Ghrelin protects against depleted uranium-induced bone damage by increasing osteoprotegerin/RANKL ratio

Depleted uranium induces thyroid damage through activation of ER stress via the thrombospondin 1-PERK pathway

Depleted uranium (DU) can cause damage to the body, but its effects on the thyroid are unclear. The purpose of this study was to investigate the DU-induced thyroid damage and its potential mechanism in order to find new targets for detoxification after DU poisoning. A model of acute exposure to DU was constructed in rats. It was observed that DU accumulated in the thyroid, induced thyroid structure disorder and cell apoptosis, and decreased the serum T4 and FT4 levels. Gene screening showed that thrombospondin 1 (TSP-1) was a sensitive gene of DU, and the expression of TSP-1 decreased with the increase of DU exposure dose and time. TSP-1 knockout mice exposed to DU had more severe thyroid damage and lower serum FT4 and T4 levels than wild-type mice. Inhibiting the expression of TSP-1 in FRTL-5 cells aggravated DU-induced apoptosis, while exogenous TSP-1 protein alleviated the decreased viability in FRTL-5 cells caused by DU. It was suggested that DU may caused thyroid damage by down-regulating TSP-1. It was also found that DU increased the expressions of PERK, CHOP, and Caspase-3, and 4-Phenylbutyric (4-PBA) alleviated the DU-induced FRTL-5 cell viability decline and the decrease levels of rat serum FT4 and T4 caused by DU. After DU exposure, the PERK expression was further up-regulated in TSP-1 knockout mice, and the increased expression of PERK was alleviated in TSP-1 over-expressed cells, as well as the increased expression of CHOP and Caspase-3. Further verification showed that inhibition of PERK expression could reduce the DU-induced increased expression of CHOP and Caspase-3. These findings shed light on the mechanism that DU may activate ER stress via the TSP 1-PERK pathway, thereby leading to thyroid damage, and suggest that TSP-1 may be a potential therapeutic target for DU-induced thyroid damage.

The roles of osteoprotegerin in cancer, far beyond a bone player

Osteoprotegerin (OPG), also known as tumor necrosis factor receptor superfamily member 11B (TNFRSF11B), is a member of the tumor necrosis factor (TNF) receptor superfamily. Characterized by its ability to bind to receptor activator of nuclear factor kappa B ligand (RANKL), OPG is critically involved in bone remodeling. Emerging evidence implies that OPG is far beyond a bone-specific modulator, and is involved in multiple physiological and pathological processes, such as immunoregulation, vascular function, and fibrosis. Notably, numerous preclinical and clinical studies have been conducted to assess the participation of OPG in tumorigenesis and cancer development. Mechanistic studies have demonstrated that OPG is involved in multiple hallmarks of cancer, including tumor survival, epithelial to mesenchymal transition (EMT), neo-angiogenesis, invasion, and metastasis. In this review, we systematically summarize the basis and advances of OPG from its molecular structure to translational applications. In addition to its role in bone homeostasis, the physiological and pathological impacts of OPG on human health and its function in cancer progression are reviewed, providing a comprehensive understanding of OPG. We aim to draw more attention to OPG in the field of cancer, and to propose it as a promising diagnostic or prognostic biomarker as well as potential therapeutic target for cancer.

Chitosan Scaffold Containing Periostin Enhances Sternum Bone Healing and Decreases Serum Level of TNF-α and IL-6 after Sternotomy in Rat

BACKGROUND

In the aftermath of bone injuries, such as cranium and sternum, bone wax (BW) is used to control bleeding from the bone surfaces during surgery. Made up of artificial substances, however, it is associated with many complications such as inflammation, increased risk for infection, and bone repair delay. We, therefore, in this study set out to design and evaluate a novel BW without the above-mentioned side-effects reported for other therapies.

METHODS

The pastes (new BW(s)) were prepared in the laboratory and examined by MTT, MIC, MBC, and degradability tests. Then, 60 adult male Wistar rats, divided into six equal groups including chitosan (CT), CT-octacalcium phosphate (OCP), CT-periostin (Post), CT-OCP-Post, Control (Ctrl), and BW, underwent sternotomy surgery. Once the surgeries were completed, the bone repair was assessed radiologically and thereafter clinically in vivo and in vitro using CT-scan, H&E, ELISA, and qRT-PCR.

RESULTS

All pastes displayed antibacterial properties and the CT-Post group had the highest cell viability compared to the control group. In contrast to the BW, CT-Post group demonstrated weight changes in the degradability test. In the CT-Post group, more number of osteocyte cells, high trabeculae percentage, and the least fibrous connective tissue were observed compared to other groups. Additionally, in comparison to the CT and Ctrl groups, higher alkaline phosphatase activity, as well as decreased level of serum tumor necrosis factor-α, interleukin-6, and OCN in the CT-Post group was evident. Finally, Runx2, OPG, and RANKL genes' expression was significantly higher in the CT-Post group than in other groups.

CONCLUSION

Our results provide insights into the desirability of pastes in terms of cellular viability, degradability, antibacterial properties, and surgical site restoration compared to the BW group. Besides, Periostin could enhance the osteogenic properties of bone tissue defect site.

Vitamin D inhibits bone loss in mice with thyrotoxicosis by activating the OPG/RANKL and Wnt/β-catenin signaling pathways

OBJECTIVE

Vitamin D and thyroid hormones have crucial roles in bone metabolism. This study aims to explore the effects of vitamin D on bone metabolism in mice with thyrotoxicosis and its mechanisms.

METHODS

12-week-old mice were randomly divided into 6 groups (6 mice/group), the control (CON) group, vitamin D (VD) group, low-dose LT4 (Low LT4) group, low-dose LT4+VD (Low LT4+VD) group, high-dose LT4 (High LT4) group, high-dose LT4+VD (High LT4+VD) group, LT4 was provided every day and vitamin D3 every other day for 12 weeks. Thyroid function, 25-hydroxy vitamin D, type I collagen carboxy-terminal peptide (CTX), and type I procollagen amino-terminal peptide were determined. In addition, microcomputed tomography, bone histology and histomorphometry, a three-point bending test, and the mRNA expression of osteoprotegerin (OPG), receptor activator of nuclear factor-κB ligand (RANKL) and β-catenin in bone were conducted.

RESULTS

The BMD of lumbar vertebrae and femur decreased and the bone microstructure was destroyed significantly in thyrotoxicosis mice. Addition of vitamin D improved the BMD and bone microstructure only in the low LT4+VD group. Mice with thyrotoxicosis had a significantly higher level of CTX (P<0.05), which was decreased by treatment with vitamin D (P<0.05). The eroded surface per bone surface (Er. S/BS) of the cancellous bone and elongated surface/endocortical perimeter (Er. S/E Pm) of the cortical bone significantly increased in the Low LT4 and High LT4 groups (P<0.05). Treatment with vitamin D significantly decreased the Er. S/BS and Er. S/E Pm. But, treatment with vitamin D did not significantly improve the toughness and rigidity of bones. The ratio of OPG to RANKL and mRNA expression of β-catenin in the Low LT4+VD group were higher than that in the Low LT4 group (P<0.05).

CONCLUSION

In mice with thyrotoxicosis, treatment with vitamin D can inhibit bone resorption and improve the BMD and trabecular bone architecture by increasing the ratio of OPG to RANKL and upregulating the expression of Wnt/β-catenin.

