Neutrophil extracellular traps - the dark side of neutrophils

Mapping current status and emerging trends in NETosis: A bibliometric study

BACKGROUND

NETosis is a critical innate immune mechanism of neutrophils that contributes to the accelerated progression of autoimmune diseases, thrombosis, cancer, and coronavirus disease 2019 (COVID-19). This study qualitatively and quantitatively analyzed the relevant literature by bibliometric methods in order to provide a more comprehensive and objective view of the knowledge dynamics in the field.

METHODS

The literature on NETosis was downloaded from the Web of Science Core Collection, analyzed with VOSviewer, CiteSpace, and Microsoft for co-authorship, co-occurrence, and co-citation analysis.

RESULTS

In the field of NETosis, the United States was the most influential countries. Harvard University was the most active institutions. Mariana J. Kaplan and Brinkmann V were, respectively, the most prolific and most co-cited authors. Frontiers in Immunology, Journal of Immunology, Plos One, Blood, Science, Journal of Cell Biology, and Nature Medicine were the most influential journals. The top 15 keywords are associated with immunological and NETosis formation mechanisms. The keywords with the strongest burst detection were mainly related to COVID-19 (coronavirus, ACE2, SARS coronavirus, cytokine storm, pneumonia, neutrophil to lymphocyte ratio), and cancer (circulating tumor cell).

CONCLUSION

Research on NETosis is currently booming. The mechanism of NETosis and its role in innate immunity, autoimmune diseases, especially systemic lupus erythematosus and rheumatoid arthritis, and thrombosis are the focus of research in the field of NETosis. A future study will concentrate on the function of NETosis in COVID-19 and recurrent metastasis of cancer.

Pathogenic cellular and molecular mediators in lupus nephritis

Kidney involvement in patients with systemic lupus erythematosus - lupus nephritis (LN) - is one of the most important and common clinical manifestations of this disease and occurs in 40-60% of patients. Current treatment regimens achieve a complete kidney response in only a minority of affected individuals, and 10-15% of patients with LN develop kidney failure, with its attendant morbidity and considerable prognostic implications. Moreover, the medications most often used to treat LN - corticosteroids in combination with immunosuppressive or cytotoxic drugs - are associated with substantial side effects. Advances in proteomics, flow cytometry and RNA sequencing have led to important new insights into immune cells, molecules and mechanistic pathways that are instrumental in the pathogenesis of LN. These insights, together with a renewed focus on the study of human LN kidney tissue, suggest new therapeutic targets that are already being tested in lupus animal models and early-phase clinical trials and, as such, are hoped to eventually lead to meaningful improvements in the care of patients with systemic lupus erythematosus-associated kidney disease.

Saxitoxin induces the release of human neutrophil extracellular traps

Saxitoxin (STX) is a potent shellfish toxin found in freshwater and marine ecosystems which threatens human health by contaminating drinking water and shellfish. The formation of neutrophil extracellular traps (NETs) is a defense mechanism employed by polymorphonuclear leukocytes (PMNs) to destroy invading pathogens, and also plays a critical role in the pathogenesis of various diseases. In this study, we aimed to investigate the role of STX on human NET formation. Typical NETs-associated characteristics were detected from STX-stimulated PMNs using immunofluorescence microscopy. Moreover, NET quantification based on PicoGreen® fluorescent dye revealed that STX triggered NET formation in a concentration-dependent manner, and NET formation peaked at 120 min (with a total time of 180 min) after induction by STX. Intracellular reactive oxygen species (iROS) detection showed that iROS were significantly elevated in STX-challenged PMNs. These findings present insight into the effects of STX on human NET formation and serve as a basis for further investigations of STX immunotoxicity.

Deciphering the Genetic Code of Autoimmune Kidney Diseases

Autoimmune kidney diseases occur due to the loss of tolerance to self-antigens, resulting in inflammation and pathological damage to the kidneys. This review focuses on the known genetic associations of the major autoimmune kidney diseases that result in the development of glomerulonephritis: lupus nephritis (LN), anti-neutrophil cytoplasmic associated vasculitis (AAV), anti-glomerular basement disease (also known as Goodpasture's disease), IgA nephropathy (IgAN), and membranous nephritis (MN). Genetic associations with an increased risk of disease are not only associated with polymorphisms in the human leukocyte antigen (HLA) II region, which governs underlying processes in the development of autoimmunity, but are also associated with genes regulating inflammation, such as NFkB, IRF4, and FC γ receptors (FCGR). Critical genome-wide association studies are discussed both to reveal similarities in gene polymorphisms between autoimmune kidney diseases and to explicate differential risks in different ethnicities. Lastly, we review the role of neutrophil extracellular traps, critical inducers of inflammation in LN, AAV, and anti-GBM disease, where inefficient clearance due to polymorphisms in DNase I and genes that regulate neutrophil extracellular trap production are associated with autoimmune kidney diseases.

COVID-19 and Sickle Cell Disease: Two Independent Risk Factors for Venous Thromboembolism

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been widely documented as a multi-systemic illness and associated with an increased incidence of thromboses. Likewise, sickle cell disease (SCD) is a hematologic disease responsible for widespread effects on the vasculature and is also associated with elevated thrombotic risk. In this review, we examine the incidence rates of venous thromboembolism (VTE) in SCD and COVID-19 independently and review the mechanisms of coagulopathy associated with both diseases. We describe the possible associations and commonalities between VTE mechanisms, as both diseases cause widespread inflammation that influences each tenet of Virchow's triad. We also discuss current anticoagulation guideline recommendations for the prevention of VTE events in each of these diseases. We report on current literature to date describing rates of VTE in SCD-COVID-19 patients and outline prospective areas of research to further understand the possible synergistic influence of coagulopathy in these patients. The association between SCD and COVID-19 remains a largely under-researched area of coagulopathy in current hematology and thrombotic literature, and our report lays out potential future prospects in the field.

Scavenger receptors mediate increased uptake of irradiated T.gondii extracts by J774 macrophages

PURPOSE

Protein extracts developed increased immunogenicity without the aid of adjuvants after gamma irradiation. Gamma irradiation of snake venom increased antivenin production by detoxification and enhanced immunity, probably due preferential uptake of irradiated venoms by macrophage scavenger receptors. We studied this uptake of irradiated soluble Toxoplasma gondii extract (STag) by the J774 macrophage cell line similar to antigen presenting cells.

MATERIAL AND METHODS

We labeled STag by biosynthesis in living tachyzoites with radioactive amino acids before purification and irradiation or by adding labels as biotin or fluorescein in stored STag, for quantitative studies or subcellular distribution visualization.

RESULTS

There was enhanced binding and uptake of irradiated STag into the cells compared to non-irradiated STag. Using fluorescein labeled antigens and morphological assays, we confirmed that cells avidly ingested both native and irradiated proteins but native STag were digested after ingestion while irradiated proteins remained in the cell, suggesting diverse intracytoplasmic pathways. Native or irradiated STag present the same in vitro sensitivity to three types of peptidases. Inhibitors of scavenger receptors (SRs) such as Dextran sulfate (SR-A1 blocker) or Probucol (SR-B blocker) affect the specific uptake of irradiated antigens, suggesting its association with enhanced immunity.

CONCLUSIONS

Our data suggests that cell SRs recognize irradiated proteins, mainly SRs for oxidized proteins, leading to antigen uptake by an intracytoplasmic pathway with fewer peptidases that prolongs presentation to nascent major histocompatibility complex I or II and enhances immunity by better antigen presentation.

Neutrophil, NETs and Behçet's disease: A review

Behçet's disease (BD) is a chronic systemic vasculitis characterized by recurrent oral and genital ulcers, skin lesions, articular, neurological, vascular and sight-threatening ocular inflammation. BD is thought to share both autoimmune and autoinflammatory disease features. BD is triggered by environmental factors such as infectious agents in genetically predisposed subjects. Neutrophils seem to play an instrumental role in BD and recent works regarding the role of neutrophils extracellular traps (NETs) provides new insight in the pathophysiology of BD and the mechanisms involved in immune thrombosis. This review provides a recent overview on the role of neutrophils and NETs in the pathogenesis of BD.

