Abstract
Increasing evidence suggests the toxicity of intracellular amyloid β-protein (Aβ) to neurons, as well as the involvement of oxidative stress in Alzheimer disease (AD). Here we show that normobaric hyperoxia (exposure of cells to 40% oxygen for five days), and consequent activation of macroautophagy and accumulation of Aβ within lysosomes, induced apoptosis in differentiated SH-SY5Y neuroblastoma cells. Cells under hyperoxia showed: (1) increased numbers of autophagic vacuoles that contained amyloid precursor protein (APP) as well as Aβ monomers and oligomers, (2) increased reactive oxygen species production, and (3) enhanced apoptosis. Oxidant-induced apoptosis positively correlated with cellular Aβ production, being the highest in cells that were stably transfected with APP Swedish KM670/671NL double mutation. Inhibition of γ-secretase, prior and/or in parallel to hyperoxia, suggested that the increase of lysosomal Aβ resulted mainly from its autophagic uptake, but also from APP processing within autophagic vacuoles. The oxidative stress-mediated effects were prevented by macroautophagy inhibition using 3-methyladenine or ATG5 downregulation. Our results suggest that upregulation of macroautophagy and resulting lysosomal Aβ accumulation are essential for oxidant-induced apoptosis in cultured neuroblastoma cells and provide additional support for the interactive role of oxidative stress and the lysosomal system in AD-related neurodegeneration.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenine / analogs & derivatives
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Adenine / pharmacology
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Amyloid Precursor Protein Secretases / antagonists & inhibitors
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Amyloid Precursor Protein Secretases / metabolism
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Amyloid beta-Peptides / metabolism*
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Apoptosis / drug effects*
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Autophagy / drug effects*
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Autophagy-Related Protein 5
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Cell Differentiation / drug effects
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Cell Nucleus / drug effects
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Cell Nucleus / metabolism
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Cell Nucleus / ultrastructure
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Cell Survival / drug effects
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Down-Regulation / drug effects
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Humans
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Intracellular Space / drug effects
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Intracellular Space / metabolism
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Lysosomal Membrane Proteins / metabolism
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Lysosomal-Associated Membrane Protein 2
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Lysosomes / drug effects
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Lysosomes / metabolism*
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Microtubule-Associated Proteins / metabolism
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Mutant Proteins / metabolism
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Neuroblastoma / metabolism*
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Neuroblastoma / pathology*
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Oxidants / pharmacology*
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Oxygen / pharmacology
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RNA, Small Interfering / metabolism
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Reactive Oxygen Species / metabolism
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Transfection
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Tretinoin / pharmacology
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Tumor Cells, Cultured
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Vacuoles / drug effects
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Vacuoles / metabolism
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Vacuoles / ultrastructure
Substances
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ATG5 protein, human
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Amyloid beta-Peptides
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Autophagy-Related Protein 5
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LAMP2 protein, human
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Lysosomal-Associated Membrane Protein 2
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Lysosomal Membrane Proteins
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Microtubule-Associated Proteins
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Mutant Proteins
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Oxidants
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RNA, Small Interfering
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Reactive Oxygen Species
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3-methyladenine
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Tretinoin
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Amyloid Precursor Protein Secretases
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Adenine
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Oxygen