Targeting bromodomain-containing protein 4 (BRD4) benefits rheumatoid arthritis

We aimed to explore the effects of bromodomain-containing protein 4 (BRD4) inhibition on tumor necrosis factor (TNF)-α-stimulated human rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS) behavior and the therapeutic implications using BRD4 inhibitor JQ1 were explored in vivo. The levels of interleukin (IL)-1β, IL-6, IL-17 and IL-18 in cultural supernatants from TNFα-stimulated RA-FLS were measured by ELISA. RA-FLS migration and invasion in vitro were investigated using wound healing and Matrigel assay. Expression of signaling pathway proteins was measured by Western blot. The in vivo effects of BRD4 inhibitor JQ1 were elucidated using collagen-induced arthritis (CIA) mice. We found BRD4 silencing reduced the secretion of IL-1β, IL-6, IL-17 and IL-18 from TNFα-stimulated human RA-FLS. Downregulation of BRD4 inhibited FBS-induced migration and invasion of human RA-FLS. BRD4 silencing decreased the phosphorylation of c-Jun and activation of NFκB in TNFα-stimulated RA-FLS. In vivo, BRD4 inhibitor JQ1 reduced the inflammatory response, autoantibody production and joint damage of CIA model. Our data suggest for the first time that BRD4 inhibition has anti-inflammatory property in RA.