scholarly journals Mast Cell Tryptase Potentiates Neutrophil Extracellular Trap Formation

2021 ◽  
pp. 1-14
Author(s):  
Gunnar Pejler ◽  
Sultan Alanazi ◽  
Mirjana Grujic ◽  
Jeremy Adler ◽  
Anna-Karin Olsson ◽  
...  
Keyword(s):  
Neutrophil Extracellular Trap ◽  
Human Neutrophils ◽  
Functional Communication ◽  
Extracellular Milieu ◽  
Extracellular Traps ◽  
Inflammatory Conditions ◽  
Histone 3 ◽  
Activated Neutrophils ◽  
Core Histones

Previous research has indicated an intimate functional communication between mast cells (MCs) and neutrophils during inflammatory conditions, but the nature of such communication is not fully understood. Activated neutrophils are known to release DNA-containing extracellular traps (neutrophil extracellular traps [NETs]) and, based on the known ability of tryptase to interact with negatively charged polymers, we here hypothesized that tryptase might interact with NET-contained DNA and thereby regulate NET formation. In support of this, we showed that tryptase markedly enhances NET formation in phorbol myristate acetate-activated human neutrophils. Moreover, tryptase was found to bind vividly to the NETs, to cause proteolysis of core histones and to cause a reduction in the levels of citrullinated histone-3. Secretome analysis revealed that tryptase caused increased release of numerous neutrophil granule compounds, including gelatinase, lactoferrin, and myeloperoxidase. We also show that DNA can induce the tetrameric, active organization of tryptase, suggesting that NET-contained DNA can maintain tryptase activity in the extracellular milieu. In line with such a scenario, DNA-stabilized tryptase was shown to efficiently degrade numerous pro-inflammatory compounds. Finally, we showed that tryptase is associated with NET formation in vivo in a melanoma setting and that NET formation in vivo is attenuated in mice lacking tryptase expression. Altogether, these findings reveal that NET formation can be regulated by MC tryptase, thus introducing a novel mechanism of communication between MCs and neutrophils.

scholarly journals Neutrophils: back in the thrombosis spotlight

Blood ◽  
2019 ◽  
Vol 133 (20) ◽  
pp. 2186-2197 ◽  
Author(s):  
Denis F. Noubouossie ◽  
Brandi N. Reeves ◽  
Brian D. Strahl ◽  
Nigel S. Key
Keyword(s):  
Animal Models ◽  
Tissue Factor ◽  
Contact System ◽  
Neutrophil Extracellular Trap ◽  
Human Neutrophils ◽  
Dependent Manner ◽  
Extrinsic Pathway ◽  
Vessel Occlusion ◽  
Activated Neutrophils

Abstract Reactive and clonal neutrophil expansion has been associated with thrombosis, suggesting that neutrophils play a role in this process. However, although there is no doubt that activated monocytes trigger coagulation in a tissue factor-dependent manner, it remains uncertain whether stimulated neutrophils can also directly activate coagulation. After more than a decade of debate, it is now largely accepted that normal human neutrophils do not synthetize tissue factor, the initiator of the extrinsic pathway of coagulation. However, neutrophils may passively acquire tissue factor from monocytes. Recently, the contact system, which initiates coagulation via the intrinsic pathway, has been implicated in the pathogenesis of thrombosis. After the recent description of neutrophil extracellular trap (NET) release by activated neutrophils, some animal models of thrombosis have demonstrated that coagulation may be enhanced by direct NET-dependent activation of the contact system. However, there is currently no consensus on how to assess or quantify NETosis in vivo, and other experimental animal models have failed to demonstrate a role for neutrophils in thrombogenesis. Nevertheless, it is likely that NETs can serve to localize other circulating coagulation components and can also promote vessel occlusion independent of fibrin formation. This article provides a critical appraisal of the possible roles of neutrophils in thrombosis and highlights some existing knowledge gaps regarding the procoagulant activities of neutrophil-derived extracellular chromatin and its molecular components. A better understanding of these mechanisms could guide future approaches to prevent and/or treat thrombosis.

scholarly journals HMGB1 promotes neutrophil extracellular trap formation through interactions with Toll-like receptor 4

2013 ◽  
Vol 304 (5) ◽  
pp. L342-L349 ◽  
Author(s):  
Jean-Marc Tadie ◽  
Hong-Beom Bae ◽  
Shaoning Jiang ◽  
Dae Won Park ◽  
Celeste P. Bell ◽  
...  
Keyword(s):  
High Mobility ◽  
Neutralizing Antibody ◽  
Sterile Inflammation ◽  
Neutrophil Extracellular Trap ◽  
Toll Like Receptor ◽  
Inflammatory Conditions ◽  
Histone 3 ◽  
Inflammatory Protein ◽  
Molecular Pattern

