Induction of micronuclei and superoxide production in neuroblastoma and glioma cell lines exposed to weak 50 Hz magnetic fields

Abstract

Extremely low-frequency (ELF) magnetic fields (MF) have been associated with adverse health effects in epidemiological studies. However, there is no known mechanism for biological effects of weak environmental MFs. Previous studies indicate MF effects on DNA integrity and reactive oxygen species, but such evidence is limited to MFs higher (greater than or equal to 100 mT) than those generally found in the environment. Effects of 10 and 30 mT fields were studied in SH-SY5Y and C6 cells exposed to 50-Hz MFs for 24 h. Based on earlier findings, menadione (MQ) was used as a cofactor. Responses to MF were observed in both cell lines, but the effects differed between the cell lines. Micronuclei were significantly increased in SH-SY5Y cells at 30 mT. This effect was largest at the highest MQ dose used. Increased cytosolic and mitochondrial superoxide levels were observed in C6 cells. The effects on superoxide levels were independent of MQ, enabling further mechanistic studies without co-exposure to MQ. The micronucleus and mitochondrial superoxide data were consistent with a conventional rising exposure -response relationship. For cytosolic superoxide, the effect size was unexpectedly large at 10 mT. The results indicate that the threshold for biological effects of ELF MFs is 10 mT or less.

Direction-Dependent Effects of Combined Static and ELF Magnetic Fields on Cell Proliferation and Superoxide Radical Production

“…Consistently with previous findings [8], this increase was observed when cytosolic superoxide level was measured 3 h after the end of MF exposure (Figure 4(a)). The effect was observable also in assays performed immediately after MF exposure, but the effect size was somewhat smaller (Figure 4(b)).…”

“…Much of the research on the radical pair mechanism has focused on cryptochromes as candidate magnetosensor molecules, and MFs are generally assumed to affect light-induced reactions in cryptochromes [1, 22]. However, the experiments of the present and previous studies [6–8, 10, 11, 17–20] were conducted in darkness (in cell culture incubators), indicating a light-independent mechanism. In a recent study specifically designed to test the cryptochrome hypothesis, presence of blue light was not necessary for the biological effects of a horizontal 50 Hz MF, and blue light was actually found to inhibit MF-induced increase of cytosolic superoxide level [24].…”

The antitumor effect of static and extremely low frequency magnetic fields against nephroblastoma and neuroblastoma

“…Although neuroblastoma cell lines are frequently used to study the biological effects and mechanisms of MF, they are always used as a model of neuronal cells or degenerative neuronal diseases. In most occasions, the goals were to study the epidemiology of low intensity ELF MF [Kesari et al, ; Höytö et al, ]. Continuous exposure, low intensity ELF MF seems to induce hyperproliferation of neuroblastoma cells [Trillo et al, ; Falone et al, ], supporting the IARC definition of EMF/MF as potential carcinogens.…”

Magnetocarcinogenesis: is there a mechanism for carcinogenic effects of weak magnetic fields?

“…On the other hand, human exposure to ELF magnetic fields !100 mT does occur particularly in occupational environments, so the experimental results and mechanisms discussed in the present paper may be relevant to human health effects even if they do not explain the childhood leukaemia findings. Micronuclei and superoxide levels in mammalian cells have been found to be affected by fields down to 10 mT [62], but further studies at lower magnetic flux densities will be critical for evaluation of the credibility of human health effects at 0.4 mT. However, this will be challenging because of the background ELF magnetic fields of cell culture incubators, and because it will be increasingly difficult to show statistically significant effects if the effect size decreases with field strength.…”