IL-38: A New Player in Inflammatory Autoimmune Disorders

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.

IL-38 Exerts Anti-Inflammatory and Antifibrotic Effects in Thyroid-Associated Ophthalmopathy

CONTEXT

Thyroid-associated ophthalmopathy (TAO) is an organ-specific autoimmune disease closely associated with Graves' disease. IL-38, a novel cytokine in the IL-1 superfamily, has been reported to be involved in the pathogenesis of various autoimmune diseases.

OBJECTIVE

We aimed to evaluate the relationship between IL-38 and TAO disease activity and its role in inflammation and fibrosis in TAO.

METHODS

Blood samples and orbital connective tissues were collected from TAO patients and controls. Orbital fibroblasts were isolated from patients with TAO. Enzyme-linked immunosorbent assay, immunohistochemistry, flow cytometry, immunofluorescence, quantitative real-time PCR and Western blot analysis were performed.

RESULTS

Here, we demonstrated that IL-38 levels decreased in the circulation and orbital connective tissues of patients with TAO compared with the controls, and levels were negatively correlated with the clinical activity score. In vitro, potent anti-inflammatory and antifibrotic effects of IL-38 were observed. Furthermore, we revealed that IL-38 can counteract the phosphorylation of star molecules in multiple classical pathways.

CONCLUSION

IL-38 plays a protective role in TAO and is associated with its pathogenesis. Our data suggest that IL-38 may be a promising marker of TAO disease activity and a potential target for TAO therapy.

IL-38 as an early predictor of the ischemic stroke prognosis

BACKGROUND

Ischemic stroke is caused by a sudden neurological defect following a vascular occlusion and elicits a local and systemic inflammation in brain tissue. Interleukin-38 is an anti-inflammatory cytokine associated with ischemic and inflammatory diseases. This study was designed to analyze the effect of tPA therapy on interleukin-38 serum level changes and the serum level of IL-38 in the prognosis of ischemic stroke patients in the next three months.

METHODS

We enrolled 29 ischemic stroke patients confirmed by a neurologist based on radiologic and clinical manifestation between 2019 September to 2020 February. The patients who had NIHSS more than 6 with no underlying inflammatory diseases were selected for tPA therapy. On admission and 24 h after tPA therapy, the IL-38 serum level was measured by ELISA kit.

RESULTS

The results showed that serum levels of IL-38 were significantly increased after tPA therapy (P < 0.001). A remarkable relationship was observed between the modified Rankin Score (mRS) and IL-38 serum changes in response to tPA therapy (P < 0.001). Besides, IL-38 serum changes following tPA were dramatically related to NIHSS at hospitalization (P = 0.007). Also, our analysis posed a positive relation between NIHSS at hospitalization and mRs criteria (P = 0.023). No notable relation has been observed between IL-38 serum levels before and after tPA and mRs (P = 0.601 and P = 0.074, respectively). Furthermore, there was no evidence for the relation between NIHSS at hospitalization and IL-38 levels before and after tPA (P = 0.457 and P = 0.105, respectively).

CONCLUSION

The results indicate that tPA could meaningfully increase the IL-38 serum level. Also, a negative correlation has been found between IL-38 serum changes in response to tPA and mRS. Since the lower changes in IL-38 serum level result in a poorer prognosis, we conclude that IL-38 serum changes might be a novel early predictor factor for ischemic stroke prognosis.

Role of IL-36γ/IL-36R Signaling in Corneal Innate Defense Against Candida albicans Keratitis

Purpose

Interleukin (IL)-36 cytokines have been shown to play either beneficial or detrimental roles in the infection of mucosal tissues in a pathogen-dependent manner, but their involvement in fungal keratitis remains elusive. We herein investigated their expression and function in mediating corneal innate immunity against Candida albicans infection.

