Glucocorticoid Regulates Interleukin-37 in Systemic Lupus Erythematosus

Interleukin-37 ameliorates cigarette smoke-induced lung inflammation in mice

Cigarette smoking (CS) is the leading cause of chronic obstructive pulmonary disease, and its severity is closely related to lung inflammation. Interleukin (IL)-37 is a newly discovered member of the IL-1 family with anti-inflammatory activity. Our study aimed to elucidate the effect of IL-37 on CS-induced lung inflammation in mice. In this study, mice were exposed to six cigarettes for 1 h three times daily (4 h smoke-free intervals) for 10 consecutive days. Mice were treated intranasally with IL-37-expressing lentivirus and empty lentivirus particles 1 day before the first CS or sham exposure. Mice were sacrificed on day 11 to evaluate the effect of IL-37 on CS-induced pulmonary inflammation in mice. Administering IL-37-expressing lentivirus significantly reduced CS-induced weight loss in mice compared to empty lentivirus controls (P < 0.05). Histological analysis showed that IL-37 significantly alleviated inflammatory cell recruitment, alveolar septum enlargement, alveolar wall attenuation, mucus hypersecretion, and goblet cell metaplasia in mouse lungs (P < 0.001). IL-37 expression also significantly inhibited CS-induced increases in inflammatory cells (including lymphocytes, neutrophils, and macrophages) in mouse lungs (P < 0.05), as well as pro-inflammatory cytokines such as IL-1β, IL-6, IL-17, monocyte chemotactic protein-1 and tumor necrosis factor-α production (P < 0.05). IL-37 also significantly reduced myeloperoxidase activity in mouse serum (P < 0.01) and lung tissues (P < 0.001). Therefore, IL-37 can ameliorate CS-induced pulmonary inflammation in mice and IL-37 may be a potential therapeutic strategy for CS-induced lung inflammatory diseases.

The intellectual base and research fronts of IL-37: A bibliometric review of the literature from WoSCC

Background

IL-37 is a recently identified cytokine with potent immunosuppressive functions. The research fronts of IL-37 are worth investigating, and there is no bibliometric analysis in this field. The purpose of this study is to construct the intellectual base and predict research hotspots of IL-37 research both quantitatively and qualitatively according to bibliometric analysis.

Methods

The articles were downloaded from the Web of Science Core Collection (WoSCC) database from the inception of the database to 1 April 2022. CiteSpace 5.8.R3 (64-bit, Drexel University, Philadelphia, PA, USA) and Online Analysis Platform of Literature Metrology (https://bibliometric.com/) were used to perform bibliometric and knowledge-map analyses.

Results

A total of 534 papers were included in 200 academic journals by 2,783 authors in 279 institutions from 50 countries/regions. The journal Cytokine published the most papers on IL-37, while Nature Immunology was the most co-cited journal. The publications belonged mainly to two categories of Immunology and Cell Biology. USA and China were the most productive countries. Meanwhile, the University of Colorado Denver in USA produced the highest number of publications followed by Radboud University Nijmegen in the Netherlands and Monash University in Australia. Charles A. Dinarello published the most papers, while Marcel F. Nold had the most co-citations. Top 10 co-citations on reviews, mechanisms, and diseases were regarded as the knowledge base. The keyword co-occurrence and co-citations of references revealed that the mechanisms and immune-related disorders were the main aspects of IL-37 research. Notably, the involvement of IL-37 in various disorders and the additional immunomodulatory mechanisms were two emerging hotspots in IL-37 research.

Conclusions

The research on IL-37 was thoroughly reviewed using bibliometrics and knowledge-map analyses. The present study is a benefit for academics to master the dynamic evolution of IL-37 and point out the direction for future research.

Biology of interleukin‑37 and its role in autoimmune diseases (Review)

Autoimmune diseases (AIDs) are characterized by dysfunction and tissue destruction, and recent studies have shown that interleukin (IL)-37 expression is dysregulated in AIDs. Among cytokines of the IL-1 family, most are pro-inflammatory agents, and as an anti-inflammatory cytokine, IL-37 may have the potential to alleviate excessive inflammation and can be used as a ligand or transcription factor that is involved in regulating innate and adaptive immunity. IL-37 plays important roles in the development of AIDs. This review summarizes the biological characteristics and functions of IL-37 and discusses the potential of IL-37 as a therapeutic target for effective cytokine therapy and as a biomarker in AIDs.

Role of interleukin-6 and interferon-α in systemic lupus erythematosus: A case-control study and meta-analysis

BACKGROUND

Systemic lupus erythematosus (SLE) is an autoimmune disorder affecting various organ systems with unknown etiology. Interleukin-6 (IL-6) and interferon-alpha (IFN-α) have been shown to have a major role in disease pathogenesis, and they correlate with SLE disease activity, but reports in the literature are conflicting. The present study aims to investigate the significance of IL-6 and IFN-α levels in SLE pathogenesis in an eastern Indian cohort.

MATERIAL AND METHODS

70 SLE patients fulfilled SLICC 2012 criteria, and 40 age- and gender-matched healthy controls (HC) were enrolled. Baseline characteristics along with disease activity were recorded for all patients. Levels of IL-6 and IFN-α were measured by using ELISA. For the meta-analysis, published articles were searched through different databases. Two independent researchers extracted data, and the meta-analysis was performed with CMA v3.1.

RESULTS

The plasma levels of IL-6 and IFN-α in SLE patients were significantly elevated compared to HC (IL-6: p < .0001, IFN-α: p = 0.01). SLEDAI score correlated positively with plasma IL-6 (p < .0001, r = 0.46) and IFN-α levels (p < .0001; r = 0.47). Meta-analysis of previous reports, including our case-control data, revealed higher IL-6 (p < .0001) and IFN-α (p = .005) in SLE patients compared to HC. Furthermore, IL-6 (p < .0001, r = 0.526) and IFN-α (p < .0001; r = 0.371) levels positively correlated with the disease activity.

CONCLUSION

IL-6 and IFN-α levels are elevated in SLE and they correlate with disease activity. Further studies with a larger sample size in different populations are required to validate our findings.

IL-37 regulates allergic inflammation by counterbalancing pro-inflammatory IL-1 and IL-33

BACKGROUND

Children with asthma have impaired production of interleukin (IL) 37; in mice, IL-37 reduces hallmarks of experimental allergic asthma (EAA). However, it remains unclear how IL-37 exerts its inhibitory properties in asthma. This study aimed to identify the mechanism(s) by which IL-37 controls allergic inflammation.

METHODS

IL-37 target cells were identified by single-cell RNA-seq of IL-1R5 and IL-1R8. Airway tissues were isolated by laser-capture microdissection and examined by microarray-based gene expression analysis. Mononuclear cells (MNC) and airway epithelial cells (AECs) were isolated and stimulated with allergen, IL-1β, or IL-33 together with recombinant human (rh) IL-37. Wild-type, IL-1R1- and IL-33-deficient mice with EAA were treated with rhIL-37. IL-1β, IL-33, and IL-37 levels were determined in sputum and nasal secretions from adult asthma patients without glucocorticoid therapy.

RESULTS

IL-37 target cells included AECs, T cells, and dendritic cells. In mice with EAA, rhIL-37 led to differential expression of >90 genes induced by IL-1β and IL-33. rhIL-37 reduced production of Th2 cytokines in allergen-activated MNCs from wild-type but not from IL-1R1-deficient mice and inhibited IL-33-induced Th2 cytokine release. Furthermore, rhIL-37 attenuated IL-1β- and IL-33-induced pro-inflammatory mediator expression in murine AEC cultures. In contrast to wild-type mice, hIL-37 had no effect on EAA in IL-1R1- or IL-33-deficient mice. We also observed that expression/production ratios of both IL-1β and IL-33 to IL-37 were dramatically increased in asthma patients compared to healthy controls.

CONCLUSION

IL-37 downregulates allergic airway inflammation by counterbalancing the disease-amplifying effects of IL-1β and IL-33.

The emerging roles of IL-36, IL-37, and IL-38 in diabetes mellitus and its complications

Diabetes mellitus is a metabolic disease caused by a combination of genetics and environmental factors. The importance of the inflammatory response occurring in the pancreas and adipose tissue in the occurrence and progression of diabetes has been gradually accepted. Excess blood glucose and free fatty acids produce large amounts of inflammatory cytokines and chemokines through oxidative stress and endoplasmic reticulum stress. There is sufficient evidence that proinflammatory mediators, such as interleukin (IL)-1β, IL-6, macrophage chemotactic protein-1, and tumor necrosis factor-α, are engaged in the insulin resistance in peripheral adipose tissue and the apoptosis of pancreatic β-cells. IL-36, IL-37, and IL-38, as new members of the IL-1 family, play an indispensable effect in the regulation of immune system homeostasis and are involved in the pathogenesis of inflammatory and autoimmune diseases. Recently, the abnormal expression of IL-36, IL-37, and IL-38 in diabetes has been reported. In this review, we discuss the emerging functions, potential mechanisms, and future research directions on the role of IL-36, IL-37, and IL-38 in diabetes mellitus and its complications.

