Neutrophil extracellular traps in immunity and disease.Nat Rev Immunol. 2018;18:134-147. [PMID: 28990587 DOI: 10.1038/nri.2017.105]

Screening and Identification of Neutrophil Extracellular Trap-related Diagnostic Biomarkers for Pediatric Sepsis by Machine Learning

Neutrophil extracellular trap (NET) is released by neutrophils to trap invading pathogens and can lead to dysregulation of immune responses and disease pathogenesis. However, systematic evaluation of NET-related genes (NETRGs) for the diagnosis of pediatric sepsis is still lacking. Three datasets were taken from the Gene Expression Omnibus (GEO) database: GSE13904, GSE26378, and GSE26440. After NETRGs and differentially expressed genes (DEGs) were identified in the GSE26378 dataset, crucial genes were identified by using LASSO regression analysis and random forest analysis on the genes that overlapped in both DEGs and NETRGs. These crucial genes were then employed to build a diagnostic model. The diagnostic model's effectiveness in identifying pediatric sepsis across the three datasets was confirmed through receiver operating characteristic curve (ROC) analysis. In addition, clinical pediatric sepsis samples were collected to measure the expression levels of important genes and evaluate the diagnostic model's performance using qRT-PCR in identifying pediatric sepsis in actual clinical samples. Next, using the CIBERSORT database, the relationship between invading immune cells and diagnostic markers was investigated in more detail. Lastly, to evaluate NET formation, we measured myeloperoxidase (MPO)-DNA complex levels using ELISA. A group of five important genes (MME, BST1, S100A12, FCAR, and ALPL) were found among the 13 DEGs associated with NET formation and used to create a diagnostic model for pediatric sepsis. Across all three cohorts, the sepsis group had consistently elevated expression levels of these five critical genes as compared to the normal group. Area under the curve (AUC) values of 1, 0.932, and 0.966 indicate that the diagnostic model performed exceptionally well in terms of diagnosis. Notably, when applied to the clinical samples, the diagnostic model also showed good diagnostic capacity with an AUC of 0.898, outperforming the effectiveness of traditional inflammatory markers such as PCT, CRP, WBC, and NEU%. Lastly, we discovered that children with high ratings for sepsis also had higher MPO-DNA complex levels. In conclusion, the creation and verification of a five-NETRGs diagnostic model for pediatric sepsis performs better than established markers of inflammation.

Advanced Immunomodulatory Biomaterials for Therapeutic Applications

The multifaceted biological defense system modulating complex immune responses against pathogens and foreign materials plays a critical role in tissue homeostasis and disease progression. Recently developed biomaterials that can specifically regulate immune responses, nanoparticles, graphene, and functional hydrogels have contributed to the advancement of tissue engineering as well as disease treatment. The interaction between innate and adaptive immunity, collectively determining immune responses, can be regulated by mechanobiological recognition and adaptation of immune cells to the extracellular microenvironment. Therefore, applying immunomodulation to tissue regeneration and cancer therapy involves manipulating the properties of biomaterials by tailoring their composition in the context of the immune system. This review provides a comprehensive overview of how the physicochemical attributes of biomaterials determine immune responses, focusing on the physical properties that influence innate and adaptive immunity. This review also underscores the critical aspect of biomaterial-based immune engineering for the development of novel therapeutics and emphasizes the importance of understanding the biomaterials-mediated immunological mechanisms and their role in modulating the immune system.

Neutrophil heterogeneity and plasticity: unveiling the multifaceted roles in health and disease

Neutrophils, the most abundant circulating leukocytes, have long been recognized as key players in innate immunity and inflammation. However, recent discoveries unveil their remarkable heterogeneity and plasticity, challenging the traditional view of neutrophils as a homogeneous population with a limited functional repertoire. Advances in single-cell technologies and functional assays have revealed distinct neutrophil subsets with diverse phenotypes and functions and their ability to adapt to microenvironmental cues. This review provides a comprehensive overview of the multidimensional landscape of neutrophil heterogeneity, discussing the various axes along which diversity manifests, including maturation state, density, surface marker expression, and functional polarization. We highlight the molecular mechanisms underpinning neutrophil plasticity, focusing on the complex interplay of signaling pathways, transcriptional regulators, and epigenetic modifications that shape neutrophil responses. Furthermore, we explore the implications of neutrophil heterogeneity and plasticity in physiological processes and pathological conditions, including host defense, inflammation, tissue repair, and cancer. By integrating insights from cutting-edge research, this review aims to provide a framework for understanding the multifaceted roles of neutrophils and their potential as therapeutic targets in a wide range of diseases.

Predictive Value of Neutrophil Extracellular Traps in Neoadjuvant Chemotherapy for Muscle-Invasive Bladder Cancer

Cisplatin-based chemotherapy is the recommended therapy for muscle-invasive bladder cancer (MIBC). However, the efficacy of MIBC for chemotherapy is only about 40%. Therefore, predictors of therapy response are urgently needed. Neutrophils form neutrophil extracellular traps (NETs), a network structure, and growing evidence indicated that it could be a prognostic and predictive marker in cancer. In MIBC, the predictive role of NETs in chemotherapy resistance is unclear. We used the Least Absolute Shrinkage and Selection Operator (LASSO) logistic regression analyses to develop a NETs-associated signature score (NETs-score) for therapeutic response prediction in the discovery cohort (GSE169455). Then the NETs score-based risk stratification was verified in two validation cohorts (Taber et al.'s cohort, our institutional cohort). In the training cohort, high NETs-score was associated with poor chemotherapy response (AUC = 0.781) and reduced recurrence-free survival (RFS) (hazard ratio [HR] = 2.07, 95% confidence interval [CI]: [1.26-3.40], p = 0.003) in MIBC patients. The NETs-score was also demonstrated to be a predictive factor for the efficacy of neoadjuvant chemotherapy in the validation cohort (AUC = 0.731). The accuracy of the NETs-score was superior to other chemotherapy response predictors such as Ba/Sq expression subtype (AUC = 0.711), BRCA2 mutation (AUC = 0.692) and ERCC2 mutation (AUC = 0.548). Furthermore, in our center cohort, the expression level of H3Cit showed a significant difference between the response and no-response group (p = 0.01). Through immunohistochemical validation, NETs was an independent predictor of MIBC neoadjuvant chemotherapy efficacy as determined by the multivariate logistic regression analysis (OR = 5.94, 95% CI: 1.20-45.50, p = 0.045). Patients with high levels of NETs predicted poor response to neoadjuvant chemotherapy. This study was the first to reveal the correlation between the level of NETs in MIBC and the efficacy of chemotherapy, which may provide a theoretical basis regarding NETs inhibitors.

Efferocytosis: The Janus-Faced Gatekeeper of Aging and Tumor Fate

From embryogenesis to aging, billions of cells perish daily in mammals. The multistep process by which phagocytes engulf these deceased cells without eliciting an inflammatory response is called efferocytosis. Despite significant insights into the fundamental mechanisms of efferocytosis, its implications in disorders such as aging and cancer remain elusive. Upon summarizing and analyzing existing studies on efferocytosis, it becomes evident that efferocytosis is our friend in resolving inflammation, yet it transforms into our foe by facilitating tumor development and metastasis. This review illuminates recent discoveries regarding the emerging mechanisms of efferocytosis in clearing apoptotic cells, explores its connections with aging, examines its influence on tumor development and metastasis, and identifies the regulatory factors of efferocytosis within the tumor microenvironment. A comprehensive understanding of these efferocytosis facets offers insights into crucial physiological and pathophysiological processes, paving the way for innovative therapeutic approaches to combat aging and cancer.

Shared Phenotypes of Immune Cells Recruited to the Cornea and the Surface of the Lens in Response to Formation of Corneal Erosions

Injuries to the cornea can lead to recurrent corneal erosions, compromising its barrier function and increasing the risk of infection. Vital as corneal integrity is to the eye's optical power and homeostasis, the immune response to corneal erosions remains poorly understood. It is also unknown whether there is coordinated immune activation between the cornea and other regions of the anterior segment to protect against microbial invasion and limit the spread of inflammation when corneal erosions occur. Using a corneal debridement wounding model, we characterized the immune cell phenotypes populating the cornea in response to erosion formation and investigated whether and which immune cells are concurrently recruited to the surface of the lens. Our studies revealed that the formation of corneal erosions induced an influx of myeloid lineage phenotypes, both M2 macrophages associated with tissue healing and wound repair, and Ly6G+ Ly6C+ myeloperoxidase+ cells resembling neutrophils/polymorphonuclear-myeloid-derived suppressor cells (PMN-MDSCs), with few regulatory T cells, into the corneal stroma under erosion sites. This leukocyte migration into the cornea when erosions develop was paralleled by the recruitment of immune cells, predominantly neutrophils/PMN-MDSCs, to the anterior, cornea-facing lens capsule. Both cornea-infiltrating and lens capsule-associated neutrophil/PMN-MDSC-like immune cells produce the anti-inflammatory cytokine IL-10. Our findings suggest a collaborative role for the lens capsule-associated immune cells in preventing infections, controlling inflammation, and maintaining homeostasis of the anterior segment during recurrent corneal erosions.

