Effect of 50-Hz Sinusoidal Magnetic Field on the Production of Superoxide Anion and the Expression of Heat-shock Protein 70 in RAW264 Cells

Abstract

There is a growing concern if the power-line frequency (50/60 Hz) magnetic field (termed in this paper ELF-MF) increases cancer risks. Since one of the major causes of cancer is cellular oxidative stress, whether the ELF-MF increases the oxidative stress is a central problem in the studies on the biological effect of the ELF-MF. Here, we have investigated the effect of 50-Hz sinusoidal magnetic field on the production of O 2 -, the expression of heat shock protein (HSP) 70 and the mitochondrial membrane potential in cell line macrophage RAW264 cells. Macrophages were exposed to or not exposed to 0.1-mT or 0.5-mT, 50-Hz sinusoidal magnetic field and were subjected to (1) assay for O 2 -(2) analysis of the expression of HSP70, and (3) measurement of the mitochondrial membrane potential with a fluorescent indicator. The 50-Hz magnetic field enhanced production of O 2 -and the expression of HSP70, both of which are consistent with previous studies. The exposure to 50-Hz magnetic field decreased mitochondrial membrane potential indicating the diminished activity of mitochondria. The uncoupler of mitochondrial function, carbonyl cyanide p-trifluoromethoxyphenylhydrazone diminished the membrane potential, as expected. On the other hand, it increased the production of O 2 -. The results collectively suggest that the 50-Hz magnetic field diminished the mitochondrial membrane potential, which led to the increase in the production of O 2 -and the expression of HSP70 protein.

Cellular Response to ELF-MF and Heat: Evidence for a Common Involvement of Heat Shock Proteins?

“…The authors did unfortunately not investigate effects of coexposures to heat and MF. A recent study showed very similar results under comparable experimental conditions, with the exception that RAW mouse macrophages instead of human K562 cells were investigated ( 44 ).…”

“…MF-induced increases in HSP expression levels were also detected in a number of immune relevant cell lines: macrophages [RAW264 cell line ( 44 )], human leukemia and lymphoma cells [CEM, HL-60, U937, K562 cells, THP-1 cells ( 20 , 42 , 45 – 47 )]. Immune relevant cells or cell lines furthermore produce extracellular HSPs as a signal molecule for immune response [e.g., Ref.…”

Immune-Modulating Perspectives for Low Frequency Electromagnetic Fields in Innate Immunity

“…It has to be pointed out that none of these studies differentiated between intra and intercellular HSPs. Enhancement of production and HSP70 expression by ELF-MFs (50 Hz, 0.1 or 0.5 mT) were also confirmed in RAW264 cells (an Abelson murine leukemia virus transformed cell line used as a macrophage model) ( 15 ). However, in other studies, with exposure of HL-60, H9c2, and Girardi heart cells to lower intensity MF and/or for shorter periods [60 Hz, 6.3 or 8.0 µT, 20 min ( 14 ); 50 Hz, 2 µT–4 mT, 15 or 30 min ( 12 )] no change in HSPs expression was detected.…”

Biological effects of chronic exposure of Blaptica dubia (Blattodea: Blaberidae) nymphs to static and extremely low frequency magnetic fields

“…These proteins are useful biomarkers that have already been used to monitor the impact of environmental factors on different invertebrate species (Singh & Lakhotia 2000, Mukhopadhyay et al 2002. MFs have been shown to induce increased transcription and translation of HSP70 (Malagoli et al 2006, Pooam et al 2017). Critical early steps in stress response induced by ambiental magnetic fields are activation of heat shock factors (HSF) and increased heat shock element (HSE) (Lin et al 1997).…”