Since the balance between ERK1/2 and JNK activities after UV-C irradiation has been reported to control the cellular outcome in human fibroblasts [72], it is likely that different combinations of activation of MAPK isoforms control distinct intracellular signaling and cellular outcomes, which contributes to TNF-α-induced IL-8 expression in synovial inflammation of RA. This evidence concerns the gene MAPK8 and rheumatoid arthritis.