Neutrophil Extracellular Traps and Their Implications in Cardiovascular and Inflammatory Disease

Neutrophils in Health and Disease: From Receptor Sensing to Inflammasome Activation

Neutrophils—polymorphonuclear cells (PMNs) are the cells of the initial immune response and make up the majority of leukocytes in the peripheral blood. After activation, these cells modify their functional status to meet the needs at the site of action or according to the agent causing injury. They receive signals from their surroundings and “plan” the course of the response in both temporal and spatial contexts. PMNs dispose of intracellular signaling pathways that allow them to perform a wide range of functions associated with the development of inflammatory processes. In addition to these cells, some protein complexes, known as inflammasomes, also have a special role in the development and maintenance of inflammation. These complexes participate in the proteolytic activation of key pro-inflammatory cytokines, such as IL-1β and IL-18. In recent years, there has been significant progress in the understanding of the structure and molecular mechanisms behind the activation of inflammasomes and their participation in the pathogenesis of numerous diseases. The available reports focus primarily on macrophages and dendritic cells. According to the literature, the activation of inflammasomes in neutrophils and the associated death type—pyroptosis—is regulated in a different manner than in other cells. The present work is a review of the latest reports concerning the course of inflammasome activation and inflammatory cytokine secretion in response to pathogens in neutrophils, as well as the role of these mechanisms in the pathogenesis of selected diseases.

PET Imaging of Neutrophil Elastase with 11C-GW457427 in Acute Respiratory Distress Syndrome in Pigs

Today, there is a lack of clinically available imaging techniques to detect and quantify specific immune cell populations. Neutrophils are one of the first immune cells at the site of inflammation, and they secrete the serine protease neutrophil elastase (NE), which is crucial in the fight against pathogens. However, the prolonged lifespan of neutrophils increases the risk that patients will develop severe complications, such as acute respiratory distress syndrome (ARDS). Here, we evaluated the novel radiolabeled NE inhibitor 11C-GW457427 in a pig model of ARDS, for detection and quantification of neutrophil activity in the lungs. Methods: ARDS was induced by intravenous administration of oleic acid to 5 farm pigs, and 4 were considered healthy controls. The severity of ARDS was monitored by clinical parameters of lung function and plasma biomarkers. Each pig was studied with 11C-GW457427 and PET/CT, before and after pretreatment with the NE inhibitor GW311616 to determine in vivo binding specificity. PET image data were analyzed as SUVs and correlated with immunohistochemical staining for NE in biopsies. Results: The binding of 11C-GW457427 was increased in pig lungs with induced ARDS (median SUVmean, 1.91; interquartile range [IQR], 1.67-2.55) compared with healthy control pigs (P < 0.05 and P = 0.03, respectively; median SUVmean, 1.04; IQR, 0.66-1.47). The binding was especially strong in lung regions with high levels of NE and ongoing inflammation, as verified by immunohistochemistry. The binding was successfully blocked by pretreatment of an NE inhibitor drug, which demonstrated the in vivo specificity of 11C-GW457427 (P < 0.05 and P = 0.04, respectively; median SUVmean, 0.60; IQR, 0.58-0.77). The binding in neutrophil-rich tissues such as bone marrow (P < 0.05 and P = 0.04, respectively; baseline median SUVmean, 5.01; IQR, 4.48-5.49; block median SUVmean, 1.57; IQR, 0.95-1.85) and spleen (median SUVmean, 2.14; IQR, 1.19-2.36) was also high in all pigs. Conclusion: 11C-GW457427 binds to NE in a porcine model of oleic acid-induced lung inflammation in vivo, with a specific increase in regional lung, bone marrow, and spleen SUV. 11C-GW457427 is a promising tool for localizing, tracking, and quantifying neutrophil-facilitated inflammation in clinical diagnostics and drug development.

Inhibition of Myeloperoxidase Pro-Fibrotic Effect by Noscapine in Equine Endometrium

Myeloperoxidase is an enzyme released by neutrophils when neutrophil extracellular traps (NETs) are formed. Besides myeloperoxidase activity against pathogens, it was also linked to many diseases, including inflammatory and fibrotic ones. Endometrosis is a fibrotic disease of the mare endometrium, with a large impact on their fertility, where myeloperoxidase was shown to induce fibrosis. Noscapine is an alkaloid with a low toxicity, that has been studied as an anti-cancer drug, and more recently as an anti-fibrotic molecule. This work aims to evaluate noscapine inhibition of collagen type 1 (COL1) induced by myeloperoxidase in equine endometrial explants from follicular and mid-luteal phases, at 24 and 48 h of treatment. The transcription of collagen type 1 alpha 2 chain (COL1A2), and COL1 protein relative abundance were evaluated by qPCR and Western blot, respectively. The treatment with myeloperoxidase increased COL1A2 mRNA transcription and COL1 protein, whereas noscapine was able to reduce this effect with respect to COL1A2 mRNA transcription, in a time/estrous cycle phase-dependent manner (in explants from the follicular phase, at 24 h of treatment). Our study indicates that noscapine is a promising drug to be considered as an anti-fibrotic molecule to prevent endometrosis development, making noscapine a strong candidate to be applied in future endometrosis therapies.

Enhanced neutrophil extracellular traps formation in AF patients with dilated left atrium

BACKGROUND

Atrial fibrillation (AF) is associated with cardiac remodelling and prothrombotic state. Enhanced neutrophil extracellular traps (NETs) formation has been reported in AF, contributing to thromboembolism.

PURPOSE

We investigated whether increased left atrium (LA) diameter and reduced left ventricular ejection fraction (LVEF) affect NETs formation and prothrombotic state in AF patients.

METHODS

In 243 AF patients (median CHA₂ DS₂ -VASc = 4) we measured LA diameter and LVEF, 123 of them with LVEF<50%. Moreover, we determined 3 markers of NETosis: circulating citrullinated histone H3 (H3cit), myeloperoxidase (MPO) and peptidylarginine deiminase 4 (PAD4), along with prothrombotic markers, including endogenous thrombin potential, plasma fibrin clot permeability (K_s ) and clot lysis time (CLT). Ischaemic cerebrovascular events, major bleeding and death were recorded during a median follow-up of 53 months, on anticoagulation.

RESULTS

LA diameter correlated positively with H3cit, MPO and PAD4, while LVEF was inversely associated with the same NETosis markers. After adjustment for age and body mass index, concentrations of MPO (per 10 units; β = -1.9, 95%CI -3.40;-0.42) and H3cit (per 10 units; β = 2.02, 95%CI 0.61-3.42) were independently associated with LVEF and LA diameter. LA diameter, but not LVEF, correlated inversely with Ks and positively with CLT. The Cox regression analysis revealed that H3cit >6.16 ng/mL (HR = 21.76, 95%CI 2.85-166.28, p = .003) and LA diameter > 46 mm (HR = 2.89, 95%CI 1.04-8.03, p = .043) independently predicted cerebrovascular ischaemic events (1.9%/year).

CONCLUSIONS

This hypothesis-generating study suggests that in AF enlarged LA diameter and reduced LVEF are associated with enhanced NETs formation, which might have clinical importance and contribute to thromboembolic events despite anticoagulation.

TGF-β1 and TGFβR2 Gene Polymorphisms in Patients with Unstable Angina

Acute coronary syndromes result from a sudden reduction in the lumen of a coronary artery as a result of atherosclerotic plaque rupture, its swelling or the formation of thrombotic lesions. Many mediators with inflammatory, prothrombotic and proatherogenic effects have been shown to be involved, including numerous cytokines, chemokines, adhesion molecules and growth factors. TGF-β1 is a pleiotropic cytokine found in various cells that regulates cell growth, differentiation and matrix production. The aim of our study was to assess the association between polymorphisms in the TGF-β1 gene (rs1800469, rs1800470) and polymorphisms in the TGFBR2 receptor gene (rs6785358, rs9838682) and the risk of unstable angina, as well as selected clinical parameters affecting the risk of ischemic heart disease. The study included 232 patients with unstable angina. The diagnosis of unstable angina was made by typical clinical presentation and confirmation of significant coronary artery lumen stenosis (>70%) during coronary angiography. There were no statistically significant differences in the distribution of TGFBR2 rs6785358 and rs9838682 genotypes and haplotypes between patients with unstable angina and control subjects. We observed increased values of plasma total and LDL cholesterol levels, as well as triglycerides, in patients with the TGFBR2 rs9838682 AA genotype. In patients with the TGFBR2 rs6785358 AA genotype, we noted increased BMI values. There were no statistically significant associations between other studied polymorphisms and clinical parameters. Polymorphisms in the TGF-β1 gene (rs1800469, rs1800470) and polymorphisms in the TGFBR2 receptor gene (rs6785358, rs9838682) are not significant risk factors for unstable angina in our population. The TGFBR2 gene rs9838682 polymorphism may influence the lipid parameters in patients with coronary artery disease.

