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Biologically-active and chemically-reactive polycyclic hydrocarbon metabolites
Abstract:
The mechanism by which polycyclic hydrocarbons produce tumours in mammalian tissues exposed to them involves biotransformation of the compounds to chemically-reactive species that covalently modify cellular informational macromolecules. In all cases known, epoxides of some form are the reactive species involved. The most common pathway is the formation of vicinal diol-epoxides, the reactive centre of the molecule commonly being adjacent to the 'bay-region'. With some hydrocarbons, the involvement in DNA binding of non-'bay-region' diol-epoxides, of a phenol epoxide and of a 'bay-region' diol-epoxide containing a phenolic function (a triol-epoxide) has also been demonstrated. The relative importance to the carcinogenic process of the different pathways leading to DNA-binding products may be reflected by the biological activities of the intermediates involved.
Insights
Polycyclic aromatic hydrocarbons (PAHs) cause cancer by transforming into reactive epoxides that damage DNA. Different epoxide types, including diol-epoxides and triol-epoxides, contribute to this DNA binding and tumor formation.
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.