Although neutrophil extracellular traps (NETs) form to prevent dissemination of pathogenic microorganisms, excessive release of DNA and DNA-associated proteins can also perpetuate sterile inflammation. In this study, we found that the danger-associated molecular pattern protein high-mobility group box 1 (HMGB1) can induce NET formation. NET formation was found after exposure of wild-type and receptor for advanced glycation end products-deficient neutrophil to HMGB1, whereas deficiency of Toll-like receptor (TLR)4 diminished the ability of neutrophils to produce NETs. Incubation of neutrophils with HMGB1 significantly increased the amount of DNA and histone 3 released as well as intracellular histone 3 citrullination, a signaling event that precedes chromatin decondensation. In vivo, neutrophils isolated from bronchoalveolar lavages of mice exposed to LPS and HMGB1 showed consistently greater ability to produce NETs compared with pulmonary neutrophils from mice that received LPS alone. In contrast, mice treated with LPS and neutralizing antibody to HMGB1 had decreased amounts of the inflammatory cytokines TNF-α and macrophage inflammatory protein 2, as well as of free DNA and histone 3 in bronchoalveolar lavage fluids. Airway neutrophils from LPS-exposed mice that had been treated with anti-HMGB1 antibodies showed decreased citrullination of histone 3. These results demonstrate that interactions between HMGB1 and TLR4 enhance the formation of NETs and provide a novel mechanism through which HMGB1 may contribute to the severity of neutrophil-associated inflammatory conditions.

Therapeutic targets in COVID-19 coagulopathy

2021 ◽  
Author(s):  
М.В. Кондашевская
Keyword(s):  
Viral Infections ◽  
Cell Types ◽  
Infectious Agents ◽  
Therapeutic Goals ◽  
Extracellular Traps ◽  
Activated Neutrophils ◽  
Life Threatening ◽  
Tight Connection ◽  
New Type

В обзоре представлены сведения о некоторых биохимических и клеточных механизмах патогенеза потенциально смертельного вирусного заболевания, получившего название COVID-19, провоцируемого вирусами из семейства коронавирусов SARS-CoV-2. Наибольшую опасность для жизни и здоровья пациентов представляет коагулопатия, обусловленная ответной реакцией на инфекцию — чрезмерной генерацией клетками пациента внеклеточных мембранных нановезикул (ВМН), которые могут спровоцировать активизацию гемостаза, приводящую к разрушительной полиорганной недостаточности. Вирусы также способны генерировать внеклеточные везикулы, называемые виросомами. Встраивая вирусные компоненты в свои виросомы, вирусы повышают персистентность за счет маскировки своих геномов, умножая вирусную инфекцию. В статье охарактеризованы свойства нейтрофильных гранулоцитов, активирующихся при инфицировании, и представлены сведения о молекулярных механизмах действия их компонентов при попадании во внеклеточное пространство. ВМН уже имеют практическое применение в качестве вакцинных носителей для иммунизации человека и животных против многих инфекционных заболеваний. В настоящее время актуальнейшей темой, обуславливающей большой практический интерес, стала роль ВМН в индуцировании иммунитета против коронавирусной инфекции. Охарактеризованы другие возможные терапевтические мишени. Virus-induced coagulopathy is a typical example of the tight connection between inflammation and thrombosis. These two reactions are linked by pro-inflammatory agents, generated by activated neutrophils and their neutrophil extracellular traps (NETs). Extracellular membrane nanobubbles (EMNs), formed by a wide variety of cell types, have recently been identified as new entrants that play a key role in coagulopathy. EMNs directly and indirectly activate coagulation systems that lead to the further upregulation of inflammation and life-threatening organ dysfunction and thrombosis. EMNs are known to be responsible for the secretion, exchange, and transmission of important active biomolecules in COVID-19. Indeed, EMNs represent an essential mechanism in intercellular communication, and the roles of EMNs in infection and thrombosis have been increasingly recognized. The extracellular microvesicles of viruses, virosomes, represent a new type of infectious agents, which determines new therapeutic goals in solving the problems of controlling viral infections. Understanding the biological nature of all these microvesicles when studying them in vivo is of paramount importance for the development of diagnostic and therapeutic methods.

scholarly journals Leukocyte proteases cleave von Willebrand factor at or near the ADAMTS13 cleavage site

