Neurotoxic effect of enteral aluminium

Prediction of the dose range for adverse neurological effects of amiodarone in patients from an in vitro toxicity test by in vitro-in vivo extrapolation

Amiodarone is an antiarrhythmic agent inducing adverse effects on the nervous system, among others. We applied physiologically based pharmacokinetic (PBPK) modeling combined with benchmark dose modeling to predict, based on published in vitro data, the in vivo dose of amiodarone which may lead to adverse neurological effects in patients. We performed in vitro–in vivo extrapolation (IVIVE) from concentrations measured in the cell lysate of a rat brain 3D cell model using a validated human PBPK model. Among the observed in vitro effects, inhibition of choline acetyl transferase (ChAT) was selected as a marker for neurotoxicity. By reverse dosimetry, we transformed the in vitro concentration–effect relationship into in vivo effective human doses, using the calculated in vitro area under the curve (AUC) of amiodarone as the pharmacokinetic metric. The upper benchmark dose (BMDU) was calculated and compared with clinical doses eliciting neurological adverse effects in patients. The AUCs in the in vitro brain cell culture after 14-day repeated dosing of nominal concentration equal to 1.25 and 2.5 µM amiodarone were 1.00 and 1.99 µg*h/mL, respectively. The BMDU was 385.4 mg for intravenous converted to 593 mg for oral application using the bioavailability factor of 0.65 as reported in the literature. The predicted dose compares well with neurotoxic doses in patients supporting the hypothesis that impaired ChAT activity may be related to the molecular/cellular mechanisms of amiodarone neurotoxicity. Our study shows that predicting effects from in vitro data together with IVIVE can be used at the initial stage for the evaluation of potential adverse drug reactions and safety assessment in humans.

Aluminium-induced synaptic plasticity injury via the PHF8-H3K9me2-BDNF signalling pathway

Aluminium is an environmental neurotoxin that comes extensively in contact with human being. The molecular mechanism of aluminium toxicity remains unclear. A number of studies have indicated that exposure to aluminium can impair learning and memory function. The purpose of this study was to investigate the mechanism of long-term potentiation(LTP) injury and the related signalling pathway activated by aluminium exposure. The results showed that aluminium treatment produced dose-dependent inhibition of LTP and reduced the activity of Histone H3K9 demethylation (H3K9me2) demethylase and the expression of the PHD (plant homeodomain) finger protein 8 (PHF8). Interestingly, there was no statistically significant difference in the expression of the PHF8 gene, suggesting that aluminium exposure only affects the translation process. Decrease in brain-derived neurotrophic factor (BDNF) expression may be related to the effect of aluminium. With correlation analysis between the hippocampal standardised field excitatory postsynaptic potential (fEPSP) amplitude and the expression of various proteins in the aluminium-exposed rat, the hippocampal standardised fEPSP amplitude was positively correlated with the expression of hippocampal PHF8 and BDNF proteins, and negatively correlated with the expression of hippocampal H3K9me2 protein. The correlation between H3K9me2 and BDNF was also considered negative. The results suggest that changes in synaptic plasticity might be related to changes in these proteins, which were induced by aluminium exposure. In conclusion, chronic aluminium exposure may inhibit PHF8 and prevent it from functioning as a demethylase. This may block H3K9me2 demethylation, decrease BDNF protein expression, and lead to LTP impairment.

Tyrosol prevents AlCl3 induced male reproductive damage by suppressing apoptosis and activating the Nrf-2/HO-1 pathway

Aluminium is a ubiquitous element that occurs naturally in the soil making human exposure to it is unavoidable. Tyrosol is present in olive oil and is known to have antioxidant effects. Therefore, the present study explores the toxic effects of aluminium chloride (AlCl₃ ) and evaluates the possible protection by tyrosol in male rats. Testicular injury was induced by the administration of AlCl₃ (34 mg kg^-1  day^-1 ). Rats were treated with either tyrosol (20 mg kg^-1 day^-1 ) or AlCl3 (34 mg kg^-1 day^-1 ). The experiment lasted for 10 weeks. Biochemical, histopathological and protein expression profiles were determined to decipher the role of tyrosol in protecting the cellular damage. Further, histomorphometric analyses of testes showed deranged architecture along with other noted abnormalities. AlCl₃ group rats' testes showed decreased GSH levels, CAT activities, Nrf-2, HO-1, bcl-2 expressions and sperm motility whereas increased caspase-3 expressions, MDA levels, abnormal and dead/live sperm ratio. However, tyrosol treatment attenuated these changes. The present results demonstrate the beneficial role of tyrosol treatment in AlCl₃ induced testicular toxicity alterations of rat.

Aluminium toxicosis: a review of toxic actions and effects

Aluminium (Al) is frequently accessible to animal and human populations to the extent that intoxications may occur. Intake of Al is by inhalation of aerosols or particles, ingestion of food, water and medicaments, skin contact, vaccination, dialysis and infusions. Toxic actions of Al induce oxidative stress, immunologic alterations, genotoxicity, pro-inflammatory effect, peptide denaturation or transformation, enzymatic dysfunction, metabolic derangement, amyloidogenesis, membrane perturbation, iron dyshomeostasis, apoptosis, necrosis and dysplasia. The pathological conditions associated with Al toxicosis are desquamative interstitial pneumonia, pulmonary alveolar proteinosis, granulomas, granulomatosis and fibrosis, toxic myocarditis, thrombosis and ischemic stroke, granulomatous enteritis, Crohn's disease, inflammatory bowel diseases, anemia, Alzheimer's disease, dementia, sclerosis, autism, macrophagic myofasciitis, osteomalacia, oligospermia and infertility, hepatorenal disease, breast cancer and cyst, pancreatitis, pancreatic necrosis and diabetes mellitus. The review provides a broad overview of Al toxicosis as a background for sustained investigations of the toxicology of Al compounds of public health importance.

Acute aluminum chloride toxicity revisited: Study on DNA damage and histopathological, biochemical and neurochemical alterations in rat brain

AIMS

Due to rapid increase in industrialization in the last few years, use of aluminum (Al) and its alloys have been increased in different industrial fields. Ample evidence supports the neurotoxic effects of chronic aluminum chloride (AlCl₃) administration in rats but acute Al toxicity has been less described so the present study was aimed to investigate the neurotoxic effects of acute AlCl₃.

MAIN METHODS

To investigate such effects 12 male albino Wistar rats were randomly divided into control and test rats. AlCl₃ at a dose of 150 mg/kg was intraperitoneally injected to test rats for 7 days. Rats were subjected to behavioral assessments 24 h after last dose and after behavioral assessment rats were sacrificed to collect brain samples for further neurochemical, biochemical and histopathological examinations.

