New view on the impact of the low-frequency electromagnetic field (50 Hz) on stress responses - hormesis effect

Abstract

New view on the impact of the low-frequency electromagnetic field (50 Hz) on stress responses - hormesis effect Klimek A, Kletkiewicz H, Siejka A, Wyszkowska J, Maliszewska J, Klimiuk M, Jankowska M, Seckl J, Rogalska J. New view on the impact of the low-frequency electromagnetic field (50 Hz) on stress responses - hormesis effect. Neuroendocrinology. 2022 Nov 2. doi: 10.1159/000527878. Abstract Introduction: Low-frequency electromagnetic field (50 Hz) (EMF) can modify crucial neuronal processes. Existing data indicate that exposure to EMF may represent a mild stressor and contribute to disturbances of hypothalamic-pituitary-adrenal (HPA) axis. The important regulatory pathways controlling HPA axis activity include two types of corticosteroid receptors: mineralocorticoid (MR) and glucocorticoid (GR) receptors. There are particularly abundant in the hippocampus, a key locus of HPA axis feedback control. The research aimed at determining whether 1) EMF exhibits hormesis, it means bidirectional action depending on EMF intensity (1 or 7 mT), and 2) repeated EMF exposure changes stress response to subsequent stress factors. Methods: The exposure (7-day, 1h/day) of adult rats to EMF (1 mT and 7 mT) was repeated 3 times. HPA axis hormones and their receptors were analysed after each following exposure. Moreover, the impact of EMF exposure on hormonal and behavioural responses to subsequent stress factor - open-field test was evaluated. Results/discussion: Our data suggest that exposure to EMF can establish a new "set-point" for HPA axis activity. The direction and dynamics of this process depend on the intensity of EMF and the number of exposures. EMF of 1 mT induced an adaptive stress response, but 7 mT EMF caused sensitization. Consequently, EMF changed the vulnerability of the organism to a subsequent stress factor. We have also shown the increase of MR mRNA abundance in hippocampus of 1 mT EMF exposed rats, which can represent the possible neuroprotective response and suggest therapeutic properties of electromagnetic fields. pubmed.ncbi.nlm.nih.gov

AI evidence extraction

Main findings

Repeated 50 Hz EMF exposure appeared to shift the HPA axis activity "set-point" in rats, with effects depending on field intensity and number of exposures. Exposure at 1 mT was associated with an adaptive stress response and increased hippocampal MR mRNA abundance, while 7 mT exposure was associated with sensitization and altered vulnerability to a subsequent stressor (open-field test).

Outcomes measured

• HPA axis hormones
• Mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) (including mRNA abundance in hippocampus)
• Hormonal responses to subsequent stressor (open-field test)
• Behavioural responses to subsequent stressor (open-field test)

Limitations

• Sample size not reported in abstract
• Details of exposure setup and dosimetry beyond field intensity not provided in abstract
• Quantitative results and statistical details not provided in abstract

Suggested hubs

• occupational-exposure (0.25)
  Study uses 50 Hz ELF magnetic field exposure (mT range), relevant to ELF exposure contexts, though no specific occupational setting is stated.

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    "study_type": "animal",
    "exposure": {
        "band": "ELF",
        "source": null,
        "frequency_mhz": 0.05000000000000000277555756156289135105907917022705078125,
        "sar_wkg": null,
        "duration": "7-day, 1 h/day exposure repeated 3 times; intensities 1 mT and 7 mT"
    },
    "population": "Adult rats",
    "sample_size": null,
    "outcomes": [
        "HPA axis hormones",
        "Mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) (including mRNA abundance in hippocampus)",
        "Hormonal responses to subsequent stressor (open-field test)",
        "Behavioural responses to subsequent stressor (open-field test)"
    ],
    "main_findings": "Repeated 50 Hz EMF exposure appeared to shift the HPA axis activity \"set-point\" in rats, with effects depending on field intensity and number of exposures. Exposure at 1 mT was associated with an adaptive stress response and increased hippocampal MR mRNA abundance, while 7 mT exposure was associated with sensitization and altered vulnerability to a subsequent stressor (open-field test).",
    "effect_direction": "mixed",
    "limitations": [
        "Sample size not reported in abstract",
        "Details of exposure setup and dosimetry beyond field intensity not provided in abstract",
        "Quantitative results and statistical details not provided in abstract"
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "50 Hz",
        "ELF-EMF",
        "low-frequency electromagnetic field",
        "hormesis",
        "HPA axis",
        "stress response",
        "hippocampus",
        "mineralocorticoid receptor",
        "glucocorticoid receptor",
        "open-field test",
        "rats",
        "1 mT",
        "7 mT"
    ],
    "suggested_hubs": [
        {
            "slug": "occupational-exposure",
            "weight": 0.25,
            "reason": "Study uses 50 Hz ELF magnetic field exposure (mT range), relevant to ELF exposure contexts, though no specific occupational setting is stated."
        }
    ]
}

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