Treatment of hydrogen molecule abates oxidative stress and alleviates bone loss induced by modeled microgravity in rats

Advancing piezoelectric 2D nanomaterials for applications in drug delivery systems and therapeutic approaches

Precision drug delivery and multimodal synergistic therapy are crucial in treating diverse ailments, such as cancer, tissue damage, and degenerative diseases. Electrodes that emit electric pulses have proven effective in enhancing molecule release and permeability in drug delivery systems. Moreover, the physiological electrical microenvironment plays a vital role in regulating biological functions and triggering action potentials in neural and muscular tissues. Due to their unique noncentrosymmetric structures, many 2D materials exhibit outstanding piezoelectric performance, generating positive and negative charges under mechanical forces. This ability facilitates precise drug targeting and ensures high stimulus responsiveness, thereby controlling cellular destinies. Additionally, the abundant active sites within piezoelectric 2D materials facilitate efficient catalysis through piezochemical coupling, offering multimodal synergistic therapeutic strategies. However, the full potential of piezoelectric 2D nanomaterials in drug delivery system design remains underexplored due to research gaps. In this context, the current applications of piezoelectric 2D materials in disease management are summarized in this review, and the development of drug delivery systems influenced by these materials is forecast.

The influence of uremic toxins on low bone turnover disease in chronic kidney disease

Uremic toxins play a crucial role in the development of low bone turnover disease in chronic kidney disease (CKD) through the induction of oxidative stress. This oxidative stress disrupts the delicate balance between bone formation and resorption, resulting in a decline in both bone quantity and quality. Reactive oxygen species (ROS) activate nuclear factor kappa-B and mitogen-activated protein kinase signaling pathways, promoting osteoclastogenesis. Conversely, ROS hinder osteoblast differentiation by facilitating the binding of Forkhead box O proteins (FoxOs) to β-catenin, triggering apoptosis through FoxOs-activating kinase phosphorylation. This results in increased osteoblastic receptor activator of nuclear factor kappa-B ligand (RANKL) expression and decreased nuclear factor erythroid 2-related factor 2 levels, compromising antioxidant defenses against oxidative damage. As CKD progresses, the accumulation of protein-bound uremic toxins such as indoxyl sulfate (IS) and p-cresyl sulfate (PCS) intensifies oxidative stress, primarily affecting osteoblasts. IS and PCS directly inhibit osteoblast viability, induce apoptosis, decrease alkaline phosphatase activity, and impair collagen 1 and osteonectin, impeding bone formation. They also reduce cyclic adenosine 3',5'-monophosphate (cAMP) production and lower parathyroid hormone (PTH) receptor expression in osteoblasts, resulting in PTH hyporesponsiveness. In summary, excessive production of ROS by uremic toxins not only reduces the number and function of osteoblasts but also induces PTH hyporesponsiveness, contributing to the initiation and progression of low bone turnover disease in CKD.

Simulated microgravity-induced oxidative stress and loss of osteogenic potential of osteoblasts can be prevented by protection of primary cilia

Oxidative stress has been considered to be closely related to spaceflight-induced bone loss; however, mechanism is elusive and there are no effective countermeasures. Using cultured rat calvarial osteoblasts exposed to microgravity simulated by a random positioning machine, this study addressed the hypotheses that microgravity-induced shortening of primary cilia leads to oxidative stress and that primary cilium protection prevents oxidative stress and osteogenesis loss. Microgravity was found to induce oxidative stress (as represented by increased levels of reactive oxygen species (ROS) and malondialdehyde production, and decreased activities of antioxidant enzymes), which was perfectly replicated in osteoblasts growing in NG with abrogated primary cilia (created by transfection of an interfering RNA), suggesting the possibility that shortening of primary cilia leads to oxidative stress. Oxidative stress was accompanied by mitochondrial dysfunction (represented by increased mitochondrial ROS and decreased mitochondrial membrane potential) and intracellular Ca2+ overload, and the latter was found to be caused by increased activity of Ca2+ channel transient receptor potential vanilloid 4 (TRPV4), as also evidenced by TRPV4 agonist GSK1016790A-elicited Ca2+ influx. Supplementation of HC-067047, a specific antagonist of TRPV4, attenuated microgravity-induced mitochondrial dysfunction, oxidative stress, and osteogenesis loss. Although TRPV4 was found localized in primary cilia and expressed at low levels in NG, microgravity-induced shortening of primary cilia led to increased TRPV4 levels and Ca2+ influx. When primary cilia were protected by miR-129-3p overexpression or supplementation with a natural flavonoid moslosooflavone, microgravity-induced increased TRPV4 expression, mitochondrial dysfunction, oxidative stress, and osteogenesis loss were all prevented. Our data revealed a new mechanism that primary cilia function as a controller for TRPV4 expression. Microgravity-induced injury on primary cilia leads to increased expression and overactive channel of TRPV4, causing intracellular Ca2+ overload and oxidative stress, and primary cilium protection could be an effective countermeasure against microgravity-induced oxidative stress and loss of osteogenic potential of osteoblasts.

Protective effects of curcumin against osteoporosis and its molecular mechanisms: a recent review in preclinical trials

Osteoporosis (OP) is one of the most common metabolic skeletal disorders and is commonly seen in the elderly population and postmenopausal women. It is mainly associated with progressive loss of bone mineral density, persistent deterioration of bone microarchitecture, and increased fracture risk. To date, drug therapy is the primary method used to prevent and treat osteoporosis. However, long-term drug therapy inevitably leads to drug resistance and specific side effects. Therefore, researchers are constantly searching for new monomer compounds from natural plants. As a candidate for the treatment of osteoporosis, curcumin (CUR) is a natural phenolic compound with various pharmacological and biological activities, including antioxidant, anti-apoptotic, and anti-inflammatory. This compound has gained research attention for maintaining bone health in various osteoporosis models. We reviewed preclinical and clinical studies of curcumin in preventing and alleviating osteoporosis. These results suggest that if subjected to rigorous pharmacological and clinical trials, naturally-derived curcumin could be used as a complementary and alternative medicine for the treatment of osteoporosis by targeting osteoporosis-related mechanistic pathways. This review summarizes the mechanisms of action and potential therapeutic applications of curcumin in the prevention and mitigation of osteoporosis and provides reference for further research and development of curcumin.

