Aluminium neurotoxicity: neurobehavioural and oxidative aspects

Mechanism and impact of heavy metal-aluminum (Al) toxicity on male reproduction: Therapeutic approaches with some phytochemicals

Heavy metals are ubiquitous environmental toxicants that have been known to have a serious effect on human and animal health. Aluminum (Al) is a widely distributed metal in nature. Al exposure has a detrimental impact on human fertility. This review focused on Al-induced male reproductive toxicity and the potential therapeutic approaches with some phytochemicals. Data from the literature showed that Al exposure is accompanied by a drastic decline in blood levels of FSH, LH, and testosterone, reduced sperm count, and affected sperm quality. Al exposure at high levels can cause oxidative stress by increasing ROS and RNS production, mediated mainly by downregulating Nrf2 signaling. Moreover, several investigations demonstrated that Al exposure evoked inflammation, evidenced by increased TNF-α and IL-6 levels. Additionally, substantial evidence concluded the key role of apoptosis in Al-induced testicular toxicity mediated by upregulating caspase-3 and downregulating Bcl2 protein. The damaging effects of Al on mitochondrial bioenergetics are thought to be due to the excessive generation of free radicals. This review helps to clarify the main mechanism involved in Al-associated testicular intoxication and the treatment strategy to attenuate the notable harmful effects on the male reproductive system. It will encourage clinical efforts to target the pathway involved in Al-associated testicular intoxication.

Hepatocellular degeneration in mice co-exposed to in-utero aluminium and cadmium: Implication of a disordered antioxidant and energy homeostatic response in the liver

The current study comprised four groups of pregnant animals viz; Control (CTR) received 10 ml/kg of normal saline, Al:10 mg/kg of AlCl3, Cd: 1.5 mg/Kg of CdCl2 Al+Cd; 10 mg/kg of AlCl3 and 1.5 mg/Kg of CdCl2. Treatment was done from pregnancy days (PNT) 7-20. After delivery, male animals were weaned on PSD 21 and sacrificed on PSD 78. From the study significant increases on serum liver enzymes in the group exposed to Cd and that exposed to Al+Cd were observed. The study further showed altered serum and hepatic antioxidant balance for the Cd, Al and Al+Cd groups compared to control. Similarly, lactate dehydrogenase (LDH) and succinate dehydrogenase (SDH) activities in the liver were elevated in Cd and Al+Cd groups while an altered liver histological feature in treated groups were also observed. it was concluded that in utero co-exposure to Al and Cd had the ability to alter hepatic functional indices.

Association between aluminum and iron exposure in maternal blood and umbilical cord blood and congenital heart defects in children

Background

Congenital heart disease (CHDs) is the major cause of mortality from birth defects, affecting up to 1% of live births worldwide. However, the relationship between aluminum (Al) and iron (Fe) levels and the risk of CHDs has yielded inconsistent results.

Methods

We conducted a pair-matched case-control study that included 97 CHDs and 194 non-CHDs to investigate the association and interaction between Al/Fe exposure and the risk of CHDs in a birth cohort study in Lanzhou, China.

Results

Higher concentrations of cord blood Al were associated with a greater risk of total CHDs (aOR = 2.826, 95% CI [1.009-7.266]) and isolated CHDs (aOR = 10.713, 95% CI [1.017-112.851]) compared to the lowest Al level. Both in maternal blood and cord blood, a significant dose-effect was observed between Al level and total CHDs (Ptrend < 0.05), but a similar pattern was not observed for Fe. High Al in addition to high Fe appeared to elicit a stronger association with CHDs than both lowest tertile of Al and Fe level in umbilical cord blood, particularly for multiple CHDs, septal defects and patent ductus arteriosus.

Conclusions

Our study suggests that exposure to Al during pregnancy (≥2,408 μg/L) is significantly associated with an increased risk of CHDs in offspring, especially septal defects, and that high levels of Al and Fe are strongly correlated with fetal heart development. Further research is needed to understand the underlying mechanisms.

Aluminium bioaccumulation in colon cancer, impinging on epithelial-mesenchymal-transition and cell death

We investigated the presence of aluminium (Al) in human colon cancer samples and its potential association with biological processes involved in cancer progression, such as epithelial to mesenchymal transition (EMT) and cell death. 25 consecutive colon samples were collected from patients undergoing colonic resection. Both neoplastic and normal mucosa were collected from each patient and subjected to histological, ultrastructural and immunohistochemical analyses. Moreover, colon samples from two Al-positive patients underwent multi-omic analyses, including whole genome sequencing and RNA sequencing (RNAseq). Morin staining, used to identify in situ aluminium bioaccumulation, showed the presence of Al in tumor areas of 24 % of patients. Transmission electron microscopy and energy-dispersive X-ray microanalysis confirmed the presence of Al specifically in intracytoplasmic electrondense nanodeposits adjacent to mitochondria of colon cancer cells. Immunohistochemical analyses for vimentin and nuclear β-catenin were performed to highlight the occurrence of the EMT phenomenon in association to Al bioaccumulation. Al-positive samples showed a significant increase in both the number of vimentin-positive and nuclear β-catenin-positive cancer cells compared to Al-negative samples. Moreover, Al-positive samples exhibited a significant decrease in the number of apoptotic cells, as well as the expression of the anti-apoptotic molecule BCL-2. Multi-omic analyses revealed a higher tumor mutational burden (TMB) in Al-positive colon cancers (n = 2) compared to a control cohort (n = 100). Additionally, somatic mutations in genes associated with EMT (GATA3) and apoptosis (TP53) were observed in Al-positive colon cancers. In conclusion, this study provides the first evidence of Al bioaccumulation in colon cancer and its potential role in modulating molecular pathways involved in cancer progression, such as EMT and apoptosis. Understanding the molecular mechanisms underlying Al toxicity might contribute to improve strategies for prevention, early detection, and targeted therapies for the management of colon cancer patients.

A detailed survey of agroecological status of Allium ursinum across the republic of Serbia: Mineral composition and bioaccumulation potential

The purpose of this study was to determine the content of twenty-two biogenic elements (BEs) and potentially toxic elements (PTEs) in the soil and fresh Allium ursinum leaves from 43 different locations, in order to examine their bioaccumulation potential. Analyses of soil and plant material were carried out by using Inductively Coupled Plasma coupled with Optical Emission Spectroscopy (ICP-OES), a mercury analyzer (Hg), liquid chromatography (Cr), and AAS hybrid technique (As). The obtained results of the investigated elements were compared with the proposed limit values. The soil contamination factor (CF) as well as plant bioaccumulation factor (BAF) were calculated and the correlation analysis was performed. The results showed that the content of some BEs/PTEs in the soil were above the limit values, with two locations highly contaminated (CF > 6) with five (Cr(VI), Cu, Mn, Ni, V) and four (As, Co, Pb, V) elements. The content of As, Cd, Cr, and Pb in the leaves was higher than the permitted levels at some locations. The BAF was high (K, Ca, Zn, As), medium (Mg, Cu, B, Ni, Na, Pb), and low (Fe, Mn, Cr). The correlation between BEs/PTEs content in the leaves and soil was not significant, except for the following elements: Cd (0.37), Ca (0.34), As (0.36), Pb (0.30), and Na (0.25). The observed medium correlation suggested that the detected elements originated both from the atmosphere and the soil. Although A. ursinum at examined locations seemed to be mostly safe for consumption, a selective mechanism of adoption of certain BEs/PTEs requires continuous monitoring of their content in the future, to avoid quantities that can jeopardize human health through its consumption.

