Schisandrin A restrains osteoclastogenesis by inhibiting reactive oxygen species and activating Nrf2 signalling

Schisandrin A Alleviates Spatial Learning and Memory Impairment in Diabetic Rats by Inhibiting Inflammatory Response and Through Modulation of the PI3K/AKT Pathway

Clinical and epidemiological research shows that people with diabetes mellitus frequently experience diabetic cognitive impairment. Schisandrin A (SchA), one of the lignans found in the dried fruit of Schisandra chinensis, has a variety of pharmacological effects on immune system control, apoptosis suppression, anti-oxidation and anti-inflammation. The goal of the current investigation was to clarify the probable neuro-protective effects of SchA against streptozotocin-induced diabetes deficiencies of the spatial learning and memory in rats. The outcomes show that SchA therapy effectively improved impaired glucose tolerance, fasting blood glucose level and serum insulin level in diabetic rats. Additionally, in the Morris water maze test, diabetic rats showed deficits in spatial learning and memory that were ameliorated by SchA treatment. Moreover, giving diabetic rats SchA reduced damage to the hippocampus structure and increased the production of synaptic proteins. Further research revealed that SchA therapy reduced diabetic-induced hippocampus neuron damage and the generation of Aβ, as demonstrated by the upregulated phosphorylation levels of insulin signaling pathway connected proteins and by the decreased expression levels of inflammatory-related factors. Collectively, these results suggested that SchA could improve diabetes-related impairments in spatial learning and memory, presumably by reducing inflammatory responses and regulating the insulin signaling system.

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.

Schisandrin A alleviates renal fibrosis by inhibiting PKCβ and oxidative stress

BACKGROUND

Renal fibrosis is a common pathway that drives the advancement of numerous kidney maladies towards end-stage kidney disease (ESKD). Suppressing renal fibrosis holds paramount clinical importance in forestalling or retarding the transition of chronic kidney diseases (CKD) to renal failure. Schisandrin A (Sch A) possesses renoprotective effect in acute kidney injury (AKI), but its effects on renal fibrosis and underlying mechanism(s) have not been studied.

STUDY DESIGN

Serum biochemical analysis, histological staining, and expression levels of related proteins were used to assess the effect of PKCβ knockdown on renal fibrosis progression. Untargeted metabolomics was used to assess the effect of PKCβ knockdown on serum metabolites. Unilateral Ureteral Obstruction (UUO) model and TGF-β induced HK-2 cells and NIH-3T3 cells were used to evaluate the effect of Schisandrin A (Sch A) on renal fibrosis. PKCβ overexpressed NIH-3T3 cells were used to verify the possible mechanism of Sch A.

RESULTS

PKCβ was upregulated in the UUO model. Knockdown of PKCβ mitigated the progression of renal fibrosis by ameliorating perturbations in serum metabolites and curbing oxidative stress. Sch A alleviated renal fibrosis by downregulating the expression of PKCβ in kidney. Treatment with Sch A significantly attenuated the upregulated proteins levels of FN, COL-I, PKCβ, Vimentin and α-SMA in UUO mice. Moreover, Sch A exhibited a beneficial impact on markers associated with oxidative stress, including MDA, SOD, and GSH-Px. Overexpression of PKCβ was found to counteract the renoprotective efficacy of Sch A in vitro.

CONCLUSION

Sch A alleviates renal fibrosis by inhibiting PKCβ and attenuating oxidative stress.

A multifunctional composite hydrogel that sequentially modulates the process of bone healing and guides the repair of bone defects

Calcium carbonate (CaCO3), which exhibits excellent biocompatibility and bioactivity, is a well-established bone filling material for bone defects. Here, we synthesized CaCO3microspheres (CMs) to use as an intelligent carrier to load bone morphogenetic protein-2 (BMP-2). Subsequently, drug-loaded CMs and catalase (CAT) were added to methacrylated gelatin (GelMA) hydrogels to prepare a composite hydrogel for differential release of the drugs. CAT inside hydrogels was released with a fast rate to eliminate H2O2and generate oxygen. Constant BMP-2 release from CMs induced rapid osteogenesis. Resultsin vitroindicated that the composite hydrogels efficiently reduced the level of intracellular reactive oxygen species, preventing cells from being injured by oxidative stress, promoting cell survival and proliferation, and enhancing osteogenesis. Furthermore, animal experiments demonstrated that the composite hydrogels were able to inhibit the inflammatory response, regulate macrophage polarization, and facilitate the healing of bone defects. These findings indicate that a multi-pronged strategy is greatly expected to promote the bone healing by modulating pathological microenvironments.

VSIG4 inhibits RANKL-induced osteoclastogenesis by enhancing Nrf2-dependent antioxidant response against reactive oxygen species production

Osteoporosis is a prevalent systemic skeletal disorder, particularly affecting postmenopausal women, primarily due to excessive production and activation of osteoclasts. However, the current anti-osteoporotic drugs utilized in clinical practice may lead to certain side effects. Therefore, it is necessary to further unravel the potential mechanisms regulating the osteoclast differentiation and to identify novel targets for osteoporosis treatment. This study revealed the most significant decline in VSIG4 expression among the VSIG family members. VSIG4 overexpression significantly inhibited RANKL-induced osteoclastogenesis and bone resorption function. Mechanistically, both western blot and immunofluorescence assay results demonstrated that VSIG4 overexpression attenuated the expression of osteoclast marker genes and dampened the activation of MAPK and NF-κB signaling pathways. Furthermore, VSIG4 overexpression could inhibit the generation of reactive oxygen species (ROS) and stimulate the expression of Nrf2 along with its downstream antioxidant enzymes via interaction with Keap1. Notably, a potent Nrf2 inhibitor, ML385, could reverse the inhibitory effect of VSIG4 on osteoclast differentiation. In line with these findings, VSIG4 overexpression also mitigated bone loss induced by OVX and attenuated the activation of osteoclasts in vivo. In conclusion, our results suggest that VSIG4 holds promise as a novel target for addressing postmenopausal osteoporosis. This is achieved by suppressing osteoclast formation via enhancing Nrf2-dependent antioxidant response against reactive oxygen species production.

Garcinone C attenuates RANKL-induced osteoclast differentiation and oxidative stress by activating Nrf2/HO-1 and inhibiting the NF-kB signaling pathway

Osteoporosis is the result of osteoclast formation exceeding osteoblast production, and current osteoporosis treatments targeting excessive osteoclast bone resorption have serious adverse effects. There is a need to fully understand the mechanisms of osteoclast-mediated bone resorption, identify new drug targets, and find better drugs to treat osteoporosis. Gar C (Gar C) is a major naturally occurring phytochemical isolated from mangosteen, and is a derivative of the naturally occurring phenolic antioxidant lutein. We used an OP mouse model established by ovariectomy (OVX). We found that treatment with Gar C significantly increased bone mineral density and significantly decreased the expression of TRAP, NFATC1 and CTSK relative to untreated OP mice. We found that Garcinone C could disrupt osteoclast activation and resorption functions by inhibiting RANKL-induced osteoclast differentiation as well as inhibiting the formation of multinucleated osteoclasts. Immunoblotting showed that Gar C downregulated the expression of osteoclast-related proteins. In addition, Gar C significantly inhibited RANKL-induced ROS production and affected NF-κB activity by inhibiting phosphorylation Formylation of P65 and phosphorylation and degradation of ikba. These data suggest that Gar C significantly reduced OVX-induced osteoporosis by inhibiting osteoclastogenesis and oxidative stress in bone tissue. Mechanistically, this effect was associated with inhibition of the ROS-mediated NF-κB pathway.

