Prion Protein-Deficient Neurons Reveal Lower Glutathione Reductase Activity and Increased Susceptibility to Hydrogen Peroxide Toxicity

摘要

The prion protein (PrP) has a central role in the pathogenesis of transmissible spongiform encephalopathies (TSE). Accumulating evidence suggests that normal cellular PrP (PrPc) may be involved in copper homeostasis and modulation of copper/zinc superoxide dismutase (Cu/ZnSOD) activity in neurons. Hydrogen peroxide (H₂O₂) is a toxic reactive oxygen species generated through normal cellular respiration, and neurons contain two important peroxide detoxifying systems (glutathione pathway and catalase). To determine whether PrP expression affects neuronal resistance to H₂O₂, we exposed primary cerebellar granule neuron cultures derived from PrP knockout (PrP-/-) and wild-type (WT) mice to H₂O₂ for 3, 6, and 24 hours. The PrP-/- neurons were significantly more susceptible to H₂O₂ toxicity than WT neurons after 6 and 24 hours’ exposure. The increased H₂O₂ toxicity may be related to a significant decrease in glutathione reductase activity measured in PrP-/- neurons both in vitro and in vivo. This was supported by the finding that inhibition of GR activity with 1,3-bis(2-chloroethyl)-1-nitrosurea (BCNU) increased H₂O₂ toxicity in WT neurons over the same exposure period. The PrP toxic peptide PrP106–126 significantly reduced neuronal glutathione reductase activity and increased susceptibility to H₂O₂ toxicity in neuronal cultures suggesting that PrP toxicity in vivo may involve altered glutathione reductase activity. Our results suggest the pathophysiology of prion diseases may involve perturbed PrPc function with increased vulnerability to peroxidative stress.