Platelet-derived growth factor stimulates osteoprotegerin production in osteoblastic cells

Osteoprotegerin (OPG) is a major regulator of osteoclastogenesis, bone resorption and vascular calcification. OPG is produced by various cell types including mesenchymally derived cells, in particular, osteoblastic cells. Here we show OPG production by osteoblastic cells was stimulated by platelet-derived growth factor (PDGF) in two human osteosarcoma cell lines (MG63, Saos-2), a mouse pre-osteoblastic cell line (MC3T3-E1) and human bone marrow stromal cells (hMSC) by 152%, 197%, 113% and 45% respectively over 24 h. OPG was measured in the cell culture medium by immunoassay. PDGF isoforms AA, BB and AB show similar stimulation of OPG production. Message for OPG was also increased similarly to the increased secretion into the culture medium. Using specific inhibitors of cell signalling we demonstrate that PDGF acts through the PDGF receptor, PKC, PI3K, ERK and P38 and not via NF-kB or JNK. The importance of PDGF in fracture healing suggests a role for OPG production in countering bone resorption during the early phase of this process.     

Interleukin-1beta up-regulates expression of neurofilament light in human neuronal cells

Elevated expression of interleukin-1 (IL-1beta), a pro-inflammatory cytokine secreted by activated microglia, is a pathogenic marker of numerous neurodegenerative processes including Alzheimer's disease (AD). We have characterized a link between IL-1beta and the 68-kDa neurofilament light (NF-L) protein, which is a major component of the neuronal cytoskeleton. Using human brain aggregate cultures, we found that IL-1beta treatment significantly increased NF-L expression in primary neurons. Analysis of mRNA levels demonstrated elevated NF-L expression within 72 h while imaging of neurons by immunofluorescent staining for NF-L confirmed IL-1beta-induced NF-L protein expression. These observations suggest a potential inflammatory-induced mechanism for deregulation of an important cytoskeletal protein, NF-L, possibly leading to neuronal dysfunction.     

Runx-2 is not essential for the vitamin D-regulated expression of RANKL and osteoprotegerin in osteoblastic cells

The differentiation and activity of osteoclasts are positively and negatively controlled by receptor activator of nuclear factor-kappaB ligand (RANKL), which is expressed on the surface of osteoblasts and stromal cells, and its decoy receptor osteoprotegerin (OPG), which is secreted by osteoblasts and stromal cells, respectively. The expression of the genes for RANKL and OPG is regulated by 1alpha,25-dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)]. Runt-related gene-2 (Runx-2) is essential for osteoblast differentiation and there are several reports that Runx-2 is involved in osteoclast formation. Therefore, to clarify the role of Runx-2 in osteoclastogenesis, we designed a series of experiments using C2 cells and C6 cells, which are derived from calvariae of runx2-deficient mice. Treatment of C2 cells and C6 cells with 1alpha,25(OH)(2)D(3) for 2-4 days increased and decreased the levels of expression of the mRNAs for RANKL and OPG, respectively, and the effects were dose-dependent. However, by day 8, the level of RANKL mRNA had fallen and that of OPG mRNA had risen. Furthermore, C6 cells induced the differentiation of mouse spleen cells into tartrate-resistant acid phosphatase-positive (TRAP-positive) multinucleated cells (osteoclast-like cells) in the presence of 10(-7)M 1alpha,25(OH)(2)D(3). Such formation of osteoclast-like cells was inhibited by exogenous OPG in a dose-dependent manner. Thus, our findings indicate that Runx-2 is not essential for the expression of RANKL and OPG, and the formation of osteoclast-like cells.     

Interleukin-11 increases cell motility and up-regulates intercellular adhesion molecule-1 expression in human chondrosarcoma cells

Interleukin‐11 (IL‐11) was originally identified as the cytokine that could induce the proliferation of human cells. Recent studies have shown that IL‐11 plays a critical role in tumor growth, angiogenesis, and metastasis. Chondrosarcoma is a type of highly malignant tumor with a potent capacity to invade locally and cause distant metastasis. However, the effects of IL‐11 on human chondrosarcoma cells are largely unknown. Here, we found that IL‐11 increased the migration and expression of intercellular adhesion molecule‐1 (ICAM)‐1 in human chondrosarcoma cells. We also found that human chondrosarcoma tissues had significant expression of the IL‐11 which was higher than that in primary chondrocytes. The phosphatidylinositol 3‐kinase (PI3K), Akt, and NF‐κB pathways were activated by IL‐11 treatment, and the IL‐11‐induced expression of ICAM‐1 and migration activity were inhibited by the specific inhibitors and mutant forms of PI3K, Akt, and NF‐κB cascades. Taken together, our results indicate that IL‐11 enhanced the migration of the chondrosarcoma cells by increasing ICAM‐1 expression through the IL‐11Rα receptor, PI3K, Akt, and NF‐κB signal transduction pathway. J. Cell. Biochem. 113: 3353–3362, 2012. © 2012 Wiley Periodicals, Inc.     