KEY FINDINGS

In the present study acute administration of AlCl₃ resulted in noticeable behavioral deficits. Cognitive deficits and neuropsychiatric disturbances were evident in AlCl₃ injected rats. Test rats also exhibited marked antioxidant enzymes, cholinergic, serotonergic and dopaminergic dysfunctions and DNA fragmentation. Histopathological alterations were observed in hippocampus and cortex of rats injected with AlCl₃.

SIGNIFICANCE

The observed effects may be due to pro-oxidant nature of Al and its participation in free radical mediated cellular injury. Al by promoting oxidative stress, impairing antioxidant defense system and altering brain neurochemistry may act as a potent neurotoxic agent as evident from observed histopathological alterations in brain of test rats. This investigation may further confirm and shed some more light on deleterious effects of acute Al intoxication on brain.

Isorhynchophylline alleviates learning and memory impairments induced by aluminum chloride in mice

BACKGROUND

To evaluate the effect of Isorhynchophylline (IRN) on the learning and memory impairments induced by aluminum chloride (AlCl3) in mice.

METHODS

Fifty male Balb-c mice (4-month-old) were randomly divided into five groups: control, AlCl3 plus vehicle, AlCl3 plus IRN (20 mg/kg), AlCl3 plus IRN (40 mg/kg) and AlCl3 plus donepezil (5 mg/kg). Learning and memory impairments were induced in mice by subcutaneously injecting with AlCl3 (50 mg/kg) once a day for 8 consecutive weeks. At the same time, mice were intragastrically given vehicle or IRN (20 and 40 mg/kg) or donepezil (5 mg/kg) 30 min before each AlCl3 injection. The spatial learning and memory function was assessed using radial arm maze. After sacrificed, the parameters of oxidative stress and cholinergic system in the brain tissues were examined with ELISA kits. Moreover, the expression of nuclear factor kappa B (NF-κB) signaling pathway was analyzed with western blotting.

RESULTS

The results showed that treatment with IRN could significantly ameliorate the cognitive deficits induced by AlCl3 in mice. In addition, treatment with IRN was found to reduce the level of malondialdehyde, enhance the activities of superoxide dismutases and catalase, increase the level of glutathione, and markedly inhibit the activity of acetylcholinesterase (AChE) in the brain tissues of the AlCl3-treated mice. Moreover, IRN significantly suppressed the phosphorylation of NF-κB p65 and IκBα in the brain tissues of AlCl3-treated mice. However, IRN did not show significant effect on the activity of butyrylcholinesterase.

CONCLUSION

Our findings demonstrated for the first time that IRN could alleviate learning and memory impairments induced by AlCl3 in mice. The neuroprotective effect of IRN against AlCl3-induced AD is probably mediated, at least in part, through inhibiting the AChE activity and reducing the oxidative damage of brain tissue via suppress the NF-κB signaling pathway. These results contributed to a better understanding of the in vivo anti-AD mechanism of IRN. It was concluded that IRN could protect the learning and memory function.

Multiple pharmacological activities of Caesalpinia crista against aluminium-induced neurodegeneration in rats: Relevance for Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia and mainly affects cognitive function of the aged populations. Aluminium, a neurotoxic metal, has been suggested as a contributing factor of AD. Caesalpinia crista is a medicinal plant known for its anti-microbial, anti-inflammatory and anti-oxidant properties. The present study was conducted in order to evaluate the neuroprotective effects of methanolic extracts of C. crista (MECC) on aluminium-induced neurodegeneration in rats. Co-administration with MECC significantly and dose dependently ameliorated the aluminium-dependent cognitive impairment, AChE hyperactivity and oxidative stress in the hippocampus and in the frontal cortex of rat brain. Moreover, MECC reduced the neuronal injury induced by aluminium as shown by the diminution of neuron loss and pyknosis in the CA1 and CA3 regions of the hippocampus. From this study, it is inferred that MECC protect against aluminium-induced behavioral alterations, cognitive function, oxidative stress and neuroinflammation in vivo. Therefore, this plant may serve as a source of natural products having multiple functions and could be utilized as an anti-AD preparation.

Safety Assessment of Alumina and Aluminum Hydroxide as Used in Cosmetics

This is a safety assessment of alumina and aluminum hydroxide as used in cosmetics. Alumina functions as an abrasive, absorbent, anticaking agent, bulking agent, and opacifying agent. Aluminum hydroxide functions as a buffering agent, corrosion inhibitor, and pH adjuster. The Food and Drug Administration (FDA) evaluated the safe use of alumina in several medical devices and aluminum hydroxide in over-the-counter drugs, which included a review of human and animal safety data. The Cosmetic Ingredient Review (CIR) Expert Panel considered the FDA evaluations as part of the basis for determining the safety of these ingredients as used in cosmetics. Alumina used in cosmetics is essentially the same as that used in medical devices. This safety assessment does not include metallic or elemental aluminum as a cosmetic ingredient. The CIR Expert Panel concluded that alumina and aluminum hydroxide are safe in the present practices of use and concentration described in this safety assessment.

Critical analysis of reference studies on the toxicokinetics of aluminum-based adjuvants

We reviewed the three toxicokinetic reference studies commonly used to suggest that aluminum (Al)-based adjuvants are innocuous. A single experimental study was carried out using isotopic 26Al (Flarend et al., Vaccine, 1997). This study used aluminum salts resembling those used in vaccines but ignored adjuvant uptake by cells that was not fully documented at the time. It was conducted over a short period of time (28days) and used only two rabbits per adjuvant. At the endpoint, Al elimination in the urine accounted for 6% for Al hydroxide and 22% for Al phosphate, both results being incompatible with rapid elimination of vaccine-derived Al in urine. Two theoretical studies have evaluated the potential risk of vaccine Al in infants, by reference to an oral "minimal risk level" (MRL) extrapolated from animal studies. Keith et al. (Vaccine, 2002) used a high MRL (2mg/kg/d), an erroneous model of 100% immediate absorption of vaccine Al, and did not consider renal and blood-brain barrier immaturity. Mitkus et al. (Vaccine, 2011) only considered solubilized Al, with erroneous calculations of absorption duration. Systemic Al particle diffusion and neuro-inflammatory potential were omitted. The MRL they used was both inappropriate (oral Al vs. injected adjuvant) and still too high (1mg/kg/d) regarding recent animal studies. Both paucity and serious weaknesses of reference studies strongly suggest that novel experimental studies of Al adjuvants toxicokinetics should be performed on the long-term, including both neonatal and adult exposures, to ensure their safety and restore population confidence in Al-containing vaccines.

