Platycarya strobilacea leaf extract inhibits tumor necrosis factor-α production and bone loss induced by Porphyromonas gingivalis-derived lipopolysaccharide.

OBJECTIVE: Remodeling of alveolar bone is controlled by osteoclast-mediated bone resorption and osteoblast-induced bone formation. LPS of Porphyromonas gingivalis, a major causative agent of periodontitis, produces proinflammatory cytokines in host immune cells, which thereby triggers osteoclastogenesis and leads to alveolar bone resorption. We investigated the anti-periodontitis potential of Platycarya strobilacea leaf extract (PLE), which is used as a traditional medicine in Asian countries.

DESIGN: TNF-α levels in cell culture media were measured using a commercially available enzyme-linked immunosorbent assay kit. Osteoclast differentiation was observed by tartrate-resistant acid phosphatase staining, and the expression levels of osteoclastogenic genes were measured by quantitative real-time PCR. Bone-resorbing activity was confirmed by the resorption pit formation, gelatin zymographic, and the cathepsin K activity assays. Osteogenic differentiation was confirmed with an ALP activity assay and alizarin red S staining.

RESULTS: PLE treatment inhibited the production of TNF-α in P. gingivalis LPS-stimulated RAW264.7 macrophages. In bone marrow-derived macrophages serving as osteoclast precursors, PLE treatment blocked RANKL-induced osteoclastogenesis and gene expression levels of the osteoclastogenic transcription factor NFATc1, DC-STAMP for osteoclast fusion, and cathepsin K for osteoclast activity. In addition, PLE treatment reduced the formation of resorption pits and the secretion of MMP 9 and cathepsin K from the differentiated osteoclasts. Furthermore, PLE treatment induced osteogenesis by increasing ALP activity and calcium content in preosteoblastic cells.

CONCLUSION: PLE inhibits P. gingivalis LPS-induced TNF-α production and bone resorption and induces bone formation. PLE may be a beneficial agent to promote oral health by inhibiting periodontitis-induced alveolar bone loss.