Abstract

Perfluorochemicals (PFCs) are known to provide a unique tool for controlled uptake and delivery of oxygen. We have characterized the effects of incremental oxygen delivery on cell viability of human ischemic cardiomyocytes using chemically inert PFCs as oxygen carrier. We have found that cell viability after prolonged ischemia depends on the dose of oxygen supplementation by oxygenated (ox) PFCs during reoxygenation. Although reoxygenation with the transient addition of oxPFCs in high concentrations (2250 microMO2 in 0.4 muM PFCs) results in decreased cell viability compared with normoxic reoxygenation, cell survival increases by 30 +/- 4% after reoxygenation with moderate oxPFC concentrations (750 muM O2 in 0.1 microM PFCs). Immunoblot analysis revealed that oxPFC-supplemented reoxygenation causes marked (16-fold) deactivation of death-associated protein kinase (DAPK) signaling an increase in mitochondrial membrane potential and a decreased steady-state level of superoxide by 19 +/- 3%. Reoxygenation with oxPFCs is further responsible for a 2-fold activation of AMP-activated protein kinase (AMPK) signaling an inadequate ATP supply by oxidative phosphorylation during reoxygenation. Addition of oxPFCs stabilizes both hypoxia-inducible factor (HIF) 1-alpha and 2-alpha during reoxygenation. Overall, these results indicate that moderate doses of oxPFCs can improve cell survival during reoxygenation, causing deactivation of DAPK, up-regulation of AMPK, and HIF1-alpha and 2-alpha stabilization. These effects of oxPFCs are dose-dependent, and they lead to a stabilization of the mitochondrial membrane potential, decreased steady-state levels of superoxide, and pacification of mitochondrial activity.