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

IL-38 as a Novel Biomarker in Multiple Myeloma Patients: A Prospective Clinical Evaluation

Introduction

Multiple myeloma (MM) is a refractory haematological malignancy. Interleukin 38 (IL-38) is a novel cytokine that has attracted significant research in recently years. However, no study has investigated IL-38 expression in MM. This study aims to investigate the expression of IL-38 in MM and to provide valuable insights for clinical treatment and efficacy evaluation.

Methods

A total of 241 patients with MM (146 males, 95 females; R-ISS stage I: 111 cases, stage II: 74 cases, stage III: 56 cases) and 50 healthy individuals were included in this study. Medical records were reviewed for staging. Interleukin-1 (IL-1), interleukin-2 receptor (IL-2R), interleukin-8 (IL-8), and tumor necrosis factor-alpha (TNF-α) were detected by chemiluminescence method, IL-38 was detected by enzyme-linked immunosorbent assay (ELISA). Immunoglobulins, free light chains (FLC) and β2-microglobulin (β2-MG) were detected by immune nephelometry, and multiple biochemical indicators were detected by automatic biochemical analyzers.

Results

Compared with healthy control group, IL-1, IL-2R, IL-8, and TNF-α were elevated in all three stages of MM. In contrast, compared with normal control group, IL-38 was significantly decreased in patients with MM. When the cut-off value of IL-38 was 18.61 pg/mL, the diagnostic efficacy for MM had a sensitivity of 0.8176 and a specificity of 0.9000.

Discussion

IL-38 exhibited decrease in MM patients (p<0.0001). It also showed a gradual increase with disease improvement after effective treatment, IL-38 may be a potential biomarker for the diagnosis and prognostic assessment of MM.

The protective role of muscone in the development of COPD

Background

Muscone, a key component of musk, exhibits anti-inflammatory properties. However, its therapeutic potential in inflammatory lung diseases, such as chronic obstructive pulmonary disease (COPD), remains largely unexplored. This study aimed to investigate whether Muscone could exert a protective effect in a mouse model of COPD in vivo.

Methods

A COPD animal model was established by exposing mice to cigarette smoke (CS) and administering lipopolysaccharide (LPS) intranasally. After 4 weeks, mice were treated daily with dexamethasone (DEX) or different doses of Muscone for 3 weeks. Mouse body weight, lung function, and histopathology were determined. Serum levels of cytokines (IL-38, IL-1β, IL-17, TGF-β, IFN-γ) were measured using ELISA and qRT-PCR. Lung expression of CXCR3, IFN-γ, IL-17A, and RORγt was assessed by immunofluorescence.

Results

The body weight of COPD mice was significantly lower than that of Muscone-treated COPD mice, consistent with decreased lung function, accompanied by reduced circulating and lung IL-38 levels. After Muscone administration, lung function was significantly improved, accompanied by upregulation of circulating and lung anti-inflammatory cytokines, including IL-38, in a dose-dependent manner, while the expression of pro-inflammatory cytokines was significantly reduced. Additionally, Muscone significantly inhibited the protein expression of CXCR3, IFN-γ, IL-17A, and RORγt in lung tissues of COPD mice.

Conclusion

This study demonstrates that Muscone improves lung function in mice with COPD, potentially through a mechanism that may involve the modulation of cytokine expression, including the potential upregulation of anti-inflammatory cytokines such as IL-38. The precise underlying mechanisms of Muscone's therapeutic effects in COPD remain to be fully elucidated. Further research is needed to investigate the correlation between COPD lung pathophysiology and the specific effects of Muscone treatment, including a more detailed analysis of the balance between pro- and anti-inflammatory mediators in COPD animal models, particularly utilizing IL-38 GKO mice to further investigate the role of IL-38 in mediating the therapeutic effects of Muscone.

