Inhibition of amyloid formation of keratin-derived peptide by rosmarinic acid.

Primary localized cutaneous amyloidosis (PLCA) is caused by the deposition of keratin amyloids in the skin and leads to severe symptoms. It is difficult to cure PLCA completely; therefore, prevention is essential. In this study, amyloid formation of a keratin-derived amyloidogenic peptide, KT5-6, was successfully inhibited by rosmarinic acid (RA), a polyphenol present in plants such as rosemary. It was also shown that RA can bind to the KT5-6 monomer and prevent further aggregation. This study also provided basic information on KT5-6 amyloids such as their secondary structure and cytotoxicity, which could serve as a basis for further studies on PLCA. Our results also contribute to the development of cosmetic drugs that use RA to prevent PLCA.