Neurobehavioral effects in offspring of mice given excess aluminum in diet during gestation and lactation

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

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

Early-life exposure to aluminum and fine motor performance in infants: a longitudinal study

BACKGROUND

Aluminum (Al) is a well-established neurotoxicant. However, little is known about its effects on the neurodevelopment of infants.

OBJECTIVES

To examine early-life exposure to Al in relation to neurodevelopment in healthy infants.

METHODS

Nail Al concentrations were measured among 747 newborn babies within 6 months of delivery in the Shanghai Birth Cohort. Neurodevelopment was assessed using Ages and stages questionnaire (third edition, ASQ-3) at ages 6 and 12 months. General linear regression models were performed to estimate the associations between Al concentrations and ASQ-3 scores.

RESULTS

After adjustment for potential confounders, early-life exposure to Al was not associated with any neurodevelopmental performance at age 6 months. However, Al level was associated with an increased risk of having a low fine motor score (quartile 4 vs. quartile 1, mean difference (MD): -1.63; 95% confidence interval (CI): -3.22, -0.05; P-trend < 0.01) at 12 months. No association was found for communication, gross motor, problem-solving, or personal-social score at 12 months.

SIGNIFICANCE

Early-life exposure to Al may be associated with poor fine motor skills in a dose-response manner among apparently healthy infants at age 12 months.

The REACH registration process: A case study of metallic aluminium, aluminium oxide and aluminium hydroxide

The European Union's REACH Regulation requires determination of potential health and environmental effects of chemicals in commerce. The present case study examines the application of REACH guidance for health hazard assessments of three high production volume (HPV) aluminium (Al) substances: metallic aluminium, aluminium oxide, and aluminium hydroxide. Among the potential adverse health consequences of aluminium exposure, neurotoxicity is one of the most sensitive targets of Al toxicity and the most critical endpoint. This case study illustrates integration of data from multiple lines of evidence into REACH weight of evidence evaluations. This case study then explains how those results support regulatory decisions on classification and labelling. Challenges in the REACH appraisal of Al compounds include speciation, solubility and bioavailability, application of assessment factors, read-across rationale and differences with existing regulatory standards. Lessons learned from the present case study relate to identification and evaluation of toxicologic and epidemiologic data; assessing data relevance and reliability; development of derived no-effect levels (DNELs); addressing data gaps and preparation of chemical safety reports.

Aluminum reproductive toxicity: a summary and interpretation of scientific reports

Publications addressing aluminum (Al)-induced reproductive toxicity were reviewed. Key details were compiled in summary tables. Approximate systemic Al exposure, a measure of bioavailability, was calculated for each exposure, based on the Al percentage in the dosed Al species, Al bioavailability, and absorption time course reports for the exposure route. This was limited to laboratory animal studies because no controlled-exposure human studies were found. Intended Al exposure was compared to unintended dietary Al exposure. The considerable and variable Al content of laboratory animal diets creates uncertainty about reproductive function in the absence of Al. Aluminum-induced reproductive toxicity in female mice and rats was evident after exposure to ≥25-fold the amount of Al consumed in the diet. Generally, the additional daily Al systemic exposure of studies that reported statistically significant results was greater than 100-fold above the typical human daily Al dietary consumption equivalent. Male reproductive endpoints were significantly affected after exposure to lower levels of Al than females. Increased Al intake increased fetus, placenta, and testes Al concentrations, to a greater extent in the placenta than fetus, and, in some cases, more in the testes than placenta. An adverse outcome pathway (AOP) was constructed for males based on the results of the reviewed studies. The proposed AOP includes oxidative stress as the molecular initiating event and increased malondialdehyde, DNA and spermatozoal damage, and decreased blood testosterone and sperm count as subsequent key events. Recommendations for the design of future studies of reproductive outcomes following exposure to Al are provided.

Solvent-tuned discriminant sensing of Al3+, Mg2+and HF2−by vanilinyl-picolinyl hydrazide Schiff base

X-ray structurally characterized solid-state emissive vanilinyl organic entity shows fluorescence sensitivity towards multi-analytes.

Impact of Prenatal and Postnatal Treatment of Sodium Fluoride and Aluminum Chloride on Some Hormonal and Sensorimotor Aspects in Rats

In most communities, there is a constant exposure to environmental pollutants with probable negative impact on the development of the nervous system. Among these pollutants are the sodium fluoride (NaF) and aluminum chloride (AlCl₃) which may represent a real threat to the proper functioning of the brain. This study comprises two fundamentally different strategies; in the first one, pregnant rats were administered a daily dose of NaF (0.15 g /L) or AlCl₃ (500 mg/L) in the drinking water either separately or in combination with each other from day 6 of gestation until just after weaning. In the second approach, the male rats born to mothers exposed to the pollutants were divided into two groups. In the first, rats were continued to be treated with the same pollutants administered to them in the drinking water at the same dose level until the age of 70 days. The rats of the second group were supplied with drinking water without either one of the pollutants for a similar period of time. The rats exposed to NaF separately or in combination with AlCl₃ during the prenatal life and subsequently through the postnatal stages exhibited disturbance in the locomotor activities. This was concomitant with alterations in plasma, PTH, ACTH, and estradiol levels. Additionally, the serum levels of LH and testosterone were altered in the two groups treated with sodium fluoride during the prenatal and up to the weaning periods or in the group which continued to have the NaF until day 70 after birth.

