Structure-based development of an osteoprotegerin-like glycopeptide that blocks RANKL/RANK interactions and reduces ovariectomy-induced bone loss in mice

Stephanine Protects Against Osteoporosis by Suppressing Osteoclastogenesis via Inhibition of the RANKL-RANK Interaction

The interaction between the receptor activator of nuclear factor-κB ligand (RANKL) and its receptor RANK is known to regulate osteoclastogenesis in bone remodelling and has become an important therapeutic target for the treatment of osteoporosis. Stephanine (SA), an isoquinoline aporphine-type alkaloid isolated from Stephania plants, possesses excellent anti-inflammatory effects and can be used for rheumatoid arthritis treatment. However, its specific role in osteoclastogenesis and osteoporosis remains unknown. In this study, we investigated the influence of SA on osteoclastogenesis in RANKL-stimulated RAW 264.7 cells and osteoporosis in an ovariectomised (OVX) mouse model and elucidated the underlying molecular mechanism. In vitro, SA can bind to RANK and RANKL with the KD values of 3.7 and 76.47 μM, respectively, and disrupt the RANKL-RANK interaction, which inhibits RANKL-stimulated RANK-tumour necrosis factor receptor associated factor 6 (TRAF6) binding and RANK signalling pathways activation, downregulates the expression of key osteoclastogenesis-related regulatory factors in osteoclast precursors, ultimately suppresses osteoclast differentiation and activation. In vivo, SA significantly ameliorated bone loss through inhibiting osteoclastogenesis in OVX mice because of the decreased number of osteoclasts and the increased trabecular bone area. SA markedly inhibited the serum levels of tartrate-resistant acid phosphatase 5b (TRACP-5b), c-telopeptide of type I collagen (CTX-I), and RANKL, whereas it increased that of osteoprotegerin (OPG) in OVX mice. Additionally, SA strikingly downregulated the OVX-induced expression of osteoclast-specific genes and proteins. Taken together, this study elucidated that SA can effectively protect against osteoporosis by suppressing osteoclastogenesis via inhibition of the RANKL-RANK interaction, which supports the potential application of SA as a natural therapeutic agent for osteoporosis.

Association of HDL and LDL levels with osteoporosis in rheumatoid arthritis: a retrospective cohort study

OBJECTIVES

A correlation exists between lipids and osteoporosis (OP), as well as between lipids and rheumatoid arthritis (RA). However, lipids, the relationship between RA and OP is still unclear. This study mainly investigates the relationship between lipid levels and OP risk in RA patients.

METHODS

Retrospective collection of RA patient data from July 2017 to May 2022, encompassing baseline demographics, treatment regimens, laboratory results, and bone mineral density (BMD) measurements. Analyses, stratified by BMD subgroups, were conducted using propensity score matching (PSM) based on age, sex, and baseline duration, and binary logistic regression to examine the interplay between lipoprotein levels and other risk factors. The relationship between continuous variables and OP risk was assessed using restricted cubic spline (RCS), followed by a reanalysis of the correlation between varying lipoprotein levels and different factors, segmented according to RCS-determined cutoffs.

RESULTS

The study included 2673 RA patients. Binary logistic regression revealed significant associations between high-density lipoprotein (HDL), low-density lipoprotein (LDL), and RA-OP (p < 0.01). Specifically, HDL emerged as a protective factor against OP (OR = 0.40, 95% CI 0.250-0.629; p < 0.001), whereas LDL was identified as a risk factor (OR = 1.56, 95% CI 1.290-1.890; p < 0.001). Furthermore, HDL (RCS cutoff point 1.28 mmol/L) showed a negative, linear correlation with RA-related OP, while LDL (RCS cutoff point 2.63 mmol/L) demonstrated a positive, linear correlation.

CONCLUSIONS

The levels of HDL and LDL may be indicators of OP occurrence in RA patients.

