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A dose threshold for a medium transfer bystander effect for a human skin cell line
Zhengfeng Liu1, Carmel E Mothersill, Fiona E McNeill
1Medical Physics and Applied Radiation Sciences Department, McMaster University, Hamilton, Ontario, Canada L8S 4K1. liuz7@mcmaster.ca
Radiation Research
|July 1, 2006
Summary
Low-dose radiation exposure may trigger bystander effects in cells, but a clear threshold remains elusive. This study suggests a survival-promoting effect below 2 mGy in human skin cells, unlike direct irradiation effects.
Area of Science:
- Radiobiology
- Cellular and Molecular Biology
- Radiation Oncology
Background:
- Radiation-induced bystander effects (RIBE) are cell signaling phenomena where unirradiated cells respond to radiation exposure.
- Mechanisms and dose-response relationships of RIBE, particularly at low radiation doses, require further elucidation.
- Understanding RIBE is crucial for accurate radiation risk assessment and radiation protection.
Purpose of the Study:
- To investigate the dose-response relationship of radiation-induced bystander effects at low gamma-ray doses.
- To determine the threshold dose for bystander effects in human skin cells.
- To compare bystander effects induced by gamma rays and neutrons at low doses.
Main Methods:
- Human skin cells were exposed to gamma radiation doses ranging from 0.04 mGy to 5 Gy.
- Culture medium from irradiated cells was transferred to unirradiated reporter cells.
- Reporter cells were analyzed for calcium fluxes and clonogenic survival.
- Comparative experiments were conducted using direct gamma irradiation and neutron irradiation.
Main Results:
- A dose threshold of approximately 2 mGy was observed for bystander effects in human skin cells, with potential survival enhancement below this dose.
- Direct gamma irradiation did not reduce cell survival until doses exceeded 7 mGy.
- Neutron irradiation did not induce significant bystander effects in the dose range of 1-33 mGy, nor at 1 Gy where direct irradiation caused cell killing.
Conclusions:
- A low-dose threshold exists for radiation-induced bystander effects in human skin cells, potentially involving hormetic effects.
- Bystander responses differ between gamma rays and neutrons, suggesting varying biological effectiveness at low doses.
- These findings have implications for understanding radiation biology and refining low-dose risk models.