An aggregation-induced emission (AIE) active probe for multiple targets: a fluorescent sensor for Zn(2+) and Al(3+) & a colorimetric sensor for Cu(2+) and F(-)

A rationally designed probe L, which consists of both cation and anion binding sites, is capable of displaying interesting aggregation induced emission (AIE) properties. L not only can sense Al(3+) and Zn(2+) through selective turn-on fluorescence responses in 9 : 1 methanol-HEPES buffer (5 mM, pH 7.3; 9 : 1, v/v) medium due to metal ion triggered AIE activity, but also can distinguish them through individual emission signals. L can also detect Cu(2+) in mixed buffer medium and F(-) in acetonitrile through sharp colorimetric responses. All the sensing processes are conspicuous through the naked eye. A theoretical study strongly backed the proposed sensing mechanisms.

Windows of sensitivity to toxic chemicals in the motor effects development

Many chemicals currently used are known to elicit nervous system effects. In addition, approximately 2000 new chemicals introduced annually have not yet undergone neurotoxicity testing. This review concentrated on motor development effects associated with exposure to environmental neurotoxicants to help identify critical windows of exposure and begin to assess data needs based on a subset of chemicals thoroughly reviewed by the Agency for Toxic Substances and Disease Registry (ATSDR) in Toxicological Profiles and Addenda. Multiple windows of sensitivity were identified that differed based on the maturity level of the neurological system at the time of exposure, as well as dose and exposure duration. Similar but distinct windows were found for both motor activity (GD 8-17 [rats], GD 12-14 and PND 3-10 [mice]) and motor function performance (insufficient data for rats, GD 12-17 [mice]). Identifying specific windows of sensitivity in animal studies was hampered by study designs oriented towards detection of neurotoxicity that occurred at any time throughout the developmental process. In conclusion, while this investigation identified some critical exposure windows for motor development effects, it demonstrates a need for more acute duration exposure studies based on neurodevelopmental windows, particularly during the exposure periods identified in this review.

Pyrene Scaffold as Real-Time Fluorescent Turn-on Chemosensor for Selective Detection of Trace-Level Al(III) and Its Aggregation-Induced Emission Enhancement

A pyrene based fluorescent probe, 3-methoxy-2-((pyren-2yl-imino)methyl)phenol (HL), was synthesized via simple one-pot reaction from inexpensive reagents. It exhibited high sensitivity and selectivity toward Al(3+) over other relevant metal ions and also displayed novel aggregation-induced emission enhancement (AIEE) characteristics in its aggregate/solid state. When bound with Al(3+) in 1:1 mode, a significant fluorescence enhancement with a turn-on ratio of over ∼200-fold was triggered via chelation-enhanced fluorescence through sensor complex (Al-L) formation, and amusingly excess addition of Al(3+), dramatic enhancement of fluorescence intensity over manifold through aggregate formation was observed. The 1:1 stoichiometry of the sensor complex (Al-L) was calculated from Job's plot based on UV-vis absorption titration. In addition, the binding site of sensor complex (Al-L) was well-established from the (1)H NMR titrations and also supported by the fluorescence reversibility by adding Al(3+) and EDTA sequentially. Intriguingly, the AIEE properties of HL may improve its impact and studied in CH3CN-H2O mixtures at high water content. To gain insight into the AIEE mechanism of the HL, the size and growth process of particles in different volume percentage of water and acetonitrile mixture were studied using time-resolved photoluminescence, dynamic light scattering, optical microscope, and scanning electron microscope. The molecules of HL are aggregated into ordered one-dimensional rod-shaped microcrystals that show obvious optical waveguide effect.

A simple nanoporous silica-based dual mode optical sensor for detection of multiple analytes (Fe3+, Al3+ and CN−) in water mimicking XOR logic gate

A simple but versatile nanoporous silica-based optical sensor was synthesized and characterized using different techniques such as XRD, BET, TGA, and FT-IR.

A highly sensitive fluorescent sensor for Al3+and Zn2+based on a diarylethene salicylhydrazide Schiff base derivative and its bioimaging in live cells

A new photochromic diarylethene based sensor with a salicylhydrazide Schiff base displayed a dual-mode with a “turn on” fluorescence response and color changes upon addition of Al³⁺or Zn²⁺.

