Chronic Exposure to External Low-Dose Gamma Radiation Induces an Increase in Anti-inflammatory and Anti-oxidative Parameters Resulting in Atherosclerotic Plaque Size Reduction in ApoE–/– Mice
Résumé
Populations living in radiation-contaminated territories,
such as Chernobyl and Fukushima, are chronically exposed
to external gamma radiation and internal radionuclide
contamination due to the large amount of137Cs released in
the environment. The effect of chronic low-dose exposure on
the development of cardiovascular diseases remains unclear.
Previously reported studies have shown that low-dose
radiation exposure could lead to discrepancies according
to dose rate. In this study, we examined the effect of very
low-dose and dose-rate chronic external exposure on
atherosclerosis development. ApoE–/– mice were chronically
irradiated with a gamma source for 8 months at two
different dose rates, 12 and 28 lGy/h, equivalent to dose
rates measured in contaminated territories, with a cumulative
dose of 67 and 157 mGy, respectively. We evaluated
plaque size and phenotype, inflammatory profile and
oxidative stress status. The results of this study showed a
decrease in plaque sizes and an increase in collagen content
in ApoE–/– mice exposed to 28 lGy/h for 8 months compared
to nonexposed animals. The plaque phenotype was associated
with an increase in anti-inflammatory and antioxidative
gene expression. These results suggest that chronic
low-dose gamma irradiation induces an upregulation of
organism defenses leading to a decrease in inflammation
and plaque size. To our knowledge, this is the first study to
describe the possible effect of chronic external very low-dose
ionizing radiation exposure for 8 months. This work could
help to identify the potential existence of a dose threshold,
below that which harmful effects are not exhibited and
beneficial effects are potentially observed. Furthermore,
these findings permit consideration of the importance of
dose rate in radiation protection.
Domaines
Sciences du Vivant [q-bio]
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