Neutrophil extracellular traps in vasculitis, friend or foe?Curr Opin Rheumatol. 2018;30:16-23. [PMID: 28957962 DOI: 10.1097/BOR.0000000000000450]

The Role of Neutrophil Extracellular Traps in the Outcome of Malignant Epitheliomas: Significance of CA215 Involvement

Neutrophil extracellular traps (NETs) were originally discovered as a part of the innate immune response of the host to bacteria. They form a web-like structure that can immobilize microorganisms or exhibit direct antimicrobial properties, such as releasing reactive oxygen species (ROS). NETs are established when neutrophils undergo a sort of cellular death following exposure to ROS, chemokines, cytokines, or other soluble factors. This process results in the release of the neutrophil's DNA in a web-like form, which is decorated with citrullinated histones (H3/H4-cit), neutrophil elastase (NE), and myeloperoxidase (MPO). Emerging studies have put into perspective that NETs play an important role in oncology as they were shown to influence tumor growth, malignant initiation, and proliferation, mediate the transition from endothelial to mesenchymal tissue, stimulate angiogenesis or metastasis, and can even help cancer cells evade the immune response. The role of NETs in cancer therapy resides in their ability to form and act as a mechanical barrier that will provide the primary tumor with a reduced response to irradiation or pharmaceutical penetration. Subsequently, cancer cells are shown to internalize NETs and use them as a strong antioxidant when pharmaceutical treatment is administered. In this review, we explored the role of NETs as part of the tumor microenvironment (TME), in the context of malignant epitheliomas, which are capable of an autonomous production of CA215, a subvariant of IgG, and part of the carcinoembryonic antigen (CEA) superfamily. Studies have shown that CA215 has a functional Fc subdivision able to activate the Fc-gamma-RS receptor on the surface of neutrophils. This activation may afterward stimulate the production of NETs, thus indicating CA215 as a potential factor in cancer therapy surveillance.

Measurement of Neutrophil Extracellular Traps as a Biomarker for the Differential Diagnosis Between Antineutrophil Cytoplasmic Antibody-Positive Individuals With Antineutrophil Cytoplasmic Antibody-Associated Vasculitis and Nonautoimmune Diseases

BACKGROUND/OBJECTIVE

Neutrophil extracellular traps (NETs) have a correlation with disease activity in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). However, it is not known whether there is an association between NETs and the presence of ANCA in other diseases. This study aimed to assess the occurrence of NETs in individuals with ANCA and whether serum NET quantitation is capable of distinguishing them with regard to the diagnosis.

METHODS

This was a cross-sectional, observational study. From the positive ANCA by indirect immunofluorescence, 94 individuals were divided into groups: AAV, infectious diseases, and neoplastic diseases. Healthy controls served for comparisons. Neutrophil extracellular traps were evaluated through the investigation of NET remnants, by detecting cell-free DNA bound to proteins such as histone, myeloperoxidase, and neutrophil elastase (NE).

RESULTS

In patients with perinuclear ANCA (p-ANCA) the detection of NETs by NE was able to distinguish AAV from infection/neoplasia and healthy controls. Receiver operating characteristic curves for serum NETs by NE in patients with p-ANCA were drawn in 2 situations: AAV versus infection/neoplasia, showing a sensitivity of 0.65 and specificity of 0.84, with an area under the curve of 65%; and AAV versus controls, showing a sensitivity of 0.84 and a specificity of 0.88, with an area under the curve of 96%.

CONCLUSIONS

For p-ANCA-positive individuals, we found higher serum NETs detected by NE-DNA in those with chronic infectious and neoplastic diseases than in AAV individuals and healthy controls. This allows us to infer that the evaluation of serum NETs may be of value as a biomarker for differential diagnosis.

Clinical guidance of pyoderma gangrenosum 2022

Pyoderma gangrenosum (PG) is a rare, neutrophilic skin disease. For the purpose of accurate diagnosis and proper treatment of PG, the Japanese clinical practice guidance for PG developed by the Japanese Dermatological Association was published in 2022. In this guidance, clinical aspects, pathogenesis, current therapies, and clinical questions on PG are described from the viewpoints of current knowledge and evidence-based medicine. Here, the English version of the Japanese clinical practice guidelines for PG is presented and is intended to be widely referred to in the clinical examination and treatment of PG.

