NB69

Field exposure to 50 Hz significantly affects wild‑type and unfolded p53 expression in NB69 neuroblastoma cells

Previous studies have shown that intermittent exposure to a 50 Hz, 100 µT sinusoidal magnetic field (MF) promotes proliferation of human neuroblastoma cells, NB69, through a free radical‑dependent activation of the p38 pathway. Martínez et al. investigated whether the oxidative stress‑sensitive protein p53 is a potential target of the MF. To that end, NB69 cells were exposed to short intervals of 30 to 120 min to the aforementioned MF parameters. Immunocytochemical analysis (Fig. 3) showed that MF exposure induced underexpression of wt p53 (18.9±1.3% below controls) and increased the expression of the unfolded isoform (54.1±6.3% above controls). The decrease in wt p53 was cytoplasmic (76.26±2.16% of controls; Fig. 3B), while the increase in unfolded p53 was observed in both the nucleus and cytoplasm (Fig. 3C). Photomicrographs (Fig. 3D and E) illustrated these effects.

MF Effects on Free Radical Levels of NB69 Cells

Martínez et al. previous studies have shown that intermittent exposure to a 50-Hz, 100-µT sine wave magnetic field (MF) promotes human NB69 cell proliferation through the activation of the epidermal growth factor receptor (EGFR) and MAPK-ERK1/2 and p38 pathways. The present work investigates the MF effects on free radical (FR) production and the potential involvement of NADPH oxidase in the MF-induced activation of MAPK pathways. NB69 cells were exposed to MF or sham and treated with DCFH-DA in the presence or absence of the free radical chelating agent NAC. The fluorescent DCF due to intracellular oxidation of DCFH-DA was analyzed by fluorescence spectroscopy and expressed in terms of ROS production. After 10 minutes of MF exposure followed by a 30-minute post-exposure incubation, the intensity of fluorescent DCF and therefore, of FR production, were significantly increased (26.67% ± 5.9% over controls, Figure 2). Such an increase was not observed in samples exposed to the MF in the presence of NAC.