Ectoine protects corneal epithelial survival and barrier from hyperosmotic stress by promoting anti-inflammatory cytokine IL-37

PURPOSE

To explore novel role and molecular mechanism of a natural osmoprotectant ectoine in protecting corneal epithelial cell survival and barrier from hyperosmotic stress.

METHODS

Primary human corneal epithelial cells (HCECs) were established from donor limbus. The confluent cultures in isosmolar medium were switched to hyperosmotic media (400-500 mOsM), with or without ectoine or rhIL-37 for different time periods. Cell viability and proliferation were evaluated by MTT or WST assay. The integrity of barrier proteins and the expression of cytokines and cathepsin S were evaluated by RT-qPCR, ELISA, and immunostaining with confocal microscopy.

RESULTS

HCECs survived well in 450mOsM but partially damaged in 500mOsM medium. Ectoine well protected HCEC survival and proliferation at 500mOsM. The integrity of epithelial barrier was significantly disrupted in HCECs exposed to 450mOsM, as shown by 2D and 3D confocal immunofluorescent images of tight junction proteins ZO-1 and occludin. Ectoine at 5-20 mM well protected these barrier proteins under hyperosmotic stress. The expression of TNF-α, IL-1β, IL-6 and IL-8 were dramatically stimulated by hyperosmolarity but significantly suppressed by Ectoine at 5-40 mM. Cathepsin S, which was stimulated by hyperosmolarity, directly disrupted epithelial barrier. Interestingly, anti-inflammatory cytokine IL-37 was suppressed by hyperosmolarity, but restored by ectoine at mRNA and protein levels. Furthermore, rhIL-37 suppressed cathepsin S and rescued cell survival and barrier in HCECs exposed to hyperosmolarity.

CONCLUSION

Our findings demonstrate that ectoine protects HCEC survival and barrier from hyperosmotic stress by promoting IL-37. This provides new insight into pathogenesis and therapeutic potential for dry eye disease.

Novel insights into IL-37: an anti-inflammatory cytokine with emerging roles in anti-cancer process

Interleukin-37 (IL-37) is a newly discovered member of IL-1 family. The cytokine was proved to have extensive protective effects in infectious diseases, allergic diseases, metabolic diseases, autoimmune diseases and tumors since its discovery. IL-37 was mainly produced by immune and some non-immune cells in response to inflammatory stimulus. The IL-37 precursors can convert into the mature forms after caspase-1 cleavage and activation intracellularly, and then bind to Smad-3 and transfer to the nucleus to inhibit the production and functions of proinflammatory cytokines; extracellularly, IL-37 binds to cell surface receptors to form IL-37/IL-18Rα/IL-1R8 complex to exert immunosuppressive function via inhibiting/activating multiple signal pathways. In addition, IL-37 can attenuate the pro-inflammatory effect of IL-18 through directly or forming an IL-37/IL-18BP/IL-18Rβ complex. Therefore, IL-37 has the ability to suppress innate and acquired immunity of the host, and effectively control inflammatory stimulation, which was considered as a new hallmark of cancer. Specifically, it is concluded that IL-37 can inhibit the growth and migration of tumor cells, prohibit angiogenesis and mediate the immunoregulation in tumor microenvironment, so as to exert effective anti-tumor effects. Importantly, latest studies also showed that IL-37 may be a novel therapeutic target for cancer monitoring. In this review, we summarize the immunoregulation roles and mechanisms of IL-37 in anti-tumor process, and discuss its progress so far and potential as tumor immunotherapy.

Imbalanced IL-37/TNF-α/CTSS signaling disrupts corneal epithelial barrier in a dry eye model in vitro

PURPOSE

To explore novel role and molecular mechanism of a natural anti-inflammatory cytokine interleukin (IL) 37 in preventing corneal epithelial barrier disruption from hyperosmolar stress as can occur in dry eye disease.

METHODS

Primary human corneal epithelial cells (HCECs) were cultured from fresh donor limbal explants. An in vitro dry eye model with hyperosmolar stress was established by switching HCECs from isosmolar (312mOsM) to hyperosmolar medium (350-500 mOsM), and some cells were treated with rhIL-37 or rhTNF-α, for different periods (2-48 h). The expression of cytokines and cathepsin S, and barrier protein integrity were evaluated by RT-qPCR, ELISA, and immunofluorescent staining with confocal microscopy.

RESULTS

The integrity of epithelial barrier was significantly disrupted in HCECs exposed to hyperosmolar medium, as shown by immunofluorescent images of tight junction (TJ, ZO-1, occludin and claudin-1) and adheren junction (E-cadherin) proteins. TNF-α accentuated hyperosmolar-induced disruption of TJ barrier functional integrity whereas exposure to IL-37 blunted or even reversed these changes. Cathepsin S, encoded by CTSS gene, was found to directly disrupt epithelial barrier integrity. Interestingly, CTSS expression was significantly induced by TNF-α and hyperosmolarity, while exogenous rhIL-37 inhibited TNF-α and CTSS expression at mRNA and protein levels following hyperosmolar stress. Furthermore, rhIL-37 restored barrier protein integrity, observed in 2D and 3D confocal immunofluorescent images, in HCECs under hyperosmolar stress.

CONCLUSION

Our findings demonstrate a novel signaling pathway by which anti-inflammatory cytokine IL-37 prevents corneal epithelial barrier disruption under hyperosmotic stress via suppressing TNF-α and CTSS expression. This study provides new insight into mechanisms protecting corneal barrier in dry eye disease.

Interleukin-37, vascular endothelial growth factor A, and transforming growth factor-β1: promising biomarkers in primary immune thrombocytopenia

BACKGROUND

Immune thrombocytopenic purpura (ITP) is an acquired autoimmune hematologic disorder with heterogeneous bleeding manifestations. Many biomarkers such as interleukin-37 (IL-37), vascular endothelial growth factor A (VEGFA), and transforming growth factor-β1 (TGFß1) have a role in immunity, inflammation, and megakaryopoiesis.

METHODS

In the present study, immunoassay of interleukin-37 as well as the gene expression of vascular endothelial growth factor A and transforming growth factor-β1 were done in 60 primary ITP patients, 60 thrombocytopenia patients, and 60 healthy volunteers.

RESULTS

Increased IL-37 level and down regulation of VEGFA and TGFß1gene expression were detected in primary ITP patients when compared with other groups. A negative correlation was observed between IL-37 and platelet count. However, a positive correlation was observed between VEGFA and TGFß1 levels and platelet count.

CONCLUSION

Current results suggested that interleukin-37, vascular endothelial growth factor A, and transforming growth factor-β may be promising indicators in the diagnosis of ITP and detection of disease severity with inexpensive and cost-effectiveness compared to the benefits.

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.

