The altered DNA damage response pathway in patients with Fanconi anemia (FA) may increase the toxicity of clinical radiotherapy. We quantitated oral cavity mucositis in irradiated Fanconi anemia Fancd2−/− mice, comparing this to Fancd2+/− and Fancd2+/+ mice, and we measured distant bone marrow suppression and quantitated the effect of the intraoral radioprotector GS-nitroxide, JP4-039 in F15 emulsion. We found that FA mice were more susceptible to radiation injury and that protection from radiation injury by JP4-039/F15 was observed at all radiation doses. Adult 10–12-week-old mice, of FVB/N background Fancd2−/−, Fancd2+/− and Fancd2+/+ were head and neck irradiated with 24, 26, 28 or 30 Gy (large fraction sizes typical of stereotactic radiosurgery treatments) and subgroups received intraoral JP4-039 (0.4 mg/mouse in 100 μL F15 liposome emulsion) preirradiation. On day 2 or 5 postirradiation, mice were sacrificed, tongue tissue and femur marrow were excised for quantitation of radiation-induced stress response, inflammatory and antioxidant gene transcripts, histopathology and assay for femur marrow colony-forming hematopoietic progenitor cells. Fancd2−/− mice had a significantly higher percentage of oral mucosal ulceration at day 5 after 26 Gy irradiation (59.4 ± 8.2%) compared to control Fancd2+/+ mice (21.7 ± 2.9%, P = 0.0063). After 24 Gy irradiation, Fancd2−/− mice had a higher oral cavity percentage of tongue ulceration compared to Fancd2+/+ mice irradiated with higher doses of 26 Gy (P = 0.0123). Baseline and postirradiation oral cavity gene transcripts were altered in Fancd2−/− mice compared to Fancd2+/+ controls. Fancd2−/− mice had decreased baseline femur marrow CFU-GM, BFUe and CFU-GEMM, which further decreased after 24 or 26 Gy head and neck irradiation. These changes were not seen in head- and neck-irradiated Fancd2+/+ mice. In radiosensitive Fancd2−/− mice, biomarkers of both local oral cavity and distant marrow radiation toxicity were ameliorated by intraoral JP4-039/F15. We propose that Fancd2−/− mice are a valuable radiosensitive animal model system, which can be used to evaluate potential radioprotective agents.

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We evaluated normal tissue specific radioprotection of the oral cavity in radiosensitive Fanconi Anemia (FA) Fancd2−/−mice with orally established tumors using mitochondrial-targeted GS-nitroxide (JP4-039). Adult (10–12 weeks old) Fancd2+/+, Fancd2+/− and Fancd2−/− mice (C57BL/6 background) and subgroups with orally established TC-1 epithelial cell tumors received a single fraction of 28 Gy or four daily fractions of 8 Gy to the head and neck. Subgroups received JP4-039 in F15 emulsion (F15/JP4-039; 0.4 mg/mouse), 4-amino-Tempo in F15 emulsion (F15/4-amino-Tempo; 0.2 mg/ mouse) or F15 emulsion alone prior to each irradiation. Oral mucosa of Fancd2−/− mice showed baseline elevated RNA transcripts for Sod2, p53, p21 and Rad51 (all P < 0.0012) and suppressed levels of Nfkb and Tgfb, (all P < 0.0020) compared with Fancd2+/+ mice. The oral mucosa in tumor-bearing mice of all genotypes showed decreased levels of p53 and elevated Tgfb and Gadd45a (P ≤ 0.0001 for all three genotypes). Intraoral F15/JP4-039, but not F15/4-amino-Tempo, modulated radiation-induced normal tissue transcript elevation, ameliorated mucosal ulceration and reduced the depletion of antioxidant stores in oral cavity tissue of all genotypes, but did not radioprotect tumors. Mitochondrial targeting makes F15/JP4-039 an effective normal tissue radioprotector for Fancd2−/− mice, as well as wild-type mice.

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