High throughput screening of Alzheimer's inhibitors

The aggregation of amyloid proteins into plaques has been associated with the onset and neurotoxicity of Alzheimer's disease and while several assays to detect plaques have been developed, they could not detect the formation of the small fibrils that are one of the early aggregates formed during plaque development. According to a spokesperson for the Alzheimer's society, approximately 55 per cent of the 18m worldwide dementia sufferers have Alzheimer's disease and this number is predicted to grow to over 34m by 2050. The new screening method, which will be published a forthcoming issue of Analytical Chemistry,​ uses capillary electrophoresis (CE) to separate the fibrils in the presence of thioflavin T (ThT) which has been extensively used for the characterising the presence of amyloid fibrils. The ThT is then detected using laser induced fluorescence (LIF) which faintly fluoresces in the absence of amyloid fibrils, but fluoresces strongly when bound to the beta-sheet structure of the fibrils at shifted excitation and emission wavelengths . The Japanese researchers, led by Associate Professor Masaru Kato from the Center for NanoBio Integration and Department of Applied Chemistry at the University of Tokyo, write that the "developed method may be used to discover compounds that inhibit beta-amyloid aggregation for the potential treatment of Alzheimer's disease". ​ The researchers studied the effectiveness of three previously reported inhibitors: melatonin, daunomycin and 3-indoleprpionic acid (3-IPA). To maximise the screening speed, a fibril seed (known to speed up the aggregation process) was added to a mixture of inhibitor and monomer and the aggregation monitored using the technique. Two different fibrils are detected using the technique within a 5 minute analysis run, with the formation of both of these being dramatically reduced in the presence of the inhibitors. The order of anti-aggregation activities of the three compounds matched the order previously reported, with daunomycin completely inhibiting aggregation for over 24 hours. 3-IPA restricted aggregate formation to one-twelfth of that observed with no inhibitor present, while melatonin restricted aggregation by only one-sixth. The researchers write that they "hope that a significant treatment for Alzheimer's disease will be discovered using this method".​