ZINC AND ALZHEIMERS-DISEASE - IS THERE A DIRECT LINK

Zinc is an essential trace element in human biology, but is neurotoxic at high concentrations. Several studies show that zinc promotes aggre gation of beta-amyloid protein, the main component of the senile plaqu es typically found in Alzheimer's disease brains. In other neurologica l disorders where neurons appear to be dying by apoptosis (gene-direct ed cell death), chelatable zinc accumulates in the perikarya of neuron s before, or during degeneration. As there is evidence for apoptotic d eath of neurons in Alzheimer's disease, an involvement of zinc in this process needs to be investigated. Zinc interacts with enzymes and pro teins, including transcription factors, which are critical for cell su rvival and could be linked to apoptotic processes. While controversial , some studies indicate that total tissue zinc is markedly reduced in several brain regions of Alzheimer's patients. At face value, it seems that a paradox exists between reports of a decrease in zinc in the Al zheimer's brain and the putative link to aberrant high zinc levels pro moting plaque formation. An hypothesis to explain this inconsistency i s presented. Neuropathological changes mediated by endogenous or exoge nous stressors may be relevant factors affecting abnormal zinc metabol ism. This paper reviews current investigations that suggest a role of zinc in the etiology of Alzheimer's disease. (C) 1997 Elsevier Science B.V.