Neutrophil Extracellular Traps: A Potential Therapeutic Target in MPO-ANCA Associated Vasculitis?

Neutrophil extracellular traps in tumor metabolism and microenvironment

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

Decreased NETosis-related regulators in neuromyelitis optica spectrum disorders after plasma exchange

OBJECTIVES

To investigate the impact of plasma exchange (PLEX) on NETosis-related regulators and their correlation with neurological improvement in NMOSD patients.

METHODS

Twelve aquaporin-4 antibodies seropositive NMOSD patients were enrolled. NETosis-related regulators (myeloperoxidase [MPO], citrullinated histone H3 [CIT-H3], peptidyl arginine deiminase 4 [PAD4], neutrophil elastase [NE], CD64), pro-inflammatory cytokines (IL-1, IL-6, IL-12, TNF-α) and anti-inflammatory cytokines (IL-10, TGF-β1) were quantitatively assessed before and after PLEX treatment. Clinical assessments included expanded disability status scale (EDSS) and visual outcome scale (VOS) scores.

RESULTS

Following PLEX, all patients showed symptom improvement, with 66.7 % achieving marked-to-moderate improvement (MMI) at 3 months. Key regulators, such as MPO, CIT-H3, PAD4, NE, and pro-inflammatory cytokines such as IL-1, IL-6, IL-12, and TNF-α, exhibited a statistically significant decrease immediately after the initial PLEX session (P < 0.05). Furthermore, CD64 levels demonstrated a substantial decline after the second PLEX session (P < 0.05). Conversely, the levels of anti-inflammatory cytokines, including IL-10 and TGF-β1, displayed an ascending trend post-PLEX. In clinical relevance analysis, among patients who reached MMI, the reductions in MPO, IL-1, and IL-6 exhibited statistically significant differences when compared to patients in the mild-to-no improvement group (P < 0.05). Pearson correlation analysis revealed that the percentage reduction in IL-6 levels after PLEX was positively correlated with the percentage reduction in patient EDSS/VOS scores (r = 0.638, P < 0.05).

CONCLUSIONS

This study highlights that reduced levels of NETosis-related regulators after PLEX contribute to clinical improvement, suggesting the potential involvement of NETosis in the acute neurological impairment observed in NMOSD.

Role of microRNAs in neutrophil extracellular trap formation and prevention: Systematic narrative review

Active neutrophils play a variety of roles in both innate and adaptive immune responses, and one of the most vital roles is the formation and release of neutrophil extracellular traps (NETs). NETs are created when neutrophils release their chromatin contents to get and eradicate pathogenic organisms essentially. While NET helps fight bacteria, viruses, parasites, and infections, it is also linked to asthma, atherosclerosis, and cancer metastasis. Thus, understanding the molecular mechanisms behind NETosis formation and its inhibition is crucial for developing safe and effective therapies. This systematic review aims to identify the list of miRNAs that are associated with the formation of NETosis and illustrate the mechanism of action by classifying them based on their expression site. Moreover, it summarizes the list of miRNAs that can be targeted therapeutically to reduce NETosis in various disorders. The current study entailed the searching of PubMed and Google Scholar for articles related to the research topic role of miRNAs in NETosis in all types of disorders. The search terms and phrases included "NETs," "neutrophil extracellular traps," "NETosis," "miRNA," "miR," and "micro-RNA." The search was limited to articles published in English since October 2024 in both databases. Following a review of 23 papers, 19 of them met the inclusion and exclusion criteria of this study. Four papers have been removed as they are duplicated or do not meet our criteria. According to the published articles till October 2024, there are 14 miRNAs involved in the molecular pathway of NETosis which are miR-155, miR-1696, miR-7, miR-223, miR-146a, miR-142a-3p, miR-3146, miR-505, miR-4512, miR-15b-5p, miR-16-5p, miR-26b-5p, miR-125a-3p and miR-378a-3p. Moreover, eight miRNAs have been identified as possible therapeutic targets for the suppression of NETosis based on in-vivo studies carried out in various organisms, which are miR-155, miR-146a, miR-1696, miR-223, miR-142a-3p, miR-3146, miR-4512, miR-16-5p. Different miRNAs that are expressed inside or outside of neutrophils can regulate and influence NETosis. Eight miRNAs have also been identified as potential therapeutic targets, which can be utilized to inhibit the molecular pathways associated with NETosis and prevent its negative effects, such as asthma, atherosclerosis, cancer metastasis, and cancer recurrence. However, further human-based research is necessary to completely understand the role of miRNAs in the development of NETosis in humans.

Cardiovascular risk in ANCA-associated vasculitis: Monocyte phenotyping reveals distinctive signatures between serological subsets

BACKGROUND AND AIMS

Anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitides (AAV) is associated with an increased cardiovascular risk, particularly the myeloperoxidase AAV serotype (MPO-AAV). Distinct alterations in monocyte phenotypes may cause accelerated atherosclerotic disease in AAV.

METHODS

A cohort including 43 AAV patients and 19 healthy controls was included for downstream analyses. Extensive phenotyping of monocytes and monocyte-derived macrophages was performed using bulk RNA-sequencing and flow cytometry. An in vitro transendothelial migration assay reflecting intrinsic adhesive and migratory capacities of monocytes was employed. Subsequent sub-analyses were performed to investigate differences between serological subtypes.

RESULTS

Monocyte subset analysis showed increased classical monocytes during active disease, whereas non-classical monocytes were decreased compared to healthy controls (HC). RNA-sequencing revealed upregulation of distinct inflammatory pathways and lipid metabolism-related markers in monocytes of active AAV patients. No differences were detected in the intrinsic monocyte adhesion and migration capacity. Compared to proteinase-3(PR3)-AAV, monocytes of MPO-AAV patients in remission expressed genes related to inflammation, coagulation, platelet-binding and interferon signalling, whereas the expression of chemokine receptors indicative of acute inflammation and monocyte extravasation (i.e., CCR2 and CCR5) was increased in monocytes of PR3-AAV patients. During active disease, PR3-AAV was linked with elevated serum CRP and increased platelet counts compared to MPO-AAV.

CONCLUSIONS

These findings highlight changes in monocyte subset composition and activation, but not in the intrinsic migration capacity of AAV monocytes. MPO-AAV monocytes are associated with sustained upregulation of inflammatory genes, whereas PR3-AAV monocytes exhibit chemokine receptor upregulation. These molecular changes may play a role in elevating cardiovascular risk as well as in the underlying pathophysiology of AAV.

Unravelling the Link between the Gut Microbiome and Autoimmune Kidney Diseases: A Potential New Therapeutic Approach

The gut microbiota and short chain fatty acids (SCFA) have been associated with immune regulation and autoimmune diseases. Autoimmune kidney diseases arise from a loss of tolerance to antigens, often with unclear triggers. In this review, we explore the role of the gut microbiome and how disease, diet, and therapy can alter the gut microbiota consortium. Perturbations in the gut microbiota may systemically induce the translocation of microbiota-derived inflammatory molecules such as liposaccharide (LPS) and other toxins by penetrating the gut epithelial barrier. Once in the blood stream, these pro-inflammatory mediators activate immune cells, which release pro-inflammatory molecules, many of which are antigens in autoimmune diseases. The ratio of gut bacteria Bacteroidetes/Firmicutes is associated with worse outcomes in multiple autoimmune kidney diseases including lupus nephritis, MPO-ANCA vasculitis, and Goodpasture's syndrome. Therapies that enhance SCFA-producing bacteria in the gut have powerful therapeutic potential. Dietary fiber is fermented by gut bacteria which in turn release SCFAs that protect the gut barrier, as well as modulating immune responses towards a tolerogenic anti-inflammatory state. Herein, we describe where the current field of research is and the strategies to harness the gut microbiome as potential therapy.

Targeting Neutrophil Extracellular Traps in Gouty Arthritis: Insights into Pathogenesis and Therapeutic Potential

Gouty arthritis (GA) is an immune-mediated disorder characterized by severe inflammation due to the deposition of monosodium urate (MSU) crystals in the joints. The pathophysiological mechanisms of GA are not yet fully understood, and therefore, the identification of effective therapeutic targets is of paramount importance. Neutrophil extracellular traps (NETs), an intricate structure of DNA scaffold, encompassing myeloperoxidase, histones, and elastases - have gained significant attention as a prospective therapeutic target for gouty arthritis, due to their innate antimicrobial and immunomodulatory properties. Hence, exploring the therapeutic potential of NETs in gouty arthritis remains an enticing avenue for further investigation. During the process of gouty arthritis, the formation of NETs triggers the release of inflammatory cytokines, thereby contributing to the inflammatory response, while MSU crystals and cytokines are sequestered and degraded by the aggregation of NETs. Here, we provide a concise summary of the inflammatory processes underlying the initiation and resolution of gouty arthritis mediated by NETs. Furthermore, this review presents an overview of the current pharmacological approaches for treating gouty arthritis and summarizes the potential of natural and synthetic product-based inhibitors that target NET formation as novel therapeutic options, alongside elucidating the intrinsic challenges of these inhibitors in NETs research. Lastly, the limitations of HL-60 cell as a suitable substitute of neutrophils in NETs research are summarized and discussed. Series of recommendations are provided, strategically oriented towards guiding future investigations to effectively address these concerns. These findings will contribute to an enhanced comprehension of the interplay between NETs and GA, facilitating the proposition of innovative therapeutic strategies and novel approaches for the management of GA.

