Photoaging of the skin from phenotype to mechanisms

The skin is increasingly exposed to ambient UV-irradiation thus increasing its risk for photooxidative damage with longterm detrimental effects like p hotoaging, which is characterized by wrinkles, loss of skin tone, and resil ience. Photoaged skin displays prominent alterations in the cellular compon ent and the extracellular matrix of the connective tissue with an accumulat ion of disorganized elastin and its microfibrillar component fibrillin in t he deep dermis and a severe loss of interstitial collagens, the major struc tural proteins of the dermal connective tissue. The unifying pathogenic age nts for these changes are UV-generated reactive oxygen species (ROS) that d eplete and damage non-enzymatic and enzymatic antioxidant defense systems o f the skin. As well as causing permanent genetic changes, ROS activate cyto plasmic signal transduction pathways in resident. fibroblasts that are rela ted to growth, differentiation, senescence, and connective tissue degradati on. This review focuses on the role of UV-induced ROS in the photodamage of the skin resulting in biochemical and clinical characteristics of photoagi ng. In addition, the relationship of photoaging to intrinsic aging of the s kin will be discussed. A decrease in the overall ROS load by efficient suns creens or other protective agents may represent promising strategies to pre vent or at least minimize ROS induced photoaging. (C) 2000 Elsevier Science Inc. All rights reserved.