title: Liposoluble antioxidants provide an effective radioprotective barrier.
abstract: Ionising radiation causes the massive generation of reactive oxygen species and induces cellular DNA damage. The antioxidant, protective effects of several compounds against gamma-ray-induced chromosomal damage were determined by the micronucleus test, evaluating the reduction in the frequency of micronuclei in cytokinesis-blocked human lymphocytes. The compounds studied were added to human blood at 25 microM, 5 min before or after irradiation with 2 Gy of caesium-137. The results suggest that different protective mechanisms are operating in each case. When the phenolic compounds are added before gamma-irradiation, their protective antimutagenic activity is based on their scavenging capacity against superoxide anion (O(2)(.-)) and, especially, hydroxyl radical ((.)OH), regardless of whether they are oil- or water-soluble compounds. When the phenolic compounds are added after gamma-irradiation treatment, the protective effect relies on activity against reactive oxygen species present in cells, i.e. lipoperoxy radicals (R(-)OO(.)), which are mainly responsible for continuous chromosomal oxidative damage. In addition, ionising radiation enhances lysosomal enzyme secretion and arachidonate release from membranes through lipo-oxygenase, cyclo-oxygenase and phospholipase activities, thus increasing the inflammatory cell response. Only oil-soluble compounds, such as carnosic acid, carnosol and delta-tocopherol, provide a significant protective antimutagenic activity. The most powerful water-soluble antioxidants lack the capacity to protect against gamma-ray-induced damage. The difference between anti-radical and anti-lipoperoxidant activities could explain the different behaviour of the compounds tested in terms of protecting against the lipid peroxidative processes. This anti-lipoperoxidant activity depends on several factors, but it is clear that only the lipo-antioxidants are effective in protecting human cells against oxidative damage, even when administered after exposure to ionising radiation.
authors.affiliation: Department of Radiology and Physical Medicine, University of Murcia, Murcia, Spain. mab@um.es
authors.forename: M
authors.initials: M
authors.lastname: Alcaraz
authors.forename: C
authors.initials: C
authors.lastname: Acevedo
authors.forename: J
authors.initials: J
authors.lastname: Castillo
authors.forename: O
authors.initials: O
authors.lastname: Benavente-Garcia
authors.forename: D
authors.initials: D
authors.lastname: Armero
authors.forename: V
authors.initials: V
authors.lastname: Vicente
authors.forename: M
authors.initials: M
authors.lastname: Canteras
mesh_terms: D016587:Antimutagenic Agents / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology*; D002588:Cesium Radioisotopes / Q000633:toxicity; D005260:Female; D005419:Flavonoids / Q000494:pharmacology; D005720:Gamma Rays / Q000009:adverse effects*; D006801:Humans; D008055:Lipids / Q000737:chemistry; D008214:Lymphocytes / Q000528:radiation effects*; D015162:Micronucleus Tests / Q000379:methods; D010636:Phenols / Q000494:pharmacology*; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D012995:Solubility; D013819:Thermoluminescent Dosimetry
chemical_list: D016587:Antimutagenic Agents; D000975:Antioxidants; D002588:Cesium Radioisotopes; D005419:Flavonoids; D008055:Lipids; D010636:Phenols; D011837:Radiation-Protective Agents; C404987:flavan-3-ol