The effect of 100 mT SMF on activation of the hsp70 promoter in a heat shock/luciferase reporter system

Abstract

Human exposure to magnetic fields, increased through use of new technologies like magnetic resonance imaging (MRI), has prompted investigations into possible effects of static magnetic fields (SMFs) on cellular processes. However, controversy still remains between many studies, which likely results from a lack of uniformity across experimental parameters, including the length of magnetic field exposure, the strength of the magnetic field, and the cell type or organism under investigation. The purpose of this research was to monitor effects of SMF exposure using real-time luminescence photometry. The study investigated the potential interaction of a 100 mT SMF on a heat shock protein (hsp70)/luciferase reporter construct in stably transfected NIH3T3 cells. Changes in heat shock promoter activation following 100 mT SMF exposure were analyzed and detected as bioluminescence in real-time. Two heat parameters were considered in combination with sham- and 100 mT-exposed experiments: no heat or 1,800 s heat. As expected, there was a significant increase in bioluminescence in response to 1,800 s of heat alone. However, no significant difference in average hsp70 promoter activation between sham and 100 mT experiments was observed for no heat or 1,800 s heat experiments. Therefore, a 100 mT SMF was shown to have no effect on the activation of the heat shock protein promoter during SMF exposure or when SMF exposure was combined with a heat insult.

Elevation of heat shock gene expression from static magnetic field exposure in vitro

“…Longer exposure durations, like those used in this study (1-440 mT, up to 48 h), Potenza et al [2004] (200-250 mT, overnight) and in Tenuzzo et al [2009] (6 mT, 24 h) show some significant response to SMF. In contrast, shorter exposure durations such as those used by Abdelmelek et al [2006] (128 mT, 1 h/day) and Belton et al [2009] (100 mT, 15 min) do not have significant responses. However, further studies need to be performed to determine if indeed changes require a much longer exposure to the magnetic fields to be induced.…”

“…The duration of exposure may also be an important factor. As described by Belton et al [], exposure duration may be a potential factor that discriminates studies with significant effects from those without, at similar flux densities. Longer exposure durations, like those used in this study (1–440 mT, up to 48 h), Potenza et al [] (200–250 mT, overnight) and in Tenuzzo et al [] (6 mT, 24 h) show some significant response to SMF.…”

“…The duration of exposure may also be an important factor. As described by Belton et al [2009], exposure duration may be a potential factor that discriminates studies with significant effects from Fig. 7.…”

“…The use two adjacent incubators and a second apparatus for the sham exposure could have affected our results despite our efforts to minimize confounding experimental factors. In this study, we used primary rat cells (Rat‐1) transiently transfected with a luciferase reporter while Belton et al [] used a transformed cell line (NIH‐3T3) that was stably transfected with a luciferase reporter. The transformed cells may respond differently to physical stress than the RAT‐1 primary cells.…”

“…For example, significant responses can be observed in [Potenza et al, 2004;Tenuzzo et al, 2009], whereas no significant response was observed in [Guisasola et al, 2002;Bodega et al, 2005;Belton et al, 2011;Abdelmelek et al, 2006]. However, non-significant increases in heat shock were also reported by [Abdelmelek et al, 2006;Belton et al, 2009].…”