Neutrophil extracellular trap formation in anti-neutrophil cytoplasmic antibody-associated and large-vessel vasculitis

Levels of neutrophil extracellular traps (NETs) were measured in plasma of healthy controls (HC, n = 30) and patients with granulomatosis with polyangiitis (GPA, n = 123), microscopic polyangiitis (MPA, n = 61), Takayasu's arteritis (TAK, n = 58), and giant cell arteritis (GCA, n = 68), at times of remission or activity and correlated with levels of the platelet-derived thrombospondin-1 (TSP-1). Levels of NETs were elevated during active disease in patients with GPA (p < 0.0001), MPA (p = 0.0038), TAK (p < 0.0001), and GCA (p < 0.0001), and in remission for GPA, p < 0.0001, MPA, p = 0.005, TAK, p = 0.03, and GCA, p = 0.0009. All cohorts demonstrated impaired NET degradation. Patients with GPA (p = 0.0045) and MPA (p = 0.005) had anti-NET IgG antibodies. Patients with TAK had anti-histone antibodies (p < 0.01), correlating with presence of NETs. Levels of TSP-1 were increased in all patients with vasculitis, and associated with NET formation. NET formation is a common process in vasculitides. Targeting NET formation or degradation could be potential therapeutic approaches for vasculitides.

EARLY INITIATION OF RENAL REPLACEMENT THERAPY IN INTENSIVE CARE UNIT PATIENTS WITH BOTH ACUTE RESPIRATORY DISTRESS SYNDROME AND SEPSIS WITH OR WITHOUT RENAL FAILURE: A RETROSPECTIVE COHORT STUDY BASED ON PROPENSITY SCORE MATCHING

ABSTRACT

Background: It is unknown whether early renal replacement therapy (RRT) initiation strategy in intensive care unit (ICU) patients with both acute respiratory distress syndrome (ARDS) and sepsis with or without renal failure is clinically beneficial. Patients and methods: A total of 818 patients with both ARDS and sepsis admitted to the ICU of Tianjin Medical University General Hospital were included in the analysis. Early RRT was defined as initiating the RRT strategy within 24 h of admission. The relationship between early RRT and clinical outcomes, including primary (30-day mortality) and secondary (90-day mortality, serum creatinine, Pa o2 /Fi o2 , duration of invasive mechanical ventilation, cumulative fluid output, and cumulative fluid balance) outcomes, was compared using propensity score matching (PSM). Results: A total of 277 patients (33.9% of the total population) underwent an early RRT initiation strategy before PSM. After PSM, a cohort of 147 patients with early RRT and 147 patients without early RRT with matched baseline characteristics (including serum creatinine at admission) were constructed. Early RRT was not significantly associated with 30- (hazard ratio [HR], 1.25; 95% confidence interval [CI], 0.85-1.85; P = 0.258) or 90-day mortality (HR, 1.30; 95% CI, 0.91-1.87, P = 0.150). At each time point within 72 h after admission, there was no significant difference in serum creatinine, Pa o2 /Fi o2 and duration of mechanical ventilation between the early and the no early RRT groups. Early RRT significantly increased total output at all time points within 72 h of admission and reached a statistically significant negative fluid balance at 48 h. Conclusions: Early RRT initiation strategies had no statistically significant survival benefit in ICU patients with both ARDS and sepsis, with or without renal failure, nor did they significantly improve serum creatinine and oxygenation or shorten the duration of mechanical ventilation. The use and timing of RRT in such patients should be thoroughly investigated.

Livin upregulation in keratinocytes of psoriasis patients to promote adhesion molecule expression

BACKGROUND

Activation of keratinocytes (KCs) is the main pathological feature of psoriasis. KCs recruit neutrophils by releasing various antimicrobial peptides and chemokines, which is also related to the expression of KC adhesion molecules. However, the regulatory mechanism governing their expression is still unclear. Livin, an inhibitor of the apoptosis protein family member involved in proliferation and metastasis of tumor cells, is significantly increased in psoriatic lesions.

OBJECTIVES

The aim of this study was to investigate the role of Livin in regulating adhesion molecule expression in KCs and release of chemokines that promote the activation and adhesion of neutrophils.

METHODS

The expression of Livin in psoriasis patients, imiquimod mouse model, and the combination of IL-17 alpha, IL-22, IL-1 alpha, OSM, and TNF-α (Mix M5)-treated HaCaT cells were detected by immunofluorescence staining, RT-qPCR, and ELISA. Livin-overexpression and knockdown in HaCaT cells transfected with HIV-1-based lentiviral vectors were used to study the function of Livin using RNA-seq. Moreover, differences in the expression of HaCaT cell adhesion molecules after regulation of Livin expression and activation of neutrophils in the co-culture model were verified.

RESULTS

Livin was upregulated in the KCs of psoriasis patients, imiquimod mouse model and Mix M5-treated HaCaT cells compared with the control groups. Livin in HaCaT cells might regulate the expression of adhesion molecules in KCs.

CONCLUSION

Thus, Livin may be a key effector molecule that regulates the expression of adhesion molecules in KCs and promotes the activation and adhesion of neutrophils.

Epigenetic mechanisms of Immune remodeling in sepsis: targeting histone modification

Sepsis is a life-threatening disorder disease defined as infection-induced dysregulated immune responses and multiple organ dysfunction. The imbalance between hyperinflammation and immunosuppression is a crucial feature of sepsis immunity. Epigenetic modifications, including histone modifications, DNA methylation, chromatin remodeling, and non-coding RNA, play essential roles in regulating sepsis immunity through epi-information independent of the DNA sequence. In recent years, the mechanisms of histone modification in sepsis have received increasing attention, with ongoing discoveries of novel types of histone modifications. Due to the capacity for prolonged effects on immune cells, histone modifications can induce immune cell reprogramming and participate in the long-term immunosuppressed state of sepsis. Herein, we systematically review current mechanisms of histone modifications involved in the regulation of sepsis, summarize their role in sepsis from an immune perspective and provide potential therapeutic opportunities targeting histone modifications in sepsis treatment.

Synovial fluid neutrophil extracellular traps could improve the diagnosis of periprosthetic joint infection

AIMS

This study aimed to explore the diagnostic value of synovial fluid neutrophil extracellular traps (SF-NETs) in periprosthetic joint infection (PJI) diagnosis, and compare it with that of microbial culture, serum ESR and CRP, synovial white blood cell (WBC) count, and polymorphonuclear neutrophil percentage (PMN%).

METHODS

In a single health centre, patients with suspected PJI were enrolled from January 2013 to December 2021. The inclusion criteria were: 1) patients who were suspected to have PJI; 2) patients with complete medical records; and 3) patients from whom sufficient synovial fluid was obtained for microbial culture and NET test. Patients who received revision surgeries due to aseptic failure (AF) were selected as controls. Synovial fluid was collected for microbial culture and SF-WBC, SF-PNM%, and SF-NET detection. The receiver operating characteristic curve (ROC) of synovial NET, WBC, PMN%, and area under the curve (AUC) were obtained; the diagnostic efficacies of these diagnostic indexes were calculated and compared.

RESULTS

The levels of SF-NETs in the PJI group were significantly higher than those of the AF group. The AUC of SF-NET was 0.971 (95% confidence interval (CI) 0.903 to 0.996), the sensitivity was 93.48% (95% CI 82.10% to 98.63%), the specificity was 96.43% (95% CI 81.65% to 99.91%), the accuracy was 94.60% (95% CI 86.73% to 98.50%), the positive predictive value was 97.73%, and the negative predictive value was 90%. Further analysis showed that SF-NET could improve the diagnosis of culture-negative PJI, patients with PJI who received antibiotic treatment preoperatively, and fungal PJI.

CONCLUSION

SF-NET is a novel and ideal synovial fluid biomarker for PJI diagnosis, which could improve PJI diagnosis greatly.Cite this article: Bone Joint Res 2023;12(2):113-120.

DUOX2 regulates secreted factors in virus-infected respiratory epithelial cells that contribute to neutrophil attraction and activation

The first line of defense against respiratory viruses relies on the antiviral and proinflammatory cytokine response initiated in infected respiratory epithelial cells. The cytokine response not only restricts virus replication and spreading, but also orchestrates the subsequent immune response. The epithelial Dual Oxidase 2 (DUOX2) has recently emerged as a regulator of the interferon antiviral response. Here, we investigated the role of DUOX2 in the inflammatory cytokine response using a model of A549 cells deficient in DUOX2 generated using Crispr-Cas9 and infected by Sendai virus. We found that the absence of DUOX2 selectively reduced the induction of a restricted panel of 14 cytokines and chemokines secreted in response to Sendai virus by 20 to 89%. The secreted factors produced by epithelial cells upon virus infection promoted the migration, adhesion, and degranulation of primary human neutrophils, in part through the DUOX2-dependent secretion of TNF and chemokines. In contrast, DUOX2 expression did not impact neutrophil viability or NETosis, thereby highlighting a selective impact of DUOX2 in neutrophil functions. Overall, this study unveils previously unrecognized roles of epithelial DUOX2 in the epithelial-immune cells crosstalk during respiratory virus infection.

