MO244CD47 BLOCKADE AMELIORATES AUTOIMMUNE VASCULITIS VIA THE EFFEROCYTOSIS OF NEUTROPHIL EXTRACELLULAR TRAPS*

Abstract Background and Aims Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is characterized by systemic necrotizing vasculitis in small vessels. The necrotic lesions consist of ANCA-mediated neutrophil extracellular traps (NETs) which represent a form of lytic cell death. The persistent NETs serve as autoantigens against ANCAs and cause organ damage in a vicious cycle. Considering dead cells are essentially cleared by phagocytic cells as a process of efferocytosis, why the NETs persist in tissue remains unclear. During efferocytosis, macrophages engulf apoptotic cells to prevent the leakage of intracellular components including toxic enzyme into the surrounding cells and these processes are regulated by the expression of CD47 as a “don’t eat me” signal. In this study, we hypothesized that ANCA-mediated NETs in AAV escape from efferocytosis via the up-regulation of CD47 and the persistent NETs amplify the disease. Method Human data: Human kidney biopsy specimens from patients with AAV and minor glomerular abnormality (MGA, as a case control) were subjected to immunohistochemistry (IHC) staining for CD47. In vitro: The expression of CD47 on neutrophils was evaluated by flow cytometry (FCM). Human neutrophils from healthy donor were treated with ANCA-IgGs from MPO-AAV patients or control IgGs. For the efferocytosis assay, macrophages were co-incubated with unstimulated, apoptotic, and ANCA-IgGs treated neutrophils in the presence of anti-CD47 monoclonal antibody (mAb) or a control antibody. The neutrophils were labeled with CFMDA cell tracker (fluorescent probe) and the efferocytosis was evaluated as neutrophil engulfed (CFMDA positive) macrophages using fluorescent microscopy. In vivo: Spontaneous crescentic glomerulonephritis-forming/Kinjoh (SCG/Kj) mice (8-week-old age) were treated with intraperitoneal injection of anti-CD47 mAb or a control antibody every 5 days for two weeks. The severity of glomerulonephritis was assessed by the levels of serum creatinine, haematuria, mRNA expression of pro-inflammatory genes, and histopathological findings. To address the immune response against the CD47 blockade, the titre of MPO-ANCA and the number of splenic cell subset was assessed by ELISA and FCM analysis, respectively. Results Human data: The IHC analysis of human renal specimens revealed that the positive area of CD47 of AAV was greater than that of MGA. In particular, the CD47-overexpressed cells were seen in glomeruli with necrotic crescent formation. In vitro: Mean fluorescence intensity (MFI) of CD47 in ANCA-IgGs treated neutrophils (NETs) was significantly higher than that in control IgGs treated neutrophils (ANCA-IgG; 442±21.4 a.u. vs control IgG; 402±10 a.u., p<0.05). In efferocytosis assay, apoptotic neutrophils were engulfed by macrophages (efferocytosis rate/ apoptotic neutrophil; 20.5±3.8%, live neutrophils; 0.9±0.5%). The efferocytosis rate of ANCA-induced NETs significantly decreased compared to apoptotic neutrophil, but anti-CD47 mAb improved the efferocytosis of ANCA-NETs (efferocytosis rate/ anti-CD47 mAb; 19.1±4.2%, control antibody; 7.7±2.2%, p<0.05). In vivo: the renal histopathological severity score, serum creatinine level of AAV mice treated with anti-CD47 mAb decreased compared to that of AAV mice treated with a control antibody (anti-CD47 mAb; 0.96±0.30 vs control antibody; 0.61±0.32 mg/dL). Although there was no significant difference in the number of splenic cells between anti-CD47 and control antibody treated mice, CD47 blockade therapy significantly reduced serum MPO-ANCA titre (28.5±10.4 vs 45.2±14.5 μg/mL) and renal mRNA expression (IFNα, IFNγ, MCP-1 and perforin) of AAV mice. Conclusion ANCA-mediated NETs might escape from efferocytosis through up-regulation of CD47 and provoke necrotizing vasculitis. CD47 blockade could be a potential novel therapeutic strategy for AAV.

