Electromagnetic noise blocks the gap-junctional intercellular communication suppression induced by 50 Hz magnetic field / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To explore whether the superposition of an electromagnetic noise can block gap-junctional intercellular communication(GJIC) suppression induced by 50 Hz 0.4 mT extremely low frequency magnetic field(ELF MF).</p><p><b>METHODS</b>Fibroblast cells of mice(NIH 3T3) were exposed to 0.4 mT ELF MF or(and) electromagnetic noise with the same intensity of MF for 24 h, and the GJIC was determined by using fluorescence recovery after photobleaching(FRAP) analysis, which was performed with a laser-scanning confocal microscope(Leica, Germany).</p><p><b>RESULTS</b>ELF MF exposure significantly inhibited GJIC with fluorescence recovery rate of 27.67% +/- 5.12% as compared with the control group(45.57% +/- 9.72%) (P < 0.01), while that of ELF MF plus noise group was (52.61% +/- 8.30%), which was significantly different from ELF MF group(P < 0.01), but not from control(P > 0.05).</p><p><b>CONCLUSION</b>Electromagnetic noise could block the GJIC suppression induced by 50 Hz 0.4 mT MF.</p>

Effects of electromagnetic noise on the enhancement of stress-activated protein kinase(SAPK) phosphorylation induced by 50 Hz magnetic fields / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the possible interference effect of electromagnetic noise exposure on phosphorylation of stress-activated protein kinase(SAPK) induced by 50 Hz magnetic field(MF).</p><p><b>METHODS</b>Chinese hamster lung(CHL) cells were exposed to sham exposure(C), 0.4 mT 50 Hz sinusoidal MF, 0.4 mT electromagnetic noise and the combined noise MF with 50 Hz MF for 3 min and 15 min respectively. After exposure, the cells were lysed, and the proteins were extracted. The SAPK and phosphorylated SAPK (activated form of SAPK) were measured indirectly by Western blot with corresponding antibodies. The percentage of phosphorylated SAPK was calculated and analyzed.</p><p><b>RESULTS</b>Exposure of cells to 50 Hz MF for 3 min and 15 min enhanced the SAPK phosphorylation. The percentage of phosphorylated SAPK were 49.3% and 57.0% respectively, and were significantly different from those of control(P < 0.05, n = 4). However, single noise MF exposure with the same intensity did not enhance the SAPK phosphorylation, the percentage of phosphorylated SAPK were 37.7% and 31.8% (P > 0.05). When cells were exposed to the combined noise MF with 50 Hz MF for 3 min, the SAPK phosphorylation was significantly inhibited (24.4%, P < 0.05); for 15 min, the SAPK phosphorylation was also decreased (39.0%), but there was no significant difference from control and 50 Hz MF exposure(P > 0.05).</p><p><b>CONCLUSION</b>Noise MF with certain intensity could inhibit the biological effect induced by 50 Hz MF.</p>

Exposure to power-frequency magnetic fields can induce activation of P38 mitogen-activated protein kinase / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To study the effects of 50 Hz power-frequency magnetic fields on signal transduction pathway of P38 mitogen-activated protein kinase (P38 MAPK), and explore the cellular signal transduction mechanism of the biological effects induced by power-frequency magnetic fields.</p><p><b>METHODS</b>Chinese hamster lung (CHL) cell line was exposed to power-frequency magnetic fields with two intensities(0.1 and 0.4 mT) for different exposure durations. The cytoplasmic protein was extracted. The phosphorylated(activated) and non-phosphorylated P38 MAPK and MKK3/MKK6 were measured by Western blotting analysis with their specific corresponding antibodies.</p><p><b>RESULTS</b>Power-frequency magnetic fields at 0.4 mT for 10 min could transitorily induce the activation of P38 MAPK and after 15 min the phosphorylation of P38 MAPK restored to control level, while 0.1 mT power-frequency magnetic fields could not induce the activation of P38 MAPK within 24 h. However, both 0.1 mT and 0.4 mT power-frequency magnetic fields could not phosphorylate(activate) the MKK3/MKK6, which is a general upstream kinase of P38 MAPK.</p><p><b>CONCLUSION</b>Power-frequency magnetic fields could transitorily activate the P38 MAPK, but not MKK3/MKK6. The activation mechanism of P38 MAPK needs to be further identified.</p>

Effects of power-frequency magnetic fields exposure on phosphorylation and enzymatic activity of stress-activated protein kinase and its upstream kinase / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To study the effects of 50 Hz power-frequency magnetic fields on signal transduction pathway of stress-activated protein kinase(SAPK), and explore the cellular signal transduction mechanism of the biological effects induced by power-frequency magnetic fields.</p><p><b>METHODS</b>Chinese hamster lung(CHL) cell line was exposed to power-frequency magnetic fields with two intensities for different exposure durations. The cytoplasmic protein was extracted and the phosphorylated portion of SAPK and SEK1/MKK4 was measured with Western blotting analysis. The SAPK enzymatic activity was measured by the solid-phase kinase assay in cells exposed to power-frequency magnetic fields for 15 min.</p><p><b>RESULTS</b>Both 0.4 mT and 0.8 mT power-frequency magnetic fields could enhance the phosphorylation of SAPK in a time-relative course manner, and reached the maximum extent at 15 min, with an increase of 20% and 17% respectively. The solid-phase kinase assay showed that the enzymatic activities of SAPK were also increased, which were 2.9 +/- 0.4 and 2.1 +/- 0.9 times of control respectively. However, the duration of SAPK phosphorylation induced by 0.8 mT was longer than that of 0.4 mT, while the duration and extent of SAPK dephosphorylation was remarkably shorter than that of 0.4 mT. The power-frequency magnetic fields under equal conditions could not phosphorylate(activate) the SEK1/MKK4.</p><p><b>CONCLUSION</b>Power-frequency magnetic fields could activate the SAPK, but not SEK1/MKK4. It is suggested that power-frequency magnetic fields may activate SAPK signal transduction pathway through a kinase other than SEK1/MKK4. The activation mechanism of SAPK of power-frequency magnetic fields needs to be identified in more detail.</p>

Abnormal shift of connexin 43 gap-junction protein induced by 50 Hz electromagnetic fields in Chinese hamster lung cells / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To study the effects of extremely low frequency magnetic fields(ELF MF) on the amount and localization of connexin 43(Cx43) gap-junction protein in the Chinese hamster lung(CHL) cells, and to explore the mechanism of ELF MF suppression on gap-junctional intercellular communication(GJIC).</p><p><b>METHODS</b>The cells were irradiated for 24 h with 50 Hz sinusoidal magnetic field at 0.8 mT without or with 12-O-tetrade-canoylphorbol-3-acetate(TPA), 5 ng/ml for 1 h. The localization of Cx43 proteins were performed by indirect immunofluorescence histochemical analysis and detected by confocal microscopy. The second experiment was conducted to examine the quantity of Cx43 proteins level in nuclei or cytoplasm and detected by Western blotting analysis.</p><p><b>RESULTS</b>The cells exposed to TPA for 1 h displayed less bright labelled spots in the regions of intercellular junction than the normal cells. Most of Cx43 labelled spots occurred in the cytoplasm and aggregated near the nuclei. At the same time, the amount of Cx43 protein in cytoplasm were increased[(2.03 +/- 0.89) in ELF group, (2.43 +/- 0.82) in TPA group] as compared to normal control(1.04 +/- 0.17) (P < 0.01).</p><p><b>CONCLUSION</b>Inhibition on GJIC function by ELF MF alone or combined with TPA may be related with the shift of Cx43 from the regions of intercellular junction to the cytoplasm.</p>