Epidermal trans-Urocanic Acid and the UV-A Induced Photoaging
of the Skin
Kerry M. Hanson and John D. Simon
The premature photoaging of the skin is mediated by the sensitization of reactive
oxygen species following absorption of ultraviolet radiation by endogenous chromophores.
Yet identification of UV-A absorbing chromophores in the skin that quantitatively
account for the action spectra of the physiological responses of photoaging has
remained elusive. This paper reports that the in vitro action spectrum for singlet
oxygen generation following excitation of trans-urocanic acid mimics the in vivo
UV-A action spectrum for the photosagging of mouse skin. The data presented provide
evidence that the UV-A excitation of trans-urocanic acid initiates chemical processes
that result in the photoaging of skin.
Proceedings of the National Academy of Sciences, USA 95, 10576 (1998)