Inhibitory effects of eugenol on RANKL-induced osteoclast formation via attenuation of NF-κB and MAPK pathways

Abstract

Bone loss diseases are often associated with increased receptor activator of NF-κB ligand (RANKL)-induced osteoclast formation. Compounds that can attenuate RANKL-mediated osteoclast formation are of great biomedical interest. Eugenol, a phenolic constituent of clove oil possesses medicinal properties; however, its anti-osteoclastogenic potential is unexplored hitherto. Here, we found that eugenol dose-dependently inhibited the RANKL-induced multinucleated osteoclast formation and TRAP activity in RAW264.7 macrophages. The underlying molecular mechanisms included the attenuation of RANKL-mediated degradation of IκBα and subsequent activation of NF-κB pathway. Furthermore, increase in phosphorylation and activation of RANKL-induced mitogen-activated protein kinase pathways (MAPK) was perturbed by eugenol. RANKL-induced expression of osteoclast-specific marker genes such as TRAP, cathepsin K (CtsK) and matrix metalloproteinase-9 (MMP-9) was remarkably downregulated by eugenol. These findings provide the first line of evidence that eugenol mediated attenuation of RANKL-induced NF-κB and MAPK pathways could synergistically contribute to the inhibition of osteoclast formation. Eugenol could be developed as therapeutic agent against diseases with excessive osteoclast activity.

• Eugenol
• MAPK pathway
• NFκB pathway
• osteoclast
• RANKL
• RAW264.7 macrophages

Acknowledgments

We thank staff of the Department of Physiology, University of Pretoria for their continuous encouragement and motivation during this work. We are thankful to the Laboratory for Microscopy and Microanalysis, University of Pretoria for their assistance in microscopy work.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

This study was supported by grants from RESCOM, University of Pretoria; the University of Pretoria Vice Chancellor’s Postdoctoral Research Fellowship and the University of Pretoria’s Strategic Institutional Research Theme in Food, Nutrition and Well-Being.