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ELISA detection of MPO-DNA complexes in human plasma is error-prone and yields limited information on neutrophil extracellular traps formed in vivo

PLoS ONE ◽

10.1371/journal.pone.0250265 ◽

2021 ◽

Vol 16 (4) ◽

pp. e0250265

Author(s):

Hubert Hayden ◽

Nahla Ibrahim ◽

Johannes Klopf ◽

Branislav Zagrapan ◽

Lisa-Marie Mauracher ◽

...

Keyword(s):

Human Plasma ◽

Dynamic Range ◽

Neutrophil Extracellular Traps ◽

Plasma Samples ◽

Dna Complexes ◽

High Background ◽

Isotype Control ◽

Extracellular Traps

Over the past years, neutrophil extracellular traps (NETs) were shown to contribute to states of acute and chronic inflammatory disease. They are composed of expelled chromatin and decorated by neutrophil-derived proteins. Therefore, the analysis of DNA complexes with myeloperoxidase (MPO) by ELISA has become an attractive tool to measure NET formation in in vitro and in vivo samples. When we used a published MPO-DNA ELISA protocol and included an isotype control for the anti-MPO coating antibody, we observed high assay specificity for in vitro prepared NET samples, whereas the specificity for in vivo plasma samples was low. In addition, the assay failed to detect in vitro generated MPO-DNA complexes when spiked into plasma. Therefore, we set out to improve the specificity of the MPO-DNA ELISA for plasma samples. We found that the use of Fab fragments or immunoglobulins from different species or reversal of the antibody pair led to either a high background or a low dynamic range of detection that did not improve the specificity for plasma samples. Also, the use of higher plasma dilutions or pre-clearing of plasma immunoglobulins were ineffective. Finally, we found that a commercial reagent designed to block human anti-mouse antibodies and multivalent substances increased the detection window between the MPO antibody and isotype control for highly diluted plasma. We applied this modified ELISA protocol to analyze MPO-DNA complexes in human blood samples of acute and chronic inflammatory conditions. While markers of neutrophil activation and NET formation such as MPO, elastase and citrullinated histone H3 correlated significantly, we observed no correlation with the levels of MPO-DNA complexes. Therefore, we conclude that ELISA measurements of MPO-DNA complexes in human plasma are highly questionable regarding specificity of NET detection. In general, plasma analyses by ELISA should more frequently include isotype controls for antibodies to demonstrate target specificity.

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The Emerging Role of Neutrophil Extracellular Traps in Arterial, Venous and Cancer-Associated Thrombosis

Frontiers in Cardiovascular Medicine ◽

10.3389/fcvm.2021.786387 ◽

2021 ◽

Vol 8 ◽

Author(s):

Yilu Zhou ◽

Weimin Tao ◽

Fuyi Shen ◽

Weijia Du ◽

Zhendong Xu ◽

...

Keyword(s):

Current Knowledge ◽

Neutrophil Extracellular Traps ◽

Vital Role ◽

Extracellular Traps ◽

Protein Components ◽

Cancer Associated Thrombosis ◽

Coagulation Pathway

Neutrophils play a vital role in the formation of arterial, venous and cancer-related thrombosis. Recent studies have shown that in a process known as NETosis, neutrophils release proteins and enzymes complexed to DNA fibers, collectively called neutrophil extracellular traps (NETs). Although NETs were originally described as a way for the host to capture and kill bacteria, current knowledge indicates that NETs also play an important role in thrombosis. According to recent studies, the destruction of vascular microenvironmental homeostasis and excessive NET formation lead to pathological thrombosis. In vitro experiments have found that NETs provide skeletal support for platelets, red blood cells and procoagulant molecules to promote thrombosis. The protein components contained in NETs activate the endogenous coagulation pathway to promote thrombosis. Therefore, NETs play an important role in the formation of arterial thrombosis, venous thrombosis and cancer-related thrombosis. This review will systematically summarize and explain the study of NETs in thrombosis in animal models and in vivo experiments to provide new targets for thrombosis prevention and treatment.

