The novel cytokine interleukin-36α is expressed in psoriatic and rheumatoid arthritis synovium

Influence of serum IL-36 subfamily cytokines on clinical manifestations of asthma

Background

The IL-36 subfamily, a member of the IL-1 superfamily, is thought to promote type 2 (T2) and non-T2 inflammation and involved in autoimmune and airway disease progression. However, its role in asthma remains unclear.

Objective

We sought to determine the contribution of the IL-36 subfamily to the clinical manifestation of asthma.

Methods

The levels of serum IL-36α, IL-36β, and IL-36γ, recognized as IL-36 subfamily agonists, and IL-36 receptor antagonist (IL-36Ra) and IL-38, recognized as IL-36 subfamily antagonists, were measured by ELISA in 110 asthma patients (55 with nonsevere and 55 with severe asthma) aged ≥20 years and 31 healthy individuals. The association of IL-36 with clinical indices and inflammatory mediators was examined. The characteristics of high and low IL-36 subgroups were explored.

Results

IL-36α, IL-36γ, and IL-36Ra levels were significantly higher in asthma patients, especially patients with severe asthma, than in healthy controls. The high IL-36γ group exhibited lower Asthma Control Test scores (P = .01), more frequent asthma exacerbations (AEs), and higher hazard ratio for AEs. The high IL-36Ra group exhibited higher values of forced expiratory volume in 1 second, more frequent severe AEs, and higher hazard ratio for severe exacerbations. The IL-36 cytokine levels, except for IL 36α, were positively correlated with IL-6, IL-13, IL-17, and/or IFN-γ levels. IL-36Ra was positively correlated with age-adjusted forced expiratory volume and forced vital capacity.

Conclusion

A systemically high IL-36 level is associated with asthma severity and with both T2 and non-T2 cytokines, and it implies poor condition and enhancement of risk of AEs in asthma patients.

LL37 complexed to double-stranded RNA induces RIG-I-like receptor signalling and Gasdermin E activation facilitating IL-36γ release from keratinocytes

The Interleukin-36 (IL-36) cytokine family have emerged as important players in mounting an inflammatory response at epithelial barriers and tailoring appropriate adaptive immune responses. As members of the Interleukin-1 superfamily, IL-36 cytokines lack a signal peptide for conventional secretion and require extracellular proteolysis to generate bioactive cytokines. Although the IL-36 family plays an important role in the pathogenesis of plaque and pustular psoriasis, little is known about the release mechanisms of these cytokines from keratinocytes and the physiological stimuli involved. Nucleic acid released from damaged or dying keratinocytes initiates early inflammatory signals that result in the breaking of tolerance associated with psoriasis pathogenesis onset. Cathelicidin peptide, LL37 binds to DNA or double-stranded RNA (dsRNA) and activates a type I Interferon responses in plasmacytoid dendritic cells and keratinocytes. Here, we demonstrate that LL37 binds to dsRNA and induces IL-36γ release from human primary keratinocytes. LL37/dsRNA complexes activate RIG-I-like Receptor signalling, resulting in Caspase-3 and Gasdermin E (GSDME) cleavage. Subsequent GSDME pore formation facilitates IL-36γ release. This response is magnified by priming with psoriasis-associated cytokines, IL-17A and IFNγ. IL-36γ release in this manner is largely independent of cell death in primary keratinocytes and lacked extracellular proteolysis of IL-36γ. Conversely, transfection of keratinocytes directly with dsRNA synthetic analogue, Poly(I:C) induces NLRP1 inflammasome activation, which facilitates IL-36γ expression and release in a GSDMD-dependent manner. Inflammasome-associated cell death also enables extracellular processing of IL-36γ by the release of keratinocyte-derived proteases. These data highlight the distinct responses triggered by dsRNA sensors in keratinocytes. Depending on the inflammatory context and magnitude of the exogenous threat, keratinocytes will release IL-36γ coupled with cell death and extracellular cleavage or release the inactive pro-form, which requires subsequent processing by neutrophil proteases to unleash full biological activity, as occurring in psoriatic skin. Cytoplasmic sensing of dsRNA in keratinocytes mediates IL-36γ release via caspase activity and GSDM pore formation Keratinocytes release IL-36γ upon stimulation with intracellular dsRNA alone or complexed to the psoriasis-associated cathelicidin anti-microbial peptide LL37. Left: Transfected dsRNA triggers NLRP1 inflammasome assembly and IL-1β release, which can enhance IL-36γ expression, resulting in IL-36γ release and extracellular cleavage by released proteases. Right: LL37/dsRNA complexes activate a MDA5-MAVS pathway facilitating the release of IL-36γ through Caspase-3 activation and GSDME pore formation.

The neuroimmune mechanism of pain induced depression in psoriatic arthritis and future directions

Patients suffering from psoriatic arthritis (PsA) often experience depression due to chronic joint pain, which significantly hinders their recovery process. However, the relationship between these two conditions is not well understood. Through a review of existing studies, we revealed that certain neuroendocrine hormones and neurotransmitters are involved in the neuroimmune interactions related to both PsA and depression. These include adrenocorticotropin-releasing hormone (CRH), adrenocorticotropin (ACTH), cortisol, monoamine neurotransmitters, and brain-derived neurotrophic factor (BDNF). Notably, the signalling pathway involving CRH, MCs, and Th17 cells plays a crucial role in linking PsA with depression; thus, this pathway may help clarify their connection. In this review, we outline the inflammatory immune changes associated with PsA and depression. Additionally, we explore how neuroendocrine hormones and neurotransmitters influence inflammatory responses in these two conditions. Finally, our focus will be on potential treatment strategies for patients with PsA and depression through the targeting of the CRH-MC-Th17 pathway. This review aims to provide a theoretical framework as well as new therapeutic targets for managing PsA alongside depression.

Autoantibody mediated deficiency of IL-36-receptor antagonist in a subset of patients with psoriasis and psoriatic arthritis

OBJECTIVE

Psoriatic arthritis (PsA) is known as a seronegative form of spondylarthropathy. The interleukin-36 cytokine family may have a major role in disease pathogenesis and particularly the related cutaneous manifestations. In light of our recent observations on (transient) autoantibody phenotypes neutralizing endogenous anti-inflammatory receptor antagonists (progranulin, IL-1Ra) in different inflammatory conditions, we set out to investigate the potential role of such antibodies targeting IL-36 cytokine family members in PsA and psoriasis without arthritic manifestations (Pso).

METHODS

In the present study we screened for hypothetic autoantibodies against the anti-inflammatory mediators IL-36 receptor antagonist (IL-36Ra) and anti-inflammatory IL-38 in PsA, Pso and inflammatory and healthy controls. Serum samples of patients with PsA (n = 254), Pso (n = 100), systemic lupus erythematosus (SLE, n = 50), rheumatoid arthritis (RA, n = 100), ulcerative colitis (UC, n = 50), Crohn´s disease (CD, n = 50), and healthy controls (n = 237) were screened for autoantibodies against IL-36Ra and IL-38 as well as IL-36Ra levels by ELISA. Biochemical analysis for immune complexes and atypic protein isoforms as well as IL-36 signaling reporter assays were performed.

RESULTS

Anti-IL-36Ra antibodies were detected in five out of 100 (5.0 %) patients with Pso, in 12 of 254 (4.72 %) patients with PsA and in one of 50 (2 %) patients with CD, but in none of the other investigated inflammatory or healthy controls. The IL-36Ra autoantibodies belonged to the IgG1 subclass and their titers ranged between 1:200 to 1:1600. They resulted in immune-complex formation, depletion of serum IL-36Ra levels and were functional in terms of facilitating unrestricted IL-36 signaling.

CONCLUSION

IL-36Ra autoantibodies were found in subgroups of patients with Pso and PsA and may drive respective pathology.

Molecular aspects of Interleukin-36 cytokine activation and regulation

Interleukin-36 (IL-36) cytokines are structurally similar to other Interleukin-1 superfamily members and are essential to convey inflammatory responses at epithelial barriers including the skin, lung, and gut. Due to their potent effects on immune cells, IL-36 cytokine activation is regulated on multiple levels, from expression and activation to receptor binding. Different IL-36 isoforms convey specific responses as a consequence of particular danger- or pathogen-associated molecular patterns. IL-36 expression and activation are regulated by exogenous pathogens, including fungi, viruses and bacteria but also by endogenous factors such as antimicrobial peptides or cytokines. Processing of IL-36 into potent bioactive forms is necessary for host protection but can elevate tissue damage. Indeed, exacerbated IL-36 signalling and hyperactivation are linked to the pathogenesis of diseases such as plaque and pustular psoriasis, emphasising the importance of understanding the molecular aspects regulating IL-36 activation. Here, we summarise facets of the electrochemical properties, regulation of extracellular cleavage by various proteases and receptor signalling of the pro-inflammatory and anti-inflammatory IL-36 family members. Additionally, this intriguing cytokine subfamily displays many characteristics that are unique from prototypical members of the IL-1 family and these key distinctions are outlined here.

