Association between adult-onset Still's disease and interleukin-18 gene polymorphisms

Associations between circulating interleukin-18 levels and adult-onset Still's disease: a meta-analysis

Objective

This study aimed to investigate the link between circulating interleukin-18 (IL-18) levels and adult-onset Still's disease (AOSD).

Methods

A thorough search was performed on MEDLINE, Embase, and Web of Science to find relevant articles. A meta-analysis was conducted to compare serum/plasma IL-18 levels in AOSD patients to those in control subjects.

Results

The meta-analysis included 13 studies with a total of 562 AOSD patients and 790 controls. The results showed a significant increase in IL-18 levels in the AOSD group compared to the control group (standard mean difference [SMD]=1.899, 95% confidence interval [CI]=1.078~2.720, p<0.001). When stratified by ethnicity, higher IL-18 levels were found in both Asian and European populations with AOSD. Subgroup analysis, regardless of variable adjustments, consistently indicated significantly higher IL-18 levels in the AOSD group. Significant elevations in IL-18 levels were observed in both small (n<50) and large groups (n>50), as well as in original and imputed data groups after data type stratification. Free IL-18 levels were significantly higher in the active group compared to the inactive group (SMD=0.900, 95% CI=0.532~1.268, p<0.001). The meta-analysis showed a positive correlation between IL-18 levels and ferritin (correlation coefficient=0.542, 95% CI=0.431~0.637, p<0.001) and C-reactive protein.

Conclusion

This meta-analysis demonstrated a significant increase in circulating IL-18 levels and a positive correlation between IL-18 levels and ferritin and C-reactive protein levels in patients with AOSD.

Adult-Onset Still's Disease (AOSD): Advances in Understanding Pathophysiology, Genetics and Emerging Treatment Options

Adult-onset Still's disease (AOSD) is a multisystemic complex disorder clinically characterised by episodes of spiking fever, evanescent rash, polyarthritis or diffuse arthralgias; multiorgan involvement may develop according to the hyper-inflammatory extent. The pathogenesis of AOSD is not completely recognised. The central role of macrophage activation, which results in T helper 1 (Th1) cell cytokine activation, is well established. Pro-inflammatory cytokines such as interleukin (IL)-1, IL-6 and IL-18 play a fundamental role in disease onset and progression. The disease may develop in both children and adults with overlapping clinical features, and although several subsets depending on the clinical manifestations and the cytokines expressed have been identified, the dichotomy between systemic juvenile idiopathic arthritis (sJIA) and AOSD nowadays has been overcome, and the pathology is considered a disease continuum between ages. Various therapeutic approaches have been evaluated thus far, and different compounds are under assessment for AOSD treatment. Historically, glucocorticoids have been employed for treating systemic manifestations of Still's disease, while conventional synthetic disease modifying anti-rheumatic drugs (csDMARDs) demonstrated efficacy in controlling the articular manifestations. Currently, biological (b) DMARDs are widely employed; IL-1 inhibitors such as anakinra and canakinumab have proven to have high efficacy and an excellent safety profile and the anti-IL-6 tocilizumab is approved for sJIA, with several trials and longitudinal studies confirming its efficacy and safety. Moreover, in the light of the 'window of opportunity', new evidence showed that the earlier these treatments are initiated, the sooner clinical inactivity can be achieved. Other treatment options are being considered since several molecules involved in the disease pathophysiology can be targeted through various mechanisms. This review will provide a broad overview of AOSD pathophysiology, insights into specific organ manifestations and the currently available treatments with the identification of potential therapeutic targets involved in AOSD pathogenesis will be outlined.

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.

Interleukin-18 cytokine in immunity, inflammation, and autoimmunity: Biological role in induction, regulation, and treatment

Interleukin-18 (IL-18) is a potent pro-inflammatory cytokine involved in host defense against infections and regulates the innate and acquired immune response. IL-18 is produced by both hematopoietic and non-hematopoietic cells, including monocytes, macrophages, keratinocytes and mesenchymal cell. IL-18 could potentially induce inflammatory and cytotoxic immune cell activities leading to autoimmunity. Its elevated levels have been reported in the blood of patients with some immune-related diseases, including rheumatoid arthritis, systemic lupus erythematosus, type I diabetes mellitus, atopic dermatitis, psoriasis, and inflammatory bowel disease. In the present review, we aimed to summarize the biological properties of IL-18 and its pathological role in different autoimmune diseases. We also reported some monoclonal antibodies and drugs targeting IL-18. Most of these monoclonal antibodies and drugs have only produced partial effectiveness or complete ineffectiveness in vitro, in vivo and human studies. The ineffectiveness of these drugs targeting IL-18 may be largely due to the loophole caused by the involvement of other cytokines and proteins in the signaling pathway of many inflammatory diseases besides the involvement of IL-18. Combination drug therapies, that focus on IL-18 inhibition, in addition to other cytokines, are highly recommended to be considered as an important area of research that needs to be explored.

Fulminant elderly adult-onset Still disease effectively treated with tocilizumab and methotrexate: A case report

RATIONALE

Adult-onset Still disease (AOSD) is a rare inflammatory disease of unknown etiology. AOSD is common in young or middle-aged adults; however, in recent years, there have been increasing reports of elderly AOSD. Differentiating AOSD from diseases such as infections and malignancies is difficult. Moreover, rare fulminant AOSD cases with resistance to corticosteroids and immunosuppressive drugs have been reported.

PATIENT CONCERNS

An 80-year-old woman presented with flaccid fever, generalized arthralgia, and erythema of the anterior chest for 2 weeks. On day 5 of hospitalization, the patient developed pleural effusion with hypoxemia and her vital signs indicated rapid progression to shock. During the clinical course, the levels of inflammatory markers, including maximum level of ferritin and white blood cells (WBCs) were elevated (252,796 ng/mL and 86,500/μV, respectively) with disseminated intravascular coagulation syndrome (DIC) and macrophage activation syndrome (MAS).

DIAGNOSIS

The patient was diagnosed with elderly AOSD as per the Yamaguchi criteria for AOSD. The state of disease was extremely severe with rapid progression and was, thus, categorized as a fulminant form of elderly AOSD.

