Release of mediators by DMSO-differentiated HL-60 cells exposed to electric interferential current and the requirement of biochemical prestimulation.
OBJECTIVE
Controversial results have been obtained with respect to the influence of biochemical prestimulation upon the action of electromagnetic fields on mammalian cells. Examined in detail has been the influence of a modulated low-frequency (interferential) current upon the release of four mediators by DMSO-differentiated HL-60 cells with and without prestimulation by the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP).


METHODS
Human promyelocytes (HL-60) cells differentiated to granulocytes by dimethylsulphoxide were exposed to a so-called interferential current (IFC) in a suspension culture. The influence of IFC treatment, an amplitude-modulated 4000 Hz current used in therapeutic applications, on the release of prostaglandine E2 (PGE2), leukotriene B4 (LTB4), thromboxane B2 (TXB2) and interleukin 8 (IL-8) was investigated. Effects of a static magnetic field were also studied.


RESULTS
In no case were significant differences between exposed and sham-exposed samples observed after 15 min exposure to selected modulation frequencies (0-125Hz, 250 microA cm(-2)). Therefore, the influence of prestimulation with different concentrations of fMLP on the release of the four mediators was investigated. fMLP alone enhanced the release of PGE2, LTB4, TXB2 and IL-8 with half of the maximum (ED50) effective concentration of approximately 10nM. Prestimulation with various concentrations of fMLP and subsequent exposure to IFC 125Hz (15 min, 250 microA cm(-2)) had no effect at low or high concentrations of fMLP, while in the middle range of concentration of approximately 100 pM fMLP a significant enhancement of PGE2, LTB4 and IL-8 was observed. This synergistic effect of fMLP and IFC was examined in detail in prestimulated cells (100pM fMLP) by varying the exposure time, current density and modulation frequency in the range 0-50 Hz. Window effects for the release of PGE2, LTB4 and IL-8 were obtained for exposure time, current density and modulation frequency whereas, in the release of TXB2, no field effect was detected.


CONCLUSIONS
The study has demonstrated the synergistic action of chemical stimulation and electric current exposure, and the existence of windows for cellular activation status, exposure time, current density and modulation frequency.
Sontag
W
W
Forschungszentrum Karlsruhe, Institut für Medizintechnik und Biophysik, Postfach 3640, D-76021 Karlsruhe, Germany. Sontag@imb.fzk.de
D002454:Cell Differentiation / Q000187:drug effects; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D015232:Dinoprostone / Q000378:metabolism; D004574:Electromagnetic Fields; D018922:HL-60 Cells; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism; D007975:Leukotriene B4 / Q000378:metabolism; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D013929:Thromboxane B2 / Q000378:metabolism
D016209:Interleukin-8; D007975:Leukotriene B4; D013929:Thromboxane B2; D009240:N-Formylmethionine Leucyl-Phenylalanine; D015232:Dinoprostone; D004121:Dimethyl Sulfoxide