NETs contribute to psoriasiform skin inflammation: A novel therapeutic approach targeting IL-36 cytokines by a small molecule tetrahydroxystilbene glucoside

BACKGROUND

Psoriasis, a chronic immune-mediated skin disease with pathological features such as aberrant differentiation of keratinocytes, dermal-epidermal inflammation, and angiogenesis. 2,3,5,4'-Tetrahydroxy stilbene 2-Ο-β-d-glucoside (2354Glu) is a natural small molecule polyhydrostilbenes isolated from Polygonum multiglorum Thunb. The regulation of IL-36 subfamily has led to new pharmacologic strategies to reverse psoriasiform dermatitis.

PURPOSE

Here we investigated the therapeutic potential of 2354Glu and elucidated the underlying mechanism in psoriasis.

METHODS

The effects of 2354Glu on IL-36 signaling were assessed by psoriasiform in vivo, in vitro and ex vivo model. The in vivo mice model of psoriasis-like skin inflammation was established by applying imiquimod (IMQ), and the in vitro and ex vitro models were established by stimulating mouse primary keratinocyte, human keratinocytes cells (HaCaT) and ex vivo skin tissue isolated from the mice back with Polyinosine-polycytidylic acid (Poly(I:C)), IMQ, IL-36γ and Lipopolysaccharide (LPS) respectively. Moreover, NETs formation was inhibited by Cl-amidine to evaluate the effect of NETs in psoriatic mouse model. The effects of 2354Glu on skin inflammation were assessed by western blot, H&E, immunohistochemistry, immunofluorescence, enzyme-linked immunosorbent assay and real-time quantitative PCR.

RESULTS

In Poly(I:C)-stimulated keratinocytes, the secretion of IL-36 was inhibited after treatment with 2354Glu, similar to the effects of TLR3, P2X7R and caspase-1 inhibitors. In aldara (imiquimod)-induced mice, 2354Glu (100 and 25 mg/kg) improved immune cell infiltration and hyperkeratosis in psoriasis by directly targeting IL-36 in keratinocytes through P2X7R-caspase-1. When treatment with 2354Glu (25 mg/kg) was insufficient to inhibit IL-36γ, NETs reduced pathological features and IL-36 signaling by interacting with keratinocytes to combat psoriasis like inflammation.

CONCLUSION

These results indicated that NETs had a beneficial effect on psoriasiform dermatitis. 2354Glu alleviates psoriasis by directly targeting IL-36/P2X7R axis and NET formation, providing a potential candidate for the treatment of psoriasis.

Role of IL-1 Family Cytokines IL-36, IL-37, IL-38 in Osteoarthritis and Rheumatoid Arthritis: A Comprehensive Review

Inflammatory cytokines, interleukin-36 (IL-36), IL-37, IL-38 belong to IL-1 family. The IL-36 subfamily obtains pro- and anti-inflammatory effects on various immune responses. Cytokine IL-37, has anti-inflammatory functions in immunity, and the recently identified IL-38 negatively associated with disease pathogenesis. To date, expression of IL-36, IL-37, IL-38 is reported dysregulated in osteoarthritis (OA) and rheumatoid arthritis (RA), and may be disease markers for arthritis-related diseases. Interestingly, expression of IL-38 was different either in OA patients or animal models, and expression of IL-36Ra in synovium was different in OA and RA patients. Moreover, functional studies have demonstrated significant role of these cytokines in OA and RA progress. These processes were related to immune cells and non-immune cells, where the cytokines IL-36, IL-37, IL-38 may regulate downstream signalings in the cells, and then involve in OA, RA development. In this review, we comprehensively discuss recent advancements in cytokines and the development of OA, RA. We hope that targeting these cytokines will become a potential treatment option for OA and RA in the future.

Emerging Role of the IL-36/IL-36R Axis in Multiple Inflammatory Skin Diseases

IL-36 is a most recent member of the IL-1 cytokine family, primarily expressed at barrier sites of the body such as the skin, lungs, and intestine. It plays a vital role in inflammation and is implicated in the development of various cutaneous; intestinal; and pulmonary disorders, including psoriasis, inflammatory bowel disease, and chronic obstructive pulmonary disease. IL-36 comprises 4 isoforms: the proinflammatory IL-36α, IL-36β, and IL-36γ and the anti-inflammatory IL-36R antagonist. An imbalance between proinflammatory and anti-inflammatory IL-36 isoforms can contribute to the inflammatory fate of cells and tissues. IL-36 cytokines signal through an IL-36R heterodimer mediating their function through canonical signaling cacade, including the NF-B pathway. Prominent for its role in psoriasis, IL-36 has recently been associated with disease mechanisms in atopic dermatitis, hidradenitis suppurativa, neutrophilic dermatoses, autoimmune blistering disease, and Netherton syndrome. The major cutaneous source of IL-36 cytokines is keratinocytes, pointing to its role in the communication between the epidermis, innate (neutrophils, dendritic cells) immune system, and adaptive (T helper [Th]1 cells, Th17) immune system. Thus, cutaneous IL-36 signaling is crucial for the immunopathological outcome of various skin diseases. Consequently, the IL-36/IL-36R axis has recently been recognized as a promising drug target for the treatment of inflammatory disorders beyond psoriasis. This review summarizes the current update on IL-36 cytokines in inflammatory skin diseases.

Immune cells in the epithelial immune microenvironment of psoriasis: emerging therapeutic targets

Psoriasis is a chronic autoimmune inflammatory disease characterized by erroneous metabolism of keratinocytes. The development of psoriasis is closely related to abnormal activation and disorders of the immune system. Dysregulated skin protective mechanisms can activate inflammatory pathways within the epithelial immune microenvironment (EIME), leading to the development of autoimmune-related and inflammatory skin diseases. In this review, we initially emphasized the pathogenesis of psoriasis, paying particular attention to the interactions between the abnormal activation of immune cells and the production of cytokines in psoriasis. Subsequently, we delved into the significance of the interactions between EIME and immune cells in the emergence of psoriasis. A thorough understanding of these immune processes is crucial to the development of targeted therapies for psoriasis. Finally, we discussed the potential novel targeted therapies aimed at modulating the EIME in psoriasis. This comprehensive examination sheds light on the intricate underlying immune mechanisms and provides insights into potential therapeutic avenues of immune-mediated inflammatory diseases.

Prognostic value of Interleukin-36s in cancers: A systematic review and meta-analysis

BACKGROUND

Interleukin-36s (IL-36s) are a category of inflammatory cytokines and an increasing number of studies over the past decade have found that different kinds of IL-36s play different roles in cancers. This systematic review and meta-analysis aimed to evaluate the prognostic value of IL-36s in different cancer types.

METHOD

Two reviewers independently searched in PubMed, Cochrane Library and EMBASE up to December 13, 2022. We extracted the hazard ratio (HR) and the confidence intervals (CIs) of the related prognostic outcomes and analyzed the pooled HR.

RESULTS

We included 12 studies including 1925 patients. In all, six studies including IL-36α, five including IL-36γ and one including IL-36β. A high expression of IL-36α was associated with better overall survival (OS) (HR = 0.48, 95 %CI: 0.37-0.62, P < 0.001) of cancer patients. The expression of IL-36γ was not related with cancers. Further, subgroup analysis showed that the expression of IL-36γ had no correlation with the OS of colorectal cancer (CRC) and non‑small cell lung cancer (NSCLC) patients. Interestingly, a high expression of IL-36γ played contrasting prognostic roles in hepatocellular carcinoma (HCC) (HR = 0.43, 95 %CI: 0.27-0.69, P < 0.001) patients and gastric cancer (GC) (HR = 1.58, 95 %CI: 1.33-1.87, P < 0.001) patients. The only IL-36β related study showed the expression of IL-36β was not correlated with the prognosis of CRC patients (P > 0.05).

CONCLUSION

IL-36α, IL-36β and IL-36γ possibly play different roles in different cancers. High expression of IL-36α may be associated with good prognostic value in cancer patients, especially in CRC patients. The association between cancers prognosis and expression of IL-36β or IL-36γ needs further evaluation. These conclusions need more clinical prognostic data for confirmation.

