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1.
Shock ; 57(1): 1-6, 2022 01 01.
Article in English | MEDLINE | ID: covidwho-2191212

ABSTRACT

BACKGROUND: The pathomechanisms of hypoxemia and treatment strategies for type H and type L acute respiratory distress syndrome (ARDS) in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-induced coronavirus disease 2019 (COVID-19) have not been elucidated. MAIN TEXT: SARS-CoV-2 mainly targets the lungs and blood, leading to ARDS, and systemic thrombosis or bleeding. Angiotensin II-induced coagulopathy, SARS-CoV-2-induced hyperfibrin(ogen)olysis, and pulmonary and/or disseminated intravascular coagulation due to immunothrombosis contribute to COVID-19-associated coagulopathy. Type H ARDS is associated with hypoxemia due to diffuse alveolar damage-induced high right-to-left shunts. Immunothrombosis occurs at the site of infection due to innate immune inflammatory and coagulofibrinolytic responses to SARS-CoV-2, resulting in microvascular occlusion with hypoperfusion of the lungs. Lung immunothrombosis in type L ARDS results from neutrophil extracellular traps containing platelets and fibrin in the lung microvasculature, leading to hypoxemia due to impaired blood flow and a high ventilation/perfusion (VA/Q) ratio. COVID-19-associated ARDS is more vascular centric than the other types of ARDS. D-dimer levels have been monitored for the progression of microvascular thrombosis in COVID-19 patients. Early anticoagulation therapy in critical patients with high D-dimer levels may improve prognosis, including the prevention and/or alleviation of ARDS. CONCLUSIONS: Right-to-left shunts and high VA/Q ratios caused by lung microvascular thrombosis contribute to hypoxemia in type H and L ARDS, respectively. D-dimer monitoring-based anticoagulation therapy may prevent the progression to and/or worsening of ARDS in COVID-19 patients.


Subject(s)
COVID-19/physiopathology , Hemostasis/physiology , Hypoxia/physiopathology , Respiratory Distress Syndrome/physiopathology , Thrombosis/physiopathology , Anticoagulants/therapeutic use , Biomarkers/blood , Blood Platelets/metabolism , COVID-19/drug therapy , Extracellular Traps/metabolism , Fibrin/metabolism , Fibrin Fibrinogen Degradation Products/analysis , Fibrinolysis , Humans , Lung/blood supply , Microvessels/physiopathology , Phenotype , Respiratory Distress Syndrome/drug therapy , SARS-CoV-2 , Thrombosis/drug therapy
2.
Genome Med ; 14(1): 135, 2022 Nov 28.
Article in English | MEDLINE | ID: covidwho-2139390

