The Neutrophil Life Cycle

Neutrophils in BCR::ABL1 negative MPN: Contributors or bystanders of fibrosis?

BCR::ABL1 negative myeloproliferative neoplasms (MPNs) are a heterogenous group of disorders characterized by clonal proliferation of hematopoietic stem and progenitor cells (HSPCs) within the bone marrow. Although the identification of somatic key driver mutations significantly increased both understanding and diagnostic accuracy of MPNs, many questions about the exact pathophysiology remain unanswered. Increased neutrophil count at diagnosis is a well-recognized predictor of worse disease evolution and survival, nonetheless the exact role of neutrophilic granulocytes within MPN pathophysiology is almost unexplored. As the majority of these cells are residing within the bone marrow, they represent a non-negligible entity within the bone marrow niche and its homeostasis. This review describes how neutrophils might contribute to the development of the inflammatory bone marrow niche, and hereby also fibrosis, associated with MPNs. The versatile functions and effects in different contexts emphasize the necessity for future research oriented to bone marrow in addition to peripheral blood.

Tumor-associated neutrophils in breast cancer: an angel or a devil?

Breast cancer is the most common malignant tumor in women, ranking first globally in both incidence and mortality rates among female malignancies, posing a severe threat to women's physical and mental health. Neutrophils are recognized as the first line of host defense against pathogens and exert beneficial effects in the body. However, emerging evidence has demonstrated that tumor-associated neutrophils (TANs) exhibit a dual role in breast cancer progression and prognosis. Therefore, elucidating their molecular mechanisms may provide novel insights for targeted therapies, potentially improving clinical outcomes for breast cancer patients. This review summarizes the interplay between TANs and breast cancer, their underlying mechanisms, and their potential as immunotherapeutic targets.

Enhancing tofacitinib's therapeutic efficacy in murine arthritis with a synbiotic formulation comprising Bacillus megaterium DSM 32963 and an Omega-3 fatty acid lysine salt

Introduction

Omega-3 polyunsaturated fatty acids (n3-PUFA) are known for their anti-inflammatory benefits, particularly in chronic conditions like rheumatoid arthritis (RA). To resolve an acute inflammation, conversion of n3-PUFA into specialized pro-resolving mediators (SPM) is crucial. Recently, it was shown that the probiotic Bacillus megaterium DSM32963 supports this conversion.

Methods

This study evaluates a synbiotic formulation combining Bacillus megaterium DSM32963 and a unique n3-PUFA-lysine salt as adjunct nutritional supplement to tofacitinib in adjuvant-induced arthritis (AIA) in rats.

Results

Our findings reveal that a combination of low-dose tofacitinib and the synbiotic (ldTofa+Syn) significantly improved all measured arthritis severity parameters, outperforming either single treatment as well as supplementation with a conventional omega-3 ethyl ester that showed no effects on disease severity. The ldTofa+Syn combination also led to a notable reduction in C-reactive protein (CRP) and markers of NETosis in joint tissue, with a significant decrease in neutrophil chemokine CXCL1 observed only in synbiotic-containing groups. Additionally, there was a marked trend towards lower levels of the key inflammatory cytokines TNFα, IL-1β, and IL-6 in the ldTofa+Syn group.

Conclusion

In conclusion, the specific synbiotic formulation shows promise as a complementary nutritional therapy for RA, improving disease outcomes and modulating immune responses.

Acute kidney injury triggers hypoxemia by lung intravascular neutrophil retention that reduces capillary blood flow

Sterile acute kidney injury (AKI) is common in the clinic and frequently associated with unexplained hypoxemia that does not improve with dialysis. AKI induces remote lung inflammation with neutrophil recruitment in mice and humans, but which cellular cues establish neutrophilic inflammation and how it contributes to hypoxemia is not known. Here we report that AKI induced rapid intravascular neutrophil retention in lung alveolar capillaries without extravasation into tissue or alveoli, causing hypoxemia by reducing lung capillary blood flow in the absence of substantial lung interstitial or alveolar edema. In contrast to direct ischemic lung injury, lung neutrophil recruitment during remote lung inflammation did not require cues from intravascular nonclassical monocytes or tissue-resident alveolar macrophages. Instead, lung neutrophil retention depended on the neutrophil chemoattractant CXCL2 released by activated classical monocytes. Comparative single-cell RNA-Seq analysis of direct and remote lung inflammation revealed that alveolar macrophages were highly activated and produced CXCL2 only in direct lung inflammation. Establishing a CXCL2 gradient into the alveolus by intratracheal CXCL2 administration during AKI-induced remote lung inflammation enabled neutrophils to extravasate. We thus discovered important differences in lung neutrophil recruitment in direct versus remote lung inflammation and identified lung capillary neutrophil retention that negatively affected oxygenation by causing a ventilation-perfusion mismatch as a driver of AKI-induced hypoxemia.

Targeting neutrophils for cancer therapy

Neutrophils are among the most abundant immune cell types in the tumour microenvironment and have been associated with poor outcomes across multiple cancer types. Yet despite mounting evidence of their role in tumour progression, therapeutic strategies targeting neutrophils have only recently gained attention and remain limited in scope. This is probably due to the increasing number of distinct neutrophil subtypes identified in cancer and the limited understanding of the mechanisms by which these subsets influence tumour progression and immune evasion. In this Review, we discuss the spectrum of neutrophil subtypes - including those with antitumour activity - and their potential to polarize towards tumour-suppressive phenotypes. We explore the molecular pathways and effector functions by which neutrophils modulate cancer progression, with an emphasis on identifying tractable therapeutic targets. Finally, we examine emerging clinical trials aimed at modulating neutrophil lineages and consider their implications for patient outcomes.

The Neutrophil-to-Lymphocyte Ratio as a Prognostic Biomarker of Fournier's Gangrene Severity: A Meta-Analysis

BACKGROUND/OBJECTIVES

Fournier's Gangrene (FG) is a severe and potentially fatal necrotizing infection of the perianal and genital regions, which necessitates prompt therapeutic interventions to prevent disease progression. Accruing evidence from recent research indicates that the neutrophil‒to-lymphocyte ratio (NLR) can predict clinical severity and mortality risk in patients with critical illnesses across various etiologies. This meta-analysis aimed to assess the efficacy of NLR as a prognostic indicator for mortality in patients with FG.

METHODS

An electronic literature search was conducted across several databases from their inception to 31 May 2024, following a predetermined protocol. Study quality was evaluated using the Cochrane risk of bias tool. A random-effect model was utilized to synthesize the available data.

RESULTS

Twelve studies reporting on 767 patients were included in the meta-analysis. Higher NLR levels at presentation were recorded in non-survivors than in survivors (MD = 4.49 [95% CI: 0.67-8.32]; p = 0.02). A 76% increased mortality risk was detected for patients with an NLR ≥ 8 (1.76 RR [1.35-2.3], p = 0.0001), and the mortality risk was more than twofold greater for patients with an NLR ≥ 10 compared to the remaining patients (RR = 2.31 [1.27-4.21], p = 0.006). All included studies exhibited a moderate to serious risk of bias.

CONCLUSIONS

This meta-analysis reveals that the NLR represents a promising biomarker that can serve as a prognostic indicator in patients with FG. Future studies should address the establishment of proper disease-specific cutoff values to aid in clinical decision-making.

