Cytokines induced neutrophil extracellular traps formation: implication for the inflammatory disease condition

Procoagulant Effect of Neutrophil Extracellular Traps, Activated Platelets, and Endothelial Cells in Patients After TAVR

BACKGROUND

Patients with severe aortic stenosis, undergoing transcatheter aortic valve replacement (TAVR), are more likely to develop thrombotic complications. However, the definite mechanisms underlying the hypercoagulation state remain unclear to date. Our objectives were to explore whether and how neutrophil extracellular traps (NETs) play a procoagulant role in patients after TAVR alone or TAVR with percutaneous coronary intervention within 1 year and further to evaluate their interactions with platelets and endothelial cells.

METHODS

The levels of plasma NETs, platelets, and endothelial cell activation markers were analyzed by ELISA. NET formation was observed by immunofluorescence. Procoagulant activity was measured by clotting time, fibrin, and TAT (thrombin-antithrombin) complex generation assays. Phosphatidylserine exposure on cells was assessed by flow cytometry.

RESULTS

Compared with pre-TAVR, controls, or severe aortic stenosis without TAVR patients, the plasma NET levels in patients after TAVR alone, especially TAVR with percutaneous coronary intervention, increased from 7 days, peaking at 3 months, and then gradually decreased until the 12th month. Furthermore, neutrophils and plasma from patients post-TAVR are more prone to promote NET formation; NETs from these patients markedly decreased clotting time and increased fibrin and TAT generation. Additionally, a high concentration of NETs induced platelet aggregation and exerted a strong cytotoxic effect on endothelial cells and transformed them into a procoagulant phenotype.

CONCLUSIONS

These results lead us to believe that NETs contribute to the hypercoagulability in patients post-TAVR. Our study may provide a new target for preventing thrombotic complications in patients post-TAVR by blocking NET generation.

Exploring neutrophil extracellular traps: mechanisms of immune regulation and future therapeutic potential

Neutrophil extracellular traps (NETs) are complex, web-like structures consisting of DNA intertwined with antimicrobial proteins, which neutrophils release upon immune activation. These structures play a crucial role in pathogen elimination, particularly in infectious diseases. However, their involvement in various pathological conditions is multifaceted and context-dependent, while NETs contribute to host defense against infections, they can also exacerbate sterile inflammation, autoimmune disorders, and tumor progression. This review provides a comprehensive analysis of the molecular mechanisms governing NET formation and examines their interactions with immune cells, emphasizing how these interactions shape immune responses and drive disease dynamics. Furthermore, it explores ongoing clinical trials and emerging therapeutic strategies targeting NETs, offering critical insights into their potential translational applications in clinical practice.

Interdisciplinary integration strategy reveals the anti-inflammatory efficacy and potential mechanism of Jianpi Qingre Tongluo prescription in rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic synovitis and associated with high rates of disability and systemic damage. Jianpi Qingre Tongluo prescription (Huangqin Qingre Chubi Capsule, HQC), an herbal formula with abundant clinical applications, has played a definite role in both clinical and experimental studies of RA. However, the specific mechanisms by which HQC relieves inflammation in RA have not been fully elucidated.

OBJECTIVE

This study aimed to elucidate the anti-inflammatory efficacy and potential molecular mechanisms of HQC in RA and provide new targets and strategies for its clinical treatment.

METHODS

An adjuvant-induced arthritis with damp-heat pattern rat model was established to observe the in vivo effects of HQC. Hematoxylin-eosin and toluidine blue staining, and enzyme-linked immunosorbent assay were used to assess potential efficacy. Bioinformatics methods and molecular docking were used to predict potential targets and intervention pathways in which HQC might act on RA. Clinical samples, overexpressed / silenced genes, and pathway agonists were selected to investigate the clinical relevance and regulatory relationships of the pathways. The regulatory mechanism of HQC was confirmed in an in vitro co-culture of neutrophils and fibroblast-like synoviocytes (FLSs) and an in vivo model.

RESULTS

HQC dose-dependently reversed synovial pathological injury and systemic inflammatory responses in rats in vivo. Integrated bioinformatics and molecular docking identified the p38 mitogen-activated protein kinase (MAPK) signaling pathway and neutrophil extracellular trap (NET) formation as the key mechanisms by which HQC exerts anti-inflammatory effects on RA. Subsequently, a high correlation between circ0005732, p38 MAPK, and clinical features of RA was confirmed in clinical samples. In vitro experiments demonstrated that HQC alleviated the proliferation and inflammatory response of FLSs by regulating circ0005732 expression to inhibit NET formation driven by the p38 MAPK signaling pathway. Finally, RT-qPCR and western blotting confirmed that HQC modulated circ0005732, p38 MAPK pathway, and NET formation to alleviate RA in vivo.

CONCLUSION

HQC exerts therapeutic effects against RA by modulating circ0005732 to inhibit p38 MAPK signaling pathway-mediated NET generation and inflammation progression.

Suramin Exerts an Ameliorative Effect on Acetic Acid-Induced Acute Colitis in Rats by Demonstrating Potent Antioxidant and Anti-Inflammatory Properties

Background and Objectives: The purpose of this study was to evaluate potential protective effects of suramin on inflammation, oxidative stress, and histopathological damage a rat model of acute colitis created with acetic acid. Materials and Methods: Wistar albino (male) rats were randomly assigned to three groups: control (n = 10), colitis + saline (n = 10), and colitis + suramin (n = 10). Rectal instillation of 4% acetic acid was used to induce acute colitis. Suramin (10 mg/kg/day) or saline was administered intraperitoneally for 15 days. Plasma concentrations of pentraxin 3 (PTX3), tumor necrosis factor-alpha (TNF-α), neutrophil extracellular traps (NETs), and malondialdehyde (MDA) were determined using enzyme-linked immunosorbent assay (ELISA) and spectrophotometric methods. In addition, vascular endothelial growth factor (VEGF) and TNF-α levels in colonic tissue were also measured. Histopathological evaluations were conducted using hematoxylin and eosin staining. Results: Significant increases in plasma and tissue inflammatory markers, oxidative stress parameters, and histopathological scores were observed when compared to control group; values were higher in colitis group. Suramin treatment significantly reduced plasma PTX3, TNF-α, NETs, and MDA levels, and colonic TNF-α and VEGF concentrations compared to the untreated colitis group. Histological analysis showed reduced epithelial injury and leukocyte presence in rats receiving suramin. Conclusions: Our findings demonstrate that suramin significantly attenuates inflammatory and oxidative damage in an experimental model of acute colitis. These results suggest that suramin may possess therapeutic potential in intestinal inflammation; however, this effect requires further support through advanced experimental and clinical studies.

Brain-Death in Rats Increases Neutrophil Extracellular Trap Formation in Donor Organs

During brain-death, increased numbers of neutrophils are recruited to organs as part of the inflammatory response. In the organ microenvironment, the recruited neutrophils may release neutrophil extracellular traps (NETs) through interaction with various pro-inflammatory stimuli, contributing to brain-death-induced endothelial activation, microthrombus formation and ultimately a decline in organ quality. To investigate whether NETs form in organs from brain-dead donors; kidneys, hearts, livers, and plasma samples were collected from brain-dead or sham-operated rats. The presence of NET-specific components, neutrophils and macrophages were analyzed through immunofluorescent microscopy. Endothelial activation and platelet infiltration were analyzed through immunohistochemistry and qRT-PCR analysis. Plasma free thiol levels were used to evaluate systemic oxidative stress. Increased neutrophils, NETs and NET/neutrophil ratios were observed in kidneys, hearts and livers of brain-dead rats compared to sham-operated rats. Numbers of NETs positively correlated with the extent of endothelial cell activation. Brain-dead animals also had increased kidney and liver macrophages, increased infiltrated platelets in the liver, and elevated systemic oxidative stress, compared to sham-operated animals. Our findings established the presence of NETs in organs from a brain-dead donor model and suggest that NETs, alongside increased inflammation and a redox imbalance, might prime organs for microvascular endothelial dysfunction and increased injury during brain-death.

O-antigen of uropathogenic Escherichia coli is required for induction of neutrophil extracellular traps

BACKGROUND

Urinary tract infections (UTIs) are prevalent bacterial infection, with uropathogenic Escherichia coli (UPEC) as the primary causative agent. The outer membrane of UPEC contains a lipopolysaccharide (LPS), which plays crucial roles in the host's immune response to infection. Neutrophils use neutrophil extracellular traps (NETs) are mechanism by which neutrophils defend against bacterial infections. However, the exact mechanism by which a bacterial LPS induces NET formation is not well understood. Therefore, the objective of this study is to identify the possible mechanism of LPS-mediated NETs and dissect the LPS domains of UPEC that predominantly modulate NET formation and NET-mediated killing.

METHODS

To investigate the mechanism of bacterial LPS-induced NET formation, we constructed UPEC CFT073 mutants that had rfaD, rfaL and the wzzE deleted with individual LPS biosynthetic genes including the inner core synthase, O-antigen ligase and O-antigen polymerase, respectively. Subsequently, we evaluated the NET/reactive oxygen species (ROS)/IL-1β induction abilities and assessed the activation of toll-like receptor 4 (TLR4)/JNK signaling by CFT073 and its mutants.

