Epigallocatechin-3-gallate inhibits osteoclastic differentiation by modulating mitophagy and mitochondrial functions

The protection of nicotinamide riboside against diabetes mellitus-induced bone loss via OXPHOS

Diabetes mellitus is a global disease that results in various complications, including diabetic osteoporosis. Prior studies have indicated a correlation between low levels of nicotinamide adenine dinucleotide (NAD+) and diabetes-related complications. Nicotinamide riboside (NR), a widely utilized precursor vitamin of NAD+, has been demonstrated to enhance age-related osteoporosis through the Sirt1/FOXO/β-catenin pathway in osteoblast progenitors. However, the impact of NR on bone health in diabetes mellitus remains unclear. In this study, we assessed the potential effects of NR on bone in diabetic mice. NR was administered to high-fat diet (HFD)/streptozotocin (STZ)-induced type 2 diabetic mice (T2DM), and various parameters, including metabolic indicators, bone quality, bone metabolic markers, and RNA sequences, were measured. Our findings confirmed that HFD/STZ-induced T2DM impaired bone microstructures, resulting in bone loss. NR effectively ameliorated insulin resistance, improved bone microarchitecture, and bone quality, reduced bone resorption, enhanced the Forkhead box O (FOXO) signaling pathway, mitigated the nuclear factor kappa B (NF-kB) signaling pathway, and ameliorated the disorder of the oxidative phosphorylation process (OXPHOS) in diabetic mice. In conclusion, NR demonstrated the capacity to alleviate T2DM-induced bone loss through the modulation of OXPHOS in type 2 diabetic mice. Our results underscore the potential of NR as a therapeutic target for addressing T2DM-related bone metabolism and associated diseases. Further cell-based studies under diabetic conditions, such as in vitro cultures of key cell types (e.g., osteoblasts and osteoclasts), are necessary to validate these findings.

Dnmt3a-mediated hypermethylation of FoxO3 promotes redox imbalance during osteoclastogenesis

Redox imbalance contributes to aberrant osteoclastogenesis and osteoporotic bone loss. In this study, we observed lower Forkhead box protein O3 (FoxO3), a transcription factor associated with cellular oxidative stress, enhanced osteoclastogenesis in osteoporosis (OP). Single-cell RNA sequencing (scRNA-seq) analysis on the human femoral head indicated that FoxO3 is widely expressed in macrophages. Furthermore, Lysm-Cre;FoxO3f/f OVX mice showed increased reactive oxygen species (ROS), enhanced osteoclastogenesis, and more bone loss than normal OVX mice. Mechanistically, we identified FoxO3 promoter methylation as a crucial factor contributing to decreased FoxO3, thereby influencing osteoclastogenesis and OC function. Intriguingly, we observed that Dnmt3a, highly expressed during osteoclastogenesis, played a pivotal role in regulating the methylation of the FoxO3 promoter. Knockdown of Dnmt3a promoted FoxO3 expression, inhibiting osteoclastogenesis and mitigating OP. Interestingly, we observed that Dnmt3a alleviated osteoclastogenesis by suppressing ROS via upregulating FoxO3 rather than inducing the dissociation of RANK and TRAF6. Collectively, this study elucidates the role and mechanism of FoxO3 in osteoclastogenesis and OP, providing a epigenetic target for the treatment of OP.

Role of Pink1 in Regulating Osteoclast Differentiation during Periodontitis

Periodontitis has recently been recognized as an inflammatory disease caused by oxidative stress, with mitochondrial dysfunction being a key factor leading to oxidative stress. PTEN-induced kinase 1 (PINK1) is an essential protein for mitochondrial quality control, which protects cells from oxidative stress by inducing mitophagy to degrade damaged mitochondria, but its role in periodontitis has not been elucidated. This study aimed to explore the contribution and underlying mechanisms of Pink1 in regulating the differentiation and function of osteoclasts during periodontitis. Here we observed a significant downregulation of PINK1 expression in periodontitis-affected tissues. Then we constructed a periodontitis model in mice with fluorescently labeled mononuclear/macrophages, and the results showed that as the modeling time extended, the alveolar bone destruction gradually worsened and was accompanied by gradually decreased Pink1 expression in osteoclasts and a significantly increased osteoclast number. In vitro experiments further demonstrated a negative correlation between Pink1 and osteoclast differentiation. In addition, alveolar bone destruction in the Pink1 knockout mice was significantly more advanced than that in the littermate wild type mice after ligature-induced periodontitis and enhanced osteoclastogenesis and bone-resorptive capacity in vitro. RNA-sequencing analysis and in vitro validation revealed that the absence of Pink1 led to a decrease in oxidative phosphorylation levels and an enhancement of calcium-mediated signaling, specifically the calcineurin-NFATc1 pathway, via an intracellular calcium source. Further mechanistic studies found that the deficiency of Pink1 inhibited mitophagy but strengthened mitochondrial-endoplasmic reticulum coupling, which, by promoting the interaction of Mfn2-IP3R-VDAC1 proteins, increased the concentration of mitochondrial calcium ions, thereby triggering more active osteoclast differentiation. The aforementioned process can be reversed by the IP3R channel inhibitor Bcl-XL. These findings unveiled that Pink1 was involved in osteoclast differentiation by regulating mitochondrial calcium transport mediated by mitochondria-associated endoplasmic reticulum membranes, providing a new theoretical basis for the pathogenesis and treatment of periodontitis.

