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author:("Zhao, taohong")
1.  Notch-RBP-J Signaling Regulates IRF8 to Promote Inflammatory Macrophage Polarization 
Nature immunology  2012;13(7):642-650.
Emerging concepts suggest that macrophage functional phenotype is regulated by transcription factors that define alternative activation states. We found that RBP-J, the major nuclear transducer of Notch signaling, augmented TLR4-induced expression of key mediators of classically activated M1 macrophages and thus innate immune responses to L. monocytogenes. Notch-RBP-J signaling controlled expression of the transcription factor IRF8 that induced downstream M1-specific genes. RBP-J promoted IRF8 protein synthesis by selectively augmenting IRAK2-dependent TLR4 signaling to the MNK1 kinase and downstream translation initiation control through eIF4E. These results define a signaling network in which Notch-RBP-J and TLR signaling are integrated at the level of IRF8 protein synthesis and identify a mechanism by which heterologous signaling pathways can regulate TLR-induced inflammatory macrophage polarization.
PMCID: PMC3513378  PMID: 22610140
2.  Feedback inhibition of osteoclastogenesis during inflammation by IL-10, M-CSF receptor shedding, and induction of IRF8 
Inflammation plays a key role in excessive bone loss in conditions such as rheumatoid arthritis and periodontitis. An important paradigm in immunology is that inflammatory factors activate feedback inhibition mechanisms to restrain inflammation and limit associated tissue damage. We hypothesized that inflammatory factors would activate similar feedback mechanisms to restrain bone loss in inflammatory settings. We have identified three mechanisms that inhibit osteoclastogenesis and are induced by inflammatory factors, such as toll-like receptor ligands and cytokines: downregulation of expression of costimulatory molecules such as TREM-2; induction of shedding and thereby inactivation of the M-CSF receptor c-Fms, leading to decreased RANK transcription; and induction of transcriptional repressors such as interferon regulatory factor 8. It is likely that these mechanisms work in a complementary and cooperative manner to fine tune the extent of osteoclastogenesis in inflammatory settings, and their augmentation may represent an alternative therapeutic approach to suppress bone resorption.
PMCID: PMC3263822  PMID: 22082370
inflammation; osteoclasts; toll-like receptors; M-CSF; c-Fms; IRF8
3.  TNF-induced osteoclastogenesis and inflammatory bone resorption are inhibited by transcription factor RBP-J 
The Notch-driven transcription factor RBP-J inhibits osteoclast formation in response to TNF.
Tumor necrosis factor (TNF) plays a key role in the pathogenesis of inflammatory bone resorption and associated morbidity in diseases such as rheumatoid arthritis and periodontitis. Mechanisms that regulate the direct osteoclastogenic properties of TNF to limit pathological bone resorption in inflammatory settings are mostly unknown. Here, we show that the transcription factor recombinant recognition sequence binding protein at the Jκ site (RBP-J) strongly suppresses TNF-induced osteoclastogenesis and inflammatory bone resorption, but has minimal effects on physiological bone remodeling. Myeloid-specific deletion of RBP-J converted TNF into a potent osteoclastogenic factor that could function independently of receptor activator of NF-κB (RANK) signaling. In the absence of RBP-J, TNF effectively induced osteoclastogenesis and bone resorption in RANK-deficient mice. Activation of RBP-J selectively in osteoclast precursors suppressed inflammatory osteoclastogenesis and arthritic bone resorption. Mechanistically, RBP-J suppressed induction of the master regulator of osteoclastogenesis (nuclear factor of activated T cells, cytoplasmic 1) by attenuating c-Fos activation and suppressing induction of B lymphocyte–induced maturation protein-1, thereby preventing the down-regulation of transcriptional repressors such as IRF-8 that block osteoclast differentiation. Thus, RBP-J regulates the balance between activating and repressive signals that regulate osteoclastogenesis. These findings identify RBP-J as a key upstream negative regulator of osteoclastogenesis that restrains excessive bone resorption in inflammatory settings.
PMCID: PMC3280875  PMID: 22249448
4.  Negative regulation of osteoclastogenesis and bone resorption by cytokines and transcriptional repressors 
Bone remodeling in physiological and pathological conditions represents a balance between bone resorption mediated by osteoclasts and bone formation by osteoblasts. Bone resorption is tightly and dynamically regulated by multiple mediators, including cytokines that act directly on osteoclasts and their precursors, or indirectly by modulating osteoblast lineage cells that in turn regulate osteoclast differentiation. The critical role of cytokines in inducing and promoting osteoclast differentiation, function and survival is covered by the accompanying review by Zwerina and colleagues. Recently, it has become clear that negative regulation of osteoclastogenesis and bone resorption by inflammatory factors and cytokines, downstream signaling pathways, and a newly described network of transcriptional repressors plays a key role in bone homeostasis by fine tuning bone remodeling and restraining excessive bone resorption in inflammatory settings. In this review we discuss negative regulators of osteoclastogenesis and mechanisms by which these factors suppress bone resorption.
