Because p38 signaling is more tightly connected to the control of osteoclast metabolism than ERK and JNK signaling, researchers have tried to apply p38 inhibitors to prevent periopathogen-induced periodontal and active alveolar bone loss with degradation of mineralized and non-mineralized tooth tissues [130,131,132] and to treat rheumatoid arthritis with synovial inflammation, overactive osteoclast function, cartilage degradation, and bone erosion [133]. Here, MAPK1 is linked to rheumatoid arthritis.