Neutrophil extracellular traps and their histones promote Th17 cell differentiation directly via TLR2

Neutrophil extracellular traps activate STING signaling to promote dendritic cell-driven rejection after liver transplantation

PURPOSE

Post-transplant immune rejection affects graft function. Interaction between neutrophil extracellular traps (NETs) with specific immune cells and the specific mechanism in liver transplantation were still unclear.

METHOD

Clinical patients RNA-Seq results were used for GSEA and KEGG analysis. C57BL/6 and C3H mouse models and clinical samples were use to describe the disease phenotype characteristics through multiple immunofluorescence, flow cytometry and etc. Cell co-culture experiments were performed to clarify the mechanism pathway process.

RESULTS

RNA-Seq results analysis indicated that the NETs formation pathway was upregulated. Animal models confirmed that in liver transplant immune rejection status the formation of NETs in situ and peripheral cells increased and the level of cell-free DNA (cf-DNA) in peripheral cells increased. Reactive oxygen species (ROS) as a predisposing factor for NETs accumulated more in immune rejection status and NETs are rich in mitochondrial DNA (mtDNA). NETs promote dendritic cell maturation through STING-related pathways. NETs formation increases in patients with liver transplant immune rejection and is positively correlated with disease severity.

CONCLUSION

We found that NETs can regulate dendritic cell maturation through STING-related pathways after liver transplantation, which may ultimately promote the occurrence of liver transplant rejection, providing a new perspective for clinical diagnosis, treatment and prevention of liver transplant rejection.

NETosis in myocardial ischemia-reperfusion injury: From mechanisms to therapies (Review)

The present review describes the mechanisms of NETosis and its role in myocardial ischemia-reperfusion injury (MIRI), focusing on the release of neutrophil extracellular traps (NETs) by activated neutrophils. NETs, composed of depolymerized chromatin and granule proteins, are crucial for pathogen entrapment, infection control and immune regulation. However, NET formation, linked to neutrophil death (NETosis), exacerbates MIRI by promoting inflammation and tissue damage. To address therapeutic strategies for NETosis in MIRI, several potential clinically significant approaches were explored, including peptidylarginine deaminase 4 inhibition, DNase therapy, antioxidants, inflammation modulation, and antithrombotic treatments, which not only provide novel diagnostic biomarkers and therapeutic targets in MIRI, but are also expected to improve patient prognosis and advance the development of personalised medicine.

Saturated fatty acid-induced neutrophil extracellular traps contribute to exacerbation and biologic therapy resistance in obesity-related psoriasis

Psoriasis patients who are obese tend to have serious clinical manifestations and poor responses to various biological agents in most cases. However, the mechanisms by which obesity exacerbates psoriasis remain enigmatic. In this study, we found that the abundance of systemic and localized cutaneous neutrophil extracellular traps (NETs) associated with the obesity-induced aggravation of psoriasis was positively correlated with disease severity and that the inhibition of NETs alleviated psoriatic dermatitis in obese mice. Mechanistically, we found that changes in fatty acid composition in obese subjects resulted in the deposition of saturated fatty acids (SFAs), which promoted the release of NETs via the TLR4-MD2/ROS signaling pathway. We further revealed that NETs potentiate IL-17 inflammation, especially γδT17-mediated immune responses, in obesity-exacerbated psoriasis patients. Moreover, SFAs induced a decreased response to anti-IL17A treatment in psoriasis-like mice, whereas the inhibition of NETs improved the beneficial effects of anti-IL17A in psoriasis-like mice with lipid metabolism disorders. Our findings collectively suggest that SFA-induced NETs play a critical role in the exacerbation of obesity-related psoriasis and provide potential new strategies for the clinical treatment of refractory psoriasis patients with lipid metabolism disorders.

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.

Idiopathic pulmonary fibrosis microenvironment: Novel mechanisms and research directions

Idiopathic Pulmonary Fibrosis (IPF) is a progressive interstitial lung disease marked by increasing dyspnea and respiratory failure. The underlying mechanisms remain poorly understood, given the complexity of its pathogenesis. This review investigates the microenvironment of IPF to identify novel mechanisms and therapeutic avenues. Studies have revealed that various cell types, including alveolar epithelial cells, fibroblasts, myofibroblasts, and immune cells, are integral to disease progression, engaging in cellular stress responses and inflammatory regulation via signaling pathways such as TGF-β, Wnt, mTOR, and ROS. Non-coding RNAs, particularly miRNAs, are critical in IPF and may serve as diagnostic and prognostic biomarkers. Regarding treatment, mesenchymal stem cells (MSCs) and their extracellular vesicles (EVs) or non-vesicular derivatives offer promise by modulating immune responses, enhancing tissue repair, and inhibiting fibrosis. Additionally, alterations in the lung microbiota are increasingly recognized as a contributing factor to IPF progression, offering fresh insights into potential treatments. Despite the encouraging results of MSC-based therapies, the precise mechanisms and clinical applications remain subjects of ongoing research. This review emphasizes the significance of the IPF microenvironment and highlights the need for further exploration to develop effective therapies that could enhance patient outcomes.

Spatiotemporally Controlled Co-Treatment of Lung Cancer and Pulmonary Immune-Related Adverse Events by Inhalable Albumin-Chaperoned Ultrathin MnO2 Nanosheets

Cancer immunotherapy is often associated with immune-related adverse events (irAE), particularly in the lungs, which can lead to treatment discontinuation and negatively impact patient outcomes. In this study, we explore a spatiotemporally controlled cotreatment of lung cancer and pulmonary irAE using inhalable albumin-chaperoned ultrathin MnO2 nanosheets (MnO2@BSA). The MnO2@BSA exhibits efficient reactive oxygen species scavenging and NIR-II photothermal properties. The inhalation route enhances MnO2@BSA accumulation in the lungs and tumor tissue, offering localized treatment with reduced systemic toxicity. We demonstrate that ultrathin MnO2@BSA nanosheets can inhibit the formation of neutrophil extracellular traps (NETs) by reducing reactive oxygen species (ROS) in neutrophils, thereby alleviating inflammation associated with irAE. In animal models, inhaled MnO2@BSA reduced lung injury and inflammatory cell infiltration, while also decreasing pro-inflammatory cytokine levels, such as TNF-α, IL-1β, and IL-6. Simultaneously, MnO2@BSA displays strong photothermal properties under 1064 nm laser irradiation, effectively ablating tumors. This photothermal therapy also induces immunogenic cell death (ICD), promoting the reuse of activated CD8+ T cells to enhance antitumor immunity. These dual effects─tumor destruction and irAE mitigation─highlight MnO2@BSA's potential as a therapeutic platform for addressing the challenges of immunotherapy in lung cancer. We anticipate that this work could contribute to the development of inhalable metal-based nanomedicine for clinical transformation in tumor immunotherapy.

Interleukin-35 inhibits NETs to ameliorate Th17/Treg immune imbalance during the exacerbation of cigarette smoke exposed-asthma via gp130/STAT3/ferroptosis axis

Cigarette smoke (CS) exposure amplifies neutrophil accumulation. IL-35, a novel cytokine with anti-inflammatory properties, is involved in protection against asthma. However, the biological roles of neutrophils and the precise molecular mechanisms of IL-35 in CS exposed-asthma remain unclear. We showed that the exacerbation of CS exposed-asthma leads to dramatically increased neutrophil counts and an imbalance in DC-Th17/Treg immune responses. RNA sequencing revealed that NETs, part of a key biological process in neutrophils, were significantly upregulated in the context of CS exposed-asthma exacerbation and that IL-35 treatment downregulated NET-associated gene expression. Targeted degradation of NETs, rather than neutrophil depletion, alleviated the CS exposed-asthma. Mechanistically, STAT3 phosphorylation promoted ferroptosis, exacerbating NET release, which in turn enhanced dendritic cell (DC) antigen presentation, activated T cells, and specifically promoted Th17 cell differentiation while inhibiting Treg cells. IL-35 acting on the gp130 receptor alleviated STAT3-mediated ferroptosis-associated NET formation. In summary, our study revealed a novel mechanism by which IL-35 inhibited NET formation, subsequently alleviating neutrophilic inflammation and restoring the DC-Th17/Treg imbalance in CS exposed-asthma, highlighting the potential of IL-35 as a targeted therapeutic strategy.