The role of the interleukin-36 axis in generalized pustular psoriasis: a review of the mechanism of action of spesolimab

Generalized pustular psoriasis (GPP) is a rare, chronic, inflammatory skin disorder characterized by recurrent flares associated with skin erythema, desquamation, and widespread superficial sterile pustules, which may be severe ("lakes of pus"). Systemic symptoms are often present, including malaise, fever, and skin pain. In GPP, innate immune responses are driven by abnormal activation of the interleukin (IL)-36-chemokine-neutrophil axis and excessive neutrophil infiltration. This review highlights the IL-36 pathway in the context of the IL-1 superfamily and describes how unopposed IL-36 signaling can lead to the development of GPP. Targeted inhibition of the IL-36 receptor (IL-36R) is an attractive therapeutic strategy in the treatment of GPP, including flare prevention and sustained disease control. Spesolimab is a first-in-class, humanized, monoclonal antibody that binds specifically to the IL-36R and antagonizes IL-36 signaling. Spesolimab was approved by the US Food and Drug Administration in September 2022 to treat GPP flares in adults and was subsequently approved for GPP flare treatment in other countries across the world. Anti-IL-36R therapy, such as spesolimab, can mitigate flares and address flare prevention in GPP, presumably through rebalancing IL-36 signaling and modulating the pro-inflammatory response of the downstream effectors.

IL-36α inhibits melanoma by inducing pro-inflammatory polarization of macrophages

Interleukin-36α (IL-36α) is essential for various inflammatory conditions, such as psoriasis and rheumatoid arthritis, whereas its role in tumor immunity is unclear. In this study, it was demonstrated that IL-36α could activate the NF-κB and MAPK signaling pathways in macrophages, leading to the expression of IL-1β, IL-6, TNF-α, CXCL1, CXCL2, CXCL3, CXCL5 and iNOS. Importantly, IL-36α has significant antitumor effects, altering the tumor microenvironment and promoting the infiltration of MHC IIhigh macrophages and CD8+ T cells while decreasing the levels of monocyte myeloid-derived suppressor cells, CD4+ T cells and regulatory T cells. This ultimately results in the inhibition of tumor growth and migration. Furthermore, IL-36α synergized with the PD-L1 antibody increased the immune cells infiltration and enhanced the anti-tumor effect of the PD-L1 antibody on melanoma. Collectively, this study reveals a new role for IL-36α in promoting anti-tumor immune responses in macrophages and suggests its potential for cancer immunotherapy.

IL36G genetic variant is independently associated with susceptibility, severity and joint involvement in psoriasis

Psoriasis (PsO) is a chronic, immune-mediated, inflammatory and polygenic dermatosis associated with both physical and psychological burden that can be triggered by injury, trauma, infections and medications. The etiology of PsO is not fully elucidated but genetic, epigenetic and environmental factors are all likely to play a role. A case-control study was carried out to evaluate the frequency of the IL36G C>T (rs13392494) and the IL36G A>G (rs7584409) variants and their association with susceptibility, joint involvement and severity of PsO. The study included 154 patients with PsO and 154 controls from Brazilian population. The severity of PsO was assessed by the Psoriasis Area and Severity Index (PASI). The IL36G (rs13392494 and rs7584409) variants were genotyped by allelic discrimination assay using the real-time polymerase chain reaction. The association between the IL36G genetic variants and the study variables was analyzed in allelic, dominant, codominant, overdominant, recessive, and haplotype models. The main results were that PsO patients were older (p < 0.001) and had higher body mass index (p < 0.001) than controls; 95.8% of the patients had plaque PsO, 16.1% had psoriatic arthritis (PsA), and 27.9% had PASI > 10. The IL36G rs1339294 variant showed no association with PsO in all genetic models while the IL36G rs7584409 variant showed a protective effect in PsO. However, the G allele of the IL36G rs7584409 in the dominant model was positively associated with PASI > 10 (p = 0.031). Moreover, patients with the GG genotype of the IL36G rs7584409 variant had about 5.0 times more chance of PsA than those with the AA genotype (p = 0.014). Regarding the haplotypes, the C/A in a recessive model (CACA versus C/G and T/A carriers) was associated with PsO (p = 0.035) while the C/G haplotype in a dominant model (C/A carriers versus C/G and T/A carriers) showed a protective effect for PsO (p = 0.041). In conclusion, the G allele of the IL36G rs7584409 variant was associated with protection to PsO; however, in patients with PsO, this same allele was associated with moderate to severe disease and PsA. These results suggest that the IL36G rs7584409 variant may be used as a possible genetic biomarker to predict severity and joint involvement of PsO.

Serum Interleukin-36 α as a Candidate Biomarker to Distinguish Behçet's Syndrome and Psoriatic Arthritis

Behçet's syndrome (BS) is a rare systemic vasculitis characterized by different clinical manifestations. As no specific laboratory tests exist, the diagnosis relies on clinical criteria, and the differential diagnosis with other inflammatory diseases can be challenging. Indeed, in a relatively small proportion of patients, BS symptoms include only mucocutaneous, articular, gastrointestinal, and non-typical ocular manifestations, which are frequently found also in psoriatic arthritis (PsA). We investigate the ability of serum interleukin (IL)-36α-a pro-inflammatory cytokine involved in cutaneous and articular inflammatory diseases-to differentiate BS from PsA. A cross-sectional study was performed on 90 patients with BS, 80 with PsA and 80 healthy controls. Significantly lower IL-36α concentrations were found in patients with BS as compared to PsA, although in both groups IL-36α was significantly increased compared to healthy controls. An empirical cut-off of 420.6 pg/mL displayed a specificity of 0.93, with a sensitivity of 0.70 (AUC 0.82) in discriminating PsA from BS. This cut-off displayed a good diagnostic performance also in BS patients lacking highly specific BS manifestations. Our results indicate that IL-36α might be involved in the pathogenesis of both BS and PsA, and might be a candidate biomarker to support the differential diagnosis of BS.

Role of Interleukin-36 in inflammatory joint diseases

Interleukin (IL)-36 is a family of cytokines that belongs to the larger IL-1 superfamily. IL-36 agonist/antagonist binds to the interleukin-36 receptor involving in physiological inflammation regulation and pathogenesis of many inflammatory diseases. In inflammatory joint diseases, the expression of IL-36 changes, and some studies have initially explored the role of IL-36 in these diseases. In psoriatic arthritis, IL-36 signal mediates plasma cell and fibroblast-like synoviocyte crosstalk presenting IL-36 agonist/antagonist imbalance. In rheumatoid arthritis, IL-36 agonists induce fibroblast-like synoviocyte to produce pro-inflammatory factors, while IL-36 antagonist deficiency leads to lesion progression. In osteoarthritis, IL-36 agonists induce chondrocytes to produce catabolic enzymes and pro-inflammatory factors. This article reviews the expression and function of IL-36 in different inflammatory joint diseases to provide a reference for revealing their pathogenic mechanisms and discovering therapeutic targets.

Evaluation of serum Interleukin 36 in Iraqi patients with Rheumatoid arthritis

Rheumatoid arthritis is a worldwide inflammatory chronic autoimmune disease with varying severity. Due to no definitive cure for this disease, current therapies aim to decrease the pain and slow further damage. The interleukin (IL)‐36 cytokine was little known for its role in rheumatoid arthritis; this research aimed to evaluate the serum IL36 levels in RA patients compared to healthy controls. This study included 80 patients with rheumatoid arthritis registered at the Rheumatology Clinic in Baghdad teaching hospital. The patients were divided into three groups based on the treatments received. Group 1 included patients treated with biological therapy (etanercept, adalimumab), Group2 patients with non-biological treatment (methotrexate hydroxychloroquine and prednisone), Group3 patients without any treatment and compared with Group 4 healthy control group. Patients is all groups were assessed for their serum IL-36 concentration; the mean IL-36 serum level was significantly higher in three groups of RA patients which include the group of patients treated with biological therapy (Enbrel (etanercept) and Humira (adalimumab) means were (1132.41±475.2,), and group of non-biological therapy patients (Methotrexate hydroxychloroquine and prednisone) (G2) means was 553.95±307, than patients' group without any treatment (G3) means was 1044.01±575.3 compared to the control (341.38±113.1) p-value> 0.00001. The patient's age and BMI were not significantly different between three groups of patient Rheumatoid arthritis. Parameters for this disease also were tested which include RF, CRP, ESR, anti-CCP and disease activity score-28 (DAS 28), there were significant differences when compared with the control group. IL-36 serum level was significantly higher in three groups of rheumatoid arthritis than those in controls, and when compared between three patients groups there was less concentration in the non-biological therapy treatment group means was 553.95±307 than in the rest of the patient groups,biology tratment, without any treatment, means were (1132.41±475.2, 1044.01±575.3) respectively. This study found that Rheumatoid arthritis patients' serum IL36 levels increased, where a non-biologic therapies reduced this cytokine. IL-36's pathogenic involvement in Rheumatoid arthritis needs more study. Keywords: Rheumatoid arthritis, IL-36, IL-1,C‐reactive protein, RF, ESR and anti-CCP.

