TOXIC AND SIGNALING EFFECTS OF PHOTOCHEMICALLY OR CHEMICALLY GENERATED SINGLET OXYGEN IN BIOLOGICAL-SYSTEMS

Singlet oxygen, generated photochemically or chemically, has damaging effects on biomolecules and exerts genotoxic, virucidal and cytotoxic effects. This is of relevance for biological systems because singlet o xygen can be produced photochemically as a result of the irradiation o f endogenous or exogenously applied photosensitizers with visible or u ltraviolet light, or in dark reactions, e.g. by stimulated phagocytes during the so-called oxidative burst. In addition, there is increasing evidence that singlet oxygen has pronounced effects on cellular signa ling events leading to the induced expression of a variety of proteins . A novel observation is the activation of transcription factor AP-2 a nd cellular signaling cascades comprising the activation of c-Jun-N-te rminal kinases (JNK/SAPK) and the NF-kappa B system.