Involvement of TLR7 MyD88-dependent signaling pathway in the pathogenesis of adult-onset Still's disease

Sex-related immunity: could Toll-like receptors be the answer in acute inflammatory response?

An increasing number of studies have highlighted the existence of a sex-specific immune response, wherein men experience a worse prognosis in cases of acute inflammatory diseases. Initially, this sex-dependent inflammatory response was attributed to the influence of sex hormones. However, a growing body of evidence has shifted the focus toward the influence of chromosomes rather than sex hormones in shaping these inflammatory sex disparities. Notably, certain pattern recognition receptors, such as Toll-like receptors (TLRs), and their associated immune pathways have been implicated in driving the sex-specific immune response. These receptors are encoded by genes located on the X chromosome. TLRs are pivotal components of the innate immune system, playing crucial roles in responding to infectious diseases, including bacterial and viral pathogens, as well as trauma-related conditions. Importantly, the TLR-mediated inflammatory responses, as indicated by the production of specific proteins and cytokines, exhibit discernible sex-dependent patterns. In this review, we delve into the subject of sex bias in TLR activation and explore its clinical implications relatively to both the X chromosome and the hormonal environment. The overarching objective is to enhance our understanding of the fundamental mechanisms underlying these sex differences.

Pyroptosis: the potential eye of the storm in adult-onset Still's disease

Pyroptosis, a form of programmed cell death with a high pro-inflammatory effect, causes cell lysis and leads to the secretion of countless interleukin-1β (IL-1β) and IL-18 cytokines, resulting in a subsequent extreme inflammatory response through the caspase-1-dependent pathway or caspase-1-independent pathway. Adult-onset Still's disease (AOSD) is a systemic inflammatory disease with extensive disease manifestations and severe complications such as macrophage activation syndrome, which is characterized by high-grade inflammation and cytokine storms regulated by IL-1β and IL-18. To date, the pathogenesis of AOSD is unclear, and the available therapy is unsatisfactory. As such, AOSD is still a challenging disease. In addition, the high inflammatory states and the increased expression of multiple pyroptosis markers in AOSD indicate that pyroptosis plays an important role in the pathogenesis of AOSD. Accordingly, this review summarizes the molecular mechanisms of pyroptosis and describes the potential role of pyroptosis in AOSD, the therapeutic practicalities of pyroptosis target drugs in AOSD, and the therapeutic blueprint of other pyroptosis target drugs.

Emerging trends in IRAK-4 kinase research

The IRAK-4 kinase lies at a critical signaling node that drives cancer cell survival through multiple mechanisms, activation, and translocation of NF-κB mediated inflammatory responses and innate immune signaling through regulation of interferon-α/β receptor (IFNα/β). Inhibition, of IRAK-4, has consequently drawn a lot of attention in recent years to address indications ranging from oncology to autoimmune disorders to neurodegeneration, etc. However, the key stumbling block in targeting IRAK-4 is that despite the inhibition of the kinase activity using an inhibitor the target remains effective, reducing the potential of an inhibitor. This is due to the "scaffolding effect" because of which although regulation of downstream processes by IRAK-4 has been primarily linked with kinase function; however, still, various reports have suggested that IRAK-4 has a non-kinase function in a variety of cell types. This is attributed to the myddosome complex formed by IRAK-4 with myd88, IRAK-2, and IRAK-1 which by itself can cause the activation of downstream effector TRAF6 despite inhibition of the kinase domain of IRAK-4. With this challenge, several groups initiated the development of targeting protein degraders of IRAK-4 using Proteolysis-Targeting Chimeras (PROTACs) technology to completely remove the IRAK-4 from the cellular milieu. In this review, we will capture all these developments and the evolving science around this target.

An Unforeseen Outcome of COVID-19: The Triggering of Adult-Onset Still’s Disease

Background:

Adult-onset Still’s disease (AOSD) is a rare auto-inflammatory disorder with unknown etiology by which an infectious trigger is usually responsible for the onset of the disease. It is diagnosed by exclusion when certain clinical, biochemical, and radiological criteria are met after excluding all other potential causes. Besides, SARS‑CoV‑2 infection is increasingly being reported to have autoimmune complications. In the literature, 3 AOSD cases have been reported to be triggered by SARS‑CoV‑2 infection and here we report the fourth.

Case presentation:

A 24-year-old female doctor suffered from fever, sore throat, and mild cough a few days after a shift in the COVID-19 ward. A week later, she developed polyarthritis, salmon-colored rash, and high-grade fever, and the laboratory findings were indicating an inflammatory syndrome. COVID-19 IgM antibodies were positive indicating recent infection. After running a battery of tests, infectious, neoplastic, and rheumatic causes of these symptoms that persisted for about 50 days were excluded which led to a diagnosis of AOSD after fulfilling its criteria with subsequent treatment with methylprednisolone. Drastic improvement was achieved with no recurrence until the date of reporting.

Conclusion:

This case presents a new consequence of COVID-19 and adds to the emerging cumulative experiences with this disease. We encourage health care professionals to report such cases to further understand the nature of this infection and its possible outcomes.

