Enhanced IL-37-IL-1R8 axis is negatively associated with inflammatory and clinical severity of chronic rhinosinusitis with nasal polyps.

Background: The importance of IL-37 and downstream signal in the pathogenesis of chronic rhinosinusitis with nasal polyps (CRSwNP) demanding further investigation. Objective: We sought to address the potential importance of the IL-37-IL-1R8 axis in regulating inflammatory response in patients with CRSwNP. Methods: Nasal polyp (NP) tissues and control sinonasal tissues were obtained from adult CRSwNP, chronic rhinosinusitis without nasal polyps patients and healthy control subjects. The mRNA and protein levels of IL-37 and IL-1R8 in nasal tissues were examined by using quantitative PCR, immunohistochemical staining, and immunoblotting. In addition, the regulation of IL-1R8 expression was evaluated in human nasal epithelial cells (HNECs) in the presence of different stimuli. Results: The mRNA and protein levels of IL-37 and IL-1R8 were significantly elevated in nasal polyps compared with that in control tissues. IL-37 and IL-1R8 were mainly distributed in the epithelial layer and lamina propria of tissues. IL-1R8 mRNA level in nasal polys was negatively associated with eosinophil and neutrophil infiltration, as well as endoscopic score and computed tomography score. Moreover, the mRNA expression of IL-1R8 in HNECs was significantly increased by toll-like receptor agonists, but significantly inhibited by proinflammatory cytokines, which can be rescued by using steroid (DEX). Conclusion: Our findings showed that enhanced IL-37-IL-1R8 axis in NP tissues was negatively associated with inflammatory and clinical severity of CRSwNP patients, which could be considered as a future therapeutic target in CRSwNP patients.

The anti-inflammatory cytokine IL-37 improves the NK cell-mediated anti-tumor response.

IL-37 is a member of the IL-1 superfamily exerting anti-inflammatory functions in a number of diseases. Extracellular IL-37 triggers the inhibitory receptor IL-1R8 that is known to regulate different NK cell pathways and functional activities including their anti-tumor effect. However, the effect of IL-37 on human NK cell functions is still to be unveiled. This study aimed to investigate the functional effect of IL-37 in human NK cells activated with IL-15. We found that IL-37 enhanced both NK cell cytotoxic activity against different tumor cell lines and cytokines production. These effects were associated with increased phosphorylation of ERK and NF-Kb. The improved NK cell activity was also strictly related to a time-dependent GSK3ß-mediated degradation of IL-1R8. The enhanced activation profile of IL-37 treated NK cells possibly due to IL-1R8 degradation was confirmed by the results with IL-1R8-silenced NK cells. Lastly, in line with these data, through the analysis of the TNM plot database of a large group of patients, IL-37 mRNA expression was found to be significantly lower in colon and skin cancers than in normal tissues. Colon adenocarcinoma and neuroblastoma patients with higher IL-37 mRNA levels had significantly higher overall survival, suggesting that the presence of IL-37 might be considered an independent positive prognostic factor for this tumor. Our results provide novel information on the mechanisms regulating IL-1R8 function in human NK cells, highlighting the IL-37-IL-1R8 axis as a potential new target to improve the anti-tumor immune response.

IL-1R8 expression in DLBCL regulates NK cell recruitment and influences patient prognosis.

