Aluminum as a risk factor for Alzheimer's disease

Evaluation of possible neuroprotective effects of virgin coconut oil on aluminum-induced neurotoxicity in an in vitro Alzheimer's disease model

Alzheimer's disease (AD) is a progressive neurological disorder that affects various cognitive functions, behavior, and personality. AD is thought to be caused by a combination of genetic and environmental factors, including exposure to aluminum (Al). Virgin coconut oil (VCO) may have potential as a natural neuroprotectant against AD. Aim of this study was to determine neuroprotective effects of VCO on Al-induced neurotoxicity in an in vitro AD model. SH-SY5Y cells were initially cultured in normal growth medium and then differentiated by reducing fetal bovine serum content and adding retinoic acid (RA). Later, brain-derived neurotrophic factor (BDNF) was added along with RA. The differentiation process was completed on the seventh day. Study groups (n = 3) were designed as control group, VCO group, Al group, Al-VCO group, Alzheimer model (AD) group, AD + Al-exposed group (AD+Al), AD + VCO applied group (AD + VCO) and AD + Al-exposed + VCO applied group (AD + Al + VCO). Specific markers of AD (hyperphosphorylated Tau protein, amyloid beta 1-40 peptide, and amyloid precursor protein) were measured in all groups. In addition, oxidative stress parameters (total antioxidant capacity, lipid peroxidase, protein carbonyl, and reactive oxygen species) and neurotransmitter-related parameters (dopamine, dopamine transporter acetylcholine, and synuclein alpha levels, acetylcholinesterase activity) were measured comparatively in the study groups. VCO reduced amyloid beta and hyperphosphorylated Tau protein levels in the study groups. In addition, oxidative stress levels decreased, and neurotransmitter parameters improved with VCO. Our study shows that VCO may have potential therapeutic effects in Alzheimer's disease and further experiments are needed to determine its efficacy.

Post-exposure self-recovery reverses oxidative stress, ameliorates pathology and neurotransmitters imbalance and rescues spatial memory after time-dependent aluminum exposure in rat brain

Aluminum is a potent neurotoxin, responsible for memory impairment and cognitive dysfunction. The neurotoxic effect of aluminum on cognitive impairment is well documented, however, exposure to aluminum in a time-dependent manner and post-exposure self-recovery still needs to be elaborated. This research aimed to (1) study the time-dependent effect of aluminum exposure by administering a total dose of 5850 mg/kg of Al over two different time periods: 30 and 45 days (130 and 195 mg/kg of AlCl3 respectively), and (2) study 20 days post-exposure self-recovery effect in both aluminum-exposed groups by giving distilled water. Cognitive abilities were investigated through Morris water maze test and hole board test and compared in both exposure and recovery groups. Oxidative stress markers and neurotransmitter levels were measured for both exposure and recovery groups. To understand the mechanism of aluminum exposure and recovery, immunohistochemical analysis of synaptophysin (Syp) and glial fibrillary acidic protein (GFAP) was performed. Results showed cognitive dysfunction, oxidative stress-induced damage, reduced neurotransmitter levels, decreased immunoreactivity of Syp, and increased GFAP. However, these parameters showed a larger improvement in the recovery group where rats were given aluminum for 30 days period in comparison to recovery group followed by 45 days of aluminum exposure. These results suggest that restoration of cognitive ability is affected by the duration of aluminum exposure. The study findings provide us with insight into the adverse effects of aluminum exposure and can be utilized to guide future preventive and therapeutic strategies against aluminum neurotoxicity.

Antioxidant dihydrolipolic acid protects against in vitro aluminum-induced toxicity

Dihydrolipoic acid (DHLA) is a natural antioxidant known for its ability to counteract metal toxicity and oxidative stress. It has shown the potential to safeguard cells from harmful environmental substances. It may hold therapeutic benefits in treating neurodegenerative disorders by defending against oxidative damage and chronic inflammation. Thus, this study aimed to explore the potential neuroprotective effects of DHLA against aluminum (Al)-induced toxicity using an Alzheimer's disease (AD) model in vitro. The study focused on two important pathways: GSK-3β and the Wnt signaling pathways. The SH-SY5Y cell line was differentiated to establish AD, and the study group were as follows: control, Al, DHLA, Al-DHLA, AD, AD-Al, AD-DHLA, and AD-Al-DHLA. The impact of DHLA on parameters related to oxidative stress was assessed. The activity of the GSK-3β pathway was measured by evaluating the levels of PPP1CA, PP2A, GSK-3β, and Akt. The Wnt signaling pathway was assessed by measuring Wnt/β-catenin in the different study groups. Exposure to DHLA significantly reduced oxidative stress by effectively decreasing the levels of reactive oxygen species, thereby protecting against protein oxidation and limiting the production of malonaldehyde. Moreover, the DHLA-treated groups exhibited a remarkable increase in the total antioxidant capacity. Furthermore, the study observed an upregulation of the Wnt signaling pathway and a downregulation of the GSK-3β pathway in the groups treated with DHLA. In summary, the neuroprotective effects of DHLA, primarily achieved by reducing oxidative stress and modulating critical imbalanced pathways associated with AD, indicate its potential as a promising addition to the treatment regimens of AD patients.

A New α + β Ti-15Nb Alloy with Low Elastic Modulus: Characterization and In Vitro Evaluation on Osteogenic Phenotype

This study aimed to produce Ti-15Nb alloy with a low elastic modulus, verify its biocompatibility, and determine whether the alloy indirectly influences cellular viability and morphology, as well as the development of the osteogenic phenotype in cells cultured for 2, 3, and 7 days derived from rat calvarias. Two heat treatments were performed to modify the mechanical properties of the alloy where the Ti-15Nb alloy was heated to 1000 °C followed by slow (-5 °C/min) (SC) and rapid cooling (RC). The results of structural and microstructural characterization (XRD and optical images) showed that the Ti-15Nb alloy was of the α + β type, with slow cooling promoting the formation of the α phase and rapid cooling the formation of the β phase, altering the values for the hardness and elastic modulus. Generally, a more significant amount of the α phase in the Ti-15Nb alloy increased the elastic modulus value but decreased the microhardness value. After the RC treatment, the results demonstrated that the Ti-15Nb alloy did not present cytotoxic effects on the osteogenic cells. In addition, we did not find variations in the cell quantity in the microscopy results that could suggest cell adhesion or proliferation modification.

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.

Antioxidant Thymoquinone and Its Potential in the Treatment of Neurological Diseases

Oxidative stress is one of the main pathogenic factors of neuron damage in neurodegenerative processes; this makes it an important therapeutic target to which the action of neuroprotectors should be directed. One of these drugs is thymoquinone. According to modern data, this substance has a wide range of pharmacological activity, including neuroprotective, which was demonstrated in experimental modeling of various neurodegenerative diseases and pathological conditions of the brain. The neuroprotective effect of thymoquinone is largely due to its antioxidant ability. Currently available data show that thymoquinone is an effective means to reduce the negative consequences of acute and chronic forms of cerebral pathology, leading to the normalization of the content of antioxidant enzymes and preventing an increase in the level of lipid peroxidation products. Antioxidant properties make this substance a promising basis for the development of prototypes of therapeutic agents aimed at the treatment of a number of degenerative diseases of the central nervous system.

