  In this study, we investigated the effects of specific low frequency
electromagnetic fields sequences on U937 cells, an in vitro model of human
monocyte/macrophage differentiation. U937 cells were exposed to electromagnetic
stimulation by means of the SyntheXer system using two similar sequences,
XR-BC31 and XR-BC31/F. Each sequence was a time series of twenty-nine wave
segments. Here, we report that exposure (4 days, once a day) of U937 cells to
the XR-BC31 setting, but not to the XR-BC31/F, resulted in increased expression
of the histone demethylase KDM6B along with a global reduction in histone H3
lysine 27 (H3K27) tri-methylation. Furthermore, exposure to the XR-BC31
sequence induced differentiation of U937 cells towards a macrophage-like
phenotype displaying a KDM6B dependent increase in expression and secretion of
the anti-inflammatory interleukins (ILs), IL-10 and IL-4. Importantly, all the
observed changes were highly dependent on the sequence's nature. Our results
open a new way of interpretation for the effects of low frequency
electromagnetic fields observed in vivo. Indeed, it is conceivable that a
specific low frequency electromagnetic fields treatment may cause changes in
chromatin accessibility and consequently in the expression of anti-inflammatory
mediators and in cell differentiation.
