201
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Colgan SP, Campbell EL, Kominsky DJ. Hypoxia and Mucosal Inflammation. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2017; 11:77-100. [PMID: 27193451 DOI: 10.1146/annurev-pathol-012615-044231] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Sites of inflammation are defined by significant changes in metabolic activity. Recent studies have suggested that O2 metabolism and hypoxia play a prominent role in inflammation so-called "inflammatory hypoxia," which results from a combination of recruited inflammatory cells (e.g., neutrophils and monocytes), the local proliferation of multiple cell types, and the activation of multiple O2-consuming enzymes during inflammation. These shifts in energy supply and demand result in localized regions of hypoxia and have revealed the important function off the transcription factor HIF (hypoxia-inducible factor) in the regulation of key target genes that promote inflammatory resolution. Analysis of these pathways has provided multiple opportunities for understanding basic mechanisms of inflammation and has defined new targets for intervention. Here, we review recent work addressing tissue hypoxia and metabolic control of inflammation and immunity.
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Affiliation(s)
- Sean P Colgan
- Department of Medicine, University of Colorado School of Medicine, Aurora, Colorado 80045; .,Mucosal Inflammation Program, University of Colorado School of Medicine, Aurora, Colorado 80045
| | - Eric L Campbell
- Department of Medicine, University of Colorado School of Medicine, Aurora, Colorado 80045; .,Mucosal Inflammation Program, University of Colorado School of Medicine, Aurora, Colorado 80045
| | - Douglas J Kominsky
- Mucosal Inflammation Program, University of Colorado School of Medicine, Aurora, Colorado 80045.,Department of Microbiology and Immunology, Montana State University, Bozeman, Montana 59717
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202
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Abstract
Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis is characterized as inflammation of small-sized to medium-sized blood vessels and encompasses several clinicopathologic entities including granulomatosis with polyangiitis, microscopic polyangiitis, eosinophilic granulomatosis with polyangiitis, and renal-limited ANCA-associated vasculitis. Over the past several decades, significant progress has been made in understanding the pathophysiology of ANCA-associated vasculitis. Although neutrophils contain a multitude of granular proteins, clinically significant autoantibodies are only recognized against myeloperoxidase and proteinase 3, both of which are present in the azurophilic granules. The propensity to develop these antibodies depends on a variety of predisposing factors such as microbial infection, genetic factors, environmental agents, and therapeutic drugs among others. These factors are usually associated with production of proinflammatory cytokines with capacity to prime the neutrophils. As a result a high proportion of neutrophils in circulation may be primed resulting in exposure of cytoplasmic proteins including myeloperoxidase and proteinase 3 on the surface of the neutrophils. Primed neutrophils are activated by interaction with ANCA in circulation. Activated neutrophils attach to and transmigrate through endothelium and accumulate within the vessel wall. These neutrophils degranulate and produce reactive oxygen radicals and ultimately die, causing tissue injury. Endothelial injury results in leakage of serum proteins and coagulation factors causing fibrinoid necrosis. B cells produce ANCAs, as well as neutrophil abnormalities and imbalances in different T-cell subtypes with excess of Th17, which perpetuate the inflammatory process.
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203
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Kalsum S, Braian C, Koeken VACM, Raffetseder J, Lindroth M, van Crevel R, Lerm M. The Cording Phenotype of Mycobacterium tuberculosis Induces the Formation of Extracellular Traps in Human Macrophages. Front Cell Infect Microbiol 2017; 7:278. [PMID: 28695112 PMCID: PMC5483443 DOI: 10.3389/fcimb.2017.00278] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Accepted: 06/06/2017] [Indexed: 12/14/2022] Open
Abstract
The causative agent of tuberculosis, Mycobacterium tuberculosis, shares several characteristics with organisms that produce biofilms during infections. One of these is the ability to form tight bundles also known as cords. However, little is known of the physiological relevance of the cording phenotype. In this study, we investigated whether cord-forming M. tuberculosis induce the formation of macrophage extracellular traps (METs) in human monocyte-derived macrophages. Macrophages have previously been shown to produce extracellular traps in response to various stimuli. We optimized bacterial culturing conditions that favored the formation of the cord-forming phenotype as verified by scanning electron microscopy. Microscopy analysis of METs formation during experimental infection of macrophages with M. tuberculosis revealed that cord-forming M. tuberculosis induced significantly more METs compared to the non-cording phenotype. Deletion of early secreted antigenic target-6 which is an important virulence factor of M. tuberculosis, abrogated the ability of the bacteria to induce METs. The release of extracellular DNA from host cells during infection may represent a defense mechanism against pathogens that are difficult to internalize, including cord-forming M. tuberculosis.
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Affiliation(s)
- Sadaf Kalsum
- Division of Microbiology and Molecular Medicine, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping UniversityLinköping, Sweden
| | - Clara Braian
- Division of Microbiology and Molecular Medicine, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping UniversityLinköping, Sweden
| | - Valerie A C M Koeken
- Division of Microbiology and Molecular Medicine, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping UniversityLinköping, Sweden.,Department of Internal Medicine and Radboud Center for Infectious Diseases, Radboud University Medical CenterNijmegen, Netherlands
| | - Johanna Raffetseder
- Division of Microbiology and Molecular Medicine, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping UniversityLinköping, Sweden
| | - Margaretha Lindroth
- Division of Microbiology and Molecular Medicine, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping UniversityLinköping, Sweden
| | - Reinout van Crevel
- Department of Internal Medicine and Radboud Center for Infectious Diseases, Radboud University Medical CenterNijmegen, Netherlands
| | - Maria Lerm
- Division of Microbiology and Molecular Medicine, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linköping UniversityLinköping, Sweden
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204
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The inflammatory role of phagocyte apoptotic pathways in rheumatic diseases. Nat Rev Rheumatol 2017; 12:543-58. [PMID: 27549026 DOI: 10.1038/nrrheum.2016.132] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Rheumatoid arthritis affects nearly 1% of the world's population and is a debilitating autoimmune condition that can result in joint destruction. During the past decade, inflammatory functions have been described for signalling molecules classically involved in apoptotic and non-apoptotic death pathways, including, but not limited to, Toll-like receptor signalling, inflammasome activation, cytokine production, macrophage polarization and antigen citrullination. In light of these remarkable advances in the understanding of inflammatory mechanisms of the death machinery, this Review provides a snapshot of the available evidence implicating death pathways, especially within the phagocyte populations of the innate immune system, in the perpetuation of rheumatoid arthritis and other rheumatic diseases. Elevated levels of signalling mediators of both extrinsic and intrinsic apoptosis, as well as the autophagy, are observed in the joints of patients with rheumatoid arthritis. Furthermore, risk polymorphisms are present in signalling molecules of the extrinsic apoptotic and autophagy death pathways. Although research into the mechanisms underlying these pathways has made considerable progress, this Review highlights areas where further investigation is particularly needed. This exploration is critical, as new discoveries in this field could lead to the development of novel therapies for rheumatoid arthritis and other rheumatic diseases.
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205
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Khan MA, Farahvash A, Douda DN, Licht JC, Grasemann H, Sweezey N, Palaniyar N. JNK Activation Turns on LPS- and Gram-Negative Bacteria-Induced NADPH Oxidase-Dependent Suicidal NETosis. Sci Rep 2017; 7:3409. [PMID: 28611461 PMCID: PMC5469795 DOI: 10.1038/s41598-017-03257-z] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 04/27/2017] [Indexed: 01/07/2023] Open
Abstract
Neutrophils cast neutrophil extracellular traps (NETs) to ensnare microbial pathogens. Nevertheless, the molecular rheostats that regulate NETosis in response to bacteria are not clearly established. We hypothesized that stress-activated protein kinase or c-Jun N-terminal Kinase (SAPK/JNK) is a molecular switch that turns on NETosis in response to increasing concentrations of lipopolysaccharide (LPS)- and Gram-negative bacteria. Here we show that Escherichia coli LPS (0111:B4; 10–25 μg/ml), but not phorbol myristate acetate (PMA), activates JNK in human neutrophils in a dose-dependent manner. JNK inhibitors SP600125 and TCSJNK6o, and a TLR4 inhibitor TAK242 suppress reactive oxygen species production and NETosis in LPS-, but not PMA-treated neutrophils. Diphenyleneiodonium suppresses LPS-induced NETosis, confirming that endotoxin induces NADPH oxidase-dependent NETosis. Immunoblots, Sytox Green assays, and confocal microscopy of cleaved caspase-3 and nuclear morphology show that JNK inhibition does not induce apoptosis in LPS-stimulated neutrophils. JNK inhibition also suppresses NETosis induced by two typical Gram-negative bacteria, E. coli and Pseudomonas aeruginosa. Therefore, we propose that neutrophils use a TLR4-dependent, JNK-mediated molecular sensing mechanism to initiate NADPH oxidase-dependent suicidal NETosis in response to increasing concentrations of LPS, and Gram-negative bacteria. The LPS-TLR4-JNK activation axis determines the fate of these cells: to be or not to be NETotic neutrophils.
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Affiliation(s)
- Meraj A Khan
- Program in Translational Medicine, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, Toronto, ON, Canada.,Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
| | - Armin Farahvash
- Program in Translational Medicine, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, Toronto, ON, Canada.,Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
| | - David N Douda
- Program in Translational Medicine, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, Toronto, ON, Canada.,Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
| | - Johann-Christoph Licht
- Program in Translational Medicine, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, Toronto, ON, Canada
| | - Hartmut Grasemann
- Program in Translational Medicine, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, Toronto, ON, Canada.,Departments of Paediatrics and Physiology, University of Toronto, Toronto, ON, Canada.,Institute of Medical Sciences, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Neil Sweezey
- Program in Translational Medicine, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, Toronto, ON, Canada.,Departments of Paediatrics and Physiology, University of Toronto, Toronto, ON, Canada
| | - Nades Palaniyar
- Program in Translational Medicine, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, Toronto, ON, Canada. .,Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada. .,Institute of Medical Sciences, Faculty of Medicine, University of Toronto, Toronto, ON, Canada.
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206
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Kenny EF, Herzig A, Krüger R, Muth A, Mondal S, Thompson PR, Brinkmann V, Bernuth HV, Zychlinsky A. Diverse stimuli engage different neutrophil extracellular trap pathways. eLife 2017; 6. [PMID: 28574339 PMCID: PMC5496738 DOI: 10.7554/elife.24437] [Citation(s) in RCA: 482] [Impact Index Per Article: 68.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 06/01/2017] [Indexed: 12/13/2022] Open
Abstract
Neutrophils release neutrophil extracellular traps (NETs) which ensnare pathogens and have pathogenic functions in diverse diseases. We examined the NETosis pathways induced by five stimuli; PMA, the calcium ionophore A23187, nigericin, Candida albicans and Group B Streptococcus. We studied NET production in neutrophils from healthy donors with inhibitors of molecules crucial to PMA-induced NETs including protein kinase C, calcium, reactive oxygen species, the enzymes myeloperoxidase (MPO) and neutrophil elastase. Additionally, neutrophils from chronic granulomatous disease patients, carrying mutations in the NADPH oxidase complex or a MPO-deficient patient were examined. We show that PMA, C. albicans and GBS use a related pathway for NET induction, whereas ionophores require an alternative pathway but that NETs produced by all stimuli are proteolytically active, kill bacteria and composed mainly of chromosomal DNA. Thus, we demonstrate that NETosis occurs through several signalling mechanisms, suggesting that extrusion of NETs is important in host defence. DOI:http://dx.doi.org/10.7554/eLife.24437.001 The immune system protects the body against microorganisms that can cause infections and diseases. Neutrophils are a type of immune cell that patrol the blood in search of germs. Once they encounter potentially harmful microbes, neutrophils eradicate them in different ways. One way to catch the germs is by using ‘neutrophil extracellular traps’, or NETs for short, to confine and kill the invaders. NETs are web-like structures made up of anti-microbial proteins and the neutrophil’s own DNA. The process of making NETs kills the neutrophil, as it eventually explodes to release the NETs. NETs play a key role in disease prevention, but producing too many NETs or producing them at the wrong time or in the wrong place can actually make certain diseases worse. Therefore, it is important to fully understand the signaling pathways and molecules the neutrophils use to make NETs. Kenny et al. exposed neutrophils from healthy people to five different compounds known to cause the cells to make NETs, including some harmful molecules, a fungus and a bacterium. Microscopy was then used to count how many neutrophils made NETs in response to each of the five stimuli. Further experiments showed that neutrophils from patients with an immune system disorder produced fewer NETs when stimulated with some of the compounds, while the other stimuli caused neutrophils to produce the same levels of NETs as healthy individuals. Kenny et al. also revealed that neutrophils use several different ways to produce and release NETs, depending on the stimulus used. Some of the ways required reactive oxygen species, such as hydrogen peroxide and enzymes, while others produced NETs without the need for these molecules. Lastly, Kenny et al. showed that the way the cells die after the NET is released is unique from other pathways that are known to kill cells. Future work will aim to identify a single molecule that can block neutrophils from releasing NETs at the wrong time and place, without affecting the important role NETs play in fighting germs. Such a molecule could be developed into a drug for people with diseases like lupus or rheumatoid arthritis, where the release of NETs makes the disease worse not better. DOI:http://dx.doi.org/10.7554/eLife.24437.002
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Affiliation(s)
- Elaine F Kenny
- Department of Cellular Microbiology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Alf Herzig
- Department of Cellular Microbiology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Renate Krüger
- Department of Paediatric Pneumology and Immunology, Outpatient Clinic for Primary Immunodeficiencies, Charité Medical School, Berlin, Germany.,Sozialpädiatrisches Zentrum, Charité Medical School, Berlin, Germany
| | - Aaron Muth
- Department of Biochemistry and Pharmacology, University of Massachusetts Medical School, Worcester, United States
| | - Santanu Mondal
- Department of Biochemistry and Pharmacology, University of Massachusetts Medical School, Worcester, United States
| | - Paul R Thompson
- Department of Biochemistry and Pharmacology, University of Massachusetts Medical School, Worcester, United States
| | - Volker Brinkmann
- Microscopy Core Facility, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Horst von Bernuth
- Department of Paediatric Pneumology and Immunology, Outpatient Clinic for Primary Immunodeficiencies, Charité Medical School, Berlin, Germany.,Sozialpädiatrisches Zentrum, Charité Medical School, Berlin, Germany.,Labor Berlin, Section for Immunology, Charité-Vivantes GmbH, Berlin, Germany.,Berlin Centre for Regenerative Therapies, Charité Medical School, Berlin, Germany
| | - Arturo Zychlinsky
- Department of Cellular Microbiology, Max Planck Institute for Infection Biology, Berlin, Germany
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207
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Takehara K, Murakami T, Kuwahara-Arai K, Iba T, Nagaoka I, Sakamoto K. Evaluation of the effect of recombinant thrombomodulin on a lipopolysaccharide-induced murine sepsis model. Exp Ther Med 2017; 13:2969-2974. [PMID: 28587368 PMCID: PMC5450552 DOI: 10.3892/etm.2017.4308] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 02/01/2017] [Indexed: 12/29/2022] Open
Abstract
To evaluate the effect of recombinant human thrombomodulin (rTM) on sepsis, the levels of nucleosome as well as high-mobility group box 1 (HMGB1) and cytokines in sera and peritoneal fluids were measured in a mouse model of lipopolysaccharide (LPS)-induced sepsis after administration of rTM. C57BL/6 mice were intraperitoneally injected with LPS (15 mg/kg; Escherichia coli O111:B4) with or without the intravenous administration of rTM (3 mg/kg; 30 min prior to or 2 h after LPS injection). The survival rates were evaluated and levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6, monocyte chemoattractant protein (MCP)-1, HMGB1 and nucleosome in sera and peritoneal fluids were analyzed by ELISA. Administration of rTM prior to or after LPS improved the survival rate of septic mice. In addition, rTM administered prior to or after LPS suppressed the level of pro-inflammatory cytokine TNF-α in sera at 1-3 h after LPS injection, whereas only the administration of rTM after LPS suppressed the levels of HMGB1 and nucleosome (late-phase mediators of sepsis) (9-12 h) in sera after the LPS injection. Furthermore, administration of rTM prior to or after LPS suppressed the level of TNF-α in the peritoneal fluids at 1-3 h after LPS injection, whereas only the administration of rTM after LPS suppressed the levels of IL-6 and MCP-1 in the peritoneal fluids at 6-9 h after LPS injection. These observations indicated that administration of rTM significantly improves the survival rate and suppresses the increased levels of TNF-α, IL-6, MCP-1, HMGB1 and nucleosome in the LPS-induced septic shock model. Thus, rTM may exert a protective action on sepsis and reduce mortality, possibly by reducing not only the levels of cytokines and chemokine but also the levels of late-phase mediators of sepsis.
