Amyloid beta toxicity consists of a Ca(2+)-independent early phase and a Ca(2+)-dependent late phase.
Amyloid beta protein (A beta), which accumulates in the senile plaques in the brain of Alzheimer's patients, is cytotoxic to neurons. A modified 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, in which a yellow redox dye, MTT, is reduced to purple formazan, is very sensitive to the effect of A beta. In primary hippocampal cultures, inhibition of MTT reduction starts within 2 h after the addition of low concentrations of A beta and reaches a plateau in 12 h. This effect of A beta is not blocked by Ca2+ channel blockers or in Ca(2+)-free medium. In contrast, lactate dehydrogenase (LDH) release and trypan blue exclusion, which are indices of cell death, start 3 days after exposure to high concentrations of A beta and are blocked by Ca2+ channel blockers such as Co2+, nicardipine, and diltiazem. When A beta was washed out from the medium after 12 h, MTT reduction recovers and LDH release does not occur, suggesting that a long-lasting inhibition of the cellular redox system may be required to induce cell death. These observations demonstrate that A beta toxicity consists of two phases-a Ca(2+)-independent early phase and a Ca(2+)-dependent late phase- and that the early phase may be required to induce the late phase.
Abe
K
K
Salk Institute for Biological Studies, San Diego, California 92138, USA.
Kimura
H
H
D016229:Amyloid beta-Peptides / Q000633:toxicity*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D016923:Cell Death; D004396:Coloring Agents; D004622:Embryo, Mammalian; D018698:Glutamic Acid / Q000633:toxicity*; D006624:Hippocampus / Q000378:metabolism*; D007700:Kinetics; D007770:L-Lactate Dehydrogenase; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009498:Neurotoxins / Q000633:toxicity*; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000633:toxicity*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013778:Tetrazolium Salts; D013844:Thiazoles; D013997:Time Factors
D016229:Amyloid beta-Peptides; D004396:Coloring Agents; D009498:Neurotoxins; D010446:Peptide Fragments; D013778:Tetrazolium Salts; D013844:Thiazoles; C078592:amyloid beta-protein (1-40); C074636:amyloid beta-protein (25-35); D018698:Glutamic Acid; D007770:L-Lactate Dehydrogenase; C022616:thiazolyl blue; D002118:Calcium