Neuroprotective effects of eugenol against aluminiuminduced toxicity in the rat brain

Aluminium (Al) is a neurotoxic metal that contributes to the progression of several neurodegenerative diseases. The aim of the present study was to evaluate the protective effect of dietary eugenol supplementation against aluminium (Al)- induced cerebral damage in rats. Male Wistar rats were divided into four groups: normal controls, rats fed a diet containing 6,000 μg g-1 eugenol, rats intoxicated daily with aluminium chloride (84 mg kg-1 body weight) p. o. and fed either a basal diet or a eugenol-containing diet. Daily oral administration of Al for four consecutive weeks to rats significantly reduced brain total antioxidant status (TAS) (11.42±0.31 μmol g-1 tissue, p<0.001) with a subsequent significant enhancement of lipid peroxidation (MDA) (32.55±1.68 nmol g-1 tissue, p<0.002). In addition, Al enhanced brain acetylcholinesterase activity (AChE) (46.22±4.90 U mg-1 protein, p<0.001), tumour necrosis factor alpha (TNF-α) (118.72±11.32 pg mg-1 protein, p<0.001), and caspase 3 (Casp-3) (8.77±1.26 ng mg-1 protein, p<0.001) levels, and in contrast significantly suppressed brain-derived neurotrophic factor (BDNF) (82.74±14.53 pg mg-1 protein, p<0.002) and serotonin (5-HT) (1.54±0.12 ng mg-1 tissue, p<0.01) levels. Furthermore, decreased glial fibrillary acidic protein (GFAP) immunostaining was noticed in the striatum of Al-intoxicated rats, compared with untreated controls. On the other hand, co-administration of dietary eugenol with Al intoxication restored brain BDNF (108.76±2.64 pg mg-1 protein) and 5-HT (2.13±0.27 ng mg-1 tissue) to normal levels, enhanced brain TAS (13.43±0.24 μmol g-1 tissue, p<0.05), with a concomitant significant reduction in TNF-α (69.98±4.74 pg mg-1 protein) and Casp-3 (3.80±0.37 ng mg-1 protein) levels (p<0.001), as well as AChE activity (24.50±3.25 U mg-1 protein, p<0.001), and increased striatal GFAP immunoreactivity, compared with Al-treated rats. Histological findings of brain tissues verified biochemical data. In conclusion, eugenol holds potential as a neuroprotective agent through its hydrophobic, antioxidant, and anti-apoptotic properties, as well as its neurotrophic ability against Al-induced brain toxicity in rats.

In ovo toxico-teratological effects of aluminum on embryonic chick heart and vascularization

In spite of extensive research and persistent arguments, the mechanism of aluminum (Al) toxicity is still obscure. It is firmly established that aluminum is a potent neurotoxicant. So, the aim based on is aluminum damage chicken heart, as well as the vitelline circulation. In the first 3 days of incubation (D0-D2), 1.0, 2.0, or 4.0 mg aluminum chloride/0.3 ml avian saline was injected into the center of each viable fertilized egg yolk (AL1, AL2, and AL3 groups, respectively). Control eggs were either uninjected (AL0) or injected (ALS, 0.3 ml saline). Crown rump length was significantly decreased, while, embryonic mortalities, growth delay, as well as congenital heart defects were increased in the eggs injected 2.0 or 4.0 mg of Al. Although no relationship is clear about the embryonic mortality induced by Al in chicken embryos to the dose concentration, the higher mortality occurs in early developmental stages in developing chick embryos. Furthermore, chick embryos exposed to 4.0 mg/Al showed a high incidence of defects of ventricular septation and ventricular myocardium. Configuration and density of branched vitelline vessels were also significantly deteriorated after injection with 4.0 mg/Al. It concluded that Al is a cardiac teratogen for a chick in a dose-dependent way. These data highlight a novel approach for aluminum in congenital cardiovascular defects. Therefore, further research is needed to explain the teratogenicity of Al on the embryonic heart development.

Protective effect of citicoline against aluminum-induced cognitive impairments in rats

The potential protective effect of citicoline on aluminum chloride-induced cognitive deficits was investigated in rats. In a Morris water maze, administration of aluminum chloride to rats for 90 days resulted in increased escape latency to reach the platform and decreased swimming speed in acquisition trials. Similarly, in probe trials, the time required to reach the hidden platform was increased and the time spent in the target quadrant was reduced. Also, administration of aluminum chloride to rats for 90 days increased the reference and working memory errors and time required to end the task in the radial arm maze. In addition, this treatment decreased the step-through latency in the passive avoidance test. Concurrently, treatment of rats with aluminum chloride for 90 days increased hippocampal glutamate, malondialdehyde, and nitrite levels and decreased intracellular reduced glutathione level. In the citicoline-treated group, aluminum chloride-induced learning and memory impairments as assessed by the Morris water maze, radial arm maze, and passive avoidance tests were inhibited. At the same time, treatment of rats with citicoline prevented the biochemical alterations induced by aluminum chloride in the hippocampus. It can be concluded that elevation of hippocampal glutamate level with consequent oxidative stress and nitric oxide (NO) overproduction may play an important role in aluminum-induced cognitive impairments. Also, our results suggest, for the first time, that citicoline can protect against the development of these cognitive deficits through inhibition of aluminum-induced elevation of glutamate level, oxidative stress, and NO overproduction in the hippocampus.

Silicon Reverses Lipid Peroxidation but not Acetylcholinesterase Activity Induced by Long-Term Exposure to Low Aluminum Levels in Rat Brain Regions

Aluminum (Al) is the most widely distributed metal in the environment and is extensively used in daily life leading to easy exposure to human beings. Besides not having a recognized physiological role, Al may produce adverse effects through the interaction with the cholinergic system contributing to oxidative stress. The present study evaluated, in similar conditions of parenteral nutrition, whether the reaction of silicon (SiO2) with Al(3+) to form hydroxyaluminosilicates (HAS) reduces its bioavailability and toxicity through intraperitoneal administrations of 0.5 mg Al/kg/day and/or 2 mg Si/kg/day in Wistar rats. Al and Si concentrations were determined in rat brain tissue and serum. Acetylcholinesterase (AChE) activity and lipid peroxidation (LPO) were analyzed in the cerebellum, cortex, hippocampus, striatum, hypothalamus, and blood. An increase in the Al concentration was verified in the Al + Si group in the brain. All the groups demonstrated enhanced Si compared to the control animals. Al(3+) increased LPO measured by thiobarbituric acid reactive substances (TBARS) in cerebellum and hippocampus, whereas SiO2 reduced it when compared with the control group. An increase of AChE activity was observed in the Al-treated group in the cerebellum whereas a decrease of this enzyme activity was observed in the cortex and hippocampus in the Al and Al + Si groups. Al and Si concentrations increased in rat serum; however, no effect was observed in blood TBARS levels and AChE activity. SiO2 showed a protective effect in the hippocampus and cerebellum against cellular damage caused by Al(3+)-induced lipid peroxidation. Thus, SiO2 may be considered an important protector in LPO induced by Al(3+).