Design, Synthesis, and Anti-Osteoporotic Characterization of Arginine N-Glycosylated Teriparatide Analogs via the Silver-catalyzed Solid-Phase Glycosylation Strategy

In spite of effective antiosteoporosis potency, teriparatide, a bone-building agent approved by the FDA (Food and Drug Administration), was proven to exhibit various side effects. In our previous work, we developed a universal strategy for synthesizing arginine N-glycosylated peptides termed silver-promoted solid-phase glycosylation (SSG) strategy. However, it is unknown whether the SSG strategy can be applied in the peptide drug design. Herein, we first reported the optimization of teriparatide via SSG strategy. Using Arg20 and/or Arg25 as the modifying positions, three series of arginine N-glycosylated teriparatide analogs were successfully synthesized, of which the introduced sugar groups included glucose, galactose, mannose, rhamnose, ribose, 2-acetamino-2-deoxy-glucose, xylose, lactose, and maltose. Among the 27 arginine N-glycosylated derivatives, Arg20-xylose and Arg25-maltose teriparatide analogs, termed PTH-1g and PTH-2i, respectively, indicated enhanced serum stability and significantly improved antiosteoporotic activities in vitro and in vivo compared with the native counterpart. They may serve as effective therapeutic candidates for treating osteoporosis.

Regulation of bone and fat balance by Fructus Ligustri Lucidi in ovariectomized mice

CONTEXT

Fructus Ligustri Lucidi (FLL), a commonly used herb of traditional Chinese medicine (TCM), is the fruit of Ligustrum lucidum Ait. (Oleaceae). The ethanol extract of FLL is a potential candidate for preventing and treating postmenopausal osteoporosis (PMOP) by nourishing the liver and kidneys.

OBJECTIVE

This study determines whether an ethanol extract of FLL has anti-osteoporotic effects in ovariectomized (OVX) mice and explores the underlying mechanism.

MATERIALS AND METHODS

The OVX model of eight-week-old C57BL/6J female mice was taken, and ovariectomy was used as PMOP. Mice were divided into five groups: sham-operated group (n = 10), OVX group (n = 10), OVX + E₂ group (n = 10; 0.039 mg/kg), OVX + FLL group (n = 10; 2 g/kg) and OVX + FLL group (n = 10; 4 g/kg). Mice were treated by gavage with FLL or CMCNa once daily for 8 weeks. We harvested uteri, femur, and tibias from mice; bone mineral density (BMD) and bone microstructure were obtained by X-ray absorptiometry and micro-CT. Furthermore, the effect of FLL on the balance of osteoblast and adipocyte differentiation was investigated using bone marrow mesenchymal stem cells (BMMSCs).

RESULTS

The results indicated that FLL did not affect OVX-induced estradiol reduction. Compared with OVX mice, FLL significantly increased BMD (63.54 vs. 61.96), Conn. D (86.46 vs. 57.00), and left tibial strength (13.91 vs. 11.27), decreased Tb. Sp (0.38 vs. 0.44) and body fat content (4.19% vs. 11.24%). FLL decreased osteoclast activity and enhanced RUNX2 expression; inhibited perilipin peroxisome proliferator-activated receptor gamma (PPARγ) expression and adipocyte differentiation from BMMSCs.

CONCLUSIONS

FLL prevented additional bone loss and improved bone microstructure in OVX mice by modulating bone and fat balance, suggesting that FLL might be a therapeutic agent for PMOP.

Pharmacological mechanisms of sinomenine in anti-inflammatory immunity and osteoprotection in rheumatoid arthritis: A systematic review

BACKGROUND

Sinomenine (SIN) is the main pharmacologically active component of Sinomenii Caulis and protects against rheumatoid arthritis (RA). In recent years, many studies have been conducted to elucidate the pharmacological mechanisms of SIN in the treatment of RA. However, the molecular mechanism of SIN in RA has not been fully elucidated.

PURPOSE

To summarize the pharmacological effects and molecular mechanisms of SIN in RA and clarify the most valuable regulatory mechanisms of SIN to provide clues and a basis for basic research and clinical applications.