EGCG Alleviates Skeletal Muscle Oxidative Damage in Heat-Stressed Pigs via Keap1/PGAM5 Complex-Mediated Mitophagy

The heat stress (HS) induced by high temperatures can result in oxidative damage to muscles, thereby compromising both muscle growth and immune function within the organism. Mitophagy serves as a pivotal pathway in alleviating excessive ROS production and subsequent oxidative damage. However, the potential role of epigallocatechin-3-gallate (EGCG), a natural antioxidant found in tea, in mitophagy under HS remains unexplored. Here, we present evidence of EGCG mitigating the oxidative-redox imbalance in porcine skeletal muscles induced by HS involving the antioxidant enzyme system mediated by the Keap1/Nrf2 pathway and mitophagy mediated by the PINK1/Parkin pathway. Importantly, we identified phosphate mutase 5 (PGAM5) for the first time as a key protein modulated by EGCG under HS conditions, regulating mitophagy. Inhibition of PGAM5 significantly attenuated the activation of mitophagy by EGCG. Molecular docking and dynamics simulations further suggested that EGCG directly binds to Keap1, disrupting the Keap1-PGAM5 protein interaction and thus promoting the release of PGAM5 and subsequently activating mitophagy. In summary, this study represents the first discovery of EGCG directly targeting Keap1/PGAM5-mediated mitophagy, which serves as a potential functional supplement for regulating the antioxidant capacity in pigs.

3D culture inhibits replicative senescence of SCAPs via UQCRC2-mediated mitochondrial oxidative phosphorylation

Stem cells derived from the apical papilla (SCAPs) play a crucial role in tooth root development and dental pulp regeneration. They are important seed cells for bone/tooth tissue engineering. However, replicative senescence remains an unavoidable issue as in vitro amplification increases. This study investigated the effect of a three-dimensional (3D) culture environment constructed with methylcellulose on SCAPs senescence. It was observed that 3D culture conditions can delay cellular senescence, potentially due to changes in mitochondrial function and oxidative phosphorylation. Transcriptome high-throughput sequencing technology revealed that the different mitochondrial states may be related to UQCRC2. Knocking down UQCRC2 expression in the 3D culture group resulted in increased production of mitochondrial reactive oxygen species, decreased mitochondrial membrane potential, and a decline in the oxygen consumption rate for oxidative phosphorylation, accelerating cell senescence. The results of this study indicated that 3D culture can mitigate SCAPs aging by maintaining UQCRC2-mediated mitochondrial homeostasis. These findings provide a new solution for the senescence of SCAPs during in vitro amplification and can promote the applications of SCAPs-based clinical translation.

Mitochondria in skeletal system-related diseases

Skeletal system-related diseases, such as osteoporosis, arthritis, osteosarcoma and sarcopenia, are becoming major public health concerns. These diseases are characterized by insidious progression, which seriously threatens patients' health and quality of life. Early diagnosis and prevention in high-risk populations can effectively prevent the deterioration of these patients. Mitochondria are essential organelles for maintaining the physiological activity of the skeletal system. Mitochondrial functions include contributing to the energy supply, modulating the Ca2+ concentration, maintaining redox balance and resisting the inflammatory response. They participate in the regulation of cellular behaviors and the responses of osteoblasts, osteoclasts, chondrocytes and myocytes to external stimuli. In this review, we describe the pathogenesis of skeletal system diseases, focusing on mitochondrial function. In addition to osteosarcoma, a characteristic of which is active mitochondrial metabolism, mitochondrial damage occurs during the development of other diseases. Impairment of mitochondria leads to an imbalance in osteogenesis and osteoclastogenesis in osteoporosis, cartilage degeneration and inflammatory infiltration in arthritis, and muscle atrophy and excitationcontraction coupling blockade in sarcopenia. Overactive mitochondrial metabolism promotes the proliferation and migration of osteosarcoma cells. The copy number of mitochondrial DNA and mitochondria-derived peptides can be potential biomarkers for the diagnosis of these disorders. High-risk factor detection combined with mitochondrial component detection contributes to the early detection of these diseases. Targeted mitochondrial intervention is an effective method for treating these patients. We analyzed skeletal system-related diseases from the perspective of mitochondria and provided new insights for their diagnosis, prevention and treatment by demonstrating the relationship between mitochondria and the skeletal system.

