Increased susceptibility to oxidative stress in scrapie-infected neuroblastoma cells is associated with intracellular iron status

The molecular mechanism of neurodegeneration in prion diseases remains largely uncertain, but one of the features of infected cells is higher sensitivity to induced oxidative stress. In this study, we have investigated the role of iron in hydrogen peroxide (H2O2)-induced toxicity in scrapie-infected mouse neuroblastoma N2a (ScN2a) cells. ScN2a cells were significantly more susceptible to H2O2 toxicity than N2a cells as revealed by cell viability (MTT) assay. After 2 h exposure, significant decrease in cell viability in ScN2a cells was observed at low concentrations of extracellular H2O2 (5-10 μM), whereas N2a cells were not affected. The increased H2O2 toxicity in ScN2a cells may be related to intracellular iron status since ferrous iron (Fe2+) chelator 2,2′-bipyridyl (BIP) prevented H2O2-induced decrease in cell viability. Further, the level of calcein-sensitive labile iron pool (LIP) was significantly increased in ScN2a cells after H2O2 treatment. Finally, the production of reactive oxygen species (ROS) was inhibited by 30% by iron chelators desferrioxamine (DFO) and BIP in ScN2a cells, whereas no significant effect of iron chelators on basal ROS production was observed in N2a cells. This study indicates that cellular resistance to oxidative stress in ScN2a cells is associated with intracellular status of reactive iron.