Among the core targets, ERK (MAPK1), JNK (MAPK8), and p38 MAPK (MAPK14) are well-defined families of MAPKs, activated by phosphorylation, and play significant roles in the inflammatory and destructive mechanisms observed in rheumatoid arthritis, including regulating pro-inflammatory cytokine production and mediating downstream signaling from IL-1, IL-17, and TNF-α receptors. This evidence concerns the gene MAPK8 and rheumatoid arthritis.