title: Influence of PMMA shielding on DNA fragmentation induced in human fibroblasts by iron and titanium ions.
abstract: In the framework of a collaborative project on the influence of the shielding on the biological effectiveness of space radiation, we studied DNA fragmentation induced by 1 GeV/nucleon iron ions and titanium ions with and without a 197-mm-thick polymethylmethacrylate (PMMA) shield in AG1522 human fibroblasts. Pulsed- and constant-field gel electrophoresis were used to analyze DNA fragmentation in the size range 1-5700 kbp. The results show that, mainly owing to a higher production of small fragments (1-23 kbp), titanium ions are more effective than iron ions at inducing DNA double-strand breaks (DSBs), their RBE being 2.4 and 1.5, respectively. The insertion of a PMMA shield decreases DNA breakage, with shielding protection factors (ratio of the unshielded/shielded cross sections for DSB production) of about 1.6 for iron ions and 2.1 for titanium ions. However, the DSB yield (no. of DSBs per unit mass per unit dose) is almost unaffected by the presence of the shield, and the relative contributions of the fragments in the different size ranges are almost the same with or without shielding. This indicates that, under our conditions, the effect of shielding is mainly to reduce the dose per unit incident fluence, leaving radiation quality practically unaffected.
authors.affiliation: Istituto Superiore di Sanità, 00161 Roma, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Dini
authors.forename: Francesca
authors.initials: F
authors.lastname: Antonelli
authors.forename: Mauro
authors.initials: M
authors.lastname: Belli
authors.forename: Alessandro
authors.initials: A
authors.lastname: Campa
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Esposito
authors.forename: Giustina
authors.initials: G
authors.lastname: Simone
authors.forename: Eugenio
authors.initials: E
authors.lastname: Sorrentino
authors.forename: Maria Antonella
authors.initials: MA
authors.lastname: Tabocchini
mesh_terms: D002478:Cells, Cultured; D004249:DNA Damage; D053938:DNA Fragmentation / Q000528:radiation effects*; D005347:Fibroblasts / Q000528:radiation effects; D020450:Heavy Ions / Q000009:adverse effects*; D006801:Humans; D007501:Iron; D018499:Linear Energy Transfer; D019904:Polymethyl Methacrylate / Q000494:pharmacology*; D011835:Radiation Protection; D014025:Titanium
chemical_list: D019904:Polymethyl Methacrylate; D014025:Titanium; D007501:Iron