Nitric oxide synthase inhibitors reduce the formation of neutrophil extracellular traps and alleviate airway inflammation in the mice model of asthma

Asthma, a widespread chronic inflammatory disease can contribute to different degrees of lung function damage. The objective of this study is to explore the potential effects of nitric oxide synthase (NOS) inhibitors in asthma using mice model induced by ovalbumin (OVA). BALB/c mice were treated with OVA to establish an asthma model. Mice were intranasally challenged with different NOS inhibitors and analyzed the impact of NOS inhibitors on the lung tissues and bronchoalveolar lavage fluid (BALF). Histopathological analysis was performed by Periodic Acid-Schiff (PAS) staining. Airway reactivity was assessed using methacholine challenge testing. The concentrations of nitric oxide (NO), Neutrophil extracellular traps (NETs), and cytokines were determined by enzyme-linked immunosorbent assay (ELISA) assay. NOS inhibitors effectively improved airway inflammation and reduced airway hyperresponsiveness. In addition, NOS inhibitors decreased the concentrations of NO, NETs, and inflammation in the airway and BALF. The decreased NO production and reduced NET formation in the lung indicate that NOS inhibitors inhibit the process of NET release to alleviate asthma.

Vaccine Specifically for Immunocompromised Individuals against Superbugs

Immunocompromised populations, including cancer patients, elderly individuals, and those with chronic diseases, are the primary targets of superbugs. Traditional vaccines are less effective due to insufficient or impaired immune cells. Inspired by the "vanguard" effect of neutrophils (NE) during natural infection, this project leverages the ability of NE to initiate the NETosis program to recruit monocytes and DC cells, designing vaccines that can rapidly recruit immune cells and enhance the immune response. The PLGA microsphere vaccine platform (MSV) with a high level of safety contains whole-bacterial antigens both internally and externally, providing initial and booster effects through programmed distribution and release of antigens after a single injection. Experimental data indicate that immunizing mice with a mixture of MSV and NE induces the formation of spontaneous gel-like neutrophil extracellular traps (NETs) at the inoculation site. These NETs recruit immune cells and prevent the diffusion of vaccine components, thereby reducing damage from bacterial toxins and enhancing vaccine biosafety. This strategy shows excellent efficacy against MRSA-induced infections in not only healthy but also immunocompromised mice.

Identification of neutrophil extracellular traps (NETs)-related molecular clusters in prostate cancer: Implications for predicting biochemical recurrence

OBJECTIVE

To identify neutrophil extracellular traps (NETs)-related molecular clusters and establish a novel gene signature for predicting biochemical recurrence in prostate cancer (PCa).

METHODS

The transcriptome and clinicaldata of PCa sampleswere obtained from The TCGA and GEO databases. To identify NET-related molecular clusters, consensus clustering analyses were performed. Using univariate Cox and Lasso regression analysis, a novel NETs-related prognostic model was formulated. To evaluate the validity of the model, both internal and external validations were carried out. At last, preliminary experimental validations were performed to verify the biological functions of ANXA3 in PCa cells.

RESULTS

After screening 75 NETs-related prognostic genes, two NET-related clusters with significantly different clinical features, immune cell infiltration, and biochemical recurrence were established. Next, a new NET-related model was constructed. In training, test, whole TCGA, and GEO cohorts, the biochemical recurrences free survival of the patients with high-risk scores was considerably lower. The AUCs for the four cohorts were 0.827, 0.696, 0.757, and 0.715, respectively. Subgroup analysis suggested that the novel NETs-related prognostic model has a strong clinical value in the identification of high-risk patients. Finally, we confirmed that chemotherapy might be more beneficial for patients at low risk. In preliminary experiments, the inhibition of ANXA3 could reduce the invasion, migration, and proliferation of PCa cells.

CONCLUSIONS

We have identified novel NETs-related clusters and developed a NETs-related model for PCa that has excellent predictive performance for predicting biochemical recurrences as well as chemotherapy efficacy.

Clinical Case of a Patient with Acute Tricuspid Valve Infective Endocarditis and A Multiplex Approach to Evaluation of The Complication Risk

Infective endocarditis (IE) is characterized by the difficulty of diagnosis, treatment and risk assessment of an unfavorable prognosis. Currently there are no approved scales and calculators for the risk of complications and death that help the practitioner make decisions, especially in patients with isolated right-sided IE. For right-sided IE, the timing of successful surgical treatment remains uncertain. Previously developed risk calculators (Italian Rizzi calculator and French Hubert) are poorly validated in a wide population of patients with IE, especially for right-sided IE. One of the required parameters of calculators is the determination of etiological affiliation. However, with negative results of microbiological studies reaching 56-83 %, this parameter becomes uninformative. Moreover, existing risk assessment tools do not take into account the activity of the disease (including laboratory activity), which intuitively is an important guideline for every doctor in decision-making. At the moment, there is a great need for the introduction of molecular biological methods to improve the quality of etiological diagnosis and in-depth study of possible biomarkers from simple (neutrophil/lymphocytic, platelet/lymphocytic and systemic immuno-inflammatory index) to more complex (neutrophil extracellular traps, cytokine profile). We present a clinical case of a young patient with acute tricuspid valve IE with giant vegetation (28 mm), complicated by severe valvular insufficiency without signs of heart failure, recurrent embolic syndrome in the pulmonary artery system with the formation of pulmonary hypertension, determining indications for cardiac surgical treatment. The etiological affiliation of IE to Staphylococcus aureus was established only by PCR. The urgent timing of intervention was determined based on an increase in new markers — neutrophil/lymphocytic index ≥20.0, systemic immuno-inflammatory index ≥2314.0 and neutrophil extracellular traps ≥14.2, indicating an extremely high risk of death. A fundamental pathohistological study of the tissue material revealed a low content of intact CD86+ proinflammatory macrophages, probably associated with their excessive destruction and uncontrolled release of copious amounts of proinflammatory cytokines, which led to rapid and severe damage to the tricuspid valve. Thus, modern management of patients with IE should be multiplex using current methods of etiological and imaging diagnostics, and aimed at early detection of patients at adverse risk for a timely differentiated approach to conservative or cardiac surgical treatment tactics.

Neutrophil extracellular traps have active DNAzymes that promote bactericidal activity

The mechanisms of bacterial killing by neutrophil extracellular traps (NETs) are unclear. DNA, the largest component of NETs was believed to merely be a scaffold with antimicrobial activity only through the charge of the backbone. Here, we demonstrate for the first time that NETs DNA is beyond a mere scaffold to trap bacteria and it produces hydroxyl free radicals through the spatially concentrated G-quadruplex/hemin DNAzyme complexes, driving bactericidal effects. Immunofluorescence staining showed potential colocalization of G-quadruplex and hemin in extruded NETs DNA, and Amplex UltraRed assay portrayed its peroxidase activity. Proximity labeling of bacteria revealed localized concentration of radicals resulting from NETs bacterial trapping. Ex vivo bactericidal assays revealed that G-quadruplex/hemin DNAzyme is the primary driver of bactericidal activity in NETs. NETs are DNAzymes that may have important biological consequences.

Neutrophil extracellular traps in tumor metabolism and microenvironment

Neutrophil extracellular traps (NETs) are intricate, web-like formations composed of DNA, histones, and antimicrobial proteins, released by neutrophils. These structures participate in a wide array of physiological and pathological activities, including immune rheumatic diseases and damage to target organs. Recently, the connection between NETs and cancer has garnered significant attention. Within the tumor microenvironment and metabolism, NETs exhibit multifaceted roles, such as promoting the proliferation and migration of tumor cells, influencing redox balance, triggering angiogenesis, and driving metabolic reprogramming. This review offers a comprehensive analysis of the link between NETs and tumor metabolism, emphasizing areas that remain underexplored. These include the interaction of NETs with tumor mitochondria, their effect on redox states within tumors, their involvement in metabolic reprogramming, and their contribution to angiogenesis in tumors. Such insights lay a theoretical foundation for a deeper understanding of the role of NETs in cancer development. Moreover, the review also delves into potential therapeutic strategies that target NETs and suggests future research directions, offering new perspectives on the treatment of cancer and other related diseases.

