Nitropyrene: DNA binding and adduct formation in respiratory tissues

Area of Science:

• Environmental Toxicology
• Biochemistry
• Pharmacology

Background:

• Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants.
• 1-nitropyrene (NP) is a mutagenic PAH found in diesel exhaust.
• Understanding NP's interaction with biological macromolecules is crucial for risk assessment.

Purpose of the Study:

• To investigate the binding of 1-nitropyrene (NP) and its metabolites to DNA and protein.
• To compare NP binding levels in different rabbit tissues: alveolar macrophages, lung, and tracheal tissue.
• To assess the impact of co-cultivation and diesel particle exposure on NP binding.

Main Methods:

• Incubation of rabbit tissues (macrophages, lung, trachea) with radiolabeled 1-nitropyrene (14C-NP).
• Quantification of NP binding to DNA and protein using radiometry.
• Identification of DNA adducts using chromatographic and spectroscopic methods.
• Intratracheal instillation of NP-coated diesel particles in rats and subsequent tissue analysis.

Main Results:

• Tracheal tissue exhibited significantly higher DNA binding of NP (136 pmole/mg DNA) compared to lung (38 pmole/mg DNA) and macrophages (26 pmole/mg DNA).
• C8-deoxyguanosine 1-aminopyrene was identified as a major NP-DNA adduct in lung tissue.
• NP also bound to protein in tracheal and lung tissues, with lower levels in macrophages.
• Co-cultivation reduced tracheal DNA binding by 45%.
• In rats, 5-8% of inhaled NP-coated diesel particle radioactivity remained in lungs after 20 hours, with 5-12% of pulmonary 14C bound to protein and no detectable DNA binding.

Conclusions:

• Tracheal tissue is a primary target for NP-induced DNA binding.
• NP metabolites form adducts with DNA, notably C8-deoxyguanosine 1-aminopyrene.
• Diesel particles facilitate NP deposition and binding in the lungs, primarily to proteins.