Expression and role of mannose receptor/terminal high-mannose type oligosaccharide on osteoclast precursors during osteoclast formation

Osteoclasts are formed from hematopoietic precursors via cell-cell fusion. We have previously reported that mannose residues are expressed on the outer membranes of monocytes during osteoclast differentiation. In the present study, we have attempted to demonstrate the pattern of expression levels of terminal high-mannose type oligosaccharide and to show that the mannose receptor is expressed on osteoclast precursor cells. Osteoclasts were formed using three different systems, namely mouse bone marrow cell culture, co-culture of mouse spleen cells with stromal cells, and RAW264.7 cell cultures. During osteoclast differentiation, the expression of terminal high-mannose type oligosaccharide gradually increased and then peaked at the stage of fusion in all three systems. Expression of the mannose receptor gradually increased during osteoclast differentiation in bone marrow cells and the co-culture system. In contrast, that in RAW264.7 cells had already been detected in the absence of the soluble receptor activator of NF-kappaB ligand and did not change during osteoclast differentiation. To ascertain whether expression of high-mannose type oligosaccharide is involved in tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cell (MNC) formation, glycosidase inhibitors were used on RAW264.7 cell culture. Castanospermine, an inhibitor of glucosidase I, inhibited the TRAP-positive MNCs, and deoxymannojirimycin, an inhibitor of alpha-mannosidase I, increased the TRAP-positive MNC formation. These results indicate that the binding of terminal high-mannose and mannose receptor is important for the process of cellular fusion in osteoclast formation.     

Canonical pathway of nuclear factor kappa B activation selectively regulates proinflammatory and prothrombotic responses in human atherosclerosis

Nuclear factor kappa B (NF-kappa B) activation has been observed in human atherosclerotic plaques and is enhanced in unstable coronary plaques, but whether such activation has a protective or pathophysiological role remains to be determined. We addressed this question by developing a short-term culture system of cells isolated from human atherosclerotic tissue, allowing efficient gene transfer to directly investigate signaling pathways in human atherosclerosis. We found that NF-kappa B is activated in these cells and that this activity involves p65, p50, and c-Rel but not p52 or RelB. This NF-kappa B activation can be blocked by overexpression of I kappa B alpha or dominant-negative I kappa B kinase (IKK)-2 but not dominant-negative IKK-1 or NF-kappa B-inducing kinase, resulting in selective inhibition of inflammatory cytokines (tumor necrosis factor alpha, IL-6, and IL-8), tissue factor, and matrix metalloproteinases without affecting the antiinflammatory cytokine IL-10 or tissue inhibitor of matrix metalloproteinases. Our results demonstrate that the canonical pathway of NF-kappa B activation that involves p65, p50, c-Rel, and IKK-2 is activated in human atherosclerosis and results in selective up-regulation of major proinflammatory and prothrombotic mediators of the disease.     

Role of FK506 binding protein 5 (FKBP5) in osteoclast differentiation

Objectives

We previously disclosed the enhanced expression of FK506 binding protein 5 (FKBP5) messenger RNA (mRNA) in bone marrow (BM) CD34⁺ cells in rheumatoid arthritis (RA), in which systemic osteoporosis takes place. Since BM CD34⁺ cells are precursors of osteoclasts, it is possible that FKBP5 overexpression might lead to osteoporosis by affecting osteoclastogenesis. We therefore explore the influences of FKBP5 in osteoclast differentiation.

Methods

Stable transfectants of RAW264.7 overexpressing murine FKBP5 gene were established. Osteoclast differentiation was induced by receptor activator of nuclear factor kappa B (NF-κB) ligand and was evaluated by tartrate-resistant acid phosphatase (TRAP) staining and pit formation assay.

Results

FKBP5 transfectants of RAW264.7 generated higher numbers of TRAP-positive multinucleated cells with increased activity of pit formation on calcium phosphate-coated culture slides than mock transfectants. The enhancement of osteoclast differentiation of FKBP5 transfectants was only partially inhibited by N-acetyl l-cysteine. Finally, glucocorticoid enhanced FKBP5 mRNA expression as well as osteoclast differentiation of RAW264.7 cells in a dose-dependent manner.

