The Role of TAK1 in RANKL-Induced Osteoclastogenesis

Insights into the role of histone lysine demethylases in bone homeostasis and skeletal diseases: A review

Histone lysine demethylases (KDMs), as important epigenetic regulators, are involved in various biological processes such as energy metabolism, apoptosis, and autophagy. Recent research shows that KDMs activate or silence downstream target genes by removing lysine residues from histone tails, and participate in the regulation of bone marrow mesenchymal stem cells (BM-MSCs), osteoblasts (OB), osteoclasts (OC), chondrocytes and other skeletal cell development, differentiation and formation. Moreover, several members of the KDM family affect the occurrence and development of bone diseases such as osteoporosis (OP), osteoarthritis (OA), osteosarcoma (OS), by regulating target genes. Specific regulation mechanisms of KDMs suggest new strategies for bone disease treatment and prevention. Despite the unique function and importance of KDMs in the skeletal system, previous studies have never systematically summarized their specific role, molecular mechanism, and clinical treatment in bone physiology and pathology. Therefore, this review summarises the expression pattern, intracellular signal transduction, and mechanism of action of the KDM family in several bone physiological and pathological conditions, aiming to highlight the important role of KDMs in bone diseases and provide a reference for the future treatment of bone diseases.

Mechanisms of isorhamnetin inhibition of osteoclast differentiation: insights from molecular dynamics simulations and in vitro/in vivo experiments

Background

Osteoporosis (OP) represents a widespread bone remodeling disorder within the domain of orthopedics, markedly compromising the quality of life in the elderly population. The need to develop more efficient therapeutic approaches to attenuate bone resorption by suppressing the excessive activation of osteoclasts (OCs) remains urgent. The plant flavonoid Isorhamnetin (Iso), recognized for its potent antioxidant properties, has been the subject of extensive research regarding its potential in treating bone-related conditions.

Method

This study adopts a comprehensive methodology to evaluate Iso's impact on bone metabolism and its therapeutic possibilities for treating OP. By integrating network pharmacology, molecular dynamics simulations, and surface plasmon resonance (SPR), we performed in vitro phenotypic analyses to systematically evaluate the inhibitory effect of Iso on OC differentiation. The mechanisms behind Iso's inhibition of OC differentiation were further elucidated. In vivo testing was also performed to substantiate the therapeutic effects of Iso in an OP animal model.

Results

At low concentrations, Iso showed no cytotoxicity and did not interfere with cell proliferation in RAW 264.7 cells. Iso effectively inhibited RANKL-induced osteoclast differentiation in these cells, while downregulating related genes levels (Nfatc1, Ctsk, Trap, c-Fos). Molecular dynamics simulations and surface plasmon resonance confirmed Iso's dual binding to both RANKL and RANK. KEGG pathway enrichment analysis results indicated that Iso modulates the MAPK, NF-κB/PI3K-AKT, and calcium signaling pathways. Western blot analysis revealed that Iso treatment targeting the RANKL/RANK binding pathway significantly downregulated phosphorylation levels of JNK, P38, AKT, and p65. Concurrently, Iso stimulation markedly increased IκBα expression, thereby rescuing its degradation. Furthermore, Iso demonstrated a robust inhibitory effect on reactive oxygen species levels in vitro. Furthermore, in OVX mice, Iso treatment increased bone density, modulated serum bone metabolism markers, and downregulated transcriptional levels of OC marker genes.

Conclusion

Iso exhibits therapeutic potential for OP by selectively targeting and disrupting the RANKL-RANK interaction. This intervention modulates the expression of intracellular transcription factors and multiple signaling pathways, thereby inhibiting the maturation of OCs. Through mitigating OC-mediated bone loss, Iso holds significant promise as a potent therapeutic agent for OP.

Clustered peptide regulating the multivalent interaction between RANK and TRAF6 inhibits osteoclastogenesis by fine-tuning signals

Bone-destructive diseases are caused by dysregulated osteoclastogenesis. Osteoclast differentiation is positively regulated by the ligand for receptor activator of nuclear factor kappa B (RANKL) binding to the RANK on progenitor cells. RANK then forms a multivalent interaction with an adapter molecule, tumor necrosis factor receptor-associated factor 6 (TRAF6), to transduce various downstream signals. We used affinity-based screening of a multivalent random-peptide library to identify a tetravalent peptide, WHD-tet, that binds to the RANK-binding region of TRAF6 through a multivalent interaction. CR4-WHD-tet, a cell-permeable form of WHD-tet, efficiently inhibited the RANKL-induced differentiation of bone-marrow cells to osteoclasts and osteoclastogenesis in a mouse model. CR4-WHD-tet specifically inhibited the recruitment of MAPK kinase 3 to TRAF6 without affecting other signal transducers in a late stage of differentiation, inhibiting the activation of p38-MAPK, which promotes the final stage. Thus, the interaction modulator CR4-WHD-tet fine-tunes the formation of a critical signaling complex to inhibit osteoclastogenesis.