INTERVENTIONS

The patient was treated with prednisolone (PSL) pulse therapy (1000 mg/d) twice and plasma exchange in the intensive care unit for the primary disease and shock. Although she recovered from shock, she developed DIC and MAS. Methotrexate (MTX; 10 mg/d) improved the DIC and MAS. However, severe pleuritis recurred and the patient developed pericarditis; her primary disease was poorly controlled. Finally, tocilizumab (TCZ) was introduced using interleukin-18 (IL-18) as a surrogate marker. The IL-18 level was measured repeatedly following admission, with the peak level (170,000 pg/mL) recorded on the 75th day of hospitalization, immediately prior to introducing TCZ.

OUTCOMES

The combined use of MTX, TCZ, and PSL was effective in suppressing elderly AOSD, which was unsuccessfully controlled with MTX and PSL. Frequent monitoring of IL-18 levels proved useful for differentiating elderly AOSD from other diseases.

LESSONS

A fulminant form of elderly AOSD was treated with a combination of MTX, TCZ, and PSL. Repeated monitoring of IL-18 levels can be useful for decision-making in treating elderly AOSD.

Interleukin-18: a biomarker with therapeutic potential in adult-onset Still's disease

INTRODUCTION

Adult-onset Still's disease (AOSD) is an autoinflammatory disease driven by the innate immune response. Given the ambiguity in clinical presentation and lack of specific diagnostic biomarkers, AOSD diagnosis is usually delayed in the early stage. Because AOSD is a rare disease with clinical heterogeneity, there is no consensus on its treatment currently. This review summarizes the current research evidence regarding the pathogenic role and the diagnostic or therapeutic potential of interleukin (IL)-18 in AOSD.

AREAS COVERED

We searched the MEDLINE database using the PubMed interface and reviewed English-language literature from 1971 to 2022. This review focusing on IL-18 discusses its pathogenic role and clinical implications in AOSD.

EXPERT OPINION

NLRP3-inflammasome activation with IL-18 overproduction plays a pathogenic role in AOSD. IL-18 is closely linked to the clinical manifestations and disease activity of AOSD and may be a diagnostic biomarker. Given its pathogenic role in AOSD, IL-18 could become a potential therapeutic target. IL-18 binding protein (IL-18BP) negatively regulates the biological activity of IL-18 by inhibiting IL-18 signaling, and a clinical trial revealed that IL-18BP (Tadekinig alfa) treatment was well-tolerated and effective for AOSD. Recently, monoclonal antibodies against IL-18 have been under evaluation in a phase 1b trial.

The Role of Interleukin 18/Interleukin 18-Binding Protein in Adult-Onset Still's Disease and Systemic Juvenile Idiopathic Arthritis

Interleukin 18 (IL-18) is a pro-inflammatory cytokine of the IL-1 family, whose activity is tightly controlled at the level of production, as well as signalization. Notably, it is buffered by its natural inhibitor, IL-18 binding protein (IL-18BP), which is massively present in circulation in normal and in most pathological conditions, thus preventing harmful pro-inflammatory systemic effects of IL-18. IL-18 has long been considered to be involved in the pathophysiology of various inflammatory diseases. However, a first clinical trial using recombinant IL-18BP for the treatment of rheumatoid arthritis and psoriasis gave disappointing results. Direct measurements of unbound, bioactive, free form of circulating IL-18 demonstrated that IL-18 was more specifically involved in adult-onset Still’s disease (AOSD) and systemic juvenile idiopathic arthritis (sJIA) but also in their most severe complication, macrophage activation syndrome (MAS). More importantly, administration of recombinant IL-18BP to patients with AOSD, and sJIA with MAS, showed promising results. This review summarizes available data regarding IL-18 and IL-18BP in AOSD and sJIA in mouse models and humans and shows the importance of IL-18/IL-18BP imbalance in these conditions, leading to the conclusion that IL-18, particularly free IL-18, may be a useful biomarker in these diseases and an interesting therapeutic target.

Serum VEGF-C as an evaluation marker of disease activity in adult-onset Still's disease

In view of the possible involvement of vascular endothelial growth factor-C (VEGF-C) in pathogenesis of adult-onset Still's disease (AOSD) based on our previous genome-wide association study (GWAS) results, the primary objective of this study, therefore, was to investigate the correlations between the content of VEGF-C in serum and clinical and biochemical markers of AOSD. Blood samples were collected from 80 patients with AOSD, 26 with rheumatoid arthritis (RA), 30 with systemic lupus erythematosus (SLE) and 31 healthy control subjects. The serum VEGF-C levels were determined using an enzyme-linked immunosorbent assay (ELISA). Statistical analysis and comparisons were conducted. A significantly higher serum VEGF-C level was observed in patients with AOSD than in HC. Serum VEGF-C levels had high AUC value of 0.8145 for distinguishing AOSD group from healthy group with sensitivity of 0.7097 and specificity of 0.8250. It also showed good diagnostic value to differentiate AOSD from other autoinflammatory diseases with sensitivity of 0.7500 and specificity of 0.5500. AOSD patients with fever, arthralgia, skin rash, sore throat, lymphadenopathy, splenomegaly hepatomegaly and pleuritis, had a higher level than those who did not have these symptoms (p = 0.0012, p = 0.0092, p = 0.0056, p = 0.0123, p = 0.0068, p = 0.0030, p = 0.0020, and p = 0.0018, respectively). The serum VEGF-C levels were also positively correlated with laboratory features and several cytokines related to AOSD disease activity. In conclusion, our study unveiled a close association between serum VEGF-C levels and AOSD including disease activity and clinical hematological manifestations, suggesting the potential utility of VEGF-C as a candidate biomarker to assess disease activity in AOSD.

Efficacy and safety of canakinumab in the treatment of adult-onset Still's disease: A systematic review

BACKGROUND

Adult-onset Still's disease (AOSD) is a rare inflammatory disease, typically characterized by spiking fever, skin rash, and arthralgia or arthritis. Its conventional treatment includes NSAIDs and corticosteroids, and DMARDs as second-line therapy. Frequently, IL-1 inhibitors are also required, mainly in patients refractory to traditional therapy. Canakinumab is a monoclonal antibody that binds IL-1β with high affinity and specificity, making it appropriate for therapeutic purposes in AOSD.

OBJECTIVE

The aim of this systematic review was to identify and compile the current data on the efficacy and safety of canakinumab in the treatment of AOSD.

