Biologically-active and chemically-reactive polycyclic hydrocarbon metabolites

Area of Science:

• Biochemistry
• Toxicology
• Molecular Biology

Background:

• Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants known to cause cancer.
• Their carcinogenic mechanism involves metabolic activation to reactive intermediates.
• These intermediates can covalently bind to cellular macromolecules, particularly DNA.

Purpose of the Study:

• To elucidate the specific biotransformation pathways of PAHs leading to carcinogenic effects.
• To identify the chemically-reactive species responsible for DNA modification.
• To understand the role of different epoxide intermediates in the carcinogenic process.

Main Methods:

• Analysis of metabolic pathways for PAH activation.
• Identification of reactive epoxide intermediates.
• Assessment of DNA adduct formation by various PAH metabolites.
• Correlation of intermediate biological activity with carcinogenic potential.

Main Results:

• PAHs are biotransformed into reactive epoxides, which are the primary species that modify DNA.
• The most common pathway involves vicinal diol-epoxides, often adjacent to the 'bay-region' of the PAH molecule.
• Other pathways include non-'bay-region' diol-epoxides, phenol epoxides, and triol-epoxides, which also bind to DNA.

Conclusions:

• The formation of specific epoxide structures is critical for PAH-induced carcinogenesis.
• Different types of epoxides contribute to DNA binding through various pathways.
• The relative importance of these pathways may be indicated by the biological activity of the involved intermediates.