Exp Mol Med.  2010 Jun;42(6):437-445. 10.3858/emm.2010.42.6.045.

Msx2 mediates the inhibitory action of TNF-alpha on osteoblast differentiation

Affiliations
  • 1Department of Molecular Genetics, School of Dentistry and Dental Research Institute, Seoul National University, Seoul 110-749, Korea. baekjh@snu.ac.kr
  • 2Clinical Research Center, School of Medicine, Inha University, Incheon 400-711, Korea.

Abstract

TNF-alpha, a proinflammatory cytokine, inhibits osteoblast differentiation under diverse inflammatory conditions; however, the underlying mechanisms in terms of the TNF-alpha signaling pathway remain unclear. In this study, we examined the role of Msx2 in TNF-alpha-mediated inhibition of alkaline phosphatase (ALP) expression and the signaling pathways involved. TNF-alpha down-regulated ALP expression induced by bone morphogenetic protein 2 (BMP2) in C2C12 and Runx2-/- calvarial cells. Over-expression of Msx2 suppressed BMP2-induced ALP expression. Furthermore, TNF-alpha induced Msx2 expression, and the knockdown of Msx2 by small interfering RNAs rescued ALP expression, which was inhibited by TNF-alpha. TNF-alpha activated the NF-kappaB and the JNK pathways. Inhibition of NF-kappaB or JNK activation reduced the inhibitory effect of TNF-alpha on ALP expression, whereas TNF-alpha-induced Msx2 expression was only suppressed by the inhibition of the NF-kappaB pathway. Taken together, these results indicate that Msx2 mediates the inhibitory action of TNF-alpha on BMP2-regulated osteoblast differentiation and that the TNF-alpha-activated NF-kappaB pathway is responsible for Msx2 induction.

Keyword

alkaline phosphatase; bone morphogenetic protein 2; cell differentiation; Msx2 protein; NF-kappaB; osteoblasts; tumor necrosis factor-alpha
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