Potential of bone marrow mesenchymal stem cells in management of Alzheimer's disease in female rats

Alzheimer's disease (AD) has been called the disease of the century with significant clinical and socioeconomic impacts. Pharmacological treatment has limited efficacy and only provides symptomatic relief without long-term cure. Accordingly, there is an urgent need to develop novel and effective medications for AD. Stem cell-based therapy is a promising approach to handling neurodegenerative diseases. Therefore, the current study aimed to explore the possible therapeutic role of single intravenous injection of bone marrow derived mesenchymal stem cells (BM-MSCs) after 4 months in management of AD in the experimental model. The work also extended to compare the therapeutic potential of BM-MSCs with 2 conventional therapies of AD; rivastigmine and cerebrolysin administered daily. BM-MSCs were able to home at the injured brains and produced significant increases in the number of positive cells for choline acetyltransferase (ChAT) and survivin expression, as well as selective AD indicator-1 (seladin-1) and nestin gene expression. Histopathological examination indicated that BM-MSCs could remove beta-amyloid plaques from hippocampus. Significant improvement in these biomarkers was similar to or better sometimes than the reference drugs, clearly showing the potential therapeutic role of BM-MSCs against AD through their anti-apoptotic, neurogenic and immunomodulatory properties.

A comparison of the in vitro cyto- and neurotoxicity of brominated and halogen-free flame retardants: prioritization in search for safe(r) alternatives

Brominated flame retardants (BFRs) are abundant persistent organic pollutants with well-studied toxicity. The toxicological and ecological concerns associated with BFRs argue for replacement by safe(r) alternatives. Though previous research identified the nervous system as a sensitive target organ for BFRs, the (neuro) toxic potential of alternative halogen-free flame retardants (HFFRs) is largely unknown. We therefore investigated the in vitro (neuro) toxicity of 13 HFFRs and three BFRs in dopaminergic pheochromocytoma (PC12) and neuroblastoma (B35) cells by assessing several cytotoxic and neurotoxic endpoints. Effects on cell viability and production of reactive oxygen species (ROS) were measured using a combined Alamar Blue and Neutral Red assay and a H2-DCFDA assay, respectively, whereas effects on calcium homeostasis were measured using single-cell fluorescent Ca(2+)-imaging. The majority of the tested flame retardants induced negligible cytotoxicity, except zinc hydroxystannate (ZHS) and zinc stannate (ZS). A considerable fraction of flame retardants affected ROS production (decabromodiphenyl ether (BDE-209), triphenylphosphate (TPP), aluminium trihydroxide (ATH), ammonium polyphosphate (APP), magnesium hydroxide (MHO), ZHS, ZS and melamine polyphosphate (MPP)). Interestingly, ATH, ZHS, ZS and montmorillonite (MMT) increased the basal intracellular calcium concentration ([Ca(2+)]i), whereas tetrabromobisphenol A (TBBPA), resorcinol bis (diphenylphosphate) (RDP), TPP, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), ATH, ZHS, ZS and MMT reduced depolarization-evoked increases in [Ca(2+)]i as a result of inhibition of voltage-gated calcium channels. These combined data on the in vitro (neuro) toxicity of HFFRs in comparison with BFRs are essential for prioritization of safe(r) flame retardants. Though additional data are required for a complete (toxic) risk assessment, our data demonstrate that several HFFRs could be suitable substitutes for BFRs.

Persistence, bioaccumulation, and toxicity of halogen-free flame retardants

Polymers are synthetic organic materials having a high carbon and hydrogen content, which make them readily combustible. Polymers have many indoor uses and their flammability makes them a fire hazard. Therefore, flame retardants (FRs) are incorporated into these materials as a safety measure. Brominated flame retardants (BFRs), which accounted for about 21% of the total world market of FRs, have several unintended negative effects on the environment and human health. Hence, there is growing interest in finding appropriate alternative halogen-free flame retardants (HFFRs). Many of these HFFRs are marketed already, although their environ- mental behavior and toxicological properties are often only known to a limited extent, and their potential impact on the environment cannot yet be properly assessed. Therefore, we undertook this review to make an inventory of the available data that exists (up to September 2011) on the physical-chemical properties, pro- duction volumes, persistence, bioaccumulation, and toxicity (PBT) of a selection of HFFRs that are potential replacements for BFRs in polymers. Large data gaps were identified for the physical-chemical and the PBT properties of the reviewed HFFRs. Because these HFFRs are currently on the market, there is an urgent need to fill these data gaps. Enhanced transparency of methodology and data are needed to reevaluate certain test results that appear contradictory, and, if this does not provide new insights, further research should be performed. TPP has been studied quite extensively and it is clearly persistent, bioaccumulative, and toxic. So far, RDP and BDP have demonstrated low to high ecotoxicity and persistence. The compounds ATH and ZB exerted high toxicity to some species and ALPI appeared to be persistent and has low to moderate reported ecotoxicity. DOPO and MPP may be persistent, but this view is based merely on one or two studies, clearly indicating a lack of information. Many degradation studies have been performed on PER and show low persistence, with a few exceptions. Additionally, there is too l ittle information on the bioaccumulation potential of PER. APP mostly has low PBT properties; however, moderate ecotoxicity was reported in two studies. Mg(OH)₂, ZHS, and ZS do not show such remarkably high bioaccumulation or toxicity, but large data gaps exist for these compounds also. Nevertheless, we consider the latter compounds to be the most promising among alternative HFFRs. To assess whether the presently reviewed HFFRs are truly suitable alternatives, each compound should be examined individually by comparing its PBT values with those of the relevant halogenated flame retardant. Until more data are available, it remains impossible to accurately evaluate the risk of each of these compounds, including the ones that are already extensively marketed.

Modulation of human α4β2 nicotinic acetylcholine receptors by brominated and halogen-free flame retardants as a measure for in vitro neurotoxicity

Brominated flame retardants (BFRs) are abundant persistent organic pollutants with well-studied toxicity. The toxicological and ecological concern associated with BFRs argues for replacement by safer alternatives. However, the (neuro)toxic potential of alternative halogen-free flame retardants (HFFRs) is unknown. Previous research identified the nervous system as a sensitive target organ for BFRs, with modulation of excitatory nicotinic acetylcholine (nACh) receptors as one of the modes of action. Since it is essential to assess the (neuro)toxic potential of HFFRs before large scale use, we measured the effects of three BFRs and 13 HFFRs on the function of human α(4)β(2) nACh receptors, expressed in Xenopus oocytes, using the two-electrode voltage-clamp technique. The results demonstrate that some BFRs (TBBPA and to a lesser extent BDE-209) and HFFRs (TPP, Alpi, APP, MMT and to a lesser extent ATH, ATO, MHO, MPP, RDP and ZHS) act as nACh receptor antagonists. Contrary, BPS, BDP, DOPO and ZS were unable to modulate nACh receptors. Despite the lack of toxicological data on HFFRs and the need for additional studies to perform a full (neuro)toxic risk assessment, the current data on antagonistic effects on nACh receptors could be an important step in prioritizing viable HFFRs for substitution of BFRs.