The precise biological function of Interleukin-1 receptor 8 (IL-1R8) in diffuse large B-cell lymphoma (DLBCL) is still not well understood. Our goal is to decipher the profile of IL-1R8 expression status in DLBCL and to explore how IL-1R8 is involved in DLBCL progression. Utilizing a tissue microarray consisting of 70 samples of DLBCL tumors alongside 15 samples of tonsillitis, our investigation revealed a parallel expression profile of IL-1R8 between the tumor tissues and tonsillitis samples (p > 0.05). Nevertheless, an intriguing association emerged, as heightened expression of IL-1R8 correlated significantly with unfavorable survival outcomes in patients with DLBCL (p < 0.05). The status of IL-1R8 expression did not directly regulate proliferation (p > 0.05) and apoptosis (p > 0.05) in DLBCL cells via CCK8 and apoptotic assays. Subsequent chemotaxis analysis indicated that natural killer (NK) cell recruitment could be suppressed by IL-1R8 signaling in DLBCL, at least partially through CXCL1 inhibition (p < 0.05). The status of IL-1R8 expression in tumor tissues exhibited a negative correlation with the density of CD57+ NK cell infiltration (p < 0.05), while it did not demonstrate a significant association with CD3+ T cells (p > 0.05), CD68+ macrophages (p > 0.05), or S-100+ dendritic cells (p > 0.05). In line with this observation, elevated levels of NK cell infiltration demonstrated a significant positive correlation with improved overall survival (OS) among patients diagnosed with DLBCL (p < 0.05). Our data suggests the immuno-regulating potential of IL-1R8 through NK cell recruitment in DLBCL, providing novel insights into future immuno-modulating therapies.

IL-1R8: A molecular brake of anti-tumor and anti-viral activity of NK cells and ILC.

Interleukin-1 receptor family members (ILRs) and Toll-Like Receptors (TLRs) play pivotal role in immunity and inflammation and are expressed by most cell types including cells of both the innate and adaptive immune system. In this context, IL-1 superfamily members are also important players in regulating function and differentiation of adaptive and innate lymphoid cells. This system is tightly regulated in order to avoid uncontrolled activation, which may lead to detrimental inflammation contributing to autoimmune or allergic responses. IL-1R8 (also known as TIR8 or SIGIRR) is a member of the IL-1R family that acts as a negative regulator dampening ILR and TLR signaling and as a co-receptor for human IL-37. Human and mouse NK cells, that are key players in immune surveillance of tumors and infections, express high level of IL-1R8. In this review, we will summarize our current understanding on the structure, expression and function of IL-1R8 and we will also discuss the emerging role of IL-1R8 as an important checkpoint regulating NK cells function in pathological conditions including cancer and viral infections.

IL-37 alleviates intervertebral disc degeneration via the IL-1R8/NF-κB pathway.

OBJECTIVE: Intervertebral disc degeneration (IDD) has been reported to be a major cause of low back pain (LBP). Interleukin (IL)-37 is an anti-inflammatory cytokine of the interleukin-1 family, which exerts salutary physiological effects. In this study, we assessed the protective effect of IL-37 on IDD progression and its underlying mechanisms. METHODS: Immunofluorescence (IF) was conducted to measure IL-37 expression in nucleus pulposus tissues. CCK-8 assay and Edu staining were used to examine the vitality of IL-37-treated nucleus pulposus cells (NPCs). Western blot, qPCR, ELISA as well as immunohistochemistry were used to assess senescence associated secreted phenotype (SASP) factors expression; and NF-κB pathway was evaluated by western blot and IF; while IL-1R8 knock-down by siRNAs was performed to ascertain its significance in the senescence phenotype modulated by IL-37. The therapeutic effect of IL-37 on IDD were evaluated in puncture-induced rat model using X-ray, Hematoxylin-Eosin, Safranin O-Fast Green (SO), and alcian blue staining. RESULTS: We found IL-37 expression decreased in the IDD process. In vitro, IL-37 suppressed SASP factors level and senescence phenotype in IL-1ß treated NPCs. In vivo, IL-37 alleviated the IDD progression in the puncture-induced rat model. Mechanistic studies demonstrated that IL-37 inhibited IDD progression by downregulating NF-κB pathway activation in NPCs by activating IL-1R8. CONCLUSION: The present study suggests that IL-37 delays the IDD development through the IL-1R8/NF-κB pathway, which suggests IL-37 as a promising novel target for IDD therapy.

IL-1R8 as Pathoimmunological Marker for Severity of Canine Chronic Enteropathy.