SARS-CoV-2 infection associated with antineutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis (ANCA-GN): a systematic review and two case reports

BACKGROUND

It has been observed that SARS-CoV-2 infections are associated with the development of various de-novo autoimmune diseases; little is known on new-onset antineutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis (ANCA-GN) after SARS-CoV-2 infections.

METHODS

We conducted a systematic review of previously reported cases with a presumed association of new-onset antineutrophil cytoplasmic antibody-associated glomerulonephritis (ANCA-GN). No language restrictions were applied during the search. The eligible articles included reports of biopsy-proven pauci-immune glomerulonephritis that occurred following SARS-CoV-2 infection. The review was registered in PROSPERO database (CRD42023407786). Two further cases are reported.

RESULTS

The mean age of SARS-CoV-2 infection-associated ANCA-GN was 48 ± 19 years. Fifty-six percent of patients showed positivity for myeloperoxidase (MPO)-ANCA. Among tested patients, 36% had concomitantly positive antinuclear antibodies, and 100% had positive rheumatoid factor. Eleven out of the 21 cases (55%) were diagnosed with ANCA-GN during hospitalization due to SARS-CoV-2 infection. The remaining cases were diagnosed after a median of 2.1 months following COVID-19. Seventy-one percent of patients showed improvement in kidney function following different treatments.

CASE REPORTS

one patient had positive p-ANCA and cryoglobulin. Another case had positive MPO-ANCA, c-ANCA, cryoglobulinemia, and rheumatoid factor.

CONCLUSION

SARS-CoV-2 infection-associated ANCA-GN patients are younger than primary ANCA-GN patients. The presence of atypical ANCA along with co-positivity with other autoantibodies can raise suspicion for SARS-CoV-2 infection-associated ANCA-GN.

Exploration of the Shared Gene Signatures and Molecular Mechanisms between Chronic Bronchitis and Antineutrophil Cytoplasmic Antibody-associated Glomerulonephritis: Evidence from Transcriptome Data

BACKGROUND

Chronic Bronchitis (CB) is a recurrent and persistent pulmonary inflammation disease. Growing evidence suggests an association between CB and Anti-neutrophil Cytoplasmic Antibody-associated Glomerulonephritis (ANCA-GN). However, the precise mechanisms underlying their association remain unclear.

AIMS

The purpose of this study was to further explore the molecular mechanism of the occurrence of chronic bronchitis (CB) associated with anti-neutrophil cytoplasmic antibody-associated glomerulonephritis (ANCA- GN).

OBJECTIVE

Our study aimed to investigate the potential shared pathogenesis of CB-associated ANCA-GN.

METHODS

Datasets of ANCA (GSE108113 and GSE104948) and CB (GSE151052 and GSE162635) were obtained from the Gene Expression Omnibus (GEO) datasets. Firstly, GSE108113 and GSE151052 were analyzed to identify common differentially expressed genes (DEGs) by Limma package. Based on common DEGs, protein-protein interaction (PPI) network and functional enrichment analyses, including GO, KEGG, and GSEA, were performed. Then, hub genes were identified by degree algorithm and validated in GSE104948 and GSE162635. Further PPI network and functional enrichment analyses were performed on hub genes. Additionally, a competitive ceRNA network was constructed through miRanda and spongeScan. Transcription factors (TFs) were predicted and verified using the TRRUST database. Furthermore, the CIBERSORT algorithm was employed to explore immune cell infiltration. The Drug Gene Interaction Database (DGIDB) was utilized to predict small-molecular compounds of CB and ANCA-GN.

RESULTS

A total of 963 DEGs were identified in the integrated CB dataset, and 610 DEGs were identified in the integrated ANCA-GN dataset. Totally, we identified 22 common DEGs, of which 10 hub genes (LYZ, IRF1, PIK3CG, IL2RG, NT5E, ARG2, HBEGF, NFATC2, ALPL, and FKBP5) were primarily involved in inflammation and immune responses. Focusing on hub genes, we constructed a ceRNA network composed of 323 miRNAs and 348 lncRNAs. Additionally, five TFs (SP1, RELA, NFKB1, HIF1A, and SP3) were identified to regulate the hub genes. Furthermore, immune cell infiltration results revealed immunoregulation in CB and ANCA-GN. Finally, some small-molecular compounds (Daclizumab, Aldesleukin, and NT5E) were predicted to predominantly regulate inflammation and immunity, especially IL-2.

CONCLUSION

Our study explores the inflammatory-immune pathways underlying CB-associated ANCA-GN and emphasizes the importance of NETs and lymphocyte differentiation, providing novel insights into the shared pathogenesis and therapeutic targets.

DNase I targeted degradation of neutrophil extracellular traps to reduce the damage on IgAV rat

BACKGROUND

In the past two years, studies have found a significant increase in neutrophil extracellular traps (NETs) in patients with IgA vasculitis (IgAV), which is correlated with the severity of the disease. NETs have been reported as an intervention target in inflammatory and autoimmune diseases. This study aimed to investigate the effect of targeted degradation of NETs using DNase I in IgAV rat model.

METHODS

Twenty-four Sprague-Dawley rats were randomly divided into three groups: the IgAV model group, the DNase I intervention group and the normal control group, with an average of 8 rats in each group. The model group was established by using Indian ink, ovalbumin, and Freund's complete adjuvant. In the intervention group, DNase I was injected through tail vein 3 days before the end of established model. The circulating cell free-DNA (cf-DNA) and myeloperoxidase-DNA (MPO-DNA) were analyzed. The presence of NETs in the kidney, gastric antrum and descending duodenum were detected using multiple fluorescences immunohistochemistry and Western blots. Morphological changes of the tissues were observed.

RESULTS

After the intervention of DNase I, there was a significant reduction in cf-DNA and MPO-DNA levels in the intervention group compared to the IgAV model group (all P<0.001). The presence of NETs in renal, gastric, and duodenal tissues of the intervention group exhibited a significant decrease compared to the IgAV model group (P < 0.01). Moreover, the intervention group demonstrated significantly lower levels of renal MPO and citrullinated histone H3 (citH3) protein expression when compared to the IgAV model group (all P < 0.05). The HE staining results of intervention group demonstrated a significant reduction in congestion within glomerular and interstitial capillaries. Moreover, there was a notable improvement in gastric and intestinal mucosa necrosis, congestion and bleeding. Additionally, there was a substantial decrease in inflammatory cells infiltration.

CONCLUSION

The degradation of NETs can be targeted by DNase I to mitigate tissue damage in IgAV rat models. Targeted regulation of NETs holds potential as a therapeutic approach for IgAV.

Impact of dual neutralization of TNF-α and IL-1β along with Gentamicin treatment on the functions of blood and splenic neutrophils and its role on improvement of S. aureus induced septic arthritis

Researches of recent past years have emphasized potential of antibiotics to improve septic arthritis but as multi-drug resistant strains like MRSA are emerging fast, new alternative therapeutic advances are high in demand. This study aims to figure out the role of neutrophils in regulating inflammatory responses of S. aureus induced septic arthritis while using TNF-α Ab or IL-1β Ab along with antibiotic gentamicin or both in combination. In this study, role of anti-oxidant enzymes were investigated and correlated with generated ROS level. While expression of TLR2, TNFR2, MMP2, RANKL, SAPK/JNK in the spleen were evaluated through western blot. Serum activity of IL-8, IL-10, IL-12, OPG, OPN, CRP was assessed using ELISA. Flow cytometry study evaluated inflamed neutrophil population. Results have shown TNF-α neutralization along with gentamicin was able to reduce arthritic swelling prominently. While combination therapy effectively reduced blood neutrophil ROS activity, arginase activity, MPO activity along with spleen bacterial burden. Serum OPG, CRP, IL-10 level got reduced while serum OPN, IL-8 and IL-12 level enhanced in treatment groups, showing mitigation of inflammatory damage. Overall, it is a novel work that observed how antibiotic and antibody therapy enhanced neutrophil function positively to combat sepsis. This study may not be fully applicable in clinical trials as it is performed with animal model. Clinical trials include crystalline and inflammatory arthritides, trauma, neoplasm. Interdisciplinary collaboration between radiology, orthopaedic surgery and knowledge of animal system responses may give better idea to find proper therapeutic approach in future research works.