Rare, rarer, lung involvement in adult-onset Still's disease: A mini-review

Adult-onset Still's disease (AOSD) is a polygenic systemic autoinflammatory disease which is associated with increased morbidity and mortality. Pulmonary involvement is a rare, but serious complication of AOSD. As in AOSD, IL-1b, IL-18, and IL-6 dominate the molecular pathogenesis, which mediate a type 1 and type 3 inflammatory signature of the adaptive immune system. This is evidenced by the success of IL-1- and IL-6 inhibition in the management of AOSD. However, anaphylactic reactions to treatment with IL-1- or IL-6-inhibitors is currently being discussed as a potential trigger for lung involvement inf AOSD, while genetic risk factors have also been identified. Clinically, pulmonary involvement in AOSD can manifest in many different forms. Parenchymal inflammation with peripheral consolidations is the most frequent form while PAH is less common, but often very difficult to manage. This mini-review provides an overview of the pathophysiology as well as the clinical presentation and the diagnostic features of pulmonary involvement in AOSD.

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.

Elevated expression of TLR2 and its correlation with disease activity and clinical manifestations in adult-onset Still's disease

This study investigated the role of Toll-like receptor 1 (TLR1), TLR2, TLR4, TLR7, and TLR9 in patients with adult-onset Still’s disease (AOSD). This study included 20 patients with AOSD and 15 healthy controls (HCs). TLR expression in the peripheral blood was quantified using flow cytometry; TLR expression pattern, in the skin lesions and lymph nodes (LNs) of patients with AOSD, was evaluated immunohistochemically. Significantly higher mean intensities of cells presenting TLR2 and TLR7 from whole blood were observed in patients with AOSD than in HCs. TLR2 expression in whole cells correlated with systemic scores, levels of lactate dehydrogenase and ferritin and serum levels of interleukin-1β (IL-1β), IL-6, and IL-18. The percentage of TLR2-positive inflammatory cells was higher in skin biopsy samples from patients with AOSD than those in HCs. TLR9-expressing positive inflammatory cell counts were higher in skin lesions from patients with AOSD than those in the HC, eczema, and psoriasis groups. The expression levels of TLR1, TLR4, TLR7, and TLR9 were higher in LNs of patients with AOSD than in those with T cell lymphoma and reactive lymphadenopathy. Circulating TLR2- and TLR7-positive cells may contribute to the pathogenesis of AOSD. Furthermore, immunohistochemical staining for TLRs in skin lesions and LNs may aid in differentiating AOSD from similar conditions.

Usefulness of Interleukin-18 as a Diagnostic Biomarker to Differentiate Adult-Onset Still's Disease With/Without Macrophage Activation Syndrome From Other Secondary Hemophagocytic Lymphohistiocytosis in Adults

Background

Interleukin (IL)-18 is markedly elevated in systemic inflammatory diseases that cause the ‘cytokine storm’ such as adult-onset Still’s disease (AOSD) and hemophagocytic lymphohistiocytosis (HLH). The differences in IL-18 between AOSD and HLH, especially in adults, is uncertain. Macrophage activation syndrome (MAS), a form of secondary HLH, is often difficult to differentiate cases of AOSD that include MAS from other secondary HLH. In this case-control study, we investigated whether serum IL-18 levels could be a useful biomarker for the differential diagnosis of AOSD with or without MAS (AOSD group) and other secondary HLH in adults (adult HLH group).

Patients and Methods

We enrolled 46 patients diagnosed with AOSD including 9 patients with MAS and 31 patients in the adult HLH group, which excluded AOSD-associated MAS. The clinical features and laboratory data were compared between the AOSD and adult HLH groups. In addition, we subdivided the AOSD group (with or without MAS) and the adult HLH group (whether lymphoma-associated or not) and compared the four groups. A logistic regression analysis was used to identify factors with high efficacy in differentiating the two groups, followed by a receiver operating characteristic (ROC) curve analysis to evaluate the differential diagnostic ability of IL-18. We analyzed the correlation between IL-18 and various laboratory parameters in the AOSD group.

Results

Serum IL-18 levels of patients in the AOSD groups were significantly higher than those of the adult HLH groups, and were closely correlated with ferritin, soluble interleukin-2 receptor (sIL-2R), and other laboratory data. Univariate and multivariate logistic regression analyses revealed that IL-18, sIL-2R, and ‘arthralgia or arthritis’ are independent factors useful in the differential diagnosis of AOSD from adult HLH. In the differential diagnosis of both groups, the area under the curve obtained from the ROC curve of IL-18 with a cutoff value of 18,550 pg/mL was 0.91 (95% confidence interval 0.83–1.00; sensitivity 90.3%, specificity 93.5%), and the differential diagnosis ability of IL-18 was superior to that of other laboratory data.

Conclusions

IL-18 could be a useful biomarker for the differential diagnosis of AOSD and adult HLH.

Distinct Effects of Interleukin-1β Inhibition upon Cytokine Profile in Patients with Adult-Onset Still's Disease and Active Articular Manifestation Responding to Canakinumab

Adult-onset Still’s disease (AOSD) is a systemic auto-inflammatory disease characterized by the presence of immunologically mediated inflammation and deficient resolution of inflammation. Canakinumab is an approved IL-1β inhibitor in the treatment of AOSD with a balanced efficacy and safety profile. Since inflammatory cytokines play a major role in the pathogenesis of AOSD, we investigated the effects of canakinumab on the cytokine profile of AOSD patients from a randomized controlled trial. Multiplex analysis and ELISA were used to test the concentrations of several cytokines at three time points—week 0 (baseline), week 1 and week 4—in two patient groups—placebo and canakinumab. Two-way repeated-measures analysis of variance revealed a significant temporal effect on the concentrations of MRP 8/14, S100A12, IL-6 and IL-18 with a significant decrease at week 4 in the canakinumab group exclusively. Comparing responders with non-responders to canakinumab showed a significant decrease in MRP 8/14, IL-1RA, IL-18 and IL-6 in responders at week 4, while S100A12 levels decreased significantly in responders and non-responders. In summary, canakinumab showed a striking effect on the cytokine profile in patients with AOSD, exhibiting a clear association with clinical response.