TRAF1 promotes osteoclastogenesis by enhancing metabolic adaptation to oxidative phosphorylation in an AKT-dependent manner

Tumor necrosis factor receptor-associated factor 1 (TRAF1) is a crucial signaling adaptor involved in multiple cellular events. However, its role in regulating osteoclastogenesis and energy metabolism remains unclear. Here, we report that TRAF1 promotes osteoclastogenesis and oxidative phosphorylation (OXPHOS). Employing RNA sequencing, we found that TRAF1 is markedly upregulated during osteoclastogenesis and is positively associated with osteoporosis. TRAF1 knockout inhibits osteoclastogenesis and increases bone mass in both normal and ovariectomized adult mice without affecting bone mass in childhood. Furthermore, TRAF1 promotes osteoclast OXPHOS by increasing the phosphorylation level of AKT. Mechanistically, TRAF1 functions to inhibit TRAF2-induced ubiquitination of Gβl, a known activator of AKT, and further upregulates AKT phosphorylation. Rescue experiments revealed that the inhibitory effects of TRAF1 knockout on osteoclastogenesis, OXPHOS, and bone mass are dependent on AKT. Collectively, our findings uncover a previously unrecognized function of TRAF1 in regulating osteoclastogenesis and energy metabolism, and establish a novel TRAF1-AKT-OXPHOS axis in osteoclasts.

Dual regulation of phaseol on osteoclast formation and osteoblast differentiation by targeting TAK1 kinase for osteoporosis treatment

INTRODUCTION

Osteoporosis is an osteolytic disorder resulting from an inequilibrium between osteoblast-mediated osteogenesis and osteoclast-driven bone absorption. Safe and effective approaches for osteoporosis management are still highly demanded.

PURPOSE

This study aimed to examine the osteoprotective effect and the mechanisms of phaseol (PHA) in vitro and in vivo.

METHODS

Virtual screening identified the potential inhibitors of transforming growth factor-beta-activated kinase 1 (TAK1) from coumestans. The interaction between PHA and TAK1 was investigated by molecular simulation, pronase and thermal resistance assays. The maturation and function of osteoclasts were determined using tartrate-resistant acid phosphatase staining, bone absorption and F-actin ring formation assays. The differentiation and calcification of osteoblasts were assessed by alkaline phosphatase staining and Alizarin Red S staining. The activity of related targets and pathways were detected using immunoblotting, immunofluorescence and co-immunoprecipitation assays. The in vivo osteoprotective effect of PHA was evaluated using a lipopolysaccharide (LPS)-induced mouse osteoporosis model.

RESULTS

Firstly, we confirmed that TAK1 was essential in controlling bone remodeling by regulating osteogenesis and osteoclastogenesis. Moreover, PHA, a coumestan compound predominantly present in leguminous plants, was identified as a potent TAK1 inhibitor through virtual and real experiments. Subsequently, PHA was observed to enhance osteoblast differentiation and calcification, while suppress osteoclast maturation and bone resorptive function in vitro. Mechanistically, PHA remarkably inhibited the TRAF6-TAK1 complex formation, and inhibited the activation of TAK1, MAPK and NF-κB pathways by targeting TAK1. In the in vivo study, PHA strongly attenuated bone loss, inflammatory responses, and osteoclast over-activation in lipopolysaccharide-induced osteoporosis mice.

CONCLUSION

PHA had a dual-functional regulatory impact on osteogenesis and osteoclastogenesis by targeting TAK1, suppressing TRAF6-TAK1 complex generation, and modulating its associated signaling pathways, ultimately leading to mitigating osteoporosis. This study offered compelling evidence in favor of using PHA for preventing and managing osteoporosis as both a bone anabolic and anti-resorptive agent.