The imbalance of circulating monocyte subgroups with a higher proportion of the CD14+CD16+CD163+ phenotype in patients with preeclampsia

BACKGROUND

Preeclampsia is a major cause of increased maternal and fetal morbidity and mortality, which is closely related to the abnormal maternal immune response. The skew of decidual macrophage polarization toward M1 phenotype has been proved to promote the pathogenesis of preeclampsia. However, it's not easy to monitor the change of decidual macrophage subtypes. The current study aims to examine the distribution of different circulating monocyte subtypes and analyze whether certain monocyte subtypes act as potential clinical indicators for preeclampsia.

METHODS

A total of 50 pregnant women [mild preeclampsia (n = 20); severe preeclampsia (n = 15); healthy pregnancy (n = 15)] and 15 healthy donors were included in the study. Medical information such as BMI, blood pressure, ALT, creatinine, thrombocyte, etc., were recorded. The frequency of different monocyte subtypes in venous blood were measured by flow cytometry. Serum level of IL-6 was detected using Roche-Hitachi cobas 8000. Serum concentration of inflammatory cytokines (IL-1β, IL-4, IL-10 and TNF-α) were measured by ELISA.

RESULTS

A circulating monocyte subset with both M1 and M2 markers (CD14+CD16+CD163+) was found to occupy an obvious higher proportion in the preeclampsia group than in the normal pregnancy group. The ratio of CD206+/CD206- M2-like monocytes was also increased in the preeclampsia group, and meanwhile, it had statistic difference between the mild- and the severe-preeclampsia group. Furthermore, the serum levels of IL-1β and TNF-α were positively correlated with the frequency of CD14+CD16+CD163+ intermediate monocytes in the preeclampsia group.

CONCLUSIONS

The increased proportion of CD14+C16+CD163+ circulating monocytes and the high ratio of CD206+/CD206- M2-like monocytes may act as potential clinical indicators for preeclampsia, with the superiority of convenience and dynamic monitoring.

Immune cells drive new immunomodulatory therapies for myocardial infarction: From basic to clinical translation

The high incidence of heart failure secondary to myocardial infarction (MI) has been difficult to effectively address. MI causes strong aseptic inflammation, and infiltration of different immune cells and changes in the local inflammatory microenvironment play a key regulatory role in ventricular remodeling. Therefore, the possibility of improving the prognosis of MI through targeted immunity has been of interest and importance in MI. However, previously developed immune-targeted therapies have not achieved significant success in clinical trials. Here, we propose that the search for therapeutic targets from different immune cells may be more precise and lead to better clinical translation. Specifically, this review summarizes the role and potential therapeutic targets of various immune cells in ventricular remodeling after MI, especially monocytes/macrophages and neutrophils, as a way to demonstrate the importance and potential of immunomodulatory therapies for MI. In addition, we analyze the reasons for the failure of previous immunomodulatory therapies and the issues that need to be addressed, as well as the prospects and targeting strategies of using immune cells to drive novel immunomodulatory therapies, hoping to advance the development of immunomodulatory therapies by providing evidence and new ideas.

Prognostic Value of Systemic Immune-Inflammation Index and NT-proBNP in Patients with Acute ST-Elevation Myocardial Infarction

Objective

Our aim was to assess systemic immune-inflammation index (SII) and NT-proBNP value either in singly or in combination to predict acute ST-elevation myocardial infarction (STEMI) patient prognosis.

Methods

Analyzed retrospectively the clinical features and laboratory data of STEMI confirmed patients in our hospital from January to December 2020. The levels of SII and NT-proBNP were detected. The Kaplan-Meier approach and Spearman's rank correlation coefficient were used to construct the overall major adverse cardiac event (MACE) curve. Multivariate Cox regression analysis was applied to detect MACE predictors. In addition, the Delong test and receiver operating characteristic (ROC) curve analyzed each factor performance on its own and composite multivariate index to predict MACEs.

Results

The MACE group showed statistically significant differences in SII, NT- proBNP in comparison to the non-MACE group (P=0.003, P <0.001). Based on Kaplan-Meier analysis, SII and NT-proBNP showed positive correlation with MACE (log-rank P < 0.001). SII and NT-proBNP were independent predicting factors for long-term MACEs in multivariate Cox regression analysis (P <0.001, HR: 2.952, 95% CI 1.565-5.566; P <0.001, HR: 2.112, 95% CI 1.662-2.683). SII and NT-proBNP exhibited a positive correlation (R = 0.187, P < 0.001) in correlation analysis. According to the ROC statistical analysis, the combination exhibited 78.0% sensitivity and 88.0% specificity in the prediction of MACE. According to the results of the AUC and Delong test, the combined SII and NT-proBNP performed better as a prognostic index than each of the individual factor indexes separately (Z = 2.622, P = 0.009; Z = 3.173, P < 0.001).

Conclusion

SII and NT-proBNP were independent indicators of clinical prognosis in acute STEMI patients, and they correlated positively. These factors could be combined to improve clinical prognosis.

Identification and validation of molecular subtype and prognostic signature for lung adenocarcinoma based on neutrophil extracellular traps

Background: Neutrophil Extracellular Traps (NETs) are fibrous networks made of DNA-histone complexes and proteins protruded from activated neutrophils. Accumulating evidences have highlighted the vital role of NETs in tumor progression and diffusion. However, limited systematic studies regarding the role of NETs in LUAD have been performed. Methods: Differentially expressed NETs-related genes and their mutation landscape were identified with TCGA database. Consensus clustering analysis was performed to determine the NETs-related subtypes of LUAD. LASSO algorithm was employed to construct a prognostic signature. Moreover, GSE30219 and GSE31210 were used as independent validation. We also constructed a lncRNA-miRNA-mRNA regulatory axis with several miRNA and lncRNA databases. Results: Consensus clustering identified two NETs-related clusters in LUAD. High NETs score was correlated with a favorable overall survival, abundant immune cell infiltration, and high activity of immune response signal pathways. Six NET-related genes (G0S2, KCNJ15, S100A12, AKT2, CTSG, and HMGB1) with significant prognostic value were screened to develop a prognostic signature. LUAD patients with low-risk had a significantly favorable overall survival both in the training set and validation set. Moreover, NETs-related risk score and clinical stage could act as an independent prognostic factor for LUAD patients. Significant correlation was obtained between risk score and tumor immune microenvironment. We also identified lncRNA BCYRN1/miR-3664-5p/CTSG regulatory axis that may be involved in the progression of LUAD. Conclusion: We developed two molecular subtypes and a prognostic signature for LUAD based on NETs-related genes. This stratification could provide more evidences for estimating the prognosis and immunotherapy of LAUD patients.

Neutrophil Extracellular Traps in Cerebral Ischemia/Reperfusion Injury: Friend and Foe

Cerebral ischemic injury, one of the leading causes of morbidity and mortality worldwide, triggers various central nervous system (CNS) diseases, including acute ischemic stroke (AIS) and chronic ischemia-induced Alzheimer's disease (AD). Currently, targeted therapies are urgently needed to address neurological disorders caused by cerebral ischemia/reperfusion injury (CI/RI), and the emergence of neutrophil extracellular traps (NETs) may be able to relieve the pressure. Neutrophils are precursors to brain injury following ischemic stroke and exert complicated functions. NETs extracellularly release reticular complexes of neutrophils, i.e., double-stranded DNA (dsDNA), histones, and granulins. Paradoxically, NETs play a dual role, friend and foe, under different conditions, for example, physiological circumstances, infection, neurodegeneration, and ischemia/reperfusion. Increasing evidence indicates that NETs exert anti-inflammatory effects by degrading cytokines and chemokines through protease at a relatively stable and moderate level under physiological conditions, while excessive amounts of NETs release (NETosis) irritated by CI/RI exacerbate the inflammatory response and aggravate thrombosis, disrupt the blood-brain barrier (BBB), and initiates sequential neuron injury and tissue damage. This review provides a comprehensive overview of the machinery of NETs formation and the role of an abnormal cascade of NETs in CI/RI, as well as other ischemia-induced neurological diseases. Herein, we highlight the potential of NETs as a therapeutic target against ischemic stroke that may inspire translational research and innovative clinical approaches.