Pathogenic and Protective Roles of Neutrophils in Chlamydia trachomatis Infection

Chlamydia trachomatis (Ct) is an obligate intracellular pathogen that causes the most commonly diagnosed bacterial sexually transmitted infection (STI) and is a leading cause of preventable blindness globally. Ct infections can generate a strong pro-inflammatory immune response, leading to immune-mediated pathology in infected tissues. Neutrophils play an important role in mediating both pathology and protection during infection. Excessive neutrophil activation, migration, and survival are associated with host tissue damage during Chlamydia infections. In contrast, neutrophils also perform phagocytic killing of Chlamydia in the presence of IFN-γ and anti-Chlamydia antibodies. Neutrophil extracellular traps (NETs) and many neutrophil degranulation products have also demonstrated strong anti-Chlamydia functions. To counteract this neutrophil-mediated protection, Chlamydia has developed several evasion strategies. Various Chlamydia proteins can limit potentially protective neutrophil responses by directly targeting receptors present on the surface of neutrophils or neutrophil degranulation products. In this review, we provide a survey of current knowledge regarding the role of neutrophils in pathogenesis and protection, including the ways that Chlamydia circumvents neutrophil functions, and we propose critical areas for future research.

Neutrophil extracellular traps potentiate effector T cells via endothelial senescence in uveitis

Autoimmune uveitis (AU) is a sight-threatening ocular autoimmune disorder that often manifests as retinal vasculitis. Increased neutrophil infiltration around retinal vessels has been reported during the progression of AU, while how they function is not fully recognized. Neutrophil extracellular traps (NETs), produced by activated neutrophils, have been suggested to be detrimental in autoimmune diseases. Here, we found that NETs were elevated in patients with active AU, and this was verified in an experimental AU (EAU) mouse model. Depletion of neutrophils or degradation of NETs with deoxyribonuclease-I (DNase I) could decrease CD4+ effector T cell (Teff) infiltration in retina and spleen to alleviate EAU. Moreover, we found that the expression of adhesion molecules, selectin, and antigen-presenting molecules was elevated in EAU retina and in retinal microvascular endothelial cells (RMECs) cocultured with NETs. The stimulated RMECs further facilitated CD4+ T cell adhesion, activation, and differentiation into Teffs. Mechanistically, NETs trigger RMEC activation by hastening cell senescence through the cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway. Slowing down senescence or inhibiting the cGAS/STING pathway in RMECs reduces the activation and differentiation of CD4+ T cells. These results suggest a deleterious role of NETs in AU. Targeting NETs would offer an effective therapeutic method.

Molecular Mechanisms and Clinical Aspects of Colitis-Associated Cancer in Ulcerative Colitis

Inflammatory bowel diseases have long been recognized as entities with a higher risk of colorectal cancer. An increasing amount of information has been published regarding ulcerative colitis-associated colorectal cancer and its unique mechanisms in recent decades, as ulcerative colitis constitutes a chronic process characterized by cycles of activity and remission of unpredictable durations and intensities; cumulative genomic alterations occur during active disease and mucosal healing, resulting in a special sequence of events different to the events associated with sporadic colorectal cancer. The recognition of the core differences between sporadic colorectal cancer and colitis-associated cancer is of great importance to understand and guide the directions in which new research could be performed, and how it could be applied to current clinical scenarios. A DSS/AOM murine model has allowed for a better understanding of the pathogenic mechanisms in colitis-associated cancer, as it is currently the closest model to this unique scenario. In this review, we provide a summary of the main molecular mechanisms and the clinical aspects of colitis-associated cancer in ulcerative colitis.

Current status and future prospects of molecular imaging in targeting the tumor immune microenvironment

Molecular imaging technologies have significantly transformed cancer research and clinical practice, offering valuable tools for visualizing and understanding the complex tumor immune microenvironment. These technologies allow for the non-invasive examination of key components within the tumor immune microenvironment, including immune cells, cytokines, and stromal cells, providing crucial insights into tumor biology and treatment responses. This paper reviews the latest advancements in molecular imaging, with a focus on its applications in assessing interactions within the tumor immune microenvironment. Additionally, the challenges faced by molecular imaging technologies are discussed, such as the need for highly sensitive and specific imaging agents, issues with data integration, and difficulties in clinical translation. The future outlook emphasizes the potential of molecular imaging to enhance personalized cancer treatment through the integration of artificial intelligence and the development of novel imaging probes. Addressing these challenges is essential to fully realizing the potential of molecular imaging in improving cancer diagnosis, treatment, and patient outcomes.

Exercise intensity and training alter the innate immune cell type and chromosomal origins of circulating cell-free DNA in humans

Exercising regularly promotes health, but these benefits are complicated by acute inflammation induced by exercise. A potential source of inflammation is cell-free DNA (cfDNA), yet the cellular origins, molecular causes, and immune system interactions of exercise-induced cfDNA are unclear. To study these, 10 healthy individuals were randomized to a 12-wk exercise program of either high-intensity tactical training (HITT) or traditional moderate-intensity training (TRAD). Blood plasma was collected pre- and postexercise at weeks 0 and 12 and after 4 wk of detraining upon program completion. Whole-genome enzymatic methylation sequencing (EM-seq) with cell-type proportion deconvolution was applied to cfDNA obtained from the 50 plasma samples and paired to concentration measurements for 90 circulating cytokines. Acute exercise increased the release of cfDNA from neutrophils, dendritic cells (DCs), and macrophages proportional to exercise intensity. Exercise training reduced cfDNA released in HITT participants but not TRAD and from DCs and macrophages but not neutrophils. For most participants, training lowered mitochondrial cfDNA at rest, even after detraining. Using a sequencing analysis approach we developed, we concluded that rapid ETosis, a process of cell death where cells release DNA extracellular traps, was the likely source of cfDNA, demonstrated by enrichment of nuclear DNA. Further, several cytokines were induced by acute exercise, such as IL-6, IL-10, and IL-16, and training attenuated the induction of only IL-6 and IL-17F. Cytokine levels were not associated with cfDNA induction, suggesting that these cytokines are not the main cause of exercise-induced cfDNA. Overall, exercise intensity and training modulated cfDNA release and cytokine responses, contributing to the anti-inflammatory effects of regular exercise.

The Role of Platelet-Neutrophil Interactions in Driving Autoimmune Diseases

Platelets and neutrophils are among the most abundant cell types in peripheral blood. Beyond their traditional roles in thrombosis and haemostasis, they also play an active role in modulating immune responses. Current knowledge on the role of platelet-neutrophil interactions in the immune system has been rapidly expanding. Notably, circulating platelet-neutrophil complexes (PNCs) have been widely detected in various inflammatory diseases and infections, closely associated with inflammatory processes affecting multiple organs. These findings emphasise the critical role of platelet-neutrophil interactions in driving and sustaining inflammatory responses. In this review, we elucidate the mechanisms by which neutrophils and platelets physically interact, leading to mutual activation. Additionally, activated platelets release pro-inflammatory factors that further modulate neutrophil effector functions, enhancing their immune response capabilities. We highlight the role of platelets in promoting the formation of neutrophil extracellular traps (NETs), which, in turn, promote local platelet activation, thereby exacerbating the immune response and sustaining chronic inflammation. Furthermore, we review current evidence on the role of platelet-neutrophil interactions in common autoimmune diseases such as systemic lupus erythematosus (SLE), systemic sclerosis (SSc), and rheumatoid arthritis (RA). Finally, we identify gaps in understanding the mechanisms of these interactions in the context of other autoimmune diseases and underscore the potential of targeting platelets and neutrophils as a therapeutic strategy for these conditions.

