within this region promote altered P2X7 function have not been elucidated. Methods and Results We analyzed the amino acid sequence of P2X7 for any potential trafficking signals and found that P2X7 contains putative Arg-X-Arg ER retention sequences. Alanine substitutions near or within these sequences were constructed, and we determined that single mutation of R574 and R578 but not R576 or K579 attenuates P2X7-stimulated activation of ERK1/2 and induction of the transcription factors FosB and ΔFosB. We found that mutation of R578 within the trafficking domain to the naturally occurring Gln substitution disrupts P2X7 localization at the plasma membrane and results in R578Q displaying a higher apparent molecular weight in comparison to wild-type receptor. We used the glycosidase endoglycosidase H to determine that this difference in mass is due in part to the R578Q mutant possessing a larger mass of oligosaccharides, indicative of improper N-linked glycosylation addition and/or trimming. Chemical cross-linking experiments were also performed and suggest that the R578Q variant also does not form trimers as well as wild-type receptor, a function required for its full activity. Conclusions These data demonstrate the distal C-terminus of P2X7 is important for oligomerization and post-translational modification of the receptor, providing a mechanism by which mutations in the trafficking domain disrupt P2X7 activity and localization at the plasma membrane.
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Affiliation(s)
- Lisa E. Wickert
- Department of Biomolecular Chemistry, The University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Joshua B. Blanchette
- Department of Biomolecular Chemistry, The University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Noelle V. Waldschmidt
- Department of Biology, St. Olaf College, Northfield, Minnesota, United States of America
| | - Paul J. Bertics
- Department of Biomolecular Chemistry, The University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - John M. Denu
- Department of Biomolecular Chemistry, The University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Loren C. Denlinger
- Department of Medicine, The University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Lisa Y. Lenertz
- Department of Biology, St. Olaf College, Northfield, Minnesota, United States of America
- * E-mail:
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Jiang LH, Baldwin JM, Roger S, Baldwin SA. Insights into the Molecular Mechanisms Underlying Mammalian P2X7 Receptor Functions and Contributions in Diseases, Revealed by Structural Modeling and Single Nucleotide Polymorphisms. Front Pharmacol 2013; 4:55. [PMID: 23675347 PMCID: PMC3646254 DOI: 10.3389/fphar.2013.00055] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 04/11/2013] [Indexed: 12/13/2022] Open
Abstract
The mammalian P2X7 receptors (P2X7Rs), a member of the ionotropic P2X receptor family with distinctive functional properties, play an important part in mediating extracellular ATP signaling in health and disease. A clear delineation of the molecular mechanisms underlying the key receptor properties, such as ATP-binding, ion permeation, and large pore formation of the mammalian P2X7Rs, is still lacking, but such knowledge is crucial for a better understanding of their physiological functions and contributions in diseases and for development of therapeutics. The recent breakthroughs in determining the atomic structures of the zebrafish P2X4.1R in the closed and ATP-bound open states have provided the long-awaited structural information. The human P2RX7 gene is abundant with non-synonymous single nucleotide polymorphisms (NS-SNPs), which generate a repertoire of human P2X7Rs with point mutations. Characterizations of the NS-SNPs identified in patients of various disease conditions and the resulting mutations have informed previously unknown molecular mechanisms determining the mammalian P2X7R functions and diseases. In this review, we will discuss the new insights into such mechanisms provided by structural modeling and recent functional and genetic linkage studies of NS-SNPs.
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Affiliation(s)
- Lin-Hua Jiang
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds Leeds, UK
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Wesselius A, Bours MJL, Henriksen Z, Syberg S, Petersen S, Schwarz P, Jørgensen NR, van Helden S, Dagnelie PC. Association of P2X7 receptor polymorphisms with bone mineral density and osteoporosis risk in a cohort of Dutch fracture patients. Osteoporos Int 2013; 24:1235-46. [PMID: 22776862 PMCID: PMC3604588 DOI: 10.1007/s00198-012-2059-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Accepted: 06/13/2012] [Indexed: 10/29/2022]
Abstract
UNLABELLED The P2X7 receptor is thought to be involved in bone physiology in a pro-osteogenic manner. Therefore, we examined associations between genetic variations in the P2X7 receptor gene and bone mineral density (BMD). We found an association between four non-synonymous polymorphism of the human P2X7 receptor and the risk of osteoporosis. INTRODUCTION The purpose of this study was to determine whether genetic variation in the P2X7 receptor gene (P2RX7) is associated with decreased BMD and risk of osteoporosis in fracture patients. METHODS Six hundred ninety women and 231 men aged≥50 years were genotyped for 15 non-synonymous P2RX7 SNPs. BMD was measured at the total hip, lumbar spine and femoral neck. RESULTS Four non-synonymous SNPs were associated with BMD. The Ala348Thr gain-of-function polymorphism was associated with increased BMD values at the lumbar spine (p=0.012). Decreased hip BMD values were associated with two loss-of-function SNPs in the P2RX7, i.e., in subjects homozygous for the Glu496Ala polymorphism as well as in subjects carrying at least one variant allele of the Gly150Arg polymorphism (p=0.018 and p=0.011; respectively). In men, we showed that subjects either heterozygous or homozygous for the Gln460Arg gain-of-function polymorphism in the P2RX7 had a significantly 40% decrease in risk of a lower T-score value (OR=0.58 [95%CI, 0.33-1.00]). CONCLUSION Thus, genetic aberrations of P2X7R function are associated with lower BMD and increased osteoporosis risk. Therefore, detection of non-synonymous SNPs within the P2RX7 might be useful for osteoporosis risk estimation at an early stage, potentially enabling better osteoporosis prevention and treatment.
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Affiliation(s)
- A Wesselius
- Department of Epidemiology, School for Public Health and Primary Care (CAPHRI), Maastricht University, Peter Debyeplein 1, P.O. Box 616, 6200, MD, Maastricht, The Netherlands.
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12
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Wesselius A, Bours MJL, Arts ICW, Theunisz EHE, Geusens P, Dagnelie PC. The P2X(7) loss-of-function Glu496Ala polymorphism affects ex vivo cytokine release and protects against the cytotoxic effects of high ATP-levels. BMC Immunol 2012; 13:64. [PMID: 23210974 PMCID: PMC3526505 DOI: 10.1186/1471-2172-13-64] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Accepted: 11/23/2012] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND The P2X(7) receptor plays an important role in cytokine release during the inflammatory response in vivo. Polymorphisms within the P2X(7) receptor gene that lead to loss of receptor function may contribute to impaired cytokine release by immune cells. Therefore, we investigated whether a known loss-of-function polymorphism (Glu496Ala) in the P2X(7) receptor gene leads to alterations in cytokine release in response to ATP. RESULTS An ex vivo whole blood model was used to induce an inflammatory reaction with the pro-inflammatory stimuli LPS and PHA (phytohemagglutinin). Blood from n=9 subjects with the Glu496Ala P2X7 SNP (P2X7MUT) and n=7 'wild-type' subjects (no P2X7 SNP; P2X7WT) was used.Addition of ATP (0.9-3 mM) to LPS/PHA-stimulated whole blood induced an increase in IL-1β release in P2X7MUT subjects, whereas decreased release was observed in P2X7WT subjects. Decreased levels of IL-6 and TNF-α in response to ATP were shown in both P2X7MUT and P2X7WT subjects, which was less pronounced in P2X7MUT subjects. ATP at 3 mM also significantly decreased levels of lactate dehydrogenase (LDH) in P2X7MUT subjects compared to P2X7WT subjects. CONCLUSIONS The presence of the non-synonymous Glu496Ala loss-of-function polymorphism within the P2X(7) receptor gene is likely to be of importance in the release of cytokines during inflammation. Furthermore, this study suggests that carriers of the Glu496Ala loss-of-function polymorphism are protected against the cytotoxic effects of high ATP-levels.
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Affiliation(s)
- Anke Wesselius
- Department of Epidemiology, Maastricht University, School for Public Health and Primary Care (CAPHRI), Peter Debyeplein 1, Maastricht, MD 6200, The Netherlands.
