Action of 50 Hz magnetic fields on cAMP content in SV40-3T3 cells: dependence on flux density and extracellular calcium

Potent stimulation of blood flow in fingers of volunteers after local short-term treatment with low-frequency magnetic fields from a novel device

A novel hand-held low-frequency magnetic stimulator (MagCell-SR) was tested for its ability to stimulate microcirculation in fingers of healthy volunteers. Blood flow during and after 5 minutes exposure was quantified using Laser Doppler Perfusion Imaging Technique. The device was positioned between the wrist and the dorsal part of the backhand. Because the increase in blood flow could be caused by a release of nitric oxide (NO) from the vascular endothelial cells we tested NO production with a fluorescence marker and quantified the measurements in cell cultures of human umbilical endothelial cells (HUVEC). Exposure increased blood flow significantly, persisted several minutes, and then disappeared gradually. In order to assess the effect of a static magnetic field, the measurements were also carried out with the device shutoff. Here, only a small increase in blood flow was noted. The application of the rotating MagCell-SR to the HUVEC cultures leads to a rapid onset and a significant increase of NO release after 15 minutes. Thus, frequencies between 4 and 12 Hz supplied by the device improve microcirculation significantly. Therefore, this device can be used in all clinical situations where an improvement of the microcirculation is useful like in chronic wound healing deficits.

Low-energy electromagnetic fields promote proliferation of vascular smooth muscle cells

The rationale was to investigate the effects of low-energy electromagnetic fields (EMF) on the proliferation of bovine coronary and murine aortic smooth muscle cells (SMC). EMF were applied to SMC at field frequencies of 25, 50, or 100 Hz, and exposure time was set to 5, 15, or 30 minutes. Significant increases in SMC-counts compared with sham exposed controls were found for all EMF-frequencies tested. The effect was most pronounced for 50 Hz fields with maximum increases of 1.2-fold over controls. Sequential double exposure of mouse aortic SMC to 50 Hz fields revealed significantly enhanced cell proliferation by 1.2 fold compared with single exposure (p < 0.05). Experiments performed on bovine SMC also revealed significant increases in cell proliferation. The results demonstrate that EMF are capable of significantly enhancing the proliferation of vascular SMC. These results rise the question whether EMF would qualify as supportive means to angio-/arteriogenic approaches.

Repetitive transcranial magnetic stimulation does not influence immunological HL-60 cells and neuronal PC12 cells

BACKGROUND

Transcranial magnetic stimulation (TMS) is a non-invasive method used in medical applications such as brain mapping or as a therapeutic tool in neurological and psychiatric disorders because it can stimulate defined regions of the brain without anaesthesia.

METHODS

The action of repetitive transcranial magnetic stimulation (rTMS) on HL-60 and PC12 cells has been investigated. The cells have been stimulated in vitro with different number of pulses (75 - 1250), different intensities (10, 20 and 40%) and different frequencies (0.25, 1 and 10 Hz) by using a double coil (2x70 mm) connected to the 'Magstim rapid'. At selected time points after treatment the following endpoints have been determined: viability, cyclic AMP (cAMP) and heat shock protein 72 (Hsp72) (HL-60 cells), and viability, cAMP, dopamine and noradrenaline (PC12 cells). Viability was measured with the alamarBlue assay, whereas cAMP, Hsp72, dopamine and noradrenaline were determined with enzyme-linked immunosorbent assay (ELISA).

RESULTS

In both cell lines viability was not influenced by rTMS treatment, the same was true for the cytosolic cAMP concentration. In HL-60 cells rTMS treatment did not change the Hsp72 content, also a protective effect of rTMS treatment on cell viability before toxic H(2)O(2) treatment was not observed. After high potassium treatment the release of the two neurotransmitters dopamine and noradrenaline in PC12 cells was enhanced 15- and 5-fold, respectively, but after rTMS treatment no change in the release of the two neurotransmitters was observed.

CONCLUSIONS

In two mammalian cell lines rTMS treatment in a variety of exposure conditions does not influence any of the measured parameters.

Response of cyclic AMP by DMSO differentiated HL-60 cells exposed to electric interferential current after prestimulation

The action of interferential current (IFC) upon intracellular content of cyclic adenosine monophosphate (cAMP) after prestimulation with the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP) has been investigated. Human promyelocytes (HL-60) differentiated to granulocytes by dimethylsulphoxide (DMSO) have been treated with different concentrations of fMLP. This enhances their cAMP content. The half maximal effective concentration (EC50) was about 4 nM. Exposure to IFC with modulation frequencies of 35 and 125 Hz (5 min, 250 microA/cm2) after prestimulation with various concentrations of fMLP had no enhancing effect at low or high concentrations of fMLP. In contrast, at medium concentrations in the range of about 100 pM fMLP, a significant enhancement of cAMP could be observed. This synergistic effect of fMLP and IFC has been examined in detail by varying the modulation frequency, current density, and exposure time. Enhancement of cAMP content could be observed at certain modulation frequencies and exposure times suggesting a window effect, whereas for the current density in the range measured (8.5 microA/cm2-2.5 mA/cm2) a constant enhancement could be observed. The synergistic effect of fMLP and IFC could only be observed in the treatment sequence of fMLP followed by IFC; an inverse sequence had no effect on the cAMP content. .