To study whether exposure of human monocytes to a pulsed ultra-wideband electromagnetic field triggers a signaling pathway responsible for the transcriptional regulation of NFKB (NF-κB)-dependent gene expression.
NFKB (NF-κB) is a critical cell signaling mediator and implicated in the modulation of a multitude of cell functions.
Furthermore, the functional activity of NFKB was examined in cells transiently transfected with "Mercury Pathway" constructs containing 4x NFKB binding sites associated either with the luciferase reporter gene system (pNF-κB-Luc) or a control vector (pTAL-Luc). If the NFKB induced by the pulsed electromagnetic field was functionally active, it would bind to the κB-binding sites in the pNF-κB-Luc plasmids and drive expression of the reporter gene (luciferase).
Three negative and positive control flasks were treated as follows: 1) 100 ng/ml lipopolysaccharide, 2) exposure to 2 Gy of gamma rays, 3) negative control sham-exposed to gamma rays.
After exposure cell were incubated and harvested at 10 min, 3 h, 8 h, and 24 h.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
0 Hz–2 GHz
Modulation type:
pulsed
Exposure duration:
intermittent, 30 min on/30 min off, for 90 min
|
|
| Frequency | 0 Hz–2 GHz |
|---|---|
| Type | |
| Waveform | |
| Charakteristic |
|
| Exposure duration | intermittent, 30 min on/30 min off, for 90 min |
| Modulation type | pulsed |
|---|---|
| Pulse width | 0.79 ns |
| Repetition frequency | 250 Hz |
| Exposure source | |
|---|---|
| Setup | Four plug-sealed T-25 flasks with 10 ml of medium were positioned vertically in a Styrofoam box that was placed in the GTEM cell. All four flasks in a row contained medium, but only the two flasks in the center positions contained suspended cells that were allowed to settle to the bottom for 30 min while the medium was brought to 37°C by a forced-air system before the UWB source was turned on. |
| Sham exposure | A sham exposure was conducted. |
| Additional info | Four sham-exposed flasks (two with cells) were placed into a second Styrofoam exposure box that was kept outside the GTEM cell in a Faraday cage. For negative and positive control, three flasks were kept unexposed in a humidified incubator at 37°C (5% CO2) in parallel with the EMF exposures. Afterwards, one of these flasks was treated with 100 ng/ml LPS, one was exposed to 2 Gy of γ rays at a dose rate of 1.28 Gy/min using a 137Cs source, and one negative control flask was sham-exposed to the γ rays (0 Gy). |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| electric field strength | 101 kV/m | peak value | measured | - | ± 4 kV/m |
Exposed cells showed 24 h post-exposure a 3.5 +/-0.2-fold increase in the NFKB DNA-binding activity. The data of the NFKB signal-specific gene arrays revealed no difference in the NFKB-dependent gene expression profiles at 8 or 24 h post-exposure, indicating that activated NFKB does not lead to the differential expression of κB-dependent target genes.
Furthermore, pulsed electromagnetic field exposure did not induce NFKB-driven luciferase activity in the transfected cells, indicating that the activation of NFKB at 24 h after the exposure is functionally inactive.
From these data, it is clear that the electromagnetic field-induced NFKB activation is only a transient response, with minimal or no downstream effect.
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