Increased blood neutrophil extracellular traps (NETs) associated with early life stress: translational findings in recent-onset schizophrenia and rodent model

Higher levels of interleukin (IL)-6 and elevated neutrophil counts are consistently reported in the blood of patients with schizophrenia. Stressors during childhood and/or adolescence are major socioenvironmental risk factors for schizophrenia and may contribute to immune dysregulation. Previous studies using blood cytokines to stratify patients with schizophrenia suggest that only a subset presents a low-grade inflammatory state. However, these studies have not addressed whether environmental factors such as childhood maltreatment contributed to identifying inflammatory clusters. Moreover, a neutrophil-related mechanism (Neutrophil Extracellular Traps; NETs) central to both the initiation and chronicity of autoimmune and inflammatory diseases has never been investigated in psychiatry. Elevated NETs in schizophrenia may predispose patients to inflammatory and autoimmune diseases resulting in reduced life expectancy. We, therefore, investigated NETs as a novel mechanism and biological target in early schizophrenia and their role together with IL-6 and childhood maltreatment in identifying cluster subgroups. We found increased NETs in the plasma of patients with early schizophrenia (n = 78) compared to both their unaffected siblings (n = 25) and community controls (n = 78), irrespective of sex, body mass index, psychoactive drug use, or tobacco smoking. Increased NETs in patients were unrelated to antipsychotic treatment, which was further tested in vitro using fresh neutrophils. By applying unsupervised two-step clustering analysis, we integrated values of NETs, IL-6, and childhood maltreatment scores. We identified two main clusters; childhood maltreatment scores and NETs were the most important variables contributing to cluster separation (high-CL1 and low-CL2), while IL-6 was the least contributor. Patients allocated in the high-CL1 (61.5%) had significantly higher childhood maltreatment scores, NETs, and IL-6 levels than the remaining groups (patients low-CL2, siblings, and controls high-CL1 and low-CL2). We complemented these findings with a rat model based on stress exposure during adolescence that results in several schizophrenia-like changes in adulthood. We found that adolescent stressed rats had higher NETs and IL-6 levels in serum compared to non-stressed rats with a tendency to produce more NETs from the bone marrow. Altogether, this study brings a novel cellular-based mechanism in schizophrenia that, combined with early-stress, could be useful to identify subgroups for more personalised treatments.

Prognostic analysis of m6A-related genes as potential biomarkers in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive, fatal lung disease with limited treatment options. N6-methyladenosine (m6A) is a reversible RNA modification and has been implicated in various biological processes. However, there are few studies on m6A in IPF. This project mainly explores the prognostic value of m6A-related genes as potential biomarkers in IPF, in order to establish a set of accurate prognostic prediction model. In this study, we used GSE28042 dataset in GEO database to screen out 218 m6A-related candidate genes with high IPF correlation and high differential expression through differentially expressed gene analysis, WGCNA and m6A correlation analysis. The genes associated with the prognosis of IPF were screened out by univariate Cox regression analysis, LASSO analysis, and multivariate Cox regression analysis, and the multivariate Cox model of prognostic risk of related genes was constructed. We found that RBM11, RBM47, RIC3, TRAF5 and ZNF14 were key genes in our model. Finally, the prognostic prediction ability and independent prognostic characteristics of the risk model were evaluated by survival analysis and independent prognostic analysis, and verified by the GSE93606 dataset, which proved that the prognostic risk model we constructed has a strong and stable prediction efficiency.

Interleukin-33 Induces Neutrophil Extracellular Trap (NET) Formation and Macrophage Necroptosis via Enhancing Oxidative Stress and Secretion of Proatherogenic Factors in Advanced Atherosclerosis

Interleukin-33 (IL-33) acts as an 'alarmin', and its role has been demonstrated in driving immune regulation and inflammation in many human diseases. However, the precise mechanism of action of IL-33 in regulating neutrophil and macrophage functioning is not defined in advanced atherosclerosis (aAT) patients. Further, the role of IL-33 in neutrophil extracellular trap (NET) formation in aAT and its consequent effect on macrophage function is not known. In the present study, we recruited n = 52 aAT patients and n = 52 control subjects. The neutrophils were isolated from both groups via ficoll/percoll-based density gradient centrifugation. The effect of IL-33 on the NET formation ability of the neutrophils was determined in both groups. Monocytes, isolated via a positive selection method, were used to differentiate them into macrophages from each of the study subjects and were challenged by IL-33-primed NETs, followed by the measurement of oxidative stress by calorimetric assay and the expression of the proinflammatory molecules by quantitative PCR (qPCR). Transcript and protein expression was determined by qPCR and immunofluorescence/ELISA, respectively. The increased expression of IL-33R (ST-2) was observed in the neutrophils, along with an increased serum concentration of IL-33 in aAT compared to the controls. IL-33 exacerbates NET formation via specifically upregulating CD16 expression in aAT. IL-33-primed NETs/neutrophils increased the cellular oxidative stress levels in the macrophages, leading to enhanced macrophage necroptosis and the release of atherogenic factors and matrix metalloproteinases (MMPs) in aAT compared to the controls. These findings suggested a pathogenic effect of the IL-33/ST-2 pathway in aAT patients by exacerbating NET formation and macrophage necroptosis, thereby facilitating the release of inflammatory factors and the release of MMPs that may be critical for the destabilization/rupture of atherosclerotic plaques in aAT. Targeting the IL-33/ST-2-NETs axis may be a promising therapeutic target for preventing plaque instability/rupture and its adverse complications in aAT.

Bibliometric and visual analysis of neutrophil extracellular traps from 2004 to 2022

Background

Neutrophil extracellular traps (NETs) are specialized structures formed by neutrophils that were initially found to be important in killing pathogenic bacteria during infection. With the development of related research, the relationship between NETs and diseases such as sepsis, cancer, and systemic lupus erythematosus has received close attention. However, there is a lack of reports that comprehensively and objectively present the current status of NETs-related studies. Therefore, this study aims to visually analyze the current status and trends of NETs-related research by means of bibliometrics and knowledge mapping.

Methods

NETs-related articles and reviews were retrieved using the Web of Science core collection subject search, and bibliometric analysis was performed in Excel 365, CiteSpace, VOSviewer, and Bibliometrix (R-Tool of R-Studio).

Results

A total of 4866 publications from 2004 to 2022 were included in the bibliometric analysis. The number of publications shows an increasing trend from year to year. Collaborative network analysis shows that the United States and Germany are the most influential countries in this field, with the highest number of publications and citations. The journal with the most publications is Frontiers in Immunology. Brinkmann Volker is an authoritative author in this field, and his publication "Neutrophil extracellular traps kill bacteria" is the most frequently cited. The literature and keyword analysis shows that the relationship between NETs and diseases (hematological diseases, sepsis, cancer, etc.) and cell death (apoptosis, necroptosis, pyroptosis, etc.) is a popular research topic. Currently, NETs and SARS-CoV-2-related studies are at the forefront of the field.

Conclusion

This study is the first to visualize the research in NETs-related fields using bibliometric methods, revealing the trends and frontiers of NETs research. This study will provide valuable references for scholars to find research focus questions and partners.

A two-stage hybrid gene selection algorithm combined with machine learning models to predict the rupture status in intracranial aneurysms

An IA is an abnormal swelling of cerebral vessels, and a subset of these IAs can rupture causing aneurysmal subarachnoid hemorrhage (aSAH), often resulting in death or severe disability. Few studies have used an appropriate method of feature selection combined with machine learning by analyzing transcriptomic sequencing data to identify new molecular biomarkers. Following gene ontology (GO) and enrichment analysis, we found that the distinct status of IAs could lead to differential innate immune responses using all 913 differentially expressed genes, and considering that there are numerous irrelevant and redundant genes, we propose a mixed filter- and wrapper-based feature selection. First, we used the Fast Correlation-Based Filter (FCBF) algorithm to filter a large number of irrelevant and redundant genes in the raw dataset, and then used the wrapper feature selection method based on the he Multi-layer Perceptron (MLP) neural network and the Particle Swarm Optimization (PSO), accuracy (ACC) and mean square error (MSE) were then used as the evaluation criteria. Finally, we constructed a novel 10-gene signature (YIPF1, RAB32, WDR62, ANPEP, LRRCC1, AADAC, GZMK, WBP2NL, PBX1, and TOR1B) by the proposed two-stage hybrid algorithm FCBF-MLP-PSO and used different machine learning models to predict the rupture status in IAs. The highest ACC value increased from 0.817 to 0.919 (12.5% increase), the highest area under ROC curve (AUC) value increased from 0.87 to 0.94 (8.0% increase), and all evaluation metrics improved by approximately 10% after being processed by our proposed gene selection algorithm. Therefore, these 10 informative genes used to predict rupture status of IAs can be used as complements to imaging examinations in the clinic, meanwhile, this selected gene signature also provides new targets and approaches for the treatment of ruptured IAs.

