Recently, signaling cross-talk between the BMP signaling pathway and other signaling pathways has been reported [4], [5] and [11]. Tumor necrosis factor (TNF), in particular, plays an important role in the pathogenesis of inflammatory bone loss via stimulation of osteoclastic bone resorption and inhibition of osteoblastic bone formation. The osteoblastic inhibition
LY2109761 caused by TNF-promoted osteoblast apoptosis through the nuclear factor-κB (NF-κB) signaling pathway [12], [13] and [14], suppression and de-stabilization of Runx2 gene transcription [15] and [16], and Runx2 degradation via up-regulated Smad ubiquitin regulatory factor (Smurf)1 and Smurf2 [17], which are ubiquitin E3 ligases
small intestine degrade some Smads [18], [19] and [20]. Furthermore, TNF associates with members of the TNF receptor-associated factor (Traf) protein family, and Traf1 and Traf2 are important in the TNF signaling pathway. Traf2 protein directly interacts with TNF receptors (TNFRs), forms heterodimers with Traf1 [21], [22] and [23], and is required for the activation of p38, JNK MAPKs, and NF-κB [24] and [25].