Chronic enteropathy (CE) is a severe multifactorial gastrointestinal disease that affects dogs and is driven by poorly characterized inflammatory pathways. Imbalance of pro-inflammatory response regulators, including IL-1R8, may be due to different factors, among which the infection with Helicobacteraceae is known to lead to a vicious circle in which excessive pro-inflammatory signaling and gastrointestinal injury reinforce each other and boost the disease. We investigated the expression of IL-1R8 in large intestine biopsies of dogs with or without clinical signs of CE and with previously assessed enterohepatic Helicobacter spp. colonization status by mean of quantitative real-time PCR. Our study revealed that IL-1R8 is downregulated in both acutely (p = 0.0074) and chronically (p = 0.0159) CE affected dogs compared to healthy controls. The data also showed that IL-1R8 expression tends to decrease with colonization by Helicobacter spp. Interestingly, a negative correlation was detected between the level of expression of IL-1R8 and the severity of macroscopic lesions identified by endoscopy and the crypt hyperplasia score. We further compared the expression levels between males and females and found no statistically significant difference between the two groups. No significant difference was observed in IL-1R8 expression profiles with the age of the animals either. Interestingly, an association was uncovered between IL-1R8 expression level and dog breed. Together, our data advance knowledge on gastrointestinal pathoimmunology in dogs and highlight the potential utilization of IL-1R8 as a diagnostic, prognostic and therapeutic biomarker for canine chronic enteropathy.

IL-1R8 Downregulation and Concomitant TLR7 and TLR9 Upregulation Are Related to the Pathogenesis of Canine Diffuse Large B-Cell Lymphoma.

Diffuse large B-cell lymphoma (DLBCL) is the most common hematological malignancy in humans and dogs. Several studies disclosed some similarities between the two species, including the constitutive activation of the NF-κB pathway as a fundamental underlying pathogenetic mechanism. In humans, the downregulation of IL-1R8 is implicated in DLBCL development, but its role in dogs has not been explored so far. To gain insight into the pathogenesis of this tumor in dogs, we evaluated the mRNA and protein expression of IL-1R8 in 12 control lymph nodes obtained from dogs not bearing tumors and from 50 dogs with DLBCL. Moreover, we analyzed through qRT-PCR the expression of TLR7, TLR9, MYC, and p52 genes that are known to be involved in the IL-1R8 regulatory network. IL-1R8 and p52 were downregulated in DLBCLs compared to control lymph nodes (p < 0.001), while a higher expression of TLR7, TLR9, and MYC was observed in DLBCLs (p < 0.01). Immunohistochemistry confirmed the gene expression results, revealing a significantly lower IL-1R8 staining score in DLBCLs compared to control lymph nodes (p < 0.0001). Taken together, these results suggest that IL-1R8 downregulation may represent one of the mechanisms driving DLBCL pathogenesis in dogs, mainly through the dysregulation of the Toll-like/interleukin receptors signaling cascade and the aberrant activation of the classical NF-κB pathway.

Interleukin-37 inhibits inflammation activation and disease severity of PM2.5-induced airway hyperresponsiveness.

We have shown in the past studies that fine particulate matter (PM2.5) exposure increases airway hyperresponsiveness and leads to lung inflammation damage. Interleukin (IL)-37 plays a inhibitory role in inflammation activation and maintenance. However, the function of IL-37 in the above processes keep unclear. We aim to explore the role of IL-37 in PM2.5-induced airway hyperresponsiveness in this study. A nose-only PM2.5 online concentration, enrichment and exposure instrument was also applied to generate mice model of airway hyperresponsiveness. A transgenic mice strain using a CMV promoter to express human IL-37b (hIL-37tg) was obtained. PM2.5 exposure was shown to increase airway resistance, followed by lung inflammation and IL-1ß, TNFα, and IL-6 release, which was inhibited by IL-37tg mice and mice administrated recombinant human IL-37 intranasally (i.n). Moreover, expression of the proliferation-related protein PCNA and migration-related proteins MMP-2, MMP-9, and Vimentin was reduced in lung tissues of IL-37tg mice and mice given recombinant human IL-37 i.n. Abnormal cell contraction, proliferation, and migration of human airway smooth muscle cells (hASMCs) incubated with PM2.5 were also decreased by IL-37 treatment. In addition, IL-37 intervention of hASMCs before PM2.5 incubation decreased cytoplasmic calcium level and expression of PCNA, MMP-2, MMP-9 and Vimentin. Finally, knockdown of the IL-37 receptor IL-1R8 gene eliminated the protective effects of IL-37 in the above responses. We conclude that IL-37 inhibits inflammation activation and disease severity of airway hyperreactivity by PM2.5 induction.

