Increased serum IL-36α and IL-36γ levels in patients with systemic lupus erythematosus: Association with disease activity and arthritis

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.

Mature IL-36γ Induces Stratum Corneum Exfoliation in Generalized Pustular Psoriasis by Suppressing Corneodesmosin

Loss-of-function sequence variations in the IL36RN gene encoding IL-36 receptor antagonist cause familial generalized pustular psoriasis, which begins shortly after birth and is difficult to treat, and its effects on the epidermis are unclear. This study investigated the involvement of IL-36 receptor agonists in the epidermal formation of generalized pustular psoriasis. We found that the IL-36 receptor agonists, especially mature IL-36γ, stimulated IL-8 and pro-IL-36γ production in the epidermis while downregulating the genes encoding epidermal cornified envelope-related proteins, for example, corneodesmosin. IL-36 receptor antagonist and monoclonal anti-IL-36γ antibodies counteracted the effect of mature IL-36γ on corneodesmosin in keratinocytes in a dose-dependent manner. In the epidermis of patients with generalized pustular psoriasis with IL36RN loss-of-function sequence variations, pro-IL-36γ was overproduced in the epidermis, and corneodesmosin protein expression was markedly decreased in the region of giant subcorneal pustules (Kogoj's spongiform pustules), with high neutrophil infiltration. IL-8 induced by mature IL-36γ stimulated the infiltration of several neutrophils in the epidermis. The newly produced pro-IL-36γ is cleaved to the mature form by neutrophil proteases. This newly produced mature IL-36γ was predicted to further suppress the gene expression of corneodesmosin, leading to significant stratum corneum exfoliation and formation of the pustules. Overall, our results elucidate the mechanism underlying the formation of Kogoj's spongiform pustules in generalized pustular psoriasis.

Helios characterized circulating follicular helper T cells with enhanced functional phenotypes and was increased in patients with systemic lupus erythematosus

Helios was related to the immunosuppressive capacity and stability of regulatory T cells. However, the significance of Helios in follicular help T (TFH) and follicular regulatory T (TFR) cells is unclear. This research aimed to clarify the significance of Helios (IKZF2) in TFH and TFR cells and its clinical value in systemic lupus erythematosus (SLE). IKZF2 mRNA in different cell subsets was analyzed. Helios+ percentages in TFH and TFR cells were identified in the peripheral blood of 75 SLE patients and 62 HCs (healthy controls). PD-1 and ICOS expression were compared between Helios+ and Helios- cells. The capacity of TFH cells to secrete IL-21 and TFR cells to secrete IL-10 was measured. Correlation analysis and receiver operating characteristic (ROC) curve analysis were conducted to assess the clinical significance of Helios-related TFH and TFR cell subsets in SLE. There was Helios expression in TFH and TFR cells. PD-1 and ICOS were lower in Helios+ TFR than in Helios- TFR. ICOS was increased in Helios+ TFH cells compared with Helios- TFH cells, and ICOS in Helios+ TFH cells was downregulated in SLE. Helios+ TFH cells secreted more IL-21 than Helios- TFH cells, and Helios+ TFH cells from SLE patients had a stronger IL-21 secretion than HCs. Helios+ TFH percentages were negatively correlated with C3 and C4 and positively related to CRP and SLEDAI, and the AUC of Helios+ TFH to distinguish SLE from HC was 0.7959. Helios characterizes circulating TFH cells with enhanced function. Increased Helios+ TFH cells could reflect the autoimmune status of SLE.

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.

New insights on IL‑36 in intestinal inflammation and colorectal cancer (Review)

Interleukin (IL)-36 is a member of the IL-1 superfamily, which includes three receptor agonists and one antagonist and exhibits a familial feature of inflammatory regulation. Distributed among various tissues, such as the skin, lung, gut and joints, the mechanism of IL-36 has been most completely investigated in the skin and has been used in clinical treatment of generalized pustular psoriasis. Meanwhile, the role of IL-36 in the intestine has also been under scrutiny and has been shown to be involved in the regulation of various intestinal diseases. Inflammatory bowel disease and colorectal cancer are the most predominant inflammatory and neoplastic diseases of the intestine, and multiple studies have identified a complex role for IL-36 in both of them. Indeed, inhibiting IL-36 signaling is currently regarded as a promising therapeutic approach. Therefore, the present review briefly describes the composition and expression of IL-36 and focuses on the role of IL-36 in intestinal inflammation and colorectal cancer. The targeted therapies that are currently being developed for the IL-36 receptor are also discussed.

