Blockade of Drp1 rescues oxidative stress-induced osteoblast dysfunction

The multifaceted roles of mitochondria in osteoblasts: from energy production to mitochondrial-derived vesicle secretion

Mitochondria in osteoblasts have been demonstrated to play multiple crucial functions in bone formation from intracellular adenosine triphosphate production to extracellular secretion of mitochondrial components. The present review explores the current knowledge about mitochondrial biology in osteoblasts, including mitochondrial biogenesis, bioenergetics, oxidative stress generation, and dynamic changes in morphology. Special attention is given to recent findings, including mitochondrial donut formation in osteoblasts, which actively generates mitochondrial-derived vesicles (MDVs), followed by extracellular secretion of small mitochondria and MDVs. We also discuss the therapeutic effects of targeting osteoblast mitochondria, highlighting their potential applications in improving bone health.

Role of oxidative stress in the concurrent development of osteoporosis and tendinopathy: Emerging challenges and prospects for treatment modalities

Both osteoporosis and tendinopathy are widely prevalent disorders, encountered in diverse medical contexts. Whilst each condition has distinct pathophysiological characteristics, they share several risk factors and underlying causes. Notably, oxidative stress emerges as a crucial intersecting factor, playing a pivotal role in the onset and progression of both diseases. This imbalance arises from a dysregulation in generating and neutralising reactive oxygen species (ROS), leading to an abnormal oxidative environment. Elevated levels of ROS can induce multiple cellular disruptions, such as cytotoxicity, apoptosis activation and reduced cell function, contributing to tissue deterioration and weakening the structural integrity of bones and tendons. Antioxidants are substances that can prevent or slow down the oxidation process, including Vitamin C, melatonin, resveratrol, anthocyanins and so on, demonstrating potential in treating these overlapping disorders. This comprehensive review aims to elucidate the complex role of oxidative stress within the interlinked pathways of these comorbid conditions. By integrating contemporary research and empirical findings, our objective is to outline new conceptual models and innovative treatment strategies for effectively managing these prevalent diseases. This review underscores the importance of further in-depth research to validate the efficacy of antioxidants and traditional Chinese medicine in treatment plans, as well as to explore targeted interventions focused on oxidative stress as promising areas for future medical advancements.

Naringenin, a flavanone constituent from Sea buckthorn pulp extract, prevents ultraviolet (UV)-B radiation-induced skin damage via alleviation of impaired mitochondrial dynamics mediated inflammation in human dermal fibroblasts and Balb/c mice models

Ultraviolet-B (UV-B) irradiation has been reported to cause oxidative stress and inflammation-mediated skin photo-damage. Furthermore, mitochondrial dynamics have been implicated to play a critical role in these processes. For the first time, we describe in this study how UVB-induced aberrant mitochondrial dynamics and inflammation interact in primary human dermal fibroblasts (HDFs). Our findings demonstrated that UV-B irradiation induced -impairment in mitochondrial dynamics by increasing mitochondrial fragmentation in HDFs. Imbalanced mitochondrial dynamics lead to the activation of NFкB and pro-inflammatory cytokines. The current study further aimed to investigate the protective effect of Naringenin (a naturally occurring flavonoid isolated from Sea buckthorn fruit pulp) against UV-B-induced mitochondrial fragmentation and inflammation in HDFs and Balb/c mice. Although Naringenin has been shown to have anti-inflammatory and antioxidant potential, its effects and mechanisms of action on UVB-induced inflammation remained unclear. We observed that Naringenin restored the UV-B-induced imbalance in mitochondrial fission and fusion in HDFs. It also inhibited the phosphorylation of NFкB and reduced the generation of pro-inflammatory cytokines. Naringenin also alleviated UV-B-induced oxidative stress by scavenging the reactive oxygen species and up-regulating the cellular antioxidant enzymes (Catalase and Nrf2). Topical application of Naringenin to the dorsal skin of Balb/c mice exposed to UV-B radiation prevented mitochondrial fragmentation and progression of inflammatory responses. Naringenin treatment prevented neutrophil infiltration and epidermal thickening in mice's skin. These findings provide an understanding for further research into impaired mitochondrial dynamics as a therapeutic target for UV-B-induced inflammation. Our findings imply that Naringenin could be developed as a therapeutic remedy against UVB-induced inflammation.

A high concentrate diet inhibits forkhead box protein A2 expression, and induces oxidative stress, mitochondrial dysfunction and mitochondrial unfolded protein response in the liver of dairy cows

High-concentrate diet induce subacute ruminal acidosis (SARA) and cause liver damage in ruminants. It has been reported that forkhead box protein A2 (FOXA2) can enhance mitochondrial membrane potential but its function in mitochondrial dysfunction induced by high concentrate diets is still unknown. Therefore, the aim of this study was to elucidate the effect of high-concentrate (HC) diet on hepatic FOXA2 expression, mitochondrial unfolded protein response (UPRmt), mitochondrial dysfunction and oxidative stress. A total of 12 healthy mid-lactation Holstein cows were selected and randomized into 2 groups: the low concentrate (LC) diet group (concentrate:forage = 4:6) and HC diet group (concentrate:forage = 6:4). The trial lasted 21 d. The rumen fluid, blood and liver tissue were collected at the end of the experiment. The results showed that the rumen fluid pH level was reduced in the HC group and the pH was lower than 5.6 for more than 4 h/d, indicating that feeding HC diets successfully induced SARA in dairy cows. Both FOXA2 mRNA and protein abundance were significantly reduced in the liver of the HC group compared with the LC group. The activity of antioxidant enzymes (CAT, G6PDH, T-SOD, Cu/Zn SOD, Mn SOD) and mtDNA copy number in the liver tissue of the HC group decreased, while the level of H2O2 significantly increased, this increase was accompanied by a decrease in oxidative phosphorylation (OXPHOS). The balance of mitochondrial division and fusion was disrupted in the HC group, as evidenced by the decreased mRNA level of OPA1, MFN1, and MFN2 and increased mRNA level of Drp1, Fis1, and MFF. At the same time, HC diet downregulated the expression level of SIRT1, SIRT3, PGC-1α, TFAM, and Nrf 1 to inhibit mitochondrial biogenesis. The HC group induced UPRmt in liver tissue by upregulating the mRNA and protein levels of CLPP, LONP1, CHOP, Hsp10, and Hsp60. In addition, HC diet could increase the protein abundance of Bax, CytoC, Caspase 3 and Cleaved-Caspase 3, while decrease the protein abundance of Bcl-2 and the Bcl-2/Bax ratio. Overall, our study suggests that the decreased expression of FOXA2 may be related to UPRmt, mitochondrial dysfunction, oxidative stress, and apoptosis in the liver of dairy cows fed a high concentrate diet.

Mitochondrial dysfunction and therapeutic perspectives in osteoporosis

Osteoporosis (OP) is a systemic skeletal disorder characterized by reduced bone mass and structural deterioration of bone tissue, resulting in heightened vulnerability to fractures due to increased bone fragility. This condition primarily arises from an imbalance between the processes of bone resorption and formation. Mitochondrial dysfunction has been reported to potentially constitute one of the most crucial mechanisms influencing the pathogenesis of osteoporosis. In essence, mitochondria play a crucial role in maintaining the delicate equilibrium between bone formation and resorption, thereby ensuring optimal skeletal health. Nevertheless, disruption of this delicate balance can arise as a consequence of mitochondrial dysfunction. In dysfunctional mitochondria, the mitochondrial electron transport chain (ETC) becomes uncoupled, resulting in reduced ATP synthesis and increased generation of reactive oxygen species (ROS). Reinforcement of mitochondrial dysfunction is further exacerbated by the accumulation of aberrant mitochondria. In this review, we investigated and analyzed the correlation between mitochondrial dysfunction, encompassing mitochondrial DNA (mtDNA) alterations, oxidative phosphorylation (OXPHOS) impairment, mitophagy dysregulation, defects in mitochondrial biogenesis and dynamics, as well as excessive ROS accumulation, with regards to OP (Figure 1). Furthermore, we explore prospective strategies currently available for modulating mitochondria to ameliorate osteoporosis. Undoubtedly, certain therapeutic strategies still require further investigation to ensure their safety and efficacy as clinical treatments. However, from a mitochondrial perspective, the potential for establishing effective and safe therapeutic approaches for osteoporosis appears promising.

Does crocin create new hope for the treatment of oral problems? A focus on periodontitis

According to the World Health Organization (WHO) reports, oral health has an indispensable role in the maintenance of human public health. However, oral problems, especially periodontitis, are known as bad players in this issue. Periodontitis, as the most prevalent oral disease, is a type of chronic illness mediated by bacterial pathogens and immune system reactions, which is linked with the destruction of tooth-protecting tissues, such as alveolar bone and periodontal ligament. Periodontitis has a high prevalence (over 40% in the United States) and can be associated with other systemic ailments, for instance, arthritis, osteoporosis, metabolic syndrome, cancer, respiratory diseases, chronic kidney disease, and Alzheimer's disease. The common treatments for periodontitis are classified into invasive (surgical) and noninvasive (antibiotic therapy, scaling, and root planning) methods; however, these therapies have not reflected enough effectiveness for related patients. New documents inform the beneficial effects of plant-based compounds in healing various disorders, like periodontitis. In conjunction with this subject, it has been revealed that crocin, as an active component of saffron, regulates the balance between osteoclasts and osteoblasts and has a stroking role in the accumulation of the most common collagen in teeth and bone (type 1 collagen). Besides, this carotenoid compound possesses anti-inflammatory and anti-oxidative effects, which can be associated with the therapeutic processes of crocin in this oral disease. Hence, this narrative review study was performed to reflect the reparative/regenerative aspects of crocin agonist periodontitis.

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.

Sirtuins mediate mitochondrial quality control mechanisms: a novel therapeutic target for osteoporosis

Mitochondria plays a role in cell differentiation and apoptosis processes. Maintaining mitochondrial function is critical, and this involves various aspects of mitochondrial quality control such as protein homeostasis, biogenesis, dynamics, and mitophagy. Osteoporosis, a metabolic bone disorder, primarily arises from two factors: the dysregulation between lipogenic and osteogenic differentiation of aging bone marrow mesenchymal stem cells, and the imbalance between osteoblast-mediated bone formation and osteoclast-mediated bone resorption. Mitochondrial quality control has the potential to mitigate or even reverse the effects. Among the Sirtuin family, consisting of seven Sirtuins (SIRT1-7), SIRT1-SIRT6 play a crucial role in maintaining mitochondrial quality control. Additionally, SIRT1, SIRT3, SIRT6, and SIRT7 are directly involved in normal bone development and homeostasis by modulating bone cells. However, the precise mechanism by which these Sirtuins exert their effects remains unclear. This article reviews the impact of various aspects of mitochondrial quality control on osteoporosis, focusing on how SIRT1, SIRT3, and SIRT6 can improve osteoporosis by regulating mitochondrial protein homeostasis, biogenesis, and mitophagy. Furthermore, we provide an overview of the current state of clinical and preclinical drugs that can activate Sirtuins to improve osteoporosis. Specific Sirtuin-activating compounds are effective, but further studies are needed. The findings of this study may offer valuable insights for future research on osteoporosis and the development of clinical prevention and therapeutic target strategies.

Mitochondrial Genetics and Function as Determinants of Bone Phenotype and Aging

PURPOSE OF REVIEW

The purpose of this review is to summarize the recently published scientific literature regarding the effects of mitochondrial function and mitochondrial genome mutations on bone phenotype and aging.

RECENT FINDINGS

While aging and sex steroid levels have traditionally been considered the most important risk factors for development of osteoporosis, mitochondrial function and genetics are being increasingly recognized as important determinants of bone health. Recent studies indicate that mitochondrial genome variants found in different human populations determine the risk of complex degenerative diseases. We propose that osteoporosis should be among such diseases. Studies have shown the deleterious effects of mitochondrial DNA mutations and mitochondrial dysfunction on bone homeostasis. Mediators of such effects include oxidative stress, mitochondrial permeability transition, and dysregulation of autophagy. Mitochondrial health plays an important role in bone homeostasis and aging, and understanding underlying mechanisms is critical in leveraging this relationship clinically for therapeutic benefit.

The role of mitochondrial dysfunction in periodontitis: From mechanisms to therapeutic strategy

Periodontitis is an inflammatory and destructive disease of tooth-supporting tissue and has become the leading cause of adult tooth loss. The most central pathological features of periodontitis are tissue damage and inflammatory reaction. As the energy metabolism center of eukaryotic cells, mitochondrion plays a notable role in various processes, such as cell function and inflammatory response. When the intracellular homeostasis of mitochondrion is disrupted, it can lead to mitochondrial dysfunction and inability to generate adequate energy to maintain basic cellular biochemical reactions. Recent studies have revealed that mitochondrial dysfunction is closely related to the initiation and development of periodontitis. The excessive production of mitochondrial reactive oxygen species, imbalance of mitochondrial biogenesis and dynamics, mitophagy and mitochondrial DNA damage can all affect the development and progression of periodontitis. Thus, targeted mitochondrial therapy is potentially promising in periodontitis treatment. In this review, we summarize the above mitochondrial mechanism in the pathogenesis of periodontitis and discuss some potential approaches that can exert therapeutic effects on periodontitis by modulating mitochondrial activity. The understanding and summary of mitochondrial dysfunction in periodontitis might provide new research directions for pathological intervention or treatment of periodontitis.

Perturbation of mitochondrial dynamics links to the aggravation of periodontitis by diabetes

Diabetes and periodontitis are prevalent diseases that considerably impact global economy and diabetes is a major risk factor of periodontitis. Mitochondrial dynamic alterations are involved in many diseases including diabetes and this study aims to evaluate their relevance with diabetes aggravated periodontitis. Sixty mice are randomly divided into 4 groups: control, periodontitis, diabetes and diabetic periodontitis. Periodontitis severity is evaluated by alveolar bone loss, inflammation and oxidative stress status. Mitochondrial structural and functional defects are evaluated by the mitochondrial fission/fusion events, mitochondrial reactive oxygen species (ROS) accumulation, complex activities and adenosine triphosphate (ATP) production. Advanced glycation end product (AGE) and Porphyromonas gingivalis are closely related to periodontitis occurrence and development. Human gingival fibroblast cells (HGF-1) are used to investigate the AGE role and lipopolysaccharide (LPS) from Porphyromonas gingivalis (P-LPS) in aggravating diabetic periodontitis by mitochondrial dynamic and function alterations. In vivo, diabetic mice with periodontitis show severe bone loss, increased inflammation and oxidative stress accumulation. Among mice with periodontitis, diabetic mice show worse mitochondrial dynamic perturbations than lean mice, along with fusion protein levels inducing more mitochondrial fission in gingival tissue. In vitro, AGEs and P-LPS co-treatment causes severe.

