Ultraviolet A radiation-induced biological effects in human skin: relevance for photoaging and photodermatosis

There is increasing evidence that longwave ultraviolet (UV) radiation (UVA; 330-400 nm) plays an important role in the pathogenesis of photodermatoses such as polymorphous light eruption as well as photoaging. In order to ful ly understand these detrimental effects it is critical to analyze the photo biological and molecular mechanisms by which UVA radiation affects the func tion of human skin cells. Tn this review, our current knowledge about the s ignal transduction pathway involved in UVA radiation-induced expression of proinflammatory genes relevant to the pathogenesis of polymorphous light er uption will be summarized. In addition, recent studies on the role of mitoc hondrial DNA mutations in UVA radiation-induced photoaging of human skill w ill be discussed. For both biological endpoints the UVA radiation-induced g eneration of singlet oxygen within human skin appears to be of critical imp ortance. These studies are of enormous clinical relevance because they indi cate that prevention of the generation of singlet oxygen or inhibition of s inglet oxygen-induced signaling pathways may prove to be critical for effec tive protection of human skin against UVA radiation-induced damage. (C) 200 0 Elsevier Science Ireland Ltd. All rights reserved.