Targeting Toll-like Receptor (TLR) Pathways in Inflammatory Arthritis: Two Better Than One?

Inflammatory arthritis is a cluster of diseases caused by unregulated activity of the immune system. The lost homeostasis is followed by the immune attack of one’s self, what damages healthy cells and tissues and leads to chronic inflammation of various tissues and organs (e.g., joints, lungs, heart, eyes). Different medications to control the excessive immune response are in use, however, drug resistances, flare-reactions and adverse effects to the current therapies are common in the affected patients. Thus, it is essential to broaden the spectrum of alternative treatments and to develop disease-modifying drugs. In the last 20 years, the involvement of the innate immune receptors TLRs in inflammatory arthritis has been widely investigated and targeting either the receptor itself or the proteins in the downstream signalling cascades has emerged as a promising therapeutic strategy. Yet, concerns about the use of pharmacological agents that inhibit TLR activity and may leave the host unprotected against invading pathogens and toxicity issues amid inhibition of downstream kinases crucial in various cellular functions have arisen. This review summarizes the existing knowledge on the role of TLRs in inflammatory arthritis; in addition, the likely druggable related targets and the developed inhibitors, and discusses the pros and cons of their potential clinical use.

Interleukin-6 inhibition: a therapeutic strategy for the management of adult-onset Still's disease

Introduction:Patients with adult-onset Still's disease have markedly elevated serum levels of proinflammatory cytokines, such as IL-1β, IL-6, and IL-18, suggesting the potential of these molecules as therapeutic targets. IL-6 accelerates macrophage and cytotoxic T-cell differentiation and neutrophil and macrophage chemotaxis and is one of the most important cytokines in the pathogenesis of adult-onset Still's disease.Areas covered:The review summarizes the importance of IL-6 in the pathogenesis of adult-onset Still's disease and clinical aspects of IL-6 inhibition from retrospective and prospective studies.Expert opinion:Adult-onset Still's disease is a systemic inflammatory disease of unknown etiology and characterized by elevated various proinflammatory cytokines. In particular, serum concentrations of IL-6 is significantly high in patients with active adult-onset Still's disease, and many case reports, cohort studies and one randomized, placebo-controlled trail have shown the efficacy of IL-6 blockade in patients with adult-onset Still's disease who were refractory to glucocorticoids and other immunosuppressive treatments. IL-6 inhibition is effective for both systemic and joint manifestations with arthritis improving slowly. There is still a concern over the triggering of macrophage activation syndrome; however, the IL-6 inhibition strategy has introduced better management of adult-onset Still's disease.

Serum sTREM-1 in adult-onset Still's disease: a novel biomarker of disease activity and a potential predictor of the chronic course

Objectives

Triggering receptor expressed on myeloid cells-1 (TREM-1) is an amplifier of inflammatory signals. Recently, a soluble form of TREM-1 (sTREM-1) was described. This study aimed to investigate the role of serum sTREM-1 in patients with adult-onset Still’s disease (AOSD).

Methods

Serum sTREM-1 levels were detected in 108 AOSD patients, 88 RA patients and 112 healthy controls (HC). The correlations of sTREM-1 with disease activity, clinical characteristics and laboratory parameters in AOSD patients were analysed by the Spearman correlation test. Risk factors for the chronic course of AOSD were evaluated by multivariate logistic regression analysis.

Results

AOSD patients had significantly higher serum sTREM-1 levels than RA patients and HC, and serum sTREM-1 levels were correlated with the systemic score, ferritin, leucocyte count, CRP, IL-1β and IL-6. The elevation in the initial sTREM-1 level by itself could discriminate patients developing the chronic course from patients developing the nonchronic course. Moreover, an elevated sTREM-1 level (> 526.4475 pg/ml) was an independent risk factor for the chronic course in active AOSD patients. Furthermore, interfering with TREM-1 engagement led to reductions in the secretion of pro-inflammatory cytokines, such as IL-1β, IL-6 and TNF-α, in neutrophils and monocytes from active AOSD patients.

Conclusion

Serum sTREM-1 levels are correlated with disease activity, and an elevation in the initial serum sTREM-1 level is a potential predictor of the chronic course in AOSD patients, which currently provides the best predictive model for identifying patients prone to developing the chronic course of AOSD.

Can SARS-CoV-2 Virus Use Multiple Receptors to Enter Host Cells?

The occurrence of the novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), responsible for coronavirus disease 2019 (COVD-19), represents a catastrophic threat to global health. Protruding from the viral surface is a densely glycosylated spike (S) protein, which engages angiotensin-converting enzyme 2 (ACE2) to mediate host cell entry. However, studies have reported viral susceptibility in intra- and extrapulmonary immune and non-immune cells lacking ACE2, suggesting that the S protein may exploit additional receptors for infection. Studies have demonstrated interactions between S protein and innate immune system, including C-lectin type receptors (CLR), toll-like receptors (TLR) and neuropilin-1 (NRP1), and the non-immune receptor glucose regulated protein 78 (GRP78). Recognition of carbohydrate moieties clustered on the surface of the S protein may drive receptor-dependent internalization, accentuate severe immunopathological inflammation, and allow for systemic spread of infection, independent of ACE2. Furthermore, targeting TLRs, CLRs, and other receptors (Ezrin and dipeptidyl peptidase-4) that do not directly engage SARS-CoV-2 S protein, but may contribute to augmented anti-viral immunity and viral clearance, may represent therapeutic targets against COVID-19.

