Suppression of amyloid fibril formation by UV irradiation

Abstract

Ultraviolet (UV) irradiation originating in the space environment has been increasing because of the destruction of the ozone layer. Although UV irradiation damages DNA, peptides, and cell structures, it also has the beneficial effects of suppressing excessive immune responses and cell proliferation. However, the effects of UV irradiation on amyloid fibril formation are unknown. Here, we analyzed its effects on amyloid fibril formation of two types of amyloidogenic proteins, human amyloid β42 (Aβ42) and human transthyretin (TTR). To study these effects, we incubated Aβ42 samples in neutral pH buffer and wild-type TTR (TTRwt) samples in acidic buffer, with and without UV irradiation. We analyzed amyloidogenicity via a thioflavin T (ThT) method and morphological changes by using electron microscopy. UV irradiation reduced the ThT fluorescence intensity of the human Aβ42 samples. For the electron microscopic analysis of Aβ42 samples, the UV irradiation induced thinning of the amyloid fiber tips. Although UV irradiation reduced the ThT fluorescence intensity of human TTRwt samples, the amounts of the aggregates did not differ with or without UV irradiation. Our experiments suggest that UV irradiation may become a useful tool for reducing the amyloid fibrils and amyloid like substances.