"Remodeling the intestinal immune microenvironment": immune regulation and tissue regeneration by mesenchymal stem/stromal cells in the repair microenvironment of inflammatory bowel disease

The global prevalence of inflammatory bowel disease (IBD) has significantly increased in recent decades. IBD is a long-term, recurring, gastrointestinal inflammatory condition that mainly comprises two primary clinical types: ulcerative colitis and Crohn's disease. The current treatment paradigm for IBD primarily focuses on symptom management. However, this approach does not support mucosal epithelial repair, maintenance of barrier homeostasis, or regulation of biological functions in the gut. Conventional therapies rely on the frequent use of high-dose medications, including antibiotics, nonsteroidal anti-inflammatory drugs, biological agents, and immunomodulators. Recently, mesenchymal stem/stromal cells (MSCs) have gained interest in tissue regeneration owing to their unique ability to differentiate and secrete regulatory factors, including extracellular vesicles (EVs), which play crucial roles in abnormal organization. Various routes of administration have been explored in preclinical and clinical studies to deliver MSCs from diverse tissue sources. The routes include intraperitoneal, intravenous, and local (intracolonic or rectal) delivery. The MSCs employed were obtained from various tissues, including bone marrow, umbilical cord, and adipose tissue. This article reviews the research framework for the application of MSCs and EVs secretion in the treatment of IBD, emphasizing key immunological effects, such as immune microenvironment regulation, intestinal barrier stabilization, and therapeutic approaches targeting intestinal barrier disorders. The discussion primarily focuses on the advantages of MSCs over other biologics, impairment of gut mucosal tissue-resident mesenchymal stem cells in IBD development, immune targets (at the cellular and molecular levels) within the framework of IBD, and the reparative effects of MSCs in the microenvironment of IBD. We aimed to present an overview of the current trends in MSC research and therapy, as well as to identify the challenges and future directions that must be addressed to advance research on MSC-mediated therapeutic strategies for IBD.

Ontogeny, dynamics, and characteristics of neutrophils during the perinatal period

This review examined the dynamic development and unique characteristics of neutrophils during the perinatal period, a critical window when the immune system undergoes rapid reprogramming, based on the mouse studies. In the mouse fetal liver-the primary hematopoietic niche before birth-hematopoietic stem cells and progenitor cells expand in parallel, with granulocyte-monocyte progenitors preferentially differentiating into neutrophils during late gestation. This process, partly driven by granulocyte colony-stimulating factor (G-CSF), substantially increases the number of neutrophils, preparing the neonates for microbial challenges after birth. After birth, there is a surge in circulating neutrophils, likely due to the mobilization of neutrophils from the liver, followed by a microbiota-dependent activation of granulopoiesis in the bone marrow. In addition to their antimicrobial functions, neonatal neutrophils exhibit immunomodulatory characteristics, such as reduced proinflammatory signaling and diminished neutrophil extracellular trap formation. These traits may contribute to tolerance to the microbes and help mitigate excessive inflammation. Finally, unresolved issues related to the phenotypic diversity and precise physiological roles of neutrophils during the perinatal period are addressed, highlighting the need for further research.

IFN-I-mediated neutropoiesis bias drives neutrophil priming and inflammatory comorbidities

Rationale: Local chronic inflammation is increasingly recognized as a driver of systemic inflammatory comorbidities; however, the underlying mechanisms remain incompletely understood. This study investigates the impact of periodontitis on the reprogramming of bone marrow hematopoiesis, with a focus on neutropoiesis bias and its contribution to the exacerbation of arthritis. Methods: Single-cell multiomics sequencing was performed on hematopoietic stem and progenitor cells (HSPCs) isolated from control and ligature-induced periodontitis (LIP) mice to characterize transcriptional and epigenetic alterations. Differentiation trajectories and key transcription factors (TFs) governing neutrophil lineage commitment were identified. Neutrophil priming was assessed using Smart-seq2, bulk RNA-seq, and lipopolysaccharide stimulation assays. The functional role of primed neutrophils in arthritis was evaluated through adoptive transfer, in vivo tracking, and functional blockade within a collagen antibody-induced arthritis model. Type I interferon (IFN-I) signaling was interrogated using Ifnar1⁻/⁻ mice and neutralizing antibodies to elucidate mechanistic pathways. Reversibility of neutropoiesis bias and arthritis aggravation was examined following ligature removal to model periodontitis resolution. Results: Transcriptional and chromatin accessibility profiling demonstrated that LIP induces a selective skewing of HSPC differentiation toward the neutrophil lineage. This reprogramming results in sustained expansion of primed neutrophils, which contribute to the aggravation of distal arthritis. Mechanistically, elevated IFN-I levels promote continuous neutropoiesis bias through activation of IFN-I signaling in HSPCs. Rarg and Nr2f6 were identified as potential TFs contributing to IFN-I-mediated neutrophil lineage commitment. Notably, resolution of periodontitis reversed the hematopoietic bias and mitigated arthritis progression. Conclusions: Periodontitis exacerbates arthritis through IFN-I-mediated neutropoiesis bias, emphasizing the necessity of controlling local chronic inflammation in the management of systemic inflammatory comorbidities.

Microbiota-shaped neutrophil senescence regulates sexual dimorphism in bladder cancer

Sex disparities have been epidemiologically demonstrated in non-reproductive cancers, yet how the sex-specific intrinsic microbiome orchestrates the immune system to affect these disparities is unclear. Here we identify a subpopulation of RETNLG+LCN2+ senescence-like neutrophils (RLSNs) that preferentially accumulate in the male tumor microenvironment and exert a strong immunosuppressive effect to limit antitumor immunity, resulting in poor prognosis for patients with bladder cancer. This difference in enrichment of RLSNs between sexes can be attributed to intestinal bacterium Alistipes shahii, which preferentially populates in females rather than males. A. shahii-associated metabolite lurasidone directly targets iron sequestrator LCN2 in RLSNs. By freeing Fe2+, lurasidone induces ferroptosis, thereby eliminating RLSNs and promoting antitumor immunity in females. In males lacking A. shahii and lurasidone, RLSNs have a survival advantage. Together, these findings demonstrate that a microbiota-lurasidone-LCN2 circuit regulates sexual disparity in bladder cancer and indicates the therapeutic potential of lurasidone for male cancer patients.

G-CSF-Induced Emergency Granulopoiesis Modulates Neutrophil Effector Function in Mice

Neutrophils function as first responders of the immune system by deploying cytotoxic armaments and orchestrating local inflammation. Their functionality is programmed during daily production in the bone marrow through granulopoiesis. During severe inflammation, increased neutrophil demand is met through activation of emergency granulopoiesis. The effect of emergency granulopoiesis on neutrophil functionality remains cryptic. In the present study, we assessed neutrophil function in mice injected with G-CSF (100 µg/kg/d for 3 days) to activate emergency granulopoiesis. We found that emergency granulopoiesis neutrophils exhibit impaired ROS production (n = 6, P = 0.003) and NETosis (n = 5, P < 0.01), but increase neutrophil elastase secretion (n = 9, P < 0.0001) and LPS-induced Tnfa, Il1b, Il1a, Il12a, and Ccl2 expression (n = 13, P < 0.01). To test the impact of emergency granulopoiesis neutrophils on the inflammatory response in vivo, we pre-treated mice with G-CSF and challenged them with zymosan to induce peritonitis. At 4 h post-zymosan injection, peritoneal neutrophils from G-CSF treated mice exhibit increased expression of Ccl2 (n = 3, P < 0.05). Subsequently, we observed enhanced peritoneal macrophage accumulation at 48 h post-zymosan administration in G-CSF-treated mice (n = 5, P < 0.05). These data indicate that emergency granulopoiesis programs neutrophils to have an enhanced immunomodulatory function that orchestrates the subsequent macrophage response in local tissue inflammation.

