ID Number		1001
Study Type		In Vitro
Model		1950, 2142 MHz (CW, W-CDMA) exposure to human glioma and microglial cells and analysis of stress response gene and protein expression and immune activation
Details		A172 (glioblastoma), H4 (neuroglioma), IMR-90 (normal fibroblasts from fetal lung), and CCD25SK (normal fibroblasts from skin) were exposed in different studies to 2.1425 GHz (CW or W-CDMA) RF at SAR levels of 0.08, 0.25, and up to 0.8 W/kg for various times up to 96 hours using an in vitro exposure system with a horn antenna and dielectric lens in an anechoic chamber. Affymetrix GeneChip (Human Genome U133 A & B Array) screening of > 44,000 targets revealed no consistent significant effect on gene expression, including hsp27 and hsp70. There was also no evidence of increased hsp phosphorylation due to RF exposure using the A172 cell line. Heat induction of heat shock proteins was used as a positive control. A subsequent study reported no effect of exposure on apoptosis or change in p53 phosphorylation at any exposure level. In studies using higher levels of exposure, various cell lines were exposed to 1950 or 2450 MHz (CW) at SARs up to 200 W/kg and assesed for activation of stress response genes. In the 2005 study, 1950 MHz (CW) exposure to MO54 human glioma cells for up to 2 h at 1, 2, or 10 W/kg did not affect growth (up to 4 days post-exposure) or Hsp27 and Hsp70 expression levels. However, exposure at 10 W/kg for 1 hr or more increased the level of phosphorylated Hsp27 (78Ser). In subsequent studies using exposure at 2450 MHz (CW) on MO54 cells, the authors report decreased cell survival and increased Hsp70 expression at SARs above 25 W/kg, with higher SARs requiring less exposure time for the effect, and exposures below 5 W/kg not having any effect even with 24 hr exposures. Raised temperature (39 degrees) also increased Hsp70 expression, although the effects were more pronounced with RF and the authors conclude exposures above 20 W/kg increased hsp70 expression even when the effect of raised temperature was taken into account. In a study using A172 (human glioblastoma) cells exposed to 2450 MHz (CW) and 2142 MHz (WCDMA), the autors report HSP 70 increased in a time- and dose-dependent manner at 50 W/kg and above. Maximal effect was observed using 100 W/kg for 1 hr. Neither RF exposure or heating had an effect on HSP 27 expression, although HSP 27 phosphorylation increased transiently at 100 W/kg and above, and to a greater extent than with heating (40 to 44°C) alone. No effects were observed at levels of base station exposure (~1 W/kg). A similar study was reported using longer-term exposure (0.08, 2.5, or 8 W/kg for 24 or 48 hours) on A172 and IMR-90 (human lung fibroblasts). The exposures represent 1x, 3x, and 10x the current ICNIRP limits (average whole body SAR). The authors conclude 2 GHz exposure has little effect on HSP70 and HSP27 expression, but may induce a transient increase in HSP27 phosphorylation at SARs >100W/kg due to thermal effects. Additional studies in mouse fiberblast cells treated +/- methylcholantherene (MCA - tumor initiator) and +/- TPA (tumor promoter) showed no effect of RF expsoure within the ICNIRP limits on transformation frequency. In a study using primary microglial cells (immune phagocytes / macrophages in brain tissue), exposure to 1950 MHz (W-CDMA) for 2 hrs at 0.2, 0.8, and 2.0 W/kg did not result in any change in markers of microglial activation, including MHC class II or inflammatory cytokine (TNF-alpha, IL-1 beta, IL-6) expression. Furhter studies in these same cell lines showed no effect of exposure on gene expression or proliferation.
Findings		Effects (only at thermal levels)
Status		Completed With Publication
Principal Investigator		Mitsubishi Chemical Safety Institute Ltd, Japan - m-sekijima@ankaken.co.jp
Funding Agency		NTT DoCoMo, Japan
Country		JAPAN
References		Sekijima, M et al. J Radiat Res (Tokyo)., (2010) 51(3):277-284 Hirose, H et al. Bioelectromagnetics., (2010) 31:104-112 Hirose, H et al. Bioelectromagnetics, (2006) 27:494-504 Wang, J et al. Bioelectromagnetics, (2006) 27:479-486 Hirose, H et al. Bioelectromagnetics, (2007) 29:55-64 Hirose, H et al. Bioelectromagnetics, (2007) 28:99-108 Iyama, T et al. Bioelectromagnetics, (2004) 25:599`-606 Miyakoshi, J et al. Bioelectromagnetics, (2005) 26:251-257 Tian, F et al. Int. J. Radiat. Biol., (2002) 78:433-440 Lerchl, A Bioelectromagnetics, (2008) 29:583-584
Comments		An annular culture dish provided three levels of exposure for a given input power in the inner, middle and outer rings. Importantly, non-uniform heating and localized thermal hot-spots were not fully characterized in the exposure system, and could have contributed to the hsp70 protein induction at higher exposure levels. In the more recent presentation, it is VERY interesting that higher levels of exposure (10 W/kg) resulted in a DECREASE in hsp27 phosphorylation, in contrast to Leszczynski et al that reported an increase in hsp27 phosphorylation.