Figure 5 Effect of lutein on the proliferation of keratinocytes measured by BrdU-incorporation assay. Proliferation of keratinocyte cell line (A, B) and primary human keratinocytes (C, D) treated with 0.5 to 15 μM of silk lutein (A, C) or c-lutein (B, D) for 24 hours prior to irradiation with UVB at various doses ranging from 8 to 32 mJ/cm2. Each bar represents the percentage of cell proliferation. Error bars are one standard deviation. *, p < 0.05