Genotoxicity Induced by Foetal and Infant Exposure to Magnetic Fields and Modulation of Ionising Radiation Effects

Abstract

Background: Few studies have investigated the toxicity and genotoxicity of extremely low frequency magnetic fields (ELF-MF) during prenatal and neonatal development. These phases of life are characterized by cell proliferation and differentiation, which might make them sensitive to environmental stressors. Although in vitro evidences suggest that ELF-MF may modify the effects of ionizing radiation, no research has been conducted so far in vivo on the genotoxic effects of ELF-MF combined with X-rays.

Aim and methods: Aim of this study was to investigate in somatic and germ cells the effects of chronic ELF-MF exposure from mid gestation until weaning, and any possible modulation produced by ELF-MF exposure on ionizing radiation-induced damage. Mice were exposed to 50 Hz, 65 μT magnetic field, 24 hours/day, for a total of 30 days, starting from 12 days post-conception. Another group was irradiated with 1 Gy X-rays immediately before ELF-MF exposure, other groups were only X-irradiated or sham-exposed. Micronucleus test on blood erythrocytes was performed at multiple times from 1 to 140 days after birth. Additionally, 42 days after birth, genotoxic and cytotoxic effects on male germ cells were assessed by comet assay and flow cytometric analysis.

Results: ELF-MF exposure had no teratogenic effect and did not affect survival, growth and development. The micronucleus test indicated that ELF-MF induced a slight genotoxic damage only after the maximum exposure time and that this effect faded away in the months following the end of exposure. ELF-MF had no effects on ionizing radiation (IR)-induced genotoxicity in erythrocytes. Differently, ELF-MF appeared to modulate the response of male germ cells to X-rays with an impact on proliferation/differentiation processes. These results point to the importance of tissue specificity and development on the impact of ELF-MF on the early stages of life and indicate the need of further research on the molecular mechanisms underlying ELF-MF biological effects.

Fig 1. Micronucleus frequencies in peripheral blood erythrocytes.

The number of animals in each group is reported inside the histogram columns. Bars represent standard error. Significance compared to C: * p<0.05; ** p<0.01; *** p<0.001.

Fig 2. (A) Relative testicular weights (testis weight/body weight * 100); (B) percentages of 1C post meiotic cells as evaluated by DNA content flow cytometric analysis of whole testis cells; (C) sperm number in cauda epididymis.

Columns represent the mean values of 7 controls (C), 11 ELF-MF exposed (E), 14 X-rays exposed (X), or 11 animals exposed to combined treatments (XE). Asterisks mark statistically different values between groups, *: p<0.05; **: p<0.005.

Fig 3. Comet assay in epididymal sperm.

(A) Mean tail intensity values obtained with alkaline and neutral comet assay. (B) Percentage of sperm carrying clearly damaged DNA (with tail intensity values higher than 10%) after neutral assay. Columns represent the mean values of 4 controls (C), 5 ELF-MF exposed (E), 8 X-rays exposed (X), or 6 animals exposed to combined treatments (XE).