Targeting neutrophil extracellular traps in cancer progression and metastasis

Neutrophils serve as pivotal effectors and regulators of the intricate immune system. Their contributions are indispensable, encompassing the obliteration of pathogens and a significant role in both cancer initiation and progression. Conversely, malignancies profoundly affect neutrophil activity, maturation, and lifespans. Cancer cells manipulate their biology to enhance or suppress the key functions of neutrophils. This manipulation is one of the most remarkable defensive mechanisms used by neutrophils, including the formation of neutrophil extracellular traps (NETs). NETs are filamentous structures comprising DNA, histones, and proteins derived from cytotoxic granules. In this review, we discuss the bidirectional interplay in which cancer elicits NET formation, and NETs concurrently facilitate cancer progression. Here, we discuss how vascular dysfunction and thrombosis induced by neutrophils and NETs contribute to an elevated risk of mortality from cardiovascular complications in patients with cancer. Ultimately, we propose a series of therapeutic strategies that hold promise for effectively targeting NETs in clinical settings.

Dynamic changes of molecular pattern and cellular subpopulation in puncture-induced tendon injury model

Tendon degeneration and injury often result in significant pain and functional impairment. Typically, tendon healing occurs through a scar-mediated response and may progress to chronic tendinopathy without timely intervention. However, the molecular mechanisms underlying early tendon repair remain poorly understood. Further investigation is also impeded by the limited availability of early tendon injury samples in clinical settings. In this study, we established a puncture-induced tendon injury model to investigate the molecular patterns and cellular subpopulations involved in early tendon injury across multiple time points. RNA sequencing identified seven gene sets with distinct expression profiles during the early stages of tendon injury. Single-cell RNA sequencing further revealed eight myeloid cell types and seven mesenchymal cell types participating in the tendon repair process. Together, these findings illuminate the molecular and cellular dynamics coordinating early tendon repair, providing insights that could inform future clinical treatments for tendinopathy and tendon injury.

Neospora caninum triggers the release of heterophil extracellular traps in chickens

Neospora caninum (N. caninum) has been recognized as a pathogen responsible for neosporosis in chicken. Heterophils, which are a crucial part of the chicken's innate immune response, employ heterophil extracellular traps (HETs) as a principal defense strategy against invading pathogens. However, whether N. caninum can trigger the release of HETs remains unclear. This study presents the first evidence that N. caninum can induce the release of HETs in chickens and delves into the mechanisms that regulate this phenomenon. The impact of N. caninum on heterophil activity was evaluated using the CCK-8 assay. N. caninum- induced HETs were characterized using scanning electron microscopy and immunofluorescence. The release of N. caninum-induced HETs was quantified using a PicoGreen-based fluorescence microplate assay. Our findings revealed that heterophil activity remained unaffected by N. caninum infection. N. caninum induced thicknesses, reminiscent of HET-like structures, which primarily consisted of a DNA skeleton, citrullinated histone (citH3), and elastin. Furthermore, an increase in reactive oxygen species (ROS) production was detected during the release of N. caninum-induced HETs, a process that was found to be dependent on ROS-mediated activation, NADPH oxidase activity, glycolysis, toll-like receptor 2/4 (TLR2/4) and MAPK signaling pathways. N. caninum induced-HETs release was shown to be ROS-dependent, involving the activation of NADPH oxidase, ERK1/2, glycolysis, p38 MAPK, and toll-like receptor signaling pathways. In conclusion, this study is the first to elucidate the release mechanism of N. caninum-induced HETs in chicken, offering significant insights into the mechanisms underlying immune innate system against N. caninum infection.

Neutrophil Extracellular Traps-Associated RNA Impedes CD4+ Treg Differentiation by TLR7-IRF7 Axis in Ankylosing Spondylitis

OBJECTIVE

Our objective was to investigate the role of neutrophil extracellular traps (NETs) in the pathogenesis of inflammatory disorders in ankylosing spondylitis (AS).

METHODS

Local and circulating NETs levels were determined by immunofluorescence (IF) and myeloperoxidase (MPO)-DNA quantification in both patients with AS and AS model SKG mice. Flow cytometry (FCM) was performed to detect the effect of NETs on CD4+ subpopulation differentiation. The therapeutic effects of the neutrophil elastase inhibitor sivelestat (SVT) and the peptidylarginine deiminase 4 (PAD4) inhibitor CI-amidine were evaluated in SKG mice. The localization of NETs and their ability to impede CD4+ Treg cell differentiation were evaluated via IF, FCM, and Western blotting. RNA sequencing and specific inhibitors were used to clarify the detailed mechanism by which NETs inhibit CD4+ Treg differentiation.

RESULTS

The NETs levels were elevated locally and systemically in both patients with AS and SKG mice, which impeded the differentiation of CD4+ Treg cells. Blocking NETs formation via SVT or CI-amidine restored the CD4+ Treg ratio and subsequently alleviated inflammation in SKG mice. NETs were internalized by CD4+ T cells, and their associated RNA activated the Toll-like receptor 7 (TLR7)-interferon regulatory factor 7 (IRF-7) axis, which then inhibited Treg differentiation. Inhibiting CD4+ T cells endocytosis, removing the bound RNA component, or blocking the TLR7-IRF-7 axis abrogated the negative effect of NETs on CD4+ Treg differentiation.

CONCLUSION

Elevated NETs impeded CD4+ Treg differentiation by activating the TLR7-IRF-7 axis via their associated RNA in AS, and targeting NETs may be a novel treatment strategy for AS and related inflammatory disorders.

The crucial role of neutrophil extracellular traps and IL-17 signaling in indomethacin-induced gastric injury in mice

The homeostasis of gastric mucosa is extremely delicate. Neutrophils, the most abundant immune cells in human circulation, are regarded crutial in the regulation of gastric mucosal immune response. Non-steroidal anti-inflammatory drugs (NSAIDs) induced gastric injury is the second major reason for gastric ulcers. The relations between neutrophils and Indomethacin-induced gastric injury are not fully understood. A mouse model of gastric injury was established using Indomethacin, followed by proteomic analysis (raw data are available via ProteomeXchange with identifier PXD058482). GO functional annotations and KEGG pathway enrichment analysis were conducted on significant differential proteins. The formation of neutrophil extracellular traps (NETs) was observed using ELISA and immunofluorescence. TEM, Western blot and Real-time PCR were applied to observe programmed death of gastric epithelial cells (GECs), and ELISA was conducted to measure levels of TNF-α and IL-1β in the gastric tissue. Deoxyribonuclease 1 (DNase 1), a NETs inhibitor, was administered intraperitoneally to inhibit NETs formation. In vitro, neutrophils were isolated from peripheral blood of mice and co-cultured with mouse GECs cell line, different dosage of Indomethacin were added to the culture dish, the levels of inflammatory factors, formation of NETs and GECs programmed death were assessed in vitro. Poly morphonuclear neutrophils (PMN) were extracted from mouse peripheral blood and single-cell RNA-sequencing (scRNA-seq) was further applied (raw data are available via Genome Sequence Archive with identifier CRA020950) to explore the intracellular mechanism of NETs formation. ELISA and immunofluorescence were performed to validate expression of IL-17 signaling pathway. After Indomethacin gavage, obvious gastric injury was observed. Proteomic analysis indicated that NETs formation played a crucial role in Indomethacin-induced gastric injury. Compared to control group, Indomethacin treatment resulted in NETs formation, elevated levels of TNF-α and IL-1β and GECs programmed death. Inhibition of NETs significantly reduced inflammatory factor levels and mitigated gastric injury caused by indomethacin. In vitro, 200 µL, 400 µL and 600 µL of Indomethacin caused excessive NETs formation in neutrophils. Besides, Indomethacin-induced NETs formation led to GECs programmed death in vitro. scRNA-seq revealed that neutrophils enrichment in the peripheral blood of Indomethacin-induced gastric injury and IL-17 signaling might be the key intracellular of NETs formation. Expressions of neutrophil IL-17R and concentration of IL-17 were significantly higher in model group. NETs formation is pivotal in Indomethacin-induced gastric injury, contributing to programmed cell death of GECs and inflammation; IL-17 signaling might be the key intracellular mechanism of NETs formation.

NETs-CD44-IL-17A Feedback Loop Drives Th17-Mediated Inflammation in Behçet's Uveitis

Behçet's uveitis (BU) is a severe ocular manifestation of Behçet's disease, typically accompanied by abnormal neutrophil infiltration and hyperactivation. However, the underlying causes of excessive neutrophil extracellular traps (NETs) production and mechanisms by which NETs contribute to the pathogenesis of BU remain incompletely understood. Neutrophils from BU patients exhibit a higher propensity for NETs release compared to healthy controls. In the experimental autoimmune uveitis (EAU), neutrophils are observed to exert pro-inflammatory effects through NETs. Clearing NETs can inhibit T helper 17 (Th17) cell differentiation and significantly alleviate EAU symptoms. In vivo and in vitro experiments demonstrate neutralizing IL-17A markedly reducing neutrophil infiltration and NETs formation in EAU. Single-cell RNA sequencing confirms that CD44 plays a key role in mediating interactions between NETs and Th17 cells. Antagonizing CD44 inhibits the proportion of Th17 cells and NETs formation. Multiplex immunofluorescence and cell communication analyses further demonstrate interactions and colocalization between NETs and CD44highCD4+T cells in EAU. NETs induce Th17 differentiation via upregulating CD44, and in turn, Th17 cells secrete IL-17A to recruit neutrophils and promote NETs formation. Interrupting NETs-CD44-IL-17A feedback loop may be a potential therapeutic target for BU.

