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Rac2 is Required for Formation of Extracellular Traps in NeutrophilsLim, Byung Hyun 25 August 2011 (has links)
Recently, it was found that pathogens are trapped and killed by neutrophil extracellular traps (NETs). The role of Rac small GTPases is explored in the formation of NET using neutrophils lacking Rac1, Rac2 or both isoforms. NET formation was observed in both wild-type and Rac1-null neutrophils. In contrast, NET formation was markedly impaired in cells lacking either Rac2 or both Rac2 and Rac1. The defect in NET formation in Rac2-null cells was rescued in the presence of exogenous reactive oxygen species sources, suggesting that Rac2-mediated ROS generation is required. In addition, the role of nitric oxide in NET formation is assessed. Blocking NO production with the nitric oxide synthase inhibitor L-NAME significantly reduced NET formation. Moreover, Rac2-null cells produced significantly less NO than Rac1-null cells or their wild type counterparts. Our data suggest that Rac2 is essential for NET formation via pathways involving both ROS and NO.
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Rac2 is Required for Formation of Extracellular Traps in NeutrophilsLim, Byung Hyun 25 August 2011 (has links)
Recently, it was found that pathogens are trapped and killed by neutrophil extracellular traps (NETs). The role of Rac small GTPases is explored in the formation of NET using neutrophils lacking Rac1, Rac2 or both isoforms. NET formation was observed in both wild-type and Rac1-null neutrophils. In contrast, NET formation was markedly impaired in cells lacking either Rac2 or both Rac2 and Rac1. The defect in NET formation in Rac2-null cells was rescued in the presence of exogenous reactive oxygen species sources, suggesting that Rac2-mediated ROS generation is required. In addition, the role of nitric oxide in NET formation is assessed. Blocking NO production with the nitric oxide synthase inhibitor L-NAME significantly reduced NET formation. Moreover, Rac2-null cells produced significantly less NO than Rac1-null cells or their wild type counterparts. Our data suggest that Rac2 is essential for NET formation via pathways involving both ROS and NO.
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Etude des neutrophiles, des « neutrophil extracellular traps » et de la protéine C1q du complément dans les réponses inflammatoires : conséquences physiopathologiques dans la polyarthrite rhumatoïde et un modèle expérimental / Study of neutrophils, neutrophil cellular traps, and the complement protein C1q in inflammatory responses : physiopathological consequences in rheumatoid arthritis and an experimental modelRibon, Matthieu 19 June 2015 (has links)
La polyarthrite rhumatoïde (PR) est une maladie auto-immune inflammatoire. La PR touche les articulations jusqu'à les détruire. Elle est caractérisée par la présence d’anticorps anti protéines citrullinées (ACPA) mais l’auto-antigène n’est toujours pas connu. Dans cette maladie, l’implication de l’immunité adaptative ne fait donc aucun doute mais le rôle de l’immunité innée reste encore flou. Le système du complément joue un rôle important dans l’immunité innée tout comme les récepteurs de type Toll (TLR) qui sont des récepteurs de celle-ci. C1q, par la reconnaissance des ses ligands, active une des voies du complément, la voie classique. Chez les patients atteints de PR, le complément est activé et un dépôt de C1q est retrouvé dans l’articulation. Le TLR9 reconnaît des ADN dérivés de bactéries ou de virus mais une expression à la surface des cellules pourrait conduire à la reconnaissance d’autres motifs comme les signaux de danger (DAMP). D’ailleurs, nous avons montré récemment qu’il existait un TLR9 exprimé à la surface des polynucléaires neutrophiles (PNN). Enfin, il a été mis en évidence récemment un nouveau mécanisme bactéricide effectué par les PNN : la formation de NET (neutrophil extracellular traps). Mais en dehors de leur rôle bactéricide, les NET ont été montrés comme pathogènes dans certaines maladies comme le lupus. Dans ce travail de thèse, je me suis intéressé à l’implication de ces acteurs, NET, C1q et TLR9 dans la PR. Nous avons montré que C1q est indispensable au développement de l’arthrite dans un modèle animal. De plus, l’expression des récepteurs au C1q par les PNN et les monocytes est corrélée à l’activité de la maladie et à l’inflammation. Nous avons montré que les NET représentent une cible pour les ACPA (ce qui en fait des auto-antigènes potentiels dans la PR) et que ces NET sont immunogènes. L’immunogénicité des NET est modulée par C1q. Enfin, il semblerait que le TLR9 ait moins d’importance dans l’arthrite. Par ce travail, nous avons montré l’importance du rôle joué par l’immunité