Fig. (4) NF-κB activity and Gadd45β gene and protein expression in rheumatoid arthritis (RA) and osteoarthritis (OA) synovium. Gadd45ß is an NF-kB induced gene that suppresses the JNK pathway by binding to MKK7. Even though NF-kB activation is much higher in RA than OA, Gadd45ß expression is similar in the two diseases. Lack of Gadd45ß can contribute to over-activation of the JNK pathway in RA. (A-D), Immunohistochemical analyses of RA and OA synovium, showing Gadd45β protein expression (brown color) in RA synovial tissue (A) and OA synovial tissue (C), as well as staining for NF-κB in consecutive RA and OA sections (B and D, respectively) [86].