Characterization of bovine ileal epithelial cell line for lectin binding, susceptibility to enteric pathogens, and TLR mediated immune responses

In this study, primary and immortalized bovine intestinal epithelial cells (BIECs) were characterized for the expression of surface carbohydrate moieties. Primary BIEC-c4 cells showed staining greater than 90 % for 16 lectins but less than 50 % staining for four lectins. Immortalized BIECs showed significantly different lectin binding profile for few lectins compared to BIEC-c4 cells. BIEC-c4 cells were studied for infectivity to E. coli, Salmonella enterica, bovine rotavirus, bovine coronavirus, and bovine viral diarrhea virus. Bovine strain E. coli B41 adhered to BIEC-c4 cells and Salmonella strains S. Dublin and S. Mbandaka showed strong cell invasion. BIEC-c4 cells were susceptible to bovine rotavirus. LPS stimulation upregulated IL-10, IL-8, and IL-6 expression and Poly I:C upregulated TLR 8 and TLR 9 expression. This study provides important knowledge on the glycoconjugate expression profile of primary and immortalized BIECs and infectivity and immune responses of primary BIECs to bacterial and viral pathogens or ligands.

Roles of Interactions Between Toll-Like Receptors and Their Endogenous Ligands in the Pathogenesis of Systemic Juvenile Idiopathic Arthritis and Adult-Onset Still's Disease

Systemic juvenile idiopathic arthritis (JIA) and adult-onset Still’s disease (AOSD) are systemic inflammatory disorders that manifest as high-spiking fever, joint pain, evanescent skin rash, and organomegaly. Their pathogenesis is unclear, but inflammation is triggered by activation of the innate immune system with aberrant production of proinflammatory cytokines. Along with extrinsic factors, intrinsic pathways can trigger an unexpected immune response. Damage-associated molecular patterns (DAMPs) induce the activation of innate immune cells, leading to sterile inflammation in systemic JIA and AOSD. These endogenous proteins interact with Toll-like receptors (TLRs), which are pattern recognition receptors, and mediate immune signaling following stimulation by pathogen-associated molecular patterns and DAMPs. Several DAMPs, such as S100 proteins, play a role in the development or severity of systemic JIA and AOSD, in which their interactions with TLRs are altered. Also, the expression levels of genes encoding DAMPs contribute to the susceptibility to systemic JIA and AOSD. Herein, we review reports that TLR and DAMP signaling initiates and/or maintains the inflammatory response in systemic JIA and AOSD, and their correlations with the clinical characteristics of those diseases. In addition, we assess their utility as biomarkers or therapeutics for systemic JIA and AOSD.

Autoinflammatory and autoimmune conditions at the crossroad of COVID-19

Coronavirus disease 2019 (COVID-19) has been categorized as evolving in overlapping phases. First, there is a viral phase that may well be asymptomatic or mild in the majority, perhaps 80% of patients. The pathophysiological mechanisms resulting in minimal disease in this initial phase are not well known. In the remaining 20% of cases, the disease may become severe and/or critical. In most patients of this latter group, there is a phase characterized by the hyperresponsiveness of the immune system. A third phase corresponds to a state of hypercoagulability. Finally, in the fourth stage organ injury and failure occur. Appearance of autoinflammatory/autoimmune phenomena in patients with COVID-19 calls attention for the development of new strategies for the management of life-threatening conditions in critically ill patients. Antiphospholipid syndrome, autoimmune cytopenia, Guillain-Barré syndrome and Kawasaki disease have each been reported in patients with COVID-19. Here we present a scoping review of the relevant immunological findings in COVID-19 as well as the current reports about autoinflammatory/autoimmune conditions associated with the disease. These observations have crucial therapeutic implications since immunomodulatory drugs are at present the most likely best candidates for COVID-19 therapy. Clinicians should be aware of these conditions in patients with COVID-19, and these observations should be considered in the current development of vaccines.

The pathological role of B cells in systemic lupus erythematosus: From basic research to clinical

Systemic lupus erythematosus (SLE) is an autoimmune disease that often occurs in females of child-bearing age. It involves multiple systems and severely threatens human life. One of the typical characteristics of SLE is the formation of immune complexes with autoantibodies produced by B cells that target various autoantigens, thus indicating the pivotal role of B cells in the pathogenesis of SLE. Increasing evidence has shown abnormal expression of B cells in the peripheral blood of SLE patients. Moreover, numerous studies have shown that B cells in SLE patients are abnormally activated, as well as aberrantly differentiated, and are involved in the inflammatory cytokine milieu, abnormal transcription factor activity, and signalling pathways. Several biological therapies targeting B cells, such as anti-CD20 antibodies, have been intensively studied in preclinical and clinical trials. However, the results have not met expectations. Therefore, new therapies targeting B cells are in great need. This review will summarize the latest progress in basic research on B cells to better understand the pathogenesis of SLE and will discuss the outcomes of B-cell-targeting treatments that provide potential therapeutic targets and strategies for SLE. Studies have clarified high levels of IL-21 in serum from SLE patients and animal models. IL-21 promotes B cell differentiation, which results in antibodies accumulation leads to SLE. Therefore, further studies on IL-21 will give new perspectives on SLE treatments. In addition, the application of drugs targeting plasma cell depletion in SLE patients may also achieve satisfied results in treatment.

