This study examined the anti-osteoclastogenic effects of baicalin on receptor activator of NF-kB ligand (RANKL)- induced RAW264.7 cells. Baicalin is a flavonoid that is produced by Scutellaria baicalensis and is known to have multiple biological properties, including antibacterial, anti- inflammatory and analgesic effects. The effects of baicalin on osteoclasts were examined by measuring 1) cell via- bility; 2) the formation of tartrate-resistant acid phosphatase (TRAP) (+) multinucleated cells; 3) RANK/RANKL signa- ling pathways and 4) mRNA levels of osteoclast-associated genes. Baicalin inhibited the formation of RANKL-stimu- lated TRAP (+) multinucleated cells and also suppressed the RANKL-stimulated activation of p-38, ERK, cSrc and AKT signaling. Baicalin also inhibited the RANKL-stimu- lated degradation of IĸB in RAW264.7 cells. In addition, the RANKL-stimulated induction of NFATc1 transcription factors was found to be abrogated by this flavonoid. Baica- lin was further found to decrease the mRNA expression of osteoclast-associated genes, including carbonic anhydrase II, TRAP and cathepsin K in the RAW264.7 cells. Our data thus demonstrate that baicalin inhibits osteoclastogenesis by inhibiting the RANKL-induced activation of signaling molecules and transcription factors in osteoclast precursors.

• Seon-Yle Ko(Department of Oral biochemistry and Institute of Dental Science, Dankook University) Correspondence