Abstract:

As a natural macromolecular protein extracted from silk, silk fibroin （SF） has been widely used as biological material in recent years due to its antioxidant and photodamage reduction effects. To study the protective effect of silk fibroin against skin photodamage, the immortalized human keratinocyte line （HaCaT） was used as a model for study of UVB injury. Intracellular reactive oxygen species （ROS） and the levels of calcium ions （Ca²⁺） were measured by ELISA and fluorescence microscopy. The expression of transient receptor potential cation channel subfamily V member 1 （TRPV1） and the expression of Claudin-1 were detected by immunofluorescence assay. In addition, western blotting was used to analyze the expression of tight junction proteins occludin and Claudin-1. The results showed that 120 mJ/cm² of UVB stimulation significantly reduced cell viability, while the presence of 100 μg/mL silk fibroin significantly increased cell viability. UVB stimulation could increase the level of intracellular ROS, activate TRPV1 channels, and induce the increase of intracellular Ca²⁺ level. Meanwhile, the levels of inflammatory cytokines interleukin-1α （IL-1α） （P<0.01） and S100A8 （P<0.05） were also significantly increased, which caused inflammation. However, the effect of UVB on HaCaT cells with the addition of silk fibroin was significantly decreased （P<0.05）. In conclusion, UVB could disrupt the structural integrity of barrier proteins, resulting in the decreased expression of the barrier proteins Claudin-1 and occludin. The addition of silk fibroin could reduce such effect and protect the tightly connected structure. Therefore, silk fibroin might have great potential to protect skin from UV-induced inflammation, barrier damage and oxidative stress damage.

Key words: silk fibroin, UVB, ROS, tight-junction protein, skin barrier