Conclusions

These results indicate that FKBP5 promotes osteoclast differentiation by a mechanism distinct from NF-κB activation. Moreover, the data suggest that FKBP5 might play a role in bone destruction and development of osteoporosis in RA as well as in glucocorticoid-induced osteoporosis.     

Ascorbic acid inhibits osteoclastogenesis of RAW264.7 cells induced by receptor activated nuclear factor kappaB ligand (RANKL) in vitro

Ascorbic acid (AA) plays a key role in the regulation of differentiation and activation of osteoclast (OCL). It was reported that AA might induce the formation of OCL in cocultures of mouse bone marrow cells and ST2 cells, but it is not clear whether AA has a direct impact on the OCL precursors. The purpose of this study was to examine the effect of AA on the differentiation of OCL precursor RAW264.7 cells, cultured with receptor-activated nuclear factor kappaB ligand (RANKL). The results showed that AA remarkably inhibited the cell proliferation at a higher concentration and RANKL alone is sufficient for osteoclastogenesis. The expression of carbonic anhydrase (CAII) mRNA and protein, the number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells (MNCs), and the percentage area of resorption lacunae induced by RANKL were decreased when AA was added to the cultures. The results demonstrate that AA inhibits RANKL-induced differentiation of OCL precursor cells into mature OCL and reduces the formation of bone resorption pits in vitro.     

Human T-cell leukemia virus type I Tax-protein-mediated activation of NF-kappa B from p100 (NF-kappa B2)-inhibited cytoplasmic reservoirs.

The human T-cell leukemia virus type I Tax protein transforms T cells through induced expression of many cellular genes, including those encoding the growth-related proteins interleukin 2 and the alpha chain of its receptor. Induction of these genes is mediated, at least in part, through Tax-dependent posttranslational activation of NF-kappa B, typically heterodimers of p50 (NF-kappa B1) and p65 (RelA). The preexisting NF-kappa B proteins are retained in the cytoplasm of cells by association with inhibitory ankyrin-motif-containing I kappa B proteins, primarily I kappa B-alpha but also including the precursor proteins p105 (NF-kappa B1) and p100 (NF-kappa B2). Here we demonstrate the existence of a previously undescribed multimeric cytoplasmic complex in which NF-kappa B dimers are associated with the p100 inhibitor in a manner dependent on the precursor protein's ankyrin domain. We also demonstrate an antagonistic effect of the Tax protein on the cytoplasmic sequestration function of p100; this in turn leads to nuclear translocation of NF-kappa B dimers liberated from multimeric complexes. Tax may exert these effects through the physical association with p100. Tax also relieves the p100-mediated inhibition of DNA binding by p50-p65 heterodimers in vitro. The results demonstrate a mechanism by which Tax may activate NF-kappa B in T cells.     

Involvement of protein kinase C in superoxide anion-induced activation of nuclear factor-kappa B in human endothelial cells