Corylifol A suppresses osteoclastogenesis and alleviates ovariectomy-induced bone loss via attenuating ROS production and impairing mitochondrial function

Osteoporosis is a systemic disease characterized by an imbalance in bone homeostasis, where osteoblasts fail to fully compensate for the bone resorption induced by osteoclasts. Corylifol A, a flavonoid extracted from Fructus psoraleae, has been identified as a potential treatment for this condition. Predictions from network pharmacology and molecular docking studies suggest that Corylifol A exhibits strong binding affinity with NFATc1, Nrf2, PI3K, and AKT1. Empirical evidence from in vivo experiments indicates that Corylifol A significantly mitigates systemic bone loss induced by ovariectomy by suppressing both the generation and activation of osteoclasts. In vitro studies further showed that Corylifol A inhibited the activation of PI3K-AKT and MAPK pathways and calcium channels induced by RANKL in a time gradient manner, and specifically inhibited the phosphorylation of PI3K, AKT, GSK3 β, ERK, CaMKII, CaMKIV, and Calmodulin. It also diminishes ROS production through Nrf2 activation, leading to a decrease in the expression of key regulators such as NFATcl, C-Fos, Acp5, Mmp9, and CTSK that are involved in osteoclastogenesis. Notably, our RNA-seq analysis suggests that Corylifol A primarily impacts mitochondrial energy metabolism by suppressing oxidative phosphorylation. Collectively, these findings demonstrate that Corylifol A is a novel inhibitor of osteoclastogenesis, offering potential therapeutic applications for diseases associated with excessive bone resorption.

Schizandrin A attenuates early brain injury following subarachnoid hemorrhage through suppressing neuroinflammation

BACKGROUND

Early brain injury (EBI) is the vital factor in determining the outcome of subarachnoid hemorrhage (SAH). Schizandrin A (Sch A), the bioactive ingredient extracted from Schisandra chinensis, has been proved to exert beneficial effects in multiple human diseases. However, the effect of Sch A on SAH remains unknown. The current study was designed to explored role and mechanism of Sch A in the pathophysiological process of EBI following SAH.

METHOD

A total of 74 male C57BL/6 J mice were subjected to endovascular perforation to establish the SAH model. Different dosages of Sch A were administrated post-modeling. The post-modeling assessments included neurological test, brain water content, RT-PCR, immunofluorescence, Nissl staining. Oxygenated hemoglobin was introduced into microglia to establish a SAH model in vitro.

RESULT

Sch A significantly alleviated SAH-induced brain edema and neurological impairment. Moreover, application of Sch A remarkably inhibited SAH-induced neuroinflammation, evidenced by the decreased microglial activation and downregulated TNF-α, IL-1β and IL-6 and expression. Additionally, Sch A, both in vivo and in vitro, protected neurons against SAH-induced inflammatory injury. Mechanismly, administration of Sch A inhibited miR-155/NF-κB axis and attenuated neuroinflammation, as well as alleviating neuronal injury.

CONCLUSION

Our data suggested that Sch A could attenuated EBI following SAH via modulating neuroinflammation. The anti-inflammatory effect was exerted, at least partly through the miR-155/NF-κB axis, which may shed light on a possible therapeutic target for SAH.

Age-related decline in melatonin contributes to enhanced osteoclastogenesis via disruption of redox homeostasis

BACKGROUND

Increased oxidative stress contributes to enhanced osteoclastogenesis and age-related bone loss. Melatonin (MT) is an endogenous antioxidant and declines with aging. However, it was unclear whether the decline of MT was involved in the enhanced osteoclastogenesis during the aging process.

METHODS

The plasma level of MT, oxidative stress status, bone mass, the number of bone marrow-derived monocytes (BMMs) and its osteoclastogenesis were analyzed in young (3-month old) and old (18-month old) mice (n = 6 per group). In vitro, BMMs isolated from aged mice were treated with or without MT, followed by detecting the change of osteoclastogenesis and intracellular reactive oxygen species (ROS) level. Furthermore, old mice were treated with MT for 2 months to investigate the therapeutic effect.

RESULTS

The plasma level of MT was markedly lower in aged mice compared with young mice. Age-related decline in MT was accompanied by enhanced oxidative stress, osteoclastogenic potential and bone loss. MT intervention significantly suppressed the receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis, decreased intracellular ROS and enhanced antioxidant capacity of BMMs from aged mice. MT supplementation significantly attenuated oxidative stress, osteoclastogenesis, bone loss and deterioration of bone microstructure in aged mice.

CONCLUSIONS

These results suggest that age-related decline of MT enhanced osteoclastogenesis via disruption of redox homeostasis. MT may serve as a key regulator in osteoclastogenesis and bone homeostasis, thereby highlighting its potential as a preventive agent for age-related bone loss.

ATP-induced cell death: a novel hypothesis for osteoporosis

ATP-induced cell death has emerged as a captivating realm of inquiry with profound ramifications in the context of osteoporosis. This study unveils a paradigm-shifting hypothesis that illuminates the prospective involvement of ATP-induced cellular demise in the etiology of osteoporosis. Initially, we explicate the morphological attributes of ATP-induced cell death and delve into the intricacies of the molecular machinery and regulatory networks governing ATP homeostasis and ATP-induced cell death. Subsequently, our focus pivots towards the multifaceted interplay between ATP-induced cellular demise and pivotal cellular protagonists, such as bone marrow-derived mesenchymal stem cells, osteoblasts, and osteoclasts, accentuating their potential contributions to secondary osteoporosis phenotypes, encompassing diabetic osteoporosis, glucocorticoid-induced osteoporosis, and postmenopausal osteoporosis. Furthermore, we probe the captivating interplay between ATP-induced cellular demise and alternative modalities of cellular demise, encompassing apoptosis, autophagy, and necroptosis. Through an all-encompassing inquiry into the intricate nexus connecting ATP-induced cellular demise and osteoporosis, our primary goal is to deepen our comprehension of the underlying mechanisms propelling this malady and establish a theoretical bedrock to underpin the development of pioneering therapeutic strategies.