Lymphatic platelet thrombosis limits bone repair by precluding lymphatic transporting DAMPs

In the musculoskeletal system, lymphatic vessels (LVs), which are interdigitated with blood vessels, travel and form an extensive transport network. Blood vessels in bone regulate osteogenesis and hematopoiesis, however, whether LVs in bone affect fracture healing is unclear. Here, we investigate the lymphatic draining function at the tibial fracture sites using near-infrared indocyanine green lymphatic imaging (NIR-ICG) and discover that lymphatic drainage insufficiency (LDI) starts on day one and persists for up to two weeks following the fracture in male mice. Sufficient lymphatic drainage facilitates fracture healing in male mice. Furthermore, we identify that lymphatic platelet thrombosis (LPT) blocks the draining lymphoid sinus and LVs, causes LDI, and inhibits fracture healing in male mice, which can be rescued by a blood thinner. Moreover, unblocked lymphatic drainage decreases neutrophils and increases M2-type macrophages of the hematoma niche to support osteoblast (OB) survival and bone marrow-derived mesenchymal stem cell (BMSC) proliferation via transporting damage-associated molecular patterns (DAMPs) in male rats. Lymphatic platelet thrombolysis also benefits senile fracture healing in female mice. These findings demonstrate that LPT limits bone regeneration by impeding lymphatic transporting DAMPs. Together, these findings represent a way forward in the treatment of bone repair.

Nanocapsuled Neutrophil Extracellular Trap Scavenger Combating Chronic Infectious Bone Destruction Diseases

Chronic infectious bone destruction diseases, such as periodontitis, pose a significant global health challenge. Repairing the bone loss caused by these chronic infections remains challenging. In addition to pathogen removal, regulating host immunity is imperative. The retention of neutrophil extracellular traps (NETs) in chronic infectious niches is found to be a barrier to inflammation resolution. However, whether ruining the existing NETs within the local infectious bone lesions can contribute to inflammation resolve and bone repair remains understudied. Herein, a nanocapsuled delivery system that scavenges NETs dual-responsively to near-infrared light as a switch and to NETs themselves as a microenvironment sensor is designed. Besides, the photothermal and photodynamic effects endow the nanocapsules with antibacterial properties. Together with the ability to clear NETs, these features facilitate the restoration of the normal host response. The immunocorrective properties and inherent pro-osteogenic effects finally promote local bone repair. Together, the NET scavenging nanocapsules address the challenge of impaired bone repair in chronic infections due to biased host response caused by excessive NETs. This study provides new concepts and strategies for repairing bone destruction attributable to chronic infections via correcting biased host responses in chronic infectious diseases.

Advances in Engineering Myeloid Cells for Cell Therapy Applications

Myeloid cells, including macrophages, neutrophils, dendritic cells, and myeloid-derived suppressor cells, play crucial roles in the innate immune system, contributing to immune defense, tissue homeostasis, and organ development. They have tremendous potential as therapeutic tools for diseases such as cancer and autoimmune disorders, but harnessing cell engineering strategies to enhance potency and expand applications is challenging. Recent advancements in stem cell research have made it possible to differentiate human embryonic stem cells and induce pluripotent stem cells into various cell types, including myeloid cells, offering a promising new approach to generate myeloid cells for cell therapy. In this review, we explore the latest techniques for the genetic engineering of myeloid cells, discussing both established and emerging methodologies. We examine the challenges faced in this field and the therapeutic potential of engineered myeloid cells. We also describe examples of engineered macrophages, neutrophils, and dendritic cells in various disease contexts. By providing a detailed overview of the current state and future directions, we aim to highlight progress and ongoing efforts toward harnessing the full therapeutic potential of genetically engineered myeloid cells.

Exploring the mechanism of Radix Bupleuri in the treatment of depression combined with SARS-CoV-2 infection through bioinformatics, network pharmacology, molecular docking, and molecular dynamic simulation

BACKGROUND

Radix Bupleuri is commonly used in treating depression and acute respiratory diseases such as SARS-CoV-2 infection in China. However, its underlying mechanism in treating major depressive disorder combined with SARS-CoV-2 infection remains unclear.

AIM

This study aims to elucidate the pharmacological mechanisms of Radix Bupleuri in treating major depressive disorder combined with SARS-CoV-2 infection, employing bioinformatics, network pharmacology, molecular docking, and dynamic simulation techniques.

METHOD

Active ingredients and drug target genes of Radix Bupleuri were collected from TCMSP, PubChem, SwissTargetPrediction, and SuperPred databases. Differentially expressed genes were analyzed using datasets of SARS-CoV-2 infection and major depression disorder from the GEO database. The key genes were identified by using GO and KEGG functional analyses and STRING database. Machine learning methods were employed to predict core target gene, and ROC curve analysis validated the models' accuracy and the core gene expression had been analyzed and validated with other datasets. Molecular docking and dynamic simulation were conducted to verify the affinity of the active ingredients with core target gene. Finally, immune infiltration and correlation analyses between core target genes and immune cells were performed.

RESULTS

A total of 15 active ingredients, 1898 differentially expressed genes related to SARS-CoV-2 infection, and 814 differentially expressed genes related to major depression disorder were collected. 18 common genes were identified at the intersection of Radix Bupleuri, major depression disorder, and SARS-CoV-2 infection. The key gene JAK2 was identified through PPI network construction and machine learning model predictions. Molecular docking showed that the binding energies of the active ingredients with JAK2 were all below - 5 kcal/mol, with petunidin exhibiting the highest affinity. Molecular dynamic simulations further suggested stable interactions with JAK2. Immune infiltration analysis suggested that Radix Bupleuri in the context of depression combined with SARS-CoV-2 infection may promote the activation and generation of B cells, CD4 T cells, and CD8 T cells, while inhibiting the activation of mature dendritic cells, macrophages, natural killer cells, and neutrophils. Correlation analysis of JAK2 with immune cells indicated an association with macrophage activation and the inhibition of memory B cells and activated B cells.

CONCLUSION

The active ingredients of Radix Bupleuri may exhibit both antidepressant and antiviral pharmacological effects in the progression of major depression disorder combined with SARS-CoV-2 infection, through a mechanism closely associated with the JAK2 target.

Inhibition of Interleukin-40 prevents multi-organ damage during sepsis by blocking NETosis

Despite intensive clinical and scientific efforts, the mortality rate of sepsis remains high due to the lack of precise biomarkers for patient stratification and therapeutic guidance. Interleukin 40 (IL-40), a novel cytokine with immune regulatory functions in human diseases, was elevated at admission in two independent cohorts of patients with sepsis. High levels of secreted IL-40 in septic patients were positively correlated with PCT, CRP, lactate (LDH), and Sequential Organ Failure Assessment (SOFA) scores, in which IL-40 levels were used to stratify the early death of critically ill patients with sepsis. Moreover, genetic knockout of IL-40 (IL-40-/-) improved outcomes in mice with experimental sepsis, as evidenced by attenuated cytokine storm, multiple-organ failure, and early mortality, compared with those of wild-type (WT) mice. Mechanistically, single-cell RNA sequencing (scRNA-seq) and bulk RNA sequencing (RNA-seq) have revealed that S100A8/9hi neutrophil influx into the peritoneal cavity along with neutrophil extracellular trap (NETs) formation accounts predominantly for the IL-40-mediated worsening of sepsis outcomes. Clinically, the IL-40 level was positively correlated with the NET-related MPO/dsDNA ratio in septic patients. Finally, with antibiotics (gentamycin), genetic knockout of IL-40 prevented polymicrobial sepsis fatalities more efficiently than without gentamycin treatment. In summary, these data reveal a novel prognostic strategy for sepsis and that IL-40 may serve as a novel therapeutic target for sepsis.

The impact of aging on neutrophil functions and the contribution to periodontitis

The increasing aging population and aging-associated diseases have become a global issue for decades. People over 65 show an increased prevalence and greater severity of periodontitis, which poses threats to overall health. Studies have demonstrated a significant association between aging and the dysfunction of neutrophils, critical cells in the early stages of periodontitis, and their crosstalk with macrophages and T and B lymphocytes to establish the periodontal lesion. Neutrophils differentiate and mature in the bone marrow before entering the circulation; during an infection, they are recruited to infected tissues guided by the signal from chemokines and cytokines to eliminate invading pathogens. Neutrophils are crucial in maintaining a balanced response between host and microbes to prevent periodontal diseases in periodontal tissues. The impacts of aging on neutrophils' chemotaxis, anti-microbial function, cell activation, and lifespan result in impaired neutrophil functions and excessive neutrophil activation, which could influence periodontitis course. We summarize the roles of neutrophils in periodontal diseases and the aging-related impacts on neutrophil functional responses. We also explore the underlying mechanisms that can contribute to periodontitis manifestation in aging. This review could help us better understand the pathogenesis of periodontitis, which could offer novel therapeutic targets for periodontitis.

