Abstract: Objective To observe the aging, apoptosis, cell cycle arrest and oxidative stress in human skin fibroblast （HSF） induced by UVB, and to detect the expression profiles of p66Shc, a determinant of oxidative stress response and life span, in this process. Methods HSF cells were exposed to UVB at a subcytotoxic dosage twice a day for three days. The cells without exposure served as control. After another 24-hour culture, SA-β-Gal staining was performed to evaluate the senescence state of the cells, flow cytometry to observe cell apoptosis; cell cycle arrest was detected by serum starvation and flow cytometry; ELISA was applied to detect intracellular levels of superoxide dismutase （SOD） and malondialdehyde （MDA）, and Western blotting to analyze the expression of p66Shc protein. Results The percentage of cells positive for SA-β-Gal staining increased from 0 to 98.3% after UVB radiation, which strongly suggested an aging state of HSF cells. The percentage of apoptotic cells increased from 0.96% to 37%, and 80.07% of the HSF cells were arrested in G0/G1 phase following the irradiation. Intracellular SOD activity decreased from （52.35 ± 4.97） ng/g to （7.81 ± 0.68） ng/g （P < 0.01）, while intracellular MDA was found to increase from （3.52 ± 0.34） ng/g to （33.91 ± 3.20） ng/g （P < 0.05）. The p66Shc protein was found to be weakly expressed in HSF in 24 hours following the exposure to UVB, and a stronger expression was noted 48 hours later. Conclusions HSF cells are induced into a state of senescence associated with oxidative stress after UVB irradiation, which may be applied as an in vitro model in aging research. The expression of p66Shc is increased in HSF during this process, and further studies are needed to explore the relation between p66Shc and oxidative stress as well as cellular aging.

Key words: Oxidative stress, Aging, p66Shc