Elevated Neutrophil Counts, Triglycerides, Monocyte/High-Density Lipoprotein Ratios, and Lower High-Density Lipoprotein in Patients with Retinal Vein Occlusion

INTRODUCTION

The aim of the study was to evaluate associations of peripheral blood immune cells and blood lipid profile levels with retinal vein occlusion (RVO).

METHODS

This retrospective study included 127 patients with RVO and 108 controls. Patients with RVO were divided into branch RVO (BRVO), central RVO (CRVO), ischemic RVO, or nonischemic RVO groups. Medical records were collected and analyzed.

RESULTS

The RVO group had higher mean neutrophil, triglyceride (TG), and monocyte/high-density lipoprotein (HDL) ratio (MHR) levels and lower HDL levels (p = 0.037, p < 0.001, p = 0.004, and p = 0.002, respectively). TG and MHR levels were significantly higher in the BRVO and CRVO groups compared with the control group (p < 0.001 and p = 0.016, respectively), but there was no difference in BRVO and CRVO group (p = 0.972 and p = 0.916, respectively). Mean HDL levels were significantly lower in the BRVO and CRVO groups than in the control group (p = 0.005), but the difference between the BRVO group and CRVO group was not significant (p = 0.290). Neutrophils, TG, and MHR were independent risk factors for RVO. HDL was an independent protective factor for RVO. Age was an independent risk factor for ischemic RVO.

CONCLUSIONS

Lower HDL, and higher neutrophil, TG, and MHR levels are associated with RVO. Age is an independent risk factor for ischemic RVO.

Changes in HDL cholesterol, particles, and function associate with pediatric COVID-19 severity

Background

Myriad roles for high-density lipoprotein (HDL) beyond atheroprotection include immunologic functions implicated in the severity of coronavirus disease-2019 (COVID-19) in adults. We explored whether there is an association between HDL and COVID-19 severity in youth.

Methods

A pediatric cohort (N = 102), who tested positive for COVID-19 across a range of disease manifestations from mild or no symptoms, to acute severe symptoms, to the multisystem inflammatory syndrome of children (MIS-C) was identified. Clinical data were collected from the medical record and reserve plasma aliquots were assessed for lipoproteins by NMR spectroscopy and assayed for HDL functional cholesterol efflux capacity (CEC). Findings were compared by COVID-19 status and symptom severity. Lipoprotein, NMR spectroscopy and CEC data were compared with 30 outpatient COVID negative children.

Results

Decreasing HDL cholesterol (HDL-c), apolipoprotein AI (ApoA-I), total, large and small HDL particles and HDL CEC showed a strong and direct linear dose-response relationship with increasing severity of COVID-19 symptoms. Youth with mild or no symptoms closely resembled the uninfected. An atypical lipoprotein that arises in the presence of severe hepatic inflammation, lipoprotein Z (LP-Z), was absent in COVID-19 negative controls but identified more often in youth with the most severe infections and the lowest HDL parameters. The relationship between HDL CEC and symptom severity and ApoA-I remained significant in a multiply adjusted model that also incorporated age, race/ethnicity, the presence of LP-Z and of GlycA, a composite biomarker reflecting multiple acute phase proteins.

Conclusion

HDL parameters, especially HDL function, may help identify youth at risk of more severe consequences of COVID-19 and other novel infectious pathogens.

Negative Pressure Wound Therapy Promotes Wound Healing by Inhibiting Inflammation in Diabetic Foot Wounds: A Role for NOD1 Receptor

Aims: Diabetic foot results in frequent amputation and quality-of-life reduction in diabetes population. These lesions are featured by a prolonged and exaggerated inflammation with a significant impairment in local bacterial invasion. Negative pressure wound therapy (NPWT) attenuates hyperinflammation in the healing of diabetic foot wounds, but the potential mechanism of NPWT down-regulated inflammatory reaction still remains elusive. This study aims to explore the inflammatory signaling involved in the effect of NPWT on diabetic ulcer. Methods: Thirty patients with diabetic foot ulceration were divided into NPWT group (treated with NPWT, n = 10), NPWT + FK565 group (treated with NPWT combined with FK565 which is NOD1 receptor ligand, n = 10) and control group (n = 10). After two weeks treatment, samples were harvested and analyzed by histochemistry for infiltration of inflammatory cells, immunofluorescence stain for NOD1, western blotting for NOD1, RIP2 (Receptor interacting protein 2), IL-1β, TAK1 (Transforming growth factor-β-activated kinase1), p65 and real time-PCR for expression of NOD1 and RIP2. Results: NPWT could notably accelerate the diabetic wound healing through alleviating inflammatory reaction. The immunofluorescence analysis results revealed that NOD1 was mainly expressed in the cytoplasm and noticeably decreased after the NPWT treatment. And NPWT obviously decreased both the mRNA and protein level of NOD1 and RIP2. Moreover, The protein expression of IL-1β, TAK1 and p65 in the NPWT-group were significant decreased. Conclusion: NPWT effectively promotes wound healing by suppressing the wound inflammation in diabetic foot, which is mediated at least in part by suppression of NOD1 receptor.

Elevated G-CSF, IL8, and HGF in patients with definite Meniere's disease may indicate the role of NET formation in triggering autoimmunity and autoinflammation

The etiology and mechanism causing Meniere’s disease (MD) are not understood. The present study investigated the possible molecular mechanism of autoimmunity and autoinflammation associated with MD. Thirty-eight patients with definite MD and 39 normal volunteers were recruited, and 48 human cytokines/chemokines were quantified. In patients with MD pure tone audiograms, tympanograms and standard blood tests were performed. The mean hearing loss in the worse ear was 44.1 dB nHL. Compared to the referents, the concentrations of TNFα, IL1α, IL8, CTACK, MIP1α, MIP1β, G-CSF, and HGF in the sera of patients with MD were significantly elevated, while those of TRAIL and PDGFBB were significantly decreased. The area under the receiver operating characteristic curve (AUC) showed that G-CSF, MIP1α, and IL8 were above 0.8 and could be used to diagnose MD (p < 0.01), and the AUCs of CTACK and HGF were above 0.7 and acceptable to discriminate the MD group from the control group (p < 0.01). The revised AUCs (1 − AUC) of TRAIL and PDGFBB were above 0.7 and could also be used in the diagnosis of MD (p < 0.01). The linear regression showed significant correlations between MIP1α and GCSF, between IL2Rα and GCSF, between IL8 and HGF, between MIP1α and IL8, and between SCF and CTACK; there was a marginal linear association between IP10 and MIP1α. Linear regression also showed that there were significant age-related correlations of CTACK and MIG expression in the MD group (p < 0.01, ANOVA) but not in the control group. We hypothesize that G-CSF, IL8, and HGF, which are involved in the development of neutrophil extracellular traps (NETs) and through various mechanisms influence the functions of macrophages, lymphocytes, and dendritic cells, among others, are key players in the development of EH and MD and could be useful in elucidating the pathophysiological mechanisms leading to MD. Biomarkers identified in the present study may suggest that both autoimmune and autoinflammatory mechanisms are involved in MD. In the future, it will be valuable to develop a cost-effective method to detect G-CSF, IL8, HGF, CTACK, MIP1α, TRAIL, and PDGFBB in the serum of patient that have diagnostic relevance.

