Effects of aluminum exposure on bone mineral density, mineral, and trace elements in rats

Rutin, Puerarin and Silymarin Regulated Aluminum-Induced Imbalance of Neurotransmitters and Metal Elements in Brain of Rats

Non-specifically binding of aluminum to various substances in the organism can result in toxicity. The accumulation of large amounts of aluminum can cause an imbalance in metal homeostasis and interfere with the synthesis and release of neurotransmitters. Flavonoids have strong metal chelating activity, which can reduce damage to the central nervous system. The purpose of this study was to investigate the protective effect of three representative flavonoids, rutin, puerarin and silymarin, on the brain toxicity induced by long-term exposure to aluminum trichloride (AlCl3). Sixty-four Wistar rats were randomly divided into eight groups (n = 8). The rats in six intervention groups were given 100 or 200 mg/kg BW/day of three different flavonoids for four weeks after a 4-week exposure to 281.40 mg/kg BW/day AlCl3·6H2O, while the rats in the AlCl3-toxicity and control groups were given the vehicle after the period of AlCl3 exposure. The results showed that rutin, puerarin, and silymarin could increase the concentrations of magnesium, iron, and zinc in the brains of the rats. Moreover, the intake of these three flavonoids regulated the homeostasis of amino acid neurotransmitters and adjusted the concentrations of monoamine neurotransmitters to normal levels. Taken together, our data suggest that rutin, puerarin, and silymarin could ameliorate AlCl3-induced brain toxicity in the rats by regulating imbalance of metal elements and neurotransmitters in the brains of rats.

Comparative Study of Time-Dependent Aluminum Exposure and Post-Exposure Recovery Shows Better Improvement in Synaptic Changes and Neuronal Pathology in Rat Brain After Short-Term Exposure

Aluminum is a ubiquitous metal that causes multiple brain pathologies such as, cognitive dysfunction and Alzheimer's disease like symptoms. Exposure to aluminum through drinking water is responsible for hampering learning and memory. This study aimed to compare (1) the time-dependent effect of aluminum exposure (keeping total exposure of 5850 mg/kg same) in two durations, 30 and 45 days, and (2) to compare post-exposure self-recovery effect after 20 days in both (30 and 45 days exposure) groups. Rats were given 130 and 195 mg/kg of AlCl₃·6H₂O for 45 and 30 days respectively, to see the time-dependent exposure effect. At the end of exposure, rats were given distilled water and allowed to self-recover for 20 days to study the recovery. Expression levels of synaptic genes (Syp, SNAP25, Nrxn1/2, PSD95, Shank1/2, Homer1, CamkIV, Nrg1/2 and Kalrn) were measured using qPCR and compared in the exposure and recovery groups. Cellular morphology of the rat brain cortex and hippocampus was also investigated. Damage in lipid and protein profile was measured by employing FTIR. Results showed downregulation of mRNA expression of synaptic genes, plaques deposition, disorganization in lipid and protein profile by increasing membrane fluidity, and disorder and alteration of protein secondary structure after both exposure periods. However, better improvement/recovery in these parameters were observed in recovery group of 30 days aluminum exposure compared to 45 days aluminum exposure group. Taken together, these results suggested that short-term exposure resulted in better restoration of lipid and protein profile after time-dependent exposure of aluminum than prolonged exposure.

Resveratrol-Tempeh reduce micronucleus frequencies bone marrow cells and stimulate osteocyte proliferation in aluminum chloride-induced mice

Aluminum (Al) is widely used for water purification, cooking pots, cosmetic and pharmaceutical preparations, toothpaste tubes, and food processing industries. Although the transport in the digestive tract is very poor but if the load is high, it can be absorbed and accumulated. About 50-70% of Al accumulates in the bones and can have an impact on human health. Resveratrol (RES), isolated from tempeh as an Indonesian food ingredient, can increase cell viability and has promising cytoprotective effects. RES has the capacity to interact with oxidative stress, so it has the potential as a therapy in bone repair. Therefore, this study aimed to evaluate the effect of RES on the number of osteocytes and bone marrow cells in Al-induced mice. Swiss Webster mice were divided into four groups: (1) untreated groups, (2) AlCl3-treated groups, (3) Al+Res5 treated groups, and (4) Al+Res10 treated groups. Al dose 200 mg/kg body weight was administered intraperitoneally. RES was given one hour after administration of Al, with doses of 5 and 10 mg/kg Body Weight. Al and RES administration is carried out for one month. All mice were sacrificed, and mouse bones were isolated for histological preparations and a half for genotoxic assays. Bone marrow cells were collected and stained with My Grunwald. The number of micronuclei polychromatic erythrocytes (MNPCE) was examined in 1,000 PCEs per animal. The number of PCEs is counted by at least 200 erythrocytes (PCE + NCE) per animal. The results showed that the administration of Al significantly increased the number of micronuclei (MN) but after administration of RES at doses of 5 and 10 mg/kg Body Weight significantly reduced the number of MN in bone marrow cells. A dose of RES 10 mg/kg BW stimulates proliferation and increases the number of osteocytes in bone significantly. It can be concluded that Al can cause genotoxicity in bone marrow cells and RES is anti-genotoxic and can stimulate osteocyte proliferation.

The Mineral Composition of Bone Marrow, Plasma, Bones and the First Antlers of Farmed Fallow Deer

An adequate supply of essential nutrients is particularly important during the skeletal growth and development of young deer, especially in males, who build new antlers each year. The aim of the research was to analyze the levels of 21 mineral elements (including the bulk elements: Ca, P, Mg, K, Na; trace elements: Li, Cr, Mn, Co, Cu, Zn, Se, Mo; and toxic elements: Be, Al, As, Cd, Sb, Ba, Pb, Ni) in the bone marrow, plasma, bones, and first antlers of farmed fallow deer (Dama dama). The mineral compositions of tissues were analyzed using inductively coupled plasma mass spectrometry. Higher concentrations of Ca, P, Mg, Cr, Zn, Se, Al, Ba and Ni were found in bone marrow than in plasma. The highest concentrations of Ca, P and Ba were recorded in fallow deer bone, while the highest concentrations of Mg, K, Na, Li, Cr, Mn, Co, Cu, Zn, Se, Mo, Be, Al, As, Sb, Pb and Ni were found in the antlers. Moreover, the research showed a significant negative relationship between Ca and Cd, and between Ca and Pb, and P and Pb (rS = −0.70, rS = −0.80, and rS = −0.66, respectively; p < 0.05) in the tissues.

Aluminum intake in the neonatal phase disrupts endochondral ossification in rodents

OBJECTIVE

This study evaluated the effects of aluminum (Al) intake on endochondral ossification during the neonatal phase.

METHOD

Twelve male newborn Gerbils (Meriones unguiculatus) were randomly divided into control (C) and aluminum (Al) groups (n = 6 animals/group). From the 1st to 15th day of life, gerbils received an AlCl₃ solution (10 mg/kg/day) via gavage. The control group received only the saline solution. On the 16th day, their tibias were processed for paraffin embedding and were submitted to histomorphometric, histochemical, and immunohistochemical analyses.

RESULTS

In the epiphyseal cartilage Al did not affect the proteoglycan content or cell proliferation; however, it increased matrix metalloprotease-2 (MMP-2) immunostaining and the hypertrophic layer thickness. In bone, Al decreased trabeculae number, trabecular width, cortical bone width, and proliferation. Furthermore, the relative frequency of bone matrix and fibrillar collagen decreased 3.9% and 16.2%, respectively. The number of osteoclasts and osteocalcin digital optical density (D.O.D) remained the same.

CONCLUSION

The results suggest that Al intake during the neonatal period impairs endochondral ossification by affecting epiphyseal cartilage and bone architecture.

