Low power microwave radiation inhibits the proliferation of rabbit lens epithelial cells by upregulating P27Kip1 expression.

Abstract

PURPOSE: The goal of this study was to examine the effects of low power microwave radiation (<10 mW/cm2) on the proliferation of cultured rabbit lens epithelial cells (RLEC). METHODS: Cultured RLEC were exposed to continuous microwave radiation at a frequency of 2,450 MHz and power densities of 0.10, 0.25, 0.50, 1.00, and 2.00 mW/cm2 for 8 h. Cell morphologic changes were observed under a phase-contrast microscope. Cell viability was measured using the MTT assay and cell cycle analysis was measured using flow cytometry. After exposure to 2.00 mW/cm2 microwave radiation for 4, 6, and 8 h, the expression of cell cycle-regulatory proteins, P21WAF1 and P27Kip1, was examined using western blot analysis. Finally, the levels of P21WAF1 and P27Kip1 mRNA were analyzed by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: After 8 h of radiation treatment, cells treated with 0.50, 1.00, and 2.00 mW/cm2 microwave radiation exhibited decreased cell viability, increased cell condensation and an inhibition of DNA synthesis. RLEC showed significant G0/G1 arrest. No obvious changes could be detected in the 0.10 and 0.25 mW/cm2 microwave treatment groups. Protein expression of P27Kip1 was markedly increased after microwave radiation. However, the mRNA levels were unchanged. On the other hand, there were no detectable differences in P21WAF1 protein expression and mRNA levels between microwave treatment and control groups. CONCLUSIONS: This study suggests that low power microwave radiation higher than 0.50 mW/cm2 can inhibit lens epithelial cell proliferation, and increase the expression of P27Kip1. These effects may account for the decline of lens epithelial proliferation after exposure to microwave radiation.

AI evidence extraction

Main findings

After 8 h exposure, 0.50, 1.00, and 2.00 mW/cm2 groups showed decreased cell viability, increased cell condensation, inhibition of DNA synthesis, and significant G0/G1 arrest; 0.10 and 0.25 mW/cm2 showed no obvious changes. P27Kip1 protein expression increased after microwave radiation while P27Kip1 mRNA was unchanged; P21WAF1 protein and mRNA showed no detectable differences versus controls.

Outcomes measured

• Cell proliferation/viability (MTT)
• Cell morphology (phase-contrast microscopy)
• DNA synthesis inhibition
• Cell cycle distribution (flow cytometry; G0/G1 arrest)
• P27Kip1 protein expression (western blot)
• P27Kip1 mRNA levels (RT-PCR)
• P21WAF1 protein expression (western blot)
• P21WAF1 mRNA levels (RT-PCR)

Limitations

• In vitro cell culture model; relevance to in vivo exposure not addressed in abstract
• Sample size and replication not reported in abstract
• Thermal control/temperature monitoring not described in abstract
• Only one frequency (2450 MHz) and limited exposure durations assessed

{
    "study_type": "in_vitro",
    "exposure": {
        "band": "microwave",
        "source": null,
        "frequency_mhz": 2450,
        "sar_wkg": null,
        "duration": "Continuous exposure for 8 h (dose-response at 0.10–2.00 mW/cm2); additional time-course at 2.00 mW/cm2 for 4, 6, and 8 h"
    },
    "population": "Cultured rabbit lens epithelial cells (RLEC)",
    "sample_size": null,
    "outcomes": [
        "Cell proliferation/viability (MTT)",
        "Cell morphology (phase-contrast microscopy)",
        "DNA synthesis inhibition",
        "Cell cycle distribution (flow cytometry; G0/G1 arrest)",
        "P27Kip1 protein expression (western blot)",
        "P27Kip1 mRNA levels (RT-PCR)",
        "P21WAF1 protein expression (western blot)",
        "P21WAF1 mRNA levels (RT-PCR)"
    ],
    "main_findings": "After 8 h exposure, 0.50, 1.00, and 2.00 mW/cm2 groups showed decreased cell viability, increased cell condensation, inhibition of DNA synthesis, and significant G0/G1 arrest; 0.10 and 0.25 mW/cm2 showed no obvious changes. P27Kip1 protein expression increased after microwave radiation while P27Kip1 mRNA was unchanged; P21WAF1 protein and mRNA showed no detectable differences versus controls.",
    "effect_direction": "harm",
    "limitations": [
        "In vitro cell culture model; relevance to in vivo exposure not addressed in abstract",
        "Sample size and replication not reported in abstract",
        "Thermal control/temperature monitoring not described in abstract",
        "Only one frequency (2450 MHz) and limited exposure durations assessed"
    ],
    "evidence_strength": "low",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "microwave radiation",
        "2450 MHz",
        "power density",
        "rabbit lens epithelial cells",
        "cell proliferation",
        "MTT",
        "cell cycle arrest",
        "G0/G1",
        "P27Kip1",
        "P21WAF1"
    ],
    "suggested_hubs": []
}

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