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Étude en temps réel des effets cellulaires et moléculaires des champs électromagnétiques radiofréquence environnementaux

Abstract : The biological and health effects of radiofrequency (RF) electromagnetic fields (EMF) exposure have been very actively studied in the past two decades, mainly triggered by concerns about potential health effects of wireless communication systems. This physical agent is among the most common, fastest-growing environmental factors, triggering concerns in the population, as even a minor effect of EMF exposure on health could have a major public health impact. While the effects of extremely low frequency electromagnetic fields (ELF EMF) on the excitation of nerve and muscle cells have been well-characterized, the only well-described effects of radiofrequency electromagnetic fields (RF EMF) on biological systems are caused by dielectric-relaxation heating. In contrast, “nonthermal” RF EMF effects refer to other potential biological effects that are not caused by temperature elevation of living tissue or cell culture medium. The investigation of such mechanisms has been hampered by the absence of robust, reliable and repeatable effects occurring as a consequence of low-level exposures, for which temperature elevation is minimal. Moreover, no plausible mechanistic hypotheses have been given concerning thermal or nonthermal effects of low-level RF EMF exposures, making difficult to draw conclusions on the basis of available experimental results. Nonetheless, in 2011, the International Agency for Research on Cancer (IARC) classified RF emitted by cell phones as “possibly carcinogenic to humans” (Class 2B). The characterization of nonthermal biological RF EMF effects is therefore of primary importance for setting safety limits since guidelines and standards have so far been set to protect from the known health risks associated only with the thermal effects of RF EMF exposures. The aim of this basic science thesis work is to characterize the effects of environmental RF EMF signals on living matter at the cellular and molecular level. In this work, we took advantage of modern and innovative methods to observe the behavior of living matter under RF EMF exposure in real time at various specific absorption rates (SAR). In particular, we have studied: (i) Specific RF EMF effects on the ionic channel TRPV1, a major thermoreceptor in our body. TRPV1 activation under RF EMF exposure was studied using the bioluminescence resonance energy transfer (BRET) technique. The implementation of this technique called for the construction and characterization of BRET probes targeting TRP channels as well as the development of a device for the remote measurement of BRET spectra, using an optical fiber. The conclusion of this part of the thesis is that RFs are able to activate the TRPV1 channel by producing a dielectric heating but in the absence of temperature increase there is no RF effect on the basal activation state of TRPV1 and no change of capsaicin maximal efficacy to activate TRPV1. (ii) The analysis of the global behavior of cells in culture under RF exposure was carried out using a modified xCELLigence system where the array of electrodes of the measuring plates were also used to expose the cells to RF EMF. Using this device, we were able to perform SH-SY5Y cell exposures with a SAR of 24 W/kg without causing heating in the culture medium or in the cell culture. No effect of RF EMF on the behavior of the neuroblastoma SH-SY5Y line could however be demonstrated, either in the absence or in the presence of a co-stimulation by a chemical agent. The conclusion of this study is that under conditions where the temperature remains stable, we have not been able to demonstrate any changes in the functioning of living cells, ether at the molecular level or at the cellular level. The tools developed in this thesis work offer important prospects both in the field of drug screening using spectral BRET, and pave the ways for future studies in bioelectromagnetics.
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Hermanus Ruigrok. Étude en temps réel des effets cellulaires et moléculaires des champs électromagnétiques radiofréquence environnementaux. Biochimie [q-bio.BM]. Université de Bordeaux, 2017. Français. ⟨NNT : 2017BORD0674⟩. ⟨tel-01782402v2⟩

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