The effect of three polyphenols and some other antioxidant substances on amyloid fibril formation by Human cystatin C

Human cystatin C (CysC) is an amyloid forming protein involved in the hereditary cerebral amyloid angiopathy (HCCAA) that affects arteries in the brain and the peripheral nervous system. In this study we measured the influence of several substances on human CysC aggregation and amyloid fibril formation, induced at pH 4 in vitro. The effect of three polyphenols: resveratrol, quercetin and curcumin and of two antioxidants: vitamin C (VitC) and N-acetyl-L-cysteine (NAC) was explored as well as the effect of sulphoraphane (SF) and alpha-lipoic acid (AL). The formation of amyloid fibrils was followed by Thioflavin T (ThT) fluorescence and by transmission electron microscopy (TEM). Effects on the length of the lag phase were revealed by following the increase of ThT fluorescence intensity with time. The amount and morphology of fibrils in comparison to prefibrillar aggregates and globular oligomers were evaluated by TEM at the plateau stage of the reaction. Thermal stabilization of the CysC monomer by the small compounds was measured by differential scanning fluorimetry (DSF). NAC, VitC and SF exhibited the largest inhibitory effect on amyloid fibril growth. The effects of polyphenols were not significant, apart from resveratrol, which partly inhibited the amyloid fibril growth.