Curcumin accelerates aggregate to fibril conversion in <i>Drosophila</i> brains.

<p>Amyloid fibrillation index as individual spectral shift (A, C, and E) and mean spectral shift with standard deviation (B, D, and F) over time, in presence (orange) or absence (black) of curcumin treatment for Aβ and Tau expressing flies. (A and B) Newly eclosed double insert Aβ_1–42 expressing flies had variable emission spectra, resulting in a wide variation in the 508/612 ratios. Some aggregates with the distinct amyloid feature were also detected (marked with triangles in the graph) in young flies. The double insert Aβ_1–42 expressing flies displays a higher amyloid fibrillation index after ten days of curcumin treatment, indicating a more organized fibril formation due to curcumin ingestion. Untreated flies did not display an increased Aβ-fibrillation index at day 10. At day 20, the overall amyloid fibrillation index had increased, but there were no differences in the amyloid-fibrillation index between untreated and treated flies. (C and D) The Aβ_{1–42 E22G} expressing flies showed a rather high amyloid fibrillation index already in newly eclosed flies. Both treated and untreated flies have higher Aβ-fibrillation index at day 5, but at day 10 the Aβ-fibrillation index was lower, especially for untreated flies. (E and F) The Tau expressing flies showed more red shifted emission spectra than the Aβ genotypes, with a higher contribution from the 612 nm emission (560 nm excitation) (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031424#pone.0031424.s003" target="_blank">Figure S3</a>), resulting in a lower amyloid fibrillation index. Note the different scale of the y-axis compared to A–D. A few aggregates with elevated amyloid fibrillation index were detected as marked by triangles in the graph. Overall the trend was the same as for Aβ expressing flies but the statistical analysis revealed that no significant differences were observed for the Tau expressing flies upon curcumin treatment. No spectra could be analyzed in Tau expressing flies at day 0, due to low detection rate and minute aggregates, resulting in low spectral intensities. (ns: non-significant; *: P<0.05, **: P<0.01; ***: P<0.001).