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Affiliation(s)
- Kazuhiro Takehara
- Department of Coloproctological Surgery, Graduate School of Medicine, Juntendo University, Tokyo 113-8421, Japan
| | - Taisuke Murakami
- Department of Host Defense and Biochemical Research, Graduate School of Medicine, Juntendo University, Tokyo 113-8421, Japan
| | - Kyoko Kuwahara-Arai
- Department of Bacteriology, Graduate School of Medicine, Juntendo University, Tokyo 113-8421, Japan
| | - Toshiaki Iba
- Department of Emergency and Disaster Medicine, Graduate School of Medicine, Juntendo University, Tokyo 113-8421, Japan
| | - Isao Nagaoka
- Department of Host Defense and Biochemical Research, Graduate School of Medicine, Juntendo University, Tokyo 113-8421, Japan
| | - Kazuhiro Sakamoto
- Department of Coloproctological Surgery, Graduate School of Medicine, Juntendo University, Tokyo 113-8421, Japan
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208
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Bierschenk D, Boucher D, Schroder K. Salmonella- induced inflammasome activation in humans. Mol Immunol 2017; 86:38-43. [DOI: 10.1016/j.molimm.2016.11.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Revised: 11/01/2016] [Accepted: 11/17/2016] [Indexed: 12/21/2022]
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209
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Angiotensin-converting enzyme enhances the oxidative response and bactericidal activity of neutrophils. Blood 2017; 130:328-339. [PMID: 28515091 DOI: 10.1182/blood-2016-11-752006] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 05/15/2017] [Indexed: 01/04/2023] Open
Abstract
Angiotensin-converting enzyme (ACE) inhibitors are widely used to reduce blood pressure. Here, we examined if an ACE is important for the antibacterial effectiveness of neutrophils. ACE knockout mice or mice treated with an ACE inhibitor were more susceptible to bacterial infection by methicillin-resistant Staphylococcus aureus (MRSA). In contrast, mice overexpressing ACE in neutrophils (NeuACE mice) have increased resistance to MRSA and better in vitro killing of MRSA, Pseudomonas aeruginosa, and Klebsiella pneumoniae ACE overexpression increased neutrophil production of reactive oxygen species (ROS) following MRSA challenge, an effect independent of the angiotensin II AT1 receptor. Specifically, as compared with wild-type (WT) mice, there was a marked increase of superoxide generation (>twofold, P < .0005) in NeuACE neutrophils following infection, whereas ACE knockout neutrophils decreased superoxide production. Analysis of membrane p47-phox and p67-phox indicates that ACE increases reduced NAD phosphate oxidase activity but does not increase expression of these subunits. Increased ROS generation mediates the enhanced bacterial resistance of NeuACE mice because the enhanced resistance is lost with DPI (an inhibitor of ROS production by flavoenzymes) inhibition. NeuACE granulocytes also have increased neutrophil extracellular trap formation and interleukin-1β release in response to MRSA. In a mouse model of chemotherapy-induced neutrophil depletion, transfusion of ACE-overexpressing neutrophils was superior to WT neutrophils in treating MRSA infection. These data indicate a previously unknown function of ACE in neutrophil antibacterial defenses and suggest caution in the treatment of certain individuals with ACE inhibitors. ACE overexpression in neutrophils may be useful in boosting the immune response to antibiotic-resistant bacterial infection.
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210
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Xu F, Zhang C, Zou Z, Fan EKY, Chen L, Li Y, Billiar TR, Wilson MA, Shi X, Fan J. Aging-related Atg5 defect impairs neutrophil extracellular traps formation. Immunology 2017; 151:417-432. [PMID: 28375544 DOI: 10.1111/imm.12740] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 03/20/2017] [Accepted: 03/28/2017] [Indexed: 12/16/2022] Open
Abstract
Formation of neutrophil extracellular traps (NETs) is an important function of the innate immune system against infections. It has been proven that aging dysregulates immunity and impairs neutrophil function. However, the influence of aging on the ability to produce NETs has yet to be fully addressed. In this study, we tested the hypothesis that a lower level of autophagy in neutrophils from aged mice was responsible for the decrease in NET formation. We demonstrated that a broad range of Toll-like receptor 2 (TLR2) ligands could efficiently induce reactive oxygen species (ROS) -dependent NET release in young mice, but not in aged ones. We further explored that the difference between young and aged mice in TLR2 ligand-induced NETosis is the result of an Atg5 defect and subsequent impaired autophagy. Furthermore, we found that lower autophagy capacity led to not only reduced NET formation, but also increased apoptosis. Our results suggest an important role of Atg5 and autophagy in maintaining the function of NETs formation in response to infection and in regulating neutrophil death. Targeting autophagy-promoted NETs may present a therapeutic strategy to improve infection defence in an aged population.
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Affiliation(s)
- Fengying Xu
- Department of Anaesthesiology, Changzheng Hospital, Second Military Medical University, Shanghai, China.,Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Chengmi Zhang
- Department of Anaesthesiology, Shanghai Xinghua Hospital, Jiaotong University School of Medicine, Shanghai, China
| | - Zui Zou
- Department of Anaesthesiology, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Erica K Y Fan
- Department of Biological Sciences, University of Pittsburgh School of Arts and Science, Pittsburgh, PA, USA
| | - Linsong Chen
- Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.,Department of Thoracic Surgery, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai, China
| | - Yuehua Li
- Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.,Research and Development, Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, PA, USA
| | - Timothy R Billiar
- Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.,McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Mark A Wilson
- Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.,Research and Development, Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, PA, USA
| | - Xueyin Shi
- Department of Anaesthesiology, Changzheng Hospital, Second Military Medical University, Shanghai, China.,Department of Anaesthesiology, Shanghai Xinghua Hospital, Jiaotong University School of Medicine, Shanghai, China
| | - Jie Fan
- Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.,Research and Development, Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, PA, USA.,McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA
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211
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Kamoshida G, Kikuchi-Ueda T, Nishida S, Tansho-Nagakawa S, Kikuchi H, Ubagai T, Ono Y. Spontaneous formation of neutrophil extracellular traps in serum-free culture conditions. FEBS Open Bio 2017; 7:877-886. [PMID: 28593142 PMCID: PMC5458474 DOI: 10.1002/2211-5463.12222] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Revised: 03/02/2017] [Accepted: 03/20/2017] [Indexed: 01/05/2023] Open
Abstract
Neutrophils play a critical role in the innate immune response. Recently, a new neutrophilic biological defense mechanism, termed neutrophil extracellular traps (NETs), has been attracting attention. Neutrophils have been observed to release both lysosomal enzymes and their nuclear contents, including unfolded chromatin, which together trap and inactivate bacteria. The environment in tissues where neutrophils act is thought to be different from that of the blood serum. In this study, we assessed the effect of serum on NET formation. We found that neutrophils spontaneously form NETs in serum‐free cultivation conditions at early times. These NETs functioned properly to trap bacteria. Furthermore, we demonstrated that reactive oxygen species play a critical role in the spontaneous formation of NETs. These results suggest that the serum condition must be considered in studies on neutrophils, including the formation and mechanism of action of NETs.
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Affiliation(s)
- Go Kamoshida
- Department of Microbiology and Immunology Teikyo University School of Medicine Tokyo Japan
| | - Takane Kikuchi-Ueda
- Department of Microbiology and Immunology Teikyo University School of Medicine Tokyo Japan
| | - Satoshi Nishida
- Department of Microbiology and Immunology Teikyo University School of Medicine Tokyo Japan
| | | | - Hirotoshi Kikuchi
- Department of Microbiology and Immunology Teikyo University School of Medicine Tokyo Japan
| | - Tsuneyuki Ubagai
- Department of Microbiology and Immunology Teikyo University School of Medicine Tokyo Japan
| | - Yasuo Ono
- Department of Microbiology and Immunology Teikyo University School of Medicine Tokyo Japan
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212
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Valatas V, Filidou E, Drygiannakis I, Kolios G. Stromal and immune cells in gut fibrosis: the myofibroblast and the scarface. Ann Gastroenterol 2017; 30:393-404. [PMID: 28655975 PMCID: PMC5479991 DOI: 10.20524/aog.2017.0146] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 03/19/2017] [Indexed: 02/07/2023] Open
Abstract
Post-inflammatory scarring is the end-result of excessive extracellular matrix (ECM) accumulation and tissue architectural destruction. It represents a failure to effectively remodel ECM and achieve proper reinstitution and healing during chronic relapsing inflammatory processes. Scarring may affect the functionality of any organ, and in the case of inflammatory bowel disease (IBD)-associated fibrosis leads to stricture formation and often surgery to remove the affected bowel. The activated myofibroblast is the final effector cell that overproduces ECM under the influence of various mediators generated by an intense interplay of classic and non-classic immune cells. This review focuses on how proinflammatory mediators from various sources produced in different stages of intestinal inflammation can form profibrotic pathways that eventually lead to tissue scarring through sustained activation of myofibroblasts.
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Affiliation(s)
- Vassilis Valatas
- Laboratory of Gastroenterology, Faculty of Medicine, University of Crete, Heraklion (Vassilis Valatas, Ioannis Drygiannakis)
| | - Eirini Filidou
- Laboratory of Pharmacology, School of Medicine, Democritus University of Thrace, Dragana, Alexandroupolis (Eirini Filidou, George Kolios), Greece
| | - Ioannis Drygiannakis
- Laboratory of Gastroenterology, Faculty of Medicine, University of Crete, Heraklion (Vassilis Valatas, Ioannis Drygiannakis)
| | - George Kolios
- Laboratory of Pharmacology, School of Medicine, Democritus University of Thrace, Dragana, Alexandroupolis (Eirini Filidou, George Kolios), Greece
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213
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Dąbrowska D, Jabłońska E, Garley M, Ratajczak-Wrona W, Iwaniuk A. New Aspects of the Biology of Neutrophil Extracellular Traps. Scand J Immunol 2017; 84:317-322. [PMID: 27667737 DOI: 10.1111/sji.12494] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 09/21/2016] [Indexed: 12/23/2022]
Abstract
The formation and release of neutrophil extracellular traps (NETs) discovered in 2004 by Volker Brinkmann and Arturo Zychlinsky cast a new light on the role of neutrophils in the non-specific immune response of the body. This discovery has resulted in the rapid development of neutrophil studies in different bacterial and autoimmune diseases as well as neoplasms. Research is also being performed on the role of different signalling pathways engaged in the induction of NETosis, a unique form of a programmed cell death leading to the creation of NETs. The literature provides information on the structure and composition of neutrophil extracellular traps. This review presents the latest data on NET formation and the role of their key components, as well as describing the intracellular signalling pathways leading to the generation of NETs that have been discovered.
