Radiation dose-rate effects on gene expression for human biodosimetry

Area of Science:

• Radiation biology
• Genomics
• Biodosimetry

Background:

• Radiation dose-rate effects are understudied for large-scale radiological events.
• Realistic scenarios involve mixed high/low dose-rate and internal/external exposures.
• Understanding biological responses to prolonged exposure and identifying low-dose rate biomarkers is crucial for clinical treatment.

Purpose of the Study:

• To investigate differential gene expression in human whole blood following acute and low dose-rate radiation exposure.
• To identify potential gene expression biomarkers for distinguishing between acute and low dose-rate radiation exposures.
• To assess the feasibility of a gene expression-based classifier for radiation biodosimetry.

Main Methods:

• Human whole blood was irradiated ex vivo to 0.56, 2.23, and 4.45 Gy at acute (1.03 Gy/min) and low (3.1 mGy/min) dose rates.
• RNA was isolated from blood cells after 24 hours and analyzed using whole human genome microarrays.
• Microarray findings were validated using quantitative real-time PCR (qRT-PCR).

Main Results:

• 454 genes showed significant differential expression after prolonged exposure across all doses.
• 598 genes were differentially expressed after acute exposure across all doses.
• Gene ontology analysis revealed enrichment in immune processes, B-cell immunity, natural killer cell activation, and cell-to-cell signaling for both exposure types. The p53 pathway was significantly enriched in all conditions. A support vector machine classifier achieved 100% accuracy in distinguishing dose-rates.

Conclusions:

• Low dose-rate radiation exposure induces distinct gene expression patterns compared to acute exposure.
• A gene expression-based classifier can successfully differentiate between low dose-rate and acute radiation exposures at 24 hours post-exposure.
• Identified genes are promising candidates for biomarkers to classify radiation exposure based on dose-rate.