title: Isoflurane differentially modulates mitochondrial reactive oxygen species production via forward versus reverse electron transport flow: implications for preconditioning.
abstract: BACKGROUND
  Reactive oxygen species (ROS) mediate the effects of anesthetic precondition to protect against ischemia and reperfusion injury, but the mechanisms of ROS generation remain unclear. In this study, the authors investigated if mitochondria-targeted antioxidant (mitotempol) abolishes the cardioprotective effects of anesthetic preconditioning. Further, the authors investigated the mechanism by which isoflurane alters ROS generation in isolated mitochondria and submitochondrial particles.
  
  
  METHODS
  Rats were pretreated with 0.9% saline, 3.0 mg/kg mitotempol in the absence or presence of 30 min exposure to isoflurane. Myocardial infarction was induced by left anterior descending artery occlusion for 30 min followed by reperfusion for 2 h and infarct size measurements. Mitochondrial ROS production was determined spectrofluorometrically. The effect of isoflurane on enzymatic activity of mitochondrial respiratory complexes was also determined.
  
  
  RESULTS
  Isoflurane reduced myocardial infarct size (40 ± 9% = mean ± SD) compared with control experiments (60 ± 4%). Mitotempol abolished the cardioprotective effects of anesthetic preconditioning (60 ± 9%). Isoflurane enhanced ROS generation in submitochondrial particles with nicotinamide adenine dinucleotide (reduced form), but not with succinate, as substrate. In intact mitochondria, isoflurane enhanced ROS production in the presence of rotenone, antimycin A, or ubiquinone when pyruvate and malate were substrates, but isoflurane attenuated ROS production when succinate was substrate. Mitochondrial respiratory experiments and electron transport chain complex assays revealed that isoflurane inhibited only complex I activity.
  
  
  CONCLUSIONS
  The results demonstrated that isoflurane produces ROS at complex I and III of the respiratory chain via the attenuation of complex I activity. The action on complex I decreases unfavorable reverse electron flow and ROS release in myocardium during reperfusion.
authors.affiliation: Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA. naohirata@mac.com
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Hirata
authors.forename: Yon Hee
authors.initials: YH
authors.lastname: Shim
authors.forename: Danijel
authors.initials: D
authors.lastname: Pravdic
authors.forename: Nicole L
authors.initials: NL
authors.lastname: Lohr
authors.forename: Philip F
authors.initials: PF
authors.lastname: Pratt
authors.forename: Dorothee
authors.initials: D
authors.lastname: Weihrauch
authors.forename: Judy R
authors.initials: JR
authors.lastname: Kersten
authors.forename: David C
authors.initials: DC
authors.lastname: Warltier
authors.forename: Zeljko J
authors.initials: ZJ
authors.lastname: Bosnjak
authors.forename: Martin
authors.initials: M
authors.lastname: Bienengraeber
mesh_terms: D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D003497:Cyclic N-Oxides / Q000378:metabolism / Q000494:pharmacology; D004579:Electron Transport / Q000187:drug effects*; D042967:Electron Transport Complex I / Q000378:metabolism; D042963:Electron Transport Complex II / Q000378:metabolism; D014450:Electron Transport Complex III / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D006439:Hemodynamics / Q000187:drug effects; D066298:In Vitro Techniques; D019157:Ischemic Preconditioning, Myocardial; D007530:Isoflurane / Q000494:pharmacology*; D008297:Male; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism*; D009203:Myocardial Infarction / Q000188:drug therapy / Q000473:pathology; D015425:Myocardial Reperfusion; D010101:Oxygen Consumption / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012402:Rotenone / Q000494:pharmacology; D013113:Spin Labels; D013482:Superoxide Dismutase / Q000378:metabolism; D014475:Uncoupling Agents / Q000494:pharmacology
chemical_list: D018685:Anesthetics, Inhalation; D003497:Cyclic N-Oxides; D017382:Reactive Oxygen Species; D013113:Spin Labels; D014475:Uncoupling Agents; D012402:Rotenone; D007530:Isoflurane; D013482:Superoxide Dismutase; D042963:Electron Transport Complex II; D003576:Electron Transport Complex IV; D042967:Electron Transport Complex I; D014450:Electron Transport Complex III; C001803:tempol