GPR125 positively regulates osteoclastogenesis potentially through AKT-NF-κB and MAPK signaling pathways

Rhusflavone Modulates Osteoclastogenesis Through RANKL-Induced AKT Signaling in Bone Marrow-Derived Macrophages

Osteoclast differentiation inhibition is a viable treatment strategy for osteoporosis because osteoclasts play a vital role in disease progression. Rhusflavone (Rhus), a biflavonoid, exhibits a sedative-hypnotic effect via the positive allosteric modulation of GABA(A) receptors. Although several biflavonoids possess activities that help prevent bone loss, the potential effects of Rhus on osteoclastogenesis have not been reported yet. In this study, we investigated the effects and underlying biological mechanisms of Rhus isolated from the dried roots of Rhus succedanea on osteoclastogenesis in primary cultured bone marrow-derived macrophages. No cytotoxicity was observed in bone marrow macrophages (BMMs) or during osteoclast differentiation. However, Rhus reduced the number of tartrate-resistant acid phosphatase (TRAP)-positive multinuclear osteoclasts during receptor activator of nuclear factor kappa B ligand (RANKL)-induced osteoclastogenesis. The results of F-actin ring formation demonstrated that Rhus suppresses the bone resorption activity of osteoclasts. Additionally, Rhus inhibits the expression of osteoclast differentiation marker proteins, specifically c-Fos and NF-ATc1. Western blot analysis revealed that Rhus primarily attenuated RANKL-mediated key signaling pathways, particularly the AKT signaling pathway. Furthermore, we found that the AKT activator and inhibitor pharmacologically abolished and enhanced the inhibitory effects of Rhus on osteoclast differentiation, respectively. Taken together, our findings provide evidence that Rhus is a promising biologically active compound that regulates osteoclast differentiation by inhibiting the AKT signaling pathway, which may contribute to future drug development.

Complex G-protein signaling of the adhesion GPCR, ADGRA3

ADGRA3 (GPR125) is an orphan adhesion G protein-coupled receptor (aGPCR) that plays a role in planar cell polarity (PCP), primarily through recruitment of the signaling components Dishevelled (DVL) during vertebrate gastrulation, and Discs large homolog 1 (Dlg1), which is implicated in cancer. Limited knowledge exists of the signaling capacity in the canonical GPCR pathways of ADGRA3. Here, we employed a series of human cell line-based signaling assays to gain insight into the heterotrimeric G protein-mediated signaling of ADGRA3. We based the design of ADGRA3 constructs on analyses of transcript variants in publicly available human liver and brain RNA-seq datasets. As cleavage in the GPCR autoproteolysis site (GPS) is a hallmark for many aGPCRs, we generated a truncated ADGRA3 (C-terminal fragment, CTF) corresponding to a potential cleavage at the GPS. We found low-level activation of Gi and Gs by ADGRA3 and slightly more by its CTF. As the N terminus of the CTF constitutes a class-defined tethered agonist known as the stachel peptide, we removed the initial three amino acids of the CTF. This resulted in abrogated G protein-mediated signaling, as observed for other aGPCRs. Due to the central role of ADGRA3 in PCP signaling through DVL recruitment, we investigated the G-protein signaling in absence of DVL1-3 and found it sustained. No transcriptional activation was observed downstream of β-catenin in an assay reporting T-cell factor/lymphoid enhancer factor (TCF/LEF)-mediated transcriptional activity. Collectively, this establishes a classical G protein-mediated signaling for ADGRA3 in addition to its association with components of non-canonical Wnt-signaling pathways.