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13
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Denlinger LC, Manthei DM, Seibold MA, Ahn K, Bleecker E, Boushey HA, Calhoun WJ, Castro M, Chinchili VM, Fahy JV, Hawkins GA, Icitovic N, Israel E, Jarjour NN, King T, Kraft M, Lazarus SC, Lehman E, Martin RJ, Meyers DA, Peters SP, Sheerar D, Shi L, Sutherland ER, Szefler SJ, Wechsler ME, Sorkness CA, Lemanske RF. P2X7-regulated protection from exacerbations and loss of control is independent of asthma maintenance therapy. Am J Respir Crit Care Med 2012; 187:28-33. [PMID: 23144325 DOI: 10.1164/rccm.201204-0750oc] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
RATIONALE The function of the P2X(7) nucleotide receptor protects against exacerbation in people with mild-intermittent asthma during viral illnesses, but the impact of disease severity and maintenance therapy has not been studied. OBJECTIVES To evaluate the association between P2X(7), asthma exacerbations, and incomplete symptom control in a more diverse population. METHODS A matched P2RX7 genetic case-control was performed with samples from Asthma Clinical Research Network trial participants enrolled before July 2006, and P2X(7) pore activity was determined in whole blood samples as an ancillary study to two trials completed subsequently. MEASUREMENTS AND MAIN RESULTS A total of 187 exacerbations were studied in 742 subjects, and the change in asthma symptom burden was studied in an additional 110 subjects during a trial of inhaled corticosteroids (ICS) dose optimization. African American carriers of the minor G allele of the rs2230911 loss-of-function single nucleotide polymorphism were more likely to have a history of prednisone use in the previous 12 months, with adjustment for ICS and long-acting β(2)-agonists use (odds ratio, 2.7; 95% confidence interval, 1.2-6.2; P = 0.018). Despite medium-dose ICS, attenuated pore function predicted earlier exacerbations in incompletely controlled patients with moderate asthma (hazard ratio, 3.2; confidence interval, 1.1-9.3; P = 0.033). After establishing control with low-dose ICS in patients with mild asthma, those with attenuated pore function had more asthma symptoms, rescue albuterol use, and FEV(1) reversal (P < 0.001, 0.03, and 0.03, respectively) during the ICS adjustment phase. CONCLUSIONS P2X(7) pore function protects against exacerbations of asthma and loss of control, independent of baseline severity and the maintenance therapy.
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Affiliation(s)
- Loren C Denlinger
- University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA.
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Jones KA, Thomsen C. The role of the innate immune system in psychiatric disorders. Mol Cell Neurosci 2012; 53:52-62. [PMID: 23064447 DOI: 10.1016/j.mcn.2012.10.002] [Citation(s) in RCA: 197] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Revised: 10/03/2012] [Accepted: 10/04/2012] [Indexed: 12/13/2022] Open
Abstract
There is by now substantial clinical evidence for an association between specific mood disorders and altered immune function. More recently, a number of hypotheses have been forwarded to explain how components of the innate immune system can regulate brain function at the cellular and systems levels and how these may underlie the pathology of disorders such as depression, PTSD and bipolar disorder. In this review we draw reference to biochemical, cellular and animal disease models, as well as clinical observations to elucidate the role of the innate immune system in psychiatric disorders. Proinflammatory cytokines, such as IL-1β IL-6 and TNFα, which feature prominently in the immune response to pathogen in the periphery, have unique and specific actions on neurons and circuits within the central nervous system. Effects of these signaling molecules on neurotransmission, memory, and glucocorticoid function, as well as animal behaviors such as social withdrawal and fear conditioning relevant to psychiatric disorders are elucidated. Finally, we highlight future directions for studies, including the use of peripheral biomarkers, relevant for developing new therapeutic approaches for treating psychiatric illnesses. This article is part of Special Issue entitled 'neuroinflammation in neurodegeneration and neurodysfunction'.
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Affiliation(s)
- Kenneth A Jones
- Lundbeck Research USA, Neuroinflammation Drug Biology Unit 215 College Road, Paramus, NJ 07652, USA.
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Manthei DM, Jackson DJ, Evans MD, Gangnon RE, Tisler CJ, Gern JE, Lemanske RF, Denlinger LC. Protection from asthma in a high-risk birth cohort by attenuated P2X(7) function. J Allergy Clin Immunol 2012; 130:496-502. [PMID: 22743305 DOI: 10.1016/j.jaci.2012.05.040] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Revised: 05/10/2012] [Accepted: 05/29/2012] [Indexed: 12/13/2022]
Abstract
BACKGROUND Viral illnesses are important factors in both asthma inception and exacerbations, and allergic sensitization in early life further enhances asthma risk through unclear mechanisms. Cellular damage caused by infection or allergen inhalation increases ATP levels in the airways with subsequent purinergic receptor activation. The purinergic receptor P2X(7) can enhance airway leukocyte recruitment to the airways, and P2X(7) knockout mice display a reduced asthma-like phenotype. OBJECTIVE Based on the P2X(7) knockout mouse, we hypothesized that children with low P2X(7) function would have decreased rates of asthma. METHODS We used a functional assay to determine P2X(7) pore-producing capacity in whole-blood samples in a birth cohort at high risk for asthma development. The P2X(7) assay was validated with known loss-of-function alleles in human subjects. P2X(7) pore status categorization was used to assess asthma and allergy status in the cohort. RESULTS Attenuated P2X(7) function was associated with lower asthma rates at ages 6 and 8 years, and the greatest effects were observed in boys. Children with asthma at age 11 years who had low P2X(7) capacity had less severe disease in the previous year. Attenuated P2X(7) function was also associated with sensitization to fewer aeroallergens. CONCLUSION P2X(7) functional capacity is associated with asthma risk or disease severity, and these relationships appear to be age related.
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Affiliation(s)
- David M Manthei
- Department of Medicine, University of Wisconsin-Madison, Madison, WI 53792, USA
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Hedl M, Abraham C. IRF5 risk polymorphisms contribute to interindividual variance in pattern recognition receptor-mediated cytokine secretion in human monocyte-derived cells. THE JOURNAL OF IMMUNOLOGY 2012; 188:5348-56. [PMID: 22544929 DOI: 10.4049/jimmunol.1103319] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Monocyte-derived cells display highly variable cytokine secretion upon pattern recognition receptor (PRR) stimulation across individuals; such variability likely affects interindividual inflammatory/autoimmune disease susceptibility. To define mechanisms for this heterogeneity, we examined PRR-induced monocyte-derived cell cytokine secretion from a large cohort of healthy individuals. Although cytokine secretion ranged widely among individuals, the magnitude of cytokine induction after individual nucleotide-binding oligomerization domain 2 (Nod2) and TLR2 stimulation (a cohort of 86 individuals) or stimulation of multiple TLRs (a cohort of 77 individuals), either alone or in combination with Nod2, was consistent intraindividually across these stimuli. Nod2 and TLRs signal through IFN regulatory factor 5 (IRF5), and common IRF5 polymorphisms confer risk for autoimmunity. We find that cells from rs2004640 IRF5 risk-associated allele carriers secrete increased cytokines upon individual or synergistic PRR stimulation in a gene dose- and ligand dose-dependent manner in both monocyte-derived dendritic cells and monocyte-derived macrophages. IRF5 expression knockdown in IRF5 risk allele carrier cells significantly decreases PRR-induced cytokines. Moreover, we find that IRF5 knockdown profoundly decreases Nod2-mediated MAPK and NF-κB pathway activation, whereas the PI3K and mammalian target of rapamycin pathways are not impaired. Finally, the IRF5 rs2004640 polymorphism is a major determinant of the variance (r(2) = 0.53) in Nod2-induced cytokine secretion by monocyte-derived cells from different individuals. We therefore show a profound contribution of a single gene to the variance in interindividual PRR-induced cytokines. The hyperresponsiveness of IRF5 disease-associated polymorphisms to a wide spectrum of microbial triggers has broad implications on global immunological responses, host defenses against pathogens, and inflammatory/autoimmune disease susceptibility.