Integrating network pharmacology and experimental verification strategies to reveal the active ingredients and molecular mechanism of Tenghuang Jiangu Capsule against osteoporosis

Tenghuang Jiangu Capsule (THJGC) is a Chinese herbal formula used for the treatment of osteoporosis and osteoarthritis in China, but its mechanism for treating osteoporosis is not clear. The aim of this study was to investigate the therapeutic effect of THJGC on osteoporosis and its intrinsic mechanism through network pharmacology and experimental validation. Drugs and potential targets were obtained from several reliable databases through network pharmacology, and these targets were integrated and analyzed using bioinformatics and molecular docking strategies. Quercetin, lignans and kaempferol were identified as key components, and the key targets included Akt1, MAPKs, and CASP3. Subsequently, UPLC-MS/MS analysis confirmed the presence of components in THJGC for the treatment of osteoporosis. In addition, using ex vivo and in vivo models, it was confirmed that THJGC inhibited H2O2-induced ROS generation and apoptosis, and reduced OVX-induced bone loss in a mouse model of osteoporosis. Our data suggest that THJGC has antioxidant, bone formation-promoting, bone resorption-inhibiting, and MC3T3-E1 apoptosis-reducing effects, and thus has anti-osteoporotic properties. In conclusion, it may be a promising pharmacologic adjuvant treatment for osteoporosis.

Exercise and vascular function in sedentary lifestyles in humans

People with sedentary lifestyles engage in minimal or no physical activity. A sedentary lifestyle promotes dysregulation of cellular redox balance, diminishes mitochondrial function, and increases NADPH oxidase activity. These changes collectively increase cellular oxidative stress, which alters endothelial function by oxidizing LDL-C, reducing NO production, and causing eNOS uncoupling. Reduced levels of nitric oxide (NO) leads to vasoconstriction, vascular remodeling, and vascular inflammation. Exercise modulates reactive oxygen species (ROS) to modify NRF2-KEAP signaling, leading to the activation of NRF2 to alleviate oxidative stress. While regular moderate exercise activates NRF2 through ROS production, high-intensity intermittent exercise stimulates NRF2 activation to a greater degree by reducing KEAP levels, which can be more beneficial for sedentary individuals. We review the damaging effects of a sedentary lifestyle on the vascular system and the health benefits of regular and intermittent exercise.

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.

Rosmarinic Acid: A Naturally Occurring Plant Based Agent Prevents Impaired Mitochondrial Dynamics and Apoptosis in Ultraviolet-B-Irradiated Human Skin Cells

Ultraviolet B (UVB) radiation is the leading cause of premature skin aging and skin cancer. UVB mediated mitochondrial dysfunction has been identified as one of the causative factors of UVB induced oxidative imbalance and apoptosis. Here, we report that UVB leads to mitochondrial fragmentation by causing imbalance in the markers regulating mitochondrial dynamics, which further contributes to ROS imbalance and activation of mitochondrial apoptotic signals. Several studies have demonstrated natural products as inhibitors of mitochondrial fission. However, to our knowledge, not much evidence has been gathered regarding utilization of Rosmarinic acid (RA) against UVB orchestrated mitochondrial fragmentation responses. Thus, in our study, we present the evidence of the efficacy of RA as a modulator of mitochondrial dynamics in UVB irradiated skin cells to prevent oxidative imbalance and apoptosis thereby preventing UVB induced photodamage.

Structural Analysis of Mitochondrial Dynamics-From Cardiomyocytes to Osteoblasts: A Critical Review

Mitochondria play a crucial role in cell physiology and pathophysiology. In this context, mitochondrial dynamics and, subsequently, mitochondrial ultrastructure have increasingly become hot topics in modern research, with a focus on mitochondrial fission and fusion. Thus, the dynamics of mitochondria in several diseases have been intensively investigated, especially with a view to developing new promising treatment options. However, the majority of recent studies are performed in highly energy-dependent tissues, such as cardiac, hepatic, and neuronal tissues. In contrast, publications on mitochondrial dynamics from the orthopedic or trauma fields are quite rare, even if there are common cellular mechanisms in cardiovascular and bone tissue, especially regarding bone infection. The present report summarizes the spectrum of mitochondrial alterations in the cardiovascular system and compares it to the state of knowledge in the musculoskeletal system. The present paper summarizes recent knowledge regarding mitochondrial dynamics and gives a short, but not exhaustive, overview of its regulation via fission and fusion. Furthermore, the article highlights hypoxia and its accompanying increased mitochondrial fission as a possible link between cardiac ischemia and inflammatory diseases of the bone, such as osteomyelitis. This opens new innovative perspectives not only for the understanding of cellular pathomechanisms in osteomyelitis but also for potential new treatment options.

Hydroxytyrosol prevents periodontitis-induced bone loss by regulating mitochondrial function and mitogen-activated protein kinase signaling of bone cells

Reactive oxygen species (ROS) overproduction promotes the alveolar bone loss during the development of periodontitis. Mitochondria are the principal source of ROS. Hydroxytyrosol (HT), a natural phenolic compound present in olive oil, is well known for its antioxidant and mitochondrial-protective prosperities. Nonetheless, the impact of HT on periodontitis and its related mechanisms underlying bone cell behavior remains unknown. Osteoclasts differentiated from RAW264.7 model and oxidative stress (OS) induced pre-osteoblast MC3T3-E1 cell injury model were treated with and without HT. Cell viability, apoptosis, differentiation, mitochondrial function along with mitogen-activated protein kinase (MAPK) signaling pathway were investigated. Meanwhile, the effect and related mechanisms of HT on bone loss in mice with periodontitis were also detected. HT inhibited osteoclast differentiation and prevented OS induced pre-osteoblast cells injury via regulating mitochondrial function as well as ERK and JNK signaling pathways. Moreover, HT attenuated the alveolar bone loss, increased bone forming activity, inhibited the osteoclasts differentiation and decreased the level of OS in mice with periodontitis. Our findings, for the first time, revealed a novel function of HT in bone remodeling of periodontitis, and highlighted its therapeutical potential for the prevention/treatment of periodontitis.

Simulated Galactic Cosmic Rays Modify Mitochondrial Metabolism in Osteoclasts, Increase Osteoclastogenesis and Cause Trabecular Bone Loss in Mice

Space is a high-stress environment. One major risk factor for the astronauts when they leave the Earth's magnetic field is exposure to ionizing radiation from galactic cosmic rays (GCR). Several adverse changes occur in mammalian anatomy and physiology in space, including bone loss. In this study, we assessed the effects of simplified GCR exposure on skeletal health in vivo. Three months following exposure to 0.5 Gy total body simulated GCR, blood, bone marrow and tissue were collected from 9 months old male mice. The key findings from our cell and tissue analysis are (1) GCR induced femoral trabecular bone loss in adult mice but had no effect on spinal trabecular bone. (2) GCR increased circulating osteoclast differentiation markers and osteoclast formation but did not alter new bone formation or osteoblast differentiation. (3) Steady-state levels of mitochondrial reactive oxygen species, mitochondrial and non-mitochondrial respiration were increased without any changes in mitochondrial mass in pre-osteoclasts after GCR exposure. (4) Alterations in substrate utilization following GCR exposure in pre-osteoclasts suggested a metabolic rewiring of mitochondria. Taken together, targeting radiation-mediated mitochondrial metabolic reprogramming of osteoclasts could be speculated as a viable therapeutic strategy for space travel induced bone loss.

