title: Calpain translocation and activation as pharmacological targets during myocardial ischemia/reperfusion.
abstract: Calpains contribute to reperfusion-induced myocardial cell death. However, it remains controversial whether its activation occurs during ischemia or reperfusion. We investigated the regulation and time-course of calpain activation secondary to transient ischemia and the efficacy of its inhibition at reperfusion as a therapeutic strategy to limit infarct size. In isolated rat hearts (Sprague-Dawley), ischemia induced a time-dependent translocation of m-calpain to the membrane that was not associated with calpain activation as assessed by proteolysis of its substrate alpha-fodrin. Translocation of calpain was dependent on Ca(2+) entry through reverse mode Na(+)/Ca(2+)-exchange and was independent of acidosis. Calpain activation occurred during reperfusion, but only after intracellular pH (pHi) normalization, and was not prevented by inhibiting its translocation during ischemia with methyl-beta-cyclodextrin. The intravenous infusion of MDL-28170 in an in vivo rat model with transient coronary occlusion during the first minutes of reperfusion resulted in a reduction of infarct size (43.9+/-3.9% vs. 60.2+/-4.7, P=0.046, n=18) and alpha-fodrin degradation. These results suggest that (1) Ca(2+)-induced calpain translocation to the membrane during ischemia is independent of its activation, (2) intracellular acidosis inhibits calpain activation during ischemia and pHi normalization allows activation upon reperfusion, and (3) calpain inhibition at the time of reperfusion appears as a potentially useful strategy to limit infarct size.
authors.affiliation: Servei de Cardiologia, Hospital Universitari Vall d'Hebron, Barcelona, Spain.
authors.forename: Víctor
authors.initials: V
authors.lastname: Hernando
authors.forename: Javier
authors.initials: J
authors.lastname: Inserte
authors.forename: Carmem Luíza
authors.initials: CL
authors.lastname: Sartório
authors.forename: Víctor M
authors.initials: VM
authors.lastname: Parra
authors.forename: Marcos
authors.initials: M
authors.lastname: Poncelas-Nozal
authors.forename: David
authors.initials: D
authors.lastname: Garcia-Dorado
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008297:Male; D009203:Myocardial Infarction / Q000150:complications / Q000473:pathology / Q000503:physiopathology; D015428:Myocardial Reperfusion Injury / Q000150:complications / Q000188:drug therapy* / Q000201:enzymology* / Q000503:physiopathology; D009206:Myocardium / Q000201:enzymology / Q000473:pathology; D011480:Protease Inhibitors / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D002135:Calcium-Binding Proteins; D011480:Protease Inhibitors; C033668:calpastatin; D002154:Calpain; C449000:m-calpain