Neurotoxic effects of aluminium on embryonic chick brain cultures

Anthrax Protective Antigen 63 (PA63): Toxic Effects in Neural Cultures and Role in Gulf War Illness (GWI)

Protective antigen (PA) 63 (PA63) is a protein derived from the PA83 component contained in the anthrax vaccine. The anthrax vaccine ("Biothrax") was administered together with other vaccines to Gulf War veterans, about 35% of whom later developed a multisymptom disease (Gulf War Illness [GWI]), with prominent neurological/cognitive/mood symptoms, among others. The disease has been traditionally attributed to exposures to toxic chemicals during the war but other factors could be involved, including vaccines received. Of these, the anthrax vaccine is the most toxic. Here, we assessed directly the PA63 toxin's harmful effects on cultured neuroblastoma 2A (N2A) cells with respect to cell spreading, process formation, apoptosis, and integrity of cell membrane, cytoskeleton, and mitochondria. We found that, when added in N2A cultures, PA63 toxin led to decreased cell spreading and cell aggregation, leading to apoptosis. The mechanisms of PA63-induced cell damage included compromised cell membrane permeability indicated by enhanced access of propidium iodide in cells. In addition, signaling pathways leading to organization of N2A cytoskeleton were negatively affected, as both actin and microtubular networks were compromised. Finally, the mitochondrial membrane potential was impaired in specific assays. Altogether, these alterations led to apoptosis as a collective toxic effect of PA63 which was substantially reduced by the concomitant addition of specific antibodies against PA63.

Evaluation of biocompatibility using in vitro methods: interpretation and limitations

The in vitro biocompatibility of novel materials has to be proven before a material can be used as component of a medical device. This must be done in cell culture tests according to internationally recognized standard protocols. Subsequently, preclinical and clinical tests must be performed to verify the safety of the new material and device. The present chapter focuses on the first step, the in vitro testing according to ISO 10993-5, and critically discusses its limited significance. Alternative strategies and a brief overview of activities to improve the current in vitro tests are presented in the concluding section.

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.

Combined administration of D-galactose and aluminium induces Alzheimer-like lesions in brain

OBJECTIVE

It has been reported that D-galactose (D-gal) can model subacute aging, and aluminum (Al) acts as a neurotoxin, but combined effects of them have not been reported. The present work aimed to reveal the effect of combined administration of D-gal and Al in mice and compare the effect of D-gal treatment with that of Al treatment.

METHODS

Al was intragastrically administered and D-gal was subcutaneously injected into Kunming mice for 10 consecutive weeks. Learning and memory, cholinergic systems, as well as protein levels of amyloid β (Aβ) and hyperphosphorylated tau were determined using Morri water maze test, biochemical assays and immunohistochemical staining, respectively.

RESULTS

The mice with combined treatment had obvious learning and memory deficits, and showed decreases in brain acetylcholine (ACh) level and in activities of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE). Formation of senile plaque (SP)-like and neurofibrillary tangle (NFT)-like structures was also observed. The behavioral and pathological changes persisted for at least 6 weeks after withdrawal of D-gal and Al.

CONCLUSION

Combined use of D-gal and Al is an effective way to establish the non-transgenic Alzheimer's disease (AD) animal model, and is useful for studies of AD pathogenesis and therapeutic evaluation.

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.

The application of in vitro data in the derivation of the acceptable daily intake of food additives

The acceptable daily intake (ADI) for food additives is commonly derived from the NOAEL (no-observed-adverse-effect level) in long-term animal in vivo studies. To derive an ADI a safety or uncertainty factor (commonly 100) is applied to the NOAEL in the most sensitive test species. The 100-fold safety factor is considered to be the product of both species and inter-individual differences in toxicokinetics and toxicodynamics. Although in vitro data have previously been considered during the risk assessment of food additives, they have generally had no direct influence on the calculation of ADI values. In this review 18 food additives are evaluated for the availability of in vitro toxicity data which might be used for the derivation of a specific data-derived uncertainty factor. For the majority of the food additives reviewed, additional in vitro tests have been conducted which supplement and support the short- and long-term in vivo toxicity studies. However, it was recognized that these in vitro studies could not be used in isolation to derive an ADI; only when sufficient in vivo mechanistic data are available can such information be used in a regulatory context. Additional short-term studies are proposed for the food additives which, if conducted, would provide data that could then be used for the calculation of data-derived uncertainty factors.

Decrease of glial fibrillary acidic protein in rat frontal cortex following aluminum treatment

Aluminum lactate was injected either intraperitoneally or stereotactically into the lateral cerebral ventricles of rats. Rats were killed at various times after treatment, and frontal cortex, hippocampus, and striatum were dissected out. Microtiter plate-based sandwich ELISA and immunohistochemistry were used to measure the glial fibrillary acidic protein (GFAP) concentration. GFAP levels were significantly decreased in frontal cortex 7 days after a single lateral ventricular injection of aluminum lactate and 14 days following systemic treatment. In contrast, neither hippocampus nor striatum exhibited any significant changes in the content of this astrocytic intermediate filament protein after aluminum treatment. Levels of a predominantly astroglial enzyme, glutamine synthetase, were also selectively reduced in the frontal cortex following intraventricular injection of aluminum. This depression exhibited a regional and temporal specificity similar to that found for GFAP. These results suggest a selective and progressive diminution of astrocytic responsivity in frontal cortex following either systemic or intraventricular aluminum dosing. The depression of GFAP levels reported here, which was found in the rat cerebral cortex 7-14 days after aluminum treatment in a species that does not form neurofilamentous aggregates, may reflect extended impairment of astrocytic function and suggests that these cells may be the primary targets of aluminum neurotoxicity.

Growth inhibitory factor and zinc affect neural cell cultures in a tissue specific manner

Deficiency of neuronal growth inhibitory factor (GIF) and abnormalities in zinc homeostasis have been suggested to play a role in the neuropathogenesis of Alzheimer's disease. We report here that embryonic chick cerebral cell cultures zinc and copper containing GIF in the presence of marmoset hippocampal extract reduces significantly and concentration dependently mitochondrial succinate dehydrogenase activity (MTT) and cell mass. In contrast, no indications could be found that GIF affected neural retina cell cultures. Our results suggest that the observed effects of GIF are not elicited by zinc.

The neurotoxic effects of ochratoxin-A are reduced by protein binding but are not affected by l-phenylalanine

Recent in vivo investigations indicate that the mycotoxin ochratoxin A (OTA) is a neurotoxicant during prenatal stages. In line with in vivo data, in our embryonic chick brain and neural retina cell cultures the markers for neuritic outgrowth and differentiation (NF68 and 160 kDa, MAP2 and MAP5) were especially negatively affected. In vivo OTA is nearly completely bound to serum constituents. In our culture system binding of OTA to BSA evoked a significant shift of the concentration-effect relationships in meningeal and brain cell cultures. As a result of the albumin binding the OTA IC5 and IC50 values of all parameters increased by nearly the same value (about 15-fold in brain and 32-fold in meningeal cell cultures). One of the mechanisms responsible for OTA toxicity is thought to be the competitive inhibition versus Phe of Phe-dependent enzymes. Therefore, in addition, we investigated the effects of l-phenylalanine (Phe) and its influence on OTA toxicity in brain and neural retina cell cultures. Phe itself was found to differently affect brain and neural retina cell cultures. However, in both cultures OTA toxicity is not diminished by Phe. Therefore, our data indicate that at least in our cultures competition with Phe-dependent processes does not play a role in OTA toxicity.