title: Autophagy is activated in compression-induced cell degeneration and is mediated by reactive oxygen species in nucleus pulposus cells exposed to compression.
abstract: OBJECTIVE
  To determine whether autophagy contributes to the pathogenesis of degenerative disc disease (DDD) or retards the intervertebral disc (IVD) degeneration, and investigate the possible relationship between compression-induced autophagy and intracellular reactive oxygen species (ROS) in nucleus pulposus (NP) cells in vitro.
  
  
  METHODS
  The autophagosome and autophagy-related markers were used to explore the role of autophagy in rat NP cells under compressive stress, which were measured directly by electronic microscopy, monodansylcadaverine (MDC) staining, immunofluorescence, western blot, and indirectly by analyzing the impact of pharmacological inhibitors of autophagy such as 3-methyladenine (3-MA) and chloroquine (CQ). And the relationship between autophagy and apoptosis was investigated by Annexin-V/propidium iodide (PI)-fluorescein staining. In addition, ROS were measured to determine whether these factors are responsible for the development of compression-induced autophagy.
  
  
  RESULTS
  Our results indicated that rat NP cells activated autophagy in response to the same strong apoptotic stimuli that triggered apoptosis by compression. Autophagy and apoptosis were interconnected and coordinated in rat NP cells exposed to compression stimuli. Compression-induced autophagy was closely related to intracellular ROS production.
  
  
  CONCLUSIONS
  Enhanced degradation of damaged components of NP cells by autophagy may be a crucial survival response against mechanical overload, and extensive autophagy may trigger autophagic cell death. Regulating autophagy and reducing the generation of intracellular ROS may retard IVD degeneration.
authors.affiliation: Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China.
authors.forename: K-G
authors.initials: KG
authors.lastname: Ma
authors.forename: Z-W
authors.initials: ZW
authors.lastname: Shao
authors.forename: S-H
authors.initials: SH
authors.lastname: Yang
authors.forename: J
authors.initials: J
authors.lastname: Wang
authors.forename: B-C
authors.initials: BC
authors.lastname: Wang
authors.forename: L-M
authors.initials: LM
authors.lastname: Xiong
authors.forename: Q
authors.initials: Q
authors.lastname: Wu
authors.forename: S-F
authors.initials: SF
authors.lastname: Chen
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001343:Autophagy / Q000187:drug effects / Q000502:physiology*; D015153:Blotting, Western; D002478:Cells, Cultured; D002738:Chloroquine / Q000494:pharmacology; D007150:Immunohistochemistry; D007403:Intervertebral Disc / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D055959:Intervertebral Disc Degeneration / Q000378:metabolism* / Q000473:pathology; D046529:Microscopy, Electron, Transmission; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013314:Stress, Mechanical
chemical_list: D017382:Reactive Oxygen Species; C025946:3-methyladenine; D002738:Chloroquine; D000225:Adenine
keywords: Apoptosis; Autophagy; Compression; Intervertebral disc; Nucleus pulposus cells; Reactive oxygen species