The Abundance of Trace Elements in Human Bone Relative to Bone Type and Bone Pathology

As the global population ages and the proportion of individuals afflicted with musculoskeletal disease spirals upward, there is an increasing interest in understanding and preventing bone-related diseases. Bone diseases, such as osteoporosis and osteoarthritis, are known to be influenced by a variety of factors including age, gender, nutrition, and genetics, but are also inherently linked to the human body's ability to produce biominerals of suitable quality. Because the crystal lattice structure and mineralogy of bone hydroxyapatite is surprisingly analogous to geological hydroxyapatite, trace element levels and exposure have long been proposed to influence the structure of biominerals as they do geological minerals (e.g., strontium substitution changes the crystal lattice of bone minerals, while toxic lead disrupt bone cellular processes leading to bone disease). Here, we explore the distribution of trace elements in human bones to evaluate the distribution of these elements with respect to bone type (cortical vs. trabecular) and bone disease (osteoarthritis vs. osteoporosis). We find higher concentrations of many metabolically active transition metals, as well as lead, in cortical bone compared to trabecular bone. When compared to patients who have osteoarthritis, and thus presumably normal bone minerals, osteoporosis patients have higher concentrations of scandium and chromium (Cr) in trabecular bone, and Cr and lead in cortical bone. Lower concentrations of barium and titanium are associated with osteoporotic trabecular bone. This survey is an exploratory cross-sectional geochemical examination of several trace element concentrations previously understudied in human bone minerals.

Factors Affecting the Aluminum, Arsenic, Cadmium and Lead Concentrations in the Knee Joint Structures

Background: Toxic elements, such as aluminum (Al), arsenic (As), cadmium (Cd), and lead (Pb), are persistent environmental pollutants that can cause adverse effects on the health of exposed individuals. Bone is one of the primary target organs of accumulation and potential damage from toxic elements. Objectives: This study was performed to determine the Al, As, Cd, and Pb concentrations in the femoral cancellous bone, femoral cartilage, anterior cruciate ligament, meniscus, tibial cartilage, tibial cancellous bone and infrapatellar fat pad. Furthermore, the aim of this study was to explore the relationships between toxic element concentrations and related factors such as gender, age, place of residence, hypertension and diabetes, and to determine the correlations among these toxic elements in knee joint structures. Methods: The samples used this study were collected from 51 patients following total knee arthroplasty. The Al, As, Cd, and Pb concentrations were determined using inductively coupled plasma optic emission spectrometry. Results: Significant differences were found in the Al, As, Cd, and Pb concentrations among the knee joint structures. Cd concentration in the tibial cancellous bone in women was significantly higher than in men. Pb concentration in the infrapatellar fat pad of urban patients was significantly higher as compared to rural patients. Al concentrations in the femoral cancellous bone, femoral cartilage, anterior cruciate ligament, meniscus and tibial cartilage were significantly higher in patients living in urban areas than in rural areas. As concentration in the tibial cancellous bone of diabetic patients was significantly higher compared to non-diabetic patients. In addition, significant Spearman's positive correlations were found between Al and Pb in the knee joint structures. Conclusion: The obtained results of the investigated toxic elements may serve as a basis for establishing the reference values of Al, As, Cd, and Pb in the knee joint structures. The results reported in the study provides novel data regarding the relationships between the toxic element concentrations and gender, age, place of residence, hypertension and diabetes in the studied structures of knee joint. Furthermore, new interactions among these toxic elements were noted.

Aluminum chloride induces G0/G1 phase arrest via regulating the reactive oxygen species-depended non-canonical STAT1 pathway in hFOB1.19 cells

Treatment with aluminum chloride (AlCl₃) suppresses the growth of osteoblastic cells; however, the molecular mechanisms underlying the impact of AlCl₃ on cell growth have not been fully characterized. In this study, we observed that exposure of hFOB1.19 cells to AlCl₃ arrested cells at G₀/G₁ phase by inducing p21 expression. Further studies indicated that AlCl₃ upregulated the phosphorylation level of signal transducer and activator of transcription 1 (STAT1) at serine 727 site (Ser727). By chromatin immunoprecipitation and electrophoretic mobility shift assay, we found that AlCl₃ promoted STAT1/DNA binding activity to p21 promoter, thus resulting in the upregulation of p21. Moreover, siRNA-mediated knockdown of STAT1 attenuated p21 level induced by AlCl₃. Notably, using hFOB1.19 cells stably expressing dominant-negative STAT1 (Ser727Ala), we demonstrated that phosphorylation of STAT1 at Ser727 site is required for p21-mediated cycle arrest induced by AlCl₃. Mechanism investigation indicated that AlCl₃ stimulated the phosphorylation of JNK, and administration of JNK inhibitor SP600125 prevented AlCl₃-induced G₀/G₁ arrest through suppressing the phosphorylation of STAT1. Notably, pretreatment with N-acetyl-cysteine, a reactive oxygen species scavenger, conferred a significantly inhibitory effect on AlCl₃-mediated activation of JNK/STAT1 signaling pathway. Taken together, our findings provide the molecular mechanism for G₀/G₁ arrest induced by AlCl₃ in osteoblastic cells.

Cytotoxicity and changes in gene expression under aluminium potassium sulfate on Spodoptera frugiperda 9 cells

Aluminium, a substance found in large amounts in nature, has been widely used for various purposes, especially food additives. The effects of long-term and excessive exposure to aluminium on human health are receiving increasing attention. The extensive human use of aluminium food additives can also cause aluminium to enter the ecosystem, where it has significant impacts on insects. This study explored the cytotoxicity and changes in gene expression under aluminium potassium sulfate toward Spodoptera frugiperda 9 cells. We found that high concentrations of aluminium resulted in cell enlargement and cell membrane breakage, decreased cell vitality, and apoptosis. Through RNA-Seq transcriptomics, we found that aluminium ions may inhibit the expression of regulatory-associated protein of mTOR, tdIns-dependent protein kinase-1, and small heat shock proteins (heat shock 70 kDa protein and crystallin alpha B), leading to changes in mTOR-related pathways (such as the longevity regulation pathway and PI3K-Akt signalling pathway), and promoting cell apoptosis. On the other hand, aluminium ions lead to the overexpression of GSH S-transferase, prostaglandin-H2 D-isomerase and pyrimidodiazepine synthase, and induce intracellular oxidative damage, which ultimately affects cell growth and apoptosis through a series of cascade reactions.

The adjuvant aluminum fate - Metabolic tale based on the basics of chemistry and biochemistry

Aluminum is inevitable component of many vaccines. The benefit of the vaccines is undeniable but effects of aluminum toxicity might be underestimated and neglected. In this review, we highlighted the mechanims of aluminum toxicity, which is still in debate. So far, all the papers that disscused the adverse aluminum effects pointed two mechanisms responsible for Al toxicity, direct Al toxicity and aluminum induced cell damage via the oxidative metabolism. According to our knowledge, which is based on basic principles of biochemistry and inorganic chemistry, we suggested that aluminum highly interferes with iron metabolism eventually resulting in iron-mediated cell damage. More importantly, in this paper, we offered easily feasible solutions, in order to avoid aluminum toxicity in the future. We suggest that as it once was, Calcium Phosphate again to be used as the adjuvant or better solution that the vaccine adjuvants should be based on zinc compounds or even better would be non-metal adjuvants, such as microcrystalline tyrosine and monosodium urate. Until an adequate adjuvant is provided, we suggest instant postponement of vaccination with vaccines which use aluminum as the adjuvant until the 12 months of age.

UBE2E3 regulates cellular senescence and osteogenic differentiation of BMSCs during aging

Background

Osteoporosis has gradually become a public health problem in the world. However, the exact molecular mechanism of osteoporosis still remains unclear. Senescence and osteogenic differentiation inhibition of bone marrow mesenchymal stem cells (BMSCs ) are supposed to play an important part in osteoporosis.

Methods

We used two gene expression profiles (GSE35956 and GSE35958) associated with osteoporosis and selected the promising gene Ubiquitin-conjugating enzyme E2 E3 (UBE2E3). We then verified its function and mechanism by in vitro experiments.

Results

UBE2E3 was highly expressed in the bone marrow and positively associated with osteogenesis related genes. Besides, UBE2E3 expression reduced in old BMSCs compared with that in young BMSCs. In in vitro experiments, knockdown of UBE2E3 accelerated cellular senescence and inhibited osteogenic differentiation of young BMSCs. On the other hand, overexpression of UBE2E3 attenuated cellular senescence as well as enhanced osteogenic differentiation of old BMSCs. Mechanistically, UBE2E3 might regulate the nuclear factor erythroid 2-related factor (Nrf2) and control its function, thus affecting the senescence and osteogenic differentiation of BMSCs.

