Enhanced type I interferon signature induces neutrophil extracellular traps enriched in mitochondrial DNA in adult-onset Still's disease

HLA-E-expressing macrophage polarization and increased NKG2A/CD94 expression in adult-onset Still's disease

We investigated the phenotypic characteristics of human leukocyte antigen (HLA)-E-expressing macrophages, NKG2A/CD94 expression in T and natural killer (NK) cells, and their interactions in patients with adult-onset Still's disease (AOSD). Peripheral blood mononuclear cells from 22 patients with AOSD and 22 healthy controls (HC) were used. Isolated monocytes were cultured first with macrophage colony-stimulating factor to differentiate into M0 macrophages and subsequently with lipopolysaccharide/interferon-γ or interleukin-4 to differentiate into M1 or M2 macrophages, respectively. HLA-E and NKG2A/CD94 expression levels were evaluated using quantitative RT-PCR and flow cytometry. HLA-E expression in M0 and M2 macrophages was significantly higher in patients with AOSD than in HC, and was positively correlated with serum C-reactive protein levels and erythrocyte sedimentation rate. NKG2A/CD94 expression in CD4 + and CD8 + T cells was significantly higher in patients with AOSD than in HC, but that in NK cells was not significantly different. In patients with AOSD, NKG2A expression in CD4 + T cells positively correlated with HLA-E expression in M0, M1, and M2 macrophages. CD94 expression in CD8 + T cells inversely correlated with HLA-E expression in M1 and M2 macrophages. NKG2A and CD94 expression in NK cells inversely correlated with HLA-E expression in M0, M1, and M2 macrophages. No significant correlation was observed between HLA-E and NKG2A/CD94 expression in HC. Increased expression of HLA-E in macrophages and NKG2A/CD94 in T cells can be observed in the inflammatory condition of AOSD. HLA-E-expressing macrophages may be associated with NKG2A/CD94 expression in T and NK cells with different correlations.

The landscape of innate and adaptive immune cell subsets in patients with adult-onset Still's disease

OBJECTIVE

Adult-onset Still's disease (AOSD) is a systemic autoinflammatory disorder. The understanding of the changes in adaptive immune cells and the crosstalk between innate and adaptive immune systems in AOSD is limited. This study aimed to examine the peripheral immune cell composition and inflammatory protein levels in AOSD patients.

METHODS

Twenty-nine active AOSD patients were enrolled. Flow cytometry was used to analyse the cell populations in peripheral blood. Antibody chips were utilized to detect the protein expression profile in serum.

RESULTS

In active AOSD patients, there was an increase in the percentage of classical and non-classical monocytes among peripheral blood mononuclear cells. The proportion of natural killer (NK) cells decreased, with an increase in CD56dim NK1 cells and a decrease in CD56bright NK2 cells compared with healthy controls (HCs). The percentage of naïve central memory T cells was decreased, while the percentage of effector and effector memory T cells was increased among adaptive lymphocytes. The proportion of naïve B and memory B cells was decreased, while plasma cells were increased in AOSD patients, indicating activation of the adaptive immune system. Additionally, the serum levels of 40 proteins were elevated in AOSD patients, primarily involved in cytokine-cytokine receptor interaction, inflammatory response and regulation of mitogen-activated protein kinase cascade.

CONCLUSION

Our findings showed the activation of the innate and adaptive immune system in AOSD. The protein-protein interaction analysis suggested potential communication between innate and adaptive cell subsets. These findings provide new insights into the pathogenesis of the disease and the development of targeted therapies.

Neutrophil activation biomarker pentraxin 3 for diagnosis and monitoring of macrophage activation syndrome occurrence in adult-onset Still's disease