Environmental and health hazards of military metal pollution

An increasing body of literature has demonstrated that armed conflicts and military activity may contribute to environmental pollution with metals, although the existing data are inconsistent. Therefore, in this paper, we discuss potential sources of military-related metal emissions, environmental metal contamination, as well as routes of metal exposure and their health hazards in relation to military activities. Emission of metals into the environment upon military activity occurs from weapon residues containing high levels of particles containing lead (Pb; leaded ammunition), copper (Cu; unleaded), and depleted uranium (DU). As a consequence, military activity results in soil contamination with Pb and Cu, as well as other metals including Cd, Sb, Cr, Ni, Zn, with subsequent metal translocation to water, thus increasing the risk of human exposure. Biomonitoring studies have demonstrated increased accumulation of metals in plants, invertebrates, and vertebrate species (fish, birds, mammals). Correspondingly, military activity is associated with human metal exposure that results from inhalation or ingestion of released particles, as well as injuries with subsequent metal release from embedded fragments. It is also notable that local metal accumulation following military injury may occur even without detectable fragments. Nonetheless, data on health effects of military-related metal exposures have yet to be systematized. The existing data demonstrate adverse neurological, cardiovascular, and reproductive outcomes in exposed military personnel. Moreover, military-related metal exposures also result in adverse neurodevelopmental outcome in children living within adulterated territories. Experimental in vivo and in vitro studies also demonstrated toxic effects of specific metals as well as widely used metal alloys, although laboratory data report much wider spectrum of adverse effects as compared to epidemiological studies. Therefore, further epidemiological, biomonitoring and laboratory studies are required to better characterize military-related metal exposures and their underlying mechanisms of their adverse toxic effects.

Protective effect of melatonin entrapped PLGA nanoparticles on radiation-induced lung injury through the miR-21/TGF-β1/Smad3 pathway

Radiation-induced lung injury (RILI) is a complication commonly found in victims suffering from nuclear accidents and patients treated with chest tumor radiotherapy, and drugs are limited for effective prevention and treatment. Melatonin (MET) has an anti-radiation effect, but its metabolic period in the body is short. In order to prolong the metabolism period of MET, we prepared MET entrapped poly (lactic-co-glycolic acid) nanoparticles (MET/PLGANPS) for the treatment of RILI. As a result, the release rate of MET/PLGANPS in vitro was lower than MET, with stable physical properties, and it caused no changes in histopathology and biochemical indicators. After 2 weeks and 16 weeks of irradiation with the dose of 15 Gy, MET and MET/PLGANPS could reduce the expression of caspase-3 proteins, inflammatory factors, TGF-β1 and Smad3 to alleviate radiation-induced lung injury. MET/PLGANPS showed better therapeutic effect on RILI than MET. In addition, we also found that high expression of miR-21 could increase the expression levels of TGF-β1, and inhibit the protective effect of MET/PLGANPS. In conclusion, MET/PLGANPS may alleviate RILI by inhibiting the miR-21/TGF-β1/Smad3 pathway, which would provide a new target for the treatment of radiation-induced lung injury.

Corydalis Saxicola Bunting Total Alkaloids Attenuate Walker 256-Induced Bone Pain and Osteoclastogenesis by Suppressing RANKL-Induced NF-κB and c-Fos/NFATc1 Pathways in Rats

Metastatic bone pain is characterized by insufferable bone pain and abnormal bone structure. A major goal of bone cancer treatment is to ameliorate osteolytic lesion induced by tumor cells. Corydalis saxicola Bunting total alkaloids (CSBTA), the alkaloid compounds extracted from the root of C. saxicola Bunting, have been shown to possess anticancer and analgesic properties. In this study, we aimed to verify whether CSBTA could relieve cancer induced bone pain and inhibit osteoclastogenesis. The in vivo results showed that CSBTA ameliorated Walker 256 induced bone pain and osteoporosis in rats. Histopathological changes also supported that CSBTA inhibited Walker 256 cell-mediated osteolysis. Further in vitro analysis confirmed that CSBTA reduced the expression of RANKL and downregulate the level of RANKL/OPG ratio in breast cancer cells. Moreover, CSBTA could inhibit osteoclastogenesis by suppressing RANKL-induced NF-κB and c-Fos/NFATc1 pathways. Collectively, this study demonstrated that CSBTA could attenuate cancer induced bone pain via a novel mechanism. Therefore, CSBTA might be a promising candidate drug for metastatic bone pain patients.