METHODS

Following the guidelines established by the PRISMA statement, we searched Scopus, Web of Science, Pubmed, and Cochrane Library for relevant literature up to March 2021. The inclusion criteria comprised: randomized controlled trials, pooled analyses, observational studies, case series, and case reports.

RESULTS

Seventeen studies published from 2012 to 2021 were evaluated; 11 of these correspond to case series or case reports, four observational studies, one placebo-controlled phase II trial, and one analysis of pooled systemic juvenile idiopathic arthritis data. In general, out of a total of 99 patients, 68.7% of these presented a complete remission of the systemic and arthritic manifestations at the end of the observation period, while 16.2% of the patients showed a partial improvement of the symptoms and the remaining (15.1%) did not show clinical improvement or were excluded. Moreover, 210 adverse events were reported in 69 patients during canakinumab treatment, of which the majority correspond to respiratory tract infections, arthralgia, disease flares, abdominal pain, nausea, and diarrhea, whereas the most common severe adverse events included macrophage activation syndrome and serious infections. Also, a corticosteroid-sparing effect was observed in a large percentage of patients.

CONCLUSION

More studies with solid evidence are needed to support the efficacy of canakinumab in AOSD, although its use is encouraged by the increasing favorable results reported and the efficacy of other IL-1 inhibitors. It was also associated with an acceptable safety profile, similar to expected in IL-1 inhibitor therapy. However, future studies with well-defined endpoints are warranted to examine further the usefulness of canakinumab in AOSD.

MicroRNA-223 inhibits neutrophil extracellular traps formation through regulating calcium influx and small extracellular vesicles transmission

Modulation of miRNAs and neutrophil extracellular traps (NETs) formation are both implicated in inflammatory disorders. Adult-onset Still's disease (AOSD) is a systemic autoinflammatory disease with neutrophilic leukocytosis and unknown etiology. Although the NETs formation is elevated in AOSD patients, the regulatory roles of miRNAs in NETs formation in AOSD remains unclear. We revealed that the circulating levels of IL-18, NETs, and miR-223 were significantly higher in active AOSD patients, compared with inactive AOSD patients or healthy controls (P < 0.005). Moreover, IL-18 increased calcium influx into neutrophils, which led to mitochondrial ROS (mROS) production and NETs formation. Elevated levels of NETs-DNA could induce miR-223 expression in neutrophils through activating Toll-like receptor 9. The upregulated miR-223 expression in neutrophils suppressed mROS production by blocking calcium influx, and subsequently inhibited IL-18-mediated NETs formation. Besides, the increased neutrophil-derived exosomal miR-223 levels were observed in active AOSD patients compared with healthy controls (P < 0.005). Our in vitro assays demonstrated that the neutrophil-derived small extracellular vesicles carried miR-223, which could repress IL-18 production in macrophages. Together, these results suggest a fine-tuned mechanism between inflammatory (IL-18 induced NETs) and anti-inflammatory (miR-223) factors in AOSD. MiR-223, mROS inhibitors, and calcium channel blockers are the potential therapeutics for autoinflammatory diseases such as AOSD.

CARD8 SNP rs11672725 Identified as a Potential Genetic Variant for Adult-Onset Still's Disease

Adult-onset Still's disease (AOSD), an autoinflammatory disorder, is related to the dysregulation of NLR3-containing a pyrin domain (NLRP3)-inflammasome signaling. We aimed to investigate the associations of genetic polymorphisms of NLRP3-inflammasome signaling with AOSD susceptibility and outcome and to examine their functional property. Fifty-three candidate single-nucleotide polymorphisms (SNPs) involved in NLRP3-inflammasome response were genotyped using Sequenom MassArray on the samples from 66 AOSD patients and 128 healthy controls. The significant SNPs were validated by direct sequencing using a TaqMan SNP analyzer. Serum levels of associated gene products were examined by ELISA. One SNP rs11672725 of CARD8 gene was identified to be significantly associated with AOSD susceptibility by using MassArray and subsequent replication validation (p = 3.57 × 10^-7; odds ratio 3.02). Functional assays showed that serum CARD8 levels were significantly lower in AOSD patients (median, 10,524.6 pg/mL) compared to controls (13,964.1 pg/mL, p = 0.005), while levels of caspase-1, IL-1β and IL-18 were significantly higher in patients (107.1 pg/mL, 2.1 pg/mL, and 1495.8 pg/mL, respectively) than those in controls (99.0 pg/mL, 1.0 pg/mL, and 141.4 pg/mL, respectively). Patients carrying rs11672725CC genotype had significantly higher serum caspase-1 and IL-18 levels (121.3 pg/mL and 1748.6 pg/mL) compared to those with CT/TT genotypes (72.6 pg/mL, p = 0.019 and 609.3 pg/mL, p = 0.046). A higher proportion of patients with rs11672725CC genotype had a systemic pattern of disease outcome, which was linked to low CARD8 levels. A novel variant, rs11672725, of the CARD8 gene was identified as a potential genetic risk for AOSD. Patients carrying the rs11672725CC genotype and C allele had low CARD8 levels, and were predisposed to a systemic pattern with an elevated expression of inflammasome signaling.

COVID-19 gone bad: A new character in the spectrum of the hyperferritinemic syndrome?

The severe form of COVID-19 share several clinical and laboratory features with four entities gathered under the term "hyperferritinemic syndromes" and including macrophage activation syndrome (MAS), adult-onset Still's disease (AOSD), catastrophic anti-phospholipid syndrome (CAPS) and septic shock. COVID-19 systemic inflammatory reaction and "hyperferritinemic syndromes" are all characterized by high serum ferritin and a life-threatening hyper-inflammation sustained by a cytokines storm which eventually leads to multi-organ failure. In this review, we analyze the possible epidemiological and molecular mechanisms responsible for hyper-inflammation in patients with severe COVID-19 and we underline the similarities between this condition and "hyperferritinemic syndromes" which would allow considering severe COVID-19 as a fifth member of this spectrum of inflammatory conditions.