Multi-stage classification of Alzheimer's disease from 18F-FDG-PET images using deep learning techniques

The study aims to implement a convolutional neural network framework that uses the 18F-FDG PET modality of brain imaging to detect multiple stages of dementia, including Early Mild Cognitive Impairment (EMCI) and Late Mild Cognitive Impairment (LMCI), and Alzheimer's disease (AD) from Cognitively Normal (CN), and assess the results. 18F-FDG PET imaging modality for brain were procured from Alzheimer's disease neuroimaging initiative's (ADNI) repository. The ResNet50V2 model layers were utilised for feature extraction, with the final convolutional layers fine-tuned for this dataset's multi-classification objectives. Multiple metrics and feature maps were utilized to scrutinize and evaluate the model's statistical and qualitative inference. The multi-classification model achieved an overarching accuracy of 98.44% and Area under the receiver operating characteristic curve of 95% on the testing set. Feature maps aided in deducing finer aspects of the model's overall operation. This framework helped classifying from the 18F-FDG PET brain images, the subtypes of Mild Cognitive Impairment (MCI) which include EMCI, LMCI, from AD, CN groups and achieved an all-inclusive sensitivity of 94% and specificity of 95% respectively.

Mechanical Properties and Corrosion Behavior of Silica Nanoparticle Reinforced Magnesium Nanocomposite for Bio-Implant Application

In this study, magnesium (Mg)-based nanocomposites reinforced with silica (SiO₂) nanoparticles were developed using the powder metallurgy process, and their mechanical and corrosion behavior were assessed. Mg-alloy AZ31 served as the matrix material, and two different weight percentages of SiO₂ nanoparticles were used as filler. According to the microstructural analysis, the composite generated a Mg₂Si phase as a result of SiO₂ dissociating during the sintering process. The microhardness of the Mg-alloy dramatically enhanced with the addition of 3% nanosilica, although the elastic modulus remained constant. Additionally, the outcomes demonstrated that the Mg₂Si phase's development in the composite constrained the mechanism of deterioration and postponed the pace of degradation, which aided in enhancing the qualities of corrosion resistance. This nanocomposite might, thus, be thought of as a potential replacement for the traditional bio-implant materials.

Avaliação da qualidade da vida aquática do Ribeirão Floriano no Munícipio de Maringá-PR

Com o desenvolvimento urbano e social das cidades, os moradores que residem nas proximidades de riachos e vales passam a sofrer as consequências do lançamento contínuo de esgoto. O objetivo deste trabalho foi avaliar a qualidade da água do Ribeirão Floriano, localizado no município de Maringá-PR. Para tanto, quatro pontos, denotados por P1, P2, P3 e P4, foram escolhidos. Para a análise de DQO todas as coletas realizadas apresentaram a mesma concentração, sendo inferior a 15 mg L-1, porém, em relação ao DBO5 no período do verão os pontos P2, P3 e P4 mostraram-se dentro do limite esperado, 2.0 mg L-1, para águas superficiais de Classe II, de acordo com a legislação. Em relação a análise da contagem de Escherichia coli os maiores valores encontrados, para a contaminação biológica do ribeirão, foram nos pontos P2 e P3, equivalentes a 2000 UFC/mL e 424 UFC/mL, respectivamente, no período da primavera. Estes dois pontos estão localizados próximos a lavanderias industriais que podem estar associados a lançamento de efluentes advindos destas empresas. Nas análises, foi determinado concentrações elevadas de cobre (Cu), alumínio (Al) e níquel (Ni), evidenciando uma distribuição equitativa da ação antrópica em todo o curso do ribeirão. Estes resultados sugerem a necessidade da implantação de programas de monitoramento ambiental em águas superficiais nos rios do município.

miR-200a-3p Regulates PRKACB and Participates in Aluminium-Induced Tau Phosphorylation in PC12 Cells

Aluminium (Al) is an environmental neurotoxin that humans are widely exposed to, but the molecular mechanism of its toxic effects is not fully understood. Many studies have shown that exposure to Al can cause abnormal phosphorylation of the tau protein that is believed as one of pathological features of Alzheimer's disease. Increasing evidence indicates that microRNAs (miRNAs) may be involved in the pathological processes of neurodegenerative diseases and are potential regulatory factors for related target genes. Phosphorylation at Ser-133 of cAMP response element-binding protein (CREB) is one of the major pathways of CREB activation, and phosphorylation at this site is controlled by protein kinase A (PKA). The catalytic subunit of PKA, cAMP-dependent protein kinase catalytic subunit beta (PRKACB), phosphorylates CREB. The target gene prediction software TargetScan showed that PRKACB was one of the target mRNAs of miR-200a-3p. The purpose of this study was to investigate whether miR-200a-3p regulates the PKA/CREB pathway by targeting PRKACB and leads to abnormal phosphorylation of the tau protein in nerve cells. The results showed that Al exposure increased the expression level of miR-200a-3p, and miR-200a-3p increased the expression of targeted downregulated PRKACB, and then decreased the PKA/CREB signalling pathway activity, leading to abnormal hyperphosphorylation of tau.

Corrosion of titanium under simulated inflammation conditions: clinical context and in vitro investigations

Titanium and alloys thereof are widely utilized for biomedical applications in the fields of orthopedics and dentistry. The corrosion resistance and perceived biocompatibility of such materials are essentially related to the presence of a thin passive oxide layer on the surface. However, during inflammation phases, the immune system and its leukocytic cells generate highly aggressive molecules, such as hydrogen peroxide and radicals, that can significantly alter the passive film resulting in the degradation of the titanium implants. In combination with mechanical factors, this can lead to the release of metal ions, nanoparticles or microscaled debris in the surrounding tissues (which may sustain chronic inflammation), bring about relevant health issues and contribute to implant loss or failure. After briefly presenting the context of inflammation, this review article analyses the state-of-the-art knowledge of the in vitro corrosion of titanium, titanium alloys and coated titanium by reactive oxygen species and by living cells with an emphasis on electrochemical and microstructural aspects. STATEMENT OF SIGNIFICANCE: Inflammation involves the production of reactive oxygen species that are known to alter the passive layer protecting titanium implants against the aggressive environment of the human body. Inflammatory processes therefore contribute to the deterioration of biomedical devices. Although review articles on biomaterials for implant applications are regularly published in the literature, none has ever focused specifically on the topic of inflammation. After briefly recalling the clinical context, this review analyses the in vitro studies on titanium corrosion under simulated inflammation conditions from the pioneer works of the 80s and the 90s till the most recent investigations. It reports about the status of this research area for a multidisciplinary readership covering the fields of materials science, corrosion and implantology.

miR-29a/b1 Regulates BACE1 in Aluminum-Induced Aβ Deposition in Vitro

Aluminum is an environmental neurotoxin that comes extensively in contact with human beings. Animal and human studies demonstrated that aluminum exposure increases the deposition of beta amyloid proteins in the brain as it was observed in Alzheimer's disease. The purpose of this study was to investigate whether miR-29a/b1 affected the expression of beta-secrete enzymes (BACE1) in the process of amyloid β-protein (Aβ) deposition caused by aluminum exposure. The study was performed using two different cell lines. Our results showed that after rat primary cortical neurons were exposed to aluminum, BACE1 gene and protein levels increased to different degrees, and the expression level of Aβ1-42 increased. In aluminum-exposed groups, the expression of miR-29a and miR-29b1 decreased, while the expression of amyloid protein Aβ1-42 and BACE1 increased. In miRs transfection groups, the expression of amyloid protein Aβ1-42 and BACE1 decreased. Aluminum may affect the expression of BACE1 by lowering miR-29a and miR-29b1. AEK293 cells were utilized in this research since they present elevated levels of miR-29a and miR-29b1. After HEK293 cells were exposed to aluminum alone, BACE1 mRNA and BACE1 protein expression levels increased with the increase of aluminum exposure dose (p < 0.05), and the level of Aβ1-42 also increased (p < 0.05). Compared with the group exposed to aluminum alone at the same doses, the expression levels of BACE1 mRNA and BACE1 protein in the miRs transfected plus aluminum-exposed groups significantly decreased (p < 0.05), and the level of Aβ1-42 also decreased (p < 0.05). This result is consistent with the investigation in rat primary neurons. The results of two types of cells showed that aluminum may cause abnormal down-regulation of the expressions of miR-29a and miR-29b1, thus negatively regulating the increase of BACE1 expression and finally leading to the increase of Aβ.

Degradation behaviors and in-vivo biocompatibility of a rare earth- and aluminum-free magnesium-based stent

Biodegradable stents can provide scaffolding and anti-restenosis benefits in the short term and then gradually disappear over time to free the vessel, among which the Mg-based biodegradable metal stents have been prosperously developed. In the present study, a Mg-8.5Li (wt.%) alloy (RE- and Al-free) with high ductility (> 40%) was processed into mini-tubes, and further fabricated into finished stent through laser cutting and electropolishing. In-vitro degradation test was performed to evaluate the durability of this stent before and after balloon dilation. The influence of plastic deformation and residual stress (derived from the dilation process) on the degradation was checked with the assistance of finite element analysis. In addition, in-vivo degradation behaviors and biocompatibility of the stent were evaluated by performing implantation in iliac artery of minipigs. The balloon dilation process did not lead to deteriorated degradation, and this stent exhibited a decent degradation rate (0.15 mm/y) in vitro, but divergent result (> 0.6 mm/y) was found in vivo. The stent was almost completely degraded in 3 months, revealing an insufficient scaffolding time. Meanwhile, it did not induce possible thrombus, and it was tolerable by surrounding tissues in pigs. Besides, endothelial coverage in 1 month was achieved even under the severe degradation condition. In the end, the feasibility of this stent for treatment of benign vascular stenosis was generally discussed, and perspectives on future improvement of Mg-Li-based stents were proposed.

Assessment of biomechanical stability and formulation of a statistical model on magnesium based composite in two different milieus

Magnesium (Mg) based temporary implants are an appealing new solution to counter the problems associated with the currently available temporary orthopaedic implants, used in fracture fixing. To make the extensive use of Mg-based implants in-vivo, mechanical integrity in the physiological environment is a prerequisite. This study presents an insight into the biomechanical stability of Mg-3Zn/HA (0, 5, and 15 wt % of HA) composites in two different milieus (simulated body fluid (SBF) and serum contained SBF (m-SBF)). After 14 days of static immersion in SBF, ~65% mechanical strength was compromised in the case of 15 wt % HA reinforcement. However, the degradation rate was slowed down by ~35% with the addition of 15 wt % HA in Mg-3Zn. Mg-3Zn/HA composite, when soaked in both fluids, was found to induce apatite layer formation on the surfaces for several days. However, in the case of m-SBF immersion, 15 wt % HA facilitated less precipitation of apatite growth when compared to SBF immersion. Nevertheless, m-SBF immersed 15 wt % HA composite facilitated better corrosion resistance and excellent mechanical stability after 14 days of immersion. The approach thereby assists in establishing an effective mechanism between the degradation and mechanical stability in in-vitro immersion. In addition, this study has also developed a semi-empirical model for prediction of the compressive strength of these composites as a function of the number of days of immersion and the content of hydroxyapatite (HA). This semi-empirical model will help in predicting the biomechanical stability for long-term in-vitro exposures, which might be of use in evaluating the effect of the in-vivo environment.

Role of mGluR 1 in synaptic plasticity impairment induced by maltol aluminium in rats

The main symptoms of Alzheimer's disease (AD) is the loss of learning and memory ability, of which biological basis is synaptic plasticity. Aluminium has been found to cause changes in synaptic plasticity, but its molecular mechanism was unclear. In this study, Sprague-Dawley rats were injected with aluminium maltol (Al(mal)₃) through the lateral ventricle to establish an AD-like model. Y-maze, electrophysiological measurements, Golgi staining, scanning electron microscopy, quantitative real-time polymerase chain reaction, and western blot techniques were used to investigate regulation of the metabolic glutamate receptor 1 (mGluR1) in synaptic plasticity impairment induced by Al(mal)₃. The results showed that Al(mal)₃ inhibited the induction and maintenance of long-term potentiation in the hippocampal CA1 region. During this process, the expression of mGluR1 was up-regulated and it inhibited the expression and phosphorylation of the N-methyl-D-aspartic acid receptors (NMDARs). This mainly affected NMDAR1 and NMDAR2B but did not affect protein kinase C expression.

Biomonitoring of Aluminum in Urine of Young Lebanese Children Living in Beirut

Background

Aluminum (Al) is a ubiquitous, toxic metal to which infants and young toddlers are highly vulnerable. High Al exposure has been associated with various human pathologies. The aim of the present biomonitoring (BM) study was to provide a background for the levels of urinary aluminum (Al) in children ages 7 months to 4 years living in Beirut.

Material/Methods

We collected and analyzed 120 urine specimens using the Shimadzu Atomic Absorption Spectrophotometer-6300 system equipped with an electrothermal atomization, and using a GFA-EX7i graphite furnace.

Results

The mean and standard deviation of Al level in urine revealed 8.978±12.275 μg/L, which is within the lower range of each of populations in Germany, Taiwan, and Poland. Vitamin intake, powder rice, and the use of Al utensils proved to be major determinants for Al level in urine (significant at 95%).

Conclusions

The Shimadzu Atomic Absorption Spectrophotometer-6300 system proved again to be an optimal and reliable instrument that can be used for the determination of Al level in urine, especially if using a GFA-EX7i pyrolytic graphite furnace. High levels of Al were found in the urine of Lebanese children. However, the frequent consumption of canned food did not prove to be a significant factor in determining the Al level in urine.