Nrf2: A promising therapeutic target in bone-related diseases

Nuclear factor erythroid-2-related factor 2 (Nrf2) plays an important role in maintaining cellular homeostasis, as it suppresses cell damage caused by external stimuli by regulating the transcription of intracellular defense-related genes. Accumulating evidence has highlighted the crucial role of reduction-oxidation (REDOX) imbalance in the development of bone-related diseases. Nrf2, a transcription factor linked to nuclear factor-erythrocyte 2, plays a pivotal role in the regulation of oxidative stress and induction of antioxidant defenses. Therefore, further investigation of the mechanism and function of Nrf2 in bone-related diseases is essential. Considerable evidence suggests that increased nuclear transcription of Nrf2 in response to external stimuli promotes the expression of intracellular antioxidant-related genes, which in turn leads to the inhibition of bone remodeling imbalance, improved fracture recovery, reduced occurrence of osteoarthritis, and greater tumor resistance. Certain natural extracts can selectively target Nrf2, potentially offering therapeutic benefits for osteogenic arthropathy. In this article, the biological characteristics of Nrf2 are reviewed, the intricate interplay between Nrf2-regulated REDOX imbalance and bone-related diseases is explored, and the potential preventive and protective effects of natural products targeting Nrf2 in these diseases are elucidated. A comprehensive understanding of the role of Nrf2 in the development of bone-related diseases provides valuable insights into clinical interventions and can facilitate the discovery of novel Nrf2-targeting drugs.

Mechanism of regulating macrophages/osteoclasts in attenuating wear particle-induced aseptic osteolysis

Joint replacement surgery is the most effective treatment for end-stage arthritis. Aseptic loosening caused by periprosthetic osteolysis is a common complication after joint replacement. Inflammation induced by wear particles derived from prosthetic biomaterials is a major cause of osteolysis. We emphasize that bone marrow-derived macrophages and their fusion-derived osteoclasts play a key role in this pathological process. Researchers have developed multiple intervention approaches to regulate macrophage/osteoclast activation. Aiming at wear particle-induced periprosthetic aseptic osteolysis, this review separately discusses the molecular mechanism of regulation of ROS formation and inflammatory response through intervention of macrophage/osteoclast RANKL-MAPKs-NF-κB pathway. These molecular mechanisms regulate osteoclast activation in different ways, but they are not isolated from each other. There is also a lot of crosstalk among the different mechanisms. In addition, other bone and joint diseases related to osteoclast activation are also briefly introduced. Therefore, we discuss these new findings in the context of existing work with a view to developing new strategies for wear particle-associated osteolysis based on the regulation of macrophages/osteoclasts.

Mechanisms of action and synergetic formulas of plant-based natural compounds from traditional Chinese medicine for managing osteoporosis: a literature review

Osteoporosis (OP) is a systemic skeletal disease prevalent in older adults, characterized by substantial bone loss and deterioration of microstructure, resulting in heightened bone fragility and risk of fracture. Traditional Chinese Medicine (TCM) herbs have been widely employed in OP treatment owing to their advantages, such as good tolerance, low toxicity, high efficiency, and minimal adverse reactions. Increasing evidence also reveals that many plant-based compounds (or secondary metabolites) from these TCM formulas, such as resveratrol, naringin, and ginsenoside, have demonstrated beneficial effects in reducing the risk of OP. Nonetheless, the comprehensive roles of these natural products in OP have not been thoroughly clarified, impeding the development of synergistic formulas for optimal OP treatment. In this review, we sum up the pathological mechanisms of OP based on evidence from basic and clinical research; emphasis is placed on the in vitro and preclinical in vivo evidence-based anti-OP mechanisms of TCM formulas and their chemically active plant constituents, especially their effects on imbalanced bone homeostasis regulated by osteoblasts (responsible for bone formation), osteoclasts (responsible for bone resorption), bone marrow mesenchymal stem cells as well as bone microstructure, angiogenesis, and immune system. Furthermore, we prospectively discuss the combinatory ingredients from natural products from these TCM formulas. Our goal is to improve comprehension of the pharmacological mechanisms of TCM formulas and their chemically active constituents, which could inform the development of new strategies for managing OP.

An Integrative Study on the Inhibition of Bone Loss via Osteo-F Based on Network Pharmacology, Experimental Verification, and Clinical Trials in Postmenopausal Women

The inhibition of bone loss remains a challenge for postmenopausal women, considering the fact that only three anabolic treatments for osteoporosis have been approved by the FDA. This study aimed to investigate the osteogenic capacities of Osteo-F, a newly developed herbal formula, upon integrating network analysis and pre-clinical studies into clinical trials. The network pharmacology analysis showed that a potential mechanism of Osteo-F is closely related to osteoblast differentiation. Consistent with the predicted mechanism, Osteo-F treatment significantly enhanced bone matrix formation and mineralization with collagen expression in osteoblasts. Simultaneously, secreted bone-forming molecules were upregulated by Osteo-F. After the administration of Osteo-F to osteoporotic mice, the femoral BMD and osteocalcin in the serum and bone tissues were significantly improved. Subsequently, a randomized, double-blinded, placebo-controlled clinical trial showed that 253 mg of Osteo-F supplementation for 24 weeks resulted in significant improvements in the Z-score and serum osteocalcin levels of postmenopausal women compared to the placebo, thus indicating bone anabolic efficacy. In the current study, the bone anabolic effect of Osteo-F was determined by activating the differentiation and mineralization of osteoblasts through integrating experiments based on network analysis into clinical trials, with synchronized, reliable evidence, demonstrating that Osteo-F is a novel bone anabolic treatment in postmenopausal women.

Schizochytrium sp. Extracted Lipids Prevent Alopecia by Enhancing Antioxidation and Inhibiting Ferroptosis of Dermal Papilla Cells

Alopecia has gradually become a problem that puzzles an increasing number of people. Dermal papilla cells (DPCs) play an important role in hair follicle (HF) growth; thus, exploring the effective chemicals or natural extracts that can remediate the growth of DPCs is vital. Our results showed that Schizochytrium sp.-extracted lipids (SEL) significantly promoted proliferation (up to 1.13 times) and survival ratio (up to 2.45 times) under oxidative stress. The treatment with SEL can protect DPCs against oxidative stress damage, reducing the reactive oxygen species (ROS) level by 90.7%. The relative gene transcription and translation were thoroughly analyzed using RNA-Seq, RT-qPCR, and Western blot to explore the mechanism. Results showed that SEL significantly inhibited the ferroptosis pathway and promoted the expression of antioxidant genes (up to 1.55-3.52 times). The in vivo application of SEL improved hair growth, with the length of new hair increasing by 16.7% and the length of new HF increasing by 92.6%, and the period of telogen shortening increased by 40.0%. This study proposes a novel therapeutic option for alopecia, with the effect and regulation mechanism of SEL on DPC systematically clarified.