Synthesis of Fluorophore Based Functional Material for Selective Detection of Al3+ Ion in Water and Decoding the AIEE Property of Its Hydrosol

A designed aggregation-induced emission enhancement (AIEE) active fluorescence probe 2,3-Bis-[(2-hydroxy-napthalen-1-ylmethylene)-amino]-but-2-enedinitrile (L) was synthesized via one step condensation method. The probe shows swift sensitivity and selectivity toward Al3+over other relevant metal ions and also exhibits significant AIEE phenomena in methanol/water mixture. Significant enhancement of fluorescence intensity is triggered via chelation-enhanced fluorescence through complex (Al3+-L) formation. A 2:1 metal to ligand ratio is observed from Job's plot based on UV - Vis absorption titration and detection limit (LOD) is found as low as 31.14 nM. Moreover, 1H NMR titrations and fluorescence reversibility by adding Al3+ and EDTA sequentially had been performed to establish the binding site of sensor complex (Al3+-L). Time-resolved photoluminescence, dynamic light scattering, optical microscopy, and on-site visualization studies have been performed to understand the AIEE mechanism of L in different volume percentage of water and methanol mixture. An INHIBIT molecular logic gate has been constructed utilizing the fluorescence behavior of the probe, L in presence of Al3+ and strong chelating ligand EDTA.

Influence of metal binding on the conformational landscape of neurofilament peptides

In order to understand the preferred modes of chelation in metal-binding peptides, quantum mechanical calculations can be used to compute energies, resulting in a hierarchy of binding affinities. These calculations often produce increasing stabilization energies the higher the coordination of the complex. However, as the coordination of a metal increases, the conformational freedom of the polypeptide chain is inevitably reduced, resulting in an entropic penalty. Estimating the magnitude of this penalty from the many different degrees of freedom of biomolecular systems is very challenging, and as a result this contribution to the free energy is often ignored. Here we explore this problem focusing on a family of phosphorylated neuropeptides that bind to aluminum. We find that there is a general negative correlation between both stabilization energy and entropy. Our results suggest that a subtle interplay between enthalpic and entropic forces will determine the population of the most favourable species. Additionally, we discuss the requirements for a possible "Metal Ion Hypothesis" based on our findings.

Zirconia Dental Implants: A Closer Look at Surface Condition and Intrinsic Composition by SEM-EDX

Modern dental implantology is based on a set of more or less related first-order parameters, such as the implant surface and the intrinsic composition of the material. For decades, implant manufacturers have focused on the research and development of the ideal material combined with an optimal surface finish to ensure the success and durability of their product. However, brands do not always communicate transparently about the nature of the products they market. Thus, this study aims to compare the surface finishes and intrinsic composition of three zirconia implants from three major brands. To do so, cross-sections of the apical part of the implants to be analyzed were made with a micro-cutting machine. Samples of each implant of a 4 to 6 mm thickness were obtained. Each was analyzed by a tactile profilometer and scanning electron microscope (SEM). Compositional measurements were performed by X-ray energy-dispersive spectroscopy (EDS). The findings revealed a significant use of aluminum as a chemical substitute by manufacturers. In addition, some manufacturers do not mention the presence of this element in their implants. However, by addressing these issues and striving to improve transparency and safety standards, manufacturers have the opportunity to provide even more reliable products to patients.

Nephroprotective Effects of Caffeine, Vanillin, and Their Combination against Experimental AlCl3-Induced Renal Toxicity in Adult Male Wistar Rats

Aluminum (Al) is known to be a nephrotoxic metal that can cause renal toxicity in both humans and animals. The use of functional foods has been reported to have significance in managing the toxic effects associated with such metals. This study aimed to assess the potential protective effects of caffeine, vanillin, and their combination in mitigating AlCl3-induced renal toxicity in adult male Wistar rats. A total of thirty (30) adult male Wistar rats weighing between 150 and 200 g were randomly divided into five groups, each consisting of six rats (n = 6). Group 1 served as the control, while the remaining treatment groups received a daily oral dose of 100 mg/kg AlCl3 for a duration of 21 days. In addition, groups 3-5 were coadministered 50 mg/kg body weight (bw) of caffeine, vanillin, and a combination (50/50 mg/kg bw) of both substances, respectively. In the results, AlCl3-treated showed a significant (p < 0.05) increase in serum biomarkers such as ALT, ALP, urea, and creatinine, and a significant (p < 0.05) decrease in serum total proteins (TPs). The renal tissue's antioxidant system, including SOD, CAT, GPx, and GSH, exhibited a significant (p < 0.05) reduction, accompanied by an elevated MDA level. However, the administration of caffeine, vanillin, and their combination resulted in a significant (p < 0.05) decrease in serum ALT, ALP, urea, and creatinine, and a significant (p < 0.05) increase in serum TP. Furthermore, following the treatment, there was a significant (p < 0.05) increase in renal SOD, CAT, GPx, and GSH levels, along with a reduction in the MDA level. In addition, the treatment for 21 days caused a significant (p < 0.05) reversal to the altered histomorphological architecture. These findings suggest that caffeine, vanillin, and their combination could potentially be an effective regimen in managing AlCl3-induced renal toxicity.

Therapeutic potential of stem cells and acitretin on inflammatory signaling pathway-associated genes regulated by miRNAs 146a and 155 in AD-like rats

Alzheimer's disease (AD) is one of the most common causes of dementia. Several drugs are used to improve the symptoms, but do not stop AD progression. There are more promising treatments that may have a significant role in AD diagnosis and treatment such as miRNAs and stem cells. The present study aims to develop a new approach for AD treatment by mesenchymal stem cells (MSCs) and/or acitretin with special reference to inflammatory signaling pathway as NF-kB and its regulator miRNAs in AD-like rat model. Fourty-five male albino rats were allotted for the present study. The experimental periods were divided into induction, withdrawal, and therapeutic phases. Expression levels of miR-146a, miR-155, necrotic, growth and inflammatory genes were assessed using RT-qPCR. Histopathological examination of brain tissues was performed in different rat groups. The normal physiological, molecular, and histopathological levels were restored after treatment with MSCs and/or acitretin. The present study demonstrates that the miR-146a and miR-155 might be used as promising biomarkers for AD. MSCs and/or acitretin proved their therapeutic potential in restoring the expression levels of targeted miRNAs and their related genes concerning NF-kB signaling pathway.

Considerations on Ossicular Reconstruction Using Lenticular Prosthesis for the Necrosed Lenticular Process During Endoscopic Tympanoplasty in Chronic Otitis Media (Mucosal) Cases

Purpose: To evaluate hearing outcome and fate of LPIRP (lenticular process of incus replacement prosthesis) prosthesis in the reconstruction of erosion of long process of the incus. Methods: In this retrospective descriptive study 17 patients with erosion of long process of incus who were operated (reconstructed with LPIRP prosthesis) between January 2015 to December 2017 in a tertiary care center were included. The hearing outcome was evaluated by comparing mean PTA and mean ABG preoperatively and postoperatively at the end of 3 months and 18 months. The graft uptake rate, reperforation, and extrusion of the prosthesis were assessed using otoendoscopy. Results: Preoperative mean PTA was 53.8 dB while mean postoperative PTA was 36.6 dB and 33.4 dB at the end of 3 and 18 months respectively (p-value ˂ 0.05). The mean preoperative ABG was 30.2 dB while the postoperative mean was 13.4 dB and 11.2 dB at the end of 3 months and 18 months respectively (p < 0.05). Extrusion with re-perforation was seen only in one case 1/17 (5.8%). Conclusion: LPIRP has all the characteristics for an ideal middle ear implant which is a cost-effective alternative in the reconstruction of an eroded long process of the incus.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-022-03317-5.