Estoque e descarte de medicamentos no domicílio: uma revisão sistemática

Resumo Este estudo teve como objetivo analisar a evidência científica nacional e internacional existente sobre o motivo do estoque e a forma de descarte dos medicamentos no domicílio. Realizou-se uma revisão sistemática da literatura de 2001 a 2016 nas bases de dados PubMed, Lilacs e Elsevier’s Scopus Database, utilizando os seguintes unitermos: "Disposal of medicines in household", "Disposal of expired drugs", "Residential expired drugs", "Management of expired medications in household". Foram selecionados 33 estudos originais após aplicação dos critérios de inclusão e exclusão. Os estudos analisados demonstraram que os principais motivos de estoque no domicílio foram: automedicação; guarda para uso futuro e sobras de tratamentos anteriores. E quanto ao descarte dos medicamentos, prevalecem práticas inadequadas, como descarte no lixo comum e na rede de esgoto. Alguns países têm adotado programas de orientação sobre o armazenamento e o descarte correto, no entanto, foi apenas encontrado um estudo que descreve um programa nacional gratuito, para orientar essas práticas. A partir das evidências cientificas verificou-se a importância do incentivo para a elaboração e a implementação de políticas públicas voltadas para o uso e descarte adequado de medicamentos no domicílio.

Mechanical, corrosion, and biocompatibility properties of Mg-Zr-Sr-Sc alloys for biodegradable implant applications

Magnesium (Mg) and its alloys are considered promising biodegradable implant materials because of their strength and natural degradation in the human body. However, the high corrosion rate of pure Mg in the physiological environment leads to rapid degradation before adequate bone healing. This mismatch between bone healing and the degradation of Mg implants supports the development of new Mg alloys with the addition of other suitable alloying elements in order to achieve simultaneously high corrosion resistance and desirable mechanical properties. This study systematically investigates the microstructure, mechanical properties, corrosion behavior, and biocompatibility of Mg-based alloys with the addition of different concentrations of scandium (Sc), i.e., Mg-0.6Zr-0.5Sr-xSc (x = 0.5, 1, 2, 3 wt.%). Results indicated that high concentration of Sc in strontium (Sr)-containing Mg alloys can alter their microstructures by suppressing the intermetallic phases along the grain boundaries and improve the corrosion resistance by forming chemically stable Sc oxide layers on the surfaces of the Mg alloys. Cytotoxicity assessment revealed that the Sc containing Mg alloys did not significantly alter the viability of human osteoblast-like SaOS2 cells. This study highlights the advantages of using Sc as an alloying element to simultaneously tune Mg alloys with higher strength and slower degradation. STATEMENT OF SIGNIFICANCE: Rare earth elements such as scandium (Sc) with both a high solid-solubility and strong affinity towards oxygen can improve the mechanical and corrosion properties of magnesium (Mg) alloys. However, the feasibility of Sc-containing Mg alloys as biodegradable implant materials is scarcely reported. This study investigates the effects of different Sc concentrations on the mechanical, corrosion, and biocompatibility properties of Mg-Zr-Sr-Sc alloys. Our findings indicated that the addition of Sc significantly improves the mechanical and corrosion properties of Mg-Zr-Sr alloys. Moreover, in vitro cytotoxicity assessment of the Mg-Zr-Sr-Sc alloys did not show any adverse effects on the viability of osteoblast-like cells.

Microstructure, mechanical properties, and degradation of Mg-Ag alloy after equal-channel angular pressing

Enhancing the strength of Mg-based biodegradable alloys without decreasing their corrosion resistance is a major engineering challenge. In addition, the growing demand for effective reduction of infections and inflammation after implant placement motivates the design of alloys with appropriate compositions or coatings. One promising alloying element is silver, whose antibacterial effect has long been known. Therefore, a Mg-4% Ag alloy was selected for this study. The alloy was investigated under three conditions: as-cast, after T4 treatment, and after T4 treatment with subsequent equal-channel angular pressing (ECAP) using a newly developed double-ECAP die, which offers an equivalent strain per pass of 1.6. The first pass through the double-ECAP die was conducted at 370 °C and the second at 330 °C using route B_C. The microstructure of the as-cast Mg-4% Ag consisted of large grains (several hundred microns) and a dendritic structure with micron-sized Mg₅₄Ag₁₇ precipitates. T4 heat treatment caused dissolution of the dendrites and formation of a solid solution without changing the grain size. Consequently, the ultimate compressive strength (UCS) was increased by approximately 30%, and the compressive strain at fracture reached approximately 23%. The compressive yield strength (CYS) remained nearly constant at approximately 30 MPa. Subsequent ECAP led to strong grain refinement (from 350 μm to 38 μm after one pass and 15 μm after two passes) and further increases in the CYS and UCS, to 45 and 300 MPa after the first pass and 62 and 325 MPa after the second pass, respectively. The as-cast alloy exhibited a very high degradation rate in a simulated body fluid at approximately 36 °C. The degradation rate of the alloy after T4 treatment was much lower. Subsequent ECAP had no significant effect on the degradation properties. Thus, it can be concluded that grain refinement has little effect on the degradation rate.

Microstructure, mechanical and corrosion properties of novel Mg-Sn-Ce alloys produced by high pressure die casting

The aim of this study was to investigate the effect of adding 1, 2 and 4% wt of cerium on the microstructure, mechanical and corrosion properties of high pressure die casting (HPDC) Mg-4Sn alloys. Microstructure analyses of the alloys were carried out using X-Ray Diffraction (XRD) and Scanning Electron microscopy (SEM). The corrosion behaviors were determined with the potentiodynamic polarization and immersion tests in Hanks Balanced Salt Solution (HBSS), which is used as the artificial body fluid. The microstructural results showed that the addition of Ce to the main alloy creates new intermetallic phases (Ce₅Sn₄ and MgSnCe). In addition, Ce addition provided effectively the grain refinement of the alloys. While the hardness and yield strength of the Mg-4Sn alloy enhanced continuously with increasing Ce content, the tensile strength and elongation reached up to 2% wt. The corrosion resistance of the main alloy was improved by the addition of 1% wt of Ce. However, the Ce content, which is more than 1% wt decreased corrosion resistance.

Enhanced recovery of aluminum from wastewater using a fluidized bed homogeneously dispersed granular reactor

The recovery of aluminum from wastewater is one of the main environmental issues that need to be addressed in the aluminum finishing industry. A new technique of converting a soft slurry into hard granules using the homogeneous granulation process in the fluidized-bed reactor (FBR) can respond to this problem. It is a better method of remediation than producing a slurry containing 70% water. This study deals with the recovery of aluminum from aqueous solutions using Fluidized-bed homogeneous granulation process (FBHGP) without seeds. The hydraulic operating conditions were optimized using Box-Behnken Design (BBD) to attain the optimum aluminum removal (AR%) and granulation ratio (GR%). Optimum values of AR% = 98.8% and GR% = 96.9% were attained at the following conditions: influent aluminum concentration, 334.1 mg L^-1_; precipitant pH, 10.4; molar ratio (MR) of precipitant to metal [OH^-]_in/[Al³⁺]_in, 2.5. The characteristics of the granules were comparable with those of orthorhombic structure of aluminum oxide (Al_2.66O₄). FBHGP was proven to be effective as dictated by the reaction mechanism in the recovery of aluminum from aluminum-rich aqueous solutions.