NEDD4 family E3 ligases in osteoporosis: mechanisms and emerging potential therapeutic targets

Osteoporosis is a systemic skeletal disorder characterized by reduced bone density and an increased risk of fractures, particularly prevalent in the aging population. Osteoporotic complications, including vertebral compression fractures, hip fractures, and distal forearm fractures, affect over 8.9 million individuals globally, placing a significant economic strain on healthcare systems. Recent advances have expanded our understanding of the mechanisms underlying osteoporosis, particularly the intricate regulatory networks involved in bone metabolism. A central player in these processes is ubiquitin-mediated proteasomal degradation, a crucial post-translational modification system that involves ubiquitin, the ubiquitin-activating enzyme (E1), ubiquitin-conjugating enzyme (E2), ubiquitin ligase (E3), deubiquitinating enzymes, and the proteasome. Among the various E3 ligases, the NEDD4 family has emerged as a key regulator of both bone development and osteoporotic pathology. This review delineates the role of NEDD4 family in osteoporosis and identifies potential drug targets within these pathways, offering insights into novel therapeutic approaches for osteoporosis through targeted intervention.

Denatonium inhibits RANKL-induced osteoclast differentiation and rescues the osteoporotic phenotype by blocking p65 signaling pathway

BACKGROUND

Bone remodeling is a critical process that maintains skeletal integrity, orchestrated by the balanced activities of osteoclasts, which resorb bone, and osteoblasts, which form bone. Osteoclastogenesis, the formation of osteoclasts, is primarily driven by NFATc1, a process activated through c-Fos and NF-κB signaling pathways in response to receptor activator of nuclear factor κB ligand (RANKL). Dysregulation of RANKL signaling is a key contributor to pathological bone loss, as seen in conditions such as osteoporosis.

METHODS

We investigated the effects of denatonium, a known bitter compound, on RANKL-induced osteoclast differentiation. We used RNA sequencing (RNA-seq) to analyze gene expression profiles in osteoclast precursors treated with denatonium. Transcription factor prediction analysis was conducted to identify key targets of denatonium action. Additionally, we performed Western blotting to examine the phosphorylation status of AKT and p65, crucial components of the NF-κB pathway. Chromatin immunoprecipitation (ChIP) assays were employed to assess the binding of p65 to promoter regions of osteoclast-related genes. Finally, we tested the therapeutic potential of denatonium in a mouse model of osteoporosis.

RESULTS

Our findings demonstrated that denatonium significantly inhibited RANKL-induced osteoclastogenesis by targeting the p65 pathway. RNA-seq analysis revealed a downregulation of osteoclast-related genes following denatonium treatment, corroborated by transcription factor prediction analysis, which highlighted p65 as a key target. Denatonium effectively blocked the phosphorylation of AKT and p65, key steps in NF-κB activation. ChIP assays further confirmed that denatonium reduced the enrichment of p65 at promoter regions critical for osteoclast differentiation. In vivo, denatonium treatment in an osteoporosis animal model led to a significant restoration of bone health, demonstrating its potential as a therapeutic agent.

CONCLUSIONS

This study identifies denatonium as an inhibitor of RANKL-induced osteoclast differentiation, potentially acting through suppression of the p65 signaling pathway. The ability of denatonium to downregulate osteoclast-related genes and inhibit key signaling events highlights its potential as a candidate for further investigation in the context of bone loss and osteoporosis.

NQO1 promotes osteogenesis and suppresses angiogenesis in DPSCs via MAPK pathway modulation

BACKGROUND

Influence on stem cells' angiogenesis and osteogenesis of NAD(P)H Quinone Dehydrogenase 1(NQO1) has been established, but its impact on dental pulp stem cells (DPSCs) is unexplored. An important strategy for the treatment of arteriosclerosis is to inhibit calcium deposition and to promote vascular repair and angiogenesis. This study investigated the function and mechanism of NQO1 on angiogenesis and osteogenesis of DPSCs, so as to provide a new ideal for the treatment of arteriosclerosis.

METHODS

Co-culture of human DPSCs and human umbilical vein endothelial cells (HUVECs) was used to detect the angiogenesis ability. Alkaline phosphatase (ALP) activity, alizarin red staining (ARS), and transplantation of HA/tricalcium phosphate with DPSCs were used to detect osteogenesis.

RESULTS

NQO1 suppressed in vitro tubule formation, migration, chemotaxis, and in vivo angiogenesis, as evidenced by reduced CD31 expression. It also enhanced ALP activity, ARS, DSPP expression and osteogenesis and boosted mitochondrial function in DPSCs. CoQ10, an electron transport chain activator, counteracted the effects of NQO1 knockdown on these processes. Additionally, NQO1 downregulated MAPK signaling, which was reversed by CoQ10 supplementation in DPSCs-NQO1sh.