Taurine and deferiprone against Al-linked apoptosis in rat hippocampus

BACKGROUND

Aluminium (Al) overload has toxic effects on multiple organ systems, especially the nervous system. Al accumulation in the brain, especially the hippocampus, is an important factor contributing to Alzheimer's disease (AD). Deferiprone (DFP), a metal chelator, is used as a potential treatment for AD. In this study, we investigated the combined effect of taurine and DFP on Al chelation and hippocampal apoptosis in Al-exposed rats, as well as the underlying mechanisms of these effects to explore a possible therapy for AD.

METHODS

Male Wistar rats were divided into seven groups: negative control group (administered saline), Al-exposure group (administered AlCl₃ and saline), and five experimental groups (administered AlCl₃ and taurine, varying doses of DFP, or taurine with varying doses of DFP). After 8 weeks of treatment, the rats were sacrificed, and the terminal deoxyribonucleotidyl transferase (TDT)-mediated dUTP-digoxigenin nick end labelling (TUNEL) assay was used to detect hippocampal apoptotic cells. Real-time quantitative PCR was used to assess the expression of the Bcl2 and Bax genes, and a western blotting assay was used to evaluate BCL2, BAX, and cleaved caspase-3 levels.

RESULTS

Compared to the negative control group, the number of apoptotic cells in the hippocampus increased, Bcl2 expression significantly decreased, and BAX and cleaved caspase-3 levels increased in the Al-exposure group. The combination of taurine and DFP exerted a protective effect by inhibiting hippocampal cell apoptosis through the BCL2, BAX, and caspase-3 signalling pathways. Compared with the taurine-administered group, the group administered taurine with DFP showed a significantly increased Bcl2 and decreased Bax expression.

CONCLUSION

The combination of taurine and DFP is a potential candidate for the treatment of AD induced by Al exposure.

Maternal and Newborn Blood Aluminum Levels and Neurodevelopment of Infants: Is there a Need for Concern?

Aluminum is a neurotoxic element that enters the human body due to its widespread usage in daily life. It has the potential to affect the neurological development of the fetus and infant adversely. This study aimed to evaluate the relationship between maternal and umbilical cord serum aluminum level and infant neurodevelopment. Over a period of March 2018 to September 2019, we conducted a prospective cohort study; 173 Mother-new-born pairs were enrolled. Aluminum levels were measured using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The correlation with Bayley Scales of Infant Development (BSID) -3rd edition score and maternal and cord serum aluminum were assessed via linear regression model. The mean concentration of maternal and cord serum aluminum was 2.58 ± 1.14 µg/dL and 1.44 ± 0.62 µg/dL, respectively. There was a significant correlation in aluminum level between maternal and umbilical cord serum (Pearson's r = 0.591, p < 0.000). There is no significant correlation between maternal and serum aluminum level, and BSID-3rd edition (cognitive, motor, language, and social-emotion) score at the average age of 6.5 months. In conclusion, maternal and cord serum aluminum levels were significantly correlated but did not correlate with infant neurodevelopment. Thus, low serum aluminum concentration and their association with child neurodevelopment deserve further investigation longitudinally in a large cohort.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s12291-021-01002-y.

Nano alum: A new solution to the new challenge

Alum adjuvant has always been the first choice when designing a vaccine. Conventional aluminum adjuvant includes aluminum hydroxide, aluminum phosphate, and amorphous aluminum hydroxyphosphate (AAHS), which could effectively induce the humoral, and to a lesser extent, cellular immune responses. Their safety is widely accepted for a variety of vaccines. However, conventional alum adjuvant is not an ideal choice for a vaccine antigen with poor immunogenicity, especially the subunit vaccine in which cellular response is highly demanded. The outbreak of COVID-19 requires a delicately designed vaccine without the antibody-dependent enhancement (ADE) effect to ensure the safety. A sufficiently powerful adjuvant that can induce both Th₁ and Th₂ immune responses is necessary to reduce the risk of ADE. These circumstances all bring new challenges to the conventional alum adjuvant. However, turning conventional microscale alum adjuvant into nanoscale is a new solution to these problems. Nanoscale alum owns a higher surface volume ratio, can absorb much more antigens, and promote the ability to stimulate the antigen-presenting cells (APCs) via different mechanisms. In this review, the exceptional performance of nano alum adjuvant and their preparation methods will be discussed. The potential safety concern of nano alum is also addressed. Based on the different mechanisms, the potential application of nano alum will also be introduced.

Global Scientific Research Landscape on Aluminum Toxicology

This study aimed to identify the landscape of current aluminum toxicity based on knowledge mapping of the 100 most-cited articles on toxicological aspects of aluminum in biological organisms. The research was searched in the Web of Science Core Collection (WoS-CC) with publications between 1945 and 2022. Data regarding authorship, title, journal, year of publication, citation count, country, keywords, study design, and research hotspots were extracted and all elected articles were analyzed. Our results showed that among the articles selected, literature review and in vivo studies were the most common study designs. The USA and England were found as the countries with most publications. Alzheimer's disease (AD), aluminum, and neurotoxicity were found as the most frequent keywords. The articles most cited in world literature suggested that aluminum exposure is associated with Alzheimer's disease, Parkinson's disease (PD), dialysis encephalopathy, amyotrophic lateral sclerosis, neurodegeneration changes, cognitive impairment, such as bone damage, oxidative alterations, and cytotoxicity.

Phytochemical: a treatment option for heavy metal induced neurotoxicity

Heavy metals are known to be carcinogenic, mutagenic, and teratogenic. Some heavy metals are necessary while present in the growing medium in moderate concentrations known to be essential heavy metals as they required for the body functioning as a nutrient. But there are some unwanted metals and are also toxic to the environment and create a harmful impact on the body, which termed to be non-essential heavy metals. Upon exposure, the heavy metals decrease the major antioxidants of cells and enzymes with the thiol group and affect cell division, proliferation, and apoptosis. It interacts with the DNA repair mechanism and initiates the production of reactive oxygen species (ROS). It subsequently binds to the mitochondria and may inhibit respiratory and oxidative phosphorylation in even low concentrations. This mechanism leads to damage antioxidant repair mechanism of neuronal cells and turns into neurotoxicity. Now, phytochemicals have led to good practices in the health system. Phytochemicals that are present in the fruits and herbs can preserve upon free radical damage. Thus, this review paper summarized various phytochemicals which can be utilized as a treatment option to reverse the effect of the toxicity caused by the ingestion of heavy metals in our body through various environmental or lifestyles ways.