Counteractive Effects of IL-33 and IL-37 on Inflammation in Osteoarthritis

Osteoarthritis (OA) is a chronic inflammatory disease where pro-inflammatory cytokines, damage-associated molecular patterns (DAMPs), and macrophages play a crucial role. However, the interactive role of these mediators, the exact cause precipitating OA and definitive treatment for OA are not known yet. Moreover, the interactive role of interleukin (IL)-33 and IL-37 with other factors in the pathogenesis of OA has not been discussed elaborately. In this study, we analyzed the expression of IL-33 and IL-37 in human OA knee and hip joint cartilage tissues. The effect of increased DAMPs, IL-33, and IL-37 on IL-6, tumor necrosis factor (TNF)-α, toll-like receptors (TLRs), and matrix metalloproteinases (MMPs) expression was delineated using human normal and osteoarthritic chondrocytes. The effect of anti-inflammatory cytokine IL-37 on various mediators of inflammation in the presence of IL-33, rHMGB-1, and LPS was investigated to delineate the effects of IL-37. Further, the effects of blocking IL-33 downstream signaling and the effects of IL-33 and IL-37 on macrophage polarization were assessed along with examining the macrophage phenotypes in human OA cartilage tissues. The results of this study revealed increased expression of IL-33 in OA cartilage and that IL-33 increases IL-6, TNF-α, TLRs, and MMPs expression and favors phenotypic conversion towards the M1 phenotype, while IL-37 and blocking IL-33 receptor ST2 have opposite effects. Overall, the results suggest that blocking IL-33 and increasing IL-37 act synergistically to attenuate inflammation and might serve as potential therapeutics in OA.

IL-33, IL-37, and Vitamin D Interaction Mediate Immunomodulation of Inflammation in Degenerating Cartilage

Chronic joint inflammation due to increased secretion of pro-inflammatory cytokines, the accumulation of inflammatory immune cells (mainly macrophages), and vitamin D deficiency leads to cartilage degeneration and the development of osteoarthritis (OA). This study investigated the effect of vitamin D status on the expression of mediators of inflammation including interleukin (IL)-33, IL-37, IL-6, tumor necrosis factor (TNF)-α, toll-like receptors (TLRs), damage-associated molecular patterns (DAMPs), and matrix metalloproteinases (MMPs) in degenerating the cartilage of hyperlipidemic microswine. Additionally, in vitro studies with normal human chondrocytes were conducted to investigate the effect of calcitriol on the expression of IL-33, IL-37, IL-6, TNF-α, TLRs, DAMPs, and MMPs. We also studied the effects of calcitriol on macrophage polarization using THP-1 cells. The results of this study revealed that vitamin D deficiency is associated with an increased expression of IL-33, IL-37, IL-6, TNF-α, TLRs, DAMPs, and MMPs, while vitamin D supplementation is associated with a decreased expression of the former. Additionally, vitamin D deficiency is associated with increased M1, while vitamin D-supplemented microswine cartilage showed increased M2 macrophages. It was also revealed that calcitriol favors M2 macrophage polarization. Taken together, the results of this study suggest that modulating expression of IL-33, IL-6, TNF-α, TLRs, DAMPs, and MMPs with vitamin D supplementation may serve as a novel therapeutic to attenuate inflammation and cartilage degeneration in osteoarthritis.

Roles of IL-1 and IL-10 family cytokines in the progression of systemic lupus erythematosus: Friends or foes?

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease of unknown etiology that can affect nearly every organ system in the body. Besides genetic and environmental factors, unbalanced pro-inflammatory and anti-inflammatory cytokines contribute to immune dysregulation, trigger an inflammatory response, and induce tissue and organ damage. Inflammatory responses in SLE can be promoted and/or maintained by the availability of cytokines that are overproduced systemically and/or in local tissues. Several key cytokines have been considered potential targets for the reduction of chronic inflammation in SLE. Recent studies indicated that dysregulated production of several cytokines, including those of the IL-1 family and IL-10 family, orchestrate immune activation and self-tolerance, play critical roles in the pathogenesis of SLE. Among IL-1 family cytokines, IL-1, IL-18, IL-33, IL-36, IL-37, and IL-38 had been the most thoroughly investigated in SLE. Additionally, IL-10 family cytokines, IL-10, IL-20, IL-22, IL-26, IL-28, and IL-29 are dysregulated in SLE. Therefore, a better understanding of the initiation and progression of SLE may provide suitable novel targets for therapeutic intervention. In this review, we discuss the involvement of inflammation in the pathogenesis of SLE, with a focus on IL-1 family and IL-10 family cytokines, and highlight pathophysiological approaches and therapeutic potential for treating SLE.

Analysis of Serum Interleukin-37 Level and Prognosis in Patients with ACS

Objective

To explore the level of serum interleukin-37 in patients with acute coronary syndrome (ACS) and its prognostic value.

Methods

Altogether, 121 continuous ACS cases from September 2017 to June 2020 were selected as the research group (RG), and 107 healthy individuals during the same period were obtained as the control group (CG). ELISA was applied to test IL-37 in the serum of the CG and the RG. Chemiluminescence immunoassay was applied to test NT-pro BNP and hs-cTnI in each group and immune scattering turbidimetry to test hs-CRP. The correlation of IL-37 with serum NT-pro BNP, hs-cTnI, and CRP was analyzed, and the value of IL-37 in diagnosis and prognosis prediction of patients with ACS was tested. Logistic regression was applied to test the independent risk factors affecting poor prognosis of patients with ACS.

Results

IL-37 was poorly expressed in patients with ACS, which had a high diagnostic value for ACS (sensitivity: 94.39%, specificity: 74.38%, and area under curve: 0.945). There was a negative correlation of IL-37 with serum NT-pro BNP, hs-cTnI, and CRP. IL-37 in patients with poor prognosis was markedly declined compared with that of patients with good prognosis, and the predicted AUC was 0.965. Logistic regression revealed that low IL-37, diabetes, high CRP, NT-pro BNP, and hs-cTnI in the blood were independent risk factors for poor prognosis in patients with ACS.

Conclusion

IL-37 is low expressed in patients with ACS, which has a good diagnostic and prognostic value for ACS, and may be applied as an important marker for the prediction of patients with ACS.

Immunomodulation of IL-33 and IL-37 with Vitamin D in the Neointima of Coronary Artery: A Comparative Study between Balloon Angioplasty and Stent in Hyperlipidemic Microswine

Inflammation is a major contributor to the development and progression of atherosclerosis. Interleukin (IL)-33 and IL-37, members of the IL-1 family, modulate inflammation, with IL-33 having a pro-inflammatory effect and IL-37 having anti-inflammatory properties. IL-37 is constitutively expressed at low levels but upregulated in inflammatory contexts. The aim of this study was to evaluate the effect of vitamin D on the expression of IL-33, IL-37, macrophages, and caspase-1 in the neointimal tissue of coronary artery in Yucatan microswine with vitamin D deficient, sufficient, and supplemented status. The intimal injury was induced by balloon angioplasty and stenting in the coronary artery, and tissues were harvested after 6 months. The expression of various proteins of interest was evaluated by immunostaining. Increased expression of IL-33 and IL-37 in the neointimal tissue of the vitamin D deficient, as compared to the sufficient and supplemented microswine, as revealed by histological evaluation and semi-quantitative analysis, suggested the immunomodulatory effect of vitamin D on the expression of IL-33 and IL-37. The minimal expression or absence of IL-33 and IL-37 expression in stented arteries is suggestive of an attenuated inflammatory response in stented arteries, compared to balloon angioplasty. The decreased IL-33 expression in the sufficient and supplemented microswine could be a potential mechanism for controlling the inflammatory process and neointima formation leading to attenuated luminal narrowing of the coronary artery. Overall, these results support supplementation of vitamin D to attenuate inflammation, neointima formation, and restenosis.

