Geraniol attenuates osteoclast differentiation by suppressingNF-kB activity and expression of osteoclastogenic genes

Abstract

Osteoporotic patients have lower bone mass due to increased bone resorption by osteoclasts. The aim of this study was to investigate the cytotoxic and antiosteoclastogenic effects of geraniol, a natural monoterpene on human CD14+ monocytes (ex vivo) and murine RAW264.7 macrophages (in vitro) using alamar blue and tartrate resistant acid phosphatase staining respectively. The anti-osteoclastogenic activity of geraniol was further explored by analyzing its effects on actin ring formation and bone resorptive function of osteoclasts. Geraniol significantly (p < 0.001) inhibited osteoclast formation in CD14+ monocytes and RAW264.7 macrophages without cytotoxicity. Moreover, reduced osteoclastogenesis in these cells led to an arrest in actin ring formation and diminished bone resorption. Analysis of underlying molecular mechanisms revealed that geraniol alleviated NF-kB activity, an indispensable upstream modulator of osteoclast formation. Furthermore, expression of key osteoclastogenic genes such as dendritic cell-specific transmembrane protein (DC-STAMP) involved in cell-cell fusion and nuclear factor of activated T-cells, cytoplasmic, calcineurin-dependent 1 (NFATc1), a master transcription factor essential for osteoclast differentiation was downregulated by geraniol. These observations indicate that inhibition of osteoclast differentiation is presumably one of the pharmacological properties of geraniol.