Asiatic acid attenuates aluminium chloride-induced behavioral changes, neuronal loss and astrocyte activation in rats

Aluminium (Al) is a potent neurotoxic metal known to cause neurodegeneration. Al exposure causes oxidative stress by accumulation of reactive oxygen species, followed by the activation of neuronal cell death in the brain. Asiatic acid (AA), the major bioactive compound of Centella asiatica (a medicinal plant), act as multifunctional drug as well as an antioxidant. Thus, the present study aimed to investigate the potential neuroprotective effect of AA against Al neurotoxicity. Rats were orally administered aluminium chloride (AlCl₃; 100 mg/kg b. wt.) dissolved in distilled water for 8 weeks or AA (75 mg/kg b. wt.) in combination with AlCl₃. The results showed that AlCl₃-intoxication causes significant impairment of memory, enhances anxiety-like behavior, acetyl cholinesterase (AChE) activity, malondialdehydes (MDA) level, and concomitant decrease in the activities of superoxide dismutase (SOD) and catalase (CAT) in the cortex and hippocampus regions of rat brain. In addition, AlCl₃-intoxication enhanced neuronal loss and reactive astrogliosis in both regions. However, co-administration of AA with AlCl₃ significantly attenuated the behavioral alterations, restored SOD and CAT activities, while reduced AChE activity and MDA content. Further, the study demonstrated that AA attenuates neuronal loss and reactive astrogliosis in rat brain. In conclusion, the study suggests that AA protects rat brain from Al neurotoxicity by inhibiting oxidative stress, neuronal loss and reactive astrogliosis.

Histological alterations and oxidative stress in adult zebrafish muscle after aluminium exposure

Aluminium (Al) is among the most abundant metals in nature, and its presence in the environment is further increasing by anthropogenic activities. In water bodies, the Al concentrations ranged between 0.001 and 50 mg/L, raising concerns about the health of aquatic organisms. For this reason, zebrafish was chosen as the model, since it is well suited for ecotoxicological studies. Adult specimens were exposed to 11 mg/L of Al for 10, 15 and 20 days to assess both the morphology and the oxidative state of muscle tissue. Considering the involvement of ROS, the activity of the main antioxidant enzymes, metallothioneins contents, but also oxidative damage and enzymes involved in energy consumption and neuromuscular transmission were assessed. Collected data showed an increase in the thickness of the endomysium and resorbed myofibrils in the organisms exposed to Al for 10 days, and an increase of myotomes' size in the organisms exposed to Al for 15 days. Moreover, the organisms exposed for less time to Al, it was evident an activation of anaerobic metabolism and the increased activity of antioxidant enzymes such as superoxide dismutase, glutathione peroxidase and glutathione S-transferases. However, these effects stabilized with increasing exposure time. In addition, only after 20 days of treatment did the oxidative damage to the proteins and the activity of acetylcholinesterase increase while the levels of metallothioneins and the lipid peroxidation were lower for all treated animals when compared to the control group. Overall, the biochemical and histological changes induced by aluminium exposure in the muscular tissue represent a relevant contribution to understanding the environmental risk due to the diffusion of this metal within the aquatic compartment.

Antiamnesic Potential of Malvidin on Aluminum Chloride Activated by the Free Radical Scavenging Property

Objectives: Malvidin, a dietary anthocyanin can be a potent drug for the treatment of neuronal toxicity. The investigation was aimed to study the antioxidant role of malvidin against aluminum chloride (AlCl₃)-induced neurotoxicity in rats. Methods: To evaluate the neuroprotective role of malvidin, the rats were divided into four different groups: group I received saline, group II received AlCl₃, and groups III and IV were administered with 100 and 200 mg/kg malvidin after AlCl₃ for 60 days. During the evaluation period, all the groups were subjected to a behavioral test. On the 61st day of the study, rat brains were removed and used for a neurochemical assay. Results: From the present study, malvidin ameliorated the effects of AlCl₃ on behavioral parameters. Biochemical investigation revealed that oral treatment of malvidin shows neuroprotective effects through regulation of antioxidant levels and neuroinflammation in the AlCl₃-exposed rats. Conclusion: The results indicate that malvidin possesses antioxidant activity via acetylcholinesterase inhibition and regulation of oxidative stress in neuronal cells. Hence, malvidin could be a potential drug in correcting Alzheimer's disease.

ROS antagonizes the protection of Parkin-mediated mitophagy against aluminum-induced liver inflammatory injury in mice

Aluminum (Al) is a food pollutant that has extensive deleterious effects on the liver. Our previous research proposed that E3 ubiquitin ligase PARK2 knockout (Parkin^-/-) could aggravate Al-induced liver damage by inhibiting mitophagy, during which the reactive oxygen species (ROS) content increases. Inhibition of mitophagy can activate inflammasome. But the link between Parkin-mediated mitophagy and liver inflammatory injury caused by Al, and the role of ROS in it remain unclear. In this study, we applied Al, Parkin^-/- and N-acetyl-L-cysteine (NAC) to act on C57BL/6N mice to investigate them. We found that Al could induce liver inflammatory injury and Parkin^-/- could aggravate it. Meanwhile, inhibition of ROS alleviated oxidative stress, mitochondrial damage, mitophagy and inflammatory injury caused by Al in Parkin^-/- mice liver. These results indicated that ROS antagonized the protection of Parkin-mediated mitophagy against Al-induced liver inflammatory damage in mice.

Role of Environmental Toxicants on Neurodegenerative Disorders

Neurodegeneration leads to the loss of structural and functioning components of neurons over time. Various studies have related neurodegeneration to a number of degenerative disorders. Neurological repercussions of neurodegeneration can have severe impacts on the physical and mental health of patients. In the recent past, various neurodegenerative ailments such as Alzheimer’s and Parkinson’s illnesses have received global consideration owing to their global occurrence. Environmental attributes have been regarded as the main contributors to neural dysfunction-related disorders. The majority of neurological diseases are mainly related to prenatal and postnatal exposure to industrially produced environmental toxins. Some neurotoxic metals, like lead (Pb), aluminium (Al), Mercury (Hg), manganese (Mn), cadmium (Cd), and arsenic (As), and also pesticides and metal-based nanoparticles, have been implicated in Parkinson’s and Alzheimer’s disease. The contaminants are known for their ability to produce senile or amyloid plaques and neurofibrillary tangles (NFTs), which are the key features of these neurological dysfunctions. Besides, solvent exposure is also a significant contributor to neurological diseases. This study recapitulates the role of environmental neurotoxins on neurodegeneration with special emphasis on major neurodegenerative disorders such as Alzheimer’s and Parkinson’s disease.

Neuroprotective effect of Bryophyllum pinnatum flavonoids against aluminum chloride-induced neurotoxicity in rats

Toxic metals such as aluminum accumulation in the brain have been associated with the pathophysiology of several neurodegenerative disorders. Bryophyllum pinnatum leaves contain a vast array of polyphenols, particularly flavonoids, that may play a role in the prevention of toxic and degenerative effects in the brain. This study assessed the neuro-restorative potential of leaves of B. pinnatum enriched flavonoid fraction (BPFRF) in aluminum-induced neurotoxicity in rats. Neurotoxicity was induced in male Wistar rats by oral administration of 150 mg/kg body weight of aluminum chloride (AlCl₃) for 21 days. Rats were grouped into five (n = 6); Control (untreated), Rivastigmine group, AlCl₃ group and BPFRF group (50 and 100 mg/kg b.wt.) for 21 days. Neuronal changes in the hippocampus and cortex were biochemically and histologically evaluated. Expression patterns of acetylcholinesterase (AChE) mRNA were assessed using semi-quantitative reverse-transcription-polymerase chain reaction protocols. Molecular interactions of BPFRF compounds were investigated in silico. The results revealed that oral administration of BPFRF ameliorated oxidative imbalance by augmenting antioxidant systems and decreasing lipid peroxidation caused by AlCl₃. BPFRF administration also contributed to the down-regulation of AChE mRNA transcripts and improved histological features in the hippocampus and cortex. Molecular docking studies revealed strong molecular interactions between BPFRF compounds, catalase, superoxide dismutase and glutathione peroxidase Overall, these findings suggest the neuroprotective effect of Bryophyllum pinnatum against aluminum-induced neurotoxicity.