METHODS

We systematically searched SciFinder, Web of Science, PubMed, China National Knowledge Internet (CNKI), the Wanfang Databases, and the Chinese Scientific Journal Database (VIP). We organized our work based on the PRISMA statement and selected studies for review based on predefined selection criteria.

OUTCOME

After screening, we identified 201 relevant studies, including 88 clinical trials and 113 in vivo and in vitro studies on molecular mechanisms. Among these studies, we selected key results for reporting and analysis.

CONCLUSIONS

We found that most of the known pharmacological mechanisms of SIN are indirect effects on certain signaling pathways or proteins. SIN was manifested to reduce the release of inflammatory cytokines such as Tumor necrosis factor-α (TNF-α), Interleukin-6 (IL-6), and IL-1β, thereby reducing the inflammatory response, and apparently blocking the destruction of bone and cartilage. The regulatory effects on inflammation and bone destruction make SIN a promising drug to treat RA. More notably, we believe that the modulation of α7nAChR and the regulation of methylation levels at specific GCG sites in the mPGES-1 promoter by SIN, and its mechanism of directly targeting GBP5, certainly enriches the possibilities and the underlying rationale for SIN in the treatment of inflammatory immune-related diseases.

Niloticin inhibits osteoclastogenesis by blocking RANKL-RANK interaction and suppressing the AKT, MAPK, and NF-κB signaling pathways

Dysregulation of osteoclasts or excessive osteoclastogenesis significantly -contributes to the occurrence and development of osteolytic diseases, including osteoporosis, inflammatory bone erosion, and tumor-induced osteolysis. The protein-protein interaction between the receptor activator of nuclear factor (NF)-κB (RANK) and its ligand (RANKL) mediates the differentiation and activation of osteoclasts, making it a key therapeutic target for osteoclastogenesis inhibition. However, very few natural compounds exerting anti-osteoclastogenesis activity by inhibiting the RANKL-RANK interaction have been found. Niloticin is a natural tetracyclic triterpenoid compound with anti-viral, antioxidative, and mosquitocidal activities. However, its role in osteoclastogenesis remains unknown. The present study found that niloticin directly binds to RANK with an equilibrium dissociation constant of 5.8 μM, blocking RANKL-RANK interaction, thereby inhibiting RANKL-induced AKT, MAPK (p38, JNK, and ERK1/2), and NF-κB (IKKα/β, IκBα, and p65) pathways activation, and reducing the expression of key osteoclast differentiation-related regulatory factors (NFATc1, c-Fos, TRAP, c-Src, β3-Integrin, and cathepsin K) in osteoclast precursors, ultimately negatively regulating osteoclastogenesis. These findings suggest that niloticin could serve as a novel osteoclastogenesis inhibitor and might have beneficial effects on bone health.

PTHG2 Reduces Bone Loss in Ovariectomized Mice by Directing Bone Marrow Mesenchymal Stem Cell Fate

Teriparatide, also known as 1-34 parathyroid hormone (PTH (1-34)), is commonly used for the treatment of osteoporosis in postmenopausal women. But its therapeutic application is restricted by poor metabolic stability, low bioavailability, and rapid clearance. Herein, PTHG2, a glycosylated teriparatide derivative, is designed and synthesized to improve PTH stability and exert more potent antiosteoporosis effect. Surface plasmon resonance (SPR) analysis shows that PTHG2 combines to PTH 1 receptor. Additional acetylglucosamine covalent bonding in the first serine at the N terminal of PTH (1-34) improves stability and increases protein hydrolysis resistance. Intermittent administration of PTHG2 preserves bone quality in ovariectomy- (OVX-) induced osteoporosis mice model, along with increased osteoblastic differentiation and bone formation, and reduced marrow adipogenesis. In vitro, PTHG2 inhibits adipogenic differentiation and promotes osteoblastic differentiation of bone marrow mesenchymal stem cells (BMSCs). For molecular mechanism, PTHG2 directs BMSCs fate through stimulating the cAMP-PKA signaling pathway. Blocking PKA abrogates the pro-osteogenic effect of PTHG2. In conclusion, our study reveals that PTHG2 can accelerate osteogenic differentiation of BMSCs and inhibit adipogenic differentiation of BMSCs and show a better protective effect than PTH (1-34) in the treatment of osteoporosis.