Adult-onset Still's disease with haemorrhagic pericarditis and tamponade preceded by acute Lyme disease

A 61-year-old Caucasian man presented with a fever of unknown origin, a transient erythematous rash on his right upper extremity and chest pressure after being treated for erythema migrans (Lyme disease). Echocardiogram demonstrated a large pericardial effusion with tamponade. He underwent pericardiostomy with tube placement. Workup for infectious and malignant etiologies was negative. Histology of the pericardium showed acute on chronic fibrinous haemorrhagic pericarditis. The patient met criteria for adult-onset Still's disease. Symptoms resolved following treatment with methylprednisolone and anakinra. We believe this is the first case of adult-onset Still's disease precipitated by acute Lyme disease.

A comprehensive review on adult onset Still's disease

Adult-onset Still's disease (AOSD) is a systemic inflammatory disorder of unknown etiology usually affecting young adults; spiking fever, arthritis and evanescent rash are commonly observed during the disease. Other frequently observed clinical features include sore throat, hepatomegaly, splenomegaly, lymphadenopathy and serositis. Furthermore, AOSD patients may experience different life-threating complications. Macrophage activation syndrome (MAS) has been reported up to 15% of AOSD patients and it is considered to be the most severe complication of the disease being characterised by high mortality rate. During AOSD, laboratory tests reflect the systemic inflammatory process showing high levels of erythrocyte sedimentation rate and C-reactive protein. In addition, the ferritin levels are typically higher than those observed in other autoimmune, inflammatory, infectious, or neoplastic diseases. Analysing AOSD disease course, 3 different clinical patterns of AOSD have been identified: i. monocyclic pattern, characterised by a systemic single episode; ii. polycyclic pattern, characterised by multiple, ≤ 1 year lasting, flares, alternating with remissions; iii. chronic pattern, related to a persistently active disease with associated polyarthritis. At present, AOSD therapeutic strategy is aimed at targeting pro-inflammatory signs and symptoms, preventing organ damage and life-threating complications and minimising adverse effects of treatment. However, the treatment of AOSD remains largely empirical, lacking controlled clinical trials. High dosages of corticosteroids are usually the first line therapy when the systemic symptoms predominate. Despite this treatment, a large percentage of patients experiences several flares with an evolution toward the chronic disease course and up to 16% of patients die during the follow up, due to AOSD-related complications. On these bases, in the last years, biological agents have been successfully used in refractory cases. Finally, multiple recent lines of evidence have suggested new insights in AOSD pathogenesis unmasking further therapeutic targets. In fact, small molecules, used in experimental MAS models, might represent new therapeutic options.

Upregulation of circulating microRNA-134 in adult-onset Still's disease and its use as potential biomarker

Adult-onset Still’s disease (AOSD) is a multi-systemic inflammatory disorder of unknown etiology. To date, no single diagnostic test is available for AOSD. Herein, we investigated the pathogenic role of microRNAs in AOSD. MicroRNA profiles in plasma from AOSD patients and healthy controls were analyzed by microarray analysis, followed by quantitative reverse transcription PCR validation. The biological functions of microRNAs were evaluated using in vitro cell-based assay. Among the differentially expressed microRNAs, microRNA-134 (miR-134) expression was positively correlated with AOSD activity scores and significantly decreased after effective treatment. An increased miR-134 level is significantly associated with the activation of Toll-like receptor 3 (TLR3). The reporter assay identified IL-18 binding protein (IL-18BP) as the target of miR-134. A negative correlation between miR-134 expression and IL-18BP mRNA levels were detected in peripheral blood cells following TLR3 ligand treatment. Lower plasma IL-18BP levels and higher IL-18 levels were also observed in active AOSD patients who had higher miR-134 expression than inactive patients. Upregulation of circulating miR-134 was associated with elevated IL-18 levels by targeting IL-18BP in AOSD patients and was positively correlated with disease activity, suggesting its involvement in AOSD pathogenesis. MiR-134 may be a novel activity indicator or potential prognostic biomarker in AOSD.

Elevated Expression of the NLRP3 Inflammasome and Its Correlation with Disease Activity in Adult-onset Still Disease

OBJECTIVE

The dysregulation of the NLRP3 (NLR containing a pyrin domain) inflammasome is involved in autoinflammatory diseases. Adult-onset Still disease (AOSD) is regarded as an autoinflammatory disease. However, the pathogenic involvement of NLRP3 inflammasome in AOSD remains unclear and NLRP3 activators in AOSD are currently unknown.

METHODS

The mRNA expression of NLRP3 inflammasome signaling in peripheral blood mononuclear cells (PBMC) from 34 patients with AOSD and 14 healthy subjects was determined using quantitative-PCR (qPCR). The changes in mRNA and protein levels of NLRP3 inflammasome signaling in PBMC treated with the potential activator [imiquimod (IMQ)] or inhibitor of NLRP3 were evaluated using qPCR and immunoblotting, respectively. The supernatant levels of interleukin (IL)-1β and IL-18 were determined by ELISA.

