MAPK8 and rheumatoid arthritis: In this study, the alcohol extract of Chaenomeles Fructus reduced the protein expression of JNK and ERK1/2 protein in the synovium of the knee joint of RA rats, suggesting that the alcohol extract of Chaenomeles Fructus can inhibit the MAPK signaling pathway, thus reducing the release of inflammatory factors and inhibiting the abnormal proliferation of the synovial membrane to inhibit joint bone erosion in RA.