Abstract: Lu Wenjing, Zhao Yu, Wang Keyu Department of Dermatology, Qilu Hospital of Shandong University （Qingdao）, Qingdao 266035, China （Lu WJ）; Department of Dermatology, Qilu Hospital of Shandong University, Jinan 250012, China （Zhao Y, Wang KY） Corresponding author: Wang Keyu, Email: qlyywky@163.com 【Abstract】 Objective To evaluate the inhibitory effect of geniposide on the oxidative damage to in vitro cultured human melanocytes, and to explore the role of PI3K-Akt signaling pathway in this inhibitory effect. Methods Epidermal melanocytes were isolated from the circumcised foreskin of healthy adolescent males, and then subjected to culture. Melanocytes at passage 2 - 3 were divided to six groups: control group receiving no treatment, geniposide group treated with 125 μmol/L geniposide alone, LY294002 group treated with 5 μmol/L LY294002 alone, H2O2 group treated with 250 μmol/L H2O2 alone, geniposide + H2O2 group firstly treated with 125 μmol/L geniposide for 24 hours followed by 4-hour treatment with 250 μmol/L H2O2, and geniposide + LY294002 + H2O2 group treated with 125 μmol/L geniposide for 24 hours, then with 5 μmol/L LY294002 for 1 hour, followed by 4-hour treatment with 250 μmol/L H2O2. After the above treatment, methyl thiazolyl tetrazolium （MTT） assay was performed to evaluate the cellular proliferative activity, Western blot analysis to determine the protein expression of Akt, phosphorylated Akt （p-Akt）, heme oxygenase1 （HO-1） and glutathione peroxidase （GPx-1）, and flow cytometry to detect the level of cellular reactive oxygen species （ROS）, and biochemical methods were used to evaluate the activity of superoxide dismutase （SOD） and catalase （CAT）. Statistical analysis was carried out by one-way analysis of variance （ANOVA） for intergroup comparison, and Student-Newman-Keuls-q （SNK-q） test for multiple com-parisons. Results Compared with the control group, the H2O2 group showed significantly decreased cellular proliferative activity （P < 0.01）, protein expression of p-Akt （P < 0.01）, HO-1 （P < 0.01） and GPx-1 （P < 0.05）, SOD activity （P < 0.01） and CAT activity （P < 0.01）, but significantly increased ROS level （P < 0.01）. Compared with the H2O2 group, the geniposide + H2O2 group showed significantly increased cellular proliferative activity （72.98% ± 8.92% vs. 50.53% ± 10.85%, P < 0.05）, up-regulated protein expression of p-Akt （P < 0.05）, HO-1 （P < 0.01） and GPx-1 （P < 0.01）, increased SOD activity （6.82 ± 1.03 U/mg vs. 1.29 ± 0.43 U/mg, P < 0.05） and CAT activity （46.08 ± 4.16 U/mg vs. 18.71 ± 3.09 U/mg, P < 0.05）, but decreased ROS level （1 284.33 ± 110.64 vs. 2 158.00 ± 222.75, P < 0.01）. The proliferative activity of melanocytes was significantly lower in the geniposide + LY294002 + H2O2 group （44.35% ± 14.85%） than in the geniposide + H2O2 group （P < 0.05）. In addition, the geniposide + LY294002 + H2O2 group showed significantly decreased protein expression of p-Akt （P < 0.01）, HO-1 （P < 0.05） and GPx-1 （P < 0.01）, SOD （1.31 ± 0.65 U/mg, P < 0.05） and CAT activity （23.25 ± 5.56 U/mg, P < 0.05）, but significantly increased ROS level （1 668.00 ± 62.03, P < 0.05）compared with the geniposide + H2O2 group. Conclusion Through the PI3K-Akt pathway, geniposide can promote the protein expression of HO-1 and GPx-1 in melanocytes, enhance SOD and CAT activity, and antagonize the oxidative damage of melanocytes.

Key words: Melanocytes, Vitiligo, Oxidative stress, Phosphatidylinositol 3?kinases, Oncogene protein v?akt, Superoxide dismutase, Catalase, Geniposide