Sakae Yumoto

Demonstration of aluminum in amyloid fibers in the cores of senile plaques in the brains of patients with Alzheimer's disease.

Aluminum (Al) exposure has been reported to be a risk factor for Alzheimers disease (senile dementia of Alzheimer type), although the role of Al in the etiology of Alzheimers disease remains controversial. We examined the presence of Al in the Alzheimers brain using energy-dispersive X-ray spectroscopy combined with transmission electron microscopy (TEM-EDX). TEM-EDX analysis allows simultaneous imaging of subcellular structures with high spatial resolution and analysis of small quantities of elements contained in the same subcellular structures. We identified senile plaques by observation using TEM and detected Al in amyloid fibers in the cores of senile plaques located in the hippocampus and the temporal lobe by EDX. Phosphorus and calcium were also present in the amyloid fibers. No Al could be detected in the extracellular space in senile plaques or in the cytoplasm of nerve cells. In this study, we demonstrated colocalization of Al and beta-amyloid (Abeta) peptides in amyloid fibers in the cores of senile plaques. The results support the following possibilities in the brains of patients with Alzheimers disease: Al could be involved in the aggregation of Abeta peptides to form toxic fibrils; Al might induce Abeta peptides into the beta-sheet structure; and Al might facilitate iron-mediated oxidative reactions, which cause severe damage to brain tissues.

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.

ALUMINUM NEUROTOXICITY IN THE RAT BRAIN

To investigate the etiology of Alzheimer’s disease, we administered aluminum to healthy rats and examined the aluminum uptake in the brain and isolated brain cell nuclei by particle-induced X-ray emission (PIXE) analysis. Ten days after the last injection, Al was detected in the rat brain and in isolated brain cell nuclei by PIXE analysis. Al was also demonstrated in the brain after 15 months of oral aluminum administration. Moreover, Al was detected in the brain and isolated brain cell nuclei from the patients with Alzheimer’s disease. Silver impregnation studies revealed that spines attached to the dendritic processes of cortical nerve cells decreased remarkably after aluminum administration. Electron microscopy revealed characteristic inclusion bodies in the hippocampal nerve cells 75 days after the injection. These morphological changes in the rat brain after the aluminum administration were similar to those reportedly observed in the brain of Alzheimer’s disease patients. Our results indicate that Alzheimer’s disease is caused by irreversible accumulation of aluminum in the brain, as well as in the nuclei of brain cells.

26Al incorporation into the brain of suckling rats through maternal milk.

Aluminium inhibits prenatal and postnatal brain development. However, aluminium incorporation into the brain of sucklings through maternal milk has not yet been well clarified because aluminium lacks a suitable isotope for radioactive tracer experiments. Using 26Al (26AlCl(3)) as a tracer, we measured 26Al incorporation into the brain of suckling rats by accelerator mass spectrometry. Lactating rats were subcutaneously injected with 26AlCl(3) from day 1 to day 20 postpartum. Suckling rats were weaned from day 21 postpartum. From day 5 to day 20 postpartum, the amounts of 26Al measured in the cerebrum, cerebellum, spinal cord, liver, and kidneys of suckling rats increased significantly. After weaning, the amounts of 26Al in the liver and kidneys decreased remarkably. Alternatively, in the cerebrum, cerebellum, and spinal cord, as much as 12 to 20% of the 26Al amounts present on day 20 postpartum remained in the tissues on day 730 postpartum. As the life span of rats is about 2 years, we conclude that considerable amounts of the 26Al taken up into the brain of suckling rats through maternal milk remained in their brain throughout their lifetime.

26AL UPTAKE AND ACCUMULATION IN THE RAT BRAIN

Abstract To investigate the cause of Alzheimers disease (senile dementia), 26Al incorporation in the rat brain was studied by accelerator mass spectrometry (AMS). When 26Al was injected into healthy rats, a considerable amount of 26Al entered the brain (cerebrum) through the blood-brain barrier 5 days after a single injection, and the brain 26Al level remained almost constant from 5 to 270 days. On the other hand, the level of 26Al in the blood decreased remarkably 75 days after injection. Approximately 89% of the 26Al taken in by the brain cell nuclei bound to chromatin. This study supports the theory that Alzheimers disease is caused by irreversible accumulation of aluminium (Al) in the brain, and brain cell nuclei.

