Masayuki Ito

Ultraviolet B (UVB) irradiation induces oxidative stress and inflammation in keratinocytes, contributing to skin damage and photoaging. Although supersulfides have recently emerged as important regulators of cellular redox homeostasis, their role in UVB-induced skin damage remains poorly understood. In this study, we investigated the effects of glutathione trisulfide (GSSSG), a representative supersulfide, in UVB-exposed normal human epidermal keratinocytes (NHEKs). UVB irradiation significantly reduced cell viability and intracellular supersulfide levels while increasing reactive oxygen species (ROS) production and the expression of IL-1α, prostaglandin E2, and p21. Pretreatment with GSSSG significantly restored intracellular supersulfide levels, improved cell viability, suppressed ROS accumulation and inflammatory mediator production, and attenuated p21 induction. Furthermore, GSSSG significantly promoted nuclear factor erythroid 2-related factor 2 nuclear translocation and increased heme oxygenase-1 production, indicating activation of antioxidant defense pathways. Knockdown of cysteinyl-tRNA synthetase 2 (CARS2), a key enzyme involved in endogenous supersulfide biosynthesis, increased cellular susceptibility to UVB-induced cytotoxicity, whereas GSSSG restored the viability of CARS2-deficient cells. Collectively, these findings suggest that GSSSG protects keratinocytes against UVB-induced oxidative stress, inflammation, and cytotoxicity. This protective activity may be mediated, at least in part, through restoration of intracellular supersulfide levels and activation of the NRF2-mediated antioxidant response.

Ultraviolet B (UVB) irradiation induces hyperpigmentation and contributes to skin photoaging. Glutathione trisulphide (GSSSG), a naturally occurring supersulphide with anti-inflammatory and antioxidant properties, has been shown to suppress α-melanocyte-stimulating hormone-induced melanogenesis and improve skin brightness. However, its efficacy under physiologically relevant UVB-induced pigmentation conditions and its skin-brightening potential in human skin-like systems remain unclear. Therefore, this study evaluated the anti-melanogenic effects of GSSSG in UVB-stimulated melanogenesis and assessed its skin-brightening efficacy in a three-dimensional (3D) skin model while investigating the relationship between melanogenesis and intracellular endogenous supersulphide levels. UVB irradiation increased melanin production while decreasing intracellular supersulphide levels. GSSSG suppressed UVB-induced melanogenesis and restored intracellular supersulphide levels. Furthermore, Cars2 knockdown reduced intracellular supersulphide levels and melanin production, suggesting a role for endogenous supersulphides in pigmentation. In addition, 0.1% GSSSG significantly improved skin brightness in a 3D skin model. These findings demonstrate the efficacy of GSSSG in both UVB-induced melanogenesis and a human skin-like model and suggest that supersulphides play context-dependent roles in melanogenesis, suppressing excessive pigmentation while supporting physiological melanin synthesis.