title: The endoplasmic reticulum stress inhibitor salubrinal inhibits the activation of autophagy and neuroprotection induced by brain ischemic preconditioning.
abstract: OBJECTIVE
  To investigate whether endoplasmic reticulum (ER) stress participates in the neuroprotective effects of ischemic preconditioning (IPC)-induced neuroprotection and autophagy activation in rat brains.
  
  
  METHODS
  The right middle cerebral artery in SD rats was occluded for 10 min to induce focal cerebral IPC, and was occluded permanently 24 h later to induce permanent focal ischemia (PFI). ER stress inhibitor salubrinal (SAL) was injected via intracerebral ventricle infusion 10 min before the onset of IPC. Infarct volume and motor behavior deficits were examined after the ischemic insult. The protein levels of LC3, p62, HSP70, glucose-regulated protein 78 (GRP 78), p-eIF2α and caspase-12 in the ipsilateral cortex were analyzed using immunoblotting. LC3 expression pattern in the sections of ipsilateral cortex was observed with immunofluorescence.
  
  
  RESULTS
  Pretreatment with SAL (150 pmol) abolished the neuroprotective effects of IPC, as evidenced by the significant increases in mortality, infarct volume and motor deficits after PFI. At the molecular levels, pretreatment with SAL (150 pmol) significantly increased p-eIF2α level, and decreased GRP78 level after PFI, suggesting that SAL effectively inhibited ER stress in the cortex. Furthermore, the pretreatment with SAL blocked the IPC-induced upregulation of LC3-II and downregulation of p62 in the cortex, thus inhibiting the activation of autophagy. Moreover,SAL blocked the upregulation of HSP70, but significantly increased the cleaved caspase-12 level, thus promoting ER stress-dependent apoptotic signaling in the cortex.
  
  
  CONCLUSIONS
  ER stress-induced autophagy might contribute to the neuroprotective effect of brain ischemic preconditioning.
authors.affiliation: Department of Pharmacology and Laboratory of Aging and Nervous Diseases, Soochow University School of Pharmaceutical Science, Suzhou 215123, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Gao
authors.forename: Xiang-yang
authors.initials: XY
authors.lastname: Zhang
authors.forename: Rong
authors.initials: R
authors.lastname: Han
authors.forename: Tong-tong
authors.initials: TT
authors.lastname: Zhang
authors.forename: Cheng
authors.initials: C
authors.lastname: Chen
authors.forename: Zheng-hong
authors.initials: ZH
authors.lastname: Qin
authors.forename: Rui
authors.initials: R
authors.lastname: Sheng
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects*; D001921:Brain / Q000098:blood supply / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D002545:Brain Ischemia / Q000378:metabolism / Q000473:pathology* / Q000628:therapy*; D002934:Cinnamates / Q000494:pharmacology*; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D019194:Ischemic Preconditioning / Q000379:methods; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects; D013890:Thiourea / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D002934:Cinnamates; C496827:salubrinal; D013890:Thiourea