Genetic Association and Expression Correlation between Colony-Stimulating Factor 1 Gene Encoding M-CSF and Adult-Onset Still's Disease

Adult-onset Still's disease (AOSD) is a rare and inflammatory disorder characterized by spiking fever, rash, arthritis, and multisystemic involvement. HLA has been shown to be associated with AOSD; however, it could not explain the innate immunity and autoinflammatory characteristics of AOSD. To assess the genetic susceptibility of AOSD, we conducted a genome-wide association study (GWAS) on a cohort of 70 AOSD cases and 688 controls following a replication study of 36 cases and 200 controls and meta-analysis. The plasma concentrations of associated gene product were determined. The GWAS, replication, and combined sample analysis confirmed that SNP rs11102024 on 5'-upstream of CSF1 encoding macrophage colony-stimulating factor (M-CSF) was associated with AOSD (P = 1.20 × 10^-8, OR (95% CI): 3.28 (2.25~4.79)). Plasma levels of M-CSF increased in AOSD patients (n = 82, median: 9.31 pg/mL), particularly in the cases with activity score ≥ 6 (n = 42, 10.94 pg/mL), compared to the healthy donors (n = 68, 5.31 pg/mL) (P < 0.0001). Patients carrying rs11102024TT genotype had higher M-CSF levels (median: 20.28 pg/mL) than those with AA genotype (6.82 pg/mL) (P < 0.0001) or AT genotype (11.61 pg/mL) (P = 0.027). Patients with systemic pattern outcome were associated with elevated M-CSF and frequently observed in TT carriers. Our data suggest that genetic variants near CSF1 are associated with AOSD and the rs11102024 T allele links to higher M-CSF levels and systemic outcome. These results provide a promising initiative for the early intervention and therapeutic target of AOSD. Further investigation is needed to have better understandings and the clinical implementation of genetic variants nearby CSF1 in AOSD.

Adult-Onset Still’s Disease

Adult-onset Still’s disease (AoSD) is a rare but clinically well-known, polygenic, systemic autoinflammatory disease. It is typically characterized by four main (cardinal) symptoms: spiking fever ≥39 °C, arthralgia or arthritis, skin rash, and hyperleukocytosis (≥10,000 cells/mm³). However, many other clinical features are possible, and it can appear in all age groups with potentially severe inflammatory onset accompanied by a broad spectrum of disease manifestation and complications. Hence, it remains a diagnostic challenge, and the clinician should first rule out infectious, tumoral, or inflammatory differential diagnoses. Determination of the total and glycosylated ferritin levels, although not pathognomonic, can help in diagnosis. New biomarkers have recently been described, but they need to be validated. The disease evolution of AoSD can be monocyclic, polycyclic, or chronic. In chronic disease, a joint involvement is often predominant, and erosions are noted in one-third of patients. Many progresses have been made in the understanding of the pathogenesis over the last decades. This chapter provides a comprehensive insight into the complex and heterogeneous nature of AoSD describing the identified cytokine signaling pathways and biomarkers. It also discusses the current evidence for the usage of biologics in AoSD to provide guidance for treatment decisions, taking into account both the efficacy and the safety of the different therapeutic options.

Pathogenesis, disease course, and prognosis of adult-onset Still's disease: an update and review

OBJECTIVE

Adult-onset Still's disease (AOSD) is a rare but clinically well-known polygenic systemic autoinflammatory disease. In this review, we aim to present frontiers in the pathogenesis, clinical features, diagnosis, biomarkers, disease course, prognosis, and treatment in AOSD.

DATA SOURCES

We retrieved information from the PubMed database up to July 2019, using various search terms and relevant words, including AOSD and Still's disease.

STUDY SELECTION

We included data from peer-reviewed journals. Both basic and clinical studies were selected.

RESULTS

Pathogenesis of AOSD involves genetic background, infectious triggers, and immunopathogenesis, mainly the activation of macrophages and neutrophils followed by a cytokine storm. Diagnosis and prognosis evaluation of AOSD is still challenging; therefore, there is an urgent need to identify better biomarkers. Biologic agents, including interleukin (IL)-1β, IL-6, and tumor necrosis factor-α antagonists in the treatment of AOSD, have good prospect.

CONCLUSION

This review highlights the advances in pathogenesis, potential biomarkers, disease course, and treatment in AOSD.

Mechanisms, biomarkers and targets for adult-onset Still's disease

Adult-onset Still’s disease (AoSD) is a rare but clinically well-known, polygenic, systemic autoinflammatory disease. Owing to its sporadic appearance in all adult age groups with potentially severe inflammatory onset accompanied by a broad spectrum of disease manifestation and complications, AoSD is an unsolved challenge for clinicians with limited therapeutic options. This Review provides a comprehensive insight into the complex and heterogeneous nature of AoSD, describing biomarkers of the disease and its progression and the cytokine signalling pathways that contribute to disease. The efficacy and safety of biologic therapeutic options are also discussed, and guidance for treatment decisions is provided. Improving the approach to AoSD in the future will require much closer cooperation between paediatric and adult rheumatologists to establish common diagnostic strategies, treatment targets and goals.

Adult-onset Still’s disease (AoSD) is not easily diagnosed, and treatment options are limited. This Review provides an overview of the disease and its pathogenesis, clinical trial results, therapeutic options and a plan to diagnose and clinically manage these patients.

Similar to systemic-onset juvenile idiopathic arthritis, adult-onset Still’s disease (AoSD) is a rare systemic autoinflammatory disease with potentially severe inflammatory onset accompanied by a broad spectrum of disease manifestation and complications.

AoSD should be considered in patients with persistent fever, and the diagnosis is based on the combination of clinical and laboratory findings as well as the exclusion of other inflammatory conditions.

Central to the pathogenesis of AoSD is the intense activation of innate immune cells and overproduction of several pro-inflammatory cytokines including IL-1, IL-6 and IL-18.

Two IL-1 antagonists have been approved for treatment of AoSD, and growing evidence suggests that other biologic agents are therapeutic options, such as anti-IL-6 and anti-IL-18 therapeutics.

As a reliable prediction of response and outcome is not possible, therapeutic decisions have to be made on the basis of clinical, biological or imaging characteristics of disease.

A close cooperation between paediatric and adult rheumatologists is required to establish common diagnostic strategies, treatment targets and goals.

Adult-Onset Still’s Disease

Adult-onset Still’s disease (AOSD) is a rare systemic, autoinflammatory disorder that often presents in adolescence and early adulthood with fever, rash, and polyarthritis. There are significant genetic and clinical similarities with systemic juvenile idiopathic arthritis (sJIA) with a different chronological disease onset. The disease can have many protean characteristics leading to delays in diagnosis. Treatment includes corticosteroids; traditional immunomodulators, such as methotrexate; and targeted biologic treatments that include IL-1 and IL-6 inhibitors.