Neutrophil extracellular traps and long COVID

Post-acute COVID-19 sequelae, commonly known as long COVID, encompasses a range of systemic symptoms experienced by a significant number of COVID-19 survivors. The underlying pathophysiology of long COVID has become a topic of intense research discussion. While chronic inflammation in long COVID has received considerable attention, the role of neutrophils, which are the most abundant of all immune cells and primary responders to inflammation, has been unfortunately overlooked, perhaps due to their short lifespan. In this review, we discuss the emerging role of neutrophil extracellular traps (NETs) in the persistent inflammatory response observed in long COVID patients. We present early evidence linking the persistence of NETs to pulmonary fibrosis, cardiovascular abnormalities, and neurological dysfunction in long COVID. Several uncertainties require investigation in future studies. These include the mechanisms by which SARS-CoV-2 brings about sustained neutrophil activation phenotypes after infection resolution; whether the heterogeneity of neutrophils seen in acute SARS-CoV-2 infection persists into the chronic phase; whether the presence of autoantibodies in long COVID can induce NETs and protect them from degradation; whether NETs exert differential, organ-specific effects; specifically which NET components contribute to organ-specific pathologies, such as pulmonary fibrosis; and whether senescent cells can drive NET formation through their pro-inflammatory secretome in long COVID. Answering these questions may pave the way for the development of clinically applicable strategies targeting NETs, providing relief for this emerging health crisis.

Mitochondrial modulation of amplified preconditioning influences of remote ischemia plus erythropoietin against skeletal muscle ischemia/reperfusion injury in rats

AIMS

Skeletal muscle ischemia and reperfusion (S-I/R) injury is relieved by interventions like remote ischemic preconditioning (RIPC). Here, we tested the hypothesis that simultaneous exposure to a minimal dose of erythropoietin (EPO) boosts the protection conferred by RIPC against S-I/R injury and concomitant mitochondrial oxidative and apoptotic defects.

MAIN METHODS

S-I/R injury was induced in rats by 3-h right hindlimb ischemia followed by 3-h of reperfusion, whereas RIPC involved 3 brief consecutive I/R cycles of the contralateral hindlimb.

KEY FINDINGS

S-I/R injury caused (i) rises in serum lactate dehydrogenase and creatine kinase and falls in serum pyruvate, (ii) structural deformities like sarcoplasm vacuolations, segmental necrosis, and inflammatory cells infiltration, and (iii) decreased amplitude and increased duration of electromyography action potentials. These defects were partially ameliorated by RIPC and dose-dependently by EPO (500 or 5000 IU/kg). Further, greater repairs of S-I/R-evoked damages were seen after prior exposure to the combined RIPC/EPO-500 intervention. The latter also caused more effective (i) preservation of mitochondrial number (confocal microscopy assessed Mitotracker red staining) and function (citrate synthase activity), (ii) suppression of mitochondrial DNA damage and indices of oxidative stress and apoptosis (succinate dehydrogenase, myeloperoxidase, cardiolipin, and cytochrome c), (iii) preventing calcium and nitric oxide metabolites (NOx) accumulation and glycogen consumption, and (iv) upregulating EPO receptors (EPO-R) gene expression.

SIGNIFICANCE

dual RIPC/EPO conditioning exceptionally mends structural, functional, and neuronal deficits caused by I/R injury and interrelated mitochondrial oxidative and apoptotic damage. Clinically, the utilization of relatively low EPO doses could minimize the hormone-related adverse effects.

NETosis: an emerging therapeutic target in renal diseases

Introduction

Neutrophil extracellular traps (NETs) are web-like structures composed of nuclear and granular components. The primary role of NETS is to prevent the dissemination of microbes and facilitate their elimination. However, this process is accompanied by collateral proinflammatory adverse effects when the NET release becomes uncontrollable, or clearance is impaired. Although NET-induced organ damage is conducted primarily and indirectly via immune complexes and the subsequent release of cytokines, their direct effects on cells are also remarkable. NETosis plays a critical pathogenic role in several renal disorders, such as the early phase of acute tubular necrosis, anti-neutrophil cytoplasmic antibody-mediated renal vasculitis, lupus nephritis, thrombotic microangiopathies, anti-glomerular basement membrane disease, and diabetic nephropathy. Their substantial contribution in the course of these disorders makes them a desirable target in the therapeutic armamentarium. This article gives an in-depth review of the heterogeneous pathogenesis and physiological regulations of NETosis and its pivotal role in renal diseases. Based on the pathogenesis, the article also outlines the current therapeutic options and possible molecular targets in the treatment of NET-related renal disorders.

Methods

We carried out thorough literature research published in PubMed and Google Scholar, including a comprehensive review and analysis of the classification, pathomechanisms, and a broad spectrum of NET-related kidney disorders.

Conclusions

NETosis plays a pivotal role in certain renal diseases. It initiates and maintains inflammatory and autoimmune disorders, thus making it a desirable target for improving patient and renal outcomes. Better understanding and clinical translation of the pathogenesis are crucial aspects to treatment, for improving patient, and renal outcomes.

Mycobacterium tuberculosis PE/PPE proteins enhance the production of reactive oxygen species and formation of neutrophil extracellular traps

Introduction

Neutrophil granulocytes predominate in the lungs of patients infected with Mycobacterium tuberculosis (Mtb) in earlier stages of the disease. During infection, neutrophils release neutrophil extracellular traps (NETs), an antimicrobial mechanism by which a DNA-backbone spiked with antimicrobial components traps the mycobacteria. However, the specific mycobacterial factors driving NET formation remain unclear. Proteins from the proline-glutamic acid (PE)/proline-proline-glutamic acid (PPE) family are critical to Mtb pathophysiology and virulence.

Methods

Here, we investigated NET induction by PE18, PPE26, and PE31 in primary human blood-derived neutrophils. Neutrophils were stimulated with the respective proteins for 3h, and NET formation was subsequently assessed using confocal fluorescence microscopy. Intracellular ROS levels and cell necrosis were estimated by flow cytometry. Additionally, the influence of phorbol-12-myristate-13-acetate (PMA), a known NADPH oxidase enhancer, on NET formation was examined. Neutrophil integrity following incubation with the PE/PPE proteins was evaluated using transmission electron microscopy.

Results

For the first time, we report that stimulation of primary human blood-derived neutrophils with Mtb proteins PE18, PPE26, and PE31 resulted in the formation of NETs, which correlated with an increase in intracellular ROS levels. Notably, the presence of PMA further amplified this effect. Following incubation with the PE/PPE proteins, neutrophils were found to remain viable and structurally intact, as verified through transmission electron microscopy, indicating the occurrence of vital NET formation.

Discussion

These findings offer valuable insights that contribute to a better understanding of host-pathogen interactions during Mtb infection. Moreover, they underscore the significance of these particular Mtb antigens in triggering NET formation, representing a distinctive and previously unrecognized function of PE/PPE antigens.

The central role of neutrophil extracellular traps (NETs) and by-products in COVID-19 related pulmonary thrombosis

Extracellular trap networks (neutrophil extracellular traps [NETs]) of polymorphonuclear neutrophils are mesh-like substances that prevent the spread of pathogens. They primarily consist of DNA skeletons, histones, granule components, and cytoplasmic proteins. NETs formation requires a certain environment and there are different pathways for NETs production. However, it is still not clear how severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) promotes NETs. NETs exert antiinflammatory effects through immune response, while they can also lead to certain adverse outcomes, such as the development of immunothrombosis. Coronavirus disease 2019 (COVID-19) is an inflammatory reaction affecting various organs caused by SARS-CoV-2, especially the lungs. NETs production and disease severity are linked with unique neutrophil clusters by single-cell RNA sequencing. NETs might exert an anti-inflammatory role in the initial stage of lung tissue inflammation. Nevertheless, numerous studies and cases have shown that they can also result in pulmonary thrombosis. There is mounting evidence that NETs are tightly related with COVID-19 pulmonary thrombosis, and many studies on the mechanisms are involved. The role and mechanism of NETs in the development of pulmonary thrombosis will be the main topics of this manuscript. Additionally, we address the potential targeting of NETs in COVID-19 patients.

