Spleen tyrosine kinase (SYK) inhibitor PRT062607 protects against ovariectomy-induced bone loss and breast cancer-induced bone destruction

hFcγRIIa: a double-edged sword in osteoclastogenesis and bone balance in transgenic mice

Rheumatoid arthritis (RA) is a chronic autoimmune disease accompanied by local and systemic bone loss. FcγRs, especially FcγRIIa (hFcγRIIa), have been implicated in the pathogenesis of RA. However, the contribution of hFcγRIIa to bone loss has not been fully elucidated. In the present study, we demonstrated the double-edged sword role of hFcγRIIa on osteoclast differentiation through investigations involving hFcγRIIa-transgenic (hFcγRIIa-Tg) mice. Our findings reveal that hFcγRIIa-Tg mice, previously shown to exhibit heightened susceptibility to collagen-induced arthritis (CIA), displayed increased osteoporosis during CIA or at advanced ages (40 weeks), accompanied by heightened in vivo osteoclast differentiation. Notably, bone marrow cells from hFcγRIIa-Tg mice exhibited enhanced efficiency in differentiating into osteoclasts and bone resorption in vitro compared to wild-type mice when stimulated with receptor activators of NF-κB ligand (RANKL). Additionally, hFcγRIIa-Tg mice exhibited augmented sensitivity to RANKL-induced bone loss in vivo, highlighting the osteoclast-promoting role of hFcγRIIa. Mechanistically, bone marrow cells from hFcγRIIa-Tg mice displayed heightened Syk self-activation, leading to mTOR-pS6 pathway activation, thereby promoting RANKL-driven osteoclast differentiation. Intriguingly, while hFcγRIIa crosslinking hindered RANKL-induced osteoclast differentiation, it activated the kinase cAbl, subsequently triggering STAT5 activation and inhibiting the expression of osteoclast-associated genes. This study provides novel insights into hFcγRIIa-mediated osteoclast biology, suggesting promising therapeutic targets for managing bone remodeling disorders.

Regorafenib Attenuates Osteoclasts Differentiation by Inhibiting the NF-κB, NFAT, ERK, and p38 Signaling Pathways

Osteolytic diseases such as osteoporosis and neoplastic bone metastases are caused by the excessive activation of osteoclasts. Inhibiting the excessive activation of osteoclasts is a crucial strategy for treating osteolytic diseases. This study investigated the roles and mechanisms of regorafenib, a tyrosine kinase inhibitor, on osteoclasts and osteolytic diseases. We first identified the potential targets and mechanisms of regorafenib on osteoclast-related osteolytic diseases using network pharmacological analysis and molecular docking techniques. Then, we verified its role and mechanism on osteoclasts via cellular and animal experiments. Network pharmacology analysis identified 89 common targets shared by regorafenib and osteoclast-related osteolytic diseases. Enrichment analysis suggested that regorafenib may act on osteoclast-related osteolytic diseases by modulating targets such as AKT1, CASP3, MMP9, and MAPK3, regulating biological processes such as cell proliferation, apoptosis, and phosphorylation regulation, and influencing signaling pathways such as MAPK, PI3K/AKT, and osteoclast differentiation. The molecular docking results indicated that regorafenib and AKT1, CASP3, MMP9, MAPK3, and MAPK14 were stably docked. Cell experiments demonstrated that regorafenib significantly inhibited osteoclast differentiation and bone resorption in RAW 264.7 cells and bone marrow macrophages in a dose-dependent manner, with up to 50% reduction at 800 nM concentration without exhibiting cytotoxic effects. Furthermore, Western blot and RT-qPCR results demonstrated that regorafenib inhibited osteoclast differentiation by blocking the transduction of RANKL-induced NF-κB, p38, ERK, and NFAT signaling pathways. In vivo studies using an ovariectomized mouse model showed that regorafenib significantly improved bone volume fraction (BV/TV), bone surface to total volume (BS/TV), and number of trabeculae (TB.N), as well as reduced trabecular separation (Tb.Sp) compared to the OVX groups (P < 0.05). TRAcP staining results revealed a reduction in the number of osteoclasts with regorafenib treatment (P < 0.01). These results indicate that regorafenib exerts its protective effects against osteoclast-related osteolytic disease by inhibiting the RANKL-induced NF-κB, NFAT, ERK, and p38 signaling pathways. This study proves that regorafenib may serve as a potential therapeutic agent for osteoclast-related osteolytic diseases.

