17-Hydroxy-jolkinolide A inhibits osteoclast differentiation through suppressing the activation of NF-κB and MAPKs.

Osteoclasts (OC) are bone-specific multinucleated giant cells (MNCs) derived from the monocyte/macrophage hematopoietic lineage cells. Inhibiting osteoclast formation is considered as an effective therapeutic approach for the treatment of the pathological bone loss. In this study, we investigated effects of 17-hydroxy-jolkinolide A (HJA), an ent-abietane diterpenoid isolated from the dried root of Euphorbia fischeriana, on osteoclastogenesis induced by RANKL. The results showed that HJA significantly inhibited RANKL-induced osteoclast formation from primary bone marrow macrophages (BMMs). HJA also prevented bone resorption by mature osteoclasts in a dose-dependent manner. In addition, the expression of osteoclastic marker genes, such as tartrate-resistant acid phosphatase (TRAP), cathepsin K (Cts K) and MMP-9, was significantly inhibited by HJA. Furthermore, HJA also significantly inhibited RANKL-induced activation of NF-κB and phosphorylation of MAPK. Our results indicate that HJA has an inhibitory role in the bone loss by preventing osteoclast formation as well as its bone resorptive activity. Therefore, HJA may be useful as a therapeutic reagent for bone loss-associated diseases.