innée dans la PR et ses modèles. / Rheumatoid artthritis (RA) is the most frequent rheumatic disease. This auto-immune disease causes pain and joint destruction. RA has been characterized by adaptative immunity involvement and anti-citrullinated protein antibodies (ACPA) production. Involvement of innate immunity is less investigated. Complement system, part of innate immunity, is activated in RA. C1q activates classical complement pathway by binding its ligands. C1q is found in joint of RA patients. On the other hand Toll-like-receptor (TLR), innate receptors could play a role in RA upon recognition of pathogen-derived DNA (TLR9). Cell surface expression of TLR9 has been reported as potentially pathological, and we describe that polymorphonuclear neutrophils (PMN) express a cell surface TLR9 wich could recognize damage associated molecular pattern (DAMP). Finally, neutrophil extracellular traps (NET) wich are expelled chromatin fiber and represent a physiological response to bacteria, have been reported as pathological in certain circumstances. We investigated the role of those three innate actors in RA. We have shown that C1q is mandatory to develop experimental arthritis and expression of their receptors on RA patient PMN and monocytes is correlated with disease activity and inflammation. We have also shown that NET are immunogenic and this immunogenicity is partly modulated and mediated by C1q. NET might trigger ACPA production in RA. Finally, it seems that involvement of TLR9 is less important in RA. With those experiments we have shown that the involvement of innate immunity in RA is more important than that has been reported so far.
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Neutrophil extracellular traps in thrombosis and inflammationMartinod, Kim Lindsay 01 January 2016 (has links)
Neutrophil extracellular traps (NETs), chromatin released by activated neutrophils, were first described for their antimicrobial properties. NETs have a backbone of DNA and histones lined with microbicidal proteins such as neutrophil elastase. NET release has pathological consequences, particularly within blood vessels where NETs can trap red blood cells and platelets, thus contributing to thrombosis (Chapter 1-Overview). NET formation (NETosis) is an active and coordinated biological process involving many enzymatic components. One enzyme in particular, peptidylarginine deiminase 4 (PAD4), citrullinates histones and is required for chromatin decondensation during NETosis. Neutrophils from PAD4-deficient mice are unable to form NETs. We obtained these mice from our collaborator Dr. Yanming Wang, and thus were able to compare PAD4-/- mice to wild-type (WT) mice in mouse models where NETs are formed. These studies have allowed for investigation of the biological relevance of PAD4 and NETs in vivo in thrombotic and/or inflammatory disease.
This dissertation focuses on mouse models of deep vein thrombosis and of sepsis. In venous stenosis, thrombosis is initiated by restricting blood flow in the inferior vena cava (IVC). Here, PAD4-/- mice were greatly protected from thrombus formation (Chapter 2). Leukocyte rolling and platelet plug formation in response to vessel injury were unaffected, indicating that endothelial and platelet activation occurred normally in these mice. The mice did not exhibit any defects in hemostasis, and could be induced to produce deep vein thrombi by infusion of WT neutrophils that formed NETs as a part of the thrombus scaffold. Because there is potential to develop anti-NET therapies in thrombosis, I investigated if NET-deficiency would render mice immunocompromised (Chapter 3). PAD4-/- mice had similar mortality in the cecal ligation puncture model, and they were protected from shock in an LPS sepsis model where NETs are released in the absence of live bacteria. Therapies aimed at NET prevention or destruction would likely be beneficial without compromising host immunity. Thus, in summary, studying PAD4-deficient mice has revealed the impact of NETs in thrombotic/inflammatory disease and identified PAD4 as an attractive therapeutic target.
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Neutrophil Extracellular Traps Promote Metastases of Colorectal Cancers through Activation of ERK Signaling by Releasing Neutrophil Elastase / 好中球細胞外トラップは好中球エラスターゼによるERKシグナルの活性化を介して大腸癌の転移を促進するOkamoto, Michio 23 May 2023 (has links)
京都大学 / 新制・課程博士 / 博士(医学) / 甲第24798号 / 医博第4990号 / 新制||医||1066(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 萩原 正敏, 教授 妹尾 浩, 教授 竹内 理 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM
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Limited Capacity of Fetal Neutrophils to Form Extracellular TrapsThompson, Ravyn January 2021 (has links)
No description available.