Transplacental passage of 26Al from pregnant rats to fetuses and 26Al transfer through maternal milk to suckling rats

Abstract Aluminium (Al) is toxic to the growth of fetuses and sucklings. However, the incorporation of Al into fetuses and sucklings in the periods of gestation and lactation has not been well clarified because Al lacks a suitable isotope for a tracer experiment. In this study, we used 26 Al (a radioisotope of Al with half-life of 716,000 yr) as a tracer, and measured 26 Al incorporation into fetuses and sucklings by accelerator mass spectrometry (AMS). To investigate Al incorporation into fetuses through transplacental passage, 26 Al ( 26 AlCl3) was subcutaneously injected into pregnant rats on day 15 of gestation. 26 Al was also subcutaneoulsy injected into lactating rats from day 1 to day 20 postpartum. By day 20 of gestation, 0.2% of the 26 Al injected into a pregnant rat had been transferred to the fetuses, and 26 Al was detected in the brain and liver of the fetuses. On day 9 postpartum, high levels of 26 Al were demonstrated in the brain, liver, kidneys and blood of suckling rats. It is concluded that 26 Al subcutaneously injected into pregnant rats and/or lactating rats is incorporated into their offspring through transplacental passage and/or maternal milk.

MICROPROBE PIXE ANALYSIS OF ALUMINIUM IN THE BRAINS OF PATIENTS WITH ALZHEIMER'S DISEASE

To investigate the cause of Alzheimers disease (senile dementia), we examined aluminium (Al) in the rat liver, and in the brains (hippocampus) of Alzheimers disease patients using heavy ion (5 MeV Si3+) microprobe and proton (2 MeV) microprobe PIXE analysis. Heavy ion microprobes (3 MeV Si2+) have several times higher sensitivity for Al detection than 2 MeV proton microprobes. (1) In the rat liver, Al was detected in the cell nuclei, where phosphorus (P) was most densely distributed. (2) We also demonstrated Al in the cell nuclei isolated from Alzheimers disease brains using heavy ion (5 MeV Si3+) microprobes. Al spectra were detected using 2 MeV proton microprobes in the isolated brain cell nuclei. Al could not be observed in areas where P was present in relatively small amounts, or was absent. Our results indicate that Alzheimers disease is caused by irreversible accumulation of Al in the nuclei of brain cells.

Aluminium toxicity in the rat liver and brain

Abstract To investigate the etiology of Alzheimers disease, we examined the brain and liver tissue uptake of aluminium 5–75 days after aluminium injection into healthy rats. Ten days after the last injection, Al was detected in the brain and the brain cell nuclei by particle-induced X-ray emission (PIXE) analysis. Al was also demonstrated in the liver and the liver cell nuclei by PIXE analysis and electron energy loss spectrometry (EELS). The morphological changes of the rat brain examined 75 days after the injection were similar to those which have been reportedly observed in the brain of patients with Alzheimers disease. These results support the theory that Alzheimers disease is caused by irreversible accumulation of aluminium in the brain, as well as in the nuclei of brain cells.

Aluminum Neurotoxicity and Alzheimer’s Disease

High aluminum concentrations have been demonstrated in the brains of patients with Alzheimer’s disease (senile dementia).1–4 Epidemiological studies have also reported that increased aluminum concentration in drinking water increases the incidence of Alzheimer’s disease.5 Based on these results, a theory that aluminum is the cause of Alzheimer’s disease has been postulated.1–5

Demonstration of Aluminum in the Brain of Patients with Alzheimer’s Disease

Epidemiological studies have revealed that increased aluminum (Al) concentration in drinking water increases the incidence of Alzheimer’s disease (senile dementia of Alzheimer’s disease type) (Martyn et al., 1989; Flaten, 1990; Neri and Hewitt, 1991). Al is a highly neurotoxic substance, and induces degeneration and death of nerve cells in the brains of humans and experimental animals (Mahurkar et al., 1973; Alfrey et al., 1976; Yumoto et al., 1992). We have reported that after subcutaneous injection of Al into rats, the numbers of dendrites and spines (postsynaptic structures of axodendritic synapses) of cortical nerve cells decreased markedly (Yumoto et al., 1992, 1993). These morphological changes were similar to those reported in the brains of patients with Alzheimer’s disease (Purpura, 1975).