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.

Interleukin-36 cytokines are overexpressed in the skin and sera of patients with bullous pemphigoid

Bullous pemphigoid (BP) is an autoimmune bullous disease, characterized by autoantibodies targeting BP180 and BP230. The role of interleukin (IL)-36, a potent chemoattractant for granulocytes, in BP remains elusive.The expression of IL-36 cytokines (IL-36α, β, γ) and their antagonists (IL-36Ra and IL-38) was analysed in the skin and serum samples of patients with BP (n = 31), psoriasis (n = 10) and healthy controls (HC) (n = 14) by quantitative polymerase chain reaction and enzyme linked immunosorbent assay, respectively. Skin and serum levels of all cytokines were correlated with the Bullous Pemphigoid Disease Area Index (BPDAI) score and with the serum concentration of pathogenic antibodies.IL-36α, IL-36β, IL-36γ and IL-36Ra were significantly (p < 0.05) overexpressed in BP skin compared to HC, without remarkable differences relative to psoriasis skin. The expression of IL-38 was significantly (p < 0.05) higher in BP compared to psoriasis skin.IL-36α and γ, but not β, serum concentrations were significantly (p < 0.05) higher in BP compared to HC. IL-36γ was significantly (p < 0.05) more expressed in the serum of psoriasis patients than BP. The serum concentration of IL-36Ra and IL-38 were similar between BP and HC, while IL-38 serum levels were significantly (p < 0.05) higher in BP compared to psoriasis patients. Serum IL-36α correlated significantly with BPDAI (r = 0.5 p = 0.001).IL-36 agonists are increased in BP patients, both locally and systemically. Serum IL-36α might represent a potential biomarker for BP. An inefficient balance between IL-36 agonists and antagonists is likely to occur during BP inflammation.

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.

CD19+CD24highCD27+ B cell and interleukin 35 as potential biomarkers of disease activity in systemic lupus erythematosus patients

BACKGROUND

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease that associates with aberrant activation of B lymphocytes and excessive autoantibodies. Interleukin 10 (IL-10)/interleukin 35 (IL-35) and IL-10/IL-35-producing regulatory B cells have been demonstrated to possess immunosuppressive functions during systemic lupus erythematosus. Here, we detected the proportion of CD19⁺CD24^highCD27⁺ B cells as well as IL-10 and IL-35 levels in peripheral blood of SLE patients and healthy individuals, and investigated their relations with clinical features of SLE.

METHODS

41 SLE patients and 25 healthy controls were recruited. The patients were divided into groups based on SLEDAI score, anti-dsDNA antibody, rash, nephritis and hematological disorder. Flow cytometry was used to detect the proportion of CD24^hiCD27⁺ B cells. ELISA was used to detect serum levels of IL-10 and IL-35.

RESULTS

Our results showed that the CD19⁺CD24^highCD27⁺ B population was decreased in active SLE patients, and anti-correlated with the disease activity. Of note, we found significant increase of IL-10 and decrease of IL-35 in SLE patients with disease activity score > 4, lupus nephritis or hematological disorders compared to those without related clinical features.

CONCLUSIONS

Reduced CD19⁺CD24^highCD27⁺ B cells expression may be involved in the pathogenesis of SLE. Moreover, we supposed that IL-35 instead of IL-10 played a crucial role in immune regulation during SLE disease.

A novel biomarker for pleural effusion diagnosis: Interleukin-36γ in pleural fluid

BACKGROUND

Numerous studies have described the critical importance of interleukin (IL) -36γ in host defense against lung infections, but it is unknown whether it plays a role in infectious pleural effusion (IPE). This study aimed to examine the levels of IL-36γ in pleural effusions of different etiologies and evaluate the diagnostic accuracy of IL-36γ in the differential diagnosis of IPE.

METHODS

A total of 112 individuals was enrolled in this research. IL-36γ levels in pleural fluids of all 112 patients were measured by enzyme-linked immunosorbent assay (ELISA). We also characterized these markers' diagnostic values across various groups.