Honeycomb Bionic Graphene Oxide Quantum Dot/Layered Double Hydroxide Composite Nanocoating Promotes Osteoporotic Bone Regeneration via Activating Mitophagy

Abnormal osteogenic and remodeling microenvironment due to osteoblast apoptosis are the primary causes of delayed fracture healing in osteoporotic patients. Magnesium (Mg) alloys exhibit biodegradability and appropriate elastic moduli for bone defects in osteoporosis, but the effect on the local bone remodeling disorder is still insufficient. Inspired by the "honeycomb," layered double hydroxide (LDH) with regular traps with graphene oxide quantum dots (GOQDs) inlayed is constructed by pulsed electrodeposition to generate GOQD/LDH composite nanocoatings on the surfaces of Mg alloy substrates. The honeycomb bionic multi-layer stereoscopic structure shows good regulation of the degradation of Mg alloy for the support of healing time required for osteoporotic bone defect. Within its lattice, the local microenvironment conducive to osteogenesis is provided by both the rescue effect of GOQD and LDH. The osteoblast apoptosis is rescued due to the activation of mitophagy to clear dysfunctional mitochondria, where the upregulation of BNIP3 phosphorylation played a key role. The osteoporotic rat model of femoral defects confirmed the improvement of bone regeneration and osseointegration of GOQD/LDH coating. In summary, honeycomb bionic composite nanocoatings with controllable degradation and excellent pro-osteogenic performance demonstrated a promising design strategy on Mg alloy implants in the therapy of osteoporotic bone defects.

NDR2 is critical for osteoclastogenesis by regulating ULK1-mediated mitophagy

Bone homeostasis primarily stems from the balance between osteoblasts and osteoclasts, wherein an augmented number or heightened activity of osteoclasts is a prevalent etiological factor in the development of bone loss. Nuclear Dbf2-related kinase (NDR2), also known as STK38L, is a member of the Hippo family with serine/threonine kinase activity. We unveiled an upregulation of NDR2 expression during osteoclast differentiation. Manipulation of NDR2 levels through knockdown or overexpression facilitated or hindered osteoclast differentiation, respectively, indicating a negative feedback role for NDR2 in the osteoclastogenesis. Myeloid NDR2-dificient mice (Lysm+NDR2fl/fl) showed lower bone mass and further exacerbated ovariectomy-induced or aging-related bone loss. Mechanically, NDR2 enhanced autophagy and mitophagy through mediating ULK1 instability. In addition, ULK1 inhibitor (ULK1-IN2) ameliorated NDR2 conditional KO-induced bone loss. Finally, we clarified a significant inverse association between NDR2 expression and the occurrence of osteoporosis in patients. The NDR2/ULK1/mitophagy axis is a potential innovative therapeutic target for the prevention and management of bone loss.

Metformin improves HPRT1-targeted purine metabolism and repairs NR4A1-mediated autophagic flux by modulating FoxO1 nucleocytoplasmic shuttling to treat postmenopausal osteoporosis

Osteoporosis is a major degenerative metabolic bone disease that threatens the life and health of postmenopausal women. Owing to limitations in detection methods and prevention strategy awareness, the purpose of osteoporosis treatment is more to delay further deterioration rather than to fundamentally correct bone mass. We aimed to clarify the pathogenesis of postmenopausal osteoporosis and optimize treatment plans. Our experiments were based on previous findings that oxidative stress mediates bone metabolism imbalance after oestrogen deficiency. Through energy metabolism-targeted metabolomics, we revealed that purine metabolism disorder is the main mechanism involved in inducing oxidative damage in bone tissue, which was verified via the use of machine-learning data from human databases. Xanthine and xanthine oxidase were used to treat osteoblasts to construct a purine metabolism disorder model. The activity and differentiation ability of osteoblasts decreased after X/XO treatment. Transcriptomic sequencing indicated that autophagic flux damage was involved in purine metabolism-induced oxidative stress in osteoblasts. Additionally, we performed serum metabolomics combined with network pharmacology to determine the pharmacological mechanism of metformin in the treatment of postmenopausal osteoporosis. HPRT1 was the potential target filtered from the hub genes, and FoxO1 signalling was the key pathway mediating the effect of metformin in osteoblasts. We also revealed that SIRT3-mediated deacetylation promoted the nuclear localization of FoxO1 to increase the expression of HPRT1. HPRT1 upregulation promoted purine anabolism and prevented the accumulation of ROS caused by purine catabolism to reverse oxidative damage in osteoblasts. We propose that purine metabolism disorder-induced oxidative stress is important for the pathogenesis of postmenopausal osteoporosis. The therapeutic mechanism of metformin should be confirmed through subsequent drug optimization and development studies to improve bone health in postmenopausal women.

