Abstract: Ren Licuan, Jia Yang′e, Yan Hualing, Wang Yong, Guo Yan, Ha Xiaomei, Zhu Shiwen, Wang Gang Department of Dermatology, Qinghai University Affiliated Hospital, Xining 810000, China Corresponding author: Yan Hualing, Email: yhlckw@163.com 【Abstract】 Objective To evaluate preventive effect of polysaccharides from Lycium ruthenicum Murray against photodamage in HaCaT cells, and to explore its possible mechanism. Methods Ultrasound?assisted extraction was used to extract polysaccharides from Lycium ruthenicum Murray in Qaidam Basin. In vitro cultured HaCaT cells were randomly divided into 3 groups: control group receiving no treatment, ultraviolet B （UVB） group irradiated with 30 mJ/cm2 UVB alone for 1 hour, experimental group pretreated with 2 g/L Lycium ruthenicum polysaccharide solution followed 6 hours later by 30 mJ/cm2 UVB radiation for 1 hour. At twelve hours after UVB radiation, an inverted microscope was used to observe cell morphology. Then, MTS assay was performed to estimate cell proliferation, flow cytometry to detect cell apoptosis, an enzyme?labeled antigen method to detect levels of malondialdehyde （MDA） and glutathione peroxidase （GSH?Px）, as well as to evaluate the activity of superoxide dismutase （SOD） and catalase （CAT）, and enzyme?linked immunosorbent assay （ELISA） to measure levels of interleukin?1 （IL?1） and tumor necrosis factor?alpha （TNF?α） in HaCaT cells and their culture supernatant. Results Compared with the control group, the UVB group showed obscure cell morphology, cell death and floating phenomenon, while cells became swollen but remained morphologically distinct in the experimental group. MTS assay revealed that the cell proliferative activity significantly differed among the above 3 groups （F = 48.88, P < 0.01）, and the cell proliferative activity was significantly lower in the UVB group （1.72 ± 0.12） than in the control group （2.34 ± 0.11, P < 0.05） and experimental group （2.11 ± 0.10, P < 0.05）. Moreover, the apoptosis rate was significantly higher in the UVB group （82.41% ± 2.49%） than in the control group （3.98% ± 0.19%, P < 0.05） and experimental group （22.79% ± 0.97%, P < 0.05）, as well as higher in the experimental group than in the control group （P < 0.05）. Compared with the control group, the UVB group showed significantly higher levels of MDA, supernatant levels of IL?1 and TNF?α, and intracellular levels of TNF?α, but significantly lower GSH?Px levels and activity of SOD and CAT （all P < 0.05）. However, there was no signifi?cant difference in the intracellular level of TNF?α between the UVB group and control group （P > 0.05）. Conclusion Lycium ruthenicum polysaccharide has protective effects against photodamage in HaCaT cells, likely by reducing the synthesis and secretion of inflammatory substances as well as free radicals.