Intraventricular administration of the cholinotoxin AF64A increases the accumulation of aluminum in the rat parietal cortex and hippocampus, but not in the frontal cortex

Aluminum induced oxidative stress, astrogliosis and cell death in rat astrocytes, is prevented by curcumin

Aluminum (Al) is recognized potent neurotoxic metal, which causes oxidative stress leading to intracellular accumulation of reactive oxygen species (ROS) and neuronal cell death in various neurodegenerative diseases. Among several medicinal plants with beneficial effects on health, curcumin acts as a multi-functional drug with antioxidant activity. Thus, the purpose of the present study was to evaluate the protective effect of curcumin against aluminum induced-oxidative stress and astrocytes death, in vitro ad in vivo. Incubation of cultured rat astrocytes with two concentrations of Al (37 μM and 150 μM) for 1 h provoked a dose-dependent reduction of the number of living cells as evaluated by Fluorescein diacetate and lactate dehydrogenase assay. Al-treated cells exhibited a reduction of both superoxide dismutase (SOD) and catalase activities. Pretreatment of astrocytes with curcumin (81 μM) prevented Al-induced cell death. Regarding in vivo study, rats were exposed acutely during three consecutive days to three different doses of Al (25 mg/kg, 50 mg/kg and 100 mg/kg, i.p injection), together with curcumin treatment (30 mg/kg). For the chronic model, animals were exposed to Al (3 g/l) in drinking water from intrauterine age to 4 months ages, plus curcumin treatment (175 mg/kg). Data showed that both acute and chronic Al intoxication induced an obvious astrogliosis within motor cortex and hippocampus, while, such effects were restored by curcumin. We showed herein that Al was highly toxic, induced astrocytes death. Then, curcumin protected astrocytes against Al-toxicity. The cytoprotective potential of curcumin is initiated by stimulation of endogenous antioxidant system.

Lack of topographical relationship between sites of aluminum deposition and senile plaques in the Alzheimer's disease brain

Aluminum has been presumed to be involved in the pathogenesis or etiology of Alzheimer's disease. Histochemical demonstration of aluminum in autopsy brains from Alzheimer's disease victims by means of the solochrome azurine method in combination with the methenamine silver technique revealed aluminum-related staining in some neocortical and hippocampal senile plaques and tangles, as well as in the cytoplasm and/or the nuclei of some neurons, and in the cytoplasm of endothelial cells of blood capillaries and pericytes around larger blood vessels. In double-stained samples (first with methenamine silver and then with solochrome azurine) only some plaques displayed the presence of aluminum, while others did not show any sign of the presence of the trace metal. The specificity and sensitivity of solochrome azurine staining was checked in paper spot-test and test-tube experiments combined with flameless atomic absorption spectrophotometry. The results suggest that aluminum is present in brain samples from Alzheimer's disease victims, but the structural localization indicates that it is not primarily involved in the etiology of the disease.

[D-Pen2,D-Pen5]enkephalin, a delta opioid agonist reduces endogenous aluminum content in the rat central nervous system

The in vivo effects of [D-Pen2,D-Pen5]enkephalin, a cyclic peptide agonist with high affinity and selectivity for the delta opioid receptors, on the endogenous aluminum content of selected areas of rat brain and spinal cord were studied by means of atomic absorption spectrophotometry. Intracerebroventricular injection of a subanalgesic dose of [D-Pen2,D-Pen5]enkephalin (0.2 microgram/3 microliters) produced a transient, time-dependent reduction of the aluminum content. This effect was statistically significant in the frontal cortex, hippocampus and striatum, but did not reach the level of significance in the medulla and thoracic spinal cord. The partial depleting effect of [D-Pen2,D-Pen5]enkephalin on aluminum content, in the range of 0.2-1.0 micrograms/3 microliters, was dose-dependent and could be reversed by naloxone pretreatment. Serum aluminum levels were unchanged after [D-Pen2,D-Pen5]enkephalin treatment. Chronic (five weeks), systemic AlCl3 treatment increased the endogenous aluminum content in all central nervous system areas examined. Interestingly, [D-Pen2,D-Pen5]enkephalin i.c.v. produced a slight depletion of this elevated metal level in these areas to values not significantly different from those of the respective control values. Chronic in vivo, as well as in vitro, effects of aluminum on opioid receptor binding characteristics were also studied. Neither the specific binding of [3H][D-Pen2,D-Pen5]enkephalin nor [3H]Tyr-D-Ala-Gly-NMePhe-Gly-ol to membranes of frontal or parietal cortices, striatum or hippocampus, prepared from rats chronically treated with AlCl3, were affected.(ABSTRACT TRUNCATED AT 250 WORDS)