AMPK/autophagy-mediated alleviation of tendinopathy by IL-38: A novel strategy for the treatment of obesity-related tendinopathy

The effect of interleukin-38 (IL-38), a recently identified member of the IL-1 family with potential applications in various inflammation-related conditions, on ER stress has not been explored. Furthermore, its role in obesity-associated tendinopathy has not been investigated. In this study, human primary tenocytes were treated with palmitate (200 or 400 μM) and palmitate plus IL-38 (0-50 ng/mL) for 24 h. Western blotting was used to assess ER stress and tendinopathogenic markers in tenocytes. Monodansylcadaverine (MDC) staining was used to evaluate autophagosomes. Apoptosis was determined by cell viability assays, caspase 3 activity assays and TUNEL assays. Cell migration was evaluated by a cell scratch assay. Small interfering (si) RNA transfection was used for target gene silencing. Treatment of tenocytes with IL-38 attenuated apoptosis, restored the balance between MMPs and TIMP-1, and alleviated ER stress under palmitate conditions. IL-38 treatment enhanced AMPK phosphorylation and promoted the expression of autophagy markers related to LC3 conversion, p62 degradation, and autophagosome formation in cultured tenocytes. The effects of IL-38 on ER stress, apoptosis, and MMP-9, MMP-13, and TIMP-1 expression in palmitate-treated tenocytes were abrogated by AMPK siRNA or 3-methyladenine (3MA). These results suggest that IL-38 alleviates ER stress through the AMPK/autophagy pathway, thereby reducing apoptosis and preventing extracellular matrix (ECM) degradation in tenocytes under hyperlipidemic conditions. This study provides a promising therapeutic avenue for treating obesity-related tendinopathy using an endogenous compound such as IL-38.

The 5' untranslated region variant rs3811050 C/T of the interleukin-38 encoding gene is associated with susceptibility to rheumatoid arthritis in Iraqi women

BACKGROUND

Interleukin (IL)-38, the latest member of the IL-1 cytokine family, is proposed to have a pathogenic role in rheumatoid arthritis (RA). It is encoded by the IL1F10 gene, which harbors single nucleotide polymorphisms (SNPs) that may predict the risk of autoimmune diseases. Among them are 5' untranslated region (UTR) SNPs, which play a key role in post-transcriptional control, but have not been studied in Iraqi RA patients.

METHODS

Two novel IL1F10 5'UTR SNPs (rs3811050 C/T and rs3811051 T/G) were explored in RA and control women (n = 120 and 110, respectively). SNPs were genotyped using TaqMan assay. An ELISA kit was used to measure serum IL-38 concentrations.

RESULTS

A reduced risk of RA was associated with rs3811050 T allele and CT genotype (corrected probability [pc] = 0.01 and < 0.001, respectively), while there was no significant association with rs3811051. Haplotype analysis demonstrated that C-T haplotype was associated with a 1.65-fold greater risk of RA, whereas a reduced risk was linked to T-G haplotype. IL-38 concentrations were higher in patients than in controls (p < 0.001). In addition, IL-38 showed acceptable performance in distinguishing between RA and control women (p < 0.001). When IL-38 concentrations were stratified according to SNP genotypes, no significant differences were found.

CONCLUSIONS

The rs3811050 variant was more likely to affect RA susceptibility in Iraqi women, and the T allele may play a role in reducing disease risk. IL-38 concentrations were elevated in RA patients, but were not affected by the rs3811050 and rs3811051 genotypes.

IL-38 alleviates atherogenic responses via SIRT6/HO-1 signaling: A promising strategy against obesity-related atherosclerosis

Interleukin-38 (IL-38), a member of the IL-1 family, is known for its anti-inflammatory properties mediated through ligand signaling in various disease models. It plays a significant role in atherosclerosis development, forming a theoretical basis for therapeutic strategies. However, the direct effects of IL-38 on atherogenic responses in the vascular endothelium and monocytes remain unclear. In this investigation, IL-38 treatment reduced THP-1 monocyte adhesion to HUVECs, decreased the expression of vascular adhesion molecules, and mitigated inflammation in the presence of palmitate. IL-38 treatment upregulated SIRT6 expression and enhanced autophagy markers such as LC3 conversion and p62 degradation. The effects of IL-38 were nullified by siRNA-mediated suppression of SIRT6 or heme oxygenase-1 (HO-1) in HUVECs and palmitate-treated THP-1 cells. These findings reveal that IL-38 mitigates inflammation through the SIRT6/HO-1 pathway, offering a potential therapeutic approach for addressing obesity-related atherosclerosis.

The emerging role of IL-38 in diseases: A comprehensive review

INTRODUCTION

Interleukin-38 (IL-38) is a new type of anti-inflammatory cytokine, which is mainly expressed in the immunity-related organs and is involved in various diseases including cardiovascular and cerebrovascular diseases, lung diseases, viral infectious diseases and autoimmune diseases.

AIM

This review aims to detail the biological function, receptors and signaling of IL-38, which highlights its therapeutic potential in related diseases.