猪IL-18 在杆状病毒/昆虫细胞中的表达

IL-18作为一种多效性细胞因子,在机体免疫应答及各种生理功能中发挥着重要的调节作用,根据猪IL-18基因序列设计1对引物,将编码猪IL-18的成熟蛋白基因亚克隆到杆状病毒转移载体pFastBacDual中,并在C端融合6个组氨酸标签以利于纯化,然后转化到含穿梭载体Bacmid的感受态细胞DH10Bac中,发生转座作用。将重组质粒转染昆虫细胞,SDS-PAGE可检测到分子量为18 kDa左右的重组蛋白,Western blotting证实该重组蛋白可与兔抗猪IL-18抗体发生特异性反应。纯化后蛋白能明显促进猪T淋巴细胞转化,表明所表达的IL-18具有较高的生物活性。此研究为进一步开发研制新型免疫佐剂奠定了基础。     

Interleukin-18 (IL-18) mRNA expression and localization of IL-18 mRNA-expressing cells in the mouse uterus

Interleukin-18 (IL-18) belongs to the interleukin-1 family and was identified as an interferon-gamma inducing factor. We investigated IL-18 mRNA-expressing cells in the mouse uterus. By RNase protection assay, IL-18 mRNA and alpha subunit of IL-18 receptor mRNA were detected in the uterus. In the uterus, IL-18 mRNA levels increased during sexual maturation. In situ hybridization analysis demonstrated IL-18 mRNA-expressing cells in the mouse uterus of different ages. At 21 days of age, IL-18 mRNA-expressing cells were detected in the luminal epithelial cells and stromal cells although the IL-18 mRNA signal was weak. At 42 days of age, IL-18 mRNA signal was mainly detected in the stromal cells located near the myometrium, and in some of the luminal and glandular epithelial cells. In the uterus of 63-day-old adult mice, a strong hybridization signal for IL-18 mRNA was detected at estrus, but was weak at diestrus. IL-18 mRNA was mainly detected in the glandular epithelial cells and stromal cells. The effect of estradiol-17beta (E(2)) on IL-18 mRNA-expressing cells in the uterus was examined in ovariectomized mice. In oil-treated mice IL-18 mRNA signal was localized in luminal epithelial cells and stromal cells, while in E(2)-treated mice IL-18 mRNA signal was localized in stromal cells alone. These results suggest that the mouse uterus has an IL-18 system, and IL-18 exerts a physiological role within the uterus in a paracrine manner, and that IL-18 gene expression is regulated by estrogen.     

Human bone marrow stromal cells express an osteoblastic phenotype in culture

Summary This study reports the selection and characterization of osteogenic precursors from human bone marrow which were isolated by two “clonings” and successive subculturing. These cell lines express alkaline phosphatase activity. Gel electrophoresis of [³H]-proline labeled cultures showed that the cloned cells produce only type I collagen. They synthetize osteocalcin and osteonectin. They respond to 1,25 dihydroxy vitamin D₃ by increasing osteocalcin synthesis and secretion, and to parathyroid hormone by increasing cyclic AMP synthesis. After the third subculture in the absence of β-glycerophosphate, these cell lines formed lots of clusters which exhibit high alkaline phosphatase activity and positive von Kossa staining. X-ray energy spectrum shows that these cells are surrounded by “budding” structures containing calcium and phosphorus with a ratio Ca:P identical to those of pure hydroxyapatite. This process was associated with⁴⁵Ca uptake into the cells. All these data support the selection of osteogenic cells which may be of considerable clinical importance.     

Parathyroid hormone effect on cell-to-cell communication in stromal and osteoblastic cells

We characterized the formation and regulation of the gap junction in calvarial osteoblasts and in a series of subtypes from marrow stromal cells. The stromal cells included osteogenic, chondro-osteogenic, and endothelial cells. The cell coupling was measured by using fluorescence dye injected into single cells, and its migration to neighboring cells was measured. The functional coupling of cells was highly expressed by the osteoblastic cells. This process is mediated through fast changes in intracellular Ca⁺² levels. Calcium ionophore (A 23187) demonstrated an uncoupling effect on the cells. In addition, the exposure of the cells to the parathyroid hormone increased the formation of the gap junction complex; the highest level was demonstrated in the osteoblastic cells. J. Cell. Biochem. 69:81–86, 1998. © 1998 Wiley-Liss, Inc.     

