Radioprotective effects of manganese-containing superoxide dismutase mimics on ataxia–telangiectasia cells

• Published in: Free radical biology & medicine 2009-08, Vol.47 (3), p.250-260
• Main Authors: Pollard, Julianne M., Reboucas, Julio S., Durazo, Armando, Kos, Ivan, Fike, Francesca, Panni, Moeen, Gralla, Edith Butler, Valentine, Joan Selverstone, Batinic-Haberle, Ines, Gatti, Richard A.
• Format: Article
• Language: English
• Subjects: AEOL10112; AEOL10113; Annexin A5 - metabolism; Antioxidants - chemistry; Antioxidants - metabolism; Apoptosis; Ataxia Telangiectasia - immunology; Ataxia Telangiectasia - metabolism; Ataxia Telangiectasia - pathology; Ataxia–telangiectasia; Biomimetic Materials - chemistry; Biomimetic Materials - metabolism; Cell Separation; Cells, Cultured; Comet Assay; Cytoprotection; EUK-134; EUK-189; EUK-8; Flow Cytometry; Free radicals; Humans; M40403; M40404; Metalloporphyrins - chemistry; Metalloporphyrins - metabolism; Mn cyclic polyamines; Mn porphyrins; Mn salens; Propidium - metabolism; Radiation-Protective Agents - chemistry; Radiation-Protective Agents - metabolism; Radioprotection; SOD mimics; Superoxide Dismutase - chemistry; Superoxide Dismutase - immunology; Superoxide Dismutase - metabolism
• ISSN: 0891-5849; 1873-4596
• DOI: 10.1016/j.freeradbiomed.2009.04.018

We tested several classes of antioxidant manganese compounds for radioprotective effects using human lymphoblastoid cells: six porphyrins, three salens, and two cyclic polyamines. Radioprotection was evaluated by seven assays: XTT, annexin V and propidium iodide flow cytometry analysis, γ-H2AX immunofluorescence, the neutral comet assay, dichlorofluorescein and dihydroethidium staining, resazurin, and colony survival assay. Two compounds were most effective in protecting wild-type and A-T cells against radiation-induced damage: MnM x -2-PyP-Calbio (a mixture of differently N-methylated MnT-2-PyP + from Calbiochem) and MnTnHex-2-PyP. MnTnHex-2-PyP protected WT cells against radiation-induced apoptosis by 58% ( p = 0.04), using XTT, and A-T cells by 39% ( p = 0.01), using annexin V and propidium iodide staining. MnTnHex-2-PyP protected WT cells against DNA damage by 57% ( p = 0.005), using γ-H2AX immunofluorescence, and by 30% ( p < 0.01), using neutral comet assay. MnTnHex-2-PyP is more lipophilic than MnM x -2-PyP-Calbio and is also >10-fold more SOD-active; consequently it is >50-fold more potent as a radioprotectant, as supported by six of the tests employed in this study. Thus, lipophilicity and antioxidant potency correlated with the magnitude of the beneficial radioprotectant effects observed. Our results identify a new class of porphyrinic radioprotectants for the general and radiosensitive populations and may also provide a new option for treating A-T patients.