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Affiliation(s)
- Matija Hedl
- Department of Internal Medicine, Yale University, New Haven, CT 06510, USA
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Shi L, Manthei DM, Guadarrama AG, Lenertz LY, Denlinger LC. Rhinovirus-induced IL-1β release from bronchial epithelial cells is independent of functional P2X7. Am J Respir Cell Mol Biol 2012; 47:363-71. [PMID: 22493010 DOI: 10.1165/rcmb.2011-0267oc] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Airway epithelial cell defenses to viral infections are often compromised in disease or injury. Danger molecules, including ATP, are released during infection and contribute to nucleotide receptor-dependent inflammatory responses, largely through P2X(7). Although respiratory epithelium has been shown to express a variety of nucleotide receptors, the functional contribution of P2X(7) to the epithelial cell inflammatory response is unclear. We used human donor bronchial epithelial cells (BECs) and primary brushed epithelium to explore responses upon nucleotide and Toll-like receptor stimulation. P2X(7) messenger RNA and protein were observed in unprimed BECs, whereas inflammatory cytokine stimulation increased both messenger RNA and protein. Functional pore activity characteristic of P2X(7) was observed in BECs, and IL-1β was rapidly released by BECs after Toll-like receptor 3 agonist, polyinosine-polycytidylic acid, priming followed by ATP administration, although no change was observed in IL-18 release. BECs produced more IL-1β after stimulation with polyinosine-polycytidylic acid than LPS, showing a different preferential response than monocytes. In addition, blockade of nucleotide receptors with oxidized ATP significantly increased human rhinovirus (HRV) recovered 24 hours after infection in BECs, whereas 2'-3'-O-(4-benzoylbenzoyl) ATP treatment of brushed epithelial cells and respiratory cell lines nonsignificantly decreased HRV recovery. IL-1β release was detected after HRV infection in both BECs and brushed cells, but BzATP did not significantly increase IL-1β release further. BEC processing of pro-IL-1β to the mature, cleaved, 17-kD form was confirmed by Western blotting. These results support the expression of functional P2X(7) in human lung epithelium, although its role in epithelial pathogen defense is likely independent of IL-1 family cytokine processing.
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Affiliation(s)
- Lei Shi
- Division of Allergy, Pulmonary & Critical Care Medicine, University of Wisconsin School of Medicine & Public Health, 600 Highland Avenue, CSC Box 9988, Madison, WI 53792, USA
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18
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Pelegrín P. Many ways to dilate the P2X7 receptor pore. Br J Pharmacol 2011; 163:908-11. [PMID: 21410461 PMCID: PMC3130938 DOI: 10.1111/j.1476-5381.2011.01325.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2011] [Revised: 02/08/2011] [Accepted: 02/09/2011] [Indexed: 11/26/2022] Open
Abstract
The P2X7 receptor is associated with two different membrane permeabilities: a small cation conductance which opens within milliseconds, followed by the appearance of a second channel carrying higher molecular weight compounds (including organic dyes) after prolonged agonist stimulation. This activation profile has also been found in cells expressing P2X2 and P2X4 receptors; however, the P2X7 receptor-dependent pathway has the unique ability to activate pro-inflammatory signalling in macrophages. In this issue of the BJP, Marques-da-Silva et al. demonstrate that colchicine is a potent inhibitor of both P2X7 and P2X2 receptor-dependent dye uptake, without affecting the ion channels. Colchicine also blocked the pro-inflammatory signalling downstream of P2X7 receptor activation, both in vitro and in vivo. This report suggests that the dye uptake associated with activation of P2X7 receptors is distinct from the P2X7 receptor ion channel and could be a therapeutic target for the treatment of chronic inflammation.
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Affiliation(s)
- Pablo Pelegrín
- Inflammation and Experimental Surgery Unit, University Hospital, Murcia, Spain.
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Geistlinger J, Du W, Groll J, Liu F, Hoegel J, Foehr KJ, Pasquarelli A, Schneider EM. P2RX7 genotype association in severe sepsis identified by a novel Multi-Individual Array for rapid screening and replication of risk SNPs. Clin Chim Acta 2011; 413:39-47. [PMID: 21640086 DOI: 10.1016/j.cca.2011.05.023] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2010] [Revised: 05/17/2011] [Accepted: 05/17/2011] [Indexed: 01/22/2023]
Abstract
BACKGROUND Functional single nucleotide polymorphisms (SNPs) are relevant to individual therapeutic approaches and may play a role in disease susceptibility. Genome-wide scans, which are now widely applied to detect disease-associated SNPs, provide only limited evidence about SNP associations. Their usefulness as disease markers requires appropriate phenotype analysis and retesting of the gene providing SNP information. Larger data sets of thousands of samples are necessary to confirm the suggested SNPs. METHODS We applied a newly established microarray-based technology that significantly accelerates and simplifies such studies. A tailor-made microarray surface chemistry, sample/probe immobilization and a primer extension reaction are central to the multi-individual array (MIA) platform, which simultaneously identifies the same variable nucleotide in thousands of samples. The set of SNPs to be typed for is highly flexible and can be adapted to the demands of defined clinical questions. RESULTS A MIA-SNP analysis of functional SNPs in the P2RX7 calcium channel is presented. One risk genotype has been verified by functional analysis using patch clamping. Two clinically relevant genotypes composed of 5 functional SNPs in the P2RX7 gene have been identified in patients with severe sepsis and septic shock, whereas no significant association has been found in patient suffering from hemophagocytic syndromes. CONCLUSIONS These results support a functional SNP genotyping of the P2RX7 gene in patients at risk of severe sepsis following surgical trauma.
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Affiliation(s)
- J Geistlinger
- Array-On GmbH, Am Schwabeplan 1b, 06466 Gatersleben, Germany
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20
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Lenertz LY, Gavala ML, Zhu Y, Bertics PJ. Transcriptional control mechanisms associated with the nucleotide receptor P2X7, a critical regulator of immunologic, osteogenic, and neurologic functions. Immunol Res 2011; 50:22-38. [PMID: 21298493 PMCID: PMC3203638 DOI: 10.1007/s12026-011-8203-4] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The nucleotide receptor P2X(7) is an attractive therapeutic target and potential biomarker for multiple inflammatory and neurologic disorders, and it is expressed in several immune, osteogenic, and neurologic cell types. Aside from its role in the nervous system, it is activated by ATP released at sites of tissue damage, inflammation, and infection. Ligand binding to P2X(7) stimulates many cell responses, including calcium fluxes, MAPK activation, inflammatory mediator release, and apoptosis. Much work has centered on P2X(7) action in cell death and mediator processing (e.g., pro-interleukin-1 cleavage by the inflammasome), but the contribution of P2X(7) to transcriptional regulation is less well defined. This review will focus on the growing evidence for the importance of nucleotide-mediated gene expression, highlight several animal models, human genetic, and clinical studies that support P2X(7) as a therapeutic target, and discuss the latest developments in anti-P2X(7) clinical trials.
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Affiliation(s)
- Lisa Y. Lenertz
- Department of Biomolecular Chemistry, School of Medicine and Public Health, The University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Monica L. Gavala
- Department of Biomolecular Chemistry, School of Medicine and Public Health, The University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Yiming Zhu
- Department of Biomolecular Chemistry, School of Medicine and Public Health, The University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Paul J. Bertics
- Department of Biomolecular Chemistry, School of Medicine and Public Health, The University of Wisconsin-Madison, Madison, Wisconsin 53706
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21
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Lenertz LY, Wang Z, Guadarrama A, Hill LM, Gavala ML, Bertics PJ. Mutation of putative N-linked glycosylation sites on the human nucleotide receptor P2X7 reveals a key residue important for receptor function. Biochemistry 2010; 49:4611-9. [PMID: 20450227 PMCID: PMC2895974 DOI: 10.1021/bi902083n] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The nucleotide receptor P2X(7) is an immunomodulatory cation channel and a potential therapeutic target. P2X(7) is expressed in immune cells such as monocytes and macrophages and is activated by extracellular ATP following tissue injury or infection. Ligand binding to P2X(7) can stimulate ERK1/2, the transcription factor CREB, enzymes linked to the production of reactive oxygen species and interleukin-1 isoforms, and the formation of a nonspecific pore. However, little is known about the biochemistry of P2X(7), including whether the receptor is N-linked glycosylated and if this modification affects receptor function. Here we provide evidence that P2X(7) is sensitive to the glycosidases EndoH and PNGase F and that the human receptor appears glycosylated at N187, N202, N213, N241, and N284. Mutation of N187 results in weakened P2X(7) agonist-induced phosphorylation of ERK1/2, CREB, and p90 ribosomal S6 kinase, as well as a decreased level of pore formation. In further support of a role for glycosylation in receptor function, treatment of RAW 264.7 macrophages with the N-linked glycosylation synthesis inhibitor tunicamycin attenuates P2X(7) agonist-induced, but not phorbol ester-induced, ERK1/2 phosphorylation. Interestingly, residue N187 belongs to an N-linked glycosylation consensus sequence found in six of the seven P2X family members, suggesting this site is fundamentally important to P2X receptor function. To address the mechanism whereby N187 mutation attenuates receptor activity, we developed a live cell proteinase K digestion assay that demonstrated altered cell surface expression of P2X(7) N187A. This is the first report to map human P2X(7) glycosylation sites and reveal residue N187 is critical for receptor trafficking and function.