RESULTS

Significantly higher mRNA levels of NLRP3 inflammasome signaling were observed in patients with AOSD compared with healthy controls. NLRP3 expressions were positively correlated with disease activity in patients with AOSD. IMQ (an effective Toll-like receptor 7 ligand; 10 µg/ml and 25 µg/ml) stimulation of PBMC from patients with AOSD induced dose-dependent increases of mRNA expression of NLRP3 (mean ± standard error of the mean, 2.06 ± 0.46 and 6.05 ± 1.84, respectively), caspase-1 (1.81 ± 0.23 and 4.25 ± 0.48), IL-1β (5.68 ± 1.51 and 12.13 ± 3.71), and IL-18 (2.32 ± 0.37 and 4.81 ± 0.51) compared with controls (all p < 0.005). IMQ stimulation of PBMC from patients similarly induced greater increases in protein expressions of NLRP3 inflammasome compared with controls. The protein expressions of NLRP3, IL-1β, and IL-18 on PBMC significantly decreased after treatment with NLRP3 inhibitor in patients with AOSD.

CONCLUSION

Increased expression of NLRP3 inflammasome and its positive correlation with disease activity in AOSD suggest its involvement in disease pathogenesis. IMQ upregulated expressions of NLRP3 inflammasome signaling, and IMQ might be an activator of NLRP3 inflammasome in AOSD.

Small Molecule Inhibition of Interleukin-1 Receptor-Associated Kinase 4 (IRAK4)

In recent years, interleukin-1 receptor-associated kinase 4, IRAK4, has become an attractive target for many medicinal chemistry programmes. Target inhibition is of potential therapeutic value in areas including autoimmune disorders, cancer, inflammatory diseases, and possibly neurodegenerative diseases. Results from high-throughput screening efforts have led, in conjunction with structure-based drug design, to the identification of highly potent and selective small molecule IRAK4 inhibitors from many diverse chemical series. In vitro and in vivo studies with entities from distinct structural classes have helped elucidate the downstream pharmacological responses associated with IRAK4 inhibition as a proof of concept in disease models, leading to the recent initiation of human clinical trials. Within this review, we will highlight the considerable effort by numerous groups dedicated to the development of small molecule IRAK4 inhibitors for the treatment of human disease.

Increased Toll-Like Receptors Activity and TLR Ligands in Patients with Autoimmune Thyroid Diseases

OBJECTIVE

Autoimmune thyroid disease (AITD) is an organ-specific disorder due to the interplay between environmental and genetic factors. Toll-like receptors (TLRs) are pattern recognition receptors expressed abundantly on monocytes. There is a paucity of data on TLR expression in AITD. The aim of this study was to examine TLR expression, activation, ligands, and downstream signaling adaptors in peripheral blood mononuclear cells (PBMCs) extracted from untreated AITD patients and healthy controls.

METHOD

We isolated PBMC of 30 healthy controls, 36 patients with untreated Hashimoto's thyroiditis, and 30 patients with newly onset Graves' disease. TLR mRNA, protein expression, TLR ligands, and TLR adaptor molecules were measured using real-time PCR, Western blot, flow cytometry, and enzyme-linked immunosorbent assay (ELISA). PBMC was simulated with TLR agonists. The effects of TLR agonists on the viability of human PBMC were evaluated using the MTT assay. The supernatants of cell cultures were measured for the pro-inflammatory cytokines, interleukin (IL)-6, tumor necrosis factor alpha (TNF-α), and IL-10 by ELISA.

RESULTS

TLR2, TLR3, TLR9, and TLR10 mRNA were significantly increased in AITD patients compared with controls. TLR2, TLR3, TLR9, high mobility group box 1 (HMGB1), and RAGE expression on monocytes was higher in patients than control at baseline and TLR agonists' stimulation. The release of TNF-α and IL-6 was significantly increased in PBMCs from AITD patients with TLR agonists, while IL-10 was significantly decreased. Downstream targets of TLR, myeloid differentiation factor 88 (MyD88), and myeloid toll/IL-1 receptor-domain containing adaptor-inducing interferon-β were significantly elevated in AITD patients. Levels of TLR2 ligands, HMGB1, and heat shock protein 60 were significantly elevated in AITD patients compared with those in controls and positively correlated with TgAb and TPOAb, while sRAGE concentration was significantly decreased in AITD patients.

CONCLUSION

This work is the first to show that TLR2, TLR3, and TLR9 expression and activation are elevated in the PBMCs of patients with AITD and TLRs may participate in the pathogenesis of AITD.

Recent Progress in the Molecular Recognition and Therapeutic Importance of Interleukin-1 Receptor-Associated Kinase 4

Toll-like receptors (TLRs) are the most upstream pattern recognition receptors in the cell, which detect pathogen associated molecular patterns and initiate signal transduction, culminating in the transcription of pro-inflammatory cytokines and antiviral interferon. Interleukin-1 receptor-associated kinase 4 (IRAK4) is a key mediator in TLR (except for TLR3) and interleukin-1 receptor signaling pathways. The loss of kinase function of IRAK4 is associated with increased susceptibility to various pathogens, while its over-activation causes autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, and cancer. The therapeutic importance of this master kinase has been advocated by a number of recent preclinical studies, where potent inhibitors have been administered to improve various TLR-mediated pathologies. Increasing studies of X-ray crystallographic structures with bound inhibitors have improved our knowledge on the molecular recognition of ligands by IRAK4, which will be crucial for the development of new inhibitors with improved potencies. In this review, we briefly discuss the structural aspect of ligand recognition by IRAK4 and highlight its therapeutic importance in the context of TLR-associated unmet medical needs.