Circulating Ageing Neutrophils as a Marker of Asymptomatic Polyvascular Atherosclerosis in Statin-Naïve Patients without Established Cardiovascular Disease

Background: Current data on the possible involvement of aging neutrophils in atherogenesis are limited. This study aimed to research the diagnostic value of aging neutrophils in their relation to subclinical atherosclerosis in statin-naïve patients without established atherosclerotic cardiovascular diseases (ASCVD). Methods: The study was carried out on 151 statin-naïve patients aged 40–64 years old without ASCVD. All patients underwent duplex scanning of the carotid arteries, lower limb arteries and abdominal aorta. Phenotyping and differentiation of neutrophil subpopulations were performed through flow cytometry (Navios 6/2, Beckman Coulter, USA). Results: The number of CD62L^loCXCR4^hi-neutrophils is known to be significantly higher in patients with subclinical atherosclerosis compared with patients without atherosclerosis (p = 0.006). An increase in the number of CD62L^loCXCR4^hi-neutrophils above cut-off values makes it possible to predict atherosclerosis in at least one vascular bed with sensitivity of 35.4–50.5% and specificity of 80.0–92.1%, in two vascular beds with sensitivity of 44.7–84.4% and specificity of 80.8–33.3%. Conclusion: In statin-naïve patients 40–64 years old without established ASCVD with subclinical atherosclerosis, there is an increase in circulating CD62L^loCXCR4^hi-neutrophils. It was also concluded that the increase in the number of circulating CD62L^loCXCR4^hi-neutrophils demonstrated moderate diagnostic efficiency (AUC 0.617–0.656) in relation to the detection of subclinical atherosclerosis, including polyvascular atherosclerosis.

Soluble ST2 as a Potential Biomarker for Abdominal Aortic Aneurysms-A Single-Center Retrospective Cohort Study

The maximal aortic diameter is the only clinically applied predictor of abdominal aortic aneurysm (AAA) progression and indicator for surgical repair. Circulating biomarkers resulting from AAA pathogenesis are attractive candidates for the diagnosis and prognosis of aneurysmal disease. Due to the reported role of interleukin 33 in AAA development, we investigated the corresponding circulating receptor molecules of soluble suppression of tumorigenesis 2 (sST2) in AAA patients regarding their marker potential in diagnosis and prognosis. We conducted a single-center retrospective cohort study in a diagnostic setting, measuring the circulating serum sST2 protein levels of 47 AAA patients under surveillance, matched with 25 peripheral artery disease (PAD) patients and 25 healthy controls. In a prognostic setting, we analyzed the longitudinal monitoring data of 50 monitored AAA patients. Slow versus fast AAA progression was defined as a <2 or ≥2 mm increase in AAA diameter over 6 months and a <4 or ≥4 mm increase over 12 months. Additionally, the association of circulating serum sST2 and AAA growth was investigated using a specifically tailored log-linear mixed model. Serum sST2 concentrations were significantly increased in AAA patients compared with healthy individuals: the median of AAA patient cohort was 112.72 ng/mL (p = 0.025) and that of AAA patient cohort 2 was 14.32 ng/mL (p = 0.039) versus healthy controls (8.82 ng/mL). Likewise, PAD patients showed significantly elevated sST2 protein levels compared with healthy controls (the median was 12.10 ng/mL; p = 0.048) but similar concentrations to AAA patients. Additionally, sST2 protein levels were found to be unsuited to identifying fast AAA progression over short-term periods of 6 or 12 months, which was confirmed by a log-linear mixed model. In conclusion, the significantly elevated protein levels of sST2 detected in patients with vascular disease may be useful in the early diagnosis of AAA but cannot distinguish between AAA and PAD or predict AAA progression.

CuO-NPs-triggered heterophil extracellular traps exacerbate liver injury in chicks by promoting oxidative stress and inflammatory responses

With the widespread use of copper oxide nanoparticles (CuO-NPs), their potential toxicity to the environment and biological health has attracted close attention. Heterophil extracellular traps (HETs) are an innate immune mechanism of chicken heterophils against adverse stimuli, but excessive HETs cause damage. Here, we explored the effect and mechanism of CuO-NPs on HETs formation in vitro and further evaluated the potential role of HETs in chicken liver and kidney injury. Heterophils were exposed to 5, 10, and 20 µg/mL of CuO-NPs for 2 h. The results showed that CuO-NPs induced typical HETs formation, which was dependent on NADPH oxidase, P38 and extracellular regulated protein kinases (ERK_1/2) pathways, and glycolysis. In in vivo experiments, fluorescence microplate and morphological analysis showed that CuO-NPs elevated the level of HETs in chicken serum and caused liver and kidney damage. Meanwhile, CuO-NPs caused hepatic oxidative stress (MDA, SOD, CAT, and GSH-PX imbalance), and also induced an increase in mRNA expression of their inflammatory and apoptosis-related factors (IL-1β, IL-6, TNF-α, COX-2, iNOS, NLRP3, and Caspase-1, 3, 11). However, these results were significantly altered by DNase I (HETs degradation reagent). In conclusion, the present study demonstrates for the first time that CuO-NPs induce the formation of HETs and that HETs exacerbate pathological damage in chicken liver and kidney by promoting oxidative stress and inflammation, providing insights into immunotoxicity and potential prevention and treatment targets caused by CuO-NPs overexposure.

Damage associated molecular patterns and neutrophil extracellular traps in acute pancreatitis

Previous researches have emphasized a trypsin-centered theory of acute pancreatitis (AP) for more than a century. With additional studies into the pathogenesis of AP, new mechanisms have been explored. Among them, the role of immune response bears great importance. Pro-inflammatory substances, especially damage-associated molecular patterns (DAMPs), play an essential role in activating, signaling, and steering inflammation. Meanwhile, activated neutrophils attach great importance to the immune defense by forming neutrophil extracellular traps (NETs), which cause ductal obstruction, premature trypsinogen activation, and modulate inflammation. In this review, we discuss the latest advances in understanding the pathological role of DAMPs and NETs in AP and shed light on the flexible crosstalk between these vital inflammatory mediators. We, then highlight the potentially promising treatment for AP targeting DAMPs and NETs, with a focus on novel insights into the mechanism, diagnosis, and management of AP.

The Effect of Paracrine Factors Released by Irradiated Peripheral Blood Mononuclear Cells on Neutrophil Extracellular Trap Formation

Neutrophil extracellular trap (NET)-formation represents an important defence mechanism for the rapid clearance of infections. However, exaggerated NET formation has been shown to negatively affect tissue-regeneration after injury. As our previous studies revealed the strong tissue-protective and regenerative properties of the secretome of stressed peripheral blood mononuclear cells (PBMCsec), we here investigated the influence of PBMCsec on the formation of NETs. The effect of PBMCsec on NET formation was assessed ex vivo in ionomycin stimulated neutrophils derived from healthy donors using flow cytometry, image stream analysis, and quantification of released extracellular DNA. The effect of PBMCsec on molecular mechanisms involved in NET formation, including Ca-flux, protein kinase C activity, reactive oxygen species production, and protein arginine deiminase 4 activity, were analysed. Our results showed that PBMCsec significantly inhibited NET formation. Investigation of the different biological substance classes found in PBMCsec revealed only a partial reduction in NET formation, suggesting a synergistic effect. Mechanistically, PBMCsec treatment did not interfere with calcium signalling and PKC-activation, but exerted anti-oxidant activity, as evidenced by reduced levels of reactive oxygen species and upregulation of heme oxygenase 1 and hypoxia inducible-factor 1 in PBMCsec-treated neutrophils. In addition, PBMCsec strongly inhibited the activation of protein arginine deiminase 4 (PAD4), ultimately leading to the inhibition of NET formation. As therapeutics antagonizing excessive NET formation are not currently available, our study provides a promising novel treatment option for a variety of conditions resulting from exaggerated NET formation.

The mechanistic basis linking cytokine storm to thrombosis in COVID-19

It is now well established that infection with SARS-CoV-2 resulting in COVID-19 disease includes a severely symptomatic subset of patients in whom an aggressive and/or dysregulated host immune response leads to cytokine storm syndrome (CSS) that may be further complicated by thrombotic events, contributing to the severe morbidity and mortality observed in COVID-19. This review provides a brief overview of cytokine storm in COVID-19, and then presents a mechanistic discussion of how cytokine storm affects integrated pathways in thrombosis involving the endothelium, platelets, the coagulation cascade, eicosanoids, auto-antibody mediated thrombosis, and the fibrinolytic system.

Neutrophils and Neutrophil Extracellular Traps in Cardiovascular Disease: An Overview and Potential Therapeutic Approaches

Recent advances in pharmacotherapy have markedly improved the prognosis of cardiovascular disease (CVD) but have not completely conquered it. Therapies targeting the NOD-like receptor family pyrin domain containing 3 inflammasome and its downstream cytokines have proven effective in the secondary prevention of cardiovascular events, suggesting that inflammation is a target for treating residual risk in CVD. Neutrophil-induced inflammation has long been recognized as important in the pathogenesis of CVD. Circadian rhythm-related and disease-specific microenvironment changes give rise to neutrophil diversity. Neutrophils are primed by various stimuli, such as chemokines, cytokines, and damage-related molecular patterns, and the activated neutrophils contribute to the inflammatory response in CVD through degranulation, phagocytosis, reactive oxygen species generation, and the release of neutrophil extracellular traps (NETs). In particular, NETs promote immunothrombosis through the interaction with vascular endothelial cells and platelets and are implicated in the development of various types of CVD, such as acute coronary syndrome, deep vein thrombosis, and heart failure. NETs are promising candidates for anti-inflammatory therapy in CVD, and their efficacy has already been demonstrated in various animal models of the disease; however, they have yet to be clinically applied in humans. This narrative review discusses the diversity and complexity of neutrophils in the trajectory of CVD, the therapeutic potential of targeting NETs, and the related clinical issues.