ABSTRACT

BACKGROUND: As circulating DNA (cirDNA) is mainly detected as mononucleosome-associated circulating DNA (mono-N cirDNA) in blood, apoptosis has until now been considered as the main source of cirDNA. The mechanism of cirDNA release into the circulation, however, is still not fully understood. This work addresses that knowledge gap, working from the postulate that neutrophil extracellular traps (NET) may be a source of cirDNA, and by investigating whether NET may directly produce mono-N cirDNA. METHODS: We studied (1) the in vitro kinetics of cell derived genomic high molecular weight (gHMW) DNA degradation in serum; (2) the production of extracellular DNA and NET markers such as neutrophil elastase (NE) and myeloperoxidase (MPO) by ex vivo activated neutrophils; and (3) the in vitro NET degradation in serum; for this, we exploited the synergistic analytical information provided by specifically quantifying DNA by qPCR, and used shallow WGS and capillary electrophoresis to perform fragment size analysis. We also performed an in vivo study in knockout mice, and an in vitro study of gHMW DNA degradation, to elucidate the role of NE and MPO in effecting DNA degradation and fragmentation. We then compared the NET-associated markers and fragmentation size profiles of cirDNA in plasma obtained from patients with inflammatory diseases found to be associated with NET formation and high levels of cirDNA (COVID-19, N = 28; systemic lupus erythematosus, N = 10; metastatic colorectal cancer, N = 10; and from healthy individuals, N = 114). RESULTS: Our studies reveal that gHMW DNA degradation in serum results in the accumulation of mono-N DNA (81.3% of the remaining DNA following 24 h incubation in serum corresponded to mono-N DNA); "ex vivo" NET formation, as demonstrated by a concurrent 5-, 5-, and 35-fold increase of NE, MPO, and cell-free DNA (cfDNA) concentration in PMA-activated neutrophil culture supernatant, leads to the release of high molecular weight DNA that degrades down to mono-N in serum; NET mainly in the form of gHMW DNA generate mono-N cirDNA (2 and 41% of the remaining DNA after 2 h in serum corresponded to 1-10 kbp fragments and mono-N, respectively) independent of any cellular process when degraded in serum; NE and MPO may contribute synergistically to NET autocatabolism, resulting in a 25-fold decrease in total DNA concentration and a DNA fragment size profile similar to that observed from cirDNA following 8 h incubation with both NE and MPO; the cirDNA size profile of NE KO mice significantly differed from that of the WT, suggesting NE involvement in DNA degradation; and a significant increase in the levels of NE, MPO, and cirDNA was detected in plasma samples from lupus, COVID-19, and mCRC, showing a high correlation with these inflammatory diseases, while no correlation of NE and MPO with cirDNA was found in HI. CONCLUSIONS: Our work describes the mechanisms by which NET and cirDNA are linked. In doing so, we demonstrate that NET are a major source of mono-N cirDNA independent of apoptosis and establish a new paradigm of the mechanisms of cirDNA release in normal and pathological conditions. We also demonstrate a link between immune response and cirDNA.


Subject(s)
COVID-19 , Cell-Free Nucleic Acids , Extracellular Traps , Animals , Mice , Neutrophils , Genomics
3.
Sci Transl Med ; 14(671): eabo5795, 2022 Nov 16.
Article in English | MEDLINE | ID: covidwho-2119264

ABSTRACT

Interstitial lung disease and associated fibrosis occur in a proportion of individuals who have recovered from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection through unknown mechanisms. We studied individuals with severe coronavirus disease 2019 (COVID-19) after recovery from acute illness. Individuals with evidence of interstitial lung changes at 3 to 6 months after recovery had an up-regulated neutrophil-associated immune signature including increased chemokines, proteases, and markers of neutrophil extracellular traps that were detectable in the blood. Similar pathways were enriched in the upper airway with a concomitant increase in antiviral type I interferon signaling. Interaction analysis of the peripheral phosphoproteome identified enriched kinases critical for neutrophil inflammatory pathways. Evaluation of these individuals at 12 months after recovery indicated that a subset of the individuals had not yet achieved full normalization of radiological and functional changes. These data provide insight into mechanisms driving development of pulmonary sequelae during and after COVID-19 and provide a rational basis for development of targeted approaches to prevent long-term complications.


Subject(s)
COVID-19 , Extracellular Traps , Humans , SARS-CoV-2 , Neutrophils , Lung
4.
Bratisl Lek Listy ; 123(11): 846-852, 2022.
Article in English | MEDLINE | ID: covidwho-2080685

ABSTRACT

BACKGROUND: Abnormal neutrophil extracellular traps are associated with lung diseases, thrombosis, increased mucosal secretion in the airways. The aim of this study is to evaluate the possible place of the most specific NETosis marker Cit-H3 protein in diagnostic algorithms by revealing its relationship with the severity, mortality and prognosis of SARS-CoV-2 pneumonia. PATIENTS AND METHODS: Patients (n = 78) who applied to the Emergency Department between March 11, 2020 and June 10, 2020, with positive SARS-CoV-2 polymerase chain reaction (PCR) test and lung involvement were included in the prospective study. Serum Cit-H3 levels and critical laboratory parameters were measured at baseline on the day of clinical deterioration and before recovery/discharge/death. Cit-C3 levels were determined by enzyme immunassay method. RESULTS: Cit-H3 levels in patients with SARS-CoV-2 pneumonia during their first admission to the hospital were significantly higher compared to the healthy control group (p < 0.05). Repeated measurements of Cit-H3 levels of the patients significantly correlated with D-dimer, procalcitonin, Neutrophil/ Lymphocyte ratio, lymphocyte, CRP, and oxygen saturation. Cit-H3 levels of the patients who died were significantly higher than that of those who survived (p < 0.05). Cit-H3 levels were found to be statistically significantly higher in patients who developed acute respiratory distress syndrome, were admitted to the intensive care unit, and had mortality (p < 0.05). CONCLUSIONS: Cit-H3 plays a role in inflammatory processes in SARS-CoV-2 pneumonia, and changes in serum Cit-H3 levels of these patients can be used to determine prognosis and mortality (Tab. 5, Fig. 1, Ref. 21).


