Increased antioxidant potential of combined topical vitamin E and C against lipid peroxidation of eicosapentaenoic acid in pig skin induced by simulated solar radiation

Purpose : To study the protective effect of topically applied vitamin E (TOC), vitamin C (ASC), or a combination of both, against the lipid peroxidation of eicosapentaenoic acid (EPA) induced by simulated solar radiation (SSR). Material and methods : EPA (25 nmol cm -2) was topically applied to pig skin explants, followed by increasing doses of TOC and ASC, either alone or combined. Epidermal lipid peroxidation was assessed after 15 min of exposure to SSR (resulting in a UVA and UVB dose of 18 and 3 kJ m -2, respectively). SSR-induced changes in the levels of TOC and ASC were determined in the stratum cornaeum and the viable epidermis. Results : SSR exposure of EPA-treated pig skin resulted in a twofold increase in epidermal lipid peroxidation (p < 0.005) which was reduced by topically applied TOC or ASC 60 min before SSR exposure (p < 0.05). Compared with TOC (5 nmol cm -2) , a 400-fold higher ASC dose was needed and only TOC provided complete protection against the lipid peroxidation of EPA. The levels of both TOC and ASC clearly increased in both skin compartments by increasing the applied dose of these two compounds (p < 0.05). In contrast to ASC, TOC was consumed by up to 55-70% during SSR exposure (p < 0.05). Compared with separate application, combined TOC and ASC efficiently protected against lipid peroxidation of EPA at doses that were five and 200 times lower, respectively. In the presence of low ASC doses, 70-100% of epidermal TOC was regenerated during SSR exposure (p < 0.05). Conclusions : Topically applied TOC and ASC protect against SSR-induced lipid peroxidation of EPA. The synergism between TOC and ASC resulted in a more efficient protection at substantially lower doses of both antioxidants. Co-supplementation of EPA with TOC and/or ASC might improve the beneficial biological effects of EPA.