Dencichine prevents ovariectomy-induced bone loss and inhibits osteoclastogenesis by inhibiting RANKL-associated NF-κB and MAPK signaling pathways

AIMS

To investigate the effect of dencichine on osteoclastogenesis in vivo and in vitro.

METHODS

RANKL-induced osteoclastogenesis were treated with different concentrations of dencichine. Pit forming assays were applied to evaluate the degree of bone resorption. Osteoclastogenic markers were detected by real-time quantitative PCR (RT-qPCR) and Western blot. Micro CT was conducted to investigate the effects of dencichine on osteoclastogenesis in ovariectomized (OVX) mice.

RESULTS

Dencichine suppressed osteoclastogenesis through the inhibition of phosphorylation of p65, p50 (NF-κB pathway), p38, ERK and JNK (MAPKs pathway) in vitro. Furthermore, dencichine inhibited the function of osteoclasts in a dose-dependent manner. In addition, the expression levels of the nuclear factor of activated T cells 1 (NFATc1) and osteoclastogenesis markers were decreased by dencichine, including MMP-9, Cathepsin K (CTSK), Tartrate-Resistant Acid Phosphatase (TRAP), C-FOS, dendritic cell specific transmembrane protein (DC-STAMP). In vivo data proved that dencichine alleviated ovariectomy-induced bone loss and osteoclastogenesis in mice.

CONCLUSION

Our results demonstrate that dencichine alleviates OVX-induced bone loss in mice and inhibits RANKL-mediated osteoclastogenesis via inhibition of NF-κB and MAPK pathways in vitro, suggesting that dencichine might serve as a promising candidate for treatment of bone loss diseases, including PMOP and rheumatoid arthritis.

(-)-Epigallocatechin-3-gallate inhibits osteoclastogenesis by blocking RANKL-RANK interaction and suppressing NF-κB and MAPK signaling pathways

Consuming green tea has many health benefits, including regulating bone metabolism and ameliorating osteoporosis, mainly in older and postmenopausal women. This osteoprotective effect has been attributed to the biologically active polyphenol (-)-epigallocatechin-3-gallate (EGCG). Although EGCG inhibits osteoclastogenesis, its underlying molecular mechanism remains to be elucidated. Interaction between receptor activator of nuclear factor (NF)-κB ligand (RANKL) and RANK plays critical roles in the differentiation and activation of osteoclasts and is therefore considered a therapeutic target for osteoclast-related diseases such as osteoporosis. In the present study, we found that EGCG can bind directly to RANK and RANKL and interfere with their interaction, thereby suppressing RANKL-induced phosphorylation of IKKα/β, IκBα, p65, JNK, ERK1/2, and p38 and key downstream regulatory factors, including nuclear factor of activated T cell c1 (NFATc1), c-Fos, tartrate-resistant acid phosphatase (TRAP), c-Src, and cathepsin K, in osteoclast precursors. This can ultimately inhibit osteoclastogenesis. Taken together, our results show that EGCG can bind directly to RANK and RANKL and block their interaction and that, by inhibiting NF-κB and mitogen-activated protein kinase (MAPK) signaling pathways, it negatively regulates RANKL-induced osteoclastogenesis in RAW 264.7 cells. Thus, regular consumption of EGCG in green tea can inhibit the development and progression of osteoclast-related diseases.

Design, synthesis, and anti-tumor activities of novel Brevinin-1BYa peptidomimetics

Brevinin-1BYa is an amphibian skin-derived peptide that exhibits promising anti-microbial activity against gram-positive and -negative bacteria. However, the anti-tumor activity of Brevinin-1BYa remains unclear, and, more importantly, its therapeutic application is limited owing to its poor protease and reduction stability. In this study, a series of novel Brevinin-1BYa derivatives, including O-linked N-acetyl-glucosamine glyclopeptides and disulfide bond mimetics, were designed and synthesized. Additionally, their anti-tumor activity against human prostate cancer cell line C4-2B, human NSCLC cell line A549 (adenocarcinoma), and human hepatoma cells line HuH-7 was investigated. Among these, the thioether bridge substituted peptidomimetic Brevinin-1BYa-3 displayed improved reduction stability, more stable secondary structure, greater protease stability, and increased anti-tumor activity compared with the original peptide, rendering it a promising leading compound for drug development, particularly for applications against malignant tumors.

Ellagic acid blocks RANKL-RANK interaction and suppresses RANKL-induced osteoclastogenesis by inhibiting RANK signaling pathways

Ellagic acid (EA) is a naturally occurring polyphenolic compound that has been shown to exhibit diverse beneficial pharmacological activities including anti-osteoclastogenesis effect. However, the molecular mechanism by which EA inhibits osteoclastogenesis remains to be elucidated. The protein-protein interaction between receptor activator of nuclear factor (NF)-κB ligand (RANKL) and its receptor RANK contributes to osteoclast differentiation and activation in bone remodeling, and is regarded as an important therapeutic target for the treatment of osteoporosis. The current study is focused on investigating whether EA can directly bind to RANKL and/or RANK and block the interaction between RANKL and RANK, thereby inhibiting downstream signaling pathways. Interestingly, we found that EA had strong affinities to RANK and RANKL, with the estimated equilibrium dissociation constants (K_D) of 2.485 × 10^-11 and 1.688 × 10^-9 M, respectively, and could disrupt the interaction between RANKL and RANK, thereby inhibiting RANKL-induced canonical RANK signaling pathways (p65, JNK, ERK, and p38) and expression of downstream master transcriptional factors (NFATc1 and c-Fos) and osteoclast-specific genes and proteins (TRAP, c-Src, and cathepsin K), which could ultimately suppress RANKL-induced osteoclast differentiation and F-actin ring formation. Taken together, our results revealed that EA could block RANKL-RANK interaction and suppress RANKL-induced osteoclastogenesis by inhibiting RANK signaling pathways in RAW 264.7 murine macrophages.

Effects of Glycosylation and d-Amino Acid Substitution on the Antitumor and Antibacterial Activities of Bee Venom Peptide HYL

Glycosylation is a promising strategy for modulating the physicochemical properties of peptides. However, the influence of glycosylation on the biological activities of peptides remains unknown. Here, we chose the bee venom peptide HYL as a model peptide and 12 different monosaccharides as model sugars to study the effects of glycosylation site, number, and monosaccharide structure on the biochemical properties, activities, and cellular selectivities of HYL derivatives. Some analogues of HYL showed improvement not only in cell selectivity and proteolytic stability but also in antitumor and antimicrobial activity. Moreover, we found that the helicity of glycopeptides can affect its antitumor activity and proteolytic stability, and the α-linked d-monosaccharides can effectively improve the antitumor activity of HYL. Therefore, it is possible to design peptides with improved properties by varying the number, structure, and position of monosaccharides. What's more, the glycopeptides HYL-31 and HYL-33 show a promising prospect for antitumor and antimicrobial drugs development, respectively. In addition, we found that the d-lysine substitution strategy can significantly improve the proteolytic stability of HYL. Our new approach provides a reference or guidance for the research of novel antitumor and antimicrobial peptide drugs.

Synthesis and anti-osteoporosis activity of novel Teriparatide glycosylation derivatives

Osteoporosis is a metabolic bone disease that is characterized by low bone mass and micro-architectural deterioration of bones. The mechanism underlying this disease implicates an imbalance between bone resorption and bone remodeling. In 2002, the US Food and Drug Administration (FDA) approved Teriparatide for the treatment of osteoporosis, and so far, this compound is the only permitted osteoanabolic. However, as a structurally flexible linear peptide, this drug may be further optimized. In this study, we develop a series of novel N-acetyl glucosamine glycosylation derivatives of Teriparatide and examine their characteristics. Of the analyzed compounds, PTHG-9 exhibits enhanced helicity, greater protease stability, and increased osteoblast differentiation promoting ability compared with the original Teriparatide. Accordingly, PTHG-9 is suggested as a therapeutic candidate for postmenopausal osteoporosis (PMOP) and other related diseases. The successful development of an enhanced osteoporosis drug proves that the method proposed herein can be used to effectively enhance the chemical and biological properties of linear peptides with various biological functions.