Transcriptome analysis of hydrogen inhibits osteoclastogenesis of mouse bone marrow mononuclear cells

Hydrogen (H2) is a major biodegradation product of implanted magnesium (Mg) alloys that are commonly used in the healing of bone fractures. Our earlier study showed that H2 can inhibit mouse bone marrow mononuclear cell (BMMC) osteoclastogenesis during the differentiation of these cells into osteoclasts, thereby facilitating fracture healing. However, the way by which H2 inhibits osteoclastogenesis remains to be elucidated. The present study used RNA-sequencing to study the transcriptome of H2-exposed BMMCs in an osteoclast-induced environment and identified the target genes and signaling pathways through which H2 exerts its biological effects. Several upregulated genes were identified: Fos, Dusp1, Cxcl1, Reln, Itga2b, Plin2, Lif, Thbs1, Vegfa and Gadd45a. Several downregulated genes were also revealed: Hspa1b, Gm4951, F830016B08Rik, Fads2, Hspa1a, Slc27a6, Cacna1b, Scd2, Lama3 and Col4a5. These differentially expressed genes were mainly involved in osteoclast differentiation cascades, as well as PI3K-AKT, Forkhead box O (FoxO), MAPK, peroxisome proliferator-activated receptor (PPAR), TNF, TGF-β, JAK-STAT, RAS, VEGF, hypoxia-inducible factor (HIF-1) and AMPK signaling pathways. In summary, the present study revealed the key genes and signaling pathways involved in the H2-mediated inhibition of osteoclastogenesis, thereby providing a theoretical basis for the significance of H2 and an experimental basis for the application of Mg alloys in the treatment of osteoporosis.

Low-Molecular-Weight Chondroitin Sulfates Alleviate Simulated Microgravity-Induced Oxidative Stress and Bone Loss in Mice

(1) Background: Many studies have shown that microgravity experienced by astronauts or long-term bedridden patients results in increased oxidative stress and bone loss. Low-molecular-weight chondroitin sulfates (LMWCSs) prepared from intact chondroitin sulfate (CS) have been demonstrated to possess good antioxidant and osteogenic activities in vitro. This study aimed to assess the antioxidant activity of the LMWCSs in vivo and evaluate their potential in preventing microgravity-induced bone loss. (2) Methods: we used hind limb suspension (HLS) mice to simulate microgravity in vivo. We investigated the effects of LMWCSs against oxidative stress damage and bone loss in HLS mice and compared the findings with those of CS and a non-treatment group. (3) Results: LMWCSs reduced the HLS-induced oxidative stress level, prevented HLS-induced alterations in bone microstructure and mechanical strength, and reversed changes in bone metabolism indicators in HLS mice. Additionally, LMWCSs downregulated the mRNA expression levels of antioxidant enzyme- and osteogenic-related genes in HLS mice. The results showed that overall effect of LMWCSs was better than that of CS. (4) Conclusions: LMWCSs protect against the bone loss caused by simulated microgravity, which may be related to their ability to reduce oxidative stress. LMWCSs can be envisaged as potential antioxidants and bone loss protective agents in microgravity.

pH-Responsive Delivery of H2 through Ammonia Borane-Loaded Hollow Polydopamine for Intervertebral Disc Degeneration Therapy

An imbalance in oxidative and inflammatory regulation is the main contributor to intervertebral disc degeneration (IDD). Hydrogen (H2) therapy is a promising antioxidation and anti-inflammatory approach. However, the key to the treatment is how to maintain the long-term effective H2 concentration in the intervertebral disc (IVD). Therefore, we developed a pH-responsive delivery of H2 through ammonia borane-loaded hollow polydopamine (AB@HPDA) for IDD therapy, which has sufficient capacity to control long-term H2 release in an acid-dependent manner in degenerative IVD. The characterization, toxicity, and pH-responsive H2 release of AB@HPDA was detected in vitro. The metabolization of AB@HPDA in the degenerated IVD was tested by in vivo imaging. The therapeutic effect of AB@HPDA on IDD was tested in vivo by X-ray, MRI, water content of the disc, and histological changes. Nuclear extracellular matrix (ECM) components, oxidative stress, and inflammation were also tested to explore potential therapeutic mechanisms. AB@HPDA has good biocompatibility at concentrations less than 500 μg/mL. The H2 release of AB@HPDA was pH responsive. Therefore, AB@HPDAs can provide efficient hydrogen therapy with controlled H2 release in response to the acidic degenerated IVD microenvironment. The metabolization of AB@HPDA in IVD was slow and lasted up to 11 days. HPDA and AB@HPDA significantly inhibited IDD, as tested by X-ray, MRI, disc water content, and histology (P < 0.05). pH-responsive H2 delivery through AB@HPDAs has the potential to efficiently treat IDD by inhibiting ECM degradation and rebalancing oxidative stress and inflammation in degenerative IVDs.

Molecular Hydrogen Prevents Osteoclast Activation in a Glucocorticoid-Induced Osteoporosis Zebrafish Scale Model

Antioxidants represent a powerful tool for many human diseases and, in particular, molecular hydrogen has unique characteristics that make it a very promising therapeutic agent against osteoporosis. Zebrafish scales offer an innovative model in which new therapeutic approaches against secondary osteoporosis are tested. Scale bone loss obtained by prednisolone (PN) treatment is characterized by increased osteoclast activity and decreased osteoblast activity highlighted with bone enzymatic assays. We used this read-out system to test the therapeutic effects of hydrogen-rich water (HRW), an innovative antioxidant approach. HRW prevented osteoclast activation and bone loss in PN-treated fish scales, as verified by both biochemical and histochemical tartrate-resistant alkaline phosphatase assays. On the other hand, HRW treatment did not prevent PN-dependent osteoblast suppression, as measured by alkaline phosphatase activity. Moreover, HRW treatment did not facilitate the reparation of resorption lacunae induced in scales by PN. Our study highlighted a specific effect of HRW on adult osteoclast activity but not in osteoblasts, introducing an intriguing new antioxidant preventive approach against osteoporosis.

Protection of primary cilia is an effective countermeasure against the impairment of osteoblast function induced by simulated microgravity

The molecular mechanism for the microgravity-induced decrease in bone formation remains unclear and there is a lack of effective specific preventative therapies. We recently reported that primary cilia of osteoblasts became shorter and even disappeared when the cells were exposed to random positioning machine (RPM)-simulated microgravity and that the microgravity-induced loss of osteogenic potential of osteoblasts could be attenuated when the resorption of primary cilia was prevented by treatment with 0.1 μM cytochalasin D. In the current study, it was further found that the loss of the osteogenic capacity of rat calvarial osteoblasts (ROBs) was associated with the inhibition of the BMP-2/Smad1/5/8 signalling pathway, of which most of the signalling proteins including BMP-2, BMPRII, Smad1/5/8 and p-Smad1/5/8 were found localized to primary cilia. Accompanying the resorption of primary cilia following the cells being exposed to simulated microgravity, the expression levels of these signalling proteins were reduced significantly. Furthermore, the expression of miRNA-129-3p, a microRNA previously reported to control cilium biogenesis, was found to be reduced quickly and changed in a similar tendency with the length of primary cilia. Moreover, overexpression of miRNA-129-3p in ROBs significantly attenuated microgravity-induced inhibition of BMP-2 signalling and loss of osteogenic differentiation and mineralization. These results indicated the important role of miRNA-129-3p in microgravity-induced resorption of primary cilia of osteoblasts and the potential of replenishing the miRNA-129-3p as an effective countermeasure against microgravity-induced loss of primary cilia and impairment of osteoblast function.