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.

Synthesis, Characterization, Corrosion Resistance and In-Vitro Bioactivity Behavior of Biodegradable Mg⁻Zn⁻Mn⁻(Si⁻HA) Composite for Orthopaedic Applications

Recently, magnesium (Mg) has gained attention as a potential material for orthopedics devices, owing to the combination of its biodegradability and similar mechanical characteristics to those of bones. However, the rapid decay rate of Mg alloy is one of the critical barriers amongst its widespread applications that have provided numerous research scopes to the scientists. In this present, porous Mg-based biodegradable structures have been fabricated through the hybridization of elemental alloying and spark plasma sintering technology. As key alloying elements, the suitable proportions of silicon (Si) and hydroxyapatite (HA) are used to enhance the mechanical, chemical, and geometrical features. It has been found that the addition of HA and Si element results in higher degree of structural porosity with low elastic modulus and hardness of the Mg⁻Zn⁻Mn matrix, respectively. Further, addition of both HA and Si elements has refined the grain structure and improved the hardness of the as-fabricated structures. Moreover, the characterization results validate the formation of various biocompatible phases, which enhances the corrosion performance and biomechanical integrity. Moreover, the fabricated composites show an excellent bioactivity and offer a channel/interface to MG-63 cells for attachment, proliferation and differentiation. The overall results of the present study advocate the usefulness of developed structures for orthopedics applications.

Is aluminum exposure a risk factor for neurological disorders?

Aluminum (Al) is widely found in the nature. Although the relation between Al and neurodegenerative diseases is still controversial, Al is related with many brain diseases including Alzheimer's disease, Parkinson's disease, and multiple sclerosis. Al exposure occurs mainly through environment, occupational, and dietary factors for humans. Al exposure with diet can be through foods, food additives, water, and contamination of Al equipment/utensils. The aim of this review is to summarize various hypotheses, which link Al and neurodegeneration, and to determine the roles of Al exposure through different sources including diet, environment, and occupation. Future studies should be done in vulnerable subgroups of population including children, patients receiving antacid or Al-containing pharmeteucials on a daily basis, patients with reduced renal function, and patients on parenteral nutrition regimens that are likely to be affected by possible adverse health effects of Al. In addition, gender, age, and Al interactions need to be determined. One of the most important challanges in future epidemiological studies is to determine which variables should be controlled. In addition, experimental studies should be more focused and translational. In this context, exposure dose, dose-response effects, and time lapse between exposures and cognitive assessments are very important.

Overview of the Relationship Between Aluminum Exposure and Health of Human Being

Aluminum is a type of ubiquitously existing naturally and widely used metal in our world. It is combined with other elements and forms different compounds. In different pH and due to other conditions, it can be released into ions of different valence states. Our century is an "aluminum age"; aluminum is used in many fields of our daily life, such as vaccine adjuvant, antacids, food additives, skin care products, cosmetics, and cooking wares, and may be as elements or contaminants appeared in a lot of foods, including infant formulae, milk products, juice, wine, sea foods, and tea. It also appears in drinking water due to the water treatment process, or naturally coming from weathering rocks and soils, or released from rocks and soils caused by pollution-induced acid rain. Due to good physical and chemical property, aluminum is being tremendously utilized in many industries. In a lot of production and process procedures, aluminum particulates are seriously exposed by workers. Many factors, such as silicon, citrate, iron, calcium, fluoride, etc., can affect absorption of aluminum in human body. Human being ingests aluminum through the respiratory and digestive system and skin. Aluminum can affect our health, especially impair central nervous system. The important damage is cognitive impairment in Al-exposed peoples, Alzheimer's disease and other neurodegenerative disorders have been related with aluminum exposure, and aluminum has been proposed as etiology.

Genetic, Transcriptome, Proteomic, and Epidemiological Evidence for Blood-Brain Barrier Disruption and Polymicrobial Brain Invasion as Determinant Factors in Alzheimer's Disease

Diverse pathogens are detected in Alzheimer's disease (AD) brains. A bioinformatics survey showed that AD genome-wide association study (GWAS) genes (localized in bone marrow, immune locations and microglia) relate to multiple host/pathogen interactomes (Candida albicans, Cryptococcus neoformans, Bornavirus, Borrelia burgdorferri, cytomegalovirus, Ebola virus, HSV-1, HERV-W, HIV-1, Epstein-Barr, hepatitis C, influenza, Chlamydia pneumoniae, Porphyrymonas gingivalis, Helicobacter pylori, Toxoplasma gondii, Trypanosoma cruzi). These interactomes also relate to the AD hippocampal transcriptome and to plaque or tangle proteins. Upregulated AD hippocampal genes match those upregulated by multiple bacteria, viruses, fungi, or protozoa in immunocompetent cells. AD genes are enriched in GWAS datasets reflecting pathogen diversity, suggesting selection for pathogen resistance, as supported by the old age of AD patients, implying resistance to earlier infections. APOE4 is concentrated in regions of high parasitic burden and protects against childhood tropical infections and hepatitis C. Immune/inflammatory gain of function applies to APOE4, CR1, and TREM2 variants. AD genes are also expressed in the blood-brain barrier (BBB), which is disrupted by AD risk factors (age, alcohol, aluminum, concussion, cerebral hypoperfusion, diabetes, homocysteine, hypercholesterolemia, hypertension, obesity, pesticides, pollution, physical inactivity, sleep disruption, smoking) and by pathogens, directly or via olfactory routes to basal-forebrain BBB control centers. The BBB benefits from statins, NSAIDs, estrogen, melatonin, memantine, and the Mediterranean diet. Polymicrobial involvement is supported by upregulation of bacterial, viral, and fungal sensors/defenders in the AD brain, blood, or cerebrospinal fluid. AD serum amyloid-β autoantibodies may attenuate its antimicrobial effects favoring microbial survival and cerebral invasion leading to activation of neurodestructive immune/inflammatory processes, which may also be augmented by age-related immunosenescence. AD may thus respond to antibiotic, antifungal, or antiviral therapy.

