EMF radiation at 2450 MHz triggers changes in the morphology and expression of heat shock proteins and glucocorticoid receptors in rat thymus

EMF radiation at 2450 MHz triggers changes in the morphology and expression of heat shock proteins and glucocorticoid receptors in rat thymus

M.J. Misa-Agustiño, J.M. Leiro-Vidal, J.L. Gomez-Amoza, M.T. Jorge-Mora, F.J. Jorge-Barreiro, A.A. Salas-Sánchez, F.J. Ares-Pena, E. López-Martín. EMF radiation at 2450 MHz triggers changes in the morphology and expression of heat shock proteins and glucocorticoid receptors in rat thymus.Life Sciences.vol. 127:1-11. April 15, 2015. doi:10.1016/j.lfs.2015.01.027

Abstract

Aims  Electromagnetic fields (EMFs) can act as inducers or mediators of stress response through the production of heat shock proteins (HSPs) that modulate immune response and thymus functions. In this study, we analyzed cellular stress levels in rat thymus after exposure of the rats to a 2.45 GHz radio frequency (RF) using an experimental diathermic model in a Gigahertz Transverse Electromagnetic (GTEM) chamber.

Main methods  In this experiment, we used H&E staining, the ELISA test and immunohistochemistry to examine Hsp70 and Hsp90 expression in the thymus and glucocorticoid receptors (GR) of 64 female Sprague–Dawley rats exposed individually to 2.45 GHz (at 0, 1.5, 3.0 or 12.0 W power). The 1 g averaged peak and mean SAR values in the thymus and whole body of each rat to ensure that sub-thermal levels of radiation were being reached.

Key findings  The thymus tissue presented several morphological changes, including increased distribution of blood vessels along with the appearance of red blood cells and hemorrhagic reticuloepithelial cells. Levels of Hsp90 decreased in the thymus when animals were exposed to the highest power level (12 W), but only one group did not show recovery after 24 h. Hsp70 presented no significant modifications in any of the groups. The glucocorticoid receptors presented greater immunomarking on the thymic cortex in exposed animals.

Significance  Our results indicate that non-ionizing sub-thermal radiation causes changes in the endothelial permeability and vascularization of the thymus, and is a tissue-modulating agent for Hsp90 and GR.

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Excerpts

When the balance between the immune, nervous and endocrine systems is altered by diverse external stimuli, the body responds by seeking to maintain homeostasis. The thymus, an essential organ of the immune system, is very sensitive to human physiological changes such as aging, pregnancy and external agents. [10].

In recent years, ionizing and non-ionizing radiation have been found to constitute an external stimulus that modulates immune responses and modifies thymus functions [6], [15] and [38]. Heat shock proteins (HSPs) regulate the maintenance of homeostasis in response to internal or external stimuli and ensure an adequate tissue environment in mammals [22]. Electromagnetic fields (EMFs) can act primarily as inducers or mediators of HSP production in response to stress [21], though the induction mechanisms are still not well understood. Anti-tumor immunity can be induced by microwave hyperthermia treatment, mediated by extracellular heat shock proteins (HSPs) carrying tumor antigens and other danger signals released by dying tumor cells [12]. In medicine and illnesses [48], HSPs are mostly associated with responses induced under stress conditions, where they function as chaperones and cytoprotective agents [27]. Since stress can provoke deterioration in cell infrastructure and alter homeostasis, HSPs are often used as biomarkers in molecular toxicology studies [14]. The glucocorticoid receptor (GR), like many signaling proteins, depends on the Hsp90 molecular chaperone for in vivo function [33]. Heat shock proteins 90 and 70 have coordinated chaperone interactions and can enhance GR stability, function, and regulation [19]. Cross-talk between the GR and other transcription factors provides a mechanism for fine control of biological responses to external stimuli. Non-ionizing radiation provokes effects on memory and increases in cortisol levels [29]. GR expression in the thymus caused by an electromagnetic source may itself be relevant in immune response ...

In this study, we analyzed cellular stress levels in rat thymus after exposure of the rats to a 2.45 GHz radio frequency using an experimental diathermic model in a GTEM chamber. Using H&E staining to detect histological and immunohistochemical changes, we examined Hsp70 and 90 as indicators of cellular stress and expression of glucocorticoid receptors ...

This study describes for the first time changes in the morphology, levels of cellular stress proteins Hsp90 and 70 and glucocorticoid receptors in the rat thymus exposed to a maximum interaction of 2.45 GHz radio frequency to the left leg of the animal in a GTEM chamber. Alterations in Hsp90, Hsp70 and the glucocorticoid receptors were accompanied by histological indications of increased thymic permeability and vascularization, with the appearance of red blood cells and hemorrhagic reticuloepithelial cells. We used the data on the thymus tissue response to the physical stimuli of non-ionizing radiation in an analysis of aspects relevant to this model of rat diathermy. PLS regression indicated a significant influence of radiation power and the weight of the animal.

Everything indicates that the acute decrease in Hsp90 90 min after exposure to radiation at the maximum power (12 W) was attributable to sub-thermal mechanisms, in spite of the significant difference in rectal temperature between irradiated and non-irradiated animals that was observed at these levels of radiation in this and prior experiments [26]. Likewise, the lack of Hsp90 recovery after exposure to 3 W indicates the participation of non-thermal mechanisms in the tissue to induce cellular tolerance or subsequent stress adaptation [39].

Conclusion

The combined study of HSP levels and morphological changes in the thymus tissue from radiation at 2.45 GHz with sub-thermal SAR levels leads us to conclude that:

1) Non-ionizing radiation at sub-thermal levels constitutes a quantitative and qualitative modulating agent for Hsp90, but not for Hsp70, in the thymus tissue.

2) There is a relationship between radiation and increased endothelial permeability and vascularization of the thymus.

3) The increase of glucocorticoid receptors in the cortical thymocytes indicates that radiation constitutes a stimulus for immune response.

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Joel M. Moskowitz, Ph.D., Director
Center for Family and Community Health
School of Public Health
University of California, Berkeley

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