Abstract 112: Multiorgan Akt Activation Is Associated with Successful CPR and Cooling Further Enhances Both Heart Cell Contraction and Akt Activation Following Ischemic Arrest
Introduction: We reported that cooling protection after mouse cardiac arrest and heart cell ischemia/reperfusion is blocked by pharmacologic or genetic Akt inhibition. We therefore examined the timing of tissue Akt activation relative to cardiopulmonary resuscitation (CPR). Given the critical role of Akt in organ survival and contractile function, we hypothesized that recovery of heart contractions after ischemic arrest will be associated with Akt activation (i.e. phosphorylation, p-Akt) and further enhanced by cooling.
Methods: Asystolic cardiac arrest was induced in C57BL6/j mice for 8 to 30 minutes using KCl injection and CPR performed as reported previously. Brain, muscle and heart p-Akt during CPR without return of heart contractions was compared to tissues from successfully resuscitated animals at 5, 15 and 30 min post-arrest. For contraction studies, cardiomyocytes from 1-2 day old C57BL6/j mice underwent 30 min ischemic arrest followed by 60 min reperfusion. Cooling (32°C) was applied during the last 10 min ischemia and extended 1 h into reperfusion. Video microscopy (32 frames/sec) compared contraction displacement within approximately 300 synchronously contracting heart cells before and after ischemic arrest. Western blots measured tissue changes in p-Akt. DAF-2 DA oxidation measured nitric oxide (NO) generation, an Akt downstream effector that enhances contraction.
Results: Compared to CPR animals without resuscitation, animals with return of heart contractions had significantly increased p-Akt at both S473 and T308 sites in heart, muscle and brain within 5 min after CPR (n = 5 each group, p < 0.01). Post-arrest cardiomyocytes similarly had increased p-Akt when contractions returned. Cooling improved contractions from less than 30% to over 50% of baseline contractility and increased p-Akt further. Along with increased p-Akt, cooling also enhanced NO during reperfusion after 30 min ischemia.
Conclusion: Successful return of heart contractions after CPR is associated with rapid multi-organ Akt activation. Cooling improves heart cell contractile function via enhanced Akt and possibly related NO effects. Strategies that rapidly modulate Akt activation and increase NO generation during CPR could improve resuscitation success.
- © 2011 by American Heart Association, Inc.