Analysis of brain regional distribution of aluminium in rats via oral and intraperitoneal administration

Agmatine prevents the memory impairment and the dysfunction of hippocampal GSK-3β and ERK signaling induced by aluminum nanoparticle in mice

The growing usage of aluminum nanoparticles (Al-NP) and their exposure may influence body function. Considering the proposed relationship between Al and the pathogenesis of Alzheimer's disease and the concern about the effect of this nanoparticle on brain health and cognitive function, the use of neuroprotective agents might be helpful. According to the reported neuroprotective effects of agmatine, in the present study, the possible protective effect of agmatine was assessed in mice model of Al-NP-induced memory impairment. In addition, due to the roles of hippocampal Glycogen synthase kinase-3 beta (GSK-3β) and ERK signaling in memory and its disorders, these pathways were also investigated. Al-NP (10 mg/kg/p.o.) with/without agmatine (5 or 10 mg/kg/i.p.) was administered to adult male NMRI mice for 5 days. Novel object recognition (NOR) test session was used to assess cognitive function. Following the behavioral assessments, the hippocampi were used to determine the phosphorylated and total levels of GSK-3β and ERK as well as GAPDH using western blot analysis. The results showed that Al-NP impaired NOR memory in mice while agmatine 10 mg/kg prevented the memory deficit induced by Al-NP. Furthermore, Al-NP activated GSK-3β as well as ERK signals within the hippocampus while agmatine prevented the effects of Al-NP on GSK-3β and ERK signals within the hippocampus. Besides supporting the neuroprotective effects of agmatine, these findings suggest the possibility of the connection of hippocampal GSK-3β and ERK signaling in the neuroprotective effect of this polyamine against Al-NP.

Mitochondrial Toxicant-Induced Neuronal Apoptosis in Parkinson's Disease: What We Know so Far

Parkinson's disease (PD) is one of the most common progressive neurodegenerative diseases caused by the loss of dopamine-producing neuronal cells in the region of substantia nigra pars compacta of the brain. During biological aging, neuronal cells slowly undergo degeneration, but the rate of cell death increases tremendously under some pathological conditions, leading to irreversible neurodegenerative diseases. By the time symptoms of PD usually appear, more than 50 to 60% of neuronal cells have already been destroyed. PD symptoms often start with tremors, followed by slow movement, stiffness, and postural imbalance. The etiology of PD is still unknown; however, besides genetics, several factors contribute to neurodegenerative disease, including exposure to pesticides, environmental chemicals, solvents, and heavy metals. Postmortem brain tissues of patients with PD show mitochondrial abnormalities, including dysfunction of the electron transport chain. Most chemicals present in our environment have been shown to target the mitochondria; remarkably, patients with PD show a mild deficiency in NADH dehydrogenase activity, signifying a possible link between PD and mitochondrial dysfunction. Inhibition of electron transport complexes generates free radicals that further attack the macromolecules leading to neuropathological conditions. Apart from that, oxidative stress also causes neuroinflammation-mediated neurodegeneration due to the activation of microglial cells. However, the mechanism that causes mitochondrial dysfunction, especially the electron transport chain, in the pathogenesis of PD remains unclear. This review discusses the recent updates and explains the possible mechanisms of mitochondrial toxicant-induced neuroinflammation and neurodegeneration in PD.

Chlorogenic acid relieves lead-induced cognitive impairments and hepato-renal damage via regulating the dysbiosis of the gut microbiota in mice

Lead (Pb), a heavy metal which is widely recognized as an environmental toxicant, is transported from the earth's crust into the human body to a significant extent. To control and reduce the hazard of Pb burdens in the human body, chlorogenic acid (CGA) has been used to antagonize Pb-induced cognitive impairments, and hepatic and renal toxicity in the present study. Seven-week-old male Kunming mice were treated with PbCl2 (1.34 g L-1 in drinking water) and/or CGA (30 mg per kg mouse per day) by gavage administration for 8 weeks. In this study, we evaluated behavior tests, serum biochemical parameters, biomarkers of oxidative stress, and community structure of gut microbiota in mice to explore the potential mechanism of the protective effect. Based on our results, CGA appreciably prevented memory impairment, the release of serum biomarkers, and oxidative stress caused by Pb intake. CGA significantly inhibited Pb-induced increase of cytoplasmic NF-κB, Bax, cytochrome C, and caspase-9 protein expressions. Furthermore, Pb + CGA treatment had a remarkable reversion effect of the gut microbiota composition change induced by Pb, for example increasing the ratio of Helicobacter from 2.95% (Pb) to 11.24% (Pb + CGA) and decreasing the ratio of the Lachnospiraceae_NK4A136_ group from 7.09% (Pb) to 2.68% (Pb + CGA), which suggests that CGA is a superior natural product to eliminate Pb-induced nephrotoxicity and hepatotoxicity.