Lead-induced actin polymerization aggravates neutrophil extracellular trap formation and contributes to vascular inflammation

Lead (Pb) exposure is widely acknowledged as a risk factor for cardiovascular diseases. Previous studies have established neutrophil involvement in Pb-induced cardiovascular injuries; however, the underlying mechanisms remain unclear. To address this knowledge gap, the binding targets of Pb in neutrophils and their roles in regulating neutrophil extracellular trap (NET) formation were investigated. Furthermore, their impact on Pb-induced vascular inflammation and other cardiovascular injuries was studied in mice. Our findings indicate, for the first time, that Pb binds to β-actin in neutrophils, influencing NET formation. Inhibition of actin polymerization reduces the release of extracellular myeloperoxidase, neutrophil elastase, and citrullinated histone H3, indicating an impediment in NET formation. Furthermore, Pb exposure exacerbates blood pressure and vascular inflammation in vascular tissues, leading to abnormal aortic blood flow in mice. These injuries are potentially associated with NET formation, which is supported by the positive correlation between NETs and vascular inflammation. Importantly, the inhibition of actin polymerization mitigates Pb-induced vascular inflammation and regulates systolic blood pressure by reducing NET formation. Collectively, our findings provide novel insights into the mechanism underlying Pb-induced cardiovascular injury, contributing to the management of the escalating risk associated with Pb-induced cardiovascular damage.

The endothelium at the interface between tissues and Staphylococcus aureus in the bloodstream

SUMMARYStaphylococcus aureus is a major human pathogen. It can cause many types of infections, in particular bacteremia, which frequently leads to infective endocarditis, osteomyelitis, sepsis, and other debilitating diseases. The development of secondary infections is based on the bacterium's ability to associate with endothelial cells lining blood vessels. The success of endothelial colonization and infection by S. aureus relies on its ability to express a wide array of cell wall-anchored and secreted virulence factors. Establishment of endothelial infection by the pathogen is a multistep process involving adhesion, invasion, extravasation, and dissemination of the bacterium into surrounding tissues. The process is dependent on the type of endothelium in different organs (tissues) and pathogenetic potential of the individual strains. In this review, we report an update on the organization of the endothelium in the vessels, the structure and function of the virulence factors of S. aureus, and the several aspects of bacteria-endothelial cell interactions. After these sections, we will discuss recent advances in understanding the specific mechanisms of infections that develop in the heart, bone and joints, lung, and brain. Finally, we describe how neutrophils bind to endothelial cells, migrate to the site of infection to kill bacteria in the tissues, and how staphylococci counteract neutrophils' actions. Knowledge of the molecular details of S. aureus-endothelial cell interactions will promote the development of new therapeutic strategies and tools to combat this formidable pathogen.

Gene Expression Profiles Reveal Distinct Mechanisms Driving Chronic Obstructive Pulmonary Disease Exacerbations

Chronic obstructive pulmonary disease (COPD) exacerbations are major contributors to morbidity and mortality, highlighting the need to better understand their molecular mechanisms to improve prevention, diagnosis, and treatment. This study investigated differential gene expression profiles and key biological processes in COPD exacerbations categorized based on sputum microbiome profiling. An observational study was performed on a cohort of 16 COPD patients, who provided blood and sputum samples during exacerbations, along with five stable-state samples as controls. Exacerbations were classified using 16S rRNA sequencing to analyze the sputum microbiota and multiplex PCR to detect respiratory viruses. Blood transcriptomic profiling was conducted using Oxford Nanopore technology, followed by differential gene expression and pathway enrichment analyses. A total of 768 regulated genes were identified across the exacerbation groups, with 35 shared genes associated with neutrophil activation. Bacterial exacerbations activated pathways related to phagocytosis and toll-like receptor signaling, while viral exacerbations were linked to pro-inflammatory responses and mitochondrial damage. Exacerbations of unknown origin showed activation of pathways involved in protozoan defense and neutrophilic asthma. Biomarkers such as IFITM3 and ISG15 for bacterial exacerbations, DEFA3 for viral, and CD47 for unknown-origin exacerbations were identified. These findings highlight distinct transcriptomic profiles and biological pathways in COPD exacerbations, emphasizing the central role of neutrophil-driven inflammation and identifying potential biomarkers for improved differential diagnosis and personalized management.

Old and New Biomarkers in Idiopathic Recurrent Acute Pericarditis (IRAP): Prognosis and Outcomes

PURPOSE OF REVIEW

To outline the latest discoveries regarding the utility and reliability of serum biomarkers in idiopathic recurrent acute pericarditis (IRAP), considering recent findings on its pathogenesis. The study highlights the predictive role of these biomarkers in potential short- (cardiac tamponade, recurrences) and long-term complications (constrictive pericarditis, death).

RECENT FINDINGS

The pathogenesis of pericarditis has been better defined in recent years, focusing on the autoinflammatory pathway. New studies have demonstrated the pivotal role of the classical inflammatory biomarkers in distinguishing pericarditis phenotypes (high-grade vs. low-grade inflammation) and in defining outcomes of this condition. Pericarditis involves intense inflammatory activity, which causes elevation of different markers, such as C-reactive protein, erythrocyte sedimentation rate, neutrophils and platelets, serum amyloid A and D-Dimer. Conversely, lymphocytes are often reduced, as well as hemoglobin during the acute phase. Cardiac troponins T and I are elevated in up to 30% of cases. A Biomarker for CRP-negative cases is needed. Other markers have been proposed for diagnosis and prognosis in IRAP, such as anti-heart antibodies and anti-intercalated disk antibodies, but we need further studies to validate them.

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.

Progesterone suppresses rhinovirus-induced airway inflammation by inhibiting neutrophil infiltration and extracellular traps formation

BACKGROUND

The process of NETosis is observed in a range of inflammatory conditions. Progesterone (P4) has been shown to alleviate inflammation caused by viral infections such as influenza and SARS-CoV-2. However, the precise molecular mechanisms responsible for this effect are not yet fully understood. Therefore, the present investigation aims to explore whether P4 can exert its anti-inflammatory properties by inhibiting NETosis and the related molecular pathways.

METHODS

Airway inflammation caused by rhinovirus serotype-1b (RV-1b) was induced in male BALB/c mice. The inflammation was assessed through histological examination and calculation of inflammatory cells present in the bronchoalveolar lavage fluid. Flow cytometry was used to analyze the inflammatory cells and NETotic neutrophils. Western blotting analysis was conducted to detect proteins associated with NETosis, inflammasome activation, and signaling. Furthermore, confocal microscopy was utilized to observe neutrophil extracellular trap (NET) structures in vivo tissues and in vitro neutrophils, neutrophil infiltration, and inflammasome formation.

RESULTS

The administration of P4 proved to be an effective treatment for reducing airway inflammation and the production of NETs caused by RV-1b infection. The infection triggered the activation of NLRP3 inflammasomes in neutrophils, which led to the maturation of IL-1β and subsequent activation of both the NF-κB and p38 signaling pathways. The activation of NF-κB signaling resulted in the secretion of downstream chemokines CCL3 and IL-6, which led to an increase in neutrophil infiltration into the lung airways. Moreover, the activation of p38 signaling led to the generation of reactive oxygen species, resulting in NETosis. However, the administration of P4 inhibited the activation of the NLRP3 inflammasome, which subsequently led to the deactivation of both the IL-1β-NF-κB and IL-1β-p38 axes. As a result, there was a reduction in neutrophil infiltration and NETosis. Furthermore, TGF-β-activated kinase 1 (TAK1) was identified as an intermediary enzyme. P4 inhibits both the NF-κB and IL-1β-p38 pathways by suppressing the activity of TAK1.

CONCLUSION

The capacity of P4 to mitigate rhinovirus-induced airway inflammation is attributed to its ability to impede the infiltration of neutrophils and NETosis. As inflammation mediated by NETosis is widespread in diverse disorders, our findings propose that P4 could potentially function as a universal therapeutic agent in the management of such ailments.

