Celastrol regulates bone marrow mesenchymal stem cell fate and bone-fat balance in osteoporosis and skeletal aging by inducing PGC-1α signaling

Celastrol alleviates diabetic vascular injury via Keap1/Nrf2-mediated anti-inflammation

Introduction: Celastrol (Cel) is a widely used main component of Chinese herbal medicine with strong anti-inflammatory, antiviral and antitumor activities. In the present study, we aimed to elucidate the cellular molecular protective mechanism of Cel against diabetes-induced inflammation and endothelial dysfunction. Methods: Type 2 diabetes (T2DM) was induced by db/db mice, and osmotic pumps containing Cel (100 μg/kg/day) were implanted intraperitoneally and were calibrated to release the drug for 28 days. In addition, human umbilical vein endothelial cells (HUVECs) were cultured in normal or high glucose and palmitic acid-containing (HG + PA) media in the presence or absence of Cel for 48 h. Results: Cel significantly ameliorated the hyperglycemia-induced abnormalities in nuclear factor (erythroid-derived 2)-like protein 2 (Nrf2) pathway activity and alleviated HG + PA-induced oxidative damage. However, the protective effect of Cel was almost completely abolished in HUVECs transfected with short hairpin (sh)RNA targeting Nrf2, but not by nonsense shRNA. Furthermore, HG + PA reduced the phosphorylation of AMP-activated protein kinase (AMPK), the autophagic degradation of p62/Kelch-like ECH-associated protein 1 (Keap1), and the nuclear localization of Nrf2. However, these catabolic pathways were inhibited by Cel treatment in HUVECs. In addition, compound C (AMPK inhibitors) and AAV9-sh-Nrf2 reduced Cel-induced Nrf2 activation and angiogenesis in db/db mice. Discussion: Taking these findings together, the endothelial protective effect of Cel in the presence of HG + PA may be at least in part attributed to its effects to reduce reactive oxygen species (ROS) and inflammation through p62/Keap1-mediated Nrf2 activation.

YAP/TAZ as Molecular Targets in Skeletal Muscle Atrophy and Osteoporosis

Skeletal muscles and bones are closely connected anatomically and functionally. Age-related degeneration in these tissues is associated with physical disability in the elderly and significantly impacts their quality of life. Understanding the mechanisms of age-related musculoskeletal tissue degeneration is crucial for identifying molecular targets for therapeutic interventions for skeletal muscle atrophy and osteoporosis. The Hippo pathway is a recently identified signaling pathway that plays critical roles in development, tissue homeostasis, and regeneration. The Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) are key downstream effectors of the mammalian Hippo signaling pathway. This review highlights the fundamental roles of YAP and TAZ in the homeostatic maintenance and regeneration of skeletal muscles and bones. YAP/TAZ play a significant role in stem cell function by relaying various environmental signals to stem cells. Skeletal muscle atrophy and osteoporosis are related to stem cell dysfunction or senescence triggered by YAP/TAZ dysregulation resulting from reduced mechanosensing and mitochondrial function in stem cells. In contrast, the maintenance of YAP/TAZ activation can suppress stem cell senescence and tissue dysfunction and may be used as a basis for the development of potential therapeutic strategies. Thus, targeting YAP/TAZ holds significant therapeutic potential for alleviating age-related muscle and bone dysfunction and improving the quality of life in the elderly.

Deciphering aging-associated molecular mechanisms in bone marrow derived hematopoietic stem cells in the elderly using NGS data