Complement therapeutics are coming of age in rheumatology

The complement system was described over 100 years ago, and it is well established that activation of this pathway accompanies the great majority of autoimmune and inflammatory diseases. In addition, over three decades of work in murine models of human disease have nearly universally demonstrated that complement activation is upstream of tissue injury and the engagement of pro-inflammatory mechanisms such as the elaboration of cytokines and chemokines, as well as myeloid cell recruitment and activation. With that background, and taking advantage of advances in the development of biologic and small-molecule therapeutics, the creation and clinical evaluation of complement therapeutics is now rapidly expanding. This article reviews the current state of the complement therapeutics field, with a focus on their use in diseases cared for or consulted upon by rheumatologists. Included is an overview of the activation mechanisms and components of the system, in addition to the mechanisms by which the complement system interacts with other immune system constituents. The various therapeutic approaches to modulating the system in rheumatic and autoimmune diseases are reviewed. To understand how best to clinically assess the complement system, methods of its evaluation are described. Finally, next-generation therapeutic and diagnostic advances that can be envisioned for the future are discussed.

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.

NETworking with cancer: The bidirectional interplay between cancer and neutrophil extracellular traps

Neutrophils are major effectors and regulators of the immune system. They play critical roles not only in the eradication of pathogens but also in cancer initiation and progression. Conversely, the presence of cancer affects neutrophil activity, maturation, and lifespan. By promoting or repressing key neutrophil functions, cancer cells co-opt neutrophil biology to their advantage. This co-opting includes hijacking one of neutrophils' most striking pathogen defense mechanisms: the formation of neutrophil extracellular traps (NETs). NETs are web-like filamentous extracellular structures of DNA, histones, and cytotoxic granule-derived proteins. Here, we discuss the bidirectional interplay by which cancer stimulates NET formation, and NETs in turn support disease progression. We review how vascular dysfunction and thrombosis caused by neutrophils and NETs underlie an elevated risk of death from cardiovascular events in cancer patients. Finally, we propose therapeutic strategies that may be effective in targeting NETs in the clinical setting.

NETosis and kidney disease: what do we know?

Neutrophils are the most abundant leukocytes in the blood. They are rapidly mobilized from the circulation to sites of inflammation and/or infection. In affected tissues, neutrophils exhibit some dramatic antimicrobial functions, including degranulation, reactive oxygen species (ROS) production, phagocytosis, and formation of neutrophil extracellular traps (NETs). Like other cells of the immune system, after fulfilling their biological duties, they enter the path of death. Depending on the conditions, they may undergo different types of cell death (apoptosis, necrosis, necroptosis, autophagy, NETosis, and pyroptosis) that require the participation of multiple signaling pathways. NETosis is a unique neutrophil cell death mechanism that gives rise to different inflammatory and autoimmune pathological conditions. Recent studies have shown that NETosis also plays a role in the formation and/or progression of kidney diseases. This review discusses the underlying mechanism of NETosis and its relationship with some major kidney diseases in light of the current knowledge.

Antibody-modified DNase I micelles specifically recognize the neutrophil extracellular traps (NETs) and promote their degradation

Neutrophil extracellular traps (NETs) are structures consisting of decondensed chromatin with associated proteins, including histones and antimicrobial peptides, released from activated neutrophils. They are believed to be one of the body's first lines of defense against infectious agents. Despite their beneficial effect on the immune response process, some studies indicate that their excessive formation and the associated accumulation of extracellular DNA (eDNA) together with other polyelectrolytes (F-actin) plays an important role in the pathogenesis of many diseases. Thus NETs formation and removal are clinically significant. The monoclonal antibody 2C5 has strong specificity for intact nucleohistones (NS) and targets NS in NETs as we previously confirmed. Creation of a nano preparation that can specifically recognize and destroy NETs represents the aim for treatment many diseases. 2C5 antibody functionalized micelles coated with DNase I were created to achieve this aim.

Contributions of animal models to mechanistic understandings of antibody-dependent disease and roles of the amplification loop

The complement system plays an important pathophysiologic role in human diseases associated with immune or ischemic insults. In addition to understanding the effector mechanisms that are important for the biological effects of the system, substantial efforts have gone into understanding which specific complement activation pathways generate these potent effects. These approaches include the use of gene-targeted mice and specific pathway inhibitors, as well as the integration of human disease genetic and biomarker studies. In some disease states, it is quite clear that the alternate pathway plays a unique role in the initiation of the complement system. However, although initially a widely unexpected finding, it has now been shown in many tissue-based disease models and in initial human studies that engagement of the amplification loop is also essential for tissue injury when the classical and/or lectin pathways initiate pathway activation through pathogenic autoantibodies. This review provides evidence for such a conclusion through animal models, focusing on pathogenic antibody passive transfer models but also other relevant experimental systems. These data, along with initial biomarkers and clinical trial outcomes in human diseases that are associated with pathogenic autoantibodies, suggest that targeting the alternative pathway amplification loop may have near-universal therapeutic utility for tissue-based diseases.

NETosis as an oncologic therapeutic target: a mini review

Neutrophil Extracellular Traps (NETs) are a key form of pro-inflammatory cell death of neutrophils characterized by the extrusion of extracellular webs of DNA containing bactericidal killing enzymes. NETosis is heavily implicated as a key driver of host damage in autoimmune diseases where injurious release of proinflammatory enzymes damage surrounding tissue and releases 70 known autoantigens. Recent evidence shows that both neutrophils and NETosis have a role to play in carcinogenesis, both indirectly through triggering DNA damage through inflammation, and directly contributing to a pro-tumorigenic tumor microenvironment. In this mini-review, we summarize the current knowledge of the various mechanisms of interaction and influence between neutrophils, with particular attention to NETosis, and cancer cells. We will also highlight the potential avenues thus far explored where we can intercept these processes, with the aim of identifying promising prospective targets in cancer treatment to be explored in further studies.

Increased levels of immature and activated low density granulocytes and altered degradation of neutrophil extracellular traps in granulomatosis with polyangiitis

Granulomatosis with Polyangiitis (GPA) is a small vessel vasculitis typically associated with release of neutrophil extracellular traps (NETs) by activated neutrophils. In this study, we further aimed to investigate the contributions of neutrophils and NETs to the complex disease pathogenesis. We characterized the phenotype of neutrophils and their capacity to induce NETs. In addition, the level of circulating NETs, determined by neutrophil elastase/DNA complexes, and the capacity of patient sera to degrade NETs were investigated from blood samples of 12 GPA patients, 21 patients with systemic lupus erythematosus (SLE) and 21 healthy donors (HD). We found that GPA patients had significantly increased levels of low-density granulocytes (LDGs) compared to HD, which displayed an activated and more immature phenotype. While the propensity of normal-density granulocytes to release NETs and the levels of circulating NETs were not significantly different from HD, patient sera from GPA patients degraded NETs less effectively, which weakly correlated with markers of disease activity. In conclusion, increased levels of immature and activated LDGs and altered degradation of circulating NETs may contribute to pathogenesis of GPA, potentially by providing a source of autoantigens that trigger or further enhance autoimmune responses.

The Presence of Antineutrophil Cytoplasmic Antibodies and Antiphospholipid Antibodies in Patients with Severe Acute Respiratory Syndrome Coronavirus 2: A Case-Control Study among Sudanese Patients

Patients infected with COVID-19 are at an increased risk for thrombosis, suggesting a possible role of COVID-19 in the induction of coagulopathy. This study aimed to investigate the presence of prothrombotic antineutrophil cytoplasmic antibodies (ANCA) and antiphospholipid antibodies (aPLs) in the course of COVID-19 infection and to correlate these markers with severity and fatality, suggesting that COVID-19-induced autoimmune thrombosis is a possible axis in the inflammatory circuit of this infection. To investigate this, we conducted a case-control study which included patients with a positive reverse transcription-polymerase chain reaction (RT-PCR) test of COVID-19 and a control group with negative COVID-19 PCR and antibody (IgG-IgM and IgA nucleoprotein) ELISA results. An indirect immunofluorescence assay using granulocyte biochips (Aesku slides from AESKU DIAGNOSTICS, Germany) was used to detect ANCA (IgG), as well as multiplex ELISA for the detection of antiphospholipid antibodies for all patients with COVID-19 and for the control group. The results revealed the detection of antiphospholipid antibodies (IgG) in one patient out of the 45 patients in the case group. 1/45(2.2%) and 7/45(15.6%) tested positive for ANCA. Five were men and two were females, with one case revealed to be positive for both aPL and ANCA. A cytoplasmic reaction on the eosinophil granulocytes was observed in 2 cases; both were positive for ANCA. Other markers (CRP, APTT, PT, INR, ESR, and neutrophil and lymphocyte counts) were included in the study, along with demographic data. No aPL or ANCA reactions were detected for any of the control groups. These findings suggest that aPL and ANCA may be induced during the course of inflammation in COVID-19 and possibly contribute to the disease's severity and mortality.

Clinical significance of acute exacerbation in interstitial lung disease with antineutrophil cytoplasmic antibody: an indicator of poor prognosis

BACKGROUND

The association between interstitial lung disease (ILD) and antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) has been increasingly recognized in recent years. The clinical features and prognostic differences between AAV-associated ILD and isolated ANCA-positive idiopathic interstitial pneumonias (IIPs) remain unclear. The purpose of this study was to determine the clinical significance and prognosis of ANCA-positive ILD to further guide clinical management.