Chitosan and solid lipid nanoparticles enhance the efficiency of alpha-lipoic acid against experimental neurotoxicity

Alpha-lipoic acid (α-LA) is characterized by its unpleasant odor, poor bioavailability and stability. Nanotechnology was applied to overcome this limitation. So we aimed in this study to formulate α-LA in two different forms of chitosan nanoparticles (CsNPs) and solid lipid nanoparticles (SLNPs) and characterize them in terms of physical properties and biological activities against aluminum chloride (AlCl₃)-induced neurotoxicity in rats. The vivo study was processed on 50 rats divided into 5 groups as follow: control, neurotoxic, treated α-LA, treated α-lipoic acid-loaded chitosan nanoparticles (α-LA-CsNPs) and treated α-lipoic acid-loaded solid lipid nanoparticles (α-LA-SLNPs) groups. The result was depicted by transmission electron microscopy (TEM) revealed that α-LA-SLNPs had a regular spherical shape while α-LA-CsNPs showed an irregular spherical form. Dynamic light scattering (DLS) analysis showed that the average particle size for α-LA-SLNPs was about 71 nm and for α-LA-CsNPs was about 126 nm. After the experimental period, we observed that AlCl₃ administration significantly increased oxidative stress, neuroinflammation and apoptosis and decreased brain fatty acid contentsand brain-derived neurotrophic factor,while α-LA, α-LA-CsNPs and α-LA-SLNPs were able to ameliorate these negative changes in the neurotoxic rats. However, the effect of the α-LA-loaded NPs was more prominent than that of pristine α-LA but the α-LA-SLNPs group was almost close to the control group. Conclusion: α-LA can attenuate neurotoxicity induced by AlCl3, attributed to its anti-inflammatory, antioxidant and anti-apoptotic activities in addition to the effectiveness of the encapsulation technique that can increase the efficiency and stability of α-LA. Moreover, α-LA-SLNPs are more efficient than α-LA-CsNPs.

Nutritional Quality of the Most Consumed Varieties of Raw and Cooked Rice in Spain Submitted to an In Vitro Digestion Model

Rice is one of the most consumed staple foods around the world and its trade is highly globalized. Increased environmental pollution generates a large amount of waste that, in many cases, is discarded close to culture fields. Some species are able to bioaccumulate toxic substances, such as metals, that could be transferred to the food chain. The main goal of this study was to evaluate the content of metallic (Al, Cd, Pb, and Cr) and metalloid elements (As) in 14 of the most consumed varieties of rice in Spain and their effects on human health. The samples were cooked, and human digestion was simulated by using a standard in vitro digestion method. Metallic and metalloid element levels were analysed by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), previous called microwave digestion. Both the human health risk index, Hazard Quotient, and Lifetime Cancer Risk did not show toxic values in any case. Rice with a higher non-digestible fraction showed a higher liberation of proteins and a lower glycemic index. There were no significant differences in the concentrations of metallic and metalloid elements in cooked rice or in the digestible fraction in all varieties analysed. However, Al concentrations were higher than other metals in all varieties studied due to its global distribution. No relationship has been observed between the digestibility of rice and the bioaccessibility of each metallic and metalloid element. All of the studied rice varieties are healthy food products and its daily consumption is safe. The regular monitoring of metals and As in rice consumed in Spain may contribute to improvements in the human health risk evaluation.

The influence of vinpocetine alone or in combination with Epigallocatechin-3-gallate, Coenzyme COQ10, Vitamin E and Selenium as a potential neuroprotective combination against aluminium-induced Alzheimer's disease in Wistar Albino Rats

Alzheimer's disease (AD) is one of such diseases that represent the most prominent cause of dementia in elderly people. To explore the possible neuroprotective effect as well as mechanism of action of Vinpocetine either alone or in combination with EGCG, CoQ10, or VE & Se in ameliorating aluminum chloride-induced AD in rats. Rats were received AlCl₃ (70 mg/kg) intraperitoneal daily dose for 30 days along with EGCG (10 mg/kg, I.P), CoQ10 (200 mg/kg, P.O), VE (100 mg/kg, P.O) & Se (1 mg/kg, P.O) as well as Vinpocetine (20 mg/kg, P.O) either alone or in combination. Results revealed that the combination of Vinpocetine with EGCG showed the best neuroprotection. This protection in the brain was indicated by the significant decrease in Aβ and ACHE. The same pattern of results were shown in the levels of monoamines and BDNF. In addition, the combination of Vinpocetine with EGCG showed more pronounced anti-inflammatory (TNF-α, IL-1β) and antioxidant (MDA, SOD, TAC) effects in comparison to other combinations. These results were confirmed using histopathological examinations as well as DNA fragmentation assays. Vinpocetine with EGCG showed pronounced protection on neurons against AD induced by AlCl₃ in rats.

Long-term exposure to environmentally relevant concentrations of ibuprofen and aluminum alters oxidative stress status on Danio rerio

Despite the ubiquitous presence of multiple pollutants in aqueous environments have been extensively demonstrated, the ecological impact of chemical cocktails has not been studied in depth. In recent years, environmental studies have mainly focused on the risk assessment of individual chemical substances neglecting the effects of complex mixtures even though it has been demonstrated that combined effects exerted by pollutants might represent a greater hazard to the biocenosis. The current study evaluates the effects on the oxidative stress status induced by individual forms and binary mixtures of ibuprofen (IBU) and aluminum (Al) on brain, gills, liver and gut tissues of Danio rerio after long-term exposure to environmentally relevant concentrations (0.1-11 μg L^-1 and 0.05 mg L^-1- 6 mg L^-1, respectively). Lipid peroxidation (LPO), Protein carbonyl content (PCC) and activity of Superoxide Dismutase (SOD), Catalase (CAT), and Glutathione Peroxidase (GPX) were evaluated. Moreover, concentrations of both toxicants and the metabolite 2-OH-IBU were quantified on test water and tissues. Results show that ibuprofen (IBU) and aluminum (Al) singly promote the production of radical species and alters the oxidative stress status in all evaluated tissues of zebrafish, nevertheless, higher effects were elicited by mixtures as different interactions take place.

Apoptosis, oxidative stress and genotoxicity in developing zebrafish after aluminium exposure

Aluminium is a non-essential metal and potentially toxic to organisms whose environmental concentration increases due to pollution. In our previous studies, the behavioral changes induced by aluminium were already shown on zebrafish, a model organism widely used for ecotoxicology screening. To examine in depth the knowledge about the toxicity mechanism induced by this metal, zebrafish embryos, at 6 hpf, have been exposed to 50, 100 and 200 µM of AlCl₃ for 72 h. Phenotypic alterations, apoptosis and oxidative stress responses have been assessed by evaluations of antioxidant defence and changes in metabolism at the end of treatment. The mRNA expression level of c-fos, appa and appb as marker genes of neural development and function were analyzed by qPCR for the highest used concentration. The data showed that aluminium significantly affected the development of zebrafish inducing morphological alterations and cell death. The oxidative state of larvae was altered, although the formation of reactive oxygen species and the levels of metallothioneins, and the activity of some antioxidant enzymes, decreased at the maximum concentration tested. In addition, at this concentration, the expression of the evaluated genes increased. The comprehensive information obtained gives a realistic snapshot of the aluminium toxicity and provides new information on the mechanism of action of this metal.

