Background:Rheumatoid arthritis (RA) is a progressive, chronic inflammatory autoimmune disease. Pro-inflammatory molecules, activated lymphocytes, and the migration of inflammatory cells are important in the development of RA. There are many unknown causes of RA. And there are many patients who are refractory to treatment with known disease-modifying anti-rheumatic drugs. So, unknown cause of RA needs to be elucidated.CD70 is a member of the tumor necrosis factor (TNF) superfamily and a ligand for CD27. The interaction of CD70 with its receptor CD27 promotes expansion and differentiation of memory and effector T cells as well as B-cell expansion and plasma cell differentiation. Hypoxia is an important micro-environmental factor in RA synovium. Hypoxia induces activation of hypoxia inducible factor (HIF). The expression of HIF-2α is up-regulated in human RA synovium. Reactive oxygen species (ROS) has been implicated in the pathophysiology of RA.Objectives:In this study, we tried to examine the presence of CD70 in RA synovium and investigate the role of CD70 in the development of RA associated with HIF-2α and ROS.Methods:Fibroblast-like synoviocyte (FLS), peripheral blood (PB) and synovial fluid (SF) were used for experiments. FLS was stimulated with recombinant human (rh)-IL-17 and rh-TNF-α. N-acetyl-L-cysteine (NAC) was used as a ROS scavenger. HIF-2α inhibitor (PT-2385) was used for examine the effect of HIF-2α in RA-FLS. RT-PCR, qPCR, western blotting, flow-cytometry, ELISA, cell migration assay, and scratch wound assay were performed.Results:CD70 mRNA is present and elevated by stimulation with IL-17 and TNF-α in both RA-FLS and osteoarthritis (OA)-FLS (Fig 1). CD70 also expresses on the surface of RA-FLS and OA FLS (Fig 2). CD70 expression on the surface of FLS is elevated by stimulation with IL-17 and TNF-α in both RA and OA. Soluble CD27 is present higher in the supernatant of RA-SF than OA-SF (Fig 3). HIF-2α mRNA, HIF-2α protein, and the amount of ROS were all elevated after treatment with IL-17 and TNF-α in RA-FLS (Fig 4, Fig 5). CD70 expression and the amount of ROS were lowered by treatment with HIF-2α inhibitor in RA-FLS (Fig 6). Decreased amount of ROS results in decreased CD70 expression on the RA-FLS (Fig 7). CD70 influenced on cell migration directly or by HIF-2α (Fig 8).Conclusion:In this study, we found the function of CD70 in RA-FLS associated with HIF-2α and ROS. First, CD70 on RA-FLS interacts with CD27 in the RA-SF and this interaction produces sCD27 (Fig. 9) and CD70 has an influence on the migration of RA-FLS. Second, IL-17 and TNF-α are critical factors to trigger the expression of CD70, HIF-2α and ROS in RA synovium. Third, CD70 is regulated by HIF-2α associated with ROS. From these results, we suggest that CD70 may be a new therapeutic target of RA. And sCD27 also may be an important diagnostic maker of RA.References:[1]Lundy SK, Sarkar S, Tesmer LA, Fox DA. Cells of the synovium in rheumatoid arthritis. T lymphocytes. Arthritis Res Ther. 2007;9(1):202.[2]Nevius E, Gomes AC, Pereira JP. Inflammatory Cell Migration in Rheumatoid Arthritis: A Comprehensive Review. Clin Rev Allergy Immunol. 2016;51(1):59-78.[3]Bowman MR, Crimmins MA, Yetz-Aldape J, Kriz R, Kelleher K, Herrmann S. The cloning of CD70 and its identification as the ligand for CD27. J Immunol. 1994;152(4):1756-61.[4]Kitajima S, Lee KL, Fujioka M, Sun W, You J, Chia GS, et al. Hypoxia-inducible factor-2 alpha up-regulates CD70 under hypoxia and enhances anchorage-independent growth and aggressiveness in cancer cells. Oncotarget. 2018;9(27):19123-35.[5]Gaber T, Dziurla R, Tripmacher R, Burmester GR, Buttgereit F. Hypoxia inducible factor (HIF) in rheumatology: low O2! See what HIF can do! Ann Rheum Dis. 2005;64(7):971-80.Disclosure of Interests:None declared
The TNF superfamily member LIGHT contributes to survival and activation of synovial fibroblasts in rheumatoid arthritis