Frequency-specific effects of pulsed magnetic field on BV2 microglial cell function

The objective of this study was to investigate the effects of pulsed magnetic field (PMF) at different frequencies on phagocytosis, migration, and the expression of inflammatory factors in microglia. BV2 microglia were subjected to PMF at different frequencies for 3 d, twice daily. The changes of cell viability, phagocytosis and migration after magnetic stimulation were detected. The mRNA and protein levels of TNF-α and IL-1β were determined using RT-PCR and ELISA. The nuclear translocation of NF-κB P65 and intracellular Ca2+ level was detected through immunofluorescence. PMF at different frequencies did not affect microglial viability. Stimulation at all frequencies enhanced the ability of microglia to phagocytosis and migration. The mRNA expression level of IL-1β and TNF-α was significantly decreased by magnetic stimulation at 20 Hz and 40 Hz. However, only the protein level of IL-1β was significantly reduced by magnetic stimulation at 20 Hz, while TNF-α remained unaffected. Magnetic stimulation at 20 Hz and 40 Hz inhibited the nuclear translocation of NF-κB P65 and increased the intracellular Ca2+ level. Repetitive magnetic stimulation can modulate the secretion of inflammatory cytokines and enhance the phagocytosis and migration capacity of microglia in a frequency-dependent manner. This variation may be linked to differences in the activation of NF-κB and calcium in microglia.