Adenoviral vector-based COVID-19 vaccines-associated cerebral venous sinus thromboses: Are those adverse events related to the formation of neutrophil extracellular traps?

In March and April 2021 several countries temporarily suspended vaccinations with adenoviral vector-based COVID-19 vaccines. Concerns of national regulators particularly regarded very rare cases of cerebral venous sinus thrombosis after immunization with this type of vaccine. Until now, these adverse events were interpreted as standard hypercoagulable events, but their clinical characteristics suggest that they may actually represent unique thrombotic disorders referred to as immunothrombosis. In this paper it is speculated that it is possible that immunothrombosis after this type of vaccine results from formation of neutrophil extracellular traps (NETs) in veins affected by stagnant blood flow. Such a stasis occurs in individuals with anatomical variants of cerebral venous outflow, which may explain why these events are primarily seen in the cerebral veins. It has already been found that SARS-CoV-2 spike protein can evoke release of NETs. There is also a question if thrombotic events after adenoviral vector-based COVID-19 vaccines could be avoided. These vaccines will still be needed to curb COVID-19 worldwide, since they do not require transportation and storage at very low temperatures. Perhaps, vaccinations with these vaccines should be performed in combination with prophylactic administration of dipyridamole, which is an inexpensive pharmaceutical agent reducing the release of NETs.

Detection of neutrophil extracellular traps in patient plasma: method development and validation in systemic lupus erythematosus and healthy donors that carry IRF5 genetic risk

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.

Neutrophil Elastase Increases Vascular Permeability and Leukocyte Transmigration in Cultured Endothelial Cells and Obese Mice

Neutrophil elastase (NE) plays a pivotal role in inflammation. However, the mechanism underlying NE-mediated inflammation in obesity remains unclear. Here, we report that NE activates protease-activated receptor-2 (PAR2), stimulates actin filament (F-actin) formation, decreases intercellular junction molecule VE-cadherin expression, and increases the permeability of human arterial endothelial cells (hECs). NE also prompts degradation of VE-cadherin and its binding proteins p120- and β-catenins via MG132-sensitive proteasomes. NE stimulates phosphorylation of myosin light-chain (MLC) and its regulator myosin phosphatase target subunit-1 (MYPT1), a target of Rho kinase (ROCK). Inhibitors of PAR2 and ROCK prohibit NE-induced F-actin formation, MLC phosphorylation, and VE-cadherin reduction in hECs, and impede monocyte transmigration through hEC monolayer pretreated with either neutrophils or NE. Further, administration of an NE inhibitor GW311616A significantly attenuates vascular leakage, leukocyte infiltration, and the expression of proinflammatory cytokines in the white adipose tissue from high-fat diet (HFD)-induced obese mice. Likewise, NE-deficient mice are resistant to HFD-induced vascular leakage in the heart. Together, NE regulates actomyosin cytoskeleton activity and VE-cadherin expression by activating PAR2 signaling in the endothelial cells, leading to increased vascular permeability and leukocyte extravasation. Hence, inhibition of NE is a potential approach to mitigate vascular injury and leukocyte infiltration in obesity-related systemic inflammation.

Junctional Adhesion Molecules: Potential Proteins in Atherosclerosis

Junctional adhesion molecules (JAMs) are cell-cell adhesion molecules of the immunoglobulin superfamily and are involved in the regulation of diverse atherosclerosis-related processes such as endothelial barrier maintenance, leucocytes transendothelial migration, and angiogenesis. To combine and further broaden related results, this review concluded the recent progress in the roles of JAMs and predicted future studies of JAMs in the development of atherosclerosis.

The role of phosphoinositide 3-kinases in immune-inflammatory responses: potential therapeutic targets for abdominal aortic aneurysm

The pathogenesis of abdominal aortic aneurysm (AAA) includes inflammatory responses, matrix metalloproteinases (MMPs) degradation, VSMC apoptosis, oxidative stress, and angiogenesis, among which the inflammatory response plays a key role. At present, surgery is the only curing treatment, and no effective drug can delay AAA progression in clinical practice. Therefore, searching for a signaling pathway related to the immune-inflammatory response is an essential direction for developing drugs targeting AAA. Recent studies have confirmed that the PI3K family plays an important role in many inflammatory diseases and is involved in regulating various cellular functions, especially in the immune-inflammatory response. This review focuses on the role of each isoform of PI3K in each stage of AAA immune-inflammatory response, making available explorations for a deeper understanding of the mechanism of inflammation and immune response during the formation and development of AAA.

Nuclear receptor NOR-1 (Neuron-derived Orphan Receptor-1) in pathological vascular remodelling and vascular remodelling

Vascular cells and their interaction with inflammatory cells and the immune system play a key role in pathological vascular remodeling. A large number of genes and proteins regulated in a coordinated manner by a small number of transcription factors are involved in this process. In recent years, research on a small subfamily of transcription factors, the NR4A subfamily, has had a major impact on our understanding of vascular biology. The NR4A1 (Nur77), NR4A2 (Nurr1) and NR4A3 (NOR-1) receptors are products of early response genes whose expression is induced by multiple pathophysiological and physical stimuli. Their wide distribution in different tissues and cells places them in the control of numerous processes such as cell differentiation, proliferation, survival and apoptosis, as well as inflammation and the metabolism of lipids and carbohydrates. This review analyzes the role of these receptors, particularly NOR-1, in pathological vascular remodeling associated with atherosclerosis, abdominal aortic aneurysm and pulmonary arterial hypertension.

Aβ1-40 Oligomers Trigger Neutrophil Extracellular Trap Formation through TLR4- and NADPH Oxidase-Dependent Pathways in Age-Related Macular Degeneration

Neutrophils participate in the advancement of the human innate immune system and respond to perceived endogenous and exogenous threats. As a response mechanism, neutrophil extracellular traps (NETs) form near pathogens and surrounding tissues during an immune response. Drusen is an important marker of Age-Related Macular Degeneration (AMD) and plays an important role in the course of AMD. Aβ1-40 is the main component of drusen. However, the relationship between NETs and AMD or Aβ1-40 is unclear. Here, we found elevated levels of NETs in the serum of AMD patients and elevated levels in the serum of mouse models. We also observed the accumulation of neutrophils in the mouse retina. In addition, the production of NETs was inhibited by PAD4 inhibitors, which can alleviate chronic inflammation. Moreover, we confirmed that Aβ1-40 can induce NETs formation via the Toll-like receptor 4 (TLR4) and neutrophil NADPH oxidase (NOX) pathways. Our study confirmed that the formation of NETs is induced by Aβ1–40, and the results suggest that NETs may play a vital role in AMD pathogenesis.

Extracellular Traps: A Novel Therapeutic Target for Severe Asthma

Asthma is a complicated disease defined by a combination of clinical symptoms and physiological characteristics. Typically, asthma is diagnosed by the presence of episodic cough, wheezing, or dyspnea triggered by variable environmental factors (allergens and respiratory infections), and reversible airflow obstruction. To date, the majority of asthmatic patients have been adequately controlled by anti-inflammatory/bronchodilating agents, but those with severe asthma (SA) have not been sufficiently controlled by high-dose inhaled corticosteroids-long-acting beta-agonists plus additional controllers including leukotriene modifiers. Accordingly, these uncontrolled patients provoke a special issue, because they consume high healthcare resources, requiring innovative precision medicine solutions. Recently, phenotyping based on biomarkers of airway inflammation has led to elucidating the pathophysiological mechanism of SA, where emerging evidence has highlighted the significance of eosinophil or neutrophil extracellular traps contributing to the development of SA. Here, we aimed to provide current findings about extracellular traps as a novel therapeutic target for asthma to address medical unmet needs.