Methods

Gene expression in mouse corneas with or without C. albicans infection was determined by regular RT- and real-time (q)-PCR, Western blot analysis, ELISA or proteome profile assay. The severity of C. albicans keratitis was assessed using clinical scoring, bacterial counting, and myeloperoxidase (MPO) activity as an indicator of neutrophil infiltration. IL36R knockout mice and IL-33-specific siRNA were used to assess the involvement IL-33 signaling in C. albicans-infected corneas. B6 CD11c-DTR mice and clodronate liposomes were used to define the involvement of dendritic cells (DCs) and macrophages in IL-36R signaling and C. albicans keratitis, respectively.

Results

IL-36γ were up-regulated in C57BL6 mouse corneas in response to C. albicans infection. IL-36 receptor-deficient mice display increased severity of keratitis, with a higher fungal load, MPO, and IL-1β levels, and lower soluble sIL-1Ra and calprotectin levels. Exogenous IL-36γ prevented fungal keratitis pathogenesis with lower fungal load and MPO activity, higher expression of sIL-1Ra and calprotectin, and lower expression of IL-1β, at mRNA or protein levels. Protein array analysis revealed that the expression of IL-33 and REG3G were related to IL-36/IL36R signaling, and siRNA downregulation of IL-33 increased the severity of C. albicans keratitis. Depletion of dendritic cells or macrophages resulted in severe C. albicans keratitis and yet exhibited minimal effects on exogenous IL-36γ-induced protection against C. albicans infection in B6 mouse corneas.

Conclusions

IL-36/IL36R signaling plays a protective role in fungal keratitis by promoting AMP expression and by suppressing fungal infection-induced expression of proinflammatory cytokines in a dendritic cell- and macrophage-independent manner.

Biology of interleukin-38 and its role in chronic inflammatory diseases

Interleukin (IL)-38 is the tenth member of the IL-1 cytokine family. IL-38 shares high similarity with IL-36Ra and IL-1Ra and can bind to their receptors, thus exerting an anti-inflammatory effect. Despite the lack of a signal peptide, IL-38 can be released from several cell types, but its maturation process remains obscure. The role of IL-38 in numerous inflammatory diseases, especially in autoimmune diseases, has been extensively studied. In this review, we discuss the characteristics, biological functions and pathways of IL-38, as well as its role in several chronic inflammatory diseases. Better understanding the role of IL-38 will pave the way for clinical treatments in the near future.

Elevated IL-38 Serum Levels in Newly Diagnosed Multiple Sclerosis and Systemic Sclerosis Patients

OBJECTIVE

Interleukin (IL)-38 is a newly discovered member of the IL-1 cytokine family with a proposed anti-inflammatory profile. We studied the probable role of this cytokine in the pathogenesis of two autoimmune diseases: multiple sclerosis (MS) and systemic sclerosis (SSc).

SUBJECTS AND METHODS

A total of 87 MS patients and 86 SSc patients (40 new and recently untreated cases and 46 treated cases) were selected for this study. Eighty-seven and 80 age- and sex-matched healthy subjects were included as controls for MS and SSc, respectively. Clinical and paraclinical features of the patients were recorded at the time of sampling. Serum IL-38 was measured by ELISA.

RESULTS

Levels of serum IL-38 did not significantly differ between the total MS or SSc patients compared to controls. However, levels of IL-38 were significantly higher in newly diagnosed patients of MS (206.43 ± 38.97 pg/mL, p < 0.0001) than in those previously treated (158.04 ± 39.45 pg/mL). Similarly, new/recently untreated cases of SSc patients showed increased IL-38 levels (185.19 ± 36.27 pg/mL, p = 0.001) compared to treated patients (166.82 ± 33.08 pg/mL). IL-38 levels in newly diagnosed MS patients (p = 0.007) and new/recently untreated SSc patients (p = 0.032) were significantly higher than those in healthy controls.

CONCLUSION

The higher serum levels of IL-38 in new or recently untreated cases of MS and SSc patients than in treated patients and healthy controls suggest the possible role of this cytokine in the development of these diseases or as part of a feedback loop to attenuate the inflammatory conditions in early stages of these diseases.