Macrophage activation syndrome (MAS) is a potentially fatal consequence of adult-onset Still's disease (AOSD), driven by a cytokine storm. Efficient early diagnosis of AOSD-associated MAS requires a sensitive and specific biomarker. In this study, we demonstrated that pentraxin 3 (PTX3), an acute phase protein, was associated with AOSD disease activity and served as a biomarker for AOSD-MAS. PTX3 levels were significantly increased in AOSD patients compared to other autoimmune diseases and healthy controls. Plasma PTX3 levels showed positive correlations with inflammatory markers, the systemic score and the HScore. In active AOSD with MAS, PTX3 levels were higher compared to those in non-AOSD haemophagocytic lymphohistiocytosis (HLH) patients. Moreover, the PTX3's area under the curve value for distinguishing AOSD with MAS exceeded that of soluble interleukin-2 receptor, ferritin and C-reactive protein. Furthermore, plasma levels of PTX3 were associated with circulating NET-DNA levels. To fully understand the underlying mechanism of PTX3 prompting AOSD and AOSD-MAS progression, we discovered that neutrophils exhibited enhanced NET formation and mitogen-activated protein kinases (MAPK) pathway activation upon PTX3 stimulation. More importantly, PTX3-induced NET formation was effectively dampened by MAPK pathway inhibitors. These findings collectively revealed that PTX3 has a favorable correlation with disease activity and may serve as a potential biomarker to differentiate AOSD patients with MAS. Additionally, PTX3 induces NET release via the MAPK pathway, suggesting a pathogenic role in AOSD-MAS.

Recent advances on neutrophil dysregulation in the pathogenesis of rheumatic diseases

PURPOSE OF REVIEW

The exact pathogenic mechanisms of rheumatic diseases (RMD) remain largely unknown. Increasing evidence highlights a pathogenic role of neutrophil dysregulation in the development of RMD.

RECENT FINDINGS

The purpose of this review is to present a current overview of recent advancements in understanding the role of neutrophil dysfunction in the development of RMD. Additionally, this review will discuss strategies for targeting pathways associated with neutrophil dysregulation as potential treatments for RMD. One specific aspect of neutrophil dysregulation, known as neutrophil extracellular traps (NETs), will be explored. NETs have been found to contribute to chronic pulmonary inflammation and fibrosis, as well as serve as DNA scaffolds for binding autoantigens, including both citrullinated and carbamylated autoantigens. Putative therapies, such as 6-gingerol or defibrotide, have demonstrated beneficial effects in the treatment of RMD by suppressing NETs formation.

SUMMARY

Recent advances have significantly reinforced the crucial role of neutrophil dysregulation in the pathogenesis of RMD. A deeper understanding of the potential mechanisms underlying this pathogenic process would aid in the development of more precise and effective targeting strategies, thus ultimately improving the outcomes of RMD.

Recent advances and evolving concepts in Still's disease

Still's disease is a rare inflammatory syndrome that encompasses systemic juvenile idiopathic arthritis and adult-onset Still's disease, both of which can exhibit life-threatening complications, including macrophage activation syndrome (MAS), a secondary form of haemophagocytic lymphohistiocytosis. Genetic insights into Still's disease involve both HLA and non-HLA susceptibility genes, suggesting the involvement of adaptive immune cell-mediated immunity. At the same time, phenotypic evidence indicates the involvement of autoinflammatory processes. Evidence also implicates the type I interferon signature, mechanistic target of rapamycin complex 1 signalling and ferritin in the pathogenesis of Still's disease and MAS. Pathological entities associated with Still's disease include lung disease that could be associated with biologic DMARDs and with the occurrence of MAS. Historically, monophasic, recurrent and persistent Still's disease courses were recognized. Newer proposals of alternative Still's disease clusters could enable better dissection of clinical heterogeneity on the basis of immune cell profiles that could represent diverse endotypes or phases of disease activity. Therapeutically, data on IL-1 and IL-6 antagonism and Janus kinase inhibition suggest the importance of early administration in Still's disease. Furthermore, there is evidence that patients who develop MAS can be treated with IFNγ antagonism. Despite these developments, unmet needs remain that can form the basis for the design of future studies leading to improvement of disease management.