Conclusion

UBE2E3 may be potentially involved in the pathogenesis of osteoporosis by regulating cellular senescence and osteogenic differentiation of BMSCs.

Long-term assessment of trace elements in franciscana dolphins from the Río de la Plata estuary and adjacent Atlantic waters

The estuary of Río de la Plata, in the eastern coast of South America, is a highly anthropized area that brings a high load of contaminants to the surrounding waters, which may have detrimental effects on the local marine fauna. The franciscana dolphin (Pontoporia blainvillei) is a small cetacean species endemic of the southwestern Atlantic Ocean listed as Vulnerable in the IUCN red list. In this study, we assessed the concentrations of 13 trace elements in bone samples from 100 franciscana dolphins that were found stranded dead or incidentally bycaught in the Río de la Plata and adjacent coast between 1953 and 2015. Elements were, in decreasing order of mean concentrations: Zn > Sr > Fe > Al > Mn > Cu > Pb > Cr > Ni > As > Hg > Cd > Se. The concentrations of Al, Cr and Fe were slightly higher in females than in males. The concentrations of As, Ni, and Pb significantly decreased with body length. Throughout the study period, the concentrations of Al, Cr, Cu, Fe, Mn and Ni significantly increased, while the concentrations of As, Pb and Sr significantly decreased. The increasing trends may be due to increased inputs from river discharges, the leather industry and petroleum refineries, while the decrease in Pb may be due to the ban in the use of this element as an additive in gasoline and as component of car batteries. This investigation supports the validity of analysing trace element in bone, a tissue available in scientific collections and museums, to retrospectively examine variation over long temporal scales and thus assess long-term trends in pollution.

Long-term exposure to low doses of aluminum affects mineral content and microarchitecture of rats alveolar bone

Aluminum (Al) is one of the most found elements in nature in many forms, and human exposure can be quite common. Therefore, it is important to investigate the effects of exposure to Al mainly at low doses and for a prolonged period, in order to simulate human exposure in the periodontium, an important structure for support and protection of the teeth. This investigation aimed to study the aluminum chloride (AlCl₃) toxicological effects in the mineral composition and micromorphology of the alveolar bone of rats. Two groups of eight male Wistar rats were used for the experiment. AlCl₃ group was exposed to AlCl₃ orally at a dose of 8.3 mg/kg/day for 60 days, while the control group received only distilled water. After that, the mandibles were collected and submitted to the following analyses: Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray microtomography analysis; blood was also collected for determination of Al circulating levels. Our data showed that AlCl₃ was capable of increasing Al circulating levels in blood. It was able to promote changes in the mineral content and triggers significant changes in the mineralized bone microstructure, such as number and thickness of trabeculae, being associated with alveolar bone-loss.

Pulp tissue reaction to a self-adhesive, resin-based direct pulp capping material containing surface pre-reacted glass-ionomer filler

OBJECTIVE

This study aimed to evaluate the effect of direct pulp capping using an experimental self-adhesive resin for direct pulp capping (SRD) containing silica and surface pre-reacted glass-ionomer (S-PRG) filler on pulpal healing and to monitor the dentin bridge formation in rat pulp 2-4 weeks after operation.

METHODS

Five types of SRDs (SRD-0: S-PRG fillers 0 wt%; SRD-1: S-PRG fillers 9.1 wt%; SRD-2: S-PRG fillers 18.4 wt%; SRD-3: S-PRG fillers 27.8 wt%; and SRD-6: S-PRG fillers 57.4 wt%) were prepared, and mineral trioxide aggregate (MTA) was used as control (n = 8). Direct pulp capping was performed on rats that were sacrificed for further evaluation 2 or 4 weeks after the operation. The pulp tissue disorganization (PTD), inflammatory cell infiltration (ICI), and reparative dentin formation were histopathologically evaluated; the data were statistically analyzed using the Kruskal-Wallis and the Mann-Whitney U tests.

RESULTS

The histopathological evaluation of SRD-1-treated test animals 2 weeks post-operation revealed inferior PTD and ICI when compared with that of MTA. Even 4 weeks after the operation in SRD-1- and SRD-2-treated rats, the PTD and ICI were inferior when compared with those of MTA. The dental specimens of SRD-0 and MTA showed orthodentin formation, whereas SRD-treated test animals showed osteodentin formation at a position slightly deeper than the site of the pulpal exposure.

SIGNIFICANCE

The reparative dentin formed by SRD-0 and MTA was genuine, whereas that formed by SRD-3 and SRD-6 was ossified and ectopic. SRD may have the potential to be utilized clinically as a direct pulp capping material.

Probabilistic Risk Analysis to Assess Dietary Exposure to Aluminum in the Taiwanese Population

Aluminum (Al) exposure at human dietary levels raises health concerns, yet little is known about the Al exposure from the Taiwanese diet. The amount of aluminum (Al)-containing food consumption in the Taiwanese total diet is increasing, which contributes to the total diet consumption., which raises the health concerns. In this study, we aim to assess estimated weekly intake (EWI) and the percentage of provisional tolerable weekly intake (%PTWI) of the dietary exposure to Al in different age-sex groups. We also applied probabilistic risk analyses to quantify the parameters' uncertainty by focusing on the distribution function for the Al concentration in food, consumption rate, and body weight in specific age groups. Results indicated that the EWIs declined with increasing age after 6-years old (7-12 > 13-15 > 16-18 > 19-64 > 65+). Results indicated that the EWIs gradually declined after 6-year of age. The EWIs of Al-rich food in cake + waffle, kelp, snacks, and bread contributed 20%, 17%, 17%, and 11%, respectively, to the total EWIs, corresponding with the much higher consumption rates for these four foods. The 75th percentile of EWIs for the children aged 34-6 years had a %PTWI valued at over 100%, indicating a potential risk of Al intake via dietary exposure. Our findings show that there is a concern about the consumption of Al-rich foods for children in Taiwan.

Long-Term Accumulation of Metals in the Skeleton as Related to Osteoporotic Derangements

The concentrations of metals in the environment are still not within the recommended limits as set by the regulatory authorities in various countries because of human activities. They can enter the food chain and bioaccumulate in soft and hard tissues/organs, often with a long half-life of the metal in the body. Metal exposure has a negative impact on bone health and may result in osteoporosis and increased fracture risk depending on concentration and duration of metal exposure and metal species. Bones are a long-term repository for lead and some other metals, and may approximately contain 90% of the total body burden in birds and mammals. The present review focuses on the most common metals found in contaminated areas (mercury, cadmium, lead, nickel, chromium, iron, and aluminum) and their effects on bone tissue, considering the possibility of the long-term bone accumulation, and also some differences that might exist between different age groups in the whole population.

Ginsenoside Rg3 Attenuates Aluminum-Induced Osteoporosis Through Regulation of Oxidative Stress and Bone Metabolism in Rats

Aluminum (Al)-induced bone metabolism disorder is a primary cause of osteoporosis. Ginsenoside Rg3 (Rg3) has demonstrated therapeutic properties in the treatment of osteoporosis. The present study aimed to identify potential bone protection mechanisms of Rg3 against Al-induced osteoporosis in rats. In this study, forty healthy male Sprague-Dawley rats were randomly allocated into groups in which they were treated with AlCl₃ (64 mg/kg/day) and/or Rg3 (20 mg/kg/day). AlCl₃ was given orally to rats for 120 days, and from the 91st day, treated orally with Rg3 for 30 days. Rg3 attenuated AlCl₃-induced accumulation of Al by decreasing the bone mineral density in the lumbar spines, femoral metaphysis, and tibia, and inhibited AlCl₃-induced oxidative stress in rat bone by decreasing the levels of reactive oxygen species and malondialdehyde, while increasing glutathione peroxidase and superoxide dismutase activity. Rg3 facilitated bone formation by increasing the concentration of calcium, phosphorus, amino-terminal propeptide of type I procollagen, and carboxyl-terminal propeptide of type I procollagen, bone alkaline phosphatase activity in serum, and type I collagen, osteocalcin, and osteopontin protein expressions. Rg3 inhibited bone resorption by decreasing the content of N-terminal cross-linking telopeptide of type I collagen, C-terminal cross-linking telopeptide of type I collagen, and tartrate-resistant acid phosphatase 5b activity in serum. Rg3 promoted the mRNA expression of growth regulation factors by increasing transforming growth factor-β1, bone morphogenetic protein-2, insulin-like growth factor I, and core-binding factor α1. The results demonstrate that Rg3 can significantly attenuate Al accumulation, facilitate bone formation, inhibit bone resorption, resist oxidative stress, and promote the expression of factors that regulate growth. The results indicate that Rg3 is effective in alleviating AlCl₃-induced osteoporosis.