Senescent neutrophils: a hidden role in cancer progression

Neutrophils have recently received increased attention in cancer because they contribute to all stages of cancer. Neutrophils are so far considered to have a short half-life. However, a growing body of literature has shown that tumor-associated neutrophils (TANs) acquire a prolonged lifespan. This review discusses recent work surrounding the mechanisms by which neutrophils can persist in the tumor microenvironment (TME). It also highlights different scenarios for therapeutic targeting of protumorigenic neutrophils, supporting the idea that, in tumors, inhibition of neutrophil recruitment is not sufficient because these cells can persist and remain hidden from current interventions. Hence, the elimination of long-lived neutrophils should be pursued to increase the efficacy of standard therapy.

Long donor leukocyte telomeres raise risk of severe COVID-19 in recipients of allogeneic hematopoietic cell transplant

Introduction

Short leukocyte telomeres are associated with an increased risk of severe COVID-19 in the general population, likely due to a weakened T-cell response to SARS-CoV-2. This may lead to an amplified neutrophil response, causing pulmonary damage. Allogeneic hematopoietic cell transplant (HCT) offers an experimental setting to examine further the role of telomere length (TL) in COVID-19 severity, as leukocyte TL in recipients post-HCT reflects TL in donor leukocytes before HCT and SARS-CoV-2 infection.

Methods

We examined the relationship between donor leukocyte TL pre-HCT and COVID-19 severity post-HCT in 87 HCT recipients hospitalized for COVID-19 between March 2020 and January 2022. Using the Telomere Shortest Length Assay (TeSLA), we measured leukocyte TL and the percentage of telomeres shorter than 3 kilobases.

Results

The risk of severe COVID-19 in HCT recipients was associated with long telomeres (P=0.005) and a lower percentage of telomeres shorter than 3 kilobases (P=0.01) in donor leukocytes. Moreover, long donor leukocyte telomeres were associated with an increased risk of recipient mortality within four months after COVID-19 hospitalization (P=0.03).

Conclusions

These findings suggest that long donor leukocyte telomeres may trigger an excessive neutrophil response and severe COVID-19 in allogeneic HCT recipients, potentially due to a transplant-related but TL-independent weak T-cell response.

An overview of host immune responses against Leishmania spp. infections

Leishmania spp. infections pose a significant global health challenge, affecting approximately 1 billion people across more than 88 endemic countries. This unicellular, obligate intracellular parasite causes a spectrum of diseases, ranging from localized cutaneous lesions to systemic visceral infections. Despite advancements in modern medicine and increased understanding of the parasite's etiology and associated diseases, treatment options remain limited to pentavalent antimonials, liposomal amphotericin B, and miltefosine. A deeper understanding of the interactions between immune and non-immune cells involved in the clearance of Leishmania spp. infections could uncover novel therapeutic strategies for this debilitating disease. This review highlights recent progress in elucidating how various cell types contribute to the regulation and resolution of Leishmania spp. infections.

Metabolic reprogramming of tumor-associated neutrophils in tumor treatment and therapeutic resistance

Tumor-associated neutrophils (TANs), pivotal immune cells within the tumor microenvironment (TME), exhibit dual potential in both pro- and anti-tumorigenic effects. These cells display remarkable heterogeneity and plasticity within the TME, adapting to hypoxic and nutrient-deprived conditions through metabolic reprogramming while critically influencing tumor progression, metastasis, and immune evasion. The metabolic reprogramming of TANs not only modulates their functional phenotypes but also reshapes tumor biological behaviors and therapeutic responses by regulating metabolic intermediates and cellular interactions within the TME. Therefore, elucidating the mechanisms underlying TANs metabolic reprogramming has significant implications for deciphering the molecular basis of tumorigenesis, identifying novel therapeutic targets, and optimizing immunotherapeutic strategies. This review systematically summarizes current knowledge regarding metabolic reprogramming mechanisms of TANs in the TME and their impact on tumor progression. We particularly focus on: 1) TAN-specific alterations in glucose, lipid, and amino acid metabolism within the TME; 2) Emerging immunotherapeutic strategies targeting TANs metabolic pathways; 3) Recent advances in understanding TAN-mediated immune evasion and therapy resistance. Furthermore, this review discusses potential challenges and corresponding solutions in targeting TANs metabolic reprogramming for therapeutic intervention, aiming to provide novel insights for advancing cancer immunotherapy.

Aging platelets shift their hemostatic properties to inflammatory functions

ABSTRACT

Platelets are crucial players in hemostasis and thrombosis but also contribute to immune regulation and host defense, using different receptors, signaling pathways, and effector functions, respectively. Whether distinct subsets of platelets specialize in these diverse tasks is insufficiently understood. Here, we used a pulse-labeling method in Mus musculus models for tracking in vivo platelet aging and its functional implications. Using in vitro and in vivo assays, we reveal that young, reticulated platelets show heightened responses in the setting of clot formation, with corresponding, increased responses to agonists, adhesion, and retractile function. Unexpectedly, aged platelets lose their hemostatic proficiency but are more prone to react to inflammatory challenge: compared with reticulated platelets, this cohort was more likely to form platelet-leukocyte aggregates and showed increased adhesion to neutrophils in vitro, as well as enhanced bactericidal function. In vivo, this was reflected in increased pulmonary recruitment of aged platelets in an acute lung injury model. Proteomic analyses confirmed the upregulation of immune pathways in this cohort, including enhanced procoagulant function. In mouse models of prolonged platelet half-life, this resulted in increased pulmonary leukocyte infiltration and inflammation upon acute lung injury. Similarly, human platelet concentrates decreased their hemostatic function and elevated their putative immunomodulatory potential in vitro over time, and in a mouse model of platelet transfusion, aged platelet concentrates resulted in augmented inflammation. In summary, we show that platelets exhibit age-dependent phenotypic shifts, allowing them to fulfill their diverse tasks in the vasculature. Because functional alterations of aging platelets extend to platelet concentrates, this may hold important implications for transfusion medicine.

Neutrophilic inflammation in bronchiectasis

Noncystic fibrosis bronchiectasis, hereafter referred to as bronchiectasis, is a chronic, progressive lung disease that can affect people of all ages. Patients with clinically significant bronchiectasis have chronic cough and sputum production, as well as recurrent respiratory infections, fatigue and impaired health-related quality of life. The pathophysiology of bronchiectasis has been described as a vicious vortex of chronic inflammation, recurring airway infection, impaired mucociliary clearance and progressive lung damage that promotes the development and progression of the disease. This review describes the pivotal role of neutrophil-driven inflammation in the pathogenesis and progression of bronchiectasis. Delayed neutrophil apoptosis and increased necrosis enhance dysregulated inflammation in bronchiectasis and failure to resolve this contributes to chronic, sustained inflammation. The excessive release of neutrophil serine proteases, such as neutrophil elastase, cathepsin G and proteinase 3, promotes a protease-antiprotease imbalance that correlates with increased inflammation in bronchiectasis and contributes to disease progression. While there are currently no licensed therapies to treat bronchiectasis, this review will explore the evolving evidence for neutrophilic inflammation as a novel treatment target with meaningful clinical benefits.

Neutrophil-derived vesicles control complement activation to facilitate inflammation resolution

Although subsets with immunosuppressive properties exist, neutrophils are typically known for their pro-inflammatory role and pathogen clearance capabilities. Here, we reveal that neutrophils can paradoxically aid in resolving inflammation by actively producing anti-inflammatory extracellular vesicles. These large aging-neutrophil-derived vesicles (LAND-Vs) do not fit into classical vesicle categorizations due to their specific size, structure, or biogenesis pathway. They are protected from efferocytotic clearance by phagocytes due to surface "do not eat me" signals and accumulate in the resolution phase of inflammation. CD55 on LAND-Vs exerts a robust, sustained anti-inflammatory effect by inhibiting complement 3 convertase, thereby reducing neutrophil recruitment and tissue damage. CD55+ LAND-Vs originate in ordered lipid raft domains, where CD55 accumulates asymmetrically during neutrophil aging, and are subsequently formed through RhoA-dependent budding. Collectively, LAND-V emerges as a pivotal physiological immunomodulator and showcases functions that transcend the limited lifespan of neutrophils, offering a therapeutic target for inflammatory and infectious diseases.