Plasma IL-36α and IL-36γ as Potential Biomarkers in Interstitial Lung Disease Associated with Rheumatoid Arthritis: a Pilot Study in the Chinese Population

Interstitial lung disease (ILD) is a frequent extra-articular manifestation of rheumatoid arthritis (RA) and increases mortality in patients with RA. Early identification of ILD, especially the usual interstitial pneumonia (UIP) pattern with a poor prognosis, is important for guiding treatment of RA-ILD and preventing damage resulting from a delay in diagnosis. Interleukin-36 (IL-36) cytokines are involved in connective tissue diseases. However, IL-36 expression in RA-ILD is unknown. In this study, the clinical relevance of plasma IL-36 cytokines was evaluated in 39 patients with RA-ILD and three other groups (30 healthy controls [HCs], 35 RA patients without ILD, and 27 patients with idiopathic pulmonary fibrosis [IPF]) in the Chinese population. Plasma IL-36α and IL-36γ concentrations were elevated in patients with RA-ILD compared with those in HCs and patients with RA. RA-ILD patients with UIP pattern had higher plasma IL-36γ concentrations than those with RA-ILD without UIP, but these were lower than those in patients with IPF. Receiver operating curve analysis suggested that IL-36α and IL-36γ were potential biomarkers for identifying ILD in patients with RA. Additionally, the optimal cutoff value of IL-36γ for distinguishing RA-ILD with the UIP pattern from RA-ILD without UIP was 555.40 pg/mL and that for distinguishing RA-ILD from IPF was 655.10 pg/mL. No significant difference in plasma IL-36β or IL-36Ra concentrations was found between patients with RA-ILD and the three other groups. We also found that the lungs originating from different types of patients with PF, including RA-ILD and IPF, and those from mice following bleomycin-induced PF were characterized by increased IL-36γ expression. Our findings suggest that using IL-36 cytokines to identify patients with RA for further ILD workups may provide additional diagnostic value to the current clinically available assays. Moreover, IL-36γ may help to identify the presence of the UIP pattern in patients with RA-ILD and to discriminate RA-ILD from IPF.

Pro- and anti-inflammatory roles of interleukin (IL)-33, IL-36, and IL-38 in inflammatory bowel disease

Interleukin-33 (IL-33), IL-36, and IL-38 are members of the IL-1 cytokine family. The expression of each cytokine has been reported to be increased in the inflamed mucosa of patients with inflammatory bowel disease (IBD). IL-33 and IL-36 have been studied for pro- and anti-inflammatory functions, and IL-38 has been characterized as an anti-inflammatory cytokine by antagonizing the IL-36 receptor (IL-36R). IL-33 is a nuclear cytokine constitutively expressed by certain cell types such as epithelial, endothelial, and fibroblast-like cells and released on necrotic cell death. IL-33 mainly induces type 2 immune response through its receptor suppression tumorigenicity 2 (ST2) from Th2 cells and type 2 innate lymphoid cells (ILC2s), but also by stimulating Th1 cells, regulatory T cells, and CD8⁺ T cells. IL-36 cytokines consist of three agonists: IL-36α, IL-36β, and IL-36γ, and two receptor antagonists: IL-36R antagonist (IL-36Ra) and IL-38. All IL-36 cytokines bind to the IL-36R complex and exert various functions through NF-κB and mitogen-activated protein kinase (MAPK) pathways in inflammatory settings. IL-33 and IL-36 also play a crucial role in intestinal fibrosis characteristic manifestation of CD. In this review, we focused on the current understanding of the pro- and anti-inflammatory roles of IL-33, IL-36, and IL38 in experimental colitis and IBD patients.

Age/autoimmunity-associated B cells in inflammatory arthritis: An emerging therapeutic target

Age/autoimmunity-associated B cells (ABCs) are a novel B cell subpopulation with a unique transcriptional signature and cell surface phenotype. They are not sensitive to BCR but rely on TLR7 or TLR9 in the context of T cell-derived cytokines for the differentiation. It has been established that aberrant expansion of ABCs is linked to the pathogenesis of systemic autoimmune diseases such as systemic lupus erythematosus. Recently, we and other groups have shown that increased ABCs is associated with rheumatoid arthritis (RA) disease activity and have demonstrated their pathogenic role in RA, indicating that targeting specific B cell subsets is a promising strategy for the treatment of inflammatory arthritis. In this review, we summarize the current knowledge of ABCs, focusing on their emerging role in the pathogenesis of inflammatory arthritis. A deep understanding of the biology of ABCs in the context of inflammatory settings in vivo will ultimately contribute to the development of novel targeted therapies for the treatment of inflammatory arthritis.

Long noncoding RNA H19 alleviates inflammation in osteoarthritis through interactions between TP53, IL-38, and IL-36 receptor

Aims

Osteoarthritis (OA) is a common degenerative joint disease characterized by chronic inflammatory articular cartilage degradation. Long noncoding RNAs (lncRNAs) have been previously indicated to play an important role in inflammation-related diseases. Herein, the current study set out to explore the involvement of lncRNA H19 in OA.

Methods

Firstly, OA mouse models and interleukin (IL)-1β-induced mouse chondrocytes were established. Expression patterns of IL-38 were determined in the synovial fluid and cartilage tissues from OA patients. Furthermore, the targeting relationship between lncRNA H19, tumour protein p53 (TP53), and IL-38 was determined by means of dual-luciferase reporter gene, chromatin immunoprecipitation, and RNA immunoprecipitation assays. Subsequent to gain- and loss-of-function assays, the levels of cartilage damage and proinflammatory factors were further detected using safranin O-fast green staining and enzyme-linked immunosorbent assay (ELISA) in vivo, respectively, while chondrocyte apoptosis was measured using Terminal deoxynucleotidyl transferase dUTP Nick-End Labeling (TUNEL) in vitro.

Results

IL-38 was highly expressed in lentivirus vector-mediated OA mice. Meanwhile, injection of exogenous IL-38 to OA mice alleviated the cartilage damage, and reduced the levels of proinflammatory factors and chondrocyte apoptosis. TP53 was responsible for lncRNA H19-mediated upregulation of IL-38. Furthermore, it was found that the anti-inflammatory effects of IL-38 were achieved by its binding with the IL-36 receptor (IL-36R). Overexpression of H19 reduced the expression of inflammatory factors and chondrocyte apoptosis, which was abrogated by knockdown of IL-38 or TP53.

Conclusion

Collectively, our findings evidenced that upregulation of lncRNA H19 attenuates inflammation and ameliorates cartilage damage and chondrocyte apoptosis in OA by upregulating TP53, IL-38, and by activating IL-36R.

Cite this article: Bone Joint Res 2022;11(8):594–607.

IL-36 Cytokines: Their Roles in Asthma and Potential as a Therapeutic

Interleukin (IL)-36 cytokines are members of the IL-1 superfamily, which consists of three agonists (IL-36α, IL-36β and IL-36γ) and an IL-36 receptor antagonist (IL-36Ra). IL-36 cytokines are crucial for immune and inflammatory responses. Abnormal levels of IL-36 cytokine expression are involved in the pathogenesis of inflammation, autoimmunity, allergy and cancer. The present study provides a summary of recent reports on IL-36 cytokines that participate in the pathogenesis of inflammatory diseases, and the potential mechanisms underlying their roles in asthma. Abnormal levels of IL-36 cytokines are associated with the pathogenesis of different types of asthma through the regulation of the functions of different types of cells. Considering the important role of IL-36 cytokines in asthma, these may become a potential therapeutic target for asthma treatment. However, existing evidence is insufficient to fully elucidate the specific mechanism underlying the action of IL-36 cytokines during the pathological process of asthma. The possible mechanisms and functions of IL-36 cytokines in different types of asthma require further studies.

