Search for thresholds in the effects of electromagnetic pulses at the level of the cell membrane – Oxylipi2

The cell membrane, which acts as a dielectric placed between conductive compartments (the physiological medium outside the cells and internal medium of the cell), is the site of the cell where the amplitude of the electromagnetic pulses is focused. Using electrical pulses with a duration of 10 nanoseconds, high field strength (several MV/m) and high frequency content, we showed that the principal effect on the cells is the electropermeabilization of their membranes. This effect does not depend on the amplitude of the field, or on the charge density in the external medium, but on the voltage difference generated at the cell membrane and the duration of the disturbance. Using lipid vesicles, we also showed that this electrical disturbance causes oxidation of membrane lipids that would be instrumental in the electropermeabilized state cells. On these vesicles, we detected and characterized by mass spectrometry the presence of oxidized lipids after the vesicles exposure to nanosecond pulses. The detection sensitivity of these changes by mass spectrometry seems to be greater than the detection of the electroporation of cells, and even more than the detection of thermal effects. We propose to study the thresholds of appearance of these changes depending on the amplitude, the number and the repetition frequency of electromagnetic pulses. Three types of signals will be delivered: electric pulses of 10 nanoseconds for which we have conditions for the controlled exposure of lipid vesicles and cells, ultra-wideband electromagnetic pulses and narrowband electromagnetic pulses. The study has two stages: the first is the exposure and analysis of vesicles (considered as ultra-simplified models of cells, easy to study) and the second is the exposure of cultured cells and the analysis of lipid membranes of these cells. In both cases, we will analyze the possible electropermeabilization of lipidic vesicles (detected by the transmembrane crossing of sugars as we have reported in M. Breton et al., J. Am. Chem. Soc., 134, 13938-41, 2012) and of cells (as detected by the transmembrane crossing of bleomycin as we have reported in A. Silve et al., Bioelectrochem., 87, 260-4, 2012). The impact of this project will consist, in terms of basic research, into an improved understanding of the mechanisms of cells electropermeabilization through the oxidation of membrane lipids, of the limits of experimental exposures that generate this oxidation, and into the extension of our observations to cells and to illuminations other than electrical signals of 10 nanoseconds. With regards to research interesting for the DGA, the impact of this project will consist of obtaining parameters of the specific effects potentially generated by ultra-wideband and narrowband electromagnetic pulses, therefore for setting exposure limits of the personnel to the electromagnetic pulses on the basis of a new highly sensitive method. We will also analyze if the thresholds of cell electropermeabilization, even reversible (i.e. without long-term consequences on cell survival) can potentially be reached.