弱极低频磁场对Actin骨架组装效率的频率窗口效应初探

A Preliminary Study on The Frequency Effects of Weak Extremely Low Frequency Magnetic Field on Cellular Actin Skeleton Assembly

前期研究发现，50Hz弱磁场辐照能明显降低细胞的微丝含量和组装效率，对actin骨架形态也有明显影响．电磁生物学效应是否与辐照场频率相关，一直受到研究者的关注．单体球状肌动蛋白（G—actin）是带电结构，电磁场频率会影响其振荡频率并对微丝聚合效率产生影响．本文从细胞骨架形态和蛋白质两层次，采用免疫荧光技术考察0．4mT，在35～140Hz范围内5个频率的极低频磁场（ELF-MF）对FL细胞中纤维状肌动蛋白（F-actin）含量的影响，并采用荧光共振能量转移技术（FRET）验证效应最明显的频率对离体G-actin组装效率的干扰程度．结果显示，相比假辐照组，细胞中F—actin含量在50Hz辐照组下降T（34．66±3．141％，110Hz次之，而另外3组（35、70和140Hz）无显著性差异．同时利用FRET方法验证，在50Hz磁场辐照下，离体环境中G．actin组装成F．actin的效率较假辐照组、35和70Hz组显著降低．经初步分析，G-actin在弱ELF—MF中受到以洛伦兹力和感生电场力的合力为主的相关电磁力干扰，致使组装效率下降，且由于工频磁场周期与微丝组装周期的特殊相干性，在50Hz频率附近可能存在一个外磁场干扰actin骨架组装的频率窗口．

In previous researches we have found that the 50 Hz magnetic field （MF） had significant effects on depressing the content and the assembly rate of cellular actin cytoskeleton, and the morphology of cells also was changed. In this study, the relationship between the frequency of extremely low frequency （ELF） MF and the field-induced-cytoskeleton effects was investigated. Since G-actin is charged particle, the electromagnetic field may affect the velocity and orientation of G-aetin＇s movement, and then finally disturb F-actin assembly process. With various frequencies, the field exposure may cause different interference results. In this study, we exposed five specific frequencies （35 Hz, 50 Hz, 70 Hz, 110 Hz, and 140 Hz） of 0.4 mT MF to FL cells and monomer actin protein for 30 min, and by using immunofluorescence technique we detected the changes of microfilament content in FL cells corresponding to the five frequencies, to see if any specific frequency MF exert stronger effect on the skeleton than others. Furthermore, fluorescence resonance energy transfer technology （FRET）was employed to verify if this possible frequency window had a remarkable effect on the efficiency of F-actin assembly in vitro. The results showed that within cells, the 50 Hz MF-exposed group had the lowest F-actin content, with a reduction of （34.66__.3.14）% compared to the Sham group, followed by the 110 Hz group, while the 35 Hz, 70 Hz, 140 Hz groups had no significant differences comparing with the Sham. In the FRET experiment, after exposing to the 0.4 mT 50 Hz MF, the FRET efficiency reduced significantly compared with the sham, 35 Hz, 70 Hz groups. The theoretical analysis showed that with exposed to the MF, F-actin assembly was mainly interfered by the induced-electric field force and the corresponding Lorentz force, under which the efficiency of the microfilament assembly decreased with a MF frequency dependent manner. Due to the coincidence that the time cycles of 50 Hz MF varying in its direction/strength is similar to that of actins binding to actin-microfilaments, we propose that 50 Hz is likely to be one of the MF frequency windows for the MF-induced-interference to cytoskeleton.