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Affiliation(s)
- D Dąbrowska
- Department of Immunology, Medical University of Bialystok, Bialystok, Poland
| | - E Jabłońska
- Department of Immunology, Medical University of Bialystok, Bialystok, Poland
| | - M Garley
- Department of Immunology, Medical University of Bialystok, Bialystok, Poland
| | - W Ratajczak-Wrona
- Department of Immunology, Medical University of Bialystok, Bialystok, Poland
| | - A Iwaniuk
- Department of Immunology, Medical University of Bialystok, Bialystok, Poland
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214
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Interactions between Neutrophils and Pseudomonas aeruginosa in Cystic Fibrosis. Pathogens 2017; 6:pathogens6010010. [PMID: 28282951 PMCID: PMC5371898 DOI: 10.3390/pathogens6010010] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 03/03/2017] [Indexed: 12/23/2022] Open
Abstract
Cystic fibrosis (CF) affects 70,000 patients worldwide. Morbidity and mortality in CF is largely caused by lung complications due to the triad of impaired mucociliary clearance, microbial infections and chronic inflammation. Cystic fibrosis airway inflammation is mediated by robust infiltration of polymorphonuclear neutrophil granulocytes (PMNs, neutrophils). Neutrophils are not capable of clearing lung infections and contribute to tissue damage by releasing their dangerous cargo. Pseudomonas aeruginosa is an opportunistic pathogen causing infections in immunocompromised individuals. P. aeruginosa is a main respiratory pathogen in CF infecting most patients. Although PMNs are key to attack and clear P. aeruginosa in immunocompetent individuals, PMNs fail to do so in CF. Understanding why neutrophils cannot clear P. aeruginosa in CF is essential to design novel therapies. This review provides an overview of the antimicrobial mechanisms by which PMNs attack and eliminate P. aeruginosa. It also summarizes current advances in our understanding of why PMNs are incapable of clearing P. aeruginosa and how this bacterium adapts to and resists PMN-mediated killing in the airways of CF patients chronically infected with P. aeruginosa.
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215
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Hazardous Effects of Titanium Dioxide Nanoparticles in Ecosystem. Bioinorg Chem Appl 2017; 2017:4101735. [PMID: 28373829 PMCID: PMC5360948 DOI: 10.1155/2017/4101735] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 02/08/2017] [Indexed: 01/21/2023] Open
Abstract
Although nanoparticles (NPs) have made incredible progress in the field of nanotechnology and biomedical research and their applications are demanded throughout industrial world particularly over the past decades, little is known about the fate of nanoparticles in ecosystem. Concerning the biosafety of nanotechnology, nanotoxicity is going to be the second most priority of nanotechnology that needs to be properly addressed. This review covers the chemical as well as the biological concerns about nanoparticles particularly titanium dioxide (TiO2) NPs and emphasizes the toxicological profile of TiO2 at the molecular level in both in vitro and in vivo systems. In addition, the challenges and future prospects of nanotoxicology are discussed that may provide better understanding and new insights into ongoing and future research in this field.
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216
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Shen XF, Cao K, Jiang JP, Guan WX, Du JF. Neutrophil dysregulation during sepsis: an overview and update. J Cell Mol Med 2017; 21:1687-1697. [PMID: 28244690 PMCID: PMC5571534 DOI: 10.1111/jcmm.13112] [Citation(s) in RCA: 181] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Accepted: 01/05/2017] [Indexed: 12/15/2022] Open
Abstract
Sepsis remains a leading cause of death worldwide, despite advances in critical care, and understanding of the pathophysiology and treatment strategies. No specific therapy or drugs are available for sepsis. Neutrophils play a critical role in controlling infection under normal conditions, and it is suggested that their migration and antimicrobial activity are impaired during sepsis which contribute to the dysregulation of immune responses. Recent studies further demonstrated that interruption or reversal of the impaired migration and antimicrobial function of neutrophils improves the outcome of sepsis in animal models. In this review, we provide an overview of the associated mediators and signal pathways involved which govern the survival, migration and antimicrobial function of neutrophils in sepsis, and discuss the potential of neutrophils as a target to specifically diagnose and/or predict the outcome of sepsis.
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Affiliation(s)
- Xiao-Fei Shen
- Department of General Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China
| | - Ke Cao
- Department of Intensive Care Unit, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China
| | - Jin-Peng Jiang
- Department of Rehabilitation Medicine, PLA Army General Hospital, Beijing, China
| | - Wen-Xian Guan
- Department of General Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China
| | - Jun-Feng Du
- Department of General Surgery, PLA Army General Hospital, Beijing, China
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217
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Koushik S, Joshi N, Nagaraju S, Mahmood S, Mudeenahally K, Padmavathy R, Jegatheesan SK, Mullangi R, Rajagopal S. PAD4: pathophysiology, current therapeutics and future perspective in rheumatoid arthritis. Expert Opin Ther Targets 2017; 21:433-447. [PMID: 28281906 DOI: 10.1080/14728222.2017.1294160] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
INTRODUCTION Peptidyl arginine deiminase 4 (PAD4) is an enzyme that plays an important role in gene expression, turning out genetic code into functional products in the body. It is involved in a key post translational modification, which involves the conversion of arginine to citrulline. It regulates various processes such as apoptosis, innate immunity and pluripotency, while its dysregulation has a great impact on the genesis of various diseases. Over the last few years PAD4 has emerged as a potential therapeutic target for the treatment of rheumatoid arthritis (RA). Areas covered: In this review, we discuss the basic structure and function of PAD4, along with the role of altered PAD4 activity in the onset of RA and other maladies. We also elucidate the role of PAD4 variants in etiology of RA among several ethnic groups and the current pre-clinical inhibitors to regulate PAD4. Expert opinion: Citrullination has a crucial role in RA and several other disorders. Since PAD4 is an initiator of the citrullination, it is an important therapeutic target for inflammatory diseases. Therefore, an in depth knowledge of the roles and activity of PAD4 is required to explore more effective ways to conquer PAD4 related ailments, especially RA.
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Affiliation(s)
- Sindhu Koushik
- a Bioinformatics , Jubilant Biosys Ltd ., Bangalore , India
| | - Nivedita Joshi
- a Bioinformatics , Jubilant Biosys Ltd ., Bangalore , India
| | | | - Sameer Mahmood
- a Bioinformatics , Jubilant Biosys Ltd ., Bangalore , India
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218
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Fetz AE, Neeli I, Rodriguez IA, Radic MZ, Bowlin GL. Electrospun Template Architecture and Composition Regulate Neutrophil NETosis In Vitro and In Vivo<sup/>. Tissue Eng Part A 2017; 23:1054-1063. [PMID: 28068879 DOI: 10.1089/ten.tea.2016.0452] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Mounting evidence indicates that neutrophils, first responders to an implanted biomaterial, prime the microenvironment for recruited immune cells by secreting factors and releasing neutrophil extracellular traps (NETs) through NETosis. In this study, we investigated the role of electrospun template architecture and composition in regulating NETosis. Electrospun polydioxanone (PDO), collagen type I (COL), and blended PDO-COL templates (PC) were fabricated with small-diameter (0.25-0.35 μm) and large-diameter (1.0-2.00 μm) fibers. Neutrophil-template interactions were evaluated in vitro for 3 and 24 h with human neutrophils, and the PDO templates were studied in vivo (rat subcutaneous model) for 1 and 7 days. Template-bound NETs were quantified by fluorescent microscopy and an On-cell Western assay. The in vitro results indicate that larger fiber diameters reduced NETosis on PDO templates, whereas the incorporation of COL attenuated NETosis independent of fiber diameter. The in vivo results similarly revealed a lower degree of NETs on large-diameter PDO templates at 1 day, resulting in marginal tissue integration of the templates at 7 days. In contrast, the small-diameter PDO templates, which were coated in a large amount of NETs at 24 h in vivo, were surrounded by capsule-like tissue at 7 days. These preliminary in vivo results validate the in vitro model and signify NETosis as a potentially significant physiological response and a critical preconditioning event for the innate immune response to templates. In conclusion, these results demonstrate the importance of characterizing the neutrophil's acute confrontation with biomaterials to engineer templates capable of promoting in situ regeneration.
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Affiliation(s)
- Allison E Fetz
- 1 Department of Biomedical Engineering, University of Memphis , Memphis, Tennessee
| | - Indira Neeli
- 2 Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Science Center , Memphis, Tennessee
| | - Isaac A Rodriguez
- 1 Department of Biomedical Engineering, University of Memphis , Memphis, Tennessee
| | - Marko Z Radic
- 2 Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Science Center , Memphis, Tennessee
| | - Gary L Bowlin
- 1 Department of Biomedical Engineering, University of Memphis , Memphis, Tennessee
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219
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Jorgensen I, Rayamajhi M, Miao EA. Programmed cell death as a defence against infection. Nat Rev Immunol 2017; 17:151-164. [PMID: 28138137 DOI: 10.1038/nri.2016.147] [Citation(s) in RCA: 647] [Impact Index Per Article: 92.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Eukaryotic cells can die from physical trauma, which results in necrosis. Alternatively, they can die through programmed cell death upon the stimulation of specific signalling pathways. In this Review, we discuss the role of different cell death pathways in innate immune defence against bacterial and viral infection: apoptosis, necroptosis, pyroptosis and NETosis. We describe the interactions that interweave different programmed cell death pathways, which create complex signalling networks that cross-guard each other in the evolutionary 'arms race' with pathogens. Finally, we describe how the resulting cell corpses - apoptotic bodies, pore-induced intracellular traps (PITs) and neutrophil extracellular traps (NETs) - promote the clearance of infection.
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Affiliation(s)
- Ine Jorgensen
- Department of Immunology, Oslo University Hospital, Sognsvannsveien 20, Rikshospitalet 0372, Oslo, Norway
| | - Manira Rayamajhi
- Camargo Pharmaceutical Services, 2505 Meridian Parkway, Suite 175, Durham, North Carolina 27713, USA
| | - Edward A Miao
- Department of Microbiology and Immunology, Lineberger Comprehensive Cancer Center, and Center for Gastrointestinal Biology and Disease, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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220
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Hu Z, Murakami T, Tamura H, Reich J, Kuwahara-Arai K, Iba T, Tabe Y, Nagaoka I. Neutrophil extracellular traps induce IL-1β production by macrophages in combination with lipopolysaccharide. Int J Mol Med 2017; 39:549-558. [PMID: 28204821 PMCID: PMC5360392 DOI: 10.3892/ijmm.2017.2870] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2016] [Accepted: 01/09/2017] [Indexed: 12/12/2022] Open
Abstract
Upon exposure to invading microorganisms, neutrophils undergo NETosis, a recently identified type of programmed cell death, and release neutrophil extracellular traps (NETs). NETs are described as an antimicrobial mechanism, based on the fact that NETs can trap microorganisms and exhibit bactericidal activity through the action of NET‑associated components. In contrast, the components of NETs have been recognized as damage‑associated molecular pattern molecules (DAMPs), which trigger inflammatory signals to induce cell death, inflammation and organ failure. In the present study, to clarify the effect of NETs on cytokine production by macrophages, mouse macrophage‑like J774 cells were treated with NETs in combination with lipopolysaccharide (LPS) as a constituent of pathogen‑associated molecular patterns. The results revealed that NETs significantly induced the production of interleukin (IL)‑1β by J774 cells in the presence of LPS. Notably, the NET/LPS‑induced IL‑1β production was inhibited by both caspase‑1 and caspase‑8 inhibitors. Furthermore, nucleases and serine protease inhibitors but not anti‑histone antibodies significantly inhibited the NET/LPS‑induced IL‑1β production. Moreover, we confirmed that caspase‑1 and caspase‑8 were activated by NETs/LPS, and the combination of LPS, DNA and neutrophil elastase induced IL‑1β production in reconstitution experiments. These observations indicate that NETs induce the production of IL‑1β by J774 macrophages in combination with LPS via the caspase‑1 and caspase‑8 pathways, and NET‑associated DNA and serine proteases are involved in NET/LPS‑induced IL‑1β production as essential components.
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Affiliation(s)
- Zhongshuang Hu
- Department of Host Defense and Biochemical Research, Juntendo University, Graduate School of Medicine, Tokyo 113‑8421, Japan
| | - Taisuke Murakami
- Department of Host Defense and Biochemical Research, Juntendo University, Graduate School of Medicine, Tokyo 113‑8421, Japan
| | - Hiroshi Tamura
- Department of Host Defense and Biochemical Research, Juntendo University, Graduate School of Medicine, Tokyo 113‑8421, Japan
| | - Johannes Reich
- Institute of Physical and Theoretical Chemistry, University of Regensburg, D‑93053 Regensburg, Germany
| | - Kyoko Kuwahara-Arai
- Department of Microbiology, Juntendo University, Graduate School of Medicine, Tokyo 113‑8421, Japan
| | - Toshiaki Iba
- Department of Emergency and Disaster Medicine, Juntendo University, Graduate School of Medicine, Tokyo 113‑8421, Japan
| | - Yoko Tabe
- Department of Clinical Laboratory Medicine, Juntendo University, Graduate School of Medicine, Tokyo 113‑8421, Japan
| | - Isao Nagaoka
- Department of Host Defense and Biochemical Research, Juntendo University, Graduate School of Medicine, Tokyo 113‑8421, Japan
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221
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Takeuchi H, Kawasaki T, Shigematsu K, Kawamura K, Oka N. Neutrophil extracellular traps in neuropathy with anti-neutrophil cytoplasmic autoantibody-associated microscopic polyangiitis. Clin Rheumatol 2017; 36:913-917. [PMID: 28124760 DOI: 10.1007/s10067-017-3546-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Revised: 01/12/2017] [Accepted: 01/14/2017] [Indexed: 12/31/2022]
Abstract
To clarify the roles of neutrophils in anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitic neuropathy, we studied neutrophil extracellular traps (NETs) in peripheral nerve vasculitis. Stored nerve samples from 17 patients with microscopic polyangiitis (MPA) were immunohistochemically analyzed using antibodies for citrullinated histone H3 (citH3) and various neutrophil enzymes. We defined merged citH3 and extracellularly released myeloperoxidase (MPO) as NET formation. We also compared NET formation between MPO-ANCA-positive/negative MPA and rheumatoid arthritis (RA)-associated vasculitic neuropathy. NETs were identified mostly in vasculitic small arterioles of 6 of 12 MPO-ANCA-positive MPA patients, and their frequency was higher (p < 0.05) than in ANCA-negative patients. NETs were not found in vasculitic neuropathy with RA or patients with chronic inflammatory demyelinating polyradiculoneuropathy. NETs were also observed in the peripheral nervous system of MPA patients as well as in the lung and kidney. These results suggest that NETs may be involved in the pathogenesis of MPA neuropathy.