Guaiacol suppresses osteoclastogenesis by blocking interactions of RANK with TRAF6 and C-Src and inhibiting NF-κB, MAPK and AKT pathways

Angelica sinensis (AS; Dang Gui), a traditional Chinese herb, has for centuries been used for the treatment of bone diseases, including osteoporosis and osteonecrosis. However, the effective ingredient and underlying mechanisms remain elusive. Here, we identified guaiacol as the active component of AS by two‐dimensional cell membrane chromatography/C18 column/time‐of‐flight mass spectrometry (2D CMC/C18 column/TOFMS). Guaiacol suppressed osteoclastogenesis and osteoclast function in bone marrow monocytes (BMMCs) and RAW264.7 cells in vitro in a dose‐dependent manner. Co‐immunoprecipitation indicated that guaiacol blocked RANK‐TRAF6 association and RANK‐C‐Src association. Moreover, guaiacol prevented phosphorylation of p65, p50, IκB (NF‐κB pathway), ERK, JNK, c‐fos, p38 (MAPK pathway) and Akt (AKT pathway), and reduced the expression levels of Cathepsin K, CTR, MMP‐9 and TRAP. Guaiacol also suppressed the expression of nuclear factor of activated T‐cells cytoplasmic 1(NFATc1) and the RANKL‐induced Ca²⁺ oscillation. In vivo, it ameliorated ovariectomy‐induced bone loss by suppressing excessive osteoclastogenesis. Taken together, our findings suggest that guaiacol inhibits RANKL‐induced osteoclastogenesis by blocking the interactions of RANK with TRAF6 and C‐Src, and by suppressing the NF‐κB, MAPK and AKT signalling pathways. Therefore, this compound shows therapeutic potential for osteoclastogenesis‐related bone diseases, including postmenopausal osteoporosis.

Longitudinal evaluation of Wnt inhibitors and comparison with others serum osteoimmunological biomarkers in osteolytic bone metastasis

Bone and the immune system are closely linked: bone regulates the hematopoietic stem cells, which are precursors of immune cells, and several immunoregulatory cytokines influence the differentiation of bone cells, thus defining the osteoimmunological system. Cytokines and growth factors produced by immune and bone cells promote tumors in bone, supporting the vicious cycle of bone metastasis. Therefore osteoimmunological molecules linking the immune and bone systems could have diagnostic and prognostic potential for bone metastases. The osteoimmunologic Wnt pathway has been recently described as an important pathway with a vital role in bone carcinogenesis and metastatic progression. We examined the Wnt inhibitor DKK-1, sclerostin and several other osteoimmunological biomarkers involved in bone metastatic progression: RANKL, OPG, OPN, matrix metalloproteinase MMP-3 and the Receptor of Advanced Glycosylated End-products sRAGE. OPN and sclerostin proved good biomarkers of metastatic bone progression; the RANKL/OPG ratio was a good indicator of bone erosion in the metastatic process, while sRAGE had a protective role against metastatic progression in bone. These results serve to define a panel of new osteoimmunological biomarkers that could be useful in assessing the progress of osteolytic bone metastases.

