The identification of biological markers of Alzheimer's disease (AD) can be extremely useful to improve diagnostic accuracy and/or to monitor the efficacy of putative therapies. In this regard, peripheral cells may be of great importance, because of their easy accessibility. After subjects were grouped according to diagnosis, the expression of conformationally mutant p53 in blood cells was compared by immunoprecipitation or by a cytofluorimetric assay. In total, 104 patients with AD, 92 age-matched controls, 15 patients with Parkinson's disease and 9 with other types of dementia were analyzed. Two independent methods to evaluate the differential expression of a conformational mutant p53 were developed. Mononuclear cells were analyzed by immunoprecipitation or by flow-cytometric analysis, following incubation with a conformation-specific p53 antibody, which discriminates unfolded p53 tertiary structure. Mononuclear cells from AD patients express a higher amount of mutant-like p53 compared to non-AD subjects, thus supporting the study of conformational mutant p53 as a new putative marker to discriminate AD from non-AD patients. We also observed a strong positive correlation between the expression of p53 and the age of patients. The expression of p53 was independent from the length of illness and from the Mini Mental State Examination value.

Here we show that human embryonic kidney (HEK) cells stably transfected with amyloid precursor protein (HEK-APP), expressed a conformational mutant-like and transcriptionally inactive p53 isoform, and turned out to be less sensitive to the cytotoxin doxorubicin in comparison with untransfected cells. Treatment of HEK-APP cells with c-and b-secretase inhibitors prevented generation of unfolded, mutant-like p53 isoform and made the cells vulnerable to doxorubicin as untransfected cells. Changes in p53 conformational state and reduced sensitivity to doxorubicin were also found in untransfected HEK cells after exposure to nanomolar concentrations of betaamyloid (Ab) and these effects were antagonized by vitamin E. The modulator effects of Ab on p53 conformational state were, at least in part, due to the intracellular peptides as (i) treatment of HEK-APP cells with an antibody that sequestered extracellular Ab did not modify the capability of the cells to express the mutant-like p53 isoform; (ii) in the presence of 1% serum exogenous Ab peptide crossed the plasma membrane, as demonstrated by confocal analysis and ELISA, and induced p53 conformational change; and (iii) in the presence of 10% serum Ab did not enter the cells and consequently did not influence the p53 conformational state. Keywords: amyloid precursor protein, human, p53, protein tertiary structure.

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Dopaminergic agonists have been usually used as adjunctive therapy for the cure of Parkinson's disease (PD). It is generally believed that treatment with these drugs is symptomatic rather then curative and does not stop or delay the progression of neuronal degeneration. However, several DA agonists of the DA D2-receptor family (including D2, D3 and D4-subtypes) have recently been shown to possess neuroprotective properties in different in vitro and in vivo experimental PD models. Here we summarize some recent data from our and other groups underlining the wide pharmacological spectrum of DA agonists currently used for treating PD patients. In particular, the mechanism of action of different DA agonists does not appear to be restricted to the stimulation of selective DA receptor subtypes being these drugs endowed with intrinsic, independent, and peculiar antioxidant effects. This activity may represent an additional pharmacological property contributing to their clinical efficacy in PD.