Alkaline Reduced Water Attenuates Oxidative Stress-Induced Mitochondrial Dysfunction and Innate Immune Response Triggered by Intestinal Epithelial Dysfunction

Redox imbalance in intestinal epithelial cells is critical in the early phases of intestinal injury. Dysfunction of the intestinal barrier can result in immunological imbalance and inflammation, thus leading to intestinal syndromes and associated illnesses. Several antioxidants have been discovered to be beneficial in resolving intestinal barrier dysfunction. Of these antioxidants, the effects of alkaline reduced water (ARW) in oxidative stress of intestinal epithelial cells and its immunokine modulation in vitro is unknown. In this study, we utilized ARW-enriched media to investigate its cytoprotective effect against H2O2-induced oxidative stress in DLD1 cells. We found that ARW rescued DLD1 from oxidative stress by diluting the influence of H2O2 on oxidative stress-activated MAPK signaling and mitochondrial dysfunction. Further, intestinal oxidative stress significantly affects immunokine profiles of Raw 264.7 cells (IL-6, IL-10, MCP, TNF-a, RANTES), which can be reversed by ARW. Collectively, ARW shields intestinal epithelial cells from oxidative stress, reducing the immunological mayhem caused by barrier failure.

Crosstalk between reactive oxygen species and Dynamin-related protein 1 in periodontitis

Excessive generation of reactive oxygen species (ROS) have great impacts on the development of periodontitis. Dynamin-related protein 1 (Drp1) mediated mitochondrial fission is the main reason and the result of excessive ROS generation. However, whether Drp1 and crosstalk between ROS and Drp1 contribute to the process of periodontitis remains elusive. We herein investigated the role and functional significance of crosstalk between ROS and Drp1 in periodontitis. Firstly, human periodontal ligament cells (hPDLCs) were treated with hydrogen peroxide (H₂O₂) and ROS inhibitor N-acetyl-cysteine (NAC) or Drp1 inhibitor mitochondrial division inhibitor 1 (Mdivi-1). Cell viability, apoptosis, osteogenic differentiation, expression of Drp1, and mitochondrial function were investigated. Secondly, mice with periodontitis were treated with NAC or Mdivi-1. Finally, gingival tissues were collected from periodontitis patients and healthy individuals to evaluate ROS and Drp1 levels. H₂O₂ induced cellular injury and inflammation, excessive ROS production, mitochondrial abnormalities, and increased expression of p-Drp1 and Drp1 in hPDLCs, which could be reversed by NAC and Mdivi-1. Moreover, both NAC and Mdivi-1 ameliorated tissue damage and inflammation, and decreased expression of p-Drp1 and Drp1 in mice with periodontitis. More importantly, patients with periodontitis presented significantly higher levels of ROS-induced oxidative damage and p-Drp1 than that in healthy individuals and correlated with clinical parameters. In summary, ROS-Drp1 crosstalk greatly promotes the development of periodontitis. Pharmacological blockade of this crosstalk might be a novel therapeutic strategy for periodontitis.

Inhibition of HMGB1 reduced high glucose-induced BMSCs apoptosis via activation of AMPK and regulation of mitochondrial functions

High mobility group box-1 (HMGB1) participates actively in oxidative stress damage, and the latter relates closely to diabetes and diabetic complications including osteoporosis, though the underlying mechanisms are elusive. This study aimed to investigate the effect of high glucose on bone marrow stromal cells (BMSCs) apoptosis and the role of HMGB1 in this process. BMSCs were isolated from 2-week-old Sprague-Dawley rats and cultured in medium containing normal glucose (NG), high glucose (HG), high glucose + glycyrrhizin (HMGB1 inhibitor, HG+GL), and high glucose + glycyrrhizin + dorsomorphin (AMPK inhibitor, HG+GL+Dm), respectively. Cell apoptosis, expression of HMGB1, AMPK, apoptotic markers, and mitochondrial functions were detected. By these approaches, we demonstrated that HG treatment significantly upregulated the expression of HMGB1 in BMSCs, which could be attenuated by GL treatment. Inhibiting HMGB1 by GL improved AMPK activation, decreased mitochondrial ROS levels, increased mitochondrial membrane potential, normalized mitochondrial fission/fusion balance, and consequently reduced apoptosis of BMSCs under HG condition. The addition of AMPK inhibitor dorsomorphin hampered this protective effect. Taken together, our data show that inhibition of HMGB1 can be an effective approach to alleviate HG-induced BMSCs apoptosis by activation of AMPK pathway and relieving mitochondrial dysfunction.

GDF11 alleviates secondary brain injury after intracerebral hemorrhage via attenuating mitochondrial dynamic abnormality and dysfunction

Intracerebral hemorrhage (ICH) is a serious public health problem with high rates of death and disability. The neuroprotective effect of Growth Differentiation Factor 11 (GDF11) in ICH has been initially proved by our previous study. Oxidative stress (OS) plays crucial roles in mediating subsequent damage of ICH. However, whether and how mitochondrial dynamic events and function participated in ICH pathophysiology, and how mitochondrial function and OS interreacted in the neuroprotective process of GDF11 in ICH remains unclarified. Based on the rat model of ICH and in vitro cell model, we demonstrated that GDF11 could alleviate ICH induced neurological deficits, brain edema, OS status, neuronal apoptosis and inflammatory reaction. In addition, mitochondrial functional and structural impairments were obviously restored by GDF11. Treatment with antioxidant protected against erythrocyte homogenate (EH) induced cell injury by restoring OS status and mitochondrial fusion fission imbalance, which was similar to the effect of GDF11 treatment. Further, inhibition of mitochondrial division with Mdivi-1 attenuated mitochondrial functional defects and neuronal damages. In conclusion, our results for the first time proposed that GDF11 protected the post-ICH secondary injury by suppressing the feedback loop between mitochondrial ROS production and mitochondrial dynamic alteration, resulting in attenuated mitochondrial function and amelioration of neural damage.