IL-1 Superfamily Members and Periodontal Diseases

Periodontitis is a complex, multifactorial chronic disease involving continuous interactions among bacteria, host immune/inflammatory responses, and modifying genetic and environmental factors. More than any other cytokine family, the interleukin (IL)-1 family includes key signaling molecules that trigger and perpetuate periodontal inflammation. Over the years, the IL-1 family expanded to include 11 members of cytokines, some with agonist activity (IL-1α, IL-1β, IL-18, IL-33, IL-36α, IL-36β, and IL-36γ), receptor antagonists (IL-1Ra, IL-36Ra), and 2 anti-inflammatory cytokines (IL-37, IL-38). The IL-1 receptor antagonist (IL-1Ra) has emerged as a pivotal player in the defense against periodontitis. IL-33 primarily induces the production of Th2-associated cytokines but acts as an "alarmin" via stimulation of mast cells. The IL-36 subclass of cytokines may be important in regulating mucosal inflammation and homeostasis. IL-37 suppresses innate and acquired immune responses. IL-38 is the most recent member of the IL-1 superfamily and has anti-inflammatory properties similar to those of IL-37 but through different receptors. However, limited evidence exists regarding the role of IL-37 and IL-38 in periodontitis. Despite the development of IL-1 blocking agents, therapeutic blockade of select IL-1 family members for periodontitis has only been partially investigated in preclinical and clinical research, while the development of IL-37 and IL-38 as novel anti-inflammatory drugs has not been considered adequately. Here, we review the key properties of the IL-1 family members and provide insights into targeting or promoting select cytokines as new therapeutic agents.

IL-38 inhibits microglial inflammatory mediators and is decreased in amygdala of children with autism spectrum disorder

Autism spectrum disorder (ASD) is characterized by impaired social interactions and communication. The pathogenesis of ASD is not known, but it involves activation of microglia. We had shown that the peptide neurotensin (NT) is increased in the serum of children with ASD and stimulates cultured adult human microglia to secrete the proinflammatory molecules IL-1β and CXCL8. This process is inhibited by the cytokine IL-37. Another cytokine, IL-38, has been reported to have antiinflammatory actions. In this report, we show that pretreatment of cultured adult human microglia with recombinant IL-38 (aa3-152, 1-100 ng/mL) inhibits (P < 0.0001) NT-stimulated (10 nM) secretion of IL-1β (at 1 ng/mL) and CXCL8 (at 100 ng/mL). In fact, IL-38 (aa3-152, 1 ng/mL) is more potent than IL-37 (100 ng/mL). Here, we report that pretreatment with IL-38 (100 ng/mL) of embryonic microglia (HMC3), in which secretion of IL-1β was undetectable, inhibits secretion of CXCL8 (P = 0.004). Gene expression of IL-38 and its receptor IL-36R are decreased (P = 0.001 and P = 0.04, respectively) in amygdala from patients with ASD (n = 8) compared to non-ASD controls (n = 8), obtained from the University of Maryland NeuroBioBank. IL-38 is increased (P = 0.03) in the serum of children with ASD. These findings indicate an important role for IL-38 in the inhibition of activation of human microglia, thus supporting its development as a treatment approach for ASD.

IL-38 alleviates the inflammatory response and the degeneration of nucleus pulposus cells via inhibition of the NF-κB signaling pathway in vitro