Eosinophil extracellular traps drive T follicular helper cell differentiation via VIRMA-dependent MAF stabilization in bullous pemphigoid

BACKGROUND

Bullous pemphigoid (BP) is an autoimmune blistering disease characterized by the presence of pathogenic autoantibodies and a substantial influx of immune cells into skin lesions. However, the role of eosinophils in BP remains inadequately elucidated.

OBJECTIVE

We sought to determine the pathologic involvement of eosinophils and eosinophil extracellular traps (EETs) in BP.

METHODS

Human samples collected from BP patients and healthy controls were utilized to explore the potential role of eosinophils and their EETs in BP patients through serologic detection, flow cytometry, and immunofluorescence. Naive CD4+ T cells isolated from healthy donors were stimulated and subjected to further analysis via RNA sequencing. We additionally evaluated the potential of targeting EETs in BP180-immunized BP-like mice and in in vitro settings.

RESULTS

We found that elevated levels of eosinophils and EETs in BP patients correlated with disease severity. The DNA components within EETs played a crucial role in driving the differentiation of naive CD4+ T cells into follicular helper T (Tfh) cells by activating coil domains containing 25 (CCDC25). Treatment with DNase I, which disrupts the structural integrity of EETs, or neutralizing antibody against CCDC25 reduced the expansion of Tfh cells and suppressed the production of autoantibodies in BP180-immunized BP-like mouse models. Additionally, we discovered that EETs induced the N6-methyladenosine methylation of the transcription factor musculoaponeurotic fibrosarcoma (MAF) via the DNA-CCDC25-VIRMA pathway, thereby enhancing its mRNA stability and promoting Tfh cell differentiation.

CONCLUSION

Our study revealed a previously unrecognized mechanism by which EETs trigger abnormal Tfh cell differentiation through CCDC25, followed by Vir-like m6A methyltransferase-associated protein (VIRMA)-mediated N6-methyladenosine modification of MAF. These insights provide promising avenues for the development of targeted therapeutic interventions in the field of BP and potentially other autoimmune diseases.

Identification of Three Distinct Subgroups in Antiphospholipid Syndrome: Implication for Sex Differences and Prognostic Outcomes from a Multicenter Study

Antiphospholipid syndrome (APS) is a heterogeneous autoimmune disease with persistent antiphospholipid antibodies. This study aimed to identify unrecognized APS subgroups from multicenter cohorts (n = 760, training: n = 415; validation: n = 345). Patients are stratified through unsupervised K-means clustering analysis. Prognostic outcomes are evaluated using Kaplan-Meier survival analyses. Proteomic analysis is conducted on primary APS patients (n = 36) and healthy controls (n = 12). Key molecule insulin-like growth factor 1 is validated using ELISA. Three clusters are identified. Cluster 1 (n = 320, 42.1%) is completely consisted of females (100%), with predominant occurrence of pregnancy morbidity (88.8%) but low incidences of thrombocytopenia (18.4%) and thrombosis (15.0%), and a favorable prognosis. Cluster 2 (n = 309, 40.7%) is predominantly female (99.4%) and characterized by high thrombosis (85.8%) and thrombocytopenia (46.6%), low pregnancy morbidity (13.6%), and poor prognosis. Cluster 3 (n = 131, 17.2%) is predominantly male (99.2%), exhibiting highest thrombosis (96.2%) and moderate thrombocytopenia (32.8%), with worst prognosis. Immunological and proteomic analyses clearly differentiated three clusters. This study reveals a distinct difference between obstetric and thrombotic APS, and a sex-based distinction within thrombotic APS. Three APS subgroups display unique clinical and molecular characteristics, and marked difference in prognostic outcomes.

Neutrophils in Type 1 Diabetes: Untangling the Intricate Web of Pathways and Hypothesis

Neutrophils are increasingly recognized as key contributors to the pathogenesis of Type 1 Diabetes (T1D), yet their precise mechanistic role in disease onset and progression remains incompletely understood. While these innate immune cells reside in pancreatic tissue and support tissue homeostasis under physiological conditions, they can also drive tissue damage by triggering innate immune responses and modulating inflammation. Within the inflammatory milieu, neutrophils establish complex, bidirectional interactions with various immune cells, including macrophages, dendritic cells, natural killer cells, and lymphocytes. Once activated, they may enhance the innate immune response through direct or indirect crosstalk with immune cells, antigen presentation, and β-cell destruction or dysfunction. These mechanisms underscore the multifaceted and dynamic role of neutrophils in T1D, shaped by their intricate immunological interactions. Further research into the diverse functional capabilities of neutrophils is crucial for uncovering novel aspects of their involvement in T1D, potentially revealing new therapeutic targets to modulate disease progression.

Neutrophils: a Central Point of Interaction Between Immune Cells and Nonimmune Cells in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease involving activation of the immune system and the infiltration of immune cells. As the first immune cells to reach the site of inflammation, neutrophils perform their biological functions by releasing many active substances and forming neutrophil extracellular traps (NETs). The overactivated neutrophils in patients with RA not only directly damage tissues but also, more importantly, interact with various other immune cells and broadly activate innate and adaptive immunity, leading to irreversible joint damage. However, owing to the pivotal role and complex influence of neutrophils in maintaining homoeostasis, the treatment of RA by targeting neutrophils is very difficult. Therefore, a comprehensive understanding of the interaction pathways between neutrophils and various other immune cells is crucial for the development of neutrophils as a new therapeutic target for RA. In this study, the important role of neutrophils in the pathogenesis of RA through their crosstalk with various other immune cells and nonimmune cells is highlighted. The potential of epigenetic modification of neutrophils for exploring the pathogenesis of RA and developing therapeutic approaches is also discussed. In addition, several models for studying cell‒cell interactions are summarized to support further studies of neutrophils in the context of RA.

Human induced pluripotent stem cells derived neutrophils display strong anti-microbial potencies

Neutrophils are essential innate immune cells with unusual anti-microbial properties while dysfunctions of neutrophils lead to severe health problems such as lethal infections. Generation of neutrophils from human induced pluripotent stem cells (hiPSCs) is highly promising to produce off-the-shelf neutrophils for transfusion therapies. However, the anti-microbial potencies of hiPSCs derived neutrophils (iNEUs) remain less documented. Here, we develop a scalable approach to generate iNEUs in a chemical defined condition. iNEUs display typical neutrophil characters in terms of phagocytosis, migration, formation of neutrophil extracellular traps (NETs), etc. Importantly, iNEUs display a strong killing potency against various bacteria such as K.pneumoniae, P.aeruginosa, E.coli and S.aureus. Moreover, transfusions of iNEUs in mice with neutrophil dysfunction largely enhance their survival in lethal infection of different bacteria. Together, our data show that hiPSCs derived neutrophils hold strong anti-microbial potencies to protect severe infections under neutrophil dysfunction conditions.

Peripheral immune profiling highlights a dynamic role of low-density granulocytes in myasthenia gravis

BACKGROUND

Myasthenia gravis (MG) is an autoimmune neuromuscular disease marked by dysregulation of several immune cell populations. Here we explored peripheral immune landscape, particularly the role of low-density granulocytes (LDGs).

METHODS

Single-cell and bulk RNA sequencing analyzed peripheral immune cells from MG patients pre- (n = 4) and after treatment (n = 2), as well as healthy controls (n = 3). Flow cytometry was employed for validating LDG subsets, and various functional assays were conducted to assess their impact on T cell proliferation and differentiation, NET formation, and ROS production.

RESULTS

Single-cell analysis highlighted a shift towards inflammatory Th1/Th17/Tfh subsets, an intense interferon-mediated immune response, and an expansion of immature myeloid subsets in MG. Flow cytometry showed increased LDGs correlated with disease severity. Unlike myeloid-derived suppressor cells, MG LDGs do not restrict T cell proliferation but induce a pro-inflammatory Th1/Th17 response. They also display enhanced spontaneous neutrophil extracellular traps (NETs) formation and basal reactive oxygen species (ROS) production. LDGs decreased after intravenous immunoglobulin and increased after prolonged immunotherapy in minimal manifestation status (MM), with reduced pro-inflammatory activity. Bulk RNA sequencing revealed significant transcriptional differences in LDGs, especially in cell cycle and granule protein genes.