RESULTS

The results showed that the O-antigen of CFT073 LPS is essential for inducing NET formation through TLR4/JNK/NOX pathways. Inhibition of either pathway significantly decreased the production of ROS, induction of NETs, and secretion of IL-1β.

CONCLUSION

Our results demonstrate that CFT073 LPS is essential for inducing ROS-dependent NETs and IL-1β secretion from neutrophils. This study also provides evidence for the crucial roles of O-antigen in the immune response to UPEC infection, as well as its potential as a therapeutic target for the treatment of UTIs.

Modulating Neutrophil Extracellular Trap Formation In Vivo with Locoregional Precision Using Differently Charged Self-Assembled Hydrogels

Neutrophil extracellular traps (NETs) are DNA networks released by neutrophils, first described as a defense response against pathogens but have since been associated with numerous inflammatory diseases. Diverse physical material properties have been shown to promote NET formation. Herein, we report the discovery that the charge of self-assembled peptide hydrogels predictably modulates the formation of NETs in vivo within the implanted material. Positively charged gels induce rapid NET release, whereas negatively charged gels do not. This differential immune response to our self-assembled peptide gels enabled the development of a material platform that allows rheostat-like modulation over the degree of NET formation with anatomical and locoregional control.

Neutrophil Extracellular Traps in Atherosclerosis: Research Progress

Atherosclerosis (AS) is a disease characterised by the accumulation of atherosclerotic plaques on the inner walls of blood vessels, resulting in their narrowing. In its early stages, atherosclerosis remains asymptomatic and undetectable by conventional pathological methods. However, as the disease progresses, it can lead to a series of cardiovascular diseases, which are a leading cause of mortality among middle-aged and elderly populations worldwide. Neutrophil extracellular traps (NETs) are composed of chromatin and granular proteins released by neutrophils. Upon activation by external stimuli, neutrophils undergo a series of reactions, resulting in the release of NETs and subsequent cell death, a process termed NETosis. Research has demonstrated that NETosis is a means by which neutrophils contribute to immune responses. However, studies on neutrophil extracellular traps have identified NETs as the primary cause of various inflammation-induced diseases, including cystic fibrosis, systemic lupus erythematosus, and rheumatoid arthritis. Consequently, the present review will concentrate on the impact of neutrophil extracellular traps on atherosclerosis formation, analysing it from a molecular biology perspective. This will involve a systematic dissection of their proteomic components and signal pathways.

Non-classical neutrophil extracellular traps induced by PAR2-signaling proteases

Neutrophil extracellular traps (NETs) are associated with diseases linked to aberrant coagulation. The blood clotting cascade involves a series of proteases, some of which induce NET formation via a yet unknown mechanism. We hypothesized that this formation involves signaling via a factor Xa (FXa) activation of the protease-activated receptor 2 (PAR2). Our findings revealed that NETs can be triggered in vitro by enzymatically active proteases and PAR2 agonists. Intravital microscopy of the liver vasculature revealed that both FXa infusion and activation of endogenous FX promoted NET formation, effects that were prevented by the FXa inhibitor, apixaban. Unlike classical NETs, these protease-induced NETs lacked bactericidal activity and their proteomic signature indicates their role in inflammatory disorders, including autoimmune diseases and carcinogenesis. Our findings suggest a novel mechanism of NET formation under aseptic conditions, potentially contributing to a self-amplifying clotting and NET formation cycle. This mechanism may underlie the pathogenesis of disseminated intravascular coagulation and other aseptic conditions.

Case report: In vivo detection of neutrophil extracellular traps in a dog with thrombosis induced by bacterial vasculitis

This case report describes NETosis as a cause of thrombosis in an 18.3 kg, 8-year-old intact male mixed-breed dog with bacterial vasculitis. The dog presented with sudden paresis of the thoracic limb, characterized by cyanosis, absent arterial pulse, and decreased peripheral blood glucose levels. Doppler ultrasound confirmed thrombosis in the dorsal common digital artery. Histopathology post-amputation revealed bacterial vasculitis, thrombosis, and infarction, with immunohistochemical staining identifying extracellular citrullinated histone H3 (CitH3), indicative of NETs involvement. Treatment included antibiotics, pentoxifylline, and anticoagulants, showing transient improvement before disease progression and euthanasia due to respiratory signs. These findings suggest NETs as a potential therapeutic target for bacterial vasculitis in similar cases.

Cytokine signalling in formation of neutrophil extracellular traps: Implications for health and diseases

Neutrophils, as essential component of the innate immune response, form a crucial part in the defence mechanisms through the release of extracellular traps (NETs). These web-like structures, composed of chromatin and antimicrobial proteins, are essential for the entrapment and inactivation of pathogens. However, either constitutive formation or inefficient clearance of NETs leads to adverse effects such as fibrosis, thrombosis, delayed wound healing and tissue damage in multiple diseases associated with sterile inflammation. This dichotomy casts NETs as both protective agents and harmful factors in several diseases such as autoimmune diseases, metabolic syndromes, systemic infections, and malignancies. Besides microbes and their products, variety of stimulants including pro-inflammatory cytokines induce NETs. The complex interactions and cross talk among the pro-inflammatory cytokines including IL-8, IL-6, GM-CSF, TNF-α, IFNs, and IL-1β activate neutrophils to form NETs and also contributes to a vicious circle of inflammatory cascade, leading to increased inflammation, oxidative stress, and thrombotic events. Emerging evidence indicates that the dysregulated cytokine milieus in diseases, such as diabetes mellitus, obesity, atherosclerosis, stroke, rheumatoid arthritis, and systemic lupus erythematosus, potentiate NETs release, thereby promoting disease development. Thus, neutrophils represent both critical effectors and potential therapeutic targets, underscoring their importance in the context of cytokine-mediated therapies for a spectrum of diseases. In the present review, we describe various cytokines and associated signalling pathways activating NETs formation in different human pathologies. Further, the review identifies potential strategies to pharmacologically modulate cytokine pathways to reduce NETs.

Pathophysiological Role of Neutrophil Extracellular Traps in Diet-Induced Obesity and Metabolic Syndrome in Animal Models

The global pandemic of obesity poses a serious health, social, and economic burden. Patients living with obesity are at an increased risk of developing noncommunicable diseases or to die prematurely. Obesity is a state of chronic low-grade inflammation. Neutrophils are first to be recruited to sites of inflammation, where they contribute to host defense via phagocytosis, degranulation, and extrusion of neutrophil extracellular traps (NETs). NETs are web-like DNA structures of nuclear or mitochondrial DNA associated with cytosolic antimicrobial proteins. The primary function of NETosis is preventing the dissemination of pathogens. However, neutrophils may occasionally misidentify host molecules as danger-associated molecular patterns, triggering NET formation. This can lead to further recruitment of neutrophils, resulting in propagation and a vicious cycle of persistent systemic inflammation. This scenario may occur when neutrophils infiltrate expanded obese adipose tissue. Thus, NETosis is implicated in the pathophysiology of autoimmune and metabolic disorders, including obesity. This review explores the role of NETosis in obesity and two obesity-associated conditions-hypertension and liver steatosis. With the rising prevalence of obesity driving research into its pathophysiology, particularly through diet-induced obesity models in rodents, we discuss insights gained from both human and animal studies. Additionally, we highlight the potential offered by rodent models and the opportunities presented by genetically modified mouse strains for advancing our understanding of obesity-related inflammation.

HMGB1 lactylation drives neutrophil extracellular trap formation in lactate-induced acute kidney injury

Rationale

Acute kidney injury (AKI) is a clinical syndrome associated with a multitude of conditions. Although renal replacement therapy (RRT) remains the cornerstone of treatment for advanced AKI, its implementation can potentially pose risks and may not be readily accessible across all healthcare settings and regions. Elevated lactate levels are implicated in sepsis-induced AKI; however, it remains unclear whether increased lactate directly induces AKI or elucidates the underlying mechanisms.

Methods

For human, the measurement of lactate in arterial blood gas is performed using the direct determination of L-lactate through an electrode oxidation method by a blood gas analyzer. For mice, enzyme-linked immunosorbent assay (ELISA) kits were employed to quantify the concentrations of lactate and AKI biomarkers in blood and cell supernatant. The mouse model of AKI was performed with a single intraperitoneal (i.p.) administration of lactate (30 mg/kg) and low-dose LPS (2 mg/kg) for 24 h. Proteomic analysis was conducted to identify lactylated proteins in kidney tissues. Techniques such as, immunoprecipitation, western blotting and immunofluorescence were used to evaluate the levels of HMGB1 lactylation, neutrophil extracellular traps (NETs)and to assess related molecular signaling pathways.