Blood ◽  
2009 ◽  
Vol 114 (8) ◽  
pp. 1666-1674 ◽  
Author(s):  
Thomas J. Raife ◽  
Wenjing Cao ◽  
Bonnie S. Atkinson ◽  
Bruce Bedell ◽  
Robert R. Montgomery ◽  
...  
Keyword(s):  
Von Willebrand Factor ◽  
Hot Spot ◽  
Peptide Bond ◽  
Cathepsin G ◽  
Human Neutrophils ◽  
Activity Levels ◽  
Activated Neutrophils ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract The function of von Willebrand factor (VWF) is regulated by proteolysis, which limits its multimeric size and ability to tether platelets. The importance of ADAMTS13 metalloprotease in VWF regulation is demonstrated by the association between severe deficiency of ADAMTS13 and thrombotic thrombocytopenic purpura (TTP). However, ADAMTS13 activity levels do not always correlate with the clinical course of TTP, suggesting that other proteases could be important in regulating VWF. We identified 4 leukocyte proteases that cleave the synthetic VWF substrate FRETS-VWF73 and multimeric VWF. Elastase and proteinase 3 (PR3) cleave multimeric VWF and FRETS-VWF73 at the V1607-T1608 peptide bond; cathepsin G and matrix metalloprotease 9 cleave VWF substrates at the Y1605-M1606 and M1606-V1607 bonds, respectively. Isolated intact human neutrophils cleave FRETS-VWF73 at the V1607-T1608 peptide bond, suggesting that elastase or PR3 expressed on leukocyte surfaces might cleave VWF. In the presence of normal or ADAMTS13-deficient plasma, cleavage of FRETS-VWF73 by resting neutrophils is abolished. However, activated neutrophils retain proteolytic activity toward FRETS-VWF73 in the presence of plasma. Although the in vivo relevance remains to be established, these studies suggest the existence of a “hot spot” of VWF proteolysis in the VWF A2 domain, and support the possibility that activated leukocytes may participate in the proteolytic regulation of VWF.

scholarly journals How Neutrophil Extracellular Traps Become Visible

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Nicole de Buhr ◽  
Maren von Köckritz-Blickwede
Keyword(s):  
Electron Microscopy ◽  
Nuclear Dna ◽  
Defense Mechanism ◽  
Neutrophil Extracellular Traps ◽  
Immune Defense ◽  
Extracellular Traps ◽  
Activated Neutrophils ◽  
Microscopy Techniques

Neutrophil extracellular traps (NETs) have been identified as a fundamental innate immune defense mechanism against different pathogens. NETs are characterized as released nuclear DNA associated with histones and granule proteins, which form an extracellular web-like structure that is able to entrap and occasionally kill certain microbes. Furthermore, NETs have been shown to contribute to several noninfectious disease conditions when released by activated neutrophils during inflammation. The identification of NETs has mainly been succeeded by various microscopy techniques, for example, immunofluorescence microscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Since the last years the development and improvement of new immunofluorescence-based techniques enabled optimized visualization and quantification of NETs. On the one handin vitrolive-cell imaging led to profound new ideas about the mechanisms involved in the formation and functionality of NETs. On the other hand different intravital,in vivo, andin situmicroscopy techniques led to deeper insights into the role of NET formation during health and disease. This paper presents an overview of the main used microscopy techniques to visualize NETs and describes their advantages as well as disadvantages.

scholarly journals Degraded neutrophil extracellular traps promote the growth of Actinobacillus pleuropneumoniae

2019 ◽  
Vol 10 (9) ◽  
Author(s):  
Nicole de Buhr ◽  
Marta C. Bonilla ◽  
Jessica Pfeiffer ◽  
Silke Akhdar ◽  
Cornelia Schwennen ◽  
...  
Keyword(s):  
Immune Cell ◽  
Bacterial Species ◽  
Severe Pneumonia ◽  
Lavage Fluid ◽  
Neutrophil Extracellular Traps ◽  
Actinobacillus Pleuropneumoniae ◽  
Degraded Dna ◽  
Human Neutrophils ◽  
Extracellular Traps

