50 Hz magnetic field influences caspase-3 activity and cell cycle distribution in ionizing radiation exposed SH-SY5Y neuroblastoma cells

Abstract

Abstract Overview

Purpose: Earlier evidence suggests that extremely low frequency magnetic fields (ELF MFs) can modify the effects of carcinogenic agents. However, studies with ionizing radiation as the co-exposure agent are sparse and inconclusive. This study investigates whether 50 Hz MFs alone, or in combination with ionizing radiation, alter cell biological variables relevant to cancer and the biological effects of ionizing radiation.

Materials and Methods

• Human SH-SY5Y neuroblastoma cells were either sham exposed or exposed to 100 or 500 μT MF for 24 hours either before or after ionizing radiation exposure (0, 0.4, or 2 Gy).
• Post-exposure, cells were assayed for viability, clonogenicity, reactive oxygen species, caspase-3 activity, and cell cycle distribution using propidium iodide staining and flow cytometry analysis.

Findings

Increased caspase-3 activity was observed in cells exposed to 500 μT MF either before or after ionizing radiation. Moreover, exposure to the 500 μT MF after ionizing radiation decreased the percentage of cells in S-phase. No changes in the ROS levels, clonogenicity, or viability were noted compared to the sham exposed groups. No effects were observed in cells exposed at 100 μT.

Conclusion

At 500 μT magnetic flux density, significant effects on SH-SY5Y cells were observed. These effects were small but may assist in understanding how MFs modify the effects of ionizing radiation. The increase in caspase-3 activity does not necessarily reflect effects on apoptosis, as no changes were seen in the subG1 phase of the cell cycle. Contrary to some earlier findings, 50 Hz MF exposure after ionizing radiation was as effective as treatment given prior to radiation.