RESULTS

Patients with tuberculous pleural effusion (TPE) and parapneumonic effusion (PPE) had exhibited markedly higher IL-36γ levels in their pleural fluid than the malignant pleural effusion (MPE) and transudative effusion patients. Furthermore, the IL-36γ concentrations in TPE patients were evidently higher than in uncomplicated parapneumonic effusion (UPPE) patients but significantly lower than in complicated parapneumonic effusion (CPPE)/empyema patients. Pleural fluid IL-36γ is a useful marker to differentiate TPE from UPPE, at a cut-off value for 657.5 pg/ml (area under the curve = 0.904, p < 0.0001) with 70.0% sensitivity and 95.7% specificity.

CONCLUSIONS

The elevated IL-36γ in pleural effusion may be used as a novel biomarker for infectious pleural effusion diagnosis, particularly in patients with CPPE/empyema, and is a potentially promising biomarker to differentiate between TPE and UPPE.

Progress in the application of body fluid and tissue level mRNAs-non-coding RNAs for the early diagnosis and prognostic evaluation of systemic lupus erythematosus

The diagnosis and differential classification of systemic lupus erythematosus (SLE) is difficult, especially in patients with early-onset SLE who are susceptible to systemic multi-organ damage and serious complications and have difficulties in individualized treatment. At present, diagnosis is based mainly on clinical manifestations and the detection of serological antinuclear antibodies. The pathogenesis of SLE involves multiple factors, is clinically heterogeneous, and lacks specific biomarkers. Therefore, it is necessary to identify new biomarkers for the diagnosis and subtype classification of SLE. Non-coding RNAs (ncRNAs) are composed of microRNAs, long non-coding RNAs, small nucleolar RNAs, circular RNAs, and transfer RNAs. They play an important role in the occurrence and development of diseases and are used widely in the early diagnosis and prognosis of autoimmune diseases. In this review, we focus on the research progress in the diagnosis and prognostic assessment of SLE using humoral to tissue level ncRNAs.

Non-immune and immune functions of interleukin-36γ suppress epithelial repair at the ocular surface

Regulation of innate inflammation is critical for maintaining tissue homeostasis and barrier function, especially in those interfacing the external environments such as the skin and cornea. Expression of pro-inflammatory cytokines by injured tissues has been shown to exacerbate the inflammatory cascade, causing tissue damage. Interleukin 36, a subfamily of the IL-1 superfamily, consists of three pro-inflammatory agonists-IL36α, IL36β, and IL36γ and an IL36 receptor antagonist (IL36Ra). The current investigation, for the first time, reports that IL36γ is the primary agonist expressed by the corneal epithelium, which is significantly upregulated following corneal injury. The function of IL36γ on non-immune cells, in addition to innate inflammatory cells, in regulating tissue homeostasis has not been well investigated. Using a loss-of-function approach via neutralizing antibody treatment, our data demonstrate that blocking endogenously expressed IL36γ in epithelial cells promotes rapid re-epithelialization in in vitro wound closure assay. Finally, by utilizing a naturally occurring antagonist IL36Ra in a well-established murine model of ocular injury, our study demonstrates that inhibition of IL36γ accelerates epithelial regeneration and suppresses tissue inflammation. Given rapid wound healing is critical for re-establishing normal tissue structure and function, our investigation on the function of IL36γ provides evidence for the development of novel IL36γ-targeting strategies to promote tissue repair.

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.

Small plaque psoriasis re-visited: A type of psoriasis mediated by a type-I interferon pathway

TNFα-inhibitor-induced psoriasis is mediated by the type-I interferon pathway, of which IFNα, LL37 and IL-36γ are major players. A subset of patients treated with TNFα inhibitors develop small plaque psoriatic lesions. Small plaque psoriasis is similarly observed in patients on immune checkpoint inhibitors (ICI), and with concurrent systemic lupus erythematosus (SLE) or positive antinuclear antibody (ANA). Small plaque psoriasis is also the predominant phenotype in Asian populations. The association between small plaque psoriasis morphology in various clinical scenarios and the type-I interferon pathway has not been previously studied. A cross-sectional study was conducted of patients who developed small plaque psoriasis and had a biopsy for diagnostic clarification between 2009 and 2017. We obtained skin specimens from 14 adults with small plaque psoriasis: four patients taking anti-TNFα treatment, four patients with antecedent SLE, three patients with concurrent ANA positivity and three patients taking ICI. Controls included three patients with chronic plaque psoriasis. Histology confirmed psoriasiform epidermal hyperplasia with focal lichenoid and spongiotic features. Immunohistochemical analysis revealed higher expression of IFNα-induced MXA, LL37 and IL-36γ in all clinical scenarios of small plaque psoriasis compared to chronic plaque psoriasis. There was decreased CD8 T-cell migration to the epidermis and variability in the number of LAMP3+ cytoplasmic dendritic cells in the dermis of small plaque psoriasis. The findings suggest that small plaque psoriasis is a unique type of psoriasis with a distinct morphology and immune-phenotype, primarily mediated by the type-I interferon pathway. Associating morphology and disease pathogenesis may help identify therapeutic targets for better disease control.

