Medical/biological study (experimental study)

Functional alterations in immature cultured rat hippocampal neurons after sustained exposure to static magnetic fields med./bio.

By: Hirai T, Yoneda Y

Published in: J Neurosci Res 2004; 75 (2): 230-240

Aim of study (acc. to author)

To investigate the effects of exposure to static magnetic fields on maturation and differentation in rat hippocampal neuron cells in vitro.

Background/further details

Hippocampal neurons and astrocytes, as well as astrocytes from brain neocortex were obtained from 18 and 19 day-old embryonic rats.

Endpoint

molecular biosynthesis: alterations in gene expression and protein synthesis in neuronal cells

Exposure

- 0 Hz
- static magnetic field

Exposure	Parameters
Exposure 1: DC/static Exposure duration: continuous up to 9 days	magnetic flux density: 100 mT

Exposure 1

Main characteristics

Frequency	DC/static
Type	magnetic field
Exposure duration	continuous up to 9 days

Exposure setup

Exposure source	permanent ferrite magnets
Chamber	CO₂ incubator at 37°C.
Setup	magnets placed on both sides of the culture dishes which were placed 10 cm away from each other
Sham exposure	A sham exposure was conducted.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	100 mT	-	measured	-	-

Exposed system:

intact cell/cell culture

Methods Endpoint/measurement parameters/methodology

molecular biosynthesis: determination of distinct neuron associated proteins and their genes (Western blot, immunofluorescence staining, RT-PCR, differential display analysis, Northern blot)
cell viability/cell division/proliferation: cell viability (MTT reduction assay), cell morphology to measure apoptotic and necrotic cell death (double fluorescent staining)
measurement of intracellular free calcium (calcium sensitive dye, fluorescence microscopy)

Investigated system:

DNA/RNA
intact cell/cell culture

Investigated organ system:

brain/CNS

Time of investigation:

after exposure

Main outcome of study (acc. to author)

Sustained exposure to static magnetic fields leads to a significantly decrease of expression of MPA-2 (microtubule-associated protein 2) and NeuN (neuronal nuclei). The expression of GAP-3 (growth-associated protein 3) was not markedly affected. In hippocampal neurons expression of GFAP (glial fibrillary acidic protein) was significantly increased. However, this was not found in astrocytes from hippocampus and neocortex.
Cell viability of investigated cells was not significantly altered by magnetic field exposure. In hippocampal neurons a marked mRNA expression of NMDA (N-methyl-D-aspartate) receptor subunits was seen. In addition, an increase of intracellular free calcium due to the ability of NMDA was observed. Finally a significant decrease in mRNA expression for a transcription factor (ALF 1) was found.
The data of this study suggest that static magnetic fields may affect cultured embryonic rat hippocampal neurons. This might be through modulated expression of particular NMDA rezeptor units and altered intracellular free calcium levels.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Ministry of Education, Culture, Sports, Science and Technology, Japan
Ministry of Health, Labour and Welfare, Japan

Saito A et al. (2009): Developmental effects of low frequency magnetic fields on P19-derived neuronal cells
Manikonda PK et al. (2007): Influence of extremely low frequency magnetic fields on Ca2+ signaling and NMDA receptor functions in rat hippocampus
Hirai T et al. (2005): Transcriptional Regulation of Neuronal Genes and Its Effect on Neural Functions: Gene Expression in Response to Static Magnetism in Cultured Rat Hippocampal Neurons
Hirai T et al. (2002): Activator protein-1 complex expressed by magnetism in cultured rat hippocampal neurons