研究のタイプ: 医学／生物学の研究 (experimental study)

[ヒト単核細胞へのパルス超広帯域電磁場(1 kV/cm)ばく露後のNFKB(NF‐kB)の核転座とDNA結合活性はkB依存性遺伝子発現を転写活性化しない] med./bio.

Nuclear translocation and DNA-binding activity of NFKB (NF-kappaB) after exposure of human monocytes to pulsed ultra-wideband electromagnetic fields (1 kV/cm) fails to transactivate kappaB-dependent gene expression

著者: Natarajan M, Nayak BK, Galindo C, Mathur SP, Roldan FN, Meltz ML
掲載誌: Radiat Res 2006; 165 (6): 645-654
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この研究は、1 kV/ cmの平均ピーク電界強度のパルス超広帯域電磁界（EMF）ばく露により、ヒト単球においてNFKB（NF-κB）依存性の遺伝子発現の転写調節に関与するシグナル伝達経路がトリガーされるか否かを調べた。ヒトMono Mac 6（MM6）細胞に間欠的にEMFパルスのばく露を与えた。パルス幅は0.79±0.01 ns、パルス繰り返し率は250 ppsで、ばく露時間は合計90分間であった。培地の温度は、EMFばく露および擬似ばく露のどちらでも37 ℃に維持された。核抽出物中の総NFKB DNA結合活性は、電気泳動移動度シフトアッセイによって測定された。その結果、EMFにばく露され、ばく露後24時間培養された細胞でのNFKB DNA結合活性は3.5±0.2倍に増加した；NFKBの活性化が観察されたので、EMFばく露に応答したκB依存性遺伝子発現の可能性を、NFKBシグナル特異的遺伝子アレイを用いて調べたが、ばく露後8または24時間におけるNFKB依存性遺伝子発現プロファイルに違いはなかった；このことは、活性化されたNFKBがκB依存性の標的遺伝子の差次的発現につながらないことを示している；一方、NFKBの機能活性も不活性であることが示された；これらの知見から、EMFによるNFKB DNA結合活性化は一時的な応答であり、下流への影響は最小限であるか、まったくないことが示された、と報告している。

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研究目的（著者による）

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.

詳細情報

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.

影響評価項目

ばく露

ばく露 パラメータ
ばく露1: 0 Hz–2 GHz
Modulation type: pulsed
ばく露時間: intermittent, 30 min on/30 min off, for 90 min

ばく露1

主たる特性
周波数 0 Hz–2 GHz
タイプ
  • electromagnetic field
波形
  • pulsed
特性
  • guided field
ばく露時間 intermittent, 30 min on/30 min off, for 90 min
Modulation
Modulation type pulsed
Pulse width 0.79 ns
Repetition frequency 250 Hz
ばく露装置
ばく露の発生源／構造
  • GTEMセル
ばく露装置の詳細 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 information 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).
パラメータ
測定量 値 種別 Method Mass 備考
電界強度 101 kV/m peak 測定値 - ± 4 kV/m
測定および計算の詳細

The parameters of the EMF were determined by recording and processing an average of 200 instantaneous UWB pulse waveforms, collected (in free space) by a D-dot probe mounted on the upper ground plane of the GTEM cell at a location corresponding to the center of the isothermal chamber placed in the lower exposure area. Field uniformity was examined by measuring the peak E-field amplitudes using the D-dot probes at nine positions on the inside bottom of each flask, the location where the cells would settle.

ばく露を受けた生物:

方法 影響評価項目／測定パラメータ／方法

研究対象とした生物試料:
調査の時期:
  • ばく露後

研究の主なアウトカム（著者による）

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.

研究の種別:

研究助成

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