Medical/biological study (experimental study)

Extremely low frequency magnetic field exposure affects DnaK and GroEL expression in E. coli cells with impaired heat shock response med./bio.

By: Del Re B, Marcantonio P, Bersani F, Giorgi G

Published in: Gen Physiol Biophys 2009; 28 (4): 420-424

Aim of study (acc. to author)

To study the ability of extremely low frequency magnetic field exposure to trigger an increase of DnaK and GroEL protein (homologous bacterial protein to heat shock proteins) levels in Escherichia coli cells not exhibiting the classic heat shock response when subjected to a 42°C heat stress.

Background/further details

Cells were divided into four groups: 1) 30°C treatment, 2) 42°C (heat shock) treatment, 3) 30°C + electromagnetic field exposure, 4) 30°C + sham exposure. Each experiment was performed in quadruplicate.

Endpoint

molecular biosynthesis: protein expression (DnaK and GroEL)

Exposure

Exposure	Parameters
Exposure 1: 50 Hz Exposure duration: continuous for 30 min. or 90 min.	magnetic flux density: 1 mT effective value

General information

Cells were treated in four groups: i) 30°C ii) 42°C (heat shock) iii) 30°C + EMF exposure iv) 30°C + sham exposure

Exposure 1

Main characteristics

Frequency	50 Hz
Type	magnetic field
Exposure duration	continuous for 30 min. or 90 min.

Exposure setup

Exposure source	Helmholtz coils
Setup	two pairs of Helmholtz coils with a diameter of 23 cm and 2 x 20 turns, kept in a thermostatic room; cells placed in round Sterlin bijou tubes with a diameter of 16 mm in the center of the coil system; field uniformity in the exposure aerea = 1%
Sham exposure	A sham exposure was conducted.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	1 mT	effective value	measured	-	-

Exposed system:

bacterium
Escherichia coli/DH5alpha (untransformed (showing regular heat shock response) and transformed with two different plasmids inducing high transposition activity and an impaired response to heat shock)

Methods Endpoint/measurement parameters/methodology

molecular biosynthesis: protein expression (DnaK and GroEL; Western blot)

Investigated system:

isolated bio./chem. substance

Time of investigation:

after exposure

Main outcome of study (acc. to author)

The data showed an increase in DnaK and GroEL protein expression in both cell types exposed to the extremely low frequency magnetic field compared with sham exposed controls. Thus, the transformed cells, although lacking a normal heat shock response to heat shock treatment, showed an enhancement of DnaK and GroEL protein levels after 30 or 90 minutes sinusoidal extremely low frequency magnetic field exposure. This result suggests that the heat shock protein induction pathway triggered by extremely low frequency magnetic field exposure could be different from that elicited by heat shock treatment.

Study character:

medical/biological study
experimental study
full/main study
Short Communication
blind study

Study funded by

Ministero dell' Università e della Ricerca (MIUR (formerly MURST (Ministero dell' Università e della Ricerca Scientifica e Tecnologica); Ministry of University and Research), Italy
Project "Effects of Electromagnetic Fields on Nervous Cells", Italy

Huwiler SG et al. (2012): Genome-wide transcription analysis of Escherichia coli in response to extremely low-frequency magnetic fields
Del Re B et al. (2006): Synthesis of DnaK and GroEL in Escherichia coli cells exposed to different magnetic field signals
Del Re B et al. (2004): Various effects on transposition activity and survival of Escherichia coli cells due to different ELF-MF signals
Del Re B et al. (2003): Extremely low frequency magnetic fields affect transposition activity in Escherichia coli
Nakasono S et al. (2000): Effect of ELF magnetic fields on protein synthesis in Escherichia coli K12
Cairo P et al. (1998): Magnetic field exposure enhances mRNA expression of sigma 32 in E. coli
Goodman EM et al. (1994): Magnetic fields alter translation in Escherichia coli