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Affiliation(s)
- Hiroki Takeuchi
- Department of Neurology, National Hospital Organization Minami-Kyoto National Hospital, Joyo-shi, Kyoto, 610-0113, Japan.
| | - Teruaki Kawasaki
- Center of Neurological and Cerebrovascular Diseases, Takeda Hospital, Kyoto, Japan
| | - Kazuo Shigematsu
- Department of Neurology, National Hospital Organization Minami-Kyoto National Hospital, Joyo-shi, Kyoto, 610-0113, Japan
| | - Kazuyuki Kawamura
- Department of Neurology, National Hospital Organization Minami-Kyoto National Hospital, Joyo-shi, Kyoto, 610-0113, Japan
| | - Nobuyuki Oka
- Department of Neurology, National Hospital Organization Minami-Kyoto National Hospital, Joyo-shi, Kyoto, 610-0113, Japan
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222
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Halder LD, Abdelfatah MA, Jo EAH, Jacobsen ID, Westermann M, Beyersdorf N, Lorkowski S, Zipfel PF, Skerka C. Factor H Binds to Extracellular DNA Traps Released from Human Blood Monocytes in Response to Candida albicans. Front Immunol 2017; 7:671. [PMID: 28133459 PMCID: PMC5233719 DOI: 10.3389/fimmu.2016.00671] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 12/19/2016] [Indexed: 12/15/2022] Open
Abstract
Upon systemic infection with human pathogenic yeast Candida albicans (C. albicans), human monocytes and polymorph nuclear neutrophilic granulocytes are the first immune cells to respond and come into contact with C. albicans. Monocytes exert immediate candidacidal activity and inhibit germination, mediate phagocytosis, and kill fungal cells. Here, we show that human monocytes spontaneously respond to C. albicans cells via phagocytosis, decondensation of nuclear DNA, and release of this decondensed DNA in the form of extracellular traps (called monocytic extracellular traps: MoETs). Both subtypes of monocytes (CD14++CD16−/CD14+CD16+) formed MoETs within the first hours upon contact with C. albicans. MoETs were characterized by the presence of citrullinated histone, myeloperoxidase, lactoferrin, and elastase. MoETs were also formed in response to Staphylococcus aureus and Escherichia coli, indicating a general reaction of monocytes to infectious microbes. MoET induction differs from extracellular trap formation in macrophages as MoETs are not triggered by simvastatin, an inhibitor of cholesterol synthesis and inducer of extracellular traps in macrophages. Extracellular traps from both monocytes and neutrophils activate complement and C3b is deposited. However, factor H (FH) binds via C3b to the extracellular DNA, mediates cofactor activity, and inhibits the induction of the inflammatory cytokine interleukin-1 beta in monocytes. Altogether, the results show that human monocytes release extracellular DNA traps in response to C. albicans and that these traps finally bind FH via C3b to presumably support clearance without further inflammation.
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Affiliation(s)
- Luke D Halder
- Department of Infection Biology, Leibniz Institute for Natural Product Research and Infection Biology , Jena , Germany
| | - Mahmoud A Abdelfatah
- Department of Infection Biology, Leibniz Institute for Natural Product Research and Infection Biology , Jena , Germany
| | - Emeraldo A H Jo
- Department of Infection Biology, Leibniz Institute for Natural Product Research and Infection Biology , Jena , Germany
| | - Ilse D Jacobsen
- Research Group Microbial Immunology, Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany; Friedrich-Schiller University, Jena, Germany
| | - Martin Westermann
- Center for Electron Microscopy of the University Hospital Jena , Jena , Germany
| | - Niklas Beyersdorf
- Institute for Virology and Immunobiology, University of Würzburg , Würzburg , Germany
| | - Stefan Lorkowski
- Institute of Nutrition, Friedrich-Schiller University , Jena , Germany
| | - Peter F Zipfel
- Department of Infection Biology, Leibniz Institute for Natural Product Research and Infection Biology, Jena, Germany; Friedrich-Schiller University, Jena, Germany
| | - Christine Skerka
- Department of Infection Biology, Leibniz Institute for Natural Product Research and Infection Biology , Jena , Germany
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223
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Mitsios A, Arampatzioglou A, Arelaki S, Mitroulis I, Ritis K. NETopathies? Unraveling the Dark Side of Old Diseases through Neutrophils. Front Immunol 2017; 7:678. [PMID: 28123386 PMCID: PMC5225098 DOI: 10.3389/fimmu.2016.00678] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 12/21/2016] [Indexed: 12/14/2022] Open
Abstract
Neutrophil extracellular traps (NETs) were initially described as an antimicrobial mechanism of neutrophils. Over the last decade, several lines of evidence support the involvement of NETs in a plethora of pathological conditions. Clinical and experimental data indicate that NET release constitutes a shared mechanism, which is involved in a different degree in various manifestations of non-infectious diseases. Even though the backbone of NETs is similar, there are differences in their protein load in different diseases, which represent alterations in neutrophil protein expression in distinct disorder-specific microenvironments. The characterization of NET protein load in different NET-driven disorders could be of significant diagnostic and/or therapeutic value. Additionally, it will provide further evidence for the role of NETs in disease pathogenesis, and it will enable the characterization of disorders in which neutrophils and NET-dependent inflammation are of critical importance.
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Affiliation(s)
- Alexandros Mitsios
- Laboratory of Molecular Hematology, Democritus University of Thrace , Alexandroupolis , Greece
| | | | - Stella Arelaki
- Laboratory of Molecular Hematology, Democritus University of Thrace, Alexandroupolis, Greece; Department of Pathology, University General Hospital of Alexandroupolis, Alexandroupolis, Greece
| | - Ioannis Mitroulis
- Department of Clinical Pathobiochemistry, Institute for Clinical Chemistry and Laboratory Medicine, Faculty of Medicine Technische Universität Dresden , Dresden , Germany
| | - Konstantinos Ritis
- Laboratory of Molecular Hematology, Democritus University of Thrace, Alexandroupolis, Greece; First Department of Internal Medicine, University Hospital of Alexandroupolis, Democritus University of Thrace, Alexandroupolis, Greece
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Nakazawa D, Kumar SV, Marschner J, Desai J, Holderied A, Rath L, Kraft F, Lei Y, Fukasawa Y, Moeckel GW, Angelotti ML, Liapis H, Anders HJ. Histones and Neutrophil Extracellular Traps Enhance Tubular Necrosis and Remote Organ Injury in Ischemic AKI. J Am Soc Nephrol 2017; 28:1753-1768. [PMID: 28073931 DOI: 10.1681/asn.2016080925] [Citation(s) in RCA: 204] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 11/30/2016] [Indexed: 12/15/2022] Open
Abstract
Severe AKI is often associated with multiorgan dysfunction, but the mechanisms of this remote tissue injury are unknown. We hypothesized that renal necroinflammation releases cytotoxic molecules that may cause remote organ damage. In hypoxia-induced tubular epithelial cell necrosis in vitro, histone secretion from ischemic tubular cells primed neutrophils to form neutrophil extracellular traps. These traps induced tubular epithelial cell death and stimulated neutrophil extracellular trap formation in fresh neutrophils. In vivo, ischemia-reperfusion injury in the mouse kidney induced tubular necrosis, which preceded the expansion of localized and circulating neutrophil extracellular traps and the increased expression of inflammatory and injury-related genes. Pretreatment with inhibitors of neutrophil extracellular trap formation reduced kidney injury. Dual inhibition of neutrophil trap formation and tubular cell necrosis had an additive protective effect. Moreover, pretreatment with antihistone IgG suppressed ischemia-induced neutrophil extracellular trap formation and renal injury. Renal ischemic injury also increased the levels of circulating histones, and we detected neutrophil infiltration and TUNEL-positive cells in the lungs, liver, brain, and heart along with neutrophil extracellular trap accumulation in the lungs. Inhibition of neutrophil extracellular trap formation or of circulating histones reduced these effects as well. These data suggest that tubular necrosis and neutrophil extracellular trap formation accelerate kidney damage and remote organ dysfunction through cytokine and histone release and identify novel molecular targets to limit renal necroinflammation and multiorgan failure.
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Affiliation(s)
- Daigo Nakazawa
- Nephrologisches Zentrum, Medizinische Klinik und Poliklinik IV, Klinikum der Universität München, Munich, Germany
| | - Santhosh V Kumar
- Nephrologisches Zentrum, Medizinische Klinik und Poliklinik IV, Klinikum der Universität München, Munich, Germany
| | - Julian Marschner
- Nephrologisches Zentrum, Medizinische Klinik und Poliklinik IV, Klinikum der Universität München, Munich, Germany
| | - Jyaysi Desai
- Nephrologisches Zentrum, Medizinische Klinik und Poliklinik IV, Klinikum der Universität München, Munich, Germany
| | - Alexander Holderied
- Nephrologisches Zentrum, Medizinische Klinik und Poliklinik IV, Klinikum der Universität München, Munich, Germany
| | - Lukas Rath
- Nephrologisches Zentrum, Medizinische Klinik und Poliklinik IV, Klinikum der Universität München, Munich, Germany
| | - Franziska Kraft
- Nephrologisches Zentrum, Medizinische Klinik und Poliklinik IV, Klinikum der Universität München, Munich, Germany
| | - Yutian Lei
- Nephrologisches Zentrum, Medizinische Klinik und Poliklinik IV, Klinikum der Universität München, Munich, Germany
| | - Yuichiro Fukasawa
- Department of Pathology, Sapporo City General Hospital, Sapporo, Hokkaido, Japan
| | - Gilbert W Moeckel
- Department of Pathology, Yale University School of Medicine, New Haven, Connecticut
| | - Maria Lucia Angelotti
- Excellence Centre for Research, Transfer and High Education for the Development of De Novo Therapies, University of Florence, Florence, Italy; and
| | - Helen Liapis
- Departments of Pathology and Immunology and Internal Medicine (Renal), School of Medicine, Washington University in St. Louis, Missouri and Arkana Laboratories, Little Rock, Arkansas
| | - Hans-Joachim Anders
- Nephrologisches Zentrum, Medizinische Klinik und Poliklinik IV, Klinikum der Universität München, Munich, Germany;
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McCoy CJ, Reaves BJ, Giguère S, Coates R, Rada B, Wolstenholme AJ. Human Leukocytes Kill Brugia malayi Microfilariae Independently of DNA-Based Extracellular Trap Release. PLoS Negl Trop Dis 2017; 11:e0005279. [PMID: 28045905 PMCID: PMC5234842 DOI: 10.1371/journal.pntd.0005279] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Revised: 01/13/2017] [Accepted: 12/21/2016] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Wuchereria bancrofti, Brugia malayi and Brugia timori infect over 100 million people worldwide and are the causative agents of lymphatic filariasis. Some parasite carriers are amicrofilaremic whilst others facilitate mosquito-based disease transmission through blood-circulating microfilariae (Mf). Recent findings, obtained largely from animal model systems, suggest that polymorphonuclear leukocytes (PMNs) contribute to parasitic nematode-directed type 2 immune responses. When exposed to certain pathogens PMNs release extracellular traps (NETs) in the form of chromatin loaded with various antimicrobial molecules and proteases. PRINCIPAL FINDINGS In vitro, PMNs expel large amounts of NETs that capture but do not kill B. malayi Mf. NET morphology was confirmed by fluorescence imaging of worm-NET aggregates labelled with DAPI and antibodies to human neutrophil elastase, myeloperoxidase and citrullinated histone H4. A fluorescent, extracellular DNA release assay was used to quantify and observe Mf induced NETosis over time. Blinded video analyses of PMN-to-worm attachment and worm survival during Mf-leukocyte co-culture demonstrated that DNase treatment eliminates PMN attachment in the absence of serum, autologous serum bolsters both PMN attachment and PMN plus peripheral blood mononuclear cell (PBMC) mediated Mf killing, and serum heat inactivation inhibits both PMN attachment and Mf killing. Despite the effects of heat inactivation, the complement inhibitor compstatin did not impede Mf killing and had little effect on PMN attachment. Both human PMNs and monocytes, but not lymphocytes, are able to kill B. malayi Mf in vitro and NETosis does not significantly contribute to this killing. Leukocytes derived from presumably parasite-naïve U.S. resident donors vary in their ability to kill Mf in vitro, which may reflect the pathological heterogeneity associated with filarial parasitic infections. CONCLUSIONS/SIGNIFICANCE Human innate immune cells are able to recognize, attach to and kill B. malayi microfilariae in an in vitro system. This suggests that, in vivo, the parasites can evade this ability, or that only some human hosts support an infection with circulating Mf.
