Effect of 6mT static magnetic field on the bcl-2, bax, p53 and hsp70 expression in freshly isolated and in vitro aged human lymphocytes.

An increasing number of evidence indicates that static magnetic fields (SMFs) are capable of altering apoptosis, mainly through modulation of Ca(2+) influx. Here we present data that suggest apoptotic-related gene expression as an alternative pathway, through which exposure to 6milliTesla (mT) SMF can interfere with apoptosis. Exposure to 6mT SMF affects the apoptotic rate (spontaneous and drug-induced) and [Ca(2+)](i) in isolated human lymphocytes; the aged cells are more susceptible to exposure than fresh ones. The exposure to 6mT exerted a protective effect on chemical or physical-induced apoptosis, irrespective of the age of the cells. The investigation of the gene expression of bcl-2, bax, p53 and hsp70 in freshly isolated and in culture-aged human lymphocytes indicates that these genes are modulated by SMF exposure in the experimental conditions used, in a gene-, age- and time-dependent manner. The exposure of isolated lymphocytes to SMF for up to 24h modulated increased bax and p53 and decreased hsp70, and bcl-2. The amount of increment and/or decrement of the proteins varied for each gene examined and was independent of the apoptotic inducers. Finally, the same stress applied to freshly isolated or aged lymphocytes resulted in different modulation of bcl-2, bax and hsp70.

Static magnetic field selects undifferentiated myelomonocytes from low-glutamine concentration stimulated U937 cells.

Reduced glutamine (GLN) concentration in the culture medium of a U937 cell line caused them to be differentiated along the monocytic pathway; cells attached to the matrix and to each other by extending pseudopodia and acquired specific functional characteristics, such as the expression of alpha-naphthyl-acetate esterase and the capacity to reduce nitroblue tetrazolium, as well as becoming active phagocytes. When U937 cells were differentiated under continuous exposure to a 6mT static magnetic field (MF) the overall differentiation process was perturbed. Surprisingly, after 5 days' exposure to the static MF, higher cell viability and differentiation were observed in cells cultured in a GLN-deprived medium than in cells grown in the same medium but in the absence of a static MF. The latter cells, particularly those that were still floating in the medium, were stimulated with TPA for a further 3 days. These cells differentiated and attached to the substrate. Conversely, the same treatment applied to cells cultured in GLN-deprived medium in the presence of the static MF resulted in resistance to TPA-induced differentiation. Indeed, these cells exhibited a round shape and in-suspension growth.

Cell shape and plasma membrane alterations after static magnetic fields exposure.

The biological effects of static magnetic fields (MFs) with intensity of 6 mT were investigated in lymphocytes and U937 cells in the presence or absence of apoptosis-inducing drugs by transmission (TEM) and scanning (SEM) electron microscopy. Lectin cytochemistry of ConA-FITC conjugates was used to analyze plasma membrane structural modifications. Static MFs modified cell shape, plasma membrane and increased the level of intracellular [Ca++] which plays an antiapoptotic role in both cell types. Modifications induced by the exposure to static MFs were irrespective of the presence or absence of apoptotic drugs or the cell type. Abundant lamellar-shaped microvilli were observed upon 24 hrs of continuous exposure to static MFs in contrast to the normally rough surface of U937 cells having numerous short microvilli. Conversely, lymphocytes lost their round shape and became irregularly elongated; lamellar shaped microvilli were found when cells were simultaneously exposed to static MFs and apoptosis-inducing drugs. In our experiments, static MFs reduced the smoothness of the cell surface and partially impeded changes in distribution of cell surface glycans, both features being typical of apoptotic cells. Cell shape and plasma membrane structure modifications upon static MFs exposure were time-dependent. Lamellar microvilli were clearly observed before the distortion of cell shape, which was found at long times of exposure. MFs exposure promoted the rearrangement of F-actin filaments which, in turn, could be responsible for the cell surface modifications. Here we report data that support biological effects of static MFs on U937 cells and human lymphocytes. However, the involvement of these modifications in the onset of diseases needs to be further elucidated.