Diabetic Peripheral Neuropathy Associated with Foot Ulcer: One of a Kind

Significance: Diabetic peripheral neuropathy (DPN) associated with a diabetic foot ulcer (DFU) is likely to be complicated with critical factors such as biofilm infection and compromised skin barrier function of the diabetic skin. Repaired skin with a history of biofilm infection is known to be compromised in barrier function. Loss of barrier function is also observed in the oxidative stress affected diabetic and aged skin. Recent Advances: Loss of barrier function makes the skin prone to biofilm infection and cellulitis, which contributes to chronic inflammation and vasculopathy. Hyperglycemia favors biofilm formation as glucose lowering led to reduction in biofilm development. While vasculopathy limits oxygen supply, the O2 cost of inflammation is high increasing hypoxia severity. Critical Issues: The host nervous system can be inhabited by bacteria. Because electrical impulses are a part of microbial physiology, polymicrobial colonization of the host's neural circuit is likely to influence transmission of action potential. The identification of perineural apatite in diabetic patients with peripheral neuropathy suggests bacterial involvement. DPN starts in both feet at the same time. Future Directions: Pair-matched studies of DPN in the foot affected with DFU (i.e., DFU-DPN) compared with DPN in the without ulcer, and intact skin barrier function, are likely to provide critical insight that would help inform effective care strategies. This review characterizes DFU-DPN from a translational science point of view presenting a new paradigm that recognizes the current literature in the context of factors that are unique to DFU-DPN.

Targeting immune checkpoints in anti-neutrophil cytoplasmic antibodies associated vasculitis: the potential therapeutic targets in the future

Anti-neutrophil cytoplasmic autoantibodies (ANCA) associated vasculitis (AAV) is a necrotizing vasculitis mainly involving small blood vessels. It is demonstrated that T cells are important in the pathogenesis of AAV, including regulatory T cells (Treg) and helper T cells (Th), especially Th2, Th17, and follicular Th cells (Tfh). In addition, the exhaustion of T cells predicted the favorable prognosis of AAV. The immune checkpoints (ICs) consist of a group of co-stimulatory and co-inhibitory molecules expressed on the surface of T cells, which maintains a balance between the activation and exhaustion of T cells. CD28, inducible T-cell co-stimulator (ICOS), OX40, CD40L, glucocorticoid induced tumor necrosis factor receptor (GITR), and CD137 are the common co-stimulatory molecules, while the programmed cell death 1 (PD-1), cytotoxic T lymphocyte-associated molecule 4 (CTLA-4), T cell immunoglobulin (Ig) and mucin domain-containing protein 3 (TIM-3), B and T lymphocyte attenuator (BTLA), V-domain Ig suppressor of T cell activation (VISTA), T-cell Ig and ITIM domain (TIGIT), CD200, and lymphocyte activation gene 3 (LAG-3) belong to co-inhibitory molecules. If this balance was disrupted and the activation of T cells was increased, autoimmune diseases (AIDs) might be induced. Even in the treatment of malignant tumors, activation of T cells by immune checkpoint inhibitors (ICIs) may result in AIDs known as rheumatic immune-related adverse events (Rh-irAEs), suggesting the importance of ICs in AIDs. In this review, we summarized the features of AAV induced by immunotherapy using ICIs in patients with malignant tumors, and then reviewed the biological characteristics of different ICs. Our aim was to explore potential targets in ICs for future treatment of AAV.

Neutrophil extracellular traps promote bronchopulmonary dysplasia-like injury in neonatal mice via the WNT/β-catenin pathway

Background

Bronchopulmonary dysplasia (BPD) is one of the most common and severe chronic diseases in preterm infants. Premature infants are susceptible to BPD due to immature lungs and adverse perinatal episodes of infection, hyperoxia, and mechanical ventilation.

Methods

Neutrophils are the first line of host defence, and the release of neutrophil extracellular traps (NETs) is an important strategy to immobilize and kill invading microorganisms. This study examined whether NETs were associated with BPD in preterm infants and contributed to hyperoxia-induced lung injury in neonatal mice via the WNT/β-catenin pathway.

Results

In this study, we found that preterm infants with BPD had higher levels of NETs in their tracheal aspirates than those without BPD. Neonatal mice treated with NETs after birth exhibited BPD-like changes in their lungs. Furthermore, the levels of Aquaporin 5 (AQP5) and surfactant-associated protein C (SPC), which represent alveolar differentiation and development, were significantly lower than those in the controls. The WNT/β-catenin pathway is one of the most well-known signalling pathways involved in lung growth. We found that the expression of the target genes c-MYC, cyclin D, and vascular endothelial growth factor (VEGF) and the important proteins WNT3a and β-catenin significantly decreased. Moreover, heparin, which is a NET inhibitor, attenuated changes in gene and protein expression, thereby attenuating BPD-like changes.

