Low dose radiation could harm cardiovascular health

Posted By News On July 14, 2017 - 2:22pm

The controversial linear no-threshold model (LNT) model has long been used by the US Nuclear Regulatory Commission as a conservative model for estimating radiation risk, but it is not without critics. People who visit a beach in Brazil, with extremely high levels of radiation, instead believe it has recuperative powers, and studies have shown similar effects.

And then groups like the International Agency for Research on Cancer, which simply look at epidemiology claims and calculate hazard, even find non-ionizing radiation like cell phones hazardous, though those finding have been cast into doubt since the discovery that Chris Portier, Ph.D., was secretly being paid by Environmental Defense Fund while he was guiding IARC Working Group selection and did not disclose his conflict of interest.

A new paper helps people who believe low levels of radiation are harmful and suggests that low exposure to doses of around 0.5 Gy (the equivalent of repeated CT scans) is associated with a significantly increased risk of cardiovascular damage, up to decades after exposure. This raises questions about the nature of long-term alterations in the heart's vascular system caused by such doses, at least in a cell study.

Drs. Soile Tapio and Omid Azimzadeh of Helmholtz Zentrum München, German Research Center for Environmental Health and colleagues studied how human coronary artery endothelial cells respond to a relatively low radiation dose of 0.5 Gy and found several permanent alterations in the cells that had the potential to adversely affect their essential functions. Endothelial cells, which form the inner layer of blood vessels, were found to produce reduced amounts of nitric oxide, an essential molecule in several physiological processes including vascular contraction. Previously, high-dose radiation (16 Gy) has been shown to persistently reduce levels of nitric oxide in the serum of mice, but this is the first study to indicate impaired nitric oxide signaling at much lower doses.

Cells damaged by low-dose radiation also produced increased amounts of reactive oxygen species (ROS), which are formed as a natural byproduct of normal oxygen metabolism and play an important role in cell signaling. Increased ROS can damage DNA and proteins, which is why supplement buyers think "antioxidant" supplements can help them.

In addition, exposed cardiac endothelial cells were found to have reduced capacity to degrade oxidized proteins and to be aging prematurely. Such harmful changes did not occur immediately (that is, within a day) but first began in the longer term (one to two weeks). As these cells do not divide rapidly in the body, this observed time in the cell culture would correspond to several years in the living organism.

All these molecular changes are indicative of long-term premature dysfunction and suggest a mechanistic explanation to the epidemiological data showing increased risk of cardiovascular disease after low-dose radiation exposure, the authors conclude.