CONCLUSION

Peripheral immune profiling sheds light on the intricate role of LDGs in MG. These cells, as a distinct subtype of neutrophils with a proinflammatory phenotype, are notable increased in MG, exacerbating chronic inflammation. Furthermore, immunotherapy expanded LDGs but reduced their proinflammatory capacities. The complex interplay of LDGs in MG underscores their potential as biomarkers and therapeutic targets.

Chronic Inflammation in Asthma: Looking Beyond the Th2 Cell

Asthma is a common chronic inflammatory disease of the airways. A substantial number of patients present with severe and therapy-resistant asthma, for which the underlying biological mechanisms remain poorly understood. In most asthma patients, airway inflammation is characterized by chronic activation of type 2 immunity. CD4+ T helper 2 (Th2) cells are the canonical producers of the cytokines that fuel type 2 inflammation: interleukin (IL)-4, IL-5, IL-9, and IL-13. However, more recent findings have shown that other lymphocyte subsets, in particular group 2 innate lymphoid cells (ILC2s) and type 2 CD8+ cytotoxic T (Tc2) cells, can also produce large amounts of type 2 cytokines. Importantly, a substantial number of severe therapy-resistant asthma patients present with chronic type 2 inflammation, despite the high sensitivity of Th2 cells for suppression by corticosteroids-the mainstay drugs for asthma. Emerging evidence indicates that ILC2s and Tc2 cells are more abundant in severe asthma patients and can adopt corticosteroid-resistance states. Moreover, many severe asthma patients do not present with overt type 2 airway inflammation, implicating non-type 2 immunity as a driver of disease. In this review, we will discuss asthma pathophysiology and focus on the roles played by ILC2s, Tc2 cells, and non-type 2 lymphocytes, placing special emphasis on severe disease forms.

New insights into the endotypes of chronic rhinosinusitis in the biologic era

Chronic rhinosinusitis (CRS) exhibits significant heterogeneity and has been generally classified as type 1 (T1), T2, and T3 endotypes according to the histopathologic and inflammatory features of the nasal mucosa. T2 inflammation has been regarded as the predominant endotype of CRS linked to disease severity and refractory conditions. The development of biological agents that specifically target key molecules involved in T2 inflammation offers a highly effective and promising therapeutic approach for CRS. Recent findings have expanded the understanding of CRS endotypes by incorporating a range of disease-related molecules for classification, with progress made on the endotyping of CRS without nasal polyps. In addition, there has been an increasing emphasis on the study of mixed inflammatory endotypes. This review examines recent findings on CRS endotyping and the related noninvasive biomarkers, as well as novel mechanisms governing endotype formation, and addresses the efficacy of biologics in targeting T2 inflammation. Further research is warranted to understand if newly identified CRS endotypes show clinical significance for precision medicine and the management and treatment of refractory CRS in the era of biologics.

Alterations in neutrophil mRNA profiles in multiple sclerosis and identification of candidate genes for further investigation

Introduction

Multiple sclerosis (MS) is a chronic and debilitating inflammatory disease of the central nervous system (CNS), characterized by demyelination and neurodegeneration. Emerging evidence implicates neutrophils in MS pathogenesis, particularly through processes like neutrophil extracellular traps (NETs) formation and degranulation, which may exacerbate inflammation and autoimmunity.

Methods

RNA sequencing of peripheral blood neutrophils from MS patients and healthy controls identified differentially expressed genes (DEGs). Pathway enrichment and protein-protein interaction (PPI) analyses highlighted potential biomarkers, validated using reverse transcription quantitative PCR (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA).

Results

Our analysis identified 1,968 DEGs in neutrophils from MS patients, comprising 1,068 upregulated and 900 downregulated genes. Pathway enrichment analysis revealed significant involvement of immune processes, including antigen presentation, B and T cell receptor signaling, intracellular signaling cascades, and neutrophil degranulation. Notably, KEGG analysis highlighted a pivotal role for upregulated genes in neutrophil extracellular traps (NETs) formation, a process increasingly associated with autoimmunity. PPI network analysis pinpointed five key hub genes-LCN2, LTF, ELANE, CAMP, and CTSG-as central players in neutrophil-mediated immune modulation. Protein-level validation using ELISA confirmed elevated levels of LCN2, ELANE, CAMP, and CTSG, consistent with transcriptomic findings, further supporting their role as biomarkers. Subsequent RT-qPCR validation demonstrated robust diagnostic potential for these genes, with area under the curve (AUC) values of 0.952 (LCN2), 0.827 (LTF), 0.968 (ELANE), 0.950 (CAMP), and 0.862 (CTSG).

Discussion

These findings uncover a previously underappreciated role for neutrophils in MS pathogenesis, driven by alterations in gene expression linked to immune modulation and NET formation. The identified biomarkers, particularly ELANE and LCN2, demonstrate strong diagnostic potential, offering a new avenue for non-invasive MS diagnostics. Beyond clinical utility, this study highlights the importance of neutrophil-driven immune responses in MS, providing mechanistic insights into the complex interplay between innate and adaptive immunity in demyelinating diseases. Furthermore, these findings suggest that targeting neutrophil-specific processes, such as NETs formation and degranulation, could mitigate inflammatory damage and provide novel therapeutic approaches for MS treatment. These results lay the groundwork for future studies exploring therapeutic strategies targeting neutrophil functions in MS.

Effects of neutrophil granule proteins on sepsis-associated lymphopenia and their relationship with CD4+ T-cell pyroptosis

Background

Neutrophil acts as a double-edged sword in the immune system. We hypothesized that an elevated neutrophil granule protein level is associated with sepsis-associated lymphopenia (SAL).

Methods

We enrolled 61 patients with sepsis admitted to the Department of Critical Care Medicine of Peking Union Medical College Hospital between May 2022 and October 2023 in this study. Clinical and immunological parameters were recorded. Levels of neutrophil granule proteins, including myeloperoxidase (MPO) and neutrophil elastase (NE), and pyroptosis factors were examined.

Results

Levels of neutrophil granule proteins (MPO, 82.9 vs. 175.3, p < 0 <.0001; NE, 56.3 vs. 144.2, p < 0.0001) were significantly higher in patients with sepsis with lymphopenia. Neutrophil granule protein levels were independently associated with SAL risk (MPO: OR = 1.0841, 95% CI, 1.0020-1.1730; NE: OR = 1.0540, 95% CI, 1.0040-1.1065). The area under the curve of MPO levels predicting SAL occurrence was 0.939 (95% CI, 0.846-0.984), and that of NE was 0.950 (95% CI, 0.862-0.989). Furthermore, neutrophil granule proteins were significantly correlated with CD4+ T cell and its pyroptosis [MPO and CD4+ T cells (r = -0.4039, p < 0.0001), CD4+NLRP3 (r = 0.4868, p < 0.0001), NE and CD4+ T cells (r = -0.5140, p < 0.0001), and CD4+NLRP3 (r = 0.6513, p < 0.0001)].

Conclusion

Increased levels of neutrophil granule proteins were significantly associated with SAL incidence, and a significant relationship between neutrophil granule proteins and the pyroptosis pathway of CD4+ T cells was revealed.

Clinical trial registration

chictr.org.cn identifier ChiCTR-ROC-17010750.

Fibrin aggravates periodontitis through inducing NETs formation from mitochondrial DNA

OBJECTIVES

This study investigated the role of fibrin on neutrophil extracellular traps (NETs) formation from neutrophils and to elucidate the involvement of mitochondria in NETs formation during periodontitis.

MATERIALS AND METHODS

Plasminogen-deficient (Plg-/-) mice were employed to evaluate the effects of fibrin deposition on inflammation, bone resorption, and neutrophil infiltration in periodontal tissues. In addition, in vitro tests evaluated fibrin's impact on neutrophil-driven inflammation. Mitochondrial reactive oxygen species (mtROS) levels within neutrophils were quantified utilizing flow cytometry and immunofluorescence in vitro. Furthermore, the anti-inflammatory properties of the mtROS scavenger, Mito-TEMPO, were confirmed to regulate the NET formation in vitro and in vivo.

RESULTS

Plasminogen deficiency resulted in increased fibrin deposition, neutrophil infiltration, inflammatory factors concentration, and alveolar bone resorption in periodontal tissues. After neutrophils were treated by fibrin in vitro, the expression of inflammatory factors, the formation of mtROS, and NETs enriched in mitochondrial DNA (mtDNA) were upregulated, which were reversed by Mito-TEMPO in vitro. Moreover, Mito-TEMPO alleviated inflammation in Plg-/- mice.

