42 °C heat stress pretreatment protects human melanocytes against 308-nm laser-induced DNA damage in vitro

Vitiligo is a common depigment of skin disorder due to loss of functional melanocytes. Recently, the phototherapy with a 308-nm xenon-chloride excimer laser (UVB laser) is wildly used in vitiligo treatment. However, excessive UVB will induce photo-damage and photo-carcinogenesis in melanocytes. Previous studies revealed a protective effect of heat on UVB-induced melanocyte damage. In this study, we combined heat stress pretreatment with UVB to evaluate whether heat stress pretreatment has an ameliorative effect on UVB-induced damage. Human primary melanocytes (HMCs) were cultured and irradiated with a 308-nm laser with/without heat treatment. MTT assay, apoptosis analysis, and comet assay were conducted to monitor the damage of HMCs. Western blot and immunofluorescence staining were performed to assess the expression and subcellular localization of HSP70. HMCs heated at 42 °C for 1 h exhibit no cytotoxicity. Furthermore, preheat treatment attenuated the UVB laser-induced injury, reduced the DNA damage, and attenuated the cell apoptosis. The level and the localization of HSP70 determined the protective effects against UVB-induced DNA damage. Combining preheat treatment with a 308-nm xenon-chloride excimer laser would be a potential therapeutic method not only promotes the repigment of vitiligo but also reduces the UVB-induced photo-damage.