Effect Of 50Hz Power Frequency Magnetic Field On Microfilament Cytoskeleton Assembly Of Fibroblasts

The exposure strength and the time that people have been exposed to electromagnetic fields (MF) are increasing steadily in nowadays. The relationship between extremely low frequency magnetic fields and tumors occurrences is one of the most concerned issues to the present environmental and health investigations. Tumor cells usually behave abnormal proliferation and cell migration. These properties are directly linked to the signal transduction pathways of growth factors and that of cell cytoskeleton. Previous results showed that epidermal growth factor receptor (EGFR) clustered in vitro and vivo induced by exposure in 0.4mT power frequency magnetic field (50Hz MF) for 30 minutes. There underline a close relationship between EGFR and F-actin. So if the EGFR signal pathway is affected by MF, the F-actin signal pathway would be involved.In this research, methods such as immunohistochemical method, western blotting, optical method, a confocal microscope, a scanning electron microscope and an atomic force microscope were used to detect the effect of 50 Hz power frequency magnetic field on microfilament assembly of Chinese Hamster Lung (CHL) cell and human amnion FL cell. Further investigations were carried out to understand the mechanism.The results can be concluded as follows: (1) Using the method of immunolabelling, we observed that intracellular stress fibers in CHL cell decreased after exposing cells to a 0.4 mT power frequency magnetic field for 30 minutes. The cell shape became more flat after exposure observed by a scanning electron microscope. The EGFR mass associated with the detergent-insoluble cytoskeleton increased after exposure to magnetic field measured by western-blotting.(2) 0.2 mT, 50Hz MF induced a decrease in cell skeleton stress fibers in FL cell. New microfilament and filopodia bundles appeared at the cell periphery after exposure. The shape of F-actin in FL cell could recover after removing the MF for 2 hours. The mean height of microfilament cytoskeleton decreased after exposure observed with a confocal microscope. The cell shapes became more flat and lamellipodia appeared after exposure. The EGFR mass associated with the detergent-insoluble cytoskeleton and the detergent-insoluble F-actin increased after exposure to MF. (3) The assembly of actin in vitro was not affected by MF, but the efficiency of assembly decreased. The changes of F-actin induced by MF could not be inhibited after clearing the free radical using α-Tocopherol, or blocking the EGFR tyrosine kinase by PD153035, or chelating the calcium ions in the medium by Ethylen glycol-bis(β-aminoethylether) -N,N,N',N'-tetraacetic acid (EGTA). But, the changes of F-actin induced by MF could be obviously inhibited by PD153035 associated with EGTA.Above results suggesting that the effect of 50Hz MF on F-actin assembly and the expression of EGFR may present field strength dependent effect. The effect on F-actin induced by MF may fundermentally have something with the decrease on assembly efficiency of F-actin, the clustering of EGFR and the inflow of calcium ions.