Opposing TNF-α/IL-1β- and BMP-2-activated MAPK signaling pathways converge on Runx2 to regulate BMP-2-induced osteoblastic differentiation

R-L Huang; Y Yuan; J Tu; G-M Zou; Q Li

doi:10.1038/cddis.2014.101

Opposing TNF-α/IL-1β- and BMP-2-activated MAPK signaling pathways converge on Runx2 to regulate BMP-2-induced osteoblastic differentiation

Cell Death Dis. 2014 Apr 17;5(4):e1187. doi: 10.1038/cddis.2014.101.

Authors

R-L Huang¹, Y Yuan¹, J Tu¹, G-M Zou², Q Li³

Affiliations

¹ 1] Department of Plastic and Reconstructive Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China [2] Shanghai Key Laboratory of Orthopaedic Implants, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China.
² Shanghai Cancer Institute, Shanghai Jiao Tong University, Shanghai 200240, China.
³ Department of Plastic and Reconstructive Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China.

Abstract

In patients who were treated with exogenous BMP-2 to repair bone fractures or defects, the levels of the inflammatory cytokines such as TNF-α and IL-1β in sera are significantly elevated, which may affect the outcome of bone regeneration. Mitogen-activated protein kinase (MAPK) cascades such as extracellular signal-regulated kinase 1/2 (ERK1/2), p38, and c-Jun NH2-terminal kinase 1/2 (JNK1/2) have a crucial role in osteogenic differentiation and are activated by both BMP-2 and TNF-α/IL-1β. However, previous studies suggested that the effects of BMP-2 and TNF-α/IL-1β in osteoblastic differentiation are opposite. Here, we investigated the exact role of MAPKs in a BMP-2 and TNF-α/IL-1β co-existed condition. Treatment with TNF-α/IL-1β inhibited BMP-2-induced alkaline phosphatase activity, calcium deposition, osteogenic transcriptional factor Runx2, and the expression of osteogenic markers in C2C12 and MC3T3-E1 cells. This inhibitory effect was independent of the canonical BMP/Smad pathway, suggesting the presence of an alternate regulatory pathway for BMP-2-induced Runx2 activity and subsequent osteoblastic differentiation. We then confirmed that BMP-2, TNF-α, and IL-1β alone can activate p38, ERK1/2, and JNK1/2, respectively. However, only inhibition of p38 and ERK1/2 signaling were required to modulate BMP-2-induced Runx2 expression. Finally, we determined that TNF-α/IL-1β decreased BMP-2-induced Runx2 expression through the activation of p38 and ERK1/2 signaling. Furthermore, strong activation of p38 and ERK1/2 signaling by transfection with CA-MKK3 or CA-MEK1 inhibited BMP-2-induced Runx2 expression and osteoblastic differentiation in C2C12 and MC3T3-E1 cells. Based on these results, we conclude that TNF-α/IL-1β- and BMP-2-activated p38 and ERK1/2 signaling have opposing roles that converge on Runx2 to regulate osteoblastic differentiation. The elucidation of these mechanisms may hasten the development of new strategies and improve the osteoinductive efficacy of BMP-2 in the clinic to enhance osteoblastic differentiation and bone formation.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Bone Morphogenetic Protein 2 / pharmacology*
Cell Differentiation / drug effects*
Cell Line
Core Binding Factor Alpha 1 Subunit / metabolism*
Enzyme Activation / drug effects
Extracellular Signal-Regulated MAP Kinases / metabolism
Humans
Interleukin-1beta / pharmacology*
MAP Kinase Signaling System / drug effects*
Mice
Models, Biological
Osteoblasts / cytology*
Osteoblasts / drug effects
Osteoblasts / metabolism
Smad Proteins / metabolism
Tumor Necrosis Factor-alpha / pharmacology*
p38 Mitogen-Activated Protein Kinases / metabolism

Substances

Bone Morphogenetic Protein 2
Core Binding Factor Alpha 1 Subunit
Interleukin-1beta
Smad Proteins
Tumor Necrosis Factor-alpha
Extracellular Signal-Regulated MAP Kinases
p38 Mitogen-Activated Protein Kinases