Effect of Aluminum Exposure on Glucose Metabolism and Its Mechanism in Rats

The effects of aluminum (Al) exposure on glucose metabolism and its mechanism were investigated. A total of 30 healthy Wistar male rats were randomly divided into two groups: control (GC) and experimental (GE). The GC group received intraperitoneal normal saline. The GE was established by intraperitoneal injected AlCl₃ solution at 10 mg/kg for 30 days. Fasting blood glucose (FBG) and serum levels of insulin (FINS) were measured. The insulin resistance index (HOMA-IR) and pancreatic β cell function index (HOMA-β) were calculated and analyzed with homeostasis model assessment (HOMA). Pancreatic tissue was taken for pathological examination. Glucose transporter 4 (GLUT4) expression in skeletal muscle was detected by quantitative PCR and Western blot. Levels of FBG and HOMA-IR in GE were higher than those in GC at day 10 and 20 (P < 0.05). FINS in GE were higher than those in GC at day 10 and 20, and lower than those in GC at day 30 (P < 0.05). HOMA-β in GE was lower than that of GC at every time point (P < 0.05). Pathology showed that pancreatic damage changed more profoundly with prolongation of time in GE. Expression levels of GLUT4 mRNA and protein in rat skeletal muscle in GE were significantly lower than those in GC (P < 0.05). The results suggested that Al exposure affected glucose metabolism through pancreatic damage and reduction of GLUT4 expression.

Aluminum toxicity related to SOD and expression of presenilin and CREB in Bombyx mori

Aluminum (Al) is an important environmental metal factor that can be potentially associated with pathological changes leading to neurotoxicity. The silkworm, Bombyx mori, is an important economic insect and has also been used as a model organism in various research areas. However, the toxicity of Al on silkworm physiology has not been reported. Here, we comprehensively investigate the toxic effects of Al on the silkworm, focusing on its effects on viability and development, superoxide dismutase (SOD) activity, and the expression of presenilin and cAMP response element-binding protein (CREB) in BmE cells and silkworm larvae. BmE cell viability decreased after treatment with aluminum chloride (AlCl₃ ) in both dose- and time-dependent manners. When AlCl₃ solution was injected into newly hatched fifth instar larvae, both larval weight gain and survival rate were significantly decreased in a manner correlating with AlCl₃ dose and developmental stage. Furthermore, when BmE cells and silkworm larvae were exposed to AlCl₃ , SOD activity decreased significantly relative to the control group, whereas presenilin expression increased more than twofold. Additionally, CREB and phosphorylated CREB (p-CREB) expression in the heads of fifth instar larvae decreased by 28.0% and 50.0%, respectively. These results indicate that Al inhibits the growth and development of silkworms in vitro and in vivo, altering SOD activity and the expressions of presenilin, CREB, and p-CREB. Our data suggest that B. mori can serve as a model animal for studying Al-induced neurotoxicity or neurodegeneration.

Size-Dependent Neurotoxicity of Aluminum Oxide Particles: a Comparison Between Nano- and Micrometer Size on the Basis of Mitochondrial Oxidative Damage