A mouse model of disuse osteoporosis based on a movable noninvasive 3D-printed unloading device

Objective

Disuse osteoporosis is a major type of bone loss disease characterized by regional bone loss and microstructure alterations. The condition is induced by a marked decrease in weight bearing over time, which usually occurs due to limb immobilization, therapeutic bed rest or space flight. To date, the most commonly used mouse model of disuse osteoporosis is constructed using the classical tail suspension method, which causes tail injury, movement inconvenience and mental stress. This study aimed to propose a noninvasive and effective method for the establishment of a mouse model of disuse osteoporosis and compared this method with the tail suspension method.

Methods

3D printing technology was applied to construct a movable unloading device. A movable noninvasive 3D-printed unloading device (3D-ULD) was used to unload the hindlimbs of the mice. The bone microstructure and bone volume of unloaded femurs were analysed through micro-CT and H&E staining, and von Kossa staining was performed for the detection of bone mineralization in the femurs. TRAP staining, IHC-CTSK and Q-PCR were performed for evaluation of the bone resorption ability, and double labelling, IHC-DMP1, ALP staining and Q-PCR assays were conducted to assess the osteogenic ability. The mechanical properties of disused bone were detected using the three-point bending test. The body, thymus and spleen weights of the mice were recorded, and the serum corticosterone level of the mice was assayed by enzyme-linked immunosorbent assay (ELISA).

Results

The micro-CT results showed significant trabecular bone loss, and 3D-ULD induced cortical bone loss in disused femurs as well as a decrease in the bone mineral density in the unloaded mice. TRAP staining and IHC-CTSK staining results indicated increases in the osteoclast number per bone perimeter (Oc.N/B.Pm) and the osteoclast surface per bone surface (Oc.S/BS) in the unloaded mice. The Ctsk, Trap and Mmp9 expression levels were significantly increased in the unloaded mice. Decreases in the ratio of the mineral surface to bone surface (MS/BS), mineral apposition rate (MAR) and bone formation rate per bone surface (BFR/BS) were found in unloaded mice in the 3D-ULD by double labelling. The IHC-DMP1 and ALP staining results showed decreases in the osteoblast number per bone perimeter (Ob.N/B.Pm) and osteoblast surface per bone surface (Ob. S/BS) in the mice unloaded in the 3D-ULD, and these mice also showed decreased Runx2, Alp and Dmp1 expression levels. Three-point bending test results showed that the mechanical properties were attenuated in the disused femurs of the unloaded mice. Less skin rupture and rare alterations in the thymus and spleen weights were found in the unloaded mice in the 3D-ULD. The ELISA results indicated the serum corticosterone level of the mice unloaded in the 3D-ULD was significantly lower than that of mice suspended by their tail.

Conclusion

This new disuse osteoporosis mouse model based on 3D-ULD could induce effective disuse bone loss with significantly alleviated side effects.

Translational potential of this article

This study proposes a new disuse osteoporosis mouse model based on 3D-ULD that can be used to better understand disuse bone loss in the future.

Magnesium implantation or supplementation ameliorates bone disorder in CFTR-mutant mice through an ATF4-dependent Wnt/β-catenin signaling

Magnesium metal and its alloys are being developed as effective orthopedic implants; however, the mechanisms underlying the actions of magnesium on bones remain unclear. Cystic fibrosis, the most common genetic disease in Caucasians caused by the mutation of CFTR, has shown bone disorder as a key clinical manifestation, which currently lacks effective therapeutic options. Here we report that implantation of magnesium-containing implant stimulates bone formation and improves bone fracture healing in CFTR-mutant mice. Wnt/β-catenin signaling in the bone is enhanced by the magnesium implant, and inhibition of Wnt/β-catenin by iCRT14 blocks the magnesium implant to improve fracture healing in CFTR-mutant mice. We further demonstrate that magnesium ion enters osteocytes, increases intracellular cAMP level and activates ATF4, a key transcription factor known to regulate Wnt/β-catenin signaling. In vivo knockdown of ATF4 abolishes the magnesium implant-activated β-catenin in bones and reverses the improved-fracture healing in CFTR-mutant mice. In addition, oral supplementation of magnesium activates ATF4 and β-catenin as well as enhances bone volume and density in CFTR-mutant mice. Together, these results show that magnesium implantation or supplementation may serve as a potential anabolic therapy for cystic fibrosis-related bone disease. Activation of ATF4-dependent Wnt/β-catenin signaling in osteocytes is identified as a previously undefined mechanism underlying the beneficial effect of magnesium on bone formation.

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Magnesium implant ameliorates bone defects and improves the impaired bone fracture healing in CFTR-deficient mice.

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Oral magnesium supplementation improves bone quality in CFTR-deficient mice.

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Extracellular Mg²⁺ enters bone cells through Mg²⁺ channels and transporters.

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Mg²⁺ elevates cAMP level to activate ATF4-dependent Wnt/β-catenin signalingin bone cells.

Molecular hydrogen enhances osteogenesis in Danio rerio embryos

Molecular hydrogen (H₂ ) has been reported to have important biological effects on bone tissue in several in vitro and in vivo models. Danio rerio (zebrafish) embryo is a good model to study osteogenesis because of its transparency, size and rapid development. In zebrafish embryo, hydrogen-rich water (HRW) does not affect vitality or growth rate up to 15%. In addition, 7% HRW treatment enhances zebrafish embryo osteogenesis, increasing the vertebral mineralization rate. In conclusion, we demonstrated the beneficial effects of hydrogen on anabolic bone functions in vivo.

Hydrogen: An Endogenous Regulator of Liver Homeostasis

Basic and clinical studies have shown that hydrogen (H₂), the lightest gas in the air, has significant biological effects of anti-oxidation, anti-inflammation, and anti-apoptosis. The mammalian cells have no abilities to produce H₂ due to lack of the expression of hydrogenase. The endogenous H₂ in human body is mainly produced by anaerobic bacteria, such as Firmicutes and Bacteroides, in gut and other organs through the reversible oxidation reaction of 2 H⁺ + 2 e^- ⇌ H₂. Supplement of exogenous H₂ can improve many kinds of liver injuries, modulate glucose and lipids metabolism in animal models or in human beings. Moreover, hepatic glycogen has strong ability to accumulate H₂, thus, among the organs examined, liver has the highest concentration of H₂ after supplement of exogenous H₂ by various strategies in vivo. The inadequate production of endogenous H₂ play essential roles in brain, heart, and liver disorders, while enhanced endogenous H₂ production may improve hepatitis, hepatic ischemia and reperfusion injury, liver regeneration, and hepatic steatosis. Therefore, the endogenous H₂ may play essential roles in maintaining liver homeostasis.