Discussion

This finding indicates that NETs are associated with BPD and can induce BPD-like changes in neonatal mice via the WNT/β-catenin pathway.

Levamisole-induced and COVID-19-induced retiform purpura: two overlapping, emerging clinical syndromes

Levamisole exposure in cocaine users is a well-recognized cause of retiform purpura, a distinctive net-like maculopapular patch. Prolonged exposure to levamisole can lead to a serious systemic syndrome known as levamisole-induced vasculitis, most commonly involving the kidneys and lungs. More recently, retiform purpura has been observed in patients with the novel coronavirus disease of 2019 (COVID-19). Due to their overlapping dermatologic and systemic manifestations, levamisole-induced and COVID-19-induced retiform purpura may mimic one another in clinical presentation. The possibility that patients may present with one or both syndromes creates a diagnostic challenge. This review of levamisole-induced and COVID-19-induced retiform purpura highlights their corresponding and distinctive features. Additionally, we propose a unique staging system for levamisole-induced retiform purpura that may be valid for future classification of COVID-19-induced retiform purpura.

Impact of neutrophil extracellular traps on fluid properties, blood flow and complement activation

Introduction

The intravascular formation of neutrophil extracellular traps (NETs) is a trigger for coagulation and blood vessel occlusion. NETs are released from neutrophils as a response to strong inflammatory signals in the course of different diseases such as COVID-19, cancer or antiphospholipid syndrome. NETs are composed of large, chromosomal DNA fibers decorated with a variety of proteins such as histones. Previous research suggested a close mechanistic crosstalk between NETs and the coagulation system involving the coagulation factor XII (FXII), von Willebrand factor (VWF) and tissue factor. However, the direct impact of NET-related DNA fibers on blood flow and blood aggregation independent of the coagulation cascade has remained elusive.

Methods

In the present study, we used different microfluidic setups in combination with fluorescence microscopy to investigate the influence of neutrophil-derived extracellular DNA fibers on blood rheology, intravascular occlusion and activation of the complement system.

Results

We found that extended DNA fiber networks decelerate blood flow and promote intravascular occlusion of blood vessels independent of the plasmatic coagulation. Associated with the DNA dependent occlusion of the flow channel was the strong activation of the complement system characterized by the production of complement component 5a (C5a). Vice versa, we detected that the local activation of the complement system at the vascular wall was a trigger for NET release.

Discussion

In conclusion, we found that DNA fibers as the principal component of NETs are sufficient to induce blood aggregation even in the absence of the coagulation system. Moreover, we discovered that complement activation at the endothelial surface promoted NET formation. Our data envisions DNA degradation and complement inhibition as potential therapeutic strategies in NET-induced coagulopathies.

Detection of Extracellular Traps in Canine Steroid-Responsive Meningitis-Arteritis

Extracellular traps (ETs) are DNA networks formed by immune cells to fight infectious diseases by catching and attacking pathogenic microorganisms. Uncontrolled ET formation or impaired ET clearance can cause tissue and organ damage. Steroid-responsive meningitis-arteritis (SRMA) represents an immune-mediated, presumably non-infectious, purulent leptomeningitis and fibrinoid-necrotizing arteritis and periarteritis of young-adult dogs. Chronic and recurrent cases of SRMA are characterized by lymphohistiocytic inflammatory cell infiltration in the meninges and perivascular tissue. This study aimed to identify extracellular traps in dogs with SRMA, a model for immune-mediated diseases in the central nervous system (CNS). Hematoxylin and eosin-stained samples of two young dogs with chronic, recurrent SRMA were examined by light microscopy for characteristic lesions and consecutive slices of affected tissues were stained for detection of ETs by immunofluorescence microscopy using antibodies against DNA–histone-1 complexes, myeloperoxidase, and citrullinated histone H3. Histology revealed purulent and lymphohistiocytic leptomeningitis (n = 2/2) with meningeal periarteritis (n = 2/2) and periadrenal located lymphohistiocytic periarteritis (n = 1). Extracellular DNA networks and inflammatory cell infiltrates of macrophages, neutrophil granulocytes, and lymphocytes were detected in the subarachnoid space of the leptomeninx (n = 2/2) and perivascularly in meningeal (n = 2/2) as well as periadrenal vessels (n = 1/1). In summary, extracellular DNA fibers and attached ET markers are detectable in affected perivascular and meningeal tissues of dogs suffering from SRMA. The proof of principle could be confirmed that ETs are present in canine, inflammatory, and non-infectious CNS diseases and possibly play a role in the pathogenesis of SRMA.

