CREB (cyclic-AMP responsive element binding protein) is a transcription factor that is target of a variety of signal transduction pathways mediating cell responses to extracellular stimuli, involving proliferation, or differentiation. Since several signal transduction pathways are involved in activation of CREB, the effects of various inhibitors on magnetic field-induced CREB binding activity were also investigated (inhibitors of different signal transduction pathways, e.g. PKA, PKC, ERK (extracellular signal-regulated kinase), p38 MAPK (p38 mitogen-activated protein kinase)). Furthermore, the relevance of intracellular and extracellular Ca2+ concentrations were examined by using Ca2+ chelators.
|The coils were placed in a mu-metal container.
|The magnetic field was very uniform (0.1%) at the center (10 x 10 x 10 cm³) of the coils where the cell cultures dishes were placed. Sham-exposed cells were handled in the same manner but without the magnetic field.
|Three groups of square copper coils 36 cm x 36 cm with the upper, middle and lower coils having 104, 52 and 104 turns, respectively. They were spaced 18 cm from each other.
|magnetic flux density
Exposure to magnetic field induced a time-dependent activation of CREB-DNA-binding. The CREB complex formation increased shortly after magnetic field exposure for 10 minutes, reaching a peak level after 1 hour, and then recovered to basal level at 4 hours after exposure.
Furthermore, the exposure to magnetic field-induced increase of CREB-DNA-binding was dependent on both extracellular and intracellular Ca2+ concentration but not on PKA, PKC, ERK, or p38 MAPK by using various signal transduction pathway inhibitors.
These results indicate that magnetic field exposure activates CREB-DNA-binding through Ca2+-related signal transduction pathways.