Dectin-1-mediated suppression of RANKL-induced osteoclastogenesis by glucan from baker's yeast

Molecular Mechanisms of Curdlan-Induced Suppression of NFATc1 Expression in Osteoclasts

Osteoclasts derived from hematopoietic stem cells express immunoreceptors on their cell surface. Previously, we showed that the β-glucan curdlan suppressed osteoclastogenesis via binding to dectin-1, a pattern recognition receptor. Curdlan negatively regulates osteoclast differentiation and bone resorption capacity by suppressing the expression of nuclear factor of activated T cells 1 (NFATc1), a master factor for osteoclast differentiation, in a dectin-1-dependent manner; however, the mechanism involved in this process has not yet been fully elucidated. In this study, we aimed to elucidate the molecular mechanism involved in the suppression of RANKL-induced osteoclast differentiation by curdlan. Real-time RT-qPCR results showed that curdlan suppressed the expression of NFATc1 in cells of the osteoclast progenitor cell line RAW264.7 overexpressing dectin-1 (d-RAW cells), without altering the expression of negative regulators. Therefore, we examined the effect of curdlan on the NF-κB pathway, which is important for the induction of NFATc1 expression. Western blot analysis results showed that curdlan addition suppressed RANKL-induced NF-κB activation in the vector control line (c-RAW) cells with low expression of dectin-1, in d-RAW cells, and the parental RAW264.7 (RAW) cells. The results of tartrate-resistant alkaline phosphatase staining and real-time RT-qPCR showed that curdlan addition suppressed osteoclast differentiation in RAW cells, suggesting the presence of a dectin-1-independent modification system. Finally, we focused on the complement receptor 3 (CR3), which binds β-glucan, and revealed that blocking the binding of β-glucan to the CD11b molecule, a component of CR3, by neutralizing antibody, recovered the suppression of IκBα degradation by curdlan. These results suggest that the suppression of osteoclast differentiation by curdlan involves not only the dectin-1-dependent pathway but also the negative regulation of NFATc1 via modification of the NF-κB pathway via CR3 recognition. The results of this study may aid to establish treatment methods for metabolic bone diseases and inflammatory bone destruction and to clarify their pathogenesis.

Yeast β-glucan-based nanoparticles loading methotrexate promotes osteogenesis of hDPSCs and periodontal bone regeneration under the inflammatory microenvironment

The regeneration of absorbed alveolar bone and reconstruction of periodontal support tissue are huge challenges in the clinical treatment of periodontitis due to the limited regenerative capacity of alveolar bone. It is essential to regulate inflammatory reaction and periodontal cell differentiation. Based on the anti-inflammatory effect of baker's yeast β-glucan (BYG) with biosafety by targeting macrophages, the BYG-based nanoparticles loading methotrexate (cBPM) were fabricated from polyethylene glycol-grafted BYG through chemical crosslinking for treatment of periodontitis. In our findings, cBPM promoted osteogenesis of human dental pulp stem cells (hDPSCs) under inflammatory microenvironment, characterized by the enhanced expression of osteogenesis-related Runx2 and activation of mitogen-activated protein kinase/extracellular signal-regulated protein kinase (MAPK/Erk) pathway in vitro. Animal experiments further demonstrate that cBPM effectively promoted periodontal bone regeneration and achieved in a better effect of recovery indicated by 19.2 % increase in tissue volume, 7.1 % decrease in trabecular separation, and a significant increase in percent bone volume and trabecular thickness, compared with the model group. Additionally, cBPM inhibited inflammation and repaired alveolar bone by transforming macrophage phenotype from inflammatory M1 to anti-inflammatory M2. This work provides an alternative strategy for the clinical treatment of periodontitis through BYG-based delivery nanoplatform of anti-inflammatory drugs.