Identification of chemical constituents of Qingjin Yiqi granules and comparative study on pharmacokinetics of 23 main bioactive components in normal and Lung-Qi deficiency rats by UPLC-MS/MS method

Qingjin Yiqi granules (QJYQ granules) are hospital preparations derived from ancient prescriptions under the guidance of academician Zhang Boli; they have the effect of invigorating qi and nourishing yin, strengthening the spleen and harmonizing the middle, clearing heat, and drying dampness, and are mainly used for patients with coronavirus disease 2019 (COVID-19) during the recovery period. However, their chemical constituents and pharmacokinetic characteristics in vivo have not been systematically investigated. In this study, 110 chemical constituents of QJYQ granules were identified using ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS), and a fast and sensitive ultra-high-performance liquid chromatography-mass spectrometry method was developed and validated for the target analytes. A rat model of lung-qi deficiency was established by subjecting mice to passive smoking combined with cold baths, and 23 main bioactive components of QJYQ granules were analyzed in normal and model rats after oral administration. The results showed that, compared to the normal group, there were significant differences in the pharmacokinetics of baicalin, schisandrin, ginsenoside Rb1, naringin, hesperidin, liquiritin, liquiritigenin, glycyrrhizic acid, and hastatoside in the model rats (P < 0.05), indicating that the in vivo processes of the above components changed under pathological conditions, suggesting that they may have pharmacological effects as active components. This study has helped identify QJYQ particulate substances and further supports their clinical application..

NFATc1-mediated expression of SLC7A11 drives sensitivity to TXNRD1 inhibitors in osteoclast precursors

Excess osteoclast activity is found in many bone metabolic diseases, and inhibiting osteoclast differentiation has proven to be an effective strategy. Here, we revealed that osteoclast precursors (pre-OCs) were more susceptible to thioredoxin reductase 1 (TXNRD1) inhibitors than bone marrow-derived monocytes (BMDMs) during receptor activator of nuclear factor kappa B ligand (RANKL)-mediated osteoclastogenesis. Mechanistically, we found that nuclear factor of activated T-cells 1 (NFATc1) upregulated solute carrier family 7 member 11 (SLC7A11) expression through transcriptional regulation during RANKL-induced osteoclastogenesis. During TXNRD1 inhibition, the rate of intracellular disulfide reduction is significantly reduced. Increased cystine transport leads to increased cystine accumulation, which leads to increased cellular disulfide stress and disulfidptosis. We further demonstrated that SLC7A11 inhibitors and treatments that prevent disulphide accumulation could rescue this type of cell death, but not the ferroptosis inhibitors (DFO, Ferro-1), the ROS scavengers (Trolox, Tempol), the apoptosis inhibitor (Z-VAD), the necroptosis inhibitor (Nec-1), or the autophagy inhibitor (CQ). An in vivo study indicated that TXNRD1 inhibitors increased bone cystine content, reduced the number of osteoclasts, and alleviated bone loss in an ovariectomized (OVX) mouse model. Together, our findings demonstrate that NFATc1-mediated upregulation of SLC7A11 induces targetable metabolic sensitivity to TXNRD1 inhibitors during osteoclast differentiation. Moreover, we innovatively suggest that TXNRD1 inhibitors, a classic drug for osteoclast-related diseases, selectively kill pre-OCs by inducing intracellular cystine accumulation and subsequent disulfidptosis.

Probucol suppresses osteoclastogenesis via activating Nrf2 signaling and ameliorates ovariectomy-induced bone loss

Osteoporosis is a systemic and endocrine bone disorder distinguished by declined bone mineral density, compromised bone strength, and destruction of trabecular structure. The abnormally excessive osteoclastogenesis and bone erosion play imperative roles in the progression of osteoporosis. However, treatment of osteoporosis is far from satisfactory due to poor adherence to existing medications and adverse reactions, there is an urgent to develop novel therapies for osteoporosis. Probucol, a synthetic compound with two characteristic phenolic rings, owns anti-inflammatory and antioxidant properties. Accumulating evidence have indicated that intracellular reactive oxygen species (ROS) is closely related to osteoclastogenesis. Hence, we investigated the potential effects of probucol on osteoclastogenesis in vivo and in vitro. In this study, TRAP staining and bone slice resorption assay showed that probucol suppressed RANKL-induced osteoclast formation and function. The mRNA and protein levels of osteoclastogenesis marker genes were reduced by probucol in a concentration-dependent manner. Besides, probucol suppressed osteoclast differentiation by inhibiting ROS production, MAPKs and NF-κB signaling pathways, while Nrf2 silencing reversed the inhibitory effect of probucol on osteoclast formation and function. Consistent with the above findings, in vivo experiments demonstrated that probucol visibly alleviated bone loss caused by estrogen deficiency. In brief, these results showed the potential of anti-oxidant compound probucol in the treatment of osteoporosis, highlighting Nrf2 as a promising target in osteoclast-related disease.

17β-estradiol plays the anti-osteoporosis role via a novel ESR1-Keap1-Nrf2 axis-mediated stress response activation and Tmem119 upregulation

Increased oxidative stress and decreased osteoblastic bone formation contribute to estrogen deficiency-induced osteoporosis. However, the role and mechanism of estrogen-deficiency in regulating oxidative stress and osteoblastic activity remain unclear. Here, we showed that estrogen-deficient bone marrow stromal/stem cells (BMSCs) exhibited impaired capacity to combat stress, characterized by increased oxidative stress, shortened cell survival and reduced osteogenic differentiation and bone formation, which were due to a decrease of nuclear factor erythroid 2-related factor 2 (Nrf2). Nrf2 re-activation induced by the pyrazinyl dithiolethione oltipraz significantly rescued the cell phenotype of estrogen-deficient BMSCs in vitro and ex vivo. Mechanistically, we found that 17β-estradiol/ESR1 (Estrogen Receptor 1) facilitated Nrf2 accumulation, and activated its target genes by competing with Nrf2 for binding to Kelch-like ECH-associated protein 1 (Keap1) via ESR1 containing a highly conserved DLL motif. Of note, oltipraz, an Nrf2 activator, rescued ovariectomy-induced osteoporosis partly by inhibiting oxidative stress and promoting osteoblastic bone formation via Nrf2-induced antioxidant signaling activation and Tmem119 (transmembrane protein 119) upregulation. Conversely, Nrf2 knockout largely blocked the bone anabolic effect of 17β-estradiol in vivo and ex vivo. This study provides insight into the mechanisms whereby estrogen prevents osteoporosis through promoting osteoblastic bone formation via Nrf2-mediated activation of antioxidant signaling and upregulation of Tmem119, and thus provides evidence for Nrf2 as a potential target for clinical prevention and treatment of menopause-related osteoporosis.