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Affiliation(s)
- Ciaran J. McCoy
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States of America
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, United States of America
| | - Barbara J. Reaves
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States of America
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, United States of America
| | - Steeve Giguère
- Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA, United States of America
| | - Ruby Coates
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States of America
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, United States of America
- Department of Biology & Biochemistry, University of Bath, Bath, United Kingdom
| | - Balázs Rada
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States of America
| | - Adrian J. Wolstenholme
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States of America
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, United States of America
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Lawrence SM, Corriden R, Nizet V. Age-Appropriate Functions and Dysfunctions of the Neonatal Neutrophil. Front Pediatr 2017; 5:23. [PMID: 28293548 PMCID: PMC5329040 DOI: 10.3389/fped.2017.00023] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Accepted: 01/30/2017] [Indexed: 12/12/2022] Open
Abstract
Neonatal and adult neutrophils are distinctly different from one another due to well-defined and documented deficiencies in neonatal cells, including impaired functions, reduced concentrations of microbicidal proteins and enzymes necessary for pathogen destruction, and variances in cell surface receptors. Neutrophil maturation is clearly demonstrated throughout pregnancy from the earliest hematopoietic precursors in the yolk sac to the well-developed myeloid progenitor cells in the bone marrow around the seventh month of gestation. Notable deficiencies of neonatal neutrophils are generally correlated with gestational age and clinical condition, so that the least functional neutrophils are found in the youngest, sickest neonates. Interruption of normal gestation secondary to preterm birth exposes these shortcomings and places the neonate at an exceptionally high rate of infection and sepsis-related mortality. Because the fetus develops in a sterile environment, neonatal adaptive immune responses are deficient from lack of antigen exposure in utero. Newborns must therefore rely on innate immunity to protect against early infection. Neutrophils are a vital component of innate immunity since they are the first cells to respond to and defend against bacterial, viral, and fungal infections. However, notable phenotypic and functional disparities exist between neonatal and adult cells. Below is review of neutrophil ontogeny, as well as a discussion regarding known differences between preterm and term neonatal and adult neutrophils with respect to cell membrane receptors and functions. Our analysis will also explain how these variations decrease with postnatal age.
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Affiliation(s)
- Shelley Melissa Lawrence
- Pediatrics, Neonatal-Perinatal Medicine, UCSD, La Jolla, CA, USA; Division of Host-Microbe Systems and Therapeutics, UCSD, La Jolla, CA, USA
| | - Ross Corriden
- Division of Host-Microbe Systems and Therapeutics, UCSD, La Jolla, CA, USA; Pharmacology, UCSD, La Jolla, CA, USA
| | - Victor Nizet
- Division of Host-Microbe Systems and Therapeutics, UCSD, La Jolla, CA, USA; Skaggs School of Pharmacy and Pharmaceutical Sciences, UCSD, La Jolla, CA, USA
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227
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Shida H, Nakazawa D, Tateyama Y, Miyoshi A, Kusunoki Y, Hattanda F, Masuda S, Tomaru U, Kawakami T, Atsumi T, Ishizu A. The Presence of Anti-Lactoferrin Antibodies in a Subgroup of Eosinophilic Granulomatosis with Polyangiitis Patients and Their Possible Contribution to Enhancement of Neutrophil Extracellular Trap Formation. Front Immunol 2016; 7:636. [PMID: 28066444 PMCID: PMC5179553 DOI: 10.3389/fimmu.2016.00636] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 12/12/2016] [Indexed: 11/26/2022] Open
Abstract
Lactoferrin (Lf) is one of the antigens of antineutrophil cytoplasmic antibodies (ANCA) and functions as an endogenous suppressor of neutrophil extracellular trap (NET) formation. However, the prevalence and pathogenicity of anti-lactoferrin antibodies (aLf) in ANCA-associated vasculitis (AAV) remain unrevealed. This study aimed to examine the significance of aLf in AAV, initially. Sixty-five sera from AAV patients, including 41 microscopic polyangiitis, 5 granulomatosis with polyangiitis, and 19 eosinophilic granulomatosis with polyangiitis (EGPA) patients, were subjected to aLf detection using enzyme-linked immunosorbent assay. Clinical characteristics were compared between aLf-positive and aLf-negative patients. Neutrophils from healthy donors were exposed to suboptimal dose (10 nM) of phorbol myristate acetate (PMA) with aLf followed by evaluation of NET formation. Results demonstrated that 4 out of 65 AAV sera (6.2%) were positive for aLf. All of them were EGPA sera (4/19, 21.1%). In EGPA, the frequency of renal involvement, serum CRP levels, and Birmingham Vasculitis Activity Score (BVAS) in the aLf-positive patients was significantly higher than those in the aLf-negative patients, and the aLf titer correlated positively with the serum CRP level and BVAS. The NET formation was particularly enhanced by combined stimulation of 10 nM PMA and 1 µg/mL aLf. IgG isolated from sera of the aLf-positive EGPA patients (250 µg/mL) enhanced NET formation induced by 10 nM of PMA, and the effect was abolished completely by absorption of the aLf. This pilot study suggests that aLf enhance NET formation induced by PMA and are associated with disease activity of EGPA.
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Affiliation(s)
- Haruki Shida
- Division of Rheumatology, Endocrinology and Nephrology, Hokkaido University Graduate School of Medicine , Sapporo , Japan
| | - Daigo Nakazawa
- Division of Rheumatology, Endocrinology and Nephrology, Hokkaido University Graduate School of Medicine , Sapporo , Japan
| | - Yu Tateyama
- Undergraduate School of Health Sciences, Hokkaido University , Sapporo , Japan
| | - Arina Miyoshi
- Division of Rheumatology, Endocrinology and Nephrology, Hokkaido University Graduate School of Medicine , Sapporo , Japan
| | - Yoshihiro Kusunoki
- Division of Rheumatology, Endocrinology and Nephrology, Hokkaido University Graduate School of Medicine , Sapporo , Japan
| | - Fumihiko Hattanda
- Division of Rheumatology, Endocrinology and Nephrology, Hokkaido University Graduate School of Medicine , Sapporo , Japan
| | - Sakiko Masuda
- Department of Pathology, Hokkaido University Graduate School of Medicine , Sapporo , Japan
| | - Utano Tomaru
- Department of Dermatology, St. Marianna University School of Medicine , Kawasaki , Japan
| | | | - Tatsuya Atsumi
- Division of Rheumatology, Endocrinology and Nephrology, Hokkaido University Graduate School of Medicine , Sapporo , Japan
| | - Akihiro Ishizu
- Department of Pathology, Hokkaido University Graduate School of Medicine , Sapporo , Japan
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228
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Abstract
Candida albicans is the most common human fungal pathogen causing diseases ranging from mucosal to systemic infections. As a commensal, C. albicans asymptomatically colonizes mucosal surfaces; however, any disruption in the host environment or under conditions of immune dysfunction, C. albicans can proliferate and invade virtually any site in the host. The ability of this highly adaptable fungal species to transition from commensal to pathogen is due to a repertoire of virulence factors. Specifically, the ability to switch morphology and form biofilms are properties central to C. albicans pathogenesis. In fact, the majority of C. albicans infections are associated with biofilm formation on host or abiotic surfaces such as indwelling medical devices, which carry high morbidity and mortality. Significantly, biofilms formed by C. albicans are inherently tolerant to antimicrobial therapy and therefore, the susceptibility of Candida biofilms to the current therapeutic agents remains low. The aim of this review is to provide an overview of C. albicans highlighting some of the diverse biofilm-associated diseases caused by this opportunistic pathogen and the animal models available to study them. Further, the classes of antifungal agents used to combat these resilient infections are discussed along with mechanisms of drug resistance.
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229
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Agraz-Cibrian JM, Giraldo DM, Mary FM, Urcuqui-Inchima S. Understanding the molecular mechanisms of NETs and their role in antiviral innate immunity. Virus Res 2016; 228:124-133. [PMID: 27923601 DOI: 10.1016/j.virusres.2016.11.033] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 11/30/2016] [Accepted: 11/30/2016] [Indexed: 01/09/2023]
Abstract
Polymorphonuclear neutrophils (PMNs) are the most abundant cells in the context of innate immunity; they are one of the first cells to arrive at the site of viral infection constituting the first line of defense in response to invading pathogens. Indeed, neutrophils are provided with several defense mechanisms including release of cytokines, cytotoxic granules and the last recently described neutrophil extracellular traps (NETs). The main components of NETs are DNA, granular antimicrobial peptides, and nuclear and cytoplasmic proteins, that together play an important role in the innate immune response. While NETs were first described as a mechanism against bacteria and fungi, recently, several studies are beginning to elucidate how NETs are involved in the host antiviral response and the prominent characteristics of this new mechanism are discussed in the present review.
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Affiliation(s)
- Juan Manuel Agraz-Cibrian
- Unidad Académica de Ciencias Químico Biológicas y Farmacéuticas, Universidad Autónoma de Nayarit, Tepic, Nayarit, Mexico.
| | - Diana M Giraldo
- Grupo Inmunovirología, Facultad de Medicina, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín, Colombia.
| | - Fafutis-Morris Mary
- Laboratorio de Inmunología, Departamento de Fisiología, CUCS, Universidad de Guadalajara, Guadalajara, Jalisco, Mexico.
| | - Silvio Urcuqui-Inchima
- Grupo Inmunovirología, Facultad de Medicina, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín, Colombia.
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230
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Neeli I, Radic M. Current Challenges and Limitations in Antibody-Based Detection of Citrullinated Histones. Front Immunol 2016; 7:528. [PMID: 27933065 PMCID: PMC5122592 DOI: 10.3389/fimmu.2016.00528] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Accepted: 11/10/2016] [Indexed: 12/31/2022] Open
Abstract
Studies on NETosis demand reliable and convenient markers to monitor the progress of this form of cell death. Because a determining step in the release of nuclear chromatin NETs requires the conversion of arginine residues to citrulline residues in histones by peptidylarginine deiminase, citrullinated histones can provide such a marker. Here, we evaluate antibody reagents for the detection of citrulline residues in histones and observe alarming differences between commercial antisera and mouse and rabbit monoclonal antibodies in their ability to detect their nominal target residues. Differences between antibodies that are currently used to detect citrulline residues in histones could jeopardize efforts to reach a scientific consensus and instead lead to inconsistent and even conflicting conclusions regarding the regulation of histone deimination. Our results will assist others in planning their initial or ongoing studies on peptidylarginine deiminase activity with the use of currently available antibodies. Furthermore, we argue that, along with the careful attention to experimental conditions and calcium concentrations, validated antibody reagents are urgently needed to avoid possible setbacks in the research on NETosis.
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Affiliation(s)
- Indira Neeli
- Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Science Center , Memphis, TN , USA
| | - Marko Radic
- Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Science Center , Memphis, TN , USA
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231
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Pieterse E, Rother N, Yanginlar C, Hilbrands LB, van der Vlag J. Neutrophils Discriminate between Lipopolysaccharides of Different Bacterial Sources and Selectively Release Neutrophil Extracellular Traps. Front Immunol 2016; 7:484. [PMID: 27867387 PMCID: PMC5095130 DOI: 10.3389/fimmu.2016.00484] [Citation(s) in RCA: 138] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2016] [Accepted: 10/21/2016] [Indexed: 01/26/2023] Open
Abstract
The release of neutrophil extracellular traps (NETs), either during "suicidal" or "vital" NETosis, represents an important strategy of neutrophils to combat Gram-negative bacteria. Lipopolysaccharide (LPS), a major component of the outer membrane of Gram-negative bacteria, is a reported stimulus for NET formation. Although it is widely acknowledged that the structural diversity in LPS structures can elicit heterogeneous immune responses, species- and serotype-specific differences in the capacity of LPS to trigger NET formation have not yet been investigated. In the present study, we compared the NET-inducing potential of LPS derived from Escherichia coli (serotypes O55:B5, O127:B8, O128:B12, O111:B4, and O26:B6), Salmonella enterica (serotype enteritidis), and Pseudomonas aeruginosa (serotype 10), under platelet-free and platelet-rich conditions in vitro, and in whole blood ex vivo. Here, we demonstrate that under serum- and platelet-free conditions, mimicking tissue circumstances, neutrophils discriminate between LPS of different bacterial sources and selectively release NETs only in response to LPS derived from E. coli O128:B12 and P. aeruginosa 10, which both induced "suicidal" NETosis in an autophagy- and reactive oxygen species (ROS)-dependent, but TLR4-independent manner. Intriguingly, in whole blood cultures ex vivo, or in vitro in the presence of platelets, all LPS serotypes induced "vital" NET formation. This platelet-dependent release of NETs occurred rapidly without neutrophil cell death and was independent from ROS formation and autophagy but required platelet TLR4 and CD62P-dependent platelet-neutrophil interactions. Taken together, our data reveal a complex interplay between neutrophils and LPS, which can induce both "suicidal" and "vital" NETosis, depending on the bacterial origin of LPS and the presence or absence of platelets. Our findings suggest that LPS sensing by neutrophils may be a critical determinant for restricting NET release to certain Gram-negative bacteria only, which in turn may be crucial for minimizing unnecessary NET-associated immunopathology.
