Impact of 1.8GHz Radiofrequency Electromagnetic Fields on Gene Expression Profiles in Rat Neurons / 预防医学

Objective To investigate the changes of gene expression in rat neurons induced by 1.8 GHz radiofrequency electromagnetic fields (RF EMF) and to screen RF EMF-responsive genes. Methods The rat primary cultured neuronal cells were divided into two groups, the radiation group and control group, from which the total RNA was extracted immediately and purified after intermittently (5min on/10min off) exposed or U34 array was applied to detect the changes of gene expression in rat neurons. Results Among 1200 candidate genes, 24 up-regulated and 10 down-regulated genes which are associated with multiple cellular functions (cytoskeleton, signal transduction pathway, metabolism, etc.) after functional classification were found by using Affymetrix microarray suite software 5.0. Although the changes in gene expression were less than 2 folds, they had statistical significance (P<0.01). Conclusion RF radiation of 1.8GHz induce the changes of many genes transcription in rat neurons, some of which indicate the negative effects of RF radiation on neurons.

Effect of 1.8 GHz radiofrequency electromagnetic fields on gene expression of rat neurons / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the changes of gene expression in rat neuron induced by 1.8 GHz radiofrequency electromagnetic fields (RF EMF) to screen for RF EMF-responsive genes and the effect of different exposure times and modes on the gene expression in neuron.</p><p><b>METHODS</b>Total RNA was extracted immediately and purified from the primary culture of neurons after intermittent exposed or sham-exposed to a frequency of 1.8 GHz RF EMF for 24 hours at an average special absorption rate (SAR) of 2 W/kg. Affymetrix Rat Neurobiology U34 array was applied to investigate the changes of gene expression in rat neuron. Differentially expressed genes (Egr-1, Mbp and Plp) were further confirmed by semi-quantitative revere transcription polymerase chain reaction (RT PCR). The expression levels of Egr-1, Mbp and Plp were observed at different exposure times (6, 24 h) and modes (intermittent and continuous exposure).</p><p><b>RESULTS</b>Among 1200 candidate genes, 24 up-regulated and 10 down-regulated genes were found by using Affymetrix microarray suite software 5.0 which are associated with multiple cellular functions (cytoskeleton, signal transduction pathway, metabolism, etc.) after functional classification. Under 24 h and 6 h intermittent exposure, Egr-1 and Plp in experiment groups showed statistic significance (P < 0.05) compared with the control groups, while expression of Mbp did not change significantly (P > 0.05). After 24 h continuous exposure, Egr-1 and Mbp in experiment groups showed statistic significance (P < 0.05) compared with the control group, while expression of Plp did not change significantly (P > 0.05). Under the same exposure mode 6 h, expression of all the 3 genes did not change significantly. Different times (6, 24 h) and modes (intermittent and continuous exposure) of exposure exerted remarkable different influences on the expression of Egr-1, Mbp, Plp genes (P < 0.01).</p><p><b>CONCLUSION</b>The changes of many genes transcription were involved in the effect of 1.8 GHz RF EMF on rat neurons; Down-regulation of Egr-1 and up-regulation of Mbp, Plp indicated the negative effects of RF EMF on neurons; The effect of RF intermittent exposure on gene expression was more obvious than that of continuous exposure; The effect of 24 h RF exposure (both intermittent and continuous) on gene expression was more obvious than that of 6 h (both intermittent and continuous).</p>

Effects of GSM 1800 MHz radiofrequency electromagnetic fields on DNA damage in Chinese hamster lung cells / 中华预防医学杂志