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Etude de la nétose du polynucléaire neutrophile dans deux modèles de réactions allergiques : le choc anaphylactique aux curares et l’asthme / Study of neutrophil netosis in two models of allergic reactions : NMBA anaphylaxis and asthmaGranger, Vanessa 29 October 2018 (has links)
La nétose du polynucléaire neutrophile (PN) correspond à la libération de filaments d’ADN recouverts de protéines appelés Neutrophil Extracellular Trap (NETs). Outre leur rôle anti-infectieux, les NETs représentent des acteurs émergents de nombreuses pathologies inflammatoires et nous avons souhaité évaluer leur implication au cours de réactions allergiques.Au cours d’une étude clinique multicentrique notre équipe a mis en évidence un mécanisme alternatif de l’anaphylaxie aux curares, impliquant les PN. La phase aiguë de ces réactions s’accompagne d’une libération de NETs dont la concentration est corrélée avec la sévérité et avec une diminution de l’expression des récepteurs activateurs des IgG à la surface des PN (FcγRs) ; ceci suggère un rôle des complexes immuns (CI) IgG/curares dans la formation des NETs au cours de ces réactions anaphylactiques.Pour confirmer cette hypothèse, la capacité d’activation de la nétose par les CI IgG a été étudiée, via la mise au point d’un modèle de stimulation in vitro des PN humains purifiés.Ce travail montre que 2 récepteurs aux IgG du PN (FcγRIIa et FcγRIIIB) contribuent à la libération de NETs en réponse à différents types de CI.En parallèle, la formation des NETs a été explorée dans un modèle de réaction allergique chronique, l’asthme. Au niveau systémique, la concentration de NETs est associée à la présence d’un asthme sévère mal contrôlé et d’une obstruction bronchique peu réversible. Inversement, la concentration de NETs dans le lavage broncho-alvéolaire est plus élevée au cours de l’asthme modéré et semble traduire un recrutement pulmonaire et une activation des PN en réponse à une colonisation microbienne.Au total nous montrons que les NETs sont libérés au cours des deux modèles de réactions allergiques choisis, aiguë (anaphylaxie aux curares) et chronique (asthme) et qu’ils pourraient représenter des biomarqueurs de sévérité. Des travaux complémentaires sont nécessaires pour déterminer dans quelle mesure les NETs contribuent à la physiopathologie des allergies. / Neutrophil netosis consists in the release of extracellular DNA filaments bound to granular proteins, called Neutrophil extracellular traps (NETs). In addition to their anti-infectious role, NETs are emerging actors of many inflammatory diseases and we decided to investigate their involvement during allergy.In a multicenter clinical study, our team highlighted an alternative mechanism of anaphylaxis to neuromuscular blocking agents (NMBA) involving neutrophils (PN). The acute phase of these reactions is characterized by NETs release which level is correlated with severity and with a decrease in IgG activating receptors (FcγRs) expression on PN; this suggests a role of immune complexes (IC) IgG / NMBA in NETs formation during these anaphylactic reactionsTo confirm this hypothesis, the ability of IgG ICs to activate netosis was studied through the development of an in vitro stimulation model of purified human PNs.This work shows that two PN IgG receptors (FcγRIIa and FcγRIIIB) contribute to NET release upon cellular activation by different ICsIn parallel, NETs formation has been explored in a model of chronic allergic reactions, asthma. At systemic level, NETs levels are associated with severe and poorly controlled asthma as well with the presence of low reversible bronchial obstruction. Conversely, NETs levels in bronchoalveolar lavage are higher in moderate asthma and appear to reflect pulmonary recruitment and activation of PN in response to microbial colonization.Taking together these results show that NETs are released during the two selected models of allergic reactions : acute (NMBA anaphylaxis) and chronic (asthma) and could be used as biomarkers of severity. Furthers works are needed to determine to what extent NETs contribute to the pathophysiology of allergy.
