Study type: Medical/biological study (experimental study)

Pulsed electromagnetic field enhances brain-derived neurotrophic factor expression through L-type voltage-gated calcium channel- and Erk-dependent signaling pathways in neonatal rat dorsal root ganglion neurons med./bio.

By: Li Y, Yan X, Liu J, Li L, Hu X, Sun H, Tian J
Published in: Neurochem Int 2014; 75: 96-104
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Aim of study (acc. to author)

The role of Ca2+ in the gene expression of the brain-derived neurotrophic factor (BDNF) in dorsal root ganglion neurons induced by exposure to a 50 Hz pulsed magnetic field should be investigated to explore the mechanisms of action underlying the promotive effect of pulsed electromagnetic fields on neuronal differentiation.

Background/further details

To examine the underlying calcium-related mechanisms of action, several co-exposure scenarios were conducted with a magnetic field and the following substances: nimodipine, ω-conotoxin GVIA, ω-agatoxin IVA, mibefradil as calcium channel blockers, thapsigargin and dantrolene as calcium stores inhibitors, PD098059 as an extracellular signal-regulated kinase (ERK) inhibitor, U73122 and U73343 as phospholipase C inhibitors, BAPTA-ΑM and EGTA as calcium chelators, caffeine as a calcium store releaser, neomycin as an IP3 blocker for reduction of intracellular calcium concentration, D-AP5 and MK801 for stimulation of calcium influx. Electrical stimulation was used as a positive control.
Cells were divided into 5 groups: 1) exposure to a 0.1 mT magnetic field, 2) exposure to a 1 mT magnetic field, 3) exposure to a 10 mT magnetic field, 4) exposure to a 100 mT magnetic field, 5) sham exposure.
Each test was conducted with at least three separate cultures prepared at different times from different rats.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 50 Hz
Exposure duration: continuous for 2 hours/day for 1 or 3 days
Exposure 2: 50 Hz
Exposure duration: continuous for 2 hours/day for 1 or 3 days
Exposure 3: 50 Hz
Exposure duration: continuous for 2 hours/day for 1 or 3 days
Exposure 4: 50 Hz
Exposure duration: continuous for 2 hours/day for 1 or 3 days

Exposure 1

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration continuous for 2 hours/day for 1 or 3 days
Additional info sinusoidal
Exposure setup
Exposure source
Setup solenoid was placed in a cell incubator; temperature was 37 °C
Sham exposure A sham exposure was conducted.
Additional info sham exposure samples were placed in a cell incubator containing the solenoid, which was "properly energized so as not to generate a pulsed magnetic field but eventually to produce the same heat as the coil used in the exposure condition"
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 0.1 mT - measured - -

Exposure 2

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration continuous for 2 hours/day for 1 or 3 days
Additional info sinusoidal
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 1 mT - measured - -

Exposure 3

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration continuous for 2 hours/day for 1 or 3 days
Additional info sinusoidal
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 10 mT - measured - -

Exposure 4

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration continuous for 2 hours/day for 1 or 3 days
Additional info sinusoidal
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 100 mT - measured - -

Reference articles

  • Bassen H et al. (1992): ELF in vitro exposure systems for inducing uniform electric and magnetic fields in cell culture media

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

Gene expression of Bdnf was significantly increased after 1 day in groups 2-4 and after 3 days in groups 1-4 compared to the sham exposure group.
The intracellular calcium concentration was significantly increased in group 2 after 1 day compared to the sham exposure group.
When extracellular calcium was bound by EGTA or BAPTA-ΑM or when the calcium influx was inhibited by nimopidine, the Bdnf gene expression and the intracellular calcium concentration significantly decreased in group 2 after 3 days compared to the sample without chelator or calcium channel blocker. Moreover, Bdnf gene expression significantly decreased in group 2 after 3 days with co-exposure to PD098059 compared to the sample without any addition.
Cell viability was not significantly influenced by exposure to the magnetic field or co-exposure to the magnetic field and nimodipine or PD098059.
The authors conclude that exposure to a 50 Hz pulsed magnetic field could increase the gene expression of the brain-derived neurotropic factor (BDNF) in dorsal root ganglion neurons via calcium influx and activation of the ERK-dependent signaling pathways. These indications for the mechanisms of action underlying the promotive effect of pulsed electromagnetic fields on neuronal differentiation should be further investigated in future studies.

Study character:

Study funded by

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