IL-18、IL-10及其比值与冠状动脉粥样硬化斑块易损性研究进展

急性冠脉综合征主要是由于具有易损性的冠状动脉粥样硬化斑块发生破裂或蚀损,继发血栓形成,并引起具有严重危害的急性冠状动脉事件.炎症反应是影响冠状动脉粥样硬化斑块易损性的主要因素,参与反应的炎症因子是近年来研究的热点.有研究发现白细胞介素-18(IL-18)作为一个促炎症因子,会增加斑块的易损性,而白细胞介素-10(IL-10)作为主要的抗炎症因子,则具有抗动脉硬化及稳定粥样斑块的作用.IL-18/IL-10的比值代表了机体促炎性与抗炎性动态平衡的状态,其比值失衡可能是影响斑块易损性的重要因素.近来有研究认为,IL-18/IL-10的比值可作为急性冠脉综合征患者近期冠脉事件的预测因子.文章就近几年来有关IL-10、IL-18及其比值与冠状动脉粥样硬化斑块易损性的研究进展作一综述,以探讨其可能的临床意义.     

Differential stimulation by PGE(2) and calcemic hormones of IL-6 in stromal/osteoblastic cells

Formation of osteoclast-like cells in mouse bone marrow cultures induced by either 1,25-dihydroxyvitamin D(3) (1,25-(OH)(2)D(3)), parathyroid hormone (PTH) or prostaglandin E(2) (PGE(2)), respectively, shows partial dependence on interleukin-6 receptor (IL-6R) activation. This suggests that locally produced IL-6 could be relevant for osteoclast formation. Therefore, we evaluated the effects of 1,25-(OH)(2)D(3), PTH, and PGE(2) on IL-6 production in stromal/osteoblastic cell lines. It appeared that these bone resorptive factors differed widely in their ability to modulate IL-6 mRNA expression and, consequently, protein synthesis in each of the cell lines studied. While 1,25-(OH)(2)D(3) was marginally effective only in ST2 cells, and PTH caused a 2- to 20-fold increase in IL-6 levels MC3T3-E1 and UMR-106 cells, PGE(2) enhanced IL-6 production in the ST2 and MC3T3-E1 cell line by two to three orders of magnitude, respectively, and also induced IL-6 in fibroblastic L929 cells. PGE(2)-stimulated IL-6 release from mesenchymal cells seems to be important for autocrine/paracrine control of osteoclast formation in health and disease.     

Effect of dexamethasone withdrawal on osteoblastic differentiation of bone marrow stromal cells

Dexamethasone is capable of directing osteoblastic differentiation of bone marrow stromal cells (BMSCs) in vitro, but its effects are not lineage-specific, and sustained exposure has been shown to down-regulate collagen synthesis and induce maturation of an adipocyte subpopulation within BMSC cultures. Such side effects might be reduced if dexamethasone is applied in a regimented manner, but the discrete steps in osteoblastic maturation that are stimulated by dexamethasone are not known. To examine this, dexamethasone was added to medium to initiate differentiation of rat BMSCs cultures and then removed after a varying number of days. Cell layers were analyzed for cell number, rate of collagen synthesis, expression of osteocalcin (OC), bone sialoprotein (BSP) and lipoprotein lipase (LpL), and matrix mineralization. Withdrawal of dexamethasone at 3 and 10 days was found to enhance cell number relative to continuous exposure, but did not affect to decrease collagen synthesis slightly. Late markers of osteoblastic differentiation, BSP expression and matrix mineralization, were also sensitive to dexamethasone and increased systematically with exposure while LpL systematically decreased. These results indicate that dexamethasone acts at both early and late stages to direct proliferative osteoprogenitor cells toward terminal maturation.     

Testosterone increases osteoprotegerin mRNA expression in mouse osteoblast cells.

The role that androgens play in the regulation of bone metabolism has been substantiated in animals and humans. We previously demonstrated that testosterone inhibits osteoclast differentiation stimulated by parathyroid hormone through the androgen receptor in mouse bone-cell cultures. However, the details of this mechanism are still unknown. The present study was aimed at examining whether testosterone would affect the mRNA levels of osteoprotegerin (OPG) and receptor activator of Nf kappa B ligand (RANKL) in mouse bone-cell cultures as well as mouse osteoblastic cell-line, MC3T3-E1 cells by employing semi-quantitative RT-PCR. Testosterone increased OPG mRNA expression in both mouse bone-cell cultures and MC3T3-E1 cells. 10-8 M PTH-(1-34) as well as 10-8M 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] inhibited OPG mRNA expression in mouse bone cells. 10-8 M testosterone antagonized OPG mRNA expression inhibited by 10-8 M PTH-(1-34), but failed to affect OPG mRNA expression inhibited by 10-8 M 1,25(OH)2D3. 10-8 M alpha-dehydrotestosterone, a non-aromatizable androgen, increased OPG mRNA expression. On the other hand, testosterone did not affect RANKL mRNA expression in MC3T3-E1 or mouse bone cells. In conclusion, the present study demonstrated that testosterone increased OPG mRNA expression in mouse bone-cell cultures and the osteoblastic cell line. These effects are likely to take place through the androgen receptor.     