Aluminum nanoparticles (AlNPs) are among the most abundantly produced nanosized particles in the market. There is limited information about the potential harmful effects of aluminum oxide due to its particle size on human health. Considering the toxic effects of Al on brain as its target tissue, in this study, the toxicity of nanoparticles, microparticles, and ionic forms of Al on rat brain and isolated mitochondria was evaluated. Sixty male Wistar rats were divided into ten groups (six rats each), in which group I was the control, and the other groups were administered different doses of Al nanoparticles, Al microparticles (AlMP), and Al ionic forms (2, 4, and 8 mg/kg, i.p.) for 28 days. After 24 h, the animals were killed, brain tissue was separated, the mitochondrial fraction was isolated, and oxidative stress markers were measured. Also, mitochondrial function was assayed by MTT test. The results showed that all forms of Al particles induced ROS formation, lipid peroxidation, protein oxidation, glutathione depletion, mitochondrial dysfunction, and gait abnormalities in a dose-dependent manner. In addition, Al particles decreased mitochondrial membrane potential. These data indicated that oxidative stress might contribute to the toxicity effects of Al. Comparison of oxidative stress markers between all forms of Al revealed that the toxic effect of AlNP on brain tissue was substantially more than that caused by AlMP and bulk form. This study showed more neurotoxicity of AlNPs compared to other forms on brain oxidative damage that probably is due to more penetration into the brain.

Behavioral effects of long-term oral administration of aluminum ammonium sulfate in male and female C57BL/6J mice

Background

Aluminum (Al) is considered to be a neurotoxic metal, and excessive exposure to Al has been reported to be a potential risk factor for neurodegenerative diseases. Al ammonium sulfate is one of the Al compounds that is widely used as a food additive. However, the effects of the oral administration of Al ammonium sulfate on physical development and behavior remain to be examined.

Methods

In this study, we investigated the effects of the administration of Al ammonium sulfate 12‐water dissolved in drinking water (0.075 mg/mL) beginning in adolescence on various types of behavior in adult female C57BL/6J mice through a battery of behavioral tests (low‐dose experiment; Experiment 1). We further examined the behavioral effects of the oral administration of a higher dose of the Al compound in drinking water (1 mg/mL) beginning in the prenatal period on behavior in adult male and female mice (high‐dose experiment; Experiment 2).

Results

In the low‐dose experiment, in which females’ oral intake of Al was estimated to be 0.97 mg Al/kg/d as adults, Al‐treated females exhibited an increase in total arm entries in the elevated plus maze test, an initial decrease and subsequent increase in immobility in the forced swim test, and reduced freezing in the fear conditioning test approximately 1 month after the conditioning session compared with vehicle‐treated females (uncorrected P < .05). However, the behavioral differences did not reach a statistically significant level after correction for multiple testing. In the high‐dose experiment, in which animals’ oral intakes were estimated to be about ten times higher than those in the low‐dose experiment, behavioral differences found in the low‐dose experiment were not observed in high‐dose Al‐treated mice, suggesting that the results of the low‐dose experiment might be false positives. Additionally, although high‐dose Al‐treated females exhibited increased social contacts with unfamiliar conspecifics and impaired reference memory performance, and high‐dose Al‐treated mice exhibited decreases in prepulse inhibition and in correct responses in the working memory task (uncorrected P < .05), the differences in any of the behavioral measures did not reach the significance level after correction for multiple testing.

Conclusion

Our results show that long‐term oral exposure to Al ammonium sulfate at the doses used in this study may have the potential to induce some behavioral changes in C57BL/6J mice. However, the behavioral effects of Al were small and statistically weak, as indicated by the fact that the results failed to reach the study‐wide significance level. Thus, further study will be needed to replicate the results and reevaluate the behavioral outcomes of oral intake of Al ammonium sulfate.

Aluminum (Al) ammonium sulfate was orally administered to C57BL/6J mice (estimated dose of 0.97‐9.78 Al mg/kg/d). Behavioral effects of Al were assessed in a battery of behavioral tests in mice in adulthood. Statistically significant behavioral differences were not found between Al‐ and vehicle‐treated mice.

N-acetyl-L-tryptophan, a substance-P receptor antagonist attenuates aluminum-induced spatial memory deficit in rats