Alendronate sodium induces G1 phase arrest and apoptosis in human umbilical vein endothelial cells by inhibiting ROS-mediated ERK1/2 signaling

Bisphosphonates are potent bone resorption inhibitors, among which alendronate sodium (ALN) is commonly prescribed for most osteoporosis patients, but long-term application of ALN can cause bisphosphonate-related osteonecrosis of jaw (BRONJ), the pathogenesis of which remains unclear. Previous studies have suggested that bisphosphonates cause jaw ischemia by affecting the biological behavior of vascular endothelial cells, leading to BRONJ. However, the impacts of ALN on vascular endothelial cells and its mechanism remain unclear. The purpose of this work is to assess the influence of ALN on human umbilical vein endothelial cells (HUVECs) and clarify the molecular pathways involved. We found that high concentration of ALN induced G1 phase arrest in HUVECs, demonstrated by downregulation of Cyclin D1 and Cyclin D3. Moreover, high concentration of ALN treatment showed pro-apoptotic effect on HUVECs, demonstrated by increased levels of the cleaved caspase-3, the cleaved PARP and Bax, along with decreased levels of anti-apoptotic protein Bcl-2. Further experiments showed that ERK1/2 phosphorylation was decreased. Additionally, ALN provoked the build-up of reactive oxygen species (ROS) in HUVECs, leading to ERK1/2 pathway suppression. N-acetyl-L-cysteine (NAC), a ROS scavenger, efficiently promoted the ERK1/2 phosphorylation and mitigated the G1 phase arrest and apoptosis triggered by ALN in HUVECs. PD0325901, an inhibitor of ERK1/2 that diminishes the ERK1/2 phosphorylation enhanced the ALN-induced G1 phase arrest and apoptosis in HUVECs. These findings show that ALN induces G1 phase arrest and apoptosis through ROS-mediated ERK1/2 pathway inhibition in HUVECs, providing novel insights into the pathogenic process, prevention and treatment of BRONJ in individuals receiving extended use of ALN.

Targeting Endoplasmic Reticulum Stress by Natural and Chemical Compounds Ameliorates Cisplatin-Induced Nephrotoxicity: A Review

Cisplatin is a chemotherapeutic that dose-dependently causes renal complications such as decreased kidney function and acute kidney injury. The endoplasmic reticulum (ER) is responsible for calcium homeostasis and protein folding and plays a major part in cisplatin's nephrotoxicity. The current article reviews how chemical and natural compounds modulate cisplatin-induced apoptosis, autophagy, and inflammation by inhibiting ER stress signaling pathways. The available evidence indicates that natural compounds (Achyranthes aspera water-soluble extract, morin hydrate, fucoidan, isoliquiritigenin, leonurine, epigallocatechin-3-gallate, grape seed proanthocyanidin, and ginseng polysaccharide) and chemicals (Sal003, NSC228155, TUG891, dorsomorphin (compound C), HC-030031, dexmedetomidine, and recombinant human erythropoietin (rHuEpo)) can alleviate cisplatin nephrotoxicity by suppression of ER stress signaling pathways including IRE1α/ASK1/JNK, PERK-eIF2α-ATF4, and ATF6, as well as PI3K/AKT signaling pathway. Since ER and related signaling pathways are important in cisplatin nephrotoxicity, agents that can inhibit the abovementioned signaling pathways may hold promise in alleviating this untoward adverse effect.

Cell life-or-death events in osteoporosis: All roads lead to mitochondrial dynamics

Mitochondria exhibit heterogeneous shapes and networks within and among cell types and tissues, also in normal or osteoporotic bone tissues with complex cell types. This dynamic characteristic is determined by the high plasticity provided by mitochondrial dynamics and is stemmed from responding to the survival and functional requirements of various bone cells in a specific microenvironments. In contrast, mitochondrial dysfunction, induced by dysregulation of mitochondrial dynamics, may act as a trigger of cell death signals, including common apoptosis and other forms of programmed cell death (PCD). These PCD processes consisting of tightly structured cascade gene expression events, can further influence the bone remodeling by facilitating the death of various bone cells. Mitochondrial dynamics, therefore, drive the bone cells to stand at the crossroads of life and death by integrating external signals and altering metabolism, shape, and signal-response properties of mitochondria. This implies that targeting mitochondrial dynamics displays significant potential in treatment of osteoporosis. Considerable effort has been made in osteoporosis to emphasize the parallel roles of mitochondria in regulating energy metabolism, calcium signal transduction, oxidative stress, inflammation, and cell death. However, the emerging field of mitochondrial dynamics-related PCD is not well understood. Herein, to bridge the gap, we outline the latest knowledge on mitochondrial dynamics regulating bone cell life or death during normal bone remodeling and osteoporosis.