Cortex- and Amygdala-Dependent Learning and Nicotinic Acetylcholine Receptor Gene Expression is Severely Impaired in Mice Orally Treated with AlCl3

Recent industrialization has increased human exposure to bio-available aluminum (Al). If more Al enters the brain than leaves, Al concentration will rise in the brain leading to neurodegenerative disorders. The aim of the present study was to determine Al concentration, neurodegeneration, and nicotinic acetylcholine receptor (nAChR) gene expression in the cortex and amygdala after oral ingestion of Al salt. The effect of Al on cortex- and amygdala-dependent learning and memory functions was also assessed. Mice were given AlCl₃ (250 mg/kg) in drinking water for 42 days. nAChR gene expression was determined in the cortex and amygdala. The mice were subjected to behavior tests (fear conditioning, fear extinction, and open field), to assess memory deficits. The acquisition of fear memory in the fear conditioning test remained unaffected due to the Al administration. However, fear extinction (which is a new learning) was severely impaired. The behavioral analysis in the open field test showed greater anxiety and less adaptability to the new environment in Al-treated animals. High Al concentration and severe neurodegeneration in the cortex were observed following Al treatment while a slight, non-significant elevation in Al concentration was observed in the amygdala of Al-treated animals. The analysis of nAChR gene expression via RT-PCR showed a significant reduction in expression of α7, α4, and β2 nAChR genes in the cortex of Al-treated animals, while in the amygdala, the level of the α4 nAChR gene remained unaltered. Oral Al ingestion causes neuropathological changes and suppresses expression of nAChR genes that lead to deficits in learning and higher anxiety in Al-treated animals.

Tissue distribution following 28 day repeated oral administration of aluminum-based nanoparticles with different properties and the in vitro toxicity

The tissue distribution and toxicity of nanoparticles (NPs) depend on their physical and chemical properties both in the manufactured condition and within the biological system. We characterized three types of commercially available aluminum-based NPs (Al-NPs), two rod-type aluminum oxide NPs (Al₂ O₃ , AlONPs), with different aspect ratios (short [S]- and long [L]-AlONPs), and spherical aluminum cerium oxide NPs (AlCeO₃ , AlCeONPs). The surface area was in order of the S-AlONPs > L-AlONPs > AlCeONPs. Very importantly, we found that AlCeONPs is Al₂ O₃ -coated CeO₂ NPs, but not AlCeO₃ NPs, and that the Al level in AlCeONPs is approximately 20% of those in S- and L-AlONPs. All three types of Al-NPs were slightly ionized in gastric fluid and rapidly particlized in the intestinal fluid. There were no significant differences in the body weight gain following 28 days of repeated oral administration of the three different types of Al-NPs. All Al-NPs elevated Al level in the heart, spleen, kidney and blood at 24 hours after the final dose, accompanied by the altered tissue level of redox reaction-related trace elements. Subsequently, in four types of cells derived from the organs which Al-NPs are accumulated, H9C2 (heart), HEK-293 (kidney), splenocytes and RAW264.7 (blood), S-AlONPs showed a very low uptake level and did not exert significant cytotoxicity. Meanwhile, cytotoxicity and uptake level were the most remarkable in cells treated with AlCeONPs. In conclusion, we suggest that the physicochemical properties of NPs should be examined in detail before the release into the market to prevent unexpected adverse health effects.

The protective role of plant biophenols in mechanisms of Alzheimer's disease

Self-assembly of amyloid beta peptide (Aβ) into the neurotoxic oligomers followed by fibrillar aggregates is a defining characteristic of Alzheimer's disease (AD). Several lines of proposed hypotheses have suggested the mechanism of AD pathology, though the exact pathophysiological mechanism is not yet elucidated. The poor understanding of AD and multitude of adverse responses reported from the current synthetic drugs are the leading cause of failure in the drug development to treat or halt the progression of AD and mandate the search for safer and more efficient alternatives. A number of natural compounds have shown the ability to prevent the formation of the toxic oligomers and disrupt the aggregates, thus attracted much attention. Referable to the abundancy and multitude of pharmacological activities of the plant active constituents, biophenols that distinguish them from the other phytochemicals as a natural weapon against the neurodegenerative disorders. This review provides a critical assessment of the current literature on in vitro and in vivo mechanistic activities of biophenols associated with the prevention and treatment of AD. We have contended the need for more comprehensive approaches to evaluate the anti-AD activity of biophenols at various pathologic levels and to assess the current evidences. Consequently, we highlighted the various problems and challenges confronting the AD research, and offer recommendations for future research.

Magnesium-based biodegradable alloys: Degradation, application, and alloying elements

In recent years, the paradigm about the metal with improved corrosion resistance for application in surgery and orthopedy was broken. The new class of biodegradable metal emerges as an alternative for biomedical implants. These metals corrode gradually with an appropriate host response and release of corrosion products. And it is absolutely necessary to use essential metals metabolized by hosting organism with local and general nontoxic effect. Magnesium serves this aim best; it plays the essential role in body metabolism and should be completely excreted within a few days after degradation. This review summarizes data from Mg discovery and its first experimental and clinical application of modern concept of Mg alloy development. We focused on biodegradable metal application in general surgery and orthopedic practice and showed the advantages and disadvantages Mg alloys offer. We focused on methods of in vitro and in vivo investigation of degradable Mg alloys and correlation between these methods. Based on the observed data, a better way for new alloy pre-clinical investigation is suggested. This review analyzes possible alloying elements that improve corrosion rate, mechanical properties, and gives the appropriate host response.

In vivo response of AZ31 alloy as biliary stents: a 6 months evaluation in rabbits

Mg-based metallic materials have been making continuing progress as vascular stents. However, the research of Mg-based materials as non-vascular stents is still at its primary stage. AZ31 stents hereby were implanted into the common bile duct of rabbits for 6 months. The results revealed an existence of 93.82 ± 1.36% and 30.89 ± 2.46% of the original volume after 1 and 3 month, respectively. Whole blood tests indicated an inflammation decreasing to normal level after 3 month implantation. A benign host response was observed via H&E staining. Nonuniform corrosion at the two ends of the stents was observed and considered the results of flow or local inflammation. Moreover, the application of Mg-based materials for different stenting treatment were reviewed and compared. Esophagus was hypothesized most destructive, whilst blood vessel and bile duct considered similar and less destructive. Trachea and nasal cavity were thought to be mildest.

Fatigue behaviors of HP-Mg, Mg-Ca and Mg-Zn-Ca biodegradable metals in air and simulated body fluid

The dynamic loading in human body, along with the corrosive body fluid, presents a great challenge for the practical use of biodegradable magnesium implants. In this study, a high purity magnesium (99.99wt.%) and two typical promising biodegradable magnesium alloys (binary Mg-1Ca and ternary Mg-2Zn-0.2Ca) were chosen as the experimental materials. Their dynamic mechanical performances were comparatively evaluated by carrying out fatigue tests in air and in simulated body fluid (SBF). The fatigue strengths of HP-Mg, Mg-1Ca and Mg-2Zn-0.2Ca were all around 90MPa in air, however, they decreased to 52MPa, 70MPa and 68MPa in SBF at 4×10(6)cycles, respectively. The fatigue cracks initiated from the microstructural defects when tested in air, but nucleated from surface corrosion pits when tested in SBF. Cyclic loading significantly increased the corrosion rates of all the experimental materials compared to that in static SBF. Moreover, based on our findings, the fatigue failure processes and interactions between material, corrosion and cyclic loading were systematically discussed.