Granulocyte concentrate splitting does not affect phenotype and function

BACKGROUND

More granulocyte concentrates (GCs) could be produced for more patients from the same donor if apheresis bags were split and stored for longer periods of time. Hence, we tested the hypothesis that splitting and extension of storage of GCs do not impair granulocyte function or viability.

STUDY DESIGN AND METHODS

Granulocyte apheresis concentrates were produced using modified fluid gelatin as a separation enhancer, split into two portions, and stored for 24 and 48 h. Granulocyte function, represented by cell migration, reactive oxygen species (ROS) production, and neutrophil extracellular trap formation (NETosis), was measured by live-cell imaging. ROS production, adhesive surface protein expression, and viability were measured by flow cytometry.

RESULTS

Splitting had no effect on any of the tested parameters. After 24 h of storage, live-cell imaging showed no significant difference in migration, time to maximum ROS production, time to half-maximum NETosis, viability, or CD11b expression, but ROS production induced by phorbol 12-myristate 13-acetate (PMA) decreased from an initial median fluorescence intensity of 1775-590 artificial units. After 48 h, PMA-induced ROS production, viability, and migration declined, as reflected by decreases in median total distance (119 vs. 63.5 μm) and median Euclidean distance (30.75 vs. 14.3 μm).

CONCLUSION

Splitting GC products has no effect on granulocyte viability or function, but extended storage >24 h does compromise granulocyte function. The findings confirm that GCs should be transfused within 24 h of collection. Longer storage cannot be recommended.

Vitamin D3 and deconvoluting a rash

BACKGROUNDAdverse drug reactions are unpredictable immunologic events presenting frequent challenges to clinical management. Systemically administered cholecalciferol (vitamin D3) has immunomodulatory properties. In this randomized, double-blinded, placebo-controlled interventional trial of healthy human adults, we investigated the clinical and molecular immunomodulatory effects of a single high dose of oral vitamin D3 on an experimentally induced chemical rash.METHODSSkin inflammation was induced with topical nitrogen mustard (NM) in 28 participants. Participant-specific inflammatory responses to NM alone were characterized using clinical measures, serum studies, and skin tissue analysis over the next week. All participants underwent repeat NM exposure to the opposite arm and then received placebo or 200,000 IU cholecalciferol intervention. The complete rash reaction was followed by multi-omic analysis, clinical measures, and serum studies over 6 weeks.RESULTSCholecalciferol mitigated acute inflammation in all participants and achieved 6 weeks of durable responses. Integrative analysis of skin and blood identified an unexpected divergence in response severity to NM, corroborated by systemic neutrophilia and significant histopathologic and clinical differences. Multi-omic and pathway analyses revealed a 3-biomarker signature (CCL20, CCL2, CXCL8) unique to exaggerated responders that is suppressed by cholecalciferol and implicates IL-17 signaling involvement.CONCLUSIONHigh-dose systemic cholecalciferol may be an effective treatment for severe reactions to topical chemotherapy. Our findings have broad implications for cholecalciferol as an antiinflammatory intervention against the development of exaggerated immune responses.TRIAL REGISTRATIONclinicaltrials.gov (NCT02968446).FUNDINGNIH and National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS; grants U01AR064144, U01AR071168, P30 AR075049, U54 AR079795, and P30 AR039750 (CWRU)).

Systemic Immune Inflammation Index is a Novel Marker in Predicting the Presence and Severity of Isolated Coronary Artery Ectasia

BACKGROUND

The underlying pathology of isolated coronary artery ectasia (CE) has not been fully elucidated.

OBJECTIVE

We aimed to examine the relationship between the systemic immune inflammation index (Sıı), which corresponds to the multiplying of the neutrophil-to-lymphocyte ratio (NLR) and the platelet counts, and isolated CE.

METHOD

The retrospective study population included 200 patients with isolated CE, 200 consecutive with obstructive coronary artery disease, and 200 consecutive with a normal coronary artery angiogram. A 2-sided p-value of <0.05 was considered significant.

RESULTS

Sıı, NLR, platelet-to-lymphocyte ratio (PLR), and monocyte-to-high density lipoprotein cholesterol ratio (MHR) were significantly higher in the CE group compared with the other groups (all p<0.001). In multivariate analysis, Sıı (p<0.001, OR = 1.005, 95% CI =1.004-1.005) was found to be an independent predictor of isolated CE. In Receiver Operating Characteristic curve analysis, Sıı had a higher Area Under the Curve than NLR, PLR, and MHR. Sıı value of >517.35 has 79% sensitivity, 76% specificity for the prediction of the CE [AUC: 0.832, (p<0.001)]. Sıı had a significant correlation with the number of ectatic coronary arteries and Markis classification (r:0.214 p=0.002; r:-0.195, p=0.006, respectively).

CONCLUSION

To the best of our knowledge, this is the first study that Sıı was significantly associated with isolated CE presence and anatomical severity.

Association of a novel nutritional index with stroke in Chinese population with hypertension: Insight from the China H-type hypertension registry study

Objective

The abbreviated TCB index (TCBI) is a novel indicator of nutritional status, calculated by multiplying the serum values of triglycerides (TG), total serum cholesterol (TC), and body weight. The research on the relationship between this index and stroke is limited. We aimed to investigate the association between TCBI and stroke in Chinese hypertensive patients.

Methods and results

A total of 13,358 adults with hypertension from the China H-type Hypertension Registry Study were enrolled. The TCBI was calculated as TG (mg/dL) * TC (mg/dL) * body weight (kg)/1,000. The primary outcome was an incidence of stroke. Multivariable adjusted models revealed an inverse association between TCBI and the prevalence of stroke. In the fully adjusted model, the results showed that the prevalence of stroke decreased by 13% (OR, 0.87; 95% CI, 0.78-0.98, p = 0.018) per SD increment of LgTCBI. When TCBI was assessed as a categorical variable, compared with those in group Q4 (TCBI ≥ 2,399), the participants in group Q3 (TCBI ≥ 1,476 and <2,399), group Q2 (TCBI ≥ 920 and <1,476), and group Q1 (TCBI < 920) had increases in stroke prevalence of 42% (OR, 1.42; 95% CI, 1.13-1.80; p-value = 0.003), 38% (OR, 1.38; 95% CI, 1.07-1.80; p-value = 0.014), and 68% (OR, 1.68; 95% CI, 1.24-2.27; p-value = 0.001), respectively. Subgroup analysis showed an interaction between age and TCBI and stroke (age < 60 years OR, 0.69; 95% CI, 0.58-0.83; vs. age ≥ 60 years OR, 0.95; 95% CI, 0.84-1.07; P for interaction = 0.001).

Conclusion

We found an independent negative association between TCBI and the prevalence of stroke, especially in hypertensive patients aged < 60 years.

The emerging role of neutrophil extracellular traps in endometritis

Endometritis is a kind of common obstetric disease in women, usually caused by various pathogenic bacteria. Neutrophil infiltration is one of the most important pathological features of endometritis. Neutrophils can reach the uterine cavity through the endometrium, and make early response to the infection caused by the pathogen. Neutrophil extracellular traps (NETs), a meshwork of chromatin fibers extruded by neutrophils, have a role in entrapping microbial pathogens. It has been confirmed that NETs have a strong antibacterial effect and play crucial roles in the occurrence and development of various diseases. However, while killing pathogenic bacteria, excessive NETs formation may cause immune damage to the body. NETs are present in endometrium of female domestic animals in different physiological periods, especially post-mating, postpartum and in the presence of lesions, especially in endometritis. Meanwhile, NETs and its products might contribute to a reduction in physical clearance and persistent endometritis. In brief, NETs is a double-edged sword and it may play a different role in the development of endometritis, which may be beneficial or harmful, and its specific mechanism needs further study. Here we provide an overview of the role of NETs in the development of endometritis and the regulatory role of selenium on NETs formation and endometritis.