Antioxidant Strategy to Prevent Simulated Microgravity-Induced Effects on Bone Osteoblasts

The effects induced by microgravity on human body functions have been widely described, in particular those on skeletal muscle and bone tissues. This study aims to implement information on the possible countermeasures necessary to neutralize the oxidative imbalance induced by microgravity on osteoblastic cells. Using the model of murine MC3T3-E1 osteoblast cells, cellular morphology, proliferation, and metabolism were investigated during exposure to simulated microgravity on a random positioning machine in the absence or presence of an antioxidant—the 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox). Our results confirm that simulated microgravity-induced morphological and metabolic alterations characterized by increased levels of reactive oxygen species and a slowdown of the proliferative rate. Interestingly, the use of Trolox inhibited the simulated microgravity-induced effects. Indeed, the antioxidant-neutralizing oxidants preserved cell cytoskeletal architecture and restored cell proliferation rate and metabolism. The use of appropriate antioxidant countermeasures could prevent the modifications and damage induced by microgravity on osteoblastic cells and consequently on bone homeostasis.

Case Report: Acute hydrotherapy with super-saturated hydrogen-rich water for ankle sprain in a professional athlete

Background: The traditional treatment of soft tissue injuries consists of the RICE protocol – rest, ice, compression, and elevation, followed for up to 72 hours after a trauma. Although designed as an immediate therapy to reduce inflammation that occurs after an acute injury, the RICE protcol might not be the best way to promote healing due to limiting blood flow. Molecular hydrogen (H ₂) has recently been put forward as a possible adjuvant treatment in musculoskeletal medicine, yet limited data are available concerning its effectiveness as a first-aid intervention.

Case report: We report here a case of an elite professional athlete who suffered a grade II ankle sprain, and who subsequently received six sessions of ankle and foot hydrotherapy (e.g. 30-min at every four hours) with super-saturated hydrogen-rich water during the first 24 hours post-injury. The pain VAS self‐completed by the patient dropped from 50 points (moderate pain) at baseline (immediately after injury) to 20 points (mild pain) at 24-h follow-up. Ankle swelling dropped by 2.8% and dorsiflexion range of movement improved by 27.9% from baseline to follow-up, respectively.

Conclusions: Our case has indicated that an acute multi-session hydrotherapy with hydrogen-rich water might be a helpful treatment in terms of pain, swelling reduction and regaining range of motion after an ankle sprain.

Hydrogen gas protects against ovariectomy-induced osteoporosis by inhibiting NF-κB activation

OBJECTIVES

Osteoporosis is a prevalent condition among postmenopausal women, and lacks satisfactory therapeutic options. Hydrogen (H2) has been shown to be effective in alleviating many diseases. This study aimed to investigate the effects of H2 on inhibiting osteoclastogenesis and bone loss in ovariectomized mice.

METHODS

Osteoclast differentiation from Raw264.7 cells was induced with receptor activator NF-κB ligand (RANKL) with or without 60% H2. The number and resorption activity of osteocalsts were assessed by tartrate-resistant acid phosphatase staining and pit formation assay, respectively. The expression of osteoclast markers and NF-κB phosphorylation were detected by western blot. NF-κB nuclear translocation was assessed by immunofluorescence. NF-κB transcriptional activity was analyzed by luciferase assay. Bone loss in mice was induced by ovariectomy (OVX). OVX mice were given either regular air or 60% H2. Bone structure was analyzed by micro-computed tomography and hematoxylin and eosin staining. Cytokine levels were measured by enzyme-linked immunosorbent assay. The data were analyzed with one-way or two-way ANOVA followed by Bonferroni post hoc tests.

RESULTS

H2 did not have any measurable effect on the proliferation of Raw264.7 cells. The number of osteoclasts and size of resorption pits of RANKL+H2-treated cells were 3 to 4 times less than RANKL treated cells. The expression of osteoclast marker genes of RANKL+H2-treated cells was 30% to 60% lower than RANKL-treated cells (P < 0.05). H2 markedly inhibited RANKL-induced activation, nuclear translocation, and transcriptional activity of NF-κB (P < 0.05, RANKL+H2 vs RANKL). The amount and density of trabecular bone and bone mineral density of ovariectomized mice were significantly less than sham-operated mice (P < 0.05 OVX vs sham). The amount of trabecular bone and bone mineral density of OVX mice that inhaled H2 were more than 40% higher, whereas the levels of serum proinflammatory cytokine interleukin 1β, IL-6, and tumor necrosis factor-α were more than 50% lower than those of OVX mice (P < 0.05).

CONCLUSIONS

These results demonstrated that H2 could be an effective therapeutic agent of postmenopausal osteoporosis.

Hydrogen inhibits the osteoclastogenesis of mouse bone marrow mononuclear cells

Hydrogen (H₂) is one of the major biodegradation products of magnesium (Mg) alloys implanted for bony fracture healing and reconstruction; H₂ thus plays a significant role in the regulation of local microenvironment and the biology of resident cells. The interactions between the H₂ and the local cells are of great interest, and a full understanding of the effect of H₂ on bone marrow mononuclear cells (BMMCs) would accelerate the development of effective strategies for successful bony healing. This study investigates how H₂, with different concentrations and durations, regulates the osteoclastogenesis of mouse BMMCs. First, using H₂ with five concentrations (0%, 2%, 25%, 50% and 75%) and three durations (5, 7 and 10 days), the osteoclastogenesis of mouse BMMCs in these H₂ conditions were measured using TRAP staining, F-actin ring formation assay, pit formation assay and RT-qPCR analysis. Based on these findings, the proliferation assay, apoptosis assay, western blot analysis and ELISA assay of BMMCs after osteoclast induction were performed. The findings showed that H₂ (especially the 50% and 75% H₂) obviously inhibited the osteoclast formation, function and osteoclast-related genes expression of osteoclast-induced BMMCs; additionally, H₂ (50%) was found to reduce the proliferation, promote the apoptosis and inhibit the expression of osteoclast-related proteins of BMMCs with the presence of osteoclast-induced medium. Therefore, H₂ significantly inhibited the osteoclastogenesis of mouse BMMCs, which may become a new therapeutic agent for anti-bony resorption and open new avenues for the translational research of Mg alloys.

Effects of Iron Overload and Oxidative Damage on the Musculoskeletal System in the Space Environment: Data from Spaceflights and Ground-Based Simulation Models

The space environment chiefly includes microgravity and radiation, which seriously threatens the health of astronauts. Bone loss and muscle atrophy are the two most significant changes in mammals after long-term residency in space. In this review, we summarized current understanding of the effects of microgravity and radiation on the musculoskeletal system and discussed the corresponding mechanisms that are related to iron overload and oxidative damage. Furthermore, we enumerated some countermeasures that have a therapeutic potential for bone loss and muscle atrophy through using iron chelators and antioxidants. Future studies for better understanding the mechanism of iron and redox homeostasis imbalance induced by the space environment and developing the countermeasures against iron overload and oxidative damage consequently may facilitate human to travel more safely in space.