Abstract Actinobacillus pleuropneumoniae (A.pp) causes severe pneumonia associated with enormous economic loss in pigs. Peracute diseased pigs die in <24 h with pneumonia. Neutrophils are the prominent innate immune cell in this infection that massively infiltrate the infected lung. Here we show that neutrophils release neutrophil extracellular traps (NETs) as response to A.pp infection. Numerous NET-markers were identified in bronchoalveolar lavage fluid (BALF) of A.pp-infected piglets in vivo, however, most NET fibers are degraded. Importantly, A.pp is able to enhance its growth rate in the presence of NETs that have been degraded by nucleases efficiently. A.pp itself releases no nuclease, but we identified host nucleases as sources that degrade NETs after A.pp infection. Furthermore, the nucleases of co-infecting pathogens like Streptococcus suis increase growth of A.pp in presence of porcine NETs. Thus, A.pp is not only evading the antimicrobial activity of NETs, A.pp is rather additionally using parts of NETs as growth factor thereby taking advantage of host nucleases as DNase1 or nucleases of co-infecting bacteria, which degrade NETs. This effect can be diminished by inhibiting the bacterial adenosine synthase indicating that degraded NETs serve as a source for NAD, which is required by A.pp for its growth. A similar phenotype was found for the human pathogen Haemophilus (H.) influenzae and its growth in the presence of human neutrophils. H. influenzae benefits from host nucleases in the presence of neutrophils. These data shed light on the detrimental effects of NETs during host immune response against certain bacterial species that require and/or efficiently take advantage of degraded DNA material, which has been provided by host nuclease or nucleases of other co-infecting bacteria, as growth source.

scholarly journals Histone Deacetylase Inhibitors Dose-Dependently Switch Neutrophil Death from NETosis to Apoptosis

Biomolecules ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 184 ◽  
Author(s):  
Hussein J. Hamam ◽  
Nades Palaniyar
Keyword(s):  
Histone Acetylation ◽  
Histone Deacetylases ◽  
Histone Deacetylase Inhibitors ◽  
Significant Inhibition ◽  
The Body ◽  
Neutrophil Extracellular Trap ◽  
Human Neutrophils ◽  
Dependent Manner ◽  
Post Translational Modification

Acetylation is an important post translational modification of histone that plays a role in regulation of physiological and pathological process in the body. We have recently shown that the inhibition of histone deacetylases (HDAC) by low concentrations of HDAC inhibitors (HDACis), belinostat (up to 0.25 µM) and panobinostat (up to 0.04 µM) promote histone acetylation (e.g., AcH4) and neutrophil extracellular trap formation (NETosis). Clinical use of belinostat and panobinostat often leads to neutropenia and the in vivo concentrations vary with time and tissue locations. However, the effects of different concentrations of these HDACis on neutrophil death are not fully understood. We considered that increasing concentrations of belinostat and panobinostat could alter the type of neutrophil death. To test this hypothesis, we treated human neutrophils with belinostat and panobinostat in the presence or absence of agonists that promote NOX-dependent NETosis (phorbol myristate acetate or lipopolysaccharide from Escherichia coli 0128) and NOX-independent NETosis (calcium ionophores A23187 or ionomycin from Streptomyces conglobatus). Increasing concentrations of HDACis induced histone acetylation in a dose-dependent manner. ROS analyses showed that increasing concentrations of HDACis, increased the degree of NOX-derived ROS production. Higher levels (>1 µM belinostat and >0.2 µM panobinostat) of AcH4 resulted in a significant inhibition of spontaneous as well as the NOX-dependent and -independent NETosis. By contrast, the degree of neutrophil apoptosis significantly increased, particularly in non-activated cells. Collectively, this study establishes that increasing concentrations of belinostat and panobinostat initially increases NETosis but subsequently reduces NETosis or switches the form of cell death to apoptosis. This new information indicates that belinostat and panobinostat can induce different types of neutrophil death and may induce neutropenia and regulate inflammation at different concentrations.

scholarly journals G-CSF–stimulated Neutrophils Are a Prominent Source of Functional BLyS

2003 ◽  
Vol 197 (3) ◽  
pp. 297-302 ◽  
Author(s):  
Patrizia Scapini ◽  
Bernardetta Nardelli ◽  
Gianpaolo Nadali ◽  
Federica Calzetti ◽  
Giovanni Pizzolo ◽  
...  
Keyword(s):  
B Cell ◽  
B Lymphocyte ◽  
Serum Levels ◽  
Surface Expression ◽  
Biologically Active ◽  
Human Neutrophils ◽  
Activated Neutrophils ◽  
B Cell Homeostasis