Chronic oral depleted uranium leads to reproductive damage in male rats through the ROS-hnRNP A2/B1-COX-2 signaling pathway

Depleted uranium (DU) is widely used in civil and military activities. The testis is one of the target organs of DU chronic toxicity. In this study, male SD rats were chronically exposed to DU by 3, 30, 300 mg U/kg through oral intake. After 6 months and 12 months of exposure, it was found that DU could lead to increased oxidative stress levels, decreased glutathione S-transferases (GSTs) expression, resulting in testicular injury and decreased serum testosterone (T) level in rats. Heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1) expression increases with the increase of DU exposure dose. After upregulation of hnRNP A2/B1 expression, the GC-1 cell injury caused by DU is aggravated, suggesting that hnRNP A2/B1 may play an important role in the reproductive toxicity of DU. At the same time, 12 months after chronic oral exposure to DU, the expression level of cyclooxygenase-2 (COX-2) and proinflammatory factor prostaglandin E2 (PGE2) in testicular tissue were increased, and the level of hnRNP A2/B1 caused by DU was decreased by reactive oxygen scavenger N-acetylcysteine (NAC). As hnRNP A2/B1 is a COX-2 regulator, DU may lead to the upregulation of hnRNP A2/B1 expression through the increase of oxidative stress level in germ cells, which in turn leads to the increase of COX-2 and PGE2 level, and ultimately result in the reproductive toxicity. In this study, the regulation mechanism of the ROS-hnRNP A2/B1-COX-2 pathway on DU-induced reproductive damage in male rats was hypothesized, providing a new target for the prevention and treatment of chronic poisoning of DU.

A review of biological effects and treatments of inhaled depleted uranium aerosol

Depleted uranium (DU) is primarily used for DU bombs and DU tanks in the military. Aerosol inhalation is considered the primary route of DU exposure. Although laboratory tests have confirmed that inhalation of DU aerosol can cause lung, kidney, and other organ damage, epidemiological studies have found no conclusive evidence that persons in areas with prolonged exposure to DU-containing bombs are affected. After the body inhaled DU aerosols, we first clear the insoluble DU through whole-lung lavage (WLL). Then we eliminate the soluble uranium by the chelating agent. Besides, reducing DU damage to tissues and cells through drugs is also an important treatment method. In future research, emphasis should be placed on the damage mechanism of DU aerosol, the laboratory and clinical research of DU chelating agents, the research on the combination of DU chelating agent and WLL, and the research and development of new drugs to prevent DU damage.

Dysregulation of the ghrelin/RANKL/OPG pathway in bone mass is related to AIS osteopenia

BACKGROUND

Osteopenia has been well documented in adolescent idiopathic scoliosis (AIS), and ghrelin has been shown to have a positive effect on bone metabolism. However, the circulating level of ghrelin is increased in AIS osteopenia, and the relationship between ghrelin and low bone mass in AIS osteopenia remains unclear.

METHOD

A total of 563 AIS and 281 age-matched controls were recruited for this study. Anthropometry and bone mass were measured in all participants. Plasma ghrelin levels were determined by enzyme-linked immunosorbent assay (ELISA) in both AIS and control groups. An improved multiplex ligation detection reaction was performed to analyze single-nucleotide polymorphisms (SNPs). Facet joints were collected and subjected to immunohistochemistry; osteogenic gene and protein expression was also measured. Furthermore, primary cells were extracted from facet joints and bone marrow to observe the response to ghrelin stimulation.

RESULTS

The body mass index was lower and circulating ghrelin was markedly higher in the AIS osteopenia group than in the control group. No significant difference was observed in four ghrelin level-related SNPs between the AIS osteopenia and control groups. RNA and protein analyses revealed higher RANKL/OPG and lower runx2 levels in AIS cancellous bone. Compared with normal primary osteoblasts and BMSCs, AIS osteopenia primary cells were insensitive to the same ghrelin concentration gradient and showed lower osteogenic ability, increases in OPG and decreases in RANKL.

CONCLUSION

Our results indicate that high circulating ghrelin levels may not result from gene variations in AIS osteopenia. Dysregulation of the ghrelin/RANKL/OPG pathway may lead to decreased osteogenic ability of osteoblasts and BMSCs, which may be related to lower bone mass in AIS osteopenia.

