Protective Effect of Castanopsis sieboldii Extract against UVB-Induced Photodamage in Keratinocytes

Ultraviolet B (UVB) rays disrupt the skin by causing photodamage via processes such as reactive oxygen species (ROS) production, endoplasmic reticulum (ER) stress, DNA damage, and/or collagen degradation. Castanopsis sieboldii is an evergreen tree native to the southern Korean peninsula. Although it is known to have antioxidant and anti-inflammatory effects, its protective effect against photodamage in keratinocytes has not been investigated. Thus, in the present study, we investigated the effect of 70% ethanol extract of C. sieboldii leaf (CSL3) on UVB-mediated skin injuries and elucidated the underlying molecular mechanisms. CSL3 treatment restored the cell viability decreased by UVB irradiation. Moreover, CSL3 significantly inhibited UVB- or tert-butyl hydroperoxide-mediated ROS generation in HaCaT cells. ER stress was inhibited, whereas autophagy was upregulated by CSL3 treatment against UVB irradiation. Additionally, CSL3 increased collagen accumulation and cell migration, which were decreased by UVB exposure. Notably, epigallocatechin gallate, the major component of CSL3, improved the cell viability decreased by UVB irradiation through regulation of ER stress and autophagy. Conclusively, CSL3 may represent a promising therapeutic candidate for the treatment of UVB-induced skin damage.