Abstract: 【Abstract】 Objective To evaluate the effect of resveratrol on apoptosis and cell cycle of human epidermal keratinocytes （HEKs） after ultraviolet B （UVB） irradiation. Methods After 12-hour treatment with 0 （control group）, 25, 50, 100, 150 and 200 μmol/L resveratrol, cell counting kit-8 （CCK8） assay, bromodeoxyuridine （BrdU） assay and lactate dehydrogenase （LDH） assay were performed to evaluate the effect of resveratrol on proliferative activity and death of HEKs. Some HEKs were divided into 4 groups: normal control group receiving no treatment, resveratrol group treated with 100 μmol/L resveratrol, UVB group irradiated with 50 mJ/cm2 UVB, and UVB + resveratrol group irradiated with 50 mJ/cm2 UVB followed by 12-hour treatment with 100 μmol/L resveratrol. Western blot analysis was conducted to determine the expression of apoptosis-related proteins poly （ADP-ribose） polymerase （PARP） and caspase-3, as well as cell cycle-related proteins cyclin B1 and cyclin E1, and flow cytometry to detect the apoptosis and determine cell cycle distribution. One-way analysis of variance was used for comparisons among multiple groups, and least significant difference-t test for multiple comparisons. Results The proliferative activity of HEKs significantly differed among the 25-, 50-, 100-, 150-, 200-μmol/L resveratrol groups and control group （F = 46.52, P < 0.001）, and was significantly lower in these resveratrol groups than in the control group （all P < 0.001）; the DNA synthesis activity of HEKs was significantly lower in the 100-μmol/L resveratrol group （0.761 ± 0.141） than in the control group （2.226 ± 0.141, t = 17.92, P < 0.001）; there was no significant difference in cell death rate among the 25-, 50-, 100- and 200-μmol/L resveratrol groups （F = 1.938, P > 0.05）. After treatment with or without UVB and/or resveratrol, there were significant differences in the apoptosis rate, proportion of cells at G1, G2 and S phases, expression of PARP, caspase-3, cyclin B1 and cyclin E1 among the 4 groups （all P < 0.05）. The UVB group showed significantly increased apoptosis rates （24.69% ± 3.54%） and cleavage levels of PARP and caspase-3 （2.190 ± 0.349, 0.090 ± 0.016, respectively） compared with the normal control group and UVB + resveratrol group （4.00% ± 0.81%, 0.926 ± 0.040, 0.024 ± 0.019, respectively, all P < 0.05）; the UVB group showed significantly decreased protein expression of cyclin E1 and cyclin B1 （0.116 ± 0.017, 0.775 ± 0.080, respectively） compared with the normal control group, and the UVB + resveratrol group showed significantly increased expression of cyclin E1 （0.287 ± 0.047）, but decreased expression of cyclin B1 （0.504 ± 0.009） compared with the UVB group （all P < 0.05）; the UVB group showed significantly decreased proportion of S-phase cells, but increased proportion of G1- and G2-phase cells compared with the UVB + resveratrol group （all P < 0.05）. Conclusion Resveratrol can decrease the proliferative activity of HEKs, inhibit apoptosis induced by UVB radiation, and regulate cell cycle progression.

Key words: Keratinocytes, Ultraviolet rays, Cell proliferation, Apoptosis, Cell cycle, Resveratrol