The effect of Schizophyllan on the differentiation of osteoclasts and osteoblasts

Schizophyllan (SPG), a β-glucan from Schizophyllum commune, is recognized for its antioxidant, immunoregulatory, and anticancer activities. In this study, its effects on bone cells, particularly osteoclasts and osteoblasts, were examined. We demonstrated that SPG dose-dependently inhibited osteoclastogenesis and reduced gene expression associated with osteoclast differentiation. SPG also decreased bone resorption and F-actin ring formation. This inhibition could have been due to the downregulation of transcription factors c-Fos and nuclear factor of activated T cells 1 (NFATc1) via the MAPKs (JNK and p38), IκBα, and PGC1β/PPARγ pathways. In coculture, SPG lowered osteoclastogenic activity in calvaria-derived osteoblasts by reducing macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor-κB ligand (RANKL) expression. In addition, SPG slightly enhanced osteoblast differentiation, as evidenced by increased differentiation marker gene expression and alizarin red staining. It also exhibited antiresorptive effects in a lipopolysaccharide-induced calvarial bone loss model. These results indicated a dual role of SPG in bone cell regulation by suppressing osteoclastogenesis and promoting osteoblast differentiation. Thus, SPG could be a therapeutic agent for bone resorption-related diseases such as osteoporosis, rheumatoid arthritis, and periodontitis.

Pleurotus sajor-caju (Fr.) Singer β-1,3-Glucanoligosaccharide (Ps-GOS) Suppresses RANKL-Induced Osteoclast Differentiation and Function in Pre-Osteoclastic RAW 264.7 Cells by Inhibiting the RANK/NFκB/cFOS/NFATc1 Signalling Pathway

Edible grey oyster mushroom, Pleurotus sajor-caju, β (1,3), (1,6) glucan possesses a wide range of biological activities, including anti-inflammation, anti-microorganism and antioxidant. However, its biological activity is limited by low water solubility resulting from its high molecular weight. Our previous study demonstrated that enzymatic hydrolysis of grey oyster mushroom β-glucan using Hevea β-1,3-glucanase isozymes obtains a lower molecular weight and higher water solubility, Pleurotus sajor-caju glucanoligosaccharide (Ps-GOS). Additionally, Ps-GOS potentially reduces osteoporosis by enhancing osteoblast-bone formation, whereas its effect on osteoclast-bone resorption remains unknown. Therefore, our study investigated the modulatory activities and underlying mechanism of Ps-GOS on Receptor activator of nuclear factor kappa-Β ligand (RANKL) -induced osteoclastogenesis in pre-osteoclastic RAW 264.7 cells. Cell cytotoxicity of Ps-GOS on RAW 264.7 cells was determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay and its effect on osteoclast differentiation was determined by tartrate-resistant acid phosphatase (TRAP) staining. Additionally, its effect on osteoclast bone-resorptive ability was detected by pit formation assay. The osteoclastogenic-related factors were assessed by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), Western blot and immunofluorescence. The results revealed that Ps-GOS was non-toxic and significantly suppressed the formation of mature osteoclast multinucleated cells and their resorption activity by reducing the number of TRAP-positive cells and pit formation areas in a dose-dependent manner. Additionally, Ps-GOS attenuated the nuclear factor kappa light chain-enhancer of activated B cells' P65 (NFκB-P65) expression and their subsequent master osteoclast modulators, including nuclear factor of activated T cell c1 (NFATc1) and Fos proto-oncogene (cFOS) via the NF-κB pathway. Furthermore, Ps-GOS markedly inhibited RANK expression, which serves as an initial transmitter of many osteoclastogenesis-related cascades and inhibited proteolytic enzymes, including TRAP, matrix metallopeptidase 9 (MMP-9) and cathepsin K (CTK). These findings indicate that Ps-GOS could potentially be beneficial as an effective natural agent for bone metabolic disease.

