Differentiation-inducing signals in osteoblasts and its application for development of bone anabolic therapy

（1）AP-1/IL-11信号通路的分析1. fosB/deltafosB基因的转录诱导体外流体剪切力（FSS）诱导成骨细胞表达deltafosB，这是一种AP-1家族转录因子，当在转基因小鼠中过度表达时能够刺激体内骨形成。进一步的机制研究表明，FSS促进fosB/deltafosB基因转录的方式依赖于钙离子、ERK和CREB，而CREB通过存在于小鼠fosB基因上游调控区的CRE-like序列起作用。2. AP-1和SmadsSmall之间的串扰是一种转录因子，作用于BMP-2的下游，BMP-2是一种众所周知的骨形成诱导剂。我们发现FSS激活的AP-1与Smad 1在物理上相互作用并在功能上协同诱导IL-11基因的转录。（2）IL-11在糖皮质激素诱导的骨质疏松症（GIO）中的致病作用1. IL-11 PTH和IL-11的抗凋亡作用可使地塞米松和足叶乙甙诱导的成骨细胞凋亡抑制50%。Bcl-2的表达，抗凋亡因子，下调这些凋亡诱导剂，这是由PTH或IL-11恢复。PTH对IL-11基因转录的抑制可诱导IL-11基因的转录，这种诱导作用可被地塞米松阻断。我们发现，这些作用都在很大程度上依赖于IL-11启动子中的AP-1结合位点。这些结果表明，IL-11在地塞米松的促凋亡作用和PTH的抗凋亡作用中均起作用。

(1)Analysis of the AP-1/IL-11 signaling pathway1.Transcriptional induction of fosB/deltafosB geneFluid shear stress (FSS) in vitro induced osteoblast expression of deltafosB, an AP-1 family transcription factor that is able to stimulate bone formation in vivo when over-expressed in transgenic mice. Further mechanistic studies revealed that FSS promoted fosB/deltafosB gene transcription in a manner dependent on calcium, ERK, and CREB, which acted via CRE-like sequences present in the mouse fosB gene upstream regulatory region.2.Crosstalk between AP-1 and SmadsSmall is a transcription factor that act downstream of BMP-2, a well-known inducer of bone formation. We found that FSS-activated AP-1 physically interacted and functionally cooperated with Smad1 to induce interleukin (IL)-11 gene transcription.(2)Pathogenic roles of IL-11 in glucocorticoid-induced osteoporosis (GIO)1.Anti-apoptotic effects of IL-11PTH as well as IL-11 suppressed dexamethasone- and etoposide-induced osteoblast apoptosis by 50 %. Expression of Bcl-2, an anti-apoptotic factor, was down-regulated by these apoptosis inducers, which was restored by PTH or IL-11. And the effect of PTH was partially blocked by an anti-IL-11 neutralizing antibody2.Transcriptional repression of IL-11 gene by dexamethasonePTH induced IL-11 gene transcription, and this induction was blocked by dexamethasone. We found that these effects were both largely dependent on the AP-1 binding site in the IL-11 promoter.Collectively, these results suggest that IL-11 plays a role in both pro-apoptotic effects of dexamethasone and anti-apoptotic effects of PTH in osteoblasts.