title: [The effect of mitochondrial oxidative stress and the expression of Bcl-2 and Bax proteins on cardiomyocyte apoptosis during hypoxia postconditioning].
abstract: OBJECTIVE
  To investigate mitochondrial oxidative stress on cardiomyocyte apoptosis and the expression of Bcl-2 and Bax proteins in cardiac sarcolemma and mitochondria after application of hypoxia postconditioning and free radical scavengers.
  
  
  METHODS
  Primary cultured neonatal rat cardiomyocytes were exposed to 3 h hypoxia (H) followed by (1) 6 h of reoxygenation (R) (H/R), (2) 3 intermittent cycles of 5 min H and R before 6 h of R (PC), (3) application of superoxide dismutase (SOD) before PC (SOD+PC), (4) application of catalase (CAT) before PC (CAT+PC), and (5) application of SOD plus CAT before PC (SOD+CAT+PC). Cardiac sarcolemma and mitochondria were isolated by differential centrifugation. Mitochondrial reactive oxygen species (ROS) was detected with fluorescent probes (DCFH-DA) and cardiomyocyte apoptosis was detected with flow cytometry. The expressions of Bcl-2 and Bax proteins in cardiac sarcolemma and mitochondria were measured by Western blot.
  
  
  RESULTS
  Mitochondrial ROS reduced significantly in PC, SOD+PC, CAT+PC and especially in SOD+CAT+PC groups (all P<0.01). The number of apoptotic cardiomyocytes reduced significantly in PC, SOD+PC and CAT+PC (all P<0.01) but not in SOD+CAT+PC groups. Bcl-2 levels increased while Bax levels decreased in cardiac sarcolemma and mitochondria in PC, SOD+PC and CAT+PC groups (all P<0.01), Bcl-2 levels decreased and Bax levels increased in H/R and PC+SOD+CAT groups (all P<0.01).
  
  
  CONCLUSIONS
  PC attenuated H/R induced ROS and cardiomyocyte apoptosis, which might be mediated by upregulating the expression of Bcl-2 and downregulating the Bax in mitochondria and sarcolemma; SOD or CAT alone did not but SOD plus CAT attenuate the anti-apoptotic effect of hypoxia postconditioning; mitochondrial ROS thus plays an important role in PC's cardioprotection.
authors.affiliation: Department of Geriatric Cardiology, First Affiliated Hospital, Guangxi Medical University, Nanning 530021, China.
authors.forename: Rong-hui
authors.initials: RH
authors.lastname: Tu
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.forename: Guo-qiang
authors.initials: GQ
authors.lastname: Zhong
authors.forename: Zhi-yu
authors.initials: ZY
authors.lastname: Zeng
authors.forename: Qing-jie
authors.initials: QJ
authors.lastname: Li
authors.forename: Yan
authors.initials: Y
authors.lastname: He
authors.forename: Yan
authors.initials: Y
authors.lastname: He
authors.forename: Jin-yi
authors.initials: JY
authors.lastname: Li
mesh_terms: D000818:Animals; D017209:Apoptosis; D015687:Cell Hypoxia; D002478:Cells, Cultured; D008928:Mitochondria / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D018384:Oxidative Stress; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: C494828:Bax protein, rat; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D051028:bcl-2-Associated X Protein