title: DNA-targeted 2-nitroimidazoles: studies of the influence of the phenanthridine-linked nitroimidazoles, 2-NLP-3 and 2-NLP-4, on DNA damage induced by ionizing radiation.
abstract: The nitroimidazole-linked phenanthridines 2-NLP-3 (5-[3-(2-nitro-1-imidazoyl)-propyl]-phenanthridinium bromide) and 2-NLP-4 (5-[3-(2-nitro-1-imidazoyl)-butyl]-phenanthridinium bromide) are composed of the radiosensitizer, 2-nitroimidazole, attached to the DNA intercalator phenanthridine by a 3- and 4-carbon linker, respectively. Previous in vitro assays showed both compounds to be 10-100 times more efficient as hypoxic cell radiosensitizers (based on external drug concentrations) than the untargeted 2-nitroimidazole radiosensitizer, misonidazole (Cowan et al., Radiat. Res. 127, 81-89, 1991). Here we have used a (32)P postlabeling assay and 5'-end-labeled oligonucleotide assay to compare the radiation-induced DNA damage generated in the presence of 2-NLP-3, 2-NLP-4, phenanthridine and misonidazole. After irradiation of the DNA under anoxic conditions, we observed a significantly greater level of 3'-phosphoglycolate DNA damage in the presence of 2-NLP-3 or 2-NLP-4 compared to irradiation of the DNA in the presence of misonidazole. This may account at least in part for the greater cellular radiosensitization shown by the nitroimidazole-linked phenanthridines over misonidazole. Of the two nitroimidazole-linked phenanthridines, the better in vitro radiosensitizer, 2-NLP-4, generated more 3'-phosphoglycolate in DNA than did 2-NLP-3. At all concentrations, phenanthridine had little effect on the levels of DNA damage, suggesting that the enhanced radiosensitization displayed by 2-NLP-3 and 2-NLP-4 is due to the localization of the 2-nitroimidazole to the DNA by the phenanthridine substituent and not to radiosensitization by the phenanthridine moiety itself.
authors.affiliation: Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
authors.forename: Garry W
authors.initials: GW
authors.lastname: Buchko
authors.forename: Michael
authors.initials: M
authors.lastname: Weinfeld
mesh_terms: D000818:Animals; D016466:CHO Cells / Q000528:radiation effects; D002417:Cattle; D015687:Cell Hypoxia; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000187:drug effects / Q000528:radiation effects*; D004249:DNA Damage; D004260:DNA Repair; D004305:Dose-Response Relationship, Drug; D005720:Gamma Rays; D007364:Intercalating Agents / Q000494:pharmacology*; D008920:Misonidazole / Q000494:pharmacology; D009593:Nitroimidazoles / Q000494:pharmacology*; D010100:Oxygen / Q000494:pharmacology; D010617:Phenanthridines / Q000494:pharmacology*; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D013329:Structure-Activity Relationship
chemical_list: C465228:5-(3-(2-nitro-1-imidazoyl)butyl)phenanthridinium; D007364:Intercalating Agents; D009593:Nitroimidazoles; D010617:Phenanthridines; D011838:Radiation-Sensitizing Agents; C059179:NLP 1; D008920:Misonidazole; D004247:DNA; D010100:Oxygen