A new simple Schiff base fluorescence "on" sensor for Al3+ and its living cell imaging

The simple Schiff base (Z)-N-benzylidenenaphthalen-1-amine (L) acts as an effective fluorescence sensor for Al(3+) by "off-on" mode, and ca. 42 times enhancement in fluorescence intensity is observed. The detection limit of L towards Al(3+) is observed to be 5 × 10(-5) M. UV/Visible and fluorescence data as well as DFT calculations confirm 1:3 coordination between Al(3+) and L through N atoms in a pyramidal shape. L is employed for imaging the Al(3+) ion in living biological cells and for the determination of the Al(3+) ion in bovine serum albumin.

Influence of Some Mineral Ions on Lipid Peroxidation in Vitro

Recently, a growing interest has been recorded in mineral content of mammalian diet, which might impair their development. Focused on the topic, we studied the effect of Al3+, Si4+, Sr2+ and Na2S on the intensity of malondialdehyde (MDA) production in vitro. MDA, as one of oxidative stress markers, was determined in rat brain homogenates in the conditions of lipid peroxidation (LP) activated by iron ions and ascorbate. Our results showed a significant increase in lipid peroxidation after addition of aluminium ions. We assume a probable impact of Al3+ on active or regulatory centres of antioxidant enzymes, resulting in the reduction of their antioxidant functions. The addition to Si4+ or Na2S to samples with Al3+ significantly decreased Fe2+-activated LP. We can explain the influence of Na2S by the formation of insoluble complexes with iron. Similarly, the effect of Si4+ can be related to the production of aluminium-silicon complexes. In our view, an optimal ratio of aluminium and silicon ions (or aluminium ions and Na2S) in the diet might have beneficial effects on brain functions.

A new fluorescent probe for Al(3+) based on rhodamine 6G and its application to bioimaging

A water-soluble rhodamine-based derivative (L) has been rationally designed for selective recognition of Al(3+) in aqueous medium with good sensitivity. The addition of Al(3+) to the aqueous solution of L induces a remarkable fluorescence enhancement along with obvious color change detected by the naked eye, due to the ring-opening mechanism of the rhodamine spirolactam, which has been proved by single crystal diffraction analyses directly. The recognizing behavior has been investigated both experimentally and computationally. Furthermore, the fluorescent probe can also be used as a bioimaging reagent for detection of Al(3+) in living cells.

A molecular assembly of piperidine carboxylic acid dithiocarbamate on gold nanoparticles for the selective and sensitive detection of Al3+ion in water samples

Schematic representation for the colorimetric sensing of Al³⁺ion using PCA-DTC-Au NPs as a probe.

A differentially selective molecular probe for detection of trivalent ions (Al3+, Cr3+and Fe3+) upon single excitation in mixed aqueous medium

A chemosensor was developed which could selectively detect and differentiate trivalent metal ions (Al³⁺, Cr³⁺and Fe³⁺) upon single excitation at two different wavelengths in aqueous medium.

A simple coumarin as a turn-on fluorescence sensor for Al(iii) ions

A simple non-Schiff's base type molecule serves as a selective chemosensor for Al³⁺ based on the chelation-enhanced fluorescence (CHEF) effect.

Aluminum alters NMDA receptor 1A and 2A/B expression on neonatal hippocampal neurons in rats

Background

High aluminum (Al) content in certain infant formula raises the concern of possible Al toxicity on brain development of neonates during their vulnerable period of growing. Results of in vivo study showed that Al content of brain tissues reached to 74 μM when oral intake up to 1110 μM, 10 times of that in the hi-Al infant formula.

Methods

Utilizing a cultured neuron cells in vitro model, we have assessed Al influence on neuronal specific gene expression alteration by immunoblot and immunohistochemistry and neural proliferation rate changes by MTT assay.

Results

Microscopic images showed that the neurite outgrowth of hippocampal neurons increased along with the Al dosages (37, 74 μM Al (AlCl₃)). MTT results also indicated that Al increased neural cell viability. On the other hand, the immunocytochemistry staining suggested that the protein expressions of NMDAR 1A and NMDAR 2A/B decreased with the Al dosages (p < 0.05).

Conclusion

Treated hippocampal neurons with 37 and 74 μM of Al for 14 days increased neural cell viability, but hampered NMDAR 1A and NMDAR 2A/B expressions. It was suggested that Al exposure might alter the development of hippocampal neurons in neonatal rats.

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.

Concurrent exposure to aluminum and stress during pregnancy in rats: Effects on postnatal development and behavior of the offspring

