title: Induction of cardioplegic arrest immediately activates the myocardial apoptosis signal pathway.
abstract: Myocardial ischemia-reperfusion, including cardioplegic arrest (CA), has been associated with cardiac apoptosis induction. However, the time course of apoptosis activation and the trigger mechanisms are still unclear. Because apoptosis inhibition may represent a novel therapeutic strategy for long-term myocardial preservation, we sought to investigate the time course of apoptosis signal-pathway induction during CA. As to method, Sprague-Dawley rats (300-350 g) were anesthetized, intubated, and mechanically ventilated. CA was initiated by infusion of ice-cold crystalloid solution (Custodiol, 10 ml/kg) into the aortic root, and hearts were rapidly excised and stored for 0, 30, 60, and 120 min in 0.9% sodium chloride solution (28 degrees C). In controls, no CA was initiated before removal and storage at 28 degrees C. In another group, calcium-rich cardioplegia was used, and an additional group received a caspase-8 inhibitor before CA induction. Left ventricular cytosolic extracts were isolated and investigated for the activity of caspase-3 and -6 (effector caspases) and caspase-8 and -9 (involved in extrinsic and intrinsic pathways of apoptosis induction). Fluorometric activity assays were performed by using specific substrates. As a result, activities of all tested caspases were significantly increased immediately after CA induction compared with controls. Administration of the caspase-8 inhibitor significantly reduced activities of all caspases. With calcium-rich cardioplegia, caspase activities were significantly lower compared with low-calcium CA. Control hearts also showed an increase of caspase activities during cold-storage ischemia without CA but had significantly different time courses compared with hearts with CA. In conclusion, our data show rapid apoptosis signal-pathway induction immediately following CA exposure. Thus apoptosis signal-pathway inhibition as a potential strategy for improved myocardial preservation would have the greatest effect when applied before CA exposure.
authors.affiliation: Center for Microvascular and Lymphatic Studies, Department of Surgery, The University of Texas-Houston Medical School, Houston, TX, USA.
authors.forename: Uwe M
authors.initials: UM
authors.lastname: Fischer
authors.forename: Charles S
authors.initials: CS
authors.lastname: Cox
authors.forename: Glen A
authors.initials: GA
authors.lastname: Laine
authors.forename: Uwe
authors.initials: U
authors.lastname: Mehlhorn
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Bloch
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Allen
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002314:Cardioplegic Solutions; D004195:Disease Models, Animal; D006321:Heart / Q000502:physiology / Q000503:physiopathology*; D006323:Heart Arrest; D006324:Heart Arrest, Induced; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000473:pathology / Q000503:physiopathology; D009206:Myocardium / Q000166:cytology / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D002314:Cardioplegic Solutions