Rivastigmine reverses aluminum-induced behavioral changes in rats

Aluminum, a known neurotoxin, has long been implicated in the pathogenesis of Alzheimer's disease. Its exposure is associated with impairment in the cholinergic system in the brain. In this study we investigated the behavioral effects of aluminum in rats and the possible effect of rivastigmine, a cholinesterase inhibitor, on the aluminum-induced behavioral changes. Rats were exposed to aluminum chloride (100 mg/kg/day i.p.) for 60 days before the start of behavioral tests. Rivastigmine was given in doses of 0.5, 1, 1.5 and 2.5 mg/kg i.p. 60 min before the behavioral tests. Five tests were investigated; open field test, Morris water maze, radial arm maze, passive avoidance test and rota-rod test. Results showed that aluminum exposure was associated with significant reductions in spontaneous locomotor and exploratory activities in open field test and significant impairments in learning and memory in Morris water maze, radial arm maze and passive avoidance tests. The behavioral impairments caused by aluminum were significantly improved by rivastigmine. Neither aluminum alone nor co-treatment with rivastigmine caused any significant alteration of the animals' performance in rota-rod test. The improvements in activity, learning and memory caused by rivastigmine were found to be dose-dependent, and the maximal improvement was encountered with its large dose (2.5 mg/kg). From these results we can conclude that rivastigmine can reverse behavioral deficits caused by aluminum intoxication.

Aluminum hydroxide injections lead to motor deficits and motor neuron degeneration

Gulf War Syndrome is a multi-system disorder afflicting many veterans of Western armies in the 1990-1991 Gulf War. A number of those afflicted may show neurological deficits including various cognitive dysfunctions and motor neuron disease, the latter expression virtually indistinguishable from classical amyotrophic lateral sclerosis (ALS) except for the age of onset. This ALS "cluster" represents the second such ALS cluster described in the literature to date. Possible causes of GWS include several of the adjuvants in the anthrax vaccine and others. The most likely culprit appears to be aluminum hydroxide. In an initial series of experiments, we examined the potential toxicity of aluminum hydroxide in male, outbred CD-1 mice injected subcutaneously in two equivalent-to-human doses. After sacrifice, spinal cord and motor cortex samples were examined by immunohistochemistry. Aluminum-treated mice showed significantly increased apoptosis of motor neurons and increases in reactive astrocytes and microglial proliferation within the spinal cord and cortex. Morin stain detected the presence of aluminum in the cytoplasm of motor neurons with some neurons also testing positive for the presence of hyper-phosphorylated tau protein, a pathological hallmark of various neurological diseases, including Alzheimer's disease and frontotemporal dementia. A second series of experiments was conducted on mice injected with six doses of aluminum hydroxide. Behavioural analyses in these mice revealed significant impairments in a number of motor functions as well as diminished spatial memory capacity. The demonstrated neurotoxicity of aluminum hydroxide and its relative ubiquity as an adjuvant suggest that greater scrutiny by the scientific community is warranted.

Curcumin attenuates aluminium-induced functional neurotoxicity in rats

Curcumin is a polyphenol extracted from the rhizome of Curcuma longa and well known as a multi-functional drug with antioxidative, anti-cancerous and anti-inflammatory activities. Curcumin's antiaging and neuroprotective potential is widely reported. In the present study, effect of curcumin treatment dose 30 mg kg(-1) day(-1) was investigated against aluminium neurotoxicity in young and old animals. Direct and indirect intakes of aluminium have been reported to be involved in the etiology of several neurodegenerative disorders like Alzheimer's and Parkinson's diseases. Long term Al was administered through drinking water at a dose of 50 mg/kg/day for 6 months in both young (4 months) and old (18 months) male Wistar rats. Result obtained demonstrates that curcumin treatment attenuates the Al-induced alterations at biochemical, behavioral and ultrastructural levels which was well reflected in the electrophysiological recordings. Our results indicate that curcumin's ability to bind redox active metals and cross the blood-brain barrier could be playing crucial role in preventing against Al-induced neurotoxicity.

Aluminum adjuvant linked to Gulf War illness induces motor neuron death in mice

Gulf War illness (GWI) affects a significant percentage of veterans of the 1991 conflict, but its origin remains unknown. Associated with some cases of GWI are increased incidences of amyotrophic lateral sclerosis and other neurological disorders. Whereas many environmental factors have been linked to GWI, the role of the anthrax vaccine has come under increasing scrutiny. Among the vaccine's potentially toxic components are the adjuvants aluminum hydroxide and squalene. To examine whether these compounds might contribute to neuronal deficits associated with GWI, an animal model for examining the potential neurological impact of aluminum hydroxide, squalene, or aluminum hydroxide combined with squalene was developed. Young, male colony CD-1 mice were injected with the adjuvants at doses equivalent to those given to US military service personnel. All mice were subjected to a battery of motor and cognitive-behavioral tests over a 6-mo period postinjections. Following sacrifice, central nervous system tissues were examined using immunohistochemistry for evidence of inflammation and cell death. Behavioral testing showed motor deficits in the aluminum treatment group that expressed as a progressive decrease in strength measured by the wire-mesh hang test (final deficit at 24 wk; about 50%). Significant cognitive deficits in water-maze learning were observed in the combined aluminum and squalene group (4.3 errors per trial) compared with the controls (0.2 errors per trial) after 20 wk. Apoptotic neurons were identified in aluminum-injected animals that showed significantly increased activated caspase-3 labeling in lumbar spinal cord (255%) and primary motor cortex (192%) compared with the controls. Aluminum-treated groups also showed significant motor neuron loss (35%) and increased numbers of astrocytes (350%) in the lumbar spinal cord. The findings suggest a possible role for the aluminum adjuvant in some neurological features associated with GWI and possibly an additional role for the combination of adjuvants.