Interruption of neutrophil extracellular traps formation dictates host defense and tubular HOXA5 stability to augment efficacy of anti-Fn14 therapy against septic AKI

The immunosuppressive, inflammatory microenvironment orchestrated by neutrophil extracellular traps (NETs) plays a principal role in pathogenesis of sepsis. Fibroblast growth factor-inducible molecule 14 (Fn14) has been established as a potential target for septic acute kidney injury (AKI), making further therapeutic benefits from combined NETs and Fn14 blockade possible. Methods: The concurrence of NETs and Fn14 in mice and patients with septic AKI were assessed by immunofluorescence, immunohistochemistry, enzyme-linked immunosorbent assay (ELISA) and in silico studies. Survival, histopathological and biochemical analyses of wild-type and PAD4-deficient CMV-Cre; PAD4 fl/fl mice with septic AKI were applied to evaluate the efficacy of either pharmacological or genetic NETs interruption in combination with Fn14 blockade. Molecular mechanisms underlying such effects were determined by CRISPR technology, fluorescence-activated cell sorter analysis (FACS), cycloheximide (CHX) pulse-chase, luciferase reporter and chromatin immunoprecipitation (ChIP) assay. Results: NETs formation is concurred with Fn14 upregulation in murine AKI models of abdominal, endotoxemic, multidrug-resistant sepsis as well as in serum samples of patients with septic AKI. Pharmacological or genetic interruption of NETs formation synergizes with ITEM-2, a monoclonal antibody (mAb) of Fn14, to prolong mice survival and provide renal protection against abdominal sepsis, the effects that could be abrogated by elimination of macrophages. Interrupting NETs formation predominantly perpetuates infiltration and survival of efferocytic growth arrest-specific protein 6+ (GAS6+) macrophages in combination with ITEM-2 therapy and enhances transcription of tubular cell-intrinsic Fn14 in a DNA methyltransferase 3a (DNMT3a)-independent manner through dismantling the proteasomes-mediated turnover of homeobox protein Hox-A5 (HOXA5) upon abdominal sepsis challenge or LPS stimuli. Pharmacological NETs interruption potentiates the anti-septic AKI efficacy of ITEM-2 in murine models of endotoxemic and multidrug-resistant sepsis. Conclusion: Our preclinical data propose that interrupting NETs formation in combination with Fn14 mAb might be a feasible therapeutic strategy for septic AKI.

Neutrophil extracellular traps in gastrointestinal cancer

Gastrointestinal (GI) cancer is a high-risk malignancy and is characterized by high mortality and morbidity worldwide. Neutrophil extracellular traps (NETs), a weblike structure consisting of chromatin DNA with interspersed cytoplasmic and granule proteins, are extruded by activated neutrophils to entrap and kill bacteria and fungi. However, accumulating evidence shows that NETs are related to the progression and metastasis of cancer. In clinical studies, NETs infiltrate primary GI cancer tissues and are even more abundant in metastatic lesions. The quantity of NETs in peripheral blood is revealed to be associated with ascending clinical tumour stages, indicating the role of NETs as a prognostic markers in GI cancer. Moreover, several inhibitors of NETs or NET-related proteins have been discovered and used to exert anti-tumour effects in vitro or in vivo, suggesting that NETs can be regarded as targets in the treatment of GI cancer. In this review, we will focus on the role of NETs in gastric cancer and colorectal cancer, generalizing their effects on tumour-related thrombosis, invasion and metastasis. Recent reports are also listed to show the latest evidences of how NETs affect GI cancer. Additionally, notwithstanding the scarcity of systematic studies elucidating the underlying mechanisms of the interaction between NETs and cancer cells, we highlight the potential importance of NETs as biomarkers and anti-tumour therapeutic targets.

Levamisole and ANCA positivity in childhood nephrotic syndrome

BACKGROUND

This study aimed to determine the prevalence of ANCA positivity in children managed with levamisole as a steroid-sparing agent for nephrotic syndrome (NS).

METHODS

Medical records of children with steroid-sensitive NS managed with levamisole therapy at Sydney Children's Hospital between 1/1/2000 and 31/12/2018 were retrospectively reviewed. Main outcome measure was side effects of levamisole therapy including ANCA positivity.