Activation of CpG-ODN-Induced TLR9 Signaling Inhibited by Interleukin-37 in U937 Human Macrophages

PURPOSE

Interleukin-37 (IL-37) is an anti-inflammatory cytokine that inhibits a broad spectrum of inflammatory responses in various human cells, including neutrophils, macrophages, and endothelial cells. The aim of this study was to identify the role of IL-37 in toll-like receptor 9 (TLR9) signaling in human macrophages.

MATERIALS AND METHODS

Human macrophage U937 cells treated with CpG-oligonucleotides (CpG-ODN), recombinant IL-37, or dexamethasone were used in an in vitro study. IL-37 small interfering RNA (siRNA) and TLR9 siRNA were used to silence endogenous IL-37 and TLR9, respectively. Expression levels of phosphorylated nuclear factor-κB (NF-κB), IκBα, IL-37, IL-1β, tumor necrosis factor-α (TNF-α), and IL-6 protein were assessed by real-time quantitative polymerase chain reaction and Western blotting. CpG-ODN-mediated IL-37 expression stimulated by dexamethasone was detected using immunofluorescent analysis.

RESULTS

U937 cells treated with CpG-ODN induced activation of the NF-κB pathway and increased the expression of the pro-inflammatory cytokines IL-1β, TNF-α, and IL-6, but reduced that of IL-37. Recombinant IL-37 attenuated phosphorylation of NF-κB and IκBα and the expression of IL-1β, TNF-α, and IL-6 stimulated by CpG-ODN. Human macrophages transfected with IL-37 siRNA augmented the expression of IL-1β, TNF-α, and IL-6 mRNA and protein in cells treated with CpG-ODN. Dexamethasone markedly inhibited expression of pro-inflammatory cytokines in U937 cells, whereas IL-37 expression was increased with the addition of dexamethasone. Inflammatory responses elicited by CpG-ODN were dependent on an MyD88-TRAF6 pathway. IL-37 inhibited CpG-ODN-induced ubiquitination of TRAF6 in U937 macrophages.

CONCLUSION

IL-37 inhibits CpG-ODN-mediated inflammatory responses through regulation of a TRAF6-NF-κB pathway in human macrophages.

Elevated levels of serum IL-36α in patients with systemic lupus erythematosus

The present study aimed to investigate the levels of IL-36α and its association with disease activity in patients with systemic lupus erythematosus (SLE). A total of 60 patients with SLE and 29 healthy controls were enrolled in the present study. Disease activity was evaluated using the SLE disease activity index (SLEDAI). The serum levels of IL-36α, IL-36 receptor antagonist (IL-36Ra) and IL-17 were assessed using ELISA. The levels of IL-36α in patients with SLE were significantly higher compared with those of healthy controls. There was a significant increase in IL-36α in the active SLE group (SLEDAI score ≥5) compared with that of the healthy controls (P<0.001). The serum IL-36α levels were higher in patients with active SLE than in patients with quiescent disease (P=0.012). IL-36Ra was downregulated in patients with SLE (P=0.007). The serum IL-17 levels were elevated in patients with SLE (P=0.036), and a positive correlation was observed between the IL-36α and IL-17 levels (r=0.453, P=0.003). The serum IL-36α levels were associated with SLEDAI (r=0.374, P=0.003), proteinuria (r=0.329, P=0.010) and complement 3 (r=-0.336, P=0.009). Patients who were receiving glucocorticoid treatment had lower IL-36α levels than those who were not receiving glucocorticoid treatment (P=0.003). Patients with lupus nephritis had higher serum IL-36α levels compared with those found in patients without lupus nephritis (P=0.037). The serum IL-36α concentration was elevated in patients with SLE, and was correlated with disease activity and IL-17 levels. The aberrant serum IL-36α levels observed in the present study and its clinical association with SLE suggest the important role of IL-36α in onset and progression of SLE. In addition, the association of IL-36α with IL-17 level indicates its involvement in the regulation of T helper 17 cytokines.

Circulating Interleukin-37 Levels in Healthy Adult Humans - Establishing a Reference Range

Interleukin (IL)-37 has an important function in limiting excessive inflammation. Its expression is increased in numerous inflammatory and autoimmune conditions and correlates with disease activity, suggesting it could have potential as a disease biomarker. Nevertheless, a reference range has yet to be determined. Our aim was to establish the first reference range of circulating IL-37 levels in healthy adult humans. PubMed was searched for studies reporting blood IL-37 concentrations in healthy adult subjects as measured by enzyme-linked immunosorbent assay. Nineteen studies were included in the analysis. Mean IL-37 levels were weighted by sample sizes, and weighted mean lower and upper levels ( ± 2SD of means) were calculated to provide a weighted mean and reference range. IL-37 levels were quantified in either serum or plasma from a total of 1035 (647 serum; 388 plasma) healthy subjects. The serum, plasma and combined matrix weighted means (reference ranges) were 72.9 (41.5 – 104.4) pg/mL, 83.9 (41.1 – 126.8) pg/mL, and 77.1 (41.4 – 112.8) pg/mL, respectively. There were no significant differences between serum and plasma means and upper and lower limits. Study means and upper IL-37 levels were significantly higher in Chinese population studies. From our analysis, a preliminary reference range for circulating IL-37 levels in healthy human adults has been established. In order to determine a reliable reference range for clinical application, large, prospective, multi-ethnic, healthy population studies are necessary. In addition, demographics, sample matrix, collection, processing and storage methods potentially affecting IL-37 detection levels should be thoroughly investigated.

IL-37bΔ1-45 suppresses the migration and invasion of endometrial cancer cells by targeting the Rac1/NF-κB/MMP2 signal pathway

Endometrial carcinoma is one of the most common malignancies in the female reproductive system. Interleukin-37 (IL-37) is a newly discovered anti-inflammatory factor belonging to the IL-1 family. IL-37 has five different isoforms, and IL-37b is the most biologically functional subtype. In recent years, the protective roles of IL-37 in different cancers, including lung and liver cancers, have been successively reported. IL-37 also plays an important role in some gynecological diseases such as endometriosis, adenomyosis, and cervical cancer. However, the role and mechanism of IL-37b, especially the mature form of IL-37b, in endometrial carcinoma have not been elucidated. The present study demonstrated that IL-37 protein was downregulated in endometrial carcinoma cells compared with the control endometrium. IL-37b did not affect the proliferation and colony-forming ability of endometrial cancer cells. A mature form of IL-37b (IL-37bΔ1-45) effectively suppressed the migration and invasion of endometrial cancer cells by decreasing the expression of matrix metalloproteinase 2 (MMP2) via Rac1/NF-κB signal pathway. However, it did not affect epithelial-mesenchymal transition (EMT) or filamentous actin (F-actin) depolymerization of endometrial cancer cells. IL-37bΔ1-45 attenuated tumor metastasis in a peritoneal metastatic xenograft model of endometrial cancer. To sum up, these results suggested IL-37b could be involved in the pathogenesis of endometrial carcinoma and provide a novel target for the diagnosis and treatment of endometrial carcinoma.

Correlation Between Level of Interleukin-37 and Rheumatoid Arthritis Progression

Background

Rheumatoid arthritis (RA) is a systemic autoimmune inflammatory disease that primarily affects joints. Interleukin-37 (IL-37) is an anti-inflammatory cytokine that is known to suppress immune response and inflammation. The objective of this study is to evaluate the correlation between level of IL-37 and RA progression using the disease activity score in 28 joints (DAS-28).

Methods

A total of 87 RA patients were separated into 4 groups based on the DAS28, referred to as the remission, mild, moderate and severe groups. 18 healthy volunteers were also included. Serum level of IL-37 and IL-37 mRNA expression level in peripheral blood mononuclear cells (PBMCs) in each individual participant as well as IL-37 mRNA expression level in synovial cells were assessed to explore their correlation with RA progression.

Results

Serum level of IL-37 and IL-37 mRNA expression levels in both PBMCs and synovial cells were all positively correlated with the severity of RA as reflected by the DAS28. Receiver operating characteristic (ROC) analysis revealed area under curve (AUC) values of 1, 0.5262 and 0.7789 for the three parameters.