Accumulation of Toxic Elements in Bone and Bone Marrow of Deer Living in Various Ecosystems. A Case Study of Farmed and Wild-Living Deer

The aim of the study was to determine the concentrations of toxic elements accumulated in the bone marrow and bones (Cervus elaphus). The studies were carried out on two groups of young stags: farmed (n = 6) and wild (n = 9). Their body weights were measured and bone and bone marrow samples were collected. The concentrations of toxic elements were analyzed using the inductively coupled plasma mass spectrometry technique. The mean aluminum content in the bone marrow and bones of the farmed animals was significantly higher than in the wild group (p < 0.05). The mean concentration of arsenic, barium and lead in the bones of the wild red deer was significantly higher than in the bones of the farmed animals (p < 0.05), while the cadmium concentration in the bones of the farmed red deer exceeded the value determined in the wild animals. A significant difference was found between the mean concentrations of aluminum, arsenic, barium, lead, vanadium and nickel in the bone marrow and bones of both red deer groups (p < 0.05). Although the study involved animals living in an uncontaminated area, the concentrations of some heavy metals were higher than values reported from industrial regions.

Effects of Chronic Aluminum Lactate Exposure on Neuronal Apoptosis and Hippocampal Synaptic Plasticity in Rats

This study investigated the effects of chronic aluminum exposure on apoptosis of hippocampal neurons, and synaptic plasticity in the hippocampus in rats. Rats were divided into the control, low-dose (L-Al), mid-dose (M-Al), and high-dose (H-Al) groups. After chronic exposure of aluminum, the Morris water maze (MWM) and open-field (OF) tests were performed to assess the behavioral performance. Electrophysiological measurements were conducted. Flow cytometry was used to assess the apoptotic processes. Quantitative real-time PCR and ELISA were performed to measure mRNA and protein expression levels of caspases. After 90 days of aluminum exposure, the aluminum contents in the brain of the rats were increased, with the increasing exposure dose. The MWM and OF tests showed that chronic exposure of aluminum significantly impaired the neurobehavior of rats. Moreover, after high-frequency stimulation (HFS), the average amplitudes of field excitatory postsynaptic potentials (fEPSPs) for the M-Al and H-Al groups were lower than the control group at 10, 20, 30, 40, 50, and 60 min. Furthermore, the apoptotic rates in the M-Al and H-Al groups were significantly higher than the control group. The qRT-PCR and ELISA showed that, compared with the control group, the mRNA and protein expression levels of caspases-3, -8, and -9 were significantly increased in the aluminum-treated groups compared with the control group. Long-term exposure to aluminum could induce the apoptosis of hippocampal neurons, damage the synaptic plasticity, and impair the learning and memory functions in rats. There might be a close relationship between the neuronal apoptosis and synaptic plasticity damage.

Heat treatment dependent cytotoxicity of silicalite-1 films deposited on Ti-6Al-4V alloy evaluated by bone-derived cells

A silicalite-1 film (SF) deposited on Ti-6Al-4V alloy was investigated in this study as a promising coating for metallic implants. Two forms of SFs were prepared: as-synthesized SFs (SF-RT), and SFs heated up to 500 °C (SF-500) to remove the excess of template species from the SF surface. The SFs were characterized in detail by X-ray photoelectron spectroscopy (XPS), by Fourier transform infrared spectroscopy (FTIR), by scanning electron microscopy (SEM) and water contact angle measurements (WCA). Two types of bone-derived cells (hFOB 1.19 non-tumor fetal osteoblast cell line and U-2 OS osteosarcoma cell line) were used for a biocompatibility assessment. The initial adhesion of hFOB 1.19 cells, evaluated by cell numbers and cell spreading area, was better supported by SF-500 than by SF-RT. While no increase in cell membrane damage, in ROS generation and in TNF-alpha secretion of bone-derived cells grown on both SFs was found, gamma H2AX staining revealed an elevated DNA damage response of U-2 OS cells grown on heat-treated samples (SF-500). This study also discusses differences between osteosarcoma cell lines and non-tumor osteoblastic cells, stressing the importance of choosing the right cell type model.

Biocompatibility and osteogenic activity of guided bone regeneration membrane based on chitosan-coated magnesium alloy

Ideally, a guided bone regeneration membrane (GBRM) should possess high strength, as for titanium membranes, along with excellent biocompatibility and osteoconductivity, as for natural absorbable collagen membranes. Besides titanium, magnesium (Mg) is another metal widely used in the biomedical field, which also exhibits biodegradability. In this study, a composite chitosan‑magnesium (CS-Mg) membrane was fabricated by dip-coating Mg alloy into chitosan solution. In vitro and in vivo tests were performed to investigate whether this membrane could be used as biodegradable GBRM, and the test results were compared with those obtained for a commercial GBRM (Heal-All). The microstructure was analyzed by scanning electron microscopy-electron dispersive spectroscopy. The degradation behavior was investigated by immersing the membranes into Dulbecco's modified Eagle medium (DMEM). The in vitro biocompatibility was evaluated by cell adhesion, cytotoxicity and alkaline phosphatase (ALP) assays using MG63 cells. The cytotoxicity and ALP assays were performed with diluted extracts of Mg, CS-Mg and Heal-All. The results show that CS-Mg has a suitable degradation rate, as well as similar cell adhesion and cytocompatibility to Heal-All. However, the 10% CS-Mg extracts exhibited higher ALP activity at 3 and 5 days (p < 0.05) compared with the medium control and the Heal-All extracts, but no differences with 10% Mg extracts (p > 0.05). Rabbit calvarial defects were used for testing the osteogenic activity in vivo. Three groups of samples were examined: CS-Mg, Heal-All, and a blank control. Higher amounts of new bone were formed for the CS-Mg and Heal-All groups (p < 0.05) compared with the blank control, whereas no significant differences between the CS-Mg and Heal-All groups were observed (p > 0.1). In conclusion, the CS-Mg membrane shows great potential for application as a biodegradable metallic GBRM with excellent osteogenic activity.

A Review of Metal Exposure and Its Effects on Bone Health

The presence of metals in the environment is a matter of concern, since human activities are the major cause of pollution and metals can enter the food chain and bioaccumulate in hard and soft tissues/organs, which results in a long half-life of the metal in the body. Metal intoxication has a negative impact on human health and can alter different systems depending on metal type and concentration and duration of metal exposure. The present review focuses on the most common metals found in contaminated areas (cadmium, zinc, copper, nickel, mercury, chromium, lead, aluminum, titanium, and iron, as well as metalloid arsenic) and their effects on bone tissue. Both the lack and excess of these metals in the body can alter bone dynamics. Long term exposure and short exposure to high concentrations induce an imbalance in the bone remodeling process, altering both formation and resorption and leading to the development of different bone pathologies.

Fas- and Mitochondria-Mediated Signaling Pathway Involved in Osteoblast Apoptosis Induced by AlCl3

Aluminum (Al) is known to induce apoptosis of osteoblasts (OBs). However, the mechanism is not yet established. To investigate the apoptotic mechanism of OBs induced by aluminum trichloride (AlCl₃), the primary OBs from the craniums of fetal Wistar rats were exposed to 0 mg/mL (control group, CG), 0.06 mg/mL (low-dose group, LG), 0.12 mg/mL (mid-dose group, MG), and 0.24 mg/mL (high-dose group, HG) AlCl₃ for 24 h, respectively. We observed that AlCl₃ induced OB apoptosis with the appearance of apoptotic morphology and increase of apoptosis rate. Additionally, AlCl₃ treatment activated mitochondrial-mediated signaling pathway, accompanied by mitochondrial membrane potential (ΔΨm) depolarization, release of cytochrome c from the mitochondria to the cytoplasm, as well as survival signal-related factor caspase-9 and caspase-3 activation. AlCl₃ exposure also activated Fas/Fas ligand signaling pathway, presented as Fas, Fas ligand, and Fas-associated death domain expression enhancement and caspase-8 activation, as well as the hydrolysis of Bid to truncated Bid, suggesting that the Fas-mediated signaling pathway might aggravate mitochondria-mediated OB apoptosis through hydrolyzing Bid. Furthermore, AlCl₃ exposure inhibited Bcl-2 protein expression and increased the expressions of Bax, Bak, and Bim in varying degrees. These results indicated that AlCl₃ exposure induced OB apoptosis through activating Fas- and mitochondria-mediated signaling pathway and disrupted B-cell lymphoma-2 family proteins.