Subject(s)
COVID-19 , Extracellular Traps , Humans , Procalcitonin , Prospective Studies , SARS-CoV-2
5.
Scand J Clin Lab Invest ; 82(6): 481-485, 2022 10.
Article in English | MEDLINE | ID: covidwho-2042400

ABSTRACT

Persisting inflammation has been discovered in lungs and other parenchymatous organs of some COVID-19 convalescents. Calprotectin, neutrophil extracellular traps (NETs), syndecan-1 and neopterin are general key inflammatory markers, and systemically enhanced levels of them may remain after the COVID-19 infection. These inflammatory markers were therefore measured in serum samples of 129 COVID-19 convalescent and 27 healthy blood donors or employees at Oslo Blood bank, Norway. Also antibodies against SARS-CoV-2 nucleocapsid antigen were measured, and timing of sampling and severity of infection noted. Whereas neopterin and NETs values remained low and those for syndecan-1 were not raised to statistically significant level, concentrations for calprotectin, as measured by a novel mixed monoclonal assay, were significantly increased in the convalescents. Antibodies against SARS-CoV-2 nucleocapsid antigen were elevated, but did not correlate with levels of inflammatory markers. Difference between the groups in only one biomarker makes evaluation of ongoing or residual inflammation in the convalescents difficult. If there is a low-grade inflammation, it would in that case involve neutrophils.


Subject(s)
COVID-19 , Extracellular Traps , Biomarkers , Blood Donors , COVID-19/diagnosis , Humans , Inflammation/diagnosis , Leukocyte L1 Antigen Complex , Neopterin , SARS-CoV-2 , Syndecan-1
6.
Front Cell Infect Microbiol ; 12: 900895, 2022.
Article in English | MEDLINE | ID: covidwho-2009847

ABSTRACT

Fungal infections are global public health problems and can lead to substantial human morbidity and mortality. Current antifungal therapy is not satisfactory, especially for invasive, life-threatening fungal infections. Modulating the antifungal capacity of the host immune system is a feasible way to combat fungal infections. Neutrophils are key components of the innate immune system that resist fungal pathogens by releasing reticular extracellular structures called neutrophil extracellular traps (NETs). When compared with phagocytosis and oxidative burst, NETs show better capability in terms of trapping large pathogens, such as fungi. This review will summarize interactions between fungal pathogens and NETs. Molecular mechanisms of fungi-induced NETs formation and defensive strategies used by fungi are also discussed.


Subject(s)
Extracellular Traps , Mycoses , Antifungal Agents , Humans , Neutrophils , Phagocytosis
7.
Nat Commun ; 13(1): 5206, 2022 09 05.
Article in English | MEDLINE | ID: covidwho-2008281

ABSTRACT

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare yet serious adverse effect of the adenoviral vector vaccines ChAdOx1 nCoV-19 (AstraZeneca) and Ad26.COV2.S (Janssen) against COVID-19. The mechanisms involved in clot formation and thrombocytopenia in VITT are yet to be fully determined. Here we show neutrophils undergoing NETosis and confirm expression markers of NETs in VITT patients. VITT antibodies directly stimulate neutrophils to release NETs and induce thrombus formation containing abundant platelets, neutrophils, fibrin, extracellular DNA and citrullinated histone H3 in a flow microfluidics system and in vivo. Inhibition of NETosis prevents VITT-induced thrombosis in mice but not thrombocytopenia. In contrast, in vivo blockage of FcγRIIa abrogates both thrombosis and thrombocytopenia suggesting these are distinct processes. Our findings indicate that anti-PF4 antibodies activate blood cells via FcγRIIa and are responsible for thrombosis and thrombocytopenia in VITT. Future development of NETosis and FcγRIIa inhibitors are needed to treat VITT and similar immune thrombotic thrombocytopenia conditions more effectively, leading to better patient outcomes.