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.

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

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

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.

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.

Compartmentalization of interleukin 36 subfamily according to inducible and constitutive expression in the kidneys of a murine autoimmune nephritis model

The interleukin (IL) 36 subfamily belongs to the IL-1 family and is comprised of agonists (IL-36α, IL-36β, IL-36γ) and antagonists (IL-36Ra, IL-38). We previously reported IL-36α overexpression in renal tubules of chronic nephritis mice. To understand the localization status and biological relationships among each member of the IL-36 subfamily in the kidneys, MRL/MpJ-Fas^lpr/lpr mice were investigated as autoimmune nephritis models using pathology-based techniques. MRL/MpJ-Fas^lpr/lpr mice exhibited disease onset from 3 months and severe nephritis at 6-7 months (early and late stages, respectively). Briefly, IL-36γ and IL-36Ra were constitutively expressed in murine kidneys, while the expression of IL-36α, IL-36β, IL-36Ra, and IL-38 was induced in MRL/MpJ-Fas^lpr/lpr mice. IL-36α expression was significantly increased and localized to injured tubular epithelial cells (TECs). CD44⁺-activated parietal epithelial cells (PECs) also exhibited higher IL-36α-positive rates, particularly in males. IL-36β and IL-38 are expressed in interstitial plasma cells. Quantitative indices for IL-36α and IL-38 positively correlated with nephritis severity. Similar to IL-36α, IL-36Ra localized to TECs and PECs at the late stage; however, MRL/MpJ-Fas^lpr/lpr and healthy MRL/MpJ mice possessed IL-36Ra⁺ smooth muscle cells in kidney arterial tunica media at both stages. IL-36γ was constitutively expressed in renal sympathetic axons regardless of strain and stage. IL-36 receptor gene was ubiquitously expressed in the kidneys and was induced proportional to disease severity. MRL/MpJ-Fas^lpr/lpr mice kidneys possessed significantly upregulated IL-36 downstream candidates, including NF-κB- or MAPK-pathway organizing molecules. Thus, the IL-36 subfamily contributes to homeostasis and inflammation in the kidneys, and especially, an IL-36α-dominant imbalance could strongly impact nephritis deterioration.

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.

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.

IL-36 cytokines and gut immunity

Interleukin 36 (IL-36) constitutes a group of cytokines that belong to the IL-1 superfamily. Emerging evidence has suggested a role of IL-36 in the pathogenesis of many inflammatory disorders. Intriguingly, in the gastrointestinal tract, IL-36 has a rather complex function. IL-36 receptor ligands are overexpressed in both animal colitis models and human IBD patients and may play both pathogenic and protective roles, depending on the context. IL-36 cytokines comprise three receptor agonists: IL-36α, IL-36β and IL-36γ, and two receptor antagonists: IL-36Ra and IL-38. All IL-36 receptor agonists bind to the IL-36R complex and exert pleiotropic effects during inflammatory settings. Here, we first briefly review the processing and secretion of IL-36 cytokines. We then focus on the current understanding of the immunology effects of IL-36 in gut immunity. In addition, we also discuss the ongoing trials that aim to blockage IL-36R signalling for treating chronic intestinal inflammation and present some unexplored questions regarding IL-36 research.

Elevated urinary IL-36γ in patients with active lupus nephritis and response to treatment

INTRODUCTION

IL-36 is a new member of the IL-1 family with pro-inflammatory properties. Serum levels of IL-36 are elevated in patients with Systemic Lupus Erythematosus (SLE). However, no data is available on urinary levels of IL-36 in Lupus Nephritis (LN). In psoriasis expression of IL-36 is site specific and expressed in skin. Hence, we studied urinary levels of IL-36 cytokines in SLE patients.