Aging is a complex process that is not yet fully understood. Despite advancements in research, a deeper understanding of the underlying biological mechanisms is necessary to develop interventions that promote healthy longevity. The aim of this study was to elucidate the complex mechanisms associated with healthy aging and longevity in healthy elderly individuals. The RNA sequencing (RNA-seq) data used in this study was obtained from the Gene Expression Omnibus (GEO) database (accession number GSE104406), which was collected from Fluorescent Activated Cell Sorting (FACS) of human bone marrow derived human hematopoietic stem cells (BM-HSCs) (Lineage-, CD34+, CD38-) young (18-30 years old) and aged (65-75 years old) donors who had no known hematological malignancy, with 10 biological replicates per group. The GEO RNA-seq Experiments Interactive Navigator (GREIN) software was used to obtain raw gene-level counts and filtered metadata for this dataset. Next generation knowledge discovery (NGKD) tools provided by BioJupies were used to obtain differentially regulated pathways, gene ontologies (GO), and gene signatures in the BM-HSCs. Finally, the L1000 Characteristic Direction Signature Search Engine (L1000CDS2) tool was used to identify specific drugs that reverse aging-associated gene signatures in old but healthy individuals. The down-regulation of signaling pathways such as longevity regulation, proteasome, Notch, apoptosis, nuclear factor kappa B (NFkB), and peroxisome proliferator-activated receptors (PPAR) signaling pathways in the BM-HSCs of healthy elderly. GO functions related to negative regulation of bone morphogenetic protein (BMP), telomeric DNA binding, nucleoside binding, calcium -dependent protein binding, chromatin-DNA binding, SMAD binding, and demethylase activity were significantly downregulated in the BM-HSCs of the elderly compared to the healthy young group. Importantly, potential drugs such as salermide, celestrol, cercosporin, dorsomorphin dihydrochloride, and LDN-193189 monohydrochloride that can reverse the aging-associated signatures in HSCs from healthy elderly were identified. The analysis of RNA-seq data based on NGKD techniques revealed a plethora of differentially regulated pathways, gene ontologies, and drugs with anti-aging potential to promote healthspan in the elderly.

Coenzyme Q10 Protects Against Hyperlipidemia-Induced Osteoporosis by Improving Mitochondrial Function via Modulating miR-130b-3p/PGC-1α Pathway

In hyperlipidemia-induced osteoporosis, bone marrow mesenchymal stem cells (BMSCs) differentiate into more adipocytes than osteoblasts, leading to decreased bone formation. It is vital to elucidate the effects of hyperlipidemia on bone metabolism and seek new agents that regulate adipocyte-osteoblast lineage allocation. CoQ10, a rate-limiting coenzyme of the mitochondrial respiratory chain, has been reported to decrease oxidative stress and lipid peroxidation by functioning as a mitochondrial antioxidant. However, its effect on hyperlipidemia-induced osteoporosis remains unknown. Here, we analyzed the therapeutic mechanisms of CoQ10 on hyperlipidemia-induced osteoporosis by using high-fat diet (HFD)-treated ApoE-/- mice or oxidized low-density lipoprotein (ox-LDL)-treated BMSCs. The serum lipid levels were elevated and bone formation-related markers were decreased in HFD-treated ApoE-/- mice and ox-LDL-treated BMSCs, which could be reversed by CoQ10. Additionally, PGC-1α protein expression was decreased in HFD-treated ApoE-/- mice and ox-LDL-treated BMSCs, accompanied by mitochondrial dysfunction, decreased ATP content and overgeneration of reactive oxygen species (ROS), which could also be antagonized by CoQ10. Furthermore, PGC-1α knockdown in vitro promoted ROS generation, BMSC apoptosis, and adipogenic differentiation while attenuating osteogenic differentiation in BMSCs. Mechanistically, it suggested that the expression of PGC1-α protein was increased with miR-130b-3p inhibitor treatment in osteoporosis under hyperlipidemia conditions to improve mitochondrial function. Collectively, CoQ10 alleviates hyperlipidemia-induced osteoporosis in ApoE-/- mice and regulates adipocyte-osteoblast lineage allocation. The possible underlying mechanism may involve the improvement of mitochondrial function by modulating the miR-130b-3p/PGC-1α pathway.

Mechanistic study of the Aldo-keto reductase family 1 member A1 in regulating mesenchymal stem cell fate decision toward adipogenesis and osteogenesis

AIMS

Akr1A1 is a glycolytic enzyme catalyzing the reduction of aldehyde to alcohol. This study aims to delineate the role of Akr1A1 in regulating the adipo-osteogenic lineage differentiation of mesenchymal stem cells (MSCs).

