Generation of hydrogen peroxide-resistant murine neuroblastoma cells: a target discovery platform for novel neuroprotective genes

Oxidative stress has been suggested to play an important role in the pathogenesis of various neurodegenerative diseases including Alzheimer’s disease (AD). Hydrogen peroxide (H₂O₂), one of the main reactive oxygen species, is converted into the highly toxic ·OH radical in the presence of redox-active transition metals, which then oxidises nucleic acids, lipids and proteins, leading to neurodegeneration and cell death. There is an urgent need to gain more knowledge about relevant therapeutic targets to combat oxidative stress and it neurotoxic effects, and how this knowledge can be utilized to develop novel neuroprotective therapies for AD. One way to identify new mechanisms combating oxidative stress was via the creation of H₂O₂-resistant cell lines and identification of the mechanisms responsible for their resistance. However, in most cases catalase overexpression or increased glutathione content was identified as the primary mode of H₂O₂ resistance in these cell lines. In this study, we have generated six different resistant neuronal cell lines or populations (from the same original murine Neuro2a neuroblastoma line) by exposing cells to increasing concentrations of H₂O₂ and performing continuous selection for survivors over a period of several months, which appear to have acquired H₂O₂ resistance based on other, novel mechanisms. These six populations showed a significant, but differential resistance against H₂O₂ when compared with the parental cell line. Using combinations of catalase-, glutathione synthesis- and glutathione peroxidase-inhibitors it was shown that the increased resistance of Neuro2a-HR cells is not solely based on an increased activity of catalase or the glutathione system, suggesting that their resistance might be based on yet unknown, novel defence mechanisms.