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Affiliation(s)
- Lisa Y. Lenertz
- Department of Biomolecular Chemistry, The University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Ziyi Wang
- Department of Biomolecular Chemistry, The University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Arturo Guadarrama
- Department of Biomolecular Chemistry, The University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Lindsay M. Hill
- Department of Biomolecular Chemistry, The University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Monica L. Gavala
- Department of Biomolecular Chemistry, The University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Paul J. Bertics
- Department of Biomolecular Chemistry, The University of Wisconsin-Madison, Madison, Wisconsin 53706
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Roger S, Gillet L, Baroja-Mazo A, Surprenant A, Pelegrin P. C-terminal calmodulin-binding motif differentially controls human and rat P2X7 receptor current facilitation. J Biol Chem 2010; 285:17514-24. [PMID: 20378545 DOI: 10.1074/jbc.m109.053082] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
P2X(7) receptors (P2X(7)R) are ATP-gated calcium-permeable cationic channels structurally unique among the P2X family by their much longer intracellular C-terminal tail. P2X(7)Rs show several unusual biophysical properties, in particular marked facilitation of currents and leftward shift in agonist affinity in response to repeated or prolonged agonist applications. We previously found the facilitation at rat P2X(7)R resulted from a Ca(2+)-calmodulin-dependent process and a distinct calcium-independent process. However, P2X(7)Rs show striking species differences; thus, this study compared the properties of ATP-evoked facilitation of currents in HEK293 cells transiently expressing the human or rat P2X(7)R as well as rat/human, human/rat chimeric, and mutated P2X(7)Rs. Facilitation at the human P2X(7)R was 5-fold slower than at the rat P2X(7)R. Facilitation did not resulting from an increase of receptor addressing the plasma membrane. We found the human P2X(7)R shows only calcium-independent facilitation with no evidence for calmodulin-dependent processes, nor does it contain the novel 1-5-16 calmodulin binding domain present in the C terminus of rat P2X(7)R. Replacement of three critical residues of this binding domain from the rat into the human P2X(7)R (T541I, C552S, and G559V) reconstituted the Ca(2+)-calmodulin-dependent facilitation, leaving the calcium-independent facilitation unaltered. The leftward shift in the ATP concentration-response curve with repeated agonist applications appears to be a property of the calcium-independent facilitation process because it was not altered in any of the chimeric or mutated P2X(7)Rs. The absence of Ca(2+)-dependent facilitation at the human P2X(7)R may represent a protective adaptation of the innate immune response in which P2X(7)R plays significant roles.
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Affiliation(s)
- Sébastien Roger
- Inserm U921, Université François Rabelais de Tours, 10 Boulevard Tonnellé, 37032 Tours, France.
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Single nucleotide polymorphisms that were identified in affective mood disorders affect ATP-activated P2X7 receptor functions. J Psychiatr Res 2010; 44:347-55. [PMID: 19931869 DOI: 10.1016/j.jpsychires.2009.10.005] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Revised: 10/09/2009] [Accepted: 10/12/2009] [Indexed: 01/08/2023]
Abstract
Genetic linkage studies have previously identified many single non-synonymous nucleotide polymorphisms (SNPs) in the human P2RX7 gene in individuals with affective mood disorders. The P2RX7 gene encodes the P2X(7) receptor (P2X(7)R) that operates as an ATP-activated Ca(2+)-permeable cationic channel and induces formation of a large pore, the two functional properties that are critical for the physiological and pathological roles of the receptor. The current knowledge regarding the effects of SNPs on the P2X(7)R functional properties, which is indispensable to help elucidate the disease mechanism, is limited. In this study, we introduced by site-directed mutagenesis twelve SNP mutations in the human P2X(7) receptor that were previously identified in or associated with affective mood disorders, expressed the resultant mutants in human embryonic kidney cells, and characterized their functional properties by electrophysiology. All mutations except Q460R gave rise to profound effects on the P2X(7)R function. G150R, E186K and I568N conferred complete loss of function. V76A, R117W, L191P, T357S and E496A resulted in strong impairment of, whereas H155Y and A348T caused significant increase in, both ATP-activated ion channel function and pore formation. Q521H reduced the receptor's sensitivity to extracellular Ca(2+) inhibition. An atomic structure model of the human P2X(7)R, based on the crystal structure of the zebrafish P2X(4) receptor, suggests that the SNP mutational effects may result from changes in subunit interaction, agonist binding and/or channel gating. These results provide essential knowledge for a better understanding of the relationships between human P2RX7 SNPs and associated pathologies as well as the receptor structure-function relationships.
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Skaper SD, Debetto P, Giusti P. The P2X7 purinergic receptor: from physiology to neurological disorders. FASEB J 2009; 24:337-45. [PMID: 19812374 DOI: 10.1096/fj.09-138883] [Citation(s) in RCA: 268] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Purine nucleotides are well established as extracellular signaling molecules. P2X receptors are ATP-gated cation channels that mediate fast excitatory transmission in diverse regions of the brain and spinal cord. Several P2X receptor subtypes, including P2X(7), have the unusual property of changing their ion selectivity during prolonged exposure to ATP, which results in progressive dilation of the channel pore and the development of permeability to molecules as large as 900 Da. The P2X(7) receptor was originally described in cells of hematopoietic origin, including macrophages, microglia, and certain lymphocytes, and mediates the influx of Ca(2+) and Na(+) ions, as well as the release of proinflammatory cytokines. P2X(7) receptors may affect neuronal cell death through their ability to regulate the processing and release of interleukin-1beta, a key mediator in neurodegeneration, chronic inflammation, and chronic pain. Activation of P2X(7) receptors provides an inflammatory stimulus, and P2X(7) receptor-deficient mice have substantially attenuated inflammatory responses, including models of neuropathic and chronic inflammatory pain. Moreover, P2X(7) receptor activity, by regulating the release of proinflammatory cytokines, may be involved in the pathophysiology of depression. The P2X(7) receptor may thus represent a critical communication link between the nervous and immune systems, while providing a target for therapeutic exploitation. This review discusses the current biology and cellular signaling pathways of P2X(7) receptor function, as well as insights into the role for this receptor in neurological/psychiatric diseases, outstanding questions, and the therapeutic potential of P2X(7) receptor antagonism.
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Affiliation(s)
- Stephen D Skaper
- Department of Pharmacology and Anesthesiology, University of Padova, Largo "E. Meneghetti" 2, 35131 Padova, Italy.
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P2X(7) Receptors in Neurological and Cardiovascular Disorders. Cardiovasc Psychiatry Neurol 2009; 2009:861324. [PMID: 20029634 PMCID: PMC2794459 DOI: 10.1155/2009/861324] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Revised: 04/26/2009] [Accepted: 04/27/2009] [Indexed: 01/22/2023] Open
Abstract
P2X receptors are ATP-gated cation channels that mediate fast excitatory transmission in diverse regions of the brain and spinal cord. Several P2X receptor subtypes, including P2X(7), have the unusual property of changing their ion selectivity during prolonged exposure to ATP, which results in a channel pore permeable to molecules as large as 900 daltons. The P2X(7) receptor was originally described in cells of hematopoietic origin, and mediates the influx of Ca(2+) and Na(+) and Ca(2+) and Na(+) ions as well as the release of proinflammatory cytokines. P2X(7) receptors may affect neuronal cell death through their ability to regulate the processing and release of interleukin-1beta, a key mediator in neurodegeneration, chronic inflammation, and chronic pain. Activation of P2X(7), a key mediator in neurodegeneration, chronic inflammation, and chronic pain. Activation of P2X(7) receptors provides an inflammatory stimulus, and P2X(7) receptor-deficient mice have substantially attenuated inflammatory responses, including models of neuropathic and chronic inflammatory pain. Moreover, P2X(7) receptor activity, by regulating the release of proinflammatory cytokines, may be involved in the pathophysiology of depression. Apoptotic cell death occurs in a number of vascular diseases, including atherosclerosis, restenosis, and hypertension, and may be linked to the release of ATP from endothelial cells, P2X(7) receptor activation, proinflammatory cytokine production, and endothelial cell apoptosis. In this context, the P2X(7) receptor may be viewed as a gateway of communication between the nervous, immune, and cardiovascular systems.
