title: Neuregulin-1 preconditioning protects the heart against ischemia/reperfusion injury through a PI3K/Akt-dependent mechanism.
abstract: BACKGROUND
  Neuregulin-1 (NRG-1), the ligand of the myocardial ErbB receptor, is a protein mediator with regulatory actions in the heart. This study investigated whether NRG-1 preconditioning has protective effects on myocardial ischemia/reperfusion (I/R) injury and its potential mechanism.
  
  
  METHODS
  We worked with an in vivo rat model with induced myocardial ischemia (45 minutes) followed by reperfusion (3 hours). NRG-1 message was detected in the heart using RT-PCR and the protein levels of NRG-1 and ErbB4 were detected by Western blotting analysis. Infarct size was assessed using the staining agent triphenyltetrazolium chloride and cardiac function was continuously monitored. The levels of creatine kinase and lactate dehydrogenase in plasma were analyzed to assess the degree of cardiac injury. The extent of cardiac apoptosis was evaluated by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay and by Western blotting analysis of cleaved caspase-3. We examined the phosphorylation of Akt in the myocardium and the effect of PI3K/Akt inhibition on NRG-1-induced cardioprotection.
  
  
  RESULTS
  Transcription and expression of NRG-1 and phosphorylation of its ErbB4 receptor were significantly upregulated in the I/R hearts. NRG-1 pretreatment reduced the infarct size following cardiac I/R in a concentration-dependent manner with an optimal concentration of 4 µg/kg in vivo. NRG-1 pretreatment with 4 µg/kg, i.v. markedly reduced the plasma creatine kinase and lactate dehydrogenase levels. Pretreatment with NRG-1 also significantly reduced the percentage of TUNEL positive myocytes and the level of cleaved caspase-3 in the I/R hearts. Pretreatment with NRG-1 significantly increased phosphorylation of Akt following I/R. Furthermore, the cardioprotective effect limiting the infarct size that was induced by NRG-1 was abolished by co-administration of the PI3K inhibitor LY294002.
  
  
  CONCLUSIONS
  The concentration of NRG-1, a new autacoid, was rapidly upregulated after myocardial I/R. NRG-1 preconditioning has cardioprotective effects against I/R injury through a PI3K/Akt-dependent mechanism in vivo.
authors.affiliation: Department of Cardiology, Beijing Anzhen Hospital, Capital Medical University, Beijing 100029, China.
authors.forename: Shan-Juan
authors.initials: SJ
authors.lastname: Fang
authors.forename: Xue-Si
authors.initials: XS
authors.lastname: Wu
authors.forename: Zhi-Hong
authors.initials: ZH
authors.lastname: Han
authors.forename: Xiao-Xia
authors.initials: XX
authors.lastname: Zhang
authors.forename: Chun-Mei
authors.initials: CM
authors.lastname: Wang
authors.forename: Xin-Yan
authors.initials: XY
authors.lastname: Li
authors.forename: Ling-Qiao
authors.initials: LQ
authors.lastname: Lu
authors.forename: Jing-Lan
authors.initials: JL
authors.lastname: Zhang
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D066246:ErbB Receptors / Q000032:analysis; D019157:Ischemic Preconditioning, Myocardial; D007770:L-Lactate Dehydrogenase / Q000097:blood; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control*; D020890:Neuregulin-1 / Q000032:analysis / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D066247:Receptor, ErbB-4
chemical_list: D053148:Caspase 3; D066246:ErbB Receptors; D007770:L-Lactate Dehydrogenase; D020890:Neuregulin-1; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D066247:Receptor, ErbB-4; C587691:Erbb4 protein, rat