Increased expression of uncoupling protein 2 in HepG2 cells attenuates oxidative damage and apoptosis

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Abstract
Introduction: Oxidative damage plays a major part in the pathogenesis of liver disease. Uncoupling proteins (UCPs) may be able to limit the generation of reactive oxygen species (ROS) and be cytoprotective. Methods: We investigated the effect of up-regulation of UCP2 in a hepatoblastoma cell line exposed to menadione or hypoxia/re-oxygenation. Results: Lipid and protein oxidation was increased in HepG2 cells exposed to ROS but this increase was significantly lower in cells over-expressing UCP2 under identical conditions. LDH release increased 2.5-fold in response to hypoxia/re-oxygenation in control HepG2 cells with no significant increase in UCP2 transfected cells. Hypoxia/re-oxygenation resulted in a reduction in liver-specific protein secretion that was attenuated in transfected cells and UCP2 over-expression also resulted in a 66% reduction in apoptosis compared with non-transfected controls. Conclusions: These data suggest that UCP2 can limit oxidative damage in HepG2 cells in response to oxidative stress resulting in improved cell function and resistance to apoptosis.