Induction of cAMP-dependent protein kinase A activity in human skin fibroblasts and rat osteoblasts by extremely low-frequency electromagnetic fields.

Abstract

Sinusoidal extremely low-frequency electromagnetic fields (ELF-EMF; 7-8 mT, 20 Hz) have already been shown to inhibit proliferation and to accelerate terminal differentiation of human skin fibroblasts in vitro. In order to elucidate the underlying processes of signal transduction, we analysed the activity of cAMP-dependent protein kinase (PKA). EMF exposure for 60 min resulted in an increased PKA activity in human skin fibroblasts (2-fold) and rat embryonic osteoblasts (1.7-fold). Long-term exposure for up to 7 days with a constant 1 h-on/1 h-off EMF exposure rhythm indicated a transient stimulation of PKA activity during the first two exposure rhythms followed by a decrease to the baseline levels of sham-exposed controls. Based on these results, we postulate that a modulation of proliferation and differentiation processes in cells of mesenchymal origin is triggered by an immediate and transient EMF-induced increase in PKA activity.

AI evidence extraction

Main findings

Exposure to sinusoidal ELF-EMF (7–8 mT, 20 Hz) for 60 min increased PKA activity in human skin fibroblasts (~2-fold) and rat embryonic osteoblasts (~1.7-fold). With long-term exposure up to 7 days (1 h-on/1 h-off), PKA activity showed transient stimulation during the first two exposure rhythms and then decreased back to baseline levels of sham-exposed controls.

Outcomes measured

• cAMP-dependent protein kinase A (PKA) activity

Limitations

• In vitro study (cell culture), limiting direct inference to human health outcomes
• Sample size and statistical details not provided in the abstract
• Exposure source and other dosimetry details beyond field strength/frequency not described in the abstract

Suggested hubs

• occupational-exposure (0.2)
  ELF-EMF exposure parameters are relevant to ELF exposure contexts, though no specific occupational setting is stated.

{
    "study_type": "in_vitro",
    "exposure": {
        "band": "ELF",
        "source": null,
        "frequency_mhz": 0.0200000000000000004163336342344337026588618755340576171875,
        "sar_wkg": null,
        "duration": "60 min; up to 7 days (1 h-on/1 h-off rhythm)"
    },
    "population": "Human skin fibroblasts and rat embryonic osteoblasts (cell cultures)",
    "sample_size": null,
    "outcomes": [
        "cAMP-dependent protein kinase A (PKA) activity"
    ],
    "main_findings": "Exposure to sinusoidal ELF-EMF (7–8 mT, 20 Hz) for 60 min increased PKA activity in human skin fibroblasts (~2-fold) and rat embryonic osteoblasts (~1.7-fold). With long-term exposure up to 7 days (1 h-on/1 h-off), PKA activity showed transient stimulation during the first two exposure rhythms and then decreased back to baseline levels of sham-exposed controls.",
    "effect_direction": "mixed",
    "limitations": [
        "In vitro study (cell culture), limiting direct inference to human health outcomes",
        "Sample size and statistical details not provided in the abstract",
        "Exposure source and other dosimetry details beyond field strength/frequency not described in the abstract"
    ],
    "evidence_strength": "low",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "extremely low-frequency electromagnetic fields",
        "ELF-EMF",
        "20 Hz",
        "7-8 mT",
        "protein kinase A",
        "PKA",
        "cAMP-dependent",
        "human skin fibroblasts",
        "rat embryonic osteoblasts",
        "signal transduction"
    ],
    "suggested_hubs": [
        {
            "slug": "occupational-exposure",
            "weight": 0.200000000000000011102230246251565404236316680908203125,
            "reason": "ELF-EMF exposure parameters are relevant to ELF exposure contexts, though no specific occupational setting is stated."
        }
    ]
}

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