Impact of aluminum sub-chronic toxicity on body weight and recognition memory of wistar rat

The aims of this study was to investigate the impact of aluminum nitrate administered in drinking water during 90 days (sub-chronic toxicity), on body weight gain, motor activity, brain aluminum accumulation and especially in recognition memory of wistar rats. Two groups of young female wistar rats were used. Treated rats received (80 mg L(-1)) of aluminum nitrate diluted in drinking water, while control rats received a drinking water only, for 3 months. An evolution of body weight, a motor activity, object recognition memory (NOR) and brain aluminum concentration has been evaluated. The body weight was taken weekly, whereas the memory abilities and the motor activity are measured once every fortnight alternatively, by submitting rats to the open field test and to the novel object recognizing memory test. The results have showed a significant decrease in rats' body weight (p < 0.05). Though, no significance was registered for motor activity. Nevertheless, a high significance is showed for recognition memory compared to control rats (p < 0.01), especially at the end of testing period, even the difference between control and aluminium treated rats in brain aluminum levels was not significant.

Impairment of mitochondrial energy metabolism in different regions of rat brain following chronic exposure to aluminium

The present study was designed with an aim to evaluate the effects of chronic aluminium exposure (10 mg/kg b.wt, intragastrically for 12 weeks) on mitochondrial energy metabolism in different regions of rat brain in vivo. Mitochondrial preparations from aluminium treated rats revealed significant decrease in the activity of various electron transport complexes viz. cytochrome oxidase, NADH cytochrome c reductase and succinic dehydrogenase as well, in the hippocampus region. The decrease in the activity of these respiratory complexes was also seen in the other two regions viz. corpus striatum and cerebral cortex, but to a lesser extent. This decrease in the activities of electron transport complexes in turn affected the ATP synthesis and ATP levels adversely in the mitochondria isolated from aluminium treated rat brain regions. We also studied the spectral properties of the mitochondrial cytochromes viz. cyt a, cyt b, cyt c1, and cyt c in both control and treated rat brains. The various cytochrome levels were found to be decreased following 12 weeks of aluminium exposure. Further, these impairments in mitochondrial functions may also be responsible for the production of reactive oxygen species and impaired antioxidant defense system as observed in our study. The electron micrographs of neuronal cells depicted morphological changes in mitochondria as well as nucleus only from hippocampus and corpus striatum regions following 12 weeks exposure to aluminium. The present study thus highlights the significance of altered mitochondrial energy metabolism and increased ROS production as a result of chronic aluminium exposure in different regions of the rat brain.

Does neurotransmission impairment accompany aluminium neurotoxicity?

Neurobehavioral disorders, except their most overt form, tend to lie beyond the reach of clinicians. Presently, the use of molecular data in the decision-making processes is limited. However, as details of the mechanisms of neurotoxic action of aluminium become clearer, a more complete picture of possible molecular targets of aluminium can be anticipated, which promises better prediction of the neurotoxicological potential of aluminium exposure. In practical terms, a critical analysis of current data on the effects of aluminium on neurotransmission can be of great benefit due to the rapidly expanding knowledge of the neurotoxicological potential of aluminium. This review concludes that impairment of neurotransmission is a strong predictor of outcome in neurobehavioral disorders. Key questions and challenges for future research into aluminium neurotoxicity are also identified.

Effect of aluminum consumption on the vestibulo-ocular reflex

The effects of chronic exposure (90 days) to Aluminum chloride (AlCl(3)) were analyzed in 3, 10 and 24 month old male rats (n=270) by investigating the function of the VOR (vestibulo-ocular reflex) in correlation with Aluminum (Al) concentrations in blood and brain. The VOR was chosen and tested in basal conditions (pre-exposure measures) and during the continuous administration of three different concentrations of AlCl(3) (0.5, 1, 2 g/l in drinking solution): the control animals being exposed to NaCl (0.125, 0.25 and 5 g/l in drinking solution). Results showed that LOAEL (Lowest Observed Adverse Effect Level) was 43.1+/-11.4 mg Al/kg-day. At this concentration the Al induced significant VOR impairment in all exposed rats, regardless of animal age. Neuroanatomical analysis showed that VOR impairment was not dependent on astrocyte damage nor evidences of amyloid deposits in the exposed rats was found. Significant changes of Al concentrations were observed in nervous tissue, while its concentration in whole blood was unaffected. Furthermore, results show that it is possible to identify an individual neurotoxic threshold for each animal and therefore hypothesize the clinical use of the VOR test for the evaluation of individual risk toxicity to chronic Al exposure.

Protective effect of Ginkgo biloba leaf extract on learning and memory deficit induced by aluminum in model rats

OBJECTIVE

To examine the protective effect of Ginkgo biloba leaf extract (GbE) on learning and memory deficit induced by aluminum chloride (AlCl(3)), and explore its mechanisms.

METHODS

The rat models with learning and memory deficit were induced by administering via gastrogavage and drinking of AlCl(3) solution. And the model rats were treated with GbE at the dose of 50, 100, 200 mg/kg every day for 2 months accompanied with drinking of AlCl(3) solution, respectively. Their abilities of spatial learning and memory were tested by Morris water maze, and the acetylcholinesterase (AChE) activity in serum was assayed with chemical method, the AChE expression in hippocampus was observed by immunohistochemistry assay, and then quantitative analysis was done by BI 2000 image analysis system.

RESULTS

Learning and memory deficit of rats could be induced by AlCl(3) solution (P < 0.01), and AChE expressions in rats hippocampus were increased (P < 0.01); GbE ameliorated learning and memory deficit and reduced AChE expression in rats hippocampus in a dose-dependent manner, while GbE significantly increased serum AChE activity at the dose of 200 mg/kg each day (P < 0.05).

CONCLUSION

GbE can ameliorate learning and memory deficit induced by AlCl(3), which may be due to its inhibition of the AChE expression in hippocampus.

Protective effects of Ginkgo biloba leaf extract on aluminum-induced brain dysfunction in rats

This study examined the protective effects of Ginkgo biloba extract (GbE) on the learning and memory function in aluminum-treated rats and potential mechanisms. Wistar rats were given daily aluminum chloride 500 mg/kg, i.g, for one month, followed by continuous exposure via the drinking water containing 1600 ppm aluminum chloride for up to 5 months. The ability of spatial learning and memory was tested by Morris water maze. Aluminum administration significantly increased escape latency and searching distance, indicative of brain dysfunction. GbE treatment (50-200 mg/kg, i.g) significantly protected against aluminum-induced brain dysfunction, as evidenced by decreased escape latency and searching distance compared with the Al alone group. To examine the mechanisms of the protection, the expressions of amyloid precursor protein (APP) and caspase-3 in brain regions were examined by immunohistochemistry. GbE treatment reduced the contents of APP and caspase-3 in hippocampus of aluminum-treated rats in a dose-dependent manner. At the highest dose of GbE (200 mg/kg), the immunostain for APP and caspase-3 was returned to normal levels. In summary, this study demonstrates that GbE is effective in improving the ability of spatial learning and memory of aluminum-intoxicated rats. This protection appears to be due to a decreased expression of APP and caspase-3 in rat brain, resulting in a decrease in the production of insoluble fragments of Abeta-amyloid.

