Roles of tocopherols and tocotrienols in modulation of damage to murine skin by ozone

These experiments were carried out to evaluate oxidative damage to skin in response to ozone. The vitamin E contents of murine skin were measured following topical application of a 5% locotrienol-rich (TRF) solution in polyethylene glycol (PEG, vehicle), or vehicle alone, to 2 sites on the backs of hairless mice. After 2 h. the sites were washed, half of the sites covered and the mice exposed 10 ppm ozone for 2 h. Ozone-exposure to vehicle-treated sites increased epidermal malondialdehyde (MDA), but had no effect on inherent skin vitamin E. Ozone significantly depleted all forms of applied vitamin E in TRF-sites, suggesting oxidative damage to skin surface layers. To localize oxidative damage, skin from ozone-exposed hairless mice was separated into upper epidermis, lower epidermis, and dermis, then concentrations of vitamins E and C and MDA in the layers measured. Ozone depleted alpha-tocopherol (22%; p<0.05) and ascorbic acid (55%; p<0.01) only in the upper epidermis. More remarkably, MDA increased 10-fold in the upper epidermis (p<0.001) and 2-fold in the lower epidermis (plt;0.05), but was unchanged in the dermis. Thus, ozone exposure induces lipid peroxidation in the skin surface layers, and this occurs before depletion of antioxidants, such as vitamins K and C. Because ozone reacts with skin surface fatty acids, topical application of vitamin E may prove beneficial in preventing oxidative damage as a result of environmental ozone exposure.