Subject(s)
COVID-19 , Extracellular Traps , Purpura, Thrombocytopenic, Idiopathic , Thrombocytopenia , Thrombosis , Vaccines , Ad26COVS1 , Animals , ChAdOx1 nCoV-19 , Extracellular Traps/metabolism , Humans , Mice , Purpura, Thrombocytopenic, Idiopathic/chemically induced , Thrombocytopenia/chemically induced , Thrombosis/prevention & control , Vaccines/metabolism
8.
Front Immunol ; 13: 953195, 2022.
Article in English | MEDLINE | ID: covidwho-1990285

ABSTRACT

Acute lung injury (ALI) is a heterogeneous inflammatory condition associated with high morbidity and mortality. Neutrophils play a key role in the development of different forms of ALI, and the release of neutrophil extracellular traps (NETs) is emerging as a common pathogenic mechanism. NETs are essential in controlling pathogens, and their defective release or increased degradation leads to a higher risk of infection. However, NETs also contain several pro-inflammatory and cytotoxic molecules than can exacerbate thromboinflammation and lung tissue injury. To reduce NET-mediated lung damage and inflammation, DNase is frequently used in preclinical models of ALI due to its capability of digesting NET DNA scaffold. Moreover, recent advances in neutrophil biology led to the development of selective NET inhibitors, which also appear to reduce ALI in experimental models. Here we provide an overview of the role of NETs in different forms of ALI discussing existing gaps in our knowledge and novel therapeutic approaches to modulate their impact on lung injury.


Subject(s)
Acute Lung Injury , Extracellular Traps , Thrombosis , Acute Lung Injury/pathology , Extracellular Traps/metabolism , Humans , Inflammation/metabolism , Neutrophils/metabolism , Thrombosis/metabolism
9.
Cells ; 11(15)2022 08 08.
Article in English | MEDLINE | ID: covidwho-1993939

ABSTRACT

Innate immunity responds to infections and inflammatory stimuli through a carefully choreographed set of interactions between cells, stimuli and their specific receptors. Of particular importance are endogenous peptides, which assume roles as defensins or alarmins, growth factors or wound repair inducers. LL-37, a proteolytic fragment of cathelicidin, fulfills the roles of a defensin by inserting into the membranes of bacterial pathogens, functions as alarmin in stimulating chemotaxis of innate immune cells, and alters the structure and efficacy of various cytokines. Here, we draw attention to the direct effect of LL-37 on neutrophils and the release of extracellular traps (NETs), as NETs have been established as mediators of immune defense against pathogens but also as important contributors to chronic disease and tissue pathogenesis. We propose a specific structural basis for LL-37 function, in part by highlighting the structural flexibility of LL-37 and its ability to adapt to distinct microenvironments and interacting counterparts.


Subject(s)
Extracellular Traps , Bacteria , Chemotaxis , Immunity, Innate , Neutrophils/metabolism
10.
Nat Rev Rheumatol ; 18(10): 552, 2022 10.
Article in English | MEDLINE | ID: covidwho-1991622
11.
Front Immunol ; 13: 951254, 2022.
Article in English | MEDLINE | ID: covidwho-1987497

