Abstract 19769: Cardiac Injury and Stunning after Ischemia is Related to Loss of PBEF/Nampt Function and is Rescued by PTEN Inhibition

Abstract

Introduction: Therapeutic hypothermia protection during cardiovascular resuscitation has been associated by us with preservation of heart tissue Pre-B-cell colony-enhancing factor (PBEF)/nicotinamide phosphoribosyltransferase (Nampt) level. This finding was associated with increased heart Akt activity that is negatively regulated by the phosphatase PTEN. We hypothesized that the PTEN inhibitor, VO-OHpic (VO), can improve heart cell survival and contractility via its role in energetic recovery following ischemia. Methods: Primary neonatal heart cells were exposed to 90 min ischemia and 180 min reperfusion to evaluate viability by propidium iodide uptake. Contractility was assessed in a stunning model of 30 min ischemia and 90 min reperfusion. VO (1μM) was given at reperfusion and PBEF/Nampt inhibitor FK866 (100 nM) was administered 1 h prior to ischemia. Akt phosphorylation and PBEF expression was detected by Western blot and ELISA assay, respectively. ATP content was measured by a fluorescent assay kit. Results: Compared to control cells, VO improved cell survival (56.3 ± 7.3 vs. 32.5 ± 7.6%, p < 0.05), a protective effect blocked by FK866. VO also rapidly improved contractile recovery following 30 min ischemia and decreased PBEF/Nampt release from heart cells, protective effects blocked by FK866. Improved contraction was related to increased Akt Thr308 and Ser473 phosphorylation and total ATP content. Conclusions: PTEN inhibition improves heart cell survival, ATP content and contractile recovery after ischemia. Protection is associated with attenuation of PBEF/Nampt cell release and is blocked by PBEF/Nampt inhibitors.