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Affiliation(s)
- Elmar Pieterse
- Department of Nephrology, Radboud University Medical Center , Nijmegen , Netherlands
| | - Nils Rother
- Department of Nephrology, Radboud University Medical Center , Nijmegen , Netherlands
| | - Cansu Yanginlar
- Department of Nephrology, Radboud University Medical Center , Nijmegen , Netherlands
| | - Luuk B Hilbrands
- Department of Nephrology, Radboud University Medical Center , Nijmegen , Netherlands
| | - Johan van der Vlag
- Department of Nephrology, Radboud University Medical Center , Nijmegen , Netherlands
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232
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Konig MF, Andrade F. A Critical Reappraisal of Neutrophil Extracellular Traps and NETosis Mimics Based on Differential Requirements for Protein Citrullination. Front Immunol 2016; 7:461. [PMID: 27867381 PMCID: PMC5095114 DOI: 10.3389/fimmu.2016.00461] [Citation(s) in RCA: 161] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 10/14/2016] [Indexed: 12/18/2022] Open
Abstract
NETosis, an antimicrobial form of neutrophil cell death, is considered a primary source of citrullinated autoantigens in rheumatoid arthritis (RA) and immunogenic DNA in systemic lupus erythematosus (SLE). Activation of the citrullinating enzyme peptidylarginine deiminase type 4 (PAD4) is believed to be essential for neutrophil extracellular trap (NET) formation and NETosis. PAD4 is therefore viewed as a promising therapeutic target to inhibit the formation of NETs in both diseases. In this review, we examine the evidence for PAD4 activation during NETosis and provide experimental data to suggest that protein citrullination is not a universal feature of NETs. We delineate two distinct biological processes, leukotoxic hypercitrullination (LTH) and defective mitophagy, which have been erroneously classified as “NETosis.” While these NETosis mimics share morphological similarities with NETosis (i.e., extracellular DNA release), they are biologically distinct. As such, these processes can be readily classified by their stimuli, activation of distinct biochemical pathways, the presence of hypercitrullination, and antimicrobial effector function. NETosis is an antimicrobial form of cell death that is NADPH oxidase-dependent and not associated with hypercitrullination. In contrast, LTH is NADPH oxidase-independent and not bactericidal. Rather, LTH represents a bacterial strategy to achieve immune evasion. It is triggered by pore-forming pathways and equivalent signals that cumulate in calcium-dependent hyperactivation of PADs, protein hypercitrullination, and neutrophil death. The generation of citrullinated autoantigens in RA is likely driven by LTH, but not NETosis. Mitochondrial DNA (mtDNA) expulsion, the result of a constitutive defect in mitophagy, represents a second NETosis mimic. In the presence of interferon-α and immune complexes, this process can generate highly interferogenic oxidized mtDNA, which has previously been mistaken for NETosis in SLE. Distinguishing NETosis from LTH and defective mitophagy is paramount to understanding the role of neutrophil damage in immunity and the pathogenesis of human diseases. This provides a framework to design specific inhibitors of these distinct biological processes in human disease.
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Affiliation(s)
- Maximilian F Konig
- Division of Rheumatology, Johns Hopkins University School of Medicine , Baltimore, MD , USA
| | - Felipe Andrade
- Division of Rheumatology, Johns Hopkins University School of Medicine , Baltimore, MD , USA
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233
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De Samber B, Niemiec MJ, Laforce B, Garrevoet J, Vergucht E, De Rycke R, Cloetens P, Urban CF, Vincze L. Probing Intracellular Element Concentration Changes during Neutrophil Extracellular Trap Formation Using Synchrotron Radiation Based X-Ray Fluorescence. PLoS One 2016; 11:e0165604. [PMID: 27812122 PMCID: PMC5094720 DOI: 10.1371/journal.pone.0165604] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 10/15/2016] [Indexed: 02/07/2023] Open
Abstract
High pressure frozen (HPF), cryo-substituted microtome sections of 2 μm thickness containing human neutrophils (white blood cells) were analyzed using synchrotron radiation based X-ray fluorescence (SR nano-XRF) at a spatial resolution of 50 nm. Besides neutrophils from a control culture, we also analyzed neutrophils stimulated for 1-2 h with phorbol myristate acetate (PMA), a substance inducing the formation of so-called Neutrophil Extracellular Traps (or NETs), a defense system again pathogens possibly involving proteins with metal chelating properties. In order to gain insight in metal transport during this process, precise local evaluation of elemental content was performed reaching limits of detection (LODs) of 1 ppb. Mean weight fractions within entire neutrophils, their nuclei and cytoplasms were determined for the three main elements P, S and Cl, but also for the 12 following trace elements: K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Se, Br, Sr and Pb. Statistical analysis, including linear regression provided objective analysis and a measure for concentration changes. The nearly linear Ca and Cl concentration changes in neutrophils could be explained by already known phenomena such as the induction of Ca channels and the uptake of Cl under activation of NET forming neutrophils. Linear concentration changes were also found for P, S, K, Mn, Fe, Co and Se. The observed linear concentration increase for Mn could be related to scavenging of this metal from the pathogen by means of the neutrophil protein calprotectin, whereas the concentration increase of Se may be related to its antioxidant function protecting neutrophils from the reactive oxygen species they produce against pathogens. We emphasize synchrotron radiation based nanoscopic X-ray fluorescence as an enabling analytical technique to study changing (trace) element concentrations throughout cellular processes, provided accurate sample preparation and data-analysis.
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Affiliation(s)
- Björn De Samber
- Department of Analytical Chemistry, Ghent University, Ghent, Belgium
- * E-mail:
| | - Maria J. Niemiec
- Department of Clinical Microbiology / MIMS, Umeå University, Umeå, Sweden
- Microbial Immunology Research Group, Hans Knöll Institute / Leibniz-Institute for Natural Product Research and Infection Biology, Jena, Germany
| | - Brecht Laforce
- Department of Analytical Chemistry, Ghent University, Ghent, Belgium
| | | | - Eva Vergucht
- Department of Analytical Chemistry, Ghent University, Ghent, Belgium
| | - Riet De Rycke
- Inflammation Research Centre, VIB and Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium
- Department of Plant Systems Biology, VIB and Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium
| | - Peter Cloetens
- European Synchrotron Radiation Facility, Grenoble, France
| | | | - Laszlo Vincze
- Department of Analytical Chemistry, Ghent University, Ghent, Belgium
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234
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Hosseinzadeh A, Thompson PR, Segal BH, Urban CF. Nicotine induces neutrophil extracellular traps. J Leukoc Biol 2016; 100:1105-1112. [PMID: 27312847 PMCID: PMC5069087 DOI: 10.1189/jlb.3ab0815-379rr] [Citation(s) in RCA: 114] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 05/20/2016] [Accepted: 05/30/2016] [Indexed: 01/09/2023] Open
Abstract
NETs serve to ensnare and kill microbial pathogens. However, NETs can at the same time contribute to tissue damage and excessive inflammation. Nicotine is a major toxic agent and has been associated with exacerbated inflammatory diseases. The current study aimed at investigating the role of nicotine, the addictive component of tobacco and electronic cigarettes, on triggering NET formation. We report that nicotine induces neutrophils to release NETs in a dose-dependent manner. Nicotine-induced NET formation is mediated via nicotine acetylcholine receptors, depends on Akt and PAD4 activation, but is Nox2-independent, as demonstrated by pharmacological inhibition of Nox2 and by use of Nox2-deficient mouse neutrophils. These findings demonstrate that nicotine induces NETs, which may in turn contribute to smoking-related diseases.
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Affiliation(s)
- Ava Hosseinzadeh
- Department of Clinical Microbiology, Umeå University, Umeå, Sweden
- Umeå Centre for Microbial Research (UCMR), Umeå, Sweden
- Laboratory for Molecular Infection Medicine, Umeå, Sweden (MIMS)
| | - Paul R Thompson
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester Massachusetts, USA
| | - Brahm H Segal
- Department of Medicine, Roswell Park Cancer Institute, Buffalo, New York, USA
- Department of Immunology, Roswell Park Cancer Institute, Buffalo, New York, USA; and
- Department of Medicine, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, USA
| | - Constantin F Urban
- Department of Clinical Microbiology, Umeå University, Umeå, Sweden;
- Umeå Centre for Microbial Research (UCMR), Umeå, Sweden
- Laboratory for Molecular Infection Medicine, Umeå, Sweden (MIMS)
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235
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Suzuki E, Maverakis E, Sarin R, Bouchareychas L, Kuchroo VK, Nestle FO, Adamopoulos IE. T Cell-Independent Mechanisms Associated with Neutrophil Extracellular Trap Formation and Selective Autophagy in IL-17A-Mediated Epidermal Hyperplasia. THE JOURNAL OF IMMUNOLOGY 2016; 197:4403-4412. [PMID: 27798153 DOI: 10.4049/jimmunol.1600383] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Accepted: 08/30/2016] [Indexed: 12/23/2022]
Abstract
IL-17A has been strongly associated with epidermal hyperplasia in many cutaneous disorders. However, because IL-17A is mainly produced by αβ and γδT cells in response to IL-23, the role of T cells and IL-23 has overshadowed any IL-17A-independent actions. In this article, we report that IL-17A gene transfer induces epidermal hyperplasia in Il23r-/-Rag1-/-- and Tcrδ-deficient mice, which can be prevented by neutrophil depletion. Moreover, adoptive transfer of CD11b+Gr-1hi cells, after IL-17A gene transfer, was sufficient to phenocopy the disease. We further show that the IL-17A-induced pathology was prevented in transgenic mice with impaired neutrophil extracellular trap formation and/or neutrophils with conditional deletion of the master regulator of selective autophagy, Wdfy3. Our data demonstrate a novel T cell-independent mechanism that is associated with neutrophil extracellular trap formation and selective autophagy in IL-17A-mediated epidermal hyperplasia.
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Affiliation(s)
- Erika Suzuki
- Division of Rheumatology, Allergy and Clinical Immunology, Department of Internal Medicine, University of California at Davis, Davis, CA 95616
| | - Emanual Maverakis
- Department of Dermatology, University of California at Davis, Davis, CA 95616
| | - Ritu Sarin
- Division of Rheumatology, Allergy and Clinical Immunology, Department of Internal Medicine, University of California at Davis, Davis, CA 95616
| | - Laura Bouchareychas
- Division of Rheumatology, Allergy and Clinical Immunology, Department of Internal Medicine, University of California at Davis, Davis, CA 95616
| | - Vijay K Kuchroo
- Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115
| | - Frank O Nestle
- Division of Genetics and Molecular Medicine, St. John's Institute of Dermatology, King's College London School of Medicine, Guy's Hospital, London SE1 9RT, United Kingdom; and
| | - Iannis E Adamopoulos
- Division of Rheumatology, Allergy and Clinical Immunology, Department of Internal Medicine, University of California at Davis, Davis, CA 95616; .,Institute for Pediatric Regenerative Medicine, Shriners Hospitals for Children Northern California, Sacramento, CA 95817
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236
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Nauseef WM, Kubes P. Pondering neutrophil extracellular traps with healthy skepticism. Cell Microbiol 2016; 18:1349-57. [PMID: 27470975 PMCID: PMC5025378 DOI: 10.1111/cmi.12652] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 07/22/2016] [Accepted: 07/25/2016] [Indexed: 12/12/2022]
Abstract
The authors engage in a dialogue that evaluates critically the state of the study of neutrophil extracellular traps (NETs), a phenomenon currently the object of considerable interest, with the goal of identifying those aspects that merit clarification in order to assign the process its proper place in our current understanding of cell biology. Since the seminal observations in the Zychlinsky laboratory that described the extrusion of filaments of nuclear DNA associated with histones and granule proteins from neutrophils stimulated in vitro, many investigators have examined the phenomenon of NET formation in numerous and diverse settings. However, an overview of work in this rapidly growing field prompts several fundamental questions about NETs, including their precise composition, the mechanisms by which they arise, their clinical relevance, and the interrelationship of those observed in vitro and in vivo. In this discussion, the authors challenge interpretation of data from some experimental settings and provide recommendations for specific studies that would address the concerns raised, improve understanding of the biological relevance of NETs, and strengthen the field.
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Affiliation(s)
- William M Nauseef
- Inflammation Program and Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, and Veterans Administration Medical Center, Iowa City, Iowa, 52240, USA.
| | - Paul Kubes
- Department of Physiology and Pharmacology, Immunology Research Group, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Alberta, T2N 4N1, Canada.
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237
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Shiogama K, Onouchi T, Mizutani Y, Sakurai K, Inada KI, Tsutsumi Y. Visualization of Neutrophil Extracellular Traps and Fibrin Meshwork in Human Fibrinopurulent Inflammatory Lesions: I. Light Microscopic Study. Acta Histochem Cytochem 2016; 49:109-16. [PMID: 27682014 PMCID: PMC5011235 DOI: 10.1267/ahc.16015] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2016] [Accepted: 06/17/2016] [Indexed: 12/17/2022] Open
Abstract
Neutrophil extracellular traps (NETs) are extracellular fibrillary structures composed of degraded chromatin and granules of neutrophil origin. In fibrinopurulent inflammation such as pneumonia and abscess, deposition of fibrillar eosinophilic material is a common histopathological finding under hematoxylin-eosin staining. Expectedly, not only fibrin fibrils but also NETs consist of the fibrillar material. The aim of the present study is to analyze immunohistochemically how NETs are involved in the inflammatory process. Archival formalin-fixed, paraffin-embedded sections accompanying marked neutrophilic infiltration were the target of analysis. Neutrophil-associated substances (citrullinated histone H3, lactoferrin, myeloperoxidase and neutrophil elastase) were evaluated as NETs markers, while fibrinogen gamma chain was employed as a fibrin marker. Light microscopically, the fibrils were categorized into three types: thin, thick and clustered thick. Lactoferrin represented a good and stable NETs marker. Thin fibrils belonged to NETs. Thick fibrils are composed of either mixed NETs and fibrin or fibrin alone. Clustered thick fibrils were solely composed of fibrin. Neutrophils were entrapped within the fibrilllar meshwork of the thin and thick types. Apoptotic cells immunoreactive to cleaved caspase 3 and cleaved actin were dispersed in the NETs. In conclusion, NETs and fibrin meshwork were consistently recognizable by immunostaining for lactoferrin and fibrinogen gamma chain.