OBJECTIVE: Nuclear factor-kappa B (NF-kappa B) plays an important role in the regulation of redox-sensitive genes which are related to the pathogenesis of various vascular diseases. Although oxygen free-radicals are known to activate NF-kappa B, the signaling pathway of oxygen free radical-induced NF-kappa B activation remains largely unclear. Thus, this study was performed to examine the possible involvement of protein kinase C (PKC) in the oxygen free radical-induced NF-kappa B activation in human umbilical vein endothelial cells (HUVECs). METHODS: Superoxide anion was generated by xanthine and xanthine oxidase. An electrophoretic mobility shift assay (EMSA) was performed using a kappa B-motif oligonucleotide and nuclear extracts from HUVECs. Immunoblot analysis using an antibody against I kappa B alpha, phosphorylated by I kappa B alpha kinase, or myristoylated alanine-rich C kinase substrate (MARCKS) phosphorylated by protein kinase C was carried out. An NF-kappa B luciferase reporter gene assay was also performed. RESULTS: The treatment of the cells with superoxide anion for 60 min increased the NF-kappa B/DNA binding activity. Immunoblot analysis showed that superoxide anion induced phosphorylation of I kappa B alpha within 10 min. Furthermore, phosphorylation of MARCKS occurred more rapidly than phosphorylation of I kappa B alpha. Pretreatment of the cells with calphostin C (100-400 nmol/l) and chelerythrine chloride (5-10 mumol/l), inhibitors of PKC, abolished the superoxide anion-induced NF-kappa B activation. Down-regulation of endogenous PKC by long-term exposure to phorbol 12-myristate 13-acetate decreased the superoxide anion-induced NF-kappa B activation to a basal level. Superoxide anion induced the luciferase reporter gene and this induction was completely inhibited by calphostin C (200 nmol/l) and 4,5-dihydroxy-1,3-benzene disulfonic acid (tiron). CONCLUSION: These results suggest that PKC is involved in the activation of NF-kappa B by superoxide anion in human endothelial cells.     

核因子-κ B p65反义寡核苷酸对大鼠肝星状细胞转化生长因子β1及细胞间黏附分子1表达的影响

目的 探讨核因子-κB p65反义寡核苷酸(NF-κB 065 ASODN)对大鼠肝星状细胞HSC炎症因子转化生长因子β 1(TGF β 1)及细胞间黏附分子1(ICAM-1)表达的影响. 方法Ⅳ型胶原酶消化密度梯度离心法分离培养大鼠HSC;人工合成NF-κB p65 ASODN并行全程硫代磷酸化修饰;观察脂质体介导的不同浓度的NF-κB p65 ASODN(0.001、0.010、0.100、1.000μmol/L)对肿瘤坏死因子(TNF)α刺激HSC产生TGF β1及ICAM-1 mRNA和蛋白质表达的影响,蛋白凝胶电脉迁移率变动分析法检测NF-κB p65 ASODN对TNF α刺激HSCNF-κB的活性影响.结果 TNF α刺激HSC后,NF-κB活性和TGF β1、ICAM-1的表达明显增强;应用NF-κB p65 ASODN(0.001～1.000 μmol/L)作用后,NF-κB活性明显减弱,且呈剂量依赖性,灰度值分别为16 070±223,15 715±199,14 999±224,14 447±228,各组比较,P值均<0.05.同时TGF β1、ICAM-1的mRNA及蛋白质表达明显减少,亦呈剂量依赖性,P值均<0.05.结论 NF-κB p65 ASODN可特异性降低HSC的NF-κB的活性,明显抑制TGF β1、ICAM-1的表达,为NF-κB p65 ASODN治疗肝纤维化提供了理论依据.     

The synthetic triterpenoid TP-222 inhibits RANKL stimulation of osteoclastogenesis and matrix metalloproteinase-9 expression

OBJECTIVE: Receptor activator of nuclear factor-kappaB ligand (RANKL) promotes osteoclast differentiation from monocyte precursors by inducing a cohort of genes, including tartrate-resistant acid phosphatase (TRAP) and matrix metalloproteinase-9 (MMP-9). A family of synthetic triterpenoids with antiinflammatory and pro-apoptotic properties was described to modulate differentiation in monocytic cell lineages. We therefore investigated the ability of the potent and bioavailable synthetic triterpenoid TP-222 to inhibit RANKL-induced osteoclast formation and MMP-9 expression from monocytic precursor cells. METHODS: Osteoclast formation was assayed by staining for TRAP-positive multinucleated cells. MMP-9 expression was measured by quantitative RT-PCR, Western blot, immunohistochemistry, and gel zymography. In vivo effects of TP-222 were assessed by daily intraperitoneal injection of 4-week-old mice for 7 days followed by measurement of osteoclast number and MMP-9 expression at the cartilage/bone junction of the epiphyseal growth plate. RESULTS: RANKL promoted and TP-222 (300 nM) inhibited osteoclast formation in cultures of RAW264.7 cells or bone marrow-derived monocytes. RANKL also induced MMP-9 expression in RAW264.7 cells and this was reduced by concurrent or subsequent addition of TP-222. TP-222 treatment significantly reduced the mean number of osteoclasts present at the cartilage/bone interface compared to vehicle-injected control mice. Morphometric analyses of tissue sections showed that TP-222 treatment reduced the amount of immunoreactive MMP-9 present in both mononucleated pre-osteoclasts and osteoclasts. CONCLUSION: Our data demonstrate that TP-222 inhibits osteoclast formation and MMP-9 expression in vitro and in vivo, and suggest that triterpenoids may be useful compounds for modulating bone resorption diseases.     