Main results

Our findings indicate that lactate serves as an independent predictor of AKI in patients with acute decompensated heart failure (ADHF). We observed that co-administration of lactate with low-dose lipopolysaccharide (LPS) resulted in lactate overproduction, which subsequently elevated serum levels of creatinine (Cre) and blood urea nitrogen (BUN). Furthermore, the combined application of lactate and low-dose LPS was shown to provoke HMGB1 lactylation within renal tissues. Notably, pretreatment with HMGB1 small interfering RNA (siRNA) effectively diminished lactate-mediated HMGB1 lactylation and alleviated the severity of AKI. Additionally, lactate accumulation was found to enhance the expression levels of NETs in the bloodstream, with circulating NETs levels positively correlating with HMGB1 lactylation. Importantly, pre-administration of HMGB1 inhibitors (glycyrrhizin) or lactate dehydrogenase A (LDH-A) inhibitors (oxamate) reversed the upregulation of NETs induced by lactate and low-dose LPS in both the blood and polymorphonuclear neutrophils (PMNs) cell supernatant, thereby ameliorating AKI associated with lactate accumulation.

Conclusions

These findings illuminate the role of lactate-mediated HMGB1 lactylation in inducing AKI in mice through the activation of the HMGB1-NETs signaling pathway.

Deciphering hub genes and immune landscapes related to neutrophil extracellular traps in rheumatoid arthritis: insights from integrated bioinformatics analyses and experiments

Background

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by synovial inflammation and progressive joint destruction. Neutrophil extracellular traps (NETs), a microreticular structure formed after neutrophil death, have recently been implicated in RA pathogenesis and pathological mechanisms. However, the underlying molecular mechanisms and key genes involved in NET formation in RA remain largely unknown.

Methods

We obtained single-cell RNA sequencing data of synovial tissues from the Gene Expression Omnibus (GEO) database and performed cellular annotation and intercellular communication analyses. Subsequently, three microarray datasets were collected for a training cohort and correlated with a bulk RNA-seq dataset associated with NETs. Differentially expressed genes were identified, and weighted gene correlation network analysis was used to characterize gene association. Using three machine learning techniques, we identified the most important hub genes to develop and evaluate a nomogram diagnostic model. CIBERSORT was used to elucidate the relationship between hub genes and immune cells. An external validation dataset was used to verify pivotal gene expression and to construct co-regulatory networks using the NetworkAnalyst platform. We further investigated hub gene expression using immunohistochemistry (IHC) in an adjuvant-induced arthritis rat model and real-time quantitative polymerase chain reaction (RT-qPCR) in a clinical cohort.

Results

Seven cellular subpopulations were identified through downscaling and clustering, with neutrophils likely the most crucial cell clusters in RA. Intercellular communication analysis highlighted the network between neutrophils and fibroblasts. In this context, 4 key hub genes (CRYBG1, RMM2, MMP1, and SLC19A2) associated with NETs were identified. A nomogram model with a diagnostic value was developed and evaluated. Immune cell infiltration analysis indicated associations between the hub genes and the immune landscape in NETs and RA. IHC and RT-qPCR findings showed high expression of CRYBG1, RMM2, and MMP1 in synovial and neutrophilic cells, with lower expression of SLC19A2. Correlation analysis further emphasized close associations between hub genes and laboratory markers in patients with RA.

Conclusion

This study first elucidated neutrophil heterogeneity in the RA synovial microenvironment and mechanisms of communication with fibroblasts. CRYBG1, RMM2, MMP1, and SLC19A2 were identified and validated as potential NET-associated biomarkers, offering insights for diagnostic tools and immunotherapeutic strategies in RA.

Advances in acute COPD exacerbation: clarifying specific immune mechanisms of infectious and noninfectious factors

Acute exacerbation of chronic obstructive pulmonary disease (AECOPD) is the main cause of hospitalization and death of patients with chronic obstructive pulmonary disease. This is largely due to bacterial resistance caused by clinical antibiotic abuse and the limited efficacy of current treatment strategies in managing noninfectious AECOPD, which presents a significant challenge for clinicians. Therefore, it is urgent for clinical treatment and prevention of AECOPD to fully understand the specific mechanism of AECOPD in the immune system and master the key differences between infectious factors and noninfectious factors. This article systematically discusses AECOPD triggered by various factors, including the activation of immune system, the recruitment and activation of inflammatory cells and the role of specific inflammatory responses, and through a comprehensive review of the literature, this article expounds the existing targeted diagnosis and treatment methods and technologies at different stages in order to provide new ideas and strategies for clinical prevention and treatment of AECOPD.

Neutrophil extracellular traps induce barrier dysfunction in DSS-induced ulcerative colitis via the cGAS-STING pathway

Peptidyl arginine deiminase 4 (PAD4)-mediated neutrophil extracellular traps (NETs) play a crucial role in the pathogenesis of ulcerative colitis (UC). The cGAS-STING intracellular DNA-sensing pathway has been recognized as a pivotal mediator of inflammation. This study aimed to explore how NETs contribute to intestinal inflammation and barrier dysfunction in UC, focusing on the cGAS-STING pathway. We observed a significant increase of STING expression in UC mouse colons, which was mitigated by blocking NET formation through PAD4 genetic knockout. Moreover, NETs were discovered to activate the cGAS-STING pathway in MC38 cells in a dose and time-dependent manner, leading to the secretion of inflammatory cytokines and impaired barrier function. Additionally, STING deficiency ameliorated the clinical colitis index, intestinal inflammation, and barrier dysfunction. These findings underscore the involvement of cGAS-STING in regulating NET-mediated intestinal inflammation, suggesting its potential as a novel therapeutic target for UC.

Neutrophil extracellular traps - an a-list-actor in a variety of diseases

Neutrophil extracellular traps (NETs) represent a response mechanism in which activated neutrophils release DNA-based webs, adorned with histones and neutrophil proteases, to capture and eliminate invasive microorganisms. However, when these neutrophils become excessively activated, much more proteases associated with NETs are liberated into surrounding tissues or bloodstreams, thereby altering the cellular milieu and causing tissue damage. Recent research has revealed that NETs may play significant roles in the emergence and progression of various diseases, spanning from infections, inflammation to autoimmune disorders and cancers. In this review, we delve deeply into the intricate and complex mechanisms that underlie the formation of NETs and their profound interplay with various clinical pathologies. We aim to describe the application perspectives of NETs related proteins in specific disease diagnosis and treatment.

Comprehensive macro and micro views on immune cells in ischemic heart disease

Ischemic heart disease (IHD) is a prevalent cardiovascular condition that remains the primary cause of death due to its adverse ventricular remodelling and pathological changes in end-stage heart failure. As a complex pathologic condition, it involves intricate regulatory processes at the cellular and molecular levels. The immune system and cardiovascular system are closely interconnected, with immune cells playing a crucial role in maintaining cardiac health and influencing disease progression. Consequently, alterations in the cardiac microenvironment are influenced and controlled by various immune cells, such as macrophages, neutrophils, dendritic cells, eosinophils, and T-lymphocytes, along with the cytokines they produce. Furthermore, studies have revealed that Gata6+ pericardial cavity macrophages play a key role in regulating immune cell migration and subsequent myocardial tissue repair post IHD onset. This review outlines the role of immune cells in orchestrating inflammatory responses and facilitating myocardial repair following IHD, considering both macro and micro views. It also discusses innovative immune cell-based therapeutic strategies, offering new insights for further research on the pathophysiology of ischemic heart disease and immune cell-targeted therapy for IHD.

Kinetics of neutrophil extracellular traps and cytokines in oral mucositis and Candida infection

OBJECTIVE

This study investigated the concentrations of neutrophil extracellular traps (NET) and salivary cytokines (IL-1β, IL-6, IL-8/CXCL8, TNF, and TGF-β1) in patients undergoing chemotherapy and their associations with oral mucositis (OM) and Candida infection.

MATERIALS AND METHODS

This prospective longitudinal study performed at a Brazilian service included 60 adults diagnosed with hematolymphoid diseases. Saliva samples were collected on days D0, D3, D10, and D15. Cytokines were analyzed by ELISA and NET formation by identification of the myeloperoxidase-DNA complex. Oral Candida spp. was cultured.

RESULTS

OM occurred in 43.3% of patients and oral candidiasis in 20%. However, 66% of individuals had positive cultures for C. albicans. Higher concentrations of IL-6, IL-8/CXCL8, and TNF and lower concentrations of TGF-β1 were observed in patients with OM. C. albicans infection contributed to the increase in IL-8/CXCL8, TGF-β1, and TNF. Individuals with OM or with oral candidiasis had significant reductions in NET formation. In contrast, individuals with C. albicans and with concomitant C. albicans and OM exhibited higher NET formation.

CONCLUSION

The kinetics of cytokine levels and NET formation in chemotherapy-induced OM appears to be altered by Candida infection, even in the absence of clinical signs of oral candidiasis.

Neutrophil exhaustion and impaired functionality in psoriatic arthritis patients

Background

Neutrophils (polymorphonuclear leukocytes, PMNs) are the most abundant subtype of white blood cells and are among the main actors in the inflammatory response. Psoriatic arthritis (PsA) is a chronic inflammatory disease affecting both the axial and peripheral joints. Typically associated with psoriasis, PsA can also affect multiple systems and organs, including the nails and entheses. Despite the involvement of PMNs in PsA, their specific role in the disease remains poorly understood. This study aimed to characterize the biological functions of PMNs and neutrophil-related mediators in PsA patients.

