Quercetin treatment of RA fibroblast-like synoviocytes (RA-FLSs) reduced the expression of the long non-coding RNA XIST, a regulator implicated in synovial fibroblast activation, and Proteasome subunit beta type-8 (PSMB8), a component of the immunoproteasome involved in antigen processing and inflammatory signaling; this downregulation was associated with reduced synoviocyte proliferation and inflammatory mediator release [28]. Here, PSMB8 is linked to rheumatoid arthritis.