Carvedilol induces the antiapoptotic proteins Nrf2 and Bcl2 and inhibits cellular apoptosis in aluminum-induced testicular toxicity in male Wistar rats

The present study was carried out to explore the protective effect of carvedilol (CARV) on aluminum chloride-induced testicular damage in Westar rats. Forty adult male rats, aged 8 weeks, were randomly divided into 4 groups (10 rats each). Group I (control group) received normal saline; whereas group II animals were supplemented with CARV in a dose of 10 mg/kg/day. Group III received AlCl3 (30 mg/kg/day) whereas group IV was co-administered CARV and AlCl3 as the same doses in group II and III respectively. The route of the application was oral gavage for CARV and I.P for AlCl3 for 20 successive days. Exposure of rats to AlCl3 for 20 consecutive days resulted in a significant decrease in serum and testicular superoxide dismutase and catalase activities, serum testosterone level, and sperm count and motility; on the other hand, an increase in nitric oxide, malondialdehyde, aluminum, and serum tumor necrosis factor-alpha levels. Furthermore, histopathological changes in the testis exhibited marked testicular damage. In addition, it revealed a significant up-regulation in the level of the expression for the apoptotic marker; Caspase-3, and down-regulation in antiapoptotic marker Bcl2 and Nrf2 genes. On the other hand, the co-administration of CARV modulated the biochemical parameters, saved sperm count and motility, and the histopathological findings, also, restored the observed changes in Caspase-3, Bcl2, and Nrf2 transcriptional genes. These data suggested that administration of CARV protects against AlCl3 induced testicular oxidative, inflammatory, and apoptosis damage.

Observable Protective Activities of Quercetin on Aluminum Chloride-Induced Testicular Toxicity in Adult Male Wistar Rat

Background:

Aluminum chloride (AlCl3 ) present in many manufactured consumable is considered as a toxic element.

Aim:

Our study evaluates the toxic effects induced by AlCl3 on the testes as well as the therapeutic tendency of Quercetin (QUE) agent as an antioxidant.

Setting and Design:

In the department of Anatomy of Medical School.

Methods and Materials:

Thirty-two male Wistar rats weighing approximately 170 ± 10 g were assigned into four groups with eight each, fed with rat chow and water ad-libitum. Group A served as control and was given distilled water throughout; Group B was given only QUE (200 mg/kg body weight) for 21 days; Group C was given only AlCl3 (300 mg/kg body weight) for 14 days; and Group D was given AlCl3 (300 mg/kg body weight) for 14 days followed with QUE (200 mg/kg body weight) for 21 days. Substance administrations were done orally.

Statistical analysis:

One-way analysis of variance was used to analyze the data, in GraphPad Prism 6.0 being the statistical software.

Results:

AlCl3 significantly reduced the relative organ (testes) weight, correlating the decrease in sperm count, sperm motility and sperm viability. Furthermore, there was a decrease in luteinizing hormone with an increase in follicle-stimulating hormone which accounted for a significant reduction in testosterone level that plays a great role in spermatogenesis, following AlCl3 treatment. The cytoarchitecture of the testes showed degenerative changes in the seminiferous tubules and leydin cells, nitric oxide synthases immunoreactivity was intense in the seminiferous epithelium of rat in Group C.

Conclusion:

These suggest that QUE antioxidant property could reverse the decrease in sperm status, hormonal effects, and functional deficit induced by aluminum chloride on the testes of Wistar rats.

Occupational exposure during metal additive manufacturing: A case study of laser powder bed fusion of aluminum alloy

Occupational exposure during metal additive manufacturing (Laser Powder Bed Fusion) using an aluminum alloy (AlSi10Mg) was assessed. Background aerosols before manufacturing, powder sieving, machine loading, manufacturing, machine unloading, powder unpacking, and machine cleaning were analyzed. Measurements were taken simultaneously at the source, in the near field, and on the operator during five manufacturing cycles. Aerosol measurement devices and physico-chemical techniques were used to determine the particle number or mass concentration (DiSCmini, core particle counter and sampling cassette), particle size distribution (NanoScan, optical particle detector and impactor), and the shape/size and chemical compositions of the inhalable particles (laser diffraction, inductively coupled plasma spectroscopy, scanning electron microscopy, energy dispersive X-ray microanalysis, and Brunauer-Emmett-Teller Method). The laser powder-bed fusion machine emitted in the additive manufacturing room an inhalable fraction of 2.37 ± 0.35 mg/m3, with an aerosol number concentration ranging from 2 × 104 to 105 #/cm3 and a mass mean aerodynamic diameter of 318 nm. A relatively low concentration level was observed in the near field of the machine with an aerosol number concentration of ∼104 #/cm3. A higher concentration level on the operator was attained during the unpacking and cleaning steps, showing an inhalable fraction of 1.73 ± 0.30 mg/m3. Al and Mg nanoparticles were aerosolized at the source (inside the laser powder-bed fusion machine) with a particle size distribution of 153 nm for Al and 117 nm for Mg and an aerosol number concentration reaching ten times that of the background aerosol level. The number or mass concentration of particles in the room atmosphere was increased to double that of the background aerosol level at specific workstations during manufacturing. Metal additive manufacturing is a source of potential occupational exposure to airborne metal nanoparticles. Particle-counting instruments showed high numbers of nanoparticles and some important peaks of particles ranging from 10 nm to 10 µm or larger at specific work tasks in the Additive Manufacturing (AM) environment. A multimetric approach was used to characterize the particle emissions resulting from this type of additive manufacturing.

Cross-sectional study based on occupational aluminium exposure population

To evaluate the different characteristics of cognitive impairment caused by occupational aluminium exposure at different ages, we surveyed 1660 workers in Shanxi Aluminium Plant, China, and assessed their cognitive function and plasma aluminium concentration. In multiple linear regression, the scores of the digit-span test (DST) and digit-span backward test (DSBT) were negatively correlated with plasma aluminium concentration when concentration reached 34.52 μg/L in younger group (＜40 years), while in the middle-aged group (≥40 years) only found when concentration reached 42.25 μg/L (β<0, P < 0.05). In logistic regression, when plasma aluminum concentration reached 42.25μg/L, odds ratios (95 % confidence interval) were 1.695 (1.062-2.705) and 3.270 (1.615-6.620) for DST, 7.644 (3.846-15.192) and 15.308 (4.180-56.059) for DSBT in middle-aged group and younger group, respectively. These results showed that aluminium exposures were associated with cognitive impairment among aluminium-exposed workers, particularly for young workers who were more susceptible.

Al and Si quantitative analysis in aqueous solutions by LIBS method

In the paper results of Laser-Induced Breakdown Spectroscopy (LIBS) measurements of Al and Si content in aqueous solutions are presented. Calibration curves exhibit good linearity and satisfying R² coefficients of determination (over 0.99). The calibration procedures were next used for the determination of Al and Si concentration in biological material transferred into water solutions of unknown Al and Si content. Obtained data were verified by the AAS method (atomic absorption spectrometry). Measurement results showed good conformity. The LIBS spectra were also processed using Factorial Analysis (FA). It was found for Si samples that instead of a classic approach based on the selection of a particular spectral line for the calibration the FA makes possible the use of entire spectra to obtain quantitative information on the investigated material.

