Neutrophil Elastase Activity as a Surrogate Marker for Neutrophil Extracellular Trap Formation following Hematopoietic Stem Cell Transplantation

Neutrophil Extracellular Traps in Pediatric Inflammatory Bowel Disease: A Potential Role in Ulcerative Colitis

Inflammatory bowel disease (IBD), encompassing Crohn's disease (CD) and ulcerative colitis (UC), is a chronic inflammatory condition of the gut affecting both adults and children. Neutrophil extracellular traps (NETs) are structures released by activated neutrophils, potentially contributing to tissue damage in various diseases. This study aimed to explore the presence and role of NETs in pediatric IBD. We compared intestinal biopsies and peripheral blood from 20 pediatric IBD patients (UC and CD) to controls. Biopsy staining and techniques for neutrophil activation were used to assess neutrophil infiltration and NET formation. We also measured the enzymatic activity of key NET proteins and evaluated NET formation in UC patients in remission. Both UC and CD biopsies showed significantly higher levels of neutrophils and NETs compared to controls (p < 0.01), with UC exhibiting the strongest association. Peripheral blood neutrophils from UC patients at diagnosis displayed increased NET formation compared to controls and CD patients. Interestingly, NET formation normalized in UC patients following remission-inducing treatment. This pilot study suggests a potential role for NETs in pediatric IBD, particularly UC. These findings warrant further investigation into the mechanisms of NET involvement and the potential for targeting NET formation as a therapeutic strategy.

Altered neutrophil extracellular traps formation among medical residents with sleep deprivation

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

Delving into the clinical impact of NETs in pediatric cancer

Pediatric cancer, a complex and heterogeneous group of diseases, continues to challenge medical research and treatment strategies. Despite advances in precision medicine and immunotherapy, certain aggressive subtypes of pediatric cancer are resistant to conventional therapies, requiring further exploration of potential therapeutic targets. Neutrophil extracellular traps (NETs), net-like structures released by neutrophils, have emerged as a potential player in the pediatric cancer landscape. However, our understanding of their role in pediatric oncology remains limited. This systematic review examines the current state of the NETs literature in pediatric cancer, focusing on the most frequent subtypes. The review reveals the scarcity of research in this area, highlighting the need for further investigation. The few studies available suggest that NETs may influence infection risk, treatment resistance and prognosis in certain pediatric malignancies. Although the field is still in its infancy, it holds great promise for advancing our understanding of pediatric cancer biology and potential therapeutic pathways. IMPACT: This review identifies a significant gap in research on neutrophil extracellular traps (NETs) in pediatric cancer. It provides a summary of existing studies and their promising findings and potential, as well as a comprehensive overview of current research on NETs in certain tumor types. It also emphasizes the lack of specific studies in pediatric cancer. The review encourages the prioritization of NET research in pediatric oncology, with the aim of improving prognosis and developing new treatments through increased understanding and targeted studies.

Plasma from patients undergoing allogeneic hematopoietic stem cell transplantation promotes NETOSIS in vitro and correlates with inflammatory parameters and clinical severity

Introduction

NETosis, the mechanism by which neutrophils release extracellular traps (NETs), is closely related to inflammation. During the allogeneic hematopoietic stem cell transplantation (allo-HSCT), different stimuli can induce NETs formation. Inflammation and endothelial injury have been associated with acute graft-versus-host disease (aGVHD) and complications after allo-HSCT. We focus on the study of NETosis and its relation with cytokines, hematological and biochemical parameters and clinical outcomes before, during and after allo-HSCT.

Methods

We evaluate the capacity of plasma samples from allo-HSCT patients to induce NETosis, in a cell culture model. Plasma samples from patients undergoing allo-HSCT had a stronger higher NETs induction capacity (NETsIC) than plasma from healthy donors throughout the transplantation process. An optimal cut-off value by ROC analysis was established to discriminate between patients whose plasma triggered NETosis (NETs+IC group) and those who did not (NETs-IC group).