Conclusion

Our results suggest that serum IL-37 level and mRNA expression levels of IL-37 in PBMCs and synovial cells are correlated with the severity of RA in a Chinese population.

IL-37 As a Potential Biotherapeutics of Inflammatory Diseases

Interleukin-37 (IL-37) was discovered as a new member of pro-inflammatory IL-1 superfamily. However, further studies suggested that IL-37 plays a critical anti-inflammatory role in innate and adaptive immunity. IL-37 may suppress the inflammatory process via intracellular SMAD family member 3 (SMAD3) and extracellular IL-18 Receptor alpha (IL-18Rα) signaling pathway, respectively. Meanwhile, the abnormal expression of IL-37 was observed in immune-mediated inflammatory diseases, such as inflammatory bowel disease, rheumatoid arthritis, atherosclerosis, systemic lupus erythematosus, asthma, and multiple sclerosis, which suggest IL-37 is a potential therapeutic target for these diseases. In this review, we summarize the anti-inflammatory mechanism of IL-37 and discuss the critical roles of IL-37 in the pathogenesis of these diseases. Further studies are required to confirm the effectiveness of IL-37 as a novel target for these inflammatory diseases.

GILZ Regulates the Expression of Pro-Inflammatory Cytokines and Protects Against End-Organ Damage in a Model of Lupus

Glucocorticoid-induced leucine zipper (GILZ) mimics many of the anti-inflammatory effects of glucocorticoids, suggesting it as a point of therapeutic intervention that could bypass GC adverse effects. We previously reported that GILZ down-regulation is a feature of human SLE, and loss of GILZ permits the development of autoantibodies and lupus-like autoimmunity in mice. To further query the contribution of GILZ to protection against autoimmune inflammation, we studied the development of the lupus phenotype in Lyn-deficient (Lyn^-/-) mice in which GILZ expression was genetically ablated. In Lyn^-/- mice, splenomegaly, glomerulonephritis, anti-dsDNA antibody titres and cytokine expression were exacerbated by GILZ deficiency, while other autoantibody titres and glomerular immune complex deposition were unaffected. Likewise, in patients with SLE, GILZ was inversely correlated with IL23A, and in SLE patients not taking glucocorticoids, GILZ was also inversely correlated with BAFF and IL18. This suggests that at the onset of autoimmunity, GILZ protects against tissue injury by modulating pro-inflammatory pathways, downstream of antibodies, to regulate the cycle of inflammation in SLE.

Different Features of Interleukin-37 and Interleukin-18 as Disase Activity Markers of Adult-Onset Still's Disease

The aim of this study was to evaluate the usefulness of serum interleukin (IL)-37 and IL-18 as disease activity markers of adult-onset Still’s disease (AOSD) and to compare their related clinical features. Forty-five patients with a set of high and subsequent low disease activity status of AOSD were enrolled. Modified Pouchot (mPouchot) score and serologic disease activity markers including levels of IL-37 and IL-18 were compared between high and low disease activity status. The relationships between disease activity parameters and differences in levels of cytokines according to each disease manifestation were evaluated in high disease activity status. mPouchot score and all disease activity markers including IL-37 and IL-18 significantly declined after treatment. Though both cytokines positively correlated with mPouchot score, the two did not correlate with each other in high disease activity status. IL-18 positively correlated with ferritin, AST, and LDH while IL-37 correlated better with CRP. The expression level of IL-37 was related to leukocytosis while IL-18 was related to pleuritis, pneumonitis, abnormal LFT, and hyperferritinemia. In addition, patients in the IL-18 dominant group presented with higher LDH levels and required a higher mean corticosteroid dose. In conclusion, IL-37 and IL-18 are disease activity markers reflecting different aspects of AOSD that can complement each other.

Correlation between circulating interleukin-18 level and systemic lupus erythematosus: a meta-analysis

This study is a meta-analysis aimed at pooling reported data and clarifying the association between circulating level of interleukin-18 and systemic lupus erythematosus (SLE). We searched medical databases including Medline/Pubmed, Embase, Scopus, The Cochrane Library, and Web of Science thoroughly to obtain all related articles published before July 15th, 2020. We pooled computed standardized mean difference (SMD) and its 95% confidence interval using STATA 13.0 and exhibited in the form of forest graph. Meta-regression and subgroup analysis were also performed to explore the source of heterogeneity. Publication bias was first evaluated by the symmetry of the funnel plot and then Egger’s linear regression test. Thirty eligible studies from eighteen regions were finally included and the relevant data from these studies were pooled. The analysis results displayed that SLE patients showed a significantly higher level of circulating IL-18 level in comparison with healthy controls (SMD = 1.56, 95% CI [1.20–1.93]; I² = 94.9%, p < 0.01). The conclusion was equally applicable in subgroups divided based on sample type, mean age, disease duration, and testing method. Patients with SLEDAI score higher than five, or who were Asian, White, Arab, or mixed ethnicity had an elevated level of IL-18, while the others didn’t. This meta-analysis has elucidated that compared with healthy people, the circulating level of IL-18 is considerably higher in SLE patients, which indicates the underlying role of IL-18 in SLE pathogenesis.

Interleukin-37 as a biomarker of mortality risk in patients with sepsis

BACKGROUND

Sepsis is a serious syndrome that is caused by an unbalanced inflammatory response to infection and can cause high mortality. The role of interleukin-37 (IL-37) in estimating the mortality in patients with sepsis remains unknown. This study aims to reveal the clinical application of IL-37 as a potentially novel biomarker to predict mortality risk in patients with sepsis.

METHODS

The serum IL-37 level in 114 adult septic patient serum samples on the day of intensive care unit (ICU) admission, 56 non-sepsis ICU patients, and 56 healthy volunteers were measured and analyzed, and the 28-day survival status and sequential organ failure assessment (SOFA) scores of the participants were compared. Furthermore, the area under the receiver operating characteristic curve (AUC) of IL-37, IL-6, and SOFA at ICU admission for 28-day survival was used to evaluate the ability of IL-37 in predicting the mortality of sepsis.

RESULTS

The serum IL-37 level at admission was elevated in patients with sepsis. Moreover, the concentration of IL-37 in patients with sepsis was significantly higher than that in non-sepsis ICU patients and the healthy control group. In addition, the concentration of serum IL-37 in non-surviving patients with sepsis was significantly higher than that in survivors. In patients with sepsis on the day of ICU admission, the AUC associated with 28-day mortality was 0.67 (p = 0.0022;95% confidence interval [95% CI], 0.57-0.77) for IL-37, 0.75 (p < 0.0001; 95% CI, 0.66-0.84) for SOFA, and 0.62 (p = 0.0342; 95% CI, 0.51-0.72) for IL-6. IL-37 and SOFA scores on the day of ICU admission of the patients with sepsis were found to be independent predictors of 28-day mortality, whereas IL-6 was not. The risk of mortality in patients with sepsis and high serum IL-37 concentration (≥107.05pg/ml) was 4.6 times that of patients with sepsis and low serum concentration. The AUC of IL-37 combined with SOFA-estimated 28-day mortality in patients with sepsis increased from 0.67 (p = 0.0022; 95% CI, 0.57-0.77) to 0.80 (p < 0.0001; 95% CI, 0.711-0.879). In addition, patients with sepsis and high serum IL-37 concentrations (≥107.05pg/ml) had poorer survival rate than those with low serum concentrations (<107.05pg/ml).

CONCLUSION

IL-37 concentrations at ICU admission are valuable for predicting the 28-day mortality risk of patients with sepsis, suggesting that IL-37 may be a novel biomarker. These findings can be used as a basis for guiding early clinical decision-making in treating patients with sepsis.

