Medical/biological study (experimental study)

CREB DNA binding activation by a 50-Hz magnetic field in HL60 cells is dependent on extra- and intracellular Ca2+ but not PKA, PKC, ERK, or p38 MAPK med./bio.

By: Zhou J, Yao G, Zhang J, Chang Z

Published in: Biochem Biophys Res Commun 2002; 296 (4): 1013-1018

Aim of study (acc. to author)

To investigate the effects of exposure to a 0.1 mT 50 Hz extremely low frequency sinusoidal magnetic field on DNA binding activity of CREB transcription factors in human cells.

Background/further details

CREB (cyclic-AMP responsive element binding protein) is a transcription factor that is target of a variety of signal transduction pathways mediating cell responses to extracellular stimuli, involving proliferation, or differentiation. Since several signal transduction pathways are involved in activation of CREB, the effects of various inhibitors on magnetic field-induced CREB binding activity were also investigated (inhibitors of different signal transduction pathways, e.g. PKA, PKC, ERK (extracellular signal-regulated kinase), p38 MAPK (p38 mitogen-activated protein kinase)). Furthermore, the relevance of intracellular and extracellular Ca²⁺ concentrations were examined by using Ca²⁺ chelators.

Endpoint

molecular biosynthesis: DNA binding behavior of CREB transcription factors

Exposure

- 50/60 Hz
- magnetic field

Exposure	Parameters
Exposure 1: 50 Hz Exposure duration: 10 min, 0.5, 1, 2, 4, and 12 hrs (sham exposure for 12 hrs)	magnetic flux density: 0.1 mT unspecified

Exposure 1

Main characteristics

Frequency	50 Hz
Type	magnetic field
Waveform	sinusoidal
Exposure duration	10 min, 0.5, 1, 2, 4, and 12 hrs (sham exposure for 12 hrs)

Exposure setup

Exposure source	coil(s)
Chamber	The coils were placed in a mu-metal container.
Setup	The magnetic field was very uniform (0.1%) at the center (10 x 10 x 10 cm³) of the coils where the cell cultures dishes were placed. Sham-exposed cells were handled in the same manner but without the magnetic field.
Additional info	Three groups of square copper coils 36 cm x 36 cm with the upper, middle and lower coils having 104, 52 and 104 turns, respectively. They were spaced 18 cm from each other.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
magnetic flux density	0.1 mT	unspecified	measured	-	-

Additional parameter details

The AC background field in the incubator was 1-2 µT and the total static MF was 18.5 mT with a 14.1 mT horizontal and 12 mT vertical components.

Measurement and calculation details

The magnetic field densities was measured using a Model EFA2 meter.

Reference articles

Zhou J et al. (2002): Gene expression of cytokine receptors in HL60 cells exposed to a 50 Hz magnetic field

Exposed system:

intact cell/cell culture
HL-60 (human acute myeloid leukaemia cells)

Methods Endpoint/measurement parameters/methodology

molecular biosynthesis: DNA binding behavior of CREB transcription factors (electrophoretic mobility shift assay)

Investigated system:

intact cell/cell culture

Time of investigation:

during exposure
after exposure

Main outcome of study (acc. to author)

Exposure to magnetic field induced a time-dependent activation of CREB-DNA-binding. The CREB complex formation increased shortly after magnetic field exposure for 10 minutes, reaching a peak level after 1 hour, and then recovered to basal level at 4 hours after exposure.
Furthermore, the exposure to magnetic field-induced increase of CREB-DNA-binding was dependent on both extracellular and intracellular Ca²⁺ concentration but not on PKA, PKC, ERK, or p38 MAPK by using various signal transduction pathway inhibitors.
These results indicate that magnetic field exposure activates CREB-DNA-binding through Ca²⁺-related signal transduction pathways.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

National Basic Research Program (Program 973), China

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