Neutrophil extracellular traps and neutrophilic dermatosis: an update review

Neutrophils have both antimicrobial ability and pathogenic effect in the immune system, neutrophil extracellular traps (NETs) formation is one of the representative behaviors of their dual role. NETs formation was triggered by pathogen-related components and pathogen non-related proteins as cytokines to exert its effector functions. Recent studies indicate that the pathogenicity of NETs contributed to several skin diseases such as psoriasis, Stevens-Johnson syndrome, toxic epidermal necrolysis, and neutrophilic dermatosis. Especially in neutrophilic dermatosis, a heterogeneous group of inflammatory skin disorders characterized with sterile neutrophilic infiltrate on dermis, NETs formation was reported as the way of participation of neutrophils in the pathogenesis of these diseases. In this review, we describe the different processes of NETs formation, then summarized the most recent updates about the pathogenesis of neutrophilic dermatosis and the participation of NETs, including pyoderma gangrenosum and PAPA syndrome, Behçet syndrome, hidradenitis suppurativa, Sweet Syndrome, pustular dermatosis and other neutrophilic dermatosis. Furthermore, we discuss the link between NETs formation and the development of neutrophilic dermatosis.

The latest advances in the use of biological DMARDs to treat Still's disease

INTRODUCTION

Currently, the therapeutic management of Still's disease, a multisystemic inflammatory rare disorder, is directed to target the inflammatory symptoms and signs of patients. The treatment varies from glucocorticoids to disease-modifying antirheumatic drugs (DMARDs), both conventional synthetic and biological (bDMARDs). Usually, in refractory patients, bDMARDs are administered.

AREAS COVERED

Among bDMARDs, IL-1 and IL-6 inhibitors are frequently used, as data reported from both clinical trials and 'real-life' experiences. Recently, innovative therapeutic strategies have suggested an early administration of bDMARDs to increase the rate of clinical response and drug-free remission. Some new targets have been also proposed targeting IL-18, IFN-γ, and JAK/STAT pathway, which could be applied to Still's disease and its life-threatening evolution.

EXPERT OPINION

Many lines of evidence improved the knowledge about the therapeutic management of Still's disease with bDMARDs. However, many unmet needs may be still highlighted which could provide the basis to arrange further specific research in increasing the rate of clinical response. In fact, Still's disease remains a highly heterogeneous disease suggesting possible diverse underlying pathogenic mechanisms, at least partially, and consequent different therapeutic strategies. A better patient stratification may help in arranging specific studies to improve the long-term outcome of Still's disease.

Neutrophil extracellular trap-induced intermediate monocytes trigger macrophage activation syndrome in adult-onset Still's disease

BACKGROUND

Adult-onset Still's disease (AOSD) is a systemic autoinflammatory disease characterized by innate immune system activation, with a high risk for macrophage activation syndrome (MAS). MAS development is associated with monocyte/macrophage activation and cytokine storm. Monocytes consist of three different subsets, classical monocytes (CMs, CD14brightCD16 -), intermediate monocytes (IMs, CD14brightCD16 +), and non-classical monocytes (NCMs, CD14dimCD16 +), each has distinct roles in inflammatory regulation. However, the frequencies and regulatory mechanism of monocyte subsets in AOSD patients have not been identified.

METHODS

We performed flow cytometry, RNA sequencing, phagocytosis analysis, and enzyme-linked immunosorbent assay to evaluate monocyte subsets, cell functions, and potential biomarkers. The effect of neutrophil extracellular traps (NETs) on monocytes was determined by evaluating mRNA levels of DNA sensors, surface CD16 expression, and inflammasome pathway activation.

RESULTS

Higher proportions of intermediate monocytes (IMs) were identified in active AOSD patients. IMs displayed higher expression of CD80, CD86, HLA-DR, and CD163 than CMs and NCMs. CD163 upregulation was noted on AOSD IMs, accompanied by increased phagocytic activity and elevated cytokine/chemokine production, including IL-1β, IL-6, CCL8, and CXCL10. The frequencies of IMs were correlated with disease activity and higher in AOSD patients with MAS (AOSD-MAS). CCL8 and CXCL10 were highly expressed in RNA sequencing of monocytes from AOSD-MAS patients and plasma CXCL10 level could serve as a potential biomarker for AOSD-MAS. Moreover, DNA-sensing pathway was activated in monocytes from AOSD-MAS patients. Stimulation with NETs derived from AOSD induced DNA sensor expression, the expansion of IMs, and inflammasome pathway activation. These effects can be abrogated by DNase I treatment.

CONCLUSIONS

Our results demonstrated that the proportions of IMs were elevated in AOSD and associated with MAS. The DNA component in NETs from AOSD plays an important role in the formation of IMs, shedding new light for the therapeutic target.

