1 / 15

Radiation

Combined genotoxicity of low-dose-rate radiation and tobacco-specific nitrosamine NNK. Radiation. NNK. The causes of cancer. Industrial products 1%. Food additives 1%. Medicines 1%. Pollution 2%. UV 3%. Alcohol 3%. Occupation 4%. Diet 35%. Reproductive and sexual behavior 7%.

eljah
Download Presentation

Radiation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Combined genotoxicity of low-dose-rate radiation and tobacco-specific nitrosamine NNK Radiation NNK

  2. The causes of cancer Industrial products1% Food additives1% Medicines1% Pollution2% UV3% Alcohol3% Occupation4% Diet35% Reproductive and sexual behavior7% Infection10% tobacco30% Doll, R. and R. Peto, The causes of cancer: quantitative estimates of avoidable risks of cancer in the United States today, J. Natl. Cancer Inst. 66, 1192 (1981)

  3. gpt delta Transgenic mouse Mutagen lEG10 DNA (80 copies/haploid in chromosome 17) Tissue λin vitro packaging gpt delta mouse (C57BL/6J background) lEG10 phage Genomic DNA lEG10 chiC gpt Assay Spi- Assay 48 kb red, gam loxP loxP gpt cat Spi- Mutant Plaques 6-TGr mutant colonies Point Mutation Deletion

  4. NNK is a tobacco-specific nitrosamine that is carcinogenic in the lung of experimental animals NNK= nicotine-derived nitrosamino ketone O O N N C H 3 IARC :Group 2B (possible human carcinogen） N 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone Cytochrome P450 CYP2A Point Mutations DNA Adducts Cancer Lung O6-methylguanine O4-methylthymine

  5. Combined treatments of gpt delta mice with NNK and g-ray radiation Animal : gpt delta mouse, 8 mice (♀), 7 weeks old Saline NNK 2 mg/mouse/day x 4 (i.p.) Sacrifice Sacrifice ▽ ▽ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ 1.5 mGy/h 1.5 mGy/h 1.0 mGy/h 1.0 mGy/h 0.5 mGy/h 0.5 mGy/h 0 mGy/h 0 mGy/h (days) (days) • Sakai et al., Int. J. Low Radiation, 1, 142-146 (2003)

  6. P < 0.05 * NNK treatments significantly enhancedgpt mutation frequencies in the lung of mice N=6 30 * 25 20.7 * 17.2 20 * * 15.2 14.3 gpt mutation frequency (10-6) 15 10 4.7 4.2 2.7 2.0 5 0 - - - - NNK + + + + Dose rate 1.5 mGy/h 1.0 mGy/h 0 mGy/h 0.5 mGy/h

  7. NNK-treatment mainly induced G:C to A:T, A:T to T:A and A:T to C:G mutations 25 [ ] Total No. of mutants sequenced [116] 20 [109] Others [83] [67] Insertion Deletion 15 gpt mutation frequency (10-6) A:T→C:G A:T→T:A G:C→C:G 10 G:C→T:A A:T→G:C [32] [35] G:C→A:T [27] 5 [17] 0 - - - - + + + + NNK 0 0 1.5 1.0 1.0 0.5 1.5 0.5 Dose rate (mGy/h)

  8. Spi- mutation frequencies in the lung of mice N=5 9 8 7 5.5 5.4 5.4 5.2 5.1 6 4.7 Spi- mutation frequency (10-6) 4.1 4.1 5 4 3 2 1 0 - - - - + + + + NNK Dose rate 1.5 mGy/h 1.0 mGy/h 0 mGy/h 0.5 mGy/h

  9. Mutation Spectra of Spi- mutants Saline NNK 6 6 5 5 others > 1 kb 4 4 2 bp ~ 1 kb 1 bp deletion Spi- mutation frequency (10-6) 3 3 2 2 1 1 0 0 Dose rate 1.0 1.0 0 0.5 1.5 0 0.5 1.5 (mGy/h)

  10. P < 0.05 * Suppression of large deletions in the mice treated with NNK + g-radiation at 1.5 mGy/h Saline + Radiation NNK + Radiation * * 0.87 * 0.80 0.75 0.76 0.9 0.9 0.59 0.8 0.8 0.7 0.7 Specific mutation frequency (10-6) 0.6 0.6 0.24 0.27 0.25 0.5 0.5 0.4 0.4 0.3 0.3 0.2 0.2 0.1 0.1 0 0 0 0.5 1 1.5 0 0.5 1 1.5 Dose rate Dose rate (mGy/h) (mGy/h)

  11. Large deletions are formed by non-homologous end-joining (NHEJ) of double-strand breaks in DNA (DSB) With short homology γ- ray - 4005 bp (Saline 1.5 mGy/h) AACTCCGGC CTTACCG AACTCCGGC TTCGATG CGAC ATTC TTCGATG AACTCCGGC CTTACCG Deletion mutant Without short homology γ- ray - 5445 bp (NNK 1.0 mGy/h) AGGCT TGCCGATTGC GTTCA AGCGCGCGTA AGCGCGCGTA TGCCGATTGC Deletion mutant

  12. NNK treatments induce mutations but suppress radiation-induced large deletions in vivo Mutations (G:C to A:T) DNA Adducts (O6-MeG) Deletion NNK Adaptive Response (MMR?/p53?) Radiation

  13. Summary • To examine the combined effects of low dose rate radiation and chemical exposure, gpt delta mice were exposed to NNK and g-irradiation, i.e., 0.5, 1.0 and 1.5 mGy per hour for 31 days. The total calculated doses were 0.34, 0.68 and 1.02 Gy, respectively. • NNK treatments significantly induced base substitutions, i.e., G:C to A:T, A:T to T:A or A:T to C:G, in the lung of mice. • The induction of base substitutions was not substantially modulated by the low dose rate g-irradiation. • The g-irradiation induced large deletions with more than 1 kb in size in the lung of mice. • The induction of large deletions at a dose rate of 1.5 mGy per hr was apparently suppressed by NNK treatments. • NNK treatments may induce protective mechanisms by which large deletions induced by g-irradiation are suppressed. • Mechanistic approach is needed to fully understand the combined effects of low dose rate radiation and chemical exposure.

  14. NIRS Wang Nenoi Hayata Masumura Ikeda Sakamoto Nohmi NIHS

  15. NNK treatments apparently suppressed largedeletion (> 1 kb) in the Lung of Mice exposed to g-radiation at a dose rate of 1.5 mGy per hour for 31 days Saline + Radiation NNK + Radiation 0.87 0.80 0.75 0.76 (7 / 43) (7 / 48) 0.9 0.9 (11 / 60) (10 / 61) 0.59 0.8 0.8 (7 / 60) 0.7 0.7 0.6 0.6 Specific mutation frequency (10-6) 0.24 0.27 0.25 0.5 0.5 0.4 (5 / 75) (2 / 42) (2 / 45) 0.4 0.3 0.3 0.2 0.2 0.1 0.1 0 0 0 0.5 1 1.5 0 0.5 1 1.5 Dose rate (mGy/h) Dose rate (mGy/h)

More Related