Abstract: Xu Qingfang, Hou Wei, Zheng Yue, Liu Chen, Gong Zijian, Lu Chun, Lai Wei. Department of Dermatology, Third Affiliated Hospital, Sun Yat-sen University, Guangzhou 510630, China Corresponding author: Lai Wei: Email：drlaiwei@163.com 【Abstract】 Objective To investigate whether ultraviolet A （UVA）-induced CatK expression is regulated by the mitogen-activated protein kinases （MAPK） signaling pathway in human dermal fibroblasts in vitro. Methods Human dermal fibroblasts were obtained from circumcised foreskin of children, and subjected to primary culture. After several passages of subculture, some fibroblasts were irradiated with UVA at a dose of 10 J/cm2. Western blot was performed to measure the expressions of total and phosphorylated JNK （t- and p-JNK） and P38 （t- and p-P38） at 0.75, 1.5, 3 and 6 hours after the irradiation. Some fibroblasts were divided into six groups: control group receiving no treatment, SP group treated with SP600125 of 800 nmol/L, SB group treated with SB203580 of 10 μmol/L, UVA group irradiated with UVA at a dose of 10 J/cm2, UVA-SP group treated with SP600125 for 1 hour before and for 1.5 or 48 hours after UVA irradiation at 10 J/cm2, UVA-SB group treated with SB203580 for 1 hour before and for 1.5 or 48 hours after UVA radiation at 10 J/cm2. Subsequently, Western blot was performed to determine the expressions of p-c-Jun and p-MAPKAPK2 in these groups at 1.5 hours after the UVA irradiation, and reverse transcription （RT）-PCR and Western blot to detect the mRNA and protein expressions of CatK at 48 hours after the UVA irradiation, respectively. Statistical analysis was carried out by t test, one way analysis of variance and least significant difference （LSD）-t test. Results The expression levels （gray values） of p-JNK and p-P38 were significantly increased at 0.75 hour （4.77 ± 0.19 and 2.44 ± 0.13 respectively, both P < 0.05） and 1.5 hours （4.68 ± 0.09 and 2.30 ± 0.04 respectively, both P < 0.05）, but showed no significant changes at 3 hours （both P > 0.05） and 6 hours （both P > 0.05） after the UVA irradiation compared with those before the irradiation （3.2 ± 0.27 and 1.61 ± 0.08 respectively）. A significant decrease was observed in the expression of p-c-Jun in the UVA-SP group and p-MAPKAPK2 in the UVA-SB group compared with the UVA group （p-c-Jun, 2.55 ± 0.48 vs. 4.85 ± 0.96; p-MAPKAPK2, 1.16 ± 0.12 vs. 2.46 ± 0.09, both P < 0.05）. The CatK mRNA and protein expressions were attenuated by 61.1% and 44.3% respectively in the UVA-SP group （both P < 0.05）, and by 71.3% and 50.4% respectively in the UVA-SB group （both P < 0.05） in comparison with the UVA group. The UVA-SP group also showed a significant reduction in CatK mRNA and protein expressions as compared with the UVA-SB group （both P < 0.05）. Conclusion Both JNK and P38 signaling pathways, especially the JNK pathway, may contribute to the upregulation of CatK expression in dermal fibroblasts induced by UVA irradiation.

Key words: Fibroblasts, Cathepsins, MAP kinase signaling system, Ultraviolet rays, Skin aging