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Novel antiosteoclastogenic activity of phloretin antagonizing RANKL-induced osteoclast differentiation of murine macrophages

Authors

  • Jung-Lye Kim,

  • Min-Kyung Kang,

  • Ju-Hyun Gong,

  • Sin-Hye Park,

  • Seon-Young Han,

  • Young-Hee Kang

    Corresponding author
    • Department of Food Science and Nutrition, Hallym University, Chuncheon, Korea
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Correspondence: Dr. Young-Hee Kang, Department of Food and Nutrition, Hallym University, Chuncheon, Kangwon-do 200-702, Korea

E-mail: yhkang@hallym.ac.kr

Fax: +82-33-254-1475

Abstract

Scope

Bone-remodeling imbalance resulting in more bone resorption than bone formation is known to cause skeletal diseases such as osteoporosis. Phloretin, a natural dihydrochalcone compound largely present in apple peels, possesses antiphotoaging, and antiinflammatory activity.

Methods and results

Phloretin inhibited receptor activator of NF-κB ligand (RANKL)-induced formation of multinucleated osteoclasts and diminished bone resorption area produced during the osteoclast differentiation process. It was also found that ≥10 μM phloretin reduced RANKL-enhanced tartrate-resistance acid phosphatase activity and matrix metalloproteinase-9 secretion in a dose-dependent manner. The phloretin treatment retarded RANKL-induced expression of carbonic anhydrase II, vacuolar-type H+-ATPase D2 and β3 integrin, all involved in the bone resorption. Furthermore, submicromolar phloretin diminished the expression and secretion of cathepsin K elevated by RANKL, being concurrent with inhibition of TRAF6 induction and NF-κB activation. RANKL-induced activation of nuclear factor of activated T cells c1 (NFATc1) and microphthalmia-associated transcription factor was also suppressed by phloretin.

Conclusion

These results demonstrate that the inhibition of osteoclast differentiation and bone resorption by phloretin entail a disturbance of TRAF6-NFATc1-NF-κB pathway triggered by RANKL. Therefore, phloretin may be a potential therapeutic agent targeting osteoclast differentiation and bone resorption in skeletal diseases such as osteoporosis.

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