Regulating Neutrophil PAD4/NOX-Dependent Cerebrovasular Thromboinflammation

Background: Neutrophil extracellular trap (NET) production has been implicated in the pathogenesis of thromboinflammatory conditions such as Sickle Cell Disease (SCD), contributing to heightened risk for ischemic stroke. NETs are catalyzed by the enzyme Peptidyl Arginine Deiminase 4 (PAD4) and neutrophil derived reactive oxygen species (ROS), especially NADPH oxidase (NOX) which interacts with PAD4 and is therefore critical for neutrophil function. However, the role that NOX-dependent ROS and NETs play in the accelerated cerebral microvascular thrombosis associated with thromboinflammatory conditions, such as SCD, has not been fully elucidated and is the aim of this study. Methods: The in-vitro effects of targeting PAD4 and NOX were examined using physiologically relevant NET assays with neutrophils isolated from healthy volunteers (control) and SCD patients. In addition, in-vivo intravascular effects of targeting PAD4 and NOX in the cerebral microcirculation of C57BL/6 and sickle transgenic mice (STM) were assessed using a photoactivation thrombosis model (light/dye) coupled with real-time fluorescence intravital microscopy. Results: We found that targeting PAD4 and NOX in human neutrophils significantly inhibited ionomycin dependent H3cit⁺ neutrophils. Targeting PAD4 and NOX in-vivo resulted in prolonged blood flow cessation in cerebrovascular arterioles as well as venules. Moreover, we were able to replicate the effects of PAD4 and NOX targeting in a clinical model of accelerated thromboinflammation by increasing blood flow cessation times in cerebral microvessels in STM. These findings concurred with the clinical setting i.e. neutrophils isolated from SCD patients, which possessed an attenuation of H3cit⁺ neutrophil production on targeting PAD4 and NOX. Conclusions: Taken together, our compelling data suggests that PAD4 and NOX play a significant role in neutrophil driven thromboinflammation. Targeting PAD4 and NOX limits pathological H3cit⁺ neutrophils, which may further explain attenuation of cerebral thrombosis. Overall, this study presents a viable pre-clinical model of prevention and management of thromboinflammatory complications such as ischemic stroke.

Neutrophil extracellular traps: A novel target for the treatment of stroke

Stroke is a threatening cerebrovascular disease caused by thrombus with high morbidity and mortality rates. Neutrophils are the first to be recruited in the brain after stroke, which aggravate brain injury through multiple mechanisms. Neutrophil extracellular traps (NETs), as a novel regulatory mechanism of neutrophils, can trap bacteria and secret antimicrobial molecules, thereby degrading pathogenic factors and killing bacteria. However, NETs also exacerbate certain non-infectious diseases by activating autoimmune or inflammatory responses. NETs have been found to play important roles in the pathological process of stroke in recent years. In this review, the mechanisms of NETs formation, the physiological roles of NETs, and the dynamic changes of NETs after stroke are summarized. NETs participate in stroke through various mechanisms. NETs promote the coagulation cascade and interact with platelets to induce thrombosis. tPA induces the degranulation of neutrophils to form NETs, leading to hemorrhagic transformation and thrombolytic resistance. NETs aggravate stroke by mediating inflammation, atherosclerosis and vascular injury. In addition, the regulation of NETs in stroke, the potential of NETs as biomarker and the treatment of stroke targeting NETs are discussed. The increasing evidences suggest that NETs may be a potential target for stroke treatment. Inhibition of NETs formation or promotion of NETs degradation plays protective effects in stroke. However, how to avoid the adverse effects of NETs-targeted therapy deserves further study. In summary, this review provides a reference for the pathogenesis, drug targets, biomarkers and drug development of NETs in stroke.

Neutrophil extracellular traps in autoimmune diseases: Analysis of the knowledge map

Introduction

Recent studies have shown much progress in the research of exosomes in AIDs. However, there is no bibliometric analysis in this research field. This study aimed to provide a bibliometrics review of the knowledge structure and research hotspots of neutrophil extracellular traps (NETs) in autoimmune diseases (AIDs).

Methods

Articles relevant to NETs in AIDs from 2010 to 2022 were retrieved through the Web of Science Core Collection (WoSCC) database. This bibliometric analysis was performed by VOSview, CiteSpace, and Scimago Graphica.

Results

A total of 289 papers analyzed in this research were from 493 organizations in 47 countries by 1537 authors. They were published in 133 journals and cited 20,180 citations from 2,465 journals. The number of annual publications in this field is growing steadily and rapidly, with the United States, China and Germany leading the research effort. Frontiers in Immunology and Journal of Immunology have significantly impacted research in this field. Kaplan, Mariana J, from the National Institutes of Health (The United States), has the most published articles, and Brinkmann, v, from Max Planck Institute for Infection Biology (Germany), is the most co-cited author. Systemic lupus erythematosus and rheumatoid arthritis are the leading topics in this field. The trend of clinical application in the future is the development of new therapies by controlling NETs in the progression of AIDs.

Conclusions

Our study summarized the research trends and developments of NETs in AIDs in recent years and would provide a reference for scholars in this field.

Lpp of Escherichia coli K1 inhibits host ROS production to counteract neutrophil-mediated elimination

Escherichia coli (E. coli) is the most common Gram-negative bacterial organism causing neonatal meningitis. The pathogenesis of E. coli meningitis, especially how E. coli escape the host immune defenses, remains to be clarified. Here we show that deletion of bacterial Lpp encoding lipoprotein significantly reduces the pathogenicity of E. coli K1 to induce high-degree of bacteremia necessary for meningitis. The Lpp-deleted E. coli K1 is found to be susceptible to the intracellular bactericidal activity of neutrophils, without affecting the release of neutrophil extracellular traps. The production of reactive oxygen species (ROS), representing the primary antimicrobial mechanism in neutrophils, is significantly increased in response to Lpp-deleted E. coli. We find this enhanced ROS response is associated with the membrane translocation of NADPH oxidase p47^phox and p67^phox in neutrophils. Then we constructed p47^phox knockout mice and we found the incidence of bacteremia and meningitis in neonatal mice induced by Lpp-deleted E. coli is significantly recovered by p47^phox knockout. Proteomic profile analysis show that Lpp deficiency induces upregulation of flagellar protein FliC in E. coli. We further demonstrate that FliC is required for the ROS induction in neutrophils by Lpp-deleted E. coli. Taken together, these data uncover the novel role of Lpp in facilitating intracellular survival of E. coli K1 within neutrophils. It can be inferred that Lpp of E. coli K1 is able to suppress FliC expression to restrain the activation of NADPH oxidase in neutrophils resulting in diminished bactericidal activity, thus protecting E. coli K1 from the elimination by neutrophils.

Neutrophil dynamics and inflammaging in acute ischemic stroke: A transcriptomic review

Stroke is among the leading causes of death and disability worldwide. Restoring blood flow through recanalization is currently the only acute treatment for cerebral ischemia. Unfortunately, many patients that achieve a complete recanalization fail to regain functional independence. Recent studies indicate that activation of peripheral immune cells, particularly neutrophils, may contribute to microcirculatory failure and futile recanalization. Stroke primarily affects the elderly population, and mortality after endovascular therapies is associated with advanced age. Previous analyses of differential gene expression across injury status and age identify ischemic stroke as a complex age-related disease. It also suggests robust interactions between stroke injury, aging, and inflammation on a cellular and molecular level. Understanding such interactions is crucial in developing effective protective treatments. The global stroke burden will continue to increase with a rapidly aging human population. Unfortunately, the mechanisms of age-dependent vulnerability are poorly defined. In this review, we will discuss how neutrophil-specific gene expression patterns may contribute to poor treatment responses in stroke patients. We will also discuss age-related transcriptional changes that may contribute to poor clinical outcomes and greater susceptibility to cerebrovascular diseases.

Peptidylarginine deiminase enzymes and citrullinated proteins in female reproductive physiology and associated diseases†

Citrullination, the post-translational modification of arginine residues, is catalyzed by the four catalytically active peptidylarginine deiminase (PAD or PADI) isozymes and alters charge to affect target protein structure and function. PADs were initially characterized in rodent uteri and, since then, have been described in other female tissues including ovaries, breast, and the lactotrope and gonadotrope cells of the anterior pituitary gland. In these tissues and cells, estrogen robustly stimulates PAD expression resulting in changes in levels over the course of the female reproductive cycle. The best-characterized targets for PADs are arginine residues in histone tails, which, when citrullinated, alter chromatin structure and gene expression. Methodological advances have allowed for the identification of tissue-specific citrullinomes, which reveal that PADs citrullinate a wide range of enzymes and structural proteins to alter cell function. In contrast to their important physiological roles, PADs and citrullinated proteins are also involved in several female-specific diseases including autoimmune disorders and reproductive cancers. Herein, we review current knowledge regarding PAD expression and function and highlight the role of protein citrullination in both normal female reproductive tissues and associated diseases.