CONCLUSIONS

This study showed that fibrin deposition in gingiva induced the NET formation in Plg-/- mice, in which the DNA in NETs was from mitochondria depending on increasing mtROS.

Neutrophils, NETs and multiple sclerosis: a mini review

Multiple sclerosis (MS), a chronic inflammatory and degenerative autoimmune disease characterized by the activation of various inflammatory cells, leads to demyelination and neuronal injury. Neutrophils, often underestimated in MS, are gaining increased attention for their significant functions in MS patients and the experimental autoimmune encephalomyelitis (EAE) animal model. Neutrophils play multiple roles in mediating the pathogenesis of autoimmune diseases, and numerous studies suggest that neutrophils might have a crucial role through neutrophil extracellular trap (NET) formation. Studies on NETs in MS are still in their infancy. In this review, we discuss the clinical perspective on the linkage between neutrophils and MS or EAE, as well as the role of NETs in the pathogenesis of MS/EAE. Further, we analyze the potential mechanisms by which NETs contribute to MS, the protective effects of NETs in MS, and their value as targets for disease intervention. NET formation and/or clearance as a therapeutic approach for MS still requires research in greater depth.

[Research Progress of Tumor-associated Neutrophils in the Occurrence and Development of Lung Cancer]

Lung cancer is the malignant tumor with the highest mortality rate worldwide. The tumor microenvironment (TME) is a key factor in the progression of lung cancer, composed of tumor cells, signaling molecules, fibroblasts, immune cells, etc. Among them, tumor associated neutrophil (TAN), as an important component of immune cells in the TME, plays multiple roles in tumor cell proliferation, invasion, angiogenesis, and metastasis due to its aberrant function, and is closely associated with poor prognosis. However, there are limited researches on the mechanism of TAN in lung cancer. This review aims to provide more scientific basis for studying the therapeutic targets of lung cancer and developing new drugs by elucidating the different subtypes of TAN and their mechanisms of action in the occurrence and development of lung cancer.
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The Role of the Immune Response to Helicobacter pylori Antigens and Its Relevance in Gastric Disorders

Helicobacter pylori (H.p.) is a Gram-negative bacterium endowed with gastric tropism. H.p. infection is widely spread throughout the world, accounting for various pathologies, such as peptic ulcer, gastric cancer, mucosa-associated lymphoid tissue lymphoma, and extra-gastric manifestations. This bacterium possesses several virulence factors, e.g., lipopolysaccharides (LPS), the toxins CagA and VacA, and adhesins, which elicit a robust immune response during the initial phase of the infection. Of note, the lipid A moiety of the LPS exhibits a lower endotoxic potency than that of other LPSs, thus facilitating infection through a mechanism of immune escape. H.p. colonization of the gastric mucosa induces an initial protective immune response with innate immune cells, e.g., neutrophils, monocytes, and macrophages, which engulf and kill bacteria. Moreover, the same cells, along with gastric epithelial cells, secrete cytokines and chemokines, which recruit T cells [T helper (h)1 and Th17 cells] to the site of infection, thus leading to H.p. eradication. In a large subset of individuals, the perturbation of such an immune equilibrium leads to a harmful response, with an expansion of T regulatory (TREG) cells, which suppress the protective immune response. In fact, TREG cells, via the production of interleukin (IL)-10, downregulate Th1- and Th17-related cytokines, thus allowing H.p. survival and the perpetuation of inflammation. As far as the humoral immune response is concerned, B cells, upon H.p. stimulation, produce autoreactive antibodies, and IgG anti-Lex antibodies are harmful to the gastric mucosa. In this review, the structure and function of H.p. antigenic components and immune mechanisms elicited by this bacterium will be described in relation to gastric damage.

Dengue virus infection: how platelet-leukocyte crosstalk shapes thrombotic events and inflammation

Dengue virus (DENV) poses a considerable threat to public health on a global scale, since about two-thirds of the world's population is currently at risk of contracting this arbovirus. Being transmitted by mosquitoes, this virus is associated with a range of illnesses and a small percentage of infected individuals might suffer from severe vascular leakage. This leakage leads to hypovolemic shock syndrome, generally known as dengue shock syndrome, organ failure, and bleeding complications. The severe form of this disease is believed to be, at least partially, associated with inflammatory and thrombotic states. These issues are significantly affected by the activation of platelets and leukocytes, as well as their interactions, which may influence its prognosis. The platelets present in a thrombus are able to attract leukocytes to the site of injury. The intricate process leads to the significant accumulation, activation, and migration of leukocytes, thereby promoting thrombotic events and triggering inflammatory responses. The occurrence of these events, combined with the direct viral infection of endothelial cells, leads to vascular endothelialitis, the disruption of cellular membranes, and the subsequent release of DAMPs. As a result, considerable damage occurs in the endothelium, which activates neutrophils and platelets; thisleads to their interaction and initiates the process of Netosis. Collectively, these processes exacerbate inflammatory and thrombotic conditions. In this respect, current research has focused on understanding whether effective anti-inflammatory protocols can prevent thrombotic events or, conversely, if efficient anticoagulant regimens may lead to a reduction in cytokine storms and tissue damage. This review article aims to illuminate the platelet leukocyte crosstalk, detailing the mechanisms through which platelets may play a role in the pathogenesis of DENV. The research outputs are particularly important in severe cases, in which case their interactions with leukocytes can exacerbate both inflammation and thrombosis in a mutually reinforcing manner.

Neutrophil extracellular traps promote pre-metastatic niche formation in the omentum by expanding innate-like B cells that express IL-10

Disseminated cancer cells in the peritoneal fluid often colonize omental fat-associated lymphoid clusters but the mechanisms are unclear. Here, we identify that innate-like B cells accumulate in the omentum of mice and women with early-stage ovarian cancer concomitantly with the extrusion of chromatin fibers by neutrophils called neutrophil extracellular traps (NETs). Studies using genetically modified NET-deficient mice, pharmacologic inhibition of NETs, and adoptive B cell transfer show that NETs induce expression of the chemoattractant CXCL13 in the pre-metastatic omentum, stimulating recruitment of peritoneal innate-like B cells that in turn promote expansion of regulatory T cells and omental metastasis through producing interleukin (IL)-10. Ex vivo studies show that NETs elicit IL-10 production in innate-like B cells by inactivating SHP-1, a phosphatase that inhibits B cell activation pathways, and by generating reactive oxygen species. These findings reveal that NETs alter immune cell dynamics in the pre-metastatic omentum, rendering this niche conducive for colonization.

The Impact of Peptidyl Arginine Deiminase 4-Dependent Neutrophil Extracellular Trap Formation on the Early Development of Intestinal Fibrosis in Crohn's Disease

BACKGROUND AND AIMS

During early phases of inflammation, activated neutrophils extrude neutrophil extracellular traps (NETs) in a peptidyl arginine deiminase 4 (PAD4)-dependent manner, aggravating tissue injury and remodeling. In this study, we investigated the potential pro-fibrotic properties and signaling of NETs in Crohn's disease (CD).

METHODS

NETs and activated fibroblasts were labeled on resected ileum from CD patients by multiplex immunofluorescence staining. NETs-treated human primary intestinal fibroblasts were analyzed by bulk RNA sequencing to uncover cell signaling pathways, and by high-throughput imaging to assess collagen production and migratory activity. Consequentially, TLR2/NF-κB pathway was evaluated by transfection of CCD-18Co fibroblasts with an NF-κB-luciferase reporter plasmid, incorporating C29 to block TLR2 signaling. A chronic dextran sulfate sodium (DSS) mouse model was used to define the specific role of PAD4 deletion in neutrophils (MRP8-Cre, Pad4fl/fl).

RESULTS

Immunofluorescence showed spatial colocalization of NETs and activated fibroblasts in ileal ulcerations of CD patients. Transcriptomic analysis revealed upregulation of pro-fibrotic genes and activation of Toll-like receptor signaling pathways in NETs-treated fibroblasts. NETs treatment induced fibroblast proliferation, diminished migratory capability, and increased collagen release. Transfection experiments indicated a substantial increase in an NF-κB expression with NETs, whereas C29 led to decreased expression and release of collagen. In line, a significant reduction in collagen content was observed in the colon of MRP8-Cre, Pad4fl/fl mice subjected to chronic DSS colitis.

CONCLUSIONS

NETs potentially serve as an initial stimulus for pathological activation of fibroblasts within the intestine via the TLR2/NF-κB pathway. Given their early involvement in inflammation, inhibition of PAD4 might offer a strategy to modulate both inflammation and fibrogenesis in CD.

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.

