Modification of membrane fluidity in melanin-containing cells by low-level microwave radiation.

Abstract

The treatment of a B16 melanoma cell line with 2.45-GHz pulsed microwaves (10 mW/cm2, 10-microseconds pulses at 100 pps, 1-h exposure; SAR, 0.2 W/kg) resulted in changes of membrane ordering as measured by EPR (electron paramagnetic resonance) reporter techniques. The changes reflected a shift from a more fluid-like phase to a more solid (ordered) state of the cell membrane. Exposure of artificially prepared liposomes that were reconstituted with melanin produced similar results. In contrast, neither B16 melanoma cells treated with 5-Bromo-2-Deoxyuridine (3 micrograms/day x 7 days) to render them amelanotic, nor liposomes prepared without melanin, exhibited the microwave-facilitated increase of ordering. Inhibition of the ordering was achieved by the use of superoxide dismutase (SOD), which strongly implicates oxygen radicals as a cause of the membrane changes. The data indicate that a significant, specific alteration of cell-membrane ordering followed microwave exposure. This alteration was unique to melanotic membranes and was due, at least in part, to the generation of oxygen radicals.

AI evidence extraction

Main findings

Exposure of B16 melanoma cells to 2.45-GHz pulsed microwaves (10 mW/cm2; SAR 0.2 W/kg; 1 h) was associated with increased membrane ordering (shift toward a more solid/ordered state) measured by EPR. Similar ordering changes occurred in melanin-reconstituted liposomes, while amelanotic B16 cells and liposomes without melanin did not show the effect. Superoxide dismutase inhibited the ordering change, implicating oxygen radicals in the observed membrane effects.

Outcomes measured

• Cell membrane ordering/fluidity (EPR reporter techniques)
• Microwave-facilitated increase of membrane ordering
• Role of oxygen radicals (inhibition by superoxide dismutase)

Limitations

• Sample size not reported in abstract
• In vitro model (cell line and liposomes); generalizability to humans not addressed
• Exposure conditions are specific (2.45 GHz pulsed microwaves; SAR 0.2 W/kg) and may not represent typical real-world exposures

Suggested hubs

• mechanisms-oxidative-stress (0.9)
  SOD inhibition implicates oxygen radicals as a mechanism for membrane changes after microwave exposure.
• rf-microwave-in-vitro (0.85)
  In vitro exposure of cells/liposomes to 2.45 GHz microwaves with reported SAR and membrane effects.

{
    "study_type": "in_vitro",
    "exposure": {
        "band": "microwave",
        "source": null,
        "frequency_mhz": 2450,
        "sar_wkg": 0.200000000000000011102230246251565404236316680908203125,
        "duration": "1-h exposure; 10-microseconds pulses at 100 pps"
    },
    "population": "B16 melanoma cell line; artificially prepared liposomes (with/without melanin)",
    "sample_size": null,
    "outcomes": [
        "Cell membrane ordering/fluidity (EPR reporter techniques)",
        "Microwave-facilitated increase of membrane ordering",
        "Role of oxygen radicals (inhibition by superoxide dismutase)"
    ],
    "main_findings": "Exposure of B16 melanoma cells to 2.45-GHz pulsed microwaves (10 mW/cm2; SAR 0.2 W/kg; 1 h) was associated with increased membrane ordering (shift toward a more solid/ordered state) measured by EPR. Similar ordering changes occurred in melanin-reconstituted liposomes, while amelanotic B16 cells and liposomes without melanin did not show the effect. Superoxide dismutase inhibited the ordering change, implicating oxygen radicals in the observed membrane effects.",
    "effect_direction": "harm",
    "limitations": [
        "Sample size not reported in abstract",
        "In vitro model (cell line and liposomes); generalizability to humans not addressed",
        "Exposure conditions are specific (2.45 GHz pulsed microwaves; SAR 0.2 W/kg) and may not represent typical real-world exposures"
    ],
    "evidence_strength": "low",
    "confidence": 0.85999999999999998667732370449812151491641998291015625,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "microwave radiation",
        "2.45 GHz",
        "pulsed microwaves",
        "SAR",
        "membrane fluidity",
        "membrane ordering",
        "EPR",
        "melanin",
        "B16 melanoma",
        "liposomes",
        "oxygen radicals",
        "superoxide dismutase"
    ],
    "suggested_hubs": [
        {
            "slug": "mechanisms-oxidative-stress",
            "weight": 0.90000000000000002220446049250313080847263336181640625,
            "reason": "SOD inhibition implicates oxygen radicals as a mechanism for membrane changes after microwave exposure."
        },
        {
            "slug": "rf-microwave-in-vitro",
            "weight": 0.84999999999999997779553950749686919152736663818359375,
            "reason": "In vitro exposure of cells/liposomes to 2.45 GHz microwaves with reported SAR and membrane effects."
        }
    ]
}

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