Molecular Mechanisms Underlying Antiproliferative and Differentiating Responses of Hepatocarcinoma Cells to Subthermal Electric Stimulation

María Luisa Hernández-Bule,María Ángeles Trillo,Alejandro Úbeda,Irina V Lebedeva

doi:10.1371/journal.pone.0084636

María Luisa Hernández-Bule, María Ángeles Trillo + Show 2 more

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https://doi.org/10.1371/journal.pone.0084636

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Journal: PloS one	Publication Date: Jan 8, 2014
Citations: 64	License type: CC BY 4.0

Affiliation: Instituto Cajal

Abstract

Capacitive Resistive Electric Transfer (CRET) therapy applies currents of 0.4–0.6 MHz to treatment of inflammatory and musculoskeletal injuries. Previous studies have shown that intermittent exposure to CRET currents at subthermal doses exert cytotoxic or antiproliferative effects in human neuroblastoma or hepatocarcinoma cells, respectively. It has been proposed that such effects would be mediated by cell cycle arrest and by changes in the expression of cyclins and cyclin-dependent kinase inhibitors. The present work focuses on the study of the molecular mechanisms involved in CRET-induced cytostasis and investigates the possibility that the cellular response to the treatment extends to other phenomena, including induction of apoptosis and/or of changes in the differentiation stage of hepatocarcinoma cells. The obtained results show that the reported antiproliferative action of intermittent stimulation (5 m On/4 h Off) with 0.57 MHz, sine wave signal at a current density of 50 µA/mm2, could be mediated by significant increase of the apoptotic rate as well as significant changes in the expression of proteins p53 and Bcl-2. The results also revealed a significantly decreased expression of alpha-fetoprotein in the treated samples, which, together with an increased concentration of albumin released into the medium by the stimulated cells, can be interpreted as evidence of a transient cytodifferentiating response elicited by the current. The fact that this type of electrical stimulation is capable of promoting both, differentiation and cell cycle arrest in human cancer cells, is of potential interest for a possible extension of the applications of CRET therapy towards the field of oncology.

Highlights

The exogenous application of electric currents has emerged as an effective therapeutic strategy in the treatment of a number of lesions and ailments [1,2]
Pathways as that of MEK/ERK1/2, which has been shown sensitive to the action of electric and electromagnetic fields [26,27] are likely to be involved in the response of those regulatory proteins
It has been reported that capacitive-resistive electric transfer (CRET) stimulation induces necrosis in human neuroblastoma cells NB69 [17,18], in HepG2 the observed decrease in the number of alive cells is not accompanied with increased rates of necrosis [15]

Summary

Introduction

The exogenous application of electric currents has emerged as an effective therapeutic strategy in the treatment of a number of lesions and ailments [1,2]. The capacitive-resistive electric transfer (CRET) is a noninvasive, electrothermal therapy that applies sine wave electric currents at frequencies between 0.4 MHz and 0.6 MHz, within the radiofrequency (RF) range, and constant amplitudes. These currents induce flow of ions (Na+, Cl2, K+, Ca+2, etc.) and dipolar molecules (water, aminoacids, proteins, polysaccharides) in the exposed living tissues. This causes collisions of ions and charged molecules with stationary molecules, which results in tissue heating [6]. The temperature increase is directly proportional to the resistance of the tissue through which current flows [7]

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