CONCLUSIONS

NQO1 inhibited angiogenesis and promoted the osteogenesis of DPSCs by suppressing MAPK signaling pathways and enhancing mitochondrial respiration.

Unveiling Genetic Potential for Equine Meat Production: A Bioinformatics Approach

In view of the predicted significant increase in global meat production, alternative sources such as horsemeat are becoming increasingly important due to their lower environmental impact and high nutritional value. This study aimed to identify SNP markers on the GeneSeek® Genomic Profiler™ Equine (Neogen, Lansing, MI, USA) that are important for horsemeat production traits. First, orthologous genes related to meat yield in cattle and common genes between horses and cattle within QTLs for body size and weight were identified. Markers for these genes were then evaluated based on predicted variant consequences, GERP scores, and positions within constrained elements and orthologous regulatory regions in pigs. A total of 268 markers in 57 genes related to meat production were analyzed. This resulted in 27 prioritized SNP markers in 22 genes, including notable markers in LCORL, LASP1, IGF1R, and MSTN. These results will benefit smallholder farmers by providing genetic insights for selective breeding that could improve meat yield. This study also supports future large-scale genetic analyses such as GWAS and Genomic Best Linear Unbiased Prediction (GBLUP). The results of this study may be helpful in improving the accuracy of genomic breeding values. However, limitations include reliance on bioinformatics without experimental validation. Future research can validate these markers and consider a wider range of traits to ensure accuracy in equine breeding.

Development of new dehydrocostuslactone derivatives for treatment of atopic dermatitis via inhibition of the NF-κB signaling pathway

Atopic dermatitis (AD), a recurrent inflammatory systemic skin disease, is difficult to cure. In the present study, several ethylenediamine-derived dehydrocostuslactone (DHCL) derivatives were prepared to assess their in vitro and in vivo anti-inflammatory activities. The results indicated that DHCL derivatives inhibited NO generation with low cytotoxicity. In particular, compound 5d exhibited the best anti-inflammatory activity. Subsequent experiments revealed that 5d not only inhibited the LPS-induced inflammatory response in RAW264.7 cells via the MAPK-NF-κB signaling pathway inhibition but also significantly decreased Th2-type cytokine levels and inhibited the NF-κB signaling pathway activation in mice with MC903-induced AD. Therefore, DHCL derivatives may be considered as new agents for the treatment of AD.

High incidence of imperforate vagina in ADGRA3-deficient mice

BACKGROUND

Ten percent of the female population suffers from congenital abnormalities of the vagina, uterus, or oviducts, with severe consequences for reproductive and psychological health. Yet, the underlying causes of most of these malformations remain largely unknown. ADGRA3 (GPR125) is involved in WNT signaling and planar cell polarity, mechanisms vital to female reproductive tract development. Although ADGRA3 is a well-established spermatogonial stem cell marker, its role within the female urogenital system remains unclear.

RESULTS

In this study, we found Adgra3 to be expressed throughout the murine female urogenital system, with higher expression pre-puberty than after sexual maturation. We generated a global Adgra3-/- mouse line and observed imperforate vagina in 44% of Adgra3-/- females, resulting in distension of the reproductive tract and infertility. Ovarian morphology, plasma estradiol, ovarian Cyp19a1, and vaginal estrogen receptor α (Esr1) expression were unaffected. However, compared to controls, a significantly lower bone mineral density was found in Adgra3-/- mice. Whereas vaginal opening in mice is an estrogen-dependent process, 17β-estradiol treatment failed to induce vaginal canalization in Adgra3-/- mice. Furthermore, a marked reduction in vaginal and ovarian progesterone receptor expression was observed concomitant with an upregulation of apoptotic regulators Bcl2, Bid, and Bmf in adult Adgra3-/- females with a closed vagina.

CONCLUSIONS

Our collective results shed new insights into the complex mechanisms by which the adhesion receptor ADGRA3 regulates distal vaginal tissue remodeling during vaginal canalization via altered sex hormone responsiveness and balance in apoptotic regulators. This highlights the potential of ADGRA3 as a target in diagnostic screening and/or therapy for obstructive vaginal malformations in humans.