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Cell signaling via the P2X(7) nucleotide receptor: linkage to ROS production, gene transcription, and receptor trafficking. Purinergic Signal 2009; 5:175-87. [PMID: 19263245 DOI: 10.1007/s11302-009-9133-7] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2008] [Accepted: 09/16/2008] [Indexed: 12/20/2022] Open
Abstract
Extracellular nucleotides can act as important intercellular signals in diverse biological processes, including the enhanced production of factors that are key to immune response regulation. One receptor that binds extracellular adenosine triphosphate released at sites of infection and injury is P2X(7), which is an ionotrophic receptor that can also lead to the formation of a non-specific pore, activate multiple mitogen-activated protein kinases (MAPKs), and stimulate the production of immune mediators including interleukin family members and reactive oxygen species (ROS). In the present report, we have investigated the signaling mechanisms by which P2X(7) promotes monocytic cell mediator production and induces transcription factor expression/phosphorylation, as well as how receptor-associated pore activity is regulated by intracellular trafficking. We report that P2X(7) stimulates ROS production in macrophages through the MAPKs ERK1/2 and the nicotinamide adenine dinucleotide phosphate oxidase complex, activates several transcription factors including cyclic-AMP response element-binding protein and components of the activating protein-1 complex, and contains specific sequences within its intracellular C-terminus that appear critical for its activity. Altogether, these data further implicate P2X(7) activation and signaling as a fundamental modulator of macrophage immune responses.
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Denlinger LC, Shi L, Guadarrama A, Schell K, Green D, Morrin A, Hogan K, Sorkness RL, Busse WW, Gern JE. Attenuated P2X7 pore function as a risk factor for virus-induced loss of asthma control. Am J Respir Crit Care Med 2008; 179:265-70. [PMID: 19201928 DOI: 10.1164/rccm.200802-293oc] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
RATIONALE Upper respiratory tract infection is a guideline accepted risk domain for the loss of asthma control. The ionotrophic nucleotide receptor P2X(7) regulates compartmentalized acute inflammation and the immune response to airway pathogens. OBJECTIVES We hypothesized that variability in P2X(7) function contributes to neutrophilic airway inflammation during a cold and thereby is linked to acute asthma. METHODS Research volunteers with asthma were enrolled at the onset of a naturally occurring cold and monitored through convalescence, assessing symptoms, lung function, and airway inflammation. P2X(7) pore activity in whole blood samples was measured using a genomically validated flow cytometric assay. MEASUREMENTS AND MAIN RESULTS Thirty-five participants with mild to moderate allergic asthma were enrolled and 31 completed all visits. P2X(7) pore function correlated with the change in nasal lavage neutrophil counts during the cold (R(s) = 0.514, P = 0.004) and was inversely related to the change in asthma symptoms (R(s) = -0.486, P = 0.009). The change in peak expiratory flow recordings, precold use of inhaled corticosteroids, and P2X(7) pore function were multivariate predictors of asthma symptoms (P = 0.001, < 0.001 and = 0.003 respectively). Attenuated P2X(7) activity was associated with the risk of losing asthma control (crude odds ratio, 11.0; 95% confidence interval, 1.1-106.4) even after adjustment for inhaled corticosteroids and rhinovirus (odds ratio, 15.0). CONCLUSIONS A whole blood P2X(7) pore assay robustly identifies participants with loss-of-function genotypes. Using this assay as an epidemiologic tool, attenuated P2X(7) pore activity may be a novel biomarker of virus-induced loss of asthma control.
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Affiliation(s)
- Loren C Denlinger
- Section of Allergy, Pulmonary, and Critical Care, Department of Medicine, University of Wisconsin School of Medicine and Public Health, 600 Highland Avenue, P.O. Box 9988, Madison, WI 53792, USA.
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Korpi-Steiner NL, Sheerar D, Puffer EB, Urben C, Boyd J, Guadarrama A, Schell K, Denlinger LC. Standardized method to minimize variability in a functional P2X(7) flow cytometric assay for a multi-center clinical trial. CYTOMETRY PART B-CLINICAL CYTOMETRY 2008; 74:319-29. [PMID: 18431793 DOI: 10.1002/cyto.b.20421] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
BACKGROUND Flow cytometric analysis of human P2X(7) pore activity segregates variant from common P2RX7 genotypes and may serve as a biomarker for cancer, pain, inflammation, and immune responses to infection. Standardization is needed to accommodate variable sample age and instrumentation differences in a multicenter clinical trial. METHODS CD14-PE-stained whole blood samples were treated with YO-PRO-1 combined with a P2X(7) agonist (BzATP) or control, followed by the addition of PI after closure of the P2X(7) pore. Recalled instrument settings from previous publications were used to adapt a standardized fluorescent particle-adjusted set-up method. Experiments were performed to compare the two methods while evaluating components of systematic variability and facilitating reliable processing of samples with varied ages. RESULTS The median YO-PRO-1 fluorescence of BzATP-treated samples had less variability when collected by the bead-adjusted method and was less influenced by the compensation strategy used. The average day-to-day coefficient of variance for assessments of P2X(7) pore activity by this method was 0.11 +/- 0.04, and the exclusion of nonviable cells was found to accommodate samples aged up to 4 days after phlebotomy. The bead-adjusted set-up method produced measurements differing by only 2.0% +/- 1.5% on two analog cytometers, and within similar decades when comparing analog to digital instruments. CONCLUSIONS These results provide a standardized method for quantitative flow cytometric analysis of P2X(7) receptor phenotypes in blood monocytes with minimal intralaboratory variation and potential for interlaboratory comparisons that can greatly facilitate multicenter functional genomic clinical studies.
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Affiliation(s)
- N L Korpi-Steiner
- Department of Medicine-Allergy, Pulmonary & Critical Care, University of Wisconsin-Madison, Madison, WI 53792, USA
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Beldi G, Wu Y, Banz Y, Nowak M, Miller L, Enjyoji K, Haschemi A, Yegutkin GG, Candinas D, Exley M, Robson SC. Natural killer T cell dysfunction in CD39-null mice protects against concanavalin A-induced hepatitis. Hepatology 2008; 48:841-52. [PMID: 18752325 PMCID: PMC2929828 DOI: 10.1002/hep.22401] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
UNLABELLED Concanavalin A (Con A)-induced injury is an established natural killer T (NKT) cell-mediated model of inflammation that has been used in studies of immune liver disease. Extracellular nucleotides, such as adenosine triphosphate, are released by Con A-stimulated cells and bind to specific purinergic type 2 receptors to modulate immune activation responses. Levels of extracellular nucleotides are in turn closely regulated by ectonucleotidases, such as CD39/NTPDase1. Effects of extracellular nucleotides and CD39 on NKT cell activation and upon hepatic inflammation have been largely unexplored to date. Here, we show that NKT cells express both CD39 and CD73/ecto-5'-nucleotidase and can therefore generate adenosine from extracellular nucleotides, whereas natural killer cells do not express CD73. In vivo, mice null for CD39 are protected from Con A-induced liver injury and show substantively lower serum levels of interleukin-4 and interferon-gamma when compared with matched wild-type mice. Numbers of hepatic NKT cells are significantly decreased in CD39 null mice after Con A administration. Hepatic NKT cells express most P2X and P2Y receptors; exceptions include P2X3 and P2Y11. Heightened levels of apoptosis of CD39 null NKT cells in vivo and in vitro appear to be driven by unimpeded activation of the P2X7 receptor. CONCLUSION CD39 and CD73 are novel phenotypic markers of NKT cells. In turn, CD39 expression [corrected] modulates nucleotide-mediated cytokine production by, and limits apoptosis of, hepatic NKT cells. Deletion of CD39 is protective in [corrected] Con A-induced hepatitis. This study illustrates a [corrected] role for purinergic signaling in NKT-mediated mechanisms that result in liver immune injury.
