24th International Conference on Nuclear Tracks in Solids Bologna, 1-5 September 2008 Study of influence of Study of influence of catechins on bystander catechins on bystander responses in alpha-particle responses in alpha-particle radiobiological experiments radiobiological experiments using thin PADC films using thin PADC films Y.L. Law and K.N. Yu Department of Physics and Materials Science, City University of Hong Kong
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24th International Conference on Nuclear Tracks in Solids Bologna, 1-5 September 2008
24th International Conference on Nuclear Tracks in Solids Bologna, 1-5 September 2008. Study of influence of catechins on bystander responses in alpha-particle radiobiological experiments using thin PADC films Y.L. Law and K.N. Yu Department of Physics and Materials Science, - PowerPoint PPT Presentation
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24th International Conference on Nuclear Tracks in Solids
Bologna, 1-5 September 2008
Study of influence of catechins Study of influence of catechins on bystander responses in on bystander responses in
alpha-particle radiobiological alpha-particle radiobiological experiments using thin PADC experiments using thin PADC
filmsfilms
Y.L. Law and K.N. YuDepartment of Physics and Materials Science,
City University of Hong Kong
24th International Conference on
Nuclear Tracks in Solids
Bologna, 1-5 September 2008ObjectivesObjectives
1. To investigate the relationship between the radiation dose and induction of DNA damages
in unirradiated cells
2. To investigate the scavenging effect of catechins
on reactive oxygen species in unirradiated cells.
24th International Conference on
Nuclear Tracks in Solids
Bologna, 1-5 September 2008IntroductionIntroduction
Radiobiological effects of ionizing radiation
Alpha particle
• Interacts with DNA Double-strand breaks (DSBs) • Free radicals DSBs
DSBs
• Most lethal• Cell death, chromosome aberration, gene mutation…
24th International Conference on
Nuclear Tracks in Solids
Bologna, 1-5 September 2008IntroductionIntroduction
Detect and quantify fluorescein labels using laser beamCounting of 10000 cells
24th International Conference on
Nuclear Tracks in Solids
Bologna, 1-5 September 2008MethodologyMethodology
21
3 4
Fixation
Capture image
Etching 37
℃
14 N KOH solution
Capture image of tracks and
cells
IR cells
24th International Conference on
Nuclear Tracks in Solids
Bologna, 1-5 September 2008Results and Results and DiscussionsDiscussionsNumber of cell hits
After fixation (CHO cells
only)
After etching(CHO cells and tracks)
Alpha-particle track
CHO cells
24th International Conference on
Nuclear Tracks in Solids
Bologna, 1-5 September 2008Results and Results and DiscussionsDiscussions
• As low as 1% of the cell nuclei were actually traversed by alpha particles in all the samples
• Bystander damages occur even at very low doses
• DNA damages in bystander cells seems to be independent of the number of irradiated cells
Number of cell hits
24th International Conference on
Nuclear Tracks in Solids
Bologna, 1-5 September 2008Results and Results and DiscussionsDiscussions
0 μM 1μM 10 μM 20 μM
* *
**
*P < 0.05, **P < 0.005 compared to the corresponding control (0 μM)
Results of TUNEL assay
For example:
Bystander sample= 33.75%
Unirradiated control
= 17.22%
Result: 16.33% of TUNEL positive
signal
24th International Conference on
Nuclear Tracks in Solids
Bologna, 1-5 September 2008Results and Results and DiscussionsDiscussions
0 μM 1μM 10 μM 20 μM
* *
**
*P < 0.05, **P < 0.005 compared to the corresponding control (0 μM)
Without any treatment
Results of TUNEL assay
Signal transduction from irradiated cells to bystander cells occurred within a short time
24th International Conference on
Nuclear Tracks in Solids
Bologna, 1-5 September 2008Results and Results and DiscussionsDiscussions
0 μM 1μM 10 μM 20 μM
* *
**
*P < 0.05, **P < 0.005 compared to the corresponding control (0 μM)
Results of TUNEL assay
24th International Conference on
Nuclear Tracks in Solids
Bologna, 1-5 September 2008Results and Results and DiscussionsDiscussions
Results of TUNEL assay
• Scavenging effect of EGCG in 1 μM on bystander cells is the most significant
• Previous study showed EGCG significantly reduced the amount of DNA strand breaks in 1-2 μM concentrations (Anderson et al., 2001)
• ROS might be involved in the induction of DNA breaks
Anderson, R.F., Fisher, L.J., Hara, Y., Harris, T., Mak, W.B., Melton, L.D., Packer, J.E., 2001. Green tea catechins partially protect DNA from OH radical-induced strand breaks and base damage through fast chemical repair of DNA radicals. Carcinogenesis. 22(8), 1189-93.