HLA-DQB1 DPB1 alleles in Japanese patients with adult-onset Still's disease

Objective: HLA class II alleles are major determinants of genetic predisposition to rheumatic diseases. Predisposing effects of HLA had been suggested in AOSD, however, ethnic differences may account for variations in AOSD association with HLA. We determined the contribution of HLA-DQB1, DPB1 alleles to susceptibility to Adult-onset Still's disease (AOSD) in the Japanese population. Methods: HLA-DQB1 and DPB1 alleles were analyzed in 87 Japanese patients with AOSD and 413 Japanese healthy subjects. Results: We found significant association between HLA-DQB1*06:02 (Pc = 0.010, odds ratio: 2.54) and AOSD, whereas there was no association between the DQB1*06:02 allele and disease phenotypes of AOSD. Moreover, we did not find a predisposing effect of the HLA-DPB1 allele to AOSD. Haplotype analysis showed that presence of DRB1*15:01-DQB1*06:02 was associated with Japanese patients with AOSD. However, conditional logistic regression tests were unable to demonstrate independent association between DRB1*1501 or DQB1*0602 and AOSD. Conclusions: Our results show significant association between AOSD and the HLA DQB1*06:02 allele, and between the DRB1*1501-DQB1*06:02 haplotype and AOSD susceptibility. These findings suggest that genetic susceptibility to AOSD depends on the genotype combinations of HLA DRB1 and DQB1 alleles.

Interleukin-37 is increased in adult-onset Still's disease and associated with disease activity

Background

Interleukin (IL)-37 has been known to play an immunosuppressive role in various inflammatory disorders, but whether it participates in the regulation of pathogenesis of adult-onset Still’s disease (AOSD) has not been investigated. In this study, we examined serum IL-37 levels and their clinical association with AOSD, and we explored the anti-inflammatory effects of IL-37 on peripheral blood mononuclear cells (PBMCs) from patients with AOSD.

Methods

Blood samples were collected from 62 patients with AOSD and 50 healthy control subjects (HC). The serum IL-37 levels were determined using an enzyme-linked immunosorbent assay (ELISA). The correlations of serum IL-37 levels with disease activity, laboratory values, and inflammatory cytokines in AOSD were analyzed by Spearman’s correlation test. The correlations between serum IL-37 levels and clinical manifestations were analyzed by Mann-Whitney U test. PBMCs from ten patients with AOSD were stimulated with recombinant human IL-37 protein, and expression levels of tumor necrosis factor (TNF)-α, IL-6, IL-10, IL-1β, and IL-18 were determined by qRT-PCR and ELISA.

Results

A significantly higher IL-37 protein level was observed in patients with AOSD than in HC. Serum IL-37 levels correlated with systemic score, laboratory values, IL-1β, IL-18, and IL-10 in patients with AOSD. The expression levels of IL-37 were closely related to the patients with AOSD who also had fever, skin rash, lymphadenopathy, splenomegaly, myalgia, and arthralgia. Moreover, the production of proinflammatory cytokines such as IL-6, IL-1β, TNF-α, and IL-18 in PBMCs from patients with AOSD was obviously attenuated after recombinant human IL-37 stimulation.

Conclusions

Increased expression of IL-37 and its positive correlation with disease activity suggest its involvement in AOSD pathogenesis. More importantly, IL-37 inhibits the expression of proinflammatory cytokines in PBMCs from patients with AOSD, indicating the potential anti-inflammatory role of IL-37 in AOSD. Thus, IL-37 may be a novel disease activity biomarker and research target in AOSD.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1555-6) contains supplementary material, which is available to authorized users.

The genetic polymorphism and expression profiles of NLRP3 inflammasome in patients with chronic myeloid leukemia

NLRP3 inflammasome has been recently reported as an important risk factor in the development of cancer. But the relationship between polymorphisms of NLRP3 inflammasome related genes and chronic myeloid leukemia (CML) is rarely reported. Therefore, the aim of the present study was to investigate the association of five genetic polymorphisms (NLRP3, IL-1β, IL-18, CARD8 and NF-κB) in 267 CML patients and 344 healthy controls. We found that the AT genotype of CARD8 (rs2043211) was significantly higher compared to TT genotype in high and intermediate risk CML patients. IL-1β (rs16944) polymorphism in early molecular response at 6 months was marginally different, with more GG and less AA genotype in BCR-ABL^IS >1% group. IL-18 (rs1946518) polymorphism was significantly different with more GG genotype in BCR-ABL^IS >1% group at 6 months. We also demonstrated that WBC count of newly diagnosed patients carrying AG genotype was significantly higher than that of GG or AA genotype of IL-1β (rs16944). The onset age of patients carrying ins/ins genotype of NF-κB (rs28362491) was significantly older than that of ins/del and del/del genotype. Moreover, IL-1β or NLRP3 mRNA expression was decreased and IL-18 mRNA expression was increased significantly in CML patients compared with controls. In conclusion, the genetic polymorphisms of NLRP3 inflammasome may be served as potential predictors for CML.

How I treat patients with adult onset Still's disease in clinical practice

Adult onset Still's disease (AOSD) is a rare systemic inflammatory disease of unknown etiology characterized by four cardinal signs which are almost always present in patients: high spiking fever, arthralgia (with or without synovitis), maculo-papular salmon-pink evanescent skin rash, striking leukocytosis with neutrophilia. Here, we review the clinical features of AOSD and describe the best practice approaches for its management, reviewing available guidelines and recommendations and providing experts' insights.

Metabolic Disturbances in Adult-Onset Still's Disease Evaluated Using Liquid Chromatography/Mass Spectrometry-Based Metabolomic Analysis

Objective

Liquid chromatography/mass spectrometry (LC/MS)-based comprehensive analysis of metabolic profiles with metabolomics approach has potential diagnostic and predictive implications. However, no metabolomics data have been reported in adult-onset Still’s disease (AOSD). This study investigated the metabolomic profiles in AOSD patients and examined their association with clinical characteristics and disease outcome.

Methods

Serum metabolite profiles were determined on 32 AOSD patients and 30 healthy controls (HC) using ultra-performance liquid chromatography (UPLC)/MS analysis, and the differentially expressed metabolites were quantified using multiple reactions monitoring (MRM)/MS analysis in 44 patients and 42 HC. Pure standards were utilized to confirm the presence of the differentially expressed metabolites.

