title: Effect of beta2-adrenergic agonist clenbuterol on ischemia/reperfusion injury in isolated rat hearts and cardiomyocyte apoptosis induced by hydrogen peroxide.
abstract: OBJECTIVE
  To observe the effect of beta2-adrenergic agonist clenbuterol on ischemia/reperfusion (I/R) injury in isolated rat hearts and hydrogen peroxide (H2O2)-induced cardiomyocyte apoptosis.
  
  
  METHODS
  Isolated rat hearts were subjected to 30 min global ischemia and 60 min reperfusion on a Langendorff apparatus. Cardiac function was evaluated by heart rate, left ventricular end-diastolic pressure (LVEDP), left ventricular systolic pressure, maximal rise rate of left ventricular pressure [+dp/dt(max)], and the coronary effluent (CF). Lactate dehydrogenase (LDH) in the coronary effluent, malondialdehyde (MDA), superoxide dismutase (SOD), and Ca2+-ATPase activity in the cardiac tissue were measured using commercial kits. The apoptotic cardiomyocyte was detected by terminal deoxynucleotidyl transferase-mediated digoxigenin-dUTP nick-end labeling (TUNEL) assay. Bax/Bcl-2 mRNA levels and the expression of caspase-3 were detected by RT-PCR and immunoblotting, respectively. Cultured newborn rat cardiomyocytes were preincubated with clenbuterol, and oxidative stress injury was induced by H2O2. Cell viability and cardiomyocyte apoptosis were evaluated by flow cytometry (FCM).
  
  
  RESULTS
  In the isolated rat hearts after I/R injury, clenbuterol significantly improved diastolic function (LVEDP and CF) and Ca2+-ATPase activity. Treatment with clenbuterol increased SOD activity and decreased the MDA level and LDH release compared with the I/R group (P<0.05). Moreover, clenbuterol decreased apoptosis, which was associated with a reduction in TUNEL-positive cells, Bax/Bcl-2 mRNA, and caspase-3 expression. In H2O2-induced cardiomyocyte injury, clenbuterol increased cell viability and attenuated cardiomyocyte apoptosis. Pretreatment with ICI118551 (selective beta2-adrenergic antagonist) decreased these effects compared with the clenbuterol-treated group (P<0.05).
  
  
  CONCLUSIONS
  Clenbuterol ameliorated ventricular diastolic function by enhancing Ca2+-ATPase activity and reduced oxidative stress and cardiac myocyte apoptosis in an experimental rat model of myocardium I/R. It decreased cardiomyocyte apoptosis induced by H2O2 in vitro. It plays a key role in the cardiac protection against myocardium I/R injury.
authors.affiliation: Department of Pharmacology, Tongji Hospital Huazhong University of Science and Technology, Wuhan 430030, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Liu
authors.forename: Ji-zhou
authors.initials: JZ
authors.lastname: Xiang
authors.forename: Lei
authors.initials: L
authors.lastname: Zhao
authors.forename: Lei
authors.initials: L
authors.lastname: Yang
authors.forename: Ben-rong
authors.initials: BR
authors.lastname: Hu
authors.forename: Qin
authors.initials: Q
authors.lastname: Fu
mesh_terms: D058666:Adrenergic beta-2 Receptor Agonists; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D053148:Caspase 3 / Q000235:genetics; D002976:Clenbuterol / Q000494:pharmacology*; D019254:Genes, bcl-2 / Q000235:genetics; D006861:Hydrogen Peroxide / Q000633:toxicity*; D066298:In Vitro Techniques; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000473:pathology*; D032383:Myocytes, Cardiac / Q000187:drug effects*; D016877:Oxidants / Q000633:toxicity*; D051381:Rats; D017208:Rats, Wistar; D015427:Reperfusion Injury / Q000473:pathology*; D012519:Sarcoplasmic Reticulum / Q000473:pathology; D051028:bcl-2-Associated X Protein / Q000235:genetics
chemical_list: D058666:Adrenergic beta-2 Receptor Agonists; D000318:Adrenergic beta-Agonists; D016877:Oxidants; D051028:bcl-2-Associated X Protein; D006861:Hydrogen Peroxide; D007770:L-Lactate Dehydrogenase; D053148:Caspase 3; D000252:Calcium-Transporting ATPases; D002976:Clenbuterol