Beta amyloid peptide (A�) has been implicated in neurotoxicity associated with Alzheimer's disease (AD).  We have previously identified two loci on the A� fibril, at N27 and K28, that are important for A� interactions with several small molecules that are known to attenuate A� toxicity in vitro (Keshet et al., 2010). We hypothesized that these sites that serve as binding loci of multiple dissimilar toxicity inhibitors have a biological relevance in the biological activity and/or toxicity of A�. We proposed that if we discovered new molecules that can bind with a high affinity at N27 or K28, these same molecules may serve as potent inhibitors for A� binding to cells and for A� toxicity. Toward that end, we performed in silico virtual screening of small molecules which bind to these two loci on A�40 fibrils using DOCK 6 and two small molecule libraries; the National Cancer Institute (NCI) diversity set (~1400 molecules), and a larger set of Central Nervous System (CNS) permeable molecules (~350,000 molecules).  The molecules were ranked according to the calculated energy scores.   Approximately 1% of the combined libraries were predicted to bind to A� fibrils with higher energy than Congo red, a known A� fibril binder and toxicity inhibitor.  We then tested three of the top scored molecules in vitro for their ability to alter A� fibril morphology, attenuate A�-cell binding, and reduce A� toxicity in differentiated SH-SY5Y cells. Results from transmission electron microscopy (TEM) showed that the three inhibitors significantly reduced the size of the A� fibrils, suggesting that the inhibitors bound to the A� fibrils and/or interacted with fibrils in some way.  Results from a flow cytometry based binding assay indicated that all 3 inhibitors led to a significant reduction in the amount of fluorescently labeled A�40 fibrils bound to cells at concentrations between 50 to 80 nM inhibitor (p<0.05).  All 3 small molecules attenuated A� toxicity at the same concentration range.  There were no significant differences in the effectiveness of inhibitors which targeted N27 versus inhibitors which targeted K28.  The results demonstrate the feasibility of this approach in identifying new molecules that attenuate A� toxicity, some of which may be therapeutically useful for the treatment of AD.

<i>In silico</i> screening and in vitro testing of potential A� toxicity inhibitors that bind to the A� fibril near N27 or K28

247th National Meeting (2014)

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In silico screening and in vitro testing of potential A� toxicity inhibitors that bind to the A� fibril near N27 or K28