Cyclosporine A Promotes Bone Remodeling in LPS-Related Inflammation via Inhibiting ROS/ERK Signaling: Studies In Vivo and In Vitro

In some inflammatory diseases of bone, osteogenesis and osteoclasis are uncoupled and the balance is usually tipped resulting in bone destruction. The underlying mechanism of osteogenic dysfunction in inflammation still needs further study. This study is aimed at investigating the effects of cyclosporine A (CsA) on bone remodeling in lipopolysaccharide- (LPS-) related inflammation. In vivo, an alveolar bone defect model was established using 10-week-old C57BL/6J mice. The mice were divided into phosphate-buffered saline (PBS), LPS, and LPS+CsA groups. After 3 weeks, micro-CT analysis and histomorphometric evaluation were conducted. In vitro, murine osteoblasts were treated with vehicle medium, LPS, LPS+CsA, LPS+extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor (LPS+PD98059), and LPS+antioxidant (LPS+EUK134). Cell proliferation, osteogenic behaviors, oxidative stress, and ERK signaling were determined. By these approaches, LPS inhibited bone remodeling and promoted oxidative stress accumulation in alveolar bone defects. When animals were treated with CsA, all LPS-induced biochemical changes ameliorated with a marked protective effect. In vitro, the reactive oxygen species (ROS) levels in mitochondria increased in LPS-treated osteoblasts, with decreased expression of osteogenic differentiation genes. The CsA, PD98059, and EUK134 presented remarkable protective effects against LPS treatment. CsA effectively enhanced bone remodeling and attenuated oxidative stress caused by LPS via inhibiting ROS/ERK signaling. Taken together, the protective effect of CsA and the inhibitory effect of ERK signaling on the maintenance of mitochondrial function and reduction of ROS levels hold promise as a potential novel therapeutic strategy for inflammatory diseases in bones.

Dynamin-related protein 1 positively regulates osteoclast differentiation and bone loss

Dynamin-related protein 1 (DRP1) is a mitochondrial membrane GTPase and regulates mitochondrial fission. In this study, we found that the cytokine RANKL increased the expression of DRP1 and its receptor proteins, Fis1, Mid49, and Mid 51, during osteoclast formation in mouse bone marrow-derived macrophages. Inactivation of the kinase GSK3β appeared to induce DRP1 expression. DRP1 knockdown or the DRP1 inhibitor Mdivi1 suppressed osteoclast differentiation via downregulation of c-Fos and NFATc1, the key transcription factor for osteoclast formation. Finally, the DRP1 inhibitor suppressed lipopolysaccharide-induced osteoclast formation in a calvarial model and ovariectomy-induced bone loss in vivo. Taken together, our data demonstrate that DRP1 positively contributes to RANKL-induced osteoclast differentiation by regulating the c-Fos-NFATc1 axis, suggesting the importance of mitochondrial DRP1 in osteoclastogenesis.

Deciphering the Underlying Mechanism of Eucommiae Cortex against Osteoporotic Fracture by Network Pharmacology

Background

Du Zhong (DZ), or Eucommiae Cortex, a traditional Chinese herbal medicine, has been used to treat osteoporosis. Although it has been reported that DZ can improve bone mass in ovariectomized rats, its pharmacological mechanisms in treating osteoporotic fractures (OPF) remain unclear.

Methods

In this study, we used a network pharmacological manner to explore its potential complicated mechanism in treating OPF. We obtained DZ compounds from TCMSP and BATMAN-TCM databases and collected potential targets of these compounds through target fishing based on TCMSP and BATMAN-TCM databases. Next, we collected the OPF targets by using CTD, GeneCards, OMIM, HPO, and GenCLiP 3 databases. And then the overlapping genes between DZ potential targets and OPF targets were used to build up the protein-protein interaction (PPI) network and to analyze their interactions and find out the big hub genes in this network. Subsequently, clusterProfiler package in R language was utilized to conduct the enrichment of Gene Ontology biological process and KEGG pathways.

Results

There were totally 93 active compounds and 916 related targets in DZ. After the enrichment analysis, we collected top 25 cellular biological processes and top 25 pathways based on the adjusted P value and found that the DZ anti-OPF effect was mainly associated with the regulation of ROS and inflammatory response. Furthermore, 64 hub genes in PPI network, such as MAPK1 (degree = 41), SRC (degree = 39), PIK3R1 (degree = 36), VEGFA (degree = 31), TP53 (degree = 29), EGFR (degree = 29), JUN (degree = 29), AGT (degree = 29), MAPK1, SRC, PIK3R1, VEGFA, and TP53, were considered as potential therapeutic targets, implying the underlying mechanisms of DZ acting on OPF.

Conclusion

We investigated the possible therapeutic mechanisms of DZ from a systemic perspective. These key targets and pathways provided promising directions for the future research to reveal the exact regulating mechanisms of DZ in treating OPF.

Deciphering the underlying mechanism of Xianlinggubao capsule against osteoporosis by network pharmacology

Background

Xianlinggubao formula (XLGB), a Chinese State Food and Drug Administration-permitted traditional Chinese herbal medicine, has been extensively used to treat osteoporosis. Although XLGB was shown to improve bone mass in ovariectomized rats and clinically alleviate osteoporosis symptoms, its pharmacological mechanisms remain unclear.

Methods

In this study, we used a network pharmacological approach to explore the potential mechanism of XLGB in treating osteoporosis. We obtained XLGB compounds from the TCMSP and TCMID databases and identified potential targets of these compounds through target fishing based on the TCMSP and Swiss Target Prediction databases. Next, we identified the osteoporosis targets by using the CTD, TTD, GeneCards, OMIM and PharmGKB databases. Then, the overlapping genes between the XLGB potential targets and the osteoporosis targets were used to establish a protein-protein interaction (PPI) network and to analyze their interactions and identify the major hub genes in this network. Subsequently, the Metascape database was utilized to conduct the enrichment of Gene Ontology biological processes and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways.

Results

There were 104 active compounds and 295 related targets identified overall. After the Metascape enrichment analysis, we identified the top 25 cellular biological processes and top 15 pathways based on the logP value and found that the XLGB-mediated anti-osteoporosis effect was mainly associated with reactive oxygen species, organonitrogen compound response and cell migration. Furthermore, 36 hub genes of XLGB, such as EGF, EGFR, MTOR, MAPK14 and NFKB1, were considered potential therapeutic targets, suggesting the underlying mechanisms of XLGB acting on osteoporosis.

Conclusion

We investigated the possible therapeutic mechanisms of XLGB from a systemic perspective. These key targets and pathways provide promising directions for future research to reveal the exact regulatory mechanisms of XLGB.

Inhibition of DNM1L and mitochondrial fission attenuates inflammatory response in fibroblast-like synoviocytes of rheumatoid arthritis

Mitochondrial fission and fusion are important for mitochondrial function, and dynamin 1-like protein (DNM1L) is a key regulator of mitochondrial fission. We investigated the effect of mitochondrial fission on mitochondrial function and inflammation in fibroblast-like synoviocytes (FLSs) during rheumatoid arthritis (RA). DNM1L expression was determined in synovial tissues (STs) from RA and non-RA patients. FLSs were isolated from STs and treated with a DNM1L inhibitor (mdivi-1, mitochondrial division inhibitor 1) or transfected with DNM1L-specific siRNA. Mitochondrial morphology, DNM1L expression, cell viability, mitochondrial membrane potential, reactive oxygen species (ROS), apoptosis, inflammatory cytokine expression and autophagy were examined. The impact of mdivi-1 treatment on development and severity of collagen-induced arthritis (CIA) was determined in mice. Up-regulated DNM1L expression was associated with reduced mitochondrial length in STs from patients with RA and increased RA severity. Inhibition of DNM1L in FLSs triggered mitochondrial depolarization, mitochondrial elongation, decreased cell viability, production of ROS, IL-8 and COX-2, and increased apoptosis. DNM1L deficiency inhibited IL-1β-mediated AKT/IKK activation, NF-κBp65 nuclear translocation and LC3B-related autophagy, but enhanced NFKBIA expression. Treatment of CIA mice with mdivi-1 decreased disease severity by modulating inflammatory cytokine and ROS production. Our major results are that up-regulated DNM1L and mitochondrial fission promoted survival, LC3B-related autophagy and ROS production in FLSs, factors that lead to inflammation by regulating AKT/IKK/NFKBIA/NF-κB signalling. Thus, inhibition of DNM1L may be a new strategy for treatment of RA.

