Multiplexed Proteomic Analysis of Oxidation and Concentrations of Cerebrospinal Fluid Proteins in Alzheimer Disease

Background: Carbonylation is an irreversible oxidative modification of proteins that has been linked to various conditions of oxidative stress, aging, physiological disorders, and disease. Increased oxidative stress is thus also considered to play a role in the pathogenesis of age-related neurodegenerative disorders such as Alzheimer disease (AD). In addition, it has recently become evident that the response mechanisms to increased oxidative stress may depend on sex. Several oxidized carbonylated proteins have been identified in plasma and brain of AD patients by use of 2-dimensional oxyblotting. Methods: In this pilot study, we estimated the concentrations and carbonylation of the most abundant cerebrospinal fluid proteins in aging women and men, both AD patients suffering from mild dementia and individuals exhibiting no cognitive decline. Oxidized carbonylated proteins were analyzed with 2-dimensional multiplexed oxyblotting, mass spectrometry, and database searches. Results: Signals for β-trace, λ chain, and transthyretins were decreased in probable AD patients compared with controls. The only identified protein exhibiting an increased degree of carbonylation in AD patients was λ chain. The concentrations of proteins did not generally differ between men and women; however, vitamin D–binding protein, apolipoprotein A-I, and α-1-antitrypsin exhibited higher extents of carbonylation in men. Conclusions: None of the brain-specific proteins exhibited carbonylation changes in probable AD patients compared with age-matched neurological controls showing no cognitive decline. The carbonylation status of proteins differed between women and men. Two-dimensional multiplexed oxyblotting is applicable to study both the concentrations and carbonylation of cerebrospinal fluid proteins.