Global trends in tumor-associated neutrophil research: a bibliometric and visual analysis

Background

Tumor-associated neutrophils (TANs) play crucial roles in tumor progression, immune response modulation, and the therapeutic outcomes. Despite significant advancements in TAN research, a comprehensive bibliometric analysis that objectively presents the current status and trends in this field is lacking. This study aims to fill this gap by visually analyzing global trends in TANs research using bibliometric and knowledge mapping techniques.

Methods

We retrieved articles and reviews related to TANs from the Web of Science core collection database, spanning the period from 2012 to2024. The data was analyzed using bibliometric tools such as Excel 365, CiteSpace, VOSviewer, and Bibliometrix (R-Tool of R-Studio) to identify key trends, influential countries and institutions, collaborative networks. and citation patterns.

Results

A total of 6l5 publications were included in the bibliometric analysis, showing a significant upward trend in TANs research over the last two decades. The United States and China emerged as the leading contributors with the highest number of publications and citations. The journal with the most publications in this field is Frontiers in Immunology, Prominent authors such as Fridlender ZG was identified as the key contributor, with his works frequently cited. The analysis highlighted major research themes. including the role of TANs in tumor microenvironment modulation, their dual functions in tumor promotion and suppression, and the exploration of TANs-targeted therapies, Emerging research hotspots include studies on TANs plasticity and their interactions with other immune cells.

Conclusion

This study is the first to employ bibliometric methods to visualize trends and frontiers in TANs research. The findings provide valuable insights into the evolution of the field, highlighting critical areas for future investigation and potential collaborative opportunities. This comprehensive analysis serves as a crucial resource for researchers and practitioners aiming to advance TAN research and its application in cancer therapy.

Enniatin B alters bovine polymorphonuclear leukocytes phagocytosis and extracellular reactive oxygen species production in vitro

Enniatins (ENNs) affect human and animal health. Different ENN analogs have been identified, but Enniatin B (ENN B) is the most detected in foods and feeds. This study investigated the effect of ENN B on bovine polymorphonuclear leukocytes (PMNs) challenged with increasing ENN B concentrations (0.625, 1.25, 2.5, 5, and 10 μM). Bovine PMNs were isolated from the peripheral blood of dairy cows to evaluate the cell viability, chemotactic function, ability to phagocyte Gram+ and Gram- microorganisms, and extracellular Reactive Oxygens Species (ROS), with or without phorbol 12-myristate-13-acetate (PMA) as a pro-inflammatory challenge. Results demonstrated that ENN B did not affect bovine PMN viability and chemotactic activity at all concentrations (p = 0.952; p = 0.218, respectively). E. coli and S. aureus phagocytosis ability were reduced by ENN B at the highest concentrations (5 and 10 μM) compared to the negative control (p ≤ 0.001; p = 0.001, respectively). Extracellular ROS production was increased by ENN B challenge under physiological and pro-inflammatory conditions (p = 0.014; p < 0.001, respectively). In conclusion, ENN B did not exert cytotoxic effects on bovine PMNs, while reduced phagocytic ability and increased the production of extracellular ROS, highlighting its potential role as an immunomodulator of the bovine innate immune response in vitro. IMPLICATIONS: Emerging mycotoxin Enniatin B is a common grain contaminant worldwide that can exert cytotoxic and immunotoxic effects in animal cells. We hypothesized that Enniatin B could in vitro affect the bovine immune response. In our study, Enniatin B did not affect bovine polymorphonuclear cell viability and chemotaxis, while a reduction of phagocytosis and a modulation of extracellular reactive oxygen species were observed. The present study shows that Enniatin B in vitro exerts a potential role as an immunomodulator of the bovine innate immune response putting animals at an increased risk of infection diseases.

Acute kidney injury triggers hypoxemia by inducing intravascular neutrophil retention that reduces lung capillary blood flow

Sterile acute kidney injury (AKI) is common in the clinic and frequently associated with hypoxemia that does not improve with dialysis and remains incompletely understood. AKI induces remote lung inflammation with neutrophil recruitment in mice and humans, but which cellular cues establish neutrophilic inflammation and how it contributes to hypoxemia is not known. Here we report that AKI induces rapid intravascular neutrophil retention in lung alveolar capillaries without any significant extravasation into tissue or alveoli, causing hypoxemia by reducing lung capillary blood flow in the absence of any significant lung interstitial or alveolar edema. In contrast to direct ischemic lung injury, lung neutrophil recruitment during remote lung inflammation did not require cues from intravascular non-classical monocytes or tissue-resident alveolar macrophages. Instead, lung neutrophil retention depended on neutrophil chemoattractant CXCL2 released by activated intravascular classical monocytes. Comparative single-cell RNA-sequencing analysis of direct and remote lung inflammation revealed that alveolar macrophages are highly activated and produce the neutrophil chemoattractant CXCL2 only in direct lung inflammation. Establishing a CXCL2 gradient into the alveolus by intratracheal administration of CXCL2 during AKI-induced remote lung inflammation enabled neutrophils to extravasate. We thus discovered important differences in lung neutrophil recruitment in direct versus remote lung inflammation and identified lung capillary neutrophil retention that negatively affects oxygenation by causing a ventilation-perfusion mismatch as a novel driver of AKI-induced hypoxemia.

Staphylococcus aureus in Inflammation and Pain: Update on Pathologic Mechanisms

Staphylococcus aureus (S. aureus) is a Gram-positive bacterium of significant clinical importance, known for its versatility and ability to cause a wide array of infections, such as osteoarticular, pulmonary, cardiovascular, device-related, and hospital-acquired infections. This review describes the most recent evidence of the pathogenic potential of S. aureus, which is commonly part of the human microbiota but can lead to severe infections. The prevalence of pathogenic S. aureus in hospital and community settings contributes to substantial morbidity and mortality, particularly in individuals with compromised immune systems. The immunopathogenesis of S. aureus infections involves intricate interactions with the host immune and non-immune cells, characterized by various virulence factors that facilitate adherence, invasion, and evasion of the host's defenses. This review highlights the complexity of S. aureus infections, ranging from mild to life-threatening conditions, and underscores the growing public health concern posed by multidrug-resistant strains, including methicillin-resistant S. aureus (MRSA). This article aims to provide an updated perspective on S. aureus-related infections, highlighting the main diseases linked to this pathogen, how the different cell types, virulence factors, and signaling molecules are involved in the immunopathogenesis, and the future perspectives to overcome the current challenges to treat the affected individuals.

Intranasal delivery of hMSC-derived supernatant for treatment of ischemic stroke by inhibiting the pro-inflammatory polarization of neutrophils

BACKGROUND

Stem cells utilized for ischemic stroke treatment often display unstable homing capabilities and diminished activity in vivo, limiting their neuroprotective efficacy. Furthermore, the optimal delivery route for stem cells remains undetermined. While the cytokines secreted by stem cells show promise in modulating post-stroke inflammation, the direct application of these supernatants in ischemic stroke treatment and the underlying mechanisms are still unclear.