Nicotinamide mononucleotide alters mitochondrial dynamics by SIRT3-dependent mechanism in male mice

Nicotinamide adenine dinucleotide (NAD+ ) is a central signaling molecule and enzyme cofactor that is involved in a variety of fundamental biological processes. NAD+ levels decline with age, neurodegenerative conditions, acute brain injury, and in obesity or diabetes. Loss of NAD+ results in impaired mitochondrial and cellular functions. Administration of NAD+ precursor, nicotinamide mononucleotide (NMN), has shown to improve mitochondrial bioenergetics, reverse age-associated physiological decline, and inhibit postischemic NAD+ degradation and cellular death. In this study, we identified a novel link between NAD+ metabolism and mitochondrial dynamics. A single dose (62.5 mg/kg) of NMN, administered to male mice, increases hippocampal mitochondria NAD+ pools for up to 24 hr posttreatment and drives a sirtuin 3 (SIRT3)-mediated global decrease in mitochondrial protein acetylation. This results in a reduction of hippocampal reactive oxygen species levels via SIRT3-driven deacetylation of mitochondrial manganese superoxide dismutase. Consequently, mitochondria in neurons become less fragmented due to lower interaction of phosphorylated fission protein, dynamin-related protein 1 (pDrp1 [S616]), with mitochondria. In conclusion, manipulation of mitochondrial NAD+ levels by NMN results in metabolic changes that protect mitochondria against reactive oxygen species and excessive fragmentation, offering therapeutic approaches for pathophysiologic stress conditions.

AKT-GSK3β Signaling Pathway Regulates Mitochondrial Dysfunction-Associated OPA1 Cleavage Contributing to Osteoblast Apoptosis: Preventative Effects of Hydroxytyrosol

Oxidative stress (OS) induces osteoblast apoptosis, which plays a crucial role in the initiation and progression of osteoporosis. Although OS is closely associated with mitochondrial dysfunction, detailed mitochondrial mechanisms underlying OS-induced osteoblast apoptosis have not been thoroughly elucidated to date. In the present study, we found that mitochondrial abnormalities largely contributed to OS-induced osteoblast apoptosis, as evidenced by enhanced production of mitochondrial reactive oxygen species; considerable reduction in mitochondrial respiratory chain complex activity, mitochondrial membrane potential, and adenosine triphosphate production; abnormality in mitochondrial morphology; and alteration of mitochondrial dynamics. These mitochondrial abnormalities were primarily mediated by an imbalance in mitochondrial fusion and fission through a protein kinase B- (AKT-) glycogen synthase kinase 3β- (GSK3β-) optic atrophy 1- (OPA1-) dependent mechanism. Hydroxytyrosol (3,4-dihydroxyphenylethanol (HT)), an important compound in virgin olive oil, significantly prevented OS-induced osteoblast apoptosis. Specifically, HT inhibited OS-induced mitochondrial dysfunction by decreasing OPA1 cleavage and by increasing AKT and GSK3β phosphorylation. Together, our results indicate that the AKT-GSK3β signaling pathway regulates mitochondrial dysfunction-associated OPA1 cleavage, which may contribute to OS-induced osteoblast apoptosis. Moreover, our results suggest that HT could be an effective nutrient for preventing osteoporosis development.

Crocin protects against dexamethasone‑induced osteoblast apoptosis by inhibiting the ROS/Ca2+‑mediated mitochondrial pathway

Osteoblast apoptosis has been identified as an important event in the development of glucocorticoid (GC)-induced osteoporosis and osteonecrosis of the femoral head. Crocin, a bioactive ingredient of saffron, has been demonstrated to induce antiapoptotic effects on numerous types of cell in vitro; however, the effects of crocin on the dexamethasone (Dex)-induced apoptosis of osteoblasts remain unclear. In the present study, the protective effects of crocin during Dex-induced apoptosis of MC3T3-E1 osteoblasts, and the underlying mechanisms, were investigated. MTT and Annexin V-FITC/PI flow cytometry assays were performed to evaluate the viability and apoptosis of cells, respectively. The mitochondrial transmembrane potential, reactive oxygen species (ROS), intracellular Ca²⁺ levels and apoptosis-associated protein expression were assessed via flow cytometry, fluorescence microscopy and western blotting. It was demonstrated that crocin pretreatment inhibited Dex-induced apoptosis of osteoblasts in a dose-dependent manner. Crocin reversed Dex-induced decreases in the mitochondrial transmembrane potential, and increases in ROS and intracellular Ca²⁺ levels. Furthermore, crocin upregulated the expression levels of B-cell lymphoma-2 (Bcl-2) and mitochondrial cytochrome c (Cyt C), and downregulated those of cleaved caspase-9, cleaved caspase-3, Bcl-2-associated X protein and cytoplasmic Cyt C. N-acetylcysteine, a ROS inhibitor, and 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid, a calcium chelator, attenuated Dex-induced osteoblast apoptosis, whereas H₂O₂ and ionomycin, a calcium ionophore that increases intracellular calcium levels, reversed the antiapoptotic effects of crocin on Dex-treated osteoblasts. These results indicated that crocin may protect osteoblasts from Dex-induced apoptosis by inhibiting the ROS/Ca²⁺-mediated mitochondrial pathway, thus suggesting that crocin has potential value as a treatment for GC-induced bone diseases.

Mitochondrial permeability transition pore: a potential drug target for neurodegeneration

The mitochondrial permeability transition pore (mPTP) has been considered a key contributor to cell death, inducing the process in several major neurodegenerative diseases. To date, the molecular nature of the mPTP remains confounding but its significance is universally acknowledged. Several targets have been screened and inhibition of mPTP has emerged as an attractive field for researchers. Nowadays, in silico-directed studies help to explore new small molecules targeting the mPTP to improve their drug-like properties and bioactivity. Here, we briefly summarize the role of mPTP in neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson disease (PD), and Huntington's disease (HD), and discusses current and future potential therapeutic targets.

RAGE-dependent mitochondria pathway: a novel target of silibinin against apoptosis of osteoblastic cells induced by advanced glycation end products

Advanced glycation end products (AGEs) can stimulate osteoblast apoptosis and have a critical role in the pathophysiology of diabetic osteoporosis. Mitochondrial abnormalities are closely related to osteoblast dysfunction. However, it remains unclear whether mitochondrial abnormalities are involved in AGE-induced osteoblastic cell apoptosis. Silibinin, a major flavonolignan compound of silimarin, has strong antioxidant and mitochondria-protective properties. In the present study, we explored the possible mitochondrial mechanisms underlying AGE-induced apoptosis of osteoblastic cells and the effect of silibinin on osteoblastic cell apoptosis. We demonstrated that mitochondrial abnormalities largely contributed to AGE-induced apoptosis of osteoblastic cells, as evidenced by enhanced mitochondrial oxidative stress, conspicuous reduction in mitochondrial membrane potential and adenosine triphosphate production, abnormal mitochondrial morphology, and altered mitochondrial dynamics. These AGE-induced mitochondrial abnormalities were mainly mediated by the receptor of AGEs (RAGE). In addition, we found that silibinin directly downregulated the expression of RAGE and modulated RAGE-mediated mitochondrial pathways, thereby preventing AGE-induced apoptosis of osteoblastic cells. This study not only provides a new insight into the mitochondrial mechanisms underlying AGE-induced osteoblastic cell apoptosis, but also lays a foundation for the clinical use of silibinin for the prevention or treatment of diabetic osteoporosis.