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Affiliation(s)
- Guido Beldi
- Liver and Transplantation Centers, Department of Medicine, Harvard Medical School, Boston, MA,Department of Visceral and Transplant Surgery, Inselspital, University Hospital, Bern, Switzerland
| | - Yan Wu
- Liver and Transplantation Centers, Department of Medicine, Harvard Medical School, Boston, MA
| | - Yara Banz
- Liver and Transplantation Centers, Department of Medicine, Harvard Medical School, Boston, MA
| | - Michael Nowak
- Division of Hematology and Oncology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
| | - Lindsay Miller
- Liver and Transplantation Centers, Department of Medicine, Harvard Medical School, Boston, MA
| | - Keiichi Enjyoji
- Liver and Transplantation Centers, Department of Medicine, Harvard Medical School, Boston, MA
| | - Arvand Haschemi
- Liver and Transplantation Centers, Department of Medicine, Harvard Medical School, Boston, MA
| | - Gennady G. Yegutkin
- MediCity Research Laboratory, University of Turku, National Public Health Institute, Turku, Finland
| | - Daniel Candinas
- Department of Visceral and Transplant Surgery, Inselspital, University Hospital, Bern, Switzerland
| | - Mark Exley
- Division of Hematology and Oncology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA
| | - Simon C. Robson
- Liver and Transplantation Centers, Department of Medicine, Harvard Medical School, Boston, MA
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Abstract
Forty-five years ago the surprising discovery was made, in a Melbourne University laboratory, that peripheral synapses exist that release neither noradrenaline nor acetylcholine. The same laboratory went on to show that one of these then novel transmitters is adenosine 5'-triphosphate (ATP), for which a class of receptors has been dubbed P2X7. Recent linkage studies have shown that the P2X7 gene is associated with major depression and bipolar disorder. This speculative paper considers possible mechanisms that could link polymorphisms in the P2X7 gene with the functioning of neural networks, especially in the hippocampus. A selective review of the neurobiological literature on the location and function of the P2X7 receptor at synapses and on astrocytes as well as microglial cells was performed in the context of determining viable hypotheses as to the function of these receptors during synaptic transmission in the neural networks of the hippocampus. It is suggested that P2X7 receptors participate in a regenerative loop at central glutamatergic synapses. In this loop glutamate-evoked release of ATP from both astrocytes and microglia cells, as well as ATP derived from an autocatalytic release from astrocytes, provides purines that can act on presynaptic P2X7 purinergic receptors. This increases glutamate release to further the amount of ATP at the synapse, leading to a new functional state of the neural network in which the synapse participates. This synaptic ATP can also act on microglia P2X7 receptors to release the cytokine tumour necrosis factor-alpha (TNF-alpha), as can glutamate, with this TNF-alpha acting on the post-synaptic neuronal membrane to increase glutamate alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors there. As synaptic ATP and glutamate are maintained by the regenerative loop they provide a sustained release of TNF-alpha, and therefore of AMPA receptor enhancement, increasing synaptic efficacy, and so contributing to the new functional state of the neural network. Infections can change this state by activating toll-like (TOL) receptors on the microglia concomitantly with their P2X7 receptor activation by the regenerative loop, thereby releasing the cytokine interleukin-1beta, which decreases the AMPA receptors in the neural membrane, so decreasing synaptic efficacy and changing the functional state of the neural network in which the synapse resides. Polymorphisms in the P2X7 gene that modify operation of the regenerative loop or the release of cytokines, as can infections, change the functional state of neural networks, which may then lead to vulnerability to mood disorders.
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Affiliation(s)
- Maxwell R Bennett
- Brain and Mind Research Institute, University of Sydney, Camperdown, Australia.
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31
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Lister MF, Sharkey J, Sawatzky DA, Hodgkiss JP, Davidson DJ, Rossi AG, Finlayson K. The role of the purinergic P2X7 receptor in inflammation. J Inflamm (Lond) 2007; 4:5. [PMID: 17367517 PMCID: PMC1838907 DOI: 10.1186/1476-9255-4-5] [Citation(s) in RCA: 192] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Accepted: 03/16/2007] [Indexed: 01/06/2023] Open
Abstract
The inflammatory process, orchestrated against a variety of injurious stimuli, is composed of three inter-related phases; initiation, propagation and resolution. Understanding the interplay between these three phases and harnessing the beneficial properties of inflammation whilst preventing its damaging effects, will undoubtedly lead to the advent of much needed therapies, particularly in chronic disease states. The P2X7 receptor (P2X7R) is increasingly recognised as an important cell surface regulator of several key inflammatory molecules including IL-1beta, IL-18, TNF-alpha and IL-6. Moreover, as P2X7R-dependent cytokine production is driven by activating the inflammasome, antagonists of this receptor are likely to have therapeutic potential as novel anti-inflammatory therapies. The function of the P2X7R in inflammation, immunity and its potential role in disease will be reviewed and discussed.
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Affiliation(s)
- Martin F Lister
- MRC Centre for Inflammation Research, The Queen's Medical Research Institute, The University of Edinburgh, 47 Little France Crescent, Edinburgh, EH16 4TJ, UK
| | - John Sharkey
- Astellas CNS Research in Edinburgh, The Chancellor's Building, The University of Edinburgh, 49 Little France Crescent, EH16 4SB, UK
| | - Deborah A Sawatzky
- MRC Centre for Inflammation Research, The Queen's Medical Research Institute, The University of Edinburgh, 47 Little France Crescent, Edinburgh, EH16 4TJ, UK
| | - Joseph P Hodgkiss
- Astellas CNS Research in Edinburgh, The Chancellor's Building, The University of Edinburgh, 49 Little France Crescent, EH16 4SB, UK
| | - Donald J Davidson
- MRC Centre for Inflammation Research, The Queen's Medical Research Institute, The University of Edinburgh, 47 Little France Crescent, Edinburgh, EH16 4TJ, UK
| | - Adriano G Rossi
- MRC Centre for Inflammation Research, The Queen's Medical Research Institute, The University of Edinburgh, 47 Little France Crescent, Edinburgh, EH16 4TJ, UK
| | - Keith Finlayson
- Astellas CNS Research in Edinburgh, The Chancellor's Building, The University of Edinburgh, 49 Little France Crescent, EH16 4SB, UK
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Hughes JP, Hatcher JP, Chessell IP. The role of P2X₇ in pain and inflammation. Purinergic Signal 2007; 3:163-9. [PMID: 18404430 PMCID: PMC2096758 DOI: 10.1007/s11302-006-9031-1] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2006] [Accepted: 01/31/2006] [Indexed: 12/15/2022] Open
Abstract
The P2X7 purinoceptor is unique amongst the P2X receptor family in that its activation is able to stimulate the release of mature, biologically active interleukin-1β (IL-1β), as well as a variety of other proinflammatory cytokines. Coupled with the predominate localisation of this receptor to immunocytes of haemopoetic origin, this receptor is an obvious candidate to play a major and pivotal role in processes of pain and inflammation. Using genetically modified animals that lack the P2X7 receptor, several investigators have shown that these mice do indeed demonstrate a blunted inflammatory response, and fail to develop pain following both inflammatory and neuropathic insult. These animals also show altered cytokine production in response to inflammatory stimulus, which is far broader than merely modulation of IL-1β release. In this short article, we review the role of the P2X7 receptor in modulating the release of cytokines and other mediators, and discuss the findings made from P2X7 receptor-deficient animals. As well as highlighting outstanding questions regarding this intriguing receptor, we also speculate as to the potential therapeutic benefit of P2X7 receptor modulation.