IL-37-induced activation of glycogen synthase kinase 3ß promotes IL-1R8/Sigirr phosphorylation, internalization, and degradation in lung epithelial cells.

Interleukin (IL)-37 diminishes a variety of inflammatory responses through ligation to its receptor IL-1R8/Sigirr. Sigirr is a Toll like receptor/IL-1R family member. We have shown that Sigirr is not stable in response to IL-37 treatment. IL-37-induced Sigirr degradation is mediated by the ubiquitin-proteasome system, and the process is reversed by a deubiquitinase, USP13. However, the molecular mechanisms by which USP13 regulates Sigirr stability have not been revealed. In this study, we investigate the roles of glycogen synthesis kinase 3ß (GSK3ß) in Sigirr phosphorylation and stability. IL-37 stimulation induced Sigirr phosphorylation and degradation, as well as activation of GSK3ß. Inhibition of GSK3ß attenuated IL-37-induced Sigirr phosphorylation, while exogenous expressed GSK3ß promoted Sigirr phosphorylation at threonine (T)372 residue. Sigirr association with GSK3ß was detected. Amino acid residues 51-101 in GSK3ß were identified as the Sigirr binding domain. These data indicate that GSK3ß mediates IL-37-induced threonine phosphorylation of Sigirr. Further, we investigated the role of GSK3ß-mediated phosphorylation of Sigirr in Sigirr degradation. Inhibition of GSK3ß attenuated IL-37-induced Sigirr degradation, while T372 mutant of Sigirr was resistant to IL-37-mediated degradation. Furthermore, inhibition of Sigirr phosphorylation prevented Sigirr internalization and association with USP13, suggesting GSK3ß promotes Sigirr degradation through disrupting Sigirr association with USP13.

IL-37 exerts therapeutic effects in experimental autoimmune encephalomyelitis through the receptor complex IL-1R5/IL-1R8.

Background: Interleukin 37 (IL-37), a member of IL-1 family, broadly suppresses inflammation in many pathological conditions by acting as a dual-function cytokine in that IL-37 signals via the extracellular receptor complex IL1-R5/IL-1R8, but it can also translocate to the nucleus. However, whether IL-37 exerts beneficial actions in neuroinflammatory diseases, such as multiple sclerosis, remains to be elucidated. Thus, the goals of the present study were to evaluate the therapeutic effects of IL-37 in a mouse model of multiple sclerosis, and if so, whether this is mediated via the extracellular receptor complex IL-1R5/IL-1R8. Methods: We used a murine model of MS, the experimental autoimmune encephalomyelitis (EAE). We induced EAE in three different single and double transgenic mice (hIL-37tg, IL-1R8 KO, hIL-37tg-IL-1R8 KO) and wild type littermates. We also induced EAE in C57Bl/6 mice and treated them with various forms of recombinant human IL-37 protein. Functional and histological techniques were used to assess locomotor deficits and demyelination. Luminex and flow cytometry analysis were done to assess the protein levels of pro-inflammatory cytokines and different immune cell populations, respectively. qPCRs were done to assess the expression of IL-37, IL-1R5 and IL-1R8 in the spinal cord of EAE, and in blood peripheral mononuclear cells and brain tissue samples of MS patients. Results: We demonstrate that IL-37 reduces inflammation and protects against neurological deficits and myelin loss in EAE mice by acting via IL1-R5/IL1-R8. We also reveal that administration of recombinant human IL-37 exerts therapeutic actions in EAE mice. We finally show that IL-37 transcripts are not up-regulated in peripheral blood mononuclear cells and in brain lesions of MS patients, despite the IL-1R5/IL-1R8 receptor complex is expressed. Conclusions: This study presents novel data indicating that IL-37 exerts therapeutic effects in EAE by acting through the extracellular receptor complex IL-1R5/IL-1R8, and that this protective physiological mechanism is defective in MS individuals. IL-37 may therefore represent a novel therapeutic avenue for the treatment of MS with great promising potential.