<p><b>OBJECTIVE</b>To study the effects of GSM 1800 MHz radiofrequency electromagnetic fields (RF EMF) on DNA damage in Chinese hamster lung (CHL) cells.</p><p><b>METHODS</b>The cells were intermittently exposed or sham-exposed to GSM 1800 MHz RF EMF (5 minutes on/10 minutes off) at a special absorption rate (SAR) of 3.0 W/kg for 1 hour or 24 hours. Meanwhile, cells exposed to 2-acetylaminofluorene, a DNA damage agent, at a final concentration of 20 mg/L for 2 hours were used as positive control. After exposure, cells were fixed by using 4% paraformaldehyde and processed for phosphorylated form of H2AX (gammaH2AX) immunofluorescence measurement. The primary antibody used for immunofluorescence was mouse monoclonal antibody against gammaH2AX and the secondary antibody was fluorescein isothiocyanate (FITC)-conjugated goat anti-mouse IgG. Nuclei were counterstained with 4, 6-diamidino-2-phenylindole (DAPI). The gammaH2AX foci and nuclei were visualized with an Olympus AX70 fluorescent microscope. Image Pro-Plus software was used to count the gammaH2AX foci in each cell. For each exposure condition, at least 50 cells were selected to detect gammaH2AX foci. Cells were classified as positive when more than five foci were detected. The percentage of gammaH2AX foci positive cells was adopted as the index of DNA damage.</p><p><b>RESULTS</b>The percentage of gammaH2AX foci positive cell of 1800 MHz RF EMF exposure for 24 hours (37.9 +/- 8.6)% or 2-acetylaminofluorene exposure (50.9 +/- 9.4)% was significantly higher compared with the sham-exposure (28.0 +/- 8.4)%. However, there was no significant difference between the sham-exposure and RF EMF exposure for 1 hour (31.8 +/- 8.7)%.</p><p><b>CONCLUSION</b>1800 MHz RF EMF (SAR, 3.0 W/kg) for 24 hours might induce DNA damage in CHL cells.</p>

Effects of GSM 1800 MHz radiofrequency electromagnetic fields on protein expression profile of human breast cancer cell MCF-7 / 中华预防医学杂志

<p><b>OBJECTIVE</b>To study the effects of GSM 1800 MHz radiofrequency electromagnetic fields (RF EMF) exposure on protein expression profile of human breast cancer cell line (MCF-7), as to exploring the possible effects on normal cell physiological function.</p><p><b>METHODS</b>MCF-7 cells were continuously or intermittently (5 minutes field on followed by 10 minutes off) exposed to RF EMF for different duration (1 hour, 3 hours, 6 hours, 12 hours, or 24 hours) at an average specific absorption rate (SAR) of 3.5 W/kg. The extracted proteins were separated by 2-dimensional electrophoresis and the protein-spot distribution of the silver-stained gels was analyzed by using PDQuest software 7.1. Each experiment was repeated three times.</p><p><b>RESULTS</b>On the average, around 1100 proteins were detected using pH 4 - 7 IPG strip. There were no differential proteins found under continuous exposure at SAR of 3.5 W/kg for 6 hours. Under other exposure conditions, we found various differentially expressed proteins in exposure groups as compared with the sham-exposed controls. Especially in 3 hours intermittent exposure and 12 hours continuous exposure, eighteen and seven differential proteins were detected, respectively. The categories and functions of these differentially expressed proteins were analyzed by searching of SWISS-PROT protein database, which suggested that these proteins should be related to the functions of biosynthesization, signal transduction, and DNA damage and repair.</p><p><b>CONCLUSIONS</b>Data indicated that the protein expression changes induced by RF radiation might depend on exposure duration and mode. Many biological processes might be affected by RF exposure.</p>

Global gene response to GSM 1800 MHz radiofrequency electromagnetic field in MCF-7 cells / 中华预防医学杂志

<p><b>OBJECTIVE</b>To investigate whether GSM 1800 MHz radiofrequency electromagnetic field (RF EMF) can change the gene expression profile in MCF-7 cells and to screen RF EMF responsive genes.</p><p><b>METHODS</b>Subcultured MCF-7 cells were intermittently (5-minute fields on/10-minute fields off) exposed or sham-exposed to GSM 1800 MHz RF EMF, which was modulated by 217 Hz EMF, for 24 hours at an average specific absorption rate (SAR) of 2.0 W/kg or 3.5 W/kg. Immediately after RF EMF exposure or sham-exposure, total RNA was isolated from MCF-7 cells and then purified. Affymetrix Human Genome U133A Genechip was applied to examine the change of gene expression profile according to the manufacturer's instruction. Data was analyzed by Affymetrix Microarray Suite 5.0 (MAS 5.0) and Affymetrix Data Mining Tool 3.0 (DMT 3.0). Quantitative reverse transcription polymerase chain reaction (RT-PCR) was used to validate the differentially expressed genes identified by Genechip analysis.</p><p><b>RESULTS</b>A small number of differential expression genes were found in each comparison after RF EMF exposure. Through reproducible and consistent analysis, no gene or five up-regulated genes were screened out after exposure to RF EMF at SAR of 2.0 W/kg or 3.5 W/kg, respectively. However, these five genes could not be further confirmed by RT-PCR.</p><p><b>CONCLUSION</b>The present study did not provide clear evidence that RF EMF exposure might distinctly change the gene expression profile in MCF-7 cells under current experimental conditions, implying that the exposure might not affect the MCF-7 cell physiology, or this cell line might be less sensitive to the RF EMF exposure.</p>

