title: Autophagy through 4EBP1 and AMPK regulates oxidative stress-induced premature senescence in auditory cells.
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.
authors: Department of Otorhinolaryngology, Head and Neck Surgery, Keio University, School of Medicine, Tokyo 160-8582, Japan.|Department of Otorhinolaryngology, Head and Neck Surgery, Kyushu University, School of Medicine, Fukuoka 812-0054, Japan.
authors: Nana Akagi
authors: NA
authors: Tsuchihashi
authors: Department of Otorhinolaryngology, Head and Neck Surgery, Keio University, School of Medicine, Tokyo 160-8582, Japan.|Department of Otorhinolaryngology, Kamio Memorial Hospital, Tokyo 101-0063, Japan.
authors: Ken
authors: K
authors: Hayashi
authors: Collaborative Research Resources, Core Instrumentation Facility, Keio University, Tokyo 160-8582, Japan.
authors: Katsuaki
authors: K
authors: Dan
authors: Department of Otorhinolaryngology, Head and Neck Surgery, Keio University, School of Medicine, Tokyo 160-8582, Japan.
authors: Fumiyuki
authors: F
authors: Goto
authors: Department of Otorhinolaryngology-Head and Neck Surgery, Nihon University, School of Medicine, Tokyo 173-8610, Japan.
authors: Yasuyuki
authors: Y
authors: Nomura
authors: Department of Otorhinolaryngology, Head and Neck Surgery, Keio University, School of Medicine, Tokyo 160-8582, Japan.
authors: Masato
authors: M
authors: Fujioka
authors: Department of Otorhinolaryngology, Head and Neck Surgery, Keio University, School of Medicine, Tokyo 160-8582, Japan.
authors: Sho
authors: S
authors: Kanzaki
authors: Department of Otorhinolaryngology, Head and Neck Surgery, Kyushu University, School of Medicine, Fukuoka 812-0054, Japan.
authors: Shizuo
authors: S
authors: Komune
authors: Department of Otorhinolaryngology, Head and Neck Surgery, Keio University, School of Medicine, Tokyo 160-8582, Japan.
authors: Kaoru
authors: K
authors: Ogawa
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001343:Autophagy / Q000187:drug effects / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins; D002460:Cell Line; D016922:Cellular Senescence / Q000187:drug effects / Q000502:physiology*; D039642:Eukaryotic Initiation Factors; D055785:Gene Knockdown Techniques; D006198:Hair Cells, Auditory / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D051379:Mice; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D015398:Signal Transduction; D014162:Transfection
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C499527:Eif4ebp1 protein, mouse; D039642:Eukaryotic Initiation Factors; D010750:Phosphoproteins; D006861:Hydrogen Peroxide; D055372:AMP-Activated Protein Kinases