Osteoclasts are multinucleated cells that are formed by the fusion of mononuclear osteoclasts, which is an essential process in bone resorption leading to bone remodeling. Herein we show that GM-CSF promoted the fusion of prefusion osteoclasts (pOCs). The expression of GM-CSF receptor-α was significantly up-regulated at the fusion stage of pOCs induced by RANKL. GM-CSF induced the expression of dendritic cell-specific transmembrane protein (DC-STAMP), which was mediated by inducing NFATc1 via induction of c-Fos. The expression of c-Fos and NFATc1 was regulated by the ERK signaling pathway. Inhibition of ERK and NFATc1 suppressed the expression of DC-STAMP and led to the fusion inhibition of pOC. However, retrovirus-mediated expression of NFATc1 in pOCs rescued the defect in pOC fusion, despite the presence of U0126 and cyclosporin A. GM-CSF-stimulated pOCs had an intact actin ring and could resorb bone. Importantly, pOCs infected with constitutively active MEK adenovirus expressed c-Fos and NFATc1, followed by the binding of NFATc1 to the DC-STAMP promoter, which enables its transcription and expression. Constitutively active MEK-infected pOCs are able to resorb bone by undergoing cell-cell fusion. Taken together, our results demonstrated that GM-CSF induced fusion of pOCs to form multinucleated osteoclasts, making the osteoclast capable of bone resorption.

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The prevention or therapeutic treatment of loss of bone mass is an important means of improving the quality of life for patients with disorders related to osteoclast-mediated bone loss. Fisetin, a flavonoid dietary ingredient found in the smoke tree (Continus coggygria), exhibits various biological activities, but its effect on osteoclast differentiation is unknown. In this study, fisetin dose-dependently inhibited the RANKL-induced osteoclast differentiation with downregulation of the activity or expression of p38, c-Fos, and NFATc1 signaling molecules. The p38/c-Fos/NFATc1-regulated expression of genes required for cell fusion and bone resorption, such as DC-STAMP and cathepsin K, was also inhibited by fisetin. Considering the rescue of fisetin's inhibitory action by NFATc1 over-expression, the cascade of p38-c-Fos-NFATc1 could be strongly involved in the inhibitory effect of fisetin on osteoclast differentiation. Furthermore, fisetin inhibited the bone-resorbing activity of mature osteoclasts. In conclusion, fisetin may be of use in the treatment of osteoclast-related disorders, including osteoporosis.

Migration and invasion comprise key steps in cancer metastasis. Through the migration and invasion into and out of lymphatic and/or blood vessels, cancer cells can be spread out into the tissues in remote site from the origin. Degradation of extracellular matrix (ECM) must be preceded prior to the metastasis of cancer cells. Matrix metalloproteinases (MMP) can degrade ECM, thus allow cells to migrate from the original site. Among MMPs, two gelatinase MMP-2 and MMP-9 play particularly important roles in ECM degradation. Here, we report that recently developed p21-activated kinase 4 inhibitor PF-3758309 shows anti-metastatic effect in A549 human lung cancer cell. PF-3758309 suppresses CREB, NF-κB, and β-catenin pathways, which are well known to be closely related with cell migration. This leads to the downregulation of MMP-2/MMP-9 expressions and the inhibition of A549 lung cancer metastasis.

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BackgroundA decrease of bone mass is a major risk factor for fracture. Several natural products have traditionally been used as herbal medicines to prevent and/or treat bone disorders including osteoporosis. Praeruptorin A is isolated from the dry root extract of Peucedanum praeruptorum Dunn and has several biological activities, but its anti-osteoporotic activity has not been studied yet.Materials and MethodsThe effect of praeruptorin A on the differentiation of bone marrow–derived macrophages into osteoclasts was examined by phenotype assay and confirmed by real-time PCR and immunoblotting. The involvement of NFATc1 in the anti-osteoclastogenic action of praeruptorin A was evaluated by its lentiviral ectopic expression. Intracellular Ca2+ levels were also measured.ResultsPraeruptorin A inhibited the RANKL-stimulated osteoclast differentiation accompanied by inhibition of p38 and Akt signaling, which could be the reason for praeruptorin A-downregulated expression levels of c-Fos and NFATc1, transcription factors that regulate osteoclast-specific genes, as well as osteoclast fusion-related molecules. The anti-osteoclastogenic effect of praeruptorin A was rescued by overexpression of NFATc1. Praeruptorin A strongly prevented the RANKL-induced Ca2+ oscillation without any changes in the phosphorylation of PLCγ.ConclusionPraeruptorin A could exhibit its anti-osteoclastogenic activity by inhibiting p38/Akt-c-Fos-NFATc1 signaling and PLCγ-independent Ca2+ oscillation.

We report anti-cancer activity of ZnO thin-film-coated chips by sustained release of zinc ions. ZnO chips were fabricated by precisely tuning ZnO thickness using atomic layer deposition, and their potential to release zinc ions relative to the number of deposition cycles was evaluated. ZnO chips exhibited selective cytotoxicity in human B lymphocyte Raji cells while having no effect on human peripheral blood mononuclear cells. Of importance, the half-maximal inhibitory concentration of the ZnO chip on the viability of Raji cells was 121.5 cycles, which was comparable to 65.7 nM of daunorubicin, an anti-cancer drug for leukemia. Molecular analysis of cells treated with ZnO chips revealed that zinc ions released from the chips increased cellular levels of reactive oxygen species, including hydrogen peroxide, which led to the down-regulation of anti-apoptotic molecules (such as HIF-1α, survivin, cIAP-2, claspin, p-53, and XIAP) and caspase-dependent apoptosis. Because the anti-cancer activity of ZnO chips and the mode of action were comparable to those of daunorubicin, the development and optimization of ZnO chips that gradually release zinc ions might have clinical anti-cancer potential. A further understanding of the biological action of ZnO-related products is crucial for designing safe biomaterials with applications in disease treatment.