MAIN METHODS

MSCs derived from human bone marrow and Wharton Jelly together with gain- and loss-of-function analysis as well as supplementation with the S-Nitrosoglutathione reductase (GSNOR) inhibitor N6022 were used to study the function of Akr1A1 in controlling MSC lineage differentiation into osteoblasts and adipocytes.

KEY FINDINGS

Akr1A1 expression, PKM2 activity, and lactate production were found to be decreased in osteoblast-committed MSCs, but PGC-1α increased to induce mitochondrial oxidative phosphorylation. Increased Akr1A1 inhibited the SIRT1-dependent pathway for decreasing the expressions of PGC-1α and TAZ but increasing PPAR γ in adipocyte-committed MSCs, hence promoting glycolysis in adipogenesis. In contrast, Akr1A1 expression, PKM2 activity and lactate production were all increased in adipocyte-differentiated cells with decreased PGC-1α for switching energy utilization to glycolytic metabolism. Reduced Akr1A1 expression in osteoblast-committed cells relieves its inhibition of SIRT1-mediated activation of PGC-1α and TAZ for facilitating osteogenesis and mitochondrial metabolism.

SIGNIFICANCE

Several metabolism-involved regulators including Akr1A1, SIRT1, PPARγ, PGC-1α and TAZ were differentially expressed in osteoblast- and adipocyte-committed MSCs. More importantly, Akr1A1 was identified as a new key regulator for controlling the MSC lineage commitment in favor of adipogenesis but detrimental to osteogenesis. Such information should be useful to develop perspective new therapeutic agents to reverse the adipo-osteogenic differentiation of BMSCs, in a way to increase in osteogenesis but decrease in adipogenesis.

Association between clinical use of nifedipine and the risk of osteoporosis: a nationwide retrospective cohort study

Nifedipine is one of the common calcium channel blockers (CCBs) for hypertension that induce peroxisome-proliferator-activated receptor γ coactivator 1-α, which is envisioned as a potential therapeutic target in bone disease. The findings of this retrospective cohort study suggest that patients who receive nifedipine may have a potential protective effect on osteoporosis in comparison to other CCBs.

INTRODUCTION

Nifedipine was one L-type dihydropyridine calcium channel blocker (CCB) that can improve bone loss. However, epidemiological studies on the association between the use of nifedipine and osteoporosis risk are limited. Thus, this study aimed to evaluate the association between the clinical use of nifedipine and the risk of osteoporosis.

METHODS

This retrospective cohort was conducted using the National Health Insurance Research Database of Taiwan from 2000 to 2013. The study includes 1225 patients receiving nifedipine (the exposed cohort) and 4900 patients receiving other CCBs (the comparison cohort). The primary outcome was the diagnosis of osteoporosis. The hazard ratios (HRs) and 95% confidence intervals (CIs) were used to assess the association between the use of nifedipine and the risk of osteoporosis.

RESULTS

Patients receiving nifedipine treatment had a reduced risk of osteoporosis as compared with those undergoing other CCB treatments (adjusted HR, 0.44; 95% CI, 0.37-0.53). Moreover, this inverse association is evident in both sexes and various age groups.

CONCLUSIONS

This population-based cohort study demonstrated that nifedipine may have potential protective effect on osteoporosis compared with other CCBs. The clinical implications of the present study need further investigation.

Hydroxysafflor Yellow A-Induced Osteoblast Differentiation and Proliferation of BM-MSCs by Up-Regulating Nuclear Vitamin D Receptor

BACKGROUND

Vitamin D receptor (VDR) is critical for mineral and bone homeostasis since it plays an essential role in the osteoblast differentiation of bone marrow mesenchymal stem cells (BM-MSCs). Hydroxysafflor yellow A (HSYA) has the potential to promote bone mineralization and inhibit bone resorption, while its detailed mechanism needs to be elaborated.

OBJECTIVE

This study intends to explore the action of HSYA on the proliferation and differentiation of BM-MSC and the underlying mechanism.

