この研究は、超低周波磁界（ELF MF：50 Hz、100 µT）ばく露がメナジオンによるDNA損傷反応に関連するタンパク質および細胞分裂周期分布に変化を引き起こすか否かを調べた。ヒトSH-SY5Y神経芽腫細胞へのELF MFの先行ばく露（24時間）終了後にメナジオン投与（濃度：1, 10, 15, 20, 25µM、投与時間：1または3時間）を行った。投与終了後に、免疫ブロット法によるDNA損傷反応関連タンパク質（γ-H2AX, Chk1, リン酸化Chk1, p21, p27, p53）レベルの評価、アルカリコメットアッセイによるDNA損傷レベルの評価、染色フローサイトメトリによる細胞分裂周期分布の評価を行った。その結果、ばく露群の細胞での主な変化は、1時間投与実験でのp21タンパク質レベルの減少、3時間投与実験での細胞周期のG1期割合増加およびS期割合減少であった；一方、メナジオン投与なしの場合においても、ELF MFばく露による同様の影響が見られた､と報告している。
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The effects of co-exposure of neuroblastoma cells to a 50 Hz magnetic field and menadione on DNA damage, cell cycle distribution and protein expression should be investigated.
In a previous study (Markkanen et al. 2008), the authors found that exposure to a 50 Hz magnetic field altered cellular responses to a treatment with menadione. Menadione is an agent that induces free radicals (by increasing mitochondrial superoxide production) and DNA damage.
Cells were divided into the following groups: pre-exposure to the magnetic field and consequent treatment with 1) no menadione (only incubation), 2) 1 µM, 3) 10 µM, 4) 15 µM, 5) 20 µM, and 6) 25 µM menadione for 1 h or 3 hours. For each exposure condition, a separate magnetic field sham exposure group was used.
Positive control was conducted.
ばく露時間: continuous for 24 hours
|ばく露時間||continuous for 24 hours|
|チャンバの詳細||cell dishes between coils in incubator with 5% CO2|
|ばく露装置の詳細||a pair of 34 cm x 46 cm coils in a Helmholtz-type configuration (22 cm distance between the coils); cell cultures were located at the center of the coil system where the magnetic flux density was uniform; no change in mechanical vibration level was observed at the location of the cell cultures when the exposure system was switched on|
|Sham exposure||A sham exposure was conducted.|
|Additional information||sham exposed cells were kept in an identical incubator; no temperature differences were observed between the exposure incubator and sham exposure incubator|
After 3 hours of incubation with and without menadione (groups 1-6) after exposure to the magnetic field, a significant increase of cells in the G1 phase and a significant decrease in the S phase were observed compared to the respective sham exposure groups. There were no effects on cell cycle distribution observed after 1 h of incubation with and without menadione after exposure to the magnetic field.
The protein expression of p21 was significantly decreased after 1 hour of incubation after exposure in groups 1-6 compared to the respective sham exposure groups.
Menadione treatment for 1 hour and 3 hours resulted in a concentration-dependent increase in DNA damage. Only in cells incubated for 1 hour, DNA damage was significantly decreased by exposure to the magnetic field (groups 1-6) compared to the respective sham exposure groups.
The authors conclude that exposure of neuroblastoma cells to a 50 Hz magnetic field might reduce DNA damage, alter cell cycle distribution and that p21 might be involved in the cellular magnetic field response. These effects were detectable in the presence and absence of menadione.