METHODS

Secretory supernatants (hMSC-L) and cell lysate products (hMSC-M) from primary human umbilical cord mesenchymal stem cells-cultured medium were administered intranasally to mice with cerebral ischemia. The neuroprotective effects of hMSC-L and hMSC-M were assessed with TTC staining, behavioral tests and pathological staining. Flow cytometry and qPCR evaluated the expression of immune cells and cytokines in the CNS and peripheral immune organs. In vitro, flow cytometry and ELISA measured the effects of hMSC-L and hMSC-M on N2 polarization and inflammatory cytokines expression in primary murine neutrophils. Western blot analysis determined the impact of hMSC-L and hMSC-M on the PPAR-γ/STAT6/SOCS1 pathway, which is crucial for N2 neutrophil polarization.

RESULTS

TTC staining, behavioral experiments, and pathological assessments reveal intranasal delivery of hMSC-L and hMSC-M significantly reduces the infarct volume of mice with cerebral ischemia, improves neurological function scores, and promotes motor function recovery. Higher concentrations of hMSC-M contributed a more pronounced effect on neuropathological improvements in ischemic mice. Intranasal delivery of hMSC-L and hMSC-M significantly reduces neutrophil infiltration in the brain post-stroke and increases the proportion of anti-inflammatory N2-subtype neutrophils, boosting the expression levels of IL-10 and TGF-β. In vitro experiments demonstrate that hMSC-L and hMSC-M promote nuclear translocation of PPAR-γ in neutrophils stimulated with PMA, activating the downstream STAT6/SOCS1 signaling pathway to encourage N2-subtype neutrophil polarization.

CONCLUSIONS

Intranasal delivery of hMSC-L and hMSC-M effectively ameliorates cerebral ischemic injury in mice, comparable to traditional administration routes like intravenous delivery. Treatment with hMSC-L and hMSC-M enhances the PPAR-γ/STAT6/SOCS1 pathway and improves the neuroinflammatory response post-stroke by increasing N2 neutrophil infiltration. These results provide a theoretical basis for a deeper understanding of the mechanisms of stem cell therapy and for exploring suitable delivery pathways of stem cell treatment.

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.

Neutrophil Engulfment in Cancer: Friend or Foe?

Neutrophils, the most abundant circulating white blood cells, are essential for the initial immune response to infection and injury. Emerging research reveals a dualistic function of neutrophils in cancer, where they can promote or inhibit tumor progression. This dichotomy is influenced by the tumor microenvironment, with neutrophils capable of remodeling the extracellular matrix, promoting angiogenesis, or alternatively inducing cancer cell death and enhancing immune responses. An intriguing yet poorly understood aspect of neutrophil-cancer interactions is the phenomenon of neutrophil engulfment by cancer cells, which has been observed across various cancers. This process, potentially mediated by LC3-associated phagocytosis (LAP), raises questions about whether it serves as a mechanism for immune evasion or contributes to tumor cell death through pathways like ferroptosis. This review examines current knowledge on neutrophil development, their roles in cancer, and the mechanisms of LAP in neutrophil engulfment by tumor cells. We discuss how manipulating LAP impacts cancer progression and may represent a therapeutic strategy. We also explore neutrophils' potential as delivery vehicles for cancer therapeutic agents. Understanding the complex functions of tumor-associated neutrophils (TANs) and the molecular mechanisms underlying LAP in cancer may open new avenues for effective therapeutic interventions and mitigate potential risks.

The success of the tumor immunotherapy: neutrophils from bench to beside

The present immune therapy was focused on the immune checkpoint blockade or Chimeric Antigen Receptor T-Cell Immunotherapy (CART) transfer, but how to activate the innate immune system to antitumor still lags out. Neutrophils are the most abundant circulating leukocytes in human, and heterogeneous neutrophils have been increasingly recognized as important players in tumor progression. They play double "edge-sward" by either supporting or suppressing the tumor growth, including driving angiogenesis, extracellular matrix remodeling to promote tumor growth, participating in antitumor adaptive immunity, or killing tumor cells directly to inhibit the tumor growth. The complex role of neutrophils in various tumors depends on the tumor microenvironment (TME) they are located, and emerging evidence has suggested that neutrophils may determine the success of tumor immunotherapy in the context of the immune checkpoint blockade, innate immune training, or drug-loaded extracellular microvesicles therapy, which makes them become an exciting target for tumor immunotherapy, but still with challenges. Here, we summarize the latest insights on how to activate neutrophils in antitumor immunity and discuss the advances of neutrophil-targeted immunotherapy strategies.

Tissue-resident immune cells: from defining characteristics to roles in diseases

Tissue-resident immune cells (TRICs) are a highly heterogeneous and plastic subpopulation of immune cells that reside in lymphoid or peripheral tissues without recirculation. These cells are endowed with notably distinct capabilities, setting them apart from their circulating leukocyte counterparts. Many studies demonstrate their complex roles in both health and disease, involving the regulation of homeostasis, protection, and destruction. The advancement of tissue-resolution technologies, such as single-cell sequencing and spatiotemporal omics, provides deeper insights into the cell morphology, characteristic markers, and dynamic transcriptional profiles of TRICs. Currently, the reported TRIC population includes tissue-resident T cells, tissue-resident memory B (BRM) cells, tissue-resident innate lymphocytes, tissue-resident macrophages, tissue-resident neutrophils (TRNs), and tissue-resident mast cells, but unignorably the existence of TRNs is controversial. Previous studies focus on one of them in specific tissues or diseases, however, the origins, developmental trajectories, and intercellular cross-talks of every TRIC type are not fully summarized. In addition, a systemic overview of TRICs in disease progression and the development of parallel therapeutic strategies is lacking. Here, we describe the development and function characteristics of all TRIC types and their major roles in health and diseases. We shed light on how to harness TRICs to offer new therapeutic targets and present burning questions in this field.

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.

New insights into constitutive neutrophil death

Neutrophils undergo rapid aging and death known as constitutive or spontaneous death. Constitutive neutrophil death (CND) contributes to neutrophil homeostasis and inflammation resolution. CND has long been considered to be apoptotic until our findings reveal that it was a heterogeneous combination of diverse death. Furthermore, dead neutrophils retain functional roles via multiple manners. This review provides an overview of current research on the mechanism and modulation of CND. More noteworthy, we also summarize the after-death events of neutrophils. The fate of neutrophils can be changed under pathological conditions, so the involvement of CND in diseases and CND-related therapeutic strategies are also addressed.

Associated factors and prognostic implications of neutropenia in individuals with HIV/AIDS

BACKGROUND

Neutropenia frequently presents as a hematological manifestation among people living with HIV/AIDS (PLWHA). This study explores the factors associated with neutropenia in PLWHA and its prognostic significance.

METHODS

We conducted a retrospective case-control study of the clinical data from 780 cases of individuals living with HIV/AIDS, who were admitted to Zhongnan Hospital of Wuhan University over the period from January 2016 to September 2020. We categorized the patients into two different groups based on absolute neutrophil Count (ANC): neutropenia group (ANC < 2.0 × 109/L, 33.7%) and non-neutropenia group (ANC ≥ 2.0 × 109/L, 66.3%). We analyzed the co-infections, blood routine test, infection indicators, lymphocyte subpopulation, bone marrow cell cytology, bone marrow morphology in both groups. Additionally, we analyzed the prognosis of the patients.

RESULTS

The results of multifactorial logistic regression showed that increased C-reactive protein (CRP) (p<0.001, adjusted odds ratio [AOR] = 0.984, 95% CI:0.975-0.993), Monocyte (MONO) (p = 0.011, AOR = 0.091, 95% CI: 0.013-0.637), CD19+B lymphocytes (p = 0.008, AOR = 0.990, 95% CI: 0.983-0.997), Bone marrow granulocyte (p = 0.017, AOR = 0.936, 95% CI: 0.883-0.992) were protective factors for neutropenia in PLWHA. Kaplan-Meier survival curve analysis showed that Grade 2 neutropenia group (ANC<0.5 × 109/L) had a worse prognosis than Grade 1 neutropenia group (0.5 × 109/L ≤ ANC<2 × 109/L, p = 0.019) and non-neutropenia group (ANC ≥ 2.0 × 109/L, p = 0.008). Older age (p = 0.002), lower hemoglobin levels (p = 0.001), and a reduced proportion of bone marrow granulocytes (p = 0.002) were associated with a poorer prognosis in PLWHA.