The emerging role of Interleukin 37 in bone homeostasis and inflammatory bone diseases

Interleukin 37 (IL-37) is a newly identified cytokine that belongs to the IL-1 family. Unlike other members of the IL-1 family, it has been demonstrated that IL-37 possesses anti-inflammatory characteristics in both innate and acquired immune responses. Recently, significant progress has been made in understanding the role of IL-37 in inflammatory signaling pathways. Meanwhile, IL-37 has also attracted more and more attention in bone homeostasis and inflammatory bone diseases. The latest studies have revealed that IL-37 palys an essential role in the regulation of osteoclastogenesis and osteoblastogenesis. The levels of IL-37 are abnormal in patients with inflammatory bone diseases such as rheumatoid arthritis (RA), osteoarthritis (OA), ankylosing spondylitis (AS), and periodontitis. In addition, in vivo studies have further confirmed that recombinant IL-37 treatment displayed therapeutic potential in these diseases. The present review article aims to provide an overview describing the biological functions of IL-37 in bone homeostasis and inflammatory bone diseases, thus shedding new light on a novel therapeutic strategy in the future.

IL-37 Was Involved in Progress of Acute Myeloid Leukemia Through Regulating IL-6 Expression

Background

Interleukin-37, which was discovered in 2000, is a natural suppressor of immune and inflammatory responses. Recent studies reported that IL-37 was abnormally expressed in several tumor patients, including those with hepatocellular carcinoma, gastric cancer, lung cancer, colon cancer, epithelial ovarian cancer, and multiple myeloma. However, the expression and potential function of IL-37 in leukemia remain unknown.

Objective

The aim of this study was to evaluate IL-37 as a prognostic factor and its possible mechanism of action.

Methods

Polymerase chain reaction products were analyzed by agarose gel electrophoresis and were purified and subsequently sequenced by a genetic testing laboratory. Human PBMC was purified from whole blood samples by using Ficoll-Paque PLUS. The concentrations of human IL-37 and human IL-6 were measured using enzyme-linked immunosorbent assay (ELISA) kits.

Results

IL-37, especially isoform b and d, was expressed in the bone marrow of AML, CML, ALL, and CLL. Importantly, IL-37 expression was downregulated in newly diagnosed AML patients and restored in patients in complete remission. Moreover, a significant association was found between IL-37 expression and NPM1 mutation or possible prognosis evaluated by karyotype and gene mutation. Further analysis revealed that IL-37 expression was negatively correlated with IL-6 expression. With regard to the mechanism, recombinant human IL-37 could suppress IL-6 expression stimulated by LPS in PBMC of AML patients.

Conclusion

Our study suggested that IL-37 may be an important prognostic factor in AML and is involved in AML via the IL-6 signaling pathway, indicating that IL-37 is an innovative research strategy for AML pathogenesis and therapy.

What is the role of pre-operative blood parameters in forecasting varicocelectomy success?

BACKGROUND

We aimed to examine the effects of pre-operative blood values on varicocelectomy success.

MATERIALS AND METHODS

A total of 130 patients who underwent varicocelectomy in our clinic were retrospectively analyzed. Operation success was defined as the return of all semen parameters (concentration, progressive motility, and morphology) to normal values 6 months after surgery. The patients were separated as two groups as benefiting from the treatment (Group A) and not (Group B).

RESULTS

The best cut-off value for the neutrophil/lymphocyte ratio (NLR), which can predict varicocelectomy success, was assigned to be 2.27, with AUC of 0.859 (%95 CI 0.795-0.922). The highest sensitivity and specificity were 0.857 and 0.731 (p < 0.001). The best cut-off value for the mean platelet volüme (MPV) value, which can predict varicocelectomy success, was assigned to be 9.45, with AUC of 0.729 (%95 CI 0.639-0.819). The highest sensitivity and specificity were 0.655 and 0.635 (p < 0.001). Binary logistic regression analysis showed NLR ratio (odds ratio (OR): 11.2, p < 0.001) and MPV (OR: 2.65, p = 0.002) parameters as independent predictive factors in predicting varicocelectomy success.

DISCUSSION AND CONCLUSION

Our study showed that low NLR ratio (≤2.27) and high MPV (≥9.45) ratio levels may be a useful pre-operative predictive tool in identifying men who benefit most from varicocelectomy in infertile patients with varicocoele.

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.

The effect of laparoscopic and open surgery on oxidative DNA damage and IL-37 in children with acute appendicitis

BACKGROUND

Although laparoscopic appendectomy (LA) is considered to be minimally invasive compared with open appendectomy (OA), there are few studies showing this in terms of cytokines and oxidative stress markers.

AIM

LA and OA techniques have been compared in terms of different conditions such as operation time and complication rate. Here, we compared how oxidative DNA damage and some cytokines levels change in relation to LA and OA.

METHOD

This study was performed in children diagnosed with acute appendicitis in our hospital. The study was conducted on 30 children with acute appendicitis in each group. Oxidative DNA damage and malondialdehyde levels were determined by high-performance liquid chromatography, and interleukin-1β, interleukin-37, ischaemia-modified albumin and total thiol levels were determined by enzyme-linked immunosorbent assays.

RESULTS

There was a dramatic decrease in ischaemia-modified albumin (IMA) levels after LA. However, there were no statistically significant differences in pre- and postoperative IMA levels in the OA group. Oxidative DNA damage and malondialdehyde levels were low significantly according to preoperative levels after the LA and OA. Total thiol levels were high in children who underwent LA while they were low after OA. In addition, postoperative interleukin-1β levels were low in both groups. Furthermore, IL-37 levels postoperatively were low in the LA group, while there was no significant change in the OA group.

CONCLUSION

LA had a more positive effect on oxidative DNA damage, IL-1β and IL-37 than the OA. In addition, surgical stress was reduced with LA.

The novel role of IL-37 to enhance the anti-inflammatory response of regulatory T cells in patients with peripheral atherosclerosis

OBJECTIVES

Regulatory T cells (Tregs) mediate immunomodulation and protect against atherosclerosis. It is considered that reducing the amount of pro-inflammatory mediators could be achieved by enhancing the anti-inflammatory response, and this may be considered one of the main targets for therapy development. The inhibitory cytokines secreted by Tregs mainly include interleukin-10 (IL-10) and transforming growth factor-beta (TGF-β). Based on its known immunosuppressive involvement with other inflammatory disorders, we hypothesized that the newly characterized cytokine interleukin-37 (IL-37) might be associated with the inhibitory functions of Treg in atherosclerosis. Immune regulatory functions of IL-37 have not been completely clarified. Accordingly, we speculated that IL-37 might play a regulatory role in the immunosuppression of Tregs in atherosclerotic disease.

METHODS

Real-time polymerase chain reaction and enzyme linked immunosorbent assay were used to test gene expression and protein levels of IL-37 in peripheral blood and localized freshly resected arterial tissues from 84 patients with peripheral arterial occlusive disease and 50 non-atherosclerotic subjects. Results were correlated to disease hallmarks. We also evaluated the ability of recombinant IL-37 to modulate Treg cytokine secretion and T cell inhibition in relation to atherosclerotic disorder in vitro.Results: Our results revealed that IL-37 was increased in patients with chronic lower limb atherosclerotic ischemia, compared to non-atherosclerotic controls. In addition, the expression levels of circulating IL-37 correlated with disease severity of chronic lower limb ischemia. Supplementation with rIL-37 augmented levels of released IL-10 and TGF-β in supernatants of T cells co-cultured with Tregs in the enrolled patients.Conclusions: Results suggest a role for IL-37 in mediating anti-inflammatory functions in the atherosclerotic process, potentially involving enhancement of Treg inhibitory function and anti-inflammatory cytokine secretion with a particularly marked direct response in severe disease.