Anthocyanin-rich extract from black rice (Oryza sativa L. Japonica) ameliorates diabetic osteoporosis in rats

Diabetic osteoporosis (DOP) is a systemic endocrine-metabolic osteopathy which has the characteristics of bone mineral density (BMD) reduction and bone microstructural destruction. Although anthocyanin-rich extract from black rice (AEBR) was reported to have a beneficial effect on diabetic rats, no studies have been performed on whether black rice anthocyanins are beneficial for diabetic osteoporosis. Therefore, in this study, a streptozotocin-induced diabetic rat model was established to investigate the protective effect of AEBR on diabetes-induced osteoporosis and its possible mechanism. AEBR at three doses (0.5, 1.0, and 2.0 g kg^-1 d^-1) were administered by oral gavage to diabetic rats for 8 weeks. The blood glucose, BMD, bone histomorphometry parameters, serum bone turnover biomarkers, bone marrow adipocyte numbers, as well as osteoprotegerin (OPG), runt-related transcription factor 2 (RUNX 2), and receptor activator of nuclear factor-κ B ligand (RANKL) protein expression in bone and serum were detected. The results indicated that AEBR dose-dependently decreased the blood glucose, increased the BMD, and decreased the serum bone turnover markers. The bone microstructure and osteoclast numbers in bone tissues returned to normal in the high AEBR dosage group; at the same time, the AEBR dose-dependently suppressed bone marrow adipogenesis. The RUNX 2 as well as the OPG/RANKL ratio in diabetic rats' bone tissues increased significantly in the AEBR treatment group. Our results indicate that AEBR administration can ameliorate bone loss caused by diabetes; this is mainly attributed to its inhibition of bone turnover, suppression of bone marrow adipogenesis, and up-regulation of RUNX 2 and the OPG/RANKL expression ratio.

Genistein and Silicon Synergistically Protects Against Ovariectomy-Induced Bone Loss Through Upregulating OPG/RANKL Ratio

We have reported that genistein (Gen) and silicon (Si) have synergistic effects on ovariectomy-induced bone loss in rat; however, the potential mechanisms behind this effect were not fully clarified yet. This study was performed to evaluate the bone protective mechanisms of concomitant intake of genistein and silicon in ovariectomized rat by OPG/RANKL axis. Three-month-old Sprague-Dawley female rats were subjected to ovariectomy (OVX) or sham surgery; after surgery, the OVX rats were randomly divided into five groups: OVX-Gen, OVX-Si, OVX-Gen-Si, OVX-E, and OVX. Genistein, silicon, and 17β-estradiol supplementation were started after ovariectomy and continued for 10 weeks. The results showed that genistein and silicon treatment increased the bone mineral density (BMD) of ovariectomized rats. In addition, the BMD of the tibia and femur were highest in the OVX-Gen-Si group compared with OVX-Gen and OVX-Si group (p < 0.05). After 10 weeks treatment with genistein and silicon, the bone structure of ovariectomized rats was recovered, there was no difference of bone histomorphometric parameters between OVX-Gen-Si, OVX-E, and SHAM group (p > 0.05), and there was no difference in the concentration of serum ALP, Ca, P, OPG, and RANKL between OVX-Gen-Si, SHAM, and OVX-E groups (p > 0.05). RT-PCR showed that genistein and silicon treatment could effectively increase the OPG mRNA expression and decreased the RANKL mRNA expression compared to that of the OVX group (p < 0.05), the OPG/RANKL mRNA ratios were significantly decreased in the OVX group (p < 0.05), and it was nearly to normal in the OVX-Gen-Si group. Immunohistochemical staining results showed that genistein and silicon supplementation could effectively increase the protein expression of OPG and decrease the protein expression of RANKL in bone tissues; there were no significant differences in OPG and RANKL positive expression areas between OVX-Gen-Si, SHAM, and OVX-E group (p > 0.05). The results above indicate that genistein and silicon supplementation can effectively reduce RANKL, increase OPG levels, and OPG/RANKL ratios in the serum and bone tissue of ovariectomized rats; this is the main mechanism by which genistein and silicon play a bone protective role in ovariectomized rats.