Results

Prior to conditioning treatment, the capacity of plasma samples to trigger NETosis was significantly correlated with the Endothelial Activation and Stress Index (EASIX) score. At day 5 after transplant, patients with a positive NETsIC had higher interleukin (IL)-6 and C-reactive protein (CRP) levels and also a higher Modified EASIX score (M-EASIX) than patients with a negative NETsIC. EASIX and M-EASIX scores seek to determine inflammation and endothelium damage, therefore it could indicate a heightened immune response and inflammation in the group of patients with a positive NETsIC. Cytokine levels, specifically IL-8 and IL-6, significantly increased after allo-HSCT with peak levels reached on day 10 after graft infusion. Only, IL-10 and IL-6 levels were significantly higher in patients with a positive NETsIC. In our small cohort, higher IL-6 and IL-8 levels were related to early severe complications (before day 15 after transplant).

Discussion

Although early complications were not related to NETosis by itself, NETosis could predict overall non-specific but clinically significant complications during the full patient admission. In summary, NETosis can be directly induced by plasma from allo-HSCT patients and NETsIC was associated with clinical indicators of disease severity, cytokines levels and inflammatory markers.

The role of neutrophil extracellular traps in sepsis and sepsis-related acute lung injury

Neutrophils release neutrophil extracellular traps (NETs) to trap pathogenic microorganisms. NETs are involved in the inflammatory response and bacterial killing and clearance. However, their excessive activation can lead to an inflammatory storm in the body, which may damage tissues and cause organ dysfunction. Organ dysfunction is the main pathophysiological cause of sepsis and also a cause of the high mortality rate in sepsis. Acute lung injury caused by sepsis accounts for the highest proportion of organ damage in sepsis. NET formation can lead to the development of sepsis because by promoting the release of interleukin-1 beta, interleukin-8, and tumor necrosis factor-alpha, thereby accelerating acute lung injury. In this review, we describe the critical role of NETs in sepsis-associated acute lung injury and review the current knowledge and novel therapeutic approaches.

The Regulation of Neutrophil Migration in Patients with Sepsis: The Complexity of the Molecular Mechanisms and Their Modulation in Sepsis and the Heterogeneity of Sepsis Patients

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Common causes include gram-negative and gram-positive bacteria as well as fungi. Neutrophils are among the first cells to arrive at an infection site where they function as important effector cells of the innate immune system and as regulators of the host immune response. The regulation of neutrophil migration is therefore important both for the infection-directed host response and for the development of organ dysfunctions in sepsis. Downregulation of CXCR4/CXCL12 stimulates neutrophil migration from the bone marrow. This is followed by transmigration/extravasation across the endothelial cell barrier at the infection site; this process is directed by adhesion molecules and various chemotactic gradients created by chemotactic cytokines, lipid mediators, bacterial peptides, and peptides from damaged cells. These mechanisms of neutrophil migration are modulated by sepsis, leading to reduced neutrophil migration and even reversed migration that contributes to distant organ failure. The sepsis-induced modulation seems to differ between neutrophil subsets. Furthermore, sepsis patients should be regarded as heterogeneous because neutrophil migration will possibly be further modulated by the infecting microorganisms, antimicrobial treatment, patient age/frailty/sex, other diseases (e.g., hematological malignancies and stem cell transplantation), and the metabolic status. The present review describes molecular mechanisms involved in the regulation of neutrophil migration; how these mechanisms are altered during sepsis; and how bacteria/fungi, antimicrobial treatment, and aging/frailty/comorbidity influence the regulation of neutrophil migration.

Selinexor, a selective inhibitor of nuclear export, inhibits human neutrophil extracellular trap formation in vitro

Neutrophils are central players in the innate immune system. To protect against invading pathogens, neutrophils can externalize chromatin to create neutrophil extracellular traps (NETs). While NETs are critical to host defense, they also have deleterious effects, and dysregulation of NETs formation has been implicated in autoimmune diseases, atherosclerosis and thrombotic conditions, cancer progression and dissemination, and acute respiratory distress syndrome. Here, we report that selinexor, a first-in-class selective inhibitor of nuclear export approved for the treatment of multiple myeloma and diffuse large B-cell lymphoma, markedly suppressed the release of NETs in vitro. Furthermore, we demonstrate a significant inhibitory effect of selinexor on NETs formation, but not on oxidative burst or enzymatic activities central to NETs release such as neutrophil elastase, myeloperoxidase or peptidyl arginine deiminase type IV. The inhibitory effect of selinexor was demonstrated in neutrophils activated by a variety of NETs-inducers, including PMA, TGF-β, TNF-α and IL-8. Maximal inhibition of NETs formation was observed using TGF-β, for which selinexor inhibited NETs release by 61.6%. These findings pave the way to the potential use of selinexor in an effort to reduce disease burden by inhibition of NETs.