4-methylumbelliferone inhibits clonogenic potency by suppressing high molecular weight-hyaluronan in fibrosarcoma cells

The inflammatory response is closely associated with cancer cell survival. It has been reported that inflammatory signaling cascades promote tumor survival and exert detrimental effects in normal tissue. Hyaluronans have different cellular functions depending on their molecular weights and high molecular weight-hyaluronan (HMW-HA) exhibits anti-inflammatory effects. A previous study determined that the co-administration of 4-methylumbelliferone (4-MU) and X-ray irradiation enhanced anti-tumor and anti-inflammatory effects in HT1080 human fibrosarcoma cells. However, many mechanisms underlie the effect of hyaluronan molecular weight on cells and the induction of anti-inflammatory effects via 4-MU. The present study aimed to determine the relationship between hyaluronan synthesis inhibition by 4-MU and its anti-inflammatory and radio-sensitizing effect in the context of hyaluronan molecular weight. The hyaluronan concentration following 2 Gy X-ray irradiation and/or 4-MU administration was analyzed via ELISA. Additionally, the mRNA expressions of hyaluronan synthase (HAS) by 4-MU and various inflammatory cytokines and interleukins (IL) following exogenous HMW-HA administration were evaluated via Reverse transcription-quantitative PCR. Invasive potential was assessed by matrigel transwell assays and cell survival following exposure to 4-MU with HMW-HA was determined using a clonogenic potency assay. The results of the present study demonstrated that 4-MU suppressed HMW-HA production by inhibiting HAS2 and HAS3 expression. In addition, the surviving fraction of fibrosarcoma cells were rescued from the cell-killing effect of 4-MU via the exogenous administration of HMW-HA. The mRNA levels of certain inflammatory cytokines, including IL-1α, IL-36γ and IL-37 were elevated following HMW-HA administration. The surviving fraction of cells irradiated with 2 Gy alone did not increase following exogenous HMW-HA administration. The results of the present study indicated that the radio-sensitizing effect of 4-MU and the inhibitory effect on hyaluronan synthesis were not closely associated. It was also revealed that IL-1α, IL-36γ and IL-37 were associated with the cell-killing effect of 4-MU in HT1080 cells.

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.

Circulating concentration of interleukin-37 in Helicobacter pylori-infected patients with peptic ulcer: Its association with IL-37 related gene polymorphisms and bacterial virulence factor CagA

The immunopathologic responses play a major role in the development of H. pylori (HP)-related gastrointestinal diseases. IL-37 is an anti-inflammatory cytokine with potent suppressive effects on innate and adaptive immune responses. Here, we investigated the IL-37 levels and two single nucleotide polymorphisms (SNPs) including rs3811047 and rs2723176 in IL-37 gene in HP-infected peptic ulcer (PU) patients to identify any relationship. Three groups, including 100 HP-infected PU patients, 100 HP-infected asymptomatic (AS) subjects and 100 non-infected healthy control (NHC) subjects were enrolled to study. Serum IL-37 levels and the genotyping at rs3811047 and rs2723176 were determined using ELISA and SSP-PCR methods, respectively. Significantly higher IL-37 levels were observed in PU patients compared with AS and NHC groups (P < 0.0001). In both PU and AS groups, the CagA⁺ HP-infected participants displayed higher IL-37 levels compared with those infected with CagA^- strains (P < 0.0001). There were significant differences between PU, AS and NHC groups regarding the distribution of genotypes and alleles at rs3811047 and rs2723176 SNPs. The genotype GG and allele G at IL-37 rs3811047 SNP, and the genotype CC and allele C at IL-37 rs2723176 SNP more frequently expressed in PU patients than total healthy subjects (AS + NHC groups) and were associated with an increased risk of PU development (genotype GG: RR = 3.08, P < 0.009; allele G: RR = 2.94, P < 0.01; genotype CC: RR = 5, P < 0.01; and allele C: RR = 5.0, P < 0.02, respectively). The PU patients with allele A at IL-37 rs2723176 SNP expressed higher amounts of IL-37 compared with patients carried allele C at the same position (P < 0.05). In AS carriers and NHC individuals, the IL-37 levels in subjects carried genotype AA or allele A at IL-37 rs2723176 SNP were higher than those carried genotype CC or allele C at the same location (P < 0.01 and P < 0.02 for AS group; P < 0.0001 and P < 0.001 for NHC subjects, respectively). The increased IL-37 levels may be considered as a valuable marker of PU development in HP-infected individuals. The SNPs rs3811047 and rs2723176 were associated with PU development. The CagA status of HP and IL-37 rs2723176 SNP may affect the IL-37 levels.

Interleukin‑37 is increased in peripheral blood mononuclear cells of coronary heart disease patients and inhibits the inflammatory reaction

It has been universally acknowledged that interleukin-37 (IL-37) has an immunosuppressive effect on various inflammatory disorders. However, whether IL-37 participates in the acute inflammation associated with coronary heart disease (CHD) has not yet been clarified. In the present study, the association between the serum levels of IL-37 and the clinical indexes of CHD were analysed. In addition, the anti-inflammatory effects of IL-37 on peripheral blood mononuclear cells (PBMCs) were studied in CHD patients. PBMCs from 46 healthy controls (HCs) and 92 CHD patients were cultured in vitro and stimulated using the recombinant IL-37 protein. The protein levels, as well as the mRNA expression of inflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-17) were analysed by enzyme-linked immunosorbent assay (ELISA) and real-time polymerase chain reaction (RT-PCR). Spearman's correlation test was performed to examine the association between the serum level of IL-37 and the levels of pro-inflammatory cytokines, certain clinical indexes, and disease activity during CHD. Compared to the HCs, the CHD patients, especially those with acute myocardial infarction, exhibited higher levels of IL-37 in their PBMCs and sera. Serum levels of IL-37 were associated with the levels of IL-17, IL-6, and TNF-α, and clinical indexes such as the left ventricular ejection fraction (LVEF), amino-N-terminal pro-plasma brain natriuretic peptide (NT-proBNP) levels, and cardiac troponin T (cTnT) levels in CHD patients. Compared to the HC group, the production of inflammatory cytokines such as IL-17, IL-6, TNF-α, and IL-1β increased in the PBMCs of CHD patients and significantly decreased after the stimulation of the cells with recombinant IL-37. The IL-37 levels in CHD patients were high, and were correlated with the levels of CHD-related pro-inflammatory cytokines and disease activity. Notably, the expression of CHD-related pro-inflammatory cytokines in the PBMCs of CHD patients decreased following the stimulation of the cells with recombinant IL-37, indicating that IL-37 exerts anti-inflammatory effects during CHD.

Effects of Er,Cr:YSGG and Diode Lasers on Clinical Parameters and Gingival Crevicular Fluid IL-1β and IL-37 Levels in Generalized Aggressive Periodontitis

Aim

The objective of the current study is to analyze the correlation between cytokine levels and periodontal parameters in aggressive periodontitis patients before and after periodontal treatment that was performed by using two different laser therapies.

Materials and Methods

Twenty-six generalized aggressive periodontitis patients were treated with three different methods (SRP, SRP+diode laser, and SRP+Er,Cr:YSGG laser) applied to three different half-jaws in the same patients. Pre- and posttreatment clinical periodontal parameters and GCF IL-1β and IL-37 levels were measured.