Association of Cigarette Smoking With Male Cognitive Impairment and Metal Ions in Cerebrospinal Fluid

Objective: Cigarette smoking might accelerate cognitive impairment; however, this has never been investigated using human cerebrospinal fluid (CSF). We conducted this study to investigate the association between cigarette smoking and cognitive impairment through metal ions in CSF. Methods: We obtained 5-ml CSF samples from routine lumbar puncture procedures in patients undergoing anterior cruciate ligament reconstruction before surgery in China. A total of 180 Chinese males were recruited (80 active smokers and 100 non-smokers). We measured specific cigarette-related neurotoxic metal ions in CSF, including iron, copper, zinc, lead, aluminum, and manganese. Sociodemographic data and history of smoking were obtained. The Montreal Cognitive Assessment (MoCA) was applied. Results: Active smokers had fewer years of education (11.83 ± 3.13 vs. 13.17 ± 2.60, p = 0.01), and higher age (33.70 ± 10.20 vs. 29.76 ± 9.58, p = 0.01) and body mass index (25.84 ± 3.52 vs. 24.98 ± 4.06, p =0.03) than non-smokers. Compared to non-smokers, active smokers had significantly higher CSF levels of iron, zinc, lead, and aluminum and lower MoCA scores (all p < 0.05). Average daily numbers of cigarettes smoked negatively correlated with the MoCA scores (r = -0.244, p = 0.048). In young smokers, CSF manganese levels negatively correlated with MoCA scores (r = -0.373, p = 0.009). Conclusions and Relevance: Cigarette smoking might be associated with male cognitive impairment, as shown by lower MoCA scores and higher levels of CSF iron, zinc, lead, and aluminum in active smokers. This might be early evidence of cigarette smoking accelerating male cognitive impairment.

Antioxidant Property of the Egyptian Propolis Extract Versus Aluminum Silicate Intoxication on a Rat's Lung: Histopathological Studies

In this study, we evaluated the inflammatory responses induced by aluminum silicate (AS) cytotoxicity in rat lungs. The prophylactic effect of propolis extract was evaluated in 60 adult male albino rats. The rats were divided into six groups: (1) a normal, healthy control group; (2) a normal group fed with 200 mL of propolis extract/Kg; (3) a low-dose positive control group injected with 5 mg/kg of AS; (4) a treated group given propolis and a low dose of AS; (5) a high-dose positive control group injected with 20 mg/kg of AS; and (6) a treated group given propolis with a high-dose of AS. At the end of the two-month experiment, the rats’ lungs were removed. For each pair of lungs, one portion was subjected to biochemical analysis and the other underwent hematoxylin and eosin (H&E) staining in order to study its histology. The rats that received AS doses displayed significant disorders in their antioxidant contents as well as in their enzymatic activities and their histopathological structures revealed severe damage to their lung tissues. Upon the rats being treated with propolis, the enzymatic and antioxidant contents improved and partial improvements in the lung structures appeared, including minimized congestion, a reduced hemorrhage of blood vessels and preserved bronchioles, alveolar ducts, and alveoli. The prophylactic effectiveness of propolis extract on the cytotoxicity of AS, owing to the antioxidant properties of propolis, were studied.

Aluminum-Induced Toxicity in Salivary Glands of Mice After Long-term Exposure: Insights into the Redox State and Morphological Analyses

Several studies indicate aluminum (Al) as a potent toxicant, mainly related to central nervous system disorders. However, investigations about the Al effects over salivary glands are still scarce. In this way, the present study aimed to investigate whether the Al chloride (AlCl₃) is able of triggering oxidative stress in parotid and submandibular glands of mice and also, if any morphological impairment is observed. For this, twenty mice were divided into two groups: Exposed group (EG), which received 18.5 mg/kg of AlCl₃ by intragastric gavage for 60 days and control group (CG), which received distilled water by intragastric gavage during the same period of time. After that, levels of reduced glutathione (GSH) and malonaldehyde (MDA) were analyzed and we performed morphological analyses by evaluating the area of parenchyma, stroma, acini, and ducts in both glands. Statistical analyses were performed by Student's t test and two-way ANOVA, adopting p < 0.05. No abnormal body weight was observed and data indicates that although both major salivary glands are susceptible to Al-induced oxidative stress, by increasing MDA and reducing GSH, only submandibular glands decreased the parenchyma and increased stroma area. Moreover, the submandibular glands showed smaller total area of acini and higher total area of ducts, in comparison with the control group. Notably, AlCl₃ induces oxidative stress in both glands, however, submandibular glands showed to be more susceptible to Al effects than parotid glands. Our study gives evidences about Al toxicity in parotid and submandibular glands and claims for new investigations to understand more mechanisms of Al-induced toxicity.

Effect of environmental toxicants on neuronal functions

In the last few years, neurodegenerative diseases like Alzheimer's disease (AD) and Parkinson's disease (PD) have attracted attention due to their high prevalence worldwide. Environmental factors may be one of the biggest reasons for these diseases related to neuronal dysfunctions. Most of neuronal disorders are strongly associated with pre- and postnatal exposure to environmental toxins released from industries. Some of the neurotoxic metals such as lead, aluminum, mercury, manganese, cadmium, and arsenic as well as some pesticides and metal-based nanoparticles have been involved in AD and PD due to their ability to produce senile/amyloid plaques and NFTs which are the main feature of these neuronal dysfunctions. Exposure to solvents is also majorly responsible for neurodegenerative disorders. The present review highlights the impact of omnipresent heavy metals with some other neurotoxins on human health and how they give rise to neuronal dysfunctions which in turn causes socio-economic consequences due to increasing pollution worldwide. Graphical abstract.

Nanoparticle Exposure and Workplace Measurements During Processes Related to 3D Printing of a Metal Object

Metal 3D printing has many potential uses within prototyping and manufacturing. Selective laser melting (SLM) is a process that uses metal powders in the micrometer range as printing material. The particle release from the entire SLM printing process is not well-studied. While the 3D printing itself often occurs in a sealed chamber, activities related to the process can potentially release harmful metal particles to the indoor working environment through resuspension of the printing powder or via incident nanoparticles generated during printing. The objective of this study was to improve the understanding of particle exposure in work processes associated with 3D printing and potential needs for interventions by a case study conducted in a 3D printing facility. In this setting, direct release and dispersion of particles throughout the workspace from processes related to metal 3D printing was investigated. The release from five activities were studied in detail. The activities included post-printing cleaning, object annealing, and preparation of new base substrate for the next printing was. Three of the five measured activities caused particles number concentrations in the working environment to increase above background levels which were found to be 8·10² cm^-3. Concentrations during chamber emptying and the open powder removal system (PRS) cleaning processes increased to 10⁴ and 5·10³ cm^-3, respectively, whereas grinding activity increased number concentrations to 2.5·10⁵ cm^-3. Size distributions showed that particles were mainly smaller than 200 nm. Respirable mass concentrations were 50.4 μg m^-3, collected on filters. This was corroborated by respirable mass measured with a DustTrak of 58.4 μg m^-3. Respirable mass concentrations were below the occupational exposure limits in Denmark for an 8 h time-weighted average.