Association between IL-37 and Systemic Lupus Erythematosus Risk

Interleukin-37 (IL-37) is an anti-inflammatory cytokine. In our former study, we found increased plasma IL-37 levels in systemic lupus erythematosus (SLE) patients. However, relationship between IL-37 levels and clinical laboratory characteristics of SLE patients has not been elucidated. In addition, association of IL37 gene polymorphism with SLE risk needs to be discussed. A group of 580 individuals (220 SLE patients and 360 healthy controls) in a Southern Chinese Han population were recruited. Plasma IL-37 levels were evaluated using enzyme-linked immunosorbent assay (ELISA). Four single-nucleotide polymorphisms (rs3811047, rs2723186, rs2723176 and rs4364030) of IL37 gene were genotyped. Relationship of IL-37 expression, IL37 gene polymorphisms and clinical characteristics was discussed. We found that plasma levels of IL-37 were negatively associated with SLE disease activity index (SLEDAI) (r_s = -0.352, P = .001), and were higher in less active patients compared with active patients (P = .003). Decreased levels of IL-37 were found in SLE patients with discoid rash when compared to patients who did not have this symptom (P < .001). Plasma IL-37 levels were significantly lower in patients with hypocomplementemia comparing to those without this feature (P = .009). Levels of IL-37 in SLE with positive proteinuria were lower than patients with negative proteinuria (P = .046). Furthermore, allele distribution of rs2723186, rs4364030 between SLE cases and healthy individuals was significantly different (P = .001, P = .010, respectively). Genotype of rs4364030 was different between SLE cases and controls (P = .015). Haplotype analysis revealed that the frequency of haplotype CG (rs2723176 (C) +rs2723186 (G)) was higher in SLE, as compared with healthy individuals (P = .002). In conclusion, the plasma levels of IL-37 were related to SLE severity, and IL37 gene polymorphisms (rs2723186, rs2723176 and rs4364030) may associate with SLE susceptibility.

Entecavir downregulates interleukin-37 in patients with chronic active hepatitis B infection

Objectives

Interleukin-37 (IL-37) has been identified as a potent inhibitor of the immune response. This study aimed to examine IL-37 expression in patients with chronic active hepatitis B (CAHB), and explore its possible regulatory role during inflammation.

Methods

Peripheral blood mononuclear cells (PBMCs) were collected from control (n = 20) and CAHB patients (n = 30) before and after treatment with entecavir (EVT) for 24 weeks. The PBMCs were cultured with lipopolysaccharide and IL-37 expression was determined by real-time polymerase chain reaction and flow cytometry. The mRNA and protein concentrations of IL-1β, IL-6, and tumor necrosis factor-alpha (TNF-α) in PBMCs were also measured.

Results

Levels of IL-37, IL-1β, IL-6, and TNF-α were significantly increased in the supernatant of PBMCs from patients with CAHB. IL-37 significantly reduced the expression of IL-1β, IL-6, and TNF-α. EVT resulted in regression of intraocular inflammation in patients with CAHB, associated with decreased production of IL-37.

Conclusion

These results suggest that increased expression of IL-37 was associated with the suppression of the inflammatory response in patients with CAHB. Furthermore, EVT treatment of CAHB was also correlated with downregulation of IL-37, indicating that EVT may partially alleviate the immune response by modulating IL-37 production.

Levels of TNF-α, IL-6, IL-17, IL-37 cytokines in patients with active vitiligo

OBJECTIVES

Vitiligo is an autoimmune disease, and its pathogenesis involves changes in cytokine levels in the affected patients. Tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, and IL-17 from pro-inflammatory cytokines, IL-37 in a recently detected anti-inflammatory activity. The aim of our study was to determine serum TNF-α, IL-6, IL-17, IL-37 levels in patients with vitiligo to understand their possible roles in the disease etiology and to compare the results with the healthy controls.

METHODS

The study included 48 generalized vitiligo patients who were diagnosed with vitiligo, had an increase in the lesions within the last 3 months, and did not receive any systemic or topical treatment during this period; furthermore, 18 healthy controls were included.

RESULTS

Patient group: n = 48, mean age = 30.48 ± 9.86 years; control group: n = 18, mean age = 28.27 ± 9.66 years. Individuals in the patient group had significantly higher serum levels of IL-37(t = 3.90, p < .001), IL-6 (t = 3.39, p < .05), IL-17 (t = 2.08, p < .05), and TNF-α (t = 4.69 p < .001) than in the control group.

CONCLUSION

The high levels of (pro-anti) inflammatory cytokines in vitiligo patients draw attention to the importance of cytokines in the pathogenesis of the disease.

IL-18 and infections: Is there a role for targeted therapies?

Interleukin (IL)-18 is a pro-inflammatory cytokine belonging to the IL-1 family, first identified for its interferon-γ-inducing properties. IL-18 regulates both T helper (Th) 1 and Th2 responses. It acts synergistically with IL-12 in the Th1 paradigm, whereas with IL-2 and without IL-12 it can induce Th2 cytokine production from cluster of differentation (CD)4⁺ T cells, natural killer (NK cells, NKT cells, as well as from Th1 cells. IL-18 also plays a role in the hemophagocytic lymphohistiocytosis, a life-threatening condition characterized by a cytokine storm that can be secondary to infections. IL-18-mediated inflammation was largely studied in animal models of bacterial, viral, parasitic, and fungal infections. These studies highlight the contribution of either IL-18 overproduction by the host or overresponsiveness of the host to IL-18 causing an exaggerated inflammatory burden and leading to tissue injury. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the coronavirus disease 2019 (COVID-19). The damage in the later phase of the disease appears to be driven by a cytokine storm, including interleukin IL-1 family members and secondary cytokines like IL-6. IL-18 may participate in this hyperinflammation, as it was previously found to be able to cause injury in the lung tissue of infected animals. IL-18 blockade has become an appealing therapeutic target and has been tested in some IL-18-mediated rheumatic diseases and infantile-onset macrophage activation syndrome. Given its role in regulating the immune response to infections, IL-18 blockade might represent a therapeutic option for COVID-19, although further studies are warranted to investigate more in detail the exact role of IL-18 in SARS-CoV-2 infection.

Roles of novel IL-1 family (IL-36, IL-37, and IL-38) members in chronic brucellosis

The secretion of interleukin (IL)-1 family cytokines is one of the most potent and earliest pro-inflammatory responses triggered by brucellosis. However, the roles of the most recently discovered IL-1 family members, IL-36, IL-37, and IL-38, in the transition into the chronic form of brucellos is remain largely unknown. Therefore, in this study, the roles of IL-36, IL-37, and IL-38 in brucella infections and their effects on the transition from the acute to chronic form of the disease were investigated. Using peripheral blood samples from 40 patients with acute brucellosis, 40 patients with chronic brucellosis, and 40 healthy control subjects, we analysed the serum concentrations of secreted IL-36, IL-37, and IL-38 using ELISA. The findings were confirmed by using RT-qPCR to analyse the mRNA levels of the genes encoding IL-36, IL-37, and IL-38 in peripheral blood mononuclear cells (PBMCs) from 10 randomly selected patients from each of the three groups. Our results showed that serum IL-37 (p < 0.001) and IL-38 (p < 0.001) concentrations were lower in patients with brucellosis than in the healthy controls. In addition, serum IL-37 and IL-38 concentrations were higher in the chronic patient group than in the acute patient group. The mRNA expression levels of IL-37 and IL1F10, genes that encode IL-38, did not affect serum cytokine secretion levels. This result suggests that the high secretion levels of IL-37 and IL-38 may be related to the progression into the chronic form of brucellosis. Our findings will aid in clarifying the mechanism of the transition of brucellosis from the acute to the chronic form of the disease.

The role of IL-37 in skin and connective tissue diseases

IL-37 was discovered as an anti-inflammatory and immunosuppressive cytokine of the IL-1 family. Significant advancements in the understanding of signaling pathways associated with IL-37 have been made in recent years. IL-37 binds to IL-18R and recruits IL-1R8 to form the IL-37/IL-1R8/IL-18Rα complex. Capase-1 plays a key role in the nuclear transduction of IL-37 signal, processing precursor IL-37 into the mature isoform, and interacting with Smad3. IL-37 exerts its role by activating anti-inflammation pathways including AMPK, PTEN, Mer, STAT3 and p62, and promoting tolerogenic dendritic cells and Tregs. In addition, IL-37 inhibits pro-inflammatory cytokines such as IL-1, IL-6, IL-8, IL-17, IL-23, TNF-α, and IFN-γ, and suppresses Fyn, MAPK, TAK1, NFκB, and mTOR signaling. The final effects of IL-37 depend on the interaction among IL-18R, IL-1R8, IL-37 and IL-18BP. Previous studies have deciphered the role of IL-37 in the development and pathogenesis of autoimmune diseases, chronic infections and cancer. In this review, we discuss the role of IL-37 in psoriasis, atopic dermatitis, Behcet's diseases, systemic lupus erythematosus, and other skin and connective tissue diseases.

Role of Interleukin 37 as a Novel Proangiogenic Factor in Juvenile Idiopathic Arthritis

OBJECTIVE

The aim of this study was to investigate interleukin 37 (IL-37) levels in the serum and synovial fluid of patients with juvenile idiopathic arthritis (JIA), its expression in peripheral blood mononuclear cells, and correlation with disease activity and angiogenesis.

