NF-kappaB or AP-1-dependent reporter gene expression is not altered in human U937 cells exposed to power-line frequency magnetic fields.

A number of studies have reported that human leukemia cells respond to exposure to power-line frequency electromagnetic fields (EMFs), providing evidence for an EMF-induced signaling pathway involving activation of protein tyrosine kinases (PTKs), phospholipase-Cy and protein kinase C (PKC). Because activation of PKC is also important in the signaling pathways that regulate the transcription factors NF-kappaB and AP-1, we evaluated the effect of exposure to a 60 Hz EMF on NF-kappaB or AP-1-dependent reporter gene expression in cells of the human promonocytic U937 leukemia cell line. Reporter genes were electroporated into U937 cells and activation of the NF-kappaB or AP-1 signaling pathway was evaluated by measuring chloramphenicol acetyltransferase (CAT) protein by CAT ELISA. In contrast to the effects of well-understood chemical or biological agents, the exposure to magnetic-field intensities of 0.08, 0.1, 1.0 or 1.3 mT had no effect on the NF-kappaB or AP-1 signaling pathways.