Photoprotection by antioxidants against UVB-radiation-induced damage in pig skin organ culture.

Topically applied antioxidants constitute an important group of protective agents against skin damage induced by ultraviolet radiation. The current study was performed to investigate whether a recently developed ex vivo pig skin model was suitable for short-term studies of the mechanism(s) of UVB-radiation-induced skin damage; the protective effect of topical application of alpha-tocopherol, l-ascorbic acid, alpha-lipoic acid, glutathione ethylester and N-acetylcysteine was tested. Increasing doses of the antioxidants were applied topically on ex vivo pig skin explants and allowed to penetrate for 60 min. Epidermal antioxidant bioavailability was measured before and 60 min after exposure to an ultraviolet B (UVB) radiation of 7.5 kJ/m2. Cell viability (trypan blue dye exclusion) and apoptosis were measured 48 h later in isolated keratinocytes. UVB-radiation-induced epidermal lipid peroxidation was determined immediately after exposure of the skin to a UVB dose of 28 kJ/m2. All antioxidants tested became bioavailable in pig skin epidermis, and none of them were depleted after UVB-radiation exposure. Increasing doses of the antioxidants tested decreased UVB-radiation-induced cell death and apoptosis. The highest doses of antioxidants prevented UVB-radiation-induced lipid peroxidation; alpha-lipoic acid only tended to decrease lipid peroxidation. In conclusion, a single topical dose of the above antioxidants on ex vivo pig skin can reduce UVB-radiation-induced oxidative stress and lipid peroxidation and thereby reduce apoptotic stimuli and cell death. Furthermore, the ex vivo pig skin model was a useful tool for testing compounds for their antioxidant activity.