Stimulation of Bruton's tyrosine kinase (BTK) and inositol 1,4,5-trisphosphate production in leukemia and lymphoma cells exposed to low energy electromagnetic fields

We examined the effects of low energy electromagnetic field (EMF) exposure on the BTK kinase activity in B18-2 ([Btk-, rBTK(wt)] DT40) chicken lymphom a B cells and NALM-6 leukemic pre-B cells. Exposure of B18-2 cells to EMF r esulted in activation of BTK within 1 to 15 minutes in 8 of 8 independent e xperiments with stimulation indexes ranging from 1.2 to 13.3. While in some experiments the BTK stimulation was transient, in others the BTK activity continued to be significantly elevated for up to 4 hours. Similarly, exposu re of NALM-6 cells to EMF resulted in activation of BTK within 30 minutes i n 7 of 7 experiments with stimulation indexes ranging from 1.2 to 7.4. Stim ulation of BTK activity in EMF exposed cells was associated with enhanced p hosphoinositide turnover and increased inositol-1,4,5-tri sphosphate (IP3) production in 7 of 13 experiments with DT40 cells and 7 of 13 experiments w ith NALM-6 cells. The likelihood and magnitude of an IP3 response after EMF exposure were similar to those after BCR ligation on DT40 cells and CD19 l igation on NALM-6 cells. These results confirm and extend our previous stud ies regarding EMF-induced biochemical signaling events in B-lineage lymphoi d cells.