Materials and methods

31 PsA patients and 22 healthy controls (HCs) were prospectively recruited. PMNs were isolated from peripheral blood and subjected to in vitro stimulation with lipopolysaccharide (LPS), N-Formylmethionyl-leucyl-phenylalanine (fMLP), tumor necrosis factor (TNF), phorbol 12-myristate 13-acetate (PMA), or control medium. Highly purified peripheral blood PMNs (>99%) were evaluated for activation status, reactive oxygen species (ROS) production, phagocytic activity, granular enzyme and neutrophil extracellular traps (NETs) release. Serum levels of matrix metalloproteinase-9 (MMP-9), myeloperoxidase (MPO), TNF, interleukin 23 (IL-23), and interleukin 17 (IL-17) were measured by ELISA. Serum Citrullinated histone H3 (CitH3) was measured as a NET biomarker.

Results

Activated PMNs from PsA patients displayed reduced activation, decreased ROS production, and impaired phagocytic activity upon stimulation with TNF, compared to HCs. PMNs from PsA patients also displayed reduced granular enzyme (MPO) and NET release. Serum analyses revealed elevated levels of MMP-9, MPO, TNF, IL-23, IL-17, and CitH3 in PsA patients compared to HCs. Serum CitH3 levels positively correlated with MPO and TNF concentrations, and IL-17 concentrations were positively correlated with IL-23 levels in PsA patients. These findings indicate that PMNs from PsA patients show reduced in vitro activation and function, and an increased presence of neutrophil-derived mediators (MMP-9, MPO, TNF, IL-23, IL-17, and CitH3) in their serum.

Conclusions

Taken together, our findings suggest that PMNs from PsA patients exhibit an "exhausted" phenotype, highlighting their plasticity and multifaceted roles in PsA pathophysiology.

Local Drug Delivery Systems as Novel Approach for Controlling NETosis in Periodontitis

Periodontitis is a chronic inflammation caused by periodontopathogenic bacteria in the dental biofilm, and also involves the inflammatory-immune response of the host. Polymorphonuclear neutrophils (PMNs) play essential roles in bacterial clearance by multiple mechanisms, including the formation of neutrophil extracellular traps (NETs) that retain and destroy pathogens. During PD progression, the interaction between PMNs, NETs, and bacteria leads to an exaggerated immune response and a prolonged inflammatory state. As a lesion matures, PMNs accumulate in the periodontal tissues and die via NETosis, ultimately resulting in tissue injury. A better understanding of the role of NETs, the associated molecules, and the pathogenic pathways of NET formation in periodontitis, could provide markers of NETosis as reliable diagnostic and prognostic tools. Moreover, an assessment of NET biomarker levels in biofluids, particularly in saliva or gingival crevicular fluid, could be useful for monitoring periodontitis progression and treatment efficacy. Preventing excessive NET accumulation in periodontal tissues, by both controlling NETs' formation and their appropriate removal, could be a key for further development of more efficient therapeutic approaches. In periodontal therapy, local drug delivery (LDD) systems are more targeted, enhancing the bioavailability of active pharmacological agents in the periodontal pocket and surrounding tissues for prolonged time to ensure an optimal therapeutic outcome.

The role of neutrophil extracellular trap formation in kidney transplantation: Implications from donors to the recipient

Kidney transplantation remains the gold standard for patients with end-stage renal disease, but severe donor organ shortage has led to long waiting lists. The utilization of expanded criteria donor kidneys within the category of deceased donors has enlarged the pool of available kidneys for transplantation; however, these grafts often have an increased risk for delayed graft function or reduced graft survival following transplantation. During brain or circulatory death, neutrophils are recruited to the vascular beds of kidneys where a proinflammatory microenvironment might prime the formation of neutrophil extracellular traps (NETs), web-like structures, containing proteolytic enzymes, DNA, and histones. NETs are known to cause tissue damage and specifically endothelial damage while activating other systems such as coagulation and complement, contributing to tissue injury and an unfavorable prognosis in various diseases. In lung transplantation and kidney transplantation studies, NETs have also been associated with primary graft dysfunction or rejection. In this review, the role that NETs might play across the different phases of transplantation, already initiated in the donor, during preservation, and in the recipient, will be discussed. Based on current knowledge, NETs might be a promising therapeutic target to improve graft outcomes.

Extracellular histones: a unifying mechanism driving platelet-dependent extracellular vesicle release and thrombus formation in COVID-19

BACKGROUND

COVID-19 can cause profound inflammation and coagulopathy, and while many mechanisms have been proposed, there is no known common pathway leading to a prothrombotic state.

OBJECTIVES

From the beginning of the COVID-19 pandemic, elevated levels of extracellular histones have been found in plasma of patients infected with SARS-CoV-2. We hypothesized that platelet activation triggered by extracellular histones might represent a unifying mechanism leading to increased thrombin generation and thrombosis.

METHODS

We utilized blood samples collected from an early clinical trial of hospitalized COVID-19 patients (NCT04360824) and recruited healthy subjects as controls. Using plasma samples, we measured the procoagulant and prothrombotic potential of circulating extracellular histones and extracellular vesicles (EVs). Platelet prothrombotic activity was assessed via thrombin generation potential and platelet thrombus growth. Circulating EVs were assessed for thrombin generation potential in vitro in plasma and enhancement of thrombotic susceptibility in vivo in mice.

RESULTS

Compared with controls, COVID-19 patients had elevated plasma levels of citrullinated histone H3, cell-free DNA, nucleosomes, and EVs. Plasma from COVID-19 patients promoted platelet activation, platelet-dependent thrombin generation, thrombus growth under venous shear stress, and release of platelet-derived EVs. These prothrombotic effects of COVID-19 plasma were inhibited by an RNA aptamer that neutralizes both free and DNA-bound histones. EVs isolated from COVID-19 plasma enhanced thrombin generation in vitro and potentiated venous thrombosis in mice in vivo.

CONCLUSION

We conclude that extracellular histones and procoagulant EVs drive the prothrombotic state in COVID-19 and that histone-targeted therapy may prove beneficial.

miR-483-5p-Containing exosomes treatment ameliorated deep vein thrombosis‑induced inflammatory response

Peripheral vascular condition, known as deep vein thrombosis (DVT), is a common ailment that may lead to deadly pulmonary embolism. Inflammation is closely connected to venous thrombosis, which results in blood stasis, leading to ischemia and hypoxia, as indicated by research. The objective of this research was to investigate the mechanism by which exosomes derived from adipose stem cells (ADSCs) prevent deep vein thrombosis. Our data showed that Exo-483 effectively reduced the thrombus weight in DVT rats by intravenous injection. Exo-483 decreased the expression of tissue factor (TF) protein, the influx of inflammatory cells into the thrombosed vein wall, and the levels of cytokines in the serum. Furthermore, Exo-483 suppressed the expression of Mitogen-activated protein kinase 1 (MAPK1) and decreased the expression of NLRP3 inflammasomes. In an oxygen-glucose deprivation (OGD) cell model, the tube-forming and migratory abilities of primary human umbilical vein endothelial cells (HUVEC) and EA.hy926 cells were suppressed by Exo-483 pretreatment.Exo-483 is also linked to regulating Dynamin-related protein 1 (DRP1) production downstream of MAPK1.By decreasing the mitochondrial localization and phosphorylation at the S616 site of DRP1, it diminishes the expression of NLRP3 inflammasomes. Moreover, according to Bioinformatics analysis, miR-483-5p was anticipated to target MAPK1. The research conducted by our team revealed that the miR-483-5p exosome derived from ADSCs exhibited anti-inflammatory properties through the modulation of downstream DRP1-NLRP3 expression by targeting MAPK1.The findings of this research propose that miR-483-5p may be regarded as an innovative treatment target for DVT.

Altered neutrophil extracellular traps formation among medical residents with sleep deprivation

Resident physicians on long-term night shifts often face sleep deprivation, affecting the immune response, notably neutrophils, vital to innate defense mechanisms. Sleep-deprived residents exhibit altered neutrophil counts and reduced phagocytosis and NADPH oxidase activity, critical to combating infections. Our study focused on neutrophil extracellular traps (NETs), a defense process against pathogens not previously linked to sleep loss. Results revealed that sleep-deprived residents exhibited a 19.8 % reduction in NET formation compared to hospital workers with regular sleep patterns (P < 0.01). Additionally, key NETs proteins, Neutrophil Elastase and Myeloperoxidase, were less active in sleep-deprived individuals (1.53mU; P < 0.01 and 0.95U; P < 0.001 decrease, accordingly). Interestingly, the ability to form NETs resumed to normal levels three months post-residency among pediatric residents. The causal relationship between reduced NETs due to sleep deprivation and the increased susceptibility to infections, as well as its implications for infection severity, is a critical area for further investigation.

