Abstract
Aims: One promising approach for treatment of Alzheimers disease (AD) is use of anti-amyloid therapies, based on the hypothesis that increases in amyloid-beta (Aβ) deposits in brain are a major cause of AD. Several groups have focused on Aβ immunotherapy with some success. Small molecules derivatives of Congo red have been shown to inhibit Aβ aggregation and protect against Aβ neurotoxicity in vitro. The agents described here are all small molecule Aβ- binding agents (SMAβBAs) derivatives of Congo red. Main Methods: Here, we have explored the anti-amyloid properties of these SMAβBAs in mice doubly transgenic for human prensenilin-1 (PS1) and APP gene mutations that cause early-onset AD. Mice were treated with either methoxy- X04, X:EE:B34 and X:034-3-OMe1. After treatment, brains were examined for Aβ-deposition, using histochemistry, and soluble and insoluble Aβ levels were determined using ELISA. Key Findings: A range of anti-amyloid activity was observed with these three compounds. PS1/APP mice treated with methoxy-X04 and X:EE:B34 showed decrease in total Aβ load, a decrease in Aβ fibril load, and a decrease in average plaque size. Treatment with methoxy-X04 also resulted in a decrease in insoluble Aβ levels. The structurally similar compound, X:034:3-OMe1, showed no significant effect on any of these measures. The effectiveness of the SMAβBAs may be related to a combination of binding affinity for Aβ and entry into brain, but other factors appear to apply as well. Significance: These data suggest that SMAβBAs may significantly decrease amyloid burden in brain during the pathogenesis of AD and could be useful therapeutics alone, or in combination with immunotherapy.
Keywords: Alzheimer's Disease, Amyloid β, Congo Red, Methoxy-X04, Transgenic mice
6