Solar UV irradiation and dermal photoaging

The skin is increasingly exposed to ambient UV-irradiation thus increasing risks for photooxidative damage with long-term detrimental effects like pho toaging, characterized by wrinkles, loss of skin tone and resilience. Photo aged skin displays alterations in the cellular component and extracellular matrix with accumulation of disorganized elastin and its microfibrillar com ponent fibrillin in the deep dermis and a severe loss of interstitial colla gens, the major structural proteins of the dermal connective tissue. The un ifying pathogenic agents for these changes are UV-generated reactive oxygen species (ROS) which deplete and damage non-enzymatic and enzymatic antioxi dant defense systems of the skin. As well as causing permanent genetic chan ges, ROS activate cytoplasmic signal transduction pathways in resident fibr oblasts that are related to growth, differentiation, senescence and connect ive tissue degradation. This review focuses on the role of UV-induced ROS i n the photodamage of the skin resulting in clinical and biochemical charact eristics of photoaging. In addition, the relationship of photoaging to intr insic aging of the skin will be briefly discussed. A decrease in the overal l ROS load by efficient sunscreens or other protective agents may represent promising strategies to prevent or at least minimize ROS-induced photoagin g. (C) 2001 Elsevier Science B.V. All rights reserved.