CoCl2 induces apoptosis via a ROS-dependent pathway and Drp1-mediated mitochondria fission in periodontal ligament stem cells

Oxygen deficiency is associated with various oral diseases, including chronic periodontitis, age-related alveolar bone loss, and mechanical stress-linked cell injury from orthodontic appliances. Nevertheless, our understanding of the impact of hypoxia on periodontal tissues and its biochemical mechanism is still rudimentary. The purpose of this research was to elucidate the effects of hypoxia on the apoptosis of human periodontal ligament stem cells (PDLSCs) in vitro and the underlying mechanism. Herein, we showed that cobalt chloride (CoCl₂) triggered cell dysfunction in human PDLSCs in a concentration-dependent manner and resulted in cell apoptosis and oxidative stress overproduction and accumulation in PDLSCs. In addition, CoCl₂ promoted mitochondrial fission in PDLSCs. Importantly, CoCl₂ increased the expression of dynamin-related protein 1 (Drp1), the major regulator in mitochondrial fission, in PDLSCs. Mitochondrial division inhibitor-1, pharmacological inhibition of Drp1, not only inhibited mitochondrial fission but also protected against CoCl₂-induced PDLSC dysfunction, as shown by increased mitochondrial membrane potential, increased ATP level, reduced reactive oxygen species (ROS) level, and decreased apoptosis. Furthermore, N-acety-l-cysteine, a pharmacological inhibitor of ROS, also abolished CoCl₂-induced expression of Drp1 and protected against CoCl₂-induced PDLSC dysfunction, as shown by restored mitochondrial membrane potential, ATP level, inhibited mitochondrial fission, and decreased apoptosis. Collectively, our data provide new insights into the role of the ROS-Drp1-dependent mitochondrial pathway in CoCl₂-induced apoptosis in PDLSCs, indicating that ROS and Drp1 are promising therapeutic targets for the treatment of CoCl₂-induced PDLSC dysfunction.

Astrocytes Attenuate Mitochondrial Dysfunctions in Human Dopaminergic Neurons Derived from iPSC

Astrocytes, the most populous glial cell type in the brain, are critical for regulating the brain microenvironment. In various neurodegenerative diseases, astrocytes determine the progression and outcome of the neuropathological process. We have recently revealed the direct involvement of mitochondrial function in human pluripotent stem cell (hiPSC)-derived dopaminergic (DA) neuronal differentiation. Using the astroglial-neuronal co-culture system, we show here that astrocytes effectively rescue defects in neurogenesis of DA neurons with mitochondrial respiratory chain disruption. Co-culture of astrocytes with defective DA neurons completely restored mitochondrial functions and dynamics insulted by mitochondrial toxins. These results suggest the significance of astroglia in maintaining mitochondrial development and bioenergetics during differentiation of hiPSC-derived DA neurons. Our study also provides an active astroglial-neuronal interaction model for future investigation of mitochondrial involvement in neurogenesis and neurodegenerative diseases.

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Role of astrocyte on the development of hiPSC-derived dopaminergic neuron

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Astrocyte protects dopaminergic neurogenesis by powering up mitochondrial respiration

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Astrocyte restores mitochondrial function and dynamics in dopaminergic neuron

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Evidence of astroglial and neuronal interaction during dopaminergic neurogenesis

Accelerated dentinogenesis by inhibiting the mitochondrial fission factor, dynamin related protein 1

Undifferentiated odontogenic epithelium and dental papilla cells differentiate into ameloblasts and odontoblasts, respectively, both of which are essential for tooth development. These differentiation processes involve dramatic functional and morphological changes of the cells. For these changes to occur, activation of mitochondrial functions, including ATP production, is extremely important. In addition, these changes are closely related to mitochondrial fission and fusion, known as mitochondrial dynamics. However, few studies have focused on the role of mitochondrial dynamics in tooth development. The purpose of this study was to clarify this role. We used mouse tooth germ organ cultures and a mouse dental papilla cell line with the ability to differentiate into odontoblasts, in combination with knockdown of the mitochondrial fission factor, dynamin related protein (DRP)1. In organ cultures of the mouse first molar, tooth germ developed to the early bell stage. The amount of dentin formed under DRP1 inhibition was significantly larger than that of the control. In experiments using a mouse dental papilla cell line, differentiation into odontoblasts was enhanced by inhibiting DRP1. This was associated with increased mitochondrial elongation and ATP production compared to the control. These results suggest that DRP1 inhibition accelerates dentin formation through mitochondrial elongation and activation. This raises the possibility that DRP1 might be a therapeutic target for developmental disorders of teeth.

The Impact of Oxidative Stress on the Bone System in Response to the Space Special Environment

The space special environment mainly includes microgravity, radiation, vacuum and extreme temperature, which seriously threatens an astronaut’s health. Bone loss is one of the most significant alterations in mammalians after long-duration habitation in space. In this review, we summarize the crucial roles of major factors—namely radiation and microgravity—in space in oxidative stress generation in living organisms, and the inhibitory effect of oxidative stress on bone formation. We discussed the possible mechanisms of oxidative stress-induced skeletal involution, and listed some countermeasures that have therapeutic potentials for bone loss via oxidative stress antagonism. Future research for better understanding the oxidative stress caused by space environment and the development of countermeasures against oxidative damage accordingly may facilitate human beings to live more safely in space and explore deeper into the universe.

Adiponectin improves the osteointegration of titanium implant under diabetic conditions by reversing mitochondrial dysfunction via the AMPK pathway in vivo and in vitro

Diabetes-induced reactive oxygen species (ROS) overproduction would result in compromised osteointegration of titanium implant (TI) and high rate of implant failure, yet the underlying mechanisms remain elusive. Adiponectin (APN) is a fat-derived adipocytokine with strong antioxidant, mitochondrial-protective and anti-diabetic efficacies. We hypothesized that mitochondrial dysfunction under diabetes may account for the oxidative stress in osteoblasts and titanium-bone interface (TBI) instability, which could be ameliorated by APN. To test this hypothesis, we incubated primary rat osteoblasts on TI and tested the cellular behaviors when subjected to normal milieu (NM), diabetic milieu (DM), DM+APN, DM+AICAR (AMPK activator) and DM+APN+Compound C (AMPK inhibitor). In vivo, APN or APN+Compound C were administered to diabetic db/db mice with TI implanted in their femurs. Results showed that diabetes induced structural damage, dysfunction and content decrease of mitochondria in osteoblasts, which led to ROS overproduction, dysfunction and apoptosis of osteoblasts accompanied by the inhibition of AMPK signaling. APN alleviated the mitochondrial damage by activating AMPK, thus reversing osteoblast impairment and improving the osteointegration of TI evidenced by Micro-CT and histological analysis. Furthermore, AICAR showed beneficial effects similar to APN treatment, while the protective effects of APN were abolished when AMPK activation was blocked by Compound C. This study clarifies mitochondrial dysfunction as a crucial mechanism in the impaired bone healing and implant loosening in diabetes, and provides APN as a novel promising active component for biomaterial-engineering to improve clinical performance of TI in diabetic patients.