METHODS

This study retrospectively reviewed the data of 379 ILD patients with available ANCA results and ultimately analysed 49 ANCA-positive patients. AAV diagnosis was based on the 2012 revised Chapel Hill Consensus Conference (CHCC) criteria, and 33 of 49 patients were diagnosed with microscopic polyangiitis (MPA). The baseline clinical information and laboratory parameters were collected and analysed at each patient's initial diagnosis.

RESULTS

Among 49 ANCA-positive ILD patients, the high-resolution computed tomography (HRCT) pattern was mainly usual interstitial pneumonia (UIP) (59.18%), followed by nonspecific interstitial pneumonia (NSIP) (26.53%). The C-reactive protein (CRP) level (43.89± 40.61 versus 18.74± 20.05, p = 0.028) and erythrocyte sedimentation rate (ESR) (71.97± 42.73 versus 40.69± 28.46, p = 0.011) were significantly higher in the MPA-ILD group than in the ANCA-IIP group. Haemoglobin (113.09 ± 24.47 versus 132.19± 13.34, p = 0.006) and albumin (32.95± 5.84 versus 36.52± 3.94, p = 0.032) levels were significantly lower. Survival was shorter among MPA-ILD patients than among ANCA-IIP patients [hazard ratio (HR) 3.38, 95% confidence interval (CI) 1.32-8.67, p = 0.040]. In the multivariable Cox analysis, a diagnosis of MPA (HR 3.91, 95% CI 1.07-14.08, p = 0.038) and acute exacerbation (AE) of ILD (HR 9.43, 95% CI 2.89-30.30, p < 0.001) were significantly independently associated with shorter survival in ANCA-positive ILD patients, and the NSIP pattern (HR 0.07, 95% CI 0.01-0.41, p = 0.003) was independently associated with prolonged survival.

CONCLUSION

ANCA-ILD patients mostly have myeloperoxidase (MPO)-ANCA positivity and an MPA diagnosis. Survival was shorter among MPA-ILD patients than among ANCA-IIP patients. Respiratory failure and AE were associated with poorer prognosis. Early antifibrotic treatment may be a reasonable treatment option in fibrotic ILD patients with ANCA positivity.

Old known and possible new biomarkers of ANCA-associated vasculitis

Antineutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV) comprises a group of multisystem disorders involving severe, systemic, small-vessel vasculitis with short- and long term serious and life-threating complications. Despite the simplification of treatment, fundamental aspects concerning assessment of its efficacy and its adaptation to encountered complications or to the relapsing/remitting/subclinical disease course remain still unknown. The pathogenesis of AAV is complex and unique, and despite the progress achieved in the last years, much has not to be learnt. Foremost, there is still no accurate marker enabling us to monitoring disease and guide therapy. Therefore, the disease management relays often on clinical judgment and follows a" trial and error approach". In the recent years, an increasing number of new molecules s have been explored and used for this purpose including genomics, B- and T-cell subpopulations, complement system factors, cytokines, metabolomics, biospectroscopy and components of our microbiome. The aim of this review is to discuss both the role of known historical and clinically established biomarkers of AAV, as well as to highlight potential new ones, which could be used for timely diagnosis and monitoring of this devastating disease, with the goal to improve the effectiveness and ameliorate the complications of its demanding therapy.

Mechanisms regulating neutrophil responses in immunity, allergy, and autoimmunity

Neutrophil granulocytes, or neutrophils, are the most abundant circulating leukocytes in humans and indispensable for antimicrobial immunity, as exemplified in patients with inborn and acquired defects of neutrophils. Neutrophils were long regarded as the foot soldiers of the immune system, solely destined to execute a set of effector functions against invading pathogens before undergoing apoptosis, the latter of which was ascribed to their short life span. This simplistic understanding of neutrophils has now been revised on the basis of insights gained from the use of mouse models and single-cell high-throughput techniques, revealing tissue- and context-specific roles of neutrophils in guiding immune responses. These studies also demonstrated that neutrophil responses were controlled by sophisticated feedback mechanisms, including directed chemotaxis of neutrophils to tissue-draining lymph nodes resulting in modulation of antimicrobial immunity and inflammation. Moreover, findings in mice and humans showed that neutrophil responses adapted to different deterministic cytokine signals, which controlled their migration and effector function as well as, notably, their biologic clock by affecting the kinetics of their aging. These mechanistic insights have important implications for health and disease in humans, particularly, in allergic diseases, such as atopic dermatitis and allergic asthma bronchiale, as well as in autoinflammatory and autoimmune diseases. Hence, our improved understanding of neutrophils sheds light on novel therapeutic avenues, focusing on molecularly defined biologic agents.

Heme Proteins and Kidney Injury: Beyond Rhabdomyolysis

Heme proteins, the stuff of life, represent an ingenious biologic strategy that capitalizes on the biochemical versatility of heme, and yet is one that avoids the inherent risks to cellular vitality posed by unfettered and promiscuously reactive heme. Heme proteins, however, may be a double-edged sword because they can damage the kidney in certain settings. Although such injury is often viewed mainly within the context of rhabdomyolysis and the nephrotoxicity of myoglobin, an increasing literature now attests to the fact that involvement of heme proteins in renal injury ranges well beyond the confines of this single disease (and its analog, hemolysis); indeed, through the release of the defining heme motif, destabilization of intracellular heme proteins may be a common pathway for acute kidney injury, in general, and irrespective of the underlying insult. This brief review outlines current understanding regarding processes underlying such heme protein-induced acute kidney injury (AKI) and chronic kidney disease (CKD). Topics covered include, among others, the basis for renal injury after the exposure of the kidney to and its incorporation of myoglobin and hemoglobin; auto-oxidation of myoglobin and hemoglobin; destabilization of heme proteins and the release of heme; heme/iron/oxidant pathways of renal injury; generation of reactive oxygen species and reactive nitrogen species by NOX, iNOS, and myeloperoxidase; and the role of circulating cell-free hemoglobin in AKI and CKD. Also covered are the characteristics of the kidney that render this organ uniquely vulnerable to injury after myolysis and hemolysis, and pathobiologic effects emanating from free, labile heme. Mechanisms that defend against the toxicity of heme proteins are discussed, and the review concludes by outlining the therapeutic strategies that have arisen from current understanding of mechanisms of renal injury caused by heme proteins and how such mechanisms may be interrupted.

Current perspectives on the diagnosis, assessment, and management of vasculitic neuropathy

INTRODUCTION

Vasculitic neuropathy can present associated with both primary and secondary systemic vasculitis as a result from underlying diseases such as rheumatic diseases and infections, Moreover, confined vasculitis in the peripheral nervous system may be present. Thus, the diagnosis and management of vasculitic neuropathy require multidisciplinary approaches.

AREAS COVERED

Current views as well as relevant clinical research on the diagnosis, assessment, and management of vasculitic neuropathy are reviewed to suggest appropriate treatment strategies. We searched PubMed and Google Scholar for reports published between July 2017 and July 2022.

EXPERT OPINION

For the treatment of vasculitic neuropathy, determining the causative primary disease is important and often requires diagnosis by tissue biopsy. Due to the scarce research on the treatment of vasculitic neuropathy, treatment is empirically based on findings from studies of systemic vasculitides involving other organs, particularly antineutrophil cytoplasmic antibody-associated vasculitis. In addition to conventional glucocorticoids and immunosuppressive agents, complement-targeted therapy, anti-B-cell therapy, and disease-specific molecular targeted therapies have recently gained relevance. Future research is needed to develop new patient-specific therapeutic options.

Neutrophils in the Pathogenesis of Rheumatic Diseases

Rheumatic diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), are a group of auto-inflammatory disorders associated with substantial morbidity and mortality. One unifying feature of these diseases is the presence of abnormal neutrophils exhibiting dysregulated neutrophil extracellular trap (NET) release, reactive oxygen species (ROS) production, degranulation, and pro-inflammatory cytokines secretion. Moreover, the release of autoantigens associated with NETs promotes the generation of autoantibodies and a breakdown of self-tolerance, thereby perpetuating inflammation and tissue injury in these patients. In recent years, targeted therapies directed at neutrophilic effector functions have shown promising results in the management of rheumatic diseases. In this review, we will highlight the emerging roles of neutrophils in the onset and progression of rheumatic diseases, and further discuss current and future therapeutic approaches targeting the pathogenic functions of neutrophils, which can modulate inflammation and hence improve patients' survival and quality of life.

