PTGS2 and rheumatoid arthritis: Expression of both COX-1 and COX-2 is increased in the synovium of patients with RA [11]; in addition, synovial fluid contains high levels of pro-inflammatory eicosanoid products from both the COX and LOX pathways [11] as well as high levels of pro-inflammatory cytokines including TNF, IL-1β, IL-17A, IL-6, IL-8 and GMCFS [50].