METHODS

Different concentrations of HSYA to BM-MSC and CCK-8, and EdU were used to detect cell viability and proliferation. The alkaline phosphatase (ALP) was used to observe the differentiation ability of BM-MSC osteoblasts. The calcium uptake and mineralization of osteoblast-like cells were observed by alizarin red staining. The level of calcium ion uptake in cells was detected by flow cytometry. AutoDock was performed for molecular docking of HSYA to VDR protein. Immunofluorescence and western blotting were performed to detect the expression of VDR expression levels. Finally, the effect of VDR was verified by a VDR inhibitor.

RESULTS

After treatment with HSYA, the proliferation and calcium uptake of BM-MSC were increased. The level of ALP increased significantly and reached its peak on the 12th day. HSYA promoted calcium uptake and calcium deposition, and mineralization of osteoblasts. The western blotting and immunofluorescence showed that HSYA increased the expression of VDR in the osteoblast-like cell's nucleus and upregulated Osteocalcin, S100 calcium-binding protein G, and CYP24A1. In addition, HYSA treatment increased the expression of osteopontin and the synthesis of osteogenic proteins, such as Type 1 collagen. After the addition of the VDR inhibitor, the effect of HSYA was weakened.

CONCLUSION

HSYA could significantly promote the activity and proliferation of osteoblasts and increase the expression level of VDR in osteoblasts. HSYA may also improve calcium absorption by osteoblasts by regulating the synthesis of calciumbinding protein and vitamin D metabolic pathway-related proteins.

A mechanistic review of chinese medicine polyphenols on bone formation and resorption

Bone reconstruction includes a steady state system of bone formation and bone absorption. This tight coupling requires subtle coordination between osteoblasts and osteoclasts. If this balance is broken, it will lead to bone mass loss, bone density reduction, and bone metabolic diseases, such as osteoporosis. Polyphenols in Chinese herbal medicines are active ingredients in plant extracts with high safety and few side effects, and they can play a role in affecting bone formation and bone resorption. Some of these have estrogen-like effects and can better target bone health in postmenopausal women. The purpose of this review is to provide comprehensive information on the mechanisms underlying the relationship between traditional Chinese medicine polyphenols and bone formation or bone resorption.

Sex-specific differences in direct osteoclastic versus indirect osteoblastic effects underlay the low bone mass of Pannexin1 deletion in TRAP-expressing cells in mice

Pannexin1 (Panx1) is a hemichannel-forming protein that participates in the communication of cells with the extracellular space. To characterize the role of osteoclastic Panx1 on bone, Panx1fl/fl;TRAP-Cre (Panx1ΔOc) mice were generated, and compared to Panx1fl/fl littermates at 6 weeks of age. Total and femoral BMD was ~20% lower in females and males whereas spinal BMD was lower only in female Panx1ΔOc mice. μCT analyses showed that cortical bone of the femoral mid-diaphysis was not altered in Panx1ΔOc mice. In contrast, cancellous bone in the distal femur and lumbar vertebra was significantly decreased in both female and male Panx1ΔOc mice compared to Panx1fl/fl controls and was associated with higher osteoclast activity in female Panx1ΔOc mice, with no changes in the males. On the other hand, vertebral bone formation was decreased for both sexes, resulting from lower mineral apposition rate in the females and lower mineralizing surface in the males. Consistent with an osteoclastic effect in female Panx1ΔOc mice, osteoclast differentiation with RANKL/M-CSF and osteoclast bone resorbing activity in vitro were higher in female, but not male, Panx1ΔOc mice, compared to Panx1fl/fl littermates. Surprisingly, although Panx1 expression was normal in bone marrow stromal-derived osteoblasts from male and female Panx1ΔOc mice, mineral deposition by male (but not female) Panx1ΔOc osteoblasts was lower than controls, and it was reduced in male Panx1fl/fl osteoblasts when conditioned media prepared from male Panx1ΔOc osteoclast cultures was added to the cell culture media. Thus, deletion of Panx1 in TRAP-expressing cells in female mice leads to low bone mass primarily through a cell autonomous effect in osteoclast activity. In contrast, our evidence suggests that changes in the osteoclast secretome drive reduced osteoblast function in male Panx1ΔOc mice, resulting in low bone mass.