Extracellular and nuclear roles of IL-37 after spinal cord injury.

Interleukin 37 (IL-37) is an anti-inflammatory cytokine of the interleukin 1 family. Transgenic mice expressing the human form of the IL37 gene (hIL-37Tg) display protective effects in several animal models of disease. Previous data from our group revealed that IL-37 limits inflammation after spinal cord injury (SCI) and ameliorates tissue damage and functional deficits. IL-37 can exert its anti-inflammatory effects by translocating to the nucleus or acting as an extracellular cytokine. However, whether this protection after SCI is mediated by translocating to the nucleus, activating of extracellular receptors, or both, is currently unknown. In the present study, we used different transgenic animals to answer this question. We demonstrated that the beneficial effects of IL-37 on functional and histological outcomes after SCI were lost in the lack of the extracellular receptor IL-1R8, indicating that IL-37 induces protection as an extracellular cytokine. On the other hand, transgenic mice with the nuclear function of IL-37 abolished (hIL-37D20ATg) showed significant improvement in locomotor skills and myelin sparing after SCI, indicating that nuclear pathway is not required for the protective actions of IL-37. Moreover, we also showed that the therapeutic effects of the recombinant IL-37 protein are produced only in the presence of the extracellular receptor IL-1R8, further highlighting the importance of the extracellular function of this cytokine after SCI. Finally, we revealed that the administration of recombinant IL-37 protein exerted therapeutic actions when administered in the lesion site but not systemically. This work demonstrated for the first time that translocation of IL-37 to the nucleus is not required for the beneficial actions of this cytokine after SCI and highlights the importance of the extracellular signaling of IL-37 to mediate neuroprotective actions.

IL-37d Negatively Regulates NLRP3 Transcription via Receptor-mediated Pathway and Alleviates DSS-induced Colitis.

BACKGROUND: Interleukin-37 (IL-37) is a new negative immune regulator. It has 5 splicing forms, IL-37a-e, and most research mainly focuses on IL-37b functions in diverse diseases. Our previous research found that IL-37d inhibits lipopolysaccharide-induced inflammation in endotoxemia through a mechanism different from that of IL-37b. However, whether IL-37d plays a role in colitis and the underlying mechanisms is still obscure. Herein, we identified whether IL-37d regulates NLRP3 inflammasome activity and determined its effect on colitis. METHODS: NLRP3 inflammasome in macrophages from IL-37d transgenic (IL-37dtg) and control wild type (WT) mice were activated by lipopolysaccharide and adenosine 5'-triphosphate. The expression of NLRP3 inflammasome components and its downstream effector, IL-1ß, were detected by real-time polymerase chain reaction, western blot, and ELISA. The models of alum-induced peritonitis and dextran sodium sulfate (DSS)-induced colitis were used to investigate the function of IL-37d on regulating the activity of NLRP3 inflammasome in vivo. RESULTS: Our results showed that the activation of NLRP3 inflammasome in macrophage and alum-induced peritonitis was inhibited by IL-37d. Strikingly, IL-37d suppressed NLRP3 expression at the priming step via inhibiting NF-κB activation by transcriptional profiling. Moreover, the recombinant protein IL-37d attenuated NLRP3 inflammasome activation and the production of IL-1ß, which could be reversed by IL-1R8 knockdown. Finally, IL-37d transgenic mice resisted DSS-induced acute colitis and NLRP3 inflammasome activation. CONCLUSION: Interleukin-37d inhibits overactivation of the NLRP3 inflammasome through regulating NLRP3 transcription in an IL-1R8 receptor-mediated signaling pathway.