METHODS

Seventy JIA patients and 50 control subjects were examined. The Juvenile Arthritis Disease Activity Score in 27 joints (JADAS-27) was calculated. Immunoassays were used to measure the serum and synovial fluid levels of IL-37, vascular endothelial growth factor (VEGF), soluble VEGF receptor 1 (sVEGF-R1), and sVEGF-R2. Relative expression of IL-37 mRNA in peripheral blood mononuclear cells and the power Doppler ultrasound score of the affected joint were measured.

RESULTS

Patients with JIA were subdivided as 20 systemic-onset, 20 polyarticular, and 30 oligoarticular (10 persistent, 20 extended) cases. Serum levels of IL-37, VEGF, VEGF-R1, and VEGF-R2 and relative IL-37 mRNA expression were significantly higher in JIA patients when compared with the control subjects (p < 0.001). These concentrations were significantly higher in systemic-onset JIA compared with those in polyarticular and oligoarticular JIA, and in polyarticular JIA when compared with oligoarticular JIA (p < 0.001). Serum, synovial, and mRNA expression levels of IL-37 were positively correlated with C-reactive protein, erythrocyte sedimentation rate, Juvenile Arthritis Disease Activity Score in 27 joints, power Doppler ultrasound score (p < 0.001), and the serum and synovial VEGF and VEGF-RI and -R2 levels (p < 0.05).

CONCLUSIONS

Our results demonstrate that IL-37 levels and mRNA expression were significantly increased in JIA patients, and their levels were positively correlated with disease activity and markers of angiogenesis (VEGF and VEGF receptors), suggesting that IL-37 may be correlated with angiogenesis.

Insight into interleukin-37: The potential therapeutic target in allergic diseases

Allergic diseases are ubiquitous diseases with detrimental effects on the quality of life of people worldwide. Common allergic diseases include asthma, allergic rhinitis (AR) and allergic dermatitis (AD). Recently, studies have shown that interleukin (IL)-37, a novel cytokine in the IL-1 family, exhibits broad protective properties in various diseases, such as autoimmune diseases and cancer. IL-37 displays its anti-inflammatory effect on diseases by curbing innate and acquired immunity as well as inflammatory reactions. IL-37 functions by forming a complex with IL-18Rα and IL-1R8 extracellularly and can be translocated to the nucleus upon forming a complex with mothers against decapentaplegic homolog 3 (Smad3) intracellularly, thereby affecting gene transcription and signaling pathway activation. In addition, increasing evidence confirms that IL-37 expression is aberrant in asthma, AR and AD, which indicates that IL-37 may also play essential roles in allergic diseases. Furthermore, accumulating data obtained from recombinant IL-37 (rIL-37)-treated mice and from IL-37 transgenic (IL-37tg) mice suggest a protective role for IL-37. This review will detail the role of IL-37 in the occurrence and development of allergic diseases and discuss the potential of IL-37 as a therapeutic target in allergic diseases.

Plasma levels and expression of interleukin-37 in patients with immune thrombocytopenia

Interleukin (IL)-37 has an important role in autoimmune diseases by suppressing immunity and inflammation; however, the role of IL-37 in immune thrombocytopenia (ITP) has remained largely elusive. The present study aimed to investigate the expression of IL-37 and its potential role in the pathogenesis of ITP. The plasma levels and expression of IL-37 in the peripheral blood mononuclear cells of patients with active ITP, ITP patients in remission and healthy controls were measured by ELISA and reverse transcription-quantitative PCR, respectively. The levels of IL-37 in patients with ITP treated with and without glucocorticoids were also determined by ELISA. Specific anti-platelet glycoprotein (GP)IIb/IIIa and/or GPIb/IX autoantibodies were assayed by modified monoclonal antibody-specific immobilization of platelet antigens. The mean value of plasma IL-37 in ITP patients was slightly higher than that in healthy controls, but this was not statistically significant. There was no correlation between IL-37 and anti-platelet autoantibodies, and no significant difference in the IL-37 concentration was identified between patients treated with and without glucocorticoids. In addition, the correlation between IL-37 and the platelet count was analyzed, with no statistical significance observed. It was therefore concluded that IL-37 may not have a pivotal role in the development of ITP. However, the lack of significant differences may be due to the limited number of patients in different groups. A larger number of ITP patients should be enrolled in the future work and achieve more accurate results.

Human gut derived-organoids provide model to study gluten response and effects of microbiota-derived molecules in celiac disease

Celiac disease (CD) is an immune-mediated disorder triggered by gluten exposure. The contribution of the adaptive immune response to CD pathogenesis has been extensively studied, but the absence of valid experimental models has hampered our understanding of the early steps leading to loss of gluten tolerance. Using intestinal organoids developed from duodenal biopsies from both non-celiac (NC) and celiac (CD) patients, we explored the contribution of gut epithelium to CD pathogenesis and the role of microbiota-derived molecules in modulating the epithelium’s response to gluten. When compared to NC, RNA sequencing of CD organoids revealed significantly altered expression of genes associated with gut barrier, innate immune response, and stem cell functions. Monolayers derived from CD organoids exposed to gliadin showed increased intestinal permeability and enhanced secretion of pro-inflammatory cytokines compared to NC controls. Microbiota-derived bioproducts butyrate, lactate, and polysaccharide A improved barrier function and reduced gliadin-induced cytokine secretion. We concluded that: (1) patient-derived organoids faithfully express established and newly identified molecular signatures characteristic of CD. (2) microbiota-derived bioproducts can be used to modulate the epithelial response to gluten. Finally, we validated the use of patient-derived organoids monolayers as a novel tool for the study of CD.

Increased serum interleukin-37 (IL-37) levels correlate with oxidative stress parameters in Hashimoto's thyroiditis

PURPOSE

Interleukin-37 (IL-37), member of the IL-1 family, is a natural suppressor of immune and inflammatory responses. Increased serum IL-37 levels were observed in several autoimmune diseases, including Graves' disease. To our knowledge, no data on Hashimoto's thyroiditis (HT) are available in the literature.

METHODS

Aim of our study was to measure serum IL-37 levels and evaluate their relationship, if any, with oxidative stress markers in HT patients. We enrolled 45 euthyroid HT patients (5 M e 40 F, median age 40 years) and 50 age- and sex-matched healthy controls. None was under L-thyroxine therapy. Serum IL-37 levels were measured by ELISA. Specific serum tests, such as derived reactive oxygen metabolites (d-ROMs), and biological anti-oxidant potential (BAP) test were performed in all subjects to investigate the changes in oxidative balance, and advanced glycation end products (AGEs) were determined as a specific marker of oxidative stress.

RESULTS

IL-37 levels were significantly higher in HT than in controls (median 475 vs. 268 pg/ml, P = 0.018). In the same patients, serum oxidants (d-ROMs) were increased and anti-oxidants (BAP) decreased compared with controls (P = 0.011 and < 0.0001, respectively), clearly indicating an enhanced oxidative stress. In addition, AGEs levels were higher in HT patients than in controls (210 vs. 140 AU/g prot, P < 0.0001) and directly correlated with IL-37 levels (P = 0.048). At multivariate analysis, the main independent predictors that influenced IL-37 levels were both anti-thyroid antibodies (P = 0.026) and AGEs levels (P = 0.001).

CONCLUSIONS

IL-37 is up-regulated in HT and may exert a protective role by counteracting oxidative stress and inflammation.

Detection of IL-37 in peripheral blood of patients with rheumatoid arthritis and its clinical significance

The study aimed to detect the expression level of interleukin-37 (IL-37) in patients with rheumatoid arthritis (RA) and explore its clinical significance. A total of 40 peripheral blood samples from active and stable RA patients were collected (40 patients with RA), and peripheral blood from 40 healthy volunteers was used as the control group. Peripheral blood serum and peripheral blood mononuclear cells (PBMCs) were isolated. The expression of IL-37 mRNA in PBMCs was detected by real-time fluorescence quantitative PCR. Serum levels of IL-37, rheumatoid factor (RF), and anticyclic citrullinated peptide antibody (CCP) were measured by enzyme-linked immunosorbent assay (ELISA). The results were then calculated and analyzed. The results showed that expression of IL-37 mRNA in the PBMCs of patients with RA was significantly higher than that in the control group ( P < 0.05). Expression of IL-37 mRNA in the PBMCs of the active period group was significantly higher than that in the stable period group ( P < 0.05). IL-37 levels in patients with RA were significantly higher than those of the control group ( P < 0.05). IL-37 levels in the active period group were also significantly higher than those of the stable period group ( P < 0.05). The comparative analysis of RF and anti-CCP antibody levels showed that IL-37 was positively correlated with RF and anti-CCP levels in patients with RA. In conclusion, the expression level of IL-37 in peripheral blood of RA patients was significantly higher than that of normal control group, and it was correlated with RF and CCP antibody levels, indicating that IL-37 plays an important role in the development of RA.

