47 million people worldwide currently live with Alzheimer’s disease and this number is estimated to triple by 2050.1 Despite extensive research there are currently no effective disease-modifying treatments for AD, which is likely due in part to a limited understanding of AD pathogenesis. One of the characteristic brain pathologies of Alzheimer’s disease are plaques composed of the β-amyloid (Aβ) peptide. Immunostaining studies have shown that sugar-derived post-translational modifications known as advanced glycation endproducts (AGEs) colocalise with Aβ plaque deposits.2-4 Additionally, in vivo and in vitro studies have demonstrated that Aβ peptides that were incubated in either methylglyoxal or glucose over several weeks were more toxic than Aβ itself.5-6 However, this non-specific incubation technique results in the formation of a complex mixture of Aβ-AGE peptides, and therefore we herein sought to examine the effect of site-specific glycation on the Aβ peptide.
In this project, we use a combination of organic and solid phase peptide synthesis to substitute the naturally occurring lysines at position 16 and 28 of Aβ42 with a commonly occurring AGE, N-(carboxyethyl)lysine (CEL), to afford three analogues namely Aβ-CEL16, Aβ-CEL28 and Aβ-CEL16&28. We then analysed the native Aβ42 and CEL-modified peptides using transmission electron microscopy (TEM) and a thioflavin T (ThT) assay over a 5 day period. At 24 h, our ThT and TEM data revealed that compared to native Aβ42, all three CEL-derivatives displayed significantly reduced amounts of fibrils. Over a further 96 h, we observed that delays in fibril formation appeared to be more pronounced for modifications at position 16 as compared to position 28. We are currently undertaking differentiated SH-SY5Y cell-culture assays to assess the effects of these peptides on mitochondrial activity and cell death.