The exact role of IL-6 in inflammatory osteoclast formation is still under debate. Our previous study demonstrated that IL-6 in the combination of sIL-6R significantly promoted low level of RANKL-induced osteoclast differentiation which was not affected by IL-6 alone. However, the precise molecular mechanisms underlying the regulation of sIL-6R-induced trans-signaling on osteoclast differentiation remains to be elucidated. Mouse bone marrow‑derived monocytes (BMMs) were isolated and cultured with RANKL and IL-6/sIL-6R in the presence or absence of sgp130. TRAP staining and pit formation assay were used to visualize multinucleated giant osteoclasts and evaluate their bone resorption ability. Western blot and real time-PCR were applied to determine the activations of IL-6 signaling pathway and osteoclastogenesis- associated signaling pathways. The results showed that sIL-6R activation of IL-6 trans-signaling enhanced IL-6 signaling cascades and promoted low concentration of RANKL-induced osteoclasts formation and bone resorption by mouse BMMs. Furthermore, blocking IL-6 trans-signaling with sgp130 abrogated this promotive effect by suppressing NF-κB and JNK signaling pathways. In conclusion, sIL-6R-mediated trans-signaling pathway plays a decisive role in promotion of low level of RANKL-induced osteoclastic differentiation by IL-6/sIL-6R and targeting the IL-6 trans-signaling pathway may represent a potential strategy for inflammatory diseases with pathological bone resorption.

IL-6 在炎性破骨细胞形成中的确切作用仍在争论中。我们之前的研究表明，sIL-6R 组合中的 IL-6 显着促进了低水平的 RANKL 诱导的破骨细胞分化，而这种分化不受单独的 IL-6 的影响。然而，sIL-6R 诱导的反式信号转导对破骨细胞分化的调控的确切分子机制仍有待阐明。在存在或不存在 sgp130 的情况下，分离小鼠骨髓来源的单核细胞 (BMM)，并与 RANKL 和 IL-6/sIL-6R 一起培养。TRAP 染色和凹坑形成试验用于观察多核巨型破骨细胞并评估其骨吸收能力。应用蛋白质印迹和实时 PCR 来确定 IL-6 信号通路和破骨细胞生成相关信号通路的激活。结果表明，IL-6 反式信号转导的 sIL-6R 激活增强了 IL-6 信号级联，并促进了低浓度的 RANKL 诱导的破骨细胞形成和小鼠 BMM 的骨吸收。此外，用 sgp130 阻断 IL-6 转信号通过抑制 NF-κB 和 JNK 信号通路消除了这种促进作用。总之，sIL-6R 介导的转信号通路在 IL-6/sIL-6R 促进低水平 RANKL 诱导的破骨细胞分化中起决定性作用，靶向 IL-6 转信号通路可能代表一种潜在的策略用于伴有病理性骨吸收的炎症性疾病。用 sgp130 阻断 IL-6 转信号通过抑制 NF-κB 和 JNK 信号通路消除了这种促进作用。总之，sIL-6R 介导的转信号通路在 IL-6/sIL-6R 促进低水平 RANKL 诱导的破骨细胞分化中起决定性作用，靶向 IL-6 转信号通路可能代表一种潜在的策略用于伴有病理性骨吸收的炎症性疾病。用 sgp130 阻断 IL-6 转信号通过抑制 NF-κB 和 JNK 信号通路消除了这种促进作用。总之，sIL-6R 介导的转信号通路在 IL-6/sIL-6R 促进低水平 RANKL 诱导的破骨细胞分化中起决定性作用，靶向 IL-6 转信号通路可能代表一种潜在的策略用于伴有病理性骨吸收的炎症性疾病。