Neuroinflammation plays an important role in the pathophysiology of Alzheimer's disease. Neurokinin substance P is a key mediator which modulates neuroinflammation through neurokinin receptor. Involvement of substance P in Alzheimer's disease is still plausible and various controversies exist in this hypothesis. Preventing the deleterious effects of substance P using N-acetyl-L-tryptophan, a substance P antagonist could be a promising therapeutic strategy. This study was aimed to evaluate the effect of N-acetyl-L-tryptophan on aluminum induced spatial memory alterations in rats. Memory impairment was induced using aluminum chloride (AlCl₃) at a dose of 10 mg/kg for 42 d. After induction of dementia, rats were exposed to 30 and 50 mg/kg of N-acetyl-L-tryptophan for 28 d. Spatial memory alterations were measured using Morris water maze. Acetylcholinesterase activity and antioxidant enzyme glutathione level were assessed in hippocampus, frontal cortex and striatum. The higher dose of N-acetyl-L-tryptophan (50 mg/kg) significantly improved the aluminum induced memory alterations. N-acetyl-L-tryptophan exposure resulted in significant increase in acetylcholinesterase activity and glutathione level in hippocampus. The neuroprotective effect of N-acetyl-L-tryptophan could be due to its ability to block substance P mediated neuroinflammation, reduction in oxidative stress and anti-apoptotic properties. To conclude, N-acetyl-L-tryptophan may be considered as a novel neuroprotective therapy in Alzheimer's disease.

Identification of the Al-binding proteins that account for aluminum neurotoxicity and transport in vivo

Studies have shown that aluminum (Al) is the most abundant neurotoxic element on Earth, and is implicated in the pathogenesis of Alzheimer's disease (AD). However, the mechanisms underlying Al-induced neurotoxicity are still largely elusive. Based on affinity analyses with Al and LC-LTQ-MS, we have found that serum albumin, brain CK-B and 14-3-3ζ protein have a high affinity for Al³⁺, and albumin has a much stronger affinity for Al than transferrin. The normal activity of CK-B, and physiological combination of 14-3-3ζ with tau can be severely perturbed by Al. We anticipate that our assay will provide a new focus concerning the mechanism underlying Al-induced neurotoxicity, and aid the design of strategies to prevent AD and other human diseases related to Al overload.

Study of potential transfer of aluminum to the brain via the olfactory pathway

Many employees in the aluminum industry are exposed to a range of aluminum compounds by inhalation, and the presence of ultrafine particles in the workplace has become a concern to occupational health professionals. Some metal salts and metal oxides have been shown to enter the brain through the olfactory route, bypassing the blood-brain barrier, but few studies have examined whether aluminum compounds also use this pathway. In this context, we sought to determine whether aluminum was found in rat olfactory bulbs and whether its transfer depended on physicochemical characteristics such as solubility and granulometry. Aluminum salts (chloride and fluoride) and various nanometric aluminum oxides (13nm, 20nm and 40-50nm) were administered to rats by intranasal instillation through one nostril (10μg Al/30μL for 10days). Olfactory bulbs (ipsilateral and contralateral relative to instilled nostril) were harvested and the aluminum content was determined by graphite furnace atomic absorption spectrometry after tissue mineralization. Some transfer of aluminum salts to the central nervous system via the olfactory route was observed, with the more soluble aluminum chloride being transferred at higher levels than aluminum fluoride. No cerebral translocation of any of the aluminas studied was detected.

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.

The Effect of Aluminum Exposure on Reproductive Ability in the Bank Vole (Myodes glareolus)

Human impact on the environment is steadily increasing the amounts of aluminum in the ecosystems. This element accumulates in plants and water, potentially exposing herbivores to its harmful effect. In heavily polluted sites, a decrease in the density of small rodent populations has been observed. This decline may be caused by many factors, including decreased fertility. The aim of the presented research was to determine how aluminum, administered at concentrations similar to those recorded in industrial districts (Al I = 3 mg/l, Al II = 200 mg/l), affects the reproductive abilities of small rodents. As the indicators of reproductive abilities, body weight, weight of the testes and accessory sex glands of males, and uterus weight of females were estimated. In females, the number of matured follicles (types 6, 7, and 8) was analyzed, while in males, the quantity and quality (matured, viable, swollen, motile, head abnormalities) of epididymal sperm cells were assessed. Moreover, the development of testes, measured by spermatogenic index, was determined. The model species was the bank vole. Our results have proven that aluminum impairs adult individuals' reproductive abilities by decreasing the quality and quantity of sperm cells and by causing morphologically abnormal development of the gonads. However, no difference in male organometric parameters was found, and only in females treated with 3 mg/l Al, the uterus weight was higher than control. No differences were found in the total number of matured follicles. These results suggest that the decline in rodent numbers in industrial districts is due, at least in part, to poorer males' reproductive abilities, resulting from exposure to aluminum contamination.