The Emerging Role of the Mitochondrial Respiratory Chain in Skeletal Aging

Maintenance of mitochondrial homeostasis is crucial for ensuring healthy mitochondria and normal cellular function. This process is primarily responsible for regulating processes that include mitochondrial OXPHOS, which generates ATP, as well as mitochondrial oxidative stress, apoptosis, calcium homeostasis, and mitophagy. Bone mesenchymal stem cells express factors that aid in bone formation and vascular growth. Positive regulation of hematopoietic stem cells in the bone marrow affects the differentiation of osteoclasts. Furthermore, the metabolic regulation of cells that play fundamental roles in various regions of the bone, as well as interactions within the bone microenvironment, actively participates in regulating bone integrity and aging. The maintenance of cellular homeostasis is dependent on the regulation of intracellular organelles, thus understanding the impact of mitochondrial functional changes on overall bone metabolism is crucially important. Recent studies have revealed that mitochondrial homeostasis can lead to morphological and functional abnormalities in senescent cells, particularly in the context of bone diseases. Mitochondrial dysfunction in skeletal diseases results in abnormal metabolism of bone-associated cells and a secondary dysregulated microenvironment within bone tissue. This imbalance in the oxidative system and immune disruption in the bone microenvironment ultimately leads to bone dysplasia. In this review, we examine the latest developments in mitochondrial respiratory chain regulation and its impacts on maintenance of bone health. Specifically, we explored whether enhancing mitochondrial function can reduce the occurrence of bone cell deterioration and improve bone metabolism. These findings offer prospects for developing bone remodeling biology strategies to treat age-related degenerative diseases.

Isolation, Characterization, and Functional Properties of Antioxidant Peptides from Mulberry Leaf Enzymatic Hydrolysates

Recent evidence suggests that mulberry leaves have good antioxidant activity. However, what the antioxidant ingredient is and how the ingredient works are still not well understood. In this study, we enzymatically hydrolyze mulberry leaf proteins (MLPs) using neutral protease and find that the mulberry leaf protein hydrolysates (MLPHs) have stronger antioxidant activity compared to MLPs. We separate the core antioxidant components in MLPHs by ion-exchange columns and molecular sieves and identify 798 antioxidant peptides by LC-MS/MS. Through bioinformatics analysis and biochemical assays, we screen two previously unreported peptides, P6 and P7, with excellent antioxidant activities. P6 and P7 not only significantly reduce ROS in cells but also improve the activities of the antioxidant enzymes SOD and CAT. In addition, both peptides are found to exert protective effects against H2O2-induced chromatin damage and cell apoptosis. Collectively, these results provide support for the application of mulberry leaf peptides as antioxidants in the medical, food and livestock industries.

Attenuating bone loss in osteoporosis: the potential of corylin (CL) as a therapeutic agent

The global prevalence of osteoporosis is being exacerbated by the increasing number of aging societies and longer life expectancies. In response, numerous drugs have been developed in recent years to mitigate bone resorption and enhance bone density. Nonetheless, the efficacy and safety of these pharmaceutical interventions remain constrained. Corylin (CL), a naturally occurring compound derived from the anti-osteoporosis plant Psoralea corylifolia L., has exhibited promising potential in impeding osteoclast differentiation. This study aims to evaluate the effect and molecular mechanisms of CL regulating osteoclast differentiation in vitro and its potential as a therapeutic agent for osteoporosis treatment in vivo. Our investigation revealed that CL effectively inhibits osteoclast formation and their bone resorption capacity by downregulating the transcription factors NFATc1 and c-fos, consequently resulting in the downregulation of genes associated with bone resorption. Furthermore, it has been observed that CL can effectively mitigate the migration and fusion of pre-osteoclast, while also attenuating the activation of mitochondrial mass and function. The results obtained from an in vivo study have demonstrated that CL is capable of attenuating the bone loss induced by ovariectomy (OVX). Based on these significant findings, it is proposed that CL exhibits considerable potential as a novel drug strategy for inhibiting osteoclast differentiation, thereby offering a promising approach for the treatment of osteoporosis.

Mini-encyclopedia of mitochondria-relevant nutraceuticals protecting health in primary and secondary care-clinically relevant 3PM innovation

Despite their subordination in humans, to a great extent, mitochondria maintain their independent status but tightly cooperate with the "host" on protecting the joint life quality and minimizing health risks. Under oxidative stress conditions, healthy mitochondria promptly increase mitophagy level to remove damaged "fellows" rejuvenating the mitochondrial population and sending fragments of mtDNA as SOS signals to all systems in the human body. As long as metabolic pathways are under systemic control and well-concerted together, adaptive mechanisms become triggered increasing systemic protection, activating antioxidant defense and repair machinery. Contextually, all attributes of mitochondrial patho-/physiology are instrumental for predictive medical approach and cost-effective treatments tailored to individualized patient profiles in primary (to protect vulnerable individuals again the health-to-disease transition) and secondary (to protect affected individuals again disease progression) care. Nutraceuticals are naturally occurring bioactive compounds demonstrating health-promoting, illness-preventing, and other health-related benefits. Keeping in mind health-promoting properties of nutraceuticals along with their great therapeutic potential and safety profile, there is a permanently growing demand on the application of mitochondria-relevant nutraceuticals. Application of nutraceuticals is beneficial only if meeting needs at individual level. Therefore, health risk assessment and creation of individualized patient profiles are of pivotal importance followed by adapted nutraceutical sets meeting individual needs. Based on the scientific evidence available for mitochondria-relevant nutraceuticals, this article presents examples of frequent medical conditions, which require protective measures targeted on mitochondria as a holistic approach following advanced concepts of predictive, preventive, and personalized medicine (PPPM/3PM) in primary and secondary care.