B lymphocyte stimulator (BLyS) is a novel member of the TNF ligand superfamily that is important in B cell maturation and survival. We demonstrate that human neutrophils, after incubation with G-CSF or, less efficiently, IFNγ, express high levels of BLyS mRNA and release elevated amounts of biologically active BLyS. In contrast, surface expression of the membrane-bound BLyS was not detected in activated neutrophils. Indeed, in neutrophils, uniquely among other myeloid cells, soluble BLyS is processed intracellularly by a furin-type convertase. Worthy of note, the absolute capacity of G-CSF–stimulated neutrophils to release BLyS was similar to that of activated monocytes or dendritic cells, suggesting that neutrophils might represent an important source of BLyS. In this regard, we show that BLyS serum levels as well as neutrophil-associated BLyS are significantly enhanced after in vivo administration of G-CSF in patients. In addition, serum obtained from two of these patients induced a remarkable accumulation of neutrophil-associated BLyS in vitro. This effect was neutralized by anti–G-CSF antibodies, indicating that G-CSF, present in the serum, stimulated neutrophils to produce BLyS. Collectively, our findings suggest that neutrophils, through the production of BLyS, might play an unsuspected role in the regulation of B cell homeostasis.

scholarly journals Neutrophil extracellular traps in cancer: not only catching microbes

2021 ◽  
Vol 40 (1) ◽  
Author(s):  
Livia Ronchetti ◽  
Nouha Setti Boubaker ◽  
Maddalena Barba ◽  
Patrizia Vici ◽  
Aymone Gurtner ◽  
...  
Keyword(s):  
Cancer Patients ◽  
White Blood Cells ◽  
Neutrophil Extracellular Traps ◽  
Neutrophil Extracellular Trap ◽  
Prognostic Role ◽  
Extracellular Traps ◽  
Activated Neutrophils ◽  
Neoplastic Process ◽  
Review Current

AbstractNeutrophils are the most abundant type of white blood cells circulating throughout the bloodstream and are often considered the frontline defenders in innate immunity. However, neutrophils are increasingly being recognized as having an important role in tumorigenesis and carcinogenesis due to their aberrant activation by molecules released into the tumor microenvironment. One defensive response of neutrophils that is aberrantly triggered during the neoplastic process is called NETosis, where activated neutrophils expel their DNA and intracellular contents in a web-like structure known as a neutrophil extracellular trap (NET). In cancer, NETosis has been linked to increased disease progression, metastasis, and complications such as venous thromboembolism. NET structures released by neutrophils can also serve as a scaffold for clot formation, shining new light on the role of neutrophils and NETosis in coagulation-mediated diseases.Here, we review current available knowledge regarding NET and the related NETosis process in cancer patients, with an emphasis on pre-clinical and clinical data fostering the identification and validation of biomarkers of NET with a predictive/prognostic role in cancer patients treated with immunotherapy agents. NETosis biomarkers, e.g., citH3, may integrate correlates of immunogenicity currently available (e.g., PD-L1 expression, TMB, TILs) and help select the subsets of patients who may most benefit from the use of the therapeutic weapons under discussion.

scholarly journals A Lipid Mediator Hepoxilin A3 Is a Natural Inducer of Neutrophil Extracellular Traps in Human Neutrophils

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
David N. Douda ◽  
Hartmut Grasemann ◽  
Cecil Pace-Asciak ◽  
Nades Palaniyar
Keyword(s):  
Cystic Fibrosis ◽  
Nadph Oxidase ◽  
Neutrophil Extracellular Trap ◽  
Lipid Mediator ◽  
Human Neutrophils ◽  
Synthetic Analog ◽  
Extracellular Traps ◽  
Cystic Fibrosis Lung Disease ◽  
Higher Doses ◽  
Hepoxilin A3

Pulmonary exacerbations in cystic fibrosis airways are accompanied by inflammation, neutrophilia, and mucous thickening. Cystic fibrosis sputum contains a large amount of uncleared DNA contributed by neutrophil extracellular trap (NET) formation from neutrophils. The exact mechanisms of the induction of NETosis in cystic fibrosis airways remain unclear, especially in uninfected lungs of patients with early cystic fibrosis lung disease. Here we show that Hepoxilin A3, a proinflammatory eicosanoid, and the synthetic analog of Hepoxilin B3, PBT-3, directly induce NETosis in human neutrophils. Furthermore, we show that Hepoxilin A3-mediated NETosis is NADPH-oxidase-dependent at lower doses of Hepoxilin A3, while it is NADPH-oxidase-independent at higher doses. Together, these results demonstrate that Hepoxilin A3 is a previously unrecognized inducer of NETosis in cystic fibrosis lungs and may represent a new therapeutic target for treating cystic fibrosis and other inflammatory lung diseases.

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