RESULTS

Seventy-one children, median age 3 years and 1 month (IQR 29-68 months) at first presentation, were subsequently managed with levamisole. 60.6% were male and 65% Caucasian. 47.9% had frequently relapsing (FR)NS and 52.1% steroid-dependent (SD)NS. Overall, there was a median reduction in relapses from 3 (IQR 1-5) to 0.4 relapses (IQR 0-1) per year after levamisole was commenced. Levamisole was successful in preventing relapse in 19 (29%) patients and was used for median 24 (22 to 25) months. Levamisole was discontinued due to relapse in 25 patients (38%) after median 12 (5-28) months. Side effects occurred in 28 patients (42.4%); the most common side effect was ANCA positivity in 12 patients. In eleven of these patients, levamisole was discontinued; in one patient, low-level titres were documented and spontaneously resolved without cessation of levamisole. Two patients developed ANCA-associated vasculitis.

CONCLUSION

ANCA positivity is a common side effect of levamisole and was seen in 18.2% of our patients. Monitoring is required to determine side effects including ANCA positivity and treatment modified accordingly.

Therapeutic ACPA inhibits NET formation: a potential therapy for neutrophil-mediated inflammatory diseases

Excessive release of neutrophil extracellular traps (NETs) is associated with disease severity and contributes to tissue injury, followed by severe organ damage. Pharmacological or genetic inhibition of NET release reduces pathology in multiple inflammatory disease models, indicating that NETs are potential therapeutic targets. Here, we demonstrate using a preclinical basket approach that our therapeutic anti-citrullinated protein antibody (tACPA) has broad therapeutic potential. Treatment with tACPA prevents disease symptoms in various mouse models with plausible NET-mediated pathology, including inflammatory arthritis (IA), pulmonary fibrosis, inflammatory bowel disease and sepsis. We show that citrulline residues in the N-termini of histones 2A and 4 are specific targets for therapeutic intervention, whereas antibodies against other N-terminal post-translational histone modifications have no therapeutic effects. Because citrullinated histones are generated during NET release, we investigated the ability of tACPA to inhibit NET formation. tACPA suppressed NET release from human neutrophils triggered with physiologically relevant human disease-related stimuli. Moreover, tACPA diminished NET release and potentially initiated NET uptake by macrophages in vivo, which was associated with reduced tissue damage in the joints of a chronic arthritis mouse model of IA. To our knowledge, we are the first to describe an antibody with NET-inhibiting properties and thereby propose tACPA as a drug candidate for NET-mediated inflammatory diseases, as it eliminates the noxious triggers that lead to continued inflammation and tissue damage in a multidimensional manner.

Vasculitis and Neutrophil Extracellular Traps in Lungs of Golden Syrian Hamsters With SARS-CoV-2

Neutrophil extracellular traps (NETs) have been identified as one pathogenetic trigger in severe COVID-19 cases and therefore well-described animal models to understand the influence of NETs in COVID-19 pathogenesis are needed. SARS-CoV-2 infection causes infection and interstitial pneumonia of varying severity in humans and COVID-19 models. Pulmonary as well as peripheral vascular lesions represent a severe, sometimes fatal, disease complication of unknown pathogenesis in COVID-19 patients. Furthermore, neutrophil extracellular traps (NETs), which are known to contribute to vessel inflammation or endothelial damage, have also been shown as potential driver of COVID-19 in humans. Though most studies in animal models describe the pulmonary lesions characterized by interstitial inflammation, type II pneumocyte hyperplasia, edema, fibrin formation and infiltration of macrophages and neutrophils, detailed pathological description of vascular lesions or NETs in COVID-19 animal models are lacking so far. Here we report different types of pulmonary vascular lesions in the golden Syrian hamster model of COVID-19. Vascular lesions included endothelialitis and vasculitis at 3 and 6 days post infection (dpi), and were almost nearly resolved at 14 dpi. Importantly, virus antigen was present in pulmonary lesions, but lacking in vascular alterations. In good correlation to these data, NETs were detected in the lungs of infected animals at 3 and 6 dpi. Hence, the Syrian hamster seems to represent a useful model to further investigate the role of vascular lesions and NETs in COVID-19 pathogenesis.

Histamine triggers the formation of neutrophil extracellular traps via NADPH oxidase, ERK and p38 pathways

Histamine plays a central role in various allergic diseases, such as allergic asthma and allergic rhinitis. Neutrophil extracellular traps (NETs) formation is a novel effector mechanism of neutrophils to defend against various stimuli. In this present study, we aimed to investigate the role of histamine on bovine NET formation, and examined its preliminary molecular mechanisms. Cell Counting Kit-8 (CCK8) and Lactate dehydrogenase assays showed that histamine had no significant influence on PMNs (polymorphonuclear leukocytes) viability. Confocal microscopy analyses identified NET structures by co-localizing the main components of NETs, and NET quantification revealed that histamine-triggered NETs were released in a dose-dependent manner. Furthermore, we found reactive oxygen species (ROS) production, phosphorylated extracellular signal-regulated kinase (ERK) and p38 proteins were significantly elevated in histamine-challenged PMNs. By applying functional inhibitors of nicotinamide adenine dinucleotide phosphate-oxidase (NADPH oxidase), ERK and p38, histamine-triggered NETs were markedly reduced, indicating their importance in histamine-triggered NET formation. Our findings described histamine-triggered NET formation, and revealed its potential molecular mechanisms via NADPH oxidase, ERK and p38 pathways. This is the first study to depict histamine-triggered NET formation, which could provide a new insight into histamine-related diseases.

