Aβ and tau toxicities in Alzheimer's are linked via oxidative stress-induced p38 activation: protective role of vitamin E.

Oxidative stress is a hallmark of Alzheimer's disease (AD). We propose that rather than causing damage because of the action of free radicals, oxidative stress deranges signaling pathways leading to tau hyperphosphorylation, a hallmark of the disease. Indeed, incubation of neurons in culture with 5 µM beta-amyloid peptide (Aβ) causes an activation of p38 MAPK (p38) that leads to tau hyperphosphorylation. Inhibition of p38 prevents Aβ-induced tau phosphorylation. Aβ-induced effects are prevented when neurons are co-incubated with trolox (the water-soluble analog of vitamin E). We have confirmed these results in vivo, in APP/PS1 double transgenic mice of AD. We have found that APP/PS1 transgenic mice exhibit a high level of P-p38 in the hippocampus but not in cortex and this is prevented by feeding animals with a diet supplemented with vitamin E. Our results underpin the role of oxidative stress in the altered cell signaling in AD pathology and suggest that antioxidant prevention may be useful in AD therapeutics.