Highly persistent polycyclic aromatic hydrocarbon-DNA adducts in mouse skin: detection by 32P-postlabeling analysis

Area of Science:

• Toxicology
• Molecular Biology
• Carcinogenesis

Background:

• Polycyclic Aromatic Hydrocarbons (PAHs) are environmental carcinogens.
• DNA adducts are biomarkers of exposure and potential initiators of carcinogenesis.
• Accurate methods for quantifying DNA adducts are crucial for risk assessment.

Purpose of the Study:

• To quantify DNA adducts in mouse skin following topical exposure to specific PAHs.
• To investigate the repair kinetics of PAH-induced DNA adducts over time.
• To explore potential reasons for the persistence of unrepaired DNA adducts.

Main Methods:

• Application of a 32P-postlabeling method for carcinogen-DNA adduct analysis.
• Topical administration of benzo[alpha]pyrene (BP), 3-methylcholanthrene (MC), and 7,12-dimethylbenz[alpha]anthracene (DMBA) to mouse skin.
• Quantification of total covalent adduct binding in mouse skin DNA at different time points post-treatment.

Main Results:

• Initial adduct levels ranged from 1 adduct per 6.0 X 10(4) to 1.3 X 10(5) nucleotides.
• After 4 weeks, adduct levels decreased to 1 adduct per 1.4 X 10(6) to 2.7 X 10(6) nucleotides.
• Significant adduct removal occurred within the first 2 weeks, with minimal repair observed between weeks 2 and 4.

Conclusions:

• PAH-induced DNA adducts in mouse skin are subject to time-dependent repair.
• A fraction of DNA adducts persists beyond 4 weeks post-exposure, indicating incomplete repair.
• Persistent adducts may reside in genomic regions with conformational alterations or protein shielding, hindering repair.