Abstract 29: Activation of the Mitochondrial Apoptotic Pathway Without Evidence of Apoptotic Cell Death after Resuscitation from Ventricular Fibrillation
Background: We have previously reported in a rat model of VF that post-resuscitation myocardial dysfunction is associated with activation of the mitochondrial apoptotic pathway. We investigated whether such process leads to apoptotic DNA fragmentation and used a ligation-mediated polymerase chain reaction (LM-PCR) which is both sensitive and specific for detecting blunt-end DNA fragments.
Methods: VF was induced in two groups of 8 rats each and left untreated for 4 mins (VF 4-mins) or 8 mins (VF 8-mins) before 8 mins of chest compression and defibrillation. One additional group served as sham. Hearts were harvested at 4-hrs post-resuscitation and the left ventricle isolated for measuring cytochrome c release, caspase-3 activation, and blunt-end DNA fragmentation.
Results: Cytosolic cytochrome c levels significantly increased in VF 4-mins (0.95 ± 0.09 ng/μg, p < 0.01) and VF 8-mins (0.90 ± 0.12 ng/μg, p < 0.05) compared to sham (0.75 ± 0.16 ng/μg). Cleaved 17-kDa caspase-3 fragments (indexed to procaspase-3) were also elevated in VF 4-mins (0.67 ± 0.54, p < 0.05) and VF 8-mins (0.72 ± 0.42, p < 0.05) compared to sham rats (0.21 ± 0.12). However, detection of DNA fragments was minimal and not different than in sham rats (Figure⇓) despite a significant reduction in cardiac index in VF 4-mins (39 ± 15 ml/min/kg, p < 0.01) and VF 8-mins (44 ± 16 ml/min/kg, p < 0.01) compared to sham rats (142 ± 54 ml/min/kg).
Conclusions: Activation of the mitochondrial apoptotic pathway was not associated with blunt-end DNA fragmentation, the hallmark of apoptotic cell death. These findings are consistent with the observation that post-resuscitation myocardial dysfunction is largely a reversible process.