High-molecular-weight Polyethylene Glycol Inhibits Myocardial Ischemia-reperfusion Injury in Vivo

Objectives: Cardiac ischemia-reperfusion (I-R) injury remains a significant problem as there are no therapies available to minimize the cell death that can lead to impaired function and heart failure. We have shown that high-molecular-weight polyethylene glycol (PEG) (15-20 kD) can protect cardiac myocytes in vitro from hypoxia-reoxygenation injury. In this study, we investigated the potential protective effects of PEG in vivo.

Methods: Adult rats underwent left anterior descending artery occlusion for 60 minutes followed by 48 hours or 4 weeks of reperfusion. One milliliter of 10% PEG solution or phosphate-buffered saline (PBS) control (n = 10 per group) was administered intravenously (IV) immediately before reperfusion.

Results: Fluorescein-labeled PEG was robustly visualized in the myocardium 1 hour after IV delivery. The PEG group had significant recovery of left ventricular ejection fraction at 4 weeks versus a 25% decline in the PBS group (P < .01). There was 50% less LV fibrosis in the PEG group versus PBS with smaller peri-infarct and remote territory fibrosis (P < .01). Cell survival signaling was upregulated in the PEG group with increased Akt (3-fold, P < .01) and ERK (4-fold, P < .05) phosphorylation compared to PBS controls at 48 hours. PEG also inhibited apoptosis as measured by TUNEL-positive nuclei (56% decrease, P < .02) and caspase 3 activity (55% decrease, P < .05).

Conclusions: High-molecular-weight PEG appears to have a significant protective effect from I-R injury in the heart when administered IV immediately before reperfusion. This may have important clinical translation in the setting of acute coronary revascularization and myocardial protection in cardiac surgery.