ABSTRACT

Neutrophil extracellular traps (NETs) are web-like structures extruded by neutrophils after activation or in response to microorganisms. These extracellular structures are decondensed chromatin fibers loaded with antimicrobial granular proteins, peptides, and enzymes. NETs clear microorganisms, thus keeping a check on infections at an early stage, but if dysregulated, may be self-destructive to the body. Indeed, NETs have been associated with autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), antiphospholipid syndrome (APS), psoriasis, and gout. More recently, increased NETs associate with COVID-19 disease severity. While there are rigorous and reliable methods to quantify NETs from neutrophils via flow cytometry and immunofluorescence, the accurate quantification of NETs in patient plasma or serum remains a challenge. Here, we developed new methodologies for the quantification of NETs in patient plasma using multiplex ELISA and immunofluorescence methodology. Plasma from patients with SLE, non-genotyped healthy controls, and genotyped healthy controls that carry either the homozygous risk or non-risk IRF5-SLE haplotype were used in this study. The multiplex ELISA using antibodies detecting myeloperoxidase (MPO), citrullinated histone H3 (CitH3) and DNA provided reliable detection of NETs in plasma samples from SLE patients and healthy donors that carry IRF5 genetic risk. An immunofluorescence smear assay that utilizes only 1 µl of patient plasma provided similar results and data correlate to multiplex ELISA findings. The immunofluorescence smear assay is a relatively simple, inexpensive, and quantifiable method of NET detection for small volumes of patient plasma.


Subject(s)
COVID-19 , Extracellular Traps , Lupus Erythematosus, Systemic , Humans , Interferon Regulatory Factors/metabolism , Neutrophils
13.
Biomolecules ; 12(8)2022 07 27.
Article in English | MEDLINE | ID: covidwho-1969083

ABSTRACT

Background: Neutrophil extracellular traps' (NETs') formation is a mechanism of defense that neutrophils deploy as an alternative to phagocytosis, to constrain the spread of microorganisms. Aim: The aim was to evaluate biomarkers of NETs' formation in a patient cohort admitted to intensive care unit (ICU) due to infection. Methods: Forty-six septic shock patients, 22 critical COVID-19 patients and 48 matched control subjects were recruited. Intact nucleosomes containing histone 3.1 (Nu.H3.1), or citrullinated histone H3R8 (Nu.Cit-H3R8), free citrullinated histone (Cit-H3), neutrophil elastase (NE) and myeloperoxidase (MPO) were measured. Results: Significant differences in Nu.H3.1 and NE levels were observed between septic shock and critical COVID-19 subjects as well as with controls (p-values < 0.05). The normalization of nucleosome levels according to the neutrophil count improved the discrimination between septic shock and critical COVID-19 patients. The ratio of Nu.Cit-H3R8 to Nu.H3.1 allowed the determination of nucleosome citrullination degree, presumably by PAD4. Conclusions: H3.1 and Cit-H3R8 nucleosomes appear to be interesting markers of global cell death and neutrophil activation when combined. Nu.H3.1 permits the evaluation of disease severity and differs between septic shock and critical COVID-19 patients, reflecting two distinct potential pathological processes in these conditions.


Subject(s)
COVID-19 , Extracellular Traps , Shock, Septic , Biomarkers/metabolism , Extracellular Traps/metabolism , Histones/metabolism , Humans , Neutrophils/metabolism , Nucleosomes/metabolism , Shock, Septic/metabolism
14.
JCI Insight ; 7(16)2022 08 22.
Article in English | MEDLINE | ID: covidwho-1950563

ABSTRACT

Dysregulation in neutrophil extracellular trap (NET) formation and degradation may play a role in the pathogenesis and severity of COVID-19; however, its role in the pediatric manifestations of this disease, including multisystem inflammatory syndrome in children (MIS-C) and chilblain-like lesions (CLLs), otherwise known as "COVID toes," remains unclear. Studying multinational cohorts, we found that, in CLLs, NETs were significantly increased in serum and skin. There was geographic variability in the prevalence of increased NETs in MIS-C, in association with disease severity. MIS-C and CLL serum samples displayed decreased NET degradation ability, in association with C1q and G-actin or anti-NET antibodies, respectively, but not with genetic variants of DNases. In adult COVID-19, persistent elevations in NETs after disease diagnosis were detected but did not occur in asymptomatic infection. COVID-19-affected adults displayed significant prevalence of impaired NET degradation, in association with anti-DNase1L3, G-actin, and specific disease manifestations, but not with genetic variants of DNases. NETs were detected in many organs of adult patients who died from COVID-19 complications. Infection with the Omicron variant was associated with decreased NET levels when compared with other SARS-CoV-2 strains. These data support a role for NETs in the pathogenesis and severity of COVID-19 in pediatric and adult patients.


