Natarajan M, Nayak B K, Galindo C, Mathur S P, Roldan F N, Meltz M L
Department of Radiation Oncology, University of Texas Health Science Center, Brooks City-Base, San Antonio, TX 78229-3900, USA.
Radiat Res. 2006 Jun;165(6):645-54. doi: 10.1667/RR3564.1.
The objective of this study was to investigate whether exposure of human monocytes to a pulsed ultra-wideband electromagnetic field (EMF) of 1 kV/cm average peak power triggers a signaling pathway responsible for the transcriptional regulation of NFKB (NF-kappaB)-dependent gene expression. Human Mono Mac 6 (MM6) cells were exposed intermittently to EMF pulses for a total of 90 min. The pulse width was 0.79+/-0.01 ns and the pulse repetition rate was 250 pps. The temperature of the medium was maintained at 37 degrees C in both sham- and EMF-exposed flasks. Total NFKB DNA-binding activity was measured in the nuclear extracts by the electrophoretic mobility shift assay. Cells exposed to the EMFs and incubated for 24 h postexposure showed a 3.5+/-0.2-fold increase in the NFKB DNA-binding activity. Since activation of NFKB was observed, the possibility of kappaB-dependent gene expression in response to exposure to the EMFs was investigated using NFKB signal-specific gene arrays. The results revealed no difference in the NFKB-dependent gene expression profiles at 8 or 24 h postexposure, indicating that activated NFKB does not lead to the differential expression of kappaB-dependent target genes. To determine whether the absence of the kappaB-dependent gene expression was due to compromised transcriptional regulation of NFKB, the functional activity of NFKB was examined in cells transiently transfected with Mercury Pathway constructs containing 4x NFKB binding sites associated either with the luciferase reporter system or a control vector. Pulsed EMF exposure did not induce NFKB-driven luciferase activity in these cells, indicating that the activation of NFKB at 24 h after the 1 kV/cm EMF exposure is functionally inactive. From these results, it is clear that the EMF-induced NFKB activation is only a transient response, with minimal or no downstream effect.
本研究的目的是调查人类单核细胞暴露于平均峰值功率为1 kV/cm的脉冲超宽带电磁场（EMF）是否会触发负责NFKB（核因子κB）依赖性基因表达转录调控的信号通路。人类单核巨噬细胞6（MM6）细胞间歇性暴露于EMF脉冲下，总计90分钟。脉冲宽度为0.79±0.01纳秒，脉冲重复率为250次/秒。在假暴露和EMF暴露的培养瓶中，培养基温度均维持在37摄氏度。通过电泳迁移率变动分析测量核提取物中的总NFKB DNA结合活性。暴露于EMF并在暴露后孵育24小时的细胞显示NFKB DNA结合活性增加了3.5±0.2倍。由于观察到NFKB的激活，使用NFKB信号特异性基因阵列研究了暴露于EMF后κB依赖性基因表达的可能性。结果显示暴露后8小时或24小时，NFKB依赖性基因表达谱没有差异，表明激活的NFKB不会导致κB依赖性靶基因的差异表达。为了确定κB依赖性基因表达缺失是否是由于NFKB转录调控受损，在瞬时转染了含有与荧光素酶报告系统或对照载体相关的4x NFKB结合位点的Mercury Pathway构建体的细胞中检查了NFKB的功能活性。脉冲EMF暴露未在这些细胞中诱导NFKB驱动的荧光素酶活性，表明在1 kV/cm EMF暴露后24小时NFKB的激活在功能上是无活性的。从这些结果可以清楚地看出，EMF诱导的NFKB激活只是一种短暂反应，下游效应最小或没有。