Increased neutrophil extracellular trap formation in oligoarticular, polyarticular juvenile idiopathic arthritis and enthesitis-related arthritis: biomarkers for diagnosis and disease activity

Objective

Neutrophil extracellular traps (NETs) are important factors in initiating and perpetuating inflammation. However, the role of NETs in different subtypes of juvenile idiopathic arthritis (JIA) has been rarely studied. Therefore, we aimed to explore the ability of JIA-derived neutrophils to release NETs and the effect of TNF-α (tumor necrosis factor-alpha) inhibitors on NET formation both in vitro and in vivo, and evaluate the associations of NET-derived products with clinical and immune-related parameters.

Methods

The ability of neutrophils to release NETs and the effect of adalimumab on NET formation was assessed via in vitro stimulation and inhibition studies. Plasma NET-derived products were detected to assess the incidence of NET formation in vivo. Furthermore, flow cytometry and western blotting were used to detect NET-associated signaling components in neutrophils.

Results

Compared to those derived from HCs, neutrophils derived from patients with oligoarticular-JIA, polyarticular-JIA and enthesitis-related arthritis were more prone to generate NETs spontaneously and in response to TNF-α or PMA in vitro. Excessive NET formation existed in peripheral circulation of JIA patients, and elevated plasma levels of NET-derived products (cell-free DNA and MPO-DNA complexes) could accurately distinguish JIA patients from HCs and were positively correlated with disease activity. Multiple linear regression analysis showed that erythrocyte sedimentation rate and TNF-α levels were independent variables and were positively correlated with cell-free DNA concentration. Notably, TNF-α inhibitors could effectively prevent NET formation both in vitro and in vivo. Moreover, the phosphorylation levels of NET-associated kinases in JIA-derived neutrophils were markedly increased.

Conclusion

Our data suggest that NETs might play pathogenic roles and may be involved in TNF-α-mediated inflammation in JIA. Circulating NET-derived products possess potential diagnostic and disease monitoring value. Furthermore, the preliminary results related to the molecular mechanisms of NET formation in JIA patients provide a theoretical basis for NET-targeted therapy.

PLASMA DYNAMICS OF NEUTROPHIL EXTRACELLULAR TRAPS AND CELL-FREE DNA IN SEPTIC AND NONSEPTIC VASOPLEGIC SHOCK: A PROSPECTIVE COMPARATIVE OBSERVATIONAL COHORT STUDY

ABSTRACT

Background: The association between neutrophil extracellular traps (NETs) and the requirement for vasopressor and inotropic support in vasoplegic shock is unclear. This study aimed to investigate the dynamics of plasma levels of NETs and cell-free DNA (cfDNA) up to 48 h after the admission to the intensive care unit (ICU) for management of vasoplegic shock of infectious (SEPSIS) or noninfectious (following cardiac surgery, CARDIAC) origin. Methods: This is a prospective, observational study of NETs and cfDNA plasma levels at 0H (admission) and then at 12H, 24H, and 48H in SEPSIS and CARDIAC patients. The vasopressor inotropic score (VIS), the Sequential Organ Failure Assessment (SOFA) score, and time spent with invasive ventilation, in ICU and in hospital, were recorded. Associations between NETs/cfDNA and VIS and SOFA were analyzed by Spearman's correlation (rho), and between NETs/cfDNA and ventilation/ICU/hospitalization times by generalized linear regression. Results: Both NETs and cfDNA remained elevated over 48 h in SEPSIS (n = 46) and CARDIAC (n = 30) patients, with time-weighted average concentrations greatest in SEPSIS (NETs median difference 0.06 [0.02-0.11], P = 0.005; cfDNA median difference 0.48 [0.20-1.02], P < 0.001). The VIS correlated to NETs (rho = 0.3-0.60 in SEPSIS, P < 0.01, rho = 0.36-0.57 in CARDIAC, P ≤ 0.01) and cfDNA (rho = 0.40-0.56 in SEPSIS, P < 0.01, rho = 0.38-0.47 in CARDIAC, P < 0.05). NETs correlated with SOFA. Neither NETs nor cfDNA were independently associated with ventilator/ICU/hospitalization times. Conclusion: Plasma levels of NETs and cfDNA correlated with the dose of vasopressors and inotropes administered over 48 h in patients with vasoplegic shock from sepsis or following cardiac surgery. NETs levels also correlated with organ dysfunction. These findings suggest that similar mechanisms involving release of NETs are involved in the pathophysiology of vasoplegic shock irrespective of an infectious or noninfectious etiology.

Citrullinated Histone H3, a Marker for Neutrophil Extracellular Traps, Is Associated with Poor Prognosis in Cutaneous Squamous Cell Carcinoma Developing in Patients with Recessive Dystrophic Epidermolysis Bullosa

Recessive dystrophic epidermolysis bullosa (RDEB) is a rare severe hereditary skin disease characterized by skin and mucosa fragility, resulting in blister formation. The most severe complication in RDEB patients is the development of cutaneous squamous cell carcinoma (SCC), leading to premature death. There is a great deal of evidence suggesting a permissive tumor microenvironment (TME) as a driver of SCC development in RDEB patients. In a cohort of RDEB patients, we characterized the immune profiles of RDEB-SCCs and compared them with clinical, histopathological, and prognostic features. RDEB-SCCs were subdivided into four groups based on their occurrence (first onset or recurrences) and grading according to clinical, histopathological parameters of aggressiveness. Thirty-eight SCCs from 20 RDEB patients were analyzed. Five RDEB patients experienced an unfavorable course after the diagnosis of the first SCC, with early recurrence or metastasis, whereas 15 patients developed multiple SCCs without metastasis. High-risk primary RDEB-SCCs showed a higher neutrophil-to-lymphocyte ratio in the tumor microenvironment and an increased proportion of neutrophil extracellular traps (NETs). Additionally, citrullinated histone H3, a marker of NETs, was increased in the serum of RDEB patients with high-risk primary SCC, suggesting that this modified form of histone H3 may serve as a potential blood marker of unfavorable prognosis in RDEB-SCCs.

IL-8 Induces Neutrophil Extracellular Trap Formation in Severe Thermal Injury

Neutrophil extracellular traps (NETs) have a dual role in the innate immune response to thermal injuries. NETs provide an early line of defence against infection. However, excessive NETosis can mediate the pathogenesis of immunothrombosis, disseminated intravascular coagulation (DIC) and multiple organ failure (MOF) in sepsis. Recent studies suggest that high interleukin-8 (IL-8) levels in intensive care unit (ICU) patients significantly contribute to excessive NET generation. This study aimed to determine whether IL-8 also mediates NET generation in patients with severe thermal injuries. IL-8 levels were measured in serum samples from thermally injured patients with ≥15% of the total body surface area (TBSA) and healthy controls (HC). Ex vivo NET generation was also investigated by treating isolated neutrophils with serum from thermal injured patients or normal serum with and without IL-8 and anti-IL-8 antibodies. IL-8 levels were significantly increased compared to HC on days 3 and 5 (p < 0.05) following thermal injury. IL-8 levels were also significantly increased at day 5 in septic versus non-septic patients (p < 0.001). IL-8 levels were also increased in patients who developed sepsis compared to HC at days 3, 5 and 7 (p < 0.001), day 10 (p < 0.05) and days 12 and 14 (p < 0.01). Serum containing either low, medium or high levels of IL-8 was shown to induce ex vivo NETosis in an IL-8-dependent manner. Furthermore, the inhibition of DNase activity in serum increased the NET-inducing activity of IL-8 in vitro by preventing NET degradation. IL-8 is a major contributor to NET formation in severe thermal injury and is increased in patients who develop sepsis. We confirmed that DNase is an important regulator of NET degradation but also a potential confounder within assays that measure serum-induced ex vivo NETosis.

Neuroinflammation in Alzheimer's disease: insights from peripheral immune cells

Alzheimer's disease (AD) is a serious brain disorder characterized by the presence of beta-amyloid plaques, tau pathology, inflammation, neurodegeneration, and cerebrovascular dysfunction. The presence of chronic neuroinflammation, breaches in the blood-brain barrier (BBB), and increased levels of inflammatory mediators are central to the pathogenesis of AD. These factors promote the penetration of immune cells into the brain, potentially exacerbating clinical symptoms and neuronal death in AD patients. While microglia, the resident immune cells of the central nervous system (CNS), play a crucial role in AD, recent evidence suggests the infiltration of cerebral vessels and parenchyma by peripheral immune cells, including neutrophils, T lymphocytes, B lymphocytes, NK cells, and monocytes in AD. These cells participate in the regulation of immunity and inflammation, which is expected to play a huge role in future immunotherapy. Given the crucial role of peripheral immune cells in AD, this article seeks to offer a comprehensive overview of their contributions to neuroinflammation in the disease. Understanding the role of these cells in the neuroinflammatory response is vital for developing new diagnostic markers and therapeutic targets to enhance the diagnosis and treatment of AD patients.