Disruption of Neuronal Calcium Homeostasis after Chronic Aluminium Toxicity in Rats

The present study was designed to investigate the possible effects of chronic aluminium exposure on the various aspects of calcium homeostasis in rat brain. Chronic aluminium administration caused significant rise in the intrasynaptosomal calcium levels. The activity of major calcium-expelling enzyme, i.e. Ca2+ ATPase was found to be lowered. Also, the calcium uptake via voltage-operated calcium channels increased significantly. Similar to the increase in intrasynaptosomal calcium, calpain activity was found to be increased. The results presented here, indicate that the toxic effects of aluminium could be mediated through modifications in the intracellular calcium homeostasis, which may lead to impaired neuronal function.

Effect of long-term aluminum feeding on lipid/phospholipid profiles of rat brain myelin

Effect of long-term (90–100 days) exposure of rats to soluble salt of aluminum (AlCl₃) on myelin lipid profile was examined. The long-term exposure to AlCl₃ resulted in a 60 % decrease in the total phospholipid (TPL) content while the cholesterol (CHL) content increased by 55 %. Consequently the TPL / CHL molar ratio decreased significantly by 62 %. The phospholipid composition of the myelin membrane changed drastically; the proportion of practically all the phospholipid classes decreased by 32 to 60 % except for phosphatidylcholine (PC) and phosphatidylethanolamine (PE). Of the latter two, proportion of PC was unchanged while PE increased in proportion by 47 %. Quantitatively, all phospholipid classes decreased by from 42 to 76% with no change in the PE content. However the membrane fluidity was not altered in Al-treated rats. Many of the changes we observe here show striking similarities with the reported phospholipid profiles of Alzheimer brains.

In vivo and in vitro effects of aluminum on the activity of mouse brain acetylcholinesterase

Cholinesterases are a large family of enzymatic proteins widely distributed throughout both neuronal and non-neuronal tissues. In Alzheimer's disease (AD), analytical as well as epidemiological studies suggest an implication of an abnormal focal accumulation of aluminum in the brain. In this devastating disease, aluminum may interfere with various biochemical processes including acetylcholine metabolism, and can thus act as a possible etiopathogenic cofactor. Acetylcholinesterase (AChE) exists in several molecular forms that differ in solubility and mode of membrane attachment rather than in catalytic activity. Mice were treated orally with aluminum chloride or aluminum lactate (Al(lac)(3)), and AChE activity in their brain homogenates was then assayed. Results showed that this in vivo treatment augmented the activity of the enzyme. An activating effect was also observed in vitro, when the aluminum compounds were added directly to mouse brain homogenates. However, the activating effect observed in vivo was much more marked than that observed in vitro. In addition, the activation produced by Al(lac)(3) was higher than that obtained after aluminum chloride treatment. Kinetics measurements of AChE activity in the absence and presence of treatment with aluminum both in vivo and in vitro are reported. The influence of the metal speciation on enzymatic activity is discussed in relation to a possible implication of aluminum in some neurodegenerative diseases.

The influence of developmental period of aluminum exposure on synaptic plasticity in the adult rat dentate gyrus in vivo

Previous studies from our group have demonstrated that chronic aluminum exposure from parturition throughout life impairs both long-term potentiation (LTP) and long-term depression (LTD) of the excitatory postsynaptic potential (EPSP) slope and reduces the population spike (PS) amplitude in the rat dentate gyrus in vivo. The present study sought to extend these findings by evaluating the developmental periods critical for aluminum-induced impairment of synaptic plasticity. Rats were exposed to aluminum (gestational, lactational and postlactational) through drinking 0.3% aluminum chloride in water over different developmental intervals: (1) prenatal exposure; (2) beginning from birth and terminating at weaning; (3) beginning at weaning throughout life; (4) beginning at birth and continuing throughout life. As adults (postnatal day 80-100), field potentials were measured in the dentate gyrus of hippocampus in response to stimulation applied to the lateral perforant path. The results showed: (1) Prenatal aluminum exposure had no effect on the magnitude of LTP as measured by the EPSP slope and LTD as measured for the PS amplitude, while it had a small effect on the magnitude of LTP as measured for the PS amplitude and LTD as measured by the EPSP slope. (2) Lactational, postlactational and throughout life exposure to aluminum impaired both LTP and LTD of the EPSP slope and PS amplitude, except that LTD of PS amplitude was not significantly changed in animals postlactationally exposed. (3) Aluminum exposure from parturition throughout life caused the greatest impairment of the range of synaptic plasticity, while prenatal aluminum exposure caused the least. From these results we conclude that the lactational period was the most susceptible to aluminum-induced impairment of synaptic plasticity and that chronic aluminum exposure from parturition throughout life is extremely disruptive to synaptic plasticity and should be avoided.

Effect of long-term aluminum feeding on kinetics attributes of tissue cholinesterases

Aluminum (Al) is considered a potential etiological factor in Alzheimer's disease (AD). Neurotoxicity from excess brain exposure to Al is documented from both clinical observations and animal experiments. A key role of the acetylcholine system in memory disturbances that characterize AD has been reported. On this basis, we studied the effect of long-term Al feeding on kinetic properties of cholinesterases employing the rat as experimental model. Animals were given prolonged treatment with soluble salts of Al (100mg AlCl(3)/kg body weight mixed with food for 100-115 days), and the kinetic properties of cholinesterases (acetylcholinesterase, AChE, and butyrylcholinesterase, BChE) were determined in different tissues. Prolonged treatment with Al had no effect on the K(m) values of the soluble and membrane-bound forms of AChE in the brain, but V(max) was instead decreased in all the components of soluble and membrane-bound forms of AChE in the brain. In addition, the Al treatment resulted in complete loss of the component II of erythrocyte membrane AChE. Surprisingly, after prolonged treatment with Al, higher V(max) was observed in all the components of soluble and membrane-bound forms of BChE in the heart and liver. Variable effects of Al exposure were observed on temperature kinetic properties of cholinesterases. Altogether these findings indicate that long-term Al feeding results in inhibition of AChE, while an opposite effect is observed on BChE. Decreased V(max) of the brain AChE could represent the mode of action through which Al may contribute to pathological processes in Al-induced neurotoxicity.