GSDMD promotes neutrophil extracellular traps via mtDNA-cGAS-STING pathway during lung ischemia/reperfusion

Lung ischemia/reperfusion injury (LIRI) is a complex pathophysiological process, with the histopathological hallmark of neutrophils migrating into the lungs. Neutrophil extracellular traps (NETs) have been suggested to exert a critical role in the pathogenesis of inflammation and infection in humans and animals, while the exact functions and underlying mechanisms of NETs in LIRI remain insufficiently elucidated. In this study, we investigated the role of pore-forming protein gasdermin D (GSDMD) on NETs release in LIRI induced by lung ischemia/reperfusion (I/R). We found that disulfiram, a GSDMD inhibitor, dramatically reduced NETs release and pathological injury in lung I/R in vivo and in vitro. Additionally, GSDMD caused mitochondrial DNA (mtDNA) leaking into the neutrophil cytosol, and then the cytoplasmic mtDNA activated the cGAS-STING signaling pathway and stimulated NETs formation in lung I/R. Furthermore, inhibition of cGAS/STING pathway could inhibit cytosol mtDNA mediated NETs formation.

[Update on Adult-Onset Still's Disease: Diagnosis, Therapy and Guideline]

Adult-onset Still's disease (ASOD) is an autoinflammatory disease of unknown etiology which is pathogenetically characterized by an involvement of the innate immune response with activation of neutrophils and an increased secretion of IL-1, IL-6, IL-18, type 1 interferons. Still's disease may occur at any age with distinct variability in signs and symptoms. Recently, the German Society of Rheumatology (DGRh) has issued an AOSD guideline which recommends diagnosing AOSD based on a characteristic combination of symptoms including intermittent fever, rash, arthralgia, and arthritis after exclusion of infections, neoplasms and other rheumatological conditions. Classification criteria according to Yamaguchi may support the clinical diagnosis. Therapy is recommended to include glucocorticosteroids and methotrexate or ciclosporin, at higher activity levels IL1-receptor antagonist anakinra, IL-1β antibody canakinumab, or IL6-receptor antibody tocilizumab. At a high disease activity, anakinra or canakinumab may be employed primarily. Local drug licensing policies may have to be considered, as these substances are not universally approved in these scenarios. Important complications to consider consist in perimyocarditis, a multi-faceted pulmonary involvement, and macrophage activation syndrome (MAS). MAS features multi-organ involvement and cytopenias. Besides supportive measures often requiring intensive care, high dose glucocorticosteroids as well as above named biologics, and if necessary, also etoposide based therapeutic regimen are used.

Circulating Calprotectin (cCLP) in autoimmune diseases

BACKGROUND AND AIM

Calprotectin (CLP) is a heterodimeric complex formed by two S100 proteins (S100A8/A9), which plays a pivotal role in innate immunity. Due to its intrinsic cytotoxic and proinflammatory properties, CLP controls cell differentiation, proliferation and NETosis and has been associated with a wide range of rheumatic diseases. Our review summarizes the widespread interest in circulating CLP (cCLP) as a biomarker of neutrophil-related inflammation, in autoimmune rheumatic disease (ARD) and non-ARD.

METHODS

A thorough literature review was performed using PubMed and EMBASE databases searching for circulating calprotectin and synonyms S100A8/A9, myeloid-related protein 8/14 (MRP8/MRP14), calgranulin A/B and L1 protein in addition to specific ARDs and autoimmune non-rheumatic diseases. We selected only English-language articles and excluded abstracts without the main text.

RESULTS

High cCLP serum levels are associated with worse structural outcomes in rheumatoid arthritis and to a lesser extent, in spondyloarthritis. In addition, cCLP can predict disease relapse in some autoimmune diseases including systemic lupus erythematosus (SLE), anti-neutrophil cytoplasmic antibodies-associated vasculitis (AAV) and some severe manifestations of connective tissue diseases, such as glomerulonephritis in SLE, AAV, juvenile idiopathic arthritis, adult-onset Still's disease and lung fibrosis in systemic sclerosis. Therefore, cCLP levels enable the identification of patients who need an accurate and tight follow-up. The clinical usefulness of cCLP as an inflammatory marker has been suggested for inflammatory/autoimmune non-rheumatic diseases, and especially for the monitoring of the inflammatory bowel diseases patients. Currently, there are only a few studies that evaluated the cCLP efficacy as a clinical biomarker in inflammatory/autoimmune non-rheumatic diseases with controversial results. Future studies are warranted to better clarify the role of cCLP in relation to the disease severity in myasthenia gravis, multiple sclerosis, chronic inflammatory demyelinating polyneuropathy, Graves' orbitopathy, autoimmune bullous diseases and uveitis.

