Abstract: Xu Xinya, Zheng Yue, Xu Qingfang, Li Yuying, Huang Yunfen, Gong Zijian, Lu Chun, Lai Wei Department of Dermatology, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou 510630, China Corresponding author: Xu Qingfang, Email: xqf69@163.com 【Abstract】 Objective To evaluate the effect of photoaging on the degradation of advanced glycation end products （AGEs） by human dermal fibroblasts. Methods Some cultured human dermal fibroblasts were subjected to repetitive ultraviolet A （UVA） radiation （UVA radiation group） to establish a photoaging cell model, which was then evaluated by cell counting kit 8 （CCK-8） assay, senescence-associated β-galactosidase staining and detection of apoptosis rate. Moreover, fibroblasts receiving no treatment served as control group. Some other primary fibroblasts were divided into 4 groups: photoaged group receiving UVA radiation, non-photoaged group receiving no treatment, AGE-treated photoaged group treated with UVA radiation followed by the treatment with 200 mg/L AGE-bovine serum albumin （BSA）, and AGE-treated non-photoaged group treated with 200 mg/L AGE-BSA alone. After the treatment with AGE-BSA for 4 - 72 hours, flow cytometry was performed to determine the fluorescence intensity of AGE-BSA in fibroblasts of the above groups. After 8-hour treatment with AGE-BSA, confocal laser scanning microscopy was performed to localize and semiquantitatively detect AGE-BSA in fibroblasts, and enzyme-linked immunosorbent assay （ELISA） was conducted to detect AGE-BSA levels in fibroblasts, as well as changes in the intracellular AGE-BSA level within 24 hours after the removal of AGE-BSA. Results Compared with the control group, the UVA radiation group showed significantly decreased cellular proliferative activity （t = 7.559, P < 0.05）, but significantly increased apoptosis rate and percentage of β-galactosidase-positive fibroblasts （t = 14.075, 43.524 respectively, both P < 0.05）. Flow cytometry revealed that the average fluorescence intensities of AGE-BSA after 4-, 8-, 16-, 24-, 48- and 72-hour treatment with AGE-BSA were significantly higher in the AGE-treated photoaged group （293.00 ± 8.19, 359.67 ± 11.59, 347.00 ± 12.29, 338.00 ± 12.77, 334.67 ± 14.22 and 336.30 ± 10.21, respectively） than in the photoaged group （all P < 0.05）, as well as in the AGE-treated non-photoaged group （222.33 ± 8.74, 276.33 ± 6.11, 256.33 ± 5.51, 243.00 ± 10.15, 236.33 ± 1.53 and 240.33 ± 1.52, respectively） than in the non-photoaged group （all P < 0.05）. Moreover, the average fluorescence intensities of AGE-BSA at different time points were all significantly higher in the AGE-treated photoaged group than in the AGE-treated non-photoaged group （all P < 0.05）. Confocal laser scanning microscopy showed that AGE-BSA was mainly localized in lysosomes after endocytic uptake into the fibroblasts, and the AGE-treated photoaged group showed significantly increased fluorescence intensity of AGE-BSA compared with the AGE-treated non-photoaged group （P < 0.05）. ELISA revealed that the intracellular AGE level in the AGE-treated non-photoaged group at 24 hours after the removal of AGE-BSA was decreased by （14.6 ± 1.2）% compared with that before the removal, and the degradation rate of AGE-BSA was significantly higher in the AGE-treated non-photoaged group than in the AGE-treated photoaged group （7.6% ± 1.4%, t = 6.604, P < 0.05）. Conclusion The internalized AGE-degradating ability decreases in photoaged fibroblasts, which may induce the accumu-lation of AGEs in photoaged skin.

Key words: Fibroblasts, Skin aging, Cell aging, Glycosylation