Results

Eighteen differentially expressed metabolites were identified in AOSD patents using LC/MS-based analysis, of which 13 metabolites were validated by MRM/MS analysis. Among them, serum levels of lysoPC(18:2), urocanic acid and indole were significantly lower, and L-phenylalanine levels were significantly higher in AOSD patients compared with HC. Moreover, serum levels of lysoPC(18:2), PhePhe, uridine, taurine, L-threonine, and (R)-3-Hydroxy-hexadecanoic acid were significantly correlated with disease activity scores (all p<0.05) in AOSD patients. A different clustering of metabolites was associated with a different disease outcome, with significantly lower levels of isovalerylsarcosine observed in patients with chronic articular pattern (median, 77.0AU/ml) compared with monocyclic (341.5AU/ml, p<0.01) or polycyclic systemic pattern (168.0AU/ml, p<0.05).

Conclusion

Thirteen differentially expressed metabolites identified and validated in AOSD patients were shown to be involved in five metabolic pathways. Significant associations of metabolic profiles with disease activity and outcome of AOSD suggest their involvement in AOSD pathogenesis.

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.

A genetic role for macrophage migration inhibitory factor (MIF) in adult-onset Still's disease

Introduction

Adult-onset still's disease (AOSD) is a rare systemic inflammatory disorder in which abnormalities in inflammatory cytokines production appear to play a pathophysiological role. Our previous work has reported increased expression of macrophage migration inhibitory factor (MIF) and revealed its correlation with disease severity and activity in AOSD. A -173 G/C single nucleotide polymorphism (SNP) (rs755622) and a -794 CATT_5-8 repeat (rs5844572) in the MIF promoter have been reported. In this study, we sought to explore the relationship between functional MIF promoter polymorphisms and MIF expression in AOSD.

Methods

100 patients and 200 controls were recruited in the study. A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay was utilized to analyze the -173 G/C SNP (rs755622) and PCR-based size discrimination assay was applied to detect the -794 CATT_5-8 repeat (rs5844572) in the MIF promoter. Plasma MIF levels were measured by ELISA. MIF mRNA levels were quantified by real-time reverse transcription (RT)-PCR. Bisulfate genomic sequencing was employed to evaluate DNA methylation status within the MIF promoter.

Results

We identified that the frequencies of MIF -794 CATT₅ (P = 0.001) allele and the expression of MIF (P <0.001) were increased in patients compared to healthy controls. Plasma levels of MIF in patients with CC genotype were higher than those of patients with GC or GG genotypes (P = 0.05). In patients with established AOSD, a higher frequency of -794 CATT₇ containing MIF genotypes was observed in those with liver dysfunction (P = 0.009). Haplotype analysis revealed a higher representation of the MIF haplotype defined by -173*C/-794 CATT₅ (C5) in AOSD patients (P = 0.001).

Conclusion

Functional promoter polymorphisms in the MIF gene influence plasma MIF levels in AOSD and may contribute to disease susceptibility or clinical presentation of AOSD.

Association of IL-18 promoter gene polymorphisms with rheumatoid arthritis: a meta-analysis

Interleukin-18(IL-18) plays a potential pathological role in rheumatoid arthritis (RA). The conclusions of the published reports on the relationship between single-nucleotide polymorphisms -607C/A (rs1946518) and -137G/C (rs187238) located in the IL-18 gene promoter and RA risk remain controversial. This meta-analysis was performed to evaluate the association between IL-18 gene promoter (-607A/C and -137C/G) polymorphisms and RA using (1) allele, (2) codominant, (3) dominant, and (4) recessive models. Literature search was conducted up to January, 2013, in PubMed, EMBASE, Spring-link, Web of Science, Wanfang (Chinese) and China National Knowledge Infrastructure (CNKI). A total of 10 studies from eight articles involving 2,662 cases and 2,168 controls for -607A/C polymorphism and 9 studies from six articles involving 1,331 cases and 1,468 controls for -137C/G polymorphism were considered in the meta-analysis. For the relationship of IL-18 -607A/C polymorphism with RA risk, significant association was observed in allele model (OR = 0.778, 95 % CI = 0.633-0.955) and dominant model (OR = 0.618, 95 % CI = 0.466-0.819). However, no significant association could be observed between -137C/G polymorphism and RA risk under all genetic models (allele model: OR = 0.940, 95 % CI = 0.777-1.138; codominant model: OR = 1.079, 95 % CI = 0.574-2.029; dominant model: OR = 0.913, 95 % CI = 0.779-1.069; recessive model: OR = 1.133, 95 % CI = 0.586-2.190). In the subgroup analysis by ethnicity, significant result was also found in Asian populations but not found in Caucasian populations for the relationship of IL-18 -607A/C polymorphism with RA risk; while no obvious association was found between IL-18 -137C/G polymorphism and RA risk. This meta-analysis indicates that IL-18 -607A/C polymorphism in promoter region may be associated with RA risk.

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 Associated with Thyroid Dysfunction: Case Report and Review of the Literature

To our knowledge, the possible unveiled interaction between adult-onset Still’s disease (AOSD) with autoimmune thyroid disease (AITD) has never been reported although it is well established that systemic autoimmune disease may usually occur in relation to AITD. As increasingly clear links of AITD with other autoimmune disease such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and primary Sjögren’s syndrome (pSS) have been reported, and the incidence of AOSD concurrent AITD draws our attention rapidly. In this study, we searched relevant literatures published in the past 30 years to explore that condition.

[Cardio-respiratory involvement in adult-onset Still's disease]

Cardiopulmonary involvement in adult-onset Still's disease is not as common as cutaneous and articular involvement. Pleuropericarditis is the most frequent thoracic manifestation. Although difficult, diagnosis of other thoracic manifestations, which may reveal the disease, is crucial, due to the high risk to life and the efficacy of new immunosuppressive agents. The pathophysiology involves essentially immunological factors, Still's disease being increasingly seen as an autoimmune inflammatory disease. Pro-inflammatory cytokines such as interleukine (IL) 1, 6 and 18 play a crucial role in macrophage activation, which is central in the pathophysiology of adult Still's disease. The classification of cardiopulmonary manifestations is based on anatomy. Cardiac lesions may involve all the tissues of the heart and the pulmonary arteries. Respiratory lesions may involve the pleura, the lung parenchyma (organizing pneumonitis, infiltrative lung disease, alveolar damage, amyloidosis), and the respiratory muscles, including the diaphragm. Finally, some manifestations may be provoked by the treatment itself. Steroids, the first-line treatment, are very effective in pleuropericarditis. Methotrexate used to be prescribed when steroids failed, but biotherapies such as IL1 and IL6 inhibitors have transformed the prognosis of forms resistant to these drugs.

