Brain and brawn: parallels in oxidative strength.

Neuronal oxidative stress occurs early in the progression of Alzheimer disease (AD), significantly before the development of the pathologic hallmarks, neurofibrillary tangles, and senile plaques. Study of Down syndrome, cases with autosomal dominant mutation, and sporadic AD all suggest amyloid-beta deposition and hyperphosphorylated tau function as compensatory responses and downstream adaptations to ensure that neuronal cells do not succumb to oxidative damage. Amyloid-beta and tau hyperphosphorylation also define vulnerable muscle cells in sporadic inclusion-body myositis (s-IBM). The role of the structural changes of s-IBM, as in AD, remains to be determined but may mark a critical response yielding a novel balance in oxidant homeostasis.