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

Mol Nutr Food Res. 2012 Aug;56(8):1223-33. doi: 10.1002/mnfr.201100831. Epub 2012 Jun 15.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acid Phosphatase / metabolism
  • Animals
  • Bone Resorption
  • Carbonic Anhydrases / metabolism
  • Cathepsin K / metabolism
  • Cell Differentiation / drug effects
  • Cells, Cultured
  • Dose-Response Relationship, Drug
  • Isoenzymes / metabolism
  • Macrophages / cytology
  • Macrophages / drug effects*
  • Macrophages / metabolism
  • Matrix Metalloproteinase 9 / metabolism
  • Mice
  • NF-kappa B / genetics
  • NF-kappa B / metabolism
  • NFATC Transcription Factors / metabolism
  • Osteoclasts / cytology
  • Osteoclasts / drug effects*
  • Osteoclasts / metabolism
  • Phloretin / pharmacology*
  • RANK Ligand / antagonists & inhibitors*
  • Silybin
  • Silymarin / pharmacology
  • TNF Receptor-Associated Factor 6 / genetics
  • TNF Receptor-Associated Factor 6 / metabolism
  • Tartrate-Resistant Acid Phosphatase
  • Vacuolar Proton-Translocating ATPases / metabolism

Substances

  • Isoenzymes
  • NF-kappa B
  • NFATC Transcription Factors
  • Nfatc1 protein, mouse
  • RANK Ligand
  • Silymarin
  • TNF Receptor-Associated Factor 6
  • Tnfsf11 protein, mouse
  • Silybin
  • Acid Phosphatase
  • Tartrate-Resistant Acid Phosphatase
  • Cathepsin K
  • Ctsk protein, mouse
  • Matrix Metalloproteinase 9
  • Vacuolar Proton-Translocating ATPases
  • Carbonic Anhydrases
  • Phloretin