Cyclic peptide conjugated photosensitizer for targeted phototheranostics of gram-negative bacterial infection

Antimicrobial photodynamic therapy (PDT) is a promising alternative to antibiotics for eradicating pathogenic bacterial infections. It holds advantage of not inducing antimicrobial resistance but is limited for the treatment of gram-negative bacterial infection due to the lack of photosensitizer (PS) capable of targeted permeating the outer membrane (OM) of gram-negative bacteria. To facilitate the targeted permeability of PS, cyclic polymyxin b nonapeptide that can specifically bind to the lipopolysaccharide on OM, is conjugated to an FDA approved PS chlorin e6 via variable linkers. Based on structure to activity study, C6pCe6 with aminohexanoic linker and P2pCe6 with amino-3, 6-dioxaoctanoic linker are identified to preferentially image gram-negative bacteria. These two conjugates also exhibit improved aqueous dispersity and enhanced ROS generation, consequently enabled their selective bactericidal activities against gram-negative bacteria upon 660 nm light irradiation. The effective photobactericidal ability of P2pCe6 is further validated on P. aeruginosa infected G. mellonella. Moreover, it is demonstrated to effectively treat the P. aeruginosa infection and accelerate the healing process at the wound site of mouse. Owing to the light irradiation triggered targeted imaging and enhanced bactericidal capacities, P2pCe6 hold great potential to serve as a potent PS for mediating the phototheranostics of gram-negative bacterial infection.

Brevilin A inhibits RANKL-induced osteoclast differentiation and bone resorption

Brevilin A (BA) is the primary component of Centipeda minima, which is widely used in Chinese traditional medicine. The anti-inflammatory and anti-tumor properties of BA have been established; however, its function in bone metabolism is not well understood. This study revealed that concentrations of BA below 1.0 µM did not inhibit the proliferation of bone marrow macrophages but did impede the differentiation and bone resorption activity of osteoclasts. Furthermore, BA suppressed the expression of osteoclast-specific genes Mmp9, Acp5, Dc-stamp, Ctsk, and Atp6v0d2. In addition, mTOR, ERK, and NFATc1 activation in bone marrow macrophages were suppressed by BA. As a whole, BA blocks the mTOR and ERK signaling pathways, which is responsible for the development and activity of osteoclasts, and the resorption of bone.

Physiological functions of podosomes: From structure and function to therapy implications in osteoclast biology of bone resorption

With increasing age, bone tissue undergoes significant alterations in composition, architecture, and metabolic functions, probably causing senile osteoporosis. Osteoporosis possess the vast majority of bone disease and associates with a reduction in bone mass and increased fracture risk. Bone loss is on account of the disorder in osteoblast-induced bone formation and osteoclast-induced bone resorption. As a unique bone resorptive cell type, mature bone-resorbing osteoclasts exhibit dynamic actin-based cytoskeletal structures called podosomes that participate in cell-matrix adhesions specialized in the degradation of mineralized bone matrix. Podosomes share many of the same molecular constitutions as focal adhesions, but they have a unique structural organization, with a central core abundant in F-actin and encircled by scaffolding proteins, kinases and integrins. Here, we conclude recent advancements in our knowledge of the architecture and the functions of podosomes. We also discuss the regulatory pathways in osteoclast podosomes, providing a reference for future research on the podosomes of osteoclasts and considering podosomes as a therapeutic target for inhibiting bone resorption.

Analysis of Communal Molecular Mechanism Between Chronic Obstructive Pulmonary Disease and Osteoporosis

Background

Chronic obstructive pulmonary disease (COPD) patients with osteoporosis (OP) usually experience more frequent exacerbations, worse quality of life, and heavier economic burden, however, few studies have investigated common molecular mechanisms of COPD and OP.

Objective

To explore the relationship between COPD and OP through bioinformatics analysis.

Methods

The miRNA microarray data of COPD and OP were retrieved from the Gene Expression Database (GEO), and the differentially expressed microRNAs (DEmiRNAs) were screened and the intersection was obtained. The Targetscan, miRDB, and miRWalk databases were used to predict the target genes of DEmiRNA, and the gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed using the R package clusterProfiler, the STRING database was used to analyze the target protein-protein interaction network (PPI) and screens to determine the core modules and core genes.

Results

Two DEmiRNAs (miR-23a-5p, miR-194-3p) have been found in COPD and OP, which have predicted 76 and 114 target genes, respectively. GO functional annotations of miR-23a-5p were significantly enriched in CD40 signaling pathway, ubiquitin-conjugating enzyme activity, etc; KEGG pathways of miR-23a-5p were significantly enriched in ubiquitin-mediated proteolysis, folate biosynthesis, and regulation of actin cytoskeleton. GO function annotations of miR-194-3p were significantly enriched in T cell activation regulation, ubiquitin protein ligase activity, and DNA transcription factor binding; KEGG pathways of miR-194-3p were significantly enriched in cell adhesion molecules, intercellular tight junctions, and lysosomal pathway. PPI analysis found target coding proteins formed complex regulatory networks. Ten core genes (TP53, SRC, PXN, CHD4, SYK, TNRC6B, PML, KAT5, BRD1 and IGF2) were picked out among them, then we used the MCODE plugin found three core subnetworks.

Conclusion

Two identical DEmiRNAs (miR-23a-5p, miR-194-3p) exist in the peripheral blood of COPD and OP patients, which are important biomarkers for COPD patients with OP and may represent novel targets for diagnosis and treatment of COPD patients with OP.