この研究は、ヒト慢性骨髄性白血病細胞株K562にそれぞれビンブラスチン、エトポシド、ケルセチン、レスベラトロールが誘導するアポトーシスに対する正弦波ELF-MF（1 mT；50 Hz）の影響を調べた。その結果、ELF-MFばく露は無処置K562の増殖および生存率に影響しなかった；またビンブラスチン、エトポシド、レスベラトロールの抗増殖作用に影響しなかった；対照的にケルセチン処置群では、ELF-MFばく露によりアポトーシス細胞の割合が有意に減少し、抗アポトーシス作用を持つBcl-2ファミリータンパク質の発現が変化した､と報告している。
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To examine the effects of exposure to an extremely low frequency magnetic field on the apoptosis induced by four different compounds (vinblastine, etoposide, quercetin, resveratrol) in human K562 leukemia cells.
In the first experiment, the effects of 1 µM vinblastine, 1 µM etoposide (used as an anti-cancer drug) and 25 µM resveratrol (a stilbenoid, potential positive health effects are discussed) either alone or in combination with an extremely low frequency magnetic field on the growth and cell viability were examined.
In the second experiment, the effects of 25 µM quercetin (a flavonoid, has been suggested as an anti-cancer drug) either alone or in combination with an extremely low frequency magnetic field on the growth, cell viability, generation of reactive oxygen species, protein expression, enzyme activity of the caspase-3, apoptosis rate and cell cycle were examined.
In the third experiment, cells were exposed to different magnetic flux densities alone or in combination with quercetin and the number of apoptotic cells was determined.
Positive controls were performed.
|ばく露時間||continuous for 24, 48 or 72 hours|
|Additional information||experiment 1 + 2|
|チャンバの詳細||cells were exposed in petri dishes or multiwell plate|
|ばく露装置の詳細||exposure system consisted of two identical apparatuses, each containing a waveform generator, a current amplifier, and a pair of Helmholtz coils; pair of Helmholtz coils had a mean radius of 13.0 ± 0.5 cm; in each coil, the number of turns was 800 with a 2 mm² wire giving a resulting resistance of 2.4 ohm and an inductance of 39 ± 1 mH; mean vertical distance between the coils was 13.5 ± 0.5 cm; current could either flow in the same direction (exposure) or in the opposite direction (sham system), where the magnetic flux density is "theoretically zero"; each coil was placed within two separate incubators (one for exposure, one for sham exposure) at a temperature of 37°C and an atmosphere of 95% air/5% CO2and 100% relative humidity.|
|Sham exposure||A sham exposure was conducted.|
In the first experiment, no significant differences were observed in the cell proliferation and cell viability between the exposed and the sham exposed cells. Vinblastine, etoposide, and resveratrol had an anti-proliferative effect on the cells. However, this effect was not influenced by the magnetic field exposure.
The second experiment showed that quercetin had an anti-proliferative effect, but this effect was attenuated by the magnetic field exposure: In cell cultures cultivated in the presence of quercetin and exposed for 48 and 72 hours, the cell viability was significantly increased and the number of apoptotic cells (also after 24 hours and as experiment 3 showed also at magnetic flux densities of 0.01 mT and 0.1 mT, but not at 2 mT) as well as the enzyme activity of the caspase-3 were significantly decreased compared to sham exposed cell cultures with quercetin. Additionally, in 48 hours-exposed cells with quercetin the numbers of cells in the G1 phase and the S phase were significantly increased and the number of cells in the G2 phase/mitosis significantly decreased compared to sham exposed cells with quercetin. The simultaneous treatment with magnetic field exposure for 24 hours and quercetin significantly increased the protein expression of Bcl-2 in comparison to the other groups and prevented the quercetin-induced significant down-regulation of Mcl-1 and Bcl-xL. After 48 hours of exposure, the protein expression of Hsp70 was significantly increased when compared to the control group, while after 72 hours it was significantly increased when simultaneously treated with exposure and quercetin. No significant changes occurred regarding the level of the reactive oxygen species.
The results indicate that extremely low frequency magnetic fields could be able to render K562 cells resistant to quercetin-induced apoptosis. Hence, these magnetic fields may have negative implications for anti-tumor therapies.