Transcriptomic analysis reveals that IL-1R8/Sigirr is a novel macrophage migration regulator and suppresses macrophage proliferation through p38 MAPK signaling pathway.

IL-1R8, also known as the Single immunoglobin interleukin-1 (IL-1)-related receptor (Sigirr), has been demonstrated as a negative regulator of IL-1R and Toll-like receptor (TLR) downstream signaling pathways and inflammation. However, the role of IL-1R8 in macrophage migration and proliferation remains unknown. Here we investigated transcriptome profiles of WT and Il1r8-deficient splenocytes and found that innate immunity and cell migration related pathways were significantly correlated with IL-1R8 expression. Cell migration-related genes were downregulated in Il1r8-/- splenocytes or IL-1R8-depleted RAW264.7 cells. Further experiments revealed that IL-1R8-depleted RAW264.7 cells or Il1r8-/- BMDMs exhibited impaired cell migration. Moreover, we found that IL-1R8 suppresses macrophage proliferation through p38 MAPK signaling pathway. Therefore, our study suggests that IL-1R8 is a new positive regulator for macrophage migration and suppresses macrophage proliferation.

IL-37b alleviates inflammation in the temporomandibular joint cartilage via IL-1R8 pathway.

OBJECTIVES: Interleukin (IL)-37 is a natural suppressor of innate inflammation. This study was conducted to explore the anti-inflammatory effects of IL-37 in temporomandibular joint (TMJ) inflammation. MATERIALS AND METHODS: The expression of IL-37 in the TMJ was measured using ELISA and IHC. Human TMJ chondrocytes were treated with IL-37b and IL-1ß, and inflammation-related factors were detected. siRNA-IL-1R8 was transfected into chondrocytes, and the affected pathways were detected. IL-37b was used in disc-perforation-induced TMJ inflammation in SD rats. Micro-CT, IHC, real-time PCR and histological staining were used to quantify the therapeutic effect of IL-37b. RESULTS: IL-37 was expressed in the synovium and the disc of patients with osteoarthritis (OA) and in the articular cartilage of condylar fracture patients. IL-37 was highly expressed in synovial fluid of patients with synovitis than in those with OA and disc displacement and was closely related to visual analogue scale (VAS) score. In vitro, IL-37b suppressed the expression of pro-inflammatory factors. In addition, IL-37b exerted anti-inflammatory effects via IL-1R8 by inhibiting the p38, ERK, JNK and NF-κB activation, while silencing IL-1R8 led to inflammation and upregulation of these signals. In disc-perforation-induced TMJ inflammation in SD rats, IL-37b suppressed inflammation and inhibited osteoclast formation to protect against TMJ. CONCLUSIONS: IL-37b may be a novel therapeutic agent for TMJ inflammation.

Staphylococcus aureus intra-mammary infection affects the expression pattern of IL-R8 in goat.

IL-1R8 is a member of Interleukin-1 receptor family acting as a negative regulator of inflammation reliant on ILRs and TLRs activation. IL-1R8 role has never been evaluated in acute bacterial mastitis. We first investigated IL-1R8 sequence conservation among different species and its pattern of expression in a wide panel of organs from healthy goats. Then, modulation of IL-1R8 during natural and experimental mammary infection was evaluated and compared in blood, milk and mammary tissues from healthy and Staphylococcus aureus infected goats. IL-1R8 has a highly conserved sequence among vertebrates. Goat IL-1R8 was ubiquitously expressed in epithelial and lymphoid tissues with highest levels in pancreas. IL-1R8 was down-regulated in epithelial mammary cells following S. aureus infection. Interestingly it was up-regulated in leukocytes infiltrating the infected mammary tissues suggesting that it could represent a target of S. aureus immune evasion.