Co-exposure to aluminum and acrylamide disturbs expression of metallothionein, proinflammatory cytokines and induces genotoxicity: Biochemical and histopathological changes in the kidney of adult rats

The individual toxic effects of aluminum and acrylamide are known but there is no data on their combined effects. The present study investigates the toxic effects after combined exposure to these toxicants on: (i) oxidative stress during combined chronic exposure to aluminum and acrylamide on kidney function (ii) correlation of oxidative stress with metallothionein (MT) and inflammatory cytokines expression, DNA damage, and histopathological changes. Rats were exposed to aluminum (50 mg/kg body weight) in drinking water and acrylamide (20 mg/kg body weight) by gavage either individually or in combination for 3 weeks. Exposure rats to aluminum chloride or acrylamide alone and in combination induced nephrotoxicity, as evidenced by a decrease in the 24-h urine volume and uric acid levels in plasma and an increase of plasma creatinine, urea, and blood urea nitrogen levels. Nephrotoxicity was objectified by a significant increase in malondialdehyde level, advanced oxidation protein, and protein carbonyl contents, whereas reduced glutathione, nonprotein thiol, vitamin C levels, catalase, and glutathione peroxidase activities showed a significant decline. Superoxide dismutase activity and its gene expression were increased. Aluminum and acrylamide co-exposure exhibited synergism in various biochemical variables and also in DNA damage. Kidney total MT levels and genes expression of MT1, MT2, and proinflammatory cytokines were increased. All these changes were supported by histopathological observations. Co-exposure to aluminum and acrylamide exhibited synergism and more pronounced toxic effects compared with their individual effects based on various biochemical variables, genotoxic, and histopathological changes. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1044-1058, 2016.

Reduction of adult hippocampal neurogenesis is amplified by aluminum exposure in a model of type 2 diabetes

In this study, we investigated the effects of chronic aluminum (Al) exposure for 10 weeks on cell proliferation and neuroblast differentiation in the hippocampus of type 2 diabetic rats. Six-week-old Zucker diabetic fatty (ZDF) and Zucker lean control (ZLC) rats were selected and randomly divided into Al- and non-Al-groups. Al was administered via drinking water for 10 weeks, after which the animals were sacrificed at 16 weeks of age. ZDF rats in both Al- and non-Al-groups showed increases in body weight and blood glucose levels compared to ZLC rats. Al exposure did not significantly affect body weight, blood glucose levels or pancreatic β-cells and morphology of the pancreas in either ZLC or ZDF rats. However, exposure to Al reduced cell proliferation and neuroblast differentiation in both ZLC and ZDF rats. Exposure to Al resulted in poor development of the dendritic processes of neuroblasts in both ZLC and ZDF rats. Furthermore, onset and continuation of diabetes reduced cell proliferation and neuroblast differentiation, and Al exposure amplified reduction of these parameters. These results suggest that Al exposure via drinking water aggravates the impairment in hippocampal neurogenesis that is typically observed in type 2 diabetic animals.

Analysis of metallic traces from the biodegradation of endomedullary AZ31 alloy temporary implants in rat organs after long implantation times

AZ31 alloy has been tested as a biodegradable material in the form of endomedullary implants in female Wistar rat femurs. In order to evaluate the accumulation of potentially toxic elements from the biodegradation of the implant, magnesium (Mg), aluminium (Al), zinc (Zn), manganese (Mn) and fluorine (F) levels have been measured in different organs such as kidneys, liver, lungs, spleen and brain. Several factors that may influence accumulation have been taken into account: how long the implant has been in place, whether or not the bone is fractured, and the presence of an MgF2 protective coating on the implant. The main conclusions and the clinical relevance of the study have been that AZ31 endomedullary implants have a degradation rate of about 60% after 13 months, which is fully compatible with fracture consolidation. Neither bone fracture nor an MgF2 coating seems to influence the accumulation of trace elements in the studied organs. Aluminium is the only alloying element in this study that requires special attention. The increase in Al recovered from the sampled organs represents 3.95% of the amount contained in the AZ31 implant. Al accumulates in a statistically significant way in all the organs except the brain. All of this suggests that in long-term tests AZ31 may be a suitable material for osteosynthesis.

Tannoid principles of Emblica officinalis renovate cognitive deficits and attenuate amyloid pathologies against aluminum chloride induced rat model of Alzheimer's disease

BACKGROUND/AIMS

Emblica officinalis is mentioned as a maharasayana in many Ayurvedic texts and promotes intelligence, memory, freedom from disease, longevity, and strength of the senses. The present study has been designed to explore the memory-enhancing effect of the tannoid principles of E. officinalis (EoT) at the biochemical, anatomical, behavioral, and molecular levels against aluminum chloride (AlCl3) induced Alzheimer's disease (AD) in rats. Aluminum is reported to have an important role in the etiology, pathogenesis, and development of AD.

METHODS

Male Wistar rats were divided into control, AlCl3 treated, AlCl3 and EoT (50, 100, and 200 mg/kg bw) co-treated, and EoT (200 mg/kg bw) alone treated groups. In control and experimental rats, behavior tests including water maze and open field test, estimation of aluminum, assay of acetylcholinesterase (AChE) activity, and expression of amyloidogenic proteins were performed.

RESULTS

Intraperitonial injection of AlCl3 (100 mg/kg bw) for 60 days significantly elevated the concentration of aluminum (Al), activity of AChE and protein expressions of amyloid precursor protein, A-beta1-42, beta-, and gamma-secretases as compared to control group in hippocampus and cortex. Co-administration of EoT orally to AlCl3 rats for 60 days significantly revert back the Al concentration, AChE activity, and A-beta synthesis-related molecules in the studied brain regions. The spatial learning, memory, and locomotor impairments observed in AlCl3 treated rats were significantly attenuated by EoT.

CONCLUSION

Therefore, EoT may be a promising therapy in ameliorating neurotoxicity of aluminum, however further studies are warranted to elucidate the exact mechanism of action of EoT.

Physical, chemical, and immunohistochemical investigation of the damage to salivary glands in a model of intoxication with aluminium citrate

Aluminum absorption leads to deposits in several tissues. In this study, we have investigated, to our knowledge for the first time, aluminum deposition in the salivary glands in addition to the resultant cellular changes in the parotid and submandibular salivary glands in a model of chronic intoxication with aluminum citrate in rats. Aluminum deposits were observed in the parotid and submandibular glands. Immunohistochemical evaluation of cytokeratin-18 revealed a decreased expression in the parotid gland with no changes in the submandibular gland. A decreased expression of α-smooth muscle actin was observed in the myoepithelial cells of both glands. The expression of metallothionein I and II (MT-I/II), a group of metal-binding proteins, which are useful indicators for detecting physiological responses to metal exposure, was higher in both glands. In conclusion, we have shown that at a certain time and quantity of dosage, aluminum citrate promotes aluminum deposition in the parotid and submandibular glands, leads to an increased expression of MT-I/II in both the glands, damages the cytoskeleton of the myoepithelial cells in both glands, and damages the cytoskeleton of the acinar/ductal cells of the parotid glands, with the submandibular glands showing resistance to the toxicity of the latter.

Role of propolis (bee glue) in improving histopathological changes of the kidney of rat treated with aluminum chloride

Humans are frequently exposed to aluminum from various food additives, therapeutic treatments and the environment, and it can be potentially toxic. This study is aimed to elucidate the protective effects of propolis against aluminum chloride (AlCl3 )-induced histopathological and immunohistochemical changes in kidney tissues of rats. Sixty Wistar Albino male rats (average weight 250-300 g) were divided into three equal groups. The first served as a negative control. The second received AlCl₃ (34 mg/kg bw, 1/ 25 LD 50). The third were administered AlCl₃ (34 mg/kg bw, 1/ 25 LD 50) plus propolis (50 mg/kg bw). Doses were given once daily via a gavage for 8 weeks every day. The results showed that shrunken glomeruli, intraglomerular congestion, loss of apical microvilli, degeneration of mitochondria and widened rough endoplasmic reticulum were also observed in the Proximal Convoluted Tubules of these animals. Treatment with propolis ameliorated the harmful effects of AlCl₃ ; this was also proved histopathologically by the noticeable improvement in the renal tissues. There were also significant variations in the expressed of ki-67 and p53 proteins. It can be concluded that propolis may be promising as a natural therapeutic agent in AlCl₃ -induced renal toxicity and oxidative stress in rat kidneys.