IL-36γ in enthesitis-related juvenile idiopathic arthritis and its association with disease activity

IL-36 has been implicated in the pathogenesis of spondyloarthropathies (SpA) like psoriasis and inflammatory bowel disease. Enthesitis-related arthritis (ERA) category of juvenile idiopathic arthritis is a form of juvenile SpA, however, no data is available on the role of IL-36 in this disease. IL-36α, β, γ and IL-36R mRNA expression in blood and synovial fluid mononuclear cells and IL-36α, γ, IL-36Ra, IL-6, and IL-17 levels were measured in serum and synovial fluid (SF). IL-36γ production by fibroblast-like synoviocytes (FLS) upon stimulation with pro-inflammatory cytokines and its effect on FLS were also studied. mRNA levels of IL-36α, IL-36γ, and IL-36R were increased in PBMCs of ERA patients as compared to healthy controls however only IL-36γ was measurable in the serum of one-third of patients. In SFMCs, all four mRNA were detectable but were lower than RA patients. SF IL-36γ levels correlated with disease activity score (r = 0.51, P < 0.0001), SF IL-6 (r = 0.4, P = 0.0063) and IL-17 levels (r = 0.57, P = 0.0018). Pro-inflammatory cytokines increased the expression of IL-36γ and IL-6 in FLS cultures. SFs from five ERA patients also increased expressions of IL-36γ and IL-6 in FLS which could be blocked by using IL-36Ra. This suggests that pro-inflammatory cytokines aid in the upregulation of IL-36γ which in turn may upregulate the expression of IL-6. This might lead to a positive feedback loop of inflammation in ERA. Association of SF levels of IL-36γ with disease activity further supports this possibility. IL-36Ra based therapy may have a role in ERA.

Interleukin-36α is elevated in diffuse systemic sclerosis and may potentiate fibrosis

Systemic sclerosis (SSc) is an autoimmune prototypical connective tissues disease that results in alterations in vasculature, inflammation and fibrosis of the skin. Interleukin-1 family cytokines has been implicated in the disease including IL-1. IL-36α is an IL-1 family member that is clearly implicated in psoriatic skin disease but its role in systemic sclerosis disease is not clear. The aim of this work is to evaluate the levels and role of IL-36α in systemic sclerosis. Early diffuse SSc patients sera was isolated along with healthy controls and IL-36 levels quantified by ELISA. In vitro analysis was also undertaken with primary dermal fibroblasts with recombinant IL-36α and keratinocyte cells were also incubated with IL-36α. Cytokines were measured by ELISA. Serum IL-36 was significantly elevated compared to healthy controls. Elevated neutrophil elastase was also elevated in the matched sera. IL-36 was not directly pro-fibrotic in dermal fibroblasts but did induce pro-inflammatory cytokines that were dependant on the MAPK pathway for their release. IL-36α also led to release of CCL20 and CCL2 in keratinocytes which may potentiate fibrosis. IL-36α is elevated in SSc serum and whilst not directly pro-fibrotic it may through keratinocytes, potentiate fibrosis through keratinocyte-immune fibroblast cross-talk.

IL-36 is Closely Related to Neutrophilic Inflammation in Chronic Obstructive Pulmonary Disease

Background

Interleukin (IL)-36α, IL-36β, and IL-36γ belong to the IL-36 family and play an important role in the pathogenesis of many diseases. Chronic obstructive pulmonary disease (COPD) may be correlated with IL-36; however, the specific role of IL-36 in COPD is unclear. In this study, we aimed to clarify whether IL-36 could be an indicator for determining COPD severity and the specific nature of the pro-inflammatory effects of IL-36 in COPD.

Methods

A total of 70 patients with COPD and 20 control subjects were included in this study. We collected peripheral blood samples from both the groups, analyzed the blood cell fractions by routine blood examination, and measured the serum levels of IL-36α, IL-36β, and IL-36γ by performing polymerase chain reaction and enzyme-linked immunosorbent assay. In addition, the correlation between the number of neutrophils and eosinophils and the level of IL-36 was also analyzed.

Results

We found that level of IL-36 in patients with COPD was positively correlated with the number of neutrophils but not with eosinophils, whereas the correlation was not found in the control group. Moreover, the level of IL-36 was negatively correlated with the level of lung function of patients with COPD, and the levels of IL-36α, IL-36β, and IL-36γ increased with advancing disease severity.

Conclusion

In COPD, the pro-inflammatory effect of IL-36 is closely related to neutrophils, and hence, IL-36 might be considered a novel biomarker for determining COPD severity.

A positive feedback loop between gastric cancer cells and tumor-associated macrophage induces malignancy progression

BACKGROUND

Hypoxia and inflammation tumor microenvironment (TME) play a crucial role in tumor development and progression. Although increased understanding of TME contributed to gastric cancer (GC) progression and prognosis, the direct interaction between macrophage and GC cells was not fully understood.

METHODS

Hypoxia and normoxia macrophage microarrays of GEO database was analyzed. The peripheral blood mononuclear cell acquired from the healthy volunteers. The expression of C-X-C Motif Chemokine Ligand 8 (CXCL8) in GC tissues and cell lines was detected by quantitative reverse transcription PCR (qRT-PCR), western-blot, Elisa and immunofluorescence. Cell proliferation, migration, and invasion were evaluated by cell counting kit 8 (CCK8), colony formation, real-time imaging of cell migration and transwell. Flow Cytometers was applied to identify the source of cytokines. Luciferase reporter assays and chromatin immunoprecipitation were used to identify the interaction between transcription factor and target gene. Especially, a series of truncated and mutation reporter genes were applied to identify precise binding sites. The corresponding functions were verified in the complementation test and in vivo animal experiment.

RESULTS

Our results revealed that hypoxia triggered macrophage secreted CXCL8, which induced GC invasion and proliferation. This macrophage-induced GC progression was CXCL8 activated C-X-C Motif Chemokine Receptor 1/2 (CXCR1/2) on the GC cell membrane subsequently hyperactivated Janus kinase 1/ Signal transducer and activator of transcription 1 (JAK/STAT1) signaling pathway. Then, the transcription factor STAT1 directly led to the overexpression and secretion of Interleukin 10 (IL-10). Correspondingly, IL-10 induced the M2-type polarization of macrophages and continued to increase the expression and secretion of CXCL8. It suggested a positive feedback loop between macrophage and GC. In clinical GC samples, increased CXCL8 predicted a patient's pessimistic outcome.

CONCLUSION

Our work identified a positive feedback loop governing cancer cells and macrophage in GC that contributed to tumor progression and patient outcome.

A review of IL-36: an emerging therapeutic target for inflammatory dermatoses

BACKGROUND

IL-36 cytokines are members of the IL-1 superfamily. Increasing evidence in the IL-36 pathway demonstrates their potential as a therapeutic target for treating inflammatory skin diseases, such as generalized pustular psoriasis (GPP).

OBJECTIVE

A narrative review was written to further study preclinical and clinical evidence for the role of IL-36 in psoriasis, atopic dermatitis (AD), hidradenitis suppurativa (HS), acne, autoimmune blistering diseases, and neutrophilic dermatoses.

RESULTS

IL-36 has important downstream effects such as inducing expression of inflammatory cytokines, antimicrobial peptides, and growth factors. Increased expression of IL-36 cytokines has been observed in the lesional skin of patients with psoriasis. Studies of other inflammatory skin diseases have also noted similar findings, albeit to a lesser extent. IL-36 inhibition has been shown to be effective in GPP and is currently being studied for other inflammatory skin diseases.

CONCLUSIONS

The IL-36 pathway contributes to pathogenesis of many inflammatory skin diseases and is a promising therapeutic target.

Increased Levels of Interleukin-36 in Obesity and Type 2 Diabetes Fuel Adipose Tissue Inflammation by Inducing Its Own Expression and Release by Adipocytes and Macrophages

Interleukin (IL)-36 is a recently described cytokine with well-known functions in the regulation of multiple inflammatory diseases. Since no data exists on how this cytokine regulates adipose tissue (AT) homeostasis, we aimed to explore the function of a specific isoform, IL-36γ, an agonist, in human obesity and obesity-associated type 2 diabetes as well as in AT inflammation and fibrosis. Plasma IL-36γ was measured in 91 participants in a case-control study and the effect of weight loss was evaluated in 31 patients with severe obesity undergoing bariatric surgery. Gene expression levels of IL36G and its receptor were analyzed in relevant human metabolic tissues. The effect of inflammatory factors and IL-36γ was determined in vitro in human adipocytes and macrophages. We found, for the first time, that the increased (P<0.05) circulating levels of IL-36γ in patients with obesity decreased (P<0.001) after weight and fat loss achieved by Roux-en-Y gastric bypass and that gene expression levels of IL36G were upregulated in the visceral AT (P<0.05) and in the peripheral blood mononuclear cells (P<0.01) from patients with obesity. We also demonstrated increased (P<0.05) expression levels of Il36g in the epididymal AT from diet-induced obese mice. IL36G was significantly enhanced (P<0.001) by LPS in human adipocytes and monocyte-derived macrophages, while no changes were found after the incubation with anti-inflammatory cytokines. The addition of IL-36γ for 24 h strongly induced (P<0.01) its own expression as well as key inflammatory and chemoattractant factors with no changes in genes associated with fibrosis. Furthermore, adipocyte-conditioned media obtained from patients with obesity increased (P<0.01) the release of IL-36γ and the expression (P<0.05) of cathepsin G (CTSG) in monocyte-derived macrophages. These findings provide, for the first time, evidence about the properties of IL-36γ in the regulation of AT-chronic inflammation, emerging as a link between AT biology and the obesity-associated comorbidities.