A novel biomarker for pleural effusion diagnosis: Interleukin-36γ in pleural fluid

BACKGROUND

Numerous studies have described the critical importance of interleukin (IL) -36γ in host defense against lung infections, but it is unknown whether it plays a role in infectious pleural effusion (IPE). This study aimed to examine the levels of IL-36γ in pleural effusions of different etiologies and evaluate the diagnostic accuracy of IL-36γ in the differential diagnosis of IPE.

METHODS

A total of 112 individuals was enrolled in this research. IL-36γ levels in pleural fluids of all 112 patients were measured by enzyme-linked immunosorbent assay (ELISA). We also characterized these markers' diagnostic values across various groups.

RESULTS

Patients with tuberculous pleural effusion (TPE) and parapneumonic effusion (PPE) had exhibited markedly higher IL-36γ levels in their pleural fluid than the malignant pleural effusion (MPE) and transudative effusion patients. Furthermore, the IL-36γ concentrations in TPE patients were evidently higher than in uncomplicated parapneumonic effusion (UPPE) patients but significantly lower than in complicated parapneumonic effusion (CPPE)/empyema patients. Pleural fluid IL-36γ is a useful marker to differentiate TPE from UPPE, at a cut-off value for 657.5 pg/ml (area under the curve = 0.904, p < 0.0001) with 70.0% sensitivity and 95.7% specificity.

CONCLUSIONS

The elevated IL-36γ in pleural effusion may be used as a novel biomarker for infectious pleural effusion diagnosis, particularly in patients with CPPE/empyema, and is a potentially promising biomarker to differentiate between TPE and UPPE.

Role of neutrophil extracellular traps in inflammatory evolution in severe acute pancreatitis

ABSTRACT

Severe acute pancreatitis (SAP) is a life-threatening acute abdominal disease with two peaks of death: the first in the early stage, characterized by systemic inflammatory response-associated organ failure; and the second in the late stage, characterized by infectious complications. Neutrophils are the main immune cells participating in the whole process of SAP. In addition to the traditional recognition of neutrophils as the origination of chemokine and cytokine cascades or phagocytosis and degranulation of pathogens, neutrophil extracellular traps (NETs) also play an important roles in inflammatory reactions. We reviewed the role of NETs in the occurrence and development of SAP and its fatal complications, including multiple organs injury, infected pancreatic necrosis, and thrombosis. This review provides novel insights into the involvement of NETs throughout the entire process of SAP, showing that targeting NETs might be a promising strategy in SAP treatment. However, precision therapeutic options targeting NETs in different situations require further investigation.

NET-Triggered NLRP3 Activation and IL18 Release Drive Oxaliplatin-Induced Peripheral Neuropathy

Oxaliplatin is an antineoplastic agent frequently used in the treatment of gastrointestinal tumors. However, it causes dose-limiting sensorimotor neuropathy, referred to as oxaliplatin-induced peripheral neuropathy (OIPN), for which there is no effective treatment. Here, we report that the elevation of neutrophil extracellular traps (NET) is a pathologic change common to both cancer patients treated with oxaliplatin and a murine model of OIPN. Mechanistically, we found that NETs trigger NLR family pyrin domain containing 3 (NLRP3) inflammasome activation and the subsequent release of IL18 by macrophages, resulting in mechanical hyperalgesia. In NLRP3-deficient mice, the mechanical hyperalgesia characteristic of OIPN in our model was reduced. In addition, in the murine model, treatment with the IL18 decoy receptor IL18BP prevented the development of OIPN. We further showed that eicosapentaenoic acid (EPA) reduced NET formation by suppressing the LPS-TLR4-JNK pathway and thereby abolished NLRP3 inflammasome activation and the subsequent secretion of IL18, which markedly prevented oxaliplatin-induced mechanical hyperalgesia in mice. These results identify a role for NET-triggered NLRP3 activation and IL18 release in the development of OIPN and suggest that utilizing IL18BP and EPA could be effective treatments for OIPN.

Mucocutaneous manifestations of Behçet's disease: Pathogenesis and management from perspectives of vasculitis

Behçet's disease (BD) is a systemic inflammatory disorder characterized by vasculitis affecting blood vessels of any caliber or type. It can present with a wide spectrum of vasculitic lesions, including erythema nodosum-like lesions and retinal vasculitis, and may also lead to larger vessel diseases, such as aortic aneurysm and deep vein thrombosis. The full etiology of BD remains unclear, but it is considered a polygenetic disease with multiple genetic risk factors that promote immune dysregulation and thrombophilia. Inflammation can be triggered by environmental factors, such as bacteria or viruses, and the dysregulation of innate and adaptive immune cell subsets. Neutrophils and lymphocytes are the primary players involved in BD pathogenesis, with specific innate (i.e., neutrophil-derived reactive oxygen species and neutrophil extracellular traps) and adaptive (i.e., anti-endothelial cell antibodies) processes inducing endothelial cell activation and chemotaxis of inflammatory cells, leading to coagulation and vasculitis. These inflammation-induced vasculitic or vasculopathic features are observed in most mucocutaneous BD lesions, although vasculitis per se is often pathologically evident only during a brief period of the disease process. Due to the multifactorial nature of BD-associated inflammation, broad-spectrum anti-inflammatory medications, including glucocorticoids and immunosuppressive drugs, have been the mainstay for managing BD. In addition, inhibitors of interleukin (IL)-1, tumor necrosis factor (TNF)-α, and IL-17, which target innate and adaptive immune functions dysregulated in BD, have emerged as promising new therapeutics. In this review, we discuss the muco-cutaneous manifestations of BD by focusing on the underlying vasculitic components in their pathologies, as well as the current array of treatment options.

Sepsis: Immunopathology, Immunotherapies, and Future Perspectives

Sepsis is a syndrome that includes physiological, pathological, and biochemical abnormalities resulting from the host immune response to infection. Despite the improved treatment modalities in recent years, the incidence and mortality of sepsis are still increasing. Sepsis immunopathology is increasingly attracting the attention of researchers. The successes experienced with immunotherapeutics in the treatment of cancer and coronavirus disease 2019, which are diseases with similar pathophysiological features and common immune defects with sepsis, have given rise to the hope that similar successes can be achieved in the treatment of sepsis. In this review, future perspectives on the immunopathology of sepsis and immunotherapeutics are presented to improve the current understanding of the disease.

Myeloperoxidase: Regulation of Neutrophil Function and Target for Therapy

Neutrophils, the most abundant white blood cells in humans, are critical for host defense against invading pathogens. Equipped with an array of antimicrobial molecules, neutrophils can eradicate bacteria and clear debris. Among the microbicide proteins is the heme protein myeloperoxidase (MPO), stored in the azurophilic granules, and catalyzes the formation of the chlorinating oxidant HOCl and other oxidants (HOSCN and HOBr). MPO is generally associated with killing trapped bacteria and inflicting collateral tissue damage to the host. However, the characterization of non-enzymatic functions of MPO suggests additional roles for this protein. Indeed, evolving evidence indicates that MPO can directly modulate the function and fate of neutrophils, thereby shaping immunity. These actions include MPO orchestration of neutrophil trafficking, activation, phagocytosis, lifespan, formation of extracellular traps, and MPO-triggered autoimmunity. This review scrutinizes the multifaceted roles of MPO in immunity, focusing on neutrophil-mediated host defense, tissue damage, repair, and autoimmunity. We also discuss novel therapeutic approaches to target MPO activity, expression, or MPO signaling for the treatment of inflammatory and autoimmune diseases.

Blood neutrophil extracellular traps: a novel target for the assessment of mammary health in transition dairy cows

Background

Mammary health is important for transition dairy cows and has been well recognized to exert decisive effects on animal welfare. However, the factors influencing mammary health are still unclear. Differential somatic cell count (DSCC) could reflect the mastitis risk since it is the percentage of neutrophils plus lymphocytes in total somatic cells and could be reflective of mammary health of dairy cows. This work aimed to investigate the assessment and prognosis of the health of transition cows based on blood neutrophil extracellular traps (NETs).

