The effect of Fenton reaction on protease-resistant prion protein (PrP ^Sc) degradation and scrapie infectivity

In prion diseases, metal imbalances in brain and/or metal substitutions for copper in prion protein suggest that metal-catalyzed oxidation (MCO) and oxidative stress may affect cellular function and accumulation of protease-resistant prion protein (PrP^Sc). We examined the effect of metal-induced oxidative stress by Fenton reaction on prion protein with regard to its degradation, insolubility, and infectivity. Precipitation and insolubility of prion protein were induced by Fenton reaction in scrapie-infected brain homogenate. Results showed an increase in hydroxylation products (thiobarbituric acid reactive substances; TBARS) and a decrease of ferrous ion (Fe²⁺) levels after Fenton reaction. Efficiency of metal-induced oxidation was higher for Fe²⁺ than Mn²⁺. Compared to untreated samples, there was increased susceptibility to proteolytic degradation of PrP^Sc after treatment with 3.12-12.5 mM Fe ²⁺-Mn²⁺/H₂O₂. Interestingly, we observed that Fenton reaction could extend incubation periods, indicating a decrease in scrapie infectivity. These results suggest that PrP^Sc hydroxylation and degradation may affect PrP conversion and the pathogenesis of prion diseases.