CONCLUSION

HIV infection can lead to reduced neutrophil counts and damage to the immune system through multiple pathways. Severe neutropenia results in a worse prognosis, making timely diagnosis and treatment of neutropenia in this population essential.

Innate immune response to bone fracture healing

The field of osteoimmunology has primarily focused on fracture healing in isolated musculoskeletal injuries. The innate immune system is the initial response to fracture, with inflammatory macrophages, cytokines, and neutrophils arriving first at the fracture hematoma, followed by an anti-inflammatory phase to begin the process of new bone formation. This review aims to first discuss the current literature and knowledge gaps on the immune responses governing single fracture healing by encompassing the individual role of macrophages, neutrophils, cytokines, mesenchymal stem cells, bone cells, and other immune cells. This paper discusses the interactive effects of these cellular responses underscoring the field of osteoimmunology. The critical role of the metabolic environment in guiding the immune system properties will be highlighted along with some effective therapeutics for fracture healing in the context of osteoimmunology. However, compared to isolated fractures, which frequently heal well, long bone fractures in over 30 % of polytrauma patients exhibit impaired healing. Clinical evidence suggests there may be distinct physiologic and inflammatory pathways altered in polytrauma resulting in nonunion. Nonunion is associated with worse patient outcomes and increased societal healthcare costs. The dysregulated immunomodulatory/inflammatory response seen in polytrauma may lead to this increased nonunion rate. This paper will investigate the differences in immune response between isolated and polytrauma fractures. Finally, future directions for fracture studies are explored with consideration of the emerging roles of newly discovered immune cell functions in fracture healing, the existing challenges and conflicting results in the field, the translational potential of these studies in clinic, and the more complex nature of polytrauma fractures that can alter cell functions in different tissues.

Neutrophils in cancer: from biology to therapy

The view of neutrophils has shifted from simple phagocytic cells, whose main function is to kill pathogens, to very complex cells that are also involved in immune regulation and tissue repair. These cells are essential for maintaining and regaining tissue homeostasis. Neutrophils can be viewed as double-edged swords in a range of situations. The potent killing machinery necessary for immune responses to pathogens can easily lead to collateral damage to host tissues when inappropriately controlled. Furthermore, some subtypes of neutrophils are potent pathogen killers, whereas others are immunosuppressive or can aid in tissue healing. Finally, in tumor immunology, many examples of both protumorigenic and antitumorigenic properties of neutrophils have been described. This has important consequences for cancer therapy, as targeting neutrophils can lead to either suppressed or stimulated antitumor responses. This review will discuss the current knowledge regarding the pro- and antitumorigenic roles of neutrophils, leading to the concept of a confused state of neutrophil-driven pro-/antitumor responses.

Inflammasome-mediated pyroptosis in defense against pathogenic bacteria

Macrophages, neutrophils, and epithelial cells are pivotal components of the host's immune response against bacterial infections. These cells employ inflammasomes to detect various microbial stimuli during infection, triggering an inflammatory response aimed at eradicating the pathogens. Among these inflammatory responses, pyroptosis, a lytic form of cell death, plays a crucial role in eliminating replicating bacteria and recruiting immune cells to combat the invading pathogen. The immunological function of pyroptosis varies across macrophages, neutrophils, and epithelial cells, aligning with their specific roles within the innate immune system. This review centers on elucidating the role of pyroptosis in resisting gram-negative bacterial infections, with a particular focus on the mechanisms at play in macrophages, neutrophils, and intestinal epithelial cells. Additionally, we underscore the cell type-specific roles of pyroptosis in vivo in these contexts during defense.

Neutrophils in cancer drug resistance: Roles and therapeutic opportunities

The tumor microenvironment (TME) is closely associated with the therapeutic response and clinical outcome of cancer drug therapies, which mainly include immunotherapy, chemotherapy and targeted therapy. Neutrophils that infiltrate tumors, also known as tumor-associated neutrophils (TANs), constitute a primary part of the TME. However, the functional importance of TANs in cancer drug therapy has long been overlooked because of their relatively short life span. Recent studies have shown that TANs play crucial protumoral or antitumoral roles in cancer drug treatment, largely because of their diversity and plasticity. This review describes the development, heterogeneity and recruitment of neutrophils in the context of cancer and emphasizes the role and mechanisms of TANs in cancer drug resistance. Additionally, several potential neutrophil-targeted strategies are discussed.

The Evolving Role of Neutrophils and Neutrophil Extracellular Traps (NETs) in Obesity and Related Diseases: Recent Insights and Advances

Obesity is a chronic, multifactorial disease characterized by persistent low-grade tissue and systemic inflammation. Fat accumulation in adipose tissue (AT) leads to stress and dysfunctional adipocytes, along with the infiltration of immune cells, which initiates and sustains inflammation. Neutrophils are the first immune cells to infiltrate AT during high-fat diet (HFD)-induced obesity. Emerging evidence suggests that the formation and release of neutrophil extracellular traps (NETs) play a significant role in the progression of obesity and related diseases. Additionally, obesity is associated with an imbalance in gut microbiota and increased intestinal barrier permeability, resulting in the translocation of live bacteria, bacterial deoxyribonucleic acid (DNA), lipopolysaccharides (LPS), and pro-inflammatory cytokines into the bloodstream and AT, thereby contributing to metabolic inflammation. Recent research has also shown that short-chain fatty acids (SCFAs), produced by gut microbiota, can influence various functions of neutrophils, including their activation, migration, and the generation of inflammatory mediators. This review comprehensively summarizes recent advancements in understanding the role of neutrophils and NET formation in the pathophysiology of obesity and related disorders while also focusing on updated potential therapeutic approaches targeting NETs based on studies conducted in humans and animal models.

Neutrophil diversity and function in health and disease

Neutrophils, the most abundant type of granulocyte, are widely recognized as one of the pivotal contributors to the acute inflammatory response. Initially, neutrophils were considered the mobile infantry of the innate immune system, tasked with the immediate response to invading pathogens. However, recent studies have demonstrated that neutrophils are versatile cells, capable of regulating various biological processes and impacting both human health and disease. Cytokines and other active mediators regulate the functional activity of neutrophils by activating multiple receptors on these cells, thereby initiating downstream signal transduction pathways. Dysfunctions in neutrophils and disruptions in neutrophil homeostasis have been implicated in the pathogenesis of numerous diseases, including cancer and inflammatory disorders, often due to aberrant intracellular signaling. This review provides a comprehensive synthesis of neutrophil biological functions, integrating recent advancements in this field. Moreover, it examines the biological roles of receptors on neutrophils and downstream signaling pathways involved in the regulation of neutrophil activity. The pathophysiology of neutrophils in numerous human diseases and emerging therapeutic approaches targeting them are also elaborated. This review also addresses the current limitations within the field of neutrophil research, highlighting critical gaps in knowledge that warrant further investigation. In summary, this review seeks to establish a comprehensive and multidimensional model of neutrophil regulation, providing new perspectives for potential clinical applications and further research.