Dynamic Changes of the Bone Marrow Niche: Mesenchymal Stromal Cells and Their Progeny During Aging and Leukemia

Mesenchymal stromal cells (MSCs) are a heterogenous cell population found in a wide range of tissues in the body, known for their nutrient-producing and immunomodulatory functions. In the bone marrow (BM), these MSCs are critical for the regulation of hematopoietic stem cells (HSC) that are responsible for daily blood production and functional immunity throughout an entire organism's lifespan. Alongside other stromal cells, MSCs form a specialized microenvironment BM tissue called "niche" that tightly controls HSC self-renewal and differentiation. In addition, MSCs are crucial players in maintaining bone integrity and supply of hormonal nutrients due to their capacity to differentiate into osteoblasts and adipocytes which also contribute to cellular composition of the BM niche. However, MSCs are known to encompass a large heterogenous cell population that remains elusive and poorly defined. In this review, we focus on deciphering the BM-MSC biology through recent advances in single-cell identification of hierarchical subsets with distinct functionalities and transcriptional profiles. We also discuss the contribution of MSCs and their osteo-adipo progeny in modulating the complex direct cell-to-cell or indirect soluble factors-mediated interactions of the BM HSC niche during homeostasis, aging and myeloid malignancies. Lastly, we examine the therapeutic potential of MSCs for rejuvenation and anti-tumor remedy in clinical settings.

Comparative transcriptomics and network pharmacology analysis to identify the potential mechanism of celastrol against osteoarthritis

INTRODUCTION

Celastrol is a promising therapeutic agent for the treatment of osteoarthritis (OA). However, the mechanism of action of celastrol is unclear. This study was aiming to identify the potential function of celastrol on OA and determine its underlying mechanism.

METHOD

Celastrol targets were collected from web database searches and literature review, while pathogenic OA targets were obtained from Online Mendelian Inheritance in Man (OMIM) and GeneCards databases. Transcriptomics data was sequenced using an Illumina HiSeq 4000 platform. Celastrol-OA overlapping genes were then identified followed by prediction of the potential function and signaling pathways associated with celastrol using gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. A celastrol-target network was constructed to identify the candidate core targets of celastrol. The predictions were then validated by performing molecular docking and molecular dynamics simulation studies.

RESULTS

In total, 96 genes were identified as the putative celastrol targets for treatment of OA. These genes were possibly involved in cell phenotype changes including response to lipopolysaccharide and oxidative stress as well as in cell apoptosis and aging. The genes also induced the mTOR pathway and AGE-RAGE signaling pathway at the intracellular level. Additionally, results indicated that 13 core targets including mTOR, TP53, MMP9, EGFR, CCND1, MAPK1, STAT3, VEGFA, CASP3, TNF, MYC, ESR1, and PTEN were likely direct targets of celastrol in OA. Finally, mTOR was determined as the most likely therapeutic target of celastrol in OA.

CONCLUSION

This study provides a basic understanding and novel insight into the potential mechanism of celastrol against OA. Key Points • Our study provides a strong indication that further study of celastrol therapy in OA is required. • mTOR is the most likely therapeutic target of celastrol in OA.

Celastrol in metabolic diseases: Progress and application prospects

Metabolic diseases are becoming increasingly common in modern society. Therefore, it is essential to develop effective drugs or new treatments for metabolic diseases. As an active ingredient derived from plants, celastrol has shown great potential in the treatment of a wide variety of metabolic diseases and received considerable attention in recent years. In reported studies, the anti-obesity effect of celastrol resulted from regulating leptin sensitivity, energy metabolism, inflammation, lipid metabolism and even gut microbiota. Celastrol reversed insulin resistance via multiple routes to protect against type 2 diabetes. Celastrol also showed effects on atherosclerosis, cholestasis and osteoporosis. Celastrol in treating metabolic diseases seem to be versatile and the targets or pathways were diverse. Here, we systematically review the mechanism of action, and the therapeutic properties of celastrol in various metabolic diseases and complications. Based on this review, potential research strategies might contribute to the celastrol's clinical application in the future.