Autophagy through 4EBP1 and AMPK regulates oxidative stress-induced premature senescence in auditory cells

Oncotarget. 2015 Feb 28;6(6):3644-55. doi: 10.18632/oncotarget.2874.

Abstract

The aim of this study was to determine whether autophagy and AMPK contribute to premature senescence in auditory cells. Incubating HEI-OC1 auditory cells with 5 mM H2O2 for 1 h induced senescence, as demonstrated by senescence-associated β-galactosidase (SA-β-gal) staining. H2O2 treatment significantly delayed population-doubling time, leaving cell viability unchanged. Furthermore, the proportion of SA-β-gal-positive cells significantly increased. Autophagy-related protein expression increased, with Atg7 and LC3-II peaking 6 h and Lamp2 peaking 24 h after H2O2 treatment. The expression of these proteins decreased 48 h after treatment. Transmission electron microscopy revealed lipofuscin and aggregates within autolysosomes, which accumulated markedly in the cytoplasm of HEI-OC1 cells 48 h after treatment. Akt and P70S6 phosphorylation markedly decreased after H2O2 treatment, but 4EBP1 phosphorylation significantly increased 48 h after treatment. After RNAi-mediated knockdown (KD) of Atg7 and AMPK, H2O2-treated cells displayed dense SA-β-gal staining. Also, premature senescence was significantly induced. These suggest that a negative feedback loop may exist between autophagy and AMPK signaling pathways in HEI-OC1 cells. In our model, oxidative stress-induced premature senescence occurred due to impaired autophagy function through 4EBP1 phosphorylation. Our results also indicate that AMPK may regulate premature senescence in auditory cells in an autophagy-dependent and independent manner.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • AMP-Activated Protein Kinases / metabolism*
  • Adaptor Proteins, Signal Transducing
  • Animals
  • Autophagy / drug effects
  • Autophagy / physiology
  • Carrier Proteins / metabolism*
  • Cell Cycle Proteins
  • Cell Line
  • Cellular Senescence / drug effects
  • Cellular Senescence / physiology*
  • Eukaryotic Initiation Factors
  • Gene Knockdown Techniques
  • Hair Cells, Auditory / cytology*
  • Hair Cells, Auditory / drug effects
  • Hair Cells, Auditory / metabolism*
  • Hydrogen Peroxide / pharmacology
  • Mice
  • Oxidative Stress / drug effects
  • Oxidative Stress / physiology
  • Phosphoproteins / metabolism*
  • Phosphorylation
  • Signal Transduction
  • Transfection

Substances

  • Adaptor Proteins, Signal Transducing
  • Carrier Proteins
  • Cell Cycle Proteins
  • Eif4ebp1 protein, mouse
  • Eukaryotic Initiation Factors
  • Phosphoproteins
  • Hydrogen Peroxide
  • AMP-Activated Protein Kinases