The present study was conducted to assess the potential combined influence of maternal restraint stress and aluminum (Al) exposure on postnatal development and behavior in the offspring of exposed rats. Female rats were concurrently exposed to 0 (control group), 50 or 100 mg/kg/day of Al administered as Al nitrate nonahydrate in drinking water with citric acid (355 or 710 mg/kg/day) for a period of 15 days prior to mating with untreated males. Aluminum exposure was maintained throughout the gestational, lactational and post-weaning periods. On days 6-20 of gestation, one-half of the pregnant animals in each group were restrained for 2 h/day. Food consumption and maternal body weight were decreased in the groups exposed to restraint only or combined with the highest Al dose. All of the animals were allowed to deliver and wean their offspring. The pups were evaluated for physical development and neuromotor maturation. Moreover, open-field activity, passive avoidance, and spatial learning in a water maze were also determined on postnatal days 30, 35 and 60, respectively. Body weight of pups treated with 100 mg/kg/day of Al was decreased relative to controls from postnatal day 12 through 21, sexual maturation was delayed in Al treated females and in males exposed to 100 mg/kg/day. Forelimb grip strength was reduced in males exposed to 100 mg/Al/kg/day and in females exposed to this Al dose plus prenatal restraint. Learning in a passive avoidance task indicated facilitated performance for Al treated rats at 100 mg/kg/day combined with prenatal restraint as evidenced by longer avoidance latencies, while learning in a water maze task showed a shorter latency to find the platform on acquisition day 2 for Al treated rats. However, no effects of Al on water maze performance were detected during the retention probe trial in which the only effect noted was an increase in the platform quadrant swim time for the prenatal restraint group. In general terms, the results of the present study did not show a notable influence of maternal restraint on the Al-induced postnatal developmental and behavioral effects in the offspring of prenatally Al-exposed rats.

Oxidative damage following chronic aluminium exposure in adult and pup rat brains

Aluminium is known to cause neurotoxic effects. In the past few years there has been an upsurge of interest in aluminium exposure through diet and environment, which might impair the development of mammals. The present in vivo study was designed to investigate the potential of aluminium to participate in either antioxidant or pro-oxidant processes in both developed and developing rat brain. Markers of oxidative stress were determined in rat brains exposed to AlCl3 (100 mg/kg body weight) for 8 weeks. The aluminium dose was given to adult rats for 8 weeks and in another group, exposure of aluminium for 60 days was done postnatally, 21 days to the feeding mother (lactation period) and 39 days to the rat pups. The results showed a statistically significant (p<or=0.01) increase in lipid peroxidation (LPx) as measured by production of malondialdehyde in both cerebrum and cerebellum of pup brains. A significant increase (p<or=0.001) in LPx was also observed in the adult group. Furthermore, aluminium exposure resulted in a significant decrease in superoxide dismutase and catalase activity in both regions of the brain of developing and developed rat brain. Thus the results of the present study suggest that in rats, aluminium (100 mg/kg body weight) has a pro-oxidant effect and thus acts as a neurotoxin.

Aluminium in Over-the-Counter Drugs

In the early 1970s, aluminium toxicity was first implicated in the pathogenesis of clinical disorders in patients with chronic renal failure involving bone (renal osteomalacia) or brain tissue (dialysis encephalopathy). Before that time the toxic effects of aluminium ingestion were not considered to be a major concern because absorption seemed unlikely to occur. Meanwhile, aluminium toxicity has been investigated in countless epidemiological and clinical studies as well as in animal experiments and many papers have been published on the subject. It is now commonly acknowledged that aluminium toxicity can be induced by infusion of aluminium-contaminated dialysis fluids, by parenteral nutrition solutions, and by oral exposure as a result of aluminium-containing pharmaceutical products such as aluminium-based phosphate binders or antacid intake. Over-the-counter antacids are the most important source for human aluminium exposure from a quantitative point of view. However, aluminium can act as a powerful neurological toxicant and provoke embryonic and fetal toxic effects in animals and humans after gestational exposure. Despite these facts, the patient information leaflets from European antacids that are available OTC show substantial differences regarding warnings from aluminium toxicity. It seems advisable that all patients should receive the same information on aluminium toxicity from patient information leaflets, in particular with regard to the increased absorption through concomitant administration with citrate-containing beverages and the use of such antacids during pregnancy.

Long-term consequences of developmental exposure to aluminum in a suboptimal diet for growth and behavior of Swiss Webster mice

Swiss Webster mice received diets containing 7 (control), 100, 500, or 1000 microg aluminum (Al)/g throughout development (conception to 35 days of age) and were tested behaviorally as adults (>90 days of age). The basal diet contained the same percent of recommended dietary amounts of phosphate, calcium, iron, magnesium, and zinc as young women usually consume. These "realistic" dietary conditions led to 12--15% growth retardation in the Al1000 group at the time of testing. Females were evaluated in a cognitive task (Morris water maze) at 3 months of age and males were evaluated in a motor test battery at 5 months of age. Al1000 females (n=16) were slower than controls in learning the Morris maze, as suggested by fewer mice with low latencies during the first three sessions of the four-session learning series. Influences of Al on cue utilization were also found in probe sessions eliminating salient or nonsalient cues. With motor testing, the Al1000 males (n=20) had significantly lower hindlimb grip strength than controls, an effect that was eliminated by covariance analysis with body weight. Subtle influences of Al on rotarod and wire suspension tests were also noted. The data suggest that developmental Al exposure under normal, but less than optimal, dietary conditions can lead to subtle but long-term effects on growth and brain function in adulthood.