Neutrophil Extracellular Traps Participate in the Pathogenesis of Lupus Through S100A10-Mediated Regulatory T-Cell Differentiation and Functional Abnormalities

In systemic lupus erythematosus (SLE), neutrophil dysregulation and neutrophil extracellular traps (NETs) formation contribute to disease pathogenesis, potentially worsening the autoimmune response. Although research indicates NETs' involvement in various autoimmune conditions, their relationship with regulatory T cells (Tregs) in SLE remains elusive. In this study, in vivo experiments were involved in administering NET injections to C57BL/6 and MRL/Ipr mice. In vitro, a co-culture system facilitated interaction between Tregs and NETs. Proteomic analysis elucidated NET composition, while RNA sequencing delineated their impact on Treg differentiation. We demonstrated that increased NET levels correlate inversely with Treg abundance in SLE patients, influencing both their proportion and functionality. NET administration reduced Treg levels and induced lupus-like symptoms in C57BL/6 mice, exacerbating symptoms in MRL/Ipr mice. DNase I treatment mitigated NET effects, restoring Treg levels and alleviating symptoms. RNA sequencing revealed altered gene expression in naïve CD4+ T cells exposed to NETs. Additionally, proteomic analysis showed S100A10 protein changes between SLE patients and healthy controls, hindering Treg differentiation. NETs influence TLR-4 of naïve CD4+ T cells via S100A10, thereby modulating Treg proportion and functionality. These findings highlight the critical role of NETs in Treg differentiation in SLE, suggesting that targeting NETs may provide a novel therapeutic approach.

NET formation-mediated in situ protein delivery to the inflamed central nervous system

Delivering protein drugs to the central nervous system (CNS) is challenging due to the blood-brain and blood-spinal cord barrier. Here we show that neutrophils, which naturally migrate through these barriers to inflamed CNS sites and release neutrophil extracellular traps (NETs), can be leveraged for therapeutic delivery. Tannic acid nanoparticles tethered with anti-Ly6G antibody and interferon-β (aLy6G-IFNβ@TLP) are constructed for targeted neutrophil delivery. These nanoparticles protect interferon-β from reactive oxygen species and preferentially accumulate in neutrophils over other immune cells. Upon encountering inflammation, neutrophils release the nanoparticles during NET formation. In the female mouse model of experimental autoimmune encephalomyelitis, intravenous administration of aLy6G-IFNβ@TLP reduce disease progression and restore motor function. Although this study focuses on IFNβ and autoimmune encephalomyelitis, the concept of hitchhiking neutrophils for CNS delivery and employing NET formation for inflamed site-specific nanoparticle release can be further applied for delivery of other protein drugs in the treatment of neurodegenerative diseases.

Fantastic proteins and where to find them - histones, in the nucleus and beyond

Animal genomes are packaged into chromatin, a highly dynamic macromolecular structure of DNA and histone proteins organised into nucleosomes. This accommodates packaging of lengthy genomic sequences within the physical confines of the nucleus while also enabling precise regulation of access to genetic information. However, histones existed before chromatin and have lesser-known functions beyond genome regulation. Most notably, histones are potent antimicrobial agents, and the release of chromatin to the extracellular space is a defence mechanism nearly as ancient and widespread as chromatin itself. Histone sequences have changed very little throughout evolution, suggesting the possibility that some of their 'non-canonical' functions are at play in parallel or in concert with their genome regulatory functions. In this Review, we take an evolutionary perspective of histone, nuclear chromatin and extracellular chromatin biology and describe the known extranuclear and extracellular functions of histones. We detail molecular mechanisms of chromatin release and extracellular chromatin sensing, and we discuss their roles in physiology and disease. Finally, we present evidence and give a perspective on the potential of extracellular histones to act as bioactive, cell modulatory factors.

The role of neutrophils in ANCA-associated vasculitis

Anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV) is a group of rare systemic autoimmune diseases characterised by necrotising inflammation of small blood vessels and usually associated with circulating ANCA. The pathophysiology of AAV is complex, involving many aspects of the innate and adaptive immune system. Neutrophils are central to the pathogenesis of AAV as they are both the target of the autoantibody and effector cells mediating vascular injury. We describe mechanisms for ANCA induced activation of neutrophils, the pathogenic mechanisms by which this leads to endothelial cell injury, and how neutrophil crosstalk modulates other aspects of the immune system in AAV.

Transcriptome analysis revealed that ischemic post-conditioning suppressed the expression of inflammatory genes in lung ischemia-reperfusion injury

Introduction

Ischemic post-conditioning (I-post C) is a recognized therapeutic strategy for lung ischemia/reperfusion injury (LIRI). However, the specific mechanisms underlying the lung protection conferred by I-post C remain unclear. This study aimed to investigate the protective mechanisms and potential molecular regulatory networks of I-post C on lung tissue.

Methods

Transcriptome analysis was performed on rat lung tissues obtained from Sham, ischemia-reperfusion (IR), and I-post C groups using RNA-seq to identify differentially expressed genes (DEGs). Subsequently, gene ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, and gene set enrichment analysis (GSEA) were conducted to elucidate significantly enriched pathways in the IR and I-post C groups. Additionally, protein-protein interaction (PPI) network analysis was carried out to examine associations among the DEGs. Pathological changes in lung tissues were assessed using hematoxylin-eosin (H&E) staining. The expression levels of CXCL1 and CXCL6 in the IR and I-post C groups were evaluated through immunofluorescence and Western blotting.

Results

Our results showed that I-post C significantly attenuated both pulmonary edema and inflammatory cell infiltration. Transcriptome analysis identified 38 DEGs in the I-post C group compared to the IR group, comprising 21 upregulated and 17 downregulated genes. Among these, seven inflammation-related DEGs exhibited co-expression patterns with the Sham and IR groups, with notable downregulation of Cxcl1 and Cxcl6. GO analysis primarily linked these DEGs to neutrophil activation, chemotaxis, cytokine activity, and CCR chemokine receptor binding. KEGG analysis revealed enriched pathways, including the IL-17, TNF, and NF-κB signaling pathways. GSEA indicated downregulation of neutrophil chemotaxis and the IL-17 signaling pathway, correlating with reduced expression of Cxcl1 and Cxcl6. Validation of Cxcl1 and Cxcl6 mRNA expression via immunofluorescence and Western blotting supported the RNA-seq findings. Furthermore, a PPI network was constructed to elucidate interactions among the 29 DEGs.

Conclusions

Through RNA-Seq analysis, we concluded that I-post C may reduce inflammation and suppress the IL-17 signaling pathway, thereby protecting against lung damage caused by LIRI, potentially involving neutrophil extracellular traps.

Single-cell and bulk RNA sequencing-based screening and identification of extracellular trap network-related genes in neutrophils in acute myocardial infarction

BACKGROUND

The neutrophil-mediated generation of neutrophil extracellular traps (NETs) results in an augmented inflammatory response and cellular tissue injury during acute myocardial infarction (AMI). Through the analysis of public database information, we discovered and confirmed putative critical genes involved in NETs-mediated AMI.

METHODS

The AMI dataset GSE66360 and the single-cell dataset GSE163465 were downloaded from the Gene Expression Omnibus database. Key genes were screened by bioinformatics. Quantitative real-time PCR (qRT-PCR) was used to verify the key genes, and then a Mendelian randomization (MR) study was conducted on the basis of the genome-wide association study to determine the causal relationship between key genes and AMI. Dimensionality reduction clustering, pseudo-time series, and cell communication were performed on the single-cell dataset to analyze the key genes screened by bulk RNA sequencing and the dynamic evolution of NETs in the AMI process. Immunohistochemistry and Western blot were used to verify the key genes.

RESULTS

Six key genes, IL1β, S100A12, TLR2, CXCL1, CXCL2, and CCL4, were screened out through bioinformatics. qRT-PCR results showed that compared with the control group, the expression of 5 key genes was upregulated in the AMI group. In the MR study, CXCL1 and CCL4 were observed to have a causal relationship with AMI. Single-cell analysis showed that NETs-related genes CCL4, CXCL2, and IL1β were highly expressed. Combining single cells, qRT-PCR and MR, gene CCL4 was selected as the focus of the study. H9c2 cardiomyocytes simulated myocardial infarction under hypoxia, and the results showed that the expression of gene CCL4 was increased. The immunohistochemical results of gene CCL4 showed that the expression was upregulated in the AMI group.

CONCLUSIONS

We found 6 key genes related to NETs-mediated cell damage during AMI. The results of MR showed that CXCL1 and CCL4 were causally related to AMI. Combining single cells, qRT-PCR and MR, gene CCL4 may play an important role in the AMI process. Our results may provide some insights into neutrophil-mediated cell damage during AMI.

Focusing on non-responders to infliximab with ulcerative colitis, what can we do first and next?