Subject(s)
COVID-19 , Extracellular Traps , Actins/metabolism , Adult , COVID-19/complications , Child , Deoxyribonuclease I , Humans , Neutrophils , SARS-CoV-2 , Systemic Inflammatory Response Syndrome
15.
Arterioscler Thromb Vasc Biol ; 42(9): 1103-1112, 2022 09.
Article in English | MEDLINE | ID: covidwho-1950525

ABSTRACT

The activating interplay of thrombosis and inflammation (thromboinflammation) has been established as a major underlying pathway, driving not only cardiovascular disease but also autoimmune disease and most recently, COVID-19. Throughout the years, innate immune cells have emerged as important modulators of this process. As the most abundant white blood cell in humans, neutrophils are well-positioned to propel thromboinflammation. This includes their ability to trigger an organized cell death pathway with the release of decondensed chromatin structures called neutrophil extracellular traps. Decorated with histones and cytoplasmic and granular proteins, neutrophil extracellular traps exert cytotoxic, immunogenic, and prothrombotic effects accelerating disease progression. Distinct steps leading to extracellular DNA release (NETosis) require the activities of PAD4 (protein arginine deiminase 4) catalyzing citrullination of histones and are supported by neutrophil inflammasome. By linking the immunologic function of neutrophils with the procoagulant and proinflammatory activities of monocytes and platelets, PAD4 activity holds important implications for understanding the processes that fuel thromboinflammation. We will also discuss mechanisms whereby vascular occlusion in thromboinflammation depends on the interaction of neutrophil extracellular traps with ultra-large VWF (von Willebrand Factor) and speculate on the importance of PAD4 in neutrophil inflammasome assembly and neutrophil extracellular traps in thromboinflammatory diseases including atherosclerosis and COVID-19.


Subject(s)
Atherosclerosis , COVID-19 , Extracellular Traps , Thrombosis , Atherosclerosis/metabolism , Extracellular Traps/metabolism , Histones/metabolism , Humans , Inflammasomes/metabolism , Inflammation/metabolism , Neutrophils/metabolism , Thromboinflammation , Thrombosis/etiology , Thrombosis/metabolism , von Willebrand Factor/metabolism
16.
Front Immunol ; 13: 872695, 2022.
Article in English | MEDLINE | ID: covidwho-1952330

ABSTRACT

The frequent severe COVID-19 course in patients with periodontitis suggests a link of the aetiopathogenesis of both diseases. The formation of intravascular neutrophil extracellular traps (NETs) is crucial to the pathogenesis of severe COVID-19. Periodontitis is characterised by an increased level of circulating NETs, a propensity for increased NET formation, delayed NET clearance and low-grade endotoxemia (LGE). The latter has an enormous impact on innate immunity and susceptibility to infection with SARS-CoV-2. LPS binds the SARS-CoV-2 spike protein and this complex, which is more active than unbound LPS, precipitates massive NET formation. Thus, circulating NET formation is the common denominator in both COVID-19 and periodontitis and other diseases with low-grade endotoxemia like diabetes, obesity and cardiovascular diseases (CVD) also increase the risk to develop severe COVID-19. Here we discuss the role of propensity for increased NET formation, DNase I deficiency and low-grade endotoxaemia in periodontitis as aggravating factors for the severe course of COVID-19 and possible strategies for the diminution of increased levels of circulating periodontitis-derived NETs in COVID-19 with periodontitis comorbidity.