The anti-inflammatory and protective role of interleukin-38 in inflammatory bowel disease

Interleukin (IL)-38 exerts an anti-inflammatory function by binding to several cytokine receptors, including the IL-36 receptor. In this study, we evaluated IL-38 expression in the inflamed mucosa of patients with inflammatory bowel disease (IBD) and investigated its functions. IL-38 mRNA expression in endoscopic biopsy samples was evaluated using quantitative PCR. IL-38 protein expression was analyzed using immunohistochemical technique. Dextran sulfate sodium-induced colitis was induced in C57BL/6 background IL-38KO mice. The IL-38 mRNA and protein expression were enhanced in the active mucosa of ulcerative colitis, but not in Crohn's disease. The ratio of IL-36γ to IL-38 mRNA expression was significantly elevated in the active mucosa of UC patients. Immunofluorescence staining revealed that B cells are the major cellular source of IL-38 in the colonic mucosa. IL-38 dose-dependently suppressed the IL-36γ-induced mRNA expression of CXC chemokines (CXCL1, CXCL2, and CXCL8) in HT-29 and T84 cells. IL-38 inhibited the IL-36γ-induced activation of nuclear-factor kappa B (NF-κB) and mitogen-activated protein kinases in HT-29 cells. DSS-colitis was significantly exacerbated in IL-38KO mice compared to wild type mice. In conclusion, IL-38 may play an anti-inflammatory and protective role in the pathophysiology of IBD, in particular ulcerative colitis, through the suppression of IL-36-induced inflammatory responses.

IL-36 cytokines imprint a colitogenic phenotype on CD4+ T helper cells

IL-36 cytokines are emerging as potent orchestrators of intestinal inflammation and are being implicated in the pathogenesis of inflammatory bowel diseases (IBD). However, the mechanisms through which these cytokines mediate these effects remain to be fully uncovered. Here, we report specifically elevated expression of IL-36α, and not IL-36β or IL-36γ in the serum of newly diagnosed, treatment naïve, paediatric IBD patients and identify T cells as primary cellular mediators of IL-36 responses in the inflamed gut. IL-36R expression on CD4⁺ T cells was found to promote intestinal pathology in a murine model of colitis. Consistent with these effects, IL-36R can act as a potent instructor of CD4⁺ T cell differentiation in vivo, enhancing Th1 responses, while inhibiting the generation of Tregs. In addition, loss of IL-36 responsiveness significantly reduced the migration of pathogenic CD4⁺ T cells towards intestinal tissues and IL-36 was found to act, uniquely among IL-1 family members, to induce the expression of gut homing receptors in proinflammatory murine and human CD4⁺ T cells. These data reveal an important role for IL-36 cytokines in driving the colitogenic potential of CD4⁺ T cells and identify a new mechanism through which they may contribute to disease pathogenesis.

The Role of Interleukins in the Pathogenesis of Dermatological Immune-Mediated Diseases

Autoimmune inflammatory diseases are primarily characterized by deregulated expression of cytokines, which drive pathogenesis of these diseases. A number of approved and experimental therapies utilize monoclonal antibodies against cytokine proteins. Cytokines can be classified into different families including the interleukins, which are secreted and act on leukocytes, the tumor necrosis factor (TNF) family, as well as chemokine proteins. In this review article, we focus on the interleukin family of cytokines, of which 39 members have been identified to this date. We outline the role of each of these interleukins in the immune system, and various dermatological inflammatory diseases with a focused discussion on the pathogenesis of psoriasis and atopic dermatitis. In addition, we describe the roles of various interleukins in psychiatric, cardiovascular, and gastrointestinal comorbidities. Finally, we review clinical efficacy and safety data from emerging late-phase anti-interleukin therapies under development for psoriasis and atopic dermatitis. Collectively, additional fundamental and clinical research remains necessary to fully elucidate the roles of various interleukin proteins in the pathogenesis of inflammatory dermatologic diseases, and treatment outcomes in patients.

IL-38 and IL-36 Target Autophagy for Regulating Synoviocyte Proliferation, Migration, and Invasion in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease leading to severe joint damage and disability. Fibroblast-like synoviocytes (FLSs) mostly contribute to the joint inflammation and destruction in RA through distinct mechanisms. However, little is known about newly discovered interleukin- (IL-) 36 and IL-38 involving in the pathology of RA. Here, we assessed the effect of IL-36 and IL-38 on RA-FLS function using IL-36 and IL-38 overexpression plasmids. We found that IL-36 inhibited synoviocytes proliferation while IL-38 showed an opposite influence. Furthermore, IL-36 and IL-38 significantly sequestered or accelerated RA-FLS migration and invasion capacity, respectively. Mechanically, IL-36 and IL-38 targeted autophagy for RA-FLS modulation. Using autophagy inhibitor 3-MA and inducer compound rapamycin, we found that autophagy negatively regulated the survival, migration, and invasion of synovial cells. Based on these results, IL-38 in combination with autophagy inhibitor 3-MA treatment demonstrated the strongest blockage of the above three activities of RA-FLS, and IL-38 overexpression reversed rapamycin-inhibited cell proliferation, migration, and invasion. Moreover, injection of IL-36 can improve the symptoms of RA in a rat model of RA. Taken together, we conclude that IL-38 and IL-36 target autophagy for regulating synoviocyte proliferation, migration, and invasion in RA.

Evaluation of Serum Interleukin-38 Levels in Different Radiographic Grades of Idiopathic Knee Osteoarthritis

The aim of this study was to assess interleukin-1β (IL-1β), IL-1Ra, IL-36, and IL-38 levels together with hs-CRP levels in patients with different radiographic grades of knee osteoarthritis (OA) in comparison to healthy individuals. Consecutive patients aged over 50 years who were admitted to our Orthopaedics and Traumatology department between November 2018 and March 2019 and diagnosed as knee OA according to the American College of Rheumatology criteria were included in this prospective case-control study. Patients with knee OA were staged according to radiographic Kellgren-Lawrence (K-L) classification and 20 patients were assigned to each group. An age and gender matched control group consisted healthy volunteers with no clinical and radiographic sign of arthritis were conducted as the control group. Venous blood samples were collected and assessed for hs-CRP, IL-1β, IL-1Ra, IL-36, and IL-38 levels using the double-antibody sandwich ELISA method. The hs-CRP, IL-1β, IL-36 and IL-38 levels did not significantly differ among controls and independent radiographic stage groups except IL-1Ra levels which was significantly higher in K-L grade 4 knee OA groups compared to healthy controls (P = 0.045). When we compared all patients with knee OA and healthy controls, we detected that IL-1 and IL-1Ra were significantly lower and IL-38 levels were significantly higher in healthy control group compared to patients with knee OA (P = <0.001, <0.001, and 0.019, respectively). According to results obtained from our study, IL-1β, IL-1Ra, and IL-38 levels significantly differed between healthy individuals and patients with knee OA. However, we did not observe a significant difference and correlation between radiographic grade of knee OA and interleukin levels.

Serum Levels of Interleukin-36 Alpha and Interleukin-36 Receptor Antagonist In Behcet’s Syndrome

Background Behcet’s syndrome (BS) is a systemic vasculitic disorder. This study aimed to investigate the levels of serum IL-36α and IL-36Ra in patients with BS.

Material and Methods A total of 80 subjects (60 BS patients and 20 healthy controls [HC]) were included.

Results The median IL-36α level was 0.11 ng/ml in the BS group and 0.09 ng/ml in the HC group (p=0.058). The mean IL-36Ra level was 13.62 pg/ml in the BS group and 13.26 pg/ml in the HC group (p=0.348). Serum IL-36Ra levels of the active group were significantly higher (p=0.037). Patients with oral ulcers and central nervous system involvement had higher serum IL36Ra levels. In the BS group, a positive correlation was found between serum IL-36Ra and CRP. In a multivariate analysis, the IL-36Ra level (OR=1.067; 95% CI=1.001–1.137; p=0.045) was independently associated with disease activity.

Conclusion According to these findings, it is not clear whether such a slight difference is clinically significant, but they suggest that the IL-36 cytokine family may play a role in the course of the disease.

