Auteurs
Luukkonen J, Juutilainen J, Naarala J. Combined effects of 872 MHz radiofrequency radiation and ferrous chloride on reactive oxygen species production and DNA damage in human SH-SY5Y neuroblastoma cells. Bioelectromagnetics April 28, 2010 Ahead of print.

Background
Humans are continuously exposed to ionizing radiation from a variety of sources.  Exposure to other environmental factors is also common. Example of these exposures include e.g., chemicals, ultrafine particles, UV radiation, air pollutants. Some of these environmental agents share a common mechanism of action with radiofrequency fields (RF) which is inducing oxidative stress and DNA damage leading to mutations. One of the most important mechanisms leading to DNA damage, oxidative stress, is defined as an imbalance between reactive oxygen species (ROS) and antioxidant defenses. Therefore, it is important to study whether RF radiation is able to enhance the genotoxicity of known mutagens.  Previous studies investigating the combined effects of RF exposure and exposure to other genotoxins and mutagens have resulted in inconsistent results.

Objective
The aim of the current study is to gain a better understanding of the possible genotoxicity-enhancing effects of RF radiation; mechanisms for such effects need to be explored.  The specific exposures considered in this study are to investigate whether ferrous chloride FeCl2-induced oxidative stress is enhanced by RF.

Methodology
Human neuroblastoma cell cultures were used in this study. Cell cultures were maintained at 37° C in a humidified atmosphere containing 5% CO2 in 75 cm2 cell culture flasks. The cell cultures were exposed in 4 groups: (1) sham-exposed control, (2) RF radiation, (3) chemical treatment, and (4) chemical treatment RF radiation. RF radiation was emitted at a specific absorption rate (SAR) of 5 W/kg using continuous waves (CW) or a modulated signal similar to that used in Global System for Mobile Communications (GSM) phones. In the ROS experiments, 10 mg/ml ferrous chloride (FeCl2) was used for inducing an increase in ROS levels. Intracellular ROS levels were measured by using a fluorescent probe while Comet assay also known as single cell gel (SCG) electrophoresis assay, was used for quantifying DNA damage level in the cells.

Results
FeCl2 caused a statistically significant increase in ROS production at all time points. Exposure to RF radiation did not affect viability significantly, nor did 10 mg/ml FeCl2. Results from the Comet assay results showed no effect of exposure to RF radiation alone, FeCl2 alone, or from combined exposure to RF radiation and FeCl2.

Interpretation and conclusions
In this study, RF radiation did not alter intracellular ROS production (and hence DNA damage) either alone or in combination with FeCl2. This result is consistent with the some previous findings. The results also suggested that RF radiation with or without chemical co-exposure does not affect cell viability, which is also consistent with results from previous studies.

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