Quercetin in Osteoporosis Treatment: A Comprehensive Review of Its Mechanisms and Therapeutic Potential

PURPOSE OF REVIEW

This review aims to provide a theoretical basis and insights for quercetin's clinical application in the prevention and treatment of osteoporosis (OP), analyzing its roles in bone formation promotion, bone resorption inhibition, anti-inflammation, antioxidant effects, and potential mechanisms.

RECENT FINDINGS

OP, a prevalent bone disorder, is marked by reduced bone mineral density and impaired bone architecture, elevating the risk of fractures in patients. The primary approach to OP management is pharmacotherapy, with quercetin, a phytochemical compound, emerging as a focus of recent interest. This natural flavonoid exerts regulatory effects on bone marrow mesenchymal stem cells, osteoblasts, and osteoclasts and promotes bone health and metabolic equilibrium via anti-inflammatory and antioxidative pathways. Although quercetin has demonstrated significant potential in regulating bone metabolism, there is a need for further high-quality clinical studies focused on medicinal quercetin.

Irpetones A and B, Anti-Osteoclastic Heptaketides from a Marine Mesophotic Zone Ircinia Sponge-Associated Fungus Irpex sp. NBUF088

Chemical investigation of Irpex sp. NBUF088, associated with an Ircinia sp. sponge located at an 84 m deep mesophotic zone, led to the discovery of two new heptaketides, named irpetones A (1) and B (2). Their structures were identified by analysis of spectroscopic data and quantum-chemical calculations. Compound 1 exhibited inhibition against the receptor activator of NF-κB ligand-induced osteoclastogenesis in bone marrow monocytes with an IC50 of 6.3 ± 0.2 μM, causing no notable cytotoxicity. It was also determined that 1 inhibited the phosphorylation of ERK1/2-JNK1/2-p38 MAPKs and the nuclear translocation of NF-κB, consequently suppressing the activation of MAPK and NF-κB signaling pathways induced by the NF-κB ligand.

LncRNA-mediated cartilage homeostasis in osteoarthritis: a narrative review

Osteoarthritis (OA) is a degenerative disease of cartilage that affects the quality of life and has increased in morbidity and mortality in recent years. Cartilage homeostasis and dysregulation are thought to be important mechanisms involved in the development of OA. Many studies suggest that lncRNAs are involved in cartilage homeostasis in OA and that lncRNAs can be used to diagnose or treat OA. Among the existing therapeutic regimens, lncRNAs are involved in drug-and nondrug-mediated therapeutic mechanisms and are expected to improve the mechanism of adverse effects or drug resistance. Moreover, targeted lncRNA therapy may also prevent or treat OA. The purpose of this review is to summarize the links between lncRNAs and cartilage homeostasis in OA. In addition, we review the potential applications of lncRNAs at multiple levels of adjuvant and targeted therapies. This review highlights that targeting lncRNAs may be a novel therapeutic strategy for improving and modulating cartilage homeostasis in OA patients.

Cinchonine: A Versatile Pharmacological Agent Derived from Natural Cinchona Alkaloids

BACKGROUND

Cinchonine is one of the Cinchona alkaloids that is commercially extracted from the Peruvian bark of Cinchona officinalis L. (Family: Rubiaceae). It is also obtained in much lower quantities from other species of Cinchona, such as Cinchona calisaya, Cinchona succirubra, and Cinchona pubescens, and in some other plants, such as Remijia peruviana. Cinchonine has been historically used as an anti-malarial agent. It also has a wide range of other biological properties, including anti-cancer, anti-obesity, anti-inflammatory, anti-parasitic, antimicrobial, anti-platelet aggregation, and anti-osteoclast differentiation.

AIM AND OBJECTIVE

This review discusses the pharmacological activity of cinchonine under different experimental conditions, including in silico, in vitro, and in vivo. It also covers the compound's physicochemical properties, toxicological aspects, and pharmacokinetics.

METHODOLOGY

A comprehensive literature search was conducted on multiple online databases, such as PubMed, Scopus, and Google Scholar. The aim was to retrieve a wide range of review/research papers and bibliographic sources. The process involved applying exclusion and inclusion criteria to ensure the selection of relevant and high-quality papers.

RESULTS

Cinchonine has numerous pharmacological properties, making it a promising compound for various therapeutic applications. It induces anti-cancer activity by activating caspase-3 and PARP-1, and triggers the endoplasmic reticulum stress response. It up-regulates GRP78 and promotes the phosphorylation of PERK and ETIF-2α. Cinchonine also inhibits osteoclastogenesis, inhibiting TAK1 activation and suppressing NFATc1 expression by regulating AP-1 and NF-κB. Its potential anti-inflammatory effects reduce the impact of high-fat diets, making it suitable for targeting obesity-related diseases. However, research on cinchonine is limited, and further studies are needed to fully understand its therapeutic potential. Further investigation is needed to ensure its safety and efficacy in clinical applications.