Subject(s)
COVID-19 , Endotoxemia , Extracellular Traps , Periodontitis , Endotoxemia/metabolism , Humans , Lipopolysaccharides/metabolism , Neutrophils , Periodontitis/pathology , SARS-CoV-2 , Spike Glycoprotein, Coronavirus
17.
Curr Opin Hematol ; 29(5): 259-265, 2022 09 01.
Article in English | MEDLINE | ID: covidwho-1948583

ABSTRACT

PURPOSE OF REVIEW: COVID-19 remains a major source of concern, particularly as new variants emerge and with recognition that patients may suffer long-term effects. Mechanisms underlying SARS-CoV-2 mediated organ damage and the associated vascular endotheliopathy remain poorly understood, hindering new drug development. Here, we highlight selected key concepts of how the complement system, a major component of innate immunity that is dysregulated in COVID-19, participates in the thromboinflammatory response and drives the vascular endotheliopathy. RECENT FINDINGS: Recent studies have revealed mechanisms by which complement is activated directly by SARS-CoV-2, and how the system interfaces with other innate thromboinflammatory cellular and proteolytic pathways involving platelets, neutrophils, neutrophil extracellular traps and the coagulation and kallikrein-kinin systems. With this new information, multiple potential sites for therapeutic intervention are being uncovered and evaluated in the clinic. SUMMARY: Infections with SARS-CoV-2 cause damage to the lung alveoli and microvascular endothelium via a process referred to as thromboinflammation. Although not alone in being dysregulated, complement is an early player, prominent in promoting the endotheliopathy and consequential organ damage, either directly and/or via the system's complex interplay with other cellular, molecular and biochemical pathways. Delineating these critical interactions is revealing novel and promising strategies for therapeutic intervention.


Subject(s)
COVID-19 , Extracellular Traps , Thrombosis , Complement System Proteins , Humans , Inflammation , SARS-CoV-2 , Thrombosis/etiology
18.
Chest ; 162(5): 1006-1016, 2022 Nov.
Article in English | MEDLINE | ID: covidwho-1944506

ABSTRACT

BACKGROUND: Excessive inflammation is pathogenic in the pneumonitis associated with severe COVID-19. Neutrophils are among the most abundantly present leukocytes in the inflammatory infiltrates and may form neutrophil extracellular traps (NETs) under the local influence of cytokines. NETs constitute a defense mechanism against bacteria, but have also been shown to mediate tissue damage in a number of diseases. RESEARCH QUESTION: Could NETs and their tissue-damaging properties inherent to neutrophil-associated functions play a role in the respiratory failure seen in patients with severe COVID-19, and how does this relate to the SARS-CoV-2 viral loads, IL-8 (CXCL8) chemokine expression, and cytotoxic T-lymphocyte infiltrates? STUDY DESIGN AND METHODS: Sixteen lung biopsy samples obtained immediately after death were analyzed methodically as exploratory and validation cohorts. NETs were analyzed quantitatively by multiplexed immunofluorescence and were correlated with local levels of IL-8 messenger RNA (mRNA) and the density of CD8+ T-cell infiltration. SARS-CoV-2 presence in tissue was quantified by reverse-transcriptase polymerase chain reaction and immunohistochemistry analysis. RESULTS: NETs were found in the lung interstitium and surrounding the bronchiolar epithelium with interindividual and spatial heterogeneity. NET density did not correlate with SARS-CoV-2 tissue viral load. NETs were associated with local IL-8 mRNA levels. NETs were also detected in pulmonary thrombi and in only one of eight liver tissues. NET focal presence correlated negatively with CD8+ T-cell infiltration in the lungs. INTERPRETATION: Abundant neutrophils undergoing NETosis are found in the lungs of patients with fatal COVID-19, but no correlation was found with viral loads. The strong association between NETs and IL-8 points to this chemokine as a potentially causative factor. The function of cytotoxic T-lymphocytes in the immune responses against SARS-CoV-2 may be interfered with by the presence of NETs.


