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Formation of DNA adducts in mouse tissues after intratracheal instillation of 1-nitropyrene
1Inhalation Toxicology Research Institute, Lovelace Biomedical and Environmental Research Institute, Albuquerque, NM 87185.
Abstract:
1-Nitropyrene (1-NP), a ubiquitous environmental pollutant, is a mammalian mutagen and causes cancer in animals. The ability of the lung, liver and kidney to form 1-NP-DNA adducts was determined in adult male B6C3F1 mice following a single intratracheal instillation of 1-NP. 1-NP-DNA adducts were isolated and characterized in mouse lung, liver and kidney by HPLC analysis of the enzymatically digested DNA. Multiple DNA adducts were present in lung, liver and kidney at 1 day after administration. One of the major adducts in lung (20% of the total eluted radioactivity) coeluted with the synthetic marker, N-(deoxyguanosin-8-yl)-1-aminopyrene (C8-dG-AP). This adduct (10% of total eluted radioactivity) and others were still present in the lung at 28 days after administration of 1-NP. One of the adducts in liver and kidney DNA digests also coeluted with C8-dG-AP. Treatment of the adducts with 0.3 M NaOH resulting in earlier eluting peaks containing radioactivity, indicative of an imidazole ring-opening adduct. A portion of the original peak of radioactivity that coeluted with C8-dG-AP and other adducts, however, was not affected by 0.3 M NaOH. Thus, the chromatographic properties and chemical behavior of the adducts formed in vivo suggest that one of the adducts in the lung is C8-dG-AP which is formed by nitroreduction of 1-NP. Other adducts may be formed via ring-oxidation followed in some instances by nitroreduction. These data indicate that DNA adducts of 1-NP metabolites may be formed in the lung (a primary site for inhaled particles), liver and kidney following inhalation of airborne particles containing 1-NP.
Insights
1-Nitropyrene (1-NP) forms DNA adducts in mouse lung, liver, and kidney. These adducts, including N-(deoxyguanosin-8-yl)-1-aminopyrene (C8-dG-AP), persist and indicate potential carcinogenicity from environmental exposure.
Area of Science:
- Environmental Toxicology
- Molecular Toxicology
- Carcinogenesis
Background:
- 1-Nitropyrene (1-NP) is a widespread environmental pollutant known to be a mutagen and animal carcinogen.
- Understanding the formation and persistence of 1-NP-DNA adducts is crucial for assessing its health risks.
Purpose of the Study:
- To investigate the formation and characterization of 1-NP-DNA adducts in the lung, liver, and kidney of mice after a single exposure.
- To determine the persistence of these DNA adducts over time.
Main Methods:
- Adult male B6C3F1 mice were intratracheally instilled with 1-NP.
- DNA was extracted from lung, liver, and kidney tissues at various time points.
- 1-NP-DNA adducts were isolated and characterized using High-Performance Liquid Chromatography (HPLC) after enzymatic DNA digestion.
- Adducts were further analyzed by chemical treatment (0.3 M NaOH) to assess their stability and structure.
Main Results:
- Multiple 1-NP-DNA adducts were detected in the lung, liver, and kidney one day after 1-NP administration.
- A major adduct in the lung coeluted with the synthetic marker N-(deoxyguanosin-8-yl)-1-aminopyrene (C8-dG-AP).
- This C8-dG-AP adduct and others remained detectable in the lung 28 days post-exposure.
- Similar adducts, including C8-dG-AP, were identified in liver and kidney DNA.
- Chemical treatment revealed both imidazole ring-opening and stable adducts, suggesting diverse metabolic pathways.
Conclusions:
- The study confirms the formation of 1-NP-DNA adducts in mouse lung, liver, and kidney following intratracheal instillation.
- The presence and persistence of adducts like C8-dG-AP suggest that 1-NP metabolites can damage DNA in multiple organs.
- These findings highlight the potential carcinogenic risk associated with 1-NP exposure, particularly via inhalation.