Tetrandrine Prevents Bone Loss in Ovariectomized Mice by Inhibiting RANKL-Induced Osteoclastogenesis

Postmenopausal osteoporosis (PMOP) is a metabolic bone disease characterized by decreased bone density and strength due to the imbalance between osteogenesis and osteoclastogenesis. Postmenopausal estrogen withdrawal increases proinflammatory cytokines and increases the serum level of Receptor activator of NF-kB ligand (RANKL)/Osteoprotegerin (OPG), which then leads to the overactivation of osteoclastogenesis. Tetrandrine, a bis-benzylisoquinoline alkaloid, has been widely used in the treatment of rheumatoid arthritis clinically in China. Here, we demonstrate that tetrandrine significantly prevented ovariectomy-induced bone loss and inhibited RANKL-induced osteoclastogenesis. In vivo, we found that intraperitoneal injection of tetrandrine (30 mg/kg) every other day markedly reduced bone loss in ovariectomized mice and the serum levels of TRAcp5b, TNF-a, IL-6, CTX-I, and RANKL/OPG were significantly decreased. In vitro, we found that tetrandrine significantly inhibited osteoclast differentiation in bone marrow monocytes (BMMs) and RAW264.7 cells according to the results of osteoclastogenesis-related gene expression, tartrate-resistant acid phosphatase (TRAP) staining and actin-ring formation as well as bone resorption assay. Mechanistically, tetrandrine inhibited RANKL-induced osteoclastogenesis by suppressing NF-kB, Ca2⁺, PI3K/AKT, and MAPKs signaling pathways. Taken together, our findings suggest that tetrandrine suppresses osteoclastogenesis through modulation of multiple pathways and has potential value as a therapeutic agent for PMOP, especially for those suffering from RA and PMOP at the same time.

l-tetrahydropalmatine suppresses osteoclastogenesis in vivo and in vitro via blocking RANK-TRAF6 interactions and inhibiting NF-κB and MAPK pathways

Bone homeostasis is delicately orchestrated by osteoblasts and osteoclasts. Various pathological bone loss situations result from the overactivated osteoclastogenesis. Receptor activator of nuclear factor κB ligand (RANKL)-activated NF-κB and MAPK pathways is vital for osteoclastogenesis. Here, we for the first time explored the effects of l-tetrahydropalmatine (l-THP), an active alkaloid derived from corydalis, on the formation and function of osteoclasts in vitro and in vivo. In RAW264.7 cells and bone marrow monocytes cells (BMMCs), l-THP inhibited osteoclastic differentiation at the early stage, down-regulated transcription level of osteoclastogenesis-related genes and impaired osteoclasts functions. Mechanically, Western blot showed that l-THP inhibited the phosphorylation of P50, P65, IκB, ERK, JNK and P38, and the electrophoretic mobility shift assay (EMSA) revealed that DNA binding activity of NF-κB was suppressed, ultimately inhibiting the expression of nuclear factor of activated T cells (NFATc1). Besides, Co-immunoprecipitation indicated that l-THP blocked the interactions of RANK and TNF receptor associated factor 6 (TRAF6) at an upstream site. In vivo, l-THP significantly inhibited ovariectomy-induced bone loss and osteoclastogenesis in mice. Collectively, our study demonstrated that l-THP suppressed osteoclastogenesis by blocking RANK-TRAF6 interactions and inhibiting NF-κB and MAPK pathways. l-THP is a promising agent for treating osteoclastogenesis-related diseases such as post-menopausal osteoporosis.

pDobz/pDobb protected diaminodiacid as a novel building block for peptide disulfide-bond mimic synthesis

The diaminodiacid strategy has been widely studied in the chemical synthesis of peptide disulfide bond mimics. Diaminodiacid building blocks, which are key intermediates, are currently under the spotlight. However, one technical bottleneck inherent in existing building blocks is the contamination problem caused by the heavy metal reagents during the deprotection process, which makes the peptides less suitable for pharmaceutical use. Herein, we describe the successful development of a p-dihydroxyborylbenzyloxycarbonyl pinacol ester (pDobz)- and p-dihydroxyborylbenzyl pinacol ester (pDobb)-based novel diaminodiacid building block that can be easily deprotected via mild treatment with amine oxide. Its efficiency and practicability were also confirmed by the total synthesis of contryphan-Vn disulfide bond mimic. The results suggested that this novel diaminodiacid building block has satisfactory Fmoc SPPS compatibility, yet only required a facile, rapid, and metal-free deprotection process. We believe this novel diaminodiacid building block could promote further development of the diaminodiacid strategy.

