Abstract: Liu Yingdi, Bai Bingxue, Ren Jing, Ma Liangjuan Department of Dermatology, Chifeng Municipal Hospital, Chifeng 024000, Inner Mongolia, China （Liu YD）; Department of Dermatology, The Second Affiliated Hospital of Harbin Medical University, Harbin 150081, China （Bai BX, Ren J, Ma LJ） Corresponding author: Ma Liangjuan, Email: maliangjuan@163.com 【Abstract】 Objective To evaluate the protective effect of exogenous biliverdin on ultraviolet B （UVB）-radiated HaCaT cells, and to explore its mechanism. Methods Cultured HaCaT cells were divided into 5 groups: control group receiving no treatment, UVB group irradiated with 30 mJ/cm2 UVB, 3 biliverdin + UVB groups treated with 100 nmol/L, 1 μmol/L and 10 μmol/L biliverdin respectively for 1 hour followed by 30 mJ/cm2 UVB radiation. After 24-hour treatment, changes in the morphology of HaCaT cells were observed, and cell counting kit 8 （CCK8） assay was performed to determine cell survival rates in the above groups. Western blot analysis was conducted to measure the protein of antioxidant signaling molecule NF-E2-related factor-2 （Nrf-2） and the photodamage signaling molecules matrix metalloproteinase-1 （MMP-1） and MMP-3. Results CCK8 assay showed that the survival rate of HaCaT cells was significantly lower in the UVB group than in the control group （P < 0.05）, but significantly higher in the 100-nmol/L, 1-μmol/L and 10-μmol/L biliverdin + UVB groups than in the UVB group （all P < 0.05）. Western blot analysis showed that the protein of MMP-1 and MMP-3 was significantly higher in the UVB group （1.150 ± 0.187, 0.979 ± 0.054 respectively） than in the control group （0.116 ± 0.018, 0.636 ± 0.035 respectively; both P < 0.01）, but was significantly lower in the 100-nmol/L, 1-μmol/L and 10-μmol/L biliverdin + UVB groups （MMP-1: 0.825 ± 0.139, 0.313 ± 0.047 and 0.286 ± 0.036 respectively; MMP-3: 0.888 ± 0.017, 0.672 ± 0.042 and 0.569 ± 0.037 respectively） than in the UVB group （all P < 0.05）. Moreover, the protein of Nrf-2 was significantly lower in the UVB group （0.906 ± 0.034） than in the control group （1.242 ± 0.141, P < 0.05）, but significantly higher in the 100-nmol/L, 1-μmol/L and 10-μmol/L biliverdin + UVB groups （1.556 ± 0.112, 1.897 ± 0.234 and 2.035 ± 0.274） than in the UVB group （all P < 0.01）. Conclusion Exogenous biliverdin protects against UVB-induced photodamage in HaCaT cells, which may be associated with Nrf-2 antioxidant signaling pathway.

Key words: Keratinocytes, Ultraviolet rays, Biliverdin, Matrix metalloproteinase 1, Matrix metallo-proteinase 3, NF-E2-related factor 2, HaCaT cells