Oxidative stress and mitochondrial dysfunction in aluminium neurotoxicity and its amelioration: a review

Aluminium is light weight and toxic metal present ubiquitously on earth which has gained considerable attention due to its neurotoxic effects. The widespread use of products made from or containing aluminium is ensuring its presence in our body. There is prolonged retention of a fraction of aluminium that enters the brain, suggesting its potential for accumulation with repeated exposures. There is no known biological role for aluminium within the body but adverse physiological effects of this metal have been observed in mammals. The generation of oxidative stress may be attributed to its toxic consequences in animals and humans. The oxidative stress has been implicated in pathogenesis of various neurodegenerative conditions including Alzheimer's disease and Parkinson's disease. Though it remains unclear whether oxidative stress is a major cause or merely a consequence of cellular dysfunction associated with neurodegenerative diseases, an accumulating body of evidence implicates that impaired mitochondrial energy production and increased mitochondrial oxidative damage is associated with the pathogenesis of neurodegenerative disorders. Being involved in the production of reactive oxygen species, aluminium may impair mitochondrial bioenergetics and may lead to the generation of oxidative stress. In this review, we have discussed the oxidative stress and mitochondrial dysfunctions occurring in Al neurotoxicity. In addition, the ameliorative measures undertaken in aluminium induced oxidative stress and mitochondrial dysfunctions have also been highlighted.

Protective effects of copper against aluminum toxicity on acetylcholinesterase and catecholamine contents of different regions of rat's brain

The probable protective effects of copper on the acetylcholinesterase activity and the catecholamine levels in cerebellum, cortex and mid-brain of rat, which was intoxicated by aluminum, were studied during short and long terms. In this respect, male Wistar rats weighing 200-250 g were received daily intraperitoneal doses of aluminum, copper and also combined doses of both metals for 15 days (Al 10 mg kg(-1) BW and Cu 1 mg kg(-1) BW), 30 days (Al 5 mg kg(-1) BW and Cu 0.5 mg kg(-1) BW) and 60 days (Al 1 mg kg(-1) BW and Cu 0.1 mg kg(-1) BW), respectively. The results obtained from the short period of exposure (15 days) showed that aluminum produced significant (P < 0.05) decreases in the acetylcholinesterase activity by 24.14, 23.30 and 25.81 %. Similarly, the catecholamine levels were reduced by 10.69, 12.25 and 12.64 % in cerebellum, cortex and mid-brain, respectively. Treatment with copper increases both acetylcholinesterase activity and catecholamine contents of cerebellum, cortex and mid-brain. Simultaneous injection of copper and aluminum increased both acetylcholinesterase activity and catecholamine contents in all three parts of rat brain when compared to aluminum-treated group. Same results were also observed following 30 and 60 days of exposures. In overall, it has been found that copper may have a protective-like ability to hinder aluminum toxicity in the brain.

Evaluating the potential role of pomegranate peel in aluminum-induced oxidative stress and histopathological alterations in brain of female rats

Studies have shown that pomegranate, Punica granatum Linn. (Lythraceae), has remarkable biological and medicinal properties. However, the effects of pomegranate peel methanolic extract (PPME) on the aluminum-induced oxidative stress and histopathological change have not been reported yet. To determine the effect of PPME (200 mg/kg bwt) on the aluminum chloride (AlCl₃; 34 mg/kg bwt)-induced neurotoxicity, aluminum accumulation in brain and oxidant/antioxidant status were determined. The change of brain structure was investigated with hematoxylin and eosin, and anti-apoptosis effects of PPME were analyzed by immunohistochemistry. The present study showed an indication of carcinogenicity in the AlCl₃-treated group representing an increase in tissue tumor markers such as tumor necrosis factor-α and angiogenin and inflammation by inducing an increase in prostaglandin E2 and prostaglandin F2α. PPME protected brain through decreasing the aluminum accumulation and stimulating antioxidant activities and anti-apoptotic proteins namely Bcl-2. Therefore, these results indicated that pomegranate peel methanolic extract could inhibit aluminum-induced oxidative stress and histopathological alternations in brain of female rats, and these effects may be related to anti-apoptotic and antioxidants activities.