High-dose dexamethasone accentuates nuclear factor-kappa b activation in endotoxin-treated mice.

We examined the effects of dexamethasone treatment on nuclear factor (NF)-kappa B activation and lung inflammation in transgenic reporter mice expressing photinus luciferase under the control of an NF-kappa B-dependent promoter (HLL mice). In vitro studies with bone marrow and peritoneal macrophages derived from these mice showed that treatment with dexamethasone blocked luciferase induction after treatment with Escherichia coli lipopolysaccharide (LPS); however, treatment of mice with intraperitoneal injection of dexamethasone at doses of 0.3 microg/g and 1 microg/g failed to inhibit NF-kappa B-dependent luciferase activity in the lungs. Furthermore, intraperitoneal treatment with 10 microg/g of dexamethasone prior to LPS paradoxically resulted in augmented luciferase activity as compared with that of mice treated with LPS alone. NF-kappa B-dependent luciferase expression in the lungs was detected by bioluminescence imaging and by measurement of luciferase activity in homogenized lung tissue. In these studies, there was an excellent correlation between indirect measurement of luciferase activity by bioluminescence in living mice and direct measurement of luciferase activity in lung tissue. Dexamethasone treatment did not affect LPS-induced neutrophilic influx or the concentration of macrophage inflammatory protein-2 in lung lavage fluid. These findings emphasize the potential error of extrapolating in vitro findings to complex in vivo events such as regulation of inflammation.     

Direct stimulation of osteoclastogenesis by MIP-1alpha: evidence obtained from studies using RAW264 cell clone highly responsive to RANKL

Macrophage inflammatory protein-1alpha (MIP-1alpha) is a member of the CC chemokines. We have previously reported the use of a whole bone marrow culture system to show that MIP-1alpha stimulates the formation of osteoclast-like multinucleated cells. Here we use rat bone marrow cells deprived of stromal cells, and clones obtained from murine macrophage-like cell line RAW264 to show that MIP-1alpha acts directly on cells in osteoclast lineage. We obtained several types of RAW264 cell clones, one of these clones, designated as RAW264 cell D clone (D clone), showed an extremely high response to receptor activator of NFkappaB ligand (RANKL) and tumor necrosis factor-alpha (TNF-alpha), while the other clone, RAW264 cell N clone (N clone), demonstrated no response to RANKL or TNF-alpha. Although both clones expressed receptor activator NFkappaB (RANK) before being stimulated for differentiation, only the D clone expressed cathepsin K when cells were stimulated to differentiate to osteoclasts. MIP-1alpha stimulated the formation of mononuclear preosteoclast-like cells from rat bone marrow cells deprived of stromal cells. MIP-1alpha also stimulated formation of osteoclast-like multinucleated cells from the D clone, when these cells were stimulated with RANKL and TNF-alpha. These findings provide strong evidence to show that MIP-1alpha acts directly on cells in the osteoclast lineage to stimulate osteoclastogenesis. Furthermore, pretreatment of RAW264 cell D clone with MIP-1alpha significantly induced adhesion properties of these cells to primary osteoblasts, suggesting a crucial role for MIP-1alpha in the regulation of the interaction between osteoclast precursors and osteoblasts in osteoclastogenesis.