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Proteasome inhibitors induce osteoclast survival by activating the Akt pathway

Han Bok Kwak1, Myeung Su Lee, Hun Soo Kim

  • 1Department of Anatomy, School of Medicine, Wonkwang University College of Medicine, Iksan, Chonbuk, Republic of Korea.

Biochemical and Biophysical Research Communications
|May 22, 2008
PubMed

Insights

Proteasome inhibitors like MG132 and ALLN prevent osteoclast apoptosis by blocking cytochrome c release and caspase activation. This survival effect is mediated by the phosphatidylinositol 3-kinase/Akt pathway, offering potential therapeutic strategies for bone diseases.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Bone Biology

Background:

  • Osteoclasts are crucial for bone remodeling.
  • Dysregulation of osteoclast survival contributes to bone diseases like osteoporosis.
  • Targeting osteoclast apoptosis is a potential therapeutic strategy.

Purpose of the Study:

  • To investigate the role of proteasome inhibitors in regulating osteoclast apoptosis.
  • To elucidate the molecular mechanisms underlying the anti-apoptotic effects of proteasome inhibitors in osteoclasts.

Main Methods:

  • Osteoclast culture and induction of apoptosis via survival factor deprivation or etoposide treatment.
  • Assessment of apoptosis using cytochrome c release and caspase cleavage assays.
  • Pharmacological inhibition of signaling pathways including PI-3K/Akt and ERK/MAPK.

Main Results:

  • Proteasome inhibitors MG132 and ALLN significantly inhibited osteoclast apoptosis under both etoposide-induced and survival factor-deprived conditions.
  • MG132 and ALLN suppressed mitochondrial cytochrome c release and pro-caspase cleavage.
  • These effects were dependent on the phosphatidylinositol 3-kinase (PI-3K)/Akt pathway, as confirmed by experiments with LY294002, but not the ERK/MAPK pathway.

Conclusions:

  • Proteasome inhibitors protect osteoclasts from apoptosis by activating the PI-3K/Akt signaling pathway.
  • This mechanism involves the inhibition of mitochondrial cell death pathways.
  • Targeting the proteasome offers a novel approach to modulate osteoclast survival for treating bone-related disorders.

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