Gamma ray‐irradiated fibroin protein from Bombyx mori protects against TNF‐α‐induced oxidative stress and inflammation in human skin keratinocytes through NF‐κB and Nrf2 signaling pathways

Abstract

Silk fibroin from Bombyx mori has traditionally been utilized for garment production; however, recently, it has become feasible to manufacture edible and cosmetic products using this material. Gamma‐ray irradiation can improve physiological activity through the modification of the structure of proteins in biological materials. In this study, we examined whether gamma ray‐irradiated fibroin protein (gFP) has a protective effect on tumor necrosis factor alpha (TNF‐α)‐induced cellular stress through a change in protein structure. First, we confirmed that the structure of FP was changed by gamma‐ray irradiation using electrophoresis, UV spectra and Fourier‐transform infrared spectroscopy (FT‐IR). We further investigated the cytoprotective potential of 20 kGy‐irradiated fibroin protein (gFP20) in human skin keratinocytes (HaCaT cells) exposed to extracellular stress. gFP20 effectively decreased TNF‐α‐induced matrix metalloproteinase‐1 (MMP‐1) overexpression and restored reduced type‐1 procollagen in HaCaT cells. This reduction occurred concomitantly with suppressed nuclear factor‐κB (NF‐κB) nuclear translocation, resulting in a decreased level of inflammatory mediator and pro‐inflammatory cytokines. Furthermore, gFP20 protected cells from TNF‐α‐induced oxidative stress by attenuating reactive oxygen species (ROS) overexpression and increasing the production of the antioxidant enzyme heme oxygenase‐1 (HO‐1) through the stimulation of the translocation of nuclear factor erythroid 2‐related factor 2 (Nrf2) into the nucleus. Taken together, our findings indicate that low‐dose irradiated fibroin protein (gFP20) could be considered as a functional material for skincare products.