MAPK1 and rheumatoid arthritis: MAPK regulates the expression of multiple genes and has been considered a potential target for treating RA or other immune-mediated chronic inflammatory diseases.200 It can transduce extracellular signals such as growth factors, neurotransmitters, hormones, stress conditions, viruses, and inflammatory factors into the cells201,202 and play a key role in the transduction of extracellular stimulation to drive intracellular responses.203 P38 MAPK, extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK) are the three main subfamilies of the MAPK pathway.204