Neutrophils in ANCA-associated vasculitis: Mechanisms and implications for management

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a group of systemic autoimmune diseases, which is typified by inflammatory necrosis predominantly affecting the small vessels and often accompanied by positive ANCA. Clinically, AAV primarily includes microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GPA), and eosinophilic granulomatosis with polyangiitis (EGPA). It has been found that in AAV pathogenesis, both innate and adaptive immunity are related to neutrophil function mutually. Many proteins, such as myeloperoxidase (MPO) and proteinase 3 (PR3), in neutrophil cytoplasm lead to the production of proteins such as MPO-ANCA and PR3-ANCA by activating adaptive immunity. In addition, through the process of neutrophil extracellular trap (NET) formation, activation of an alternative complement pathway and the respiratory burst can stimulate the neutrophils close to vascular endothelial cells and will participate the vessel inflammation. This review aims to reveal the potential mechanisms regulating the association between the neutrophils and various types of AAVs and to emphasize the results of recent findings on these interactions. Moreover, multiple underlying signaling pathways involved in the regulation of neutrophils during AAV processes have also been discussed. The ultimate goal of this review is to identify novel biomarkers and therapeutic targets for AAV management in the future.

Environmental factors influencing the risk of ANCA-associated vasculitis

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a group of diseases characterized by inflammation and destruction of small and medium-sized blood vessels. Clinical disease phenotypes include microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GPA), and eosinophilic granulomatosis with polyangiitis (EGPA). The incidence of AAV has been on the rise in recent years with advances in ANCA testing. The etiology and pathogenesis of AAV are multifactorial and influenced by both genetic and environmental factors, as well as innate and adaptive immune system responses. Multiple case reports have shown that sustained exposure to silica in an occupational environment resulted in a significantly increased risk of ANCA positivity. A meta-analysis involving six case-control studies showed that silica exposure was positively associated with AAV incidence. Additionally, exposure to air pollutants, such as carbon monoxide (CO), is a risk factor for AAV. AAV has seasonal trends. Studies have shown that various environmental factors stimulate the body to activate neutrophils and expose their own antigens, resulting in the release of proteases and neutrophil extracellular traps, which damage vascular endothelial cells. Additionally, the activation of complement replacement pathways may exacerbate vascular inflammation. However, the role of environmental factors in the etiology of AAV remains unclear and has received little attention. In this review, we summarized the recent literature on the study of environmental factors, such as seasons, air pollution, latitude, silica, and microbial infection, in AAV with the aim of exploring the relationship between environmental factors and AAV and possible mechanisms of action to provide a scientific basis for the prevention and treatment of AAV.

Detection of neutrophil extracellular traps in patient plasma: method development and validation in systemic lupus erythematosus and healthy donors that carry IRF5 genetic risk

Neutrophil extracellular traps (NETs) are web-like structures extruded by neutrophils after activation or in response to microorganisms. These extracellular structures are decondensed chromatin fibers loaded with antimicrobial granular proteins, peptides, and enzymes. NETs clear microorganisms, thus keeping a check on infections at an early stage, but if dysregulated, may be self-destructive to the body. Indeed, NETs have been associated with autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), antiphospholipid syndrome (APS), psoriasis, and gout. More recently, increased NETs associate with COVID-19 disease severity. While there are rigorous and reliable methods to quantify NETs from neutrophils via flow cytometry and immunofluorescence, the accurate quantification of NETs in patient plasma or serum remains a challenge. Here, we developed new methodologies for the quantification of NETs in patient plasma using multiplex ELISA and immunofluorescence methodology. Plasma from patients with SLE, non-genotyped healthy controls, and genotyped healthy controls that carry either the homozygous risk or non-risk IRF5-SLE haplotype were used in this study. The multiplex ELISA using antibodies detecting myeloperoxidase (MPO), citrullinated histone H3 (CitH3) and DNA provided reliable detection of NETs in plasma samples from SLE patients and healthy donors that carry IRF5 genetic risk. An immunofluorescence smear assay that utilizes only 1 µl of patient plasma provided similar results and data correlate to multiplex ELISA findings. The immunofluorescence smear assay is a relatively simple, inexpensive, and quantifiable method of NET detection for small volumes of patient plasma.

Increased MPO in Colorectal Cancer Is Associated With High Peripheral Neutrophil Counts and a Poor Prognosis: A TCGA With Propensity Score-Matched Analysis

Background

Myeloperoxidase (MPO) has been demonstrated to be a local mediator of inflammation in tissue damage in various inflammatory diseases. Given its controversial effect on colorectal cancer (CRC), there has been growing interest in investigating the role of this enzyme in CRC. The mechanism underlying MPO activity and CRC progression requires further clarification.

Methods

The expression and function of MPO in CRC were evaluated using TCGA analysis. TCGA, TIMER, and Human Cell Landscape analyses were used to analyze the correlation between MPO expression and neutrophil infiltration in CRC. Spearman's bivariate correlation analysis was used to verify the correlation between MPO levels in CRC and the peripheral neutrophil count. In the clinical analysis, 8,121 patients who underwent elective surgery for CRC were enrolled in this retrospective cohort study from January 2008 to December 2014. Propensity score matching was used to address the differences in baseline characteristics. The Kaplan-Meier method and Cox regression analysis were used to identify independent prognostic factors in patients with CRC.

Results

MPO was upregulated in CRC tissues, which is related to malignant progression and worse survival in CRC patients from TCGA analysis. MPO was significantly correlated with the infiltration level of neutrophils in CRC in TCGA, TIMER, and Human Cell Landscape analyses. MPO was positively correlated with the peripheral neutrophil count. Data of the 8,121 patients who underwent CRC surgery were available for analysis. After propensity score matching, 3,358 patients were included in each group. Kaplan-Meier survival curves showed that high preoperative neutrophil levels were associated with decreased overall survival (OS; P < 0.001) and disease-free survival (DFS; P = 0.015). The preoperative neutrophil count was an independent risk factor for OS (hazard ratio [HR], 1.157; 95% confidence interval [CI], 1.055-1.268; P = 0.002) and DFS (HR, 1.118; 95% CI, 1.009-1.238; P = 0.033).

Conclusions

Our research indicates that increased MPO levels in CRC are significantly correlated with high preoperative neutrophil counts, and both serve as prognostic indicators for worse survival in CRC patients. Our study suggests that neutrophils may be key players in the mechanism linking MPO levels with poor CRC outcomes.

The emerging role of neutrophilic extracellular traps in intestinal disease

Neutrophil extracellular traps (NETs) are extracellular reticular fibrillar structures composed of DNA, histones, granulins and cytoplasmic proteins that are delivered externally by neutrophils in response to stimulation with various types of microorganisms, cytokines and host molecules, etc. NET formation has been extensively demonstrated to trap, immobilize, inactivate and kill invading microorganisms and acts as a form of innate response against pathogenic invasion. However, NETs are a double-edged sword. In the event of imbalance between NET formation and clearance, excessive NETs not only directly inflict tissue lesions, but also recruit pro-inflammatory cells or proteins that promote the release of inflammatory factors and magnify the inflammatory response further, driving the progression of many human diseases. The deleterious effects of excessive release of NETs on gut diseases are particularly crucial as NETs are more likely to be disrupted by neutrophils infiltrating the intestinal epithelium during intestinal disorders, leading to intestinal injury, and in addition, NETs and their relevant molecules are capable of directly triggering the death of intestinal epithelial cells. Within this context, a large number of NETs have been reported in several intestinal diseases, including intestinal infections, inflammatory bowel disease, intestinal ischemia–reperfusion injury, sepsis, necrotizing enterocolitis, and colorectal cancer. Therefore, the formation of NET would have to be strictly monitored to prevent their mediated tissue damage. In this review, we summarize the latest knowledge on the formation mechanisms of NETs and their pathophysiological roles in a variety of intestinal diseases, with the aim of providing an essential directional guidance and theoretical basis for clinical interventions in the exploration of mechanisms underlying NETs and targeted therapies.

An Emerging Role for Neutrophil Extracellular Traps in IgA Vasculitis: A Mini-Review

Immunoglobulin A vasculitis (IgAV) is the most common systemic small vessel vasculitis in childhood. Its clinical manifestations are non-thrombocytopenic purpura, accompanied by gastrointestinal tract, joint, kidney and other organ system involvement. The pathogenesis of IgAV has not been fully elucidated. It may be related to many factors including genetics, infection, environmental factors, and drugs. The most commonly accepted view is that galactose-deficient IgA1 and the deposition of IgA and complement C3 in small blood vessel walls are key contributors to the IgAV pathogenesis. Extensive neutrophil extracellular traps (NETs) in the peripheral circulation and skin, kidney, and gastrointestinal tissue of patients with IgAV has been identified in the past two years and is associated with disease activity. This mini-review provides a possible mechanism for NETs involvement in the pathogenesis of IgAV.