Applications of Metals for Bone Regeneration

The regeneration of bone tissue is the main purpose of most therapies in dental medicine. For bone regeneration, calcium phosphate (CaP)-based substitute materials based on natural (allo- and xenografts) and synthetic origins (alloplastic materials) are applied for guiding the regeneration processes. The optimal bone substitute has to act as a substrate for bone ingrowth into a defect, as well as resorb in the time frame needed for complete regeneration up to the condition of restitution ad integrum. In this context, the modes of action of CaP-based substitute materials have been frequently investigated, where it has been shown that such materials strongly influence regenerative processes such as osteoblast growth or differentiation and also osteoclastic resorption due to different physicochemical properties of the materials. However, the material characteristics needed for the required ratio between new bone tissue formation and material degradation has not been found, until now. The addition of different substances such as collagen or growth factors and also of different cell types has already been tested but did not allow for sufficient or prompt application. Moreover, metals or metal ions are used differently as a basis or as supplement for different materials in the field of bone regeneration. Moreover, it has already been shown that different metal ions are integral components of bone tissue, playing functional roles in the physiological cellular environment as well as in the course of bone healing. The present review focuses on frequently used metals as integral parts of materials designed for bone regeneration, with the aim to provide an overview of currently existing knowledge about the effects of metals in the field of bone regeneration.

Water-soluble factors eluated from surface pre-reacted glass-ionomer filler promote osteoblastic differentiation of human mesenchymal stem cells

Surface pre-reacted glass‑ionomer (S‑PRG)-containing dental materials, including composite and coating resins have been used for the restoration and/or prevention of dental cavities. S‑PRG is known to have the ability to release aluminum, boron, fluorine, silicon, and strontium ions. Aluminum ions are known to be inhibitors whereas boron, fluorine, silicon, and strontium ions are known to be promoters of mineralization, via osteoblasts. However, it remains to be clarified how an aqueous eluate obtained from S‑PRG containing these ions affects the ability of mesenchymal stem cells (MSCs), which are known to be present in dental pulp and bone marrow, to differentiate into osteogenic cell types. The present study demonstrated that 200‑ to 1,000‑fold‑diluted aqueous eluates obtained from S‑PRG significantly upregulated the mRNA expression level of the osteogenic differentiation marker alkaline phosphatase in human MSCs (hMSCs) without exhibiting the cytotoxic effect. In addition, the 500‑ to 1,000‑fold‑diluted aqueous eluates obtained from S‑PRG significantly and clearly promoted mineralization of the extracellular matrix of hMSCs. It was additionally demonstrated that hMSCs cultured on the cured resin composites containing S‑PRG fillers exhibited osteogenic differentiation in direct correlation with the weight percent of S‑PRG fillers. These results strongly suggested that aqueous eluates of S‑PRG fillers promoted hard tissue formation by hMSCs, implicating that resins containing S‑PRG may act as a useful biomaterial to cover accidental exposure of dental pulp.

Assessment of the effect of strontium, lead, and aluminum in bone on dual-energy x-ray absorptiometry and quantitative ultrasound measurements: A phantom study

PURPOSE

Dual-energy X-ray absorptiometry (DXA) is the gold standard technique to measure areal bone mineral density (aBMD) for the diagnosis of osteoporosis. Because DXA relies on the attenuation of photon to estimate aBMD, deposition of bone-seeking metallic elements such as strontium, lead, and aluminum that differ in atomic numbers from calcium can cause inaccurate estimation of aBMD. Quantitative ultrasound (QUS) is another technique available to assess bone health by measuring broadband ultrasound attenuation (BUA), speed of sound (SOS), and an empirically derived quantity called stiffness index (SI). Because the acoustic properties are not prone to significant change due to changes in microscopic atomic composition of bone, it is hypothesized that QUS is unaffected by the presence of bone-seeking elements in the bone. The objective of this study was to investigate the effect of strontium, lead, and aluminum on DXA-derived aBMD and QUS parameters using bone-mimicking phantoms compatible with both techniques.

METHODS

Bone-mimicking phantoms were produced by homogeneously mixing finely powdered hydroxyapatite compounds that contain varying concentrations of strontium, lead, or aluminum with porcine gelatin solution. Seven strontium-substituted phantoms were produced with varying molar ratio of Sr/(Sr + Ca) ranging from 0% to 2%. Four lead-doped phantoms and four aluminum-doped phantoms were constructed with the respective analyte concentrations ranging from 50 to 200 ppm. An additional 0 ppm phantom was produced to be used as a baseline for the lead and aluminum phantom measurements. All phantoms had uniform volumetric bone mineral density (vBMD) of 200 mg/cm³ , and were assessed using a Hologic Horizon^® DXA device and a Hologic Sahara^® QUS device. Furthermore, theoretical aBMD bias for mol/mol% substitution of calcium with the three bone-seeking elements was calculated.

RESULTS

Strong positive linear relationship was found between aBMD measured by DXA and strontium concentration (P < 0.001, r = 0.995). From the measurement of lead and aluminum phantoms using DXA, no statistically significant relationship was observed between aBMD and the analyte concentrations. For the QUS system, with an exception of BUA and lead concentration that exhibited statistically significant relationship (P < 0.038, r = 0.899), no statistically significant change was observed in all QUS parameters with respect to the clinically relevant concentration of all three elements. The calculated theoretical aBMD bias induced by 1 mol/mol% substitution of calcium with strontium, lead, and aluminum were 10.8%, 4.6%, and -0.7%, respectively.

CONCLUSION

aBMD measured by DXA was prone to overestimation in the presence of strontium, but acoustic parameters measured by QUS are independent of strontium concentration. The deviation in aBMD induced by the clinically relevant concentrations of lead and aluminum under 200 ppm could not be detected using the Hologic Horizon^® DXA device. Furthermore, the SI measured by the QUS system was not affected by lead or aluminum concentrations used in this study.

Aluminum exposure for 60days at an equivalent human dietary level promotes peripheral dysfunction in rats

Aluminum (Al) is a neurotoxic associated with a number of chronic human diseases. We investigated the effects of Al exposure at doses similar to human dietary levels and at a high level exposure to Al on the peripheral nervous system. Wistar male rats were divided into two major groups and received orally: 1) First group - Low level - rats were subdivided and treated for 60days: a) Control - received ultrapure water; b) AlCl₃ - received Al at 8.3mg/kg body weight (bw) for 60days; and 2) Second group - High level - rats were subdivided and treated for 42days: C) Control - received ultrapure water through oral gavage; d) AlCl₃ - received Al at 100mg/kg bw for 42days. Von Frey hair test, plantar test, the presence of catalepsy and the spontaneous motor activity were investigated. Reactive oxygen species, lipid peroxidation and total antioxidant capacity, immunohistochemistry to investigate the nerve inflammation and, the specific presence of Al in the sciatic nerve fibers were investigated. Al exposure at a representative human dietary level promotes the development of mechanical allodynia, catalepsy, increased inflammation in the sciatic nerve, systemic oxidative stress and, is able to be retained in the sciatic nerve. The effects of low-dose Al were similar to those found in rats exposed to Al at a dose much higher (100mg/kg). Our findings suggest that Al may be considered toxic for the peripheral nervous system, thus inducing peripheral dysfunction.