Polyphenols (S3) Isolated from Cone Scales of Pinus koraiensis Alleviate Decreased Bone Formation in Rat under Simulated Microgravity

In order to screen out an effective bone loss protectant from natural plant polyphenol and to elucidate the mechanism of the plant polyphenols that alleviate bone loss under simulated microgravity, the proliferation activities of 9 total polyphenol extracts from natural product (TPENP) on osteoblasts were measured. Polyphenols (S3) was isolated from total polyphenols of cone scales from pinus koraiensis (Korean pine). ALP activity in osteoblasts and MDA level in femur were measured. Mechanical properties and microstructure of the distal cancellous region of the femur in rat were tested. Various bone metabolism markers, enzymes activity and genes expression were also analyzed. The results showed that S3 has the highest activity of osteoblast proliferation. S3 promoted ALP activity in osteoblasts, enhanced mechanical properties and microstructure of the distal cancellous region of femur in rat, decreased MDA level, elevated the serum concentration of BALP, PINP and activities of SOD, CAT, GSH-Px in femur under simulated microgravity. In addition, S3 enhanced the expression of NRF-2, β-catenin, p-GSK3-β, OSX, RUNX2, Osteonectin, Osteocalcin, ALP and collagen I. These results indicated that S3 can alleviated bone loss induced by simulated microgravity through abate the inhibition of the oxidative stress on Wnt/β-catenin signaling pathway.

Regulation of the Response of Caenorhabditis elegans to Simulated Microgravity by p38 Mitogen-Activated Protein Kinase Signaling

The in vivo function of p38 mitogen-activated protein kinase (MAPK) signaling in regulating the response to simulated microgravity is still largely unclear. Using Caenorhabditis elegans as an assay system, we investigated the in vivo function of p38 MAPK signaling in regulating the response of animals to simulated microgravity and the underlying molecular mechanism. Simulated microgravity treatment significantly increased the transcriptional expressions of genes (pmk-1, sek-1, and nsy-1) encoding core p38 MAPK signaling pathway and the expression of phosphorylated PMK-1/p38 MAPK. The pmk-1, sek-1, or nsy-1 mutant was susceptible to adverse effects of simulated microgravity. The intestine-specific activity of PMK-1 was required for its function in regulating the response to simulated microgravity, and the entire p38 MAPK signaling pathway could act in the intestine to regulate the response to simulated microgravity. In the intestine, SKN-1 and ATF-7, two transcriptional factors, were identified as downstream targets for PMK-1 in regulating the response to simulated microgravity. Therefore, the activation of p38 MAPK signaling may mediate a protection mechanism for nematodes against the adverse effects of simulated microgravity. Additionally, our results highlight the potential crucial role of intestinal cells in response to simulated microgravity in nematodes.

Molecular basis for oxidative stress induced by simulated microgravity in nematode Caenorhabditis elegans

Caenorhabditis elegans is an important in vivo assay system for toxicological studies. Herein, we investigated the role of oxidative stress and the underlying molecular mechanism for induced adverse effects of simulated microgravity. In nematodes, simulated microgravity treatment induced a significant induction of oxidative stress. Genes (mev-1, gas-1, and isp-1) encoding a molecular machinery for the control of oxidative stress were found to be dysregulated in simulated microgravity treated nematodes. Meanwhile, genes (sod-2, sod-3, sod-4, sod-5, aak-2, skn-1, and gst-4) encoding certain antioxidant defense systems were increased in simulated microgravity treated nematodes. Mutation of mev-1, gas-1, sod-2, sod-3, aak-2, skn-1, or gst-4 enhanced susceptibility to oxidative stress induced by simulated microgravity, whereas mutation of isp-1 induced a resistance to oxidative stress induced by simulated microgravity. Mutation of sod-2, sod-3, or aak-2 further suppressed the recovery effect of simulated microgravity toxicity in nematodes after simulated microgravity treatment for 1h. Moreover, administration of ascorbate could inhibit the adverse effects including the induction of oxidative stress in simulated microgravity treated nematodes. Mutation of any of the genes encoding metallothioneins or the genes of hsp-16.1, hsp-16.2 and hsp-16.48 encoding heat-shock proteins did not affect the induction of oxidative stress in simulated microgravity treated nematodes. Our results provide a molecular basis for the induction of oxidative stress in simulated microgravity treated organisms.

Molecular hydrogen: a preventive and therapeutic medical gas for various diseases

Since the 2007 discovery that molecular hydrogen (H2) has selective antioxidant properties, multiple studies have shown that H2 has beneficial effects in diverse animal models and human disease. This review discusses H2 biological effects and potential mechanisms of action in various diseases, including metabolic syndrome, organ injury, and cancer; describes effective H2 delivery approaches; and summarizes recent progress toward H2 applications in human medicine. We also discuss remaining questions in H2 therapy, and conclude with an appeal for a greater role for H2 in the prevention and treatment of human ailments that are currently major global health burdens. This review makes a case for supporting hydrogen medicine in human disease prevention and therapy.

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.

Hydrogen-rich saline prevents bone loss in diabetic rats induced by streptozotocin

PURPOSE

As an antioxidant molecule, hydrogen has been received much more attention and reported to be used as the treatment strategy for various diseases. In this study, we hypothesize that systemic delivery of hydrogen saline water may improve the reservation of bone tissue in the tibias and femurs of osteoporotic rats caused by diabetes mellitus (DM), which is characterized by increased levels of oxidative stress and overproducing reactive oxygen species (ROS).

METHODS

The animals were divided into three groups of 12 animals and lavaged with normal saline (normal control and DM), or hydrogen saline water (DM + HRS). General status, blood glucose level, tibial and femoral mechanical strength, and micro-CT scans of the proximal tibia were recorded and analyzed.

RESULTS

After 12 weeks, the glucose level was significantly decreased in the DM + HRS group compared with that of the DM group. Micro-CT scans showed that bone volume/total volume, connectivity density, trabecular thickness, and trabecular number were significantly increased compared with the DM group. Mechanical results of energy, stiffness and elastic modulus in the DM + HRS group were significantly higher than in the other groups for the tibia and femur.

CONCLUSIONS

The results indicate that the systemic delivery of hydrogen saline water, which is safe and well tolerated, preserves bone volume and decreases fracture risks in streptozotocin-induced diabetic status rats, whose bone structure or inherent material properties of bone tissues are changed.