Aluminium incorporation into the brain of rat fetuses and sucklings

Aluminium is highly neurotoxic and inhibits prenatal and postnatal development of the brain in humans and experimental animals. However, the incorporation of aluminium into the brain of fetuses and sucklings during gestation and lactation has not been well clarified because aluminium lacks a suitable isotope for a tracer experiment. In this study, we used 26Al (a radioisotope of aluminium with a half-life of 716,000 years) as a tracer, and measured 26Al incorporation into the brain of rat fetuses and sucklings by using accelerator mass spectrometry. 26Al (26AlCl3) was subcutaneously injected into pregnant rats and lactating rats. By day 21 of gestation, considerable amounts of the 26Al injected into the pregnant rats had been transferred to the brain and nuclear fraction (brain cell nuclei) of the rat fetuses. From day 5 to day 20 postpartum, the amounts of 26Al measured in the brain of suckling rats increased significantly. On day 20 postpartum, 26Al was found in the nuclear fraction isolated from the brain of suckling rats. It is concluded that 26Al subcutaneously injected into pregnant rats and/or lactating rats was incorporated into the brain and nuclear fraction (brain cell nuclei) of fetuses and sucklings through the transplacental passage and/or maternal milk.

Lifelong feeding of a high aluminum diet to mice

In three experiments, high aluminum diets (1000 microg Al/g diet) were fed to mice throughout their life span to determine whether neurodegenerative changes were seen with aging. Brain Al concentrations were slightly lower in Al-treated mice than controls. Generally, no increased mortality or gross evidence of neurodegeneration was seen in Al-treated mice. Eighteen and 24 month old Swiss Webster mice fed the high aluminum diet differed from controls on some neurobehavioral tests, but differences were no greater than previously seen with shorter term exposure in younger mice. Both brain Al concentration and susceptibility to oxidative damage, as measured with TBARS, were lower in the Al-treated aged mice than in controls. In addition, Al-treated aged Swiss Webster and C57BL/6J mice showed somewhat enhanced performance in the Morris water maze. Finally, Al treatment did not exacerbate the effect of MPTP treatment on a grip strength measure in either 66 or 235 day old male mice. Swiss Webster and C57BL/6J mice do not appear to provide useful models for studying Al-induced neurodegenerative changes in aging.

Altered dopamine turnover in murine hypothalamus after low-dose continuous oral administration of aluminum

Aluminum, a known neurotoxic substance, has been suggested as a possible contributing factor in the pathogenesis of Alzheimer's disease. Ground-water pollution by aluminum has been recently reported. In the current study groups of 5 male BALB/c mice were administered aluminum ammonium sulfate in drinking water ad libitum at 0, 5, 25, and 125 mg/L aluminum for 4 weeks. At the termination of aluminum exposure, their brains were removed and dissected into cerebrum, cerebellum, medulla oblongata, midbrain, corpus striatum, and hypothalamus. The concentration of norepinephrine (NE), dopamine (DA), dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), serotonin (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA), were determined in each brain area. DA, DOPAC, and HVA levels were lower in the hypothalamus of aluminum-treated mice, most notably in the low-dose group, as compared with control. No marked alterations in NE, 5-HT, and 5-HIAA levels were detected in any brain region. Changes in the concentration of DA and its metabolites measured in the hypothalamus suggest an inhibition of DA synthesis by aluminum.

Behavioral consequences of marginal iron deficiency during development in a murine model

Marginal iron deficiency is a common nutritional disorder in human populations world-wide; however, the neurobehavioral effects of chronic marginal iron (Fe) intakes during development are poorly characterized in animals. For this reason, we investigated whether mice reared on marginal Fe diets during pre- and postnatal development would experience neurobehavioral deficits. Swiss-Webster mice reared on either control (75 ppm Fe) or marginal iron (12.5 ppm) diets were assessed for changes in behavior on postnatal days 30, 40, and 50 using a neurobehavioral test battery. Because alterations in tissue mineral status can lead to an oxidative stress, markers of both protein (glutamine synthetase) and lipid oxidation (TBARS) were measured. Marginal iron animals exhibited a 20-55% reduction in grip strength. Although both marginal iron males and females demonstrated persistent lowering of body weights, statistical analysis using weight as the covariate demonstrated that the grip strength reductions were independent of body weight changes. This reduction in grip strength occurred in conjunction with a 25-45% lowering of brain iron in the marginal iron animals. Despite dramatic reductions in both brain and liver iron, hematocrits were unaffected by dietary iron reductions. Oxidative stress was indicated by an elevation in noniron-stimulated TBARS in the cerebellum of marginal iron animals. These data suggest that a chronic marginal Fe deficiency during critical periods of growth can result in functional changes in motor development even in the absence of iron deficiency anemia; furthermore, alterations in mineral status and oxidative stress may be mechanisms contributing to these observed changes.