Aluminum exposure at human dietary levels promotes vascular dysfunction and increases blood pressure in rats: A concerted action of NAD(P)H oxidase and COX-2

Aluminum (Al) is a non-essential metal and a significant environmental contaminant and is associated with a number of human diseases including cardiovascular disease. We investigated the effects of Al exposure at doses similar to human dietary levels on the cardiovascular system over a 60day period. Wistar male rats were divided into two major groups and received orally: 1) Low aluminum level - rats were subdivided and treated for 60days as follows: a) Untreated - ultrapure water; b) AlCl₃ at a dose of 8.3mg/kg bw for 60days, representing human Al exposure by diet; and 2) High aluminum level - rats were subdivided and treated for 42days as follows: C) Untreated - ultrapure water; d) AlCl₃ at 100mg/kg bw for 42days, representing a high level of human exposure to Al. Effects on systolic blood pressure (SBP) and vascular function of aortic and mesenteric resistance arteries (MRA) were studied. Endothelium and smooth muscle integrity were evaluated by concentration-response curves to acetylcholine (ACh) and sodium nitroprusside. Vasoconstrictor responses to phenylephrine (Phe) in the presence and absence of endothelium and in the presence of the NOS inhibitor L-NAME, the potassium channels blocker TEA, the NAD(P)H oxidase inhibitor apocynin, superoxide dismutase (SOD), the non-selective COX inhibitor indomethacin and the selective COX-2 inhibitor NS 398 were analyzed. Vascular reactive oxygen species (ROS), lipid peroxidation and total antioxidant capacity, were measured. The mRNA expressions of eNOS, NAD(P)H oxidase 1 and 2, SOD1, COX-2 and thromboxane A2 receptor (TXA-2 R) were also investigated. Al exposure at human dietary levels impaired the cardiovascular system and these effects were almost the same as Al exposure at much higher levels. Al increased SBP, decreased ACh-induced relaxation, increased response to Phe, decreased endothelial modulation of vasoconstrictor responses, the bioavailability of nitric oxide (NO), the involvement of potassium channels on vascular responses, as well as increased ROS production from NAD(P)H oxidase and contractile prostanoids mainly from COX-2 in both aorta and mesenteric arteries. Al exposure increased vascular ROS production and lipid peroxidation as well as altered the antioxidant status in aorta and MRA. Al decreased vascular eNOS and SOD1 mRNA levels and increased the NAD(P)H oxidase 1, COX-2 and TXA-2 R mRNA levels. Our results point to an excess of ROS mainly from NAD(P)H oxidase after Al exposure and the increased vascular prostanoids from COX-2 acting in concert to decrease NO bioavailability, thus inducing vascular dysfunction and increasing blood pressure. Therefore, 60-day chronic exposure to Al, which reflects common human dietary Al intake, appears to pose a risk for the cardiovascular system.

The Effects of Nigella Sativa Seed Extract on Bone Healing in an Experimental Model

The purpose of this study was to histologically evaluate the effects on bone healing of nigella sativa seed extract applied on calvarial defects in an ovariectomized rat model. The study included 32 female rats weighing 280 to 310 g with an average age of 3 months. A defect was created with a trephine burr on each rat calvarium. The rats were divided into 2 groups (control and study) of 8 animals each. All the defects were grafted with a gelatin sponge mixed with normal saline. In the study group, nigella sativa seed extract was applied systemically using an oro-gastric tube. Half of the animals in each group were sacrificed after 2 weeks, and the others after 4 weeks. In the control groups, the defects were not completely filled with regenerated bone. Osteoblast cells were observed more in the study groups. A higher rate of osteoclasts was determined in the control groups. In addition, the nigella sativa group had a statistically greater amount of bone formation than the others group at both 2 weeks and 4 weeks (P <0.05). The systemic application of nigella sativa seed extract demonstrated incredibly positive effects on enhanced bone healing in this experimental osteoporotic model.

Europium-Doped Gd2O3 Nanotubes Increase Bone Mineral Density in Vivo and Promote Mineralization in Vitro

Europium-doped Gd₂O₃ nanotubes (Gd₂O₃:Eu³⁺ NTs) have been extensively applied in the field of bioscience for their photostability and magnetic properties. Nevertheless, the distribution and interaction between Gd₂O₃:Eu³⁺ NTs and metabolism of bone are not yet sufficiently understood. In this study, a systematic study of the toxicity and distribution of Gd₂O₃:Eu³⁺ NTs in mice after oral administration was carried out. The results showed that a small number of the Gd₂O₃:Eu³⁺ NTs could pass through biological barriers into the lung, liver, and spleen, but a high concentration was observed in bone. Furthermore, the effects of Gd₂O₃:Eu³⁺ NTs on bone metabolism were systematically studied in vitro and in vivo when accumulating in bone. After being administered to mice, the Gd₂O₃:Eu³⁺ NTs extremely enhanced the bone mineral density and bone biomechanics. In vitro the Gd₂O₃:Eu³⁺ NTs increased the alkaline phosphatase (ALP) activity and mineralization and promoted the expression of osteogenesis genes in preosteoblasts MC3T3-E1 through activation of the BMP signaling pathway. This study will be significant for appropriate application of Gd₂O₃:Eu³⁺ NTs in the biomedical field and expounding the molecular mechanism of bone metabolism.

Aluminum exposure for one hour decreases vascular reactivity in conductance and resistance arteries in rats

AIMS

Aluminum (Al) is an important environmental contaminant; however, there are not enough evidences of Al-induced cardiovascular dysfunction. We investigated the effects of acute exposure to aluminum chloride (AlCl₃) on blood pressure, vascular reactivity and oxidative stress.

METHODS AND RESULTS

Male Wistar rats were divided into two groups: Untreated: vehicle (ultrapure water, ip) and AlCl₃: single dose of AlCl₃ (100mg/kg,ip). Concentration-response curves to phenylephrine in the absence and presence of endothelium, the nitric oxide synthase inhibitor l-NAME, the potassium channel blocker tetraethylammonium, and the NADPH oxidase inhibitor apocynin were performed in segments from aortic and mesenteric resistance arteries. NO released was assessed in aorta and reactive oxygen species (ROS), malondialdehyde, non-protein thiol levels, antioxidant capacity and enzymatic antioxidant activities were investigated in plasma, aorta and/or mesenteric arteries. After one hour of AlCl₃ exposure serum Al levels attained 147.7±25.0μg/L. Al treatment: 1) did not affect blood pressure, heart rate and vasodilator responses induced by acetylcholine or sodium nitroprusside; 2) decreased phenylephrine-induced vasoconstrictor responses; 3) increased endothelial modulation of contractile responses, NO release and vascular ROS production from NADPH oxidase; 4) increased plasmatic, aortic and mesenteric malondialdehyde and ROS production, and 5) decreased antioxidant capacity and affected the antioxidant biomarkers non-protein thiol levels, glutathione peroxidase, glutathione-S-transferase, superoxide dismutase and catalase enzymatic activities.

CONCLUSION

AlCl₃-acute exposure reduces vascular reactivity. This effect is associated with increased NO production, probably acting on K⁺ channels, which seems to occur as a compensatory mechanism against Al-induced oxidative stress. Our results suggest that Al exerts toxic effects to the vascular system.

Validation and comparable analysis of aluminum in the popular Chinese fried bread youtiao by wavelength dispersive XRF

Aluminum (Al) is an element in alum commonly used as a raising agent for Chinese flour products, especially for a typical fried food youtiao. In the present study, the feasibility of wavelength dispersive X-ray fluorescence spectrometry (WDXRF) for analysis of aluminum levels in youtiao was examined. Youtiao samples spiked with known amounts of aluminum were used for calibration. Linearity, accuracy, precision, and detection and quantification limits were tested, based on three calibration curves. For further validation, test youtiao samples were analyzed by both WDXRF and inductively coupled plasma optical emission spectrometry (ICP-OES). Comparison of the two methods showed that measurement performance was not significantly different. Taken together, these results indicate that WDXRF can form the basis of a rapid and simple methodology for measuring the aluminum content of youtiao, and that it is a good candidate for replacing ICP-OES for analyzing Al-containing flour products.

