Session Type: Poster Session (Tuesday)
Session Time: 9:00AM-11:00AM
Background/Purpose: Rheumatoid arthritis (RA) is a chronic autoimmune disorder, characterized by joint inflammation and bone destruction. The fibroblast-like synoviocyte(FLS) contributes to the pathogenesis of RA through cellular proliferation and production of cytokines or chemokines. Recently, blockade of the bromodomain and extra-terminal domain (BET) family protein was reported to be a potential therapeutic target by inhibiting epigenetic interaction between bromodomains and acetylated histones. This study aimed to investigate the effects of bromodomain-containing protein 4 (BRD4) inhibition on tumor necrosis factor (TNF)-α-stimulated RA-FLS and osteoclast using BRD4 inhibitor, I-BET762.
Methods: RA-FLSs were treated with TNF-α in the presence of I-BET762 for 48 h. The cell viability and proliferation were measured after 24, 48, and 72 h in I-BET762-treated RA-FLS using CCK-8 colormetric assay. We then screened pro-inflammatory mediators by using the human inflammation antibody array. The levels of interleukin (IL)-6, IL-8 and CXCL-10 were measured in culture supernatants of TNF-α-stimulated RA-FLS by ELISA. Migrations were analyzed by the wound healing assay. We compared the expression of BRD2, BRD3 and BRD4 level by BRD4 specific inhibition in RA. Expression of c-Myc was detected by using Western blot. PBMC isolated from buffy coat were cultured with M-CSF and RANKL for 14 days in the presence or absence of I-BET762. Cells were stained with tartrate-resistant acid phosphatase (TRAP) and the number was counted by light microscopy. The ability of actin formation in osteoclast was evaluated by immunofluorecent stain.
Results: I-BET762 had no effect on cytotoxicity and proliferation of RA-FLS. I-BET762 reduced the secretion of IL-6, CXCL-10 and regulated upon activation, normal T cell expressed, and secreted (RANTES) from RA-FLS in the antibody array. Level of IL-6, IL-8 and CXCL-10 were significantly decreased after treatment with I-BET762 by ELISA. The number of migrated cells decreased in response to I-BET762 compared with the vehicle. The expression levels of BRD2, BRD3 and BRD4 proteins did not change with I-BET762. Expression of the target molecule, c-Myc, was decreased in I-BET762 treated RA-FLSs. TRAP-positive multinucleated (more than three nuclei) cells were reduced in a dose-dependent manner. The actin formation of podosome, actin belt and actin ring were inhibited in the presence of I-BET762.
Conclusion: Inhibition of BRD4 by I-BET762 led to down-regulation of pro-inflammatory mediators, migration and expression of c-Myc in RA-FLSs. The differentiation of osteoclast and resorption activity was inhibited by I-BET762. These data suggest that the I-BET762 may have anti-inflammatory properties and prevent bone loss in RA.
To cite this abstract in AMA style:Kim R, Yoo H, Kang S, Park J, Kim S, Lee E, Park J, Song Y. Bromodomain Inhibitor, I-BET762 Inhibits Production of Pro-inflammatory in Rheumatoid Arthritis Fibroblast-like Synoviocytes and Differentiation of Osteoclast [abstract]. Arthritis Rheumatol. 2019; 71 (suppl 10). https://acrabstracts.org/abstract/bromodomain-inhibitor-i-bet762-inhibits-production-of-pro-inflammatory-in-rheumatoid-arthritis-fibroblast-like-synoviocytes-and-differentiation-of-osteoclast/. Accessed September 27, 2021.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/bromodomain-inhibitor-i-bet762-inhibits-production-of-pro-inflammatory-in-rheumatoid-arthritis-fibroblast-like-synoviocytes-and-differentiation-of-osteoclast/