Adult-onset Still's disease: Advances in the treatment

Adult-onset Still's disease (AOSD) is a rare systemic inflammatory disorder mainly characterized by persistent high spiking fevers, evanescent rash, and joint involvement. The pathogenesis of AOSD is only partially known, but pro-inflammatory cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-1, IL-6, IL-18, and IFN-γ seem to play a major role in this disorder. AOSD is at the crossroad of auto-inflammatory syndromes and autoimmune diseases. It is diagnosed by exclusion to determine the presence of high serum ferritin levels, which is usually >1000 μg/L. AOSD is generally treated with non-steroidal anti-inflammatory drugs, corticosteroids, and disease-modifying anti-rheumatic drugs (DMARDs). Although information on biologic therapy in the management of AOSD is scarce, these drugs represent a major breakthrough in the management of patients with AOSD refractory to corticosteroids or conventional DMARDs or in patients presenting life-threatening manifestations. In this regard, TNF-α, IL-1, and IL-6 antagonists had been proved effective in patients with AOSD.

Expression of TLR-7, MyD88, NF-kB, and INF-α in B Lymphocytes of Mayan Women with Systemic Lupus Erythematosus in Mexico

Background

Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease involving multiple organs. It is currently accepted that several genetic, environmental, and hormonal factors are contributing to its development. Innate immunity may have a great influence in autoimmunity through Toll-like receptors. TLR-7 recognizing single-strand RNA has been involved in SLE. Its activation induces intracellular signal with attraction of MyD88 and NF-kBp65, leading to IFN-α synthesis which correlate with disease activity.

Objective

To assess the expression of TLR-7, MyD88, and NF-kBp65 in B lymphocytes of Mayan women with SLE.

Methods

One hundred patients with SLE and 100 healthy controls, all of them Mayan women, were included. TLR-7 was analyzed on B and T lymphocytes, and MyD88 and NF-kB only in B lymphocytes. Serum INF-α level was evaluated by ELISA.

Results

Significant expression (p < 0.0001) of TLR-7 in B and T lymphocytes and serum IFN-α increased (p = 0.034) was observed in patients. MyD88 and NF-kBp65 were also increased in B lymphocytes of patients. TLR-7 and NF-kBp65 expression correlated, but no correlation with INF-α and disease activity was detected.

Conclusion

Data support the role of TLR-7 and signal proteins in the pathogenesis of SLE in the Mayan population of Yucatán.

PTPN22 Variant R620W Is Associated With Reduced Toll-like Receptor 7-Induced Type I Interferon in Systemic Lupus Erythematosus

OBJECTIVE

Protein tyrosine phosphatase nonreceptor type 22 (PTPN22) is associated with an increased risk of systemic lupus erythematosus (SLE). PTPN22 encodes Lyp, and a disease-associated coding variant bears an R620W substitution (LypW). LypW carriage is associated with impaired production of type I interferon (IFN) by myeloid cells following Toll-like receptor (TLR) engagement. The aim of this study was to investigate the effects of LypW carriage on TLR signaling in patients with SLE.

METHODS

Plasma IFNα concentrations and whole-blood IFN gene scores were compared in SLE patients who were LypW carriers and those who were noncarriers. TLR-7 agonist R848-stimulated IFNα and tumor necrosis factor levels, IFN-dependent gene expression, and STAT-1 activation were determined in peripheral blood mononuclear cells (PBMCs) and/or plasmacytoid dendritic cells (PDCs) obtained from these patients. The effect of LypW expression on the systemic type I IFN response to R848 stimulation in vivo was assessed in transgenic mice.

RESULTS

Plasma IFNα levels and whole-blood IFN gene signatures were comparable in SLE patients who were LypW carriers and those who were noncarriers. However, PBMCs from LypW carriers produced less IFNα and showed reduced IFN-dependent gene up-regulation and STAT-1 activation after R848 stimulation. The frequency of PDCs producing IFNα2 and the per-cell IFNα2 levels were significantly reduced in LypW carriers. LypW-transgenic mice displayed reduced TLR-7-induced circulating type I IFN responses.

CONCLUSION

PDCs from SLE patients carrying the disease-associated PTPN22 variant LypW showed a reduced capacity for TLR-7 agonist-induced type I IFN production, even though LypW carriers displayed systemic type I IFN activation comparable with that observed in noncarriers. LypW carriage identifies SLE patients who may harbor defects in TLR- and PDC-dependent host defense or antiinflammatory functions.

Adult-onset Still's disease-pathogenesis, clinical manifestations, and new treatment options

Adult-onset Still's disease (AOSD), a systemic inflammatory disorder, is often considered a part of the spectrum of the better-known systemic-onset juvenile idiopathic arthritis, with later age onset. The diagnosis is primarily clinical and necessitates the exclusion of a wide range of mimicking disorders. AOSD is a heterogeneous entity, usually presenting with high fever, arthralgia, skin rash, lymphadenopathy, and hepatosplenomegaly accompanied by systemic manifestations. The diagnosis is clinical and empirical, where patients are required to meet inclusion and exclusion criteria with negative immunoserological results. There are no clear-cut diagnostic radiological or laboratory signs. Complications of AOSD include transient pulmonary hypertension, macrophage activation syndrome, diffuse alveolar hemorrhage, thrombotic thrombocytopenic purpura and amyloidosis. Common laboratory abnormalities include neutrophilic leukocytosis, abnormal liver function tests, and elevated acute-phase reactants (ESR, CRP, ferritin). Treatment consists of anti-inflammatory medications. Non-steroidal anti-inflammatory drugs have limited efficacy, and corticosteroid therapy and disease-modifying anti-rheumatic drugs are usually required. Recent advances have revealed a pivotal role of proinflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin (IL)-1, IL-6, IL-8, and IL-18 in disease pathogenesis, giving rise to the development of novel targeted therapies aiming at optimal disease control. The review aims to summarize recent advances in pathophysiology and potential therapeutic strategies in AOSD.

