Topical Curcumin as Chemoprotector Against Photoproducts Production: The Role of Cyclobutyl Pyrimidine Dimers, 8-Hydroxy2ʹDeoxyguanosine Expression and Epidermal Hyperplasia in Acute and Chronic UVB-Induced Mice

BACKGROUND: Ultraviolet B (UVB) exposure leads to formation of photoproducts leading to cellular damage. Prevention using sunscreen can sometimes be inadequate and can be an economic burden. Recent studies have suggested the photoprotective effect of curcumin. OBJECTIVE: To examine the acute and chronic photoprotective effect of topical curcumin, using cyclobutyl pyrimidine dimers (CPD) and 8-hydroxy2ʹdeoxyguanosine (8-OHdG) expression as markers of DNA-induced damage, and epidermal hyperplasia on UVB-induced mice. METHODS: Three treatment groups were established. Group A (negative control) consisted of 5 mice, Group B and C were further divided into two categories to assess acute and chronic effects of topical curcumin and UVB radiation. Each consisted of six subgroups of five mice. Subgroup 1; UVB exposure only (positive control) subgroup 2; acetone and UVB exposure, subgroup 3–6; topical curcumin application of 100nM, 1µM, 10µM, and 100µM concentrations, respectively. In Group C, there were two categories that received 3x/week UVB exposure for three weeks which effects were being observed at 24 hours and 10 days after the last exposure. The topical curcumin dose was 2mg/mL/cm(2) applied 30 minutes prior to 343mJ/cm(2)/day UVB irradiation. Skin biopsy was done one hour after the last UVB exposure for immunohistochemical and histopathology examinations. RESULTS: Topical curcumin showed a limited yet robust protective effect against CPD and 8-OHdG expression in Group B, while in Group C all concentrations showed significant CPD and 8-OHdG inhibition after 10 days of UVB exposure. The 10µM and 100µM concentrations showed the best epidermal hyperplasia inhibition effect (p<0.05). No significant differences were found in terms in efficacy either in single nor daily application. CONCLUSION: Topical curcumin can prevent the formation of the photoproducts CPD and 8-OHdG and epidermal hyperplasia in both acute and chronic exposure in UVB-induced mice.