Stroke-derived neutrophils demonstrate higher formation potential and impaired resolution of CD66b + driven neutrophil extracellular traps

Background

Recent evidence suggests a merging role of immunothrombosis in the formation of arterial thrombosis. Our study aims to investigate its relevance in stroke patients.

Methods

We compared the peripheral immunological profile of stroke patients vs. healthy controls. Serum samples were functionally analyzed for their formation and clearance of Neutrophil-Extracellular-Traps. The composition of retrieved thrombi has been immunologically analyzed.

Results

Peripheral blood of stroke patients showed significantly elevated levels of DNAse-I (p < 0.001), LDG (p = 0.003), CD4 (p = 0.005) as well as the pro-inflammatory cytokines IL-17 (p < 0.001), INF-γ (p < 0.001) and IL-22 (p < 0.001) compared to controls, reflecting a T_H1/T_H17 response. Increased counts of DNAse-I in sera (p = 0.045) and Neutrophil-Extracellular-Traps in thrombi (p = 0.032) have been observed in patients with onset time of symptoms longer than 4,5 h. Lower values of CD66b in thrombi were independently associated with greater improvement of NIHSS after mechanical thrombectomy (p = 0.045). Stroke-derived neutrophils show higher potential for Neutrophil-Extracellular-Traps formation after stimulation and worse resolution under DNAse-I treatment compared to neutrophils derived from healthy individuals.

Conclusions

Our data provide new insight in the role of activated neutrophils and Neutrophil-Extracellular-Traps in ischemic stroke. Future larger studies are warranted to further investigate the role of immunothrombosis in the cascades of stroke.

Trial registration

DRKS, DRKS00013278, Registered 15 November 2017, https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00013278

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-022-02707-0.

Adenoviral vector-based COVID-19 vaccines-associated cerebral venous sinus thromboses: Are those adverse events related to the formation of neutrophil extracellular traps?

In March and April 2021 several countries temporarily suspended vaccinations with adenoviral vector-based COVID-19 vaccines. Concerns of national regulators particularly regarded very rare cases of cerebral venous sinus thrombosis after immunization with this type of vaccine. Until now, these adverse events were interpreted as standard hypercoagulable events, but their clinical characteristics suggest that they may actually represent unique thrombotic disorders referred to as immunothrombosis. In this paper it is speculated that it is possible that immunothrombosis after this type of vaccine results from formation of neutrophil extracellular traps (NETs) in veins affected by stagnant blood flow. Such a stasis occurs in individuals with anatomical variants of cerebral venous outflow, which may explain why these events are primarily seen in the cerebral veins. It has already been found that SARS-CoV-2 spike protein can evoke release of NETs. There is also a question if thrombotic events after adenoviral vector-based COVID-19 vaccines could be avoided. These vaccines will still be needed to curb COVID-19 worldwide, since they do not require transportation and storage at very low temperatures. Perhaps, vaccinations with these vaccines should be performed in combination with prophylactic administration of dipyridamole, which is an inexpensive pharmaceutical agent reducing the release of NETs.

Neutrophil degranulation and myocardial infarction

Myocardial infarction (MI) is one of the most common cardiac emergencies with high morbidity and is a leading cause of death worldwide. Since MI could develop into a life-threatening emergency and could also seriously affect the life quality of patients, continuous efforts have been made to create an effective strategy to prevent the occurrence of MI and reduce MI-related mortality. Numerous studies have confirmed that neutrophils play important roles in inflammation and innate immunity, which provide the first line of defense against microorganisms by producing inflammatory cytokines and chemokines, releasing reactive oxygen species, and degranulating components of neutrophil cytoplasmic granules to kill pathogens. Recently, researchers reported that neutrophils are closely related to the severity and prognosis of patients with MI, and neutrophil to lymphocyte ratio in post-MI patients had predictive value for major adverse cardiac events. Neutrophils have been increasingly recognized to exert important functions in MI. Especially, granule proteins released by neutrophil degranulation after neutrophil activation have been suggested to involve in the process of MI. This article reviewed the current research progress of neutrophil granules in MI and discusses neutrophil degranulation associated diagnosis and treatment strategies.

Molecular Basis for Paradoxical Activities of Polymorphonuclear Neutrophils in Inflammation/Anti-Inflammation, Bactericide/Autoimmunity, Pro-Cancer/Anticancer, and Antiviral Infection/SARS-CoV-II-Induced Immunothrombotic Dysregulation

Polymorphonuclear neutrophils (PMNs) are the most abundant white blood cells in the circulation. These cells act as the fast and powerful defenders against environmental pathogenic microbes to protect the body. In addition, these innate inflammatory cells can produce a number of cytokines/chemokines/growth factors for actively participating in the immune network and immune homeostasis. Many novel biological functions including mitogen-induced cell-mediated cytotoxicity (MICC) and antibody-dependent cell-mediated cytotoxicity (ADCC), exocytosis of microvesicles (ectosomes and exosomes), trogocytosis (plasma membrane exchange) and release of neutrophil extracellular traps (NETs) have been successively discovered. Furthermore, recent investigations unveiled that PMNs act as a double-edged sword to exhibit paradoxical activities on pro-inflammation/anti-inflammation, antibacteria/autoimmunity, pro-cancer/anticancer, antiviral infection/COVID-19-induced immunothrombotic dysregulation. The NETs released from PMNs are believed to play a pivotal role in these paradoxical activities, especially in the cytokine storm and immunothrombotic dysregulation in the recent SARS-CoV-2 pandemic. In this review, we would like to discuss in detail the molecular basis for these strange activities of PMNs.

Trehalose Activates Hepatic and Myocardial Autophagy and Has Anti-Inflammatory Effects in db/db Diabetic Mice

Db/db mice (carrying a mutation in the gene encoding leptin receptor) show autophagy suppression. Our aim was to evaluate the effect of autophagy inducer trehalose on liver and heart autophagy in db/db mice and to study inflammation dysregulation and the suitability of chitinases’ expression levels as diabetes markers. Thirty-eight male db/db mice and C57/BL mice (control) were used. The db/db model manifested inflammation symptoms: overexpression of TNF-α in the spleen and underexpression of IL-10 in the liver and spleen (cytokine imbalance). Simultaneously, we revealed decreased expression of chitotriosidase (CHIT1) and acid mammalian chitinase (CHIA) in the liver of db/db mice. CHIA expression in db/db mice is significantly lower only in the spleen. Trehalose treatment significantly reduced blood glucose concentration and glycated hemoglobin. Treatment of db/db mice by trehalose was followed by increased autophagy induction in the heart and liver (increased autolysosomes volume density studied by morphometric electron-microscopic method). Trehalose exerted beneficial cardiac effects possibly via increased lipophagy (uptake of lipid droplets). The autophagy activation by trehalose had several positive effects on the heart and liver of db/db mice; therefore, lipophagy activation seems to be a promising therapy for diabetes.

Physiological and Pathophysiological Roles of Metabolic Pathways for NET Formation and Other Neutrophil Functions

Neutrophils are the most numerous cells in the leukocyte population and essential for innate immunity. To limit their effector functions, neutrophils are able to modulate glycolysis and other cellular metabolic pathways. These metabolic pathways are essential not only for energy usage, but also for specialized effector actions, such as the production of reactive oxygen species (ROS), chemotaxis, phagocytosis, degranulation, and the formation of neutrophil extracellular traps (NETs). It has been demonstrated that activated viable neutrophils can produce NETs, which consists of a DNA scaffold able to bind granule proteins and microorganisms. The formation of NETs requires the availability of increased amounts of adenosine triphosphate (ATP) as it is an active cellular and therefore energy-dependent process. In this article, we discuss the glycolytic and other metabolic routes in association with neutrophil functions focusing on their role for building up NETs in the extracellular space. A better understanding of the requirements of metabolic pathways for neutrophil functions may lead to the discovery of molecular targets suitable to develop novel anti-infectious and/or anti-inflammatory drugs.

