title: Nerve growth factor protects the ischemic heart via attenuation of the endoplasmic reticulum stress induced apoptosis by activation of phosphatidylinositol 3-kinase.
abstract: BACKGROUND
  Increased expression of nerve growth factor (NGF) has been found in the myocardium suffered from ischemia and reperfusion (I/R). The pro-survival activity of NGF on ischemic heart has been supposed to be mediated by phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling pathway. Endoplasmic reticulum (ER) stress, which is activated initially as a defensive response to eliminate the accumulated unfolded proteins, has shown a critical involvement in the ischemia induced myocardial apoptosis. This study was aimed to investigate whether NGF induced heart protection against I/R injury includes a mechanism of attenuation of ER stress-induced myocardial apoptosis by activation of PI3K/Akt pathway.
  
  
  METHODS
  Isolated adult rat hearts were perfused with a Langendörff perfusion system. Hearts in the Sham group were subjected to 225 min of continuous Krebs-Henseleit buffer (KHB) perfusion without ischemia. Hearts in I/R group were perfused with KHB for a 75-min of equilibration period followed by 30 min of global ischemia and 120 min of KHB reperfusion. Hearts in the NGF group accepted 45 min of euilibration perfusion and 30 min of NGF pretreatment (with a final concentration of 100 ng/ml in the KHB) before 30 min of global ischemia and 120 min of reperfusion. Hearts in K252a and LY294002 groups were pretreated with either a TrkA inhibitor, K252a or a phosphatidyl inositol 3-kinase inhibitor, LY294002 for 30 min before NGF (100 ng/ml) administration. Cardiac hemodynamics were measured from the beginning of the perfusion. Cardiac enzymes and cardiac troponin I (cTnI) were assayed before ischemia and at the end of reperfusion. Myocardial apoptosis rate was measured by TUNEL staining, and expression of glucose-related protein 78 (GRP78), CCAAT/enhancer-binding protein homologous protein (CHOP), caspase-12, total- and phospho-(Ser473)-Akt were assessed by Western blot analyses.
  
  
  RESULTS
  NGF pretreatment significantly improved the recovery of post-ischemia cardiac hemodynamics. Reduced creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH) activity and cTnI levels, as well as decreased myocardial apoptosis ratio were observed in the NGF group. The improvement of NGF on recovery of cardiac function and alleviation of myocardial injury were completely abolished by K252a or LY294002. GRP78, caspase-12 and CHOP were highly expressed in ischemic myocardium, while NGF significantly inhibited the overexpression of these proteins which were involved in ER stress-induced myocardial apoptosis. NGF pretreatment also induced phosphorylation of Akt. When the activation of PI3K/Akt pathway is blocked by LY294002, the NGF induced suppression of the apoptosis-related proteins expression was reversed.
  
  
  CONCLUSIONS
  NGF pretreatment may protect the ischemic heart via inhibition of the ER stress-induced apoptosis; this pro-survival effect is mediated by PI3K/Akt pathway.
authors.affiliation: Department of Anesthesiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
authors.forename: Ke
authors.initials: K
authors.lastname: Wei
authors.affiliation: Department of Anesthesiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.affiliation: Department of Anesthesiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Xie
authors.affiliation: Department of Anesthesiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
authors.forename: Xuechao
authors.initials: X
authors.lastname: Hao
authors.affiliation: Department of Anesthesiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Luo
authors.affiliation: Department of Anesthesiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
authors.forename: Su
authors.initials: S
authors.lastname: Min
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053454:Caspase 12 / Q000378:metabolism; D002867:Chromones / Q000494:pharmacology; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D006360:Heat-Shock Proteins / Q000378:metabolism; D008297:Male; D009025:Morpholines / Q000494:pharmacology; D017202:Myocardial Ischemia / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D020932:Nerve Growth Factor / Q000378:metabolism / Q000494:pharmacology*; D009924:Organ Culture Techniques; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D017208:Rats, Wistar; D051742:Transcription Factor CHOP / Q000378:metabolism; D019210:Troponin I / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP
chemical_list: D053454:Caspase 12; D002867:Chromones; D006360:Heat-Shock Proteins; D009025:Morpholines; D020932:Nerve Growth Factor; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D051742:Transcription Factor CHOP; D019210:Troponin I; C497251:Ddit3 protein, rat; C051684:GRP78 protein, rat; D000091342:Endoplasmic Reticulum Chaperone BiP; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C506443:Casp12 protein, rat
keywords: apoptosis.; endoplasmic reticulum; ischemia/reperfusion injury; nerve growth factor