title: Uncoupling protein downregulation in doxorubicin-induced heart failure improves mitochondrial coupling but increases reactive oxygen species generation.
abstract: OBJECTIVE
  Doxorubicin-based chemotherapy is limited by the development of dose-dependent left ventricular dysfunction and congestive heart failure caused by reactive oxygen species (ROS). Uncoupling proteins (UCP) can inhibit mitochondrial ROS production as well as decrease myocyte damage from exogenous ROS. Prior studies have shown that cardiac UCP2 and UCP3 mRNA expression is decreased with acute doxorubicin treatment. However, the expression of UCP protein in hearts with doxorubicin cardiotoxicity and the resultant changes in mitochondrial function and oxidant stress have not been determined.
  
  
  METHODS
  Heart failure was induced in Sprague-Dawley rats with intraperitoneal injections of doxorubicin (2 mg/kg t.i.w., total dose: 18 mg/kg). Mitochondria were isolated from mice receiving doxorubicin or saline injections for determination of UCP2 and UCP3 expression. In addition, mitochondrial respiration, ATP synthesis and ROS production were determined.
  
  
  RESULTS
  Doxorubicin-induced heart failure was associated with significant decreases in UCP2 and UCP3 protein expression compared with nonfailing hearts (P < 0.05). While the rates of state 3 and state 4 respiration and ATP synthesis were lower in mitochondria isolated from failing hearts, the respiratory control ratio was 15% higher (P < 0.05), and the ratio of ATP production to oxygen consumption was 25% higher (P < 0.05) in mitochondria from failing hearts, indicating greater coupling between citric acid cycle flux and mitochondrial ATP synthesis. However, the decrease in UCP expression was associated with 50% greater mitochondrial ROS generation (P < 0.05).
  
  
  CONCLUSIONS
  Downregulation of myocardial UCP2 and UCP3 in the setting of doxorubicin-induced heart failure is associated with improved efficiency of ATP synthesis, which might compensate for abnormal energy metabolism. However, this beneficial effect is counterbalanced by greater oxidant stress.
authors.affiliation: Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, 333 Cedar Street, FMP 3, New Haven, CT 06520, USA.
authors.forename: Heiko
authors.initials: H
authors.lastname: Bugger
authors.forename: Cinthia
authors.initials: C
authors.lastname: Guzman
authors.forename: Christoph
authors.initials: C
authors.lastname: Zechner
authors.forename: Monica
authors.initials: M
authors.lastname: Palmeri
authors.forename: Kerry S
authors.initials: KS
authors.lastname: Russell
authors.forename: Raymond R
authors.initials: RR
authors.lastname: Russell
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000633:toxicity*; D015536:Down-Regulation; D004317:Doxorubicin / Q000633:toxicity*; D006333:Heart Failure / Q000139:chemically induced / Q000378:metabolism* / Q000503:physiopathology; D066298:In Vitro Techniques; D007473:Ion Channels / Q000096:biosynthesis*; D008297:Male; D051379:Mice; D008929:Mitochondria, Heart / Q000187:drug effects* / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000096:biosynthesis*; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism*; D000071246:Uncoupling Protein 2; D000071247:Uncoupling Protein 3; D016277:Ventricular Function, Left / Q000187:drug effects
chemical_list: D000903:Antibiotics, Antineoplastic; D007473:Ion Channels; D024101:Mitochondrial Proteins; D017382:Reactive Oxygen Species; C000604390:Ucp2 protein, mouse; C000604391:Ucp2 protein, rat; C000604393:Ucp3 protein, mouse; C000604394:Ucp3 protein, rat; D000071246:Uncoupling Protein 2; D000071247:Uncoupling Protein 3; D004317:Doxorubicin; D000255:Adenosine Triphosphate
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