Epigenetic Effectiveness of Complete Carcinogens: Specific Interactions of Polycyclic Aromatic Hydrocarbons and Aminoazo Dyes with Cholesterol and Apolipoprotein A-I

During a co-precipitation of cholesterol (Chol) and slight amounts of polycyclic aromatic hydrocarbons (PAHs) or aminoazo dyes (AZOs) in aqueous albumin solution, complex particles are formed; on their surfaces apolipoproteins with an amphipathic α-helix (e.g. apoA-I) are more or less firmly adsorbed. An efficacy index can be calculated from the strength of the hydrophobic interactions between apoA-I and the [Chol/PAH]- or [Chol/AZO]-complex, and the solubility of the PAH or AZO in an aqueous medium, which correlates to the carcinogenicity of these compounds. A short-term test for PAHs and AZOs is described, in which the efficacy index can be determined in the simplest manner without any great expenditure on equipment. The previous results suggest that the parent compounds of the PAHs and AZOs can be involved in a specific interaction with cholesterol-domains of the plasma membrane of a cell. The changes in membrane fluidity and architecture caused by these specific interactions could modulate the distribution and/or activity of membrane proteins which are critical to the regulation of cellular proliferation.

Oxidation of Azo Dyes by Peroxidase: Additional Evidence of a One-Electron Mechanism of Oxidation of Dimethylaminoazobenzene and Sudan I (Solvent Yellow 14)

In the presence of hydrogen peroxide, peroxidase oxidized aminoazo dyes, the non-aminoazo dye 1-phenylazo-2-hydroxynaphthalene (Sudan I, Solvent Yellow 14), and its C-hydroxy derivatives. The oxidation of azo dyes is a pH-dependent reaction; while slightly acidic conditions are optimal for the aminoazo dyes, a basic pH suits better for Sudan I and its hydroxy derivatives. The oxidation of the carcinogenic Sudan I and dimethylaminoazobenzene catalyzed by peroxidase was investigated in detail. Oxygen consumption was not observed in incubations of peroxidase, azo dyes and hydrogen peroxide. However, oxygen uptake was observed after the addition of glutathione, which indicates that free radical metabolites of these compounds are formed by peroxidase. The results suggest that peroxidase metabolizes Sudan I and dimethylaminoazobenzene through a one-electron oxidation mechanism, giving rise to free radicals. Three of the products of Sudan I oxidation by peroxidase with a hitherto unknown structure were characterized partly by UV/VIS and mass spectroscopy.