Comet assay as a procedure for detecting possible genotoxicity induced by non-ionizing radiation

• Main Author: Zsuzsanna Nemeth
• Format: Article
• Language: English
• Published: Frontiers Media S.A. 2015-05-01
• Series: Frontiers in Genetics
• Subjects: Comet Assay; DNA Damage; DNA Repair; Genotoxicity; non-ionising radiation
• Online Access: http://journal.frontiersin.org/Journal/10.3389/conf.fgene.2015.01.00014/full

Non-ionizing radiation (NIR) is the term given to radiation in the part of the electromagnetic spectrum that does not have enough energy to ionize atoms or molecules directly. The NIR includes electric and magnetic fields up to 300 GHz, infrared, visible, and ultraviolet radiation (UV). People are exposed to non-ionizing radiation by several man-made sources every day. From highest to lowest energy, this includes for example microwave ovens, cell phones, baby monitors, cordless phones, garage-door openers etc. Extremely low frequency (ELF) waves are produced by high voltage power lines and indoor electrical wiring systems. Radiofrequency (RF) waves can cause tissue heating at high intensities. Some forms of non-ionizing radiation can induce damage of tissues if exposed to high intensity fields. For instance, exposure to ultraviolet light from the sun for a prolonged period of time is known to cause skin cancers (Narayanan et al., 2010); even moderate amounts can cause skin burns. There is a big concern amongst the public and authorities regarding possible adverse health effects from exposure to electromagnetic fields (EMFs), in particular the radiation generated by power lines and wireless communication devices. In 2002 the International Agency for Research on Cancer (IARC) concluded that extremely low frequency magnetic fields (from power lines) are possibly carcinogenic (Group 2B of IARC classification). The same conclusion was reached in 2011 with respect to radiofrequency fields from mobile phones. UVB and UVA radiation has been classified by IARC as Group I: the agent is carcinogenic to humans. It is therefore not surprising that a lot of research was (and still is) devoted to the investigation of biological effects of non-ionizing radiation. In many cases the link has been established between genotoxicity and carcinogenicity and the possibility that non-ionising radiations including EMFs are carcinogenic so it follows that studies on the mutagenicity and genotoxicity of such agents are also important issues. In our laboratory we use comet assay for testing genotoxicity of non-ionizing radiation for more than ten years. In the experiments we use whole blood samples (human or dog), cell lines (e.g. H295R cell line) or 3 dimensional in vitro skin tissue (epidermis) models. In our protocol a slightly modified alkaline Comet assay method of Singh et al. (1988) is used. On our poster there will be presented a brief summary of our experiments with exposure to different types of radiation (ELF, RF, and intermediate frequency). In our protocols the non-ionizing radiation was often combined with ionizing radiation to see whether the non-ionizing radiation can influence the repair of the DNA damage induced by ionizing radiation. For the evaluation of the slides mainly Komet 4.0 image analysis system software (Kinetic Imaging, Liverpool, UK) was used, but as we got familiarized with other methods for slide evaluation like grading the comets by visual scoring into 5 categories or the CaspLab software, the comparison of these three methods will be also presented.