The total synthesis of a contryphan-Vn disulfide bond mimic utilizing a novel pDobz/pDobb based diaminodiacid building block via the diaminodiacid strategy.

Epigenetic Control of Mesenchymal Stem Cell Fate Decision via Histone Methyltransferase Ash1l

Previous research indicates that knocking out absent, small, or homeotic-like (Ash1l) in mice, a histone 3 lysine 4 (H3K4) trimethyltransferase, can result in arthritis with more severe cartilage and bone destruction. Research has documented the essential role of Ash1l in stem cell fate decision such as hematopoietic stem cells and the progenitors of keratinocytes. Following up on those insights, our research seeks to document the function of Ash1l in skeletal formation, specifically whether it controls the fate decision of mesenchymal progenitor cells. Our findings indicate that in osteoporotic bones, Ash1l was significantly decreased, indicating a positive correlation between bone mass and the expression of Ash1l. Silencing of Ash1l that had been markedly upregulated in differentiated C3H10T1/2 (C3) cells hampered osteogenesis and chondrogenesis but promoted adipogenesis. Consistently, overexpression of an Ash1l SET domain-containing fragment 3 rather than Ash1lΔN promoted osteogenic and chondrogenic differentiation of C3 cells and simultaneously inhibited adipogenic differentiation. This indicates that the role of Ash1l in regulating the differentiation of C3 cells is linked to its histone methyltransferase activity. Subcutaneous ex vivo transplantation experiments confirmed the role of Ash1l in the promotion of osteogenesis. Further experiments proved that Ash1l can epigenetically affect the expression of essential osteogenic and chondrogenic transcription factors. It exerts this impact via modifications in the enrichment of H3K4me3 on their promoter regions. Considering the promotional action of Ash1l on bone, it could potentially prompt new therapeutic strategy to promote osteogenesis. Stem Cells 2019;37:115-127.

18β-Glycyrrhetinic Acid Inhibits Osteoclastogenesis In Vivo and In Vitro by Blocking RANKL-Mediated RANK-TRAF6 Interactions and NF-κB and MAPK Signaling Pathways

Bone metabolism is determined by a delicate balance between bone resorption by osteoclasts and bone formation by osteoblasts. The imbalance due to over-activated osteoclasts plays an important role in various diseases. Activation of NF-κB and MAPK signaling pathways by receptor activator of nuclear factor -κB ligand (RANKL) is vital for osteoclastogenesis. Here, we for the first time explored the effects of 18β-glycyrrhetinic acid (18β-GA), a pentacyclic triterpenoid found in the Glycyrrhiza glabra L roots, on RANKL-induced osteoclastogenesis, osteoclast functions and signaling pathways in vitro and in vivo. In bone marrow monocytes (BMMs) and RAW264.7 cells, 18β-GA inhibited osteoclastogenesis, decreased expression of TRAP, cathepsin K, CTR and MMP-9, blocked actin ring formation and compromised osteoclasts functions in a dose-dependent manner at an early stage with minimal effects on osteogenic and adipogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). For underlying molecular mechanisms, 18β-GA inhibited RANKL-induced phosphorylation of p65, p50, and IκB, blocked p65 nuclear translocation and decreased the DNA-binding activity of NF-κB. Besides, 18β-GA inhibited the activation of the MAPK pathways. Co-immunoprecipitation showed that 18β-GA treatment blocked RANK-TRAF6 association at an upstream site. In vivo, 18β-GA treatment inhibited ovariectomy-induced osteoclastogenesis and reduced bone loss in mice. Overall, our results demonstrated that 18β-GA inhibited RANKL-induced osteoclastogenesis by inhibiting RANK expression in preosteoclasts and blocking the binding of RANK and TRAF6 which lead to the inhibition of NF-κB and MAPK signaling pathways. 18β-GA is a promising novel candidate in the treatment of osteoclast-related diseases such as postmenopausal osteoporosis.