Scientific premise for the involvement of neutrophil extracellular traps (NETs) in vaccine-induced thrombotic thrombocytopenia (VITT)

Following on from the devastating spread of COVID-19, a major global priority has been the production, procurement, and distribution of effective vaccines to ensure that the global pandemic reaches an end. However, concerns were raised about worrying side effects, particularly the occurrence of thrombosis and thrombocytopenia after administration of the Oxford/AstraZeneca and Johnson & Johnson's Janssen COVID-19 vaccine, in a phenomenon being termed vaccine-induced thrombotic thrombocytopenia (VITT). Similar to heparin-induced thrombocytopenia (HIT), this condition has been associated with the development of anti-platelet factor 4 antibodies, purportedly leading to neutrophil-platelet aggregate formation. Although thrombosis has also been a common association with COVID-19, the precise molecular mechanisms governing its occurrence are yet to be established. Recently, increasing evidence highlights the NLRP3 (NOD-like, leucine-rich repeat domains, and pyrin domain-containing protein) inflammasome complex along with IL-1β and effete neutrophils producing neutrophil extracellular traps (NETs) through NETosis. Herein, we propose and discuss that perhaps the incidence of VITT may be due to inflammatory reactions mediated via IL-1β/NLRP3 inflammasome activation and consequent overproduction of NETs, where similar autoimmune mechanisms are observed in HIT. We also discuss avenues by which such modalities could be treated to prevent the occurrence of adverse events and ensure vaccine rollouts remain safe and on target to end the current pandemic.

Cluster analysis of splenocyte microRNAs in the pig reveals key signal regulators of immunomodulation in the host during acute and chronic Toxoplasma gondii infection

BACKGROUND

Toxoplasma gondii is an obligate intracellular protozoan parasite that can cause a geographically widespread zoonosis. Our previous splenocyte microRNA profile analyses of pig infected with T. gondii revealed that the coordination of a large number of miRNAs regulates the host immune response during infection. However, the functions of other miRNAs involved in the immune regulation during T. gondii infection are not yet known.

METHODS

Clustering analysis was performed by K-means, self-organizing map (SOM), and hierarchical clustering to obtain miRNA groups with the similar expression patterns. Then, the target genes of the miRNA group in each subcluster were further analyzed for functional enrichment by Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Reactome pathway to recognize the key signaling molecules and the regulatory signatures of the innate and adaptive immune responses of the host during T. gondii infection.

RESULTS

A total of 252 miRNAs were successfully divided into 22 subclusters by K-means clustering (designated as K1-K22), 29 subclusters by SOM clustering (designated as SOM1-SOM29), and six subclusters by hierarchical clustering (designated as H1-H6) based on their dynamic expression levels in the different infection stages. A total of 634, 660, and 477 GO terms, 15, 26, and 14 KEGG pathways, and 16, 15, and 7 Reactome pathways were significantly enriched by K-means, SOM, and hierarchical clustering, respectively. Of note, up to 22 miRNAs mainly showing downregulated expression at 50 days post-infection (dpi) were grouped into one subcluster (namely subcluster H3-K17-SOM1) through the three algorithms. Functional analysis revealed that a large group of immunomodulatory signaling molecules were controlled by the different miRNA groups to regulate multiple immune processes, for instance, IL-1-mediated cellular response and Th1/Th2 cell differentiation partly depending on Notch signaling transduction for subclusters K1 and K2, innate immune response involved in neutrophil degranulation and TLR4 cascade signaling for subcluster K15, B cell activation for subclusters SOM17, SOM1, and SOM25, leukocyte migration, and chemokine activity for subcluster SOM9, cytokine-cytokine receptor interaction for subcluster H2, and interleukin production, chemotaxis of immune cells, chemokine signaling pathway, and C-type lectin receptor signaling pathway for subcluster H3-K17-SOM1.

CONCLUSIONS

Cluster analysis of splenocyte microRNAs in the pig revealed key regulatory properties of subcluster miRNA molecules and important features in the immune regulation induced by acute and chronic T. gondii infection. These results contribute new insight into the identification of physiological immune responses and maintenance of tolerance in pig spleen tissues during T. gondii infection.

PEGylation of Metal Oxide Nanoparticles Modulates Neutrophil Extracellular Trap Formation

Novel metal oxide nanoparticle (NP) contrast agents may offer safety and functionality advantages over conventional gadolinium-based contrast agents (GBCAs) for cancer diagnosis by magnetic resonance imaging. However, little is known about the behavior of metal oxide NPs, or of their effect, upon coming into contact with the innate immune system. As neutrophils are the body's first line of defense, we sought to understand how manganese oxide and iron oxide NPs impact leukocyte functionality. Specifically, we evaluated whether contrast agents caused neutrophils to release web-like fibers of DNA known as neutrophil extracellular traps (NETs), which are known to enhance metastasis and thrombosis in cancer patients. Murine neutrophils were treated with GBCA, bare manganese oxide or iron oxide NPs, or poly(lactic-co-glycolic acid) (PLGA)-coated metal oxide NPs with different incorporated levels of poly(ethylene glycol) (PEG). Manganese oxide NPs elicited the highest NETosis rates and had enhanced neutrophil uptake properties compared to iron oxide NPs. Interestingly, NPs with low levels of PEGylation produced more NETs than those with higher PEGylation. Despite generating a low rate of NETosis, GBCA altered neutrophil cytokine expression more than NP treatments. This study is the first to investigate whether manganese oxide NPs and GBCAs modulate NETosis and reveals that contrast agents may have unintended off-target effects which warrant further investigation.

Association of Lipoproteins with Neutrophil Extracellular Traps in Patients with Abdominal Aortic Aneurysm

Neutrophil extracellular traps (NETs) are DNA–protein structures released by neutrophils in response to various stimuli, including oxidized, low-density lipoprotein (oxLDL). Accumulating evidence suggests a role for NETs in the pathogenesis of abdominal aortic aneurysm (AAA). In this study, we investigated the potential association of lipoprotein particles and NETs in AAA in comparison to non-AAA control groups. The concentrations of neutrophil myeloperoxidase (MPO), the NET parameters citrullinated histone H3 (citH3) and circulating cell-free DNA (cfDNA), as well as of blood lipids were determined in plasma or serum of patients with AAA (n = 40), peripheral artery occlusive disease (PAD; n = 40) and healthy donors (n = 29). A sandwich ELISA detecting oxidized phosphatidylcholine in association with apolipoprotein B-100 (oxPL/apoB) was applied to measure oxidized phospholipids in circulation. The effect of lipoparticles on NET formation was tested using a DNA release assay with isolated human neutrophils. Plasma MPO, citH3 and cfDNA levels were significantly increased in AAA patients in comparison to healthy donors and PAD patients. Plasma concentrations of citH3 positively correlated with serum oxPL/apoB in AAA patients. In functional in vitro assays, the addition of oxLDL induced NET formation in pre-stimulated neutrophils. In conclusion, our data suggest a promoting role of oxLDL on NET formation in AAA patients.

NET-Mediated Pathogenesis of COVID-19: The Role of NETs in Hepatic Manifestations

Some coronavirus disease-2019 (COVID-19) patients exhibit multi-organ failure, which often includes the liver. Indeed, liver disease appears to be an emerging feature of COVID-19 infections. However, the exact mechanism behind this remains unknown. Neutrophil extracellular traps (NETs) have increasingly been attributed as major contributors to various liver pathologies, including sepsis, ischemic-reperfusion (I/R) injury, and portal hypertension in the setting of chronic liver disease. Although vital in normal immunity, excessive NET formation can drive inflammation, particularly of the endothelium. Collectively, we propose that NETs observed to be elevated in severe COVID-19 infection play principal roles in liver injury in addition to acute lung injury. Herein, we discuss the potential mechanisms underlying COVID-induced liver injury including cytopathic effects from direct liver infection, systemic inflammatory response syndrome, and hypoxic injury, encompassing I/R injury and coagulopathy. Further research is required to further elucidate the role of NETs in COVID. This holds potential therapeutic significance, as inhibition of NETosis could alleviate the symptoms of acute respiratory distress syndrome and liver injury, as well as other organs.

Inhibition of NETosis for treatment purposes: friend or foe?

Active neutrophils participate in innate and adaptive immune responses through various mechanisms, one of the most important of which is the formation and release of neutrophil extracellular traps (NETs). The NETs are composed of network-like structures made of histone proteins, DNA and other released antibacterial proteins by activated neutrophils, and evidence suggests that in addition to the innate defense against infections, NETosis plays an important role in the pathogenesis of several other non-infectious pathological states, such as autoimmune diseases and even cancer. Therefore, targeting NET has become one of the important therapeutic approaches and has been considered by researchers. NET inhibitors or other molecules involved in the NET formation, such as the protein arginine deiminase 4 (PAD4) enzyme, an arginine-to-citrulline converter, participate in chromatin condensation and NET formation, is the basis of this therapeutic approach. The important point is whether complete inhibition of NETosis can be helpful because by inhibiting this mechanism, the activity of neutrophils is suppressed. In this review, the biology of NETosis and its role in the pathogenesis of some important diseases have been summarized, and the consequences of treatment based on inhibition of NET formation have been discussed.