Interleukin-37 (IL-37) Suppresses Pertussis Toxin-Induced Inflammatory Myopathy in a Rat Model

Background

Recent data have demonstrated the potential immunosuppressive roles of interleukin-37 (IL-37) in several diseases, but whether it is involved in the pathogenesis of inflammatory myopathy has not been elucidated.

Material/Methods

An experimental autoimmune myositis (EAM) model was built by subcutaneous injections of pertussis toxin (PTX) and purified rabbit myosin (10mg/kg) emulsified with an equal volume of conventional complete Freund’s adjuvant (CFA) in a Lewis model. Autoimmune myositis Lewis model rats were divided into 3 groups: group A rats (control group) were injected with CFA in saline weekly; group B (IL-37 group) rats were injected with saline with IL-37 and CFA in saline weekly; and group C (IL-37 + SIS3 group) rats were injected with IL-37, CFA, and SIS3. ELISA was also used to assess the expressions of TNF-α, IL-6, IL-1β, TGF-β1, and CK. HE staining was performed to assess pathological changes in lung and muscle tissues.

Results

The expressions of TNF-α, IL-6, IL-1β, TGF-β1, and CK significantly increased in autoimmune myositis Lewis model rats. After IL-37 treatment, the expression of TNF-α, IL-6, IL-1β, TGF-β1, and CK was significantly reduced, as were the inflammatory responses of lung and muscle. However, SIS3 reduced the effects of IL-37 on the autoimmune myositis Lewis model rats.

Conclusioans

These findings indicate that IL-37 protects against inflammatory response via regulating Smad3 in autoimmune myositis Lewis model rats.

Plasma interleukin-37 is increased and inhibits the production of inflammatory cytokines in peripheral blood mononuclear cells in systemic juvenile idiopathic arthritis patients

Background

Interleukin (IL)-37 has emerged as a novel anti-inflammatory cytokine that play an immunosuppressive role in regulating inflammatory response. This study aimed to measure IL-37 levels in the plasma and peripheral blood mononuclear cells (PBMCs) of patients with systemic juvenile idiopathic arthritis (sJIA), and to establish the correlation between IL-37 levels and disease activity, laboratory parameters and inflammatory cytokines.

Methods

The mRNA levels of IL-37 in PBMCs and plasma IL-37 concentrations in 46 sJIA patients and 30 age- and sex-matched healthy controls were measured by real-time polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. The correlations between plasma IL-37 levels and disease activity, laboratory parameters and inflammatory cytokines in sJIA were analyzed by Spearman correlation test. PBMCs from the sJIA patients were stimulated with recombinant human IL-37 (rhIL-37) protein, expressions of IL-1β, IL-6, TNF-α and IL-17 were detected by RT-PCR and ELISA.

Results

Plasma levels of IL-37 and relative IL-37 mRNA expression were significantly elevated in sJIA patients, especially in active sJIA patients, when compared with the healthy controls (P < 0.001). Furthermore, patients with active disease showed higher IL-37 mRNAs and plasma protein levels than those with inactive disease as well as healthy controls. Plasma IL-37 levels were correlated with disease activity and inflammatory cytokines (IL-6, TNF-α, IL-17 and GM-CSF) in sJIA patients. The productions of inflammatory cytokines such as IL-6, TNF-α, IL-17 in PBMCs from sJIA patients were obviously decreased after recombinant IL-37 stimulation, whereas the production of IL-1β was not changed.

Conclusions

Our results demonstrate that levels of IL-37 were higher in sJIA patients, which were correlated with disease activity and sJIA related inflammatory cytokines. In addition, rhIL-37 down-regulates the expressions of inflammatory cytokines form PBMCs in sJIA patients, suggesting that IL-37 may have the potential role as a natural inhibitor for the pathogenesis and therapy of sJIA.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1655-8) contains supplementary material, which is available to authorized users.

High Interleukin-37 (IL-37) Expression and Increased Mucin-Domain Containing-3 (TIM-3) on Peripheral T Cells in Patients with Rheumatoid Arthritis

Background

Anti-inflammatory mediators such as mucin-domain containing-3 (TIM-3) and IL-37 play an important role in the regulation of Th1-mediated immunity. This study was designed to investigate the proportions of various T cell subsets and monocytes in the peripheral blood of rheumatoid arthritis (RA) patients, as well as the level of TIM-3 on these cells and serum cytokine levels.

Material/Methods

We enrolled 59 RA patients and 46 age- and sex-matched healthy controls in this study. The proportion of T cells and TIM-3 expression on these T cells were determined by flow cytometry. Cytokine levels in serum were determined by ELISA.

Results

Compared with the healthy controls, the proportions of CD3⁺CD4⁺ T cells and CD3⁺CD4⁺CD25⁺CD127^low T cells in the peripheral blood were significantly higher in RA patients. However, RA patients had significantly lower proportions of CD3⁺CD8⁺ T cells and CD3⁺CD4⁻CD8⁻ T cells. TIM-3 was highly expressed on CD3⁺CD4⁺, CD3⁺CD8⁺, CD3⁺CD4⁺CD25⁺CD127^low, and CD3⁺CD4⁻CD8⁻ T cells, as well as CD14⁺ monocytes, in RA patients. Nevertheless, no correlation between TIM-3 level and an RA disease activity score of 28 was found. The elevated serum levels of IL-6 and IL-37 were positively correlated with tumor necrosis factor-α (TNF-α).

Conclusions

Both pro-inflammatory cytokines (TNF-α and IL-6) and anti-inflammatory mediators (TIM-3 and IL-37) simultaneously contribute to the pathogenesis of RA. TIM-3 and IL-37 may be used as potential biomarkers of active RA.

TNF-α and plasma albumin as biomarkers of disease activity in systemic lupus erythematosus

OBJECTIVES

Composite criteria/indices are presently used to diagnose and monitor patients with systemic lupus erythematosus (SLE). Biomarkers for these purposes would be helpful in clinical practice. We therefore evaluated a large panel of cytokines and basic laboratory tests and investigated their performance as discriminators versus controls and as biomarkers of disease activity (DA).

METHODS

We examined 437 patients with SLE, fulfilling American College of Rheumatology-82 criteria, and 322 matched controls. DA was assessed according to both SLE DA Index 2000 (SLEDAI-2K) and SLE Activity Measure (SLAM). British Isles Lupus Activity Group (BILAG) was used to assess renal DA. Additionally, 132 patients self-assessed their Global Disease Activity (PtGDA). Mesoscale Discovery 30-plex cytokine assay and routine blood chemistry was performed on fasting EDTA-plasma.

RESULTS

Of 26 tested biomarkers, we identified TNF-α as the superior discriminator between patients with SLE and controls (median=4.5 pg/mL, IQR=3.1-6.2 vs median=2.3 pg/mL, IQR=2.0-2.8). The strongest correlations to SLEDAI-2K and SLAM were obtained with TNF-α (Spearman rho (ρ)=0.32 and ρ=0.34, respectively), partly driven by the nephritis subgroup, and with p-albumin (ρ=-0.33 and ρ=-0.31, respectively). P-albumin was decreased and TNF-α was increased in patients with kidney involvement (renal BILAG A/B vs C/D/E, p=4×10-16 and p=6×10-9 respectively). IP-10 was increased in patients with joint involvement (SLAM item 24≥2 vs ≤1, p=0.0005) but did not differ when comparing patients with active/inactive kidney involvement. The most powerful correlations to PtGDA was observed with p-albumin (ρ=-0.42), IL-6 (ρ=0.30) and TNF-α (ρ=0.29).

CONCLUSION

TNF-α and p-albumin both performed well as discriminators between patients with SLE and controls and as proxies for DA according to both rheumatologists' and patients' assessments. In particular, renal DA was well reflected by TNF-α. We propose that the TNF-α and p-albumin merit further investigations as clinically useful biomarkers in SLE. We also observed that the pattern of activated cytokines varies with organ involvement.

Expression of inflammatory cytokines in serum and peritoneal fluid from patients with different stages of endometriosis

OBJECTIVE

To investigate the level of inflammatory cytokines in endometriosis patients, and explore the relationship between IL-37 concentration and endometriosis stages.

METHODS

Inflammatory cytokine concentrations from 27 patients with different stages of endometriosis and 52 controls without endometriosis were examined by ELISA. Then, the specificity and sensitivity of cytokines for distinguishing from controls and the different stages of endometriosis were analyzed using the ROC curve.

