Expression of cathepsin B in acutely photodamaged fibroblasts and its significance

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