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Affiliation(s)
- Jane P Hughes
- Neurology & GI CEDD, GlaxoSmithKline, Third Avenue, Harlow, Essex, CM19 5AW, UK
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Künzli BM, Berberat PO, Giese T, Csizmadia E, Kaczmarek E, Baker C, Halaceli I, Büchler MW, Friess H, Robson SC. Upregulation of CD39/NTPDases and P2 receptors in human pancreatic disease. Am J Physiol Gastrointest Liver Physiol 2007; 292:G223-30. [PMID: 16920697 DOI: 10.1152/ajpgi.00259.2006] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Chronic inflammation, fibrosis, atrophy, malignant transformation, and thromboembolic events are hallmarks of chronic pancreatic disease. Extracellular nucleotides have been implicated as inflammatory mediators in many pathological situations. However, there are minimal data detailing expression of ectonucleotidases and type-2 purinergic receptors (P2R) in chronic pancreatitis and pancreatic cancer. We have therefore defined tissue distribution and localization of the CD39 family of ectonucleotidases and associated P2R in human disease. Transcripts of ectonucleotidases (CD39 and CD39L1) together with P2R (P2X7, P2Y2, and P2Y6) are significantly increased in both chronic pancreatitis and pancreatic cancer. CD39 and CD39L1 are preferentially associated with the vasculature and stromal elements in pathological tissues. P2X7 mRNA upregulation was associated with chronic pancreatitis, and heightened protein expression was found to be localized to infiltrating cells. P2Y2 was markedly upregulated in biopsies of pancreatic cancer tissues and expressed by fibroblasts adjacent to tumors. High-tissue mRNA levels of CD39 significantly correlated with better long-term survival after tumor resection in patients with pancreatic cancer. Heightened expression patterns and localization patterns of CD39, P2X7, and P2Y2 infer associations with chronic inflammation and neoplasia of the pancreas. Our data suggest distinct roles for CD39 and P2-purinergic signaling in both tissue remodeling and fibrogenesis with respect to human pancreatic diseases.
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Affiliation(s)
- Beat M Künzli
- Liver and Transplantation Centers, Beth Israel Deaconess Medical Center, Harvard University, Boston, Massachusetts, 02215, USA
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Bours MJL, Swennen ELR, Di Virgilio F, Cronstein BN, Dagnelie PC. Adenosine 5'-triphosphate and adenosine as endogenous signaling molecules in immunity and inflammation. Pharmacol Ther 2006; 112:358-404. [PMID: 16784779 DOI: 10.1016/j.pharmthera.2005.04.013] [Citation(s) in RCA: 766] [Impact Index Per Article: 42.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2005] [Accepted: 04/20/2005] [Indexed: 02/07/2023]
Abstract
Human health is under constant threat of a wide variety of dangers, both self and nonself. The immune system is occupied with protecting the host against such dangers in order to preserve human health. For that purpose, the immune system is equipped with a diverse array of both cellular and non-cellular effectors that are in continuous communication with each other. The naturally occurring nucleotide adenosine 5'-triphosphate (ATP) and its metabolite adenosine (Ado) probably constitute an intrinsic part of this extensive immunological network through purinergic signaling by their cognate receptors, which are widely expressed throughout the body. This review provides a thorough overview of the effects of ATP and Ado on major immune cell types. The overwhelming evidence indicates that ATP and Ado are important endogenous signaling molecules in immunity and inflammation. Although the role of ATP and Ado during the course of inflammatory and immune responses in vivo appears to be extremely complex, we propose that their immunological role is both interdependent and multifaceted, meaning that the nature of their effects may shift from immunostimulatory to immunoregulatory or vice versa depending on extracellular concentrations as well as on expression patterns of purinergic receptors and ecto-enzymes. Purinergic signaling thus contributes to the fine-tuning of inflammatory and immune responses in such a way that the danger to the host is eliminated efficiently with minimal damage to healthy tissues.
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Affiliation(s)
- M J L Bours
- Maastricht University, Department of Epidemiology, Nutrition and Toxicology Research Institute Maastricht, P.O. Box 616, 6200 MD Maastricht, The Netherlands.
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Denlinger LC, Coursin DB, Schell K, Angelini G, Green DN, Guadarrama AG, Halsey J, Prabhu U, Hogan KJ, Bertics PJ. Human P2X7 pore function predicts allele linkage disequilibrium. Clin Chem 2006; 52:995-1004. [PMID: 16613995 DOI: 10.1373/clinchem.2005.065425] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Innate immune response amplification is achieved by leukocyte expression of the purinergic nucleotide receptor P2X7, an extracellular nucleotide-gated pore. Previously, low P2X7 pore activity in whole blood was associated with loss-of-function genotypes in correlation with a decreased ratio of lipopolysaccharide-stimulated tumor necrosis factor-alpha to interleukin-10, of relevance to a variety of infectious and inflammatory disorders. We hypothesized that evaluation of participants with discordance between the P2X7 genotype and pore status would disclose additional alleles, linkage disequilibrium, and novel functional correlates of genotype to phenotype. METHODS Comparison of whole-blood pore results with restriction fragment length polymorphism data for known loss-of-function genotypes from 200 healthy participants optimized the diagnostic threshold for low pore activity by ROC curve analysis. We identified novel alleles and inferred haplotypes by sequencing outlier genomic templates and by linkage analysis. RESULTS With a refined threshold of low activity, a normal pore result had only a 2% probability of association with known loss-of-function variants. By contrast, the positive predictive value of low pore activity was 59% for identifying known alleles. DNA samples from this discordant group contained 28 P2X7 sequence variations. Linkage analysis demonstrated that A1513C, T1729A, and G946A are inherited independently from one another, although these loss-of-function variants are in disequilibrium with other alleles. When we segregated pore activity data according to genotypes, nonsynonymous sequence variations (G474A and A1405G) appeared to exhibit modulatory effects on P2X7 pore activity. CONCLUSIONS Direct analysis of pore activity demonstrates functional interactions between P2X7 alleles. The performance characteristics of the whole-blood pore assay enables correlation of genomic variation with concomitant investigation of functional performance in clinical studies.
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Affiliation(s)
- Loren C Denlinger
- Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA.
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Roberts JA, Vial C, Digby HR, Agboh KC, Wen H, Atterbury-Thomas A, Evans RJ. Molecular properties of P2X receptors. Pflugers Arch 2006; 452:486-500. [PMID: 16607539 DOI: 10.1007/s00424-006-0073-6] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2006] [Accepted: 03/10/2006] [Indexed: 12/23/2022]
Abstract
P2X receptors for adenosine tri-phosphate (ATP) are a distinct family of ligand-gated cation channels with two transmembrane domains, intracellular amino and carboxy termini and a large extracellular ligand binding loop. Seven genes (P2X(1-7)) have been cloned and the channels form as either homo or heterotrimeric channels giving rise to a wide range of phenotypes. This review aims to give an account of recent work on the molecular basis of the properties of P2X receptors. In particular, to consider emerging information on the assembly of P2X receptor subunits, channel regulation and desensitisation, targeting, the molecular basis of drug action and the functional contribution of P2X receptors to physiological processes.
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Affiliation(s)
- Jonathan A Roberts
- Department of Cell Physiology & Pharmacology, Medical Sciences Building, University of Leicester, Leicester, LE1 9HN, UK
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Ferrari D, Pizzirani C, Adinolfi E, Lemoli RM, Curti A, Idzko M, Panther E, Di Virgilio F. The P2X7Receptor: A Key Player in IL-1 Processing and Release. THE JOURNAL OF IMMUNOLOGY 2006; 176:3877-83. [PMID: 16547218 DOI: 10.4049/jimmunol.176.7.3877] [Citation(s) in RCA: 827] [Impact Index Per Article: 45.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Human IL-1 family proteins are key mediators of the host response to infections, injury, and immunologic challenges. The mechanism by which IL-1 activates proinflammatory responses in target cells, and the plasma membrane receptors involved, is fairly well known. This has led to the development of innovative drugs that block IL-1 downstream to its synthesis and secretion. On the contrary, the mechanism of IL-1 and other IL-1 family members (e.g., IL-18) maturation and release is incompletely understood. Accruing evidence points to a plasma membrane receptor for extracellular ATP, the P2X(7) receptor, as a key player in both processes. A deeper understanding of the mechanism by which the P2X(7) receptor triggers IL-1 maturation and exteriorization may suggest novel avenues for the treatment of inflammatory diseases and provide a deeper insight in the fundamental mechanism of protease activation and cellular export of proteins lacking a leader sequence.
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Affiliation(s)
- Davide Ferrari
- Department of Experimental and Diagnostic Medicine, Section of General Pathology, University of Ferrara, Italy.
