Biselyngbyaside, isolated from marine cyanobacteria, inhibits osteoclastogenesis and induces apoptosis in mature osteoclasts.
ABSTRACT The mass and function of bones depend on the maintenance of a complicated balance between osteoclast-mediated bone resorption and osteoblast-mediated bone formation. An inhibitor of osteoclast differentiation and/or function is expected to be useful for treatment of bone lytic diseases such as osteoporosis, rheumatoid arthritis, and tumor metastasis into bone. Biselyngbyaside is a recently isolated macrolide compound from marine cyanobacteria Lyngbya sp. that shows wide-spectrum cytotoxicity toward human tumor cell lines. In this study, we investigated the effects of biselyngbyaside on osteoclast differentiation and function. Biselyngbyaside inhibited receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis in mouse monocytic RAW264 cells and primary bone marrow-derived macrophages at a low concentration. Similarly, biselyngbyaside suppressed osteoblastic cell-mediated osteoclast differentiation in cocultures. In the RANKL-induced signaling pathway, biselyngbyaside inhibited the expression of c-Fos and NFATc1, which are important transcription factors in osteoclast differentiation. In mature osteoclasts, biselyngbyaside decreased resorption-pit formation. Biselyngbyaside also induced apoptosis accompanied by the induction of caspase-3 activation and nuclear condensation, and these effects were negated by the pancaspase inhibitor z-VAD-FMK. Taken together, the present findings indicate that biselyngbyaside suppresses bone resorption via inhibition of osteoclastogenesis and induction of apoptosis. Thus, biselyngbyaside may be useful for the prevention of bone lytic diseases.
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ABSTRACT: The promoter of the murine gene encoding inducible nitric oxide synthase (iNOS) contains an NF-kappa B site beginning 55 base pairs upstream of the TATA box, designated NF-kappa Bd. Reporter constructs containing truncated promoter regions, when transfected into macrophages, revealed that NF-kappa Bd is necessary to confer inducibility by bacterial lipopolysaccharide (LPS). Oligonucleotide probes containing NF-kappa Bd plus the downstream 9 or 47 base pairs bound proteins that rapidly appeared in the nuclei of LPS-treated macrophages. The nuclear proteins bound to both probes in an NF-kappa Bd-dependent manner, but binding was resistant to cycloheximide only for the shorter probe. The proteins binding both probes reacted with antibodies against p50 and c-rel but not RelB; those binding the shorter probe also reacted with anti-RelA (p65). Pyrrolidine dithiocarbamate, which acts as a specific inhibitor of NF-kappa B, blocked both the activation of the NF-kappa Bd-binding proteins and the production of NO in LPS-treated macrophages. Thus, activation of NF-kappa B/Rel is critical in the induction of iNOS by LPS. However, additional, newly synthesized proteins contribute to the NF-kappa Bd-dependent transcription factor complex on the iNOS promoter in LPS-treated mouse macrophages.Journal of Biological Chemistry 03/1994; 269(7):4705-8. · 4.65 Impact Factor
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ABSTRACT: Although best known for its role in T lymphocyte activation, the calcineurin/nuclear factor of activated T cells (NFAT) signaling pathway is also known to be involved in a wide range of other biological responses in a variety of different cell types. Here we have investigated the role of the calcineurin/NFAT signaling pathway in the regulation of osteoclast differentiation. Osteoclasts are bone-resorbing multinucleated cells that are derived from the monocyte/macrophage cell lineage after stimulation with a member of the tumor necrosis factor family of ligands known as receptor activator of nuclear factor-kappaB ligand (RANKL). We now report that inhibition of calcineurin with either the immunosuppressant drugs cyclosporin A and FK506, or the retrovirally mediated ectopic expression of a specific calcineurin inhibitory peptide, all potently inhibit the RANKL-induced differentiation of the RAW264.7 monocyte/macrophage cell line into mature multinucleated osteoclasts. In addition, we find that NFAT family members are expressed in RAW264.7 cells and that their expression is up-regulated in response to RANKL stimulation. Most importantly, we find that ectopic expression of a constitutively active, calcineurin-independent NFATc1 mutant in RAW264.7 cells is sufficient to induce these cells to express an osteoclast-specific pattern of gene expression and differentiate into morphologically distinct, multinucleated osteoclasts capable of inducing the resorption of a physiological mineralized matrix substrate. Taken together, these data define calcineurin as an essential downstream effector of the RANKL-induced signal transduction pathway leading toward the induction of osteoclast differentiation and furthermore, indicate that the activation of the NFATc1 transcription factor is sufficient to initiate a genetic program that results in the specification of the mature functional osteoclast cell phenotype.Journal of Biological Chemistry 05/2004; 279(14):13984-92. · 4.65 Impact Factor
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ABSTRACT: Whether p38 and extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase cascades are required for inducible nitric oxide synthase (iNOS) and tumor necrosis factor (TNF) accumulation in RAW 264.7 murine macrophages exposed to lipopolysaccharide (LPS) plus recombinant interferon-gamma (rIFN-gamma) was investigated. By use of Western blotting for iNOS detection and ELISA for quantitation of TNF secretion, three selective inhibitors of these pathways were tested (the p38 inhibitors SB202190 and SB203580 and the MEK 1,2/ERK inhibitor PD98059). Dose-related inhibition of iNOS production was demonstrated when inhibitors were added 1 h before, simultaneously with, or 1 h after LPS plus rIFN-gamma stimulation. In contrast, inhibition of TNF secretion was observed only when cells were preincubated with these agents. Thus, both the p38 and ERK pathways are involved in the up-regulation of iNOS and TNF production by murine macrophages, and specific inhibitors of these pathways block macrophage iNOS production even when added 1 h after activation of these cells.The Journal of Infectious Diseases 05/1999; 179(4):939-44. · 5.85 Impact Factor