Significance of neutrophil extracellular traps-related gene in the diagnosis and classification of atherosclerosis

Atherosclerosis (AS) is a pathological process associated with various cardiovascular diseases. Upon different stimuli, neutrophils release reticular complexes known as neutrophil extracellular traps (NETs). Numerous researches have indicated a strong correlation between NETs and AS. However, its role in cardiovascular disease requires further investigation. By utilizing a machine learning algorithm, we examined the genes associated with NETs that were expressed differently in individuals with AS compared to normal controls. As a result, we identified four distinct genes. A nomogram model was built to forecast the incidence of AS. Additionally, we conducted analysis on immune infiltration, functional enrichment and consensus clustering in AS samples. The findings indicated that individuals with AS could be categorized into two groups, exhibiting notable variations in immune infiltration traits among the groups. Furthermore, to measure the NETs model, the principal component analysis algorithm was developed and cluster B outperformed cluster A in terms of NETs. Additionally, there were variations in the expression of multiple chemokines between the two subtypes. By studying AS NETs, we acquired fresh knowledge about the molecular patterns and immune mechanisms implicated, which could open up new possibilities for AS immunotherapy.

The role of neutrophils and neutrophil extracellular traps (NETs) in stages, outcomes and pregnancy complications

Neutrophils are the main components of innate immunity to eliminate infectious pathogens. Neutrophils play a role in several stages of the reproductive cycle, and their presence in the female reproductive system is highly regulated, so their function may change during pregnancy. Emerging evidence suggests that neutrophils are important at all stages of pregnancy, from implantation, placentation, and connective tissue regeneration to birth, as well as birth itself. Neutrophil extracellular traps (NETs) are defined as extracellular strands of unfolded DNA together with histone complexes and neutrophil granule proteins. NET formation is a new mechanism of these cells for their defense function. These strands containing DNA and antimicrobial peptides were initially recognized as one of the defense mechanisms of neutrophils, but later it was explained that they are involved in a variety of non-infectious diseases. Since the source of inflammation and tissue damage is the irregular activity of neutrophils, it is not surprising that NETosis are associated with a number of inflammatory conditions and diseases. The overexpression of NET components or non-principled NET clearance is associated with the risk of production and activation of autoantibodies, which results in participation in autoinflammatory and autoimmune disorders (SLE, RA), fibrosis, sepsis and other disorders such as vascular diseases, for example, thrombosis and atherosclerosis. Recent published articles have shown the role of neutrophils and extracellular traps (NETs) in pregnancy, childbirth and pregnancy-related diseases. The aim of this study was to identify and investigate the role of neutrophils and neutrophil extracellular traps (NETs) in the stages of pregnancy, as well as the complications caused by these cells.

Bulk and single-cell RNA sequencing analysis with 101 machine learning combinations reveal neutrophil extracellular trap involvement in hepatic ischemia-reperfusion injury and early allograft dysfunction

BACKGROUND

Hepatic ischaemia-reperfusion injury (HIRI) is a major clinical concern during the perioperative period and is closely associated with early allograft dysfunction (EAD), acute rejection (AR) and long-term graft survival. Neutrophil extracellular traps (NETs) are extracellular structures formed by the release of decondensed chromatin and granular proteins following neutrophil stimulation. There is growing evidence that NETs are involved in the progression of various liver transplantation complications, including ischaemia-reperfusion injury (IRI). This study aimed to comprehensively analyse the expression patterns of NET-related genes (NRGs) in HIRI, identify HIRI subtypes with distinct characteristics, and develop a reliable EAD prediction model.

METHODS

Microarray, bulk RNA-seq, and single-cell sequencing datasets were obtained from the GEO database. Initially, differentially expressed NRGs (DE-NRGs) were identified using differential gene expression analyses. We then utilised a non-negative matrix factorisation (NMF) algorithm to classify HIRI samples. Subsequently, we employed machine learning algorithms to screen the hub NRGs related to EAD and developed an EAD prediction model based on these hub NRGs. Concurrently, we assessed the expression patterns of hub NRGs at the single-cell level using the HIRI. Additionally, we validated C5AR1 expression and its effect on HIRI and NETs formation in a rat orthotopic liver transplantation (OLT) model.

RESULTS

In this study, we identified 11 DE-NRGs in the HIRI context. Based on these 11 DE-NRGs, HIRI samples were classified into two distinct clusters. Cluster1 exhibited a low expression of DE-NRGs, minimal neutrophil infiltration, mild inflammation, and a low incidence of EAD. Conversely, Cluster2 displayed the opposite phenotype, with an activated inflammatory subtype and a higher incidence of EAD. Furthermore, an EAD prediction model was developed using the four hub NRGs associated with EAD. Based on risk scores, HIRI samples were classified into high- and low-risk groups. The OLT model confirmed substantial upregulation of C5AR1 expression in the liver tissue, accompanied by increased formation of NETs. Treatment with a C5AR1 antagonist improved liver function, reduced tissue inflammation, and decreased NETs formation.

CONCLUSIONS

This study distinguished two apparent HIRI subtypes, established a predictive model for EAD, and validated the effect of C5AR1 on HIRI. These findings provide novel perspectives for the development of advanced clinical strategies to enhance the outcomes of liver transplant recipients.

Neutrophil Extracellular Traps in Cardiovascular and Aortic Disease: A Narrative Review on Molecular Mechanisms and Therapeutic Targeting

Neutrophil extracellular traps (NETs), composed of DNA, histones, and antimicrobial proteins, are released by neutrophils in response to pathogens but are also recognized for their involvement in a range of pathological processes, including autoimmune diseases, cancer, and cardiovascular diseases. This review explores the intricate roles of NETs in different cardiovascular conditions such as thrombosis, atherosclerosis, myocardial infarction, COVID-19, and particularly in the pathogenesis of abdominal aortic aneurysms. We elucidate the mechanisms underlying NET formation and function, provide a foundational understanding of their biological significance, and highlight the contribution of NETs to inflammation, thrombosis, and tissue remodeling in vascular disease. Therapeutic strategies for preventing NET release are compared with approaches targeting components of formed NETs in cardiovascular disease. Current limitations and potential avenues for clinical translation of anti-NET treatments are discussed.

Neutrophil Extracellular DNA Traps in Response to Infection or Inflammation, and the Roles of Platelet Interactions

Neutrophils present the host's first line of defense against bacterial infections. These immune effector cells are mobilized rapidly to destroy invading pathogens by (a) reactive oxygen species (ROS)-mediated oxidative bursts and (b) via phagocytosis. In addition, their antimicrobial service is capped via a distinct cell death mechanism, by the release of their own decondensed nuclear DNA, supplemented with a variety of embedded proteins and enzymes. The extracellular DNA meshwork ensnares the pathogenic bacteria and neutralizes them. Such neutrophil extracellular DNA traps (NETs) have the potential to trigger a hemostatic response to pathogenic infections. The web-like chromatin serves as a prothrombotic scaffold for platelet adhesion and activation. What is less obvious is that platelets can also be involved during the initial release of NETs, forming heterotypic interactions with neutrophils and facilitating their responses to pathogens. Together, the platelet and neutrophil responses can effectively localize an infection until it is cleared. However, not all microbial infections are easily cleared. Certain pathogenic organisms may trigger dysregulated platelet-neutrophil interactions, with a potential to subsequently propagate thromboinflammatory processes. These may also include the release of some NETs. Therefore, in order to make rational intervention easier, further elucidation of platelet, neutrophil, and pathogen interactions is still needed.

Temporal changes in biomarkers of neutrophil extracellular traps and NET-promoting autoantibodies following adenovirus-vectored, mRNA, and recombinant protein COVID-19 vaccination

Neutrophil extracellular traps (NETs) play a role in innate pathogen defense and also trigger B-cell response by providing antigens. NETs have been linked to vaccine-induced thrombotic thrombocytopenia. We postulated a potential link between NET biomarkers, NET-promoting autoantibodies, and adverse events (AEs) after COVID-19 vaccine boosters. Healthy donors (HDs) who received ChAdOx1-S (A), mRNA-1273 (M), or recombinant protein (MVC-COV1901) vaccines at the National Taiwan University Hospital between 2021 and 2022 were recruited. We measured serial NET-associated biomarkers, citrullinated-histone3 (citH3), and myeloperoxidase (MPO)-DNA. Serum citH3 and MPO-DNA were significantly or numerically higher in HDs who reported AEs (n = 100, booster Day 0/Day 30, p = 0.01/p = 0.03 and p = 0.30/p = 0.35, respectively). We also observed a positive correlation between rash occurrence in online diaries and elevated citH3. A linear mixed model also revealed significantly higher citH3 levels in mRNA-1273/ChAdOx1-S recipients than MVC-COV1901 recipients. Significant positive correlations were observed between the ratios of anti-heparin platelet factor 4 and citH3 levels on Booster Day 0 and naïve and between the ratios of anti-NET IgM and citH3 on Booster Day 30/Day 0 in the AA-M and MM-M group, respectively. The increased levels of citH3/MPO-DNA accompanied by NET-promoting autoantibodies suggest a potential connection between mRNA-1273/ChAdOx1-S vaccines and cardiovascular complications. These findings provide insights for risk assessments of future vaccines.

Single-cell immune profiling of mouse liver aging reveals Cxcl2+ macrophages recruit neutrophils to aggravate liver injury

BACKGROUND AND AIMS

Immune cells play a crucial role in liver aging. However, the impact of dynamic changes in the local immune microenvironment on age-related liver injury remains poorly understood. We aimed to characterize intrahepatic immune cells at different ages to investigate key mechanisms associated with liver aging.