IL-37 inhibits the maturation of dendritic cells through the IL-1R8-TLR4-NF-κB pathway.

Mature dendritic cells (DCs) play a pathogenic role in atherosclerosis. Our previous study demonstrated that exogenous interleukin (IL)-37 suppresses the maturation of DCs, induces the T-regulatory (Treg) cell response, and attenuates atherosclerosis in ApoE-/- mice. The aim of the present study was to explore the molecular mechanism of IL-37 on the maturation of DCs throughout the development of atherosclerosis. The expression of interleukin-1 receptor 8 (IL-1R8), which is a single Ig-domain receptor that was recently found to be pivotal for the extracellular function of IL-37, Toll-like receptor (TLR) 4 and p65, was measured in ApoE-/- mice and IL-37 transgenic (IL-37tg) ApoE-/- mice. IL-1R8 was mainly expressed in aortic plaque-infiltrated DCs and at significantly higher levels in IL-37tg atherosclerotic mice, accompanied by lower levels of TLR4 and p65. Furthermore, IL-37 eliminated the maturation of DCs induced by oxidized low-density lipoprotein (oxLDL) and caused marked upregulation of IL-1R8 in vitro and downregulation of TLR4 and p65, which was consistent with the experiments in mice. However, the inhibitory effect of IL-37 on the maturation of DCs in vitro was abolished when IL-37 was used to treat DCs isolated from IL-1R8-deficient and TLR4-deficient mice. Therefore, this study indicated that IL-37 inhibited the maturation of DCs via the IL-1R8-TLR4-NF-κB pathway and attenuated atherosclerosis in ApoE-/- mice.

Increased expression of IL-1R8 and a possible immunomodulatory role of its ligand IL-37 in allergic rhinitis patients.

Allergic rhinitis (AR) is a chronic inflammatory airway disease that is caused by an abnormal T cell response. T helper (Th)-17 cells and Th2 cells are the CD4+ T cell subsets implicated in the pathogenesis of AR. The suppression of excessive responses of these Th17 and Th2 cells has been reported to be an effective therapeutic approach to treat AR patients, and continuous efforts are being undertaken to find new methods to modulate the function of these cells. Recent studies have shown that IL-1R8 and its ligand IL-37 negatively regulate the immune response. In this study, we investigated the immunomodulatory the roles of IL-37/IL-1R8 axis in AR patients. We found that IL-1R8 expression was very low on dendritic cells (DCs) and resting CD4+ T cells but increased strongly on CD4+ T cells following T cell activation. Furthermore, IL-1R8 expression on CD4+ T cells was markedly higher in AR patients than in healthy controls. The IL-1R8 ligand IL-37 could act on CD4+ T cells to inhibit IL-17 and IL-4 production but could not influence DC-induced IL-17- and IL-4-producing CD4+ T cell responses. Meanwhile, recombinant IL-37 (rIL-37) did not influence IL-6, IL-1ß, and IL-10 production by DCs and expression of co-stimulatory molecules (including CD80, CD40, CD86 and HLA-DR) in DCs. Thus, IL-37 may regulate aberrant T cell immune response of allergic rhinitis mainly through CD4+ T cells, not DCs. The immunomodulatory roles of the IL-37/IL-1R8 axis indicate the therapeutic potential of this axis in AR.

Characterization of a long isoform of IL-1R8 (TIR8/SIGIRR).

IL-1R8, also known as SIGIRR or TIR8, is a trans-membrane protein belonging to the IL-1 receptor family. The human gene includes ten exons, and alternative splicing can result in different isoforms. We, herein, characterized a longer isoform of IL-1R8 containing an in-frame additional sequence between the TIR domain and the C-terminal portion of the protein. IL-1R8 Long (IL-1R8L1) mRNA was specifically expressed and regulated in distinct cell lines, in a manner similar to the classic isoform. Overexpression of IL-1R8L1 resulted in the production of a corresponding protein that showed a pattern of cell localization similar to the classic isoform. An antibody directed against an IL-1R8L1 specific peptide, detected this novel isoform in different cell lines and tissues where this protein may complement the anti-inflammatory functions of classic IL-1R8.

