H2O2-mediated oxidative stress versus cold ischemia-reperfusion: mitochondrial respiratory defects in cultured human endothelial cells

Oxidative stress to vascular endothelium plays an important role in cold ischemia-reperfusion (CIR) injury. We compared mitochondrial and plasma membrane integrity in human endothelial cells after 20-min exposure to 500 μM H 2 O 2 or 8-hr cold ischemia and simulated reperfusion. In both groups, plasma membrane integrity was maintained but respiration was significantly decreased, as measured by high-resolution respirometry. Uncoupling was more pronounced after H 2 O 2 exposure compared with CIR. After H 2 O 2 exposure, complex I respiration was significantly reduced, whereas CIR resulted additionally in a significant inhibition of complex II and IV respiration. Our results point to a partial overlap of the patterns of mitochondrial defects after H 2 O 2 -mediated and CIR injury. In this respect, H 2 O 2 exposure proved to be a useful model to study the mechanisms of CIR injury to human endothelial cells, whereas the full pattern of CIR injury could not be induced by a pulse of hydrogen peroxide exposure.