THP-1 cells were exposed to 50 Hz, 1 mT electromagnetic field for 4-6 h while incubated with hydrogen peroxide (as positive control), the bacterium Staphylococcus aureus or interferon-gamma/lipopolysaccharide. Staphylococcus aureus was also exposed to determine the growth rate.
Additional experiments were performed with aminoguanidine as nitric oxide blocker.
Exposure duration: continuous for 4 h to 6 h
Exposure duration: continuous for 7 h
|Setup||Helmholtz coils with 25 cm diameter and 400 turns of copper wire, positioned parallel to the ground, producing a vertical magnetic field; field homogeneous (<5%) within the 30 mm high exposure area with a diameter of 30 mm round the center of the coils; Helmholtz coils placed inside an incubator|
|Sham exposure||A sham exposure was conducted.|
|magnetic flux density||1 mT||-||measured||-||+/- 0.05 mT|
The growth curve of exposed bacteria (both magnetic flux densities) was lower than the control.
The electromagnetic field exposure alone increased nitric oxide levels in THP-1 cells. The increase was even more prominent for Staphylococcus aureus-induced cells and appeared earlier than the increase in cells without electromagnetic field exposure (e.g. bacterial treatment alone). However, a slight decrease was observed in inducible nitric oxide synthase levels under electromagnetic field exposure.
Increased cGMP levels in response to electromagnetic field exposure were closely correlated with increased nitric oxide levels.
Extremely low frequency electromagnetic fields alone caused increased hsp70 levels in a time-dependent manner. When cells were induced with Staphylococcus aureus or interferon-gamma/lipopolysaccharide, electromagnetic field exposure produced even higher levels of hsp70.
Extremely low frequency electromagnetic fields suppressed caspase-9 activation by a small extent (i.e. slight decrease in apoptosis).
The data confirm that an extremely low frequency electromagnetic field affects bacterial growth and the response of the immune system to bacterial challenges, suggesting that an extremely low frequency electromagnetic field could be exploited for beneficial uses (e.g. as a non-pharmacological therapeutic agent against infectious diseases).