Metal-Phenolic Networks-Reinforced Extracellular Matrix Scaffold for Bone Regeneration via Combining Radical-Scavenging and Photo-Responsive Regulation of Microenvironment

The limited regulation strategies of the regeneration microenvironment significantly hinder bone defect repair effectiveness. One potential solution is using biomaterials capable of releasing bioactive ions and biomolecules. However, most existing biomaterials lack real-time control features, failing to meet high regulation requirements. Herein, a new Strontium (Sr) and epigallocatechin-3-gallate (EGCG) based metal-phenolic network with polydopamine (PMPNs) modification is prepared. This material reinforces a biomimetic scaffold made of extracellular matrix (ECM) and hydroxyapatite nanowires (nHAW). The PMPNs@ECM/nHAW scaffold demonstrates exceptional scavenging of free radicals and reactive oxygen species (ROS), promoting HUVECs cell migration and angiogenesis, inducing stem cell osteogenic differentiation, and displaying high biocompatibility. Additionally, the PMPNs exhibit excellent photothermal properties, further enhancing the scaffold's bioactivities. In vivo studies confirm that PMPNs@ECM/nHAW with near-infrared (NIR) stimulation significantly promotes angiogenesis and osteogenesis, effectively regulating the microenvironment and facilitating bone tissue repair. This research not only provides a biomimetic scaffold for bone regeneration but also introduces a novel strategy for designing advanced biomaterials. The combination of real-time photothermal intervention and long-term chemical intervention, achieved through the release of bioactive molecules/ions, represents a promising direction for future biomaterial development.

Short-term regulation of TSFM level does not alter amyloidogenesis and mitochondrial function in type-specific cells

BACKGROUND

Mitochondrial Ts translation elongation factor (TSFM) is an enzyme that catalyzes exchange of guanine nucleotides. By forming a complex with mitochondrial Tu translation elongation factor (TUFM), TSFM participates in mitochondrial protein translation. We have previously reported that TUFM regulates translation of beta-site APP cleaving enzyme 1 (BACE1) via ROS (reactive oxygen species)-dependent mechanism, suggesting a potential role in amyloid precursor protein (APP) processing associated with Alzheimer's disease (AD), which led to the speculation that TSFM may regulate APP processing in a similar way to TUFM.

METHODS AND RESULTS

Here, we report that in cultured cells, knockdown or overexpression TSFM did not change protein levels in BACE1 and APP. Besides, the levels of cytoplasmic ROS and mitochondrial superoxide, in addition to ATP level, cell viability and mitochondrial membrane potential were not significantly altered by TSFM knockdown in the short term. Further transcriptome analysis revealed that expression of majority of mitochondrial genes were not remarkably changed by TSFM silencing. The possibility of TSFM involved in cardiomyopathy and cancer development was uncovered using bioinformatics analysis.

CONCLUSIONS

Collectively, short-term regulation of TSFM level in cultured cells does not cause a significant change in proteins involved in APP processing, levels in ROS and ATP associated with mitochondrial function. Whereas our study could contribute to comprehend certain clinical features of TSFM mutations, the roles of TSFM in cardiomyopathy and cancer development might deserve further investigation.

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.

Mitochondrial Dysfunction in Periodontitis and Associated Systemic Diseases: Implications for Pathomechanisms and Therapeutic Strategies

Periodontitis is a chronic infectious disorder damaging periodontal tissues, including the gingiva, periodontal ligament, cementum, and alveolar bone. It arises from the complex interplay between pathogenic oral bacteria and host immune response. Contrary to the previous view of "energy factories", mitochondria have recently been recognized as semi-autonomous organelles that fine-tune cell survival, death, metabolism, and other functions. Under physiological conditions, periodontal tissue cells participate in dynamic processes, including differentiation, mineralization, and regeneration. These fundamental activities depend on properly functioning mitochondria, which play a crucial role through bioenergetics, dynamics, mitophagy, and quality control. However, during the initiation and progression of periodontitis, mitochondrial quality control is compromised due to a range of challenges, such as bacterial-host interactions, inflammation, and oxidative stress. Currently, mounting evidence suggests that mitochondria dysfunction serves as a common pathological mechanism linking periodontitis with systemic conditions like type II diabetes, obesity, and cardiovascular diseases. Therefore, targeting mitochondria to intervene in periodontitis and multiple associated systemic diseases holds great therapeutic potential. This review provides advanced insights into the interplay between mitochondria, periodontitis, and associated systemic diseases. Moreover, we emphasize the significance of diverse therapeutic modulators and signaling pathways that regulate mitochondrial function in periodontal and systemic cells.

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.

