title: Moderate hypothermia initiated during oxygen-glucose deprivation preserves HL-1 cardiomyocytes.
abstract: OBJECTIVE
  Therapeutic hypothermia (TH) is an acknowledged strategy for neuroprotection for patients suffering from hypoxic-anoxic brain injury (HAI). Albeit similar pathomechanisms of HAI for both brain and heart, moderate TH (32-34°C) has not been established as a heart-protective measure. Therefore, we investigated the cardioprotective effects of moderate TH on oxygen-glucose deprivation/re-oxygenation (OGD/R)-induced injury in HL-1 cardiomyocytes.
  
  
  METHODS
  Cardiac OGD/R injury was induced by exposing HL-1 cardiomyocytes to 0.2% oxygen in serum/glucose-free medium for 6h. OGD injured cells were subsequently re-oxygenated with 21% oxygen in complete medium. Two hypothermic protocols were investigated: Post-OGD cooling to 33.5°C for 24 h initiated at the start of re-oxygenation and intra-OGD cooling to 33.5°C for 24 h initiated after 3 h of OGD and maintained throughout the re-oxygenation phase. Cell viability was determined by LDH and cTnT releases. Mitochondria dysfunction was evaluated by intracellular ATP content and cellular metabolic activity was accessed by MTT reduction. Activation of caspase 3 was analyzed by Western blot.
  
  
  RESULTS
  OGD/R-induced injury resulted in increased cell death (higher LDH and cTnT releases), mitochondrial impairment (decreased ATP content), and decreased cellular metabolic activity (decreased MTT reduction). Only intra-OGD cooling attenuated both OGD and OGD-R-induced injuries (significantly decreased LDH and cTnT releases and increased ATP contents and MTT reduction). Furthermore, caspase 3 activation was abated by intra-OGD cooling. No protective effects were observed by post-OGD cooling.
  
  
  CONCLUSIONS
  Moderate TH initiated during OGD is a promising intervention for the protection of cardiomyocytes from OGD/R-induced injury. The attenuation of mitochondrial dysfunction and apoptosis by intra-OGD cooling are beneficial effects of hypothermia-induced cardioprotection, resulting in minimized myocardial cell death after OGD and OGD-R-induced injuries.
authors.affiliation: Department of Congenital Heart Disease/Pediatric Cardiology, German Heart Institute Berlin, Augustenburger Platz 1, 13353 Berlin, Germany. Electronic address: giang.tong@charite.de.
authors.forename: Giang
authors.initials: G
authors.lastname: Tong
authors.affiliation: Department of Congenital Heart Disease/Pediatric Cardiology, German Heart Institute Berlin, Augustenburger Platz 1, 13353 Berlin, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Walker
authors.affiliation: Department of Neonatology, Charité - University Medical Center, Augustenburger Platz 1, 13353 Berlin, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Bührer
authors.affiliation: Department of Congenital Heart Disease/Pediatric Cardiology, German Heart Institute Berlin, Augustenburger Platz 1, 13353 Berlin, Germany; Department of Pediatric Cardiology, Charité - University Medical Center, Augustenburger Platz 1, 13353 Berlin, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Berger
authors.affiliation: Department of Congenital Heart Disease/Pediatric Cardiology, German Heart Institute Berlin, Augustenburger Platz 1, 13353 Berlin, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Miera
authors.affiliation: Department of Congenital Heart Disease/Pediatric Cardiology, German Heart Institute Berlin, Augustenburger Platz 1, 13353 Berlin, Germany.
authors.forename: Katharina Rose Luise
authors.initials: KR
authors.lastname: Schmitt
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002316:Cardiotonic Agents / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000502:physiology; D004789:Enzyme Activation; D005947:Glucose / Q000378:metabolism*; D007036:Hypothermia, Induced; D000860:Hypoxia / Q000378:metabolism; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*
chemical_list: D002316:Cardiotonic Agents; D053148:Caspase 3; D005947:Glucose; D010100:Oxygen
keywords: Cardioprotection; Oxygen–glucose deprivation; Re-oxygenation injury; Targeted temperature management; Therapeutic hypothermia