Figure 3.

HaCaT keratinocytes were significantly protected from solar‐simulated radiation (SSR) and ultraviolet A (UVA)‐induced cyclobutane pyrimidine dimer (CPD), 8‐oxo‐7,8‐dihydroguanine (8‐oxoGua) and alkali labile sites (ALS) by palythine at a range of concentrations. (a) HaCaT keratinocytes were untreated, exposed to ultraviolet radiation (UVR) (20 J cm⁻² SSR) with 0·3%, 4% or 10% w/v palythine. CPDs were measured immediately after exposure using immunocytochemistry immunofluorescence. Columns represent mean + SD (n = 3). Cells irradiated without palythine showed a significant increase in CPD production (P = 0·003, paired t‐test) compared with unirradiated control. Palythine at 0·3–10% w/v showed a significant reduction in CPD compared with irradiated control (P < 0·001, one‐way anova with Dunnett's multiple comparisons test). There was no significant difference in protection between any concentration of palythine (P = 0·332). (b) Typical fluorescent images for each condition. (c) Cells were irradiated with 5 J cm⁻² SSR or 20 J cm⁻² UVA radiation with or without 0·3% of palythine and ALS, CPD and 8‐oxoGua production were measured for both spectra tested. The irradiated control was set at 100% for a given experimental run. The effect of palythine is given relative to the control. For SSR – ALS: P = 0·0006, n = 3; CPD: P < 0·001, n = 3; 8‐oxoGua: P < 0·001, n = 3. For UVA – ALS: P < 0·001, n = 3; CPD: P < 0·001, n = 3; 8oxoGua P < 0·001, n = 3, paired t‐test. **P < 0·01; ***P < 0·001.