Effect of aluminium-induced Alzheimer like condition on oxidative energy metabolism in rat liver, brain and heart mitochondria

Prolonged exposure of rats to aluminium (Al) can result in an Alzheimer-like condition. To get better insights into the biochemical defects underlying AD, senility and ageing we exposed rats for long durations (90-100 days) to soluble salt of aluminium (AlCl3) and checked its influence on mitochondrial respiratory activity in the liver, brain and heart. In the liver and brain mitochondria the ADP/O ratio was impaired with NAD+ linked substrates. State three respiration decreased with glutamate in the liver. For succinate, the ADP/O ratio decreased in the liver mitochondria while state three and four respiration decreased in the brain mitochondria. In both the tissues respiration rates decreased with ascorbate + TMPD as the substrate. In the heart mitochondria ADP/O ratios with NAD+ linked substrates decreased, while respiration rates increased with all the substrates except for ascorbate + TMPD. Temperature kinetics data showed different effects on ATPase in the mitochondria from the three tissues. Data on lipid/phospholipid profiles suggested that the observed changes in energy metabolism were not mediated via lipid changes. Long-term exposure to Al resulted in approximately 100% increase in Al content of liver and brain mitochondria but in the heart there was phenomenal 11-fold increase, indicating thereby that the effects of Al exposure were indirect rather than direct due to Al accumulation.

Aluminium-induced biphasic effect

Increased bioavailability of aluminium has raised concerns about the toxic effect of aluminium. The cholinotoxic effect of aluminium is already well established. The biological response of an organism following exposure to a chemical may be biphasic. Although aluminium-induced biphasic change has been reported in diverse organ systems, the biphasic effect on cholinergic system has received less attention. In vitro and in vivo studies have demonstrated an aluminium-induced biphasic effect on the marker enzyme of cholinergic system, acetylcholinesterase. The biphasic effect of aluminium on the acetylcholinesterase enzyme activity may be due to the direct neurotoxic effect of the metal and the level of aluminium accumulated. Among various hypotheses, peroxidation-induced changes in the structure of membrane following aluminium accumulation seems to explain the biphasic effect of aluminium on acetylcholinesterase activity.

Biphasic effect of aluminium on cholinergic enzyme of rat brain

The cholinotoxic effect of aluminium has been widely reported. In vitro aluminium has a biphasic effect on acetylcholinesterase activity. The present study analyses its in vivo effect in brain regions. Rats were exposed to aluminium chloride by the oral route at a dose of 320 mg/kg body weight for shorter (4 and 14 days) and longer (60 days) duration. Acetylcholinesterase activity in olfactory bulb, striatum and hypothalamus brain regions increased after 4 and 14 days and decreased after 60 days of aluminium exposure. Aluminium level in the brain regions studied increased significantly. No significant change in body weight of rats exposed to aluminium was found. The biphasic change in acetylcholinesterase activity may be due to slow accumulation of aluminium in the brain regions and its effect on the enzyme.

Effect of small variations of aluminum intake on calcium metabolism in young rats

BACKGROUND

While in the adult Al intoxication requires high dosages, little is known on the threshold level of Al toxicity in the young.

METHODS

Weaning rats were fed for 90 days ore of four diets differing by their content in Ca (7.5 vs < 0.5 g/< g diet)(Ca+/-) and Al (10.6 vs 8.4 mg/kg)(Al+/-); Al supplementation was 30% above the standard level of diet. Ca and Al levels were measured in liver, bone (femur), and brain.

RESULTS

Ca- had a significant negative effect on growth which was further reduced by Al+; in Ca sufficient/Al+ animals, Al concentrations were significantly increased in bone and brain and tended to increase in liver; Ca decreases observed in these three organs were only significant in brain. Ca deficiency further enhanced the Al deposit in bone at both levels of Al intakes, and reduced Ca concentrations in these three organs in Al+ animals; in Ca-/Al- animals, the decrease in Ca displayed in the three tissues reached a significant level in brain.

CONCLUSIONS

This study suggests that in the growing subject the side effects of small variations of Al intake can be enhanced when they are combined with other mineral imbalances.

Oral aluminum administration during pregnancy and lactation produces gastric and renal lesions in rat mothers and delay in CNS development of their pups

The expression of the neurofilament protein of the highest molecular weight (NF-H) is developmentally and spatially regulated. For example, the MAb RMO24.9, directed against a phosphorylated epitope in the tail domain of NF-H, immunohistochemically labels specific tracts within the rat brainstem prenatally, but does not label diencephalic tracts until after postnatal day 10 (P10). A diet providing 300 mg/kg/d Al (as Al lactate) to rat dams throughout gestation causes behavioral deficits in their offspring (Bernuzzi et al., 1989). We repeated this regimen by substituting 120 mM Al lactate (pH 6.5) for drinking water during gestation and lactation, and examined the distribution of immunolabeling by RMO 24.9 after exposure to Al. Tracts within the diencephalon that bind RMO 24.9 on P11 in control pups did not bind the MAb until P14 in Al-treated pups. In these preliminary experiments, Al seemed to have caused a developmental delay in the expression of phosphorylated NF-H in the pups of mothers that received Al during gestation. However, subsequent experiments showed that the neuropathology observed--and that reported by other investigators using similar Al levels--may not be the result of the direct effects of Al on the pups. Throughout lactation, treated dams appeared progressively more cachexic. Unlike the normal viscera of pair-watered controls, the stomachs of treated dams were ulcerated, and their kidneys had decreased cortical thickness and contained stones. Lesions such as these compromise a rat's ability to absorb nutrients, to excrete toxins, and to regulate water and electrolytes. In a lactating dam, these alterations could compromise the dam's ability to nourish her pups. Our experiments point out that the mechanisms of Al toxicity-- already complex in the adult--are further complicated in a system in which the pup is dependent on the mother for delivery of both nutrients and toxins. It is therefore impossible to determine the cause of any neuropathology in the pup in a system where Al delivery overlies a background of multisystem defect and altered maternal homeostasis.

Evaluation of the developmental neuroendocrine and reproductive toxicology of aluminium

Two experiments evaluating functional endpoints pertaining to the developmental neuroendocrine effects of aluminum in the rat are reported. A total of 31 timed mated dams were fed by daily gastric gavage 0, 5, 25, 50, 250, 500 or 1000 mg/kg body weight/day aluminum as a solution of aluminum lactate in distilled water from days 5 to 15 of gestation. The 390 offspring were evaluated for morphological and physiological parameters of reproductive functioning, including birth weight, anogenital distance (AGD), timing of vaginal opening, regularly of oestrous cycles, duration of pseudopregnancy (PSP), number of superovulated oocytes, and gonadal weight. No consistent or reproducible findings suggestive of toxic effect were found in the parameters of birth weight, AGD, timing of vaginal opening, duration of PSP, number of superovulated oocytes, and adult gonadal weight. A temporary increase in the proportion of aberrant oestrous cycles was detected during the first four cycles after vaginal opening, in the 250 mg/body weight/day group, with none by the fifth consecutive oestrous cycle. These results suggest that, apart from a transient disturbance of oestrous cycle regularity, aluminum does not have a developmental reproductive toxic effect.