CONCLUSION

This article provides a comprehensive review of the association between interleukin-38 and related diseases, using interleukin-38 as a keyword and searching the relevant literature through Pubmed and Web of science up to July 2023.

A novel signature of interleukins 36α, 37, 38, 39 and 40 in ankylosing spondylitis

The current study examined five cytokines, three belong to interleukin (IL)-1 family (IL-36α, IL-37 and IL-38), one belongs to IL-12 family (IL-39) and one has not been assigned to a family (IL-40), in the serum of 110 male patients with ankylosing spondylitis (AS) and 103 male controls. Studies regarding these cytokines in AS are very limited. Therefore, the significance of IL-36α, IL-37, IL-38, IL-39 and IL-40 as biomarkers of AS was evaluated. Cytokine levels were measured using enzyme-linked immunosorbent assay kits. Results revealed that serum levels (median and interquartile range) of IL-36α (90.7; 53.7-166.2 vs 39.7; 31.3-59.2 pg/mL; probability [p] < 0.001), IL-37 (161.3; 62.8-236.6 vs 58.4; 46.8-80.7 ng/mL; p < 0.001), IL-38 (135.8; 78.2-213.5 vs 65.8; 51.1-87.1 pg/mL; p < 0.001), IL-39 (57.7; 34.1-92.3 vs 29.1; 19.3-58.6 ng/L; p < 0.001) and IL-40 (3.89; 2.99-6.19 vs 2.10; 1.75-2.68 ng/L; p < 0.001) were significantly higher in AS patients than in controls. Besides, they were of value in distinguishing between AS patients and controls as evidenced by the receiver operating characteristic curve analysis: area under the curve = 0.797 (IL-36α), 0.75 (IL-37), 0.797 (IL-38), 0.728 (IL-39) and 0.886 (IL-40). Some of these cytokines were significantly correlated, but no correlation with AS activity was found. In conclusion, the levels of IL-36α, IL-37, IL-38, IL-39 and IL-40 were up-regulated in the serum of AS patients regardless of age, age at disease onset, disease duration, disease activity or HLA-B27.

Interleukin-38 promoter variants and risk of COVID-19 among Iraqis

Coronavirus disease-19 (COVID-19) has recently emerged as a respiratory infection with a significant impact on health and society. The pathogenesis is primarily attributed to a dysregulation of cytokines, especially those with pro-inflammatory and anti-inflammatory effects. Interleukin-38 (IL-38) is a recently identified anti-inflammatory cytokine with a proposed involvement in mediating COVID-19 pathogenesis, while the association between IL38 gene variants and disease susceptibility has not been explored. Therefore, a pilot study was designed to evaluate the association of three gene variants in the promoter region of IL38 gene (rs7599662 T/A/C/G, rs28992497 T/C and rs28992498 C/A/T) with COVID-19 risk. DNA sequencing was performed to identify these variants. The study included 148 Iraqi patients with COVID-19 and 113 healthy controls (HC). Only rs7599662 showed a significant negative association with susceptibility to COVID-19. The mutant T allele was presented at a significantly lower frequency in patients compared to HC. Analysis of recessive, dominant and codominant models demonstrated that rs7599662 TT genotype frequency was significantly lower in patients than in HC. In terms of haplotypes (in order: rs7599662, rs28992497 and rs28992498), frequency of CTC haplotype was significantly increased in patients compared to HC, while TTC haplotype showed significantly lower frequency in patients. The three SNPs influenced serum IL-38 levels and homozygous genotypes of mutant alleles were associated with elevated levels. In conclusion, this study indicated that IL38 gene in terms of promoter variants and haplotypes may have important implications for COVID-19 risk.

IL-38 orchestrates proliferation and differentiation in human keratinocytes

Interleukin (IL)-38 is a member of the IL-1 cytokine family with reported anti-inflammatory activity. The highest constitutive IL-38 expression is detected in the skin, where it is mainly produced by differentiating keratinocytes. However, little data are available regarding its biological functions. In this study, we investigated the role of IL-38 in skin physiology. We demonstrate here that dermal fibroblasts and epithelial cells of skin appendages, such as eccrine sweat glands and sebaceous glands, also express IL-38. Next, using two- and three-dimensional cell cultures, we show that endogenous expression of IL-38 correlates with keratinocyte differentiation and its ectopic overexpression inhibits keratinocyte proliferation and enhances differentiation. Accordingly, immunohistochemical analysis revealed downregulation of IL-38 in skin pathologies characterized by keratinocyte hyperproliferation, such as psoriasis and basal or squamous cell carcinoma. Finally, intracellular IL-38 can shuttle between the nucleus and the cytoplasm and its overexpression modulates the activity of the transcription regulators YAP and ID1. Our results indicate that IL-38 can act independently from immune system activation and suggest that it may affect the epidermis directly by decreasing proliferation and promoting differentiation of keratinocytes. These data suggest an important role of keratinocyte-derived IL-38 in skin homeostasis and pathologies characterized by epidermal alterations.