Aluminum overload increases oxidative stress in four functional brain areas of neonatal rats

BACKGROUND

Higher aluminum (Al) content in infant formula and its effects on neonatal brain development are a cause for concern. This study aimed to evaluate the distribution and concentration of Al in neonatal rat brain following Al treatment, and oxidative stress in brain tissues induced by Al overload.

METHODS

Postnatal day 3 (PND 3) rat pups (n =46) received intraperitoneal injection of aluminum chloride (AlCl3), at dosages of 0, 7, and 35 mg/kg body wt (control, low Al (LA), and high Al (HA), respectively), over 14 d.

RESULTS

Aluminum concentrations were significantly higher in the hippocampus (751.0 ± 225.8 ng/g v.s. 294.9 ± 180.8 ng/g; p < 0.05), diencephalon (79.6 ± 20.7 ng/g v.s. 20.4 ± 9.6 ng/g; p < 0.05), and cerebellum (144.8 ± 36.2 ng/g v.s. 83.1 ± 15.2 ng/g; p < 0.05) in the HA group compared to the control. The hippocampus, diencephalon, cerebellum, and brain stem of HA animals displayed significantly higher levels of lipid peroxidative products (TBARS) than the same regions in the controls. However, the average superoxide dismutase (SOD) activities in the cerebral cortex, hippocampus, cerebellum, and brain stem were lower in the HA group compared to the control. The HA animals demonstrated increased catalase activity in the diencephalon, and increased glutathione peroxidase (GPx) activity in the cerebral cortex, hippocampus, cerebellum, and brain stem, compared to controls.

CONCLUSION

Aluminum overload increases oxidative stress (H2O2) in the hippocampus, diencephalon, cerebellum, and brain stem in neonatal rats.

Lethality, accumulation and toxicokinetics of aluminum in some tissues of male albino rats

In the present work, the lethality percentiles including median lethal doses (LD50), accumulation, distribution and toxicokinetics of aluminum in the liver, kidney, intestine, brain and serum of male albino rats, following a single oral administration were studied throughout 1, 3, 7, 14 and 28 days. The estimated LD50 at 24 h was 3.45 g Al/kg body weight (b.wt.). The utilized dose of Al was 1/50 LD50 (0.07 g Al/kg b.wt.). Aluminum residues, in Al-treated rats, were significantly decreased in response to the experimental periods and were negatively correlated with time. In addition, the hepatic, renal, intestinal, brain and serum Al contents were significantly higher than the corresponding controls at all experimental periods, except the brain that showed significant depletion when compared with its corresponding control after 28 days. Kinetically, the highest average of Al area under concentration − time curves (AUCtotal, μg/g day) and area under moment concentration − time curves (AUMCtotal, µg/g day2) recorded in the brain followed by kidney, serum, intestine and liver. The longest elimination half-life time ( t1/2, day) and the mean residence time (MRT, day) were recorded in the brain followed by the liver, kidney, serum and intestine. On the other hand, the slowest clearance rates (Cls, L/day) of Al, in order, were recorded in brain, kidney, serum, intestine and the liver. The elimination rate constant ( Lz, day−1) of Al from the brain was less than that in the intestine and serum was less than that in the liver and kidney. The computed maximum concentrations ( Cmax) of Al in the intestine > kidney > serum > brain > liver were recorded after 3, 3.8, 2.2, 5.4 and 3.8 days, respectively. The computed starting concentration ( C0, μg) of Al in serum was higher than its level in the intestine followed by the brain, kidney and liver.

The impairment of one-trial passive avoidance learning in chicks caused by prenatal aluminum exposure

Prenatal aluminum exposure may affect the development of the embryo and alter the capacity for learning and memory in adults. The chick embryo is a good experimental model to study the effect of prenatal toxin exposure on cognitive defects in offspring, because it eliminates maternal confounding variables. In the present study, we applied a one-trial passive avoidance-learning task in day-old chicks to examine the effects of prenatal aluminum chloride injections (2, 20, and 200 mM in 200 µl per egg, daily over a period of 4 successive days) on memory consolidation. The data suggest that chicks injected with aluminum chloride (20 mM) daily from E12 to E15 had significantly impaired short-term memory, intermediate-term memory, and long-term memory (LTM) after training (p < .05) but chicks injected with aluminum chloride (2 mM) had impaired LTM only.