Determination of reference intervals for neutrophil granular enzymes is affected by cell isolation techniques

OBJECTIVES

Neutrophils and their granular enzymes such as neutrophil elastase (NE) and myeloperoxidase (MPO) play important roles in inflammatory diseases, and might be utilized as biomarkers for disease severity and progression. The aim of this study was to determine reference intervals for NE and MPO activity in healthy volunteers comparing two methods of neutrophil isolation.

METHODS

Neutrophils were isolated using ficoll density gradient centrifugation or immunomagnetic negative selection in two separate volunteers' cohorts. Subsequently, cells were lysed and incubated with chromogens for NE and MPO activity measurements, then measured with a microplate reader at 415 or 450 nm respectively.

RESULTS

The enzymatic activity of NE and MPO depended on the neutrophil isolation technique. Both enzymatic activities were significantly higher (P < 0.001) after isolating neutrophils with ficoll density gradient centrifugation than using the immunomagnetic negative selection.

CONCLUSIONS

We demonstrated that neutrophil isolation is an important factor that influences the outcome of enzymatic activity measurements. Techniques based on immunomagnetic negative selection are favorable, specifically for investigations related to NE and MPO activity. When using NE and MPO activity measurements in clinical practice, care must be taken to interpret the data depending on the applied cell isolation technique.

Uncovering the multifaceted roles played by neutrophils in allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (alloHSCT) is a life-saving procedure used for the treatment of selected hematological malignancies, inborn errors of metabolism, and bone marrow failures. The role of neutrophils in alloHSCT has been traditionally evaluated only in the context of their ability to act as a first line of defense against infection. However, recent evidence has highlighted neutrophils as key effectors of innate and adaptive immune responses through a wide array of newly discovered functions. Accordingly, neutrophils are emerging as highly versatile cells that are able to acquire different, often opposite, functional capacities depending on the microenvironment and their differentiation status. Herein, we review the current knowledge on the multiple functions that neutrophils exhibit through the different stages of alloHSCT, from the hematopoietic stem cell (HSC) mobilization in the donor to the immunological reconstitution that occurs in the recipient following HSC infusion. We also discuss the influence exerted on neutrophils by the immunosuppressive drugs delivered in the course of alloHSCT as part of graft-versus-host disease (GVHD) prophylaxis. Finally, the potential involvement of neutrophils in alloHSCT-related complications, such as transplant-associated thrombotic microangiopathy (TA-TMA), acute and chronic GVHD, and cytomegalovirus (CMV) reactivation, is also discussed. Based on the data reviewed herein, the role played by neutrophils in alloHSCT is far greater than a simple antimicrobial role. However, much remains to be investigated in terms of the potential functions that neutrophils might exert during a highly complex procedure such as alloHSCT.

Effects and Mechanism of Noninvasive Positive-Pressure Ventilation in a Rat Model of Heart Failure Due to Myocardial Infarction

BACKGROUND Impaired heart function induced by myocardial infarction is a leading cause of chronic heart failure (HF). This study aimed to investigate the effects and mechanism of noninvasive positive-pressure ventilation (NIPPV) in a rat model of HF due to myocardial infarction. MATERIAL AND METHODS To explore the therapeutic effect and mechanism of NIPPV on acute myocardial infarction-induced HF, we established a rat model of HF by ligating the anterior descending branch of the left coronary artery and confirmed by ultrasonic cardiography and brain natriuretic peptide 45 detection. RESULTS The levels of heat-shock protein (HSP)-70 increased and matrix metalloproteinase (MMP)-2, MMP-9, and tumor necrosis factor (TNF)-alpha decreased in the group that received NIPPV treatment compared with the control group. In addition, the histopathologic results showed less severe inflammatory infiltration and a smaller area of myocardial fibrosis in the NIPPV treatment group. CONCLUSIONS In a rat model of HF due to myocardial infarction, NIPPV resulted in increased levels of HSP70 and reduced expression of MMP2, MMP9, and TNF-alpha and reduced myocardial neutrophil infiltration and fibrosis. Taken together, we showed that NIPPV is an effective treatment for HF induced by myocardial infarction by inhibiting the release of inflammatory factors and preventing microvascular embolism.