Dimeric bis (heptyl)-Cognitin Blocks Alzheimer's β-Amyloid Neurotoxicity Via the Inhibition of Aβ Fibrils Formation and Disaggregation of Preformed Fibrils

Aims: Fibrillar aggregates of beta-amyloid protein (A beta) are the main constituent of senile plaques and considered to be one of the causative events in the pathogenesis of Alzheimer's disease (AD). Compounds that could inhibit A beta fibrils formation, disaggregate preformed A beta fibrils as well as reduce their associated neurotoxicity might have therapeutic values for treating AD. In this study, the inhibitory effects of bis (heptyl)-cognitin (B7C), a multifunctional dimer derived from tacrine, on aggregation and neurotoxicity of A beta(1-40) were evaluated both in vitro and in vivo. Methods: Thioflavin T fluorescence assay was carried out to evaluate A beta aggregation, MTT and Hoechst-staining assays were performed to investigate A beta-associated neurotoxicity. Fluorescent probe DCFH-DA was used to estimate the accumulation of intracellular reactive oxygen stress (ROS). Morris water maze was applied to determine learning and memory deficits induced by intracerebroventricular infusion of A beta in rats. Results: B7C (0.1-10 mu M), but not tacrine, effectively inhibited A beta fibrils formation and disaggregated preformed A beta fibrils following co-incubation of B7C and A beta monomers or preformed fibrils, respectively. In addition, B7C markedly reduced A beta fibrils-associated neurotoxicity in SH-SY5Y cell line, as evidenced by the increase in cell survival, the decrease in Hoechst-stained nuclei and in intracellular ROS. Most encouragingly, B7C (0.1 and 0.2 mg/kg), 10 times more potently than tacrine (1 and 2 mg/kg), inhibited memory impairments after intracerebroventricular infusion of A beta in rats, as evidenced by the decrease in escape latency and the increase in the spatial bias in Morris water maze test along with upregulation of choline acetyltransferase activity and downregulation of acetylcholinesterase activity. Conclusion: These findings provide not only novel molecular insight into the potential application of B7C in treating AD, but also an effective approach for screening anti-AD agents.