Behavioral effects of aluminum in mice: influence of restraint stress

The influence of restraint stress on potential aluminum (Al)-induced behavioral changes was assessed in CD-1 mice. Three groups of adult mice were given 0, 300 and 600 mg Al/kg body weight per day in drinking water for 2 weeks. One-half of the animals in each group were concurrently subjected to restraint stress during 1 h per day throughout the study. After cessation of treatment, open-field activity, active avoidance learning, and motor resistance and coordination of the animals were evaluated. At the end of the behavioral testing period, mice were killed and Al concentrations were determined in a number of tissues. There were no remarkable effects of Al, restraint stress or their combined administration on either open-field activity or on the number of avoidances in an automatic reflex conditioner. However, a lower motor resistance and coordination in a rotarod were observed following exposure to Al at 600 mg/kg/day, restraint alone or concurrent administration of Al (300 and 600 mg/kg/day) plus restraint stress. The levels of Al in whole brain and cerebellum were significantly enhanced in mice exposed to Al plus restraint. Although the present results scarcely show Al-induced neurobehavioral effects, the influence of restraint stress on Al levels in whole brain and cerebellum can be the basis for further studies on the potential role of this element in certain neurological disorders.

Effects of dietary aluminum on pubertal mice

Puberty is a period of rapid growth and nervous system maturation, but it is little studied as a sensitive period for neurotoxicant effects. In this experiment, diets containing 7 (control), 100, 500, 750, or 1000-microg aluminum (Al.)/g diet as Al lactate and 3.2% citrate (to promote Al absorption) were fed to male mice beginning at puberty (45 days of age) for either 4 or 8 weeks. ANOVAs were conducted to identify group differences from control, and regression analysis with Al intake was used to evaluate dose-response trends. Dose-responsive effects of dietary Al on brain weight, Al, and Mn concentration, and on grip strength were seen at the end of the 4-week exposure. Although brain Al concentration was also elevated at the end of the 8-week exposure, no dose-responsive effects on other variables were noted. Neither exposure influenced auditory startle amplitude. The period after puberty was sensitive to dietary Al exposure, but affected variables apparently recovered when exposure continued into young adulthood.

Membrane composition can influence the rate of Al3+-mediated lipid oxidation: effect of galactolipids

In the first part of the present study we investigated the effects of pre-natal and early postnatal exposure of mice to high levels of dietary Al3+ on myelin lipid composition and lipid oxidation. We found: (1) a significantly higher (104%; P<0.01) content of brain myelin galactolipids in the high-Al3+ group than in controls, and, (2) a significant correlation (r2=0.70; P<0.01) between the concentration of myelin galactolipids and TBARS (2-thiobarbituric acid-reactive substances) content, a parameter of lipid oxidation. Based on these results, we evaluated in an in vitro model (liposomes) whether galactolipids could affect the capacity of Al3+ to stimulate Fe2+-initiated lipid oxidation, and whether this effect could be due to the promotion of changes in membrane physical properties (membrane phase separation and rigidification). The presence of galactolipids (10-40 mol%) in the liposomes caused a concentration-dependent increase in the stimulatory effect of Al3+ on Fe2+-induced TBARS production, and on the ability of Al3+ to induce phase separation and membrane rigidification. The capacity of Al3+ (10-100 microM) to induce lateral phase separation in liposomes composed of phosphatidylcholine/phosphatidylserine/galactolipid (36:24:40, molar ratio) was correlated significantly (r2=0.99; P<0. 001) with the stimulatory action of Al3+ on Fe2+-induced TBARS production. We propose that the high content of galactolipids found in myelin from Al3+-intoxicated mice could favour Al3+-induced changes in membrane physical properties, with the subsequent acceleration of lipid oxidation rates.

Rat embryos cultured under copper-deficient conditions develop abnormally and are characterized by an impaired oxidant defense system

Rat embryos (gestation days 9.0 and 10.0) obtained from dams that were fed a Cu-adequate (8 micrograms Cu/g) or Cu-deficient (< 0.5 micrograms Cu/g diet were cultured for 48 hr in Cu-adequate (16.2 microM) or Cu-deficient (1.0 microM) rat serum. Control embryos cultured in control serum were morphologically normal. Embryos from Cu-deficient dams developed abnormally when cultured in Cu-deficient serum; the abnormalities included distended hindbrains, blisters, blood pooling, and cardiac defects. Control embryos cultured in Cu-deficient serum and Cu-deficient embryos cultured in control serum also showed abnormal development, but to a lesser degree than that of the Cu-deficient embryos cultured in Cu-deficient serum. To test the idea that the above abnormalities were due in part to free radical induced damage occurring secondary to an impaired oxidant defense system, a chemiluminescence assay was used to detect superoxide dismutase (SOD) activity in the cultured embryos. SOD activity was lowest in embryos cultured in Cu-deficient serum. When the Cu-deficient serum was supplemented with antioxidants (CuZnSOD or glutathione peroxidase), its teratogenicity was reduced. These data support the idea that an impaired oxidant defense system contributes to the dysmorphology associated with Cu deficiency. However, the Cu-deficient embryos also had low cytochrome c oxidase activity compared to control embryos--thus, multiple factors are likely contributing to Cu deficiency-induced abnormalities.