APPROACH AND RESULTS

We carried out single-cell RNA sequencing on mouse liver tissues at 4 different ages, namely, the newborn, suckling, young, and aged stages. The transcriptomic landscape, cellular classification, and intercellular communication were analyzed. We confirmed the findings by multiplex immunofluorescence staining, flow cytometry, in vitro functional experiments, and chimeric animal models. Nine subsets of 89,542 immune cells with unique properties were identified, of which Cxcl2+ macrophages within the monocyte/macrophage subset were preferentially enriched in the aged liver. Cxcl2+ macrophages presented a senescence-associated secretory phenotype and recruited neutrophils to the aged liver through the CXCL2-CXCR2 axis. Through the secretion of IL-1β and TNF-α, Cxcl2+ macrophages stimulated neutrophil extracellular traps formation. Targeting the CXCL2-CXCR2 axis limited the neutrophils migration toward the liver and attenuated age-related liver injury. Moreover, the relationship between Cxcl2+ macrophages and neutrophils in age-related liver injury was further validated by human liver transplantation samples.

CONCLUSIONS

This in-depth study illustrates that the mechanism of Cxcl2+ macrophage-driven neutrophil activation involves the CXCL2-CXCR2 axis and provides a potential therapeutic strategy for age-related liver injury.

Human Macrophages Activate Bystander Neutrophils' Metabolism and Effector Functions When Challenged with Mycobacterium tuberculosis

Neutrophils are dynamic cells, playing a critical role in pathogen clearance; however, neutrophil infiltration into the tissue can act as a double-edged sword. They are one of the primary sources of excessive inflammation during infection, which has been observed in many infectious diseases including pneumonia and active tuberculosis (TB). Neutrophil function is influenced by interactions with other immune cells within the inflammatory lung milieu; however, how these interactions affect neutrophil function is unclear. Our study examined the macrophage-neutrophil axis by assessing the effects of conditioned medium (MΦ-CM) from primary human monocyte-derived macrophages (hMDMs) stimulated with LPS or a whole bacterium (Mycobacterium tuberculosis) on neutrophil function. Stimulated hMDM-derived MΦ-CM boosts neutrophil activation, heightening oxidative and glycolytic metabolism, but diminishes migratory potential. These neutrophils exhibit increased ROS production, elevated NET formation, and heightened CXCL8, IL-13, and IL-6 compared to untreated or unstimulated hMDM-treated neutrophils. Collectively, these data show that MΦ-CM from stimulated hMDMs activates neutrophils, bolsters their energetic profile, increase effector and inflammatory functions, and sequester them at sites of infection by decreasing their migratory capacity. These data may aid in the design of novel immunotherapies for severe pneumonia, active tuberculosis and other diseases driven by pathological inflammation mediated by the macrophage-neutrophil axis.

Neutrophil extracellular traps in bacterial infections and evasion strategies

Neutrophils are innate immune cells that have a vital role in host defense systems. Neutrophil extracellular traps (NETs) are one of neutrophils' defense mechanisms against pathogens. NETs comprise an ejected lattice of chromatin associated with histones, granular proteins, and cytosolic proteins. They are thought to be an efficient strategy to capture and/or kill bacteria and received intensive research interest in the recent years. However, soon after NETs were identified, it was observed that certain bacteria were able to evade NET entrapment through many different mechanisms. Here, we outline the recent progress of NETs in bacterial infections and the strategies employed by bacteria to evade or withstand NETs. Identifying the molecules and mechanisms that modulate NET release will improve our understanding of the functions of NETs in infections and provide new avenues for the prevention and treatment of bacterial diseases.

Top Five Stories of the Cellular Landscape and Therapies of Atherosclerosis: Current Knowledge and Future Perspectives

Atherosclerosis (AS) is characterized by impairment and apoptosis of endothelial cells, continuous systemic and focal inflammation and dysfunction of vascular smooth muscle cells, which is documented as the traditional cellular paradigm. However, the mechanisms appear much more complicated than we thought since a bulk of studies on efferocytosis, transdifferentiation and novel cell death forms such as ferroptosis, pyroptosis, and extracellular trap were reported. Discovery of novel pathological cellular landscapes provides a large number of therapeutic targets. On the other side, the unsatisfactory therapeutic effects of current treatment with lipid-lowering drugs as the cornerstone also restricts the efforts to reduce global AS burden. Stem cell- or nanoparticle-based strategies spurred a lot of attention due to the attractive therapeutic effects and minimized adverse effects. Given the complexity of pathological changes of AS, attempts to develop an almighty medicine based on single mechanisms could be theoretically challenging. In this review, the top stories in the cellular landscapes during the initiation and progression of AS and the therapies were summarized in an integrated perspective to facilitate efforts to develop a multi-targets strategy and fill the gap between mechanism research and clinical translation. The future challenges and improvements were also discussed.

Trauma-induced innate immune activation and disseminated intravascular coagulation

Dysregulated innate immunity participates in the pathomechanisms of disseminated intravascular coagulation (DIC) in trauma-induced coagulopathy. Accidental and regulated cell deaths and neutrophil extracellular traps release damage-associated molecular patterns (DAMPs), such as histones, nuclear and mitochondrial DNA, and high-mobility group box 1, into circulation immediately after trauma. DAMP-induced inflammation activation releases tissue factor-bearing procoagulant extracellular vesicles through gasdermin D-mediated pore formation and plasma membrane rupture by regulated cell death. DAMPs also evoke systemic inflammation, platelet, coagulation activation, and impaired fibrinolysis associated with endothelial injury, leading to the dysfunction of anticoagulation systems, which are the main pathophysiological mechanisms of DIC. All these processes induce systemic thrombin generation in vivo, not restricted to the injury sites immediately after trauma. Thrombin generation at the site of injury stops bleeding and maintains homeostasis. However, DIC associated with endothelial injury generates massive thrombin, enhancing protease-activated, receptor-mediated bidirectional interplays between inflammation and coagulation, aggravating the diverse actions of thrombin and disturbing homeostasis. Insufficiently regulated thrombin causes disseminated microvascular thrombosis, resulting in tissue hypoxia due to reduced oxygen delivery, and mitochondrial dysfunction due to DAMPs causes tissue dysoxia. In addition, DAMP-induced calcium influx and overload, as well as neutrophil activation, play a role in endothelial cell injury. Tissue hypoxia and cytotoxicity result in multiple organ dysfunction in DIC after trauma. Controls against dysregulated innate immunity evoking systemic inflammation, thrombin generation, and cytotoxicity are key issues in improving the prognosis of DIC in trauma-induced coagulopathy.

A Narrative Review: The Role of NETs in Acute Respiratory Distress Syndrome/Acute Lung Injury

Nowadays, acute respiratory distress syndrome (ARDS) still has a high mortality rate, and the alleviation and treatment of ARDS remains a major research focus. There are various causes of ARDS, among which pneumonia and non-pulmonary sepsis are the most common. Trauma and blood transfusion can also cause ARDS. In ARDS, the aggregation and infiltration of neutrophils in the lungs have a great influence on the development of the disease. Neutrophils regulate inflammatory responses through various pathways, and the release of neutrophils through neutrophil extracellular traps (NETs) is considered to be one of the most important mechanisms. NETs are mainly composed of DNA, histones, and granuloproteins, all of which can mediate downstream signaling pathways that can activate inflammatory responses, generate immune clots, and cause damage to surrounding tissues. At the same time, the components of NETs can also promote the formation and release of NETs, thus forming a vicious cycle that continuously aggravates the progression of the disease. NETs are also associated with cytokine storms and immune balance. Since DNA is the main component of NETs, DNase I is considered a viable drug for removing NETs. Other therapeutic methods to inhibit the formation of NETs are also worthy of further exploration. This review discusses the formation and mechanism of NETs in ARDS. Understanding the association between NETs and ARDS may help to develop new perspectives on the treatment of ARDS.

Neutrophil extracellular traps and neutrophilic dermatosis: an update review

Neutrophils have both antimicrobial ability and pathogenic effect in the immune system, neutrophil extracellular traps (NETs) formation is one of the representative behaviors of their dual role. NETs formation was triggered by pathogen-related components and pathogen non-related proteins as cytokines to exert its effector functions. Recent studies indicate that the pathogenicity of NETs contributed to several skin diseases such as psoriasis, Stevens-Johnson syndrome, toxic epidermal necrolysis, and neutrophilic dermatosis. Especially in neutrophilic dermatosis, a heterogeneous group of inflammatory skin disorders characterized with sterile neutrophilic infiltrate on dermis, NETs formation was reported as the way of participation of neutrophils in the pathogenesis of these diseases. In this review, we describe the different processes of NETs formation, then summarized the most recent updates about the pathogenesis of neutrophilic dermatosis and the participation of NETs, including pyoderma gangrenosum and PAPA syndrome, Behçet syndrome, hidradenitis suppurativa, Sweet Syndrome, pustular dermatosis and other neutrophilic dermatosis. Furthermore, we discuss the link between NETs formation and the development of neutrophilic dermatosis.

