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

[超低周波磁界にばく露したマウスにおける脳のhsp70発現およびDNA損傷:量‐反応研究] med./bio.

Brain hsp70 expression and DNA damage in mice exposed to extremely low frequency magnetic fields: a dose-response study.

掲載誌: Int J Radiat Biol 2013; 89 (7): 562-570

この研究は、マウスの脳において、超低周波磁界ばく露強度(50 Hzばく露レベル0、0.1、0.2、1、2 mT;1日15時間で7日間連続ばく露)と熱ショックタンパク(hsp70発現およびDNA損傷に量‐反応関係があるか否かを調べた。成獣雄CD1マウスを合計96匹用いた。擬似ばく露群(32匹)、4つのばく露レベル群(各16匹)のそれぞれの半数はばく露終了直後に、残りの半数は24時間後に、それぞれ線条体海馬小脳のHsp70発現およびDNA損傷を調べた。その結果、hsp70のmRNA とその対応タンパク質の両方に、ばく露による変化は何も見られなかったが、例外として、0.1 mTにおいて海馬のmRNAのみが若干上昇した;1および2 mTにばく露し、ばく露の直後に調べた場合にのみ、対照群に比較して脳の3つの領域の標本でのDNA鎖切断が高まった;24時間後に調べた場合、このようなDNA鎖切断はベースラインまで回復していた、と報告している。

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研究目的(著者による)

To evaluate whether there is a dose-response relationship between exposure to extremely low frequency magnetic fields at different magnetic flux densities and the protein expression of the heat shock protein Hsp70 and DNA damage in the brain of mice.

詳細情報

8 groups of mice were exposed to 4 different magnetic flux densities (2 groups for every flux density). Each group consisted of 4 subgroups: 1.) directly killed after exposure (n=4), 2.) 24 hours killed after exposure (n=4), 3.) directly killed after sham exposure (n=2) and 4.) 24 hours killed after sham exposure (n=2).
The positive control for the protein expression of Hsp70 was performed via an increased environmental temperature until rectal temperature reached 42°C and as a positive control for the DNA damage, mice were radiated with x-rays (6 Gy).

影響評価項目

ばく露

ばく露 パラメータ
ばく露1: 50 Hz
ばく露時間: 15 hours/day for 7 days
ばく露2: 50 Hz
ばく露時間: 15 hours/day for 7 days
ばく露3: 50 Hz
ばく露時間: 15 hours/day for 7 days
ばく露4: 50 Hz
ばく露時間: 15 hours/day for 7 days

ばく露1

主たる特性
周波数 50 Hz
タイプ
  • magnetic field
波形
  • sinusoidal
ばく露時間 15 hours/day for 7 days
ばく露装置
ばく露の発生源/構造
チャンバの詳細 mice were exposed in a plastic cage in the centre of the apparatus
ばく露装置の詳細 rectangular coils arranged horizontally in a Helmholtz-like configuration, apparatus placed in a temperature-controlled room (22±1°C)
Sham exposure A sham exposure was conducted.
Additional information during sham exposure the magnetic flux density was 0.06 µT
パラメータ
測定量 種別 Method Mass 備考
磁束密度 0.1 mT effective value - - -

ばく露2

主たる特性
周波数 50 Hz
タイプ
  • magnetic field
波形
  • sinusoidal
ばく露時間 15 hours/day for 7 days
ばく露装置
ばく露の発生源/構造
  • E1と同じ装置
Sham exposure A sham exposure was conducted.
パラメータ
測定量 種別 Method Mass 備考
磁束密度 0.2 mT effective value - - -

ばく露3

主たる特性
周波数 50 Hz
タイプ
  • magnetic field
波形
  • sinusoidal
ばく露時間 15 hours/day for 7 days
ばく露装置
ばく露の発生源/構造
Sham exposure A sham exposure was conducted.
パラメータ
測定量 種別 Method Mass 備考
磁束密度 1 mT effective value - - -

ばく露4

主たる特性
周波数 50 Hz
タイプ
  • magnetic field
波形
  • sinusoidal
ばく露時間 15 hours/day for 7 days
ばく露装置
ばく露の発生源/構造
  • E1と同じ装置
Sham exposure A sham exposure was conducted.
パラメータ
測定量 種別 Method Mass 備考
磁束密度 2 mT effective value - - -

Reference articles

  • Mariucci G et al. (2010): [超低周波磁界にばく露したCD1マウスにおける脳のDNA損傷及び70-kDa熱ショックタンパク質発現]

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:
  • ばく露中
  • ばく露後

研究の主なアウトカム(著者による)

No differences were observed among the groups regarding food intake and body weight gain.
Between the groups, no changes were found in the expression of Hsp70 (mRNA and protein). Only in the hippocampus of 0.1 mT exposed mice, a weak, but significant increase in the expression of the hsp70 mRNA was found in comparison to sham exposed animals.
Directly after exposure to magnetic flux densities of 1 and 2 mT, a significant increase regarding DNA damage was found compared to sham exposed mice. However, 24 hours after the exposure, the DNA damage recovered and no significant differences between the exposed and the sham exposed mice were found.
The authors conclude, that exposure to extremely low frequency magnetic fields may lead to reversible DNA damage in the brain of mice, but does not affect Hsp70 expression.

研究の種別:

研究助成

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