Interleukin-36α inhibits colorectal cancer metastasis by enhancing the infiltration and activity of CD8+ T lymphocytes

Colorectal cancer is one of the deadliest cancers, and the discovery of new diagnostic biomarkers and therapeutic targets is vital. Interleukin-36α (IL-36α) is a proinflammatory factor that can initiate the inflammatory response and promote the systemic T helper-1 (Th1) immune response. In this study, we investigated the immunological role of IL-36α in CRC. We found that IL-36α was downregulated in human CRC tissues. Patients with high IL-36α levels showed better survival and low IL-36α expression was significantly associated with greater tumor distal metastasis and TNM stage. We constructed two cell lines overexpressing IL-36α (CT26-IL-36α and HT29-IL-36α cells). In vitro assays revealed that IL-36α overexpression reduced the proliferation, migration, and invasion of CT26-IL-36α, and HT29-IL-36α cells. Using CT26-vector and CT26-IL-36α tumor mouse model and lung metastasis models, we found that IL-36α overexpression elicited a significant antitumor effect and inhibited lung metastasis in vivo. These inhibitory effects were associated with an increase in the number of CD3+CD8+ T lymphocytes within the tumor tissue as well as increased cytokine production in CD8+ T lymphocytes present in the tumor, spleen, and draining lymph nodes. Furthermore, we revealed that CT26-IL-36α cells enhanced the secretion of CXCL10 and CXCL11 from chemotactic CD8+ T lymphocytes, as compared with CT26-vector cells. Taken together, these results suggest that IL-36α is a promising therapeutic agent for targeting CRC by promoting the activation, proliferation, and tumor infiltration of T lymphocytes.

LncRNA THUMPD3-AS1 enhances the proliferation and inflammatory response of chondrocytes in osteoarthritis

OBJECTIVE

Long noncoding RNAs (lncRNAs) regulate the occurrence and development of osteoarthritis (OA), whereas the biological roles and mechanisms of the lncRNA THUMPD3-AS1 (THUMPD3 antisense RNA 1) in OA remain still unclear. This study described the role and molecular mechanism of lncRNA THUMPD3-AS1 in regulating OA biology.

METHOD

The knee normal and OA cartilage tissues from ten participants were sequenced to reveal the differentially expressed lncRNAs. The interleukin (IL)-1β-stimulated C28/I2 cell served as OA cells. Flow cytometry assays, Western blot, enzyme-linked immunosorbent assays were used for our experiments.

RESULTS

The results revealed that lncRNA THUMPD3-AS1 was downregulated in OA cartilage tissues and IL-1β-stimulated chondrocyte cell line. Overexpression of lncRNA THUMPD3-AS1 alleviated cell apoptosis and facilitated inflammatory responses, whereas knockdown had opposite effects. LncRNA THUMPD3-AS1 markedly increased the cyclin E2, cyclin-dependent kinase 4, B-cell lymphoma 2, tumor necrosis factor-α, nitric oxide, and IL-6 levels, and decreased the caspase-3 level. Furthermore, the target proteins of phosphorylation were identified as nuclear factor-κB p65 and mitogen-activated protein kinase p38, which could be indirectly suppressed by lncRNA THUMPD3-AS1 knockdown.

CONCLUSION

Our findings highlight the different effects of lncRNA THUMPD3-AS1 on cell apoptosis and inflammatory response, which extend the multiple functions of lncRNA epigenetics in OA biology.

The Role of IL-36 in the Pathophysiological Processes of Autoimmune Diseases

A member of the interleukin (IL)-1 superfamily was IL-36, which contained IL-36α, IL-36β, IL-36γ, and IL-36Ra. Heterotrimer complexes, consisting of heterodimeric receptor complexes and IL-36 agonist, gave signals through intracellular functional domains, so as to bind to downstream proteins and induce inflammatory response. IL-36 agonists upregulated mature-associated CD80, CD86, MHCII, and inductively produced several pro-inflammatory cytokines through the IL-36R-dependent manner in dendritic cells (DCs). Besides, DCs had the ability to initiate the differentiation of helper T (Th) cells. Up to date, the role of IL-36 in immunity, inflammation and other diseases is of great importance. Additionally, autoimmune diseases were characterized by excessive immune response, resulting in damage and dysfunction of specific or multiple organs and tissues. Most autoimmune diseases were related to inflammatory response. In this review, we will conclude the recent research advances of IL-36 in the occurrence and development of autoimmune diseases, which may provide new insight for the future research and the treatment of these diseases.

IL-36 in chronic inflammation and fibrosis - bridging the gap?

IL-36 is a member of the IL-1 superfamily and consists of three agonists and one receptor antagonist (IL-36Ra). The three endogenous agonists, IL-36α, -β, and -γ, act primarily as proinflammatory cytokines, and their signaling through the IL-36 receptor (IL-36R) promotes immune cell infiltration and secretion of inflammatory and chemotactic molecules. However, IL-36 signaling also fosters secretion of profibrotic soluble mediators, suggesting a role in fibrotic disorders. IL-36 isoforms and IL-36 have been implicated in inflammatory diseases including psoriasis, arthritis, inflammatory bowel diseases, and allergic rhinitis. Moreover, IL-36 has been connected to fibrotic disorders affecting the kidney, lung, and intestines. This review summarizes the expression, cellular source, and function of IL-36 in inflammation and fibrosis in various organs, and proposes that IL-36 modulation may prove valuable in preventing or treating inflammatory and fibrotic diseases and may reveal a mechanistic link between inflammation and fibrosis.

Importance of lymphocyte-stromal cell interactions in autoimmune and inflammatory rheumatic diseases

Interactions between lymphocytes and stromal cells have an important role in immune cell development and responses. During inflammation, stromal cells contribute to inflammation, from induction to chronicity or resolution, through direct cell interactions and through the secretion of pro-inflammatory and anti-inflammatory mediators. Stromal cells are imprinted with tissue-specific phenotypes and contribute to site-specific lymphocyte recruitment. During chronic inflammation, the modified pro-inflammatory microenvironment leads to changes in the stromal cells, which acquire a pathogenic phenotype. At the site of inflammation, infiltrating B cells and T cells interact with stromal cells. These interactions induce a plasma cell-like phenotype in B cells and T cells, associated with secretion of immunoglobulins and inflammatory cytokines, respectively. B cells and T cells also influence the stromal cells, inducing cell proliferation, molecular changes and cytokine production. This positive feedback loop contributes to disease chronicity. This Review describes the importance of these cell interactions in chronic inflammation, with a focus on human disease, using three selected autoimmune and inflammatory diseases: rheumatoid arthritis, psoriatic arthritis (and psoriasis) and systemic lupus erythematosus. Understanding the importance and disease specificity of these interactions could provide new therapeutic options.

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

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

Translational Research Studies Unraveling the Origins of Psoriatic Arthritis: Moving Beyond Skin and Joints

Patients with psoriatic arthritis (PsA) are suffering from a decreased quality of life despite currently available treatments. In the latest years, novel therapies targeting the IL-17/IL-23 and TNF pathways improved clinical outcome. Despite this, remission of disease is not achieved in a considerable group of patients, continuous treatment is very often required to reach clinical remission, and prevention of PsA in patients with psoriasis (PsO) is currently impossible. A better understanding of PsA pathogenesis is required to develop novel treatment strategies that target inflammation and destruction more effectively and at an early stage of the disease, or even before clinically manifest disease. The skin is considered as one of the sites of onset of immune activation, triggering the inflammatory cascade in PsA. PsO develops into PsA in 30% of the PsO patients. Influenced by environmental and genetic factors, the inflammatory process in the skin, entheses, and/or gut may evolve into synovial tissue inflammation, characterized by influx of immune cells. The exact role of the innate and adaptive immune cells in disease pathogenesis is not completely known. The involvement of activated IL-17A+ T cells could implicate early immunomodulatory events generated in lymphoid organs thereby shaping the pathogenic inflammatory response leading to disease. In this perspective article, we provide the reader with an overview of the current literature regarding the immunological changes observed during the earliest stages of PsA. Moreover, we will postulate future areas of translational research aimed at increasing our knowledge on the molecular mechanisms driving disease development, which will aid the identification of novel potential therapeutic targets to limit the progression of PsA.

IL-36 cytokines in inflammatory and malignant diseases: not the new kid on the block anymore

The IL-36 family of cytokines were first identified in 2000 based on their sequence homology to IL-1 cytokines. Over subsequent years, the ability of these cytokines to either agonise or antagonise an IL-1R homologue, now known as the IL-36 Receptor (IL-36R), was identified and these cytokines went through several cycles of renaming with the current nomenclature being proposed in 2010. Despite being identified over 20 years ago, it is only during the last decade that the function of these cytokines in health and disease has really begun to be appreciated, with both homeostatic functions in wound healing and response to infection, as well as pathological functions now ascribed. In the disease context, over activation of IL-36 has now been associated with many inflammatory diseases including Psoriasis and inflammatory bowel diseases, with roles in cancer also now being investigated. This review summarises the current knowledge of IL-36 biology, its role in inflammatory diseases and focuses on an emerging role for IL-36 in cancer.