RESULTS

The difference in serum concentrations of IL-37, IL-17A, IL-10, and IL-2 between the endometriosis and control groups was statistically significant (p < .01). Compared with controls, significantly higher levels of serum IL-37 and IL-10, and significantly lower levels of serum IL-17A and IL-2 were detected in patients with endometriosis (p < .01). Furthermore, IL-2 concentration was significantly higher in peritoneal fluid (PF) in the endometriosis group (p = .0034), IL-10 concentrations in PF were significantly lower in the early-stages of endometriosis than in the more advanced groups (p = .0439), and IL-4 concentration in PF was significantly higher in more advanced endometriosis (p = .0228). The sensitivity and specificity of serum IL-37 for distinguishing endometriosis were 81.48% and 83.33%, respectively, and the cutoff concentration was 69.84 pg/ml. For IL-17A, the sensitivity and specificity were 96.30% and 100%, respectively, and the cutoff concentration was 57.54 pg/ml. For IL-10, the sensitivity and specificity was 92.59% and 100%, respectively, and the cutoff concentration was 3.301 pg/ml. For IL-2, the sensitivity and specificity were 74.07% and 93.75%, respectively, and the cutoff concentration was 1.813 pg/ml. For PF IL-2, the sensitivity and specificity were 29.73% and 100%, respectively, and the cutoff concentration was 1.06 pg/ml.

CONCLUSIONS

IL-37, IL-17A, IL-10, and IL-2 may play a significant role in immune response in endometriosis. IL-37 levels may be used as a diagnostic marker for endometriosis.

Reviews of Interleukin-37: Functions, Receptors, and Roles in Diseases

Interleukin-37 (IL-37) is an IL-1 family cytokine discovered in recent years and has 5 different isoforms. As an immunosuppressive factor, IL-37 can suppress excessive immune response. IL-37 plays a role in protecting the body against endotoxin shock, ischemia-reperfusion injury, autoimmune diseases, and cardiovascular diseases. In addition, IL-37 has a potential antitumor effect. IL-37 and its receptors may serve as novel targets for the study, diagnosis, and treatment of immune-related diseases and tumors.

Interleukin-37: A crucial cytokine with multiple roles in disease and potentially clinical therapy

Interleukin (IL)-37, a new IL-1 family member, has received increasing attention in recent years. In the past decade, it has been determined that IL-37 is expressed in various normal cells and tissues and is regulated by inflammatory stimuli and pro-cytokines via different signal transduction pathways. Recently, it has been found that IL-37 is expressed in a variety of cancers, chronic inflammatory and autoimmune disorders, and exerts anti-inflammatory effects. Moreover, a growing body of literature demonstrates that IL-37 plays a vital role in inhibiting both innate and adaptive immune responses as well as inflammatory reactions. In addition, IL-37 may prove to be a new and potentially useful target for effective cytokine therapy. Further evidence is needed to clarify in more detail the effects of IL-37 in experimental and clinical studies. Based on an extensive summary of published data, the aim of this review is to outline the current knowledge of IL-37, including the location, structure, expression, regulation and function, as well as the potential clinical applications of this cytokine.

Overview of the IL-1 family in innate inflammation and acquired immunity

The interleukin-1 (IL-1) family of cytokines and receptors is unique in immunology because the IL-1 family and Toll-like receptor (TLR) families share similar functions. More than any other cytokine family, the IL-1 family is primarily associated with innate immunity. More than 95% of living organisms use innate immune mechanisms for survival whereas less than 5% depend on T- and B-cell functions. Innate immunity is manifested by inflammation, which can function as a mechanism of host defense but when uncontrolled is detrimental to survival. Each member of the IL-1 receptor and TLR family contains the cytoplasmic Toll-IL-1-Receptor (TIR) domain. The 50 amino acid TIR domains are highly homologous with the Toll protein in Drosophila. The TIR domain is nearly the same and present in each TLR and each IL-1 receptor family. Whereas IL-1 family cytokine members trigger innate inflammation via IL-1 family of receptors, TLRs trigger inflammation via bacteria, microbial products, viruses, nucleic acids, and damage-associated molecular patterns (DAMPs). In fact, IL-1 family member IL-1a and IL-33 also function as DAMPs. Although the inflammatory properties of the IL-1 family dominate in innate immunity, IL-1 family member can play a role in acquired immunity. This overview is a condensed update of the IL-1 family of cytokines and receptors.

Measurement of Elevated IL-37 Levels in Acute Ischemic Brain Injury: A Cross-sectional Pilot Study

Interleukin (IL)-37 is a new member of the IL-1 cytokine family with a defined role as a negative feedback inhibitor of proinflammatory responses. IL-37 has yet to be evaluated in non-immune-mediated neurological diseases, such as ischemic or hemorrhagic strokes. This study aimed to measure urine and serum IL-37 levels in patients with ischemic stroke. Twelve patients consented for our study. Two sets of serum and urine samples were obtained and analyzed, one upon admission to the hospital and the second the next morning. The trends in serum levels of IL- 37 in six stroke patients and the trends in the urine levels of eight stroke patients were measured by real-time polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). Our pilot study showed IL-37 levels in urine in stroke patients ranging between 210 and 4,534. Serum IL-37 levels were in the range of 44 - 5,235 in patients with ischemic stroke. Three patients who presented within three hours of stroke onset had IL-37 serum levels of 2,655 pg/ml, 3,517 pg/ml, and 5,235 pg/ml, respectively. In all others, it ranged much less than that, with the trend of delayed presentation giving lower IL-37 levels. The study shows a rather stable early elevation of serum IL-37 levels post-ischemic stroke. IL-37 plays a certain role in mediating post-stroke inflammation with a significant increase in serum levels of this novel cytokine observed in ischemic stroke patients. Further large-scale studies need to be done to establish its definite role. A prospective "CRISP" trial is registered with the ClinicalTrials.gov (Identifier: NCT03297827) to determine the role of IL-37 in modulating post-stroke inflammation.

Anti-inflammatory effects of hypoxia-preconditioned human periodontal ligament cell secretome in an experimental model of multiple sclerosis: a key role of IL-37

Recent research has widely investigated the anti-inflammatory effects of mesenchymal stem cells and their secretory products, termed the secretome, in the treatment of multiple sclerosis (MS). The present study examined the capacity of the conditioned medium (CM) from human periodontal ligament stem cells (hPLSCs) under hypoxia (H-hPDLSCs-CM) to suppress experimental autoimmune encephalomyelitis (EAE), a murine model of MS. To induce EAE, female C57BL/6 mice were immunized with myelin oligodendroglial glycoprotein peptide_35–55. At the onset of symptoms, H-hPDLSCs-CM was infused via the tail vein of mice. Our results demonstrate the efficacy of H-hPDLSCs-CM treatment in diminishing clinical and histologic disease score. A key finding from this study is the marked expression of anti-inflammatory cytokine IL-37, paralleled by the suppression of proinflammatory cytokines in mice with EAE that were treated with H-hPDLSCs-CM. In addition, a consequent modulation of oxidative stress, autophagic, and apoptotic markers was observed in mice with EAE after hPDLSCs-CM administration. In addition, to provide additional evidence of the molecular mechanisms that underlie H-hPDLSCs-CM, we investigated its therapeutic action in scratch injury–exposed NSC-34 neurons, an in vitro model of injury. This model reproduces severe inflammation and oxidative stress conditions as observed after EAE damage. In vitro results corroborate the ability of hPDLSCs-CM to modulate inflammatory, oxidative stress, and apoptotic pathways. Taken together, our findings suggest H-hPDLSCs-CM as a new pharmacologic opportunity for the management of MS.—Giacoppo, S., Thangavelu, S. R., Diomede, F., Bramanti, P., Conti, P., Trubiani, O., Mazzon, E. Anti-inflammatory effects of hypoxia-preconditioned human periodontal ligament cell secretome in an experimental model of multiple sclerosis: a key role of IL-37.

Suppression of innate inflammation and immunity by interleukin-37

IL-37 is unique in the IL-1 family in that unlike other members of the family, IL-37 broadly suppresses innate immunity. IL-37 can be elevated in humans with inflammatory and autoimmune diseases where it likely functions to limit inflammation. Transgenic mice expressing human IL-37 (IL37-tg) exhibit less severe inflammation in models of endotoxin shock, colitis, myocardial infarction, lung, and spinal cord injury. IL37-tg mice have reduced antigen-specific responses and dendritic cells (DCs) from these mice exhibit characteristics of tolerogenic DCs. Compared to aging wild-type (WT) mice, aging IL37-tg mice are protected against B-cell leukemogenesis and heart failure. Treatment of WT mice with recombinant human IL-37 has been shown to be protective in several models of inflammation and injury. IL-37 binds to the IL-18 receptor but then recruits the orphan IL-1R8 (formerly TIR8 or SIGIRR) in order to function as an inhibitor. Here, we review the discovery of IL-37, its production, release, and mechanisms by which IL-37 reduces inflammation and suppresses immune responses. The data reviewed here suggest a therapeutic potential for IL-37.