Molecular hydrogen suppresses activated Wnt/β-catenin signaling

Molecular hydrogen (H₂) is effective for many diseases. However, molecular bases of H₂ have not been fully elucidated. Cumulative evidence indicates that H₂ acts as a gaseous signal modulator. We found that H₂ suppresses activated Wnt/β-catenin signaling by promoting phosphorylation and degradation οf β-catenin. Either complete inhibition of GSK3 or mutations at CK1- and GSK3-phosphorylation sites of β-catenin abolished the suppressive effect of H₂. H₂ did not increase GSK3-mediated phosphorylation of glycogen synthase, indicating that H₂ has no direct effect on GSK3 itself. Knock-down of adenomatous polyposis coli (APC) or Axin1, which form the β-catenin degradation complex, minimized the suppressive effect of H₂ on β-catenin accumulation. Accordingly, the effect of H₂ requires CK1/GSK3-phosphorylation sites of β-catenin, as well as the β-catenin degradation complex comprised of CK1, GSK3, APC, and Axin1. We additionally found that H₂ reduces the activation of Wnt/β-catenin signaling in human osteoarthritis chondrocytes. Oral intake of H₂ water tended to ameliorate cartilage degradation in a surgery-induced rat osteoarthritis model through attenuating β-catenin accumulation. We first demonstrate that H₂ suppresses abnormally activated Wnt/β-catenin signaling, which accounts for the protective roles of H₂ in a fraction of diseases.

Attenuation of hind-limb suspension-induced bone loss by curcumin is associated with reduced oxidative stress and increased vitamin D receptor expression

Treatment with curcumin attenuated modeled microgravity-induced bone loss, possibly through abating oxidative stress and activating vitamin D receptor. Curcumin might be an effective countermeasure for microgravity-induced bone loss but remains to be tested in humans.

INTRODUCTION

Bone loss is one of the most important complications for human crewmembers who are exposed to long-term microgravity in space and also for bedridden people. The aim of the current study was to elucidate whether treatment with curcumin attenuated bone loss induced by microgravity.

METHODS

We used hind-limb suspension (HLS) and rotary wall vessel bioreactor (RWVB) to model microgravity in vivo and in vitro, respectively. We investigated the effects of curcumin consumption (40 mg kg(-1) body weight day(-1), via daily oral gavages) on Sprague-Dawley (SD) rats exposed to HLS for 6 weeks. Then, we investigated the effects of incubation with curcumin (4 μM) on MC3T3-E1 and RAW264.7 cells cultured in RWVB.

RESULTS

Curcumin alleviated HLS-induced reduction of bone mineral density in tibiae and preserved bone structure in tibiae and mechanical strength in femurs. Curcumin alleviated HLS-induced oxidative stress marked by reduced malondialdehyde content and increased total sulfhydryl content in femurs. In cultured MC3T3-E1 cells, curcumin inhibited modeled microgravity-induced reactive oxygen species (ROS) formation and enhanced osteoblastic differentiation. In cultured RAW264.7 cells, curcumin reduced modeled microgravity-induced ROS formation and attenuated osteoclastogenesis. In addition, curcumin upregulated vitamin D receptor (VDR) expression in femurs of rats exposed to HLS and MC3T3-E1 cells exposed to modeled microgravity.

CONCLUSION

Curcumin alleviated HLS-induced bone loss in rats, possibly via suppressing oxidative stress and upregulating VDR expression.

Beneficial biological effects and the underlying mechanisms of molecular hydrogen - comprehensive review of 321 original articles

Therapeutic effects of molecular hydrogen for a wide range of disease models and human diseases have been investigated since 2007. A total of 321 original articles have been published from 2007 to June 2015. Most studies have been conducted in Japan, China, and the USA. About three-quarters of the articles show the effects in mice and rats. The number of clinical trials is increasing every year. In most diseases, the effect of hydrogen has been reported with hydrogen water or hydrogen gas, which was followed by confirmation of the effect with hydrogen-rich saline. Hydrogen water is mostly given ad libitum. Hydrogen gas of less than 4 % is given by inhalation. The effects have been reported in essentially all organs covering 31 disease categories that can be subdivided into 166 disease models, human diseases, treatment-associated pathologies, and pathophysiological conditions of plants with a predominance of oxidative stress-mediated diseases and inflammatory diseases. Specific extinctions of hydroxyl radical and peroxynitrite were initially presented, but the radical-scavenging effect of hydrogen cannot be held solely accountable for its drastic effects. We and others have shown that the effects can be mediated by modulating activities and expressions of various molecules such as Lyn, ERK, p38, JNK, ASK1, Akt, GTP-Rac1, iNOS, Nox1, NF-κB p65, IκBα, STAT3, NFATc1, c-Fos, and ghrelin. Master regulator(s) that drive these modifications, however, remain to be elucidated and are currently being extensively investigated.

Monochromatic computed microtomography using laboratory and synchrotron sources and X-ray fluorescence analysis for comprehensive analysis of structural changes in bones

A combination of X-ray tomography at different wavelengths and X-ray fluorescence analysis was applied in the study of two types of bone tissue changes: prolonged presence in microgravity conditions and age-related bone growth. The proximal tail vertebrae of geckos were selected for investigation because they do not bear the supporting load in locomotion, which allows them to be considered as an independent indicator of gravitational influence. For the vertebrae of geckos no significant differences were revealed in the elemental composition of the flight samples and the synchronous control samples. In addition, the gecko bone tissue samples from the jaw apparatus, spine and shoulder girdle were measured. The dynamics of structural changes in the bone tissue growth was studied using samples of a human fetal hand. The hands of human fetuses of 11-15 weeks were studied. Autonomous zones of calcium accumulation were found not only in individual fingers but in each of the investigated phalanges. The results obtained are discussed.

Mineralization initiation of MC3T3-E1 preosteoblast is suppressed under simulated microgravity condition

Microgravity decreases the differentiation of osteoblast. However, as this process is multistage and complex, the mechanism by which microgravity inhibits osteoblast differentiation is still unclear. We have previously found that 24 h acute treatment of simulated microgravity (SM) with a random positioning machine (RPM) significantly inhibited the differentiation of preosteoblasts and have explored whether osteoblasts show different response to microgravity condition at other stages, such as the mineralizing-stage. Murine MC3T3-E1 preosteoblasts induced for osteogenic differentiation for seven days were cultured either under normal gravity or SM conditions for 24 h. SM treatment significantly suppressed mineralized nodule formation. Alkaline phosphatase (ALP) activity was dramatically decreased, and the expression of ALP gene was downregulated. Expression of well-known markers and regulators for osteoblasts differentiation, including osteocalcin (OC), type I collagen α1 (Col Iα1), dentin matrix protein 1 (DMP1) and runt-related transcription factor 2 (Runx2), were downregulated. Western blot analysis showed that the phosphorylated extracellular signal-regulated kinase (p-ERK) level was lower under SM condition. Thus, the initiation of osteoblast mineralization is suppressed by SM condition, and the suppression may be through the regulation of ALP activity and the osteogenic gene expression. ERK signaling might be involved in this process. These results are relevant to the decrease of osteoblast maturation and bone formation under microgravity condition.