Cross-Talk among Polymorphonuclear Neutrophils, Immune, and Non-Immune Cells via Released Cytokines, Granule Proteins, Microvesicles, and Neutrophil Extracellular Trap Formation: A Novel Concept of Biology and Pathobiology for Neutrophils

Polymorphonuclear neutrophils (PMNs) are traditionally regarded as professional phagocytic and acute inflammatory cells that engulf the microbial pathogens. However, accumulating data have suggested that PMNs are multi-potential cells exhibiting many important biological functions in addition to phagocytosis. These newly found novel activities of PMN include production of different kinds of cytokines/chemokines/growth factors, release of neutrophil extracellular traps (NET)/ectosomes/exosomes and trogocytosis (membrane exchange) with neighboring cells for modulating innate, and adaptive immune responses. Besides, PMNs exhibit potential heterogeneity and plasticity in involving antibody-dependent cellular cytotoxicity (ADCC), cancer immunity, autoimmunity, inflammatory rheumatic diseases, and cardiovascular diseases. Interestingly, PMNs may also play a role in ameliorating inflammatory reaction and wound healing by a subset of PMN myeloid-derived suppressor cells (PMN-MDSC). Furthermore, PMNs can interact with other non-immune cells including platelets, epithelial and endothelial cells to link hemostasis, mucosal inflammation, and atherogenesis. The release of low-density granulocytes (LDG) from bone marrow initiates systemic autoimmune reaction in systemic lupus erythematosus (SLE). In clinical application, identification of certain PMN phenotypes may become prognostic factors for severe traumatic patients. In the present review, we will discuss these newly discovered biological and pathobiological functions of the PMNs.

Advances in cutaneous vasculitis research and clinical care

Vasculitis is characterized by inflammation and destruction of blood vessels, resulting in downstream ischemic tissue damage. Diagnosis of vasculitis is a careful exercise in clinical-pathologic correlation, depending upon the clinical manifestations, organs involved, the size of affected blood vessels, imaging, and laboratory findings. While some vasculitis subtypes may be confined to the skin, serious internal organ involvement or underlying disease states may also occur. Accordingly, the skin plays an important role in the diagnostic process and may be prognostically important in some cases, signifying more severe systemic disease. The skin also provides opportunities for tissue-based translational research, improving understanding of disease pathophysiology. Dermatologists, therefore, play a critical role in evaluating vasculitis and helping to advance vasculitis clinical care and research. Recent updates in vasculitis nomenclature and terminology, evidence-based diagnosis, pathogenesis, and investigations of targeted therapies are changing vasculitis research and leading to fundamental shifts in disease management. Treatment advances favoring evidence-based and targeted, rather than broadly immunosuppressive, therapies are in development, while a multicenter trial for skin-limited vasculitis is ongoing. Collaborative multidisciplinary research networks are key to current and future advances in vasculitis research. In this review, we describe recent developments in vasculitis clinical care and research, starting with a discussion of efforts to develop diagnostic and classification criteria, followed by updates on the evaluation and treatment of vasculitis.

Neutrophil Extracellular Traps (NETs) and Vasculitis

Background: Neutrophil extracellular traps (NETs) have been implicated in host immune responses. Attempts have been made to examine how NETs affect the pathogenesis of complications such as autoimmune and vascular disorders. Aim: This study aimed to explore the relationship between NETs and vasculitis. Material and Methods: The current study entailed the searching of PsycINFO, PubMed, Web of Science, and CINAHL for articles related to the research topic. The search terms and phrases included "vasculitis," "NETs," "neutrophil extracellular traps," "NETosis," and "pathogenesis." The search was limited to articles published between 2009 and 2019. Results: Researchers have shown that NETs contribute to the pathogenesis of vasculitis through different mechanisms and processes, including renal failure and vascular damage. The protective effects of NETs have also been highlighted. Discussion: Overall, some scholars have shown the effectiveness of using DNase I and the PAD4 inhibitor Cl-amidine to treat vasculitis by restricting NET formation. However, observations have been noted in only animal experimental models. Conclusion: Neutrophil hyperactivity and its role in vasculitis are not yet fully understood. More studies aiming to determine the accurate function of NETs in vasculitis pathogenesis, particularly in humans, should be undertaken. Intensive research on NETs and vasculitis can increase the knowledge of medical practitioners and contribute to the development of new treatment methods to enhance patient outcomes in the future.