STATEMENT OF SIGNIFICANCE

The loosening rate of titanium implants in diabetic patients is high. The underlying mechanisms remain elusive and, with the rapid increase of diabetic morbility, efficacious strategies to mitigate this problem have become increasingly important. Our study showed that the mitochondrial impairment and the consequent oxidative stress in osteoblasts at the titanium-bone interface (TBI) play a critical role in the diabetes-induced poor bone repair and implant destabilization, which could become therapeutic targets. Furthermore, adiponectin, a cytokine, promotes the bio-functional recovery of osteoblasts and bone regeneration at the TBI in diabetes. This provides APN as a novel bioactive component used in material-engineering to promote the osteointegration of implants, which could reduce implant failure, especially for diabetic patients.

Dynamin-Related Protein 1 Inhibition Attenuates Cardiovascular Calcification in the Presence of Oxidative Stress

RATIONALE

Mitochondrial changes occur during cell differentiation and cardiovascular disease. DRP1 (dynamin-related protein 1) is a key regulator of mitochondrial fission. We hypothesized that DRP1 plays a role in cardiovascular calcification, a process involving cell differentiation and a major clinical problem with high unmet needs.

OBJECTIVE

To examine the effects of osteogenic promoting conditions on DRP1 and whether DRP1 inhibition alters the development of cardiovascular calcification.

METHODS AND RESULTS

DRP1 was enriched in calcified regions of human carotid arteries, examined by immunohistochemistry. Osteogenic differentiation of primary human vascular smooth muscle cells increased DRP1 expression. DRP1 inhibition in human smooth muscle cells undergoing osteogenic differentiation attenuated matrix mineralization, cytoskeletal rearrangement, mitochondrial dysfunction, and reduced type 1 collagen secretion and alkaline phosphatase activity. DRP1 protein was observed in calcified human aortic valves, and DRP1 RNA interference reduced primary human valve interstitial cell calcification. Mice heterozygous for Drp1 deletion did not exhibit altered vascular pathology in a proprotein convertase subtilisin/kexin type 9 gain-of-function atherosclerosis model. However, when mineralization was induced via oxidative stress, DRP1 inhibition attenuated mouse and human smooth muscle cell calcification. Femur bone density was unchanged in mice heterozygous for Drp1 deletion, and DRP1 inhibition attenuated oxidative stress-mediated dysfunction in human bone osteoblasts.

CONCLUSIONS

We demonstrate a new function of DRP1 in regulating collagen secretion and cardiovascular calcification, a novel area of exploration for the potential development of new therapies to modify cellular fibrocalcific response in cardiovascular diseases. Our data also support a role of mitochondrial dynamics in regulating oxidative stress-mediated arterial calcium accrual and bone loss.

Drp1-dependent mitochondrial fission mediates osteogenic dysfunction in inflammation through elevated production of reactive oxygen species

Although previous studies have implicated pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), to be detrimental for osteogenic activity, the related regulatory mechanisms are not yet fully validated. Since mitochondria host several essential metabolic processes and play a pivotal role in cellular functions, whether and how mitochondrial function contributes to inflammation-induced bone destruction needs further exploration. Our findings revealed that TNF-α impaired osteoblast function, including decreased mRNA levels of osteogenic markers, suppressed ALP expression and activity, and compromised cellular viability. Moreover, increased reactive oxygen species (ROS)-mediated oxidative stress in the TNF-α-treated group enhanced excessive mitochondrial fragmentation and disrupted mitochondrial function. However, treatment with antioxidant N-acetyl cysteine (NAC) or mitochondrial division inhibitor Mdivi-1 protected the cells from these adverse phenomena. These findings provide new insights into the role of the Drp1-dependent mitochondrial pathway in the osteogenic dysfunction during inflammation, indicating that this pathway may be a target for the development of new therapeutic approaches for the prevention and treatment of inflammation-induced bone destruction.

Mfn2 protects dopaminergic neurons exposed to paraquat both in vitro and in vivo: Implications for idiopathic Parkinson's disease

Mitochondrial dynamics and quality control play a critical role in the maintenance of mitochondrial homeostasis and function. Pathogenic mutations of many genes associated with familial Parkinson's disease (PD) caused abnormal mitochondrial dynamics, suggesting a likely involvement of disturbed mitochondrial fission/fusion in the pathogenesis of PD. In this study, we focused on the potential role of mitochondrial fission/fusion in idiopathic PD patients and in neuronal cells and animals exposed to paraquat (PQ), a commonly used herbicide and PD-related neurotoxin, as models for idiopathic PD. Significantly increased expression of dynamin-like protein 1 (DLP1) and a trend towards reduced expression of Mfn1 and Mfn2 were noted in the substantia nigra tissues from idiopathic PD cases. Interestingly, PQ treatment led to similar changes in the expression of fission/fusion proteins both in vitro and in vivo which was accompanied by extensive mitochondrial fragmentation and mitochondrial dysfunction. Blockage of PQ-induced mitochondrial fragmentation by Mfn2 overexpression protected neurons against PQ-induced mitochondrial dysfunction in vitro. More importantly, PQ-induced oxidative damage and stress signaling as well as selective loss of dopaminergic (DA) neurons in the substantia nigra and axonal terminals in striatum was also inhibited in transgenic mice overexpressing hMfn2. Overall, our study demonstrated that disturbed mitochondrial dynamics mediates PQ-induced mitochondrial dysfunction and neurotoxicity both in vitro and in vivo and is also likely involved in the pathogenesis of idiopathic PD which make them a promising therapeutic target for PD treatment.

[Influences of vibration on rapid osteogenic response of osteoblasts]

OBJECTIVE

This study investigated the rapid response of osteoblasts, which were derived from low-magnitude high-frequency vibration (LMHFV). Refractory period-derived memory response was also observed.

METHODS

MC3T3-E1 cells were incubated and received LMHFV stimulation (0.49 g, 40 Hz) for 30 min. After application of LMHFV, mRNA levels of earlier osteogenic differentiation markers Runt-related transcription factor 2 (Runx2), collagen typeⅠ(Col-Ⅰ), and alkaline phosphatase (ALP) were immediately detected by real-time fluorescence quantitative polymerase chain reaction in the absence or presence of antioxidant. Simultaneously, concentrations of mitochondrial reactive oxygen species (ROS) and average mitochondrial length were also measured.

RESULTS

Osteoblasts in the vibration group showed decreased gene expressions of Runx2, Col-Ⅰ, and ALP (P<0.01) and increased levels of mitochondrial ROS (P<0.01) and shortened mitochondria (P<0.01), whereas antioxidant treatment resulted in recovery from changes in the above indicators (P<0.01).

CONCLUSIONS

LMHFV can downregulate mRNA levels of early osteogenic differentiation markers, promote ROS generation, and mitochondrial fission. 
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