Results

There was a statistically significant decrease (p < 0.05) between pretreatment and posttreatment clinical periodontal parameters and IL-1β and IL-37 levels. When the reduction rates of IL-37 and IL-1β levels after treatment were evaluated, the decrease in IL-37 and IL-1β levels after treatment was lowest in the SRP group and highest in the SRP+Er,Cr:YSGG group. In addition, the amount of decrease in IL-1β in SRP+diode and SRP+Er,Cr:YSGG groups was found to be higher than that in IL-37. Furthermore, there was a positive correlation between IL-37 and IL-1β in all groups (p < 0.01).

Conclusion

Er,Cr:YSGG laser is more effective than diode laser for the treatment of aggressive periodontitis. IL-37 and IL-1β are cytokines that function together and thus must be evaluated together.

Role of IL-37 in Cardiovascular Disease Inflammation

Inflammation is closely related to the pathogenesis and prognosis of cardiovascular disease (CVD). Interleukin-37 (IL-37), an anti-inflammatory IL-1 family cytokine, shifts cytokine expression from pro- to anti-inflammation via regulation of macrophage polarization and lipid metabolism. In macrophages, IL-37 functions through both intracellular and extracellular pathways to regulate the activity of NF-kB and PTEN as well as the expression of cytokines, including IL-1β, IL-6, and IL-10. Moreover, IL-37 levels are increased in the serum of patients with heart failure, atherosclerosis, and acute coronary syndrome with no evidence of anti-inflammatory effects. However, transgenic overexpression of IL-37 improves cardiac infarct and attenuates atherosclerosis plaque expansion. Hence, it is worthwhile to investigate the precise mechanism and role of IL-37 in the pathogenesis of CVD, which may provide deeper understanding of the inflammatory response in this context. This review summarizes the regulatory role of IL-37 in systematic inflammation induced by CVD and highlights recent advancements in the clinical application of IL-37 as a therapeutic agent or biomarker for diagnosis of CVD.

Production of functional human interleukin 37 using plants

KEY MESSAGE

We demonstrate for the first time that a fully bioactive human IL-37, a newly discovered cytokine acting as a fundamental inhibitor of innate immunity, can be recombinantly produced in plant cells. Interleukin 37 (IL-37), a newly discovered member of the interleukin (IL)-1 family of cytokines, plays a pivotal role in limiting innate inflammation and suppressing acquired immune responses, thus holding high potential for treating a wide array of human inflammatory and autoimmune disorders. In this study, we have developed transgenic plants as a novel expression platform for production of human IL-37 (IL-37). Plant transformation vectors synthesizing various forms of the b isoform of IL-37, including an unprocessed full-length precursor form (proIL-37b), a mature form (matIL-37b) and an IL-37 fusion protein in which IL-37b was fused to soybean agglutinin (SBA-IL-37b), have been constructed and introduced into tobacco plants. The expression of all forms of IL-37b was driven by a strong constitutive 35S promoter. Transgenic tobacco plants were generated with each of these constructs. Depending on the form of IL-37b being produced, the expression level of proIL-37b reached approximately 1% of TSP, while matIL-37b expression was substantially lower (0.01% TSP). Fusion to SBA substantially increased the expression of matIL-37b, with the expression level of fusion protein accounting for 1% of TSP. Functional analysis using a cell-based in vitro assay showed that plant-made matIL-37b and proIL-37b are both biologically active, but plant-made matIL-37b exhibited significantly greater biological activity than proIL-37b. These results demonstrate that plants have great potential of being a green bioreactor for low-cost, large-scale production of biologically active IL-37.

Interleukin-37 inhibits osteoclastogenesis and alleviates inflammatory bone destruction

Excessive osteoclast formation is one of the important pathological features of inflammatory bone destruction. Interleukin‐37 (IL‐37) is an anti‐inflammatory agent that is present throughout the body, but it displays low physiological retention. In our study, high levels of the IL‐37 protein were detected in clinical specimens from patients with bone infections. However, the impact of IL‐37 on osteoclast formation remains unclear. Next, IL‐37 alleviated the inflammatory bone destruction in the mouse in vivo. We used receptor activator of nuclear factor‐κB ligand and lipopolysaccharide to trigger osteoclastogenesis under physiological and pathological conditions to observe the role of IL‐37 in this process and explore the potential mechanism of this phenomenon. In both induction models, IL‐37 exerted inhibitory effects on osteoclast differentiation and bone resorption. Furthermore, IL‐37 decreased the phosphorylation of inhibitor of κBα and p65 and the expression of nuclear factor of activated T cells c1, while the dimerization inhibitor of myeloid differentiation factor 88 reversed the effects. These data provide evidence that IL‐37 modulates osteoclastogenesis and a theoretical basis for the clinical application of IL‐37 as a treatment for bone loss–related diseases.

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.

IL-37 isoform D downregulates pro-inflammatory cytokines expression in a Smad3-dependent manner

IL-37 is a new member of IL-1 family and possesses five different isoforms (named as IL-37 a–e). IL-37b has been demonstrated as a physiological suppressor of immune responses. However, the function of other isoforms remains unknown. Here, we show that IL-37d possesses anti-inflammatory roles both in vitro and in vivo. Firstly, IL-37d is expressed in peripheral blood mononuclear cells (PBMCs) and umbilical cords-derived mesenchymal stem cells (UCMSCs). Secondly, IL-37d overexpression markedly inhibits IL-1β-induced IL-6 production in A549 cells. Consistently, bone marrow-derived macrophages (BMDMs) from IL-37d transgenic mice express low levels of pro-inflammatory cytokines (such as IL-6 and TNF-α) following LPS stimulation, compared with those from wild-type mice. Furthermore, IL-37d transgenic mice produce less pro-inflammatory cytokines, and show much less degree of LPS-induced endotoxemia in vivo. Mechanistically, IL-37d interacts with Smad3 and promotes nuclear translocation of pSmad3. SIS3 (a specific Smad3 inhibitor) treatment completely blocks the inhibitory effects of IL-37d. Thus, our data indicate that IL-37d is a functional cytokine that negatively regulates pro-inflammatory cytokines expression in a Smad3-dependent manner.

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.

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.

Interleukin 37 promotes angiogenesis through TGF-β signaling

IL-37 is a novel pro-angiogenic cytokine that potently promotes endothelial cell activation and pathological angiogenesis in our previous study, but the mechanisms behind the pro-angiogenic effect of IL-37 are less well understood. Extending our observations, we found that TGF-β interacts with IL-37, and potently enhances the binding affinity of IL-37 to the ALK1 receptor complex, thus allowing IL-37 to signal through ALK1 to activate pro-angiogenic responses. We further show that TGF-β and ALK1 are required in IL-37 induced pro-angiogenic response in ECs and in the mouse model of Matrigel plug and oxygen-induced retinopathy. The result suggests that IL-37 induces pro-angiogenic responses through TGF-β, which may act as the bridging molecule that mediates IL-37 binding to the TGF-β receptor complex.

IL-37 increased in patients with acute coronary syndrome and associated with a worse clinical outcome after ST-segment elevation acute myocardial infarction

BACKGROUND

IL-37 emerges as a natural suppressor of inflammatory responses. The potential role of IL-37 in the pathology of atherosclerosis is unclear. The purpose of this study was to assess IL-37 profile in acute coronary syndrome (ACS) and the prognostic role of this cytokine in patients with ST-segment elevation acute myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI).

