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PI3K/Akt mediates expression of TNF-alpha mRNA and activation of NF-kappaB in calyculin A-treated primary osteoblasts

L Qiu1, L Zhang, L Zhu

  • 1Department of Endodontics, China Medical University, Shenyang, China. drqlh@yahoo.com

Oral Diseases
|February 6, 2009
PubMed
Abstract

Insights

Calyculin A activates the PI3K/Akt pathway, increasing tumor necrosis factor-alpha (TNF-alpha) mRNA and activating NF-kappaB in osteoblasts. This highlights the role of protein phosphatases in osteoblast signaling.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Protein phosphatases play critical roles in cellular signaling.
  • Tumor necrosis factor-alpha (TNF-alpha) is a key cytokine in bone metabolism.
  • The role of protein phosphatases in osteoblast response to TNF-alpha is not fully understood.

Purpose of the Study:

  • To investigate the effect of calyculin A (CA), a protein phosphatase inhibitor, on TNF-alpha expression in primary osteoblasts.
  • To identify the signaling pathways involved in CA-induced changes in osteoblasts.

Main Methods:

  • Primary osteoblasts were isolated from rat calvaria.
  • Cells were treated with CA, and TNF-alpha and GAPDH mRNA expression was analyzed by RT-PCR.
  • Activation of Akt and NF-kappaB was assessed by western blotting.

Main Results:

  • CA treatment significantly increased TNF-alpha mRNA expression and Akt phosphorylation.
  • The PI3K inhibitor LY294002 blocked CA-induced TNF-alpha mRNA expression and Akt phosphorylation.
  • CA stimulated NF-kappaB phosphorylation and nuclear translocation, which were also inhibited by LY294002.

Conclusions:

  • Calyculin A activates the PI3K/Akt pathway, leading to increased TNF-alpha mRNA expression and NF-kappaB activation in primary osteoblasts.
  • NF-kappaB activation involves both phosphorylation and nuclear translocation.
  • These findings elucidate a novel signaling cascade involving protein phosphatases in osteoblast function.

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