Decreased spontaneous electrical activity in neuronal networks exposed to radiofrequency 1,800 MHz signals.

The rapid development of wireless communications has raised questions about their potential health risks. So far, the only identified biological effects of radiofrequency fields (RF) are known to be caused by heating, but the issue of potential nonthermal biological effects, especially on the central nervous system (CNS), remains open. We previously reported a decrease in the firing and bursting rates of neuronal cultures exposed to a Global System for Mobile (GSM) RF field at 1,800 MHz for 3 min (Moretti D, Garenne A, Haro E, Poulleier de Gannes F, Lagroye I, Lévêque P, Veyret B, Lewis N. Bioelectromagnetics 34: 571-578, 2013). The aim of the present work was to assess the dose-response relationship for this effect and also to identify a potential differential response elicited by pulse-modulated GSM and continuous-wave (CW) RF fields. Spontaneous bursting activity of neuronal cultures from rat embryonic cortices was recorded using 60-electrode multielectrode arrays (MEAs). At 17-28 days in vitro, the neuronal cultures were subjected to 15-min RF exposures, at specific absorption rates (SAR) ranging from 0.01 to 9.2 W/kg. Both GSM and CW signals elicited a clear decrease in bursting rate during the RF exposure phase. This effect became more marked with increasing SAR and lasted even beyond the end of exposure for the highest SAR levels. Moreover, the amplitude of the effect was greater with the GSM signal. Altogether, our experimental findings provide evidence for dose-dependent effects of RF signals on the bursting rate of neuronal cultures and suggest that part of the mechanism is nonthermal. NEW & NOTEWORTHY In this study, we investigated the effects of some radiofrequency (RF) exposure parameters on the electrical activity of neuronal cultures. We detected a clear decrease in bursting activity, dependent on exposure duration. The amplitude of this effect increased with the specific absorption rate (SAR) level and was greater with Global System for Mobile signal than with continuous-wave signal, at the same average SAR. Our experiment provides unique evidence of a decrease in electrical activity of cortical neuronal cultures during RF exposure.

Full-Spectral Multiplexing of Bioluminescence Resonance Energy Transfer in Three TRPV Channels.

Multiplexed bioluminescence resonance energy transfer (BRET) assays were developed to monitor the activation of several functional transient receptor potential (TRP) channels in live cells and in real time. We probed both TRPV1 intramolecular rearrangements and its interaction with Calmodulin (CaM) under activation by chemical agonists and temperature. Our BRET study also confirmed that: (1) capsaicin and heat promoted distinct transitions, independently coupled to channel gating, and that (2) TRPV1 and Ca2+-bound CaM but not Ca2+-free CaM were preassociated in resting live cells, while capsaicin activation induced both the formation of more TRPV1/CaM complexes and conformational changes. The BRET assay, based on the interaction with Calmodulin, was successfully extended to TRPV3 and TRPV4 channels. We therefore developed a full-spectral three-color BRET assay for analyzing the specific activation of each of the three TRPV channels in a single sample. Such key improvement in BRET measurement paves the way for the simultaneous monitoring of independent biological pathways in live cells.

Effects of GSM and UMTS mobile telephony signals on neuron degeneration and blood-brain barrier permeation in the rat brain.

Blood-brain barrier (BBB) permeation and neuron degeneration were assessed in the rat brain following exposure to mobile communication radiofrequency (RF) signals (GSM-1800 and UMTS-1950). Two protocols were used: (i) single 2 h exposure, with rats sacrificed immediately, and 1 h, 1, 7, or 50 days later, and (ii) repeated exposures (2 h/day, 5 days/week, for 4 weeks) with the effects assessed immediately and 50 days after the end of exposure. The rats' heads were exposed at brain-averaged specific absorption rates (BASAR) of 0.026, 0.26, 2.6, and 13 W/kg. No adverse impact in terms of BBB leakage or neuron degeneration was observed after single exposures or immediately after the end of repeated exposure, with the exception of a transient BBB leakage (UMTS, 0.26 W/kg). Fifty days after repeated exposure, the occurrence of degenerating neurons was unchanged on average. However, a significant increased albumin leakage was detected with both RF signals at 13 W/kg. In this work, the strongest, delayed effect was induced by GSM-1800 at 13 W/kg. Considering that 13 W/kg BASAR in the rat head is equivalent to 4 times as much in the human head, deleterious effects may occur following repeated human brain exposure above 50 W/kg.