AS Dawe1, RK Bodhicharla2, NS Graham3, ST May3, T Reader2, B Loader4, A Gregory4, M Swicord5, G Bit-Babik5 and DI de Pomerai2
1South African National Bioinformatics Institute, University of Western Cape, Cape Town, South Africa
2School of Biology, University of Nottingham, Nottingham, UK
3Nottingham Arabidopsis Stock Centre, University of Nottingham, School of Biosciences, Sutton Bonington, UK
4Enabling Metrology Laboratory, National Physical Laboratory, Teddington, UK
5Motorola Research Laboratories, Fort Lauderdale, Florida, USA
Summary of research published in Bioelectromagnetics, Vol. 30, No. 8, pp. 602-612.
This work is an MTHR (UK Mobile Telecommunications Health Research)-funded study to determine the reproducibility and robustness of the effects we had earlier reported, where low-intensity continuous-wave (CW) microwave fields apparently up-regulated heat-shock gene expression in the model nematode C. elegans (de Pomerai et al., 2000, Nature 405, 417-8).
In our previous study, published 3 years ago (Dawe et al., 2006, Bioelectromagnetics 27, 88-97), we established that power leakage causing a very slight rise (0.1-0.2°C) in the temperature of exposed but not sham samples was the most likely explanation for the observed increase in hsp-16.1 reporter expression at a nominal exposure temperature of 26.0°C. The present paper follows this up with a survey of global gene-expression changes in wild-type C. elegans following exposure to similar (in fact, somewhat lower) CW microwave fields. In an effort to promote good practice (as per MIAME guidelines (Editor’s note: MIAME stands for a standards effort to identify the Minimum Information required to unambiguously specify critical details About a Microarray Experiment)) for future gene-array studies in this field, we have made our gene-array data publicly accessible through the NCBI (National Center for Biotechnology Information) GEO (Gene Expression Omnibus) database (accession number GSE10787), and have also used a statistical correction for false discovery rate.
Our overall conclusion is that no genes show reproducible and statistically convincing changes in expression level across 5 replica microwave-exposed arrays as compared to 5 sham arrays. By contrast, when comparing 2 arrays from worms subjected to mild heat shock at 30°C against the 5 original sham arrays, >1500 statistically significant changes were recorded, including very major (up to 95-fold) changes in heat-shock gene expression. The up-regulation of one of these heat-shock genes has been confirmed independently using an hsp-16.2::GFP reporter, whereas two similar reporters (cyp-34A9::GFP and daf-16::GFP) were not up-regulated, broadly confirming the gene-array results for both genes. This reinforces our previous conclusion that weak microwave irradiation does not induce a heat-shock response nor any significant changes in gene expression in the nematode C. elegans; our earlier work suggesting such a response appears to reflect a subtle thermal artefact (see Dawe et al., 2006).
Miklós Antal1, János László2
1Department of Anatomy, Histology and Embryology, University of Debrecen,
Debrecen, Nagyerdei krt. 98, 4012-Hungary
2Section for Mathematics, Hungarian Academy of Sciences,
Budapest, Nádor u. 7, 1051-Hungary
Summary of article appearing in Biolelectromagnetics, Vol. 30, No. 6, pp 438-445
Nearly one third of the human population experiences severe chronic pain in some point in life. For many patients, pain continues to produce severe distress, dominating and disrupting the quality of their lives. Much of currently available clinical treatment is only partially effective and may be accompanied by adverse side effects or have abuse potential. The search for reliable, safe and effective treatments for neuropathic pain remains a major challenge, and, not surprisingly, patients have been continuously exploring alternative approaches. Among a number of other treatment strategies, magnetic therapy is increasingly used to alleviate pain.
Magnetic field therapy as a self-care intervention has led to the conduct of more than 50 randomized controlled human trials. Results obtained from studies that tested the analgesic efficacy of static magnetic field (SMF) therapy in chronic pain are inconsistent. However, since the parameters of the applied SMFs and the pain models that were supposed to be treated varied from investigation to investigation, results obtained from these earlier studies are far from being reliable and hardly comparable.
To avoid the obvious problems in the interpretation of the results of earlier studies, we investigated the effectiveness of SMF exposure in pain attenuation by utilizing a fully controllable, reproducable, and thus reliable experimental approach. First, we used an apparatus for the generation of an inhomogeneous SMF, the parameters of which has been carefully tested and adjusted to whole-body exposure of experimental animals. Secondly, we tested the effectiveness of SMF exposure on a well established animal model of neuropathic pain (partial nerve ligation in mice), and studied how the whole-body exposure to SMF may influence pain responsiveness in the experimental animals. Our results showed that exposure to inhomogeneous SMF in the first postoperative week could not prevent the development of pain. However, the effectiveness of a daily exposure to inhomogeneous SMF was much more prominent, when it was applied between postoperative days 15 and 28. In this case, pain threshold was already noticeably increased after the first treatment and it practically reached the control values by the end of the fortnight long exposure period.
Although we can not identify the mechanisms and sites of action at the moment, it is likely that whole-body SMF exposure may have an influence on the chemical reorganization mechanisms of pain processing neural circuits. It may act on the pain processing apparatus of the central nervous system after the development of central sensitization, and inhibit processes that maintain the increased sensitivity to external stimuli in neuropathic pain.