Interleukin-36γ aggravates macrophage foam cell formation and atherosclerosis progression in ApoE knockout mice

Atherosclerosis-related cardiovascular diseases are the leading cause of mortality worldwide. Macrophage-derived foam cell formation is a critical early event in atherogenesis. However, the molecular pathways involved in this disease have not been fully elucidated. Interleukin (IL)-36 plays a crucial role in inflammation, and this study was conducted to investigate the possible role of IL-36γ in the pathogenesis and regulation of atherosclerosis. In this study, we show that IL-36γ regulates inflammatory responses and lipoprotein metabolic processes in macrophages and exerts its atherosclerosis-promoting effects by increasing macrophage foam cell formation and uptake of oxidized low-density lipoproteins. Mechanistically, IL-36γ specifically upregulates expression of the scavenger receptor CD36 through the phosphoinositide 3-kinase pathway in macrophages. These results contribute to our understanding of IL-36γ as a novel regulator of foam cell formation and atherogenesis progression.

The Role of IL-36 in Infectious Diseases: Potential Target for COVID-19?

IL-36 is a member of the interleukin 1 cytokine family, which is currently experiencing a renaissance due to the growing understanding of its context-dependent roles and advances in our understanding of the inflammatory response. The immunological role of IL-36 has revealed its profound and indispensable functional roles in psoriasis, as well as in several inflammatory diseases, including inflammatory bowel disease (IBD), systemic lupus erythematosus, rheumatoid arthritis (RA) and cancer. More recently, an increasing body of evidence suggests that IL-36 plays a crucial role in viral, bacterial and fungal infections. There is a growing interest as to whether IL-36 contributes to host protective immune responses against infection as well as the potential implications of IL-36 for the development of new therapeutic strategies. In this review, we summarize the recent progress in understanding cellular expression, regulatory mechanisms and biological roles of IL-36 in infectious diseases, which suggest more specific strategies to maneuver IL-36 as a diagnostic or therapeutic target, especially in COVID-19.

Interleukin-36α suppresses growth of non-small cell lung cancer in vitro by reducing angiogenesis

Interleukin (IL)-36α, a newly recognized IL-1 family member, has been previously reported to play a pivotal role in autoimmunity diseases and acute inflammatory reactions. Recently, several studies have indicated that IL-36α has potential anticancer effects against certain types of cancer. However, the expression pattern and functional role of IL-36α in non-small cell lung cancer (NSCLC) have not been elucidated. Here, we report that the mRNA and protein levels of IL-36α are significantly reduced in NSCLC tissues. Low levels of intratumoral IL-36α are correlated with higher tumor status, advanced TNM stage, increased vascular invasion and shorter overall survival (OS). Intratumoral IL-36α expression is an independent prognostic factor for OS (hazard ratio = 3.081; P = 0.012) in patients with NSCLC. Overexpression of IL-36α in lung cancer cells did not disturb cell proliferation, apoptosis or cell-cycle distribution in vitro, but markedly inhibited tumor growth in vivo. Mechanistically, IL-36α reduced the expression and secretion of vascular endothelial growth factor A through inhibiting hypoxia-inducible factor 1α expression. Finally, decreased IL-36α expression was associated with high microvessel density and vascular endothelial growth factor A in patients with NSCLC. Together, our findings suggest that IL-36α expression is a valuable marker indicating poor prognosis in patients with NSCLC.

Exploring the Role of IL-36 Cytokines as a New Target in Psoriatic Disease

Unmet needs in the treatment of psoriasis call for novel therapeutic strategies. Pustular psoriasis and psoriatic arthritis often represent a therapeutic challenge. Focus on IL-36 cytokines offers an interesting approach, as the IL-36 axis has been appointed a critical driver of the autoinflammatory responses involved in pustular psoriasis. Two IL-36R blocking antibodies, imsidolimab and spesolimab, are currently undergoing phase II and III clinical trials, with promising results.

Elevated sputum IL-36 levels are associated with neutrophil-related inflammation in COPD patients

BACKGROUND

Interleukin (IL)-36, including IL-36α, IL-36β, and IL-36γ in the IL-1 family, are agonists of their receptors. IL-36 expression is associated with inflammation, including lung infection in humans. However, there is no information on its role in the inflammation of different types of chronic obstructive pulmonary disease (COPD).

OBJECTIVE

This study focused on the sputum IL-36α, IL-36β, and IL-36γ levels in stable COPD patients and their relationship with lung function and other cytokines in different inflammatory types of COPD patients.

METHODS

Sputum specimens were collected from 73 stable COPD patients and 20 age- and gender-matched healthy controls. The levels of sputum IL-36α, IL-36β, and IL-36γ and other cytokines were quantified and sputum cells were characterized. The potential relationship between the levels of sputum IL-36α, IL-36β, or IL-36γ and lung functional measures, inflammatory cells, and cytokines was analyzed.

RESULTS

In comparison with the healthy controls, sputum IL-36α and IL-36γ levels significantly increased in COPD (106.8 pg/mL vs. 76.9 pg/mL P =.001, 397.9 pg/mL vs. 359.5 pg/mL P =.006). The sputum IL-36α and IL-36γ levels were significantly higher in the neutrophilic and mixed granulocytic types than that in the eosinophilic and paucigranulocytic types of COPD patients. The sputum IL-36α levels were positively correlated with sputum IL-36γ levels and the numbers of sputum neutrophils, and the sputum IL-36γ levels were positively correlated with the numbers of sputum lymphocytes in COPD patients.

CONCLUSIONS

Elevated levels of sputum IL-36α and IL-36γ were detected in COPD patients and may provide insights into the inflammatory pathways in neutrophilic COPD.

IL-36α Exerts Proinflammatory Effects in Aspergillus fumigatus Keratitis of Mice Through the Pathway of IL-36α/IL-36R/NF-κB

Purpose

To explore the role of IL-36α in corneas infected by Aspergillus fumigatus.

Methods

The experimental group was comprised of 15 corneas with fungal keratitis, and 15 healthy donor corneas were included in the control group. IL-36α was detected in normal and infected corneas of humans and C57BL/6 mice. Mice corneas were infected with A. fumigatus with or without pretreatment of recombinant mouse (rm) IL-36α and IL-36α neutralizing antibody (Ab). Primary macrophages were stimulated with 75% ethanol-killed A. fumigatus with or without pretreatment of rmIL-36α. The severity of the disease was documented by clinical score and photographs with a slit lamp. PCR, western blot, and immunostaining were used to determine the expression of IL-36α, IL-1β, IL-6, and TNF-α. Polymorphonuclear neutrophilic leukocyte infiltration was assessed by myeloperoxidase (MPO) assay and flow cytometry. Macrophage infiltration was tested by immunofluorescent staining and flow cytometry.

Results

IL-36α mRNA and protein were significantly elevated in human and mice corneas after infection. The rmIL-36α treatment of C57BL/6 mice increased clinical score, MPO levels, macrophage infiltration, and expression of the proinflammatory cytokines IL-1β, IL-6, and TNF-α compared with the infected controls, which showed a decrease due to IL-36α Ab treatment. In primary macrophages, IL-36α expression was also significantly increased by A. fumigatus. The rmIL-36α treatment upregulated IL-1β, IL-6, and phosphorylated nuclear factor (NF)-κB expression, which was significantly inhibited by rmIL-36Ra.

Conclusions

IL-36α act as a proinflammatory cytokine in A. fumigatus keratitis by promoting the infiltration of neutrophils and macrophages and increasing the secretion of IL-1β, IL-6, and TNF-α, in addition to regulating expression of phosphorylated NF-κB.

Signalling and putative therapeutic molecules on the regulation of synoviocyte signalling in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by symmetrical and chronic polyarthritis. Fibroblast-like synoviocytes are mainly involved in joint inflammation and cartilage and bone destruction by inflammatory cytokines and matrix-degrading enzymes in RA. Approaches that induce various cellular growth alterations of synoviocytes are considered as potential strategies for treating RA. However, since synoviocytes play a critical role in RA, the mechanism and hyperplastic modulation of synoviocytes and their motility need to be addressed. In this review, we focus on the alteration of synoviocyte signalling and cell fate provided by signalling proteins, various antioxidant molecules, enzymes, compounds, clinical candidates, to understand the pathology of the synoviocytes, and finally to achieve developed therapeutic strategies of RA.

Cite this article: Bone Joint Res 2021;10(4):285–297.