Management of apolipoprotein D and klotho levels, redox pattern and oxidative damages in plasma from MCI and Alzheimer′s Disease patients
Résumé
The production of reactive oxygen species (ROS) leading to oxidative damage and neuronal cell death plays an early and important role in the pathogenesis of Alzheimer’s disease (AD). This study aimed to determine the progression of the anti-aging, neuroprotective and antioxidant proteins levels Klotho and apolipoprotein D, the levels of reduced thiols and protein carbonyls in plasma from mild cognitive impairment (MCI) and from AD patients at different stages of the disease. We have measured these different markers in plasma from patients at each disease stage and from age-matched controls (n=10). The total antioxidant capacity (TAC) was measured by electrochemical detection with the Free Radical analyzer Apollo 4000, total reduced protein thiols were quantified with the Ellman’s reagent (5,5'- dithiobis-[2-nitrobenzoic acid], DTNB), Klotho level was evaluated using a sandwich enzyme-linked immunosorbent assay kit.(Human Klotho DuoSet ELISA kit, R&D Systems, Inc.), apolipoprotein D and protein carbonyls were analyzed by Western Blot. The TAC is not different between controls and MCI patients but significantly decreased in AD groups. Protein carbonyl levels were similar in controls and MCI patients but were increased progressively increased between mild, moderate and severe AD patients. Klotho increased in MCI as well as in mild and moderate AD while apolipoprotein D level remained unchanged in MCI and in AD. Interestingly, protein carbonyls and reduced thiols levels are correlated with the clinical MoCA and MMSE scores. Moreover, there is a correlation between TAC and level of carbonyl proteins in plasma. Our results indicate that the antioxidant capacity decreases with the progression of the disease while oxidized proteins increases. Interestingly, these peripheral markers of oxidative stress are negatively correlated with clinical score.