Abstract 17095: Caveolin-1 Mediates Cellular Protective Effects of a High-Molecular Weight Polyethylene Glycol-Based Copolymer, PEG 15-20 During Hypoxia-Reoxygenation in Cardiac Myocytes
Ischemic heart disease is the primary etiology for the development of heart failure. We recently demonstrated that PEG 15-20 protects cardiac myocytes from hypoxia-reoxygenatiion (H-R)-induced cell death and preserves ventricular function. In the present study we investigated our hypothesis that PEG 15-20 exerts its beneficial effect by stabilizing sarcolemmal lipid rafts particularly by its effect on Caveolin-1 (Cav-1). Cav-1 alongwith Cav-3, the principal structural components of caveolar domains are abundantly expressed in the myocardium and implicated in the pathogenesis of ischemic injury. Cardiac myocytes were exposed to 30 minutes of hypoxia (2% O2, 5% CO2, 93% N2) followed by 3 hours of reoxygenation (5% CO2, 95% air) with cells treated with 5% PEG 15-20 during reoxygenation. Adenoviral-mediated knockdown of Cav-1 in cardiac myocytes by RNA interference reversed the anti-apoptotic effect of PEG 15-20 both in terms of caspase 3 activity (6.7±1.2 vs. 3.8±0.76 fluorometric units/mg protein) and TUNEL staining (38±7 vs. 17±3 apoptotic cells). Cav-1 knockdown also abrogated the decrease in oxidative stress mediated by PEG 15-20 during H-R as measured by superoxide radical generation (4.3±0.65 vs. 1.4±0.32 nmoles/min/mg protein with PEG 15-20 alone). Further Cav-1 knockdown mitigated the increased pro-survival phosphorylation of Akt, GSK-3β and ERK1/2 observed with PEG15-20 during H-R. Importantly maintenance of cardiac myocyte β-adrenergic signaling that is critical for myocardial function that was observed with PEG 15-20 treatment during H-R in cardiac myocytes was also reversed with knockdown of Cav-1(16±1.8 vs. 28±2.6 pmol cAMP/mL with PEG 15-20 alone). Finally, confocal microscopy revealed that PEG 15-20 mediated preservation of sarcolemmal lipid-raft architecture during H-R was abolished in cells deficient in Cav-1as seen by increased lipid raft coalescence. These studies demonstrate that PEG 15-20 primarily exerts its cardiac-specific pro-survival and anti-apoptotic effects during H-R by binding and stabilizing Cav-1 in the caveolar domains. Therapeutic strategies to augment maintenance of lipid raft micro architecture in the cardiac sarcolemmal membrane may improve survival after ischemic injuries.
- © 2011 by American Heart Association, Inc.