Results

Eighty-four transition Holstein dairy cows were selected. The serum was sampled in all the animals at week 1 pre- and postpartum, and milk was sampled at week 1 postpartum. Based on the DSCC in milk at week 1, cows with lower (7.4% ± 4.07%, n = 15) and higher (83.3% ± 1.21%, n = 15) DSCCs were selected. High DSCC cows had higher levels of red blood cell counts (P < 0.05), hemoglobin (P = 0.07), and hematocrit (P = 0.05), higher concentrations of serum oxidative variables [(reactive oxygen species (P < 0.05), malondialdehyde (P < 0.05), protein carbonyl (P < 0.05), and 8-hydroxy-2-deoxyguanosine (P = 0.07)], higher levels of serum and milk NETs (P < 0.05) and blood-milk barrier indicators, including serum β-casein (P = 0.05) and milk immunoglobulin G2 (P = 0.09), than those of low DSCC cows. In addition, lower concentrations of serum nutrient metabolites (cholesterol and albumin) (P < 0.05) and a lower level of serum deoxyribonuclease I (P = 0.09) were observed in high DSCC cows than in low DSCC cows. Among the assessments performed using levels of the three prepartum serum parameters (NETs, deoxyribonuclease I and β-casein), the area under the curve (0.973) of NETs was the highest. In addition, the sensitivity (1.00) and specificity (0.93) were observed for the discrimination of these cows using NETs levels with a critical value of 32.2 ng/mL (P < 0.05).

Conclusions

The formation of NETs in blood in transition dairy cows may damage the integrity of the blood-milk barrier and thereby increase the risk for mastitis in postpartum cows.

Specific signature biomarkers highlight the potential mechanisms of circulating neutrophils in aneurysmal subarachnoid hemorrhage

Background: Aneurysmal subarachnoid hemorrhage (aSAH) is a devastating hemorrhagic stroke with high disability and mortality. Neuroinflammation and the immunological response after aSAH are complex pathophysiological processes that have not yet been fully elucidated. Therefore, attention should be paid to exploring the inflammation-related genes involved in the systemic response to the rupture of intracranial aneurysms.

Methods: The datasets of gene transcriptomes were downloaded from the Gene Expression Omnibus database. We constructed a gene co-expression network to identify cluster genes associated with aSAH and screened out differentially expressed genes (DEGs). The common gene was subsequently applied to identify hub genes by protein-protein interaction analysis and screen signature genes by machine learning algorithms. CMap analysis was implemented to identify potential small-molecule compounds. Meanwhile, Cibersort and ssGSEA were used to evaluate the immune cell composition, and GSEA reveals signal biological pathways.

Results: We identified 602 DEGs from the GSE36791. The neutrophil-related module associated with aSAH was screened by weighted gene co-expression network analysis (WGCNA) and functional enrichment analysis. Several small molecular compounds were predicted based on neutrophil-related genes. MAPK14, ITGAM, TLR4, and FCGR1A have been identified as crucial genes involved in the peripheral immune activation related to neutrophils. Six significant genes (CST7, HSP90AB1, PADI4, PLBD1, RAB32, and SLAMF6) were identified as signature biomarkers by performing the LASSO analysis and SVM algorithms. The constructed machine learning model appears to be robust by receiver-operating characteristic curve analysis. The immune feature analysis demonstrated that neutrophils were upregulated post-aSAH and PADI4 was positively correlated with neutrophils. The NETs pathway was significantly upregulated in aSAH.

Conclusion: We identified core regulatory genes influencing the transcription profiles of circulating neutrophils after the rupture of intracranial aneurysms using bioinformatics analysis and machine learning algorithms. This study provides new insight into the mechanism of peripheral immune response and inflammation after aSAH.

PAD4 and Its Inhibitors in Cancer Progression and Prognosis

The systemic spread of malignancies and the risk of cancer-associated thrombosis are major clinical challenges in cancer therapy worldwide. As an important post-translational modification enzyme, peptidyl arginine deiminase 4 (PAD4) could mediate the citrullination of protein in different components (including nucleus and cytoplasm, etc.) of a variety of cells (tumor cells, neutrophils, macrophages, etc.), thus participating in gene regulation, neutrophil extracellular trap (NET) and macrophage extracellular trap (MET). Thereby, PAD4 plays an important role in enhancing the growth of primary tumors and facilitating the distant metastasis of cancer cells. In addition, it is related to the formation of cancer-associated thrombosis. Therefore, the development of PAD4-specific inhibitors may be a promising strategy for treating cancer, and it may improve patient prognosis. In this review, we describe PAD4 involvement in gene regulation, protein citrullination, and NET formation. We also discuss its potential role in cancer and cancer-associated thrombosis, and we summarize the development and application of PAD4 inhibitors.

Correlation between Neutrophil Extracellular Traps (NETs) Expression and Primary Graft Dysfunction Following Human Lung Transplantation

Primary graft dysfunction (PGD) is characterized by alveolar epithelial and vascular endothelial damage and inflammation, lung edema and hypoxemia. Up to one-third of recipients develop the most severe form of PGD (Grade 3; PGD3). Animal studies suggest that neutrophils contribute to the inflammatory process through neutrophil extracellular traps (NETs) release (NETosis). NETs are composed of DNA filaments decorated with granular proteins contributing to vascular occlusion associated with PGD. The main objective was to correlate NETosis in PGD3 (n = 9) versus non-PGD3 (n = 27) recipients in an exploratory study. Clinical data and blood samples were collected from donors and recipients pre-, intra- and postoperatively (up to 72 h). Inflammatory inducers of NETs' release (IL-8, IL-6 and C-reactive protein [CRP]) and components (myeloperoxidase [MPO], MPO-DNA complexes and cell-free DNA [cfDNA]) were quantified by ELISA. When available, histology, immunohistochemistry and immunofluorescence techniques were performed on lung biopsies from donor grafts collected during the surgery to evaluate the presence of activated neutrophils and NETs. Lung biopsies from donor grafts collected during transplantation presented various degrees of vascular occlusion including neutrophils undergoing NETosis. Additionally, in recipients intra- and postoperatively, circulating inflammatory (IL-6, IL-8) and NETosis biomarkers (MPO-DNA, MPO, cfDNA) were up to 4-fold higher in PGD3 recipients compared to non-PGD3 (p = 0.041 to 0.001). In summary, perioperative elevation of NETosis biomarkers is associated with PGD3 following human lung transplantation and these biomarkers might serve to identify recipients at risk of PGD3 and initiate preventive therapies.

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

Background

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

Methods

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

Results

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

Conclusion

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

Biological Effects of Intravenous Vitamin C on Neutrophil Extracellular Traps and the Endothelial Glycocalyx in Patients with Sepsis-Induced ARDS

(1) Background: The disease-modifying mechanisms of high-dose intravenous vitamin C (HDIVC) in sepsis induced acute respiratory distress syndrome (ARDS) is unclear. (2) Methods: We performed a post hoc study of plasma biomarkers from subjects enrolled in the randomized placebo-controlled trial CITRIS-ALI. We explored the effects of HDIVC on cell-free DNA (cfDNA) and syndecan-1, surrogates for neutrophil extracellular trap (NET) formation and degradation of the endothelial glycocalyx, respectively. (3) Results: In 167 study subjects, baseline cfDNA levels in HDIVC (84 subjects) and placebo (83 subjects) were 2.18 ng/µL (SD 4.20 ng/µL) and 2.65 ng/µL (SD 3.87 ng/µL), respectively, p = 0.45. At 48-h, the cfDNA reduction was 1.02 ng/µL greater in HDIVC than placebo, p = 0.05. Mean baseline syndecan-1 levels in HDIVC and placebo were 9.49 ng/mL (SD 5.57 ng/mL) and 10.83 ng/mL (SD 5.95 ng/mL), respectively, p = 0.14. At 48 h, placebo subjects exhibited a 1.53 ng/mL (95% CI, 0.96 to 2.11) increase in syndecan-1 vs. 0.75 ng/mL (95% CI, 0.21 to 1.29, p = 0.05), in HDIVC subjects. (4) Conclusions: HDIVC infusion attenuated cell-free DNA and syndecan-1, biomarkers associated with sepsis-induced ARDS. Improvement of these biomarkers suggests amelioration of NETosis and shedding of the vascular endothelial glycocalyx, respectively.

Abrogation of neutrophil inflammatory pathways and potential reduction of neutrophil-related factors in COVID-19 by intravenous immunoglobulin

Pathogenesis of lung injury in COVID-19 is not completely understood, leaving gaps in understanding how current treatments modulate the course of COVID-19. Neutrophil numbers and activation state in circulation have been found to correlate with COVID-19 severity, and neutrophil extracellular traps (NETs) have been found in the lung parenchyma of patients with acute respiratory distress syndrome (ARDS) in COVID-19. Targeting the pro-inflammatory functions of neutrophils may diminish lung injury in COVID-19 and ARDS. Neutrophils were isolated from peripheral blood of healthy donors, treated ex vivo with dexamethasone, tocilizumab and intravenous immunoglobulin (IVIG) and NET formation, oxidative burst, and phagocytosis were assessed. Plasma from critically ill COVID-19 patients before and after clinical treatment with IVIG and from healthy donors was assessed for neutrophil activation-related proteins. While dexamethasone and tocilizumab did not affect PMA- and nigericin-induced NET production ex vivo, IVIG induced a dose-dependent abrogation of NET production in both activation models. IVIG also reduced PMA-elicited reactive oxygen species production, but did not alter phagocytosis. COVID-19 patients were found to have elevated levels of cell-free DNA, neutrophil elastase and IL-8 as compared to healthy controls. Levels of both cell-free DNA and neutrophil elastase were lower 5 days after 4 days of daily treatment with IVIG. The lack of impact of dexamethasone or tocilizumab on these neutrophil functions suggests that these therapeutic agents may not act through suppression of neutrophil functions, indicating that the door might still be open for the addition of a neutrophil modulator to the COVID-19 therapeutic repertoire.

Identifying Hub Genes and Immune Cell Infiltration for the Progression of Carotid Atherosclerotic Plaques in the Context of Predictive and Preventive Using Integrative Bioinformatics Approaches and Machine-Learning Strategies

Emerging evidence shows that carotid atherosclerosis is related to the activation of immune-related pathways and inflammatory cell infiltration. However, the immune-linked pathways that helped in the advancement of the carotid atherosclerotic plaque and the association of such plaques with the infiltration status of the body's immune cells still unclear. Here, the expression profiles of the genes expressed during the progression of the carotid atherosclerotic plaques were retrieved from the Gene Expression Omnibus database and 178 differentially expressed genes were examined. The Weighted Gene Coexpression Network Analysis technique identified one of the brown modules showed the greatest correlation with carotid atherosclerotic plaques. In total, 66 intersecting genes could be detected after combining the DEGs. LASSO regression analysis was subsequently performed to obtain five hub genes as potential biomarkers for carotid atherosclerotic plaques. The functional analysis emphasized the vital roles played by the inflammation- and immune system-related pathways in this disease. The immune cell infiltration results highlighted the significant correlation among the CD4+ T cells, B cells, macrophages, and CD8+ T cells. Thereafter, the gene expression levels and the diagnostic values related to every hub gene were further validated. The above results indicated that macrophages, B cells, CD4+ T cells, and CD8 + T cells were closely related to the formation of the advanced-stage carotid atherosclerotic plaques. Based on the results, it could be hypothesized that the expression of hub genes (C3AR1, SLAMF8, TMEM176A, FERMT3, and GIMAP4) assisted in the advancement of the early-stage to advanced-stage carotid atherosclerotic plaque through immune-related signaling pathways. This may help to provide novel strategies for the treatment of carotid plaque in the context of predictive, preventive, and personalized medicine.

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

Background

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

Methods

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

Results

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

Conclusion

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

Neuropilin-1 in the pathogenesis of preeclampsia, HIV-1, and SARS-CoV-2 infection: A review

This review explores the role of transmembrane neuropilin-1 (NRP-1) in pregnancy, preeclampsia (PE), human immunodeficiency virus type 1 (HIV-1) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. Since these conditions are assessed independently, this review attempts to predict their comorbid clinical manifestations. Dysregulation of NRP-1 contributes to the pathogenesis of PE by (a) impairing vascular endothelial growth factor (VEGF) signaling for adequate spiral artery remodeling and placentation, (b) inducing syncytiotrophoblast (ST) cell apoptosis and increasing ST-derived microparticle circulation and (c) by decreasing regulatory T cell activity predisposing maternal immune intolerance. Although NRP-1 is upregulated in SARS-CoV-2 placentae, its exploitation for SARS-CoV-2 internalization and increased infectivity may alter angiogenesis through the competitive inhibition of VEGF. The anti-inflammatory nature of NRP-1 may aid its upregulation in HIV-1 infection; however, the HIV-accessory protein, tat, reduces NRP-1 expression. Upregulated NRP-1 in macrophages and dendritic cells also demonstrated HIV-1 resistance/reduced infectivity. Notably, HIV-1-infected pregnant women receiving antiretroviral therapy (ART) to prevent vertical transmission may experience immune reconstitution, impaired decidualization, and elevated markers of endothelial injury. Since endothelial dysfunction and altered immune responses are central to PE, HIV-1 infection, ART usage and SARS-CoV-2 infection, it is plausible that an exacerbation of both features may prevail in the synergy of these events. Additionally, this review identifies microRNAs (miRNAs) mediating NRP-1 expression. MiR-320 and miR-141 are overexpressed in PE, while miR-206 and miR-124-3p showed increased expression in PE and HIV-1 infection. Additionally, miR-214 is overexpressed in PE, HIV-1 and SARS-CoV-2 infection, implicating treatment strategies to reduce these miRNAs to upregulate and normalize NRP-1 expression. However, inconsistencies in the data of the role and regulation of miRNAs in PE, HIV-1 and SARS-CoV-2 infections require clarification. This review provides a platform for early diagnosis and potential therapeutic intervention of PE, HIV-1, and SARS-CoV-2 infections independently and as comorbidities.

Molecular mechanisms and therapeutic target of NETosis in diseases

Evidence shows that neutrophils can protect the host against pathogens in multiple ways, including the formation and release of neutrophil extracellular traps (NETs). NETs are web‐like structures composed of fibers, DNA, histones, and various neutrophil granule proteins. NETs can capture and kill pathogens, including bacteria, viruses, fungi, and protozoa. The process of NET formation is called NETosis. According to whether they depend on nicotinamide adenine dinucleotide phosphate (NADPH), NETosis can be divided into two categories: “suicidal” NETosis and “vital” NETosis. However, NET components, including neutrophil elastase, myeloperoxidase, and cell‐free DNA, cause a proinflammatory response and potentially severe diseases. Compelling evidence indicates a link between NETs and the pathogenesis of a number of diseases, including sepsis, systemic lupus erythematosus, rheumatoid arthritis, small‐vessel vasculitis, inflammatory bowel disease, cancer, COVID‐19, and others. Therefore, targeting the process and products of NETosis is critical for treating diseases linked with NETosis. Researchers have discovered that several NET inhibitors, such as toll‐like receptor inhibitors and reactive oxygen species scavengers, can prevent uncontrolled NET development. This review summarizes the mechanism of NETosis, the receptors associated with NETosis, the pathology of NETosis‐induced diseases, and NETosis‐targeted therapy.

Role of Citrullinated Collagen in Autoimmune Arthritis

Citrullination of proteins plays an important role in protein function and it has recently become clear that citrullinated proteins play a role in immune responses. In this study we examined how citrullinated collagen, an extracellular matrix protein, affects T-cell function during the development of autoimmune arthritis. Using an HLA-DR1 transgenic mouse model of rheumatoid arthritis, mice were treated intraperitoneally with either native type I collagen (CI), citrullinated CI (cit-CI), or phosphate buffered saline (PBS) prior to induction of autoimmune arthritis. While the mice given native CI had significantly less severe arthritis than controls administered PBS, mice receiving cit-CI had no decrease in the severity of autoimmune arthritis. Using Jurkat cells expressing the inhibitory receptor leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1), Western blot analysis indicated that while CI and cit-CI bound to LAIR-1 with similar affinity, only CI induced phosphorylation of the LAIR ITIM tyrosines; cit-CI was ineffective. These data suggest that cit-CI acts as an antagonist of LAIR-1 signaling, and that the severity of autoimmune arthritis can effectively be altered by targeting T cells with citrullinated collagen.

Increased histone citrullination in juvenile idiopathic arthritis

Objective

Posttranslational modifications (PTMs) of proteins are crucial for regulating various biological processes. However, protein alteration via PTMs, and consequently, the creation of new epitopes, can induce abnormal autoimmune responses in predisposed individuals. Immunopathogenesis of several rheumatic diseases, including the most common childhood form, juvenile idiopathic arthritis (JIA), is associated with the generation of autoantibodies against such modified proteins. Dysregulated generation of neutrophil extracellular traps (NETs) can be a source of post-translationally altered proteins. Thus, we investigated the role of PTMs and the presence of NET-associated markers in JIA patients.

Methods

We recruited 30 pediatric patients with JIA (20 with active disease and 10 in remission) and 30 healthy donors. The serum concentrations of citrullinated histone H3 (citH3), peptidyl arginine deiminases (PADs), and NET-related products were detected using ELISA, and the number of citH3+ neutrophils was assessed using flow cytometry.

