Abstract 323: A Peptide Inhibitor of PTEN Improves Mouse Survival After Cardiac Arrest
Introduction: Prior works from our laboratory found that cooling protection after cardiac arrest is mediated by enhanced Akt activation and in cardiomyocyte the cooling protection can be reproduced using PTEN chemical inhibitor. The current study extend these works by designing a cell-permeable peptide, TAT-PTEN9c, which is more specific for PTEN. Hypothesis: We hypothesized that TAT-PTEN9c interferes with endogenous PTEN binding to cell membrane adaptor resulting in increased Akt activation, enhanced glucose utilization and improved mouse survival after cardiac arrest. Methods: Mouse cardiomyocytes were isolated from 1-3 day old mouse pups. Western blot was used to determine the efficacy of TAT-PTEN9c for Akt activation. The effect of TAT-PTEN9c on mouse survival after cardiac arrest was determined in a mouse model. TAT-PTEN9c (7.5 mg/kg) was given intravenously (IV) after CPR. As a measure of impaired glucose utilization, sorbitol content in heart and brain was determined by a fluorescence assay of NADH formation using sorbitol dehydrogenase and NAD + . Results: TAT-PTEN9c peptide enhanced Akt activation in mouse cardiomyocytes in a concentration-dependent manner. Akt phosphorylation was observed at 1 μM and further increased with 10 μM TAT-PTEN9c. TAT-PTEN9c blocked the binding of endogenous PTEN to MAGI2 in a co-immunoprecipitation assay, while TAT-PTEN3a control had no inhibitory effect. In a mouse model of cardiac arrest, survival was significantly increased in the TAT-PTEN9c treated group compared to saline controls at 4 h (10/15, 67% vs. 6/15, 40%, P < 0.05) after CPR. TAT-PTEN9c improved MAP at both R30 min and R2h. The treated mice had increased Akt phosphorylation at R15 min in both heart and brain tissues with significantly decreased sorbitol content and reduced release of taurine and glutamate into blood, suggesting improved metabolic recovery and glucose utilization. Conclusion: TAT-PTEN9c can be used after CPR in a mouse SCA model to rapidly enhance Akt activation and decrease glucose shunting to the polyol pathway in critical organs, preventing osmotic injury and early cardiovascular collapse and death.