STATEMENT OF SIGNIFICANCE

Fatigue strength and life are vital parameters to the design of metallic implant devices. For the corrosion fatigue of biomedical magnesium alloys, we reported the corrosion fatigue behavior of AZ91D and WE43 in SBF (Acta Biomaterialia, 6 (2010) 4605-4613), and till now there is no other reports to our knowledge. We spent 3years to finish the fatigue testing and get S-N curves for three more magnesium biomaterials, and our significant finding is that the fatigue strengths of HP-Mg, Mg-1Ca and Mg-2Zn-0.2Ca are all around 90MPa in air but 52MPa, 70MPa and 68MPa in SBF at 4×10(6)cycles, which will provide the first-hand data for the future magnesium implants design.

Microstructures, mechanical properties and corrosion resistances of extruded Mg-Zn-Ca-xCe/La alloys

Magnesium alloys are considered as good candidates for biomedical applications, the influence of Ce/La microalloying on the microstructure, mechanical property and corrosion performance of extruded Mg-5.3Zn-0.6Ca (wt%) alloy has been investigated in the current study. After Ce/La addition, the conventional Ca2Mg6Zn3 phases are gradually replaced by new Mg-Zn-Ce/La-(Ca) phases (T1'), which can effectively divide the Ca2Mg6Zn3 phase. The Ca2Mg6Zn3/T1' structure in Mg-Zn-Ca-0.5Ce/La alloy is favorably broken into small particles during the extrusion, resulting in an obvious refinement of secondary phase. The dynamic recrystallized grain size is dramatically decreased after 0.5Ce/La addition, and the tensile yield strength is improved, while further addition reverses the effect, due to the grain coarsening. However, the corrosion resistance of extruded Mg-Zn-Ca alloy deteriorates after Ce/La addition, because the diameter of secondary phase particle is remarkably decreased, which increases the amount of cathodic sites and accelerates the galvanic corrosion process.

Evaluation of the toxic potential of calcium carbide in the third instar larvae of transgenic Drosophila melanogaster (hsp70-lacZ)Bg(9)

In the present study the toxic potential of calcium carbide (CaC2) was studied on the third instar larvae of transgenic Drosophila melanogaster (hsp70-lacZ)Bg(9). The third instar larvae were exposed to 2, 4, 8, 16 and 32×10(-3)g/ml of CaC2 in diet for 24h. The results reveal that the dose 2×10(-3)g/ml was not toxic but the remaining doses showed a dose dependent significant increase in the hsp70 expression, β-galactosidase activity, tissue damage, oxidative stress markers (lipid peroxidation and protein carbonyl content), glutathione-S-transferase activity, expression of Caspase 3 and 9, apoptotic index and DNA damage (midgut cells). A significant reduction as compared to control group in total protein, glutathione content and acetylcholinesterase activity was also observed. The Inductively Coupled Plasma Atomic Emission Spectroscopy analysis (ICPAES) reveals the presence of copper, iron, sodium, aluminium, manganese, calcium, nickel and mercury. The toxic effects of CaC2 in the present study may be attributed to the impurities present in it.

An integrated experimental and theoretical investigation of the vibrational modes and molecular structure of a chelate, tetraaqua cysteine aluminum(III)

The complex formed by Al(3+) and cysteine in aqueous solution has been studied by potentiometry, Raman spectroscopy and DFT calculations (DFT:B3LYP/6-311++G(∗∗)). Atomic charges, frontier molecular orbitals, electrostatic potential contour surface, electrostatic potential map and donor-acceptor second order perturbative energies were examined. The [Al(Cys)(H2O)4](2+) complex adopts a distorted octahedral geometry. Cysteine should act as a bidentate ligand through the oxygen of the carboxylate and the nitrogen of the amino group. The molecule has high HOMO-LUMO energy gap, intense intramolecular charge transfer and positive electrostatic potential.

Design and construction of new potentiometric sensors for determination of Al3+ ion based on (Z)-2-(2-methyl benzylidene)-1-(2,4-dinitrophenyl) hydrazine

(Z)-2-(2-methyl benzylidene)-1-(2,4-dinitrophenyl) hydrazine (L) was used as an active component of PVC membrane electrode (PME), coated graphite electrode (CGE) and coated silver wire electrode (CWE) for sensing Al(3+) ion. The electrodes exhibited linear Nernstian responses to Al(3+) ion in the concentration range of 1.0×10(-6) to 1.0×10(-1)M (for PME, LOD=8.8×10(-7)M), 5.5×10(-7) to 2.0×10(-1)M (for CWE, LOD=3.3×10(-7)M) and 1.5×10(-7) to 1.0×10(-1)M (for CGE, LOD=9.2×10(-8)M). The best performances were observed with the membranes having the composition of L:PVC:NPOE:NaTPB in the ratio of 5:35:57:3 (w/w; mg). The electrodes have a response time of 6s and an applicable pH range of 3.5-9.1. The sensors have a lifetime of about 15weeks and exhibited excellent selectivity over a number of mono-, bi-, and tri-valent cations including alkali, alkaline earth metal, heavy and transition metal ions. Analytical utility of the proposed sensor has been further tested by using it as an indicator electrode in the potentiometric titration of Al(3+) with EDTA. The electrode was also successfully applied for the determination of Al(3+) ion in real and pharmaceutical samples.

Beraprost sodium protects against chronic brain injury in aluminum-overload rats

Background

Aluminum overload can cause severe brain injury and neurodegeneration. Previous studies suggest that prostacyclin synthase (PGIS) expression and prostacyclin receptor (IP) activation are beneficial for treatment of acute traumatic and ischemic brain injury. However, the potential value of PGIS/IP signaling pathway to chronic brain injury is still unclear. In this study, we investigated the change of PGIS/IP signaling pathway and the effect of beraprost sodium (BPS) on chronic brain injury in chronic aluminum-overload rats.

Methods

Rat model of chronic cerebral injury was established by chronic intragastric administration of aluminum gluconate(Al³⁺ 200 mg/kg per day,5d a week for 20 weeks). The methods of ELISA, qRT-PCR and Western blotting were used to detect the PGI2 level and the PGIS and IP mRNA and protein levels in hippocampi of chronic aluminum-overload rats, respectively. Rat hippocampal superoxide dismutase (SOD) activity and malondialdehyde (MDA) content also were measured. The effects of BPS (6, 12 and 24 μg⋅kg^-1) on brain injury in chronic aluminum-overload rats were evaluated.

Results

Compared with the control group, PGIS mRNA expression, PGI2 level, and the IP mRNA and protein expressions significantly increased in hippocampi of chronic aluminum-overload rats. Administration of BPS significantly improved spatial learning and memory function impairment and hippocampal neuron injury induced by chronic aluminum overload in rats. Meanwhile, administration of BPS resulted in a decrease of PGI2 level and downregulation of PGIS and IP expressions in a dose-dependent manner. Aluminum overload also caused a decrease of SOD activity and an increase of MDA content. Administration of BPS significantly blunted the decrease of SOD activity and the increase of MDA content induced by aluminum overload in rats.

