Effect of IL-17 on osteoclast differentiation of RAW264 cells

Abstract

Orthodontic tooth movement requires alterations in bone remodeling patterns in the alveolar bone underlying the tooth targeted for movement. Interleukin-17 A (IL-17) is a proinflammatory cytokine that is mainly secreted by activated T cells. The direct effects of IL-17 on the differentiation of osteoclast precursors into osteoclasts and on the function of osteoclasts remains unknown. We investigated the effects of IL-17 on osteoclast differentiation using RAW264 cells as osteoclast precursors. We tested the effect of IL-17 on the proliferation and differentiation of RAW264 cells, and on the expression of IL-17 receptors. Expression of IL-17 RC was confirmed on RAW264 cells by FACS analysis. IL-17 did not affect the proliferation, but suppressed the differentiation of RAW264 cells in the presence of soluble RANKL into osteoclasts in a dose-dependent manner. Phosphorylation of p38 MAP kinase was further enhanced in the presence of RANKL compared with the control, which was reduced by IL-17 in a dose-dependent manner.
These results suggest that RANKL-induced osteoclast differentiation is suppressed by IL-17. Furthermore, it is suggested that inhibition of p38 MAP kinase phosphorylation by IL-17 may be one of the factors that suppresses the differentiation of osteoclast precursors into osteoclasts.