BACKGROUND

Ulcerative colitis (UC) is a chronic immune-mediated inflammation of the colorectum, for which infliximab (IFX) is currently the mainstay of treatment. However, one-third of patients with UC still fail to benefit from the IFX therapy, and early exposure to IFX impairs the efficacy of other subsequent biologics. Therefore, personalized therapeutic system is urgently needed to assist in clinical decision-making and precision treatment.

METHODS

Four microarray datasets of colonic biopsies from UC patients treated with IFX were obtained from the GEO database to form the Training Cohort and Validation Cohort. Differentially expressed genes (DEGs) in Training Cohort were identified and enriched for GO, KEGG and immune cell infiltration analysis. A prediction model for IFX efficacy was developed based on the LASSO and Logistic regression. The predictive accuracy of the model was verified by the Validation Cohort, and the model-genes/proteins were validated by immunohistochemistry. Gene-drug, gene-ncRNA interaction analysis were performed to identify drugs or non-coding RNAs (ncRNAs) that potentially interacted with the model-genes. Homology Modeling and Molecular Docking were conducted to filter the optimal candidate as the subsequent adjuvant or alternative for IFX in predicted non-responders. At last, the down-regulation of the key model-gene/protein CYP24A1 by the drug candidate Deferasirox was verified by Western Blot and qRT-PCR Assay based on cellular experiments.

RESULTS

A total of 113 DEGs were identified in the Training Cohort, mainly enriched in inflammatory cell chemotaxis, migration, and response to molecules derived from intestinal microbiota. Activated pro-inflammatory innate immune cells, including neutrophils, M1 macrophages, activated dendritic cells and mast cells, were significantly enriched in colons of non-responders. The prediction model based on three model-genes (IFI44L, CYP24A1, and RGS1) exhibited strong predictive efficacy, with AUC values of 0.901 and 0.80 in the Training and Validation Cohorts, respectively. Higher expression of the three model-genes/proteins in colons of non-responders to IFX was confirmed by clinical colonic mucosal biopsies. 4 Drugs (Calcitriol, Lunacalcipol, Deferasirox, Telaprevir), 15 miRNAs and 66 corresponding lnRNAs interacting with model-genes were identified. The protein 3D structure of the key model-gene/protein (human-derived CYP24A1) was developed. Through the Molecular Docking and cellular experimental validation, Deferasirox, which significantly down-regulated both the RNA and protein expression of CYP24A1, was identified as the optimal adjuvant or alternative for IFX in predicted non-responders with UC.

CONCLUSION

This study developed a novel prediction model for pre-assessing the efficacy of IFX in patients with UC, as the first step towards personalized therapy. Meanwhile, drugs and non-coding RNAs were provided as potential candidates to develop the next-step precise treatment for the predicted non-responders. In particular, Defeasirox appears to hold promise as an adjuvant or alternative to IFX for the optimization of UC therapy.

Neutrophil extracellular traps promote M1 macrophage polarization in gouty inflammation via targeting hexokinase-2

Peptidylarginine deiminase 4 (PAD4)-dependent neutrophil extracellular trap (NET) formation is a new neutrophil death mechanism. Increased NET formation has been demonstrated to be associated with gouty inflammation. Macrophages release proinflammatory mediators and chemokines in acute gouty inflammation and subsequently lead to inflammatory cascades. However, whether NETs regulate macrophage function and polarization and further contribute to gout development remains unclear. Herein, we investigated the relationship between monosodium urate (MSU) crystal-induced NETs and macrophages and the associated mechanisms in gouty inflammation. Elevated NET formation and CD86+ macrophage infiltration were observed in human gouty arthritis (GA). In vitro, MSU crystal-induced NETs or NET-associated histone H3 treatments modulated nod-like receptor protein 3 (NLRP3) inflammasome activation, M1 polarization, and metabolic changes in macrophages. These effects were eliminated by hexokinase-2 (HK-2) silencing. Moreover, NET formation and inflammation were significantly reduced in PAD4-/- GA mice. Pharmacological inhibition of NET formation with Cl-Amidine or NET degradation with DNase Ⅰ significantly reduced M1 polarization of macrophages and ameliorated inflammation in GA mice. In sum, MSU crystal-induced NETs promote M1 polarization and NLRP3 activation in macrophages via targeting HK-2. Cell-free DNA and histone H3 may be the driving elements behind the NET-induced M1 macrophage polarization, NLRP3 activation, and metabolic changes. Targeting NETs could be a potential therapeutic strategy for gout flare.

Identification of neutrophil extracellular traps genes as potential biomarkers in psoriasis based on bioinformatics analysis

The epidermal infiltration of neutrophils is a hallmark of psoriasis (PSO) and its activation leads to the release of neutrophil extracellular traps (NETs). However, the molecular mechanism of NETs-related genes (NETRGs) has not been extensively studied in PSO. To define NETs-related-biomarkers for PSO. The GSE13355 and GSE78097 datasets, and NETRGs gene set were included in this study. The datasets used in this study were all microarray data. The weighted gene co-expression network analysis (WGCNA) and machine learning algorithms were used to mine key genes. Later on, single-gene gene set enrichment analysis (GSEA) and immune infiltration analysis were implemented. Finally, the expression of key genes was verified using quantitative real-time fluorescence PCR (qRT-PCR). A total of 3 key genes (S100A9, CLEC7A, and CXCR4) were derived, and they all had excellent diagnostic performance. The single-gene GSEA enrichment results indicated that the key genes were mainly enriched in the chemokine signaling pathway and humoral immune response in the high-expression group, while focal adhesion was enriched in the low-expression group. The correlation analysis indicated that all key genes were strongly negatively correlated with resting mast cells and TGF-β family member receptor, while they were strongly positively correlated with activated CD4 memory T cells and antigen processing and presentation. Lastly, the experimental results showed that the expression trends of key genes were consistent with public database. In this study, we successfully screened three potential PSO diagnostic genes (S100A9, CLEC7A and CXCR4) that were closely related to NETs, and these findings not only provided new molecular marker candidates for the precise diagnosis of PSO patients, but also revealed possible future therapeutic targets. However, further in-depth research and validation were necessary.

The pivotal role of neutrophil extracellular traps in cardiovascular diseases: Mechanisms and therapeutic implications

Cardiovascular diseases (CVDs) continue to pose a significant burden on global health, prominently contributing to morbidity and mortality rates worldwide. Recent years have witnessed an increasing recognition of the intricate involvement of neutrophil extracellular traps (NETs) in the pathology of diverse cardiovascular conditions. This review provides a comprehensive analysis of the multifaceted functions of NETs in cardiovascular diseases, shedding light on the impact on atherosclerosis, myocardial infarction, heart failure, myocarditis, atrial fibrillation, aortic stenosis, and the potential therapeutic avenues targeting NETs.

Neutrophil extracellular traps in homeostasis and disease

Neutrophil extracellular traps (NETs), crucial in immune defense mechanisms, are renowned for their propensity to expel decondensed chromatin embedded with inflammatory proteins. Our comprehension of NETs in pathogen clearance, immune regulation and disease pathogenesis, has grown significantly in recent years. NETs are not only pivotal in the context of infections but also exhibit significant involvement in sterile inflammation. Evidence suggests that excessive accumulation of NETs can result in vessel occlusion, tissue damage, and prolonged inflammatory responses, thereby contributing to the progression and exacerbation of various pathological states. Nevertheless, NETs exhibit dual functionalities in certain pathological contexts. While NETs may act as autoantigens, aggregated NET complexes can function as inflammatory mediators by degrading proinflammatory cytokines and chemokines. The delineation of molecules and signaling pathways governing NET formation aids in refining our appreciation of NETs' role in immune homeostasis, inflammation, autoimmune diseases, metabolic dysregulation, and cancer. In this comprehensive review, we delve into the multifaceted roles of NETs in both homeostasis and disease, whilst discussing their potential as therapeutic targets. Our aim is to enhance the understanding of the intricate functions of NETs across the spectrum from physiology to pathology.

CXCR1 and CXCR2 are potential neutrophil extracellular trap-related treatment targets in ulcerative colitis: insights from Mendelian randomization, colocalization and transcriptomic analysis

Objectives

There is already substantial evidence indicating that neutrophil extracellular trap (NET) formation contributes to the inflammatory cascade in ulcerative colitis (UC). However, the precise regulatory mechanisms governing this process remain elusive. This study aimed to determine the role of NET-related genes in UC and reveal possible mechanisms.