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38
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Kawamura H, Aswad F, Minagawa M, Govindarajan S, Dennert G. P2X7 receptors regulate NKT cells in autoimmune hepatitis. THE JOURNAL OF IMMUNOLOGY 2006; 176:2152-60. [PMID: 16455971 DOI: 10.4049/jimmunol.176.4.2152] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Adenine nucleotides induce danger signals in T cells via purinergic receptors, raising the question whether they exert similar effects on innate immunity. Here we show that micromolar concentrations of nicotinamide adenine dinucleotide (NAD) induce a rapid increase of annexin V staining in NKT cells in vitro, a response that requires expression of P2X(7)Rs. Consistent with this result, treatment of mice with NAD causes a temporary decrease of NKT cells in the liver and protects from Con A- and alpha-galactosylceramide-induced hepatitis, both of which require functional NKT cells. Resistance to liver injury is associated with decreased cytokine production by NKT cells in NAD-treated mice. In contrast, when NAD is injected into Con A- or alpha-galactosylceramide-primed mice, liver injury is exacerbated and cytokine production by NKT cells is increased. This effect is caused by P2X(7)R-mediated stimulation of activated NKT cells. In agreement, mice lacking P2X(7)Rs on lymphocytes suffer reduced liver injury, and animals lacking ADP-ribosyltransferase, the enzyme that uses NAD to attach ADP-ribosyl groups to cell surfaces, are also resistant to Con A-induced hepatitis. These results prompt the conclusion that engagement of P2X(7)Rs on NKT cells inhibits naive, while stimulating activated cells, resulting in suppression or stimulation of autoimmune hepatitis.
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MESH Headings
- Animals
- Annexin A5/metabolism
- Cells, Cultured
- Cytokines/biosynthesis
- Female
- Hepatitis, Autoimmune/immunology
- Hepatitis, Autoimmune/metabolism
- Hepatitis, Autoimmune/prevention & control
- Killer Cells, Natural/drug effects
- Killer Cells, Natural/immunology
- Killer Cells, Natural/metabolism
- Liver/injuries
- Liver/metabolism
- Liver/pathology
- Lymphocyte Activation
- Macrolides/metabolism
- Macrolides/pharmacology
- Mice
- Mice, Knockout
- NAD/pharmacology
- Receptors, Purinergic P2/deficiency
- Receptors, Purinergic P2/genetics
- Receptors, Purinergic P2/metabolism
- Receptors, Purinergic P2X7
- T-Lymphocytes, Regulatory/drug effects
- T-Lymphocytes, Regulatory/immunology
- T-Lymphocytes, Regulatory/metabolism
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Affiliation(s)
- Hiroki Kawamura
- Departments of Molecular Microbiology and Immunology, University of Southern California Keck School of Medicine, Los Angeles, 90033, USA
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Chen L, Brosnan CF. Exacerbation of Experimental Autoimmune Encephalomyelitis in P2X7R−/−Mice: Evidence for Loss of Apoptotic Activity in Lymphocytes. THE JOURNAL OF IMMUNOLOGY 2006; 176:3115-26. [PMID: 16493071 DOI: 10.4049/jimmunol.176.5.3115] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The purinergic receptor P2X7R is a nucleotide-gated ion channel that has been proposed to function as a major regulator of inflammation. In this study we examined the role of this receptor in regulating inflammation in the CNS by determining the effects of the loss of this receptor (P2X7R-/-) on experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis. We show here that P2X7R-/- mice developed more severe clinical and pathological expression of EAE than wild type (WT) controls and that spleen and lymph node cells from P2X7R-/- mice proliferated more vigorously to Ag in vitro. Bone marrow (BM) radiation chimeras revealed that enhanced susceptibility to EAE was detected in chimeric mice of WT host engrafted with P2X7R-/- BM cells, indicating that the genotype of the BM cells regulated disease susceptibility. Coculture of P2X7R-/- macrophages with WT lymphocytes and vice versa showed that enhanced proliferative activity resided within the P2X7R-/- lymphocyte population and correlated with reduced levels of IFN-gamma and NO and apoptosis of lymphocytes. mRNA and protein for IFN-gamma were also significantly reduced in the CNS of P2X7R-/- mice with EAE. FACS analysis of cells isolated from the CNS showed significantly fewer annexin V/propidium iodide-positive lymphocytes in the CNS of P2X7R-/- mice early in the disease, and TUNEL staining of inflamed CNS tissues supported this result. From these data we conclude that enhanced susceptibility of P2X7R-/- mice to EAE reflects a loss of apoptotic activity in lymphocytes, supporting an important role for this receptor in lymphocyte homeostasis.
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MESH Headings
- ADP Ribose Transferases/biosynthesis
- ADP Ribose Transferases/genetics
- Animals
- Apoptosis/genetics
- Apoptosis/immunology
- Cell Transplantation
- Cells, Cultured
- Coculture Techniques
- Encephalomyelitis, Autoimmune, Experimental/genetics
- Encephalomyelitis, Autoimmune, Experimental/immunology
- Encephalomyelitis, Autoimmune, Experimental/pathology
- Flow Cytometry
- Genetic Predisposition to Disease
- Lymphocyte Subsets/immunology
- Lymphocyte Subsets/metabolism
- Lymphocyte Subsets/pathology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Myelin Proteins
- Myelin-Associated Glycoprotein/physiology
- Myelin-Oligodendrocyte Glycoprotein
- Peptide Fragments/physiology
- Radiation Chimera
- Receptors, Purinergic P2/deficiency
- Receptors, Purinergic P2/genetics
- Receptors, Purinergic P2/physiology
- Receptors, Purinergic P2X7
- Spinal Cord/immunology
- Spinal Cord/pathology
- Spleen/cytology
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Affiliation(s)
- Lanfen Chen
- Department of Pathology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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Shemon AN, Sluyter R, Fernando SL, Clarke AL, Dao-Ung LP, Skarratt KK, Saunders BM, Tan KS, Gu BJ, Fuller SJ, Britton WJ, Petrou S, Wiley JS. A Thr357 to Ser polymorphism in homozygous and compound heterozygous subjects causes absent or reduced P2X7 function and impairs ATP-induced mycobacterial killing by macrophages. J Biol Chem 2005; 281:2079-86. [PMID: 16263709 DOI: 10.1074/jbc.m507816200] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The P2X(7) receptor is a ligand-gated cation channel that is highly expressed on mononuclear leukocytes and that mediates ATP-induced apoptosis and killing of intracellular pathogens. There is a wide variation in P2X(7) receptor function between subjects, explained in part by four loss-of-function polymorphisms (R307Q, E496A, I568N, and a 5'-intronic splice site polymorphism), as well as rare mutations. In this study, we report the allele frequencies of 11 non-synonymous P2X(7) polymorphisms and describe a fifth loss-of-function polymorphism in the gene (1096C --> G), which changes Thr(357) to Ser (T357S) with an allele frequency of 0.08 in the Caucasian population. P2X(7) function was measured by ATP-induced ethidium(+) influx into peripheral blood lymphocytes and monocytes and, when compared with wild-type subjects, was reduced to 10-65% in heterozygotes, 1-18% in homozygotes, and 0-10% in compound heterozygotes carrying T357S and a second loss-of-function polymorphism. Overexpression of the T357S mutant P2X(7) in either HEK-293 cells or Xenopus oocytes gave P2X(7) function of approximately 50% that of wild-type constructs. Differentiation of monocytes to macrophages, which also up-regulates P2X(7), restored P2X(7) function to near normal in cells heterozygous for T357S and to a value 50-65% of wild-type in cells homozygous for T357S or compound heterozygous for T357S/E496A. However, macrophages from subjects that are compound heterozygous for either T357S/R307Q or T357S/stop codon had near-to-absent P2X(7) function. These functional deficits induced by T357S were paralleled by impaired ATP-induced apoptosis and mycobacteria killing in macrophages from these subjects. Lymphocytes, monocytes, and macrophages from subjects homozygous for T357S or compound heterozygous for T357S and a second loss-of-function allele have reduced or absent P2X(7) receptor function.
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Affiliation(s)
- Anne N Shemon
- Department of Medicine, University of Sydney, Level 5, Spurrett Building, Nepean Hospital, Penrith, New South Wales 2750, Australia
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Tuberculosis in the Intensive Care Unit: The North American Perspective. TROPICAL AND PARASITIC INFECTIONS IN THE INTENSIVE CARE UNIT 2005. [PMCID: PMC7121205 DOI: 10.1007/0-387-23380-6_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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