Figure 1.

Effect of curcumin on insulin amyloid formation and cytotoxicity. The effect of curcumin on insulin amyloid formation was assayed by far-UV CD spectroscopy and ThT fluorescence at different times of incubation in aggregating conditions. In panels A–C are reported the CD spectra of insulin in the absence and in the presence of curcumin (10 and 100 µM) at 12 (A), 18 (B) and 24 hours (C) of incubation in comparison to the native protein. The ThT fluorescence emission was recorded at 482 nm upon excitation at 450 nm (D). Protein concentration were 0.3 mg/mL and 8 µM for CD and ThT measurements, respectively. (E) Cytotoxicity of insulin amyloid aggregates formed in the presence of curcumin. SH-SY5Ycells were exposed for 24 hours to insulin incubated for 0, 12, 18 and 24 hours in aggregating condition in the absence and in the presence of curcumin (10 and 100 µM) and cell viability was evaluated by MTT assay. Data are expressed as average percentage of MTT reduction ± SD relative to control cells from triplicate wells from 5 separate experiments (p < 0.01). CTR_Cur represents cell exposed to curcumin at the higher working concentration. Other experimental details are described in the Methods section.