Background/Purpose: Decoy receptor 3 (DcR3) is a secreted decoy tumor necrosis factor receptor and competitively binds and inhibits the TNF family including Fas-ligand (FasL), LIGHT, and TL1A. DcR3 is overexpressed in tumor cells and might benefit tumors by helping them to avoid cytotoxic and regulatory effects of the ligands. We previously reported that DcR3 overexpressed in rheumatoid synovial fibroblasts (RA-FLS) stimulated by TNFα protects the cells from Fas-induced apoptosis. We recently reported that DcR3 induces VLA-4 expression in THP-1 macrophages to inhibit cycloheximide-induced apoptosis, and that DcR3 binds to TL1A expressed on RA-FLS resulting in the negative regulation of cell proliferation induced by inflammatory cytokines. Therefore, DcR3 may regulate gene expressions in RA-FLS by binding to TL1A on RA-FLS as a ligand. In the present study, we studied interleukin (IL)-12B as one of the key molecules in DcR3-TL1A signaling in RA-FLS based on the genes expression profiles regulated by DcR3.

Methods: Microarray assay. Four individual lines of primary cultured RA-FLS were incubated with either recombinant human DcR3-Fc protein or control IgG1 for 12 hours. Gene expressions were detected by microarray assay and the profiles were analyzed. Real-time polymerase chain reaction (real-time PCR). RA and osteroarthritis (OA) -FLS were stimulated with various concentration of DcR3-Fc or control IgG1 for 12 hours. Further, RA-FLS were incubated with DcR3-Fc for 12 hours after overnight pre-incubation with anti-TL1A antibody. The relative expression levels of IL-12B mRNA were quantified by real-time PCR. Western blotting. RA-FLS was stimulated with DcR3-Fc or control IgG1 for 24 hours. The expression of IL-12B p40 protein in RA-FLS was investigated by western blotting.

Results: Microarray data analysis revealed that DcR3 up-regulates or down-regulates the expression of various genes n RA-FLS. Among the most significantly regulated 100 genes by DcR3, 45 genes were up-regulated and 55 genes were down-regulated. The profiles indicated that shared p40 subunit (IL-12B) of IL-12 and IL-23 was up-regulated by DcR3-Fc (fold change 1.65). Real-time PCR revealed that DcR3-Fc significantly increased the expression of IL-12B mRNA in RA-FLS in a dose dependent manner (113% with 10ng/ml, 135% with 100ng/ml, and 218% with 1000ng/ml) compared with control IgG1. In contrast, DcR3-Fc did not increase IL-12B mRNA in OA-FLS. Anti-TL1A antibody inhibited the up-regulation of IL-12B expression in RA-FLS induced by DcR3-Fc. Western blotting confirmed that IL-12B p40 protein in RA-FLS was increased when stimulated with DcR3-Fc.

Conclusion: IL-12 consisted of IL-12A (p35) and IL-12B induces Th1 immune responses. Meanwhile, IL-23 consisted of IL-23A (p19) and IL-12B is involved in the inflammatory pathway via IL-17. In this study, we revealed that DcR3 increased the expression of IL-12B in RA-FLS in a disease-specific fashion by binding to membrane-bound TL1A as a ligand. DcR3 may affect the pathogenesis of RA through IL-12B.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/interleukin-12b-is-up-regulated-by-decoy-receptor-3-in-specifically-rheumatoid-synovial-fibroblasts/