title: Morphine-Induced Preconditioning: Involvement of Protein Kinase A and Mitochondrial Permeability Transition Pore.
abstract: BACKGROUND
  Morphine induces myocardial preconditioning (M-PC) via activation of mitochondrial large conductance Ca2+-sensitive potassium (mKCa) channels. An upstream regulator of mKCa channels is protein kinase A (PKA). Furthermore, mKCa channel activation regulates mitochondrial bioenergetics and thereby prevents opening of the mitochondrial permeability transition pore (mPTP). Here, we investigated in the rat heart in vivo whether 1) M-PC is mediated by activation of PKA, and 2) pharmacological opening of the mPTP abolishes the cardioprotective effect of M-PC and 3) M-PC is critically dependent on STAT3 activation, which is located upstream of mPTP within the signalling pathway.
  
  
  METHODS
  Male Wistar rats were randomised to six groups (each n = 6). All animals underwent 25 minutes of regional myocardial ischemia and 120 minutes of reperfusion. Control animals (Con) were not further treated. Morphine preconditioning was initiated by intravenous administration of 0.3 mg/kg morphine (M-PC). The PKA blocker H-89 (10 μg/kg) was investigated with and without morphine (H-89+M-PC, H-89). We determined the effect of mPTP opening with atractyloside (5 mg/kg) with and without morphine (Atr+M-PC, Atr). Furthermore, the effect of morphine on PKA activity was tested in isolated adult rat cardiomyocytes. In further experiments in isolated hearts we tested the protective properties of morphine in the presence of STAT3 inhibition, and whether pharmacological prevention of the mPTP-opening by cyclosporine A (CsA) is cardioprotective in the presence of STAT3 inhibition.
  
  
  RESULTS
  Morphine reduced infarct size from 64±5% to 39±9% (P<0.05 vs. Con). H-89 completely blocked preconditioning by morphine (64±9%; P<0.05 vs. M-PC), but H-89 itself had not effect on infarct size (61±10%; P>0.05 vs. Con). Also, atractyloside abolished infarct size reduction of morphine completely (65±9%; P<0.05 vs. M-PC) but had no influence on infarct size itself (64±5%; P>0.05 vs. Con). In isolated hearts STAT3 inhibitor Stattic completely abolished morphine-induced preconditioning. Administration of Stattic and mPTP inhibitor cyclosporine A reduced infarct size to 31±6% (Stat+CsA, P<0.05 vs. Con). Cyclosporine A alone reduced infarct size to 26±7% (CsA P<0.05 vs. Con). In cardiomyocytes, PKA activity was increased by morphine.
  
  
  CONCLUSIONS
  Our data suggest that morphine-induced cardioprotection is mediated by STAT3-activation and inhibition of mPTP, with STA3 located upstream of mPTP. There is some evidence that protein kinase A is involved within the signalling pathway.
authors.affiliation: Department of Anesthesiology, University Hospital Duesseldorf, Moorenstr. 5, 40225, Duesseldorf, Germany.
authors.forename: Marianne
authors.initials: M
authors.lastname: Dorsch
authors.affiliation: Department of Anesthesiology, University Hospital Duesseldorf, Moorenstr. 5, 40225, Duesseldorf, Germany.
authors.forename: Friederike
authors.initials: F
authors.lastname: Behmenburg
authors.affiliation: Department of Anesthesiology, University Hospital Duesseldorf, Moorenstr. 5, 40225, Duesseldorf, Germany.
authors.forename: Miriam
authors.initials: M
authors.lastname: Raible
authors.affiliation: Department of Anesthesiology, University Hospital Duesseldorf, Moorenstr. 5, 40225, Duesseldorf, Germany.
authors.forename: Dominic
authors.initials: D
authors.lastname: Blase
authors.affiliation: Department of Anesthesiology, University Hospital Duesseldorf, Moorenstr. 5, 40225, Duesseldorf, Germany.|Department of Anesthesiology and Critical Care Medicine, Hadassah University Hospital, Jerusalem, Israel.|Department of Biochemistry and Molecular Biology, The Hebrew University of Jerusalem, Ein Kerem Campus, Jerusalem, Israel.
authors.forename: Hilbert
authors.initials: H
authors.lastname: Grievink
authors.affiliation: Department of Anesthesiology, Laboratory of Experimental Intensive Care and Anesthesiology (L.E.I.C.A.), Academic Medical Center (AMC), University of Amsterdam, Meibergdreef 9, 1100 DD, Amsterdam, The Netherlands.
authors.forename: Markus W
authors.initials: MW
authors.lastname: Hollmann
authors.affiliation: Department of Anesthesiology, University Hospital Duesseldorf, Moorenstr. 5, 40225, Duesseldorf, Germany.|Institute of Cardiovascular Physiology, Heinrich-Heine-University, Universitaetsstr. 1, 40225, Duesseldorf, Germany.
authors.forename: André
authors.initials: A
authors.lastname: Heinen
authors.affiliation: Department of Anesthesiology, University Hospital Duesseldorf, Moorenstr. 5, 40225, Duesseldorf, Germany.
authors.forename: Ragnar
authors.initials: R
authors.lastname: Huhn
mesh_terms: D000818:Animals; D001278:Atractyloside / Q000494:pharmacology; D002316:Cardiotonic Agents / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism / Q000502:physiology*; D016572:Cyclosporine / Q000494:pharmacology; D004734:Energy Metabolism; D066298:In Vitro Techniques; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism / Q000502:physiology*; D000083162:Mitochondrial Permeability Transition Pore; D009020:Morphine / Q000627:therapeutic use*; D009203:Myocardial Infarction / Q000473:pathology / Q000517:prevention & control; D017202:Myocardial Ischemia / Q000473:pathology*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D011897:Random Allocation; D017208:Rats, Wistar; D015424:Reperfusion; D050796:STAT3 Transcription Factor / Q000378:metabolism / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects; D013449:Sulfonamides / Q000494:pharmacology
chemical_list: D002316:Cardiotonic Agents; D007546:Isoquinolines; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D050796:STAT3 Transcription Factor; C494088:Stat3 protein, rat; D013449:Sulfonamides; D001278:Atractyloside; D009020:Morphine; D016572:Cyclosporine; D017868:Cyclic AMP-Dependent Protein Kinases; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide