Cells were divided into the following groups: exposure to the magnetic field for 1) 1 hour, 2) 6 hours and 3) 24 hours. For each exposure group, a separate sham exposure group was used.
THP-1 cells were used as a model for human monocytes/macrophages. All cell cultures were incubated with 10 μg/mL Escherichia coli lipopolysaccharides for immunological stimulation of cells. Cells were partly treated with selective inhibitors of proteinkinase B (Ly294002) and ERK (PD980559) to study the underlying mechanisms of action.
|Chamber||solenoids for exposure and sham exposure were located in magnetically shielded plastic chambers and installed in two different commercial CO2 incubators|
|Setup||the exposure system comprised two identical exposure chambers for exposure and sham exposure each with a 160-turn solenoid coil (22 cm length, 6 cm radius, copper wire diameter of 1.25×10−5 cm); identical currents were present in the sham exposure solenoid, but with the dual-winded coils turned in the opposite direction to generate the same thermal load without the generation of an magnetic field; the field uniformity was 98% near the center of the solenoid and the cell cultures were placed within this region; temperatures were recorded and no significant temperature changes were observed (± 0.1°C)|
|Sham exposure||A sham exposure was conducted.|
Protein expression and gene expression of HO-1 were significantly increased in the nucleus of cells exposed for 6 hours (group 2) compared to the sham exposure with a concurrent significant decrease in the cytoplasm indicating a translocation into the nucleus. Moreover, exposure to the magnetic field led an significant increase of p-NF-kB p65 protein expression in the nucleus with a peak after 24 hours (group 3) while SIRT1 protein expression was significantly increased in the cytoplasm compared to the sham exposure with a peak after 1 hour (group 1) and a following decrease over time. Treatment with inhibitors of protein kinase B and ERK inhibited Nrf2 nuclear translocation and HO-1 protein expression in cells exposed to the magnetic field. Exposure to the magnetic field for 6 hours significantly decreased the ROS content and enzyme activity of the glutathione peroxidase, while significantly increasing the amount of glutathione and the enzyme activity of glutathione reductase in cells compared to the sham exposure.
The authors conclude that a short 50 Hz magnetic field exposure might have a protective role against oxidative stress in stimulated THP-1 cells via the regulation of Nrf-2/HO-1 and SIRT1/NF-kB pathways associated with intracellular glutathione accumulation.