title: Chelation of lysosomal iron protects against ionizing radiation.
abstract: Ionizing radiation causes DNA damage and consequent apoptosis, mainly due to the production of hydroxyl radicals (HO•) that follows radiolytic splitting of water. However, superoxide (O2•-) and H2O2 also form and induce oxidative stress with resulting LMP (lysosomal membrane permeabilization) arising from iron-catalysed oxidative events. The latter will contribute significantly to radiation-induced cell death and its degree largely depends on the quantities of lysosomal redox-active iron present as a consequence of autophagy and endocytosis of iron-rich compounds. Therefore radiation sensitivity might be depressed by lysosome-targeted iron chelators. In the present study, we have shown that cells in culture are significantly protected from ionizing radiation damage if initially exposed to the lipophilic iron chelator SIH (salicylaldehyde isonicotinoyl hydrazone), and that this effect is based on SIH-dependent lysosomal stabilization against oxidative stress. According to its dose-response-modifying effect, SIH is a most powerful radioprotector and a promising candidate for clinical application, mainly to reduce the radiation sensitivity of normal tissue. We propose, as an example, that inhalation of SIH before each irradiation session by patients undergoing treatment for lung malignancies would protect normally aerated lung tissue against life-threatening pulmonary fibrosis, whereas the sensitivity of malignant lung tumours, which usually are non-aerated, will not be affected by inhaled SIH.
authors.affiliation: Division for Biochemistry, Department for Medical Biochemistry and Biophysics, Karolinska Institute, 171 77 Stockholm, Sweden Carsten.Berndt@ki.se
authors.forename: Carsten
authors.initials: C
authors.lastname: Berndt
authors.forename: Tino
authors.initials: T
authors.lastname: Kurz
authors.forename: Markus
authors.initials: M
authors.lastname: Selenius
authors.forename: Aristi P
authors.initials: AP
authors.lastname: Fernandes
authors.forename: Margareta R
authors.initials: MR
authors.lastname: Edgren
authors.forename: Ulf T
authors.initials: UT
authors.lastname: Brunk
mesh_terms: D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D005720:Gamma Rays; D006367:HeLa Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007501:Iron / Q000378:metabolism*; D007502:Iron Chelating Agents / Q000378:metabolism* / Q000494:pharmacology; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology / Q000528:radiation effects; D018384:Oxidative Stress
chemical_list: D007502:Iron Chelating Agents; D006861:Hydrogen Peroxide; D007501:Iron