Increased apoptosis and DNA double-strand breaks in the embryonic mouse brain in response to very low-dose X-rays but not 50 Hz magnetic fields

Abstract

The use of X-rays for medical diagnosis is enhancing exposure to low radiation doses. Exposure to extremely low-frequency electromagnetic or magnetic fields is also increasing. Epidemiological studies show consistent associations of childhood leukaemia with exposure to magnetic fields but any causal relationship is unclear. A limitation in assessing the consequence of such exposure is the availability of sensitive assays. The embryonic neuronal stem and progenitor cell compartments are radiosensitive tissues. Using sensitive assays, we report a statistically significant increase in DNA double-strand break (DSB) formation and apoptosis in the embryonic neuronal stem cell compartment following in utero exposure to 10–200 mGy X-rays. Both endpoints show a linear response. We also show that DSB repair is delayed following exposure to doses below 50 mGy compared with 100 mGy. Thus, we demonstrate in vivo consequences of low-dose radiation. In contrast to these impacts, we did not observe any significant induction of DSBs or apoptosis following exposure to 50 Hz magnetic fields (100 or 300 µT). We conclude that any DSB induction by treatment with magnetic fields is lower than following exposure to 10 mGy X-rays. For comparison, certain procedures involving computed tomography scanning are equivalent to 1–5 mGy X-rays.

The effects of extremely low frequency magnetic fields on mutation induction in mice

“…These findings are in conjunction with those of Scarfi and coauthors (2005) and more recently still Saha and co-authors (2014). Whilst using similar experimental parameters (50 Hz intermittent, (5 min on/10 min off) magnetic field at 300 µT for 15 hours), the findings of Saha et al (2014) provide further evidence of an inability of ELF-MFs to cause direct DNA damage. Owing to its rapid recruitment to sites following the introduction of DNA DSBs, Saha and co-authors quantified the tumour suppressor p53 binding protein 1 (53BP1) foci numbers as a direct signalling response to the formation of DSBs.…”

“…This in turn enabled the authors to detect a statistically significant increase in 53BP1 foci following a 10 mGy dose X-rays. Though, the minimum detectable response was calculated to equate to approximately 0.233 DSB per cell, which corresponds to an estimated dose of 22 mGy (Saha et al, 2014 While ELF-MF could potentially be carcinogenic, the culmination of these findings appears to support the inability of ELF-MF exposure to cause a direct carcinogenic effect and fundamentally any potential role in the initiation of carcinogenesis can be confidently excluded. However, as was previously mentioned, the current understanding in the causation of cancer points to at least a two pathway system, the first of which being a genotoxic pathway while the second assumes ELF-MF partakes in an epigenetic role (Vijayalaxmi & Obe, 2005).…”

“…Despite this, the majority of studies conducted to date have found no consistent evidence of magnetic field induced effects on genotoxicity using an array of field intensities: 0.001-1 mT (Paile et al, 1995;Luceri et al, 2005;Stronati et al, 2004;Testa et al, 2004;Luukkonen et al, 2011;Saha et al, 2014), and 5-400 mT (Antonopoulos et al, 1995;Tateno et al, 1998;Miyakoshi et al, 2000). Yet there have also been several studies, both in vivo and in vitro where positive correlations have been reported; for example a significant three-fold elevation in SCE was observed in mouse m5S cells exposed to 400 mT (50 Hz) for 40 hours (Yaguchi et al, 1999).…”

Toxicogenetic biomonitoring of occupational risk induced by ionizing radiation

“…Epidemiological studies show an association between IR at low doses (1 to 5 mGy) and development of leukemia. Leukemia is a complex disease that may have etiologies related to the lifestyle and occupational and environmental exposure, but there are also associations between leukemia (Polychronakis et al, 2013) due to genetic instability related to increased single and double strand DNA breaks that can lead to the chromosomal alterations and formation of MN (Saha et al, 2014), as noted in mutagenicity analysis of professionals occupationally exposed to IR in this study. There are also reports that IR can lead to apoptosis, as observed in embryonic neuronscells (Leuraud et al, 2015).…”

Human umbilical cord blood stem cells applied in therapy for ionizing radiation injury

“…And sometimes may produce a series of biological effects on the body that causing radiation damage. Such as human hematopoietic system, immune system, nervous system and reproductive system damage or irreversible lesions likes cancer [1].…”