Regulation of osteoprotegerin secretion from primary cultures of human bone marrow stromal cells

Osteoprotegerin (OPG) is a soluble receptor for receptor activator of NF kappa B-ligand, a factor required for osteoclastogenesis. OPG secreted from bone marrow stromal cells is believed to inhibit osteoclast differentiation and several agents known to influence bone resorption have been demonstrated to regulate mRNA levels of OPG. In this report we have investigated the secretion of OPG protein from primary cultures of human bone marrow stromal cells. An ELISA was developed for measuring the concentration of OPG in culture medium. OPG secretion was decreased by 50% when the human bone marrow stromal cells were treated with 1 microM of prostaglandin E(2), possibly through activation of the protein kinase A-pathway since stimulation of protein kinase A by forskolin also inhibited OPG secretion. Treatment with phorbol 12,13 di butyrate, an activator of the protein kinase C-pathway, potently stimulated the secretion of OPG from human bone marrow stromal cells. The cells were also stimulated with inflammatory mediators and glucocorticoids. Treatment with interleukin-1 alpha (IL-1 alpha) and tumor necrosis factor-alpha (TNF-alpha) stimulated OPG secretion to 500% and 400% of control whereas dexamethasone decreased OPG production by 40%. In conclusion, an ELISA measuring OPG in cell culture media was developed. Using this ELISA, the amount of OPG secreted from human bone marrow stromal cells was clearly detectable, and the secretion of OPG-protein was potently regulated by prostaglandin E(2), forskolin, phorbol 12,13 di butyrate, IL-1 alpha, TNF-alpha, and dexamethasone.     

Beta-catenin up-regulates Nanog expression through interaction with Oct-3/4 in embryonic stem cells

It is well known that mouse embryonic stem (ES) cells can be maintained by the presence of leukemia inhibitory factor (LIF). Recent studies have revealed that Wnt also exhibits activity similar to LIF. The molecular mechanism behind the maintenance of ES cells by these factors, however, is not fully understood. In this study, we found that LIF enhances level of nuclear beta-catenin, a component of the Wnt signaling pathway. Expression of an activated mutant of beta-catenin led to the long-term proliferation of ES cells, even in the absence of LIF. Furthermore, it was found that beta-catenin up-regulates Nanog in an Oct-3/4-dependent manner and that beta-catenin physically associates with Oct-3/4. These results suggest that up-regulating Nanog through interaction with Oct-3/4 involves beta-catenin in the LIF- and Wnt-mediated maintenance of ES cell self-renewal.     

Trail down-regulates the release of osteoprotegerin (OPG) by primary stromal cells

The soluble member of the TNF-R superfamily osteoprotegerin (OPG) is abundantly released under basal conditions by both mesenchymal stem cells (MSC) and fibroblasts and by endothelial cells upon stimulation with inflammatory cytokines. Since MSC, fibroblasts and endothelial cells represent key elements of the normal and tumor microenvironment and express detectable levels of surface TRAIL receptors, we investigated the effect of TRAIL on OPG release. Unexpectedly, recombinant TRAIL decreased the spontaneous OPG release in all cell types examined. Moreover, TRAIL decreased OPG release also in stromal cells co-cultured with lymphoma cells and counteracted the OPG induction by TN-alpha in HUVEC and MSC. Such down-regulation was not due to a masking effect in the ELISA quantification of the OPG released in the culture supernatants due to binding of OPG to its ligands (TRAIL and RANKL), as demonstrated by competition experiments with recombinant TRAIL and by the lack of RANKL release/induction. In addition, OPG down-regulation was not due to induction of cytotoxic effects by TRAIL, since the degree of apoptosis in response to TRAIL was negligible in all primary cell types. With regards to the possible molecular mechanism accounting for the down-regulation of OPG release by TRAIL, we found that treatment of MSC with TRAIL significantly decreased the phosphorylation levels of p38/MAPK. There is a suggestion that this pathway is involved in the stabilization of OPG mRNA. In this respect, the ability of TRAIL to decrease the release of OPG, in the absence of cell cytotoxicity, was mimicked by the p38/MAPK inhibitor SB203580.