Does aluminum exposure of pregnant animals lead to accumulation in mothers or their offspring?

There is concern that environmental and dietary aluminum (Al) might cause developmental toxicity. To better understand this concern, we reviewed published studies which administered Al compounds to pregnant animals and measured accumulation of Al in mother, fetus, or born offspring. A total of 7 studies were identified which administered Al during gestation and evaluated fetal accumulation. Another 7 studies administered Al at least until birth and then evaluated accumulation in mothers and/or pups. These 14 studies included 4 different Al compounds (hydroxide, chloride, lactate, and citrate) administered by 4 different routes (gavage, feed, intraperitoneal injection, and subcutaneous injection) with total doses ranging from 13.5 to 8,400 mg/kg. Fetal Al levels were not increased in 6 of 7 studies and pup Al levels were not increased in 4 of 5 studies in which they were measured. Maternal Al levels were increased in some studies, but there was no consistent pattern of organ-specific accumulation and several positive studies were contradicted by subsequent reports from the same laboratory. Placental levels were increased in 6 of 9 studies and were greater than corresponding fetal levels. The weight of evidence in these studies suggests that environmental and dietary Al exposures are unlikely to pose risks of Al accumulation to pregnant animals or their fetuses.

Aluminum exposure and metabolism

Aluminum (Al) is a nonessential, toxic metal to which humans are frequently exposed. Oral exposure to aluminum occurs through ingestion of aluminum-containing pharmaceuticals and to a lesser extent foods and water. Parenteral exposure to aluminum can occur via contaminated total parenteral nutrition (TPN), intravenous (i.v.) solutions, or contaminated dialysates. Inhalation exposure may be important in some occupational settings. The gut is the most effective organ in preventing tissue aluminum accumulation after oral exposure. Typically gastrointestinal absorption of aluminum from diets is < 1%. Although the mechanisms of aluminum absorption have not been elucidated, both passive and active transcellular processes and paracellular transport are believed to occur. Aluminum and calcium may share some absorptive pathways. Aluminum absorption is also affected by the speciation of aluminum and a variety of other substances, including citrate, in the gut milieu. Not all absorbed or parenterally delivered aluminum is excreted in urine. Low glomerular filtration of aluminum reflects that most aluminum in plasma is nonfiltrable because of complexation to proteins, predominantly transferrin. The importance of biliary secretion of aluminum is debatable and the mechanism(s) is poorly understood and appears to be saturable by fairly low oral doses of aluminum.

Myelin is a preferential target of aluminum-mediated oxidative damage

The capacity of Al3+ to promote oxidative damage to brain membranes was investigated both in vitro and in vivo. In vitro, Al3+ and related metals (Sc3+, Ga3+, In3+, Be2+, Y3+, and La3+) stimulated Fe2+-initiated lipid and protein oxidation in brain myelin and synaptic membranes. Al3+, Sc3+, Y3+, and La3+ significantly promoted protein-associated carbonyl production in myelin, while in synaptic membranes, the stimulatory effect was observed in the presence of Ga3+, In3+, Y3+, Sc3+, and La3+. In myelin the magnitude of the stimulation of lipid oxidation followed the order Sc3+, Y3+, La3+ > Al3+, Ga3+, In3+ > Be2+. When compared to mitochondria and microsomal and synaptic membranes, myelin showed a marked susceptibility to Al3+-mediated lipid peroxidation. The differential susceptibility of myelin compared to synaptic membranes could not be explained by differences in membrane composition, since the relative content of negatively charged phospholipids (binding sites) was similar for both membranes, and myelin had a lower content of poly-unsaturated fatty acids (substrates of lipid oxidation) and a higher concentration of alpha-tocopherol compared to synaptic membranes. In a model of Al3+ intoxication imposed to mice during pregnancy and early development, a 72% higher content of lipid peroxidation products was found in brain myelin. The fluidity of myelin evaluated by the polarization fluorescence of 1,3-diphenylhexatriene was significantly higher in the Al3+-intoxicated mice than in controls. Since myelin has a high relative content of lipid:protein compared to other membranes, these results support our hypothesis that ions without redox capacity can stimulate in vitro and in vivo lipid oxidation by promoting phase separation and membrane rigidification, thus accelerating lipid oxidation.

The effect of social learning on a conditioned avoidance response of rats treated prenatally with aluminum lactate

Aluminum (Al) has been proven to be a behavioral teratogenic agent in a number of experimental studies. Prenatal exposures to Al lactate have been shown to cause cognitive deficits in a variety of species. The present experiment was carried out on SPRD rat pups treated prenatally with Al lactate to determine whether observational conditioning (social learning) would reverse the impairment in learning described previously following such treatment. A conditioned avoidance response was used as an observational learning task. The results provide evidence that Al-treated pups are capable of social learning (i.e., the performance of the avoidance response improved as a result that Al-treated learning); however, the response latency of the avoidance response was not different in these animals from those that were not exposed to such facilitation, suggesting that additional factors are involved in the effects of prenatal aluminum intoxication on cognitive processes.