Pulsed electromagnetic fields partially preserve bone mass, microarchitecture, and strength by promoting bone formation in hindlimb-suspended rats

A large body of evidence indicates that pulsed electromagnetic fields (PEMF), as a safe and noninvasive method, could promote in vivo and in vitro osteogenesis. Thus far, the effects and underlying mechanisms of PEMF on disuse osteopenia and/or osteoporosis remain poorly understood. Herein, the efficiency of PEMF on osteoporotic bone microarchitecture, bone strength, and bone metabolism, together with its associated signaling pathway mechanism, was systematically investigated in hindlimb-unloaded (HU) rats. Thirty young mature (3-month-old), male Sprague-Dawley rats were equally assigned to control, HU, and HU + PEMF groups. The HU + PEMF group was subjected to daily 2-hour PEMF exposure at 15 Hz, 2.4 mT. After 4 weeks, micro-computed tomography (µCT) results showed that PEMF ameliorated the deterioration of trabecular and cortical bone microarchitecture. Three-point bending test showed that PEMF mitigated HU-induced reduction in femoral mechanical properties, including maximum load, stiffness, and elastic modulus. Moreover, PEMF increased serum bone formation markers, including osteocalcin (OC) and N-terminal propeptide of type 1 procollagen (P1NP); nevertheless, PEMF exerted minor inhibitory effects on bone resorption markers, including C-terminal crosslinked telopeptides of type I collagen (CTX-I) and tartrate-resistant acid phosphatase 5b (TRAcP5b). Bone histomorphometric analysis demonstrated that PEMF increased mineral apposition rate, bone formation rate, and osteoblast numbers in cancellous bone, but PEMF caused no obvious changes on osteoclast numbers. Real-time PCR showed that PEMF promoted tibial gene expressions of Wnt1, LRP5, β-catenin, OPG, and OC, but did not alter RANKL, RANK, or Sost mRNA levels. Moreover, the inhibitory effects of PEMF on disuse-induced osteopenia were further confirmed in 8-month-old mature adult HU rats. Together, these results demonstrate that PEMF alleviated disuse-induced bone loss by promoting skeletal anabolic activities, and imply that PEMF might become a potential biophysical treatment modality for disuse osteoporosis.

Treatment with hydrogen molecules prevents RANKL-induced osteoclast differentiation associated with inhibition of ROS formation and inactivation of MAPK, AKT and NF-kappa B pathways in murine RAW264.7 cells

The bone protective effects of the hydrogen molecule (H2) have been demonstrated in several osteoporosis models while the underlying molecular mechanism has remained unclear. Osteoclast differentiation is an important factor related to the pathogenesis of bone-loss related diseases. In this work, we evaluated the effects of incubation with H2 on receptor activator of NFκB ligand (RANKL)-induced osteoclast differentiation. We found that treatment with H2 prevented RANKL-induced osteoclast differentiation in RAW264.7 cells and BMMs. Treatment with H2 inhibits the ability to form resorption pits of BMMs stimulated by RANKL. Treatment with H2 reduced mRNA levels of osteoclast-specific markers including tartrate resistant acid phosphatase, calcitonin receptor, cathepsin K, metalloproteinase-9, carbonic anhydrase typeII, and vacuolar-type H(+)-ATPase. Treatment with H2 decreased intracellular reactive oxygen species (ROS) formation, suppressed NADPH oxidase activity, down-regulated Rac1 activity and Nox1 expression, reduced mitochondrial ROS formation, and enhanced nuclear factor E2-related factor 2 nuclear translocation and heme oxygenase-1 activity. In addition, treatment with H2 suppressed RANKL-induced expression of nuclear factor of activated T cells c1 and c-Fos. Furthermore, treatment with H2 suppressed NF-κB activation and reduced phosphorylation of p38, extracellular signal-regulated kinase, c-Jun-N-terminal kinase, and protein kinases B (AKT) stimulated with RANKL. In conclusion, hydrogen molecules prevented RANKL-induced osteoclast differentiation associated with inhibition of reactive oxygen species formation and inactivation of NF-κB, mitogen-activated protein kinase and AKT pathways.

Treatment with resveratrol attenuates sublesional bone loss in spinal cord-injured rats

BACKGROUND AND PURPOSE

Sublesional osteoporosis predisposes individuals with spinal cord injury (SCI) to an increased risk of low-trauma fracture. The aim of the present work was to investigate the effect of treatment with resveratrol (RES) on sublesional bone loss in spinal cord-injured rats.

EXPERIMENTAL APPROACH

Complete SCI was generated by surgical transaction of the cord at the T10-12 level. Treatment with RES (400 mg·kg(-1) body mass per day(-1) , intragastrically) was initiated 12 h after the surgery for 10 days. Then, blood was collected and femurs and tibiae were removed for evaluation of the effects of RES on bone tissue after SCI.

KEY RESULTS

Treatment of SCI rats with RES prevented the reduction of bone mass including bone mineral content and bone mineral density in tibiae, preserved bone structure including trabecular bone volume fraction, trabecular number, and trabecular thickness in tibiae, and preserved mechanical strength including ultimate load, stiffness, and energy in femurs. Treatment of SCI rats with RES enhanced femoral total sulfhydryl content, reduced femoral malondialdehyde and IL-6 mRNA levels. Treatment of SCI rats with RES suppressed the up-regulation of mRNA levels of PPARγ, adipose-specific fatty-acid-binding protein and lipoprotein lipase, and restored mRNA levels of Wnt1, low-density lipoprotein-related protein 5, Axin2, ctnnb1, insulin-like growth factor 1 (IGF-1) and receptor for IGF-1 in femurs and tibiae.

CONCLUSIONS AND IMPLICATIONS

Treatment with RES attenuated sublesional bone loss in spinal-cord-injured rats, associated with abating oxidative stress, attenuating inflammation, depressing PPARγ signalling, and restoring Wnt/β-catenin and IGF-1 signalling.

