Macroautophagy-generated increase of lysosomal amyloid β-protein mediates oxidant-induced apoptosis of cultured neuroblastoma cells

Autophagy. 2011 Dec;7(12):1528-45. doi: 10.4161/auto.7.12.18051.

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

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenine / analogs & derivatives
  • Adenine / pharmacology
  • Amyloid Precursor Protein Secretases / antagonists & inhibitors
  • Amyloid Precursor Protein Secretases / metabolism
  • Amyloid beta-Peptides / metabolism*
  • Apoptosis / drug effects*
  • Autophagy / drug effects*
  • Autophagy-Related Protein 5
  • Cell Differentiation / drug effects
  • Cell Nucleus / drug effects
  • Cell Nucleus / metabolism
  • Cell Nucleus / ultrastructure
  • Cell Survival / drug effects
  • Down-Regulation / drug effects
  • Humans
  • Intracellular Space / drug effects
  • Intracellular Space / metabolism
  • Lysosomal Membrane Proteins / metabolism
  • Lysosomal-Associated Membrane Protein 2
  • Lysosomes / drug effects
  • Lysosomes / metabolism*
  • Microtubule-Associated Proteins / metabolism
  • Mutant Proteins / metabolism
  • Neuroblastoma / metabolism*
  • Neuroblastoma / pathology*
  • Oxidants / pharmacology*
  • Oxygen / pharmacology
  • RNA, Small Interfering / metabolism
  • Reactive Oxygen Species / metabolism
  • Transfection
  • Tretinoin / pharmacology
  • Tumor Cells, Cultured
  • Vacuoles / drug effects
  • Vacuoles / metabolism
  • Vacuoles / ultrastructure

Substances

  • ATG5 protein, human
  • Amyloid beta-Peptides
  • Autophagy-Related Protein 5
  • LAMP2 protein, human
  • Lysosomal-Associated Membrane Protein 2
  • Lysosomal Membrane Proteins
  • Microtubule-Associated Proteins
  • Mutant Proteins
  • Oxidants
  • RNA, Small Interfering
  • Reactive Oxygen Species
  • 3-methyladenine
  • Tretinoin
  • Amyloid Precursor Protein Secretases
  • Adenine
  • Oxygen