Cichoric acid targets RANKL to inhibit osteoclastogenesis and prevent ovariectomy-induced bone loss

BACKGROUND AND AIM

Osteoporosis, a systemic metabolic bone disease, is characterized by the decline of bone mass and quality due to excessive osteoclast activity. Currently, drug-targeting osteoclasts show promising therapy for osteoporosis. In this study, we investigated the effect of cichoric acid (CA) on receptor activator of nuclear kappa-B ligand (RANKL)-induced osteoclastogenesis and the bone loss induced by ovariectomy in mice.

EXPERIMENTAL PROCEDURE

Molecular docking technologies were employed to examine the interaction between CA and RANKL. CCK8 assay was used to evaluate the cell viability under CA treatment. TRAcP staining, podosome belt staining, and bone resorption assays were used to test the effect of CA on osteoclastogenesis and osteoclast function. Further, an OVX-induced osteoporosis mice model was employed to identify the effect of CA on bone loss using micro-CT scanning and histological examination. To investigate underlying mechanisms, network pharmacology was applied to predict the downstream signaling pathways, which were verified by Western blot and immunofluorescence staining.

KEY RESULTS

The molecular docking analysis revealed that CA exhibited a specific binding affinity to RANKL, engaging multiple binding sites. CA inhibited RANKL-induced osteoclastogenesis and bone resorption without cytotoxic effects. Mechanistically, CA suppressed RANKL-induced intracellular reactive oxygen species, nuclear factor-kappa B, and mitogen-activated protein kinase pathways, followed by abrogated nuclear factor activated T-cells 1 activity. Consistent with this finding, CA attenuated post-ovariectomy-induced osteoporosis by ameliorating osteoclastogenesis.

CONCLUSIONS AND IMPLICATIONS

CA inhibited osteoclast activity and bone loss by targeting RANKL. CA might represent a promising candidate for treating osteoclast-related diseases, such as osteoporosis.

Genome-wide association study of growth curve parameters reveals novel genomic regions and candidate genes associated with metatarsal bone traits in chickens

The growth and development of chicken bones have an enormous impact on the health and production performance of chickens. However, the development pattern and genetic regulation of the chicken skeleton are poorly understood. This study aimed to evaluate metatarsal bone growth and development patterns in chickens via non-linear models, and to identify the genetic determinants of metatarsal bone traits using a genome-wide association study (GWAS) based on growth curve parameters. Data on metatarsal length (MeL) and metatarsal circumference (MeC) were obtained from 471 F2 chickens (generated by crossing broiler sires, derived from a line selected for high abdominal fat, with Baier layer dams) at 4, 6, 8, 10, and 12 weeks of age. Four non-linear models (Gompertz, Logistic, von Bertalanffy, and Brody) were used to fit the MeL and MeC growth curves. Subsequently, the estimated growth curve parameters of the mature MeL or MeC (A), time-scale parameter (b), and maturity rate (K) from the non-linear models were utilized as substitutes for the original bone data in GWAS. The Logistic and Brody models displayed the best goodness-of-fit for MeL and MeC, respectively. Single-trait and multi-trait GWASs based on the growth curve parameters of the Logistic and Brody models revealed 4 618 significant single nucleotide polymorphisms (SNPs), annotated to 332 genes, associated with metatarsal bone traits. The majority of these significant SNPs were located on Gallus gallus chromosome (GGA) 1 (167.433-176.318 Mb), GGA2 (96.791-103.543 Mb), GGA4 (65.003-83.104 Mb) and GGA6 (64.685-95.285 Mb). Notably, we identified 12 novel GWAS loci associated with chicken metatarsal bone traits, encompassing 35 candidate genes. In summary, the combination of single-trait and multi-trait GWASs based on growth curve parameters uncovered numerous genomic regions and candidate genes associated with chicken bone traits. The findings benefit an in-depth understanding of the genetic architecture underlying metatarsal growth and development in chickens.