Neutrophil extracellular DNA traps activate the TLR9 signaling pathway of pancreatic ductal epithelial cells in patients with type 2 autoimmune pancreatitis

The presence of neutrophil infiltration around the pancreatic ducts has been found to be associated with type 2 autoimmune pancreatitis (AIP). However, the functional role and clinical significance of neutrophil migration in the progression of pancreatitis is not fully understood. Here, we found that neutrophil extracellular traps (NETs) are abundant around the pancreatic duct in patients with type 2 AIP. We also observed an increased expression of toll-like receptor 9 (TLR9) in pancreatic ductal epithelial cells (HPDEC) in type 2 AIP patients compared to other pancreatic diseases. TLR9 acts as the DNA component of NETs (NET-DNA) receptor in HPDEC, which senses extracellular DNA and subsequently activates the NF-κB pathway to promote neutrophil recruitment and induce NET formation. In addition, our results indicated that the hydroxychloroquine (HCQ), acting as a TLR9 antagonist, could effectively inhibit the activation of inflammatory pathways, reduce neutrophil migration and block the positive feedback loop. The intervention positions HCQ acts as a potential target drug for the clinical treatment of type 2 AIP.

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 (NETs) as a Potential Target for Anti-Aging: Role of Therapeutic Apheresis

Neutrophil extracellular traps (NETs) are large structures composed of chromatin, histones and granule-derived proteins released extracellularly by neutrophils. They are generally considered to be a part of the antimicrobial defense strategy, preventing the dissemination of pathogens. However, overproduction of NETs or their ineffective clearance can drive various pathologies, many of which are associated with advanced age and involve uncontrolled inflammation, oxidative, cardiovascular and neurodegenerative stress as underlying mechanisms. Targeting NETs in the elderly as an anti-aging therapy seems to be a very attractive therapeutic approach. Therapeutic apheresis with a specific filter to remove NETs could be a promising strategy worth considering.

Kuiyangling Enema Alleviates Ulcerative Colitis Mice by Reducing Levels of Intestinal NETs and Promoting HuR/VDR Signaling

Purpose

Kuiyangling is a traditional Chinese medicine formula used for the treatment of ulcerative colitis, but the specific mechanism remains unclear. Imbalance in NETs regulation is one of the important factors contributing to the onset of ulcerative colitis (UC). The HuR/VDR signaling pathway plays a significant role in restoring the intestinal mucosal barrier in UC. The aim of this study is to explore the mechanism of Kuiyangling in the treatment of ulcerative colitis.

Methods

A mouse model of ulcerative colitis using 3% DSS water was considered, and model, normal, Kuiyangling medium- (5 g·kg-1) and high-dose (10 g·kg-1), and mesalazine (50 mg·kg-1) groups were created. Measurements of colon length, spleen index, histopathological variances, subcellular structure observations, ROS content, and NET-related proteins (PAD4, MPO, citH3) were obtained through HE staining, electron microscopy, live imaging, and Western blotting assays. Immunohistochemistry and immunofluorescence analyses were conducted to assess the levels of HuR/VDR protein complex, ZO-1, Occludin, Claudin-7, and intestinal NETs. An ELISA kit was utilized to determine cytokine levels, LC-MS was performed to analyze the composition of Kuiyangling, and next-generation sequencing was conducted for detection of the intestinal mucosal transcriptome.

Results

Kuiyangling reduced DAI, splenic index, and ROS content; maintained mucosal structure; decreased inflammation; and increased colon length and body mass index. Western blotting indicated that Kuiyangling reduced PAD4,MPO, and citH3 levels. Kuiyangling decreased NETs and increased the expression levels of ZO-1, Occludin, and Claudin-7, as well as up-regulating HuR, VDR, and HuR/VDR proteins. Kuiyangling reduced IL-1β, IL-6, and TNF-α levels while increasing TGF-β, IL-10, and IL-37 levels. Kuiyangling reduced inflammatory response proteins and elevated the levels of anti-inflammatory and intestinal barrier proteins, possibly inhibiting the TNF and oxidative phosphorylation signaling pathways.

Conclusion

Kuiyangling enema in treating ulcerative colitis in mice, associated with a reduction in intestinal NETs and enhancement of HuR-mediated intestinal barrier signaling pathways.

Spleen tyrosine kinase inhibitors disrupt human neutrophil swarming and antifungal functions

Neutrophils communicate with one another and amplify their destructive power through swarming, a collective process that synchronizes the activities of multiple neutrophils against one target. The sequence of activities contributing to swarming against clusters of fungi has been recently uncovered. However, the molecular signals controlling the neutrophils' activities during the swarming process are just emerging. Here, we report that spleen tyrosine kinase (SYK) inhibitors severely impair neutrophil swarming responses, resulting in the complete loss of fungal restriction. These findings are enabled by a microscale platform to probe the biology of human neutrophils swarming against uniformly sized clusters of growing Candida albicans, a representative opportunistic fungal pathogen. We take advantage of the ability to monitor large arrays of swarms and quantify the effect of multiple chemical inhibitors on different phases of human neutrophil swarming. We show that inhibitors that interfere with PI3Ky signaling disrupt the regulation of the initiation of swarming, while the activation of JNK signaling is essential for the activation of biochemical antifungal functions. Furthermore, we reveal that granulocyte colony-stimulating factors (GCSF and GM-CSF) can partially rescue the antifungal functions of neutrophils exposed to SYK inhibitors. These findings advance our understanding of neutrophil swarming biology in humans and lay the foundation for novel therapeutics that may restore neutrophil function during immunosuppression.

IMPORTANCE

Neutrophils can amplify their destructive power through swarming, a crucial process against large targets that individual neutrophils cannot destroy. However, the molecular mechanisms controlling this process are just emerging. Here, we leveraged microscale tools to probe the biology of swarming against fungi. We used multiple chemical inhibitors and mapped SYK, PI3Ky, and JNK signaling roles during human neutrophil swarming against fungal clusters of Candida albicans. We also found that treating human neutrophils with GCSF and GM-CSF rescues some neutrophil antifungal function during SYK inhibition. These findings advance our understanding of swarming biology in humans while laying the foundation for developing therapeutics that enhance neutrophil function during immunosuppression.

Nanoscopy reveals integrin clustering reliant on kindlin-3 but not talin-1

BACKGROUND

Neutrophils are the most abundant leukocytes in human blood, and their recruitment is essential for innate immunity and inflammatory responses. The initial and critical step of neutrophil recruitment is their adhesion to vascular endothelium, which depends on G protein-coupled receptor (GPCR) triggered integrin inside-out signaling that induces β2 integrin activation and clustering on neutrophils. Kindlin-3 and talin-1 are essential regulators for the inside-out signaling induced β2 integrin activation. However, their contribution in the inside-out signaling induced β2 integrin clustering is unclear because conventional assays on integrin clustering are usually performed on adhered cells, where integrin-ligand binding concomitantly induces integrin outside-in signaling.

METHODS

We used flow cytometry and quantitative super-resolution stochastic optical reconstruction microscopy (STORM) to quantify β2 integrin activation and clustering, respectively, in kindlin-3 and talin-1 knockout leukocytes. We also tested whether wildtype or Pleckstrin homology (PH) domain deleted kindlin-3 can rescue the kindlin-3 knockout phenotypes.

RESULTS

GPCR-triggered inside-out signaling alone can induce β2 integrin clustering. As expected, both kindlin-3 and talin-1 knockout decreases integrin activation. Interestingly, only kindlin-3 but not talin-1 contributes to integrin clustering in the scenario of inside-out-signaling, wherein a critical role of the PH domain of kindlin-3 was highlighted.

CONCLUSIONS

Since talin was known to facilitate integrin clustering in outside-in-signaling-involved cells, our finding provides a paradigm shift by suggesting that the molecular mechanisms of integrin clustering upon inside-out signaling and outside-in signaling are different. Our data also contradict the conventional assumption that integrin activation and clustering are tightly inter-connected by showing separated regulation of the two during inside-out signaling. Our study provides a new mechanism that shows kindlin-3 regulates β2 integrin clustering and suggests that integrin clustering should be assessed independently, aside from integrin activation, when studying leukocyte adhesion in inflammatory diseases.