Circulating immune-complexes and complement activation through the classical pathway in myeloperoxidase-ANCA-associated glomerulonephritis

Background

Anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis (AAGN) is the fulminant glomerular diseases with poor renal prognosis. Activation of the complement system has recently been reported in the pathogenesis of AAGN, but it remains to be clarified as to which complement pathway is mainly involved.

Methods

20 patients with myeloperoxidase (MPO)-AAGN were retrospectively evaluated. Using serum samples, circulating immune-complexes (CICs) were assessed by the monoclonal rheumatoid factor assay, and C5a and C5b-9 were assessed by ELISA. Complement activation through the classical pathway was further evaluated by the WIESLAB® Complement System Classical Pathway kit. The affinities of ANCAs were evaluated by a competitive inhibition method using ELISA, and were classified into the high, and low-affinity group. Deposition of complement components, such as C3, C5, C4d, C5b-9, factor Bb, mannan-binding lectin serine peptidase (MASP)-1, MASP-2, and mannose/mannan-binding lectin (MBL), in frozen renal sections were analyzed by immunofluorescence staining.

Results

CICs were found to be positive in 65% of the patients. All CIC-positive patients belonged to the high-affinity group. Furthermore, serum C5a and C5b-9 were significantly increased in MPO-AAGN patients, and these levels positively correlated with CIC levels. A significant negative correlation was also found between levels of WIESLAB® classical pathway kit and CICs. By immunofluorescence staining, glomerular deposition of C4d, C5, and C5b-9 were observed in similar distributions in MPO-AAGN patients, whereas the deposition of MASP-1, MASP-2, MBL, and factor Bb were minimal.

Conclusions

These results suggest the involvement of immune-complex induced complement activation through the classical pathway in the pathogenesis of MPO-AAGN.

Presepsin production in monocyte/macrophage-mediated phagocytosis of neutrophil extracellular traps

Presepsin, a biomarker discovered in Japan, has been clinically applied as a diagnostic aid for sepsis. Recently, however, it has been reported that presepsin levels are elevated in patients with severe systemic lupus erythematosus without infection, suggesting the existence of a production mechanism that does not involve bacterial phagocytosis. In this study, we aimed to elucidate the mechanism of presepsin production without bacterial phagocytosis and explore the clinical significance of presepsin. Neutrophil extracellular traps (NETs) were induced by Escherichia coli and phorbol myristate acetate (PMA) in neutrophils isolated from the peripheral blood of healthy subjects. NET induction alone did not increase presepsin levels, but co-culturing with monocytes significantly increased them. The addition of a NET formation inhibitor also suppressed presepsin levels, suggesting that presepsin production is greatly influenced by monocyte phagocytosis of NETs. Phagocytosis of NETs by THP-1 and U937 cells, which was induced by CD14 expression, also increased presepsin levels. This study suggests that presepsin can be used to assess the severity of inflammatory diseases, such as autoimmune diseases, and monitor treatment effects.

Antineutrophilic cytoplasmic antibody-associated vasculitis and the kidney

PURPOSE OF REVIEW

The purpose of this review is to highlight recent studies that have emerged on the topic of ANCA-associated vasculitis with some historical context. The review also discusses how the adult data is relevant to pediatric patients.

RECENT FINDINGS

Pediatric studies on AAV are lacking. Therapies targeted to the inflammatory cascade specifically implicated in AAV, such as MPO inhibitors and complement mediators, are emerging. The PEXIVAS study recently called into question the routine use of plasma exchange (PLEX) in severe AAV, with no difference in ESKD or mortality found between patients who did or did not receive PLEX. Longer maintenance duration of nearly 48 months is preferred as compared with shorter duration in patients who are not on dialysis because of higher relapse rates in children with AAV.

SUMMARY

Current treatment in AAV includes corticosteroids, rituximab, and cyclophosphamide for induction. Maintenance therapy commonly consists of azathioprine or rituximab. Plasma exchange (PLEX) is no longer recommended for induction therapy for AAV but some experts still consider this as an option for patients who are not responding to therapy or have severe disease at presentation. However, emerging novel therapies may be on the horizon.

The Expanding Role of Extracellular Traps in Inflammation and Autoimmunity: The New Players in Casting Dark Webs

The first description of a new form of neutrophil cell death distinct from that of apoptosis or necrosis was discovered in 2004 and coined neutrophil extracellular traps "(NETs)" or "NETosis". Different stimuli for NET formation, and pathways that drive neutrophils to commit to NETosis have been elucidated in the years that followed. Critical enzymes required for NET formation have been discovered and targeted therapeutically. NET formation is no longer restricted to neutrophils but has been discovered in other innate cells: macrophages/monocytes, mast Cells, basophils, dendritic cells, and eosinophils. Furthermore, extracellular DNA can also be extruded from both B and T cells. It has become clear that although this mechanism is thought to enhance host defense by ensnaring bacteria within large webs of DNA to increase bactericidal killing capacity, it is also injurious to innocent bystander tissue. Proteases and enzymes released from extracellular traps (ETs), injure epithelial and endothelial cells perpetuating inflammation. In the context of autoimmunity, ETs release over 70 well-known autoantigens. ETs are associated with pathology in multiple diseases: lung diseases, vasculitis, autoimmune kidney diseases, atherosclerosis, rheumatoid arthritis, cancer, and psoriasis. Defining these pathways that drive ET release will provide insight into mechanisms of pathological insult and provide potential therapeutic targets.

Neutrophil Extracellular Traps in ANCA-Associated Vasculitis and Interstitial Lung Disease: A Scoping Review

BACKGROUND

Deregulated neutrophil extracellular traps (NETs) formation is implicated in various diseases, including ANCA-associated vasculitis and pulmonary fibrosis (PF). Lung involvement is frequent in AAV, and interstitial lung diseases (ILDs) are strongly related to MPO-ANCA positivity and mainly reported in microscopic polyangiitis. The association between AAV and ILD is a strong indicator of poor prognosis and limited survival. Neutrophils, ANCA and NET interplay in PF development in AAV. This study aimed to review the literature concerning the implications of NET in lung fibrogenesis specifically focused on AAV associated with ILD, and the potential of NET as a theranostic marker.

METHODS

Through scoping review methodology, we used a descriptive thematic analysis to understand the pathogenic role of NETs in patients with AAV and pulmonary fibrosis and their further role as a theranostic marker of this disease.

RESULTS

The implications of NET in the pathogenesis of AAV and ILD, as well as an association between these two diseases, have been identified, but the underlying pathophysiological mechanisms are still unknown. The pharmacological or genetic inhibition of NET release reduces disease severity in multiple inflammatory disease models, indicating that NETs are potential therapeutic targets. In this regard, despite the lack of clinical data, we may hypothesise that an optimal management of AAV-ILD patients would require not only B-cells targeted therapy, but also NETs inhibition.

CONCLUSION

Preliminary findings seem to display a lack of efficacy of traditional immunosuppressants, such as Rituximab, in this subset of patients, while to date no patients suffering from a definite ILD have been enrolled in clinical trials. Further insights would be provided by their employment, as a combination treatment, in common clinical practice. Although we can imagine that the inhibition of NETs in patients with AAV-ILD could reduce severity and mortality, we still lack the scientific basis that could improve our understanding of the disease from a molecular point of view.

Aluminum induced intestinal dysfunction via mechanical, immune, chemical and biological barriers

Aluminum is the most abundant metal element in the Earth's crust, which exists naturally in the form of aluminum compounds. Aluminum is mainly absorbed through the gastrointestinal tract, which varies with different aluminum compounds. During this process, aluminum could induce the disruption of intestinal mucosa barrier. However, its underlying mechanism has not been elucidated yet. Previous studies have reported that aluminum can firstly promote the apoptosis of intestinal epithelial cells, destroy the structure of tight-junction proteins, and increase the intestinal permeability, injuring the mechanical barrier of gut. Also, it can induce the activation of immune cells to secrete inflammatory factors, and trigger immune responses, interfering with immune barrier. Moreover, aluminum treatment can regulate intestinal composition and bio-enzyme activity, impairing the function of chemical barrier. In addition, aluminum accumulation can induce an imbalance of the intestinal flora, inhibit the growth of beneficial bacteria, and promote the proliferation of harmful bacteria, which ultimately disrupting biological barrier. Collectively, aluminum may do extensive damage to intestinal barrier function covering mechanical barrier, immune barrier, chemical barrier and biological barrier.

