Biological effects of ultrashort electric pulses in a neuroblastoma cell line: the energy density role

Abstract

Background

Despite the numerous literature results about biological effects of electromagnetic field (EMF) exposure, the interaction mechanisms of these fields with organisms are still a matter of debate. Extremely low frequency (ELF) MFs can modulate redox homeostasis and we showed that 24 h exposure to 50 Hz–1 mT has a pro-oxidant effect and effects on the epigenome of SH-SY5Y cells, decreasing miR-34b/c expression through the hypermethylation of their promoter.

Methods

Here, we investigated the role of the electromagnetic deposited energy density (ED) during exposures lasting 24 h to 1 mT amplitude MFs at a frequency of 50 Hz in inducing the above mentioned effects. To this end, we delivered ultrashort electric pulses, in the range of microsecond and nanosecond duration, with the same ED of the previously performed magnetic exposure to SH-SY5Y cells. Furthermore, we explored the effect of higher deposited energy densities. Analysis of i) gene and microRNA expression, ii) cell morphology, iii) reactive oxygen species (ROS) generation, and iv) apoptosis were carried out.

Results

We observed significant changes in egr-1 and c-fos expression at very low deposited ED levels, but no change of the ROS production, miR-34b/c expression, nor the appearance of indicators of apoptosis. We thus sought investigating changes in egr-1 and c-fos expression caused by ultrashort electric pulses at increasing deposited ED levels. The pulses with the higher deposited ED caused cell electroporation and even other morphological changes such as cell fusion. The changes in egr-1 and c-fos expression were more intense, but, again, no change of the ROS production, miR-34b/c expression, nor apoptosis induction was observed.

Conclusions

These results, showing that extremely low levels of electric stimulation (never investigated until now) can cause transcriptional changes, also reveal the safety of the electroporating pulses used in biomedical applications and open up the possibility to further therapeutic applications of this technology.

Keywords:

• Energy density
• extremely low frequency magnetic fields
• ultra-short electric pulses
• SH-SY5Y
• immediate early genes

Acknowledgments

We are especially grateful to Professor Tom Vernier for the thorough revision of English and the critical reading of the manuscript. The authors also want to thank Francesca Pacchierotti for her helpful critical review of the manuscript.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article.

Additional information

Funding

This research was undertaken during a Short Term Scientific Mission funded within the framework of COST Action EMF-MED (COST Action BM1309), supported by COST (European Cooperation in Science and Technology) Program. The funding support of CNRS, Université Paris-Saclay and Gustave Roussy is also acknowledged. The work was also partially supported by H2020 MSCA-IF OPTIC BIOEM GA-661041 and Marie Sklodowska-Curie.  The funding support of CNRS, Université Paris-Saclay and Gustave Roussy is also acknowledged.

Notes on contributors

Claudia Consales

Claudia Consales, PhD, Specialist in Medical Genetics, is a Researcher at the laboratory of ‘Health & Environment’, Division Health Protection Technologies, ENEA, Rome Italy.

Caterina Merla

Caterina Merla, PhD, Electronic Engineer, is a Researcher at the Laboratory of ‘Biomedical Technologies’, Division Health Protection Technologies, ENEA, Rome Italy.

Barbara Benassi

Barbara Benassi, PhD, is the Head of the Laboratory ‘Health & Environment’, Division of Health Protection Technologies, ENEA, Rome, Italy.

Tomás Garcia-Sanchez

Tomás Garcia-Sanchez, PhD, is a Marie Sklodowska Curie fellow at Department of Information and Communication Technologies of the Universitat Pompeu Fabra, Barcelona, Spain.

Adeline Muscat

Adeline Muscat, is a Technician at CNRS, Université Paris-Saclay, Institut Gustave Roussy, Villejuif, France.

Franck M. André

Franck M. André, PhD, is a Researcher at the Unit of Metabolic and Systemic Aspects of the Oncogenesis (METSY) of CNRS, Université Paris-Saclay, Gustave Roussy, Villejuif, France.

Carmela Marino

Carmela Marino, is the Head of the Division of Health Protection Technologies, ENEA, Rome, Italy.

Lluis M. Mir

Lluis M. Mir, PhD, Dr. h. c. of UNMSM (Perou), UAB (Argentina) and UL (Slovenia) is DRCE CNRS Emeritus at the unit of Metabolic and Systemic Aspects of the Oncogenesis (METSY) of CNRS, Université Paris-Saclay, Gustave Roussy, Villejuif, France.