METHODS

In a case-control study, we prospectively enrolled 216 patients undergoing the first coronary angiography, which consisted of 5 groups: normal (n=57), stable angina (SAP, n=36), unstable angina (UAP, n=42), non-STEMI (n=36), STEMI (n=45). Plasma IL-37, IL-6 and serum amyloid A (SAA) were measured using a commercially ELISA kit. Besides, in a prospective cohort study, 125 patients with STEMI of onset <12h undergoing PPCI were enrolled and divided into 2 groups according to the concentrations of IL-37 (<341.1pg/ml or ≥341.1pg/ml). In-hospital major adverse cardiac event (MACE) including nonfatal myocardial infarction (MI), target lesion revascularization, acute heart failure, and cardiac death were estimated for prognosis.

RESULTS

IL-37 was gradually increased in accordance with the severity of coronary artery disease. The circulating concentration of IL-37 was remarkably higher in the ACS patients than in either of the normal or SAP patients (p<0.05), and especially higher in the AMI patients including STEMI and non-STEMI than in the angina pectoris subjects no matter SAP or UAP (p<0.05). There was no statistical difference of IL-37 between normal and SAP patients, STEMI and non-STEMI patients (p>0.05). The trend of the change of IL-37 was consistent with that of SAA or IL-6. A higher circulating concentration of IL-37 before PPCI was accompanied with the decreased LVEF and the increased NT-proBNP concentrations, and independently predictive of in-hospital MACE rate in patients with STEMI undergoing PPCI (OR=3.652, 95% CI=1.113-11.983, p<0.05).

CONCLUSIONS

We demonstrated the IL-37 profile in patients with acute coronary syndrome and the increased IL-37 concentration was associated with a worse clinical in-hospital outcome in STEMI patients undergoing PPCI.

Genomic Variant in IL-37 Confers A Significant Risk of Coronary Artery Disease

The interleukin 1 family plays an important role in the immune and inflammatory responses. Coronary artery disease (CAD) is a chronic inflammatory disease. However, the genetic association between IL-37, the seventh member of the IL-1 family, and CAD is unknown. Here we show that a single nucleotide polymorphism in the IL-37 gene (rs3811047) confers a significant risk of CAD. We have performed an association analysis between rs3811047 and CAD in two independent populations with 2,501 patients and 3,116 controls from China. Quantitative RT-PCR analysis has been performed to determine if the IL-37 expression level is influenced by rs3811047. We show that the minor allele A of rs3811047 is significantly associated with CAD in two independent populations under a recessive model (P_adj = 5.51 × 10^-3/OR = 1.56 in the GeneID Northernern population and P_adj = 1.23 × 10^-3/OR = 1.45 in the GeneID Central population). The association became more significant in the combined population (P_adj = 9.70 × 10^-6/OR = 1.47). Moreover, the association remains significant in a CAD case control population matched for age and sex. Allele A of rs3811047 shows significant association with a decreased mRNA expression level of IL-37 (n = 168, P = 3.78 × 10^-4). These data suggest that IL37 is a new susceptibility gene for CAD, which provides a potential target for the prevention and treatment of CAD.

IL-37 a New IL-1 Family Member Emerges as a Key Suppressor of Asthma Mediated by Mast Cells

In 1986, we reported a multiple biological effect of IL-1 including immunological, inflammatory, and tumor killing activity. Since then other IL-1 family cytokines have been discovered, some with inflammatory and other with anti-inflammatory activity. In this review article, we speculate on the possible inhibitory effect of IL-37 in the light of new findings. IL-37, formerly termed IL-1 family member 7 (IL-1F7), binding IL-18 receptor α chain, acts as a cytokine with intracellular as well as extracellular functionality and as a natural inhibitor of immune responses and inflammation. IL-37 inhibits many pro-inflammatory cytokine and increases anti-inflammatory cytokines such as IL-10. Asthma pathogenesis involves multiple cell types including mast cells, which are important cellular constituents of the human innate and adaptive immunity. IL-37 has an impact on inflammatory cytokines generated by mast cells and is beneficial for and protective in asthma. However, the precise mechanism(s), safety, and tolerability of IL-37 are unclear and still remain a mystery.

ABBREVIATIONS

GBP (Guanylate Binding Proteins); HMGB1 (High Mobility Group Box protein 1); NLRP (Nucleotide-like Receptor Pyrin domain 1); ASC (Apoptosis-associated Speck-like protein containing CARD, Caspase Recruitment Domain); FGF2 (Fibroblast Growth Factor 2).

Elevated serum interleukin-37 level is a predictive biomarker of poor prognosis in epithelial ovarian cancer patients

PURPOSE

Interleukin-37 (IL-37) has been identified as a novel anti-inflammatory cytokine which is involved in tumor development. This study aimed to evaluate the expression of IL-37 in serum and determine its clinical significance in human epithelial ovarian cancer (EOC).

METHODS

Enzyme-linked immunosorbent assay (ELISA) was performed to examine the serum IL-37 levels in 76 patients with EOC and 76 healthy controls. The association of IL-37 levels with clinical factors and prognosis of EOC patients was analyzed. The diagnostic accuracy of serum IL-37 was performed by receiver operator characteristic (ROC) curve analysis.

RESULTS

Serum IL-37 levels in patients with EOC (187.3 ± 75.57 pg/ml) were significantly higher than those in healthy controls (84.89 ± 28.92 pg/ml, P < 0.001). High serum IL-37 levels were significantly associated with FIGO stage (P < 0.001), tumor size (P = 0.002), lymph node metastasis (P = 0.021), positive recurrence (P = 0.047) and residual tumor size (P < 0.001). The Kaplan-Meier survival analysis demonstrated that high serum IL-37 levels were significantly associated with poor overall survival and the progression-free survival (log-rank, P = 0.026, and P = 0.039, respectively). Univariate and multivariate analysis indicated that serum IL-37 levels (HR = 3.007, 95% CI 2.125-4.842, P = 0.008) were an independent prognostic factor for EOC patients. ROC curve analyses revealed an AUC (the areas under the ROC curve) of 0.881 (95% CI 0.829-0.945; P < 0.001).

CONCLUSIONS

High serum IL-37 levels are associated with an unfavorable prognosis of EOC patients. IL-37 may serve as a promising and useful prognostic biomarker for EOC.

Interleukin-37 and Dendritic Cells Treated With Interleukin-37 Plus Troponin I Ameliorate Cardiac Remodeling After Myocardial Infarction

BACKGROUND

Excessive immune-mediated inflammatory reactions play a deleterious role in postinfarction ventricular remodeling. Interleukin-37 (IL-37) emerges as an inhibitor of both innate and adaptive immunity. However, the exact role of IL-37 and IL-37 plus troponin I (TnI)-treated dendritic cells (DCs) in ventricular remodeling after myocardial infarction (MI) remains elusive.

METHODS AND RESULTS

MI was induced by permanent ligation of the left anterior descending artery. Our results showed that treatment with recombinant human IL-37 significantly ameliorated ventricular remodeling after MI, as demonstrated by decreased infarct size, better cardiac function, lower mortality, restricted inflammatory responses, decreased myocardial fibrosis, and inhibited cardiomyocyte apoptosis. In vitro, we examined the phenotype of IL-37 plus TnI-conditioned DCs of male C57BL/6 mice and their capacity to influence the number of regulatory T cells. Our results revealed that IL-37 plus TnI-conditioned DCs obtained the characteristics of tolerogenic DCs (tDCs) and expanded the number of regulatory T cells when co-cultured with splenic CD4+ T cells. Interestingly, we also found that adoptive transfer of these antigen-loaded tDCs markedly increased the number of regulatory T cells in the spleen, attenuated the infiltration of inflammatory cells in the infarct hearts, decreased myocardial fibrosis, and improved cardiac function.

