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

Interleukin 38 improves insulin resistance in hyperlipidemic skeletal muscle cells via PPARδ/SIRT1-mediated suppression of STAT3 signaling and oxidative stress

The cytokine interleukin-38 (IL-38), a recently discovered member of the IL-1 family, has been shown to regulate inflammation and improve hepatic endoplasmic reticulum stress and lipid metabolism in individuals with obesity. However, its impact on insulin signaling in skeletal muscle cells and the underlying mechanisms remain unclear. In vitro obesity models were established using palmitate treatment, and Western blot analysis was performed to assess target proteins. Commercial kits were used to measure glucose uptake in cultured myocytes. Our study showed that IL-38 treatment alleviated the impairment of insulin signaling, including IRS-1 and Akt phosphorylation, and increased glucose uptake in palmitate-treated C2C12 myocytes. Increased levels of STAT3-mediated signaling and oxidative stress were observed in these cells following palmitate treatment, and these effects were reversed by IL-38 treatment. In addition, IL-38 treatment upregulated the expression of PPARδ, SIRT1 and antioxidants. Knockdown of PPARδ or SIRT1 using appropriate siRNAs abrogated the effects of IL-38 on insulin signaling, oxidative stress, and the STAT3-dependent pathway. These results suggest that IL-38 alleviates insulin resistance by inhibiting STAT3-mediated signaling and oxidative stress in skeletal muscle cells through PPARδ/SIRT1. This study provides fundamental evidence to support the potential use of IL-38 as a safe therapeutic agent for the treatment of insulin resistance and type 2 diabetes.

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 in Behçet's disease: Gene expression in bronchoalveolar lavage from patients having pulmonary involvement

The etiological complexity of Behçet disease (BD), an immune-mediated rare form of vasculitis characterized by multi-organ involvement, is still elusive due to an incomplete understanding of the synergy between genetic susceptibility, environmental triggers, and an abnormal immune response. The diagnosis of BD relies on clinical symptoms. Lung inflammatory disorders are severe conditions of patients with BD, here we focus on the expression of biomarkers in BD patients with pulmonary manifestations. Aiming to identify additional discriminating biomarker patterns, we measured and compared protein and gene expression of IL-38 and a broad panel of selected genes in bronchoalveolar cells of patients suffering from BD with and without pulmonary involvement compared to controls. ELISA and RT-PCR analysis were applied. The first principal analysis highlighted decreased IL-38 level in BD patients compared to Rheumatoid Arthritis (RA) patients and controls: BD patients expressed lower IL-38 levels, particularly in cases with pulmonary involvement. The area under the curve (AUC) of the receiver-operating characteristic curve showed that IL-38 may be an eventual biomarker for BD. Co-cultured recombinant IL-38 and stimulated memory PBMCs of active BD, were able to suppress IL-17 and NLRP3 inflammasome and ameliorate the secretion of IL-10 and TGFβ. Transcription factors of the IL-1 family (IL-1β, IL-18, IL-32, IL-33 and IL-37) along with IFN-γ, IL-17, RORγt, Foxp3, TGFβ, IL-10 and NLRP3 inflammasome were the parameters that are the main contributor to the segregation between BD with and without lung involvement. Our results indicate that IL-38 might be involved in the pathogenesis of BD and the combined gene expression in BAL suggests distinct mechanisms governing the inflammatory disorders in the lung.