CONCLUSION

Overall, this review article explains the pharmacological activity of cinchonine, its synthesis, and physicochemical properties, toxicological aspects, and pharmacokinetics.

Extracellular vesicles derived from M1 macrophages enhance rat midpalatal suture expansion by promoting initial bone turnover and inflammation

BACKGROUND

Midpalatal suture (MPS) expansion can be affected by many factors, and researchers have attempted to regulate the initial inflammatory stage of expansion to optimize clinical outcomes and their underlying mechanisms. This study aimed to investigate the potential effects and mechanisms of M1 macrophage small extracellular vesicles during rat MPS expansion.

MATERIALS AND METHODS

RAW264.7 cells were induced to M1 or M2 polarization and, small extracellular vesicles were isolated from the polarized macrophages. Male Sprague-Dawley rats (6-7 weeks) were administered 70 ± 5 g expansion force devices for 7 days. Rats with expanders without force served as controls. M1/M2 small extracellular vesicles were injected into the MPS region (50 µg/day) in the M1 and M2 small extracellular vesicle-assisted groups, while 0.9% saline was injected into the expansion-only group. Suture width, bone mass, and morphological changes in the region of interest (ROI) were examined.

RESULTS

The M1 small extracellular vesicle-assisted group showed a significantly increased MPS suture width in vivo (P < 0.001), and less bone mass was observed in the ROI (P < 0.05). Histological examination showed that the M1 small extracellular vesicle-assisted group exhibited a wider palatal area and obvious fibrous tissue rearrangement. The expression of RANKL and the number of osteoclasts were increased (P < 0.01) in the bony edges, and the p65 protein expression was significantly higher (P < 0.001).

CONCLUSIONS

M1 macrophage-derived small extracellular vesicles have a positive effect in MPS expansion and increase p65 protein content and RANKL expression, thus promoting bone turnover. This study may contribute to the clinical application of small extracellular vesicles in the expansion of the palatal suture.

Growth charts for Marfan syndrome in the Netherlands and analysis of genotype-phenotype relationships

To optimize care for children with Marfan syndrome (MFS) in the Netherlands, Dutch MFS growth charts were constructed. Additionally, we aimed to investigate the effect of FBN1 variant type (haploinsufficiency [HI]/dominant negative [DN]) on growth, and compare MFS-related height increase across populations. Height and weight data of individuals with MFS aged 0-21 years were retrospectively collected. Generalized Additive Models for Location, Scale and Shape (GAMLSS) was used for growth chart modeling. To investigate genotype-phenotype relationships, FBN1 variant type was included as an independent variable in height-for-age and BMI-for-age models. MFS-related height increase was compared with that of previous MFS growth studies from the United States, Korea, and France. Height and weight data of 389 individuals with MFS were included (210 males). Height-for-age, BMI-for-age, and weight-for-height charts reflected the tall and slender MFS habitus throughout childhood. Mean increase in height of individuals with MFS compared with the general Dutch population was significantly lower than in the other three MFS populations compared to their reference populations. FBN1-HI variants were associated with taller height in both sexes, and decreased BMI in females (p-values <0.05). This Dutch MFS growth study broadens the notion that genetic background and MFS variant type (HI/DN) influence tall and slender stature in MFS.

Recent advances of the mammalian target of rapamycin signaling in mesenchymal stem cells

Mammalian target of rapamycin (mTOR) is a serine/threonine kinase involved in a variety of cellular functions, such as cell proliferation, metabolism, autophagy, survival and cytoskeletal organization. Furthermore, mTOR is made up of three multisubunit complexes, mTOR complex 1, mTOR complex 2, and putative mTOR complex 3. In recent years, increasing evidence has suggested that mTOR plays important roles in the differentiation and immune responses of mesenchymal stem cells (MSCs). In addition, mTOR is a vital regulator of pivotal cellular and physiological functions, such as cell metabolism, survival and ageing, where it has emerged as a novel therapeutic target for ageing-related diseases. Therefore, the mTOR signaling may develop a large impact on the treatment of ageing-related diseases with MSCs. In this review, we discuss prospects for future research in this field.