title: Hypothermia treatment preserves mitochondrial integrity and viability of cardiomyocytes after ischaemic reperfusion injury.
abstract: BACKGROUND
  Haemorrhagic shock after traumatic injury carries a high mortality. Therapeutic hypothermia has been widely used in critical illness to improve the outcome in haemorrhagic shock by activation of cardiac pro-survival signalling pathways. However, the role played by the mitochondria in the cardioprotective effects of therapeutic hypothermia remains unclear. We investigated the effects of therapeutic hypothermia on mitochondrial function and integrity after haemorrhagic shock using an in vitro ischaemia-reperfusion model.
  
  
  METHODS
  H9c2 cardiomyocytes received a simulated ischaemic reperfusion injury under normothermic (37 °C) and hypothermic (31 °C) conditions. The cardiomyocytes were treated with hypoxic condition for 18 h in serum-free, glucose-free culture medium at pH 6.9 and then shifted to re-oxygenation status for 6h in serum-containing cell culture medium at pH 7.4. Cellular survival, mitochondrial integrity, energy metabolism and calcium homeostasis were studied.
  
  
  RESULTS
  Hypothermia treatment lessened cell death (15.0 ± 12.7 vs. 31.9 ± 11.8%, P=0.025) and preserved mitochondrial number (81.3 ± 17.4 vs. 45.2 ± 6.6, P=0.03) against simulated ischaemic reperfusion injury. Hypothermia treatment ameliorated calcium overload in the intracellular (1.5 ± 0.2 vs. 9.5 ± 2.8, P<0.001) and intra-mitochondrial (1.0 ± 0.3 vs. 1.6 ± 0.3, P=0.014) compartments against the injury. Mitochondrial integrity was more preserved by hypothermia treatment (50.1 ± 26.6 vs. 14.8 ± 13.0%, P<0.01) after the injury. Mitochondrial ATP concentrations were maintained with hypothermia treatment after injury (16.7 ± 9.5 vs. 6.1 ± 5.1 μM, P<0.01).
  
  
  CONCLUSIONS
  Hypothermia treatment at 31 °C can ameliorate cardiomyocyte damage caused by simulated ischaemic reperfusion injuries. Mitochondrial calcium homeostasis, energy metabolism, and membrane integrity are preserved and play critical roles during therapeutic hypothermia treatment.
authors.affiliation: Department of Emergency Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan. Electronic address: chhuang730@ntu.edu.tw.
authors.forename: Chien-Hua
authors.initials: CH
authors.lastname: Huang
authors.affiliation: Division of Cardiology, Department of Internal Medicine, Cardinal Tien Hospital Yonghe Branch, New Taipei City, Taiwan. Electronic address: chiang5184@pchome.com.tw.
authors.forename: Chih-Yen
authors.initials: CY
authors.lastname: Chiang
authors.affiliation: Institute of Pharmacology, National Yang-Ming University, Taipei, Taiwan. Electronic address: motorbird21@yahoo.com.tw.
authors.forename: Ren-How
authors.initials: RH
authors.lastname: Pen
authors.affiliation: Department of Emergency Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan. Electronic address: mshanmshan@gmail.com.
authors.forename: Min-Shan
authors.initials: MS
authors.lastname: Tsai
authors.affiliation: Graduate Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Taiwan. Electronic address: shwchen@ntu.edu.tw.
authors.forename: Huei-Wen
authors.initials: HW
authors.lastname: Chen
authors.affiliation: Department of Emergency Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan. Electronic address: dtemer01@gmail.com.
authors.forename: Chiung-Yuan
authors.initials: CY
authors.lastname: Hsu
authors.affiliation: Department of Internal Medicine (Cardiology), College of Medicine, National Taiwan University, Taipei, Taiwan. Electronic address: tdwang@ntu.edu.tw.
authors.forename: Tzung-Dau
authors.initials: TD
authors.lastname: Wang
authors.affiliation: Department of Emergency Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan. Electronic address: mhma@ntu.edu.tw.
authors.forename: Matthew Huei-Ming
authors.initials: MH
authors.lastname: Ma
authors.affiliation: Department of Emergency Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan. Electronic address: scchen@ntu.edu.tw.
authors.forename: Shyr-Chyr
authors.initials: SC
authors.lastname: Chen
authors.affiliation: Department of Emergency Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan; Department of Internal Medicine, Lotung Poh-Ai Hospital, Yilan County, Taiwan. Electronic address: wjchen1955@ntu.edu.tw.
authors.forename: Wen-Jone
authors.initials: WJ
authors.lastname: Chen
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002470:Cell Survival; D002478:Cells, Cultured; D006801:Humans; D007036:Hypothermia, Induced / Q000379:methods*; D066298:In Vitro Techniques; D019157:Ischemic Preconditioning, Myocardial; D009206:Myocardium / Q000473:pathology*; D032383:Myocytes, Cardiac / Q000473:pathology*; D018384:Oxidative Stress; D051381:Rats; D015427:Reperfusion Injury / Q000473:pathology* / Q000628:therapy; D017694:Rewarming; D012771:Shock, Hemorrhagic / Q000473:pathology*; D015398:Signal Transduction
chemical_list: D002118:Calcium
keywords: Cardiomyocyte; Hypothermia; Ischaemia reperfusion; Mitochondria