Secretory products of DPSC mitigate inflammatory effects in microglial cells by targeting MAPK pathway

Activated microglial cells in the central nervous system (CNS) are the main contributors to neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. Inhibiting their activation will help in reducing inflammation and oxidative stress during pathogenesis, potentially limiting the progression of the diseases. The immunomodulation properties of dental pulp-derived stem cells (DPSC) make it a promising therapy for neurodegenerative disorders. This study aims to determine whether secretory factors of DPSC (DPSC℗) inhibit inflammation and proliferation of microglial cells and define the molecular mechanisms. Our quantitative RT-PCR analysis showed that the DPSC℗ reduced the markers of the inflammation and induced anti-inflammatory molecules in microglial cells. DPSC ℗ reduced the intracellular and mitochondrial reactive oxygen species (ROS) production and mitochondrial membrane potential in microglial cells. In addition, DPSC ℗ decreased the cellular bioenergetics parameters related to oxygen consumption rate (OCAR) and extracellular acidification rate (ECAR). We found that DPSC℗ inhibited microglial cell proliferation by activating a checkpoint molecule, Chk1 leading an arrest at the G1 phase of the cell cycle. To define the mechanism, we performed the western blot analysis and observed that the MAPK P38 pathway was inhibited by DPSC℗. Furthermore, a System biology analysis revealed that the BDNF and GDNF, secretory factors of DPSC, blocked at the phosphorylation site (Tyr 182) of the P38 molecule resulting in the inhibition of downstream signaling of inflammation. These data suggest that the DPSC℗ may be a potential therapeutic agent for neurodegenerative diseases.

Polyphenols as potential preventers of osteoporosis: A comprehensive review on antioxidant and anti-inflammatory effects, molecular mechanisms, and signal pathways in bone metabolism

Osteoporosis (OP) is a skeletal disorder characterized by decreased bone density, alterations in bone microstructure, and increased damage to the bones. As the population ages and life expectancy increases, OP has become a global epidemic, drawing attention from scientists and doctors. Because of polyphenols have favorable antioxidant and anti-allergy effects, which are regarded as potential methods to prevent angiocardipathy and OP. Polyphenols offer a promising approach to preventing and treating OP by affecting bone metabolism, reducing bone resolution, maintaining bone density, and lowering the differentiation level of osteoclasts (OC). There are multiple ways in which polyphenols affect bone metabolism. This article provides an overview of how polyphenols inhibit oxidative stress, exert antibacterial effects, and prevent the occurrence of OP. Furthermore, we will explore the regulatory mechanisms and signaling pathways implicated in this process.

Secretome of Dental Pulp-Derived Stem Cells Reduces Inflammation and Proliferation of Glioblastoma Cells by Deactivating Mapk-Akt Pathway

Background

Dental pulp-derived stem cells (DPSC) is a promising therapy as they modulate the immune response, so we evaluated the inhibitory effect of DPSC secretome (DPSC℗) on the proliferation and inflammation in human glioblastoma (GBM) cells (U-87 MG) and elucidated the concomitant mechanisms involved.

Methods

The U87-MG cells were cultured with DPSC℗ for 24 h and assessed the expression of inflammatory molecules using quantitative reverse transcription-polymerase chain reaction (qRT-PCR), generation of reactive oxygen species (ROS), and mitochondrial functionality using a seahorse flux analyzer. MTT (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide) assay and cell cycle analysis were performed to evaluate the proliferation and cell cycle. Finally, the protein levels were determined by western blot.

Results

DPSC℗ reduced the inflammation and proliferation of U-87 MG cells by down-regulating the pro-inflammatory markers and up-regulating anti-inflammatory markers expressions through ROS-mediated signaling. Moreover, DPSC℗ significantly reduced the mitochondrial membrane potential (MMP) in the cells. The cellular bioenergetics revealed that all the parameters of oxygen consumption rate (OCAR) and the extracellular acidification rate (ECAR) were significantly decreased in the GBM cells after the addition of DPSC℗. Additionally, DPSC℗ decreased the GBM cell proliferation by arresting the cell cycle at the G1 phase through activation (phosphorylation) of checkpoint molecule CHK1. Furthermore, mechanistically, we found that the DPSC℗ impedes the phosphorylation of the mitogen-activated protein kinases (P38 MAPK) and protein kinase B (AKT) pathway.

Conclusion

Our findings lend the first evidence of the inhibitory effects of DPSC℗ on proliferation and inflammation in GBM cells by altering the P38 MAPK-AKT pathway.