Results

The serum levels of citH3 and PADs were higher in active as well as in remission JIA patients than in healthy donors. Similarly, the number of citH3+ neutrophils was higher in the peripheral blood of patients with JIA, implying an enhanced process of NETosis. This was effectively reflected by elevated serum levels of NET-associated products, such as neutrophil elastase, LL37, and cell-free DNA-histone complexes. Additionally, 16.7% of active JIA patients were seropositive for carbamylated autoantibodies, the levels of which declined sharply after initiation of anti-TNFα therapy.

Conclusion

Collectively, our data suggest that the accelerated process of NETosis and PTMs in JIA may result in the generation of anti-citrullinated/carbamylated autoantibodies against various epitopes later in life, which could be prevented by effectively regulating inflammation using immune therapy.

Role of aging in Blood-Brain Barrier dysfunction and susceptibility to SARS-CoV-2 infection: impacts on neurological symptoms of COVID-19

COVID-19, which is caused by Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2), has resulted in devastating morbidity and mortality worldwide due to lethal pneumonia and respiratory distress. In addition, the central nervous system (CNS) is well documented to be a target of SARS-CoV-2, and studies detected SARS-CoV-2 in the brain and the cerebrospinal fluid of COVID-19 patients. The blood-brain barrier (BBB) was suggested to be the major route of SARS-CoV-2 infection of the brain. Functionally, the BBB is created by an interactome between endothelial cells, pericytes, astrocytes, microglia, and neurons, which form the neurovascular units (NVU). However, at present, the interactions of SARS-CoV-2 with the NVU and the outcomes of this process are largely unknown. Moreover, age was described as one of the most prominent risk factors for hospitalization and deaths, along with other comorbidities such as diabetes and co-infections. This review will discuss the impact of SARS-CoV-2 on the NVU, the expression profile of SARS-CoV-2 receptors in the different cell types of the CNS and the possible role of aging in the neurological outcomes of COVID-19. A special emphasis will be placed on mitochondrial functions because dysfunctional mitochondria are also a strong inducer of inflammatory reactions and the "cytokine storm" associated with SARS-CoV-2 infection. Finally, we will discuss possible drug therapies to treat neural endothelial function in aged patients, and, thus, alleviate the neurological symptoms associated with COVID-19.

GSDMD-dependent neutrophil extracellular traps promote macrophage-to-myofibroblast transition and renal fibrosis in obstructive nephropathy

Renal fibrosis is a common consequence of various progressive nephropathies, including obstructive nephropathy, and ultimately leads to kidney failure. Infiltration of inflammatory cells is a prominent feature of renal injury after draining blockages from the kidney, and correlates closely with the development of renal fibrosis. However, the underlying molecular mechanism behind the promotion of renal fibrosis by inflammatory cells remains unclear. Herein, we showed that unilateral ureteral obstruction (UUO) induced Gasdermin D (GSDMD) activation in neutrophils, abundant neutrophil extracellular traps (NETs) formation and macrophage-to-myofibroblast transition (MMT) characterized by α-smooth muscle actin (α-SMA) expression in macrophages. Gsdmd deletion significantly reduced infiltration of inflammatory cells in the kidneys and inhibited NETs formation, MMT and thereby renal fibrosis. Chimera studies confirmed that Gsdmd deletion in bone marrow-derived cells, instead of renal parenchymal cells, provided protection against renal fibrosis. Further, specific deletion of Gsdmd in neutrophils instead of macrophages protected the kidney from undergoing fibrosis after UUO. Single-cell RNA sequencing identified robust crosstalk between neutrophils and macrophages. In vitro, GSDMD-dependent NETs triggered p65 translocation to the nucleus, which boosted the production of inflammatory cytokines and α-SMA expression in macrophages by activating TGF-β1/Smad pathway. In addition, we demonstrated that caspase-11, that could cleave GSDMD, was required for NETs formation and renal fibrosis after UUO. Collectively, our findings demonstrate that caspase-11/GSDMD-dependent NETs promote renal fibrosis by facilitating inflammation and MMT, therefore highlighting the role and mechanisms of NETs in renal fibrosis.

Improving anticancer effect of aPD-L1 through lowering neutrophil infiltration by PLAG in tumor implanted with MB49 mouse urothelial carcinoma

BACKGROUND

The PD-L1 antibody is an immune checkpoint inhibitor (ICI) attracting attention. The third-generation anticancer drug has been proven to be very effective due to fewer side effects and higher tumor-specific reactions than conventional anticancer drugs. However, as tumors produce additional resistance in the host immune system, the effectiveness of ICI is gradually weakening. Therefore, it is very important to develop a combination therapy that increases the anticancer effect of ICI by removing anticancer resistance factors present around the tumor.

METHODS

The syngeneic model was used (n = 6) to investigate the enhanced anti-tumor effect of PD-L1 antibody with the addition of PLAG. MB49 murine urothelial cancer cells were implanted into the C57BL/6 mice subcutaneously. PLAG at different dosages (50/100 mpk) was daily administered orally for another 4 weeks with or without 5 mpk PD-L1 antibody (10F.9G2). PD-L1 antibody was delivered via IP injection once a week.

RESULTS

The aPD-L1 monotherapy group inhibited tumor growth of 56% compared to the positive group, while the PLAG and aPD-L1 co-treatment inhibited by 89%. PLAG treatment effectively reduced neutrophils infiltrating localized in tumor and converted to a tumor microenvironment with anti-tumor effective T-cells. PLAG increased tumor infiltration of CD8 positive cytotoxic T-cell populations while effectively inhibiting the infiltration of neoplastic T-cells such as CD4/FoxP3. Eventually, neutrophil-induced tumor ICI resistance was resolved by restoring the neutrophil-to-lymphocyte ratio to the normal range. In addition, regulation of cytokine and chemokine factors that inhibit neutrophil infiltration and increase the killing activity of cytotoxic T cells was observed in the tumors of mice treated with PLAG + aPD-L1.

CONCLUSIONS

PLAG effectively turned the tumor-promoting microenvironment into a tumor-suppressing microenvironment. As a molecule that increases the anti-tumor effectiveness of aPD-L1, PLAG has the potential to be an essential and effective ICI co-therapeutic agent.

Unveiling Leukocyte Extracellular Traps in Inflammatory Responses of the Central Nervous System

Over the past nearly two decades, increasing evidence has uncovered how immune cells can actively extrude genetic material to entrap invading pathogens or convey sterile inflammatory signals that contribute to shaping immune responses. Originally identified in neutrophils, the release of decondensed chromatin fibers decorated with antimicrobial proteins, called extracellular traps (ETs), has been recognized as a specific form of programmed inflammatory cell death, which is now known to occur in several other leukocytes. Subsequent reports have shown that self-DNA can be extruded from immune cells even in the absence of cell death phenomena. More recent data suggest that ETs formation could exacerbate neuroinflammation in several disorders of the central nervous system (CNS). This review article provides an overview of the varied types, sources, and potential functions of extracellular DNA released by immune cells. Key evidence suggesting the involvement of ETs in neurodegenerative, traumatic, autoimmune, and oncological disorders of the CNS will be discussed, outlining ongoing challenges and drawing potentially novel lines of investigation.

Neutrophil activation in patients with anti-neutrophil cytoplasmic autoantibody-associated vasculitis and large-vessel vasculitis

Objective

To assess markers of neutrophil activation such as calprotectin and N-formyl methionine (fMET) in anti-neutrophil cytoplasmic autoantibody-associated vasculitis (AAV) and large-vessel vasculitis (LVV).

Methods

Levels of fMET, and calprotectin, were measured in the plasma of healthy controls (n=30) and patients with AAV (granulomatosis with polyangiitis (GPA, n=123), microscopic polyangiitis (MPA, n=61)), and LVV (Takayasu’s arteritis (TAK, n=58), giant cell arteritis (GCA, n=68)), at times of remission or flare. Disease activity was assessed by physician global assessment. In vitro neutrophil activation assays were performed in the presence or absence of formyl peptide receptor 1 (FPR1) inhibitor cyclosporine H.

Results

Levels of calprotectin, and fMET were elevated in patients with vasculitis as compared to healthy individuals. Levels of fMET correlated with markers of systemic inflammation: C-reactive protein (r=0.82, p<0.0001), and erythrocyte sedimentation rate (r=0.235, p<0.0001). The neutrophil activation marker, calprotectin was not associated with disease activity. Circulating levels of fMET were associated with neutrophil activation (p<0.01) and were able to induce de novo neutrophil activation via FPR1-mediated signaling.

Conclusion

Circulating fMET appears to propagate neutrophil activation in AAV and LVV. Inhibition of fMET-mediated FPR1 signaling could be a novel therapeutic intervention for systemic vasculitides.