Medical/biological study (experimental study)

Low-intensity microwave irradiation does not substantially alter gene expression in late larval and adult Caenorhabditis elegans med./bio.

By: Dawe AS, Bodhicharla RK, Graham NS, May ST, Reader T, Loader B, Gregory A, Swicord M, Bit-Babik G, de Pomerai DI

Published in: Bioelectromagnetics 2009; 30 (8): 602-612

Aim of study (acc. to author)

To study the effects of low-intensity microwave irradiation on gene expression in the nematode Caenorhabditis elegans using a microwave exposure system that minimises temperature differences between sham exposed and exposed conditions (< / = 0.1°C).

Background/further details

In a previous study (de Pomerai et al. 2000), the authors suggested that low-intensity microwave fields could induce a non-thermal heat-shock response in the nematode Caenorhabditis elegans. This effect has been reinterpreted as a subtle thermal artefact caused by small temperature disparities (<0.2 °C) between exposed and sham exposed conditions (Dawe et al. 2006).
Larval stage L4 and adult worms were exposed. Positive controls were performed with mild heat shock (30°C). Five microarrays of pooled triplicate RNA populations from sham exposed and exposed worms, respectively, were compared.

Endpoint

molecular biosynthesis: gene expression

Exposure

Exposure	Parameters
Exposure 1: 1 GHz Modulation type: CW Exposure duration: continuous for 1.5 h ,2.5 h or 6 h	power: 0.5 W SAR: 0.9 mW/kg minimum SAR: 3 mW/kg maximum

Exposure 1

Main characteristics

Frequency	1 GHz
Type	electromagnetic field
Exposure duration	continuous for 1.5 h ,2.5 h or 6 h

Modulation

Modulation type	CW

Exposure setup

Exposure source	TEM cell
Setup	silver-plated TEM cell for exposure; copper TEM cell for sham exposure
Sham exposure	A sham exposure was conducted.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
power	0.5 W	-	-	-	-
SAR	0.9 mW/kg	minimum	measured and calculated	-	-
SAR	3 mW/kg	maximum	measured and calculated	-	-

Reference articles

Dawe AS et al. (2006): A small temperature rise may contribute towards the apparent induction by microwaves of heat-shock gene expression in the nematode Caenorhabditis Elegans

Exposed system:

invertebrate
Caenorhabditis elegans (wild-type N2 or different transgenic strains (CL2070, TJ356, BC20306) with reporter gene constructs, encoding the green fluorescent protein (GFP) under control of heat-shock promotor or other not heat-inducible promotor

Methods Endpoint/measurement parameters/methodology

molecular biosynthesis: gene expression (microarray (Affymetrix C.elegans Genome GeneChip); reporter gene expression (detection of reporter gene product GFP; fluorometry)

Investigated system:

DNA/RNA
dead worms extracts

Time of investigation:

after exposure

Main outcome of study (acc. to author)

No genes showed consistent expression changes across all five microarray comparisons, and all expression changes appeared modest after normalisation (< / = 40% up-regulated or down-regulated). The number of statistically significant differences in gene expression (846) was less than the false-positive rate expected by chance (1131).
The authors conclude that the pattern of gene expression in L4/adult Caenorhabditis elegans is unaffected by low-intensity microwave exposure; the minor changes found could well be false positives.

Study character:

medical/biological study
experimental study
full/main study

Study funded by

Mobile Telecommunications and Health Research (MTHR), UK

Fasseas MK et al. (2015): Response of Caenorhabditis elegans to wireless devices radiation exposure
Dawe AS et al. (2008): Continuous wave and simulated GSM exposure at 1.8 W/kg and 1.8 GHz do not induce hsp16-1 heat-shock gene expression in Caenorhabditis elegans
Zhao TY et al. (2007): Exposure to cell phone radiation up-regulates apoptosis genes in primary cultures of neurons and astrocytes
Zhao R et al. (2007): Studying gene expression profile of rat neuron exposed to 1800 MHz radiofrequency electromagnetic fields with cDNA microassay
Dawe AS et al. (2006): A small temperature rise may contribute towards the apparent induction by microwaves of heat-shock gene expression in the nematode Caenorhabditis Elegans
Whitehead TD et al. (2006): Gene expression does not change significantly in C3H 10T(1/2) cells after exposure to 847.74 CDMA or 835.62 FDMA radiofrequency radiation
Qutob SS et al. (2006): Microarray gene expression profiling of a human glioblastoma cell line exposed in vitro to a 1.9 GHz pulse-modulated radiofrequency field
Gurisik E et al. (2006): An in vitro study of the effects of exposure to a GSM signal in two human cell lines: monocytic U937 and neuroblastoma SK-N-SH
Whitehead TD et al. (2006): The number of genes changing expression after chronic exposure to Code Division Multiple Access or Frequency DMA radiofrequency radiation does not exceed the false-positive rate
de Pomerai D (2006): Retraction of: Non-thermal heat-shock response to microwaves
de Pomerai DI et al. (2002): Growth and maturation of the nematode Caenorhabditis elegans following exposure to weak microwave fields
de Pomerai DI et al. (2000): Microwave radiation induces a heat-shock response and enhances growth in the nematode Caenorhabditis elegans
Daniells C et al. (1998): Transgenic nematodes as biomonitors of microwave-induced stress