Moderate-intensity rotating magnetic fields do not affect bone quality and bone remodeling in hindlimb suspended rats

Abundant evidence has substantiated the positive effects of pulsed electromagnetic fields (PEMF) and static magnetic fields (SMF) on inhibiting osteopenia and promoting fracture healing. However, the osteogenic potential of rotating magnetic fields (RMF), another common electromagnetic application modality, remains poorly characterized thus far, although numerous commercial RMF treatment devices have been available on the market. Herein the impacts of RMF on osteoporotic bone microarchitecture, bone strength and bone metabolism were systematically investigated in hindlimb-unloaded (HU) rats. Thirty two 3-month-old male Sprague-Dawley rats were randomly assigned to the Control (n = 10), HU (n = 10) and HU with RMF exposure (HU+RMF, n = 12) groups. Rats in the HU+RMF group were subjected to daily 2-hour exposure to moderate-intensity RMF (ranging from 0.60 T to 0.38 T) at 7 Hz for 4 weeks. HU caused significant decreases in body mass and soleus muscle mass of rats, which were not obviously altered by RMF. Three-point bending test showed that the mechanical properties of femurs in HU rats, including maximum load, stiffness, energy absorption and elastic modulus were not markedly affected by RMF. µCT analysis demonstrated that 4-week RMF did not significantly prevent HU-induced deterioration of femoral trabecular and cortical bone microarchitecture. Serum biochemical analysis showed that RMF did not significantly change HU-induced decrease in serum bone formation markers and increase in bone resorption markers. Bone histomorphometric analysis further confirmed that RMF showed no impacts on bone remodeling in HU rats, as evidenced by unchanged mineral apposition rate, bone formation rate, osteoblast numbers and osteoclast numbers in cancellous bone. Together, our findings reveal that RMF do not significantly affect bone microstructure, bone mechanical strength and bone remodeling in HU-induced disuse osteoporotic rats. Our study indicates potentially obvious waveform-dependent effects of electromagnetic fields-stimulated osteogenesis, suggesting that RMF, at least in the present form, might not be an optimal modality for inhibiting disuse osteopenia/osteoporosis.

Rac1 GTPase silencing counteracts microgravity-induced effects on osteoblastic cells

Bone cells exposed to real microgravity display alterations of their cytoskeleton and focal adhesions, two major mechanosensitive structures. These structures are controlled by small GTPases of the Ras homology (Rho) family. We investigated the effects of RhoA, Rac1, and Cdc42 modulation of osteoblastic cells under microgravity conditions. Human MG-63 osteoblast-like cells silenced for RhoGTPases were cultured in the automated Biobox bioreactor (European Space Agency) aboard the Foton M3 satellite and compared to replicate ground-based controls. The cells were fixed after 69 h of microgravity exposure for postflight analysis of focal contacts, F-actin polymerization, vascular endothelial growth factor (VEGF) expression, and matrix targeting. We found that RhoA silencing did not affect sensitivity to microgravity but that Rac1 and, to a lesser extent, Cdc42 abrogation was particularly efficient in counteracting the spaceflight-related reduction of the number of focal contacts [-50% in silenced, scrambled (SiScr) controls vs. -15% for SiRac1], the number of F-actin fibers (-60% in SiScr controls vs. -10% for SiRac1), and the depletion of matrix-bound VEGF (-40% in SiScr controls vs. -8% for SiRac1). Collectively, these data point out the role of the VEGF/Rho GTPase axis in mechanosensing and validate Rac1-mediated signaling pathways as potential targets for counteracting microgravity effects.

Bone cell senescence: mechanisms and perspectives

Age-related bone loss is in large part the consequence of senescence mechanisms that impact bone cell number and function. In recent years, progress has been made in the understanding of the molecular mechanisms underlying bone cell senescence that contributes to the alteration of skeletal integrity during aging. These mechanisms can be classified as intrinsic senescence processes, alterations in endogenous anabolic factors, and changes in local support. Intrinsic senescence mechanisms cause cellular dysfunctions that are not tissue specific and include telomere shortening, accumulation of oxidative damage, impaired DNA repair, and altered epigenetic mechanisms regulating gene transcription. Aging mechanisms that are more relevant to the bone microenvironment include alterations in the expression and signaling of local growth factors and altered intercellular communications. This review provides an integrated overview of the current concepts and interacting mechanisms underlying bone cell senescence during aging and how they could be targeted to reduce the negative impact of senescence in the aging skeleton.

Cytoplasmic reactive oxygen species and SOD1 regulate bone mass during mechanical unloading

Oxidative stress contributes to the pathogenesis of age-related diseases as well as bone fragility. Our previous study demonstrated that copper/zinc superoxide dismutase (Sod1)-deficient mice exhibit the induction of intracellular reactive oxygen species (ROS) and bone fragility resulting from low-turnover bone loss and impaired collagen cross-linking (Nojiri et al. J Bone Miner Res. 2011;26:2682-94). Mechanical stress also plays an important role in the maintenance of homeostasis in bone tissue. However, the molecular links between oxidative and mechanical stresses in bone tissue have not been fully elucidated. We herein report that mechanical unloading significantly increased intracellular ROS production and the specific upregulation of Sod1 in bone tissue in a tail-suspension experiment. We also reveal that Sod1 loss exacerbated bone loss via reduced osteoblastic abilities during mechanical unloading. Interestingly, we found that the administration of an antioxidant, vitamin C, significantly attenuated bone loss during unloading. These results indicate that mechanical unloading, in part, regulates bone mass via intracellular ROS generation and the Sod1 expression, suggesting that activating Sod1 may be a preventive strategy for ameliorating mechanical unloading-induced bone loss.

Hydrogen water consumption prevents osteopenia in ovariectomized rats

BACKGROUND AND PURPOSE

Accumulating evidence indicates an important role of oxidative stress in the progression of osteoporosis. Recently, it was demonstrated that hydrogen gas, as a novel antioxidant, could selectively reduce hydroxyl radicals and peroxynitrite anion to exert potent therapeutic antioxidant activity. The aim of the present work was to investigate the effect of hydrogen water (HW) consumption on ovariectomy-induced osteoporosis.

EXPERIMENTAL APPROACH

Ovariectomized rats were fed with HW (1.3 ± 0.2 mg·L⁻¹) for 3 months. Then, blood was collected and femur and vertebrae were removed for evaluation of the effect of HW on bone.

KEY RESULTS

HW consumption in ovariectomized rats had no significant effect on oestrogen production, but prevented the reduction of bone mass including bone mineral content and bone mineral density in femur and vertebrae, and preserved mechanical strength including ultimate load, stiffness, and energy, and bone structure including trabecular bone volume fraction, trabecular number, and trabecular thickness in femur, and preserved mechanical strength including ultimate load and stiffness, and bone structure including trabecular bone volume fraction and trabecular number in vertebrae. In addition, treatment with HW abated oxidative stress and suppressed IL-6 and TNF-α mRNA expressions in femur of ovariectomized rats; treatment with HW increased femur endothelial NOS activity and enhanced circulating NO level in ovariectomized rats.

CONCLUSIONS AND IMPLICATIONS

HW consumption prevents osteopenia in ovariectomized rats possibly through the ablation of oxidative stress induced by oestrogen withdrawal.

Physical exercise and intermittent administration of lactulose may improve autism symptoms through hydrogen production

Autism is neuro-developmental disorder. Oxidative stress is enhanced in some children with autism. Hydrogen is a gas with anti-oxidative effects suggested for treating or prevention of some medical problems. It is hypothesized that lactulose or hydrogen water may provide hydrogen to reduce oxidative stress in autism.