CONCLUSIONS

Our results reveal a beneficial role of IL-37 or tDCs treated with IL-37 plus TnI in post-MI remodeling that is possibly mediated by reestablishing a tolerogenic immune response, indicating that IL-37 or adoptive transfer of IL-37 plus TnI-treated tDCs may be a novel therapeutic strategy for ventricular remodeling after MI.

Tuberculosis-sensitized monocytes sustain immune response of interleukin-37

Roles of human IL-37 in infections remain poorly characterized. Although plasma IL-37 is elevated in patients with tuberculosis (TB), IL-37 source and immune correlate in TB have not been investigated. It is also unknown whether and how TB can influence the ability of immune cells to mount innate responses of IL-37 and pre-inflammatory cytokines. Here, we demonstrated that IL-37b-producing monocytes coincided with a source of elevated plasma IL-37b in TB patients. While IL-37b production in TB was associated with prolonged/complicated TB, TB burdens and inflammatory reactions, it negatively correlated with immune responses of pro-inflammatory cytokines IL-1β, IL-6 and TNF-α or IL-10. Interestingly, mycobacterial re-infection of monocytes from TB patients, but not healthy BCG-vaccinated controls, enhanced or sustained IL-37b production by cultured monocytes. TB-sensitized monocytes from TB patients mounted more robust immune responses of IL-37b than those of pre-inflammatory cytokines during mycobacterial re-infection in culture. Our data represent new findings in terms of IL-37b responses, immune correlates and potential mechanisms in TB patients.

Interleukin-37 suppresses tumor growth through inhibition of angiogenesis in non-small cell lung cancer

BACKGROUND

Interleukin-37 (IL-37), a newly identified member of the IL-1 family, has been known to play an immunosuppressive role in a variety of inflammatory disorders, but whether it participates in the regulation of pathogenesis of non-small cell lung cancer (NSCLC) has not been investigated.

METHODS

Real-time polymerase chain reaction (PCR), western blotting, and immunohistochemical staining were employed to detect IL-37 expression in NSCLC tissues and corresponding adjacent tissues. The correlations between IL-37 expression and clinicopathological characteristics, prognosis were analyzed. Stable clone with overexpression of IL-37 was generated in H1299 cell lines. Cell growth, cell cycle and cell apoptosis assays were carried out for detecting proliferation and apoptosis of H1299 cells. The effects of IL-37 on NSCLC progression in vivo was performed in a xenografted lung tumor model in nude mice. The concentrations of IL-37 and VEGF in the s growth medium supernatants were quantified by ELISA. The antiangiogenic effect of IL-37 on HUVEC was measured by tube formation assay.

RESULTS

IL-37 mRNA and protein expressions were significantly decreased in NSCLC tissues, and decreased intratumoral IL-37 expression was significantly associated with tumor state, TNM stage and poor prognosis in NSCLC patients. In addition, intratumoral IL-37 expression was an independent prognostic factors for Overall survival (hazard ratio = 2.047; P = 0.011). Overexpression of IL-37 exerted no direct effect on cell proliferation and apoptosis of H1299 lung cancer cells in vitro, but significantly inhibited tumor growth in a H1299 xenograft model in vivo. Furthermore, there was no significant change in immune cell infiltration in IL-37 over-expressing tumors; instead, we found decreased microvessel density (MVD) and VEGF levels in IL-37-expressing tumors. Additional studies showed IL-37 could directly inhibit HUVEC cells growth and capillary structure formation. Finally, we found that decreased IL-37 expression was associated with high MVD in NSCLC patients.

CONCLUSIONS

Our findings demonstrate a protective role for IL-37 in lung cancer development, possibly through inhibiting tumor angiogenesis. IL-37 could serve as a promising therapeutic target for NSCLC.

IL-37 Is a Novel Proangiogenic Factor of Developmental and Pathological Angiogenesis

OBJECTIVE

Angiogenesis is tightly controlled by growth factors and cytokines in pathophysiological settings. Interleukin 37 (IL-37) is a newly identified cytokine of the IL-1 family, some members of which are important in inflammation and angiogenesis. However, the function of IL-37 in angiogenesis remains unknown. We aimed to explore the regulatory role of IL-37 in pathological and physiological angiogenesis.

APPROACH AND RESULTS

We found that IL-37 was expressed and secreted in endothelial cells and upregulated under hypoxic conditions. IL-37 enhanced endothelial cell proliferation, capillary formation, migration, and vessel sprouting from aortic rings with potency comparable with that of vascular endothelial growth factor. IL-37 activates survival signals including extracellular signal-regulated kinase 1/2 and AKT in endothelial cells. IL-37 promoted vessel growth in implanted Matrigel plug in vivo in a dose-dependent manner with potency comparable with that of basic fibroblast growth factor. In the mouse model of retinal vascular development, neonatal mice administrated with IL-37 displayed increased neovascularization. We demonstrated further that IL-37 promoted pathological angiogenesis in the mouse model of oxygen-induced retinopathy.

CONCLUSIONS

Our findings suggest that IL-37 is a novel and potent proangiogenic cytokine with essential role in pathophy siological settings.

IL-37 mediates the antitumor activity in renal cell carcinoma

Interleukin (IL)-37 is a natural suppressor of innate inflammatory and immune responses. IL-37 plays an important role in renal function and antitumor activity. The aim of this study was to investigate the role of IL-37 in renal cell carcinoma (Rcc). Serum IL-37 levels in 120 Rcc patients and 50 healthy controls were measured by enzyme-linked immunosorbent assay (ELISA). The Rcc cell lines A498 and Caki-1 were cultured with 0-100 ng/mL of recombinant human IL-37 protein (rhIL-37). Cancer cells were transfected with or without pcDNA3.1-IL-6 to alter IL-6 expression. Cell migration, proliferation, and apoptosis were tested by wound-healing assay, MTT, and flow cytometry, respectively. Levels of IL-6, pSTAT3 Y705, Bcl-2, cyclin D1, and HIF-1α were detected by qRT-PCR, ELISA, or western blot. Additionally, therapeutic effect of rhIL-37 was also confirmed in SCID mice. The expression of IL-37 was decreased in Rcc patients and was negatively correlated with tumor progression. In vitro, IL-37 markedly inhibited the migration and proliferation, and promoted apoptosis in Rcc cells. Furthermore, the expressions of IL-6, pSTAT3 Y705, HIF-1α, Bcl-2, and cyclin D1 were decreased by IL-37. However, these effects were reversed by the transfection of pcDNA3.1-IL-6. In vivo, tumor growth and gene expressions of IL-6 and HIF-1α were suppressed by IL-37. In conclusion, IL-37 might serve as a novel tumor suppressor in Rcc and exert its antitumor activity through inhibiting IL-6/STAT3 signaling.

