Inhibition of postinfarction ventricular remodeling by high molecular weight polyethylene glycol

Background: Myocardial infarction (MI) is a major etiology for the development of heart failure. We have previously shown that high molecular weight polyethylene glycol (PEG) can protect cardiac myocytes from hypoxia-reoxygenation injury in vitro. In this study, we investigated the potential protective effects of 15-20 kD PEG postinfarction without reperfusion. Methods: One milliliter of PEG 15-20 was delivered intravenously following permanent left anterior descending ligation in adult male rats with phosphate buffer saline (PBS) as control (n ¼ 9 in each group). Echocardiography was performed at baseline and at 8 wk post-MI. Left ventricles (LVs) were harvested to quantify fibrosis, apoptosis, cell survival signaling, regulation of b-adrenergic signaling, and caveolin (Cav) expression. Results: The PEG group had significant recovery of LV function at 8 wk compared with the PBS group. There was less LV fibrosis in both the infarct and remote territory. Cell survival signaling was upregulated in the PEG group with increased Akt and ERK phosphorylation. PEG inhibited apoptosis as measured by terminal deoxynucleotidyl transferase [TdT]- mediated dUTP nick-end labeling positive nuclei and caspase-3 activity. There was maintenance of Cav-1, Cav-2, and Cav-3 expression following PEG treatment versus a decline in the PBS group. Negative regulators of b-adrenergic signaling, G protein-coupled receptor kinase-2, and b-arrestin 1 and 2 were all upregulated in PBS-treated samples compared to normal control; however, PEG treatment led to decreased expression. Conclusions: These data suggest that PEG 15-20 may have significant protective effects post- MI even in the setting of no acute reperfusion. Upregulation of Cav expression appears to be a key mechanism for the beneficial effects of PEG on ventricular remodeling and function.