Kidney tonifying traditional Chinese medicine: Potential implications for the prevention and treatment of osteoporosis

The aging global population is increasingly affected by osteoporosis (OP), which is one of the most significant threats to the elderly. Moreover, its prevention and treatment situations have become increasingly severe. Therefore, it is imperative to develop alternatives or complementary drugs for preventing and treating osteoporosis. Kidney tonifying traditional Chinese medicine (KTTCM) has been used for the treatment of osteoporosis for a long time. Pharmacological studies have shown that kidney tonifying traditional Chinese medicine can promote osteoblasts, inhibit osteoclasts, and regulate the level of estrogen and plays vital roles in stimulating osteogenesis, restraining adipogenesis of marrow mesenchymal stem cells (MSCs), regulating the metabolism of calcium and phosphorus, and inhibiting oxidative stress. These effects are mediated by OPG/RANKL/RANK, BMP/Smads, MAPKs, and Wnt/β-catenin systems. To develop a safe, synergistic, effective, and homogenized TCM formula with robust scientific evidence to provide faster and more economical alternatives, the anti-osteoporosis ingredients and pharmacological mechanisms of kidney tonifying traditional Chinese medicine are recapitulated from the perspective of molecular and cell biology, and the safety and toxicity of kidney tonifying traditional Chinese medicine have also been reviewed in this paper.

Receptor activator of nuclear factor-κB ligand-mediated osteoclastogenesis signaling pathway and related therapeutic natural compounds

Osteoclast is a hematopoietic precursor cell derived from the mononuclear macrophage cell line, which is the only cell with bone resorption function. Its abnormal activation can cause serious osteolysis related diseases such as rheumatoid arthritis, Paget’s disease and osteoporosis. In recent years, the adverse effects caused by anabolic anti-osteolytic drugs have increased the interest of researchers in the potential therapeutic and preventive effects of natural plant derivatives and natural compounds against osteolytic diseases caused by osteoclasts. Natural plant derivatives and natural compounds have become major research hotspots for the treatment of osteolysis-related diseases due to their good safety profile and ability to improve bone. This paper provides an overview of recent advances in the molecular mechanisms of RANKL and downstream signaling pathways in osteoclast differentiation, and briefly outlines potential natural compounds with antiosteoclast activity and molecular mechanisms.

Prussian Blue Nanozyme Normalizes Microenvironment to Delay Osteoporosis

Osteoporosis (OP) is the most common orthopedic disease in the elderly and the main cause of age-related mortality and disability. However, no satisfactory intervention is currently available in clinical practice. Thus, an effective therapy to prevent or delay the development of OP should be devised. Osteoclastogenesis overactivation and excessive bone resorption are the main characteristics of OP. Accordingly, a paradigm for nanozyme-mediated normalization of the disease microenvironment to regulate osteoclast differentiation and delay OP is proposed. Hollow Prussian blue nanozymes (HPBZs) are prepared via template-free hydrothermal synthesis and selected as representative nanozymes. The intrinsic osteoclast activity-remodeling bioactivities of the HPBZs are explored in vitro and in vivo, focusing on their impact on osteogenesis and specific molecular mechanisms using an OP murine model. The HPBZs significantly normalize the OP microenvironment, thereby inhibiting osteoclast formation and osteoclast resorption, possibly owing to the suppression of intracellular reactive oxygen species generation, the mitogen-activated protein kinase, and nuclear factor κB signaling pathways. Consistently, in an ovariectomy-induced OP murine model, HPBZ treatment significantly attenuates osteoporotic bone loss in vivo. The findings confirm the HPBZ-mediated normalization of the disease microenvironment for the treatment of OP and suggest its application to other inflammation-related diseases.

Aminooxyacetic acid hemihydrochloride inhibits osteoclast differentiation and bone resorption by attenuating oxidative phosphorylation

Osteoclasts undergo active metabolic reprogramming to acquire the energy needed during differentiation and bone resorption. Compared with immature osteoclasts, mature osteoclasts comprise higher levels of electron transport chain enzymes and more metabolically active mitochondria. Of all energy metabolism pathways, oxidative phosphorylation is considered to be the most efficient in supplying energy to osteoclasts. We found that the malate-aspartate shuttle inhibitor aminooxyacetic acid hemihydrochloride inhibits osteoclastogenesis and bone resorption by inhibiting exchange of reducing equivalents between the cytosol and the mitochondrial matrix and attenuating mitochondrial oxidative phosphorylation in vitro. The weakening of the oxidative phosphorylation pathway resulted in reduced mitochondrial function and inadequate energy supply along with reduced reactive oxygen species production. Furthermore, treatment with aminooxyacetic acid hemihydrochloride helped recover bone loss in ovariectomized mice. Our findings highlight the potential of interfering with the osteoclast intrinsic energy metabolism pathway as a treatment for osteoclast-mediated osteolytic diseases.

Schisandrin A from Schisandra chinensis Attenuates Ferroptosis and NLRP3 Inflammasome-Mediated Pyroptosis in Diabetic Nephropathy through Mitochondrial Damage by AdipoR1 Ubiquitination

Schisandra chinensis, as a Chinese functional food, is rich in unsaturated fatty acids, minerals, vitamins, and proteins. Hence, this study was intended to elucidate the effects and biological mechanism of Schisandrin A from Schisandra chinensis in DN. C57BL/6 mice were fed with a high-fat diet and then injected with streptozotocin (STZ). Human renal glomerular endothelial cells were stimulated with 20 mmol/L d-glucose for DN model. Schisandrin A presented acute kidney injury in mice of DN. Schisandrin A reduced oxidative stress and inflammation in model of DN. Schisandrin A reduced high glucose-induced ferroptosis and reactive oxygen species (ROS-)-mediated pyroptosis by mitochondrial damage in model of DN. Schisandrin A directly targeted AdipoR1 protein and reduced LPS+ATP-induced AdipoR1 ubiquitination in vitro model. Schisandrin A activated AdipoR1/AMPK signaling pathway and suppressed TXNIP/NLRP3 signaling pathway in vivo and in vitro model of DN. Conclusively, our study revealed that Schisandrin A from Schisandra chinensis attenuates ferroptosis and NLRP3 inflammasome-mediated pyroptosis in DN by AdipoR1/AMPK-ROS/mitochondrial damage. Schisandrin A is a possible therapeutic option for DN or other diabetes.

Methyl 3,4-dihydroxybenzoate inhibits RANKL-induced osteoclastogenesis via Nrf2 signaling in vitro and suppresses LPS-induced osteolysis and ovariectomy-induced osteoporosis in vivo

Osteoporosis deteriorates bone mass and biomechanical strength and is life-threatening to the elderly. In this study, we show that methyl 3,4-dihydroxybenzoate (MDHB), an antioxidant small-molecule compound extracted from natural plants, inhibits receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclastogenesis in vitro. Furthermore, MDHB attenuates the activation of mitogen-activated protein kinase (MAPK) and NF-κB pathways by reducing the levels of reactive oxygen species (ROS), which leads to downregulated protein expression of c-Fos and nuclear factor of activated T cells c1 (NFATc1). We also confirm that MDHB upregulates the protein expression of nuclear factor-erythroid 2-related factor 2 (Nrf2), an important transcription factor involved in ROS regulation, by inhibiting the ubiquitination-mediated proteasomal degradation of Nrf2. Next, animal experiments show that MDHB has an effective therapeutic effect on lipopolysaccharide (LPS)- and ovariectomized (OVX)-induced bone loss in mice. Our study demonstrates that MDHB can upregulate Nrf2 and suppress excessive osteoclast activity in mice to treat osteoporosis.