The immunopathogenesis of a cytokine storm: The key mechanisms underlying severe COVID-19

A cytokine storm is marked by excessive pro-inflammatory cytokine release, and has emerged as a key factor in severe COVID-19 cases - making it a critical therapeutic target. However, its pathophysiology was poorly understood, which hindered effective treatment. SARS-CoV-2 initially disrupts angiotensin signalling, promoting inflammation through ACE-2 downregulation. Some patients' immune systems then fail to shift from innate to adaptive immunity, suppressing interferon responses and leading to excessive pyroptosis and neutrophil activation. This amplifies tissue damage and inflammation, creating a pro-inflammatory loop. The result is the disruption of Th1/Th2 and Th17/Treg balances, lymphocyte exhaustion, and extensive blood clotting. Cytokine storm treatments include glucocorticoids to suppress the immune system, monoclonal antibodies to neutralize specific cytokines, and JAK inhibitors to block cytokine receptor signalling. However, the most effective treatment options for mitigating SARS-CoV-2 infection remain vaccines as a preventive measure and antiviral drugs for the early stages of infection. This article synthesizes insights into immune dysregulation in COVID-19, offering a framework to better understand cytokine storms and to improve monitoring, biomarker discovery, and treatment strategies for COVID-19 and other conditions involving cytokine storms.

Phase partitioning of the neutrophil oxidative burst is coordinated by accessory pathways of glucose metabolism and mitochondrial activity

Neutrophils are a part of the innate immune system and produce reactive oxygen species (ROS) to extinguish pathogens. The major source of ROS in neutrophils is NADPH oxidase, which is fueled by NADPH generated via the pentose phosphate pathway; however, it is unclear how other accessory glucose metabolism pathways and mitochondrial activity influence the respiratory burst. We examined the temporal dynamics of the respiratory burst and delineated how metabolism changes over time after neutrophil activation. Bone marrow-derived neutrophils were stimulated with phorbol 12-myristate 13-acetate, and the respiratory burst was measured via extracellular flux analysis. Metabolomics experiments utilizing 13C6-glucose highlighted the activation of glycolysis as well as ancillary pathways of glucose metabolism in activated neutrophils. Phorbol 12-myristate 13-acetate stimulation acutely increased 13C enrichment into glycerol 3-phosphate (G3P) and citrate, whereas increases in 13C enrichment in the glycogen intermediate, UDP-hexose, and end products of the hexosamine and serine biosynthetic pathways occurred only during the late phase of the oxidative burst. Targeted inhibition of the G3P shuttle, glycogenolysis, serine biosynthesis, and mitochondrial respiration demonstrated that the G3P shuttle contributes to the general magnitude of ROS production; that glycogen contributes solely to the early respiratory burst; and that the serine biosynthetic pathway activity and complex III-driven mitochondrial activity influence respiratory burst duration. Collectively, these results show that the neutrophil oxidative burst is highly dynamic, with coordinated changes in metabolism that control the initiation, magnitude, and duration of ROS production.

The heterogeneity of neutrophils in cancer and its implication for therapeutic targeting

Neutrophils have a pivotal role in safeguarding the host against pathogens and facilitating tissue remodeling. They possess a large array of tools essential for executing these functions. Neutrophils have a critical role in cancer, where they are largely associated with negative clinical outcome and resistance to therapy. However, the specific role of neutrophils in cancer is complex and controversial, owing to their high functional diversity and acute sensitivity to the microenvironment. In this Perspective, we discuss the accumulated evidence that suggests that the functional diversity of neutrophils can be ascribed to two principal functional states, each with distinct characteristics: classically activated neutrophils and pathologically activated immunosuppressive myeloid-derived suppressor cells. We discuss how the antimicrobial factors in neutrophils can contribute to tumor progression and the fundamental mechanisms that govern the pathologically activated myeloid-derived suppressor cells. These functional states play divergent roles in cancer and thus require separate consideration in therapeutic targeting.

Neutrophil Extracellular Traps Drive Kidney Stone Formation

Introduction

This study aims to explore the contribution of neutrophil extracellular traps (NETs) to kidney stones.

Methods

The microarray data from GSE73680 and bioinformatic analysis were applied to identify differentially expressed genes in patients with kidney stones. A rat model of kidney stones was established through ethylene glycol and ammonium chloride administration. The plasma was collected for examining cf-DNA, DNase I, MPO-DNA, H3Cit and NE. Superoxide dismutase, malondialdehyde, creatinine, blood urea nitrogen, and calcium were examined through biochemical analysis. MPO, H3Cit, and NE in kidney tissues were detected via immunofluorescence staining. Cell apoptosis was evaluated through TUNEL assays. HE, Periodic Acid-Schiff and Von Kossa staining were applied to determine histological structure, calcium deposits and stone formation in the kidneys. Neutrophil elastase inhibitor Sivelestat (SIVE) was administrated for NET suppression in rats.

Results

A total of 403 differentially expressed genes including 270 upregulated and 133 downregulated genes were identified between renal papillary tissues with Randall's plaque and normal tissues. Gene ontology enrichment, KEGG pathway and protein-protein interaction network analysis of these dysregulated genes were performed. Moreover, increased NET markers including cf-DNA, DNase I, MPO-DNA, H3Cit and NE and calcium deposits were observed in patients with kidney stones. Subsequently, we established a rat model of kidney stones. We found that NET formation was significantly elevated in kidney stone rats, and renal tubular injury and apoptotic cells were enhanced as kidney stones developed. Strikingly, we found that suppression of NETs via SIVE could significantly reduce calcium deposits and apoptotic cells and alleviate tubular injury, thus improving kidney function.

Conclusion

NETs drive the formation of kidney stones, thus aggravating kidney injury. Our study identifies NETs as a potential diagnostic and therapeutic biomarker for nephrolithiasis.

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.

Neutrophil Extracellular Traps Induce Brain Edema Around Intracerebral Hematoma via ERK-Mediated Regulation of MMP9 and AQP4

Perihematomal edema (PHE) significantly aggravates secondary brain injury in patients with intracerebral hemorrhage (ICH), yet its detailed mechanisms remain elusive. Neutrophil extracellular traps (NETs) are known to exacerbate neurological deficits and worsen outcomes after stroke. This study explores the potential role of NETs in the pathogenesis of brain edema following ICH. The rat ICH model was created, immunofluorescence and Western blot were used to examine neutrophil accumulation, NET markers citrullinated histone H3 (CitH3) and myeloperoxidase (MPO), tight junction proteins (ZO-1 and Occludin), Aquaporin-4 (AQP4), matrix metalloproteinase-9 (MMP-9), and ERK phosphorylation (p-ERK) in brain tissues surrounding the hematoma. TUNEL staining and behavioral tests were employed to evaluate neuronal apoptosis and neurological dysfunction, while blood-brain barrier (BBB) permeability and brain edema were also measured by Evans blue and brain water content. Furthermore, the molecular mechanisms related to NETs-induced PHE were investigated using NETs, ERK, MMP-9 and AQP4 regulators, respectively. Ly6G+ neutrophils surrounding the hematoma developed NETs within 3 days post-ICH. NETs decreased tight junction proteins, destroyed BBB integrity, promoted brain edema, increased neuronal apoptosis, and exacerbated neurological deficits. Conversely, inhibition of NETs mitigated PHE, reduced neuronal apoptosis, and improved neurological functions. Mechanistically, NET-induced PHE was originated from impairment of BBB tight junction via ERK/MMP9 pathway, coupled with ERK-mediated AQP4 downregulation in perihematomal regions. These findings elucidated the effects of NETs on PHE, which offered promising insights for targeting NETs to relieve brain edema and secondary brain injury post-ICH.

A novel biomarker of COVI-19: MMP8 emerged by integrated bulk RNAseq and single-cell sequencing

COVID-19 has been emerging as the most influential illness which has caused great costs to the heath of population and social economy. Sivelestat sodium (SS) is indicated as an effective cure for lung dysfunction, a characteristic symptom of COVID-19 infection, but its pharmacological target is still unclear. Therefore, a deep understanding of the pathological progression and molecular alteration is an urgent issue for settling the diagnosis and therapy problems of COVID-19. In this study, the bulk ribonucleic acid sequencing (RNA-seq) data of healthy donors and non-severe and severe COVID-19 patients were collected. Then, target differentially expressed genes (DEGs) were screened through integrating sequencing data and the pharmacological database. Besides, with the help of functional and molecular interaction analyses, the potential effect of target gene alteration on COVID-19 progression was investigated. Single-cell sequencing was performed to evaluate the cell distribution of target genes, and the possible interaction of gene-positive cells with other cells was explored by intercellular ligand-receptor pattern analysis. The results showed that matrix metalloproteinase 8 (MMP8) was upregulated in severe COVID-19 patients, which was also identified as a targeting site to SS. Additionally, MMP8 took a core part in the regulatory interaction network of the screened DEGs in COVID-19 and was dramatically correlated with the inflammatory signaling pathway. The further investigations indicated that MMP8 was mainly expressed in myelocytes with a high degree of heterogeneity. MMP8-positive myelocytes interacted with other cell types through RETN-TLR4 and RETN-CAP1 ligand-receptor patterns. These findings emphasize the important role of MMP8 in COVID-19 progression and provide a potential therapeutic target for COVID-19 patients.

