BETA-AMYLOID INDUCES APOPTOSIS IN HUMAN-DERIVED NEUROTYPIC SH-SY5Y CELLS

Alzheimer's disease is primarily characterized by neurofibrillary tang les, senile plaques, and neurodegeneration. The major component of sen ile plaques is the beta-amyloid peptide (beta A4), which has been show n to be toxic to neurons in vitro. To date, the mechanism of beta A4-i nduced neurotoxicity has not been determined in human-derived neurons. In this report, we present evidence that programmed cell death, or ap optosis, is involved in the neurotoxic activity of beta A4(25-35) and beta A4(25-35) in the human-derived neurotypic cell line SH-SY5Y cells . The evidence for beta A4-induced apoptosis includes: (1) labeling of cell nuclei for DNA nicked ends; (2) morphological changes in ultrast ructure that are consistent with apoptosis (shrunken cells with pyknot ic nuclei); (3) DNA laddering which can be blocked by aurintricarboxyl ic acid (ATA), an inhibitor of apoptosis; and (4) marginal release of intracellular lactate dehydrogenase (LDH), an indicator of necrosis. T hese results suggest that apoptosis is the major event involved in bet a A4-induced cytotoxicity in SH-SY5Y cells. A variety of reagents were tested to determine their activities against beta A4-induced DNA ladd ering. Nerve growth factor and free radical scavengers were inactive i n this system. While ATA blocked DNA laddering resulting from either b eta A4 or okadaic acid treatment, Congo red specifically attenuated on ly beta A4-induced DNA fragmentation. These results suggest that compo unds which bind fibrillar beta-peptides can protect this human neuroty pic cell line against apoptosis induced by beta A4.