Increased Circulating Cell-Free DNA Levels and mtDNA Fragments in Interventional Cardiologists Occupationally Exposed to Low Levels of Ionizing Radiation

Circulating cell-free DNA (ccf-DNA) and mtDNA (ccf-mtDNA) have often been used as indicators of cell death and tissue damage in acute and chronic disorders, but little is known about changes in ccf-DNA and ccf-mtDNA concentrations following radiation exposure. The aim of the study was to investigate the impact of chronic low-dose radiation exposure on serum ccf-DNA levels and ccf-mtDNA fragments (mtDNA-79 and mtDNA-230) of interventional cardiologists working in high-volume cardiac catheterization laboratory to assess their possible role as useful radiation biomarkers. We enrolled 50 interventional cardiologists (26 males; age=48.4 +/- 10 years) and 50 age- and gender-matched unexposed controls (27 males; age=47.6 +/- 8.3 years). Quant-iT dsDNA High-Sensitivity assay was used to measure circulating ccf-DNA isolated from serum samples. Quantitative analysis of mtDNA fragments was performed by real-time PCR. No significant relationships were found between ccf-DNA and ccf-mtDNA, and age, gender, smoking, or other clinical parameters. Ccf-DNA levels (44.2 +/- 31.1 vs. 30.6 +/- 19.2 ng/ml, P=0.013), ccf-mtDNA-79 (2.6 +/- 2.1 vs. 1.1 +/- 0.8, P < 0.01), and ccf-mtDNA-230 copies (2.0 +/- 1.8 vs. 1.04 +/- 0.9, P=0.02) were significantly higher in interventional cardiologists compared with the non-exposed group. In a subset (n=15) of interventional cardiologists with a reliable reconstruction of cumulative professional exposure (59.7 +/- 48.4 mSv; range: 1.4-182 mS), ccf-DNA (53.2 +/- 41.3 vs. 36.4 +/- 22.9 and 32.2 +/- 20.5, P=0.08), mtDNA-79 (2.4 +/- 2.1 vs. 2.03 +/- 1.7 and 1.09 +/- 0.82, P=0.05), and mtDNA-230 (2.0 +/- 2.2 vs. 1.5 +/- 1.4 and 1.04 +/- 0.9, P=0.09) tended to be significantly increased in high-exposure subjects compared with both low-exposure interventional cardiologists and controls. Our results provide evidence for a possible role of circulating DNA as a relevant biomarker of cellular damage induced by exposure to chronic low-dose radiation. Environ. Mol. Mutagen. 56:293-300, 2015. (c) 2014 Wiley Periodicals, Inc.