A preliminary study on the frequency effects of weak extremely low frequency magnetic field on cellular actin skeleton assembly

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-actin'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.