Traditional Chinese medicine promotes bone regeneration in bone tissue engineering

Bone tissue engineering (BTE) is a promising method for the repair of difficult-to-heal bone tissue damage by providing three-dimensional structures for cell attachment, proliferation, and differentiation. Traditional Chinese medicine (TCM) has been introduced as an effective global medical program by the World Health Organization, comprising intricate components, and promoting bone regeneration by regulating multiple mechanisms and targets. This study outlines the potential therapeutic capabilities of TCM combined with BTE in bone regeneration. The effective active components promoting bone regeneration can be generally divided into flavonoids, alkaloids, glycosides, terpenoids, and polyphenols, among others. The chemical structures of the monomers, their sources, efficacy, and mechanisms are described. We summarize the use of compounds and medicinal parts of TCM to stimulate bone regeneration. Finally, the limitations and prospects of applying TCM in BTE are introduced, providing a direction for further development of novel and potential TCM.

Lignans as Pharmacological Agents in Disorders Related to Oxidative Stress and Inflammation: Chemical Synthesis Approaches and Biological Activities

Plant lignans exhibit a wide range of biological activities, which makes them the research objects of potential use as therapeutic agents. They provide diverse naturally-occurring pharmacophores and are available for production by chemical synthesis. A large amount of accumulated data indicates that lignans of different structural groups are apt to demonstrate both anti-inflammatory and antioxidant effects, in many cases, simultaneously. In this review, we summarize the comprehensive knowledge about lignan use as a bioactive agent in disorders associated with oxidative stress and inflammation, pharmacological effects in vitro and in vivo, molecular mechanisms underlying these effects, and chemical synthesis approaches. This article provides an up-to-date overview of the current data in this area, available in PubMed, Scopus, and Web of Science databases, screened from 2000 to 2022.

Schisandrin A alleviates mycophenolic acid-induced intestinal toxicity by regulating cell apoptosis and oxidative damage

The gastrointestinal side effects of mycophenolic acid affect its efficacy in kidney transplant patients, which may be due to its toxicity to the intestinal epithelial mechanical barrier, including intestinal epithelial cell apoptosis and destruction of tight junctions. The toxicity mechanism of mycophenolic acid is related to oxidative stress-mediated the activation of mitogen-activated protein kinases (MAPK). Schisandrin A (Sch A), one of the main active components of the Schisandra chinensis, can protects intestinal epithelial cells from deoxynivalenol-induced cytotoxicity and oxidative damage by antioxidant effects. The aim of this study was to investigate the protective effect and potential mechanism of Sch A on mycophenolic acid-induced damage in intestinal epithelial cell. The results showed that Sch A significantly reversed the mycophenolic acid-induced cell viability reduction, restored the expression of tight junction protein ZO-1, occludin and reduced cell apoptosis. In addition, Sch A inhibited mycophenolic acid-mediated MAPK activation and reactive oxygen species (ROS) increase. Collectively, our study showed that Sch A protected intestinal epithelial cells from mycophenolic acid intestinal toxicity, at least in part, by reducing oxidative stress and inhibiting MAPK signaling pathway.

The Dibenzyl Isoquinoline Alkaloid Berbamine Ameliorates Osteoporosis by Inhibiting Bone Resorption

Postmenopausal osteoporosis (PMOP) is a kind of primary osteoporosis that is characterized by decreased bone density and strength. Berbamine is a nonbasic quaternary benzylisoquinoline plant alkaloid that has been widely used in the clinic to treat leukopenia in China. We found that berbamine inhibited RANKL-induced osteoclastogenesis of bone marrow-derived macrophages (BMMs) in vitro, which mainly occurred in the middle phase and late phase. The gene and protein expression levels of osteoclast-related molecules, including CTSK, MMP-9, NFATc1, CD44 and DC-STAMP, were also downregulated by berbamine. In vivo, we treated PMOP mice with berbamine for 8 weeks and found that the extent of osteoporosis was alleviated significantly according to micro-CT scanning, hematoxylin-eosin staining, DC-STAMP immunohistochemical staining and TRAP immunohistochemical staining in the distal femurs of the mice. Our findings demonstrate that berbamine has an inhibitory effect on the osteoclastogenesis of BMMs and can prevent bone loss after ovariectomy in vivo. This study provides evidence that berbamine is a potential drug for the prevention and treatment of PMOP.

HO-1 in Bone Biology: Potential Therapeutic Strategies for Osteoporosis

Osteoporosis is a prevalent bone disorder characterized by bone mass reduction and deterioration of bone microarchitecture leading to bone fragility and fracture risk. In recent decades, knowledge regarding the etiological mechanisms emphasizes that inflammation, oxidative stress and senescence of bone cells contribute to the development of osteoporosis. Studies have demonstrated that heme oxygenase 1 (HO-1), an inducible enzyme catalyzing heme degradation, exhibits anti-inflammatory, anti-oxidative stress and anti-apoptosis properties. Emerging evidence has revealed that HO-1 is critical in the maintenance of bone homeostasis, making HO-1 a potential target for osteoporosis treatment. In this Review, we aim to provide an introduction to current knowledge of HO-1 biology and its regulation, focusing specifically on its roles in bone homeostasis and osteoporosis. We also examine the potential of HO-1-based pharmacological therapeutics for osteoporosis and issues faced during clinical translation.

Azilsartan Suppresses Osteoclastogenesis and Ameliorates Ovariectomy-Induced Osteoporosis by Inhibiting Reactive Oxygen Species Production and Activating Nrf2 Signaling

Osteoporosis is characterized by a decrease in bone mass and destruction of the bone microarchitecture, and it commonly occurs in postmenopausal women and the elderly. Overactivation of osteoclasts caused by the inflammatory response or oxidative stress leads to osteoporosis. An increasing number of studies have suggested that intracellular reactive oxygen species (ROS) are strongly associated with osteoclastogenesis. As a novel angiotensin (Ang) II receptor blocker (ARB), azilsartan was reported to be associated with the inhibition of intracellular oxidative stress processes. However, the relationship between azilsartan and osteoclastogenesis is still unknown. In this study, we explored the effect of azilsartan on ovariectomy-induced osteoporosis in mice. Azilsartan significantly inhibited the receptor activator of nuclear factor-κB ligand (RANKL)-mediated osteoclastogenesis and downregulated the expression of osteoclast-associated markers (Nfatc1, c-Fos, and Ctsk) in vitro. Furthermore, azilsartan reduced RANKL-induced ROS production by increasing the expression of nuclear factor erythroid 2-related factor 2 (Nrf2). Mechanistically, azilsartan inhibited the activation of MAPK/NF-κB signaling pathways, while Nrf2 silencing reversed the inhibitory effect of azilsartan on MAPK/NF-κB signaling pathways. Consistent with the in vitro data, azilsartan administration ameliorated ovariectomy (OVX)-induced osteoporosis, and decreased ROS levels in vivo. In conclusion, azilsartan inhibited oxidative stress and may be a novel treatment strategy for osteoporosis caused by osteoclast overactivation.