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.

Iron Dyshomeostasis Participated in Rat Hippocampus Toxicity Caused by Aluminum Chloride

Aluminum (Al) alters iron regulatory factors content and leads to the changes in iron-related proteins causing iron accumulation. But limited evidence ascertains this hypothesis. Therefore, our experiment was conducted and four groups of male Wistar rats were orally administrated of 0, 50, 150, and 450 mg/kg BW/d aluminum chloride (AlCl₃) for 90 days by drinking water, respectively. The cognitive function, pathological lesion of hippocampus, oxidative stress, as well as iron-related proteins and iron regulatory factors expression were detected. The results showed that AlCl₃ remarkably induced the oxidative stress and pathological lesion in the hippocampus and impaired the learning-memory ability. The contents of Al and iron increased in all AlCl₃-exposed groups. Meanwhile, the increased divalent metal transporter 1 (DMT1) expression enhanced iron import and the decreased ferroportin 1 (Fpn1) expression reduced iron export in AlCl₃-exposed groups. The iron accumulated and ferritin heavy chains (Fth) expression decreased in all AlCl₃-exposed groups led to an increase in free iron. The study also showed that iron regulatory factor iron regulatory protein 2 (IRP2) was decreased and hepcidin was increased in AlCl₃-exposed groups. The results indicated that AlCl₃ induces iron dyshomeostasis presenting as iron accumulation, the disordered expression of iron import, export, store, and regulatory proteins in rat hippocampus accompanied with oxidative stress, pathological lesion, and impaired learning-memory ability.

Theoretical characterization of Al(III) binding to KSPVPKSPVEEKG: Insights into the propensity of aluminum to interact with key sequences for neurofilament formation

Classical molecular dynamic simulations and density functional theory are used to unveil the interaction of aluminum with various phosphorylated derivatives of the fragment KSPVPKSPVEEKG (NF13), a major multiphosphorylation domain of human neurofilament medium (NFM). Our calculations reveal the rich coordination chemistry of the resultant structures with a clear tendency of aluminum to form multidentate structures, acting as a bridging agent between different sidechains and altering the local secondary structure around the binding site. Our evaluation of binding energies allows us to determine that phosphorylation has an increase in the affinity of these peptides towards aluminum, although the interaction is not as strong as well-known chelators of aluminum in biological systems. Finally, the presence of hydroxides in the first solvation layer has a clear damping effect on the binding affinities. Our results help in elucidating the potential structures than can be formed between this exogenous neurotoxic metal and key sequences for the formation of neurofilament tangles, which are behind of some of the most important degenerative diseases.

Geraniol attenuates oxidative stress, bioaccumulation, serological and histopathological changes during aluminum chloride-hepatopancreatic toxicity in male Wistar rats

Aluminum chloride (AlCl₃) has different industrial applications including manufacturing paint and water treatment. The present study was designed to evaluate the alleviating effect of geraniol against AlCl₃-induced hepatopancreatic toxicity. To this end, forty male Wistar rats were divided into control (0.9% NaCl, IP), geraniol (100 mg/kg orally), AlCl₃ (70 mg/kg, IP), and AlCl₃ (70 mg/kg, IP) plus geraniol (100 mg/kg orally) groups and then were treated daily for 28 days. Based on the results, serum cholesterol, triglyceride, as well as liver and pancreas enzymes increased significantly (P < 0.05) while the level of insulin significantly decreased in AlCl₃-treated rats compared to the control group (P < 0.05). The presence of geraniol relieved the toxic effects of AlCl₃ as well. On the other hand, the level of malondialdehyde (MDA) increased in the AlCl₃-treated group while the activities of glutathione peroxidase and the total antioxidant activity demonstrated a reduction. However, the MDA level decreased while the antioxidant enzymes increased in co-treated with geraniol group. Histopathological examination revealed that simultaneous treatment with geraniol in AlCl₃ intoxicated rats ameliorate the liver lesions such as necrosis, inflammatory cell infiltration, vacuolar degeneration, along with hyperemia and the cell density of the Langerhans islands. Finally, the results indicated that geraniol attenuated the side effect of AlCl₃-induced hepatopancreatic toxicity.

Aluminum Exposure and Gestational Diabetes Mellitus: Associations and Potential Mediation by n-6 Polyunsaturated Fatty Acids

As the earth's third most abundant element with various industrial applications, aluminum (Al) has received increasing concerns over its potential adverse health effects. Although Al exposure has been suggested to increase the risks of type 2 diabetes, little has been done to explore Al exposure in pregnant women and potential impact on the incidence of gestational diabetes mellitus (GDM). Our present study demonstrated positive associations between Al concentrations in maternal plasma collected in the first trimester of pregnancy and GDM risks (P_trend < 0.001) based on a nested case-control study from Wuhan, China, including 305 GDM cases and 305 healthy controls. The highest tertile of plasma Al concentrations corresponded to an odds ratio of 4.03 (95% confidence interval: [2.14, 7.58]) relative to the lowest tertile, after the adjustment for established GDM risk factors and other plasma metals. We also observed significant correlations between plasma Al and several plasma polyunsaturated fatty acids (PUFA; e.g., linoleic acid 18:2 n-6) levels. In addition, mediation effects on the associations of Al exposure with GDM risks were observed for n-6 PUFAs (estimated mediation percentage: 48.3%) and total PUFAs (48.9%). Our study is not only by far the largest study of its kind to demonstrate maternal Al exposure and the association with GDM risks, but it also offers an insight into the potential mediation roles of n-6 PUFAs in an epidemiological setting. These findings contribute to a better understanding of perinatal Al exposure and GDM risks.

Natural Compounds Rosmarinic Acid and Carvacrol Counteract Aluminium-Induced Oxidative Stress

Aluminum accumulation, glutathione (GSH) and malondialdehyde (MDA) concentrations as well as catalase (CAT) and superoxide dismutase (SOD) activities were determined in erythrocytes and brain and liver homogenates of BALB/c mice treated with Al3+ (7.5 mg/kg/day (0.15 LD50) as AlCl3 (37.08 mg/kg/day), whereas HCl (30.41 mg/kg/day) was used as Cl- control, the treatments were performed for 21 days, i.p., in the presence and absence of rosmarinic acid (0.2805 mg/kg/day (0.05 LD50), 21 days, i.g.) or carvacrol (0.0405 mg/kg/day (0.05 LD50), 21 days, i.g.). The treatment with AlCl3 increased GSH concentration in erythrocytes only slightly and had no effect on brain and liver homogenates. Rosmarinic acid and carvacrol strongly increased GSH concentration in erythrocytes but decreased it in brain and liver homogenates. However, AlCl3 treatment led to Al accumulation in mice blood, brain, and liver and induced oxidative stress, assessed based on MDA concentration in the brain and liver. Both rosmarinic acid and carvacrol were able to counteract the negative Al effect by decreasing its accumulation and protecting tissues from lipid peroxidation. AlCl3 treatment increased CAT activity in mice brain and liver homogenates, whereas the administration of either rosmarinic acid or carvacrol alone or in combination with AlCl3 had no significant effect on CAT activity. SOD activity remained unchanged after all the treatments in our study. We propose that natural herbal phenolic compounds rosmarinic acid and carvacrol could be used to protect brain and liver against aluminum induced oxidative stress leading to lipid peroxidation.