Amyloid β levels in human red blood cells.

UNLABELLED: Amyloid β-peptide (Aβ) is hypothesized to play a key role by oxidatively impairing the capacity of red blood cells (RBCs) to deliver oxygen to the brain. These processes are implicated in the pathogenesis of Alzheimer's disease (AD). Although plasma Aβ has been investigated thoroughly, the presence and distribution of Aβ in human RBCs are still unclear. In this study, we quantitated Aβ40 and Aβ42 in human RBCs with ELISA assays, and provided evidence that significant amounts of Aβ could be detected in RBCs and that the RBC Aβ levels increased with aging. The RBC Aβ levels increased with aging. On the other hand, providing an antioxidant supplement (astaxanthin, a polar carotenoid) to humans was found to decrease RBC Aβ as well as oxidative stress marker levels. These results suggest that plasma Aβ40 and Aβ42 bind to RBCs (possibly with aging), implying a pathogenic role of RBC Aβ. Moreover, the data indicate that RBC Aβ40 and Aβ42 may constitute biomarkers of AD. As a preventive strategy, therapeutic application of astaxanthin as an Aβ-lowering agent in RBCs could be considered as a possible anti-dementia agent. TRIAL REGISTRATION: Controlled-Trials.com ISRCTN42483402

Correlation between RBC PLOOH and Aβ40 (A) or Aβ42 (B) concentration after 12 weeks administration of astaxanthin (N = 30).

<p>X-axis is concentration of RBC Aβ. Y-axis is concentration of RBC PLOOH [phosphatidylcholine hydroperoxide (PCOOH) and phosphatidylethanolamine hydroperoxide (PEOOH)] that had been measured in our former human study <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049620#pone.0049620-Nakagawa3" target="_blank">[12]</a>.</p

Correlation between RBC astaxanthin and Aβ40 (A) or Aβ42 (B) concentrations after 12 weeks administration of astaxanthin (N = 30).

<p>X-axis is the concentration of RBC Aβ. Y-axis is concentration of RBC astaxanthin that had been measured in our former human study <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049620#pone.0049620-Nakagawa3" target="_blank">[12]</a>.</p

Changes in Amyloid β levels in RBC and plasma before and after a 12 week administration of 0, 6 or 12 mg astaxanthin.

<p>Means ± SE are shown.</p><p>Significantly different between before and after astaxanthin administration: *<i>P</i><0.05.</p><p>Blood samples (RBC and plasma) that had been obtained from our former human study <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049620#pone.0049620-Nakagawa3" target="_blank">[12]</a> were subjected to Aβ determination.</p