Objective To study the role of reactive oxygen species (ROS) in adaptive response induced by 900 MHz microwave radiation in mouse bone marrow stromal cells (BMSCs) exposed to γ rays.
Methods BMSCs were pre-exposed to 900 MHz radiofrequency fields (RF) at 120 μW/cm2 power intensity for 4 h/d for 5 d and then subjected to an acute dose of 1.5 Gy γ-ray radiation. The level of DNA strand breaks was assessed by alkaline comet assay and γ-H2AX foci technique to confirm adaptive response induced by microwave radiation. The cells were exposed to 500 nmol/L melatonin (an inhibitor for ROS) 4 h prior to the RF exposure to measure the level of ROS using flow cytometer and confirm adaptive response.
Results The cells exposed to RF showed a significantly increase of ROS (2.10) as compared to the control group (1.16) (P < 0.01). The cells preexposed to RF showed significant decreased DNA damage as well as reduced tail length, tail moment, and γ-H2AX foci (8.57 μm, 2.58, and 5.28, respectively) compared with those exposed to γ-radiation alone (21.62 μm, 5.68, and 19.73, respectively) (P < 0.001), indicating that RF induced adaptive response. However, when the cells were subjected to melatonin prior to RF, the ROS level was decreased to 1.53 (P < 0.01), and the DNA damage induced by subsequent γ-ray radiation decreased significantly as the tail length, tail moment, and γ-H2AX foci were increased (17.90 μm, 4.10, and 20.8, respectively) (P < 0.001), indicating that adaptive response was inhibited.
Conclusion ROS might play a role in the adaptive response induced by 900 MHz radiofrequency field at 120 μW/cm2 power density.
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