Natural Killer Cell Cytolytic Function in Korean Patients with Adult-onset Still’s Disease

Objective.

To investigate natural killer (NK) cell proportions, NK cell cytotoxicity, and interleukin 18 (IL-18) expression, in patients with adult-onset Still’s disease (AOSD).

Methods.

Forty-five patients with AOSD (active = 22, inactive = 23) and 32 healthy controls were included. The proportions of NK cells among peripheral blood mononuclear cells were assessed by flow cytometry. IL-18 and IL-18-binding protein (IL-18BP) concentrations were measured by ELISA. Twenty-four patients with AOSD and 18 controls were examined for cytotoxic activity of NK cells by co-incubating NK cells with NK-sensitive K562 cells. The association of NK cell function with clinical and laboratory measures was investigated.

Results.

The proportions of NK cells were significantly lower in patients with active AOSD than in patients with inactive disease and controls. NK cell cytotoxic function was significantly lower in patients with AOSD than in controls. NK cell proportions and cytotoxic functions were reexamined in 11 and 6 patients, respectively, after treatment. Low NK cell proportion and cytotoxic dysfunction were improved with clinical improvements of the patients. IL-18 and IL-18BP levels were much higher in patients with active AOSD than in controls. NK cell cytotoxic functions were consistently low and IL-18 and IL-18BP levels were constantly high in patients with AOSD, regardless of disease activity.

Conclusion.

Low NK cell proportion, defective cytotoxic function, and elevated IL-18 levels may be significant features of AOSD. After resolution of the acute phase, low NK cell proportion was recovered and NK cell cytolytic function was restored along with clinical improvement. These findings possibly contribute to immunologic abnormalities in AOSD.

Adult-Onset Still's Disease: From Pathophysiology to Targeted Therapies

Adult-onset Still's disease (AOSD) is a systemic inflammatory disorder affecting primarily young individuals. The diagnosis is primarily clinical and necessitates the exclusion of a wide range of mimicking disorders. Given the lack of solid data in regard to the underlying pathogenetic mechanisms, treatment of AOSD has been for years largely empirical. Recent advances have revealed a pivotal role of several proinflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1), interleukin-6 (IL-6), interleukin-8 (IL-8), and interleukin-18 (IL-18) in disease pathogenesis, giving rise to the development of new targeted therapies aiming at optimal disease control.

Relationship between interleukin 18 polymorphisms and susceptibility to chronic hepatitis B virus infection

AIM

To identify the relationship between the tagging single nucleotide polymorphism sites (tagSNPs) of the Interleukin-18 (IL-18) gene and genetic susceptibility to chronic hepatitis B virus infection in Chinese patients.

METHODS

Five hundred and one cases of chronic hepatitis B virus (HBV) infection and 301 HBV natural clearance controls were studied. Two tagSNPs in the IL-18 gene (rs1946518A/C and rs574424C/G) were genotyped by the Multiplex Snapshot technique. The genotype and allele frequencies were calculated and analyzed.

RESULTS

In the genotypes of rs1946518, the AA type was present at a higher frequency in the patients compared to those in the controls. Odds ratio (OR) of the AA genotype for the comparison with that of the AC and the CC genotype was 1.537 (95% confidence intervals (CI): 1.116-2.218, P = 0.009 < 0.025). In phenotypes, the allele C at rs1946518 was of a significantly lower frequency in the patients with chronic hepatitis B than that in the controls (P = 0.017 < 0.025). OR of the allele A for the comparison with that of the allele C was 1.279 (95% CI: 1.045-1.567). As for the rs574424 genotypes, no significant difference in this genotype distribution or in this allele frequency between the patients and the control subjects was observed. No significant difference in the haplotype frequencies between the patients with chronic hepatitis B and HBV natural clearance individuals was displayed.

CONCLUSION

The data suggest that genotype AA and the allele A of the IL-18 at position rs1946518 are closely associated with the resistance to chronic hepatitis B and may be the dangerous gene. However, no statistical association was found between polymorphisms of rs574424 for IL-18 and hepatitis B.

[Autoinflammatory diseases as cause of wound healing defects]

Ulcerations of the skin and mucosal membranes are a common feature of autoinflammatory diseases. They can give raise to chronic wound healing defects and should be considered in the differential diagnosis of chronic skin ulcers. The increased activation of the innate immune system in the absence of an apparent provocation for inflammation is a hallmark of autoinflammatory diseases. Mutations and alterations of signaling pathways regulating the innate immune response to physical trauma/tissue damage result into an unrestrained activation of the inflammasome, which leads to increased activation of Interleukin-1. Uncontrolled recruitment and activation of myeloid effector cells within the wound site lead to the release of potent proteases that cause the degradation of structural components of the skin. The majority of these diseases respond well to immunosuppressive and immunomodulatory treatment regimes. Therapeutic resistance converts the acute inflammatory response into a chronic and non-resolving inflammatory process that leads to tissue degeneration. In this article we will focus on the review of those autoinflammatory diseases that often display ulcerative cutaneous and aphthous lesions including pyoderma gangrenosum, Behçet disease, PAPA syndrome and hyperimmunoglobulinemia D with periodic fever syndrome (HIDS). Furthermore, the article will be complemented by an overview of those inflammatory diseases that are associated with non-ulcerative cutaneous manifestations.