Drug-induced cutaneous vasculitis and anticoagulant-related cutaneous adverse reactions: insights in pathogenesis, clinical presentation, and treatment

Drug-induced vasculitis and anticoagulant-related skin reactions are commonly encountered in the inpatient and outpatient settings. The spectrum of clinical presentation is broad and ranges from focal, skin-limited disease, to more extensive cutaneous and soft tissue necrosis, to potentially fatal systemic involvement. The prompt recognition of these adverse events can have a significant impact on patient morbidity and mortality. We highlight the key features of the clinical presentation with an emphasis on primary lesion morphology, distribution, and epidemiology of purpuric drug reactions. The proposed pathophysiology, histologic findings, and therapeutic interventions of these potentially life-threatening diseases are discussed.

Oleic and Linoleic Acids Induce the Release of Neutrophil Extracellular Traps via Pannexin 1-Dependent ATP Release and P2X1 Receptor Activation

Non-esterified fatty acids (NEFAs) such as oleic acid (OA) and linoleic acid (LA) are associated with a higher incidence of infectious diseases such as metritis and mastitis during the bovine peripartum. Fatty acids can induce an increase in the release of ATP, and changes in the expression levels of purinergic receptors in bovine polymorphonuclears (PMN) during peripartum have also been reported. PMN respond to inflammatory processes with production of ROS, release of proteolytic and bactericidal proteins, and formation of neutrophil extracellular traps (NETs). NETs formation is known to require ATP production through glycolysis. Studies have shown that the above-mentioned metabolic changes alter innate immune responses, particularly in PMN. We hypothesized that NEFAs induce the formation of NETs through ATP release by Pannexin 1 and activation of purinergic receptors. In this study, we found that OA and LA induce NET formation and extracellular ATP release. Carbenoxolone, a pannexin-1 (PANX1) inhibitor, reduced OA- and LA-induced ATP release. We also found that P2X1, P2X4, P2X5, P2X7, and PANX1 were expressed at the mRNA level in bovine PMN. Additionally, NEFA-induced NET formation was completely abolished with exposure to NF449, a P2X1 antagonist, and partially inhibited by treatment with etomoxir, an inhibitor of fatty acid oxidation (FAO). Our results suggest that OA and LA induce NET formation and ATP release via PANX1 and activation of P2X1. These new data contribute to explaining the effects of NEFA high concentrations during the transition period of dairy cattle and further understanding of pro-inflammatory effects and outcome of postpartum diseases.

Anti-neutrophil cytoplasmic antibodies (ANCA): Antigen interactions and downstream effects

Neutrophils are the most abundant leukocytes in circulation and are key "first responders" in the immune response to infectious and non-infectious stimuli. Unlike other immune cells, neutrophils can mount a robust response (including a change in surface markers and the production of extracellular traps and reactive oxygen species) just minutes after sensing a disturbance. It has been speculated that, in some individuals, the activation of neutrophils inadvertently leads to the generation of anti-neutrophil cytoplasmic autoantibodies (ANCA) against particular neutrophil proteins (antigens) such as myeloperoxidase (MPO) and proteinase 3 (PR3). In these individuals, continuous ANCA-antigen interactions are thought to drive persistent activation of neutrophils, chronic immune activation, and disease, most notably, small vessel vasculitis. There are significant gaps however in our understanding of the underlying mechanisms and even the pathogenicity of ANCA given that vasculitis can develop in the absence of ANCA, and that ANCA have been found in circulation in other conditions with no apparent contribution to disease. These gaps are particularly evident in the context of human studies. Herein, we review knowledge on neutrophil-derived ANCA antigens PR3 and MPO, ANCA generation, and ANCA-antigen interaction(s) that may promote immune activation and disease.

