Speaker
Mrs
Ana Belchior
(Instituto Superior Técnico, Instituto Tecnológico e Nuclear)
Description
The need to better understand the risk associated with the exposure to low doses of ionizing radiation is the driving force of several studies currently being performed. In view of adaptive responses, bystander effects and cell death, the validity of the linear non-threshold relationship between dose and subsequent effects has been challenged. The way cell populations react to low radiation doses cannot be fully explained with a model obtained extrapolating to the low dose region the behavior of cells´ response to high radiation doses. Bystander effects are non-targeted effects induced in cells that were not irradiated but were in contact with irradiated ones or received signals from the culture medium. Cell death therefore appears to be a main safeguard mechanism, in particular necrosis or apoptosis. In the low dose region either bystander effects or cell death are pivotal to understand the underlying mechanisms of cellular response.
The aim of the present study was to evaluate the influence of the number of irradiated cells in the non-irradiated areas. To analyze the spatial effects of the bystander signal, according with the number of irradiated cells, we exposed only a part of the cells plated on the cell dish to α-particles. The cell dish has 3.5 cm of diameter and depending on the study, approximately, 3/4 or 1/2 of this area was shielded by aluminum foils, being the irradiated areas differ from each other by a factor of 2. In order to pursue this objective a human lung cancer cell line, A549, was exposed to several doses of α-particles emitted by 210Po, namely 5, 10, 50 and 100 mGy. The non-irradiated areas were divided in two concentric areas with the same number of cells. Making use of the radiation induced extranuclear/extracellular technique γ-H2AX, we quantified, in situ the cellular damage, by means of DSBs and using the apo-trace organic molecule we quantified the cell death via apoptosis.
Our results indicate that the cellular induced damage decrease with the distance to the irradiated area. In addition, we observed an increase of cellular damage in the non-irradiated areas when a higher number of irradiated cells are considered. We can also conclude that the number of irradiated cells influence the cellular damage induced in non-irradiated areas that were either in contact with or received signals from irradiated cells.
Primary author
Mrs
Ana Belchior
(Instituto Superior Técnico, Instituto Tecnológico e Nuclear)
Co-authors
Dr
Octávia Monteiro Gil
(Instituto Superior Técnico, Instituto Tecnológico e Nuclear)
Dr
Pedro Almeida
(Universidade de Lisboa, Faculdade de Ciências, Instituto de Biofísica e Engenharia Biomédica)
Dr
Pedro Vaz
(Instituto Superior Técnico, Instituto Tecnológico e Nuclear)