Conclusions

BPS has a significant neuroprotective effect on chronic brain injury induced by aluminum overload in rats. Remodeling the balance of PGIS/IP signaling pathway and inhibition of oxidative stress involve in the neuroprotective mechanism of BPS in aluminum-overload rats. The PGIS/IP signaling pathway is a potential therapeutic strategy for chronic brain injury patients.

Electrodeposition of a porous strontium-substituted hydroxyapatite/zinc oxide duplex layer on AZ91 magnesium alloy for orthopedic applications

Magnesium alloy is a potential biomedical implant because of its outstanding biodegradability and mechanical properties. But the poor corrosion resistance of AZ91 magnesium alloy in physiological solution limits its biomedical applications. In order to improve the corrosion resistance and biological performance of AZ91 magnesium alloy, we have fabricated a strontium-substituted porous hydroxyapatite (Sr-HAP)/zinc oxide (ZnO) duplex layer on AZ91 magnesium alloy by electrodeposition. The porous Sr-HAP/ZnO duplex-layer coating on AZ91 magnesium alloy was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, high-resolution scanning electron microscopy and energy dispersive X-ray analysis. Also, the mechanical properties of the duplex-layer coating were evaluated using adhesion and Vickers micro-hardness tests. The effects of the duplex-layer coating on the corrosion behavior of AZ91 magnesium alloy were also investigated in simulated body fluid using electrochemical studies. The potentiodynamic polarization and electrochemical impedance spectroscopy results indicated that the corrosion resistance of AZ91 magnesium alloy was significantly improved by the duplex-layer coating. The in vitro cell-material interaction of the duplex-layer coating was observed with human osteosarcoma MG63 cells for cell viability at 1, 4 and 7 days of incubation and the coating exhibited good biocompatibility. Hence, from the obtained results we believe that the duplex-layer made of ZnO together with porous Sr-HAP on AZ91 magnesium alloy could provide effective corrosion protection and enhanced bioactivity. Thus, duplex-layer-coated AZ91 magnesium alloy can serve as a promising candidate for orthopedic applications.

Effects of aluminium on β-amyloid (1-42) and secretases (APP-cleaving enzymes) in rat brain

Chronic administration of aluminium has been proposed as an environmental factor that may affect some pathological changes related to neurotoxicity and Alzheimer's disease (AD). The abnormal generation and deposition of β-amyloid (Aβ) in senile plaques are hallmark features in the brains of AD patients. Furthermore, Aβ is generated by the sequential cleavage of the amyloid precursor protein (APP) via the APP cleaving enzyme (α-secretase, or β-secretase) and γ-secretase. In the present study, we investigated the modulation of Aβ deposition and neurotoxicity in aluminium-maltolate-treated (0, 15, 30, 45 mmol/kg body weight via intraperitoneal injection) in experimental rats. We measured Aβ1-40 and Aβ1-42 in the cortex and hippocampus in rat brains using ELISA. Subtypes of α-secretase, β-secretase, and γ-secretase, including ADAM9, ADAM10, ADAM17 (TACE), BACE1, presenilin 1 (PS1) and nicastrin (NCT), were determined using western blotting analyses. These results indicated that aluminium-maltolate induced an AD-like behavioural deficit in rats at 30 and 45 mmol/kg body weight. Moreover, the Aβ1-42 content increased significantly, both in the cortex and hippocampus, although no changes were observed in Aβ1-40. Furthermore, ADAM9, ADAM10, and ADAM17 decreased significantly; in contrast, BACE1, PS1, and NCT showed significant increase. Taken together, these results suggest that the changes in secretases may correlate to the abnormal deposition of Aβ by aluminium in rat brains.

Hippocampal neuronal metal ion imbalance related oxidative stress in a rat model of chronic aluminum exposure and neuroprotection of meloxicam

Neurodegenerative diseases remain a significant unresolved societal burden afflicting millions of people worldwide. Neurons in the brain are highly sensitive to oxidative stress, which can be induced by metal toxicity. In this paper, a chronic aluminum overload-induced model of neurodegeneration was used to investigate whether metal ions (Al, Fe, Mn, Cu and Zn)-related oxidative stress was involved in neurodegenerative mechanism and to identify the protective action of meloxicam against rat hippocampal neuronal injury. The metal ion contents, activity of superoxide dismutase (SOD), and content of malondialdehyde (MDA) were detected. The results showed that the spatial learning and memory (SLM) function was significantly impaired in chronic aluminum overload rats. Considerable karyopycnosis was observed in hippocampal neurons. The SOD activity was weakened and the MDA content increased both significantly. In the hippocampus, Al, Fe, Mn, Cu, and Zn contents increased by 184.1%, 186.1%, 884.2%, 199.4% and 149.2%, respectively. Meloxicam administration (without Al) had no effect compared with the control group, while meloxicam treatment with aluminum exposure significantly protected rats from SLM function impairment, neuron death, lower SOD activity, higher MDA content and brain metal ion imbalance. Our findings suggest that the cerebral metal ion imbalance-related oxidative stress is involved in mechanism of cerebral injury and neurodegeneration induced by chronic Al overload in rats, and that meloxicam protects neurons by reducing metal ion imbalance-related oxidative stress.

Spatial distribution of deaths due to Alzheimer's disease in the state of São Paulo, Brazil

CONTEXT AND OBJECTIVE

Alzheimer's disease is a common cause of dementia and identifying possible spatial patterns of mortality due to this disease may enable preventive actions. The objective of this study was to identify spatial distribution patterns of mortality due to Alzheimer's disease in the state of São Paulo.

DESIGN AND SETTING

Ecological and exploratory study conducted in all municipalities in the state of São Paulo.

METHODS

Data on Alzheimer's disease mortality in the state of São Paulo between 2004 and 2009 were obtained from DATASUS (the Department of Informatics in the Brazilian Ministry of Health). Death rates per 100,000 inhabitants were then calculated and spatial analysis was performed by constructing a death rate map, global Moran index and local Moran index, which were used to obtain the Moran map. The kernel technique was also applied. The Terra View 4.0.0 software was used.

RESULTS

13,030 deaths due to Alzheimer were reported in the state of São Paulo (rate of 5.33 deaths/100,000 inhabitants). São José do Rio Preto, Ribeirão Preto, Bauru and Araçatuba had higher rates. The Moran index was I = 0.085 (P < 0.002). The Moran map identified 42 municipalities that merit intervention and the kernel estimator identified a high density of deaths in the northwestern region of the state.

CONCLUSION

Higher densities of deaths due to Alzheimer were concentrated more to the north and northwest of the state of São Paulo. It was possible to identify municipalities that have priority for interventions to reduce the death rates due to this disease.

Effects of alloying elements on the corrosion behavior and biocompatibility of biodegradable magnesium alloys: a review

This review elaborates the effects of alloying elements on the microstructure, mechanical properties, corrosion and biocompatibility of biodegradable magnesium alloys.