Altered glycolipid and glycerophospholipid signaling drive inflammatory cascades in adrenomyeloneuropathy

X-linked adrenomyeloneuropathy (AMN) is an inherited neurometabolic disorder caused by malfunction of the ABCD1 gene, characterized by slowly progressing spastic paraplegia affecting corticospinal tracts, and adrenal insufficiency. AMN is the most common phenotypic manifestation of adrenoleukodystrophy (X-ALD). In some cases, an inflammatory cerebral demyelination occurs associated to poor prognosis in cerebral AMN (cAMN). Though ABCD1 codes for a peroxisomal transporter of very long-chain fatty acids, the molecular mechanisms that govern disease onset and progression, or its transformation to a cerebral, inflammatory demyelinating form, remain largely unknown. Here we used an integrated -omics approach to identify novel biomarkers and altered network dynamic characteristic of, and possibly driving, the disease. We combined an untargeted metabolome assay of plasma and peripheral blood mononuclear cells (PBMC) of AMN patients, which used liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry (LC-Q-TOF), with a functional genomics analysis of spinal cords of Abcd1(-) mouse. The results uncovered altered nodes in lipid-driven proinflammatory cascades, such as glycosphingolipid and glycerophospholipid synthesis, governed by the β-1,4-galactosyltransferase (B4GALT6), the phospholipase 2γ (PLA2G4C) and the choline/ethanolamine phosphotransferase (CEPT1) enzymes. Confirmatory investigations revealed a non-classic, inflammatory profile, consisting on the one hand of raised plasma levels of several eicosanoids derived from arachidonic acid through PLA2G4C activity, together with also the proinflammatory cytokines IL6, IL8, MCP-1 and tumor necrosis factor-α. In contrast, we detected a more protective, Th2-shifted response in PBMC. Thus, our findings illustrate a previously unreported connection between ABCD1 dysfunction, glyco- and glycerolipid-driven inflammatory signaling and a fine-tuned inflammatory response underlying a disease considered non-inflammatory.

The evaluation of plasma and leukocytic IL-37 expression in early inflammation in patients with acute ST-segment elevation myocardial infarction after PCI

OBJECTIVE

Acute ST-segment elevation myocardial infarction (ASTEMI) is accompanied by increased expression of inflammation and decreased expression of anti-inflammation. IL-37 was found to be involved in the atherosclerosis-related diseases and increased in acute coronary syndrome. However, the level of IL-37 in blood plasma and leukocytes from patients with ASTEMI after percutaneous coronary intervention (PCI) has not been explored.

METHODS

We collected peripheral venous blood from consented patients at 12 h, 24 h, and 48 h after PCI and healthy volunteers. Plasma IL-37, IL-18, IL-18-binding protein (BP), and high sensitive C reaction protein (hs-CRP) were quantified by ELISA and leukocytic IL-37 and ICAM-1 by immunoblotting.

RESULTS

Plasma IL-37, IL-18, and IL-18 BP expression decreased compared to those in healthy volunteers while hs-CRP level was high. Both leukocytic IL-37 and ICAM-1 were highest expressed at 12 h point but significantly decreased at 48 h point.

CONCLUSION

These findings suggest L-37 does not play an important role in the systematic inflammatory response but may be involved in leukocytic inflammation in ASTEMI after PCI.

The growing spectrum of anti-inflammatory interleukins and their potential roles in the development of sepsis

Sepsis, recognized as a deadly immunological disorder, is one of the major causes of death in intensive care units globally. Traditionally, sepsis was characterized by an excessive systemic proinflammatory response to invasive microbial pathogens. However, failures of highly sophisticated trials directed toward the uncontrolled inflammatory reaction have led to an appeal by experts for reevaluation of the present approach toward sepsis. With accumulated evidence, a principal role for immunosuppression in severe sepsis has been evaluated. Different pathways of negative regulation in the pathophysiological process of sepsis have been investigated. Significant among these regulatory elements are the anti-inflammatory cytokines. In the past few years, several interleukins (ILs) have been identified and characterized, among which IL-35 and IL-37 represent newly identified ones in the spectrum of anti-inflammatory cytokines. In this study, we focus on regulatory cytokines of the IL family (including the old members: IL-4, IL-10, and IL-13, and newly discovered ones: IL-35 and IL-37) to address current knowledge regarding their structural and functional characteristics as well as their roles in the development of sepsis. Although the exact roles for these cytokines are pending further elucidation, the current advances in our understanding of mechanisms that regulate the immune responses during severe sepsis may lead to the identification of new diagnostic or treatment targets.

Levels of interleukin-37 in gingival crevicular fluid, saliva, or plasma in periodontal disease

BACKGROUND AND OBJECTIVE

The aim of this study was to compare the levels of levels of interleukin-37 (IL-37) in gingival crevicular fluid, saliva and plasma in patients with periodontal disease and patients with healthy periodontium and to correlate these levels with clinical parameters.

MATERIAL AND METHODS

Samples of gingival crevicular fluid, whole saliva and plasma were collected from systemically healthy, nonsmoker periodontally healthy controls (group 1, n = 20), gingivitis patients (group 2, n = 20) and chronic periodontitis patients (group 3, n = 20). Full-mouth clinical periodontal parameters, including probing depth, plaque index, gingival index and bleeding on probing, were also recorded. IL-37 levels in the biofluid samples were determined by ELISA. Data were tested statistically using the Kruskal-Wallis test followed by the Mann-Whitney U-test.

RESULTS

The concentration of IL-37 in gingival crevicular fluid was significantly lower in group 3 than in groups 1 and 2 (p = 0.001), whereas the total amounts in gingival crevicular fluid samples were similar (p > 0.05). The salivary and plasma concentrations of IL-37 were similar in the study groups (p > 0.05). There were negative correlations between gingival crevicular fluid IL-37 concentrations and gingival crevicular fluid volume in all groups (p < 0.05). There was also a negative correlation between the gingival crevicular fluid IL-37 concentration and gingival index in group 3 (p < 0.05).

CONCLUSIONS

IL-37 was expressed in all biofluids. According to our findings, the total amount of IL-37 in gingival crevicular fluid, or salivary or plasma concentrations of IL-37, may not be useful diagnostic markers to differentiate periodontal disease and the periodontally healthy condition. The difference in gingival crevicular fluid IL-37 concentration between the study groups may be a result of the variation in gingival crevicular fluid volume, as suggested by the negative correlation between gingival crevicular fluid volume and gingival crevicular fluid IL-37 concentration. In the light of our findings, it seems that IL-37 is not involved in periodontal disease. Further comprehensive studies may clarify this issue more clearly.

Interleukin-37 ameliorates myocardial ischaemia/reperfusion injury in mice

Innate immune and inflammatory responses are involved in myocardial ischaemia/reperfusion (I/R) injury. Interleukin (IL)-37 is a newly identified member of the IL-1 family, and functions as a fundamental inhibitor of innate immunity and inflammation. However, its role in myocardial I/R injury remains unknown. I/R or sham operations were performed on male C57BL/6J mice. I/R mice received an injection of recombinant human IL-37 or vehicle, immediately before reperfusion. Compared with vehicle treatment, mice treated with IL-37 showed an obvious amelioration of the I/R injury, as demonstrated by reduced infarct size, decreased cardiac troponin T level and improved cardiac function. This protective effect was associated with the ability of IL-37 to suppress production of proinflammatory cytokines, chemokines and neutrophil infiltration, which together contributed to a decrease in cardiomyocyte apoptosis and reactive oxygen species (ROS) generation. In addition, we found that IL-37 inhibited the up-regulation of Toll-like receptor (TLR)-4 expression and nuclear factor kappa B (NF-kB) activation after I/R, while increasing the anti-inflammatory IL-10 level. Moreover, the administration of anti-IL-10R antibody abolished the protective effects of IL-37 in I/R injury. In-vitro experiments further demonstrated that IL-37 protected cardiomyocytes from apoptosis under I/R condition, and suppressed the migration ability of neutrophils towards the chemokine LIX. In conclusion, IL-37 plays a protective role against mouse myocardial I/R injury, offering a promising therapeutic medium for myocardial I/R injury.