Lysophosphatidic acid exerts protective effects on HEI-OC1 cells against cytotoxicity of cisplatin by decreasing apoptosis, excessive autophagy, and accumulation of ROS

Lysophosphatidic acid (LPA) is an active phospholipid signaling molecule that binds to six specific G protein-coupled receptors (LPA1-6) on the cell surface and exerts a variety of biological functions, including cell migration and proliferation, morphological changes, and anti-apoptosis. The earliest study from our group demonstrated that LPA treatment could restore cochlear F-actin depolymerization induced by noise exposure, reduce hair cell death, and thus protect hearing. However, whether LPA could protect against cisplatin-induced ototoxicity and which receptors play the major role remain unclear. To this end, we integrated the HEI-OC1 mouse cochlear hair cell line and zebrafish model, and found that cisplatin exposure induced a large amount of reactive oxygen species accumulation in HEI-OC1 cells, accompanied by mitochondrial damage, leading to apoptosis and autophagy. LPA treatment significantly attenuated autophagy and apoptosis in HEI-OC1 cells after cisplatin exposure. Further investigation revealed that all LPA receptors except LPA3 were expressed in HEI-OC1 cells, and the mRNA expression level of LPA1 receptor was significantly higher than that of other receptors. When LPA1 receptor was silenced, the protective effect of LPA was reduced and the proportion of apoptosis cells was increased, indicating that LPA-LPA1 plays an important role in protecting HEI-OC1 cells from cisplatin-induced apoptosis. In addition, the behavioral trajectory and in vivo fluorescence imaging results showed that cisplatin exposure caused zebrafish to move more actively, and the movement speed and distance were higher than those of the control and LPA groups, while LPA treatment reduced the movement behavior. Cisplatin caused hair cell death and loss in zebrafish lateral line, and LPA treatment significantly protected against hair cell death and loss. LPA has a protective effect on hair cells in vitro and in vivo against the cytotoxicity of cisplatin, and its mechanism may be related to reducing apoptosis, excessive autophagy and ROS accumulation.

Icaritin ameliorates RANKL-mediated osteoclastogenesis and ovariectomy-induced osteoporosis

A rapidly aging society and longer life expectancy are causing osteoporosis to become a global epidemic. Over the last five decades, a number of drugs aimed at reducing bone resorption or restoring bone mass have been developed, but their efficacy and safety are limited. Icaritin (ICT) is a natural compound extracted from anti-osteoporosis herb Epimedium spp. and has been shown to inhibit osteoclast differentiation. However, the molecular mechanism by which ICT weaken RANKL-induced osteoclast differentiation has not been completely investigated. Here, we evaluated the anti-osteoclastogenic effect of ICT in vitro and the potential drug candidate for treating osteoporosis in vivo. In vitro study, ICT was found to inhibit osteoclast formation and bone resorption function via downregulating transcription factors activated T cell cytoplasm 1 (NFATc1) and c-fos, which further downregulate osteoclastogenesis-specific gene. In addition, the enhanced mitochondrial mass and function required for osteoclast differentiation was mitigated by ICT. The histomorphological results from an in vivo study showed that ICT attenuated the bone loss associated with ovariectomy (OVX). Based on these results, we propose ICT as a promising new drug strategy for osteoporosis that inhibits osteoclast differentiation.

Mitophagy Effects of Protodioscin on Human Osteosarcoma Cells by Inhibition of p38MAPK Targeting NIX/LC3 Axis

Protodioscin (PD) is a steroidal saponin with various pharmacological activities, including neuro-protective, anti-inflammatory, and anti-tumor activities. However, the effect of PD on human osteosarcoma (OS) cells is unclear. In this study, we found that PD significantly inhibits the growth of human HOS and 143B OS cells through the upregulation of apoptotic-related proteins (cleaved caspase-3, cleaved caspase-9, and cleaved PARP) and mitophagy-related proteins (LC3B and NIX), which contribute to the induction of apoptosis, and MMP (mitochondrial membrane potential) dysfunction and mitophagy. The inhibition of LC3 or NIX was shown to decrease apoptosis and mitophagy in PD-treated OS cells. The knockdown of p38MAPK by siRNA decreased mitochondrial dysfunction, autophagy, mitophagy, and the NIX/LC3B expression in the PD-treated OS cells. A binding affinity analysis revealed that the smaller the KD value (-7.6 Kcal/mol and -8.9 Kcal/mol, respectively), the greater the binding affinity in the PD-NIX and PD-LC3 complexes. These findings show the inhibitory effects of PD-induced mitophagy in human OS cells and may represent a novel therapeutic strategy for human OS, by targeting the NIX/LC3 pathways.

Mitochondrial quality control and its role in osteoporosis

Mitochondria are important organelles that provide cellular energy and play a vital role in cell differentiation and apoptosis. Osteoporosis is a chronic metabolic bone disease mainly caused by an imbalance in osteoblast and osteoclast activity. Under physiological conditions, mitochondria regulate the balance between osteogenesis and osteoclast activity and maintain bone homeostasis. Under pathological conditions, mitochondrial dysfunction alters this balance; this disruption is important in the pathogenesis of osteoporosis. Because of the role of mitochondrial dysfunction in osteoporosis, mitochondrial function can be targeted therapeutically in osteoporosis-related diseases. This article reviews different aspects of the pathological mechanism of mitochondrial dysfunction in osteoporosis, including mitochondrial fusion and fission, mitochondrial biogenesis, and mitophagy, and highlights targeted therapy of mitochondria in osteoporosis (diabetes induced osteoporosis and postmenopausal osteoporosis) to provide novel targets and prevention strategies for the prevention and treatment of osteoporosis and other chronic bone diseases.