Du-Zhong (Eucommia ulmoides Oliv.) Cortex Extract Alleviates Lead Acetate-Induced Bone Loss in Rats

The purpose of this study was to evaluate the protective effect of Du-Zhong cortex extract (DZCE) on lead acetate-induced bone loss in rats. Forty female Sprague-Dawley rats were randomly divided into four groups: group I (control) was provided with distilled water. Group II (PbAc) received 500 ppm lead acetate in drinking water for 60 days. Group III (PbAc+DZCE) received 500 ppm lead acetate in drinking water, and given intragastric DZCE (100 mg/kg body weight) for 60 days. Group IV (DZCE) was given intragastric DZCE (100 mg/kg body weight) for 60 days. The bone mineral density, serum biochemical markers, bone histomorphology, and bone marrow adipocyte parameters were analyzed using dual-energy X-ray absorptiometry, biochemistry, histomorphometry, and histopathology, respectively. The results showed that the lumbar spine and femur bone mineral density was significantly decreased in PbAc group compared with the control (P < 0.05); however, this decrease was inhibited by the intake of Du-Zhong cortex extract (P < 0.05, vs. PbAc group; P > 0.05, vs. control and DZCE group). Serum calcium and serum phosphorus in the PbAc+DZCE group were greater than that in the PbAc group (P < 0.05). The PbAc group had higher ALP, osteocalcin, and RANKL than the control group (P < 0.01), and they were significantly lower in the PbAc+DZCE group compared with the PbAc group. There were no significant differences of ALP, osteocalcin, and RANKL among the PbAc+DZCE, control, and DZCE groups (P > 0.05). Serum OPG and OPG/RANKL ration were significantly higher in the PbAc+DZCE group than that in the PbAc group (P < 0.05). The bone histomorphometric analyses showed that bone volume and trabecular thickness in the femoral trabecular bone were significantly lower in the PbAc group than that in the control group, but those were restored in the PbAc+DZCE groups. The bone marrow adipocyte number, percent adipocyte volume per tissue volume (AV/TV), and mean adipocyte diameter were significantly increased in the PbAc group compared to the control (P < 0.01), and those were restored in the PbAc+DZCE group. The differences of those parameters between PbAc+DZCE, DZCE, and the control group were not significant. The results above indicate that the Du-Zhong cortex extract has protective effects on both stimulation of bone formation and suppression of bone resorption in lead-exposed rats, therefore, Du-Zhong cortex extract has the potential to prevent or treat osteoporosis resulting from lead expose.

Salidroside Improves Bone Histomorphology and Prevents Bone Loss in Ovariectomized Diabetic Rats by Upregulating the OPG/RANKL Ratio

Postmenopausal diabetic women have a high risk of fractures. Salidroside has preventive effects on estrogen deficiency-induced osteoporosis and has hypoglycemic effects on diabetes in rats. However, whether salidroside inhibits bone loss in postmenopausal diabetic patients is still unknown. Here, we established a rat model of osteoporosis to investigate the protective effects of salidroside on bone loss induced by ovariectomy combined with diabetes, also investigating the underlying mechanisms. Two-month-old female Sprague-Dawley rats were divided into three equal groups (10 rats in each group): control group (with sham operation, treated with drug vehicle); OVX/T1DM group (ovariectomized diabetic rats); OVX/T1DM-SAL group, comprising ovariectomized diabetic rats treated with salidroside (20 mg/kg body weight) by gavage. The results showed that after 60 consecutive days of treatment, the bone mineral density (BMD) of OVX/T1DM-SAL increased significantly compared with the OVX/T1DM group (p < 0.01). The level of serum bone turnover markers, including alkaline phosphatase (ALP), cross linked c-telopeptide of type I collagen (CTX-1), osteocalcin, N-terminal propeptide of type I procollagen (PINP), and tartrate-resistant acid phosphatase 5b (TRACP 5b) were all increased in the OVX/T1DM group compared with the control (p < 0.01), and those were decreased by salidroside treatment. Meanwhile, the bone histopathological changes were also attenuated, and the bone marrow adipogenesis was inhibited in salidroside treated rats. Moreover, protein and mRNA ratio of bone osteoprotegerin (OPG)/receptor activator of nuclear factor-κB ligand (RANKL) was upregulated in ovariectomized diabetic rats by salidroside treatment. The results above indicated that the protective effect of salidroside on bone loss induced by ovariectomy and diabetes was mainly due to its ability to suppress bone turnover, inhibit bone marrow adipogenesis, and up-regulate the OPG/RANKL ratio.