AF64A-induced brain damage and its relation to dementia

Several data obtained in the AF64A-model are of particular relevance for our understanding of the pathogenesis and progression of Alzheimer's disease. The AF64A-induced withdrawal of cholinergic function in the rat hippocampus was associated with reversible functional changes in other neurotransmitters, including noradrenaline, serotonin, somatostatin and glutamate, thereby mimicking changes in Alzheimer's disease. Identical changes in markers for synaptic vesicles were found in Alzheimer's disease and AF64A-model. A study on the role of gender revealed a higher susceptibility to the neurotoxic action of AF64A in female rats. The cholinergic deficit was also responsible for a disinhibition of the negative feedback regulation of glucocorticoids. Increased exposure to glucocorticoids, however, enhanced the vulnerability of hippocampal cholinergic neurons to AF64A. These data indicate that the AF64A-induced cholinergic deficit in the rat brain represents a reliable tool to study several mechanisms possibly involved in Alzheimer's disease.

Neurotoxic effect of enteral aluminium

Long Evans rats were treated for 90 days with water-soluble, insoluble or chelated aluminium compounds. The daily treatments given were as follows: controls, NaCl (100 mg/kg body weight) plus citric acid (30 mg/kg); AlCl3 (30 or 100 mg/kg); Al(OH)3 (100 mg/kg) plus citric acid (30 mg/kg); Al(OH)3 (300 mg/kg). Their learning ability was determined in the labyrinth test at day 90, and the choline-acetyltransferase, acetylcholinesterase activity and aluminium content of the brains were measured. Soluble and chelated aluminium compounds seriously worsened the learning ability, and the aluminium content of the brain was elevated. Acetylcholinesterase activity increased and choline-acetyltransferase activity decreased, resulting in a diminished cholinergic activity, which is a characteristic of Alzheimer's disease.

Aluminum toxicity and Alzheimer's disease. Is there a connection?

Similarities between Alzheimer's disease and aluminum toxicity have led to the suggestion that a causal relationship may exist. However, the two disorders differ in many respects. The author reviews the evidence concerning the relationship between aluminum toxicity and Alzheimer's disease and answers the question, is there a connection?

Cholinotoxic effects of aluminum in rat brain

The in vivo and in vitro effects of Al on the cholinergic system of rat brain were studied. The amount of Al accumulated after the chronic, intraperitoneal administration of aluminium gluconate (Al-G) or AlCl3, both at a dose of 1 mg/ml/100 g of body weight, increased in the frontal and parietal cortices, the hippocampus, and the striatum. Significantly decreased choline acetyltransferase activities after chronic Al treatment were measured in the parietal cortex, the hippocampus, and the striatum, but not in the frontal cortex. The acetylcholinesterase activity was not changed significantly in any brain area investigated. Both Al-G and AlCl3 administrations resulted in a general decrease (to 40-70% of the control values) in the specific l-[3H]nicotine binding, involving all brain areas studied. The specific (-)-[3H]quinuclidinyl benzilate binding was reduced (to 40-60% of the control values) only after 25 days of Al treatment. Al-G and AlCl3 were equivalent in eliciting these reductions in vitro studies revealed different alterations of the cholinergic system in response to Al treatment. No changes were observed either in choline acetyltransferase activity or in cholinergic receptor bindings. Both Al-G and Al2(SO4)3 treatments, however, exhibited a biphasic effect on the acetylcholinesterase activity. At low Al concentrations (10(-8)-10(-6) M), the activity was slightly increased, whereas at higher concentrations (10(-6)-10(-4) M), it was inhibited by a maximum of 25% as compared to the controls. Thus, these cholinotoxic effects are probably due not to a direct interaction between the metal and the cholinergic marker proteins, but rather to a manifestation and consequence of its neurodegenerative effects.