Effects of Aluminum Exposure on the Bone Stimulatory Growth Factors in Rats

Aluminum (Al) is considered to be a potentially toxic metal and inhibits bone formation. Transforming growth factor β1 (TGF-β1) and bone morphogenetic protein 2 (BMP-2) play an important role in regulating the bone formation. Therefore, this study aimed to investigate the effects of Al on the TGF-β1 and BMP-2 in rats. In this study, Wistar rats were randomly divided into Al-treated group and control group. The Al-treated rats were provided with drinking water containing 100 mg/L AlCl3, and the control rats were given distilled water for 30, 60, and 90 days, respectively. Ten rats were sacrificed in each group every 30 days. The Al-treated rats showed lower body weight and higher serum and bone levels of Al compared with the control rats. The expression levels of TGF-β1 and BMP-2 were also significantly decreased in the Al-treated rats. Serum levels of bone gamma-carboxyglutamic acid protein (BGP), carboxy-terminal propeptide of type I procollagen (PICP), and bone alkaline phosphatase (B-ALP) were markedly lower in the Al-treated groups than in the control group. These results indicate that Al inhibits the expression of TGF-β1 and BMP-2 in bone, which inhibits the activity of osteoblasts and reduces the synthesis of BGP, B-ALP, and type I collagen, thereby inhibiting bone formation.

Aluminum trichloride inhibits osteoblastic differentiation through inactivation of Wnt/β-catenin signaling pathway in rat osteoblasts

Exposure to aluminum (Al) suppresses bone formation. Osteoblastic differentiation plays a key role in the process of bone formation. However, the effect of Al on osteoblastic differentiation is still controversial, and the mechanism remains unclear. To investigate the effect of Al on osteoblastic differentiation and whether Wnt signaling pathway was involved in it, the primary rat osteoblasts were exposed to 1/40 IC50, 1/20 IC50 and 1/10 IC50 of aluminum trichloride (AlCl3) for 24h, respectively. The activity analysis of alkaline phosphate, qRT-PCR analysis of type I collagen, alkaline phosphate, Wnt3a and Dkk-1, Western blot analysis of p-GSK3β, GSK3β and β-catenin protein and Immunofluorescence staining for β-catenin suggested that AlCl3 inhibited osteoblastic differentiation and Wnt/β-catenin pathway. Moreover, we found exogenous Wnt3a application reversed the inhibitory effect of AlCl3 on osteoblastic differentiation, accompanied by activating the Wnt/β-catenin pathway. Taken together, these findings suggest that AlCl3 inhibites osteoblastic differentiation through inactivation of Wnt/β-catenin pathway in osteoblasts.

Aluminum Chloride Induces Osteoblasts Apoptosis via Disrupting Calcium Homeostasis and Activating Ca(2+)/CaMKII Signal Pathway

Aluminum promotes osteoblast (OB) apoptosis. Apoptosis is induced by the disordered calcium homeostasis. Therefore, to investigate the relationship between Al-induced OB apoptosis and calcium homeostasis, calvarium OBs from neonatal rats (3-4 days) were cultured and exposed to 0.048-mg/mL Al(3+) or 0.048-mg/mL Al(3+) combined with 5 μM BAPTA-AM (OBs were pretreated with 5 μM BAPTA-AM for 1 h, then added 0.048 mg/mL Al(3+)), respectively. Then OB apoptosis rate, intracellular calcium ions concentration ([Ca(2+)]i), mRNA expression level of calmodulin (CaM), and protein expression levels of CaM and p-CaMKII in OBs were examined. The result showed that AlCl3 increased OB apoptosis rate, and [Ca(2+)]i and p-CaMKII expression levels and decreased CaM expression levels, whereas BAPTA-AM relieved the effects. These results proved that AlCl3 induced OB apoptosis by disrupting the intracellular Ca(2+) homeostasis and activating the Ca(2+)/CaMKII signal pathway. Our findings can provide new insights for revealing the apoptosis mechanism of OBs exposed to AlCl3.

Systematic review of potential health risks posed by pharmaceutical, occupational and consumer exposures to metallic and nanoscale aluminum, aluminum oxides, aluminum hydroxide and its soluble salts

Abstract Aluminum (Al) is a ubiquitous substance encountered both naturally (as the third most abundant element) and intentionally (used in water, foods, pharmaceuticals, and vaccines); it is also present in ambient and occupational airborne particulates. Existing data underscore the importance of Al physical and chemical forms in relation to its uptake, accumulation, and systemic bioavailability. The present review represents a systematic examination of the peer-reviewed literature on the adverse health effects of Al materials published since a previous critical evaluation compiled by Krewski et al. (2007) . Challenges encountered in carrying out the present review reflected the experimental use of different physical and chemical Al forms, different routes of administration, and different target organs in relation to the magnitude, frequency, and duration of exposure. Wide variations in diet can result in Al intakes that are often higher than the World Health Organization provisional tolerable weekly intake (PTWI), which is based on studies with Al citrate. Comparing daily dietary Al exposures on the basis of "total Al"assumes that gastrointestinal bioavailability for all dietary Al forms is equivalent to that for Al citrate, an approach that requires validation. Current occupational exposure limits (OELs) for identical Al substances vary as much as 15-fold. The toxicity of different Al forms depends in large measure on their physical behavior and relative solubility in water. The toxicity of soluble Al forms depends upon the delivered dose of Al(+3) to target tissues. Trivalent Al reacts with water to produce bidentate superoxide coordination spheres [Al(O2)(H2O4)(+2) and Al(H2O)6 (+3)] that after complexation with O2(•-), generate Al superoxides [Al(O2(•))](H2O5)](+2). Semireduced AlO2(•) radicals deplete mitochondrial Fe and promote generation of H2O2, O2 (•-) and OH(•). Thus, it is the Al(+3)-induced formation of oxygen radicals that accounts for the oxidative damage that leads to intrinsic apoptosis. In contrast, the toxicity of the insoluble Al oxides depends primarily on their behavior as particulates. Aluminum has been held responsible for human morbidity and mortality, but there is no consistent and convincing evidence to associate the Al found in food and drinking water at the doses and chemical forms presently consumed by people living in North America and Western Europe with increased risk for Alzheimer's disease (AD). Neither is there clear evidence to show use of Al-containing underarm antiperspirants or cosmetics increases the risk of AD or breast cancer. Metallic Al, its oxides, and common Al salts have not been shown to be either genotoxic or carcinogenic. Aluminum exposures during neonatal and pediatric parenteral nutrition (PN) can impair bone mineralization and delay neurological development. Adverse effects to vaccines with Al adjuvants have occurred; however, recent controlled trials found that the immunologic response to certain vaccines with Al adjuvants was no greater, and in some cases less than, that after identical vaccination without Al adjuvants. The scientific literature on the adverse health effects of Al is extensive. Health risk assessments for Al must take into account individual co-factors (e.g., age, renal function, diet, gastric pH). Conclusions from the current review point to the need for refinement of the PTWI, reduction of Al contamination in PN solutions, justification for routine addition of Al to vaccines, and harmonization of OELs for Al substances.

Osteoporosis in neurodegeneration

Osteoporosis affects bone microarchitecture and reduces bone mass. There are more than 200 million people with osteoporosis worldwide, and the prevalence is slowly increasing. The highest prevalences are found in Scandinavia and USA, also slowly increasing. A parallel increase in neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, Amyotrophic lateral sclerosis, and multiple sclerosis has been noted since the middle of this century. Osteoporosis is more common in patients with each of these neurodegenerative conditions than in the general population. Several metals with neurotoxic properties accumulate in bone and can substitute for calcium in hydroxyapatite, the main mineral component of bone. Especially cadmium, but also lead, aluminum and arsenic affect bone mineral density negatively. Metals with neurotoxic properties have also been found in brain and cerebrospinal fluid from patients with Alzheimer's disease, Parkinson's disease, Amyotrophic lateral sclerosis, and multiple sclerosis, and markers for neurodegeneration such as amyloid beta peptide and amyloid precursor protein have been detected in bone tissue from patients with osteoporosis. A common mechanism contributing to the pathogenesis of both neurodegeneration and osteoporosis can be suspected. The hypothesis that neurodegenerative disorders are associated with osteoporosis is presented and discussed.