Subject(s)
COVID-19 , Extracellular Traps , Humans , Extracellular Traps/physiology , SARS-CoV-2 , T-Lymphocytes, Cytotoxic , Interleukin-8 , Lung , Neutrophils/pathology , RNA, Messenger/metabolism
19.
Front Immunol ; 13: 879157, 2022.
Article in English | MEDLINE | ID: covidwho-1933664

ABSTRACT

During the COVID-19 pandemic, vaccination is the most important countermeasure. Pharmacovigilance concerns however emerged with very rare, but potentially disastrous thrombotic complications following vaccination with ChAdOx1. Platelet factor-4 antibody mediated vaccine-induced immune thrombotic thrombocytopenia (VITT) was described as an underlying mechanism of these thrombotic events. Recent work moreover suggests that mechanisms of immunothrombosis including neutrophil extracellular trap (NET) formation might be critical for thrombogenesis during VITT. In this study, we investigated blood and thrombus specimens of a female patient who suffered severe stroke due to VITT after vaccination with ChAdOx1 in comparison to 13 control stroke patients with similar clinical characteristics. We analyzed cerebral thrombi using histological examination, staining of complement factors, NET-markers, DNase and LL-37. In blood samples at the hyper-acute phase of stroke and 7 days later, we determined cell-free DNA, myeloperoxidase-histone complexes, DNase activity, myeloperoxidase activity, LL-37 and inflammatory cytokines. NET markers were identified in thrombi of all patients. Interestingly, the thrombus of the VITT-patient exclusively revealed complement factors and high amounts of DNase and LL-37. High DNase activity was also measured in blood, implying a disturbed NET-regulation. Furthermore, serum of the VITT-patient inhibited reactive oxygen species-dependent NET-release by phorbol-myristate-acetate to a lesser degree compared to controls, indicating either less efficient NET-inhibition or enhanced NET-induction in the blood of the VITT-patient. Additionally, the changes in specific cytokines over time were emphasized in the VITT-patient as well. In conclusion, insufficient resolution of NETs, e.g. by endogenous DNases or protection of NETs against degradation by embedded factors like the antimicrobial peptide LL-37 might thus be an important factor in the pathology of VITT besides increased NET-formation. On the basis of these findings, we discuss the potential implications of the mechanisms of disturbed NETs-degradation for diagnostic and therapeutic approaches in VITT-related thrombogenesis, other auto-immune disorders and beyond.


Subject(s)
COVID-19 , Extracellular Traps , Purpura, Thrombocytopenic, Idiopathic , Stroke , Thrombocytopenia , Thrombosis , Vaccines , Deoxyribonuclease I/metabolism , Deoxyribonucleases , Female , Humans , Neutrophils , Pandemics , Peroxidase/metabolism , Platelet Factor 4/metabolism , Purpura, Thrombocytopenic, Idiopathic/metabolism , Stroke/etiology , Stroke/metabolism , Thrombocytopenia/chemically induced , Thrombocytopenia/metabolism , Thrombosis/etiology , Thrombosis/metabolism , Vaccines/metabolism
20.
Handb Exp Pharmacol ; 276: 43-64, 2022.
Article in English | MEDLINE | ID: covidwho-1930202

ABSTRACT

Neutrophils, the most abundant leukocytes in circulation and the first responders to infection and inflammation, closely modulate both acute and chronic inflammatory processes. Resting neutrophils constantly patrol vasculature and migrate to tissues when challenges occur. When infection and/or inflammation recede, tissue neutrophils will be subsequently cleaned up by macrophages which collectively contribute to the resolution of inflammation. While most studies focus on the anti-microbial function of neutrophils including phagocytosis, degranulation, and neutrophil extracellular traps (NETs) formation, recent research highlighted additional contributions of neutrophils beyond simply controlling infectious agents. Neutrophils with resolving characteristics may alter the activities of neighboring cells and facilitate inflammation resolution, modulate long-term macrophage and adaptive immune responses, therefore having important impacts on host pathophysiology. The focus of this chapter is to provide an updated assessment of recent progress in the emerging field of neutrophil programming and memory in the context of both acute and chronic diseases.


Subject(s)
Extracellular Traps , Neutrophils , Humans , Immunity, Innate , Inflammation , Macrophages , Neutrophils/pathology , Phagocytosis
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