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Neutrophil extracellular traps activate IL-8 and IL-1 expression in human bronchial epithelia

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00144.2019 ◽

2020 ◽

Vol 319 (1) ◽

pp. L137-L147 ◽

Cited By ~ 1

Author(s):

Kristin M. Hudock ◽

Margaret S. Collins ◽

Michelle Imbrogno ◽

John Snowball ◽

Elizabeth L. Kramer ◽

...

Keyword(s):

Neutrophil Extracellular Traps ◽

Gm Csf ◽

Extracellular Traps ◽

Tnf Α ◽

Multiple Donors ◽

Novel Target ◽

Induced Changes ◽

Air Liquid Interface

Neutrophil extracellular traps (NETs) provide host defense but can contribute to the pathobiology of diverse human diseases. We sought to determine the extent and mechanism by which NETs contribute to human airway cell inflammation. Primary normal human bronchial epithelial cells (HBEs) grown at air-liquid interface and wild-type (wt)CFBE41o- cells (expressing wtCFTR) were exposed to cell-free NETs from unrelated healthy volunteers for 18 h in vitro. Cytokines were measured in the apical supernatant by Luminex, and the effect on the HBE transcriptome was assessed by RNA sequencing. NETs consistently stimulated IL-8, TNF-α, and IL-1α secretion by HBEs from multiple donors, with variable effects on other cytokines (IL-6, G-CSF, and GM-CSF). Expression of HBE RNAs encoding IL-1 family cytokines, particularly IL-36 subfamily members, was increased in response to NETs. NET exposure in the presence of anakinra [recombinant human IL-1 receptor antagonist (rhIL-1RA)] dampened NET-induced changes in IL-8 and TNF-α proteins as well as IL-36α RNA. rhIL-36RA limited the increase in expression of proinflammatory cytokine RNAs in HBEs exposed to NETs. NETs selectively upregulate an IL-1 family cytokine response in HBEs, which enhances IL-8 production and is limited by rhIL-1RA. The present findings describe a unique mechanism by which NETs may contribute to inflammation in human lung disease in vivo. NET-driven IL-1 signaling may represent a novel target for modulating inflammation in diseases characterized by a substantial NET burden.

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How Neutrophil Extracellular Traps Become Visible

Journal of Immunology Research ◽

10.1155/2016/4604713 ◽

2016 ◽

Vol 2016 ◽

pp. 1-13 ◽

Cited By ~ 47

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.

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Cisplatin Fails To Stimulate Production Of Reactive Oxygen Species and Release Of Neutrophil Extracellular Traps By Human Neutrophils In Vitro

Blood ◽

10.1182/blood.v122.21.4714.4714 ◽

2013 ◽

Vol 122 (21) ◽

pp. 4714-4714

Author(s):

Leonardo Pasalic ◽

Campbell Heather ◽

Shane Thomas ◽

Vivien M Chen

Keyword(s):