PMCID: PMC3239342  PMID: 21861861
5.  IL-27 inhibits human osteoclastogenesis by abrogating RANKL-mediated induction of NFATc1 and suppressing proximal RANK signaling 
Arthritis and rheumatism  2010;62(2):402.
IL-27 has stimulatory and regulatory immune functions and is expressed in rheumatoid arthritis synovium. We investigated the effects of IL-27 on human osteoclastogenesis to determine whether IL-27 can stimulate or attenuate osteoclast-mediated bone resorption that is a hallmark of rheumatoid arthritis.
Osteoclasts were generated from blood-derived human CD14+ cells. The effects of IL-27 on osteoclast formation were evaluated by counting the number of TRAP+ multinucleated cells and measuring expression of osteoclast-related genes. The induction of NFATc1 and the activation of signaling pathways downstream of RANK were measured by immunoblotting. The expression of key molecules implicated in osteoclastogenesis (NFATc1, RANK, costimulatory receptors, ITAM-harboring adaptors) was measured by real time RT-PCR. Murine osteoclast precursors were obtained from bone marrow. Responsiveness to IL-27 of synovial fluid macrophages derived from RA patients was also tested.
IL-27 inhibited human osteoclastogenesis, suppressed the induction of NFATc1, downregulated expression of RANK and TREM-2, and inhibited RANKL-mediated activation of ERK, p38 and NF-κB in osteoclast precursors. Synovial fluid macrophages derived from RA patients were refractory to the effects of IL-27. In contrast to humans, IL-27 only moderately suppressed murine osteoclastogenesis, likely due to low expression of the IL-27 receptor subunit WSX-1 on murine osteoclast precursors.
IL-27 inhibits human osteoclastogenesis by a direct mechanism suppressing responses of osteoclast precursors to RANKL. Our findings suggest that in addition to its well-known anti-inflammatory effects, IL-27 plays a homeostatic role in restraining bone erosion. This homeostatic function is compromised under conditions of chronic inflammation such as RA synovitis.
PMCID: PMC2822027  PMID: 20112358
Osteoclastogenesis; Cytokines; Interleukins; RANKL; Rheumatoid Arthritis
6.  Interferon regulatory factor 8 regulates bone metabolism by suppressing osteoclastogenesis 
Nature medicine  2009;15(9):1066-1071.
Bone metabolism results from a balance between osteoclast-driven bone resorption and osteoblast-mediated bone formation. Diseases such as periodontitis and rheumatoid arthritis are characterized by increased bone destruction due to enhanced osteoclastogenesis1,2. Here we report that interferon regulatory factor 8 (IRF8), a transcription factor expressed in immune cells, is a key regulatory molecule for osteoclastogenesis. IRF8 expression in osteoclast precursors was downregulated during the initial phase of osteoclast differentiation induced by receptor activator of nuclear factor κB ligand (RANKL, also called TRANCE, ODF, and OPGL), which is encoded by the Tnfsf11 gene. Mice deficient in IRF8 exhibited severe osteoporosis due to increased numbers of osteoclasts, and enhanced bone destruction following lipopolysaccharide (LPS) administration. Irf8–/– osteoclast precursors underwent increased osteoclastogenesis in response to RANKL and tumor necrosis factor α (TNFα). IRF8 suppressed osteoclastogenesis by inhibiting the function and expression of nuclear factor of activated T cells c1 (NFATc1). Our results show that IRF8 inhibits osteoclast formation under physiological and pathological conditions, and suggest a model where downregulation of inhibitory factors like IRF8 contributes to RANKL-mediated osteoclastogenesis.
PMCID: PMC2755267  PMID: 19718038
7.  IFN-γ down-regulates Secretoglobin 3A1 gene expression 
STAT1 mediates Interferon (IFN)-dependent positive and negative regulation of inflammatory gene expression in lung. In this study, we examined the effect of IFN-γ on the expression of SCGB3A1 which is thought to play crucial roles in inflammation and epithelial cell differentiation in lung. We found that expression of SCGB3A1 was down-regulated by IFN-γ in a time- and dose-dependent manner in the murine transformed Clara Cells (mtCC) line. IFN-γ induced the phosphorylation of STAT1, which binds to a STAT-binding element (SBE) in the SCGB3A1 gene promoter, leading to decreased transcriptional activation of this gene.
PMCID: PMC2792195  PMID: 19135978
SCGB3A1; Uteroglobin-related protein 2; IFN-γ

Results 1-7 (7)