THU0043 IL-25 ALLEVIATES RHEUMATOID ARTHRITIS BY INHIBITING TH17 IMMUNE RESPONSE 
Authors: dan liu, LV Yanyan
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> Rheumatoid arthritis (RA) is a prevalent common autoimmune disease characterized by chronic inflammation of the joint and synovial hyperplasia and progressive destruction of articular cartilage and bon. Accumulating evidence highlighted that an imbalance between pro- and anti-inflammatory cytokines maybe a key mechanism for disease progression in RA. IL-25 is reported to play an anti-inflammatory role in autoimmune and inflammatory diseases through the downregulation of Th1 and Th17 cell responses However, the exact role of IL-25 in the pathogenesis of RA remains to be elucidated. <h3>Objectives</h3> Explore the role of IL-25 in the pathogenesis of RA, and provide the scientific evidence of IL-25 relevant biological agent. <h3>Methods</h3> 1.The study was first to analyze the relationship between IL-25 and DAS28 score, CRP and anti-CCP in RA patients. Test IL-1β, IL-6, IL-17A, TNF-α and IFN-γ through ELISA, then analyze the relationship with IL-25. CD4<sup>+</sup> T cells from PBMCs of the 5 RA patients and 5 HCs were isolated under the manual of EasySep™ Human CD4<sup>+</sup> T Cell Isolation Kit and stimulated with anti-CD3 plus anti-CD28 in the presence or absence of rhIL-25. 2.CIA model was established to explore the mechanism of IL-25. The expression of CII specific IgG1 and IgG2a, as well as IL-1β, IL-6, IL-17A and TNF-α in CIA serum were examined using ELISA assay. The ROR-γ,T-bet, GATA-3 mRNA levels in knee joints and spleen were assessed by real-time qPCR analysis. In vitro, CD4<sup>+</sup> T cells from spleen were isolated from CIA mice and cultured with or without recombinant mouse (rm)IL-25 for 24h to control the expression IL-17A. Cells were stimulated with plate-bound anti-CD3 plus anti-CD28 in the presence or absence of recombinant mouse (rm) IL-25 with different dose for 24 h. <h3>Results</h3> 1.The expression of IL-25 were upregulated in the serum and synovial fluid in RA patients. Serum IL-25 levels were positively associated with DAS28 score, ESR and C-reactive protein. However, no significant correlation was observed between serum IL-25 levels, RF and anti-CCP. IL-25 serum levels was positively correlated with the concentrations of IL-1β, IL-6, IL-17A and TNF-α, respectively. However, no significant correlation was observed between serum IL-25 and IFN-γ level. 2. IL-25 can alleviate inflammatory response of CIA mouse and inhibite IL-17 differentiation. The serum levels of IL-1β, IL-6, IL-17A and TNF-α in IL-25-treated mice were markedly reduced compared with those in WT mice, except IFN-γ. RT-qPCR also demonstrated that the transcription levels of IL-17A and ROR-γt were decreased in the synovial tissue of IL-25-treated mice. RmIL-25 treatment significantly inhibited IL-17A production in a dose-dependent manner, and the mRNA level of the key TFs for Th17 cells (ROR-γt), as well as IL-17A, were also decreased. <h3>Conclusion</h3> IL-25 is upregulated in the serum and synovial fluid of RA patients. High levels of IL-25 was associated with disease severity and inflammation response in RA patients. IL-25 inhibits CD4+ T-cell activation and differentiation into Th17 cells, without affecting Th1 cells in RA. Systemic administration of IL-25 attenuates arthritis onset and joint damage in CIA mice. IL-25 of multi - target regulation further be used in the clinical treatment of RA. <h3>Disclosure of Interests</h3> None declared