Anti-inflammatory mechanism of tocilizumab, a humanized anti-IL-6R antibody: effect on the expression of chemokine and adhesion molecule

We studied the influence of IL-6 on chemokine production from peripheral blood mononuclear cells (PBMC), fibroblastic synovial cells and human umbilical vessel endothelial cells (HUVEC). Moreover, we examined the effect of IL-6 on the adhesion of U937 cells to HUVEC. For chemokine production, PBMC, fibroblastic synovial cells and HUVEC were cultured with IL-6 or IL-6 + soluble IL-6R (sIL-6R) for 24 h and then the production of MCP-1 and IL-8 were measured in supernatants. IL-6 and IL-6 + sIL-6R induced production of both MCP-1 and IL-8 in PBMC and synovial cells, respectively. In HUVEC, IL-6 + sIL-6R induced MCP-1 production, but inhibited IL-8 production. For adhesion molecule expression, the production of soluble form of adhesion molecules in HUVEC culture supernatant were measured by ELISA and the expression of adhesion molecules on cell surface were examined by flow cytometry analysis. Soluble ICAM-1 was detectable in IL-6 + sIL-6R-treated HUVEC and IL-6 + sIL-6R-induced ICAM-1 expression on cell membrane of HUVEC. In addition, U937 cells were added to HUVEC, which were pre-treated with IL-6 + sIL-6R for 24 h, and 3 h later attached U937 cells were counted. The adhesion of U937 cells to HUVEC was augmented when HUVEC was pretreated by IL-6 + sIL-6R. This adhesion was suppressed by anti-ICAM-1 antibody and anti-IL-6R antibody, but not by antibodies against VCAM-1 or E-selectin. In conclusion, IL-6 signaling plays an important role in inflammatory cell migration by increasing the rate of cell adhesion and by inducing chemokine production in inflamed joints.