Aluminum exposure and toxicity in neonates: a practical guide to halt aluminum overload in the prenatal and perinatal periods

BACKGROUND

During the last years, human newborns have been overexposed to biologically reactive aluminum, with possible relevant consequences on their future health and on their susceptibility to a variety of diseases. Children, newborns and particularly preterm neonates are at an increased risk of aluminum toxicity because of their relative immaturity.

DATA SOURCES

Based on recent original publications and classical data of the literatures, we reviewed the aluminum content in mother's food during the intrauterine life as well as in breast milk and infant formula during lactation. We also determined the possible role of aluminum in parenteral nutrition solutions, in adjuvants of vaccines and in pharmaceutical products. A special focus is placed on the relationship between aluminum overexposure and the insurgence of bone diseases.

RESULTS

Practical points of management and prevention are suggested. Aluminum sources that infants may receive during the first 6 months of life are presented. In the context of prevention of possible adverse effects of aluminum overload in fetal tissues during development, simple suggestions to pregnant women are described. Finally, practical points of management and prevention are suggested.

CONCLUSIONS

Pediatricians and neonatologists must be more concerned about aluminum content in all products our newborns are exposed to, starting from monitoring aluminum concentrations in milk- and soy-based formulas in which, on the basis of recent studies, there is still too much aluminum.

Suppressive effects of subchronic aluminum overload on the splenic immune function may be related to oxidative stress in mice

Aluminum (Al) is widely used in daily life and was recently recognized as a possible source of human intoxication because of its ability to accumulate in organs. The objective of the present study was to investigate the effects of subchronic Al overload on splenic immune function in mice. Furthermore, we have preliminarily explored its mechanism. The Al overload model was established via intragastric administration of Al once a day for 60 days. The body weight, spleen weight, and splenic coefficient were determined. The concentration of Al in the spleen was detected by inductively coupled plasma-mass spectrometry. The cytokine mRNA expression of spleen tissues was detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Biochemical methods were used to detect superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and malondialdehyde (MDA) contents in spleen tissue. Body weight, spleen weight, and cytokine mRNA expression of spleen tissues were significantly reduced by Al overload. SOD and GSH-Px activities were also decreased, while the MDA content was increased in subchronic Al overload mice. The results indicate that subchronic exposure to aluminum trichloride (AlCl3) would result in Al accumulation, which suppressed spleen immune function through a mechanism related to oxidative stress.

Aluminum induces osteoblast apoptosis through the oxidative stress-mediated JNK signaling pathway

Aluminum (Al) is considered to be a potentially toxic metal. Al exposure inhibits bone formation. Few studies have investigated the mechanism of inhibitory effects of Al on bone formation. Thus, in this study, osteoblasts were cultured and exposed to different concentrations of Al to investigate the mechanism behind the inhibitory effects of Al on bone formation. Al-treated osteoblasts showed signs of oxidative stress and a high apoptosis rate. The levels of osteoblasts activity markers (bone gamma-carboxyglutamic acid protein and bone alkaline phosphatase) were significantly lower in the Al-treated groups than in the control group. The c-Jun N-terminal kinase (JNK), a major signaling pathway in regulating cell apoptosis, was activated. The phosphorylation state of JNK was significantly increased. The mRNA and protein expression of c-Jun were both significantly upregulated. The pro-apoptotic genes (caspase 3, caspase 9, bax, and factor-related apoptosis ligand) were significantly increased. However, Bcl-2, an anti-apoptotic gene, was significantly decreased. In conclusion, the results of this study indicate that Al induces osteoblast apoptosis by activating the oxidative stress-mediated JNK pathway, which causes cell injuries and reduces the number and function of osteoblasts, thereby inhibiting bone formation.

Effects of aluminum on immune functions of cultured splenic T and B lymphocytes in rats

The effects of Aluminum (Al) exposure on immune functions of cultured splenic T and B lymphocytes of rats were studied. The lymphocytes were isolated from spleen of healthy male Wistar rats weighing 110-120 g. The cultured cells in RPMI-1640 medium were exposed to 0 (control group), 0.035 (low-dose group), 0.07 (medial-dose group), and 0.14 (high-dose group) mg/mL Al(3+) as aluminum trichloride (AlCl(3)) in an incubator under 5% CO(2) at 37°C for 24 h. The T and B lymphocyte proliferation was measured with a tetrazolium dye colorimetric assay. The levels of interleukin (IL)-2, IL-6, and tumor necrosis factor (TNF)-α were determined by iodine [(125)I] IL-2, IL-6, and TNF-α radioimmunoassay kits, respectively. The proportions of CD3(+), CD4(+), and CD8(+) T lymphocytes were measured with a flow cytometer. The results showed that the T and B lymphocyte proliferation, the levels of IL-2, IL-6, TNF-α, the proportions of CD3(+) and CD4(+) T lymphocytes, and the ratio of CD4(+)/CD8(+) T lymphocytes were lowered by Al treatments, while the proportion of CD8(+) T lymphocytes was increased. These findings indicate that Al exposure can inhibit the immune functions of splenic T and B lymphocytes of rats in vitro.

Aluminium exposure disrupts elemental homeostasis in Caenorhabditis elegans

Aluminium (Al) is highly abundant in the environment and can elicit a variety of toxic responses in biological systems. Here we characterize the effects of Al on Caenorhabditis elegans by identifying phenotypic abnormalities and disruption in whole-body metal homeostasis (metallostasis) following Al exposure in food. Widespread changes to the elemental content of adult nematodes were observed when chronically exposed to Al from the first larval stage (L1). Specifically, we saw increased barium, chromium, copper and iron content, and a reduction in calcium levels. Lifespan was decreased in worms exposed to low levels of Al, but unexpectedly increased when the Al concentration reached higher levels (4.8 mM). This bi-phasic phenotype was only observed when Al exposure occurred during development, as lifespan was unaffected by Al exposure during adulthood. Lower levels of Al slowed C. elegans developmental progression, and reduced hermaphrodite self-fertility and adult body size. Significant developmental delay was observed even when Al exposure was restricted to embryogenesis. Similar changes in Al have been noted in association with Al toxicity in humans and other mammals, suggesting that C. elegans may be of use as a model for understanding the mechanisms of Al toxicity in mammalian systems.

Effects of subchronic aluminum exposure on the reproductive function in female rats

The aim of this study was to investigate the effects of aluminum (Al) exposure on the reproductive function in female rats. Forty female Wistar (5 weeks old) rats, weighing 110-120 g, were divided randomly into four groups. They were orally administrated with 0, 64.18, 128.36, and 256.72 mg aluminum chloride (AlCl(3)) per kilogram body weight in drinking water for 120 days. Levels of Al, estrogen (E(2)), progestogen (P), testosterone (T), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) in serum were measured at the end of experiment. The results showed that levels of E(2), P, FSH, and LH were significantly lower and Al concentration was significantly higher in all three Al-treated groups than those in the control group (GC). The level of T was significantly higher in the low- and medium-dose groups (GL and GM) (P < 0.05) but not in high-dose group (GH) compared with GC. The results suggest that the reproductive function of female rats is inhibited under long-term Al exposure in an Al dose-dependent manner.

Suppressive effects of aluminum trichloride on the T lymphocyte immune function of rats

Aluminum (Al) has increasingly been used in the daily life, and could cause the change of human health because it can accumulate in the organs. A rat model was thus used to examine potential effect of Al on the immune function. Forty male Wistar rats (5 weeks old) weighed 110-120 g were randomly allocated into four groups and were orally exposed to 0, 64.18, 128.36, and 256.72 mg/kg body weight aluminum trichloride (AlCl3) in drinking water for 120 days. The levels of CD3+, CD4+, CD8+ T lymphocyte, acid non-specific activity esterase (ANAE+) in blood, and interleukin-2 (IL-2) and tumor necrosis factor-α (TNF-α) in serum were determined at the end of experiment. The results showed that the proportions of CD3+, CD4+ T lymphocyte, the ratio of CD4+/CD8+, and the levels of ANAE+, IL-2, and TNF-α were significantly reduced in AlCl3-treated rats, while the proportion of CD8+ T lymphocyte was increased in an AlCl3-dose dependent manner. Our findings indicate that a long term exposure of AlCl3 could suppress the T lymphocyte immune function of rats.