Figure 1.

The Frequency of UVB Exposure Dictates a Trade-off between Skin Protection Programs

(A) Schematic presentation of the experimental procedure. Mouse skin was UVB irradiated every 24, 48, or 72 hr or untreated (Control).

(B) Melanin level of C57BL/6 mice skin upon 60 days of UVB radiation (50 mJ/cm²) at indicated periodicity normalized to untreated controls; Error bars indicate SEM. ^∗p < 0.05 (n = 4).

(C) Fontana-Masson (melanin) and H&E staining of ear sections from the representative mice after 60 days of treatment. Scale bars, 50 μm.

(D) DNA damage analysis (see STAR Methods) by Thymine dimer (TˆT) staining (red) of ear sections. DAPI staining (cell nuclei) appears in blue. Left: DNA-damage level immediately upon a single UVB dose (50 mJ/cm²) (+UV). Right: the accumulated DNA damage of ears that did not received the final UV dose (−UV). Scale bars, 20 μm.

(E) DNA damage (TˆT) quantification. Error bars indicate SEM. ^∗∗∗p < 0.001 (n = 4 mice; n = 10 images from each section).

(F) Epidermal thickness quantification of the mice skin treated as in (A). Error bars represent SEM. ^∗∗∗p < 0.001 (n = 6).

(G) Schematic of the 24-hr- or 48-hr-interval cAMP treatments in cell culture.

(H) Fontana-Masson, Ki67, and DAPI (cell nuclei) staining (n = 6) of melanoma cells upon single or double cAMP stimulation. Vehicle-treated cells were used as a control. Error bars represent SEM. ^∗p < 0.05. Scale bars, 20 μm for pigmentation and 50 μm for proliferation.

See also Figure S1.