Ginsenoside Rk1 protects human melanocytes from H2O2-induced oxidative injury via regulation of the PI3K/AKT/Nrf2/HO-1 pathway

Vitiligo is a cutaneous depigmentation disorder caused by melanocyte injury or aberrant functioning. Oxidative stress (OS) is considered to be a major cause of the onset and progression of vitiligo. Ginsenoside Rk1 (RK1), a major compound isolated from ginseng, has antioxidant activity. However, whether RK1 can protect melanocytes against oxidative injury remains unknown. The aim of the present study was to investigate the potential protective effect of RK1 against OS in the human PIG1 melanocyte cell line induced with hydrogen peroxide (H2O2), and to explore its underlying mechanism. PIG1 cells were pretreated with RK1 (0, 0.1, 0.2 and 0.4 mM) for 2 h followed by exposure to 1.0 mM H2O2 for 24 h. Cell viability and apoptosis were determined with Cell Counting Kit-8 and flow cytometry assays, respectively. The activity levels of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) were analyzed using ELISA kits. Protein expression levels, including Bax, caspase-3, Bcl-2, phosphorylated-AKT, AKT, nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), cytosolic Nrf2 and nuclear Nrf2, were analyzed using western blot analysis. In addition, the expression and localization of Nrf2 were detected by immunofluorescence. RK1 treatment significantly improved cell viability, reduced the apoptotic rate and increased the activity levels of SOD, CAT and GSH-Px in the PIG1 cell line exposed to H2O2. In addition, RK1 treatment notably induced Nrf2 nuclear translocation, increased the protein expression levels of Nrf2 and HO-1, and the ratio of phosphorylated-AKT to AKT in the PIG1 cells exposed to H2O2. Furthermore, LY294002 could reverse the protective effect of RK1 in melanocytes against oxidative injury. These data demonstrated that RK1 protected melanocytes from H2O2-induced OS by regulating Nrf2/HO-1 protein expression, which may provide evidence for the application of RK1 for the treatment of vitiligo.