Pre-exposure to 50 Hz magnetic fields modifies menadione-induced DNA damage response in murine L929 cells

Abstract

Purpose: Effects on DNA damage response were investigated in murine L929 cells exposed to 50 Hz magnetic fields (MF) with or without ultraviolet B (UVB, wavelength 280–320 nm) radiation or menadione (MQ).

Materials and methods: Cells were exposed to MF at 100 or 300 μT combined with MQ (150 μM, 1 hour) or UVB radiation (160 J/m²) using various exposure schedules. The samples were stained with propidium iodide (PI) and analysed by flow cytometer for cell cycle stages. Apoptotic cells were defined as sub G₁ events.

Results: In cells first exposed to 100 μT MF for 24 h, the response to subsequent MQ treatment was significantly altered so that the proportion of sub G₁ cells was decreased and the proportion of cells in the G₂/M phase was increased. When a 300 μT MF was used, also the proportion of cells in the G₁ phase was decreased. MF exposures after MQ treatment did not alter responses to MQ. No effects were found from MF exposure alone or from MF combined with UVB radiation.

Conclusions: The results strengthen previous findings suggesting that pre-exposure to MF can alter cellular responses to other agents, and indicate that MF as low as 100 μT has measurable impacts on cancer-relevant cellular processes such as DNA-damage.

Keywords:

• Adaptive response
• apoptosis
• cell cycle arrest
• combined exposure
• ELF
• non-ionizing radiation