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

[超低周波電磁界による成獣の海馬における神経新生のエピジェネティックな変化] med./bio.

Epigenetic modulation of adult hippocampal neurogenesis by extremely low-frequency electromagnetic fields

著者: Leone L, Fusco S, Mastrodonato A, Piacentini R, Barbati SA, Zaffina S, Pani G, Podda MV, Grassi C
掲載誌: Mol Neurobiol 2014; 49 (3): 1472-1486
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この研究は、超低周波電磁界（ELFEFs）にばく露したマウスの海馬に神経新生の増強が見られるか否か、またこのような神経新生の増強が空間学習および記憶を改善させるか否かを調べた。C57bl/6マウス38匹を同数ずつのばく露群と擬似ばく露群に分け、ELFEFs（1mT、50Hz）に1日3.5時間、12日間ばく露（擬似ばく露）した。インビトロ実験では、新生仔の海馬から単離した神経幹細胞（NSCs）を用い、同じELFEFsに1日24時間、2日間ばく露（擬似ばく露）した。動物実験では、ばく露（擬似ばく露）後にモリス水迷路試験、新規物体認知試験を行い、最後に脳組織標本の免疫蛍光アッセイを行った。さらには、動物実験およびインビトロ実験の試料を、RT-PCR法、クロマチン免疫沈降、ウェスタンブロット法で分析し、各種の遺伝子発現、DNAと特定タンパクの結合などを調べた。その結果、ELFEFsばく露群では、空間学習および記憶が改善されたことを示すタスク成績が見られた；そのような効果の海馬でのメカニズムに関係すると著者が考えるインビトロ試験の様々な結果を報告している。

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研究目的（著者による）

To investigate the effects of extremely low frequency magnetic fields on spatial memory and learning in mice as well as its underlying molecular mechanisms.

詳細情報

In previous studies, the authors reported that mice exposed to extremely low frequency magnetic fields showed an increased neurogenesis in the hippocampus (e.g. Podda et al., 2014). Further understanding of this phenomen could help to develop novel therapeutic approaches in the treatment of neurological disorders.
For an in vivo experiment, mice (n=38) were randomly divided into an exposure and a sham exposure group. Different examinations were performed:
1.) For immunohistochemical analysis, 7 mice from each group received daily injections of 100 mg bromodeoxyuridine per kg body weight before each exposure (12 days). Mice were killed 1 day (n=4) or 40 days (n=3) after the last exposure or sham exposure session and the brain was taken for examinations.
2.) 30 days after the last exposure (n=16) or sham exposure (n=14) session, the Morris water maze was performed.
3.) 36 days after the last exposure or sham exposure session, the novel recognition test was performed (each n=8).
For an in vitro experiment, neural stem cells were cultivated in an incubator while exposed or sham exposed. Partially, the calcium channel blocker nifedipine was added to the cell cultures. Different examinations were performed:
1.) For proliferation and immunohistochemical analysis, cells were exposed or sham exposed for 6 or 24 hours while cultivated in proliferation medium.
2.) Cells were exposed or sham exposed for up to 10 days in differentiation medium. Gene expression was examined during the first 2 days (after 0, 6, 12, 24, and 48 hours) and protein expression on the first exposure day as well as from day 6 to 10.

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: 3.5 hours per day for 12 days
in vivo
ばく露2: 50 Hz
ばく露時間: 6, 12 or 24 hours per day for up to 10 days
in vitro

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 3.5 hours per day for 12 days
Additional information in vivo
ばく露装置
ばく露の発生源／構造
チャンバの詳細 3 to 4 animals in a plastic cage (33 Œ 15 Œ 13 cm) which was put in the solenoid
ばく露装置の詳細 solenoid was made of copper wire wrapped around a Plexiglas cylinder (diameter 20 cm; length 42 cm) with open extremities in which the cage was positioned; geometry of the system assured field uniformity within the entire length of the cage
Sham exposure A sham exposure was conducted.
パラメータ
測定量 値 種別 Method Mass 備考
磁束密度 1 mT - - - -

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 6, 12 or 24 hours per day for up to 10 days
Additional information in vitro
ばく露装置
ばく露の発生源／構造
  • E1と同じ装置
ばく露装置の詳細 solenoid was placed inside an CO2 incubator
Sham exposure A sham exposure was conducted.
Additional information control cell cultures were put in another incubator; maximum temperature increase due to exposure was 0.4°C ± 0.1°C
パラメータ
測定量 値 種別 Method Mass 備考
磁束密度 1 mT - - - -

Reference articles

  • Podda MV et al. (2014): [超低周波電磁界はマウス海馬の新生ニューロンの生存率を高める]
  • Cuccurazzu B et al. (2010): [超低周波（50Hz）電磁界へのばく露は成獣のC57BL/6マウスの海馬における神経新生を強める]
  • Hansson Mild K et al. (2009): [労働者の電磁界ばく露、ばく露票評価法における未解決問題の再検討]
  • Piacentini R et al. (2008): [超低周波電磁界はCa(v)1-チャネル活性上昇を介してイン・ビトロでの神経新生を促進する]
  • Wolf FI et al. (2005): [50Hzの超低周波電磁界は細胞増殖及びDNA損傷を強める：可能性のあるレドックスメカニズムの関与]
  • Grassi C et al. (2004): [50 Hz電磁界が電位依存性Ca2+チャンネルに与える影響と神経内分泌細胞の増殖と死亡の変調におけるその役割]
  • Czeh B et al. (2002): [慢性的な心理社会的ストレスおよびそれに随伴する反復的経頭蓋磁気刺激：ストレスホルモンレベルおよび成人海馬神経発生への影響]

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:
研究対象とした臓器系:
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）

In the in vivo experiment, exposed mice showed significantly enhanced memory and learning abilities compared to sham exposed mice. Additionally, immunohistochemistry revealed that the cell proliferation and cell differentiation were significantly increased in the exposed mice in comparison to the sham exposed ones.
Also in the in vitro experiment, in exposed cell cultures, the cell proliferation was significantly higher and the cell differentiation was significantly more enhanced than in sham exposed cell cultures. Additionally, exposure partially led to significant changes in the gene expression of Hes1 (increased after 0 and 24 hours, decreased after 6 and 12 hours), NeuroD1 (increased after 24 hours), Neurogenin1 (increased after 24 and 48 hours) and Mash1 (increased after 0 and 6 hours, decreased after 12 and 48 hours). Furthermore, in a exposed cell cultures, the acetylation of histone and the protein expression of phosphorylated CREB were significantly increased compared to the sham exposure. An addition of nifedipine prevented the exposure-induced effects.
The authors conclude that extremely low frequency magnetic fields could enhance hippocampal neurogenesis and improve learning and memory abilities of mice.

研究の種別:

研究助成

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