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Affiliation(s)
- Kazuya Shiogama
- Department of Pathology, Fujita Health University School of Medicine
| | - Takanori Onouchi
- Department of Pathology, Fujita Health University School of Medicine
| | | | - Kouhei Sakurai
- Department of Diagnostic Pathology, Banbuntane-Houtokukai Hospital, Fujita Health University School of Medicine
| | - Ken-ichi Inada
- Department of Diagnostic Pathology, Banbuntane-Houtokukai Hospital, Fujita Health University School of Medicine
| | - Yutaka Tsutsumi
- Department of Pathology, Fujita Health University School of Medicine
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Lin CF, Chen CL, Chien SY, Tseng PC, Wang YC, Tsai TT. Oxidative Stress Facilitates IFN-γ-Induced Mimic Extracellular Trap Cell Death in A549 Lung Epithelial Cancer Cells. PLoS One 2016; 11:e0162157. [PMID: 27575372 PMCID: PMC5004888 DOI: 10.1371/journal.pone.0162157] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2015] [Accepted: 08/18/2016] [Indexed: 01/01/2023] Open
Abstract
We previously demonstrated that IFN-γ induces an autophagy-regulated mimic extracellular trap cell death (ETosis) in A549 human lung cancer cells. Regarding reactive oxygen species (ROS) are involved in ETosis, this study investigated the role of oxidative stress. After IFN-γ stimulation, a necrosis-like cell death mimic ETosis occurred accompanied by the inhibition of cell growth, aberrant nuclear staining, and nucleosome release. ROS were generated in a time-dependent manner with an increase in NADPH oxidase component protein expression. STAT1-mediated IFN regulatory factor-1 activation was essential for upregulating ROS production. By genetically silencing p47phox, IFN-γ-induced ROS and mimic ETosis were significantly attenuated. This mechanistic study indicated that ROS may mediate DNA damage followed by histone H3 citrullination. Furthermore, ROS promoted IFN-γ-induced mimic ETosis in cooperation with autophagy. These findings further demonstrate that ROS regulates IFN-γ-induced mimic ETosis in lung epithelial malignancy.
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Affiliation(s)
- Chiou-Feng Lin
- Department of Microbiology and Immunology, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110, Taiwan
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei 110, Taiwan
- * E-mail:
| | - Chia-Ling Chen
- Translational Research Center, Taipei Medical University, Taipei 110, Taiwan
| | - Shun-Yi Chien
- Department of Microbiology and Immunology, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110, Taiwan
| | - Po-Chun Tseng
- Department of Microbiology and Immunology, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110, Taiwan
| | - Yu-Chih Wang
- Department of Microbiology and Immunology, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110, Taiwan
| | - Tsung-Ting Tsai
- Department of Microbiology and Immunology, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110, Taiwan
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239
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Akk A, Springer LE, Pham CTN. Neutrophil Extracellular Traps Enhance Early Inflammatory Response in Sendai Virus-Induced Asthma Phenotype. Front Immunol 2016; 7:325. [PMID: 27617014 PMCID: PMC4999646 DOI: 10.3389/fimmu.2016.00325] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 08/15/2016] [Indexed: 12/30/2022] Open
Abstract
Paramyxoviral infection in childhood has been linked to a significant increased rate of asthma development. In mice, paramyxoviral infection with the mouse parainfluenza virus type I, Sendai virus (Sev), causes a limited bronchiolitis followed by persistent asthma traits. We have previously shown that the absence of cysteine protease dipeptidyl peptidase I (DPPI) dampened the acute lung inflammatory response and the subsequent asthma phenotype induced by Sev. Adoptive transfer of wild-type neutrophils into DPPI-deficient mice restored leukocyte influx, the acute cytokine response, and the subsequent mucous cell metaplasia that accompanied Sev-induced asthma phenotype. However, the exact mechanism by which DPPI-sufficient neutrophils promote asthma development following Sev infection is still unknown. We hypothesize that neutrophils recruited to the alveolar space following Sev infection elaborate neutrophil extracellular traps (NETs) that propagate the inflammatory cascade, culminating in the eventual asthma phenotype. Indeed, we found that Sev infection was associated with NET formation in the lung and release of cell-free DNA complexed to myeloperoxidase in the alveolar space and plasma that peaked on day 2 post infection. Absence of DPPI significantly attenuated Sev-induced NET formation in vivo and in vitro. Furthermore, concomitant administration of DNase 1, which dismantled NETs, or inhibition of peptidylarginine deiminase 4 (PAD4), an essential mediator of NET formation, suppressed the early inflammatory responses to Sev infection. Lastly, NETs primed bone marrow-derived cells to release cytokines that can amplify the inflammatory cascade.
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Affiliation(s)
- Antonina Akk
- Department of Medicine, Division of Rheumatology, Washington University School of Medicine , Saint Louis, MO , USA
| | - Luke E Springer
- Department of Medicine, Division of Rheumatology, Washington University School of Medicine , Saint Louis, MO , USA
| | - Christine T N Pham
- Department of Medicine, Division of Rheumatology, Washington University School of Medicine , Saint Louis, MO , USA
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240
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Wątły J, Potocki S, Rowińska-Żyrek M. Zinc Homeostasis at the Bacteria/Host Interface-From Coordination Chemistry to Nutritional Immunity. Chemistry 2016; 22:15992-16010. [DOI: 10.1002/chem.201602376] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Indexed: 12/17/2022]
Affiliation(s)
- Joanna Wątły
- Faculty of Chemistry; University of Wroclaw; F. Joliot-Curie 14 50-383 Wroclaw Poland
| | - Sławomir Potocki
- Faculty of Chemistry; University of Wroclaw; F. Joliot-Curie 14 50-383 Wroclaw Poland
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241
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Okubo K, Kamiya M, Urano Y, Nishi H, Herter JM, Mayadas T, Hirohama D, Suzuki K, Kawakami H, Tanaka M, Kurosawa M, Kagaya S, Hishikawa K, Nangaku M, Fujita T, Hayashi M, Hirahashi J. Lactoferrin Suppresses Neutrophil Extracellular Traps Release in Inflammation. EBioMedicine 2016; 10:204-15. [PMID: 27453322 PMCID: PMC5006695 DOI: 10.1016/j.ebiom.2016.07.012] [Citation(s) in RCA: 99] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2016] [Revised: 07/10/2016] [Accepted: 07/12/2016] [Indexed: 11/19/2022] Open
Abstract
Neutrophils are central players in the innate immune system. They generate neutrophil extracellular traps (NETs), which protect against invading pathogens but are also associated with the development of autoimmune and/or inflammatory diseases and thrombosis. Here, we report that lactoferrin, one of the components of NETs, translocated from the cytoplasm to the plasma membrane and markedly suppressed NETs release. Furthermore, exogenous lactoferrin shrunk the chromatin fibers found in released NETs, without affecting the generation of oxygen radicals, but this failed after chemical removal of the positive charge of lactoferrin, suggesting that charge-charge interactions between lactoferrin and NETs were required for this function. In a model of immune complex-induced NET formation in vivo, intravenous lactoferrin injection markedly reduced the extent of NET formation. These observations suggest that lactoferrin serves as an intrinsic inhibitor of NETs release into the circulation. Thus, lactoferrin may represent a therapeutic lead for controlling NETs release in autoimmune and/or inflammatory diseases.
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Affiliation(s)
- Koshu Okubo
- Department of Nephrology and Endocrinology, Graduate School of Medicine, The University of Tokyo, Japan; Apheresis and Dialysis Center, School of Medicine, Keio University, Japan; Department of General Medicine, School of Medicine, Keio University, Japan
| | - Mako Kamiya
- Laboratory of Chemical Biology & Molecular Imaging, Graduate School of Medicine, The University of Tokyo, Japan
| | - Yasuteru Urano
- Laboratory of Chemical Biology & Molecular Imaging, Graduate School of Medicine, The University of Tokyo, Japan
| | - Hiroshi Nishi
- Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, United States
| | - Jan M Herter
- Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, United States
| | - Tanya Mayadas
- Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, United States
| | - Daigoro Hirohama
- Department of Nephrology and Endocrinology, Graduate School of Medicine, The University of Tokyo, Japan; Research Center for Advanced Science and Technology, The University of Tokyo, Japan
| | - Kazuo Suzuki
- Inflammation Program, Graduate School of Medicine, Chiba University, Japan
| | - Hiroshi Kawakami
- Division of Food and Nutrition, Graduate School of Human Sciences, Kyoritsu Women's University, Japan
| | - Mototsugu Tanaka
- Department of Nephrology and Endocrinology, Graduate School of Medicine, The University of Tokyo, Japan
| | - Miho Kurosawa
- Department of Nephrology and Endocrinology, Graduate School of Medicine, The University of Tokyo, Japan; Department of General Medicine, School of Medicine, Keio University, Japan
| | | | - Keiichi Hishikawa
- Department of Advanced Nephrology and Regenerative Medicine, The University of Tokyo, Japan
| | - Masaomi Nangaku
- Department of Nephrology and Endocrinology, Graduate School of Medicine, The University of Tokyo, Japan
| | - Toshiro Fujita
- Department of Nephrology and Endocrinology, Graduate School of Medicine, The University of Tokyo, Japan; Research Center for Advanced Science and Technology, The University of Tokyo, Japan
| | - Matsuhiko Hayashi
- Apheresis and Dialysis Center, School of Medicine, Keio University, Japan; Department of General Medicine, School of Medicine, Keio University, Japan
| | - Junichi Hirahashi
- Department of Nephrology and Endocrinology, Graduate School of Medicine, The University of Tokyo, Japan; Apheresis and Dialysis Center, School of Medicine, Keio University, Japan; Department of General Medicine, School of Medicine, Keio University, Japan.
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242
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NETosis markers: Quest for specific, objective, and quantitative markers. Clin Chim Acta 2016; 459:89-93. [DOI: 10.1016/j.cca.2016.05.029] [Citation(s) in RCA: 125] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 05/24/2016] [Accepted: 05/30/2016] [Indexed: 01/13/2023]
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243
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Hoffmann JHO, Enk AH. Neutrophil extracellular traps in dermatology: Caught in the NET. J Dermatol Sci 2016; 84:3-10. [PMID: 27481818 DOI: 10.1016/j.jdermsci.2016.07.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 07/03/2016] [Accepted: 07/04/2016] [Indexed: 01/21/2023]
Abstract
Neutrophil, or polymorphonuclear granulocytes (PMN) constitute the most abundant type of leucocytes in peripheral human blood. One of the major advances in the last decade was the discovery of neutrophil extracellular trap (NET) formation: a process by which neutrophils externalize web-like chromatin strands decorated with antimicrobial peptides. These structures were soon implicated in immune defense and auto-immunity alike and now link neutrophils to the pathogenesis of a variety of diseases of dermatological relevance. Currently, NET formation is mainly subdivided into suicidal and vital NETosis. Controversy exists regarding the capacity of NETs to kill pathogens, and little is known about the way NETs are formed in vivo. Here, we discuss the current terminology, methods for NET quantification, pathways leading to NET formation, and the role of NETs in systemic and cutaneous immune defense and auto-immunity, with a focus on psoriasis and systemic lupus erythematosus.
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Affiliation(s)
| | - Alexander H Enk
- Department of Dermatology, University of Heidelberg, Germany
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244
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Abstract
During apoptosis or activation, cells can release a subcellular structure, called a membrane microvesicle (also known as microparticle) into the extracellular environment. Microvesicles bud-off as a portion of cell membrane with its associated proteins and lipids surrounding a cytosolic core that contains intracellular proteins, lipids, and nucleic acids (DNA, RNA, siRNA, microRNA, lncRNA). Biologically active molecules on the microvesicle surface and encapsulated within can act on recipient cells as a novel mode of intercellular communication. Apoptosis has long been known to be involved in the development of diseases of autoimmunity. Abnormally persistent microvesicles, particularly apoptotic microvesicles, can accelerate autoimmune responses locally in specific organs and tissues as well as systemically. In this review, we focus on studies implicating microvesicles in the pathogenesis of autoimmune diseases and their complications.
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245
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Salvesen GS, Hempel A, Coll NS. Protease signaling in animal and plant-regulated cell death. FEBS J 2016; 283:2577-98. [PMID: 26648190 PMCID: PMC5606204 DOI: 10.1111/febs.13616] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 11/23/2015] [Accepted: 11/30/2015] [Indexed: 12/26/2022]
Abstract
This review aims to highlight the proteases required for regulated cell death mechanisms in animals and plants. The aim is to be incisive, and not inclusive of all the animal proteases that have been implicated in various publications. The review also aims to focus on instances when several publications from disparate groups have demonstrated the involvement of an animal protease, and also when there is substantial biochemical, mechanistic and genetic evidence. In doing so, the literature can be culled to a handful of proteases, covering most of the known regulated cell death mechanisms: apoptosis, regulated necrosis, necroptosis, pyroptosis and NETosis in animals. In plants, the literature is younger and not as extensive as for mammals, although the molecular drivers of vacuolar death, necrosis and the hypersensitive response in plants are becoming clearer. Each of these death mechanisms has at least one proteolytic component that plays a major role in controlling the pathway, and sometimes they combine in networks to regulate cell death/survival decision nodes. Some similarities are found among animal and plant cell death proteases but, overall, the pathways that they govern are kingdom-specific with very little overlap.
