TRAF6/ERK/p38 pathway is involved in interleukin-17-mediated autophagy to promote osteoclast precursor cell differentiation.

To investigate the effects of interleukin (IL)-17-mediated autophagy on the TNF receptor associated factor (TRAF6)/extracellular signal-regulated kinase (ERK)/p38 pathway and osteoclast differentiation. Mouse bone marrow-derived macrophages (BMM) were cultured with a medium containing 30†ng/mL macrophage colony stimulating factor and 50†ng/mL receptor activator of nuclear factor-kappa B ligard (RANKL), and IL-17 (0.01, 0.1, 1.0, 10†ng/mL) was added for intervention (IL-17 group). Tartrate-resistant acid phosphatase (TRAP) staining was used to observe TRAP positive multinucleated cells; phalloidin fluorescent staining was used to detect actin ring circumference; toluidine blue staining was used to analyze bone resorption lacuna formation. To further examine the mechanism of the effect of IL-17-mediated autophagy on the differentiation of osteoclasts, the control group used RANKL medium to culture mouse macrophage RAW264.7 cells, while the IL-17 group was treated with IL-17 (0.01, 0.1, 1.0, /mL). Western blot was used to detect the expression of autophagy-related proteins Beclin-1, microtubule-associated protein 1 light chain 3 (LC3) and osteoclast-related proteins c-fos and nuclear factor of activated T cell 1 (NFATc1) after treatment with different concentrations of IL-17. The expression of LC3, NFATc1, TRAF6/ERK/p38 signaling pathway related proteins were detected in IL-17 and autophagy inhibitor 3-MA group. The number of TRAP positive multinucleated cells, the circumference of the actin ring and the area of bone resorption lacuna in IL-17 group treated with IL-17 (0.01, 0.1, were significantly higher than those in the control group. In IL-17 treated RAW264.7 cells, the expression of c-fos, NFATc1, Beclin-1, LC3, TRAF6, p-ERK, and p-p38 was all significantly up-regulated (all 0.05). After treatment with the autophagy inhibitor 3-MA, the expression levels of LC3, NFATc1, TRAF6, p-ERK, and p-p38 all decreased significantly (all 0.05). IL-17 can promote the expression of autophagy proteins and enhance the differentiation ability of osteoclast precursor cells, and the TRAF6/ERK/p38 signaling pathway may be involved in this process.