Pharmaceutical immunoglobulins reduce neutrophil extracellular trap formation and ameliorate the development of MPO-ANCA-associated vasculitis

Objectives: Intravenous immunoglobulin (IVIG) therapy is effective against some autoimmune diseases. We examined the effects of pharmaceutical immunoglobulins on the development of MPO-ANCA-associated vasculitis (MPO-AAV).Methods: Peripheral blood neutrophils were pretreated with 5 mg/ml sulfo-immunoglobulins (IVIG-S) and then exposed to 100 nM phorbol myristate acetate (PMA). Thereafter, neutrophil extracellular traps (NETs) were detected by flow cytometry. Next, Wistar-Kyoto rats were given oral administration of 10 mg/kg/day propylthiouracil for 28 days and intraperitoneal (i.p.) injection of 1 μg PMA on days 0 and 7. These rats were divided into two groups: Group 1 with i.p. injection of 400 mg/kg IVIG-S on days 8-12 and Group 2 with vehicle similarly. ANCA titers were chronologically determined by indirect immunofluorescence. On day 28, all rats were killed to examine NET formation in the peritoneum and the development of AAV.Results: IVIG-S significantly inhibited NET formation induced by PMA in vitro. NET amounts in the peritoneum in Group 1 were significantly smaller than in Group 2, and ANCA titers in Group 1 were significantly lower than in Group 2. The degree of pulmonary hemorrhage in Group 1 was also smaller than in Group 2.Conclusion: IVIG-S reduce NET formation and ameliorate the development of MPO-AAV.

Neutrophil trafficking to lymphoid tissues: physiological and pathological implications

Recent advances have provided evidence for the involvement of neutrophils in both innate and adaptive immunity, robustly challenging the old dogma that neutrophils are short-lived prototypical innate immune cells solely involved in acute responses to microbes and exerting collateral tissue damage. There is now ample evidence showing that neutrophils can migrate into different compartments of the lymphoid system where they contribute to the orchestration of the activation and/or suppression of lymphocyte effector functions in homeostasis and during chronic inflammation, such as autoimmune disorders and cancer. In support of this notion, neutrophils can generate a wide range of cytokines and other mediators capable of regulating the survival, proliferation and functions of both T and B cells. In addition, neutrophils can directly engage with lymphocytes and promote antigen presentation. Furthermore, there is emerging evidence of the existence of distinct and diverse neutrophil phenotypes with immunomodulatory functions that characterise different pathological conditions, including chronic and autoimmune inflammatory conditions. The aim of this review is to discuss the mechanisms implicated in neutrophil trafficking into the lymphoid system and to provide an overview of the immuno-regulatory functions of neutrophils in health and disease in the context of adaptive immunity. Copyright © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Levamisole adulterated cocaine associated ANCA vasculitis: review of literature and update on pathogenesis

Levamisole is an antihelminth drug and a common cocaine contaminant, present in an estimated 71% of cocaine samples in the US. Levamisole-contaminated cocaine has been linked to an ANCA-associated vasculitis with cutaneous, renal, and pulmonary manifestations. We report the case of a 46 year old woman with known cocaine exposure who presents with recurrent, large purpuric and maculopapular rash of the extremities and face and review existing cases of levamisole/cocaine-associated ANCA vasculitis, We summarize the clinical presentation, treatment, and outcomes of levamisole induced vasculitis. There is emerging research on pathogenesis relating to neutrophil extracellular traps (NETs). We review studies implicating role of NETs in the pathogenesis of levamisole induced vasculitis. Further research to explore the use of NETs as therapeutic targets in drug induced vasculitis is needed.

Nuclear cytometry and chromatin organization

The nuclear-targeting chemical probe, for the detection and quantification of DNA within cells, has been a mainstay of cytometry-from the colorimetric Feulgen stain to smart fluorescent agents with tuned functionality. The level of nuclear structure and function at which the probe aims to readout, or indeed at which a DNA-targeted drug acts, is shadowed by a wide range of detection modalities and analytical methods. These methods are invariably limited in terms of the resolution attainable versus the volume occupied by targeted chromatin structures. The scalar challenge arises from the need to understand the extent and different levels of compaction of genomic DNA and how such structures can be re-modeled, reported, or even perturbed by both probes and drugs. Nuclear cytometry can report on the complex levels of chromatin order, disorder, disassembly, and even active disruption by probes and drugs. Nuclear probes can report defining features of clinical and therapeutic interest as in NETosis and other cell death processes. New cytometric approaches continue to bridge the scalar challenges of analyzing chromatin organization. Advances in super-resolution microscopy address the resolution and depth of analysis issues in cellular systems. Typical of recent insights into chromatin organization enabled by exploiting a DNA interacting probe is ChromEM tomography (ChromEMT). ChromEMT uses the unique properties of the anthraquinone-based cytometric dye DRAQ5™ to reveal that local and global 3D chromatin structures effect differences in compaction. The focus of this review is nuclear and chromatin cytometry, with linked reference to DNA targeting probes and drugs as exemplified by the anthracenediones.