Abstract:

Zheng Yunpeng, Chen Xu, Huang Dan, Xu Song, Gu Heng*. *Department of Physical Therapy, Institute of Dermatology, Chinese Academy of Medical Sciences and Peking Union Medical College, Nanjing 210042, China Corresponding authors: Gu Heng, Email: guheng@aliyun.com; Chen Xu, Email: doctor_chx@126.com 【Abstract】 Objective To evaluate the effects of ultraviolet A （UVA） on autophagy in human skin fibroblasts （HSFs）. Methods Cultured HSFs were randomly divided into chronic and acute UVA radiation groups. HSFs in the chronic UVA radiation groups were irradiated with UVA at 5, 10 and 20 J/cm2 separately once a day for 4 consecutive days, with HSFs receiving no radiation serving as the chronic radiation control group; HSFs in the acute UVA radiation groups received a single session of radiation with 5, 10, 30 and 60 J/cm2 UVA separately, with HSFs receiving no radiation serving as the acute radiation control group. After additional culture for different durations, methyl thiazolyl tetrazolium （MTT） assay was performed to evaluate the proliferative activity of HSFs, monodansylcadaverin （MDC） staining to determine autophagy levels, and Western blot analysis to track the conversion of the microtubule-associated protein 1 light chain-3 （LC3） -Ⅰto LC3-Ⅱ. Statistical analysis was carried out by using one-way analysis of variance followed by Students-Newman-Keuls （SNK） test for multiple-group comparisons and by the independent sample t test for two-group comparisons. Results The cellular proliferative activity significantly decreased in the 3 chronic radiation groups at 1 hour after the final UVA radiation compared with the chronic radiation control group （F = 155.5, P < 0.05）, and in the 4 acute radiation groups at 1, 6 and 12 hours after UVA radiation compared with the acute radiation control group（F = 1 335, 1 649, 2 774, all P < 0.05）. MDC staining showed that the autophagy levels in HSFs significantly increased in the 3 chronic radiation groups after UVA radiation compared with the chronic radiation control group （F = 748.62, P > 0.05）, but showed no significant changes in any of the acute radiation groups at 1, 6 or 12 hours after UVA radiation compared with the acute radiation control group （F = 0.014, 0.004, 0.002, all P > 0.05）. The ratio of LC3-Ⅱ to LC3-Ⅰwas significantly elevated in all the 3 chronic radiation groups at 1 hour after UVA radiation compared with the chronic radiation control group （t = 9.002, 21.772, 18.33, all P < 0.05）, but experienced no obvious changes in any of the acute radiation groups at 1, 6 or 12 hours after UVA radiation compared with the acute radiation control group （F = 0.13, 0.27, 0.06, all P > 0.05）. Conclusion Chronic UVA radiation can upregulate autophagy levels in HSFs, but acute UVA radiation has no evident effects on it.