CD97 inhibits osteoclast differentiation via Rap1a/ERK pathway under compression

Acceleration of tooth movement during orthodontic treatment is challenging, with osteoclast-mediated bone resorption on the compressive side being the rate-limiting step. Recent studies have demonstrated that mechanoreceptors on the surface of monocytes/macrophages, especially adhesion G protein-coupled receptors (aGPCRs), play important roles in force sensing. However, its role in the regulation of osteoclast differentiation remains unclear. Herein, through single-cell analysis, we revealed that CD97, a novel mechanosensitive aGPCR, was expressed in macrophages. Compression upregulated CD97 expression and inhibited osteoclast differentiation; while knockdown of CD97 partially rescued osteoclast differentiation. It suggests that CD97 may be an important mechanosensitive receptor during osteoclast differentiation. RNA sequencing analysis showed that the Rap1a/ERK signalling pathway mediates the effects of CD97 on osteoclast differentiation under compression. Consistently, we clarified that administration of the Rap1a inhibitor GGTI298 increased osteoclast activity, thereby accelerating tooth movement. In conclusion, our results indicate that CD97 suppresses osteoclast differentiation through the Rap1a/ERK signalling pathway under orthodontic compressive force.

Identification of mitophagy-related biomarkers in human osteoporosis based on a machine learning model

Background: Osteoporosis (OP) is a chronic bone metabolic disease and a serious global public health problem. Several studies have shown that mitophagy plays an important role in bone metabolism disorders; however, its role in osteoporosis remains unclear. Methods: The Gene Expression Omnibus (GEO) database was used to download GSE56815, a dataset containing low and high BMD, and differentially expressed genes (DEGs) were analyzed. Mitochondrial autophagy-related genes (MRG) were downloaded from the existing literature, and highly correlated MRG were screened by bioinformatics methods. The results from both were taken as differentially expressed (DE)-MRG, and Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis were performed. Protein-protein interaction network (PPI) analysis, support vector machine recursive feature elimination (SVM-RFE), and Boruta method were used to identify DE-MRG. A receiver operating characteristic curve (ROC) was drawn, a nomogram model was constructed to determine its diagnostic value, and a variety of bioinformatics methods were used to verify the relationship between these related genes and OP, including GO and KEGG analysis, IP pathway analysis, and single-sample Gene Set Enrichment Analysis (ssGSEA). In addition, a hub gene-related network was constructed and potential drugs for the treatment of OP were predicted. Finally, the specific genes were verified by real-time quantitative polymerase chain reaction (RT-qPCR). Results: In total, 548 DEGs were identified in the GSE56815 dataset. The weighted gene co-expression network analysis(WGCNA) identified 2291 key module genes, and 91 DE-MRG were obtained by combining the two. The PPI network revealed that the target gene for AKT1 interacted with most proteins. Three MRG (NELFB, SFSWAP, and MAP3K3) were identified as hub genes, with areas under the curve (AUC) 0.75, 0.71, and 0.70, respectively. The nomogram model has high diagnostic value. GO and KEGG analysis showed that ribosome pathway and cellular ribosome pathway may be the pathways regulating the progression of OP. IPA showed that MAP3K3 was associated with six pathways, including GNRH Signaling. The ssGSEA indicated that NELFB was highly correlated with iDCs (cor = -0.390, p < 0.001). The regulatory network showed a complex relationship between miRNA, transcription factor(TF) and hub genes. In addition, 4 drugs such as vinclozolin were predicted to be potential therapeutic drugs for OP. In RT-qPCR verification, the hub gene NELFB was consistent with the results of bioinformatics analysis. Conclusion: Mitophagy plays an important role in the development of osteoporosis. The identification of three mitophagy-related genes may contribute to the early diagnosis, mechanism research and treatment of OP.