The Myeloid-Kidney Interface in Health and Disease

Kidney homeostasis is highly dependent upon the correct functioning of myeloid cells. These cells form a distributed surveillance network throughout the kidney, where they play an integral role in the response to organ threat. Dysregulation of resident proinflammatory and profibrotic macrophages leads to kidney structural damage and scarring after kidney injury. Fibrosis throughout the kidney parenchyma contributes to the progressive functional decline observed in CKD, independent of the etiology. Circulating myeloid cells bearing intrinsic defects also affect the kidney substructures, such as neutrophils activated by autoantibodies that cause GN in ANCA-associated vasculitis. The kidney can also be affected by disorders of myelopoiesis, including myeloid leukemias (acute and chronic myeloid leukemias) and myelodysplastic syndromes. Clonal hematopoiesis of indeterminate potential is a common, newly recognized premalignant clinical entity characterized by clonal expansion of hyperinflammatory myeloid lineage cells that may have significant kidney sequelae. A number of existing therapies in CKD target myeloid cells and inflammation, including glucocorticoid receptor agonists and mineralocorticoid receptor antagonists. The therapeutic indications for these and other myeloid cell-targeted treatments is poised to expand as our understanding of the myeloid-kidney interface evolves.

ANCA-Associated Vasculitic Neuropathies: A Review

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is a systemic disorder that frequently affects the peripheral nervous system and consists of three distinct conditions: microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GPA, previously Wegener’s granulomatosis), and eosinophilic granulomatosis with polyangiitis (EGPA, previously Churg-Strauss syndrome). The neuropathic features associated with this condition usually include mononeuritis multiplex, which reflects the locality of lesions. Findings suggestive of vasculitis are usually found in the epineurium and occur diffusely throughout the nerve trunk. Nerve fiber degeneration resulting from ischemia is sometimes focal or asymmetric and tends to become conspicuous at the middle portion of the nerve trunk. The attachment of neutrophils to endothelial cells in the epineurial vessels is frequently observed in patients with ANCA-associated vasculitis; neutrophils play an important role in vascular inflammation by binding of ANCA. The positivity rate of ANCA in EGPA is lower than that in MPA and GPA, and intravascular and tissue eosinophils appear to participate in neuropathy. Immunotherapy for ANCA-associated vasculitis involves the induction and maintenance of remission to prevent the relapse of the disease. A combination of glucocorticoids along with cyclophosphamide, rituximab, methotrexate, or mycophenolate mofetil is considered depending on the severity of the condition of the organ to induce remission. A combination of low-dose glucocorticoids and azathioprine, rituximab, methotrexate, or mycophenolate mofetil is recommended to maintain remission. The efficacy of anti-interleukin-5 therapy (i.e., mepolizumab) was demonstrated in the case of refractory or relapsing EGPA. Several other new agents, including avacopan, vilobelimab, and abatacept, are under development for the treatment of ANCA-associated vasculitis. Multidisciplinary approaches are required for the diagnosis and management of the disorder because of its systemic nature. Furthermore, active participation of neurologists is required because the associated neuropathic symptoms can significantly disrupt the day-to-day functioning and quality of life of patients with ANCA-associated vasculitis.

Remission of Granulomatosis with Polyangiitis Only After Resection of a Pulmonary Nodule

Granulomatosis with polyangiitis (GPA) is characterized by necrotizing granulomatous lesions and is classified as ANCA-associated vasculitis (AAV). We herein report a case of GPA that was remitted by resection of a pulmonary lesion without immunosuppressive therapy. We detected activated neutrophils and neutrophil extracellular traps (NET) formation in resected lung tissue by immunofluorescence. Activated neutrophils and NETs might be involved in the pathophysiology of AAV and induce the vicious cycle of ANCAs and NETs. In cases of GPA with no other severe lesions, the reevaluation of the disease activity after diagnostic resection is crucial for considering the need for immunosuppressive therapy.

NETosis in ischemic/reperfusion injuries: An organ-based review

Neutrophil extracellular trap (NETosis), the web-like structures induced by neutrophil death, is an important inflammatory mechanism of the immune system leading to reactive oxygen species production/coagulopathy, endothelial dysfunction, atherosclerosis, and ischemia. NETosis exerts its role through different mechanisms such as triggering Toll-like receptors, inflammatory cytokines, platelet aggregation, neutrophil activation/infiltration, and vascular impairment. NETosis plays a key role in the prognosis of coronary artery disease, ischemic injury of kidney, lung, gastrointestinal tract and skeletal muscles. In this review, we explored the molecular mechanisms involved in NETosis, and ischemic/reperfusion injuries in body organs.

Patients with COVID-19: in the dark-NETs of neutrophils

SARS-CoV-2 infection poses a major threat to the lungs and multiple other organs, occasionally causing death. Until effective vaccines are developed to curb the pandemic, it is paramount to define the mechanisms and develop protective therapies to prevent organ dysfunction in patients with COVID-19. Individuals that develop severe manifestations have signs of dysregulated innate and adaptive immune responses. Emerging evidence implicates neutrophils and the disbalance between neutrophil extracellular trap (NET) formation and degradation plays a central role in the pathophysiology of inflammation, coagulopathy, organ damage, and immunothrombosis that characterize severe cases of COVID-19. Here, we discuss the evidence supporting a role for NETs in COVID-19 manifestations and present putative mechanisms, by which NETs promote tissue injury and immunothrombosis. We present therapeutic strategies, which have been successful in the treatment of immunο-inflammatory disorders and which target dysregulated NET formation or degradation, as potential approaches that may benefit patients with severe COVID-19.

Neutrophil-Dependent Immunity During Pulmonary Infections and Inflammations

Rapid recruitment of neutrophils to an inflamed site is one of the hallmarks of an effective host defense mechanism. The main pathway through which this happens is by the innate immune response. Neutrophils, which play an important part in innate immune defense, migrate into lungs through the modulation actions of chemokines to execute a variety of pro-inflammatory functions. Despite the importance of chemokines in host immunity, little has been discussed on their roles in host immunity. A holistic understanding of neutrophil recruitment, pattern recognition pathways, the roles of chemokines and the pathophysiological roles of neutrophils in host immunity may allow for new approaches in the treatment of infectious and inflammatory disease of the lung. Herein, this review aims at highlighting some of the developments in lung neutrophil-immunity by focusing on the functions and roles of CXC/CC chemokines and pattern recognition receptors in neutrophil immunity during pulmonary inflammations. The pathophysiological roles of neutrophils in COVID-19 and thromboembolism have also been summarized. We finally summarized various neutrophil biomarkers that can be utilized as prognostic molecules in pulmonary inflammations and discussed various neutrophil-targeted therapies for neutrophil-driven pulmonary inflammatory diseases.

Emerging nanomaterials applied for tackling the COVID-19 cytokine storm

During the global outbreak of coronavirus disease 2019 (COVID-19), a hyperinflammatory state called the cytokine storm was recognized as a major contributor to multiple organ failure and mortality. However, to date, the diagnosis and treatment of the cytokine storm remain major challenges for the clinical prognosis of COVID-19. In this review, we outline various nanomaterial-based strategies for preventing the COVID-19 cytokine storm. We highlight the contribution of nanomaterials to directly inhibit cytokine release. We then discuss how nanomaterials can be used to deliver anti-inflammatory drugs to calm the cytokine storm. Nanomaterials also play crucial roles in diagnostics. Nanomaterial-based biosensors with improved sensitivity and specificity can be used to detect cytokines. In summary, emerging nanomaterials offer platforms and tools for the detection and treatment of the COVID-19 cytokine storm and future pandemic.

ULK1 Inhibition as a Targeted Therapeutic Strategy for Psoriasis by Regulating Keratinocytes and Their Crosstalk With Neutrophils

Psoriasis is a common inflammatory skin disease resulting from an interplay of keratinocytes and immune cells. Previous studies have identified an essential role of autophagy in the maintenance of epidermal homeostasis including proliferation and differentiation. However, much less is known about the role of autophagy-related proteins in the cutaneous immune response. Herein, we showed that ULK1, the key autophagic initiator, and its phosphorylation at Ser556 were distinctively decreased in the epidermis from lesional skin of psoriasis patients. Topical application of SBI0206965, a selective ULK1 inhibitor, significantly attenuated epidermal hyperplasia, infiltration of neutrophils, and transcripts of the psoriasis-related markers in imiquimod (IMQ)-induced psoriasiform dermatitis (PsD). In vitro, ULK1 impairment by siRNA and SBI0206965 arrested cell proliferation and promoted apoptosis of keratinocytes but had a marginal effect on the expression of proinflammatory mediators under steady status. Surprisingly, SBI0206965 blocked the production of chemokines and cytokines in keratinocytes stimulated by neutrophils. Of interest, the pro-apoptotic and anti-inflammatory effects of ULK1 inhibition cannot be fully replicated by autophagic inhibitors. Our findings suggest a self-regulatory process by downregulating ULK1 to maintain the immune homeostasis of psoriatic skin via regulating keratinocytes and their crosstalk with neutrophils, possibly through both autophagy-dependent and independent mechanisms. ULK1 might be a potential target for preventing or treating psoriasis.