Inhibition of caspase-3 improves contractile recovery of stunned myocardium, independent of apoptosis-inhibitory effects.
OBJECTIVE
The aim of this study was to investigate whether the caspase-3 inhibitor Ac-DEVD-CHO functionally improves stunned myocardium.


BACKGROUND
Degradation of troponin I contributes to the pathogenesis of myocardial stunning, whereas the role of apoptosis is unknown. Caspase-3 is an essential apoptotic protease that is specifically inhibited by Ac-DEVD-CHO.


METHODS
Isolated working hearts of rats were exposed to 30 min of low-flow ischemia, followed by 30 min of reperfusion. Ac-DEVD-CHO (0.1 to 1 micromol/l) was added 15 min before ischemia/reperfusion or 5 min before reperfusion. Cardiac output, external heart power, left ventricular (LV) developing pressure and contractility (dp/dt(max)) were measured. Apoptosis was assessed by TUNEL staining and internucleosomal deoxyribonucleic acid fragmentation. Caspase-3 processing and troponin I cleavage were determined by immunoblotting. Caspase-3 activity was measured using a fluorogenic substrate.


RESULTS
The addition of Ac-DEVD-CHO before ischemia/reperfusion or before reperfusion dose-dependently and significantly (p < 0.05) improved post-ischemic recovery of cardiac output, external heart power, LV developing pressure and dp/dt(max), compared with the vehicle (0.01% dimethyl sulfoxide). Ac-DEVD-CHO was similarly effective when given before reperfusion. Ac-DEVD-CHO blocked ischemia/reperfusion-induced caspase-3 activation, but cardiomyocyte apoptosis was unaffected. Troponin I cleavage was not inhibited by Ac-DEVD-CHO.


CONCLUSIONS
Caspase-3 is activated in stunned myocardium. Inhibition of caspase-3 by Ac-DEVD-CHO significantly improves post-ischemic contractile recovery of stunned myocardium, even when given after the onset of ischemia. The mechanism(s) of protection by Ac-DEVD-CHO appear to be independent of apoptosis. Inhibition of caspase-3 is a novel therapeutic strategy to improve functional recovery of stunned myocardium.
Ruetten
H
H
Aventis Pharmaceuticals, Frankfurt, Germany.
Badorff
C
C
Ihling
C
C
Zeiher
A M
AM
Dimmeler
S
S
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002302:Cardiac Output / Q000187:drug effects / Q000502:physiology; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000502:physiology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D020287:In Situ Nick-End Labeling; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects* / Q000502:physiology; D015428:Myocardial Reperfusion Injury / Q000503:physiopathology; D017682:Myocardial Stunning / Q000503:physiopathology*; D009842:Oligopeptides / Q000494:pharmacology*; D010477:Perfusion; D051381:Rats; D017207:Rats, Sprague-Dawley; D019210:Troponin I / Q000378:metabolism; D016277:Ventricular Function, Left / Q000187:drug effects / Q000502:physiology
D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D009842:Oligopeptides; D019210:Troponin I; C099158:acetyl-aspartyl-glutamyl-valyl-aspartal; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases