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Nrf2 negatively regulates osteoblast differentiation via interfering with Runx2-dependent transcriptional activation

Eiichi Hinoi1, Sayumi Fujimori, Liyang Wang

  • 1Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan.

The Journal of Biological Chemistry
|April 15, 2006
PubMed

Insights

Nuclear factor E2 p45-related factor 2 (Nrf2) negatively regulates osteoblast differentiation by inhibiting the Runx2 transcription factor. Nrf2 overexpression impairs bone formation markers and osteocalcin promoter activity.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Bone Biology

Background:

  • Nuclear factor E2 p45-related factor 2 (Nrf2) is a transcription factor regulating detoxifying and antioxidative genes.
  • Osteoblastic differentiation is crucial for bone formation and maintenance.

Purpose of the Study:

  • To investigate the role of Nrf2 in regulating osteoblastic differentiation.
  • To elucidate the molecular mechanisms underlying Nrf2's function in bone cells.

Main Methods:

  • In situ hybridization and Western blotting to detect Nrf2 expression in mouse bone tissues.
  • Overexpression of Nrf2 in MC3T3-E1 osteoblastic cells.
  • Assays for alkaline phosphatase activity, mineralized matrix formation, and osteocalcin promoter activity.
  • Coimmunoprecipitation and mammalian two-hybrid assays to study protein interactions.
  • Analysis of Nrf2 binding to the osteocalcin promoter.

Main Results:

  • Nrf2 mRNA and protein were upregulated in osteoblasts from ovariectomized mice and in neonatal mouse bone.
  • Nrf2 overexpression inhibited alkaline phosphatase activity, mineralized matrix formation, and Runx2-dependent osteocalcin promoter activity.
  • Nrf2 physically interacted with Runx2 and bound to the antioxidant-responsive element-like-2 sequence of the osteocalcin promoter.
  • Nrf2's inhibitory effect on Runx2 activity was partially dependent on the ARE-like-2 sequence.

Conclusions:

  • Nrf2 acts as a negative regulator of osteoblastic differentiation.
  • Nrf2 inhibits osteoblast differentiation by interfering with Runx2 transcriptional activity.
  • These findings reveal a novel role for Nrf2 in bone metabolism and suggest potential therapeutic targets for bone diseases.

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