Endothelial cell preservation at 10 degrees C minimizes catalytic iron, oxidative stress, and cold-induced injury

There is growing evidence that oxidative stress plays an important role in mediating the injury induced by hypothermia during the preservation of cells and tissues for clinical or research use. In cardiovascular allografts, endothelial cell loss or injury may lead to impaired control of vascular permeability and tone, thrombosis, and inflammation. We hypothesized that hypothermia-induced damage to the endothelium is linked to increases in intracellular catalytic iron pools and oxidative stress. In this study, bovine aortic endothelial cells and cell culture methods were used to model the response of the endothelium of cardiovascular tissues to hypothermia. Confluent cells were stored at 0 degrees C to 25 degrees C and cell damage was measured by lipid peroxidation (LPO) and lactate dehydrogenase release. Varying the bleomycin-detectible iron (BDI) in cells modulated cold-induced LPO and cell injury. In untreated cells, injury was highest at 0 degrees C and a minimum at 10 degrees C. A similar temperature-dependent trend was found in BDI levels and cell plating efficiencies. Arrhenius plots of cell killing and iron accumulation rates showed biphasic temperature dependence, with minima at 10 degrees C and matching activation energies above and below 10 degrees C. These findings imply that the mechanisms underlying the hypothermic increase in catalytic iron, oxidative stress, and cell killing are the same and that preservation of the endothelium may be optimized at temperatures above those routinely used.