Reactive Oxygen Species ◽

Fluorescent Microscopy ◽

Neutrophil Extracellular Traps ◽

Vehicle Control ◽

Human Neutrophils ◽

Oxygen Species ◽

Extracellular Traps ◽

Spontaneous Production ◽

Confocal Fluorescent Microscopy

Background Cisplatin is a commonly used antineoplastic agent for treatment of a broad range of cancers. Cisplatin-based treatment has been associated with a significant risk of venous thromboembolism. The mechanisms through which cisplatin contributes to a prothrombotic state remain unclear. Neutrophil extracellular traps (NETs) consist of web-like DNA–histone core decorated with granule proteins and are released from activated neutrophils in a process dependent on reactive oxygen species (ROS), in particular hypochlorous acid (HOCl). Recently, NETs have been shown to play an important role in initiation and propagation of venous thrombus in a number of animal models of deep vein thrombosis. The aim of this study was to investigate whether NETs may provide a potential link between cisplatin and venous thromboembolism. Methods and Results To assess the effect of cisplatin on release of NETs by ex vivo human neutrophils isolated by positive immunomagnetic selection we visualised NETs release by confocal fluorescent microscopy and performed fluorimetric quantification of cell-free DNA (CFDNA) using either SYTOX Green nucleic acid stain (10 µM) or an ultrasensitive fluorescent assay Picogreen Quant IT (Invitrogen). In contrast to stimulation with phorbol 12-myristate 13-acetate (PMA) (25 nM),which resulted in 22 ng/104neutrophils of detectable CFDNA, neither of these two assays could detect any significant release of CFDNA by human neutrophils exposed to cisplatin (15 µM) for 2 or 4 hours above baseline similar with vehicle control. Furthermore, confocal fluorescent microscopy imaging of neutrophils stained with non-cell permeable DNA dye SYTOX Red (Invitrogen) demonstrated no difference in NET formation between control and cisplatin treated human neutrophils. Thus we could not demonstrate that NETS are produced in response to cisplatin treatment. In view of consistent reports that NET formation is ROS dependent we decided to investigate whether cisplatin exposure leads to production of ROS by human neutrophils. Few published studies into the effects of cisplatin on the production of ROS by human neutrophils in vitro offer conflicting results. We used flow cytometry and fluorescent probe hydroethidine (HE) for detection of intercellular superoxide anion radical in HL60 granulocytic cells in the presence of cisplatin (up to 50 µM). Differentiation down the granulocytic lineage after stimulation with ATRA was confirmed by light microscopy and by flow cytometry. Capacity of differentiated HL60 cells to generate NET formation after PMA stimulation was confirmed by fluorescence microscopy. Cisplatin failed to augment the spontaneous production of ROS by ATRA differentiated HL60 cells. The number of viable ethidium-high cells in cisplatin treated group did not differ from the vehicle control indicating no detectable production of ROS in response to cisplatin. In contrast, positive control treatment with PMA (25 nM) and menadione (40 µM) resulted in 4- and 20-fold increase in viable ethidium-high population respectively. ROS generation by human neutrophils was measured by a colorimetric assay for chlorination of extracellular taurine to determine if exposure to cisplatin results in the production of HOCl by human neutrophils in vitro. Treatment of resting neutrophils with cisplatin (15 µM) for 30 min or 120 min was not associated with an increase in the spontaneous production of HOCl above the baseline. Furthermore, the PMA (25 nM)-activated generation of HOCl production was not increased by pre-treating neutrophils with cisplatin indicating that there was no potentiation of ROS by pre-treatment with cisplatin. Discussion and Conclusion Our results suggest that cisplatin fails to induce release of NETs or HOCl from human neutrophils in vitro. These negative findings seem to be at odds with the well described pro-oxidative actions of cisplatin. One possible explanation centres on reported findings that the pro-oxidative effects of cisplatin are dependent on the mitochondrial generation of ROS whilst the mitochondria-generated ROS appear not to be instrumental to NET formation. Therefore, we postulate that cisplatin may not be able to induce NET formation by human neutrophils, which are known to contain few mitochondria, due to a sub-threshold ROS signal. Therefore it appears that cisplatin-associated increased risk of venous thrombosis is unlikely to be mediated through NETs. Disclosures: No relevant conflicts of interest to declare.

