APP and Alzheimer disease: Interestingly, it has also been demonstrated that Aβ [176] and APP [172] could reduce Cu2+ to Cu+, which in turn can catalyze the decomposition of hydrogen peroxide via the Fenton reaction,Cu+ (Fe2+) + H2O2 → Cu2+ (Fe3+) + •OH + OH−, generating reactive hydroxyl radicals (•OH), capable of damaging DNA, lipids, and proteins and further contributing to the AD pathology [137].