Inhibition of MAP kinase in synovium by treatment with tocilizumab in rheumatoid arthritis

To investigate the histological changes of mitogen-activated protein kinase (MAPK) in synovium with tocilizumab in rheumatoid arthritis (RA), synovial tissue samples were assessed from ten methotrexate (MTX)-treated RA patients for control and ten tocilizumab with MTX-treated RA patients. The synovium was observed using hematoxylin and eosin (H&E) stain and analyzed immunohistochemically for the expression of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), matrix metalloproteinase-3 (MMP-3), CD4 (T cell), CD20 (B cell), CD68 (macrophage), vascular endothelial growth factor (VEGF), CD29 (β-1 integrin), phospho-p38 MAPK (Tyr180/Tyr182), phospho-p44/42 MAPK [extracellular signal-regulated kinase (ERK) 1/ERK2], and phospho-c-Jun N-terminal kinase (JNK). H&E staining showed that there is a significant difference of cell proliferation; however, there is no change of hypervascularity in the synovium between both groups. An immunohistochemical examination showed that the decrease of CD29 (β-1 integrin) and JNK was found significant, while ERK was increased in the tocilizumab group. CD20, B-lymphocyte, was decreased in the tocilizumab group compared with the MTX group significantly. IL-6 was completely blocked in the patients who received tocilizumab. TNF-α was similarly expressed in the interstitial cells of synovium of patients in both groups. MMP-3 and CD68 were similarly expressed on the surface of synovium. VEGF was less expressed in both groups. These findings indicate that the inhibition of CD20, CD29, and JNK in MAPK may be involved in the efficacy of tocilizumab compared with MTX treatment in RA.