Neutrophils in oncolytic virus immunotherapy

Oncolytic viruses have emerged as a highly promising modality for cancer treatment due to their ability to replicate specifically within tumors, carry therapeutic genes, and modulate the immunosuppressive tumor microenvironment through various mechanisms. Additionally, they show potential synergy with immune checkpoint inhibitors. A study report indicates that from 2000 to 2020, 49.5% of oncolytic viruses were administered intratumorally and 35% intravenously during clinical trials. However, both administration methods face significant challenges, particularly with intravenous delivery, which encounters issues such as non-specific tissue uptake, neutralizing antibody responses, and antiviral effects mediated by various immune cells. Despite extensive research into the antiviral roles of CD8+ T cells and NK cells in oncolytic virus therapy, neutrophils-constituting approximately 50% to 70% of human peripheral blood leukocytes-have received relatively little attention. Neutrophils are the most abundant leukocyte subset in peripheral circulation, known for their phagocytic activity. Beyond their traditional roles in bacterial and fungal infections, emerging literature suggests that neutrophils also play a critical role in the body's antiviral responses. Given the gaps in understanding the role of neutrophils in oncolytic virus therapy, this article reviews current literature on this topic. It aims to provide a theoretical foundation for developing oncolytic virus-based cancer therapies and enhancing their anti-tumor efficacy in future clinical treatments.

Prolonged Survival of Neutrophils Induced by Tumor-Derived G-CSF/GM-CSF Promotes Immunosuppression and Progression in Laryngeal Squamous Cell Carcinoma

Tumor-associated neutrophils (TANs) play a crucial role in tumor progression and exhibit prolonged survival. However, the mechanism underlying their extended lifespan and significance in laryngeal squamous cell carcinoma (LSCC) remains unclear. Herein, it is observed that apoptosis of TANs is significantly delayed owing to induction by tumor-derived G-CSF and GM-CSF through the activation of the PI3K-AKT signaling pathway, upregulation of anti-apoptotic Mcl-1 expression, and downregulation of activated Caspase-3 levels. It is found that prolonged survival of TANs leads to the accumulation of aged CXCR4+ neutrophils that exhibit potent immunosuppressive properties and are associated with poor patient prognosis. Furthermore, extended survival promotes the enhanced immunosuppressive function of CD8+ T cells by TANs, thereby facilitating the in vitro and in vivo progression and growth of human LSCC tumors. Importantly, this effect could be reversed by blocking G-CSF and GM-CSF stimulation of neutrophils. These findings elucidate the pivotal role of pathologically prolonged neutrophil survival in impairing CD8+ T cell immunity and suggest targeting it as a potential therapeutic strategy for tumors.

CMTM3 regulates neutrophil activation and aggravates sepsis through TLR4 signaling

Regulation of neutrophil activation plays a significant role in managing sepsis. CKLF-like MARVEL transmembrane domain containing (CMTM)3 is a membrane protein involved in immune response. Here, we find that CMTM3 expression is elevated in sepsis and plays a crucial role in mediating the imbalance of neutrophil migration. Cmtm3 knockout improves the survival rate of septic mice, mitigate inflammatory responses, and ameliorate organ damage. Mechanistically, the deletion of Cmtm3 reduced the expression of Toll-like receptor 4 (TLR4) on neutrophils, leading to a decrease in the expression of C-X-C motif chemokine receptor 2 (CXCR2) on the cell membrane. This resulted in a reduced migration of neutrophils from the bone marrow to the bloodstream, thereby attenuating their recruitment to vital organs. Our findings suggest that targeting CMTM3 holds promise as a therapeutic approach to ameliorate the dysregulation of neutrophil migration and multi-organ damage associated with sepsis.

Single-cell proteomics delineates murine systemic immune response to blast lung injury

Victims of explosive events frequently suffer from blast lung injuries. Immune system has been implicated in the pathogenesis of this disease. However, systemic immune responses underlying the progression and recovery of injury repair remain poorly understood. Here, we depict the systemic landscape of immune dysregulation during blast lung injury and uncover immune recovery patterns. Single-cell analyses reveal dramatic changes in neutrophils, macrophages, monocytes, dendritic cells, and eosinophils after a gas explosion, along with early involvement of CD4 T, CD8 T, and Th17 cells. We demonstrate that myeloid cells primarily exert functions during the acute phase, while the spleen serves as an alternative source of granulocytes. Granulopoiesis is initiated in the bone marrow at a later stage during blast lung injury recovery, rather than at the acute stage. These findings contribute to a better understanding of the pathogenesis and provide valuable insights for potential immune interventions in blast lung injury.

Unraveling the complex role of neutrophils in lymphoma: From pathogenesis to therapeutic approaches (Review)

Lymphoma, a malignancy of the lymphatic system, which is critical for maintaining the body's immune defenses, has become a focal point in recent research due to its intricate interplay with neutrophils-white blood cells essential for combating infections and inflammation. Unlike prior perceptions associating neutrophils only with tumor support, contemporary studies underscore their intricate and multifaceted involvement in the immune response to lymphoma. Recognizing the nuanced participation of neutrophils in lymphoma is crucial for developing innovative treatments to improve patient outcomes.

Cell-mediated nanoparticle delivery systems: towards precision nanomedicine

Cell-mediated nanoparticle delivery systems (CMNDDs) utilize cells as carriers to deliver the drug-loaded nanoparticles. Unlike the traditional nanoparticle drug delivery approaches, CMNDDs take the advantages of cell characteristics, such as the homing capabilities of stem cells, inflammatory chemotaxis of neutrophils, prolonged blood circulation of red blood cells, and internalization of macrophages. Subsequently, CMNDDs can easily prolong the blood circulation, cross biological barriers, such as the blood-brain barrier and the bone marrow-blood barrier, and rapidly arrive at the diseased areas. Such advantageous properties make CMNDDs promising delivery candidates for precision targeting. In this review, we summarize the recent advances in CMNDDs fabrication and biomedical applications. Specifically, ligand-receptor interactions, non-covalent interactions, covalent interactions, and internalization are commonly applied in constructing CMNDDs in vitro. By hitchhiking cells, such as macrophages, red blood cells, monocytes, neutrophils, and platelets, nanoparticles can be internalized or attached to cells to construct CMNDDs in vivo. Then we highlight the recent application of CMNDDs in treating different diseases, such as cancer, central nervous system disorders, lung diseases, and cardiovascular diseases, with a brief discussion about challenges and future perspectives in the end.

The Promise of a Pointillist Perspective for Comparative Immunology

Most studies in comparative immunology involve investigations into the detailed mechanisms of the immune system of a nonmodel organism. Although this approach has been insightful, it has promoted a deep understanding of only a handful of species, thus inhibiting the recognition of broad taxonomic patterns. Here, we call for investigating the immune defenses of numerous species within a pointillist framework, that is, the meticulous, targeted collection of data from dozens of species and investigation of broad patterns of organismal, ecological, and evolutionary forces shaping those patterns. Without understanding basic immunological patterns across species, we are limited in our ability to extrapolate and/or translate our findings to other organisms, including humans. We illustrate this point by focusing predominantly on the biological scaling literature with some integrations of the pace of life literature, as these perspectives have been the most developed within this framework. We also highlight how the more traditional approach in comparative immunology works synergistically with a pointillist approach, with each approach feeding back into the other. We conclude that the pointillist approach promises to illuminate comprehensive theories about the immune system and enhance predictions in a wide variety of domains, including host-parasite dynamics and disease ecology.

