An increasing body of evidence indicates that oxidative stress and damage play a 
role in the pathogenesis of a number of diseases associated with 
neurodegeneration, including Down syndrome (DS), Alzheimer's disease (AD) and 
Pick's disease (PD). Although oxidative stress is a common element in these 
diseases, specific clinico-pathological phenotypes have been described for each 
disorder. Development of these phenotypes might be linked, among others, to 
differences in antioxidant response. The present study is designed to 
investigate expression of peroxiredoxins (Prxs), the newly characterized family 
of highly conserved antioxidant enzymes, and other antioxidant enzymes in 
frontal cortex and cerebellum of DS, AD and PD patients using the technique of 
proteomics. Levels of Prx I, Mn superoxide dismutase (SOD2) and 
glutathione-S-transferase omega1 in DS, AD and PD were not significantly 
different from that of controls in both brain regions investigated. In contrast, 
Prx II was significantly increased (P<0.05) in frontal cortex of DS, AD and PD, 
whereas Prx III was decreased in frontal cortex of DS (P<0.01) and PD (P<0.001). 
Interestingly, Prx VI displayed a significant increase (P<0.05) only in PD 
frontal cortex. The present data indicate that differential regulation of 
antioxidant enzymes exist in DS, AD and PD, suggestive of the diversity as well 
as distinct functional roles of these proteins. Moreover, while up-regulation of 
Prx II appears to provide evidence for the existence of compensatory response in 
increased cell loss, up-regulation of Prx VI may be used to discriminate PD from 
AD as well as DS.