Low levels of ionising radiation can be harmful to the cardiovascular system, according to a new German study.
Research published in the latest edition of the International Journal of Radiation Biology, today (13 July 2017) claims that low exposure to doses of about 0.5 Gy – the equivalent of repeated CT scans – is associated with a significantly increased risk of cardiovascular damage, even decades after exposure.
The authors say this raises questions about the nature of long-term alterations in the heart’s vascular system caused by such doses.
Dr Soile Tapio and Dr Omid Azimzadeh, of Helmholtz Zentrum München, German Research Centre for Environmental Health, and colleagues found several permanent alterations in the human coronary artery endothelial cells that had the potential to adversely affect their essential functions when they respond to a radiation dose of 0.5 Gy.
They discovered that endothelial cells produce reduced amounts of nitric oxide, which is an essential molecule in several physiological processes including vascular contraction.
Although it has been shown that high-dose radiation of 16 Gy persistently reduces levels of nitric oxide in the serum of mice, this is the first study to suggest there is impaired nitric oxide signalling at much lower doses.
The researchers also found that cells damaged by low-dose radiation produce increased amounts of reactive oxygen species (ROS), which are formed as a natural by-product of normal oxygen metabolism and play an important role in cell signalling. Increased ROS can damage DNA and proteins.
Exposed cardiac endothelial cells were found to have reduced capacity to degrade oxidised proteins and to be ageing prematurely. Such harmful changes did not occur within a day but first began in one to two weeks.
The research team say these molecular changes indicate long-term premature dysfunction and suggest a mechanistic explanation to the epidemiological data showing increased risk of cardiovascular disease after low-dose radiation exposure.
Azimzadeh O, Subramanian V, Ständer S et al. International Journal of Radiation Biology; Proteome analysis of irradiated endothelial cells reveals persistent alteration in protein degradation and the RhoGDI and NO signalling pathways. International Journal of Radiation Biology 13 July 2017 [abstract]
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