P7C3 Ameliorates Bone Loss by Inhibiting Osteoclast Differentiation and Promoting Osteogenesis

Bone homeostasis, the equilibrium between bone resorption and formation, is essential for maintaining healthy bone tissue in adult humans. Disruptions of this process can lead to pathological conditions such as osteoporosis. Dual-targeted agents, capable of inhibiting excessive bone resorption and stimulating bone formation, are being explored as a promising strategy for developing new treatments to address osteoporosis. In this study, we investigated the effects of P7C3 on bone remodeling and its potential therapeutic role in osteoporosis treatment in mice. Specifically, P7C3 can remarkably suppress receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclast differentiation in bone marrow macrophages via the Akt-NF-κB-NFATc1 signaling pathway. Additionally, RNA sequencing (RNAseq) analysis revealed that P7C3 promoted osteoblast differentiation and function through the Wnt/β-catenin signaling pathway, thereby enhancing bone formation. Furthermore, μCT analysis and histological examination of bone tissues from P7C3-treated mice showed attenuation of both Ti-induced bone erosion and ovariectomy (OVX)-induced bone loss. These findings suggest that P7C3 may have a novel function in bone remodeling and may be a promising therapeutic agent for the treatment of osteoporosis. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Ubiquitin-specific peptidases: Players in bone metabolism

Osteoporosis is an ageing-related disease, that has become a major public health problem and its pathogenesis has not yet been fully elucidated. Substantial evidence suggests a strong link between overall age-related disease progression and epigenetic modifications throughout the life cycle. As an important epigenetic modification, ubiquitination is extensively involved in various physiological processes, and its role in bone metabolism has attracted increasing attention. Ubiquitination can be reversed by deubiquitinases, which counteract protein ubiquitination degradation. As the largest and most structurally diverse cysteinase family of deubiquitinating enzymes, ubiquitin-specific proteases (USPs), comprising the largest and most structurally diverse cysteine kinase family of deubiquitinating enzymes, have been found to be important players in maintaining the balance between bone formation and resorption. The aim of this review is to explore recent findings highlighting the regulatory functions of USPs in bone metabolism and provide insight into the molecular mechanisms governing their actions during bone loss. An in-deep understanding of USPs-mediated regulation of bone formation and bone resorption will provide a scientific rationale for the discovery and development of novel USP-targeted therapeutic strategies for osteoporosis.

COX-2/PGE2/VEGF signaling promotes ERK-mediated BMSCs osteogenic differentiation under hypoxia by the paracrine action of ECs

Understanding the crosstalk between endothelial cells (ECs) and bone-marrow mesenchymal stem cells (BMSCs) in response to hypoxic environments and deciphering of the underlying mechanisms are of great relevance for better application of BMSCs in tissue engineering. Here, we demonstrated that hypoxia promoted BMSCs proliferation, colony formation, osteogenic markers expression, mineralization, and extracellular signal-regulated protein kinase (ERK) phosphorylation, and that PD98059 (ERK inhibitor) blocked hypoxia-induced osteogenic differentiation. Hypoxia enhanced ECs migration, cyclooxygenase 2 (COX-2) and integrin α_vβ₃ expression, and prostaglandin E₂ (PGE₂), vascular endothelial growth factor (VEGF) secretion. NS398 (selective COX-2 inhibitor) and LM609 (integrin α_vβ₃ specific inhibitor) impaired the ECs response to hypoxia, and exogenous PGE₂ partially reversed the effects of NS398. BMSCs: ECs co-culture under hypoxia upregulated BMSCs osteogenesis and ERK phosphorylation, as well as ECs migration, integrin α_vβ₃ expression, and PGE₂ and VEGF secretion. NS398 (pretreated ECs) lessened PGE₂, VEGF concentrations of the co-culture system. NS398-treated ECs and AH6809 (combined EP1/2 antagonist)/L-798106 (selective EP3 antagonist)/L-161982 (selective EP4 antagonist)/SU5416 [VEGF receptor (VEGFR) inhibitor]-treated BMSCs impaired the co-cultured ECs-induced enhancement of BMSCs osteogenic differentiation. In conclusion, hypoxia enhances BMSCs proliferation and ERK-mediated osteogenic differentiation, and augments the COX-2-dependent PGE₂ and VEGF release, integrin α_vβ₃ expression, and migration of ECs. COX-2/PGE₂/VEGF signaling is involved in intercellular BMSCs: ECs communication under hypoxia.