Apoptosis plays a significant role in maladaptive remodeling and
ventricular dysfunction following
ischemia-reperfusion injury. There is a critical need for novel approaches to inhibit apoptotic cell death following reperfusion, as this loss of cardiac myocytes can progressively lead to
heart failure. We investigated the ability and signaling mechanisms of a high-molecular-weight
polyethylene glycol-based copolymer, PEG 15-20, to protect cardiac myocytes from
hypoxia-reoxygenation (H-R)-induced cell death and its efficacy in preserving ventricular function following extended hypothermic
ischemia and warm reperfusion as relevant to
cardiac transplantation. Pretreatment of neonatal rat ventricular myocytes with a 5% PEG
solution led to a threefold decline in apoptosis after H-R relative to untreated controls. There was a similar decline in
caspase-3 activity in conjunction with inhibition of
cytochrome c release from the inner mitochondrial membrane. Treatment with PEG also reduced
reactive oxygen species production after H-R, and sarcolemmal
lipid-raft architecture was preserved, consistent with membrane stabilization. Cell survival signaling was upregulated after H-R with PEG, as demonstrated by increased phosphorylation of Akt, GSK-3β, and ERK1/2. There was also maintenance of cardiac myocyte β-
adrenergic signaling, which is critical for myocardial function. PEG 15-20 was very effective in preserving left ventricular function following prolonged hypothermic
ischemia and warm reperfusion. PEG 15-20 has a potent protective antiapoptotic effect in cardiac myocytes exposed to H-R injury and may represent a novel therapeutic strategy to decrease myocardial cell death and
ventricular dysfunction at the time of reperfusion during
acute coronary syndrome or following prolonged donor heart preservation.