MAPK8 and rheumatoid arthritis: In the present study, IL-1β stimulation markedly induced both the phosphorylation of MAPKs and the translocation of NF-κB into the cell nucleus in RA-FLS, whereas MASM treatment considerably inhibited the phosphorylation of MAPKs, including JNK, ERK and p38, and the translocation of NF-κB into the nucleus, especially at a high concentration of 20 μM.