Schisandrin A protects against isoproterenol‑induced chronic heart failure via miR‑155

Schisandrin A (Sch A) has a protective effect on cardiomyocytes. Circulating miR-155 levels are related to chronic heart failure (CHF). The present study aimed to clarify the role and the molecular mechanism of Sch A in CHF. C57BL/6JGpt mice were used for an isoproterenol (ISO)-induced CHF model to collect heart samples. Echocardiography was employed to detect heartbeat indicators. The degree of myocardial hypertrophy was evaluated based on the measurement of heart weight (HW), body weight (BW) and tibia length (TL) and the observation using hematoxylin-eosin staining. Sprague-Dawley rats were purchased for the separation of neonatal rat ventricular myocytes (NRVMs), which were treated with ISO for 24 h. Transfection regulated the level of miR-155. The viability of NRVMs was detected via MTT assay. The mRNA and protein levels were measured via reverse transcription-quantitative PCR and western blotting and immunofluorescence was used to detect the content of α-smooth muscle actin (α-SMA). Treatment with ISO resulted in rising left ventricular posterior wall thickness, intra-ventricular septum diastole, left ventricular end diastolic diameter, left ventricular end systolic diameter, HW/BW, HW/TL and falling ejection fraction and fractional shortening, the trend of which could be reversed by Sch A. Sch A ameliorated myocardial hypertrophy in CHF mice. In addition, Sch A inhibited ISO-induced upregulated expressions of atrial natriuretic peptide, B-type natriuretic peptide, B-myosin heavy chain and miR-155 in myocardial tissue. Based on the results in vitro, Sch A had no significant effect on the viability of NRVMs when its concentration was <24 µmol/l. Sch A inhibited the levels of miR-155, α-SMA and the phosphorylation levels of AKT and cyclic AMP response-element binding protein (CREB) in ISO-induced NRVMs, which was reversed by the upregulation of miR-155. Schisandrin A mediated the AKT/CREB signaling pathway to prevent CHF by regulating the expression of miR-155, which may shed light on a possible therapeutic target for CHF.

Roburic acid attenuates osteoclastogenesis and bone resorption by targeting RANKL-induced intracellular signaling pathways

Excessive activity of osteoclasts contributes to skeletal diseases such as osteoporosis and osteolysis. However, current drugs targeting osteoclast have various deficiencies, placing natural compounds as substitutions of great potential. Roburic acid (RA) is a triterpenoid exacted from Radix Gentianae Macrophyllae, which exhibits inhibitory effects on inflammation and oxidation. By employing an in vitro osteoclastogenesis model, this study investigates the effects and mechanisms of RA on intracellular signaling induced by receptor activator of nuclear factor-κB ligand (RANKL). As expected, RA at a concentration scope from 1 to 10 μM dampened the osteoclast differentiation of bone marrow macrophages (BMMs) but without cell toxicity. Interestingly, RA showed no effect on osteoblastogenesis in vitro. Furthermore, RA mitigated F-actin ring formation, hydroxyapatite resorption, and gene expression in osteoclasts. Mechanistically, RA suppressed TNF receptor-associated factor 6 (TRAF6), the crucial adaptor protein following RANKL-RANK binding. On the one hand, RA downregulated the nuclear factor-κB (NF-κB) activity, extracellular regulated protein kinases (ERK) phosphorylation, and calcium oscillations. On the other hand, RA upregulated the antioxidative response element (ARE) response and the protein expression of heme oxygenase (HO)-1. These upstream alterations eventually led to the suppression of the nuclear factor of activated T cells 1 (NFATc1) activity and the expression of proteins involved in osteoclastogenesis and bone resorption. Furthermore, by using an ovariectomized (OVX) mice model, RA was found to have therapeutic effects against bone loss. On account of these findings, RA could be used to restrain osteoclasts for treating osteoporosis and other osteolytic diseases.

Betaine Attenuates Osteoarthritis by Inhibiting Osteoclastogenesis and Angiogenesis in Subchondral Bone

Osteoarthritis (OA) is the most common type of arthritis with no effective therapy. Subchondral bone and overlying articular cartilage are closely associated and function as “osteo-chondral unit” in the joint. Abnormal mechanical load leads to activated osteoclast activity and increased bone resorption in the subchondral bone, which is implicated in the onset of OA pathogenesis. Thus, inhibiting subchondral bone osteoclast activation could prevent OA onset. Betaine, isolated from the Lycii Radicis Cortex (LRC), has been demonstrated to exert anti-inflammatory, antifibrotic and antiangiogenic properties. Here, we evaluated the effects of betaine on anterior cruciate ligament transection (ACLT)-induced OA mice. We observed that betaine decreased the number of matrix metalloproteinase 13 (MMP-13)-positive and collagen X (Col X)-positive cells, prevented articular cartilage proteoglycan loss and lowered the OARSI score. Betaine decreased the thickness of calcified cartilage and increased the expression level of lubricin. Moreover, betaine normalized uncoupled subchondral bone remodeling as defined by lowered trabecular pattern factor (Tb.pf) and increased subchondral bone plate thickness (SBP). Additionally, aberrant angiogenesis in subchondral bone was blunted by betaine treatment. Mechanistically, we demonstrated that betaine suppressed osteoclastogenesis in vitro by inhibiting reactive oxygen species (ROS) production and subsequent mitogen-activated protein kinase (MAPK) signaling. These data demonstrated that betaine attenuated OA progression by inhibiting hyperactivated osteoclastogenesis and maintaining microarchitecture in subchondral bone.

The Novel Antioxidant Compound JSH-23 Prevents Osteolysis by Scavenging ROS During Both Osteoclastogenesis and Osteoblastogenesis

Inflammatory osteolysis is a pathological skeletal disease associated with not only the production of inflammatory cytokines but also local oxidative status. Excessive reactive oxygen species (ROS) promote bone resorption by osteoclasts and induce the apoptosis of osteoblasts. In consideration of the lack of effective preventive or treatments options against osteolysis, the exploitation of novel pharmacological compounds/agents is critically required. In our study, we found that a novel antioxidant compound, JSH-23, plays a role in restoring bone homeostasis by scavenging intracellular ROS during both osteoclastogenesis and osteoblastogenesis. Mechanically, JSH-23 suppressed RANKL-induced osteoclastogenesis, bone resorption and the expression of specific genes (including NFATc1, c-Fos, TRAP, CTSK and DC-STAMP) via inhibition of the NF-κB signaling pathway. Meanwhile, JSH-23 suppressed RANKL-induced ROS generation via the TRAF6/Rac1/NOX1 pathway and the enhanced expression of Nrf2/HO-1. In addition, JSH-23 attenuated H₂O₂-induced apoptosis and mineralization reduction in osteoblasts by reducing ROS production and enhancing Nrf2/HO-1 expression. Our in vivo results further revealed that JSH-23 exerts its protective effects on bone mass through its antioxidant activity. In conclusion, our results show that the application of JSH-23 might be a novel and plausible strategy for the treatment of osteolysis-related disease.

