Photo-induced inhibition of Alzheimer's β-amyloid aggregation in vitro by rose bengal

The abnormal aggregation of beta-amyloid (A beta) peptides in the brain is a major pathological hallmark of Alzheimer's disease (AD). The suppression (or alteration) of A beta aggregation is considered to be an attractive therapeutic intervention for treating AD. We report on visible light-induced inhibition of All aggregation by xanthene dyes, which are widely used as biomolecule tracers and imaging markers for live cells. Among many xanthene dyes, rose bengal (RB) under green LED illumination exhibited a much stronger inhibition effect upon photo-excitation on A beta aggregation than RB under dark conditions. We found that RB possesses high binding affinity to A beta; it exhibits a remarkable red shift and a strong enhancement of fluorescence emission in the presence of A beta. Photo-excited RB interfered with an early step in the pathway of A beta self-assembly and suppressed the conformational transition of A beta monomers into beta-sheet-rich structures. Photo-excited RB is not only effective in the inhibition of A beta aggregation, but also in the reduction of All-induced cytotoxicity. (C) 2014 Elsevier Ltd. All rights reserved.