METHODS

A total of 196 patients with SLE [97 active LN patients (ALN), 42 inactive LN (ILN) and 57 active lupus patients with no renal involvement (ANR)] and 25 healthy subjects were recruited for the study after obtaining informed consent. Urinary and plasma IL-36α, IL-36γ and IL-36Ra levels were measured by ELISA.

RESULTS

Out of 196 patients 178 were females. Urinary IL-36γ levels in SLE patients [0(14.3) pg/ml] were significantly higher than healthy controls [0(0) pg/ml, (P < 0.01)]. Patients with ALN [0(40.6) pg/ml] had significantly higher IL-36γ when compared to ANR [0(0) pg/ml] as well as ILN [0(0) pg/ml]. Urinary IL-36γ levels in ALN patients had a fair correlation with renal SLEDAI (r = 0.26, P = 0.004).The levels reduced significantly post 3 months in patients with ALN. No inverse relationship was noted between IL-36Ra and IL-36α/IL36γ levels.

CONCLUSION

Urinary IL-36γ is produced locally in kidney, correlates with renal disease activity and reduces upon treatment, suggesting that it may have a role in pathogenesis of LN.

Interleukin (IL)-1 family cytokines could differentiate primary immune thrombocytopenia from systemic lupus erythematosus-associated thrombocytopenia

Background

Primary immune thrombocytopenia (ITP) is an autoimmune-mediated disorder characterized by a decreased platelet count. Systemic lupus erythematosus (SLE) is also an autoimmune disease in which thrombocytopenia is a common hematologic manifestation. Interleukin (IL)-1 family cytokines are major proinflammatory and immunoregulatory mediators. This study aimed to investigate the role of IL-1 cytokines in patients with ITP and SLE and the potential pathophysiologic mechanism to differentiate SLE-associated thrombocytopenia (SLE-TP) from ITP.

Methods

Multiplex cytokine assay and real-time polymerase chain reaction (RT-PCR) were used to measure IL-1 cytokines in 17 newly diagnosed ITP patients, 17 SLE-TP patients, 19 SLE patients without thrombocytopenia (SLE-NTP), and 10 healthy controls.

Results

The serum levels of IL-1β, IL-18, IL-36α, IL-36β, IL-36γ, and IL-33 were decreased significantly in ITP patients compared with SLE-TP patients, SLE-NTP patients, and healthy controls (P<0.05). While there was no significant difference in the serum level of IL-37 between ITP and SLE-TP patients, there was a positive correlation between the platelet count and IL-37 level in ITP patients. Our data suggested that serum IL-1β, IL-18, IL-36α, IL-36β, IL-36γ, IL-33, and IL-37 could be considered biomarkers in the diagnosis of ITP.

Conclusions

Serum IL-1β, IL-18, IL-36α, IL-36β, IL-36γ, and IL-33 could be considered biomarkers to differentiate SLE-TP from ITP patients.

Increased serum IL-36γ levels are associated with disease severity in myasthenia gravis patients

BACKGROUND

Interleukin 36 (IL-36), as a gradually recognized cytokine, is involved in the occurrence and evolution of autoimmune diseases. Nevertheless, the relationship between myasthenia gravis (MG) and IL-36 is rarely reported.

METHODS

We evaluated the serum levels of IL-36 (IL-36α, IL-36β and IL-36γ) by enzyme-linked immunosorbent assay (ELISA). Further, clinical parameters in 97 MG patients and 49 healthy controls (HCs) were carefully measured.

RESULTS

Serum IL-36γ levels were significantly elevated in the MG patients compared with the HCs (p < 0.0001). Compared to those in remission, patients in the acute phase exhibited higher levels of IL-36α and IL-36γ (p = 0.038 and p = 0.011, respectively). Furthermore, patients with generalized MG (GMG) exhibited markedly higher serum IL-36γ levels than those with ocular MG (OMG) (p = 0.003).

CONCLUSIONS

The serum levels of IL-36γ in patients with MG were increased and positively correlated with disease severity and may thus have potential as a serological MG marker.