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Modulation fonctionnelle des cellules dendritiques par les « Neutrophil Extracellular Traps » / Functional modulation of dendritic cells by « Neutrophil Extracellular Traps »Barrientos, Lorena 04 November 2013 (has links)
Les polynucléaires neutrophiles (PN) sont des cellules essentielles au cours de la réponse immunitaire innée ; recrutés rapidement au site inflammatoire où ils participent à la phase aigüe, ils vont aussi contribuer à la résolution de l’inflammation. Ils peuvent en effet moduler la réponse adaptative par interaction avec les lymphocytes (Ly) ou les cellules dendritiques (DC) via des médiateurs solubles ou des interactions cellulaires directes. Les Neutrophil Extracellular Traps (NETs) libérés par les PN activés pourraient jouer un rôle important dans ce contexte. Les NETs sont des filaments de chromatine décondensée associés à des protéines issues principalement des granulations et du cytoplasme. Ils sont essentiels dans la réponse anti-infectieuse mais semblent également impliqués dans la physiopathologie de certaines maladies auto-immunes et inflammatoires. L’objectif de ce travail a été d’évaluer les effets des NETs sur la maturation des DC dans un contexte inflammatoire au cours duquel les PN et les DC peuvent co-exister, assurant ainsi un pont entre immunité innée et immunité adaptative. La première partie de ce travail a consisté à développer un modèle de production, isolement et caractérisation des NETs issus de PN sanguins humains. L’ionophore de calcium A23187 a été choisi pour induire les NETs et l'enzyme de restriction AluI a permis la récupération de fragments de NETs de taille hétérogène. Certains des composants de ces NETs sont quantifiables (ADN, élastase, histone 3 en particulier), et nous avons montré qu’ils conservaient leurs capacités bactéricides in vitro. Ces échantillons de NETs constituent donc un outil biologique standardisé, permettant d’évaluer leurs effets sur des cellules ou des tissus. Dans la deuxième partie de ce travail, nous avons mis en évidence que ces NETs purifiés régulaient négativement la maturation de moDC induites par le LPS (expression de HLA-DR, CD80, CD83, CD86 et production de TNFα, IL-12, IL-6, IL-23). De plus, les NETs diminuent la capacité de ces moDC à induire la prolifération des LyT, et leur polarisation est modulée en favorisant la production de cytokines de type Th2 (IL-5 et IL-13) aux dépens de cytokines de types Th1 (INFγ) et Th17 (IL-17). De manière intéressante, la capacité de migration des moDC activées par le LPS n’est pas modifiée en présence de NETs. En résumé, ces résultats suggèrent que les NETs pourraient jouer un rôle immunorégulateur sur la maturation des moDC dans des conditions inflammatoires. Les NETs produits par les PN activés pourraient ainsi participer à la régulation indispensable de la réponse inflammatoire. / Polymorphonuclear neutrophils (PMN) are innate immune cells rapidly recruited to the inflammatory sites where they play a major role during the acute phase response but also contribute to resolution and repair. They can also modulate the adaptive response by interacting with lymphocytes (Ly) or dendritic cells (DC) via soluble mediators or cell-cell contacts. Activated PMN release Neutrophil Extracellular Traps (NETs) that could play a role in this context. NETs are decondensed chromatin fibers associated with granule and cytoplasmic proteins. As they are mainly involved in host defense against infection, they contribute to some autoimmune and inflammatory diseases. The aim of this work was to evaluate NET effects on DC maturation in an inflammatory context where PMN and DC co-exist, thus bridging innate and adaptive immunity. We first developed a model to induce, isolate and characterize NETs from human PMN. Calcium ionophore A23187 was chosen to induce NETs and the restriction enzyme AluI allowed the recovery of heterogeneous-sized fragments of NETs. Some of their components were quantified (DNA, elastase, histone 3, in particular) and we found that they retained their bactericidal activity. These NETs samples thus constitute a new and important biological tool to study their effects on immune cells or tissues. In the second part of this work, we found that isolated NETs were able to down-regulate LPS-induced moDC maturation as evidenced by the expressions of HLA-DR, CD80, CD83, CD86 and cytokine release (TNFα, Il-6, IL-12, Il-23). Moreover, the presence of NETs during moDC maturation lead to a decrease capacity of these moDC to induce T lymphocyte proliferation and modulated polarization by promoting the production of Th2 cytokines (IL-5 and IL-13) and decreasing Th1 cytokines (INFγ) and Th17 (IL- 17). Interestingly, moDC migration capacity was not modified when moDC maturation was done in the presence of NETs. In summary, these data suggest that NETs could downregulate DC activation. NETs produced by activated PMN could thus participate to the regulation of inflammation.