Interleukin-38 in atherosclerosis

Chronic inflammation caused by immune cells and their mediators is a characteristic of atherosclerosis. Interleukin-38 (IL-38), a member of the IL-1 family, exerts multiple anti-inflammatory effects via specific ligand-receptor interactions. Upon recognizing a specific receptor, IL-38 restrains mitogen-activated protein kinase (MAPK), nuclear factor kappa B (NK-κB), or other inflammation-related signaling pathways in inflammatory disease. Further research has shown that IL-38 also displays anti-atherosclerotic effects and reduces the occurrence and risk of cardiovascular events. On the one hand, IL-38 can regulate innate and adaptive immunity to inhibit inflammation, reduce pathological neovascularization, and inhibit apoptosis. On the other hand, it can curb obesity, reduce hyperlipidemia, and restrain insulin resistance to reduce cardiovascular disease risk. Therefore, this article expounds on the vital function of IL-38 in the development of atherosclerosis to provide a theoretical basis for further in-depth studies of IL-38 and insights on the prophylaxis and treatment of atherosclerosis.

Interleukin-38 promotes skin tumorigenesis in an IL-1Rrp2-dependent manner

Interleukin-38 (IL-38) is strongly associated with chronic inflammatory diseases; however, its role in tumorigenesis is poorly understood. We demonstrated that expression of IL-38, which exhibits high expression in the skin, is downregulated in human cutaneous squamous cell carcinoma and 7,12-dimethylbenzanthracene/12-O-tetradecanoyl phorbol-13-acetate-induced mouse skin tumorigenesis. IL-38 keratinocyte-specific knockout mice displayed suppressed skin tumor formation and malignant progression. Keratinocyte-specific deletion of IL-38 was associated with reduced expression of inflammatory cytokines, leading to reduced myeloid cell infiltration into the local tumor microenvironment. IL-38 is dispensable for epidermal mutagenesis, but IL-38 keratinocyte-specific deletion reduces proliferative gene expression along with epidermal cell proliferation and hyperplasia. Mechanistically, we first demonstrated that IL-38 activates the c-Jun N-terminal kinase (JNK)/activator protein 1 signal transduction pathway to promote the expression of cancer-related inflammatory cytokines and proliferation and migration of tumor cells in an IL-1 receptor-related protein 2 (IL-1Rrp2)-dependent manner. Our findings highlight the role of IL-38 in the regulation of epidermal cell hyperplasia and pro-tumorigenic microenvironment through IL-1Rrp2/JNK and suggest IL-38/IL-1Rrp2 as a preventive and potential therapeutic target in skin cancer.

An overview of the biological and multifunctional roles of IL-38 in different infectious diseases and COVID-19

Undoubtfully, the normal immune system can make a potential response to variable pathogens and neutralize or kill them depending on the type of infection through innate and acquired immunity. Cytokines have poly-peptide nature and are considered as signaling molecules that could amplify or alleviate immune responses besides their other biological functions. Interleukin 38 (IL-38) is a member of the IL-1 family cytokine that, however, its anti-inflammatory role has been observed in different autoimmune diseases like systemic lupus erythematosus (SLE), psoriasis, and Sjogren’s syndrome; there is a controversy about the cytokine pro-inflammatory function. In the current review, we skimmed IL-38 structure, signaling mechanism, and its immunological functions, IL-38-producing immune cells. Also, we argued about the role of this cytokine in viral infections including hepatitis B (HBV), hepatitis C (HCV), influenza (Flu), and COVID-19. Also, it illustrated the IL-38 protective effects on sepsis. Moreover, we explained the modulatory role of IL-38 in the COVID-19 cytokine storm.