Methods

Employing a two-sample MR methodology, we investigated the correlations between NET-associated genes (NRGs) and UC with summary data derived from a genome-wide association study (12,366 cases vs. 33,609 controls) and FinnGen (8,279 cases vs. 261,098 controls). The main analysis employed the inverse variance weighted method, supplemented by the MR-Egger method and weighted median method. Sensitivity analysis was conducted to rule out the interference of heterogeneity and pleiotropy among utilized instrument variables. The colocalization analysis was used to determine whether the identified NRGs and UC shared casual variants. Cross-tissue expression analysis was performed to characterize the expression patterns of target NRGs, while multi-gene correlation analysis and GSEA analysis were conducted to explore the mechanisms by which target NRGs promote UC and NET formation. Immunohistochemistry was used to validate the protein expression of target NRGs in the colon tissue of UC patients.

Results

After the validation of two datasets, seven NRGs were associated with the risk of UC. The higher expression of ITGB2 was associated with increased UC risk, while the expression of CXCR1, CXCR2, IRAK4, MAPK3, SIGLEC14, and SLC22A4 were inversely associated with UC risk. Colocalization analysis supported the correlation between CXCR1/2 and UC risk. Expression analysis indicated that CXCR1/2 were down-regulated in peripheral blood, but up-regulated in colon tissue. GSEA analysis and correlation analysis indicated that CXCR1/2 promoted UC and NET formation through neutrophil chemotaxis and PAD4-mediated pathways, separately. Immunohistochemical results confirmed the high expression of CXCR1/2 in colon tissues of UC patients.

Conclusions

Our study identified CXCR1/2 as candidate targets in UC among all NRGs through multi-method argumentation, providing new insights of the regulation mechanisms of NET formation in the pathogenesis of UC.

Effects of exogenous deoxyribonuclease I in collagen antibody-induced arthritis

BACKGROUND

Rheumatoid arthritis (RA) is associated with a high concentration of extracellular DNA (ecDNA). This could be a consequence of the inflammation, but the ecDNA could also be involved in the unknown etiopathogenesis of RA. Clearance of ecDNA is hypothesized to prevent the development of RA. This study aimed to analyze the effects of exogenous deoxyribonuclease I (DNase I) administration in an animal model of RA.

METHODS

The collagen antibody-induced arthritis (CAIA) model of RA was induced in adult female DBA/1J mice. CAIA mice were treated with saline or DNase I (10 mg/kg) every 12 h for the whole duration of the experiment. Arthritic scores were assessed. Paw volume and temperature were assessed using a plethysmometer and a thermal camera, respectively. Plasma ecDNA and its subcellular origin were analyzed using fluorometry and real-time PCR. DNase activity was quantified with single radial enzyme diffusion method.

RESULTS

The CAIA model was successfully induced as proved by a higher volume, temperature and the overall arthritis score in comparison to controls. The administration of DNase I resulted in a nearly two-fold increase in serum DNase activity. Still, it did affect neither plasma ecDNA, nor the arthritis score or other measures of joint inflammation.

CONCLUSION

Our results suggest that exogenous DNase I does not prevent the development of CAIA in mice. Whether this is true for other animal models of arthritis or clinical RA requires further research. EcDNA does not seem to be involved in the pathogenesis of CAIA. Additional studies are also needed to elucidate the role of ecDNA in the development of RA, focusing especially on its origin and inhibition of ecDNA release.

Single-Cell RNA Sequencing Reveals Transcriptional Landscape of Neutrophils and Highlights the Role of TREM-1 in EAE

BACKGROUND AND OBJECTIVES

Neutrophils, underestimated in multiple sclerosis (MS), are gaining increased attention for their significant functions in patients with MS and the experimental autoimmune encephalomyelitis (EAE) animal model. However, the precise role of neutrophils in cervical lymph nodes (CLNs), the primary CNS-draining lymph nodes where the autoimmune response is initiated during the progression of EAE, remains poorly understood.

METHODS

Applying single-cell RNA sequencing (scRNA-seq), we constructed a comprehensive immune cell atlas of CLNs during development of EAE. Through this atlas, we concentrated on and uncovered the transcriptional landscape, phenotypic and functional heterogeneity of neutrophils, and their crosstalk with immune cells within CLNs in the neuroinflammatory processes in EAE.

RESULTS

Notably, we observed a substantial increase in the neutrophil population in EAE mice, with a particular emphasis on the significant rise within the CLNs. Neutrophils in CLNs were categorized into 3 subtypes, and we explored the specific roles and developmental trajectories of each distinct neutrophil subtype. Neutrophils were found to engage in extensive interactions with other immune cells, playing crucial roles in T-cell activation. Moreover, our findings highlighted the strong migratory ability of neutrophils to CLNs, partly regulated by triggering the receptor expressed on myeloid cells 1 (TREM-1). Inhibiting TREM1 with LR12 prevents neutrophil migration both in vivo and in vitro. In addition, in patients with MS, we confirmed an increase in peripheral neutrophils with an upregulation of TREM-1.

DISCUSSION

Our research provides a comprehensive and precise single-cell atlas of CLNs in EAE, highlighting the role of neutrophils in regulating the periphery immune response. In addition, TREM-1 emerged as an essential regulator of neutrophil migration to CLNs, holding promise as a potential therapeutic target in MS.

The role of neutrophils in autoimmune diseases

Historically, neutrophils have been primarily regarded as short-lived immune cells that act as initial responders to antibacterial immunity by swiftly neutralizing pathogens and facilitating the activation of adaptive immunity. However, recent evidence indicates that their roles are considerably more complex than previously recognized. Neutrophils comprise distinct subpopulations and can interact with various immune cells, release granular proteins, and form neutrophil extracellular traps. These functions are increasingly recognized as contributing factors to tissue damage in autoimmune diseases. This review comprehensively examines the physiological functions and heterogeneity of neutrophils, their interactions with other immune cells, and their significance in autoimmune diseases, including systemic lupus erythematosus, rheumatoid arthritis, antiphospholipid syndrome, antineutrophil cytoplasmic antibody-associated vasculitis, multiple sclerosis, and others. This review aims to provide a deeper understanding of the function of neutrophils in the development and progression of autoimmune disorders.

Innate immune sensing of cell death in disease and therapeutics

Innate immunity, cell death and inflammation underpin many aspects of health and disease. Upon sensing pathogens, pathogen-associated molecular patterns or damage-associated molecular patterns, the innate immune system activates lytic, inflammatory cell death, such as pyroptosis and PANoptosis. These genetically defined, regulated cell death pathways not only contribute to the host defence against infectious disease, but also promote pathological manifestations leading to cancer and inflammatory diseases. Our understanding of the underlying mechanisms has grown rapidly in recent years. However, how dying cells, cell corpses and their liberated cytokines, chemokines and inflammatory signalling molecules are further sensed by innate immune cells, and their contribution to further amplify inflammation, trigger antigen presentation and activate adaptive immunity, is less clear. Here, we discuss how pattern-recognition and PANoptosome sensors in innate immune cells recognize and respond to cell-death signatures. We also highlight molecular targets of the innate immune response for potential therapeutic development.

The emerging role of neutrophil extracellular traps in the progression of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease with a complex etiology. Neutrophil extracellular traps (NETs are NETwork protein structures activated by neutrophils to induce the cleavage and release of DNA-protein complexes). Current studies have shown the critical involvement of NETs in the progression of autoimmune diseases, Neutrophils mostly gather in the inflammatory sites of patients and participate in the pathogenesis of autoimmune diseases in various ways. NETs, as the activated state of neutrophils, have attracted much attention in immune diseases. Many molecules released in NETs are targeted autoantigens in autoimmune diseases, such as histones, citrulline peptides, and myeloperoxidase. All of these suggest that NETs have a direct causal relationship between the production of autoantigens and autoimmune diseases. For RA in particular, as a disorder of the innate and adaptive immune response, the pathogenesis of RA is inseparable from the generation of RA. In this article, we investigate the emerging role of NETs in the pathogenesis of RA and suggest that NETs may be an important target for the treatment of inflammatory autoimmune diseases.

NETs: Important players in cancer progression and therapeutic resistance

Neutrophil extracellular traps (NETs) are web-like structures composed of cytoplasmic contents, DNA chromatin and various granular proteins released by neutrophils in response to viruses, bacteria, immune complexes and cytokines. Studies have shown that NETs can promote the occurrence, development and metastasis of tumors. In this paper, the mechanism underlying the formation and degradation of NETs and the malignant biological behaviors of NETs, such as the promotion of tumor cell proliferation, epithelial mesenchymal transition, extracellular matrix remodeling, angiogenesis, immune evasion and tumor-related thrombosis, are described in detail. NETs are being increasingly studied as therapeutic targets for tumors. We have summarized strategies for targeting NETs or interfering with NET-cancer cell interactions and explored the potential application value of NETs as biomarkers in cancer diagnosis and treatment, as well as the relationship between NETs and therapeutic resistance.