Grass carp Il-2 promotes neutrophil extracellular traps formation via inducing ROS production and autophagy in vitro

Interleukin (IL)-2 has been reported to regulate neutrophil functions in humans, mice, pigs and chicken although it is a key regulator of T cells. Consistently, we found that grass carp (Ctenopharyngodon idellus) interleukin-2 (gcIl-2) is capable of modulating the antimicrobial activities of neutrophils via regulating granzyme B- and perforin-like gene expression in our previous study. In the present study, stimulation of gcIl-2 on neutrophil extracellular traps (NETs) formation in grass carp neutrophils was demonstrated by detecting free DNA release, histone H3 citrullination and morphological changes of the cells. Further investigation revealed that reactive oxygen species (ROS) production from NADPH oxidase but not mitochondria was involved in NETosis induced by gcIl-2. Aside from ROS, autophagy was disclosed to be indispensable for NETosis induced by gcIl-2. These converging lines of evidence suggested that fish Il-2 could induce NETs formation via NADPH oxidase-derived ROS- and autophagy-dependent pathways in fish species which is evolutionarily conserved with that in mammals. It is noteworthy that these two pathways did not interplay with each other in Il-2-stimulated NETosis. The mechanisms governing autophagy induced by Il-2 were also explored in the present study, showing that Il-2 modulated the action of high mobility group box 1 (HMGB1) protein to stimulate autophagy, leading to NETs formation in fish neutrophils. These results provided a new insight to the function of Il-2 in fish neutrophils, and a clue about the regulation of NETosis in the lower vertebrates.

Cyclosporine A alleviates colitis by inhibiting the formation of neutrophil extracellular traps via the regulating pentose phosphate pathway

BACKGROUND

The aberrant formation of neutrophil extracellular traps (NETs) has been implicated in ulcerative colitis (UC), a chronic recurrent intestinal inflammation. Cyclosporine A (CsA) is now applied as rescue therapy for acute severe UC. In addition, it has been certained that CsA inhibits the formation of NETs in vitro and the mechanism of which was still vague. The study aimed to explore the mechanism CsA inhibits the NETs formation of colitis in vivo and in vitro.

METHODS

NETs enrichment in clinical samples was analyzed using databases from Gene Expression Omnibus and verified in our center. Dextran sulfate sodium (DSS)-induced acute colitis mice model was used to investigate the effect of CsA on NETs of colonic tissue expression. To clarify the mechanism, intracellular energy metabolites were examined by Liquid Chromatograph Mass Spectrometer, and reactive oxygen species (ROS) levels were examined by fluorescence intensity in neutrophils treated with CsA after LPS stimulation. The transcriptional level and activity of G6PD of neutrophils were also assessed using qRT-PCR and WST-8. RNA Sequencing was used to detect differentially expressed genes of neutrophils stimulated by LPS with or without CsA. The expression levels of related proteins were detected by western blot.

RESULTS

NETs enrichment was especially elevated in moderate-to-severe UC patients compared to HC. NETs expression in the colon from DSS colitis was decreased after CsA treatment. Compared with neutrophils stimulated by LPS, NETs formation and cellular ROS levels were decreased in LPS + CsA group. Cellular ribulose 5-phosphate and NADPH/NADP + related to the pentose phosphate pathway (PPP) were reduced in LPS + CsA group. In addition, CsA could decrease G6PD activity in neutrophils stimulated with LPS, and the results were further verified by inhibiting G6PD activity. At last, P53 protein was highly expressed in LPS + CsA group compared with the LPS group. Intracellular G6PD activity, ROS level and NETs formation, which were downregulated by CsA, could be reversed by a P53 inhibitor.

CONCLUSION

Our results indicated CsA could alleviate the severity of colitis by decreasing the formation of NETs in vivo. In vitro, CsA reduced ROS-dependent NETs release via downregulating PPP and cellular ROS levels by decreasing G6PD activity directly by activating the P53 protein.

Interleukin-4 during post-exercise recovery negatively correlates with the production of phagocyte-generated oxidants

Exhaustive run induced a biphasic oxidative response of circulating phagocytes in 16 amateur sportsmen. The first phase involved an increment just after exercise of enhanced whole blood chemiluminescence normalized per phagocyte count, whereas in the second phase a decrement from 1 h post-exercise and ongoing till 24 h. We tested whether plasma Interleukin IL-4, IL-8, IL-10 and Tumor Necrosis Factor α concentrations change in response to exhaustive run and whether there are associations between their levels and delta resting. Moreover, IL-8 and IL-10 significantly increased immediately post-exercise and after 1 h, but later normalized. Tumor necrosis factor α rose by 1.1-times only just after exercise. However, none of these cytokines showed any correlation with the investigated chemiluminescence. Exercise did not alter plasma concentrations of IL-4. However, pre-exercise IL-4 negatively correlated with measured luminescence just after exercise (ρ = -0.54, p < 0.05), and also tended to be negatively associated with decrements of the second phase at 1 h post-exercise ρ = -0.45, p = 0.08. It is suggested that plasma IL-4, by a negative association with blood phagocytes oxidants production, could be involved in the maintenance of proper balance between oxidants and anti-oxidants during strenuous exercise and post-exercise recovery.

Isolation methods determine human neutrophil responses after stimulation

Studying neutrophils is challenging due to their limited lifespan, inability to proliferate, and resistance to genetic manipulation. Neutrophils can sense various cues, making them susceptible to activation by blood collection techniques, storage conditions, RBC lysis, and the isolation procedure itself. Here we assessed the impact of the five most used methods for neutrophil isolation on neutrophil yield, purity, activation status and responsiveness. We monitored surface markers, reactive oxygen species production, and DNA release as a surrogate for neutrophil extracellular trap (NET) formation. Our results show that neutrophils isolated by negative immunomagnetic selection and density gradient methods, without RBC lysis, resembled untouched neutrophils in whole blood. They were also less activated and more responsive to milder stimuli in functional assays compared to neutrophils obtained using density gradients requiring RBC lysis. Our study highlights the importance of selecting the appropriate method for studying neutrophils, and underscores the need for standardizing isolation protocols to facilitate neutrophil subset characterization and inter-study comparisons.

Mitochondria-induced formation of neutrophil extracellular traps is enhanced in the elderly via Toll-like receptor 9

Neutrophil extracellular traps are potent antimicrobial weapons; however, their formation during sterile inflammation is detrimental, and the mechanism of induction is still unclear. Since advanced age is the primary clinical risk factor for poor outcomes in inflammatory diseases, we hypothesized that sterile stimuli, represented by mitochondria, would induce neutrophil extracellular trap formation in an age-dependent manner. Therefore, we analyzed induction of neutrophil extracellular traps in patients grouped according to age or immune status and observed that neutrophils from elderly patients responded to the presence of mitochondria with enhanced neutrophil extracellular trap formation. These neutrophil extracellular traps were also found to be more oxidized and exhibited higher resistance to DNase I degradation. Additionally, a higher concentration of residual neutrophil extracellular traps was detected in the plasma of the elderly. This plasma was capable of priming neutrophils through TLR9-mediated signaling, leading to further neutrophil extracellular trap formation, which was successfully inhibited with chloroquine. Finally, in a mouse model of mitochondria-induced acute lung injury, we observed that neutrophils from aged mice displayed impaired chemotactic activity but exhibited a trend of higher neutrophil extracellular trap formation. Thus, we propose that residual neutrophil extracellular traps circulating in the elderly preactivate neutrophils, making them more prone to enhanced neutrophil extracellular trap formation when exposed to mitochondria during sterile inflammation. Further investigation is needed to determine whether this vicious circle could be a suitable therapeutic target.

Bacterial Magnetosome-Hitchhiked Quick-Frozen Neutrophils for Targeted Destruction of Pre-Metastatic Niche and Prevention of Tumor Metastasis

Premetastatic niche (PMN) is a prerequisite for tumor metastasis. Destruction of PMN can significantly suppress the tumor metastasis. Bone marrow-derived cells are usually recruited into the premetastatic organs to support PMN formation, which can be orchestrated by tumor-derived secreted factors. Neutrophils can chemotactically migrate towards the inflammatory sites and consume tumor-derived secreted factors, capable of acting as therapeutic agents for a broad-spectrum suppression of PMN formation and metastasis. However, neutrophils in response to inflammatory signals can release neutrophil extracellular traps (NETs), promoting the tumor metastasis. Herein, live neutrophils are converted into dead neutrophils (C NE) through a quick-frozen process to maintain PMN-targeting and tumor-derived secreted factor-consuming abilities but eliminate NET-releasing shortcomings. Considering macrophages-regulated remodeling of the extracellular matrix in PMN, bacterial magnetosomes (Mag) are further hitchhiked on the surface of C NE to form C NEMag , which can repolarize macrophages from M2 to M1 phenotype for further disruption of PMN formation. A series of in vitro and in vivo assessments have been applied to confirm the effectiveness of C NEMag in suppression of PMN formation and metastasis. This study presents a promising strategy for targeted anti-metastatic therapy in clinics.