Aging- and photoaging-dependent changes of enzymic and nonenzymic antioxidants in the epidermis and dermis of human skin in vivo

This is a comprehensive study of the changes in major antioxidant enzymes a nd antioxidant molecules during intrinsic aging and photoaging processes in the epidermis and dermis of human skin in vivo. We show that the activitie s of superoxide dismutase and glutathione peroxidase are not changed during these processes in human skin in vivo. Interestingly, the activity of cata lase was significantly increased in the epidermis of photoaged (163%) and n aturally aged (118%) skin (n = 9), but it was significantly lower in the de rmis of photoaged (67% of the young skin level) and naturally aged (55%) sk in compared with young (n = 7) skin. The activity of glutathione reductase was significantly higher (121%) in naturally aged epidermis. The concentrat ion of alpha -tocopherol was significantly lower in the epidermis of photoa ged (56% of young skin level) and aged (61%) skin, but this was not found t o be the case in the dermis. Ascorbic acid levels were lower in both epider mis (69% and 61%) and dermis (63% and 70%) of photoaged and naturally aged skin, respectively. Glutathione concentrations were also lower. Uric acid d id not show any significant changes. Our results suggest that the component s of the antioxidant defense system in human skin are probably regulated in a complex manner during the intrinsic aging and photoaging processes.