Bioactive Materials for Bone Regeneration: Biomolecules and Delivery Systems

Novel tissue regeneration strategies are constantly being developed worldwide. Research on bone regeneration is noteworthy, as many promising new approaches have been documented with novel strategies currently under investigation. Innovative biomaterials that allow the coordinated and well-controlled repair of bone fractures and bone loss are being designed to reduce the need for autologous or allogeneic bone grafts eventually. The current engineering technologies permit the construction of synthetic, complex, biomimetic biomaterials with properties nearly as good as those of natural bone with good biocompatibility. To ensure that all these requirements meet, bioactive molecules are coupled to structural scaffolding constituents to form a final product with the desired physical, chemical, and biological properties. Bioactive molecules that have been used to promote bone regeneration include protein growth factors, peptides, amino acids, hormones, lipids, and flavonoids. Various strategies have been adapted to investigate the coupling of bioactive molecules with scaffolding materials to sustain activity and allow controlled release. The current manuscript is a thorough survey of the strategies that have been exploited for the delivery of biomolecules for bone regeneration purposes, from choosing the bioactive molecule to selecting the optimal strategy to synthesize the scaffold and assessing the advantages and disadvantages of various delivery strategies.

Immunoglobulin G-dependent inhibition of inflammatory bone remodeling requires pattern recognition receptor Dectin-1

Immunoglobulin G (IgG) antibodies are major drivers of inflammation during infectious and autoimmune diseases. In pooled serum IgG (IVIg), however, antibodies have a potent immunomodulatory and anti-inflammatory activity, but how this is mediated is unclear. We studied IgG-dependent initiation of resolution of inflammation in cytokine- and autoantibody-driven models of rheumatoid arthritis and found IVIg sialylation inhibited joint inflammation, whereas inhibition of osteoclastogenesis was sialic acid independent. Instead, IVIg-dependent inhibition of osteoclastogenesis was abrogated in mice lacking receptors Dectin-1 or FcγRIIb. Atomistic molecular dynamics simulations and super-resolution microscopy revealed that Dectin-1 promoted FcγRIIb membrane conformations that allowed productive IgG binding and enhanced interactions with mouse and human IgG subclasses. IVIg reprogrammed monocytes via FcγRIIb-dependent signaling that required Dectin-1. Our data identify a pathogen-independent function of Dectin-1 as a co-inhibitory checkpoint for IgG-dependent inhibition of mouse and human osteoclastogenesis. These findings may have implications for therapeutic targeting of autoantibody and cytokine-driven inflammation.

Different Roles of Dendritic Cells for Chronic Rhinosinusitis Treatment According to Phenotype

Dendritic cells (DCs) are antigen-presenting cells derived from the bone marrow that play an important role in the association between the innate and adaptive immune responses. The onset and development of chronic rhinosinusitis (CRS) involve a serious imbalance in immune regulation and mechanical dysfunction caused by an abnormal remodeling process. Recent studies have shown that an increase in DCs in CRS and their function of shaping the nasal mucosal immune response may play an important role in the pathogenesis of CRS. In this review, we discuss DC subsets in mice and humans, as well as the function of DCs in the nasal sinus mucosa. In addition, the mechanism by which DCs can be used as targets for therapeutic intervention for CRS and potential future research directions are also discussed.

Biological Effects of β-Glucans on Osteoclastogenesis

Although the anti-tumor and anti-infective properties of β-glucans have been well-discussed, their role in bone metabolism has not been reviewed so far. This review discusses the biological effects of β-glucans on bone metabolisms, especially on bone-resorbing osteoclasts, which are differentiated from hematopoietic precursors. Multiple immunoreceptors that can recognize β-glucans were reported to be expressed in osteoclast precursors. Coordinated co-stimulatory signals mediated by these immunoreceptors are important for the regulation of osteoclastogenesis and bone remodeling. Curdlan from the bacterium Alcaligenes faecalis negatively regulates osteoclast differentiation in vitro by affecting both the osteoclast precursors and osteoclast-supporting cells. We also showed that laminarin, lichenan, and glucan from baker’s yeast, as well as β-1,3-glucan from Euglema gracilisas, inhibit the osteoclast formation in bone marrow cells. Consistent with these findings, systemic and local administration of β-glucan derived from Aureobasidium pullulans and Saccharomyces cerevisiae suppressed bone resorption in vivo. However, zymosan derived from S. cerevisiae stimulated the bone resorption activity and is widely used to induce arthritis in animal models. Additional research concerning the relationship between the molecular structure of β-glucan and its effect on osteoclastic bone resorption will be beneficial for the development of novel treatment strategies for bone-related diseases.