Adaptive response in human blood lymphocytes exposed to non-ionizing radiofrequency fields: resistance to ionizing radiation-induced damage

Abstract

The aim of this preliminary investigation was to assess whether human peripheral blood lymphocytes which have been pre-exposed to non-ionizing radiofrequency fields exhibit an adaptive response (AR) by resisting the induction of genetic damage from subsequent exposure to ionizing radiation. Peripheral blood lymphocytes from four healthy donors were stimulated with phytohemagglutinin for 24 h and then exposed for 20 h to 1950 MHz radiofrequency fields (RF, adaptive dose, AD) at an average specific absorption rate of 0.3 W/kg. At 48 h, the cells were subjected to a challenge dose (CD) of 1.0 or 1.5 Gy X-irradiation (XR, challenge dose, CD). After a 72 h total culture period, cells were collected to examine the incidence of micronuclei (MN). There was a significant decrease in the number of MN in lymphocytes exposed to RF + XR (AD + CD) as compared with those subjected to XR alone (CD). These observations thus suggested a RF-induced AR and induction of resistance to subsequent damage from XR. There was variability between the donors in RF-induced AR. The data reported in our earlier investigations also indicated a similar induction of AR in human blood lymphocytes that had been pre-exposed to RF (AD) and subsequently treated with a chemical mutagen, mitomycin C (CD). Since XR and mitomycin-C induce different kinds of lesions in cellular DNA, further studies are required to understand the mechanism(s) involved in the RF-induced adaptive response.

Keywords: X-rays; adaptive response; human lymphocytes; micronucleus; radiofrequency.

Fig. 1.

Arrangement of Petri dishes in the waveguide. Lymphocytes cultures in Petri dishes are kept in the outer positions (0.3 W/kg SAR), while dummy samples are located in the inner ones.

Fig. 2.

RF exposure set up. Schematic presentation of the set-up used to expose the cells to 1950 MHz (UMTS signal) radiofrequency field/sham. The signal generator and power sensors are connected to a computer installed with home-made software for continuous monitoring and recording of the power level as it was adjusted to achieve the required 0.3 W/kg SAR.

Fig. 3.

Experimental protocols. Panel A: exposure of cultures to X-rays (XR). AD_XR: adaptive dose of 1.0 cGy XR. CD_XR: challenge dose of 1.0 or 1.5 Gy XR; Panel B: exposure of RF/sham experimental cultures. AD_RF: adaptive dose of 1950 MHz RF at 0.3 W/kg SAR. CD_XR: challenge dose of 1.0 or 1.5 Gy XR; Panel C: treatment of cultures using MMC. AD_MMC: adaptive dose of 1 ng/ml MMC. CD_MMC: challenge dose of 100 ng/ml MMC.