Resistance of human cerebrospinal fluid to<i>in vitro</i>oxidation is directly related to its amyloid-β content

Abstract

Amyloid-beta (A beta) peptide, a major constituent of senile plaques and a hallmark of Alzheimer's disease (AD), is normally secreted by neurons and can be found in low concentrations in cerebrospinal fluid (CSF) and plasma where it is associated with lipoproteins. However, the physiological role of A beta secretion remains unknown. We measured the resistance to in vitro oxidation of CSF obtained from 20 control subjects and 30 patients with AD, and correlated it with CSF levels of antioxidants, lipids and A beta. We found that the oxidative resistance, expressed as a duration of the oxidation lag-phase, was directly related to CSF levels of A beta 1-40, A beta 1-42 and ascorbate and inversely to levels of fatty acids. These data suggest that, besides ascorbate, A beta is another major physiological antioxidant for CSF lipoproteins.