Effects of mobile-phone microwave on dimethylbenz (a) anthracene induced mammary carcinoma development in rats / 中华预防医学杂志

<p><b>OBJECTIVE</b>To investigate whether exposure to 900 MHz GSM wireless communication signals enhances mammary tumor development and growth induced by low dose dimethylbenz (a) anthracene (DMBA).</p><p><b>METHODS</b>Five hundred female Sprague Dawley (SD) rats were treated with a single dose of 35 mg/kg. DMBA and then divided into 5 groups: one control group without exposure, and 4 groups with exposure in blinded fashion. The specific absorption rates (SAR) were 0, 0.44, 1.33 and 4.00 W/kg for the 4 exposure groups, respectively. Exposure started on the next day after DMBA administration and lasted 4 hours/day, 5 days/week for 26 weeks. Rats were weighted and palpated weekly for the presence of tumors, and killed at the end of 26-week exposure period. All mammary glands were examined histopathologically.</p><p><b>RESULTS</b>The incidence of mammary carcinoma in sham-exposure group was 37% (37/100). And mammary carcinoma incidences in the other groups of the exposure dose (0.44, 1.33 and 4.00 W/kg) were 25% (25/100), 34% (34/99) and 38% (38/100) respectively. There were no statistically significant differences between sham- and mobile phone microwave-exposed groups. In addition, the histopathological morphology of mammary tumor model in SD rats was observed. By microscopical examination two types of mammary tumor in this model were found, that was malignant or benign one. The former included adenocarcinoma and squamous cell carcinoma, and the latter included adenoma, fibroadenoma and cyst. Sometimes the histopathological morphology of mammary tumor appeared various since several kinds of histopathological features existed in the same individual.</p><p><b>CONCLUSION</b>This study does not provide the evidence that 900 MHz GSM microwave exposure might promote DMBA-induced mammary tumor development in rats.</p>

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>

The effect of extremely low frequency magnetic fields on cytochrome oxidase subunit 1 mRNA transcription / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To clone and identify MF-1 gene which responded to extremely low frequency magnetic fields(ELF MF) in Daudi cells, and explore the response universality of MF-1 gene in several MF-sensitive cell lines, so as to provide experimental basis for revealing the mechanism of biological effects induced by magnetic field.</p><p><b>METHODS</b>The DNA fragment of MF-1 was cloned and sequenced; the mRNA level of MF-1 gene were analysed in MF-sensitive cell lines(HL-60, L1210 and CHL) by Northern blot after these cells being treated with 0.1 mT and 0.8 mT MF for 20 minutes and 24 hours, respectively.</p><p><b>RESULTS</b>The MF-1 cDNA sequence had 100% homology with cytochrome oxidase subunit 1 gene(CO1) by searching Gene Bank database; the transcription of CO1 in HL-60, L1210 and CHL cell lines which exposed to 0.1 mT and 0.8 mT MF for 20 minutes were significantly lower(0.38 +/- 0.12 and 0.37 +/- 0.04) than that of control(0.58 +/- 0.12) and so did for 24 hours exposure(0.46 +/- 0.09 and 0.45 +/- 0.09 vs 0.65 +/- 0.06) (P < 0.05).</p><p><b>CONCLUSION</b>CO1 is a MF-responsive gene. Cytochrome oxidase activity may be affected through low level of CO1 transcription by magnetic fields, thus induce bioeffects in organisms.</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>