Background Decoy receptor 3 (DcR3) is a secreted decoy tumor necrosis factor receptor and competitively binds and inhibits the TNF family including Fas-ligand, 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 TNF-alpha protects the cells from Fas-induced apoptosis . We recently reported that DcR3 binds to TL1A expressed on RA-FLS resulting in the negative regulation of cell proliferation induced by inflammatory cytokines . Further, we newly revealed the gene expression profiles in RA-FLS regulated by DcR3 by using microarray data analysis. The profiles indicated that centrosomal protein 70kDa (CEP70) was down-regulated by DcR3 (fold change 1.87)  in addition to tryptophan hydroxylase 1 . Centrosome forms the backbone of cell cycle progression mechanism. Further, CEP family protein is the active component of centrosome and plays a vital role in centriole biogenesis and cell cycle progression control .
Objectives In this study, we analysed CEP70 expression in RA-FLS stimulated with DcR3 in detail to reveal the involvement of CEP70 and DcR3 in the pathognenesis of RA.
Methods Real-time polymerase chain reaction (real-time PCR). RA and osteroarthritis (OA) -FLS were stimulated with 1ng/ml of recombinant human TNFα or IgG1 for 24 h, or with various concentration of DcR3-Fc or control IgG1 for 12 h. Further, RA-FLS were incubated with DcR3-Fc for 12 h after overnight pre-incubation with anti-TL1A antibody. The relative expression levels of CEP70 mRNA were quantified by real-time PCR.
Immunohistochemistry. Anti-CEP70 antibody was applied to frozen sections of synovial tissues from patients with RA or OA overnight. Sections were stained with HistoFine simple stain Kit and DAB chromogen, followed by counterstaining with hematoxylin.
Results Real-time PCR revealed that the expression of CEP70 mRNA in RA-FLS was higher than that in OA-FLS and that TNFα significantly decreased the expression of CEP70 mRNA in RA and OA-FLS (RA, 51%; OA, 59%). DcR3-Fc also significantly decreased the expression of CEP70 mRNA in RA-FLS in a dose dependent manner (81% with 10ng/ml, 73% with 100ng/ml, and 57% with 1000ng/ml). In contrast, DcR3-Fc did not decrease CEP70 mRNA in OA-FLS. Anti-TL1A antibody inhibited the down-regulation of CEP70 expression in RA-FLS induced by DcR3-Fc. Immunohistochemistrical analysis revealed that CEP70 protein was expressed dominantly in superficial lining layer of rheumatoid synovium compared with that of OA synovium.
Conclusions In this study, we revealed that CEP70 was increased in RA-FLS and that the expression of CEP70 in RA-FLS was decreased by DcR3 by binding to membrane-bound TL1A in a disease-specific fashion. DcR3 may affect the pathogenesis of RA through CEP70.
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Disclosure of Interest None declared