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Amyloid β Toxicity Consists of a Ca 2+ ‐Independent Early Phase and a Ca 2+ ‐Dependent Late Phase
Author(s) -
Abe Kazuho,
Kimura Hideo
Publication year - 1996
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1996.67052074.x
Subject(s) - trypan blue , chemistry , toxicity , mtt assay , lactate dehydrogenase , cytotoxicity , microbiology and biotechnology , biophysics , biochemistry , biology , cell growth , in vitro , enzyme , organic chemistry
Amyloid β protein (Aβ), 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 Aβ. In primary hippocampal cultures, inhibition of MTT reduction starts within 2 h after the addition of low concentrations of Aβ and reaches a plateau in 12 h. This effect of Aβ is not blocked by Ca 2+ 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 Aβ and are blocked by Ca 2+ channel blockers such as Co 2+ , nicardipine, and diltiazem. When Aβ 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 Aβ 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.