Plasma IL-37 Elevated in Patients with Chronic Heart Failure and Predicted Major Adverse Cardiac Events: A 1-Year Follow-Up Study

A great number of basic and clinical studies have demonstrated that inflammatory cytokines play an important role in the development and progression of chronic heart failure (CHF). However, there is limited information about the role of novel cytokine interleukin-37 (IL-37) in heart failure. We measured plasma IL-37 levels by enzyme-linked immunosorbent assay (ELISA) in 158 patients with chronic heart failure and 30 control subjects. Our results showed that plasma IL-37 levels were significantly elevated in patients with CHF compared with healthy controls (143.73 ± 26.83 pg/ml versus 45.2 ± 11.56 pg/ml, P < 0.001). Furthermore, plasma IL-37 levels were positively correlated with hs-CRP, hs-TnT, and NT-proBNP and negatively correlated with left ventricular ejection function (LVEF). 11 patients died of cardiovascular cause, and 27 HF patients were rehospitalized for worsening HF within 12 months. Multivariate Cox regression analysis showed that plasma IL-37 is an independent predictor of major adverse cardiac events (MACE). Furthermore, CHF patients with >99 pg/ml plasma IL-37 had significantly higher incidences of MACE within 12 months. Our data suggest that plasma IL-37 may play a role in the pathogenesis of CHF and may be a novel predictor of poor prognosis in HF patients.

Elevated IL-37, IL-18 and IL-18BP serum concentrations in patients with primary Sjögren's syndrome

The objectives of this study were to examine the serum levels of interleukin (IL)-37 and its clinical association in patients with primary Sjögren's syndrome (pSS) and to investigate whether or not IL-37 participates in the regulation of the pathogenesis of pSS. ELISA was used to analyse the serum levels of IL-37, total IL-18 and IL-18 binding protein (IL-18BP). The level of free IL-18 was calculated based on the mass action law. The correlations between the IL-37 serum levels with the laboratory values and the total IL-18 and IL-18BP serum levels were analyzed by a Spearman's correlation test. The serum levels of IL-37 in the patients with pSS were significantly increased compared with the healthy controls (HCs). The levels were especially elevated in the patients with pSS with positive anti-Ro/SSA and/or anti-La/SSB antibodies. Furthermore, the patients with pSS showed high serum levels of total IL-18, free IL-18 and IL-18BP compared with the HCs. Strikingly, the IL-37 levels were significantly positively correlated with the antibody levels in the patients with pSS, including rheumatoid factor, anti-Ro/SSA, and anti-La/SSB and the total IL-18 and IL-18BP serum levels. The serum levels of IL-37, which were correlated with antibody production and the serum levels of total IL-18 and IL-18BP, were elevated in the patients with pSS. IL-37, an important anti-inflammatory cytokine, may participate in the regulation of the pathogenesis of pSS.

Clinical associations of IL-10 and IL-37 in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by the development of autoantibodies to nuclear antigens and inflammatory responses mediated by multiple cytokines. Although previous studies have determined clinical associations between SLE and the anti-inflammatory cytokines IL-10 and IL-37, their role in the disease, or their potential as biomarkers, remains unclear. We examined serum levels of IL-10 and IL-37 in a large cohort of SLE patients, with detailed longitudinal clinical data. We demonstrate a statistically significant association of serum IL-10 with disease activity, with higher levels in active compared to inactive disease. High first visit IL-10 was predictive of high subsequent disease activity; patients with IL-10 in highest quartile at first visit were 3.6 times more likely to have active disease in subsequent visits. Serum IL-37 was also higher in SLE patients compared to control, and was strongly associated with Asian ethnicity. However, IL-37 was not statistically significantly associated with disease activity. IL-37 was significantly reduced in patients with organ damage but this association was attenuated in multivariable analysis. The data suggest that IL-10, but not IL-37, may have potential as a biomarker predictive for disease activity in SLE.

Effects of salvianolate on bone metabolism in glucocorticoid-treated lupus-prone B6.MRL-Fas (lpr) /J mice

Aim

To investigate the bone-protective effects of salvianolate (Sal), a total polyphenol from Radix Salviae miltiorrhizae, on bone tissue in the spontaneous lupus-prone mouse model, B6.MRL-Fas^lpr/J, undergoing glucocorticoid (GC) treatment.

Methods

Fifteen-week-old female B6.MRL-Fas^lpr/J mice were administered either a daily dose of saline (lupus group), prednisone 6 mg/kg (GC group), Sal 60 mg/kg (Sal group); or GC plus Sal (GC + Sal group) for a duration of 12 weeks. Age-matched female C57BL/6J wild-type (WT) mice were used for control. Micro-computed tomography assessments, bone histomorphometry analysis, bone biomechanical test, immunohistochemistry and immunoblotting analysis for bone markers, and renal histology analysis were performed to support our research endeavor.

Results

Lupus mice developed a marked bone loss and deterioration of mechanical properties of bone due to an increase in bone resorption rather than suppression of bone formation. GC treatment strongly inhibited bone formation in lupus mice. Sal treatment significantly attenuated osteogenic inhibition, and also suppressed hyperactive bone resorption, which recovered the bone mass and mechanical properties of bone in both the untreated and GC-treated lupus mice.

Conclusion

The data support further preclinical investigation of Sal as a potential therapeutic strategy for the treatment of systemic lupus erythematosus-related bone loss.

Elevated plasma interleukin-37 levels in systemic lupus erythematosus patients

This study aims to evaluate the plasma interleukin (IL)-37 levels in systemic lupus erythematosus (SLE) patients, as well as its association with major clinical and laboratory features. Ninety consecutively selected SLE patients and 78 community-based healthy controls were recruited. Plasma IL-37 levels were detected by enzyme-linked immunosorbent assay (ELISA). The major clinical and laboratory data of SLE patients were also recorded. The results showed that IL-37 level was significantly higher in the plasma of patients with SLE compared with controls ( p = 0.028). The correlation of plasma IL-37 levels with major clinical and laboratory data of SLE patients was also analyzed, and the results showed that anti-Sm and anti-RNP were negatively associated with plasma IL-37 levels of SLE patients, while C3 was positively associated with plasma IL-37 levels of SLE patients. No significant associations of IL-37 with other clinical and laboratory parameters were observed (all p > 0.05). In conclusion, elevated plasma IL-37 level and its associations with anti-Sm, anti-RNP and C3 in SLE patients suggest that IL-37 may be implicated in this disease.

Increased serum level of IL-37 in patients with multiple sclerosis and neuromyelitis optica

Multiple sclerosis (MS) is a common autoimmune disease of central nervous system in which neurodegenerative and inflammatory mechanisms cause alternate neurological impairments. Many inflammatory and anti-inflammatory cytokines were suggested as contributor in MS pathogenesis, and the balance between these opposing cytokines can regulate MS severity. IL-37, an anti-inflammatory cytokine, is the most recently identified member of IL-1 family, which acts as a natural inhibitor of innate immunity. However, the role of IL-37 in MS has not investigated so far. Therefore, in this study, we aimed to measure serum level of IL-37 in patients with relapsing remitting multiple sclerosis (RRMS) and neuromyelitis optica (NMO). In a case-control study, plasma was collected from healthy controls (n = 49) and also patients with RRMS (n = 122) and NMO (n = 31). Serum level measurement of IL-37 was performed using enzyme-linked immunoassay (ELISA) method. The serum levels of IL-37 were 247.46 ± 74.02 and 312.00 ± 86.72 and 114.63 ± 20.58 in RRMS and NMO patients and healthy controls, respectively, showing statistically significant difference between them (P = 0.00). Furthermore, we found a positive correlation between the serum levels of IL-37 and EDSS of patients (r = +0.31 and P = 0.00). In summary, the serum level of IL-37 was found to be significantly increased in MS patients compared to healthy controls. Furthermore, the mean serum level of IL-37 was correlated with disease severity. This suggests that IL-37 may be part of a feed-back loop to control underlying inflammation in MS pathogenesis. However, further studies will be required to indicate exact role of IL-37 in the MS pathomechanisms.