Figure 2.

The IGF-1R regulates the production of ROS following UVB irradiation. Keratinocytes were grown in EpiLife Complete [(+)IGF-1R] or EpiLife NoIn [(−)IGF-1R] media for 24 h. (A–D) Both (+)IGF-1R keratinocytes (A and B) and (−)IGF-1R keratinocytes (C and D) were treated with 0 (A and C) or 600 μM H₂O₂ (B and D) for an additional 24 h. At that time, keratinocyte were examined for the induction of senescence by assaying for the presence of senescence-associated β-galactosidase activity. (E) To measure the production of ROS, both (+)IGF-1R and (−)IGF-1R keratinocytes were loaded with CM-H₂DCFDA dye for 15 min before UVB irradiation. Cells were harvested at 15 min after irradiation, and the fluorescence was measured. The relative induction of ROS was standardized for total cell number by the subsequent staining and measurement of DAPI fluorescence. Error bars indicate the SE of the mean; the asterisk indicates significant difference between irradiated (+)IGF-1R and (−)IGF-1R keratinocyte percentages (p < 0.01, t test). The data represent three independent assays.