Developmental patterns of aluminum and five essential mineral elements in the central nervous system of the fetal and infant guinea pig

Al is found in the developing conceptus, but little information is available concerning its tissue distribution and its changes in concentration with age. Because Al has affinity for many of the same biological ligands as the essential mineral cations Ca, Mg, Zn, Fe, and Mn, we hypothesized that Al might show a pattern of developmental concentrations that was similar to one or more of these elements in the brain, a major target of Al toxicity. Concentrations of Al, Ca, Mg, Zn, Fe, and Mn were measured in spinal cord, brainstem, cerebellum, and forebrain of guinea pig fetuses on gestation day (GD) 30 and 45, at birth, and on postnatal day (PND) 3, 6, and 12. Dams were fed commercial guinea pig chow, which contained 47 micrograms Al/g. Tissue Al and Mn were measured with electrothermal atomic absorption spectrophotometry (ETAAS), and the other elements with inductively coupled axial plasma spectroscopy (ICAP-AES). Al concentrations in the brain regions were highest in spinal cord, brainstem, and cerebellum, and decreased during late gestation and lactation. Al did not show marked increases in regional brain concentrations during the final third of gestation as did Fe, Mg, and Zn. In contrast to Fe and Ca, Al did not accumulate in placenta. Al was the only element to show higher concentrations in spinal cord than in any other tissue at birth. In summary, the tissue distribution of Al did not follow that of essential cations as examined in this study.

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.

Aluminum alters iron and manganese uptake and regulation of surface transferrin receptors in primary rat oligodendrocyte cultures

Transferrin (Tf) is a major transport protein for both iron (Fe) and aluminum (Al), as well as manganese (Mn) and it can mediate cellular uptake of these elements via cell surface Tf receptors. To study the effect of Al-Tf on Tf receptor regulation, primary oligodendrocyte cultures were prepared from cortices of newborn rats. The effects of Al-Tf on 54Mn and 59Fe uptake were compared to those of apo-, Fe-, or Mn-Tf (1.25 microM). To examine changes in cell surface Tf binding capacity, preincubation (4 h, 37 degrees C) was performed with apo-, Al- or Fe-Tf and homologous receptor binding studies were subsequently conducted with 125I-Fe-Tf at 4 degrees C. Incubation with Al-Tf, but not with equimolar amounts of Al chloride or Al citrate, led to dose-related increases in cellular Al. Incubation with either Al- or Fe-Tf decreased 59Fe uptake, while incubation with either Al- or Mn-Tf decreased 54Mn uptake. Surface Tf receptor sites/cell were 1.05, 0.60 and 0.46 x 10(5) after incubations with equivalent amounts of apo-, Fe-, and Al-Tf respectively. The data suggest that Al-Tf down-regulates surface Tf receptors on oligodendrocytes and can limit Fe and Mn uptake through this mechanism.

Zinc status does not affect aluminum deposition in tissues of rats

To examine whether zinc deficiency would increase the toxicity of dietary aluminum, weanling, male Sprague-Dawley rats were fed purified diets containing either 2 or 30 mg Zn/kg diet, with or without 500 mg Al/kg diet for 28 d. Individually pair-fed rats were fed the 30 mg Zn/kg diet with or without added aluminum to control for inanition secondary to zinc deficiency. Rats fed the 2 micrograms Zn/kg diet showed evidence of zinc deficiency, including anorexia, growth retardation, and depressed concentrations of zinc in tibias and livers. Zinc deficiency did not significantly increase the concentrations of aluminum in the tibias, livers, kidneys, or regions of the brain examined (cerebrum, cerebellum, midbrain, and hippocampus). Inclusion of aluminum in the diet did not alter aluminum concentrations in the various tissues. Under the conditions of this study, zinc deficiency did not result in greater sensitivity to dietary aluminum exposure.

Reproductive and developmental toxicity of aluminum: a review

It is well known that aluminum is a developmental toxicant when administered parenterally. However, until recently, there was little concern about embryo/fetal consequences of aluminum ingestion because bioavailability was considered low. The importance of the route of exposure and the chemical form of the aluminum compound on the developmental toxicity of this element are now well established. Although no evidence of maternal and embryo/fetal toxicity was observed when high doses of aluminum hydroxide were given orally to pregnant rats and mice during organogenesis, signs of maternal and developmental toxicity were found in mice when aluminum hydroxide was given concurrently with citric or lactic acids. On the other hand, studies in rabbits have shown that aluminum-induced behavioral toxicity is greater in adult and aged animals than in young adults. However, maternal dietary exposure to excess A1 during gestation and lactation which did not produce maternal toxicity would be capable of causing permanent neurobehavioral deficits in weanling mice and rats. Adverse effects of parenteral aluminum administration on the mouse male reproductive system have also been reported. The embryo/fetal toxicity of aluminum administration, the potential reproductive toxicology of aluminum exposure, and the neurodevelopmental effects of aluminum are here reviewed.