title: Effects of inhibition of myocardial extracellular-responsive kinase and P38 mitogen-activated protein kinase on mechanical function of rat hearts after prolonged hypothermic ischemia.
abstract: BACKGROUND
  Mitogen-activated protein kinases (MAPKs), including extracellular-responsive kinase (ERK) and p38 MAPK, are activated by stresses associated with hypothermia-rewarming and ischemia-reperfusion. Their activation in heart is associated with beneficial (preconditioning) and adverse effects (apoptosis and impaired contractility). This study determined whether ERK and p38 MAPK activities are altered by hypothermic ischemia and normothermic reperfusion and the consequences of their inhibition on recovery of myocardial function.
  
  
  METHODS
  Left ventricular work (L x min(-1) x mm Hg) was assessed during normothermic perfusion (30 min) of isolated rat hearts that were either freshly excised or previously subjected to hypothermic storage (8 hr, 3 degrees C) and rewarming (10 min, 37 degrees C) before normothermic reperfusion (30 min). Phospho-specific immunoblot analysis of p38 MAPK was performed in hearts and various cultured cells.
  
  
  RESULTS
  Compared with fresh hearts, hearts subjected to hypothermia and rewarming demonstrated impaired left ventricular work (1.96+/-0.53, n=12 vs. 8.37+/-0.46, n=4, <0.05) during reperfusion. The ERK inhibitor, PD98059 (20 microM), present during storage and rewarming, caused modest improvement (3.66+/-0.75, n=9, <0.05). The p38 MAPK inhibitor, SB202190 (10 microM), when present during reperfusion, improved recovery (to 6.12+/-0.75, n=6, <0.05); it was ineffective if present only during rewarming (1.52+/-0.88, n=4). In rat2 fibroblasts, hypothermia and rewarming activated p38 MAPK and its downstream kinase MAPK-activated protein kinase 2, but not c-Jun N-terminal kinase/stress-activated protein kinase.
  
  
  CONCLUSIONS
  Myocardial p38 MAPK and MAPK-activated protein kinase 2 are stimulated by hypothermia, ischemia, and rewarming and are detrimental to recovery of mechanical function of hearts subjected to prolonged hypothermic storage. Inhibition of p38 MAPK may be useful in protocols to improve the recovery of mechanical function of cold-stored hearts.
authors.affiliation: Department of Pharmacology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada. sandy.clanachan@ualberta.ca
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Clanachan
authors.forename: Jagdip S
authors.initials: JS
authors.lastname: Jaswal
authors.forename: Manoj
authors.initials: M
authors.lastname: Gandhi
authors.forename: Drell A
authors.initials: DA
authors.lastname: Bottorff
authors.forename: Jason
authors.initials: J
authors.lastname: Coughlin
authors.forename: Barry A
authors.initials: BA
authors.lastname: Finegan
authors.forename: James C
authors.initials: JC
authors.lastname: Stone
mesh_terms: D000818:Animals; D004789:Enzyme Activation; D005419:Flavonoids / Q000494:pharmacology*; D007036:Hypothermia, Induced; D007093:Imidazoles / Q000494:pharmacology*; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors*; D017202:Myocardial Ischemia / Q000503:physiopathology*; D010766:Phosphorylation; D011725:Pyridines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016277:Ventricular Function, Left / Q000187:drug effects*; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D005419:Flavonoids; D007093:Imidazoles; D011725:Pyridines; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one