Human recombinant butyrylcholinesterase purified from the milk of transgenic goats interacts with beta-amyloid fibrils and suppresses their formation in vitro

Background. In Alzheimer's disease (AD), brain butyr, lcholinesterase (BChE) co-localizes with beta-amyloid (A beta) fibrils. Aims: In vitro testing of the significance of this phenomenon to AD progress. Methods: A thioflavine T (ThT) fluorogenic assay, photo-induced cross-linking and quantifiable electron microscopy served to compare the effect on A beta fibril formation induced by highly purified recombinant human BChE (rBChE) produced in the milk of transgenic goats with that of serum-derived human BChE. Results: Both proteins at 1:50 and 1:25 ratios to A beta dose-dependently prolonged the ThT lag time and reduced the apparent rate of A beta fibril formation compared to A beta alone. Photo-induced cross-linking tests showed that rBChE prolonged the persistence of amyloid dimers, trimers and tetramers in solution, whereas A beta alone facilitated precipitation of such multimers from solution. Transmission electron microscopy showed that rBChE at 1:100 to A beta prevented the formation of larger, over 150-nm-long, A beta fibrils and reduced fibril branching compared to A beta alone as quantified by macro programming of Image Pro (R) Plus software. Conclusion: Our findings demonstrate that rBChE interacts with A beta fibrils and can attenuate their formation, extension and branching, suggesting further tests of rBChE, with unlimited supply and no associated health risks, as a therapeutic agent for delaying the formation of amyloid toxic oligomers in AD patients. Copyright (c) 2008 S. Karger AG, Basel.