title: UV-B-induced formation of reactive oxygen species and oxidative damage of the cyanobacterium Anabaena sp.: protective effects of ascorbic acid and N-acetyl-L-cysteine.
abstract: Reactive oxygen species (ROS) are involved in the oxidative damage of the cyanobacterium Anabaena sp. caused by UV-B (280-315 nm) radiation. UV-B-induced overproduction of ROS as well as the oxidative stress was detected in vivo by using the ROS-sensitive probe 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA). Thiobarbituric acid reactive substances (TBARS) and fluorometric analysis of DNA unwinding (FADU) methods were adapted to measure lipid peroxidation and DNA strand breaks in Anabaena sp. Moderate UV-B radiation causes an increase of ROS production, enhanced lipid peroxidation and DNA strand breaks, yielding a significantly decreased survival. In contrast, the supplementation of UV-A in our work only showed a significant increase in total ROS levels and DNA strand breaks while no significant effect on lipid peroxidation, chlorophyll bleaching or survival was observed. The presence of ascorbic acid and N-acetyl-L-cysteine (NAC) reversed the oxidative stress and protected the organisms from chlorophyll bleaching and the damage of photosynthetic apparatus induced by UV-B significantly, resulting in a considerably higher survival rate. Ascorbic acid also exhibited a significant protective effect on lipid peroxidation and DNA strand breaks while NAC did not show a substantial effect. These results suggest that ascorbic acid exhibited significantly higher protective efficiency with respect to DNA strand breaks and survival than NAC while NAC appears to be especially effective in defending the photosynthetic apparatus from oxidative damage.
authors.affiliation: Institut für Botanik und Pharmazeutische Biologie, Friedrich-Alexander-Universität, Staudtstrasse 5, D-91058 Erlangen, Germany.
authors.forename: Yu-Ying
authors.initials: YY
authors.lastname: He
authors.forename: Donat P
authors.initials: DP
authors.lastname: Häder
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology*; D017033:Anabaena / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D000975:Antioxidants / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000494:pharmacology*; D002734:Chlorophyll / Q000528:radiation effects; D004249:DNA Damage; D004269:DNA, Bacterial / Q000187:drug effects / Q000528:radiation effects; D016166:Free Radical Scavengers / Q000494:pharmacology*; D015227:Lipid Peroxidation / Q000187:drug effects / Q000528:radiation effects; D018384:Oxidative Stress / Q000187:drug effects*; D010788:Photosynthesis / Q000528:radiation effects; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014466:Ultraviolet Rays
chemical_list: D000975:Antioxidants; D004269:DNA, Bacterial; D016166:Free Radical Scavengers; D017382:Reactive Oxygen Species; D002734:Chlorophyll; D001205:Ascorbic Acid; D000111:Acetylcysteine