Neutrophil Extracellular Trap Formation Model Induced by Monosodium Urate and Phorbol Myristate Acetate: Involvement in MAPK Signaling Pathways

Neutrophil extracellular traps (NETs) formation is a key process in inflammatory diseases like gout, but the underlying molecular mechanisms remain incompletely understood. This study aimed to establish a model to examine the formation of NETs induced by monosodium urate (MSU) and phorbol 12-myristate 13-acetate (PMA) and to elucidate their molecular pathways. Laser confocal microscopy was used to visualize NET formation, while flow cytometry was employed to detect reactive oxygen species (ROS) production. The microstructure of neutrophils was observed by transmission electron microscopy, and the expression of key proteins was determined by Western blotting. Additionally, the effect of various inhibitors targeting the MAPK signaling pathway on NET formation was evaluated. They include the Ras inhibitor Salirasib, Raf inhibitor Vemurafenib, ERK inhibitor PD98059, and p38 MAPK inhibitor SB203580, as well as NADPH oxidase inhibitor DPI and neutrophil elastase inhibitor Alvelestat. The results showed that MSU and PMA triggered significant NET formation, which was accompanied by increased ROS levels, lactate dehydrogenase release, dsDNA, and IL-8. Notably, selective MAPK pathway inhibitors and DPI and Alvelestat, except for SB203580, effectively down-regulated these indicators. These data indicated that the activation of a signaling pathway involving Ras-Raf-ERK, which is dependent on ROS, is crucial for the induction of NET formation by MSU and PMA. Given the involvement of NETs in multiple pathologies, our findings could potentially serve as molecular targets for the intervention and treatment of crystal-related diseases, especially for gout.

Influence of sodium ferulate on neutrophil extracellular traps-platelet activation-mediated endothelial dysfunction in immune small vasculitis

Objective

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is an autoimmune disease that is challenging to treat. This study aimed to identify the effect of sodium ferulate on endothelial dysfunction mediated by neutrophil extracellular trap (NET)-platelet activation in AAV to provide potential strategies for AAV treatment.

Material and Methods

An animal model of myeloperoxidase (MPO)-AAV passive immune vasculitis was established using anti-MPO immunoglobulin G and Rag2 knockout mice. The efficacy and mechanism of action of sodium ferulate in AAV were explored in cultured and isolated endothelial progenitor cells (EPCs), and messenger ribonucleic acid gene expression, relative protein expression, and protein fluorescence intensity were determined through quantitative polymerase chain reaction, Western blotting, and immunofluorescence, respectively. Serum antibody concentrations were determined by enzyme-linked immunosorbent assay, and flow cytometry was used in determining the expression levels of platelet-selectin (CD62p) and procaspase-activating compound-1 (PAC-1) on the surfaces of the platelets. The EPCs' ultramicroscopic structure was observed through transmission electron microscopy.

Results

The expression levels of ANCA, histone H3 citrullinated, and MPO protein fluorescence intensity in MPO-AAV mice were inhibited by sodium ferulate, and the expression levels of CD62p and PAC-1 on the cell surface were reduced. The relative expression levels of β-trace protein (β-TG), soluble thrombomodulin, inducible nitric oxide synthase (iNOS), and tumor necrosis factor α decreased. We found that sodium ferulate inhibited NETs' free DNA and mitigated damage in EPCs. In addition, relative expression levels of von Willebrand Factor, β-TG, and iNOS and serum concentrations of PAC-1, β-TG, and iNOS were inhibited.

Conclusion

Sodium ferulate can treat AAV by inhibiting NET release and platelet activation and reducing endothelial cell damage.

HSYA ameliorates venous thromboembolism by depleting the formation of TLR4/NF-κB pathway-dependent neutrophil extracellular traps

Neutrophil extracellular traps (NETs), released by activated neutrophils, are implicated in various medical conditions, including venous thromboembolism (VTE). To develop effective therapeutic strategies for VTE, it is crucial to elucidate the mechanisms involved. In this study, we explored the role of NETs in VTE pathogenesis and assessed the impact of hydroxyl safflower yellow pigment A (HSYA) treatment on VTE pathogenesis. Various biochemical, pharmacological, and functional assessments were performed in human samples and VTE mouse models. Our findings revealed that NETs formation was enhanced in VTE patients and mouse model. NETs were shown to reduce the viability and integrity of endothelial cells and facilitated ferroptosis in human umbilical vein endothelial cells (HUVECs) in a concentration-dependent manner. Depletion of NETs using the NE inhibitor Alvelestat significantly alleviated ferroptosis in VTE mice. Similarly, NETs depletion markedly attenuated thrombus formation and vein wall thickness in VTE mice. Notably, NETs treatment induced a significant elevation in total N6-Methyladenosine (m6A) RNA methylation level in HUVECs, with the most significant increase observed in methyltransferase-like 3 (METTL3). Mechanistically, the TLR4/NF-κB pathway was activated, and silencing METTL3 reversed the NETs-induced activation of this pathway in HUVECs. Rescue assays illustrated that METTL3 regulated the viability and ferroptosis of NETs-stimulated HUVECs by mediating TLR4 mRNA stability. Additionally, we found that HSYA exerted protective effects against ferroptosis in NETs-induced HUVECs and VTE mice. In summary, HSYA ameliorates VTE by depleting neutrophil extracellular traps through the inhibition of the TLR4/NF-κB pathway, thus providing a novel therapeutic strategy for treating VTE.

Regulating NETs contributes to a novel antiatherogenic effect of MTHSWD via inhibiting endothelial injury and apoptosis

Neutrophil extracellular traps (NETs) are implicated in the occurrence and progression of atherosclerosis (AS), which can result in adverse cardiovascular events. We investigated the potential mechanism of action of Modified Taohong Siwu Decoction (MTHSWD) against AS based on its effect on NETs. A model of unstable plaque in AS was established by tandem stenosis (TS) of the right common carotid artery in ApoE-/- mice combined with a western diet (WD). The research found that MTHSWD reduced the weight of mice with AS to varying degrees, and significantly decreased the levels of plasma total cholesterol (TC) and triglycerides (TG). Meanwhile, we found that MTHSWD not only significantly improved cardiac EF, FS, cardiac hypertrophy, and ventricular remodeling, but also ameliorated the silent and depressed hypoactivity state caused by AS in ApoE-/- mice. Additionally, the study revealed that MTHSWD improved the severity of AS, protected the vascular structure, increased plaque stability and vessel patency. It also significantly reduced vascular cell apoptosis, platelet aggregation, and the presence of inflammatory cells such as neutrophils (NEUs), as well as the expression of neutrocyte elastase (NE) and myeloperoxidase (MPO), which are components of NETs. Subsequently, NEUs studies have shown that MTHSWD not only significantly reduces the dsDNA content of NETs, but also lowers the expression of NETs components NE and citH3. NETs treating the human umbilical vein endothelial cells (HUVECs) demonstrated that NETs differentially increased the protein expression of endothelial inflammatory adhesion factors CD62P, VCAM-1 and ICAM-1, while significantly decreasing the viability of HUVECs. Pharmacological treatment discovered that MTHSWD significantly improved HUVECs viability impaired by NETs, and promoted the growth and proliferation of endothelial cells. Furthermore, it significantly reduced early and late apoptosis of HUVECs caused by NETs, decreased the expression of pro-apoptotic proteins BAX and Cleaved-Caspase-3, and increased the expression of anti-apoptotic protein Bcl-2. Thus, study suggests that MTHSWD may improve body weight, lipid levels, cardiac function, vigour, and the severity of AS in ApoE-/- AS mice. The novel effect of MTHSWD against AS may be attributed to the inhibition of endothelial injury and apoptosis through the regulation of NETs. This, in turn, reduces the levels of platelets, inflammatory cells, and components of NETs in AS plaques, achieving a benign cycle that protects endothelial cells and vascular structure and function. This result provides some clues and evidence for studying the mechanism of action and clinical application of MTHSWD and its active ingredients against AS.