Adult onset Still's disease (AOSD) in the era of biologic therapies: dichotomous view for cytokine and clinical expressions

Adult onset Still's disease (AOSD) is a rare inflammatory disorder characterized by hectic spiking fever, evanescent rash and joint involvement. Prognosis is highly variable upon disease course and specific involvements, ranging from benign and limited outcome to chronic destructive polyarthritis and/or life-threatening events in case of visceral complications or reactive hemophagocytic lymphohistiocytosis (RHL). AOSD remains a debatable entity at the frontiers of autoimmune diseases and autoinflammatory disorders. The pivotal role of macrophage cell activation leading to a typical Th1 cytokine storm is now well established in AOSD, and confirmed by the benefits using treatments targeting TNF-α, IL-1β or IL-6 in refractory patients. However, it remains difficult to determine predictive factors of outcome and to draw guidelines for patient management. Herein, reviewing literature and relying on our experience in a series of 8 refractory AOSD patients, we question nosology and postulate that different cytokine patterns could underlie contrasting clinical expressions, as well as responses to targeted therapies. We therefore propose to dichotomize AOSD according to its clinical presentation. On the one hand, 'systemic AOSD' patients, exhibiting the highest inflammation process driven by excessive IL-18, IL-1β and IL-6 production, would be at risk of life-threatening complications (such as multivisceral involvements and RHL), and would preferentially respond to IL-1β and IL-6 antagonists. On the other hand, 'rheumatic AOSD' patients, exhibiting pre-eminence of joint involvement driven by IL-8 and IFN-γ production, would be at risk of articular destructions, and would preferentially respond to TNF-α blockers.

Adult-onset Still's disease

First described in 1971, adult-onset Still's disease (AOSD) is a rare multisystemic disorder considered as a complex (multigenic) autoinflammatory syndrome. A genetic background would confer susceptibility to the development of autoinflammatory reactions to environmental triggers. Macrophage and neutrophil activation is a hallmark of AOSD which can lead to a reactive hemophagocytic lymphohistiocytosis. As in the latter disease, the cytotoxic function of natural killer cells is decreased in patients with active AOSD. IL-18 and IL-1β, two proinflammatory cytokines processed through the inflammasome machinery, are key factors in the pathogenesis of AOSD; they cause IL-6 and Th1 cytokine secretion as well as NK cell dysregulation leading to macrophage activation. The clinico-biological picture of AOSD usually includes high spiking fever with joint symptoms, evanescent skin rash, sore throat, striking neutrophilic leukocytosis, hyperferritinemia with collapsed glycosylated ferritin (<20%), and abnormal liver function tests. According to the clinical presentation of the disease at diagnosis, two AOSD phenotypes may be distinguished: i) a highly symptomatic, systemic and feverish one, which would evolve into a systemic (mono- or polycyclic) pattern; ii) a more indolent one with arthritis in the foreground and poor systemic symptomatology, which would evolve into a chronic articular pattern. Steroid- and methotrexate-refractory AOSD cases benefit now from recent insights into autoinflammatory disorders: anakinra seems to be an efficient, well tolerated, steroid-sparing treatment in systemic patterns; tocilizumab seems efficient in AOSD with active arthritis and systemic symptoms while TNFα-blockers could be interesting in chronic polyarticular refractory AOSD.

A potential role of myeloid DAP12-associating lectin (MDL)-1 in the regulation of inflammation in rheumatoid arthritis patients

The pathogenic roles of myeloid DAP12-associating lectin-1(MDL-1) and DAP12 in human rheumatoid arthritis (RA) remain unknown. Frequencies of MDL-1-expressing monocytes in 22 active RA patients, 16 inactive RA patients, 12 osteoarthritis (OA) patients and 10 healthy controls (HC) were determined by flow-cytometry analysis. The mRNA expression levels of MDL-1 and DAP12 on PBMCs were evaluated by quantitative PCR, and their protein expression levels in the synovium were examined by immunohistochemistry. Significantly higher median percentages of circulating MDL-1-expressing monocytes were observed in active RA patients (53.6%) compared to inactive RA patients (34.1%), OA patients (27.9%), and HC (21.2%). Levels of MDL-1 and DAP12 gene expression in PBMCs and their protein expression in the synovium were significantly higher in active RA patients than in inactive RA or OA patients. MDL-1 levels were positively correlated with parameters of disease activity, articular damage, and levels of proinflammatory cytokines. MDL-1 activator (Dengue virus type 2 antigen) stimulation on PBMCs resulted in significantly enhanced levels of proinflammatory cytokines in RA patients compared to those in OA patients or HC, indicating that MDL-1 activation is functional. Frequencies of MDL-1-expressing monocytes and levels of MDL-1 and DAP12 gene expression significantly decreased after effective therapy. Concordant overexpression of MDL-1 and DAP12 were correlated with increased production of proinflammatory cytokines in RA patients, suggesting their roles in regulating articular inflammation.