Hyperactivation of Nrf2 leads to hypoplasia of bone in vivo

Area of Science:

• Molecular Biology
• Cell Biology
• Physiology

Background:

• Keap1 negatively regulates Nrf2, a key transcription factor for cytoprotection.
• The Keap1-Nrf2 system's role in bone formation is suggested but not fully understood.
• Keap1-null mice are not viable, posing challenges for studying Nrf2 hyperactivation's effects on bone.

Purpose of the Study:

• To investigate the impact of Nrf2 hyperactivation due to Keap1 deficiency on bone formation.
• To elucidate the mechanisms underlying skeletal phenotypes in Keap1-deficient models.
• To determine if renal phenotypes in Keap1-deficient mice are linked to skeletal abnormalities.

Main Methods:

• Generation of viable Keap1-deficient mice (NEKO mice) by deleting Nrf2 in Keap1-null mice.
• Phenotypic analysis of NEKO mice, including body size and bone density measurements.
• Comparative analysis with renal-specific Keap1-deficient mice.
• In vitro studies using primary cell cultures from Keap1-null mice to assess osteoclast and osteoblast differentiation.

Main Results:

• NEKO mice exhibited reduced body size and low bone density.
• Skeletal phenotypes were not observed in renal-specific Keap1-deficient mice, decoupling them from nephrogenic diabetes insipidus.
• Impaired osteoblast differentiation, not osteoclast differentiation, was identified as the cause of bone hypoplasia.
• Nrf2 hyperactivation due to Keap1 deficiency leads to impaired osteoblast differentiation and reduced bone formation.

Conclusions:

• Appropriate Keap1 control of Nrf2 activity is essential for maintaining bone homeostasis.
• Nrf2 hyperactivation negatively impacts osteoblast differentiation, contributing to bone hypoplasia.
• The study provides insights into the molecular mechanisms regulating bone formation and redox homeostasis.