Abstract:Background: Many studies suggest oxidative stress as an early feature of Alzheimer's Disease (AD). However, evidence of established oxidative stress in AD peripheral cells is still inconclusive, possibly due to both, differences in the type of samples and the heterogeneity of oxidative markers used in different studies.Objective: The aim of this study was to evaluate blood-based redox alterations in Alzheimer's Disease in order to identify a peculiar disease profile. Method:To that purpose, we measured the activity of Superoxide Dismutase, Catalase and Glutathione Peroxidase both in the extracellular and the intracellular blood compartments of AD, MCI and control subjects. The amount of an open isoform of p53 protein (unfolded p53), resulting from oxidative modifications was also determined.Results: Decreased SOD, increased GPx activity and higher p53 open isoform were found in both AD and MCI plasma compared to controls. In blood peripheral mononuclear cells, SOD activity was also decreased in both AD and MCI, and unfolded p53 increased exquisitely in younger AD males compared to controls. Conclusion:Overall, these data highlight the importance of considering both extracellular and intracellular compartments, in the determination of antioxidant enzyme activities as well as specific oxidation end-products, in order to identify peculiar blood-based redox alterations in AD pathology.

Alzheimer's disease is one of the most common causes of dementia nowadays, and its prevalence increases over time. Because of this, accurate methods for the analysis of specific biomarkers for an early diagnosis of this disease are much needed. Recently, the levels of unfolded isoform of the multifunctional protein p53 in plasma have been proved to increase selectively in Alzheimer's Disease patients in comparison with healthy subjects, thus entering the list of biomarkers that can be used for the diagnosis of this illness. We present here the development of an electrochemical immunosensor based on nanostructured screen-printed carbon electrodes for the quantification of unfolded p53 in plasma samples. The sensor shows a suitable linear range (from 2 to 50 nM) for its application in real blood samples and a very low limit of detection (0.05 nM). The concentration of unfolded p53 has been accurately detected in plasma of elderly people in healthy conditions, subjects with mild cognitive impairment (MCI) and Alzheimer's Disease (AD) subjects, obtaining results with no significant differences to those provided by an ELISA assay. This result supports the possibility of measuring unfolded p53 levels with a cheap, simple and miniaturized device with a promising future for point-of-care applications in the early diagnosis of Alzheimer's dementia.

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