The IL-1 family cytokines and receptors in autoimmune diseases

The role of the cytokines and receptors of the IL-1 family in inflammation is well known. Several cytokines of the family have a powerful inflammatory activity, with IL-1β being the best-characterized factor. The inflammatory activity of IL-1 cytokines is regulated by other factors of the family, including receptor antagonists, soluble receptors and anti-inflammatory cytokines. The causative role of IL-1β is well-established in autoinflammatory diseases, mainly due to gain-of-function mutations in genes encoding the IL-1β-maturing inflammasome. Exaggerated production of IL-1β and IL-18 correlates with disease and disease severity also in several autoimmune and chronic inflammatory and degenerative pathologies, although it is not clear whether they have a causative role or are only involved in the downstream disease symptoms. A better understanding of the pathological role of IL-1 family cytokines in autoimmunity involves a deeper evaluation, in the pathological situations, of the possible anomalies in the feed-back anti-inflammatory mechanisms that in physiological reactions control and dump IL-1-mediated inflammation. Thus, we expect that IL-1 cytokines may be pathogenic only when, in addition to enhanced production, there is a concomitant failure of their control mechanisms. In this review we will examine the current knowledge on the role of IL-1 family cytokines in autoimmune and chronic inflammatory and degenerative diseases, with a particular focus on their endogenous control mechanisms, mainly based on soluble receptors/inhibitors and receptor antagonists. This will allow us to formulate a knowledge-based hypothesis on the involvement of IL-1 cytokines in the pathogenesis vs. the clinical features of these diseases.

Biology of IL-36 Signaling and Its Role in Systemic Inflammatory Diseases

Interleukin (IL)-36 is a member of the IL-1 superfamily and includes three agonists (IL-36α, IL-36β, and IL-36γ) and an antagonist (IL-36Ra). IL-36 agonists bind to heterodimeric receptor complexes. Then, the heterotrimer complexes signal via intracellular functional domains, binding to downstream signaling proteins and inducing inflammatory responses. In this review, we summarized the current knowledge about the biological role of IL-36 and its correlation with systemic inflammatory diseases. The information collected will help to increase the understanding of the potential of IL-36 and may give clues for developing novel therapeutic strategies.

IL-36 Promotes Systemic IFN-I Responses in Severe Forms of Psoriasis

Psoriasis is an immune-mediated skin disorder associated with severe systemic comorbidities. Whereas IL-36 is a key disease driver, the pathogenic role of this cytokine has mainly been investigated in skin. Thus, its effects on systemic immunity and extracutaneous disease manifestations remain poorly understood. To address this issue, we investigated the consequences of excessive IL-36 activity in circulating immune cells. We initially focused our attention on generalized pustular psoriasis (GPP), a clinical variant associated with pervasive upregulation of IL-36 signaling. By undertaking blood and neutrophil RNA sequencing, we demonstrated that affected individuals display a prominent IFN-I signature, which correlates with abnormal IL-36 activity. We then validated the association between IL-36 deregulation and IFN-I over-expression in patients with severe psoriasis vulgaris (PV). We also found that the activation of IFN-I genes was associated with extracutaneous morbidity, in both GPP and PV. Finally, we undertook mechanistic experiments, demonstrating that IL-36 acts directly on plasmacytoid dendritic cells, where it potentiates toll-like receptor (TLR)-9 activation and IFN-α production. This effect was mediated by the upregulation of PLSCR1, a phospholipid scramblase mediating endosomal TLR-9 translocation. These findings identify an IL-36/ IFN-I axis contributing to extracutaneous inflammation in psoriasis.

IL-1 Family Members Mediate Cell Death, Inflammation and Angiogenesis in Retinal Degenerative Diseases

Inflammation underpins and contributes to the pathogenesis of many retinal degenerative diseases. The recruitment and activation of both resident microglia and recruited macrophages, as well as the production of cytokines, are key contributing factors for progressive cell death in these diseases. In particular, the interleukin 1 (IL-1) family consisting of both pro- and anti-inflammatory cytokines has been shown to be pivotal in the mediation of innate immunity and contribute directly to a number of retinal degenerations, including Age-Related Macular Degeneration (AMD), diabetic retinopathy, retinitis pigmentosa, glaucoma, and retinopathy of prematurity (ROP). In this review, we will discuss the role of IL-1 family members and inflammasome signaling in retinal degenerative diseases, piecing together their contribution to retinal disease pathology, and identifying areas of research expansion required to further elucidate their function in the retina.