title: [Association between endoplasmic reticulum stress pathway mediated by inositol-requiring kinase 1 and AECII apoptosis in preterm rats induced by hyperoxia].
abstract: OBJECTIVE
  To study the association between endoplasmic reticulum stress (ERS) pathway mediated by inositol-requiring kinase 1 (IRE1) and the apoptosis of type II alveolar epithelial cells (AECIIs) exposed to hyperoxia.
  
  
  METHODS
  The primarily cultured AECIIs from preterm rats were devided into an air group and a hyperoxia group. The model of hyperoxia-induced cell injury was established. The cells were harvested at 24, 48, and 72 hours after hyperoxia exposure. An inverted phase-contrast microscope was used to observe morphological changes of the cells. Annexin V/PI double staining flow cytometry was performed to measure cell apoptosis. RT-PCR and Western blot were used to measure the mRNA and protein expression of glucose-regulated protein 78 (GRP78), IRE1, X-box binding protein-1 (XBP-1), and C/EBP homologous protein (CHOP). An immunofluorescence assay was performed to measure the expression of CHOP.
  
  
  RESULTS
  Over the time of hyperoxia exposure, the hyperoxia group showed irregular spreading and vacuolization of AECIIs. Compared with the air group, the hyperoxia group showed a significantly increased apoptosis rate of AECIIs and significantly increased mRNA and protein expression of GRP78, IRE1, XBP1, and CHOP compared at all time points (P<0.05). The hyperoxia group had significantly greater fluorescence intensity of CHOP than the air group at all time points. In the hyperoxia group, the protein expression of CHOP was positively correlated with the apoptosis rate of AECIIs and the protein expression of IRE1 and XBP1 (r=0.97, 0.85, and 0.88 respectively; P<0.05).
  
  
  CONCLUSIONS
  Hyperoxia induces apoptosis of AECIIs possibly through activating the IRE1-XBP1-CHOP pathway.
authors.affiliation: Department of Pediatrics, Affiliated Hospital of Jiangsu University, Zhenjiang, Jiangsu 212001, China. lhy5154@163.com.
authors.forename: Hui-Min
authors.initials: HM
authors.lastname: Ju
authors.forename: Hong-Yan
authors.initials: HY
authors.lastname: Lu
authors.forename: Yan-Yu
authors.initials: YY
authors.lastname: Zhang
authors.forename: Qiu-Xia
authors.initials: QX
authors.lastname: Wang
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhang
mesh_terms: D000818:Animals; D017209:Apoptosis; D002478:Cells, Cultured; D059865:Endoplasmic Reticulum Stress / Q000502:physiology*; D004722:Endoribonucleases / Q000502:physiology*; D004847:Epithelial Cells / Q000502:physiology; D005260:Female; D018496:Hyperoxia / Q000378:metabolism / Q000473:pathology*; D009097:Multienzyme Complexes / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D011650:Pulmonary Alveoli / Q000473:pathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D051742:Transcription Factor CHOP / Q000502:physiology; D000071717:X-Box Binding Protein 1 / Q000502:physiology
chemical_list: C497251:Ddit3 protein, rat; C575026:Ern1 protein, rat; D009097:Multienzyme Complexes; D000071717:X-Box Binding Protein 1; C000605545:Xbp1 protein, rat; D051742:Transcription Factor CHOP; D017346:Protein Serine-Threonine Kinases; D004722:Endoribonucleases