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Recognition of Neutrophil Extracellular Traps by the Cytosolic DNA Sensor cGASApel, Falko 11 February 2019 (has links)
Neutrophile Granulozyten produzieren „Neutrophil Extracellular Traps“ (NETs), ein mit antimikrobiellen Molekülen bestücktes Netzwerk aus Chromatinfasern, das während eines Zelltodprogramms namens „NETosis“ von den sterbenden Neutrophilen ausgestoßen wird. Ihre netzartige Struktur erlaubt es ihnen, eine weitere Verbreitung des Infektionserregers zu verhindern; zudem erzeugen sie eine hohe lokale Konzentration an toxischen Molekülen, die Mikroorganismen töten können. Unter normalen Bedingungen werden NETs von Nukleasen zerkleinert und anschließend von Makrophagen entfernt. Wenn dieser Aufräummechanismus gestört ist, aktivieren NETs das Immunsystem und führen zur Produktion von Autoantikörpern oder entzündungsfördernden Zytokinen. NETs werden mit einer wachsenden Liste von inflammatorischen und Autoimmunerkrankungen in Verbindung gebracht. Wie genau dabei NETs durch das Immunsystem erkannt werden, ist noch nicht bekannt.
In der vorliegenden Arbeit zeige ich, dass NETs durch den zytosolischen DNA Sensor „cyclic GMP-AMP synthase“ (cGAS) detektiert werden können und dass dadurch die Expression von Typ I Interferonen (TIIFN) induziert wird. Zu Beginn demonstriere ich, dass NETs durch rekombinantes cGAS erkannt werden und dass mit isolierten NETs stimulierte Immunzellen cGAS-abhängig TIIFN produzieren. Des Weiteren zeige ich, dass Neutrophile, die NETosis begehen, in Nachbarzellen ebenfalls cGAS-anhängig TIIFN induzieren können. Abschließend konnte ich diese Ergebnisse in einem in vivo Mausmodel für systemische NET-Produktion bestätigen. Die vorliegende Arbeit zeigt einen Mechanismus, wie NETs durch das Immunsystem erkannt werden und dadurch sowohl zur Entstehung als auch zur Progression von Krankheiten beitragen kann. Sie ermöglicht dementsprechend die Entwicklung neuer Interventionsstrategien, welche zur Heilung oder Linderung einer Vielzahl von Erkrankungen beitragen können. / The first line of cellular defense of the immune system are neutrophils. They are the most abundant white blood cell, which exert an array of antimicrobial effector functions. Neutrophils release neutrophil extracellular traps (NETs), a composite of chromatin and antimicrobial molecules, into the extracellular space during a form of regulated cell death called NETosis. Their net-like structure prevent further dissemination of the invader and establishes a high local concentration of toxic molecules that mediate pathogen killing. NETs provide a platform for undesired immune activation and contribute to the production of autoantibodies and pro-inflammatory cytokines. NETs are implicated in a growing list of inflammatory and autoimmune diseases, but the exact mechanism how NETs are recognized by the immune system is not fully understood.
In this study, I demonstrate that the cytosolic DNA sensor cyclic GMP-AMP synthase (cGAS) senses NETs and induces the production of type I interferons (TIIFN). I first showed that NETs are recognized by recombinant cGAS and that cells treated with isolated NETs produce TIIFN in a cGAS dependent mechanism. Secondly, I demonstrate that neutrophils undergoing NETosis are taken up by neighboring immune cells and induce cGAS-dependent TIIFN expression. Lastly, I confirmed our in vitro results in a mouse model of systemic NET induction. Wildtype mice injected with Concanavalin A significantly upregulate the expression of interferon stimulated genes, while cGAS-/- mice and Cybb-/- mice, which are incapable of producing NETs, fail to induce this response.
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Extracellular Bactericidal Functions of Porcine NeutrophilsScapinello, Sarah Elizabeth 12 January 2010 (has links)
Neutrophils are one of the main effector cells of innate immunity and were shown to kill bacteria by phagocytosis more than 100 years ago. Neutrophils are also capable of antimicrobial activity by producing extracellular structures named neutrophil extracellular traps (NETs). This thesis is an investigation of porcine neutrophils and their ability to produce NETs, as well as the antimicrobial ability of secretions from activated porcine neutrophils in combating a variety of common porcine pathogens. Porcine neutrophils were found to produce NET-like structures, and secretions from activated neutrophils were found to possess variable bactericidal activity against common pathogens of swine. Antimicrobial proteins dependent on elastase activity were shown to be partially responsible for the bactericidal activities of activated neutrophils. Several antimicrobial proteins and peptides were identified via proteomic techniques. This work allows for better understanding of innate immunity in swine, and identification of potential targets for addressing porcine health. / Ontario Ministry of Agriculture Food & Rural Affairs, Ontario Pork, Natural Sciences and Engineering Research Council of Canada
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