CONCLUSION

Our literature review supports a relevant role of cCLP as potential prognostic biomarker mirroring local or systemic inflammation, especially in chronic inflammatory rheumatic diseases.

Improving Diagnosis and Clinical Management of Acquired Systemic Autoinflammatory Diseases

Systemic autoinflammatory diseases (SAID) are conditions caused by dysregulation or disturbance of the innate immune system, with neutrophils and macrophages the main effector cells. Although there are now more than 40 distinct, genetically defined SAIDs, the genetic/molecular diagnosis remains unknown for a significant proportion of patients with the disease onset in adulthood. This review focuses on new developments related to acquired/late onset SAID, including phenocopies of monogenic disorders, Schnitzler's syndrome, Adult onset Still's disease, VEXAS syndrome, and autoinflammatory complications associated with myelodysplastic syndrome.

Adult-onset Still’s disease: A disease at the crossroad of innate immunity and autoimmunity

Adult-onset Still’s disease (AOSD) is a rare disease affecting multiple systems and organs with unknown etiology, and the clinical symptoms are usually described as spiking fever, arthritis, evanescent salmon-pink eruptions, lymphadenopathy, splenomegaly, and other manifestations. The laboratory indicators are not specific, often presenting as increased leukocyte counts and neutrophil percentage, elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), hyperferritinemia, and increased inflammatory factors. ANA, ENA, and RF are negative. According to those unspecific clinical presentations and laboratory findings, infection, tumor, connective tissue disease, and other diseases must be ruled out before diagnosis. The diagnosis of AOSD is a great challenge for clinicians. The mechanism of AOSD pathogenesis is complicated and still being studied. There is a new opinion that atypical persistent skin eruptions (APSEs) with specific histological manifestations are unique for AOSD, and APSEs might be on a spectrum with classical evanescent eruptions. Studies on APSEs showed that IL-1β and IFN-γ are strongly correlated with the pathogenesis of necrosis keratinocytes in APSEs. IL-1β is strongly involved in inflammatory disease when it is abnormal, and plays an important role in the pathogenesis of neutrophil dermatosis. In the early stage of AOSD, skin lesions appear to be evanescent urticaria-like eruptions accompanied by fever, and only neutrophils infiltrate around the blood vessels in the dermis pathologically. As the course of the disease progresses, IL-1β is gradually released. Through the stimulation of other inflammatory factors and the influence of unknown factors, IL-1β gradually infiltrates into the stratum corneum and finally accumulates around the necrotic keratinocytes of the stratum corneum. However, the detailed mechanism is still unknown. IFN-γ could play a pro-inflammatory or regulatory role in some disorders. IL-1β can enhance the expression of IFN-γ, and IFN-γ can cause keratinocyte apoptosis by activating the autocrine of caspase. Also, several pieces of evidence indicate that adaptive immunity is also involved in the pathogenesis of AOSD. Increased α-soluble receptors of IL-2 may suggest T-cell activation and proliferation in AOSD patients. Increased IL-4- and IFN-γ-producing T cells were found in active AOSD and related to disease severity. Frequencies of Treg cells in AOSD were significantly lower and were inversely correlated with disease severity. According to these, more and more researchers have reached a consensus that AOSD is a disease at the crossroads of innate immunity and autoimmunity. In this review, we will provide a comprehensive insight into AOSD, describing research progress and the immunological mechanism contribution to the disease. In the meantime, different treatment options and the efficacy and safety of various biologic agents are also discussed. A further understanding of AOSD requires closer cooperation among doctors from different departments, and this review will provide a new idea for diagnosis and therapeutic options.