Oral polypodium leucotomos extract protects against ultraviolet induced damage to human skin

Abstract

Ultraviolet radiation (UVR) induces acute epidermal and dermal damage that can lead to long-term changes such as photo-aging and skin cancer. Currently the most widely accepted method of photo-protection is the use of topical sunscreens. An oral photoprotective agent acting against UVR induced photooxidative stress would have substantial benefits over topical photo-protection in the prevention of solar UVR damage. Previous studies on Polypodium leucotomos (PL) have shown that this natural plant extract has immunomodulating and antioxidative properties. Oral administration of PL may lead to photoprotection of skin. We tested this hypothesis by exposing 10 healthy subjects of skin types II-III to varying doses of UVR from a solar simulator without PL, and 30 minutes, 1 hour (hr), 1.5 hr, 2 hrs and 3 hrs after administration of oral PL (7.5 mg/kg). Evaluation of the degree of erythema of all skin sites was performed 24 hrs later. Biopsies were obtained from skin sites exposed to the 2× minimal erythema dose (MED) from PL-treated and non-treated skin after 24 or 72 hrs. Clinically, there was a significant decrease in the erythema response of skin exposed within 2 hrs after oral administration of PL (p < 0.01) when compared to PL-untreated skin. Histologically, there was a significant decrease in sunburn cells at 24 hrs (p < 0.05), DNA damage analyzed by antibodies against cyclobutane pirymidine dimers at 24 hrs (p < 0.001), proliferation visualized by Ki 67 at 72 hrs (p < 0.001), and dermal mast cell infiltration at 24 and 72 hrs (p < 0.05). In total, more than 50% of all biopsies showed Langerhans cells preservation, and this was seen in all biopsies taken at 72 hrs. Also, there was less vasodilation in PL-treated skin. In conclusion, oral PL appears to be an effective photoprotective agent by decreasing acute UVR induced skin damage such as DNA damage and Langerhans cells depletion. This short-term observation may indicate that oral PL could serve to be effective in decreasing short-term UVR damage and this may contribute to prevention of photo-induced skin cancer.