50 Hz magnetic field influences caspase-3 activity and cell cycle distribution in ionizing radiation

Abstract

50 Hz magnetic field influences caspase-3 activity and cell cycle distribution in ionizing radiation exposed SH-SY5Y neuroblastoma cells Nieminen V, Martikainen MV, Kalliomäki S, Virén T, Seppälä J, Juutilainen J, Naarala J, Luukkonen J. 50 Hz magnetic field influences caspase-3 activity and cell cycle distribution in ionizing radiation exposed SH- SY5Y neuroblastoma cells. Int J Radiat Biol. 2024 Jun 26:1-10. doi: 10.1080/09553002.2024.2369105. Abstract Purpose: Earlier evidence suggests that extremely low frequency magnetic fields (ELF MFs) can modify the effects of carcinogenic agents. However, the studies conducted so far with ionizing radiation as the co-exposure agent are sparse and have provided inconclusive results. We investigated whether 50 Hz MFs alone, or in combination with ionizing radiation alter cell biological variables relevant to cancer and the biological effects of ionizing radiation. Materials and methods: Human SH-SY5Y neuroblastoma cells were sham exposed or exposed to 100 or 500 μT MF for 24 h either before or after ionizing radiation exposure (0, 0.4 or 2 Gy). After the exposures, cells were assayed for viability, clonogenicity, reactive oxygen species, caspase-3 activity, and cell cycle distribution. Cell cycle distribution was assayed with propidium iodide staining followed by flow cytometry analysis and ROS levels were assayed together with cell viability by double staining with DeepRed and Sytox Blue followed by flow cytometry analysis. Results: Increased caspase-3 activity was observed in cells exposed to 500 μT MF before or after ionizing radiation. Furthermore, exposure to the 500 μT MF after the ionizing radiation decreased the percentage of cells in S-phase. No changes in the ROS levels, clonogenicity, or viability of the cells were observed in the MF exposed groups compared to the corresponding sham exposed groups, and no MF effects were observed in cells exposed at 100 μT. Conclusions: Only the 500 μT magnetic flux density affected SH-SY5Y cells significantly. The effects were small but may nevertheless help to understand how MFs modify the effects of ionizing radiation. The increase in caspase-3 activity may not reflect effects on apoptosis, as no changes were observed in the subG1 phase of the cell cycle. In contrast to some earlier findings, 50 Hz MF exposure after ionizing radiation was not less effective than MF treatment given prior to ionizing radiation. pubmed.ncbi.nlm.nih.gov

AI evidence extraction

Main findings

Increased caspase-3 activity was observed with 500 µT 50 Hz magnetic field exposure given before or after ionizing radiation. Exposure to 500 µT after ionizing radiation decreased the percentage of cells in S-phase. No changes were observed in ROS levels, clonogenicity, or viability versus sham, and no magnetic-field effects were observed at 100 µT.

Outcomes measured

• Cell viability
• Clonogenicity
• Reactive oxygen species (ROS)
• Caspase-3 activity
• Cell cycle distribution (including S-phase; subG1 mentioned)

Limitations

• Studies with ionizing radiation as co-exposure are described as sparse and previously inconclusive (contextual limitation).
• Effects reported as small by the authors.
• No sample size or replication details provided in the abstract.

Suggested hubs

• elr-elf (0.9)
  In vitro study of 50 Hz (ELF) magnetic field exposure at 100–500 µT.
• ionizing-radiation-coexposure (0.75)
  Assesses ELF magnetic field exposure before/after ionizing radiation (0–2 Gy) and interaction-relevant endpoints.

{
    "study_type": "in_vitro",
    "exposure": {
        "band": "ELF",
        "source": null,
        "frequency_mhz": 0.05000000000000000277555756156289135105907917022705078125,
        "sar_wkg": null,
        "duration": "24 h (before or after ionizing radiation exposure)"
    },
    "population": "Human SH-SY5Y neuroblastoma cells",
    "sample_size": null,
    "outcomes": [
        "Cell viability",
        "Clonogenicity",
        "Reactive oxygen species (ROS)",
        "Caspase-3 activity",
        "Cell cycle distribution (including S-phase; subG1 mentioned)"
    ],
    "main_findings": "Increased caspase-3 activity was observed with 500 µT 50 Hz magnetic field exposure given before or after ionizing radiation. Exposure to 500 µT after ionizing radiation decreased the percentage of cells in S-phase. No changes were observed in ROS levels, clonogenicity, or viability versus sham, and no magnetic-field effects were observed at 100 µT.",
    "effect_direction": "mixed",
    "limitations": [
        "Studies with ionizing radiation as co-exposure are described as sparse and previously inconclusive (contextual limitation).",
        "Effects reported as small by the authors.",
        "No sample size or replication details provided in the abstract."
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "50 Hz",
        "extremely low frequency",
        "ELF magnetic field",
        "magnetic flux density",
        "100 µT",
        "500 µT",
        "ionizing radiation",
        "SH-SY5Y",
        "neuroblastoma cells",
        "caspase-3",
        "cell cycle",
        "S-phase",
        "ROS",
        "viability",
        "clonogenicity"
    ],
    "suggested_hubs": [
        {
            "slug": "elr-elf",
            "weight": 0.90000000000000002220446049250313080847263336181640625,
            "reason": "In vitro study of 50 Hz (ELF) magnetic field exposure at 100–500 µT."
        },
        {
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            "weight": 0.75,
            "reason": "Assesses ELF magnetic field exposure before/after ionizing radiation (0–2 Gy) and interaction-relevant endpoints."
        }
    ]
}

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