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Antibodies Against Pseudomonas aeruginosa Alkaline Protease Directly Enhance Disruption of Neutrophil Extracellular Traps Mediated by This Enzyme

Frontiers in Immunology ◽

10.3389/fimmu.2021.654649 ◽

2021 ◽

Vol 12 ◽

Author(s):

Chendi Jing ◽

Chenghua Liu ◽

Yu Liu ◽

Ruli Feng ◽

Run Cao ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Alkaline Protease ◽

Chronic Infection ◽

Active Sites ◽

Neutrophil Extracellular Traps ◽

Lung Infection ◽

Bacterial Burden ◽

Extracellular Traps

Extracellular traps released by neutrophils (NETs) are essential for the clearance of Pseudomonas aeruginosa. Alkaline protease (AprA) secreted by P. aeruginosa negatively correlates with clinical improvement. Moreover, anti-AprA in patients with cystic fibrosis (CF) can help identify patients with aggressive forms of chronic infection. However, the mechanism underlying the clinical outcomes remains unclear. We demonstrated that aprA deficiency in P. aeruginosa decreased the bacterial burden and reduced lung infection. AprA degraded NET components in vitro and in vivo but did not affect NET formation. Importantly, antibodies induced by AprA acted as an agonist and directly enhanced the degrading activities of AprA. Moreover, antisera from patients with P. aeruginosa infection exhibited antibody-dependent enhancement (ADE) similar to that of the antibodies we prepared. Our further investigations showed that the interaction between AprA and the specific antibodies might make the enzyme active sites better exposed, and subsequently enhance the recognition of substrates and accelerate the degradation. Our findings revealed that AprA secreted by P. aeruginosa may aggravate infection by destroying formed NETs, an effect that was further enhanced by its antibodies.

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Degraded neutrophil extracellular traps promote the growth of Actinobacillus pleuropneumoniae

Cell Death and Disease ◽

10.1038/s41419-019-1895-4 ◽

2019 ◽

Vol 10 (9) ◽

Cited By ~ 6

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.

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NontypeableHaemophilus influenzaeInitiates Formation of Neutrophil Extracellular Traps

Infection and Immunity ◽

10.1128/iai.00660-10 ◽

2010 ◽

Vol 79 (1) ◽

pp. 431-438 ◽

Cited By ~ 74

Author(s):

Richard A. Juneau ◽

Bing Pang ◽

Kristin E. D. Weimer ◽

Chelsie E. Armbruster ◽

W. Edward Swords

Keyword(s):

Otitis Media ◽

Bacterial Species ◽

Outer Membrane Proteins ◽

Neutrophil Extracellular Traps ◽

Bacterial Surface ◽

Persistent Infections ◽

Extracellular Traps ◽

Molecular Patterns

ABSTRACTNontypeableHaemophilus influenzae(NTHI) is a leading cause of otitis media infections, which are often chronic and/or recurrent in nature. NTHI and other bacterial species persistin vivowithin biofilms during otitis media and other persistent infections. These biofilms have a significant host component that includes neutrophil extracellular traps (NETs). These NETs do not mediate clearance of NTHI, which survives within NET structures by means of specific subpopulations of lipooligosaccharides on the bacterial surface that are determinants of biofilm formationin vitro. In this study, the ability of NTHI and NTHI components to initiate NET formation was examined using anin vitromodel system. Both viable and nonviable NTHI strains were shown to promote NET formation, as did preparations of bacterial DNA, outer membrane proteins, and lipooligosaccharide (endotoxin). However, only endotoxin from a parental strain of NTHI exhibited equivalent potency in NET formation to that of NTHI. Additional studies showed that NTHI entrapped within NET structures is resistant to both extracellular killing within NETs and phagocytic killing by incoming neutrophils, due to oligosaccharide moieties within the lipooligosaccharides. Thus, we concluded that NTHI elicits NET formation by means of multiple pathogen-associated molecular patterns (most notably endotoxin) and is highly resistant to killing within NET structures. These data support the conclusion that, for NTHI, formation of NET structures may be a persistence determinant by providing a niche within the middle-ear chamber.