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Affiliation(s)
- Guy S. Salvesen
- Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Anne Hempel
- Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Nuria Sanchez Coll
- Centre for Research in Agricultural Genomics, Campus UAB, Edifici CRAG, Bellaterra 08193, Barcelona, Spain
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246
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Söderberg D, Segelmark M. Neutrophil Extracellular Traps in ANCA-Associated Vasculitis. Front Immunol 2016; 7:256. [PMID: 27446086 PMCID: PMC4928371 DOI: 10.3389/fimmu.2016.00256] [Citation(s) in RCA: 133] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2016] [Accepted: 06/15/2016] [Indexed: 12/13/2022] Open
Abstract
A group of pauci-immune vasculitides, characterized by neutrophil-rich necrotizing inflammation of small vessels and the presence of antineutrophil cytoplasmic antibodies (ANCAs), is referred to as ANCA-associated vasculitis (AAV). ANCAs against proteinase 3 (PR3) (PR3-ANCA) or myeloperoxidase (MPO) (MPO-ANCA) are found in over 90% of patients with active disease, and these ANCAs are implicated in the pathogenesis of AAV. Dying neutrophils surrounding the walls of small vessels are a histological hallmark of AAV. Traditionally, it has been assumed that these neutrophils die by necrosis, but neutrophil extracellular traps (NETs) have recently been visualized at the sites of vasculitic lesions. AAV patients also possess elevated levels of NETs in the circulation. ANCAs are capable of inducing NETosis in neutrophils, and their potential to do so has been shown to be affinity dependent and to correlate with disease activity. Neutrophils from AAV patients are also more prone to release NETs spontaneously than neutrophils from healthy blood donors. NETs contain proinflammatory proteins and are thought to contribute to vessel inflammation directly by damaging endothelial cells and by activating the complement system and indirectly by acting as a link between the innate and adaptive immune system through the generation of PR3- and MPO-ANCA. Injection of NET-loaded myeloid dendritic cells into mice results in circulating PR3- and MPO-ANCA and the development of AAV-like disease. NETs have also been shown to be essential in a rodent model of drug-induced vasculitis. NETs induced by propylthiouracil could not be degraded by DNaseI, implying that disordered NETs might be important for the generation of ANCAs. NET degradation was also highlighted in another study showing that AAV patients have reduced DNaseI activity resulting in less NET degradation. With this in mind, it might be that prolonged exposure to proteins in the NETs due to the overproduction of NETs and/or reduced clearance of NETs is important in AAV. However, not all ANCAs are pathogenic and some might possibly also aid in the clearance of NETs. A dual role for ANCAs in relation to circulating NET levels has been proposed because a negative correlation was observed between PR3-ANCA and NET remnants in patients in remission.
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Affiliation(s)
- Daniel Söderberg
- Department of Medical and Health Sciences, Linköping University , Linköping , Sweden
| | - Mårten Segelmark
- Department of Medical and Health Sciences, Linköping University, Linköping, Sweden; Department of Nephrology, Linköping University, Linköping, Sweden
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247
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Hwang JY, Randall TD, Silva-Sanchez A. Inducible Bronchus-Associated Lymphoid Tissue: Taming Inflammation in the Lung. Front Immunol 2016; 7:258. [PMID: 27446088 PMCID: PMC4928648 DOI: 10.3389/fimmu.2016.00258] [Citation(s) in RCA: 119] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 06/17/2016] [Indexed: 01/09/2023] Open
Abstract
Following pulmonary inflammation, leukocytes that infiltrate the lung often assemble into structures known as inducible Bronchus-Associated Lymphoid Tissue (iBALT). Like conventional lymphoid organs, areas of iBALT have segregated B and T cell areas, specialized stromal cells, high endothelial venules, and lymphatic vessels. After inflammation is resolved, iBALT is maintained for months, independently of inflammation. Once iBALT is formed, it participates in immune responses to pulmonary antigens, including those that are unrelated to the iBALT-initiating antigen, and often alters the clinical course of disease. However, the mechanisms that govern immune responses in iBALT and determine how iBALT impacts local and systemic immunity are poorly understood. Here, we review our current understanding of iBALT formation and discuss how iBALT participates in pulmonary immunity.
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Affiliation(s)
- Ji Young Hwang
- Division of Clinical Immunology and Rheumatology, Department of Medicine, University of Alabama at Birmingham , Birmingham, AL , USA
| | - Troy D Randall
- Division of Clinical Immunology and Rheumatology, Department of Medicine, University of Alabama at Birmingham , Birmingham, AL , USA
| | - Aaron Silva-Sanchez
- Division of Clinical Immunology and Rheumatology, Department of Medicine, University of Alabama at Birmingham , Birmingham, AL , USA
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248
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Yan H, Zhou HF, Akk A, Hu Y, Springer LE, Ennis TL, Pham CTN. Neutrophil Proteases Promote Experimental Abdominal Aortic Aneurysm via Extracellular Trap Release and Plasmacytoid Dendritic Cell Activation. Arterioscler Thromb Vasc Biol 2016; 36:1660-1669. [PMID: 27283739 DOI: 10.1161/atvbaha.116.307786] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 05/27/2016] [Indexed: 12/16/2022]
Abstract
OBJECTIVE We previously established that neutrophil-derived dipeptidyl peptidase I (DPPI) is essential for experimental abdominal aortic aneurysm (AAA) development. Because DPPI activates several neutrophil serine proteases, it remains to be determined whether the AAA-promoting effect of DPPI is mediated by neutrophil serine proteases. APPROACH AND RESULTS Using an elastase-induced AAA model, we demonstrate that the absence of 2 neutrophil serine proteases, neutrophil elastase and proteinase-3, recapitulates the AAA-resistant phenotype of DPPI-deficient mice. DPPI and neutrophil serine proteases direct the in vitro and in vivo release of extracellular structures termed neutrophil extracellular traps (NETs). Administration of DNase1, which dismantles NETs, suppresses elastase-induced AAA in wild-type animals and in DPPI-deficient mice reconstituted with wild-type neutrophils. NETs also contain the cathelicidin-related antimicrobial peptide that complexes with self-DNA in recruiting plasmacytoid dendritic cells (pDCs), inducing type I interferons (IFNs) and promoting AAA in DPPI-deficient mice. Conversely, depletion of pDCs or blockade of type I IFNs suppresses experimental AAA. Moreover, we find an abundance of human cathelicidin peptide, a 37 amino acid sequence starting with 2 leucines and the human orthologue of cathelicidin-related antimicrobial peptide, in the vicinity of pDCs in human AAA tissues. Increased type I IFN mRNA expression is observed in human AAA tissues and circulating IFN-α is detected in ≈50% of the AAA sera examined. CONCLUSIONS These results suggest that neutrophil protease-mediated NET release contributes to elastase-induced AAA through pDC activation and type I IFN production. These findings increase our understanding of the pathways underlying AAA inflammatory responses and suggest that limiting NET, pDC, and type I IFN activities may suppress aneurysm progression.
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Affiliation(s)
- Huimin Yan
- John Cochran VA Medical Center, Saint Louis, Missouri USA; the Department of Medicine, Division of Rheumatology and the Department of Surgery, Section of Vascular Surgery, Washington University School of Medicine, Saint Louis, Missouri, USA
| | - Hui-Fang Zhou
- John Cochran VA Medical Center, Saint Louis, Missouri USA; the Department of Medicine, Division of Rheumatology and the Department of Surgery, Section of Vascular Surgery, Washington University School of Medicine, Saint Louis, Missouri, USA
| | - Antonina Akk
- John Cochran VA Medical Center, Saint Louis, Missouri USA; the Department of Medicine, Division of Rheumatology and the Department of Surgery, Section of Vascular Surgery, Washington University School of Medicine, Saint Louis, Missouri, USA
| | - Ying Hu
- John Cochran VA Medical Center, Saint Louis, Missouri USA; the Department of Medicine, Division of Rheumatology and the Department of Surgery, Section of Vascular Surgery, Washington University School of Medicine, Saint Louis, Missouri, USA
| | - Luke E Springer
- John Cochran VA Medical Center, Saint Louis, Missouri USA; the Department of Medicine, Division of Rheumatology and the Department of Surgery, Section of Vascular Surgery, Washington University School of Medicine, Saint Louis, Missouri, USA
| | - Terri L Ennis
- John Cochran VA Medical Center, Saint Louis, Missouri USA; the Department of Medicine, Division of Rheumatology and the Department of Surgery, Section of Vascular Surgery, Washington University School of Medicine, Saint Louis, Missouri, USA
| | - Christine T N Pham
- John Cochran VA Medical Center, Saint Louis, Missouri USA; the Department of Medicine, Division of Rheumatology and the Department of Surgery, Section of Vascular Surgery, Washington University School of Medicine, Saint Louis, Missouri, USA
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249
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Tran TM, MacIntyre A, Hawes M, Allen C. Escaping Underground Nets: Extracellular DNases Degrade Plant Extracellular Traps and Contribute to Virulence of the Plant Pathogenic Bacterium Ralstonia solanacearum. PLoS Pathog 2016; 12:e1005686. [PMID: 27336156 PMCID: PMC4919084 DOI: 10.1371/journal.ppat.1005686] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Accepted: 05/18/2016] [Indexed: 12/21/2022] Open
Abstract
Plant root border cells have been recently recognized as an important physical defense against soil-borne pathogens. Root border cells produce an extracellular matrix of protein, polysaccharide and DNA that functions like animal neutrophil extracellular traps to immobilize pathogens. Exposing pea root border cells to the root-infecting bacterial wilt pathogen Ralstonia solanacearum triggered release of DNA-containing extracellular traps in a flagellin-dependent manner. These traps rapidly immobilized the pathogen and killed some cells, but most of the entangled bacteria eventually escaped. The R. solanacearum genome encodes two putative extracellular DNases (exDNases) that are expressed during pathogenesis, suggesting that these exDNases contribute to bacterial virulence by enabling the bacterium to degrade and escape root border cell traps. We tested this hypothesis with R. solanacearum deletion mutants lacking one or both of these nucleases, named NucA and NucB. Functional studies with purified proteins revealed that NucA and NucB are non-specific endonucleases and that NucA is membrane-associated and cation-dependent. Single ΔnucA and ΔnucB mutants and the ΔnucA/B double mutant all had reduced virulence on wilt-susceptible tomato plants in a naturalistic soil-soak inoculation assay. The ΔnucA/B mutant was out-competed by the wild-type strain in planta and was less able to stunt root growth or colonize plant stems. Further, the double nuclease mutant could not escape from root border cells in vitro and was defective in attachment to pea roots. Taken together, these results demonstrate that extracellular DNases are novel virulence factors that help R. solanacearum successfully overcome plant defenses to infect plant roots and cause bacterial wilt disease.
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Affiliation(s)
- Tuan Minh Tran
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - April MacIntyre
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Martha Hawes
- Department of Soil, Water and Environmental Science, University of Arizona, Tucson, Arizona, United States of America
| | - Caitilyn Allen
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
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250
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Effect of Continuous-Wave Low-Intensity Ultrasound in Inflammatory Resolution of Arthritis-Associated Synovitis. Phys Ther 2016; 96:808-17. [PMID: 26586863 DOI: 10.2522/ptj.20140559] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Accepted: 11/10/2015] [Indexed: 11/17/2022]
Abstract
BACKGROUND Low-intensity ultrasound (LIUS) can reduce pain and improve function in arthritic joints. Neutrophils are first-line actors in host defense that recruit macrophages. Dead neutrophils are removed during resolution of inflammation. Delayed neutrophil clearance can lead to extended inflammation or even chronic autoimmune disease. Although neutrophil extracellular traps (NETs) in arthritic tissue are involved in the pathogenesis of arthritis, their functional role has not been clarified. OBJECTIVES This study aimed to investigate the effect of LIUS on synovial inflammation and its resolution via neutrophil clearance. METHODS Synovitis was induced by intra-articular injection of complete Freund's adjuvant (CFA) into the left knee joint of 58 adult male Sprague-Dawley rats. Low-intensity ultrasound (1 MHz, 200 mW/cm(2)) was applied for 10 minutes daily. Neutrophil clearance was assessed with the expression of myeloperoxidase (MPO). In addition, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining and NET formation in the synovium were observed. In neutrophil and macrophage cultures from peripheral blood, the effect of NET clearance by LIUS was investigated. RESULTS In CFA-induced synovitis, MPO-positive neutrophils peaked after 2 to 3 days, filling the inflammatory core. Monocytes and macrophages in the periphery later infiltrated the core and were reduced thereafter. Low-intensity ultrasound reduced synovial hyperplasia and induced earlier MPO clearance. Neutrophils in the core of the inflamed synovium exhibited NET formation, which LIUS increased. Low-intensity also induced NETs in peripheral polymorphonuclear cells in an intensity-dependent manner and potentiated phorbol myristate acetate (PMA)-induced NETosis. The PMA-induced NETs were cleared by macrophages; clearance was enhanced by LIUS. LIMITATIONS The effect of LIUS on CFA-induced inflammation was observed only during the acute phase. Although the effect of LIUS on NETosis in the in vitro neutrophil culture system was clear, the in vivo NETosis cannot be quantified. CONCLUSIONS Neutrophil extracellular traps act in inflammatory synovitis, and LIUS enhanced the NETs and resulted in neutrophil clearance by enhancing the phagocytosis of macrophages, which might be a factor underlying the therapeutic effect of LIUS in arthritic synovium.
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