Neutrophils inhibit bone formation by directly contacting osteoblasts and suppressing osteogenic differentiation

Neutrophils have been extensively studied for their critical roles in supporting immune defense mechanisms, initiating bone regeneration, and promoting angiogenesis. Nonetheless, the influence of neutrophils on physiological conditions, particularly in the context of bone development, remains incompletely understood. In this study, we examined the effects of non-inflammatory neutrophils on bone physiology by depleting Ly6G+ neutrophils and inducing neutropenia through myelosuppression. Our results demonstrated a notable increase in bone mass and a decrease in the bone marrow cavity upon depletion of the neutrophils. These effects were attributed to the direct interaction between neutrophils and osteoblasts, independent of reduced secretion of typical inflammatory cytokines or diminished osteoclast differentiation. This observation suggests a non-inflammatory function of neutrophils within the endosteal microenvironment, where they regulate osteogenic differentiation to preserve optimal bone mass, shape healthy three-dimensional bone trabecular structures, and create ample space for hematopoietic niche development.

Atomic Force Microscopy and Scanning Ion-Conductance Microscopy for Investigation of Biomechanical Characteristics of Neutrophils

Scanning probe microscopy (SPM) is a versatile tool for studying a wide range of materials. It is well suited for investigating living matter, for example, in single-cell neutrophil studies. SPM has been extensively utilized to analyze cell physical properties, providing detailed insights into their structural and functional characteristics at the nanoscale. Its long-standing application in this field highlights its essential role in cell biology and immunology research, significantly contributing to understanding cellular mechanics and interactions. In this review, we discuss the application of SPM techniques, specifically atomic force microscopy (AFM) and scanning ion-conductance microscopy (SICM), to study the fundamental functions of neutrophils. In addition, recent advances in the application of SPM in single-cell immunology are discussed. The application of these techniques allows for obtaining data on the morphology, topography, and mechanical and electrochemical properties of neutrophils with high accuracy.

Exposure to coal dust exacerbates cognitive impairment by activating the IL6/ERK1/2/SP1 signaling pathway

Coal dust (CD) is a common pollutant, and epidemiological surveys indicate that long-term exposure to coal dust not only leads to the occurrence of pulmonary diseases but also has certain impacts on cognitive abilities. However, there is little open-published literature on the effects and specific mechanisms of coal dust exposure on the cognition of patients with Mild Cognitive Impairment (MCI) and Alzheimer's Disease (AD). An animal model has been built in this study with clinical population samples to explore the changes in neuroinflammation and cognitive abilities with coal dust exposure. In the animal model, compared to C57BL/6 mice, APP/PS1 mice exposed to coal dust exhibited more severe cognitive impairment, accompanied by significantly elevated levels of neuroinflammatory factors Apolipoprotein E4 (AOPE4) and Interleukin-6 (IL6) in the hippocampus, and more severe neuronal damage. In clinical sample sequencing, it was found that there is significant upregulation of AOPE4, neutrophils, and IL6 expression in the peripheral blood of MCI patients compared to normal individuals. Mechanistically, cell experiments revealed that IL6 could promote the phosphorylation of ERK1/2 and enhance the expression of transcription factor SP1, thereby promoting AOPE4 expression. The results of this study suggest that coal dust can promote the upregulation of IL6 and AOPE4 in patients, exacerbating cognitive impairment.

Knowledge landscape of tumor-associated neutrophil: a bibliometric and visual analysis from 2000-2024

Background

Neutrophils have long been consistently adjudged to hold a dominant position in acute inflammation, which once led people to undervalue their role in chronic malignancy. It is now acknowledged that neutrophils also infiltrate into the tumor microenvironment in substantial quantities and form a highly abundant immune population within the tumor, known as tumor-associated neutrophils (TANs). There has been a surge of interest in researching the eminent heterogeneity and plasticity of TANs in recent years, and scholars increasingly cotton on to the multifaceted functions of TANs so that strenuous endeavors have been devoted to enunciating their potential as therapeutic targets. Yet it remains much left to translate TAN-targeted immunotherapies into clinical practice. Therefore, there is great significance to comprehensively appraise the research status, focal point, and evolution trend of TAN by using bibliometric analysis.

Methods

Publications related to TAN research from 2000 to 2024 are extracted from the Web of Science Core Collection. Bibliometric analysis and visualization were performed by tools encompassing Microsoft Excel, VOSviewer, CiteSpace, R-bibliometrix, and so on.

Results

The bibliometric analysis included a total of 788 publications authored by 5291 scholars affiliated with 1000 institutions across 58 countries/regions, with relevant articles published in 324 journals. Despite China's maximum quantity of publications and top 10 institutions, the United States is the leading country with the most high-quality publications and is also the global cooperation center. FRONTIERS IN IMMUNOLOGY published the most papers, whereas CANCER RESEARCH is the highest co-cited journal. Israeli professor Fridlender, Zvi G. is the founder, pioneer, and cultivator with the highest citation counts and H-index in the TAN area. Our analysis prefigures the future trajectories: TAN heterogeneity, neutrophil extracellular trap, the crosstalk between TANs and immunocytes, and immunotherapy will likely be the focus of future research.

Conclusion

A comprehensive bibliometric and visual analysis is first performed to map the current landscape and intellectual structure of TAN, which proffers fresh perspectives for further research. The accurate identification of distinct TAN subpopulations and the precise targeting of key pro-tumor/anti-tumor subpopulations hold immense potential to develop into a TAN-targeted immunotherapy.

Osteocalcin-expressing neutrophils from skull bone marrow exert immunosuppressive and neuroprotective effects after TBI

Neutrophils from skull bone marrow (Nskull) are activated under some brain stresses, but their effects on traumatic brain injury (TBI) are lacking. Here, we find Nskull infiltrates brain tissue quickly and persistently after TBI, which is distinguished by highly and specifically expressed osteocalcin (OCN) from blood-derived neutrophils (Nblood). Reprogramming of glucose metabolism by reducing glycolysis-related enzyme glyceraldehyde 3-phosphate dehydrogenase expression is involved in the antiapoptotic and proliferative abilities of OCN-expressing Nskull. The transcription factor Fos-like 1 governs the specific gene profile of Nskull including C-C motif chemokine receptor-like 2 (CCRL2), arginase 1 (Arg1), and brain-derived neurotrophic factor (BDNF) in addition to OCN. Selective knockout of CCRL2 in Nskull demonstrates that CCRL2 mediates its recruitment, whereas high Arg1 expression is consistent with its immunosuppressive effects on Nblood, and the secretion of BDNF facilitating dendritic growth contributes to its neuroprotection. Thus, our findings provide insight into the roles of Nskull in TBI.

Zinc Supplementation Reduces the Formation of Neutrophil Extracellular Traps by Decreasing the Expression of Peptidyl Arginine Deiminase 4

SCOPE

Neutrophils play a decisive role during the immediate defense against infections. However, as observed during rheumatoid arthritis, activated neutrophils can also cause tissue damage. Previous studies indicate that zinc supplementation may alter certain neutrophil functions. However, precise underlying mechanisms and possible effects of zinc deficiency remain incompletely understood. The objective of this study is to investigate the effects of changes in zinc status on formation of neutrophil extracellular traps (NETs) and other fundamental neutrophil functions.

METHODS AND RESULTS

Interleukin (IL)-17 and tumor necrosis factor (TNF)-α are used to simulate the inflammatory environment observed in autoimmune diseases. The study analyzes the impact of the zinc status on NETs release, using a fluorescence plate reader, and on the expression of peptidylarginine deiminase 4 (PAD4), S100A8/A9, and certain cytokines by PCR and western blot. These results show that zinc supplementation significantly reduces NETs formation and downregulates PAD4 protein expression. Zinc supplementation results in increased protein expression of interleukin-1 receptor antagonist (IL-1RA) and IL-8 in stimulated cells.

CONCLUSION

The results suggest that changes in extracellular zinc availability may influence the functions of neutrophils. Therefore, maintaining an appropriate zinc level is advisable for preserving innate immunity and to prevent hyper-activation of neutrophils.