Serum levels of novel anti-inflammatory cytokine Interleukin-38 in diabetes patients infected with latent tuberculosis (DM-LTB-3)

IL-38 is a recently discovered, novel anti-inflammatory cytokine, which belongs to the IL-1β family. The role played by this cytokine in diabetes-tuberculosis nexus is not known. Serum levels of IL-38, TNF-α, IL-6, and IL-1β in Normal Glucose Tolerance (NGT) and chronic Diabetes (DM) subjects, both with and without latent tuberculosis (LTB) (n = 256) were quantified by ELISA. While, serum levels of IL-38 were significantly reduced, the levels of TNF-α, IL-6, and IL-1β were not altered, in LTB infected diabetes patients. While no significant secretion of IL-38 was detected in the quantiferon supernatant, secretion of TNF-α, IL-6, and IL-1β was significantly reduced in LTB infected diabetes patients. The decreased systemic levels of IL-38 and reduced in vitro secretion of other pro-inflammatory cytokines might represent a crucial pathway associated with diabetes-tuberculosis nexus.

The emerging roles of IL-36, IL-37, and IL-38 in diabetes mellitus and its complications

Diabetes mellitus is a metabolic disease caused by a combination of genetics and environmental factors. The importance of the inflammatory response occurring in the pancreas and adipose tissue in the occurrence and progression of diabetes has been gradually accepted. Excess blood glucose and free fatty acids produce large amounts of inflammatory cytokines and chemokines through oxidative stress and endoplasmic reticulum stress. There is sufficient evidence that proinflammatory mediators, such as interleukin (IL)-1β, IL-6, macrophage chemotactic protein-1, and tumor necrosis factor-α, are engaged in the insulin resistance in peripheral adipose tissue and the apoptosis of pancreatic β-cells. IL-36, IL-37, and IL-38, as new members of the IL-1 family, play an indispensable effect in the regulation of immune system homeostasis and are involved in the pathogenesis of inflammatory and autoimmune diseases. Recently, the abnormal expression of IL-36, IL-37, and IL-38 in diabetes has been reported. In this review, we discuss the emerging functions, potential mechanisms, and future research directions on the role of IL-36, IL-37, and IL-38 in diabetes mellitus and its complications.

Biological Role, Mechanism of Action and the Importance of Interleukins in Kidney Diseases

Each year, the number of patients who are diagnosed with kidney disease too late is increasing, which leads to permanent renal failure. This growing problem affects people of every age, sex and origin, and its full etiopathogenesis is not fully understood, although the involvement of genetic susceptibility, infections, immune disorders or high blood pressure is suggested. Difficulties in making a correct and quick diagnosis are caused by the lack of research on early molecular markers, as well as educational and preventive activities among the public, which leads to the late detection of kidney diseases. An important role in the homeostasis and disease progression, including kidney diseases, is attributed to interleukins, which perform several biological functions and interact with other cells and tissues of the body. The aim of this article was to systematize the knowledge about the biological functions performed by interleukins in humans and their involvement in kidney diseases development. In our work, we took into account the role of interleukins in acute and chronic kidney disease and kidney transplantation.

Immunobiological Properties and Clinical Applications of Interleukin-38 for Immune-Mediated Disorders: A Systematic Review Study

Exponential growth in the usage of "cytokines" (as seroimmunobiomarkers) has facilitated more accurate prognosis, early diagnosis, novel, and efficient immunotherapeutics. Numerous studies have reported immunopathophysiological and immunopathological processes of interleukin-38 (IL-38). Therefore, in this systematic review article, the authors aimed to present an updated comprehensive overview on the immunobiological mechanisms, diagnostic, and immune gene-based therapeutic potentials of IL-38. According to our inclusion and exclusion criteria, a total of 216 articles were collected from several search engines and databases from the January 2012 to July 2021 time interval by using six main keywords. Physiologic or pathologic microenvironments, optimal dosage, and involved receptors affect the functionalities of IL-38. Alterations in serum levels of IL-38 play a major role in the immunopathogenesis of a wide array of immune-mediated disorders. IL-38 shows anti-inflammatory activities by reduction or inhibition of pro-inflammatory cytokines, supporting the therapeutic aspects of IL-38 in inflammatory autoimmune diseases. According to the importance of pre-clinical studies, it seems that manipulation of the immune system by immunomodulatory properties of IL-38 can increase the accuracy of diagnosis, and decipher optimal clinical outcomes. To promote our knowledge, more collaboration is highly recommended among laboratory scientists, internal/infectious diseases specialists, oncologists, immunologists, diseases-specific biomarkers scientists, and basic medical researchers.