A four-step model for the IL-6 amplifier, a regulator of chronic inflammations in tissue-specific MHC class II-associated autoimmune diseases

It is commonly thought that autoimmune diseases are caused by the breakdown of self-tolerance, which suggests the recognition of specific antigens by autoreactive CD4+ T cells contribute to the specificity of autoimmune diseases (Marrack et al., 2001; Mathis and Benoist, 2004). In several cases, however, even for diseases associated with class II major histocompatibility complex (MHC) alleles, the causative tissue-specific antigens recognized by memory/activated CD4+ T cells have not been established (Mocci et al., 2000; Skapenko et al., 2005). Rheumatoid arthritis (RA) and arthritis in F759 knock-in mice (F759 mice) are such examples (Atsumi et al., 2002; Brennan et al., 2002; Falgarone et al., 2009). These include associations with class II MHC and CD4 molecules; increased numbers of memory/activated CD4+ T cells; and improved outcomes in response to suppressions and/or deficiencies in class II MHC molecules, CD4+ T cells, and the T cell survival cytokine IL-7. Regarding the development of arthritis in F759 mice, it is not only the immune system, but also non-immune tissue that are involved, indicating that the importance of their interactions (Sawa et al., 2006, 2009; Ogura et al., 2008; Hirano, 2010; Murakami et al., 2011). Furthermore, we have shown that local events such as microbleeding together with an accumulation of activated CD4+ T cells in a manner independent of tissue antigen-recognitions induces arthritis in the joints of F759 mice (Murakami et al., 2011). For example, local microbleeding-mediated CCL20 expression induce such an accumulation, causing arthritis development via chronic activation of an IL-17A-dependent IL-6 signaling amplification loop in type 1 collagen+ cells that is triggered by CD4+ T cell-derived cytokine(s) such as IL-17A, which leads to the synergistic activation of STAT3 and NFκB in non-hematopoietic cells in the joint (Murakami et al., 2011). We named this loop the IL-6-mediated inflammation amplifier, or IL-6 amplifier for short (Ogura et al., 2008; Hirano, 2010; Murakami et al., 2011). Thus, certain class II MHC-associated, tissue-specific autoimmune diseases, including some RA subtypes, may be induced by local events that cause an antigen-independent accumulation of effector CD4+ T cells followed by the induction of the IL-6 amplifier in the affected tissue. In other words, in certain cases, the target tissue itself may determine the specificity of the autoimmune disease via activation of the IL-6 amplifier. To explain this hypothesis, we have proposed a four-step model for MHC class II-associated autoimmune diseases (Murakami et al., 2011): (1) T cell activation regardless of antigen specificity; (2) local events inducing a tissue-specific accumulation of activated T cells; (3) transient activation of the IL-6 amplifier; and (4) enhanced sensitivity to cytokines in the target tissue. The interaction of these events results in chronic activation of the IL-6 amplifier and subsequent manifestation of autoimmune diseases. Thus, the IL-6 amplifier, which is chronically activated by these four events, is a critical regulator of chronic inflammations in tissue-specific MHC class II-associated autoimmune diseases.

Interleukin-18 promoter polymorphisms in Japanese patients with rheumatoid arthritis: protective effect of the T allele and T/T genotype at rs360722

Rheumatoid arthritis (RA) is a chronic inflammatory disease with a strong genetic contribution to its pathogenesis. Among numerous candidate genes, cytokine gene polymorphisms have been implicated. Interleukin-18 (IL-18) induces production of tumor necrosis factor-α and promotes T helper (Th)1-type immune responses. This study investigates the association between IL-18 promoter polymorphisms and RA susceptibility. A total of 2471 Japanese case-control samples (1493 RA patients and 978 healthy controls) were examined. Three haplotype tag single-nucleotide polymorphisms, rs1946518A/C, rs360718T/G, and rs360722T/C, spanning from the 5'UTR to intron 1 were genotyped using allelic discrimination with the use of specific TaqMan probes, and three haplotypes (A-T-T, C-T-C, and A-G-C) were determined. Among these polymorphisms, the frequency of the T allele at rs360722, which tags the A-T-T haplotype, was significantly lower in the RA patient group compared with the normal subjects [0.46 versus 0.49, P = 0.0061, Fisher's exact probability test, odds ratio (OR) = 0.85, 95% confidence interval (CI) = 0.75-0.95]. Having the T/T genotype further increased the significance (0.20 versus 0.27, P = 0.0006, OR = 0.72, 95% CI = 0.58-0.86). Therefore, presence of the T allele and T/T genotype at rs360722 reduces the susceptibility of Japanese people to RA.

Association of polymorphisms of interleukin-18 gene promoter region with polycystic ovary syndrome in chinese population

BACKGROUND

Recent research shows that polycystic ovary syndrome (PCOS) may have an association with low-grade chronic inflammation, and that PCOS may induce an increase in serum interleukin-18 (IL-18) levels.

METHODS

To investigate the polymorphisms of the IL-18 gene promoters with PCOS, two single nucleotide polymorphisms (SNPs) in the promoter of the IL-18 gene (at positions -607C/A and -137G/C) in 118 Chinese women with PCOS and 79 controls were evaluated using polymerase chain reaction (PCR).

RESULTS

No significant differences were found in the genotype distribution, allele frequency and haplotype frequency between the PCOS and control groups. Further analysis demonstrated a relationship between IL-18 gene promoter polymorphisms and PCOS insulin resistance (IR). Regarding the -137 allele frequency, G and C allele frequencies were 93.5% and 6.5%, respectively, in the PCOS with IR patients; G and C allele frequencies were 85.4% and 14.6%, respectively, in PCOS patients without IR (chi2 = 3.601, P = 0.048).

CONCLUSIONS

The presence of a polymorphism in the IL-18 gene was found to have no correlation with the occurrence of PCOS. Carriage of the C allele at position -137 in the promoter of the IL-18 gene may play a protective role from the development of PCOS IR.

[Adult-onset Still's disease, Schnitzler syndrome, and autoinflammatory syndromes in adulthood]

Adult-onset Still's disease (AoSD), Schnitzler syndrome, and cases of adult-onset autoinflammatory syndromes [10-15% of cases of familial Mediterranean fever (FMF) and tumor necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS)] are characterized by a genetic predisposition, with increased interleukin (IL)-1beta and IL-18 production and TNF-alpha signaling, respectively. As a result, periodic fever and inflammation at barrier tissues (synovial tissues, serous membranes, and the skin) are encountered in such patients. Pathophysiological insights into these diseases have renewed interest in research on IL-1beta in rheumatic diseases and have opened new therapeutic avenues. Recently published studies have shown that patients with Schnitzler syndrome, methotrexate-refractory AoSD, and colchicine-refractory FMF or contraindications to colchicines in FMF respond well to treatment with the soluble IL-1 receptor antagonist anakinra. For TRAPS patients, the p75 TNF-alpha receptor/Fc-IgG1 fusion protein etanercept is the treatment of first choice.