A pterostilbene derivative suppresses osteoclastogenesis by regulating RANKL-mediated NFκB and MAPK signaling in RAW264.7 cells.

Background: A dysfunctional osteoclast activity is often the cause of bone destructive diseases, such as osteoporosis, periodontitis, erosive arthritis, and cancer. The NFκB ligand (RANKL) has been identified as a major mediator of bone resorption. Agents that suppress RANKL signaling have the potential to inhibit bone resorption or osteoclastogenesis. The present study aimed to determine the effect of a pterostilbene derivative (PTERC-T) for suppressing RANKL or tumor cells-induced osteoclastogenesis in RAW264.7 murine macrophages.

Methods: Cytotoxicity was measured by MTT assay and inhibitory effect on osteoclastogenesis was analyzed by counting the number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells and measuring the expression levels of the osteoclast-specific genes. The reactive oxygen species (ROS) generation was detected by FACS. Further, signaling pathways were analyzed by immunofluorescence and immunoblot analyses.

Results: PTERC-T suppressed the differentiation of monocytes to osteoclasts in a dose and time-dependent manner. The expression of osteoclast marker genes like TRAP, cathepsin K (CTSK), matrix metalloproteinase 9 (MMP9) and transcription factors c-Fos, and nuclear factor of activated T cells cytoplasmic 1 (NFATc1) were also diminished by PTERC-T. PTERC-T scavenged intracellular ROS generation within osteoclast precursors during RANKL-stimulated osteoclastogenesis. Mechanistically, PTERC-T abrogated the phosphorylation of MAPKs (ERK and JNK) and inhibited RANKL-induced activation of NFκB by suppressing IκBα phosphorylation and preventing NFκB/p65 nuclear translocation.

Conclusions: This study thus identifies PTERC-T as an inhibitor of osteoclast formation and provides evidence for its role in preventing osteoporosis and other bone related disorders. However, further studies are needed to establish its efficacy in vivo.