Ionizing radiation and atherosclerosis: current knowledge and future challenges.

The evaluation of the health effects of low-dose ionizing radiation has always been a focus of debate and investigation within the scientific community. During the last decade, epidemiological studies provided evidence that an excess risk of cardiovascular diseases (CVDs) can be associated with moderate and low dose radiation. The precise quantification of CVD risk in the low-dose radiation range (<500 mSv) is not well characterized, and it is unclear whether there is a threshold dose below which there is no risk. A limited number of studies with imaging surrogate endpoints and cardiovascular biomarkers in asymptomatic patients revealed early signs of cardiovascular alterations, even at a low dose. In vitro studies have shown that several mechanisms, including endothelial dysfunction, inflammation, oxidative stress, alterations of coagulation and platelet activity may have a relevant role in radiation-induced cardiovascular effects. Exposure to high-dose data in experimental models accelerates the development of atherosclerosis, predisposing to the formation of an inflammatory, thrombotic plaque phenotype, especially in animals that are genetically predisposed to this disease. On the contrary, low dose exposure produced both protective and detrimental effects, suggesting that multiple mechanisms may influence radiation-induced atherosclerosis. However, only very limited and specific information can be obtained from cell cultures and animal models. Planned studies of radiation-exposed cohorts need to be conducted to explore biological mechanisms of low-dose radiation-associated cardiovascular disease. Further investigations with functional imaging to assess vascular function and cardiovascular biomarkers have great potential for providing new insights into low-dose radiation cardiovascular risk, especially in occupational exposure and modern medicine.