High IL-1R8 expression in breast tumors promotes tumor growth and contributes to impaired antitumor immunity.

Tumors develop numerous strategies to fine-tune inflammation and avoid detection and eradication by the immune system. The identification of mechanisms leading to local immune dysregulation is critical to improve cancer therapy. We here demonstrate that Interleukin-1 receptor 8 (IL-1R8 - previously known as SIGIRR/TIR8), a negative regulator of Toll-Like and Interleukin-1 Receptor family signaling, is up-regulated during breast epithelial cell transformation and in primary breast tumors. IL-1R8 expression in transformed breast epithelial cells reduced IL-1-dependent NF-κB activation and production of pro-inflammatory cytokines, inhibited NK cell activation and favored M2-like macrophage polarization. In a murine breast cancer model (MMTV-neu), IL-1R8-deficiency reduced tumor growth and metastasis and was associated with increased mobilization and activation of immune cells, such as NK cells and CD8+ T cells. Finally, immune-gene signature analysis in clinical specimens revealed that high IL-1R8 expression is associated with impaired innate immune sensing and T-cell exclusion from the tumor microenvironment. Our results indicate that high IL-1R8 expression acts as a novel immunomodulatory mechanism leading to dysregulated immunity with important implications for breast cancer immunotherapy.

Interleukin 37 limits monosodium urate crystal-induced innate immune responses in human and murine models of gout.

BACKGROUND: Interleukin (IL)-37 has emerged as a fundamental inhibitor of innate immunity. Acute gout is a self-limiting inflammatory response to monosodium urate (MSU) crystals. In the current study, we assessed the preventive and therapeutic effect of recombinant human IL-37 (rhIL-37) in human and murine gout models. METHODS: We investigated the expression of IL-37 in patients with active and inactive gouty arthritis and assessed the effect of rhIL-37 in human and murine gout models: a human monocyte cell line (THP-1) and human synovial cells (containing macrophage-like and fibroblast-like synoviocytes) exposed to MSU crystals, a peritoneal murine model of gout and a murine gouty arthritis model. After inhibition of Mer receptor tyrosine kinase (Mertk), levels of IL-1ß, IL-8 and chemokine (C-C motif) ligand 2 (CCL-2) were detected by ELISA and expression of mammalian homologs of the drosophila Mad gene 3 (Smad), suppressor of cytokine signaling 3 (SOCS3), NACHT-LRR-PYD-containing protein 3 (NLRP3), and IL-8R of THP-1 were assessed by qPCR and western blot to explore the molecular mechanisms. RESULTS: Our studies strongly indicated that rhIL-37 played a potent immunosuppressive role in the pathogenesis of experimental gout models both in vitro and in vivo, by downregulating proinflammatory cytokines and chemokines, markedly reducing neutrophil and monocyte recruitment, and mitigating pathological joint inflammation. In our studies, rhIL-37 suppressed MSU-induced innate immune responses by enhancing expression of Smad3 and IL-1R8 to trigger multiple intracellular switches to block inflammation, including inhibition of NLRP3 and activation of SOCS3. Mertk signaling participated in rhIL-37 inhibitory pathways in gout models. By inhibition of Mertk, the anti-inflammatory effect of rhIL-37 was partly abrogated, and IL-1R8, Smad3 and S​OCS3 expression were suppressed, whereas NLRP3 expression was reactivated. CONCLUSIONS: Our studies reveal that IL-37 limits runaway inflammation initiated by MSU crystal-induced immune responses, partly in a Mertk-dependent fashion. Thus, rhIL-37 has both preventive and therapeutic effects in gouty arthritis.