Abstract: Hou Wei *, Xu Qingfang, Liu Chen, Zheng Yue, Lai Wei. *Department of Dermatology, First Affiliated Hospital of Xinjiang Medical University, Urumqi 830054, China Corresponding author: Lai Wei, Email: drlaiwei@163.com 【Abstract】 Objective To investigate the changes in cathepsin B （CatB） expression in acutely photodamaged human dermal fibroblasts （HDFs） and their significance. Methods HDFs were isolated from the foreskin of children, and subjected to primary culture and subculture. The fourth- to eighth-passage HDFs were used in the following experiment. HDFs were divided into two groups to receive irradiation with different doses of ultraviolet A （UVA） for different durations （acutely photodamaged group） or remain unirradiated （control group）. Cell counting kit-8 （CCK8） assay was conducted to evaluate the proliferative activity of HDFs after irradiation with UVA at 5, 10, 15, 20 and 25 J/cm2 respectively. Western blot and quantitative real-time reverse transcription PCR were performed to measure the protein and mRNA expressions of CatB respectively in HDFs at 24, 48 and 72 hours after exposure to UVA at 10 J/cm2, and at 48 hours after exposure to UVA at 10, 15, 20 and 25 J/cm2. Statistical analysis was carried out by analysis of variance and least significant difference （LSD） test using the SPSS 13.0 software. Results UVA radiation induced a decrease in the proliferative activity of HDFs. When the dose of UVA was ≤ 10 J/cm2, the survival rate of HDFs maintained higher than 85%, and significant differences were observed in cell survival rate between unirradiated and irradiated HDFs at 24, 48 and 72 hours （all P < 0.05）. Western blot showed that the gray value of CatB protein in the acutely photodamaged group irradiated with 10 J/cm2 UVA was significantly higher than that in the control group at 24 hours （0.76 ± 0.14 vs. 0.35 ± 0.01, P < 0.05）, 48 hours （1.34 ± 0.38 vs. 0.45 ± 0.12, P < 0.05） and 72 hours （0.82 ± 0.09 vs. 0.61 ± 0.06, P < 0.05）. Increased mRNA expressions of CatB were also observed in the acutely photodamaged group compared with the control group at 24 hours （0.149 ± 0.009 vs. 0.089 ± 0.015, P < 0.05）, 48 hous （0.173 ± 0.009 vs. 0.091 ± 0.010, P < 0.05） and 72 hours （0.185 ± 0.158 vs. 0.111 ± 0.017, P < 0.05） after UVA radiation at 10 J/cm2. The gray value of CatB protein was 0.99 ± 0.07, 1.49 ± 0.14, 1.89 ± 0.08, 2.07 ± 0.06 in HDFs at 48 hours after exposure to UVA of 10, 15, 20 and 25 J/cm2, respectively, significantly higher than that in the control group （0.60 ± 0.05, all P < 0.05）. Similarly, the mRNA expression of CatB was up-regulated in HDFs at 48 hours after UVA radiation at 10, 15, 20 and 25 J/cm2 compared with the unirradiated HDFs. Conclusion The protein and mRNA expressions of CatB are up-regulated in acutely photodamaged HDFs induced by UVA radiation.

Key words: Fibroblasts, Ultraviolet rays, Radiation injuries, experimental, Cathepsin B