Previous studies have suggested that the inflammatory response contributes to the onset of intervertebral disc degeneration (IVDD). Interleukin (IL)-38, a newly discovered cytokine of the IL-1 family, has been demonstrated to play an anti-inflammatory role in autoimmune diseases, such as Crohn's disease, rheumatoid arthritis and psoriasis. However, whether IL-38 participates in the pathogenesis of IVDD remains unknown. In this study, human disc tissues from IVDD patients and rat disc tissues from an IVDD model were collected to measure the expression of IL-38 in the IVDD groups and the control groups by western blot and immunohistochemical staining. To further determine the role of IL-38 in IVDD, human nucleus pulposus cells (HNPCs) were stimulated with TNF-α to generate an in vitro model of inflammation to mimic the local inflammatory environment of the lumbar disc. The inflammatory response and HNPC degeneration markers were measured after stimulation with TNF-α and IL-38. IL-38 was upregulated in both the human and rat degenerated disc tissues compared with the control tissues. In vitro, IL-38 significantly decreased the TNF-α-induced expression of IL-1β, IL-6, COX-2, MMP-13 and ADAMTS-5 in the HNPCs, and IL-38 also alleviated the TNF-α-induced reductions in type II collagen and aggrecan. Moreover, IL-38 inhibited the activation of the NF-κB signaling pathway in the HNPC-based model of inflammation by reducing the expression level of the NF-κB P-P65 protein. In conclusion, IL-38 could alleviate the inflammatory response and HNPC degeneration in vitro via the inhibition of the NF-κB signaling pathway. These results suggest that IL-38 may be a new strategy for the treatment of IVDD.

A Phase II Open-Label Study of Bermekimab in Patients with Hidradenitis Suppurativa Shows Resolution of Inflammatory Lesions and Pain

The objective of this study was to evaluate the safety and efficacy of bermekimab, an IL-1α inhibitor, in the treatment of hidradenitis suppurativa (HS). This study was a phase II, multicenter, open-label study of two dose cohorts of bermekimab in patients with moderate-to-severe HS who are naïve to or have failed prior anti-TNF therapy. Patients with HS (n = 42) were divided into groups A and B based on whether or not they had previously failed an anti-TNF therapy. In group A (n = 24), bermekimab was administered subcutaneously at a dose of 400 mg weekly (13 doses) in patients who had previously failed anti-TNF therapy; in group B (n = 18), bermekimab was administered subcutaneously at a dose of 400 mg weekly (13 doses) in patients who were anti-TNF naïve. Bermekimab, previously found to be effective in treating HS, was evaluated using a subcutaneous formulation in patients with HS naïve to or having failed anti-TNF therapy. There were no bermekimab-related adverse events with the exception of injection site reactions. Bermekimab was effective despite treatment history, with 61% and 63% of patients naïve to and having failed anti-TNF therapy, respectively, achieving HS clinical response after 12 weeks of treatment. A significant reduction in abscesses and inflammatory nodules of 60% (P < 0.004) and 46% (P < 0.001) was seen in anti-TNF naïve and anti-TNF failure groups, respectively. Clinically and statistically significant reduction was seen in patients experiencing pain, with the Visual Analogue Scale pain score reducing by 64% (P < 0.001) and 54% (P < 0.001) in the anti-TNF naïve and anti-TNF failure groups, respectively. IL-1α is emerging as an important clinical target for skin disease, and bermekimab may represent a new therapeutic option for treating moderate-to-severe HS.

Omega Fatty Acids and Inflammatory Bowel Diseases: An Overview

Inflammatory bowel diseases (IBD) are chronic, inflammatory processes that affect the gastrointestinal tract and are mainly represented by ulcerative colitis (UC) and Crohn’s disease (CD). Omega 3 (ω3) fatty acids (eicosapentanoic acid and docosahexaenoic acid) show an indispensable role in the inflammatory processes and, for these reasons, we aimed to review the effects of these acids on UC and CD. Databases such as PUMED and EMBASE were searched, and the final selection included fifteen studies that fulfilled the inclusion criteria. The results showed that ω3 fatty acids reduce intestinal inflammation, induce and maintain clinical remission in UC patients, and are related with the reduction of proinflammatory cytokines, decrease disease activity and increase the quality of life of CD patients. Furthermore, the consumption of these fatty acids may be related to a reduced risk of developing IBD. Many studies have shown the beneficial effects of ω3 as adjunctive in the treatment or prevention of UC or CD. Nevertheless, most were performed with a small number of patients and there are many variations in the mode of consumption, the type of food or the type of formulation used. All these factors substantially interfere with the results and do not allow reliable comparisons.