Non-flavonoid polyphenols in osteoporosis: preclinical evidence

The development of progressive osteopenia and osteoporosis (OP) is due to the imbalance between bone resorption and bone formation, determining a lower bone resistance, major risks of fractures, with consequent pain and functional limitations. Flavonoids, a class of polyphenols, have been extensively studied for their therapeutic activities against bone resorption, but less attention has been given to a whole series of molecules belonging to the polyphenolic compounds. However, these classes have begun to be studied for the treatment of OP. In this systematic review, comprehensive information is provided on non-flavonoid polyphenolic compounds, and we highlight pathways implicated in the action of these molecules that act often epigenetically, and their possible use for OP treatment and prevention.

Hypoxia inhibits RANKL-induced ferritinophagy and protects osteoclasts from ferroptosis

Ferroptosis is a new form of regulated cell death. Several studies have demonstrated that ferroptosis was involved in multiple diseases. However, the precise role of ferroptosis in osteoporosis remains unclear. Here, we demonstrated that ferroptosis was involved in osteoclasts over the course of RANKL-induced differentiation, and it was induced by iron-starvation response and ferrintinophagy. Mechanistically, under normoxia but not hypoxia, ferroptosis could be induced due to iron-starvation response (increased transferrin receptor 1, decreased ferritin) followed by RANKL stimulation, and this was attributed to the down-regulation of aconitase activity. We further investigated intracellular iron homeostasis and found that ferritinophagy, a process initiated by FTH-NCOA4 complex autophagosome degradation, was activated followed by RANKL stimulation under normoxia. Interestingly, these processes could not be observed under hypoxia. Moreover, we demonstrated that HIF-1α contributed to the decrease of ferritinophagy and autophagy flux under hypoxia. Additionally, HIF-1α impair autophagy flux via inhibition of autophagosome formation under hypoxia in BMDMs. In vivo study, we indicated that HIF-1α specific inhibitor 2ME2 prevent OVX bone loss. In conclusion, our study comprehensively investigated the role of ferroptosis in osteoclasts in vitro and in vivo, and innovatively suggested that targeting HIF-1α and ferritin thus inducing ferroptosis in osteoclasts could be an alternative in treatment of osteoporosis.

919 syrup inhibits ROS-mediated leptin-induced anorexia by activating PPARγ and improves gut flora abnormalities

BACKGROUND

Women with postpartum psychiatric disorders are prone to severe anorexia. Clinical studies have revealed the efficacy of 919 syrup, a traditional Chinese medicine mixture against postpartum illnesses, such as in regulating maternal mood and improving postpartum anorexia.

AIM

This study investigated the mechanisms through which 919 syrup improved anorexia induced by postpartum stress, focussing on the combined peroxisome proliferator-activated receptor gamma (PPARγ) and leptin signalling pathway, and its effects on the structure of the gut flora.

METHODS

Mice were randomly divided into five groups-control group, immobilisation stressed (IS) group (normal saline), pioglitazone (Piog; western medicine control) group, 919 syrup low-dose (TJD; 13.5 g/kg) group, and 919 syrup high-dose (TJG; 27.0 g/kg) group. The control group was housed normally. The other groups received IS for 3 h daily for 21 days. The treatments were initiated following the first postnatal day and were administered by gastric gavage. All mice were sacrificed under anaesthesia on postnatal day 22. Blood, hypothalamus, stomach, and faecal specimens were collected. Gene and protein expression levels of components of the PPARγ-leptin signalling pathway in the serum, hypothalamus, and stomach were determined. Immunofluorescence staining for proopiomelanocortin (POMC), phosphorylated signal transducer and activator of transcription 3 (pSTAT3), and leptin was performed to observe their spatial distributions in the hypothalamus and stomach. 16s rRNA gene sequencing and bioinformatics analysis of fecal specimens were performed.

RESULTS

After IS, postpartum mice showed significantly reduced appetite and body weight, accompanied by abnormalities in the structure of the gut flora. Treatment with 919 syrup (27.0 g/kg) downregulated malondialdehyde and upregulated catalase, glutathione peroxidase, and superoxide dismutase by activating PPARγ, thereby affecting the expression of leptin signalling pathway components (leptin, leptin receptor, pSTAT3, POMC, and cocaine and amphetamine-related transcript and neuropeptide Y), and modulated the gut flora in stressed mice.

CONCLUSION

919 syrup improved appetite in mice with postnatal stress by activating PPARγ to induce crosstalk with the leptin signalling pathway, this mechanism was similar to that of PPARγ agonists. 919 syrup also improved gut flora structure, and the changes in the relative abundances of the gut flora strongly correlated with the expression levels of PPARγ and leptin pathway components.

(-)-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.

Schisandrin A restrains osteoclastogenesis by inhibiting reactive oxygen species and activating Nrf2 signalling

Objectives

Intracellular reactive oxygen species (ROS) induced by receptor activator of NF‐kB ligand (RANKL) has been proven to be a critical factor in the development of osteoclasts. This study aimed to prove that schisandrin A (Sch), a novel anti‐oxidant compound, is able to suppress osteoclastogenesis and prevent bone loss in ovariectomized (OVX) mice by suppressing ROS via nuclear factor erythroid 2‐related factor (Nrf2).

Material and Methods

Micro‐CT was used to detect bone formation. The effects of Sch on receptor activator of nuclear factor‐κB (NF‐κB) ligand (RANKL)‐induced reactive oxygen species (ROS) were measured by dihydroethidium (DHE) staining in vivo and 2',7'‐dichlorodihydrofluorescein diacetate (DCFH‐DA) staining in vitro. Immunofluorescence staining was used to detect the expression of Nrf2 in vivo. siRNA was used to evaluate the effect of Nrf2 in osteoclastogenesis.

Results

Sch suppresses RANKL‐induced ROS production by regulating nuclear factor erythroid 2‐related factor (Nrf2) in vitro and vivo. Mechanistically, Sch enhances the expression of Nrf2 by regulating the degradation of Nrf2. Further, Sch suppresses phosphorylation of P65 and its nuclear translocation, as well as the degradation of IκBα. Collectively, our findings reveal that Sch protects against OVX‐induced bone loss by suppressing ROS via Nrf2.

Conclusions

Our results showed the potential of anti‐oxidant compound schisandrin A in the treatment of osteoporosis, highlighting Nrf2 as a novel promising target in osteoclast‐related disease.