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Erythromycin suppresses neutrophil extracellular traps in smoking-related chronic pulmonary inflammation

Cell Death and Disease ◽

10.1038/s41419-019-1909-2 ◽

2019 ◽

Vol 10 (9) ◽

Cited By ~ 5

Author(s):

Hui Zhang ◽

Shi-Lin Qiu ◽

Qi-Ya Tang ◽

Xiu Zhou ◽

Jian-Quan Zhang ◽

...

Keyword(s):

Adaptive Immunity ◽

Cigarette Smoke ◽

Critical Role ◽

Neutrophil Extracellular Traps ◽

Airflow Limitation ◽

Chronic Obstructive ◽

Myeloid Dendritic Cells ◽

Extracellular Traps

Abstract Neutrophil extracellular traps (NETs) may play a critical role in smoking-related chronic airway inflammation. However, the mechanism by which NETs induced by cigarette smoke initiate the adaptive immunity in chronic obstructive pulmonary disease (COPD) is not fully understood. In this study, we explored the effects of NETs induced by cigarette smoke on the myeloid dendritic cells (mDCs) and Th1 and Th17 cells. Additionally, we observed the inhibitory effect of erythromycin on NETs induced by cigarette smoke. We found that elevated NET levels in the sputum of COPD patients were correlated with the circulating Th1 response, mDC activation and airflow limitation. NETs induced by cigarette smoke extract (CSE) could activate monocyte-derived mDCs and promote Th1 and Th17 differentiation in vitro. Erythromycin effectively inhibited NET formation induced by CSE. In vivo, erythromycin decreased NETs in the airway and ameliorated emphysema with Th1 and Th17 cell down-regulation and CD40+ and CD86+ mDCs suppression in mice chronically exposed to cigarette smoke. These findings provide direct evidence that NETs promote the differentiation of Th1 and Th17 and play a role in the adaptive immunity of smoking-related chronic lung inflammation. Erythromycin is a potential therapeutic strategy for NETs inhibition in COPD.

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In vivo induction of neutrophil extracellular traps by Mycobacterium tuberculosis in a guinea pig model

Innate Immunity ◽

10.1177/1753425917732406 ◽

2017 ◽

Vol 23 (7) ◽

pp. 625-637 ◽

Cited By ~ 8

Author(s):

Georgina Filio-Rodríguez ◽

Iris Estrada-García ◽

Patricia Arce-Paredes ◽

María M Moreno-Altamirano ◽

Sergio Islas-Trujillo ◽

...

Keyword(s):

Mycobacterium Tuberculosis ◽

Guinea Pig ◽

Neutrophil Extracellular Traps ◽

Post Inoculation ◽

Extracellular Traps ◽

Guinea Pig Model ◽

In Vivo Induction ◽

Proteins And Peptides

In 2004, a novel mechanism of cellular death, called ‘NETosis’, was described in neutrophils. This mechanism, different from necrosis and apoptosis, is characterized by the release of chromatin webs admixed with microbicidal granular proteins and peptides (NETs). NETs trap and kill a variety of microorganisms. Diverse microorganisms, including Mycobacterium tuberculosis, are NET inducers in vitro. The aim of this study was to examine whether M. tuberculosis can also induce NETs in vivo and if the NETs are bactericidal to the microorganism. Guinea pigs were intradermally inoculated with M. tuberculosis H37Rv, and the production of NETs was investigated at several time points thereafter. NETs were detected as early as 30 min post-inoculation and were clearly evident by 4 h post-inoculation. NETs produced in vivo contained DNA, myeloperoxidase, elastase, histones, ROS and acid-fast bacilli. Viable and heat-killed M. tuberculosis, as well as Mycobacterium bovis BCG were efficient NET inducers, as were unilamellar liposomes prepared with lipids from M. tuberculosis. In vitro, guinea pig neutrophils also produced NETs in response to M. tuberculosis. However, neither the in vivo nor the in vitro-produced NETs were able to kill M. tuberculosis. Nevertheless, in vivo, neutrophils might propitiate recruitment and activation of more efficient microbicidal cells.

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